Designed Synthesis And Catalytic Oxidation Properties Of Hierarchical Pores Silica Based Catalyst

Porous silica materials have caught much attention in catalysis and petrochemical because of their unique pore structure, large pore volume, tunability of pore size and high specific surface area. However, there are some drawbacks in traditional porous silica ma-terials limit their applications, such as bulky molecules with size larger than the mouth of the pores are excluded from the internal surface so that bulky molecules can only be cat-alytically converted utilizing the outer surfaces of the porous silica, which can not make full use of the catalytic active sites in porous silica. Moreover, even if the reactants are small enough to enter the pores, a slow mass transport to and away from the catalytic cen-ters can increase the possibility of secondary reactions. To data, creation of hierarchical pores to silica has been proven to be a key approach to overcome this problem. In addition, functionalization of silica can improve its chemical inertness and catalyze specific chemi-cal reactions. Therefore, we functionalized porous silica with metal-doped, organic group modification and metal oxides loading.We fabricated a series of functionalization hierar-chical pores silica materials, and researched the effects of the hierarchical pores structure to the catalytic activity of pores silica composite materials.The micro-meso porous silica materials doped with iron oxide were prepared by the combination of molecular imprinting technique and sol-gel method with the assistance of organosilicon. The best ratio of inorganic silicon and organic silicon is 7:1, and the best ratio of silicon and iron is 15:1. The obtained materials were used to catalyze the hydroxylation of phenol, and the conversion rate is 22.1% at 2 h, which is higher than the 16.2% of mesoporous silica. The results showed that the selective adsorption of reactant molecules by the imprinted microporous was beneficial to the improvement of catalytic efficiency of the catalyst.Multicore-shell structure silicate materials with bimodal mesoporous was prepared via a microemulsion-polymerization-assisted approach, the ultrasmall iron oxide parti-cles is movable inside the mesoporous silica shell. The pore size, catalytic activity and magnetism of the materials could be regulated by vary the ratio of iron oxide particles to styrene. The obtained catalyst was applied as an effective heterogeneous catalyst for hydroxylation of phenol, and the conversion rate of phenol is 31.5%, the selectivity to hydroquinone is 97.4%. The catalytic activity of the obtained catalyst is higher than the Fe2O3 nanoparticles. The total oxidation of methylene blue with aqueous hydrogen per-oxide further confirm that the unique bimodal mesoporous structures of the catalyst is beneficial to improve the oxidation performance of the catalyst.Importantly, the catalyst can be easily recovered by external magnetic field and reused in successive catalytic cycles without significant loss of activity.Titanosilicate zeolite beads with hierarchical porosity and 0.2-1.0 mm of diameter have been synthesized from a titanosilicate solution, employing a porous anion-exchange resin as shape and structure-directing template. The characterization results showed the existence of crystalline TS-1 nanoparticles and of a network of connected large meso/macropores in the interior of the beads. These bead-materials are active and selective heterogeneous catalysts in two classes of industrially relevant oxidation reactions:the hydroxylation of phenol and the epoxidation of alkenes. The TOF of phenol is 49.7 h-1, which is similar to that of TS-1 (52.5 h-1.The TOF of alkenes is 23.3 h-1 with the bead as catayst, which is higher than that of TS-1 (8.0 h-1). The improved catalytic performance of the titanosilicate beads is mainly ascribed to the large meso/macropores favoring the diffusion of reagents and products to and from the titanium active sites. Notably, the bead format of these cat-alysts causes their spontaneous settling upon stopping of the agitation, thus enabling their straightforward separation from the reaction mixture. In addition, the effective utilization rate of hydrogen peroxide rate reaches 48.2% with the HPB-TS-1 as catalyst, which is far higher than the hierarchical mesoporous silica based catalytic materials containing iron.A new and facile method has been developed for the fabrication of hollow γ-Fe2O3/TS-1 composite microspheres by hydrothermal process with the assistance of citric. The shell of the hollow microspheres construct by nano-Fe2O3 intermeshed with TS-1 nanocrys-tal, and citric is the bridge to connect the nano-Fe2O3 together with TS-1 nanocrystal through hydrogen bond. And plenty of microporous and mesoporous existence in the shell. The hollow γ-Fe2O3/TS-1 composite microspheres served as Fenton-like catalyst show high catalytic activity in degradation of phenol due to the the unique structure and the synergistic effect between the nano-Fe2O3 and the isolated Ti4+ in the framework of the titanosilicate zeolite. The titanosilicate zeolites in the hollow composite microsphere improve the stability and catalytic activity of iron oxide nanoparticles. Importantly, the superparamagnetism of the catalystfacilitates its separation, recycling and utilization.