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Nitrous oxide (N2O) is an important greenhouse gas (GHG) which has a global warming potential 310 times that of carbon dioxide (CO2) over a hundred year lifespan. N2O is generated during microbial nitrification and denitrification, which are common in aquaculture systems. To date, few studies have been conducted to quantify N2O emission from aquaculture. Additionally, very little is known with respect to the microbial pathways through which N2O is formed in aquaculture systems. This review suggests that aquaculture can be an important anthropogenic source of N2O emission. The global N2O-N emission from aquaculture in 2009 is estimated to be 9.30 × 1010 g, and will increase to 3.83 × 1011g which could account for 5.72% of anthropogenic N2O-N emission by 2030 if the aquaculture industry continues to increase at the present annual growth rate (about 7.10%). The possible mechanisms and various factors affecting N2O production are summarized, and two possible methods to minimize N2O emission, namely aquaponic and biofloc technology aquaculture, are also discussed. The paper concludes with future research directions. [ABSTRACT FROM AUTHOR]

In this paper we show the performance of a new CO2 sorbent consisting of a dry physical mixture of a Ca-based sorbent and a SiO2 nanostructured powder. Thermo-gravimetric analysis (TGA) performed at conditions close to the Ca-looping process demonstrate that the rate of CO2 capture by the mixture is enhanced during the fast carbonation stage of practical interest in applications. Moreover, the residual capture capacity of the mixture is increased. SEM/EDX, physisorption, and XRD analyses indicate that there is a relevant interaction between the nanostructured SiO2 skeleton and CaO at high temperatures, which serves to improve the efficiency of the transfer of CO2 to small reactive pores as well as the stability of the sorbent pore structure. [ABSTRACT FROM AUTHOR]

In recent years, many problems of elemental sulfur depositsinnatural gas transmission line systems have been noted. These problemsoccur very often immediately downstream of a pressure reduction facility.To prevent the apparition of solid sulfur deposits causing securityand maintenance problems it is imperative to determine sulfur solubilityin natural gas at pressures and temperatures corresponding to transportconditions. In a previous work (Serin et al. J. Supercrit.Fluids2010, 53, 12–16),an original experimental apparatus was designed, and experimentalsaturation values of carbon dioxide in sulfur were obtained. The protocolprinciple is schematically divided into three steps: saturation, trapping,and quantification. In this work, experimental sulfur solubility inmethane was measured and compared to available studies at 363.15 Kin the pressure range from (4 to 25) MPa. This paper presents thesemeasurements and the improvements of the trapping and quantificationsteps that have been made to get these solubility data. [ABSTRACT FROM AUTHOR]

Our previous publications have demonstrated that thinglassy polymer films respond to highly sorbing penetrants, such asCO2, quite differently than thick films. These studiesfocused on CO2permeation behavior and revealed that, forthin films, CO2permeability at constant CO2pressure goes through a maximum followed by a continual decreasein permeability owing to physical aging. So far, thick and thin glassypolymer films have been compared in the context of permeability, butlack of substantial means of obtaining thin film sorption data hasprevented adequate comparison of thick and thin films in the contextof gas solubility. In this paper, spectroscopic ellipsometry is usedto obtain simultaneously the film thickness and CO2sorptioncapacity for thin glassy polymer films. This allows a more comprehensivelook at CO2permeability, sorption, and diffusivity asa function of both CO2pressure and exposure time. Theevidence reported here suggests that thin film sorption behavior issubstantially different than that of thick film counterparts. Partialmolar volume is determined from sorption-induced swelling data. Fractionalfree volume and diffusivity are calculated as a function of CO2pressure. Dual sorption model parameters are presented forMatrimid thin films for different aging times. Dynamic ellipsometryexperiments show that refractive index minima, fractional free volumemaxima, and CO2diffusivity maxima correlate well withobserved CO2permeability maxima observed for thin Matrimidfilms. The results support the claim that plasticization and physicalaging are competing processes but that aging dominates over long timescales. The CO2diffusivity behavior over time is mostaffected by the competing effects of plasticization and aging, andthe evolution of CO2diffusivity is shown to be the maincontributing factor to changes in CO2permeability at constantpressure. [ABSTRACT FROM AUTHOR]

Polytetrafluoroethylene (PTFE) plasma sputtering of polypropylene (PP) membranes allows the formation of an ultrathin fluorinated hydrophobic surface that retains the microporous surface structure of the underlying membrane. The absorption results presented in this paper show that the novel PP membrane material performs well for the separation of CO2from other gases, using an amine-based solvent. Hollow fiber membrane experiments show that the plasma-treated hollow fiber membrane has a superior CO2mass transfer rate to untreated PP when coupled with monoethanolamine solvent flowing through the fiber lumen for at least 45 h of absorption time. The CO2mass-transfer rate through the treated hollow fiber membrane is also comparable with that of other researchers who have absorbed CO2into amine solvents using PTFE hollow fibers and higher than that measured using packed column technology with structured packing and amine solvents. [ABSTRACT FROM AUTHOR]

In this paper, we present two different approaches to represent/predict the gas hydrate phase equilibria for the carbon dioxide, methane, or ethane + pure water system in the presence of various types of porous media with different pore sizes. The studied porous media include silica gel, mesoporous silica, and porous silica glass. First, a correlation is presented, which estimates the hydrate suppression temperature due to the pore effects from the ice point depression (IPD). In the second place, several mathematical models are proposed using the least squares support vector machine (LSSVM) algorithm for the determination of the dissociation pressures of the corresponding systems. The results indicate that although the applied correlation based on the (IPD) leads to obtaining reliable results for the gas hydrate systems in the presence of porous silica glass media, the developed LSSVM models seem to be more general due to their predictive capability over all of the investigated systems. [ABSTRACT FROM AUTHOR]

Improvement in the efficiency of CO2separation from flue gases is a high-priority research area to reduce the total energy cost of carbon capture and sequestration technologies in coal-fired power plants. Efficient CO2removal from flue gases by adsorption systems requires the design of novel sorbents capable of capturing, concentrating, and recovering CO2on a cost-effective basis. This paper describes the preparation of an aminosilane-functionalized cellulosic polymer sorbent with enhanced CO2sorption capacity and promising performance for use in postcombustion carbon capture via rapid temperature-swing adsorption systems. The introduction of aminosilane functionalities onto the backbone of cellulose acetate was achieved by the anhydrous grafting of N-(2-aminoethyl)-3-aminoisobutyldimethylmethoxysilane. The dry sorption capacity of the modified cellulosic polymer reached 27 cc (STP) CO2/cc sorbent (1.01 mmol/g sorbent) at 1 atm and 39 cc (STP) CO2/cc sorbent (1.46 mmol/g sorbent) at 5 atm and 308 K. The amine loading achieved was 5.18 mmol amine(nitrogen)/g sorbent. Exposure to water vapor after the first dry sorption cycle increased the dry sorption capacity of the sorbent by 12% at 1 atm, suggesting its potential for rapid cyclic adsorption processes under humid feed conditions. The CO2sorbent was characterized in terms of chemical composition, density changes, molecular structure, thermal stability, and surface morphology. [ABSTRACT FROM AUTHOR]

