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Ionic Liquids 英超联赛直播液体

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CO2作为碳氧资源的转化利用对于经济社会的可持续发展具有重要意义。环状碳酸酯在有机合成、溶剂、纺织、印染等领域具有广泛用途。CO2与环氧化合物合 成环状碳酸酯是典型的原子经济性反应[1],现已报道的催化体系不同程度存在一些问题,如催化剂成本高、活性不高、催化剂不易分离、易流失等问题。我们合 成了一系列不同类型硅胶接枝的双季铵盐英超联赛直播液体,路线如Fig.1所示。其中MCM-41接枝的TMEDA+I-在环氧丙烷与CO2的反应中表现出较优的 催化性能,TOF可达>60h-1。催化剂重复使用多次而活性没有明显下降,且对于合成其它环状碳酸脂也表现出很好的催化活性。

介孔MCM-41.jpg

王利国,王培学,杨本群,等. 介孔 Mcm-41 接枝双季胺化英超联赛直播液体高效催化环氧化合物与 Co2环化反应合成环状碳酸酯[C]. 第二十八届中国化学会年会第1分会场摘要集.2012,18.

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.

Keywords: alcoholysis;  disubstituted ureas;  N-substituted carbamates;  TiO2/SiO2;  phosgenefree

★★★☆☆ Wang LG,Shang JP,Liu SM,et al. Environmentally Benign And Effective Syntheses Of N-substituted Carbamates Via Alcoholysis Of Disubstituted Ureas Over Tio2/sio2 Catalyst[J]. Pure And Applied Chemistry,2012,84:461-471.

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.

Keywords: Dimethyl carbonate; Ethylene carbonate; Transesterification; Binary zinc–yttrium oxide

★★★☆☆ L. Wang et al. / Catalysis Communications 16 (2011) 45–49

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.

Keywords: Glycerol carbonate; Urea; Glycerol; Lanthanum oxide; Solid base

★★★☆☆ L. Wang et al. / Catalysis Communications 12 (2011) 1458–1462