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Catalysts, Volume 7, Issue 7 (July 2017)

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Cover Story Conversion of carbohydrates to furanic derivatives is of prime interest for many applications. In [...] Read more.
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Open AccessArticle Activated Carbon Supported Mo-Ti-N Binary Transition Metal Nitride as Catalyst for Acetylene Hydrochlorination
Catalysts 2017, 7(7), 200; doi:10.3390/catal7070200
Received: 5 May 2017 / Revised: 17 June 2017 / Accepted: 27 June 2017 / Published: 30 June 2017
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Abstract
Recently, many scientists have focused on the development of green industrial technology. However, the process of synthesizing vinyl chloride faces the problem of Hg pollution. Via a novel approach, we used two elements Mo and Ti to prepare an inexpensive and green binary
[...] Read more.
Recently, many scientists have focused on the development of green industrial technology. However, the process of synthesizing vinyl chloride faces the problem of Hg pollution. Via a novel approach, we used two elements Mo and Ti to prepare an inexpensive and green binary transition metal nitride (BTMN) as the active ingredient in a catalyst with nano-sized particles and an excellent degree of activation, which was supported on activated carbon. When the Mo/Ti mole ratio was 3:1, the conversion of acetylene reached 89% and the selectivity exceeded 98.5%. The doping of Ti in Mo-based catalysts reduced the capacity of adsorption for acetylene and also increased the adsorption of hydrogen chloride. Most importantly, the performance of the BTMN excelled those of the individual transition metal nitrides, due to the synergistic activity between Mo and Ti. This will expand the new epoch of the employment of transition metal nitrides as catalysts in the hydrochlorination of acetylene reaction. Full article
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Open AccessArticle Highly Effective Dual Transition Metal Macrocycle Based Electrocatalyst with Macro-/Mesoporous Structures for Oxygen Reduction Reaction
Catalysts 2017, 7(7), 201; doi:10.3390/catal7070201
Received: 30 April 2017 / Revised: 16 June 2017 / Accepted: 19 June 2017 / Published: 30 June 2017
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Abstract
Metal macrocycle based non-noble metal electrocatalysts (NNMEs) with highly efficient oxygen reduction reaction (ORR) activity, good stability, and excellent resistance to the methanol cross-over effect have been regarded as one of the most important alternatives for Pt or Pt based alloys, which are
[...] Read more.
Metal macrocycle based non-noble metal electrocatalysts (NNMEs) with highly efficient oxygen reduction reaction (ORR) activity, good stability, and excellent resistance to the methanol cross-over effect have been regarded as one of the most important alternatives for Pt or Pt based alloys, which are widely used in fuel cells. However, the expensive price of most metal macrocycles hinder further investigation of such a family of NNMEs in large production for practical applications. Here, we introduce a simple strategy to synthesize metal macrocycle based porous carbon (MMPC) material with low cost and easy production of metal macrocycles (hemin (Hm) and vitamin B12 (VB12)) as raw materials by using a hard template of MgO. The pyrolysis of MMPC under the optimal temperature at 900 °C shows comparative ORR performance relative to commercial Pt/C, which could be attributed to the large surface area, macro-/mesoporous structure, the carbon layer encapsulating transition metal based oxides, as well as N-doped carbon species. In addition, MMPC (900) displays a better electrochemical property than 20 wt % Pt/C in terms of durability and tolerance to methanol in O2-saturated 0.1 M KOH media. Full article
(This article belongs to the Special Issue Mesostructured Materials and Their Catalytic Applications)
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Open AccessArticle High Active Zn/Mg-Modified Ni–P/Al2O3 Catalysts Derived from ZnMgNiAl Layered Double Hydroxides for Hydrodesulfurization of Dibenzothiophene
Catalysts 2017, 7(7), 202; doi:10.3390/catal7070202
Received: 14 June 2017 / Revised: 29 June 2017 / Accepted: 29 June 2017 / Published: 4 July 2017
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Abstract
A series of ZnMgNiAl layered double hydroxides (LDHs) containing 20 wt.% Ni and different Zn/Mg molar ratios were prepared by a coprecipitation method, and then were introduced with H2PO4 via a microwave-hydrothermal method. With the resulting mixtures as the
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A series of ZnMgNiAl layered double hydroxides (LDHs) containing 20 wt.% Ni and different Zn/Mg molar ratios were prepared by a coprecipitation method, and then were introduced with H2PO4 via a microwave-hydrothermal method. With the resulting mixtures as the precursors, Zn/Mg-modified ZnMgNi–P/Al2O3 catalysts were prepared. The Zn/Mg molar ratio affected the formation of Ni2P and Ni12P5 in nickel phosphides. The ZnMgNi–P/Al2O3 catalyst with a Zn/Mg molar ratio of 3:1 exhibits the best dibenzothiophene hydrodesulfurization (HDS) activity. Compared with the Ni–P/Al2O3 catalyst prepared from the impregnation method, the ZnMgNi–P/Al2O3 catalyst shows a higher HDS activity (81.6% vs. 54.3%) and promotes the direct desulfurization of dibenzothiophene. Full article
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Open AccessArticle Rapid Jatropha-Castor Biodiesel Production with Microwave Heating and a Heterogeneous Base Catalyst Nano-Ca(OH)2/Fe3O4
Catalysts 2017, 7(7), 203; doi:10.3390/catal7070203
Received: 31 March 2017 / Revised: 14 June 2017 / Accepted: 19 June 2017 / Published: 4 July 2017
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Abstract
In this study, a nano-Ca(OH)2/Fe3O4 catalyst was used to produce biodiesel from a 1:1 mixed jatropha-castor oil. By loading Ca(OH)2 onto Fe3O4 nanoparticles, it increased the specific surface area by almost 40%, which improved
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In this study, a nano-Ca(OH)2/Fe3O4 catalyst was used to produce biodiesel from a 1:1 mixed jatropha-castor oil. By loading Ca(OH)2 onto Fe3O4 nanoparticles, it increased the specific surface area by almost 40%, which improved the catalytic activity as it provided a larger area for the reactants to interact. The main purpose of mixing jatropha oil with castor oil was to lower the viscosity of the castor oil. The transesterification reaction was carried out at elevated temperature, using a microwave heating system. Moreover, it was shown that the preferred reaction conditions are using high temperature and short reaction duration. The optimized yield of methyl ester was 95%, achieved by using a catalyst with a Ca:Fe ratio of 7:1, temperature of 65 °C, methanol/oil ratio of 12:1, and reaction time of 35 min. The catalyst was shown to be reusable, easily recyclable, and its activity was very stable. Only 2% of the catalyst was lost, and the yield was 3% lower after ten successive applications. The solid, magnetic base catalyst could be easily separated from the reaction products, unlike homogeneous catalysts. Full article
(This article belongs to the Special Issue Nanostructured Materials for Applications in Heterogeneous Catalysis)
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Open AccessFeature PaperArticle Acidity-Reactivity Relationships in Catalytic Esterification over Ammonium Sulfate-Derived Sulfated Zirconia
Catalysts 2017, 7(7), 204; doi:10.3390/catal7070204
Received: 31 May 2017 / Revised: 29 June 2017 / Accepted: 29 June 2017 / Published: 5 July 2017
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Abstract
New insight was gained into the acidity-reactivity relationships of sulfated zirconia (SZ) catalysts prepared via (NH4)2SO4 impregnation of Zr(OH)4 for propanoic acid esterification with methanol. A family of systematically related SZs was characterized by bulk and surface
[...] Read more.
