In situ synthesis of molybdenum oxide@N-doped carbon from biomass for selective vapor phase hydrodeoxygenation of lignin-derived phenols under H2 atmosphere

Abstract

The vapor phase hydrodeoxygenation (HDO) of lignin-derived phenols under H₂ atmosphere has great significance for producing high-quality fuels and commodity chemicals. Herein, we reported a simple, green method to prepare molybdenum oxide@N-doped carbon (MoO_x@NC) via in situ pyrolysis of molybdenum precursor preloaded cellulose and demonstrated its catalytic performance for vapor phase HDO of lignin-derived phenols. When the pyrolysis temperature was at 600 °C, the catalyst (MoO_x@NC-600) exhibited the best catalytic performance in vapor phase HDO of guaiacol. Through systematically investigating the parameters, such as: reaction temperature, WHSV, residence time, and concentration, the optimal reaction conditions for vapor phase HDO of guaiacol were 450 °C and 1 h⁻¹ with atmospheric H₂. The concentration of the feed was 20% in mesitylene, and the residence time was about 3.3 s. The carbon yield of aromatic hydrocarbons was 83.3%, with 65.7% benzene, 15.5% toluene and 2.1% alkylbenzenes. In addition, other lignin-derived phenols were also investigated and desired results were achieved with the MoO_x@NC-600 catalyst. Furthermore, MoO_x@NC-600 showed good stability due to the N-doped carbon formed on the surface of the MoO_x particles. The catalysts were characterized using elemental analysis, AAS, BET, XRD, XPS, TEM, and EDS mapping. The high catalytic performance of MoO_x@NC-600 toward lignin-derived phenols HDO can be attributed to the synergistic effect of the carbon supports and Mo⁵⁺ (molybdenum oxynitrides), Mo^δ+ (Mo₂N) and Mo⁴⁺ on the surface of the MoO_x particles.