Catalysts

1972 KiB

Open AccessArticle

PtRu Nanoparticles Deposited by the Sulfite Complex Method on Highly Porous Carbon Xerogels: Effect of the Thermal Treatment

by Cinthia Alegre, David Sebastián, María Elena Gálvez, Rafael Moliner, Alessandro Stassi, Antonino Salvatore Aricò, María Jesús Lázaro and Vincenzo Baglio

Catalysts 2013, 3(3), 744-756; https://doi.org/10.3390/catal3030744 - 23 Sep 2013

Cited by 10 | Viewed by 6649

Abstract

Highly porous carbon xerogels (CXGs) were synthesized to be used as support for PtRu nanoparticles. Metal particles were deposited on CXGs by means of the sulfite complex method for the first time. Catalysts so-obtained were submitted to thermal treatment in H₂, [...] Read more.

Highly porous carbon xerogels (CXGs) were synthesized to be used as support for PtRu nanoparticles. Metal particles were deposited on CXGs by means of the sulfite complex method for the first time. Catalysts so-obtained were submitted to thermal treatment in H₂, at different temperatures, in order to increase the particle size and thus the intrinsic activity. Physico-chemical characterizations included N₂ physisorption, X-Ray diffraction, X-ray photoelectron spectroscopy and transmission electron microscopy. Highly dispersed alloyed PtRu particles were obtained, with crystal sizes ranging from 1.6 to 2.0 nm. PtRu-catalysts were tested in half-cell for the methanol oxidation reaction (MOR). The resulting thermal treatment was effective in increasing both particle size and catalytic activity toward MOR. Full article

(This article belongs to the Special Issue Carbon Catalysts)

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738 KiB

Open AccessArticle

Application of Photocatalysts and LED Light Sources in Drinking Water Treatment

by Maryam Izadifard, Gopal Achari and Cooper H. Langford

Catalysts 2013, 3(3), 726-743; https://doi.org/10.3390/catal3030726 - 12 Sep 2013

Cited by 51 | Viewed by 9175

Abstract

This study investigates a cross-section of TiO₂ compositions for which existing evidence suggests the prospect of improved performance compared to standard Degussa P25. In the context of a program aimed toward a 365 nm LED based photo-reactor, the question is whether a [...] Read more.

This study investigates a cross-section of TiO₂ compositions for which existing evidence suggests the prospect of improved performance compared to standard Degussa P25. In the context of a program aimed toward a 365 nm LED based photo-reactor, the question is whether a distinctly superior photocatalyst composition for drinking water treatment is now available that would shape design choices. An answer was sought by synthesizing several photocatalysts with reported high reactivity in some context in the literature, and by performing photocatalysts reactivity tests using common pollutants of water system including Natural Organic Matter (NOM) and Emerging Contaminants (ECs) from the pesticide and pharmaceutical classes. 365 nm Light Emitting Diodes (LEDs) were used as the irradiation source. Since LEDs are now available in the UV, we did not examine the TiO₂modifications that bring band gap excitation into the region beyond 400 nm. The results suggest that the choice of the photocatalyst should be best made to fit the reactor design and photocatalyst mounting constraints such as mass transport, reactive surface, and light field. No photocatalyst composition overall, superior for all classes emerged. Full article

(This article belongs to the Special Issue Photocatalysts)

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528 KiB

Open AccessReview

Ionic Liquid Immobilized Organocatalysts for Asymmetric Reactions in Aqueous Media

by Yupu Qiao and Allan D. Headley

Catalysts 2013, 3(3), 709-725; https://doi.org/10.3390/catal3030709 - 11 Sep 2013

Cited by 34 | Viewed by 8346

Abstract

Ionic liquids are organic salts with melting points typically below ambient or reaction temperature. The unique combination of physical properties of ionic liquids, such as lack of measurable vapor pressure, high thermal and chemical stability, make them ideal to be used as reusable [...] Read more.

Ionic liquids are organic salts with melting points typically below ambient or reaction temperature. The unique combination of physical properties of ionic liquids, such as lack of measurable vapor pressure, high thermal and chemical stability, make them ideal to be used as reusable homogenous support for catalysts. In addition, the solubility of ionic liquids in various reaction media can be controlled and easily fine-tuned by modification of the structures of their cations and anions. As a result, ionic liquid immobilized organocatalysts are very effective in aqueous media and can be separated easily from organic solvents, as well as aqueous phases by simply adjusting the polarity of the media. Ionic liquid immobilized organocatalysts are not only very versatile compounds that are effective catalysts for a wide spectrum of reactions, but are also environmentally friendly and recyclable organocatalysts. Herein, we provide a summary of the past decade in the area of asymmetric catalysis in aqueous media for a wide variety of reactions in which ionic liquid and related ammonium salt immobilized organocatalysts are used. Full article

