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Volume 9
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Catalysts, Volume 9, Issue 6 (June 2019) – 77 articles

Cover Story (view full-size image): In this paper, Fujita and co-workers report on a new system for transfer hydrogenation of various ketones and aldehydes using glucose as a hydrogen donor catalyzed by an iridium complex. In this catalytic system, transfer hydrogenation reaction proceeds based on the cooperativity of iridium and a functional ligand. It should be noted that glucose is inexpensive, easily obtained from natural renewable resources, and safe to handle. Furthermore, environmentally benign water can be used as a solvent in the present catalytic system. View this paper.
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16 pages, 16183 KiB  
Article
Oxygen Evolution Reaction of Co-Mn-O Electrocatalyst Prepared by Solution Combustion Synthesis
by Kyoung Ryeol Park, Jae Eun Jeon, Ghulam Ali, Yong-Ho Ko, Jaewoong Lee, HyukSu Han and Sungwook Mhin
Catalysts 2019, 9(6), 564; https://doi.org/10.3390/catal9060564 - 24 Jun 2019
Cited by 17 | Viewed by 6616
Abstract
High-performance oxygen evolution reaction (OER) electrocatalysts are needed to produce hydrogen for energy generation through a carbon-free route. In this work, the solution combustion synthesis (SCS) method was employed to synthesize mixed phases of Co- and Mn-based oxides, and the relationships between the [...] Read more.
High-performance oxygen evolution reaction (OER) electrocatalysts are needed to produce hydrogen for energy generation through a carbon-free route. In this work, the solution combustion synthesis (SCS) method was employed to synthesize mixed phases of Co- and Mn-based oxides, and the relationships between the crystalline structure and the catalytic properties in the mixed phases were established. The mixed phases of Co- and Mn-based oxides shows promising OER properties, such as acceptable overpotential (450 mV for 10 mA∙cm−2) and Tafel slope (35.8 mV∙dec−1), highlighting the use of the mixed phases of Co- and Mn-based oxides as a new efficient catalysts for water splitting. Electronic structure of the mixed phases of Co- and Mn based oxides is studied in detail to give insight for the origin of high catalytic activities. In addition, excellent long-term stability for OER in alkaline media is achieved for the mixed phase of Co- and Mn based oxides. Full article
(This article belongs to the Special Issue Electrocatalytic Water Oxidation)
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12 pages, 4408 KiB  
Article
Microstructural Changes in La0.5Ca0.5Mn0.5Fe0.5O3 Solid Solutions under the Influence of Catalytic Reaction of Methane Combustion
by Evgeny Yu. Gerasimov, Vladimir A. Rogov, Igor P. Prosvirin, Lyubov A. Isupova and Sergey V. Tsybulya
Catalysts 2019, 9(6), 563; https://doi.org/10.3390/catal9060563 - 24 Jun 2019
Cited by 10 | Viewed by 3439
Abstract
This article attempts to study changes in the microstructure of solid solutions with the perovskite structure La0.5Ca0.5Mn0.5Fe0.5O3 under the action of the methane oxidation reaction medium. By the methods of XRD, XPS and HRTEM [...] Read more.
This article attempts to study changes in the microstructure of solid solutions with the perovskite structure La0.5Ca0.5Mn0.5Fe0.5O3 under the action of the methane oxidation reaction medium. By the methods of XRD, XPS and HRTEM the initial condition of the structure and the surface of the perovskite were both investigated. A feature of the structure of this solid solution is the presence of planar defects in the direction of the planes (101). After the methane oxidation reaction, a similar study of perovskite structure was conducted to obtain the changes. It was shown that under the action of the reaction medium, Ca1−xMnxO particles form on the surface of the perovskite phase, while planar defects in La0.5Ca0.5Mn0.5Fe0.5O3 structure remain. In situ XRD experiments on perovskite calcination in helium current up to 750 °C showed the formation of a similar Ca1−xMnxO phase on the perovskite surface. Full article
(This article belongs to the Special Issue Catalytic Concepts for Methane Combustion)
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4 pages, 1037 KiB  
Comment
1,4-NADH Biomimetic Co-Factors with Horse Liver Alcohol Dehydrogenase (HLADH), Utilizing [Cp*Rh(bpy)H](OTf) for Co-factor Regeneration, Do in Fact, Produce Chiral Alcohols from Reactions with Achiral Ketones
by Richard H. Fish
Catalysts 2019, 9(6), 562; https://doi.org/10.3390/catal9060562 - 24 Jun 2019
Cited by 7 | Viewed by 4007
Abstract
In this Catalysts Comment Article, we will present our latest published results [...] Full article
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11 pages, 3985 KiB  
Article
Photocatalytic Performance of NiO/NiTiO3 Composite Nanofiber Films
by Bozhi Yang, Xuefeng Bai, Jiaxuan Wang, Minghao Fang, Xiaowen Wu, Yan’gai Liu, Zhaohui Huang, Cheng-Yen Lao and Xin Min
Catalysts 2019, 9(6), 561; https://doi.org/10.3390/catal9060561 - 24 Jun 2019
Cited by 27 | Viewed by 5337
Abstract
Photocatalytic degradation of pollutants is one of the cleanest technologies for environmental remediation. Herein, we prepared NiO/NiTiO3 heterostructure nanofiber (200 nm) films by electrospinning and high temperature heat treatment, using nickel acetate and tetrabutyltitanate as nickel and titanium sources, respectively. The NiO/NiTiO [...] Read more.
