Catalysts

1888 KiB

Open AccessArticle

Synthesis and Evaluation of Ni Catalysts Supported on BaCe_0.5Zr_0.3−xY_0.2Ni_xO_3−δ with Fused-Aggregate Network Structure for the Hydrogen Electrode of Solid Oxide Electrolysis Cell

by Ryosuke Nishikawa, Katsuyoshi Kakinuma, Hanako Nishino, Manuel E. Brito, Srikanth Gopalan and Hiroyuki Uchida

Catalysts 2017, 7(7), 223; https://doi.org/10.3390/catal7070223 - 24 Jul 2017

Cited by 4 | Viewed by 4482

Abstract

Nickel nanoparticles loaded on the electron–proton mixed conductor BaCe_0.5Zr_0.3−xY_0.2Ni_xO_3−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, [...] Read more.

Nickel nanoparticles loaded on the electron–proton mixed conductor BaCe_0.5Zr_0.3−xY_0.2Ni_xO_3−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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5108 KiB

Open AccessArticle

Solvent-Free Microwave-Induced Oxidation of Alcohols Catalyzed by Ferrite Magnetic Nanoparticles

by Nuno M. R. Martins, Luísa M. D. R. S. Martins, Carlos O. Amorim, Vitor S. Amaral and Armando J. L. Pombeiro

Catalysts 2017, 7(7), 222; https://doi.org/10.3390/catal7070222 - 24 Jul 2017

Cited by 41 | Viewed by 6190

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⁺ ( [...] Read more.

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 1–6 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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3199 KiB

Open AccessArticle

Conversion of Cellulose to Lactic Acid by Using ZrO₂–Al₂O₃ Catalysts

by Panya Wattanapaphawong, Osamu Sato, Koichi Sato, Naoki Mimura, Prasert Reubroycharoen and Aritomo Yamaguchi

Catalysts 2017, 7(7), 221; https://doi.org/10.3390/catal7070221 - 21 Jul 2017

Cited by 28 | Viewed by 7097

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 [...] Read more.

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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2722 KiB

Open AccessArticle

Electroreduction of CO₂ into Ethanol over an Active Catalyst: Copper Supported on Titania

by Jing Yuan, Li Liu, Rong-Rong Guo, Sheng Zeng, Huan Wang and Jia-Xing Lu

Catalysts 2017, 7(7), 220; https://doi.org/10.3390/catal7070220 - 20 Jul 2017

Cited by 27 | Viewed by 7541

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 [...] Read more.

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 (FE_ethanol) of 27.4%, which is approximately 10-fold higher than that for Cu NPs (FE_ethanol= 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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7570 KiB

Open AccessArticle

Recyclable Fe₃O₄ Nanoparticles Catalysts for Aza-Michael Addition of Acryl Amides by Magnetic Field

by Zhen-Xing Li, Dan Luo, Ming-Ming Li, Xiao-Fei Xing, Zheng-Zheng Ma and Hao Xu

Catalysts 2017, 7(7), 219; https://doi.org/10.3390/catal7070219 - 20 Jul 2017

Cited by 28 | Viewed by 7336

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 [...] Read more.

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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2655 KiB

Open AccessFeature PaperReview

Catalytic Conversion of Carbohydrates to Furanic Derivatives in the Presence of Choline Chloride

by François Jérôme and Karine De Oliveira Vigier

Catalysts 2017, 7(7), 218; https://doi.org/10.3390/catal7070218 - 20 Jul 2017

Cited by 19 | Viewed by 6608

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 [...] Read more.

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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3526 KiB

Open AccessArticle

Co-Immobilization of Superoxide Dismutase with Catalase on Soft Microparticles Formed by Self-Assembly of Amphiphilic Poly(Aspartic Acid)

by Siyu Mao, Rong Li, Wenchen Wang, Wei Feng and Peijun Ji

Catalysts 2017, 7(7), 217; https://doi.org/10.3390/catal7070217 - 19 Jul 2017

Cited by 5 | Viewed by 4597

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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1985 KiB

Open AccessArticle

Highly ordered Nanomaterial Functionalized Copper Schiff Base Framework: Synthesis, Characterization, and Hydrogen Peroxide Decomposition Performance

by Fatemeh Rajabi, María Pinilla-de Dios and Rafael Luque

Catalysts 2017, 7(7), 216; https://doi.org/10.3390/catal7070216 - 19 Jul 2017

Cited by 5 | Viewed by 6125

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 [...] Read more.

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

(This article belongs to the Special Issue Activation of Dioxygen and Liquid Phase Oxidation Catalysis for Fine Chemistry)

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3199 KiB

Open AccessFeature PaperArticle

Mo(VI) Complexes Immobilized on SBA-15 as an Efficient Catalyst for 1-Octene Epoxidation

by Jovita Moreno, Jose Iglesias and Juan Antonio Melero

Catalysts 2017, 7(7), 215; https://doi.org/10.3390/catal7070215 - 18 Jul 2017

Cited by 13 | Viewed by 4959

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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4092 KiB

Open AccessArticle

Sulfur-Doped TiO₂: Structure and Surface Properties

by Sara Cravanzola, Federico Cesano, Fulvio Gaziano and Domenica Scarano

Catalysts 2017, 7(7), 214; https://doi.org/10.3390/catal7070214 - 18 Jul 2017

Cited by 61 | Viewed by 9545

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 [...] Read more.

