Nanoporous Al2O3 Designed as Protective Matrix for Zeolite in Catalytic Cracking

The resistance to coking and metal deposition from heavier crude feedstocks is important to a fluid catalytic cracking (FCC) catalyst. The catalytic cracking of n-hexadecane (n-C16H34) as a model compound was studied on the ultrastable Y zeolite (USY) catalysts with nanoporous (up, 5-50 nm pore diameter) Al2O3. A combination of two np Al2O3 types with well controlled pore size (7 nm or 35 nm) was employed as binder and matrix. The catalyst made with the matrix from the combination of the two pore sizes, with an average pore size of around 14 nm, exhibited higher cracking activity and lower rate of degradation by coking, similar to the catalyst with the single matrix pore size of 14 nm. A USY zeolite catalyst fabricated with only the small pore size np Al2O3 exhibited better resistance to hydrothermal regeneration under model conditions than a catalyst with the large pore size up Al2O3. A catalyst partly containing small pore size np Al2O3 exhibited better resistance to hydrothermal regeneration after intentional deposition of vanadium than a catalyst made of the small pore size np SiO2. Therefore, the small pore size np Al2O3 has functions to protect the zeolite component and its activity, against both of high temperature steam and vanadium species, by binding on the zeolite surface and trapping the vanadium which easily moves over np SiO2 during regeneration. Furthermore, it was clarified that the large pore size np Al2O3 in the mixed matrix can also act as a trapping site for Ni deposition to reduce coking with hydrogen generation on the deposited Ni and protection of the zeolite component activity.