CO2 Mole Research Articles

Quantitative Raman Spectroscopic Determination of the Composition, Pressure, and Density of CO2-CH4 Gas Mixtures

The Raman spectra for pure CO2 and CH4 gases and their ten gas mixtures were collected at pressures and temperatures ranging from 2 MPa to 40 MPa and room temperature (∼24°C) to 300°C, respectively. A systematic analysis was carried out to establish a methodology for the quantitative determination of the composition, pressure, and density of CO2-CH4 mixtures. The shift in the peak position of the υ1 band for CH4 was sufficiently large to enable the accurate determination of the pressure of pure CH4 and CH4-dominated fluids (>50 mol% CH4). An equation representing the observed relationship of the peak position of the υ1 band of CH4, density, and composition was developed to calculate the density of CO2-CH4 mixtures. The Raman quantification factor F (CH4)/F (CO2) was demonstrated to be near a constant value of 5.048 ± 0.4 and was used to determine the CH4 to CO2 molar ratio in an unknown CO2-CH4‐bearing fluid with high internal pressure (>10 MPa) based on the Raman peak area ratio. The effect of temperature on the variation in Raman spectral parameters was also investigated at temperatures up to 300°C. The results showed that the effect of temperature must be considered when Raman spectral parameters are used to calculate the pressure, density, and composition of CO2-CH4 gas mixtures. Raman spectroscopic analysis results obtained for six samples prepared in fused silica capillary capsules were validated by comparison with the results obtained from microthermometry measurements.

Impact of Fuel Type on Toxic Emissions from a Non-premixed Boundary Layer Laminar Flame in Microgravity – A Numerical Study

Examples from non-premixed boundary combustion representative of fire in microgravity environment are presented. A low forced flow of 0.25 m/s is present, which is typical of air circulation speeds in a spacecraft. The numerical simulations have been conducted to evaluate the modes of heat transfer with an emphasis on a discussion about the effects of various fuels on chemical emissions such as soot, CO, CO2 and unburnt hydrocarbons in reduced-gravity conditions. Typically, evaporation temperature is smaller for heptane than dodecane, and thus a lengthening of the heptane flame seems more pronounced as compared to that of dodecane flame with an increase in the visible flame zone by a factor of 2.3 times. A rapid regression rate of heptane due to the enhanced heat feedback contributes to an additional energy by a factor of 80% in heat release rate as compared to dodecane. In all the cases, only about 15% of the heat generated by an exothermic chemical reaction is supplied to the pyrolysis surface, and a large portion of energy is convected with the forward gas flow. The CO molar fraction reaches to a maximum of about 11% for dodecane and 8% for other fuels as ethylene, propane, propylene and heptane. The maximum mean value of CO concentration depends mainly on fuel injection rate, and appears practically insensitive to oxidizer flow velocity. Dodecane and heptane with a longer carbon chain produces more CO and less unburnt hydrocarbons than ethylene, propane and propylene. The existence of large unburnt toxic gas fuels even for a smaller flame size because of the absence of natural convection has important considerations for spacecraft fire safety due to smoke/gas incapacitation.

High-temperature pyrolysis experiments and chemical kinetics of diisopropyl methylphosphonate (DIMP), a simulant for Sarin

