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Ein Eisen‐Kupfer‐Zeolith (Fe‐Cu‐ZSM‐5) katalysiert die selektive Oxidation von Methan zu Methanol mit wässrigem Wasserstoffperoxid. Das Eisen aktiviert die Kohlenstoff‐Wasserstoff‐Bindung, während das Kupfer dafür sorgt, dass Methanol als Hauptprodukt gebildet wird. Der Katalysator ist stabil und wiederverwendbar und aktiviert Methan mit >90 % Selektivität und 10 % Umsatz in einem geschlossenen Katalysezyklus (siehe Schema).

The oxidation of methane, the main component of natural gas, to selectively form oxygenated chemical feedstocks using molecular oxygen has been a long-standing grand challenge in catalysis. Here, using gold nanoparticles supported on the zeolite ZSM-5 we introduce a method to oxidise methane to methanol and acetic acid in water at temperatures between 120-240 °C using molecular oxygen in the absence of any added co-reductant. Electron microscopy reveals that the catalyst does not contain gold atoms or clusters, but rather gold nanoparticles are the active component while a mechanism involving surface adsorbed species is proposed in which methanol and acetic acid are formed via parallel pathways.

structure structure (solids and liquids) D 2000 -006The Hydride Anion in an Extended Transition Metal Oxide Array: LaSrCoO 3 H 0.7 .-The title compound is prepared by reaction of CaH 2 and LaSrCoO 4 (sealed Pyrex tube, 450 • C, 8 d). LaSrCoO 3 H 0.7 crystallizes in the orthorhombic space group Immm, as revealed by powder synchrotron XRD. The structure contains oxide chains bridged by hydride anions to form a two-dimensional extended network. The metal centers are strongly coupled by their bonding with both oxide and hydride ligands to produce magnetic ordering at temperatures up to at least 350 K. The preparation method may prove to be a general route to transition metal oxide hydrides, opening up previously uncharted areas in electronic and magnetic materials synthesis. -(HAYWARD, M. A.; CUSSEN, E. J.; CLARIDGE, J. B.; BIERINGER, M.; ROSSEINSKY, M. J.; KIELY, C.

The direct transformation of methane to methanol remains a significant challenge for operation at a larger scale. Central to this challenge is the low reactivity of methane at conditions that can facilitate product recovery. This review discusses the issue through examination of several promising routes to methanol and an evaluation of performance targets that are required to develop the process at scale. We explore the methods currently used, the emergence of active heterogeneous catalysts and their design and reaction mechanisms and provide a critical perspective on future operation. Initial experiments are discussed where identification of gas phase radical chemistry limited further development by this approach. Subsequently, a new class of catalytic materials based on natural systems such as iron or copper containing zeolites were explored at milder conditions. The key issues of these technologies are low methane conversion and often significant overoxidation of products. Despite this, interest remains high in this reaction and the wider appeal of an effective route to key products from C–H activation, particularly with the need to transition to net carbon zero with new routes from renewable methane sources is exciting.

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Bimetallic Pd-Fe catalysts supported on TiO 2 are shown to be highly effective toward the selective oxidation of benzyl alcohol to benzaldehyde via the in situ production of H 2 O 2 from molecular H 2 and O 2 , under conditions where no reaction is observed with molecular O 2 alone. The rate of benzyl alcohol oxidation observed over supported Pd-Fe nanoparticles is significantly higher than those of either Pd-Au or Pd-only analogues. This enhanced activity can be attributed to the bifunctionality of the Pd-Fe catalyst to both synthesize H 2 O 2 and catalyze the production of oxygen-based radical specie,s as indicated by an electron paramagnetic resonance analysis. Further studies also reveal the noninnocent nature of the solvent, resulting in the propagation of radical generation pathways.

Metrics & MoreArticle RecommendationsCONSPECTUS: Methane represents one of the most abundant carbon sources for fuel or chemical production. However, remote geographical locations and high transportation costs result in a substantial proportion being flared at the source. The selective oxidation of methane to methanol remains a grand challenge for catalytic chemistry due to the large energy barrier for the initial C−H activation and prevention of overoxidation to CO 2 . Indirect methods such as steam reforming produce CO and H 2 chemical building blocks, but they consume large amounts of energy over multistage processes. This makes the development of the low-temperature selective oxidation of methane to methanol highly desirable and explains why it has remained an active area of research over the last 50 years.The thermodynamically favorable oxidation of methane to methanol would ideally use only molecular oxygen. Nature effects this transformation with the enzyme methane monooxygenase (MMO) in aqueous solution at ambient temperature with the addition of 2 equiv of a reducing cofactor. MMO active sites are Fe and Cu oxoclusters, and the incorporation of these metals into zeolitic frameworks can result in biomimetic activity. Most approaches to methane oxidation using metal-doped zeolites use high temperature with oxygen or N 2 O; however, demonstrations of catalytic cycles without catalyst regeneration cycles are limited. Over the last 10 years, we have developed Fe-Cu-ZSM-5 materials for the selective oxidation of methane to methanol under aqueous conditions at 50 °C using H 2 O 2 as an oxidant (effectively O 2 + 2 reducing equiv), which compete with MMO in terms of activity. To date, these materials are among the most active and selective catalysts for methane oxidation under this mild condition, but industrially, H 2 O 2 is an expensive oxidant to use in the production of methanol. This observation of activity under mild conditions led to new approaches to utilize O 2 as the oxidant. Supported precious metal nanoparticles have been shown to be active for a range of C−H activation reactions using O 2 and H 2 O 2 , but the rapid decomposition of H 2 O 2 over metal surfaces limits efficiency. We identified that this decomposition could be minimized by removing the support material and carrying out the reaction with colloidal AuPd nanoparticles. The efficiency of methanol production with H 2 O 2 consumption was increased by 4 orders of magnitude, and crucially it was demonstrated for the first time that molecular O 2 could be incorporated into the methanol produced with 91% selectivity. The understanding gained from these two approaches provides valuable insight into possible new routes to selective methane oxidation which will be presented here in the context of our own research in this area.