Kinetic and economic analysis of reactive capture of dilute carbon dioxide with Grignard reagents

Abstract

Carbon Dioxide Utilisation (CDU) processes face significant challenges, especially in the energetic cost of carbon capture from flue gas and the uphill energy gradient for CO2reduction. Both of these stumbling blocks can be addressed by using alkaline earth metal compounds, such as Grignard reagents, as sacrificial capture agents. We have investigated the performance of these reagents in their ability to both capture and activate CO2directly from dried flue gas (essentially avoiding the costly capture process entirely) at room temperature and ambient pressures with high yield and selectivity. Naturally, to make the process sustainable, these reagents must then be recycled and regenerated. This would potentially be carried out using existing industrial processes and renewable electricity. This offers the possibility of creating a closed loop system whereby alcohols and certain hydrocarbons may be carboxylated with CO2and renewable electricity to create higher-value products containing captured carbon. A preliminary Techno-Economic Analysis (TEA) of an example looped process has been carried out to identify the electrical and raw material supply demands and hence determine production costs. These have compared broadly favourably with existing market values.

Highly integrated CO2capture and conversion: direct synthesis of cyclic carbonates from industrial flue gas

“…27 In this report we demonstrate the capability of simple metal halides-based catalysts to convert the CO 2 from diluted flows to cyclic carbonates under semibatch conditions. 28 With the catalytic and kinetic data at hand, the opportunity and the limitations of employing a flow of industrial flue gas as an impure CO 2 source for the synthesis of cyclic organic carbonates are assessed by employing the most active catalytic system. Thus, the first direct application of industrial flue gas for the synthesis of cyclic carbonates and, in general, the first application of flue gas in catalysis under ambient conditions is reported.…”

Demonstration of CO2 Conversion to Synthetic Transport Fuel at Flue Gas Concentrations

“…Overall, the presence of small quantities of water would primarily serve to only reduce reaction yield. Previous work carried out by our group has indicated that the reaction of Grignard reagents with oxygen is relatively slow compared to its reaction with CO2, although flue gas streams with very high oxygen levels may see trace amounts of the oxygen products, MgO, methanol, and possibly dimethyl ether (Goebel and Marvel, 1933;Dowson et al, 2015).…”

“…Previous work carried out by this group has identified organometallics and particularly Grignard reagents as being suitable for the direct conversion of flue gas concentration of CO2 into value-added products such as acetic, terephthalic, and adipic acids (Dowson et al, 2015). The organomagnesium reagent, which was shown to react readily with CO2, even at low partial pressures, can then be regenerated from the by-product magnesium dihalide (MgX2).…”

Reactive capture using metal looping: the effect of oxygen

“…An alternative approach, investigated previously by the authors, used sacrificial Grignard reagents to capture and convert CO 2 directly from the gas phase to a range of potentially valuable carboxylic acid products under room temperature conditions. 8 Since the by-product of the reaction, the magnesium dihalide, is the commercial feedstock for highly efficient magnesium production by electrolysis, in principle the sacrificial Grignard reagent could be regenerated. 9 This approach would combine the capture and conversion of the CO 2 into a single exothermic room-temperature process, which would allow the overall conversion of an alcohol into the carboxylic acid of the next member of the homologous series, with a carbon chain one atom longer than the starting alcohol ( Figure 1).…”