Solubility and fractionation of lipides in sulfur dioxide

Summary The solubilities of several fatty acids and their methyl esters in SO₂ have been determined as a function of temperature. SO₂ dissolves much smaller amounts of acid than the organic solvents commonly used with lipides. In this respect it resembles solvents of high polarity, such as nitromethane, acetonitrile, or furfural. Methyl esters are more than a hundred times more soluble in SO₂ than are the acids. Acids, methyl esters, and glycerides can be fractionated efficiently in this solvent. Project supported in part by a grant from the Fish and Wildlife Service, U.S. Department of the Interior, and by the Hormel Foundation.     

Cationic polymerization in iodine/liquid sulfur dioxide system

Investigations concerning the initiation step in cationic polymerization of alpha-methylstyrene in liquid SO₂ initiated by iodine have been made, based on the analysis of the low molecular weight components soluble in methanol by gas chromatography coupled with mass spectrometry. The results suggest that the formation of the alpha-methylstyrene diiodide is not possible, probably due to steric hindrance. HI formed from the carbocation (generated by the attack of iodine on the monomer at-60°) may initiate the polymerization.     

Cationic polymerization in iodine/liquid sulfur dioxide system

Summary Poly(alpha-methylstyrene) with narrow molecular weight distribution (MWD) was obtained by cationic polymerization initiated by iodine in methylene chloride/liquid SO₂ (80/20 vol.%) or toluene/liquid SO₂ (45/55 vol.%) mixed solvent at-60°C. The average number molecular weights of the product polymers increased with monomer conversion but the dependence was not linear because of the low initiation efficiency at the beginning of the reaction. On addition of a fresh feed of monomer at the end of the polymerization, the added feed was polymerized at the same rate with an increase of molecular weight. The low dispersity was kept after the second monomer addition. The initiation efficiency increased during the polymerization.     

Cationic polymerization in iodine/liquid sulfur dioxide system

The cationic polymerization of alpha-methylstyrene initiated by iodine was investigated in dichloromethane and liquid SO₂. Reactions carried out in SO₂ were faster with an increase of molecular weight at higher iodine concentration at-60°C. The increase of molecular weight with conversion and the values of average number of polymer chains less than theoretical suggest the presence of living or long-lived propagation species.     

Solubility of alkanes in a polystyrene matrix

The solubilities of seven alkanes in a matrix of uncrosslinked polystyrene were measured at several different temperatures. A gravimetric method reported earlier was used to monitor the sorption of the solvents. The experimental measurements showed unambiguously that the solubility of the alkanes diffusing into a polystyrene matrix reached a constant and reproducible value typical for each system and temperature. These values could be interpreted very well with the Flory–Huggins solubility parameter (χ = a(entropic contribution to x) + b(enthalpic contribution to x)/T[absolute temperature in Kelvin (K)]) or with the van't Hoff equation (ln K_S = ΔS/R(gas constant) ? ΔH/RT, where K_S is the equilibrium constant, ΔS is the entropy change, and ΔH is the enthalpy change). © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

纯氧燃烧法生产液体二氧化硫的工艺改进

对纯氧燃烧法生产液体二氧化硫工艺中常见故障进行了分析,针对焚硫炉损坏、二氧化硫气体冷却器堵塞、焦炭过滤器堵塞等问题提出改进措施,并通过生产验证了新工艺设计合理,取得了较好的效果.     

Solubility of gabapentin in supercritical carbon dioxide

The purpose of this study was to measure the solubility of gabapentin in supercritical carbon dioxide at different pressures and temperatures of 16–40 MPa and 308–338 K, respectively. The measured solubility data revealed that solubility of gabapentin was 8.97 × 10⁻⁵–7.36 × 10⁻³ based on the mole fraction in supercritical carbon dioxide at the aforementioned operational conditions. At last, the obtained results were correlated using four density based semi-empirical correlations namely Bartle et al., Mendez-Santiago and Teja (MST), Chrastil and Kumar and Johnston (K–J). The results revealed that according to the obtained average absolute relative deviations (AARD) for the used density based correlations of MST (AARD % = 9.88%), Chrastil (AARD % = 9.47%), K–J (AARD % = 11.5%) and Bartle et al. (AARD % = 9.29%), none of the correlations can be considered as the most accurate one. In other words, all the examined semi-empirical correlations are in the same level of accuracy.     

