Influence of Y on the performance of Mg-Al-Y catalysts via hydrotalcite-like precursors for the synthesis of diethyl carbonate from ethyl carbamate and ethanol

Abstract

A series of Mg-Al-Y mixed oxides (CHT-Y) with different Y3+:(Al3++Y3+) atomic ratios were obtained by thermal decomposition of Y-containing hydrotalcite-like compounds. Then, they were characterized using XRD, TGA, XPS, SEM, ICP, CO2-TPD and N2 adsorption-desorption measurement. Meanwhile, all the mixed oxide catalysts were evaluated for the synthesis of diethyl carbonate (DEC) from ethyl carbamate (EC) and ethanol. The results showed that the texture, structure, basic property as well as catalytic activity of CHT-Y were closely associated with the content of Y in the catalyst. Importantly, the role of basic sites was studied in overall reaction and in every comprising reaction path identified in this research. It was found that the reaction of EC and ethanol could be improved by the moderate and strong basic sites of catalyst, while the side-reactions towards undesired products were strongly catalyzed over the catalyst with high basic strength. As a result, the best result was achieved over the catalyst with Y3+:(Al3++Y3+)=0.3. Under the optimal reaction conditions, the yield of EC reached 63.8% with a high DEC selectivity of 81.6%. Furthermore, the reusability test and catalyst characterization indicated that CHT-Y catalyst was heterogeneous and could be reused at least fourth time without obvious loss of reactivity.