二氧化碳诱导的可逆离子液体中钯纳米颗粒的合成及应用研究

Synthesis of palladium nanoparticles in carbon dioxide induced reversible ionic liquids and their application

本文采用二氧化碳诱导的1,8-二氮杂二环十一碳-7-烯(DBU)和醇溶液形成的可逆离子液体为介质,通过热还原的方法制备了金属钯纳米颗粒,研究了醇的链长对粒子尺寸的影响.通过透射电子显微镜(TEM)和同步辐射小角X射线散射(SAXS)原位表征等手段对纳米颗粒的形貌和粒径等进行了表征.研究发现,在没有二氧化碳时,DBU与醇组成的溶液中合成的钯呈块状;在加入二氧化碳形成的离子液体中合成的钯纳米颗粒粒径均匀,分散性好,粒子尺寸与离子液体中醇的链长关系不大. TEM表征得到的钯纳米粒子尺寸明显大于SAXS原位表征得到的离子液体中粒子的尺寸,说明在分离过程中钯粒子发生团聚现象.此外,我们研究了该液体体系中金属钯纳米颗粒催化对甲基硝基苯和邻硝基苯甲醛加氢反应.结果表明,钯纳米颗粒对硝基的还原具有较高的催化活性,且在醛基存在时可以对硝基进行定向加氢.

We synthesized Pd particles in reversible ionic liquid formed by carbon dioxide induction of 1,8-diazabicyclo[5.4.0]undec-7-ene(DBU) and 1-hexanol solution. Transmission electron microscopy(TEM) and small-angle X-ray scattering(SAXS) were used to characterize their morphology and size. The particles have smaller size and more uniform size distribution compared with those synthesized in the mixed solution without carbon dioxide. The particles size obtained by TEM is obviously larger than that obtained by SAXS, which indicates the aggregation of the Pd particles in the separation and washing processes of TEM characterization. Then we studied the catalytic performance of Pd nanoparticles in p-nitrotoluene and 2-nitrobenzaldehyde hydrogenation reaction. The results showed that the nanoparticles have high catalytic activity and selectivity for nitro group with aldehyde group unchanged.