Hydrogen Effects in Metal Catalysts

The interaction of hydrogen with metals is the cause or basis of a host of phenomena ranging from the chemisorption of hydrogen on the surface, its dissolution in the metal, catalytic reactions involving hydrogen as a reactant or as an astoichiometric component, etc., to the formation of metal hydrides. Hydrogen -induced corrosion and hydrogen embrittlement of steel are well known in chemical process industry and metallurgy. Catalytic reactions on metal or metal-oxide catalysts in the presence of hydrogen, often under pressure, are some of the major chemical, petroleum, and petrochemical processes of today, e.g., ammonia, methanol, Fischer-Tropsch, Oxo and other syntheses, hydrogenation of oils and fats, catalytic reforming, hydrode-sulfurization/hydrotreating, hydrocracking, and hydrogenation/ dehydrogenation.     

Cu系催化剂在催化反应中的研究进展

Cu是常用的金属催化剂,具有加氢、脱氢和氧化等催化性能,铜基催化剂在化学工业中应用广泛。主要介绍了铜基催化剂在甲醇水蒸汽重整制氢、CO催化氧化消除、合成甲醇、草酸二甲酯加氢合成乙二醇、乙醇脱氢制乙酸乙酯等领域的研究进展。     

5-羟甲基糠醛催化氢化制备2,5-呋喃二甲醇的研究进展

2,5-呋喃二甲醇（BHMF）在合成树脂、药物等方面具有重要应用。随着化石资源的日益缩减,由可再生的生物质基平台分子5-羟甲基糠醛（HMF）催化制备BHMF引起人们的广泛关注。本文在总结了HMF及BHMF物化性质的基础上,介绍了HMF在分子氢、醇类、甲酸3种不同的氢供体中催化加氢制备BHMF的研究近况,总结了贵金属、非贵金属、双金属或多金属协同催化体系在该加氢反应中的应用进展,同时分析了反应过程中温度、时间、催化剂载体、反应溶剂种类及酸值等因素对HMF转化率及BHMF得率的影响。最后对HMF催化转化制备BHMF的研究前景进行了总结和展望,提出了使用醇类代替氢气作为氢供体,开发非贵金属及金属协同催化体系将是该选择性氢化反应的重要研究方向之一。     

Catalytic transfer hydrogenation on a hydrogen-absorbing alloy (CaNi5) using hydriding–dehydriding properties

By using the characteristics of a hydrogen-absorbing alloy, the hydrogen produced by catalytic dehydrogenation of saturated compounds can be absorbed to form metal hydrides, and, vice versa, the resulting metal hydrides are able to hydrogenate efficiently unsaturated compounds upon dehydriding. Gas-phase reactions between 2-butene and 2-propanol on a hydrogen-absorbing alloy CaNi₅ have been studied in the temperature range of 393–473 K. CaNi₅ showed interesting characteristics as an active catalyst for the catalytic transfer hydrogenation of butene from propanol as a hydrogen donor. 2-propanol was effectively dehydrogenated at 423 K to yield acetone in which the dissociated hydrogen was completely absorbed by CaNi₅ to form the metal hydride. When the alloy was hydrided to some extent, butene was hydrogenated by the absorbed hydrogen in the metal hydride to produce butane. The overall reaction on CaNi₅ was expressed as catalytic transfer hydrogenation of 2-butene from 2-propanol through intermediate formation of metal hydrides, rather than the direct reaction between butene and propanol on the alloy. Thus, CaNi₅ effectively repeated hydriding–dehydriding cycles: hydriding of CaNi₅ by 2-propanol dehydrogenation with subsequent dehydriding for the hydrogenation of 2-butene. The use of hydrogen-absorbing CaNi₅ provides a novel reaction system for the catalytic transfer hydrogenation. This revised version was published online in July 2006 with corrections to the Cover Date.     

PdxSy材料的制备及其在催化领域的研究进展

在催化领域,Pd_xS_y多年来一直被认为是金属钯中毒形成的不良产物而不受重视。但是近年来,Pd_xS_y材料被发现在催化加氢、催化氧化、电催化以及可见光催化制氢方面表现出独特的催化性能。本文比较了Pd_xS_y材料的传统制备方法和绿色创新合成技术,综述了Pd_xS_y材料作为催化剂在催化加氢、催化氧化、电催化以及可见光催化制氢方面的研究工作。比较发现,Pd_xS_y材料的传统制备方法存在毒害大、三废多、周期长等缺点,这些缺点在很大程度上限制了该材料的发展前景,需要在制备方法上进行更深入的创新研究。同时,Pd_xS_y材料在多个催化领域,尤其是在可见光催化制氢方面的优异性能,使其在催化材料领域备受关注。     

Catalytic C-C bond formation via capture of hydrogenation intermediates

Although catalytic hydrogenation has been practiced for over a century, use of hydrogen as a terminal reductant in catalytic C-C bond formation has been restricted to processes involving migratory insertion of carbon monoxide, e.g., alkene hydroformylation and related Fischer-Tropsch-type reactions. In an effort to develop hydrogenation as a new method for catalytic cross-coupling, a catalytic system enabling capture of hydrogenation intermediates was recently developed in our lab. These results support the feasibility of developing a broad new family of hydrogen-mediated C-C bond formations.     

