Effect of catalyst on formation of poly(methyl methacrylate) brushes by surface initia
负载固相的铑基催化剂应用于烯烃氢甲酰化反应的研究进展
2018年第37卷第4期 CHEMICAL INDUSTRY AND ENGINEERING PROGRESS·1433·化 工 进展负载固相的铑基催化剂应用于烯烃氢甲酰化反应的研究进展高李杰1，孟凯2，姜伟丽1，周广林1，周红军1，余长春1（1中国石油大学(北京)新能源研究院，生物燃气高值利用北京市重点实验室，北京102249；2山东省纤维检验局，山东 济南 250021）摘要：负载固相的催化剂因其简便的分离循环操作以及可观的催化性能而广受关注，但存在反应活性较差、金属流失量较大、催化剂制备成本较高等问题。
本文首先从不同负载材料的角度综述了近年来该类催化剂最新的研究进展，主要探讨了载体的表面性质、催化剂的制备方法、膦配体等对催化性能的影响；最后介绍了新型的单原子催化剂所取得的突破性进展。
分析表明：具有“类均相”特点的多孔有机聚合物的催化活性很好，而超支化聚合物功能化的磁性纳米催化剂的稳定性更佳。
另外还对负载型铑催化剂未来的研究方向进行了展望：需要进一步加深对多孔有机聚合物的化学结构的理解，以便对其更好地表征；借助一些先进的表征技术如高角环状暗场扫描透射电镜和密度泛函理论的计算来深入研究载体结构对单原子催化剂的催化性能的影响。
关键词：催化剂载体；氢甲酰化反应；多相反应；烯烃；纳米粒子中图分类号：O643.3 文献标志码：A 文章编号：1000–6613（2018）04–1433–09 DOI ：10.16085/j.issn.1000-6613.2017-1096Research progress of immobilized Rh-based catalysts on solid supportsfor olefin hydroformylationGAO Lijie 1，MENG Kai 2，JIANG Weili 1，ZHOU Guanglin 1，ZHOU Hongjun 1，YU Changchun 1（1Institute of New Energy ，Beijing Key Laboratory of Biogas Upgrading Utilization ，China University of Petroleum ，Beijing 102249，China ；2Shandong Fiber Inspection Bureau ，Jinan 250021, Shandong, China ）Abstract: Due to its simple separation ，easy recycling and excellent catalytic performance, the immobilized Rh-based catalyst on solid supports attracts much attention. However ，there are some problems such as poor reactivity ，large amount of metal loss and high cost on catalyst preparation. In this paper ，the recent progress of these catalysts in recent years is summarized from the perspective of different supported materials. The effects of the surface properties of the supported catalysts, their preparation methods and the phosphine ligands on the catalytic performance are discussed. Finally ，the breakthroughs in the new single-atom catalysts are introduced. The results show that the catalytic activity of porous organic polymers is very good ，while the stability of hyperbranched polymer functionalized magnetic nano-catalysts is better. Future research should be committed to understanding the chemical structure of porous organic polymers in order to better characterize them ，and the effect of the carrier structure on the catalytic performance of single-atom catalysts with the assistance of some advanced characterization techniques such as high-angle annular dark field scanning transmission electron microscopy and density functional theory calculations.Key words ：catalyst support ；hydroformylation reaction ；multiphase reaction ；olefin ；nanoparticle1 氢甲酰化反应氢甲酰化反应是工业应用最广泛的均相催化反收稿日期：2017-06-07；修改稿日期：2017-12-19。
有机胺催化制备聚碳酸酯二元醇
第26卷第5期高分子材料科学与工程Vol.26,No.5 2010年5月POL YM ER MA TERIAL S SCIENCE AND EN GIN EERIN GMay 2010有机胺催化制备聚碳酸酯二元醇郝俊松1,杜 娟1,刘少勇2,訾少宝2,李再峰1(1.生态化工教育部重点实验室,青岛科技大学化学院,山东青岛266042;2.烟台华大化学工业有限公司,山东烟台264002)摘要:以碳酸二甲酯(DMC )和1,42丁二醇(BDO )为原料,在三乙胺等有机胺类催化剂催化下,酯交换制备出聚碳酸酯二元醇(PCDL )。
采用核磁共振和红外光谱等分析手段鉴定产物的结构;凝胶渗透色谱分析减压时间对PCDL 分子量分布的影响。
详细研究了原料摩尔比(DMC/BDO )、催化剂用量、减压时间等因素对反应过程的影响,优化了PCDL 的合成工艺参数。
实验结果表明,当DMC/BDO 的摩尔比为112～1125,催化剂用量占BDO 的质量分数为0.5%,采用阶段控温方式制备出数均分子量在1600g/mol 左右的PCDL 。
关键词:碳酸二甲酯;有机胺;酯交换反应;绿色工艺中图分类号:TQ323.4+1 文献标识码:A 文章编号:100027555(2010)0520009204收稿日期:2009203225基金项目:山东省自然科学基金资助项目(Y2008B08);山东省中青年科学家奖励基金(2007BS04001);山东省科技攻关计划2008GG10003008通讯联系人:李再峰,主要从事材料物理化学研究, E 2mai :lizfengphd @ 聚氨酯是由多元醇和多异氰酸酯逐步聚合制备得到的,常用的多元醇主要是聚酯多元醇和聚醚多元醇。
而由聚碳酸酯二元醇(PCDL )[1,2]合成的聚氨酯材料克服了传统聚酯型与聚醚型聚氨酯材料的缺点,具有优良的力学性能、耐水解稳定性和耐体内氧化性[3]。
因此,聚碳酸酯型聚氨酯的合成与应用研究受到广泛关注[4]。
DMC催化CO_2和环氧丙烷的调节共聚反应及其影响因素
第27卷第11期高分子材料科学与工程Vol .27,N o .11 2011年11月POLYM ER MATERIALS SCIENCE AND ENGINEERINGNo v .2011DMC 催化C O 2和环氧丙烷的调节共聚反应及其影响因素周统昌1,2,邹志强1,2,刘言平1,2,罗建新1,2,张 敏1,陈立班1(1.中国科学院广州化学研究所,广东广州510650; 2.中国科学院研究生院北京100039)摘要:以聚醚多元醇、二缩三乙二醇或季戊四醇作为分子量调节剂,用Zn -Co 双金属氰化物(DM C )高效催化CO 2和环氧丙烷(PO )调节共聚合成了数均分子量为3000～8000的多官能度脂肪族聚碳酸酯多元醇,共聚物的分子量基本符合设计要求。
几种分子量调节剂均能成功合成两官能度或四官能度的共聚产物,产物中碳酸酯键含量最高可达60%,催化效率最高达663g /g 催化剂,副产物最低可控制到4%。
文中还考察了温度、压力、调节剂及催化剂用量对共聚反应的影响,发现60℃的低温更有利于CO 2和环氧丙烷的共聚反应,而且要获得碳酸酯键含量较高的产物,需控制调节剂和催化剂的比例。
关键词:双金属氰化物催化剂;调节共聚;CO 2;环氧丙烷中图分类号:T Q 316.33+8 文献标识码:A 文章编号:1000-7555(2011)11-0017-04收稿日期:2010-10-22基金项目:广东省自然科学基金资助项目(9151065004000005);广东省工业攻关项目(2008B010600046)通讯联系人:张 敏,主要从事二氧化碳共聚的研究,E -mail :zhangmin @gic .ac .cn 自1969年Inoue [1]成功催化CO 2和环氧化物共聚以来,调节共聚得到的低分子量脂肪族聚碳酸酯多元醇(APC )在聚氨酯领域的应用已成为最具有工业前景的应用领域。
Takeda [2],Inoue [3],Kuyper [4],Shi -mazaki [5]先后报道了用调节共聚得到低分子量APC ,但是碳酸酯键含量都在15%以下,且副产物的含量高达20%到35%,实际上接近于聚醚而不是聚碳酸酯。
TS_1分子筛催化剂的修饰改性方法研究进展
郭洪臣等 用 ［１５］ ＮＨ３·Ｈ２Ｏ 处理钛硅分子筛，处理后，分子筛的骨架结构没有被破坏．ＴＳ－１分子筛 参 与 丙 烯 环 氧 化 反 应 时 与 双 氧 水 作 用 ，增 加 了 钛 （Ⅵ ）－ 超 氧 化 物 的 量 ，利 于 分 子 筛 的 催 化 性 能 的 提 高 ．
有机碱改性主要利用季铵碱的碱性和模板剂作用，对 ＴＳ－１原粉二次水热结晶，使部分非骨架钛转 化 为 骨架钛［１６］．Ｗａｎｇ等 用 ［１７－１８］ ＴＰＡＯＨ 对 ＴＳ－１ 进 行 改 性，Ｔｉ骨 架 的 重 新 架 构，骨 架 钛 含 量 增 加，大 大 地 提 升
目前，硅烷化改性方法均采用硅烷化试 剂，通 过 浸 渍 方 式 处 理 ＴＳ－１ 分 子 筛 催 化 剂．但 是 硅 烷 化 试 剂 易 水 解 ，进 而 覆 盖 催 化 剂 的 活 性 中 心 ，并 且 溶 剂 消 耗 量 大 ，难 以 回 收 ，严 重 污 染 环 境 ． １．２ 酸 改 性
经典合 成 方 法 中，由 于 有 机 钛 酯 与 有 机 硅 酯 的 水 解 速 率 不 一 致，水 解 过 程 不 易 控 制，容 易 形 成 非 骨 架
Ｔｉ．非骨架 Ｔｉ本身并不具有催化氧化活性但会引起双氧水的大量分解，由此导致 ＴＳ－１催化性能的 降 低．同 时非骨架钛的含量难以控制，这导致钛硅分子筛的活性和稳定性差．因此需要对 钛 硅 分 子 筛 进 行 改 性 处 理， 以减少非骨架 Ｔｉ的存在．酸性条件可以有效脱除非骨架钛物种，是一种传统的分子筛改性方法 ． ［９－１０］
半导体制造技术
Semiconductor Manufacturing Technology半导体制造技术Instructor’s ManualMichael QuirkJulian SerdaCopyright Prentice HallTable of Contents目录OverviewI. Chapter1. Semiconductor industry overview2. Semiconductor materials3. Device technologies—IC families4. Silicon and wafer preparation5. Chemicals in the industry6. Contamination control7. Process metrology8. Process gas controls9. IC fabrication overview10. Oxidation11. Deposition12. Metallization13. Photoresist14. Exposure15. Develop16. Etch17. Ion implant18. Polish19. Test20. Assembly and packagingII. Answers to End-of-Chapter Review QuestionsIII. Test Bank (supplied on diskette)IV. Chapter illustrations, tables, bulleted lists and major topics (supplied on CD-ROM)Notes to Instructors:1)The chapter overview provides a concise summary of the main topics in each chapter.2)The correct answer for each test bank question is highlighted in bold. Test bankquestions are based on the end-of-chapter questions. If a student studies the end-of-chapter questions (which are linked to the italicized words in each chapter), then they will be successful on the test bank questions.2Chapter 1Introduction to the Semiconductor Industry Die:管芯 defective:有缺陷的Development of an Industry•The roots of the electronic industry are based on the vacuum tube and early use of silicon for signal transmission prior to World War II. The first electronic computer, the ENIAC, wasdeveloped at the University of Pennsylvania during World War II.•William Shockley, John Bardeen and Walter Brattain invented the solid-state transistor at Bell Telephone Laboratories on December 16, 1947. The semiconductor industry grew rapidly in the 1950s to commercialize the new transistor technology, with many early pioneers working inSilicon Valley in Northern California.Circuit Integration•The first integrated circuit, or IC, was independently co-invented by Jack Kilby at Texas Instruments and Robert Noyce at Fairchild Semiconductor in 1959. An IC integrates multiple electronic components on one substrate of silicon.•Circuit integration eras are: small scale integration (SSI) with 2 - 50 components, medium scale integration (MSI) with 50 – 5k components, large scale integration (LSI) with 5k to 100kcomponents, very large scale integration (VLSI) with 100k to 1M components, and ultra large scale integration (ULSI) with > 1M components.1IC Fabrication•Chips (or die) are fabricated on a thin slice of silicon, known as a wafer (or substrate). Wafers are fabricated in a facility known as a wafer fab, or simply fab.