(This article belongs to the Special Issue Ionic Liquids in Catalysis)

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2603 KiB

Open AccessReview

Gold Nanoparticle-Biological Molecule Interactions and Catalysis

by Jonathan G. Heddle

Catalysts 2013, 3(3), 683-708; https://doi.org/10.3390/catal3030683 - 03 Sep 2013

Cited by 31 | Viewed by 12550

Abstract

This review gives a brief summary of the field of gold nanoparticle interactions with biological molecules, particularly those with possible catalytic relevance. Gold nanoparticles are well known as catalysts in organic chemistry but much is unknown regarding their potential as catalysts of reactions [...] Read more.

This review gives a brief summary of the field of gold nanoparticle interactions with biological molecules, particularly those with possible catalytic relevance. Gold nanoparticles are well known as catalysts in organic chemistry but much is unknown regarding their potential as catalysts of reactions involving biological molecules such as protein and nucleic acids. Biological molecules may be the substrate for catalysis or, if they are the ligand coating the gold particle, may be the catalyst itself. In other cases biological molecules may form a template upon which gold nanoparticles can be precisely arrayed. As relatively little is currently known about the catalytic capabilities of gold nanoparticles in this area, this review will consider templating in general (including, but not restricted to, those which result in structures having potential as catalysts) before going on to consider firstly catalysis by the gold nanoparticle itself followed by catalysis by ligands attached to gold nanoparticles, all considered with a focus on biological molecules. Full article

(This article belongs to the Special Issue New Trends in Gold Catalysts)

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1045 KiB

Open AccessArticle

Nanostructured Carbon Materials as Supports in the Preparation of Direct Methanol Fuel Cell Electrocatalysts

by María Elena Gálvez, Laura Calvillo, Cinthia Alegre, David Sebastián, Isabel Suelves, Sara Pérez-Rodríguez, Verónica Celorrio, Elena Pastor, Juan Ignacio Pardo, Rafael Moliner and María Jesús Lázaro

Catalysts 2013, 3(3), 671-682; https://doi.org/10.3390/catal3030671 - 21 Aug 2013

Cited by 14 | Viewed by 7194

Abstract

Different advanced nanostructured carbon materials, such as carbon nanocoils, carbon nanofibers, graphitized ordered mesoporous carbons and carbon xerogels, presenting interesting features such as high electrical conductivity and extensively developed porous structure were synthesized and used as supports in the preparation of electrocatalysts for [...] Read more.

Different advanced nanostructured carbon materials, such as carbon nanocoils, carbon nanofibers, graphitized ordered mesoporous carbons and carbon xerogels, presenting interesting features such as high electrical conductivity and extensively developed porous structure were synthesized and used as supports in the preparation of electrocatalysts for direct methanol fuel cells (DMFCs). The main advantage of these supports is that their physical properties and surface chemistry can be tailored to adapt the carbonaceous material to the catalytic requirements. Moreover, all of them present a highly mesoporous structure, diminishing diffusion problems, and both graphitic character and surface area can be conveniently modified. In the present work, the influence of the particular features of each material on the catalytic activity and stability was analyzed. Results have been compared with those obtained for commercial catalysts supported on Vulcan XC-72R, Pt/C and PtRu/C (ETEK). Both a highly ordered graphitic and mesopore-enriched structure of these advanced nanostructured materials resulted in an improved electrochemical performance in comparison to the commercial catalysts assayed, both towards CO and alcohol oxidation. Full article

(This article belongs to the Special Issue Carbon Catalysts)

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4520 KiB

Open AccessArticle

Investigation on the Stability of Supported Gold Nanoparticles

by Michela Signoretto, Federica Menegazzo, Valentina Trevisan, Francesco Pinna, Maela Manzoli and Flora Boccuzzi

Catalysts 2013, 3(3), 656-670; https://doi.org/10.3390/catal3030656 - 21 Aug 2013

Cited by 12 | Viewed by 8273

Abstract

The procedures leading to the preservation of catalytic performances of Au/ZrO₂ samples have been investigated. The three potential causes of deactivation, namely the particle growth by sintering of gold nanoparticles, the metal leaching and the formation of un-reactive species which inhibit the [...] Read more.

