| With the continuous development of society and the shortage of other non-renewable resources,straw biomass to manufacture fuel ethanol has attracted the attention of people.Due to the complexity of straw structure,straw depolymerization can make effective components fully exposed in order to efficient conversion of straw.However,current researches main focuse on the depolymerization method instead of the formation mechanism of the product,greatly limiting the effect of the conversion of straw liquid fuels and chemical products.Therefore,the study on the depolymerization method and the mechanism of product formation is important practical value.This paper has been studied for this situation,and the results were given as follows:(1)The results by acid depolymerization showed the surface morphology become loose,formed cracks and channels;the crystallinity of cellulose were increased from 54.37%to 59.19%;FTIR result showed main features of hemicellulose absorption peaks were weaken or disappeared.After deployment with 2%sulfuric acid at 120℃,The major depolymerization products were arabinose,xylose,glucose,furfural,5-hydroxymethyl furfural,and acetic acid.Cellobiose and formic acid were detected in the liquid after treatment with 3%sulfuric acid for 210 min.When the increase of acid concentration,the type of depolymerization product did not increased.Finally,this study proposed the mechanism of acid depolymerization and the formation pathway of product.(2)The kinetic model was used to study dynamic process from wheat straw by sulfuric acid at different concentrations.This method was satisfactorily developed to explain the generative process of xylose,glucose,arabinose,acetic acid and furfural.The rate of formation and degradation constants of glucose,xylose,arabinose,acetic acid,and furfural were obtained by kinetic model.The activation energies of xylose formation with H2SO4 were 44.99 kJ/mol.Considering the total sugar content and the total content of by-products under different conditions,the optimum depolymerization conditions were obtained after pretreatment with 3%sulfuric acid catalysis at 130 ℃ for 75 min.(3)The results by alkali depolymerization showed that samples loose surface structure,formed cracks and channels;the crystallinity of cellulose were increased from 54.37%to 61.99%;FTIR result showed main features of lignin absorption peaks were weaken or disappeared.When reaction time was longer than 300 min,the content of cellulose was up to 57.26%.In addition,the depolymerization products were 4-hydroxybenzaldehyde,lilacaldehyde,vanillin,p-coumaric acid,ferulic acid.However,the depolymerization products with acid pretreatment were glucose,xylose,arabinose,acetic acid,and furfural.(4)The content of cellulose and lignin be used as an index to study the alkali depolymerization method,when wheat straw was raw material.The primary and secondary order of factors on the effects of pretreatment was as follows:reaction time>sodium hydroxide concentration>Liquid-solid ratio.The optimum conditions were obtained at 80.16 ℃,sodium hydroxide 3.24%,processing time 200min.Under this condition of the depolymerization,the content of cellulose was 55.77%and the content of lignin was 8.41%. |
