Preparation And Characterization Of Catalysts For Methanol

Methanol is an important chemical raw material and a potential fuel for automobile and fuel cell. There is a sustained interest in the research and discovery in methanol synthesis all over the world. Though the synthesis process had already been industrialized, there are still many drawbacks in this catalytic system such as low single- pass conversion of synthesis gas feed, and the performance of catalysts needs to be improved further. Consequently, the research and development of new catalysts with high activity would be one of the key objectives for researchers.In this paper, the CuO/ZnO/Al2O3 catalysts were prepared and tested for methanol synthesis, and by applying various characterizing methods, such as XRD, TEM, SEM, TPR, SEM, the effect of ratio of Cu /Zn /Al in Cu-based catalysts, solution concentration, calcination temperatures, Mn promoter on structure of catalysts and catalytic properties have been investigated. Hydro-thermal synthesis and ultrasonic method have been explored initially as new methods for methanol synthesis, they were hoped to improve the performance of the catalyst.Results show: the different Cu/Zn/Al ratio were compared, the best ratio in CuO/ZnO/Al2O3 catalyst for methanol synthesis is 4.5/4.5/1; Some kinds of solution concentration were checked relatively, for example, 0.1M,0.3M,0.5M,0.8M and1.0M, the activity of catalyst is the best when the solution concentration is 0.3M; When the calcination temperature were 300℃,350℃,400℃,500℃,600℃relativily, the activity of the catalysts were evaluated. The best calcination temperature was 350℃, with the increase of calcination temperature, the particle size was increased, meanwhile, the surface area as well as the adsorption capacity to H2 and CO of catalysts decreased. It suggested that higher calcination temperature induced a sinter of catalysts, which was harmful for methanol synthesis, when the calcination temperature rised to 500℃, the activity decreased markedly; The Mn promoter effected the performance of the catalysts, the activity was the best when Mn% was 2%, Mn promter prevented CuO particle growing, dispersed the active component, the adsorption capactity of H2 increased, Mn promoter improved the activity and thermal stability of Cu/Zn/Al catalyst, but it had no effection to the selectivity of methanol.The new methods for methanol synthesis were studied tentatively in this paper. Compared to the co-precipitation, the activity of the catalysts prepared by the hydro-thermal synthesis were no better than that of the catalysts prepared by the co-precipitation, the main reason was no supporter or promoter, the supporter is the disperser and the frame of charging the active component. The supporter was related to activity,selectivity,thermal-stability,mechanical robustness and transitivity. The macroscopical structure of catalysts, which effected the activity and selectivity, were determined by the supporter. So these work provided some conditions to improve the performance of catalysts, it became the foundation of the further research; The activity of the catalysts prepared by the ultrasonic method were better than that of the co-precipitation. It was because that the ultrasonic wave and co-precipitation made CuO and ZnO paticle combined more tightly, distributed the active component equably, the catalyst particle were smaller than that of catalysts prepared by co-precipitation, the superfine particle were useful to improve the activity.While modern catalytic industry and new catalytic technology are developing rapidly, the co-precipitation method for methanol synthesis should adopt modern technology. The superfine particle have some merits, which make it represent high catalytic activity, for example, large specific surface area, high surface atom ratio; meanwhile, it can react at low temperature, disperse more quickly; decrease the secondary reaction and increase the selectivity because of low melting point and high diffusibility. Consequently, it will become the main direction that exploiting new superfine catalysts with nanotechnology.