Atmospheric Pressure CO2 Research Articles

Enhanced CO2 Hydrogenation Performance of CoCrNiFeMn High Entropy Alloys

CO2 hydrogenation is a promising process for removing anthropogenic CO2 emissions and yielding C1 chemicals that can be utilized as fuels and valuable precursors for chemical synthesis. Commercial high-entropy alloys (HEAs) have widespread application in various fields owing to their exceptional thermal stability and tunable microstructure. However, their potential application as catalysts is often limited by the low exposure of active sites. In this study, the commercial CoCrNiFeMn powder was applied for atmospheric pressure CO2 hydrogenation and enhanced its catalytic performance by a combined treatment of ball milling and high-temperature H2 reduction. The high-energy ball milling results in a morphological transition in CoCrNiFeMn HEAs from spherical to irregular. This transformation leads to a significant decrease in particle size and more surface reactive sites. The high-temperature H2 reduction promoted the atomic rearrangement on the CoCrNiFeMn surface, thereby improving its alloy structural homogeneity. These modifications greatly improve the performance of CoCrNiFeMn for CO2 hydrogenation. This work introduces a facile modification approach to facilitate the catalytic efficiency of commercial HEAs in CO2 hydrogenation with high selectivity.

Surface loss probability of atomic oxygen on silica under atmospheric-pressure CO2

Abstract The surface loss probability γ O of atomic oxygen was measured for SiO2 in atmospheric-pressure CO2 and Ar/CO2(3.05%) mixture at 300 K. O atoms were produced via the photolysis of CO2 using a 172 nm Xe2 excimer lamp. After irradiation by Xe2 lamp, the working gas flowed through a quartz tube, causing O atoms to be lost on its inner surface. By measuring the density of O atoms at the end of the tube for different tube lengths, we obtained the value of γ O on the inner surface of the tube. The measured value was 5.5 × 10 − 4 ± 50 % , which falls within the range of referred values of γ O ( 1 × 10 − 5 to 1 × 10 − 3 ) at 4 to 1300 Pa measured using low-pressure O2 plasmas. Despite the 2 to 5 orders of magnitude pressure difference, no significant difference in γ O was obtained. The potential influence of the difference in background gas (CO2 and O2) on the value of γ O was also considered.

Ionic Polymers with Phenolic Hydroxyl Groups as Hydrogen Bond Donors Toward Enhanced Catalytic Performance for CO2 Conversion

AbstractIn this study, imidazolium‐based multifunctional ionic polymer (IP 1–IP 3) series, co‐incorporated with phenolic hydroxyl groups as hydrogen bond donors (HBDs) and Cl− as nucleophiles, are synthesized by a facile quaternization method. The physicochemical characterizations of these IPs are systematically examined by using FTIR, XPS, BET, TGA, CO2‐TPD, SEM with elemental mapping and TEM methods. Their catalytic activities are evaluated toward the conversion of carbon dioxide (CO2) and epoxides into cyclic carbonates under solvent‐ and additive‐free environments. Apart from the synergy effect between HBDs and Cl−, it is found that the types of the spacer linking the two imidazole units in the diimidazole precursors (L1–L3) also play an important role in the catalytic activity. And IP 2, with a pyridine spacer as a Lewis base site, exhibits the best catalytic performance under solvent‐free mild conditions i. e., atmospheric pressure CO2, 80 °C, and 5 h. Notably, the catalyst demonstrates a good substrate applicability. Furthermore, IP 2 exhibited good reusability, stability, and it can be recycled for ten successive runs with stable and potential catalytic activity. This study provides an alternative route to construct IPs with efficient activity for CO2 catalytic conversion and fixation under mild‐conditions.