Due to the high toxicity of chemical warfare (CW) agents, laboratory experiments are carried out using CW surrogates. Diisopropyl Methylphosphonate (DIMP), an organophosphate compound (OPC), is a crucial CW surrogate that has a chemical structure similar to the deadly nerve agent Sarin (GB). In this work, high-temperature pyrolysis of DIMP is conducted in a shock tube within a temperature range of 1400 - 1800 K at near 1 atm pressure. Laser absorption spectroscopy was used to obtain carbon monoxide mole fraction time-histories during high-temperature pyrolysis for DIMP. In order to predict the CO mole fraction time-histories during DIMP pyrolysis, a reaction mechanism was developed using the Lawrence Livermore National Lab (LLNL)’s OPC mechanism. Several important reactions of DIMP and its important intermediates during pyrolysis were studied at the CBS-QB3 level of theory, and corresponding reaction rates were determined using transition state theory. The reactions related to methyl phosphonic acid (MPA) and methyl(oxo)phosphoniumolate (MOPO) were added from literature and by analogies with similar compounds. Thermochemical properties of crucial species involved in DIMP pyrolysis were calculated using the CBS-QB3 composite method and were updated in the model. A reaction mechanism was compiled for DIMP pyrolysis using these rates. Two versions of this mechanism (‘Model A’ and ‘Model B’) were generated to understand the significance of new reactions in predicting CO mole fraction time histories. Significant improvement in the prediction of CO was observed compared to the LLNL model with either of these mechanisms. A reaction path analysis was conducted to understand the formation pathways of CO during DIMP pyrolysis. Finally, sensitivity analysis was performed to get insights into important reactions leading to CO formation. It was found that the H-abstraction from MOPO by methyl radical plays an important role in CO formation.

Disparate responses of soil-atmosphere CO2 exchange to biophysical and geochemical factors over a biocrust ecological succession in the Tabernas Desert

There is growing evidence that dryland soils could act as substantial but so far disregarded carbon sinks at the global scale. In drylands, potential abiotic processes of CO2 uptake are still debated while estimates of the biotic contribution of photosynthetizing biocrusts to the net carbon uptake remain uncertain. This uncertainty is partly attributable to a common neglect of the underlying soil and spatiotemporal variability of soil CO2 fluxes. Moreover, it is still unknown how those fluxes evolve during the ecological succession of biocrusts and which factors control them. Therefore, in this study, we aimed to (1) identify those factors and use them for predictions, and (2) explain the inter-annual variation of cumulative CO2 fluxes over the succession. We conducted 2 years of continuous measurements of the topsoil CO2 molar fraction (χs) and microclimatic variables and estimated the soil-atmosphere CO2 flux using the gradient method. Statistical spatiotemporal models were developed of χs dynamics and cumulative annual fluxes. A soil CO2 uptake potentially due to coupled gypsum dissolution-calcite precipitation was consistently detected at night, with cumulative values ranging from −4 to −65 gC m−2 depending on succession stage. In comparison, cumulative soil CO2 emissions ranged from 101 to 307 gC m−2 depending on succession stage. The succession stage, soil water content (ϑw), and temperature (Ts) and the interactions of these variables explained and efficiently predicted the daily averaged χs dynamics. Soil CO2 emissions were more sensitive to ϑw and Ts in late successional stages, apparently because of organic carbon accumulation and higher porosity. Our measurements suggest that CO2 consumption processes were progressively counterbalanced by the increase in biological CO2 production during succession. That is probably why those processes could mainly be detected in early successional stages and more generally in drylands, as they sustain a low biological activity. However, such processes could be ubiquitous in ecosystems but difficult to detect. We discuss the implication of those results for the extensive dryland soils in the context of climate change.

Supercritical Antisolvent Technique for the Production of Breathable Naringin Powder.

Flavonoids are polyphenolic compounds largely present in fruits and vegetables possessing antioxidant properties, anti-inflammatory and antibacterial activities. Their use in clinical practice is very poor due to their low bioavailability, susceptibility to oxidation and degradation. Moreover, their slight solubility in biological fluids and a consequent low dissolution rate leads to an irregular absorption from solid dosage forms, even though, anti-inflammatory formulations could be used as support for several disease treatment, i.e. the COVID-19 syndrome. To improve flavonoid bioavailability particle size of the powder can be reduced to make it breathable and to promote the absorption in the lung tissues. Supercritical fluid based antisolvent technique has been used to produce naringin particles, with size, shape and density as well as free flowing properties able to fit inhalation needs. The dried particles are produced with the removal of the solvent at lower temperatures compared to the most used traditional micronization processes, such as spray drying. The best breathable fraction for naringin particles is obtained for particles with a d50~7 µm manufactured at 35 °C-150 bar and at 60 °C-130 bar, corresponding to 32.6% and 36.7% respectively. The powder is produced using a high CO2 molar fraction (0.99) that assure a better removal of the solvent. NuLi-1 cell line of immortalised bronchial epithelial cells adopted to evaluate powder cytotoxicity indicated after 24 h absence of toxicity at concentration of 25 µM.

