GB778966A - Recovery of hydrogen peroxide by fractional distillation of the products of the oxidation of alcohols - Google Patents

Abstract

<PICT:0778966/III/1> Hydrogen peroxide is recovered from the crude reaction mixtures obtained by partial oxidation of lower aliphatic alcohols, such as isopropyl alcohol, by distilling the mixture to remove the residual alcohol as distillate, submitting the partially purified aqueous peroxide to a partial-evaporation and two-stage rectification process, steamstrippinig the bottoms from the second rectification zone to remove the last traces of organic material, and withdrawing purified aqueous hydrogen peroxide from the stripping zone. The residues from the evaporator are stripped in a second stripping zone by the vapours from the first stripping zone; and the vapours from the second stripping zone are passed into the evaporator. A crude reaction mixture containing isopropyl alcohol (52 per cent), hydrogen peroxide (6.5 per cent), acetone (13.5 per cent) and water (27.4 per cent) is introduced through line 1 into fractionating column 2, wherein it is fractionated at a reboiler temperature of 100 DEG C., the stillhead pressure being maintained at 550 mm. Hg. The isopropyl alcohol/water azeotrope together with acetone is taken overhead; and an aqueous solution of hydrogen peroxide (27.6 per cent) containing organic impurities is withdrawn from the base of column 2 to surge-tank 10. Additional water may be added to column 2, if necessary, through line 9. The dilute acqeous hydrogen peroxide is conveyed from tank 10 to tubular evaporator 13, which is made of stainless steel. The liquid is circulated through the evaporator and lines 14, 15, 12, by a pump; and evaporation is effected at a pressure of 150 mm. to give a liquid-residue containing 55 per cent H2O2. Some of this liquid-residue is transferred through line 16 to the top of stripper 32. Vapours containing water, hydrogen peroxide and organic impurities flow through line 17 to fractionating column 18, and the condensate formed therein is returned to evaporator 13 via line 20. The vapours leaving the top of column 18 are further fractionated in column 21, which is operated at top pressure of 110 mm. and a bottom temperature of 64 DEG C. Water-vapour passes overhead from column 21, and a 30-60 per cent H2O2 solution is withdrawn as bottoms. This solution is treated in stripping column 26 countercurrently with steam (in the proportion of about twice the weight of feed from line 25), and a minor amount of reflux-water is introduced through inlet 28. The stripping column is operated at a top pressure of 430 mm. and a bottom temperature of 97 DEG C. The vapours taken off from the head of stripper 26 are conveyed to the ase of stripper 32, wherein they flow up through the downflowing liquid-residue from evaporator 13. Stripper 32 is operated at top presure of 250 mm. and a bottom temperature of 76 DEG C.; and the weight-ratio of liquid feed to gaseous feed thereto is between 1 : 10 and 1:20. The vapours leaving the top of stripper 32 are passed to evaporator 13; and the stripped liquid, which contains organic impurities, is withdrawn from the base and discarded. The peroxide solution obtained at the base of stripper 26 contains 29 per cent H2O2 and only a trace of organic impurity; it may be withdrawn, wholly or in part, from the system as product, or it may be further concentrated and purified in evaporator 39 and fractionating columns 44, 48, 53. Hydrogen peroxide at a concentration as high as 85 per cent may be collected on catch-tray 56, and withdrawn from the system via line 59. Specifications 708,339 and 731,238 are referred to.