纳米金催化剂研究进展

比较详细的介绍了金催化剂的应用研究情况．尤其对CO的常温脱除、富氢条件下CO的选择性氧化．邻二醇的选择性氧化以及烃类的选择性氧化等反应过程进行了较为详细的介绍,具有一定的参考价值。     

金基催化剂在环保领域中的应用研究进展

金基催化剂长期以来被认为是一种无催化活性的催化剂,近年来受到越来越多的关注。文章综述了金基催化剂在催化CO氧化、水汽变换、脱硫和氢化等化学反应方面的应用。文章还介绍了金基催化剂的商业应用。     

纳米金催化剂在CO低温氧化和选择性氧化中的研究进展

介绍了纳米金催化剂在CO低温氧化和丙烯直接环氧化反应中的研究进展。在CO低温氧化反应中,催化剂的活性相和载体都具有明显的尺寸效应,纳米金颗粒和载体之间的相互作用主要表现载体不仅可以改变纳米金颗粒的大小和形状,而且也影响了氧的活化,从而提高反应活性;在丙烯直接环氧化反应中,由H2和O2在金颗粒表面反应生成的过氧化物种是反应中间体;在选择性氧化和选择性加氢反应中,金催化剂表现出优良的活性和稳定性。     

CO低温氧化负载金催化剂研究进展

从合成方法、制备条件和金粒子尺寸、载体效应等方面介绍了影响负载型纳米Au催化剂催化活性的因素、可能的反应机理。评述了选择适当的合成方法可以有效地控制金粒子直径,并使其均匀分散于载体之上,从而得到更好的催化活性。适当的焙烧温度与载体类型也是获得高活性催化剂的必要条件。     

金催化剂及其研究进展

对金催化剂的载体及制备方法,尤其是对近年来金催化剂研究成果和应用情况进行了较详细地讨论。重点论述了沉积-沉淀法、溶胶-凝胶法和聚合物保护法等催化剂的制备方法以及在加氢脱氯、加氢脱硫等领域中的应用,并对金催化剂的进一步研究提出看法。     

二氧化铈载金催化剂催化CO氧化的研究进展

将金纳米颗粒负载在二氧化铈上,形成负载型催化剂,能应用于多种反应体系,表现出良好的催化活性,有着广阔的发展前景。综述了二氧化铈载金催化剂在一氧化碳催化氧化中的应用研究进展,介绍了二氧化铈载金催化剂中金的结构、价态和纳米尺寸,载体二氧化铈的形貌、结构、尺寸和氧空位以及金和载体二氧化铈两者之间的相互作用对一氧化碳催化氧化性能的影响。     

负载型金催化剂在化工中的应用

综合评述了制备负载型金催化剂的研究现状，并着重探讨了负载型纳米金催化剂在化学工业中应用的研究进展。涉及到的主要反应包括CO，烷烃，1，2－二醇类等的选择性氧化，CO和H2的共同消除，甲烷的催化燃烧，CO2的氢化，低温水气转换反应以及丙烯醛的选择性氢化等。     

金催化剂在丙烯气相直接环氧化反应中的应用

环氧丙烷（PO）是一种重要的有机化工原料。近来发现采用沉积-沉淀法将金高度分散在一些含钛物质表面上时,能够催化H2-O2-丙烯气相体系直接合成PO。金粒大小和分散状态,载体及助剂等因素对催化剂性能有重要影响。主要就催化剂性能的影响因素,反应及失活机理等方面的研究进展情况进行了总结和评述,以利于将来深入地研究。     

工业化CO变换催化剂研究进展

总结了传统工业用变换催化剂的研究进展情况,介绍了变换催化剂的新型助剂及其优缺点、工业化应用前景。     

负载型金催化剂上的CO氧化

在过去的10年中，由于含有微小的纳米级金的负载型金催化剂的特殊活性，因此对此催化剂的研究热情空前高涨。这种催化剂上的一氧化碳低温氧化已经得到深入研究。尽管研究的步伐在加快，但是如制备参数和催化活性的关系、活性中心的性质和反应的机理等的议题仍然是时下争论的课题。这些争论的解决需要进一步的研究。     

Oxidation Catalysis by Supported Gold Nano-Clusters

The historical notion regarding the inability of gold to catalyze reactions has been discarded in view of recent studies, which have clearly demonstrated the high catalytic efficiency of supported nano-gold catalysts. Although nano-Au catalysts are known to catalyze a variety of reactions, the major focus has been on CO oxidation catalysis. In this work we focus on the important aspects related to the CO oxidation reaction. Special emphasis is placed on the studies undertaken on model nano-Au systems as these studies have considerably enhanced the understanding of the oxidation process. Gold in a highly dispersed state can selectively oxidize CO in the presence of excess hydrogen (of tremendous interest to state-of-the-art low-temperature fuel cells); related studies are addressed in this review. The nano-gold catalysts have also been investigated for the direct vapor-phase oxidation of propylene to propylene oxide in the presence of molecular oxygen; these investigations are highlighted in this work.     

