Au@CuO-MO_x Core-shell Catalyst And Its Catalytic Performance For Ethynylation Of Formaldehyde

As a basic organic chemical raw material,1,4-butynediol（BD）is produced by the reaction of formaldehyde of acetylene,and its downstream derivatives such as 1,4-butanediol（BDO）,tetrahydrofuran（THF）,γ-Butyrolactone（GBL）,polybutylene terephthalate（PBT）and polyurethane（PU）,etc.Ther are highly value-added fine chemicals or polyester materials that are in high demand,which has stimulated and driven the production and technological innovation of 1,4-butynediol.The research on high performance acetylene catalysts,the core technology for the synthesis of 1,4-butynediol from ethynylation of formaldehyde,has attracted much attention.In this work,based on the new Au@Cu₂O core-shell structure catalyst studied by the previous group,the St（?）ber method was used to introduce silica for secondary coating and metal oxide Mg O as an additive to regulate the multi-center synergy of the catalyst in order to improve the stability and catalytic activity of the catalyst in use,as follows:1.The sandwich core-shell structure catalyst Au@CuO@SiO₂ was prepared by chemical reductive deposition combined with the St（?）ber method to investigate the effects of Au core and SiO₂ shell layer on the presence state of CuO species,surface acidity and basicity,and to explore its conformational relationship with the performance of ethynylation of formaldehyde.It was found that SiO₂,as the shell layer,played the role of spatial confinement,and cooperated with the strong electromagnetic effect of Au core to confine Cu species in it,which not only made the catalyst highly dispersed;but also inhibited the aggregation and growth of Cu species as well as the loss of active components,and thus improved the catalytic activity and stability of formaldehyde ethynylation.2.The influence of Au nano-core and promoter Mg O on the texture,presence state and surface acidity and basicity of CuO-based catalyst was studied by introducing promoter Mg by the sol-gel method.The research shows that Mg O as an assistant improves the dispersion of the catalyst and provides rich basic sites.Under the effect of the long-range electromagnetic effect of Au,it further regulates the molar ratio of copper and magnesium atoms in the catalyst shell to realize the synchronous regulation of the active center Cu⁺and the base center.At the same time,it regulates the electronic configuration and quantity of the active center Cu⁺,and finally obtains the best catalytic activity.When Cu:Mg=0.5,Mg O has the best regulation on active center Cu⁺and alkali center.3.On the basis of Au@CuO@SiO₂ core-shell nano-catalysts,two different methods of introducing Mg O additives by impregnation and sol-gel methods were used to successfully prepare double-limited and double-centered Au@CuO@SiO₂-Mg O and Au@CuO-Mg O@SiO₂ core-shell structure nanocatalysts,and to study the effects of different ways of introducing Mg O additives on the performance of Au@CuO@SiO₂sandwich structured catalysts on the weave,chemical environment and acetylation performance of formaldehyde ethynylation.It was found that Mg-O-Si structures were formed by Au@CuO@SiO₂-Mg O and Au@CuO-Mg O@SiO₂ catalysts during the synthesis process.The formation of Mg-O-Si bonds would result in strong interaction between copper species and support,and improve the stability of Cu⁺.In the method of introducing Mg by sol-gel method and then SiO₂ coating,part of Mg inside the shell will diffuse to the outside and enter the network structure of SiO₂ to form Mg-O-Si bonds.In the method of introducing Mg by impregnation method,Mg acts on the surface.Compared with the sample Au@CuO@SiO₂-Mg O acting on the surface,the sample Au@CuO-Mg O@SiO₂ is more likely to inhibit the over-reduction of Cu²⁺,improve the stability of Cu⁺,and then improve the ethynylation activity and stability.