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Well-defined Au, Rh and AuRh nanoparticles were synthesized by colloidal chemical co-reduction, immobilized on rutile titania nanorods, and evaluated in the gas-phase hydrodeoxygenation (HDO) of guaiacol, an important product of lignin pyrolysis. Au/TiO 2 appears active, stable and selective for the HDO of guaiacol to phenol in broad temperature and conversion ranges, making this model catalyst the first reported example of gold efficiency for the hydroprocessing of a lignin derivative. Furthermore, upon nanoalloying Au with Rh, the main HDO product at 280 °C switches from phenol to cyclohexane, which is tentatively ascribed to a cooperative effect. [ABSTRACT FROM AUTHOR]

Abstract: Bio-oils coming from ligno-cellulosic biomass are suitable material for the production of second generation biofuels. The oxygenated compounds have to be eliminated to confer good properties to these bio-oils and to permit their addition to traditional fuels. Hydrodeoxygenation (HDO) process which allows O-elimination by C–O bond cleavage under H2 can be realized with the same type of catalysts as those used in HDS, supported CoMoS or NiMoS phases. In this work, the support effect associated with CoMoS catalysts has been investigated in guaiacol HDO reaction. Zirconia and titania supports have been compared with the traditional industrially used γ-alumina and it appeared that zirconia as support gave very efficient conversion of guaiacol into deoxygenated hydrocarbons with a totally different selectivity. The difference in selectivity allowed us to propose a different reaction scheme compared to γ-alumina and titania supported CoMoS. [ABSTRACT FROM AUTHOR]

Abstract: Unsupported and alumina-supported MoS2 and CoMoS catalysts have been compared in the hydrodeoxygenation (HDO) reaction of guaiacol (2-methoxyphenol), a typical model molecule for bio-oils coming from the pyrolysis of ligno-cellulosic biomass. The goal of this work was to understand the cobalt promoting effect on MoS2 phase in this type of catalytic reaction. It appeared clearly that in the presence of the CoMoS phase, the direct deoxygenation (DDO) pathway involved in guaiacol conversion was strongly increased as compared to the non-promoted MoS2 in the bulk or supported state. This effect is similar to the well-known increase of direct desulfurization (DDS) pathway by cobalt promoter in the hydrodesulfurization (HDS) of refractory sulfur compounds over molybdenum sulfide catalysts. [ABSTRACT FROM AUTHOR]

The effect of the nature of Pd salt (PdCl 2 , Pd(NO 3 ) 2 or Pd(acac) 2 ) in lowering Ni 2 P/C synthesis temperature and their effect on guaiacol hydrodeoxygenation reaction were investigated. Pd addition led to a partial lowering of Ni x P y O z /C (precursor) reduction temperature. For each Pd salt, both the decrease in synthesis temperature and the degree of reduction of Ni x P y O z were different. While the latter was related to Pd particle size (the bigger the particles were, the higher was the amount of Ni x P y O z reduced), the former depends both on the contact between Pd and Ni x P y O z (direct contact is needed) and on Pd particle size (the smaller the particles, the higher the decrease in synthesis temperature). Reaction data revealed that Pd addition suppressed guaiacol hydrogenation. Catalysts characterization revealed that the product distribution was dependent upon the relative proportion on the two types of Ni active sites of Ni 2 P. [ABSTRACT FROM AUTHOR]

[Display omitted] • Phase formation of Cu 3 P during the reduction process was studied by in situ XRD and in situ XAS. • Deoxygenation of guaiacol using Cu 3 P supported on SiO 2 was demonstrated for the first time. • Guaiacol adsorption on the Cu 3 P surface was proposed by a combined DFT and experimental approach. In situ characterization has become indispensable technique in the heterogeneous catalyst development because it provides insights into the composition and fundamental nature of materials in a dynamic process. In this work, in situ analysis including X-ray absorption spectroscopy (XAS) and X-ray diffraction (XRD) could disclose phase transition via several intermediates during the reduction of copper phosphate precursor (CuHPO 4 ·H 2 O) to copper phosphide on high surface silica support (Cu 3 P/SiO 2). The synthesized Cu 3 P/SiO 2 was further used as a catalyst for hydrodeoxygenation (HDO) reaction of guaiacol, a well-known representative model compound in lignin-derivatives upgrading. Many major products, such as cyclic hydrocarbons, demethylated, deoxygenated, and methylated compounds, were detected in the reaction mixture. The highest selectivity of catechol (72 mol%) was obtained at reaction condition of 300 °C and 50 bar H 2 after 150 min. The density-functional theory (DFT) calculations revealed the local electronic charge nature and the different roles of Cu and P active sites towards the interaction between reactants/intermediates and the Cu 3 P surfaces. The findings of the phase transition during the Cu 3 P synthesis and its catalytic activity to the guaiacol HDO reaction, the first to be reported, is beneficial for improving the efficiency metal phosphide-based catalyst for lignin-derived bio-oil into biofuels in the future. [ABSTRACT FROM AUTHOR]

• New semi-continuous set-up designed for lignin catalytic hydroconversion. • Catalytic reactions performed at various residence times for kinetic measurement. • Gaseous products evolution dynamically followed during the conversion. • Liquid and solid fractions separated and fully characterized (GPC, GCxGC, NMR). • Reaction scheme is given and discussed as a base for further modelling study. The valorization of lignin coming from pulp industry or bio-ethanol refineries into renewable chemicals is one of the great challenges of the biorefinery concept. Among the several processes proposed to depolymerize lignin, catalytic hydroconversion appeared efficient to get high liquid yield and can provide targeted aromatic monomers. A new semi-continuous set-up consisting in a batch reactor opened on the gas-phase was implemented to carry out the catalytic lignin liquefaction into phenolic and deoxygenated aromatic compounds with continuous H 2 feeding. The interest of this equipment is the continuous removing of light products and water from the reacting mixture whereas the hydrogen donor solvent is reintroduced in the reactor via a reflux/condensing system. A Co-promoted Mo sulfide catalyst was used and thanks to efficient separation and extensive analysis, the components of the different gaseous, liquid and solid fractions obtained were identified and quantified. The evolution of the various fractions in function of the time and the deep investigation of the composition, allowed to propose a reaction scheme for the lignin depolymerization in those operating conditions. [ABSTRACT FROM AUTHOR]