Carbon dioxide reforming of methane over 5 wt.% Ni/CaO-Al2O3 catalyst

Methane reforming by carbon dioxide was investigated over 5 wt.% Ni/CaO-Al2O3 catalyst. X-ray diffraction (XRD) and temperature-programmed reduction (TPR) techniques were applied to characterise the catalyst. The catalyst exhibited high activity and very good stability at stoichiometric methane and carbon dioxide feed. The addition of steam in the reacting mixture was tested and proved beneficial for the conversion of methane and the drastic decrease in carbon deposition. The kinetic behaviour of the catalyst was investigated as a function of temperature and methane and carbon dioxide partial pressures. The apparent activation energies of the two reactants CH4 and CO2 were estimated 25.5 +/- 2.0 and 23.6 +/- 1.8 kcal/mol, respectively and that of CO was 24.6 +/- 1.2 kcal/mol while hydrogen activation energy was estimated at 35.2 +/- 3.2 kcal/mol. Partial pressure dependencies of the reaction rates were obtained at 630 degreesC. The increase of H-2 partial pressure resulted in an acceleration of the CO formation, while an increase in CO partial pressure demonstrated the inhibiting role in H-2 formation and the conversion of the reactants. (C) 2002 Elsevier Science B.V All rights reserved.