Effect of phosphorus-modification of titania supports on the iridium-catalyzed synthesis of benzimidazoles
Effect of phosphorus-modification of titania supports on the iridium-catalyzed synthesis of benzimidazoles
复制标题
二氧化钛载体磷改性对铱催化苯并咪唑合成的影响
DOI：
10.1016/j.cattod.2020.02.014
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发表时间：
2020
期刊：
影响因子：
5.3
通讯作者：
Iwamoto Shinji
中科院分区：
文献类型：
--
作者：
Yu Han;Wada Kenji;Fukutake Tatsuhiro;Feng Qi;Uemura Shinobu;Isoda Kyosuke;Hirai Tomomi;Iwamoto Shinji
用磷物种对铱催化剂的二氧化钛载体进行改性，大大提高了氢转移合成苯并咪唑的活性。结果表明：水热法制备的掺磷金红石型二氧化钛负载铱催化剂对2-硝基苯胺（1a）和苯甲醇（2a）合成2-苯基苯并咪唑（3aa）的活性比未改性金红石型二氧化钛负载铱催化剂高近5倍。XPS深度剖面研究证实，掺杂剂主要存在于金红石载体的表面上。因此，采用湿法浸渍的方法，用磷酸对超细二氧化钛进行表面改性。使用这样改性的二氧化钛使铱催化剂的活性提高了2.7倍以上。FTIR和XPS研究表明二氧化钛表面存在双齿磷物种，H2-TPR研究表明磷改性促进了在较高温度下还原的铱物种的形成，这将适用于本催化剂。
Modification of titania supports for iridium catalysts by phosphorus species greatly enhanced the activity for the synthesis of benzimidazoles via hydrogen transfer. Two series of phosphorus-modified titanias were used: The iridium catalysts supported on phosphorus-doped rutile titania prepared by the hydrothermal method showed nearly 5 times higher activity for the reaction of 2-nitroaniline (1a) and benzyl alcohol (2a) to 2-phenylbenzimidazole (3aa) than the catalysts supported on unmodified rutile. XPS depth profile study substantiated that the dopant was present mainly on the surface of the rutile support. Therefore, a facile wet impregnation method was applied to modify the surface of anatase titania with phosphoric acid. The use of thus-modified titania enhanced the activity of the iridium catalysts by more than 2.7 times. The FTIR and XPS studies revealed the presence of bidentate phosphorus species on the surface of titania, and the H2-TPR study indicated that phosphorus-modification promoted the formation of iridium species reduced at higher temperature, which would be suitable for the present catalysis.