Functionalized hypercrosslinked polymers (HCPs) with surface areas between 213 and 1124 m(2)/g based on a range of monomers containing different chemical moieties were evaluated for CO2 capture using a pressure swing adsorption (PSA) methodology under humid conditions and elevated temperatures. The networks demonstrated rapid CO2 uptake reaching maximum uptakes in under 60 s. The most promising networks demonstrating the best selectivity and highest uptakes were applied to a pressure swing setup using simulated flue gas streams. The carbazole, triphenylmethanol and triphenylamine networks were found to be capable of converting a dilute CO2 stream (>20%) into a concentrated stream (>85%) after only two pressure swing cycles from 20 bar (adsorption) to 1 bar (desorption). This work demonstrates the ease with which readily synthesized functional porous materials can be successfully applied to a pressure swing methodology and used to separate CO2 from N-2 from industrially applicable simulated gas streams under more realistic conditions.

Reducing the cost of capturing CO2 from point source emitters is a major challenge facing Carbon Capture, Utilisation and Storage. While Solid Ionic Liquids (SoILs) have been shown to allow selective and rapid CO2 capture by pressure swing separation of flue gases, expectations of their high cost hinders their potential application. Cellulose is found to be a reliable, cheap and sustainable support for a range of SoILs, reducing the total sorbent cost by improving the efficiency of the ionic liquid through increased ionic surface area that results from coating. It was also found that cellulose support imparts surface characteristics, which increased total sorbent uptake. Combined, these effects allowed a 4 to 8-fold improvement in uptake per gram of ionic liquid for SoILs that have previously shown high uptake and a 9 to 39-fold improvement for those with previously poor uptake, offering the potential to drastically reduce the amount of ionic liquid required to separate a given gas volume. Furthermore, the fast kinetics are retained which means het rapid cycling can be achieved which results in high separation capacity relative to conventional temperature swing process. The projected reduction in plant size and operational costs represents a potentially ground-breaking step forward is carbon dioxide capture technologies.

In this work, two simple processes for carbon dioxide (CO2) such as capture and utilization have been combined to form a whole systems approach to carbon capture and utilization (CCU). The first stage utilizes a pressure swing adsorption (PSA) system, which offers many benefits over current amine technologies. It was found that high selectivity can be achieved with rapid adsorption/desorption times while employing a cheap, durable sorbent that exhibits no sorbent losses and is easily regenerated by simple pressure drops. The PSA system is capable of capturing and upgrading the CO2 concentration of a waste gas stream from 12.5% to a range of higher purities. As many CCU end processes have some tolerance toward impurities in the feed, in the form of nitrogen (N-2), for example, this is highly advantageous for this PSA system since CO2 purities in excess of 80% can be achieved with only a few steps and minimal energy input. Non-thermal plasma is one such technology that can tolerate, and even benefit from, small N-2 impurities in the feed, therefore a 100% pure CO2 stream is not required. The second stage of this process deploys a nanosecond pulsed corona discharge reactor to split the captured CO2 into carbon monoxide (CO), which can then be used as a chemical feedstock for other syntheses. Corona discharge has proven industrial applications for gas cleaning and the benefit of pulsed power reduces the energy consumption of the system. The wire-in-cylinder geometry concentrates the volume of gas treated into the area of high electric field. Previous work has suggested that moderate conversions can be achieved (9%), compared to other non-thermal plasma methods, but with higher energy efficiencies (>60%).

The need to create a new approach to carbon capture processes that are economically viable has led to the design and synthesis of sorbents that selectively capture carbon dioxide by physisorption. Solid Ionic Liquids (SoILs) were targeted because of their tunable properties and solid form under operational conditions. Molecular modelling was used to identify candidate SoILs and a number of materials based on the low cost, environmentally friendly acetate anion were selected. The materials showed excellent selectivity for carbon dioxide over nitrogen and oxygen and moderate sorption capacity. However, the rate of capture was extremely fast, in the order of a few seconds for a complete adsorb-desorb cycle, under pressure swing conditions from 1 to 10 bar. This showed the importance of rate of sorption cycling over capacity and demonstrates that smaller inventories of sorbents and smaller process equipment are required to capture low concentration CO2 streams. Concentrated CO2 was isolated by releasing the pressure back to atmospheric. The low volatility and thermal stability of SoILs mean that both plant costs and materials costs can be reduced and plant size considerably reduced.

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 CO2 reduction. 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 CO2 directly 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 CO2 and 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.

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The first page of this article is displayed as the abstract.