Process for the preparation of dialkyl carbonates

Claim 1

A process for the preparation of a dialkyl carbonate of the formula O═C(OR).sub.2, in which R represents straight-chain or branched alkyl having up to 4 carbon atoms, by reaction of carbon monoxide (CO) with an alkyl nitrate of the formula RONO, in which R has the meaning given, in the presence or absence of an inert gas and in the presence or absence of the parent alcohol ROH and in the presence or absence of NO over a supported metal catalyst at elevated temperature in a continuous gas phase reaction, wherein the supports used are oxidic or hydroxidic compounds of V, Nb, Ta, or combinations thereof, said metal being present in the form of a halide of a metal selected from the group consisting of palladium, platinum, iridium, ruthenium and rhodium, or a complex thereof, in which said metal halide or said halogen-containing metal complex can be generated in situ in the process reactor under the reaction conditions from the metal or a halogen-free metal compound by means of hydrogen halide, the catalyst is furthermore provided with or without an addition of an antimony, bismuth, aluminum, copper, vanadium, niobium, tantalum, tin, iron, cobalt, nickel compound or a mixture of a plurality thereof, and the reaction is carried out at a nitrite:CO volume ratio of 0.1-10:1 and a temperature of 50°-150° C., in which the addition of hydrogen halide is continued in an amount in which the hydrogen halide is discharged from the reactor together with the reaction mixture.