http://www.mdpi.com/journal/catalysts Latest open access articles published in Catalysts at http://www.mdpi.com/journal/catalysts/ http://www.mdpi.com/2073-4344/2/1/121/ The effect of gold presence on carbon monoxide oxidation and ethanol steam reforming catalytic behavior of two Ce-Zr-Co mixed oxides catalysts with a constant Co charge and different Ce/Zr ratios was investigated. The Ce-Zr-Co mixed oxides were obtained by the pseudo sol-gel like method, based on metallic propionates polymerization and thermal decomposition, whereas the gold-supported Ce-Zr-Co mixed oxides catalysts were prepared using the direct anionic exchange. The catalysts were characterized using XRD, TPR, and EDXS-TEM. The presence of Au in doped Ce-Zr-Co oxide catalyst decreases the temperature necessary to reduce the cobalt and the cerium loaded in the catalyst and favors a different reaction pathway, improving the acetaldehyde route by ethanol dehydrogenation, instead of the ethylene route by ethanol dehydration or methane re-adsorption, thus increasing the catalytic activity and selectivity into hydrogen. http://www.mdpi.com/2073-4344/2/1/121/ Fri, 03 Feb 2012 00:00:00 CET Catalysts 2012-02-03 2 1 Article 121 138 2073-4344 Influence of Gold on Ce-Zr-Co Fluorite-Type Mixed Oxide Catalysts for Ethanol Steam Reforming 2012-02-03 doi: 10.3390/catal2010121 Julio Cesar Vargas Svetlana Ivanova Sébastien Thomas Anne-Cécile Roger Véronique Pitchon http://www.mdpi.com/2073-4344/2/1/101/ Supported gold catalysts are highly active in oxidation reactions. Beside the most frequently studied CO oxidation, they are readily applied in the epoxidation of more or less complex olefinic compounds using air or oxygen directly or other oxidants like peroxides of various kinds. Less frequently though, the reverse reaction, ring opening with single or double C–O scission is also investigated. These and other ring making and breaking reactions are reviewed, and the catalytic roles of gold species are described. http://www.mdpi.com/2073-4344/2/1/101/ Wed, 01 Feb 2012 00:00:00 CET Catalysts 2012-02-01 2 1 Review 101 120 2073-4344 Monometallic Supported Gold Catalysts in Organic Transformations: Ring Making and Ring Breaking 2012-02-01 doi: 10.3390/catal2010101 Krisztián Csankó Pál Sipos István Pálinkó http://www.mdpi.com/2073-4344/2/1/85/ Catalytic hydrogenation of anthracene was studied over Ni supported on Hβ-zeolite catalyst under supercritical carbon dioxide (sc-CO2) solvent. Hydrogenation of anthracene in sc-CO2 yielded 100% conversion at 100 °C, which is attributed to the reduced mass transfer limitations, and increased solubility of H2 and substrate in the reaction medium. The total pressure of 7 MPa was found to be optimum for high selectivity of octahydroanthracene (OHA). The conversion and selectivity for OHA increased with an increase in H2 partial pressure, which is attributed to higher concentration of hydrogen atoms at higher H2 pressures. The selectivity reduced the pressure below 7 MPa because of enhanced desorption of the tetrahydro-molecules and intermediates from Ni active sites, due to higher solubility of the surface species in sc-CO2. The selectivity of OHA increased with the increase in catalyst weight and reaction time. The rate of hydrogenation of anthracene was compared with that found for napthalene and phenanthrene. The use of acetonitrile as co-solvent or expanded liquid with CO2 decreased the catalytic activity. http://www.mdpi.com/2073-4344/2/1/85/ Mon, 30 Jan 2012 00:00:00 CET Catalysts 2012-01-30 2 1 Article 85 100 2073-4344 Hydrogenation of Anthracene in Supercritical Carbon Dioxide Solvent Using Ni Supported on Hβ-Zeolite Catalyst 2012-01-30 doi: 10.3390/catal2010085 Endalkachew Sahle-Demessie Venu Gopal Devulapelli Ashraf Aly Hassan http://www.mdpi.com/2073-4344/2/1/68/ Direct catalytic valorization of