The effect of reaction product on the rate of addition of acetic acid to epichlorohydrin in the presence of chromium(III) acetate

The kinetics of addition of acetic acid to epichlorohydrin carried out in the presence of both the reaction product and chromium(III) acetate catalyst have been studied. At an equimolar ratio of reagents the dilution of the reacting mixture with the reaction product has been found not to affect the reaction order. The presence of product in the starting mixture, as well as temperature increase, considerably reduces the selectivity of reaction. Side reactions of epichlorohydrin are activated. Activation energy, enthalpy and entropy of the reaction all decrease in the presence of reaction product. © 2001 Society of Chemical Industry     

Kinetics of addition of acetic acid to epichlorohydrin in the presence of DMF or DMSO

The kinetics of reaction between acetic acid and epichlorohydrin carried out in the presence of DMF or DMSO was studied. In addition, the conductivity of the reaction mixture was measured. The conductivity was found to increase considerably as the reaction proceeded. This was explained in terms of the formation of new effective forms of catalysts: the ammonium salt (in case of DMF) or sulphonium salt (for DMSO). A reaction scheme has been proposed, taking into account the active catalyst forms. The set of kinetic equations describing the reaction has been developed and the appropriate rate constants evaluated.     

Kinetics of addition of acetic acid to epichlorohydrin in the presence of alkali metal acetates

The kinetics of the reaction between acetic acid and epichlorohydrin in the presence of lithium, sodium and potassium acetates have been studied. The composition of the reaction mixture was followed chromatographically. Beside the two isomeric products of addition of epichlorohydrin to acetic acid, the presence was found of glycidyl acetate, glycerine dichlorohydrin and other products of parallel and subsequent reactions between the substrates and chlorohydroxyesters. A mechanism of the reaction, which takes into account the formation of the identified compounds has been proposed and a set of appropriate differential and balance equations developed. The rate constants for individual reactions as well as the catalysts used have been determined.     

Kinetics of acetic acid addition to epichlorohydrin in the presence of chromium acetate and chromic anhydride

The kinetics of the reaction between acetic acid and epichlorohydrin in the presence of chromium acetate and chromic anhydride have been studied. The isolation method revealed the reagents reacted with partial orders. A reduction of chromium from the oxidation level +6 to +3 has been observed when chromic anhydride was used as catalyst. A mathematical model for the overall process has been developed and the mechanism of reaction discussed.     

Kinetics of addition of acrylic and methacrylic acids to epichlorohydrin in the presence of chromium(III) ethanoate

The kinetics of the reaction between acrylic and methacrylic acids with epichlorohydrin in the presence of chromium(III) ethanoate have been studied. A mathematical model for the overall process has been developed and the mechanism of reaction discussed. © 1999 Society of Chemical Industry     

Kinetics and mechanism of reaction between acrylic acid or methacrylic acid and some oxiranes in the presence of N,N-dimethylaniline catalyst

The reactions of acrylic and methacrylic acids in ethylene oxide, propylene oxide, or glycerin epichlorohydrin were carried out in DMF in the presence of N, N-dimethylaniline catalyst. The kinetic equations describing these equations have been devised and activation parameters ΔH^#, ΔS^#, and ΔG^# calculated. The mechanism of the reaction has been proposed and verified by using kinetic and instrumental methods © 1998 SCI     

A highly regioselective synthesis of δ-lactones from meadowfoam fatty acids

Meadowfoam fatty acids, when treated with mineral acid catalysts in the presence of polar nonparticipating solvents, undergo a facile ring closure to form δ-lactones. Perchloric and sulfuric acids catalyze the cyclization at concentrations of 0.6–13 mole equivalents, both neat and in the presence of solvent. Under constant acid concentrations, methylene chloride was found to increase the rate of reaction, the regioselectivity for the formation of δ-lactone, and the overall yield. In the absence of solvent, increased acid concentration improved the yield of lactone but reduced regioselectivity for the δ-isomer. Solvent polarity plays a significant role in the regioselectivity of the cyclization for δ-lactone, with solvents of higher dielectric strength providing larger δ/γ ratios (38:1) and higher yields up to 92%.     

羧酸和烯烃酯化反应的催化剂研究进展

综述了20世纪60年代以来羧酸和烯烃酯化合成羧酸酯反应中催化剂的研究进展,包括磺酸类催化剂、多磷酸、离子液体、硅酸盐类催化剂、沸石分子筛催化剂、离子交换树脂、杂多酸类催化剂等,比较了各类催化剂的催化活性,并展望了羧酸和烯烃酯化反应的催化剂研究方向。     

A highly stable and efficient catalyst for direct synthesis of LPG from syngas

Liquefied petroleum gas (LPG) fuel was directly synthesized from syngas over a hybrid catalyst which contained a methanol synthesis catalyst and zeolite. The new hybrid catalyst composed of (Pd–Ca/SiO₂) and β-zeolite, showed a high activity and selectivity for LPG production. X-ray diffraction (XRD) characterization of the catalyst was used to analyze the deactivation of (Pd–Ca/SiO₂)/β-zeolite.     

