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Highlights: [•] A facile and universal self-precipitation route for mesoporous metal oxides preparation. [•] CuCeO x catalysts with high surface area and homogeneous mesostructure. [•] Catalysts combined promoted reducibility and surface oxygen concentration. [•] Mesostructured metal oxides with superior low-temperature catalytic efficiency. [•] Catalysts possess remarkable enhanced reaction rate and selectivity. [Copyright &y& Elsevier]

Abstract: A series of novel Pd/Co3AlO catalysts derived from hydrotalcite-like compounds (HTlcs) have been prepared and investigated for total oxidation of toluene. The HTlcs phase Co–Al precursors were prepared by coprecipitation method and Pd active species were introduced by different approaches, i.e., impregnation (IMP), wet ion exchange (WIE) or directly at coprecipitation stage (COP). It is found that all hydrotalcite-derived Pd/Co3AlO catalysts are much more active than the Pd/Co3AlO catalyst prepared via traditional thermal combustion method (TCB) in toluene elimination. The activities of all synthesized catalysts obey the following sequence: Pd/Co3AlO (COP)>Pd/Co3AlO (WIE)≥Pd/Co3AlO (IMP)>Pd/Co3AlO (TCB). Excellent catalytic activities of the novel hydrotalicite-derived Pd/Co3AlO catalysts could be contributed to their high surface area, small mean crystallized size of support and highly dispersed PdO particles. Besides, they are well positively associated with catalyst reducibilities and the amounts of oxygen vacancies. According to the XPS, TEM and TPR results, it was found that the strong synergistic effect between Co3O4 and PdO, but not the amount of the surface palladium species which are generally believed to be the active sites, is the main factors determining the catalytic activity in this work. The stability tests indicate that all Pd/Co3AlO catalysts have no obvious deactivation, and some catalysts even show improved activities during the reaction process due to the emergence of metal Pd. [ABSTRACT FROM AUTHOR]

In the selective catalytic reduction (SCR) of NO x with NH 3 , a catalyst usually exhibits a seesaw effect on de-NO x activity and N 2 selectivity at low temperatures. Herein, we designed metal-organic frameworks (MOFs) with dual-ligand coordination to regulate the electronic and morphological structure for a breakthrough of the seesaw effect. The developed catalyst attained a noteworthy NO x conversion exceeding 90% within 60–330 ℃ with increased N 2 selectivity. The dual-ligand coordination leads to more defects and a more uniform electron distribution for delocalization of electrons, thereby improving de-NO x activity. Furthermore, the dual-ligand coordination manifests a Si-O-Mn bond for amplifying both de-NO x activity and thermal stability. Additionally, the dual ligands and Mn produce a hollow sea-urchin-like morphology with more exposed active sites for concentrating reactants and intermediates to improve electron transfer efficiency in N 2 selectivity. This work clarifies the mechanism of dual-ligand regulation for electron-morphology to simultaneously enhance de-NO x activity and N 2 selectivity. [Display omitted] • TEOS&Mn-BTC with more defects and structure tunability is designed by dual-ligand coordination. • Si-O-Mn bond formed by dual ligands leads to electron-metal-carrier coordination structure. • Self-assembly of block copolymers with ligands and Mn forms hollow sea-urchin-like microsphere. • The electron-morphology regulation breaks the seesaw effect between activity and selectivity. [ABSTRACT FROM AUTHOR]

Reactivity loss by intermediates aggregation and water vapor inhibition are two major and longstanding challenges for the noble-metal-based catalysts in oxygenated volatile organic compounds (OVOCs) oxidation. Herein, the core-shell Pd@CoO Janus sites are creatively designed and stabilized over the HSAPO-34 support. Quasi in situ XPS spectra reveal that the strong interactions in Pd@CoO Janus sites promote the charge redistribution and electron back-donation through Pd-O-Co coordination. Therefore, abundant positively charged Pd2+ sites are formed and oxygen species transformation is facilitated, which significantly promote the low-temperature efficiency of acetone oxidation. Furthermore, the Pd@CoO/HSAPO-34 catalyst facilitates H 2 O molecules dissociation and produce reactive OH Ter and OH Tri species, which considerably promotes the rapid decomposition of aldehyde intermediate via attacked CH 2 O* group, ensuring low-temperature oxidation of acetone. This work provides valuable guidance to develop specific catalysts with functional active sites for rationally utilizing H 2 O molecules to improve low-temperature performance and modulate reaction pathways during OVOCs oxidation. [Display omitted] • Thermal-depolymerization was employed to synthesize the Pd@CoO Janus sites. • Charge redistribution through Pd-O-Co coordination facilitates reactant activation. • Positively charged Pd2+ and activated Co-O coordination promote acetone oxidation. • Pd@CoO/HSAPO-34 catalyst facilitates the dissociation of H 2 O molecules. • Surface OH Tri and OH Ter groups accelerate aldehyde intermediate degradation. [ABSTRACT FROM AUTHOR]

Abstract: The catalytic reduction behaviors of N2O by CH4 have been investigated over Fe-USY catalyst by examining the influences of CH4, NO, O2, or their mixtures in detail. The observations show that NO and O2, which inevitably exist in the gases emitted from industrial sources, such as the nitric acid plant, inhibit the selective catalytic reduction of N2O by CH4 (N2O–CH4 SCR) to some degree, shifting the temperature for >90% N2O conversion to over 450°C. The prohibition of O2 can be ascribed to its occupying active sites and oxidizing CH4-derived intermediates. The negative effect of NO is very prominent, inhibiting the N2O conversion by strongly occupying the active sites and gradually moving the reaction pathways from N2O–CH4 SCR to NO-assisted N2O decomposition, where the former is more efficient than the latter for N2O decomposition under the same operation conditions. In addition, the amount of reducing agent CH4 has also influenced the N2O conversion profile. [Copyright &y& Elsevier]

We investigated the industrially important PtSn/Al 2 O 3 catalysts prepared with uniform particle sizes (∼ 1 nm) and varied compositions using molecular complexes of Pt(II) and Sn(II). Our best catalyst, with a Sn:Pt ratio of around 2, exhibited a high initial propylene productivity of about 1.1 mol C 3 H 6 (g catalyst)−1 h−1. Elaborate electron microscopy studies revealed significant compositional variations in the catalyst, highlighting the practical challenges in achieving or confirming the theoretically predicted optimum Sn:Pt ratio. It is also found that the catalytic activities correlate well with the Pt dispersion, suggesting the structure-insensitive nature of the dehydrogenation reaction applies to these ultrasmall Pt-Sn nanoparticles. The presence of Pt-rich particles in the catalysts did not produce noticeable degradations in the reaction selectivity, indicating a wide composition range for Pt-Sn nanoparticles to be effective at the 1 nm size range. These findings emphasize the importance of detailed analysis of compositional distributions for understanding and optimizing nanoalloys. [Display omitted] • PtSn/Al 2 O 3 catalysts with uniform particle sizes and varied compositions are prepared using Pt(II)-Sn(II) complexes. • High initial C 3 H 6 productivity of 1.1 mol C 3 H 6 g catalyst -1 h-1 is achieved by our best catalyst with Sn:Pt ratio of around 2. • Significant compositional variations in the catalysts are revealed through comprehensive electron microscopy studies. • Structure-insensitive nature of propane dehydrogenation reaction applies to these ultrasmall Pt-Sn nanoparticles. [ABSTRACT FROM AUTHOR]