Solvents liquid sulfur dioxide

Liquid sulfur dioxide expands by ca 10% when warmed from 20 to 60°C under pressure. Pure liquid sulfur dioxide is a poor conductor of electricity, but high conductivity solutions of some salts in sulfur dioxide can be made (216). Liquid sulfur dioxide is only slightly miscible with water. The gas is soluble to the extent of 36 volumes pet volume of water at 20°C, but it is very soluble (several hundred volumes per volume of solvent) in a number of organic solvents, eg, acetone, other ketones, and formic acid. Sulfur dioxide is less soluble in nonpolar solvents (215,217,218). The use of sulfur dioxide as a solvent and reaction medium has been reviewed (216,219). 

Liquid solvents are used to extract either desirable or undesirable compounds from a liquid mixture. Solvent extraction processes use a liquid solvent that has a high solvolytic power for certain compounds in the feed mixture. For example, ethylene glycol has a greater affinity for aromatic hydrocarbons and extracts them preferentially from a reformate mixture (a liquid paraffinic and aromatic product from catalytic reforming). The raffinate, which is mainly paraffins, is freed from traces of ethylene glycol by distillation. Other solvents that could be used for this purpose are liquid sulfur dioxide and sulfolane (tetramethylene sulfone). 

Inert solvents such as dimethyl ether [22], liquid sulfur dioxide or petroleum ether [23] were used to improve the quality of the sulfated alcohol or the reaction conditions. Solvents immiscible in water, such as petroleum ether [24], carbon tetrachloride [25], or butyl alcohol [26], as well as water-soluble sol-... 

Sodium hydrosulfite is produced through the Formate process where sodium formate solution, sodium hydroxide, and liquid sulfur dioxide reacted in the presence of a recycled stream of methanol solvent. Other products are sodium sulfite, sodium bicarbonate, and carbon monoxide. In the reactor, sodium hydrosulfite is precipitated to form a slurry of sodium hydrosulfite in the solution of methanol, methyl formate, and other coproducts. The mixture is sent to a pressurized filter system to recover sodium hydrosulfite crystals that are dried in a steam-heated rotary drier before being packaged. Heat supply in this process is highly monitored in order not to decompose sodium hydrosulfite to sulfite. Purging is periodically carried out on the recycle stream, particularly those involving methanol, to avoid excessive buildup of impurities. Also, vaporized methanol from the drying process and liquors from the filtration process are recycled to the solvent recovery system to improve the efficiency of the plant. 

This reaction represents a neutralization reaction in liquid sulfur dioxide. It makes no difference that the solvent does not ionize or that SOCl2 is a covalent molecule. The utility of the solvent concept is not that it correctly predicts that solvents undergo some autoionization. The value of the solvent concept is that it allows us to correctly predict how reactions would take place if the solvent ionized. Note that in this case SOCl2 does not ionize, but if it did it would produce S02+ (the acidic species characteristic of the solvent) and Cl-. 

Solvent dewaxing removes wax from lubricating oil stocks, promoting crystallization of the wax. Solvents include furfural, phenol, cresylic acid-propane (DuoSol), liquid sulfur dioxide (Eleleanu process), B,B-dichloroethyl ether, methyl ethyl ketone, nitrobenzene, and sulfur-benzene. The process yields de-oiled waxes, wax-free lubricating oils, aromatics, and recovered solvents. 

One of the major advantages of oxonium salts is that alkylations can be effected under reaction conditions that are generally much milder than those necessary with the more conventional alkyl halides or sulfonates. Triethyloxonium tetrafluoroborate, for example, has usually been employed at room temperature in dichloromethane or dichloroethane solution. Occasionally chloroform16-22 or no solvent at all4-20 is used. Difficult alkylations can be effected in refluxing dichloroethane.29 30 The less soluble trimethyloxonium tetrafluoroborate has been used as a suspension in dichloromethane or dichloroethane, or as a solution in nitromethane or liquid sulfur dioxide. Reports of alkylations in water23 and trifluoroacetic acid21 have also appeared. Direct fusion with trimethyloxonium tetrafluoroborate has succeeded in cases where other conditions have failed.25-30... 

Selenium trioxide, Se03, is white, crystalline, and hygroscopic. It can be prepared by the action of sulfur trioxide on potassium selenate or of phosphorous pentoxide on selenic acid. It forms selenic acid when dissolved in water. The pure trioxide is soluble in a number of oiganic solvents. A solution in liquid sulfur dioxide is a selenonating agent. It is stable in very dry atmospheres at room temperature and on heating it decomposes first to selenium pentoxide [12293-89-9] and then to selenium dioxide. 

