Controllable Acid/Base Propriety of Sulfate Modified Mixed Metal Oxide Derived from Hydrotalcite for Synthesis of Propylene Carbonate

Zhongxie Ding,Zhen Liu,Xiaoqian Ren,Xingguang Zhang,Wenlong Xu,Jiecan Shen,Jinhua Liang,Min Jiang

doi:10.3390/catal9050470

Abstract

Ammonium persulfate modified mixed metal oxide derived from hydrotalcite with tunable acid/base properties can be prepared via thermal decomposition of Mg-Al hydrotalcite-type precursors and ammonium persulfate. By controlling the ammonium persulfate content, these sulphur mutated samples, denoted as SMgAlO-y (y = 1; 3; 5; 7), were investigated in this research. The resulted materials were characterized by XRD, SEM, FT-IR spectra, Py-IR spectra, XPS, Hammett indicator, CO2-TPD, as well as NH3-TPD. Furthermore, the acid-base property of the sample surface was determined by inverse gas chromatography measurements (IGC). Among all the obtained outcomes, the target SMgAlO-5 demonstrated the maximal Ka/Kb value, and it presented the highest activity as a catalyst in the synthesis of propylene carbonate (PC) through 1,2-propylene glycol and urea, giving the yield of 97.2% at the optimized reaction condition, which indicated that the PC yield counted on the synergic effect of the acidity and basicity on catalysts.

Highlights

Propylene carbonate (PC) is a typical inert organic solvent and is widely applied to synthesize dimethyl carbonate, diethyl carbonate, and macromolecular polymers [1,2,3,4,5,6]
Encouraged by the preceding achievements, we report the synthesis of propylene carbonate (PC) from 1,2-propylene glycol (PG) and urea by constructing the mixed metal oxide derived from hydrotalcite catalysts with controllable acid/base properties [23,24,25,26]
The catalyst morphology can be directly elucidated through scanning electron microscope (SEM) images of MgAlO and SMgAlO-y, which are presented in Figure 1b,c and images of MgAlO (b), and SMgAlO-5 (c)

Summary

Introduction

Propylene carbonate (PC) is a typical inert organic solvent and is widely applied to synthesize dimethyl carbonate, diethyl carbonate, and macromolecular polymers [1,2,3,4,5,6]. Propylene glycol, used as raw material in this method, is a byproduct in the transesterification process for the synthesis of dimethyl carbonate [10,11,12]. In this regard, such synthetic strategy conforms to the concept of environmentally-friendly process. The requirement of reaction conditions is extremely harsh when these materials were applied as catalysts in the synthesis process, which constricted by thermodynamic equilibrium, and an additional vacuum condition is obligatory [17]. The reaction may bring γ-valerolactone into the yield mixture through a Catalysts 2019, 9, 470; doi:10.3390/catal9050470 www.mdpi.com/journal/catalysts

Methods

Results

Discussion

Conclusion