bioethanol to 1-butanol over different alumina supported catalysts was studied. Thirteen (13) heterogeneous catalysts were screened in search for the optimal material composition for direct one-pot conversion of ethanol to 1-butanol. For the most promising catalyst, a 25% ethanol conversion with 80% selectivity (among liquid carbon products) to 1-butanol could be reached at 250 °C. Additionally, the reaction kinetics and mechanisms were further investigated upon use of the most suitable catalyst candidate. http://www.mdpi.com/2073-4344/2/1/68/ Fri, 13 Jan 2012 00:00:00 CET Catalysts 2012-01-13 2 1 Article 68 84 2073-4344 One-Pot Liquid-Phase Catalytic Conversion of Ethanol to 1-Butanol over Aluminium Oxide—The Effect of the Active Metal on the Selectivity 2012-01-13 doi: 10.3390/catal2010068 Toni Riittonen Esa Toukoniitty Dipak Kumar Madnani Anne-Riikka Leino Krisztian Kordas Maria Szabo Andras Sapi Kalle Arve Johan Wärnå Jyri-Pekka Mikkola http://www.mdpi.com/2073-4344/2/1/56/ Ethanol and pentose were produced from lignocellulosic napiergrass by the simultaneous saccharification and fermentation process (SSF) using hydrolytic enzyme and S. Cerevisiae. After the ethanol was removed, the pentose solution was subjected to photocatalytic hydrogen evolution with Pt-loaded TiO2 under UV-irradiation. This process converted 100 g of napiergrass into 12.3 g of ethanol and 1.76 g of hydrogen whose total combustion energy of (∆H) was 615 kJ. This was close to the ∆H (639 kJ) of the pentose (13.6 g) and hexose (27.4 g) obtained by the cellulose-saccharification of 100 g of napiergrass. http://www.mdpi.com/2073-4344/2/1/56/ Thu, 22 Dec 2011 00:00:00 CET Catalysts 2011-12-22 2 1 Article 56 67 2073-4344 Hydrogen Evolution from Napiergrass by the Combination of Biological Treatment and a Pt-Loaded TiO2-Photocatalytic Reaction 2011-12-22 doi: 10.3390/catal2010056 Tsutomu Shiragami Takayuki Tomo Hikaru Tsumagari Yasuyuki Ishii Masahide Yasuda http://www.mdpi.com/2073-4344/2/1/38/ Base metal promoted gold/titania catalysts were synthesized, characterized and tested in CO oxidation reaction. Catalysts containing dopant metals in higher oxidation states exhibited higher activity than catalysts containing dopants in reduced states. The activity of fresh catalysts promoted by Cu, Fe and Ni was similar to the unpromoted one, but treatment in reducing and oxidizing atmospheres revealed the supremacy of the copper promoted catalyst. The sequential deposition method proved to be better than the co-deposition—precipitation method. An attempt to explain these differences using XPS, FTIR and H2 TPR was performed. http://www.mdpi.com/2073-4344/2/1/38/ Thu, 22 Dec 2011 00:00:00 CET Catalysts 2011-12-22 2 1 Article 38 55 2073-4344 The Influence of Base Metal (M) Oxidation State in Au-M-O/TiO2 Systems on Their Catalytic Activity in Carbon Monoxide Oxidation 2011-12-22 doi: 10.3390/catal2010038 Jan Mizera Nika Spiridis Robert P. Socha Małgorzata Zimowska Ryszard Grabowski Katarzyna Samson Józef Korecki http://www.mdpi.com/2073-4344/2/1/24/ Gold has been considered as an active catalyst only when suitable techniques of preparation provided high metal dispersion. A comprehensive survey of the different methods now available for preparing active gold catalysts is reported with particular attention to the role of the supporting material in determining catalyst characteristics. http://www.mdpi.com/2073-4344/2/1/24/ Wed, 21 Dec 2011 00:00:00 CET Catalysts 2011-12-21 2 1 Review 24 37 2073-4344 The Art of Manufacturing Gold Catalysts 2011-12-21 doi: 10.3390/catal2010024 Laura Prati Alberto Villa http://www.mdpi.com/2073-4344/2/1/1/ A novel preparation method was developed for the preparation of gold/iron oxide supported catalysts using the bimetallic carbonyl cluster salts [NEt4]4[Au4Fe4(CO)16] and [NEt4][AuFe4(CO)16] as precursors of highly