Carbon Dioxide Molecules Research Articles

Critical Role of Interfacial Sites between Nickel and CeO2 Support in Dry Reforming of Methane: Revisit of Reaction Mechanism and Origin of Stability

Dry reforming of methane (DRM) is one of the effective catalytic routes to utilize methane and carbon dioxide molecules. The supported Ni catalysts on lanthanide oxides show remarkable reactivities...

Solvent-Free cycloaddition of carbon dioxide and epichlorohydrin catalyzed by surface-attached imidazolium-type poly(ionic liquid) monolayers

Design and synthesis of effective catalysts for the conversion of epoxy compounds to cyclic carbonate under the presence of carbon dioxide molecules is essential for the utilization of carbon dioxide. Herein, we report that the surface-attached imidazolium-type poly(ionic liquid) bearing amine moieties is an efficient catalyst for the conversion of epoxy compound and carbon dioxide to cyclic carbonate. The effect of chemical structure of the synthesized catalyst and the reaction conditions on the catalytic efficiency is systematically studied. The results show that the catalyst with bromide anion can effectively catalyze the reaction under 1.5 MPa carbon dioxide pressure at 120 °C with the catalyst content of 10 mg mL−1, reaching the conversion rate up to 90 %. Moreover, the synthesized catalyst can be separated from the cyclic carbonate products by centrifugation. The recyclability and reversibility measurements reveal that the decay of the catalytic activity is mainly resulted from the adsorption of the cyclic carbonate products on the catalysts. The catalytic activity of the synthesized catalyst towards conversion of epichlorohydrin and carbon dioxide to cyclic carbonate can be recovered after extraction of the adsorbed cyclic carbonate products.

Soft x-ray photoabsorption spectra of photoionized CH4 and CO2 plasmas

In this work we report soft x-ray (SXR) photoabsorption measurements in neutral methane and carbon dioxide molecules and their corresponding photoionized plasmas. The SXR radiation was generated by a table-top laser produced plasma source based on a double stream gas puff target. At low SXR intensities only features related to neutral molecules are present in the absorption spectrum. On the other hand, as the radiation intensity increases, we observe new absorption features in the low photon energy side of the spectrum. In that case fragments such as neutral and ionized molecules, atoms and atomic ions are found to contribute to the absorption spectrum of the plasmas. To our knowledge these are the first measurements where this laser plasma based SXR source is used to both create and probe a molecular plasma. Emphasis is placed on identifying the fragment species and the corresponding transitions.

An algebraic alternative for the accurate simulation of CO2 Raman spectra

AbstractWe present an accurate simulation of the Raman spectrum of the carbon dioxide molecule in the 1150–1500 cm−1 spectral range, comparing the results obtained using the three polyad schemes found in the literature of this molecule. The description of the molecule with the algebraic U1(2)×U(3)×U2(2) local model encompasses both stretching and bending degrees of freedom. A detailed analysis of the Hamiltonian interactions for the three polyad schemes provides fittings with root mean square deviations in the range 0.14–0.20 cm−1, involving 19 parameters taking into account the 178 experimental term energies found in the literature. Using a limited subset of 9 experimental transition moments, we optimize 5 partial derivatives of the mean polarizability and simulate the Raman spectrum of CO2 for the three polyad schemes. Comparing the calculated results with the experimental spectrum, we obtain an overall good agreement for the three polyads. However, an inspection in detail of the spectrum seems to show a slight preference for polyad P212 albeit not due to the interaction characterizing the polyad but due to anharmonic effects and energy distribution. Finally, we assess the effect of the Fermi resonance over CO2 Raman line intensities.

Analysis of Si3N4 waveguides for on-chip gas sensing by optical absorption within the mid-infrared region between 2.7 and 3.4 µm

We theoretically investigated the use of a Si3N4 on SiO2 waveguide as an optical interaction part with sensed molecules for multi-gas wideband on-chip spectroscopic sensing. From the analysis, we show that a simple strip Si3N4 waveguide can be employed to achieve acceptable values of performance in term of detection limit, compactness, polarization, and fabrication tolerance for the detection of water vapor (H2O), carbon dioxide (CO2), Nitrous oxide (N2O), Ammonia (NH3), Ethylene (C2H4), and Methane (CH4) gas molecules, with a wideband operation between 2.7 and 3.4 µm optical wavelength. The results show that a simple Si3N4 waveguide structure could attain competitive performance required for generic on-chip spectroscopic sensing for environmental and agricultural usage.

