Synthesis, structural analysis and evaluation of the catalytic activity of a non-symmetric N-(salicylidene)diethylenetriamine complex of copper(II) (original) (raw)
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Catalysis Today, 1997
Highly active oxidation catalysts have been made by treating dehydrated zeolite NaY with excesses of the neutral tetranuclear copper(II) precursor (iJ~4-O)L4Cu4Cl 6 (A, L = N,N-diethylnicotinamide) in methylene chloride, followed by methylene chloride washing, drying and oxidation with 0 2 at 220°C. The loaded samples contain from 3.4 to 14.3% w/w total copper, depending on the amount of A used. Previous measurements with a different 'titration' loading method together with analytical and spectroscopic data for materials loaded with different excesses of A indicate 2.9-13.8% w/w copper on the zeolite surface (50 m2/g) due to a zeolite-solution equilibrium with A. Oxidation of the most heavily loaded sample with 0 2 gives a catalyst that is ten times more active per gram for CO oxidation than bulk CuO at 450°C. The most lightly loaded sample oxidizes CO 115 times faster than bulk CuO on a per gram CuO basis. Turnover numbers at infinitely dilute CuO loading approach 75% of the TON for bulk CuO, suggesting that CO oxidation on bulk CuO involves more than one CuO site. Prospects for catalyst development through transmetallation chemistry and different loading methods are discussed. activity per unit mass than bulk materials because of their high dispersion .
Nanostructured Nonprecious Metal Catalysts for Oxygen Reduction Reaction
Accounts of Chemical Research, 2013
P latinum-based catalysts represent a state of the art in the electrocatalysis of oxygen reduction reaction (ORR) from the point of view of their activity and durability in harnessing the chemical energy via direct electrochemical conversion. However, because platinum is both expensive and scarce, its widespread implementation in such clean energy applications is limited. Recent breakthroughs in the synthesis of high-performance nonprecious metal catalysts (NPMCs) make replacement of Pt in ORR electrocatalysts with earth-abundant elements, such as Fe, Co, N, and C, a realistic possibility. In this Account, we discuss how we can obtain highly promising MÀNÀC (M: Fe and/or Co) catalysts by simultaneously heat-treating precursors of nitrogen, carbon, and transition metals at 800À1000°C. The activity and durability of resulting catalysts depend greatly on the selection of precursors and synthesis chemistry. In addition, they correlate quite well with the catalyst nanostructure. While chemists have presented no conclusive description of the active catalytic site for this class of NPMCs, they have developed a designed approach to making active and durable materials, focusing on the catalyst nanostructure. The approach consists of nitrogen doping, in situ carbon graphitization, and the usage of graphitic structures (possibly graphene and graphene oxides) as carbon precursors. Various forms of nitrogen, particularly pyridinic and quaternary, can act as n-type carbon dopants in the MÀNÀC catalysts, assisting in the formation of disordered carbon nanostructures and donating electrons to the carbon. The CNx structures are likely a crucial part of the ORR active site(s). Noteworthy, the ORR activity is not necessarily governed by the amount of nitrogen, but by how the nitrogen is incorporated into the nanostructures.
2015
He is a member of Mexico's National System of Researchers (SNI). His current research interests include the synthesis, characterization, and applications of porous catalytic materials and applications of polymers with electrical properties. Dr. Jin An Wang is a professor of Chemical Engineering at the National Polytechnic Institute in Mexico. He is a National Researcher and a member of Mexican Academy of Sciences. In 1995, he received a Doctor degree in Chemical Engineering from East China University of Sciences and Technology, China. He specializes in catalysis research, including catalysis for ultraclean fuels; hydrogen production, petroleum reforming, and environmental catalysis; and advanced catalytic materials. Dr. Wang has published 140 refereed papers, edited 2 books and 3 special issues of research journals, invented 5 patents, and delivered over 50 invited lectures worldwide. He served as chairman of 6 international symposia and guest editors of Catalysis Today, Advanced Materials Research, and Materials Research Society Symposium Proceedings. Contents Preface XIII Section Specialized Characterization 1 Chapter X-Ray Spectroscopy-The Driving Force to Understand and Develop Catalysis 3 Jakub Szlachetko and Jacinto Sá lysts (and their ample range of applications), such as nano-zero-valent-iron (nZVI), iron oxides, nanoferrites, zinc glutarate, metal-organic frameworks (MOFs), titanium-modified SBA-15, graphene oxide-hausmannite (Mn 3 O 4) composites, and metal oxides, supported on silica. The largest section of the book is Part 3, comprising seven chapters on photocatalysis, from the reaction basics and a review of materials available to specific new materials and developments. Photocatalytic processes have received much attention because of the potential of using sun light (possibly the more available renewable energy) and new environmentally friendly "green" technologies. Part 4 is focused on materials for electrocatalytic applications (such as sensors and energy conversion and storage): silver-copper nanoalloys and graphene-metal oxide nanohybrid materials, covering the synthesis, structure, and properties of the materials. Final section, Part 5, reviews the extensive field of biotechnology applications of synthetic DNA catalysts. Finally, the editors, we like to acknowledge the motivation and expertise provided by all the authors, some of them starting a promising career with bright ideas and some of them consolidated in the field with a remarkable background; constructing this book has been a several steps journey and they have maintained committed with the task. However, we also like to acknowledge InTech's editorial staff and their valuable support all along the way.