dispersed nanoparticles over different supports. A series of catalysts with different metal loadings were prepared and tested in the complete oxidation of dichlorobenzene, toluene, methanol and in the preferential oxidation of CO in the presence of H2 (PROX) as model reactions. The characterization by BET, XRD, TEM, H2-TPR, ICP-AES and XPS point out the way the nature of the precursors and the thermal treatment conditions affected the dispersion of the active phase and their catalytic activity in the studied reactions. http://www.mdpi.com/2073-4344/2/1/1/ Wed, 21 Dec 2011 00:00:00 CET Catalysts 2011-12-21 2 1 Article 1 23 2073-4344 Gold/Iron Carbonyl Clusters for Tailored Au/FeOx Supported Catalysts 2011-12-21 doi: 10.3390/catal2010001 Rosa Bonelli Stefano Zacchini Stefania Albonetti http://www.mdpi.com/2073-4344/1/1/175/ Low-temperature water-gas shift reaction (WGS) using gold catalyst is expected to be an attractive technique to realize an efficient on-site hydrogen production process. In this paper, Au/Fe3O4 catalysts for promoting the WGS below 150 °C were developed by a preliminary reduction of Au/iron oxide (Fe3+) catalyst utilizing high reactivity of Au nano-particles. The reduction was conducted under a CO, H2, or CO/H2O stream at either 140 or 200 °C, and the effect of reduction conditions on the characteristics of the Au/Fe3O4 catalyst and on the catalytic activity in WGS at 80 °C was investigated. The reaction progress during the pre-reduction treatment was qualitatively analyzed, and it was found that the iron oxide in Au/Fe2O3 calcined at 200 °C was easily reduced to Fe3O4 phase in all reduction conditions. The reduction conditions affected the characteristics of both Au and iron oxide, but all of the reduced catalysts had small Fe3O4 particles of less than 20 nm with Au particles on the surface. The surface area and content of cationic Au were high in the order of CO, H2, CO/H2O, and 140, 200 °C. In the WGS test at 80 °C using the developed catalysts, the activities of the catalysts pre-reduced by CO at 140 or 200 °C and by H2 at 140 °C were very high with 100% CO conversion even at such a low temperature. These results indicated that factors such as higher surface area, crystallized Fe3O4, and cationic Au content contributed to the catalytic activity. http://www.mdpi.com/2073-4344/1/1/175/ Fri, 09 Dec 2011 00:00:00 CET Catalysts 2011-12-09 1 1 Article 175 190 2073-4344 Pre-Reduction of Au/Iron Oxide Catalyst for Low-Temperature Water-Gas Shift Reaction Below 150 °C 2011-12-09 doi: 10.3390/catal1010175 Shinji Kudo Taisuke Maki Takashi Fukuda Kazuhiro Mae http://www.mdpi.com/2073-4344/1/1/155/ Au-based catalysts supported on carbon materials with different structures such as graphite (G) and fishbone type carbon nanofibers (CNF-F) were prepared using two different methods (impregnation and gold-sol) to be tested in the water gas shift (WGS) reaction. Atomic absorption spectrometry, transmission electron microscopy (TEM), temperature-programmed oxidation (TPO), X-ray diffraction (XRD), Raman spectroscopy, elemental analyses (CNH), N2 adsorption-desorption analysis, temperature-programmed reduction (TPR) and temperature-programmed decomposition were employed to characterize both the supports and catalysts. Both the crystalline nature of the carbon supports and the method of gold incorporation had a strong influence on the way in which Au particles were deposited on the carbon surface. The higher crystallinity and the smaller and well dispersed Au particle size were, the higher activity of the catalysts in the WGS reaction was noted. Finally, catalytic activity showed an important dependence on the reaction temperature and steam-to-CO molar ratio. http://www.mdpi.com/2073-4344/1/1/155/ Fri, 09 Dec 2011 00:00:00 CET Catalysts 2011-12-09 1 1 Article 155 174 2073-4344 Nano-Scale Au