New insight was gained into the acidity-reactivity relationships of sulfated zirconia (SZ) catalysts prepared via (NH4)2SO4 impregnation of Zr(OH)4 for propanoic acid esterification with methanol. A family of systematically related SZs was characterized by bulk and surface analyses including XRD, XPS, TGA-MS, N2 porosimetry, temperature-programmed propylamine decomposition, and FTIR of adsorbed pyridine, as well as methylbutynol (MBOH) as a reactive probe molecule. Increasing surface sulfation induces a transition from amphoteric character for the parent zirconia and low S loadings <1.7 wt %, evidenced by MBOH conversion to 3-hydroxy-3-methyl-2-butanone, methylbutyne and acetone, with higher S loadings resulting in strong Brønsted-Lewis acid pairs upon completion of the sulfate monolayer, which favored MBOH conversion to prenal. Catalytic activity for propanoic acid esterification directly correlated with acid strength determined from propylamine decomposition, coincident with the formation of Brønsted-Lewis acid pairs identified by MBOH reactive titration. Monodispersed bisulfate species are likely responsible for superacidity at intermediate sulfur loadings. Full article
(This article belongs to the Special Issue Mesostructured Materials and Their Catalytic Applications)
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Open AccessArticle DeNOx Abatement Modelling over Sonically Prepared Copper USY and ZSM5 Structured Catalysts
Catalysts 2017, 7(7), 205; doi:10.3390/catal7070205
Received: 24 May 2017 / Revised: 29 June 2017 / Accepted: 30 June 2017 / Published: 6 July 2017
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Abstract
Metallic supports play an important role as structured reactor internals. Due to their specific properties including enhanced heat and mass transport, high mechanical resistivity and elimination of local hot-spots, they are commonly used in gas exhaust abatement from stationary and automotive industries. In
[...] Read more.
Metallic supports play an important role as structured reactor internals. Due to their specific properties including enhanced heat and mass transport, high mechanical resistivity and elimination of local hot-spots, they are commonly used in gas exhaust abatement from stationary and automotive industries. In this study, the performance of three structured supports with deposited Cu/USY (Ultrastabilised Y—zeolite) for deNOx abatement were modelled. Based on kinetic and flow resistance experimental results, the one-dimensional (1D) model of structured reactor was developed. The performance of the structured reactors was compared by the length of the reactor necessary to achieve an arbitrary 90% NOx conversion. The performed simulations showed that the sonochemically prepared copper USY and ZSM-5 zeolites deposited on metallic supports may be successfully used as catalysts for deNOx process. Full article
(This article belongs to the Special Issue Structured and Micro-Structured Catalysts and Reactors)
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Open AccessArticle Cerium Coordination Polymer Based Composite Mimicking Peroxidase for Detection of Nitroaniline
Catalysts 2017, 7(7), 206; doi:10.3390/catal7070206
Received: 7 May 2017 / Revised: 21 June 2017 / Accepted: 23 June 2017 / Published: 7 July 2017
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Abstract
Cerium coordination polymer (CeCP) was synthesized with 1,3,5-benzenetricarboxylic acid as the ligand. By using the carboxyl groups on the surface of CeCP as the anchors, platinum nanoparticles were formed on CeCP forming the composite CeCP@Pt. The composite was characterized by measuring TEM images,
[...] Read more.
Cerium coordination polymer (CeCP) was synthesized with 1,3,5-benzenetricarboxylic acid as the ligand. By using the carboxyl groups on the surface of CeCP as the anchors, platinum nanoparticles were formed on CeCP forming the composite CeCP@Pt. The composite was characterized by measuring TEM images, and EDS and XPS spectra. CeCP@Pt was used to catalyze the oxidation of 3,3,5,5-tetramethylbenzidine in the presence of H2O2. The activity assay demonstrated that CeCP@Pt exhibited an activity similar to that of horseradish peroxidase, but with a much higher activity. CeCP@Pt was utilized to detect nitroaniline, being able to detect trace amount of nitroaniline (>3.125 × 10−4 mg/mL). Full article
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Open AccessArticle Newly Designed Ternary Metallic PtPdBi Hollow Catalyst with High Performance for Methanol and Ethanol Oxidation
Catalysts 2017, 7(7), 208; doi:10.3390/catal7070208
Received: 13 June 2017 / Revised: 2 July 2017 / Accepted: 6 July 2017 / Published: 10 July 2017
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Abstract
This paper reported the fabrication of ternary metallic PtPdBi hollow nanocatalyst through a facile, one-pot, wet-chemical method by adopting sodium borohydride and polyvinylpyrrolidone as reducing agent and surfactant directing agent, respectively. The hollow structure offers novel morphology and large surface areas, which are
[...] Read more.
