GB811400A - Separation of vinyl ethers by distillation - Google Patents

Abstract

A process for separating a vinyl alkyl ether or vinyl alkoxyalkyl ether containing 3 to 14 carbon atoms in the alkyl or alkoxyalkyl group from a mixture thereof with an aliphatic alkanol or alkoxy substituted alkanol comprises: (i) heating the mixture to form a vapour; (ii) contacting the vapour with an amount of water sufficient to form a constant boiling mixture with substantially all the vinyl ether and with an organic solvent having a higher boiling point than the constant boiling mixture which is capable of reducing the volatility of the alkanol and has the general formula HO(CH2CH2)xR1, where R1 is H or a C1 to C6 alkyl or alkoxyalkyl group and x is an integer not greater than 4; and (iii) fractionally distilling to separate the constant boiling mixture from the less volatile alkanol solvent mixture and recovering the vinyl ether from the constant boiling mixture. The <PICT:0811400/III/1> solvent preferably boils at least 15 DEG C. higher than the constant boiling mixture and not within 15 DEG C. of the alkanol. It is preferably introduced in amounts of 5 to 50 parts by volume per part of volume. Preferably the solvent/water mixture is introduced countercurrently to the ether/alkanol mixture at 0.25 to 5 times the feed rate of the latter. The vinyl ether/alkanol mixture is fed into the middle of distillation column 11 and a mixture of water and the organic solvent is fed into the top of the column. The water and ether form an azeotropic vapour which passes from the top of the column to condenser 12. The condensate is collected in decanter 13 where it separates into a lower aqueous layer which is returned to the top of column 11 via line 15 and an upper ethereal layer which is transferred to column 14 via line 16. Pure ether is removed from column 14 by line 19. The solvent/alkanol mixture which collects the bottom of column 11 is removed via line 21 to column 22, where it is separated into its components. The solvent is returned to the top of column 11 via condenser 23 and line 26 if it is more volatile than the alkanol, or by line 25 if it is less volatile. The use of an excess of water should preferably be avoided as it would be difficult to separate from the alkanol. Examples are given which include the feed rates, water-solvent ratios, azeotrope compositions and distillation temperatures for the following mixtures: vinyl 2-butoxyethyl ether/2-butoxyethanol with ethylene glcyol as solvent; 2 - ethylhexyl vinyl ether/2 - ethylhexanol with ethylene glycol monomethyl ether, di-ethylene glycol monoethyl ether, and ethylene glycol monoethyl ether as solvents.