The Preparation Of One-dimensional Materials-supported Palladium Composite Nanocatalysis And Their Performance Tests In Heck Reaction

Palladium nanocatalysts possess highly catalytic performance, fine size and great surfactivity, and more and more researchers pay attention to them. But, traditional palladium nanocatalysts have many shortages in liquid reactions, for instance, the sintering of catalysts, the leaching of active center and the separation of productions and catalysts, leading to enormous waste of resources as well. Based on this, this paper prepared three novel one-dimensional nanofibers-supported palladium nanoparticles composite catalysts by combining eletrospinning and chemical in-situ reduction, thermal carbonization methods, and researched applications of supported palladium nanoparticles catalyst in Heck reaction, the main content and results as follows:Firstly, polymer polyvinyl pyrrolidone-supported palladium nanoparticles catalyst was prepared by combining eletrospinning and chemical in-situ reduction method; it integrates the flexible, low-cost and processed easily polymer materials with functional noble metal palladium nanoparticles, scanning electron microscope and transmission electron microscopy show palladium nanoparticles/polyvinyl pyrrolidone composite nanofibers well arranged and distributed, palladium nanoparticles evenly distribute in polyviiyl pyrrolidone matrix, this composite catalyst has great performances in hydrogenation of p-nitrotoluene and Heck reaction and the catalytic activity did not significantly reduced in recycled three times.Secondly, polyacrylonitrile-anchored palladium nanoparticles catalysts were obtained through eletrospinning, impregnation, chemical modification, chemical reduction and thermal carbonization methods, catalysts were represented by a series of instruments and inspected their catalytic performances in Heck reaction. Results show that as-prepared palladium nanoparticles/carbon nanofibers catalyst has good nanofibers and palladium nanoparticles morphology when hydrogen is reduction agent. This composite catalyst has great performances in Heck reaction and the catalytic activity did not significantly reduced in recycled five times.Lastly, on the basis of the preparation of carbon nanofibers, fabricating series of electrospinning precursor solution by controlling the content of polystyrene. Polystyrene and polyacrylonitrile acted as thermal degradable polymer (TDP) and carbon precursor polymer (CPP) respectively. In this experiment, polystyrene is a kind of diffuse type cocatalyst in electrospinning precursor solution; polystyrene macromolecular compounds had the low thermal-decomposition temperature in the process of high temperature carbonization and leaved behind many pores. PAN and PS matrixes are incompatible; phase separation happened between PAN and PS in the bicomponent fibers. Results show that meso-or nanopores/nanochannels in the range of several to tens of nanometer is found, they uniformly distribute in the nanofibers and hole through the nanofibers, porous carbon nanofibers have specific surface area of250m2/g, and the catalyst has excellent catalytic performance and good recycle performance in Heck reaction. This method can improve the catalyst pore structure and the catalyst performance, increasing the catalyst’s inner specific surface area can improve the process that reactants contract with active center and heighten catalytic selectivity and activity, carbon materials can involve in electron transfer and transmission.In conclusion, the one-dimensional nanofibers matrix-loaded palladium nanoparticles materials can effectively anchor activity center, nanoparticles have the high degree of dispersion and effectively improve the atom economy. At the same time, this method can effectively inhibit the agglomeration of nanoparticles, inactivation and leaching of nanoparticles. Catalysts are reusable after reaction and reduce the economic value, and composite materials have a range of practical application value. The design of one-dimensional nanocatalytic materials provides reference.