| 摘要 |
<p>A catalytic cracking catalyst and process for converting a hydrocarbon feedstock at elevated temperature in the substantial absence of hydrogen, into lower average molecular weight, lower boiling hydrocarbons useful as transportation fuels. The catalyst is a composite of a crystalline aluminosilicate zeolite in concentration ranging as high as about 80 percent, based on the total weight of the catalyst, within a mesoporous silica-alumina matrix. The matrix, preferably, is constituted of silica sols modified by alumina and clay and it is characterized as of polymodal pore size distribution, as measured by mercury porosimetry, a first mode wherein at least 75 percent, preferably about 80 percent to 90 percent, of the pore volume measured between 45 Angstroms and 2000 Angstroms is in pores greater than 16OAngstroms in diameter, and a second mode wherein up to about 20 percent of the pore diameters are greater than 100 Angstroms but less than 160 Angstroms in diameter. These catalysts are highly active, and selective, in the production of olefins without high coke made. The attrition-resistance of these catalysts, as measured by the Davison Index, is quite low, ranging generally from about 1 to about 8, more generally from about 1 to about 5, or less. <IMAGE></p> |
