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Specific features of the catalytic behavior of supported palladium nanoparticles were analyzed in terms of both the size of the particles and their interaction with the support. The influence of these factors on the activity and selectivity of palladium nanoparticles in carbon-carbon bond hydrogenolysis, hydrogenation of aromatic compounds, olefins, and acetylenes, hydrodechlorination, as well as complete oxidation of organic compounds was discussed. It was shown that the optimal nanoparticle size depends on the type of the reaction and also such factors as the nature of interaction between the nanoparticles and support, absorptivity of the substrates and catalytic reaction products, and electronic and crystal structure of the nanoparticles. [ABSTRACT FROM AUTHOR]

The NO x reduction with n-C6H14 was studied over a 3% Ag/Al2O3 catalyst in the presence of hydrogen. The catalyst performance was evaluated by varying the H2 concentration from 0 to 1600 ppm and by comparing the results with blank runs in which an empty reactor with no catalyst was used. Two distinct reaction pathways were revealed: one at low-temperature (Treact < 370 °C) and another one at high-temperature (Treact > 370–390 °C). Co-feeding of H2 promotes the reaction within the 150–360 °C interval. The high-temperature pathway (Treact > 370–390 °C) seems to be almost independent of hydrogen co-feeding. The homogeneous gas-phase NO x oxidation initiated by NO presumably plays an important role in this high-temperature pathway. [ABSTRACT FROM AUTHOR]

The catalytic properties of new Pd-Zn/Al2O3 catalysts in selective acetylene hydrogenation in an acetylene-ethylene mixture at 30–120°C and atmospheric pressure are reported. The catalysts prepared from the bimetallic complex Pd-Zn(OOCMe)4(OH2) are much more selective than the catalysts prepared by simultaneously supporting the homonuclear complexes Pd3(OOCMe)6 and Zn(OOCMe)2 · 2H2O. It is demonstrated by diffuse reflectance IR spectroscopy of adsorbed CO that the heat treatment of the supported bimetallic complex at 250°C in flowing H2 yields a Pd-Zn alloy on the surface. It is this alloy that ensures the high selectivity of the Pd-Zn/Al2O3 catalysts. [ABSTRACT FROM AUTHOR]

The effect of electron irradiation on the properties of the systems 1% Pd/C, 1% Pd/Al2O3, and 1% Pd/TiO2 is studied in gas-phase and liquid-phase toluene hydrogenation. An increase in the irradiation dose to 120-900 Mrad increases the catalytic activity by a factor of 2-8 relative to that of the original system. XPS data for the Pd/C catalyst suggest that, after irradiation with high-energy electrons, the metal particles are stabilized on the surface of the carbon support, their degree of dispersion is increased, and their sintering is suppressed. These inferences are consistent with the observed changes in catalytic properties. [ABSTRACT FROM AUTHOR]

A key goal of organic chemistry is to develop new principles for the control of reactions, which can be used to create promising materials demanded in all fields of scientific research and industry. This review is an overview of the scientific advances, which have been made by the N. D. Zelinsky Institute of Organic Chemistry of the Russian Academy of Sciences in the past decade within the framework of current trends in organic chemistry. The review covers the results, which are significant for fundamental research and hold great promise for the application in different areas, from the production of materials, petrochemistry, and chemical ecology to medicine, agriculture, and food industry. [ABSTRACT FROM AUTHOR]

This document discusses the applications of mono- and bimetallic nanoparticles in catalysis. The design, synthesis, and characterization of metal nanoparticles have been a focus of attention in heterogeneous catalysis due to their unique properties. The size of nanoparticles can affect catalytic activity and reaction products. Bimetallic nanoparticles have become a prevailing concept in catalyst development, as they can lead to different structures and interactions. The document also highlights the importance of controllable synthesis and the use of modern methods to understand the catalytic behavior of these systems. Several research papers and reviews on nanocatalyst preparation have been published, including studies on single-atom catalysts. The document includes examples of specific studies on the preparation and performance of mono- and bimetallic catalysts. The authors express their gratitude to the contributors of this special issue on mono- and bimetallic nanoparticles in catalysis. [Extracted from the article]

