Patent GB-767449-A (GB)
Title: Process for separating solutes having different degrees of ionization
IPC: B01J47/00
Filed: 1954-06-09
Abstract: Aqueous mixtures of sodium chloride/ethylene glycol (obtained e.g. by hydrolysis of ethylene chlorhydrine followed by neutralization), sodium chloride/glycerol, di- or tri-chloracetic acid/acetic acid, ammonium chloride/glycine or ammonium sulphate/ethyl alcohol are separated by the following procedure in which the first component is referred to as "A" and the second as "B."  A solute A having an ionization constant of at least 5 x 10-2 is separated from an aqueous solution of A and the solute B, having an ionization constant not exceeding 2 x 10-1 and not exceeding 70 per cent of that of A, (a) by feeding the aqueous solution to a midsection of a column containing a body of granular ion exchange resin, capable of absorbing B and having an ion identical with an ion of A, which body of granular ion exchange resin is immersed in an aqueous liquid, feeding water to an end section of the column and causing it to flow lengthwise within the column, feeding a further amount of the ion exchange resin to the opposite end section of the column and withdrawing ion exchange resin at a corresponding rate from the end section of the column into which water is being fed, withdrawing a resulting liquor fraction consisting essentially of an aqueous solution of A in a form substantially free of B from the end section of the column into which the ion exchange resin is fed, and withdrawing another resulting liquor fraction consisting essentially of an aqueous solution of B in a form substantially free from A, from a midsection of a column at a point between the point of feed of the starting solution and the point of feed of water to the column; or (b) by a method comprising a plurality of operating cycles, the first of which cycles involves feeding to a bed of a similar ion exchange resin, a sufficient amount of the aqueous starting solution so that part of B is preferentially absorbed by the resin leaving the remainder of B and A in surrounding liquor, feeding water to the bed to displace liquid therefrom, collecting successive fractions of the displaced effluent liquor, whereby there are obtained effluent fractions (1) containing A in a form substantially free from B, (2) containing both of the solutes, and (3) containing B in a form substantially free from A, and the second of which cycles comprises feeding a fore-portion of said fraction (2) to the bed of ion-exchange resin, then feeding to the bed a further amount of the starting solution containing both of the solutes, next feeding to the bed a later portion of the fraction (2), next feeding to the bed at least a portion of said fraction (3) and finally feeding water to the bed and, during this second cycle collecting successive portions of the effluent liquor similar in kind to those collected in the first cycle, repeating at least once this second cycle of operations and withdrawing a portion of said fraction (3) as product from one or more of the cycles.  In a modification of (b), the fractions (1), (2) and (3) are initially obtained from sources other than the starting solution, e.g. by mixing the ingredients, and thereafter recycled in a similar manner, further fractions being collected and recycled at least once, and a portion of (3) being retained as product.  Preferred procedures and full operational details are given (see Group III).  Reference has been directed by the Comptroller to Specification 709,550, [Group I].ALSO:A solute A having an ionization constant of at least 5 X 10-2 is separated from an aqueous solution of A and a solute B having an ionization constant not exceeding 2 X 10-1 and not exceeding 70 per cent of that of A, by (a) feeding the aqueous solution to a mid-section of a column containing a body of granular ion exchange resin, capable of absorbing B and having an ion identical with an ion of A, which body of granular ion exchange resin is immersed in an aqueous liquid, feeding water to an end section of the column and causing it to flow lengthwise within the column, feeding a further amount of the ion exchange resin to the opposite end section of the column and withdrawing ion exchange resin at a corresponding rate from the end section of the column into which water is being fed, withdrawing a resulting liquor fraction consisting essentially of an aqueous solution of A in a form substantially free of B from the end section of the column into which the ion exchange resin is fed, and withdrawing another resulting liquor fraction consisting essentially of an aqueous solution of B in a form substantially free of A from a mid-section of the column at a point between the point of feed of the starting solution and the point of feed of water to the column or (b) by a method comprising a plurality of operating cycles, the first of which cycles involves feeding to a bed of a similar ion exchange resin, a sufficient amount of the aqueous starting solution so that part of B is preferentially absorbed by the resin leaving the remainder of B and A in surrounding liquor, feeding water to the bed to displace liquid therefrom, collecting successive fractions of the displaced effluent liquor, whereby there are obtained effluent fractions (1) containing A in a form substantially free from B, (2) containing both of the solutes, and (3) containing B in a form substantially free from A, and the second of which cycles comprises a fore-portion of said fraction (2) to the bed of ion exchange resin, then feeding to the bed a further amount of the starting solution containing both of the solutes, next feeding to the bed a later portion of the fraction (2), next feeding to the bed at least a portion of said fraction (3) and finally feeding water to the bed and, during this second cycle of the feeding operations of the process collecting successive portions of the effluent liquor similar in kind to those collected in the first cycle, repeating at least once this second cycle of operations and withdrawing a portion of said fraction (3) as product from one or more of the cycles.  In a modification of (b), the fractions (1), (2) and (3) are initially obtained from sources other than the starting solution, e.g. by mixing the ingredients, and thereafter recycled in a similar banner, further fractions being collected and recycled at least once, and a portion of (3) being retained as product.  In method (b), the starting solution fed to the bed in the second and subsequent cycles should be fed to the bed preferably when the concentration of A in the fraction B being fed to the bed has reached a maximum value and is about to decrease.  Sodium chloride/ethylene glycol; sodium chloride/glycerol; acetic acid/di- or trichloracetic acid; ammonium chloride/glycine; ammonium sulphate/ethyl alcohol are specific mixtures referred to. By this method a concentration of B in the product greater than that in the mixture may be obtained; increased concentration of A or B in the starting solution increases the concentration of B in the product, and by repeating several cycles of the fixed bed operation, the concentration may be built up to an increased level.  Solute A should have a normality of at least 1 to obtain this increase in concentration over that in starting solution, and a normality of 2 or higher is preferred.  A solute, e.g. sodium chloride, ammonium chloride or sodium sulphate, having an ion in common with the exchange resin may be added to the mixture if desired to increase the concentration.  Temperatures between the boiling and congealing points of the liquor may be used.  A continuous process may be arranged with static bed operation by using two or more of said beds in parallel, but not in phase as regards the cycle of operations.  The flow of liquor may be upward or downward in either embodiment.  Reference has been directed by the Comptroller to Specification 709,550 [Group I]