Journal of CO2 Utilization最新文献

A series of metal oxides, i.e., CuO、NiO、Co₃O₄、ZrO₂、Al₂O₃, catalysts were prepared by hydrothermal method and evaluated in the production of glycerol carbonate by coupling of glycerol and CO₂ under lower temperature. The results show that CuO showed the best catalytic performance (glycerol conversion and the glycerol carbonate selectivity were 89.0 % and 69.4 %, respectively) at 120 ℃ under 3.0 MPa of CO₂ for 5 h. This is the highest yield of glycerol carbonate using same mothed reported in the literature so far. The structures, morphologies and surface properties of the catalysts were characterized by X-ray powder diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), N₂ adsorption-desorption, Temperature programmed reduction (H₂-TPR), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), Temperature programmed desorption (TPD). It is speculated that the high catalytic activity of CuO mainly depends on its unique structure and acid-base physicochemical properties. In addition, the CuO catalyst was used 7 times without obvious deactivation, which suggesting this catalysis has excellent reusability.

Converting waste or hazardous chemicals into valuable products is a paramount consideration from economic, environmental, and sustainability standpoints. Diverse strategies are under exploration to convert CO₂ into valuable or fine chemicals, encompassing electrocatalysis, thermo- and photo-catalysis, and chemical fixation. Amid these avenues, the electrochemical CO₂ reduction reaction (CO₂RR) emerges as exceptionally promising, driven by its manifold advantages and the growing accessibility of renewable electricity sources. While CO₂RR has witnessed substantial advancements, most endeavors remain in the proof-of-concept phase, necessitating improved catalytic efficiency and stability to enable industrialization. Realizing the industrial viability of CO₂RR technology mandates meticulous consideration of a myriad of electrocatalyst-related factors. This review delves into critical industrial criteria and recent catalytic materials with the potential to drive CO₂ reduction at an industrial scale. These factors, akin to other catalytic processes, closely relate to catalytic activity, product selectivity, catalyst/system stability, and catalyst cost. In this context, we investigated the criteria that define electrocatalysts as industrially feasible, considering factors such as Faradaic efficiency, current density, energy efficiency, stability, overpotential, and the choice of catalyst materials. Furthermore, we highlight prime examples demonstrating high potential for this process and categorize them based on the reaction products. To offer a comprehensive perspective, this review also discusses the fundamental principles of CO₂RR, covering the physicochemical properties of CO₂, cell configurations, electrolyte compositions, and the role of electrocatalysts. We also address the economic significance of various CO₂RR products.

The reverse water-gas shift reaction (rWGS) is of particular interest as it is the first step to producing high-added-value products from carbon dioxide (CO₂) and renewable hydrogen (H₂), such as synthetic fuels or other chemical building blocks (e.g. methanol) through a modified Fischer-Tropsch process. However, side reactions and material deactivation issues, depending on the conditions used, still make it challenging. Efforts have been put into developing and improving scalable catalysts that can deliver high selectivity while at the same time being able to avoid deactivation through high temperature sintering and/or carbon deposition. Here we design a set of perovskite ferrites specifically tailored to the hydrogenation of CO₂ via the reverse water-gas shift reaction. We tailor the oxygen vacancies, proven to play a major role in the process, by partially substituting the primary A-site element (Barium, Ba) with Praseodymium (Pr) and Samarium (Sm), and also dope the B-site with a small amount of Nickel (Ni). We also take advantage of the exsolution process and manage to produce highly selective Fe-Ni alloys that suppress the formation of any by-products, leading to up to 100% CO selectivity.

The development of efficient processes for value-added utilization of low-concentration CO₂ is an on-going challenge. In this work, we present a sequential system based on diamine platforms for the direct utilization of low-concentration sources of CO₂ (≤15%) in the production of cyclic ureas. Specifically, the low-concentration CO₂ is captured by ethylenediamine to form ethylenediamine carbamate (EDA-CA), which subsequently undergoes the intramolecular dehydration to give ethyleneurea (EU) in the presence of frustrated Lewis pairs (FLPs) on the facet-engineered CeO₂. Remarkably, the productivity of EU obtained from EDA-CA in the sequential system (9.5 mmol·g_cat⁻¹·h⁻¹) is ∼4 times higher compared to the traditional catalytic system (2.4 mmol·g_cat⁻¹·h⁻¹) using ethylenediamine and pure CO₂ (3 MPa). Density functional theory calculations demonstrated that the FLPs on facet-engineered CeO₂ significantly reduce the energy barrier for the nucleophilic attack of N-containing segment towards the carbonyl carbon in EDA-CA (rate-limiting step), ultimately optimizing the intramolecular cyclization efficiency of EDA-CA. This work not only provides an innovation tandem approach that enables the production of cyclic ureas from low-concentration CO₂, but also opens up a promising avenue for the direct utilization of low-concentration CO₂ for value-added applications in the future.

