Ce和Mg改性的γ-Al_2O_3负载Pt催化剂催化乙二醇水相重整制氢

Hydrogen Production by Aqueous-Phase Reforming of Ethylene Glycol over Pt Catalysts Supported on γ-Al_2O_3 Modified with Ce and Mg

采用浸渍法制备了Ce和Mg改性的-γAl2O3负载Pt乙二醇水相重整制氢催化剂.采用催化活性评价、N2物理吸附、CO化学吸附、X射线衍射(XRD)和程序升温还原(TPR)等手段系统研究了催化剂的活性、选择性及物化性质.实验结果表明,Ce和Mg改性的-γAl2O3负载Pt催化剂的活性明显高于Pt/-γAl2O3催化剂.在498 K和2.58 MPa条件下,乙二醇的转化率由72.3%提高到100%,氢的选择性接近100%.在Pt/(Ce)-γAl2O3和Pt/(Mg)-γAl2O3催化剂的XRD谱中,除了-γAl2O3特征峰外,还分别出现了CeO2和Mg-Al层状化合物及微弱的Mg-Al尖晶石结构化合物的特征峰.Ce的存在促进了Pt对乙二醇的吸附-裂解作用和CO水煤气变换反应;Mg的存在中和了-γAl2O3表面的酸性,增加了载体的碱性中心,影响了PtCl62-的分散,抑制了乙二醇的脱水反应.

Pt catalysts supported on γ-Al2O3 modified with Ce or Mg were prepared by impregnation with a H2PtCl6 aqueous solution and used in the hydrogen production by aqueous-phase reforming of ethylene glycol. Catalytic activity testing, N2 physical adsorption, CO chemical adsorption, X-ray diffraction （XRD）, and temperature-programmed reduction （TPR） were employed to evaluate the activity, hydrogen selectivity, and physicochemical properties of the catalysts. The results indicate that Pt catalysts supported on γ-Al2O3 modified with Ce or Mg show higher activity than the Pt/γ-Al2O3 catalyst. At the temperature of 498 K and pressure of 2.58 MPa, the conversion of ethylene glycol is increased from 72.3% over Pt/γ-Al2O3 to 100% over Pt/（Ce） γ-Al2O3 or Pt/（Mg）γ-Al2O3, and the selectivity for hydrogen almost reaches 100%. The characteristic peaks attributed to CeO2, Mg-Al layer chemical component, and Mg-Al spinel have been observed besides the γ-Al2O3 peak in the XRD patterns of Pt/（Ce）γ-Al2O3 and Pt/（Mg）γ-Al2O3. The presence of Ce not only increases the dispersion of Pt on the surface of γ-Al2O3, but also improves the adsorption-cracking of ethylene glycol on Pt and water-gas shift reaction; while the presence of Mg neutralizes the acidity of γ-Al2O3, influences the dispersion of PtCl6^2- , and inhibits the dehydration of ethylene glycol.