New Catalysts May Provide Insights into Role of Nonframework Alumina in Catalytic Cracking Catalysis

摘要

Catalysts utilized in Fluid Catalytic Cracking(FCC)are typically comprised of zeolite Y in some form of silica-alumina matrix.During the 1980's,much attention was focused on the role of active sites in the zeolite crystal lattice.Reaction pathways were explained in context of the zeolite cell constant or unit cell size.In recent years,more attention has been given to the role of extra-lattice or nonframework aluminum atoms.Several authors have proposed reaction pathways in which nonframework alumina provides an initiation site for olefin formation,thereby enhancing overall reaction rates.Such theories,coupled with unit cell size theory promulgated in the 1980's,provided impetus for development of a new family of FCC catalysts which have recently been introduced to the FCC community.These catalysts provide,among other features,a high intrinsic activity and may offer additional insights into the respective roles of zeolite framework and nonframework alumina in FCC catalysis.