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Catalysts, Volume 4, Issue 3 (September 2014), Pages 215-345

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Editorial

Jump to: Research, Review

Open AccessEditorial New Trends in Gold Catalysts
Catalysts 2014, 4(3), 299-304; doi:10.3390/catal4030299
Received: 26 June 2014 / Revised: 9 July 2014 / Accepted: 9 July 2014 / Published: 16 July 2014
Cited by 4 | PDF Full-text (991 KB) | HTML Full-text | XML Full-text
Abstract
Gold is an element that has fascinated mankind for millennia. The catalytic properties of gold have been a source of debate, due to its complete chemical inertness when in a bulk form, while it can oxidize CO at temperatures as low as [...] Read more.
Gold is an element that has fascinated mankind for millennia. The catalytic properties of gold have been a source of debate, due to its complete chemical inertness when in a bulk form, while it can oxidize CO at temperatures as low as ~200 K when in a nanocrystalline state, as discovered by Haruta in the late 1980s [1]. Since then, extensive activity in both applied and fundamental research on gold has been initiated. The importance of the catalysis by gold represents one of the fasted growing fields in science and is proven by the promising applications in several fields, such as green chemistry and environmental catalysis, in the synthesis of single-walled carbon nanotubes, as modifiers of Ni catalysts for methane steam and dry reforming reactions and in biological and electrochemistry applications. The range of reactions catalyzed by gold, as well as the suitability of different supports and the influence of the preparation conditions have been widely explored and optimized in applied research [2]. Gold catalysts appeared to be very different from the other noble metal-based catalysts, due to their marked dependence on the preparation method, which is crucial for the genesis of the catalytic activity. Several methods, including deposition-precipitation, chemical vapor deposition and cation adsorption, have been applied for the preparation of gold catalysts over reducible oxides, like TiO2. Among these methods, deposition-precipitation has been the most frequently employed method for Au loading, and it involves the use of tetrachloroauric (III) acid as a precursor. On the other hand, the number of articles dealing with Au-loaded acidic supports is smaller than that on basic supports, possibly because the deposition of [AuCl4] or [AuOHxCl4x] species on acidic supports is difficult, due to their very low point of zero charge. Despite this challenge, several groups have reported the use of acidic zeolites as supports for gold. Zeolites are promising supports for Au stabilization, because of the presence of ion-exchange sites, such as NH4+, that can be substituted by Au+ ions through the elimination of NH4Cl [3]. Moreover, zeolites, due to their high thermal stability, the presence of a large surface area and micropores, may hinder Au sintering. [...] Full article
(This article belongs to the Special Issue New Trends in Gold Catalysts)
Open AccessEditorial Perovskite Catalysts—A Special Issue on Versatile Oxide Catalysts
Catalysts 2014, 4(3), 305-306; doi:10.3390/catal4030305
Received: 28 July 2014 / Accepted: 1 August 2014 / Published: 7 August 2014
Cited by 3 | PDF Full-text (931 KB) | HTML Full-text | XML Full-text
Abstract
Perovskite-type catalysts have been prominent oxide catalysts for many years due to attributes such as flexibility in choosing cations, significant thermal stability, and the unique nature of lattice oxygen. Nearly 90% metallic elements of the Periodic Table can be stabilized in perovskite’s [...] Read more.
Perovskite-type catalysts have been prominent oxide catalysts for many years due to attributes such as flexibility in choosing cations, significant thermal stability, and the unique nature of lattice oxygen. Nearly 90% metallic elements of the Periodic Table can be stabilized in perovskite’s crystalline framework [1]. Moreover, by following the Goldschmidt rule [2], the A- and/or B-site elements can be partially substituted, making perovskites extremely flexible in catalyst design. One successful example is the commercialization of noble metal-incorporated perovskites (e.g., LaFe0.57Co0.38Pd0.05O3) for automotive emission control used by Daihatsu Motor Co. Ltd. [3]. Thus, growing interest in, and application of perovskites in the fields of material sciences, heterogeneous catalysis, and energy storage have prompted this Special Issue on perovskite catalysts. [...] Full article
(This article belongs to the Special Issue Perovskite Catalysts)

