In-situ catalytic cracking of coal pyrolysis tar coupled with steam reforming of ethane over carbon based catalyst

In-situ catalytic cracking of coal tar coupling with steam reforming of ethane (SRE) over activated carbon supported nickel (Ni/AC) was conducted to improve light tar yield. The results show that the content and yield of light tar (the fraction having boiling point below 360 °C) under ethane/steam reforming atmosphere increase by 58.7% and 62.2% with Ni/AC, respectively, and phenol oil raised by 112.5% compared with the non-upgrading tar. Compared with the upgrading process under N2, the benzenes and phenols in the tar gained from upgrading process under ethane/steam mixed atmosphere increases by 99.3% and 21.5%, specially, C3 alkyl substituted benzene and cresol increases from 2.2% and 9.2% to 5.1% and 15.0%. Meanwhile, when using deuterated ethane (C2D6) and deuterated water (D2O) as tracers, tar component with deuterium atom can be detected by GC/MS and 2H NMR. These reveal that Ni/AC can simultaneously catalyze coal tar cracking and SRE, thus the small radicals such as CHx, C2Hx and H generated from SRE can combine with the radicals from tar cracking to avoid excessive cleavage of tar. Coupled with the MS analysis of typical substances, the reaction mechanism of upgrading process was inferred. •In-situ catalytic cracking of coal tar with SRE over Ni/AC improves light tar yield.•Light oil content in tar obtained under SRE reaches 2 times that under non-upgrading.•Benzenes and phenols in upgrading tar from ethane/steam are higher than that from N2.•Isotopic trace reveals that Ni/AC can simultaneously catalyze tar cracking and SRE.•Radicals from SRE combined with tar cracking radicals avoid tar excessive cleavage.