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12092 KiB

Open AccessArticle

Mixed Zinc/Manganese on Highly Reduced Graphene Oxide: A Highly Active Nanocomposite Catalyst for Aerial Oxidation of Benzylic Alcohols

by Mohamed E. Assal, Mohammed Rafi Shaik, Mufsir Kuniyil, Mujeeb Khan, Abdulrahman Yahya Alzahrani, Abdulrahman Al-Warthan, Mohammed Rafiq H. Siddiqui and Syed Farooq Adil

Catalysts 2017, 7(12), 391; https://doi.org/10.3390/catal7120391 - 15 Dec 2017

Cited by 27 | Viewed by 7587

Abstract

Nanocomposites of highly reduced graphene oxide (HRG) and ZnO_x nanoparticles doped manganese carbonate containing different percentages of HRG were prepared via a facile co-precipitation method. The prepared sample calcined at 300 °C yielded i.e., ZnO_x(1%)–MnCO₃/(X%)HRG (where X = [...] Read more.

Nanocomposites of highly reduced graphene oxide (HRG) and ZnO_x nanoparticles doped manganese carbonate containing different percentages of HRG were prepared via a facile co-precipitation method. The prepared sample calcined at 300 °C yielded i.e., ZnO_x(1%)–MnCO₃/(X%)HRG (where X = 0–7), calcination at 400 °C and 500 °C, yielded different manganese oxides i.e., ZnO_x(1%)–MnO₂/(X%)HRG and ZnO_x(1%)–Mn₂O₃/(X%)HRG respectively. The prepared catalyst were subjected to catalytic evaluation and a comparative catalytic study between carbonates and oxides for the liquid-phase aerobic oxidation of benzylic alcohols to corresponding aldehydes using molecular oxygen as an eco-friendly oxidant without adding additives or bases. The influence of various parameters such as percentage of HRG, reaction time, catalyst amount, calcination and reaction temperature was systematically examined to optimize reaction conditions using oxidation of benzyl alcohol as a substrate model. It was found that the catalytic performance is remarkably enhanced after using HRG as catalyst co-dopant for the aerobic oxidation of alcohols, possibly owing to the presence of carbon defects and oxygenated functional groups on HRG surface. The as-synthesized catalysts were characterized by SEM, EDX, XRD, Raman, TGA, BET, and FT-IR. Under optimal conditions, the catalyst with composition ZnO_x(1%)–MnCO₃/(1%)HRG calcined at 300 °C exhibited remarkable specific activity (57.1 mmol·g⁻¹·h⁻¹) with 100% conversion of benzyl alcohol and more than 99% product selectivity within extremely short time (7 min). The as-prepared catalyst was re-used up to five consecutive times without significant decrease in its activity and selectivity. To the best of our knowledge, the achieved specific activity is the highest so far compared to the earlier reported catalysts used for the benzyl alcohol oxidation. A wide range of substituted benzylic and aliphatic alcohols were selectively oxidized into their corresponding aldehydes with complete convertibility and selectivity in short reaction times without over-oxidation to the acids. Due to their significant low cost, superior reproducibility, excellent catalytic efficiency, the ZnO_x(1%)–MnCO₃/(X%)HRG nanocomposites possess several application prospect in other organic chemistry reactions. Full article

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

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8025 KiB

Open AccessArticle

A Green Route to Copper Loaded Silica Nanoparticles Using Hyperbranched Poly(Ethylene Imine) as a Biomimetic Template: Application in Heterogeneous Catalysis

by Dimitris Tsiourvas, Aggeliki Papavasiliou, Evangelia G. Deze, Sergios K. Papageorgiou, Fotios K. Katsaros, George E. Romanos, Evangelos Poulakis, Constantine J. Philippopoulos, Qi Xin and Pegie Cool

Catalysts 2017, 7(12), 390; https://doi.org/10.3390/catal7120390 - 14 Dec 2017

Cited by 9 | Viewed by 5522

Abstract

Copper containing silica nanostructures are easily produced through a low cost versatile approach by means of hyperbranched polyethyleneimine (PEI), a water soluble dendritic polymer. This dendritic molecule enables the formation of hybrid organic/inorganic silica nanoparticles in buffered aqueous media, at room temperature and [...] Read more.

