Synthesis of ethylene carbonate from cyclocondensation of ethylene glycol and urea over ZnO•Cr2O3 catalyst system controlled by co-precipitation method

Abstract

KEYWORDSZnO·Cr2O3 catalyst has been synthesized by low temperature, pH controlled co-precipitation route and characterized employing techniques of Brunauer, Emmett, and Teller (BET) surface area measurement, ammonia desorption technique, X-ray diffraction (XRD) and scanning electron microscopy (SEM). These characterizations reveal the catalyst to possess ZnO·ZnCr2O4 composition. The catalysts have been tested for their performance for the first time, in the synthesis of ethylene carbonate from cyclocondensation of ethylene glycol and urea. Effect of catalyst concentration, temperature and molar ratio of reactants has been studied to obtain the optimum conversion and selectivity of ethylene glycol and urea to ethylene carbonate. A maximum yield of 85.75% of ethylene carbonate was obtained at a temperature of 423 K and urea: ethylene glycol molar ratio of 1:1.5. A tentative mechanism of the reaction is proposed on the basis of analysis of reactants, products and modeling of the transition state for the reaction under density function theory using Gaussian09W software. Our studies suggest a consecutive mechanism for the reaction. In the first step, urea and ethylene glycol react to produce 2-hydroxyethyl carbamate, which undergoes further reaction to produce ethylene carbonate (EC) and ammonia. Urea Zinc chromite Ethylene glycol Co-precipitation Cyclocondensation Ethylene carbonate

Rational and Statistical Approaches in Enhancing the Yield of Ethylene Carbonate in Urea Transesterification with Ethylene Glycol over Metal Oxides

“…An identical conclusion was drawn by Bhanage . Bhadauria studied Cr-containing zinc oxide materials, while Zhao investigated Fe-containing materials. In both studies the formation of the spinel phases (ZnCr 2 O 4 and ZnFe 2 O 4 ) was found to be important, promoting EC yield.…”

Low temperature pretreatment of sugarcane bagasse at atmospheric pressure using mixtures of ethylene carbonate and ethylene glycol

“…EC and EG can be converted to each other under certain conditions. 51,52 EC and EG are also renewable chemicals as technologies on the conversion of lignocellulose to EG have been demonstrated. 53,54 A low energy consumption lignocellulose pretreatment process was developed in the present study with the use of an acid-catalysed EC-EG system.…”

“…33 EG also can be converted into EC to compensate for the loss of EC during decomposition. 52 The low temperature pretreatment process with the use of acidified EC-EG solutions is shown in Fig. 4.…”

DFT-Assisted Mechanism Evolution of the Carbonylation of Ethylene Glycol to Ethylene Carbonate by Urea over Zn(NCO)2·2NH3 Catalyst

“…The synthesis of cyclic carbonates from diols and urea has attracted attention recently because of many benefits such as mild operating conditions, high yield, and easy availability of raw materials. Various oxides, such as CaO, La 2 O 3 , MgO, ZnO 2 , Al 2 O 3 , zinc/iron, and ZnO–Cr 2 O 3 , have been used as catalysts. Recent studies on the carbonylation of methanol suggest ZnO to be the best catalyst for these reactions and that ZnO completely dissolves in the reaction mixture, making the reaction homogeneously catalyzed by Zn­(NCO) 2 ·2NH 3 . , It has been suggested that the reaction between EG and urea catalyzed by metal oxides proceeds through a consecutive mechanism.…”