Research On The Preparation Of Hydrocarbon Liquid Fuel By Pyrolysis Of Lignin Catalyzed By Molecular Siev

Biomass pyrolysis oil has the prospect of replacing traditional fossil fuels,but the biooil produced by direct pyrolysis has the defects of high oxygen content,strong acidity,low calorievalue,poor stability and high viscosity.Catalytic pyrolysis technology is an effective way to improve the quality of bio-oil.Zeolite catalyst is the most widely used catalyst in catalytic pyrolysis.In catalytic pyrolysis,the pore diameter of zeolite should adapt to the molecular size of biomass pyrolysis oil in order to play the maximum catalytic performance.Therefore,the molecular dynamic diameter of alkali lignin pyrolysis bio-oil,the preparation and catalytic performance of multi-stage pore zeolite catalyst were studied.The bio-oil products were collected by pyrolysis of alkali lignin at different temperatures.The bio-oil obtained from pyrolysis at different temperatures was detected and analyzed by GC/MS,and the composition and percentage of bio-oil were analyzed.The pyrolysis products of bio-oil are mainly aromatic oxygen-containing compounds,which are classified and counted according to the number of methoxy and phenolic hydroxyl groups.The results showed that phenolic compounds,catechol compounds and guaiacol compounds were the main compounds in the pyrolysis temperature range of 350-600℃.The content of phenolic compounds in Guaiac decreased sharply with the increase of pyrolysis temperature,while the content of phenolic compounds increased significantly.Three different types of group contribution methods,Joback method,Lijie method and Tahami method,combined with Bird kinetic diameter calculation model,were used to calculate the kinetic diameter of each component of the pyrolysis bio-oil product of alkali lignin at 350-600℃.The results of kinetic diameter distribution calculated by three group contribution methods were similar,and the Joback group contribution method was more accurate in estimating the kinetic diameter of aromatic compounds.When the pyrolysis temperature is 350-450℃,the kinetic diameter distribution is mainly concentrated in the range of [0.60,0.66)nm,while when the pyrolysis temperature is 550-600℃,the kinetic diameter distribution is mainly concentrated in the range of [0.54-0.60)nm.A series of hydrogen-type multi-stage pore zeolite catalysts were prepared by alkali treatment and ion exchange with ZSM-5 zeolite as raw material.The molecular sieve was characterized by XRD,TEM,N2 adsorption-desorption technology and NH3-TPD technology.The crystalline phase,morphology,pore structure parameters and acid distribution of zeolite were analyzed.The results show that the higher the concentration of NaOH solution is,the more mesoporous structures there are,which reduces the mass transfer resistance in the catalytic process.However,too high the concentration of NaOH solution will lead to the destruction of the microporous structure and thus affect the catalytic performance.Finally,a series of zeolites were used for catalytic pyrolysis of alkali lignin,and the results showed that the coke product decreased by 18% and the liquid bio-oil product content increased by about 7% after using zeolites catalyst.HZSM5-2 had the best catalytic effect on the conversion rate of hydrocarbon products in alkali-lignin pyrolysis oil,and the percentage content of hydrocarbon products reached 94%.