Investigating the hydroisomerization of n-pentane using Pt supported on ZSM-5, desilicated ZSM-5, and modified ZSM-5/MCM-41

Abstract

The hydroisomerization of n-alkanes is a promising way to enhance the octane number of fuels over noble metal-promoted zeolites. Due to mass transfer limitations, zeolites with microporous structure and acidic properties suffer from lower selectivity to isomerized products. In this work, a series of hierarchical ZSM-5 and MCM-41/ZSM-5 composites are synthesized by desilication and desilication-reassembly methods to investigate the shape effect of pores on the Hydroisomerization of n-pentane. The physicochemical properties of the prepared samples were evaluated using XRD, XRF, N2 adsorption-desorption, FTIR, FE-SEM, HR-TEM, ICP-OES, and NH3-TPD. The catalytic performance of the prepared samples was carried out at atmospheric pressure in the temperature range of 200–400 °C. The ZSM-5/MCM-41 sample synthesized under a pH value of 8.5 showed a 10% and 15% higher yield of iso-Pentane and about 10%-20% higher conversion of n-pentane than the parent ZSM-5 and desilicated ZSM-5 respectively. These results demonstrated that a well-developed micro/mesoporous structure with a higher specific surface area (more than 400 m2/g) could provide better mass transfer properties and accessibility of active sites for reactant molecules. Also, a better balance between acidic and metallic sites and higher dispersion of Pt prevents further secondary cracking reactions and enhances the RON of the product stream.