Environmental-Friendly Synthesis of Alkyl Carbamates from Urea and Alcohols with Silica Gel Supported Catalysts
oleh: Yubo Ma, Lei Wang, Xiaodong Yang, Ronghui Zhang
| Format: | Article |
|---|---|
| Diterbitkan: | MDPI AG 2018-11-01 |
Deskripsi
TiO<sub>2</sub>/SiO<sub>2</sub>, Cr<sub>2</sub>O<sub>3</sub>-NiO/SiO<sub>2</sub>, and TiO<sub>2</sub>-Cr<sub>2</sub>O<sub>3</sub>/SiO<sub>2</sub> were prepared by the impregnation method for alkyl carbamate synthesis using urea as the carbonyl source. Up to 97.5% methyl carbamate yield, 97% ethyl carbamate yield, and 96% butyl carbamate yield could be achieved, respectively. The catalysts were characterized by ICP-AES, BET, XRD, XPS, NH<sub>3</sub>-TPD, and EPMA. Catalytic activity investigation revealed that TiO<sub>2</sub>/SiO<sub>2</sub>, Cr<sub>2</sub>O<sub>3</sub>-NiO/SiO<sub>2</sub>, and TiO<sub>2</sub>-Cr<sub>2</sub>O<sub>3</sub>/SiO<sub>2</sub> were effective catalysts for methyl carbamate (MC), ethyl carbamate (EC), and butyl carbamate (BC), respectively. The recycling tests suggested that these silica gel supported catalyst system is active, stable, and reusable. A total of 96⁻97% alkyl carbamate (methyl, ethyl, and butyl) could be obtained in a 2 L autoclave, and these data suggested that our catalyst system is relatively easy to scale up.