Preparation and characterization of nickel/rhodium/aluminum oxide catalyst and catalytic methane-steam reforming

Methane has been identified as highly suitable fuel for the production of hydrogen for fuel cells by the process of catalytic steam reforming. The steam reforming reaction of hydrocarbons is usually a strongly endothermic reaction and involves a combination of steam reforming and the water gas shift reaction. The steam reforming usually occurs at higher temperature between 650°C and 875°C. Presently much work is being carried out on improving the kinetics of these reformers by utilizing various new catalyst blends. Lowering of the operating temperature is also desirable.; The intention of this work was to propose and to develop a series of high performance NiAl-layered double hydroxide (LDH) catalysts containing Rh cations prepared by coprecipitation and impregnation methods. All together, twenty catalysts were prepared for this work.; All catalysts were characterized by Brunauer, Emmett, and Teller (BET) surface area measurements, pore volume, X-ray diffraction analysis (XRD), Thermogravimetric Analysis (TGA)IDifferential Scanning Calorimetry (DSC) and Energy Dispersive X-ray Spectroscopy (EDS). BET surface area analysis showed that the specific surface area and the pore volume for all catalysts increased with calcination temperatures up to 400°C. The XRD patterns for all samples were typical of a hydrotalcite-like material and the formation of nickel aluminate is a sign of strong metal-support interaction in the catalyst. The TGA profiles showed that the majority of the weight loss occurs below 400°C. The DSC profile showed the weight loss was attributed to physisorbed water, indicating the removal of the inter layer water molecule. Finally the EDS showed that neither nitrogen nor carbon was found in any of the samples.; From the twenty catalysts prepared, four catalysts and a commercial catalyst were evaluated for their performance in the steam reforming of methane. This evaluation was performed at the reaction temperature of 500°C and a ratio of the mass of catalyst to molar flow rate of methane (W/Fmethane) of 3314 kg-cat-s/kmoles. One of these four catalysts was chosen to collect kinetic data at reaction temperatures of 500°C, 525°C, 550°C and 575°C, and ratios of mass of catalyst to molar flow rate of methane (W/Fmethane) of 2367, 2761, 3314, 4142 and 5524 kg -cat-s/kmoles.; The influence of pH on the precursors formed during the precipitation procedure, calcination temperature and preparation methods were studied. Methane conversion, Hydrogen (H2) selectivity and Hydrogen (H2) yield were used to evaluate the catalysts performance and to compare the catalysts performance with the commercial catalyst. The Rh Ni(II)-Al(III) LDH based catalysts prepared for this work gave both better performance and catalyst stability than the commercial catalyst.; Finally a kinetic model for methane reforming process was developed. The power rate low model was used to fit the experimental data. The values of the kinetic parameters of the rate models were estimated by using non-linear regression procedure which minimized the sum of squared residuals of the measured (experimental) flow rates of carbon monoxide (CO) and carbon dioxide (CO 2) less the predicted values of them.