Microwave-Assisted Dry and Bi-reforming of Methane over M-Mo/TiO2 (M = Co, Cu) Bimetallic Catalysts

Microwave (MW) methodology has opened up new opportunities for chemical reactions by providing novel routes that are not practical by conventional heating. This paper reports on M-Mo bimetallic catalysts (M = Co or Cu) supported on TiO2 for methane reforming, i.e., dry reforming of methane (DRM) and bi-reforming of methane under MW irradiation. Experimental results displayed outstanding activity of such M-Mo/TiO2 catalysts, on which high reaction efficiency of methane reforming can be sustained at a much lower MW power of 100 W compared to literature results of 200 W. The molar ratio of M/Mo at 1.0 (CoMo1 and CuMol) displayed the highest catalytic activity for MW-assisted methane reforming under all tested conditions. For DRM, about 81% CH4 and 86% CO2 were converted to syngas with a H-2/CO ratio of 0.9 over the CoMo1 catalyst while the CuMo1 catalyst translated 76% CH4 and 62% CO2 into syngas with a H-2/CO ratio of 0.8. In the presence of H2O (steam), the H-2/CO ratio higher than 2, i.e., 2.2, could be obtained over the Co-Mo catalyst with an input steam-to-methane (S/C) molar ratio of 0.1, while the CuMo1 counterpart required an S/C of 0.2 introduced into the feed to produce such a syngas ratio (H-2/CO) of 2.1. The reason behind the excellent performance of the Co-Mo/TiO2 catalyst is the good exposure of the well-defined hexagonal MW absorber. Meanwhile, the formation of a high dielectric layer of MoO2 surrounding active Cu-0 can promote the MW absorption of the Cu-Mo/TiO2 catalyst and thereby enhance its catalytic performance. The Co-Mo catalyst exhibited better activity than the Cu-Mo samples given that the magnetic properties of Co particles led to a higher MW absorption ability. Both M-Mo/TiO2 catalysts exhibited brilliant stability under MW irradiation.