Acid-base sites synergistic catalysis over Mg-Zr-Al mixed metal oxide toward synthesis of diethyl carbonate

Tingting Yan; Weihan Bing; Ming Xu; Yinwen Li; Yusen Yang; Guoqing Cui; Lan Yang; Min Wei

doi:10.1039/c7ra13629c

Acid-base sites synergistic catalysis over Mg-Zr-Al mixed metal oxide toward synthesis of diethyl carbonate

RSC Adv. 2018 Jan 26;8(9):4695-4702. doi: 10.1039/c7ra13629c. eCollection 2018 Jan 24.

Authors

Tingting Yan¹, Weihan Bing¹, Ming Xu¹, Yinwen Li¹, Yusen Yang¹, Guoqing Cui¹, Lan Yang¹, Min Wei¹

Affiliation

¹ State Key Laboratory of Chemical Resource Engineering, Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology Beijing 100029 P. R. China yanglan@mail.buct.edu.cn weimin@mail.buct.edu.cn.

Abstract

In heterogeneous catalysis processes, development of high-performance acid-base sites synergistic catalysis has drawn increasing attention. In this work, we prepared Mg/Zr/Al mixed metal oxides (denoted as Mg₂Zr _x Al_1-x -MMO) derived from Mg-Zr-Al layered double hydroxides (LDHs) precursors. Their catalytic performance toward the synthesis of diethyl carbonate (DEC) from urea and ethanol was studied in detail, and the highest catalytic activity was obtained over the Mg₂Zr_0.53Al_0.47MMO catalyst (DEC yield: 37.6%). By establishing correlation between the catalytic performance and Lewis acid-base sites measured by NH₃-TPD and CO₂-TPD, it is found that both weak acid site and medium strength base site contribute to the overall yield of DEC, which demonstrates an acid-base synergistic catalysis in this reaction. In addition, in situ Fourier transform infrared spectroscopy (in situ FTIR) measurements reveal that the Lewis base site activates ethanol to give ethoxide species; while Lewis acid site facilitates the activated adsorption of urea and the intermediate ethyl carbamate (EC). Therefore, this work provides an effective method for the preparation of tunable acid-base catalysts based on LDHs precursor approach, which can be potentially used in cooperative acid-base catalysis reaction.