Preface to Special Issue: CO 2 capture storage and utilization

摘要/Abstract

摘要： Reducing the anthropogenic CO₂ emissions from fossil resource combustion and human activities has become one of the major challenges we are facing today. Beyond those practical applications for the utilization of CO₂, such as the synthesis of salicylic acid, methanol, urea, NaHCO₃-Na₂CO₃ chemicals and recently developed polycarbonate synthesis, scientists are still seeking new materials and technologies for efficient capture, storage and conversion of CO₂ with consideration into reducing CO₂ emission at a large amount. Until now, CO₂ capture and utilization is not only an academic event but a social and government guiding project all over the world. The special issue in Journal of Energy Chemistry is an update of recent research works on the topic of carbon capture storage and utilization (CCUS) which covers the material and technology innovations for CO₂ capture and utilization. Five reviews, two communications and seventeen research articles are included in this special issue. As a first step for limiting the CO₂ emission, efficient capture of CO₂ with a cost-effective strategy, is likely to rely on new adsorbents and the development of technologies that can reduce energy consumption, especially for the separation of low concentrated CO₂ from coal-fired power plant flue gas and selective capture of CO₂ from humid gases. CO₂ molecules are often preferred to be adsorbed in porous materials with high surface area and abundant sorption sites. The concept of molecular basket sorbent (MBS) for CO₂ capture has been proposed by Song et al. in this special issue. They use polyethylenimine (PEI) or polyethylene glycol (PEG) to reside in the mesopore structure of SBA-15, TUD-1 and fumed silica HS-5 materials to provide plenty of amine sites for CO₂ adsorption. Zhong et al. synthesize a type of 2D covalent triazine-based framework material (namely, CTF-DCBT) for efficient capture of CO₂. CTF-DCBT contains ultramicropore (6.5 Å) and high heteroatom contents (11.24 wt% of N and 12.61 wt% of S), which is responsible for the highly selective CO₂/N₂ and CO₂/CH₄ preferential adsorption. Porous carbon materials with well-developed heteroatom doped sites are widely examined as CO₂ adsorbents. In the work of Ahn et al., nitrogen-doped carbon materials are synthesized by the carbonization of a low-cost porous covalent triazine polymer, PCTP-3. The textural properties of the porous carbon materials are additionally activated by KOH, to form a narrow micropore size distribution. A type of porous carbon sphere with highly developed ultra-microporosity and uniform pore size is prepared by Zhou and Zhuo et al. These well-designed porous carbon materials on purpose are examined as excellent adsorbents with high CO₂ capture capacity and selectivity. Pfeiffer and co-workers systematically investigate the CO₂ chemisorption process on a series of alkaline pentalithium aluminate (β-Li₅AlO₄) based solid solution. With an addition of alkaline carbonate compound or iron exchange with the aluminum position into β-Li₅AlO₄, the CO₂ chemisorption enhances. CO₂ molecules are more likely to reside on the superficial position of those (modified) alkaline solid solution adsorbents. CO₂ capture by ionic liquids (ILs) has also attracted wide attention. In the contributions of Yu et al. and Sun et al., a series of ILs monomers and ILs polymers (PILS) and a type of layered hybrids material containing ILs are prepared, respectively. Both the PILs and BMIMCl/LP layered hybrids are identified as efficient adsorbents with high CO₂ capture capacity. Zhang et al. select a series of [CnMIm][Tf₂N] ILs as physical CO₂ adsorbents and the adsorption condition is operated under a wide temperature and pressure range, which is appealing at higher temperature. Kanoh et al. examine the capacity and kinetics of CO₂ capture over K₂CO₃ adsorbent. In this work, a detailed study on the influence of temperature with changed moisture conditions and further insight into the NaHCO₃ formation mechanism has been carried out. Shi et al. employ a combination of WGS reaction and elevated-temperature pressure swing adsorption technology to deeply remove trace CO₂ and CO impurities to harvest high purity H₂ gas. The technology is based on potassium promoted hydrotalcite adsorbents, which can reduce the residual CO₂ concentration to 3.5 ppm after 12 h of temperature swing operation at 450 °C. In the search of highly efficient CO ₂ adsorbents under different real working conditions, Wang et al. and Ahn et al. critically review the development of molten salts modified MgO-based adsorbents and Amine-functionalized