钯催化芳基硼酸与芳卤偶联反应的工业应用新进展

钯催化芳基硼酸与芳卤偶联反应(即Suzuki反应)是用于碳碳键形成的重要方法之一,在有机合成中应用十分广泛。本文着重综述了钯催化Suzuki偶联反应在工业化应用方面的一些新进展。     

Oxidation and reduction effects of propane–oxygen on Pd–chlorine/alumina catalysts

Pd–chloride precursor salt was used to prepare Pd/Al₂O₃ catalysts. TPSR measurements showed three distinct reactions for the oxidation of propane on palladium surface under excess of hydrocarbon: complete oxidation, steam reforming and propane hydrogenolysis. Propane oxidation on palladium catalysts was related to the Pd²⁺ sites observed on Pd/Al₂O₃ through infrared of adsorbed carbon monoxide. In fresh catalysts reduced by H₂, the IR spectra showed the linear and bridge adsorbed CO species on the Pd⁰ surface. After propane reaction, a new band at 2130 cm^-1 related to CO adsorption on Pd²⁺ species was noted. Carbon monoxide species adsorbed on Pd⁰ were also observed in all samples after reaction. Our results suggest surface ratios of Pd⁰/PdO during the propane oxidation. On the other hand, time on stream conversions of the complete oxidation of propane were affected by either the water generated during the reaction or added as a reactant at 10 vol%. The water generated by the reaction helped to eliminate chlorine residues in the form of oxychloride species leading to an increasing of the activity. However, the presence of water into the reaction mixture caused a strong decreasing of the activity. The inhibition mechanism of propane oxidation in the presence of water consisted in the dissociative adsorption of water on palladium sites with the possible formation of palladium hydroxide (Pd–OH) at the surface, diminishing the number of active surface sites. Dynamic fluctuations into the reaction conditions supported the idea that a pseudo‐equilibrium adsorption–desorption of water was reached. After water removal or increasing in the reaction temperature the equilibrium was shifted to the direction of OH–Pd decomposition. This behavior suggests that the inhibitory effect of water is a reversible phenomenon, being a function of the amount of water and the reaction temperature. This revised version was published online in July 2006 with corrections to the Cover Date.     

Pd deposited on Cu(110): a highly performant catalyst for the 1,3-butadiene hydrogenation reaction

The catalytic properties, with respect to the 1,3-butadiene hydrogenation reaction, of strained Pd films on Cu(110) (lattice mismatch 8%) has been probed as a function of the film thickness. The characterization of the adlayer has been made by the combined use of STM with LEED and AES. For deposits below 10¹⁵ Pd/cm² (i.e., about 1 ML) the catalytic activity is near zero. This is the consequence of the formation of a Pd–Cu surface alloy with tendency for Cu to migrate/segregate to the surface. The catalytic activity suddenly increases to reach a maximum value for about 3 ML; the activity is then one order of magnitude higher than that of the pure Pd(110) surface. This is the consequence of the presence of a strained Pd overlayer, with Pd surface atoms having very unusual geometry, and hence very peculiar electronic and chemical properties. The catalytic activity then decreases as the Pd coverage is increased, and tends to values near that of the pure Pd(110). Gradual relaxation of the film geometry towards that of the normal fcc Pd structure probably exists.     

MoV-based catalysts in ethane oxidation to acetic acid: Influence of additives on redox chemistry

The formation of acetic acid and/or ethylene by oxidation of ethane is strongly dependent on X additives or Y promotor added to MoVO-based catalysts. MoV_0.4X_0.12YO_z (X = Nb; Y = Pd;  = 10⁻⁴) catalysts were prepared by the slurry method and their structural properties were studied by in situ (redox conditions) XRD, Raman and XPS techniques. The reactivity during reduction and reoxidation was analysed by thermal analysis (TGA/DSC). The oxidation of ethane was carried out in a conventional fixed bed microreactor with on line analysis by gas chromatography. Results show that Nb exerts mainly a structural effect as it is responsible for the stabilisation of molybdenum (VI) by formation of solid solutions with V, and that Pd modifies the rate of reduction of the solid catalysts. The increase of selectivity to acetic acid observed by Pd promotion is likely due to the transformation of ethylene to acetic acid occurring on neighboring Pd–V active sites.     

