Title : Catalysis of Zeolitic Imidazole framework 7 Non Phosgene route for Methyl N Phenyl Carbamate synthesis
Isocyanates are widely used in industries as important precursors for the synthesis of polyurethane, pesticides, and herbicides. These materials are commercially produced by the reaction between amine and phosgene which is known as un-environmental friendly due to their drawbacks, including toxicity, corrosion problem, and yielding salt and organic halogen compound as a waste. Hence, considering environmental pollution and safety issues, many of studies are accomplished to develop a non-phosgene reaction as one of an alternative route. Synthesis Methyl N-phenyl carbamate (MPC) as an intermediate precursor of isocyanate is one of the attractive process, which is conducted by reacting aniline and dimethyl carbonate (DMC). DMC itself is known as an environmentally benign building block and serves as a methoxycarbonylation agent. In this study, Zeolitic Imidazole Framework-7 (ZIF-7) has been used as a catalyst for methoxycarbonylation reaction of aniline and DMC to produce MPC. ZIF-7 was prepared by the solvothermal method, in which four types of difference zinc precursor, including Zn(OAc)2, ZnCl2, Zn(NO3)2, and ZnBr2 reacts with benzimidazole. The results show that ZIF-7 synthesized by zinc acetate precursor exhibits the highest activity among other precursors. The aniline conversion and MPC yield achieve 97.53% and 84.42%, respectively, while the reaction is conducted at 190°C for 2 hours. Reusability study confirmed that catalytic activity of catalyst could be maintained during 4 times reuses. The catalyst was characterized by Fourier Transform Infrared (FT-IR), Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), CHON elemental analysis, Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-EAS), and proton NMR.