Preparation And Treatment Of Palladium Composite Catalyst And Its Application In Catalytic Reaction

Catalytic materials play an important role in the human development.About thirty-five percent of global GDP and ninety percent of the chemical product depends on the catalytic process.Noble metal catalysts play an active role in petroleum refining,chemical raw materials,low toxic pesticide,artificial fertilizer,automobile exhaust absorption and so on.However,there are still many problems,such as high price,limited resource,complex preparation process.Therefore,how to prepare the excellent noble metal catalysts becomes an important research topic.There are two main aspects to improve the performance of the noble metal catalysts.One is preparing the noble metal nanoparticles with specific morphology.The other is to explore the new carrier with special structures and properties,which not only can disperse the noble metal in the surface and channel of the carrier for saving the amount and cost of the noble metal catalysts,but also can further improve the catalytic activity though the potential interaction between the active sites and the noble metal.Therefore,this paper main focuses on improving the catalyst performance and exploring the new catalyst.The compound catalyst is made by mixing palladium nanocrystals with acid modified carbon nanotubes,then treated by a green simple eco-friendly method.The effective method to remove PVP from the Pd-NPs by water steam treatment in a lab-made reactor can significantly enhances the catalytic activity.In addition,the MXene supported palladium catalyst was prepared by the impregnation method,and then the performance of catalyst was investigated under light and dark condition.According to the performance of the catalyst,we can explore the more proper and efficient catalyst to the Suzuki reaction.Here are the results.(1)Though using palladium chloride acid sodium solution as the precursor,the palladium cube and palladium octahedral nanocrystals were prepared by the colloid method,and the fresh Pd-NCs covered with PVP were supported on CNTs by the traditional impregnation method.Colloidal method employing PVP as the stabilizer has been proven particularly suitable for preparing Pd-NPs with controlled morphology.However,the PVP can strongly absorb on Pd-NPs surface and acts as a physical barrier to restrict the free access of reactants to the active sites.To date,the effective method for removing PVP has been on trial for different concentrations of nitric acid.By controlling the different condition,such as temperature,time,and so on,the method can successfully remove PVP from the carbon nanotubes supported Pd nanocrystal.At the same time,it can maintain the original morphology and structure of palladium metal nanocrystals.We use the Suzuki reaction as a probe reaction to prove that the environmentally friendly high-pressure steam treatment method can significantly improve the performance of palladium nanocrystals.(2)The absence of PVP and the preservation of the shape and distribution of the Pd nanoparticels(Pd-NPs)were confirmed with TEM.We compare the(100)dominated Pd-NCs with the(111)dominated Pd-NOs.The results proves that the(100)dominated Pd-NCs present higher catalytic performance that that of(111)dominated Pd-NOs for the Suzuki coupling reaction over the clean Pd-NPs catalysts.(3)The palladium supported MXene catalyst was prepared by the traditional impregnation method.Under the condition of weak alkaline,the size of the metal nanoparticles disperse uniformly.Though the treatment of hydrogen reduction,we use Suzuki as a probe reaction.According to the photo-thermal characteristics,we use the Suzuki reaction as the probe reaction under light condition.We use the gas chromatography to test the product.The results showed that the catalytic performance of the palladium supported catalyst improve significantly under the light condition.