pH对共沉淀法制备甲苯催化燃烧用Cu-Co-Ce复合氧化物催化剂的影响

Effects of pH on Cu-Co-Ce mixed oxide catalyst prepared by coprecipitation method for toluene catalytic combustion

采用共沉淀法通过调节溶液pH(2~11)制备一系列的Cu-Co-Ce复合氧化物催化剂,并测试催化剂在甲苯催化燃烧反应中的性能。使用热分析、X线衍射分析、低温N2吸附脱附分析、H2程序升温还原分析和X线光电子能谱对催化剂的结构和织构特性进行表征。研究pH对催化剂的比表面积、表面氧浓度、晶粒尺寸、还原温度和甲苯催化燃烧活性的影响。结果表明:随pH增大,催化剂的比表面积、表面氧浓度和甲苯转化率的变化趋势为先增大后略降低,而晶粒尺寸和H2程序升温还原峰的温度则出现相反趋势。Cu、Co、Ce氧化物之间相互作用的强弱被认为是pH对催化剂影响的根本原因。pH=9的条件下制得的Cu-Co-Ce复合氧化物催化剂展现最优的甲苯催化燃烧活性,当反应温度大于300℃时可实现甲苯的完全转化。

To investigate their performance in the catalytic combustion reaction of toluene,a series of Cu-Co-Ce mixed oxide catalysts were prepared by varying pH(from 2 to 11)of the solution during the co-precipitation process.Thermogravimetric analysis,X-ray diffraction,low temperature N2 adsorption-desorption,H2 temperature-programmed reduction and X-ray photoelectron spectroscopy were used to characterize the structure and texture properties of catalysts.The effects of pH on specific surface area,surface oxygen concentration,crystallite size,reduction temperature and catalytic combustion activity of toluene of catalyst were studied.Results showed that the change tendencies of specific surface area and surface oxygen concentration were consistent with that of toluene conversion with the increase of pH(that is,first increased and then slightly decreased),while the crystallite size or the reduction peak temperature of H2 temperature-programmed reduction showed an opposite tendency.The strength of the interaction between the three oxide species of copper,cobalt and cerium was considered to be the most intrinsic reason for the effect of pH on the catalyst.Among the tested catalysts,the Cu-Co-Ce mixed oxide catalyst prepared at pH=9 had the best toluene catalytic activity,and toluene was completely converted in the temperature range above 300℃.