Friction Performance and Mechanism of the Molybdenum Disulfide Film in Carbon Dioxide Atmosphere

In this work, the tribological properties of MoS2 films were investigated in air, vacuum and carbon dioxide environments by means of experiments and First-principles calculations. The results showed that the MoS2 film had the lowest and more stable coefficient of friction in carbon dioxide atmosphere than that in other environments. The MoS2 film usually loses some S atoms to produce S-vacancy defects during sputtering deposition, which can be filled by carbon dioxide molecules in a way of chemisorption. The strong repulsive force always existed at the interfaces of MoS2 adsorbed with carbon dioxide molecules, which was responsible for the low friction coefficient of MoS2 films in carbon dioxide. In the future, the MoS2 film is likely to be widely used on Mars that is well known for its CO2-rich atmosphere.

Experimental analysis of the CO2/CH4 Replacement Efficiency due to Sodium Chloride Presence in Natural Gas Hydrates Reservoirs

Nowadays natural gas hydrates represent a promising opportunity for counteracting several crucial issues of the 21th century. They are a valid answer to the continuously increasing energy demand, moved by the global population growth; moreover, considering their conformation and the possibility of using them for carbon dioxide permanently storage, gas hydrates may become a carbon neutral energy source, where for each methane molecule recovered, another carbon dioxide molecule is entrapped in solid form. Considering that the combustion of one methane molecule for energy production leads to the formation of one CO2 molecule, the hydrates exploitation can be considered a clean process in terms of impact on the climate change. This work shows how the presence of sodium chloride affects the CO2/CH4 replacement process into a gas hydrates reservoir. Replacement experimental results carried out in pure demineralised water were compared with the same values performed in a mixture of water and salt, having a concentration of 37 g/l. Some parameters of interest were discussed, such us methane hydrates formed before the replacement process, total amount of hydrates (composed by both species) reached at the end of the whole process, CO2 moles that formed hydrate, quantity of hydrate present before the replacement process which were actually involved in the CO2/CH4 exchange and carbon dioxide amount which led to the formation of new hydrates structures.

Synthesis of SrTiO3 submicron cubes with simultaneous and competitive photocatalytic activity for H2O splitting and CO2 reduction.

Single crystalline strontium titanate (SrTiO3) submicron cubes have been synthesized based on a molten salt method. The submicron cubes showed superior photocatalytic activity towards both water splitting and carbon dioxide reduction, in which methane (CH4) and hydrogen (H2) were simultaneously produced. The average production rate of methane up to 8 h is 4.39 μmol g−1 h−1 but drops to 0.46 μmol g−1 h−1. However, the average production rate of hydrogen is 14.52 before 8 h but then increases to 120.23 μmol g−1 h−1 after 8 h. The rate change of the two processes confirms the competition between the H2O splitting and CO2 reduction reactions. Band structure and surface characteristics of the SrTiO3 submicron cubes were characterized by diffuse reflective UV-Vis spectroscopy, Mott–Schottky analysis, X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). The results reveal that the simultaneous and competitive production of methane and hydrogen is due to a thermodynamics factor, as well as the competition between the adsorption of carbon dioxide and water molecules on the surface of the faceted SrTiO3. This work demonstrates that SrTiO3 photocatalysts are efficient in producing sustainable fuels via water splitting and carbon dioxide reduction reactions.

The role of carbon dioxide in acute brain injury.

Carbon dioxide is a common gas in the air which has been widely used in medical treatment. A carbon dioxide molecule consists of two oxygen atoms and one carbon atom through a covalent bond. In the body, carbon dioxide reacts with water to produce carbonic acid. In healthy people, carbon dioxide is maintained within a narrow range (35–45 mmHg) by physiological mechanisms. The role of hypocapnia (partial pressure of carbon dioxide < 35 mmHg) and hypercapnia (partial pressure of carbon dioxide > 45 mmHg) in the nervous system is intricate. Past researches mainly focus on the effect of hypocapnia to nerve protection. Nevertheless, Hypercapnia seems to play an important role in neuroprotection. The mechanisms of hypocapnia and hypercapnia in the nervous system deserve our attention. The purpose of this review is to summarize the effect of hypocapnia and hypercapnia in stroke and traumatic brain injury.

