Synthesis and characterization of Mo-blue-based sulfided CoMo catalysts for guaiacol HDO

Abstract

Saccharose (SA) and citric acid (CA) were used as additives in P-doped CoMo/Al₂O₃ catalysts (Mo, Co and P at 12, 3, and 1.6 wt%, respectively) intended to be applied in guaiacol hydrodeoxygenation (HDO). One-pot impregnating solutions were prepared by MoO₃ digestion in aqueous H₃PO₄, followed by C₄H₆CoO₄•4H₂O addition. Organics were added (SA/Co=1, CA/Co=2) at two different preparation stages to assess the effect of that step on catalysts properties. Method I: SA or CA was added in as-prepared Co-Mo-P impregnating solution, followed by pore-filling impregnation of alumina support. Method II: SA or CA at aforementioned concentrations was impregnated on the pristine carrier, followed by drying (120 °C, 2 h). Co-Mo-P phases were further deposited on modified supports through corresponding one-pot solutions. All materials were dried (120 °C) but not calcined. Cobalt complexation by CA and Mo-blue LMCT complex formation (SA-modified solids) were identified (UV-vis, oxidic samples). Partially reduced molybdenum (Mo⁶⁺ => Mo⁵⁺, by XPS) was observed after either organics addition that effect being more evident in SA-modified solids. Materials were gas-phase sulphided (H₂S/H₂ 10%, 400 °C, 2 h) then studied by HR-TEM. Co-Mo-P phases impregnation in one-pot solution simultaneously deposited with SA rendered the materials of the highest MoS₂ dispersion.