Zeolite T membrane_ preparation, characterization, pervaporation of water_organic liquid mixtures

Zeolite T membrane_ preparation, characterization, pervaporation of water_organic liquid mixtures
Zeolite T membrane_ preparation, characterization, pervaporation of water_organic liquid mixtures

Journal of Membrane Science 236(2004)

17–27

Zeolite T membrane:preparation,characterization,pervaporation

of water/organic liquid mixtures and acid stability

Ying Cui,Hidetoshi Kita,Ken-Ichi Okamoto ?

Department of Advanced Materials Science and Engineering.Faculty of Engineering,Yamaguchi University,Ube,Yamaguchi 7558611,Japan

Received 6June 2003;received in revised form 8December 2003;accepted 18December 2003

Abstract

Zeolite T membranes were prepared by hydrothermal synthesis on porous mullite tubes seeded with zeolite T crystals,using milk-like aluminosilicate gel prepared from precipitated silica as a silica source with a molar composition of SiO 2:Al 2O 3:Na 2O:K 2O:H 2O =1:0.05:0.26:0.09:14.After 30h of the synthesis at 373K,a zeolite crystal layer of about 20?m in thickness was formed on the outer surface of the tube,which was composed of two layers,namely the top surface layer and the intermediate layer under the top surface layer.FE-SEM observation indicated the presence of well-intergrown zeolite T crystals packed densely in the intermediate layer,which appeared as an active layer for separation rather than the top surface layer.

With increasing the kinetic diameter of gas from CO 2to C 3H 8,the gas permeance decreased by more than three orders in magnitude,indicating a very little amount of defects for the membrane.The membranes displayed high performance of pervaporation (PV)for water/organic liquid mixtures.The excellent PV performance was attributed to the combined effects of the preferential adsorption of water and the molecular sieving.The zeolite T membranes were stable in acetic acid solutions,but not in hydrochloric acid solution because of the dealumination.The zeolite T membranes also showed excellent performance of PV for water/acetic acid mixtures.?2004Elsevier B.V .All rights reserved.

Keywords:Zeolite T;Membrane separation;Pervaporation;Gas permeation

1.Introduction

Pervaporation (PV)has attracted increasing attention as an effective and energy-ef?cient technique for the separation of azeotrope or close-boiling liquid mixtures [1,2].Zeo-lite membranes have advantages over polymer membranes,such as better chemical and thermal stability,and have the potential to continuously separate mixtures of molecules by both adsorption and molecular sieving because the zeolite pores are of molecular size.So far most of the studies on zeolite membranes have been focused on zeolite A [3,4],FAU-type zeolites (X and Y)[5–7],mordenite [8,9]and MFI-type zeolite (ZSM-5and silicalite)[10–12].Zeolite NaA membranes with excellent performances for PV of water/organic liquids are currently commercially available and have been applied for the dehydration of some organic solvents in a large scale [13,14].

?

Corresponding author.Tel.:+81-836-35-9961;fax:+81-836-85-9601.

E-mail address:okamotok@yamaguchi-u.ac.jp (K.-I.Okamoto).In general,with an increase in Al content in the frame-work,the hydrophilicity of a zeolite increases,whereas the acid resistance simultaneously decreases because a strong acid leaches Al from the zeolite to decompose its frame-work structure [15,16].Zeolite NaA membranes cannot be applied for dehydration of organic liquids containing an acid because of their instability in acidic media.On the other hand,ZSM-5zeolite membranes are stable toward acid but have poor performance for the dehydration of or-ganic liquids because of the hydrophobic character [17].A zeolite membrane with a medium Si/Al ratio might be preferable for the dehydration of organic liquids containing acid.For example,recently,mordenite membranes were found to be highly water-selective in PV of water/organic liquid mixtures and stable under acidic conditions [18,19].Zeolite T with Si/Al ratio of 3–4is considered to be less hydrophilic but more stable to acid than zeolites A,X and Y .Zeolite T is an intergrowth-type zeolite of erionite and offretite and its preparation,features of structure and ap-plications have been widely investigated [20–26].Erionite has 8-ring channels parallel to the c-axis,of which the pore

0376-7388/$–see front matter ?2004Elsevier B.V .All rights reserved.doi:10.1016/j.memsci.2003.12.018

18Y.Cui et al./Journal of Membrane Science236(2004)17–27

size is0.36nm×0.51nm.On the other hand,offretite has 12-ring main channels parallel to the c-axis and8-ring sub channels normal to the c-axis,of which the pore sizes are 0.67nm×0.68nm and0.36nm×0.49nm,respectively. Either of pure phases is obtained only in the presence of organic template,whereas intergrowth-type zeolite T can be prepared with template-free mediums[27–34].The frame-work structures of offretite and erionite are different but closely related.Because of the similarity of their structures that are alternately composed ofε-cage and D6R,they al-ways exist together in the crystallized products[21,22,25]. According to Yang and Evmiridis[25],the synthesized ze-olite T is mainly an offretite phase,but it may also contain small amounts of stacking faults of erionite https://www.360docs.net/doc/d85966319.html,rger pyridine molecules cannot penetrate into the cavities of the crystals,whereas smaller n-hexane molecules(0.43nm in kinetic diameter)can penetrate,resulting in a much lower adsorption capacity for pyridine,probably because the large pore openings are effectively blocked by the stacking faults. We have reported the preparation of zeolite T membranes from a clear aluminosilicate solution with a composition of SiO2:Al2O3:Na2O:K2O:H2O=1:0.019:0.30:0.09:16 (in moles)using colloidal silica as a silica source without template,and the membranes synthesized at373K for24h showed high PV performance for water/ethanol mixture [35].

In a preliminary study,we replaced colloidal silica with cheaper precipitated silica for preparation of zeolite T crystal https://www.360docs.net/doc/d85966319.html,ing a milk-like aluminosilicate gel,we achieved a higher synthesis yield of zeolite T in a shorter prepara-tion time.We investigated the synthesis of zeolite T mem-branes using this milk-like gel.In this paper,we report on the synthesis of zeolite T membranes and their permeation and acid-stability properties.We have already reported on their application to esteri?cation reactions[36,37].

2.Experiments

2.1.Membrane preparation

The milk-like aluminosilicate gel was prepared by mixing precipitated silica(Nihon Silica Ind.;Nipsil VN3),sodium aluminate,sodium hydroxide,potassium hydroxide and distilled water,followed by stirring at303K for24h.The molar composition was SiO2:Al2O3:Na2O:K2O:H2O= 1:0.05:0.26:0.09:14.The Si/Al ratio in the present recipe is 10,which is1/2.6of that previously reported[35].The outer surface of a porous tubular mullite support(Nikkato Corp., 12mm in outer diameter,1.5mm in thickness,1.3?m in average pore size)was polished with SiC paper(600),thor-oughly washed with water,and simply rubbed with a water slurry of zeolite T powders.The seeded support tube of 10cm in length was placed in the230ml aluminosilicate gel and the hydrothermal synthesis was carried out at373K for2–50h.For comparison,zeolite T membranes were also prepared on unseeded support tubes.Finally,the mem-branes were well washed with water and dried at348K for3h.

2.2.Characterization and permeation experiments Zeolite T membranes were characterized by X-ray diffraction(XRD)using a Shimadzu XD-3diffractometer and?eld emission scanning electron microscope(FE-SEM) on a JEOL JSM-6335F microscope.

