Oleum production

Production from Oleum. Production of SO2 from oleum was developed at Stauffer Chemical Company and is used commercially by Rhc ne-Poulenc to produce Hquid sulfur dioxide. It can be kitegrated with an existing oleum operation or with a concentrated sulfuric acid-consuming operation. 

The absorption of SO for oleum production is carried out over a relatively narrow temperature range. The upper temperature is set to provide a reasonable partial pressure driving force for the oleum concentration used. The lower practical temperature limit is the freezing point of oleums, which is high enough to be a problem in shipping and handling as well. For some oleum uses it is practical to add small amounts of HNO as an antifreeze (100). 

The oleum collection vessel should be fitted with a means of determining the level (sight glass) and a high-level alarm to warn the operator of the need to empty the vessel and to give an indication, from records, of excessive oleum production. The discharge of oleum from the vessel is normally a manual operation, although in the case where oleum is pumped to the SO2 scrubber, hard-wired interlocks must be used to prevent the transfer of oleum when the scrubber is not in operation. 

Mixed-Meta.1 Oxides. Generally, iron oxide is the principal component of mixed-metal oxides. These affect the sulfuric and oleum consumption in HF production. 

Sulfation and Sulfonation. a-Olefin reactions involving the introduction of sulfur-containing functional groups have commercial importance. As with many derivatives of olefins, several of these products have appHcations in the area of surfactants (qv) and detergents. Typical sulfur reagents utilized in these processes include sulfuric acid, oleum, chlorosulfonic acid, sulfur trioxide, and sodium bisulfite. 

Sulfonation. The main sulfonation product of quinoline at 220°C is 8-quinoHnesulfonic acid [85-48-3]-, at 300°C it rearranges to 6-quinolinesulfonic acid [65433-95-6] (10). Optimum conditions for sulfonation, 2 h at 140°C and a 1 4 quinoline/40% (wt) oleum ratio, produces 80% yield. The yield drops to 64% at 130°C with a 1 3 reactant ratio (11). Somewhat higher, but variable, yields of 8-quinoHnesulfonic acid hydrochloride [85-48-3] have been reported with chlorosulfonic acid (12). 

By 1987, sulfur trioxide reagent use in the United States exceeded that of oleum for sulfonation. Sulfur trioxide source is divided between Hquid SO and in situ sulfur burning. The latter is integrated into sulfonation production faciUties. 

Typically, the oil is subjected to several successive oleum contacts ("treats") at ca 60—65°C. This charge ratio of feedstock oleum is generally empirically determined, but depends in part on the degree of aromatic removal required for the product. In the case of white oil manufacture, 100 parts of... 

The viscosity of sulfonation and sulfation reaction mixtures increases with conversion, often producing extremely high viscosities. Figure 1 provides temperature—viscosity curves for oleum and SO -detived products. Sulfonation process design must accommodate such viscosities. 

Fig. 1. Sulfonated and sulfated acid products viscosities after 98% conversions at varying temperatures where the vertical line indicates the maximum temperature for batch sulfonation using SO to minimi2e color deterioration lines A—C represent branched C 2 alkyl ben2ene (BAB) sulfonic acid from SO, oleum (settied), and oleum (whole mixture), respectively lines D and E, lauryl alcohol 3-ethoxylate sulfuric ester (SO ) and lauryl alcohol sulfuric ester...

Details for the nonsolvent batch oleum sulfonation process for the production of BAB sulfonic acid have been described, including an exceUent critique of processing variables (257). Relatively low reaction temperatures (ca 25—30°C) are necessary in order to obtain acceptable colored sulfonate, which requires refrigerated cooling (Table 9, example D). 

Batch Stirred Tank SO Sulfonation Processes. If the color of the derived sulfonate is not critical, such as ia the productioa of oil-soluble ag-emulsifiers, a simple batch sulfoaatioa procedure can be employed based on vaporizing liquid SO (Niaol Labs, 1952) (13,263). Pilot Chemical Company adapted the original Morrisroe 60—70% oleum—SO2 solvent sulfonation process (256) to utilize 92% Hquid SO —8% Hquid SO2 mixtures, and more recently usiag 100% Hquid SO. This cold sulfoaatioa low viscosity sulfoaatioa process produces exceUeat quaHty products, and reportedly has also been adapted for continuous processiag as weU. The derived sulfonic acid must be stripped of SO2 solvent after completing sulfonation and digestion. 