Crystal-Liquid Segregation in Silicocarbonatite Magma Leads to the Formation of Calcite Carbonatite

Abstract A suite of silicocarbonatite and lamprophyre rocks from SW Ireland, with mantle affinity and primitive composition, are used as a proxy for parental carbonated silicate magmas to model early magmatic evolution. Reconstruction of volatile ratios is validated using global occurrences. At 1200°C, the point at which melts transition from ionic liquids with exceptionally low viscosity (0.06 PaS) to covalently polymerised liquid (viscosity up to 1.3 PaS) is 33 mol% SiO2. Incremental and significant increase in magma density accompanies magma ponding, due to dehydration of magmas from model molar CO2/(CO2 + H2O) of 0.60 in plutonic settings to 0.75 for initial subvolcanic magmas. Magma-crystal density differences dictate that repeated influxes of magmas into an inflating magma chamber sustain a mechanical boundary layer between dense (silicate and oxide) mineral layers and a calcite ± phlogopite flotation assemblage. The range of critical CO2 concentration at which calcite floats (10–13 wt% CO2) may be extended by the presence of additional volatiles and fluid bubbles. The model accommodates a range of phenomena observed or inferred for alkaline/carbonatite complexes, including the following: 1, a growing calcite-dominated flotation assemblage with an apparently early magmatic mineralisation; 2, a residual liquid with high concentrations of incompatible metals; 3, variable carbonatite–pyroxenite–phoscorite rock relations; and 4, multiple phases of overprinting metasomatism.

Effect of the Cu/ZnO/SBA‐15/kaolinite preparation method on the catalyst structural properties and catalytic performance at CO2 hydrogenation at low pressure

AbstractCarbon dioxide catalytic hydrogenation to methanol in the presence of nanocatalysts has been recognized as one of the most effective ways to fix and utilize the emitted CO2. In this study, Cu/ZnO/SBA‐15 catalyst has been synthesized by three different methods: “impregnation‐sol–gel autocombustion” method, impregnation method and direct synthesis method using triblock copolymer Pluronic P123 as a template. Cu/ZnO/SBA‐15 catalysts comprising kaolinite clay have been used in CO2 hydrogenation to methanol for the first time to make the methanol synthesis more cost‐effective. The performance of catalysts upon hydrogenation of CO2 was evaluated in a fixed‐bed tubular micro‐activity reactor at 20 bar with H2 to CO2 molar ratio 3 to 1 and 250°C. Results showed that the highest methanol production, with STY of 36 mg CH3OHh−1gcat−1, could be obtained using the catalyst prepared by “impregnation‐sol–gel autocombustion”. This synthesis method allowed to obtain catalyst with the smallest crystallite size and a good dispersion of the active phase over and into SBA‐15. The CO2 conversion reached 15.9%, which is close to conversion level provided by commercial Cu catalyst.

Carbon recycling efficiency in subduction zones constrained by the effects of H2O-CO2 fluids on partial melt compositions in the mantle wedge

