Function Detection And Mechanism Analysis About Self-exothermic Process During Phos-phoric Acid Plus Hydrogen Peroxide Pretreat-ment Of Lignocellulose

Pretreatment is an important part of the resource utilization of lignocellulose.The concentrated phosphoric acid plus hydrogen peroxide(PHP)pretreatment is a newly developed method.In the previous studies,PHP pretreatment achieved great abilities.Besides,material sharply expansion and temperature rapidly rise to more than 100 ℃(self-exothermic phenomenon)were discovered unexpectedly.However,correlation between abilities and selfexothermic process is unknown at present,and the realization path of self-exothermic heat is also unknown.To this end,this study carried out three aspects about PHP pretreatment,including self-exothermic function,generation mechanism and inducing factors.Results of this study are detailed described as follows:(1)During PHP pretreatment of eight kinds of biomass,the exothermic duration ranged from 20.50 min to 68.73 min,and the highest temperature ranged from 115.5 ℃ to 126.5 ℃,indicating self-exothermic process own universal raw material adaptability.Two sets of different self-exothermic pretreatment systems were designed to detect functions of self-exothermic.It was found that the maximum lignin removal potential,hemi-cellulose removal potential and pollutant degradation potential of violent self-exothermic system were better than weak self-exothermic system.Obviously,self-exothermic process could efficiently help decompose lignocellulose and degrade pollutants.(2)On the one hand,control variable method was used to study influence of pretreatment conditions on heat released.The conditions are solid-liquid ratio,temperature and concentration of PHP solution.As expected,they were proportional to the self-exothermic intensity within a certain range.On the other hand,biomass compositions were studied by removing or adding.Compositions were extracts,lignin,cellulose,hemicellulose,lignin and ash.Amazingly,inherent ash could catalyze the degradation of lignocellulose and make selfexothermic process more violent.(3)The elements with higher content and removal rate were K,Ca,Mn,Mg,Fe,Ba and Sr.Among them,Fe,Mn and Mg were selected as typical elements for further study.By hydroponics with aqueous solution,different biomass with different metal contents were obtained.Different heat released during PHP pretreatment verified catalytic potential of Fe,Mn and Mg to promote self-exothermic process.Among them,Fe had the strongest catalytic effect,and the more Fe content,the more promoted the pretreatment self-exothermic heat.Based on above results and previous conclusions,the mechanism of self-exothermic process during PHP pretreatment of lignocellulose could be explained as follows: Beginning with dissolvement of hemicellulose by phosphoric acid and produce of acetic acid.Later,metal minerals were chained released,short-chain fatty acids and corresponding peracids were chained generated,strong oxidizing free radicals were chained formed by catalysis of metals,lignocellulose were chained degraded,and temperature of the system continued to rise sharply.This was an autocatalytic chain process.By solving basic questions of this study,it is helpful to clarify the key scientific essence about in situ effect of biomass endogenous ash on realizing efficient deconstruction of lignocellulosic materials.Besides,it is of great significance for promoting related industrialization technical level.