Research on electro-catalytic steam reforming of methane with modified Ni/γ-Al₂O₃ catalysts

A novel electro-catalytic technique for catalytic methane steam reforming was developed. Based on the conventional industrial Ni-based catalyst, aseries of catalysts, including Ni/γ-Al₂O₃, Ni-MgO/γ-Al₂O₃ and Ni-CaO/γ-Al₂O₃, were prepared using incipient wetness impregnation method with Ni as the active component, γ-Al₂O₃ as the carrier, and MgO or CaO as the promoter. Experiments were performed to investigate the effects of electric current intensity, reforming temperature, and molar ratio of water vapor to methane (water/carbon ratio, S/C) on CH₄ conversion, H₂ yield, CO selectivity and catalyst stability. The results indicated that the electro-catalytic technique had good adaptability, and the introduction of electric current could improve the CH₄ conversion and increase the H₂ yield. Such effects were more intensive at lower reforming temperatures. Among the three catalysts, Ni-CaO/γ-Al₂O₃ catalyst exhibited the best catalytic efficiency, with the CH₄ conversion over 95% under conditions of 4.5 A, S/C of 3, and 700℃. Stability tests of the catalysts showed that the electric current could improve the stability of catalysts and delay the deactivation caused by coke deposition. The characterization results proved that the presence of electric current enhanced the reduction degree of NiO in the catalyst and inhibited NiC_x conversion to graphite carbon, resulting the delay of catalyst deactivation caused by carbon deposition over reactive sites.