Method for upgrading used sulfuric acids

Details Method for upgrading used sulfuric acids Method for upgrading used sulfuric acids

1999-03-30

2001-12-25

Manoharan, Virginia (Department: 1764)

Concentrating evaporators

Processes

C159SDIG001, C159SDIG001, C159S031000, C159SDIG002, C159S016300, C203S012000, C203S040000, C203S042000, C203S093000, C203S094000, C203S096000, C203S041000, C203S092000, C203S095000, C203S097000, C203S098000, C423S522000, C423S531000, C055S423000, C202S197000

Reexamination Certificate

active

06332949

ABSTRACT:

The present invention relates to a process for concentrating spent sulphuric acids, particularly sulphuric acids which arise during the nitration of hydrocarbons with nitric acid in the presence of sulphuric acid, wherein single- or multi-stage concentration is effected under vacuum.
In this connection, the disposal or reutilisation of spent sulphuric acid which arises during the manufacture of nitrated products constitutes a problem, since the sulphuric acid constitutes a significant proportion of the manufacturing costs in the process. Amongst other considerations, this has led to attempts to avoid the use of sulphuric acid altogether (Kirk-Othmer, Encycl. Chem. Tech., 3rd Edition 1981, Volume 15, pages 928-929).
The most widely used process for concentrating spent sulphuric acid is what is termed the Pauling process [Bodenbrenner, von Plessen, Vollmüller, Dechema-Monogr. 86 (1980), 197], in which a relatively pure 96% sulphuric acid can be recovered. The disadvantages of this process are the high specific investment costs and operating costs. Moreover, SO
2
and NO
x
by-products are formed by the oxidative destruction of part of the organic compounds.
In most vacuum concentration processes for spent sulphuric acids, the vapours also contain appreciable amounts of sulphuric acids in addition to other compounds. Despite the installation of distillation stages for separation, sulphuric acid is entrained and reoccurs in the condensate and thus in the liquid waste.
Avoiding these problems has hitherto proved to be very costly technically and economically. According to U.S. Pat. No. 4,409,064, a water film is maintained above a packing during the concentration of spent sulphuric acids and a considerable amount of water is sprayed on to a distributor in order to wash the sulphuric acid out of the vapours.


REFERENCES:
patent: 3789902 (1974-02-01), Shah et al.
patent: 4409064 (1983-10-01), Vora et al.
patent: 4857281 (1989-08-01), Beckhaus et al.
patent: 5275701 (1994-01-01), Mazzafro et al.
Kirk-Othmer, Encycl. Chem. Tech., 3rd Edition, (month unavailable) 1981, vol. 15, pp. 928-929, Nitrobenzene and Nitrotoluenes.
Bodenbenner, von Plessen, Vollmüller, Dechema-Monogr. 86, (month unavailable) 1980, pp. 197-219, Das Pauling-Verfahren zur Regeneration von Abfallschwefelsaure.

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