GB695464A - Improvements relating to the manufacture of phenols - Google Patents

Abstract

Phenols containing one or more unsubstituted alkyl substituents or hydrogen-free mixtures containing such phenols are passed in vapour phase over an acidic catalyst at 300-550 DEG C., such catalyst consisting of a mixture of oxides which have been co-precipitated or mixed while still wet. The pressure may be atmospheric or higher. The phenols suffer dealkylation, disproportionation as regards alkyl groups, and degradation of alkyl groups. When another phenol or an aromatic hydrocarbon is present transfer of alkyl groups may also take place. The process is facilitated by the addition of 10-30 per cent of steam to the vapour. Preferred catalysts contain silica as the major constituent, with one or more other oxides, e.g. alumina, beryllia, magnesia, zirconia, titania, especially silica - alumina or silica - zirconia-beryllia. They should be free from alkali metal ions and the feed-stock should not contain aromatic bases. The catalyst may be reactivated when necessary by treatment with air at 450-550 DEG C. In the examples: (1) o-cresol is partly converted into its isomers, phenol, xylenols and other products; (2) m- or p-cresol yields some phenol; (3) p-cresol gives a mixture of the three cresols, phenol, xylenols and neutral material; (4) a mixture of the three cresols is enriched with the m-isomer, phenol, xylenols and neutral material also being formed; (5) p-ethylphenol gives (a) all three ethylphenols, diethylphenols, phenol and ethylene, or (b) phenol, p-cresol and other materials; (b) p-propylphenol yields the three propylphenols, phenol, C7-alkyl and C8-alkyl phenols and propene; (7) 3-methyl-5-ethylphenol is converted into the three ethylphenols, cresols, phenol and ethylene; (8) 3 : 5-xylenol gives phenol, cresols, xylenols, trimethylphenols and neutral material; (9) a mixture of 3 : 4-xylenol and benzene is converted into phenol, cresols, xylenols, trimethylphenols, a mixture of methylbenzenes and neutral material; (10) a mixture of phenol and xylenols yields a product containing also cresols; (11) a tar oil fraction boiling at 220-250 DEG C. is mixed with benzene and passed over the catalyst; the phenolic product is fractionated, yielding phenol, cresols and other products. The catalyst is silica-beryllia-zirconia in example (3) and silica-alumina in the others. The feedstock is mixed with steam except in cases 5b, 9 and 11. By-products include hydrocarbons, diaryl ethers and heterocyclic oxygen compounds. The Provisional Specification contains a further example in which p-cresol with steam is passed over silica-alumina, giving phenol, cresols, xylenols and other products.ALSO:Catalysts for the dealkylation and/or isomerization of alkylphenols comprise an acidic mixture of oxides which have been co-precipitated or mixed while still wet. Preferred catalysts contain silica as the major constituent with alumina, beryllia, magnesia, zirconia or titania, especially silica-aluminia (see Specification 571,123), or silica-zirconia-beryllia. They should be free from alkali metal ions and the feed-stock should not contain aromatic bases. They can be reactivated when necessary by treatment with air at 450-550 DEG C. Typical catalysts are prepared by (1) adding water glass to a solution of zirconium oxychloride, beryllium nitrate, ammonium sulphate and sulphuric acid, washing and drying the gel; and (2) adding water glass to a solution of aluminium sulphate and ammonium sulphate and treating as before. Analysis figures are given. Examples are given of the use of these catalysts.