MeCeOx(Me=In,Zr)固溶催化剂制备及催化合成碳酸二甲酯研究

Preparation of MeCeOx(Me=In,Zr)Solid Solution Catalyst for the Application in the Synthesis of Dimethyl Carbonate

采用液相共沉淀法制备了MeCeOx(Me=In,Zr)双金属氧化物固溶催化剂。借助X射线衍射(XRD)、X射线光电子能谱(XPS)、程序升温还原(H 2-TPR)、程序升温脱附(CO2-TPD、CH 3OH-TPD)及漫反射傅里叶变换红外光谱(DRIFTS)等手段对催化剂物化性质进行了分析表征。在系统考察不同金属氧化物种类和掺杂量的基础上,对比研究了不同金属氧化物掺杂改性CeO2制得固溶催化剂的结构性质及催化行为。结果表明:不同金属氧化物掺杂改性制得的MeCeOx(Me=In,Zr)双金属氧化物,由于形成的固溶结构增大了氧空位缺陷浓度;InCeOx具有最大的氧空位缺陷浓度和CO2、CH 3OH分子化学吸附量;在反应压力1.0 MPa、反应温度140℃,反应空速(GHSV)3600 mL/(g·h)、V(CO2)/V(CH 3OH)/V(N2)=4∶1∶5条件下,InCeOx表现出优异的催化性能,碳酸二甲酯(DMC)选择性91.3%,CH 3OH转化率8.4%,碳酸二甲酯STY(时空产率)达0.11 g DMC·h^-1·g^-1 cat。原位红外分析进一步揭示了氧空位活化CO2及中间体单配位甲氧基的形成是碳酸二甲酯高选择性的关键。

MeCeOx(Me=In,Zr)bimetallic oxide catalysts were prepared by liquid-phase co-precipitation method with a matrix of CeO2.The physiochemical properties of MeCeOx were characterized by X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),temperature programmed reduction(H 2-TPR),temperature programmed desorption(CO2-TPD,CH 3OH-TPD),and diffuse reflectance infrared fourier transform spectroscopy(DRIFTS)techniques.Based on the systematic investigation of the types and doping amounts of various metal oxides,the structure properties and catalytic behavior of solid solution catalysts prepared by doping CeO2 with different metal oxides were comparatively studied in this paper.The results show that the solid solution structure formed by MeCeOx bimetal oxide catalysts increases the concentration of oxygen vacancy defects.The InCeOx solid solution catalyst exhibit the largest concentration of oxygen vacancy defects,resulting in the improve chemical adsorption for CO2 and CH 3OH molecules.Under the condition of reaction pressure 1.0 MPa,reaction temperature 140℃,reaction space velocity(GHSV)3600 mL/(g·h)and V(CO2)/V(CH 3OH)/V(N2)=4∶1∶5,the InCeOx shows the excellent catalytic performance with dimethyl carbonate selectivity of 91.3%,CH 3OH conversion of 8.4%,and dimethyl carbonate STY(Space Time Yield)of 0.11 g DMC·h^-1·g^-1 cat.In addition,further in-depth DRIFTS study show that activation of CO2 with oxygen vacancies and the formation of terminal methoxy as the intermediate are the crucial to the enhance selectivity of dimethyl carbonate.