| The synthesis of aniline by one step amination of benzene has always been a great challenge.Titanium silicalite-1?TS-1?exhibited good catalytic activity in the one-step amination reaction of benzene.However,the narrow microporous channels of traditional TS-1 hindered the diffusion of reactant,so it was important to synthesize hierarchical TS-1 with microporous-mesoporous or microporous-macroporous composite structures.In this work,two different types of hierarchical TS-1 were designed and synthesized,and their structural properties were characterized by various characterization methods.Then the two different types of hierarchical TS-1 were applied to the one-step amination of benzene to aniline.A bifunctional catalyst Cu/TS-1@MCM-41 was synthesized by self-assembly method and incipient-wetness impregnation method,which using CTAB as a structure-directing agent?SDA?to synthesize a layer of MCM-41 on the surface of TS-1 molecular sieve.The physical properties and the properties of the pore structure of the core-shell Cu/TS-1@MCM-41 were characterized by XRD,BET,SEM,TEM,FT-IR,XPS and other characterization methods,and Cu/TS-1@MCM-41 was used in the one-step amination of benzene with aqueous ammonia as the ammonia source and hydrogen peroxide as the oxidant to synthesize aniline.The results showed that the micropore structure with 0.55nm inside Cu/TS-1@MCM-41zeolites were connected with the 3.3 nm mesoporous outside and the reactant can pass through the mesoporous into the internal micropore.The active component Cu was present in the form of divalent CuO and was uniformly distributed throughout the catalyst.The maximum yield of aniline was 1.97%and the selectivity of aniline was 91.63%under the conditions of reaction temperature 60?,reaction time 4 h and catalyst dosage 0.5 g.There was no by-product phenol formation.The possible reaction pathway was proposed based on the experimental results.A series of copper-based bimetallic catalysts were synthesized using TS-1zeolite as support.The bimetallic supported catalysts were screened in the reaction system of benzene to aniline and the effect of the loading of bimetallic active components on the yield and selectivity of aniline was further studied.The results showed that the bimetallic supported Cu-Ni/TS-1 catalyst exhibited the best bimetallic catalytic activity.When the loadings of the active components CuO and NiO were 2.5 wt%and 2.5 wt%,respectively,the catalyst 2.5Cu-2.5Ni/TS-1exhibited the best catalytic activity,the rate of aniline formation was 18.019?mol·g-1·h-11 and the catalytic selectivity of aniline was 63.78%.The metal encapsulated hollow TS-1 zeolite 2.5Cu-2.5Ni@HTS-1?0.5-48?was prepared by post-treatment of 2.5Cu-2.5Ni/TS-1 zeolite with TPAOH solution throughdissolution-recrystallizationprocess.Andmetalencapsulated2.5Cu-2.5Ni@HTS-1?0.5-48?zeolites were characterized by XRD,BET,SEM,TEM,FT-IR and XPS,and used in one-step amination of benzene to aniline in solvent-free system.The results showed that many mesoporous and even macroporous cavities were formed in the 2.5Cu-2.5Ni@HTS-1?0.5-48?zeolite treated with TPAOH solution,and the framework of TS-1 zeolite was retained while the pore volume of micropore or macropore was increased.The introduction of active component Ni made the dispersion of Cu more uniform and formed the Cu-Ni oxide alloy.The aniline formation rate of 2.5Cu-2.5Ni@HTS-1?0.5-48?catalyst was24.676?mol·g-1·h-1,which was 73.31%higher than that of 2.5Cu/TS-1 catalyst,and the selectivity of aniline was 76.74%.The possible reaction pathway was proposed based on the reaction results. |
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