Catalysts

2728 KiB

Open AccessArticle

Activated Carbon-Supported Tetrapropylammonium Perruthenate Catalysts for Acetylene Hydrochlorination

by Xing Li, Haiyang Zhang, Baochang Man, Lijuan Hou, Chuanming Zhang, Hui Dai, Mingyuan Zhu, Bin Dai, Yanzhao Dong and Jinli Zhang

Catalysts 2017, 7(10), 311; https://doi.org/10.3390/catal7100311 - 24 Oct 2017

Cited by 18 | Viewed by 4258

Abstract

The Ru-based catalysts, including Ru/AC (activated carbon), TPAP (tetrapropylammonium perruthenate)/AC, TPAP/AC-HNO₃, and TPAP/AC-HCl, were prepared and assessed for the direct synthesis of vinyl chloride monomer. The results indicate that the TPAP/AC-HCl catalyst exhibits the best performance with the conversion falling from [...] Read more.

The Ru-based catalysts, including Ru/AC (activated carbon), TPAP (tetrapropylammonium perruthenate)/AC, TPAP/AC-HNO₃, and TPAP/AC-HCl, were prepared and assessed for the direct synthesis of vinyl chloride monomer. The results indicate that the TPAP/AC-HCl catalyst exhibits the best performance with the conversion falling from 97% to 91% in 48 hours’ reaction under the conditions of 180 °C, a GHSV(C₂H₂) of 180 h⁻¹, and the feed ratio V_HCl/V_C2H2 of 1.15. The substitution of RuCl₃ precursor with high valent TPAP species leads to more ruthenium oxides active species in the catalysts; the acidification treatment of carrier in TPAP/AC catalyst can produce an enhanced interaction between the active species and the modified functional groups on the carrier, and it is beneficial to inhibit the carbon deposition and sintering of ruthenium species in the reaction process, greatly increase the adsorption ability of reactants, and further increase the amount of dominating active species in the catalysts, thus improving the catalytic performance. This also provides a promising strategy to explore high efficient and economic mercury-free catalysts for the hydrochlorination of acetylene. Full article

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8010 KiB

Open AccessArticle

Water–Gas Shift Reaction over Ni/CeO₂ Catalysts

by Ludmilla Bobrova, Dmitry Andreev, Eugene Ivanov, Natalia Mezentseva, Mikhail Simonov, Lev Makarshin, Alexander Gribovskii and Vladislav Sadykov

Catalysts 2017, 7(10), 310; https://doi.org/10.3390/catal7100310 - 20 Oct 2017

Cited by 27 | Viewed by 11364

Abstract

This paper reports the results of a study of a water–gas shift reaction over nickel–ceria catalysts with different metal loading. Within this study, the overall CO conversion and observed kinetic behavior were investigated over the temperature range of 250–550 °C in different reactor [...] Read more.

This paper reports the results of a study of a water–gas shift reaction over nickel–ceria catalysts with different metal loading. Within this study, the overall CO conversion and observed kinetic behavior were investigated over the temperature range of 250–550 °C in different reactor configurations (fixed-bed and microchannel reactors). The quasi-steady state kinetics of the CO water–gas shift reaction was studied for fractions of Ni-containing cerium oxide catalysts in fixed-bed experiments at lab-scale level using a very dilute gas (1% CO + 1.8% H₂O in Не). A set of experiments with a microchannel reactor was performed using the feed composition (CO:H₂O:H₂:N₂ = 1:2:2:2), representing a product gas from methane partial oxidation. The results were interpreted using computational models. The kinetic parameters were determined by regression analysis, while mechanistic aspects were considered only briefly. Simulation of the WGS reaction in the microreactor was also carried out by using the COMSOL Multiphysics program. Full article

(This article belongs to the Special Issue Nanostructured Materials for Applications in Heterogeneous Catalysis)

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2343 KiB

Open AccessArticle

Synthesis of Biolubricant Basestocks from Epoxidized Soybean Oil

by Rosa Turco, Riccardo Tesser, Rosa Vitiello, Vincenzo Russo, Salvatore Andini and Martino Di Serio

Catalysts 2017, 7(10), 309; https://doi.org/10.3390/catal7100309 - 19 Oct 2017

Cited by 37 | Viewed by 5471

Abstract

This work deals with the preparation of biolubricant basestocks through the ring-opening reaction of epoxidized soybean oil (ESO) by alcohols in presence of solid acid catalysts (SAC-13 resin). To this end, different experimental runs were carried out in a lab-scale reactor, analyzing the [...] Read more.

This work deals with the preparation of biolubricant basestocks through the ring-opening reaction of epoxidized soybean oil (ESO) by alcohols in presence of solid acid catalysts (SAC-13 resin). To this end, different experimental runs were carried out in a lab-scale reactor, analyzing the effect of the alcohol (methanol, ethanol, 2-propanol, 2-butanol), catalyst mass loading (from 1 to 10 wt % with respect to the oil mass) and operating temperature (60–90 °C). The main focus of investigation was oxirane conversion. The study was complemented by FT-IR, ¹H NMR and kinematic viscosity characterization of the different products of the ring-opening reaction. Experimental conversion data were fitted through a suitable kinetic model. Values of the best-fitting parameters in terms of rate constant, activation energy and catalyst reaction order were obtained, and were potentially useful for the design of an industrial process. Full article

(This article belongs to the Special Issue Catalytic Sustainable Processes in Biorefineries)

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4397 KiB

Open AccessArticle

Alcohol Dehydrogenation on Kraft Lignin-Derived Chars with Surface Basicity

by Francisco J. García-Mateos, Imane Moulefera, Juana M. Rosas, Abdelghani Benyoucef, José Rodríguez-Mirasol and Tomás Cordero

Catalysts 2017, 7(10), 308; https://doi.org/10.3390/catal7100308 - 19 Oct 2017

Cited by 19 | Viewed by 4228

Abstract

The properties of lignin and its potential as a renewable source make it an ideal precursor for carbon products. Specifically, the high content of Na observed in Kraft lignin makes this industrial by-product an interesting precursor for the preparation of catalysts for different [...] Read more.

