Catalytic performance of supported Ni in the hydrodesulfurization of dibenzothiophene

Abstract

To reduce pollution, sulfur, nitrogen, and other heteroatoms are removed from fuels by hydrotreatment (HDT). Conventional HDT catalysts are based on Ni-MoS2 phases dispersed over -Al2O3. Despite the myriad of papers studying these catalysts, it is somehow surprising to learn that the role of Ni in these catalysts is not yet fully understood. Most literature considers that Ni is either converted to some form of catalytically inactive nickel sulfide or that it mixes with MoS2 to act as a strong catalytic promoter. In this work, we focused on analyzing whether well-dispersed supported nickel nanoparticles can be active in the hydrodesulfurization of dibenzothiophene; one of the most refractory molecules composing diesel and marine fuels. We dispersed nickel using the principles of the strong electrostatic adsorption (SEA) method over silica (~neutral acidity), Al2O3 (Lewis acidity), H+-Y zeolite (Brönsted-Lewis acidity), and microporous-mesoporous H+-Y zeolite (similar Brönsted-Lewis acidity than its microporous counterpart). The results showed that Ni nanoparticles are catalytically active in the hydrodesulfurization of DBT and that zeolites provide them with long-term stability. In addition, using SEA impregnation and providing mesoporosity to the zeolite improved the catalytic performance. Overall, we demonstrate that Ni nanoparticles may behave in the same manner as noble metals such as Pt, Pd, and Ir behave in hydrodesulfurization. We discuss some of the probable reasons for such behavior and remark on the role of Ni in hydrotreatment.