Mechanochemically-derived iron atoms on defective boron nitride for stable propylene production.

Single-atom catalysts (SACs), possessing a uniform metal site structure, are a promising class of materials for selective oxidations of hydrocarbons. However, their design for targeted applications requires careful choice of metal-host combinations and suitable synthetic techniques. Here, we report iron atoms stabilised on defective hexagonal boron nitride (h-BN) mechanochemical activation in a ball mill as an effective catalyst for propylene production NO-mediated oxidative propane dehydrogenation (NO-ODHP), reaching 95% selectivity at 6% propane conversion and maintaining stable performance for 40 h on stream.

CeO-Supported Single-Atom Cu Catalysts Modified with Fe for RWGS Reaction: Deciphering the Role of Fe in the Reaction Mechanism by In Situ/Operando Spectroscopic Techniques.

Reverse water-gas shift (RWGS) reaction has attracted much attention as a potential approach for CO valorization via the production of synthesis gas, especially over Fe-modified supported Cu catalysts on CeO. However, most studies have focused solely on investigating the RWGS reaction over catalysts with high Cu and Fe loadings, thus leading to an increase in the complexity of the catalytic system and, hence, preventing the gain of any reliable information about the nature of the active sites and reaction mechanism. In this work, a CeO-supported single-atom Cu catalyst modified with iron was synthesized and evaluated for the RWGS reaction.

Highly Efficient Low-loaded PdO/AlSiO Catalyst for Ethylene Dimerization.

Ethylene dimerization is an industrial process that is currently carried out using homogeneous catalysts. Here we present a highly active heterogeneous catalyst containing minute amounts of atomically dispersed Pd. It requires no co-catalyst(s) or activator(s) and significantly outperforms previously reported catalysts tested under similar reaction conditions.

Well-Defined Supported ZnO Species: Synthesis, Structure, and Catalytic Performance in Nonoxidative Dehydrogenation of C-C Alkanes.

ConspectusZinc oxide (ZnO) is a multipurpose material and finds its applications in various fields such as rubber manufacturing, medicine, food additives, electronics, etc. It has also been intensively studied in photocatalysis due to its wide band gap and environmental compatibility. Recently, heterogeneous catalysts with supported ZnO species have attracted more and more attention for the dehydrogenation of propane (PDH) and isobutane (iBDH) present in shale/natural gas.

Fundamentals of Unanticipated Efficiency of GdO-based Catalysts in Oxidative Coupling of Methane.

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 GdO-based catalysts at 700 °C using NO as the oxidant.

Lattice-Stabilized Chromium Atoms on Ceria for NO Synthesis.

The development of selective catalysts for direct conversion of ammonia into nitrous oxide, NO, will circumvent the conventional five-step manufacturing process and enable its wider utilization in oxidation catalysis. Deviating from commonly accepted catalyst design principles for this reaction, reliant on manganese oxide, we herein report an efficient system comprised of isolated chromium atoms (1 wt %) stabilized in the ceria lattice by coprecipitation. The latter, in contrast to a simple impregnation approach, ensures firm metal anchoring and results in stable and selective NO production over 100 h on stream up to 79% NO selectivity at full NH conversion.

Controlling Metal-Oxide Reducibility for Efficient C-H Bond Activation in Hydrocarbons.

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.

Performance Descriptors for Catalysts Based on Molybdenum, Tungsten, or Rhenium Oxides for Metathesis of Ethylene with 2-Butenes to Propene.

The metathesis of ethylene with 2-butenes to propene is an established large-scale process. However, the fundamentals behind in situ transformation of supported WO , MoO , or ReO species into catalytically active metal-carbenes and the intrinsic activity of the latter as well as the role of metathesis-inactive cocatalysts are still unsolved. This is detrimental for catalyst development and process optimization.

Low-Valent Manganese Atoms Stabilized on Ceria for Nitrous Oxide Synthesis.

