Integrated Process Of In-situ Catalytic Cracking With Steam Reforming Of Ethane Of Coal Pyrolysis Tar

A new process to improve light tar yield by coupling in-situ catalytic cracking of coal pyrolysis tar with steam reforming of ethane was put forward.The effect law of catalysts and reaction conditions on the tar yield and composition in the in-situ upgrading process of coal pyrolysis tar were studied.Meanwhile,the formation mechanism of tar was also explored.In a fixed-bed reaction device which arranged as coal in the upper layer,catalyst in the lower layer and two separated by quartz wool at atmospheric pressure,the effects of catalyst types,Ni loading in the catalyst,catalyst dosage and reaction temperature on the tar and gas yield of Pingshuo coal pyrolysis process were studied under N₂ and C₂H₆/H₂O mixed atmospheres,respectively.The results showed that at 650?,the tar yield of the coal pyrolysis in C₂H₆/H₂O mix atmosphere?CP-E&S?without catalyst reached the highest value of 18.8wt.%.Ni/AC has the best lightening tar effect in the four catalysts?Char,AC,Co/AC,Ni/AC?,the light tar content and yield reached 71.5 wt.%and 13.2 wt.%with Ni/AC,which increased by 55.4%and 53.4%,respectively,compared with non-upgrading.Besides,the best upgrading effect was obtained when metal loading of Ni/AC is 10 wt.%and the mass ratio of coal to catalyst is 0.2.In order to understand the changes in the structure and composition of upgraded tar,coal tar was analyzed by simulated distillation,nuclear magnetic resonance?NMR?,and gas chromatography/mass spectrometry?GC/MS?.The results showed that in the integrated process with Ni/AC the yield of light oil and phenol in tar is 2.5 and 1.9 times that with non-upgrading,respectively;Ni/AC significantly increased the content of light components such as C1-C3 alkyl-substituted benzene,phenols,C2-C3 alkyl-substituted naphthalene and uncondensed aromatics.These proved that Ni/AC can significantly improve the coal tar quality.Catalysts were characterized by Raman spectroscopy,N₂ adsorption and desorption,XRD,SEM,etc.It was found that Ni/AC has the characteristics of large specific surface area and high degree of structural disorder.Meanwhile,catalyst activity was stable after repeated use.The mechanism of in-situ upgrading of coal pyrolysis tar during the coupling process was studied by quantitative experiments in different atmospheres and isotope tracing experiments.Compared with upgrading process in N₂ atmosphere,tar and light tar yield in C₂H₆/H₂O atmosphere increased by 38.1%and 43.1%,respectively.The results of ¹H NMR and ¹³C NMR showed that the content of protons of CH,CH₂ or CH₃ in the?position to the aromatic ring?H_??and the content of methyl carbon in fatty carbon?CH₃?in tar increased;the results of GC/MS showed that selectivity of C1-C3 alkyl-substituted benzene,C1-C2 alkyl-substituted phenol,and ethyl-containing benzenes and phenols in tar have been improved,all indicating that after the alkyl long side chain on the aromatic ring is broken,these fragment combined with active free radicals generated by the activation of C₂H₆ and H₂O.The results of isotope tracer and MS of typical tar components showed that D₂O and C₂D₆ are in the form of?D,?CD_x,?C₂D_x and other free radicals combined with tar cracking fragments during integrated process of catalytic cracking of tar coupled with steam reforming of ethane,which increases light tar yield,and mechanism of tar upgrading process was speculated.