PV experiments were carried out using an apparatus illus-trated in Fig.1a.The effective membrane area was20cm2 and the inside of the membrane tube was evacuated through a vacuum line.The permeate vapor was collected by a cold trap cooled by liquid nitrogen.The downstream pressure was maintained below0.1333224×https://www.360docs.net/doc/d85966319.html,position analysis of the feed and permeate was performed on a gas chromato-graph equipped with3m column packed with Polarpack Q, poly(ethylene glycol)-1000supported on Shimalite F.The PV performance of membrane was evaluated by permeation ?ux Q in kg m?2h?1and separation factorα.The separa-tion factor of water over organic liquid is de?ned as

αW/O=

y W/y O

W O

where x and y are the weight fractions of the components in the feed and the permeate,respectively;subscripts W and O refer to water and organic liquid components,

respectively.

Fig.1.Schematic illustration of:(a)batch-type PV apparatus and(b)gas permeation cell.

Y.Cui et al./Journal of Membrane Science236(2004)17–2719 Single-gas permeation experiments were carried out for

He,H2,CO2,O2,N2,CH4,and C3H8gases at303–473K

by means of a vacuum time-lag method using a permeation

cell illustrated in Fig.1b.The effective membrane area was

19cm2and the permeation side was kept under vacuum.

Prior to the gas permeation measurements,the membrane in

the cell was completely dried by evacuating both sides of

the membrane at473K for20h.

2.3.Acid-stability tests

Acid-stability tests of zeolite T crystal were carried out

by immersing the sample powder in a50wt.%acetic acid

solution at348K for7days or in0.5–1M hydrochloride acid

solutions at358K for1h.The equivalent ratio of the acid

used over the alkali cation in zeolite T was about12.After

the acid treatment,the samples were washed with water

and dried,and then characterized by ion coupled plasma

(ICP)elemental analysis and X-ray diffraction.The acid

stability of zeolite T membrane was also evaluated from PV

performances for water/ethanol mixture before and after the

acid treatment.

3.Results and discussion

3.1.Membrane preparation and characterization

Zeolite T membranes were hydrothermally synthesized on

the seeded and unseeded mullite tubes at373K for2–50h.

The PV performances of the resulting zeolite T membranes

are summarized in Table1.At the synthesis time of2h,the

membrane showed a very high permeation?ux without the

selectivity.After5h of synthesis,the membrane showed

Table1

PV performances for a water/ethanol mixture of zeolite T membranes

prepared on seeded mullite tubes at373K for different synthesis time

Membrane no.Synthesis

time(h)PV performance a

Flux(kg m?2h?1)αW/E

12High1 25 1.19120 38 1.18490 410 1.00880 519 1.18900 620 1.49750 730 1.37900 830 1.082200 930 1.10900 1030 1.11630 11300.931560 12300.64730 13300.75770 1430 1.071200 15420.65290

a At348K and10wt.%of x W.a fairly low performance ofαW/E of120and a?ux of

1.2kg m?2h?1.After10h of the synthesis,the membrane showed a fairly high performance ofαW/E of880and a ?ux of1.0kg/(m2h).In the range of the synthesis time of 10–30h,no clear and systematic change in the membrane performance was observed,because the PV performance varied somewhat largely from membrane sample to sample. For example,for eight membranes prepared under the same conditions of373K and30h(No.7–14in Table1),the per-meation?ux ranged from0.64to1.37kg m?2h?1,and the separation factor ranged from630to2200.At the further prolonged synthesis time,the membrane surface became very rough and the selectivity decreased.On the other hand, there was no selectivity found for the membranes prepared on the unseeded tubes,even if the synthesis time was pro-longed up to50h.Dense and permselective crystalline layer was formed only on the seeded tubes.No zeolite crystal powder was formed in the liquid phase even after42h of the synthesis on the seeded tubes.

Fig.2shows the XRD patterns of the zeolite T mem-branes,zeolite T powder and seeded and unseeded mullite tubes.The XRD pattern of the zeolite T powder syn-thesized at373K for120h was consistent with that of offretite/erionite(T)type zeolite reported in the literature [25].The seeded tube showed very weak peaks of zeolite T besides strong peaks of the mullite substrate.For the mem-brane after4h,the zeolite T peaks appeared more clearly but were still weak compared with the substrate peaks,but no amorphous band was observed.Zeolite T crystal peaks became much stronger with increasing synthesis time and were observed very clearly for the membrane after30h. The morphology of membrane was observed with FE-SEM.Fig.3shows FE-SEM photographs of the

outer

010********

2 (deg)

I

n

t

e

n

s

i

t

y

Fig.2.XRD patterns for(a)mullite tube,(b)seeded mullite tube and zeolite T membranes synthesized at373K for(c)4h,(d)30h and(e) zeolite T powder synthesized at373K for120h.

20Y.Cui et al./Journal of Membrane Science 236(2004)

17–27

Fig.3.FE-SEM photographs (104×)of the surface of (a)porous mullite tube,(b)seeded tube,and zeolite T membranes synthesized at 373K for (c)12h and (d)30h.

surface of the mullite tube,seeded tube and zeolite T mem-branes.The surface of the support was rather rough and large pores of several micrometers or more were observed.The seed crystals were deposited rather continuously and preferentially in places such as larger pores.A surface layer composed of very small particles in coagulated state was formed on the outer surface after 12h of the synthesis.After 30h of the synthesis,the surface was covered with ran-domly oriented rod-like zeolite T crystals of less than 1?m in diameter.However,their packing was still rather loose.Fig.4shows FE-SEM images of the cross section of the seeded mullite tube and zeolite T membranes.The thick-nesses of membrane layer increased with increasing syn-thesis time from a few micrometers at 5h of the synthesis through about 10?m at 12h and up to 20?m at 30h,and an intermediate layer was observed under the top surface layer after 12h of the synthesis and it also increased in thickness and looked denser than the top layer after 30h.Fig.5shows magni?ed FE-SEM photographs of typical parts of the in-termediate layer.It is important to note the presence of the

well-intergrown zeolite T crystals packed densely in the in-termediate layer,which seemed to take an important role in separation rather than the top surface layer.3.2.Permeation properties

3.2.1.Single-gas permeation

It is important for elucidation of the membrane morphol-ogy and permeation mechanism of the zeolite T membranes to investigate their single-gas permeation properties.Fig.6shows plots of the permeance R versus the kinetic diame-ter of gas molecule at different temperatures.With increas-ing kinetic diameter from 0.33nm for CO 2to 0.43nm for C 3H 8,the R decreased by more than three orders in mag-nitude,suggesting a kind of molecular sieving behavior for the zeolite T membrane.

Fig.7shows plots of R versus the reciprocal of the square root of the molecular weight M of gas for the zeolite T mem-brane.For comparison,the plots for zeolite NaA membrane previously reported [4]are also included in this ?gure.The

Y.Cui et al./Journal of Membrane Science236(2004)17–27

21

Fig.4.FE-SEM photographs(2000×)of the cross section of(a)seeded support tube and zeolite T membranes synthesized at373K for(b)5h,(c)12h and(d)30h.

zeolite NaA membrane completely dried showed a linear relationship between R and M?1/2at each temperature,sug-gesting a Knudsen diffusion mechanism.On the other hand, the zeolite T membrane did not show such a linear relation-ship between R and M?1/2.The larger gases,namely C3H8 and CH4,showed much lower R values than those evaluated by assuming the Knudsen diffusion from the R values of H2 and He,whereas CO2showed much higher R values.The R of CO2signi?cantly depended on the temperature and the maximum was observed around378K.