Supported on Carbon Materials for the Low Temperature Water Gas Shift (WGS) Reaction 2011-12-09 doi: 10.3390/catal1010155 Sonia Gil Amaya Romero Antonio de Lucas Paula Sánchez Fernando Dorado Ana Raquel de la Osa Jesús Manuel García-Vargas Jose Luis Valverde http://www.mdpi.com/2073-4344/1/1/97/ Mesoporous silica materials (MSM) with ordered and controllable porous structure, high surface area, pore volume and thermal stability are very suitable catalyst supports, because they provide high dispersion of metal nanoparticles and facilitate the access of the substrates to the active sites. Since the conventional wet-impregnation and deposition-precipitation methods are not appropriate for the incorporation of gold nanoparticles (AuNPs) into MSM, considerable efforts have been made to develop suitable methods to synthesize Au/MSM catalysts, because the incorporation of AuNPs into the channel system can prevent their agglomeration and leaching. In this review, we summarize the main methods to synthesize active gold catalysts supported on MSM. Examples and details of the preparative methods, as well as selected applications are provided. We expect this article to be interesting to researchers due to the wide variety of chemical reactions that can be catalyzed by gold supported catalysts. http://www.mdpi.com/2073-4344/1/1/97/ Fri, 02 Dec 2011 00:00:00 CET Catalysts 2011-12-02 1 1 Review 97 154 2073-4344 Synthesis of Gold Catalysts Supported on Mesoporous Silica Materials: Recent Developments 2011-12-02 doi: 10.3390/catal1010097 Luis-Felipe Gutiérrez Safia Hamoudi Khaled Belkacemi http://www.mdpi.com/2073-4344/1/1/83/ The structural and functional design of metal nanoparticles has recently allowed remarkable progress in the development of high-performance catalysts. Gold nanoparticles (AuNPs) are among the most innovative catalysts, despite bulk Au metal being regarded as stable and inactive. The hybridization of metal NPs has attracted major interest in the field of advanced nanocatalysts, due to electro-mediated ligand effects. In practical terms, metal NPs need to be supported on a suitable matrix to avoid any undesirable aggregation; many researchers have reported the potential of polymer-supported AuNPs. However, the use of conventional polymer matrices make it difficult to take full advantage of the inherent properties of the metal NPs, since most of active NPs are imbedded inside the polymer support. This results in poor accessibility for the reactants. Herein, we report the topochemical synthesis of Au and palladium (Pd) bimetallic NPs over the surfaces of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized cellulose nanofibers (TOCNs), and their exceptional catalytic performance. Highly-dispersed AuPdNPs were successfully synthesized in situ on the crystal surfaces of TOCNs with a very high density of carboxylate groups. The AuPdNPs@TOCN nanocomposites exhibit excellent catalytic efficiencies in the aqueous reduction of 4-nitrophenol to 4-aminophenol, depending on the molar ratios of Au and Pd. http://www.mdpi.com/2073-4344/1/1/83/ Fri, 25 Nov 2011 00:00:00 CET Catalysts 2011-11-25 1 1 Article 83 96 2073-4344 Synthesis and Catalytic Features of Hybrid Metal Nanoparticles Supported on Cellulose Nanofibers 2011-11-25 doi: 10.3390/catal1010083 Akihiro Azetsu Hirotaka Koga Akira Isogai Takuya Kitaoka http://www.mdpi.com/2073-4344/1/1/69/ Bimetallic nanoparticles have attracted significant attention as their electrochemical and catalytic properties being superior to those of the individual component nanoparticles. In this study, gold-silver hybrid nanoparticles (AuAgNPs) with an Aucore-Agshell nanostructure were successfully synthesized on zinc oxide (ZnO) whiskers. The as-prepared nanocatalyst, denoted AuAgNPs@ZnO whisker, exhibits an excellent catalytic efficiency in the aqueous reduction