| This paper is a research for the combination method of autohydro lysis pre-treatment process and CTMP(Chemi-thermo mechanical Pulp)pulping,providing poplar biomass refinery for becoming a new way.As people realize that clean pulping should be environmentally friendly,the concept of identity comes to be popular.Extracting part of hemicelluloses from poplar wood raw materials prior to Chemi-thermo mechanical pulping can not only realize a high value-added utilization of biomass resources but also ensure the production of traditional pulps and fiber products,which benefits the new efficient use of bio-resources and maximize the development resources.After hot water pretreatment,the different individual components of wood raw materials would change.First,a part of the hemicelluloses dissolved in hot water.Second,the internal structure of the wood chips was fractured,reducing the refining energy required for the subsequent CTMP pulping process and improving the strength properties of the obtained pulp.Third,the yield and brightness of obtained pulp dropped significantly.In this study,the characteristic of poplar wood chips pretreated with different autohydrolysis intensities was studied.The effects of different autohydrolysis intensities on the color parameters of the chips,the subsequent CTMIP pulping and pulp bleaching process were explored in order to provide a theoretical basis for autohydrolysis pretreatment process in industrial production.Poplar wood chips were used as the raw material in this study,the autohydrolysis pretreatment with different severity factors(the combination of autohydrolysis temperature and time)was performed with a liquid/solid ratio of 10:1 kg/kg,and then the obtained wood chips were analyzed in the subsequent experiment.Firstly,effects of the wood chips' yield and its lignin content,the wood chips' color,and the pH value of the autohydrolysis liquor were investigated.The experimental results showed that the yield of the auto hydrolyzed poplar wood chips decreased as the autohydrolysis severity factor aggravated continually.The yield of the autohydrolyzed chips decreased from 97.21%to 83.21%when the severity factor was increasee from 2.07 to 3.72.Meanwhile,the chroma index a*of the wood chips increased from 2.29 to 9.03,and the chroma index L*decreased fron 83.26 to 54.96.The chroma index h*only increased from 17.07 to 18.58.Within the scope of this study,the pH value of autohydrolysis liquor declined from 5.28 to 3.55.Then,two kinds of lignin,that is,Klason lignin and dioxane lignin,were obtained after purifying the autohydrolyzed wood chips and control sample(without autohydrolysis pretreatment)using two different methods,respectively.The results showed that with the increase of the autohydrolysis severity factor the content of Klason lignin and acid soluble lignin was reduced from 26.09%to 19.84%.The dioxane lignin yields of control sample and pretreated wood chip at the severity factor of 3.72 were 24.64%and 15.52%,respectively.Finally,the IR spectroscopy and 13C-NMRanalysis for the dioxane lgnin of the poplar wood chips showed that the basic structure of lignin in the autohydro ly zed wood chips didn't have significant change with increasing the severity factor compared to the control sample.When the severity factor reached 3.72,the infrared spectra peak value of benzene hydroxyl was increased,indicating that the content of benzene hydroxyl in the dioxane lignin of the chips was increased.The phenolic guaiacl and syringle units changed after the thermal treatment,and the condensation reaction happened between C5 and the side chain,which caused the elongation of the conjugated system in lignin and the extra absorption for lignin in the visible spectrum... |
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