Iron-based nanocatalyst for the acceptorless dehydrogenation reactions (original) (raw)
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Low-Valent Iron(I) Amido Olefin Complexes as Promotors for Dehydrogenation Reactions
Angewandte Chemie (International ed. in English), 2015
Fe(I) compounds including hydrogenases show remarkable properties and reactivities. Several iron(I) complexes have been established in stoichiometric reactions as model compounds for N2 or CO2 activation. The development of well-defined iron(I) complexes for catalytic transformations remains a challenge. The few examples include cross-coupling reactions, hydrogenations of terminal olefins, and azide functionalizations. Here the syntheses and properties of bimetallic complexes [MFe(I) (trop2 dae)(solv)] (M=Na, solv=3 thf; M=Li, solv=2 Et2 O; trop=5H-dibenzo[a,d]cyclo-hepten-5-yl, dae=(N-CH2 -CH2 -N) with a d(7) Fe low-spin valence-electron configuration are reported. Both compounds promote the dehydrogenation of N,N-dimethylaminoborane, and the former is a precatalyst for the dehydrogenative alcoholysis of silanes. No indications for heterogeneous catalyses were found. High activities and complete conversions were observed particularly with [NaFe(I) (trop2 dae)(thf)3 ].
Catalysis Communications, 2010
The iron nanoparticles that are encapsulated by microporous and mesoporous silica shells were synthesized for the generation of CO x-free hydrogen through the catalytic decomposition of ammonia. The encapsulated iron nanoparticles show excellent catalytic activity, giving 100% ammonia conversion in the 650-670°C range. The core-shell structured catalysts are highly stable under the adopted reaction conditions owing to the stable silica shells that effectively prevent aggregation of iron nanoparticles. In contrast, the naked iron nanoparticles deactivated gradually at 670°C and lost 18% ammonia conversion in a period of 63 h.
Iron-based Nanomaterials in the Catalysis
Advanced Catalytic Materials - Photocatalysis and Other Current Trends, 2016
Available data on catalytic applications of the iron-containing nanomaterials are reviewed. Main synthesis methods of nZVI, nano-sized iron oxides and hydroxides, core-shell and alloy structures, ferrites, iron-containing supported forms, and composites are described. Supported structures include those coated and on the basis of polymers or inert inorganic materials (i.e., carbon, titania or silica). Description of catalytic processes includes the decomposition reactions (in particular photocatalytic processes), reactions of dehydrogenation, oxidation, alkylation, CC coupling, among a series of other processes. Certain attention is paid to magnetic recovery of catalysts from reaction systems and their reuse up to several runs almost without loss of catalytic activity.
Abstract During the last decade, a significant number of distinct methods have been developed for the preparation as well as materials and process characterization of nano zero-valent iron (nZVI), iron oxides, and other iron-containing nanomaterials. Synthesis methods generally fall into traditional wet chemistry means such as borohydride reduction, sophisticated modern synthesis techniques, and “green” methods using benign solvents and various plant extracts and microorganisms. Various characterization techniques have been employed to investigate the structure, composition, morphology, stability, and textural and surface properties of these iron-based nanomaterials. The tunable physical and chemical properties of these materials offer solutions to persistent contaminants in the environment. However, the majority of environmental applications have been conducted only at the laboratory scale. The small size of iron nanoparticles promotes effective surface dispersion and their large specific surface area causes enhanced reactivity for facile liquid-phase pollutant degradation. Researchers are beginning to incorporate green chemistry principles early on into synthesis methods to create novel iron nanomaterials. Applying green chemistry principles to the development of new nanomaterials and applications can lead to design rules that are eco-friendly and benign in the context of protecting the environment and overall human health. Recent innovations in iron nanomaterial synthesis have resulted in several benefits including cost reductions and increased availability for large-scale applications. For example, nZVI materials can catalyze oxidative degradation of organic solvents in water more effectively when they are combined with emulsion liquid membranes. Iron nanoparticles have also been applied in free and supported forms to reach a considerable decontamination levels due to their relatively low toxicity. Moreover, it is possible to tailor the activity and stability of iron nanoparticles by modifying their structural support. Iron nanoparticles prepared from polyphenols are generally active, stable, easy to handle, and regenerable catalysts. Therefore, there are tremendous opportunities for industrial manufacturers to design their production processes in ways that can minimize or eliminate adverse environmental impact at various stages of development. Adequate delivery and transport models of iron nanomaterials in soil and groundwater need to be developed as they are critical to engineering applications. Future studies also need to evaluate the potential adverse impacts of these iron nanomaterials could have on environment outside the remediation zone. Instrumentation and analytical measurement techniques need to be developed in order to monitor, evaluate, and predict the overall reactivity, transport, and fate of nanoparticles in the environment. The lifetime of iron nanomaterials introduced to the environment will continue to be a significant issue requiring long-term studies. In this work, we provide a review of green synthesis, characterization, and environmental applications of iron nanomaterials. Such current information is valuable for future research in this fast-growing field.
Angewandte Chemie International Edition, 2015
Efficient hydrogen evolution reaction (HER) through effective and inexpensive electrocatalysts is a valuable approach for clean and renewable energy systems. Here, singleshell carbon-encapsulated iron nanoparticles (SCEINs) decorated on single-walled carbon nanotubes (SWNTs) are introduced as a novel highly active and durable non-noble-metal catalyst for the HER. This catalyst exhibits catalytic properties superior to previously studied nonprecious materials and comparable to those of platinum. The SCEIN/SWNT is synthesized by a novel fast and low-cost aerosol chemical vapor deposition method in a one-step synthesis. In SCEINs the single carbon layer does not prevent desired access of the reactants to the vicinity of the iron nanoparticles but protects the active metallic core from oxidation. This finding opens new avenues for utilizing active transition metals such as iron in a wide range of applications.