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Propane dehydrogenation (PDH) to propene is an important alternative to oil-based cracking processes, to produce this industrially important platform chemical.sup.1,2. The commercial PDH technologies utilizing Cr-containing (refs. .sup.3,4) or Pt-containing (refs. .sup.5-8) catalysts suffer from the toxicity of Cr(vi) compounds or the need to use ecologically harmful chlorine for catalyst regeneration.sup.9. Here, we introduce a method for preparation of environmentally compatible supported catalysts based on commercial ZnO. This metal oxide and a support (zeolite or common metal oxide) are used as a physical mixture or in the form of two layers with ZnO as the upstream layer. Supported ZnO.sub.x species are in situ formed through a reaction of support OH groups with Zn atoms generated from ZnO upon reductive treatment above 550 °C. Using different complementary characterization methods, we identify the decisive role of defective OH groups for the formation of active ZnO.sub.x species. For benchmarking purposes, the developed ZnO-silicalite-1 and an analogue of commercial K-CrO.sub.x/Al.sub.2O.sub.3 were tested in the same setup under industrially relevant conditions at close propane conversion over about 400 h on propane stream. The developed catalyst reveals about three times higher propene productivity at similar propene selectivity. Propene is obtained through propane dehydrogenation using catalysts that are toxic, expensive or demanding to regenerate with ecologically harmful compounds, but the ZnO-based alternative reported here is cheap, clean and scalable., Author(s): Dan Zhao [sup.1] [sup.2] , Xinxin Tian [sup.2] [sup.3] , Dmitry E. Doronkin [sup.4] , Shanlei Han [sup.1] [sup.2] , Vita A. Kondratenko [sup.2] , Jan-Dierk Grunwaldt [sup.4] , [...]

Improving the selectivity in the oxidative coupling of methane to ethane/ethylene poses a significant challenge for commercialization. The required improvements are hampered by the uncertainties associated with the reaction mechanism due to its complexity. Herein, we report about 90 % selectivity to the target products at 11 % methane conversion over Gd2O3‐based catalysts at 700 °C using N2O as the oxidant. Sophisticated kinetic studies have suggested the nature of adsorbed oxygen species and their binding strength as key parameters for undesired methane oxidation to carbon oxides. These descriptors can be controlled by a metal oxide promoter for Gd2O3. [ABSTRACT FROM AUTHOR]

The present study of oxidative coupling of methane (OCM) over MnOx−Na2WO4/support catalysts demonstrated that the selectivity to C2H6 and C2H4 (C2‐hydrocarbons) is affected by the kind of support, co‐fed water, and the kind of oxidant (O2 vs. N2O). In addition to previous studies with MnOx−Na2WO4/SiO2, an enhancing water effect was obtained using catalysts based on TiO2‐ or ZrO2‐containing supports. However, a negative effect on methane conversion was established for SiO2−Al2O3‐supported catalysts. Temporal analysis of products with isotopic tracers suggests that the ability of MnOx−Na2WO4 to generate diatomic adsorbed oxygen species depends on the kind of support and is the key property for the water effect. The strength of the water effect on the activity decreases with an increase in the surface area of working catalysts. The kind of support also affects products selectivity due to its influence on the mobility/releasability of lattice oxygen in supported MnOx−Na2WO4. Among the prepared catalysts, MnOx−Na2WO4/TiO2 was found to be promising for H2O‐assisted OCM. The use of N2O instead of O2 further increases the selectivity to C2‐hydrocarbons to 84 % at 6.8 % CH4 conversion due to the formation of predominantly monoatomic oxygen species from N2O that selectively convert CH4 into C2H6. [ABSTRACT FROM AUTHOR]

Knowing the structure of catalytically active species/phases and providing methods for their purposeful generation are two prerequisites for the design of catalysts with desired performance. Herein, we introduce a simple method for precise preparation of supported/bulk catalysts. It utilizes the ability of metal oxides to dissolve and to simultaneously precipitate during their treatment in an aqueous ammonia solution. Applying this method for a conventional VOx−Al2O3 catalyst, the concentration of coordinatively unsaturated Al sites was tuned simply by changing the pH value of the solution. These sites affect the strength of V−O−Al bonds of isolated VOx species and thus the reducibility of the latter. This method is also applicable for controlling the reducibility of bulk catalysts as demonstrated for a CeO2−ZrO2−Al2O3 system. The application potential of the developed catalysts was confirmed in the oxidative dehydrogenation of ethylbenzene to styrene with CO2 and in the non‐oxidative propane dehydrogenation to propene. Our approach is extendable to the preparation of any metal oxide catalysts dissolvable in an ammonia solution. [ABSTRACT FROM AUTHOR]

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The oxidative dehydrogenation of propane with CO2 (CO2-ODP) is a promising technology for the efficient production of propene in tandem with CO2 reduction to CO. However, the rational design of high-performance catalysts for this green process is still challenged by limited understanding of the nature of active sites and the reaction mechanism. In this work, the effects of SnO2 promoter on Pt/CeO2 activity and propene selectivity in CO2-ODP are elucidated through varying the Sn/Pt molar ratio. When the ratio increases, propane conversion gradually decreases, while the propene selectivity increases. These dependences are explained by increasing the electron density of Pt through the promoter. The strength of this effect is determined by the Sn/Pt ratio. Owing to the electronic changes of Pt, CO2-ODP becomes more favorable than the undesired CO2 reforming of propane. Sn-modified Pt—O—Ce bonds are reasonably revealed as the active sites for CO2-ODP occurring through a redox mechanism involving the activation of CO2 over oxygen vacancies at Sn-modified Pt and CeO2 boundaries. These atomic-scale understandings are important guidelines for purposeful development of high-performance Pt-based catalysts for CO2-ODP. [ABSTRACT FROM AUTHOR]