Preparation Of Supported Palladium-based Nanocatalysts And Their Catalytic Performance For Suzuki And Heck Reactions

Because the C-C cross coupling reaction has a very large application,it is very important to prepare high efficient catalyst for C-C cross coupling reaction.In recent years,the heterogeneous Pd catalyst has made rapid development,so it is widely used in a variety of C-C cross coupling reaction,but because the palladium is expensive,high cost,so to explore a new way to extend the use frequency and reduce the consumption of catalyst used in the process of Pd are very necessary.At the same time,we can also learn from the bimetallic type reported in the literature to find a metal or metal oxide to promote the catalytic activity of Pd,so as to enhance the catalytic activity of Pd metal in the same circumstances.The aim of this paper is to study the high performance nano-Pd catalyst which can catalyze the cross-coupling reaction of Heck and Suzuki.Based on the carbon nanofibers as the catalyst carrier,it is expected that a reactor can carry Pd / CNFs,thereby eliminating the need for filtering recovery steps,which will reduce the process of causing the catalyst loss.It is hoped that the catalytic system can catalyze the reactions by some simple treatments after each reaction.At the same time,this paper also hopes to explore a new additive can improve the catalytic activity of Pd.The research contents of this paper are as follows:?1?Pd NPs/CNFs was prepared on the basis of previous research.The catalyst can be prepared by electrospinning process,hydration hydrazine solution under ice bath condition liquid phase reduction process and high temperature carbonation process.UV-vis diffuse reflection test showed that PdCl₂ / PAN could be reduced to Pd / PAN by hydrazine hydrate solution under ice bath condition.FESEM results show that the surface of the carrier fiber is smooth,the diameter is even,the arrangement is neat,and the diameter of Pd nanoparticles loaded on the fiber is between 11¹5 nm.The results show that the catalyst has good substrate compatibility for Suzuki reaction and maintains stable catalytic performance during the cycle.The catalysts had the characteristics of low dosage and high activity when they used in Heck reactions and exhibited good catalytic activity for various Heck reaction substrates.?2?The unique,recyclable G-reactor @ Ag-CNFs-Pd reactor with CNFs-Pd attached to the inner wall can be successfully constructed by using simple method and cheap glass materials.The catalyst CNFs-Pd attached to the inner wall can be prepared by an electrospinning process,a hydrogen reduction process and a final carbonation process.The reactor can be used directly in the next catalytic reaction without separation and recovery,and avoids the loss and contamination of Pd / CNFs caused by the recovery process.The SEM results show that the catalyst is a nanostructure of the coexistence of the sphere and the fiber,which allows the catalyst to adhere tightly to the inner wall of the reactor.The G-reactor @ Ag-CNFs-Pd can catalyze the Suzuki reaction up to eight times without significant shedding.?3?The Pd-Ce_xO_y/CNFs catalysts can be prepared by the method of impregnation and immersion.The optimal catalytic effect was obtained under the condition of the reaction temperature of 120? when the dosage of Pd-Ce_xO_y/CNFs was 5.7 mg and the solvent was DMF and the acid binding agent was triethylamine.Under these optimum reaction conditions,Pd-Ce_xO_y/CNFs and Pd-CNFs which contain the same amount of Pd exhibited different catalytic activity.The Heck reaction of iodobenzene and n-butyl acrylate catalyzed by Pd-Ce_xO_y/CNFs butyl than Pd-CNFs catalyst can advance 4 h to complete the reaction.Compared with Pd-CNFs,the Pd-Ce_xO_y/CNFs prepared by the impregnation method showed a similar regular when the Suzuki reaction of iodobenzene and benzene boric acid was catalyzed.The products were not obtained when the Ce_xO_y-CNFs was used in Heck and Suzuki reactions.In conclusion,the combination of Ce_xO_y and Pd-CNFs enhanced the catalytic activity of Pd-CNFs,and Ce_xO_y played an auxiliary role in this process.