Pretreatment Assisted By Naphthol Derivatives And Resource Utilization Of Wood Fibers

As a sustainable fossil fuel substitute,biomass mainly comprises cellulose,hemicellulose,and aromatic lignin.However,the recalcitrant structure of natural lignocellulosic biomass hinders the efficient conversion of biomass.In order to destroy the dense lignocellulosic matrix,starting from the inhibition of lignin repolymerization reaction,it is hoped that the simple modification of lignin can both promote lignocellulosic enzymatic digestion and achieve resource utilization of lignin with the help of pyrolysis process.On the basis of exploring the key mechanism of influence of naphthol derivatives on dilute acid pretreatment,the effects of naphthol derivatives on enzymatic hydrolysis efficiency of different fiber raw materials were compared.Meanwhile,in order to address the problem of lignin waste liquor produced in the organosolv pretreatment process,the rich lignin contained in it was converted into bio-oil and biochar in the form of high temperature pyrolysis,and the influence of lignin structural modification on the pyrolysis characteristics and product formation pattern was investigated.The main conclusions are as follows:(1)The addition of 2-naphthol and its carboxylic acid derivatives assisted the dilute acid pretreatment of poplar wood,which effectively enhanced the removal rate of lignin from the material and thus promoted the efficiency of cellulose hydrolysis of the material.The addition of2-naphthol and 3-hydroxy-2-naphthoic acid made the pretreated material produce more negative surface charge,promoted the effective binding of cellulose and cellulase,and reduced the molecular weight of residual lignin in the pretreated material,inhibited the repolymerization of lignin during dilute acid pretreatment,and reduced the ineffective adsorption of cellulase and lignin.Meanwhile,the addition of 2-naphthol and 3-hydroxy-2-naphthoic acid also decreased theβ-β structure content and β-5 structure content,increased the total phenolic hydroxyl content,and promoted the depolymerization of lignin in the pretreatment.In addition,the addition of 3-hydroxy-2-naphthoic acid significantly increased the content of carboxylic acid groups on lignin,which proved the reaction between 3-hydroxy-2-naphthoic acid and lignin during the pretreatment process.(2)The enzymatic hydrolysis yield of the three agricultural wastes,wheat stalk,corn stover and corn cob,was significantly increased by the addition of 3-hydroxy-2-naphthoic acid to the dilute acid pretreatment.In addition,the enzymatic hydrolysis yield of the materials was also significantly improved by adding 3-hydroxy-2-naphthoic acid to the dilute acid pretreatment,hot water pretreatment and organosolv pretreatment of corn stover.Through the experimental optimization of the comprehensive severity factor and the amount of 3-hydroxy-2-naphthoic acid added,it was concluded that for corn stover,the addition of 2%(w/w)of 3-hydroxy-2-naphthoic acid to assist dilute sulfuric acid(1%(w/w))pretreatment for 2 h at 180 °C resulted in the best enzymatic hydrolysis,with a final cellulose conversion rate of 69.01%,and a growth rate of31.99%.(3)Organosolv lignin with high purity was obtained by adding naphthol derivatives to assist the organosolv pretreatment,in which the percentage of acid insoluble lignin was close to 90%of the total lignin sample.The content of volatile and fixed carbon of organosolv lignin was much higher than that of commercial lignin,with higher HHV.The molecular weight of the organosolv lignin obtained after the addition of naphthol derivatives to assist the organosolv pretreatment was reduced and the dispersion was more homogeneous.After pyrolysis of organosolv lignin samples,the surface area and pore volume of organosolv lignin biochar without additives were the largest.The organosolv lignin with 2-naphthol added had the highest oil yield(15%),and its pyrolysis biochar had the largest average pore size;the organosolv lignin with 3-hydroxy-2-naphthoic acid added had the highest coking rate(39%),poor thermal stability and easy degradation,and its pyrolysis bio-oil had the highest carbon content and HHV.Phenols,aldehydes and esters are the main components of lignin bio-oil,and the pyrolysis of lignin with organosolv is beneficial to the formation of toluene in oil.