Study On Light Aromatics Of Chemical-looping Pyrolysis From Typical Western Coal

The key to preparing BTX by chemical-looping pyrolysis technology of coal is the application of chemical-looping technology.The release of the lattice oxygen of the oxygen carrier in chemical-looping pyrolysis has a certain reforming effect on coal pyrolysis volatiles,the advantages of increasing the added value of products,simplifying the process route,and improving the atom utilization rate.Therefore,it is a great significance to carry out chemical-looping pyrolysis of coal to produce light aromatics.In this paper,an experimental study on the preparation of light aromatics by bituminous coal and oxygen carrier mixed pyrolysis was carried out through qualitative,kinetic parameter introduction,external standard quantification,and pyrolysis product distribution.Then,the polygeneration of light aromatics prepared by pyrolysis of bituminous coal and oxygen carrier/catalyst was studied,and the mechanism of chemical-looping pyrolysis was discussed and compared with a brief economic analysis through the oxygen carrier regeneration cycle experiment.The main research content and conclusions of this paper are as follows:(1)Using the thermogravimetric-mass spectrometry-fourier transform infrared spectrometer,gas chromatography-mass spectrometry and tubular furnace reactor were used.In the reactor,the law of catalytic pyrolysis of Ningxia bituminous coal to produce light aromatic hydrocarbons(BTX)was investigated.Results showed that compared with the pyrolysis of bituminous coal,the weight loss of bituminous coal increases by 10%in the presence of(Fe2O3+MoSi2)/HZSM-5,the solid phase conversion rate increased significantly,and the relative content of BTX in the liquid product reached 59.61 area%,which was higher than the theoretical value of the 1:1 mixture of 39.84 area%.Fe2O3 and MoSi2 showed significant synergistic effect on the preparation of BTX.Subsequently,the yield of BTX reached 7.78 mg/(g·coal),which was significantly higher than the value reported in the literature.In the pyrolysis main weight loss zone(350?600?),the Ea of bituminous coal and(Fe2O3+MoSi2)/HZSM-5 catalyst mixed pyrolysis was reduced by 8.253 kJ/mol.In the pyrolysis reaction of bituminous coal,the Fe2O3 component has obvious deoxidation effect and it is favorable for the conversion of polycyclic aromatic hydrocarbons to monocyclic aromatic hydrocarbons,because the release of lattice oxygen is conducive to the depolymerization reaction of macromolecular liquid products.At the same time,the hydrodeoxygenation of MoSi2 will also promote the conversion of phenol products to BTX.(2)Study on the production of light aromatics by chemical-looping pyrolysis of coal on atmospheric pressure fixed bed reactor.Results showed that compared with bituminous coal pyrolysis,after the introduction of 10 wt.%-(Fe2O3+Co3O4)/HZSM-5,the char yield decreased by 7.5%,the gas phase yield increased by 5.55%,and the oil phase yield did not increase large,but the relative content of light aromatics increased by 31.54 area%;the H2 yield was 0.03 L/g,the increment reached 87.5%,the CO yield was 0.05 L/g,the increment reached 200%,the CO2 yield decreased by 0.011 L/g,the yields of CH4,olefins,and alkynes all increased,and the relative floating value was small;the introduction of water vapor increased the synthesis gas yield to 0.15 L/g.After 10 regeneration cycles,the oxygen carrier/catalyst,the total yield of BTX decreased by about 3.8%;after 15 regeneration cycles,the gas yield decreased by 10%.This was due to the fact that as the number of reductions increases,the structure of the effective carrier is destroyed to a certain extent,which has a certain impact on the results of polygeneration.(3)The mechanism of chemical-looping pyrolysis was discussed through oxygen carrier regeneration cycle and product distribution.When the light volatiles stay on the surface of the oxygen carrier,the lattice oxygen will combine with the ethyl cation of monobenzene ring or naphthalene branch to form an ethyl oxygen bond,weakening the bond energy.For heavy volatiles,lattice oxygen will undergo certain bond-breaking reformation of large molecular substances such as single benzene ring multi-branched chain,single benzene ring complex single-branched chain,polyphenyl ring multi-branched chain.Then small molecules will enter the catalyst pores for cracking and aromatization,thereby improving the quality of light aromatics.