Preparation Of Kraft Lignin-Derived Ordered Mesoporous Carbon Solid Acids And Research On Catalytic Reaction Of Fructose To 5-HMF

Sulfonated lignin-derived ordered mesoporous carbon?LDMC-SO₃H?was prepared from kraft lignin via phenolation and evaporation induced self-assembly method followed by sulfonation.The as-prepared LDMC-SO₃H was applied to the dehydrate of fructose into 5-hydroxymethylfurfural?5-HMF?.Firstly,through thermochemical phenolation modification,kraft lignin was degraded into phenolic compounds with low molecular weight,which partly replaced phenol and crosslinked with formaldehyde to form lignin-phenolic-formaldehyde?LPF?resin as carbon precursor.The effects of template types and dosage,template mass ratio of two templates and carbonization temperature on the orderliness of lignin-derived mesoporous carbon materials were investigated,repectively.LDMC-SO₃H was prepared via sulfonation treatment in concentrated sulfuric acid.LDMC-SO₃H was characterized by SAXS,TEM,BET,TGA,FTIR,NH₃-TPD and acid-base titration,respectively.The result show that template could be completely removed at 400?.The obtained LDMC-SO₃H bearing sulfonic acid density of 0.65mmol/g possessed a well-ordered two-dimensional hexagonal mesoporous characteristic.The optimized conditions for preparing LDMC-SO₃H were as follows:the molar ratio of F127 to phenol was 0.013 and the carbonization temperature was900?.Under these conditions,the specific surface area,pore volume and pore diameter were 261.68 m²/g,0.067 cm³/g and 3.41 nm,respectively.Then,the optimized LDMC-SO₃H were employed in dehydration of fructose to5-HMF.And the kinetics of dehydration reaction of fructose to 5-HMF using LDMC-SO₃H as catalyst and the adsorption behaviors on LDMC-SO₃H were studied,respectively.The conversion of fructose was 100%,the yield of 5-HMF and reaction selectivity were 97.98%under the optimal reaction conditions of reaction temperature and time of 140°C and 2 h,initial fructose concentration of 100 g/L,catalyst load of10 wt%as well as DMSO of solvent.In addition,compared with other commercial catalysts?HZSM-5,PTA,Amberlyst 15?,LDMC-SO₃H had excellent catalytic activity,easy to be recycled and reused.After 9 recycling,the yield of 5-HMF was still as high as 83.08%.Kinetics study of fructose dehydration in DMSO revealed that fructose conversion in DMSO without catalyst or catalyzed by LDMC-SO₃H may obey pseudo-first-order kinetics,and the activation energy of latter?72 kJ/mol?was much lower than that of former?114 kJ/mol?.Adsorption kinetics studies indicated that almost no 5-HMF adsorbed onto LDMC-SO₃H probably had a great contribution to the high selectivity of up to 97.98%,while the fructose adsorption on LDMC-SO₃H was a diffusion-controlling adsorption process with more following Bangham kinetic model and Weber-Morris kinetic model owing to the characteristics of ordered mesostructure of LDMC-SO₃H.