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Biobased nanofiber aerogels are ones of the attractive emerging materials in the fields of biochemistry and materials chemistry, but their poor humidity stability due to high hydrophilicity has limited their practical uses. In this paper, a new series of hydrophobic nanofibrous aerogels made from regenerated chitosan and alkyl aldehydes were prepared via a simple one-pot reaction followed by supercritical drying. Hexanal-modified chitosan aerogel shows excellent hydrophobicity with a water contact angle of ∼136°, a low density of 0.04–0.07 g cm–3, and structurally homogeneous three-dimensional nanofiber network at the nanoscale. Systematic investigations using various alkyl aldehydes revealed that pentanal-modified aerogel has similar high hydrophobicity and low density compared to the hexanal-modified material, while heptanal- and octanal-modified aerogels show drastic shrinkage during gelation. The aldehyde modification also suppresses permeation of water droplets into aerogel monoliths as well as reduc...

Ultrasound has been used as an advanced oxidation method for wastewater treatment. Sonochemical degradation of organic compounds in aqueous solution occurs by pyrolysis and/or reaction with hydroxyl radicals. Moreover, kinetics of sonochemical degradation has been proposed. However, the effect of ultrasonic frequency on degradation rate has not been investigated. In our previous study, a simple model for estimating the apparent degradation rate of methylene blue was proposed. In this study, sonochemical degradation of methylene blue was performed at various frequencies. Apparent degradation rate constant was evaluated assuming that sonochemical degradation of methylene blue was a first-order reaction. Specifically, we focused on effects of ultrasonic frequency and power on rate constant, and the applicability of our proposed model was demonstrated. Using this approach, maximum sonochemical degradation rate was observed at 490 kHz, which agrees with a previous investigation into the effect of frequency on the sonochemical efficiency value evaluated by KI oxidation dosimetry. Degradation rate increased with ultrasonic power at every frequency. It was also observed that threshold power must be reached for the degradation reaction to progress. The initial methylene blue concentration and the apparent degradation rate constant have a relation of an inverse proportion. Our proposed model for estimating the apparent degradation rate constant using ultrasonic power and sonochemical efficiency value can apply to this study which extended the frequency and initial concentration range.

Techniques for the degradation of hazardous organic compounds have been investigated such as solvent extraction, incineration, chemical dehalogenation and biodegradation, etc. Ultrasound has been found to be an attractive advanced technology for the degradation of hazardous organic compounds in water. In addition, the sonochemical reaction is enhanced by particle addition. However, the enhancement mechanism of particle addition has not been investigated well, because ultrasound enhances not only chemical reaction but also mass transfer. In this study, the degradation process of methylene blue as the model hazardous organic compound by ultrasonic irradiation was investigated. The effects of ultrasonic irradiation condition on degradation rate were investigated. The effect of ultrasonic frequency on improvement of degradation reaction by particle addition was also investigated. In addition, the effects of ultrasonic frequency on ultrasonic power and chemical efficiency were investigated by calorimetry and SE value. The degradation rate constants were estimated from the results of temporal change of the concentration of methylene blue assuming first order kinetics for the decomposition. There was a linear relation in the degradation rate and the ultrasonic power. In addition, the degradation rates at 127 kHz and 490 kHz were much larger than that at 22.8 kHz. The effect of ultrasonic frequency on sonochemical efficiency has been investigated, and the sonochemical effects in the range of frequency of 200 - 500 kHz are 10 times larger than those in the lower or higher frequency regions. Therefore, the degradation rate of methylene blue was considered to estimate using sonochemical efficiency. The degradation process of methylene blue was intensified by particle addition, and the degradation rate increased with increasing amount of particle. On the other hand, the enhancement of degradation rate by particle addition was influenced by both ultrasonic frequency and species of particle. The relationship between particle size and resonance diameter of ultrasound is considered to influence the enhancement of ultrasonic degradation process.

The product selectivity, reaction pathway, and the effects of acid and base on the kinetics were studied for the methylation of phenol in supercritical methanol without catalyst at 380 °C and 0.237 g cm-3. The reaction gave o-cresol as the major product and p-cresol and anisole in much smaller amounts, where the ortho/para ratio was above 12. The high ortho-selectivity suggests that the methylation proceeds locally around the phenolic OH group. Since no rearrangement was observed from anisole to o-cresol, the high ortho-selectivity was never ascribed to the rearrangement mechanism via anisole. Comparative experiments were carried out for other substituted benzenes to show that the phenolic OH group itself plays an essential role in the supercritical methylation. It was also found, in contrast to ordinary acid-catalyzed alkylations, that the supercritical methylation was retarded by acid and accelerated by base. The results were interpreted by a new reaction mechanism that the phenolic OH group acts as an ...

