Catalysts

10 pages, 462 KiB

Open AccessArticle

Preparation and Photocatalytic Properties of Sr_2−xBa_xTa₃O₁₀₋_yN_zNanosheets

by Shintaro Ida^1,2,3,*, Yohei Okamoto¹, Hidehisa Hagiwara^1,2 and Tatsumi Ishihara^1,2

¹ Department of Applied Chemistry, Faculty of Engineering, Kyushu University, Motooka 744, Nishi-ku, Fukuoka 819-0395, Japan

² International Institute for Carbon Neutral Energy Research (I2CNER), Kyushu University, Motooka 744, Nishi-ku, Fukuoka 819-0395, Japan

³ Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency, 4-1-8 Honcho Kawaguchi, Saitama 332-0012, Japan

Catalysts 2013, 3(1), 1-10; https://doi.org/10.3390/catal3010001 - 16 Jan 2013

Cited by 24 | Viewed by 7985

Abstract

Sr_2−xBa_xTa₃O₁₀_−yN_z (x = 0.0, 0.5, 1.0) nanosheets were prepared by exfoliating layered perovskite compounds (CsSr_2−xBa_xTa₃O₁₀_−yN_z). The Sr [...] Read more.

Sr_2−xBa_xTa₃O₁₀_−yN_z (x = 0.0, 0.5, 1.0) nanosheets were prepared by exfoliating layered perovskite compounds (CsSr_2−xBa_xTa₃O₁₀_−yN_z). The Sr_1.5Ba_0.5Ta₃O_9.7N_0.2nanosheet showed the highest photocatalytic activity for H₂ production from the water/methanol system among the Sr_2−xBa_xTa₃O_9.7N_0.2 nanosheets prepared. In addition, Rh-loaded Sr_1.5Ba_0.5Ta₃O_9.6N_0.3 nanosheet showed the photocatalytic activity for oxygen and hydrogen production from water. The ratio of hydrogen to oxygen evolved was around two. These results indicate that the Rh-loaded Sr_1.5Ba_0.5Ta₃O_9.6N_0.3 nanosheet is a potential catalyst for photocatalytic water splitting. Full article

(This article belongs to the Special Issue Photocatalysts)

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16 pages, 2490 KiB

Open AccessArticle

Partial Oxidation of n-Butane over a Sol-Gel Prepared Vanadium Phosphorous Oxide

by Juan M. Salazar and Keith L. Hohn^*

Department of Chemical Engineering, Kansas State University, 1016 Durland Hall, Manhattan, KS 66506, USA

Catalysts 2013, 3(1), 11-26; https://doi.org/10.3390/catal3010011 - 16 Jan 2013

Cited by 5 | Viewed by 8143

Abstract

Vanadium phosphorous oxide (VPO) is traditionally manufactured from solid vanadium oxides by synthesizing VOHPO₄∙0.5H₂O (the precursor) followed by in situ activation to produce (VO)₂P₂O₇ (the active phase). This paper discusses an alternative synthesis method [...] Read more.

Vanadium phosphorous oxide (VPO) is traditionally manufactured from solid vanadium oxides by synthesizing VOHPO₄∙0.5H₂O (the precursor) followed by in situ activation to produce (VO)₂P₂O₇ (the active phase). This paper discusses an alternative synthesis method based on sol-gel techniques. Vanadium (V) triisopropoxide oxide was reacted with ortho-phosphoric acid in an aprotic solvent. The products were dried at high pressure in an autoclave with a controlled excess of solvent. This procedure produced a gel of VOPO₄ with interlayer entrapped molecules. The surface area of the obtained materials was between 50 and 120 m²/g. Alcohol produced by the alkoxide hydrolysis reduced the vanadium during the drying step, thus VOPO₄ was converted to the precursor. This procedure yielded non-agglomerated platelets, which were dehydrated and evaluated in a butane-air mixture. Catalysts were significantly more selective than the traditionally prepared materials with similar intrinsic activity. It is suggested that the small crystallite size obtained increased their selectivity towards maleic anhydride. Full article

(This article belongs to the Special Issue Aerogel Catalyst)

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9 pages, 261 KiB

Open AccessCommunication

Enzyme-Catalyzed Transetherification of Alkoxysilanes

by Vincenzo Abbate^1,*,†, Kurt F. Brandstadt², Peter G. Taylor¹ and Alan R. Bassindale^1,*

¹ Department of Chemistry and Analytical Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK

² Dow Corning Corporation, 2200 W Salzburg Rd, Midland, MI 48686, USA

^† Present address: Institute of Pharmaceutical Science, King's College London, 150 Stamford Street, London SE1 9NH, UK.

Catalysts 2013, 3(1), 27-35; https://doi.org/10.3390/catal3010027 - 18 Jan 2013

Cited by 10 | Viewed by 9473

Abstract

We report the first evidence of an enzyme-catalyzed transetherification of model alkoxysilanes. During an extensive enzymatic screening in the search for new biocatalysts for silicon-oxygen bond formation, we found that certain enzymes promoted the transetherification of alkoxysilanes when tert-butanol or 1-octanol were [...] Read more.