Applied Surface Science, 2014
Surface/structure functionalization of copper-based catalysts by metal-support and/or metal-metal interactions a b s t r a c t Cu-based catalysts have recently attracted great attention both in catalysis and electro-catalysis fields due to their excellent catalytic performance and low cost. Given that their performance is determined, to a great extent, by Cu sites local environment, considerable efforts have been devoted on the strategic modifications of the electronic and structural properties of Cu sites. In this regard, the feasibility of tuning the local structure of Cu entities by means of metal-support or metal-metal interactions is investigated. More specifically, the physicochemical properties of Cu entities are modified by employing: (i) different oxides (CeO 2 , La 2 O 3 , Sm 2 O 3 ), or (ii) ceria-based mixed oxides (Ce 1−x Sm x O ı ) as supporting carriers, and (iii) a second metal (Cobalt) adjacent to Cu (bimetallic Cu-Co/CeO 2 ). A characterization study, involving BET, XRD, TPR, and XPS, reveal that significant modifications on structural, redox and electronic properties of Cu sites can be induced by adopting either different oxide carriers or bimetallic complexes. Fundamental insights into the tuning of Cu local environment by metal-support or metal-metal interactions are provided, paving the way for real-life industrial applications. (M. Konsolakis). 1 www.tuc.gr/konsolakis.html. necessary the fine tuning of copper sites local environment in order to obtain active and stable electro-catalysts.
Copper Supported on Mesoporous Structured Catalysts for NO Reduction
Catalysts
Nitrogen oxides (NOx) are one of the pollutants of greatest concern in terms of atmospheric contamination and, consequently, human health. The main objective of this work, is the synthesis of structured carbon catalysts, introducing on their surface metals and nitrogen groups, catalytically active in NO reduction. Structured catalysts represent an attractive alternative to powder catalysts because they have better thermal stability and lower pressure drop. The catalysts were synthesized by coating a melamine foam using precursor solutions of carbon xerogels with and without nitrogen (using melamine and urea as precursors), and impregnated with transition metals (Fe, Ni and Cu). The introduction of nitrogen and metals modified the textural properties of the materials. Samples synthesized with melamine presented the highest amount of nitrogen, while the highest content of copper, found to be the most active transition metal for NO reduction, was found in structured catalysts impregnat...
Applied Catalysis B: Environmental, 1997
Cu/Mg/Al mixed oxides (CuO = 4.Ck12.5 wt%), obtained by calcination of hydrotalcite-type (HT) anionic clays, were investigated in the selective catalytic reduction (SCR) of NO by NH3, either in the absence or presence of oxygen, and their behaviours were compared with that of a CuO-supported catalyst (CuO = 10.0 wt%), prepared by incipient wetness impregnation of a Mg/Al mixed oxide also obtained by calcination of an HT precursor. XRD analysis, UV-visible-NIR diffuse reflectance spectra and temperature-programmed reduction analyses showed the formation, in the mixed oxide catalysts obtained from HT precursors, mainly of octahedrally coordinated Cu '+ ions, more strongly stabilized than Cucontaining species in the supported catalyst, although the latter showed a lower percentage of reduction. The presence of well dispersed Cu 2f ions improved the catalytic performances, although similar behaviours were observed for all catalysts in the absence of oxygen. On the contrary, when the mixture with excess oxygen was fed, very interesting catalytic performances were obtained for the catalyst richest in copper (CuO = 12.5 wt%). This catalyst exhibited a behaviour comparable to that of a commercial V205-W03/Ti02 catalyst, without any deactivation phenomena after four consecutive cycles and following 8 h of time-on-stream at 653 K. Decreasing the copper content or increasing the calcination time and temperature led to considerably poorer performances and catalytic behaviours similar to that of the CuO-supported catalyst, due to the side-reaction of NH3 combustion on the free Mg/Al mixed oxide surface. 0 1997 Elsevier Science B.V.
Catalysis Today, 2002
The influence of ammonia and nitric oxide oxidation on the selective catalytic reduction (SCR) of NO by ammonia with copper/nickel and vanadium oxide catalysts, supported on titania or alumina have been investigated, paying special attention to N 2 O formation. In the SCR reaction, the VTi catalyst had a higher activity than VAl at low temperatures, while the CuNiAl catalyst had a higher activity than CuNiTi. A linear relationship between the reaction rate of ammonia oxidation and the initial reduction temperature of the catalysts obtained by H 2 -TPR showed that the formation rate of NH species in copper/nickel catalysts would be higher than in vanadia catalysts. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) showed that copper/nickel catalysts presented ammonia coordinated on Lewis acid sites, whereas ammonium ion adsorbed on Brønsted acid sites dominated on vanadia catalysts. The NO oxidation experiments revealed that copper/nickel catalysts had an increase of the NO 2 and N 2 O concentrations with the temperature. NO could be adsorbed on copper/nickel catalysts and the NO 2 intermediate species could play an important role in the reaction mechanism. It was suggested that the presence of adsorbed NO 2 species could be related to the N 2 O formation.
Nanomaterials (Basel, Switzerland), 2018
This work highlights the importance of the hydrophilicity of a catalyst's active sites on an oxygen reduction reaction (ORR) through an electrochemical and physico-chemical study on catalysts based on nitrogen-modified carbon doped with different metals (Fe, Cu, and a mixture of them). BET, X-ray Powder Diffraction (XRPD), micro-Raman, X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM), Scanning Transmission Electron Microscopy (STEM), and hydrophilicity measurements were performed. All synthesized catalysts are characterized not only by a porous structure, with the porosity distribution centered in the mesoporosity range, but also by the presence of carbon nanostructures. In iron-doped materials, these nanostructures are bamboo-like structures typical of nitrogen carbon nanotubes, which are better organized, in a larger amount, and longer than those in the copper-doped material. Electrochemical ORR results highlight that the presence of iron and nitrogen...