Thermochemical conversion of CO₂ in biomass gasification is a promising technology for utilizing CO₂ as a feedstock to produce a CO-rich gas. Simultaneous decomposition reactions of biomass and various gas-solid and gas-gas reactions form the product gas in this process. The overlap in sub-processes makes it challenging to assess the conversion of feedstock CO₂ with common methods like mass balancing. This work introduces stable carbon isotope ratio analysis (δ¹³C) to identify the sourcing of carbonaceous product gas components and determine the conversion of CO₂. This methodology is applied to evaluate experiments conducted for one hour of continuous operation in a lab-scale fluidized bed gasifier. Softwood pellets and wood char are used as fuel, with Olivine as a bed material, a target heating temperature of 1000 °C and atmospheric pressure. Product gas with more than 80 vol% CO was generated when wood char was used as fuel. Stable carbon isotope measurements show that CO₂ is converted at 48–93% in this process, underpinning the position of biomass CO₂ gasification as carbon capture and utilization technology. These results were up to 25% higher than suggested by mass balancing, with higher discrepancies at lower CO₂ conversions when using softwood as fuel. Therefore, stable carbon isotope ratio measurement can be a valuable tool for improving the process understanding of biomass CO₂ gasification. The results can be used for carbon accounting and the technical development of gasifiers with high CO₂ utilization efficiency.

Integral coal honeycomb monoliths were easily prepared achieving the cell densities typical of commercial cordierites through extrusion plus physical activation. Different techniques such as volumetric adsorption, TGA, TPD and transient kinetic analysis were employed to study their interaction with CO₂ at different temperatures (35–100 °C) and under both static and dynamic atmosphere. The CO₂ capture capacity resulted to be 0.95 mmol/g at 35 °C, much higher than that of previously studied clay honeycomb adsorbents. The CO₂ uptake exhibited fast second order kinetics, and a wide operative window for a highly efficient CO₂ removal was found. Moreover, due to a weak interaction, most CO₂ adsorbed could be released at 110 °C, what allows minimizing the costs related to controlled regeneration if ones wants to reuse the captured CO₂ but at the same time prevents from desorption when this is undesirable. Treatment of the coal honeycomb monolith with a 1:1 CO₂+CH₄-containing stream revealed, through gas chromatography analysis, the conversion into syngas at relatively low temperatures (50% at 750 °C) in spite of the metal-free character of the monolith. Moreover, this activity reached 90% and remained quite stable for at least 12 h at 900 °C. These results demonstrate the potential of preparing honeycomb monoliths from coal as a strategy to diversify the uses of this abundant natural resource and as an alternative in the field of CO₂ capture and valorization.

Microbial electrosynthesis (MES) enables the production of carbon-neutral chemicals using CO₂ as a carbon source. Acetic acid is the main MES product, but recent studies show the direct production of elongated carboxylic acids, e.g., butyric and caproic acid. However, the production of elongated acids in MES systems is still inefficient due to the low growth rates of acetogenic bacteria and to limited solventogenic rates. Subsequently, researchers have produced elongated carboxylic acids directly from acetic acid or have operated MES systems at low pH to favor solventogenesis. However, the effect the addition of different chain elongation precursors and the operation pH exerts in the bioelectrochemical production of elongated acids remains unclear. To investigate this, three pH-controlled MES systems were operated in this study with continuous liquid and gas supply. MES systems elongating acetic acid at pH 6 achieved higher butyric (0.71 vs. 0.42 g L⁻¹) and caproic acid (0.71 vs. 0.42 g L⁻¹) titers in the absence of CO₂ sparging. Additionally, lowering the pH to 5 in the MES systems fed with CO₂ and acetic acid improved the elongated acids titers, reaching 0.72 g L⁻¹ butyric and 0.33 g L⁻¹ caproic acid. The 16 S rRNA analysis showed the community was dominated by Oscillibacter at pH 6, and by Clostridium at pH 5. Furthermore, the first scanning electron microscopy pictures revealing biofilm stratification in MES cathodes were taken in this study, where homogeneous rod-shaped bacteria biofilm layers, in contact with the graphite cathode, were covered by heterogeneous biofilm layers.

