Catalytic hydrodenitrogenation of indole over molybdenum nitride and

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catalytic performance of novel hierachically porous material beta-MCM-48 for diesel hydrodesulfuriza

Synthesis and catalytic performance of novel hierachically porous material beta-MCM-48for diesel hydrodesulfurizationAijun Duan •Chengyin Wang •Zhen Zhao •Zhangfa Tong •Tianshu Li •Huadong Wu •Huili Fan •Guiyuan Jiang •Jian LiuPublished online:22June 2013ÓSpringer Science+Business Media New York 2013Abstract Novel hierachically porous material Beta-MCM-48was successfully synthesized from Beta zeolite seeds by two-step hydrothermal crystallization method using Cetyltrimethylammonium Bromide as the mesostructure directing agent.Beta-MCM-48composite synthesized at the optimization conditions possessed Beta microporous struc-ture and cubic Ia3d mesoporous structure simultaneously.Meanwhile,the acidity of Beta-MCM-48was similar to Beta zeolite and higher than MCM-48mesoporous material.A series of Al 2O 3-Beta-MCM-48supported NiMo catalysts with different Beta-MCM-48contents were prepared by the incipient-wetness impregnation method.The catalytic per-formances were evaluated using DaQing Fluid Catalytic Cracking diesel as feedstock in a high pressure microreactor.Hydrodesulfurization results indicated that NiMo/Al 2O 3-Beta-MCM-48catalyst exhibited better activities than that of NiMo/Al 2O 3traditional catalyst.NiMo/Al 2O 3-Beta-MCM-48catalyst obtained the highest activity as the Beta-MCM-48content in the support was 20wt %,and the corresponding sulfur content of the hydrotreated product reached to 23.02l g g -1.Keywords Catalyst ÁHydrodesulfurization ÁMicro-mesoporous composite materials ÁBeta-MCM-48ÁDiesel oil1IntroductionIn order to promote the sustained economic development and overall social progress,environmental protection efforts were intensiﬁed in different countries.The envi-ronmental emission regulations and fuel speciﬁcations became more and more stringent,especially the sulfur content of transportation fuels was limited to a very low level [1–3].Meanwhile,the demand for ultraclean diesel is growing.The impetus to remove the sulfur in fuels became more signiﬁcant for the scientiﬁc researches.Being the key technique to produce ultraclean fuels,hydrotreating pro-cess should have the appropriate catalysts with high activity,selectivity and suitable structures to realize deep hydrodesulfurization (HDS)of diesel [4].Thus,the design and development of novel catalyst materials with big pore sizes and suitable acidity attract much attention of the scientists and researchers,since large pore size can elimi-nate the diffusion resistance of reactant molecules and reasonable acidity could improve the hydrogenation and hydrogenolysis reactions of C–S bonds in sulﬁdes [5].Mesoporous materials possess uniform pore sizes,well-deﬁned pore arrangement,and relatively large speciﬁc surface area,which can effectively diminish the diffusion resistance,therefore these kinds of materials are considered to be the ideal support candidates for catalytic processes.Since the discovery of M41S in 1992,a variety of meso-porous materials have caught more and more attention in their synthesis and application.Many researchers applied mesoporous material MCM-41in different reactions and found it having good performances [6,7].But the char-acteristic drawbacks of MCM-41still limited its wide application,such as its weak skeleton and lower stability,and two-dimensional (2D)hexagonal (p6mm)structures with relatively lower diffusivity [8].Comparing withA.Duan ÁC.Wang ÁZ.Zhao (&)ÁT.Li ÁH.Wu ÁH.Fan ÁG.Jiang ÁJ.LiuState Key Laboratory of Heavy Oil Processing,China University of Petroleum,Beijing 102249,People’s Republic of China e-mail:zhenzhao@Z.TongGuangxi Key Laboratory of Petrochemical Resource Processing and Process Intensiﬁcation Technology,Guangxi University,Nanning 530004,People’s Republic of ChinaJ Porous Mater (2013)20:1195–1204DOI 10.1007/s10934-013-9703-5MCM-41,mesoporous material MCM-48exhibits three-dimensional(3D)cubic Ia3d mesostructure which facili-tates the diffusion of large sulfur-bearing molecules throughout the pore channels without pore blockage[9,10]. Thus the suitable properties make MCM-48a potential use for hydrotreating catalysts[11].Although mesoporous materials with larger pore diam-eters will be beneﬁcial to overcome the diffusion con-straints of large reactant molecules,their acidity and hydrothermal stability are still very low compared with the conventional supports,which are related to their amor-phous frameworks and limit their wide use in the catalytic processes.Many measures have been considered to improve the acidity and stability of mesoporous materials, and the synthesis of micro-mesoporous composite materi-als[12–14]is one of the efﬁcient ways to adjust their physico-chemical properties since the incorporation of microporous zeolite into the conﬁguration of micro-meso-porous materials will signiﬁcantly contribute to modify the surface properties and interphase strength of the compos-ites.Many types of micro-mesoporous materials were synthesized by different methods involving the one-step and two-step hydrothermal crystallization methods with single or double template agents,postsynthesis treatments, and nonaqueous synthesis[15–17].Ooi and his coworkers[18]synthesized Beta-MCM-41 composite material by two-step crystallization method,and the composite material showed a good catalytic performance in palm oil cracking reaction.Xiao and his groups[19] synthesized mesoporous MAS-3and MAS-8aluminosili-cates using Cetyltrimethylammonium Bromide(CTAB)as template from L zeolite precursor,and the results showed that the walls of these two materials contained the structural units of L zeolite.Pinnavaia et al.[20–22]prepared the hexagonal Al-MSU-S mesoporous materials from the zeo-lite seeds of Y,Beta and ZSM-5via self-assembly method. Mazaj[23]prepared an aluminium-free Ti-Beta-SBA-15 composite through the post-synthesis incipient wet deposi-tion of Ti-Beta nanoparticles solution on the SBA-15matrix.Lima and his cooperators[24]synthesized a micro-mesoporous Beta-TUD-1composite material via seeding method,which was an effective catalyst for conversion of xylose into furfural.In this paper,a novel Beta-MCM-48hierachically por-ous composite was successfully synthesized from Beta zeolite seeds by two-step hydrothermal crystallization method using CTAB as the mesostructure directing agent. Al2O3-Beta-MCM-48supported NiMo bimetallic catalysts were also prepared.The catalytic performances were studied by using DaQing Fluid Catalytic Cracking(FCC) diesel.The physicochemical properties of materials and catalysts were characterized by various techniques.2Material and method2.1MaterialsCetyltrimethylammonium bromide(99%,CTAB)and tetraethyl orthosilicate(99%,TEOS)were purchased from Sigma-Aldrich.Tetraethylammonium hydroxide solution (25%,TEAOH)were purchased from Hangzhou Yanshan Chemical Reagent Co.Ltd,NaOH(AR grade),and Na-AlO2(AR grade)were purchased from Sinopharm Chemi-cal Reagent Co.Ltd,People’s Republic of China.All reagents were used as received without further puriﬁcation.2.2Preparation of composite materials2.2.1Synthesis of beta nanocluster solutionTypical synthesis procedure of Beta nanocluster solution was as follows:0.19g of NaOH,0.23g of NaAlO2,and21.43g of TEOS were added into25.95g of TEAOH aqueous solu-tion(25%),and the mixture molar ratio of Al2O3/SiO2/ Na2O/TEAOH/H2O was 1.0/100/1.4/15/360,then the mixture was kept stirring for4h at room temperature before being transferred into an autoclave to age for12h at 140°C to obtain zeolite Beta nanocluster solution.2.2.2Synthesis of MCM-48MCM-48was synthesized by using CTAB as structure directing agent according to the literature[25].A typical synthesis procedure was as follows: 1.90g NaOH and 12.754g CTAB was dissolved in101g of H2O,the mixture was then kept stirring for1h.Finally,21.43g TEOS (containing6g SiO2)was added dropwise and kept stir-ring,the molar ratio of mixture was SiO2/CTAB/NaOH/ H2O=1/0.35/0.476/56;the mixture was stirred at room temperature for6h and then was transferred into an auto-clave for additional reaction at100°C for72h.The product of MCM-48was collected byﬁltration,dried at100°C,and calcined at550°C in air for6h to remove the template.2.2.3Synthesis of beta-MCM-48compositesFor syntheses of the Beta-MCM-48composites(denoted as BM48),0.89g NaOH and4.89g CTAB was dissolved in adequate H2O,the mixture was then kept stirring for1h until CTAB was dissolved thoroughly.Finally,36g zeolite nanocluster(equivalent to the SiO2containing of6g)was added and kept stirring,then acetic acid was used to adjust pH value of the mixture solution until reached to11. The molar ratios of mixture were Al2O3/SiO2/CTAB/H2O=1/100/13/11300.The mixture was stirred at room temperature for6h and then transferred into an autoclave for additional hydrothermal treatment at110°C for48h. The product of BM48was obtained by means ofﬁltration, dried at110°C,and calcined at550°C in air for6h to remove the templates.2.2.4Preparation of H-BM48The protonated form of BM48was ion-exchanged two times with1.0M NH4Cl at80°C for1h before being dried and calcined at550°C in air for4h.2.3Preparation of supportsThe corresponding supports were obtained by mechanical mixing of BM48and Al2O3.The supports were denoted as Al2O3-BM48-x%,where x represents different mass fractions of BM48in composite supports.2.4Preparation of NiMo supported catalystsThe Al2O3-BM48and Al2O3supported NiMo catalysts were prepared by two-step incipient-wetness impregnation method with aqueous solutions of ammonium heptamo-lybdate and nickel nitrate.After each impregnation step,the prepared catalyst precursors were dispersed in an ultra sonic bath for30min to assist the dispersion of active metals on the surface of composite supports.The prepared samples were dried at 110°C for12h,and calcined at550°C for4h.The supported catalysts were obtained with the constant amounts of Mo(MoO310wt%)and Ni(NiO3.5wt%).2.5Characterization of supports and catalystsNitrogen adsorption and desorption measurements were performed at liquid nitrogen temperature of-196°C on a Micromeritics ASAP2020system.The samples were outgassed under vacuum at350°C for4h prior to mea-surement.Total surface area was calculated according to the BET method.Meso-and micropore volumes were determined by the BJH and t-plot methods(desorption).Powder X-ray diffraction(XRD)patterns were recorded on an XRD-6000powder diffractometer under40kV and 30mA in the2h interval of5°–50°with a step size of0.02°and scan rate of1°min-1using Cu K a radiation.Transmission electron microscopy(TEM)was per-formed on a Philips Tecnai G2F20equipment with an accelerating voltage of300kV.A few mg of the powdered samples was suspended in2ml ethanol,and the suspension was treated in a sonicator for1h.Then,the suspension needed to be settled for15min,before a drop was taken and dispersed on a300mesh copper grid coated with holey carbonﬁlm.FT-IR spectra were obtained in the wave number range from1,750–400cm-1via an FTS-3000spectrophotometer. The measured wafer was prepared with the weight ratio of sample to KBr for1/100.The nature of acid sites of the materials was tested by pyridine-adsorbed Fourier transformed infrared spectros-copy(Py-FTIR)experiments using a MAGNAIR560FTIR instrument(Nicolet Co.,America)with a resolution of 1cm-1,The samples were dehydrated at500°C for5h under a vacuum of1.33910-3Pa,followed by adsorp-tion of puriﬁed pyridine vapor at room temperature for 20min.The system was then degassed and evacuated at different temperatures,and the IR spectra were recorded.H2-TPR was tested on a self-assembly instrument with a TCD detector.For the TPR experiments,the samples were pretreated in situ at550°C for1h and then cooled down to room temperature under Ar stream.The reduction step was performed with an H2/Ar mixture(10v%Ar)at a constant ﬂow rate of40mL min-1with a heating rate of 10°C min-1from room temperature to1,000°C.27Al MAS NMR spectra were recorded with a Bruker Avanced III500MHz spectrometer.The27Al spectra were obtained at130.327MHz with a0.9l s pulse width,6l s delay time and12kHz spinning speed.3Experimental procedureThe HDS performances of FCC diesel were evaluated in a ﬁxed-bed inconel reactor with2g catalysts.All the cata-lysts were presulﬁded by2wt%CS2-cyclohexane and H2 mixture for4h at the temperature of320°C and the pressure of4MPa.After catalyst presulfurization,the catalyst was evaluated under the traditionally commercial conditions with temperature of350°C,the pressure of 5.0MPa,H2/oil ratio of600mL mL-1and LHSV of 1.0h-1.Then the catalytic HDS performance of different catalysts could be evaluated for their desulfurization efﬁ-ciencies of diesel.The typical properties of diesel were listed in Table1.The total sulfur contents in the feed and products were measured by using a LC-4coulometric sulfur analyzer system.The catalytic activity was estimated by HDS efﬁ-ciency,which is deﬁned as follows:HDS%efﬁ-ciency=[(S f-S p)/S f]9100%;where S f and S p are the sulfur concentrations in feed and product respectively.4Results and discussion4.1The effect of synthesis conditions for structureof materials4.1.1The effect of H2O/SiO2The amount of water used in the initial synthesis system can signiﬁcantly affect the silica framework,and H2O/SiO2 ratio was an important factor on the material structure[26, 27].In this paper,the effect of H2O content was investi-gated with molar gel composition of Al2O3/SiO2/CTAB/ H2O=1/100/13/7300-13300.XRD proﬁles of the as-synthesized samples are depicted in Fig.1a.It’s observed that when H2O/SiO2ratio was73,the synthesized material was not well-ordered;as the H2O/SiO2ratio increased to 93,MCM-41formed;further increased of H2O/SiO2ratio to113,well-ordered cubic MCM-48structure was found, indicating that the formation of long-range order of cubic Ia3d structure of MCM-48was motivated by higher H2O/ SiO2.While H2O/SiO2ratio exceeded133,the ordering degree decreased.This may be related to that if the H2O/ SiO2ratio was low,high SiO2concentration could lead to a rapid polymerization of the silicate species,and the incomplete hydrolysis resulted in linear chain formation with residual organic groups[26].This would weaken the electrostatic interaction between silicon-aluminum aggre-gate and micelles which was the necessary impetus to the assembly of mesoporous material according to the poly-merization-assembly-arranging speculation[28],so the ordering degree would decrease.Oppositely,at higher molar ratio of H2O/SiO2,the hydrolysis proceeded faster, while the polymerization and condensation of the silicate species took place too slow,which could also decrease the ordering degree of mesoporous material.4.1.2The effect of CTAB/SiO2The inﬂuence of CTAB concentration was investigated with molar gel composition of Al2O3/SiO2/CTAB/H2O=1/100/ x/11300,where x=6,13,20and27.XRD proﬁles of the ﬁnal samples are shown in Fig.1b.It was observed that when the CTAB concentration was low,XRD pattern showed the typical peaks of the hexagonal MCM-41struc-ture;by increasing the CTAB/SiO2ratio from0.13to0.20,XRD patterns showed the characteristic peaks assigned to the reﬂections of the cubic structure between3and5°indicating the formation of well-ordered cubic MCM-48. When the CTAB concentration further increased to0.27,the structure of lamellar phase was observed.The phase transitions from hexagonal to cubic and lamellar mesophases as the increase of CTAB/SiO2ratio may be attributed to that the system couldn’t form enough micelles to direct mesoporous structure effectively at low CTAB con-centration.On this occasion,parts of negative ions could convert into amorphous aluminosilicates,which resulted in the decrease of ordering degree.Oppositely,high contents of CTAB produced more CTA?cations,furthermore,based on the charge density matching principle,the correspondingly charge density of inorganic negative anions increased,leading to a higher accumulation of surfactants,which inhibited the efﬁcient assembly and regular array of silicon-aluminum aggregate to form mesoporous conﬁgurations[29,30].4.1.3Inﬂuence of pH of the gelThe inﬂuence of pH value was investigated with molar gel composition of Al2O3/SiO2/CTAB/H2O=1/100/13/11300. Corresponding XRD proﬁles were depicted in Fig.1c.It can be observed that when pH value was10,well-ordered cubic MCM-48formed;if pH values of the system were too high or too low both do harm to the formation of MCM-48. Meanwhile,the polymerization/depolymerization equilib-rium of the silicate species maintained well at the pH value of10.However,as pH increased,silicon-aluminum aggre-gate would exist in the form of monomer with high charge density,in which the depolymerization effect was weak, resulting in the decrease of ordering degree.When pH became lower,the excessive depolymerization effect led to the decrease of charge density of silicon-aluminum aggre-gate.This could restrain the necessary electrostatic interac-tion between silicon-aluminum aggregate and micelles in process of assembling mesoporous material,which was also disadvantageous to the ordering degree of materials[31,32].4.1.4Inﬂuence of SiO2/Al2O3of beta precursorThe inﬂuence of SiO2/Al2O3was investigated with molar gel composition of Al2O3/SiO2/CTAB/H2O=x/100/13/ 11300.XRD proﬁles of theﬁnal samples are depicted inTable1The typical properties of diesel feedstockProperties Density@20°C(g cm-3)S(l g g-1)N(l g g-1)Distillation/°CIBP30%50%70%FBPData0.87981,290920158212238279374Fig.1d.It can be observed that as the SiO2/Al2O3of beta precursor increased,the crystallinity of mesoporous material increased,when the SiO2/Al2O3=100,the crystallinity was the highest.Oppositively,the intensity of Beta diffraction peak became lower with the increase of SiO2/Al2O3ratio.Brieﬂy,high SiO2/Al2O3ratio favored for the assembly of mesopore structure,but was unfavorable to the synthesis of microspore Beta zeolite [33].This might be explained by that,as SiO2/Al2O3 decreased,the hydrolytic action of aluminum became increased,so the pH value of system decreased and lower pH value could result in the inhibition of the necessary electrostatic interaction between silicon-aluminum aggregate and micells,which was bad to form an order material.Based on the above discussion,BM48microporous-mesoporous material could be synthesized at the optimal conditions of Al2O3/SiO2/CTAB/H2O=1/100/13/11300; pH=10;crystallized at110°C for3d.The optimized sample of BM48was characterized by many techniques to obtain the typical physico-chemical property,involving its structure and acid distribution.Furthermore,BM48was used as the catalyst additive to prepare NiMo bimetallic supported hydrotreating catalyst and the corresponding HDS performance was evaluated in a microreactor.4.2Characterizations of materials4.2.1XRD analysis of materialsFigure2is XRD of the synthesized samples.As shown in Fig.2a,the XRD patterns in the range of small angles of the MCM-48sample displayed a distinct diffraction sharp peak indexed as(211);simultaneously,a peak indexed as (220)and a series of overlapping peaks indexed as(321) (400),(420)and(332)also appeared.It clearly indicated that MCM-48had a well-ordered mesoporous structure which belonged to the bicontinuous cubic space group of Ia3d[29].According to the location of(211),the unit cell parameter a0of MCM-48was7.78nm.The diffraction peaks of BM48sample in Fig.2agreed well with those of MCM-48sample,indicating that it also had a typical cubic mesoporous structure.The peak intensities of BM48were relatively lower than those of MCM-48,which might be ascribed to that zeolite nanoclusters with bigger crystal sizes were more difﬁcult to be assembled by the meso-structure directing agent[34].The large angle X-ray diffraction patterns of samples are shown in Fig.2b.It’s observed that both BM48and Beta zeolite showed very intensive diffraction peaks at7.6°and 22.4°indexed as the characteristic peaks of zeolite Beta[35],which meant that BM48material had the microporous structure of Beta zeolite.The peak intensities of BM48were comparatively weaker since the crystallization time of Beta nanocluster emulsion was shorter than that of Beta zeolite. However,the pure MCM-48exhibited no sharp peak in the high angle diffraction pattern.Brieﬂy,it’s concluded that BM48was a hierachically porous composite containing MCM-48and Beta zeolite structures all in one.4.2.2N2adsorption analysis of materialsFigure3a shows N2adsorption–desorption isotherms of different materials.Obviously,the isotherm of zeolite Beta belonged to the typical type I,while both of MCM-48and BM48showed the type IV isotherm and H1-type hysteresis loop,indicating that they both had mesoporous structure [36].The hysteresis loop of BM48was lower,but more sharper than that of MCM-48,indicating BM48a very narrow range of pore size distribution(PSD).Figure3b shows PSD curve of materials,the pore size distribution of materials showed a binary pore pattern,while the existence of the pore size value of2.4nm which was ascribed to mesoporous pore of particles and the pore size value of3.8nm was attributed to the pore between particles, it’s obvious that MCM-48and BM48both showed these two types pores in PSD,indicating that the structure of BM48 held the characteristics of mesoporous MCM-48.On the contrary,Beta showed the characteristics of microporous zeolite and no ordered mesopore structure was found in its PSD.However,in comparison with pure mesoporous material of MCM-48,BM48micro-mesoporous material showed a narrow PSD and the mean pore size was2.3nm, which was a little smaller than that of MCM-48.Table2shows the textural and structural properties of materials calculated form adsorption isotherm.As shown in Table2,both BM48and MCM-48exhibited high surface areas,even higher than that of Beta.Due to the contribution of Beta zeolite,BM48had relatively higher V mic/V mes than MCM-48.Moreover,compared with MCM-48,BM48had a wider pore diameter and thicker pore wall,which might be derived from the assembling of the zeolite primary unit into the mesoporous framework of MCM-48[8].4.2.3FT-IR spectra result of materialsFigure4shows the FT-IR spectra of materials.As is shown, in the spectrum of MCM-48,the bands centered at*460, 810and1,030cm-1,which belonged to the vibrations of Si–O–Si[37],were observed.The framework vibration spectrum of BM48was similar to that of MCM-48,indicatingthat BM48had similar skeletal structure as MCM-48.However,other two distinct bands at 520and 570cm -1,which could be assigned to the six-and ﬁve-member rings presented in the structure of zeolite Beta [35],were observed in the FT-IR spectra of BM48and Beta.But the intensities of bands in BM48were much lower than those of MCM-48,which agreed with the results of XRD and TEM analysis.This result indicated that there was some Beta zeolite precursors assembled in the BM48material.4.2.4TEM characterizations of materialsTEM images of materials are shown in Fig.5.It can be seen that MCM-48showed well ordered cubic 3D meso-porous channels [26].According to the scale of image,the pore of 2–3nm was clearly visible,in coincident with the results of N 2adsorption and XRD analysis.Similar to the channels of MCM-48,BM48possessed a typical Ia3d cubic structure.The average sizes of beta in BM48were about 5nm.The wall thickness of BM48was much lessthan 5nm,thus these Beta micro-crystal particles couldn’t be introduced into the wall conﬁguration of BM48but existed as single nanoparticles.Therefore,it could also be deduced that only Beta precursor units existed in the wall framework of BM48.4.2.527Al MAS NMR measurementFigure 6was the 27Al MAS NMR spectra of materials.As is shown,the spectrum of MCM-48only contained a peak at *54ppm,which was generally ascribed to aluminum species in tetrahedral surroundings (AlO 4structural unit)situated in the framework [27].However,the spectra of zeolite Beta and BM48displayed two sharp peaks at *54and 0ppm.The signal at 0ppm was assigned to the octahedrally coordinated non-framework aluminum species (AlO 6structural unit).It’s observed that the distribution of chemical shift of tetrahedral aluminum in Al-MCM-48was broad,indicating that the Al coordination surrounding was composite,and the signal at 0ppm was very weak,dem-onstrating that only tetrahedral aluminum species existed in Al-MCM-48.The distributions of chemical shift of tetra-hedral aluminum in BM48and Beta were concentrated,and the intensities of peak were very strong.Meanwhile,both spectra of BM48and Beta showed weak signal at 0ppm.In brief,the aluminum coordination surrounding of BM48was similar to that of Beta,therefore,it is possible to deduce that some Al species in zeolite Beta nanocrystals were ﬁxed into BM48framework.4.2.6Pyridine-FTIR of materialTable 3lists the acid strength distributions and the acid quantity of the samples was calculated from the results of pyridine-adsorbed IR spectra degassed at 200and 350°C.The peaks at 1,446and 1,577cm -1were attributed to pyridine adsorbed on L acid sites,and the peak atTable 2Textural properties of different materials Samples S BET (m 2g -1)a V t (cm 3g -1)b V mes (cm 3g -1)c V mic (cm 3g -1)d V mic /V mes a 0(nm)e d BJH (nm)f b w (nm)g MCM-48928.70.740.760.340.457.3 2.5 1.3BM48907.50.660.580.450.788.5 2.2 1.6Beta 5020.34–0.22–––Al 2O 3206.80.48a Surface area was calculated by the BET method with a relative pressure (P/P 0)range of 0.05–0.30in the adsorption isothermb The total pore volume was obtained at a relative pressure (P/P 0)of 0.98c Mesopore volumed Micropore volumee XRD unit cell parameter (a 0)f d BJH is the mesopore diametergb w is the wall thickness,the thickness of the mesoporous materials were evaluated using the formula t =[1-(V p q )/(1?V p q )](a 0/x 0),where V p is the pore volume,q is the density of the pore wall (2.2g/cm 3),a 0is the unit cell parameter,and x 0is a constant (3.0919)1,546cm -1was assigned to pyridine adsorbed onto B acidsites,while the peak at 1,490cm -1was ascribed to pyri-dine adsorbed onto both B and L acid sites.The results showed that BM48possessed much larger amounts of total acidity,especially higher amounts of medium and strong acid sites than MCM-48,and the acidity level was similar to that of Beta.4.3Catalytic activityHDS performances of NiMo series catalysts for FCC diesel are shown in Fig.7.Obviously,the addition of BM48tothe catalyst support could improve the hydrotreating per-formances under the same traditional conditions,and the evaluation results proved that the catalyst of NiMo/Al 2O 3-BM48–20%with 20wt%BM48in the support exhibited the highest HDS conversion,which could reach 98.1%,Meanwhile,all the relative catalytic activities of catalysts were much better than that of traditional NiMo/Al 2O 3supported catalyst(96.7%).The highest catalytic activities of NiMo/Al 2O 3-BM48-20%catalyst might be attributed to the following reasons:(1)the proper introduction of BM48could increase the speciﬁc surface area and total pore volume of the catalysts,which were beneﬁcial to the higher dispersion of active metals.However,the average pore diameters decreased with the BM48amount increased,drastic shrinkage of pore diameter was harmful to the diffusion of large molecules such as the steric hindered alkyl-substituted DBTs [38].Therefore,the introductionofFig.5TEM images of MCM-48and BM48Table 3Amounts of Bro¨nsted and Lewis acid sites determined by pyridine-FTIR of the catalysts Samples200°C/l mol g -1350°C/l mol g -1LB L ?B L B L ?B BM48231.0100331.0226.2100.0226.2MCM-48186.90186.975.0075.0Beta252.3145.1397.4247.6128.5376.1Degassed temperatures at 200and 350°C represented the amounts of total and strong acid sites respectivelyNote :L and B stands for Lewis and Bro¨nsted acid。