We report the first evidence of an enzyme-catalyzed transetherification of model alkoxysilanes. During an extensive enzymatic screening in the search for new biocatalysts for silicon-oxygen bond formation, we found that certain enzymes promoted the transetherification of alkoxysilanes when tert-butanol or 1-octanol were used as the reaction solvents. Full article

(This article belongs to the Special Issue Biomimetic Catalysts)

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38 pages, 1949 KiB

Open AccessReview

Brookite, the Least Known TiO₂ Photocatalyst

by Agatino Di Paola^*, Marianna Bellardita and Leonardo Palmisano

"Schiavello-Grillone" Photocatalysis Group, Dipartimento di Energia, Ingegneria dell'Informazione, e modelli Matematici (DEIM), Università di Palermo, Viale delle Scienze, 90128 Palermo, Italy

Catalysts 2013, 3(1), 36-73; https://doi.org/10.3390/catal3010036 - 18 Jan 2013

Cited by 535 | Viewed by 32459

Abstract

Brookite is the least studied TiO₂ photocatalyst due to the difficulties usually encountered in order to obtain it as a pure phase. In this review, a comprehensive survey of the different methods available for preparing brookite powders and films is reported. Attention [...] Read more.

Brookite is the least studied TiO₂ photocatalyst due to the difficulties usually encountered in order to obtain it as a pure phase. In this review, a comprehensive survey of the different methods available for preparing brookite powders and films is reported. Attention has been paid both to the most traditional methods, such as hydrothermal processes at high temperatures and pressures, and to environmentally benign syntheses using water soluble compounds and water as the solvent. Papers reporting the photocatalytic activity of pure and brookite-based samples have been reviewed. Full article

(This article belongs to the Special Issue Photocatalysts)

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14 pages, 703 KiB

Open AccessArticle

Microvolume TOC Analysis as Useful Tool in the Evaluation of Lab Scale Photocatalytic Processes

by Monika Kus¹, Stefan Ribbens¹, Vera Meynen^1,2 and Pegie Cool^1,*

¹ Laboratory of Adsorption and Catalysis, University of Antwerp (UA), Universiteitsplein 1, B-2610 Wilrijk, Belgium

² Flemish Institute for Technology Research, VITO, Boeretang 200, B-2400 Mol, Belgium

Catalysts 2013, 3(1), 74-87; https://doi.org/10.3390/catal3010074 - 22 Jan 2013

Cited by 10 | Viewed by 9627

Abstract

Analysis methods that require small volumes of aqueous samples can be of large benefit for applications when expensive chemicals are involved or available volumes are substantially small and concentrations are low. A new method is presented to allow microvolume liquid injections on TOC [...] Read more.

Analysis methods that require small volumes of aqueous samples can be of large benefit for applications when expensive chemicals are involved or available volumes are substantially small and concentrations are low. A new method is presented to allow microvolume liquid injections on TOC equipment using a special designed Shimadzu gas injection kit^® in combination with a high precision syringe and Chaney adapter. Next to details on the methodology of microvolume TOC injections, the technique is shown to be beneficial to evaluate the efficiency of photocatalytic dye degradation on titania materials in terms of CO₂ conversion simultaneously with classic UV-Vis analysis measurements within a lab scale photocatalytic test setup (volume <100 mL). The possibility to allow multiple microvolume samplings in short time intervals during several hours without a substantial decrease in volume/catalyst ratio is of particular value for the evaluation of photocatalysts. By combining both techniques at short time intervals, additional knowledge of the degradation process/mechanism, kinetics and the efficiency can be obtained in a direct way. Moreover, the developed μV-TOC analysis is specifically useful in those applications in which low sample volumes in combination with low concentrations are involved. For example, μV-TOC can similarly be put into service in a wide range of small volume setups, e.g., analytes from high-throughput screening, pharmaceutical applications and other advanced oxidation processes that formally could not be analyzed due to limited sample volumes and often low concentrations. Full article

(This article belongs to the Special Issue Photocatalysts)

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16 pages, 720 KiB

Open AccessArticle

Coating SiO₂ Support with TiO₂ or ZrO₂ and Effects on Structure and CO Oxidation Performance of Pt Catalysts

by Mi-Young Kim¹, Jae-Soon Choi^1,*

, Todd J. Toops¹, Eun-Suk Jeong², Sang-Wook Han², Viviane Schwartz³ and Jihua Chen³

¹ Fuels, Engines, and Emissions Research Center, Oak Ridge National Laboratory, Knoxville, TN 37932, USA

² Department of Physics Education and Institute of Fusion Science, Chonbuk National University, Jeonju 561-756, Korea

³ Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA

Catalysts 2013, 3(1), 88-103; https://doi.org/10.3390/catal3010088 - 6 Feb 2013

Cited by 44 | Viewed by 13956

Abstract

In this work, we studied how TiO₂ and ZrO₂ coatings enhance the CO oxidation performance of SiO₂-supported Pt catalysts under conditions relevant to automotive emissions control. SiO₂ was coated with metal oxides TiO₂ or ZrO₂ by [...] Read more.

