Selective hydrogenation of carbon dioxide (CO2) into value-added chemicals has aroused great interest. The chemical inertness of CO2 and diverse reaction pathways usually require the construction of enabled catalysts. To date, cobalt (Co) catalysts characteristic of metallic and/or divalent Co components show great potential for CO2 hydrogenation. To better regulate the CO2 hydrogenation, it is necessary to summarize the current progress of cobalt catalysts for selective hydrogenation of CO2. In this Perspective, first, hydrogenation of CO2 into methane over metallic Co sites is introduced. Second, hydrogenation of CO2 into methanol and C2+ alcohols is discussed by constructing mixed-valent cobalt sites. Third, hydrogenation of CO2 into light olefins and C5+ liquid fuels over cobalt-containing hybrid catalysts is introduced. Fourth, the reaction paths for selective hydrogenation of CO2 over cobalt catalysts are illustrated. Finally, the current challenges and prospects of cobalt-based nanocatalysts for hydrogenation of CO2 are proposed.

Cobalt Catalysts Enable Selective Hydrogenation of CO2 toward Diverse Products: Recent Progress and Perspective.

CO2 capture from industry sectors or directly from the atmosphere is drawing much attention on a global scale because of the drastic changes in the climate and ecosystem which pose a potential threat to human health and life on Earth. In the past decades, CO2 capture technology relied on classical liquid amine scrubbing. Due to its high energy consumption and corrosive property, CO2 capture using solid materials has recently come under the spotlight. A variety of porous solid materials were reported such as zeolites and metal–organic frameworks. However, amine-functionalized porous materials outperform all others in terms of CO2 adsorption capacity and regeneration efficiency. This review provides a brief overview of CO2 capture by various amines and mechanistic aspects for newcomers entering into this field. This review also covers a state-of-the-art regeneration method, visible/UV light-triggered CO2 desorption at room temperature. In the last section, the current issues and future perspectives are summarized.

https://pubs.acs.org/doi/pdf/10.1021/acsomega.2c03385

Review on CO2 Capture Using Amine-Functionalized Materials

Lowering the regeneration temperature for solid CO2-capture materials is one of the critical tasks for economizing CO2-capturing processes. Based on reported pKa values and nucleophilicity, we compared two different polyethylenimines (PEIs): branched PEI (BPEI) and linear PEI (LPEI). LPEI outperformed BPEI in terms of adsorption and desorption properties. Because LPEI is a solid below 73–75 °C, even a high loading amount of LPEI can effectively adsorb CO2 without diffusive barriers. Temperature-programmed desorption (TPD) demonstrated that the desorption peak top dropped to 50.8 °C for LPEI, compared to 78.0 °C for BPEI. We also revisited the classical adsorption model of CO2 on secondary amines by using in situ modulation excitation IR spectroscopy, and proposed a new adsorption configuration, R1(R2)-NCOOH. Even though LPEI is more expensive than BPEI, considering the long-term operation of a CO2-capturing system, the low regeneration temperature makes LPEI attractive for industrial applications.

/pdf/branched-versus-linear-structure-lowering-the-co2-desorption-1xpbxk00.pdf

Branched Versus Linear Structure: Lowering the CO2 Desorption Temperature of Polyethylenimine-Functionalized Silica Adsorbents

Hydrate-based gas separation is a promising method for CO2 capture from CO2/CH4 gas mixtures, and with improved gas separation efficiency, rate of hydrate formation, and gas uptake, this process has the potential to be taken from the lab scale to industry. In this regard, a significant body of work has been conducted in recent years with the aim to enhance the kinetics of the hydrate-based CO2 capture process. The present study presents a review of the kinetic studies performed on the enhancement of hydrate-based CO2 capture from CO2/CH4 in terms of using additives, porous media, nanofluids, etc. Future research directions are also discussed. The present review aims to aid understanding of the mechanism of the hydrate-based CO2 capture process and to provide references for the development of hydrate-based CO2 capture technology toward industrial applications in the near future. 

Minireview of Hydrate-Based CO2 Separation from a CO2/CH4 Gas Mixture: Progress and Outlook

A novel kinetic model for liquid-phase selective oxidation of glycerol over Au-supported catalysts, involving the reactions in the bulk liquid phase, the formation of reactive oxygen species on Au metal and support, and three reactions of different oxygen species, was developed. The innovations of this model are that the catalyst has two types of active sites, definition of the coverage of active sites on the Au (as α), and the consideration of the different active species involved in each reaction. This approach enabled optimization of the reaction conditions and highlighted aspects of the catalyst design to maximize the target product yield. The model is highly versatile and successfully predicts the oxidation behavior under a wide range of conditions. It also predicted the experimental results reported by other researchers. Therefore, the model is expected to be a useful tool for catalyst design and prediction of reaction conditions in liquid-phase biomass conversion. 

Comprehensive Study on Kinetic Modeling of Liquid-Phase Selective Oxidation Using Au-Supported Catalysts for Efficient Production of Value-Added Chemicals from Glycerol

Industrial applications of solid adsorbents for direct capture of CO2 from the atmosphere require lowering the regeneration temperature (typically 80–100 °C) to save the energy and operation cost. ...

Alina Gau

Papers

Toward Carbon Dioxide Capture from the Atmosphere: Lowering the Regeneration Temperature of Polyethylenimine-Based Adsorbents by Ionic Liquid

Operando spectroscopic monitoring of active species in CO2 hydrogenation at elevated pressure and temperature : steady-state versus transient analysis