Effect of support on the apparent activity of palladium oxide in catalytic methane combustion

Abstract

The support effect on the low temperature catalytic oxidation of methane over palladium catalysts was studied by comparing a series of metal oxides as the support. Samples of 0.010 g/g Pd catalysts supported on different grades and/or phases of TiO2, Al2O3, and ZrO2 were prepared via incipient impregnation and their catalytic activity was evaluated using a laboratory plug‐flow reactor. The specific surface area of the supports determined by nitrogen adsorption varied from about 13‐220 m2/g. Initial experiments conducted with titania (anatase) as a support showed a low apparent activity and a poor thermal stability. Focusing on anatase, we have successfully improved its thermal stability by additions of Al2O3 or by doping with CeO2, or La2O3. However, contrary to expectations based on some information in the literature, we have found that the activity decreased in the sequence of Al2O3 > ZrO2 > TiO2, and was not a direct function of specific surface area. This was especially evident in the case of titania. The surface structure of the support and the nature of its interaction with the active component PdO seem to play a far more important role in activity than the apparent specific surface area. Moreover, anatase‐supported catalysts present a very rapid deactivation, whereas rutile‐supported catalysts are relatively stable. The observed phenomena could potentially be related to the interaction between support and the active phase of palladium. Several models have been proposed to describe the strong metal‐support interaction, but either charge transfer or encapsulation seems to be the most probable.

Synthesis of Vinyl Acetate Monomer Over PdCu Alloys: The Role of Surface Oxygenation in the Reaction Path

“…[109] These modifications also create vacancies in surface oxidative processes, which can enhance catalytic activity. [110] In this study, we observed improvements in the oxidation and reduction processes of oxygen in the catalyst, as evidenced by experimental results demonstrating higher mobility of coordinated oxygen atoms in each crystalline phase. [111] We compared this improvement to that of the PCZA catalyst, which Al +2 is commonly used for acetoxidation processes on PdAu (100) surfaces.…”

Will It Be Possible to Put into Practice the Mitigation of Ventilation Air Methane Emissions? Review on the State-of-the-Art and Emerging Materials and Technologies

“…In the article [102], it is indicated that Pd on Al 2 O 3 support had a higher activity than Pd-Pt or Pd-Pt-Rh on the same support. Activity of Pd over alumina, zirconia, and anatase-support in [101] for the same temperature was different. Modification by Ca addition led to high oxygen mobility and strong Pd support interaction [82].…”

“…Catalytic performance is strongly dependent on the nature of the support [75,95,101] and depends on the interaction between the support and active phases [81]. The comparison of the influence of additives in catalysts by various authors on a chemical reaction is not easy.…”

Current Progress on Methods and Technologies for Catalytic Methane Activation at Low Temperatures

“…[103] TiO 2 can improve metal dispersion due to its large specific surface area and potent affinity for noble metals. [104] Moreover, as sulfating support, Ti-containing catalysts display higher tolerance toward SO 2 and H 2 O. [105] Through an ultrasonic-assisted sol-gel method, Ti was introduced into an alumina carrier.…”