Liquid sulfur trioxide

Caution Rubber gloves and a protective pace shield should be worn while handling liquid sulfur trioxide, and the reaction should be carried out in a hood. 

Liquid sulfur trioxide may be purchased in stabilized form as Sulfan B," m.p. 17°, b.p. about 45°. Caution must be exercised in handling sulfur trioxide. The liquid is highly corrosive to the skin and the vapor may cause injury if inhaled. The powerful oxidizing and dehydrating effects of sulfur trioxide should not... 

The commercial production of stabilized liquid sulfur trioxide and the assessment of its advantages led to increased use [47-49]. Later development of specialized sulfur burners with catalytic conversion of sulfur dioxide to sulfur trioxide in air by vanadium pentoxide has established this method as an alternative to liquid sulfur trioxide. 

In the literature a number of different techniques for the preparation of a-sulfo fatty acid esters can be found. There is equipment for small-scale and commercial scale sulfonation. Stirton et al. added liquid sulfur trioxide dropwise to the fatty acids dispersed or dissolved in chloroform, carbon tetrachloride, or tetrachoroethylene [44]. The molar ratio of S03/fatty acid was 1.5-1.7 and the reaction temperature was increased to 65 °C in the Final stage of sulfonation. The yield was 75-85% of the dark colored a-sulfonated acid. The esterification of the acid was carried out with either the a-sulfonic acid alone, in which case the free sulfonic acid served as its own catalyst, or with the monosodium salt and a mineral catalyst. 

Sulfonating the asphalt with a liquid sulfonating agent, such as liquid sulfur trioxide... 

Used industrially as a chemical intermediate for pharmaceuticals and herbicides used in the manufacture of flame-resistant products used as a stabilizer for liquid sulfur trioxide. 

Stabilized levitation, 23 866-867 Stabilized liquid sulfur trioxide, 23 517 Stabilized polystyrenes, 23 366 Stabilized zirconia... 

Unsaturation, in oils, 10 826 Unsensitization phenomenon, 19 237 Unshaped refractories, 6 491 Unslaked lime, 15 29 Unstabilized liquid sulfur trioxide, 23 517 Unstable angina, 5 109 Unstable flows, 11 761-765 Unstable node, in separating nonideal liquid mixtures, 22 303 Unstable nodes, residue curve maps, 8 790 Unstable reagents, measurement strategies for, 14 621... 

Dinitrogen pentoxide has been used for aromatic nitration in other media and some are notable. While a solution of dinitrogen pentoxide in carbon tetrachloride will not convert 1,3-dinitrobenzene to 1,3,5-trinitrobenzene, a solution in concentrated sulfuric acid at 160 °C will effect this conversion. In this medium dinitrogen pentoxide is fully ionized to nitronium and nitrate ions. Solutions of dinitrogen pentoxide in liquid sulfur trioxide have been used for the nitration of some deactivated pyridines. ... 

Nitrosyl fluoride is an oxidizer in rocket propellants. Other apphcations are in organic synthesis where it is a fluorinating agent. The compound also is a stabdizer for liquid sulfur trioxide. 

Reaction with cold nitric acid results primarily in the formation of 5-nitrosalicylic acid [96-97-9]. However, reaction with fuming nitric acid results in decarboxylation as well as the formation of 2,4,6-trinitrophenol [88-89-1] (picric acid). Sulfonation with chlorosulfonic acid at 160°C yields 5-sulfosalicylic acid [56507-30-3]. At higher temperatures (180°C) and with an excess of chlorosulfonic acid, 3,5-disulfosalicylic acid forms. Sulfonation with liquid sulfur trioxide in tetrachloroethylene leads to a nearly quantitative yield of 5-sulfosalicylc acid (1). 

Sulfosalicylic acid is prepared by heating 10 parts of salicylic acid with 50 parts of concentrated sulfuric acid, by chlorosulfonation of salicylic acid and subsequent hydrolysis of the acid chloride, or by sulfonation with liquid sulfur trioxide in tetrachloroethylene. It is used as an intermediate in the production of dyestuffs, grease additives, catalysts, and surfactants. It is also useful as a colorimetric reagent for ferric iron and as a reagent for albumin. Table 9 shows the physical properties of salicylic acid derivatives. 

Sulfur trioxide is distilled by heating 60% fuming sulfuric acid contained in the flask. Spent acid may be fortified with Sulfan B, stabilized liquid sulfur trioxide obtainable from the General Chemical Company, 40 Rector St., New York. Undiluted Sulfan B solidifies in the flask after a few heatings, and subsequent reheating may be dangerous. 

Materials of Construction. Resistance of alloys to concentrated sulfuric acid corrosion increases with increasing chromium, molybdenum, copper, and silicon content. The corrosiveness of sulfuric acid solutions is highly dependent on concentration, temperature, acid velocity, and acid impurities. An excellent summary is available (114). Good general discussions of materials of construction used in modem sulfuric acid plants may be found in References 115 and 116. More detailed discussions are also available (117—121). For nickel-containing alloys Reference 122 is appropriate. An excellent compilation of the relatively scarce literature data on corrosion of alloys in liquid sulfur trioxide and oleum may be found in Reference 122. 

S03 (liq.). The data on the heat of solution of liquid sulfur trioxide in water are Thomsen,15 39.17ieoo Giran,3 39.440<> Grau and Roth,2 4I.I85000. 

Liquid sulfur trioxide is used for sulfonation, especially in the manufacture of detergents. In the past, the difficulty was the instability of the sulfur trioxide. However, under the trade name Sulfans , stabilized forms of sulfur trioxide are available several patented inhibitors such as boron compounds, methane sulfonyl chloride, sulfur, tellurium, and phosphorus oxychloride inhibit crystallization or conversion to a polymer. 

Manufacture Chlorosulfonic acid is produced by the reaction of liquid sulfur trioxide with hydrogen chloride or by the gas phase reaction of sulfur trioxide, from catalyst tray contact in sulfuric acid plants, with an excess of dry hydrogen chloride at high temperatures. 

Phosgene is claimed to form a 1 1 adduet, COClj.SOClj, with SOClj at ambient temperatures in a mildly exothermic reaction [1782] the adduct, a colourless liquid, is reported to stabilize liquid sulfur trioxide [1782]. 

Phosgene (0.1-1.5 wt.%) Is reported to stabilize liquid sulfur trioxide against... 

The rearrangement of alcohol with a tertiary y0-carbon in the presence of an acid is illustrated in Scheme 1, along with its competing reactions to form corresponding alkyl chlorides. In addition, the mechanism for the formation of a cyclic sulfate from pinacolone and liquid sulfur trioxide is provided in Scheme 2. 

In 1960 in India, the production of liquid sulfur trioxide was less than 100 tonnes per annum (TPA). Today there are plants in India which produce more than 100 TPD of liquid or gaseous sulfur trioxide with purity of 99-99.5%. The total production of pure sulfur trioxide in India can be estimated as about 300,000 MTs in the year 2003 60% of the production is for captive use. 

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