Review on sorption-enhanced methanation of renewable hydrogen and carbon dioxide

Methane obtained through the Sabatier reaction offers a promising pathway toward achieving carbon neutrality by facilitating efficient energy and hydrogen storage and balancing. The high purity required for methane in the gas grid and combustion engines presents a significant challenge, as the gas purification process is both energy-intensive and costly. Ideally, a pure methane stream should be produced directly during the reaction between carbon dioxide and hydrogen, eliminating the need for separation steps. Hydrogen gas produced from renewable sources or from the surplus of energy production and carbon dioxide collected from the flue gases of industries can be reacted together to obtain a carbon neutral fuel. Due to the thermodynamic limitations of carbon dioxide methanation, producing a pure stream of methane in a single process step with conventional technology employing commercial nickel catalysts is unfeasible. However, the removal of one of the products, water from the reactive catalyst sites, can shift the equilibrium towards methane. A bifunctional material that combines water adsorption sites and catalytic synthesis sites in close proximity presents a promising solution compared to traditional mechanical mixtures of catalyst and sorbent. While the research on this approach is still limited, it has been demonstrated to effectively yield high-purity methane. This article provides a focused and comprehensive review of the existing literature, evaluating both the potential and challenges associated with the sorption-enhanced methodology. The findings suggest that sorption-enhanced methanation holds significant promise for large-scale production, with further research needed to address the remaining challenges.