Pyrolysis of sawdust coupled with steam reforming for simultaneously production of heavy organics and hydrogen

Abstract

In hydrotreatment of bio-oil, it is difficult to convert the aliphatic compounds with the carbon number less than four into liquid fuel via hydrodeoxygenation. Thus, ideally, the very light organics of bio-oil could be reformed to generate hydrogen for further upgrading the heavier organics in bio-oil to biofuel or fine chemicals. In this study, the pyrolysis of poplar sawdust coupled with the simultaneously steam reforming of the bio-oil (pyro-reforming) were studied over Ni/SBA-15 catalyst at the medium temperature range from 450 to 650 °C for transforming mainly the light aliphatic compounds into H2. The results showed that the effective steam reforming of the aliphatic compounds like carboxylic acid and small aldehydes/ketones took place to remarkable extent from 550 °C, while the furans, anhydrate sugars, light phenols and heavy phenolics of fused ring structures could be largely retained in the resulting bio-oil. Coking reached the maximum with increasing temperature to 500 °C from cracking/polymerization of the volatiles. Further increase of temperature to 650 °C accelerated steam reforming and gasification of precursors of coke, shifting the morphology of coke from amorphous form to unregular carbon nanotube structures (stringed beads-like) and making the coke more aromatic and more resistant to oxidation. Nevertheless, in overall, the coke produced from 450 to 650 °C was aliphatic with low C/H ratio, low thermal stability and low crystallinity, originating from the significant contribution from the aliphatic compounds in the bio-oil for coking.