Hierarchical ZSM-48-Supported Nickel Catalysts with Enhanced Hydroisomerization Performance of Hexadecane

The high crystallinity ZSM-48 zeolites were synthesized in the hydrothermally system which contained H2N(CH2)6NH2 (HDA). Hierarchical ZSM-48 zeolites can be formed during the alkali treatment, but uncontrollable silicon extraction occurred at higher Si/Al ratios. HDA as the organic template agent can prevent the uncontrollable silicon extraction acting as a Si-protecting agent. Micropores remained unchanged, but mesopores formed after the alkali treatment. Meanwhile, Brønsted and Lewis acid sites also increased at high temperature after the same treatment. The effects of the alkali treatment are studied through choosing the hexadecane hydroisomerization as a probe reaction. The conversion of hexadecane and iso-hexadecane selectivity increased after alkali treatment because the formation of new mesopores accelerated molecule diffusion, and the increased Brønsted acid sites facilitated the hydroisomerization reaction. However, the adding of HDA during the alkali treatment decreased the conversion because the surface Si/Al ratio increased.