These results strongly indicate that the zeolite T mem-branes prepared in this study had little or a very little defects (or nonzeolitic pores)and their gas permeation behavior was controlled by zeolitic pores of erionite inter-stacked in of-fretite,of which the pore size is0.36nm×0.51nm.Thus, propane molecules with the kinetic diameter of0.43nm could hardly permeate through the zeolite T membranes. CO2molecules with the smaller kinetic diameter of0.33nm showed the highest permeance among the gases investigated. This is probably because of the af?nity of CO2molecules to zeolite T,which leads to a high adsorption coverage of CO2in zeolitic pores and a high permeability.Thus,the ze-olite T membranes have high CO2separation performance, and the detail will be reported elsewhere.It is reasonably considered from the above-mentioned results and discussion that a combined effect of molecular sieving and preferen-tial adsorption is operative in gas separation and PV of wa-ter/organic liquid through the zeolite T membranes.

3.2.2.PV of water/organic liquid mixtures

Table2shows comparison of PV performances for wa-ter/organic(10/90wt.%)liquid mixtures between zeolite T and other zeolite membranes[4,7,35].The zeolite T mem-branes were highly water-permeable toward these organic liquids except for methanol and displayed high permeation ?uxes and separation factors.Their PV performances were not so high as those of zeolite NaA membranes,but much higher than those of zeolite NaX and NaY membranes.It is noted that the zeolite T membranes were synthesized using the milk-like gel prepared from precipitated silica,of which

22Y.Cui et al./Journal of Membrane Science236(2004)

17–27

Fig.5.Magni?ed FE-SEM photographs of the intermediate layer of zeolite T membrane synthesized at373K for30h.

Table2

PV performances of zeolite membranes toward water/organic liquid mix-tures(x W=10wt.%)

Membrane Separation

system T(K)Flux

(kg m?2h?1)

αW/O Ref.

Zeolite T a Methanol3230.1637This work Ethanol348 1.10900

2-Propanol348 2.208,900

Acetone3230.45880

DMF3330.452,900

NaA Methanol3230.572,100[4]

Ethanol348 2.1510,000

2-Propanol348 1.7610,000

NaX Ethanol348 1.91170[7]

NaY Ethanol348 1.59130

Zeolite T Ethanol348 1.252,200[35]

2-Propanol348 1.7710,000

a Membrane No.9in Table1.

0.01

0.1

1

10

100

1000

0.250.30.350.40.45

Kinetic Diameter (nm)

R

×

1

1

[

m

o

l

/

m

2

.

s

.

P

a

]

Fig.6.Plots of permeance R vs.kinetic diameter of gas molecule for zeolite T membrane(No.11in Table1)at303,378and473K.

the PV performances were as high as those of the zeolite T membranes synthesized from colloidal silica[35].

Fig.8shows the feed composition dependence of the per-meation?uxes of water and ethanol components,q W and q E, and separation factorαW/E for PV of water/ethanol system. With an increase in x W,the q W increased initially largely, then gradually and?nally again largely.On the other hand, with a decrease in x E,the q E hardly decreased in spite of a decrease in the driving force in the range of x E above 60wt.%and then decreased linearly.As a result,with an increase in x W,theαW/E increased initially,reached a max-imum around x W of10wt.%,and then decreased gradually.

2

4

6

00.20.40.60.8

M-1/2

R

×

1

8

[

m

o

l

/

m

2

.

s

.

P

a

]

1

2

3

R

×

1

8

[

m

o

l

/

m

2

.

s

.

P

a

]

Fig.7.Plots of R vs.M?1/2of gas for zeolite T membrane(No.11in Table1)at308K( ,?),378K(?,?)and473K(?,?).

Y.Cui et al./Journal of Membrane Science 236(2004)17–2723

123450

50100

x E [ wt%]

q W [ k g /m 2

h ]

0.01

0.02

050

100

W q E [ k g /m 2

h ]

W /E

Fig.8.Feed composition dependence of permeation ?ux and separation factor for PV of water/ethanol system at 348K.

Figs.9and 10show the temperature dependence of the permeation ?ux and separation factor for PV of wa-ter/ethanol and water/methanol systems,respectively.At x W of 10wt.%,with increasing temperature,q E and q M in-creased more largely than q W ,and as a result the αW /E and αW /M decreased slightly.This was different from the be-havior for zeolite NaA membranes,where both Q and αin-creased largely and the higher performance was achieved at the higher temperature.The PV through the zeolite T mem-branes was also still preferable at the higher temperature,because the large increase in q W compensated for the rather small decrease in α.It is interesting to compare the perme-ation ?ux of each component between the single-component and mixed-component systems.The q W decreased signi ?-cantly for the mixed-component system compared with the single-component system,because of the signi ?cant de-crease in the driving force (or decrease in x W from 100to 10wt.%).However,the decrease in q W was much larger for water/methanol than water/ethanol.On the other hand,the q M increased about twice for the mixed-component system,but such an increase in q E was not observed.It is noted that the rather poor performance of the zeolite T membranes for PV of water/methanol mixtures is apparently related to the fairly large increase in q M in the presence of small amount of water and the signi ?cantly large decrease in q W in the presence of large amount of methanol.

0.001

0.01

0.1

1

10

2.83

3.2

3.4

1000/

T (K -1

)

F l u x ( k g /m 2

h )

9001000

1100

W /E

Fig.9.Temperature dependence of permeation ?ux and separation factor for PV of water/ethanol liquid mixture (x W =10wt.%)(open keys)and each single component (closed keys).

0.001

0.01

0.1

1

10

3 3.2

3.4

1000/

T (K -1

)

F l u x ( k g /m 2

h )

3545

55

W /M

Fig.10.Temperature dependence of the permeation ?ux and separation factor in PV of water/methanol liquid mixture (x W =10wt.%open keys)and each single component (closed keys).

24Y.Cui et al./Journal of Membrane Science 236(2004)

17–27

50

100

150

200

0.5P /P s

A d s o r p t i o n [ c m 3

(S T P )/ g ]

1

Fig.11.Vapor sorption isotherms of water (?,?),methanol ( ,?),ethanol (?,?),and 2-propanol (?,?)measured at 298K on zeolite T powder.Open keys:adsorption run,closed keys:desorption run.

Fig.11shows adsorption isotherms of water,methanol,ethanol,and 2-propanol vapors on zeolite T powder at 298K.With increasing the vapor activity,the adsorption increased sharply and then saturated.Table 3lists the Si/Al ratio and the adsorptions of water and alcohols at the activity of 0.9for zeolite T powder,together with the data for zeolites NaA and NaY [4,7].It is noted that zeolite NaA and zeolite T have still large adsorption capacities for ethanol,indicat-ing that ethanol molecules can penetrate into the cavities of the zeolite crystals in spite of a little larger molecular size compared to the zeolitic pores.It is well known that zeolite NaA with a Si/Al ratio of unity is the most hydrophilic and with an increase in Si/Al ratio the resulting zeolite becomes less hydrophilic.In the case of zeolite NaA,the adsorption of water vapor was only 2.4and 4times larger than those of methanol and ethanol,respectively,at 298K,whereas the separation factors of PV ,αW /M and αW /E ,were as high as 2100and 10000,respectively,at a x W of 10wt.%and at 323and 348K as listed in Table 2.The high PV performance of zeolite NaA membranes was attributed to the completely preferential adsorption,that is,the capillary condensation