Nitrous oxide, N O, exhibits unique reactivity in oxidation catalysis, but the high manufacturing costs limit its prospective uses. Direct oxidation of ammonia, NH , to N O can ameliorate this issue but its implementation is thwarted by suboptimal catalyst selectivity and stability, and the lack of established structure-performance relationships. Systematic and controlled material nanostructuring offers an innovative approach for advancement in catalyst design.

Highly efficient Bi-promoted ZrO-based materials for non-oxidative propane dehydrogenation.

Surface or bulk promotion of ZrO-based catalysts with BiO facilitates the removal of lattice oxygen from ZrO under reductive conditions resulting in the formation of coordinatively unsaturated Zr cations. The catalysts demonstrated an industrially relevant propene yield at 600 °C. The results highlight the importance of the usage of suitable promoters for controlling catalyst performance.

1,3-Thia-zole-4-carbo-nitrile.

The title compound, CHNS, is a 1,3-thia-zole substituted in the 4-position by a nitrile group. In the crystal, C-H⋯N hydrogen bonds and aromatic π-π stacking inter-actions are observed.

Performance descriptors of nanostructured metal catalysts for acetylene hydrochlorination.

Controlling the precise atomic architecture of supported metals is central to optimizing their catalytic performance, as recently exemplified for nanostructured platinum and ruthenium systems in acetylene hydrochlorination, a key process for vinyl chloride production. This opens the possibility of building on historically established activity correlations. In this study, we derived quantitative activity, selectivity and stability descriptors that account for the metal-dependent speciation and host effects observed in acetylene hydrochlorination.

Identifying Performance Descriptors in CO Hydrogenation over Iron-Based Catalysts Promoted with Alkali Metals.

Alkali metal promoters have been widely employed for preparation of heterogeneous catalysts used in many industrially important reactions. However, the fundamentals of their effects are usually difficult to access. Herein, we unravel mechanistic and kinetic aspects of the role of alkali metals in CO hydrogenation over Fe-based catalysts through state-of-the-art characterization techniques, spatially resolved steady-state and transient kinetic analyses.

Ceria-Supported Gold Nanoparticles as a Superior Catalyst for Nitrous Oxide Production via Ammonia Oxidation.

The production of nitrous oxide, N O, via NH oxidation is not on a practical scale due to the lack of a suitable catalyst. Instead, it is produced via thermal decomposition of NH NO , rendering N O too costly and limiting its prospective uses. Herein, we report CeO -supported Au nanoparticles (2-3 nm) as a highly selective catalyst for low-temperature NH oxidation to N O, exhibiting two orders of magnitude higher space-time yield than the state-of-the-art Mn-Bi/α-Al O and remarkable stability over 70 h on stream.

In situ formation of ZnO species for efficient propane dehydrogenation.

Propane dehydrogenation (PDH) to propene is an important alternative to oil-based cracking processes, to produce this industrially important platform chemical. The commercial PDH technologies utilizing Cr-containing (refs. ) or Pt-containing (refs.

Current status and perspectives in oxidative, non-oxidative and CO-mediated dehydrogenation of propane and isobutane over metal oxide catalysts.

Conversion of propane or butanes from natural/shale gas into propene or butenes, which are indispensable for the synthesis of commodity chemicals, is an important environmentally friendly alternative to oil-based cracking processes. Herein, we critically analyse recent developments in the non-oxidative, oxidative, and CO-mediated dehydrogenation of propane and isobutane to the corresponding olefins over metal oxide catalysts. Particular attention is paid to (i) comparing the developed catalysts in terms of their application potential, (ii) structure-activity-selectivity relationships for tailored catalyst design, and (iii) reaction-engineering aspects for improving product selectivity and overall process efficiency.

Oxide of lanthanoids can catalyse non-oxidative propane dehydrogenation: mechanistic concept and application potential of EuO- or GdO-based catalysts.