The extent of CO2 transfer from subducting lithologies to the overlying mantle wedge in general and to the arc magma source regions in particular remains debated. The limit of CO2 transfer to the sub-arc mantle could be estimated if the effects of CO2 on the primary hydrous melt compositions of mantle wedge can be assessed in relation to the observed compositions of primitive arc magmas. Here we present new piston cylinder and multi-anvil experiments using Au75Pd25 and Au capsules on four depleted peridotite + H2O ± CO2 starting compositions with 3.5 wt.% H2O and XCO2 [=molar CO2/ (CO2+H2O)] of 0–0.17. Experiments were performed at 2–4 GPa and 1200°C to constrain how the presence of variable CO2 in slab-derived aqueous fluids affects the composition of peridotite partial melts. All experiments consisted of low degree melts (<10 wt.%) in equilibrium with olivine + orthopyroxene ± clinopyroxene. Melts at 2–4 GPa are basaltic for XCO2 of 0–0.10 and become SiO2-poor and CaO-rich at XCO2 > 0.10. Comparison between our experimental partial melt compositions with a global dataset of the most primitive arc magmas suggests that the upper limit of XCO2 in fluids inducing melting in mantle wedges is ∼0.10 at 2–4 GPa. We apply these new constrains to an H2O and CO2 mass balance model for subduction zones and estimate that at least 34–86% of CO2 entering subduction zones bypasses the sub-arc melt generation zone and is subducted to the convecting mantle, either carried by the slab or by the down-dragged limb of the mantle wedge directly above the slab.

Experimental study of the solar-driven steam gasification of coal in an improved updraft combined drop-tube and fixed-bed reactor

Solar-driven steam gasification of coal particles promises a new approach for efficiently storing concentrated solar power (CSP) in producer syngas and achieving solid fuels energetic upgrade. A 1.5-kWth improved updraft solar reactor combined with drop-tube and fixed-bed for the steam gasification of coal was designed, fabricated, and experimentally studied under a 7-kWe high-flux solar simulator (HFSS). The gasifier retains the advantages of the efficient radiative heat transfer, long particle residence time and excellent particle size adaptation to the conventional combined drop-tube and fixed-bed reactors (CDFR) while, however, improving pyrolysis conditions by changing the moving direction of the steam and feedstock to use the high-temperature producer gas to preheat coal particles. The aim of this work was to achieve a proof of concept for the newly designed solar gasifier applied to coal gasification. Additionally, a comprehensive parametric study considering different H2O/coal molar ratios (0.8–2.2), coal feeding rates (1.0–1.5 g/min), carrier gas flow-rates (2.5–3.5 Nl/min), temperature (1050 °C and 1150 °C) and heights of reticulate porous ceramic (3 cm and 6 cm) was conducted for optimizing the syngas composition and evaluating the gasification performance. The experimental data indicated the syngas yield increased obviously from 57.92% to 64.63% with the increasing temperature, while the increasing steam content favored H2, CO2 and CH4 and reduced CO mole fraction. The increasing heights of the reticulate porous ceramic (RPC) extended the particle residence time, resulting in the carbon conversion rate increasing over 8%. Maximum amounts of produced syngas over 100 mmol/min and carbon conversion rates over 70% were achieved. The coal energy content was solar-upgraded by a factor of 1.17 at 1150 °C. Compared with the conventional CDFR, the carbon conversion rate was promoted from 51.66% to 64.63% with the increasing pyrolysis temperature (up to 400 °C).

The effect of the round jet parameters on infrared radiation characteristics

In this study, the effects of nozzle size, CO2 and H2O molar fraction, pressure, and temperature on the infrared characteristics of round jets are studied. The backward Monte Carlo method is used to calculate the spectral radiation characteristics and infrared images. The results show that kλ is insensitive to the molar fraction of the species, and it is slightly more sensitive to pressure. Temperature has the greatest effect on the kλ. In addition, the effects of characteristic length of the jet, molar fraction of the species, and pressure on the infrared characteristics are similar. (1) When the characteristic optical thickness of the jet is thick enough, with the increasing of above parameters, the spectral radiance increases at 3 ∼ 3.6 μm and 4.6 ∼ 5 μm, while it decreases around 4.3 μm. The magnitude of the two radiance peaks near 4.1 μm and 4.4 μm remain almost unchanged. However, the peak position moves to both sides. (2) Otherwise, there will be only one radiance peak in 4.1 ∼ 4.4 μm. The height of radiance peak decreases with the decrease of characteristic optical thickness.

