The Study Of Modified Zeolites In The Alkylation Of Benzene With Propylene

β,MCM-22 zeolites were modified, the catalytic properties of the modified catalysts in the alkylation of benzene with propylene, as well as the relations between catalytic properties and acidity of catalysts, was studied systematacially,which provides an important theoretics for promoting the industrialization of new catalyst.β,MCM-22 zeolites were modified with different phosphorus sources ((NH4)2HPO4,NH4H2PO4,H3PO4),different phosphorus contents(P wt%:0.5%,1.0%,1.5%,2.0%). β zeolite was also modified by different concentration of sodium hydroxide solutions(0.05M,0.1M,0.2M). The synthesis of cumene was carried out in a fixed-bed microreactor under liquid-phase over the modified zeolites, the results show that the zeolites modified by proper phosphorus content exhibit excellent reaction selectivity; the selectivity of cumene increased, the content of n-propylbenzene decreased by half and oligomers also decreased; but the catalytic activity was reduced by the alkali-treatment. The acidic properties on surface of the modified catalysts were characterized with TG-DTA, NH3-TPD and FTIR. the results show that the modification of βzeolite by phosphorus decreases the total amount of acid, suppresses acid strength. Phosphorus mainly modified surface acid site of zeolites. The content of phosphorus affects the conditions phosphorus of zeolites surface. While the total acid amount of βzeolite modified with sodium hydroxide solution increased . A siliceous species was selectively dissolved from the framework of zeolite. The acidic property of the zeolites was great influenced by the concentration of sodium hydroxide solution. The relations between catalytic properties and acidity properties of catalysts, was studied. Results show that the strongest acid site of zeolites is against the alkylation of benzene with propylene. The activity of zeolite is related to the acidic intensity and the acidic amount.