In this work, we studied how TiO₂ and ZrO₂ coatings enhance the CO oxidation performance of SiO₂-supported Pt catalysts under conditions relevant to automotive emissions control. SiO₂ was coated with metal oxides TiO₂ or ZrO₂ by sol-gel method and the subsequent Pt loading was done by incipient wetness method. The prepared catalysts Pt/TiO₂-SiO₂ and Pt/ZrO₂-SiO₂ were compared with Pt/SiO₂ and Pt/Al₂O₃ in fresh, sulfated, and hydrothermally aged states. The structure of the catalysts was characterized with BET, XRD, TEM, EDS, EXAFS, XANES, TPD and TPR to help interpret the CO oxidation performance. Higher dispersion, stability, and oxidation state of Pt were achieved on TiO₂-SiO₂ and ZrO₂-SiO₂ supports due to stronger metal-support interaction leading to superior CO oxidation performance compared to Pt/SiO₂ and Pt/Al₂O₃. TiO₂ and ZrO₂ coatings introduced surface acidity but negligible basicity, which is a likely reason for the weak and low adsorption of SO₂. The results suggest that the sol-gel coating of SiO₂ with metal oxides could be an attractive strategy for designing automotive oxidation catalysts with enhanced performance such as low-temperature activity, sulfur tolerance, and hydrothermal stability. Full article

(This article belongs to the Special Issue Catalytic Combustion)

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21 pages, 483 KiB

Open AccessArticle

Preparation of Thiophene-Fused and Tetrahydroquinoline-Linked Cyclopentadienyl Titanium Complexes for Ethylene/α-Olefin Copolymerization

by Sung Hun Kim¹, Ji Hae Park¹, Bo Geun Song², Seung-Woong Yoon², Min Jeong Go³, Junseong Lee³ and Bun Yeoul Lee^1,*

¹ Department of Molecular Science and Technology, Ajou University, Suwon 443-749, Korea

² Honam Petrochemical Company and Catalyst Research Team 5th, 24-1 Jang-Dong, Yuseong-Gu, Daejeon 305-726, Korea

³ Department of Chemistry, Chonnam National University, 77 Yongbong-ro, Buk-gu, Gwangju 500-757, Korea

Catalysts 2013, 3(1), 104-124; https://doi.org/10.3390/catal3010104 - 6 Feb 2013

Cited by 18 | Viewed by 8618

Abstract

A synthetic scheme was developed for the large-scale preparation of a dimethylthiophene-fused and tetrahydroquinaldine-linked dimethylcyclopentadienyl titanium complex (2), which is a high-performance homogeneous Ziegler catalyst. 2,3,4,5-Tetramethyl-4,5-dihydrocyclopenta[b]thiophen-6-one was prepared without chromatography purification on the 40-g scale in a laboratory setting, [...] Read more.

A synthetic scheme was developed for the large-scale preparation of a dimethylthiophene-fused and tetrahydroquinaldine-linked dimethylcyclopentadienyl titanium complex (2), which is a high-performance homogeneous Ziegler catalyst. 2,3,4,5-Tetramethyl-4,5-dihydrocyclopenta[b]thiophen-6-one was prepared without chromatography purification on the 40-g scale in a laboratory setting, from which the ligand precursor for 2 was obtained in 65% yield on a 50-g scale in a one-pot without the need for chromatography purification. Metallation was achieved in a high yield (78%) through reaction of the dilithiated compound with TiCl₄. Many derivatives were prepared by employing the same synthetic scheme as applied for 2. Among them, the titanium complex prepared from 2-methyl-4,5-dimethyl-6-(2-n-butyl-2,3,4,5-tetrahydroquinolin-8-yl)-4H-cyclopenta[b]thiophene exhibited an exceptionally high activity. Under commercially relevant high-temperature polymerization conditions (160 °C), this compound showed a higher activity than 2 (126 × 10⁶ g/molTi∙h versus 72 × 10⁶ g/molTi∙h), albeit with the formation of a polymer of slightly lower molecular weight (M_w, 159,000 versus 218,000) and with a slightly lower 1-octene content (9.3 mol% versus 12 mol%). Full article

(This article belongs to the Special Issue Molecular Catalysis for Precise Olefin Polymerization)

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12 pages, 327 KiB

Open AccessArticle

Oligomerization of Ethylene to Produce Linear α-Olefins Using Heterogeneous Catalyst Prepared by Immobilization of α-Diiminenickel(II) Complex into Fluorotetrasilicic Mica Interlayer

by Hideki Kurokawa^1,*, Kazuki Miura¹, Kazuhiro Yamamoto², Tsutomu Sakuragi², Takao Sugiyama¹, Masa-aki Ohshima¹ and Hiroshi Miura¹

¹ Graduate School of Science & Engineering, Saitama University, 255, Shimo-okubo, Sakura-ku, Saitama-shi, Saitama, 338-8570, Japan

² Japan Polychem Corporation, 1 Toho-cho, Yokkaichi-shi, Mie, 510-0848, Japan

Catalysts 2013, 3(1), 125-136; https://doi.org/10.3390/catal3010125 - 6 Feb 2013

Cited by 17 | Viewed by 8574

Abstract

Heterogeneous catalysts for production of linear α-olefins from ethylene were prepared by the direct reaction of the α-diimine ligand [L: R-N=C(R')-C(R')=N-R; R' = Me and R = 2,6-Me₂Ph (L5), 2,5-Me₂Ph (L1), 2-MePh ( [...] Read more.