Solubility of astaxanthin in supercritical carbon dioxide

The solubility of astaxanthin in carbon dioxide was measured under supercritical conditions of a pressure range from 80 to 300 bar, and temperature range from 303 to 333 K, by using a dynamic flow-type. The solubility of astaxanthin increasing from 0.42×10⁻⁵ to 4.89×10⁻⁵ with higher temperature and pressure maintains certain density of supercritical carbon dioxide. The solubility data obtained were applied to the Chrastil model, based on the density of carbon dioxide. The data fitted well with the Chrastil model at most experimental conditions.     

Absorption of nitrogen dioxide and sulfur dioxide in methanol

Gas-liquid chromatography was employed to determine the activity coefficients of NO₂ and SO₂ at infinite dilution in methanol. The infinite dilution activity coefficients at 301.2 K were found to be 15.5 ± 0.1 and 0.491 ± 0.055 for the systems NO₂-methanol and SO₂-methanol, respectively. These values were subsequently used along with the single parameter Wilson equation to predict vapor-liquid equilibrium data for the systems NO₂-N₂-methanol and SO₂-N₂-methanol.     

二氧化硫催化还原为单质硫的研究进展

介绍了以H₂、CO、NH₃、炭及烃类物质为还原剂将SO₂催化还原为单质硫的研究进展，指出以CO和C₂H₄为还原剂的研究将更有实际意义。     

Electrochemical oxidation of benzene and biphenyl in liquid sulfur dioxide: formation of conductive deposits

The electrochemical oxidation of benzene and biphenyl in liquid SO₂ on a platinum electrode results in the formation of passivating films when performed in the presence of a quaternary ammonium perchlorate as a background electrolyte. In contrast, when the electrolyte is a quaternary ammonium tetrafluoroborate, dendrite-like conducting deposits are obtained. Elemental analyses, ir and xps spectra show that the films and deposits are products of the polyphenylene type containing variable amounts of oxygen. The oxidation product of benzene obtained in the presnece of BF₄^? is not conductive in the dry state when it is purified and exempt from electrolyte (σ < 10^?8 Ω^?1 cm^?1), whereas the unpurified product is fairly conductive in the dry state (σ = 10^?3 Ω^?1 cm^?1).     

The effect of continuous slow monomer addition technique on cationic polymerization in liquid sulfur dioxide

Summary The polymerizations of styrene and alpha-methylstyrene in liquid sulfur dioxide have been investigated by the use of the slow, continuous monomer addition technique in the presence of m-chloroperbenzoic acid or CF₃SO₃H as initiator. Quasiliving polymerization has been obtained in Sty/MCPBA/–40°C/liquid SO₂ system. The formed polymer is insoluble in the medium indicating that in liquid SO₂ the propagating species remain active even in a heterogeneous system.     

Solubility of fatty acids in supercritical carbon dioxide

The solubilities of lauric, linoleic, myristic, oleic, palmitic and stearic acid in supercritical carbon dioxide (SC-CO₂) at different pressures and temperatures were measured. The solubility values obtained in this work were compared with previously published data, and possible causes for observed discrepancies were discussed. The solubilities of the six fatty acids were modeled by Chrastil’s equation, and estimated model parameters were used to plot the solubility isotherms of fatty acids at 313, 323 and 333°K (40, 50 and 60°C) as a function of SC-CO₂ density. The comparison of solubility isotherms of fatty acids and vegetable oil suggests that separation of fatty acids from triglycerides might be possible by using SC-CO₂ at densities less than 700 kg/m³. From the effect of temperature on fatty-acid and vegetable-oil solubility, it seems that the extraction yield could be increased without sacrificing the selectivity of SC-CO₂ for fatty acids by choosing a higher operating temperature. The data also suggest that fractionation of certain fatty acids might be possible by manipulating the processing conditions. Given the values of the constants, Chrastil’s equation could serve as a guideline for choosing appropriate processing conditions and predicting the effect of pressure and temperature of SC-CO₂ on solute solubility.     