This paper reported the fabrication of ternary metallic PtPdBi hollow nanocatalyst through a facile, one-pot, wet-chemical method by adopting sodium borohydride and polyvinylpyrrolidone as reducing agent and surfactant directing agent, respectively. The hollow structure offers novel morphology and large surface areas, which are conducive to enhancing the electrocatalytic activity. The electrocatalytic properties of hollow PtPdBi nanocatalyst were investigated systematically in alkaline media through cyclic voltammetry and the as-prepared PtPdBi nanocatalyst displays greatly enhanced electrocatalytic activities towards methanol and ethanol oxidation. The calculated mass activities of PtPdBi electrocatalyst are 2.133 A mgPtPd−1 for methanol oxidation reaction and 5.256 A mgPtPd−1 for ethanol oxidation reaction, which are much better than that of commercial Pt/C and commercial Pd/C. The as-prepared hollow nanocatalyst may be a potential promising electrocatalyst in fuel cells and also may be extended to the applications of other desirable functions. Full article
(This article belongs to the Special Issue Advances in Electrocatalysis)
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Open AccessArticle Low-Temperature Synthesis of Anatase/Rutile/Brookite TiO2 Nanoparticles on a Polymer Membrane for Photocatalysis
Catalysts 2017, 7(7), 209; doi:10.3390/catal7070209
Received: 31 May 2017 / Revised: 28 June 2017 / Accepted: 4 July 2017 / Published: 10 July 2017
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Abstract
Removing pollutants from water by using the photocatalyst TiO2 is a highly-promising method. A large amount of work has been done to increase the activity of TiO2, whereas the main two findings are increasing the surface area and applying mixed
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Removing pollutants from water by using the photocatalyst TiO2 is a highly-promising method. A large amount of work has been done to increase the activity of TiO2, whereas the main two findings are increasing the surface area and applying mixed phase modifications (anatase, brookite, and rutile). Here, we present a method to directly synthesize non-agglomerated TiO2 nanoparticles with different crystal phase ratios via low temperature dissolution-precipitation (LTDRP) on a porous microfiltration membrane (polyethersulfone). The amount of hydrochloric acid and the temperature was varied between 0.1–1 M and 25–130 °C, respectively, while the concentration of titanium precursor (titanium(IV) isopropoxide) was kept unchanged. The TiO2 nanoparticles and the membrane were thoroughly characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), measuring the water contact angle and permeation flux, and examining the degradation of methylene blue. The mixed phase anatase/brookite with a main component being anatase exhibited the highest photocatalytic activity in removing methylene blue. Higher synthesis temperature induces enhanced crystallinity and, subsequently, the degradation rate of methylene blue was improved. Additionally, the photocatalytic activity remains high and unchanged for up to nine repeated cycles, i.e., full recovery of the photocatalytic properties is sustained. Full article
(This article belongs to the Special Issue Catalysis in Membrane Reactors)
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Open AccessFeature PaperArticle Solventless Coupling of Epoxides and CO2 in Compressed Medium Catalysed by Fluorinated Metalloporphyrins
Catalysts 2017, 7(7), 210; doi:10.3390/catal7070210
Received: 22 June 2017 / Revised: 22 June 2017 / Accepted: 7 July 2017 / Published: 14 July 2017
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Abstract
Metal complexes of meso-arylporphyrins (Cr(III), Fe(III), and Zn(II)) were evaluated in the coupling reaction of cyclohexene oxide (CHO) with CO2 in compressed medium, where the Cr complexes were demonstrated to be the most active systems, leading predominantly to copolymerisation products. It
[...] Read more.
Metal complexes of meso-arylporphyrins (Cr(III), Fe(III), and Zn(II)) were evaluated in the coupling reaction of cyclohexene oxide (CHO) with CO2 in compressed medium, where the Cr complexes were demonstrated to be the most active systems, leading predominantly to copolymerisation products. It is noteworthy that no addition of solvent was required. To improve the catalytic activity, and to simultaneously increase the solubility in compressed CO2, a new fluorinated catalyst, tetrakis(4-trifluoromethylphenyl)porphyrinatochromium(III) chloride (CrCl-pCF3TPP), was applied to this reaction. The alternating copolymerisation of CHO with CO2, using the Cr(III) fluorinated porphyrin catalyst, required the use of a co-catalyst, bis(triphenylphosphine)iminium chloride (PPNCl), with the best yields of copolymers being obtained at 80 °C, and CO2 pressures in the range of 50–110 bar, over a period of 24 h, with a low catalyst/substrate molar ratio (0.07%). The polycarbonate’s structure was analysed by 1H NMR, 13C NMR, and MALDI-TOF spectroscopy, which demonstrated high carbonate incorporations (98–99%). Gel permeation chromatography revealed number-average molecular weights (Mn) in the range of 4800–12,800 and narrow molecular weight distributions (Mw/Mn ≤ 1.63). Full article
(This article belongs to the Special Issue Catalysis in Innovative Solvents)
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Open AccessArticle Arenesulfonic Acid-Functionalized Bentonite as Catalyst in Glycerol Esterification with Acetic Acid
Catalysts 2017, 7(7), 211; doi:10.3390/catal7070211
Received: 13 May 2017 / Revised: 28 June 2017 / Accepted: 3 July 2017 / Published: 14 July 2017
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Abstract
The present study is focused on the synthesis of arenesulfonic acid-functionalized bentonite as a catalyst to produce monoacetin, diacetin, and triacetin from glycerol and acetic acid using toluene as solvent and a water removing agent. The best conditions for the present reaction with
[...] Read more.
The present study is focused on the synthesis of arenesulfonic acid-functionalized bentonite as a catalyst to produce monoacetin, diacetin, and triacetin from glycerol and acetic acid using toluene as solvent and a water removing agent. The best conditions for the present reaction with acetic acid were an acetic acid:glycerol:toluene molar ratio of 7:1:1.4, 100 °C, and 0.074 wt % of catalyst (based on the total weight of glycerol). Under the reaction conditions, 96% glycerol conversion was achieved within 0.5 h from the start of the reaction. The maximum selectivity of 66% and 74% were achieved for diacetin and triacetin after 0.5 and 3 h of reaction, respectively, without formation of any byproduct. The arenesulfonic acid-functionalized bentonite was characterized by X-ray diffraction, thermogravimetric analysis, Fourier transform infrared spectroscopy, N2 adsorption/desorption experiments (Brunauer, Emmett and Teller, BET, method), field emission scanning electron microscopy, and the surface acidity was determined by back titration. Without significant treatment, the catalyst was reusable for 5 consecutive runs. Full article
(This article belongs to the Special Issue Glycerol Conversion by Heterogeneous Catalysis)
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Open AccessArticle Pure and Fe-Doped Mesoporous Titania Catalyse the Oxidation of Acid Orange 7 by H2O2 under Different Illumination Conditions: Fe Doping Improves Photocatalytic Activity under Simulated Solar Light
Catalysts 2017, 7(7), 213; doi:10.3390/catal7070213
Received: 5 May 2017 / Revised: 11 July 2017 / Accepted: 11 July 2017 / Published: 18 July 2017
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Abstract
A sample of mesoporous TiO2 (MT, specific surface area = 150 m2·g−1) and two samples of MT containing 2.5 wt.% Fe were prepared by either direct synthesis doping (Fe2.5-MTd) or impregnation (Fe2.5-MTi). Commercial TiO2 (Degussa P25, specific
[...] Read more.