This paper demonstrates the potential of Eu2O3 and Gd2O3 as catalysts for non-oxidative propane dehydrogenation to propene. They reveal a higher activity than the state-of-the-art bare ZrO2-based catalysts due to the higher intrinsic activity of Gdcus or Eucus in comparison with that of Zrcus (cus = coordinatively unsaturated).

Effect of Formaldehyde in Selective Catalytic Reduction of NO by Ammonia (NH-SCR) on a Commercial VO-WO/TiO Catalyst under Model Conditions.

The impact of formaldehyde (HCHO, formed in vehicle exhaust gases by incomplete combustion of fuel) on the performance of a commercial VO-WO/TiO catalyst in NH-SCR of NO under dry conditions has been analyzed in detail by catalytic tests, in situ FTIR and transient studies using temporal analysis of products (TAP). HCHO reacts preferentially with NH to a formamide (HCONH) surface intermediate. This deprives NH partly from its desired role as a reducing agent in the SCR and diminishes NO conversion and N selectivity.

ZnO Nanoparticles Encapsulated in Nitrogen-Doped Carbon Material and Silicalite-1 Composites for Efficient Propane Dehydrogenation.

Non-oxidative propane dehydrogenation (PDH) is an attractive reaction from both an industrial and a scientific viewpoint because it allows direct large-scale production of propene and fundamental analysis of C-H activation respectively. The main challenges are related to achieving high activity, selectivity, and on-stream stability of environment-friendly and cost-efficient catalysts without non-noble metals. Here, we describe an approach for the preparation of supported ultrasmall ZnO nanoparticles (2-4 nm, ZnO NPs) for high-temperature applications.

Controlling the speciation and reactivity of carbon-supported gold nanostructures for catalysed acetylene hydrochlorination.

Carbon-supported gold catalysts have the potential to replace the toxic mercuric chloride-based system applied industrially for acetylene hydrochlorination, a key technology for the manufacture of polyvinyl chloride. However, the design of an optimal catalyst is essentially hindered by the difficulties in assessing the nature of the active site. Herein, we present a platform of carbon supported gold nanostructures at a fixed metal loading, ranging from single atoms of tunable oxidation state and coordination to metallic nanoparticles, by varying the structure of functionalised carbons and use of thermal activation.

A meta-analysis of catalytic literature data reveals property-performance correlations for the OCM reaction.

Decades of catalysis research have created vast amounts of experimental data. Within these data, new insights into property-performance correlations are hidden. However, the incomplete nature and undefined structure of the data has so far prevented comprehensive knowledge extraction.

Alcohol Synthesis from CO , H , and Olefins over Alkali-Promoted Au Catalysts-A Catalytic and In situ FTIR Spectroscopic Study.

Au/TiO and Au/SiO catalysts containing 2 wt % Au and different amounts of K or Cs were tested for alcohol synthesis from CO , H , and C H /C H . 1-Propanol or 1-butanol/isobutanol were obtained in the presence of C H or C H . Higher yields of the corresponding alcohols were obtained over TiO -based catalysts in comparison with their SiO -based counterparts.

Control of coordinatively unsaturated Zr sites in ZrO for efficient C-H bond activation.

Due to the complexity of heterogeneous catalysts, identification of active sites and the ways for their experimental design are not inherently straightforward but important for tailored catalyst preparation. The present study reveals the active sites for efficient C-H bond activation in C-C alkanes over ZrO free of any metals or metal oxides usually catalysing this reaction. Quantum chemical calculations suggest that two Zr cations located at an oxygen vacancy are responsible for the homolytic C-H bond dissociation.

Unraveling the H Promotional Effect on Palladium-Catalyzed CO Oxidation Using a Combination of Temporally and Spatially Resolved Investigations.

The promotional effect of H on the oxidation of CO is of topical interest, and there is debate over whether this promotion is due to either thermal or chemical effects. As yet there is no definitive consensus in the literature. Combining spatially resolved mass spectrometry and X-ray absorption spectroscopy (XAS), we observe a specific environment of the active catalyst during CO oxidation, having the same specific local coordination of the Pd in both the absence and presence of H.