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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3910 KiB

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

by Francesca S. Freyria, Matteo Compagnoni, Nicoletta Ditaranto, Ilenia Rossetti, Marco Piumetti, Gianguido Ramis and Barbara Bonelli

Catalysts 2017, 7(7), 213; https://doi.org/10.3390/catal7070213 - 18 Jul 2017

Cited by 28 | Viewed by 5990

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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1376 KiB

Open AccessReview

In Silico Studies of Small Molecule Interactions with Enzymes Reveal Aspects of Catalytic Function

by Rajni Verma and Katie Mitchell-Koch

Catalysts 2017, 7(7), 212; https://doi.org/10.3390/catal7070212 - 14 Jul 2017

Cited by 20 | Viewed by 9359

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 [...] Read more.

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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2191 KiB

Open AccessArticle

Arenesulfonic Acid-Functionalized Bentonite as Catalyst in Glycerol Esterification with Acetic Acid

by Maryam Tangestanifard and Hassan S. Ghaziaskar

Catalysts 2017, 7(7), 211; https://doi.org/10.3390/catal7070211 - 14 Jul 2017

Cited by 27 | Viewed by 5679

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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2161 KiB

Open AccessFeature PaperArticle

Solventless Coupling of Epoxides and CO₂ in Compressed Medium Catalysed by Fluorinated Metalloporphyrins

by Rui M. B. Carrilho, Lucas D. Dias, Raquel Rivas, Mariette M. Pereira, Carmen Claver and Anna M. Masdeu-Bultó

Catalysts 2017, 7(7), 210; https://doi.org/10.3390/catal7070210 - 14 Jul 2017

Cited by 19 | Viewed by 5490

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 (M_n) in the range of 4800–12,800 and narrow molecular weight distributions (M_w/M_n ≤ 1.63). Full article

(This article belongs to the Special Issue Catalysis in Innovative Solvents)

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1806 KiB

Open AccessArticle

Low-Temperature Synthesis of Anatase/Rutile/Brookite TiO₂ Nanoparticles on a Polymer Membrane for Photocatalysis

by Kristina Fischer, Alina Gawel, David Rosen, Maria Krause, Amira Abdul Latif, Jan Griebel, Andrea Prager and Agnes Schulze

Catalysts 2017, 7(7), 209; https://doi.org/10.3390/catal7070209 - 10 Jul 2017

Cited by 118 | Viewed by 10947

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 [...] Read more.

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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1380 KiB

Open AccessArticle

Newly Designed Ternary Metallic PtPdBi Hollow Catalyst with High Performance for Methanol and Ethanol Oxidation

by Zhiping Xiong, Shumin Li, Hui Xu, Ke Zhang, Bo Yan and Yukou Du

Catalysts 2017, 7(7), 208; https://doi.org/10.3390/catal7070208 - 10 Jul 2017

Cited by 9 | Viewed by 5403

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 mg_PtPd⁻¹ for methanol oxidation reaction and 5.256 A mg_PtPd⁻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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5038 KiB

Open AccessFeature PaperReview

Bimetallic Nanoparticles in Alternative Solvents for Catalytic Purposes

by Trung Dang-Bao, Daniel Pla, Isabelle Favier and Montserrat Gómez

Catalysts 2017, 7(7), 207; https://doi.org/10.3390/catal7070207 - 7 Jul 2017

Cited by 55 | Viewed by 9887

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 [...] Read more.

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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3172 KiB

Open AccessArticle

Cerium Coordination Polymer Based Composite Mimicking Peroxidase for Detection of Nitroaniline

by Xi Wang, Kunkun Zheng and Peijun Ji

Catalysts 2017, 7(7), 206; https://doi.org/10.3390/catal7070206 - 7 Jul 2017

Cited by 2 | Viewed by 4742

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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1088 KiB

Open AccessArticle

DeNO_x Abatement Modelling over Sonically Prepared Copper USY and ZSM5 Structured Catalysts

by Przemysław J. Jodłowski, Łukasz Kuterasiński, Roman J. Jędrzejczyk, Damian Chlebda, Anna Gancarczyk, Sylwia Basąg and Lucjan Chmielarz

Catalysts 2017, 7(7), 205; https://doi.org/10.3390/catal7070205 - 6 Jul 2017

Cited by 17 | Viewed by 5069

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 deNO_x 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% NO_x 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 deNO_x process. Full article

(This article belongs to the Special Issue Structured and Micro-Structured Catalysts and Reactors)

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Open AccessFeature PaperArticle

Acidity-Reactivity Relationships in Catalytic Esterification over Ammonium Sulfate-Derived Sulfated Zirconia

by Abdallah I. M. Rabee, Gamal A. H. Mekhemer, Amin Osatiashtiani, Mark A. Isaacs, Adam F. Lee, Karen Wilson and Mohamed I. Zaki

Catalysts 2017, 7(7), 204; https://doi.org/10.3390/catal7070204 - 5 Jul 2017

Cited by 43 | Viewed by 8589

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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3805 KiB

Open AccessArticle

Rapid Jatropha-Castor Biodiesel Production with Microwave Heating and a Heterogeneous Base Catalyst Nano-Ca(OH)₂/Fe₃O₄

by Ken-Lin Chang, Yuan-Chung Lin, Syu-Ruei Jhang, Way Lee Cheng, Shang-Cyuan Chen and Sung-Yuan Mao

Catalysts 2017, 7(7), 203; https://doi.org/10.3390/catal7070203 - 4 Jul 2017

Cited by 14 | Viewed by 5057

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 [...] Read more.