The radical cation 85 is also formed by the dissociation of in solvents such as fluorosulfuric acid and liquid sulfur dioxide. The second product of this... 

This process, commercialized by Edeleanu Gesellschaft, m.b.H., employs a solvent mixture composed of benzene and liquid sulfur dioxide. The same solvents are used in the Edeleanu process for selective solvent refining. Generally, the volume ratio of the two solvents is 80 parts of benzene to 20 parts of sulfur dioxide for dewaxing (58). For selective solvent refining the solvents are blended in the proportion of about 75% sulfur dioxide and 25% benzene. 

Edeleanu Process (Liquid Sulfur Dioxide). The forerunner of ail commercial solvent extraction processes, the Edeleanu process, has been pre-eminently successful for treating low molecular weight stocks in the kerosene-spray oil boiling range. 

Solvent extraction has become the most widely used method of refining lubricating oils. Selective solvents which extract the less desirable constituents include phenol, furfural, dichloroethyl ether, mixtures of cresylic acid and propane, and liquid sulfur dioxide. Liquid propane precipitates asphaltic constituents and wax and retains the more desirable oil components in solution. Dewaxing may also be accomplished by other solvents such as mixtures of benzene and methyl ethyl ketone. 

Curiously, when liquid sulfur dioxide is used as a solvent and Mel as the quatemizing agent, one ortho methyl group retards the rate by 1% and the second by 44%.73 Although nonadditivity is observed, these kinetic effects are surprisingly small. 

The quantitative effects of a-substituents in decreasing the rates of these reactions are not additive and also depend considerably on solvent and alkylating agent. They are low in liquid sulfur dioxide as a solvent where solvation effects are small and the high dielectric constant increases the bond breaking in the transition state. For 3- and 4-substituted pyridines a Bronsted correlation exists between the rates of quatemization and the pKa values (78AHC(22)86). 

The application of the solvent system concept to liquid sulfur dioxide chemistry stimulated the elucidation of reactions such as those of aluminum sulfite. However, there is no direct evidence at all for the formation of S02+ in solutions of thionyl halides. In fact, there is evidence to the contrary. When solutions of thionyl bromide or thionyl chloride are prepared in 3JS-labeled (S ) sulfur dioxide, almost no exchange takes place. The half-life for the exchange is about two years or more. If ionization took place ... 

The solvents used vary with die nature of the products involved. Widely used are water, hexane, acetone, isopropyl alcohol, furfural, xylene, liquid sulfur dioxide, and tributyl phosphate. Solvent extraction is an important method of both producing and purifying such products as lubrication and vegetable oils, pharmaceuticals, and nonferrous metals,... 

Using liquid sulfur dioxide as a Lewis-acid solvent for the alkoxyalkylation and alkylation of allylsilanes has been investigated50. The reaction of acetals with allylsilanes results in the formation of homoallyl ethers 11 in excellent yields (equation 8). 

Pure crystalline I2+Sb2F11 has been prepared by the reaction of iodine with antimony pentafluoride in liquid sulfur dioxide as solvent.789 After removal of insoluble SbF3, deep blue crystals of l2+Sb2Fn were obtained from the solution. An X-ray crystallographic structure determination showed the presence of the discrete... 

Liquid sulfur dioxide-benzene process a mixed-solvent process for treating lubricating-oil stocks to improve viscosity indexes also used for dewaxing. 

The 3-substituted 1,2,3-triazole 1-oxides 448 were alkylated at the oxygen by trimethyloxonium tetrafluoroborate using liquid sulfur dioxide as the solvent affording hygroscopic 3-substituted l-methoxy-l,2,3-triazolium tetrafluoroborate 507 in high yield (1987ACSA(B)724).The reactivity of these salts has not been reported (Scheme 147). 

When solvent refined lignite (SRL) produced from North Dakota lignite was treated with liquid sulfur dioxide, the bulk of the coal liquid dissolved except for the saturated hydrocarbons and the mineral rich residue. The S02-solublc part did not contain any saturated hydrocarbons. The THF extract of the insolubles was mostly alkanes ranging from n-dodecane (C 2H26 to n tetra tetrancontane (C44Hgg). 

Liquid sulfur dioxide was used to separate the liquefaction products from Texas lignite when Tetralin had been used as the hydrogen donor solvent. The large excess of Tetralin present with the lignite liquefaction products did not interfere with the liquid sulfur dioxide separation procedure. The chemical composition of the fractions were similar to that of SRC and SRL. 

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