首页> 外文期刊>Microporous and mesoporous materials: The offical journal of the International Zeolite Association >Microwave-assisted synthesis of ultra small bare gold clusters supported over Al2O3 and TiO2 as catalysts in reduction of 4-nitrophenol to 4-aminophenol
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Microwave-assisted synthesis of ultra small bare gold clusters supported over Al2O3 and TiO2 as catalysts in reduction of 4-nitrophenol to 4-aminophenol

机译:微波辅助合成的Al2O3和TiO2上负载的超小裸金簇作为催化剂将4-硝基苯酚还原为4-氨基苯酚

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In this work I present a novel method to prepare ultra small bare gold clusters (Au-n) loaded over different supports. Size selected gold clusters protected by glutathione ligand (Au-25(SG)(18)) was prepared and deposited over aluminium dioxide (Al2O3 Puralox SCCa-190HPV) and anatase titanium dioxide (TiO2) by impregnation method with doping percentage 0.5 and 1 wt %. Then the doped catalysts were irradiated 1 h by microwave synthesis labstation at 80 degrees C and 500 W to remove the glutathione ligands (GSH) and leave the bare gold clusters (Au-25) supported over alumina and titania as a strategy for enhancing their catalytic activity and selectivity. The high resolution transmission electron microscope analysis confirmed the particle size of protected (1 wt % Au-25(SG)(18)/Al2O3) and bare (1 wt % Au-25/Al2O3) gold clusters over alumina have the same size distribution (similar to 1 nm). The TEM images of doped gold clusters over TiO2 before and after microwave treatment are clearer than alumina. This means the gold clusters over alumina and titania did not suffer from any agglomeration by microwave treatment. From nitrogen sorption isotherms at -196 degrees C for the protected and bare gold clusters over supports showed two different loop types of isotherms H3 and H1, respectively. Their specific surface area S-BET, pore volume and average pore diameter were calculated. The pore size distribution of supported gold clusters before and after microwave treatment was measured. These results confirmed the ligands were removed from the supported gold clusters by microwave treatment. The pores in alumina and titania which were blocked by the protected clusters have become available. Reduction of 4-nitrophenol (4-NP) into 4-aminophenol (4-AP) in presence of NaBH4 was used as a test reaction to compare the catalytic activity of supported bare and protected gold clusters over alumina. The results showed that the 1 wt % Au-25/Al2O3 catalyst exhibited the best catalytic performance in the reduction of 4-NP into 4-AP and revealed 100% conversion following 90 s stirring at room temperature. The extreme catalytic activity of the ultra small gold clusters attributed to their electronic properties and geometrical configuration. (C) 2016 Elsevier Inc. All rights reserved.
机译:在这项工作中,我提出了一种新颖的方法来制备负载在不同支撑物上的超小型裸金簇(Au-n)。制备了由谷胱甘肽配体(Au-25(SG)(18))保护的按尺寸选择的金团簇,并通过掺杂方法以掺杂百分比0.5和1 wt%的浸渍方法沉积在氧化铝(Al2O3 Puralox SCCa-190HPV)和锐钛型二氧化钛(TiO2)上%。然后将掺杂的催化剂通过微波合成实验室在80摄氏度和500瓦下辐照1 h,以去除谷胱甘肽配体(GSH)并保留负载在氧化铝和二氧化钛上的裸金簇(Au-25)作为增强其催化作用的策略活性和选择性。高分辨率透射电子显微镜分析证实了氧化铝上受保护的(1 wt%Au-25(SG)(18)/ Al2O3)和裸露的(1 wt%Au-25 / Al2O3)金簇的粒径具有相同的尺寸分布(类似于1 nm)。微波处理前后,TiO2上掺杂金团簇的TEM图像比氧化铝清晰。这意味着通过微波处理,氧化铝和二氧化钛上的金簇没有遭受任何团聚。支撑物上受保护和裸露的金簇在-196℃下的氮吸附等温线分别显示出等温线H3和H1的两种不同的环型。计算它们的比表面积S-BET,孔体积和平均孔径。测量了微波处理前后负载的金簇的孔径分布。这些结果证实了通过微波处理从负载的金簇中除去了配体。氧化铝和二氧化钛中的孔被保护的团簇堵塞了。在NaBH4存在下将4-硝基苯酚(4-NP)还原为4-氨基苯酚(4-AP)用作测试反应,以比较负载的裸露和受保护的金簇在氧化铝上的催化活性。结果表明,在室温下搅拌90 s后,1 wt%的Au-25 / Al2O3催化剂在将4-NP还原为4-AP中表现出最佳的催化性能,并显示出100%的转化率。超小金簇的极强催化活性归因于其电子性能和几何构型。 (C)2016 Elsevier Inc.保留所有权利。

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