| With the development of human society,progress in technology and increasingly frequent trade exchanges,people’s demand for energy and resources is increasing day by day.However,due to the excessive exploitation and unreasonable utilization of natural resources,oil resources are tending to be exhausted,and human beings are facing a serious survival crisis.Furfural,as an important platform compound,is produced by hydrolysis of hemicellulose in biomass catalyzed by acid.It not only has a wide range of sources,but also has a very broad application prospects,which can replace petrochemical products.However,the backward production mode in industry not only caused low utilization of resources,but also brought about serious pollution.Therefore,it is urgent to develop a clean and efficient production process of furfural.The effects of temperature,reaction time,type and concentration of catalysts,and liquid-solid ratio on furfural yield,cellulose retaining rates,microstructure and chemical composition of solid products,distillate and residual liquid organic composition were investigated in this paper,with corncob as raw materials and various gentle organic Bronsted acids and Lewis acids as catalysts.The hydrothermal degradation of corncob was carried out in an autoclave.At the end of the reaction was distilled by steam stripping.After the decompression and cooling of the autoclave,the solid-liquid mixture was taken out,and separated into the residual liquor and solid products.The results showed that the sum of furfural yield increased firstly and then decreased with increasing temperature and liquid-solid ratio,while it increased continuously with the increasing of reaction time and the concentration of FeCl3.And the effect of acetic acid concentration on sum of furfural yield was not significant.The influence degree of factors on furfural yield were temperature>reaction time>FeCl3 concentration>liquid-solid ratio>acetic acid concentration.The sum of cellulose retaining rate decreased with the increasing of temperature,FeCl3 concentration,residence time and liquid-solid ratio,but increased with the increase of acetic acid concentration.The degree of factors affecting cellulose retention rate was temperature>FeCl3 concentration>acetic acid concentration>reaction time>liquid-solid ratio.The purity of furfural in the organic phase of distillate was≥97.9%.The main organic compounds in the organic phase of residual liquid were furfural,5-hydroxymethyl furfural and vanillin,GC-MS areas of which varied with the parameters,reflecting the hydrolysis extent of hemicellulose,cellulose and lignin,respectively.What’s more,the effects of temperature and reaction time on corncob hydrolysis were studied seperately.With increasing reaction time,furfural yield increased at 170℃,increased firstly and then decreased at 180℃,but decreased at 190℃.And furfural yield was more sensitive at 170℃ than higher temperature.Cellulose retaining rate decreased with increasing reaction time at 170℃ and 190℃,but this trend was not significant at 180℃.Citric acid using alone obtained the highest furfural yield and high cellulose retaining rate among experiments with single catalysts addition,while AlCl3 obtained the lowest furfural yield and cellulose retaining rate,and levulinic acid also appeared in the residue solution.The highest furfural yield obtained by the combination of acetic acid and FeCl3 was 47.6%,while the cellulose retaining rate was 71.84%.The experimental parameters were 180℃ of temperature,60 min of reaction time,6wt.%of acetic acid concentration,20 mM of FeCl3 concentration and 5 mL.g-1 of liquid to solid ratio.The yield of furfural obtained by citric acid and AICl3 was low,and the cellulose retaining rate was only 8.38%,while the lignin and coke content of the product was high to 80.8%.Besides,the introduction of NaCl into acetic acid and FeCl3 catalyzed single-phase system had adverse effects on furfural yield and cellulose retaining rate. |
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