Benzylation of naphthalene over a mesoporous ZSM-5 zeolite microsphere catalyst

Abstract

A microspherical ZSM-5 zeolite aggregated from nanosized zeolite crystals with intra- and inter-crystalline mesoporous structures (MMZ- 5) was prepared using presilanized silica as silica source. The acidic properties of this mesoporous zeolite were characterized via Fourier transform infrared spectroscopy (FTIR) in combination with pyridine (Py) and 2,6-di-tert-butylpyridine (DTBPy). Compared with conventional microporous ZSM- 5, the MMZ- 5 zeolite possessed more Lewis acid sites and many more accessible Brönsted acid sites for bulky DTBPy molecule (1.05 nm in diameter). This mesoporous zeolite thus afforded both effective active sites and reaction voids allowing the reaction of larger molecules, resulting in enhanced catalytic activity and stability of the MMZ-5 zeolite during the benzylation of naphthalene with benzyl chloride (BC) to form bulky monobenzylnaphthalenes and dibenzylnaphthalenes, during which the selectivity for monobenzylnaphthalenes was estimated to be about 79%. Moreover, the selectivity for dibenzylnaphthalenes was enhanced with increasing reaction time, owing to the consecutive reactions between monobenzylnaphthalenes and BC occurring at the effective reaction voids of the MMZ-5 zeolite. The distribution of the monobenzylnaphthalene isomers (α-BN and β-BN) was found to be independent of both reaction temperature and extent of BC conversion, the α-BN/β-BN molar ratio being about 83:17. © Editorial office of Acta Physico-Chimica Sinica.