Tuning Adsorption-Induced Responsiveness of a Flexible Metal–Organic Framework JUK-8 by Linker Halogenation

Flexible stimuli-responsive metal–organic frameworks have become promising candidates for numerous applications in gas-related technologies; however, the methods of fine tuning their responses are still limited and sought after. In this work, we demonstrate control over the adsorption properties of a flexible platform by incorporating halogen substituents (X = F, Cl, Br, I) into an eightfold interpenetrated isoreticular series [Zn(oba)(X-pip)]n (JUK-8X; X-pip = 4-pyridyl-functionalized benzene-1,3-dicarbo-5-halogenohydrazide; oba2– = 4,4′-oxydibenzoic carboxylate). The introduced halogen atoms allow for precise tuning of CO2 gate-opening pressures from p/p0 = 0.08 for the parental JUK-8 to 0.78 for the chlorine-functionalized JUK-8Cl. The presence of fluorine or chlorine substituent in the X-pip linker practically does not influence the maximum molar CO2 uptake as compared to JUK-8, whereas larger bromine or iodine atoms increase this uptake by 59 and 48%, respectively. Utilizing in situ powder X-ray diffraction (PXRD) during CO2 adsorption for a model JUK-8F, we propose a detailed mechanism of phase transitions including positions of the adsorbed gas molecules for the two loaded phases. Density functional theory calculations supported by in situ PXRD measurements at a saturation pressure shed light on the unusual CO2 adsorption properties of JUK-8Br and JUK-8I. Overall, our report demonstrates the use of halogen interactions for the control of a gas-responsive system and provides insightful guidance for the further development of flexible, adaptable materials.

Pyrolysis-catalytic steam/dry reforming of processed municipal solid waste for control of syngas H2:CO ratio

The production of syngas from the pyrolysis-catalytic reforming of processed municipal solid waste in the form of refuse derived fuel has been investigated experimentally using a two-stage fixed bed reactor with a 10 wt% Ni–Al2O3 catalyst. The reforming gases used were a combination of steam and carbon dioxide (dry reforming). The main focus of the research was to manipulate the H2:CO ratio in the syngas for targeted end-use applications by optimizing the process conditions, including the input steam/CO2 reforming gas ratio. The experimental results showed that at higher steam:CO2 ratios, there was a marked increase in H2 yield due to the endothermic nature of the steam and CO2 reforming processes. The catalytic reforming temperature also had a major influence on H2 yield, with increasing temperature raising the hydrogen yield to a maximum of ∼41.0 mmol gRDF−1 at 955 °C catalyst temperature. The H2:CO molar ratio was also affected by the process variables and were interdependent on them. For example, the influence of an increase in the catalytic reforming temperature as the content of steam in the reforming gas input was also increased, produced a maximum H2:CO molar ratio of ∼4.7:1 achieved at an input steam:CO2 ratio of 75:25 and a catalyst temperature of 700 °C. Whereas, at higher CO2 content in the reforming gas, the product H2:CO ratio was ∼1:1. Also, for a steam:CO2 input ratio of 50:50, the H2:CO ratio produced was ∼2:1 and for higher steam content in the reforming gas the product H2:CO was ∼3:1. Design of Experiments (DoE) modelling was carried out using the experimental data to identify the process conditions that would produce a target syngas H2:CO molar ratio of 1:1 and 2:1. The predicted optimised process conditions from the DoE modelling produced experimental results close to the targeted syngas H2:CO molar ratios, thereby validating the DoE model.