•The five stages of IC fabrication are:Wafer preparation: silicon is purified and prepared into wafers.Wafer fabrication: microchips are fabricated in a wafer fab by either a merchant chip supplier, captive chip producer, fabless company or foundry.Wafer test: Each individual die is probed and electrically tested to sort for good or bad chips.Assembly and packaging: Each individual die is assembled into its electronic package.Final test: Each packaged IC undergoes final electrical test.•Key semiconductor trends are:Increase in chip performance through reduced critical dimensions (CD), more components per chip (Moore’s law, which predicts the doubling of components every 18-24 months) andreduced power consumption.Increase in chip reliability during usage.Reduction in chip price, with an estimated price reduction of 100 million times for the 50 years prior to 1996.The Electronic Era•The 1950s saw the development of many different types of transistor technology, and lead to the development of the silicon age.•The 1960s were an era of process development to begin the integration of ICs, with many new chip-manufacturing companies.•The 1970s were the era of medium-scale integration and saw increased competition in the industry, the development of the microprocessor and the development of equipment technology. •The 1980s introduced automation into the wafer fab and improvements in manufacturing efficiency and product quality.•The 1990s were the ULSI integration era with the volume production of a wide range of ICs with sub-micron geometries.Career paths•There are a wide range of career paths in semiconductor manufacturing, including technician, engineer and management.2Chapter 2 Characteristics of Semiconductor MaterialsAtomic Structure•The atomic model has three types of particles: neutral neutrons（不带电的中子）, positively charged protons（带正电的质子）in the nucleus and negatively charged electrons（带负电的核外电子） that orbit the nucleus. Outermost electrons are in the valence shell, and influence the chemical and physical properties of the atom. Ions form when an atom gains or loses one or more electrons.The Periodic Table•The periodic table lists all known elements. The group number of the periodic table represents the number of valence shell electrons of the element. We are primarily concerned with group numbers IA through VIIIA.•Ionic bonds are formed when valence shell electrons are transferred from the atoms of one element to another. Unstable atoms (e.g., group VIIIA atoms because they lack one electron) easily form ionic bonds.•Covalent bonds have atoms of different elements that share valence shell electrons.3Classifying Materials•There are three difference classes of materials:ConductorsInsulatorsSemiconductors•Conductor materials have low resistance to current flow, such as copper. Insulators have high resistance to current flow. Capacitance is the storage of electrical charge on two conductive plates separated by a dielectric material. The quality of the insulation material between the plates is the dielectric constant. Semiconductor materials can function as either a conductor or insulator.Silicon•Silicon is an elemental semiconductor material because of four valence shell electrons. It occurs in nature as silica and is refined and purified to make wafers.•Pure silicon is intrinsic silicon. The silicon atoms bond together in covalent bonds, which defines many of silicon’s properties. Silicon atoms bond together in set, repeatable patterns, referred to asa crystal.•Germanium was the first semiconductor material used to make chips, but it was soon replaced by silicon. The reasons for this change are:Abundance of siliconHigher melting temperature for wider processing rangeWide temperature range during semiconductor usageNatural growth of silicon dioxide•Silicon dioxide (SiO2) is a high quality, stable electrical insulator material that also serves as a good chemical barrier to protect silicon from external contaminants. The ability to grow stable, thin SiO2 is fundamental to the fabrication of Metal-Oxide-Semiconductor (MOS) devices. •Doping increases silicon conductivity by adding small amounts of other elements. Common dopant elements are from trivalent, p-type Group IIIA (boron) and pentavalent, n-type Group VA (phosphorus, arsenic and antimony).•It is the junction between the n-type and p-type doped regions (referred to as a pn junction) that permit silicon to function as a semiconductor.4Alternative Semiconductor Materials•The alternative semiconductor materials are primarily the compound semiconductors. They are formed from Group IIIA and Group VA (referred to as III-V compounds). An example is gallium arsenide (GaAs).•Some alternative semiconductors come from Group IIA and VIA, referred to as II-VI compounds. •GaAs is the most common III-V compound semiconductor material. GaAs ICs have greater electron mobility, and therefore are faster than ICs made with silicon. GaAs ICs also have higher radiation hardness than silicon, which is better for space and military applications. The primary disadvantage of GaAs is the lack of a natural oxide.5Chapter 3Device TechnologiesCircuit Types•There are two basic types of circuits: analog and digital. Analog circuits have electrical data that varies continuously over a range of voltage, current and power values. Digital circuits have operating signals that vary about two distinct voltage levels – a high and a low.Passive Component Structures•Passive components such as resistors and capacitors conduct electrical current regardless of how the component is connected. IC resistors are a passive component. They can have unwanted resistance known as parasitic resistance. IC capacitor structures can also have unintentional capacitanceActive Component Structures•Active components, such as diodes and transistors can be used to control the direction of current flow. PN junction diodes are formed when there is a region of n-type semiconductor adjacent to a region of p-type semiconductor. A difference in charge at the pn junction creates a depletion region that results in a barrier voltage that must be overcome before a diode can be operated. A bias voltage can be configured to have a reverse bias, with little or no conduction through the diode, or with a forward bias, which permits current flow.•The bipolar junction transistor (BJT) has three electrodes and two pn junctions. A BJT is configured as an npn or pnp transistor and biased for conduction mode. It is a current-amplifying device.6• A schottky diode is formed when metal is brought in contact with a lightly doped n-type semiconductor material. This diode is used in faster and more power efficient BJT circuits.•The field-effect transistor (FET), a voltage-amplifying device, is more compact and power efficient than BJT devices. A thin gate oxide located between the other two electrodes of the transistor insulates the gate on the MOSFET. There are two categories of MOSFETs, nMOS (n-channel) and pMOS (p-channel), each which is defined by its majority current carriers. There is a biasing scheme for operating each type of MOSFET in conduction mode.