Selective Dissolution of Hemicellulose from Populus tomentosa Carr.by Deep Eutectic Solvent Pretreatment
Using Populus tremula as raw material,glycerol(Gly)and ethylene glycol(EG)were used to form six binary alcohol deep eutectic solvent(DES)systems with three different metal chloride salts(FeCl3,AlCl3,and CuCl2),respectively,as well as choline chloride(ChCl)with Gly or EG with the addition of three metal salts to form six ternary alcohol DES systems.The effects of these binary and ternary DESs on the selective solubilization of hemicellulose were investigated.The ratio of hemicellulose removal rate/lignin removal rate(R)was used as the evaluation index to screen out the DES with the best effect on the selective dissolution of hemicellulose.The effects of DES ratio,pretreatment temperature,and pretreatment time on the the main component content and the preferential dissolution of hemicellulose in poplar wood were systematically investigated.The experimental results showed that when the molar ratio of ChCl/EG/FeCl3 was 1∶2∶0.2 at 100 ℃ for 2 h,the ternary DES of ChCl/EG/FeCl3 showed the hemicellulose and lignin removal rates of 45.01％and 9.49％,respectively,with the R value as high as 4.74,which demonstrated a good preferential solubilization of hemicellulose.Meanwhile,the methods of FT-IR,BET,and X-ray diffraction were used to analyze the changes of micro-morphology and structural properties of poplar wood treated with ternary DES under optimized conditions.It echoed the conclusion that the ternary DES of ChCl/EG/FeCl3 could achieve selective preferential solubilization of hemicellulose under optimized conditions while lignin only solubilized in a small amount.
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维普
