Palladium Composite Catalyst Supported On The Reactor And Its Performance Test In Heck And Suzuki Reaction

Precious metals palladium because of its excellent catalytic performance is widely used in organic synthesis industry. However, There were some defects over the conventional palladium-based catalyst,including high cost, producing palladium black, reunion and inactivation. Considering that metal nanoparticles have unique advantages of small size, large surface area, so it is of good behaviour in catalytic field. This paper aimed to on the basis of preparation of one-dimensional carbon fiber supported palladium nanoparticles composite catalyst, combined with electrospinning technology, chemical reduction, and low temperature carbonization method to make the palladium-based catalyst directly attached to the inner wall of a specific device so as to design a new catalytic reactor. The reactor together with catalyst builds up an overall catalytic system and independently catalyzes Heck and Suzuki coupling reaction. The advantages in this system are that the catalyst attached on the surface of the reactor has no need of filtration and then reuse for the subsequent studies. The specific content of this paper is as follows:(1)A method of electrospinning in combination with chemical modification, impregnation-reduction and high temperature carbonization had been applied to prepare palladium nanoparticles attached on the modified polyacrylonitrile(PAN) carbon nanofibers composite catalyst, and investigated its catalytic performance of the Heck reaction. The results show that the method of chemical modification greatly increased the loading of palladium nanoparticles on fiber surface and this type of catalyst present superior catalytic properties in Heck reaction. There is no significant loss after five cycle runs.(2)On this basis, polyacrylonitrile(PAN) precursor solution mixed with another polymer polystyrene(PS) as the thermal decomposition of polymers, that means polystyrene(PS) decomposed during high temperature carbonization stage and left with a structure of porous morphology in the modified carbon nanofiber. This method is able to.increase the specific surface area of catalyst and further increase the loading of the palladium content on fibers. This kind of catalyst catalyzes Heck reaction with a relatively short time, and lower catalyst dosage under full transformation.(3)A new type of catalytic reactor has been designed, namely with electrospun PAN-Pd Cl2 fibers to the inner surface of the reactor and the catalyst can attach to the reactor firm Ly even suffering a reduction, pre-oxidation and carbonization process. The reactor can independently catalyze Heck reaction and showed excellent catalytic activity. Because of the conditions of Suzuki coupling reaction are mild, the fibers that attached on the inner wall and reducd by hydrazine hydrate but without pre-oxidation and carbonization process can be used as catalyst and catalyze Suzuki coupling reaction. The result show that the reactor and this type of catalyst present excellent performance in phenylboronic acid and iodobenzene of Suzuki reaction.In a word, the design of Pd-based composite material catalyst attached on the inner wall of reactor can further decrease the the loss of catalyst in the process of recycling amd the catalyst can reused more times within the reactor. A train of thought has been provided for the preparation of supported palladium catalyst and the design of new reactor by this paper.