Copper containing silica nanostructures are easily produced through a low cost versatile approach by means of hyperbranched polyethyleneimine (PEI), a water soluble dendritic polymer. This dendritic molecule enables the formation of hybrid organic/inorganic silica nanoparticles in buffered aqueous media, at room temperature and neutral pH, through a biomimetic silicification process. Furthermore, the derived hybrid organic/inorganic materials dispersed in water can be easily loaded with various copper amounts, due to the presence of PEI, which, despite having been integrated in the silica network, retains its strong copper chelating ability. Following calcination, the obtained copper loaded nanopowders are characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), N₂ adsorption, Temperature programmed reduction (TPR) and UV-Vis diffuse reflectance (UV-Vis-DR) techniques and evaluated for automotive exhaust purification under simulated conditions at the stoichiometric point. Effective control over final materials’ pore structural and morphological characteristics is provided by employing different buffer solutions, i.e., tris(hydroxymethyl)aminomethane (Tris) or phosphate buffer. It was found that the enhancement of the nanopowders textural features, obtained in the presence of Tris buffer, had a great impact on the material’s catalytic behavior, improving significantly its activity towards pollutants oxidation. Full article

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

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2855 KiB

Open AccessCommunication

Low-Dimensional ReS₂/C Composite as Effective Hydrodesulfurization Catalyst

by Juan Antonio Aliaga, Trino Zepeda, Juan Francisco Araya, Francisco Paraguay-Delgado, Eglantina Benavente, Gabriel Alonso-Núñez, Sergio Fuentes and Guillermo González

Catalysts 2017, 7(12), 377; https://doi.org/10.3390/catal7120377 - 5 Dec 2017

Cited by 7 | Viewed by 5541

Abstract

Single-layer, ultrasmall ReS₂ nanoplates embedded in amorphous carbon were synthesized from a hydrothermal treatment involving ammonium perrhenate, thiourea, tetraoctylammonium bromide, and further annealing. The rhenium disulfide, obtained as a low dimensional carbon composite (ReS₂/C), was tested in the hydrodesulfurization of [...] Read more.

Single-layer, ultrasmall ReS₂ nanoplates embedded in amorphous carbon were synthesized from a hydrothermal treatment involving ammonium perrhenate, thiourea, tetraoctylammonium bromide, and further annealing. The rhenium disulfide, obtained as a low dimensional carbon composite (ReS₂/C), was tested in the hydrodesulfurization of light hydrocarbons, using 3-methylthiophene as the model molecule, and showed enhanced catalytic activity in comparison with a sulfide CoMo/γ-Al₂O₃ catalyst. The ReS₂/C composite was characterized by X-ray diffraction (XRD), Raman spectroscopy, N₂ adsorption–desorption isotherms, scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). The improved catalytic performance of this ReS₂/C composite may be ascribed to the presence of a non-stoichiometric sulfur species (ReS_2−x), the absence of stacking along the c-axis, and the ultra-small basal planes, which offer a higher proportion of structural sulfur defects at the edge of the layers, known as a critical parameter for hydrodesulfurization catalytic processes. Full article

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

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3591 KiB

Open AccessArticle

Enhanced Photodegradation Activity of Hydrogen-Terminated Si Nanowires Arrays with Different-Oriented Crystal Phases

by Longfei Song, Linqu Luo, Jianjun Song, Hongchao Zhang, Xuan Li, Shuiling Cheng, Wei Jin, Jie Tang, Lei Liu and Fengyun Wang

Catalysts 2017, 7(12), 371; https://doi.org/10.3390/catal7120371 - 1 Dec 2017

Cited by 9 | Viewed by 4077

Abstract

Although Si nanowires (NWs) arrays are superior candidates for visible light photocatalysis, reports about the photodegradation activity of various crystal-orientated Si NWs are still insufficient. Here, light-doped hydrogen-terminated Si NWs arrays with different crystal orientations were prepared via a metal-assisted chemical etching method [...] Read more.