•For many years, nMOS transistors have been the choice of most IC manufacturers. CMOS, with both nMOS and pMOS transistors in the same IC, has been the most popular device technology since the early 1980s.•BiCMOS technology makes use of the best features of both CMOS and bipolar technology in the same IC device.•Another way to categorize FETs is in terms of enhancement mode and depletion mode. The major different is in the way the channels are doped: enhancement-mode channels are doped opposite in polarity to the source and drain regions, whereas depletion mode channels are doped the same as their respective source and drain regions.Latchup in CMOS Devices•Parasitic transistors can create a latchup condition(???????) in CMOS ICs that causes transistors to unintentionally（无心的） turn on. To control latchup, an epitaxial layer is grown on the wafer surface and an isolation barrier（隔离阻障）is placed between the transistors. An isolation layer can also be buried deep below the transistors.Integrated Circuit Productsz There are a wide range of semiconductor ICs found in electrical and electronic products. This includes the linear IC family, which operates primarily with anal3og circuit applications, and the digital IC family, which includes devices that operate with binary bits of data signals.7Chapter 4Silicon and Wafer Preparation8z Semiconductor-Grade Silicon•The highly refined silicon used for wafer fabrication is termed semiconductor-grade silicon (SGS), and sometimes referred to as electronic-grade silicon. The ultra-high purity of semiconductor-grade silicon is obtained from a multi-step process referred to as the Siemens process.Crystal Structure• A crystal is a solid material with an ordered, 3-dimensional pattern over a long range. This is different from an amorphous material that lacks a repetitive structure.•The unit cell is the most fundamental entity for the long-range order found in crystals. The silicon unit cell is a face-centered cubic diamond structure. Unit cells can be organized in a non-regular arrangement, known as a polycrystal. A monocrystal are neatly arranged unit cells.Crystal Orientation•The orientation of unit cells in a crystal is described by a set of numbers known as Miller indices.The most common crystal planes on a wafer are (100), (110), and (111). Wafers with a (100) crystal plane orientation are most common for MOS devices, whereas (111) is most common for bipolar devices.Monocrystal Silicon Growth•Silicon monocrystal ingots are grown with the Czochralski (CZ) method to achieve the correct crystal orientation and doping. A CZ crystal puller is used to grow the silicon ingots. Chunks of silicon are heated in a crucible in the furnace of the puller, while a perfect silicon crystal seed is used to start the new crystal structure.• A pull process serves to precisely replicate the seed structure. The main parameters during the ingot growth are pull rate and crystal rotation. More homogeneous crystals are achieved with a magnetic field around the silicon melt, known as magnetic CZ.•Dopant material is added to the melt to dope the silicon ingot to the desired electrical resistivity.Impurities are controlled during ingot growth. A float-zone crystal growth method is used toachieve high-purity silicon with lower oxygen content.•Large-diameter ingots are grown today, with a transition underway to produce 300-mm ingot diameters. There are cost benefits for larger diameter wafers, including more die produced on a single wafer.Crystal Defects in Silicon•Crystal defects are interruptions in the repetitive nature of the unit cell. Defect density is the number of defects per square centimeter of wafer surface.•Three general types of crystal defects are: 1) point defects, 2) dislocations, and 3) gross defects.Point defects are vacancies (or voids), interstitial (an atom located in a void) and Frenkel defects, where an atom leaves its lattice site and positions itself in a void. A form of dislocation is astacking fault, which is due to layer stacking errors. Oxygen-induced stacking faults are induced following thermal oxidation. Gross defects are related to the crystal structure (often occurring during crystal growth).Wafer Preparation•The cylindrical, single-crystal ingot undergoes a series of process steps to create wafers, including machining operations, chemical operations, surface polishing and quality checks.•The first wafer preparation steps are the shaping operations: end removal, diameter grinding, and wafer flat or notch. Once these are complete, the ingot undergoes wafer slicing, followed by wafer lapping to remove mechanical damage and an edge contour. Wafer etching is done to chemically remove damage and contamination, followed by polishing. The final steps are cleaning, wafer evaluation and packaging.Quality Measures•Wafer suppliers must produce wafers to stringent quality requirements, including: Physical dimensions: actual dimensions of the wafer (e.g., thickness, etc.).Flatness: linear thickness variation across the wafer.Microroughness: peaks and valleys found on the wafer surface.Oxygen content: excessive oxygen can affect mechanical and electrical properties.Crystal defects: must be minimized for optimum wafer quality.Particles: controlled to minimize yield loss during wafer fabrication.Bulk resistivity(电阻系数): uniform resistivity from doping during crystal growth is critical. Epitaxial Layer•An epitaxial layer (or epi layer) is grown on the wafer surface to achieve the same single crystal structure of the wafer with control over doping type of the epi layer. Epitaxy minimizes latch-up problems as device geometries continue to shrink.Chapter 5Chemicals in Semiconductor FabricationEquipment Service Chase Production BayChemical Supply Room Chemical Distribution Center Holding tank Chemical drumsProcess equipmentControl unit Pump Filter Raised and perforated floorElectronic control cablesSupply air ductDual-wall piping for leak confinement PumpFilterChemical control and leak detection Valve boxes for leak containment Exhaust air ductStates of Matter• Matter in the universe exists in 3 basic states (宇宙万物存在着三种基本形态): solid, liquid andgas. A fourth state is plasma.Properties of Materials• Material properties are the physical and chemical characteristics that describe its unique identity.• Different properties for chemicals in semiconductor manufacturing are: temperature, pressure andvacuum, condensation, vapor pressure, sublimation and deposition, density, surface tension, thermal expansion and stress.Temperature is a measure of how hot or cold a substance is relative to another substance. Pressure is the force exerted per unit area. Vacuum is the removal of gas molecules.Condensation is the process of changing a gas into a liquid. Vaporization is changing a liquidinto a gas.Vapor pressure is the pressure exerted by a vapor in a closed container at equilibrium.Sublimation is the process of changing a solid directly into a gas. Deposition is changing a gas into a solid.Density is the mass of a substance divided by its volume.Surface tension of a liquid is the energy required to increase the surface area of contact.Thermal expansion is the increase in an object’s dimension due to heating.Stress occurs when an object is exposed to a force.Process Chemicals•Semiconductor manufacturing requires extensive chemicals.