Experimental Study On The Preparation Of Biomass Components By Deep Eutectic Solvent And The Thermal Conversion Characteristics

With the depletion of non-renewable fossil resources and increasing energy demand,the scientific research on the use of renewable resources of lignocellulosic biomass to produce fuel ethanol,bio-based materials and platform compounds has gradually attracted researchers' attention,during the process of treating lignocellulosic biomass,select a suitable separation or treatment method to separate the lignin component and cellulose component from the biomass,and the full utilization of each component is the key to the efficient conversion and utilization of lignocellulosic biomass.In this thesis,the pine wood biomass in the paper industry raw materials is used as the research object,and the green economical lactic acid(Lac)and choline chloride(ChCl)are used as raw materials to synthesize the medium solvent used for biomass treatment,that is the Deep Eutectic Solvent(DES).The DES formed by hydrogen bonding donor Lac and hydrogen bonding acceptor ChCl with different molar ratios were studied to regulate the reaction temperature and reaction time,under these conditions the classification efficiency of pine wood components and the dissolution of single component of lignin were studied under different regulatory factors of reaction temperature and reaction time.In addition,with the help of high magnification scanning electron microscopy(SEM),Fourier infrared spectroscopy(FT-IR),X-ray diffraction(XRD),thermal weight loss analysis(TGA)and other techniques instruments to analyze and characterize the physical and chemical properties,chemical structure and functional groups,etc.and conduct in-depth analysis of the thermal degradation behavior and pyrolysis conversion products of the single component of lignin,and the in-depth analysis of the thermal degradation behavior and pyrolysis conversion products of the single component of lignin,the research found that:During the treatment of pine biomass with DES,changes in reaction temperature,DES species,and reaction time all had significant effects on the extraction rate(X2)of pine lignin.When the molar ratio of ChCl to Lac in DES is 1:5 and the reaction temperature is 150?,DES has the best selectivity for dissolving pine lignin.It was found that the reaction temperature had the most significant effect on X2 during the processing of pine raw materials by DES,followed by the reaction time,and the molar ratio of ChCl and Lac in DES had the least effect on X2.After treatment of pine wood with DES,cellulose-rich solid residues and nano-scale DES-lignin can be obtained.It can be seen that when using DES to process pine wood raw materials,most of the lignin in the raw materials can be removed.The purity of the lignin component is higher,and with the increase of DES treatment temperature,the dispersibility of DES-lignin is gradually improved,the diffusion diffraction characteristics are gradually enhanced,and the content of aryl ether bonds is lower.According to the study of the pyrolysis and transformation characteristics of lignin,it was found that the lignin macromolecule connection bond and the side chain breaking reaction mainly occurred in the pyrolysis temperature region of 1 50?300?,and the lignin molecule degradation reaction mainly occurred in the temperature region of 300?600?.The corresponding mass losses of L100?,L130?,and L150? were 42.51%,36.23%,and 36.35%.With the gradual increase of the pyrolysis temperature,the yield of coke gradually decreases,which is due to the cleavage and recombination reaction of the lignin structural unit connection between DES-lignin at 400?600?.At the same time,a more stable aromatic compound is formed,As the pyrolysis temperature rises to 700?,the lignin carbonization reaction mainly occurs,the coke yield gradually stabilizes,the quality of coke continues to improve,and the calorific value gradually increases.When the pyrolysis temperature reaches 550?,The calorific value of coke has exceeded 30MJ/kg,which has reached the level of high calorific value coal,and the surface of DES-lignin pyrolytic coke has a porous structure,this pore structure will enhance the coke adsorption performance.The pine lignin obtained through the DES-biomass refining process not only retains the basic structure of the original lignin,but also obtains a uniform nano-lignin.This nano-lignin can be widely used in hydrogels,biomedicine,material additives,surfactants and sunscreen cosmetics.And it has very good application development prospects.