Room-Temperature Ionic Liquids and Composite Materials: Platform Technologies for CO₂ Capture

Abstract

Clean energy production has become one of the most prominent global issues of the early 21st century, prompting social, economic, and scientific debates regarding energy usage, energy sources, and sustainable energy strategies. The reduction of greenhouse gas emissions, specifically carbon dioxide (CO(2)), figures prominently in the discussions on the future of global energy policy. Billions of tons of annual CO(2) emissions are the direct result of fossil fuel combustion to generate electricity. Producing clean energy from abundant sources such as coal will require a massive infrastructure and highly efficient capture technologies to curb CO(2) emissions. Current technologies for CO(2) removal from other gases, such as those used in natural gas sweetening, are also capable of capturing CO(2) from power plant emissions. Aqueous amine processes are found in the vast majority of natural gas sweetening operations in the United States. However, conventional aqueous amine processes are highly energy intensive; their implementation for postcombustion CO(2) capture from power plant emissions would drastically cut plant output and efficiency. Membranes, another technology used in natural gas sweetening, have been proposed as an alternative mechanism for CO(2) capture from flue gas. Although membranes offer a potentially less energy-intensive approach, their development and industrial implementation lags far behind that of amine processes. Thus, to minimize the impact of postcombustion CO(2) capture on the economics of energy production, advances are needed in both of these areas. In this Account, we review our recent research devoted to absorptive processes and membranes. Specifically, we have explored the use of room-temperature ionic liquids (RTILs) in absorptive and membrane technologies for CO(2) capture. RTILs present a highly versatile and tunable platform for the development of new processes and materials aimed at the capture of CO(2) from power plant flue gas and in natural gas sweetening. The desirable properties of RTIL solvents, such as negligible vapor pressures, thermal stability, and a large liquid range, make them interesting candidates as new materials in well-known CO(2) capture processes. Here, we focus on the use of RTILs (1) as absorbents, including in combination with amines, and (2) in the design of polymer membranes. RTIL amine solvents have many potential advantages over aqueous amines, and the versatile chemistry of imidazolium-based RTILs also allows for the generation of new types of CO(2)-selective polymer membranes. RTIL and RTIL-based composites can compete with, or improve upon, current technologies. Moreover, owing to our experience in this area, we are developing new imidazolium-based polymer architectures and thermotropic and lyotropic liquid crystals as highly tailorable materials based on and capable of interacting with RTILs.

Solid Adsorbents for Low-Temperature CO2 Capture with Low-Energy Penalties Leading to More Effective Integrated Solutions for Power Generation and Industrial Processes

“…In this review, recent advances on researches of solid adsorbents for CO 2 capture is summarized, readers who are interested in other CO 2 capture technologies such as absorption, oxy-fuel, and chemical looping are directed to references (Bara et al, 2010;Blamey et al, 2010;Karadas et al, 2010;Toftegaard et al, 2010;Du et al, 2012;Zhang et al, 2012;Sunil and Merched, 2014). We will focus on the low-temperature adsorbents because they can (i) potentially match the requirements in Figure 3 and (ii) be suitable for using in the integrated energy-chemical solutions (Figure 2).…”

【Original Contribution】 Effect of Ionic Liquid Additives on CO2Permeation and CO2/N2Selectivity through Facilitated Transport Membranes

“…Recently, ionic liquids (ILs), which are room temperature molten salts, have attracted considerable attention as a CO2 separation media because of unique properties such as non-volatility, good thermal stability and liquidity over a wide temperature range 13,14) . Such specific properties are suitable for gas separation membranes.…”

Methodology of non-equilibrium thermodynamics for kinetics research of CO2 capture by ionic liquids

“…It is reported that the capture of CO 2 alone will increase the energy requirements of a plant by 25%-40% [3]. Therefore, many scientists all over the world are focusing on the investigations of the environment-friendly capture technology with higher efficiency and lower energy consumption compared with the current technologies [3][4][5][6][7][8][9].…”

“…However, due to the corrosion, volatility, toxicity of the amines, and their high regeneration energy requirement in the applications, in recent years, scientists all over the world have designed and synthesized many ionic liquids (ILs) as absorbents to absorb and separate CO 2 from the gas mixtures [5][6][7][8][9][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30]. The IL-based CO 2 capture technology is considered to be a promising and competitive way to separate CO 2 because of its advantages of non-volatility, recycling, environment-friendliness, functionality, and high efficiency of CO 2 capture [9].…”