Patent GB-362215-A (GB)
Title: An improved method of producing esters from olefines
IPC: C07C67/04
Filed: 1931-01-20
Abstract: <PICT:0362215/IV/1> Esters are obtained by bringing an olefine or a mixture of olefines and a substantially anhydrous organic acid such as glacial acetic acid into a contact zone wherein contact between olefine and acid is maintained for a prolonged period, for example, from two to four hours, at a suitable elevated temperature, and continuously withdrawing the ester from the contact zone.  The process is perferably carried out by passing a stream of hydrocarbons rich in olefines in countercurrent contact with an anhydrous liquid organic acid in the presence of sulphuric acid, maintaining the contact at a suitable elevated temperature for a prolonged period, continuously withdrawing the fluid product containing ester and sulphuric acid from the reaction, and recovering the ester therefrom, for example, by extraction with a low-boiling solvent such as a low-boiling hydrocarbon, for example, pentane or hexane, or a hydrocarbon mixture, for example, gasoline, the solvent being then separated from the ester by distillation, the ester recovered, and the solvent and sulphuric acid returned to the process to be used again.  The temperature of the contact zone may be between 50 DEG and 150 DEG  C., for example, about 75 DEG  C., and the pressure may be adjusted to a value somewhat lower than the vapour pressure of the hydrocarbon or hydrocarbon mixture at this temperature.  In carrying out the process, a tower 1 which is packed with bell-cap plates, Raschig rings, or the like provided, if desired, with stirring means to operate on each plate, and insulated against heat loss by a suitable covering 2 in which heating or cooling coils may be embedded, may be fed with fatty acid and sulphuric acid from pipes 5 and 7 respectively entering a manifold 3 and passing through a heater 4.  A pipe 6 may be used for the introduction of additional sulphuric acid, or of a hydrocarbon oil such as gas oil or kerosene, particularly gas oil containing 2 to 5 per cent of sulphonated castor oil or similar agent.  The mixture flowing downwards through the tower 1 comes into contact with a stream of olefine-containing gas such as a cracked oil or gas or a condensate or portion therefrom, for example, a mixture of propane and propylene, or of butane and butylene, or other unsaturated hydrocarbons containing more than two carbon atoms, introduced at the base through a pipe 8.  Any saturated hydrocarbons and unreacted unsaturated hydrocarbons in the initial gas escape through a pipe 9.  The product flows out by a pipe 10 through a heat-exchanger 11 and a cooler 12, and is discharged through a pipe 13 into an extraction vessel or tower 15, which may be similar to the tower 1, fed through a pipe 16 with low-boiling hydrocarbons which may be a portion of the unabsorbed hydrocarbons from the pipe 9, if these are suitable. The solvent rich in fatty acid esters flows out through a pipe 19, and sulphuric acid substantially freed from esters passes through a pipe 17, the heat-exchanger 11, and a pipe 18 back to the tower 1.  The ester solution preheated in a heat-exchanger 20 is forced into a tower 21, after further preheating in a coil 22 which acts as a refluxing device for the tower.  The vapours from this tower flow by a pipe 23 to a condenser 24 and receiver 25 from which the solvent is removed through a pipe 26, to be conducted back to the tower 15.  The tower 21 may be heated by a closed coil or by the introduction of superheated steam through a pipe 28, condensed steam being removed from the receiver 25 through a pipe 27.  The ester freed from the solvent flows through a pipe 29 through the heat-exchanger 20, cooler 30, and pipe 31 to storage.  The sulphuric acid should be above 53 DEG  B<\>ae in all cases, but more concentrated acid should be used for the lower olefines such as propylene than for the higher olefines such as hexylene or amylene.  As an alternative method, the ester may be recovered from the liquid from the tower 1 by dilution with water and fractional distillation, the sulphuric acid being reconcentrated and returned to the tower.  An example is given.