Heterogeneous catalysts for production of linear α-olefins from ethylene were prepared by the direct reaction of the α-diimine ligand [L: R-N=C(R')-C(R')=N-R; R' = Me and R = 2,6-Me₂Ph (L5), 2,5-Me₂Ph (L1), 2-MePh (L2), or Ph (L3); R' = 1,8-naphth-diyl and R = Ph (L4)] and Ni²⁺ ion-exchanged fluorotetrasilicic mica. Only high molecular weight polyethylene was obtained in the reaction using the L5/Ni²⁺-Mica procatalyst activated by AlEt₃ (TEA) as an activator, whereas the TEA-activated L1- and L2/Ni²⁺-Mica procatalysts afforded a mixture of a large amount of low-molecular weight polyethylene and a small amount of oligomers having 4-22 carbons. The procatalyst consisting of Ni²⁺-Mica and the L3 ligand that possesses non-substituted phenyl groups on the iminonitrogen atoms effectively promoted the oligomerization of ethylene after its activation with TEA, resulting in the fact that the ethylene oligomers were produced with a moderate catalytic activity (101 g-ethylene g-cat⁻¹ h⁻¹ at 0.7 MPa-ethylene) in the presence of TEA. When the backbone was varied from the butane moiety (L3) to acenaphthene (L4), the solid product dramatically increased. The weight percentage of the oligomers in the total products increased with the increasing reaction temperature; however, an insignificant increase in the oligomers was observed when the ethylene pressure was decreased. Full article

(This article belongs to the Special Issue Molecular Catalysis for Precise Olefin Polymerization)

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11 pages, 573 KiB

Open AccessArticle

Precise Active Site Analysis for TiCl₃/MgCl₂ Ziegler-Natta Model Catalyst Based on Fractionation and Statistical Methods

by Shougo Takahashi, Toru Wada, Toshiaki Taniike and Minoru Terano^*

School of Materials Science, Japan Advance Institute of Science and Technology, 1-1 Asahidai, Nomi, Ishikawa 923-1292, Japan

Catalysts 2013, 3(1), 137-147; https://doi.org/10.3390/catal3010137 - 7 Feb 2013

Cited by 18 | Viewed by 7431

Abstract

In heterogeneous Ziegler-Natta catalysts for olefin polymerization, isolation of a single type of active sites is a kind of ambition, which would solve long-standing questions on the relationship between active site and polymer structures. In this paper, polypropylene produced by TiCl₃/MgCl [...] Read more.

In heterogeneous Ziegler-Natta catalysts for olefin polymerization, isolation of a single type of active sites is a kind of ambition, which would solve long-standing questions on the relationship between active site and polymer structures. In this paper, polypropylene produced by TiCl₃/MgCl₂ model catalysts with minimum Ti heterogeneity was analyzed by combined solvent fractionation and the two-site statistical model. We found that the active sites of the model catalysts were classified into only three types, whose proportions were dependent on the Ti dispersion state. The addition of external donors not only newly formed highly isospecific sites, but also altered the stereochemical nature of the other active sites. Full article

(This article belongs to the Special Issue Molecular Catalysis for Precise Olefin Polymerization)

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9 pages, 251 KiB

Open AccessArticle

Ethylene Polymerization Using (Imino)vanadium(V) Dichloride Complexes Containing (Anilido)methyl-pyridine, -quinoline Ligands–Halogenated Al Alkyls Catalyst Systems

by Atsushi Igarashi¹, Wenjuan Zhang², Wen-Hua Sun²

and Kotohiro Nomura^1,*

¹ Department of Chemistry, Tokyo Metropolitan University, 1-1 Minami Osawa, Hachioji, Tokyo 192-0397, Japan

² Institute of Chemistry, Chinese Academy of Sciences, Zhongguancun, Beijing 100190, China

Catalysts 2013, 3(1), 148-156; https://doi.org/10.3390/catal3010148 - 7 Feb 2013

Cited by 5 | Viewed by 6038

Abstract

The effect of ligand and Al cocatalysts in ethylene polymerization, using V(N-1-adamantyl)Cl₂(L) [L = 2-(2,6-Me₂C₆H₃)NCH₂(C₉H₆N), 8-(2,6-Me₂C₆H₃)NCH₂(C₉H₆ [...] Read more.

The effect of ligand and Al cocatalysts in ethylene polymerization, using V(N-1-adamantyl)Cl₂(L) [L = 2-(2,6-Me₂C₆H₃)NCH₂(C₉H₆N), 8-(2,6-Me₂C₆H₃)NCH₂(C₉H₆N)] and V(N-2-MeC₆H₃)Cl₂[2-(2,6-R'₂C₆H₃)NCH₂(C₅H₄N)] (R' = Me, ⁱPr), has been explored. The reaction products in the presence of Et₂AlCl or Me₂AlCl cocatalyst were polyethylene whereas the reaction product of the 2-methylphenylimido analogues in the presence of MAO cocatalyst was 1-butene with high selectivity, suggesting that the catalyst/cocatalyst nuclearity effect plays a role in this catalysis. Full article

(This article belongs to the Special Issue Molecular Catalysis for Precise Olefin Polymerization)

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19 pages, 476 KiB

Open AccessReview

Half-Titanocenes Containing Anionic Ancillary Donor Ligands: Effective Catalyst Precursors for Ethylene/Styrene Copolymerization

by Kotohiro Nomura

Department of Chemistry, Tokyo Metropolitan University, 1-1 Minami Osawa, Hachioji, Tokyo 192-0397, Japan

Catalysts 2013, 3(1), 157-175; https://doi.org/10.3390/catal3010157 - 18 Feb 2013

Cited by 14 | Viewed by 8166

Abstract

This review summarizes recent results for ethylene/styrene copolymerization using half-titanocenes containing anionic donor ligands, Cp’TiX₂(Y) (X = halogen, alkyl; Y = aryloxo, ketimide etc.)–cocatalyst systems. The product composition, the styrene incorporation and microstructures in the resultant copolymers are highly influenced [...] Read more.