二硫化钼基纳米材料在电催化制氢中的研究进展

第49卷第12期当代化工 Vol.49，No.122020年12月 Contemporary Chemical Industry December，2020基金项目：国家自然科学基金（项目编号：22065028）；内蒙古自治区高等学校科学研究项目（项目编号：NJZY18382）；内蒙古自治区自然科学基金（项目编号：2017MS(LH)0202）；内蒙古自治区高等学校科学研究项目（项目编号：NJZY17102）。

收稿日期：2020-07-31 作者简介：王娜（1978-），女，内蒙古自治区包头市人，讲师，博士，2017年毕业于内蒙古工业大学化学工艺专业，研究方向：纳米催化剂的设计与合成。

E -mail：*******************。

通信作者：胡宇强（1980-），男，讲师，博士，研究方向：金属有机合成及电化学性能研究。

E -mail：******************.cn。

二硫化钼基纳米材料在电催化制氢中的研究进展王娜1，叶菲菲3，胡宇强2（1. 包头师范学院化学学院，包头 010403；2. 内蒙古工业大学化工学院，呼和浩特 010051；3. 海南华侨中学，海口 570206）摘要：概括近年来在电催化制氢领域中具有特定形态、小尺寸、少片层和其他结构特征的MoS 2纳米材料的制备方法以及应用方面的最新研究进展。

此外，讨论二硫化钼纳米片在电催化制氢催化活性方面所面临的关键障碍，并进一步发现通过增加活性位点的暴露、增加MoS 2的导电性以及制造缺陷等策略能提高其活性。

最后，提出制备高催化性能MoS 2的潜在途径，并对未来硫化钼基材料的实际应用前景进行了展望。

关键词：二硫化钼；电催化；纳米材料；析氢反应中图分类号：TQ032.41 文献标识码： A 文章编号： 1671-0460（2020）12-2827-05Research Progress of MoS 2-based Nanomaterialsfor Hydrogen Evolution ReactionWANG Na 1, YE Fei-fei 3, HU Yu-qiang 2（1. Department of Chemistry, Baotou Teachers’ College, Baotou 014030，China ；2. College of Chemical Engineering, Inner Mongolia University of Technology, Hohhot 010051, China ；3. Hainan Overseas Chinese Middle School, Haikou 570206, China ）Abstract : The preparation methods of MoS 2 nanomaterials with definite morphologies, small size, few-layer and other structural features were summarized, and the recent research progress in the applications was discussed. Moreover, the critical obstacles faced by MoS 2 nanosheets with respect to their catalytic activities of HER were analyzed, and the strategies for improving activity were put forward, such as increasing the exposure of active sites, conductivity and defects. In the end, some suggestions on the pathways achieving high performance MoS 2 nanosheets were also put forward, and perspective on practical application of MoS 2 in the future was prospected. Key words : MoS 2; Electrocatalysis; Nanomaterials; Hydrogen evolution reaction化石燃料作为现代工业的基础，过量开采和使用正在引发全球性环境污染和能源危机问题，寻找可行的化石燃料替代能源日益受到各国关注[1]。

NiFe-MOF衍生的Fe掺杂Ni基硒化物作为高效的析氧催化剂

第49卷第22期2021年11月广州化工Guangzhou Chemical IndustryVol.49No.22Nov.2021NiFe-MOF衍生的Fe掺杂Ni基硒化物作为高效的析氧催化剂*王天河，黄亭亭，秦子菁，任威威，蒋庆，唐文强，谢华明，雷英(四川轻化工大学化学工程学院，四川自贡643000)摘要：发展高效、耐用的析氧反应(OER)电催化剂是大规模电解水的关键。

本文以多孔网络结构的NiFe双金属有机骨架(MOFs)为前驱体，通过水热硒化过程，定向转化成纳米团簇结构的NiFe硒化物。

其中，Ni0.67Fe0.33Se在1.0M KOH电解质中显示极低的过电位(297mV)和较小的Tafel斜率(55.0mV/dec),12h测试过程中保持了良好的稳定性。

关键词：析氧反应；金属有机骨架；NiFe硒化物；水热法.中图分类号：0657.3文献标志码：A文章编号：1001-9677(2021)022-0030-04 NiFe-MOF Derived Fe-doped Ni-based Selenides for EfficientOxygen Evolution Catalysts*WANG Tian-he,HUANG Ting-ting,QIN Zi-jing,REN Wei-wei,JIANG Qing,TANG Wen-qiang,XIE Hua-ming,LEI Ying(College of Chemical Engineering,Sichuan University of Science&Engineering,Sichuan Zigong643000,China) Abstract:The development of high efficient and durable electrocatalyst for oxygen evolution reaction(OER)is the key technology for large-scale industrial water splitting.NiFe bimetallic organic frameworks(MOFs)with porous network structure were used as precursors to be directionally transformed into NiFe selenides with nanocluster structure via hydrothermal selenization process.Among them,Ni067Fe033Se exhibited very low overpotential(297mV)and small Tafel slope(55.0mV/dec)in1.0M KOH electrolyte,and maintained good stability during overall12h test.Key words：oxygen evolution reaction；metal organic framework；NiFe selenide;hydrothermal method随着绿色、可持续和可再生能源氢能源越来越受到关注，产氢、储氢以及氢能转化技术等成为研究热点电化学水裂解是一种极有前途的清洁产氢方法，然而析氢过程伴随着的动力学缓慢的析氧反应(OER)却限制了水裂解过程⑵。