Heat integration and waste minimization of biomass steam gasification in a bubbling fluidized bed reactor

Steam gasification of biomass generates a hydrogen-rich product gas that is diluted in unreacted steam and contaminated with tar. In this study, a novel heat integration alternative is conceptualized through syngas cooling to near-ambient temperature via an indirect water condenser downstream of a bubbling fluidized bed gasifier. The steam generated from heat recovery is used for biomass gasification, whereas the condensed bio-oil (unreacted tar and steam) is collected and recycled to the gasifier for further conversion. A one-dimensional kinetic model is developed and tested against experimental data from the literature on steam gasification of bio-oil and steam gasification of biomass in two separate bubbling fluidized bed gasifiers. The average absolute deviation of model predictions for CO2, CO, CH4 and H2 mole fractions are 60.85%, 14.25%, 30.17% and 10.75% for bio-oil steam gasification and 80.63%, 27.70%, 67.28% and 4.71% for biomass steam gasification, respectively. Based on the agreement observed between the model predictions and experimental data over substantial ranges of operating conditions, the same approach is adopted for modeling integrated biomass and recycled bio-oil gasification. Increasing bio-oil recycle ratio increases water conversion and chemical efficiency at the cost of decreasing carbon conversion and thermal efficiency of biomass gasification process. In addition to reactor temperature and steam-to-biomass ratio, tar recycle ratio can be utilized as an optimization variable to compromise between process chemical and thermal efficiencies, as well as wastewater production. Finally, an economic analysis shows that an incremental return on investment of >33% is achievable for the integrated process.

Understanding and improving the modular properties of high-performance SSZ-13 membranes for effective flue gas treatment

High-performance tube-supported standard oil synthetic zeolite-13 (SSZ-13) membranes were prepared using low-temperature ozone calcination and modularized in different-sized permeation cells. The hydrophobic SSZ-13 membrane exhibited robust, marked CO2/N2 separation performances at a H2O vapor partial pressure of 10 kPa at 50 °C (CO2 permeance of 1.3 × 10−7 mol∙m−2 s−1∙Pa−1 and CO2/N2 separation factor (SF) of ca. 31.5). However, these intrinsic values were obtained at high feed flow rates, where the optimal recovery of CO2 molecules cannot be obtained. Thus, we correlated membrane (permeance and SF) and feed stream (Reynolds number) properties, finding that convective mass transfer from feed to outer membrane surface (Sherwood number) was described by the Reynolds number and cell dimensions. This further accounted for the CO2 molar flux and CO2/N2 SF. Based on this, we proposed critical parameters (comprising total feed flow rate and pressure, and characteristic module dimension) to describe the representative module properties of the recovery, purity, and process efficiency (PE) for CO2. Finally, the PE of the membrane unit was improved in double-stage configuration, yielding noticeable improvements in CO2 purity and PE at the slight expense of CO2 recovery. Crucially, the process-based module properties were well understood and predicted using the feed stream properties.

Selective Photocatalytic Reduction of CO2 to Syngas Over Tunable Metal-Perovskite Interface.

The extensive emission of CO2 results in critical environmental issues, such as global warming. Photocatalytic CO2 conversion is a meaningful route to convert CO2 into useful chemicals. However, the highly selective reduction of CO2 with the avoidance of hydrogen evolution is still challenging. Herein, the photocatalytic reduction CO2 to synthesis gas (syngas) was achieved on a metal Ag socketed perovskite LaFeO3 (LFO) catalytic interface prepared by an in-situ exsolution method. The conduction band of Ag-exsolved LFO is more negative than LFO, benefiting efficient CO2 reduction. By tuning the dopant Ag cation in the lattice to nanoparticles pinned on the surface, the CO formation rate was improved around five-fold from 0.51 to 2.41 μmol g-1 h-1 . Meanwhile, the H2 /CO molar ratio also showed strong dependence on the modality of Ag at the metal-perovskite interface. The design offers a promising pathway for transforming CO2 to valuable chemicals based on efficient photocatalysts design.

