Carbon Capture Science & Technology最新文献

Viscosity and absorption capacity are the main indexes to evaluate functionalized ionic liquids. Based on the precise design strategy of both anion and cation absorption, a dual-functionalized protic IL diethylenetriamine methylurea ([DETAH][MEUR]) for trapping CO₂ was successfully synthesized. The absorption and regeneration properties of the ILs solution were tested, and the changes in the physical properties of ILs before and after CO₂ absorption were compared. The experimental results showed that the [DETAH][MEUR] solution had relatively low viscosity, excellent absorption property with 2.05 mol CO₂/mol IL at 40 °C and 0.5 mol/L concentration, and its regeneration efficiencies still kept above 90.09 % after five cycles. In addition, the mechanism of the absorption reaction was explored by combining Fourier transform infrared (FT-IR) spectroscopy, carbon nuclear magnetic resonance (¹³C NMR) spectroscopy, and density functional theory (DFT) calculation methods. It shows that in [DETAH][MEUR] solution, the N atom losing proton (-NH) in the anion is the main absorption site, and the primary amine (-NH₂) in the protonated cation [DETAH]⁺ of secondary amine is used as an auxiliary cooperative trapping CO₂. Hopefully, this work can provide a new way for the research and development of green CO₂ absorbents.

This study introduces an Integrated Carbon Capture and Utilisation-Reverse Water Gas Shift (ICCU-RWGS) approach, a novel method for in situ CO₂ adsorption and conversion, leveraging the synergistic effects of CaO within a NaCl-CaCl₂ molten salt blend to enhance CO₂ capture and conversion efficiency. Building upon this foundation, we optimize CaO concentration and operating temperature to maximize CO₂ uptake and conversion performance. The research focuses on integrating CaO with a NaCl-CaCl₂ molten salt blend (mass ratio 4:6) to improve CO₂ sorption and conversion performance. Findings show significant enhancements in CO₂ uptake and CO yield with the presence of molten salt compared to systems without it. The optimal operating temperature and CaO concentration are identified for maximum CO yield. Characterisation techniques like in-situ infrared spectroscopy, XRD, and SEM provide insights into the behavior of CaO in the molten salt, revealing the solubility of the partial carbonate formed from CO₂ and CaO, dispersion of CaO particles, and their morphological characteristics. Overall, the study demonstrates the potential of CaO-molten salt integration in improving ICCU-RWGS process efficiency and contributes to the development of more effective and sustainable ICCU technologies.

The integrated carbon capture and utilization (ICCU) technology has been considered a prospective strategy for mitigating carbon emissions issues. Compared to conventional CO₂ capture and utilization, the ICCU process reduces transporting, product purification, construction, and operation costs. However, few works focus on investigating the effect of in-situ CO₂ conversion on the sintering of CaO at high temperatures. In this work, Cu/CaO dual functional materials (DFMs) were synthesized and used in the Calcium Looping-Reverse Water-Gas Shift (CaL-RWGS) process at 650 °C. The results showed that it is thermodynamically feasible to couple the CaL with the RWGS reaction. In the cyclic CO₂ capture test, Ca₁Cu_0.1 DFMs showed desirable CO₂ capture performance (11.34 mmol/g_DFMs) and self-activated phenomenon in the first 15 cycles. Moreover, Cu nanoparticle catalysts in the DFMs effectively inhibited the sintering of CaO by accelerating the desorption of CO₂ from the CaO surface and converting it to CO during the conversion stage. In-situ DRIFTS of Ca₁Cu_0.1 DFMs revealed that formates might be the RWGS intermediates in CaL-RWGS.