This paper reports the experimental study on the preservation of CO2hydrate crystal samples at domestic freezer conditions for 3 weeks. These samples were characterized by initial hydrate mass fractions of 0.95 and 0.50, by particle diameters of smaller than 2.8, 2.8–4.0, and 5.6–8.0 mm and greater than 8.0 mm, and also by preservation temperatures at 258 and 253 K. The results revealed that the stability of CO2hydrate depends on the particle size, the initial hydrate mass fractions in the samples, and the preservation temperatures. Better stability was observed for CO2hydrate crystal samples of larger particle size and lower initial hydrate fraction and preserved at lower temperature. Visual observations of CO2hydrate crystal samples showed that dissociation occurs on the surface of the crystal samples. These experimental results indicated the possibility of the development of novel food/drink products containing CO2hydrate. [ABSTRACT FROM AUTHOR]

Work reported in this paper is the continuation of a previous work (Atilhan et al. J. Chem. Eng. Data2011, 56, 212–221) and reports measurements of density and phase envelope characteristics of three synthetic natural gas-like mixtures. These mixtures consist of primarily 0.9000 methane in mole fraction and variable amounts of ethane, propane, 2-methylpropane, butane, 2-methylbutane, and pentane as well as the presence or absence of nitrogen and carbon dioxide. A high-pressure single-sinker magnetic suspension densimeter was used to measure the density of the mixtures along three isotherms at (250, 350, and 450) K with pressures up to 150 MPa. Density measurements are compared to the GERG04 and AGA-8 equations of state, which are the two leading models used for natural gas density predictions. Predictions from both equations have a similar agreement with the data, yet it is observed that GERG04 model shows better performance in predictions with deviations less than around 0.2 % at different temperatures (T= 350 K and T= 450 K) and pressures (p> 20 MPa). An isochoric apparatus was used for phase envelope experiments, and the data are compared to several cubic biparametric, cubic triparametric, and molecular-based equation of states. Equation-of-state predictions for the mixtures and comparison with the experimental data are shown. Equation-of-state predictions show substantial deviations around the entire phase envelope for the third mixture, in which the nitrogen and carbon dioxide have not been included. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks with unsaturated metal centers in their crystal structures, such as Ni/DOBDC and Mg/DOBDC, are promising adsorbents for carbon dioxide capture from flue gas due to their high CO2capacities at subatmospheric pressures. However, stability is a critical issue for their application. In this paper, the stabilities of Ni/DOBDC and Mg/DOBDC are investigated. Effects of steam conditioning, simulated flue gas conditioning, and long-term storage on CO2adsorption capacities are considered. Results show that Ni/DOBDC can maintain its CO2capacity after steam conditioning and long-term storage, whereas Mg/DOBDC does not. Nitrogen isotherms for Mg/DOBDC show a drop in surface area after steaming, corresponding to the decrease in CO2adsorption, which may be caused by a reduction of unsaturated metal centers in its structure. Conditioning with dry simulated flue gas at room temperature only slightly affects CO2adsorption in Ni/DOBDC. However, introducing water vapor into the simulated flue gas further reduces the CO2capacity of Ni/DOBDC. [ABSTRACT FROM AUTHOR]

One possible way to reduce our carbon footprint is using postcombustion capture (PCC) processes to remove CO2from flue gases. Because of the highly dynamic characteristics of such processes, real-time performance monitoring is a very complex task. This paper presents a method for monitoring the concentrations of CO2, SOx, and a CO2capturing agent (β-alanine) during a process in a PCC pilot plant. A partial least-squares (PLS) model was built to estimate these concentrations from Fourier transform infrared (FTIR) spectra of the capturing solvent during processing in a model PCC plant. The model predicts the species concentrations to within 0.05 mol/L, provided that the concentrations stayed within the calibration window of the model. Next to that, it is paramount that the solutions used for model calibration consist of the same solution matrix as the real process medium. The model was eventually used to monitor an emulated PCC process online during 24 h of processing. This demonstrated that events such as saturation of the capturing agent with CO2, water replenishment, and switching to safety protocols can be followed accurately. The combination of an FTIR spectrometer and a PLS model can be used to extract process information in real-time. [ABSTRACT FROM AUTHOR]

Nitrosamines are a class of carcinogenic, mutagenic, and teratogenic compounds generally produced from the nitrosation of amine. This paper investigates the mechanism for the formation of nitrosodimethylamine (NDMA) from the nitrosation of dimethylamine (DMA) by four common nitrosating agents (NCl) in the absence and presence of CO2 using the DFT method. New insights are provided into the mechanism, emphasizing that the interactions of CO2 with amine and nitrosating agents are both potentially important in influencing the role of CO2 (catalyst or inhibitor). The role of CO2 as catalyst or inhibitor mainly depends on the nitrosating agents involved. That is, CO2 shows the catalytic effect when the weak nitrosating agent Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed. is involved, whereas it is an inhibitor in the nitrosation induced by the strong nitrosating agent N2O3 or ONCl. To conclude, CO2 serves as a "double-edged sword" in the nitrosation of amine. The findings will be helpful to expand our understanding of the pathophysiological and environmental significance of CO2 and to develop efficient methods to prevent the formation of carcinogenic nitrosamines. [ABSTRACT FROM AUTHOR]

The present paper proposes to use the group contribution (GC) polar perturbed-chain-statistical associating fluid theory (GC-PPC-SAFT) equation of state (EoS), that has already been used with success on various organic mixtures, and extend it to model simultaneously the liquid–liquid equilibrium (LLE) and vapor–liquid equilibrium (VLE) of hydrocarbons water systems, in wide ranges of pressure and temperature. Mixtures of water with aliphatics, aromatics, alcohols, carbon dioxide, and hydrogen sulfide have been investigated. Pure water is assumed associative (according to the 4C association scheme) and dipolar; the aromatic compounds are quadrupolar. Alcohols are autoassociative with a 3B association scheme. A cross-association between water and alcohols or H2S is taken into account. Cross association between water and other polar molecules (CO2or aromatic molecules) was also taken into account explicitly. Only one set of cross association parameters εcross/kand κcrossvalues were used for all the water aromatic mixtures considered here. εcross/kwas adjusted on experimental data, whereas κcrossis set to the value found for pure water. For each system, the same binary interaction parameter kijwas used for simultaneous modeling LLE and VLE. This parameter was correlated to pseudo-ionization energy parameters for pure compounds through London’s dispersion force theory, and reused from previous works [Nguyen-Huynh, D.; Passarello, J.P.; Tobaly, P.; de Hemptinne, J.C. Ind. Eng. Chem. Res., 2008, 47, 8847–8858]. For pure water, the average deviation on vapor pressure is 3.36% and that on volume 4.74%. The water solubility in the organic phase is very well reproduced (AAD = 7.5% for water n-hexane), but most importantly the hydrocarbon solubility in water shows an overall AAD of 30% which is very small considering the very low solubility values. Trends are similar for all families as tabulated in the manuscript and detailed in the Supporting Information. [ABSTRACT FROM AUTHOR]

