Hoechst Celanese Corporation

Virginia Chemicals Inc.

Joseph L Bush

Charles E Winslow

Leonard C Ellis

Daniel D Dickens

Aqueous co-product, produced by distillation of reaction filtrate from a batch reaction for manufacturing sodium dithionite by reacting sodium formate, sodium hydroxide, and sulfur dioxide in aqueous methanol solution, is rapidly evaporated to remove about 80% of its water content, so that only the determined quantity of water remains with its determined contents of alkali metal compounds, and is utilized as an admixed component of a succeeding batch.

Method for re-use of aqueous co-product from manufacture of sodium

Vent gas from the condenser-scrubber system of a reactor, in which dithionites are made by reacting a formate, sulfur dioxide, and an alkali in aqueous methanol, is reduced in its ethylene oxide content to less than 10 ppm maintaining the ratio of sulfur dioxide to ethylene oxide entering the scrubber to greater than 1.0, preferably greater than 2.5, and most preferably greater than 3.0 and at a temperature of -20.degree. C. to 0.degree. C.

Method of reducing ethylene oxide emissions

There is disclosed a method for the production of dust-free sodium dithionite from the reaction of a alkaline formate sulfur dioxide and an alkaline metal agent in the presence of a thiosulfate reactive compound by introducing a water-soluble polymer having a molecular weight less than 60,000 and delaying the start of the alkaline metal agent until the sodium formate and the sulfur dioxide have begun to be introduced into the reactor.

Method for producing dust-free sodium dithionite

A method is taught for increasing the yield of anhydrous sodium dithionite by adding an organic compound that is thiosulfate reactive to a batch reactor containing a puddle solution of methanol and fed with formic acid or an alkali formate as a first feed, an aqueous alkali compound as a second feed, an aqueous alkali formate solution as a third feed, and a methanolic SO.sub.2 solution as a fourth feed. This organic compound may be added prior to, combined with, or concurrently with one of the four feeds to the reactor. Preferably, it is added concurrently with the third feed and throughout the entire course of the reaction, ending with the beginning of the cooling period. A suitable addition rate is 0.4-0.6 wt. %/minute, preferably 0.5 wt. %/minute. All of the organic compound is consumed, and at least a portion of the thiosulfate ion is destroyed. The organic compound is selected from the group consisting of epoxy compounds having the formula ##STR1## or halogenated hydrocarbons having the general formula R.sub.2 X or XR.sub.2 X, R.sub.1 being hydrogen, an alkyl group containing from 1 to 8 carbon atoms, a halogenated alkyl group containing from 1 to 2 carbon atoms, a phenyl group, or a substituted phenyl group. The compound represented by this formula includes ethylene oxide, propylene oxide, butylene oxide, epichlorohydrin, epibromohydrin, and styrene oxide. R.sub.2 is a primary or secondary alkyl group containing from 1 to 8 carbon atoms, an allyl group or a 2-methylallyl or 2-ethylallyl group, and X is a halogen atom. Suitable compounds include methyl iodide and allyl chloride.

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Chesapeake, VA, United States of America

Joseph L Bush