The Study On The Construction Of Novel Selective Oxidation Catalyst Based On The Flaky SBA-15

SBA-15, because of its pore size adjustable, it has a highly ordered two-dimensional hexagonal mesoporous structure and highly hydrothermal stability, so it has more potential application value in many fields, such as catalysis, adsorption, immobilization of enzyme, chromatographic supports and sensor. The traditional morphology of SBA-15 is fiber-like or rod-like, in recent years, many researchers have successfully introduced transition metals(e.g. Al,Ti,Zr,Mn,Ga and V) into the mesoporous materials, their presence made the obtained SBA-15-derived materials exhibiting fascinating framework changes. Among them, in most of reported studies on ZrSBA-15, the focus is mainly on their synthesis or catalytic evaluation when they were directly used as catalysts. That is to say, utilizing ordered ZrSBA-15 as a platform to design highly improved catalytic composites has been rarely reported. Moreover, as for the catalytic performance of ZrSBA-15-based catalysts, besides the framework composition and surface chemistry, their morphological features and textural properties are also determining factors; as they can largely influence the active site number, the accessibility of active sites on a given catalyst surface and inside the pores, as well as the diffusion of the reactant or product molecules, so the textural properties and morphological features of the catalysts can not be ignored.In this paper, a series of HPW/PEHA/ZrSBA-15 catalysts with varied Zr contents were synthesized by changing the initial molar ratios of Zr/Si, and used for the selective oxidation reaction of benzyl alcohol. The catalysts were characterized by N2 adsorption-desorption, XRD, SEM, TEM, XPS, FT-IR and ICP-AES analysis techniques. It was found that, through simply tuning the initial molar ratios of Zr/Si, both the morphology and catalytic performance of resultant catalysts can be tailored. More interestingly, the incorporation of zirconium ions, which can endow the ordered framework with enhanced acidity, can effectively stabilize loaded pentaethylenehexamine(PEHA) and facilitate a higher dispersion and attraction of HPW clusters. By carefully screening the catalytic results of the selective oxidation of benzyl alcohol, an optimal value of Zr/Si molar ratio was found to be 0.05, under which platelet ZrSBA-15 with ordered framework can be facilely obtained, leading to a maximum catalytic activity with negligible loss in selectivity and conversion even after five times of recycling test.This work aimed to establish the interplay between zirconium salt usage during the synthesis system and morphology/catalytic performance of HPW/PEHA/SBA-15, taking the selective oxidation of benzyl alcohol for benzaldehyde as a model reaction. It was firstly confirmed that the usage of zirconium content played an extremely important role towards the appropriate composites with expectable catalytic performance and recyclability. To further verify that the modified catalytic materials which are prepared by the appropriate method based on the sheet of SBA-15 will have a higher catalytic performance. Through the use of them, the protection will be achieved. It also lays a solid foundation for the future application of the new catalytic materials based on the sheet of SBA-15 for their synthesis.