Other Applications. Hydroxylamine-O-sulfonic acid [2950-43-8] h.2is many applications in the area of organic synthesis. The use of this material for organic transformations has been thoroughly reviewed (125,126). The preparation of the acid involves the reaction of hydroxjlamine [5470-11-1] with oleum in the presence of ammonium sulfate [7783-20-2] (127). The acid has found appHcation in the preparation of hydra2ines from amines, aUphatic amines from activated methylene compounds, aromatic amines from activated aromatic compounds, amides from esters, and oximes. It is also an important reagent in reductive deamination and specialty nitrile production. 

Fig. 1. Flow diagram of production of sulfur dioxide from oleum 1, 30% oleum exchanger 2, SO vaporizer 3, reactor 4, coolant surge tank 5, coolant ckculatkig pump 6, coolant exchangers 7, sludge and acid pump 8, scmbber 9, SO2 cooler 10, gas cleaner 11, SO2 compressor 12, pulsation damper and 13, SO2 condenser. CM is the condensate FRC, flow recording controller PIC, pressure kidicatkig controller SM, steam TC, temperature recorder ...

Gas leaving the economizer flows to a packed tower where SO is absorbed. Most plants do not produce oleum and need only one tower. Concentrated sulfuric acid circulates in the tower and cools the gas to about the acid inlet temperature. The typical acid inlet temperature for 98.5% sulfuric acid absorption towers is 70—80°C. The 98.5% sulfuric acid exits the absorption tower at 100—125°C, depending on acid circulation rate. Acid temperature rise within the tower comes from the heat of hydration of sulfur trioxide and sensible heat of the process gas. The hot product acid leaving the tower is cooled in heat exchangers before being recirculated or pumped into storage tanks. 

Sulfur dioxide concentrations in oleum ate rarely specified or measured, but typical values are considerably higher than in acids of <99 wt % concentrations. This occurs because oleum is produced at relatively low temperatures in the presence of appreciable SO2 in the gas phase, thus lea ding to high solubihty. It is not possible to strip SO2 from oleums by air blowing, a technique that is ftequentiy appHed to product acids of <99% concentration. 

Passing a stream of nitrogen at 95—100°C through a reaction mixture of ethyl ether and 30 wt % oleum prepared at 15°C results in the entrainment of diethyl sulfate. Continuous operation provides a >50% yield (96). The most economical process for the manufacture of diethyl sulfate starts with ethylene and 96 wt % sulfuric acid heated at 60°C. The resulting mixture of 43 wt % diethyl sulfate, 45 wt % ethyl hydrogen sulfate, and 12 wt % sulfuric acid is heated with anhydrous sodium sulfate under vacuum, and diethyl sulfate is obtained in 86% yield the commercial product is >99% pure (97). 

Electrophilic substitution reactions of unsubstituted quinoxaline or phenazine are unusual however, in view of the increased resonance possibilities in the transition states leading to the products one would predict that electrophilic substitution should be more facile than with pyrazine itself (c/. the relationship between pyridine and quinoline). In the case of quinoxaline, electron localization calculations (57JCS2521) indicate the highest electron density at positions 5 and 8 and substitution would be expected to occur at these positions. Nitration is only effected under forcing conditions, e.g. with concentrated nitric acid and oleum at 90 °C for 24 hours a 1.5% yield of 5-nitroquinoxaline (19) is obtained. The major product is 5,6-dinitroquinoxaline (20), formed in 24% yield. 

Phenyl-l,2-benzisoxazole has been reported to give a disulfonic acid of unknown structure on treatment with 40% oleum (67AHC(8)277). The chlorosulfonation of 1,2-benzisoxazole-3-acetic acid has been reported to give a mixture of the two products shown in Scheme 26. 

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