芳樟叶浸出液还原制备对硝基苯酚加氢银催化剂

Biosynthesis of Silver Catalyst for 4-Nitrophenol Hydrogenation by Reducing Cinnamomum Camphora Leaf Extract

采用芳樟叶浸出液,通过原位还原和等体积浸渍的方法制备负载型纳米银催化剂,并以对硝基苯酚(4-NP)加氢反应为模型反应,考察催化剂载体,焙烧条件等对负载型纳米银催化剂性能的影响,并采用扫描电镜(SEM),热重分析(TG)和红外光谱(FT-IR)等表征手段对催化剂进行表征。结果表明,以TiO_2为载体制备的纳米银催化剂具有较好的催化活性;植物还原法制备的催化剂表面纳米银颗粒较小((7.3±2.4)nm),催化效果较好。当体系中Ag与4-NP的物质的量之比为1:230时,完全反应时间小于或等于10 min。对催化剂进行一定条件的焙烧处理,能在一定程度上提高催化剂的活性和重复使用性,将催化剂于400℃下焙烧1h,催化活性最佳:将催化剂于400℃下焙烧2h,催化剂重复使用性最好。对芳樟叶浸出液与银的作用机理进行初步研究,表明劳樟叶浸出液中的杂环化合物能通过羰基与银络合,从而起到防止催化剂表面纳米银颗粒团聚的作用。

The supported nano-silver catalyst（Ag/TiO2） was prepared by in situ reduction and incipient wetness impregnation method using the aqueous extract of cinnamomum camphora leaf, and the effects of carriers and calcination conditions on performance of the catalyst were investigated by 4-nitrophenol（4-NP） hydrogenation. The catalyst was characterized by means of scanning electron microscope（SEM）, thermogravimetric analysis（TG） and Fourier transform infrared spectrophotometer（FT-lR）. The results showed that the biosynthesized Ag/TiOz catalyst, with Ag nanoparticle size （7.3±2.4） nm, demonstrated excellent performance in catalyzing hydrogenation of 4-NP, and when the molar ratio of Ag to 4-NP was 1：230, the time for complete conversion of 4-NP to Aminophenol （4-AP） was less than or equal to 10 min. The catalytic activity and reusability of the catalyst could be improved through calcination. The catalyst calcined at 400 ℃ for I h in air exhibited better catalytic activity and calcined at 400℃ for 2 h exhibited better reusability. The action mechanism of Ag and cinnamomum camphora leaf extract was studied and the results showed that the heterocyclic compounds in the extract could complex with Ag through carbonyl groups, which prevented the Ag nanoparticles on the surface of catalyst gathering.