Synthetic natural gas (SNG) is of great interest in reducing fossil energy consumption while maintaining compatibility with existing NG infrastructure and end-use applications equipment. SNG can be produced using clean H₂ generated from renewable or nuclear energy and CO₂ captured from stationary sources or the atmosphere. In this study, we develop an engineering process model of SNG production using Aspen Plus® and production scales reported by the industry. We examine the levelized cost and life cycle greenhouse gas (GHG) emissions of SNG production under various CO₂ supply scenarios. Considering the higher cost of H₂ transportation compared with CO₂ transportation, we assume that CO₂ feedstock is transported via pipeline to the H₂ production location, which is collocated with the SNG plant. We also evaluate the cost of CO₂ captured from the atmosphere, assuming the direct air capture process can occur near the SNG facility. Depending on the CO₂ supply chain, the levelized cost of SNG is estimated to be in the range of $45–76 per million British thermal units (MMBtu) on a higher heating value (HHV) basis. The SNG production cost may be reduced to $27–57/MMBtu-HHV by applying a tax credit available in the United States for low-carbon H₂ production (45 V). With a lower electricity price of 3ȼ/kWh for water electrolysis and accounting for a 45 V tax credit, the SNG cost reaches parity with the cost of fossil NG. Depending on the CO₂ supply chain, SNG can reduce life cycle GHG emissions by 52–88 % compared with fossil NG.

With the intensification of the global greenhouse effect, the utilization and fixation of CO₂ has become one of the most important research fields in our world. However, there are still enormous challenges in achieving efficient fixation and conversion of carbon dioxide into high-value chemicals. Herein, the cycloaddition reaction strategy is adopted to achieve the fixation of supercritical carbon dioxide (SC-CO₂) and the high-value conversion of carbon resources to propylene carbonate (PC) by using propylene oxide (PO) as the reaction precursor. Under tetrabutylammonium bromide (TBAB) as a catalyst and water (H₂O) as a green solvent, the reaction factors, such as reaction temperature, reaction pressure, catalyst amount, water concentration and molar ratio of reactants, is conducted through the high-throughput screening technology to explore the catalytic performance in a self-designed microchannel reactor. The results indicate that the yield of PC can reach 91.82 % (along with a high selectivity of 99.12 %) at a reaction temperature of 160 ℃, reaction pressure of 8 MPa, catalyst amount of 0.72 mol %, reactants molar ratio of 8, and the residence time of 482 s. Besides, the thermodynamic and kinetic for carbonate synthesis are studied to fully understand the reaction process, and the activation energy of is explored. This work is more efficient than most similar reported works, which provide valuable insights into the practical application of CO₂ in the supercritical state combined with microfluidics for synthesizing high-value monomers.

The cycloaddition reaction of CO₂ with epoxides such as limonene epoxide (LE) to form cyclic carbonates is considered a promising alternative for reducing CO₂ emissions. In this work, CO₂ fixation on LE to produce cyclic carbonates was carried out over Zn/SBA-15 with tetrabutylammonium bromide (TBAB) as co-catalyst and over NH₃X-Zn/SBA-15 (X= Cl, Br, or I) catalysts. The catalysts were characterized by FT-IR, XRD, N₂ adsorption–desorption isotherms, TEM, NH₃-TPD, XPS, TGA and Py-FTIR. The Zn/SBA-15 support mainly presents Lewis’s acid sites of medium acidity; the surface area was 512 m²/g and 378 m²/g and the pore size were 9 nm and 7.2 nm, for Zn/SBA-15 and NH₃Cl-Zn/SBA-15, respectively. The functionalization of Zn/SBA-15 was verified by FTIR, UV-vis, and XPS analysis. It was found that when Zn/SBA-15 was used as catalyst that reaction time had a significative effect on LE conversion and in the case of limonene carbonate selectivity, co-catalyst concentration variation had the main effect. Zn/SBA-15 catalyst can be reused up to 5 times without significant changes neither in conversion nor in limonene carbonate selectivity. The best LE conversion and limonene carbonate selectivity was 33% and 93%, respectively (1 M LE, 200 mg Zn/SBA-15, 7% TBAB; 30 bar, 18 h, 700 rpm and 20 mL diethyl carbonate). The reported catalytic system is a promising system for obtaining limonene carbonate using a heterogeneous catalyst.