of 4-nitrophenol to 4-aminophenol; the turnover frequency was up to 40 times higher than that of each component nanoparticle. Their unique features were attributed to the electronic ligand effect at the bimetallic interface. In addition, the AuAgNPs were synthesized on a ZnO whisker-containing paper with a fiber-network microstructure, which was prepared via a papermaking technique. The paper-structured AuAgNPs composite possessed both a paper-like practical utility and a good catalytic performance. Furthermore, the on-paper synthesis process for these bimetallic nanocatalysts is facile. These easy-to-handle nanocatalyst hybrid composites are expected to find a wide range of applications in various chemical and catalytic processes. http://www.mdpi.com/2073-4344/1/1/69/ Fri, 25 Nov 2011 00:00:00 CET Catalysts 2011-11-25 1 1 Article 69 82 2073-4344 In Situ Synthesis of Bimetallic Hybrid Nanocatalysts on a Paper-Structured Matrix for Catalytic Applications 2011-11-25 doi: 10.3390/catal1010069 Hirotaka Koga Yuuka Umemura Takuya Kitaoka http://www.mdpi.com/2073-4344/1/1/52/ The present study tries to give an insight to the combination of the homogeneous and heterogeneous catalytic properties in a new class of materials. Well dispersed gold nanoparticles on an ionic liquid layer supported on a mineral carrier have been prepared. This work is concentrated on the characterizations and understanding of the interactions between all the components of the catalytic system. The application of the materials in the reaction of oxidation of carbon monoxide shows rather unexpected results—a good catalytic activity completely independent of the temperature. http://www.mdpi.com/2073-4344/1/1/52/ Fri, 25 Nov 2011 00:00:00 CET Catalysts 2011-11-25 1 1 Article 52 68 2073-4344 Gold Functionalized Supported Ionic Liquids Catalyst for CO Oxidation 2011-11-25 doi: 10.3390/catal1010052 Svetlana Ivanova Luis Francisco Bobadilla Anna Penkova Francisca Romero Sarria Miguel Angel Centeno Jose Antonio Odriozola http://www.mdpi.com/2073-4344/1/1/40/ The adsorption energies and the activation energy barriers for a series of reactions catalyzed by gold surfaces and obtained theoretically through density functional theory (DFT) based calculations were considered to clarify the role of the low coordinated gold atoms and the role of doping in the catalytic activity of gold. The effect of the surface steps was introduced by comparison of the activation energy barriers and of the adsorption energies on flat gold surfaces such as the Au(111) surface with those on stepped surfaces such as the Au(321) or the Au(110) surfaces. It is concluded that the presence of low coordinated atoms on the latter surfaces increases the adsorption energies of the reactants and decreases the activation energy barriers. Furthermore, the increasing of the adsorption energy of the reaction products can lead to lower overall reaction rates in the presence of low gold coordinated atoms due to desorption limitations. On the other hand, the effect of doping gold surfaces with other transition metal atoms was analyzed using the dissociation reaction of molecular oxygen as a test case. The calculations showed that increasing the silver content in some gold surfaces was related to a considerable increment of the reactivity of bimetallic systems toward the oxygen dissociation. Importantly, that increment in the reactivity was enhanced by the presence of low coordinated atoms in the catalytic surface models considered. http://www.mdpi.com/2073-4344/1/1/40/ Mon, 21 Nov 2011 00:00:00 CET Catalysts 2011-11-21 1 1 Review 40 51 2073-4344 Catalytic Reactions on Model Gold Surfaces: Effect of Surface Steps and of Surface Doping 2011-11-21 doi: 10.3390/catal1010040 José L. C. Fajín Maria Natália D. S. Cordeiro José R. B. Gomes http://www.mdpi.com/2073-4344/1/1/18/ It is