Aerosol Route to TiO₂–SiO₂Catalysts with Tailored Pore Architecture and High Epoxidation Activity

Abstract

Herein, we present the aerosol-assisted sol − gel preparation of hierarchically porous TiO 2 − SiO 2 catalysts having a spherelike shell morphology and a high Ti dispersion. In order to control the porosity at the micro-, meso-, and macrolevels, we use the evaporation-induced self-assembly (EISA) of a surfactant, possibly combined with polymer beads as hard templates. These catalysts are tested for the epoxidation of cyclohexene with cumene hydroperoxide as the oxidant, and their performance is compared to the reference TS-1 zeolite. The high catalytic performance observed with the catalysts prepared by aerosol stems from their high speci fi c surface area, but also from the short di ff usion path length generated by the meso-/macropore architecture which provides entryways for bulky reactants and products. Besides, these materials can incorporate a higher Ti loading than TS-1 zeolite, while ensuring a good control over the Ti speciation. Thus, the unique features of the aerosol process which is also known to be scalable allow us to prepare catalytic materials with high epoxidation activity, also for bulky olefins.

Hybrid chemoenzymatic heterogeneous catalyst prepared in one step from zeolite nanocrystals and enzyme–polyelectrolyte complexes

“…On the rst hand, aerosol processing is well suited for the preparation of many types of inorganic heterogeneous catalysts. [39][40][41][42][43][44][45][46][47] In fact, aerosol methods were already demonstrated to be successful and scalable to form TS-1 microspheres with a hierarchical porosity. 48 On the second hand, spray drying is also widely used to dry proteins for food and pharmaceutical applications.…”

Hollow zeolite microspheres as a nest for enzymes: a new route to hybrid heterogeneous catalysts

“…This pore size is related to the templating effect of F127 micelles, swollen due to the additional incorporation of TPA + cations. 35,65 Thus the shell of the hollow spheres is porous enough to allow for the diffusion of individual GOx, whose size is 6.0 Â 5.2 Â 7.8 nm 3 . 66 To have a better insight into the macroporosity of the aerosolmade catalyst, a Hg porosimetry experiment was carried out.…”

“…A rst way to increase the enzyme loading could be to immobilize it onto a Ti-SiO 2 epoxidation catalyst possibly prepared by a bottom-up sol-gel approach to generate larger pores. 34,35 Such mesostructured materials may possess a much larger accessible surface area for the enzyme coupled with a higher silanol content, allowing to increase the enzyme loading. Yet, in the presence of water (which is required for the enzyme) such amorphous mixed oxides rapidly deactivate.…”

CO2 Hydrogenation to Methanol with Ga‐ and Zn‐Doped Mesoporous Cu/SiO2 Catalysts Prepared by the Aerosol‐Assisted Sol‐Gel Process**

“…[29] Leveraging on sacrificial pore-generating agents, the texture of the materials can be fine-tuned. [26,30] The versatility of sol-gel chemistry gives access to a wide range of materials. Interestingly, the rapid drying of the droplets allows forming solids in metastable states, including highly homogeneous metallosilicates, which are of great interest in the field of heterogeneous catalysis.…”