徐奕德 ( 中国科学院大连化学物理研究所催化基础

文章编号:025329837(2004)0920688205研究论文:688～692收稿日期:2003211227.　第一作者:刘红梅,女,1976年生,博士研究生.联系人:徐奕德.Tel :(0411)84379189;E 2mail :xuyd @.基金项目:国家基础研究发展规划(973计划)项目(G 1999022406).分子筛的酸处理对Mo/HZSM 25催化甲烷无氧芳构化反应性能的影响刘红梅,　申文杰,　刘秀梅,　包信和,　徐奕德(中国科学院大连化学物理研究所催化基础国家重点实验室,辽宁大连116023)摘要:采用HNO 3溶液对HZSM 25分子筛进行预处理,并以处理后的分子筛为载体制备了Mo/HZSM 25催化剂.结果表明,改性的Mo/HZSM 25催化剂在甲烷无氧脱氢芳构化反应中表现出很好的稳定性,显著地抑制了积炭物种在催化剂表面的形成.SEM ,XRD 和1H MAS NMR 等表征结果表明,酸处理在一定程度上降低了HZSM 25分子筛的结晶度,使部分Al 物种脱离骨架结构,迁移到骨架外形成新的表面Al 羟基,从而使HZSM 25分子筛上B 酸中心的数目明显减少.未经改性的Mo/HZSM 25催化剂表面,平均每个晶胞中有1112个B 酸位,而改性的Mo/HZSM 25催化剂表面,平均每个晶胞中仅有0188个B 酸位.这表明过多的酸性位存留在催化剂上会引起积炭的生成,降低催化剂的稳定性.关键词:钼,HZSM 25分子筛,甲烷,脱氢芳构化,酸处理,脱铝中图分类号:O643 文献标识码:AE ffect of Acid T reatment of Z eolite on C atalytic Perform ance ofMo/HZSM 25for Methane Dehydroarom atizationL IU Hongmei ,S HEN Wenjie ,L IU Xiumei ,BAO Xinhe ,XU Y ide3(S tate Key L aboratory of Catalysis ,Dalian Institute of Chemical Physics ,The Chinese Academy of Sciences ,Dalian 116023,L iaoning ,China )Abstract :The pretreatment with HNO 3solution was applied to modify HZSM 25zeolite ,and the Mo/HZSM 25catalyst prepared by using the modified HZSM 25zeolite as support showed higher stability in methane dehy 2droaromatization than that prepared by using unmodified HZSM 25zeolite.Meanwhile ,the formation of coke was distinctly suppressed on the Mo catalyst supported on the modified HZSM 25zeolite.The effect of acid treat 2ment on the structure of HZSM 25zeolite and Mo/HZSM 25catalyst was studied by SEM ,XRD and 1H MAS NMR techniques.The results suggested that the acid treatment of HZSM 25led to an obvious dealumination and a decrease in the crystallinity of HZSM 25zeolite.A part of Al species was extracted from the zeolite framework and formed extra 2framework Al 2OH groups ,resulting in an evident decrease of the number of Br nsted acid sitesremained on the zeolite surface.As demonstrated in the 1H MAS NMR experiment ,the number of B acid sites per unit cell was 1112on the Mo/HZSM 25catalyst prepared using unmodified zeolite as support ,but it was only 0188on the Mo catalyst supported on modified HZSM 25zeolite.The result indicated that too many B acid sites on the catalyst would cause severe coking and decrease the catalyst stability.K ey w ords :molybdenum ,HZSM 25zeolite ,methane ,dehydroaromatization ,acid treatment ,dealumination 1993年大连化学物理研究所首先报道了甲烷无氧脱氢芳构化反应[1],该反应因对甲烷活化及天然气的综合利用具有重要意义而引起了广泛的关注.近十年来,有关甲烷无氧芳构化反应的基础研第25卷第9期催　化　学　报2004年9月Vol.25No.9Chi nese Journal of CatalysisSeptember 2004究取得了很大进展[2～4].为了获得具有较高活性和稳定性的甲烷无氧芳构化催化剂,人们仔细地筛选了多种金属活性组分及载体.结果表明,以HZSM25分子筛作为载体担载的Mo催化剂表现出了最好的催化活性[5～8]. 作为一种脱氢2酸催化双功能催化剂,Mo/ HZSM25的催化行为是由分子筛的酸性位和所担载的Mo组分协同作用而产生的.甲烷的C2H键活化以及最初的C2C键形成发生在碳化钼物种上,而进一步的聚合和环化则发生在HZSM25分子筛的B 酸性位上[9].同时,HZSM25分子筛独特的孔道结构对反应产物分布也起到重要的择形作用[8].尽管Mo/HZSM25催化剂具有很多适于甲烷无氧芳构化反应的优良特性,但反应中形成的大量积炭仍会使催化剂迅速失活.已有实验证明,沉积在分子筛酸性位上的积炭物种(以稠环芳烃为主)是导致催化剂失活的主要原因[10].既然B酸性位在甲烷无氧芳构化反应中表现出双重作用,那么确定合适的酸性位数目对于开发具有优良活性和稳定性的催化剂就变得尤为重要.研究人员做了大量工作,希望可以找到合适的方法来调变HZSM25分子筛的酸性,以改善Mo/HZSM25催化剂的催化性能,抑制积炭的生成并提高催化剂的稳定性.这方面的研究工作主要集中在添加第二金属组分上.结果表明,适量添加W,Zr,Pt,Fe和Co等元素可以不同程度地提高催化剂的活性,抑制积炭的生成,进而提高催化剂的稳定性[11,12].但是,在甲烷无氧芳构化反应的研究工作中对催化剂载体进行修饰的报道比较少见. 本文采用酸处理方法对HZSM25分子筛进行改性,并以改性的分子筛为载体制备Mo/HZSM25催化剂,考察了催化剂在甲烷无氧芳构化反应中的催化性能.同时,采用SEM,XRD和1H MAS NMR 等技术研究了酸处理对HZSM25分子筛及Mo/ HZSM25催化剂结构产生的影响.1　实验部分1.1　HZSM25分子筛酸处理及催化剂制备将30g的HZSM25分子筛(南开大学试剂厂, n(SiO2)/n(Al2O3)=50)与300ml的HNO3溶液(5 mol/L)混合,在373K回流10h,并不断搅拌.将处理过的分子筛过滤,洗涤至中性并干燥.未经酸处理及经过酸处理的HZSM25分子筛分别被命名为HZSM25(U T)和HZSM25(TA).Mo/HZSM25催化剂采用常规的浸渍方法制备,其中w(Mo)=6%.用一定浓度的(N H4)6Mo7O24・4H2O溶液浸渍HZSM2 5分子筛,室温放置24h后在393K烘干,然后在773K焙烧6h即可.以HZSM25(U T)和HZSM25 (TA)分子筛为载体制备的催化剂分别被命名为Mo/HZSM25(U T)和Mo/HZSM25(TA).1.2　催化剂活性评价催化剂活性评价在固定床气体连续流动反应器上进行,反应管内径8mm,催化剂用量015g.原料气为超高纯甲烷和10%超高纯氮的混合气(氮用作内标).反应温度973K,压力1011325Pa,空速1500h-1.反应产物由Varian CP23800型气相色谱仪在线分析.OV2101毛细管柱分离CH4,C2H4, C2H6,C6H6,C7H8,C8H10和C10H8,由FID检测; Heyesep2D填充柱分离H2,N2,CO,CH4,CO2,C2H4和C2H6,由TCD检测.根据碳数平衡计算包括积炭在内的各组分相对含量,产物产率均以转化的甲烷数表示[13].1.3　催化剂表征 SEM表征在Hitachi2600型扫描电镜上进行. XRD测试在Rigaku D/MAX2RB型X射线衍射仪上进行.样品在室温下测定,采用Cu Kα射线(λ=0115418nm),管电压40kV,管电流50mA.扫描范围2θ=5°～50°,扫描速度5°/min. 1H MAS NMR实验在Bruker DRX2400型核磁共振仪上进行,使用BBO MAS探头和4mm的ZrO2样品管,共振频率40011MHz.化学位移以三甲基硅丙基磺酸钠为外标.实验前将样品在673K 和1133Pa下处理24h以除去样品上吸附的水.对所得谱图进行拟合,根据HZSM25分子筛原粉的硅铝比计算出每个晶胞中含有的B酸位数目,即可由核磁谱图中峰面积的比值定量计算出各样品中每个分子筛晶胞所含有的不同种类羟基的数目. TG A实验在Perkin2Elmer TGS22型热分析仪上进行.样品量为20mg,空气流速为30ml/min,以10K/min的速率从313K升温至1023K,自动记录TG曲线.2　结果与讨论2.1　催化剂表征结果图1给出了不同HZSM25分子筛样品的SEM 照片.可以看出,经过酸处理后分子筛晶体表面变得粗糙并且出现部分破损.这表明酸处理在一定程986第9期刘红梅等:分子筛的酸处理对Mo/HZSM25催化甲烷无氧芳构化反应性能的影响图1　不同HZSM 25分子筛样品的SEM 照片Fig 1　SEM images of different HZSM 25zeolite samples(a )HZSM 25(U T ),(b )HZSM 25(TA )(HZSM 25(U T )HZSM 25zeolite untreated ,HZSM 25(TA )HZSM 25zeolite treated with acid ;the same below )度上破坏了HZSM 25分子筛晶体结构的规整性.图2　不同HZSM 25分子筛及Mo/HZSM 25催化剂样品的XR D 谱Fig 2　XRD patterns of different HZSM 25zeolite andMo/HZSM 25catalyst samples(1)HZSM 25(U T ),(2)HZSM 25(TA ),(3)Mo/HZSM 25(U T ),(4)Mo/HZSM 25(TA )(The Mo loading is 6%,the same below ) 图2示出了不同HZSM 25分子筛和Mo/HZSM 25催化剂样品的XRD 谱.可以看出,与酸处理前的HZSM 25分子筛相比,酸处理后的分子筛结晶度下降到95%,但分子筛的骨架结构没有改变,这与SEM 结果相一致.在处理前和处理后的HZSM 25分子筛上担载Mo 物种后,分子筛的特征衍射峰强度均有所下降,且没有任何新的特征峰出现.这说明,在HZSM 25(U T )分子筛和HZSM 25(TA )分子筛表面,担载的Mo 物种都可以高度分散,而且分子筛的晶相结构不发生改变.表1　不同HZSM 25分子筛和Mo/HZSM 25催化剂样品的1H MAS NMR 定量分析结果Table 1　Numerical results of 1H MAS NMR experiment for differentHZSM 25zeolite and Mo/HZSM 25catalyst samples Sample Number of hydroxyls per unit cell B acid H 2OH Al 2OH Si 2OH HZSM 25(U T ) 3.70 1.680.450.49Mo/HZSM 25(U T ) 1.120.210.200.07HZSM 25(TA ) 2.91 1.250.580.25Mo/HZSM 25(TA )0.880.190.240.05 表1列出了不同HZSM 25分子筛和Mo/HZSM 25催化剂样品的1H MAS NMR 实验的定量分析结果.可以看出,酸处理对分子筛表面的各种羟基都产生了明显的影响.酸处理后,HZSM 25分子筛每个晶胞中B 酸性位的数目由3170下降到2191;而非骨架Al 羟基的数目则有所增加.这说明酸处理造成了分子筛脱铝,部分B 酸中心结构遭到了破坏,骨架中的Al 物种迁移到骨架外,形成新的表面Al 羟基.文献[14]也报道了酸处理会导致分子筛脱铝的实验结果.表1的结果还表明,将Mo 物种担载在HZSM 25(U T )上,会对分子筛表面各种类型的羟基造成明显的影响.在Mo/HZSM 25(U T )催化剂表面,平均每个晶胞中的B 酸中心数目只有1112个,与分子筛原粉相比下降了70%.同样,将096催　化　学　报第25卷Mo 物种担载在HZSM 25(TA )上也会使分子筛的羟基数目明显下降,在Mo/HZSM 25(TA )催化剂表面,平均每个晶胞中只有0188个B 酸位.以上结果表明,对分子筛进行脱铝预处理,可以使催化剂上的酸性位更少.2.2　分子筛酸处理后对催化剂性能的影响图3示出了不同Mo/HZSM 25催化剂样品在甲烷无氧芳构化反应中的催化性能.可以看出,虽然在反应初期Mo/HZSM 25(TA )催化剂上甲烷的转化率和芳烃的产率均略低于Mo/HZSM 25(U T )催化剂,但是随着反应的进行,Mo/HZSM 25(TA )催化剂表现出了相当好的稳定性.反应24h 后,Mo/HZSM 25(U T )上甲烷的转化率由1612%下降到510%,B TX (包括苯、甲苯和二甲苯)的收率由814%下降到311%;而在Mo/HZSM 25(TA )催化剂上,反应24h 后甲烷的转化率仍维持在815%,B TX 收率为615%.同时,萘的生成也在Mo/HZSM 25(TA )催化剂上得到了促进.图3　不同Mo/HZSM 25催化剂样品对甲烷无氧芳构化反应的催化性能Fig 3　Catalytic performance of different Mo/HZSM 25catalyst samples for methane dehydroaromatization(1)Mo/HZSM 25(U T ),(2)Mo/HZSM 25(TA )(BTXbenzene ,toluene and xylene)图4　经24h 甲烷无氧芳构化反应后不同Mo/HZSM 25催化剂样品的DTG 谱Fig 4　DTG profiles of different Mo/HZSM 25catalyst samplesafter methane dehydroaromatization for 24h(1)Mo/HZSM 25(U T ),(2)Mo/HZSM 25(TA )2.3　积炭催化剂的TG A 实验结果图4给出了经过24h 甲烷无氧芳构化反应后不同积炭Mo/HZSM 25催化剂样品的D TG 谱.可以看出,Mo/HZSM 25(U T )积炭催化剂和Mo/HZSM 25(TA )积炭催化剂在烧炭过程中均出现了两个峰温明显不同的谱峰,这说明催化剂上存在两种与O 2反应能力不同的积炭物种.根据文献和我们以前的工作,高温峰对应的积炭主要落位于分子筛酸中心上,这种积炭物种是导致催化剂失活的主要因素;低温峰对应的积炭主要形成在Mo 物种表面,几乎不会引起催化剂的失活[10,15～17].两个峰面积的相对大小即可认为是不同温度下烧掉的积炭质量的相对大小.将D TG 谱中得到的两种积炭的相对含量与TG A 实验中得到的绝对积炭量相关联,即可计算出催化剂上各种积炭物种的含量. 表2列出了不同积炭Mo/HZSM 25催化剂样品的D TG 实验结果.可以看出,经过相同条件下甲烷无氧脱氢芳构化反应后,在Mo/HZSM 25(TA )催化剂上形成的积炭量明显少于Mo/HZSM 25(U T )催化剂,其中高温峰积炭量的差别尤为明显.由于高温峰积炭物种主要沉积在分子筛的酸中心上,而1H MAS NMR 实验结果表明,Mo/HZSM 25(TA )催化剂上的酸性位数目明显少于Mo/HZSM 25(U T )催化剂,因此在Mo/HZSM 25(TA )催化剂表面上,能196第9期刘红梅等:分子筛的酸处理对Mo/HZSM 25催化甲烷无氧芳构化反应性能的影响够引起催化剂失活的高温峰积炭物种的生成受到了极大的抑制,催化剂的稳定性得到了显著的改善.表2　经24h甲烷无氧芳构化反应后不同Mo/HZSM25催化剂样品的DTG结果Table2　DTG results of different Mo/HZSM25catalyst samples after methane dehydroaromatization for24hSample Peak temperature(K)Peak1Peak2Coke amount(mg/g)Peak1Peak2TotalMo/HZSM25(U T)75982422.055.177.1 Mo/HZSM25(TA)74181717.827.845.6 反应机理的研究表明,分子筛的酸中心在甲烷无氧脱氢芳构化反应中起着重要作用[9].首先,甲烷被Mo物种活化生成中间过渡态产物,该产物需要在B酸中心的催化作用下继续聚合和环化才能生成目的产物芳烃.同时,B酸性位也是积炭形成的活性位.催化剂的评价结果表明,带有少量B酸位的Mo/HZSM25(TA)催化剂在反应中表现出了很好的稳定性.这说明,在甲烷无氧芳构化反应中少量的B酸中心就可以达到反应的要求,过多的酸性位只会导致更多积炭物种的生成,降低催化剂的稳定性.利用酸处理对HZSM25分子筛进行脱铝改性以减少Mo/HZSM25催化剂上的酸性位数目是一种有效的提高催化剂稳定性的方法.参考文献1　Wang L Sh,Tao L X,Xie M S,Xu G F,Huang J Sh,Xu Y D.Catal L ett,1993,21(1/2):352　Xu Y D,Lin L W.A ppl Catal A,1999,188(1/2):533　Lunsford J H.Catal Today,2000,63(224):1654　Xu Y D,Bao X H,Lin L W.J Catal,2003,216(1/2): 3865　Xu Y D,Liu Sh T,Wang L Sh,Xie M S,Guo X X.Catal L ett,1995,30(124):1356　Weckhuysen B M,Wang D,Rosynek M P,Lunsford J H.J Catal,1998,175(2):3387　刘社田,徐奕德,郭燮贤,王林胜,谢茂松.催化学报(Liu Sh T,Xu Y D,Guo X X,Wang L Sh,Xie M S.Chin J Catal),1995,16(2):1028　Zhang Ch L,Li Sh,Yuan Y,Zhang W X,Wu T H,Lin L W.Catal L ett,1998,56(4):2079　Ding W P,Li S,Meitzner G D,Iglesia E.J Phys Chem B,2001,105(2):50610　Lu Y,Xu Zh Sh,Tian Zh J,Zhang T,Lin L W.Catal L ett,1999,62(224):21511　Shu Y Y,Xu Y D,Wong S T,Wang L Sh,Guo X X.J Catal,1997,170(1):1112　Liu Sh T,Dong Q,Ohnishi R,Ichikawa M.Chem Com2 m un,1997,(15):145513　徐奕德,舒玉瑛,叶芬,许国旺(Xu Y D,Shu Y Y,Y e F,Xu G W).CN1247103.200014　Shu Y Y,Ohnishi R,Ichikawa M.Catal L ett,2002,81 (1/2):915　刘红梅,李涛,田丙伦,徐奕德.催化学报(Liu H M, Li T,Tian B L,Xu Y D.Chin J Catal),2001,22(4): 37316　刘红梅,李涛,徐奕德.高等学校化学学报(Liu H M, Li T,Xu Y D.Chem J Chin U niv),2002,23(8):1556 17　Liu H M,Li T,Tian B L,Xu Y D.A ppl Catal A, 2001,213(1):103(Ed YHM)296催　化　学　报第25卷。

211064108_PtSn

化工进展Chemical Industry and Engineering Progress2023 年第 42 卷第 3 期PtSn/MgAl 2O 4-sheet 催化剂的制备及其PDH 反应性能张孟旭，王红琴，李金，安霓虹，戴云生，钱颖，沈亚峰（昆明贵金属研究所，稀贵金属综合利用新技术国家重点实验室，云南昆明 650106）摘要：近年来，因为页岩气大规模开采的成功可以为丙烷脱氢制丙烯（PDH ）工艺提供大量廉价的丙烷，丙烷脱氢制丙烯已成为最有前途和最具吸引力的丙烯生产技术。

目前工业上丙烷脱氢主要采用的是负载型PtSn/Al 2O 3催化剂。

然而在丙烷脱氢高温反应中，PtSn 纳米粒子易烧结和积炭使催化剂遭受严重的失活。

为了解决上述问题，本文合成了片状的MgAl 2O 4尖晶石载体负载PtSn 金属纳米粒子，制备了PtSn/MgAl 2O 4-sheet 催化剂。

该催化剂具有较大的孔径，有利于PDH 反应中反应物的吸附和产物的脱附，提高了催化剂的活性同时降低了积炭含量。

同时片状的MgAl 2O 4尖晶石载体的（111）面与PtSn 纳米颗粒存在着强的相互作用，阻止了PtSn 纳米颗粒在高温反应中的烧结。

在丙烷脱氢反应中，丙烷的转化率达到了43.2%，丙烯的选择性达到了95.0%，失活速率仅为0.008h −1，其性能优于商用的PtSn/Al 2O 3催化剂。

关键词：丙烷脱氢；铂锡催化剂；形貌控制；丙烯；镁铝尖晶石中图分类号：TQ426.82 文献标志码：A 文章编号：1000-6613（2023）03-1365-08Preparation of PtSn/MgAl 2O 4-sheet catalyst and its PDH reactionperformanceZHANG Mengxu ，WANG Hongqin ，LI Jin ，AN Nihong ，DAI Yunsheng ，QIAN Yin ，SHEN Yafeng(State Key Laboratory of Advanced Technologies for Comprehensive Utilization of Platinum Metals, Kunming Institute ofPrecious Metals, Kunming 650106, Yunnan, China)Abstract: In recent years, propane dehydrogenation to propylene (PDH) has become the most promising and attractive propylene production technology because the successful large-scale exploitation of shale gas can provide a large amount of cheap propane. Currently, supported PtSn/Al 2O 3 catalysts are mainly used for propane dehydrogenation in industry. In the high temperature reaction of propane dehydrogenation, PtSn nanoparticles are prone to sintering and coke deposition, which causes severe catalyst deactivation. To solve the above problems, we synthesized PtSn/MgAl 2O 4-Sheet catalyst by using MgAl 2O 4-Sheet spinel as support. The catalyst had a large pore size, which was favorable for the adsorption of reactants and the desorption of products in the PDH reaction, and thus improves the activity of the catalyst and reduced the content of coke. Meanwhile, the (111) plane of the MgAl 2O 4 spinel support had a strong interaction with the PtSn nanoparticles, which prevented the sintering of PtSn nanoparticles in the high temperature reaction. In the propane dehydrogenation reaction with the prepared catalyst, the conversion of propane reached 43.2%, the selectivity of propylene reached 95.0%, and the deactivation研究开发DOI ：10.16085/j.issn.1000-6613.2022-0919收稿日期：2022-05-17；修改稿日期：2022-07-19。

