Intensification of Deep Hydrodesulfurization Through a Two-stage Combination of Monolith and Trickle Bed Reactors

Deep hydrodesulfurization (HDS) is an important process to produce high quality liquid fuels with ultra-lowsulfur. Process intensification for deep HDS could be implemented by developing new active catalysts and/or new types of reactors. In this work, the kinetics of dibenzothiophene (DBT) hydrodesulfurization over Ni-P/SBA-15/cordierite catalyst was investigated at 340-380℃ and 3.0-5.0 MPa. The first-order reaction model with respect to both DBT and H₂ was used to fit the kinetics data in a batch recycle operation system. It is found that both the activation energy and rate constant over the Ni-P monolithic catalyst under our operating conditions are close to those over conventionally used HDS catalysts. Comparative performance studies of two types of reactors, i.e., trickle bed reactor and monolithic reactor, were performed based on reactor modeling and simulation. The results indicate that the productivity of themonolithic reactor is 3 times higher than that of the trickle bed reactor on a catalyst weight basis since effective utilization of the catalyst is higher in the monolithic reactor, but the volumetric productivity of the monolithic reactor is lower for HDS of DBT. Based on simulation results, a tworeactor-in-series configuration for hydrodesulfurization is proposed, in which a monolithic reactor is followed by a tickled bed reactor so as to attain intensified performance of the system converting fuel oil of different sulfur-containing compounds. It is illustrated that the two reactor scheme outperforms the trickle bed reactor both on reactor volume and catalyst mass bases while the content of sulfur is reduced from 200 μg·g^-1 to about 10 μg·g^-1.