Mesoporous Sn‐TiO₂ Catalysts by Molecular Protection Strategy for the Baeyer‐Villiger Oxidation of Cyclohexanone with Molecular Oxygen

Abstract

In order to improve the catalytic performance of tin-doped samples in the Baeyer-Villiger oxidation of cyclohexanone with molecular oxygen as oxidant, the mesoporous Sn-TiO 2 catalysts with more incorporation of tin species were successfully prepared via a simple vapor-phase self-assembly method followed by molecular protection strategy treated with ethylenediamine solution. The physical and chemical properties of these prepared samples can be characterized by different methods including XRD, N 2 sorption, Raman, ICP, UV-vis DRS, pyridine-adsorbed IR, SEM and TEM. The characterization results indicated that the ethylenediamine can protect the ordered mesopores of anatase TiO 2 , which would be beneficial to the more tetrahedrally homogeneous incorporation of tin species resulting in the promotion of Lewis acidity. The ordered mesoporous 18Sn-TiO 2 -EN catalyst with highest surface areas, pore volume and appropriate Lewis acidity showed the highest catalytic performance, whose cyclohexanone conversion, caprolactone selectivity and TON value were up to 94.1%, 95.2% and 3.7, respectively, and it showed good catalytic stability.

Sn‐Ti Submicrospheres with Tunable Particle Size for Cyclohexanone Baeyer‐Villiger Oxidation

“…However, it would be dropped owing to the submicrospheres aggregations when the water amount was 5.0 mL. The pore volume would gradually increase, which may be owing to the larger bond length of SnÀ O (0.205 nm) than TiÀ O (0.198 nm) [28] and the formation of some rutile TiO 2 phases resulting in the partial distortion of the mesoporous structures based on the XRD patterns.…”

TiO2-Based Water-Tolerant Acid Catalysis for Biomass-Based Fuels and Chemicals

“…This is due to the difference in ionic radii of Al and Ti that will induce the formation of distorted Al–O–Ti bonds in titania lattice, creating a greater number of coordinatively unsaturated metal sites and hence, improved Lewis acidity can be achieved. Promoting effect of dopant metal on the Lewis acidity of TiO 2 was also noticed in the case of Sn . Decoration of metal nanoparticles on TiO 2 nanotubes (NT) has also a considerable effect on Brønsted and Lewis acidity .…”

“…Promoting effect of dopant metal on the Lewis acidity of TiO 2 was also noticed in the case of Sn. 28 Decoration of metal nanoparticles on TiO 2 nanotubes (NT) has also a considerable effect on Brønsted and Lewis acidity. 29 This is due to the presence of strong metal−TiO 2 interactions via metal−O−Ti bonds that will show a direct effect on the coordination structure of metal sites and thus the acidity of metal/TiO 2 catalysts.…”

Evaporation‐Induced Self‐Assembly Method Route to TiO2−SiO2 Catalysts with Hierarchical Pores and Their Oximation of Ketones and Aldehydes

“…[24][25][26][27][28][29] However, the precursor accumulation would be happened owing to the relatively higher temperature resulting in the decreased catalytic performance. The evaporation-induced self-assembly method (EISA) has been widely applied to the preparation of mesoporous metal oxides in our group [30][31][32] because it can evaporate the solvent at a lower temperature and promote the formation of valence bonds, where it would not only conducive to the uniform dispersion for the different components, but also avoid the active elements loss by filtration operation resulting in its amount improvement. Therefore, evaporation-induced self-assembly method can be expected to prepare the titanosilicates with hierarchical pores and higher titanium content.…”