silica composite materials, respectively. Molten salts-modified MgO-based adsorbents show their advantages in the high adsorption capacity (the highest CO₂ capture capacity of 12.9 mmol g^-1 as reported), low cost, wide availability and suitable for the CO₂ capture at intermediate temperature range (200 –400 °C). Amine-functionalized silica composite materials are promising candidates for post-combustion CO₂ capture from low CO₂ concentrated flue gases. They show the advantages of excellent CO₂ uptake, selectivity, less sensitive to moisture and facile for the regeneration. Besides CO₂ capture, considerations about the recycling and utilization of CO₂ when using CO₂ as the abundant carbon resource are in progress to accomplish the challenging task of carbon neutral process. Direct catalytic conversion of CO₂ to value added chemicals or fuels has aroused great attention in both academic and commercial fields. Hydrogenation of CO₂ to formic acid and CO and other carbonaceous products in the lower carbon chemical valence state has been widely studied. Jin et al. investigate the auto-catalytic role of Zn/ZnO interface, which is formed in-situ during the reaction, in the transformation of CO₂ to formic acid in the water medium. They also provide an overview of the current advances in research of highly efficient reduction of CO₂ or NaHCO₃ into formic acid/formate by in-situ hydrogen from water dissociation with a metal/metal oxide redox cycle under mild hydrothermal condition. In the review made by Huang et al., the catalytic performance of CO₂-to-CO conversion and recent updates in designing of heterogeneous catalysts with high CO product selectivity and high temperature robustness are specifically elaborated. In the contribution of Chen et al., Ca(OH)₂ and 10% Ni/ZrO₂ are introduced in the biomass conversion processes of cellulose. Ca(OH)₂ greatly enhances the H₂ production rate with a yield of 36.4%, while the in-situ reforming of light gases and carbon capture processes significantly suppress the CO₂ formation. Ma et al. delicately design a dual active center containing Salen-Cu(II)@MIL-101(Cr) via the “ship in a bottle” approach, which is developed as the active catalyst for the synthesis of propylene carbonate from CO₂ and propylene oxide. The sorption enhanced methane reforming process of CO₂ has been studied by Pfeiffer et al. and Courson et al., by using CaO-NiO mixed oxide and CaO-Ca₁₂Al₁₄O₃₃, respectively. The studied catalyst systems show excellent chemical stability in obtaining syngas (H₂ + CO) with high CH₄ conversion and H₂ yield. Smart conversion processes such as chemical looping and mineral carbonation of CO₂ are capable of utilizing CO₂ at large quantities. Haider et al. describe the use of copper(II) oxides in combination with limestone in the form of a mechanical pelletizer as the oxygen carriers in the chemical looping processes. The oxygen carriers exhibit an enhanced crushing strength with high CO yield. Li et al. report the mineral carbonation processes of blast furnace slag with intention to reduce substantial CO₂ emission at large quantities. As a recyclable extractant, (NH₄)₂SO₄, is used to extract calcium and magnesium from blast furnace slag by using low-temperature roasting to fix CO₂ through aqueous carbonation. Alternatively, electrochemical reduction of CO₂ provides another promising way in reducing CO₂ emission, which can be delivered in the form of renewable energy. Co-electrolysis of CO₂ and H₂O using high-temperature solid oxide electrolysis cells (SOECs) into valuable chemicals is the topic of contribution made by Wang and Bao et al. The review discusses the so far cathode material development, the alternative cathode materials preparation strategies and the possible cathode reaction mechanism for CO₂/H₂O electrolysis. Different reaction modes of the CO₂/H₂O co-electrolysis in SOECs are summarized to offer new strategies to enhance the CO₂ conversion. Kang et al. report a nitrogen doped tin oxide material with enhanced Faradaic efficiency (90%) for CO₂ electro-reduction to formate, which also shows sulfur tolerance. The combined catalyst structure of partially reduced metallic tin and N-doped tin oxide (Sn/N-SnO₂) is identified as the key for CO₂ to formate electro-reduction. In summary, all these high quality works provided by the outstanding contributions in this highly attentive research area of CCUS will render this special issue to contribute a broad vision for the future research activities. Finally, we would like to express our sincere thanks to the reviewers and the editors for giving your time and expertise to review the papers and facilitate the publication of this issue.

