Journal of CO2 Utilization最新文献

In this work, 25 % weight percentages of UiO-66 in TiO₂ nanoflower composite was treated with varying quantities of Tetraethylenepentamine (TEPA) to improve photoconversion of CO₂ into fuel using visible light (VL). The results revealed that maximum production rates of CH₄ and CH₃OH on TNF@25 %U-TEPA(2) sample were 64.59 and 2.47 µmol g_cat⁻¹ h⁻¹, respectively, at the optimum conditions of V-LP=150 W, P_CO2 =73 KPa, P_H2O =15 KPa and T=332.15 K. 15 LHHW models were evaluated based on different assumptions of rate determining step and the most abundant surface intermediate to obtain kinetics of the CO₂ photoconversion. The chosen model was the one that was closest to the experimental data. Furthermore, the kinetic rate and adsorption coefficients at T= 298.15–338.15 K and V-LP=150 W were obtained for the best-selected model. Finally, at T= 298.15–338.15 K, the activity energy of the produced CH₄ was determined as 3.6 kJ mol⁻¹.

Catalysis has optimized and improved production rates in many industrial processes. Conventional catalysis plays a key role in the mass-production of otherwise difficult to obtain substances. Plasma catalysis, plasma incorporation to appropriate catalysts, has been shown in literature to further outperform the typical conventional methods, and has shown potential to become a key production method in deep space exploration and survival. However, it faces a few more challenges that hinder it from being used industrially. In this review, we discuss known mechanisms in literature and the instrumentation and diagnostics that were utilized to be able to determine and explain these mechanisms in detail, and thus have led to the development of plasma catalysts with up to 80 % conversion rates for CO₂ conversion processes. We also discuss diagnostics that may be employed in the near future to reveal the last few unconventional mechanisms that must be explained in order to address the current instability and short life of catalysts due to the harsh conditions of plasma. In successful implementations of diagnostics in literature, they have proven to be the key to unlocking the knowledge required to develop appropriate catalysts optimized for converting CO₂ in a plasma environment.

Nowadays there is an urgent need for mitigating CO₂ emissions through clean energy and the development of new carbon capture and utilization (CCU) technologies. Among others, the use of bifunctional ionic liquids (ILs) addressed simultaneously CO₂ capture and conversion steps, having applied successfully to the propylene carbonate production case. In this work, a systematic evaluation of all representative cyclic carbonate literature was made, covering ethylene, propylene, butylene, hexylene, cyclohexene, and styrene cyclic carbonates, in order to guide the product role within the integrated CCU (ICCU) concept. The multiscale strategy combining molecular simulation (DFT -Density Functional Theory-, COSMO -COnductor-like Screening MOdel-), process simulation (COSMO/Aspen methodology), and life cycle assessment (LCA) was used to set up, simulate and evaluate the processes. ICCU configuration is the best approach when compared with sequential configuration for energy consumption analysis (reduction of 28, 28, 22, 11 and 6 %, respectively, for ethylene, propylene, butylene, hexylene, and cyclohexene cases) and CO₂ emissions associated (reduction of 38, 40, 31 and 14 %, respectively, for ethylene, propylene, butylene, and hexylene cases). The main variable of the results is the boiling point of the cyclic carbonate since heavy products impose technical limitations and even discard ICCU alternative. The ICCU concept works since all cyclic carbonates’ reaction enthalpies are higher than that of the IL-CO₂ one, which reduces heating requirements. Finally, energy demand can be slightly further reduced, partially recycling the cyclic carbonate to the capture unit.

