The Effect of a Magnetic Field on the Kinetic Characteristics of Electrons in Gas Mixtures Containing Nitrogen, Carbon Dioxide, and Water Molecules

Quenching of excited alkali atoms and related effects in flames: Part II. Measurements and discussion

Low oil recovery which is very predominant in shale oil reservoirs has stimulated petroleum engineers to investigate the applications of enhanced oil recovery methods in these formations. One such application is the injection of gases into the formation to stimulate increased oil recovery. In many gas flooding projects performed in the field, the miscibility of the gas injected is usually the most desired displacement mechanism, and carbon dioxide (CO2) gas has been recognized to be the best performing gas for injection due to its ability to be miscible with oil in the reservoir at low pressures compared to other gases such as nitrogen. This minimum miscibility pressure (MMP) is of very crucial importance because it is the primary limiting factor in the feasibility of a miscible gas flooding project. However, there are other limiting factors such as cost and availability and, in these instances, nitrogen (N2) and lean gas are the more preferred candidate as opposed to carbon dioxide gas. Mixing carbon dioxide gas with lean gas or with nitrogen in a required ratio can allow us to design an injection gas that will be suitable enough to satisfy both the availability and cost constraints and at the same time allow us to achieve a reachable and reasonable miscibility pressure. The objective of this paper is to investigate the effect of mixing nitrogen gas and carbon dioxide gas in a 50:50 ratio on oil recovery in tight oil formations. The experiment was performed with controlled constraints such as the same core sample, same crude oil and same core cleaning and saturation process which was repeated for each trial. The oil used was live oil from Eagle ford formation, and the gases used were nitrogen (99.9% purity), carbon dioxide and a mixture of nitrogen and carbon dioxide in a 50:50 ratio. The injection pressure ranged from 1000 to 5000 psi with pressure increments of 1000 psi, and the same flooding time was 6 h. The potential of the N2, CO2 and N2–CO2 mixture for improving oil recovery was assessed along with the breakthrough time. The results showed that CO2 gas had the highest recovery followed by the N2–CO2 mixture and N2 gas had the lowest recovery. The gas breakthrough time results showed that the N2–CO2 mixture had the longest breakthrough time, N2 had the shortest breakthrough time, and CO2 had a significantly longer breakthrough time than pure N2 gas. The RF increased with increasing pressure, but the gas breakthrough time decreased with increasing pressure. However, the incremental RF decreased in all three cases when the injection pressure was above 3000 psi.

Methane hydrate exists in huge amounts in certain locations, in sea sediments and the geological structures below them, at low temperature and high pressure. Production methods are in development to produce the methane to a floating platform. There it can be reformed to produce hydrogen and carbon dioxide, in an endothermic process. Some of the methane can be burned to provide heat energy to develop all needed power on the platform and to support the reforming process. After separation, the hydrogen is the valuable and transportable product. All carbon dioxide produced on the platform can be separated from other gases and then sequestered in the sea as carbon dioxide hydrate. In this way, hydrogen is made available without the release of carbon dioxide to the atmosphere, and the hydrogen could be an enabling step toward a world hydrogen economy.

We have investigated the ability of two modular phyllosilicates (palygorskite and sepiolite) to store CO2 molecules inside their structural channels by means of classical molecular dynamics. Several models containing an increasing supercritical-CO2/H2O ratio into the phyllosilicate channels have been built and the structural and dynamic properties of carbon dioxide and water molecules investigated in detail. We found that both clay minerals can achieve this goal, with sepiolite being able to store more carbon dioxide molecules (and more stably) than palygorskite, due to the larger channels of the former. Interestingly, with the increase of CO2 molecules inside the minerals, the diffusivity of both water and carbon dioxide drastically decreases and carbon dioxide molecules tend to arrange themselves in an ordered pattern.

According to the present data, KA zeolite, which can adsorb only water vapor, helium, and hydrogen, has the greatest selectivity in drying. The feasibility of using this zeolite in devices for selective drying of gases used in gas-analysis systems was studied. The results of the experiments were approximated by the thermal equation of the theory of bulk filling of micropores. The limiting value of the adsorption depends on the temperature, and it can be calculated according to the density of the adsorbed phase and the adsorption volume. The critical diameters of the water and carbon dioxide molecules are close to the dimensions of the KA-zeolite pores, something that determines the activated nature of the adsorption of these substances. Experiments on coadsorption of water vapor and carbon dioxide by a fixed bed of KA-zeolite under dynamic conditions showed that the adsorption of these substances has a frontal nature. The time of the protective action of the layer of zeolite during adsorption af water vapor exceeded by more than an order the time of the protective action during adsorption of carbon dioxide. The results showed that this adsorbent can be used for selective drying of gas mixtures containing carbon dioxide in batch-operationmore » devices. Beforehand, the adsorbent should be regenerated with respect to moisture, and then it should be saturated with carbon dioxide by blowing the adsorbent with a gas mixture of the working composition until the equilibrium state is reached.« less

Molecular dynamics study on growth of carbon dioxide and methane hydrate from a seed crystal