Salen配体

Zeolite-encapsulated Ru(III)tetrahydro-Schiﬀbase complex:An eﬃcient heterogeneous catalyst for the hydrogenation ofbenzene under mild conditionsPing Chen,Binbin Fan,Minggang Song,Chun Jin,Jinghong Ma,Ruifeng Li*Key Laboratory of Coal Science and Technology,MOE,Institute of Special Chemicals,Taiyuan University of Technology,79West Yinze Street,Taiyuan 030024,PR ChinaReceived 7January 2006;received in revised form 7April 2006;accepted 7April 2006Available online 18April 2006AbstractA series of Ru(III)tetrahydro-Schiﬀbase complexes (denoted as Ru[H 4]-Schiﬀbase with Schiﬀbase =salen,salpn and salcn,see Scheme 1)were encapsulated in the supercages of zeolite Y by ﬂexible ligand method.The prepared catalysts were characterized by X-ray diﬀraction,diﬀuse reﬂectance UV–Vis spectroscopy,Infrared spectroscopy,elemental analysis,as well as N 2adsorption tech-niques.It was shown that upon encapsulation in zeolite Y,Ru(III)tetrahydro-Schiﬀbase complexes exhibited higher activity for the hydrogenation of benzene than the corresponding Ru(III)-Schiﬀbase complexes.This indicates that hydrogenation of the C @N bond of the Schiﬀbase ligands led to a modiﬁcation of the coordination environment of the central Ru(III)cations.The stability of the prepared catalysts has also been conﬁrmed against leaching of the complex molecule from the zeolite cavities,as revealed by the result that no loss of catalytic activity was observed within three successive runs with regeneration.Ó2006Elsevier B.V.All rights reserved.Keywords:Benzene hydrogenation;Ru(III)tetrahydro-Schiﬀbase complex;Encapsulation;Zeolite Y1.IntroductionTransition metal complexes have been extensively used for homogeneous hydrogenation of organic substrates such as benzene due to their high selectivity under mild reaction conditions [1,2].However,the diﬃcult recovery and recy-cling of the catalysts limit their reuse.Therefore,increasing demands have been generated for the preparation of eﬀec-tive heterogeneous catalysts.In this context,immobiliza-tion of metal complex is an attractive strategy.Up to date,several methods,such as covalent bonding of ligands with host materials,entrapment or occlusion of complex molecule in polymer matrices or porous inorganic materi-als by steric hindrance,and adsorption of the complexes on the support via ionic interaction,have been examinedfor the immobilization of transition metal complexes [3].Among them,the physical encapsulation of transition metal complex molecules into the supercages of zeolites gains incomparable advantages for homogeneous and con-ventional heterogeneous catalysts [4–7].Upon encapsula-tion in the cavities of the zeolites with FAU and EMT topological structures,palladium and rhodium salen com-plexes are highly active for the selective hydrogenation of 1,5-cyclooctadiene to cyclooctene [8],particularly chiral palladium salen complex makes it possible of enantioselec-tive hydrogenation of unsaturated organic compounds such as 3-methyl-2-cyclohexenone [9].In addition,palla-dium and nickel salen complexes grafted on mesostruc-tured silicates and delaminated ITQ zeolites also show good catalytic performance in the hydrogenation of imines [10],while Ru(III)-Schiﬀbase complex anchored on poly-mer exhibits considerably improved catalytic eﬃciency for the hydrogenation of styrene [11].The catalytic activity1566-7367/$-see front matter Ó2006Elsevier B.V.All rights reserved.doi:10.1016/j.catcom.2006.04.003*Corresponding author.Tel./fax:+863516010112.E-mail address:rﬂi@ (R.Li)./locate/catcomCatalysis Communications 7(2006)969–973of transition metal Schiﬀbase complexes in a given process is highly dependent on the environment of metal center and their conformationalﬂexibility[12].Compared to Schiﬀbase ligands,the corresponding tetrahydro-Schiﬀbase ligands possess stronger N-basicity and higherﬂexibility owing to the hydrogenation of C@N bond[13].It was found that zeolite-encapsulated Cu(II)tetrahydro-salen complex is more active than the encapsulated Cu(II)salen for the oxidation of cycloalkane in the presence of H2O2 [14].To the best of our knowledge,the hydrogenation per-formance of transition metal tetrahydro-salen complex has not been reported yet.Here,we report the preparation of zeolite Y encapsulated Ru(III)tetrahydro-Schiﬀbase com-plexes by usingﬂexible ligand method and their catalytic property in an industrially important reaction of benzene hydrogenation(see Scheme1).2.Experimental2.1.Preparation of ligandsSchiﬀbase L(L=salen,salph and salcn)was prepared by following the procedures reported in Ref.[13,15]. Ligand[H4]L was prepared with the following method [16]:0.01mol Schiﬀbase L was dissolved in60ml metha-nol,followed by the addition of0.011mol NaBH4at ambi-ent temperature.After2h of stirring,the solvent was removed by distilling under vacuum conditions.The solid product was washed with distilled water and re-crystallized from ethanol.The purity of the ligands was conﬁrmed by IR and1H NMR before coordination to Ru(III)cations.2.2.Preparation of zeolite Y encapsulated Ru(III) complexesZeolite Y was ion-exchanged with RuCl3aqueous solution(0.005mol/l,Liquid/Solid=20ml/g)at room temperature for24h,and then washed with deionized water and dried at100°C overnight.The obtained Ru-Y was mixed with an excessive amount of tetrahydro-Schiﬀbase ligands(n ligand/n Ru=3:1mol/mol),followed by heat-ing in a sealed glass ampoule for24h under vacuum conditions at temperatures of150,130and130°C for Ru[H4]-salen,Ru[H4]-salpn and Ru[H4]-salcn,respectively. The resultant materials were soxhlet-extracted with acetone to remove the complex molecules on the external surface and the free ligands.The extracted samples were dried at 373K for24h under vacuum conditions.2.3.Characterization of zeolite Y encapsulated Ru(III) complexesRu content was determined by an inductively coupled plasma-atomic emission spectrometer(TJA Atom Scan 16).X-ray power diﬀraction(XRD)patterns were recorded on a Rigaku Dmax X-ray diﬀractometer(Ni-ﬁltered, CuK a radiation).Infrared spectra(IR)were measured on a FTIR spectrometer by using the conventional KBr pellet method.Diﬀuse reﬂectance(DR)UV–Vis spectra in the range of200–800nm were measured against a halon white reference standard by a Perkin–Elmer Lambda Bio40spec-trophotometer equipped with an integration sphere.The Brunauer–Emmett–Teller(BET)surface area was mea-sured on a NOVA1200instrument.Before the measure-ment,the sample was evacuated at200°C for12h.2.4.Catalytic testHydrogenation of benzene was carried out in a Parr4842 stainless steel batch reactor,which is equipped with a gauge,a thermocouple,an internal mechanic stirring sys-tem,gas inlet valves,liquid sampling valves and a temper-ature-programmed electric heater.In a typical batch,0.36g catalyst and30.0ml(26.4g)benzene were employed.To remove the air,the closed reactor was purged with hydro-gen for three times.When the temperature reached60°C, hydrogen was charged into the reactor.The stirring speed was maintained at a value as high as600rpm in order to eliminate the diﬀusion problem.The product was analyzed by a GC-9A gas chromatography equipped with aﬂame ionization detector.3.Results and discussion3.1.Characterization of catalystsNo remarkable diﬀerence was observed from the XRD patterns of the zeolitic host before and after complexation as well as the further soxhlet-extraction,indicating that the zeolite framework was not signiﬁcantly aﬀected by the for-mation of complexes.The BET surface areas of diﬀerent Ru[H4]L-Y are given in Table1.Clearly,inclusion of Ru(III)Schiﬀbase com-plex considerably reduced the adsorption capacity and the surface area of the zeolite host.This is indicative of the presence of Ru(III)complexes in the zeolite cavities rather than on the external surface.The surface area,as]970P.Chen et al./Catalysis Communications7(2006)969–973expected,decreased with increasing molecular dimensions of ligands.The surface areas of Ru[H 4]salen-Y,Ru[H 4]-salpn-Y and Ru[H 4]salcn-Y were 500,465and 484m 2/g,respectively,in contrast to 570m 2/g of Ru-Y.Table 1also shows the Ru content in diﬀerent samples.Although all samples were prepared from the same Ru(III)-exchanged zeolite Y matrix,their Ru content were obviously diﬀerent,and decreased with the increase in the complex molecule size.Irrespective of its coincidence with our previous results on the encapsulation of Ru(III)-Schiﬀbase com-plexes in zeolite Y [17],it is diﬀerent from the inclusion of Mn(III)salen complex in zeolite X and zeolite Y by zeo-lite synthesis method and template synthesis method,respectively [18,19].It was argued that the increase in the complex size could enhance its physical entrapment in zeo-lite supercages,resulting in an increase in the encapsulation eﬃciency.The contrary results might arise from the diﬀer-ent preparation methods.Concerning the ﬂexible ligand method,an increase in the ligand size would cause its diﬀu-sion into the zeolite channels diﬃcult,and consequently hindering its access to Ru(III)cations and the formation of complex molecules in the supercages of zeolite Y.IR spectra of Ru-Y and Ru[H 4]L-Y are shown in Fig.1.Although in the low-wavenumber region the bands for the encapsulated complexes were overlapped by the framework vibration of the zeolite matrix,in the range from 1200to 1600cm À1,the bands due to C–N,C @C and atomic ring vibrations could be clearly distinguished for the zeolite-encapsulated Ru(III)tetrohydro-Schiﬀbase complex sam-ples,while these bands were not observed for the Ru-Y.The encapsulation of Ru(III)tetrohydro-Schiﬀbase com-plexes in zeolite Y was further conﬁrmed by DR UV–Vis spectroscopy.It is evident in Fig.2that after complexation and further soxhlet-extraction,a relatively intense absorp-tion band could still be seen around 325nm in the DR UV–Vis spectra of all zeolite Y encapsulated Ru(III)tetrohydro-Schiﬀbase samples.As we know,this band is attributed to ligand-to-metal charge transfer (CT),giving a strong evidence for the formation of Ru(III)tetrahydro-Schiﬀbase complex molecules inside the cavity of zeolite Y.3.2.Hydrogenation of benzeneTable 2compares the catalytic results for the hydroge-nation of benzene over Ru-Y,RuL-Y and Ru[H 4]L-Y sam-ples.RuL-Y was prepared by the same method as that used for Ru[H 4]L-Y [17].Under the same reaction conditions,RuL-Y and Ru[H 4]L-Y catalysts gave much higher ben-zene conversion than Ru-Y despite that the product was only cyclohexane for all the catalysts.This indicates that the electronic environment of central Ru(III)ions drasti-cally inﬂuences the catalytic performance.This also gives another piece of evidence for the successful complexation of Ru(III)ions with the tetrahydro-Schiﬀbase ligands inside the zeolitic host.Nevertheless,it is worth noting that all Ru[H 4]L-Y catalysts showed higher activity than the corresponding RuL-Y materials,as revealed by the fact that the Ru[H 4]L-Y catalysts gave a TOF being 2–4times as high as that obtained for the RuL-Y samples.At a reac-tion time of 2h,the benzene conversion reached 75.3%with a TOF of 4361over the Ru[H 4]salen-Y catalyst.In contrast,the Rusalen-Y sample only gave a benzene con-version of 19.7%,and thus a TOF of 1155,although it con-tained a comparable number of complex molecules.A further increase in the reaction time to 3h could result in a benzene conversion of 98.3%over the Ru[H 4]salen-YTable 1Ru content and surface area of Ru-Y and Ru[H 4]L-Y samples Catalyst Ru content (wt%)Surface area (m 2/g)Ru-Y1.00571Ru[H 4]salen-Y 0.82500Ru[H 4]salpn-Y 0.57465Ru[H 4]salcn-Y0.44484P.Chen et al./Catalysis Communications 7(2006)969–973971catalyst.Homogeneous catalysis and Ru(III)cations play a minor role since at the same reaction conditions neat Rusalen and Ru-Y with a comparable Ru content to Rusalen-Y both showed a conversion of about 2.5%.It was suggested that hydride complexes as intermediate species or starting materials play a key role in most hydro-genation reactions [20].The required dihydrogen molecule cleavage is proposed to occur as a result of the interaction of a ﬁlled metal d orbit with the empty sigma antibonding molecular orbit of H 2,which could weaken the H–H bond.In addition,an electron-rich atmosphere around the metal atom may also facilitate the breaking of the H–H bond [20].Compared to the Schiﬀbase ligands,the hydrogenated tetrahydro-Schiﬀbase ligands have stronger N-basicity and more ﬂexibility because of the hydrogenation of C @N bond [13].This makes the metal center electron-rich,pro-moting the appropriate overlap of the ﬁlled metal d orbit with the empty sigma antibonding molecular orbit of H 2,and hence favoring the cleavage of H–H bond,which is a crucial step in the hydrogenation reaction.It is noteworthy that although three types of Ru[H 4]L-Y catalysts all showed higher activity than the corresponding RuL-Y ana-logues,the degree substantially decreased with increasing ligand size.The conversion obtained over the Ru[H 4]sa-len-Y at the reaction time of 2h was about 3.8times as high as that obtained on the Rusalen-Y.In contrast,for the Ru[H 4]salcn-Y catalyst,it was only about 1.7times ashigh as that of its corresponding Schiﬀbase analogue.This indicates that the eﬀect of the C @N bond hydrogenation on the metal center weakens with the ligand size.Eﬀect of the reaction temperature on the hydrogenation of benzene over the Ru[H 4]salen-Y catalyst is illustrated in Fig.3.As expected,the benzene conversion was highly dependent on the reaction temperature.It sharply increased with increasing reaction temperature when the temperature was lower than 60°C.When the reaction was carried out at 60°C for 2h,the benzene conversion was 75.3%in contrast to 19.4%at 50°C.Regardless of this,a further increase in the reaction temperature to 70°C had no such an apparent eﬀect.The inﬂuence of hydrogen pressure was investigated at 60°C between 2.0and 4.0MPa.The relationship between the hydrogen pressure and the benzene conversion is shown in Fig.4.Obviously,the benzene conversion obtained at 3.0MPa was higher than those obtained at 2.0andTable 2Catalytic results of diﬀerent catalysts in benzene hydrogenation a Catalyst Ru content (wt%)Reaction time (h)Conversion (%)TOF b(mol/(mol Æh À1))Ru-Y0.872 2.614748.7611.5Rusalen c 22.5141Rusalen-Y0.81219.71115448.5675.2Ru[H 4]salen-Y 0.82275.34361398.3Rusalpn-Y0.5528.3717420.9644.9Ru[H 4]salpn-Y 0.57223.61967452.0672.9Rusalcn-Y 0.432 6.0663416.3632.3Ru[H 4]salcn-Y 0.44210.21101423.5648.1aReaction conditions:0.36g catalyst,26.4g benzene,60°C,3.0MPaH 2.bThe amount of the converted benzene per mole of Ru(III)complexes per hour.c0.0135g Rusalen,26.4g benzene,60°C,3.0MPa H 2.972P.Chen et al./Catalysis Communications 7(2006)969–9734.0MPa,showing that the optimum hydrogen pressure was 3.0MPa.This is in accordance with the results reported by Wang and co-workers for the partial hydrogenation of benzene to cyclohexene on a Ru–Zn/m-ZrO2catalyst[21]. This was accounted for by assuming a competitive adsorp-tion between hydrogen and benzene on the same active sites on the basis of the slow adsorption theory and the existence of a stagnant waterﬁlm around the catalysts. However,the eﬀect of hydrogen pressure depends on the reaction system and the catalytic mechanism.Therefore, the reason is not unambiguous yet for the moment,and further studies are in progress.The stability and recycling possibility of the prepared Ru[H4]salen-Y catalyst in benzene hydrogenation were fur-ther investigated.After one reaction run,the catalyst was recovered by the centrifugation of hot reaction mixture so as to avoid the readsorption of possibly leached complex molecules,and further washed with ethanol and dried at 90°C under vacuum conditions.The dried sample was then used for the next run under the same reaction conditions. Fig.5shows the catalytic results of three successive recy-cles.It is clear that the obtained benzene conversion was almost the same within three reaction runs,verifying that Ru[H4]salen-Y is highly stable and can be reused.This is further conﬁrmed by the following experiment.When the reaction was performed for2h,the catalyst was separated from the reaction mixture,and left the reaction for another 2h.It was found that the benzene conversion remained at 75%without a further increase.In contrast,if the catalyst was not separated,the benzene in the reaction mixture was completely converted.This proves that the reaction is cat-alyzed heterogeneously since homogeneous catalysis,as above discussed,plays a negligible role.This is also sup-ported by the ICP analysis that a trace amount of Ru was observed in the reaction liquid.Thus,the possibility of leaching of the complex molecules from the zeolite cav-ities could be excluded.Otherwise,the benzene conversion would decrease because of a reduction in active sites of the encapsulated complex molecules.4.ConclusionsA series of Ru(III)tetrahydro-Schiﬀbase complexes have been encapsulated in zeolite Y,and show much higher activity than the corresponding Ru(III)Schiﬀbase ana-logues for the hydrogenation of benzene under mild condi-tions.This results from a modiﬁcation of the coordination environment of central Ru(III)cations by the hydrogena-tion of C@N bond,and consequently a more H2coordina-tion activation.The prepared catalysts are also highly stable and reusable,as veriﬁed by the unchanged activity within three successive reaction runs and no further increase in the benzene conversion with increasing reaction time after removing the catalyst.AcknowledgementThis work is supported by the National Science Founda-tion of China(Nos.20443004and50472083). References[1]A.M.Trzeciak,J.J.Ziolkowski,J.Mol.Catal.88(1994)13.[2]R.Skoda-Fo¨ldes,L.Kolla´r,A.Arcadi,J.Mol.Catal.101(1995)37.[3]A.Crosman,W.F.Hoelderich,J.Catal.232(2005)43.[4]K.J.Balkus Jr.,A.K.Khanmamedova,K.M.Dixon,F.Bedioui,Appl.Catal.A143(1996)159.[5]R.A.Sheldon,I.W.C.E.Arends,H.E.B.Lempers,Catal.Today41(1998)387.[6]N.Herron,Inorg.Chem.259(1986)4714.[7]B.Fan,W.Fan,R.Li,J.Mol.Catal.A201(2003)137.[8]S.Ernst,E.Fuchs,X.Yang,Microporous Mesoporous Mater.35(2000)137.[9]S.Ernst,H.Disteldorf,X.Yang,Microporous Mesoporous Mater.22(1998)457.[10]V.Ayala,A.Corma,M.Iglesias,J.A.Rinco´n,F.Sa´nchez,J.Catal.224(2004)170.[11]D.R.Patel,M.K.Dalal,R.N.Ram,J.Mol.Catal.A109(1996)141.[12]N.S.Venkataramanan,G.Kuppuraj,S.Rajagopal,Coord.Chem.Rev.249(2005)1249.[13]A.Boettcher,H.Elias,E.G.Jaeger,ngfelderova,M.Mazur,L.Mueller,H.Paulus,P.Pelikan,M.Rudolph,M.Valko,Inorg.Chem.32(1993)4131.[14]C.Jin,W.Fan,Y.Jia,B.Fan,J.Ma,R.Li,J.Mol.Catal.A249(2006)23.[15]C.R.Jacob,S.P.Varkey,P.Ratnasamy,Appl.Catal.A182(1999)91.[16]S.Velusamy,T.Punniyamurthy,Tetrahedron Lett.44(2003)8955.[17]P.Chen,M.Song,B.Fan,R.Li,Ranliao Huaxue Xuebao,J.FuelChem.Tech.34(2006)336.[18]C.R.Jacob,S.P.Varkey,P.Ratnasamy,Appl.Catal.A168(1998)353.[19]A´.Zsigmond,A.Horva´th,F.Notheisz,J.Mol.Catal.A171(2001)95.[20]E.A.Cagnola,M.E.Quiroga, D.A.Liprandi,P.C.L’Argentie`re,Appl.Catal.A274(2004)205.[21]J.Wang,Y.Wang,S.Xie,M.Qiao,H.Li,K.Fan,Appl.Catal.A272(2004)29.P.Chen et al./Catalysis Communications7(2006)969–973973。

