Layered cracking catalyst and method of manufacture and use thereof

Abstract

A layered catalyst suited to the catalytic cracking of heavy feeds comprises a core and a shell. The shell comprises at least 5 wt % of at least 1 molecular sieve having openings of at least 8 angstroms. The core comprises at least 10 wt % of at least 1 molecular sieve having openings comprising a 12 or less-membered ring and has a reduced, if any, content of said molecular sieve having openings of at least 8 angstroms, relative to its concentration in the shell. Suitable molecular sieve materials having openings of at least 8 angstroms include MCM-41, VPI-5, MCM-9 and layered metal oxides, e.g., pillared clays. The required molecular sieve of the core can include zeolite Y, Ultrastable Y or intermediate pore size zeolites such as ZSM-5. The shell which may further contain a metals passivator can act as a metals sink, and can remove metals from the unit by attrition. The catalyst is preferably prepared by forming the core and then coating or encapsulating the core with a shell material. The shell may also comprise an attritable coating of an amorphous rare earth oxide, aluminum oxide and aluminum phosphate composite, which traps metals.