• A chemical solution is a chemical mixture. The solvent is the component of the solution present in larger amount. The dissolved substances are the solutes.•Acids are solutions that contain hydrogen and dissociate in water to yield hydronium ions. A base is a substance that contains the OH chemical group and dissociates in water to yield the hydroxide ion, OH-.•The pH scale is used to assess the strength of a solution as an acid or base. The pH scale varies from 0 to 14, with 7 being the neutral point. Acids have pH below 7 and bases have pH values above 7.• A solvent is a substance capable of dissolving another substance to form a solution.• A bulk chemical distribution (BCD) system is often used to deliver liquid chemicals to the process tools. Some chemicals are not suitable for BCD and instead use point-of-use (POU) delivery, which means they are stored and used at the process station.•Gases are generally categorized as bulk gases or specialty gases. Bulk gases are the relatively simple gases to manufacture and are traditionally oxygen, nitrogen, hydrogen, helium and argon.The specialty gases, or process gases, are other important gases used in a wafer fab, and usually supplied in low volume.•Specialty gases are usually transported to the fab in metal cylinders.•The local gas distribution system requires a gas purge to flush out undesirable residual gas. Gas delivery systems have special piping and connections systems. A gas stick controls the incoming gas at the process tool.•Specialty gases may be classified as hydrides, fluorinated compounds or acid gases.Chapter 6Contamination Control in Wafer FabsIntroduction•Modern semiconductor manufacturing is performed in a cleanroom, isolated from the outside environment and contaminants.Types of contamination•Cleanroom contamination has five categories: particles, metallic impurities, organic contamination, native oxides and electrostatic discharge. Killer defects are those causes of failure where the chip fails during electrical test.Particles: objects that adhere to a wafer surface and cause yield loss. A particle is a killer defect if it is greater than one-half the minimum device feature size.Metallic impurities: the alkali metals found in common chemicals. Metallic ions are highly mobile and referred to as mobile ionic contaminants (MICs).Organic contamination: contains carbon, such as lubricants and bacteria.Native oxides: thin layer of oxide growth on the wafer surface due to exposure to air.Electrostatic discharge (ESD): uncontrolled transfer of static charge that can damage the microchip.Sources and Control of Contamination•The sources of contamination in a wafer fab are: air, humans, facility, water, process chemicals, process gases and production equipment.Air: class number designates the air quality inside a cleanroom by defining the particle size and density.Humans: a human is a particle generator. Humans wear a cleanroom garment and follow cleanroom protocol to minimize contamination.Facility: the layout is generally done as a ballroom (open space) or bay and chase design.Laminar airflow with air filtering is used to minimize particles. Electrostatic discharge iscontrolled by static-dissipative materials, grounding and air ionization.Ultrapure deiniozed (DI) water: Unacceptable contaminants are removed from DI water through filtration to maintain a resistivity of 18 megohm-cm. The zeta potential represents a charge on fine particles in water, which are trapped by a special filter. UV lamps are used for bacterial sterilization.Process chemicals: filtered to be free of contamination, either by particle filtration, microfiltration (membrane filter), ultrafiltration and reverse osmosis (or hyperfiltration).Process gases: filtered to achieve ultraclean gas.Production equipment: a significant source of particles in a fab.Workstation design: a common layout is bulkhead equipment, where the major equipment is located behind the production bay in the service chase. Wafer handling is done with robotic wafer handlers. A minienvironment is a localized environment where wafers are transferred on a pod and isolated from contamination.Wafer Wet Cleaning•The predominant wafer surface cleaning process is with wet chemistry. The industry standard wet-clean process is the RCA clean, consisting of standard clean 1 (SC-1) and standard clean 2 (SC-2).•SC-1 is a mixture of ammonium hydroxide, hydrogen peroxide and DI water and capable of removing particles and organic materials. For particles, removal is primarily through oxidation of the particle or electric repulsion.•SC-2 is a mixture of hydrochloric acid, hydrogen peroxide and DI water and used to remove metals from the wafer surface.•RCA clean has been modified with diluted cleaning chemistries. The piranha cleaning mixture combines sulfuric acid and hydrogen peroxide to remove organic and metallic impurities. Many cleaning steps include an HF last step to remove native oxide.•Megasonics(兆声清洗) is widely used for wet cleaning. It has ultrasonic energy with frequencies near 1 MHz. Spray cleaning will spray wet-cleaning chemicals onto the wafer. Scrubbing is an effective method for removing particles from the wafer surface.•Wafer rinse is done with overflow rinse, dump rinse and spray rinse. Wafer drying is done with spin dryer or IPA(异丙醇) vapor dry (isopropyl alcohol).•Some alternatives to RCA clean are dry cleaning, such as with plasma-based cleaning, ozone and cryogenic aerosol cleaning.Chapter 7Metrology and Defect InspectionIC Metrology•In a wafer fab, metrology refers to the techniques and procedures for determining physical and electrical properties of the wafer.•In-process data has traditionally been collected on monitor wafers. Measurement equipment is either stand-alone or integrated.•Yield is the percent of good parts produced out of the total group of parts started. It is an indicator of the health of the fabrication process.Quality Measures•Semiconductor quality measures define the requirements for specific aspects of wafer fabrication to ensure acceptable device performance.•Film thickness is generally divided into the measurement of opaque film or transparent film. Sheet resistance measured with a four-point probe is a common method of measuring opaque films (e.g., metal film). A contour map shows sheet resistance deviations across the wafer surface.•Ellipsometry is a nondestructive, noncontact measurement technique for transparent films. It works based on linearly polarized light that reflects off the sample and is elliptically polarized.•Reflectometry is used to measure a film thickness based on how light reflects off the top and bottom surface of the film layer. X-ray and photoacoustic technology are also used to measure film thickness.•Film stress is measured by analyzing changes in the radius of curvature of the wafer. Variations in the refractive index are used to highlight contamination in the film.•Dopant concentration is traditionally measured with a four-point probe. The latest technology is the thermal-wave system, which measures the lattice damage in the implanted wafer after ion implantation. Another method for measuring dopant concentration is spreading resistance probe. •Brightfield detection is the traditional light source for microscope equipment. An optical microscope uses light reflection to detect surface defects. Darkfield detection examines light scattered off defects on the wafer surface. Light scattering uses darkfield detection to detectsurface particles by illuminating the surface with laser light and then using optical imaging.