Preparation Of Levoglucosan By Fast Pyrolysis Using Lignocellulose Pretreated With Crude Glycerol

At present,a large number of agricultural and forestry wastes are discarded and burned,which not only lows utilization value,but also causes environmental pollution.Its main component is lignocellulose,which can be converted into high-valued levoglucosan via fast pyrolysis.Organic solvent pretreatment can effectively promote the conversion of lignocellulose into levoglucan,thereby increase the yield of levoglucosan.Crude glycerol is a by-product of biodiesel.With the increase of biodiesel production,it becomes a cheap and surplus resource,and is urgent to find new utilization approach.Studying crude glycerol pretreatment prior to fast pyrolysis of lignocellulose to yield levoglucosan can alleviate the environmental pollution caused by the excess of crude glycerol,which has certain social significance and economic value.In this paper,lignocellulose was pretreated by chemical method.The optimal effect of glycerol/alkali pretreatment on the composition and structure of lignocellulose under different conditions of temperature and time or concentration,and then the influence factors of glycerol and alkali pretreatment on the yiled of levoglucosan from fast pyrolysis of lignocellulose were investigated.First,pure glycerol was used as pretreatment solvent of corn cob.The effect of different pretreatment temperature and time on the composition,structure and yield of levoglucosan from fast pyrolysis product of corncob was investigated.The results showed that pure glycerol pretreatment increased the content of cellulose and crystallinity in corn cob,removed lignin and AAEMs,and then promoted the increase in the yield of levoglucosan from 6.9 wt% to 15.3～44.5 wt%,which increased with the increase of pretreatment time or temperature.Two kinds of crude glycerol were prepared in this paper to pretreat sugarcane bagasse.At the condition of 220 ℃ and 6 min,crude glycerol pretreatment could remove 95.3～95.6% of AAEMs and 45.0～79.4% of lignin,increase 44.1～66.2% cellulose,improve the pyrolysis characteristic parameters,and improve the yield of levoglucosan from 8.4 wt% to 21.0～25.2 wt%,which was superior to pure glycerol pretreatment(14.4 wt%).The fermentation performance of the crude glycerol-rich waste liquid after crude glycerol pretreatment was evaluated by fermentation experiments,and its fermentation performance was found to be comparable with that of pure glycerol,indicating that the glycerol-rich waste liquid can be converted and utilized by fermentation.The effect of crude glycerol pretreatment was superior to pure glycerol pretreatment.The main difference between the two kinds of glycerol is the alkaline substance.Therefore,this paper investigated the effect of different temperatures and alkali concentration on the composition,structure,and content of levoglucosan.The results showed that alkali pretreatment also has obvious optimization effects on components and structure.With the increase of alkali concentration or pretreatment temperature,the degree of cellulose enrichment,the removal rate of hemicellulose,AAEMs and lignin were improved.The content of levoglucoasn also increased with the increase of the alkali concentration or temperature of the pretreatment,and the content of levoglucosan increased from 3.5% to 5.5～34.8%.