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Catalysts, Volume 3, Issue 4 (December 2013), Pages 757-997

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Research

Jump to: Review

Open AccessArticle Sulfonate Ionic Liquid as a Stable and Active Catalyst for Levoglucosenone Production from Saccharides via Catalytic Pyrolysis
Catalysts 2013, 3(4), 757-773; doi:10.3390/catal3040757
Received: 25 July 2013 / Revised: 5 September 2013 / Accepted: 18 September 2013 / Published: 30 September 2013
Cited by 4 | PDF Full-text (775 KB) | HTML Full-text | XML Full-text
Abstract
In this study, various types of ionic liquids (ILs) were examined for catalytic activity in the pyrolysis of cellulose for the production of levoglucosenone, which is a valuable and versatile compound for the synthesis of a variety of novel compounds. Cellulose was [...] Read more.
In this study, various types of ionic liquids (ILs) were examined for catalytic activity in the pyrolysis of cellulose for the production of levoglucosenone, which is a valuable and versatile compound for the synthesis of a variety of novel compounds. Cellulose was simply mixed with the ILs and subjected for the pyrolysis, typically at 300 °C, to produce volatile products, including levoglucosenone, separated from the ILs phase. The type of IL anion significantly affected the catalysis, and the use of ILs bearing sulfonate anion resulted in distinguished yields of levoglucosenone and IL recoveries for the reutilization. Detailed thermogravimetric analysis and discussion on properties of ILs revealed the active and thermally stable nature of the sulfonate ILs. Catalytic pyrolysis with those ILs was applied to the conversion of other saccharides composed of glucose molecules, resulting in a preferential formation of levoglucosenone but at low yields as compared to that from cellulose. Full article
(This article belongs to the Special Issue Ionic Liquids in Catalysis)
Open AccessArticle Palladium-Catalyzed Polyfluorophenylation of Porphyrins with Bis(polyfluorophenyl)zinc Reagents
Catalysts 2013, 3(4), 839-852; doi:10.3390/catal3040839
Received: 9 August 2013 / Revised: 25 September 2013 / Accepted: 8 October 2013 / Published: 22 October 2013
Cited by 2 | PDF Full-text (259 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
A facile and efficient method for the synthesis of pentafluorophenyl- and related polyfluorophenyl-substituted porphyrins has been achieved via palladium-catalyzed cross-coupling reactions of brominated porphyrins with bis(polyfluorophenyl)zinc reagents. The reaction is applicable to a variety of free-base bromoporphyrins, their metal complexes, and a [...] Read more.
A facile and efficient method for the synthesis of pentafluorophenyl- and related polyfluorophenyl-substituted porphyrins has been achieved via palladium-catalyzed cross-coupling reactions of brominated porphyrins with bis(polyfluorophenyl)zinc reagents. The reaction is applicable to a variety of free-base bromoporphyrins, their metal complexes, and a number of bis(polyfluorophenyl)zinc reagents. Full article
(This article belongs to the Special Issue Palladium Catalysts for Cross-Coupling Reaction)
Open AccessArticle Formic Acid Oxidation over Hierarchical Porous Carbon Containing PtPd Catalysts
Catalysts 2013, 3(4), 902-913; doi:10.3390/catal3040902
Received: 24 August 2013 / Revised: 15 October 2013 / Accepted: 22 October 2013 / Published: 31 October 2013
Cited by 1 | PDF Full-text (578 KB) | HTML Full-text | XML Full-text
Abstract
The use of high surface monolithic carbon as support for catalysts offers important advantage, such as elimination of the ohmic drop originated in the interparticle contact and improved mass transport by ad-hoc pore design. Moreover, the approach discussed here has the advantage [...] Read more.
