Journal of CO2 Utilization最新文献

The gas-phase CO₂ electroreduction to formate represents one of the most promising CO₂ conversion processes due to its scalability, as the product concentration surpasses 30 % wt. However, the use of alkaline media anolytes, intended to improve the efficiency and selectivity of formate production, causes the carbonate and bicarbonate salts to precipitate over the Gas Diffusion Electrode (GDE). This precipitation clogs the porous structure, leading to a rapid loss of electrode stability. In this work, we address this issue by proposing the use of acid anolytes, based on K₂SO₄, to mitigate the precipitation of insoluble salt on the GDE structure, thereby achieving longer and more stable GDE operation times. Various anolyte concentrations and pHs are evaluated, with 0.3 M K₂SO₄ at pH 1, adjusted using H₂SO₄, providing the best compromise. This condition inhibited potassium carbonate and bicarbonate precipitation, as observed through XRD, SEM, and EDS analysis, while maintaining high CO₂ electroreduction to formate performance, with a concentration of 69 g L⁻¹, and a Faradaic Efficiency of 33 %. Furthermore, the anolyte flowrate per geometric area is optimized to maximize the system performance. At a flowrate of 0.85 mL min⁻¹ cm⁻², enhanced concentration of 88 g L⁻¹ and a Faradaic Efficiency of 42 % are reached. Besides, long-term experiments demonstrated that GDEs used with alkaline conditions exhibit a larger deactivation constant (0.7652) compared to the GDEs used with acid anolytes (0.3891). This indicates that salt precipitation more rapidly reduces GDE performance under alkaline conditions. These results represent a promising advance in obtaining longer-lasting GDEs, which are crucial to successfully scaling up the CO₂ electroreduction to formate.

Acetate ester compounds find widespread use in various applications such as surface coatings, ink formulations, pharmaceuticals, and adhesives. It is essential to investigate the phase transition behavior of amyl acetate, amyl acetoacetate, and isoamyl acetoacetate in high-pressure supercritical CO₂ (SC-CO₂). The vapor-liquid equilibria (VLE) of the SC-CO₂ + amyl acetate, SC-CO₂ + amyl acetoacetate, and SC-CO₂ + isoamyl acetoacetate systems were examined at different temperatures (313.2 ≤ T ≤ 393.2 K) and pressures (1.67 ≤ P ≤ 20.76 MPa). The solubility curve of these systems shows Type-I phase behavior, and the critical points of these binary mixtures were observed between the critical properties of the pure components involved in the systems. The solubility of amyl acetate, amyl acetoacetate, and isoamyl acetoacetate in the SC-CO₂ + amyl acetate, SC-CO₂ + amyl acetoacetate, and SC-CO₂ + isoamyl acetoacetate systems increases with increasing temperature at constant pressure. The two-parameter model of Peng-Robinson equation of state along with a mixing rule, accurately correlated the phase transition behavior and critical mixtures curves for all three systems. The binary interaction parameters (BIPs) were adjusted, and the minimum root mean square deviation percentage was identified for all three systems. The calculated error% was found to be within reasonable limits, with values of 4.95 %, 3.93 %, and 4.18 % for SC-CO₂ + amyl acetate, SC-CO₂ + amyl acetoacetate, and SC-CO₂ + isoamyl acetoacetate systems, respectively. Furthermore, the interaction parameters for the SC-CO₂ + amyl acetoacetate mixture was found to be temperature-dependent, and the tested linear regression correlation coefficient for the BIPs parameters of (k_ij) and (η_ij) are 0.98533 and 0.99083, respectively. This is the first research study on the phase behavior of acetate ester compounds in SC-CO₂ solvents, and the results have a significant impact on industries at different operating conditions.

We synthesized a core-shell resin structure with abundant architecture and excellent thermal stability through polymerization. Imidazole ionic liquid with varying carbon chain lengths was immobilized on the surface, resulting in the preparation of metal-free, halogen-free core-shell catalysts with different carbon chain lengths via HCO_3^- exchange. Characterization using FT-IR, XPS, and various techniques revealed the exceptional performance of our synthetic catalyst in terms of its internal structure. After extensive experimentation, we discovered that the synthesized catalyst exhibits dual functionality for epoxidation and CO₂ cycloaddition reactions without requiring solvents or co-catalysts. The epoxidation system demonstrated remarkable conversion rates and selectivity while also exhibiting strong recyclability in heterogeneous reactions, according to kinetic parameters, the reaction order of styrene, TBHP and catalyst during epoxidation is approximately 1, the reference factor for this reaction was calculated to be 6.7×10⁹ (L²·mol⁻²·min⁻¹), with an activation energy of 48.9 kJ/mol obtained from analyzing reaction rates at different temperatures. In the CO₂ cycloaddition reaction, our catalyst exhibited an advantage in catalyzing ring-opening reactions, achieving a conversion rate of 95 % for styrene oxide within six hours along with over 99 % selectivity towards cyclic carbonate formation. It is suggested that the epoxide reaction is carried out in steps, and it is inferred that the catalyst PS-ImC₄HCO₃ and TBHP are produced into peroxy intermediate active species TBA and HCO₄, and the reaction between HCO_4^- and styrene is the determination step of the total reaction. The reaction rate constant k=0.009 of the absolute step is calculated based on the global optimization algorithm