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 AccessArticle

High Active Zn/Mg-Modified Ni–P/Al₂O₃ Catalysts Derived from ZnMgNiAl Layered Double Hydroxides for Hydrodesulfurization of Dibenzothiophene

by Feng Li, Jinrong Liang, Wenxi Zhu, Hua Song, Keliang Wang and Cuiqin Li

Catalysts 2017, 7(7), 202; https://doi.org/10.3390/catal7070202 - 4 Jul 2017

Cited by 4 | Viewed by 4462

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 [...] Read more.

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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4664 KiB

Open AccessArticle

Highly Effective Dual Transition Metal Macrocycle Based Electrocatalyst with Macro-/Mesoporous Structures for Oxygen Reduction Reaction

by Xinxin Jin, Yan Xie and Jiahui Huang

Catalysts 2017, 7(7), 201; https://doi.org/10.3390/catal7070201 - 30 Jun 2017

Cited by 12 | Viewed by 6231

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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1727 KiB

Open AccessArticle

Activated Carbon Supported Mo-Ti-N Binary Transition Metal Nitride as Catalyst for Acetylene Hydrochlorination

by Hui Dai, Mingyuan Zhu, Haiyang Zhang, Feng Yu, Chao Wang and Bin Dai

Catalysts 2017, 7(7), 200; https://doi.org/10.3390/catal7070200 - 30 Jun 2017

Cited by 9 | Viewed by 4991

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 AccessReview

A Review on Selective Catalytic Reduction of NO_x by NH₃ over Mn–Based Catalysts at Low Temperatures: Catalysts, Mechanisms, Kinetics and DFT Calculations

by Fengyu Gao, Xiaolong Tang, Honghong Yi, Shunzheng Zhao, Chenlu Li, Jingying Li, Yiran Shi and Xiaomi Meng

Catalysts 2017, 7(7), 199; https://doi.org/10.3390/catal7070199 - 29 Jun 2017

Cited by 209 | Viewed by 16132

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 NO_x by NH₃ from stationary sources. Mn-based LTC have been widely investigated due to its various valence [...] Read more.

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 NO_x 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 MnO_x–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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Open AccessArticle

Ordered PtSn/C Electrocatalyst: A High Performance Material for the Borohydride Electrooxidation Reaction

by Francielle Bortoloti and Antonio C. D. Angelo

Catalysts 2017, 7(7), 198; https://doi.org/10.3390/catal7070198 - 29 Jun 2017

Cited by 4 | Viewed by 3711

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 [...] Read more.

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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Open AccessArticle

The Effects of CeO₂ Nanorods and CeO₂ Nanoflakes on Ni–S Alloys in Hydrogen Evolution Reactions in Alkaline Solutions

by Meiqin Zhao, Yao Li, Haifeng Dong, Lixin Wang, Zhouhao Chen, Yazhou Wang, Zhiping Li, Meirong Xia and Guangjie Shao

Catalysts 2017, 7(7), 197; https://doi.org/10.3390/catal7070197 - 27 Jun 2017

Cited by 10 | Viewed by 6120

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 [...] Read more.

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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5319 KiB

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

by Malaya R. Nanda, Zhongshun Yuan, Hengfu Shui and Chunbao (Charles) Xu

Catalysts 2017, 7(7), 196; https://doi.org/10.3390/catal7070196 - 25 Jun 2017

Cited by 21 | Viewed by 5449

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 [...] Read more.

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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1863 KiB

Open AccessArticle

Hydrothermal Carbonation Carbon-Coated CdS Nanocomposite with Enhanced Photocatalytic Activity and Stability

by Yuanliang Ma, Zhongkun Zhao, Zhurui Shen, Qiang Cai, Huiming Ji and Leichao Meng

Catalysts 2017, 7(7), 194; https://doi.org/10.3390/catal7070194 - 24 Jun 2017

Cited by 17 | Viewed by 6091

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 [...] Read more.

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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1580 KiB

Open AccessCommunication

Intramolecular Transfer of Pd Catalyst on Carbon–Carbon Triple Bond and Nitrogen–Nitrogen Double Bond in Suzuki–Miyaura Coupling Reaction

by Takeru Kamigawara, Hajime Sugita, Koichiro Mikami, Yoshihiro Ohta and Tsutomu Yokozawa

Catalysts 2017, 7(7), 195; https://doi.org/10.3390/catal7070195 - 23 Jun 2017

Cited by 15 | Viewed by 5970

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. [...] Read more.

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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