The procedures leading to the preservation of catalytic performances of Au/ZrO₂ samples have been investigated. The three potential causes of deactivation, namely the particle growth by sintering of gold nanoparticles, the metal leaching and the formation of un-reactive species which inhibit the reaction, have been evaluated. In particular, this paper deals with the stability of gold nanoparticles: (1) under storage conditions; (2) with time on stream for a gas phase reaction (LT-WGSR); (3) with time on stream for a liquid phase reaction (furfural oxidative esterification). Full article

(This article belongs to the Special Issue New Trends in Gold Catalysts)

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1015 KiB

Open AccessArticle

Complete Toluene Oxidation on Pt/CeO₂-ZrO₂-ZnO Catalysts

by Min Yeong Kim, Tomoya Kamata, Toshiyuki Masui and Nobuhito Imanaka

Catalysts 2013, 3(3), 646-655; https://doi.org/10.3390/catal3030646 - 02 Aug 2013

Cited by 11 | Viewed by 7267

Abstract

A 0.4 wt%Pt/Ce_0.76Zr_0.19Zn_0.05O_1.95 catalyst was prepared by the evaporative drying method. The catalytic toluene oxidation activity of the catalyst was investigated and the calcination temperature dependence on the toluene oxidation activity was characterized. It was confirmed [...] Read more.

A 0.4 wt%Pt/Ce_0.76Zr_0.19Zn_0.05O_1.95 catalyst was prepared by the evaporative drying method. The catalytic toluene oxidation activity of the catalyst was investigated and the calcination temperature dependence on the toluene oxidation activity was characterized. It was confirmed that only CO₂ and steam were produced by the complete oxidation of toluene, and no toluene-derived compounds were detected as by-products with a gas chromatography-mass spectrometer. Toluene was completely oxidized at 320 °C on the 0.4 wt%Pt/Ce_0.76Zr_0.19Zn_0.05O_1.95catalyst calcined at 500 °C. The toluene oxidation activity slightly decreased with increasing the calcination temperature of the catalyst. However, significant deactivation was not recognized in the present 0.4 wt%Pt/Ce_0.76Zr_0.19Zn_0.05O_1.95 catalyst, and toluene was completely oxidized at 360 °C even after calcination at 1000 °C. From these results, it became obvious that the 0.4 wt%Pt/Ce_0.76Zr_0.19Zn_0.05O_1.95 catalyst has high thermal stability for toluene oxidation activity. Full article

(This article belongs to the Special Issue Catalytic Combustion)

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1287 KiB

Open AccessArticle

Photocatalytic Activity of Vis-Responsive Ag-Nanoparticles/TiO₂ Composite Thin Films Fabricated by Molecular Precursor Method (MPM)

by Likius S. Daniel, Hiroki Nagai, Naoya Yoshida and Mitsunobu Sato

Catalysts 2013, 3(3), 625-645; https://doi.org/10.3390/catal3030625 - 31 Jul 2013

Cited by 33 | Viewed by 11071

Abstract

The Ag-nanoparticles (Ag-NP)/TiO₂ composite thin films with various amounts of Ag (10 mol% ≤ n ≤ 80 mol%) were examined as a potential photocatalyst by decoloration reaction of methylene blue (MB) in an aqueous solution. These composite thin films of ca. 100 [...] Read more.

The Ag-nanoparticles (Ag-NP)/TiO₂ composite thin films with various amounts of Ag (10 mol% ≤ n ≤ 80 mol%) were examined as a potential photocatalyst by decoloration reaction of methylene blue (MB) in an aqueous solution. These composite thin films of ca. 100 nm thickness were fabricated by the MPM at 600 °C in air. The decoloration rates monitored by the absorption intensity of the MB solution indicated that the composite thin films of Ag with an amount less than 40 mol% are not effective under vis-irradiation, though they can work as a photocatalyst under UV-irradiation. Further, the UV-sensitivity of the composite thin films gradually decreased to almost half the level of that of the TiO₂ thin film fabricated under the identical conditions when the Ag amount increased from 10 to 40 mol%. Contrarily, the composite thin films of Ag content larger than 50 mol% showed the vis-responsive activity, whose level was slightly lower than the decreased UV-sensitivity. Diffuse reflectance spectra suggested that the vis-responsive activity of the composite thin films is due to the conductivity, localized surface plasmon resonance and surface plasmon resonance of Ag-NP. It was also elucidated that the vis-responsive level of the composite thin films corresponds to their electrical conductivity that depends on the Ag content. Full article

(This article belongs to the Special Issue Photocatalysts)

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530 KiB

Open AccessArticle

Dye Modification Effects on TaON for Photocatalytic Hydrogen Production from Water

by Hidehisa Hagiwara, Masakiyo Nagatomo, Chihiro Seto, Shintaro Ida and Tatsumi Ishiahara

Catalysts 2013, 3(3), 614-624; https://doi.org/10.3390/catal3030614 - 23 Jul 2013

Cited by 20 | Viewed by 8416

Abstract

Modification effects of porphyrin dyes on the photocatalytic activity of tantalum (oxy)nitride (TaON) were investigated. The nitrogen content in tantalum (oxy)nitride was increased by increasing the heat treatment period. The optimized nitridation conditions were found to be calcination at 800 °C for 14 [...] Read more.