This review summarizes recent results for ethylene/styrene copolymerization using half-titanocenes containing anionic donor ligands, Cp’TiX₂(Y) (X = halogen, alkyl; Y = aryloxo, ketimide etc.)–cocatalyst systems. The product composition, the styrene incorporation and microstructures in the resultant copolymers are highly influenced by the anionic donor employed. A methodology for an exclusive synthesis of the copolymers even under high temperature and high styrene concentrations has been introduced on the basis of a proposed catalytically-active species in this catalysis. Full article

(This article belongs to the Special Issue Molecular Catalysis for Precise Olefin Polymerization)

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13 pages, 571 KiB

Open AccessArticle

A Comparative Study on the Homo-, Co- and Ter-Polymerization Using Ethylene, 1-Decene and p-Methylstyrene

by Dong Jin Yang, Hyun Jun Kim and Dong Hyun Kim^*

Convergent Technology R&D Division, Korea Institute of Industrial Technology, Ansan-si, Korea

Catalysts 2013, 3(1), 176-188; https://doi.org/10.3390/catal3010176 - 22 Feb 2013

Cited by 3 | Viewed by 7728

Abstract

We synthesized polyethylene (PE), poly(ethylene-co-1-decene), poly(ethylene-co-p-methylstyrene) and poly(ethylene-ter-1-decene-ter-p-methystyrene) using a rac-Et(Ind)₂ZrCl₂metallocene catalyst and a methylaluminoxane cocatalyst system. The materials were characterized using nuclear magnetic resonance spectroscopy [...] Read more.

We synthesized polyethylene (PE), poly(ethylene-co-1-decene), poly(ethylene-co-p-methylstyrene) and poly(ethylene-ter-1-decene-ter-p-methystyrene) using a rac-Et(Ind)₂ZrCl₂metallocene catalyst and a methylaluminoxane cocatalyst system. The materials were characterized using nuclear magnetic resonance spectroscopy and Fourier transform infrared spectroscopy. We compared and studied the kinetics, thermal properties and mechanical ones of these polymers. T_g was related to the amorphous phase of the polymers, whereas the tensile strength and storage modulus (E’) were related to the crystalline phase. We also found that PE has the highest crystallinity through differential scanning calorimetry and wide-angle X-ray scattering analysis. The polymerization rates of poly(ethylene-co-1-decene) and poly(ethylene-ter-1-decene-ter-p-methystyrene) were always higher than that of polyethylene. Full article

(This article belongs to the Special Issue Molecular Catalysis for Precise Olefin Polymerization)

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30 pages, 1729 KiB

Open AccessReview

Heterogeneous Photocatalysis: Recent Advances and Applications

by Alex Omo Ibhadon^1,* and Paul Fitzpatrick²

¹ Centre for Environmental and Marine Sciences, Faculty of Science, University of Hull, Scarborough Campus, Scarborough YO11 3AZ, UK

² Tech Innovation, Capenhurst Technology Park, Capenhurst, Chester, CH1 6EH, UK

Catalysts 2013, 3(1), 189-218; https://doi.org/10.3390/catal3010189 - 1 Mar 2013

Cited by 1177 | Viewed by 70013

Abstract

Semiconductor heterogeneous photocatalysis, the subject of this review, is a versatile, low-cost and environmentally benign treatment technology for a host of pollutants. These may be of biological, organic and inorganic in origin within water and air. The efficient and successful application of photocatalysis [...] Read more.

Semiconductor heterogeneous photocatalysis, the subject of this review, is a versatile, low-cost and environmentally benign treatment technology for a host of pollutants. These may be of biological, organic and inorganic in origin within water and air. The efficient and successful application of photocatalysis demands that the pollutant, the catalyst and source of illumination are in close proximity or contact with each other. The ability of advanced oxidation technology to remove low levels of persistent organic pollutants as well as microorganisms in water has been widely demonstrated and, progressively, the technology is now being commercialized in many areas of the world including developing nations. This review considers recent developments in the research and application of heterogeneous semiconductor photocatalysis for the treatment of low-level concentrations of pollutants in water and air using titanium dioxide as a “model” semiconductor. The review considers charge transport characteristics on the semiconductor surface, photocatalyst reactor design and organic degradation mechanistic pathways. The effects of photoreactor operating parameters on the photocatalytic process are discussed in addition to mineralization and disinfection kinetics. Full article

(This article belongs to the Special Issue Photocatalysts)

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13 pages, 396 KiB

Open AccessArticle

Photocatalytic Oxidation Processes for Toluene Oxidation over TiO₂ Catalysts

by Hisahiro Einaga^*, Keisuke Mochiduki and Yasutake Teraoka

Department of Energy and Material Sciences, Faculty of Engineering Sciences, Kyushu University, Kasuga, Fukuoka 816-8580, Japan

Catalysts 2013, 3(1), 219-231; https://doi.org/10.3390/catal3010219 - 4 Mar 2013

Cited by 47 | Viewed by 9701

Abstract

Gas-solid heterogeneous photooxidation of toluene over TiO₂ catalyst was studied to investigate the factors controlling the catalytic activities. The toluene photooxidation behavior on TiO₂ was strongly affected by the formation and oxidation behavior of intermediate compounds on TiO₂, and [...] Read more.

