Promoting effect of Pd modification on the M/TiO2 (M = V, Ce, Mn) catalyst for catalytic oxidation of dichloromethane (DCM)

Oxidation of Methanol and Dichloromethane on TiO2-CeO2-CuO, TiO2-CeO2 and TiO2-CuO@VUKOPOR®A Ceramic Foams

The application-attractive form of TiO₂, CeO₂ and CuO-based open-cell foam supported catalysts was designed to investigate their catalytic performance in oxidation of two model volatile organic compounds-methanol and dichloromethane. TiO₂-CeO₂, TiO₂-CuO and TiO₂-CeO₂-CuO catalysts as thin films were deposited on VUKOPOR^®A ceramic foam using a reverse micelles-controlled sol-gel method, dip-coating and calcination. Three prepared catalytic foams were investigated via light-off tests in methanol and dichloromethane oxidation in the temperature range of 45-400 °C and 100-500 °C, respectively, at GHSV of 11, 600 h^-1, which fits to semi-pilot/industrial conditions. TiO₂-CuO@VUKOPOR^®A foam showed the best catalytic activity and CO₂ yield in methanol oxidation due to its low weak Lewis acidity, high weak basicity and easily reducible CuO species and proved good catalytic stability within 20 h test. TiO₂-CeO₂-CuO@VUKOPOR^®A foam was the best in dichloromethane oxidation. Despite of its lower catalytic activity compared to TiO₂-CeO₂@VUKOPOR^®A foam, its highly-reducible -O-Cu-Ce-O- active surface sites led to the highest CO₂ yield and the highest weak Lewis acidity contributed to the highest HCl yield. This foam also showed the lowest amount of chlorine deposits.

Catalytic Oxidation of Propane and Carbon Monoxide by Pd Nanoparticles on Mn/TiO2 Catalysts

The present work shows experimental results on the catalytic oxidation of C3H8 and CO by Pd nanoparticles supported on MnOx/TiO2 synthesized by the sol–gel method. The results show a strong interaction between Pd and MnOx/TiO2; likewise, the annealing temperature of the TiO2 support modified the catalytic properties of the Pd–MnOx/TiO2 catalyst. In this line, the catalysts with 1 and 2 wt% of Pd loading supported on MnOx/TiO2 showed outstanding catalytic activity oxidizing C3H8 and CO within two temperature intervals: 200–400 °C and 25–200 °C, respectively. The Pd–MnOx/TiO2 catalyst also displayed very high stability during long-term tests and the addition of Pd nanoparticles reduced greatly the oxidation temperature of MnOx/TiO2. The outcomes revealed that the Pd–Mn interaction promoted the formation of new Pd0/Pd2+ active sites as well as the formation of oxygen vacancies and reduced Ti4+ to Ti3+ species, which led to the improvement of the Mn3+ and Mn4+ redox features, thus boosting the catalytic oxidation capacity of the Pd–MnOx/TiO2 catalyst.

Graphical Abstract

Catalytic ozonation of dichloromethane at low temperature and even room temperature on Mn-loaded catalysts

Five Mn-loaded catalysts were synthesized on γ-Al₂O₃, TiO₂, ZrO₂, nano γ-Al₂O₃ and nanoZrO₂ supports. The catalytic ozonation of DCM (dichloromethane) was evaluated under industrial conditions (i.e., temperature, O₃ input, H₂O and SO₂ content). According to results, >90% DCM conversion without O₃ residue was achieved for all samples at 120 °C and an O₃/DCM ratio of 6. At 20–120 °C, the highest Mn³⁺ content, abundant surface oxygen species and more weak acid sites led to the best performance of Mn/nanoAl₂O₃ (M/A-II). At 20 °C and 120 °C, 80% and 95% DCM can be degraded respectively on M/A-II at 20 °C with matched surface oxygen species and acidity. An O₃/DCM ratio of 6 was optimal for performance and economy. For the effects of complex exhaust, both H₂O and SO₂ deactivated M/A-II. The H₂O-induced deactivation was recoverable and also removed surface-deposited chlorine-containing species, enhancing the HCl selectivity. Finally, the Cl equilibrium of the reaction was comprehensively analyzed.

The collaboration of abundant surface oxygen species and weak acid sites at low temperatures ensures the best functioning of M/A-II.