Solubility of β-carotene in ethanol- and triolein-modified CO2

Modification of an experimental device and methodology improved speed and reproducibility of measurement of solubility of β-carotene in pure and modified SuperCritical (SC) CO₂ at (313 to 333) K. Solubilities of β-carotene in pure CO₂ at (17 to 34) MPa ranged (0.17 to 1.06) μmol/mol and agreed with values reported in literature. The solubility of β-carotene in CO₂ modified with (1.2 to 1.6) % mol ethanol increased by a factor of 1.7 to 3.0 as compared to its solubility in pure CO₂ under equivalent conditions. The concentration of triolein in equilibrated ternary (CO₂ + β-carotene + triolein) mixtures having excess triolein reached values (0.01 to 0.39) mmol/mol corresponding to its solubility in pure SC CO₂ under equivalent conditions. Under these conditions, the solubility of β-carotene in triolein-modified CO₂ increased by a factor of up to 4.0 in relation with its solubility in pure CO₂ at comparable system temperature and pressure, reaching an uppermost value of 3.3 μmol/mol at 333 K and 32 MPa. Unlike in the case of ethanol, where enhancements in solubility where relatively independent on system conditions, solubility enhancements using triolein as co-solvent increased markedly with system pressure, being larger than using (1.2 to 1.6) % mol ethanol at about (24 to 28) MPa, depending on system temperature. The increase in the solubility β-carotene in SC CO₂ as a result of using ethanol or triolein as co-solvent apparently does not depend on the increase in density associated with the dissolution of the co-solvent in CO₂. Enhancements may be due to an increase in the polarizability of SC CO₂, which possibly growths markedly as triolein dissolves in it when the system pressure becomes higher.     

The thermal degradation of poly(diethyl fumarate)

The kinetics and mechanism of the thermal degradation of poly(diethyl fumarate) (PDEF) were studied by thermogravimetry, as well as by analysis of the thermolysis volatiles and polymer residue. The characteristic mass loss temperatures were determined, as were the overall thermal degradation activation energies of three PDEF samples of varying molar mass. Ethylene and ethanol were present in the thermolysis volatiles at degradation temperatures below 300 °C, while diethyl fumarate was also evidenced at higher degradation temperatures. The amount of monomer increased with increasing degradation temperature. The dependence of the molar mass of the residual polymer on the degradation time and temperature was established and the number of main-chain scissions per monomer unit, s/P₀, calculated. A thermal degradation mechanism including de-esterification and random main-chain scission is proposed. The thermal degradation of PDEF was compared to the thermolysis of poly(ethyl methacrylate) (PEMA), poly(diethyl itaconate) (PDEI) and poly(ethyl acrylate) (PEA).     

Measurements and predictions of density and carbon dioxide solubility in binary mixtures of ethanol and n-decane

The solubility of carbon dioxide (CO₂) in binary mixtures of ethanol and n-decane has been measured using an in-house developed pressure-volume-temperature (PVT) apparatus at pressures up to 6 MPa and two different temperatures (303.2 and 323.2 K). Three different binary mixtures of ethanol and n-decane were prepared, and the densities of the prepared mixtures were measured over the studied pressure and temperature ranges. The experimental data of CO₂ solubility in the prepared mixtures and their saturated liquid densities were then reported at each temperature and pressure. The solubility data indicated that the gas solubility reduced as the ethanol mole fraction in the liquid mixture increased. The dissolution of CO₂ in the liquid mixtures resulted in the increase in the saturated liquid densities. The impact of gas dissolution on the saturated liquid densities was more pronounced at the lower temperature and lower ethanol compositions. The experimental solubility and density data were compared with the results of two cubic equations of state (EOSs), Soave–Redlich–Kwong (SRK) and Peng–Robinson (PR). The modeling results demonstrated that both EOSs could predict the solubility data well, while the saturated liquid densities calculated with the PR EOS were much better than those predicted with the SRK EOS.     

