Synthesis of cyclopentadiene trimer (tricyclopentadiene) over zeolites and Al-MCM-41: The effects of pore size and acidity

摘要

Cyclopentadiene trimer (tricyclopentadiene) is an important raw material during the synthesis of high-energy-density fuel. In this study, tricyclopentadiene was synthesized through a [4+2] cycloaddition between endo-dicyclopentadiene and cyclopentadiene over microporous zeolites (ZSM-5, HY) and mes-oporous Al-MCM-41 catalysts. The catalytic activity was strongly influenced by the average pore size and the Bronsted acidity of the catalyst. Of the tested catalysts, the NH_4F-treated Al-MCM-41 catalyst, which had meso-sized pores (3.4 nm in average) and enhanced Broensted acidity, exhibited the best dicyclopent-adiene conversion, tricyclopentadiene selectivity and yield. The average pore size of the catalyst also influenced the isomer distribution of the tricyclopentadiene products: the mesoporous catalysts produced mixtures of exo- and endo-tricyclopentadiene, which favored the exo-fraction (approximately 40 mol%) compared to the microporous catalysts (approximately 20 mol%). The differences in the reaction pathways followed by the zeolites and Al-MCM-41 catalysts were discussed. To investigate the structural and acidic properties of the catalysts, various characterization techniques were applied, such as low-angle X-ray diffraction, N_2 adsorption-desorption, ammonia temperature-programmed desorption, and Fourier transform-infrared spectroscopy of adsorbed pyridine.