Photocatalytic degradation of pollutants is one of the cleanest technologies for environmental remediation. Herein, we prepared NiO/NiTiO3 heterostructure nanofiber (200 nm) films by electrospinning and high temperature heat treatment, using nickel acetate and tetrabutyltitanate as nickel and titanium sources, respectively. The NiO/NiTiO3 heterostructure has advantages of good photodegradation rate constant and stability. By controlling the temperature, we can optimize the phase composition of these nanofibers for better photocatalytic performance. Based on our findings of the Rhodamine B degradation results, the best performance was obtained with 10% NiO and 90% NiTiO3; 92.9% of the Rhodamine B (5 mg/L) was degraded after reaction under full spectrum irradiation for 60 min. More importantly, the repeating test showed that these nanofiber films can remain active and stable after multiple cycles. The mechanisms of the photocatalysis reactions were also discussed. This demonstration provides a guideline in designing a new photocatalyst that we hope will serve the environmental needs for this and the coming century. Full article
(This article belongs to the Special Issue Electrocatalysis/Photocatalysis for CO2 Conversion, H2 Production, and Pollutant Removal)
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15 pages, 4082 KiB  
Article
Insights over Titanium Modified FeMgOx Catalysts for Selective Catalytic Reduction of NOx with NH3: Influence of Precursors and Crystalline Structures
by Liting Xu, Qilei Yang, Lihua Hu, Dong Wang, Yue Peng, Zheru Shao, Chunmei Lu and Junhua Li
Catalysts 2019, 9(6), 560; https://doi.org/10.3390/catal9060560 - 24 Jun 2019
Cited by 10 | Viewed by 3299
Abstract
Titanium modified FeMgOx catalysts with different precursors were prepared by coprecipitation method with microwave thermal treatment. The iron precursor is a key factor affecting the surface active component. The catalyst using FeSO4 and Mg(NO3)2 as precursors exhibited enhanced [...] Read more.
Titanium modified FeMgOx catalysts with different precursors were prepared by coprecipitation method with microwave thermal treatment. The iron precursor is a key factor affecting the surface active component. The catalyst using FeSO4 and Mg(NO3)2 as precursors exhibited enhanced catalytic activity from 225 to 400 °C, with a maximum NOx conversion of 100%. Iron oxides existed as γ-Fe2O3 in this catalyst. They exhibited highly enriched surface active oxygen and surface acidity, which were favorable for low-temperature selective catalytic reduction (SCR) reaction. Besides, it showed advantage in surface area, spherical particle distribution and pores connectivity. Amorphous iron-magnesium-titanium mixed oxides were the main phase of the catalysts using Fe(NO3)3 as a precursor. This catalyst exhibited a narrow T90 of 200/250–350 °C. Side reactions occurred after 300 °C producing NOx, which reduced the NOx conversion. The strong acid sites inhibited the side reactions, and thus improved the catalytic performance above 300 °C. The weak acid sites appeared below 200 °C, and had a great impact on the low-temperature catalytic performance. Nevertheless, amorphous iron-magnesium-titanium mixed oxides blocked the absorption and activation between NH3 and the surface strong acid sites, which was strengthened on the γ-Fe2O3 surface. Full article
(This article belongs to the Special Issue Rational Design of Non-precious Metal Oxide Catalysts by Means of Advanced Synthetic and Promotional Routes)
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15 pages, 4395 KiB  
Article
Preparation of Palladium Nanoparticles Decorated Polyethyleneimine/Polycaprolactone Composite Fibers Constructed by Electrospinning with Highly Efficient and Recyclable Catalytic Performances
by Cuiru Wang, Juanjuan Yin, Shiqi Han, Tifeng Jiao, Zhenhua Bai, Jingxin Zhou, Lexin Zhang and Qiuming Peng
Catalysts 2019, 9(6), 559; https://doi.org/10.3390/catal9060559 - 22 Jun 2019
Cited by 92 | Viewed by 6786
Abstract
Nano-sized palladium nanoparticles showed high catalytic activity with severe limitations in catalytic field due to the tendency to aggregate. A solid substrate with large specific surface area is an ideal carrier for palladium nanoparticles. In present work, polyethyleneimine/polycaprolactone/Pd nanoparticles (PEI/PCL@PdNPs) composite catalysts were [...] Read more.
