Diisopropyl sulfate

Indirect Hydration. Indirect hydration is based on a two-step reaction of propylene and sulfuric acid. In the first step, mixed sulfate esters, primarily isopropyl hydrogen sulfate, but also diisopropyl sulfate, form. These are then hydrolyzed, forming the alcohol and sulfuric acid. 

The principal reactions are reversible and a mixture of products and reactants is found in the cmde sulfate. High propylene pressure, high sulfuric acid concentration, and low temperature shift the reaction toward diisopropyl sulfate. However, the reaction rate slows as products are formed, and practical reactors operate by using excess sulfuric acid. As the water content in the sulfuric acid feed is increased, more of the hydrolysis reaction (Step 2) occurs in the main reactor. At water concentrations near 20%, diisopropyl sulfate is not found in the reaction mixture. However, efforts to separate the isopropyl alcohol from the sulfuric acid suggest that it may be partially present in an ionic form (56,57). 

Early epidemiological studies suggested an association between the manufacture of isopropyl alcohol and paranasal sinus cancer/ The risk for laryngeal cancer may also have been elevated in these workers. The increased cancer incidence, however, appears to be associated with some aspect of the strong-acid manufacturing process rather than the isopropyl alcohol itself It is unclear whether the cancer risk is due to the presence of diisopropyl sulfate, which is an intermediate in the process, to isopropyl oils, which are formed as byproducts, or to other agents, such as sulfuric acid. ... 

Diisopropyl sulfate is an intermediate in the indirect hydration (strong- or weak-acid) process for the preparation of isopropanol from propylene. It has no other known industrial use. No data were available on levels of occupational exposure to diisopropyl sulfate (lARC, 1992). 

Exposure to diisopropyl sulfate occurs in production of isopropanol (see this volume). 

No measurement of exposure to diisopropyl sulfate was available for the industrial processes investigated in the epidemiological studies. It is therefore difficult to assess the contribution of diisopropyl sulfate to the increased cancer risks. Furthermore, exposure to mists and vapours from strong inorganic acids, primarily sulfuric acid, probably plays a role in increasing these risks.]... 

Diisopropyl sulfate was tested for carcinogenicity by subcutaneous injection in one strain of rats and by skin application in one strain of mice. It produced local sarcomas in rats and skin papillomas and carcinomas in mice. In a screening study in two strains of mice, an increased incidence of lung adenomas was obsen ed following subcutaneous injection (lARC, 1992). 

There is inadequate evidence in humans for the carcinogenicity of diisopropyl sulfate. There is sufficient evidence in experimental animals for the carcinogenicity of diiso-... 

Diisopropyl sulfate is possibly carcinogenic to humans (Group 2B). 

Dihydroxybenzenes (see Catechol Hydroquinone Resorcinol) Dihydro xymethylfuratrizine Diisopropyl sulfate... 

To confirm some of the above types of information and to get some quantitative data on the absorption of propylene and butylenes in recycle alkyUtion acid, and the solubility of diisopropyl sulfate and diisobutyl sulfates in hydrocarbons, some fundamental work, unpublished, was done by Midwest Research Institute in Kansas City, Missouri, in the early 1960 s for Texaco Development Corporation. 

It was confirmed in the work at Midwest Research that propylene could be reacted with recycle alkylation acid to give a high yield of diisopropyl sulfate (DIPS), and that the DIPS could be extracted with hydrocarbon solvents, including isobutane. The isopropyl acid sulfate (IPS) is quite insoluble in hydrocarbons and only a small amount is extracted along with the DIPS. Since the reaction of propylene with sulfuric acid is an equilibrium reaction, some IPS is always present. It was found that some of the conjunct polymer is also extracted with the DIPS. It was anticipated that the water would stay in the acid phase or raffinate, and this was found to be the case. 

The used catalyst is reacted with propylene to convert the acid to diisopropyl sulfate. The diisopropyl sulfate is extracted with isobutane, the extract treated with a small amount of used catalyst, leaving a weak acid containing the conjunct polymer and water. The isobutane extract free of conjunct polymer and water is charged to alkylation, along with additional olefin and fresh make-up acid. A discussion of the reaction conditions required and the variables Involved In the four steps of the process are given. 

With propylene, higher temperatures and more concentrated sulfuric acid are needed to promote the desired reactions with isobutane (and the formation of alkylate). In many refineries, rather substantial fractions of the isopropyl sulfates do not react. The sulfates that do not react decrease acidity and increase acid consumption. The diisopropyl sulfates, which dissolve in the hydrocarbon phase, increase the need for either caustic or acid washing. Improved operating conditions have recently been developed to promote more complete reactions of these sulfates in the reactor (and hence higher yields of alkylate) plus lower acid consumption (26). 

Benzene, toluene and chlorobenzene were also alkylated by C1-C3 alkyl sulfates in the presence of chlorosulfonic acid catalyst, which proved the intermediacy of alkyl sulfates in alkylation of benzenes by alkenes-chlorosulfonic acid mixture. Diisopropyl sulfate showed strong alkylating properties only in the presence of chlorosulfonic acid. 

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