(477a) Microwave Catalytic Decomposition of Natural Gas to Clean Hydrogen and Carbon Nanomaterials Via Modular Process Intensified Production

Microwave-driven catalytic decomposition of natural gas has a great potential to be adopted for the hydrogen production industry. The process took advantage of the convenience of microwave heating, which provided lower catalyst bulk temperature, instant start and stop on reactions, as well as faster heating and cooling. The process generated only hydrogen as a gas product, and solid carbon as by-product. The gas separation became much easier because all it took was to separate the hydrogen from the unreacted methane. Regarding solid products, carbon nanotubes were the new pursuit for the targeted product. It was of high value, which has huge potential to be used in both carbon fiber production as well as carbon-based semiconductors. The United States Department of Energy (DOE) has set up a goal of reducing the hydrogen selling price to $1/kg in a decade. This team started a DOE funded project to work toward this goal from 2020. As of today, the team has developed two series of catalysts for the microwave-driven catalytic decomposition of natural gas. One series of catalysts was to use carbon nanotube as support, Ni as active catalytic site, and Fe, Cu, or Pd as a promoter. The conversion of methane under this series of catalysts ranged from 30% to 55%. These catalysts were excellent microwave absorbers. The promoters helped extend the activity of Ni catalyst to 6~10 h when compared to Ni only catalyst lasting about 1 h. The other series of catalysts was SrTiO supported Ni. The conversion of methane using this catalyst is comparable to the previous catalyst. However, the microwave attenuation of these catalysts still needs to be improved because the reduction process of these catalyst played a significant role in microwave absorption ability. Lastly, MgO was introduced to this SrTiO to help disperse the Ni nanoparticles, which has improved the performance of the Ni-SrTiO system. The improved SrTiO catalyst achieved methane conversion ranging from 20% to 50%. An alternative route for improving the performance of Ni-SrTiO was under development by another team member. La and Ca were used to replace Sr, resulting in a LaCaNiTiO catalyst, which has achieved a methane conversion of around 15%. Carbon nanotubes/nanofibers of 10-80 nm diameter were produced as solid carbon. Our team members from Pacific Northwest National lab have optimized the catalyst loading as well as conducted high resolution transmission electronic microscope for imaging the carbon products. In addition, they have simulated the hydrogen selling price as around $2/kg using our technology, which could be as low as $1/kg if base-growth of carbon nanotubes could be developed. We have our commercial partner working on the pilot testing of the commercial Ni based catalyst for scaling up the process. The effluent gas from microwave plasma conversion of methane was used as feedstock. The effluent underwent catalytic decomposition to generate hydrogen and carbon nanotube at a larger scale. Currently, a pilot reactor of 36 kW has been installed. The testing is in process. The eventual goal of this project is to achieve microwave only driven reaction for catalytic conversion of methane to hydrogen, remove the carbon emissions, and significantly reduce the cost of clean hydrogen production.