聚苯并噁嗪固载钯基纳米催化剂在芳香醇氧化反应中的应用

以球状聚苯并噁嗪为载体, 采用浸渍热解法合成了钯炭纳米催化剂. 通过透射电子显微镜观察发现, 钯纳米粒子几乎全部均匀分布在载体上, 且尺寸均一, 平均直径约为3.5 nm. 结果表明, 载体表面含有丰富的含氮含氧官能团, 氮和氧原子与钯之间存在相互作用, 从而使聚苯并噁嗪能够有效固载钯纳米粒子. 采用相同的方法进一步合成Pd-Au/C和Pd-Pt/C双金属催化剂, Pd-Au和Pd-Pt纳米粒子也展现出良好的分散性, 无明显团聚现象, 平均直径分别为4.3和4.2 nm, 进一步说明聚苯并噁嗪对金属活性组分的有效固载. 将催化剂应用于苯甲醇氧化反应, 其中Pd₁-Au₁/C在2 h的转化率为98%, 对产物苯甲醛的选择性大于99%, 该催化剂经过焙烧可恢复催化活性, 表现出良好的循环稳定性, 并能将不同取代基的芳香醇氧化为相应的醛, 是一种良好的醇氧化催化剂.

Palladium-based Nanocatalysts Supported on Polybenzoxazine for Aromatic Alcohol Oxidation

Carbon supported palladium-based nanocatalysts were synthesized via an impregnation-pyrolysis method,based on a spherical polybenzoxazine as support,owing to the interaction between nitrogen groups and metal nanoparticles.Transmission electron microscope(TEM)images of Pd/C catalyst showed that palladium nanoparticles were uniformly distributed over the support with an average size of about 3.5 nm.The cha-racterization results of Fourier transform infrared spectroscopy(FTIR),X-ray photoelectron spectroscopy(XPS)and temperature programmed desorption(CO 2-TPD)analysis,showed that a mount of nitrogen and oxygen functional groups existed on the support.The nitrogen and oxygen atoms might have interactions with Pd atoms,which could effectively immobilize palladium nanoparticles and obtain well dispersed palladium-carbon nanocatalysts.The bimetallic Pd-Au/C and Pd-Pt/C catalysts were prepared via the same method to further enhance the catalytic activity.The average particle size of Pd-Au and Pd-Pt nanoparticles were 4.3 and 4.2 nm,respectively,without an obvious agglomeration,which demonstrated the effective immobilization role of polybenzoxazine support.The catalysts were evaluated by the benzyl alcohol oxidation reaction at 80℃and water as solvent.The Pd 1-Au 1/C catalyst exhibited the highest conversion of>98%within 2 h and the selectivity to benzaldehyde of>99%,revealing the excellent catalytic performances.Moreover,the catalyst could be used for several runs and easily regenerated by calcination.Furthermore,the catalyst could also oxidize aromatic alcohols with different substituents into corresponding aldehydes,such as 4-methyl benzyl alcohol,4-methoxybenzyl alcohol,2-methyl benzyl alcohol and so on,providing an excellent catalyst for aromatic alcohol oxidation.