GB894592A - Process for the recovery of tungstic acid catalyst - Google Patents

Abstract

Tungsten values are recovered from tungstic acid catalyst used in the oxidation of olefinically unsaturated compounds by bringing aqueous solutions of tungstic acid, generally rendered alkaline by the addition of sodium hydroxide and containing from 0,05 to 5% by weight of tungstic acid, into contact with an ion-exchange resin and thereafter eluting tungstic acid values with an aqueous solution of alkali metal chloride and finally precipitating the tungstic acid catalyst values from the eluted solution. The elution is preferably effected with 2-30% strength sodium chloride at temperatures preferably between 15 DEG and 60 DEG C. The sodium tungstate solutions so obtained are then rendered acidic, to a pH preferably between 2-6,5, by the addition of an inorganic or organic acid, thereby precipitating the tungstic acid, which may be separated by filtration or other means. If the organic oxidation reaction involves the use of aqueous hydrogen peroxide, the initial tungstic acid is in the form of pertungstic acid. Specified ion-exchange resins are those obtained by the sulphonation of polystyrene and co-polymers thereof with vinyl benzene, sulphonated phenol formaldehyde resins, amino nitrogenous resins derived from styrene and its co-polymers and cross linked polymers of a glycidol ester of acrylic acid or an alpha-substituted acrylic acid, which cross-linked polymers have been treated with ammonia or a primary or secondary amine. The resins are preferably used in their hydroxyl form. The aqueous medium contacted with the ion exchange resin may contain unreacted olefinically unsaturated material, the oxidized reaction products, hydrogen peroxide and reaction by-products. According to an example, "Amberlite" (Registered Trade Mark) was converted to the hydroxyl form by passing sodium hydroxide solution therethrough and thereafter an aqueous tungstic acid catalyst solution, which had been adjusted to a pH between 9 and 10 by the addition of sodium hydroxide, was passed through at 25 DEG C. Elution with a 4% sodium chloride solution produced a sodium tungstate solution which was treated with concentrated hydrochloric acid to precipitate the tungstic acid, followed by heating at 80 DEG -100 DEG C. After washing with water and dilute hydrochloric acid, tungstic acid values were dissolved in hydrogen peroxide solution to form a catalyst for oxidation of olefinically unsaturated organic compounds. Reference is made to Specification 626,882 which describes the process for recovering chromium, molybdenum, tungsten or uranium in the form of oxygen-containing complex anions from a solution by contacting it with an ion-exchange resin and eluting with a solution of an acid, salt or base.ALSO:Allyl alcohol is oxidised to glycerol in the presence of a tungstic acid solution in hydrogen peroxide. A hydrogen peroxide solution containing 2.14 milimoles of H2WO4 was mixed with allyl alcohol at 70 DEG C. and further hydrogen peroxide added. Sodium hydroxide was added, the unreacted allyl alcohol distilled off and the glycerol recovered by fractional distillation. Specification 626,882 [Group III] is referred to.