Characterization of bimetallic rhodium-germanium catalysts prepared by surface redox reaction

The preparation of bimetallic rhodium-germanium/silica and rhodium-germanium/alumina catalysts was investigated by controlled surface reaction. Their catalytic performances were measured for two gas phase reactions (toluene hydrogenation at 323 K and cyclohexane dehydrogenation at 543 K) and for a liquid phase reaction (citral hydrogenation at 343 K).

Elemental analysis of bimetallic catalysts showed that germanium can be deposited by redox reaction between hydrogen activated on a parent monometallic rhodium catalyst and germanium tetrachloride dissolved in water (catalytic reduction method). EDX microanalysis of rhodium-germanium/silica catalysts indicated that rhodium and germanium were deposited in close contact on the silica support. However, on alumina-supported catalysts, germanium deposition occurred also separately on the support. For the different test reactions, the catalytic properties of rhodium were strongly altered by the addition of germanium. On alumina-supported catalysts, interesting catalytic effects were observed in citral hydrogenation when not only close contact exists between both metals but when, in addition, the second metal was deposited on the support in the close vicinity of rhodium.     

Preparation of recoverable Ru catalysts for liquid-phase oxidation and hydrogenation reactions

We here report the synthesis, characterization and catalytic performance of new supported Ru(III) and Ru(0) catalysts. In contrast to most supported catalysts, these new developed catalysts for oxidation and hydrogenation reactions were prepared using nearly the same synthetic strategy, and are easily recovered by magnetic separation from liquid phase reactions. The catalysts were found to be active in both forms, Ru(III) and Ru(0), for selective oxidation of alcohols and hydrogenation of olefins, respectively. The catalysts operate under mild conditions to activate molecular oxygen or molecular hydrogen to perform clean conversion of selected substrates. Aryl and alkyl alcohols were converted to aldehydes under mild conditions, with negligible metal leaching. If the metal is properly reduced, Ru(0) nanoparticles immobilized on the magnetic support surface are obtained, and the catalyst becomes active for hydrogenation reactions.     

金属氮化物/碳化物催化剂加氢性能研究进展

介绍了过渡金属氮化物/碳化物独特的晶体结构和电子性能及其与催化性能的内在联系。综述了过渡金属氮化物/碳化物在涉氢反应中催化加氢机理的研究进展,以及过渡金属氮化物/碳化物在加氢脱硫(HDS)、加氢脱氮(HDN)和其他涉氢反应中的应用。与传统的过渡金属硫化物催化剂相比,过渡金属氮化物/碳化物具有更加优异的氢吸附、活化和转移能力。     

过渡金属氮化物催化性能研究进展

过渡金属氮化物具有类似于Pt族贵金属的催化性能得到了广泛的研究.综述了过渡金属氮化钼及助剂促进的氮化钼在加氢脱硫与脱氮、氨合成与分解、芳烃加氢和其他涉氢反应(如炔烃、烯烃加氢、丙酮缩合、肼的分解)中的应用,并介绍了其他金属氮化物(如氮化钒、氮化钴)在催化反应中的应用.     

Fatty methyl ester hydrogenation to fatty alcohol part I: Correlation between catalyst properties and activity/selectivity

Fatty alcohols, derived from natural sources, are commercially produced by hydrogenation of fatty acids or methyl esters in slurry-phase or fixed-bed reactors. One slurry-phase hydrogenation of methyl ester process flows methyl esters and powdered copper chromite catalyst into tubular reactors under high hydrogen pressure and elevated temperature. In the present investigation, slurry-phase hydrogenations of C₁₂ methyl ester were carried out in semi-batch reactions at nonoptimal conditions (i.e., low hydrogen pressure and elevated temperature). These conditions were used to accentuate the host of side reactions that occur during the hydrogenation. Some 14 side reaction routes are outlined. As an extension of this study, copper chromite catalyst was produced under a number of varying calcination temperatures. Differences in catalytic activity and selectivity were determined by closely following side reaction products. Both activity and selectivity correlate well with the crystallinity of the copper chromite surface; they increase with decreasing crystallinity. The ability to follow the wide variety of side reactions may well provide an additional tool for the optimized design of hydrogenation catalysts.     

