Current solutions for CO2 emissions reduction mainly rely on capturing CO2 emitted from power stations and its storage. Such processes are based on CO2 separation via either amine scrubbing, pressure swing adsorption, or membrane separation followed by cryogenic liquefaction. The purified CO2 is then stored in geological formation, or used for enhanced oil recovery.
The process is energy intensive, leading to high capital and operating costs. Also, it is not clear what would be the long-term consequences of the CO2 storage in underground reservoirs. An alternative to CO2 storage is its chemical transformation into fuels and chemicals that can potentially replace (at least partially) the fossil feedstocks used in chemical industry.
Being a harmful greenhouse gas, CO2 is also an excellent source of carbon, non- flammable and non-corrosive. Resources are abundant, including flue gases from coal- and natural gas-fired power plants, biogas and landfill gas (up to 50 mol% CO2), and off-gas streams in several industrial processes such as ammonia pro- duction and fermentation. There are also large resources of CO2 accompanying natural gas and oil production wells (associated petroleum gas); this CO2 is typically vented into the atmosphere with flare gas.
Conversion of captured CO2 into synthetic fuels and chemicals is an attractive avenue for reduction of CO2 emissions and, as such, this topic has attracted the interest of many research groups around the world. Many research efforts have focused on photochemical and electrochemical reduction of CO2 into a variety of products, including formic acid and methanol, in aqueous environments using water as a source of H2 for CO2 reduction. This approach is apparently attractive as it only uses water and CO2 as the starting materials and the sun or (potentially) renewable electricity as a source of energy. However, photochemical CO2 reduction has inherent limitations of solar energy utilization, while electro-chemical reduction of CO2 has low efficiencies of electricity utilization. Both processes are limited by low CO2 solubility in water and have severe diffusion limitations. An alternative approach is thermocatalytic conversion that combines the use of high temperatures with a heterogeneous catalyst, providing fast reaction rates and, therefore, allowing for large volume production.