Zn/Al/Pb Mixed Oxides as Efficient Heterogeneous Catalysts for the Synthesis of Methyl N-Phenyl Carbamate

Abstract

Dimethyl carbonate aminolysis is an effective and green pathway for the synthesis of methyl N -phenyl carbamate (MPC), which is an important intermediate for the synthesis of polyurethanes and many other chemicals. In this work, we demonstrate the fabrication of Zn/Al/Pb mixed oxides as efficient and stable heterogeneous catalysts for MPC synthesis. The catalysts are prepared via facile coprecipitation and subsequent thermal annealing. Their micromorphology and physical–chemical properties are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), scanning TEM (STEM), X-ray photoelectron spectroscopy (XPS), and NH 3 -TPD. The results show that rather than being doped into ZnO and/or Al 2 O 3 , PbO is highly dispersed in the ZnO/Al 2 O 3 base forming ultrafine nanoparticles. Despite the weak interactions within the mixed oxides, the high density of active sites generates outstanding catalytic activity and cycling stability for MPC synthesis, with an aniline conversion of almost 100% and MPC yield of up to 90% during six repeated tests, providing great potential for their further application.

Efficient Activation of CO2 over Ce-MOF-derived CeO2 for the Synthesis of Cyclic Urea, Urethane, and Carbamate

“…The homogeneous titanium complex has also been found effective for synthesizing cyclic urea from alkyl ammonium carbamate . Several heterogeneous catalysts, including Au decorated in the polymer matrix, metal oxides (including CeO 2 ), silica-based catalysts, and MOF, have been reported for this reaction. − Sn and Ni metal complexes have been utilized for carbamate synthesis. − Moreover, CeO 2 has also been explored for carbamate synthesis …”

Highly efficient synthesis of novel bio-based pentamethylene dicarbamate via carbonylation of pentanediamine with ethyl carbamate over well-defined titanium oxide catalysts

“…Therefore, efficient syntheses of dicarbamates are of great importance for the non-phosgene syntheses of diisocyanates. [2][3][4][5][6][7][8] Pentamethylene diisocyanate (PDI) is an emerging isocyanate with high performance applied in the syntheses of high-grade polyurethane coatings, adhesives, elastomers, and wind turbine blades. 9,10 As the feedstock for the production of PDI, PDA is a natural five-carbon diamine produced from lysine, which is obtained from biomass such as forage corn starch through bio-fermentation engineering.…”

“…Therefore, efficient syntheses of dicarbamates are of great importance for the non-phosgene syntheses of diisocyanates. 2–8…”