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 TiO 2 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/TiO 2 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 CuMo1) displayed the highest catalytic activity for MW-assisted methane reforming under all tested conditions. For DRM, about 81% CH 4 and 86% CO 2 were converted to syngas with a H 2 /CO ratio of 0.9 over the CoMo1 catalyst while the CuMo1 catalyst translated 76% CH 4 and 62% CO 2 into syngas with a H 2 /CO ratio of 0.8. In the presence of H 2 O (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/TiO 2 catalyst is the good exposure of the well-defined hexagonal MW absorber. Meanwhile, the formation of a high dielectric layer of MoO 2 surrounding active Cu 0 can promote the MW absorption of the Cu–Mo/TiO 2 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/TiO 2 catalysts exhibited brilliant stability under MW irradiation.