The use of high surface monolithic carbon as support for catalysts offers important advantage, such as elimination of the ohmic drop originated in the interparticle contact and improved mass transport by ad-hoc pore design. Moreover, the approach discussed here has the advantage that it allows the synthesis of materials having a multimodal porous size distribution, with each pore size contributing to the desired properties. On the other hand, the monolithic nature of the porous support also imposes new challenges for metal loading. In this work, the use of Hierarchical Porous Carbon (HPC) as support for PtPd nanoparticles was explored. Three hierarchical porous carbon samples (denoted as HPC-300, HPC-400 and HPC-500) with main pore size around 300, 400 and 500 nm respectively, are used as porous support. PtPd nanoparticles were loaded by impregnation and subsequent chemical reduction with NaBH4. The resulting material was characterized by EDX, XRD and conventional electrochemical techniques. The catalytic activity toward formic acid and methanol electrooxidation was evaluated by electrochemical methods, and the results compared with commercial carbon supported PtPd. The Hierarchical Porous Carbon support discussed here seems to be promising for use in DFAFC anodes. Full article
(This article belongs to the Special Issue Carbon Catalysts)
Open AccessArticle An Ionic Liquid Solution of Chitosan as Organocatalyst
Catalysts 2013, 3(4), 914-921; doi:10.3390/catal3040914
Received: 29 August 2013 / Revised: 9 October 2013 / Accepted: 24 October 2013 / Published: 11 November 2013
Cited by 2 | PDF Full-text (199 KB) | HTML Full-text | XML Full-text
Abstract
Chitosan, which is derived from the biopolymer chitin, can be readily dissolved in different ionic liquids. The resulting homogeneous solutions were applied in an asymmetric Aldol reaction. Depending on the type of ionic liquid used, high asymmetric inductions were found. The influence [...] Read more.
Chitosan, which is derived from the biopolymer chitin, can be readily dissolved in different ionic liquids. The resulting homogeneous solutions were applied in an asymmetric Aldol reaction. Depending on the type of ionic liquid used, high asymmetric inductions were found. The influence of different additives was also studied. The best results were obtained in [BMIM][Br] without an additive. Full article
(This article belongs to the Special Issue Ionic Liquids in Catalysis)
Open AccessArticle Rate Parameter Distributions for Isobutane Dehydrogenation and Isobutene Dimerization and Desorption over HZSM-5
Catalysts 2013, 3(4), 922-941; doi:10.3390/catal3040922
Received: 10 October 2013 / Revised: 1 November 2013 / Accepted: 4 November 2013 / Published: 15 November 2013
Cited by 1 | PDF Full-text (661 KB) | HTML Full-text | XML Full-text
Abstract
Deconvolution of the evolved isobutene data obtained from temperature-programmed, low-pressure steady-state conversion of isobutane over HZSM-5 has yielded apparent activation energies for isobutane dehydrogenation, isobutene dimerization and desorption. Intrinsic activation energies and associated isobutane collision frequencies are also estimated. A combination of [...] Read more.
Deconvolution of the evolved isobutene data obtained from temperature-programmed, low-pressure steady-state conversion of isobutane over HZSM-5 has yielded apparent activation energies for isobutane dehydrogenation, isobutene dimerization and desorption. Intrinsic activation energies and associated isobutane collision frequencies are also estimated. A combination of wavelet shrinkage denoising, followed by time-varying flexible least squares of the evolved mass-spectral abundance data over the temperature range 150 to 450 °C, provides accurate, temperature-dependent, apparent rate parameters. Intrinsic activation energies for isobutane dehydrogenation range from 86 to 235.2 kJ mol−1 (average = 150 ± 42 kJ mol−1) for isobutene dimerization from 48.3 to 267 kJ mol−1 (average = 112 ± 74 kJ mol−1) and for isobutene desorption from 64.4 to 97.8 kJ mol−1 (average = 77 ± 12 kJ mol−1). These wide ranges reflect the heterogeneity and acidity of the zeolite surface and structure. Seven distinct locations and sites, including Lewis and Brønsted acid sites can be identified in the profiles. Isobutane collision frequencies range from 10−0.4 to 1022.2 s−1 and are proportional to the accessibility of active sites, within the HZSM-5 micropores or on the external surface. Full article
Open AccessArticle Facile and Efficient Acetylation of Primary Alcohols and Phenols with Acetic Anhydride Catalyzed by Dried Sodium Bicarbonate
Catalysts 2013, 3(4), 954-965; doi:10.3390/catal3040954
Received: 22 September 2013 / Revised: 10 October 2013 / Accepted: 15 November 2013 / Published: 3 December 2013
Cited by 4 | PDF Full-text (234 KB) | HTML Full-text | XML Full-text
Abstract
A variety of primary alcohols and phenols were reacted with acetic anhydride at room temperature in the presence of sodium bicarbonate to produce corresponding esters in good to excellent yields. The acetylation of 4-nitrobenzyl alcohol was also carried out using other bicarbonates [...] Read more.
