Solubility of carbon dioxide in aqueous solutions of 2-amino-2-ethyl-1,3-propanediol

The solubilities of carbon dioxide in aqueous solutions of 2-amino-2-ethyl-1,3-propanediol (AEPD) were measured at 313.15, 323.15, and 333.15 K over the partial pressure range of carbon dioxide from 1 to 3000 kPa. The concentrations of aqueous AEPD solutions were 10 and 30 mass%. The solubilities of carbon dioxide in aqueous 10 mass% AEPD solutions at 313.15 K and 30 mass% at 333.15 K were compared with those in aqueous solutions of various amines such as monoethanolamine (MEA), 2-amino-2-methyl-1,3-propanediol (AMPD), 2-amino-2-methyl-1-propanol (AMP), and N-methyldiethanolamine (MDEA).     

Solubility of carbon dioxide in aqueous solution of 2-amino-2-methyl-1-propanol and piperazine

In this work, new experimental results of the vapour-liquid equilibrium (VLE) of CO₂ in aqueous 2-amino-2-methyl-1-propanol (AMP) and piperazine (PZ) have been presented in the temperature range of 298-328 K and PZ concentration range of 2-8 mass%, keeping the total amine concentration in the solution at 30 mass%. The partial pressures of CO₂ were in the range of 0.1-1450 kPa. A thermodynamic model was developed to correlate and predict the VLE of CO₂ in aqueous AMP + PZ. The electrolyte nonrandom two liquid (ENRTL) theory has been used to develop the VLE model for the quaternary system (CO₂ + AMP + PZ + H₂O) to describe the equilibrium behaviour of the solution. The experimental data from this work and data available in the literature were used to regress the ENRTL interaction parameters. The model predictions are in good agreement with the experimental data of CO₂ solubility in aqueous blends of this work as well as those reported in the literature. The current model can also predict speciation, heat of absorption, pH of the CO₂ loaded solution, and amine volatility.     

Adsorption kinetics of nonionic surfactants using the drop volume method

The kinetic results obtained for the nonionic surfactantsn-octyl,n-decyl, andn-dodecyl dimethyl andn-octyl, andn-decyl diethyl phosphine oxide show purely diffusion controlled adsorption. The drop volume technique applied in a static and dynamic version proves to be useful to measure the adsorption kinetics in the form of surface tensions in function of time. Comparisons of the results obtained from both the static and the dynamic measuring procedure confirm the validity of a theory applied to interpret the kinetic data.Nomenclature a Langmuir parameter - c ₀ surfactant bulk concentration - D diffusion coefficient - surface concentration - ₀ equilibrium surface concentration - ¯ (t)/ ₀ reduced surface concentration - maximum value of - R gas law constant - surface tension - ₀ surface tension of pure water - t time - T absolute temperature     

Kinetics of chemical absorption of carbon dioxide into aqueous calcium acetate solution

Increasing energy demand in the world leads to more electricity generation mainly at fossil fuel power plants. Greenhouse gases are thus produced and mostly emitted to the atmosphere directly, resulting in global warming and climate change. Carbon dioxide is believed to be a main pollutant among greenhouse gases responsible from global warming. Conventional systems using mostly amine solutions to capture carbon dioxide at the source have some disadvantages, and alternatives are constantly being searched. In this work, a benign system of aqueous calcium acetate solution was investigated for this purpose. Calcium acetate is easy to produce, relatively cheap, environmentally friendly, nonhazardous, and noncorrosive. These properties make it a great alternative for use in capturing carbon dioxide. This absorption process is accompanied by chemical reaction. Therefore, the reaction kinetics needs to be investigated before its use in absorbers. A stirred cell reactor was used in the experiments using aqueous calcium acetate solution of different concentrations (2-20% w/w) and different carbon dioxide concentrations in gas mixtures (4.5-100% v/v dry carbon dioxide) at temperatures ranging from 286 to 352 K. The Gibbs free energy change for the overall reaction between carbon dioxide and aqueous calcium acetate solution was found to be –2.75 kJ/mol that shows the reaction is exergonic and occurs spontaneously. It was also found out that the reaction is pseudo–first order with respect to carbon dioxide which was also proven by calculating the Hatta number. Activation energy and Arrhenius (frequency) constant were also determined experimentally.     