A sample of mesoporous TiO2 (MT, specific surface area = 150 m2·g−1) and two samples of MT containing 2.5 wt.% Fe were prepared by either direct synthesis doping (Fe2.5-MTd) or impregnation (Fe2.5-MTi). Commercial TiO2 (Degussa P25, specific surface area = 56 m2 g−1) was used both as a benchmark and as a support for impregnation with either 0.8 or 2.5 wt.% Fe (Fe0.80-IT and Fe2.5-IT). The powders were characterized by X-ray diffraction, N2 isotherms at −196 °C, Energy Dispersive X-ray (EDX) Spectroscopy, X-ray Photoelectron Spectroscopy (XPS), Diffuse Reflectance (DR) ultra-violet (UV)-Vis and Mössbauer spectroscopies. Degradation of Acid Orange 7 (AO7) by H2O2 was the test reaction: effects of dark-conditions versus both UV and simulated solar light irradiation were considered. In dark conditions, AO7 conversion was higher with MT than with Degussa P25, whereas Fe-containing samples were active in a (slow) Fenton-like reaction. Under UV light, MT was as active as Degussa P25, and Fe doping enhanced the photocatalytic activity of Fe2.5-MTd; Fe-impregnated samples were also active, likely due to the occurrence of a photo-Fenton process. Interestingly, the Fe2.5-MTd sample showed the best performance under solar light, confirming the positive effect of Fe doping by direct synthesis with respect to impregnation. Full article
(This article belongs to the Special Issue Mesostructured Materials and Their Catalytic Applications)
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Open AccessArticle Sulfur-Doped TiO2: Structure and Surface Properties
Catalysts 2017, 7(7), 214; doi:10.3390/catal7070214
Received: 29 May 2017 / Revised: 30 June 2017 / Accepted: 11 July 2017 / Published: 18 July 2017
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Abstract
A comprehensive study on the sulfur doping of TiO2, by means of H2S treatment at 673 K, has been performed in order to highlight the role of sulfur in affecting the properties of the system, as compared to the
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A comprehensive study on the sulfur doping of TiO2, by means of H2S treatment at 673 K, has been performed in order to highlight the role of sulfur in affecting the properties of the system, as compared to the native TiO2. The focus of this study is to find a relationship among the surface, structure, and morphology properties, by means of a detailed chemical and physical characterization of the samples. In particular, transmission electron microscopy images provide a simple tool to have a direct and immediate evidence of the effects of H2S action on the TiO2 particles structure and surface defects. Furthermore, from spectroscopy analyses, the peculiar surface, optical properties, and methylene blue photodegradation test of S-doped TiO2 samples, as compared to pure TiO2, have been investigated and explained by the effects caused by the exchange of S species with O species and by the surface defects induced by the strong H2S treatment. Full article
(This article belongs to the Special Issue Titanium Dioxide Photocatalysis)
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Open AccessFeature PaperArticle Mo(VI) Complexes Immobilized on SBA-15 as an Efficient Catalyst for 1-Octene Epoxidation
Catalysts 2017, 7(7), 215; doi:10.3390/catal7070215
Received: 13 June 2017 / Revised: 8 July 2017 / Accepted: 11 July 2017 / Published: 18 July 2017
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Abstract
SBA-15 materials were functionalized through a post-synthetic methodology with molybdenum-Schiff bases to provide catalytic activity in epoxidation reactions. Thus, glycidoxypropyl functionalities were first attached to the surface of the mesostructured silica, followed by the reaction of the immobilized oxirane groups with 2-amino propyl
[...] Read more.
SBA-15 materials were functionalized through a post-synthetic methodology with molybdenum-Schiff bases to provide catalytic activity in epoxidation reactions. Thus, glycidoxypropyl functionalities were first attached to the surface of the mesostructured silica, followed by the reaction of the immobilized oxirane groups with 2-amino propyl pyridine. This reaction allowed the obtaining of (hydroxypropyl)-2-aminomethyl pyridine ligands, directly tethered to the surface of the mesoporous silica-based SBA-15, which resulted in excellent chelating ligands to immobilize dioxo molydenum species by a reaction with MoO2(acac)2. This investigation comprises a thorough characterization of the process for building the immobilized molybdenum-Schiff base complexes, as well as the use of the obtained materials in 1-octene oxidation in the presence of organic hydroperoxides. These materials displayed high intrinsic catalytic activity in the epoxidation of 1-octene with organic hydroperoxides under a wide variety of conditions, although both the reaction solvent as well as the nature of the organic hydroperoxide, exerted a dramatic influence on the catalytic activity of these heterogeneous oxidation catalysts. Thus, whereas nonpolar solvents provided good epoxide yields with high efficiency in the use of the oxidant, polar solvents depressed the catalytic activity of the supported Mo-Schiff bases. These results have been ascribed to the competition with the solvent, when polar, for binding to the metal sites, thus avoiding the formation of the hydroperoxo-metal cycle and the epoxidation of the olefin. The catalysts presented here show good reusability with low catalytic activity decay after the first reuse. Full article
(This article belongs to the Special Issue Mesostructured Materials and Their Catalytic Applications)
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Open AccessArticle Highly ordered Nanomaterial Functionalized Copper Schiff Base Framework: Synthesis, Characterization, and Hydrogen Peroxide Decomposition Performance
Catalysts 2017, 7(7), 216; doi:10.3390/catal7070216
Received: 7 June 2017 / Revised: 11 July 2017 / Accepted: 12 July 2017 / Published: 19 July 2017
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Abstract
An immobilized copper Schiff base tridentate complex was prepared in three steps from SBA-15 supports. The immobilized copper nanocatalyst (heterogeneous catalyst) was characterized by Fourier transform infrared spectroscopy (FT-IR), cross polarization magic angle spinning (CP-MAS), 13-carbon nuclear magnetic resonance (13C-NMR), atomic
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An immobilized copper Schiff base tridentate complex was prepared in three steps from SBA-15 supports. The immobilized copper nanocatalyst (heterogeneous catalyst) was characterized by Fourier transform infrared spectroscopy (FT-IR), cross polarization magic angle spinning (CP-MAS), 13-carbon nuclear magnetic resonance (13C-NMR), atomic absorption spectroscopy (AAS), thermogravimetric analysis (TGA), and N2-physisorption. Moreover, morphological and structural features of the immobilized nanocatalyst were analyzed using transmission electron microscopy (TEM) and X-ray powder diffraction spectrometry (PXRD). After characterizing the nanocatalyst, the catalytic activity was determined in hydrogen peroxide (H2O2) decomposition. The high decomposition yield of H2O2 was obtained for low-loaded copper content materials at pH 7 and at room temperature. Furthermore, the nanocatalyst exhibited high activity and stability under the investigated conditions, and could be recovered and reused for at least five consecutive times without any significant loss in activity. No copper leaching was detected during the reaction by AAS measurements. Full article
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Open AccessArticle Co-Immobilization of Superoxide Dismutase with Catalase on Soft Microparticles Formed by Self-Assembly of Amphiphilic Poly(Aspartic Acid)
Catalysts 2017, 7(7), 217; doi:10.3390/catal7070217
Received: 14 June 2017 / Revised: 12 July 2017 / Accepted: 17 July 2017 / Published: 19 July 2017
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Abstract
Through genetic engineering technology, catalase (CAT) and superoxide dismutase (SOD) have been separately fused to an elastin-like polypeptide (ELP). Thus, the enzymes can be purified through phase transition. Hexadecylamine-modified poly(aspartic acid) (HPASP) is able to self-assemble, forming soft microparticles. The HPASP microparticles were
[...] Read more.
