The electronic structure effect in heterogeneous catalysis

Using a combination of density functional theory calculations and X-ray emission and absorption spectroscopy for nitrogen on Cu and Ni surfaces, a detailed picture is given of the chemisorption bond. It is suggested that the adsorption bond strength and hence the activity of transition metal surfaces as catalysts for chemical reactions can be related to certain characteristics of the surface electronic structure.     

Self-supported chiral catalysts for heterogeneous asymmetric catalysis

A conceptually new strategy for chiral catalyst immobilization, self-supported catalysts, in heterogeneous asymmetric catalysis is highlighted in the present article. Various homochiral metal-organic polymers with diverse structures have been designed and readily prepared through coordination assembly of modular polytypic/polyfunctional ligands and metal ions without using any supports. These polymers have been successfully employed as chiral catalysts in a variety of heterogeneous asymmetric ractions, including hydrogenation, epoxidation, sulfoxidation, carbonyl-ene reactions, diethylzinc addition, and Michael addition. The self-supported heterogeneous chiral catalysts showed activity and enanioselectivity comparable or even superior to those obtained with their corresponding homogeneous counterparts, and could be readily recovered and reused several times without significant loss of activity or enantioslectivity.     

Hybrid organic-inorganic solids for heterogeneous asymmetric catalysis

This paper provides a short review of recent progress in the design and synthesis of chiral organic–inorganic hybrid solids and their applications in heterogeneous asymmetric catalysis. Homochiral hybrid solids containing catalytic sites can be readily prepared by linking appropriately designed chiral bridging ligands with metal ion or metal cluster nodes. Heterogeneous asymmetric catalysts with enantioselectivity as high as 99.2 and turnover number (TON) as high as 20,000 have been obtained based on these hybrid organic–inorganic solids. The modular nature of the present approach promises to lead to a variety of practically useful heterogeneous asymmetric catalysts for many organic transformations.     

组合化学在多相催化领域中的应用

本文系统综述了新近兴起的技术——组合化学在多相催化领域中的研究进展。通过对组合催化研究的两个关键因素催化剂库合成及催化剂高通量筛选技术的评价分析认为,在对已有的催化体系和催化剂优化的同时，如何高效研制新催化材料及开发新筛选检测技术，是组合催化研究的主导思想，对此的深刻理解和运用，将增强实验室的创新能力。     

Electrochemical promotion of heterogeneous catalysis

The catalytic activity and selectivity of metals interfaced with solid electrolytes can be altered dramatically and reversibly via potential application. The increase in catalytic rate can be several orders of magnitude higher than that anticipated from Faraday's Law. This new phenomenon of electrochemical promotion is of considerable theoretical and potentially practical importance in heterogeneous catalysis. In this paper the main phenomenological features of electrochemical promotion (or NEMCA effect) are surveyed and the origin of the effect is discussed in view of recent surface spectroscopic and quantum mechanical studies.     

Nanotechnology: applications and potentials for heterogeneous catalysis

Nanotechnology offers the potential to design, synthesize, and control at nanometer length scale. While the catalysis community has many techniques at their disposal to synthesize catalytic materials at such a scale, the ability to fully design and control is still lacking. Examples are presented to illustrate what can nanotechnology do for heterogeneous catalysis to help achieve the goal of designing catalysts for perfect selectivity in a chemical reaction. Some current state-of-the-art approaches and potential limitations are discussed. Some examples of what can catalysis do for nanotechnology are also presented. However, this aspect is much less studied, although it offers rich opportunities for the catalysis community.     

Ammonia synthesis: The bellwether reaction in heterogeneous catalysis

This is a personal account of the Havreholm Conference with a choice of topics dealing with catalytic ammonia synthesis. Among the general concepts that were retained are: the rate determining step with rates of adsorption and desorption of nitrogen; the direct activated dissociative adsorption of N₂; the surface crystalline anisotropy of iron; the role of promoters in industrial iron based catalysts; and the atomic structure of the metallic surface on the industrial multiply promoted catalyst. Finally, a new isotope jump technique to measure an upper limit to the real turnover frequency is discussed.     

From quantum physics to heterogeneous catalysis

The development of the understanding of catalytic reactions on metal surfaces in general and the ammonia synthesis reaction in particular is discussed. The paper will give a personal perspective on the discussions that took place at the meeting at Havreholm Hall in September 1993.     

