PROCESS FOR THE SIMULTANEOUS PREPARATION OF CARBOXYLIC-ACID ANHYDRIDES AND, OPTIONALLY, CARBOXYLIC-ACID ESTERS

1. A process for the common preparation of carboxylic acids and carboxylic anhydrides and, if appropriate, carboxylic acid esters of the general formulae RCOOH, RCOOCOR and RCOOR respectively, by reacting a dialkyl ether of the general formula ROR and an alcohol of the general formula ROH with carbon monoxide, optionally containing up to 10% by volume of hydrogen, in the presence of a catalyst system comprising carbonyl complexes of noble metals of group VIII of the Periodic Table ; an alkali metal iodide, organophosphonium iodide or organoammonium iodide ; an alkyl iodide of the general formula RI and, if appropriate, compounds of carbonyl forming non-noble metals of groups IV, V, VI, VII or VIII of the Periodic Table, where R in each case denotes the same alkyl radical having 1 to 4 carbon atoms, which comprises employing the dialkyl ether and the alcohol in the molar ratio 9 : 1 to 1 : 9 and carrying out the reaction under anhydrous conditions at temperatures of from 50 to 250 degrees C and pressures of from 0.1 to 120 bar.