Solubilities of CO2 in hydroxyl ammonium ionic liquids at elevated pressures

Solubilities of CO₂ in eight hydroxyl ammonium ionic liquids 2-hydroxy ethylammonium formate (HEF), 2-hydroxy ethylammonium acetate (HEA), 2-hydroxy ethylammonium lactate (HEL), tri-(2-hydroxy ethyl)-ammonium acetate (THEAA), tri-(2-hydroxy ethyl)-ammonium lactate (THEAL), 2-(2-hydroxy ethoxy)-ammonium formate (HEAF), 2-(2-hydroxy ethoxy)-ammonium acetate (HEAA) and 2-(2-hydroxy ethoxy)-ammonium lactate (HEAL) at the temperatures ranging from 303 to 323 K and the pressures ranging from 0 to 11 MPa were determined. The solubility data were correlated using Krichevisky–Kasarnovsky equation, from which Henry's constants and the partial volumes of CO₂ at different temperature were obtained. Results showed that Krichevsky–Kasarnovsky equation can correlate the solubilities of CO₂ in these hydroxyl ammonium ionic liquids (ILs) well. Comparison showed that the solubility of CO₂ in these eight hydroxyl ammonium ionic liquids was in sequence: THEAL > HEAA > HEA > HEF > HEAL > THEAA ≈ HEL > HEAF.     

Extraction of aroma compounds in blackcurrant buds by alternative solvents: Theoretical and experimental solubility study

This study was designed to evaluate the performance of nine alternative solvents (α-pinene, MeTHF, ethyl acetate, methyl acetate, ethyl lactate, butanol, isopropanol, ethanol and CO₂ supercritical fluid) for extracting aromas from blackcurrant buds (Ribes nigrum L) compared to that of n-hexane, commonly used. This study has been performed via experimentation and simulation using Hansen solubility methodology for the comprehension of the dissolving mechanism. Experimentally, the extracts were analysed to compare the solvents performance in terms of aroma compositions. The results indicated that an alternative solvent, i.e. MeTHF, could be the most promising one for n-hexane substitution with good yield and selectivity of aromas.     

Influence of supercritical drying fluids on structures and properties of low-density Cu-doped SiO2 composite aerogels

The Cu-doped SiO₂ composite aerogels were successfully prepared by sol–gel process and subsequently supercritical drying with ethanol and CO₂. The Cu-doped SiO₂ composite aerogels had porous texture, low density (<100 mg cm^?3) and high specific surface area (>800 m² g^?1), which were investigated by FESEM and nitrogen adsorption desorption porosimetry. The FTIR spectra of the aerogels showed that the ethanol-dried aerogels had been modified by ethyl while the corresponding CO₂-dried aerogels had more Si–OH groups. The phase structure and thermal stability were investigated by XRD and TGA, respectively. Due to the reducibility of ethanol, the copper was crystalline in ethanol-dried sample. The Cu-doped SiO₂ composite aerogels dried with supercritical ethanol had larger pore diameter and better thermal stability under 400 °C in comparison with CO₂-dried composite aerogels. The structures and properties of Cu-doped SiO₂ composite aerogels are obviously affected by supercritical drying conditions. The effect research could instruct the synthesis of different state of Cu in composite aerogels.     

Reaction Calorimetry for the Development of Ultrasound-Induced Polymerization Processes in CO2-Expanded Fluids

A strong viscosity increase upon polymerization hinders radical formation during an ultrasound-induced bulk polymerization. Since CO₂ acts as a strong anti-solvent for most polymers, it can be used to reduce the viscosity of the reaction mixture. In this work, a process for the ultrasound-induced polymerization in CO₂-expanded fluids has been developed. Temperature oscillation calorimetry has been applied to study the influence of CO₂ on the viscosity during the ultrasound-induced polymerization. In contrast to polymerizations in bulk, the results show that a low viscosity is maintained during polymerization reactions in CO₂-expanded methyl methacrylate (MMA). As a consequence, a constant or even increasing polymerization rate is observed when pressurized CO₂ is applied. Moreover, the ultrasound-induced polymer scission in CO₂-expanded MMA is demonstrated, which appears to be a highly controlled process. Finally, a preliminary sustainable process design is presented for the production of 10 kg/hour pure PMMA (specialty product) in CO₂-expanded MMA by ultrasound-induced initiation.     

Quercetin enhances vitamin D2 stability and mitigate the degradation influenced by elevated temperature and pH value

Vitamin D₂ (vit. D₂) is a nutraceutical essentially needed for good health. However, it is susceptible to oxygen and high temperature. The use of natural products such as bioflavonoids possessing anti-degradative effect of vit. D₂ degradation has not been described before. A combinational effect of vit. D₂ with quercetin showed a positive effect and inhibited vit. D₂ degradation when exposed to high temperature (50 ℃ and 75 ℃) at different time points. The results obtained revealed vit. D₂ degradation was drastically increased with longer incubation under thermal treatment. However, quercetin and vit. D₂ groups were able to significantly inhibit the degradation of vit. D₂ and stabilize it, evaluated through the retention percentage. We also exposed vit. D₂ at solutions with different pH values (1, 4, 5, 7, 10). Quercetin exerted vit. D₂ anti-degradation at different pH values as well as under thermal pressure at different time points. Conclusively, quercetin can be an effective way to reduce temperature and pH induced degradation of vit. D₂.     

