Literature review of the catalytic pyrolysis of methane for hydrogen and carbon production

This review highlights recent developments and future perspectives in CO_x-free hydrogen production through methane pyrolysis. We give detailed discussions on thermal and catalytic methane cracking into hydrogen and carbon. Various types of solid and liquid catalysts were reviewed in terms of hydrogen selectivity, methane conversion, and deactivation. Some pilot scale technology was discussed; however, large-scale industrialisation is impeded by rapid solid catalyst deactivation, low-priced carbon (by-product) of molten catalysts, harsh conditions for reactor materials, and performance of stable molten catalysts. For catalytic methane cracking in molten catalysts (salt or metal), substantial advances in catalyst development, product separation, and reactor design are still required to commercialise methane pyrolysis for hydrogen production. To provide guidance to future works in this area, the review is specifically focused on (i) design of catalysts (ii) recent developments of molten salt-based methane cracking, (iii) reactor design and process design.