US Patent 7335295 Coated zeolite catalysts and use for hydrocarbon conversion

There is provided a coated zeolite catalyst in which the accessibility of the acid sites on the external surfaces of the zeolite is controlled and a process for converting hydrocarbons utilizing the coated zeolite catalyst. The zeolite catalyst comprises core crystals of a first zeolite and a discontinuous layer of smaller size second crystals of a second zeolite which cover at least a portion of the external surface of the first crystals The coated zeolite catalyst finds particular application in hydrocarbon conversion processes where catalyst activity in combination with zeolite structure are important for reaction selectivity, e.g., catalytic cracking, alkylation, disproportional of toluene, isomerization, and transalkylation reactions.