Impact of carbon dioxide on the surface tension of 1-hexanol aqueous solutions

Effects of carbon dioxide presence on the surface tension and adsorption kinetics of 1-hexanol solutions were investigated. Experiments were performed at a range of carbon dioxide vapor pressures and varying concentrations of 1-hexanol aqueous solution. Both dynamic and steady-state surface tensions of 1-hexanol aqueous solution were found to decrease with carbon dioxide pressure, and a linear relationship was observed between the steady-state surface tension and carbon dioxide pressure. To explain the experiments, adsorption and desorption of the two species (1-hexanol and carbon dioxide) from two sides of the vapor-liquid interface were considered. A modified Langmuir isotherm, the modified Langmuir equation of state and the modified kinetic transfer equation were developed. The resulting steady-state and dynamic surface tension data were modeled using the modified Langmuir equation of state and the modified kinetic transfer equation, respectively. Equilibrium constants and adsorption rate constants of 1-hexanol and carbon dioxide were evaluated through a minimization procedure for CO₂ pressures ranging from 0 to 690 kPa. From the steady-state modeling, the equilibrium parameters for 1-hexanol and carbon dioxide adsorption from vapor phase and liquid phase were found unchanged at different pressures of carbon dioxide. From the dynamic modeling, the adsorption rate constants for 1-hexanol and carbon dioxide from vapor phase and liquid phase were found to decrease with carbon dioxide pressure. Some fluctuations in the fitting parameters of the dynamic modeling (adsorption rate constants) were observed. These fluctuations may be due to experimental errors, or more likely the limitations of the model used. A major limitation of the model is related to large differences in adsorption/desorption between initial and final stages of the process, and a single set of property parameters cannot describe both initial and final states of the system. Variations may occur depending on which set of data, of initial or final states, is used in the model predictions over the entire time range.     

An FTIR spectroscopic study and quantification of 2-amino-2-methyl-1-propanol,piperazine and absorbed carbon dioxide in concentrated aqueous solutions

This study reports the investigation of carbon dioxide (CO₂) absorption into an amine blend solution of 2-amino-2-methyl-1-propanol (AMP) and piperazine (PZ). The reaction in the liquid phase between CO₂ and the amines were qualitatively and quantitatively monitored by Fourier Transform Mid-Infrared spectroscopy (mid-FTIR). A multivariate partial least square regression (PLS2) model was obtained to quantify free or non-reacted AMP and PZ and absorbed CO₂ in all chemical forms, i.e. no differentiation was made into carbonates or carbamates. The calibration model was constructed using a single wide region and 270 calibration samples. The concentration of AMP, PZ and CO₂ from 568 samples were simultaneously predicted with low relative errors.     

低活性无烟煤固定床二氧化碳催化气化反应动力学研究

在内径18 mm的固定床反应器中研究了福建低活性无烟煤二氧化碳催化气化反应动力学。考察了消除内外扩散影响的实验条件。在750 ℃～907 ℃，以碳酸钠为催化剂分别测定了永安丰海筛无烟煤、永安加福筛无烟煤和永定无烟煤的转化率与时间的关系；以碳酸钾及纸浆黑液为催化剂测定了永定无烟煤的转化率与时间的关系。永安加福筛无烟煤采用均相一级反应模型及未反应缩芯模型进行拟合，得出气化反应速率常数、反应活化能和指前因子，与热天平的实验结果进行比较，固定床反应速率常数明显变大，活化能和指前因子也大，是由于固定床中有较高的二氧化碳到煤粒表面的传递速率和较高的升温速率所致。     

Highly efficient chemical fixations of carbon dioxide and carbon disulfide by cycloaddition to aziridine under atmospheric pressure

Cycloaddition of aziridine with carbon dioxide was successfully catalyzed by alkali metal halide or tetraalkylammonium halide to give the corresponding 5-membered cyclic urethane, 1,3-oxazolidin-2-one, selectively. The reaction can be performed at ambient temperature under atmospheric pressure. Analoguous reaction of aziridine with carbon disulfide also successfully gave the corresponding 5-membered cyclic dithiourethane, 1,3-thioxazolidine-2-thione.     

Reaction kinetics of the reaction between carbon dioxide and glycidyl methacrylate using tetraoctylammonium chloride as catalyst

Carbon dioxide was absorbed in an organic solutions of glycidyl methacrylate (GMA) in a semi-batch stirred tank with a plane gas-liquid interface at 101.3 kPa to obtain the absorption rate of carbon dioxide, from which the reaction kinetics of the reaction between carbon dioxide and GMA as studied using tetraoctylammonium chloride as catalyst. The reaction rate constants were estimated from the mass transfer mechanism accompanied by the pseudo-first-order reaction with respect to the concentration of carbon dioxide. An empirical correlation formula between the reaction rate constants and the solubility parameters of solvents such as toluene, N-methyl-2-pyrrolidinone, and dimethyl sulfoxide is presented.     

