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 H 2 O–THF (tetrahydrofuran) co-solvent system, and the effects of Bronsted acids (H 2 SO 4 , HCl, HNO 3 ) 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 Cl − > SO 4 2− > NO 3 − . When combined with a salt, the anion effect can be ranked in SO 4 2− > Cl − > NO 3 − , both for the HMF yield and the summary yield of furans. Based on the best anion of SO 4 2− , 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 NO 3 − is so poor that no liquid product can be detected when any alkali metal cations is combined with HNO 3 . The performance of H 2 SO 4 /Na 2 SO 4 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.