Methane decomposition to hydrogen and carbon nanotubes in arc with molten metal electrodes

A difficult decarbonization challenge is to replace CO2-emitting gas-fired furnaces in industrial chemical processes, especially for high temperature processes. One of the examples of heavily CO2-emitting industries is mining, refining, and production of structural materials, such as iron, steel, cement, and aluminum. One solution is to displace or enhance these materials with carbon materials that can be produced in an economically viable and CO2-free manner, such as through methane plasma pyrolysis. Methane plasma pyrolysis is a technique primarily used to produce turquoise hydrogen and carbon black, the existing industrial example is Monolith Inc. Importantly, methane is the second most abundant anthropogenic greenhouse gas that is 28 times as potent as CO2 at trapping heat in the atmosphere.

However, the process of methane pyrolysis can be further upgraded to co-produce high-value carbon nanomaterials instead of carbon black, e.g., carbon nanotubes (CNTs). CNTs can be spun into fibers that can be used in building or structural materials, and these products have an enormous global market. However, scientific understanding of industrial-scale chemically reactive plasma is still primitive.

The primary goal of this project is to explore the scientific principles underlying CNT synthesis from CH4 and its gas mixtures in an innovative plasma arc with molten metal electrodes. The use of methane as the carbon source instead of a consumable graphite electrode makes this method continuous and scalable for industrial production.

Methane arc experiments are different from the other arcs because the nanomaterial of interest is produced from a gaseous precursor and not from the evaporated electrode. Nevertheless, the evaporating anode material is important as it serves as a source of catalyst nanoparticles required for SWCNTs formation. A photograph of the running arc with a molten metal anode (low carbon steel) and the setup diagram showing its operations and controls are shown below.