| abstract |
A layered composition of matter, MCM-56, has an X-ray diffraction pattern including lines at d-spacing values of 12.4+/-0.2, 9.9+/-0.3, 6.9+/-0.1, 6.2+/-0.1, 3.55+/-0.07 and 3.42+/-0.07 Angstroms and has been selectively modified so that the ratio of the number of active acid sites at its external surface to the number of internal active acid sites is greater than that of the unmodified material. When used as an additive to a large pore zeolite catalyst in the catalytic cracking of a petroleum feedstock, the modified MCM-56 gives an improved gasoline yield/octane relationship, an improved coke selectivity and a higher combined gasoline and potential alkylate yield than an identical catalyst containing unmodified MCM-56. |