Understanding the interface between soluble metal complexes and supported metal particles is important in order to reveal reaction mechanisms in a new generation of highly active homogeneous transition metal catalysts. In this study, we show that, in the case of palladium forming on a carbon (Pd/C) catalyst from a soluble Pd(0) complex Pd2dba3, the nature of deposited particles on a carbon surface turns out to be much richer than previously assumed, even if a very simple experimental procedure is utilized without the use of additional reagents and procedures. In the process of obtaining a heterogeneous Pd/C catalyst, highly active "hidden" metal centers are formed on the carbon surface, which are leached out by the solvent and demonstrate diverse reactivity in the solution phase. The results indicate that heterogeneous catalysts may naturally contain trace amounts of molecular monometallic centers of a different nature by easily transforming them to the homogeneous catalytic system. In line with a modern concept, a heterogenized homogeneous catalyst precursor was found to leach first, leaving metal nanoparticles mostly intact on the surface. In this study, we point out that the previously neglected soft leaching process contributes to high catalyst activity. The results we obtained demand for leaching to be reconsidered as a flexible tool for catalyst construction and for the rational design of highly active and selective homogeneous catalytic systems, starting from easily available heterogeneous catalyst precursors. [ABSTRACT FROM AUTHOR]

Despite a large number of studies focusing on single‐ site (surface organometallic, single‐atom and single‐atom alloy) catalysts much less attention is devoted to kinetic analysis of such reactions. This mini‐review addresses some kinetic features of single‐site catalysis including both qualitative and quantitative aspects. [ABSTRACT FROM AUTHOR]

To lessen air pollution led by diesel exhaust emission, regeneration of soot deposited in diesel particulate filter (DPF) by catalysts has attracted great attention. It is necessary to study effects of catalysts and soluble organic fraction (SOF) on soot oxidation using thermogravimetric analysis (TGA) for improving regeneration process. The diesel soot is simulated by Printex U (PU) particles, and the SOF originates from 0# diesel fuel and 15W lubricating oil. The TGA results are evaluated by the peak temperature Tp, comprehensive combustion index S and combustion stable index Rw, respectively. Compared with ZrO2 and CeO2 catalysts, the best catalytic effect on soot oxidation is achieved when the Pt catalyst is mixed with PU at 1:1 mass ratio. With the increasing of Pt catalyst, the comprehensive combustion performance of PU becomes inferior because of heat transfer poverty. Soot oxidation performance gets degradation after adding the simulative SOF. When the mass ratio of PU/Pt/15W reaches 1:1:0.1, the comprehensive combustion performance presents the comparatively superior state. The values of S and Rw indexes of PU/Pt/15W mixture at 1:1:0.1 mass ratio reach the largest of 9.459 × 10–8%2 min−2 °C−3 and 30.85 × 105, respectively. This work investigates the soot oxidation in the presence of catalyst and SOF based on previous researches, which benefits the optimization of catalytic regeneration strategy for DPF application. [ABSTRACT FROM AUTHOR]

Those catalysts are engineered for conventional thermal oxidation catalysis but also sequential adsorption-catalytic, photocatalytic, and plasma-catalytic oxidation processes. This Special Issue collects three reviews, eight articles, and two communications related to the design of catalysts for environmental applications, such as the transformation of several pollutants into harmless or valuable products. The authors showed that the addition of Au improved the activity of the Al SB 2 sb O SB 3 sb -supported Cu and Pt catalysts and had a positive effect on SO SB 2 sb production by widening its production window, especially for the platinum-based catalyst. [Extracted from the article]

