Chemical process
OwnerLiou-Liang Horng, Chung Y. Shen +1inventors
InventorsLiou-Liang Horng, Chung Y. Shen, Mark E. Jason
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Abstract
There is disclosed herein improved processes for the preparation of mixtures of alkali metal salts of 1-hydroxy-3-oxa-1,2,4,5-pentane tetracarboxylate and alkali metal salts of 3,6-dioxa-1,2,4,5,7,8-octane hexacarboxylate wherein by-product calcium carbonate produced by the process of making such mixtures is employed in a recycle pattern to prepare additional amounts of mixtures of said compounds.
Claims17
A process for preparing a mixture of the alkali metal salts of 1-hydroxy-3-oxa-1,2,4,5-pentane tetracarboxylic acid and 3,6-dioxa-1,2,4,5,7,8-octane hexacarboxylic acid by means of a calcium ion catalyzed reaction which comprises:
- a. reacting the salts of maleic and D,L-tartaric acids in alkaline medium;
- b. reducing the calcium content of said reaction product mixture to the extent that the molar ratio of calcium to the D,L-tartrate succinate reaction products is less than about 1:10 by precipitation of calcium carbonate;
- c. recovering the calcium carbonate removed in step (b) and recycling it to step (a) to prepare additional amounts of reaction product, and
- d. recovering and purifying the remainder of the reaction product from step (b).
A process for preparing a mixture of the alkali metal of 1-hydroxy-3-oxa-1,2,4,5-pentane tetracarboxylic acid and 3,6-dioxa-1,2,4,5,7,8-octane hexacarboxylic acid which comprises the steps of:
- a. forming an aqueous reaction mixture comprising from about 20% to 60% by weight of both calcium and monovalent cation salts of maleic acid and D,L-tartaric acid, said mixture corresponding to the over-neutralized mixture which is formed by combining:
- (i) maleic and D,L-tartaric acids in a maleic to D,L-tartaric molar ratio of from about 0.5:1 to about 8:1;
- (ii) a source of calcium cations in an amount such that the molar ratio of calcium to D,L-tartaric acid ranges from about 0.1:1 to 2.0:1 with the ratio of moles of calcium to total moles of maleic and D,L-tartaric acid being less than 1;
- and
- (III) a neutralizing agent comprising an hydroxide of a monovalent cation in an amount such that the ratio of moles of monovalent cation to moles of maleic acid plus moles of D,L-tartaric acid minus moles of calcium ranges from about 2.1:1 to 3.8:1;
- (b) maintaining said aqueous reaction mixture at a temperature of from about 20.degree. C. to 120.degree. C. for a time period sufficient to form a reaction product mixture of said 1-hydroxy-3-oxa-1,2,4,5-pentane tetracarboxylic acid salts and 3,6-dioxa-1,2,4,5,7,8-octane hexacarboxylic acid salts;
- (c) treating the filtrate from step (b) with a carbonate whereby calcium carbonate precipitates;
- (d) removing the calcium carbonate from the filtrate and recycling it to step (a) to prepare additional amounts of reaction product and
- (e) recovering and purifying the filtrate from step (d).
Dependencies are inferred from the claim text.