Solubility of chlorpheniramine maleate in supercritical carbon dioxide

Solubility of chlorpheniramine maleate in supercritical carbon dioxide at different temperatures (308–338 K) and pressures (160–400 bar) is measured using static method coupled with gravimetric method. The measured solubility data demonstrated that the solubility of chlorpheniramine maleate was changed between 1.54 × 10⁻⁵ and 4.26 × 10⁻⁴ based on the mole fraction as the temperature and pressure are changed. The general trend of measured solubility data shows a direct effect of pressure and temperature on the solubility of chlorpheniramine maleate. Finally, the obtained solubilities correlated using four semi-empirical density-based correlations including Mendez Santiago–Teja (MST), Kumar and Johnston (KJ), Bartle et al., and Chrastil models. Although the results of modeling showed that the KJ model leads to the average absolute relative deviation percent (AARD %) of 8.1% which is the lowest AARD %, deviation of other utilized correlations are rather the same.     

Solubility of butane and isobutane in molten polypropylene and polystyrene

The solubility of butane and isobutane in molten polypropylene (PP) and polystyrene (PS) was measured at pressures up to 3 MPa and along four isotherms from 438 to 483 K for PP and from 348 to 473 K for PS. The solubility increased with increasing pressure and decreasing temperature. At 438 K and 2 MPa, the solubilities of butane and isobutane in PP were 0.15 and 0.11 g‐gas/g‐polym, respectively. At 423 K and 2 MPa, the solubilities of butane and isobutane in PS were 0.08 and 0.05 g‐gas/g‐polym, respectively. Solubility could be correlated with the Sanchez‐Lacombe equation of state with temperature‐dependent binary interaction parameters to within 4.4% average relative deviation. Henry's constant for these gases in the PP and PS obtained in this work were used to determine correlation equations along with literature data. Polym. Eng. Sci. 44:2083–2089, 2004. © 2004 Society of Plastics Engineers.     

Catalyst effectiveness in sulfur dioxide oxidation

The sensitivity of the relationship between catalyst effectiveness in SO₂ oxidation and the Thiele parameter to: (1) the kinetic expression with respect to the presence or absence of strong SO₃ inhibition, (2) the activation energy in the range of 16–32 kcal/g mol, (3) the conversion of SO₂ up to 90%, (4) the temperature at the exterior surface of the pellet in the range of 450–600°C, and (5) the feed composition ranging from 6–10% SO₂ in air, was investigated. A nonisothermal model was used and the calculations were carried close to equilibrium. Far from equilibrium, the relationship is essentially unaffected except by conversion at the pellet surface for the case of strong product inhibition. Close to equilibrium, the relationship is significantly influenced by conversion, temperature, and the inlet composition but the form of the kinetics is not important. The activation energy is not a significant variable. Catalyst size, surface area, and density were not specified while it was necessary to fix the ratios of the transport properties for the calculations. The properties of the American Cyanamid V₂O ₅ catalyst were used for this purpose.     

高硫煤还原磷石膏制SO2

在N2气氛下研究了高硫煤还原磷石膏的热分解反应特性,利用烟气分析仪分析析出的气体成分。研究了不同颗粒尺寸的高硫煤对磷石膏分解的影响,结果表明,高硫煤颗粒尺寸在97—147μm有利于磷石膏分解制SO2的反应。研究还发现原料摩尔比对磷石膏的反应历程有显著的影响,当摩尔比为1∶1.96时,磷石膏还原分解的固体产物有CaS和CaO;当摩尔比降为1∶1.18时,固体产物中CaO大量增加,而仅有少量CaS存在;当摩尔比降到1∶0.98时,固体产物中除了CaO和CaS外,还发现了未反应完的CaSO4。所以摩尔比在1∶1.18时有利于高硫煤还原磷石膏制SO2。     

New organic chemistry of sulfur dioxide

Simple 1,3-dienes undergo highly stereoselective hetero-Diels-Alder additions with SO2 at low temperature giving sultines. These reactions that are faster than the more exothermic cheletropic additions of SO2-producing sulfolenes. This has led to the invention of a new C-C bond-forming reaction combining electron-rich dienes and alkenes with SO2. The reaction cascade has been exploited to develop combinatorial, one-pot, four-component syntheses of polyfunctional sulfones, sulfonamides, and sulfonic esters. It also allows us to generate, in one-pot operations, enantiomerically enriched polypropionate fragments containing up to three contiguous stereogenic centers and a (E)-alkene unit. These fragments can be used directly in further C-C bond-forming reactions, such as cross-aldol condensations, thus permitting the expeditious construction of complicated natural products of biological interest (e.g., Baconipyrones, Rifamycin S, Apoptolidinone) and analogues. New ene reactions of SO2 have also been discovered; they open new avenues to organic synthesis.