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Transition metal phosphide nanoparticles supported on silica were used as catalysts to investigate the hydrodeoxygenation of methyl laurate (used as a model compound for vegetable oils). Ni2P, Ni1Mo1P, and Ni1.6Mo0.4P were synthesized using a molecular precursor route. The nanoparticles were added to the silica support without any changes in their structure or particle size. As a reference and for comparison, MoP/SiO2 was also prepared by the phosphite method. The prepared catalysts were characterized by X‐ray diffraction, X‐ray photoelectron spectroscopy, transmission electron microscopy, and chemical analysis. A higher conversion is reached with the MoP/SiO2 monometallic catalyst, close to that with Ni1Mo1P/SiO2. However, this observation is misleading because the differences in dispersion obscure the result that the intrinsic activity (turnover frequency) of the bimetallic catalyst, prepared by a molecular precursor route, is significantly higher than that of the monometallic catalyst, prepared by the phosphite route, revealing a synergistic effect on the catalytic activity due to the formation of the bimetallic phosphide. [ABSTRACT FROM AUTHOR]

Abstract: The steam reforming of phenol in the low-temperature range of 350–550°C was studied over 0.5wt% Rh supported on Ce0.15Zr0.85O2, Zr0.93La0.07O2, and Ce0.13Zr0.83La0.04O2 mixed metal oxides. The reforming specific activity (per gram of catalyst basis) was found to depend on (a) Rh dispersion, (b) the concentration (μmolg−1) of labile oxygen species of support, as determined by “oxygen storage capacity” measurements, and (c) the promotion of the water–gas shift (WGS) reaction rate, all of which largely influenced by the support chemical composition. The addition of 4atom% La3+ into the Ce0.15Zr0.85O2 crystal structure was found to largely promote the dispersion of Rh, to increase significantly (by a factor of 1.75) the concentration of surface basic sites (μmolm−2) of Ce0.13Zr0.83La0.04O2 compared to Ce0.15Zr0.85O2 support, to prevent to a large extent the inhibiting role of hydrogen in the rate of WGS reaction, and to influence significantly the concentration and structure of surface reaction intermediates of the WGS, namely: formate (HCOO–) and –OH groups formed on the support, and adsorbed CO formed on the Rh metal. The 0.5wt% Rh/Ce0.13Zr0.83La0.04O2 catalyst led to a significantly better performance towards steam reforming of phenol in terms of phenol conversion, H2-yield, and CO/CO2 product ratio in the 350–450°C range compared to a commercial Ni-based catalyst (44wt% Ni) used for steam reforming reactions. At 400°C, the 0.5wt% Rh/Ce0.13Zr0.83La0.04O2 catalyst exhibited approximately 54% and 50%, respectively, higher phenol conversion and hydrogen yield, compared to the Ni-based industrial catalyst. The significantly lower CO/CO2 product ratio obtained in the case of Rh/Ce0.13Zr0.83La0.04O2 compared to that obtained in the other supported-Rh catalysts is in agreement with the higher kinetic rate for the WGS reaction observed in the former catalyst. [Copyright &y& Elsevier]

Abstract: The differences in surface reactivity of LaCoO3 and Ru/LaCoO3 solids after pre-treatment in a hydrogen or oxygen gas atmosphere towards oxidative steam reforming (OSR) of propane was probed by performing temperature-programmed desorption (TPD) of CO and CO2, temperature-programmed surface reaction (TPSR) of C3H8, transient isothermal oxidation of “carbon” formed after TPSR of C3H8, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) studies. The TPD of CO and CO2 studies revealed a greater adsorption of these molecular product species of the OSR of propane on the surface of LaCoO3 than Ru/LaCoO3 solid, while XPS studies performed after reduction in hydrogen revealed a higher concentration of Co2+ in the LaCoO3 than Ru/LaCoO3 solid catalyst composition. The Ru/LaCoO3 solid was found to exhibit after an induction period enhanced reactivity towards H2 production for the OSR of propane reaction compared to LaCoO3 after hydrogen reduction at 750°C. These results led to the conclusion that the introduction of a small amount of Ru (0.8wt%) on lanthanum cobaltite surface leads to a higher concentration of metallic cobalt (Co0) after hydrogen reduction is performed, thus favouring the enhancement of necessary active catalytic sites on the Co, LaCoO3 and La2O3 surfaces formed. TPSR of propane used as model compound of diesel revealed the participation of surface lattice oxygen of both LaCoO3 and Ru/LaCoO3 pre-oxidized solids as well as the formation of hydrogen by reaction of propane on the Co0 (metallic state) surface once the latter is formed. A greater reactivity of propane during TPSR was observed over the Ru/LaCoO3 solid surface for either oxidative or reductive pre-treatments. Also, a lower amount (2.13mmol/g) of “carbon” deposition was found on Ru/LaCoO3 compared to LaCoO3 (3.65mmol/g) at the end of the TPSR of propane experiment. These results provide important fundamental information on the role of Ru in the Ru/LaCoO3 system towards catalytic oxidative steam reforming of propane. [Copyright &y& Elsevier]