Synthesis of Propylene Carbonate Catalyzed by Copper-containing Hydrotalcite-like Compounds
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Synthesis of Propylene Carbonate Catalyzed by Copper-containing Hydrotalcite-like Compounds Xianmei Xie*, Lian Duan, Zhenghuang Wu, Lina Wang, Kai Yan, Lei Du College of Chemistry and Chemical Engineering, Taiyuan University of Technology, Taiyuan 030024, PR China *Corresponding author. Tel: (0351)6018564; Fax: (0351)6018564; E-mail: [email protected] ABSTRACT CuFe-Hydrotalcite-Like Compounds (CuFe-HTLcs) were synthesized by coprecipitation with Cu(NO3)2⋅6H2O, Fe(NO3)3⋅9H2O, NaOH and Na2CO3 solution. The sample with Cu2+ / Fe3+ = 2 was of the highest crystalline characterized by XRD and particle size distribution. The synthesis of propylene carbonate from 1,2-propanediol (PG) and urea was performed to evaluate the catalytic activities of the CuFe-HTLcs. The effects of reaction time, temperature, dosage of catalyst on the synthesis of propylene carbonate were fully discussed. The optimal reaction conditions were determined by using orthogonal test design: reaction temperature 170 ºC, dosage of catalyst 0.2 g, and molar ratio of PG to urea 2:1, reaction time 3 h. Under the optimal conditions, the conversion of urea nearly reached 100 %, and the selectivity of propylene carbonate was up to 90.4%. INTRODUCTION Propylene carbonates have been found numerous applications as both excellent inert solvents with low toxicity, biodegradability and high boiling point and reactive intermediates used for pharmaceutical and polymer synthesis, etc. [1-5]. Propylene carbonates could be synthesized from 1, 2-propanediol (PG) with phosgene, transesterification of PG with alkyl carbonate [6, 7], direct oxidation of olefins with carbon dioxide [8, 9]. In addition, propylene carbonates are mainly produced industrially by the cyclo-addition of carbon dioxide with propylene oxide [10]. Compared with those traditional routes for synthesis of propylene carbonates, the route from urea and PG shows lots of advantages, such as cheap and easily available feedstock, mild reaction condition and safe operation. Some metal oxide catalysts have been applied in this reaction to improve the conversion and selectivity. The catalytic performance of the catalysts for the synthesis of propylene carbonates and the mechanism of the reaction were also investigated [1]. Up to now, there has not been information available using hydrotalcites as catalysts for the synthesis of propylene carbonates. In the present work, CuFe-Hydrotalcite-like compounds (CuFe-HTLcs) are, for the first time, introduced into the synthesis of propylene carbonates from urea and PG. The CuFe-HTLcs showed excellent catalytic performance, and the selectivity of propylene carbonates reached 90.4%. At the same time, the conversion of urea is near 100%. EXPERIMENTAL Preparation and characterization of catalysts
The methods employed for CuFe-HTLcs preparation have been described previously [11]. Briefly, desired volumes of 1.0 M Cu(NO3)2⋅6H2O, 0.5 M Fe(NO3)3⋅9H2O were mixed to form one solution. The mixed solution was acutely stirred, and at the same time, 1.0 M NaOH solution and 0.5 M Na2CO3
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