Optimizing the Microstructure of SnO₂–CeO₂ Binary Oxide Supported Palladium Catalysts for Efficient and Stable Methane Combustion

Abstract

The preparation of palladium-based catalysts with both high catalytic activity and hydrothermal stability currently appears as a critical topic in methane combustion. Herein, we propose a facile strategy to boost the performance of SnO2–CeO2 binary oxide supported palladium catalysts by tuning the composition of supports. The coexistence of SnO2 and CeO2 phases in an appropriate ratio is favorable for the formation of both Pd x Ce1–x O2−δ and Pd x Sn1–x O2−δ solid solutions due to the reduced crystallite size. This unique microstructure could enhance the metal–support interaction to stabilize the active PdO phase and promote its reoxidation, meanwhile generating more oxygen vacancies to improve the reducibility of PdO. On account of the facilitated conversion of PdO ↔ Pd, coupled with the low-temperature dissociation of methane promoted by abundant active oxygen species, the Pd/5Sn5Ce catalyst exhibits a superior catalytic activity with a T 99 of ca. 360 °C, a robust stability under both dry and wet conditions, and an excellent thermal stability during heating–cooling light-off tests.

Enhanced Methane Combustion Performance over Zinc-Aided Co3O4 by Engineering the Reactivity of Active Oxygen Species

“…Meanwhile, a further increment in the Zn content afforded less oxygen vacancies and thus inferior catalytic efficiency. These verified the vital role of oxygen vacancies in CH 4 oxidation. ,,,, According to the Mv-K model, the lattice oxygen was first extracted, and then, the oxygen vacancies were created in the initial sites, which should be replenished through the effective oxygen spillover from oxygen in the gas phase to regenerate the surface O latt and then finish the catalytic cycle . Rich oxygen vacant sites could serve as a reservoir for the surface lattice oxygen and confer the O latt adjacent to oxygen vacancies more active. , The effect of Zn on the ability of catalysts to extract surface lattice oxygen was proven by XPS, H 2 -TPR, and O 2 -TPD results.…”

“…It was established that oxygen vacancy could be created and diffused easily, playing an important part in catalytic oxidation for Co 3 O 4 -based materials. 55,58 50,55,58,62,63 According to the Mv-K model, the lattice oxygen was first extracted, and then, the oxygen vacancies were created in the initial sites, which should be replenished through the effective oxygen spillover from oxygen in the gas phase to regenerate the surface O latt and then finish the catalytic cycle. 16 Rich oxygen vacant sites could serve as a reservoir for the surface lattice oxygen and confer the O latt adjacent to oxygen vacancies more active.…”

Size-Controlled Palladium Nanoparticles Encapsulated in Silicalite-1 for Methane Catalytic Combustion

“…Water vapor would accelerate the deactivation of Pd-based catalysts at a low temperature due to the competitive adsorption between H 2 O and CH 4 ; the hydroxyls would block the metal site and inhibit the activation of CH 4 . , In this work, 5 vol % water vapor was introduced into the reactor to investigate the water resistance of these samples. As mentioned above, the influence of hydroxyl species usually works at a relatively low temperature (<450 °C) of the methane combustion reaction; , thus, the water resistance test was performed at 380 °C. As shown in Figure S13a, the activity of Pd/S-1-in catalysts significantly decreased due to the presence of water vapor.…”

“…29,30 In this work, 5 vol % water vapor was introduced into the reactor to investigate the water resistance of these samples. As mentioned above, the influence of hydroxyl species usually works at a relatively low temperature (<450 °C) of the methane combustion reaction; 31,32 thus, the water resistance test was performed at 380 °C. As shown in Figure S13a, the activity of Pd/S-1-in catalysts significantly decreased due to the presence of water vapor.…”

Synthesis of Heteroatom Pd-ZrOx Species on Zeolite for Complete Methane Oxidation

“…Oxide- (such as Al 2 O 3 , CeO 2 , ZrO 2 , etc.) supported Pd-based catalysts have also been widely studied for complete methane oxidation reactions. − Among them, ZrO 2 has its own unique advantages including acid–base amphoteric substances, high stability, and so on. , Especially, some evidence indicates that the interaction between Pd and ZrO 2 would promote the dispersion of Pd. − However, it is still difficult to obtain highly dispersed Pd species on ZrO 2 due to the small surface area of zirconia, which limits the catalytic performance of a ZrO 2 -supported Pd-based catalyst for complete methane oxidation. − We propose that the advantage of a large surface area of zeolite can be combined to prepare highly dispersed zirconia species on zeolite by decreasing the content of Zr and further controllably prepare Pd on highly dispersed Zr species to improve the dispersion of Pd. As a result, enhanced catalytic performance for complete methane oxidation could be achieved.…”