A variety of primary alcohols and phenols were reacted with acetic anhydride at room temperature in the presence of sodium bicarbonate to produce corresponding esters in good to excellent yields. The acetylation of 4-nitrobenzyl alcohol was also carried out using other bicarbonates and carbonates. The reaction in the presence of cesium bicarbonate and lithium carbonate gave 4-nitrobenzyl acetate in excellent yield, while in the presence of Na2CO3, K2CO3, Cs2CO3, or KHCO3 the yield was in the range of 80%–95%. Calcium carbonate and cobaltous carbonate did not promote the acetylation of 4-ntirobenzyl alcohol using acetic anhydride. The acetylation of 4-nitrobenzyl alcohol was carried out using ethyl acetate, THF, toluene, diethyl ether, dichloromethane and acetonitrile, and gave good yields ranging from 75%–99%. Toluene was the best solvent for the reaction, while diethyl ether was the poorest. Full article
Open AccessArticle Influence of Gold on Hydrotalcite-like Compound Catalysts for Toluene and CO Total Oxidation
Catalysts 2013, 3(4), 966-977; doi:10.3390/catal3040966
Received: 17 November 2013 / Revised: 3 December 2013 / Accepted: 3 December 2013 / Published: 12 December 2013
Cited by 6 | PDF Full-text (333 KB) | HTML Full-text | XML Full-text
Abstract
X6Al2HT500 hydrotalcites, where X represents Mg, Fe, Cu or Zn were synthetized and investigated before and after gold deposition for toluene and CO total oxidation reactions. The samples have been characterized by specific areas, XRD measurements and Temperature [...] Read more.
X6Al2HT500 hydrotalcites, where X represents Mg, Fe, Cu or Zn were synthetized and investigated before and after gold deposition for toluene and CO total oxidation reactions. The samples have been characterized by specific areas, XRD measurements and Temperature Programmed Reduction. Concerning the toluene total oxidation, the best activity was obtained with Au/Cu6Al2HT500 catalyst with T50 at 260 °C. However, catalytic behavior of Au/X6Al2HT500 sample in both reactions depends mainly on the nature of the support. Full article
(This article belongs to the Special Issue New Trends in Gold Catalysts)
Open AccessArticle Investigation of the Deactivation Phenomena Occurring in the Cyclohexane Photocatalytic Oxidative Dehydrogenation on MoOx/TiO2 through Gas Phase and in situ DRIFTS Analyses
Catalysts 2013, 3(4), 978-997; doi:10.3390/catal3040978
Received: 16 August 2013 / Revised: 13 September 2013 / Accepted: 10 December 2013 / Published: 13 December 2013
Cited by 3 | PDF Full-text (379 KB) | HTML Full-text | XML Full-text
Abstract
In this work, the results of gas phase cyclohexane photocatalytic oxidative dehydrogenation on MoOx/SO4/TiO2 catalysts with DRIFTS analysis are presented. Analysis of products in the gas-phase discharge of a fixed bed photoreactor was coupled with in situ [...] Read more.
In this work, the results of gas phase cyclohexane photocatalytic oxidative dehydrogenation on MoOx/SO4/TiO2 catalysts with DRIFTS analysis are presented. Analysis of products in the gas-phase discharge of a fixed bed photoreactor was coupled with in situ monitoring of the photocatalyst surface during irradiation with an IR probe. An interaction between cyclohexane and surface sulfates was found by DRIFTS analysis in the absence of UV irradiation, showing evidence of the formation of an organo-sulfur compound. In particular, in the absence of irradiation, sulfate species initiate a redox reaction through hydrogen abstraction of cyclohexane and formation of sulfate (IV) species. In previous studies, it was concluded that reduction of the sulfate (IV) species via hydrogen abstraction during UV irradiation may produce gas phase SO2 and thereby loss of surface sulfur species. Gas phase analysis showed that the presence of MoOx species, at same sulfate loading, changes the selectivity of the photoreaction, promoting the formation of benzene. The amount of surface sulfate influenced benzene yield, which decreases when the sulfate coverage is lower. During irradiation, a strong deactivation was observed due to the poisoning of the surface by carbon deposits strongly adsorbed on catalyst surface. Full article
(This article belongs to the Special Issue Advances in Catalyst Deactivation) Print Edition available

Review

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Open AccessReview Mesoporous Silica Based Gold Catalysts: Novel Synthesis and Application in Catalytic Oxidation of CO and Volatile Organic Compounds (VOCs)
Catalysts 2013, 3(4), 774-793; doi:10.3390/catal3040774
Received: 28 June 2013 / Revised: 5 August 2013 / Accepted: 26 September 2013 / Published: 15 October 2013
Cited by 6 | PDF Full-text (2817 KB) | HTML Full-text | XML Full-text
Abstract
Gold nanoparticles, particularly with the particle size of 2–5 nm, have attracted increasing research attention during the past decades due to their surprisingly high activity in CO and volatile organic compounds (VOCs) oxidation at low temperatures. In particular, CO oxidation below room [...] Read more.