Although Si nanowires (NWs) arrays are superior candidates for visible light photocatalysis, reports about the photodegradation activity of various crystal-orientated Si NWs are still insufficient. Here, light-doped hydrogen-terminated Si NWs arrays with different crystal orientations were prepared via a metal-assisted chemical etching method (MACE), which simply modulated the concentration of the oxidizer, H₂O₂. Their dye photodegradation activities were systematically and comprehensively investigated. When compared with Si NWs arrays with crystal orientations of (110) and (111), Si NWs arrays with (100) crystal orientation exhibit a superior photodegradation activity and stability due to the anisotropy of optical and physical properties. The n-type Si NWs arrays exhibit better photodegradation activity than the p-type Si NWs arrays of the same crystal orientation and similar length. The results provide a further understanding of the synthesis of Si NWs arrays with various orientations, and the relationships between photodegradation activity/stability and crystal orientations. Full article

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

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7107 KiB

Open AccessArticle

Engineering Pyrite-Type Bimetallic Ni-Doped CoS₂ Nanoneedle Arrays over a Wide Compositional Range for Enhanced Oxygen and Hydrogen Electrocatalysis with Flexible Property

by Guowei He, Wei Zhang, Yida Deng, Cheng Zhong, Wenbin Hu and Xiaopeng Han

Catalysts 2017, 7(12), 366; https://doi.org/10.3390/catal7120366 - 27 Nov 2017

Cited by 32 | Viewed by 6910

Abstract

The development of cheap and efficient catalytic electrodes is of great importance, to promote the sluggish overall water-splitting systems associated with the large-scale application of clean and renewable energy technologies. In this work, we report the controlled synthesis of pyrite-type bimetallic Ni-doped CoS [...] Read more.

The development of cheap and efficient catalytic electrodes is of great importance, to promote the sluggish overall water-splitting systems associated with the large-scale application of clean and renewable energy technologies. In this work, we report the controlled synthesis of pyrite-type bimetallic Ni-doped CoS₂ nanoneedle (NN) arrays supported on stainless steel (SS) (designated as Ni_xCo₁₋_xS₂ NN/SS, 0 ≤ x ≤ 1) and the related compositional influence on electrocatalytic efficiencies for the oxygen and hydrogen evolution reaction (OER/HER). Impressively, the Ni_0.33Co_0.67S₂ NN/SS displays superior activity and faster kinetics for catalyzing OER (low overpotential of 286 mV at 50 mA cm⁻²; Tafel value of 55 mV dec⁻¹) and HER (low overpotential of 350 mV at 30 mA cm⁻²; Tafel value of 76 mV dec⁻¹) than those of counterparts with other Ni/Co ratios and also monometallic Ni- or Co-based sulfides, which is attributed to the optimized balance from the improved electron transfer capability, increased exposure of electrocatalytic active sites, and favorable dissipation of gaseous products over the nanoneedle surface. Furthermore, the conductive, flexible SS support and firmly attached in-situ integrated feature, result in the flexibility and remarkable long-term stability of as-prepared binder-free Ni_0.33Co_0.67S₂ NN/SS electrode. These results demonstrate element-doping could be an efficient route at the atomic level to design new materials and further optimize the surface physicochemical properties for enhancing the overall electrochemical water splitting activity. Full article

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

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10958 KiB

Open AccessArticle

Styrene Oxidation to Valuable Compounds over Nanosized FeCo-Based Catalysts: Effect of the Third Metal Addition

by Ana Paula Saraiva Oliveira, Igor Santos Gomes, Alcineia Conceição Oliveira, Josue M. Filho, Gilberto Dantas Saraiva, João Maria Soares, Francisco Ferreira De Sousa and Adriana Campos

Catalysts 2017, 7(11), 323; https://doi.org/10.3390/catal7110323 - 30 Oct 2017

Cited by 13 | Viewed by 7854

Abstract

Nanosized FeCo-based solids were prepared via distinct preparation procedures. The catalytic performances of the solids for styrene oxidation in the presence of hydrogen peroxide were evaluated. The addition of promoters in FeCo such as Sn, Mo, or Cu was also investigated. The catalysts [...] Read more.

