The one-pot synthesis of methylene diphenyl-4,4′-dicarbamate

• The one-pot synthesis of MDC uses aniline, DMC and formalin as raw materials.
• MPC synthesis and its condensation proceed in one reactor without separation.
• Aniline conversion is 100% and MDC yield is 73.9% (based on HCHO).
• The presence of aniline and Zn(OAc)2 have obvious effect on MPC condensation.
• The deactivated catalyst can be easily regenerated by treatment with acetic acid.

Methylene diphenyl-4,4′-dicarbamate (MDC) is an intermediate for the preparation of methylene diphenyl diisocyanate. This paper reports the one-pot synthesis of MDC using aniline, dimethyl carbonate, and formalin as raw materials. Phenyl N-methyl carbamate (MPC) synthesis was carried out in a batch reactor using Zn(OAc)2 as the catalyst, following which, without any separation, an Hβ catalyst and formalin were added to continue to MPC condensation to give MDC. It was found that there were interactions between the MPC synthesis and MPC condensation, such that the presence of aniline could inhibits MPC condensation. Zn(OAc)2 was also found to adsorb on the Hβ surface to form Si–O–Zn bonds during the condensation, decreasing the quantity of strong acid sites on the Hβ and reducing the catalytic performance. Under the optimal conditions for the one-pot synthesis of MDC, aniline conversion was 100% and the MDC yield was 73.9% (based on HCHO). The deactivated catalyst could be easily regenerated by treatment with acetic acid. The filter cake was dried and calcined to obtain regenerated Hβ and the filtrate was dried by vacuum rotary evaporation to obtain Zn(OAc)2. No significant loss in catalytic activity was observed for the regenerated catalyst.

Figure optionsDownload high-quality image (133 K)Download as PowerPoint slide