氮化钼的制备、表征及其在催化中的应用

进口水汽含量 /（ppm）
平均出口水汽含量 /（ppm）
比表面积 / m2/g
温度 /K
混合物
WC03 WC04 WC05 WC06 WC07
276 444 1095 1294 2782
1320 1500 3290 3440 4390
115.0
933
133.0 933
97.2 933
63.4 933
725 ℃ ：晶格氧
used
680 ℃ ： MoO3 880 ℃: MoO2
MoO2 Mo
在催化反应中的应用
按催化反应类型可分为
• 加氢(丁二烯等二烯烃选择加氢、CO2和CO加氢等) • 加氢精制
HDN（喹啉、吡啶、吲哚、苯并呋喃等） HDS（噻吩、苯并噻吩、二苯并噻吩等） • 脱氢及氢解（环己烷脱氢、乙烷氢解） • 异构化反应（正己烷异构） • 氨合成与分解 • 肼分解 • NO加氢还原 • F-T合成
1.22
17
0.012
1.92
110
0.060
1.64
120
0.066
2.22
122
0.074
2.41
140
0.086
2.48
MoO3 MoO3
MoO3 , MoO2, Mo2OxN1-X(L)
MoO , 2
Mo2OxN1-X
MoO , 2
Mo2OxN1-X
MoO2, Mo2OxN1-X(L),Mo2N
程序升温还原法合成β-Mo2N0.78/γ-Al2O3
(NH4)6Mo7O24·4H2O 水溶液 γ-Al2O3
浸渍法
H2 /N2 1%O2/N2
MoO3 /γ-Al2O3

2014-ACS Appl. Mater. Interfaces-酚变醌

© 2014 American Chemical Society
■
mesoporous carbon,16 graphene,2 and carbon nanoﬁber (CNF),17 have been widely employed as the immobilization materials of enzymes in biosensors, which can be attributed to their large speciﬁc surface area, excellent conductivity, and satisfactory biocompatibility. Among these materials, CNF possesses much larger functionalized surface area compared to that of CNT and is more suitable for immobilization and stability of enzyme. It has been proven that CNF is an outstanding matrix for the development of biosensors, which is far superior to the carbon nanotube.17 Notably, the CNF possesses a history of more than a century; the carbon ﬁlaments discovered in 1889 may be the earliest CNF.18 After more than a century of development, various methods used for CNF preparation have been developed, such as arc-discharge,19 laser ablation,20 chemical vapor deposition (CVD) methods,21 and others. Electrospinning, known as a facile and convenient process technique, produces nanoﬁbers or microﬁbers with diﬀerent diameters using a variety of polymers. Carbonization of electrospun polyacrylonitrile nanoﬁbers can be employed to fabricate CNF.22 In addition, to our best knowledge, CNF from CVD usually contains some impurities, e.g., metal catalyst and graphite particle, which requires a further complicated

