Exceptionally high yields of furfural from assorted raw biomass over solid acids

Abstract

Development of stable and recyclable solid acid catalysts in the efficient valorisation of hemicellulose to yield C₅ sugars and furfural is vital to boost the prospects of using lignocelluloses for chemicals synthesis. Using an silicoaluminophosphate, namely SAPO-44, as a catalyst, an environmentally benign process of furfural synthesis from diversified real substrates (without any treatment or the need for separation of its components) is shown. In an efficient one-pot methodology, at 443 K and in the presence of a biphasic solvent system, selective conversions of hemicelluloses from raw biomass (bagasse, rice husk and wheat straw) to extraordinarily high yields of furfural of about 93% were attainable. Under similar reaction conditions, an 82% yield of furfural is also achievable directly from isolated hemicellulose within 10 h. Hydrophilic SAPO-44, having higher hydrothermal stability, showed similar activity for all the substrates for a minimum of up to 8 times in recycling runs. Various physico-chemical characterizations (X-ray diffraction, thermogravimetric analysis-derivative thermogravimetry, temperature programmed desorption-NH₃, N₂ sorption, solid-state nuclear magnetic resonance spectroscopy) of fresh and spent catalysts were used to improve SAPO-44 stability.