Preparation And Catalytic Properties Of Hollow SiO₂ Materials By Using Resorcinol-formaldehyde As Template

Micro/nano hollow microspheres are a new type of materials with a cavity inside.Because of its dual properties of porous structure and nano-size,they possess large specific surface area,messiness of surface modification and cavity size control,which have been widely used in the fields of catalysis,drug carrier,lightweight filler and so on.As a unique type of hollow materials,the rattle-type materials,integrates the external shell and internal nuclear materials,which always shows better performance.However,the reported methods for the preparation of hollow materials are usually complicated and time consuming.In this paper,resorcinol-formaldehyde(RF)resin was used as template,and the coated a SiO2 by hydrolysis of tetraethyl orthosilicate.Then hollow SiO2 and its composite microspheres were prepared by calcining or acid-washing.The main contents are as follows:(1)The Fe-RF@SiO2 core-shell particles were synthesized by sol-gel method using Fe ions incorperated resorcinol-formaldehyde resin(Fe-RF)particles as raw materials.Citric acid as used here to stablize Fe3+ against percipitation.Finally,the formation of catalyst Fe2O3 and removal of RF resin template were achieved by calcination,and hollow Fe2O3@SiO2 particles were obtained The method is simple and effective.Under the optimum preparation conditions,the hollow particles can degradate 96.4%of the methylene blue in 30 min.This is mainly because the material has a large specific surface area of 278.8 m2/g,a higher Fe loading amount of 29.8 wt%,and the SiO2 shell prevents the growth of Fe2O3 grains.(2)Hollow SiO2 microspheres were prepared by acid washing method using resorcinol-formaldehyde resin as template.Compared with the traditional calcination method,our method is simple,effective and the time saving.In addition,the surface of hollow SiO2 particles are richer in functional groups than those obtained by calcination.Finally,the formation mechanism of hollow SiO2 microspheres was proposed.(3)The size and morphology of hollow SiO2 microspheres were effectively regulated by adding citric acid and FeCl3.We find that:a.The size of hollow SiO2 microspheres increased with the increase of citric acid content.b.The size of hollow SiO2 microspheres decreased by increasing the amount of FeCl3,and the morphology of the microspheres changed from a well-dispersed sphere to a continuous worm with a smoother surface.Finally,based on this method,hollow Au@SiO2 microspheres were also successfully prepared,indicating that washing method can also be used to prepare rattle-type materials.