Morphological effect of β zeolite nanocrystallite aggregates as the support of Pt catalyst for the hydroisomerization of n-heptane

A bifunctional catalyst Pt/H beta-n (Pt loading: 0.4 wt%) was prepared by the impregnation of an aqueous solution of chloroplatinic acid with beta zeolite, wherein the beta zeolite support has an unusual morphology of egg-like microspheres assembled by nanocrystallites. Other two control catalysts were also prepared using a beta support with micro-sized crystals and a commercial one with varying crystal sizes. The catalysts were characterized by XRD, SEM, ICP, N-2 sorption isotherms and mesopore size distribution, and evaluated in the hydroisomerization of n-heptane in an atmospheric fixed bed flow reactor. Though Pt/H beta-n has similar acidity and Pt loading (0.4 wt%) to the two control catalysts, it exhibits remarkably higher conversion of n-heptane and selectivity to isomerization. According to the characterization data, the higher activity of Pt/H beta-n is the result of the faster diffusion of reactants in shorter channels of nanocrystallines and the uniformly distributed mesopores within the microspheres.