Nano-sized palladium nanoparticles showed high catalytic activity with severe limitations in catalytic field due to the tendency to aggregate. A solid substrate with large specific surface area is an ideal carrier for palladium nanoparticles. In present work, polyethyleneimine/polycaprolactone/Pd nanoparticles (PEI/PCL@PdNPs) composite catalysts were successfully designed and prepared by electrospinning and reduction methods using PEI/PCL elexctrospun fiber as carrier. The added PEI component effectively regulated the microscopic morphology of the PEI/PCL fibers, following a large number of pit structures which increased the specific surface area of the electrospun fibers and provided active sites for loading of the palladium particles. The obtained PEI/PCL@PdNPs catalysts for reductions of 4-nitrophenol (4-NP) and 2-nitroaniline (2-NA) exhibited extremely efficient, stable, and reusable catalytic performance. It was worth mentioning that the reaction rate constant of catalytic reduction of 4-NP was as high as 0.16597 s−1. Therefore, we have developed a highly efficient catalyst with potential applications in the field of catalysis and water treatment. Full article
(This article belongs to the Special Issue New Trends in the Photocatalytic Removal of Organic Dyes)
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14 pages, 4911 KiB  
Article
Oxygen Vacancy Enhanced Photoreduction Cr(VI) on Few-Layers BiOBr Nanosheets
by Yin Peng, Pengfei Kan, Qian Zhang and Yinghua Zhou
Catalysts 2019, 9(6), 558; https://doi.org/10.3390/catal9060558 - 21 Jun 2019
Cited by 30 | Viewed by 5366
Abstract
2D nanomaterials, with unique structural and electronic features, had been demonstrated as excellent photocatalysts, whose catalytic properties could be tunable with surface defect engineering. In this work, few-layer BiOBr nanosheets with oxygen vacancies (BiOBr-Ov) have been fabricated by a simple solvothermal reaction with [...] Read more.
2D nanomaterials, with unique structural and electronic features, had been demonstrated as excellent photocatalysts, whose catalytic properties could be tunable with surface defect engineering. In this work, few-layer BiOBr nanosheets with oxygen vacancies (BiOBr-Ov) have been fabricated by a simple solvothermal reaction with the help of ethylene glycol. The obtained BiOBr-Ov exhibited the superior photocatalytic performance with a complete reduction of Cr(VI) (20 mg/L) within 12 min by visible light irradiation. Moreover, Cr(VI) with a high concentration (such as 30 mg/L) only requires 2 min to be photoreduced completely under solar light irradiation. The enhanced photocatalytic performance is contributed to the existence of oxygen vacancies. It has been proved by the results of electrochemical impedance and photocurrent that oxygen vacancies can effectively suppress recombination of photogenerated carriers. Full article
(This article belongs to the Special Issue Photocatalysis: Activity of Nanomaterials)
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16 pages, 2929 KiB  
Article
The Impact of CeO2 Loading on the Activity and Stability of PdO/γ-AlOOH/γ-Al2O3 Monolith Catalysts for CH4 Oxidation
by Hamad AlMohamadi and Kevin J. Smith
Catalysts 2019, 9(6), 557; https://doi.org/10.3390/catal9060557 - 21 Jun 2019
Cited by 8 | Viewed by 3427
Abstract
This study reports on the activity and stability of PdO/γ-AlOOH/γ-Al2O3 monolith catalysts, promoted with varying amounts of CeO2, for CH4 oxidation. Although the beneficial effects of CeO2 have been reported for powdered catalysts, this study used [...] Read more.