88‐2: The Characteristics Analysis for Laser Cutting Process of Multilayers Display Panels

In this study, we analyzed the laser cutting characteristics of pulse transverse electrical discharge in gas at atmospheric pressure (TEA) CO2 and ultraviolet (UV) pulse laser processing in a multilayer display panels. First, the numerical calculation for was performed to confirm the thermal characteristics of each materials and optical field distribution at the interface of different material layers. Also, processing characteristics were experimentally confirmed by measuring cutting profile and adhesion characteristics of layer interface. Experimental results show that the characteristics of multi layers polymer cutting have different trend from those in a single‐layer because of the optical and thermal properties of each layer. In particular, the interface of layers had a substantial affect due to optical field distributions and thermal characteristic difference. Also, the optical absorbance of layers affect adhesion at the interface. The result suggests proper processing condition to enhance the laser ablation processing quality of multilayer display panel. In conclusion, understanding the characteristics of multilayer laser cutting processing is important for determining the optimal conditions for display panel micromachining and enhancing the quality of laser cutting for the cutting edge technology.

Carbonation of Recycled Concrete Aggregates for New Concrete and Concrete Fines to Make Cement-Free Hollow Blocks

Mineral carbonation provides a way to increase the recycling of concrete waste in added-value products, and contributes to the principles of the circular economy. At present, most concrete waste is still downcycled. The high water absorption of recycled concrete aggregates, among other factors, impedes their recycling in the concrete industry. The quality of coarse recycled concrete aggregates (RCA) can, however, be enhanced by carbonation. Even when starting with high-grade RCA obtained from a selective demolition process, the carbonation process can decrease the water absorption of the RCA to as low as 3.0%. Concrete with a 50% replacement rate of carbonated RCA can be produced without a significant compressive strength reduction. The research further shows that carbonation can be performed at atmospheric pressure and low CO2 concentrations (e.g., 10%). The recycled concrete fines (RCF, 0–4 mm) in combination with 25% stainless steel slag were used to make zero-cement hollow blocks (39 × 19 × 9 cm) by carbonation curing without using any hydraulic binder. The hollow blocks have a compressive strength of 15.4 MPa at the lab scale. Both technologies were demonstrated on a pilot scale. In both processes, CO2 is immobilized in the resulting construction product. The developed production processes use less primary raw materials and cause less greenhouse-gas emissions than the production of traditional concrete products.

Tuning basic poly(ionic liquid) solutions towards atmospheric pressure CO2 capture

Ionic liquids and poly(ionic liquid)s are interesting materials for CO2 capture, however, the deployment of their industrial application has been delayed on account of economic and technical issues that demand further optimization. The control over viscosity has serious consequences over the process, therefore, this work is focused on the study of imidazolium and pyrrolidinium-derived ILs and PILs with basic anions, such as acetate, hydroxide, and imidazolate that were synthesized and characterized by NMR, ATR-FTIR, TGA, and DSC. Different solvents and concentrations were tested in the preparation of PIL and IL solutions, which were used to capture CO2 by bubbling this gas at room temperature and atmospheric pressure (1 atm). The evaluation of the CO2 sorption capacity of each sample was carried out through the analysis of quantitative 13C NMR. The poly(1-vinyl-3-ethylimidazolium) acetate showed and sorption capacity of 5.68 mmol CO2/g PIL, and also the capacity to capture CO2 from exhaust gas mixture and the possibility to be recycled at least 5 times.

Self-consistent treatment of gas heating in modeling of a coaxial DBD in atmospheric pressure CO2

This work is devoted to the numerical study of characteristics of dielectric barrier discharge maintained in a coaxial reactor in atmospheric pressure . The numerical model is based on the drift-diffusion theory of gas discharges, and takes into account the gas heating in a self-consistent manner. The effect of incorporating gas heating into the discharge properties, specifically, on decomposition, is investigated for wide range of amplitude and frequency of the applied voltage. Calculations revealed a significant effect of gas heating on conversion. Calculations with a constant (room) gas temperature led to a strong overestimation of conversion level.

Laboratory tests of CO2 laser collective Thomson scattering for measurements of ion temperature in the divertor.

Collective Thomson scattering (CTS) is a diagnostic method that measures the ion velocity distribution of a plasma. CO2 laser CTS measurements are challenging because of the inherently small Doppler broadening and scattering signals that are difficult to detect. We implemented a heterodyne detection scheme to measure spectrum changes of less than a GHz. To maximize the collected light at small scattering angles, we designed a unique light collection approach consisting of a customized conical-shaped (axicon) lens with a hole in the center. The axicon lens is used to collect the scattered light emitted within an annular cross-section from the scattering volume while the probe beam is passed through the hole at the center of the lens. The performance of the heterodyne detection scheme and annular collection approach was demonstrated using a Transverse Excited Atmospheric pressure CO2 laser with a pulse energy of 160 mJ at λ = 10.59 µm.

