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- Title
Environmentally benign and effective syntheses of N-substituted carbamates via alcoholysis of disubstituted ureas over TiO<sub>2</sub>/SiO<sub>2</sub> catalyst.
- Authors
Liguo Wang; Jianpeng Shang; Shimin Liu; Lequan Liu; Shiguo Zhang; Youquan Deng
- Abstract
Catalytic syntheses of cyclohexyl carbamates via alcoholysis of dicyclohexyl urea (DCU), which can be synthesized from CO2 and amines, were first investigated with low-molecular-weight alcohols, i.e., methanol, ethanol, butan-1-ol. TiO2/SiO2 catalyst was prepared by wet impregnation method using tetrabutyl titanate as titanium source. The catalyst was characterized by inductively coupled plasma/atomic emission spectroscopy (ICP/AES), N2 adsorption, X-ray diffraction (XRD), field emission/scanning electron microscopy (FE/SEM), transmission electron microscopy TEM), and NH3/temperature-programmed desorption (TPD) in detail. TiO2/SiO2 with 5 wt % loadings and calcination at 600 °C exhibited better catalytic activity, and excellent yields of >95 % with 98 % selectivities for desired carbamates were achieved. Accordingly, the strong acidity was considered to be responsible for its superior activity. Moreover, the catalytic activity can essentially be preserved during the recycling tests. The scope was also expanded to synthesize other alkyl or aryl carbamates via alcoholysis of the corresponding disubstituted ureas, and 94 % yields with 96 % selectivities can be achieved. It provided a good candidate for the organic carbamates syntheses via a phosgene/halogen-free and effective route.
- Subjects
CARBAMATES; ALCOHOLYSIS; TITANIUM dioxide; METAL catalysts; MOLECULAR weights; SCANNING electron microscopy; ORGANIC synthesis; ACIDITY
- Publication
Pure & Applied Chemistry, 2012, Vol 84, Issue 3, p461
- ISSN
0033-4545
- Publication type
Article