Steam reforming of typical small organics derived from bio-oil: Correlation of their reaction behaviors with molecular structures

[Display omitted] •Molecular structures of organics significantly affected coking in steam reforming.•Coking in reforming of furfural and guaiacol relate to π-conjugated ring structures.•Coke from furfural/guaiacol was graphite-like and the form of nanotube.•Coke was more amorphous and disordered from reforming of the aliphatic organics.•DRIFTS studies indicated formation of CC and CH functionalities at even 100 °C. This study investigated the steam reforming of a series of organic molecules with varied molecular structures (methanol, formic acid, ethanol, acetic acid, acetaldehyde, acetone, furfural, guaiacol), aiming to understand the impacts of functionalities of these organics on their reaction behaviors. The results showed that molecular structures drastically influenced reactivity and tendencies towards coking during steam reforming. Methanol and formic acid could effectively be reformed and coking was insignificant, as no cracking of CC bonds involved in their conversion. Ethanol, acetic acid, acetaldehyde or acetone was more difficult to be reformed, and coking was significant, especially for acetone or acetaldehyde bearing the carbonyl functionality that could be retained in the precursors of coke. The substantial amount of coke formed in steam reforming of furfural and guaiacol originating from their π-conjugated ring structures and the coke was more graphite-like. In comparison, the coke from reforming of ethanol, acetic acid, acetaldehyde or acetone were more disordered. The in situ DRIFTS studies of steam reforming indicated that the CC and CH functionalities were generated even at 100 °C, which could contribute to coking, when they could not be effectively gasified via steam reforming.