The Investigation On Molding Condition Of MCM-22 Zeolite Catalyst For Alkylation Of Benzene With Propylene

The effect of extrusion molding condition on the physical and chemical properties as well as catalytic performances of zeolite catalysts has been systematically investigated with MCM-22 zeolite as objective and the alkylation of benzene with propylene to produce cumene as model reaction, which was expected to provide enforceable and scientific basic reference for the further development of the macro-properties of catalysts.The physical and chemical properties of the zeolites prepared here under different molding conditions were analysed by means of some testing technology and characterization methods, such as particle strength measurement, NH₃-TPD acidity characterization, N₂ adsorption-desorption together with mercury penetration pore size distribution test for porous materials. The effects of molding conditions on the mechanical strength, pore structure, the total acid content and the other physical properties of MCM-22 zeolite catalyst were investigated. The results showed: (1) the mechanical strength of zeolite catalysts was large when inorganic acid and tartaric acid were taken as peptizer and extrusion promoter respectively. With the increase of water powder ratio and nitric acid peptizer, the zeolite catalyst strength was first increased and then decreased. The zeolite strength was increased with the increase of adhesive and extrusion promoter, but was decreased with the increase of hole-expanding agent content and powder granularity. Taking the strength of MCM-22 zeolite catalyst as objective function, the suitable molding condition decided by orthogonal experiments was that: the SB powder content of 30%, the water powder ratio of 0.8, the nitric acid content of 10%, no hole-expanding agent and the sesbania powder content of 3%. (2) Peptizer, extrusion promoter and hole-expanding agent had significant influence on the pore structure of MCM-22 zeolite catalyst. The pore volume of catalyst was larger with organic acid as peptizer and sesbania as extrusion promoter. With the increase of nitric acid content, the specific surface area was increased and the specific pore volume of catalysts was first increased and then decreased. Taking PEG20000 as hole-expanding agent, the optimum effect was obtained at the mass fraction of 10%. (3) The total acid content of MCM-22 zeolite was increased with the increase of nitric acid content, and was first increased and then decreased with the increase of PEG20000 content. The total acid content of the catalysts with inorganic acid as peptizer was more than that of organic acid. Taking the total acid content of MCM-22 zeolite catalyst as objective function, the suitable molding condition decided by orthogonal experiments was that: the nitric acid content of 10%, hole-expanding agent content of 10% and the sesbania powder content of 3%. Taking the alkylation of benzene with propylene as model reaction, the catalytic performances of MCM-22 zeolite catalyst prepared in this work were also experimentally valuated by means of the semi-continuous gas-liquid reactor and liquid-liquid continuous reactor. The results showed that water powder ratio and adhesive had little influence on reaction performance of MCM-22 zeolite catalyst. When inorganic acids were used as peptizators, the catalysts showed the better activity and higher selectivity of target product can be got then catalyst with organic acid. The selectivity to cumene produced in the molded catalysts reached their maximum with the nitric acid amount of 10%. The selectivity of cumene can be increased when tartaric acid was taken as extrusion promoter. Hole-expanding agent had great impact on the selectivity of cumene. The selectivity of cumene reached the largest value when the amount PEG20000 as hole-expanding agent was 10%. Peptizer, extrusion promoter and hole-expanding agent probably will have influences on the stability of MCM-22 zeolite catalyst.