纳米多相催化材料在常温反应中的应用

近年来,纳米材料在化学反应过程中扮演着越来越重要的角色。纳米材料作为多相催化剂,具有高活性、高选择性、高稳定性而且易于回收利用等优点。将精心设计的纳米材料用于催化一系列反应,使其在常温下进行,可以促进资源的高效利用和节能减排,在化工领域有着广阔的应用前景。本文详细介绍了以下几种类型的纳米材料,即金属纳米粒子材料、固载型金属离子复合物纳米材料、金属氧化物纳米材料和固体酸纳米材料。并阐述了上述纳米材料的结构特点及在催化方面的优势,同时结合实例,着重探讨了上述纳米材料作为多相催化剂在氧化反应、还原反应、偶联反应等多种节能高效反应中的应用。纳米材料因其多方面的优点以及广阔的应用范围,是一种极具发展潜力的多相催化材料。     

光电解水产活性氢/氧耦合加氢/氧化过程用水滑石基纳米材料

加氢/氧化催化是现代化学工业中最广泛的催化过程,传统加氢/氧化催化需要高温高压、消耗大量氢气/氧气(或双氧水等),且存在高成本、高能耗、低选择性等问题。因此,如何在温和条件下绿色高效地实现加氢还原/氧化反应,是目前催化领域的研究热点和难点之一。光电催化过程因其能量来源广泛、清洁环保,且结合了光催化和电催化的优势,已成为当前研究热点,而光电分解水产生H2/O2过程涉及高反应活性的中间物种(活性氢*H、活性氧*O)的产生。利用光电解水产生的中间*H/*O物种,并使其直接参与加氢/氧化催化过程,实现一步光电解水制活性氢/氧耦合加氢/氧化过程,有望极大提高反应的效率。通过对催化剂结构进行调控,使得耦合过程可在温和的反应条件下进行,同时可避免因使用氢气/氧气等导致的安全和耗能等问题。本文综述了光电分解水过程,传统化工的加氢/氧化过程以及光电分解水与加氢/氧化耦合反应等方面的发展,介绍了水滑石基纳米材料在光电解水耦合加氢/氧化过程中的结构和性能优势,并对未来研究方向进行了展望,以期为高附加值有机化学品的高选择性低成本制备提供思路。     

Complementary structure sensitive and insensitive catalytic relationships

The burgeoning field of nanoscience has stimulated an intense interest in properties that depend on particle size. For transition metal particles, one important property that depends on size is catalytic reactivity, in which bonds are broken or formed on the surface of the particles. Decreased particle size may increase, decrease, or have no effect on the reaction rates of a given catalytic system. This Account formulates a molecular theory of the structure sensitivity of catalytic reactions based on the computed activation energies of corresponding elementary reaction steps on transition metal surfaces. Recent progress in computational catalysis, surface science, and nanochemistry has significantly improved our theoretical understanding of particle-dependent reactivity changes in heterogeneous catalytic systems. Reactions that involve the cleavage or formation of molecular pi-bonds, as in CO or N(2), must be distinguished from reactions that involve the activation of sigma-bonds, such as CH bonds in methane. The activation of molecular pi-bonds requires a reaction center with a unique configuration of several metal atoms and step-edge sites, which can physically not be present on transition metal particles less than 2 nm. This is called class I surface sensitivity, and the rate of reaction will sharply decrease when particle size decreases below a critical size. The activation of sigma chemical bonds, in which the activation proceeds at a single metal atom, displays a markedly different size relationship. In this case, the dependence of reaction rate on coordinative unsaturation of reactive surface atoms is large in the forward direction of the reaction, but the activation energy of the reverse recombination reaction will not change. Dissociative adsorption with cleavage of a CH bond is strongly affected by the presence of surface atoms at the particle edges. This is class II surface sensitivity, and the rate will increase with decreasing particle size. Reverse reactions such as hydrogenation typically show particle-size-independent behavior. The rate-limiting step for these class III reactions is the recombination of an adsorbed hydrogen atom with the surface alkyl intermediate and the formation of a sigma-type bond. Herein is our molecular theory explaining the three classes of structure sensitivity. We describe how reactions with rates that are independent of particle size and reactions with a positive correlation between size and rate are in fact complementary phenomena. The elucidation of a complete theory explaining the size dependence of transition metal catalysts will assist in the rational design of new catalytic systems and accelerate the evolution of the field of nanotechnology.     