从废TDI氢化触媒中回收金属钯

阐述了从废TDI氢化触媒中回收贵金属钯的工艺方法。通过对废触媒中钯的焚烧富集、除杂、精制等工艺步骤,使钯的回收率达到98％以上,产品纯度达到国家标准要求QqPd-2,Pd％≥99．95％）。     

3,5-二羟基苯甲酸转移加氢动力学

研究了3,5-二羟基苯甲酸(DHB)为原料采用催化转移加氢法合成3,5-二氧代环己烷羧酸(DOC)的过程,得到了以5％Pd／C为催化剂、甲酸钠为氢供体的3,5-二羟基苯甲酸转移加氢宏观反应动力学。研究发现,在实验条件下原料3,5-二羟基苯甲酸的反应级数为0,供体甲酸钠和催化剂分别为一级;当氢供体大量过量时,3,5-二羟基苯甲酸的吸附速率是反应的控速步骤,初步探讨了反应过程的机理。     

两种芳香族聚酮的合成及其性能

采用以过渡金属Pd（Ⅱ）为活性中心的催化体系,催化一氧化碳(CO)与苯乙烯（St） 、对乙基苯乙烯（ESt）的间歇共聚合反应,得到具有规整结构的交替共聚产物STCO 和ESTCO.动力学研究表明, ESt比St具有更高的共聚合反应活性,但在间歇聚合条件下失活较早,表现为ESt需要较高的CO压力与之相匹配,说明烯烃的活性越高,所需的CO压力区间也越高.由于在苯环上引入对乙基基团,ESTCO与STCO相比,熔点和结晶度略有下降,但在有机溶剂中的溶解性增强.     

Control of the β-Hydride Elimination Making Palladium-Catalyzed Coupling Reactions more Diversified

Pd(II)-catalyzed coupling reactions were developed using β-heteroatom elimination and protonolysis reaction to quench the carbon–palladium bond in the presence of halide ions or nitrogen ligands (pyridine, bipyridine, phenanthroline, etc.) for regenerating the divalent palladium species. Halide ions or nitrogen ligands are necessary for the catalytic cycle and high yield of the reactions. For Pd(0)-catalyzed reactions, control of β-hydride elimination is also a challenge for making coupling reactions more diversified. Different kinds of ligands were used to make the coupling reaction suitable for aliphatic compounds. Recently, examples using chloride ion or bathophenanthroline for this purpose were also developed.     

Influence of Pt–Pd/TS-1 Catalyst Preparation on Epoxidation of Olefins with Hydrogen Peroxide

The catalytic performance of the platinum–palladium/titanium silicalite, which was a common catalyst for the direct epoxidation of olefins with hydrogen and oxygen, was tested by epoxidation of allyl chloride with hydrogen peroxide. The epoxidation capacity of the TS-1catalyst was reduced after loading palladium and platinum on it. Ti leaching and crystallinity decrease were observed by XRD and FT-IR. The decomposition of hydrogen peroxide was accelerated by the supported Pd and Pt. These contributed to the loss of epoxidation capacity of TS-1. Ti leaching and crystallinity decrease were probably main causes. We propose that the Ti leaching had the most important influence on the loss of epoxidation capacity     

Vibrationally Excited CO2 Formed in CO + NO Reaction on Pd(110) Surface in High Surface Temperature Range

The infrared chemiluminescence spectra of CO₂ formed during steady-state CO+NO reaction over Pd(110) indicated that the temperature of the bending vibrational mode was much higher than that of the antisymmetric one at higher surface temperatures such as 800–850 K. Especially, in the high temperature range, more vibrationally excited CO₂ was formed from CO+NO reaction than CO+O₂ reaction. On the basis of the result, we propose the model structure of reaction intermediates for CO₂ formation in CO+NO reaction, which is different from that in CO+O₂ reaction.