Extraction of lanthanides from aqueous solution by using room-temperature ionic liquid and supercritical carbon dioxide in conjunction

For the first time, the study of a three-step extraction system of water/ionic liquid/supercritical CO2 has been performed. Extraction of trivalent lanthanum and europium from an aqueous nitric acid solution to a supercritical CO2 phase via an imidazolium-based ionic liquid phase is demonstrated, and extraction efficiencies higher than 87 % were achieved. The quantitative extraction is obtained by using different fluorinated beta-diketones with and without the addition of tri(n-butyl)phosphate. The complexation phenomenon occurring in the room-temperature ionic-liquid (RTIL) phase was evidenced by using luminescence spectroscopy.     

Reaction kinetics of carbon dioxide with glycidyl methacrylate using immobilized trioctylamine supported on poly(styrene-CO-vinylbenzyl chloride) as a catalyst

A soluble polymer-supprted catalyst containing pendant trioctylammonium chloride was synthesized by the radical copolymerization of p-chloromethylated styrene with styrene followed by the addition reaction of the resulting copolymer with trioctylamine. Absorption rate of carbon dioxide into glycidyl methacrylate (GMA) solutions containing the catalyst was measured using a semi-batch stirred tank with a plane gas-liquid interface at 101.3 kPa. The reaction kinetics of the reaction between carbon dioxide and GMA was evaluated using the absorption rate and the mass transfer mechanism of carbon dioxide. Solvents such as toluene, N-methyl-2-pyrrolidinone, and dimethyl sulfoxide influenced the reaction rate constants. Furthermore, this catalyst was compared to the monomeric tetraoctylammonium chloride under the same reaction conditions.     

Effects of pressure on the kinetics of the dehydration of carbonic acid and the hydrolysis of CO2 in aqueous solution

The pressure dependence of the dehydration reaction of H₂CO₃ was measured in acidic aqueous solution for pressures up to 1 kbar using a high-pressure stopped-flow instrument. The corresponding volume of activation was found to be 6.4±0.4 cm³-mol^–1 at 25°C and 0.5 ionic strength. Volume equation calculations result in a value of –9.9±1.9cm³-mol^–1 for the volume of activation for the hydrolysis of CO₂ under the same conditions. For the first time, the reaction mechanism can be interpreted in terms of dissociative and associative modes, respectively. These data are used to construct an overall reaction volume profile.     

Cold crystallization and postmelting crystallization of PLA plasticized by compressed carbon dioxide

The cold crystallization at temperature T_cc (melting > T_cc > glass transition) and the postmelting crystallization of polylactic acid plasticized by compressed carbon dioxide (CO₂) were studied using a high-pressure differential scanning calorimeter. The kinetics of the two kinds of crystallization were evaluated by the Avrami equation as a function of pressure at certain temperatures. The effects of using talc as a nucleation agent on the two types of crystallization under pressure were also investigated. The results show that compressed CO₂ increased the mobility of the polymer chains in solid state, resulting in an increased rate of cold crystallization. The decreased rate of postmelting crystallization was mainly in the nucleation-controlled region, which indicates that the number of nuclei was decreased by the compressed CO₂. The growth rate of the two crystallization types followed the Avrami equation, but the kinetics of each depended upon temperature and pressure. The inclusion of talc accelerated postmelting crystallization but had little effect on cold crystallization. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2630–2636, 2008     

Kinetic study of CO2 absorption in aqueous solutions of 2-((2-aminoethyl)amino)-ethanol using a stirred cell reaction calorimeter

In the literature, aqueous 2-((2-aminoethyl)amino) ethanol (AEEA) is identified as a promising solvent for postcombustion CO₂ capture. In this work, the kinetics of CO₂ absorption in the aqueous AEEA, containing a primary and a secondary amino group, is studied over a wide temperature range of 303.15-343.15 K and the amine concentration in the range of 0.47-2.89 M using the fall-in-pressure technique in a stirred cell reaction calorimeter setup with a horizontal gas-liquid interface. The overall rate constants for (AEEA + H₂O + CO₂) reaction system are estimated in the pseudo–first-order reaction regime. The kinetic models based on zwitterion and the termolecular reaction mechanisms are used to predict kinetic rate constants. The experimental kinetic data are better correlated using the zwitterion mechanism (AAD 9.18%) than that of the termolecular mechanism (AAD 10.4%). The density, viscosity, and physical solubility of pure components and aqueous binary mixtures of AEEA are also measured at the similar temperature and concentration ranges of rate kinetics. Empirical models are proposed to predict pure component density and viscosity data with AAD of 0.02% and 7.17%, respectively. The Redlich-Kister model, the Grunberg-Nissan model, and the O'Connell's model are used to correlate experimental density, viscosity, and physical solubility data of the binary mixtures with AAD of 0.034%, 4.92%, and 6.5%, respectively. The reaction activation energy (E_a ∼ 32 kJ/mol) of the (AEEA + H₂O + CO₂) system is calculated from the Arrhenius power-law model using the zwitterion mechanism, which indicates lower energy barrier than that of the reported value for monoethanolamine (∼44 kJ/mol) in the literature.     