Abstract: Reducing the anthropogenic CO₂ emissions from fossil resource combustion and human activities has become one of the major challenges we are facing today. Beyond those practical applications for the utilization of CO₂, such as the synthesis of salicylic acid, methanol, urea, NaHCO₃-Na₂CO₃ chemicals and recently developed polycarbonate synthesis, scientists are still seeking new materials and technologies for efficient capture, storage and conversion of CO₂ with consideration into reducing CO₂ emission at a large amount. Until now, CO₂ capture and utilization is not only an academic event but a social and government guiding project all over the world. The special issue in Journal of Energy Chemistry is an update of recent research works on the topic of carbon capture storage and utilization (CCUS) which covers the material and technology innovations for CO₂ capture and utilization. Five reviews, two communications and seventeen research articles are included in this special issue. As a first step for limiting the CO₂ emission, efficient capture of CO₂ with a cost-effective strategy, is likely to rely on new adsorbents and the development of technologies that can reduce energy consumption, especially for the separation of low concentrated CO₂ from coal-fired power plant flue gas and selective capture of CO₂ from humid gases. CO₂ molecules are often preferred to be adsorbed in porous materials with high surface area and abundant sorption sites. The concept of molecular basket sorbent (MBS) for CO₂ capture has been proposed by Song et al. in this special issue. They use polyethylenimine (PEI) or polyethylene glycol (PEG) to reside in the mesopore structure of SBA-15, TUD-1 and fumed silica HS-5 materials to provide plenty of amine sites for CO₂ adsorption. Zhong et al. synthesize a type of 2D covalent triazine-based framework material (namely, CTF-DCBT) for efficient capture of CO₂. CTF-DCBT contains ultramicropore (6.5 Å) and high heteroatom contents (11.24 wt% of N and 12.61 wt% of S), which is responsible for the highly selective CO₂/N₂ and CO₂/CH₄ preferential adsorption. Porous carbon materials with well-developed heteroatom doped sites are widely examined as CO₂ adsorbents. In the work of Ahn et al., nitrogen-doped carbon materials are synthesized by the carbonization of a low-cost porous covalent triazine polymer, PCTP-3. The textural properties of the porous carbon materials are additionally activated by KOH, to form a narrow micropore size distribution. A type of porous carbon sphere with highly developed ultra-microporosity and uniform pore size is prepared by Zhou and Zhuo et al. These well-designed porous carbon materials on purpose are examined as excellent adsorbents with high CO₂ capture capacity and selectivity. Pfeiffer and co-workers systematically investigate the CO₂ chemisorption process on a series of alkaline pentalithium aluminate (β-Li₅AlO₄) based solid solution. With an addition of alkaline carbonate compound or iron exchange with the aluminum position into β-Li₅AlO₄, the CO₂ chemisorption enhances. CO₂ molecules are more likely to reside on the superficial position of those (modified) alkaline solid solution adsorbents. CO₂ capture by ionic liquids (ILs) has also attracted wide attention. In the contributions of Yu et al. and Sun et al., a series of ILs monomers and ILs polymers (PILS) and a type of layered hybrids material containing ILs are prepared, respectively. Both the PILs and BMIMCl/LP layered hybrids are identified as efficient adsorbents with high CO₂ capture capacity. Zhang et al. select a series of [CnMIm][Tf₂N] ILs as physical CO₂ adsorbents and the adsorption condition is operated under a wide temperature and pressure range, which is appealing at higher temperature. Kanoh et al. examine the capacity and kinetics of CO₂ capture over K₂CO₃ adsorbent. In this work, a detailed study on the influence of temperature with changed moisture conditions and further insight into the NaHCO₃ formation mechanism has been carried out. Shi et al. employ a combination of WGS reaction and elevated-temperature pressure swing adsorption technology to deeply remove trace CO₂ and CO impurities to harvest high purity H₂ gas. The technology is based on potassium promoted hydrotalcite adsorbents, which can reduce the residual CO₂ concentration to 3.5 ppm after 12 h of temperature swing operation at 450 °C. In the search of highly efficient CO ₂ adsorbents under different real working conditions, Wang et al. and Ahn et al. critically review the development of molten salts modified MgO-based adsorbents and Amine-functionalized silica composite materials, respectively. Molten