Gold nanoparticles, particularly with the particle size of 2–5 nm, have attracted increasing research attention during the past decades due to their surprisingly high activity in CO and volatile organic compounds (VOCs) oxidation at low temperatures. In particular, CO oxidation below room temperature has been extensively studied on gold nanoparticles supported on several oxides (TiO2, Fe2O3, CeO2, etc.). Recently, mesoporous silica materials (such as SBA-15, MCM-41, MCM-48 and HMS) possessing ordered channel structures and suitable pore diameters, large internal surface areas, thermal stabilities and excellent mechanical properties, have been investigated as suitable hosts for gold nanoparticles. In this review we highlight the development of novel mesoporous silica based gold catalysts based on examples, mostly from recently reported results. Several synthesis methods are described herein. In detail we report: the modification of silica with organic functional groups; the one-pot synthesis with the incorporation of both gold and coupling agent containing functionality for the synthesis of mesoporous silica; the use of cationic gold complexes; the synthesis of silica in the presence of gold colloids or the dispersion of gold colloids protected by ligands or polymers onto silica; the modification of silica by other metal oxides; other conventional preparation methods to form mesoporous silica based gold catalysts. The gold based catalysts prepared as such demonstrate good potential for use in oxidation of CO and VOCs at low temperatures. From the wide family of VOCs, the oxidation of methanol and dimethyldisulfide has been addressed in the present review. Full article
(This article belongs to the Special Issue Catalytic Combustion)
Open AccessReview Palladium-Catalyzed Intermolecular Oxidative Amination of Alkenes with Amines, Using Molecular Oxygen as Terminal Oxidant
Catalysts 2013, 3(4), 794-810; doi:10.3390/catal3040794
Received: 25 July 2013 / Revised: 29 September 2013 / Accepted: 8 October 2013 / Published: 16 October 2013
Cited by 7 | PDF Full-text (719 KB) | HTML Full-text | XML Full-text
Abstract
In this review, we summarize recent progress from our group with regard to Pd-catalyzed oxidative amination of alkenes with amines. Intermolecular oxidative amination of alkenes with secondary anilines was induced using a palladium-complex catalyst combined with molybdovanadophosphate as a co-catalyst under dioxygen, [...] Read more.
In this review, we summarize recent progress from our group with regard to Pd-catalyzed oxidative amination of alkenes with amines. Intermolecular oxidative amination of alkenes with secondary anilines was induced using a palladium-complex catalyst combined with molybdovanadophosphate as a co-catalyst under dioxygen, leading to allylic amines and enamines in good yields with high selectivities. The reaction proceeded efficiently, using molecular oxygen as the terminal oxidant. In addition, palladium-catalyzed oxidative amination of alkenes with anilines as primary amines was achieved using molecular oxygen as the sole oxidant, producing (Z)-N-alkenyl-substituted anilines in high yields. Full article
(This article belongs to the Special Issue Palladium Catalysts for Cross-Coupling Reaction)
Open AccessReview Carbon-Supported PtRuMo Electrocatalysts for Direct Alcohol Fuel Cells
Catalysts 2013, 3(4), 811-838; doi:10.3390/catal3040811
Received: 10 August 2013 / Revised: 16 September 2013 / Accepted: 18 September 2013 / Published: 21 October 2013
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Abstract
The review article discusses the current status and recent findings of our investigations on the synthesis and characterization of carbon-supported PtRuMo electrocatalysts for direct alcohol fuel cells. In particular, the effect of the carbon support and the composition on the structure, stability [...] Read more.