Table 3

Adsorptions of water,methanol,ethanol,and 2-propanol for zeolites T,NaA,NaY powder at vapor activity of 0.9and 298K Zeolite Adsorption (cm 3(STP)/g)

Type Pore size (nm)Si/Al ratio Water (0.264)a MeOH (0.380)a EtOH (0.430)a 2-Propanol (0.470)a T 0.36×00.51 4.018010562 6.9NaA 0.411340140825NaY

0.74

2.1

390

185

120

a

Kinetic diameter of adsorbed molecule (nm)cited from Ref.[38].

of water molecules in zeolitic and nonzeolitic pores and the blocking of other molecules from entering the pores [4].Ze-olite NaY with a Si/Al ratio of 2.1had the larger adsorption of water vapor than zeolite NaA because of the larger ze-olitic pores,but the smaller adsorption ratios of water over methanol and ethanol,namely 2.1and 3.2,respectively,because of the less hydrophilicity.As a result,zeolite NaY membranes displayed the much lower PV separation fac-tors with slightly higher permeation ?uxes.It is noteworthy that the zeolite NaY membranes had also little defects and displayed excellent PV performances for polar/nonpolar or-ganic liquids such as ethanol/ethyl-t -butyl ether due to the preferential adsorption of polar organic molecules [7].

Zeolite T with a Si/Al ratio of 4.0had the much smaller water adsorption and the slightly lower adsorption ratios of water over methanol and ethanol,namely about 1.7and 2.9,respectively,than zeolite NaY .However,the zeolite T mem-branes displayed much higher PV selectivity than zeolite NaY membranes.This is explained based on the smaller ze-olitic pores for zeolite T than for zeolite NaY .In the present case,the kinetic diameter of one of the penetrant pair (water molecule)is smaller than the pore size of zeolitic channels but that of the other (organic molecule)is similar to or a little larger,and the loading of penetrant molecules in ze-olitic channels is rather high.Therefore,it is considered that the PV behavior is signi ?cantly affected by the combined effects of competitive adsorption and single ?le diffusion in the zeolitic pores [39,40].In the case of water/ethanol system,the ratio of single-component-permeation ?ux of water over ethanol was 320at 348K,which was much larger than the adsorption ratio of water over ethanol (2.9at 298K),indicating ethanol molecules can enter into the ze-olitic pores but cannot easily diffuse in them.The αW /E of 900at x W =10wt.%was three times larger than the ratio of the single-component-permeation ?ux as a result of the larger q W value compared to the additive rule.This is proba-bly due to the highly preferential adsorption of water.In the competitive adsorption process,the less-hydrophilic prop-erty of zeolite T seemed to be compensated by the smaller ze-olitic pores.On the other hand,in the case of water/methanol system,the ratio of single-component-permeation ?ux of water over methanol was 95,whereas the αW /E was about 37at x W =10wt.%.The smaller value was due to the about two times larger q M value at x W =10wt.%compared to the value evaluated from the additivity,whereas the q W

Y.Cui et al./Journal of Membrane Science 236(2004)17–27

25

Table 4

Variation in Si/Al ratio of zeolite T powder with acid treatment Acid treatment conditions

Si/Al ratio (ICP)No treatment

4.050wt.%acetic acid for 7days at 348K 4.10.5M HCl for 1h at 358K 8.91.0M HCl for 1h at 358K

43

value was as small as that evaluated from the additivity.The af ?nity of zeolite T to water is not high enough to block methanol molecules from entering into the zeolitic pores and methanol molecules penetrated in the pores disturb the

diffusion of water molecules in the zeolitic pores,whereas the diffusion of methanol molecules is enhanced by water molecules because of the single ?le diffusion.3.3.Acid stability

Zeolite T powder samples were treated with acidic solu-tions (in large excess of H +toward cation in zeolite)and their Si/Al ratio and XRD patterns were measured.The re-sults are summarized in Table 4and Fig.12.The Si/Al ra-tio of the zeolite T powder before the acid treatment was 4.0.After the treatment with a 50wt.%acetic acid solution at 348K for 7days,neither Si/Al ratio nor XRD pattern changed,indicating the stability of the zeolite T powder to acetic acid under the conditions.On the other hand,both of them changed after the treatment with a 0.5or 1.0M hy-drochloric solution at 358K for 1h.With the 0.5M HCl treatment,the Si/Al ratio increased about twice and a small broad band appeared around 20–30?of 2θ.With the 1M HCl treatment,the Si/Al ratio increased up to 43and the XRD peaks characteristic to zeolite T crystal disappeared

010

20304050

2 (degree)

I n t e n s i t y

Fig.12.XRD patterns for:(a)zeolite T powder and samples treated with (b)50wt.%acetic acid at 348K for 7days,and (c)0.5M HCl and (d)1.0M HCl solutions at 358K for 1h.

Table 5

Variation in PV performance of zeolite T membrane (No.13in Table 1)for water/ethanol mixture (x W =10wt.%)at 348K with 0.1M HCl treatment at 300K for a day

PV performance Flux (kg m ?2h ?1)

αW /E Before treatment 0.75770After treatment

0.69

46

completely and a broad amorphous band appeared,indicat-ing the decomposition of the crystalline structure due to the dealumination.Krais [31]and Cichocki [41]investigated the resistance to acidic medium of zeolites by testing the water vapor adsorption capacity.Krais reported that zeolite T was practically stable to HCl solutions less than 2N under the given condition (at 300K for 1h with the equivalent ratio of HCl over the alkali cation in zeolite T of 3).This is different from the present result mentioned above,probably because of the much smaller equivalent ratio of HCl.

The acid-stability of zeolite T membranes was investi-gated by measuring PV performance before and after acid treatment.As listed in Table 5,after soaking the zeolite T membrane in a 0.1M HCl solution at 300K for 1day,the separation factor for PV of water/ethanol signi ?cantly de-creased.Thus,the zeolite T membranes were not practically stable to hydrochloric acid solutions.

Fig.13shows the feed composition dependence of per-meation ?ux and separation factor for PV of water/acetic

0.5

1

1.52

2.50

20

406080

100

x A [wt%]

q W [k g /m 2

h ]

0.01

0.02

0.03

q A [k g /m 2

h ]10

100100010000

αW /A

Fig.13.Feed composition dependence of permeation ?ux and separation factor for PV of water/acetic acid liquid mixtures at 348K.Open keys:?rst run,closed keys:second run.

26Y.Cui et al./Journal of Membrane Science236(2004)17–27

Table6

Variation in PV performance of zeolite T membrane(No.12in Table1) for water/ethanol mixture(x W=10wt.%)at348K between before and after PV for the acetic acid solutions

PV performance

q W(kg m?2h?1)q E(kg m?2h?1)αW/E Before the PV0.630.008730 After the PV a0.420.012320

a The membrane was desorbed at483K for60h in vacuo.

acid liquid mixtures through a zeolite T membrane at348K. The PV experiment runs were carried out with increasing feed composition of acetic acid x A.After the?rst runs for a week,a PV experiment was repeated for a feed with x A of50wt.%.The zeolite T membrane showed excellent PV performances with high water permeation?uxes and high separation factors especially in the range of x A less than 50wt.%.After the membrane was exposed on the feed so-lution with x A of90wt.%,the PV performance at x A of 50wt.%slightly decreased to0.9kg m?2h?1of Q and520 ofαW/A.After these PV experiments for the acetic acid solu-tions,the membrane was subjected to PV for a water/ethanol mixture.The results are summarized in Table6.After the PV experiments for the acetic acid solutions,the?ux and the separation factor decreased down to67and44%,respec-tively.However,these decreases might be due to adsorption of acetic acid molecules in the zeolite pores that signi?cantly affects water adsorption coverage.These PV results together with the characterization results with Si/Al ratio and XRD pattern indicate the zeolite T membranes are practically sta-ble to carboxylic acids such as acetic acid under the given conditions.