Screening and Isolation of Effective Microbes for Decomposition Process among Different Organic Waste

Organic waste is material that is biodegradable and comes from either plant or animal. It can be decomposed over time by microbes into methane, carbon dioxide, water, and other simple organic molecules. Microorganism especially bacteria and fungus are able to decompose cellulose by an enzyme known as cellulase. Since plants are made up from cellulose, this study is focused on isolating and identifying the microbes that are responsible in decomposing the organic waste by screening for the microorganisms that are able to produce cellulose enzyme. In this experiment, the bacteria were isolated from three different samples, which are; compost product, decayed wood and empty fruit bunch mix with oil palm frond. The samples were collected from the fresh decomposing organic waste. The samples undergo serial dilution, screening the ability of the microorganism to solubilize phosphate by using National Botanical Research Institute’s Phosphate media (NBRIP) and screening the ability of the microorganism to produce cellulose enzyme by using Carboxymethyl Cellulose Media (CMC) treated with Congo Red and NaCl for confirmation of the targeted effective microbes. The result shows that the targeted effective microbes will produce the halo zone or clear zone formation after being treated with Red Congo and NaCl solution on CMC media and producing a halo zone on NBRIP media. In this experiment, we manage to isolate and identify the bacteria that is responsible in producing cellulase enzyme and solubilizing phosphate that is known as Streptomyces sanglieri. Application of effective microbes will promote the plant uptake due to its ability in converting the nutrient into available form to the plant.

A molecular dynamics study on the CO2 permeability of microalgae lipid membrane

Reducing the amount of carbon emissions has been a formidable challenge especially to countries experiencing rapid economic growth. This prompted the development of various materials and methodologies to capture emissions to address climate change. The current study aimed to contribute in the development of carbon dioxide capture through the biological approach by using microorganisms such as microalgae. Biological fixation involving microalgae involves a complex process that has not been fully understood as current experimental methods can only deliver analysis on a macroscopic scale. The study demonstrated the dynamics of carbon dioxide molecules in the atomic scale using molecular dynamics. The permeation coefficient of carbon dioxide molecules was calculated at different range of temperature and salinity using the inhomogeneous solubility diffusion model. The GROMOS53a6 and SPC force field was used for the interaction of molecules. Moreover, the force autocorrelation function was used to calculate the diffusion coefficient. The resulting diffusion coefficients were in a good agreement with experimental data. The highest permeation coefficient of 2.3994 × 10−3 cm s−1 was calculated at 330 K 0.55 M conditions. Due to the nonpolar nature of carbon dioxide molecule, the mobility as it permeates inside the bilayer was not affected. Hence, the study suggests that the temperature and salinity does not prevent nor significantly affects the permeability of microalgae lipid membrane from carbon dioxide molecules.

Field-free molecular alignment of carbon dioxide molecules measured with above-threshold ionization yields

We present measurements of above-threshold ionization (ATI) of CO2 in a pump-probe experiment where the pump pulse creates a rotational wave packet and the linearly polarized probe pulse generates the ATI spectrum as a function of the pump-probe delay time, which sweeps over the revival time of field-free alignment and its quarter fractions. The observed alignment signals, which are the electron yields of ATI by a probe pulse as a function of a delay between the pump and probe pulse, are compared with the calculated alignment parameter [Formula: see text]. The results are explained by nuclear spin statistics and the wave packet evolution of the CO2 molecule in terms of the highest occupied molecular orbital.

A numerical analysis of a microwave induced coaxial surface wave discharge fed with a mixture of oxygen and hexamethyldisiloxane for the purpose of deposition

A microwave induced coaxial surface wave discharge with a feeding gas mixture of oxygen and hexamethyldisiloxane used for the deposition of polymer coatings is numerically analysed by a volume-averaged zero-dimensional modelling formalism. A set of edge-to-centre ratios are analytically estimated for a self-consistent description of the positive ion and reactive neutral flux at the radial walls (Kemaneci et al 2017 J. Phys. D: Appl. Phys. 50 245203). The simulation results are compared with the measurements of a wide variety of distinct particle concentrations as well as of the electron temperature and an agreement is obtained with respect to the input power, the pressure and the oxygen to hexamethyldisiloxane flow ratios. The net charge density is dominated by Si2OC5H with a negligible degree of electronegativity. Hexamethyldisiloxane is fragmented into methyl radical via the electron impact dissociation and the dissociative ionization. Large amounts of hydrocarbons, water, carbon monoxide, carbon dioxide and hydrogen molecules are produced. A significant portion of the net hydrocarbon and carbon monoxide production rates is formed by the emission from the solid surfaces due to the hydrogen and oxygen atom flux. The essential roles of C3H9SiO molecules and Si2OC5H ions on the deposition process are verified.

Investigation of a Gas Hydrate Dissociation-Energy-Based Quick-Freezing Treatment for Sludge Cell Lysis and Dewatering.