Background: Recognizing effects of static magnetic field (SMF) of varying flux density on flora and fauna is attempted. For this purpose, the influence of static magnetic field upon molecules of water, nitrogen, ammonia, carbon dioxide, methane and molecular oxygen was studied. Methods: Computations of the effect of SMF of 0.1, 1, 10 and 100T flux density were performed in a computer vacuum involving advanced computational methods. Results: It was shown that SMF polarizes molecules depending on applied flux density but it neither ionizes nor breaks valence bonds. Three-molecular conglomerates of very dense packing form systems involving supramolecular orbitals. These orbitals deteriorate with an increase in the SMF flux density developing highly polarized structures. They are entirely different from these originally formed out of SMF. Conclusions: Small inorganic molecules commonly present in living organisms of flora and fauna can substantially influence functioning of those organisms when exposed to SMF.

Simulation of the interaction of methane, carbon dioxide and coal

Clathrate hydrates are non-stoichiometric compounds of water and gas molecules coexisting at relatively low temperatures and high pressures. The gas molecules are trapped in cage-like structures of the water molecules by hydrogen bonds. There are several hydrate deposits in permafrost and oceanic sediments with an enormous amount of energy. The energy content of methane in hydrate reservoirs is considered to be up to 50 times that of conventional petroleum resources, with about 2,500 to 20,000 trillion m3 of methane gas. More than 220 hydrate deposits in permafrost and oceanic sediments have been identified to date. The exploration and production of these deposits to recover the trapped methane gas could overcome the world energy challenges and create a sustainable energy future. Furthermore, global warming is a major issue facing the world at large and it is caused by greenhouse gas emissions such as carbon dioxide. As a result, researchers and organizations have proposed various methods of reducing the emission of carbon dioxide gas. One of the proposed methods is the geological storage of carbon dioxide in depleted oil and gas reservoirs, oceanic sediments, deep saline aquifers, and depleted hydrate deposits. Studies have shown that there is the possibility of methane gas production and carbon dioxide storage in hydrate reservoirs using the injection of carbon dioxide and nitrogen gas mixture. However, the conventional hydrocarbon production methods cannot be used for the hydrate reservoirs due to the nature of these reservoirs. In addition, thermal stimulation and depressurization are not effective methods for methane gas production and carbon sequestration in hydrate-bearing sediments. Therefore, the gas replacement method for methane production and carbon dioxide storage in clathrate hydrate is investigated in this paper. The research studies (experiments, modeling/simulation, and field tests) on CO2/N2 gas mixture injection for the optimization of methane gas recovery in hydrate reservoirs are reviewed. It was discovered that the injection of the gas mixture enhanced the recovery process by replacing methane gas in the small and large cages of the hydrate. Also, the presence of N2 molecules significantly increased fluid injectivity and methane recovery rate. In addition, a significant amount of free water was not released and the hydrate phase was stable during the replacement process. It is an effective method for permanent storage of carbon dioxide in the hydrate layer. However, further research studies on the effects of gas composition, particle size, and gas transport on the replacement process and swapping rate are required.

Zeolites have long been considered as excellent candidate materials for gas separation and purification. Most of the worldwide industrial adsorption applications of molecular sieve zeolites utilize zeolites X, A and Y. Chabazite zeolite however, has pore dimensions between those for zeolites X, A and Y and hence has promising separation features for specific application but has not been utilized in any major industrial separation or purification applications to date. Some early work on alkali-exchanged chabazites revealed a diminished porosity and surface area due to pore blockage. This initial work was based on limited experimental data and preliminary analytical techniques and analysis. As a result, this initial pessimistic assessment of the merits of chabazite zeolite has led to a loss of interest in this material for adsorption applications. In this study, a pure phase chabazite was synthesized and ion-exchanged to produce potassium chabazite (KCHA), sodium chabazite (NaCHA) and lithium chabazite (LiCHA). Attempts were successful to produce a fully exchanged potassium chabazite, which is a unique product that has not been reported in the literature to date. The adsorption of nitrogen and carbon dioxide was studied since these gases are component of flue gas and the application to which chabazites were to be directed was CO2 capture form flue gas. Adsorption equilibrium isotherms for CO2 and N2 were measured at pressures up to 101.3 kPa and temperatures of 273, 303 and 333 K. More importantly, this work focused on determining fundamental properties of adsorbate-adsorbent interactions which require low pressure measurements hence low pressure isotherms, down to 0.001 kPa, were measured. These data provide valuable information to study the adsorption behavior in the Henry’s law region. The results showed that porosity characterization of KCHA using the conventional approach of nitrogen at 77 K reveals a surface area of only 17.82 m2 g-1 and a diminished pore volume (by density functional calculation) of 0.005 cm3 g-1, compared to 584.4 m2 g-1 and 0.214 cm3 g-1 using carbon dioxide at 273 K, respectively, calculated from the revised Toth model and CO2 isotherm data at 273K. These findings strongly suggested that KCHA is a highly porous adsorbent, in spite of the large size of K+ ions which block access of the N2 molecules to the pore space. It is concluded that traditional methods of characterization are not suitable in the case of pore blockage leading to incorrect interpretation of adsorbent properties. It was initially hypothesized that carbon dioxide molecules enjoy large freedom within the zeolite pores, however, virial plots developed from equilibrium isotherms showed anomalous behavior for carbon dioxide adsorption at 273 K on NaCHA and KCHA at loadings lower than 1.5 gmole kg-1, which correspond to pressure of about 0.15 kPa. This suggested that carbon dioxide molecules were not at true equilibrium condition, but rather were subject to steric hindrance due to partial pore blockage. Adsorbed phase densities calculated from van der Waals constants confirmed the pore blockage phenomenon on KCHA, however, it also reveals a slight blockage against nitrogen molecules on NaCHA. On the synthesized chabazites, carbon dioxide affinities and heats of adsorption were considerably higher than those for nitrogen for which their adsorption equilibria differ significantly due to screening against nitrogen molecules in KCHA and partially in NaCHA. Carbon dioxide entropy measurement revealed a concave trend, demonstrating an appreciable loss of degrees of freedom within increase in loading. Carbon dioxide desorption isotherms showed low pressure hysteresis at 273 K with residuals of 0.37 and 0.57 molecule cavity-1 on NaCHA and KCHA, respectively, at pressures lower than 0.05 kPa. This outcome confirmed the pore blockage occurrence suggesting a low pressure encapsulation. The combined use of the statistical theory of the radial distribution function (rdf) and the theory of the perfect 3D lattice gas to describe the encapsulation process underestimated the number of accommodated molecules compared to the experimental results. The individual implementation of Lennard-Jones and quadrupolar potentials to describe the adsorbate-adsorbate and adsorbate-host interactions, respectively, affected the performance of the models.