4.Conclusions

1.Zeolite T membranes were successfully prepared by the

hydrothermal synthesis at373K for10–30h on seeded porous mullite tubes from a milk-like aluminosilicate gel with the composition SiO2:Al2O3:Na2O:K2O:H2O= 1:0.05:0.26:0.09:14.

2.Single-component gas permeation experiments displayed

that the zeolite T membranes had a very little amount of defects and their gas permeation behavior was affected by the synergetic effect of preferential adsorption and molecular sieving.

3.The zeolite T membranes displayed the highest PV per-

formance for water/organic liquid mixtures next to zeo-lite NaA membranes,which was attributed to the syn-ergetic effects of competitive adsorption and single?le diffusion in the zeolitic pores.

4.The zeolite T membranes were practically stable to acetic

acid solutions,and can be used for the dehydration of organic liquids containing organic acid.Acknowledgements

This work was supported partly by a Grant-in-aid for Scienti?c Research(A)(No.13355031)from the Ministry of Education,Culture,Sports,Science and Technology of Japan.

References

[1]F.Lipnizki,R.W.Field,P.-K.Ten,Pervaporation-based hybrid pro-

cess:a review of process design,J.Membrane Sci.153(1999)183, and references therein.

[2]X.Feng,R.Y.M.Huang,Liquid separation by membrane pervapora-

tion;a review,Ind.Eng.Chem.Res.36(1997)1048,and references therein.

[3]H.Kita,K.Horii,Y.Ohtoshi,K.Tanaka,K.I.Okamoto,Synthesis

of a zeolite NaA membrane for pervaporation of water/organic liquid mixtures,J.Mater.Sci.Lett.14(1995)206.

[4]K.I.Okamoto,H.Kita,K.Horii,K.Tanaka,Zeolite NaA membrane:

preparation,single-gas permeation,and pervaporation and vapor per-meation of water/organic liquid mixtures,Ind.Eng.Chem.Res.40 (2001)163.

[5]H.Kita,T.Inoue,H.Asamura,K.Tanaka,K.I.Okamoto,NaY zeo-

lite membrane for the pervaporation separation of methanol-methyl tert-butyl ether mixtures,J.Chem.Soc.,https://www.360docs.net/doc/d85966319.html,mun.(1997)45.

[6]H.Kita,H.Asamura,K.Tanaka,K.I.Okamoto,Preparation and per-

vaporation properties of X-and Y-type zeolite membranes,in:I.Pin-nau,B.D.Freemann(Eds.),ACS Symposium Series744,Membrane Formation and Modi?cation,American Chemical Society,Washing-ton,DC,2000,p.330.

[7]H.Kita,K.Fuchida,T.Horita,H.Asamura,K.I.Okamoto,Prepara-

tion of faujasite membranes and their permeation properties,Sep.Pu-rif.Technol.25(2001)261.

[8]N.Nishiyama,K.Ueyama,M.Matsukata,Synthesis of defect-free

zeolite–alumina composite membranes by a vapor-phase transport methodology,Micropor.Mater.7(1996)299.

[9]X.Lin,E.Kikuchi,M.Matsukata,Preparation of mordenite mem-

branes on?-alumina tubular supports for pervaporation of wa-ter/isopropyl alcohol mixtures,https://www.360docs.net/doc/d85966319.html,mun.(2000)957. [10]T.Sano,H.Yanagishita,Y.Kiyozumi,F.Mizukami,K.Haraya,

Separation of ethanol/water mixture by silicalite membrane on per-vaporation,J.Membrane Sci.95(1994)221.

[11]Q.Liu,R.D.Noble,J.L.Falconer,H.H.Funke,Organic/water sepa-

ration by pervaporation with a zeolite membrane,J.Membrane Sci.

117(1996)163.

[12]X.Lin,H.Kita,K.I.Okamoto,Silicalite membrane preparation,

characterization,and separation performance,Ind.Eng.Chem.Res.

40(2001)4069.

[13]Y.Morigami,M.Kondo,J.Abe,H.Kita,K.I.Okamoto,The?rst

large-scale pervaporation plant using tubular-type module with zeolite NaA membrane,Sep.Purif.Technol.25(2001)251.

[14]M.Kondo,M.Komori,H.Kita,K.I.Okamoto,Tubular-type perva-

poration module with zeolite NaA membrane,J.Membrane Sci.133 (1997)133.

[15]R.Szostak,Molecular Sieves,Principles of Synthesis and Identi?-

cation,Van Nostrand Reinhold,New York,1989,p.313.

[16]M.Muller,G.Harvey,R.Prins,Comparison of the dealumination of

zeolites beta,mordenite,ZSM-5and ferrierite by thermal treatment, leaching with oxalic acid and treatment with SiCl4by1H,29Si and 27Al MAS NMR,Micropor.Mesopor.Mater.34(2000)135. [17]J.Hedlund,M.Noack,P.K?lsch,D.Creaser,J.Caro,J.Serte,

ZSM-5membranes synthesized without organic templates using a seeding technique,J.Membrane Sci.159(1999)263.

Y.Cui et al./Journal of Membrane Science236(2004)17–2727

[18]G.Li,E.Kikuchi,M.Matsukata,Separation of water–acetic acid

mixtures by pervaporation using a thin mordenite membrane,Sep.Pu-rif.Technol.32(2003)199.

[19]L.Casado,R.Mallada,C.Tellez,J.Coronas,M.Menendez,J.San-

tamaria,Preparation,characterization and pervaporation performance of mordenite membranes,J.Membrane Sci.216(2003)135. [20]S.Ueda,M.Nishimura,M.Koizumi,Synthesis of offretite–erionite

type zeolite from solution phase,Stud.Surf.Sci.Catal.24(1985) 105.

[21]X.Wang,R.Xu,Studies on the transformation between erionite and

offretite in T-type zeolite,Stud.Surf.Sci.Catal.24(1985)111. [22]K.Lillerud,J.Raeder,H.Johan,On the synthesis of erionite–offretite

intergrowth zeolites,Zeolites6(1986)474.

[23]M.Occelli,R.A.Innes,S.S.Pollack,J.V.Sanders,Quaternary am-

monium cation effects on the crystallization of offretite–erionite type zeolites.Part1.Synthesis and catalytic properties,Zeolites7(1987) 265.

[24]W.Inaoka,S.Kasahara,T.Fukushima,K.Igawa,Synthesis and

characterization of zeolites,Stud.Surf.Sci.Catal.60(1991)37. [25]S.Yang,N.P.Evmiridis,Synthesis and characterization of an of-

fretite/erionite type zeolite,Micropor.Mater.6(1996)19.

[26]S.S.Khvoshchev,M.A.Shubaeva,I.V.Karetina,Y.V.Shapoval,Syn-

thesis and characterization of low-silica erionite–offretite,in:Pro-ceedings of the12th International Zeolite Conference,vol.3,1998, 1999,p.1961.

[27]L.Mouda?,R.Dutartre, F.Fajula, F.Figueras,Synthesis of

TMA-offretite from natural silicates,Appl.Catal.20(1986)189.