Much of the previous research on carbon capture and storage (CCS) has focused on individual technologies for disposing of CO2, such as capture, storage, sequestration, or transport. Moreover, recent research work considers utilization of CO2as fuels, chemicals, or nutrients for bioreactors. To efficiently manage CO2and the economic benefits achieved by this process, the CO2transport and processing infrastructure supporting CCS will have to be constructed at a macro-scale. This paper introduces a scalable and comprehensive infrastructure model for CO2utilization and disposal that generates an integrated, profit-maximizing CCS system. The proposed model determines where and how much CO2to capture, store, transport, utilize or sequester to maximize total annual profit while meeting the CO2mitigation target. The applicability of the proposed model is demonstrated using a case study for treating CO2emitted by an industrial complex on the eastern coast of Korea in 2020. The results may be important in systematic planning of a CCS infrastructure and in assisting national and international policy makers to determine investment strategies for developing CCS infrastructures. [ABSTRACT FROM AUTHOR]

In this paper, we report microsecond molecular dynamics simulations of the kinetic pathway of CO2hydrate formation triggered by hydroxylated silica surfaces. Our simulation results show that the nucleation of the CO2hydrate is a three-stage process. First, an icelike layer is formed closest to the substrates on the nanosecond scale. Then, on the submicrosecond timescale, a thin layer with intermediate structure is induced to compensate for the structure mismatch between the icelike layer and the final stable CO2hydrate. Finally, on the microsecond timescale, the nucleation of the first CO2hydrate motif layer is generated from the intermediate structure that acts as nucleation seeds. We also address the effects of the distance between two surfaces. [ABSTRACT FROM AUTHOR]

The constant-volume method is used to determine the solubility of CO2in methanol, ethanol, n-propanol, n-butanol, n-propanol, ethylene glycol, propylene glycol, acetone, 2-butanone, ethylene glycol monomethyl ether, and ethylene glycol monoethyl ether under the pressure of 6 MPa and the temperature variations from (288.15 to 318.15) K in this paper. It is found by contrast that ketones have a greater ability to dissolve CO2than alcohols, ethers, and glycols, which also indicate that both the carbonyl group and the ether bond in solvents can promote the CO2absorption, but hydroxyl group will inhibit the CO2absorption. [ABSTRACT FROM AUTHOR]

In this paper, two commercial polymers, poly(vinyl ethyl ether) (PVEE) and poly(1-decene) (P-1-D), are tested to thicken CO2for CO2enhanced oil recovery (EOR). First, a series of laboratory tests are conducted to measure the cloud-point pressures of either polymer at different polymer solubilities in supercritical CO2and the equilibrium interfacial tensions (IFTs) of a light crude oil-pure or polymer-thickened CO2system under different reservoir conditions. Second, a capillary viscometer is used to measure the viscosities of polymer-thickened CO2at different test pressures. Third, a total of six high-pressure CO2coreflood tests are performed to examine the effects of polymer-thickened CO2on the total CO2EOR. It is found that at the same and low polymer solubility in pure CO2, the measured cloud-point pressure of PVEE is much lower than that of P-1-D. The measured equilibrium IFT for polymer-thickened CO2at a high pressure is much lower than that for pure CO2. The PVEE- or P-1-D-thickened CO2viscosity is approximately (13 to 14) times higher than the pure CO2viscosity. The CO2coreflood test results show that PVEE- or P-1-D-thickened CO2flooding can further enhance oil recovery after a pure CO2breakthrough. The CO2breakthrough can be significantly delayed if polymer-thickened CO2is injected directly. [ABSTRACT FROM AUTHOR]

This paper presents the bubble-point pressure data of CO2in ionic liquids 1-butyl-1-methyl-pyrrolidinium bis(trifluoromethylsulfonyl)imide ([BMP][Tf2N]) and 1-butyl-1-methylpyrrolidinium methylsulfate ([BMP][MeSO4]). In our research, the high-pressure phase behavior of carbon dioxide in [BMP][Tf2N] and [BMP][MeSO4] were observed at pressure up to about 100 MPa in a temperature range from (303.15 to 373.15) K in 10 K intervals by using a high-pressure variable-volume view cell. To investigate the effect of different anion on the solubility of CO2in the [BMP] cation based ionic liquids, we compared three [BMP] cation based systems; [BMP][Tf2N] +, [BMP][TfO] +, and [BMP][MeSO4] + CO2. In all systems, at lower mole fraction of CO2(below 0.3), the solubility is approximately the same, however above 0.3 mol fraction, the ration between pressure and CO2mol fraction decreases sharply. Although these experiments have used the same cation, it would appear that the ratio decreases more sharply as the alkyl group chain length of the anion decreases. It can also be observed that when the alkyl group chain lengths are similar, the system containing fluoroalkyl group chain shows higher solubility. However at this stage a thorough analysis of these effects cannot be made. Additionally, the solubility of CO2decreases linearly with rising temperatures at a fixed mole fraction of CO2. The experimental data for the CO2+ ionic liquid system were correlated using the Peng−Robinson equation of state. [ABSTRACT FROM AUTHOR]

Dawsonite-type compounds, with the general formula MAlCO3(OH)2, where M = Na+, K+, or NH4+, recently have become attractive materials because of their potential interest in geochemical CO2 sequestration, CO2 capture in power plants, and heterogeneous catalysis. However, the number of studies assessing the properties of these materials is limited. In the present paper, we report a theoretical reevaluation of the structural and essential physicochemical properties of Na-, K-, and NH4-dawsonites as determined by density functional theory (DFT) investigations. The calculated structure of Na- and K-dawsonites is in good agreement with previous data, while for NH4AlCO3(OH)2, the calculations suggest orientation disorder of the ammonium ions in the structure. The normal-mode analysis, electronic and bonding properties, and elastic properties are reported for the three analogue dawsonites. The calculated formation enthalpy is -1714, -1699, and -1655 kJ/mol for K-, Na-, and NH4-dawsonite, respectively. This study comprises a first step toward a better understanding of the diversity of dawsonite intrinsic properties, which is required to tune their practical applications. [ABSTRACT FROM AUTHOR]