Nanosized FeCo-based solids were prepared via distinct preparation procedures. The catalytic performances of the solids for styrene oxidation in the presence of hydrogen peroxide were evaluated. The addition of promoters in FeCo such as Sn, Mo, or Cu was also investigated. The catalysts were characterized with XRD, Raman spectroscopy, TEM, chemical analyses, EPR and SEM-EDS. Of these solids obtained via four different methods, the catalyst prepared via the NC and CM procedures enabled a partial incorporation of the Sn into the FeCo matrix forming a very active phase, namely the Heusler alloy. This was ascribed to the high initial dispersion of Sn as a promoter into the FeCo matrix, which led to available FeCoSn (FCS) particles well dispersed and stable on the catalyst surface. In the case of incorporating Mo or Cu to the nanosized FeCo catalyst, a poor stability towards leaching was observed when operating under the same reaction conditions. Cu was much less active than both Sn and Mo, mainly leading to acetophenone, ethylbenzene, 2-phenyl ethanol, 2-phenyl acetic acid, and 2-phenyl acetaldehyde products. The best catalytic results under the optimized reaction conditions, especially at 50 °C and styrene/H₂O₂ molar ratio of 1 were achieved with nanosized FCS. This solid had a conversion of ca. 70% and selectivity for aldehydes of ca. 27%, and the selectivity for the condensation products was 29%. Full article

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

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8010 KiB

Open AccessArticle

Water–Gas Shift Reaction over Ni/CeO₂ Catalysts

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

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

Cited by 32 | Viewed by 12132

Abstract

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

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

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

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5302 KiB

Open AccessArticle

Continuous-Flow Monolithic Silica Microreactors with Arenesulphonic Acid Groups: Structure–Catalytic Activity Relationships

by Agnieszka Ciemięga, Katarzyna Maresz, Janusz J. Malinowski and Julita Mrowiec-Białoń

Catalysts 2017, 7(9), 255; https://doi.org/10.3390/catal7090255 - 30 Aug 2017

Cited by 17 | Viewed by 5037

Abstract

The performance of monolithic silica microreactors activated with sulphonic acid groups and a packed bed reactor with Amberlyst 15 resin were compared in the esterification of acetic acid with n-butanol. The monolithic microreactors were made of single silica rods with complex pore architecture, [...] Read more.

The performance of monolithic silica microreactors activated with sulphonic acid groups and a packed bed reactor with Amberlyst 15 resin were compared in the esterification of acetic acid with n-butanol. The monolithic microreactors were made of single silica rods with complex pore architecture, differing in the size of mesopores, and in particular, flow-through macropores which significantly affected the flow characteristic of the continuous system. The highest ester productivity of 105.2 mol·mol_H⁺⁻¹·h⁻¹ was achieved in microreactor M1 with the largest porosity, characterized by a total pore volume of 4 cm³·g⁻¹, mesopores with 20 nm diameter, and large flow-through macropores 30–50 μm in size. The strong impact of the permeability of the monoliths on a reaction kinetics was shown. Full article

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

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3622 KiB

Open AccessArticle

Fabrication of Crumpled Ball-Like Nickel Doped Palladium-Iron Oxide Hybrid Nanoparticles with Controlled Morphology as Effective Catalyst for Suzuki–Miyaura Coupling Reaction

by Seongwan Jang, Taewoo Kim and Kang Hyun Park

Catalysts 2017, 7(9), 247; https://doi.org/10.3390/catal7090247 - 24 Aug 2017

Cited by 12 | Viewed by 5499

Abstract

We report a facile synthetic strategy for nickel-doped palladium-iron oxide hybrid nanoparticles with controllable morphology. In this synthetic method, the morphology of the nanoparticles was regulated by the amount of triphenylphosphine used. When 1 mmol of triphenylphosphine was used as a capping agent, [...] Read more.

