Catalytic Technologies for the Conversion and Reuse of CO2

Abstract

The case of the catalytic technologies for the conversion and reuse of CO2 is different from that discussed in Volume 2 regarding the elimination of non-CO2 GHGs (N2O, CH4, fluorocarbons) because the issue is the development of cost-and energy-effective catalytic routes for carbon dioxide conversion to usable products. This is a fast-growing area for the crucial relevance of these technologies in closing the carbon cycle in energy and chemical production. Two main cases are discussed. The first is when CO2 is used as reactant to produce added-value chemicals, particularly CO2-containing polymers, that is, when the C-O bonds in CO2 are not broken. The second case is when renewable energy sources are used for the conversion of CO2 and thus the main impact is on the indirect GHG reduction due to the introduction of renewable energy in the value chain. The general relevance is thus for the possibility to substitute progressively the use of fossil fuels through the so-called solar fuels and chemicals, with use of CO2 to produce energy-vectors (to store/transport renewable energy) or to produce chemicals substituting those derived from fossil sources. This is the general growing area of the so-called Power-to-X processes and in a longer-term perspective of the so-called artificial leaf devices. It is possible to distinguish between first generation approaches, which are already a pilot stage or even higher stage of development and are based on the use of thermal catalysis in the step of CO2 conversion, and second generation processes, based on photo-or electro-catalytic conversion of CO2 and which thus allow a more direct and energy efficient link with the use of renewable energy sources.