Kinetic regularities, catalyst deactivation and reactivation

Funding text 1 The research is funded from Ministry of Education and Science of the Russian Federation Program No. 075–03–2021–287/6 (Russia). Funding text 2 XPS measurements were carried out at the Central laboratories of Tomsk Polytechnic University (Analytical Center). HRTEM was carried out at the Innovation centre for Nanomaterials and Nanotechnologies of Tomsk Polytechnic University. The ICP-OES analysis was carried out using the core facilities of “Physics and Chemical methods of analysis” of Tomsk Polytechnic University. Fundação para a Ciência e a Tecnologia for Scientific Employment Stimulus Institutional Call (CEECINST/00102/2018), UIDB/50006/2020 and UIDP/50006/2020 (LAQV), UIDB/00100/2020 and UIDP/00100/2020 (Centro de Química Estrutural).Betulin, being a pentacyclic triterpene alcohol and an extractive from birch bark, along with its oxo-derivatives, has a broad range of physiological properties of interest for synthesis of pharmaceuticals. Instead of oxidizing betulin with strong and toxic oxidizing agents the present study shows a possibility of using liquid-phase oxidation of betulin with air over supported Ag NPs catalysts as an alternative method for synthesis of its oxo-derivatives. Based on catalytic studies, high resolution transmission electron microscopy, X-ray photoelectron spectroscopy and ultraviolet-visible diffuse reflectance spectroscopy, the evolution of the surface of nanosilver catalysts during the catalysis was demonstrated, as well as under the impact of reactant gas composition. The kinetic regularities and causes of deactivation of supported Ag NPs catalysts were revealed. An approach to the regeneration of silver catalysts was proposed. Kinetic analysis with numerical data fitting was performed resulting in an adequate description of the concentration dependencies.publishersversionpublishe

Reductive Amination of Ketones with Benzylamine Over Gold Supported on Different Oxides

Reductive amination of cyclohexanone with benzylamine was investigated at 100 °C under 30 bar hydrogen in toluene with five different gold catalysts prepared by deposition–precipitation method and supported on TiO2, La2O3/TiO2, CeO2/TiO2, La2O3 and CeO2. Size of metallic gold varied in the range of 2.6–3.6 nm. The best catalysts in reductive amination of cyclohexanone with benzylamine were 4 wt% Au/TiO2 and 4 wt% Au/CeO2/TiO2 giving 72% and 79% yield of the desired amine. The most acidic and basic catalysts were also unselective and exhibited low activity towards imine hydrogenation. The best catalyst 4 wt% Au/CeO2/TiO2 gave in reductive amination of propiophenone 56% selectivity to the corresponding amine at 20% conversion in 5 h.</p

Modified Ag/TiO2 systems: Promising catalysts for liquid-phase oxidation of alcohols

The current work is the first study concerning the liquid-phase oxidation of n-octanol and betulin over modified and unmodified Ag/TiO2 catalysts. Catalytic activity of nanosilver catalysts supported on titania for alcohols selective oxidation can be enhanced by modification of the support with Ce, Fe or Mg oxides. In most cases reductive or oxidative pretreatments of these catalysts were detrimental for their activity. The main reason for performance of Ag/MxOy/TiO2 catalysts is changes of the electronic state of the supported Ag, and especially changes in the surface concentration of Ag+ ions. Monovalent Ag+ ions are active sites in silver-containing catalysts for n-octanol, as well as for betulin oxidation. The obtained results show a potential of silver-containing catalysts for liquid phase oxidation of alcohols, and by selecting the optimum modifier and the support as well as, pretreatment conditions the catalytic properties and stabilization of the active sites can be optimized

Modified Ag/TiO2 systems: Promising catalysts for liquid-phase oxidation of alcohols

The current work is the first study concerning the liquid-phase oxidation of n-octanol and betulin over modified and unmodified Ag/TiO2 catalysts. Catalytic activity of nanosilver catalysts supported on titania for alcohols selective oxidation can be enhanced by modification of the support with Ce, Fe or Mg oxides. In most cases reductive or oxidative pretreatments of these catalysts were detrimental for their activity. The main reason for performance of Ag/MxOy/TiO2 catalysts is changes of the electronic state of the supported Ag, and especially changes in the surface concentration of Ag+ ions. Monovalent Ag+ ions are active sites in silver-containing catalysts for n-octanol, as well as for betulin oxidation. The obtained results show a potential of silver-containing catalysts for liquid phase oxidation of alcohols, and by selecting the optimum modifier and the support as well as, pretreatment conditions the catalytic properties and stabilization of the active sites can be optimized