The properties of lignin and its potential as a renewable source make it an ideal precursor for carbon products. Specifically, the high content of Na observed in Kraft lignin makes this industrial by-product an interesting precursor for the preparation of catalysts for different applications. In this work, basic activated carbons with different textural properties and surface chemistry were obtained from Kraft lignin by direct carbonization at various temperatures. The influence of a further washing treatment and partial gasification with CO₂ was also evaluated. The carbon catalysts were tested as catalysts for the alcohol decomposition reaction. In this sense, 2-propanol, a molecule widely used for testing the acidic-basic character of heterogeneous catalysts, was selectively transformed into acetone, meanwhile, ethanol and methanol yielded mainly acetaldehyde and formaldehyde, respectively. Full article

(This article belongs to the Special Issue Catalytic Sustainable Processes in Biorefineries)

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2148 KiB

Open AccessArticle

Concept of Vaporized Urea Dosing in Selective Catalytic Reduction

by Rafal Sala, Piotr Bielaczyc and Marek Brzezanski

Catalysts 2017, 7(10), 307; https://doi.org/10.3390/catal7100307 - 19 Oct 2017

Cited by 10 | Viewed by 7517

Abstract

This work tried to identify the influence of dosing vaporized urea solution in a selective catalytic reduction (SCR) system. In the SCR method, optimising the urea evaporation and mixing properties can significantly improve the NO_x conversion efficiency in the catalyst. It can [...] Read more.

This work tried to identify the influence of dosing vaporized urea solution in a selective catalytic reduction (SCR) system. In the SCR method, optimising the urea evaporation and mixing properties can significantly improve the NO_x conversion efficiency in the catalyst. It can also exert a positive effect on the uniformity of NH₃ concentration distribution across the catalyst face. The concept of an electrically evaporated urea-dosing system was investigated and it was found that urea pre-heating prior to introduction into the exhaust gas is favourable for enhancing NO_x removal under steady-state and transient engine operation. In the urea evaporating system the heating chamber was of a cylindrical tube shape and the urea vapour was introduced into the exhaust by means of a Venturi orifice. The concept urea dosing was only a custom-made solution, but proved to be superior to the regular dosing system operating in the liquid phase. Full article

(This article belongs to the Special Issue Selective Catalytic Reduction of NO_x)

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Open AccessFeature PaperReview

Application of Artificial Neural Networks for Catalysis: A Review

by Hao Li, Zhien Zhang and Zhijian Liu

Catalysts 2017, 7(10), 306; https://doi.org/10.3390/catal7100306 - 18 Oct 2017

Cited by 175 | Viewed by 19195

Abstract

Machine learning has proven to be a powerful technique during the past decades. Artificial neural network (ANN), as one of the most popular machine learning algorithms, has been widely applied to various areas. However, their applications for catalysis were not well-studied until recent [...] Read more.

Machine learning has proven to be a powerful technique during the past decades. Artificial neural network (ANN), as one of the most popular machine learning algorithms, has been widely applied to various areas. However, their applications for catalysis were not well-studied until recent decades. In this review, we aim to summarize the applications of ANNs for catalysis research reported in the literature. We show how this powerful technique helps people address the highly complicated problems and accelerate the progress of the catalysis community. From the perspectives of both experiment and theory, this review shows how ANNs can be effectively applied for catalysis prediction, the design of new catalysts, and the understanding of catalytic structures. Full article

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Open AccessFeature PaperReview

Recent Advances in Graphene Based TiO₂Nanocomposites (GTiO₂Ns) for Photocatalytic Degradation of Synthetic Dyes

by Rita Giovannetti, Elena Rommozzi, Marco Zannotti and Chiara Anna D’Amato

Catalysts 2017, 7(10), 305; https://doi.org/10.3390/catal7100305 - 16 Oct 2017

Cited by 123 | Viewed by 10774

Abstract

Synthetic dyes are widely used in textile, paper, food, cosmetic, and pharmaceutical industries. During industrial processes, some of these dyes are released into the wastewater and their successive release into rivers and lakes produces serious environmental problems. TiO₂ is one of the [...] Read more.

Synthetic dyes are widely used in textile, paper, food, cosmetic, and pharmaceutical industries. During industrial processes, some of these dyes are released into the wastewater and their successive release into rivers and lakes produces serious environmental problems. TiO₂ is one of the most widely studied and used photocatalysts for environmental remediation. However, it is mainly active under UV-light irradiation due to its band gap of 3.2 eV, while it shows low efficiency under the visible light spectrum. Regarding the exploration of TiO₂ activation in the visible light region of the total solar spectrum, the incorporation of carbon nanomaterials, such as graphene, in order to form carbon-TiO₂ composites is a promising area. Graphene, in fact, has a large surface area which makes it a good adsorbent for organic pollutants removal through the combination of electrostatic attraction and π-π interaction. Furthermore, it has a high electron mobility and therefore it reduces the electron-hole pair recombination, improving the photocatalytic activity of the semiconductor. In recent years, there was an increasing interest in the preparation of graphene-based TiO₂ photocatalysts. The present short review describes the recent advances in TiO₂ photocatalyst coupling with graphene materials with the aim of extending the light absorption of TiO₂ from UV wavelengths into the visible region, focusing on recent progress in the design and applications in the photocatalytic degradation of synthetic dyes. Full article

(This article belongs to the Special Issue Nanomaterials for Environmental Purification and Energy Conversion)

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2103 KiB

Open AccessFeature PaperArticle

Flame-Made Cu/TiO₂ and Cu-Pt/TiO₂ Photocatalysts for Hydrogen Production

by Massimo Bernareggi, Maria Vittoria Dozzi, Luca Giacomo Bettini, Anna Maria Ferretti, Gian Luca Chiarello and Elena Selli

Catalysts 2017, 7(10), 301; https://doi.org/10.3390/catal7100301 - 16 Oct 2017

Cited by 29 | Viewed by 6012

Abstract

The effect of Cu or Cu-Pt nanoparticles in TiO₂ photocatalysts prepared by flame spray pyrolysis in one step was investigated in hydrogen production from methanol photo-steam reforming. Two series of titanium dioxide photocatalysts were prepared, containing either (i) Cu nanoparticles (0.05–0.5 wt%) [...] Read more.

The effect of Cu or Cu-Pt nanoparticles in TiO₂ photocatalysts prepared by flame spray pyrolysis in one step was investigated in hydrogen production from methanol photo-steam reforming. Two series of titanium dioxide photocatalysts were prepared, containing either (i) Cu nanoparticles (0.05–0.5 wt%) or (ii) both Cu (0 to 0.5 wt%) and Pt (0.5 wt%) nanoparticles. In addition, three photocatalysts obtained either by grafting copper and/or by depositing platinum by wet methods on flame-made TiO₂ were also investigated. High hydrogen production rates were attained with copper-containing photocatalysts, though their photoactivity decreased with increasing Cu loading, whereas the photocatalysts containing both Cu and Pt nanoparticles exhibit a bell-shaped photoactivity trend with increasing copper content, the highest hydrogen production rate being attained with the photocatalyst containing 0.05 wt% Cu. Full article

(This article belongs to the Special Issue Titanium Dioxide Photocatalysis)

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2104 KiB

Open AccessFeature PaperReview

Brookite: Nothing New under the Sun?

by Matteo Monai, Tiziano Montini and Paolo Fornasiero

Catalysts 2017, 7(10), 304; https://doi.org/10.3390/catal7100304 - 13 Oct 2017

Cited by 70 | Viewed by 9706

Abstract

Advances in the synthesis of pure brookite and brookite-based TiO₂ materials have opened the way to fundamental and applicative studies of the once least known TiO₂ polymorph. Brookite is now recognized as an active phase, in some cases showing enhanced performance [...] Read more.

