Jinghua Wang,Hongyou Cui,Jiangang Wang,Zhihe Li,Ming Wang,Weiming Yi
Conversion of glucose to 5-hydromethyl furfural (HMF) and levulinic acid (LA) was systematically investigated in LiCl·3H 2 O without additional catalyst. Based on the experimental investigations by using glucose, fructose and HMF as the reaction substrate separately, corresponding reaction kinetics in LiCl·3H 2 O were modelled by first-order assumption. Kinetic analysis demonstrates that high temperature favors the formation of LA, while low temperature facilitates to selectively form humins. To achieve high LA yield, at least a temperature of 140 °C is required. Without additional catalyst converting glucose to LA in LiCl·3H 2 O, humins was predominantly derived from glucose and HMF, and glucose isomerization is the reaction rate-determining step. The activation energies of the main reactions are 160.96 kJ/mol (glucose to HMF), 139.20 kJ/mol (fructose to HMF), and 71.81–76.48 kJ/mol (HMF to LA) respectively. The activation energies for humins formation were 23.45 kJ/mol from glucose, 49.54 kJ/mol from fructose, and 42.15–65.85 kJ/mol from HMF, respectively. It is verified that LiCl·3H 2 O, as compared to aqueous medium, is an excellent reaction medium for converting glucose to LA as it can provide the active centers for fructose to HMF reaction and HMF to LA reaction, but lack of highly efficient Lewis acid for glucose isomerization. With the addition of Lewis acid (such as AlCl 3 and FeCl 3 ), as high as 83.4% of LA yield can be obtained respectively when directly converting glucose, with the total selectivities of LA and HMF of 95%.
Molten salt hydrate (MSH) is a good solvent for cellulose dissolution and an effective catalyst for cellulose conversion. In this work, a series of MSH was evaluated in terms of cellulose dissolvability, regeneration performance, and catalytic activity in cellulose conversion into 5-hydroxymethylfurfural (HMF). ZnBr 2 ·3H 2 O–LiCl·3H 2 O showed good performance on cellulose dissolution and conversion. The effects of ZnBr 2 ·3H 2 O concentration, reaction temperature, and time on cellulose conversion into HMF in ZnBr 2 ·3H 2 O–LiCl·3H 2 O were optimized, and 48.7% HMF yield was reached at 60 wt.% ZnBr 2 ·3H 2 O. The species of ZnBr 2 ·3H 2 O–LiCl·3H 2 O were analyzed, and the function of species concentration was correlated with the product yield from the conversion of fructose. It was found that Br − and H + were the active species for fructose dehydration into HMF. ZnBr 3 − and H + catalyzed the conversion of fructose into furfural, which competed with the production of HMF. The reaction mechanism was proposed to understand the cooperate of species in MSH for cellulose conversion.
Gang Liu,Yujiao Xie,Chunjie Wei,Chang Liu,Feng Song,Xiuyu Sun,Yuan Zhang,Hongyou Cui
The one-pot approach was developed by using molten salt hydrate consisting of ZnCl 2 ·4H 2 O and LiCl·3H 2 O to produce 5-hydroxymethylfurfural (5-HMF) from cellulose . Cellulose was dissolved and regenerated to study the interaction of cellulose and molten salt hydrate. The effects of ZnCl 2 ·4H 2 O concentration, reaction time, and temperature on the conversion of cellulose to 5-HMF were investigated. 5-HMF yield increased when ZnCl 2 ·4H 2 O was mixed with LiCl·3H 2 O, and the maximum value (44.1%) was reached at 160 °C and 90 min when ZnCl 2 ·4H 2 O concentration was 64.9 mol%. The species of ZnCl 2 ·4H 2 O–LiCl·3H 2 O were analyzed, and the function of species concentration was correlated with the 5-HMF yield from the conversion of glucose and fructose. It was found that the synergistic catalysis of ZnCl 3 − , Zn 2+ , Zn(OH) + , H + as well as Li + promoted the efficiently cellulose conversion to 5-HMF.
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