Synthesis, characterization and evaluation of sulfonic resins as catalysts

Ion-exchange resins have been often used as catalysts especially those based on styrene-divinylbenzene copolymers with sulfonic acid groups in the aromatic rings of polymer chains. That is due to the advantages of heterogenous catalysis over the homogeneous acid catalysis. Moreover, resin catalysts can often lead to high selectivity in organic reactions due to the matrix effects. Therefore, the study of copolymers synthesis conditions to determine the type of polymer structure produced as well as the characterization of sulfonic resins obtained thereof are of great interest. The current paper describes the synthesis, characterization and evaluation as catalysts of sulfonic resins derived from polymer supports synthesized by aqueous suspension polymerization of styrene and divinylbenzene. The reaction conditions were varied and polymer supports with different physical properties and morphological characteristics were obtained. The polymer supports were chemically modified by sulfonation. The resultant sulfonic resins had their catalyst activity evaluated in the esterification of acetic acid with n-butanol.     

2-vinyloxy ethyl phthalimide polymerization initiated by 1-(isobutoxy) ethyl acetate in the presence of ethyl aluminum dichloride and either ethyl acetate or ethyl benzoate

2-Vinyloxy ethyl phthalimide (ImVE) was polymerized using 1-(isobutoxy) ethyl acetate as the initiator in the presence of ethyl aluminum dichloride and either ethyl acetate or ethyl benzoate. The resulting polymers have a narrow molecular weight distribution, and their molecular weight can be controlled within a narrow range by varying the monomer and initiator concentrations. Diblock copolymers with n-butyl vinyl ether can also be formed. The behavior of the polymerization is consistent with a living cationic mechanism. A brief comparison of the title system with other initiating systems is also presented. © 1996 John Wiley & Sons, Inc.     

Hydrolysis and polycondensation of ethyl silicates. 2. Hydrolysis and polycondensation of ETS40 (ethyl silicate 40)

The effects of catalysts, pH and reaction conditions on the course of the hydrolysis and condensation of ETS40 (ethyl silicate 40), and on the composition of the reaction products were studied with the aid of gas and gel chromatography, potentiometry and gelation tests. Strong acids (HCl, HClO₄, HNO₃, H₂SO₄, p-toluenesulphonic acid), weak acids (Cl₃, CCOOH, ClCH₂COOH, (COOH)₂, CH₃COOH and HCOOH) and bases (LiOH, NH₄,OH) were used as catalysts.

The hydrolysis rate increased with increasing temperature, catalyst concentration, initial water concentration and initial ethyl silicate concentration, whereas it decreased with increasing number of Si atoms in the ethyl silicate molecules. At pH 0–7 the hydrolysis was acid catalysed, but at pH above 7.0 it was base catalysed. Simultaneously with the hydrolysis, condensation occurred at a rate which increased with increasing temperature, catalyst concentration, ETS40 concentration and, above all, with increasing initial water concentration. The condensation rate depended on the pH. The condensation was at its slowest for pH around 2.0. For pH below 2.0, the condensation increased with increasing hydrogen ion concentration; for pH above 2.0 the condensation increased with decreasing hydrogen ion concentration. Phosphoric acid and hydrofluoric acid increased the rate of condensation considerably. The reaction of ETS40 with water at pH around 2.0 gave rise during the hydrolysis to solutions of ethoxyhydroxysiloxanes with an average of 14–20 Si atoms in a molecule, which displayed long-term stability.     

Kinetics of ethanol dehydrogenation into ethyl acetate

The kinetics of gas-phase dehydrogenation of ethanol into ethyl acetate over a copper-zinc-chromium catalyst has been investigated in a flow reactor at pressures of 10–20 atm and temperatures of 230–290°C. For the process occurring under kinetic control, the rate constants of two reactions and the adsorption constants of five components have been determined using the Langmuir-Hinshelwood model. A kinetic model has been developed for the process. This model provides means to design a reactor for dehydrogenation of ethanol into ethyl acetate in different regimes.     