高活性离子液体催化酯化反应的研究

制备了4种吡啶、三乙胺类水溶性离子液体,考察了其催化制备油酸乙酯的活性。结果表明,这4种离子液体催化活性很高,在醇酸摩尔比6∶1,反应温度77℃,反应时间6 h,催化剂用量8%反应条件下,乙基吡啶硫酸氢盐活性最高,酯化转化率可达95.9%;在催化混合脂肪酸的酯化反应中,4种离子液体均表现出较高活性,酯化转化率均高于94%,且离子液体稳定性好,可循环使用。     

Ring‐opening polymerization of epichlorohydrin and its copolymerization with other alkylene oxides by quaternary catalyst system

An effective quaternary catalyst consisting of trialkyl aluminum, phosphoric acid, electron donor, and water for ring‐opening polymerization of epichlorohydrin (ECH), as well as its copolymerization with ethylene oxide (EO), propylene oxide (PO), and allyl glycidyl ether (AGE) to obtain elastomers, were studied. We investigated the optimum composition for the quaternary catalyst; the character of the catalyst; the reactivity of the four alkylene oxides during homopolymerization and copolymerization; the behavior of ECH, EO, and PO during terpolymerization; and glass transition temperatures of the copolymer and terpolymers. The results showed that the nitrogen‐containing electron donors are suitable as the third component, whereas oxygen‐containing electron donors are not. Water as the fourth component can increase the molecular weight of the homopolymer and copolymers of ECH. According to the polymerizability of tetrahydrofuran with the quaternary catalyst and the reactivity ratios of the four alkylene oxides, the quaternary catalyst was assumed to be of a coordinated anionic type. The reactivity ratios for these four alkylene oxides were determined to be EO > PO > AGE > ECH. They were verified by terpolymerization of ECH, EO, and PO. The glass transition temperature of the terpolymer exhibits a minimum value at nearly 3:1 molar ratio of PO to EO, when the molar ratio of ECH used is constant at the beginning of terpolymerization. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2446–2454, 2001     

高效催化剂对切片性能的影响

研究了在1万t/a连续聚酯装置上使用高效催化剂合成的半消光切片的相对分子质量及其分布、结晶性能、流变性能以及热稳定性能，并与相同装置由常规催化剂合成的切片相对比。高效催化剂与常规催化剂制备切片具有相同的相对分子质量及其分布、结晶机理和流变性能。2种催化剂制备切片的热分解稳定性基本相同，高效催化剂制备切片的热降解稳定性略逊于常规催化剂切片，但可以满足纺丝加工要求。从总体上看，使用高效催化剂不会影响切片的内在质量。     

Hydroxyalkylation of barbituric acid. II. Synthesis of polyetherols with pyrimidine ring

The route of synthesis of new polyetherols with pyrimidine ring from barbituric acid (BA) was presented. The polyetherols were obtained in two steps: synthesis of hydroxymethyl derivative of BA followed by reaction of the latter with neat ethylene or propylene oxides. Physical properties of the products and preliminary application for fabrication of thermal stability polyurethane foams were determined. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Reactions of trithiocyanuric acid with oxiranes. II. Kinetics and mechanism of reactions

The study of the kinetics of the addition of trithiocyanuric acid to oxiranes (i.e., ethylene oxide and propylene oxide) in DMSO solution in the presence of triethylamine as a catalyst is described. The effects of the acid group concentration, the concentration of oxirane, and the catalyst on the course of the reaction was studied. The rate equation describing the addition was derived. The reaction order with respect to the oxirane, catalyst, and reactive groups of the acid were 0.5, 0.5, and 1.5, respectively. The mechanism of addition was proposed. The influence of temperature on the course of the reaction was also studied. The activation parameters (ΔH^#, ΔS^#, ΔG^#) were calculated. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 2081–2088, 2000     

A highly efficient synthesis approach of supported Pt-Ru catalyst for direct methanol fuel cell

A highly efficient synthesis approach of urea-assisted homogeneous deposition (HD) coupled with H₂ reduction has been employed to synthesize carbon-supported Pt-Ru catalyst with high metal loading of 60 wt%. The urea-assisted HD method permits in situ gradual and homogeneous generation of hydroxide ions, resulting in smaller Pt-Ru nanaoparticles deposited on the carbon support along with better particle size distribution compared with the catalyst prepared by the conventional impregnation-NaBH₄ reduction. The Pt-Ru catalyst prepared by the HD-H₂ method has demonstrated greatly enhanced catalytic activity towards methanol oxidation and much improved fuel cell performance compared with the one prepared by impregnation-NaBH₄ reduction. HD-H₂ method is simple with mild synthesis condition, but provides very efficient approach for the preparation of Pt-based catalysts for fuel cells.     

