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

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 degrees 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.