GB835569A - Manufacture of phenol - Google Patents

Abstract

Pure solid sodium sulphite is obtained as a by-product in a process for manufacturing phenol in which the product from the quenching of a sodium hydroxide fusion of benzene sulphonic acid with water or sodium sulphite or bisulphite solution, is partially or completely neutralized prior to the separation of the sodium sulphite, by the addition of a solution of sodium bisulphite or by the introduction of sulphur dioxide under conditions resulting in the precipitation of solid sodium sulphite. The quenched fusion mass may be completely neutralized, semi-neutralized, i.e. 75-100%, or partially neutralized, i.e. 40-75%, and in each case solid sodium sulphite may be centrifuged off from the phenol layer and the aqueous solution of sodium sulphite which may be used as such for quenching or converted to bisulphite solution for neutralizing. The sodium sulphite obtained is a mixture of that formed in the fusion reaction and a more pure sample formed during the neutralization and comparative analyses are given of sodium sulphite obtained according to the invention and a sample derived from the fusion operation without prior bisulphite treatment of the sodium phenate. Flow sheets showing complete and partial neutralization and phenol finishing are given together with a detailed example.ALSO:Phenol is manufactured by a process in which the product from the quenching of a sodium hydroxide fusion of benzene sulphonic acid with water or sodium sulphide or bisulphite solution, is partially or completely neutralized prior to the separation of the sodium sulphite, by the addition of a solution of sodium bisulphite or by the introduction of sulphur dioxide under conditions resulting in the precipitation of solid sodium sulphite. The slurry of sodium phenate and sodium sulphite resulting from the quenching of the fused mass may be completely neutralized with bisulphite solution or by gassing with sulphur dioxide to give three layers, the top being wet phenol, the middle being sodium sulphite solution and the lower solid sodium sulphite. The phenol layer is removed for finishing and the residue centrifuged to give solid sodium sulphite (a mixture of that formed in the fusion reaction and a more pure sample formed in the neutralization and sodium sulphite solution. The quenched fusion mass may also be semi-neutralized, i.e. to an extent of 75 to 100%. Three layers are again obtained but the phenol layer must be treated with bisulphite solution before finishing and the sodium sulphite solution obtained contains some sodium phenate which may be recycled. Alternatively the quenched fusion mass may be partially neutralized, i.e. to an extent of 40 to 75%, preferably about 50%. In this case further sodium sulphite is precipitated but no phenol layer separates. The mixture is centrifuged to separate the solid sulphite from the solution which is then completely neutralized and the phenol layer separated from the aqueous sodium sulphite solution, no solid being precipitated in the second step. The phenol layer separated from the neutralization contains in addition to water, sodium sulphite and sodium benzene sulphonate which may be removed by extraction with water and recycled to the fusion stage. The phenol may then be purified by distillation. The solid sodium sulphite is recovered as a by-product and the sodium sulphite solution used in the quenching stage or converted to bisulphite solution by gassing with sulphur dioxide and used in the neutralization. Flow sheets are given of the complete neutralization, partial neutralization and phenol finishing stages and a detailed example of the whole process is given.