甲烷二氧化碳重整制氢

Research ArticleNi/SiO2Catalyst Prepared with Nickel NitratePrecursor for Combination of CO2Reforming andPartial Oxidation of Methane:Characterization and Deactivation Mechanism InvestigationSufang He,1Lei Zhang,2Suyun He,2Liuye Mo,3Xiaoming Zheng,3Hua Wang,1and Yongming Luo21Research Center for Analysis and Measurement,Kunming University of Science and Technology,Kunming650093,China2Faculty of Environmental Science and Engineering,Kunming University of Science and Technology,Kunming650500,China3Institute of Catalysis,Zhejiang University,Key Lab of Applied Chemistry of Zhejiang Province,Hangzhou310028,ChinaCorrespondence should be addressed to Y ongming Luo;environcatalysis222@Received5August2014;Revised6January2015;Accepted6January2015Academic Editor:Mohamed BououdinaCopyright©2015Sufang He et al.This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use,distribution,and reproduction in any medium,provided the original work is properly cited.The performance of Ni/SiO2catalyst in the process of combination of CO2reforming and partial oxidation of methane to produce syngas was studied.The Ni/SiO2catalysts were prepared by using incipient wetness impregnation method with nickel nitrate as a precursor and characterized by FT-IR,TG-DTA,UV-Raman,XRD,TEM,and H2-TPR.The metal nickel particles with the average size of37.5nm were highly dispersed over the catalyst,while the interaction between nickel particles and SiO2support is relatively weak.The weak NiO-SiO2interaction disappeared after repeating oxidation-reduction-oxidation in the fluidized bed reactor at 700∘C,which resulted in the sintering of metal nickel particles.As a result,a rapid deactivation of the Ni/SiO2catalysts was observed in2.5h reaction on stream.1.IntroductionThe Ni-based catalyst has recently attracted considerable attention due to the plentiful resources of nickel,as well as its low cost and good catalytic performance comparable to those of noble metals for many catalytic reactions,such as hydrogenation of olefins and aromatics[1],methane reforming[2],and water-gas shift reaction[3].Therefore,Ni-based catalyst is believed to be the most appropriate catalyst applied in the industrial process[4–6].It is generally accepted that the catalytic performance of Ni-based catalyst is closely related to several parameters,including the properties of support,preparation method,and active phase precursor employed.Support plays an important role in determining the performance of Ni-based catalyst.Generally,a support with high surface areas is very necessary since it is effective in increasing Ni dispersion and improving thermal stability, hence not only providing more catalytically active sites,but also decreasing the deactivation over time of the catalysts due to sintering and migration effects[7,8].For its good thermostability,availability,and relative high specific surface area,SiO2support was widely used for preparing Ni-based catalyst[9].In particular,spherical silica is successfully used as a catalyst support in fluidized bed reactor due to its high mechanical strength.The method of catalyst preparation is another key param-eter which needs to be optimized because it will result in different structural and textural properties of Ni-based catalyst.Therefore,numerous methods,including precipi-tation,homogeneous deposition-precipitation,and sol-gel techniques,have been developed to enhance the performance of Ni-based catalyst[10–18].However,allthe above method-ologies mentioned are too complex or expensive to scaleHindawi Publishing Corporation Journal of NanomaterialsVolume 2015, Article ID 659402, 8 pages /10.1155/2015/659402up in industry.The incipient wetness impregnation(IWI) is one of the most extensively used method[19–23]due to its simplicity in practical execution on both laboratory and industrial scales,in addition to its facility in controlling the loading amount of the active ingredient.In addition,the choice of the precursor salt is also crucial since it determines whether the Ni-based catalyst will be prepared successfully or not.As an efficient precursor,two terms must be met:firstly,high solubility is desirable because the precursor concentration in the impregnation solution must be high[24];secondly,the ability to be decomposed during calcinations is prerequisite since the precursor must be fully transformed into oxide particles without leaving side species that may modify the properties of the support [24].As a result,owing to its commercial availability and low cost,as well as its high solubility in water and effortless decomposition at moderate temperatures,nickel nitrate is the precursor most often used in the preparation of Ni-based catalyst[23,24].In this paper,Ni/SiO2catalyst was prepared by incipient wetness impregnation(IWI)with nickel nitrate as precursor and tested in the process of combination of CO2reforming and partial oxidation of methane(CRPOM)to produce syngas.TG-DTA,HR-TEM,IR,UV-Raman,XRD,and H2-TPR were employed to characterize the Ni/SiO2catalysts in detail to reveal the relationship between synthesis,properties, and catalytic performances as well as to investigate the causes of deactivation.2.Experimental Section2.1.Catalyst Preparation.The Ni/SiO2catalysts were pre-pared with IWI using nickel nitrate as precursor according to our previous works[21,22].The SiO2was commer-cially obtained(S BET=498.8m2/g,Nanjing Tianyi Inorganic Chemical Factory).Prior to use,the SiO2was pretreated with5%HNO3aqueous solution for48h and then washed with deionized water until the filtrate was neutrality.The size of SiO2was selected between60and80mesh.It was then impregnated with an aqueous solution of nickel nitrate. The obtained sample was dried overnight at100∘C and subsequently calcined in air at700∘C for4h.Unless otherwise stated,the loading of Ni was3wt%,and the calcination temperature was700∘C.The Ni/SiO2catalyst was designated as3NiSN.2.2.Catalytic Reaction.The catalytic reaction was performed in a fluidized-bed reactor that was comprised of a quartz tube (I.D.=20mm,H=750mm)under atmospheric pressure at700∘C.Prior to reaction,2mL of catalyst was reduced at700∘C for60min under a flow of pure hydrogen at atmospheric pressure with a flow rate of50mL/min.A reactant gas stream that consisted of CH4,CO2,and O2,with a molar ratio of1/0.4/0.3,was used with a gas hourly space velocity(GHSV)of9000h−1.The feed gas was controlled by mass flow controllers.The effluent gas cooled in an ice trap was analyzed with an online gas chromatograph that was equipped with a packed column(TDX-01)and a thermal conductivity detector.Under our reaction conditions,the oxygen in the feed gas was completely consumed in all cases.2.3.Catalyst Characterization.FTIR spectra were measured using a Nicolet560spectrometer equipped with a MCT detector.The samples were tabletted to thin discs with KBr.Thermogravimetric analysis(TGA)and differential ther-mal analysis(DTA)were performed on a PERKIN ELMER-TAC7/DX with a heating rate of10∘C/min under oxygen (99.99%,20mL/min).The samples were pretreated with oxygen flow at383K for1h.UV-Raman spectra were carried out with a Jobin Yvon LabRam-HR800instrument,using325.0nm Ar+laser radi-ation.The excitation laser was focused down into a round spot approximately2μm in diameter.The resolution was 4cm−1and1000scans were recorded for every spectrum.The catalysts were ground to particle diameters<150μm before analysis.X-ray powder diffraction(XRD)patterns of samples were obtained with an automated power X-ray diffractometer (Rigku-D/max-2550/PC,Japan)equipped with a computer for data acquisition and analysis,using Cu Kαradiation, at40kV and300mA.The reduced samples were priorly reduced at700∘C for1h and cooled to room temperature in hydrogen atmosphere,but the fresh samples were used directly after calcined in air at700∘C for4h.All the samples were ground to fine powder in an agate mortar before XRD measurements.Transmission electron microscopy(TEM)images were recorded on a Philips-FEI transmission electron microscope (Tecnai G2F30S-Twin,Netherlands),operating at300kV. Samples were mounted on a copper grid-supported carbon film by placing a few droplets of ultrasonically dispersed suspension of samples in ethanol on the grid,followed by drying at ambient conditions.H2-temperature-programmed reduction(H2-TPR) experiments were performed in a fixed-bed reactor(I.D.= 4mm).50mg samples were used and reduced under a stream of5%H2/N2(20mL/min)from50∘C to800∘C with a ramp of7∘C/min.Hydrogen consumption of the TPR was detected by a TCD and its signal was transmitted to a personal computer.The experiments for reduction-oxidation cycle(redox) performance were performed as follows.The catalysts were pretreated with H2flow at700∘C for1h and then were cooled down to room temperature and reoxidized in O2at different temperature for1h.The reoxidized samples were then performed by H2-TPR experiments as above.3.Results and Discussion3.1.Catalytic Activity Measurements.The catalytic perfor-mance of Ni/SiO2was shown in Figure1.A rapid deactivation was detected for the3NiSN,and the corresponding conver-sion of CH4(X CH4)decreased from∼58%to∼25%within 1.5h reaction on stream.In order to investigate the causes of deactivation,the3NiSN catalyst was characterized by TG-DTA,HR-TEM,IR,UV-Raman,XRD,and H2-TPR in detail.Time on stream (h)60555045403530252015C o n v e r s i o n o f C H 4(%)Figure 1:CH 4conversion versus time on 3NiSN catalyst for combination of CO 2reforming and partial oxidation of methane to produce syngas (reaction temperature:700∘C,CH 4/CO 2/O 2=1/0.4/0.3,and GHSV =9000h −1).Wavenumber (nm)Figure 2:FT-IR spectra of 3NiSN (dried at 100∘C)and nickel nitrate (Ni(NO 3)2).3.2.Catalyst Characterization Results3.2.1.FT-IR Analysis.The FT-IR spectra of 3NiSN before cal-cination and Ni(NO 3)2precursor were illustrated in Figure 2.Two intense bands of Ni(NO 3)2centered at 1620cm −1and 1376cm −1were ascribed to asymmetric and symmetric vibra-tions of nitrate,respectively [25].After Ni(NO 3)2being impregnated on SiO 2,the position of the two bands of Ni(NO 3)2shifted to higher wavenumber about 1643cm −1and1385cm −1,respectively.Similar to our previous study [23],this shift to higher wavenumber might be contributed to the interaction between nickel nitrate and support SiO 2.3.2.2.Thermal Analysis.In order to study the formation of NiO from precursor,thermal analysis of 3NiSN before calcination was carried out (shown in Figure 3).The extra water should be removed by holding the precursor under O 2at 110∘C for 1h.The thermal oxidation degradation of the dried 3NiSN consisted of two main steps.The first weight loss (9.1wt%)at 110–240∘C region in TG together with a differential peak at around 224∘C in DTG curve was probably due to the dehydration of 3NiSN.The second large weight loss at region of 240–380∘C (11.1wt%)in TG,accompanied with a small endothermic peak around 293∘C in DTA,had been attributed to thermoxidative degradation of nickel nitrate.This decomposition step exhibited a differential peak around 277∘C in DTG profile.Above 380∘C,practically weight loss could not be observed any more.The TG-DTA curves confirmed the absolute volatility of water and nitrate and also the formation of NiO over catalysts around 380∘C.The calcination of 3NiSN beyond 380∘C would enhance the interaction between the NiO and SiO 2support,according to our earlier study [23].3.2.3.UV-Raman Analysis.Further evidence for the for-mation of NiO might be drawn from UV-Raman spectra exhibited in Figure 3.Herein,the spectrum for NiO was included as a reference.As seen from Figure 4,the intense and sharp peak at 1139cm −1,together with three weak peaks at 900,732,and 578cm −1,was assigned to the Raman responses of NiO.Similar to NiO reference,the peaks of 3NiSN center at about 1135,900,726,and 580cm −1were also attributed to NiO.Furthermore,compared with the reference of NiO,the four Raman peaks of NiO over 3NiSC appeared more intensive,thus suggesting that the NiO particles over 3NiSN catalyst were larger [23,26,27].3.2.4.XRD Analysis.XRD measurements were carried out to understand the crystalline structure of 3NiSN catalysts,and the results were presented in Figure5.The XRD patterns of all samples exhibited a broad and large peak around 22∘,which was attributed to amorphous silica of support.After calcination,the sample showed only the fcc-NiO phase,with typical reflections of the (111),(200),and (220)planes at 2θ=37∘,43∘,63∘,respectively.After being reduced with H 2for 4h,the peaks assigned to NiO disappeared,and three other peaks around 44∘,52∘,and 76∘for Ni (111),Ni (200),and Ni (220)planes were detected,thus inferring the successful transformation of NiO to metallic Ni after reduction with H 2.3.2.5.TEM Analysis.Further insight on the aggregation of Ni particles over the 3NiSN could be obtained by TEM analysis.Figures 6(a)and 6(b)exhibited the TEM images of 3NiSN after reduction and deactivation,respectively.The Ni particles over both catalysts were approximately spherical in shape.Highly dispersed Ni particles were detected for the Ni/SiO 2just after reduction.However,obvious glomeration200300400500600700Temperature (∘C)T G +D T G(a)200300400500600700Temperature (D T A∘C)(b)Figure 3:(a)TG +DTG and (b)DTA thermogram of 3NiSN dried at 100∘C.Raman shift (cm −1)I n t e n s i t y (a .u .)Figure 4:UV-Raman spectra of 3NiSN (calcined at 700∘C for 4h)and NiO (as a reference).of Ni particles was observed for the 3NiSN catalyst after deactivation.In order to make a profound analysis,the corresponding particle size distributions obtained from TEM were summarized in Figures 6(c)and 6(d)for 3NiSN after reduction and deactivation,respectively.The particle size values of reduced 3NiSN were distributed in a range of 16.1–84.0nm with the average size around 37.5nm.As for 3NiSN after deactivation,the mean size increased to 50.4nm2θ(deg)Ni NiOI n t e n s i t y (a .u .)Figure 5:XRD patterns of 3NiSN before and after reduction in H 2for 4h.with distributed range of 36.0–73.6nm.An evident particle aggregation was formed over 3NiSN catalyst,which was in accordance with the XRD result.3.2.6.H 2-TPR Analysis.TPR is an efficient method to char-acterize the reducibility of supported nickel-based catalysts.