Water vapor adsorption by dry soils: A potential link between the water and carbon cycles

Water vapor adsorption (WVA) by soil is a potential contributor to the water cycle in drylands. However, continuous in-situ estimates of WVA are still scarce and the understanding of its coupling with carbon cycle and ecosystem processes remains at an incipient stage.Here we aimed to (1) identify periods of WVA and improve the understanding of the underlying processes involved in its temporal patterns by using the gradient method; (2) characterize a potential coupling between water vapor and CO2 fluxes, and (3) explore the effect of soil properties and biocrusts ecological succession on fluxes. We assumed that the nocturnal soil CO2 uptake increasingly reported in those environments could come from WVA enhancing geochemical reactions involving calcite.We measured continuously during ca. 2 years the relative humidity and CO2 molar fraction in soil and atmosphere, in association with below- and aboveground variables, over the biocrusts ecological succession. We estimated water vapor and CO2 fluxes with the gradient method, and cumulative fluxes over the study. Then, we used statistical modelling to explore relationships between variables.Our main findings are (1) WVA fluxes during hot and dry periods, and new insights on their underlying mechanisms; (2) a diel coupling between water vapor and CO2 fluxes and between cumulative fluxes, well predicted by our models; and (3) cumulative CO2 influxes increasing with specific surface area in early succession stages, thus mitigating CO2 emissions.During summer drought, as WVA was the main water source, it probably maintained ecosystem processes such as microbial activity and mineral reactions in this dryland. We suggest that WVA could drive the nocturnal CO2 uptake in those moments and discuss biogeochemical mechanisms potentially involved. Additional research is needed to monitor soil water vapor and CO2 uptake and separate their biotic and abiotic components as those sinks could grow with climate change.

Intrinsic kinetics of CO2 methanation on low-loaded Ni/Al2O3 catalyst: Mechanism, model discrimination and parameter estimation

The mechanism and kinetic of CO2 methanation reaction of 9.5 % Ni/Al2O3 catalyst is analysed under a wide range of operating conditions. Once the catalyst activity is stabilized, the influence of temperature, total pressure and space velocity is studied for kinetic characterisation. A data set comprising of 153 experimental runs has been used to develop a kinetic model capable to accurately predict the reaction rate. Ni/Al2O3 catalyst shows an apparent activation energy of 80.1 kJ mol−1 in CO2 hydrogenation. Data obtained under differential mode adjust quite precisely to a power-law model with H2O inhibition, with a water adsorption constant of 3.1 atm−1 and apparent orders of 0.24 and 0.27 for H2 and CO2, respectively. Based on DRIFTS results, we propose for the first time the H-assisted CO formation route, which is compared with the more conventionally reported carbonyl route, and describe the corresponding reaction rate LHHW equation, resulting in notable improvement for mean deviation (D) of 7.0 % in our model related to that based on the carbonyl route (D = 20.1 %) usually suggested for catalysts with higher Ni loads around 20 %. The H-assisted CO formation route considers the formate species decomposition into carbonyls via H-assisted CO formation mechanism and further carbonyls hydrogenation into CHO as the rate determining step. Thus, the LHHW mechanism, in which carbonyls as well as formate species participate in CO2 methanation, is capable to reflect the kinetics of lowly-loaded Ni/Al2O 3 catalyst with high accuracy under relevant process conditions (315−430 °C, 1−6 bar, H2 to CO2 molar ratios between 1–16 and, different reagents and products partial pressures).

Assessing NO2-Hydrocarbon Interactions during Combustion of NO2/Alkane/Ar Mixtures in a Shock Tube Using CO Time Histories

Modern gas turbines use combustion chemistry during the design phase to optimize their efficiency and reduce emissions of regulated pollutants such as NOx. The detailed understanding of the interactions during NOx and natural gas during combustion is therefore necessary for this optimization step. To better assess such interactions, NO2 was used as a sole oxidant during the oxidation of CH4 and C2H6 (the main components of natural gas) in a shock tube. The evolution of the CO mole fraction was followed by laser-absorption spectroscopy from dilute mixtures at around 1.2 atm. The experimental CO profiles were compared to several modern detailed kinetics mechanisms from the literature: models tuned to characterize NOx-hydrocarbons interactions, base-chemistry models (C0–C4) that contain a NOx sub-mechanism, and a nitromethane model. The comparison between the models and the experimental profiles showed that most modern NOx-hydrocarbon detailed kinetics mechanisms are not very accurate, while the base chemistry models were lacking accuracy overall as well. The nitromethane model and one hydrocarbon/NOx model were in relatively good agreement with the data over the entire range of conditions investigated, although there is still room for improvement. The numerical analysis of the results showed that while the models considered predict the same reaction pathways from the fuels to CO, they can be very inconsistent in the selection of the reaction rate coefficients. This variation is especially true for ethane, for which a larger disagreement with the data was generally observed.

