Effects Of High Temperature Hot Water Microburst On The Structure And Pulping Properties Of Poplar Fibers

Some papermaking enterprises in China are exploringhigh-temperature hydrothermal pretreatment to extract the hemicellulose from hardwoods,such as poplar and eucalyptus,and subsequently convert the main monosaccharide into high value-added chemicals and functional sugars.The obtained wood fiber after pretreatment is usually applied in pulping and papermaking.After high temperature hydrothermal pretreatment,the microstructure and morphology of poplar wood changed,which is called microexplosion phenomenon.In the high-temperature hydrothermal pretreatment process,a combined severity factor?CSF?as a macroscopic variable was used to invetigate the microburst phenomenon of raw materials and the degradation of each component.Accordingly,the effects of microburst on the dissolution and degradation of each component in wood chips and the performance of subsequent chemical pulp were comprehensively determined.Therefore,this study mportant for researchers and industrial representatives for the future combination of biomass refining and pulp making.Firstly,The CSF as the severity of high temperature hydrothermal pretreatment is used to balance the enzymatic saccharification and lignin structural properties of cellulose.The extracted lignin was characterized by FTIR,TGA,³¹P NMR and 2D HSQC NMR.An optimum CSF approximately 8.37 was obtained with a negligible glucose concentration of 1.19 g/L and a hemicellulose removal rate of 74.71%.The pretreated substrate was hydrolyzed reaching an enzyme saccharification yield of 83.92%.the residual lignin in solid exhibited excellent structural properties such as high hydroxyl content?2.34 mmol/g of aliphatic hydroxyl group and 2.43 mmol/g of phenolic hydroxyl group?and high?-O-4 aryl ether bond?27.86%?content.According to data analysis,we found that the ratio of specific surface area and crystallinity of the relative intensity factor between the degree of variation and microburst derived function relations.Therefore,we first put forward the concept of microburst coefficient the concept of microburst coefficient???,and used to measure the size of the degree of microburst,and the degree of microburst was identified with three levels:slight microburst,severe microburst and suppression of microburst.The results showed that the raw material of poplar was at a slight micro-explosive level,and the components of poplar have a relatively low removal number,the content of each component in the prehydrolysate was almost zero.Under the severe microburst conditions,a significant change in the degradation of the three components,the crystallinity of cellulose,the concentration of sugars and acetic acid in the pre-hydrolyzate was found,the components of poplar get into a large number of degradation stage.Under the microburst suppression level,the deposition of lignin,fiber collapse,and other factors have a negative effect on the microburst,and the dissolution of each component shows a slow growth or decline trend.Caustic soda performs caustic soda and kraft cooking on wood chips of different micro-explosive grades.It was found that the micro-explosion treatment facilitated the caustic soda method and the kraft pulping process,and the obtained slurry had a high yield of fine pulp,and the potassium permanganate value was low,but the degree of polymerization became small.After slight micro-explosion treatment,the whiteness of caustic soda pulp decreased slightly;after severe micro-explosion treatment,the whiteness of pulp increased significantly,from 28.47%to 33.23%of raw materials;reduce.After inhibiting the micro-explosion treatment,the pseudo-lignin deposition and fiber collapse inhibited the micro-explosion,hindering the penetration of the liquid,and the pseudo-lignin also consumed some of the liquid.Moreover,the microfibrous structure in the poplar cell wall was destroyed,and the fiber strength was lowered,so that the viscosity of the slurry decreased remarkably,from 1647.21 to 985.26.The influence law of micro-explosion on kraft pulping is similar to that of caustic soda method.