Study On Mould Forming Process And Mechanical Strength Of Solid Catalyst

Besides favorable catalytic activity, selectivity and service life, the promising catalyst in industrial application should be of proper geomorphic shape and size corresponding to the reaction process, and the adequate mechanical strength to support the weight of catalyst itself, and resist the shocks resulting from variance of temperature, pressure, and stress during reactions. All these mechanical performances depend upon the forming process of catalyst. However, the research works on the mechanical strength of the catalyst in macro (statistical) scopic viewpoints are carried out comparatively deep, but the understanding about in elemental rules of mechanical strength during forming process of catalyst are not sufficient. Therefore basing upon this inspiration, the systematic studies on the molding forming process of single catalyst pellet and the effects of concerned factors are investigated in semimicroscopic viewpoints, in order to reveal some fundamental regularities of process. In this paper, two assemblies of special test equipments have been designed and fabricated by authors in our laboratory: namely Catalyst Molding Process Analyzer (CMPA) and Catalyst Mechanical Process Tester (CMPT). These new skills are developed for the dynamic studies on whole mold forming process and crushing process of Fe-Cr WGHS catalyst pellet. Based on the orthogonal experimental design, the effects of some factors during the forming process of solid catalyst, such as predensification proportion, calcination time, calcination temperature and content of graphite on the mechanical strength of catalyst pellets are systematically examined, and the molding conditions have been optimized. Based on the experimental data, the relationship between catalyst density and forming pressure are educed, and the physical significances of some related parameters are described. The parameter of macro scopic elastic moduls has been suggested to character the mechanical properties of molding catalyst. The effects of molding pressure on mechanical properties of catalyst pellets are discussed, and results show that there exists a optimal molding pressure for the ideal mechanical properties: when over-high or over-low pressure is applied, the specific surface area and side crushing strength of catalyst pellets will decreased. The "rebound effect" will be undermined by the unsuitable pressure maintain process, resulting in the apparent decrease of mechanical strength of catalyst pellets. The effects of the geometric shapes of molding punches on the mechanical strength, density and catalytic activity of catalyst have been also investigated, and it is found that the column catalyst pellets with top spherical shape, which are fabricated by two-concave punches could show maximal mechanical strength, and keep their inherent catalytic activity.