1. Field of the Invention
The present invention relates to hydrocarbon cracking catalysts and uses thereof in catalytic cracking in order to obtain gasoline having an enhanced octane value. An additional benefit of the novel process of this invention resides in the fact that the octane boost which is obtained is at the expense of a smaller loss of gasoline product than has heretofore been possible.
2. Description of the Prior Art
Hydrocarbon conversion processes utilizing crystalline aluminosilicates have been the subject of extensive investigation during recent years as is obvious from both the patent and scientific literature. Crystalline aluminosilicates have been found to be particularly effective for a wide variety of hydrocarbon conversion processes, including the catalytic cracking of a gas oil to produce motor fuels and have been described and claimed in many patents.
Hydrocarbon cracking catalysts comprising a zeolite dispersed in a matrix are known; see, for example, U.S. Pat. Nos. 3,140,249, 3,352,796, 3,647,718, 4,581,340, 4,581,341 and 4,493,902.
It is also known in the art to use a mixture of zeolites for various hydrocarbon conversions. Thus, for example, U.S. Pat. No. 4,137,152 discloses a cracking process utilizing a mixture of faujasite and mordenite.
U.S. Pat. No. 3,894,934 discloses catalytic cracking of hydrocarbons using a large-pore zeolite and ZSM-5.
U.S. Pat. No. 3,871,993 discloses a process for upgrading the octane value of a naphtha using shape-selective catalysts such as ZSM-5, ZSM-11, ZSM-12, ZSM-21, mordenite, etc.
U.S. Pat. No. 3,702,886 discloses the use of ZSM-5 zeolites alone or in combination with other materials such as zeolites or inert materials for catalytic cracking of hydrocarbons.
U.S. Pat. No. 3,804,747 discloses a hydrocarbon conversion process utilizing a mixture of zeolites X and Y.
U.S. Pat. No. 3,758,403 discloses catalytic cracking comprising a large-pore zeolite such as zeolite Y and a small-pore zeolite such as ZSM-5 in a siliceous matrix. The matrix may be active or inactive such as silica-alumina or alumina. The use of a ZSM-5 type zeolite results in obtaining a fuel of increased octane number.
U.S. Pat. No. 3,769,202 discloses a combination catalyst comprising a mixture of two different zeolites, one having a pore size greater than 8 Angstrom units and the other having a pore size of less than 7 Angstrom units. The zeolites are mixed with an inorganic oxide matrix such as silica-alumina. The catalyst is stated to be suitable for cracking and hydrocracking of hydrocarbons.
U.S. Pat. No. 3,925,195 discloses a cracking process utilizing a catalyst comprising a mixture of rare earth hydrogen Y-type zeolites and hydrogen or transition metal exchange mordenite, calcium exchanged type A zeolite or hydrogen exchanged erionite in an amorphous matrix.
U.S. Pat. No. 3,764,520 discloses a catalyst comprising a mixture of two different zeolites, one having a pore size within the range of 6 to 15 Angstrom units and the other having a pore size of less than 6 Angstrom units in combination with an inorganic oxide support.
U.S. Pat. No. 4,287,048 discloses an ultra-stable Y type crystalline aluminosilicate in admixture with a small-pore crystalline aluminosilicate zeolite selected from the group consisting of erionite, mordenite, zeolite A, chabazite, offretite and a catalytic inorganic oxide matrix.
U.S. Pat. No. 4,309,280 discloses a process for increasing the gasoline octane number and/or a total gasoline yield in catalytic cracking by adding a crystalline aluminosilicate zeolite having a silica-to-alumina mole ratio greater than about 12 and a constraint index within the approximate range of 1:12 to a cracking unit which contains a zeolite cracking catalyst such as zeolite Y.
European Patent 243629 discloses a cracking catalyst for producing high octane gasoline comprising zeolite Beta or ZSM-20 which may also contain up to 30 wt. % of a secondary zeolite which can be zeolite X, zeolite Y, ferrierite, mordenite and mixtures thereof. These catalysts contain a matrix and the ratio of the primary zeolite to the secondary zeolite is at least 1:1.
Perrotta et al in the Journal of Catalysis, Vol. 55, pages 240-249 (1978) discloses catalytic cracking of a gas oil with an omega-faujasite system wherein the catalyst is prepared by a co-crystallization technique.
The catalytic properties of zeolite L have been studied, i.e., see Parra et al, Journal of Catalysis, Vol. 40, pages 52-60 (1975), A. W. Peters et al, in an abstract entitled Octane Catalyst Design Strategies in Catalytic Cracking, said abstract having been published in connection with the 10th North American Meeting of the Catalysis Society held in San Diego on May 17-22, 1987.
The simple fact remains that there has been no recognition of utilizing a mixture of zeolite L and Y in the catalytic cracking of gas oil in order to produce gasoline having an enhanced octane value at a minimum loss of gasoline yield.