非均相法催化制备生物柴油的最新研究进展

非均相连续化工艺是生物柴油规模化工业生产的发展方向。多相催化剂的研制和新型工艺过程的开发一直是生物柴油领域的研究热点,也是实现生物柴油绿色、经济、高效生产的关键。分析了酯交换反应可能的反应机理,综述了国内外生物柴油非均相酸碱催化剂的最新研究进展,评述了多种固体酸碱催化剂在生物柴油的制备中优异的催化性能和存在的问题,介绍了多种新型多相生物柴油反应器及反应分离耦合工艺在生物柴油连续化制备中的应用,最后展望了生物柴油未来的发展前景,指出新型固体酸碱双功能催化剂与先进多相连续反应分离耦合工艺的开发将推动生物柴油领域不断发展。     

Rapeseed oil transesterification by heterogeneous catalysis

Methyl fatty esters derived from vegetable oils are a promising fuel for direct injection diesel engines. This study’s purpose was to identify a heterogeneous catalyst to selectively produce methyl fatty esters from low erucic rapeseed oil. Most experiments were at atmospheric pressure and approximately the corresponding boiling point temperature of the mixture, 60–63 C. However, the catalytic activity of an anion exchange resin was tested at 200 C and 68 atm (1000 psig) and at 91 C and 9.2 atm (135 psig). All samples were analyzed by thin layer chromatography with samples from the elevated temperature and pressure experiments also analyzed by mass spectroscopy. The most promising catalyst examined was CaO·MgO. The activities of the catalysts CaO and ZnO appear to be enhanced with the addition of MgO, therefore the transesterification reaction mechanism may be, in this instance, bifunctional. The anion exchange resin catalyst at 200 C and 68 atm generated substantial amounts of both methyl fatty esters and straight-chain hydrocarbons, even though these reactions did not go to completion. At 91 C and 9.2 atm the cracking also occurred but at a substantially reduced rate, and no transesterification was noted.     

Alcoholysis of triacylglycerols by heterogeneous catalysis

Synthesis of fatty acid esters by alcoholysis, especially methanolysis of triacylglycerols was investigated using metal salts of amino acids as catalysts. The methanol to oil molar ratio was 6:1. It could be shown that salts containing a quaternary amino or a highly basic group as e.g. a guanidino group have catalytic activity in alcoholysis. Some of these salts are insoluble in monovalent alcohols, glycerol, and fatty acids esters and are therefore suitable catalysts for heterogeneously catalysed alcoholysis. Zinc salts of arginine, carnitine or histidine are among others suited for industrial use. These catalysts are also suitable for heterogeneously catalysed interesterification.     

多相催化臭氧化技术中催化剂的研究进展

近年来,以产生大量自由基(·OH)为主体的高级氧化技术越来越受到人们的关注.作为高级氧化技术的一种新形式,多相催化臭氧化技术将催化剂的吸附性、催化作用和臭氧的氧化能力很好地结合起来,可大幅提高有机物的矿化度,而催化剂在该技术对不同有机物的净化过程中起到了重要的作用.介绍了催化臭氧化过程的反应机理,综述了不同催化剂在催化...     

分数维几何在非均相催化中的应用

80年代以来,分数维几何已用于非均相催化研究。介绍了分数维几何在定量评估催化反应的结构敏感性、鉴别活性位、催化材料的性能测试、计算机模拟催化剂表面形貌设计及催化反应工程等方面的研究动向。     

Recent topics in heterogeneous catalysis of heteropolyacids

First, the state of the art of the catalyst design based on heteropoly compounds is briefly overviewed. Then, selected topics of solid heteropoly catalysts, that is, the selective oxidation of isobutyric acid and isobutane over molybdovanadophosphoric acids, the methyl t-butyl ether synthesis in pseudoliquid of heteropolyacids, and the shape-selective and bifunctional (combined with noble metals) acid catalysis of cesium and ammonium salts of tungstophosphoric acid are described based on the recent studies from our laboratory.     

Ligand effects in heterogeneous catalysis and electrochemistry

Ligand effects in surface reactivity are discussed on the basis of extensive density functional theory calculations. The d-band model is reviewed and it is shown that it can be used to rationalize trends in reactivity in heterogeneous catalysis and electrochemistry.     

碳材料在多相催化过程中的应用

碳是自然界中存在最为广泛的元素,具有丰富的结构和形态。碳材料不仅可以作为理想的催化剂载体,其本身也表现出对多种催化过程的优异性能。综述了碳材料在化学品制造、环境催化与能源催化等领域的最近研究进展,并总结了碳材料在这些过程中的催化作用机理。     

The dicarbonylation and hydrodimerization of unsaturated hydrocarbons via heterogeneous palladium catalysis

Graphite and polymer-supported palladium catalysts, coupled with copper/lithium cocatalysts, have been found very effective for the oxidative carbonylation of unsaturated hydrocarbons. Hex-3-ene-1,6-dioate has been generated in 85% selectivity from 1,3-butadiene,-olefins yield dimethyl succinate derivatives. Butadiene hydrodimerization via analogous platinum catalysis selectively provides 1,6-octadiene, or 2,7-octadienyl formate. Mechanisms for the product selectivity are described.     

A molybdenum-centred model for nitrogenase catalysis

Density functional theory has been used to relate the intrinsic N₂ binding affinities of the Fe and Mo sites of the iron–molybdenum cofactor of nitrogenase (FeMoco) to those of known N₂ complexes. The results indicate that initial N₂ binding to FeMoco is reversible, and that Mo is the preferred site. A mechanism for N₂ reduction is proposed in which a partially reduced MoNNH₂ species undergoes cleavage across a MoFeS₂ face of FeMoco.