Research

Jump to: Editorial, Review

Open AccessArticle Enantiocomplementary Preparation of (S)- and (R)-Arylalkylcarbinols by Lipase-Catalysed Resolution and Mitsunobu Inversion: Impact of Lipase Amount
Catalysts 2014, 4(3), 215-225; doi:10.3390/catal4030215
Received: 13 February 2014 / Revised: 4 April 2014 / Accepted: 23 May 2014 / Published: 26 June 2014
Cited by 4 | PDF Full-text (1203 KB) | HTML Full-text | XML Full-text
Abstract
A series of arylalkylcarbinol derivatives were deracemized through sequential combination of Candida antarctica lipase B (CAL-B) catalyzed resolution by hydrolysis and Mitsunobu stereoinversion. The (S)-acetates were obtained in 71%–99% ee and 76%–89% yields. An enantiocomplementarity was established for the hydrolysis [...] Read more.
A series of arylalkylcarbinol derivatives were deracemized through sequential combination of Candida antarctica lipase B (CAL-B) catalyzed resolution by hydrolysis and Mitsunobu stereoinversion. The (S)-acetates were obtained in 71%–99% ee and 76%–89% yields. An enantiocomplementarity was established for the hydrolysis and acylation reactions with CAL-B lipase. Thus, the (S) and (R) enantiomers of Indan-1-yl acetate, 1,2,3,4-tetrahydro-1-naphthalenol acetate and 1-(2-naphthyl) ethyl acetate were obtained in 91%–99% ee and 76%–89% yield. Full article
(This article belongs to the Special Issue Enzymes in Organic Synthesis)
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Open AccessArticle Catalytic Activity of Mono- and Bi-Metallic Nanoparticles Synthesized via Microemulsions
Catalysts 2014, 4(3), 256-275; doi:10.3390/catal4030256
Received: 19 March 2014 / Revised: 9 May 2014 / Accepted: 13 June 2014 / Published: 1 July 2014
Cited by 4 | PDF Full-text (2638 KB) | HTML Full-text | XML Full-text
Abstract
Water-in-oil (w/o) microemulsions were used as a template for the synthesis of mono- and bi-metallic nanoparticles. For that purpose, w/o-microemulsions containing H2PtCl6, H2PtCl6 + Pb(NO3)2 and H2PtCl6 + Bi(NO) [...] Read more.
Water-in-oil (w/o) microemulsions were used as a template for the synthesis of mono- and bi-metallic nanoparticles. For that purpose, w/o-microemulsions containing H2PtCl6, H2PtCl6 + Pb(NO3)2 and H2PtCl6 + Bi(NO)3, respectively, were mixed with a w/o-microemulsion containing the reducing agent, NaBH4. The results revealed that it is possible to synthesize Pt, PtPb and PtBi nanoparticles of ~3–8 nm in diameter at temperatures of about 30°C. The catalytic properties of the bimetallic PtBi and PtPb nanoparticles were studied and compared with monometallic platinum nanoparticles. Firstly, the electrochemical oxidation of formic acid to carbon monoxide was investigated, and it was found that the resistance of the PtBi and PtPb nanoparticles against the catalyst-poisoning carbon monoxide was significantly higher compared to the Pt nanoparticles. Secondly, investigating the reduction of 4-nitrophenol to 4-aminophenol,we found that the bimetallic NPs are most active at 23 °C, while the order of the activity changes at higher temperatures, i.e., that the Pt nanoparticles are the most active ones at 36 and 49 °C. Furthermore, we observed a strong influence of the support, which was either a polymer or Al2O3. Thirdly, for the hydrogenation of allylbenzene to propylbenzene, the monometallic Pt NPs turned out to be the most active catalysts, followed by the PtPb and PtBi NPs. Comparing the two bimetallic nanoparticles, one sees that the PtPb NPs are significantly more active than the respective PtBi NPs. Full article