•Critical dimensions (CDs) are measured to achieve precise control over feature size dimensions.The scanning electron microscope is often used to measure CDs.•Conformal step coverage is measured with a surface profiler that has a stylus tip.•Overlay registration measures the ability to accurately print photoresist patterns over a previously etched pattern.•Capacitance-voltage (C-V) test is used to verify acceptable charge conditions and cleanliness at the gate structure in a MOS device.Analytical Equipment•The secondary-ion mass spectrometry (SIMS) is a method of eroding a wafer surface with accelerated ions in a magnetic field to analyze the surface material composition.•The atomic force microscope (AFM) is a surface profiler that scans a small, counterbalanced tip probe over the wafer to create a 3-D surface map.•Auger electron spectroscopy (AES) measures composition on the wafer surface by measuring the energy of the auger electrons. It identifies elements to a depth of about 2 nm. Another instrument used to identify surface chemical species is X-ray photoelectron spectroscopy (XPS).•Transmission electron microscopy (TEM) uses a beam of electrons that is transmitted through a thin slice of the wafer. It is capable of quantifying very small features on a wafer, such as silicon crystal point defects.•Energy-dispersive spectrometer (EDX) is a widely used X-ray detection method for identifying elements. It is often used in conjunction with the SEM.• A focused ion beam (FIB) system is a destructive technique that focuses a beam of ions on the wafer to carve a thin cross section from any wafer area. This permits analysis of the wafermaterial.Chapter 8Gas Control in Process ChambersEtch process chambers••The process chamber is a controlled vacuum environment where intended chemical reactions take place under controlled conditions. Process chambers are often configured as a cluster tool. Vacuum•Vacuum ranges are low (rough) vacuum, medium vacuum, high vacuum and ultrahigh vacuum (UHV). When pressure is lowered in a vacuum, the mean free path(平均自由行程) increases, which is important for how gases flow through the system and for creating a plasma.Vacuum Pumps•Roughing pumps are used to achieve a low to medium vacuum and to exhaust a high vacuum pump. High vacuum pumps achieve a high to ultrahigh vacuum.•Roughing pumps are dry mechanical pumps or a blower pump (also referred to as a booster). Two common high vacuum pumps are a turbomolecular (turbo) pump and cryopump. The turbo pump is a reliable, clean pump that works on the principle of mechanical compression. The cryopump isa capture pump that removes gases from the process chamber by freezing them.。
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Article
Promoting effects of Fe2O3 to Pt electrocatalysts toward methanol oxidation reaction in alkaline electrolyte
Guihua Song, Haifang Yang, Yafei Sun, Jingyi Wang, Weidong Qu, Qiang Zhang, Lingjuan Ma, Yuanyuan Feng *
Chinese Journal of Catalysis 38 (卷 第3期 |
available at
journal homepage: /locate/chnjc
Key Laboratory of Life‐Organic Analysis, College of Chemistry and Chemical Engineering, Qufu Normal University, Qufu 273165, Shandong, China
A R T I C L E I N F O
1. Introduction Direct methanol fuel cells (DMFCs) show great potential as future power sources for automobile power and portable elec‐ tronic devices owing to a number of advantages, such as the low operating temperature (< 100 °C), high energy efficiency, convenient transportation, low environmental pollution and fast start‐up time [1]. To date, the noble metal Pt is still the most active catalyst material both for the anodic and cathodic reactions of DMFCs and cannot be completely replaced by other base metals. Owing to the high cost of Pt, the commercial ap‐ plication of DMFCs has been limited. In addition, Pt is easily poisoned by the CO‐like intermediates in the process of the methanol electro‐oxidation reaction (MOR). The intermediates adsorb on the surface of Pt atoms, resulting in a significant de‐ crease in the catalytic performance of Pt, which further in‐ creases the cost of DMFCs. Over the past decades, a number of studies have focused on the investigation of Pt‐free electrocatalysts or the modification of Pt catalysts [2,3]. The traditional modification was accom‐ plished through the addition of other components or promot‐ ers. The components themselves exhibit no catalytic activity toward the reactions but can promote the activity of Pt during catalysis. It is well known that the addition of Ru to Pt catalysts
Heterogeneous photo-Fenton____ degradation of polyacrylamide
Journal of Hazardous Materials 162(2009)860–865Contents lists available at ScienceDirectJournal of HazardousMaterialsj o u r n a l h o m e p a g e :w w w.e l s e v i e r.c o m /l o c a t e /j h a z m atHeterogeneous photo-Fenton degradation of polyacrylamide in aqueous solution over Fe(III)–SiO 2catalystTing Liu,Hong You ∗,Qiwei ChenDepartment of Environmental Science and Engineering,Harbin Institute of Technology,P.O.Box 2606,202Haihe Road,Harbin 150090,PR Chinaa r t i c l e i n f o Article history:Received 29December 2007Received in revised form 8April 2008Accepted 22May 2008Available online 28May 2008Keywords:Photo-Fenton PolyacrylamideFe(III)–SiO 2catalystHeterogeneous catalysisa b s t r a c tThis article presents preparation,characterization and evaluation of heterogeneous Fe(III)–SiO 2catalysts for the photo-Fenton degradation of polyacrylamide (PAM)in aqueous solution.Fe(III)–SiO 2catalysts are prepared by impregnation method with two iron salts as precursors,namely Fe(NO 3)3and FeSO 4,and are characterized by Brunauer–Emmett–Teller (BET),X-ray diffraction (XRD)and X-ray photoelectron spectroscopy (XPS)methods.The irradiated Fe(III)–SiO 2is complexed with 1,10-phenanthroline,then is measured by UV–vis-diffuse reflectance spectroscopy (UV–vis-DRS)and XPS to confirm the oxidation state of Fe in solid state.By investigating the photo-Fenton degradation of PAM in aqueous solution,the results indicate that Fe(III)–SiO 2catalysts exhibit an excellent photocatalytic activity in the degradation of PAM.Moreover,the precursor species and the OH −/Fe mole ratio affect the photocatalytic activity of Fe(III)–SiO 2catalysts to a certain extent.Finally,the amount of Fe ions leaching from the Fe(III)–SiO 2catalysts is much low.