Perfluoromethacrylate-styrene statistical copolymers synthesized in CO2-expanded monomers

Statistical copolymers of perfluoroalkyl ethyl methacrylate (Zonyl-TM) and styrene (S) were synthesized in CO₂-expanded monomer medium at a low initial pressure of 25 MPa. Different Zonyl-TM/S feed ratios were used during copolymerizations, and it was determined that the increase in the Zonyl-TM content and decrease of the CO₂ amount in the comonomer feed resulted in a decrease of the molecular weights of copolymers due to earlier precipitation of copolymers giving shorter chains. The cloudy CO₂-expanded liquid monomer phase was found to be the main loci of copolymerization. In addition, the increase in the Zonyl-TM feed ratio resulted in an increase in the critical degree of the polymerization time (J _crit) as the time when the copolymer chains start to precipitate. The higher the Zonyl-TM content used in the feed, the higher the J _crit time and the lower the weight-average molecular weight (M _w) of the copolymer obtained. Thermal analysis results of the copolymer indicated that the copolymers are stable up to 387–403 °C.     

Photo-thermal Cooperative Carbonylation of Ethanol with CO2 on Cu2O-SrTiCuO3-x

Carbonylation of ethanol with CO₂ as carbonyl source into value-added esters is of considerable significance and interest, while remains of great challenge due to the harsh conditions for activation of inert CO₂ in that the harsh conditions result in undesired activation of α-C−H and even cleavage of C−C bond in ethanol to deteriorate the specific activation of O−H bond. Herein, we propose a photo-thermal cooperative strategy for carbonylation of ethanol with CO₂, in which CO₂ is activated to reactive CO via photo-catalysis with the assistance of *H from thermally-catalyzed dissociation of alcoholic O−H bond. To achieve this proposal, an interfacial site and oxygen vacancy both abundant SrTiCuO_3-x supported Cu₂O (Cu₂O-SrTiCuO_3-x) has been designed. A production of up to 320 μmol g⁻¹ h⁻¹ for ethyl formate with a selectivity of 85.6 % to targeted alcoholic O−H activation has been afforded in photo-thermal assisted gas-solid process under 3.29 W cm⁻¹ of UV/Vis light irradiation (144 °C) and 0.2 MPa CO₂. In the photo-driven activation of CO₂ and following carbonylation, CO₂ activation energy decreases to 12.6 kJ mol⁻¹, and the cleavage of alcoholic α-C−H bond has been suppressed.     

Surface characterization of flat and rough films of perfluoromethacrylate-methylmethacrylate statistical copolymers synthesized in CO2-expanded monomers

Statistical copolymers of perfluoroalkyl ethyl methacrylate (Zonyl-TM) and methylmethacrylate were synthesized in CO₂-expanded monomer mixture at a low pressure of 10–13 MPa for the first time. M _w of the copolymers was found to decrease with the increase of Zonyl-TM content. Flat films of these copolymers were obtained by dip coating from their chloroform solutions and were characterized using contact angle measurements, optical microscopy, and 3D profilometry. The increase in the Zonyl-TM content of the copolymers resulted in a decrease of the total surface free energy. Superhydrophobic and oleophobic rough copolymer films were also prepared by applying a phase-separation process where THF was used as the solvent and ethanol as the non-solvent. Surface roughness increased with the increase in the nonsolvent ratio resulting in an increase in the water contact angle from 103° to 151° and hexadecane contact angle from 49° to 73°.     

GC Methods for the Determination of Methanol and Ethanol in Insulating Mineral Oils as Markers of Cellulose Degradation in Power Transformers

