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 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.     

A highly regioselective catalyst of epichlorohydrin acidolysis

The effect of the catalytic system on the course of addition of carboxylic acids to epichlorohydrin was studied. A high regioselectivity of addition was observed in the presence of chromium(III) acetate. The regioselectivity improved with the size of the carboxylic acid molecule. © 1998 Society of Chemical Industry     

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     

Effects of acetic acid addition methods on butyl acetate enzymatic synthesis

Abstract

Butyl acetate is a versatile chemical due to its excellent solvency for polymers, resins, and oils. In this work, the butyl acetate synthesis was studied by the esterification of n-butanol with acetic acid using the commercial immobilized lipase Novozym^® 435. The acetic acid and n-butanol concentrations have to be limited in the enzymatic synthesis of this ester due to the deleterious effects caused by these reagents on the enzyme. Three methods of acetic acid addition (single, stepwise and continuous addition) were investigated to minimize the acid concentration. A significant drop on acid conversion was observed in the presence of a higher concentration of the reagents when single or stepwise acid addition was used. However, a solvent-free system using a continuous addition of acetic acid favored butyl acetate synthesis, reaching a conversion of 84% at 60?°C, employing 5?wt% of enzyme and n-butanol/acetic acid final molar ratio equal to 1/1.     

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     

乙酸(酯)-甲醛缩合制丙烯酸(酯)研究进展

近年来,通过乙酸（酯）和甲醛缩合制备丙烯酸的新路线吸引了学术界和工业界的广泛关注。此新路线的优点是过程简单,原料可从天然气、煤化工产品中获得,成本低廉,对可持续生产丙烯酸具有十分重要的意义。国内外研究者针对这一反应开发了多种类型的催化剂,包括钒磷氧（VPO）类催化剂、负载型碱金属/碱土金属以及离子液体等。本文综述了不同种类催化剂近期的研究成果,总结了三类催化剂的优缺点。指出均相的离子液体催化剂具有反应温度低、能耗少、选择性高的特点,但反应为间歇操作,产物分离困难、催化剂较难重复利用,催化效率偏低。VPO类催化剂和碱金属/碱土金属类催化剂,反应温度较高（320～400℃）,但可实现连续反应,产物分离方便,催化效率较高。相比于VPO类催化剂,碱金属/碱土金属类催化剂涉及的反应较少,对目标产物的选择性较高,但整体催化效能低于VPO类催化剂,且失活催化剂再生困难。最新的研究结果表明,经典的有机相法制备VPO前体可以被更加简便、经济与环境友好的一锅水相法取代。空气氛中简单焙烧即可完成催化剂前体的活化。不仅大大简化了催化剂制备,而且所得催化剂的小试性能优异,从而为后续应用奠定了重要基础。     

X‐ray photoelectron spectroscopy investigation of the interaction of U(VI) and Fe(III) with natural humic acid in aqueous solutions

Complexes of U(VI) and Fe(III) with natural humic acid (NHA) were studied by X‐ray photoelectron spectroscopy (XPS). It follows from the analysis of the uranium and iron concentrations at the surface and in the bulk of the humates that the reaction in solution is heterogeneous. The NHA reacts as a particle. In solutions containing either U(VI) or Fe(III), NHA reacts similar with Fe(III) and U(VI). However, in a mixed solution of Fe(III) and U(VI), NHA reacts predominantly with iron. In comparison to Fe(III) complexes, the complexes with U(VI) are formed mostly in the inner of the NHA particle. Therefore, the concentration ratio U/Fe as measured by XPS increases by powdering of the particles. Salts of Fe(III) can be used to inhibit the uranium migration in form of its soluble humates.     

Electrodeposition of chromium from Cr (III) electrolytes in the presence of formic acid

Chromium coatings deposited from sulphate, chloride and perchlorate electrolytes based on the [Cr(H₂O)₄(HCOO)]²⁺ complex ion were investigated. The current efficiency reached 30% in the case of chloride electrolyte for various current densities in the range 4–10 A dm^-2 depending on pH. Such a large current efficiency is due to the catalytic effect of the chloride ions on the electroreduction of the chromium complex to metallic chromium. Deposition of chromium from sulphate electrolyte took place with a current efficiency of 16% which rose for higher pH and lower current densities. Semi-bright and bright coatings with thickness of approximately 10m of good adhesion to a copper electrode were deposited from chloride and sulphate electrolytes.     

Reactions of hydroxymethyl derivatives of uric acid with oxiranes. II. An analysis of reaction course and product structure

Polyetherols containing thermostable purine rings are obtained in reactions of hydroxymethyl derivatives of uric acid with an excess of ethylene oxide or propylene oxide. By using elementary analytical tools and ¹H‐NMR spectroscopy, it was possible to follow the course of reaction at various molar ratios of reagents. A migration of formaldehyde molecules from N‐hydroxymethyl groups or from oligooxymethylene bridges to the end of oxyalkyl chains was observed. At the same time, the O‐hydroxymethyl groups are successively blocked by oxiranes. The most probable structure of polyetherols is proposed. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1955–1962, 2002     

乙炔法合成醋酸乙烯催化剂的研究进展

从催化剂载体、活性组分、反应机理三个方面回顾了国内外乙炔法合成醋酸乙烯催化剂的研究进展，并对今后的发展方向进行了展望。     

Oxidation of cyclohexanone to adipic acid with a cobalt acetate/oxygen/acetic acid system

The liquid phase oxidation of cyclohexanone to adipic acid at 378 K using oxygen as the oxidising agent and cobalt acetate as the catalyst in an acetic acid medium was investigated both at atmospheric pressure and at a pressure of 0.5MN m⁻². The effects of catalyst concentration, solvent concentration and partial pressure of oxygen, were studied at a constant stirrer speed of 535 rev min⁻¹. Increasing the solvent concentration and decreasing the catalyst concentration (up to 0.113×10⁻³ kmol m⁻³) had positive effects on the overall first order reaction rate constant. It was also found to vary linearly with gas flow rate.     