Conversion of CO₂ into single-carbon (C1) or multi-carbon (C2+) compounds with high value-added chemicals is highly desirable but challenging. Under moderate, environmentally amiable conditions, photocatalysis may afford the deactivation and controllable C–C coupling of CO₂. Here, we prepared K₂Fe₂O₄/rGO, a photocatalyst containing magnetic ferrite, for CO₂ photocatalytic reduction. The optimized K₂Fe₂O₄/5 %rGO demonstrated the most efficient CO₂-to-methane conversion performance of 23.35 µmol g⁻¹ h⁻¹, which is 3.24 and 2.49 times the conversion rate constant of K₂Fe₂O₄ and rGO as photocatalytic catalysts, respectively. Therefore, the photocatalytic conversion of CO₂ to hydrocarbons [e.g., C_nH_2n+2, C_nH_2n, and C_nH_2n-2 (n = 1–5)] with K₂Fe₂O₄/rGO is an excellent method, with 100 % selectivity, for the production of multi-carbon hydrocarbons: 43 % CH₄ and 57 % C2+. The time-varying concentrations of hydrocarbon profiles for the photocatalytic reduction of CO₂ afford strong evidence for understanding the mechanisms underlying photoreduction. In an alkaline solution, K₂Fe₂O₄/rGO can mediate CO₂ photocatalytic reduction with simultaneous deoxygenation and C–C coupling.

Carbon-based materials have attracted significant attention in various catalytic applications. However, they are rarely reported for high-temperature catalytic reactions, owing to their limited thermal stability compared to other common materials such as silica and alumina, especially in oxidation reactions. CO₂ methanation became a pivotal research hotspot due to its ability to contribute to greenhouse gas mitigation. In addition, CO₂ methanation reactions can be carried out below 400 °C in a hydrogen atmosphere, which suits the thermal stability of many modified carbon materials. However, the number of reviews on CO₂ methanation does not match the huge number of the experimental publications on CO₂ methanation particularly reviews on carbon-supported catalysts. Motivated by the paucity of literature, including reviews on carbon-supported catalysts for CO₂ methanation, this review is focused on the catalytic performance of the carbon-supported catalysts of CO₂ methanation. It offers significant comparisons among all reported carbon-supported catalysts, providing a comprehensive study on the effect of the carbonaceous supports, such as graphene, biochar, and carbon nanotubes on the catalytic activity. In addition, it investigates the impact of promoters on the catalytic performance of the carbon-supported catalysts in CO₂ methanation and highlights the preparation methods and their optimized metal compositions that lead to the highest activity and selectivity. We conclude with a brief synopsis on the current challenges and perspectives on the future directions. This study paves the way for broader usage of carbon-supported catalysts for different thermal catalytic applications, not limited to CO₂ methanation.

With the development of the circular economy and low-carbon society, the large-scale application of construction solid waste in buildings, such as recycled concrete, is becoming imperative. Accurately predicting the carbonation depth of recycled concrete is of great significance. Quantitatively analyzing the impact of each parameter on carbonation and elucidating the relationships between these parameters present challenges in predicting the carbonation of recycled concrete. In this study, different machine learning models and prediction equation models were applied and compared to predict the carbonation depth of 576 datasets associated with recycled concrete. The machine learning models used include Automation Machine Learning (AutoML), LightGBM, CatBoost, Neural Networks, Extra Trees, Random Forest, XGBoost, KNN (K-Nearest Neighbor). The results indicate that the machine learning method shows higher accuracy than the traditional equation, the AutoML model exhibits the best prediction accuracy among the investigated machine learning models, and carbonation test results further verified the favorable carbonation depth prediction effects of AutoML model. Furthermore, SHAP (Shapley Additive Explanations) was utilized to quantitatively analyze and explain the prediction results. The results demonstrate that carbonation time and the water to cement (W/C) ratio of recycled concrete have the most significant impact on the carbonation depth of recycled concrete buildings.

DFT calculations on synthesis of benzothiazoles via cyclization of 2-aminothiophenols with CO₂ and triethoxysilane have revealed a novel mechanism that fundamentally differs from previously proposed mechanisms. In this new mechanism, the acetate anion plays a pivotal role in both stages of the reaction: first, in the formation of the formoxysilane intermediate via CO₂ reduction, and second, in its subsequent transformation to the product, benzothiazoles. The acetate anion acts as a nucleophile to activate the Si−H bond of triethoxysilane in the CO₂ reduction stage and as a base, deprotonating 2-aminothiophenol and generating a HOAc molecule, which then acts as a proton shuttle in the subsequent transformations leading to the final product. Throughout the whole reaction process, it is the acetate anion that plays a substantial role in catalyzing the reaction by activating the Si–H bond of triethoxysilane, contrasting with the previous notion that the imidazolium cation activates CO₂ through the formation of a NHC-CO₂ adduct. Furthermore, the proposed mechanism offers a rational explanation for the observed inefficiency of imidazolium trifluoromethansulfonate as a catalyst for this reaction. The elucidation of this new mechanism sheds light on the intricate details of the benzothiazole synthesis and may inspire further investigations in this field.