©2008Elsevier B.V.All rights reserved.1.Introduction“Produced water”is the largest volume of waste generated by the oil industry.In particular,with the application of polymer flood-ing technology in tertiary oil recovery processes in China,a kind of new produced water containing polyacrylamide (PAM),a high molecular weight polymer,have been produced.The conventional method to dispose of such produced water is either re-injected into the subsurface for permanent disposal or discharged directly to the marine environment.However,both methods have caused serious contamination to the ground water and surface water.On the other hand,the current physical treatment processes (settling separation and filtration)can not satisfy the treatment requirement.Hence,the treatment technologies of produced water containing PAM have become a key problem in oil industry in China.Physical [1,2],biological [3,4]and chemical methods [5]are presently used for treatment of PAM.It was found that the degrada-tion ratio of PAM in aqueous solution was slow by using biological methods.Recently,some investigators have reported the successful application of advanced oxidation processes for PAM degradation [6,7].One of advanced oxidation processes,Fenton (a powerful source of oxidative HO •generated from H 2O 2in the presence of Fe 2+ions)or photo-Fenton reaction has been used in the degradation of∗Corresponding author.Tel.:+8645186283118;fax:+8645186283118.E-mail address:youhong@ (H.You).many organic compounds [8,9].Even though these systems are con-sidered as a very effective approach to remove organic compounds,it should be pointed out that there is a major drawback because the post-treatment of Fe sludge is an expensive process.This short-coming can be overcome by using heterogeneous photo-Fenton reaction.Therefore,a lot of effort has been made in developing heterogeneous photo-Fenton catalysts.For example,Parra et al.pre-pared Nafion/Fe structured membrane catalyst and used it in the photo-assisted immobilized Fenton degradation of 4-chorophenol [10].However,Nafion/Fe structured membrane catalyst is much expensive for practical use.Thus,the low cost supports such as the C structured fabric [11,12],activated carbon [13],mesoporous silica SBA-15[14–16],zeolite [17,18]and clay [19–21],have been used for the immobilization of active iron species.Remirez et al.prepared the catalysts using four iron salts as precursors for the heteroge-neous Fenton-like oxidation of Orange II solutions [22].The results showed that the nature of the iron salt had a significant effect on the process performance.So,it is necessary to discuss the photo-catalytic activities of the catalysts by using different iron salts as precursors.In this paper,a series of Fe(III)–SiO 2catalysts were prepared at different OH −/Fe mole ratio and by using two iron salts as precur-sors,namely Fe(NO 3)3and FeSO 4.All catalysts were characterized by BET,XRD and XPS.The oxidation state of Fe in the solid state was detected by the UV–vis-DRS and XPS measurement.The pho-tocatalytic activity of Fe(III)–SiO 2catalyst was evaluated in the photo-assisted Fenton degradation of PAM in aqueous solution in0304-3894/$–see front matter ©2008Elsevier B.V.All rights reserved.doi:10.1016/j.jhazmat.2008.05.110T.Liu et al./Journal of Hazardous Materials 162(2009)860–865861the presence of H 2O 2and UV light at an initial solution pH of 6.8.The effects of the precursor species and the OH −/Fe mole ratio on the photocatalytic activities of Fe(III)–SiO 2catalysts were also stud-ied.In addition,the leaching behavior of Fe from the catalyst surface was discussed.2.Experimental 2.1.MaterialsThe analytical grade PAM,H 2O 2(30%,w/w),Fe(NO 3)3·9H 2O,FeSO 4·7H 2O,NaOH and 1,10-phenanthroline were used for this experiment without further purification.The average molecular weight of PAM was 5000000Da and degree of hydrolysis of PAM was about 30%.Silica gel (40–60mesh)as a support was purchased from Qingdao Ocean Chemical Company,China.The aqueous solu-tion of PAM was prepared by dissolving a weighed quantity of PAM in distilled water.2.2.Preparation of the catalystsA series of catalysts were prepared by two methods as follows:(1)Two catalysts were prepared by impregnation of 20g silicagel in aqueous solution containing 0.05mol/L Fe(NO 3)3and 0.05mol/L FeSO 4,respectively and kept stirring for 6h.After aging for 40h at 105◦C,the samples were separated and washed several times with deionized water,then dried overnight at 80◦C.The dried samples were calcined at 500◦C for 5h in an oven.Finally,two Fe(III)–SiO 2catalysts were obtained,namely S-Fe 3+and S-Fe 2+.(2)Twenty grams of silica gel carrier were first added into the aque-ous solution containing 0.05mol/L Fe(NO 3)3and 0.05mol/L FeSO 4,respectively and kept under vigorous stirring for 2h.Then,NaOH aqueous solution with different concentration was added drop by drop under stirring until the OH −/Fe 3+or OH −/Fe 2+mole ratio was equal to 1and 2.After aging for 40h at 105◦C,the solid product were separated and washed several times with deionized water and dried overnight at 80◦C.The dried samples were calcined at 500◦C for 5h in an oven and the catalysts were named as S-Fe 3+/1,S-Fe 3+/2,S-Fe 2+/1and S-Fe 2+/2,respectively.2.3.Characterization of the catalystsThe iron content of Fe(III)–SiO 2catalysts were verified by an inductively coupled plasma (ICP)(Model:Perkin-Elmer 5300DV)after acidic digestion of the catalysts.Brunauer–Emmett–Teller (BET)specific surface area,total pore volume and average pore size of synthesized Fe(III)–SiO 2catalysts were measured by adsorption of nitrogen at 77K,by using auto-mated volumetric adsorption instrument (model Quantachrome Autosorb-1).X-ray diffraction (XRD)measurement was employed using a Rigaku D/max-rB system with Cu K ␣radiation operating at 45kV and 40mA.The 2Âranged from 10to 90◦.X-ray photo-electron spectroscopy (XPS)measurements were performed using a PHI 5700spectrometer.The X-ray source was operated at 250W and 12.5kV and the C 1s signal was adjusted to 284.62eV as the reference.The curve fitting was achieved by using a Physical Electronics PC-ACCESSESCA-V6.0E program with a Gaussian–Lorentzian sum function.Finally,UV–vis-diffuse reflectance spectroscopy (UV–vis-DRS)measurements were recorded on TU1901with a sphere reflectanceaccessory.Fig.1.Schematic diagram of three-phase fluidized bed photoreactor.2.4.Catalytic activityThe photocatalytic activities of Fe(III)–SiO 2catalysts were evaluated by degradation of PAM from aqueous solutions in a three-phase fluidized bed photoreactor (Fig.1).The light source was UV lamp (Philips,8W,254nm)fixed inside of a cylindrical quartz tube.The total volume of PAM aqueous solution was 1500mL.In order to ensure a good dispersion of Fe(III)–SiO 2catalysts and good mix-ture in solution,compressed air was bubbled from the bottom at a flow rate of 3.3L/min.For each experiment,the concentration of PAM and H 2O 2were 100and 200mg/L,respectively.The cata-lyst loading was fixed at 1.0g/L.The Fe(III)–SiO 2catalyst and H 2O 2were added into the photoreactor,at the same time,UV light was turned on and this was considered as the initial time for reaction.Then,samples were withdrawn at time intervals.The concentration of PAM in solution was measured by starch-CdI 2spectrophotom-etry [23].To determine mineralization of PAM solution,the total organic carbon (TOC)of the reaction solution was measured by a TOC-V CPN Shimadzu TOC analyzer.In addition,the concentration of Fe in reaction solution was monitored by ICP.2.5.Characterization of Fe(III)–SiO 2after the reactionIn order to know the oxidation state of Fe on Fe(III)–SiO 2catalyst surface under irradiation,the 1,10-phenanthroline was used which would be complexed with Fe(II)–SiO 2in solid state [17].0.03%1,10-phenanthroline and 0.6mol/L acetate buffer (pH 8.60)was added into the photoreactor and the S-Fe 2+/1catalyst was irradiated for 2h.After reaction,the sample was filtered,washed several times and dried,then characterized by UV–vis-DRS and XPS measure-ment.3.Results and discussion3.1.Characterization of the catalysts before reactionThe content of Fe in Fe(III)–SiO 2catalysts is shown in Table 1.It is observed that the Fe content in catalysts increases with the increase of OH −/Fe mole ratio in both Fe(NO 3)3and FeSO 4used as precursor.It should be mentioned that,with the increase of OH −/Fe mole ratio,the structure of iron species in the solution develops from the low-molecular-weight species into high polymerization degree cationic polymer [24].Therefore,with the increase of OH −/Fe mole ratio,862T.Liu et al./Journal of Hazardous Materials 162(2009)860–865Table 1The content of Fe in catalysts and the results of BET tests Samples The content of Fe (wt.