Study On The Reduction Of Plant Extracts Such As Clove To Prepare Pd Nanocatalysts And Catalyze The Suzuki Coupling Reaction

The supported nano-palladium catalysts were prepared by reduction with clove leaves and corncob as reducing agent,corresponding leaf filter and activated carbon as carrier and Na₂PdCl₄ as precursors.The prepared nano-palladium catalysts were characterized by UV-Vis,XRD,TEM,FT-IR and the Suzuki coupling reaction was studied by the above-prepared palladium nanocatalyst.The supported nano-palladium catalyst with loading of 3 wt%was prepared by using clove leaf extract?CLE?as reducing agent,Na₂PdCl₄ as precursors,clove leaf extract and activated carbon as carrier.The nanocrystalline catalyst is mainly composed of Pd?110?crystal face,which belongs to the face-centered oblique structure.The morphology is spherical and uniform.The particle size distribution range is 1.42nm-4.48 nm and the average particle size is 2.79 nm.It could be deduced from the FT-IR analysis that the water-soluble heterocyclic compounds containing-OH,such as alkali and phenol in CLE,acted as reducing agents during the reaction.When Suzuki coupling reaction of p-bromotoluene with phenylboronic acid over above-prepared catalyst was carried out under the reaction condition of K₂CO₃ as the base,EtOH/H₂O?volume ratio 1:1?as the solvent,60?of the reaction temperature and 0.01 mmol%of the catalyst amount,product yield reached 99.08%.The supported nano-palladium catalyst with 1 wt%loading was prepared by using corncob extract?CCE?as reducing agent and Na2PdCl4 as precursors and corncob extract as carrier.The nanocatalyst is mainly composed of Pd?110?crystal face and belongs to the face-centered oblique structure.The morphology is mainly spherical and dispersed uniformly.The particle size distribution is between 1.84nm-4.92nm,and the average particle size is 3.35 nm.From the FT-IR analysis,it can be deduced that the water-soluble heterocyclic compounds containing-OH,such as ketones and phenols in CCE,act as reducing agents during the reaction.The Suzuki coupling reaction of p-bromotoluene with phenylboronic acid was catalyzed when the reaction was carried out with K2CO3 as the base,the solvent was EtOH/H2O?volume ratio 1:1?,the reaction temperature was 60?and the amount of catalyst was 0.01 mmol%Product yield reached 98.19%.Two kinds of Pd/C catalysts with loading of 5 wt%were prepared by using CCE and CLE as reducing agent,using activated carbon as carrier and Na₂PdCl₄ as precursors.The Pd-NPs of the two Pd/C catalysts prepared were spherical and dispersed uniformly,and the particle size distribution was narrow,and the average particle sizes were 2.79 nm-3.35 nm,respectively.When the amount of catalyst was0.01 mmol%at 60?,the yield was 99.08%and 99.19%,respectively,when catalyzed by Suzuki coupling reaction of bromotoluene with phenylboronic acid for 30 min.When the two catalysts were recycled for 5 times,the yield could still kept above 95%.The experimental results show that the use of CCE and CLE can effectively reduce Pd²⁺to Pd⁰.Compared with CCE and CLE slag as the carrier,the prepared Pd/C catalysts have smaller particles with higher catalytic performance and repeated utilization rate.