Pd/Al2O3 and Pd–M/Al2O3 catalysts (M = Au, Ag, Cu, Ce, Fe, Ni, Co, Zn) were obtained by ion exchange and impregnation. Pd/Al2O3 had high initial activity in the conversion of ethanol into α-alcohols, but lost 90% of its activity after 10 h of operation because of deactivation caused by the chemisorption of the by-product (CO) on Pd atoms. Modification of Pd with gold or silver led to an increase in the rate of Pd deactivation. As a result, the Pd–Au and Pd–Ag systems were less active and stable. In contrast, the Pd–Fe, Pd–Co, Pd–Ni, Pd–Cu, Pd–Zn, and Pd–Ce systems exhibited higher resistance to CO poisoning than Pd and demonstrated high activity and stability. The observed tendencies in the catalytic action of the mono- and bimetallic systems were explained within the framework of the d band model proposed by Hammer and Norskov. Pd–Cu/Al2O3 was most effective in the target process; it is not poisoned by CO and allows ethanol conversion into α-alcohols at 95% selectivity, while the time of its stable operation is at least 100 h. The structure of the Pd–Cu catalytic system was studied by TEM, EDA, XPS, TPR-H2, and TPD-NH3. A model of active catalyst sites was proposed. [ABSTRACT FROM AUTHOR]

Recent results obtained in studying mono- and bimetallic catalysts for selective hydrogenation of unsaturated carbonyl compounds, even unsaturated ones, acetylenic and nitro compounds as well as CO and bio-available alcohols oxidation are reviewed from the standpoint of the strong interaction between the metal nanoparticles, on the one hand, and two metals in the composition of bimetallic nanoparticles, on the other hand. Such interactions were demonstrated to result in partial positive or negative charging of metal nanoparticles, which, in turn, changes their adsorption and catalytic properties, especially with respect to the reactions involving hydrogen. Among the systems studied, Au–Pt, Au–Pd, Au–Cu, Au–Fe, Pt–WOx, Fe–Pd, Fe–Pt, Fe–Cu nanoparticles prepared by the redox procedure are considered to be most perspective in diverse catalytic applications because of the proper combination of the particle size and the electronic state of the metals. [ABSTRACT FROM AUTHOR]

Abstract: The Pd-Ag/CeO2 catalysts were prepared by the impregnation of highly dispersed CeO2 with a solution of the heteroatomic complex PdAg2(OAc)4(HOAc)4. Samples obtained after the thermolysis of PdAg2(OAc)4(HOAc)4 in N2 and H2 contained Pd-Ag alloy and Pd particles immobilized on CeO2. The Pd0-CeO2 metal oxide centers formed at the interface were highly active in the low-temperature reaction of CO oxidation. The particles of Pd were absent from the Pd-Ag/CeO2 sample prepared by the decomposition of PdAg2(OAc)4(HOAc)4 in an atmosphere of O2; in this case, a significant portion of the Pd-Ag phase was covered with a film of CeO2, which dramatically slowed down the rate of reaction at low temperatures. [ABSTRACT FROM AUTHOR]

Non-thermal plasma (NTP) catalysis has attracted widespread attention in volatile organic compounds (VOCs). Combining NTP with heterogeneous catalyst has been proved to reduce the formation of unwanted by-products and improve the energy efficiency of the process. The mechanisms of interaction with plasma and catalyst and VOCs oxidation in plasma catalysis are particularly hot research topic. This paper reviewed the mechanism of non-thermal plasma catalysis on volatile organic compounds removal. In the first part, the interaction between plasma and catalyst is disscussed. And the different catalysis systems and discharge types are presented in the second part. In the third part, attention is given to the influence of critical parameters on the removal processes. Finally, based on a large number of literatures, an extended review is presented detailly on the treatment of VOCs with plasma-catalysis system including the oxidation pathways. Moreover, future works of this promising technology are discussed. [ABSTRACT FROM AUTHOR]