(a)(b)Particle diameter (nm)0.250.200.150.100.050.00R e l a t i v e p a r t i c l e n u m b e r (%)(c)0.200.150.100.050.00R e l a t i v e p a r t i c l e n u m b e r (%)Particle diameter (nm)(d)Figure 6:TEM images of (a)reduced 3NiSN and (b)deactivated 3NiSN,and histogram of the particle size distribution obtained from sampling of nanoparticles from TEM data (c)for reduced 3NiSN and (d)for deactivated 3NiSN.TPR profiles of 3NiSN catalysts were depicted in Figure 7.Two reduction peaks were observed for the fresh 3NiSN cata-lyst (just calcined)at 430∘C and 450∘C.The low-temperature peak might be contributed to the reduction of NiO which is negligible weak interaction with SiO 2.The high-temperature peak was caused by the reduction of nickel oxide which interacted weakly with SiO 2.Furthermore,ttthe reduction-oxidation cycle (redox)performance of a catalyst would strongly influence the catalytic activity for an oxidation involved reaction [28].Therefore,the redox performances of 3NiSN catalysts were investigated,and the corresponding experiment results were depicted in Figure 7.After beingreduced in H 2flow at 700∘C for 1h,the 3NiSN catalysts were reoxidized in O 2at different temperatures and then tested with H 2-TPR.No clear reduction peak of NiO was detected for 3NiSN with reoxidized temperature below 300∘C.As reoxidization temperature increased from 400to 700∘C,the rereduction temperature increased from ∼290to ∼370∘C;however,it was always less than the temperature needed to reduce the NiO of fresh 3NiSN.Distinctly,the weak NiO-SiO 2interaction over 3NiSN catalyst disappeared with repeat-ing oxidation-reduction-oxidation process.Studies from the previous work show that the strong interaction between NiO and support could suppress efficiently the sintering of200300400500600Temperature (FED C B A∘C)H 2c o n s u m p t i o n (a .u .)Figure 7:The reduction-oxidation cycle (redox)performance of 3NiSN catalysts with different reoxidization temperature (A:300∘C;B:400∘C;C:500∘C;D:600∘C;E:700∘C;F:fresh,just calcined).metallic nickel [21–23].Therefore,the disappearance of NiO-SiO 2interaction would lead to the sintering of active nickel particles at high reaction temperature.3.2.7.Effect of the Particle Size of Ni.It is generally accepted that the crystalline size of metallic nickel plays an important role in the catalytic performance for nickel-catalyzed reac-tions:smaller metallic Ni size helps to provide more active sites to reach the much better catalytic activity.Our previous works had also demonstrated this view [21,22].In order to investigate the particle size dependence of the catalytic reaction,the 3NiSN catalysts after different time (1.5h,2.0h,and 2.5h)reaction on stream were taken out to be estimated by XRD and calculated with the Scherrer equation (shown in Figure 8).For all the 3NiSN (even after deactivation),only Ni and amorphous SiO 2phase detected by XRD.No NiO phase was found,which meant no significant change in Ni phase was observed for 3NiSN even after deactivation.Noteworthily,the diffraction intensity of nickel crystalline increased with reaction time,which indicated the crystalline size of nickel on 3NiSN increased with reaction time.The crystalline size of nickel on 3NiSN as a function of reaction time was shown in Figure 9.The crystalline size of nickel was ∼30.3nm,∼32.6nm,∼33.6nm,and ∼34.6nm,for 3NiSN after 0h,1.5h,2h,and 2.5h reaction on stream,respectively.The change trend of Ni size was in conformance with the catalytic activity of 3NiSN in process of bined with H 2-TPR results above,with the process of CRPOM proceeding,the NiO-SiO 2interaction over 3NiSN catalyst weakened down as it disappeared.At the same time,the crystalline size of nickel increased with the weakening of NiO-SiO 2interaction,finally leading to the sintering of active nickel particles over 3NiSNcatalyst.2θ(deg)NiI n t e n s i t y (a .u .)Figure 8:The effect of reaction time on the XRD patterns of3NiSN.Reaction time (h)353433323130C r y s t a l l i n e s i z e o f n i c k e l (n m )Figure 9:Crystalline size of nickel as a function of reaction time.By comprehensively analyzing the characterization results,important information could be concluded.On one hand,graphic carbon was not detected in the spent 3NiSN catalyst by XRD and TEM,suggesting that no carbon deposition was formed during the reaction.On the other hand,except for the characteristic XRD peak of metallic nickel,no other nickel species (such as NiO)was detected,indicating that the transformation of active metallic Ni was not the reason for deactivation of 3NiSN.Importantly,the weak interaction between Ni and support disappeared asthe reaction proceeding,resulting in sintering of active nickel particles.This was the reason that3NiSN catalyst showed a rapid deactivation in the CRPOM reaction.4.ConclusionsIn this work,Ni/SiO2catalysts were prepared with nickel nitrate precursor by IWI method and characterized by FT-IR,TG-DTA,UV-Raman,XRD,TEM,and H2-TPR.By being calcined around380∘C,water and nitrate were volatilized absolutely to form NiO,which could be reduced into metallic Ni after being treated with H2at700∘C.The active nickel particles(around37.5nm)of3NiSN catalyst were dispersed highly but weakly interacted with SiO2support.However, this weak interaction disappeared after repeating oxidation-reduction-oxidation in the fluidized bed reactor at700∘C. Therefore,3NiSN catalyst suffered from obvious sintering of the active nickel particle.In light of these,a rapid deactivation of3NiSN was shown in the process of combination of CO2 reforming and partial oxidation of methane(CRPOM)to produce syngas.Conflict of InterestsThe authors declare that there is no conflict of interests regarding the publication of this paper. AcknowledgmentsThe authors thank the financial supports of National Natural Foundation of China(nos.21003066,21367015,and51068010) and Zhejiang Province Key Science and Technology Innova-tion Team(2012R10014-03).References[1]B.Pawelec,P.Casta˜n o,J.M.Arandes et al.,“Katalizatory ni-klowe i rutenowo-niklowe na no´s nikach zawierających zeolit ZSM-5i tlenek glinu.Wybrane wła´s ciwo´s ci fizykochemiczne i katalityczne,”Applied Catalysis A:General,vol.7,no.7,pp.20–33,2007.[2]T.V.Choudhary and V.R.Choudhary,“Energy-efficient syngasproduction through catalytic oxy-methane reforming reac-tions,”Angewandte Chemie,vol.47,no.10,pp.1828–1847,2008.[3]K.-R.Hwang,S.-W.Lee,S.-K.Ryi,D.-K.Kim,T.-H.Kim,and J.-S.Park,“Water-gas shift reaction in a plate-type Pd-membrane reactor over a nickel metal catalyst,”Fuel Processing Technology, vol.106,pp.133–140,2013.[4]D.P.Liu,X.-Y.Quek,H.H.A.Wah,G.M.Zeng,Y.D.Li,andY.H.Yang,“Carbon dioxide reforming of methane over nickel-grafted SBA-15and MCM-41catalysts,”Catalysis Today,vol.148, no.3-4,pp.243–250,2009.[5]V.R.Choudhary,B.S.Uphade,and A.S.Mamman,“Partialoxidation of methane to syngas with or without simultaneous CO2and steam reforming reactions over Ni/AlPO4,”Microp-orous and Mesoporous Materials,vol.23,no.1-2,pp.61–66,1998.[6]E.Ruckenstein and Y.H.Hu,“Combination of CO2reformingand partial oxidation of methane over NiO/MgO solid solution catalysts,”Industrial and Engineering Chemistry Research,vol.37,no.5,pp.1744–1747,1998.[7]J.Newnham,K.Mantri,M.H.Amin,J.Tardio,and S.K.Bhargava,“Highly stable and active Ni-mesoporous alumina catalysts for dry reforming of methane,”International Journal of Hydrogen Energy,vol.37,no.2,pp.1454–1464,2012.[8]M.Garc´ıa-Di´e guez,I.S.Pieta,M.C.Herrera,rrubia,and L.J.Alemany,“Nanostructured Pt-and Ni-based catalysts for CO2-reforming of methane,”Journal of Catalysis,vol.270, no.1,pp.136–145,2010.[9]L.Yao,J.Zhu,X.Peng,D.Tong,and C.Hu,“Comparative studyon the promotion effect of Mn and Zr on the stability of Ni/SiO2 catalyst for CO2reforming of methane,”International Journal of Hydrogen Energy,vol.38,no.18,pp.7268–7279,2013.[10]S.Tada,T.Shimizu,H.Kameyama,T.Haneda,and R.Kikuchi,“Ni/CeO2catalysts with high CO2methanation activity and high CH4selectivity at low temperatures,”International Journal of Hydrogen Energy,vol.37,no.7,pp.5527–5531,2012.[11]I.Rossetti,C.Biffi,C.L.Bianchi et al.,“Ni/SiO2and Ni/ZrO2catalysts for the steam reforming of ethanol,”Applied Catalysis B:Environmental,vol.117-118,pp.384–396,2012.[12]X.L.Yan,Y.Liu,B.R.Zhao,Y.Wang,and C.-J.Liu,“Enhancedsulfur resistance of Ni/SiO2catalyst for methanation via the plasma decomposition of nickel precursor,”Physical Chemistry Chemical Physics,vol.15,no.29,pp.12132–12138,2013. [13]W.S.Xia,Y.H.Hou,G.Chang,W.Z.Weng,G.-B.Han,and H.-L.Wan,“Partial oxidation of methane into syngas(H2+CO) over effective high-dispersed Ni/SiO2catalysts synthesized by a sol-gel method,”International Journal of Hydrogen Energy,vol.37,no.10,pp.8343–8353,2012.[14]L.Li,S.He,Y.Song,J.Zhao,W.Ji,and C.-T.Au,“Fine-tunable Ni@porous silica core-shell nanocatalysts:synthesis, characterization,and catalytic properties in partial oxidation of methane to syngas,”Journal of Catalysis,vol.288,pp.54–64, 2012.[15]D.P.Liu,Y.F.Wang,D.M.Shi et al.,“Methane reformingwith carbon dioxide over a Ni/ZiO2-SiO2catalyst:influence of pretreatment gas atmospheres,”International Journal of Hydrogen Energy,vol.37,no.13,pp.10135–10144,2012. [16]M.V.Bykova,D.Y.Ermakov,V.V.Kaichev et al.,“Ni-based sol-gel catalysts as promising systems for crude bio-oil upgrading:guaiacol hydrodeoxygenation study,”Applied Catalysis B:Environmental,vol.113-114,pp.296–307,2012. [17]M.Xue,S.Hu,H.Chen,Y.Fu,and J.Shen,“Preparationof highly loaded and dispersed Ni/SiO2catalysts,”Catalysis Communications,vol.12,no.5,pp.332–336,2011.[18]R.Nares,J.Ram´ırez,A.Guti´e rrez-Alejandre,and R.Cuevas,“Characterization and hydrogenation activity of Ni/Si(Al)—MCM-41catalysts prepared by deposition-precipitation,”Indus-trial and Engineering Chemistry Research,vol.48,no.3,pp.1154–1162,2009.[19]A.Corma,A.Martinez,V.Martinezsoria,and J.B.Monton,“Hydrocracking of vacuum gasoil on the novel mesoporous MCM-41aluminosilicate catalyst,”Journal of Catalysis,vol.153, no.1,pp.25–31,1995.[20]T.Halachev,R.Nava,and L.Dimitrov,“Catalytic activityof(P)NiMo/Ti-HMS and(P)NiW/Ti-HMS catalysts in the hydrogenation of naphthalene,”Applied Catalysis A:General, vol.169,no.1,pp.111–117,1998.[21]S.He,H.Wu,W.Yu,L.Mo,H.Lou,and X.Zheng,“Combi-nation of CO2reforming and partial oxidation of methane to produce syngas over Ni/SiO2and Ni–Al2O3/SiO2catalysts with different precursors,”International Journal of Hydrogen Energy, vol.34,no.2,pp.839–843,2009.[22]S.F.He,Q.S.Jing,W.J.Yu,L.Y.Mo,H.Lou,and X.M.Zheng,“Combination of CO2reforming and partial oxidation of methane to produce syngas over Ni/SiO2prepared with nickel citrate precursor,”Catalysis Today,vol.148,no.1-2,pp.130–133,2010.[23]S.He,X.Zheng,L.Mo,W.Yu,H.Wang,and Y.Luo,“Characterization and catalytic properties of Ni/SiO2catalysts prepared with nickel citrate as precursor,”Materials Research Bulletin,vol.49,pp.108–113,2014.[24]E.Marceau,M.Che,J.ˇCejka,and A.Zukal,“Nickel(II)nitrate vs.acetate:influence of the precursor on the structure and reducibility of Ni/MCM-41and Ni/Al-MCM-41catalysts,”ChemCatChem,vol.2,no.4,pp.413–422,2010.[25]J.Chen and Q.Z.Song,Organic Spectral Analysis,BIT Press,Beijing,China,1996.[26]J.F.Xu,W.Ji,Z.X.Shen et al.,“Raman spectra of CuOnanocrystals,”Journal of Raman Spectroscopy,vol.30,no.5,pp.413–415,1999.[27]H.Richter,Z.P.Wang,and L.Ley,“The one phonon Ramanspectrum in microcrystalline silicon,”Solid State Communica-tions,vol.39,no.5,pp.625–629,1981.[28]Z.Zhao,Y.Yamada,A.Ueda,H.Sakurai,and T.Kobayashi,“The roles of redox and acid-base properties of silica-supported vanadia catalysts in the selective oxidation of ethane,”Catalysis Today,vol.93–95,pp.163–171,2004.Scientifica Corrosion Polymer ScienceCeramics Composites Nanoparticles International Journal of Biomaterials Nanoscience TextilesJournal of Nanotechnology Crystallography The Scientific World Journal Coatings Advances in Materials Science and Engineering S mart MaterialsResearch Metallurgy Journal ofBioMed Research International Materials Journal of Journal ofNanomaterials。

