Preparation of furans from catalytic conversion of corn stover in H2O-THF co-solvent system - The effects of acids combined with alkali metal cations

The preparation of furans from catalytic conversion of corn stover is investigated in H2O-THF (tetrahydrofuran) co-solvent system, and the effects of Bronsted acids (H2SO4, HCl, HNO3) combined with alkali metal cations (Li+, Na+,K+) are studied systematically. It is found that the effect of individual acid in promoting the summary yield of 5-hydroxymethylfurfural (HMF) and furfural (FF) can be ordered as CI- > SO42- > NO3-. When combined with a salt, the anion effect can be ranked in SO42- > Cl - > NO3, both for the HMF yield and the summary yield of furans. Based on the best anion of SO42-, the impacts of the combined cations can be finely ranked as Na+ > K+ > Li+. For the system with Cl-, it ranks in K+ > Li+ > Na+ for the HMF yield or the summary yield of furans. The performance of NO3- is so poor that no liquid product can be detected when any alkali metal cations is combined with HNO3. The performance of H2SO4/Na2SO4 is the best among 9 tested combined catalysts, and the yield of HMF and FF from corn stover conversion under optimized conditions are 76% and 81% respectively. (C) 2019 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.