The catalytic reforming of tar from pyrolysis and gasification of brown coal: Effects of parental carbon materials on the performance of char catalysts

The carbon structure of char as catalysts is very crucial as it greatly governs the catalytic activity of char for tar reforming reactions. More importantly, the char structure also plays an important role in affecting the interactions between the inherent metal species and carbon atoms, thus affecting the catalytic performances. This study aims to investigate the effects of char structure on the reforming of tar derived from the gasification and pyrolysis of Shengli brown coal. Chars prepared from five kinds of acid-washed carbonaceous materials, including biomass, brown coal, bituminous coal, anthracite and graphite, were used as tar reforming catalysts in this work. The different effectiveness of H-form char catalysts from the different ranking carbon materials have clearly shed light on the effects of char structure on tar reforming. Results show that the chars from biomass and low rank coals featured obviously higher catalytic activity than those from high rank fuels. The variation in char structure that was revealed by FT-Raman has greatly exerted impacts on tar yields as well as tar compositions. Interestingly, the supply of steam (in the gasification condition) did not always see the reduction in tar yields, very much depending on the type of char catalysts used in the experiments. •Char catalysts for tar reforming were prepared from five different carbon materials.•The large aromatic ring systems in tar were preferentially reformed.•The steam played little role in tar reduction when char catalysts were from low rank fuels.•The amorphous char structure with O-containing complexes was favorable for tar reforming.