Towards a unified theory of plant photosynthesis and hydraulics

The global carbon and water cycles are governed by the coupling of CO2 and water vapour exchanges through the leaves of terrestrial plants, controlled by plant adaptations to balance carbon gains and hydraulic risks. We introduce a trait-based optimality theory that unifies the treatment of stomatal responses and biochemical acclimation of plants to environments changing on multiple timescales. Tested with experimental data from 18 species, our model successfully predicts the simultaneous decline in carbon assimilation rate, stomatal conductance and photosynthetic capacity during progressive soil drought. It also correctly predicts the dependencies of gas exchange on atmospheric vapour pressure deficit, temperature and CO2. Model predictions are also consistent with widely observed empirical patterns, such as the distribution of hydraulic strategies. Our unified theory opens new avenues for reliably modelling the interactive effects of drying soil and rising atmospheric CO2 on global photosynthesis and transpiration.

Role of metal-support interaction for atmospheric pressure CO2 hydrogenation over Pd/(Ti)-SBA-15 catalyst: Effect of titanium composition on products selectivity

Abstract The potential role of metal-support interaction for tuning the product selectivity during atmospheric pressure CO2 hydrogenation has been demonstrated on Pd/(Ti)-SBA-15 catalyst. Highly dispersed Pd NPs on SBA-15 (Pd/SBA-15) was synthesized and further modified with titanium of varying composition. Comparison of catalytic activity of Pd/Ti-SBA-15 with its counterparts (Pd/SBA-15 and Pd/TiO2) illustrated the significance of strong Pd-Ti interface in this catalyst and its role in tuning the product selectivity of CO2 hydrogenation. The generation of an ample amount of oxygen vacancies in the Pd/Ti-SBA-15 catalyst with maximum metallic Pd sites in close vicinity of Ti is proposed to boost the CO2 hydrogenation activity.

Reaction of CO3−• with trinitrotoluene (TNT) in CO2 plasma: Experimental and theoretical study on the formation of [TNT + O]−• and its fragmentation pathways

It has previously been demonstrated that 2,4,6-trinitrotoluene (TNT) exhibits characteristic reactivity with negative reactant ions generated in air or O2 during atmospheric-pressure chemical ionization (APCI). For instance, the reaction products were TNT−• (m/z 227) for O2−•, [TNT−H•]− (m/z 226) for NO3−, and [TNT − OH•]− (m/z 210) and [TNT − NO•]− (m/z 197) for O3−•. In this work, reactions of TNT in atmospheric pressure CO2 plasma were examined. [TNT + O]−• (m/z 243) was found as the major ion in addition to TNT−•, [TNT + O − OH•]− (m/z 226), [TNT + O − O2H•]− (m/z 210), [TNT + O − NO•]− (m/z 213), and [TNT + O − NO2•]− (m/z 197). Because CO3−• was detected as the only reactant ion in CO2 plasma, it was concluded that [TNT + O]−• was formed by the reaction of CO3−• with TNT. To elucidate the structure of [TNT + O]−•, tandem mass spectrometry analysis for [TNT + O]−• was performed and the fragmentation pathways were examined by density functional theory. It was proposed that the methyl group of TNT migrates flexibly in the ring to afford the observed fragment anions. In the terminal product ion of C7H3O4− (m/z 151), π orbital electrons in the ring are most delocalized by forming four carbonyl (CO) bonds and an exo cyclic methylene (CCH2) group.

Unprecedented stability in Au@Co core-shell bimetallic catalyst supported on SBA-15 (Au@Co/SBA-15) for atmospheric pressure CO hydrogenation

Bimetallic nanoparticles demonstrating synergistic effect (electronic or geometric modification) often show distinct chemical and physical properties compared with the parent metals. In catalysis, this provides opportunities to engineer solid materials with appreciable activity, selectivity, and stability. In the present study, we have synthesized Au@Co core–shell bimetallic nanoparticles by colloidal synthesis approach with a focus to study and explore the synergistic effect between Au and Co in Au@Co bimetallic catalyst supported on SBA-15 on Fischer Tropsch (FT) reaction. The deactivation of catalyst is a significant drawback in CO hydrogenation (syngas conversion/FT synthesis), and the present study provides the design of a new material, which resists the surface cobalt oxide formation and inactive coke formation and gives efficient CO conversion with high stability.

