Patent GB-616197-A (GB)
Title: Manufacture of vinyl ethers
IPC: C07C43/16
Filed: 1946-08-29
Abstract: Vinyl ethers are made by feeding an alcohol and acetylene, the former not being in excess, to a completely etherified polyhydric alcohol heated to between 130 and about 200 DEG  C. and containing in solution or suspension a catalyst which has been prepared by treating an alkali metal alcoholate with acetylene and removing the alcohol so formed.  In preparing the catalyst, an alkali metal alcoholate may be dissolved in a completely etherified polyhydric alcohol, optionally containing a little of the alcohol corresponding to the alcoholate, and the solution then treated with acetylene, preferably at a raised temperature, the formation of the catalyst being indicated by the darkening of the solution. The concentration of the solution may be 2-3 per cent, calculated as alkali metal.  Alcohol is liberated from the alcoholate during the production of the catalyst, and since the catalyst is unstable to alcohol the latter must be removed as completely as possible, preferably by distillation under reduced pressure or by a current of gas.  For the same reason the presence of excess alcohol during the preparation of the vinyl ethers should be avoided.  The alcoholate used in preparing the catalyst may be derived from the alcohol to be subsequently converted into vinyl ether and may be prepared as described in Specification 304,585, [Class 2 (iii)]. The production of the vinyl ethers may be effected at atmospheric or slightly raised pressure, and either pure or diluted acetylene may be used, e.g. acetylene produced by the thermal decomposition of paraffin oils.  The alcohol may be fed to the catalyst solution in liquid or vapour form, and if the boiling point of the vinyl ether produced is sufficiently low the process may be effected continuously by allowing the ether to distil off as it is formed and adding fresh catalyst solution as required.  In an example, a solution of potassium ethylate in diethylene glycol ethyl butyl ether containing a little ethanol is treated with dry acetylene at 145 DEG  C. in a glass tower until a deep black solution is obtained, and acetylene and ethanol are then fed to the bottom of the tower, the addition of ethanol being adjusted so as to avoid its accumulation in the solution, which would be indicated by a change in the colour of the solution; vinyl ethyl ether distils continuously from the tower and is fractionated and condensed. Examples are given also of the production in similar manner of vinyl n-butyl ether, vinyl cyclohexyl ether, and vinyl tertbutyl ether.  Other alcohols which may be converted into vinyl ethers are methanol, n- and iso-propyl alcohol, secondary butanol, amyl alcohols, hexanols, and partly etherified polyhydric alcohols such as ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, and mono- and di-alkyl ethers of glycerol.  Other completely etherified polyhydric alcohols which may be used as reaction media are diethylene glycol dimethyl, diethyl, dipropyl and dibutyl ethers and tetraethylene glycol dimethyl ether. Specifications 369,297, 427,036, 430,764 and French Specification 849,862 also are referred to.