添加乙酸乙酯对生物油稳定性的影响

以稻草秸秆快速热裂解生物油为样品,选取乙酸乙酯作为添加剂,按不同质量分数(分别为1%、6%、11%、16%和21%)添加到生物油中,考察原始生物油(空白组)及乙酸乙酯组生物油理化特性随贮存时间的变化规律。结果表明,随着乙酸乙酯添加质量分数增大,各乙酸乙酯组(1%、6%、11%、16%和21%)生物油最终pH值比空白组分别提高0.66%、2.33%、3.65%、4.32%和6.31%;最终含水率比空白组分别降低10.90%、20.17%、28.19%、30.27%和35.10%;最终运动黏度比空白组分别降低13.69%、39.08%、57.99%、66.00%和73.58%。FT-IR和GC-MS分析结果表明,添加乙酸乙酯能抑制生物油老化反应。此外,GC-MS分析结果还证实乙酸乙酯可以减少生物油内有机酸含量。     

Oxymethylation of trifluoromethanesulfonamide with paraformaldehyde in ethyl acetate

Acid-catalyzed reaction of trifluoromethanesulfonamide with paraformaldehyde in ethyl acetate led to the formation of oxymethylated products that did not form in the reaction carried out in sulfuric acid. Following products were obtained: 5-trifluoromethylsulfonyl-1,3-dioxazinane, 3,7-bis-(trifluoromethylsulfonyl)-1,5,3,7-dioxadiazocane, and a complex of trifluoromethanesulfonamide with 2,4,8,10-tetraoxospiro[5,5]undecene, 1:1. The spiroring resulted from the cyclization of pentaerythritol under the action of formaldehyde. The pentaerythritol formed in its turn by oxymethylation of the methyl group of ethyl acetate with paraformaldehyde followed by the reduction of the COOEt group into CH₂ OH by the formaldehyde.     

Hydrogenation of ethyl acetate over supported rhenium catalysts

Re/Sibunite is a more active and selective catalyst for hydrogenation of ethyl acetate to ethanol under elevated temperatures and hydrogen pressures than Re/θ-Al₂O₃ and Re/γ-Al₂O₃. The activity of the catalyst is increased on replacing NH₄ReO₄ with HReO₄ and treatment of the support with a 13% solution of HNO₃. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1006–1008, May, 1999.     

Anodic perfluoroalkylation of the enol acetate of ethyl acetoacetate

Electrochemical perfluoroalkylation of the enol acetate of ethyl acetoacetate was studied in the conditions of the Kolbe reaction. The yields of alkylation products depend on the competing adsorption of the enol acetate, the solvent, and perfluorocarboxylates on the surface of a platinum electrode.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2948–2951, December, 1996.     

Acidity function of methanesulfonic acid solutions in ethyl acetate

The acidity function of solutions of methanesulfonic acid (MSA) in ethyl acetate (EA) was measured by the indicator method at 25 °C in the 0.4—100% concentration range. Molecular complexes formed by MSA and EA show a higher ionizing activity than H₅O₂ ⁺ ions. The relative ionizing activity of the MSA·EA complexes and ion pairs formed by MSA and DMF was determined.     

改性固体酸催化合成乙酸乙酯

鉴于经典酯化反应中,浓硫酸作为催化剂存在高腐蚀性、污染(废酸)性、危险性等诸多弊端,使用固体酸是当前最有效的解决途径之一.本文以改性强酸型离子树脂为催化剂,以乙酸的单程转化率为评价依据,通过单一因素分析法优化乙酸乙酯的制备条件.利用扫描电镜、X射线衍射分析仪对固体酸进行表征.SEM分析结果表明,Fe~(3+)改性固体酸树脂出现大量孔状结构;试验确定了乙酸乙酯的最佳制备条件为:乙醇与乙酸的体积比为1.4∶1,催化剂用量为1.2 g,反应时间为1.5 h,乙酸的单程转化率可达62.7%,总转化率为89.3%;重复试验发现,改性树脂经过连续5次使用后,乙酸的单程转化率依然可达57%,明显高于浓硫酸催化的效果.     

Lipase-mediated selective acetylation of primary alcohols in ethyl acetate

An environmental friendly process to selectively acetylate primary alcohols was demonstrated. The esterification process consists of treatment of a primary alcohol in the presence of immobilized C. antarctica lipase (Novozyme-435) in ethyl acetate at room temperature. Primary alcohols were acetylated in the presence of secondary alcohols and phenols.     

H2-D2 equilibration reaction on palladium/sulfonic resins

Resin supported palladium metal was prepared from [Pd(NH₃)₄]-form sulfonic resin by treatment: with H₂. The CO adsorption and H₂-D₂ equilibration reaction were greatly promoted by treatment above 373 K where Pd(II) was reduced to Pd(O) as indicated by XPS study. The reaction rate is of the 2.5th order with respect to the metal sites.

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, , [Pd(NH₃)₄]- H₂. CO H₂-D₂ 373 , Pd(II) Pd(0), . 2, 5 .