Global emissions of greenhouse gases, as CH4 and CO2, have been increasing in the last few decades and are recognized as one of the main anthropic causes of global warming. In this context, the Paris Agreement (ratified in 2016) sets the aim to hold the global warming well below 2°C. Many studies are focusing on CO2 storage and chemical recycling. Among these methods, CO2 methanation, also called Sabatier’s reaction (CO2 + 4H2 = CH4 + 2H2O), is regarded as the most potential way for CO2 utilization because of its high activity and moderate reaction condition, making it possible for commercial production. On the other hand, the so-called dry reforming reaction converting methane and CO2to synthesis gas (DRM: CO2 + CH4 ⇌ 2 CO + 2 H2) is another important reaction for getting value-added products from such greenhouse gases. The CO2 methanation reaction is exothermic and thermodynamically favoured at low temperatures and high pressures, but when the reaction is carried out at temperatures typically above 300°C, the equilibrium increasingly favours several competing reactions, including the reverse water gas shift reaction, the Bosh reaction and the dry reforming of methane. Being all such side reactions exothermic, especially, the DRM reaction, high operating temperatures, usually in the range of 900–1273 K, are requested to achieve the desirable conversion levels. Nickel catalysts are the most commonly used in CO2 methanation and as well in the DRM. Reducible oxide supports and basic promoters enhance the reducibility of Ni catalysts, improve the CO2 activation and boost carbon removal, thus, limiting the deactivation of catalysts occurring during DRM. Based on recent results on Ni catalysts for DRM and CO2 methanation reactions, the present contribution will focus on an overview of catalyst design and promotion effects, focusing on the chemical composition and support effect in enhancing the catalytic performances.
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