A modified duplex PSA has been proposed, which could yield sharp separation and has the potential for process intensification. The performances for the original and the modified duplex PSA have been evaluated for two types of systems: the CO2−N2−13X zeolite with single component adsorption and the N2−O2−5A zeolite with competing adsorption. Part 1 of the companion papers presents the simulation studies on the separation of the CO2−N2mixture. The purities of both products were in excess of 99 mol % with the modified duplex PSA against 78 mol % CO2and 95 mol % N2with the original duplex PSA for the same conditions. The bed sizes and energy requirements for the modified duplex PSA were one-half of those for the original duplex PSA. Part 2 presents studies on the separation of the N2−O2mixture. [ABSTRACT FROM AUTHOR]

In this paper, oil recovery and permeability reduction of a tight sandstone reservoir in immiscible and miscible CO2flooding processes are experimentally studied. First, a series of saturation tests are conducted to determine the onset pressure of asphaltene precipitation from a light crude oil−CO2system. Second, the vanishing interfacial tension (VIT) technique is applied to determine the minimum miscibility pressure (MMP) between the light crude oil and CO2. Third, a total of nine CO2coreflood tests under immiscible and miscible conditions are performed through the so-called dry, secondary, and tertiary oil recovery processes, respectively. It is found that the onset pressure of asphaltene precipitation is much lower than the MMP. In the CO2secondary oil recovery process, the coreflood test data show that, when the injection pressure is between the onset pressure of asphaltene precipitation and the MMP, the oil recovery factor is higher but the oil effective permeability reduction is larger at a higher injection pressure in the immiscible CO2flooding. They both reach almost constant maximum values in the miscible CO2flooding (P≥ MMP). It is also found that, in three different miscible CO2oil recovery processes, the CO2tertiary flooding process gives the lowest oil recovery factor but the largest oil effective permeability reduction. This is attributed to the most severe codeposition of asphaltenes and metal carbonates. However, the CO2dry or secondary flooding process has a significantly higher oil recovery factor but a much smaller oil effective permeability reduction due to asphaltene deposition alone in the former process or codeposition of asphaltenes and metal carbonates in the latter process. [ABSTRACT FROM AUTHOR]

It is well-known that amines have the tendency to undergo aerial carbonation to form sec-ammonium N-carboxylates (carbamates). In fact, carbamate formation may be a quite general and functionally important phenomenon throughout biology, as carbamate moieties are key components in the biological fixation of CO2by living organisms. Currently, there is renewed interest in the use of amino acids for removal of CO2from gas streams that also contain oxygen. These facts justify the wide interest in research on the formation of carbamate derivatives from carbon dioxide, an aspect that this paper explores for the “amino bile acids”. The 24-amine derivatives of cholic (24-amine-CA) and chenodeoxycholic (24-amine-CDCA) acids were synthesized following literature procedures. These compounds were recrystallized in water. The empirical formula evidenced that half of the molecules retain the expected amine structure for the compound (in its protonated form) but the remaining 50% have a carbamate moiety resulting from aerial carbonation of the amino group. Both compounds recrystallize as salts and contain some water molecules as guests. In both crystals, the molecular arrangements lead to favorable electrostatic interactions between the negative charge of the carbamate group and the positive one of the ammonium, since they are located very close to each other. It is remarkable that the O7−H group of ammonium molecules of 24-amine-CDCA is located in a large hydrophobic region and does not participate in the hydrogen bond network. This absence has not been reported in any crystal structure of bile acids. It is also noteworthy that the N25 atom of the carbamic molecules does not participate in hydrogen bonding. The presence of the O12−H hydroxyl group in 24-amine-CA leads to a different hydrogen bond network with respect to 24-amine-CDCA, but the strong ammonium-carboxylate interaction remains. For comparative studies, 3-amine-CA was also recrystallized in water, under the same conditions of 24-amine derivatives. The 3-amine-CA crystallizes in its zwitterionic form. Since a strong ammonium-carboxylate interaction is observed, forming a N−H···O24 hydrogen bond, it is concluded that it can be the main reason for which the carbamate reaction has not taken place in the 3-amine derivative. This interaction appears in the 24-amine derivatives once the carbamates are formed. [ABSTRACT FROM AUTHOR]

Steam hydration of lime is an effective method for restoring CO2capture activity but gives rise to high particle attrition rates in a fluid bed reactor. This paper describes the phenomenon of Ca(OH)2superheating, also referred to as superheated dehydration (SD). The potential of an attrition-free lime reactivation process using this phenomenon is also investigated. Attrition rates of the sorbent are measured when a reactivation step using steam hydration is implemented every three carbonation/calcination cycles. It has been shown that the presence of CO2during the dehydration step reduces attrition during subsequent cycles. Experiments performed in a small fluid bed reactor show that the presence of 40−100% CO2during the dehydration step increases the initiation temperature of the decomposition of Ca(OH)2from 445 to 618 °C. The thermodynamic equilibrium water vapor pressure for the dehydration reaction at 618 °C is 516 kPa, whereas no water vapor was detected in the reactor during the dehydration step before the temperature reached 618 °C. Under these circumstances it is proposed that the Ca(OH)2is in a nonequilibrium “superheated state”. A CO2capture cycling experiment, with a reactivation step every three carbonation/calcination cycles, maintained an average activity of 60%, creating only 3.25% of fines < 150 μm after 28 carbonations. The reactivation step consisted of hydrating the sorbent at a temperature of 270 °C and dehydrating it in 100% CO2with a 23 min hold at 520 °C. It is proposed that the SD phenomenon may be a key step in the development of an industrially feasible method of lime reactivation for use in CO2capture and in thermal energy storage applications. [ABSTRACT FROM AUTHOR]

The present paper summarizes and reinterprets the results for a series of measurements of solid−liquid equilibria for binary systems formed by carbon dioxide or nitrous oxide with a series of hydrofluorocarbons (fluoromethane, difluoromethane, trifluoromethane, pentafluoromethane, 1,1,1,2-tetrafluoroethane, 1,1,1-trifluoroethane, and 1,1-difluoroethane). All of the systems form eutectics. The contribution from heat capacity and activity coefficients to the liquidus courses represented by the Schröder equation were analyzed for each system included in the present study. The performed analysis showed that both mentioned contributions are small and, to a great extent, are mutually compensating each other and thus could be disregarded. The results showed that, for the systems under study, the liquidus curve down to the eutectic point may be represented by the Schröder equation involving two quantities only: the temperature at triple point and the enthalpy of fusion of the system components. [ABSTRACT FROM AUTHOR]