We investigate the potential to reduce costs and greenhouse gas emissions of the utilization of direct air capture of CO₂ (DAC) for the production of algal biofuel. We examine four integrated designs for a DAC system comprised of solid amine monolith adsorbents delivering CO₂ at the required level for algae cultivation with a photobioreactor (PBR)-based fuel production facility. We show that the integration of DAC with this biofuel production facility provides cost and greenhouse gas emissions benefits. Heat integration decreases operating expenses by reducing energy demand for heating requirements. Mass integration, utilizing flue gas CO₂ as a carbon source for the PBRs, decreases the DAC system scale, resulting in both capital and operating cost savings. The most advantageous option depends on the interplay of heat and mass integration while matching the diurnal rhythm of algal growth with the inherently steady pace and energy requirements of the DAC system and fuel production. For these technologies, the DAC-PBR mass and energy integration provides an 18 % cost reduction and a 50 % reduction in greenhouse gas emissions for the current state of the technology.

Light olefins are critical chemical materials with high global demand. The syngas-to-olefins (STO) process offers a promising pathway for light olefin production due to the versatility of syngas production technologies from various energy sources. However, achieving high carbon monoxide (CO) conversion and selectivity for olefins remains a challenge in catalytic development. This review categorizes STO catalysts into conventional Fischer-Tropsch catalysts, including unsupported and supported metal-based catalysts (with supports such as carbon, graphene, graphene oxide, zeolites, and metal oxides), as well as bifunctional, hybrid, and emerging core@shell structured catalysts. Another type of catalyst is core@shell structure catalyst, which is a developing method widely used for FT reactions. The performance of these catalysts is influenced by their materials, chemical compositions, operating conditions, and synthesis techniques. Unsupported catalysts, especially Fe-based and Co-based, exhibit high CO conversion but face issues like rapid deactivation and complex processing requirements. Supported catalysts enhance surface area, metal dispersion, and stability, with promoters such as Na, Mg, K, Mn, Zn, V, Zr, and Cu oxides improving catalytic activity through better CO adsorption and bond modulation. Zeolites, due to their acidic properties, significantly impact reactant adsorption and activation. Catalyst preparation methods, including impregnation, co-precipitation, sol-gel, and hydrothermal synthesis, alongside post-synthesis treatments like calcination and reduction, critically affect catalyst performance. This review provides a comprehensive overview of the light olefin production from syngas, detailing the roles of various catalysts and the impact of material types, operating conditions, and synthesis techniques on catalyst activity, and selectivity. The insights aim to guide future research and development towards more efficient and sustainable light olefin production processes.

The influence of the support on catalytic activity and stability of supported 2Cr-Fe bimetallic catalysts for the CO₂-assisted dehydrogenation (DH) of n-octane has been investigated. Four MgO modified supports viz; MgO-CeO₂ (MgCe), MgO-ZrO₂ (MgZr), MgO-CeO₂-ZrO₂ (MgCeZr) and MgO-SiO₂ (MgSi) were synthesized by the sol-gel combustion technique. The supported catalysts were in turn prepared by vacuum impregnation and thereafter tested for the CO_2-assisted DH of n-octane. The catalysts were characterized by inductively coupled plasma optical emission spectroscopy (ICP-OES), X-ray diffraction (XRD), N₂-physisorption, Raman spectroscopy, transmission electron microscopy (TEM), electron dispersive x-ray (EDX), temperature programmed desorption of CO₂ (CO₂-TPD), temperature programmed reduction and oxidation (H₂-TPR and CO₂-TPO), electron paramagnetic resonance (EPR) and thermal gravimetric analysis (TGA) techniques. Raman results showed that the CrO_x is stabilized as mono- and/or polynuclear Cr(VI) species over the 2Cr-Fe/MgCe catalyst, which are reduced to lower oxidation state species during the DH reaction. The 2Cr-Fe/MgZr, 2Cr-Fe/MgCeZr and 2Cr-Fe/MgSi catalysts stabilized the CrO_x as polymerized species, forming the more active Cr-O-Fe polymer units on the catalysts’ surface. XRD, TEM and EDX results showed that the ZrO₂-containing supports have smaller particles and stabilized the active metal oxides in a more dispersed amorphous state. The CO₂-TPO of the pre-reduced catalysts and EPR of the used catalysts indicated that the 2Cr-Fe/MgCeZr undergoes significant re-oxidation by CO₂ during the catalytic process. The 2Cr-Fe/MgCe was the least active, while the 2Cr-Fe/MgZr catalyst showed the best performance and stability over three regeneration cycles. Selectivity to C8 products (octenes and aromatics) was found to strongly depend on the surface basicity of the catalysts. Deactivation of the catalysts was found to follow first order kinetics and coke deposition was identified as the major cause.