Acid-Base Balance, Blood Gases Saturation, and Technical Tactical Skills in Kickboxing Bouts According to K1 Rules.

Simple SummaryThe aim of our study was to analyze the changes in ABB after a three-round kickboxing fight and the level of technical and tactical skills presented during the fight. Fighting in kickboxing under K1 rules takes place with a high presence of anaerobic metabolism. Kickboxing athletes must have a good tolerance for metabolic acidosis and the ability to conduct an effective duel despite ABB disorders. Properly developed post-workout regeneration also plays an extremely important role. Background: Acid–base balance (ABB) is a major component of homeostasis, which is determined by the efficient functioning of many organs, including the lungs, kidneys, and liver, and the proper water and electrolyte exchange between these components. The efforts made during competitions by combat sports athletes such as kickboxers require a very good anaerobic capacity, which, as research has shown, can be improved by administering sodium bicarbonate. Combat sports are also characterized by an open task structure, which means that cognitive and executive functions must be maintained at an appropriate level during a fight. The aim of our study was to analyze the changes in ABB in capillary blood, measuring levels of H+, pCO2, pO2, HCO3−, BE and total molar CO2 concentration (TCO2), which were recorded 3 and 20 min after a three-round kickboxing bout, and the level of technical and tactical skills presented during the fight. Methods: The study involved 14 kickboxers with the highest skill level (champion level). Statistical comparison of mentioned variables recorded prior to and after a bout was done with the use of Friedman’s ANOVA. Results: 3 min after a bout, H+ and pO2 were higher by 41% and 11.9%, respectively, while pCO2, HCO3−, BE and TO2 were lower by 14.5%, 39.4%, 45.4% and 34.4%, respectively. Furthermore, 20 min after the bout all variables tended to normalization and they did not differ significantly compared to the baseline values. Scores in activeness of the attack significantly correlated (r = 0.64) with pre–post changes in TCO2. Conclusions: The disturbances in ABB and changes in blood oxygen and carbon dioxide saturation observed immediately after a bout indicate that anaerobic metabolism plays a large part in kickboxing fights. Anaerobic training should be included in strength and conditioning programs for kickboxers to prepare the athletes for the physiological requirements of sports combat.

Machine learning applied to the retrieval of three-dimensional scalar fields of laminar flames from hyperspectral measurements

Accurate measurement of three-dimensional temperature and species mole fraction fields for combustion systems provides comprehensively detailed information for optimizing combustion process and improving combustion efficiency. The state-of-art three-dimensional combustion diagnostic techniques for temperature and species mole fraction reconstructions, either laser-based or radiation imaging-based, require solving problems of huge matrices with iterative processes based on the multiple projection measurements of flame emission or absorption. These techniques are typically computationally intensive, with limited spatial resolution and can be hardly applied to retrieve three-dimensional temperature and multiple species mole fractions simultaneously. In the present study, we extended the machine learning methodology we previously proposed (Ren et al. 2021) for the reconstruction of two-dimensional temperature and mixture species mole fraction fields to three-dimensional for a group of non-axisymmetric flames with different equivalence ratios. The developed method demonstrates its excellent capability to retrieve three-dimensional temperature with CO2, H2O, and CO mole fractions simultaneously for these targeted flames. The accuracy of the machine learning reconstructions was found to be excellent, while computational effort was reduced by at least five orders of magnitude, as opposed to conventional gradient-based optimization methods.