The calcium looping cycles method has been identified as an attractive method for CO2capture during coal combustion and gasification processes. However, it is well-known that the capture capacity of CaO undergoes a rapid decrease after mutiple cycles. In order to improve the stability of CO2capture capacity in CaO, this paper focuses on the development and performance of the synthetic CaO/La2O3sorbents for calcium looping cycles.The sorbents were synthesized by three different methods: dry physical mixing, wet chemistry, and sol−gel combustion synthesis (SGCS). Their multicyclic CO2capture capacity and the effect of the additive La2O3were investigated in a fixed bed reactor system. The results indicate that the additive of La2O3plays a positive role in the carbonation/calcination reactions, and the SGCS-made synthetic sorbent is composed of ultrafine well-dispersed hollow structured particles which are beneficial to the gas-phase diffusion on the surface area and can prevent small CaO particles from agglomeration effectively. As a result, the novel synthetic sorbent with the molar ratio of Ca to La of 10:1 made by the SGCS method provides the best performance of a carbonation conversion of 72% under mild calcination conditions and a carbonation conversion of 36% under severe calcination conditions (high temperature and high CO2concentration) after 20 cycles. [ABSTRACT FROM AUTHOR]

In this paper, mutual interactions between each of three different crude oils and CO2are experimentally studied. Three crude oils include two light crude oils and one medium crude oil. First, a series of saturation tests are conducted to determine the onset pressure of asphaltene precipitation for each crude oil−CO2system. Second, the equilibrium interfacial tension (IFT) between each crude oil and CO2is measured as a function of the equilibrium pressure. The so-called minimum miscibility pressure (MMP) of each crude oil−CO2system is determined by applying the vanishing interfacial tension (VIT) technique. Third, the oil-swelling effect and initial strong light-components extraction are observed during the IFT measurements. It is found that the onset pressure of asphaltene precipitation is lower if the asphaltene content of the crude oil is higher. It is also found that the measured equilibrium IFT is reduced almost linearly with the equilibrium pressure in three distinct pressure ranges for the two light crude oil−CO2systems and in two different pressure ranges for the medium crude oil−CO2system. The determined MMP is higher if the crude oil is heavier. The oil-swelling effect occurs at a low pressure, but the initial strong light-components extraction becomes dominant at a high pressure. [ABSTRACT FROM AUTHOR]

The present paper reports isothermal three-phase equilibria (hydrate aqueous gas phases) for the carbon dioxide (CO2) ethane (C2H6) mixed-gas hydrate system at (274.15, 279.15, and 284.15) K and the carbon dioxide (CO2) tetrafluoromethane (CF4) mixed-gas hydrate system at (274.15 and 279.15) K. None of the equilibrium pressure−composition curves of hydrate, aqueous, and gas phases shows discontinuity in the gradient. Both CO2 C2H6and CO2 CF4mixed-gas hydrates are the structure-I hydrate under the present experimental conditions, which is supported by the results of in situ Raman spectroscopy. [ABSTRACT FROM AUTHOR]

The constant-volume method is used to determine the solubility of CO2in dimethyl carbonate (DMC) under the pressure of 6 MPa and the temperature variations from (280.7 to 327.66) K in this paper. It is found by contrast that DMC has greater ability to dissolve CO2than propylene carbonate and methanol at the same temperature. Furthermore, the solubility of CO2in DMC at room temperature 298.47 K is close to that of methanol at 263.15 K. Therefore, DMC is expected to become an effective and low-cost absorbent for precombustion CO2capture. [ABSTRACT FROM AUTHOR]

The influences of metal (iron, magnesium, aluminum, and zinc) on thermal properties for paraffin/intumescent flame retardants (IFR) as a phase change material were studied in this paper. Thermogravimetric analysis (TGA), thermogravimetric analysis−Fourier transform infrared spectrometry (TGA-FTIR), microscale combustion calorimetry (MCC), cone calorimetry (CONE), and differential scanning calorimetry (DSC) were used to characterize the thermal properties of the sample. The results revealed that metal could affect the thermal degradation and increase the char yield for a paraffin/IFR system. The volatilized products for the combustible gases were decreased, and carbon dioxide was increased for paraffin/IFR with metal compared to that without metal. Also, the flame retardant efficiency of IFR in paraffin could be improved by adding metal. However, the changes of the thermal properties for the metal−PCM were not in accord with increasing metal in the paraffin/IFR system. Also, the flame retardant mechanism for paraffin/IFR with metal was proposed. [ABSTRACT FROM AUTHOR]

The low pressure solubility of carbon dioxide in eight commercially available room temperature ionic liquids was measured at 10, 25, and 40 °C using a transient thin liquid film technique. In this paper, carbon dioxide solubility is reported as the Henry’s law constant for each system. Experimental results were interpreted using regular solution theory where Eyring’s reaction rate theory was successfully applied to estimate the solubility parameter of each ionic liquid from its activation energy of viscosity. Consistent with the regular solution theory, the carbon dioxide solubility was found to be inversely proportional to the solubility parameter of the ionic liquid, and Henry’s law constants were successfully correlated with the square of the difference between ionic liquid and carbon dioxide solubility parameters. [ABSTRACT FROM AUTHOR]

This paper extended the experimental results of carbon dioxide partitioning in gas/liquid equilibrium with a NaCl−H2O−monoethylene glycol (MEG) mixed solvent. The experiments were conducted systematically at 3−70 °C, 0−6.0 m NaCl, and 0−99 wt % MEG concentrations. CO2partitioning to the NaCl−H2O−MEG solution is complicated due to nonideal behavior in the solvent. A self-consistent activity model is proposed to describe the effect of monoethylene glycol (MEG) on CO2partitioning in gas/MEG/water/salt solutions using pure H2O as the reference state. Pitzer theory was used to calculate the effect of salt, and a semiempirical equation was applied to correlate the effects of MEG at different temperatures and ionic strengths. The equation is applicable to CO2partitioning at 0−6 mol of NaCl and 0−97% MEG mixed solution at 0−90 °C. This model can be incorporated with Pitzer type activity coefficient models to predict the solubility of carbon dioxide in the presence of MEG and salt solutions. [ABSTRACT FROM AUTHOR]

Separation of high-pressure carbon dioxide from fluorocarbons is important for the production of fluoropolymers such as poly(tetrafluoroethylene). Typical polymeric membranes plasticize under high CO2partial pressure conditions and fail to provide adequate selective separations. Torlon, a polyamide−imide polymer, with the ability to form interchain hydrogen bonding, is shown to provide stability against aggressive CO2plasticization. Torlon membranes in the form of asymmetric hollow fibers (the most productive form of membranes) are considered for an intended separation of CO2/C2F4. To avoid safety issues with tetrafluoroethylene (C2F4), which could detonate under testing conditions, safer surrogate mixtures (C2H2F2and C2H4) are considered in this paper. Permeation measurements (at 35 °C) indicate that the Torlon membranes are not plasticized even up to 1250 psi of CO2. The membranes provide mixed gas CO2/C2H2F2and CO2/C2H4selectivities of 100 and 30, respectively, at 1250 psi partial pressures of CO2. On the basis of the measured separation performances of CO2/C2H2F2and CO2/C2H4mixtures, the selectivity of the CO2/C2F4mixture is expected to be greater than 100. Long-term stability studies indicate that the membranes provide stable separations over a period of 5 days at 1250 psi partial pressures of CO2, thereby making the membrane approach attractive. [ABSTRACT FROM AUTHOR]

