Methane pyrolysis into hydrogen and solid carbon: A comparative analysis of conventional and microwave heating approaches

The conversion of methane into hydrogen and carbon represents a promising pathway towards decarbonised energy. When methane is produced from renewable sources, pyrolysis of methane is regarded as a technology with a negative carbon footprint, as the carbon is captured in solid form. The objective of this study was to investigate methane pyrolysis in a fluidized bed, with a focus on comparing the efficiency of two heating methods: microwave and conventional heating. As evidenced by thermodynamic analysis, the methane pyrolysis reaction occurs between 750 °C and 950 °C. At these elevated temperatures, methane conversion is remarkably efficient, accompanied by a high hydrogen yield and the sequestration of carbon into a turbostratic structure. The results of this research demonstrate that microwave heating, in addition to being a more energy-efficient method, achieves superior methane conversion compared to conventional heating. The conversion for microwave and conventional heating were 96% and 85%, respectively. Furthermore, it was demonstrated that the carbon removal from the surface of the catalyst is possible with carbon dioxide flow, which enhances the conversion over the course of an extended period. The optimal temperature for carbon removal was determined to be 850 °C, offering an ideal balance between efficiency and catalyst durability. These findings open new perspectives for optimizing methane pyrolysis processes at an industrial scale. It is stated that the direct catalytic methane pyrolysis in a microwave-heated fluidised bed can produce CO 2 -free hydrogen and solid carbon with no need for costly gas separation units offering an environmentally friendly and economically viable alternative to traditional hydrogen production methods. • Catalyst reached 96% conversion at 950 °C with microwaves, beating thermal heating. • Methane conversion rises with increased catalytic bed volume and contact time. • Methane conversion stayed stable after 6 h at 950 °C using conventional heating.