%)BET surface area (m 2/g)Total porevolume (cm 3/g)Average porewidth (˚A)SiO 20419.00.9388.9969S-Fe 3+0.404446.00.9988.7406S-Fe 3+/10.496462.0 1.0288.4524S-Fe 3+/20.684470.0 1.0488.2624S-Fe 2+0.184442.60.9888.6380S-Fe 2+/10.534411.80.9996.5204S-Fe 2+/20.976314.91.07135.8424the polymerization degree of iron which was absorbed on SiO 2car-rier increased.It indicates that increasing OH −concentration can improve the loading of Fe in Fe(III)–SiO 2catalyst.The BET surface area,total pore volume and average pore width of the investigated Fe(III)–SiO 2catalysts are also listed in Table 1.The surface area of S-Fe 3+and S-Fe 2+catalysts were 446.0and 442.6m 2/g,respectively,higher than the SiO 2carrier.When using Fe(NO 3)3as precursor,with the increase of OH −/Fe mole ratio,the surface area and total pore volume of catalysts increased and the average pore width of catalysts changed a little.On the contrary,when using FeSO 4as precursor,with the increase of OH −/Fe mole ratio,the surface area of catalysts reduced,while the total pore vol-ume of catalysts and the average pore width of catalysts increased.The results show that the pore structure of Fe(III)–SiO 2catalysts prepared by the second method are affected remarkably by the precursor species and the OH −/Fe mole ratio.The XRD patterns of S-Fe 3+,S-Fe 3+/2,S-Fe 2+and S-Fe 2+/2cata-lysts are illustrated in Fig.2.The pattern showed a typical broad peak,which indicated that silica gel used as a support was a pure amorphous structure.On the other hand,the XRD patterns did not show iron oxides peaks,even for catalyst with 6.2wt.%of iron (not shown in the figure).It may be proposed that the XRD techniques are not sensitive enough to detect little iron oxides because the higher background of XRD measurement caused by amorphous SiO 2.The oxidation state of Fe on the surface of catalysts was charac-terized by XPS and the results are presented in Fig.3.The binding energy of Fe 2p 3/2was determined to be 710.945eV,710.595eV and 710.975eV for S-Fe 3+,S-Fe 3+/1and S-Fe 3+/2catalyst,respectively,which was ascribable to Fe 2O 3[25].When FeSO 4was used as the precursor,the Fe 2p 3/2peak was found at 711.195eV,711.345eV and 711.850eV for S-Fe 2+,S-Fe 2+/1and S-Fe 2+/2catalyst,respectively,strongly suggesting that the iron on the catalysts was Fe(III)[21].When FeSO 4was used as precursor,the binding energy of Fe 2p 3/2Fig.2.XRD patterns of the Fe(III)–SiO 2catalysts.Fig.3.XPS spectra of the Fe 2p region for the Fe(III)–SiO 2catalysts.in catalysts were higher than that of catalysts prepared by Fe(NO 3)3.It was difficult to give an adequate explanation of increasing in the binding energy of Fe 2p 3/2yet.O 1s survey scan further indicated the oxygen status on the catalyst surface.As shown in Fig.4,the O 1s region can be fitted into four peaks,which are attributed to the chemisorbed oxygen,the lattice oxygen of SiO 2,the lattice oxygen of Fe 2O 3and the chemically or physically adsorbed water.Accord-ing to the reports [26,27],the chemisorbed oxygen can take an active part in the oxidation process and greatly improve the cat-alyst activity.It can be seen from Table 2that the percentage of chemisorbed oxygen of catalyst was improved when FeSO 4was used as precursor and the S-Fe 2+/1catalyst had the highest per-centage of chemisorbed oxygen.3.2.Characterization of the catalysts after the reactionThe catalyst was characterized by UV–vis-DRS and XPS to confirm the formation of Fe(II)–SiO 2when Fe(III)–SiO 2was irradi-ated by photon.The UV–vis diffuse reflectance absorption spectra of Fe(III)–SiO 2catalyst before and after reaction are shown in Fig.5.The results clearly shows a new broad absorption band at 505–525nm after irradiation which is characteristic band of [Fe(1,10-phenanthroline)]2+complex [17].It is accounted for that the Fe(III)–SiO 2on irradiation with photon isconverted into Fe(II)–SiO 2that would be complexed with 1,10-phenanthroline in solid state.The binding energy of Fe 2p for the catalyst before and after reaction is shown in Fig.6.It is observed that the binding energy of Fe 2p 3/2is slightly shifted to lower BE value from 711.345to 710.600eV after irradiation,which is due to the reduction of Fe(III)–SiO 2to Fe(II)–SiO 2during the irradiation.Fig.4.O 1s curve fitting of S-Fe 2+/1catalyst.T.Liu et al./Journal of Hazardous Materials 162(2009)860–865863Table 2XPS data of O element on the surface of the catalysts CatalystsBinding energy (eV)Percentage of O ad or O L (%)O ad aO L b (SiO 2)O L b (Fe 2O 3)O L c (H 2O)O ad O L (SiO 2)O L (Fe 2O 3)O L (H 2O)S-Fe 3+531.80532.80529.79533.8926.9448.52 2.9521.59S-Fe 3+/1531.80532.80529.99533.8924.1644.39 3.5727.87S-Fe 3+/2531.80532.84529.79533.8927.7344.597.4820.2S-Fe 2+531.80532.80529.79533.8931.3942.28 4.3621.98S-Fe 2+/1531.81532.87529.79533.7938.4634.537.6019.41S-Fe 2+/2531.89532.80529.99533.7032.2230.0711.9325.79a The chemisorbed oxygen.b The latter oxygen.cThe chemically or physically adsorbed water.Fig.5.UV–vis diffuse reflectance spectra of S-Fe 2+/1catalyst:(a)Fe(III)–SiO 2and (b)Fe(II)–(1,10-phenanthroline)–SiO 2sample.3.3.Degradation and mineralization of PAM by heterogeneous photo-Fenton processesThe degradation of 100mg/L PAM in aqueous solutions under different conditions was preformed by using S-Fe 2+/1as a photo-Fenton catalyst at an initial solution pH of 6.8,and theresults are shown in Fig.7.In the presence of UV lamp,about 5%degradation of PAM in aqueous solution was observed,indicating that the degra-dation of PAM caused by direct photolysis is very limited.In the presence of 1.0g/L S-Fe 2+/1catalyst,the removal of PAM was less than 5%,which was caused by the adsorption of PAM on the catalyst.With 1.0g/L S-Fe 2+/1catalyst and 200mg/L H 2O 2in dark,the degra-dation of PAM was low,implying that the PAM degradation in the course of heterogeneous Fenton reaction is limited in neutral cir-cumstance.In the presence of UV and 200mg/L H 2O 2without anyFig.6.XPS spectra of the Fe 2p region for the S-Fe 2+/1catalyst:(a)Fe(III)–SiO 2and (b)Fe(II)–(1,10-phenanthroline)–SiO 2sample.catalyst,the concentration of PAM decreased significantly.It is due to the oxidation of PAM by •OH radicals formed direct photolysis of H 2O 2.In the presence of 1.0g/L S-Fe 2+/1catalyst,UV and 200mg/L H 2O 2,the concentration of PAM decreased rapidly and about 94%PAM degradation in 90min.As the leaching of Fe from Fe(III)–SiO 2catalyst was negligible (described as follows),the degradation of PAM in aqueous solutions was almost caused by the heterogeneous photo-Fenton reaction,indicating that S-Fe 2+/1catalyst exhibits a good photocatalytic activity in PAM