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- Environmentally benign and effective syntheses of N-substituted carbamates via alcoholysis of disubstituted ureas over TiO2/SiO2 catalyst
- 更新时间:2014-04-10;信息类型:SCI论文
- 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), N-2 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 degrees 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.
- 链接地址:http://www.ionike.com/download/article/2014-04-10/160.html
- Dehydrogenative amide synthesis from alcohol and amine catalyzed by hydrotalcite-supported gold nanoparticles
- 更新时间:2014-04-10;信息类型:SCI论文
- Hydrotalcite-supported nano-gold (Au/HT) was found to be a highly efficient heterogeneous catalyst for the dehydrogenative synthesis of amide from alcohol and amine. Amines and alcohols with different structures could be converted into the amides under mild reaction conditions with up to 98% isolated yields. Mechanism exploration suggested that ester might be the reaction intermediate.
- 链接地址:http://www.ionike.com/download/article/2014-04-10/158.html
- Oxidative imination of toluenes catalyzed by Pd–Au/silica gel under mild reaction conditions
- 更新时间:2014-04-10;信息类型:SCI论文
- A Pd–Au/SiO2 catalyst was prepared for the oxidative imination of toluenes with up to 99% yields in the absence of dehydrating agents under mild conditions. Nanoparticles with a PdO layer and PdO–Au core may be the active structure for the reaction.
- 链接地址:http://www.ionike.com/download/article/2014-04-10/157.html
- Nano-Gold Catalysis in Fine Chemical Synthesis
- 更新时间:2014-04-10;信息类型:SCI论文
- ★★★★★ Zhang Y,Cui XJ,Shi F,et al. Nano-gold Catalysis In Fine Chemical Synthesis[J]. Chem. Rev.,2012,112:2467-2505.
- 链接地址:http://www.ionike.com/download/article/2014-04-10/156.html
- Recent advances in ionic liquid catalysis
- 更新时间:2014-04-10;信息类型:SCI论文
- Due to their unique properties, ionic liquids have offered great potential for developing clean catalytic technologies. After a short introduction of their advantages in green catalysis, recent advances in ionic liquid catalysis are reviewed with emphasis on four hot fields, viz. biomass conversion in ionic liquids, catalytic production of fine chemicals in ionic liquids, supported ionic liquid phase catalysis, as well as Friedel–Crafts reactions in ionic liquids. In particular, through selected samples, we show here the advantages and potential of ionic liquids in exploring cleaner catalytic technologies, as compared to traditional catalytic processes. Finally, further development of ILs in catalysis is briefly prospected.
- 链接地址:http://www.ionike.com/download/article/2014-04-10/153.html
- Efficient synthesis of dimethyl carbonate via transesterification of ethylene carbonate with methanol over binary zinc-yttrium oxides
- 更新时间:2014-04-10;信息类型:SCI论文
- The binary zinc–yttrium oxides were prepared by co-precipitation method, characterized and tested in the synthesis of DMC via transesterification of ethylene carbonate with methanol. The catalytic results showed that the catalyst with Zn/Y molar ratio of 3 and calcined at 400 °C exhibited superior catalytic activity, corresponding to TOF of 236 mmol/gcat h. Appropriate content of yttrium in the catalyst enhanced the catalytic activity remarkably. Moreover, the abundance of medium basic sites (7.2bH_b9.8, as determined by Hammett indicator method) was considered to be responsible for the superior catalytic activity.
- 链接地址:http://www.ionike.com/download/article/2014-04-10/151.html
- Efficient synthesis of glycerol carbonate from glycerol and urea with lanthanum oxide as a solid base catalyst
- 更新时间:2014-04-10;信息类型:SCI论文
- Lanthanum oxide catalyst prepared by precipitation method and calcined at 600 °C exhibited better catalytic activity in the catalytic synthesis of glycerol carbonate from glycerol and urea with TOF up to 1506 mmol/g·h. It was proposed that the lanthanum oxide catalyst with more strong basic sites (TdN400 °C) exhibited higher catalytic activity. Accordingly, the catalyst containing appropriate amount of La2O2CO3 phase exhibited higher catalytic activity. Moreover, the recycling experiments demonstrated that the catalytic activity can be essentially preserved during the recycling tests investigated.
- 链接地址:http://www.ionike.com/download/article/2014-04-10/150.html
- Fe2O3-supported nano-gold catalyzed one-pot synthesis of N-alkylated anilines from nitroarenes and alcohols
- 更新时间:2014-04-10;信息类型:SCI论文
- Here, we show the one-step synthesis of N-alkylated anilines from nitrobenzenes and alcohols catalyzed by nano-gold catalyst. The yields to N-alkylated anilines were B90% under mild conditions. The mechanism of this reaction was explored. It shows promise for clean and simple synthesis of N-alkylated anilines.
- 链接地址:http://www.ionike.com/download/article/2014-04-10/149.html
- New attempt for CO2 utilization: One-pot catalytic syntheses of methyl, ethyl and n-butyl carbamates
- 更新时间:2014-04-10;信息类型:SCI论文
- The direct production of methyl, ethyl and n-butyl carbamates (MC, EC and BC) from NH3, CO2 and alcohols could efficiently be catalyzed by V2O5, and ca. 11–25% yields with 98% selectivity for alkyl carbamates could be obtained. The catalyst could be recycled six times without obvious decrease in catalytic activity. XRD and XPS analysis showed that in-situ produced (NH4)2V3O8 was the catalytically active species.
- 链接地址:http://www.ionike.com/download/article/2014-04-10/147.html
- Quaternary Ammonium Ionic Liquids as Bi-functional Catalysts for One-step Synthesis of Dimethyl Carbonate from Ethylene Oxide, Carbon Dioxide and Methanol
- 更新时间:2014-04-10;信息类型:SCI论文
- One kind of novel ionic liquids (ILs) with a tertiary amino moiety and a quaternary ammonium group were synthesized and identified by FT-IR, 1H and 13C NMR. The elemental chemical state and basicity of ILs were determined by XPS and Hammett indicator method, respectively. Then the catalytic performance of these bifunctional catalysts was investigated in one-step synthesis of dimethyl carbonate (DMC) from ethylene oxide (EO), carbon dioxide and methanol. The best catalytic performance with 99% EO conversion and a maximum of 74% DMC selectivity was obtained using [N111,6N11]I as catalyst under optimized reaction conditions. And the catalyst could be reused for several times. Normally, stronger basicity could be obtained by altering the anions with different nucleophilicity in ILs and a better catalytic activity could be achieved correspondingly. A mechanism that both the ring opening of epoxide through nucleophilic attacks and the transesterification play an important role in the reaction was proposed based on experimental results.
- 链接地址:http://www.ionike.com/download/article/2014-04-10/139.html