Patent GB-776664-A (GB)
Title: Process for removing acids from aqueous solutions of organic solutes with ion exchange resins
IPC: B01J41/04
Filed: 1954-05-11
Abstract: Organic solutes having ionization constants not exceeding 1.75 X 10-5 at 25 DEG  C. are recovered from their aqueous solutions containing a strong acid having an ionization constant of at least 1.4 X 10-3 at 25 DEG  C. by feeding the solution into contact with a bed of an anion-exchange resin in the sulphate form, whereby at least the strong acid solute is absorbed by the resin and thus converts at least a portion of the resin to the bisulphate form, separating therefrom the treated solution and eluting the loaded resin with water to remove, firstly, any absorbed organic solute and thereafter the absorbed strong acid solute, whereby the anion exchange resin is regenerated to the sulphate form.  In the process, the strong acid is chemically absorbed; the organic solute is only physically absorbed and remains wholly or in part in the solution surrounding the resin granules.  The solution of solutes is preferably fed to a water-immersed bed of the resin with consequent displacement of an equal volume of water and then water is fed to elute the loaded resin; the water first displaces a solution of the organic solute and then displaces the chemically absorbed strong acid solute, the two effluents being collected in separate fractions, with consequent regeneration of the resin.  Specified organic solutes include various lower aliphatic water-soluble alcohols, glycols, mono-ethers of ethylene and polyethylene glycols, polyhydric alcohols, carboxylic acids, ketones and amides.  Strong acids mentioned are sulphuric, hydrochloric, hydrobromic, nitric, phosphoric, pyrophosphoric, ethylene disulphonic, benzene sulphonic, toluene sulphonic, naphthalene sulphonic and the chloracetic acids.  Suitable anion-exchange resins are those described in Specifications 654,706 and 679,850, [both in Group IV (a)], and U.S.A.  Specification 2,341,907; the preferred resins are those concess is normally effected at from about room temperature to about 90 DEG F., under substantially atmospheric pressure.  The method may be used to recover the organic solutes from their aqueous solutions containing salts of the strong acids by passing the solution through a cation-exchange resin in hydrogen form to convert the salts into the corresponding free acids and then treating the acid solutions as above.  Thus, the salt solution may be passed down a column, the upper portion of which contains the cation exchanger and the lower portion, the anion-exchanger; the treated solution is eluted with water to recover the organic solute and the column then is regenerated by an upward flow of water so removing the strong acid. According to examples: (1) an anion-exchange resin obtained by condensation of trimethylamine with a copolymer of styrene with ethyl vinyl benzene and divinyl benzene is converted into its sulphate form by treatment with aqueous sulphuric acid and then washed with water in a column; then a quantity of an aqueous solution of ethylene glycol and HCl is fed down the column of water-immersed resin and thereafter water is passed downwardly to displace aqueous glycol and then upwardly to displace aqueous HCl and so regenerate the resin; in like manner the solutes are separately recovered as solutions from aqueous solutions of (2) acrylamide and sulphuric acid, (4) glycerine and sulphuric acid, (5) ethylene glycol and sulphuric acid, (6) ethylene glycol and ethylene disulphonic acid, (8) ethanol and sulphuric acid, (9) acetic acid and sulphuric acid, (10) acetic and chloracetic acids and (11) methyl ethyl ketone and phosphoric acid using the same or similar exchange resin.  Another Example (7) relates to the separation of solutes from aqueous sucrose containing sodium chloride (see Group VI). Methanol, isopropyl alcohol, penta-erythritol, propylene glycol, butylene glycol, polyethylene glycol, propionic acid, acetone and acetamide are other organic solutes mentioned.ALSO:Strong acids having ionization constants of at least 1.4 X 10-3 at 25 DEG C. are recovered from their aqueous solutions containing organic substances having ionization constants not exceeding 1.75 X 10-5 at 25 DEG C. by feeding the solution into contact with a bed of an anion-exchange resin in the sulphate form, whereby at least the strong acid is absorbed by the resin and thus converts at least a portion of the resin to the bisulphate form, separating therefrom the treated solution and eluting the loaded resin with water to remove firstly any absorbed organic substance and thereafter the absorbed strong acid substance, whereby the anion exchange resin is regenerated to the sulphate form.  In the process, the strong acid is chemically absorbed; the organic substance is only physically absorbed and remains wholly or in part in the solution surrounding the resin granules.  The solution is preferably fed to a water-immersed bed of the resin with consequent displacement of an equal volume of water and then water is fed to elute the loaded resin; the water first displaces a solution of the organic substance and then displaces the chemically absorbed strong acid, the two effluents being collected in separate fractions, with consequent regeneration of the resin.  Specified organic substances include various lower aliphatic water-soluble alcohols, glycols, mono ethers of ethylene and polyethylene glycols, polyhydric alcohols, carboxylic acids, ketones and amides, methanol, ethanol, isopropyl alcohol, penta-erythritol, propylene glycol, butylene glycol, polyethylene glycol, propionic, acetic and chloroacetic acid, acetone, acetamide, acrylamide, glycerine, methyl ethyl ketone trimethylamine and sucrose.  Strong acids mentioned are sulphuric, hydrochloric, hydrobromic, nitric, phosphoric and pyrophosphoric acids.  Suitable anion-exchange resins are those described in Specifications 654,706 and 679,850 [both in Group IV(a)] and U.S.A.  Specification 2,341,907; the preferred resins are those containing quaternary nitrogen groups.  The process is normally effected at from about room temperature to about 90 DEG F., under substantially atmospheric pressure.  The method may be used to recover the organic solutes from their aqueous solutions containing salts of the strong acids by passing the solution through a cation-exchange resin in hydrogen form to convert the salts into the corresponding free acid and then treating the acid solutions as above.  Thus, the salt solution may be passed down a column, the upper portion of which contains the cation exchanger and the lower portion, the anion-exchanger; the treated solution is eluted with water to recover the organic solute and the column then is regenerated by an upward flow of water so removing the strong acid.ALSO:Sucrose is recovered from its aqueous solution containing a strong acid having an ionisation constant of at least 1.4 x 10-3 at 25 DEG C. by feeding the solution into contact with a bed of an anion-exchange resin in the sulphate form, whereby at least the strong acid solute is absorbed by the resin and thus converts at least a portion of the resin to the bisulphate form, separating therefrom the treated solution and eluting the loaded resin with water to remove firstly any absorbed sucrose and thereafter the absorbed strong acid solute, whereby the anion exchange resin is regenerated to the sulphate form (see Group IV(b).  In the process, the strong acid is chemically absorbed; the sucrose is only physically absorbed and remains wholly or in part in the solution surrounding the resin granules.  In Example 7, an aqueous solution of sucrose, containing sodium chloride is passed down a column containing a bed of a cation-exchanger on a bed of anion exchanger in sulphate form as above described to give an aqueous effluent of sucrose free from acid.