Liposomes were prepared by the supercritical reverse phase evaporation method developed in our laboratory using various phospholipids with different hydrocarbon chains. The effects of the length of alkyl chain and number of unsaturated bonds of phospholipids on the properties of liposomal membranes were examined through trapping efficiency measurements, transmission electron microscopic observations, and osmotic response measurements. The trapping efficiency for water-soluble drugs of liposomes prepared by our method was greatly higher than that of liposomes prepared by the conventional Bangham method. Liposomes prepared using unsaturated phospholipids showed a high trapping efficiency compared with those prepared using saturated phospholipids. In addition, the trapping efficiency of liposomes prepared using 1-palmitoyl-2-oleoyl phosphatidylcholine (POPC), a complex phospholipid with both saturated and unsaturated alkyl groups, had a value intermediate between L-alpha-dipalmitoyl-phosphtidylcholine (DPPC), a saturated phospholipid, and L-alpha-dioleoylphosphatidylcholine (DOPC), an unsaturated phospholipid. That is, the trapping efficiency of liposomes was dependent on the number of unsaturated bonds rather than the alkyl chain length of phospholipid molecule and it increased with increasing bulkiness of the molecule. The osmotic response was higher for liposomes prepared using unsaturated phospholipids than for those formed by saturated phospholipids.

Critical properties of dimethyl ether (DME, RE-170) and its three binary mixtures with hydrocarbons, propane (HC-290), butane (HC-600), and 2-methyl propane (HC-600a), were measured with uncertaint...

Formation of water (W) in supercritical carbon dioxide (scCO2) (W/scCO2) type microemulsions was examined using four hybrid surfactants, the sodium 1-oxo-1-[4-(tridecafluorohexyl)phenyl]-2-alkanesu...

Isobaric vapor−liquid equilibria were measured for the six binary systems heptafluoropropyl methyl ether (HFE-347mcc) or 1,1,1,2,3,3-hexafluoro-3-propane (HFE-449mec-f) with 1-propanol, 2-butanone, or ethyl acetate at atmospheric pressure. The mixtures HFE-347mcc and HFE-449mec-f with 1-propanol both formed a minimum boiling azeotrope. The mixtures HFE-449mec-f with 2-butanone and with ethyl acetate formed maximum boiling azeotropes. The experimental data were correlated by the Wilson and NRTL activity coefficient models. The Wilson and NRTL equations gave similar results.

UV/visible absorption spectroscopy was applied to measure the microscopic solvent dipolarity/polarizability, π*, and hydrogen-bond-acceptor basicity, β, parameters of supercritical CO2/n-alcohol mixtures. Experiments were conducted at 45 °C by varying the pressure between 86 and 230 bar, the type of n-alcohol from methanol to n-hexanol, and the n-alcohol mole fraction, x2, from 0 to 0.05. The effect of our experimental conditions on maximum Δπ* changes can be represented in the following order: system pressure (Δπ* ≈ 0.4) > n-alcohol mole fraction (Δπ* ≈ 0.3) > type of n-alcohol (Δπ* ≈ 0.1). However, the corresponding order for Δβ changes was as follows: n-alcohol mole fraction (Δβ ≈ 0.6) > type of n-alcohol (Δβ ≈ 0.3) > system pressure (Δβ ≈ −0.1). Under our experimental conditions, the π* parameters of the mixtures were below the corresponding value for liquid cyclohexane, whereas β parameters at x2 = 0.05 approached the values for liquid alcohols under ambient conditions. Because the solvent strength...

Azeotropic mixtures composed of hydrofluoroethers (HFEs) and solvents are expected to be candidates for alternative cleaning solvents in the future. For determining appropriate azeotropic mixtures containing HFEs, ASOG group pair parameters relating to CF2, CHF2, CHF, CH2, O (HFE), OH, CO, COO, and O(ether) groups were determined from literature binary vapor–liquid equilibrium data at 101.3 kPa. Average deviations between predicted and literature values were 0.023 in mole fraction vapor phase for 37 binary systems containing 25 azeotropic mixtures constituted by the HFEs, alcohols, ketones, esters and ethers.