Through genetic engineering technology, catalase (CAT) and superoxide dismutase (SOD) have been separately fused to an elastin-like polypeptide (ELP). Thus, the enzymes can be purified through phase transition. Hexadecylamine-modified poly(aspartic acid) (HPASP) is able to self-assemble, forming soft microparticles. The HPASP microparticles were used to co-immobilize SOD-ELP and CAT-ELP through amidation reaction. Circular dichroism (CD) confirmed that the secondary structures of the co-immobilized enzymes have been preserved. Fluorescence spectra showed that the co-immobilized enzymes exhibited a higher stability than the free enzymes. Dismutation of superoxide by superoxide dismutase (SOD) generates hydrogen peroxide. By using the co-immobilized enzymes (SOD-ELP/CAT-ELP@HPASP), the generated hydrogen peroxide of SOD-ELP can be decomposed in situ by CAT-ELP. Activity assay results demonstrated that the superoxide anion (•O2) scavenging ability is 63.15 ± 0.75% for SOD-ELP/CAT-ELP@HPASP. The advantages of the approach of enzyme co-immobilization include the fact that the soft support HPASP itself is a polypeptide in nature, the stability of immobilized enzymes is improved, and a high activity has been achieved. Potentially SOD-ELP/CAT-ELP@HPASP can be applied in the cosmetic industry. Full article
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Open AccessArticle Recyclable Fe3O4 Nanoparticles Catalysts for Aza-Michael Addition of Acryl Amides by Magnetic Field
Catalysts 2017, 7(7), 219; doi:10.3390/catal7070219
Received: 20 June 2017 / Revised: 11 July 2017 / Accepted: 18 July 2017 / Published: 20 July 2017
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Abstract
A nanostructure-based catalytic system has the advantages of both homogeneous and heterogeneous catalysis. It is of great significance to develop the sustainable and green process of homogeneous catalytic reaction. We report a novel, efficient and recyclable magnetic Fe3O4 nanoparticles-catalyzed aza-Michael
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A nanostructure-based catalytic system has the advantages of both homogeneous and heterogeneous catalysis. It is of great significance to develop the sustainable and green process of homogeneous catalytic reaction. We report a novel, efficient and recyclable magnetic Fe3O4 nanoparticles-catalyzed aza-Michael addition reaction of acryl amides, and the magnetic nanoparticles catalysts can be recovered by external magnetic field. Both primary amine and secondary amine can react with various acryl amides providing a good output to target products successfully at room temperature. Further experiments reveal that the magnetic Fe3O4 nanoparticles-based catalyst shows excellent yields, which can be recycled 10 times, and, at the same time, it maintains a high catalytically activity. In this catalytic system, the tedious separation procedures are replaced by external magnetic field, which gives us a different direction for choosing a catalyst in a nanostructure-based catalytic system. Full article
(This article belongs to the Special Issue Magnetic Nanocatalysts)
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Open AccessArticle Electroreduction of CO2 into Ethanol over an Active Catalyst: Copper Supported on Titania
Catalysts 2017, 7(7), 220; doi:10.3390/catal7070220
Received: 15 June 2017 / Revised: 15 July 2017 / Accepted: 18 July 2017 / Published: 20 July 2017
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Abstract
A simple, inexpensive, and novel method was used to prepare electrocatalysts from Cu supported on titanium dioxide (Cu/TiO2). XRD, SEM, and TEM characterizations confirmed different loadings of Cu nanoparticles (NPs) on TiO2. Cyclic voltammetry tests indicated that Cu/TiO2
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A simple, inexpensive, and novel method was used to prepare electrocatalysts from Cu supported on titanium dioxide (Cu/TiO2). XRD, SEM, and TEM characterizations confirmed different loadings of Cu nanoparticles (NPs) on TiO2. Cyclic voltammetry tests indicated that Cu/TiO2 exhibited lower overpotential for CO2 reduction than that of Cu NPs. Moreover, 40 wt % Cu/TiO2 exhibited the highest faradaic efficiency for ethanol (FEethanol) of 27.4%, which is approximately 10-fold higher than that for Cu NPs (FEethanol = 2.7%). The 40 wt % Cu/TiO2 electrocatalyst exhibits a stable current density of 8.66 mA/cm2 over a 25 h stability test. The high efficiency towards CO2 electroreduction to ethanol may be attributed to the synergistic effect of Cu and TiO2 NPs. This work highlights the importance of compositional effect of NPs on their catalytic activities and provides a strategy for designing efficient catalysts for CO2 electroreduction in the future. Full article
(This article belongs to the Special Issue Advances in Electrocatalysis)
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Open AccessArticle Conversion of Cellulose to Lactic Acid by Using ZrO2–Al2O3 Catalysts
Catalysts 2017, 7(7), 221; doi:10.3390/catal7070221
Received: 26 June 2017 / Revised: 19 July 2017 / Accepted: 19 July 2017 / Published: 21 July 2017
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Abstract
Lactic acid has a wide range of applications in many industries, both as an ingredient and as an intermediate. Here, we investigated the catalytic conversion of cellulose to lactic acid by using heterogeneous mixed-oxide catalysts containing ZrO2. Although pure ZrO2
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Lactic acid has a wide range of applications in many industries, both as an ingredient and as an intermediate. Here, we investigated the catalytic conversion of cellulose to lactic acid by using heterogeneous mixed-oxide catalysts containing ZrO2. Although pure ZrO2 has catalytic activity for the conversion of cellulose to lactic acid, the yield of lactic acid obtained is not satisfactory. In contrast, a series of ZrO2–Al2O3 catalysts containing various percentages of ZrO2 provided higher yields of lactic acid. The ZrO2–Al2O3 catalysts had more Lewis acid sites and far fewer base sites than ZrO2. This suggests that the Lewis acid sites on ZrO2–Al2O3 catalysts are more important than the base sites for the conversion of cellulose to lactic acid. Full article
(This article belongs to the Special Issue Catalysis of Biomass-Derived Molecules)
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Open AccessArticle Solvent-Free Microwave-Induced Oxidation of Alcohols Catalyzed by Ferrite Magnetic Nanoparticles
Catalysts 2017, 7(7), 222; doi:10.3390/catal7070222
Received: 28 June 2017 / Revised: 16 July 2017 / Accepted: 16 July 2017 / Published: 24 July 2017
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Abstract
A series of first-row-transition-metal ferrite magnetic nanoparticles (NPs) MFe2O4 [M = Mn2+ (1), Fe2+ (2), Co2+ (3), Ni2+ (4), Cu2+ (5) or Zn2+ (
