【摘要】 采用XRD和XPS方法考察了Cu ZnO Al2 O3 甲醇合成催化剂在高温焙烧、还原和反应过程中活性组分的动态变化 .结果表明 ,高温焙烧可造成活性组分晶粒的生长 ,ZnO晶粒比CuO晶粒更易于生长和在表面富集 ,从而引起Cu/Zn比下降 .在还原和反应过程中 ,一方面H与Cu相互作用引起的Cu粒子表面自由能的降低远大于H对ZnO的影响 ,使得Cu粒子的生长在热力学上更有利 ;另一方面 ,由于Cu的熔点较低 ,造成Cu粒子的表面迁移活化能较低 ,表面扩散系数较高 ,受表面扩散所支配的粒子移动引起的晶粒生长较快 ,而ZnO由于熔点较高 ,在氢气气氛中粒子生长较慢 .与焙烧后的催化剂相比 ,还原及反应后的催化剂表面Cu/Zn比明显增大更多还原

【Abstract】 The dynamic transformation of active components in the Cu ZnO Al 2O 3 catalyst for methanol synthesis during the calcination, reduction and reaction was investigated by XRD and XPS methods. The results showed that, when the catalyst was calcined in air, the particle size of the components increases with increasing calcination temperature, ZnO crystal grain grows faster than CuO crystal grain and aggregates on the surface of the catalyst, resulting in a decrease of the surface Cu/Zn ratio. During the reduction and reaction, the decrease in surface free energy of Cu crystal grain due to the interaction between hydrogen and Cu particle is more than that of ZnO crystal grain, which is favorable for growth of the Cu crystal grain. The lower melting point of Cu makes the Cu particles own a lower activation energy of surface migration and a higher surface diffusion coefficient, therefore the growth of the Cu crystal grain controlled by surface diffusion is faster. But the ZnO crystal grain grows slower in the reducing atmosphere because of its higher melting point. In comparison with the calcined catalyst, the surface Cu/Zn ratio of the catalyst after reduction and reaction increases obviously.更多还原