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Active states of palladium and copper for the oxidative carbonylation of phenol and bisphenol-A were investigated using X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) for Pd and Cu K-edges. The initial states of Pd and Cu were carbon-supported metallic Pd and cuprous oxide, respectively. During oxidative carbonylation, however, the metallic character of palladium was enhanced, as indicated by Pd K-edge XANES spectra taken before and after the reaction. Furthermore, Pd&z.sbnd;Pd coordination number increased from ca. 6.0 to 11.0, as determined by the quantitative EXAFS analyses of Pd K-edge. The initial crystalline cuprous oxide was converted by reaction with Bu4NBr into an unusual linear cuprous dibromide complex stabilized by tetrabutylammonium cation. Qualitative XANES and EXAFS analyses of Cu K-edge identified the structural and electronic configuration of the cuprous complex that was found to be the active main catalyst. There was a direct correlation between the formation of the cuprous complex and the catalytic activity and selectivity. Based on these results, a possible catalytic reaction scheme was proposed for the oxidative carbonylation of phenols with the catalytic system of Pd/C, an inorganic cuprous compound and Bu4NBr. [Copyright &y& Elsevier]

Based on previous observation that the addition of manganese onto Ni/Al2O3 catalysts reduced the coke formation in the carbon dioxide reforming of methane, effects of the preparation method for Mn-promoted Ni/Al2O3 catalysts on the catalytic activity and stability were investigated. A coprecipitated catalyst, Ni–MnOx/MnAl2O4, showed higher coke resistance and more stable activity than an impregnated Ni/MnO/γ-Al2O3 catalyst and the well-known Ni0.03Mg0.97O catalyst at 923 K with a feed gas ratio CH4/CO2 of 1 without a diluent gas. In coprecipitated Ni–MnOx/MnAl2O4 catalysts, MnAl2O4, γ-Al2O3, and Ni(0) were observed as major crystalline phases with XRD and potassium was detected on the surface with EPMA. Comparison of H2 chemisorption and XRD suggested that the surface of large metallic nickel particles was partly blocked by manganese oxides, and the structure was confirmed by XAFS. For impregnated Ni/MnO/γ-Al2O3 catalysts, addition of potassium stabilized its catalytic activity further, to the level achieved by coprecipitated Ni–MnOx/MnAl2O4 catalysts. These results indicate that very stable Ni/Al2O3 catalysts for the carbon dioxide reforming of methane can be prepared by addition of both potassium and manganese as promoters. [Copyright &y& Elsevier]

[Display omitted] • Pt/UiO66-xNH 2 catalysts were synthesized by the microwave-solvothermal method. • TOF Pt over Pt/UiO66-NH 2 catalysts were 1.8–3.2 times higher than that of Pt/UiO-66. • Transferring from DCOx to HDO reaction, confirmed by increase in C 18 /C 17 ratio. • Showing a good catalytic stability for coke deposition during HDO reaction. With the aim of developing more efficient catalysts based on MOF materials for biomass upgrading through the hydrodeoxygenation, a novel Pt/UiO-66-based catalyst was first designed by introducing amino groups, together with creating mixing-linker defect using 5-amino-isophthalic acid as a mixed linker, were successfully synthesized with a microwave-solvothermal method. XPS and CO-chemisorption measurements revealed that the presence of amino groups significantly enhance the reducibility of the PtCl 6 2- and PtCl 4 2- phases to the Pt0 phase. As a result, the catalytic performance of these catalysts in the HDO of oleic acid was enhanced, as demonstrated by the 1.8–3.2-fold higher turnover frequency compared to the original Pt/UiO-66 catalyst. Interestingly, the presence of amino-defective linker facilitated the transition from decarbonylation to the hydrodeoxygenation reaction, as confirmed by the significant increase in C 18 /C 17 ratio. Importantly, the modified catalysts were shown to possess a good catalytic stability, thus preventing coke deposition on the UiO-66 structure. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A new core@shell catalyst is developed for partial methane oxidation. • SiO 2 @V 2 O 5 @Al 2 O 3 nanostructure is an efficient and thermally stable catalyst. • The thickness of Al 2 O 3 shells over SiO 2 @V 2 O 5 cores can be controlled. • SiO 2 @V 2 O 5 @Al 2 O 3 -(50) nanostructures feature the best catalytic activity at 600 °C. • A highly disperse vanadium species is formed. Abstract The stable tetrahedral geometry and high C H bond dissociation energy of methane complicate its direct catalytic conversion; for example, the selective oxidation of methane to formaldehyde, which avoids the production of carbon dioxide by full oxidation and is therefore important for the versatile utilization of natural gas, is still viewed as challenging. Here, we utilize hydrothermal synthesis followed by atomic layer deposition (ALD) to prepare an efficient and thermally stable catalyst based on novel SiO 2 @V 2 O 5 @Al 2 O 3 core@shell nanostructures, showing that the thickness of Al 2 O 3 shells over SiO 2 @V 2 O 5 cores can be tuned by controlling the number of ALD cycles. Catalytic methane oxidation experiments performed in a flow reactor at 600 °C demonstrate that SiO 2 @V 2 O 5 @Al 2 O 3 nanostructures obtained after 50 ALD cycles exhibit the best catalytic activity (methane conversion = 22.2%; formaldehyde selectivity = 57.8%) and outperform all previously reported vanadium-based catalysts at 600 °C. The prepared catalysts are subjected to in-depth characterization, which reveals that their Al 2 O 3 shell provides new surfaces for the generation of highly disperse T d monomeric species with a V O Al bond by promoting interactions between Al 2 O 3 and V 2 O 5 nanoparticles during ALD. Moreover, the surface Al 2 O 3 shell is found not only to protect V 2 O 5 nanoparticles against sintering at 600 °C, but also to anchor the produced T d monomeric vanadium species responsible for the high catalytic performance. [ABSTRACT FROM AUTHOR]