CO_2加氢制二甲醚La_(1-y)Zr_yCu_(0.7)Zn_(0.3)O_x/HZSM-5催化剂的性能研究

Synthesis of Dimethyl Ether from CO_2 Hydrogenation over La_(1- y)Zr_yCu_(0. 7)Zn_(0. 3)O_x/ HZSM-5 Catalysts

先采用溶胶凝胶法制备了La_(1-y)Zr_yCu_(0.7)Zn_(0.3)O_x(y代表Zr/La+Zr的摩尔比,分别为0,0.1,0.2,0.3,0.4,0.5),接着采用研磨法将其与HZSM-5分子筛均匀混合形成La_(1-y)Zr_yCu_(0.7)Zn_(0.3)O_x/HZSM-5催化剂,考察了不同Zr含量催化剂在CO2加氢合成二甲醚反应中的催化性能.并以XRD、N2等温吸附脱附、H2-TPR、NH3-TPD对催化剂结构进行表征,研究了Zr含量对催化剂结构及表面酸性的影响.结果表明,催化剂性能与Zr含量有密切联系,适量的Zr可以促进催化剂中活性组分的分散,降低活性组分的晶粒尺寸,加强了活性组分与其它组分之间的相互作用,提供合适的表面酸性,从而能促进CO2的转化,提高二甲醚的选择性,降低副产物CO的选择性.此外还考察了反应温度、空速对催化剂反应性能的影响及催化剂的稳定性.

Catalysts derived from perovskite-type precursors for dimethyl ether synthesis from hydrogenation of CO2 were prepared by a sol-gel method,using citric acid as complexing agent. The catalytic performance of the catalyst was studied. The influence of Zr loading was investigated. XRD,N2 isothermal adsorption-desorption,H2-TPR and NH3-TPD were employed to investigate the surface structure and performance of the catalysts. The results indicated La0. 7Zr0. 3Cu0. 7Zn0. 3Ox/ HZSM-5 catalyst could provide a suitable surface acidity,exhibited higher DME selectivity and lower CO selectivity due to Zr addition can promote disperse of Cu species and decrease the grain size of Cu species and therefore improve the activity of the catalyst. In addition,the influence of reaction temperature and space velocity on the performance was also investigated. The stability of the catalyst was tested.