Photoelectrochemical water splitting into active hydrogen/oxygen species coupling with hydrogenation/oxidation process using layered double hydroxides-based nanocatalysts

Hydrogenation/oxidation processes are regarded as the most widely used catalytic reactions in modern chemical development. However, the traditional reaction process always requires harsh reaction conditions (such as high temperature, high pressure, a lot of hydrogen/oxygen consumption, etc), the high cost, overconsumption of energy and low selectivity is always limiting its further development. Therefore, conducting the hydrogenation/oxidation reaction efficiently under mild conditions is one of the greatest challenges in this field. Photoelectrocatalysis has been widely studied due to its wide, clean and sustainable energy sources, which combines the advantages of both photocatalysis and electrocatalysis. Moreover, the process of generating H₂/O₂ by photoelectrocatalytic water splitting involves the production of highly reactive intermediate species (active hydrogen *H and active oxygen *O) which can be used by directly coupling the hydrogenation/oxidation catalytic processes, and the efficiency of coupled reaction will be greatly improved. The review here summarizes the research progress of photoelectrocatalysis from three aspects: active species of intermediate products produced by photoelectrochemical water splitting, hydrogenation/oxidation reaction of the traditional chemical industry, and coupling photoelectrochemical water splitting with hydrogenation/oxidation process using layered double hydroxides (LDHs)-based nanomaterials. It is expected to provide ideas for the high selectivity and low cost preparation of high value-added organic chemicals.     

构件化催化剂的研究现状与应用

与传统的用于固定床催化反应器的颗粒催化剂相比，构件化催化剂因具有床层压降低，温度和浓度梯度小等优点而越来越受到人们的关注，已在环保、催化燃烧以及催化精馏等领域得到了广泛的应用，并正在被研究用于甲烷化、烷烃蒸汽转化、加氢/脱氢以及制氢等过程中。此外，在液相加氢和废水等水溶液中有机物种的氧化以及生化过程等三相反应中的应用也显示了极大的发展潜力。     

STRUCTURE AND PROPERTIES OF MICROCRYSTALLINE CATALYSTS

Supported metal catalysts are widely used because it is possible to prepare them in a highly dispersed form, consisting of very small microcrystals, which provide a maximum available surface area for the catalytic reaction [1]. Superficially, one might expect that the effectiveness of the material as a catalyst would be simply proportional to the surface area. In this case the specific catalytic activity would be independent of the size of the microcrystals. Size-independent specific activity is observed in a number of reactions, such as hydrogenation of benzene on alumina-supported platinum [2]. For other reactions, the specific catalytic activity is dependent on the size of the mircrocrystals. It is possible that the surface of a very small microcrystal is either more or less active than that of a larger crystal. Figure 1 shows the specific activity of the catalyst for deuteration of benzene and for hydrogen exchange with benzene on nickel catalysts [3]. Note that the smaller microcrystals are more active than the larger crystals for the hydrogenation reaction, but the smaller microcrystals are less effective for the exchange reaction. Such observations can be discussed in terms of the number and nature of the surface sites on a microcrystal [3—5].     

Struktur-Aktivitätsbeziehungen von Hydrierkatalysatoren

Structure / Activity Correlations of Hydrogenation Catalysts The reason for different activities of group VIII metal catalysts in several hydrogenation reactions is unknown. The activity of group VIII metal catalysts decreases in the hydrogenation of crotonaldehyde to butyraldehyde in the following sequence Pd > Pt > Ni > Rh > Co; Ir. However in the hydrogenation of butyraldehyde to butanol the sequence of metals is inversely. The hydrogenations of crotonaldehyde and butyraldehyde proceed as ligand addition reactions. The reaction rate depends on the nucleophilicity of atomically chemisorbed hydrogen. Whereas the reaction rate in the hydrogenation of crotonaldehyde increases, the hydrogenation rate of butyraldehyde decreases with the nucleophilicity of atomically chemisorbed hydrogen.     

金属氧化物在OX-ZEO催化剂中催化COx加氢制低碳烯烃研究进展

金属氧化物-分子筛（OX-ZEO）双功能催化剂可实现CO _x 加氢制低碳烯烃的高选择性转化。本文概述了OX-ZEO催化CO _x 加氢制低碳烯烃反应中金属氧化物的研究进展,通过对CO _x 加氢制甲醇/乙烯反应热力学分析指出了“接力催化”的优势,重点讨论了金属氧化物的种类和组成、制备方法及金属氧化物和分子筛的“亲密度”对催化性能的影响,探讨了催化反应机理、氧空位的作用及抑制副反应的策略。分析了OX-ZEO催化反应面临的问题和挑战,展望了OX-ZEO催化体系的发展趋势,认为通过元素掺杂、助剂修饰、优化制备条件等可提高金属氧化物的氧空位含量,进而可提高催化活性,也可通过对金属氧化物进行表面疏水改性抑制副产物CO₂,提高C原子利用率。     

水滑石材料用于催化脱氢的研究进展

催化脱氢反应广泛应用于化工生产和制氢工艺领域,因此,开发高效且适应苛刻反应条件的脱氢催化剂十分关键.水滑石材料(LDHs)由于具有特殊二维层状结构、金属阳离子的灵活可调性以及插层阴离子的易交换性等特点,可为催化脱氢的应用开展许多智能化设计策略.首先,介绍了LDHs的催化用途及其作用机制,主要介绍了LDHs及其插层材料作...