Catalytic Alkali and Transition Metal Cations to Produce Low-Emission Hydrogen from Methane Pyrolysis

Methane pyrolysis provides an opportunity to utilize abundant fossil fuel resources to produce high quantities of hydrogen with low CO2 emissions. Using a catalytic molten salt bubble column for this reaction is a promising method to reduce the reactor temperature without deactivating the catalyst, producing a separable solid carbon byproduct. Some transition metal chlorides have been examined in recent literature, but there is information lacking as to what properties of the active metal make good catalysts. We show here that the Lewis acidity of the transition metal cation plays a large role in the overall hydrogen production of the melt, with CrCl2 being the most active. Additionally, low-cost salts such as MgCl2 and CaCl2 are moderately catalytic, and catalysis is improved with increasing concentration in the molten solution. Combining the findings of which cationic properties result in a good catalyst offers insight into how the molten salt can be designed to operate for large-scale pyrolysis.