Solar thermal catalytic reforming of natural gas: A review on chemistry, catalysis and system design

Solar radiation is an abundant and environmentally benign energy source. However, its capture and effective utilization is one of the most difficult challenges faced by modern science. An effective way to capture solar energy is to convert it to chemical energy using concentrated solar power and thermochemical conversion routes, such as methane reforming. Methane, the main component of natural gas, is poised to become a leading feedstock in the near term, partly due to recent developments in shale gas extraction. Solar-to-chemical energy conversion can be achieved by reforming methane into synthesis gas, a mixture of carbon monoxide and hydrogen, in a single, highly endothermic catalytic process when reacted with steam or carbon dioxide. This review highlights different aspects of solar thermal reforming of methane, including thermodynamics, challenges related to catalyst activity and stability and reactor design. Equilibrium limitations are discussed in detail with respect to solar thermal reforming. Recent developments in methane reforming catalysis are critically reviewed in a broad scope, addressing catalyst deactivation drawbacks and focusing on alternative catalysts. The potential of the low-temperature solar methane steam reforming and the related technological challenges are discussed, including catalyst requirements. Future directions are also outlined.