salts-modified MgO-based adsorbents show their advantages in the high adsorption capacity (the highest CO₂ capture capacity of 12.9 mmol g^-1 as reported), low cost, wide availability and suitable for the CO₂ capture at intermediate temperature range (200 –400 °C). Amine-functionalized silica composite materials are promising candidates for post-combustion CO₂ capture from low CO₂ concentrated flue gases. They show the advantages of excellent CO₂ uptake, selectivity, less sensitive to moisture and facile for the regeneration. Besides CO₂ capture, considerations about the recycling and utilization of CO₂ when using CO₂ as the abundant carbon resource are in progress to accomplish the challenging task of carbon neutral process. Direct catalytic conversion of CO₂ to value added chemicals or fuels has aroused great attention in both academic and commercial fields. Hydrogenation of CO₂ to formic acid and CO and other carbonaceous products in the lower carbon chemical valence state has been widely studied. Jin et al. investigate the auto-catalytic role of Zn/ZnO interface, which is formed in-situ during the reaction, in the transformation of CO₂ to formic acid in the water medium. They also provide an overview of the current advances in research of highly efficient reduction of CO₂ or NaHCO₃ into formic acid/formate by in-situ hydrogen from water dissociation with a metal/metal oxide redox cycle under mild hydrothermal condition. In the review made by Huang et al., the catalytic performance of CO₂-to-CO conversion and recent updates in designing of heterogeneous catalysts with high CO product selectivity and high temperature robustness are specifically elaborated. In the contribution of Chen et al., Ca(OH)₂ and 10% Ni/ZrO₂ are introduced in the biomass conversion processes of cellulose. Ca(OH)₂ greatly enhances the H₂ production rate with a yield of 36.4%, while the in-situ reforming of light gases and carbon capture processes significantly suppress the CO₂ formation. Ma et al. delicately design a dual active center containing Salen-Cu(II)@MIL-101(Cr) via the “ship in a bottle” approach, which is developed as the active catalyst for the synthesis of propylene carbonate from CO₂ and propylene oxide. The sorption enhanced methane reforming process of CO₂ has been studied by Pfeiffer et al. and Courson et al., by using CaO-NiO mixed oxide and CaO-Ca₁₂Al₁₄O₃₃, respectively. The studied catalyst systems show excellent chemical stability in obtaining syngas (H₂ + CO) with high CH₄ conversion and H₂ yield. Smart conversion processes such as chemical looping and mineral carbonation of CO₂ are capable of utilizing CO₂ at large quantities. Haider et al. describe the use of copper(II) oxides in combination with limestone in the form of a mechanical pelletizer as the oxygen carriers in the chemical looping processes. The oxygen carriers exhibit an enhanced crushing strength with high CO yield. Li et al. report the mineral carbonation processes of blast furnace slag with intention to reduce substantial CO₂ emission at large quantities. As a recyclable extractant, (NH₄)₂SO₄, is used to extract calcium and magnesium from blast furnace slag by using low-temperature roasting to fix CO₂ through aqueous carbonation. Alternatively, electrochemical reduction of CO₂ provides another promising way in reducing CO₂ emission, which can be delivered in the form of renewable energy. Co-electrolysis of CO₂ and H₂O using high-temperature solid oxide electrolysis cells (SOECs) into valuable chemicals is the topic of contribution made by Wang and Bao et al. The review discusses the so far cathode material development, the alternative cathode materials preparation strategies and the possible cathode reaction mechanism for CO₂/H₂O electrolysis. Different reaction modes of the CO₂/H₂O co-electrolysis in SOECs are summarized to offer new strategies to enhance the CO₂ conversion. Kang et al. report a nitrogen doped tin oxide material with enhanced Faradaic efficiency (90%) for CO₂ electro-reduction to formate, which also shows sulfur tolerance. The combined catalyst structure of partially reduced metallic tin and N-doped tin oxide (Sn/N-SnO₂) is identified as the key for CO₂ to formate electro-reduction. In summary, all these high quality works provided by the outstanding contributions in this highly attentive research area of CCUS will render this special issue to contribute a broad vision for the future research activities. Finally, we would like to express our sincere thanks to the reviewers and the editors for giving your time and expertise to review the papers and facilitate the publication of this issue.