Gas-solid heterogeneous photooxidation of toluene over TiO₂ catalyst was studied to investigate the factors controlling the catalytic activities. The toluene photooxidation behavior on TiO₂ was strongly affected by the formation and oxidation behavior of intermediate compounds on TiO₂, and their accumulation decreased the reaction rate for toluene photooxidation. The formation and oxidation behavior of the byproduct compounds depended on the initial concentration of toluene and water vapor. In situ Fourier transform infrared (FTIR) studies revealed that water vapor promoted the cleavage of the aromatic ring and facilitated CO₂ formation. At the reaction temperature of 300 K, the deposition of Pt on TiO₂ suppressed CO formation, whereas catalytic activity was decreased due to the increase in the amount of intermediate compounds. On the other hand, Pt/TiO₂ showed higher activity than TiO₂ at 353 K, in spite of the increase of the intermediate compounds. Full article

(This article belongs to the Special Issue Photocatalysts)

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15 pages, 316 KiB

Open AccessArticle

Biomimetic Catalysts for Oxidation of Veratryl Alcohol, a Lignin Model Compound

by Gustavo González-Riopedre, María Isabel Fernández-García, Esther Gómez-Fórneas and Marcelino Maneiro^*

Department of Inorganic Chemistry, Faculty of Sciences, University of Santiago de Compostela, Lugo 27002, Spain

Catalysts 2013, 3(1), 232-246; https://doi.org/10.3390/catal3010232 - 4 Mar 2013

Cited by 25 | Viewed by 9491

Abstract

Kraft pulp has to be bleached to eliminate the chromophoric structures, which cause a darkening of the pulp. In Nature, an equivalent role is assumed by ligninolytic enzymes such as lignin peroxidases, manganese peroxidases and laccases. The development of low molecular weight manganese [...] Read more.

Kraft pulp has to be bleached to eliminate the chromophoric structures, which cause a darkening of the pulp. In Nature, an equivalent role is assumed by ligninolytic enzymes such as lignin peroxidases, manganese peroxidases and laccases. The development of low molecular weight manganese peroxidase mimics may achieve environmentally-safe bleaching catalysts for the industry. Herein we report the synthesis and characterization of six manganese(III) complexes 1–6, incorporating dianionic hexadentate Schiff base ligands (H₂L¹-H₂L⁴)and different anions. Complex 4, Mn₂L²₂(H₂O)₂(DCA)₂ was crystallographically characterized. Complexes 1–4 behave as more efficient mimics of peroxidase in contrast to 5–6. We have studied the use of these complexes as catalysts for the degradation of the lignin model compound veratryl alcohol. The biomimetic catalysts were used in conjunction with chlorine-free inexpensive co-oxidants as dioxygen or hydrogen peroxide. Yields up to 30% of veratryl alcohol conversion to veratraldehyde have been achieved at room temperature in presence of air flow using 0.5% of catalyst. Full article

(This article belongs to the Special Issue Biomimetic Catalysts)

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14 pages, 2469 KiB

Open AccessArticle

Inactivation of E. Coli in Water Using Photocatalytic, Nanostructured Films Synthesized by Aerosol Routes

by Jinho Park¹, Eric Kettleson^1,2, Woo-Jin An¹, Yinjie J. Tang¹ and Pratim Biswas^1,*

¹ Aerosol and Air Quality Research Laboratory, Department of Energy, Environmental and Chemical Engineering, School of Engineering and Applied Science, Washington University in St. Louis, Campus Box 1180, St. Louis, MO 63130, USA

² Department of Environmental Health, University of Cincinnati, Cincinnati, OH 45267, USA

Catalysts 2013, 3(1), 247-260; https://doi.org/10.3390/catal3010247 - 4 Mar 2013

Cited by 15 | Viewed by 7704

Abstract

TiO₂ nanostructured films were synthesized by an aerosol chemical vapor deposition (ACVD) method with different controlled morphologies: columnar, granular, and branched structures for the photocatalytic inactivation of Escherichia coli (E. coli) in water. Effects of film morphology and external applied [...] Read more.

TiO₂ nanostructured films were synthesized by an aerosol chemical vapor deposition (ACVD) method with different controlled morphologies: columnar, granular, and branched structures for the photocatalytic inactivation of Escherichia coli (E. coli) in water. Effects of film morphology and external applied voltage on inactivation rate were investigated. As-prepared films were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffractometry (XRD), and UV-VIS. Photocatalytic and photoelectrochemical inactivation of E. coli using as-prepared TiO₂ films were performed under irradiation of UVA light (note: UVA has a low efficiency to inactivate E. coli). Inactivation rate constants for each case were obtained from their respective inactivation curve through a 2 h incubation period. Photocatalytic inactivation rate constants of E. coli are 0.02/min (using columnar films), and 0.08/min (using branched films). The inactivation rate constant for the columnar film was enhanced by 330% by applied voltage on the film while that for the branched film was increased only by 30%. Photocatalytic microbial inactivation rate of the columnar and the branched films were also compared taking into account their different surface areas. Since the majority of the UV radiation that reaches the Earth’s surface is UVA, this study provides an opportunity to use sunlight to efficiently decontaminate drinking water. Full article

(This article belongs to the Special Issue Photocatalysts)

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15 pages, 369 KiB

Open AccessArticle

Phosphine-Thiophenolate Half-Titanocene Chlorides: Synthesis, Structure, and Their Application in Ethylene (Co-)Polymerization

by Xiao-Yan Tang^1,2, Jing-Yu Liu^1,* and Yue-Sheng Li¹

¹ State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China

² University of the Chinese Academy of Sciences, Changchun Branch, Changchun 130022, China

Catalysts 2013, 3(1), 261-275; https://doi.org/10.3390/catal3010261 - 6 Mar 2013

Cited by 4 | Viewed by 6627

Abstract

A series of novel half-titanocene complexes CpTiCl₂[S-2-R-6-(PPh₂)C₆H₃] (Cp = C₅H₅, 2a, R = H; 2b, R = Ph; 2c, R = SiMe₃) have been synthesized by [...] Read more.