Carbon dioxide and its different compounds are generated as primary greenhouse gases from the flue gases of coal-fired thermal power plants, boilers, and other stationary combustion processes. This greenhouse gas causes global warming after being emitted to the environment. To deal with this problem, a new dry scrubbing process was tested in this study. A three-stage countercurrent fluidized bed adsorber was developed, designed, and fabricated. It was used as a removal apparatus and operated in a continuous regime for the two-phase system. The height of each stage was 0.30 m, and the inner diameter was 0.10 m. The paper presents the removal of CO2from gas mixtures by chemical sorption on porous granular calcium oxide particles in the reactor at ambient temperature. The advantages of a multistage fluidized bed reactor for high mass transfer and high gas−solid contact can enhance the removal of the gas when using a dry method. The effects of the operating parameters such as sorbent, superficial gas velocity, and the Weir height on CO2removal efficiency in the multistage fluidized bed were investigated. The results indicate that the removal efficiency of the carbon dioxide was around 71% at a high solid flow rate corresponding to lower gas velocity at room temperature. In comparison with wet scrubbers, this dry process appears to have lower cost, less complicated configuration, and simpler disposal of used sorbent. The results in this study assume importance from the perspective of use of a multistage fluidized bed adsorber for control of gaseous pollutants at high temperature. [ABSTRACT FROM AUTHOR]

In this work, the cross-flow model is compared with the cocurrent flow model and the countercurrent flow model for the process of removing CO2from natural gas. According to the comparison result, the cross-flow model is used for the analysis of the process of CO2removal from the natural gas. Analysis results indicate that the membrane area is not a monodrome function of the selectivity and both the effects of the fast gas (CO2) permeability and the slow gas (CH4) permeability on membrane area and CH4recovery are studied. Similar analysis is carried out for the operating pressures. Both the single stage system and the two-stage system with a recycle are studied. In order to reduce the membrane area required, membranes with high permeability and selectivity less than 100 are preferable. With increasing feed side pressure and decreasing permeate side pressure, the membrane area required decreases and the CH4recovery increases. For the single-stage system using a commercial membrane with selectivity of 20, the CH4recovery is lower than 90% at a product purity of 98%. Only when the membrane with selectivity higher than 50 is used, the separation of CH4recovery >98% and product purity >98% target can be fulfilled by the single stage system. Using the two-stage system with a membrane selectivity of 20, the separation target can be achieved. In the two-stage system, the permeate gas of the first stage has to be compressed before it can be sent to the next stage. The compression energy required between stages is estimated to be 107.5 KJ/m3(STP) of feed for the process discussed in this paper. Even considering the conversion factor between heat and electricity of 3−4, the energy consumption of a two-stage membrane system is still much less than that of the amine absorption process which is about 600−900 KJ/(m3(STP) of feed). [ABSTRACT FROM AUTHOR]

Trans-3-phenyl-2-propenoic acid (cinnamic acid; trans-cinnamic acid) is widely used in food, cosmetics, and pharmaceuticals because of its reported antimicrobial, antifungal, and antioxidant properties. This paper is devoted to the experimental measurement of the solubility of solid trans-cinnamic acid in pure supercritical CO2and in supercritical CO2with ethanol as a cosolvent. Measurements were carried out at T= (313.15 to 343.15) K and at p= (10 to 40) MPa. Two different thermodynamic models were applied to represent the solubility data obtained: a cubic type equation of state, the Soave−Redlich−Kwong (SRK-EoS) was employed to correlate the solubility data and the group contribution associating EoS (GCA-EoS) was also applied but in a completely predictive manner. In addition, values for the thermophysical properties of trans-cinnamic acid are also advocated. [ABSTRACT FROM AUTHOR]

Environmentally benign supercritical carbon dioxide (scCO2) has been utilized as an “ecologically responsible” solvent for a wide variety of applications. However, nonpolar scCO2is generally a very poor solvent for polar polymers which limits its use as a processing solvent in high resolution photolithography. In this paper, we report the synthesis of fluorinated scCO2compatible additives and demonstrate their utility to help dissolve polar polymers in scCO2. We have designed and synthesized a series of quaternary ammonium salts (QAS) as scCO2additives. The ability of these salts to assist in the dissolution of model acidic and protected polar polymers has been compared. For our studies we have chosen three different polar reference polymers. Addition of millimolar quantities of the QAS to the scCO2solvent helped to dissolve the protected model polymer under moderate supercritical conditions. To explicitly investigate the interactions between the QAS additive and the various functionalities on the polymers we have carried out computational simulations using a fully atomistic force field adapted from optimized potentials for liquid simulations (OPLS). These studies combining both theory and experiment showed that the architecture of the cation and the basic nature and size of the anion are crucial in designing more efficient additives. Finally, on the basis of these findings we report the lithographic evaluation of a standard commercially available polymer photoresist using an appropriate scCO2compatible QAS additive after development in scCO2. Well-resolved, negative-tone patterns as small as 100 nm were obtained by e-beam exposure, indicating the excellent potential of using scCO2as the processing solvent in the presence of the QAS additives to form high-resolution structures. [ABSTRACT FROM AUTHOR]

The pressure−volume−temperature (PVT) properties of polymer/gas solutions are characterized by determining their volume dilation at a known temperature and pressure. This paper presents the results of an experiment that measured the volume swelling of linear and branched polypropylene (PP) with CO2using a new PVT measurement apparatus. The swellings and specific volumes for linear and branched PP/CO2are compared. The swelling mechanism that occurred due to CO2dissolution, and the effects of the branched structure on volume swelling are investigated and discussed. Due to its entangled branch structure, the branched PP underwent a lesser degree of volume swelling than did the linear PP. [ABSTRACT FROM AUTHOR]

Concern over global warming has increased interest in quantification of the dissolution of CO2in (sub-)surface water. The mechanisms of the mass transfer of CO2in aquifers and of transfer to surface water have many common features. The advantage of experiments using bulk water is that the underlying assumptions to the quantify mass-transfer rate can be validated. Dissolution of CO2into water (or oil) increases the density of the liquid phase. This density change destabilizes the interface and enhances the transfer rate across the interface by natural convection. This paper describes a series of experiments performed in a cylindrical PVT-cell at a pressure range of pi= 10−50 bar, where a fixed volume of CO2gas was brought into contact with a column of distilled water. The transfer rate is inferred by following the gas pressure history. The results show that the mass-transfer rate across the interface is much faster than that predicted by Fickian diffusion and increases with increasing initial gas pressure. The theoretical interpretation of the observed effects is based on diffusion and natural convection phenomena. The CO2concentration at the interface is estimated from the gas pressure using Henry’s solubility law, in which the coefficient varies with both pressure and temperature. Good agreement between the experiments and the theoretical results has been obtained. [ABSTRACT FROM AUTHOR]

