Reductive carbonylation of nitrobenzene to N,N-diethyl-N'-phenylurea

Reductive carbonylation of nitrobenzene with carbon monoxide and diethylamine at 363-443 K and initial CO pressures 6-17 MPa in the presence of a catalyst consisting of sulfur or a sulfur compound and a vanadium(Ti) compound in a basic medium yields N,N-diethyl-N'-phenylurea as the main product. Formation of the side products (aniline, N,N'-diphenylurea, and N-phenylformamide) is affected significantly by water admixtures. The efficiency of sulfur components increases in the order: S : CS2 : H2S : COS = 1 : 1.2 : 5.7 : 8. The presence of the vanadium(V) compound, although not prerequisite, has promoting effect. The selectivity and reaction rate of the carbonylation increases with increasing CO pressure. Water affects negatively above all the selectivity of the reaction (at 0.24 wt.% water in diethylamine, maximum selectivity exceeds 80%, at. 1.6 wt.% water it is only ca 60%). The effect of reaction conditions and the course of side reactions is discussed.