We report a facile synthetic strategy for nickel-doped palladium-iron oxide hybrid nanoparticles with controllable morphology. In this synthetic method, the morphology of the nanoparticles was regulated by the amount of triphenylphosphine used. When 1 mmol of triphenylphosphine was used as a capping agent, the main morphology of the nanoparticles was crumpled balls composed of nanosheets with an average particle size of 215 nm. The nanoparticles showed higher catalytic activity in the Suzuki–Miyaura coupling reaction than did other nanoparticles at equal amounts of Pd. This strategy allowed the reduction of the Pd loading in hybrid nanoparticles while still providing the performance level required for the reaction. Full article

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

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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 4444

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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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 4982

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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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 6036

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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3570 KiB

Open AccessArticle

Effect of Ce/Y Addition on Low-Temperature SCR Activity and SO₂ and H₂O Resistance of MnO_x/ZrO₂/MWCNTs Catalysts

by Lifu Dong, Yinming Fan, Wei Ling, Chao Yang and Bichun Huang

Catalysts 2017, 7(6), 181; https://doi.org/10.3390/catal7060181 - 8 Jun 2017

Cited by 20 | Viewed by 5398

Abstract

The effects of SO₂ and H₂O on the low-temperature selective catalytic reduction (SCR) activity over MnO_x/ZrO₂/MWCNTs and MnO_x/ZrO₂/MWCNTs catalysts modified by Ce or Y was studied. MnCeZr and MnYZr catalysts reached nearly [...] Read more.

The effects of SO₂ and H₂O on the low-temperature selective catalytic reduction (SCR) activity over MnO_x/ZrO₂/MWCNTs and MnO_x/ZrO₂/MWCNTs catalysts modified by Ce or Y was studied. MnCeZr and MnYZr catalysts reached nearly 100% and 93.9% NO_x conversions at 200 °C and 240 °C, respectively. They displayed a better SO₂ tolerance, and the effect of H₂O was negligible. The structural properties of the catalysts were characterized by XRD, H₂-TPR, XPS, and FTIR before and after the reaction. The results showed that Ce could increase the mobility of the oxygen and improve the valence and the oxidizability of manganese, while the effect of Y was the opposite. This might be the main reason why the catalytic activity of MnCeZr was better than MnYZr in the presence or absence of SO₂ and H₂O. Doping Ce or Y broadened the active temperature window. Ce or Y, which existed in the catalysts with a high dispersion or at the amorphous state, preferred to react with SO₂ to form sulfate species, and protected the manganese active sites from combing with SO₂ to some extent, which coincided with the theory of ionic polarization. Full article

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

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4071 KiB

Open AccessArticle

Near-Graphite Coke Deposit on Nano-HZSM-5 Aggregates for Methanol to Propylene and Butylene Reaction

by Yu Sang, Aihua Xing, Chuanfu Wang, Zhihua Han and Yulong Wu

Catalysts 2017, 7(6), 171; https://doi.org/10.3390/catal7060171 - 1 Jun 2017

Cited by 16 | Viewed by 5574

Abstract

Nanocrystal HZSM-5 zeolite aggregates with different SiO₂/Al₂O₃ molar ratios were prepared under low temperature and were used to catalyze the conversion of methanol to propylene and butene. The coke location, coke content, and coke species deposited on HZSM-5 [...] Read more.