degradation.It is assumed that Fe(III)species on the surface of catalysts transform to Fe(II)species under irradiation of UV light,then,the Fe(II)species generate •OH radicals by the decomposition of H 2O 2[28,29].At the same time,the UV light irradiates hydrogen peroxide to produce the •OH radicals.Finally,PAM is oxidized by •OH radicals.Therefore,the mechanism for the photo-Fenton degradation of PAM using Fe(III)–SiO 2catalyst as a heterogeneous catalyst is proposed below:H 2O 2+h →2•OH(1)Fe(III)−X +H 2O +h →Fe(II)−X +•OH +H +(2)Fe(II)−X +H 2O 2→Fe(III)−X +OH −+•OH (3)PAM +•OH →Intermediates →CO 2+H 2O(4)where X represents the surface of Fe(III)–SiO 2catalyst.The mineralization process of PAM aqueous solutions under dif-ferent conditions was measured and the results are shown in Fig.8.Only with 8W UV,there was almost no mineralization of PAM.In the present of 1.0g/L S-Fe 2+/1catalyst and 200mg/L H 2O 2in dark,about 20%TOC of PAM was removed after 180min,indicating that the mineralization of PAM by heterogeneous Fenton reaction is limited in neutral circumstance.In the presence of 8W UV and 200mg/L H 2O 2,the mineralization of PAM is significant,about 40%Fig.7.Degradation of PAM under different conditions:(a)1g/L S-Fe 2+/1catalyst,(b)8W UV,(c)1g/L S-Fe 2+/1catalyst +200mg/L H 2O 2,(d)8W UV +200mg/L H 2O 2and (e)8W UV +200mg/L H 2O 2+1g/L S-Fe 2+/1catalyst.864T.Liu et al./Journal of Hazardous Materials 162(2009)860–865Fig.8.Mineralization of PAM under different conditions:(a)8W UV,(b)1g/L S-Fe 2+/1catalyst +200mg/L H 2O 2,(c)8W UV +200mg/L H 2O 2and (d)8W UV +200mg/L H 2O 2+1g/L S-Fe 2+/1catalyst.TOC of PAM was removed after 180min.With the present 1.0g/L S-Fe 2+/1catalyst,8W UV and 200mg/L H 2O 2,the mineralization of PAM was significantly accelerated.After 180min,about 70%TOC of PAM was removed,suggesting that the S-Fe 2+/1catalyst show a significant photocatalytic activity for the mineralization of PAM.3.4.Effects of the precursor species and the OH −/Fe mole ratio on the PAM degradationTo check the photocatalytic activity of catalysts prepared by different methods,degradation of PAM in aqueous solutions by Fe(III)–SiO 2catalysts was evaluated and the results are presented in Fig.9.It was observed that the catalysts prepared with two pre-cursor species and different OH −/Fe mole ratio showed different photocatalytic activity.At the same OH −/Fe mole ratio,catalysts prepared with FeSO 4shown a higher photocatalytic activity than Fe(NO 3)3.The most effective catalyst seems to be that prepared with FeSO 4and the OH −/Fe mole ratio at 1.By using S-Fe 2+/1cata-lyst,98.6%of degradation was obtained after 120min.In contrast,S-Fe 3+/1catalyst gave rise to the less photocatalytic activity,which produced an efficiency degradation of 89.7%.The different photo-catalytic activity was observed when two precursors are used.The results are not clear,and it will be the aim of further work (iron oxidation state effect).3.5.Fe leaching from Fe(III)–SiO 2catalystsIn addition to having a high photocatalytic activity,stability is another important factor for a catalyst prepared.Theconcentra-Fig.9.Degradation of PAM by using different Fe(III)–SiO 2catalysts.Fig.10.Fe concentration in solution by using different Fe(III)–SiO 2catalysts.tion of Fe ions in solution with different catalysts was examined by ICP and the results are shown in Fig.10.It can be seen that there is no significant difference in the patterns of the curves.The concentration of Fe ions increased as reaction time increased,and reached a peak value,then followed by a decrease.The same phe-nomenon has been reported by Feng et al.[30],but the reason is still not clear.At the same OH −/Fe mole ratio,the Fe leaching from the catalysts prepared by Fe(NO 3)3was usually lower than the catalysts prepared by FeSO 4.The maximum concentration of Fe among all the catalysts was 0.17mg/L,suggesting that the Fe leach-ing from the Fe(III)–SiO 2catalysts is negligible,and the degradation of PAM aqueous solutions are almost caused by the heterogeneous photo-Fenton reaction in neutral circumstance.After 120min of the reaction,the percentage of Fe leached from the S-Fe 2+/1catalyst is only about 0.62%,the results also suggest that the catalysts have a long-term stability.4.ConclusionsFe(III)–SiO 2catalysts have been synthesized by two methods with Fe(NO 3)3and FeSO 4as precursors,and were characterized by the BET,XRD and XPS method.The percentage of chemisorbed oxygen on the surface of catalysts prepared by FeSO 4is higher than that prepared by Fe(NO 3)3.The results confirm the formation of Fe(II)–SiO 2when Fe(III)–SiO 2was irradiated by photon.The photocatalytic activities of Fe(III)–SiO 2catalysts were eval-uated by the degradation of PAM from aqueous solution in the photo-Fenton reaction and all the catalysts exhibited a better photocatalytic activities.However,the precursor species and the OH −/Fe mole ratio have influence on the photocatalytic activi-ties of the catalysts.At the same OH −/Fe mole ratio,the catalysts could present the better photocatalytic activities when using FeSO 4as precursor.The best efficiency for the degradation of PAM in heterogeneous photo-Fenton reaction was 94%degrada-tion in 90min and 70%TOC removal in 180min at an initial pH of 6.8.Finally,it was observed that Fe leaching from Fe(III)–SiO 2cata-lysts was negligible,indicating that the catalysts have a long-term stability and the degradation of PAM from aqueous solution are almost caused by the heterogeneous photo-Fenton reaction.AcknowledgmentsThe authors gratefully acknowledge the financial supports from the National Basis Research Foundation of China (973Program,No.2004CB418505)and the Research 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溶胶_凝胶和碳热还原法制备高比表面积碳化硅_王冬华
２．３ ＳｉＣ－Ｘ０．６５ 和 Ｘ０．６５ 的 Ｎ２ 吸 附 等 温 线 和 ＢＪＨ 孔分布图
氮吸附常用于分析样品 的 孔 结 构。ＳｉＣ－Ｘ０．６５样 品 的 Ｎ２ 吸附－脱附等温 线 和 孔 径 分 布 曲 线 如 图 ３（ａ）所 示。 吸 脱 附 曲 线在 ０．６～０．９ 相 对 压 力 区 间 内，样 品 显 示 出 氮 吸 附 量 的 突 增 ，表 明 样 品 中 具 有 介 孔 和 大 孔 结 构 。 ［１３］ 表 １ 列 举 了 根 据 ＢＪＨ 方法计算的孔参数 。 ［１４］ 结 果 表 明 ，样 品 具 有 较 高 的 比 表 面积 １３１ ｍ２／ｇ，孔 径 分 布 较 宽，最 可 几 孔 直 径 为 １６ｎｍ。ＢＥＴ 结 果 表 明 ，添 加 含 氢 硅 油 后 ，所 得 碳 化 硅 样 品 具 有 孔 结 构 。
第 ３９ 卷 第 ９ 期 ２０１１ 年 ９ 月
化 工 新 型 材 料 ＮＥＷ ＣＨＥＭＩＣＡＬ ＭＡＴＥＲＩＡＬＳ
Ｖｏｌ．３９ Ｎｏ．９ ·７４·
溶胶－凝胶和碳热还原法制备高比表面积碳化硅
王冬华
（渭南师范学院化学化工系，渭南 ７１４０００）
摘 要 采用糠醇、正硅酸乙酯作为碳源、硅源，在 溶 胶－凝 胶 过 程 中 加 入 硝 酸 钴 为 催 化 剂，含 氢 硅 油 为 结 构 助 剂，通 过碳热还原的方法制备出高比表面积碳化硅。采 用 ＸＲＤ、ＦＴ－ＩＲ、ＳＥＭ、ＨＲＴＥＭ 及 低 温 氮 吸 附－脱 附 对 所 制 备 的 样 品 进 行表征。结果表明，所得碳化硅具有高的比表面积 １３１ ｍ２／ｇ；含 氢 硅 油 的 特 殊 结 构 是 形 成 多 孔 碳 化 硅 的 主 要 原 因 ；所 得 碳化硅具有特殊的光致发光性能。
聚碳酸酯的非光气合成法
第27卷第8期高分子材料科学与工程Vol.27,No.82011年8月POLYMER MATERIALS SCIENCE AND ENGINEERINGAug 2011聚碳酸酯的非光气合成法荀红娣,王小梅,周宏勇,王家喜(河北工业大学化工学院,天津300130)摘要:以双酚A(BPA ),碳酸二丁酯(DBC)为原料,制备出双酚A 单丁基碳酸酯(I )和双酚A 二丁基碳酸酯(II),用核磁共振波谱表征其结构。
通过I 、II 的熔融自缩聚及I I 与BPA 酯交换反应合成了双酚A 型聚碳酸酯(PC),用凝胶渗透色谱法(GPC)和热失重法(T GA)对PC 的分子量和热力学性质进行分析。
研究发现,I I 自缩聚更易得到高分子量的PC,II 在230 自聚6h 后产物的 M w 可达3 1 104,其主链降解温度(50%)已达475 ,开拓了一种非光气合成聚碳酸酯PC 的途径。
关键词:双酚A;碳酸二丁酯;双酚A 聚碳酸酯;非光气法;环境友好过程中图分类号:T Q 323.4+1 文献标识码:A 文章编号:1000 7555(2011)08 0013 04收稿日期:2010 07 14通讯联系人:王家喜,主要从事绿色催化及功能高分子研究,E mai ll:jw ang252004@双酚A 型聚碳酸酯(PC)是一种无定型、高抗击、具有良好透明性能的热塑性工程塑料,工业上通常采用双酚A(BPA)和光气缩合聚合反应制备PC,由于这一过程存在着严重的环境问题,发展一种环境友好的聚碳酸酯合成方法,成为绿色化学的需要[1,2]。
Desi moned [3]等以BPA 和碳酸二苯酯(DPC)为原料制得PC 缩聚物,Su 等报道了碳酸二甲酯(DM C)和BPA 反应制备聚碳酸酯[4]。
由于DPC 大多采用光气与苯酚反应制备,BPA 与DM C 反应活性较低,提高反应温度后很难保持合适的原料配比,制备的PC 分子量较低[5]。