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Catalytichydrodenitrogenationofindoleovermolybdenumnitrideandcarbideswithdifferentstructures

SenziLia,JaeSungLeea,*,TaeghwanHyeon1,b,KennethS.SuslickbaDepartmentofChemicalEngineeringandSchoolofEnvironmentalEngineering,PohangUniversityofScienceandTechnology,

Pohang,Seoul790-784,SouthKoreabSchoolofChemicalScience,UniversityofIllinoisatUrbana-ChampaignUrbana,IL61801,USA

Received22September1998;receivedinrevisedform5January1999;accepted14January1999

AbstractThehydrodenitrogenation(HDN)ofindolehasbeenstudiedoverMo2NandMo2Cwithdifferentstructures.Thedifferenceinactivitywasmodestandthestructureofthecatalystsexertedamoresigni®canteffectthanthechemicalcomposition.Moreevidentdifferencewasobservedinselectivity,andherethecompositionwasthemostimportantfactor.SonochemicallypreparedMo2CwasanactivecatalystforHDNreaction.Itformedplate-likeaggregatesoflooselypackedMo2C(fcc)

particles.ThecrystallinityofsonochemicallypreparedMo2Cwasimprovedduringthereaction,anditsbehaviorinHDN

becamesimilartoMo2C(fcc)preparedbytheTPRmethod.#1999ElsevierScienceB.V.Allrightsreserved.

Keywords:Hydrodenitrogenation;Indole;Molybdenumnitride;Molybdenumcarbides

1.IntroductionHydrodenitrogenation(HDN),atreatmentprocesstoremoveorganonitrogencompoundsfrompetroleumorcoal-derivedfeedstocks,isoneofthehydropuri®-cationprocessesintheoilre®neryindustry.Thesehydrotreatingprocessesminimizetheformationofairpollutantsandpoisoningofthecatalystsusedinthedownstream.GroupIVandgroupVIIImetalsul®dessupportedonalumina,typicallyCo(Ni)±Mo/g-Al2O3,

havebeenusedascommercialhydrotreatingcatalystsformorethan40years.Inrecentyears,however,thesecatalystsarefacingstrongchallengesfrommorestringentenvironmentalconstraintsandneedsofuti-lizinglowqualityhydrocarbonfeedstocks.Theirdrawbacksincludeexcessivehydrogenconsumptionandtherequirementofsevereoperatingconditionssuchashightemperaturesandpressures.Thus,envir-onmentalproblemsandenergysavingmotiveshavebecomeadrivingforcefordevelopingnewhydro-treatingcatalysts.Atemperature-programmedreactionmethodwasintroducedbyBoudartandcoworkers[1±4]tosynthe-sizeunsupportedMo2NandMo2Cpowderswithhighspeci®csurfaceareas.Sincethen,avarietyofhydro-gentransferreactionsincludinghydrodesulfurization(HDS)andhydrodenitrogenation(HDN)havebeenstudiedoversupportedandunsupportedmolybdenumnitrideandcarbidecatalysts,andsomeencouraging

AppliedCatalysisA:General184(1999)1±9*Correspondingauthor.Tel.:+82-562-279-2266;fax:+82-562-279-5799;e-mail:jlee@postech.ac.kr1Presentaddress:SchoolofChemicalEngineering,Seoul

NationalUniversity,Seoul151-742,SouthKorea.

0926-860X/99/$±seefrontmatter#1999ElsevierScienceB.V.Allrightsreserved.PII:S0926-860X(99)00044-7resultshavebeenobtained[5±10].LeeandBoudart[5]foundthatunsupported󰁡-MoC1Àxhasthiophene

HDSactivitycomparabletothatofsul®dedMo/Al2O3.Schlatteretal.[6]reportedthatMo2Nand

Mo2CshowedquinolineHDNactivitycomparableto

thatofcommercialsul®dedNi±Mo/Al2O3.MarkelandVanZee[7]revealedastrongresistancepropertyofMo2Nagainstbeingsul®dedinthiopheneHDS.Choietal.[9]investigatedpyridineHDNonmolyb-denumcarbideswithdifferentspeci®csurfaceareas.Mostoftheaboveresultshaveshownthatmolybde-numnitridesandcarbidesaresuperiortoorcompar-abletocommercialhydrotreatingcatalysts.RecentlySuslicketal.[11±13]havedevelopedanewsynthetictechnique,i.e.,sonochemicalsynthesisofnano-structuredinorganicmaterials,toproducemolybdenumcarbidepowderswithhighspeci®csur-faceareas.Whensolutionsofvolatileorganometalliccompoundsareirradiatedwithhighintensityultra-sound,highsurfaceareasolidsareproducedconsist-ingofagglomeratesofnanometerclusters.Theyhavesynthesizednano-structuredmolybdenumcarbidesfromtheultrasonicirradiationofmolybdenumhex-acarbonyl.Thecatalyticstudiesofdehydrogenationofcyclohexaneandhydrogenolysisofethaneovertheproducedmaterialshaveshownthatsonochemicallypreparedmolybdenumcarbideisahighlyselectivedehydrogenationcatalyst[13].MotivatedbyourpreviousworkrevealingthatMo2NisanactivecatalystforHDNofindole[14],weinvestigatedHDNofindoleoverdifferentphasesofMo2CandMo2N,aimedatobtaininganinsightintotheeffectofstructuresofmolybdenumcarbidesandnitrideonthereactionratesandselectivityofHDNofindole.Sincenano-structuredMo2Chasshownitscatalyticpotentialinavarietyofreactions,HDNofindoleoversonochemicallypreparedMo2Cwasalsoinvestigated.2.Experimental2.1.TPRsynthesisofMo2NandMo2CAtemperature-programmedreaction(TPR)proce-durewasemployedforthepreparationofmolybde-numnitrideandcarbideswithdifferentcrystalstructures.Foreachbatch,4mmolMoO3wasloadedinaU-shapedquartzreactioncellstuffedwithaplugofquartzwoolatthebottomtoholdthepowders.ThetemperatureofthesynthesisreactorwascontrolledbyaPIDcontrollerwithalocalthermocouplemountedaxiallyalongthelengthofthereactorwhichwaslocatedinanelectricfurnace.ToproduceMo2Nwith