A series of novel half-titanocene complexes CpTiCl₂[S-2-R-6-(PPh₂)C₆H₃] (Cp = C₅H₅, 2a, R = H; 2b, R = Ph; 2c, R = SiMe₃) have been synthesized by treating CpTiCl₃ with the sodium of the ligands, 2-R-6-(PPh₂)C₆H₃SNa, which were prepared by the corresponding ligands and NaH. These complexes have been characterized by ¹H, ¹³C and ³¹P NMR as well as elemental analyses. Structures for 2a–b were further confirmed by X-ray crystallography. Complexes 2a–b adopt five-coordinate, distorted square-pyramid geometry around the titanium center, in which the equatorial positions are occupied by sulfur and phosphorus atoms of the chelating phosphine-thiophenolate and two chlorine atoms, and the cyclopentadienyl ring is coordinated on the axial position. The complexes 2a–c were investigated as the catalysts for ethylene polymerization and copolymerization of ethylene with norbornene in the presence of MMAO or Ph₃CB(C₆F₅)₄/ⁱBu₃Al as the cocatalyst. All complexes exhibited low to moderate activities towards homopolymerization of ethylene. However, they displayed moderate to high activities towards copolymerization of ethylene with norbornene. Full article

(This article belongs to the Special Issue Molecular Catalysis for Precise Olefin Polymerization)

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12 pages, 1868 KiB

Open AccessArticle

Defect-Driven Restructuring of TiO₂ Surface and Modified Reactivity Toward Deposited Gold Atoms

by Kenneth Park^1,*, Vincent Meunier², Minghu Pan³ and Ward Plummer⁴

¹ Department of Physics, Baylor University, Waco, TX 76798, USA

² Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, Troy, NY 12180, USA

³ Center of Nanophase Materials Sciences, Oak Ridge National Laboratory, TN 37831, USA

⁴ Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803, USA

Catalysts 2013, 3(1), 276-287; https://doi.org/10.3390/catal3010276 - 8 Mar 2013

Cited by 5 | Viewed by 7317

Abstract

A partially reduced TiO2 surface exhibits increasingly complex nature when forming various defects, whose stoichiometry, structure and properties are markedly different from those of bulk TiO2. Using scanning tunneling microscopy and density functional theory, we investigate different types of surface defects formed by [...] Read more.

A partially reduced TiO2 surface exhibits increasingly complex nature when forming various defects, whose stoichiometry, structure and properties are markedly different from those of bulk TiO2. Using scanning tunneling microscopy and density functional theory, we investigate different types of surface defects formed by Ti interstitials on TiO2 (110) and their reactivity toward deposited gold atoms. Sub-stoichiometric strands greatly enhance bonding of Au by transferring the excess charges from the reduced Ti3+ onto the strands. Thus the sub-stoichiometric strands behave as strong electron donor sites toward reactants. On the contrary, fully stoichiometric nanoclusters provide increased Au bonding through its 1-coordinated oxygen, which acts as a strong electron acceptor site. Specific interactions between Au and defects as well as the implication of electron donor/acceptor complexes for catalytic reactions are discussed. Full article

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

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22 pages, 5075 KiB

Open AccessArticle

Electron Transfer at Gold Nanostar Assemblies: A Study of Shape Stability and Surface Density Influence

by Mariana Chirea

Chemistry and Biochemistry Department, Faculty of Sciences, Universidade do Porto, Rua Campo Alegre 687, 4169-007, Porto, Portugal

Catalysts 2013, 3(1), 288-309; https://doi.org/10.3390/catal3010288 - 12 Mar 2013

Cited by 28 | Viewed by 12292

Abstract

Gold nanostars of ~70 nm tip to tip distances were synthesized by a seed mediated method and covalently self-assembled on 1,5-pentanedithiol modified electrodes. Electron transfer kinetics at the AuNS/dithiol modified electrodes were studied as a function of AuNS surface density which was varied [...] Read more.

Gold nanostars of ~70 nm tip to tip distances were synthesized by a seed mediated method and covalently self-assembled on 1,5-pentanedithiol modified electrodes. Electron transfer kinetics at the AuNS/dithiol modified electrodes were studied as a function of AuNS surface density which was varied by increasing their self-assembly time from 8 h, 16 h, 24 h to 32 h. Excellent electrocatalytic properties of AuNSs were observed toward electrochemistry of [Fe(CN)₆]^4−/3− redox couple. The apparent heterogeneous electron transfer constant, k_et, has progressively increased with the surface density of AuNSs bonded to the electrodes from 0.65 × 10⁻⁵ cm s⁻¹ (8 h), 1.47 × 10⁻⁵ cm s⁻¹ (16 h), 3.95 × 10⁻⁵ cm s⁻¹ (24 h) to an excellent 85.0 × 10⁻⁵cm s⁻¹ (32 h). Electrochemical charging of nanostars was confirmed, for the first time, by 79 times increase of double layer capacitance, C_dl, from 0.34 µF (8 h) to 27 µF (32 h). The electrochemical charging of AuNSs had also a strong influence on the electron tunneling process through the 1,5PDT molecules being more efficient at dense layers of AuNSs. The tunneling parameter, β, has decreased from 1.13 Å⁻¹ (16 h) to 0.50 Å⁻¹ (32 h). The AuNSs were chemically stable toward [Fe(CN)₆]^4−/3− showing no change in shape after electrochemical measurements. Full article