A gas Hydrate dissociation-energy-based Quick-Freezing treatment (HbQF) was applied for sewage sludge cell rupture and dewatering. Carbon dioxide (CO2) and water (H2O) molecules in sewage create CO2 gas hydrates, and subsequently the sludge rapidly freezes by releasing the applied pressure. Cell rupture was observed through a viability evaluation and leachate analysis. The decreased ratios of live cell to dead cells, increased osmotic pressure, and increased conductivity showed cell lysis and release of electrolytes via HbQF. The change in physicochemical properties of the samples resulting from HbQF was investigated via zeta potential measurement, rheological analysis, and particle size measurement. The HbQF treatment could not reduce the sludge water content when combined with membrane-based filtration post-treatment because of the pore blocking of fractured and lysed cells; however, it could achieve sludge microbial cell rupture, disinfection, and floc disintegration, causing enhanced reduction of water content and enhanced dewatering capability via a sedimentation post process. Furthermore, the organic-rich materials released by the cell rupture, investigated via the analysis of protein, polysaccharide, total organic carbon, and total nitrogen, may be returned to a biological treatment system or (an) aerobic digester to increase treatment efficiency.

Modulation of membrane permeability by carbon dioxide.

Promoting drug delivery across the biological membrane is a common strategy to improve bioavailability. Inspired by the observation that carbonated alcoholic beverages can increase the absorption rate of ethanol, we speculate that carbon dioxide (CO2 ) molecules could also enhance membrane permeability to drugs. In the present work, we have investigated the effect of CO2 on the permeability of a model membrane formed by 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine lipids to three drug-like molecules, namely, ethanol, 2',3'-dideoxyadenosine, and trimethoprim. The free-energy and fractional-diffusivity profiles underlying membrane translocation were obtained from μs-timescale simulations and combined in the framework of the fractional solubility-diffusion model. We find that addition of CO2 in the lipid environment results in an increase of the membrane permeability to the three substrates. Further analysis of the permeation events reveals that CO2 expands and loosens the membrane, which, in turn, facilitates permeation of the drug-like molecules. © 2019 Wiley Periodicals, Inc.

Experimental study of the reaction of NO2− ions with CO2 molecules at temperatures and energies relevant to the Martian atmosphere

Comprehensive theoretical models of the Martian ionosphere require reliable kinetic data for ion – molecule reactions over a wide range of temperatures. In situ measurements of the negative ions have not yet been performed and so ion chemical modelling is relied upon, which indicate that nitrite anions, NO2−, are important. Thus, in the present work the gas phase reaction of NO2− with carbon dioxide molecules, CO2, has been studied at the temperatures and energies relevant to the Martian atmosphere. The rate coefficient was measured over the temperature range 220 ± 2 K to 334 ± 2 K using a variable temperature selected ion flow tube (VT-SIFT) instrument. Additionally, a commercial Tandem Quadrupole Mass Spectrometer (TQMS) has been exploited to explore the reaction occurring during NO2−/CO2 collisions over the centre-of-mass energies from near-thermal to 6 eV. Two different channels of the reaction were studied. Under the thermal conditions of the VT-SIFT, the reaction is seen to proceed slowly via ternary association ultimately producing CO3– ions, the measured effective ternary rate coefficient in helium being k3 = (3.8 ± 1.5) × 10−30 cm6 s−1 at 220 ± 2 K and k3 = (0.5 ± 0.2) × 10−30 cm6 s−1 at 334 ± 2 K. The effective ternary rate coefficient can be greater in the Martian atmosphere where CO2 is the stabilizing gas. In the TQMS experiment, CO3– production occurs via a binary reaction above a threshold energy of 1.8 ± 0.2 eV. These experimental data can be used to refine the existing ion-chemical models of the Martian atmosphere.

Molecular scale modeling approach to evaluate stability and dissociation of methane and carbon dioxide hydrates

A comprehensive knowledge and precise estimation of the dynamic, structural, and thermodynamic characteristics of hydrates are needed to assess the stability of gas hydrates. Thermodynamic model and experimental studies can be utilized to compute the physical and dynamic properties of hydrate structures. The use of molecular dynamic (MD) simulation is a well-established approach in gas hydrate studies at the atomic level where the properties of interest are obtained from the numerical solution of Newtonian equations. The present work uses MD simulations by employing the constant temperature-constant pressure (NPT), constant temperature-constant volume (NVT) conditions, and the consistent valence force field (CVFF) to monitor the stability and decomposition of methane and carbon dioxide gas hydrates with different compositions. The effects of temperature and composition on the hydrate stability are investigated. In this study, we also compute the radial distribution function, mean square displacement, diffusion coefficient, lattice parameter, potential energy, dissociation enthalpy as well as the density of methane and carbon dioxide under various thermodynamic and process conditions. The formation of methane and carbon dioxide bubbles is studied to investigate bubble evolution during hydrate dissociation. The sizes of methane and carbon dioxide bubbles are not the same due to different solubility conditions of methane and carbon dioxide in liquid water. In addition, the influences of pressure and temperature on the lattice parameter and density of clathrate hydrates are discussed. The obtained results are consistent with previous theoretical and experimental findings, implying that the methodology followed in this work is reliable. The most stable arrangement of methane and carbon dioxide molecules in the gas hydrate is found. The insights/findings of this study might be useful to further understand detailed transport phenomena (e.g., molecular interactions, gas production rate, carbon dioxide replacement, and carbon dioxide capture) involved in the process of carbon dioxide injection into gas hydrate reservoirs.