Utilization of low-calcium fly ash via direct aqueous carbonation with a low-energy input: Determination of carbonation reaction and evaluation of the potential for CO2 sequestration and utilization

Environmental impacts from coal-fired power generation that produces large amounts of CO2 and fly ash are of great interest. To reduce negative environmental impacts, fly ash utilization was investigated via a direct aqueous carbonation with a low-energy input in which the alkali calcium content in the fly ash reacted with CO2 to form carbonate. Raw fly ash was characterized to understand the potential for direct aqueous carbonation of fly ash. The performance of the fly ash as a calcium source for direct aqueous carbonation at atmospheric pressure was investigated for different solid–liquid ratios and introduced CO2 concentrations. Variations in fly ash elemental composition, reaction solution pH, CO2 concentration in the reactor outlet, CO2 uptake efficiency, CaCO3 content and degree of carbonation were used to illustrate this process reaction. The maximum CO2 uptake efficiency was ~0.016 g-CO2/g-fly ash. This value was compared with previous studies, and the CO2 uptake efficiency was comparable despite the use of a low-energy input method, i.e., direct aqueous carbonation with atmospheric pressure and unconcentrated CO2. The calculated maximum degree of carbonation was 31.0%, which corresponds to 0.0063 g-CO2/g-fly ash. Carbonated product characterization confirmed the carbonation reaction mechanism and safety for further utilization. A comparison of CO2 uptake efficiency in this work with previous work, and considering the energy input and reactive species content, is provided. An assessment of the CO2 reduction potential is provided.

Direct synthesis of polycarbonate diols from atmospheric flow CO2 and diols without using dehydrating agents

The direct synthesis of polycarbonate diols from atmospheric pressure CO2 and α,ω-diols was achieved by using a heterogeneous CeO2 catalyst and a CO2 flow semi-bath reactor.

Polarization spectroscopy for quantitative analysis of atmospheric CO2 and air plasma flows

This article demonstrates the feasibility of polarization spectroscopy as a diagnostic tool for quantitative analysis of atmospheric pressure plasma conditions. Atmospheric pressure air and CO2 plasma flows created in a microwave-powered plasma torch are investigated. A detailed line-by-line simulation approach is employed to interpret the polarization spectra recorded in the resonator of the plasma torch. The line-by-line code for the simulation of polarization spectroscopy of O2 Schumann–Runge has been developed and verified with measurements in atmospheric pressure O2 plasma for a previous study. In this study, this simulation code for O2 absorption is used to model the polarization spectra measured in CO2 plasma and determine the inner energy distribution of the molecules for the first time. The resulting vibrational and rotational temperatures are Tvib=6115K and Trot=2660K. In order to simulate measurements in air plasma, the line-by-line code is extended to enable two-species modeling using O2 Schumann–Runge as well as NOγ absorption. The new two-species simulation approach allows for the determination of the relative number density nO2/nNO=1500±100. This paper clearly demonstrates the value of polarization spectroscopy as a quantitative measurement technique for atmospheric pressure plasma applications.

Early-stage kinetics and char structural evolution during CO2 gasification of Morupule coal in a wire-mesh reactor