Reducing atmospheric CO₂ levels to combat global warming is a pressing concern today. Numerous methods have been employed to capture CO₂ from flue gases. One particularly promising approach is the use of carbonic anhydrases (CAs) as biocatalysts for the rapid conversion of CO₂ to H₂CO₃. However, the widespread application of CAs for CO₂ capture has been hampered by their inherent instability under real-world conditions. In this study, we have successfully engineered a chimeric carbonic anhydrase with vastly improved physicochemical properties, particularly with respect to its resilience to high temperatures, alkaline pH, and saline environments. Using computational design, we created various hybrid CAs with enhanced resistance to elevated temperatures. Among them, a chimeric CA known as SPS, generated by domain exchange between SazCA and PmCA, exhibited superior heat stability compared to its parent CAs. SPS showed 10 % higher enzymatic activity and retained 80–13 % of its activity during a period of 3 h to 24 h of incubation at 100℃. SPS's apparent k_cat and K_m values were 4.84 × 10⁸ s⁻¹ and 13.7 mM, respectively. Structural analysis revealed that SPS forms dimers, which contributes to its robustness. Furthermore, we introduced modifications in the form of SPS_1 and SPS_2 variants by incorporating one or two loop sequences from the halotolerant dCAII into SPS. These modifications significantly improved the stability of the CA in alkaline and saline conditions. In particular, SPS showed remarkable efficiency in hydrating CO₂ in seawater. Given these compelling results, we propose that hybrid CAs such as SPS, SPS_1, and SPS_2 hold great promise for facilitating CO₂ hydration in a wide range of applications.

Synopsis

Greenhouse gas sequestration is an immediate need. This study reports an engineered and highly stable carbonic anhydrase for CO₂ sequestration and greenhouse gas reduction.

Aerogels based on natural polymers are of increasing interest in the biomedical field due to their biocompatibility, bioactivity, biodegradability and, in certain cases, extracellular matrix biomimicry. However, sterility has been a critical quality attribute limiting the use of aerogels in biomedicine. This work introduces a new and environmental-friendly technique based on the use of CO₂ called in situ sterilization that enables the manufacturing of sterile aerogel in a one-pot process. Starch aerogel cylinders and alginate aerogel beads enclosed within sterilization pouches were produced using this approach. The study involved the redesign of the flow diagram for aerogel production and the study of the effect of key parameters in the process (additive type and content, agitation, CO₂ flow regime type and duration) on the resulting material. The obtained materials were evaluated regarding their texture (helium pycnometry, N₂ adsorption-desorption analysis, SEM) and their sterility against three standardized bioindicators. Finally, the sterile aerogel materials were put in contact with NIH-3T3 cells assessing their cytocompatibility. Under the optimal operating conditions with 4.5 h of processing time, the aerogels were sterile, cytocompatible and had a porosity of ca. 80 % and a specific surface area of ca. 80 m²/g and 200 m²/g, for starch and alginate aerogels, respectively. Results allowed to identify the feasible operating region as well as the optimum processing values to obtain the typical nanostructure of aerogels, whilst ensuring suitable regulatory sterilization levels for aerogel implantation and cytocompatibility of the sterile material with fibroblastic cells.

Surface functional groups (SFGs) play a key role in adsorption of any target molecule and CO₂ is no exception. In fact, due to its quadrupole nature, different SFGs may attract either the oxygen or the carbon atoms to facilitate improved sorption characteristics in porous materials, hence the proliferation of this approach in the context of carbon capture via solid adsorbents. However, actual processes involve CO₂ capture/removal from a mixed gas stream that may have a non-negligible water content. The presence of humidity significantly hampers the sorption properties of classical physisorbents. To overcome this, the surface of the adsorbent can be modified to include hydrophobic/hydrophilic SFGs making the materials more resilient to moisture. However, the mechanisms behind H₂O-tolerance depend greatly on the characteristics of SFGs themselves. Herein, a multitude of hydrophobic and hydrophilic SFGs (e.g. carbonyls, halogens, hydroxyls, nitro groups, phenyls, various alkyl chains and etc.) for physical CO₂ adsorption are reviewed within the context of their separation performance in a humid environment, highlighting their merits and limitations as well as their impact on cooperative or competitive H₂O – CO₂ adsorption.

This study explores the combined effects of coal fly ash (FA) and CO₂ curing on the flexural strength, compressive strength, and water resistance of magnesium potassium phosphate cement (MKPC). Additionally, the hydration products and microstructure of MKPC and MKPC-FA blends are examined using X-ray diffraction (XRD), thermogravimetric analysis (TGA), mercury injection porosity (MIP), and scanning electron microscopy (SEM). The results demonstrate that carbonation curing effectively improves the mechanical strength and water resistance of MKPC-FA blends by refining the pore structure and reducing porosity. Incorporating fly ash into magnesium phosphate cement leads to a longer setting time and appropriate enhancement in the water resistance of MKPC-FA blends. It should be mentioned that the mechanical strength of MKPC-FA blends declines with increasing fly ash content, and carbonation curing can partially ameliorate these negative effects. Therefore, both incorporating fly ash and storing carbon dioxide have positive effects on the durability and environmental sustainability aspects associated with MKPC preparation.