New catalytic system of N,N′-diphenylurea synthesis from nitrobenzene, carbon monoxide and water or aniline

Abstract

The influence of aniline (PhNH 2) on the reductive carbonylation of nitrobenzene (PhNO 2) by carbon monoxide and an excess of methanol, catalyzed by ( w w % with respect to PhNO 2): sulfur (10), sodium methoxide (2), ammonium metavanadate (0.1), at 423 ± 2 K and starting pressure of CO 13 MPa (298 K) was investigated. Methyl- N-phenylcarbamate (MPC) is formed predominantly, via the formation of the intermediate N,N′-diphenylurea (DPU) which is subsequently alcoholyzed by methanol. N-Phenylformamide (NPF) is the main by product. In the presence of water, PhNO 2 is carbonylatively reduced to PhNH 2, and DPU is formed by reductive carbonylation from PhNO 2, CO and PhNH 2. Thus, DPU can be obtained directly from PhNO 2 in a one-step process. If an excess of PhNH 2 is applied, the conversion of PhNO 2 is practically total, a small amount of NPF is formed as in the case of the reductive carbonylation of PhNO 2 in the presence of methanol. The efficiency of other tested sulfur compounds increases in the sequence: S < CS 2 ⪡ Na 2S < H 2S < COS. The dominant effect of sulfur components, a basic environment as well as the promotive effect of vanadium(V) compounds on the reductive carbonylation and carbonylative reduction of nitrocompounds has been confirmed.