Simultaneous hydrogenation and ring opening of aromatics for diesel upgrading on Pt/zeolite catalysts. The influence of zeolite pore topology and reactant on catalyst performance

The influence of zeolite pore size and dimensionality in bifunctional Pt/zeolite catalysts has been studied for the combined hydrogenation and ring opening of aromatics in diesel fuels. The formation of high cetane ring opening products (ROP) from tetralin (C10) was seen to be favored on large-pore zeolites (beta, USY, mordenite) as compared to medium-pore zeolites (ZSM-5, MCM-22). The latter zeolites imposed serious steric restrictions for the formation and/or diffusion of ROP as supported from molecular docking simulation results. Among the large-pore zeolites, beta and USY having a tri-dimensional pore structure produced higher yields of ROP than mordenite possessing a one-dimensional pore system. The maximum yield of ROP from tetralin was obtained for the Pt/beta catalyst. However, Pt/USY was more effective than Pt/beta for the ring opening of bulkier aromatic reactants that could be present in real diesel feeds (e.g. 1-methylnaphthalene). In this case, the molecular docking results suggested that the diffusion of the desired ROP was restricted in the pores of zeolite beta, while they could freely diffuse in the faujasite structure having internal cages of larger diameter (ca. 1.2 nm) than the pore openings (ca. 0.74 nm).