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

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14 pages, 276 KiB

Open AccessArticle

Broad Spectrum Microbicidal Activity of Photocatalysis by TiO₂

by Ryuichi Nakano^1,2,†, Masayuki Hara^2,*,†, Hitoshi Ishiguro^2,3, Yanyan Yao^2,3, Tsuyoshi Ochiai^2,4

, Kazuya Nakata^2,4, Taketoshi Murakami², Jitsuo Kajioka², Kayano Sunada^2,5, Kazuhito Hashimoto^5,6, Akira Fujishima^2,4 and Yoshinobu Kubota^2,3

¹ Department of Microbiology and Immunology, School of Medicine, Teikyo University, 2-11-1 Kaga, Itabashi-ku, Tokyo 173-8605, Japan

² Kanagawa Academy of Science and Technology, 3-2-1 Sakado, Takatsu-ku, Kawasaki, Kanagawa 213-0012, Japan

³ Department of Urology, Graduate School of Medicine, Yokohama City University, 3-9, Fukuura, Kanazawa-ku, Yokohama, Kanagawa 236-0004, Japan

⁴ Division of Photocatalyst for Energy and Environment, Research Institute for Science and Technology, Tokyo University of Science, 1-3 Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan

⁵ Research Center for Advanced Science and Technology, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904, Japan

⁶ Department of Applied Chemistry, Faculty of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyyoo-ku, Tok 113-8656, Japan

^† These authors contributed equally to this work.

Catalysts 2013, 3(1), 310-323; https://doi.org/10.3390/catal3010310 - 21 Mar 2013

Cited by 101 | Viewed by 12358

Abstract

Photocatalytically active titanium dioxide (TiO₂) is widely used as a self-cleaning and self-disinfecting material in many applications to keep environments biologically clean. Several studies on the inactivation of bacteria and viruses by photocatalytic reactions have also been reported; however, only few [...] Read more.

Photocatalytically active titanium dioxide (TiO₂) is widely used as a self-cleaning and self-disinfecting material in many applications to keep environments biologically clean. Several studies on the inactivation of bacteria and viruses by photocatalytic reactions have also been reported; however, only few studies evaluated the spectrum of the microbicidal activity with photocatalysis for various species. There is a need to confirm the expected effectiveness of disinfection by photocatalysis against multidrug-resistant bacteria and viruses. In this study, microbicidal activity of photocatalysis was evaluated by comparing the inactivation of various species of bacteria and viruses when their suspensions were dropped on the surface of TiO₂-coated glass. Gram-positive bacteria, e.g., methicillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus faecalis, and penicillin-resistant Streptococcus pneumoniae, were easily inactivated by photocatalysis, whereas some gram-negative bacteria, e.g., Escherichia coli and multidrug-resistant Pseudomonas aeruginosa, were gradually inactivated by photocatalysis. Influenza virus, an enveloped virus, was significantly inactivated by photocatalysis compared with feline calicivirus, a non-enveloped virus. The effectiveness of microbicidal activity by photocatalysis may depend on the surface structure. However, they are effectively inactivated by photocatalysis on the surface of TiO₂-coated glass. Our data emphasize that effective cleaning and disinfection by photocatalysis in nosocomial settings prevents pathogen transmission. Full article

(This article belongs to the Special Issue Photocatalysts)

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14 pages, 1874 KiB

Open AccessArticle

Hydroformylation of 1-Hexene over Rh/Nano-Oxide Catalysts

by Maija-Liisa Kontkanen¹, Matti Tuikka^1,2, Niko M. Kinnunen¹, Sari Suvanto¹ and Matti Haukka^1,2,*

¹ Department of Chemistry, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland

² Department of Chemistry, University of Jyväskylä, P.O. Box 35, University of Jyväskylä, Finland

Catalysts 2013, 3(1), 324-337; https://doi.org/10.3390/catal3010324 - 21 Mar 2013

Cited by 19 | Viewed by 8320

Abstract

The effect of nanostructured supports on the activity of Rh catalysts was studied by comparing the catalytic performance of nano- and bulk-oxide supported Rh/ZnO, Rh/SiO₂ and Rh/TiO₂ systems in 1-hexene hydroformylation. The highest activity with 100% total conversion and 96% yield [...] Read more.

The effect of nanostructured supports on the activity of Rh catalysts was studied by comparing the catalytic performance of nano- and bulk-oxide supported Rh/ZnO, Rh/SiO₂ and Rh/TiO₂ systems in 1-hexene hydroformylation. The highest activity with 100% total conversion and 96% yield of aldehydes was obtained with the Rh/nano-ZnO catalyst. The Rh/nano-ZnO catalyst was found to be more stable and active than the corresponding rhodium catalyst supported on bulk ZnO. The favorable morphology of Rh/nano-ZnO particles led to an increased metal content and an increased number of weak acid sites compared to the bulk ZnO supported catalysts. Both these factors favored the improved catalytic performance. Improvements of catalytic properties were obtained also with the nano-SiO₂ and nano-TiO₂supportsin comparison with the bulk supports. All of the catalysts were characterized by scanning electron microscope (SEM), inductively coupled plasma mass spectrometry (ICP-MS), BET, powder X-ray diffraction (PXRD) and NH₃- temperature-programmed desorption (TPD). Full article

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Catalysts, Volume 3, Issue 1 (March 2013) – 22 articles , Pages 1-362

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