Effect of H2S and CO on the transformation of 2-ethylphenol as a model compound of bio-crude over sulfidedMo-based catalysts: propositions of promoted active sites for deoxygenation pathways based on an experimental study

Abstract

Promoted (CoMo/Al₂O₃ and NiMo/Al₂O₃) and unpromoted (Mo/Al₂O₃) catalysts were tested in the hydrodeoxygenation of 2-ethylphenol as a model compound of bio-crude under various partial pressures of H₂S and CO. The catalytic tests were carried out at 340 °C under 7 MPa of total pressure in a fixed-bed microreactor. H₂S, needed to maintain the sulfidation level of the catalysts, showed promoting or inhibiting effects depending on the catalyst tested and the deoxygenation pathway considered. Over the three catalysts, H₂S was found to slightly promote the HYD pathway, which first involves the hydrogenation of the aromatic ring, whereas it strongly inhibited the DDO pathway, which consists of a direct C–O bond scission, particularly on the CoMo/Al₂O₃ catalyst. In addition, a strong though reversible inhibition by CO was found over CoMo/Al₂O₃ for both deoxygenation pathways, while a limited effect was observed over NiMo/Al₂O₃. Differences in inhibition induced by H₂S and CO observed over both promoted catalysts suggested that different active sites are involved in the hydrodeoxygenation of 2-ethylphenol, depending on the nature and the localisation of promoters and on the transformation pathway.