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

Abstract

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 CuMo1) 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 H2/CO ratio of 0.9 over the CoMo1 catalyst while the CuMo1 catalyst translated 76% CH4 and 62% CO2 into syngas with a H2/CO ratio of 0.8. In the presence of H2O (steam), the H2/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 (H2/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 Cu0 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.

Microwave-Assisted Synthesis of Cu@IrO2 Core-Shell Nanowires for Low-Temperature Methane Conversion

“…16 As a second example, with a Mo-M/TiO 2 (with M = Cu and Co) structure used in the context of a microwave-assisted, methane bi-reforming reaction, the presence of Cu 0 appeared to not only promote microwave absorption but also increase catalytic activity. 17 Therefore, the use of Cu as the core of the catalyst is desirable, because of its proven capability to yield higher selectivity and activity. However, studies of Cu-containing core@shell catalysts, especially in the context of methane conversion, are fairly limited.…”

“…The addition of Cu in the catalyst was also perceived to have improved upon the catalytic activity and selectivity . As a second example, with a Mo-M/TiO 2 (with M = Cu and Co) structure used in the context of a microwave-assisted, methane bi-reforming reaction, the presence of Cu 0 appeared to not only promote microwave absorption but also increase catalytic activity . Therefore, the use of Cu as the core of the catalyst is desirable, because of its proven capability to yield higher selectivity and activity.…”

Coke-Resistant Ni–Co/ZrO2–CaO-Based Microwave Catalyst for Highly Effective Dry Reforming of Methane by Microwave Catalysis

“…For the DRM reaction, (CH 4 + CO 2 → 2CO + 2H 2 ΔH = 247 kJ/mol), , the molecular structure of methane and carbon dioxide is extremely steady and has high dissociation energies (respectively 435 (CH 3 -H) and 532 (CO-O) kJ/mol), which are difficult to activate. Moreover, DRM reaction is a strongly endothermic reaction, which needs high reaction temperature and consumes a lot of energy. , Although there are a lot of researches on the DRM reaction, there are still problems such as high reaction temperature and energy consumption and catalyst deactivation due to coke formation. − Therefore, it is extremely desirable to exploit a novel method to reduce the energy consumption and temperature required for the DRM reaction and to exploit an outstanding catalyst with high activity and stability.…”

“…For the DRM reaction, (CH 4 + CO 2 → 2CO + 2H 2 ΔH = 247 kJ/mol), 15,16 the molecular structure of methane and carbon dioxide is extremely steady and has high dissociation energies (respectively 435 (CH 3 -H) and 532 (CO-O) kJ/mol), which are difficult to activate. Moreover, DRM reaction is a strongly endothermic reaction, which needs high reaction temperature and consumes a lot of energy.…”

One-Step Synthesis of Nanostructured Cu–Mn/TiO2 via Flame Spray Pyrolysis: Application to Catalytic Combustion of CO and CH4

“…Titanium dioxide TiO 2 has been a particularly promising material in various catalytic fields, especially as a catalyst carrier, due to high surface area, outstanding chemical stability, and excellent oxygen storage capacity. − Moreover, the effect of the strong bimetallic heterogeneous catalysts and TiO 2 support interaction is responsible for the high dispersion and remarkable stability of the bimetal supported TiO 2 catalysts . Min et al prepared an ordered mesoporous Cu–Mn/TiO 2 heterogeneous catalyst via a wet-impregnation manner and proposed that the mesoporous anatase serves as a stable substrate with a high surface area for Cu–Mn species and a promoter for the synergistic elimination of organic pollutants.…”