Upgrading of bio-oil derived from biomass constituents over hierarchical unilamellar mesoporous MFI nanosheets

Abstract

tUnilamellar mesoporous MFI nanosheets (UMNs) were, for the first time, applied to the catalytic pyrol-ysis of the constituents of lignocellulosic biomass: cellulose, hemicellulose and lignin. A representativemesoporous catalyst, Al-SBA-15, was also applied to the same process for the purpose of comparison. Thecatalysts were characterized by N2adsorption–desorption, X-ray diffraction, temperature programmeddesorption of ammonia, and transmission electron microscopy. The synthesized UMN catalyst was com-posed of a random assembly of zeolite nanosheets with a thickness of 2.5 nm. UMN was shown to havestrong Brønsted acid sites, whereas Al-SBA-15 had weak acid sites. Catalytic pyrolysis experiments werecarried out using Py-GC/MS. The product distribution was analyzed in order to evaluate catalytic activity.Acidity had a considerable influence on catalytic activity; UMN, with a higher acidity than Al-SBA-15,exhibited higher activities for cracking and deoxygenation, producing bio-oil with a lower oxygen con-tent and with a better overall quality. Levoglucosan, which was the main product of the non-catalyticpyrolysis of cellulose, was converted to aromatics and furans on the acid sites of the catalysts. Ketones,alcohols and cyclo-compounds, the main products of the non-catalytic pyrolysis of xylan, were also con-verted to aromatics and furans by catalytic upgrading. The main products of the non-catalytic pyrolysisof lignin were phenolics, which were converted to aromatics and lighter phenolics (alkyl phenolics andmethoxy phenolics) in the presence of catalysts. Increasing the catalyst dose improved the quality of theproduct oil even further.