Enhanced hydroisomerization performance over highly mesoporous ZSM-48 zeolites constructed by organosilane surfactant

Abstract

One-dimensional ZSM-48 zeolite had been widely accepted as an acid support for the hydroisomerization of long chain n-alkanes. In current works, highly mesoporous ZSM-48 zeolites were fabricated by the assistance of 3-aminopropyltriethoxy-silane (APTES) by its strong self-condensation on the nanocrystal surface. The zeolites with enhanced mesoporosity were characterized by FTIR, XRD, N2-physisorption, NH3-TPD, Py-IR, SEM, TEM, etc. to investigate the changes in properties. The results suggested that the crystal of zeolite sizes, morphology, and porosity of ZSM-48 were controllably tuned, although the incorporation of APTES induced the loss of crystallinity and the increase of SiO2/Al2O3 ratio. The downsized ZSM-48 crystals with enhanced mesoporous structure could reduce diffusion channel direction length, as well as simultaneously improve the accessibility of acidic sites. The catalytic effect of n-hexadecane isomerization was evaluated in a reactor as fixed bed and the results showed that the properly addition of mesopore generating agent improved the catalytic activity compared with the Pt catalyst supported on parent ZSM-48 zeolite. The yield of i-C16 over Pt/ZSM-48–0.02 catalyst was achieved at approximately 81 wt%, with conversion of 93 wt%, and selectivity of 87 wt%. This proposed method presented a novel and straightforward approach for synthesizing highly mesoporous ZSM-48 zeolites.