A new method, the supercritical reverse phase evaporation method, for the preparation of liposomes in one step using supercritical carbon dioxide without any organic solvent toxic to the human body...

Recovery of Constituent Monomers from Polyethylene Terephthalate with Supercritical Methanol

Critical properties of binary mixtures of 1,2,2,2-tetrafluoroethyl trifluoromethyl ether (HFE-227me) with two hydrofluoroethers, trifluoromethoxymethane (HFE-143m) and methyl pentafluoroethyl ether (HFE-245mc), were measured. The uncertainties were ± 10 mK in temperature, ± 0.5 kPa in pressure, and ± 1.0 kg·m-3 in density. The experimental data were correlated with equations proposed by Higashi.

Solubility and adsorption of high pressure carbon dioxide (CO2) to poly(styrene) (PS) were measured at 313.2 K and pressures up to 17 MPa using a quartz crystal microbalance (QCM) as a detector. Two kinds of PS film, made by dip coating (d-PS) and plasma polymerization (p-PS), were used as samples. The amount of adsorption onto both films was almost the same within the experimental range. The solubility to both films increased almost linearly against activity of CO2 up to unity, and that to p-PS was slightly higher than that to d-PS. Above unity, the solubility to p-PS film increased with the increase in activity. In contrast, solubility to d-PS sharply decreased near the unity and became a constant value.

Ultrasound has been found to be an attractive advanced technology for the degradation of hazardous organic compounds in water. In addition, the sonochemical reaction is enhanced by particle addition. However, the enhancement mechanism of particle addition has not been investigated well, because ultrasound enhances not only chemical reactions but also mass transfer. In this study, the ultrasonic degradation of methylene blue was carried out, and the effects of the ultrasonic irradiation condition on the degradation rate were investigated. The effect of ultrasonic frequency on the improvement of degradation by particle addition was also investigated. The order of degradation rate with frequency was the same as the tendency of sonochemical efficiency value obtained using KI oxidation dosimetry method (SE KI). The degradation process of methylene blue was intensified by particle addition, and the degradation rate increased with increasing amount of particle addition. The enhancement of degradation rate by particle addition was influenced by both ultrasonic frequency and type or diameter of particles.

超臨界メタノール中におけるジベンジルエーテル (DBE) の熱分解反応を行った。反応温度は643, 693K, 反応圧力は10, 15, 20MPaであり, DBEのモル分率が0.02と0.20の2種類の組成の反応原液を用いた。反応の主生成物はトルエンであり, 副生成物としてベンズアルデヒド, ベンジルアルコール, ベンジルメチルエーテルが得られた。超臨界メタノール中におけるDBEの熱分解反応はラジカル熱分解反応と, メタノールとの加溶媒分解反応が第一段階の反応として並発して起こり, さらに第一段階の反応生成物の第二段階目の反応も起きていることがわかった。推定される反応経路に基づいて導出された速度式を Runge-Kutta 法で解き, 最適の速度定数の値を Simplex 法により決定した。ラジカル熱分解反応および加溶媒分解反応の速度定数の値は圧力の増加にともない減少した。ラジカル熱分解速度が高圧になるほど減少するのは溶媒であるメタノールによるかご効果によるものと思われる。DBEの初期モル分率が0.20の場合の方が0.02の場合よりラジカル熱分解反応の速度定数の値が大きいことから, DBEの濃度が高くなるほど, ラジカルとDBEの分解生成物との間での反応の影響が大きいことがわかった。また, ラジカル熱分解反応と加溶媒分解反応により消失するDBEの割合を調べたところ, 高圧になるほど加溶媒分解反応によって消失する割合が大きくなることがわかった。

Techniques such as solvent extraction, incineration, chemical dehalogenation, and biodegradation have been investigated for the degradation of hazardous organic compounds. We found ultrasound to be an attractive technology for the degradation of hazardous organic compounds in water. However, the effects of ultrasonic frequency on degradation rate constants were not investigated quantitatively. In this study, the degradation process of a model for hazardous organic compound methylene blue was investigated using ultrasonic irradiation. The study focused on the effects of ultrasonic frequency and ultrasonic power on the degradation rate constant. The apparent degradation rate constants were estimated based on time dependence of methylene blue concentration assuming pseudo-first-order kinetics for the decomposition. A linear relationship between the apparent degradation rate constant and ultrasonic power was identified. In addition, the apparent degradation rate constants at frequencies of 127 and 490 kHz were much larger than those at 22.8 kHz. A relationship between the apparent degradation rate constant and the sonochemical efficiency value (SE value) was also found. Based on these results, a simple model for estimating the apparent degradation rate constant of methylene blue based on the ultrasonic power and the SE value is proposed in this study.

