CRACKING ACTIVITY AND HYDROTHERMAL STABILITY OF MCM-41 AND ITS COMPARISON WITH AMORPHOUS SILICA-ALUMINA AND A USY ZEOLITE

It has been found that the cracking activity of MCM-41 for a reaction catalyzed by strong acids site, such as n-heptane cracking, is much lo wer than that of a USY zeolite, and similar to that of amorphous silic a-alumina. The higher activity of USY is due to the presence of strong er Bronsted acid sites in the zeolite. In the case of gas oil cracking , the greater accessibility of the large molecules to acid sites in MC M-41 relative to USY makes the difference in activity between these tw o catalysts much smaller than for the pure hydrocarbon. In the calcine d state MCM-41 is more active and gives more gasoline and less gases a nd coke than amorphous silica-alumina. However, when the catalysts wer e steamed, the pores of MCM-41 collapsed and its surface area and gas oil cracking was strongly reduced, resulting in a much less active cat alyst than the steamed amorphous silica-alumina. An increase in the po re walls diameter from 7 to 11 Angstrom did not solve the hydrothermal stability limitations of the MCM-41. Samples with higher Al content s howed a stronger surface area reduction upon steaming. (C) 1996 Academ ic Press, Inc.