Methanol and ethanol in transformer oils have been recently proposed as new markers of thermal and mechanical degradation of cellulose (the solid insulation in power transformers). In this work, we optimized and compared the performance of two headspace gas chromatographic methods based on flame ionization (HS–GC–FID) and mass spectrometry detection (HS–GC–MS) to determine methanol and ethanol in insulating mineral oil. For methanol and ethanol, the detection limits were 12 and 27 μg kg^?1 (HS–GC–FID) and 1.3 and 3.1 μg kg^?1 (HS–GC–MS). Repeatability was evaluated in transformer oils for both the methods at different concentration levels of analytes and RSD values were found to lie between 1.8 and 16 %. The accuracy of the methods was assessed under a proficiency test (Cigré JWG A2/D1.46). The methods were compared by a F-test and a one-sided paired t test performed on 21 transformer oils in service. Correlations of methanol and ethanol content in sampled oils against their actual time of service are provided. For each sample, the content of traditional markers (furan-2-carbaldehyde and CO₂) was also measured, finding a correlation between light alcohols and CO₂ content. This indicates that methanol and ethanol determination may be helpful in providing further information on the thermal degradation conditions of transformers’ solid insulation. The method developed is currently routinely applied by the laboratories of Sea Marconi Technologies for the assessment of transformers’ conditions.     

Bioactivity and Mechanical Properties of Polydimethylsiloxane (PDMS)-CaO-SiO2 Hybrids with Different PDMS Contents

Silica-titania and titania aerogels were prepared by supercritical drying using different solvents such as low temperature CO₂ (353 K), high temperature CO₂ (553 K), ethanol (553 K) and ethanol with zeolite (553 K) and their efficiencies for the removal of benzene from a synthetic air mixture were investigated. The aerogels obtained showed both large capacities for benzene adsorption and high photocatalytic activity for its decomposition in the adsorbed state. The degree of benzene removal by silica-titania aerogel seemed to depend on the crystallinity of the titania and was in the order low temperature CO₂ < high temperature CO₂ < ethanol = ethanol with zeolite. The amount of CO₂ liberated by the photocatalytic decomposition of benzene also followed the same sequence. Titania aerogels showed the greatest efficiency in the decomposition of benzene, while the amount of CO₂ evolved was lower than those of the silica-titania systems investigated. The adsorption capacity of benzene basically depended on the silica matrix and was not greatly influenced by the difference in the crystallinity of titania.     

Experimental study on equilibrium solubility (at low partial pressures), density, viscosity and corrosion rate of carbon dioxide in aqueous solutions of ascorbic acid

In this paper, ascorbic acid as a new carbon dioxide (CO₂) absorbent was investigated. The equilibrium solubility of CO₂ into 0.5, 1 and 1.5 mol dm⁻³ (M) aqueous ascorbic acid solutions were measured experimentally with a stirred batch reactor at total atmospheric pressure over the CO₂ partial pressure ranging from 0 to 45 kPa and temperatures between 298 and 313 K. The results of the gas solubility are presented as loading capacity (mol CO₂/mol ascorbic acid) as function of partial pressure of CO₂ for all experimental runs. Experimental results showed that solubility of CO₂ increases with increase in molar concentration of ascorbic acid solution at a given temperature and decreases with increase in temperature at a given concentration. The densities and viscosities of the ascorbic acid solutions were measured at the same conditions of the solubility measurement. Some corrosion rate tests were also performed on carbon steel at temperature of 308 K. It was observed that viscosity and corrosion rate increase when the molar concentration of ascorbic acid solution increases.     

CO2-expanded bio-based liquids as novel solvents for enantioselective biocatalysis

For the first time, CO₂-expanded bio-based liquids were reported as novel and sustainable solvents for biocatalysis. Herein, it was found that by expansion with CO₂, 2-methyltetrahydrofuran (MeTHF), and other bio-based liquids, which were not favorable solvents for immobilized Candida antarctica lipase B (Novozym 435) catalyzed transesterification, were tuned into excellent reaction media. Especially, for the kinetic resolution of challenging bulky secondary substrates such as rac-1-adamantylethanol, the lipase displayed very high activity with excellent enantioselectivity (E value > 200) in CO₂-expanded MeTHF (MeTHF concentration 10% v/v, 6 MPa), whereas there was almost no activity observed in conventional organic solvents.     

Equilibrium solubility of carbon dioxide in 2(methylamino)ethanol

In this paper the equilibrium solubility of carbon dioxide in 1.0 M, 2.0 M and 4.0 M 2(methylamino)ethanol (MAE) is measured at 303, 313 and 333 K, and at CO₂ partial pressures ranging from 1 to 100 kPa using stirred cell reactor. The Kent-Eisenberg model was used to predict the solubility of carbon dioxide in MAE solutions. The equilibrium constant representing hydrolysis of carbamate ion is correlated with temperature, CO₂ partial pressure and amine concentration by non-linear regression, using experimental results of carbamate ion concentrations. The model predicted results showed good agreement with the experimental solubility results. The solubility profile of CO₂ in MAE showed better performance when compared with other commercial amines.     