Understanding the intrinsic gasification kinetics and structural evolution of char is crucial in the effective design of industrial gasifiers. This work studies the kinetics of Morupule coal gasification in atmospheric pressure CO2 at isothermal temperatures of 900–1050 °C using a rapid heating wire-mesh reactor (WMR). The gasification reaction order was determined by varying the concentration of CO2 in the reactor atmosphere. The bulk chemical structure and surface chemistry of the early-stage residual chars were characterised using Raman and X-Ray photoelectron spectroscopy, respectively. Gasification reaction rates were significantly higher than those presented in published literature with an activation energy of 320 kJ mol−1 and a pre-exponential factor in the order of 1010 s−1. In a chemical reaction controlled kinetic regime, the reaction order was found to be zero and increased to 0.6 in a mixed chemical reaction plus pore diffusion controlled kinetic regime. The bulk chemistry of the chars was largely unaffected by CO2 in the conversion range studied. However, surface chemistry analyses revealed a decrease in the carbon content, through the depletion of CC/CC bonds, resulting in the development of char surface porosity. Residual chars from gasification experiments showed a lower combustion reactivity to those produced under inert pyrolysis conditions. This study provides insights on direct gasification (i.e. no char preparation in a separate pyrolysis stage) for kinetic determinations and a concomitant extensive characterisation of char structural properties.

Effect of Atmosphere on Duplex Oxide Formed on 9Cr Steel at 550 °C

Commercial F91 steel was exposed to atmospheric pressure CO2 and laboratory air at 550 °C for exposure times up to 1000 h. In both atmospheres, a Fe-rich duplex oxide scale formed, but with different morphology, oxide phases and growth rates. In CO2, the duplex morphology was observed at the onset of oxidation and it was found that the cooling rate affect the oxide phases formed on the outer scale. In air, the alloy initially formed a protective chromium rich oxide layer, followed by the nucleation and growth of duplex iron-rich oxide nodules at random locations, leading to breakaway oxidation. Alloy carburization was also observed in CO2 but not in air environment.

Role of exposed crystal facets in the atmospheric pressure CO hydrogenation on Co[formula omitted]O[formula omitted] nanostructures

Co3O4 nanostructures with different exposed planes are studied for atmospheric pressure CO hydrogenation. Existence of different facets is characterized by HR-TEM and found Co3O4 - NSP (nanospheres) expose (112) facet, NB (nanobelts) exhibit (110) plane and (100) is the dominant surface facet in NC (nanocubes). Different catalytic activity is demonstrated by the specific facet of Co3O4 catalysts. CO hydrogenation is facet dependent and the catalytic activity follows the order of Co3O4-NB > Co3O4-NC > Co3O4-NSP.

CO2 Utilization via Direct Aqueous Carbonation of Synthesized Concrete Fines under Atmospheric Pressure.

Mineral carbonation using alkaline wastes is an attractive approach to CO2 utilization. Owing to the difference between waste CO2 and feedstock CO2, developing CO2 utilization technologies without CO2 purification and pressurization is a promising concept. This study investigated a potential method for CO2 utilization via direct aqueous carbonation of synthesized concrete fines under atmospheric pressure and low CO2 concentration. The carbonation reaction with different solid–liquid ratios and different concentrations of introduced CO2 was examined in detail. Under basic conditions, a CO2 uptake of 0.19 g-CO2/g-concrete fines demonstrated that direct aqueous carbonation of concrete fines under atmospheric pressure and low CO2 concentration is effective. The CaCO3 concentration, degree of carbonation, and reaction mechanism were clarified. Furthermore, characterization of the carbonated products was used to evaluate ways of utilizing the carbonated products.

An approach to modeling resource optimization for substitutable and interdependent resources

We develop a hierarchical approach to modeling organism acclimation to changing availability of and requirements for substitutable and interdependent resources. Substitutable resources are resources that fill the same metabolic or stoichiometric need of the organism. Interdependent resources are resources whose acquisition or expenditure are tightly linked (e.g., light, CO2, and water in photosynthesis and associated transpiration). We illustrate the approach by simulating the development of vegetation with four substitutable sources of N that differ only in the cost of their uptake and assimilation. As the vegetation develops, it uses the least expensive N source first then uses progressively more expensive N sources as the less expensive sources are depleted. Transition among N sources is based on the marginal yield of N per unit effort expended, including effort expended to acquire C to cover the progressively higher uptake costs. We illustrate the approach to interdependent resources by simulating the expenditure of effort to acquire light energy, CO2, and water to drive photosynthesis in vegetation acclimated to different conditions of soil water, atmospheric vapor pressure deficit, CO2 concentration, and light levels. The approach is an improvement on the resource optimization used in the earlier Multiple Element Limitation (MEL) model.