The catalytic selective hydrogenation of multiunsaturated hydrocarbons, especially in pyrolysis products, to corresponding mono-olefins is a widely exploited way for the large-scale production of polymer-grade olefins as well as fuel upgrading. Thermodynamic and/or kinetic parameters could be effective for selective operation. The latter is primarily influenced by catalyst formulation, including promoters, support type, and metal dispersion and distribution. The solution to achieve an economically attractive commercial implementation lies in defining the optimal catalyst design and operating conditions. The theoretical and practical aspects of catalysis for the selective hydrogenation of acetylene to ethylene are reviewed and the potential new ways to improve catalyst formulation are examined. [ABSTRACT FROM AUTHOR]

Effect of the phase composition of aluminum oxide [γ- and (δ + θ) phase] and introduction of zinc additives on the catalytic properties of 0.5% Pd/Al2O3 systems in the reaction of liquid-phase hydrogenation of acetylene into ethylene under an elevated pressure in a flow-through mode was studied. An increase in the activity of the Pd catalyst upon modification with zinc is only observed in the case of a system supported by the mixed phase of (δ + θ) aluminum oxide. XAFS spectroscopy was used to find that the increase in the activity and selectivity with respect to ethylene (in the presence of carbon monoxide) on the (0.5% Pd-0.62% Zn)/(δ + θ)-Al2O3 catalyst is correlated with the formation of the PdZn intermetallic compound. [ABSTRACT FROM AUTHOR]

This review summarizes the recent advances in the construction of organic and hybrid systems having considerable potential for practical applications in pharmacology, medicine, materials science, petrochemistry, and chemistry of high-energy compounds. The methodological classification of the approaches into classical and interdisciplinary is proposed. Examples of the efficient application of these approaches for investigating complex molecular systems, as well as for developing new methods of synthesis are given. [ABSTRACT FROM AUTHOR]

The literature data on the synthesis and properties of oxo-functionalized acyclic and cyclic sulfides obtained by the catalytic multicomponent reactions of 1,3-dicarbonyl compounds with formaldehyde and S-nucleophiles are summarized. An approach to the multimolecular four-component heterocyclization of 1,3-dicarbonyl compounds with CHO and S- and N-nucleophiles in the synthesis of sulfanyl-substituted azaheterocycles is discussed. [ABSTRACT FROM AUTHOR]

The review summarizes recent advances in the selective synthesis of complex molecular systems starting from simple readily available precursors. Such systems have a great potential for application in pharmacology, medicine, and materials science. The efficiency of the application of catalysis and structural studies for the development of new methods of synthesis is demonstrated. [ABSTRACT FROM AUTHOR]

The article discusses the theory that Ag/Al2O3 may catalyze, driven by the hydrogen borrowing mechanism. It presents the first example of the heterogeneous catalysis of the title reaction under mild conditions and studies the relationship between structural factors and catalytic properties. It suggests that Ag/Al2O3 is the first example of a heterogeneous catalyst for the one-step synthesis of N-substitute anilines from nitroaromatics alcohol.

The present article consists a critical up-to-date review of the research conducted so far on the selective catalytic reduction of NOx with hydrogen under lean-burn conditions as an alternative technology to the existing NH3- and HC-SCR. Noble Metal based catalysts are described in detail with emphasis on the analysis of the various reaction mechanisms that have been put forward in the literature. The influence of the nature of the support chemical composition and the preparation method and structure of the catalysts on the reaction mechanism is also discussed. Finally, the effects of various reaction parameters on the catalysts activity, selectivity and stability with reaction time are discussed in detail. [ABSTRACT FROM AUTHOR]

