Catalyst for the dehalogenation of .alpha.-halogenated carboxylic acids

A method of purifying impure mono-.alpha.-halogenated carboxylic acids of the formula:

• ##STR2## in which X is Cl and R.sub.1 and R.sub.2 are identical or different and represent X.sub.1, H.sub.1, a straight or branched alkyl radical with 1 to 12 carbon atoms or a cycloalkyl radical with 3 to 12 carbon atoms, said method comprising dehalogenating the impure mono-.alpha.-halogenated carboxylic acids with hydrogen in the presence of a catalytic charge of:
• a) a rare metal of ruthenium, rhodium, palladium, osmium, iridium, or platinum which has been deposited on an inert support wherein the inert support is selected from carbon, silica, silicon carbide, aluminum and boron carbide and which has been used to dehalogenate .alpha.-halogenated carboxylic acids in the presence of hydrogen,
• b) a rare metal of ruthenium, rhodium, palladium, osmium iridium or platinum which has been deposited on an inert support, wherein the inert support is selected from carbon, silica, silicon carbide, aluminum and boron carbide and which is such that the granulometry of b) is very much less than that of a) to form a homogeneous mixture as a result of the action of currents of .alpha.-halogenated carboxylic acids and hydrogen;
• and distilling the mixture from the dehalogenation to produce relatively pure R.sub.1 CHXCOOH.