Understanding the Role of NbO_x on Pt/Al₂O₃ for Effective Catalytic Propane Oxidation

Abstract

Catalytic combustion is an effective way to eliminate volatile organic compound (VOC) pollution, such as propane. However, it is still a significant challenge to develop effective catalysts. Herein, we report NbO x -doped Pt/Al2O3 catalysts synthesized by a facile impregnation method for effective propane oxidation. New types of acidic sites are generated on the surface of Pt/Al2O3 when NbO x is added, and the acidity is gradually improved. NbO x is beneficial for the formation of Pt0 species, which obviously improves the catalytic performance. Pt-10Nb/Al2O3 gives the highest propane conversion (86.6%) at 250 °C. Furthermore, the prereduced Pt-10Nb/Al2O3-R with more Pt0 content shows higher conversion (90.1%). The specific reaction rate of Pt-Nb/Al2O3 is related to the Pt0/(Pt0 + Pt2+) ratio. Pt-10Nb/Al2O3-R with the Pt0/(Pt0 + Pt2+) value of 0.86 rather than Pt-15Nb/Al2O3 with a higher one gives the highest specific reaction rate of 76.1 μmol gPt –1 s–1, which may be attributed to the synergistic roles of Pt0 and Pt2+ species.

Insights into Different Reaction Behaviors of Propane and CO Oxidation over Pt/CeO2 and Pt/Nb2O5: The Crucial Roles of Support Properties

“…It is clear that the Pt/CeO 2 catalyst contains only oxidized Pt species (mainly Pt 2+ species), while a small portion of metallic Pt 0 species (with a concentration of 6.3%) can be observed in the Pt/Nb 2 O 5 catalyst. The presence of metallic Pt species in Pt/Nb 2 O 5 catalyst can be ascribed to the promoted reduction of PtO x species by the abundant medium strong and strong acid sites in Nb 2 O 5 (Figure c), namely, the strong acid sites enhance the reducibility of PtO x species, which is consistent with the previous works . Regarding the O 1s XPS spectra (Figure b), three oxygen species (e.g., O a , O b , and O c ) are observed in the Pt/CeO 2 and Pt/Nb 2 O 5 catalysts.…”

“…Figure shows the XPS spectra of Pt 4f and O 1s of the Pt/CeO 2 and Pt/Nb 2 O 5 catalysts. In Figure a, the peaks with binding energies (BEs) at 71.6 and 74.8 eV can be attributed to Pt 4f 7/2 and Pt 4f 5/2 of Pt 0 species, respectively . The peaks with BEs of 72.7 and 76.0 eV correspond to Pt 4f 7/2 and Pt 4f 5/2 of Pt 2+ species, respectively.…”

“…In addition, the oxides supports may has some features which would affect the catalytic activity. For instance, it is known to all that CeO 2 contains abundant oxygen vacancies, while the transition metal oxide of Nb 2 O 5 possesses more strong acid sites. , Zhao et al found that new types of acidic sites generated on the surface of Pt/Al 2 O 3 , and the reducibility of PtO x species and oxidation resistance of Pt 0 species were improved after addition of Nb 2 O 5 promoter, which obviously enhanced the catalytic performance. Nb 2 O 5 oxide is considered to be favorable for activation the C–O bond and C–C bond .…”

Modification of Beta Zeolites and Their Application in Catalytic Oxidation of Propane

“…Developing efficient and appropriate methods to reduce propane emissions is of great significance to improve the environment. [11][12][13][14] In the past, most people used precious metals to catalyze the degradation of waste gas such as propane, for instance, Garetto et al studied the deep oxidation of propane on platinum loaded beta molecular sieves, they found that propane combustion on Pt-supported catalysts would proceed then via two simultaneous mechanisms, which the main oxidation pathway on platinum and a contributing oxidation pathway on the metal-oxide interfacial region. The subsequent oxidation mechanism increased the density of propane molecules adsorbed in the interface region.…”

Catalytic Combustion of Propane over Pt-Mo/ZSM-5 Catalyst: The Promotional Effects of Molybdenum

“…The catalysts with 5% W loading had the highest content of Pt 0 and exhibited the best catalytic activity as well as enhanced stability. Luo's Group [25] prepared Pt-Nb/Al 2 O 3 catalysts and found that the doping of Nb could significantly increase the content of Pt 0 . The authors declared that the increase in catalytic combustion activity of propane was the result of the combined effect of Pt 0 and Pt 2+ .…”