Оценка положения и ширины работающего слоя регенеративного патрона изолирующего респиратора в условиях полноты достаточной статистики

Обоснована процедура экспериментального определения параметров асимптотики концентрации углекислого газа при исследовании динамической сорбционной активности регенеративного патрона изолирующего респиратора на химически связанном кислороде. Показано, что погрешность оценивания доли непоглощенных молекул углекислого газа на основе выборочного контроля в рамках схемы Бернулли уменьшается, если дисперсию оценки в условиях полноты достаточной статистики искать на классе смещенных оценок. Полученные результаты можно использовать для расчета феноменологических констант модели рабочего процесса изолирующего дыхательного аппарата, оптимизации температурного режима его регенеративного патрона и обоснования гарантированного срока защитного действия аппарата.

Formation of Carbon Dioxide Attached Fragment Ions in the Fragmentation of Deprotonated Tolfenpyrad and Tebufenpyrad

The in-source collision-induced dissociation (CID) and MS/MS mass spectra of deprotonated tolfenpyrad and tebufenpyrad both showed an unusual fragment ion at m/z 187, but its fragmentation pattern and structure could not be explained by logical neutral losses. Accurate mass measurement indicated that the mass difference between this fragment ion and the dominant fragment ion at m/z 143 equaled to a carbon dioxide (CO2) molecule. The isolation of the fragment ion m/z 143 in the mass analyzer could spontaneously give rise to the ion m/z 187. The Gibbs free energy of carbon dioxide addition to deprotonated pyrazole ion was significantly negative from the computational results. According to these results, we derived a proposal for the formation and structure of the ion m/z 187, which was an attachment of molecular carbon dioxide to the fragment ion m/z 143 to produce a carboxylate anion. The trace carbon dioxide was speculated to be derived from the residual atmosphere or collision gas in the instrument. This study is valuable for the qualitative and quantitative mass spectrometry analysis of pesticides containing the pyrazole functional group.

Infrared Radiation in the Energetics of the Atmosphere

A review of the processes in the Earth’s atmosphere that affect its energetics is presented. The energetics balance of the Earth and its atmosphere as a whole is considered, and the results of NASA programs for the monitoring of the global temperature and concentration of carbon dioxide and water in the atmosphere are presented. The spectra of the optically active components of the atmosphere in the infrared region are analyzed on the basis of classical methods of molecular spectroscopy. Spectroscopic data from the HITRAN databank facilitate the analysis and lead to a simple scheme whereby the three main greenhouse components—carbon dioxide, water vapor in the form of free water molecules, and a water droplet—create an infrared radiation flux directed toward the Earth’s surface. This radiation is created by water molecules in the range of 0–580 cm–1, the atmospheric radiation in the range of 580–780 cm–1 is determined by the molecules of water and carbon dioxide. At frequencies above 780 cm–1, the contribution to atmospheric radiation due to water molecules is approximately 5%, and the other is determined by the emission of water microdroplets, which partially form clouds. According to this model, at the present atmospheric composition, 52% of the radiation flux to the Earth’s surface is created by atmospheric water vapor, and 32% is due to microdroplets of water in the atmosphere, which include about 0.4% of atmospheric water and 14% of the radiation flux is determined by carbon dioxide molecules. Doubling the mass of atmospheric carbon dioxide, which will occur in about 120 years at the current rate of growth of atmospheric carbon dioxide, will lead to an increase in the atmospheric radiation flux towards the Earth by 0.7 W/m2, and a 10% increase in the atmospheric concentration of water molecules increases this radiation flux by 0.3 W/m2. Doubling of the mass of atmospheric carbon dioxide in a real atmosphere leads to an increase in the global temperature of 2.0 ± 0.3 K in a real atmosphere, according to NASA data analysis. If the concentration of other components does not change, then the change in global temperature will be 0.4 ± 0.2 K, and the contribution to this change due to industrial emissions of carbon dioxide into the atmosphere is 0.02 K.