Advances in the synthesis of pure brookite and brookite-based TiO₂ materials have opened the way to fundamental and applicative studies of the once least known TiO₂ polymorph. Brookite is now recognized as an active phase, in some cases showing enhanced performance with respect to anatase, rutile or their mixture. The peculiar structure of brookite determines its distinct electronic properties, such as band gap, charge–carrier lifetime and mobility, trapping sites, surface energetics, surface atom arrangements and adsorption sites. Understanding the relationship between these properties and the photocatalytic performances of brookite compared to other TiO₂ polymorphs is still a formidable challenge, because of the interplay of many factors contributing to the observed efficiency of a given photocatalyst. Here, the most recent advances in brookite TiO₂ material synthesis and applications are summarized, focusing on structure/activity relation studies of phase and morphology-controlled materials. Many questions remain unanswered regarding brookite, but one answer is clear: Is it still worth studying such a hard-to-synthesize, elusive TiO₂ polymorph? Yes. Full article

(This article belongs to the Special Issue Titanium Dioxide Photocatalysis)

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Open AccessReview

Reactivity of Trapped and Accumulated Electrons in Titanium Dioxide Photocatalysis

by Shigeru Kohtani, Akira Kawashima and Hideto Miyabe

Catalysts 2017, 7(10), 303; https://doi.org/10.3390/catal7100303 - 13 Oct 2017

Cited by 59 | Viewed by 7849

Abstract

Electrons, photogenerated in conduction bands (CB) and trapped in electron trap defects (Ti_ds) in titanium dioxide (TiO₂), play crucial roles in characteristic reductive reactions. This review summarizes the recent progress in the research on electron transfer in photo-excited TiO [...] Read more.

Electrons, photogenerated in conduction bands (CB) and trapped in electron trap defects (Ti_ds) in titanium dioxide (TiO₂), play crucial roles in characteristic reductive reactions. This review summarizes the recent progress in the research on electron transfer in photo-excited TiO₂. Particularly, the reactivity of electrons accumulated in CB and trapped at Ti_ds on TiO₂ is highlighted in the reduction of molecular oxygen and molecular nitrogen, and the hydrogenation and dehalogenation of organic substrates. Finally, the prospects for developing highly active TiO₂ photocatalysts are discussed. Full article

(This article belongs to the Special Issue Titanium Dioxide Photocatalysis)

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Open AccessArticle

Improved Catalytic Performance of Lipase Supported on Clay/Chitosan Composite Beads

by Ni Tu, Jianxin Shou, Huaping Dong, Jin Huang and Yimin Li

Catalysts 2017, 7(10), 302; https://doi.org/10.3390/catal7100302 - 13 Oct 2017

Cited by 13 | Viewed by 4012

Abstract

Clay/chitosan composite beads were prepared and used as the carrier to support lipase by adsorption, to improve the activity and stability of lipase in the hydrolysis of olive oil. Under conditions of pH 6.0, 25 °C and adsorption for 10 h, immobilized lipases [...] Read more.

Clay/chitosan composite beads were prepared and used as the carrier to support lipase by adsorption, to improve the activity and stability of lipase in the hydrolysis of olive oil. Under conditions of pH 6.0, 25 °C and adsorption for 10 h, immobilized lipases on chitosan bead (CB–lipase) and three clay/chitosan composite beads, at different clay to chitosan proportions of 1:8 (CCB-8-lipase), 1:5 (CCB-5-lipase) and 1:3 (CCB-3-lipase), were prepared. By comparing the activity of these immobilized lipases, CCB-5-lipase showed the highest activity, followed by CCB-8-lipase > CCB-3-lipase > CB-lipase; this improvement was attributed to the synergetic effect of enrichment of olive oil by clay at the reaction surface and better biocompatibility of chitosan with lipase molecules. The optimum pH and temperature in the reaction respectively changed from 7.0 and 30 °C for free lipase to 7.5 and 35 °C for immobilized forms. Furthermore, the thermal stability and repeated usability of these immobilized lipases were sequenced as CCB-3-lipase > CCB-5-lipase > CCB-8-lipase > CB–lipase, due to greater rigidity of immobilized lipase with the addition of clay, which was further confirmed by SEM. The study shows that the incorporation of clay with chitosan creates a good synergetic effect to improve the catalytic performance of immobilized lipase on clay/chitosan composite. Full article

(This article belongs to the Special Issue Biocatalysis and Biotransformations)

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555 KiB

Open AccessArticle

PEG₁₀₀₀-Based Dicationic Acidic Ionic Liquid/Solvent-Free Conditions: An Efficient Catalytic System for the Synthesis of Bis(Indolyl)methanes

by Yi-Ming Ren, Mao-Dong Xu and Xiong Wang

Catalysts 2017, 7(10), 300; https://doi.org/10.3390/catal7100300 - 11 Oct 2017

Cited by 14 | Viewed by 3634

Abstract

An efficient procedure has been researched for the solvent-free synthesis of bis(indolyl)methanes via a one-pot reaction of indoles and aldehydes or ketones promoted by PEG₁₀₀₀-based dicationic acidic ionic liquid (PEG₁₀₀₀-DAIL). The catalyst PEG₁₀₀₀-DAIL could be reused seven [...] Read more.

An efficient procedure has been researched for the solvent-free synthesis of bis(indolyl)methanes via a one-pot reaction of indoles and aldehydes or ketones promoted by PEG₁₀₀₀-based dicationic acidic ionic liquid (PEG₁₀₀₀-DAIL). The catalyst PEG₁₀₀₀-DAIL could be reused seven times with excellent results. Furthermore, through this method, a highly chemoselective reaction of benzaldehyde and acetophenone with indole could be achieved. Full article

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

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Open AccessArticle

Biotransformation of Ergostane Triterpenoid Antcin K from Antrodia cinnamomea by Soil-Isolated Psychrobacillus sp. AK 1817

by Chien-Min Chiang, Tzi-Yuan Wang, An-Ni Ke, Te-Sheng Chang and Jiumn-Yih Wu

Catalysts 2017, 7(10), 299; https://doi.org/10.3390/catal7100299 - 11 Oct 2017

Cited by 10 | Viewed by 4913

Abstract

Antcin K is one of the major ergostane triterpenoids from the fruiting bodies of Antrodia cinnamomea, a parasitic fungus that grows only on the inner heartwood wall of the aromatic tree Cinnamomum kanehirai Hay (Lauraceae). To search for strains that have the [...] Read more.