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A series of first-row-transition-metal ferrite magnetic nanoparticles (NPs) MFe2O4 [M = Mn2+ (1), Fe2+ (2), Co2+ (3), Ni2+ (4), Cu2+ (5) or Zn2+ (6)] were prepared by the co-precipitation method and characterized by Fourier transform infrared (FTIR) spectroscopy, powder X-ray diffraction (XRD), scanning electron microscope - energy dispersive X-ray spectrometry (SEM-EDS), vibrating sample magnetometer (VSM) and X-ray photoelectron spectroscopy (XPS). Those NPs were used as catalysts for the microwave-assisted oxidation of various alcohols in solvent-free medium. MnFe2O4 (1), CoFe2O4 (3) and CuFe2O4 (5) act as catalysts for the conversion of alcohols to the corresponding ketones or aldehydes with a yield range of 81 to 94% in 2 h at 120 °C using t-BuOOH as an oxidant. These catalysts can be readily isolated by using an external magnet and no significant loss of activity is observed when reused up to 10 consecutive runs. The effects of some parameters, such as temperature, time, type of oxidant and presence of organic radicals, on the oxidation reactions were also investigated. The presented literature overview highlights the advantages of our new 16 NPs catalytic systems in terms of efficiency and economy, mainly due the used microwave (MW) heating mode. Full article
(This article belongs to the Special Issue Magnetic Nanocatalysts)
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Open AccessArticle Synthesis and Evaluation of Ni Catalysts Supported on BaCe0.5Zr0.3−xY0.2NixO3−δ with Fused-Aggregate Network Structure for the Hydrogen Electrode of Solid Oxide Electrolysis Cell
Catalysts 2017, 7(7), 223; doi:10.3390/catal7070223
Received: 16 June 2017 / Revised: 14 July 2017 / Accepted: 18 July 2017 / Published: 24 July 2017
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Abstract
Nickel nanoparticles loaded on the electron–proton mixed conductor BaCe0.5Zr0.3−xY0.2NixO3−δ (Ni/BCZYN, x = 0 and 0.03) were synthesized for use in the hydrogen electrode of a proton-conducting solid oxide electrolysis cell (SOEC). The Ni nanoparticles,
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Nickel nanoparticles loaded on the electron–proton mixed conductor BaCe0.5Zr0.3−xY0.2NixO3−δ (Ni/BCZYN, x = 0 and 0.03) were synthesized for use in the hydrogen electrode of a proton-conducting solid oxide electrolysis cell (SOEC). The Ni nanoparticles, synthesized by an impregnation method, were from 45.8 nm to 84.1 nm in diameter, and were highly dispersed on the BCZYN. The BCZYN nanoparticles, fabricated by the flame oxide synthesis method, constructed a unique microstructure, the so-called “fused-aggregate network structure”. The BCZYN nanoparticles have capability of constructing a scaffold for the hydrogen electrode with both electronically conducting pathways and gas diffusion pathways. The catalytic activity on Ni/BCZYN (x = 0 and 0.03) catalyst layers (CLs) improved with the circumference length of the Ni nanoparticles. Moreover, the catalytic activity on the Ni/BCZYN (x = 0.03) CL was higher than that of the Ni/BCZYN (x = 0) CL. BCZYN (x = 0.03) possesses higher electronic conductivity than BCZYN (x = 0) due to the Ni doping, resulting in an enlarged effective reaction zone (ERZ). We conclude that the proton reduction reaction in the ERZ was the rate-determining step on the hydrogen electrode, and the reaction was enhanced by improving the electronic conductivity of the electron–proton mixed conductor BCZYN. Full article
(This article belongs to the Special Issue Nanostructured Materials for Applications in Heterogeneous Catalysis)
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Open AccessArticle Chiral Catalyst Deactivation during the Asymmetric Hydrogenation of Acetophenone
Catalysts 2017, 7(7), 193; doi:10.3390/catal7070193
Received: 18 May 2017 / Revised: 14 June 2017 / Accepted: 20 June 2017 / Published: 23 June 2017
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Abstract
Asymmetric hydrogenation in solution catalyzed by chiral catalysts is a powerful tool to obtain chiral secondary alcohols. It is possible to reach conversions and enantiomeric excesses close to 99%, but that frequently requires the use of non-optimal amounts of catalysts or long reaction
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Asymmetric hydrogenation in solution catalyzed by chiral catalysts is a powerful tool to obtain chiral secondary alcohols. It is possible to reach conversions and enantiomeric excesses close to 99%, but that frequently requires the use of non-optimal amounts of catalysts or long reaction times. That is in part caused by the lack of kinetic information needed for the design of large-scale reactors, including few reported details about catalyst deactivation. In this work, we present a kinetic model for the asymmetric hydrogenation in solution of acetophenone, a prochiral substrate, catalyzed by different bisphosphine-diamine Ru complexes. The experimental data was fitted with a first order model that includes first order deactivation of the catalyst and the presence of residual activity. The fit of the experimental data is very good, and an analysis of the kinetic and deactivation parameters gives further insight into the role of each ligand present in the Ru catalysts. This is the first report of a kinetic analysis of homogenous complexes’ catalysis including an analysis of their deactivation. Full article
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Open AccessArticle Hydrothermal Carbonation Carbon-Coated CdS Nanocomposite with Enhanced Photocatalytic Activity and Stability
Catalysts 2017, 7(7), 194; doi:10.3390/catal7070194
Received: 3 May 2017 / Revised: 12 June 2017 / Accepted: 19 June 2017 / Published: 24 June 2017
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Abstract
Herein, a novel CdS nanocomposite is fabricated by a facile one-pot hydrothermal method assisted by glucose and polyvinylpyrrolidone (PVP). The as-prepared CdS is coated with a thin layer, which is determined to be hydrothermal carbonation carbon (HTCC) mainly containing semiconductive polyfuran. The as-prepared
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Herein, a novel CdS nanocomposite is fabricated by a facile one-pot hydrothermal method assisted by glucose and polyvinylpyrrolidone (PVP). The as-prepared CdS is coated with a thin layer, which is determined to be hydrothermal carbonation carbon (HTCC) mainly containing semiconductive polyfuran. The as-prepared HTCC-coated CdS shows superior photocatalytic activity for the degradation of Rhodamine B (RhB) under visible light irradiation (λ ≥ 420 nm). The optimum sample (glucose content of 0.1 g) shows a degradation rate four-times that of pure CdS reference. Moreover, it also shows an improved stability, and the activity can be maintained at 96.2% after three cycles of recycling. The enhanced photocatalytic activity and stability of nanocomposite can mainly be attributed to: (i) The addition of PVP in the reaction solution can significantly increase the specific surface area of CdS and thus offer more active sites; (ii) The HTCC in the nanocomposite can expand the range of light absorption; (iii) The HTCC layer can form a heterojunction with CdS and improve the charge separation and transfer. Full article
(This article belongs to the Special Issue Nanostructured Materials for Applications in Heterogeneous Catalysis)
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Open AccessCommunication Intramolecular Transfer of Pd Catalyst on Carbon–Carbon Triple Bond and Nitrogen–Nitrogen Double Bond in Suzuki–Miyaura Coupling Reaction
Catalysts 2017, 7(7), 195; doi:10.3390/catal7070195
Received: 24 March 2017 / Revised: 19 June 2017 / Accepted: 20 June 2017 / Published: 23 June 2017
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Abstract
Intramolecular transfer of t-Bu3P-ligated Pd catalyst on a carbon–carbon triple bond (C≡C) and nitrogen–nitrogen double bond (N=N) was investigated and compared with the case of a carbon–carbon double bond (C=C), which is resistant to intramolecular transfer of the Pd catalyst.
