1,2-Dichloroethane Deep Oxidation over Bifunctional Ru/Ce_<i>x</i>Al_<i>y</i> Catalysts

Ru/Ce_<i>x</i>Al_<i>y</i> catalysts were synthesized with impregnation of RuCl₃ aqueous solution on Ce_<i>x</i>Al_<i>y</i> (Al₂O₃–CeO₂) and used in 1,2-dichloroethane (1,2-DCE) oxidation. Characterization by X-ray diffraction, Raman, NH₃-temperature-programmed desorption (TPD), CO₂-TPD, X-ray photoelectron spectroscopy, and H₂-temperature-programmed reduction indicates that CeO₂ exists as a form of face-centered cubic fluorite structure, whereas the chemical states and the structure of Ru species are dependent on the Ce content. The reducibility and acidity of catalysts increase with Ce/Ce + Al ratio. However, the latter is promoted only in a Ce/Ce + Al range of 0–0.25 and then decreases quickly. Ru/Ce_<i>x</i>Al_<i>y</i> catalysts have considerable activity for 1,2-DCE combustion. TOF_Ru of 1,2-DCE oxidation increases with strong acid, which is ascribed to a synergy of reducibility and acidity. Ru greatly inhibits the chlorination through the decreases in both Cl deposition and CH₂CHCl formation. High stability of Ru/Ce₁₀Al₉₀ maintains at 280 °C for at least 25 h with CO₂ selectivity of 99% or higher. In situ Fourier transform infrared spectroscopy indicates that 1,2-DCE dissociates to form ClCH₂–CH₂O– species, which is an intermediate species for the production of CH₃CHO and CH₂CHCl, the former responsible for deep oxidation

Highly Active and Selective Hydrogenation of CO₂ to Ethanol by Ordered Pd–Cu Nanoparticles

Carbon dioxide (CO₂) hydrogenation to ethanol (C₂H₅OH) is considered a promising way for CO₂ conversion and utilization, whereas desirable conversion efficiency remains a challenge. Herein, highly active, selective and stable CO₂ hydrogenation to C₂H₅OH was enabled by highly ordered Pd-Cu nanoparticles (NPs). By tuning the composition of the Pd-Cu NPs and catalyst supports, the efficiency of CO₂ hydrogenation to C₂H₅OH was well optimized with Pd₂Cu NPs/P25 exhibiting high selectivity to C₂H₅OH of up to 92.0% and the highest turnover frequency of 359.0 h^–1. Diffuse reflectance infrared Fourier transform spectroscopy results revealed the high C₂H₅OH production and selectivity of Pd₂Cu NPs/P25 can be ascribed to boosting *CO (adsorption CO) hydrogenation to *HCO, the rate-determining step for the CO₂ hydrogenation to C₂H₅OH

Low-Temperature Methane Combustion over Pd/H-ZSM-5: Active Pd Sites with Specific Electronic Properties Modulated by Acidic Sites of H‑ZSM‑5

Pd/H-ZSM-5 catalysts could completely catalyze CH₄ to CO₂ at as low as 320 °C, while there is no detectable catalytic activity for pure H-ZSM-5 at 320 °C and only a conversion of 40% could be obtained at 500 °C over pure H-ZSM-5. Both the theoretical and experimental results prove that surface acidic sites could facilitate the formation of active metal species as the anchoring sites, which could further modify the electronic and coordination structure of metal species. PdO_<i>x</i> interacting with the surface Brönsted acid sites of H-ZSM-5 could exhibit Lewis acidity and lower oxidation states, as proven by the XPS, XPS valence band, CO-DRIFTS, pyridine FT-IR, and NH₃-TPD data. Density functional theory calculations suggest PdO_<i>x</i> groups to be the active sites for methane combustion, in the form of [AlO₂]­Pd­(OH)-ZSM-5. The stronger Lewis acidity of coordinatively unsaturated Pd and the stronger basicity of oxygen from anchored PdO_<i>x</i> species are two key characteristics of the active sites ([AlO₂]­Pd­(OH)-ZSM-5) for methane combustion. As a result, the PdO_<i>x</i> species anchored by Brønsted acid sites of H-ZSM-5 exhibit high performance for catalytic combustion of CH₄ over Pd/H-ZSM-5 catalysts