Solvent-free Oxidation of Primary Alcohols to Aldehydes using Supported Gold Catalysts

Supported Au catalysts are investigated for the oxidation of primary alcohols under solvent-free conditions in the absence of base. Three representative primary alcohols have been investigated: benzyl alcohol, octan-1-ol and geraniol using a range of supports for gold nanocrystals prepared using coprecipitation, deposition precipitation and impregnation. For benzyl alcohol and octan-1-ol selective oxidation to the corresponding aldehydes is observed, particularly with Au/CeO₂, whereas for more acidic supports, e.g. Fe₂O₃, subsequent oxidation of the aldehydes to the corresponding acids, forming an ester (benzyl benzoate, octyl octanoate, respectively) by reaction with the alcohol, by a standard acid-catalysed mechanism. Alternatively, the mechanism of ester generation could involve hemiacetal formation between the aldehyde and residual alcohol, followed by direct oxidation to the observed ester. The reaction of geraniol is much more complex and the reaction is carried out in the presence and absence of acids to gain a full understanding of the interplay between oxidation and isomerisation reactions. Comparison with other active catalysts reveals that using Au catalysts in solvent free conditions gives very high turnover frequencies for the synthesis of the aldehydes with 100% selectivity (150 h⁻¹ and 26 h⁻¹ for benzyl alcohol and octan-1-ol, respectively), which are comparable to the best reported to date for these reactions.     

Future Directions and Industrial Perspectives Micro- and macro-kinetics: Their relationship in heterogeneous catalysis

Attempts to model macroscopic steady-state rates of catalytic reactions on the basis of microscopic kinetic parameters for elementary steps, determined independently from transient kinetic data on model, single-crystal metal catalysts, will be reviewed. The methods used in getting microkinetic parameters will be discussed. Recent studies which determine microkinetics for more complex model catalysts consisting of vapor-deposited metal islands on single-crystal oxides will also be outlined. Finally, thedegree of rate control of a step will also be mathematically defined. This new concept is useful in kinetic modeling, and in putting terms such asrate-controlling step andrate-limiting step into a more rigorous framework.     

银催化剂在乙烯环氧化反应中的应用研究进展

银催化剂因其优异的选择性、催化活性及热稳定性能在环氧乙烷工业中得到了广泛的应用。本文从银催化剂制备、银催化剂载体的发展两个方面概述银催化剂在乙烯环氧化反应中的应用,以期对银催化剂在乙烯环氧化反应中的应用有深入的了解。     

Activity of Gold Catalysts in the Liquid-Phase Oxidation of O-Hydroxybenzyl Alcohol

Gold catalysts prepared by impregnation of HAuCl₄ on Fe₂O₃, ZnO, CaO, and Al₂O₃ and aged in a solution of Na₂CO₃ (IWI/Na₂CO₃ method) are able to catalyze the oxidation of o-hydroxybenzyl alcohol (salicylic alcohol) under mild conditions. The reaction rate is even higher than that using analogous catalysts prepared by co-precipitation. Salicylic aldehyde is the main reaction product with a selectivity >90% at 90% conversion. The influence of the reaction conditions on the catalytic activity is also discussed.     

Comparison of the activity of Au/CeO2 and Au/Fe2O3 catalysts for the CO oxidation and the water-gas shift reactions

We compare the activity and relevant gold species of nanostructured gold–cerium oxide and gold–iron oxide catalysts for the CO oxidation by dioxygen and water. Well dispersed gold nanoparticles in reduced form provide the active sites for the CO oxidation reaction on both oxide supports. On the other hand, oxidized gold species, strongly bound on the support catalyze the water-gas shift reaction. Gold species weakly bound to ceria (doped with lanthana) or iron oxide can be removed by sodium cyanide at pH ≥12. Both parent and leached catalysts were investigated. The activity of the leached gold–iron oxide catalyst in CO oxidation is approximately two orders of magnitude lower than that of the parent material. However, after exposure to H₂ up to 400 °C gold diffuses out and is in reduced form on the surface, a process accompanied by a dramatic enhancement of the CO oxidation activity. Similar results were found with the gold–ceria catalysts. On the other hand, pre-reduction of the calcined leached catalyst samples did not promote their water-gas shift activity. UV–Vis, XANES and XPS were used to probe the oxidation state of the catalysts after various treatments.     

金催化剂在环氧丙烷尾气回收中的应用研究

采用沉积-沉淀法制备了Au负载催化剂。通过对CO在催化剂上的低温催化氧化反应的研究,考察了载体选择,Au的质量分数,金属助剂修饰和反应温度等对反应的影响。结果表明,载体的选择和Au的含量对催化活性都有较大影响,γ-Al2O3是除氧实验中性能优良的催化剂载体材料。使用金属氧化物修饰载体可起到提高催化剂活性,增强催化剂稳定性的作用。     

Methanol synthesis and reverse water-gas shift kinetics over clean polycrystalline copper

The kinetics of simultaneous methanol synthesis and reverse water-gas shift from CO₂/H₂ mixtures have been measured at low conversions over a clean polycrystalline Cu foil at pressures of 5 bar. An absolute rate of 1.2 × 10^–3 methanol molecules produced per second per Cu surface atom was observed at 510 K, with an activation energy of 77 ± 10 kJ/mol. The rate of CO production was 0.12 molecules per second per Cu surface atom at this temperature, with an activation energy of 135 ± 5 kJ/mol. The rates, normalized to the metallic Cu surface area, are equal to those measured over real, high-area Cu/ZnO catalysts. The surface after reaction was examined by XPS and TPD. It was covered by almost a full monolayer of adsorbed formate, but no other species like carbon or oxygen in measurable amounts. These results prove that a highly active site for methanol synthesis on real Cu/ZnO catalysts is metallic Cu, and suggest that the rate-determining step in methanol synthesis is one of the several steps in the further hydrogenation of adsorbed formate to methanol.