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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
XRD and XPS methods were used to investigate the dynamic changes of the active components of Cu ZnO Al 2 O 3 catalyst during calcination, reduction and reaction at high temperature.The results show that the calcination at high temperature can cause the growth of the active component grains, The grain is easier to grow and enriched on the surface, which leads to the decrease of Cu / Zn ratio.In the process of reduction and reaction, on the one hand, the interaction between H and Cu reduces the surface free energy of Cu particles much more than that of H, Making the growth of Cu particles thermodynamically more favorable; on the other hand, due to the lower melting point of Cu, Cu particles caused by the surface activation activation energy is lower, the surface diffusion coefficient is higher, by the surface diffusion particles dominated by the movement of the crystal Particle growth is faster, and ZnO due to the higher melting point, the growth of particles in the hydrogen atmosphere slower.Compared with the calcined catalyst, the reduction and reaction of the catalyst surface Cu / Zn ratio increased significantly