Protein hydrolysis under anaerobic,saline conditions in presence of acetic acid

The hydrolysis of soluble proteins in an anaerobic, saline (24 g dm^?3 NaCl) and mesophilic (37 °C) environment was studied. The inhibitory effect of a volatile fatty acid, acetic acid (HAc), on the hydrolysis rate and hydrolytic biomass activity for a model saline wastewater with a high protein load (total organic carbon, 1153 mg dm^?3 and 1572 mg dm^?3 proteins) was studied. Initial inhibitor concentrations were tested in the range of 0–2000 mg dm^?3 HAc. The microbiological characterization was performed using a total microorganism count by epifluorescence, and hydrolytic bacterial activity was determined by plate count. The protein hydrolysis was modeled according to first order kinetics. The effect of biomass on hydrolysis was analyzed by varying its concentration in the range of 42–210 mg dm^?3 volatile suspended solids. The following apparent hydrolysis kinetic constants (K_h) for proteins at 37 °C were obtained: 1.3, 0.8, 0.6, 0.2 and 0.1 d^?1 for initial concentrations of 250, 500, 750, 880, and 1000 mg dm^?3 HAc, respectively. At concentrations of HAc greater than 1000 mg dm^?3, total inhibition of hydrolysis was observed. The intrinsic hydrolysis constant ( ) at 37 °C, without inhibition, was 2.3 d^?1. The hydrolysis kinetic constant was not affected by the biomass concentration. The hydrolysis kinetics constant was filted to three models: Luong, Levenspiel and non‐competitive inhibition. The model that best represented the experimental data was Luong, obtaining an inhibition constant (K_I) of 1087 mg dm^?3 of HAc and the exponent γ = 0.54. The hydrolysis was inhibited by the presence of HAc, which corresponds to an intermediate compound of the anaerobic process. Copyright © 2004 Society of Chemical Industry     

Dehydration of carboxylic acids on the MgO(100) surface

The interaction of formic and acetic acids with the MgO(100) surface has been studied under UHV conditions using XPS and TPD. Both acids dissociated heterolytically on the MgO surface, forming surface formate and acetate species respectively. The carboxylates decomposed at 520 K into dehydration products H₂O + CO from HCOO, and H₂O+CH₂CO from CH₃COOH.     

Oxidation of m-cresol acetate in the presence of acetic anhydride (preparation of m-hydroxybenzyl alcohol diacetate)

A study was made of regularities of oxidation of m-cresol acetate to m-hydroxybenzyl alcohol diacetate. It was shown that during oxidation of m-cresol acetate at a temperature of 170° and a concentration of acetic anhydride of 6·5 × 10⁻³ mole/l. The yield of m-hydroxybenzyl alcohol diacetate on converted m-cresol acetate reaches 45 mole %.     

醋酸甲酯水解用杂多酸类催化剂的筛选

针对醋酸甲酯水解悬浮催化蒸馏工艺的要求,对杂多酸盐类酸性材料用作醋酸甲酯水解反应的催化剂进行了探索。从催化反应性能以及结构稳定性等方面对杂多酸及其盐进行评价和表征。实验证明,不同杂多酸及其盐的催化性能与杂多阴离子和阳离子的种类、阳离子取代基数目等因素有关,其中NH4H2PW12O40催化性能最好,反应重复性能也比较好;杂多酸铵盐反应前后结构无明显变化,具有良好的结构稳定性;NH₄H₂PW₁₂O₄₀的酸强度和总酸量也较高。     

叔碳酸合成工艺条件优化

以二异丁烯、一氧化碳为原料,羰基铜溶液为催化剂,在加压和混酸反应介质存在的条件下合成了叔碳酸。考察了反应温度、压力、催化剂用量以及烯烃加料时间对反应收率的影响,确立了优化条件,小试收率达80％以上,经中试放大收率可达90％。     

CH4和CO2在临氧条件下多相催化合成乙酸

在总结国内外CH₄-CO₂直接合成乙酸和CH₄、CO₂在临氧条件下活化转化的研究进展基础上，论证了在CH₄-CO₂体系引入氧改善热力学和在多相催化作用下直接合成乙酸的可行性。     

Study on controlled free‐radical polymerization in the presence of dithiobenzoic acid (DTBA)

Polymerizations of methylacrylate, styrene and methyl methacrylate were carried out in the presence dithiobenzoic acid (DTBA). The results exhibit controlled polymerization characters: well‐controlled molecular weight, narrow molecular weight distribution (minimal value: 1.08), molecular weight linearly increasing with conversion and first‐order kinetics of polymerization. The polymers were characterized by ¹H NMR and GPC. The effect of temperature and molar ratio DTBA/AIBN on polymerization was investigated. A mechanism is proposed to explain the controlled polymerization characters. © 2000 Society of Chemical Industry