Patent ES-204580-A1 (ES)
Title: Recovery of pure phenol by distillation of reaction mixtures
IPC: C07C37/68
Filed: 1952-07-17
Abstract: <PICT:0745343/IV(a)/1> In the recovery of pure phenol from mixtures derived from the catalytic decomposition of isopropylbenzene hydroperoxide, the mixture is either submitted to fractional distillation under such conditions that phenyldimethylcarbinol remains behind in the distillation-residues while phenol, together with other products, passes over as distillate, or alternatively, the mixture is submitted to heat treatment whereby the carbinol is decomposed into methylstyrene and water. In either case the phenol-containing mixture freed from carbinol is subjected to fractional distillation to obtain pure phenol. The process obviates the decomposition of the carbinol, and consequent contamination of phenol with methylstyrene, during the separation of the finished product. It is preferred to remove the catalyst and the acetone from the hydroperoxide decomposition mixture before the separation or pyrolysis of the carbinol. The heat treatment of the mixture is preferably carried out after the methylstyrene has been distilled off, for otherwise polymerization of the latter would take place. In an example, a mixture obtained by acidic decomposition of isopropylbenzene hydroperoxide contained acetone, water, isopropylbenzene, methylstyrene, phenol, acetophenone, phenyldimethylcarbinol and some higher boiling compounds. After removal of acetone by distillation, the mixture was fed into column A (see Figure) which was operated at a pressure of 200 mm. Hg absolute. The overhead fraction contained most of the isopropylbenzene, some methylstyrene, and a little phenol which was recovered by extraction with alkali. The residue from the base of column A was fed into column B, which was operated at 100 mm. Hg. The distillate from column B contained 800 parts of phenol and only 0.8 parts of carbinol, besides methylstyrene, isopropylbenzene, traces of acetophenone, and a little water. The residue withdrawn from the base of column B was pyrolysed at 325 DEG C. to decompose the carbinol to methylstyrene, and the cumylphenol to methylstyrene, isopropylbenzene and phenol. The pyrolysed product was fractionated to give a distillate consisting mainly of phenol with some methylstyrene and isopropylbenzene, and this mixture was combined with the distillate from column B to give a mixture, containing 915 parts of phenol and 0.8 parts of carbinol, which was fed to column C. The distillate from column C consisted mainly of isopropylbenzene and methylstyrene with a little phenol, which was recovered by caustic alkali extraction. From two plates up from the base of column C phenol vapour was removed and passed through column D. The overhead vapour from column D, upon condensation, gave 890 parts of pure phenol, while polymeric products formed during the distillation were obtained as residue. Specifications 670,444 and 724,190 are referred to.ALSO:<PICT:0745343/III/1> In the recovery of pure phenol from mixtures derived from the catalytic decomposition of isopropylbenzene hydroperoxide, the mixture is either submitted to fractional distillation under such conditions that phenyldimethylcarbinol remains behind in the distillation-residues while phenol, together with other products, passes over as distillate, or alternatively, the mixture is submitted to heat treatment whereby the carbinol is decomposed into methylstyrene and water. In either case the phenol-containing mixture freed from carbinol is subjected to fractional distillation to obtain pure phenol. The process obviates the decomposition of the carbinol, and consequent contamination of phenol with methylstyrene, during the separation of the finished product. It is preferred to remove the catalyst and the acetone from the hydroperoxide decomposition mixture before the separation or pyrolysis of the carbinol. The heat treatment of the mixture is preferably carried out after the methylstyrene has been distilled off, for otherwise polymerization of the latter would take place. In an example, a mixture obtained by acidic decomposition of isopropylbenzene hydroperoxide contained acetone, water, isopropylbenzene, methylstyrene, phenol, acetophenone, phenyldimethylcarbinol and some higher boiling compounds. After removal of acetone by distillation, the mixture contained 923 parts of phenol and 37 parts of carbinol. This mixture was fed into column A (see Fig. 1) which contained 40 plates and was operated at a pressure of 200 mm. Hg. absolute at the top of the column. The overhead fraction contained most of isopropylbenzene, some methylstyrene, and a little phenol which was recovered by extraction with alkali. The residue from the base of column A was fed into column B of 45 plates, operated at 100 mm. Hg. and a reflux ratio of 4:1. The distillate from column B contained 800 parts of phenol and only 0.8 parts of carbinol, besides methylstyrene, isopropylbenzene, traces of acetophenone, and a little water. The residue withdrawn from the base of column B was pyrolyzed at 325 DEG C. to decompose the carbinol to methylstyrene, and the cumylphenol to methylstyrene, isopropylbenzene and phenol. The pyrolyzed product was fractionated to give a distillate consisting mainly of phenol with some methylstyrene and isopropylbenzene and this distillate was combined with the distillate from column B to give a mixture, containing 915 parts of phenol and 0.8 parts of carbinol, which was fed to column C (50 plates). The distillate from column C consisted mainly of isopropylbnezene and methylstyrene with a little phenol, which was recovered by caustic alkali extraction. From two plates up from the base of column C phenol vapour was removed and passed through column D (5 plates). The overhead vapour from column D, upon condensation, gave 890 parts of pure phenol, while polymeric products formed during the distillation were obtained as residue. In another example, the distillate from column B was charged with water into a batch distillation apparatus, replacing column C. This apparatus was fitted with a packed column (6 ft. X 1 1/4 inch). Isopropylbenzene and methylstyrene were distilled over as azeotropes with water while aqueous phenol was returned to the still. Subsequently, as a second fraction, the phenol/water azeotrope was distilled over and, finally, pure anhydrous phenol was taken off. The separation of hydrocarbons in column A may also be effected by azeotropic distillation with water. The heat treatment of the phenol-containing mixture may be carried out rapidly, by flash distillation at 300 DEG C., or by introducing the mixture into a column the lower part of which is heated at 300 DEG C. to 350 DEG C. Alternatively, the mixture may be heated for a longer time at 200 DEG C., in which case methylstyrene is removed from the mixture as it is formed in order to avoid polymerization. The heat treatment may also be carried out at higher temperatures up to 400 DEG C. whereby the p-cumyl phenol is cracked. Specifications 670,444 [Group IV(b)] and 724,190 are referred to.