[28]M.G.Howden,Synthesis of https://www.360docs.net/doc/d85966319.html,ing various organic

compounds as templates,Zeolites7(1987)255.

[29]M.G.Howden,Synthesis of offretite.Part https://www.360docs.net/doc/d85966319.html,ing a combina-

tion of tetramethylammonium cations and monoethanolamine or 1,2-diaminoethane as template,Zeolites7(3)(1987)260.[30]L.Mouda?,P.Massiani,F.Fajula,F.Figueras,In?uence of sodium

ions in the synthesis of offretite,Zeolites7(1987)63.

[31]S.Krais,Synthetic erionite-zeolite T,Pet.Coal.38(1996)57.

[32]J.P.Verduijn,Manufacture of offretite-type zeolites,PCT Int.Appl.

9703020,1997.

[33]F.Gao,X.Li,G.Zhu,S.Qui, B.Wei, C.Shao,O.Terasaki,

The synthesis of offretite single crystals in the system containing pyrocatechol or F,Mater.Lett.48(2001)1.

[34]F.Gao,G.Zhu,X.Li,S.Qiu,B.Wei,C.Shao,O.Terasaki,The

synthesis of offretite single crystals using pyrocatechol as complex agent,Stud.Surf.Sci.Catal.135(2001)519.

[35]S.Takaki,H.Kita,K.I.Okamoto,Symp.Ser.Soc.Chem.Eng.Jpn.

66(1998)90.

[36]K.Tanaka,R.Yoshikawa,C.Ying,H.Kita,K.I.Okamoto,Appli-

cation of zeolite membranes to esteri?cation reactions,Catal.Today 67(2001)121.

[37]K.Tanaka,R.Yoshikawa,C.Ying,H.Kita,K.I.Okamoto,Ap-

plication of zeolite T membrane to vapor-permeation-aided ester-i?cation of lactic acid with ethanol,Chem.Eng.Sci.57(2002) 1577.

[38]M.E.van Leeuwen,Derivation of Stockmayer potential parameters

for polar?uids,Fluid Phase Equilibr.99(1994)1.

[39]J.Caro,M.Noack,P.Kolsch,R.Schafer,Zeolite membranes-state

of their development and perspective,Micropor.Mesopor.Mater.38 (2000)3.

[40]B.H.Jeong,Y.Hasegawa,K.Sotowa,K.Kusakabe,S.Morooka,

Permeation of binary mixtures of benzene and saturated C4–C7 hydrocarbons through an FAU-type zeolite membrane,J.Membrane Sci.213(2003)115.

[41]A.Cichocki,Changes of properties of zeolite T crystals during

gradual treatment with hydrochloric acid,Krist.Technol.13(1978) 991.

雅思口语素材汇总之端午节

雅思口语素材汇总之端午节 雅思口语素材:Dragon Boat Festival(端午节) Qu Yuan The Dragon Boat Festival, also called the Duanwu Festival, is celebrated on the fifth day of the fifth month according to the Chinese calendar. For thousands of years, the festival has been marked by eating zong zi (glutinous rice(糯米)wrapped to form a pyramid using bamboo or reed leaves) and racing dragon boats. The festival is best known for its dragon-boat races, especially in the southern provinces where there are many rivers and lakes. This regatta(赛舟会)commemorates the death of Qu Yuan , an honest minister who is said to have committed suicide by drowning himself in a river. Qu was a minister of the State of Chu situated in present-day Hunan and Hubei provinces, during the Warring States Period (475-221BC)(战国时期). He was upright, loyal and highly esteemed for his wise counsel that brought peace and prosperity to the state. However, when a dishonest and corrupt prince vilified Qu, he was disgraced and dismissed from office. Realizing that the country was now in the hands of evil and corrupt officials, Qu grabbed a large stone and leapt into the Miluo River on the fifth day of the fifth month. Nearby fishermen rushed over to try and save him but were unable to even recover his body. Thereafter, the state declined and was eventually conquered by the State of Qin. The people of Chu who mourned the death of Qu threw rice into the river to feed his ghost every year on the fifth day of the fifth month. But one year, the spirit of Qu appeared and told the mourners that a huge reptile(爬行动物)in the river had stolen the rice. The spirit then advised them to wrap the rice in silk and bind it with five different-colored threads before tossing it into the river. During the Duanwu Festival, a glutinous rice pudding called zong zi is eaten to symbolize the rice offerings to Qu. Ingredients such as beans, lotus seeds(莲子), chestnuts(栗子), pork fat and the golden yolk of a salted duck egg are often

雅思口语常用背诵素材

口语常用背诵素材 一,喜好和厌恶: 1.(释放压力)I guess most young people enjoy listening to music. It’s a perfect way to reduce stress/relieve stress. (*It’s a perfect stress-buster.) 2.(休闲)I think the best way to relax and kill time (kick back and relax) is to be with friends. Chatting with them helps me unwind/wind down (* Chatting with them is very therapeutic). 3.(放松)I found it pretty relaxing to flick through a magazine before going to bed (*before hitting the sack/hitting the hay). 4.(运动)Jogging on sunny days and simply basking in the sun(bathing in the sun) is super enjoyable(pleasurable). /Jogging is my favorite workout. It can always cheer me up after I’ve been down and depressed. And it can help me shed some unwanted weight. 5.(喜欢,提升心情)I’m quite into watching sitcom (I’m fascinated by, I’m crazy about, I adore, I’m very fond of...). Spending 20 minutes in front of the screen and having a good laugh after dinner really puts me in a better mood/ switch my mood/ lift my spirits. 6.(天气)I fancy spring most compared to the other three. Summer is simply too hot and stuffy (*muggy), and you can’t stay out for two minutes without getting sweaty and smelly. Autumn is too dry and winter too freezing cold. 7.(电影)I’m a movie buff (Movies are my biggest pastime), and I would either catch one on my couch or go to the movie theatre when they have the one I like on the big screen./ It's a great form of relaxation for me to while away the hours of a long flight, to keep my family together on the sofa, and to give me a bit of a thrill. 8.(无聊困难)I’m terrible at what I study now./(History is never my forte/ my strong suit). The classes are kind of a drag (It’s super dull/ *It’s mind-numbing), and there’s always loads of (tons of) homework to do. Memorizing those facts and years is a lot of effort (is tricky; is no picnic; is challenging for me). 9.(不能忍)I can’t stand (I hate, I totally dislike) the busy traffic in my city. I’m sick and tired of always getting stuck in traffic for a long time during rush hours. It really bothers me (It drives me crazy, *It drives me up the wall). 10. (受欢迎)Hip-hop is really trendy (is catching on, is all the rage) among young people these days. 二,时间和地点 11. (优点)What’s great about my home town is that there are plenty of shopping malls, coz I’m a shopaholic and I can shop for hours. 12. (远)The stadium is quite far away from where I live, and every time I want to do there, it takes me roughly 40 minutes by bus to arrive. (It’s one-hour drive from the city center.) 13. (方便)My apartment is in the center/heart of the city, a handy location where I can find supermarkets and clubs right on my doorstep. It’s a bit noisy though. 14. (近)I’m a movie-goer and and there’s a movie theater pretty close to my home, so I go there quite often (frequently). (close to my home= *within walking distance of my home , *in close proximity to my home) 15. (经常)I have a heavy workload at school, so I have to go to the library to study pretty much

