Collection of Czechoslovak Chemical Communications - digital archive 

Abstract

A three component catalytic system consisting of (i) elemental sulfur or sulfur compounds (CS₂, H₂S, COS), (ii) an alkali methoxide or triethylamine, and (iii) vanadium(V) compounds (V₂O₅, NH₄VO₃) has been applied as catalyst for reductive carbonylation of nitrobenzene to methyl N-phenyl carbamate with carbon monoxide and methanol at a temperature of 423 ± 2 K and an initial carbon monoxide pressure of 10-14 MPa/298 K. The efficiency of sulfur compounds increased in the sequence S:CS₂:H₂S:COS = 1:1.6:7.9:13.8. Hydrogen sulfide decreased however the selectivity of the reaction to the carbamate and increased that to aniline. Formation of the latter amine is increased especially in the presence of water in the reaction mixture and of hydrogen in the synthesis gas above 40 vol.%. The efficiency of the bases decreased in order CH₃OK > CH₃ONa = NaOH > (C₂H₅)₃N and of vanadium compounds in the sequence NH₄VO₃ > V₂O₅. The catalyst system thus allows to effect the reductive carbonylation of aromatic nitro compounds in the absence of transition metal compounds.