In a very recent paper (Ruiz-Reina, E.; Carrique, F.J. Phys. Chem. B2008, 112, 11960.) we studied the effect of water dissociation and CO2contamination on the equilibrium electrical double layer of spherical particles in salt-free concentrated suspensions in aqueous solutions. It was shown that in most cases (dilute to moderately concentrated suspensions), the neglecting of those effects would lead to a very poor description of common salt-free suspensions, especially if the suspensions have been in contact with air. In the present contribution we explore the influence of the latter effects on the dc electrophoresis in realistic salt-free suspensions. This kind of system consists of aqueous suspensions without any electrolyte added during the preparation. The ionic species in solution can solely be (i) the “added counterions” stemming from the particles that counterbalance their surface charge, (ii) the H+and OH−ions from water dissociation, and (iii) the ions produced by the atmospheric CO2contamination. Our model follows the classical Poisson−Boltzmann approach, a spherical cell model and the appropriate local chemical reactions. We have applied it to the study of the electrophoretic mobility of a spherical particle for different particle volume fractions ϕ and surface charge densities. The numerical results have shown the quite large influence that water dissociation ions and/or CO2contamination have on the electrophoretic mobility at low-moderate particle volume fractions. In those situations the role of the added counterions is screened by the other ionic species. These effects yield the mobility to reach plateau values instead of further increasing as volume fraction decreases. It is concluded that it is necessary to take into account the water dissociation influence for ϕ lower than approximately 10−2, whereas the atmospheric contamination, if the suspensions have been exposed to the atmosphere, is not negligible if ϕ < 10−1. The present work sets the basis for further theoretical models concerning particularly the ac electrokinetics and dielectric response of such systems. [ABSTRACT FROM AUTHOR]

In this paper we illustrate the use of subcritical carbon dioxide to precipitate ultrafine solid particles. The process has been developed to attain rapid, high, and uniform supersaturation by drastic reduction of the solution temperature and is named PPRGEL (precipitation by pressure reduction of gas-expanded liquids). Rapid pressure reduction over a CO2-expanded liquid solution from 40−70 to 1 bar at 303 K reduces the solution temperature by 30−80 K in a very short span of time (0.5−1.5 min) and facilitates precipitation of ultrafine particles. The process performance has been evaluated for particle production of cholesterol from 100 mL of its acetone and ethanol solutions (5−10 mg/mL) at 40–70 bar and 303 K using a 1 L high-pressure vessel. Particles with a size range of 200 nm to 7 μm and morphologies of near-spherical to needles have been produced with a change in operating conditions. [ABSTRACT FROM AUTHOR]

Squalene is applied in various fields of application. In contact with oxygen, it reacts to compounds with undesirable properties. Therefore, squalene often is hydrogenated to squalane, which is stable. Hydrogenation can advantageously be carried out with the additional application of supercritical carbon dioxide, which serves as a promoter for transporting hydrogen into the liquid phase and enhances equilibrium concentrations for squalane and squalene in the gaseous phase. In this paper, measurement and correlation of the relevant phase equilibrium data of the quaternary system are reported for search of optimized reaction conditions. In addition to literature data, VLE data are presented for the systems CO2−squalane, CO2−squalene, H2−squalane, CO2−H2−squalene, and CO2−H2−squalene−squalane, in the temperature and pressure ranges of (310 to 350) K and (150 to 350) bar. The quaternary system CO2−H2−squalene−squalane and all subsystems can be correlated with cubic equations of state. For this work, the program package PE, available from the Institute for Thermal and Separation Processes, Hamburg University of Technology, was used, applying the Soave−Redlich−Kwong equation of state (SRK-EOS) with the Mathias−Klotz−Prausnitz (MKP) mixing rule. On the basis of measurements and on literature data, it is possible to correlate the experimental data and predict phase behavior in the process relevant ranges. [ABSTRACT FROM AUTHOR]

This paper demonstrated an in situ headspace gas chromatography (GC) technique for monitoring bacterial growth using a commercial GC system with a multiple headspace extraction (sampling) mode. The technique was based on measuring the carbon dioxide mass in the headspace of a closed sample vial during the bacteria growth. A mathematic equation was derived in order to calculate the integrated amount of carbon dioxide produced by bacterial growth during the incubation. The method can be used to monitor the bacterial growth rate in a given cultural medium. The present method is very simple, sensitive, and safe. [ABSTRACT FROM AUTHOR]

This work presents an all-inclusive set of regulated and nonregulated emission factors for the main propulsion engine (ME), auxiliary engine (AE) and an auxiliary boiler on a Suezmax class tanker while operating at sea. The data include criteria pollutants (carbon monoxide, nitrogen oxides, sulfur oxides, and particulate matter), a greenhouse gas (carbon dioxide), the principal speciated hydrocarbons needed for human health risk assessments, and a detailed analysis of the PM into its primary constituents (ions, elements, organic, and elemental carbon). Measurements followed ISO 8178-1 methods with modifications described in the paper. The vessel burned two fuels: a heavy fuel oil in the ME and boiler and a distillate fuel in the AE.The weighted NOx emissions for the ME and AE are 19.87 ± 0.95 and 13.57 ± 0.31 g/kWh, respectively. The weighted PM mass emissions factor is 1.60 ± 0.08 g/kWh for the ME and 0.141 ± 0.005 g/kWh for the AE, with the sulfate content of the PM being the root cause for the difference. For the ME, sulfate with associated water is about 75% of total PM mass, and the organic carbon ranges from 15 to 25% of the PM mass. A deeper analysis showed that the conversion of fuel sulfur to sulfate in the ME ranged from 1.4 to 5%. This article also provides emission factors for selected polycyclic aromatic hydrocarbons, heavy alkanes, carbonyls, light hydrocarbon species, metals, and ions for the ME, AE, and the boiler. [ABSTRACT FROM AUTHOR]

This paper outlines a new CaCO3 calcination method for producing a stream of CO2 (suitable for permanent geological storage after purification and compression). The process is based on the use of very hot CaO particles (T > 1000 °C) to transfer heat from a circulating fluidized bed combustor (CFBC) to a calciner (fluidized with CO2 and/or steam). Since the fluidized bed combustor and calciner have separate atmospheres, the CO2 resulting from the decomposition of CaCO3 can be captured, while the CO2 generated in the combustion of the fuel in air is emitted to the atmosphere. We demonstrate that with this system it is possible to reduce the CO2 emissions of a cement plant by around 60%. Furthermore, since the key pieces of equipment are similar to the commercial CFBCs used in power generation plants, it is possible to establish the additional investment required for the system and to estimate the cost per ton of CO2 avoided for this process to be about 19 $/tCO2 avoided. [ABSTRACT FROM AUTHOR]