Antcin K is one of the major ergostane triterpenoids from the fruiting bodies of Antrodia cinnamomea, a parasitic fungus that grows only on the inner heartwood wall of the aromatic tree Cinnamomum kanehirai Hay (Lauraceae). To search for strains that have the ability to biotransform antcin K, a total of 4311 strains of soil bacteria were isolated, and their abilities to catalyze antcin K were determined by ultra-performance liquid chromatography analysis. One positive strain, AK 1817, was selected for functional studies. The strain was identified as Psychrobacillus sp., based on the DNA sequences of the 16S rRNA gene. The biotransformation metabolites were purified with the preparative high-performance liquid chromatography method and identified as antcamphin E and antcamphin F, respectively, based on the mass and nuclear magnetic resonance spectral data. The present study is the first to report the biotransformation of triterpenoids from A. cinnamomea (Antrodia cinnamomea). Full article

(This article belongs to the Special Issue Catalyzed Synthesis of Natural Products)

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Open AccessReview

A Review on the Production and Purification of Biomass-Derived Hydrogen Using Emerging Membrane Technologies

by Hang Yin and Alex C.K. Yip

Catalysts 2017, 7(10), 297; https://doi.org/10.3390/catal7100297 - 06 Oct 2017

Cited by 56 | Viewed by 8693

Abstract

Hydrogen energy systems are recognized as a promising solution for the energy shortage and environmental pollution crises. To meet the increasing demand for hydrogen, various possible systems have been investigated for the production of hydrogen by efficient and economical processes. Because of its [...] Read more.

Hydrogen energy systems are recognized as a promising solution for the energy shortage and environmental pollution crises. To meet the increasing demand for hydrogen, various possible systems have been investigated for the production of hydrogen by efficient and economical processes. Because of its advantages of being renewable and environmentally friendly, biomass processing has the potential to become the major hydrogen production route in the future. Membrane technology provides an efficient and cost-effective solution for hydrogen separation and greenhouse gas capture in biomass processing. In this review, the future prospects of using gas separation membranes for hydrogen production in biomass processing are extensively addressed from two perspectives: (1) the current development status of hydrogen separation membranes made of different materials and (2) the feasibility of using these membranes for practical applications in biomass-derived hydrogen production. Different types of hydrogen separation membranes, including polymeric membranes, dense metal membranes, microporous membranes (zeolite, metal-organic frameworks (MOFs), silica, etc.) are systematically discussed in terms of their fabrication methods, gas permeation performance, structure stability properties, etc. In addition, the application feasibility of these membranes in biomass processing is assessed from both practical and economic perspectives. The benefits and possibilities of using membrane reactors for hydrogen production in biomass processing are also discussed. Lastly, we summarize the limitations of the currently available hydrogen membranes as well as the gaps between research achievements and industrial application. We also propose expected research directions for the future development of hydrogen gas membrane technology. Full article

(This article belongs to the Special Issue Catalytic Sustainable Processes in Biorefineries)

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Open AccessArticle

HDO of Methyl Palmitate over Silica-Supported Ni Phosphides: Insight into Ni/P Effect

by Irina V. Deliy, Ivan V. Shamanaev, Evgeny Yu. Gerasimov, Vera P. Pakharukova, Ilya V. Yakovlev, Olga B. Lapina, Pavel V. Aleksandrov and Galina A. Bukhtiyarova

Catalysts 2017, 7(10), 298; https://doi.org/10.3390/catal7100298 - 04 Oct 2017

Cited by 26 | Viewed by 4696

Abstract

Two sets of silica-supported nickel phosphide catalysts with a nickel content of about 2.5 and 10 wt % and Ni/P molar ratio 2/1, 1/1 and 1/2 in each set, were prepared by way of a temperature-programmed reduction method using (Ni(CH₃COO)₂ [...] Read more.

Two sets of silica-supported nickel phosphide catalysts with a nickel content of about 2.5 and 10 wt % and Ni/P molar ratio 2/1, 1/1 and 1/2 in each set, were prepared by way of a temperature-programmed reduction method using (Ni(CH₃COO)₂) and ((NH₄)₂HPO₄) as a precursor. The Ni_xP_y/SiO₂ catalysts were characterized using chemical analysis N₂ physisorption, XRD, TEM, ³¹P MAS NMR. Methyl palmitate hydrodeoxygenation (HDO) was performed in a trickle-bed reactor at 3 MPa and 290 °C with LHSV ranging from 0.3 to 16 h⁻¹. The Ni/P ratio was found to affect the nickel phosphide phase composition, PO_x groups content and catalytic properties in methyl palmitate HDO with the TOF increased along with a decline of Ni/P ratio and a growth of PO_x groups’ content. Taking into account the possible routes of methyl palmitate conversion (metal-catalyzed hydrogenolysis or acid-catalyzed hydrolysis), we proposed that the enhancement of acid PO_x groups’ content with the Ni/P ratio decrease provides an enhancement of the rate of methyl palmitate conversion through the acceleration of acid-catalyzed hydrolysis. Full article

(This article belongs to the Special Issue Recent Progress in Transition Metal Phosphide Catalysts for the Hydroprocessing of Petroleum or Biomass Feedstocks)

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Open AccessArticle

Immobilization of Pyrroloquinoline Quinone-Dependent Alcohol Dehydrogenase with a Polyion Complex and Redox Polymer for a Bioanode

by Yuki Sakurada, Kouta Takeda, Hiroyuki Ohno and Nobuhumi Nakamura

Catalysts 2017, 7(10), 296; https://doi.org/10.3390/catal7100296 - 03 Oct 2017

Cited by 4 | Viewed by 5209

Abstract

A bioanode for ethanol oxidation was prepared by immobilizing the recombinant pyrroloquinoline quinone (PQQ)-dependent alcohol dehydrogenase from Pseudomonas putida KT 2440 (PpADH) with polyion complex (PIC) and redox polymer. The PIC based on poly-l-lysine (PLL) and poly-l-glutamic acid (PGA) was suitable [...] Read more.

