Carbon formation on and deactivation of nickel-based/zirconia anodes in solid oxide fuel cells running on methane

Novel Ni-W-Mg mixed oxide catalysts (NiWMgOx) were prepared by homogeneous precipitation and attempted for the methanation of CO2 Adding W remarkably promoted the activity with improved stability, anti-CO-poisoning ability and resistance against coke formation compared to the undoped NiMgOx catalyst The superior reactivity of monodentate formate towards hydrogenation than that of bidentate formate species was identified by DRIFTS analysis and the formation of more active monodentate formate species was indisputably facilitated by W additives, leading to the greatly enhanced catalytic activity H-2-TPR and CO2-TPD characterization showed that doping W increased the number of stable CO2 adsorption sites and helped in anchoring the Ni sites as a result of strengthened Ni-Mg interaction, both of which were responsible for the enhanced CO2 methanation activity and the improved resistance against sintering (C) 2016 Elsevier BV All rights reserved

A novel W-doped Ni-Mg mixed oxide catalyst for CO2 methanation

The oxidative chemistry of methane over supported nickel catalysts

The Effect of Support Interaction on the Sulfidability of Al2O3- and TiO2-Supported CoW and NiW Hydrodesulfurization Catalysts

Two series of phosphorus containing NiW/Al2O3 catalysts were prepared by different preparation methods and varying phosphorus content from 0 to 7.6 wt.% P2O5. The influence of the phosphorus concentration and the preparation procedure on the structure and the dispersion of the compounds formed in the oxide form of the catalysts was studied. Diffuse reflectance spectroscopy (DRS), infrared spectroscopy (IR) and X-ray photoelectron spectroscopy (XPS) were used for the characterization of the catalysts. It was demonstrated that introduction of phosphorus in NiW/Al2O3 catalysts impedes the formation of NiAl2O4 and increases the amount of Ni2+(Oh) ions in the oxide form of the samples. This effect of phosphorus is better expressed when phosphorus is first introduced to alumina, followed by co-impregnation with nickel and tungsten. Surface AlPO4 is formed in the phosphorus containing samples irrespective of the preparation procedure. Phosphorus is distributed as a monolayer up to concentrations of 1.3 P at/nm2 in both series of catalysts. It was also found that the increased phosphorus content in the samples leads to an increased degree of polymerization of the tungsten species via WOW bonds. The presence of phosphorus changes the dispersion of the active components. Evaluation of the average particle size of tungsten species shows that it increases from 10Afor the phosphorus free sample up to 20–25Afor the samples with high phosphorus content. The relationship between the structure of the phosphorus promoted NiW/Al2O3 catalysts and their hydrodesulfurization activity is discussed.

Effect of phosphorus concentration and method of preparation on the structure of the oxide form of phosphorus-nickel-tungsten/alumina hydrotreating catalysts

A series of Ni/WO3–Al2O3 catalysts have been prepared by systematically varying the weight loading of WO3–Al2O3 and the pH during adsorption/impregnation. The catalysts developed an increased interaction between the impregnated nickel and the supported metal oxide; the charge on the mixed oxide resulted in the impregnated nickel cation to be preferentially adsorbed onto tungsten sites of the composite supports. The amount of nickel associated with tungsten oxide was found to be a function of both the tungsten oxide weight loading and the impregnation pH. An increase in the negative charge due to hydrolysis of the tungsten oxide phase in the aqueous impregnant is proposed to result in a tungsten oxide associated nickel that is twice as large for the catalysts prepared at pH 6 than that at pH 4. The Ni/support interaction formed during adsorption/impregnation and drying were studied by temperature-programmed reduction (TPR) and temperature-programmed oxidation (TPO). The tungsten oxide and associated nickel were found to form a nickel tungstate compound which reacted with H2 at ca. 1050 K but could be regenerated by TPO. An Ni/Al2O4 type surface compound was also formed that was reduced at ca. 1150 K.

Cr. Contescu

Papers

Temperature-programmed reduction and oxidation of nickel supported on WO3–Al2O3 composite oxides