Turquoise Hydrogen: Methane Pyrolysis as a Low-CO2 Source of H2

Methane pyrolysis offers a promising route for large-scale H2 production with carbon sequestration from natural gas. Earlier works have focused on gas-phase pyrolysis. However, the removal of the deposited carbon from the reactor without burning, the fouling of heat transfer surfaces and reactor blockages have limited commercialization of the technology. Liquid-phase pyrolysis, in which the gas is decomposed in molten metal or molten salt, may facilitate easier carbon separation and heat transfer, but often results in significant amounts of the liquid media species being trapped in the carbon. The high operating temperatures needed for the thermal decomposition also pose significant engineering challenges. The temperatures can be lowered by the use of catalysts. However, deactivation, loss of catalysts and their costs require further innovative solutions for the process to become economic. This chapter details the current status of the different pyrolysis variants, their reaction routes and pyrolysis performances, and discusses potential ways forward.