Methane Pyrolysis Using a Multiphase Molten Metal Reactor

Methane pyrolysis is a unique approach toward generating hydrogen and valuable carbon products, with the added advantage of low to near-zero CO₂ emissions. Currently, the most popular method for hydrogen production is steam methane reforming, which generates more than 10 kg of CO₂ for every 1 kg of hydrogen. By comparison, methane pyrolysis produces hydrogen and solid carbon with no CO_x biproduct. Methane pyrolysis on a conventional solid catalyst exhibits low activation energy, but the carbon coproduct cannot be separated and rapidly poisons the surface (coking). On the other hand, molten liquid metal catalysts have been shown to have the advantage of separatable carbon, but their high activation energy limits the rate of the reaction and potential for economic industrialization. In this work, methane pyrolysis was shown using a multiphase molten metal reactor where both liquid and solid metal alloy catalysts were in equilibrium. Catalytic measurements using a Sn-Ni melt showed that operating the reactor in the two-phase region of the Sn-Ni phase diagram decreased the apparent activation energy from 355 kJ/mol in the liquid-only melt to 158 kJ/mol, all while maintaining the ability to separate and recover graphitic carbon.