International Journal of Hydrogen Energy, Vol.39, No.36, 20992-21006, 2014
Hydrogen production by autothermal reforming of methane over NiPd catalysts: Effect of support composition and preparation mode
NiPd/Ce0.3Zr0.3O2/Al2O3 and NiPd/La2O3/Ce0.5Zr0.5O2/Al2O3 catalysts were prepared by incipient wetness co-impregnation method or sequential impregnation method for auto-thermal reforming of methane (ATR of CH4). The influence of the preparation mode, Ce0.5Zr0.5O2 and La2O3 additives on the physicochemical properties of NiPd supported catalysts and the effect on their activity to produce hydrogen by ATR of CH4 were investigated. Characterization of fresh and spent Ni-based catalysts by X-ray fluorescence spectroscopy, N-2 adsorption, X-ray diffraction, H-2 temperature-programmed reduction, high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy were performed. It was demonstrated that support composition determines NiO dispersion as well as reducibility of Ni species through different strength of Ni-support interaction. The preparation method modifies the phase composition and catalyst ability for reduction. The catalyst evolution under reaction conditions was studied. The NiO (similar to 15 nm) and NiPd alloy (similar to 18 nm) phases were observed in the spent catalysts. It was found that the Nr degrees/NiO ratio can be regulated by support composition and preparation mode of catalysts. It is demonstrated that studied catalysts provide high methane conversion of 90-100%, CO yield of 55-85% and H-2 yield of 55-75% in ATR of CH4 at 750-950 degrees C. The optimal composition and preparation method of catalyst were selected. The best ATR of CH4 performance is provided by 10 Ni0.5Pd/10Ce(0.3)Zr(0.5)O(2)/Al2O3 catalyst prepared by Pd/Ni sequential impregnation method that can be associated with peculiarity of NiPd particles structure and the optimal ratio between NiO species with different ability for reduction. Copyright (c) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.