雅思口语素材

雅思口语素材 Document serial number【LGGKGB-LGG98YT-LGGT8CB-LGUT-

Useful Expressions: Words and phrases Friends and communication: solidify/ strengthen/ enhance/ promote communication / connection with mutual understanding relationship network/circle of f r i e n d s cultivate/develop friendship with s b . keep steady relationship with sb. establish interpersonal networksac build up the social circle spur message transmission Knowledge and experience widen one’s outlook broaden one’s vision/horizon acquire knowledge and skills comprehensive/overall quality

expand/enlarge one’s scope of knowledge knowledge reserve/base/storage theoretical knowledge practical skills social experience broaden one’s knowledge base promote one’s overall/ comprehensive competence accumulate experiences learn lessons from past experiences Work and experience the scarcity of employment o p p o r t u n i t i lay the foundations for career p r o s p e r i t y

雅思口语素材

U s e f u l E x p r e s s i o n s: Words and phrases Friends and communication: mutual understanding solidify/ strengthen/ enhance/ promote communication / connection with relationship network/circle of friends cultivate/develop friendship with sb. keep steady relationship with sb. establish interpersonal networksac build up the social circle spur message transmission Knowledge and experience widen one’s outlook broaden one’s vision/horizon acquire knowledge and skills comprehensive/overall quality expand/enlarge one’s scope of knowledge knowledge reserve/base/storage theoretical knowledge practical skills social experience broaden one’s knowledge base promote one’s overall/ comprehensive accumulate experiences competence learn lessons from past experiences Work and experience the scarcity of employment opportunities lay the foundations for career prosperity immerse oneself in endless job tasks boost/augment/enhance efficiency be adept in boost one’s c ompetitiveness Health and pressure diminish individuals' leisure time drive away lassitude lighten one’s burden homework/workforce overload

近期雅思口语卡片新题素材汇总

近期雅思口语卡片新题素材汇总 人物Describe a classmate of yours Describe a good friend Describe a happy person Describe a colleague Describe a neighbor Describe your own personality Describe a family member Describe a child you know Describe an old person Describe an old person who has influenced you the most Describe a successful person Describe a singer Describe a sportsman Describe a movie star Describe a character in TV or movie Describe a teacher of yours Describe a famous person that you want to spend a day with.地点Describe a building at schools Describe a historical place

Describe a monument Describe an interesting building Describe a lake, river or sea. Describe a peaceful place Describe a leisure place Describe a park Describe a place of interest Describe a natural beauty Describe a city you want to live in Describe a place you have visited Describe a place you always go for shopping

Simon考官范文-雅思口语素材2(Cook整理)

一.雅思P2相关话题 一日假期 和外国朋友一起吃饺子的建议 1.The best way to eat a dumpling is in one bite. “Dumplings are designed to be consumed in one mouthful, as it’s the best way to enjoy the combination of the meat filling and the very thin and springy flour wrapper,” If you can’t use chopsticks, eat your dumplings with your fingers. Avoid using a fork at all costs, as piercing the dumpling will compromise the flavour. 3.Mix two parts vinegar with one part soy sauce for the perfect dumpling sauce. Add young ginger slices too, Chili oil is also a great addition when available. 4.Dumplings are just one element of dim sum. “Dim sum doesn’t just include dumplings. It’s also braised dishes like pork ribs, chicken feet, and beef balls. It’s actually small tapas-style dishes that are eaten in Cantonese restaurants at lunchtime,” 5.Xiao long bao dumplings are different from others as they contain broth. They originated in the Jiangnan region of China and are prepared in bamboo steaming baskets called xiao long, hence the name. 6.When eating xiao long bao or a dumpling with a ~soupy~ interior, opt for chopsticks and a spoon. “As soon as the dumplings arrive at your table, lift one from the steamer basket onto a soup spoon. Next, tear the skin of the dumpling by pressing the chopsticks from the side of the dumpling onto the spoon. The broth will ooze out onto the spoon. Sip the soup then enjoy the dumpling in one mouthful.” 7.You can tell whether your dumpling was cooked fresh or frozen by looking at the skin. “The skin of a freshly made dumpling is springy and light. “Frozen ones tend to be soggy.” 8.When makingdumplingsat home, try to keep your packages small.

(完整word版)雅思口语素材整理汇总

雅思口语素材训练 by Tina Li Do you like music??A—肯定:Definitely yes, everyone enjoys music, and I am no exception! I love... 否定 :Well, honestly speaking, music is really not my cup of tea, simply because... ( 给出直接原因) What—pop, techno ( 电音音乐), hip-hop, rock, meditation ( 冥想乐) and especially light music.( 罗列名词) Where—Normally speaking, I would like to listen to music with my earphones when I take a ride on public transportation. ( 给出一个具体的场景) When—As long as I couldn’t go to sleep, I’d like to listen to some light music to calm myself down. ( 给出一个条件 :As long as I..., I would...)

Who—My most favourite singers include Adele, James Blunt, Avril Lavigne, and so forth. ( 喜欢的歌手) Why—I am fond of music mainly because it can cheer me up greatly when I feel down/low/ blue/bored/tired/depressed. ( 心情不好的时候让我高兴起来)?Besides, I also believe that music is an indispensable part of culture and tradition, through which I could have a better understanding of different cultures around the world, including cowboy culture, African-American street culture, the three main reli- gions and so on. ( 有助于理解不同的文化) Do you like watching movies?? A—Speaking of movies, yes, I am a big fan of all types of movies, such as...?What—comedy, action, romance, sci-fi, manga, vampire, zombie, animation...

雅思口语part 2 素材分类整理

做有偿工作的人 Describe a person you know who is doing a paid job. You should say: Who this person is What job it is; How long the job lasted; And explain why you or this person chose to do this job. 让你笑的小孩 Describe a time that a child did something that made you laugh. You should say: When this happened Who the child was What the child did And explain why it was funny 特殊的旅行 Describe an educational trip you went on when you were in school. You should say: When and where you went; Who you went with; What you did; And explain what you learned on this trip.

Describe an electronic machine you want to buy. You should say: What it is When you know this machine What specific And explain why you want this machine 难忘的广告 Describe an unforgettable advertisement (that you saw or heard liked) You should say: Where you saw or heard it What kind of advertisement it was What the contents of the advertisement were (or, what product or service was advertised) And explain how you felt when you saw or heard this advertisement/why you like it

【2019-2020】雅思口语话题素材-精选word文档 (1页)