Stimulation of hydrogen production in algal cells grown under high CO2 concentration and low temperature

When cells ofChlamydomonas sp. MGA 161, a marine green alga, were cultivated at a high CO₂ concentration (15% CO₂) and low temperature (15°C), the growth lag time was much longer, but the starch accumulated was two times higher than under the basal conditions (5% CO₂ 30°C). When the cells grown in the high-CO₂/low-temperature conditions were incubated under dark anaerobic conditions, the degradation of starch and production of hydrogen and ethanol were remarkably higher than those grown under the basal conditions. The lag time of cell growth was shortened, whereas the high capacity of starch accumulation and hydrogen production was maintained, by cultivating the cells alternately every 12 h under the basal and high-CO₂/low-temperature conditions. Using this dual system, in which the cultivation was alternated between the two conditions, the total productivity was significantly improved.     

The Effect of Functional Groups on the Phase Behavior of Carbon Dioxide Binaries and Their Role in CCS

In recent years we have focused our efforts on investigating various binary mixtures containing carbon dioxide to find the best candidate for CO₂ capture and, therefore, for applications in the field of CCS and CCUS technologies. Continuing this project, the present study investigates the phase behavior of three binary systems containing carbon dioxide and different oxygenated compounds. Two thermodynamic models are examined for their ability to predict the phase behavior of these systems. The selected models are the well-known Peng–Robinson (PR) equation of state and the General Equation of State (GEOS), which is a generalization for all cubic equations of state with two, three, and four parameters, coupled with classical van der Waals mixing rules (two-parameter conventional mixing rule, 2PCMR). The carbon dioxide + ethyl acetate, carbon dioxide + 1,4-dioxane, and carbon dioxide + 1,2-dimethoxyethane binary systems were analyzed based on GEOS and PR equation of state models. The modeling approach is entirely predictive. Previously, it was proved that this approach was successful for members of the same homologous series. Unique sets of binary interaction parameters for each equation of state, determined for the carbon dioxide + 2-butanol binary model system, based on k₁₂–l₁₂ method, were used to examine the three systems. It was shown that the models predict that CO₂ solubility in the three substances increases globally in the order 1,4-dioxane, 1,2-dimethoxyethane, and ethyl acetate. CO₂ solubility in 1,2-dimethoxyethane, 1.4-dioxane, and ethyl acetate reduces with increasing temperature for the same pressure, and increases with lowering temperature for the same pressure, indicating a physical dissolving process of CO₂ in all three substances. However, CO₂ solubility for the carbon dioxide + ether systems (1,4-dioxane, 1,2-dimethoxyethane) is better at low temperatures and pressures, and decreases with increasing pressures, leading to higher critical points for the mixtures. By contrast, the solubility of ethyl acetate in carbon dioxide is less dependent on temperatures and pressures, and the mixture has lower pressures critical points. In other words, the ethers offer better solubilization at low pressures; however, the ester has better overall miscibility in terms of lower critical pressures. Among the binary systems investigated, the 1,2-dimethoxyethane is the best solvent for CO₂ absorption.     

Solubility of chlorobutane,ethyl methacrylate and trifluoroethyl acrylate in supercritical carbon dioxide

In this work, the solubility of chlorobutane, ethyl methacrylate and trifluoroethyl acrylate in supercritical carbon dioxide (SC CO₂) was determined. The solubility of hexane, styrene and chlorobenzene was also measured for comparison. The effect of the polar substitute on the solubility of different kind of compound in SC CO₂ was discussed. The dependence of the solubility of the solute on the density of the binary system was also investigated and a proximate linear relationship existed between this solubility and density.     

TG-FTIR study on thermal degradation in air of some new diazoaminoderivatives

The study on the thermal behavior of some new diazoaminoderivatives was aimed to follow the structure-thermal stability-degradation mechanism correlation by means of the TG-FTIR technique and formation enthalpies. The TG-DTG-DTA curves reveal the thermal degradation in air (30–900 °C) to show two ranges as a function of temperature (time), where the gaseous species resulting by degradation are eliminated: the first, an endothermic one which is identical to that under nitrogen atmosphere and the second, an exothermal one. As made evident by the identification of the individual gaseous species by their characteristic absorbances as well as those obtained by TG-FTIR the compounds C₂H₂, H₂C = NH, SO_2, NH_3, CO₂, H₂O, HCl are eliminated in the first domain while CO₂, SO₂, H₂O in the second, which afforded the advancement of the most probable degradation mechanism.