Modification effects of porphyrin dyes on the photocatalytic activity of tantalum (oxy)nitride (TaON) were investigated. The nitrogen content in tantalum (oxy)nitride was increased by increasing the heat treatment period. The optimized nitridation conditions were found to be calcination at 800 °C for 14 h under a NH₃ gas flow (25 mL min⁻¹). Among the porphyrin dyes examined, pentamethylene bis[4-(10,15,20-triphenylporphine-5-yl) benzoate]-dizinc (II) (Zn-TPPD) showed the most positive effect on the photocatalytic activity of TaON for H₂ production from Na₂S aqueous solution. From the results of the photocatalytic reaction using various combinations of catalyst components, it was found that the modification dye and PtO_x co-catalysts were necessary to achieving photocatalytic H₂ formation. In the PtO_x/Zn-TPPD/TaON photocatalyst, the expected charge transfer mechanism was a two-step excitation of both TaON and Zn-TPPD, and the oxidation and reduction sites were TaON and PtO_x co-catalyst, respectively. These results indicate that dye modification has the potential to improve the photocatalytic activity of various (oxy)nitride photocatalysts. Full article

(This article belongs to the Special Issue Photocatalysts)

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1231 KiB

Open AccessArticle

Fabrication and Catalytic Activity of Thermally Stable Gold Nanoparticles on Ultrastable Y (USY) Zeolites

by Takashi Sanada, Chika Murakami, Kinga Góra-Marek, Keiko Iida, Naonobu Katada and Kazu Okumura

Catalysts 2013, 3(3), 599-613; https://doi.org/10.3390/catal3030599 - 09 Jul 2013

Cited by 12 | Viewed by 8185

Abstract

Au was deposited on ultrastable Y (USY) zeolites using an ion-exchange method. Up to 5.5 wt% Au was introduced into the NH₄-form of USY zeolites. In contrast, deposition of Au hardly took place on the H- and Na-forms of Y-type zeolites, [...] Read more.

Au was deposited on ultrastable Y (USY) zeolites using an ion-exchange method. Up to 5.5 wt% Au was introduced into the NH₄-form of USY zeolites. In contrast, deposition of Au hardly took place on the H- and Na-forms of Y-type zeolites, NH₄-forms of mordenite, and ZSM-5. Treatment of the Au-loaded USY zeolite in a H₂ atmosphere, afforded Au⁰ nanoparticles. These particles were thermally stable even at 973 K, where their mean particle diameter was 3.7 nm. In contrast, highly aggregated Au particles were observed after thermal treatment at temperatures lower than 523 K, followed by storage in air for a month. The resulting particle sizes were in good correlation with the IR band intensity of the adsorbed CO and the catalytic activity of Au in the aerobic oxidation of benzyl alcohol. The Au nanoparticles showed highest activity when the Au/USY zeolite was thermally treated at 673–973 K. A negligible deactivation was observed after repeating the reaction at least 12 times. In the case of Au/TiO₂ catalyst prepared by the deposition-precipitation method, the highest activity was observed at 573 K, which was lower than the temperature used for the Au/USY zeolites. This study demonstrated the potential use of the NH₄-form of USY zeolites for supporting Au. Full article

(This article belongs to the Special Issue New Trends in Gold Catalysts)

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1250 KiB

Open AccessArticle

Isotopic Labeling Study of the Formation of Calix[5]pyrroles Catalyzed by Bi(NO₃)₃

by Luis Chacón-García, Claudia A. Contreras-Celedón and Melissa Tapia-Juárez

Catalysts 2013, 3(3), 588-598; https://doi.org/10.3390/catal3030588 - 08 Jul 2013

Cited by 3 | Viewed by 8460

Abstract

One of the more elusive classes of macrocycles includes the calix[5]pyrroles, which can be obtained from pyrrole and acetone in the presence of low concentrations of Bi(NO₃)₃-5H₂O. An isotopic labeling experiment aided the proposal of a mechanism [...] Read more.

One of the more elusive classes of macrocycles includes the calix[5]pyrroles, which can be obtained from pyrrole and acetone in the presence of low concentrations of Bi(NO₃)₃-5H₂O. An isotopic labeling experiment aided the proposal of a mechanism to explain the formation of calix[5]pyrrole at low acid concentrations and the exclusive formation of calix[4]pyrrole at high acid concentrations. We assume that the mechanism involves HNO₃, which is released from the Bi salt. Full article

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Catalysts, Volume 3, Issue 3 (September 2013) – 11 articles , Pages 588-756

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