镁铝水滑石负载超细纳米钯催化剂的超声辅助环境友好制备及其催化Suzuki反应性能

Ultrasonic-assisted Environmentally-friendly Preparation of MgAl-Layered Double Hydroxides Supported Ultrafine Pd Nanocatalysts and Their Catalytic Properties for Suzuki Reaction

以镁铝水滑石(MgAI-LDH)为载体,在不加入任何化学还原剂和稳定剂的条件下,利用超声波将MgAI-LDH的表面羟基激发出具有较强还原性的氢自由基,原位还原Pd^(2+)为Pd^(0),制备出MgAI-LDH负载纳米钯催化剂(Pd/LDH)。采用XRD、FT-IR-TEM和N_(2)物理吸附等对所制备的Pd/LDH进行了分析与表征。在300W超声功率和25℃下,还原时间20min所得Pd/LDH上的PdNPs均匀分布在LDH表面及介孔孔道内,粒径分布在1.15-2.81nm,平均粒径为1.49nm。当反应温度为60℃,溶剂为乙醇水溶液(体积比6:6),催化剂用量为0.10%mol,碳酸钾为碱时,催化4-硝基溴苯与苯基硼酸的Suzuki偶联反应的收率为96.58%。此方法为环境友好制备纳米金属催化剂提供了合理的技术方案。

With MgAl-layered double hydroxides(MgAl-LDH)as a carrier,the MgAl-LDH supported nano-palladium catalyst(Pd/LDH)is prepared via in situ reduction of Pd^(2+) to Pd^(0) by ultrasonic-excited hydrogen radicals with strong reducibility from the surface hydroxyl groups of MgAl-LDH without adding any chemical reducing agents and stabilizers.The prepared Pd/LDH is characterized via XRD,FT-IR,TEM and N_(2) physical ad-sorption.The PdNPs on the Pd/LDH obtained under 300W ultrasonic power at 25T1 for 20niin are uniformly distributed on the surface of the LDH and in the mesoporous pores,with a particle size distribution of 1.15nm to 2.8 lnm,and an average particle size of 1.49nm.When the reaction temperature is 60℃,the ethanol aqueous solution(volume ratio is 6:6)is used as the solvent,the catalyst amount is 0.10%(mol),and the potassium carbonate is employed as the base,the yield of catalyzed Suzuki coupling reaction of 4-nitrobromobenzene and phenylboronic acid is 96.58%.This method provides a reasonable technical solution for the environment-friendly preparation of nano-metal catalysts.