demonstrated that the support effects play a crucial role in the gold nanocatalysis. Two types of support are considered—the “inert” support of hexagonal boron nitride (h-BN) with the N and B vacancy defects and the “active” support of rutile TiO2(110). It is demonstrated that Au and Au2 can be trapped effectively by the vacancy defects in h-BN. In that case, the strong adsorption on the surface defects is accompanied by the charge transfer to/from the adsorbate. The excess of the positive or negative charge on the supported gold clusters can considerably promote their catalytic activity. Therefore gold clusters supported on the defected h-BN surface can not be considered as pseudo-free clusters. We also demonstrate that the rutile TiO2(110) support energetically promotes H2 dissociation on gold clusters. We show that the formation of the OH group near the supported gold cluster is an important condition for H2 dissociation. We demonstrate that the active sites towards H2 dissociation on the supported Aun are located at corners and edges of the gold cluster in the vicinity of the low coordinated oxygen atoms on TiO2(110). Thus catalytic activity of a gold nanoparticle supported on the rutile TiO2(110) surface is proportional to the length of the perimeter interface between the nanoparticle and the support. http://www.mdpi.com/2073-4344/1/1/18/ Thu, 17 Nov 2011 00:00:00 CET Catalysts 2011-11-17 1 1 Article 18 39 2073-4344 Role of the Support Effects on the Catalytic Activity of Gold Clusters: A Density Functional Theory Study 2011-11-17 doi: 10.3390/catal1010018 Min Gao Andrey Lyalin Tetsuya Taketsugu http://www.mdpi.com/2073-4344/1/1/3/ The emphasis of this review is atomically monodisperse Aun nanoclusters catalysts (n = number of metal atom in cluster) that are ideally composed of an exact number of metal atoms. Aun which range in size from a dozen to a few hundred atoms are particularly promising for nanocatalysis due to their unique core-shell structure and non-metallic electronic properties. Aun nanoclusters catalysts have been demonstrated to exhibit excellent catalytic activity in hydrogenation and oxidation processes. Such unique properties of Aun significantly promote molecule activation by enhancing adsorption energy of reactant molecules on catalyst surface. The structural determination of Aun nanoclusters allows for a precise correlation of particle structure with catalytic properties and also permits the identification of catalytically active sites on the gold particle at an atomic level. By learning these fundamental principles, one would ultimately be able to design new types of highly active and highly selective gold nanocluster catalysts for a variety of catalytic processes. http://www.mdpi.com/2073-4344/1/1/3/ Wed, 07 Sep 2011 00:00:00 CEST Catalysts 2011-09-07 1 1 Review 3 17 2073-4344 Atomically Monodisperse Gold Nanoclusters Catalysts with Precise Core-Shell Structure 2011-09-07 doi: 10.3390/catal1010003 Yan Zhu Rongchao Jin Yuhan Sun http://www.mdpi.com/2073-4344/1/1/1/ There is something intrinsically fascinating about catalysts. The thought that a material can speed up a reaction by hundreds or thousands of times without being consumed is truly amazing. I frequently have the pleasure of teaching undergraduate and graduate chemical reaction engineering courses that include sections on catalysts. I have found that students take an immediate interest in catalysts and are fascinated by how they work. I certainly have been captivated with catalysts myself, as I have devoted my entire academic career to studying their properties. [...] http://www.mdpi.com/2073-4344/1/1/1/ Mon, 09 May 2011 00:00:00 CEST Catalysts 2011-05-09 1 1 Editorial 1 2 2073-4344 Welcome to Catalysts––A New Open Access Journal for a Growing Scientific Community 2011-05-09 doi: 10.3390/catal1010001 Keith Hohn