Graphene-supported palladium catalyst, preparation method and application thereof

Abstract

The invention discloses a graphene-supported palladium catalyst, which includes following raw materials, by volume, 2-10 parts of a material A, 30-50 parts of ethylene glycol, 100-150 parts of graphene and 5-20 parts of a KTiNbO5 nano sheet solution, wherein the material A includes the raw materials of PdCl2 and hydrochloric acid being 30-37% in concentration, wherein the weight / volume ratio of the PdCl2 to the hydrochloric acid is (0.01-0.1) g : (10-40) ml. The invention also provides the preparation method and an application of the graphene-supported palladium catalyst. In the invention, a conventional method of the graphene-supported palladium catalyst is replaced by the preparation method, which is free of surfactants, is small in particle size, is simple in operation, can be used in synthesis of cinnamic acid, is high in yield of cinnamic acid, is simple in separation and after-treatment, is mild in reaction conditions and is green and economical.

Description

technical field [0001] The invention relates to the technical field of graphene-supported palladium catalysts, in particular to a graphene-supported palladium catalyst and its preparation method and application. Background technique [0002] Heck discovered the Heck reaction in 1972. Since the end of the 20th century, the Heck reaction has gradually developed into an increasingly widely used organic synthesis method. After entering the 20th century, the Heck reaction has been a research hotspot in catalytic chemistry and organic chemistry. The Heck reactants are mainly halogenated aromatic hydrocarbons (mainly iodine) reacting with alkenes containing α-electron-withdrawing groups catalyzed by Pd(0), Pd(II) or Pd-containing complex catalysts to generate aromatic alkenes. The reaction undergoes five steps: oxidative addition of Pd, coordination of Pd and double bonds, cis-coplanar insertion, cis-coplanar β-H elimination, and reductive elimination. In the reaction, Pd(0) was ...

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Problems solved by technology

[0005] The traditional method uses NaBH 4 or LiAlH 4 Make Pd 2+ When reducing to Pd, a surfactant needs to be added, and the added reducing agent is not easy to disperse evenly in the solution. During the reduction, the metal often agglomerates, and the prepared catalyst has a large particle size.

[0006] In addition, at present, the industry mainly utilizes the Perkin reaction to synthesize cinnamic acid. Its disadvantages are low activity of acetic anhydride, high reaction temperature (140-180 ° C), low yield (38-45%), etc., which are not conducive to industrial production. The laboratory uses benzaldehyde and malonic acid as raw materials to synthesize cinnamic acid through Knoevenagel condensation reaction, and reflux reaction at 90°C for 1.5h. The yield of cinnamic acid can reach 96.28%, but the above methods all use benzaldehyde as raw material, so In order to prevent the polymerization between benzaldehyde, not only need to add a polymerization inhibitor (such as 4-tert-butylcatechol), and benzaldehyde is easily oxidized to benzoic acid, so it is difficult to separate from the product cinnamic acid, and post-reaction treatment requires water Steam distillation, activated carbon decolorization time-consuming and labor-intensive process

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