Epoxidation of olefines with PDMS membranes containing zeolite occluded manganese diimine complexes

A new composite catalyst for selective epoxidation of olefins with tert-butyl hydroperoxide (tBHP) is reported. The catalyst contains manganese diimine complexes (cis-Mn bis-2,2′-Bipyridyl), occluded within a NaY zeolite, in turn incorporated in a polydimethylsiloxane membrane (cis-[Mn(bpy)₂]²⁺-NaY-PDMS). The three-step synthesis consists of a Mn²⁺exchange of NaY, ligand sorption to form cis-[Mn(bpy)₂]²⁺-NaY and incorporation of the latter in a PDMS membrane. The major differences between [Mn(bpy)₂]²⁺-NaY as such and occluded in PDMS are observed in the sorption and catalytic characteristics. With the membrane system, the use of a solvent becomes obsolete. Whereas optimal cyclohexene oxidation with [Mn(bpy)₂]²⁺-NaY occurs with hydrogen peroxide in acetone, tBuOOH proves to be a better oxidant for [Mn(bpy)₂]²⁺-NaY-PDMS. The reactions in batch and fed-batch reactors are discussed. A simple regeneration procedure, monitored by FT-IR spectroscopy is proposed.     

Extraction of halide quaternary salts in an organic solvent/water system: Hydrodynamics and mass transfer

The hydrodynamic characteristics and mass transfers of halide quaternary salts between two immiscible phases in a stirred membrane permeation cell were investigated. The concentration of quaternary salt, temperature, solvent and the four kinds of halide quaternary salts were evaluated to achieve the extractive optimum condition. The diffusivity, overall mass‐transfer coefficients and individual mass‐transfer coefficients were determined and correlated in terms of the conventional Sh‐Re‐Sc relationship. The transfer time of quaternary salts across the membrane and the thickness of the hydrodynamic diffusion boundary layer were determined as well, so as to characterize the extractive phenomenon of quaternary salts between the two phases that is useful in phase‐transfer catalysis.     

Models for the formation of poly(butylene terephthalate): effect of water on the kinetics of the titanium tetrabutylate-catalysed reactions: 3

In an effort to investigate the mechanism of catalysis of titanium tetrabutoxide on the polycondensation of poly(butylene terephthalate), alcoholysis and hydrolysis reactions were studied with the aid of model molecules. The retarding effect of water has also been taken into account. Appropriate kinetic equations are derived and discussed and the results compared with experimental data obtained at different molar ratios of reactants.     

丁酸异戊酯催化合成研究进展

综述了采用FeCl3·6H2O、十二水合硫酸铁铵、硫酸铝、硫酸钛、杂多酸(盐)、对甲苯磺酸、氨基磺酸、强酸性阳离子交换树脂DOOX和脂肪酶等催化合成丁酸异戊酯的方法     

On the Direct Addition of Amine N–H to Ch≡C Triple Bonds with Late Transition Metal Catalysts

The kinetics of the transition metal-catalysed direct addition of amine NH bonds to carbon--carbon multiple bonds (hydroamination) has been explored by in situ spectroscopic techniques. From an open mass balance it was concluded that an intermediate species was formed during the cyclisation of 6-aminohex-1-yne. This species was identified as the enamine 2-methylene-piperidine, which is the primary hydroamination product.     

过渡金属碳化物的催化研究进展

过渡金属碳化物作为一种催化新材料得到了人们广泛的关注,在催化加氢、脱氢、脱硫(HDS)、脱氮(HDN)和重整等方面,表现出优良的催化活性和选择性.综述了碳化钒、碳化钼、碳化钨、碳化铁、碳化钛等碳化物的催化性能和碳化物在各个反应中的催化机理的研究进展.     

甲基磺酸镧催化缩醛化反应性能的研究

以正辛醛和乙二醇为原料,甲基磺酸镧为催化剂,合成了正辛醛缩乙二醇。采用正交实验法考察了影响收率的因素。其最优条件为,正辛醛∶乙二醇∶催化剂∶带水剂为1m o l∶1.2m o l∶7.5g∶75mL,反应在回流温度下进行,反应时间3.0h,收率可达87.2%。用此方法合成了其它三种缩醛,同样获得满意结果。证明甲基磺酸镧对缩醛化反应具有较高的催化活性。     

镍基均相络合催化剂苯加氢反应动力学研究

采用工业上应用较成功的HC-402-2型镍基均相Z iegler型络合催化剂,在排除扩散影响的条件下,研究了苯均相催化加氢制环己烷的反应动力学。在反应温度150~210℃、总压1.0~2.4MPa的范围内,考察了反应温度、氢分压和苯浓度对反应速率的影响。实验结果表明,苯加氢均相催化反应对苯浓度的反应级数为零级,对氢分压的反应级数为一级,反应活化能为36 435.27 J/mol。经检验,该动力学模型的相关系数大于0.9,模型合理,能够描述实际反应过程。     

Electrocatalytic hydrogenation of cyclohexanone: Simple dynamic cell design

The electrocatalytic hydrogenation of cyclohexanone has been investigated with catalytic powder particles made of metal nanoaggregates deposited on a nonconductive material such as activated carbon and alumina. The catalytic powder particles were suspended in the solution under vigorous stirring conditions. The brief contact of the powder particles with a porous carbon cathode was sufficient to form adsorbed hydrogen on the metallic nanoaggregates through water electrolysis and initiate the electrohydrogenation process. It is demonstrated that the key parameters of the electrohydrogenation process are both the nature of the metallic nanoaggregates and the nature of the non-conductive material. The hydrodynamics of the solution under vigorous stirring conditions have also been studied for the particular cell used in the present study.     

Cis–trans isomerization of olefinic alcohols promoted by Rh(I) complexes

Homogeneous hydrogenation and isomerization reaction of cis-2-butene-1,4-diol has been investigated in ethanol by using tris(triphenylphosphine)chlororhodium(I), RhCl(PPh₃)₃, and triethylamine at 303 K and 0.01–0.1 MPa partial hydrogen pressure. Under reduced H₂ pressure, the geometric isomerization reaction occurs, to a high extent, leading to trans-2-butene-1,4-diol up to 93% selectivity at 90% conversion of the cis analogous. Effects of H₂ partial pressure as well as triethylamine, added phosphine and olefin concentrations on the rate of reaction and on the products distribution were also investigated. The results obtained can be interpreted on the basis of a proposed mechanism in which RhH(PPh₃)₃ is the active species. The high selectivity towards cis-trans isomerization of cis-2-butene-1,4-diol is attributed to steric factors of the Rh(I) coordinated triphenylphosphine groups.