A bioanode for ethanol oxidation was prepared by immobilizing the recombinant pyrroloquinoline quinone (PQQ)-dependent alcohol dehydrogenase from Pseudomonas putida KT 2440 (PpADH) with polyion complex (PIC) and redox polymer. The PIC based on poly-l-lysine (PLL) and poly-l-glutamic acid (PGA) was suitable for immobilizing PpADH on the electrode. PpADH was immobilized using only one redox polymer, aminoferrocene, which was attached to the PGA backbone (PGA-AmFc) on the electrode. The anodic current density at 0.6 V (vs. Ag/AgCl) was 22.6 μA·cm⁻². However, when the number of the cycles was increased, the catalytic current drastically decreased. PpADH was immobilized using PGA-AmFc and PIC on the electrode. The anodic current density at 0.5 V (vs. Ag/AgCl) was 47.3 μA·cm⁻², and the performance maintained 74% of the initial value after five cycles. This result indicated that the combination of PIC and PGA-AmFc was suitable for the immobilization of PpADH on the electrode. In addition, the long-term stability and catalytic current density were improved by using the large surface area afforded by the gold nanoparticles. Full article

(This article belongs to the Special Issue Biocatalysis and Biotransformations)

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Open AccessArticle

Promoting the Synthesis of Ethanol and Butanol by Salicylic Acid

by Jinxin Zou, Lei Wang and Peijun Ji

Catalysts 2017, 7(10), 295; https://doi.org/10.3390/catal7100295 - 01 Oct 2017

Cited by 2 | Viewed by 4830

Abstract

Multiwalled carbon nanotubes (MWCNTs) were functionalized with salicylic acid (SA). The copper-cobalt catalyst was impregnated on the SA functionalized MWCNTs (SA-MWCNTs). The catalyst copper-cobalt/SA-MWCNTs was used to catalyze the synthesis of alcohols from synthesis gas. Salicylic acid can promote the synthesis of ethanol [...] Read more.

Multiwalled carbon nanotubes (MWCNTs) were functionalized with salicylic acid (SA). The copper-cobalt catalyst was impregnated on the SA functionalized MWCNTs (SA-MWCNTs). The catalyst copper-cobalt/SA-MWCNTs was used to catalyze the synthesis of alcohols from synthesis gas. Salicylic acid can promote the synthesis of ethanol and butanol from synthesis gas, thus reducing the synthesis of methanol. This work demonstrated that salicylic acid not only can be used to functionalize carbon nanotubes, but also can enhance the production of ethanol and butanol from synthesis gas. On the other hand, the copper-cobalt catalyst supported on MWCNTs of 30 nm in diameter can synthesize more ethanol and butanol than supported on MWCNTs of 15 and 50 nm in diameter, indicating that the diameter of MWCNTs also has an effect on the synthesis of alcohols. Full article

(This article belongs to the Special Issue Nanomaterials for Environmental Purification and Energy Conversion)

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Open AccessArticle

Transformation of Sugar Maple Bark through Catalytic Organosolv Pulping

by Georges Koumba-Yoya and Tatjana Stevanovic

Catalysts 2017, 7(10), 294; https://doi.org/10.3390/catal7100294 - 30 Sep 2017

Cited by 12 | Viewed by 3788

Abstract

The catalytic organosolv pulping of sugar maple bark was performed adopting the concept of forest biorefinery in order to transform bark into several valuable products. Our organosolv process, consisting of pre-extracting the lignocellulosic material followed by pulping with ferric chloride as a catalyst, [...] Read more.

The catalytic organosolv pulping of sugar maple bark was performed adopting the concept of forest biorefinery in order to transform bark into several valuable products. Our organosolv process, consisting of pre-extracting the lignocellulosic material followed by pulping with ferric chloride as a catalyst, was applied to sugar maple bark. The pre-extraction step has yielded a mixture of phenolic extractives, applicable as antioxidants. The organosolv pulping of extractives-free sugar maple bark yielded a solid cellulosic pulp (42.3%) and a black liquor containing solubilized bark lignin (24.1%) and products of sugars transformation (22.9% of hemicelluloses), mainly represented by furfural (0.35%) and 5-hydroxymethyl furfural (HMF, 0.74%). The bark cellulosic pulp was determined to be mainly constituted of glucose, with a high residual lignin content, probably related to the protein content of the original bark (containing cambium tissue). The biorefinery approach to the transformation of a solid bark residue into valuable biopolymers (lignin and cellulose) along with phenolic antioxidants from pre-extraction and the HMF derivatives from black liquor (applicable for 2,5-diformylfuran production) is an example of a catalytic process reposing on sustainable engineering and green chemistry concepts. Full article

(This article belongs to the Special Issue Biocatalysis and Biotransformations)

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Open AccessArticle

Total Oxidation of Naphthalene with Zirconia-Supported Cobalt, Copper and Nickel Catalysts

by María S. Leguizamón Aparicio, Marco A. Ocsachoque, Delia Gazzoli, Irma L. Botto and Ileana D. Lick

Catalysts 2017, 7(10), 293; https://doi.org/10.3390/catal7100293 - 30 Sep 2017

Cited by 10 | Viewed by 4858

Abstract

ZrO₂ nH₂O (hydrogel) impregnated with transition metals (Cu, Co, and Ni) was studied in this work as a precursor for the synthesis of CuO/ZrO₂ (CuZ), CoO_x/ZrO₂ (CoZ), and NiO/ZrO₂ (NiZ) catalysts, employed in the naphthalene [...] Read more.

ZrO₂ nH₂O (hydrogel) impregnated with transition metals (Cu, Co, and Ni) was studied in this work as a precursor for the synthesis of CuO/ZrO₂ (CuZ), CoO_x/ZrO₂ (CoZ), and NiO/ZrO₂ (NiZ) catalysts, employed in the naphthalene oxidation reaction. Fresh and catalytically used materials were characterized by different physicochemical techniques, to compare the bulk and surface behavior, with particular attention to the effect of the supported metal species’ properties on the catalytic activity. Techniques such as X-ray diffraction (XRD), temperature programmed reduction (TPR), differential scanning calorimetry (DSC), Brunauer–Emmett–Teller (BET) surface area analyzer, diffuse reflectance spectroscopy (DRS UV–vis), and Raman spectroscopy, allow for establishing structural and textural aspects of the support, as well as the surface coordination and the accessibility of supported species. Results were in agreement with the CuZ > CoZ > NiZ sequence for the activity in naphthalene oxidation reaction. Electronic properties, ionic sizes, oxide phase deposition on the support surface, reducibility, metal–support interaction, and local site symmetry of metals seem to be decisive factors for the catalytic interaction with the gaseous phase. Full article

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3931 KiB

Open AccessArticle

Morpholine-Modified Pd/γ-Al₂O₃@ASMA Pellet Catalyst with Excellent Catalytic Selectivity in the Hydrogenation of p-Chloronitrobenzene to p-Chloroaniline

by Wei Wang, Wenlong Xu, Kedar Bahadur Thapa, Xiaorui Yang, Jinhua Liang, Liyan Zhu and Jianliang Zhu

Catalysts 2017, 7(10), 292; https://doi.org/10.3390/catal7100292 - 30 Sep 2017

Cited by 15 | Viewed by 5704

Abstract

An amino poly (styrene-co-maleic anhydride) polymer (ASMA) encapsulated γ-Al₂O₃ pellet material has been synthesized successfully. After loading with Pd species and modified with morpholine, the inorganic-organic hybrid material shows an excellent catalytic property in the selective hydrogenation [...] Read more.