Hydrothermal reactions can convert lignin into carbon dots, and the process often uses acids as additives, but the mechanism of action is not clear. In this study, lignin-based carbon dots were successfully prepared by HNO₃-assisted one-pot hydrothermal method. The mechanism of the influence of the acidic environment on the structure and optical properties of lignin-based carbon dots was also investigated by changing the addition amount of HNO₃. It was found that the particle size distribution of carbon dots collected was 1-5 nm, and they could emit bright blue fluorescence under violet light irradiation with the highest fluorescence quantum yield of 10.17%. HNO₃ acts on the branched chains and ether bonds of alkali lignin, prompting the depolymerization of lignin and re-cross-linking and condensation to form lignin-based carbon dots. With the increase of HNO₃ addition, the carbon core of lignin-based carbon dots gradually transformed from amorphous structure to complete graphene-like structure, and the emission wavelength of lignin-based carbon dots shifted from 517 nm to 499 nm, and the fluorescence quantum yield was increased from 2.61% to 10.17% by the effect of integrated N doping, which is of great significance for the analysis of the conformational relationship of lignin-based carbon dots, and for the guidance of the high-efficiency synthesis of lignin-based carbon dots.

Recently, clathrate hydrate-based CO₂ separation is considered as one of the most attractive processes for reducing CO₂ emissions because of its effective energy utilization, environmental friendliness, and economic viability. The ionic semi-clathrate hydrate, a quaternary salt used to facilitate hydrate formation, is particularly shown interest because it can boost CO₂ capture by improving the physical and chemical interactions between host lattice and guest molecules for hydrate formation. A reduced pressure of 1 MPa or less is high enough for effective gas trapping at 280 K using a semi-clathrate hydrate. The operating parameters, ionic hydrate structure, and promoter concentration affect CO₂ capture. The efficiency of the CO₂ separation process can be significantly reduced by inhibitory effects at a particular salt concentration. Research has been conducted using tetra-n-butyl-ammonium and phosphonium salts because their crystal structure and morphology are favorable to form semi-clathrate hydrates. However, only a few lookups on environment-friendly and appropriate characterization strategies of the hydrates and novel promoters, and their design, and operability have been performed. This review addresses the mechanisms involving the size of CO₂ molecules in an ionic hydrate network, the characterization methods of the hydrates, promoter integration and their overall performance analysis. In addition to that, operational strategies of the semi-clathrate hydrate-based CO₂ capture processes, the drawbacks and future routes to research CO₂ capture using semi-clathrate hydrates have been addressed.

Large amounts of CO₂ were discharged into the atmosphere, resulting in a severe greenhouse effect and inducing ecological environmental problems that threaten human survival. Integrated carbon dioxide capture and conversion (ICCC) with Dual Functional Materials (DFMs) was a promising process to capture CO₂ emission in flue gas and convert it into value-added chemicals, reducing energy consumption and economic cost. The catalytic component of DFMs enhances hydrogen source activation and promotes carbonate hydrogenation to produce high value-added chemicals. The hydrogenation process achieved the regeneration of dual-functional materials, which is the key to realizing the ICCC process. This research focuses on DFMs development with different hydrogen sources (hydrogen or light alkanes) for the ICCC process in recent years. In addition, the reaction mechanism and catalytic components modification were discussed to improve the in-situ conversion activity of the ICCC process. Finally, future prospects were anticipated to guide the development and application scenarios of DFMs in the ICCC process.

The separation of CO₂ has been recognized as a potential approach to address the impacts of climate change resulting from the emission of flue gases into the environment. Efficient separation technologies are required to effectively remove CO₂ from flue gases. To resolve this problem, membrane-based gas separation is considered an economically viable and energy-efficient technology over conventional techniques. Functional polymeric membranes have gained a lot of interest for their attractive gas separation performance. Thus, this work aims to critically review the recent developments of functional polymeric membranes designed for CO₂ separation from flue gases. Starting with a background on flue gases and polymeric membranes, a brief discussion on Robeson's upper bound for CO₂/N₂ separation is provided. After that, a detailed analysis of the current advancements in different membrane modification approaches, such as mixed matrix, grafting, layer-by-layer assembly, and interfacial polymerization, for improved performance of polymeric membranes is provided. Furthermore, the effect of CO₂ on polymeric membranes (plasticization and aging), the current global market and key market players in the membranes-based gas separation field are discussed thoroughly. Finally, a concise remark on the future directions of polymeric membranes for CO₂ separation from flue gases is presented.