To reduce the environmental impact of cement production and carbon emissions, the use of supplementary cementitious materials to replace part of the clinker and carbonation curing are two of the most effective strategies for reducing carbon dioxide emissions in the cement and concrete industry. This study mainly explores the effects of calcined clay on cement-based materials under different curing conditions (normal curing and carbonation curing), as well as the synergistic effect of calcined clay and carbide slag under different curing conditions. The results demonstrate that: (1) Calcined clays can undergo pozzolanic reactions with hydration products such as Ca(OH)₂. Additionally, the acceleration of the carbonation rate by calcined clay is comparable to that of quartz powder, yet the strength during the later stages of carbonation is slightly higher than that of the sample with added quartz, possibly due to the generation of more gel. (2) The addition of quartz helps to enhance the rate of carbonation. However, when cement is replaced by quartz and burnt clay at the same time (the dilution effect is dominant and the diffusion of CO₂ is fast), it will cause premature carbonation of the samples, resulting in the later carbonation strength being lower than the normal cured strength. (3) The dilution effect caused by the large dosage replacement of calcined clay and calcium carbide slag leads to a reduction in strength. However, the higher Ca(OH)₂ content in carbide slag and its synergistic effect with calcined clay can mitigate some of the negative effects of dilution.

This study executed a series of tests to validate and assess the mechanical characteristics, pore structures, and chemical components of carbon consuming concrete (CCC), which employs an electric arc furnace (EAF) slag to enhance carbon consumption. Mixing variables were categorized based on the cement replacement ratio of electric arc furnace reduction slag (ERS) powder and the use of nanobubble water, which captured carbon dioxide (CO₂). The mechanical performance was appraised through a compressive strength test, while the shrinkage behavior in a high-concentration CO₂ atmosphere was observed to compare autogenous, drying, and carbonation shrinkage. Matrix homogeneity was determined through mercury intrusion porosimetry (MIP) analysis. Energy-dispersive spectrometer (EDS) mapping, differential thermogravimetry (DTG), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) were employed to examine the quantity of carbon fixation and the production of major components. The inclusion of ERS exhibited positive impacts on durability, such as increasing carbonation shrinkage resistance and reducing porosity in the long term. Concurrently, enhancements in compressive strengths were observed owing to the elevated formation of major components. Ultimately, it was established that the incorporation of ERS positively influences the amount of CO₂ consumption.

Global warming, primarily driven by emissions of greenhouse gases, particularly carbon dioxide, has emerged as a widely acknowledged concern. Hence, the development of novel carbon capture materials with high capacity and low cost holds substantial practical significance. This study investigates the influence of aging time, pH, and copper salt on the synthesis of Cu₂(OH)PO₄ and its CO₂ adsorption performance. Cu₂(OH)PO₄ adsorbents were synthesized under various aging time, pH, and copper salt conditions, and their morphology and surface functional groups were characterized. Experimental findings indicate that excessively prolonged or abbreviated aging times adversely affect the formation of distinct, discernible lamellar structures within the material. Different pH levels influence the stacking configuration of the lamellae, impacting both their thickness and size. Under acidic conditions, lamellae exhibit dispersed three-dimensional stacking; under neutral conditions, lamellae notably enlarge and demonstrate two-dimensional stacking; at pH 9, lamellae stack three-dimensionally and aggregate. Additionally, the CO₂ adsorption performance of Cu₂(OH)PO₄ adsorbents synthesized with different copper salts varies. By examining the relationship between surface functional group content and CO₂ adsorption capacity, we deduced the mechanism by which various synthesis conditions affect both surface functional groups and adsorption capacity. Cu₂(OH)PO₄ synthesized with a 24 h aging time, pH 7, and CuSO₄ as the copper salt exhibits the highest CO₂ adsorption capacity, achieving 1.006 mmol/g.