An amino poly (styrene-co-maleic anhydride) polymer (ASMA) encapsulated γ-Al₂O₃ pellet material has been synthesized successfully. After loading with Pd species and modified with morpholine, the inorganic-organic hybrid material shows an excellent catalytic property in the selective hydrogenation of p-chloronitrobenzene (p-CNB) to p-chloroaniline (p-CAN). In this procedure, morpholine can connect with the polymer layer in a form of amide bond and acts as an unparalleled immobilized dechlorination inhibitor, which can avoid further dechlorination efficiently and keeps stability due to the repulsive effect from the surviving C-O-C bond. The catalyst as prepared was characterized by using XRD, TGA, SEM, TEM, FT-IR, and ICP-OES, and it was further tested in the selective hydrogenation of p-CNB. It shows a supreme catalytic activity (almost 100%) and selectivity (up to 99.51%) after recycling for even 10 times, much superior to the blank alumina supported palladium (47.09%). Full article

(This article belongs to the Special Issue Heterogeneous Catalysis & Hydrogen Storage)

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3211 KiB

Open AccessArticle

Conductive Cotton Filters for Affordable and Efficient Water Purification

by Fang Li, Qin Xia, Qianxun Cheng, Mingzhi Huang and Yanbiao Liu

Catalysts 2017, 7(10), 291; https://doi.org/10.3390/catal7100291 - 29 Sep 2017

Cited by 9 | Viewed by 7118

Abstract

It is highly desirable to develop affordable, energy-saving, and highly-effective technologies to alleviate the current water crisis. In this work, we reported a low-cost electrochemical filtration device composing of a conductive cotton filter anode and a Ti foil cathode. The device was operated [...] Read more.

It is highly desirable to develop affordable, energy-saving, and highly-effective technologies to alleviate the current water crisis. In this work, we reported a low-cost electrochemical filtration device composing of a conductive cotton filter anode and a Ti foil cathode. The device was operated by gravity feed. The conductive cotton filter anodes were fabricated by a facile dying method to incorporate carbon nanotubes (CNTs) as fillers. The CNTs could serve as adsorbents for pollutants adsorption, as electrocatalysts for pollutants electrooxidation, and as conductive additives to render the cotton filters highly conductive. Cellulose-based cotton could serve as low-cost support to ‘host’ these CNTs. Upon application of external potential, the developed filtration device could not only achieve physically adsorption of organic compounds, but also chemically oxide these compounds on site. Three model organic compounds were employed to evaluate the oxidative capability of the device, i.e., ferrocyanide (a model single-electron-transfer electron donor), methyl orange (MO, a common recalcitrant azo-dye found in aqueous environments), and antibiotic tetracycline (TC, a common antibiotic released from the wastewater treatment plants). The devices exhibited a maximum electrooxidation flux of 0.37 mol/h/m² for 5.0 mmol/L ferrocyanide, of 0.26 mol/h/m² for 0.06 mmol/L MO, and of 0.9 mol/h/m² for 0.2 mmol/L TC under given experimental conditions. The effects of several key operational parameters (e.g., total cell potential, CNT amount, and compound concentration) on the device performance were also studied. This study could shed some light on the good design of effective and affordable water purification devices for point-of-use applications. Full article

(This article belongs to the Special Issue Nanomaterials for Environmental Purification and Energy Conversion)

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1259 KiB

Open AccessArticle

Co-Production of Ethanol and 1,2-Propanediol via Glycerol Hydrogenolysis Using Ni/Ce–Mg Catalysts: Effects of Catalyst Preparation and Reaction Conditions

by Russel N. Menchavez, Matthew J. Morra and B. Brian He

Catalysts 2017, 7(10), 290; https://doi.org/10.3390/catal7100290 - 29 Sep 2017

Cited by 10 | Viewed by 8268

Abstract

Crude glycerol from biodiesel production is a biobased material capable of co-producing biofuels and chemicals. This study aimed to develop a line of Ni catalysts supported on cerium–magnesium (Ce–Mg) to improve the process efficiency of glycerol hydrogenolysis for ethanol and 1,2-propanediol (1,2-PDO). Results [...] Read more.

Crude glycerol from biodiesel production is a biobased material capable of co-producing biofuels and chemicals. This study aimed to develop a line of Ni catalysts supported on cerium–magnesium (Ce–Mg) to improve the process efficiency of glycerol hydrogenolysis for ethanol and 1,2-propanediol (1,2-PDO). Results showed that catalytic activity was greatly improved by changing the preparation method from impregnation to deposition precipitation (DP), and by adjusting calcination temperatures. Prepared via DP, the catalysts of 25 wt % Ni supported on Ce–Mg (9:1 mol/mol) greatly improved the effectiveness in glycerol conversion while maintaining the selectivities to ethanol and 1,2-PDO. Calcination at 350 °C provided the catalysts better selectivities of 15.61% to ethanol and 67.93% to 1,2-PDO. Increases in reaction temperature and time improved the conversion of glycerol and the selectivity to ethanol, but reduced the selectivity to 1,2-PDO. A lower initial water content led to a higher conversion of glycerol, but lower selectivities to ethanol and 1,2-PDO. Higher hydrogen application affected the glycerol conversion rate positively, but the selectivities to ethanol and 1,2-PDO negatively. A comparison to the commercial Raney^® Ni catalyst showed that the Ni/Ce–Mg catalyst developed in this study showed a better potential for the selective co-production of ethanol and 1,2-PDO from glycerol hydrogenolysis. Full article

(This article belongs to the Special Issue Enabling Technologies toward Green Catalysis)

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1180 KiB

Open AccessArticle

Study of 8 Types of Glutathione Peroxidase Mimics Based on β-Cyclodextrin

by Liwu Wang, Xiaonan Qu, Ying Xie and Shaowu Lv

Catalysts 2017, 7(10), 289; https://doi.org/10.3390/catal7100289 - 28 Sep 2017

Cited by 12 | Viewed by 4164

Abstract

Glutathione peroxidase is key for the removal of H₂O₂ and other hydroperoxides and therefore, it has an important role in the maintenance of the reactive oxygen species (ROS) metabolic balance in vivo. The native enzymes of the glutathione peroxidase family [...] Read more.

