GB727715A - Improvements in the manufacture of phenols - Google Patents

Abstract

<PICT:0727715/IV (b)/1> Phenols are produced by a process in which the corresponding aryl sulphonic acid or an alkali metal salt thereof as solid, slurry or aqueous solution is fed continuously and simultaneously with an alkali metal hydroxide into an externally heated reaction vessel rotated about a substantially horizontal axis, to pass in a longitudinal direction therein through a preheating zone, a fusion or reaction zone and a discharge zone, the residence time in the reaction zone at a temperature of 320-420 DEG C. being sufficient to bring about substantial completion of the phenate forming reaction, after which the alkali metal phenate and sulphite are separated and the phenol liberated from the alkali metal phenate. The apparatus consists of a rotatable reaction vessel 1 divided into four interconnecting compartments by weirs 2. Each compartment contains several loose spherical steel balls 3, and the discharge compartment 4, has six rectangular slots 5 set equidistantly around the circumference, and beneath the slots is a water tank 6. Two circular steel collars 7 are situated on either side of these slots and a stationary circular plate 8, designed to minimize ingress of air, fits between them for two thirds of the diameter of the vessel. The ends are closed by stationary end plates 9, which make a seal with the aid of packing glands 10 onto the rim of the vessel, and the whole vessel is set in a furnace 11. In the manufacture of phenol, benzene sulphonic acid or its sodium salt and caustic soda are fed through inlets 12 and 13 into the preheating zone 14 where they are mixed, dehydrated and fused. The frothing in this zone and in the reaction zone 15 is minimized by the moving surface of the vessel. The fused material flows over the weirs, becoming progressively thicker as the sodium sulphite content increases, and finally falls through the slots 5 into water, the slurry of sodium sulphite and sodium phenate being pumped away continuously for isolation of the phenol. Air is removed from the vessel when required, by blowing in steam through pipe 16. The heating of the vessel is controlled so that a temperature of 350-420 DEG C. is maintained in the second and third compartments, preferably 390-410 DEG C. for phenol, and 340-360 DEG C. for resorcinol manufacture. The feed is arranged so that the charge is retained for 8-30 minutes after fusion for phenol, and for 30-60 minutes for resorcinol. Sodium benzene sulphonate for use in the continuous fusion apparatus is obtained by neutralizing benzene sulphonic acid with an aqueous slurry of sodium sulphite in a ball mixer at 105 DEG C. for 5-10 minutes. The amount of water used is so regulated that the slurry of sodium benzene sulphonate contains 33-42 per cent by weight of water. The slurry may be mixed with 80 per cent caustic soda and used as a single feed in the apparatus described above.ALSO:<PICT:0727715/III/1> A reaction vessel for the production of a phenol (see Group IV (b)), into which the corresponding aryl sulphonic acid or an alkali metal salt thereof as solid, slurry, or aqueous solution is fed simultaneously with an alkali metal hydroxide, consists of an externally-heated reaction vessel rotated about a substantially horizontal axis along which the reactants pass through a preheating zone, a fusion or reaction zone and a discharge zone, the residence time in the reaction zone at a temperature of 320-420 DEG C. being sufficient to bring about substantial completion of the phenate-forming reaction, after which the alkali-metal phenate and sulphite are separated and the phenol liberated from the phenate. The apparatus illustrated consists of the reaction vessel 1, a horizontal mild steel cylinder, rotated at 20-30 r.p.m., divided into four interconnecting compartments by weirs 2, which are from one-eighth to one-fifth of the vessel diameter in height. The length of the cylinder is from three to five times the diameter. Each compartment contains several loose spherical steel balls 3, the diameter of which approximates to or slightly exceeds the weir height. The discharge compartment 4 has six rectangular slots 5 set equidistantly around the circumference, and beneath the slots is a water tank 6. Two circular steel collars 7 are situated on either side of these slots and a stationary circular plate 8, designed to minimize ingress of air, fits between them for two-thirds of the diameter of the vessel. The ends are closed by stationary end-plates 9, which make a seal with the aid of packing glands 10 on to the rim of the vessel, and the whole vessel is set in a furnace 11. In the process the reactants are fed through 12 and 13 into the preheating zone 14, where they are mixed, dehydrated and fused. The frothing in this zone and in reaction zone 15 is minimized by the moving surface of the vessel. The fused material flows over the weirs, becoming progressively thicker as the sulphite content increases, and finally falls through the slots 5 into the water, the resultant slurry being pumped away continuously for isolation of the phenol. Air is removed from the vessel when required, by blowing in steam through pipe 16.