Aromatization and isomerization of methylcyclohexane over Ni catalysts supported on different supports

In this work, nickel metal supported on different supports (SiO₂, Al₂O₃, ZSM-5) were prepared by spraying nickel nitrate on the supports and calcined at 873 K. Then, they were characterized by XRD, XRF, N₂ adsorption–desorption, NH₃-TPD, MCH-TPD, H₂-TPR, and pyridine-FTIR, and tested as catalysts for the dehydrogenation aromatization and isomerization of methylcyclohexane (MCH) under the conditions of S-Zorb catalytic adsorption desulfurization (T = 673 K, P = 1.5 MPa, WHSV = 5 h⁻¹). The H₂-TPR results showed that the interaction of NiO with support decreased in the order of NiO/ZSM-5-Fe < NiO/ZSM-5 < NiO/Al₂O₃ < NiO/SiO₂. The decrease of the interaction appeared to facilitate the reduction of Ni and therefore to promote the dehydrogenation aromatization of MCH. It was found that a direct correlation existed between the gasoline components yields, cracking activity and the total number of different supports acid sites measured by NH₃-TPD tests. Higher total acidity of ZSM-5 resulted in gasoline loss because of higher cracking activity of MCH. The number of total acid sites of NiO/ZSM-5-Fe decreased and the medium strong Brönsted acid sites necessary for MCH isomerization increased after the modification of ZSM-5 by iron metal. So, NiO/ZSM-5-Fe exhibited enhanced MCH conversion, aromatic and isomerization yields when compared to NiO/ZSM-5 and other Ni-based catalysts. This study shows that NiO/ZSM-5-Fe catalyst may be possible to be integrated into the S-Zorb system achieving the recovery of the octane number of gasoline.