Glutathione peroxidase is key for the removal of H₂O₂ and other hydroperoxides and therefore, it has an important role in the maintenance of the reactive oxygen species (ROS) metabolic balance in vivo. The native enzymes of the glutathione peroxidase family (GPx) have many defects, such as instability in vitro and poor availability. GPx mimetics has become a topic of considerable interest in artificial enzyme research. Many forms of GPx mimics have been synthesized, by including selenium and tellurium (double-bridged and single-bridged, 2-substituted and 6-substituted) in a mother molecule but differences the GPx mimics enzymatic activity have rarely been compared. We designed and synthesized eight cyclodextrin derivatives and used two types of enzyme assays to determine their activities. The results show that: (a) tellurium-containing GPx mimics have higher activity than that of selenium-containing GPx mimics; (b) dual-bridged mimics have higher activity than bis-bridged mimics; and (c) 2-position modified cyclodextrin has higher activity than 6-position modified cyclodextrin. Full article

(This article belongs to the Special Issue Biocatalysis and Biotransformations)

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1203 KiB

Open AccessArticle

Polycyclic Ketone Monooxygenase (PockeMO): A Robust Biocatalyst for the Synthesis of Optically Active Sulfoxides

by Gonzalo De Gonzalo, Maximilian J. L. J. Fürst and Marco W. Fraaije

Catalysts 2017, 7(10), 288; https://doi.org/10.3390/catal7100288 - 27 Sep 2017

Cited by 21 | Viewed by 4750

Abstract

A recently discovered, moderately thermostable Baeyer-Villiger monooxygenase, polycyclic ketone monooxygenase (PockeMO), from Thermothelomyces thermophila has been employed as a biocatalyst in a set of asymmetric sulfoxidations. The enzyme was able to catalyze the oxidation of various alkyl aryl sulfides with good selectivities and [...] Read more.

A recently discovered, moderately thermostable Baeyer-Villiger monooxygenase, polycyclic ketone monooxygenase (PockeMO), from Thermothelomyces thermophila has been employed as a biocatalyst in a set of asymmetric sulfoxidations. The enzyme was able to catalyze the oxidation of various alkyl aryl sulfides with good selectivities and moderate to high activities. The biocatalytic performance was able to be further increased by optimizing some reaction parameters, such as the addition of 10% v v⁻¹ of water miscible solvents or toluene, or by performing the conversion at a relatively high temperature (45 °C). PockeMO was found to display an optimum activity at sulfide concentrations of 50 mM, while it can also function at 200 mM. Taken together, the data show that PockeMO can be used as robust biocatalyst for the synthesis of optically active sulfoxides. Full article

(This article belongs to the Special Issue Biocatalysis and Biotransformations)

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2411 KiB

Open AccessArticle

Enzymatic Systems for Cellulose Acetate Degradation

by Oskar Haske-Cornelius, Alessandro Pellis, Gregor Tegl, Stefan Wurz, Bodo Saake, Roland Ludwig, Andries Sebastian, Gibson S. Nyanhongo and Georg M. Guebitz

Catalysts 2017, 7(10), 287; https://doi.org/10.3390/catal7100287 - 27 Sep 2017

Cited by 40 | Viewed by 10273

Abstract

Cellulose acetate (CA)-based materials, like cigarette filters, contribute to landscape pollution challenging municipal authorities and manufacturers. This study investigates the potential of enzymes to degrade CA and to be potentially incorporated into the respective materials, enhancing biodegradation. Deacetylation studies based on Liquid Chromatography-Mass [...] Read more.

Cellulose acetate (CA)-based materials, like cigarette filters, contribute to landscape pollution challenging municipal authorities and manufacturers. This study investigates the potential of enzymes to degrade CA and to be potentially incorporated into the respective materials, enhancing biodegradation. Deacetylation studies based on Liquid Chromatography-Mass Spectrometry-Time of Flight (LC-MS-TOF), High Performance Liquid Chromatography (HPLC), and spectrophotometric analysis showed that the tested esterases were able to deacetylate the plasticizer triacetin (glycerol triacetate) and glucose pentaacetate (cellulose acetate model compound). The most effective esterases for deacetylation belong to the enzyme family 2 (AXE55, AXE 53, GAE), they deacetylated CA with a degree of acetylation of up to 1.8. A combination of esterases and cellulases showed synergistic effects, the absolute glucose recovery for CA 1.8 was increased from 15% to 28% when an enzymatic deacetylation was performed. Lytic polysaccharide monooxygenase (LPMO), and cellobiohydrolase were able to cleave cellulose acetates with a degree of acetylation of up to 1.4, whereas chitinase showed no activity. In general, the degree of substitution, chain length, and acetyl group distribution were found to affect CA degradation. This study shows that, for a successful enzyme-based deacetylation system, a cocktail of enzymes, which will randomly cleave and generate shorter CA fragments, is the most suitable. Full article

(This article belongs to the Special Issue Biocatalysis and Biotransformations)

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4067 KiB

Open AccessArticle

Hydrogen Production from Cyclic Chemical Looping Steam Methane Reforming over Yttrium Promoted Ni/SBA-16 Oxygen Carrier

by Sanaz Daneshmand-Jahromi, Mohammad Reza Rahimpour, Maryam Meshksar and Ali Hafizi

Catalysts 2017, 7(10), 286; https://doi.org/10.3390/catal7100286 - 25 Sep 2017

Cited by 45 | Viewed by 7044

Abstract

In this work, the modification of Ni/SBA-16 oxygen carrier (OC) with yttrium promoter is investigated. The yttrium promoted Ni-based oxygen carrier was synthesized via co-impregnation method and applied in chemical looping steam methane reforming (CL-SMR) process, which is used for the production of [...] Read more.

In this work, the modification of Ni/SBA-16 oxygen carrier (OC) with yttrium promoter is investigated. The yttrium promoted Ni-based oxygen carrier was synthesized via co-impregnation method and applied in chemical looping steam methane reforming (CL-SMR) process, which is used for the production of clean energy carrier. The reaction temperature (500–750 °C), Y loading (2.5–7.4 wt. %), steam/carbon molar ratio (1–5), Ni loading (10–30 wt. %) and life time of OCs over 16 cycles at 650 °C were studied to investigate and optimize the structure of OC and process temperature with maximizing average methane conversion and hydrogen production yield. The synthesized OCs were characterized by multiples techniques. The results of X-ray powder diffraction (XRD) and energy dispersive X-ray spectroscopy (EDX) of reacted OCs showed that the presence of Y particles on the surface of OCs reduces the coke formation. The smaller NiO species were found for the yttrium promoted OC and therefore the distribution of Ni particles was improved. The reduction-oxidation (redox) results revealed that 25Ni-2.5Y/SBA-16 OC has the highest catalytic activity of about 99.83% average CH₄ conversion and 85.34% H₂ production yield at reduction temperature of 650 °C with the steam to carbon molar ratio of 2. Full article

(This article belongs to the Special Issue Nanomaterials for Environmental Purification and Energy Conversion)

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4804 KiB

Open AccessReview

Two-Dimensional Material Molybdenum Disulfides as Electrocatalysts for Hydrogen Evolution

by Lei Yang, Ping Liu, Jing Li and Bin Xiang

Catalysts 2017, 7(10), 285; https://doi.org/10.3390/catal7100285 - 25 Sep 2017

Cited by 74 | Viewed by 10365

Abstract

Recently, transition metal dichalcogenides (TMDs), represented by MoS₂, have been proven to be a fascinating new class of electrocatalysts in hydrogen evolution reaction (HER). The rich chemical activities, combined with several strategies to regulate its morphologies and electronic properties, make MoS [...] Read more.

