Effect of Carbon Foam Catalyst on Tar Upgrading During Low Rank Coal Pyrolysis

Carbon foam catalysts (CF1, CF2, CF3) were prepared by spontaneous foaming method using Liulin coal (LL) as raw materials, and the pyrolysis experiments of Xinjiang Naomaohu long-flame coal (NMH) and Inner Mongolia Shengli lignite coal (SL) were performed by Py-GC/MS at 700 ℃. The effects of carbon foam catalysts with different pore structure on the distribution of gaseous tar products were investigated. The results show that compared with normal semicoke catalyst (SC), carbon foam catalysts have more significant advantages in improving the quality of tar from coal pyrolysis. The catalytic performance of carbon foam catalysts is closely related to its pore structure and chemical character. After the action of CF1, the total amount of tar during pyrolysis of NMH and SL is significantly increased (the increase rates are 10.26% and 31.31%, respectively), which is related to its suitable specific surface area (281.14 m2/g), rich micropore structure (microporous area accounts for 88.96% of the total specific surface area), and appropriate reactivity. CF2 and CF3 with rich hierarchical pore structure and higher reactivity make the total amount of NMH and SL tar decrease. In addition, the relative content of light aromatic hydrocarbons in gaseous tar of coal pyrolysis increases and the relative content of compounds containing O, N and S decreases by CF catalysts. These results indicate that these CF catalysts can significantly promote catalytic cracking, deoxidation, aromatization, and other reactions during the pyrolysis of NMH and SL, and can directionally control the distribution of gaseous tar from coal pyrolysis.