Lyotropic liquid crystalline phases have immediate relevance in biology because of the prevalence of organized lipid structures in living systems. The incorporation of hydrophilic reagents in water domains with well-defined nanoscale geometry favors the construction of nanostructured materials of inorganics, and/or the inorganic−organic hybrids. In this paper, the lamellar mesophases composed of calcium dodecyl sulfate (CDS), n-pentanol, and ammonia (5 wt% NH 3·H 2O in water) were constructed and used as the precipitation media of calcium carbonate (CaCO 3). Under the atmosphere of carbon dioxide gas, the occurring solid−liquid−gas reaction resulted only in rhombohedral calcite particles at the beginning, then ultimately in layer-cake aggregates of calcite and stick-bundle aggregates of aragonite. Furthermore, the aragonite content increased with the proceeding time interval of the three-phase reaction, indicating a special crystallization habit of CaCO 3in the lamellar mesophases of CDS. Aside from these, the influence of the structure of CDS lamellar mesophases on the formation of CaCO 3crystals is also discussed. These imply an effective biomimetic approach for the simultaneous fabrication of metastable aragonite and thermodynamically stable calcite under mild conditions. [ABSTRACT FROM AUTHOR]

This paper reports the three-phase (ice + hydrate + guest-rich vapor) equilibrium pressure−temperature conditions at temperatures (243 to 273) K in the systems of water and each of the following guest gases: methane, ethane, propane, and carbon dioxide. The measurements were also performed for the water-rich liquid + hydrate + guest-rich vapor three-phase equilibrium conditions at temperatures above 273 K. The pressure ranges of the present measurements in the four systems are (0.971 to 2.471) MPa in the methane system, (0.122 to 0.637) MPa in the ethane system, (41.0 to 280.0) kPa in the propane system, and (0.364 to 0.963) MPa in the carbon dioxide system. On the basis of the obtained three-phase equilibrium data, the quadruple points for the ice + water-rich liquid + hydrate + guest-rich vapor were also determined in the respective systems. The measurements were carried out using the batch, isochoric procedure. Fine-grained ice powders with diameters of (1 to 2) mm were used to form the hydrate. The measured data were compared with the corresponding data reported in the literature. [ABSTRACT FROM AUTHOR]

Carbon dioxide (CO 2) has found wide application in the water-alternating-foam (WAF) processes for enhanced oil recovery (EOR), but few research works have been reported concerning the effect of water solubility on the CO 2foam rheology in a porous medium. In this paper, an X-ray computed tomography (CT) study is carried out to investigate CO 2foam flow in a consolidated Bentheimer sandstone core saturated with surfactant solution under different system pressures. As a contrast gas with much lower solubility, nitrogen foam flow is also investigated to show the essence of gas solubility effects. Careful considerations were made on the selection of contrast gases, surfactant, and experimental procedures to focus on the effect of water solubility of the gas on foam rheology in porous media. It is observed from the experiments that CO 2foam has lower pressure loss and clearly suppressed entrance effect. With the increment of system pressure, the liquid saturation increases and the pressure loss decreases significantly for CO 2foam flow in the sample core, while little change can be observed for N 2foam flow. It can be concluded that water solubility is one of the important influential factors for CO 2foam rheology in porous media. [ABSTRACT FROM AUTHOR]

This paper deals with the effect of modification with alkali metals (Li, Na, K) in M xLa 1− xNi 0.3Al 0.7O 3− d( x= 0, 0.2, 0.5, 0.8, and 1.0) mixed-oxide perovskites as catalysts for the dry reforming of methane to produce syngas. The perovskite-type oxides have been synthesized by a sol−gel method using propionic acid as solvent and have been characterized by techniques such as Fourier-transform infrared (FT-IR), Bruner Emmet Teller surface area (BET), spectroscopy, X-ray diffraction (XRD), temperature programmed reduction (TPR), scanning electron microscopy (SEM), energy dispersive X-ray spectrometer (EDS), and carbon analysis (CA). Characterization of the M xLa 1− xNi 0.3Al 0.7O 3− dsamples has shown that by applying this synthetic method it is possible to obtain highly crystalline, homogeneous, and pure solids with well-defined structures. However, when lanthanum was replaced by potassium or lithium, the reduction temperature was increased and the reaction temperature had to be increased to obtain good activity. After establishment of the optimal catalytic and experimental conditions, the selected catalysts did not show significant deactivation even after 15 h on stream, maintaining their activity and selectivity in the production of synthesis gas. Among all catalysts, Li 0.2La 0.8Ni 0.3Al 0.7O 2.8showed less coke formation; Na 0.5La 0.5Ni 0.3Al 0.7O 2.5showed high yield; and K 0.5La 0.5Ni 0.3Al 0.7O 2.5produced an H 2/CO ratio close to 1 over a wide temperature range. These catalysts showed the best activities in lithium-, sodium-, and potassium-promoted series, respectively. In reactivity tests, methane conversions in excess of 90% and selectivities for H 2up to 80% at 850 °C under 1 atm have been achieved. [ABSTRACT FROM AUTHOR]

Research on amine-based carbon dioxide (CO 2) capture has mainly focused on improving the effectiveness and efficiency of the CO 2capture process. The objective of our work is to explore relationships among key parameters that affect the CO 2production rate. From a survey of relevant literature, we observed that the significant parameters influencing the CO 2production rate include the reboiler heat duty, solvent concentration, solvent circulation rate, and CO 2lean loading. While it is widely recognized that these parameters are related, the exact nature of the relationships are unknown. This paper presents a regression study conducted with data collected at the International Test Center for CO 2capture (ITC) located at University of Regina, Saskatchewan, Canada. The regression technique was applied to a data set consisting of data on 113 days of operation of the CO 2capture plant, and four mathematical models of the key parameters have been developed. The models can be used for predicting the performance of the plant when changes occur in the process. By manipulation of the parameter values, the efficiency of the CO 2capture process can be improved. [ABSTRACT FROM AUTHOR]

The influence of liquid and supercritical carbon dioxide and liquid propane on the structural properties of both ionic and nonionic surfactant-based liquid crystal films is discussed in this paper. Swelling of the films, measured using in situ small-angle neutron scattering (SANS), was found to be dependent on the solubility of the propane/carbon dioxide in the micelles of the respective liquid crystals. Additionally, under certain pressure conditions the structural properties of some of the films were observed to change, ultimately leading to a loss of order in the micellar arrays of the liquid crystals. [ABSTRACT FROM AUTHOR]