Recently, transition metal dichalcogenides (TMDs), represented by MoS₂, have been proven to be a fascinating new class of electrocatalysts in hydrogen evolution reaction (HER). The rich chemical activities, combined with several strategies to regulate its morphologies and electronic properties, make MoS₂ very attractive for understanding the fundamentals of electrocatalysis. In this review, recent developments in using MoS₂ as electrocatalysts for the HER with high activity are presented. The effects of edges on HER activities of MoS₂ are briefly discussed. Then we demonstrate strategies to further enhance the catalytic performance of MoS₂ by improving its conductivity or engineering its structure. Finally, the key challenges to the industrial application of MoS₂ in electrocatalytic hydrogen evolution are also pointed out. Full article

(This article belongs to the Special Issue Nanostructured Materials for Applications in Heterogeneous Catalysis)

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2347 KiB

Open AccessFeature PaperArticle

Synthesis of Stereodiblock Polybutadiene Using Cp*Nd(BH₄)₂(thf)₂ as a Catalyst

by Ryo Tanaka, Yuto Shinto, Yuushou Nakayama and Takeshi Shiono

Catalysts 2017, 7(10), 284; https://doi.org/10.3390/catal7100284 - 25 Sep 2017

Cited by 11 | Viewed by 5257

Abstract

Butadiene polymerization, in both a highly cis- and trans-specific manner, was achieved by using a Cp*Nd(BH₄)₂(thf)₂–Bu₂Mg system as an initiator. The cis-/trans- ratio can be tuned by the amount of [...] Read more.

Butadiene polymerization, in both a highly cis- and trans-specific manner, was achieved by using a Cp*Nd(BH₄)₂(thf)₂–Bu₂Mg system as an initiator. The cis-/trans- ratio can be tuned by the amount of trialkylaluminum-depleted modified methylaluminoxane (dMMAO). The cis-regularity of the polymer was much higher than those obtained by Nd(BH₄)₃(thf)₃. The molecular weight of cis-regular polymer was increased according to polymer yield, showing that there was no termination or chain transfer reaction during the polymerization. Synthesis of stereodiblock polybutadiene, which showed a high melting temperature (T_m) compared with stereodiblock polyisoprene, was also performed by the addition dMMAO during the polymerization. Full article

(This article belongs to the Special Issue Catalysts for the Controlled Polymerization of Conjugated Dienes)

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11428 KiB

Open AccessArticle

Reactive Magnetron Sputter Deposition of Bismuth Tungstate Coatings for Water Treatment Applications under Natural Sunlight

by Marina Ratova, Rafaela B. P. Marcelino, Patterson P. De Souza, Camila C. Amorim and Peter J. Kelly

Catalysts 2017, 7(10), 283; https://doi.org/10.3390/catal7100283 - 23 Sep 2017

Cited by 21 | Viewed by 5398

Abstract

Bismuth complex oxides, in particular, bismuth tungstate, have recently attracted attention as promising photocatalytic materials for water treatment processes. In the present work, photocatalytic bismuth tungstate films were prepared by pulsed direct current (DC) reactive magnetron sputtering of Bi and W targets in [...] Read more.

Bismuth complex oxides, in particular, bismuth tungstate, have recently attracted attention as promising photocatalytic materials for water treatment processes. In the present work, photocatalytic bismuth tungstate films were prepared by pulsed direct current (DC) reactive magnetron sputtering of Bi and W targets in an Ar/O₂ atmosphere onto spherically-shaped glass beads. The uniform coverage of the substrate was enabled by the use of oscillating bowl placed underneath the magnetrons. The atomic ratio of Bi/W was varied through the variation of the power applied to the magnetrons. The deposited coatings were analyzed by the scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), X-ray photoelectron spectroscopy and atomic force microscopy. The photocatalytic properties of the films were studied via the methylene blue (MB) degradation process under artificial (fluorescent light) and natural (sunlight) irradiation, and compared to the photocatalytic performance of titanium dioxide coatings deposited onto identical substrates. The results showed that the photocatalytic performance of bismuth tungstate and bismuth oxide-coated beads was superior to that exhibited by TiO₂-coated beads. Overall, reactive magnetron co-sputtering has been shown to be a promising technique for deposition of narrow band gap bismuth-based semiconducting oxides onto irregularly-shaped substrates for potential use in water treatment applications. Full article

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3953 KiB

Open AccessArticle

Active Site Mimicry of Glutathione Peroxidase by Glutathione Imprinted Selenium-Containing Trypsin

by Yi Huang, Dan-Yang Ge, Hui Zong, Ju-Xin Yin, Xiao-Nan Qu and Shao-Wu Lv

Catalysts 2017, 7(10), 282; https://doi.org/10.3390/catal7100282 - 22 Sep 2017

Cited by 6 | Viewed by 4526

Abstract

In order to overcome the instability of natural glutathione peroxidase (GPx), scientists endeavor to produce GPx mimics. The popular method first uses biological imprinting (BI) to produce the substrate binding sites and then employs chemical mutation (CM) to obtain the catalytic site. However, [...] Read more.

In order to overcome the instability of natural glutathione peroxidase (GPx), scientists endeavor to produce GPx mimics. The popular method first uses biological imprinting (BI) to produce the substrate binding sites and then employs chemical mutation (CM) to obtain the catalytic site. However, BICM has a drawback in that the catalytic site is not clear. Some researchers therefore tried to change the order of the method. These new GPx mimics were prepared by first producing the catalytic site through chemical mutation, and then employing biological imprinting to produce the substrate binding sites (CMBI). It has a clear catalytic site, but its determination of enzyme activity and kinetic analysis are still not elucidated. In this study, we used CMBI to synthesize a GPx mimic using trypsin as the imprinted molecule and GSSG as the template molecule and compared the enzyme activity of the four intermediates (Trypsin-SeO₂H (TSeO₂H), Trypsin-Se-SG (TSeSG), Imprinted Trypsin-Se-SG (ITSeSG), Cross-linked Imprinted Trypsin-Se-SG (CITSeSG), we analyzed the properties of intermediate products. All values are the means of at least four determinations, ITSeSG was produced from TSeSG through bio-imprinting, the activity of GPx mimics synthesized by CMBI was 5.7 times greater than native GPx, because of bio-imprinting make K_mGSH value of the mimics decreased from 4.82 ± 0.27 mM (TSeSG) to 0.52 ± 0.05 mM (ITSeSG). This proves that bio-imprinting is the reason for increased substrate binding capability. Full article

(This article belongs to the Special Issue Biocatalysis and Biotransformations)

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