Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acids and salts thereof
Patent
1998-05-28
2000-02-08
O'Sullivan, Peter
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acids and salts thereof
423181, 423395, 423399, 562513, 562575, 562584, 562589, C07C 59265, C07C 5908
Patent
active
060229926
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention is in the field of acid-salt metathetic processes in aqueous solution of the kind that are described by the equation I different anions.
In the above equation I, the left hand side members MX and HY conventionally denote the starting materials, i.e. the reactants, and the right hand side members MY and HX the products. In keeping with that convention, when the reaction proceeds from left to right it is referred to as a forward reaction and when it proceeds from right to left it is referred to as a backward reaction.
BACKGROUND OF THE INVENTION
Metathetic processes of the kind specified occur in aqueous solution under conditions in which the forward reaction is favored. Where one of the products MY and HX is water insoluble or volatile and accordingly precipitates or evaporates from the solution, the equilibrium of the reaction is constantly shifted from left to right leading to a continuous forward reaction. Depending on whether the desired product is the salt MY or the acid HX or possibly the two of them, the reaction solution and/or the precipitate must be worked up for the recovery of the desired product therefrom. Where, however, both the product MY and HX are water soluble, a steady state will be reached after a while in which the forward and backward reactions are in equilibrium and some kind of intervention is accordingly required for inducing continuation of the forward reaction. In the following, a metathetic reaction of the kind specified in which one of the two products is of limited water solubility or higher volatility and accordingly separates from the aqueous reaction mixture in the course of the reaction, will be referred to as spontaneous forward reaction while a reaction in which both products are water soluble and intervention is required for shifting the equilibrium from left to right and thereby induce continuation of the forward reaction, will be referred to as an induced forward reaction.
A typical example of metathetic processes with spontaneous forward reactions are the so-called wet process production of phosphoric acid by reaction of calcium phosphate with sulfuric acid, and the recovery of citric acid from a fermentation liquor by the so-called liming/acidulation process, which may be described, respectively, by the following Equations II and III PO.sub.4II
Typical examples for metathetic processes with induced forward reactions are production of the multi-nutrient fertilizer potassium nitrate from potassium chloride and nitric acid, in which the product of interest is a salt; and the conversion of ammonium lactate, which is a direct product of lactic acid fermentation, into free lactic acid by reaction with sulfuric acid, the product of interest here being an acid. These two processes are described, respectively, by the following equations IV and V
In reaction IV the main product is KNO.sub.3 and in reaction V the product of interest is HLa. In both reactions, the products are water soluble which makes it necessary to induce the forward reaction.
Solvent extraction is commonly applied for the inducement of forward reactions by product separation in metathetic processes. Alkanols, ethers, esters, ketones and other oxygen-carrying, water-immiscible compounds are well known acid extractants operating through salvation of the acid (solvating extractants). Acid binding in such extracting operations is relatively weak and as a result, the solvating extractants are effective only at relatively high acid activities, and by themselves are, as a rule, not capable of providing the driving force required for the inducement of the forward reaction. While the reaction of potassium chloride with sulfuric acid to form potassium sulfate and hydrochloride acid can be facilitated by acid extraction with alkanols, at the acidity levels required for efficient extraction, the acidic salt KHSO.sub.4 is formed rather than K.sub.2 SO.sub.4. In addition, Cl.sup.- /SO.sub.4.sup.2- extraction selectively is low which entails that for effective separation of
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Korngold, E., et al., "Water Desalination by Ion-Exchange Hollow Fibers," salination 84:123-135 (1991).
O'Sullivan Peter
Yissum Research Development Company of the Hebrew University of
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