(This article belongs to the Special Issue Synthesis of Nanostructured Catalytic Materials from Microemulsions)
Open AccessArticle Selective Hydrogenation of m-Dinitrobenzene to m-Nitroaniline over Ru-SnOx/Al2O3 Catalyst
Catalysts 2014, 4(3), 276-288; doi:10.3390/catal4030276
Received: 19 May 2014 / Revised: 23 June 2014 / Accepted: 25 June 2014 / Published: 14 July 2014
Cited by 2 | PDF Full-text (2525 KB) | HTML Full-text | XML Full-text
Abstract
Series catalysts of Ru-SnOx/Al2O3 with varying SnOx loading of 0–3 wt% were prepared, and their catalytic activity and selectivity have been discussed and compared for the selective hydrogenation of m-dinitrobenzene (m-DNB) to m [...] Read more.
Series catalysts of Ru-SnOx/Al2O3 with varying SnOx loading of 0–3 wt% were prepared, and their catalytic activity and selectivity have been discussed and compared for the selective hydrogenation of m-dinitrobenzene (m-DNB) to m-nitroaniline (m-NAN). The Ru-SnOx/Al2O3 catalysts were characterized by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and hydrogen temperature-programmed reduction (H2-TPR) and desorption (H2-TPD). Under the modification of SnOx, the reaction activity increased obviously, and the best selectivity to m-NAN reached above 97% at the complete conversion of m-DNB. With the increasing of the SnOx loading, the amount of active hydrogen adsorption on the surface of the catalyst increased according to the H2-TPD analysis, and the electron transferred from Ru to SnOx species, as determined by XPS, inducing an electron-deficient Ru, which is a benefit for the absorption of the nitro group. Therefore, the reaction rate and product selectivity were greatly enhanced. Moreover, the Ru-SnOx/Al2O3 catalyst presented high stability: it could be recycled four times without any loss in activity and selectivity. Full article
(This article belongs to the Special Issue Metal Catalysts Recycling and Heterogeneous/Homogeneous Catalysis)
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Open AccessArticle Polymer Supported Triphenylphosphine-Palladium Acetate Complex PS-TPP-Pd(OAc)2 as a Heterogeneous and Reusable Catalyst for Indirect Reductive Amination of Aldehydes
Catalysts 2014, 4(3), 289-298; doi:10.3390/catal4030289
Received: 9 April 2014 / Revised: 27 June 2014 / Accepted: 30 June 2014 / Published: 15 July 2014
Cited by 2 | PDF Full-text (645 KB) | HTML Full-text | XML Full-text
Abstract
Indirect reductive amination of aldehydes, catalyzed by polymer supported triphenylphosphine-palladium acetate complex PS-TPP-Pd(OAc)2 catalyst have been developed. The imine is prepared with molecular sieves in the first stage, followed by reduction with potassium formate catalyzed by PS-TPP-Pd(OAc)2. The recovered [...] Read more.
Indirect reductive amination of aldehydes, catalyzed by polymer supported triphenylphosphine-palladium acetate complex PS-TPP-Pd(OAc)2 catalyst have been developed. The imine is prepared with molecular sieves in the first stage, followed by reduction with potassium formate catalyzed by PS-TPP-Pd(OAc)2. The recovered catalyst could be reused for four consecutive cycles without loss in activity and provided an excellent yield of the desired products. Full article
(This article belongs to the Special Issue Metal Catalysts Recycling and Heterogeneous/Homogeneous Catalysis)
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Review

