Improved hydrogenation function of Pt@SOD incorporated inside sulfided NiMo hydrocracking catalyst

Abstract

A multifunctional catalyst with Pt incorporated inside sodalite cages (SOD) encapsulated in ZSM-5 supported with Ni and Mo was synthesized, characterized and evaluated as a hydrocracking catalyst for the conversion of triglycerides to kerosene and diesel. The Pt@SOD was further encapsulated inside hierarchical mesoporous ZSM-5 zeolite to prepare a bifunctional catalyst (H-ZSM-5 for acid functionality and sulfided NiMo along with Pt@SOD for hydrogenation functionality). Metal dispersion, temperature programmed reduction (TPR, H₂) and temperature programmed desorption (TPD, ammonia) studies were done to evaluate the bifunctional nature of the catalyst. The sulfided NiMo-Pt@SOD-ZSM-5 catalyst showed improved catalytic activity compared to the sulfided NiMo-ZSM-5 catalyst under severe reaction conditions of low hydrogen/feed ratio. We show for the first time that it is possible to operate at low H₂ concentrations during hydroprocessing of triglycerides with 99% conversion and 93% selectivity for diesel range compounds at 250 NL L⁻¹ and 380 °C temperature. Computational studies showed that H₂ molecules activated by Pt inside the sodalite cages are available for reactions outside the cages. The synthesized catalyst showed high hydrodeoxygenation activity even at lower pressure (50–60 bar) and hydrogen/feed ratios of 500–1500 NL L⁻¹. The catalyst showed better stability against deactivation (4 times less coke deposition) than sulfided NiMo-ZSM-5 catalyst during a continuous run due to the presence of Pt@SOD.