【2019-2020】雅思口语话题素材-精选word文档 本文部分内容来自网络整理,本司不为其真实性负责,如有异议或侵权请及时联系,本司将立即删除! == 本文为word格式,下载后可方便编辑和修改! == 雅思口语话题素材 雅思口语素材总结雅思口语要求学生平时多多的积累素材,在口语方面要不断的加强练习。烤鸭们要多模拟不同的场景,多用丰富的口语短语,这 样你的雅思口语水平才能越来越高。下面是常用的一些口语短语,供大家参考! 1、 a change of pace 改变步调;换口味 You cant do these chemistry experiments all day long . You certainly need a change of pace . 2、 a far cry from 相距甚远 The published book is a far cry from the early manuscript . 3、 and how 的确 A : Shes a good dancer . B : And how . 4、 a matter of time 时间问题 It is only a matter of time . 5、 a phone call away 一个电话之远,即愿意过来帮忙 If you need my help , do let me know . Just remember I am a phone call away . 6、 a while back 不久以前 Well , I listened to that CD you lent me a while back . 7、 all along 一直 I knew it all along . 8、 anything but 绝对不 I was anything but happy about going . 9、 account for 解释 How do you account for it ? 10、 after all 毕竟;终究 A : Ive just seen the X - rays and your teeth look just fine . B : I see . Then there is nothing to worry about after all . 11、allergic to 对过敏 Oh man ! Something in this room is making my eyes itch . I must be allergic to something . 12、 at sbs service 愿为某人服务 I am at your service at any time . 13、 around the clock 24小时不停 Martha studied around the clock for management exam . 14、 as far as I know 就我所知 But as far as I know , he once won the world champion at the Olympic Games . 15、 at home with 对很熟悉 She is at home with problems like this . 16、 back out 退出 A : Wasnt Bert supposed to sing tonight ? B : Yes , but he backed out at last minute . 17、be cut out for 适合于,有做某事物的天赋 She is cut out for a dancer . 18、 be absorbed in 全神贯注于某事物 She has been absorbed in a horrorfiction . I cant tear her away . 19、 be addicted to 对某事物上瘾 She has been addicted to drugs for years . 20、 be attached to 对某事物有感情 A : Im amazed that you are still driving that old car of yours . I thought you would have gotten rid of it years ago . B : It runs well and Ive actually been quite attached to it .

雅思口语话题素材积累:Hometown

雅思口语雅思托福技巧雅思口语-美联国际教育雅思口语话题素材积累:Hometown 2014-02-18 17:00 类别:雅思口语来源:enguo 责编:meten 考生们在练习备考雅思口语过程中,可以多从身边的生活中取材,锻炼自己的口语表达能力。下面小编就为大家整理了雅思口语话题素材:Hometown,希望对大家备考有所帮助。 1、Where do you come from? 2、What tourist attractions are there in your hometown? Would a foreign visitor enjoy them? 3、Did you learn much about the history of your hometown in school? 4、What do you think needs to change in your hometown? 5、What place(s) in your hometown do you go to in your spare time? 6、Why did you choose to live here/there? 7、What do you like about your hometown? 8、What do you think needs to be done to make your hometown a better place to live in? 9、For you, what benefits are there to living in a big city? 10、What facilities does your hometown have? 11、What sorts of buildings are there in your hometown? 12、What's the most attractive part of your hometown? 13、What forms of transport do visitors use to come to your hometown? 14、How could your hometown attract more visitors? 15、Has the weather in your hometown changed much in recent years? Important: At the moment (2012) in China, there are about 30 different topics being used in Part 1. These topics and questions are in the examiner's question book(topic pool), the examiner is not allowed to make his or her own questions in Part 1 test. 众所周知,雅思口语考试是非常重视临场发挥的,虽然这些雅思口语考试试题看上去都很平常,但是还是要求大家在自己熟悉的题目和熟悉的事物中发挥自己的真实水平,所以大家一定不能掉以轻心,平时就要多加训练,在考场上正常甚至超常发挥出来。

雅思口语高分模板汇总

雅思口语高分模板汇总 多看一些雅思口语高分模板,有助于提升英语说话的逻辑,还能增强我们遣词造句的能力。下面就和大家分享,来欣赏一下吧。 雅思口语高分模板:描述兴趣爱好的话题 雅思口语高分模板一: From a middle class family, I was born in Hsin Ying, Tainan on October 10th, 1965. My father is a civil official at Tainan City Government. My mother is a house wife good at . Although I am the only child of my parents, I am by no mans a spoiled one. On the contrary, I have been expected to be . I study hard at school. Besides texts knowledge, journalism is my favorite; whenever reading, my heart is filled with great joy and interesting. 从中产阶级家庭,我出生在Hsin Ying,台南1965年10月10日。我父亲是台南市政府的一名公务员。我母亲是一位善于烹饪的家庭主妇。虽然我是我父母的独生子女,但我决不是一个被宠坏的孩子。相反,我被认为是一个成功的受过高等教育的人。我在学校努力学习。除了文字知识,新闻是我的最爱;每当阅读,我心中充满了极大的乐趣和乐趣。

雅思口语考试素材

雅思口语试题参考素材 1.被污染的地方 Last vacation, I went to Hainan with my family.Hainan is such a wonderful place that I will never forget it. It's really a good place where gave me a rather good impression. I feel so wonderful during the journey, as I have experienced a lot of things for the first time. The sky is also brighter and clearer than that I had ever seen. It was my first time to experience the sea and the beach in the sunshine. When sitting on the cruise, I could clearly see the ocean waves pushing the windows of the cruise. But last week, I went to Hainan again. I went to the beach the second time, but this trip changed my idea about its scenery. There were a lot of rubbish. The water was full of flotsam and refuse.When I walked along the sea, terrible smell went into my nose.The beach had been affected by pollution.Due to poor management, people who visited there damaged the environment. It is to be regretted that a beautiful place has gone.

雅思口语素材汇编

描述一个未来你想安家的地方。 This place is a coastal mountain in Hong Kong, I have been there followed a tour group last winter vacation.The mountain is not high, but it is arborous.And when you walk in the mountain,you will find the air is particularly fresh. The sky way stretching from the foot of the mountain to the peak , and there are many apartment buildings and villas in there. Down from the mountain is the ocean, it has soft beach as well as clear seawater,sea birds flying overhead time to time. The inhabitants of the mountain exercise along the highway by running or cycling every morning. I am aspire to live in that place because it isvery comfortable. In addition to the good environment , another reason I choose to make a home there is that, Hong Kong is an international metropolis, and there are a lot of employment opportunities, I think I can find a nice job there. And Hong Kong are referred to as the shopping paradise, the stuff is superior in quality and the price is relatively cheap. But in Hong Kong, people have a rapid pace of life, I think I can’t adapt to the fast pace of life. So living in the mountain far away from the downtown is a good choice for me because I can go to work in downtown during the day, and go back to the mountain to release the pressure of a day at night. In addition,the traffic is very developed in Hong Kong, so there is no need to worry about the traffic, I can arrive quickly at the downtown if i want. 我喜欢的一个喜剧演员是马特·勒布朗,他在情景喜剧《老友记》中饰演乔伊·崔比安尼。剧中乔伊与钱德勒为共租公寓的室友,是一位没什么天分但很执着的龙套演员,他从没有拍过什么很重要的角色,但是对于每一个上镜机会他都非常珍惜,非常认真。在拍戏方面的每一点进步都会让他非常兴奋。我觉得他是《六人行》里最单纯最可爱的一个人,他四肢发达、头脑简单,他的很多台词都非常搞笑,动作也很滑稽。另外乔伊是一个非常善良,富有爱心的人,他非常关心他的五个朋友,总能给人带去温暖。马特真的把这个演员演活了。从乔伊身上我们能看到自己的影子,虽然我们都是平凡的普通人,但是为了自己的梦想一直在努力,就算遇到很多挫折依然很乐观。我觉得这是马特塑造的这个角色最成功的地方,它能给人带去希望。 One of my favorite comedian is Matt Leblanc, he played in the situation come dy Friends,which i watched a couple years ago,he played in friends as the cha racter,Joey Tribbiani . In Friends ,joey is an actor, an utility man.Although he had never took a chance to play a big role,he cherish every chance he got.An d with one hundred percent of the effort.Every bit of progress in performance would make him very excited. I think he is a simple person as well as the most lovely one in Friends.he is limbs developed but simple-minded, and many of his lines are very funny, actionsare also very funny, Matt just make the ch

相关文档
最新文档