US EPA

7479079 

Journal Article 

Synthesis of 4-chlorophenyl isocyanate by thermal decomposition of carbamate 

Dai, Y; Wang, Y; Wang, Q; Liu, L; Wang, G 

2009 

1 

Shiyou Huagong
ISSN: 1000-8144 

38 

1 

52-57 

Chinese 

The process for synthesizing of 4-chlorophenyl isocyanate (4CPI) by thermal decomposition of carbamate and using Bi2O3 catalyst was studied. The starting reactant methyl N-(4-chlorophenyl) carbamate (M4CPC) was firstly synthesized from p-chloroaniline and dimethyl carbonate. The structure and properties of M4CPC were investigated by means of H NMR, FTIR and TG analysis. From TG results, the appropriate temperatures for thermal decomposition of M4CPC were decided in the range of 150-200°C. Under normal pressure, solvents with higher dielectric constants were suitable for the liquid thermal and catalytic decomposition of M4CPC. With low toxic N, N'-dimethy lacetamide as solvent, the main byproduct of the thermal decomposition of M4CPC to 4CPI was N, N'-bis (4-chlorophenyl) urea. Under optimal reaction conditions: mole fraction of M4CPC 10%, mass ratio of catalyst Bi2O3 to M4CPC 0.05, reaction temperature 162-164°C and reaction time 1 h, conversion of M4CPC is 90.4%, selectivity to 4CPI is 66.0%. 

4-chlorophenyl isocyanate; Carbamate; Dimethyl carbonate; P-chloroaniline; Thermal decomposition