The review article discusses the current status and recent findings of our investigations on the synthesis and characterization of carbon-supported PtRuMo electrocatalysts for direct alcohol fuel cells. In particular, the effect of the carbon support and the composition on the structure, stability and the activity of the PtRuMo nanoparticles for the electrooxidation of CO, methanol and ethanol have been studied. Different physicochemical techniques have been employed for the analysis of the catalysts structures: X-ray analytical methods (XRD, XPS, TXRF), thermogravimetry (TGA) and transmission electron microscopy (TEM), as well as a number of electrochemical techniques like CO adsorption studies, current-time curves and cyclic voltammetry measurements. Furthermore, spectroscopic methods adapted to the electrochemical systems for in situ studies, such as Fourier transform infrared spectroscopy (FTIRS) and differential electrochemical mass spectrometry (DEMS), have been used to evaluate the oxidation process of CO, methanol and ethanol over the carbon-supported PtRuMo electrocatalysts. Full article
(This article belongs to the Special Issue Carbon Catalysts)
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Open AccessReview Catalysts Supported on Carbon Materials for the Selective Hydrogenation of Citral
Catalysts 2013, 3(4), 853-877; doi:10.3390/catal3040853
Received: 14 August 2013 / Revised: 22 September 2013 / Accepted: 11 October 2013 / Published: 22 October 2013
Cited by 12 | PDF Full-text (695 KB) | HTML Full-text | XML Full-text
Abstract
The heterogeneously catalyzed selective-hydrogenation of citral is one of the more feasible ways for obtaining its appreciated unsaturated-alcohols, nerol and geraniol, which are present in over 250 essential oils. Thus, citral has very recently come to be produced petro-chemically in very large [...] Read more.
The heterogeneously catalyzed selective-hydrogenation of citral is one of the more feasible ways for obtaining its appreciated unsaturated-alcohols, nerol and geraniol, which are present in over 250 essential oils. Thus, citral has very recently come to be produced petro-chemically in very large quantities, and so partial hydrogenation of citral has become a very economical route for the production of these compounds. However, the selective hydrogenation of citral is not easy, because citral is an α,β-unsaturated aldehyde which possesses three double bonds that can be hydrogenated: an isolated C=C bond and the conjugated C=O and C=C bonds. For this reason, in catalyst selection there are several important issues which affect the product selectivity, for example, the active metal and metal particle size which are factors related to the catalyst preparation method, catalyst precursor, or support surface area, as well as other factors such as porosity, the addition of a second catalytic metal, and, of course, the type of catalyst support. About this last one, carbon materials are very interesting supports for this type of hydrogenation reaction due to their unique chemical and textural properties. This review collects and analyzes the results obtained in the selective hydrogenation of citral catalyzed by carbon material supported metals. Full article
(This article belongs to the Special Issue Carbon Catalysts)
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Open AccessReview Ionic Liquids: The Synergistic Catalytic Effect in the Synthesis of Cyclic Carbonates
Catalysts 2013, 3(4), 878-901; doi:10.3390/catal3040878
Received: 19 August 2013 / Revised: 27 September 2013 / Accepted: 8 October 2013 / Published: 22 October 2013
Cited by 17 | PDF Full-text (669 KB) | HTML Full-text | XML Full-text
Abstract
This review presents the synergistic effect in the catalytic system of ionic liquids (ILs) for the synthesis of cyclic carbonate from carbon dioxide and epoxide. The emphasis of this review is on three aspects: the catalytic system of metal-based ionic liquids, the [...] Read more.
This review presents the synergistic effect in the catalytic system of ionic liquids (ILs) for the synthesis of cyclic carbonate from carbon dioxide and epoxide. The emphasis of this review is on three aspects: the catalytic system of metal-based ionic liquids, the catalytic system of hydrogen bond-promoted ionic liquids and supported ionic liquids. Metal and ionic liquids show a synergistic effect on the cycloaddition reactions of epoxides. The cations and anions of ionic liquids show a synergistic effect on the cycloaddition reactions. The functional groups in cations or supports combined with the anions have a synergistic effect on the cycloaddition reactions. Synergistic catalytic effects of ILs play an important role of promoting the cycloaddition reactions of epoxides. The design of catalytic system of ionic liquids will be possible if the synergistic effect on a molecular level is understood. Full article
(This article belongs to the Special Issue Ionic Liquids in Catalysis)
Open AccessReview Titania Photocatalysis beyond Recombination: A Critical Review
Catalysts 2013, 3(4), 942-953; doi:10.3390/catal3040942
Received: 26 September 2013 / Revised: 23 October 2013 / Accepted: 5 November 2013 / Published: 15 November 2013
Cited by 22 | PDF Full-text (242 KB) | HTML Full-text | XML Full-text
Abstract
This short review paper shows the significance of recombination of a photoexcited electron and a hole in conduction and valence bands, respectively, of a titania photocatalyst, since recombination has not yet been fully understood and has not been evaluated adequately during the [...] Read more.
This short review paper shows the significance of recombination of a photoexcited electron and a hole in conduction and valence bands, respectively, of a titania photocatalyst, since recombination has not yet been fully understood and has not been evaluated adequately during the past several decades of research on heterogeneous photocatalysis. Full article
(This article belongs to the Special Issue Photocatalysts)

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