Synthesis of highly improved Ziegler‐Natta catalyst

The effects of media viscosity, mixing speed, and injection time on catalyst average particle size (APS), particle size distribution (PSD), and morphology in both conditions, with and without emulsifier, were investigated. Supports were prepared using a so‐called recrystallization method; then they were catalyzed under the same condition. To show the effects of emulsifier on the final product's properties such as catalyst activity, polymer isotacticity, and so on, two types of catalysts were polymerized and finally their results were compared. Scanning electron microscopy micrographs were used for morphological study. Results show that by increasing the media viscosity and injection time, APS of the catalyst support was decreased. But by increasing the mixing speed, APS was decreased and PSD was broadened. It was found that emulsifier reduces the sensitivity of APS and PSD of catalyst when the support preparation conditions are changed. Consequently, by employing emulsifier, highly improved catalyst was produced. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

乙烯和环烯烃共聚用有机金属催化剂

配位催化共聚是制备环烯烃共聚物的主要方法,目前商品化的环烯烃共聚物主要由乙烯与降冰片烯或者四环十二碳烯共聚得到。共聚单体及其含量是决定环烯烃共聚物性能的关键因素,而决定共聚单体含量的最核心因素是催化剂。本文从催化剂结构的角度出发,综述了乙烯和降冰片烯/四环十二碳烯共聚用有机金属催化剂,从双茂有机金属催化剂、单茂有机金属催化剂、非茂有机金属催化剂、后过渡金属催化剂等部分进行论述,同时论述了催化剂结构及关键聚合工艺（如温度、压力、单体浓度等）对催化活性及共聚单体插入量的重要影响。此外,由于乙烯与四环十二碳烯共聚活性低,未来针对该共聚反应的研究会继续进行。合成更多新结构的配体、开发更高活性的催化剂、构建更经济有效的反应体系将会是新的研究重点。     

A highly active and stable Fe-Mn catalyst for slurry Fischer–Tropsch synthesis

A highly stable and active Fe-Mn catalyst for slurry Fischer–Tropsch synthesis (FTS) was prepared and scaled up for the application in the industrial pilot plant at Institute of Coal Chemistry (ICC), Chinese Academy of Sciences (CAS). One Lab-scale catalyst and one scaled-up catalyst are introduced in the present paper. The particle size of the Lab-scale catalyst is about 5–15 μm, while it is increased to 30–90 μm for the scaled-up catalyst. Simultaneously, the morphology of the catalyst was greatly improved after the catalyst being scaled up. Both the Lab-scale and scale-up catalysts show high FTS activity. CO conversion of the Lab-scale catalyst and the scaled-up one are over 70.0% (H₂/CO = 0.67, 275 °C, 1.5 MPa and 3000 h⁻¹) and 55.0% (H₂/CO = 0.67, 260 °C, 1.5 MPa and 2000 h⁻¹), respectively. The catalysts also possess excellent stability, no obvious deactivation was observed during stable run of 4200 h and 1200 h on stream for the two catalysts. However, the Lab-scale catalyst produced more methane (about 8–10 wt%) and C_2–4 (22–30 wt%) and less C5⁺ hydrocarbon (55–70 wt%). Meanwhile, the hydrocarbon distribution of the catalyst was greatly improved for after the catalyst being scaled up, and the distribution of hydrocarbon products become much preferable. The selectivity to methane was well controlled at about 5 wt%, and the sum of and was increased to 91–93 wt%. On the whole, the scaled-up catalyst satisfies the requirements of the application for FTS in the industrial pilot plant of slurry bubble column reactor (SBCR) at ICC, CAS.     

A highly active Au/Al2O3 catalyst for cyclohexane oxidation using molecular oxygen

The selective oxidation of cyclohexane to cyclohexanone and cyclohexanol has been investigated over Au/Al₂O₃ catalysts using molecular oxygen in a solvent-free system. The catalysts were prepared by a modified direct anionic exchange method and characterized by AAS, N₂ adsorption and TEM. The results showed that the catalytic performance of Au/Al₂O₃ is very high in terms of turnover frequency. Moreover, the nano-size effect of gold is also reported in the reaction.