A comparison has been made of plasma-catalysis with thermal-catalysis and plasma alone for the removal of low concentrations of propane and propene from synthetic air using a one-stage, catalyst-in discharge configuration. In all cases, plasma-catalysis produces better hydrocarbon destructions (~40%) than thermal catalysis at low temperatures. At higher temperatures, little difference is observed between plasma-catalytic and thermal-catalytic operation. Plasma operation by itself had a similar effectiveness to plasma-catalysis at low temperatures but was significantly lower (up to 50%) as the temperature was raised. By examining the form of the temperature dependence for the plasma-catalytic destruction processes, it is possible to phenomenologically distinguish two contributions to the destruction; one that is specifically plasma-induced and another (at higher temperatures) in which both plasma and thermal activation have similar mechanisms. [ABSTRACT FROM AUTHOR]

The kinetic study of hydrogen oxidation with or without the presence of CO has been used as a tool to study the relative oxygen and CO adsorption strength on Pt nanoparticles, which are important parameters for fuel cell catalysts. It was found that the activation energy, which is determined by the oxygen binding energy, is influenced by the CNF graphite sheet orientation, CNF oxygen groups and catalyst preparation method. A weaker bonding of oxygen was indicated for Pt nanoparticles supported on platelet compared to Pt on fishbone CNFs. Moreover, oxygen seemed to be more strongly bonded to Pt particles on CNFs prepared by deposition–precipitation compared to those prepared by incipient wetness impregnation and a metal-oxide colloid method. Enhanced CO-adsorption was indicated for Pt supported on carbon nanofibers with introduced oxygen groups. [ABSTRACT FROM AUTHOR]

The interaction of LnCl3 ·6H2O (Ln = Pr, Nd, and Tb) with the alkoxy derivatives of aluminum (RO)nAlCl3-n (where R = Et or iso-Bu; n = 1-3) in organic solvents was studied. It was found that the reaction of the crystal water of LnCl3 · 6H2O with (RO)nAlCl3-n resulted in the partial dehydration of the crystal hydrates with the formation of an alcohol (ROH) and the LnCl3 · 3H2O · 3(RO)mAl(OH)Cl2-m complex (m = 1, 2). The solid colloidal particles of this complex and a solvent form a lanthanide-containing gel. The physico-chemical (including luminescence) and catalytic properties of the complex in butadiene polymerization and 1,1 -gem-dibromo-2-phenylcyclopropane dehalogenation were studied. [ABSTRACT FROM AUTHOR]

The paramount progress in the field of organic–inorganic hybrid nanomaterials was stimulated by numerous applications in chemistry, physics, life sciences, medicine, and technology. Currently, in the field of hybrid materials, researchers may choose either to mimic complex natural materials or to compete with nature by constructing new artificial materials. The deep mechanistic understanding and structural insight achieved in recent years will guide a new wave in the design of hybrid materials at the atomic and molecular levels. [ABSTRACT FROM AUTHOR]

Bimetallic core/shell nanoparticles (NPs) are the subject of intense research due to their unique electronic, optical and catalytic properties. Accurate and independent control over the dimensions of both core and shell would allow for unprecedented catalytic performance. Here, we demonstrate that both core and shell dimensions of Pd/Pt core/shell nanoparticles (NPs) supported on Al2O3 substrates can be controlled at the sub-nanometer level by using a novel strategy based on atomic layer deposition (ALD). From the results it is derived that the main conditions for accurate dimension control of these core/shell NPs are: (i) a difference in surface energy between the deposited core metal and the substrate to obtain island growth; (ii) a process yielding linear growth of the NP cores with ALD cycles to obtain monodispersed NPs with a narrow size distribution; (iii) a selective ALD process for the shell metal yielding a linearly increasing thickness to obtain controllable shell growth exclusively on the cores. For Pd/Pt core/shell NPs it is found that a minimum core diameter of 1 nm exists above which the NP cores are able to catalytically dissociate the precursor molecules for shell growth. In addition, initial studies on the stability of these core/shell NPs have been carried out, and it has been demonstrated that core/shell NPs can be deposited by ALD on high aspect ratio substrates such as nanowire arrays. These achievements show therefore that ALD has significant potential for the preparation of tuneable heterogeneous catalyst systems. [ABSTRACT FROM AUTHOR]