Synthesis of Ga-modified ZSM-48 with improved hydroisomerization performance of n-dodecane

Abstract

A series of Ga-modified ZSM-48 zeolites (GaZSM-48) with nanoparticle-assembled morphology were synthesized by applying the dynamic hydrothermal method. XRD, XPS, FT-IR and ⁷¹Ga NMR results verify that Ga species are introduced into the ZSM-48 molecular sieve framework. The acid amount and the acid strength are reduced by Ga modification, especially for Brønsted acid. The n-dodecane hydroisomerization performances of Pt-supported ZSM-48 and GaZSM-48 are investigated. The results show that the Pt/GaZSM-48-x has higher isomer selectivity compared with the original ZSM-48. Pt/GaZSM-48-1 provides the best iso-dodecane yield of 76%. The ratio of mono-methyl isomers (MOB) and multi-methyl isomers (MUB) of Pt/GaZSM-48-1 is 1.58 at 340 °C, which is 3 times higher than that of the original ZSM-48. The zero-length column (ZLC) method is adopted to study the diffusivity, and the results show that the diffusion resistance is reduced by the Ga modification, and the TOF of the Ga-modified ZSM-48 catalyst is about 1.21–2.73 times that of the original ZSM-48 catalyst.