Fast synthesis of hierarchical mordenite templated by nanocrystalline cellulose for isomerization of α-Pinene

Abstract

Mordenite molecular sieves were employed for the isomerization of α-pinene to produce limonene and camphene. To decrease diffusion resistance of α-pinene molecules, nanocrystalline cellulose (NCC) was employed as the mesoporous filler to prepare hierarchical mordenite within 6 h under microwave radiation. NCC crystals present as a rod-like morphology twining around crystals and interact with Al(OH)xOy and Si(OH)xOy species. Stronger interaction with Al(OH)xOy species inhibits the incorporation of aluminum into zeolitic framework. The acidity decreases due to a lower surface Si/Al ratio. Besides creating mesopores and macropores, NCC inhibits the growth or assembly of crystals in the short transverse direction of particles. Compared to mordenite without NCC, conversion increases by ∼50 % and the total yields of camphene and limonene are ∼52 % using mordenite catalysts with NCC. It indicates that macro/mesopores enhance the diffusion of α-pinene in mordenites, increase the accessibility of α-pinene with acid sites. After 5-times cycle tests, the conversion decreases from 63 % to 43 % due to the destruction of zeolitic structure during thermal treatment. In this study, a green synthesis route templated with NCC and green application in isomerization of α-pinene are proposed. These results are important for the synthesis of zeolites using biomass templates rapidly for biomass conversion process.