Patent GB-834260-A (GB)
Title: Apparatus for the continuous nitration of toluene by the counter-current method
IPC: B01J19/18
Filed: 1956-08-30
Abstract: <PICT:0834260/III/1> Apparatus for the continuous treatment of a liquid by another liquid by the countercurrent method with simultaneous separation of the product from the residuary material, characterized by a vertically - disposed reaction tube (1) for holding the reaction liquid, said tube being free of internal baffles, an outlet (3) at or adjacent to the upper end of the product and an outlet (2) disposed at the lower end for discharging by siphoning the residuary treatment liquid, an inlet (6) for supplying the treatment liquid at a distance from the upper end of the reaction tube determined by the desired intensity of the emulsification and by the desired rate of throughput of the treating liquid, and a further inlet tube (7) for supplying a reactant at the same distance from the lower end, the region of the reaction tube situated between said two inlets being provided with a stirring device (9) which effects only radial whirling of the reaction liquid.  The reation tube may be enclosed in a tubular jacket, not illustrated, for the purpose of adjusting the reaction temperature by the admission of a cooling or heating medium.  This jacket is advantageously subdivided by partitions into sections, on account of the unequal temperature conditions obtaining at different levels of the reaction tube.ALSO:<PICT:0834260/IV (b)/1> Apparatus for the continuous nitration of toluene by the countercurrent method with simultaneous separation of the nitrated toluene from the residuary acid, characterized by a vertically disposed reaction tube (1) for holding the reaction liquid, said tube being free of internal baffles, an outlet (3) at or adjacent to the upper end for the nitrated toluene and an outlet (2) disposed at the lower end for discharging by siphoning the residuary acid, an inlet 6 for supplying the nitrating acid at a distance from the upper end of the reaction tube determined by the desired intensity of the emulsification and by the desired rate of throughput of the acid, and a further inlet tube 7 for supplying toluene at the same distance from the lower end, the region of the reaction tube situated between said two inlets being provided with a stirring device 9 which effects only radial whirling of the reaction liquid.  The reaction tube may be enclosed in a tubular jacket, not illustrated, for the purpose of adjusting the reaction temperature by the admission of a cooling or heating medium.  This jacket is advantageously subdivided by partitions into sections, on account of the unequal temperature conditions obtaining at different levels of the reaction tube. The length of the siphon tube 2 is so selected that during nitration the upper zone of the reaction tube 1 is filled, for example, with mononitrotoluene, the lower zone with residuary acid, and the middle reaction zone with toluene and fresh nitrating acid in addition to said two liquid components.  The two level tubes 5 and 8 are filled with toluene and nitrating acid to a determined level, depending on the specific gravities.  This equilibrium of the system is maintained when the stirring mechanism is in rotation, since whirling in the radial direction only is effected by said stirring mechanism.  The equilibrium is disturbed as soon as toluene and nitrating acid are introduced into the level tubes 8 and 5, respectively, from above.  This current of liquid continues in the reaction tube; the heavier nitrating acid in the reaction zone sinks downward, while the lighter toluene rises to the top.  The two nonmiscible liquids thereby react with one another and, providing suitable temperatures and times of stay are observed, a complete conversion takes place of the toluene to mononitrotoluene, or of an already nitrated toluene to a higher stage of nitration. The nitrated product is separated in the decomposition zone from the acid residues and leaves the reaction tube through the outlet 3.  The nitrating acid, which travels through the reaction zone in the opposite direction, is separated in the lower decomposition zone, in the form of residuary acid, from the toluene or mononitrotoluene and passes out through the siphon 2 from the reaction tube.  The reaction liquids are thus supplied and discharged automatically and continuously without requiring throttle or shut-off members.  Using the apparatus of the invention and with an inlet 6 spaced from the upper end of the reaction tube 1 at a distance equal to onequarter of the length of the tube 1 and an inlet 7 spaced from the lower end of the tube by the same distance nitrating acid, containing 34.5% by weight of nitric acid and 62.8% by weight of sulphuric acid and having a specific gravity of 1.77, was used to treat 200 c.cs. of toluene and 75 c.c. of water per hour at a temperature of about 40 DEG  C. at the toluene inlet and about 75 DEG  C. at the acid inlet, with a reaction temperature of about 75 DEG  C. and maintained by hot water.