Nanocrystal HZSM-5 zeolite aggregates with different SiO₂/Al₂O₃ molar ratios were prepared under low temperature and were used to catalyze the conversion of methanol to propylene and butene. The coke location, coke content, and coke species deposited on HZSM-5 aggregates were investigated. The near-graphite carbon on the external surface of HZSM-5 zeolite (SiO₂/Al₂O₃ molar ratio = 400) was distinguished by transmission electron microscopy (TEM) and energy dispersive spectrometer (EDS). The carbon distributions in the micropores and on the external surface of the spent HZSM-5 were revealed by thermogravimetric analysis (TGA) and Brunauer-Emmett-Teller (BET) results. Coke preferred to deposit in the mircopores of low SiO₂/Al₂O₃ molar ratio samples (200, 300) with relatively uniform Al distribution, while coke also preferred to deposit on the external surface and in the intergranular spaces of high SiO₂/Al₂O₃ molar ratio sample (400) with an obviously poor Al core and rich Al shell. Full article

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

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17154 KiB

Open AccessArticle

Highly Dispersed PdNPs/α-Al₂O₃ Catalyst for the Selective Hydrogenation of Acetylene Prepared with Monodispersed Pd Nanoparticles

by Huoli Zhang, Youchao Wang, Yan Wang, Jianliang Cao, Peng Kang, Qingjie Tang and Mingjie Ma

Catalysts 2017, 7(5), 128; https://doi.org/10.3390/catal7050128 - 28 Apr 2017

Cited by 14 | Viewed by 7206

Abstract

Pd nanoparticles (PdNPs) stabilized by methyl cellulose (MC) were synthesized in an aqueous solution, which are monodispersed nanoparticles. PdNPs/α-Al₂O₃ catalyst was prepared with monodispersed PdNPs and showed better catalytic performance than Pd/α-Al₂O₃ catalyst prepared by the incipient [...] Read more.

Pd nanoparticles (PdNPs) stabilized by methyl cellulose (MC) were synthesized in an aqueous solution, which are monodispersed nanoparticles. PdNPs/α-Al₂O₃ catalyst was prepared with monodispersed PdNPs and showed better catalytic performance than Pd/α-Al₂O₃ catalyst prepared by the incipient wetness impregnation method using Pd(NO₃)₂ as a precursor. The catalysts were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD) and inductively coupled plasma mass spectrometry (ICP-MS). It was found that monodispersed PdNPs were spherical or elliptical nanoparticles with exposed (111) and (100) facets, and the PdNPs/α-Al₂O₃ catalyst showed a more concentrated distribution of Pd particles on the surface of α-Al₂O₃ support than the Pd/α-Al₂O₃ catalyst. The preparation method achieved the highly dispersed PdNPs/α-Al₂O₃ catalyst with smaller Pd particle size and decreased the aggregation of Pd active sites, which was responsible for higher acetylene conversion and ethylene selectivity. Full article

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

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Review

Jump to: Research

5517 KiB

Open AccessReview

Recent Advances in Transition-Metal-Mediated Electrocatalytic CO₂ Reduction: From Homogeneous to Heterogeneous Systems

by Da-Ming Feng, Yun-Pei Zhu, Ping Chen and Tian-Yi Ma

Catalysts 2017, 7(12), 373; https://doi.org/10.3390/catal7120373 - 1 Dec 2017

Cited by 53 | Viewed by 9692

Abstract

Global climate change and increasing demands for clean energy have brought intensive interest in the search for proper electrocatalysts in order to reduce carbon dioxide (CO₂) to higher value carbon products such as hydrocarbons. Recently, transition-metal-centered molecules or organic frameworks have [...] Read more.

Global climate change and increasing demands for clean energy have brought intensive interest in the search for proper electrocatalysts in order to reduce carbon dioxide (CO₂) to higher value carbon products such as hydrocarbons. Recently, transition-metal-centered molecules or organic frameworks have been reported to show outstanding electrocatalytic activity in the liquid phase. Their d-orbital electrons are believed to be one of the key factors to capture and convert CO₂ molecules to value-added low-carbon fuels. In this review, recent advances in electrocatalytic CO₂ reduction have been summarized based on the targeted products, ranging from homogeneous reactions to heterogeneous ones. Their advantages and fallbacks have been pointed out and the existing challenges, especially with respect to the practical and industrial application are addressed. Full article

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

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Two-Dimensional Material Molybdenum Disulfides as Electrocatalysts for Hydrogen Evolution

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

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

Cited by 78 | Viewed by 10936

Abstract

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

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

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

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