Experimental studies for the mol wt estimation by pressure was performed with a batch polymerization of phthalic anhydride (PA) and ethylene glycol (EG). Experimental results show that the pressure in the reactor can be utilized to estimate the mol wt of products. © 1993 John Wiley & Sons, Inc.

Pressure effects on the phase separation of aqueous solutions of poly(N-isopropylacrylamide) (pNIPA) and poly(N-isopropylacrylamide-co-acrylic acid) (pNIPA/AAc) were examined at pressures up to 250 MPa. The cloud point temperature first increased and then decreased as the pressure was raised. The copolymer solutions had higher maximum temperature and pressure than the pNIPA solutions. Though the cloud point curve of pNIPA solutions had no concentration dependence, the cloud point curve of pNIPA/AAc solutions shifted toward higher temperature and pressure with decreasing concentration

Decomposition of Polyethylene 2,6-Naphthalene Dicarboxylate to Constituent Monomers Using Supercritical Methanol

Polychlorinated biphenyls (PCBs) were made harmless using supercritical water hydrolysis with an alkali catalyst such as sodium hydroxide. PCBs over a wide concentration range from 2 wt% in transformer oil to pure state were dechlorinated to biphenyl and, in some parts, decomposed to phenol, gases and other small molecules at 30 MPa, 653-723 K, and 20-100 min of reaction time. Furthermore no dioxins were detected in both gaseous and liquid products. Supercritical water hydrolysis has advantages as follows: (1) it dechlorinates pure PCBs rapidly and completely, (2) it realizes the selective dechlorination of dilute PCBs in transformer oil without thermal deterioration of the oil, and (3) it can reduce corrosion problems by neutralizing the product of hydrogen chloride.

The effects of surfactant mixing on interfacial tension and on microemulsion formation were examined for systems of air/water and water/supercritical CO2 (scCO2) interfaces and for water/scCO2 microemulsions. A fluorinated surfactant, sodium bis(1H,1H,2H,2H-heptadecafluorodecyl)-2-sulfosuccinate (8FS(EO)2), was mixed with the three hydrocarbon surfactants, Pluronic L31, Tergitol TMN-6, and decyltrimethylammonium chloride (DeTAC), at equimolar ratio. For all the cases, the interfacial tension was significantly lowered by the mixing. The positive synergistic effect suggests that the mixed surfactants tend to pack more closely on the interface than the pure constituents. It was found, however, that the microemulsion formation in scCO2 was never facilitated by the mixing, except for the case of TMN-6. This is probably due to the segregation of the surfactants into hydrocarbon-rich and fluorocarbon-rich phases on the microemulsion surface.

Aniline is easily N-methylated in supercritical methanol without catalyst at 350 degrees C and 0.237 g cm-3 to give mono-N-methylaniline with high selectivity, and the reaction rate is increased by a small amount of base (LiOH, NaOH, KOH, and CH3ONa), indicating a difference in the reaction mechanism from the ordinary acid-catalyzed one.

Ene reaction of allylbenzene and N-methylmaleimide was studied in water and ethanol solvents at subcritical temperatures (220–310 °C). Subcritical water was inappropriate for this reaction, because it rapidly hydrolyzed N-methylmaleimide. Subcritical ethanol was found to be a very promising solvent. The highest ene product yield in ethanol reached 40% in 480 min, and the highest trans-selectivity was 92%. The yields in pure ethanol were comparable to those in 1,2,4-trichlorobenzene with 10% hydroquinone added as a polymerization inhibitor. Addition of hydroquinone had a negligible effect on the yield in ethanol, suggesting that the solvent ethanol itself acts as an inhibitor of the side reactions. It is also expected that the polar environment and the high vapor pressure of ethanol favored pericyclic association between the apolar starting compounds.

To clarify the relationship between the structure and the ability of fluorinated AOT analogues for W/scCO2 microemulsion formation, we examined the AOT analogues having fluoroalkyl groups of differ...

We examined the ability for microemulsion formation of fluorinated surfactants containing perfluoropolyether moieties for the CO2-philic tail group and carboxylic acid ammonium or poly(ethylene glycol) methyl ether for the hydrophilic groups and found that the hydrophilic CO2-philic balance of surfactants plays an important role in the formation of microemulsions.