Direct Air Capture and Integrated Conversion of Carbon Dioxide into Cyclic Carbonates with Basic Organic Salts

Abstract

Direct air capture and integrated conversion is a very attractive strategy to reduce CO2 concentration in the atmosphere. However, the existing capturing processes are technologically challenging due to the costs of the processes and the low concentration of CO2. The efficient valorization of the CO2 captured could help overcome many techno-economic limitations. Here, we present a novel economical methodology for direct air capture and conversion that is able to efficiently convert CO2 from the air into cyclic carbonates. The new approach employs commercially available basic ionic liquids, works without the need for sophisticated and expensive co-catalysts or sorbents and under mild reaction conditions. The CO2 from atmospheric air was efficiently captured by IL solution (0.98 molCO2/molIL) and, subsequently, completely converted into cyclic carbonates using epoxides or halohydrins potentially derived from biomass as substrates. A mechanism of conversion was evaluated, which helped to identify relevant reaction intermediates based on halohydrins, and consequently, a 100% selectivity was obtained using the new methodology.

Materials for Direct Air Capture and Integrated CO2 Conversion: Advancement, Challenges, and Prospects

“…The process of extracting CO 2 directly from the atmosphere holds significant climate-related advantages, but it is accompanied by substantial costs, as does the subsequent sequential conversion . To date, the examples of DACC are based on two-step reactions, first performing the capture and second, the conversion (Figure ), yielding: cyclic carbonate, CO, formate, − methanol − and methane . In this section, each of these products will be described in detail.…”

“…Our methodology demonstrates exceptional performance, with the IL solution efficiently capturing CO 2 from the atmospheric air (0.98 mol CO 2 /mol IL by bubbling air with 425 ppm of CO 2 ), and subsequently achieving complete conversion into cyclic carbonates using substrates derived from epoxides or halohydrins, potentially sourced from biomass. Mild condition was employed in this work, 40 °C; atmospheric CO 2 (0.04%) and 16 h, resulting in >99% yield …”

“… Slow kinetics of sorption : When contrasting the capture process using pure CO 2 with that of atmospheric CO 2 , the total time can stretch from under 15 min to a lengthy 16 to 72 h, ,, respectively. In the combination of capture and conversion, the rate-limiting step is the initial sorption, especially when it is arduous to capture the gas from such a diluted source, as the atmospheric air that contains around 0.04% of CO 2 .…”

“…However, limited examples using atmospheric air to directly reuse the CO 2 are observed. Thus, far, the products observed from the reutilization of atmospheric CO 2 include cyclic carbonate, CO, formate, − methanol, − and more recently methane …”

Multi-Functional Polymer Membranes Enable Integrated CO2 Capture and Conversion in a Single, Continuous-Flow Membrane Reactor under Mild Conditions

“…To reduce the energy intensity and costs associated with CO 2 capture, there is currently significant interest in the development of intensified processes that integrate CO 2 capture with the conversion of CO 2 to valuable products. For example, there are recent examples in the literature − of multifunctional catalytic materials with amine or alkali-metal hydroxide functional groups for capturing CO 2 from dilute streams such as flue gas or air and catalytic sites (e.g., metals, halogens) for converting the captured CO 2 with H 2 , steam, or epoxides to produce methane, formic acid, syngas (H 2 + CO), or cyclic carbonate products. While such multifunctional materials could improve the efficiency of CO 2 capture by eliminating the need to compress and transport high-pressure CO 2 , these technologies require a two-step temperature-swing process to first capture CO 2 at low temperatures and then convert CO 2 at higher temperatures in a separate unit process (i.e., similar to sorbent-based carbon capture; see Figure a).…”