Jump to: Editorial, Research

Open AccessReview Structured Perovskite-Based Catalysts and Their Application as Three-Way Catalytic Converters—A Review
Catalysts 2014, 4(3), 226-255; doi:10.3390/catal4030226
Received: 14 March 2014 / Revised: 9 June 2014 / Accepted: 11 June 2014 / Published: 1 July 2014
Cited by 13 | PDF Full-text (3544 KB) | HTML Full-text | XML Full-text
Abstract
Automotive Three-Way Catalysts (TWC) were introduced more than 40 years ago. Despite that, the development of a sustainable TWC still remains a critical research topic owing to the increasingly stringent emission regulations together with the price and scarcity of precious metals. Among [...] Read more.
Automotive Three-Way Catalysts (TWC) were introduced more than 40 years ago. Despite that, the development of a sustainable TWC still remains a critical research topic owing to the increasingly stringent emission regulations together with the price and scarcity of precious metals. Among other material classes, perovskite-type oxides are known to be valuable alternatives to conventionally used TWC compositions and have demonstrated to be suitable for a wide range of automotive applications, ranging from TWC to Diesel Oxidation Catalysts (DOC), from NOx Storage Reduction catalysts (NSR) to soot combustion catalysts. The interest in these catalysts has been revitalized in the past ten years by the introduction of the concept of catalyst regenerability of perovskite-based TWC, which is in principle well applicable to other catalytic processes as well, and by the possibility to reduce the amounts of critical elements, such as precious metals without seriously lowering the catalytic performance. The aim of this review is to show that perovskite-type oxides have the potential to fulfil the requirements (high activity, stability, and possibility to be included into structured catalysts) for implementation in TWC. Full article
(This article belongs to the Special Issue Perovskite Catalysts)
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Open AccessReview Catalyst-Controlled Site-Selectivity Switching in Pd-Catalyzed Cross-Coupling of Dihaloarenes
Catalysts 2014, 4(3), 307-320; doi:10.3390/catal4030307
Received: 29 May 2014 / Revised: 28 July 2014 / Accepted: 5 August 2014 / Published: 20 August 2014
Cited by 8 | PDF Full-text (500 KB) | HTML Full-text | XML Full-text
Abstract
Pd-catalyzed, site-selective mono-cross-coupling of substrates with two identical halo groups is a useful method for synthesizing substituted monohalogenated arenes. Such arenes constitute an important class of compounds, which are commonly identified as drug components and synthetic intermediates. Traditionally, these site-selective reactions have [...] Read more.
Pd-catalyzed, site-selective mono-cross-coupling of substrates with two identical halo groups is a useful method for synthesizing substituted monohalogenated arenes. Such arenes constitute an important class of compounds, which are commonly identified as drug components and synthetic intermediates. Traditionally, these site-selective reactions have been realized in a “substrate-controlled” manner, which is based on the steric and electronic differences between the two carbon-halogen bonds of the substrate. Recently, an alternative strategy, “catalyst-controlled” site-selective cross-coupling, has emerged. In this strategy, the preferred reaction site of a dihaloarene can be switched, merely by changing the catalyst used. This type of selective reaction further expands the utility of Pd-catalyzed cross-coupling. In this review, we summarize the reported examples of catalyst-controlled site-selectivity switching in Pd-catalyzed cross-coupling of dihaloarenes. Full article
(This article belongs to the Special Issue Palladium Catalysts for Cross-Coupling Reaction)
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Open AccessReview Palladium-Catalyzed Cross-Coupling Reactions of Perfluoro Organic Compounds
Catalysts 2014, 4(3), 321-345; doi:10.3390/catal4030321
Received: 25 June 2014 / Revised: 19 August 2014 / Accepted: 21 August 2014 / Published: 10 September 2014
Cited by 5 | PDF Full-text (2029 KB) | HTML Full-text | XML Full-text
Abstract
In this review, we summarize our recent development of palladium(0)-catalyzed cross-coupling reactions of perfluoro organic compounds with organometallic reagents. The oxidative addition of a C–F bond of tetrafluoroethylene (TFE) to palladium(0) was promoted by the addition of lithium iodide, affording a trifluorovinyl [...] Read more.
In this review, we summarize our recent development of palladium(0)-catalyzed cross-coupling reactions of perfluoro organic compounds with organometallic reagents. The oxidative addition of a C–F bond of tetrafluoroethylene (TFE) to palladium(0) was promoted by the addition of lithium iodide, affording a trifluorovinyl palladium(II) iodide. Based on this finding, the first palladium-catalyzed cross-coupling reaction of TFE with diarylzinc was developed in the presence of lithium iodide, affording α,β,β-trifluorostyrene derivatives in excellent yield. This coupling reaction was expanded to the novel Pd(0)/PR3-catalyzed cross-coupling reaction of TFE with arylboronates. In this reaction, the trifluorovinyl palladium(II) fluoride was a key reaction intermediate that required neither an extraneous base to enhance the reactivity of organoboronates nor a Lewis acid additive to promote the oxidative addition of a C–F bond. In addition, our strategy utilizing the synergetic effect of Pd(0) and lithium iodide could be applied to the C–F bond cleavage of unreactive hexafluorobenzene (C6F6), leading to the first Pd(0)-catalyzed cross-coupling reaction of C6F6 with diarylzinc compounds. Full article
(This article belongs to the Special Issue Palladium Catalysts for Cross-Coupling Reaction)

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