96/04966 Synthesis of mesoporous molecular sieves and their application for catalytic conversion of polycyclic aromatic hydrocarbons

Abstract

Molecular sieves such as Y and ZSM-5 are widely used catalysts in acid-catalyzed reactions for the production of fuels, petrochemicals, and fine chemicals. Despite their enormous use as environmentally safe catalysts, they are limited to convert relatively small molecules as their pore size is restricted to micropore size range (usually 1.4 nm). However, with the growing demand of technologies for treating heavier feeds, as well as for synthesizing large molecules for producing commodities and fine chemicals, it is necessary to develop catalysts with wider pores. Recently, Mobil workers have reported a new series of mesoporous molecular sieves: MCM-41 is one of the members of this extensive family of mesoporous series possessing a hexagonal array of uniform mesopores. Many reports have since appeared on synthesis and characterization of these new materials. However, information on their catalytic activity is still very limited. The pore dimensions of these materials can be tailored (in the range of 1.5-10.0 nm or more) through the choice of surfactant and auxiliary chemicals as templates and the crystallization conditions in the synthesis procedure. The BET surface area of these materials is more than 1000 m{sup 2}/g with high sorption capacities of 0.7 cc/g and greater. Moreover, these materialsmore » can be synthesized in a large range of framework Si/Al ratios and therefore can develop acid sites of different strength. Hence, these new mesoporous aluminosilicate molecular sieves, Al-MCM-41, might open new possibilities in developing catalysts for processing large molecules.« less