Patent GB-927090-A (GB)
Title: Preparation of a phenol
IPC: B01D3/14
Filed: 1960-12-01
Abstract: <PICT:0927090/III/1> In a method for the preparation of a phenol by separating cumene, or a cumene substituted in the nucleus by one or more alkyl groups, from an alkylated aromatic hydrocarbon product, oxidizing the cumene to its hydroperoxide, cleaving the hydroperoxide with acid to convert it into the phenol, and separating the phenol from the neutralized cleavage products, at least one of the separation stages is carried out by fractional distillation under elevated pressure maintained by superimposing an inert gas, such as nitrogen or natural gas, on the system via the condensate drum. In the preparation of phenol itself, benzene is reacted with propene at a temperature of 300 DEG  to 575 DEG F. in the presence of a catalyst.  The reaction-product is depropanized, and the mixture of cumene and benzene is fed through line 2 into distillation tower 4. Benzene vapours are withdrawn through line 6, and passed through heat exchanger 24 and cooler 10; the condensate so obtained being collected in drum 12 which is maintained under a pressure of about 25 p.s.i.g. by imposing a blanket of natural gas through line 16.  The pressure in drum 12 is controlled by valves 15 and 17.  A portion of the benzene condensate is refluxed to tower 4, the remainder being withdrawn from the system through line 20.  Liquid cumene is withdrawn from the base of tower 4 and is passed to stage 32 where it is oxidized with air at a temperature of 190 DEG -260 DEG F.  The hydroperoxide product is neutralized with sodium carbonate and passed to distillation tower 28 which is operated under reduced pressure. The heat required for tower 28 is obtained by withdrawing liquid from a tray in the lower part of the tower, passing it via line 26 into heat exchanger 24 (where it is raised to boiling point by the hot vapours from tower 4), and then returning the boiling liquid to a lower tray in tower 28.  Cumene vapours, withdrawn from the top of tower 28, are condensed in cooler 38.  Part of the condensate is refluxed to tower 28, and the remainder is withdrawn from the system. The concentrated cumene hydroperoxide, withdrawn from the base of tower 28, is heated with sulphuric acid and acetone in stage 48.  The cleavage product, after neutralization with sodium hydroxide and sodium phenate, is passed to stage 50 for separation of crude acetone from crude phenol.  The lower boiling fraction, comprising acetone, acetaldehyde and a -methylstyrene, is passed via line 56 to distillation tower 54, the base of which is maintained at a pressure of 10 to 100 p.s.i.g.; and acetaldehyde is withdrawn overhead.  The liquid withdrawn from the base tower 54 is distilled in tower 68, the base of which is maintained at a pressure of 500 to 1500 mm. Hg. absolute; and acetone is obtained as heads-product, while methylstyrene is removed from the base. The higher boiling fraction from stage 50 is distilled in zone 84, from which a vapour fraction, comprising phenol, methylstyrene and mesityl oxide, is taken off and condensed.  The condensate is fractionated in column 90, the head of which is maintained at a pressure of 18 to 25 p.s.i.g. by imposing a blanket of inert gas over the condensate in reflux drum 104.  The vapours, comprising methylstyrene and mesityl oxide, withdrawn from the head of tower 90 are passed through heat exchangers 66 and 82 in order to supply the heat required for the operation of towers 54 and 68.  The vapours are then condensed in cooler 102, and the condensate is collected in drum 104.  The temperature in heat exchangers 66 and 82 may be controlled by valve 101.  Aqueous phenol is withdrawn from the base of tower 90, and is dehydrated in stage 114.  The synthesis of cresol from cymene is mentioned.ALSO:In a method for the preparation of a phenol by separating cumene or a cumene substituted in the nucleus by one or more alkyl groups, from an alkylated aromatic hydrocarbon product, oxidizing the cumene to its hydroperoxide, cleaving the hydroperoxide with acid to convert it into the phenol, and separating the phenol from the neutralized cleavage products, at least one of the separation stages is carried out by fractional distillation under elevated pressure maintained by superimposing an inert gas, such as nitrogen or natural gas, on the system via the condensate drum. In the preparation of phenol itself benzene is reacted with propene at a temperature of 300 DEG  to 575 DEG F. in the presence of a catalyst.  The reactionproduct is depropanized, and the mixture of cumene and benzene is fed through line 2 into distillation tower 4.  Benzene vapours are withdrawn through line 6, and passed through heat exchanger 24 and cooler 10; the condensate so obtained being collected in drum 12 which is maintained under a pressure of about 25 p.s.i.g. by imposing a blanket of natural gas through line 16.  The pressure in drum 12 is controlled by valves 15 and 17.  A portion of the benzene condensate is refluxed to tower 4, the remainder being withdrawn from the system through line 20.  Liquid cumene is withdrawn from the base of tower 4 and is passed to stage 32 where it is oxidized with air at a temperature <PICT:0927090/IV(a)/1> of 190 DEG -260 DEG F.  The hydroperoxide product is neutralized with sodium carbonate and passed to distillation tower 28 which is operated under reduced pressure. The heat required for tower 28 is obtained by withdrawing liquid from a tray in the lower part of the tower, passing it via line 26 into heat exchanger 24 (where it is raised to boiling point by the hot vapours from tower 4), and then returning the boiling liquid to a lower tray in tower 28. Cumene vapours, withdrawn from the top of tower 28, are condensed in cooler 38.  Part of the condensate is refluxed to tower 28, and the remainder is withdrawn from the system. The concentrated cumene hydroperoxide, withdrawn from the base of tower 28, is heated with sulphuric acid and acetone in stage 48. The cleavage product, after neutralization with sodium hydroxide and sodium phenate, is passed to stage 50 for separation of crude acetone from crude phenol.  The lower boiling fraction, comprising acetone, acetaldehyde and a -methyl-styrene, is passed via line 56 to distillation tower 54, the base of which is maintained at a pressure of 10 to 100 p.s.i.g.; and acetaldehyde is withdrawn overhead.  The liquid withdrawn from the base tower 54 is distilled in tower 68, the base of which is maintained at a pressure of 500 to 1500 mm. Hg. absolute; and acetone is obtained as heads-product, while methylstyrene is removed from the base. The higher boiling fraction from stage 50 is distilled in zone 84, from which a vapour fraction, comprising phenol, methylstyrene and mesityl oxide, is taken off and condensed.  The condensate is fractioned in column 90, the head of which is maintained at a pressure of 18 to 25 p.s.i.g. by imposing a blanket of inert gas over the condensate in reflux drum 104.  The vapours, comprising methylstyrene and mesityl oxide, withdrawn from the head of tower 90 are passed through heat exchangers 66 and 82 in order to supply the heat required for the operation of towers 54 and 68.  The vapours are then condensed in cooler 102, and the condensate is collected in drum 104.  The temperature in heat exchangers 66 and 82 may be controlled by valve 101.  Aqueous phenol is withdrawn from the base of tower 90, and is dehydrated in stage 114.  The synthesis of cresol from cymene is mentioned.