Investigation of coking behaviors of model compounds in bio-oil during steam reforming

Abstract

Sugars and the derivatives of sugars are important fractions in bio-oil, understanding coking behaviors of which are important for development of the robust coking–resistant catalyst for steam reforming of bio-oil. In this study, steam reforming of glucose, xylose, acetic acid and furfuryl alcohol (FA) was carried out, aiming to correlate coking behaviors with molecular structure of these organics. Acetic acid, as a small aliphatic molecule, could be effectively reformed and produced the lowest amount of coke deposit. The carbonyl functionality, the multiple hydroxyl groups in the sugars and the furan ring in FA made polymerisation/cracking to form coke as the dominant reaction route in their steam reforming, diminished hydrogen production while led to rapid catalyst deactivation. The coke formed from acetic acid and FA was more aromatic, containing more CC species, while that from glucose and xylose was more aliphatic, containing more carbonyl functionalities, which projected structural characteristics of the feedstock. In addition, morphologies of the coke formed from acetic acid was mainly carbon nanotube. In comparison, the coke from the sugars and FA was mainly the amorphous coke with cobalt particles wrapped inside, which was more thermally stable, especially for that from FA, relating to the aromatic ring in FA.