Efficient Catalytic Combustion of Cyclohexane over PdAg/Fe₂O₃ Catalysts under Low-Temperature Conditions: Establishing the Degradation Mechanism Using PTR-TOF-MS and in Situ DRIFTS

Abstract

Cyclohexane, a typical volatile organic compound (VOC), poses high risks to the environment and humans. Herein, synthesized PdAg/Fe2O3 catalysts exhibited exceptional catalytic performance for cyclohexane combustion at lower temperatures (50% mineralization temperature (T 50) of 199 °C, 90% mineralization temperature (T 90) of 315 °C) than Pd/Fe2O3 (T 50 of 262 °C, T 90 of 335 °C) and Fe2O3 (T 50 of 305 °C, T 90 of 360 °C). In addition, PdAg/Fe2O3 displayed enhanced stability by alloying Ag with Pd. The redox and acidity of the PdAg/Fe2O3 were studied by XPS, H2-TPR, and NH3-TPD. In situ diffuse reflectance infrared Fourier transform spectroscopy and proton-transfer-reaction time-of-flight mass spectrometry were applied to identify the intermediates formed on the catalyst surface and in the tail gas during oxidation, respectively. Results suggested that loading PdAg onto Fe2O3 significantly enhanced the adsorption and activation of oxygen and cyclohexane, oxidative dehydrogenation of cyclohexane to benzene, and catalytic cracking of cyclohexane to olefins at low temperatures. This in-depth study will benefit the design and application of efficient catalysts for the effective combustion of VOCs at low temperatures.

Synergistic effects of Fe-substitutional-doping and a surface close-contact Fe2O3/CeO2 heterojunction in Fe/CeO2 for enhanced CH4 photocatalytic conversion

“…However, all these peaks have shifted to the much lower temperature side for 1 : 3 Fe 2 O 3 /CeO 2 -900/6 (black line), indicating significantly improved low temperature reducibility of Fe 2 O 3 and CeO 2 in 1 : 3 Fe 2 O 3 /CeO 2 -900/6 as a result of their strong interactions. 42,43 Moreover, the first two reduction peak at low temperature (288 and 372 °C) can be attributed to the reduction of Fe 3+ in the Ce–Fe–O solid solution, 44 proving the generation of solid solution. 44,45…”

Confining Co-Based Nanocatalysts by Ultrathin Nanotubes for Efficient Transfer Hydrogenation of Biomass Derivatives

“…Furthermore, according to the high-resolution XPS spectra of O 1s in Figure c, there were three types of O species in the prepared catalysts. In the case of CoAl NT 160‑H , the deconvoluted peaks centered at 530.45, 531.46, and 532.54 eV were attributed to the O α (surface lattice oxygen), O β (defects of surface O species), and O γ (surface adsorbed O species), respectively. , Obviously, the deconvoluted peak of O α moved to lower binding energy from 530.1 eV (am-Al 2 O 3 ), to 530.57 eV (Co/am-Al 2 O 3 ) and 530.45 eV (CoAl NT 160‑H ), demonstrating the enhanced electronegativity on O species. Additionally, the binding energy of Al 2p was located at 74.34 eV for am-Al 2 O 3 (Figure S6), while it moved toward higher binding energy for Co/am-Al 2 O 3 and CoAl NT 160‑H due to the strong interaction between Co species and am-Al 2 O 3 .…”

“…In the case of CoAl NT 160-H , the deconvoluted peaks centered at 530. 45 S6), 46 while it moved toward higher binding energy for Co/am-Al 2 O 3 and CoAl NT 160-H due to the strong interaction between Co species and am-Al 2 O 3 . The above results confirmed that CoAl NT 160-H with the unique confinement effect exhibited stronger electronic interaction between Co species and am-Al 2 O 3 nanotubes, making Co NPs more electropositive.…”

Harnessing Solar Energy Towards Synergistic Photothermal Catalytic Oxidation of Volatile Organic Compounds

“…The proton transfer reaction-time of flight-mass spectrometry (PTR-TOF-MS) is an analytical tool that can provide quality information on the reaction pathways for mixed VOCs streams. [156,157] The process of scaling up could involve the substitution of expensive earth metals with more affordable options, such as post-transition metals and MXenes, which have excellent light absorption and photon-to-heat conversion efficiency, making them potentially useful for solar thermal applications. In addition, the design of various carbon polymer composites such as semiconductor/ organic polymer composites, carbon-based/organic polymer composites, and carbon-based/semiconductor composites to harvest and convert solar energy is due to the abundance of surface sites, oxygen vacancies, and high photothermal conversion efficiency.…”