Patent GB-249834-A (GB)
Title: Improvements in preparation of alcohols from olefine-bearing gases
IPC: C07C29/06
Filed: 1926-03-01
Abstract: 249,834. Petroleum Chemical Corporation, (Assignees of Davis, H. S.). March 30, 1925, [Convention date]. Acyclic hydrocarbons; ethereal sulphates; monohydric alcohols.-An acid-absorption product of propylene, capable of hydrolysis to isopropyl alcohol, is prepared from a gas mixture containing propylene and other unsaturated hydrocarbons by first freeing the mixture from water vapour and unsaturated hydrocarbons more reactive to the acid than propylene, and then exposing it to prolonged contact with an absorbing acid having an initial concentration of about 100 per cent, the most dilute acid employed containing not more than 7 per cent of water. Preferably the gas mixture, containing ethylene and propylene, resulting from the fractionation according to the process of Specification 248,375, of the products from the cracking of hydrocarbons is employed. In the process described, the gas mixture is oil-scrubbed and is passed from a holder 22 through a chamber 57 where it is treated with iron oxide alkali &c. to remove sulphuretted hydrogen. To effect the preliminary removal of water vapour and the highly reactive unsaturated hydrocarbons, the gases are next passed up through long tubular vertical scrubbing towers 1, 2, which may be filled with inert packing means such as porcelain rings, 78-85 per cent sulphuric acid being flowed down the towers in the opposite direction to the gas stream. Substantially, no absorption of the propylene is effected by this acid. Higher concentrated acid may be employed if some loss of propylene is allowable. The acid is supplied from a reservoir 11 to a tank 9 from which it is forced by a pump P to the top of the tower 2 through a pipe 13, returning to the tank 9 through a pipe 14. The acid passes from tank 9 to tank 16 from which it is circulated by pump P<1> through pipe 17, tower 1 and pipe 18, back to the tank 16. The acid may be caused to overflow from tank 16 through pipe 19 into a tank 20 in which it is diluted with water from a main 21, the mixture being treated in a still 23 to obtain the mixed butyl, amyl and isopropyl alcohols formed. The gases next pass from tower 2 to towers 3-6 where they are treated on the counter-current principle with sulphuric acid of concentrations from 93 per cent acid up to 20 per cent oleum, but preferably 100 per cent acid, to absorb the propylene. Fresh acid is supplied from a reservoir 36 to a tank 35 from which it is circulated through the last tower 6 by means of a pump P<2>. Tank 35 overflows into a tank 39 supplying tower 5, the acid passing finally through tank 43, supplying tower 4, to tank 47, supplying tower 3. The absorption product is drawn off from time to time or continuously from tank 47 to a dilution tank 50 supplied with water from main 21, and may then be run into a steam still 51 having a fractionating column and condenser C from which a constant boiling mixture of isopropyl alcohol and water, B.P. 80.4‹ C., is ob. tained. The temperature in the towers may be kept about 30‹ C. by cooling devices such as ring jets 65 providing a flow of water down the ex. teriors of the towers, the water being collected to a drain 68 by flanges 67. Pressures above atmospheric, e.g. up to 2 atmospheres, may be employed in the towers. The return pipes from the towers to the acid tanks are each provided with a bend a retaining sufficient liquid to counteract the gas pressure in the towers, the acid tanks being kept under atmospheric pressure only. Any gas reaching the tanks is returned through a main 60 and pump 61 to the pipe 7 supplying the towers. Oleum may be added to tanks 9. 16 to maintain the concentration of the acid therein, if it is not desired to use the acid from tank 11. The. gases finally pass from tower 6 to a reservoir 56, and preferably contain only about one per cent of propylene. The gases now consist mainly of ethylene, and may be further treated for the production of ethyl alcohol or ether. The preliminary removal of water vapour and of the highly reactive unsaturated substances may also be effected by treatment for a very short period with hot strong sulphuric acid.