We have performed a number of quantum chemical simulations to examine water cluster catalyzed decomposition of formic acid. The decomposition of formic acid consists of two competing pathways, dehydration, and decarboxylation. We use the Gaussian 4 method of the Gaussian09 software to locate and optimize a transition state of the decomposition reaction and obtain the activation energy. The decomposition starts by transferring a proton of a formic acid to a water molecule. The de Broglie wavelength of a proton is similar to the width of the potential barrier of the decomposition reaction at low temperature. The tunneling, in which a proton penetrates the potential barrier, enhances the decomposition rate. Water molecules serve as the catalyst in the decomposition and reduce the activation energy. The relay of a proton from a water molecule to a neighboring water molecule is accomplished with little change of the geometry of a molecule, resulting in the reduction of the activation energy. Two water molecules are actively involved in the decomposition reaction to reduce the activation energy. We have also examined the effect of water clusters with three, four, and five water molecules on the decomposition reaction. The noncovalent distance between a hydrogen atom of a water molecule and an oxygen atom of a neighboring water molecule decreases in a water cluster due to the cooperative many-body interactions. A water molecule in a water cluster becomes a better proton donor as well as a better proton acceptor. The activation energy of the decomposition is further decreased by the catalytic effect of a water cluster. We calculate the reaction rate using the transition state theory corrected by the tunneling effect of a proton. The calculated reaction rate of the decarboxylation is smaller than that of the dehydration when less than three water molecules are included in the simulation. However, the major product of the decomposition of a formic acid becomes carbon dioxide and hydrogen molecule formed by the decarboxylation when a water cluster with more than four water molecules serves as catalyst in the decomposition of formic acid.

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.

Adsorption–desorption isotherms for nitrogen, carbon dioxide, oxygen and helium on as-received TCM-128 ultramicroporous carbon are reported for pressures up to 60 atm at 35 °C. Evidence is presented that suggests that there are regions in the carbon that are composed of tiny hydrophobic constrictions in series, which are hardly penetrated, and more open pores inside. At room temperature, water molecules cannot penetrate these constrictions in reasonable time due to a clustering effect, while the much bigger, but unclustered nitrogen and carbon dioxide molecules do penetrate these constrictions at a measurable rate. These regions are responsible for unexpected hysteresis observed for nitrogen and carbon dioxide at 35 °C and the unusually large amount of helium adsorbed.

The thermal decomposition of natural mixtures of huntite and hydromagnesite

Theoretical molecular behaviour analysis of the hydrogen rich gas production from the steam reforming process of formic acid (HCOOH) has been studied by quantum chemical calculation. The dehydrogenation of formic acid molecules in aqueous and vacuum conditions yields the formation of carbon dioxide (CO2), hydrogen (H2) gases, and water (H2O) molecules. The geometric properties of formic acid, water, carbon dioxide, hydrogen, reactant (HCOOH + H2O), and product (CO2 + H2 + H2O) molecules were carried out using DFT/B3LYP method in TmoleX software with a def-SV(P) basis set. The method validation was done by comparing the fundamental features of the optimized formic acid geometry with the literatures. The reactivity, stability, electron donating-accepting electron property, and energetic behaviour of every single molecule, reactant, and product were studied and explained by the energy of HOMO and LUMO, band gap energy (∆E), chemical potential (μ), the global hardness (η), softness (σ), and electronegativity (χ).