On the mechanism of irreversible carbon dioxide binding with a frustrated lewis pair: solvent-assisted frustration and transition-state entropic encouragement

The mechanism of irreversible carbon dioxide binding with a Lewis pair Mes(3)P:AlCl(3) (Mes=2,4,6-C(6)H(2)Me(3)) is computationally investigated to reveal that the steric congestion is not the driving force for the activation of CO(2). Instead, we find that the specific solute-solvent interaction between the Lewis acid and a bromobenzene molecule lowers the effective binding energy of the Lewis pair. This solvation effect affects the reaction in a similar manner to the steric encumbering of conventional frustrated Lewis pairs. Additionally, the transition state toward the CO(2) binding becomes extraordinarily flexible upon solvation. This flexibility encourages the adduct formation entropically and thus lowers the free-energy barrier of the reaction. We conclude that this combination of energy-barrier lowering through solvent-assisted frustration and the entropic encouragement generates a feasible activation route for CO(2) under mild conditions.     

Preparation and photocatalytic activity of TiO2-coated granular activated carbon composites by a molecular adsorption-deposition method

TiO₂ nanoparticle-coated granular activated carbon (GAC) composite photocatalysts (CPs) were successfully prepared by a molecular adsorption-deposition (MAD) method. The CPs were detected by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), BET surface area and UV-Vis adsorption spectroscopy, and their photoactivity was evaluated by methyl orange (MO) photodegradation. The results show that small-sized TiO₂ nanoparticles were dispersed well, deposited on the surface of GAC, and showed slight blue shift in comparison with pure TiO₂. With the increase in TiO₂ content, the CPs showed band gaps in lower energy, smaller surface areas and the higher content of Ti³⁺ ions. Compared with pure TiO₂ and others CPs samples, CPs-382 sample showed the highest photoactivity due to the optimum TiO₂ content and surface area besides the synergic effect of photocatalytic degradation of TiO₂ and adsorptive property of GAC. In addition, the CPs could be very easily reclaimed, recycled and reused for methyl orange removal while high photoactivity is preserved. Supported by the Natural Science Foundation of Hunan Province (Grant No. 06JJ50150), the Scientific Research Fund of Science and Technology Department of Hunan Province (Grant No. 2007GK3060) and Jishou University (Grant No. JSDXKYZZ200648)     

Separation and determination of diversiform phytosterols in food materials using supercritical carbon dioxide extraction and ultraperformance liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry

This paper presents at first time that the ultra-performance™ liquid chromatographic atmospheric pressure chemical ionization mass spectrometer (UPLC-APCI-MS) was used as an efficient method for the identification and quantification of diversiform phytosterols in food materials. The sample preparation consisted of extraction by supercritical carbon dioxide fluid extraction (SCE) and saponification by refluxing with ethanolic KOH, and then the non-saponificable fraction was extracted with petroleum ether. This fraction was subjected to solid phase extraction (SPE) on silica gel cartridge and then the sterols were eluted with hexane-ethyl acetate. Sterols were separated on an Acquity UPLC™ BEH C18 column (100 mm × 1.0 mm, 1.7 μm particle size) with a gradient of methanol/water (1% acetonitrile) at a flow of 0.1 mL min⁻¹. The determination was performed in selective ion monitoring mode. The quality parameter of the developed method was established using 6-ketocholestanol as internal standard. Limits of quantification (LOQ) were 0.1754, 0.0341, 0.0500, 0.0205, 0.0225, 0.3674, 0.0241, 0.0272, 0.0076 μg L⁻¹ and 0.1525 μg mL⁻¹ for 6-ketocholestanol, desmosterol, ergosterol, cholesterol, lanosterol, cholestanol, campesterol, stigmasterol, β-sitosterol, and stigmastanol, respectively. The intra- and inter-day determination precision for the 10 phytosterols were less than 5 and 6% in relative standard deviations, and their recoveries were located in the range of 94-107%. The developed approach has been applied successfully for efficient determination of diversiform phytosterols in food materials, including corn, sesame, oat and peanut.     

Cesium carbonate catalyzed efficient synthesis of quinazoline-2,4(1H,3H)-diones using carbon dioxide and 2-aminobenzonitriles

Abstract

An efficient protocol for the synthesis of quinazoline-2,4(1H,3H)-diones derivatives from 2-aminobenzonitriles with carbon dioxide using catalytic amount of cesium carbonate has been developed. 6,7-Dimethoxyquinazoline-2,4(1H,3H)-dione, which is one of the key intermediate for the synthesis of several drugs (Prazosin, Bunazosin and Doxazosin) was synthesized. The effect of different reaction parameters like influences of bases, solvent, temperature, CO₂ pressure and reaction time were investigated for the title reaction.