Jianpeng Shang

A new route of CO2 catalytic activation: syntheses of N-substituted carbamates from dialkyl carbonates and polyureas

This paper reports an effective route for the syntheses of N-substituted dicarbamates from dialkyl carbonates and polyurea derivatives, in which polyurea derivatives could be successfully synthesized from aliphatic diamines and CO2 in the absence of any catalyst. Under the optimized reaction conditions, various N-substituted carbamates were successfully synthesized with 93–98% isolated yields over a MgO–ZnO catalyst. The catalyst could be reused for several runs without deactivation. The catalysts were characterized with X-ray photoelectron spectroscopy, X-ray diffraction and temperature-programmed desorption.

CO2 activation and fixation: highly efficient syntheses of hydroxy carbamates over Au/Fe2O3

This paper reports an effective route for the syntheses of hydroxy carbamates from the reaction of CO2, epoxides and amines catalyzed by a Au/Fe2O3 catalyst. Under the optimized reaction conditions, various hydroxy carbamates were successfully synthesized with 92–98% isolated yields. The catalyst could be reused for several runs without deactivation. A plausible reaction mechanism was proposed by which the hydroxy carbamate was formed through an ammonium carbamate intermediate and the catalyst mainly promoted further nucleophilic addition between the epoxide and ammonium carbamate.

Green synthesis of polyureas from CO2 and diamines with a functional ionic liquid as the catalyst

A series of ionic liquids (P4,4,4,6BF4, P4,4,4,6Triz, as well as the newly prepared anion dual-functionalized amino-triz IL P4,4,4,6ATriz, etc.) were prepared, and their catalytic performance was tested in the synthesis of polyureas from CO2 and diamines. Under the optimized reaction conditions, good to excellent yields of various polyureas were achieved with different diamines over P4,4,4,6ATriz catalyst. It can be found that the catalytic performance is essentially consistent with the basicity of ILs (as determined by TPD method). The solid products were characterized extensively by 13C NMR, FT-IR, XRD, DSC and TGA. From these results, it could be concluded that the solid products based on diamines and CO2 have the polyurea structure with the urea linkage and connected by hydrogen bonds, which resulted in their high resistance to solvents and excellent thermal stability.

Green and Practical Synthesis of Carbamates from Ureas and Organic Carbonates

Abstract A practical method for the synthesis of carbamates from ureas and organic carbonates was developed with 100% atom economy using La2O3/SiO2 as catalyst without any additional solvent. The scope of the protocol is demonstrated in the synthesis of 14 carbamates with various functional groups in excellent yields (76–95%).

Efficient synthesis of 2-oxazolidinones from epoxides and carbamates catalyzed by amine-functionalized ionic liquids

A series of amine-functionalized ionic liquids were prepared and their catalytic performance was tested in the synthesis of 2-oxazolidinones from epoxides and carbamates. Under optimized reaction conditions, good to excellent yields of various 2-oxazolidinones were achieved with different epoxides and carbamates. Moreover, the amine-functionalized ionic liquid catalyst could be easily recovered and reused without significant loss in activity.

Environmentally benign and effective syntheses of N-substituted carbamates via alcoholysis of disubstituted ureas over TiO2/SiO2 catalyst

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.

Bi2O3 modification of HZSM-5 for methanol-to-propylene conversion: evidence of olefin-based cycle

Bi2O3-modified HZSM-5 catalysts were prepared via a traditional wetness impregnation approach, and used for the methanol-to-propylene conversion reaction. The selectivity for propylene increases significantly with bismuth loading, while that for ethylene shows the opposite trend. However, the Bi2O3/HZSM-5 catalysts have significantly lower capacities for methanol conversion than the parent HZSM-5. The underlying causes are the reduced acid site strength, narrower pore openings, and reduced pore width in Bi2O3/HZSM-5. This work provides insights into the olefin-based cycle operation for methanol-to-olefin reactions using modified HZSM-5 catalysts.