Study On The Regulation Of Hemicellulose Products From Catalytic Pyrolysis Of Hydrophobic Ionic Liquids Enhanced By Electrochemistry

Biomass energy is the most abundant energy resource on the earth.Biomass contains three elements of hydrocarbon,hydrogen and oxygen.The ash content of combustion products is low with no serious pollution problem.Biomass can be regard as inexhaustible and inexhaustible.If we can realize the vigorous development and utilization of biomass energy,it greatly promote the development of society,not only alleviate the energy crisis,reduce environmental pollution.At present,pyrolysis is a promising technology in the utilization of biomass energy.The main component of biomass is lignocellulose.cellulose,lignocellulose and lignin are three major sources of lignocellulose.The pyrolysis behavior of biomass is a comprehensive reflection of the three main components.Current research is aimed at each independent component of lignocellulose.Cellulose is one of the main component in biomass.There are most research on the pyrolysis of cellulose.Catalysts are introduced to improve the pyrolysis efficiency and products quality.The bio-oil phase of pyrolysis contains a large number of high value-added chemicals,on the other hand,it can apply to liquid fuel.The gas produced by pyrolysis can be used as fuel gas.Biochar can be used as adsorbent materials.The data of hemicellulose pyrolysis are very limited.However,the content of hemicellulose in lignocellulose is second only to that of cellulose.Due to the complexity structure of hemicellulose,the main components of hemicellulose are usually chosen as model compounds for hemicellulose pyrolysis.In order to explore evolution regulation of pyrolysis products,xylan was regard as model compounds for hemicellulose in this study.The relationship between lignocellulose and ionic liquids started with the dissolution of lignocellulose in ionic liquids.Ionic liquids have unique advantages of good electrical conductivity,high thermal stability,wide liquid range,stable electrochemical window and its structure can be designed.It can be used as heat medium,conductive material and catalyst for the reaction.It is technically feasible to use ionic liquid pyrolysis with temperature gradient and electrochemical voltage gradient.Exploring the influence of temperature and voltage on pyrolysis products is helpful to grasp the evolution law of products and to targeted regulation the pyrolysis products.Ultimately,the efficient utilization of hemicellulose is realized.In this study,the research purpose is to study the product evolution of xylan.A low temperature catalytic pyrolysis system of hydrophobic conductive ionic liquids was constructed,The pyrolysis kinetics of xylan and ionic liquid catalysts was simulated and calculated.The temperature gradient pyrolysis experiment of xylan was carried out at low temperature?160-280??.The pyrolysis products were analysed and characterized,and the best pyrolysis temperature of xylan was synthetically evaluated.On this basis,voltage gradient catalytic cracking experiments were conducted to study the regulation of products under different voltage.The main results are as follows:?1?Five kinds of ionic liquids were successfully synthesized according to the structural characteristics of hemicellulose and the properties of ionic liquids,namely[Hmim]Cl,[Hmim]Br,[Hmim]PF₆,[Hmim]BF₄,[Hmim]SbF₆.[Hmim]Cl and[Hmim]Br were the raw materials for synthesizing the other three hydrophobic ionic liquids.The thermal stability analysis and conductivity test of hydrophobic ionic liquids was conducted.The thermal stability of[Hmim]BF₄ was satisfied the requirement of pyrolysis temperature,and its conductivity performance was superior to other ionic liquids.Finally,[Hmim]BF₄ was selected for subsequent catalytic pyrolysis experiments.?2?Thermogravimetric analysis of xylan and xylan/[Hmim]BF₄ showed that pyrolysis was divided into four stages.The final solid residue rate exhibited that the solid residue yield of individual xylan pyrolysis?24.12%?was higher than that of the mixed sample?3.09%?,which indicated that[Hmim]BF₄ inhibited coke production.?3?Xylan catalytic pyrolysis was carried out at[Hmim]BF₄ with temperature gradient of 160-280?,the three-phase products of xylan pyrolysis were analyzed by GC-MS,SEM and FT-IR,respectively.The results showed that[Hmim]BF₄ had a good catalytic effect on the pyrolysis of xylan,and[Hmim]BF₄ was easier to obtain liquid products.Biochar was cracked into smaller granular substances at 260?.The gas-phase product yield reached the maximum at 260 C?148ml?.The liquid phase results showed that xylan produced aldehydes,alcohols,olefins,benzene,carboxylic acids and ketones at different temperatures.The relative content of furfural reached the maximum value of 90%at 260?,and 260?was chosen as the optimal pyrolysis temperature.?4?Under the optimum temperature of 260?,voltage gradients?1V,1.5V,2V,2.5V,3V,3.5V?catalyzed the pyrolysis of xylan in[Hmim]BF₄.The three-phase products of xylan pyrolysis were characterized by GC-MS,SEM and FT-IR,respectively.The results showed that the gas yield was the largest at 3V?450ml?,which was more than that obtained by temperature gradient pyrolysis.The gas production can be promoted by controlling the voltage.When applied voltage,the relative content of4-H-cyclopentene can above 90%,which is higher than that of temperature gradient pyrolysis.It was proved that electrochemistry would enhance the deoxidation reaction of liquid products and increased the yield of hydrocarbon products.