Frédéric Richard

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 °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.

Hydrodeoxygenation of Cresols Over Mo/Al2O3 and CoMo/Al2O3 Sulfided Catalysts

The hydrodeoxygenation (HDO) of cresol isomers was investigated at 340xa0°C under 4xa0MPa over Mo/Al2O3 and CoMo/Al2O3 sulfided catalysts. Over both catalysts, the reactivity of cresols followed the order: m-cresolxa0>xa0p-cresolxa0>xa0o-cresol. These phenolic compounds were converted by two deoxygenation routes. The desired direct deoxygenation (DDO) route, leading to toluene, was strongly promoted by cobalt. On the contrary, the HYDrogenation route (yielding methylcyclohexenes and methylcyclohexane) was favored over Mo/Al2O3 and practically not affected by the presence of cobalt. To explain the formation of these deoxygenated products, the participation of different kinds of active sites such metal-decorated edge and brim-model was suggested. Thus, we proposed a reaction mechanism involving a schematic CoMoS active site which allowed to explain (i) the highest reactivity of m-cresol by the involvement of a stabilized cationic intermediate and (ii) the lowest reactivity of o-cresol, ascribed to a steric hindrance of methyl group during the initial tautomerization step.Graphical Abstractxa0

Zeolite-catalyzed acylation of heterocyclic compounds — VI. One-step synthesis of 3-(benzofuran-2-carbonyl)pentane-2,4-dione from 2-acetylbenzofuran over HY-zeolite

Abstract The reaction between 2-acetylbenzofuran and acetic anhydride at 60°C in the presence of HY-zeolite ( Si Al = 16 ) led to a single final product: 3-(benzofuran-2-carbonyl)pentane-2,4-dione resulting from two consecutive acylation steps on the side chain. It was obtained in a 90% purity at around 50% conversion of 2-acetylbenzofuran. Other minor products and intermediates were also identified. A mechanism is proposed to account for the formation of the various products.

Hierarchization of Mordenite as NiW Sulfide Catalysts Support: Towards Efficient Hydrodesulfurization

NiW‐based catalysts were supported on Al2O3, commercial mordenite (HM), and hierarchical mordenite prepared by acid–base–acid treatment (HM–M). Their catalytic performance was evaluated in the hydrodesulfurization (HDS) of dibenzothiophene (DBT) and 4,6‐dimethyldibenzothiophene (4,6‐DMDBT) at 613u2005K under 4u2005MPa as total pressure. In the HDS of DBT, NiW/Al2O3 exhibited better catalytic activity than NiW/HM and NiW/HM–M. On the contrary, NiW/HM–M exhibited the highest catalytic performance in the HDS of 4,6‐DMDBT, attributed to different factors: an improved dispersion of the active phase, a better accessibility to the active sites owing to the creation of mesoporosity, and an additional reaction route (isomerization) owing to the acidic properties of the zeolitic support. These results show the potential interest of hierarchical mordenite as support for HDS catalysts, with the presence of mesoporosity beneficial to the HDS of large and refractory molecules.

Transformation of ketones over sulfided CoMo/Al2O3 catalyst — factors affecting thiol selectivity

Abstract The competitive transformation of cyclopentanone and of two thiols (cyclopentanethiol and cyclohexanethiol) was carried out on a sulfided CoMo/Al2O3 catalyst at 220°C under atmospheric pressure in the presence of H2/H2S (90/10xa0vol.%). The results made it possible to explain the good selectivity in cyclopentanethiol obtained in the thioreduction of cyclopentanone. This is the consequence of the inhibition due to a competition to adsorption, of the thiol desulfurization into the corresponding olefin. The kinetic order with respect to cyclopentanone of the transformation of cyclohexanethiol into cyclohexene was found equal to −0.6.