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Intramolecular transfer of t-Bu3P-ligated Pd catalyst on a carbon–carbon triple bond (C≡C) and nitrogen–nitrogen double bond (N=N) was investigated and compared with the case of a carbon–carbon double bond (C=C), which is resistant to intramolecular transfer of the Pd catalyst. Suzuki–Miyaura coupling reaction of equimolar 4,4’-dibromotolan (1a) or 4,4’-dibromoazobenzene (1b) with 3-isobutoxyphenylboronic acid (2) was carried out in the presence of t-Bu3P-ligated Pd precatalyst 3 and KOH/18-crown-6 as a base at room temperature. In both cases, the diphenyl-substituted product was selectively obtained, indicating that the Pd catalyst walked from one benzene ring to the other through the C≡C or N=N bond after the first substitution with 2. Taking advantage of this finding, we conducted unstoichiometric Suzuki–Miyaura polycondensation of 1.3 equiv. of 1 and 1.0 equiv. of phenylenediboronic acid (ester) 6 in the presence of 3 and CsF/18-crown-6 as a base, obtaining high-molecular-weight conjugated polymer with a boronic acid (ester) moiety at both ends, contrary to the Flory principle. Full article
(This article belongs to the Special Issue Suzuki–Miyaura Cross-Coupling Reaction and Potential Applications)
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Open AccessArticle Selective Hydrogenolysis of Glycerol and Crude Glycerol (a By-Product or Waste Stream from the Biodiesel Industry) to 1,2-Propanediol over B2O3 Promoted Cu/Al2O3 Catalysts
Catalysts 2017, 7(7), 196; doi:10.3390/catal7070196
Received: 29 April 2017 / Revised: 19 June 2017 / Accepted: 23 June 2017 / Published: 25 June 2017
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Abstract
The performance of boron oxide (B2O3)-promoted Cu/Al2O3 catalyst in the selective hydrogenolysis of glycerol and crude glycerol (a by-product or waste stream from the biodiesel industry) to produce 1,2-propanediol (1,2-PDO) was investigated. The catalysts were characterized
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The performance of boron oxide (B2O3)-promoted Cu/Al2O3 catalyst in the selective hydrogenolysis of glycerol and crude glycerol (a by-product or waste stream from the biodiesel industry) to produce 1,2-propanediol (1,2-PDO) was investigated. The catalysts were characterized using N2-adsorption-desorption isotherm, Inductively coupled plasma atomic emission spectroscopy (ICP-AES), X-ray diffraction (XRD), ammonia temperature programmed desorption (NH3-TPD), thermogravimetric analysis (TGA), temperature programmed reduction (TPR), and transmission electron microscopy (TEM). Incorporation of B2O3 to Cu/Al2O3 was found to enhance the catalytic activity. At the optimum condition (250 °C, 6 MPa H2 pressure, 0.1 h−1 WHSV (weight hourly space velocity), and 5Cu-B/Al2O3 catalyst), 10 wt% aqueous solution of glycerol was converted into 1,2-PDO at 98 ± 2% glycerol conversion and 98 ± 2% selectivity. The effects of temperature, pressure, boron addition amount, and liquid hourly space velocity were studied. Different grades of glycerol (pharmaceutical, technical, or crude glycerol) were used in the process to investigate the stability and resistance to deactivation of the selected 5Cu-B/Al2O3 catalyst. Full article
(This article belongs to the Special Issue Glycerol Conversion by Heterogeneous Catalysis)
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Open AccessArticle The Effects of CeO2 Nanorods and CeO2 Nanoflakes on Ni–S Alloys in Hydrogen Evolution Reactions in Alkaline Solutions
Catalysts 2017, 7(7), 197; doi:10.3390/catal7070197
Received: 8 May 2017 / Revised: 15 June 2017 / Accepted: 16 June 2017 / Published: 27 June 2017
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Abstract
Composite coatings synthesized by different morphologies of CeO2 in supergravity devices are highly active in hydrogen evolution reactions (HERs). By adding CeO2 nanoflakes (CeO2 Nf) or CeO2 nanorods (CeO2 Nr), the change in the microstructures of composites becomes quite distinct. Moreover, most Ni–S
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Composite coatings synthesized by different morphologies of CeO2 in supergravity devices are highly active in hydrogen evolution reactions (HERs). By adding CeO2 nanoflakes (CeO2 Nf) or CeO2 nanorods (CeO2 Nr), the change in the microstructures of composites becomes quite distinct. Moreover, most Ni–S alloys are attached on the surface of CeO2 and roughen it compare with pure CeO2. In order to make the expression more concise, this paper uses M instead of Ni–S. At a current density of 10 mA/cm2, overpotentials of Ni–S/CeO2 Nr (M–CeO2 Nr) and Ni–S/CeO2 Nf (M–CeO2 Nf) are 200 mV and 180 mV respectively, which is lower than that of Ni–S (M-0) coating (240 mV). The exchange current density (j0) values of M–CeO2 Nf and M–CeO2 Nr are 7.48 mA/cm2 and 7.40 mA/cm2, respectively, which are higher than that of M-0 (6.39 mA/cm2). Meanwhile, double-layer capacitances (Cdl) values of M–CeO2 Nf (6.4 mF/cm2) and M–CeO2 Nr (6 mF/cm2) are 21.3 times and 20 times of M-0 (0.3 mF/cm2), respectively Full article
(This article belongs to the Special Issue Advances in Electrocatalysis)
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Open AccessArticle Ordered PtSn/C Electrocatalyst: A High Performance Material for the Borohydride Electrooxidation Reaction
Catalysts 2017, 7(7), 198; doi:10.3390/catal7070198
Received: 13 March 2017 / Revised: 2 June 2017 / Accepted: 4 June 2017 / Published: 29 June 2017
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Abstract
This work used a rotating disc electrode and quasi-steady state polarization curves to investigate the sodium borohydride electrooxidation of ordered intermetallic PtSn/C in alkaline solution. Under similar experimental conditions, PtSn/C proved to be a better electrocatalyst than Pt in an overall process that
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This work used a rotating disc electrode and quasi-steady state polarization curves to investigate the sodium borohydride electrooxidation of ordered intermetallic PtSn/C in alkaline solution. Under similar experimental conditions, PtSn/C proved to be a better electrocatalyst than Pt in an overall process that involved eight electrons. Assays performed in the presence of thiourea and S2− species evidenced that a chemical hydrolysis step took place, followed by electrochemical oxidation of the generated H2. The results presented herein suggest that PtSn/C constitutes a promising electrode material for application in alkaline borohydride fuel cell. Full article
(This article belongs to the Special Issue Advances in Electrocatalysis)
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Review

Jump to: Research

Open AccessFeature PaperReview Bimetallic Nanoparticles in Alternative Solvents for Catalytic Purposes
Catalysts 2017, 7(7), 207; doi:10.3390/catal7070207
Received: 24 June 2017 / Revised: 4 July 2017 / Accepted: 5 July 2017 / Published: 7 July 2017
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Abstract
Bimetallic nanoparticles represent attractive catalytic systems thanks to the synergy between both partners at the atomic level, mainly induced by electronic effects which in turn are associated with the corresponding structures (alloy, core-shell, hetero-dimer). This type of engineered material can trigger changes in
