Upgrading of coal pyrolysis tar by catalytic cracking coupled with steam reforming of ethane

The purpose of this paper is to improve the light tar yield by coupling in-situ catalytic cracking of coal tar with steam reforming of ethane (SRE) over carbon-based catalysts. The tar upgrading experiments using Pingshuo coal (PS) as coal sample were performed in an atmospheric pressure fixed bed reactor under nitrogen and a mixed atmos- phere of ethane and steam. Semi-coke (char),activated carbon (AC),AC supported cobalt and nickel (Co / AC,Ni /AC) were used as upgrading catalysts to comparatively examine the effects of catalyst types and reaction atmosphere on tar and gas products. Meanwhile,the tar was analyzed by means of characterization methods such as simulated distil- lation and GC-MS in order to understand the composition and properties of the tar product obtained in the upgrading process. The results show that Ni / AC can simultaneously catalyze the coal tar cracking and SRE,thus the small radi- cals such as ·CHx ,·C2 Hx and ·H produced from SRE can combined with the radicals from tar cracking to avoid an excessive cleavage of tar. Compared with the non-upgrading tar,the content and yield of light tar (the fraction hav- ing boiling point below 360 ℃ ) increase by 54. 3% and 52. 4% with Ni / AC,respectively. Besides,the yield of aro- matic components such as BTEXN (benzene,toluene,ethylbenzene,xylene and naphthalene) in tar is significantly im- proved. When Ni / AC is used,the tar yield and light tar yield increase by 38. 1% and 35. 3% ,respectively,in the mixed atmosphere of ethane and steam (coupling process) compared with those in nitrogen. Also,the contents of C2-C3 alkyl substituted benzene and C1-C2 alkyl substituted phenol in the tar are improved. It explains the activated eth- ane and steam participate in the tar formation process. The overall effect of in-situ catalytic cracking of coal pyrolysis tar is to convert heavy components in the tar into light tar and pyrolysis gas. The upgrading effect is closely related to the active components of the catalyst,and the reaction atmosphere plays an important role in the formation of coal tar.