Process for the preparation of alkali metal salts of ether-carboxylic acids

A process for the manufacture of alkali metal salts of an ether-carboxylic acid of the general formula I

• R--(OC.sub.m H.sub.2m).sub.n --O--CH.sub.2 COOM (I)
• in which R stands for an alkyl group having from 1 to 22 carbon atoms, an aryl group of an aralkyl group, m stands for the number 2 or 3, n stands for a number in the range of from 0 to 20 and M stands for an alkali metal selected from the group consisting of lithium, sodium and potassium, which comprises oxidizing an ether-alcohol of the general formula II
• R--(OC.sub.m H.sub.2m).sub.n --O--CH.sub.2 CH.sub.2 OH (II)
• in which R, m and n are defined as above, in the aqueous phase with oxygen or an oxygen containing gas at elevated temperatures in the presence of an alkali metal hydroxide and a precious metal catalyst wherein an aqueous, alkali lye containing solution of ether alcohols in a thin layer on a solid carrier or in the form of micrometric particles at a pH value of at least 9 is brought into contact with oxygen or an oxygen containing gas as a continuous phase, wherein the concentration of the ether alcohols in the aqueous phase is in the range from at least 0.5 to 15 weight-%-related to the total weight of the aqueous phase.