Study On Catalytic Pyrolysis Characteristics And Co-pyrolysis Behavior Of Low Rank Coal

Catalytic pyrolysis,which involves the pyrolysis of coal in the presence of catalyst,has emerged as an important means to improve the tar yield and quality.Biomass could be used as hydrogen donor to improve tar yield during co-pyrolysis of coal and biomass.This paper reported the effect of zeolite catalysts on Yulin coal(YLC)and Hulunbeier(HLC)pyrolysis behavior under the condition of lower catalyst addition(5%)and low temperature(450 ?),and investigated the product yields and tar distribution of YLC and walnut shell(HTK)co-pyrolysis with different HTK blend ratio and ZSM-22 zeolite catalyst.According above content,the main results are summarized as follows:Fixed-bed reactor was used to investigate the effect of different zeolite and alkaline modified zeolite catalysts on the product yields of YLC pyrolysis.The results showed that larger pore size of HY zeolite promoted the generation of tar(16.37 wt%).Compared with the untreated HY and HBeta zeolites,the alkali-treated HY and HBeta catalysts decreased tar yield,whereas increased gas yield.It is found that HY zeolite improved tar yield obtained from pyrolysis of YLC and HLC,and the catalytically produced tar contained more arenes,and less aliphatics,alcohols,phenols and nitrogen-containing compounds.Fourier Transform Infrared(FTIR)technique was used to simuttaneously detect gas products,mainly including CO2,CO,CH4 and H2O.HY zeolite promoted the generation of gases.The related kinetics of catalytic pyrolysis of YLC was fited tosome single reaction,first-order model(300?350 ?,400?450 ? and 600?650 ?).The pyrolysis of YLC over HY,USY and Ni supported catalysts were studied.It is found that the supported catalysts improved tar yield from YLC pyrolysis.Mo/HY-CA and Ni/USY showed better performance in producing more tar with the yield of 16.81 wt%and 17.16 wt%,respectively.ZSM-22 and modified ZSM-22 zeolite catalysts were characterized by BET,SEM-EDS and NH3-TPD.The research reports the catalytic pyrolysis of YLC to determine the effects of ZSM-22 and modified ZSM-22 zeolite catalysts on the yields of pyrolysis products(char,tar,gas)and the distribution of tar.The results showed that ZSM-22 and modified ZSM-22 zeolite catalysts result in a higher tar yield,whereas lower char yield is produced.Co/ZSM-22 showed better performance in upgrading tar quality in terms of high selectivity for aliphatics(49.50%)and arenes(21.01%).Co-Mo/ZSM-22 catalyst with 1:2 metal ratio increased the selectivity of aliphatics and arenes.Co-pyrolysis characteristics of YLC and HTK were determined in a fixed bed reactor and thermogravimetric analysis(TGA).The higher tar actual yield compared with the theoretial vaule fully proved the synergy effect in co-pyrolysis process.Especiall,when the blend ratio of HTK is 50%,the tar actual yield increased by 4.87 wt%.The tar obtained from co-pyrolysis contained more oxygen-containing compounds.ZSM-22 catalyst improved the selectivity of aliphatics and arenes,whereas inhibited those of oxygen containing compounds.