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Bimetallic nanoparticles represent attractive catalytic systems thanks to the synergy between both partners at the atomic level, mainly induced by electronic effects which in turn are associated with the corresponding structures (alloy, core-shell, hetero-dimer). This type of engineered material can trigger changes in the kinetics of catalyzed processes by variations on the electrophilicity/nucleophilicity of the metal centers involved and also promote cooperative effects to foster organic transformations, including multi-component and multi-step processes. Solvents become a crucial factor in the conception of catalytic processes, not only due to their environmental impact, but also because they can preserve the bimetallic structure during the catalytic reaction and therefore increase the catalyst life-time. In this frame, the present review focuses on the recent works described in the literature concerning the synthesis of bimetallic nanoparticles in non-conventional solvents, i.e., other than common volatile compounds, for catalytic applications. Full article
(This article belongs to the Special Issue Catalysis in Innovative Solvents)
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Open AccessReview In Silico Studies of Small Molecule Interactions with Enzymes Reveal Aspects of Catalytic Function
Catalysts 2017, 7(7), 212; doi:10.3390/catal7070212
Received: 20 May 2017 / Revised: 7 July 2017 / Accepted: 10 July 2017 / Published: 14 July 2017
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Abstract
Small molecules, such as solvent, substrate, and cofactor molecules, are key players in enzyme catalysis. Computational methods are powerful tools for exploring the dynamics and thermodynamics of these small molecules as they participate in or contribute to enzymatic processes. In-depth knowledge of how
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Small molecules, such as solvent, substrate, and cofactor molecules, are key players in enzyme catalysis. Computational methods are powerful tools for exploring the dynamics and thermodynamics of these small molecules as they participate in or contribute to enzymatic processes. In-depth knowledge of how small molecule interactions and dynamics influence protein conformational dynamics and function is critical for progress in the field of enzyme catalysis. Although numerous computational studies have focused on enzyme–substrate complexes to gain insight into catalytic mechanisms, transition states and reaction rates, the dynamics of solvents, substrates, and cofactors are generally less well studied. Also, solvent dynamics within the biomolecular solvation layer play an important part in enzyme catalysis, but a full understanding of its role is hampered by its complexity. Moreover, passive substrate transport has been identified in certain enzymes, and the underlying principles of molecular recognition are an area of active investigation. Enzymes are highly dynamic entities that undergo different conformational changes, which range from side chain rearrangement of a residue to larger-scale conformational dynamics involving domains. These events may happen nearby or far away from the catalytic site, and may occur on different time scales, yet many are related to biological and catalytic function. Computational studies, primarily molecular dynamics (MD) simulations, provide atomistic-level insight and site-specific information on small molecule interactions, and their role in conformational pre-reorganization and dynamics in enzyme catalysis. The review is focused on MD simulation studies of small molecule interactions and dynamics to characterize and comprehend protein dynamics and function in catalyzed reactions. Experimental and theoretical methods available to complement and expand insight from MD simulations are discussed briefly. Full article
(This article belongs to the Special Issue Computational Methods and Their Application in Catalysis)
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Open AccessFeature PaperReview Catalytic Conversion of Carbohydrates to Furanic Derivatives in the Presence of Choline Chloride
Catalysts 2017, 7(7), 218; doi:10.3390/catal7070218
Received: 30 June 2017 / Revised: 12 July 2017 / Accepted: 13 July 2017 / Published: 20 July 2017
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Abstract
The synthesis of furanic derivatives (5-hydroxymethylfurfural (HMF), furfural…) from carbohydrates is of high interest for a wide range of applications. These reactions are carried out in the presence of various solvents, and among them choline chloride can be used. It is a salt
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The synthesis of furanic derivatives (5-hydroxymethylfurfural (HMF), furfural…) from carbohydrates is of high interest for a wide range of applications. These reactions are carried out in the presence of various solvents, and among them choline chloride can be used. It is a salt that can form a low melting mixture with a carbohydrate (fructose, glucose…) or a deep eutectic mixture with carboxylic acid. A review of the studies performed in the conversion of carbohydrates to furanic derivatives in the presence of choline chloride is presented here with the advantages and drawbacks of this solvent. Choline chloride can enhance the selectivity to HMF by stabilizing effect and allows the conversion of highly concentrated feed. However, the extraction of the products from these solvents still needs improvement. Full article
(This article belongs to the Special Issue Catalysis in Innovative Solvents)
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Open AccessReview A Review on Selective Catalytic Reduction of NOx by NH3 over Mn–Based Catalysts at Low Temperatures: Catalysts, Mechanisms, Kinetics and DFT Calculations
Catalysts 2017, 7(7), 199; doi:10.3390/catal7070199
Received: 23 April 2017 / Revised: 18 June 2017 / Accepted: 21 June 2017 / Published: 29 June 2017
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Abstract
It is a major challenge to develop the low–temperature catalysts (LTC, <250 °C) with excellent efficiency and stability for selective catalytic reduction (SCR) of NOx by NH3 from stationary sources. Mn-based LTC have been widely investigated due to its various valence
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It is a major challenge to develop the low–temperature catalysts (LTC, <250 °C) with excellent efficiency and stability for selective catalytic reduction (SCR) of NOx by NH3 from stationary sources. Mn-based LTC have been widely investigated due to its various valence states and excellent redox performance, while the poisoning by H2O or/and SO2 is one of the severe weaknesses. This paper reviews the latest research progress on Mn-based catalysts that are expected to break through the resistance, such as modified MnOx–CeO2, multi-metal oxides with special crystal or/and shape structures, modified TiO2 supporter, and novel carbon supporter (ACF, CNTs, GE), etc. The SCR mechanisms and promoting effects of redox cycle are described in detail. The reaction kinetics will be a benefit for the quantitative study of Eley–Rideal (ER) and Langmuir–Hinshelwood (LH) mechanisms. This paper also introduces the applications of quantum-chemical calculation using density functional theory to analyze the physic-chemical properties, explicates the reaction and poisoning mechanisms, and directs the design of functional catalysts on molecule levels. The intensive study of H2O/SO2 inhibition effects is by means of the combination analysis of in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and density functional theory (DFT), and the amplification of tolerance mechanisms will be helpful to design an excellent SCR catalyst. Full article
(This article belongs to the Special Issue Small Molecule Activation and Catalysis)
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