This study reports on the activity and stability of PdO/γ-AlOOH/γ-Al2O3 monolith catalysts, promoted with varying amounts of CeO2, for CH4 oxidation. Although the beneficial effects of CeO2 have been reported for powdered catalysts, this study used a cordierite (2MgO.2Al2O3.5SiO2) mini-monolith (400 cells per square inch, 1 cm diameter × 2.5 cm length; ~52 cells), washcoated with a suspension of γ-Al2O3 combined with boehmite (γ-AlOOH), followed by sequential deposition of Ce and Pd (0.5 wt.%) by wetness impregnation. The monolith catalysts’ CH4 oxidation activity and stability were assessed in the presence of CO, CO2, H2O and SO2 at low temperature (≤550 °C), relevant to emission control from lean-burn natural gas vehicles (NGVs). The CeO2 loading (0 to 4 wt.%) did not significantly impact the adhesion and thermal stability of the washcoat, but CeO2 reduced the inhibition of CH4 oxidation by H2O and SO2. The catalyst activity, measured by temperature-programmed methane oxidation (TPO) in a dry feed gas with 0.07 vol.% CH4, showed that adding CeO2 to the γ-AlOOH/γ-Al2O3 washcoat suppressed the activity of the catalysts; whereas, CeO2 improved the catalyst activity when H2O (2 and 5 vol.%) was present in the feed gas. Moreover, adding CeO2 decreased catalyst deactivation that occurred in the presence of 10 vol.% H2O and 5 ppmv SO2 at 500 °C, measured over a 25 h time-on-stream (TOS) period. The highest catalyst activity and stability for CH4 oxidation in the presence of H2O was obtained by adding 2 wt.% CeO2 to the washcoat. Full article
(This article belongs to the Special Issue Catalytic Concepts for Methane Combustion)
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8 pages, 2228 KiB  
Article
Fabrication of C/Co-FeS2/CoS2 with Highly Efficient Hydrogen Evolution Reaction
by Yuan Gao, Ka Wang, Haizeng Song, Han Wu, Shancheng Yan, Xin Xu and Yi Shi
Catalysts 2019, 9(6), 556; https://doi.org/10.3390/catal9060556 - 21 Jun 2019
Cited by 12 | Viewed by 5768
Abstract
The mainstream strategy for designing hydrogen electrocatalysts is to adjust their surface electronic structure; however, the conductivity of the electrocatalyst and the synergy with its substrate are still challenges to overcome. In this work, we report a carbon-doped Co-FeS2/CoS2 (C/Co-FeS [...] Read more.
The mainstream strategy for designing hydrogen electrocatalysts is to adjust their surface electronic structure; however, the conductivity of the electrocatalyst and the synergy with its substrate are still challenges to overcome. In this work, we report a carbon-doped Co-FeS2/CoS2 (C/Co-FeS2/CoS2) electrode, prepared via a hydrothermal process with carbon cloth (CC) as the substrate and carbon doping. The C/Co-FeS2/CoS2 electrode shows excellent catalytic activity in the hydrogen evolution reaction (HER) with an overpotential of 88 mV at a current density of −10 mA∙cm−2 in 0.5 M H2SO4 solution. The Tafel slope is 66 mV∙dec−1. Such superior performance is attributed to the high electrical conductivity of the electrocatalyst and its synergy with the substrate. Our study provides an efficient alternative in the field of electrocatalysis. Full article
(This article belongs to the Section Electrocatalysis)
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14 pages, 2633 KiB  
Article
Synergistic Effect in Zinc Phthalocyanine—Nanoporous Gold Hybrid Materials for Enhanced Photocatalytic Oxidations
by David Steinebrunner, Günter Schnurpfeil, Andre Wichmann, Dieter Wöhrle and Arne Wittstock
Catalysts 2019, 9(6), 555; https://doi.org/10.3390/catal9060555 - 20 Jun 2019
Cited by 16 | Viewed by 6331
Abstract
Nanoporous gold (npAu) supports were prepared as disks and powders by corrosion of Au-Ag alloys. The npAu materials have pore sizes in the range of 40 nm as shown by scanning electron microscopy (SEM). The surface was modified by a self-assembled monolayer (SAM) [...] Read more.
Nanoporous gold (npAu) supports were prepared as disks and powders by corrosion of Au-Ag alloys. The npAu materials have pore sizes in the range of 40 nm as shown by scanning electron microscopy (SEM). The surface was modified by a self-assembled monolayer (SAM) with an azidohexylthioate and then functionalized by a zinc (II) phthalocyanine (ZnPc) derivative using “click chemistry”. By atomic absorption spectroscopy (AAS) and inductively coupled plasma mass spectrometry (ICP-MS) the content of zinc was determined and the amount of immobilized ZnPc on npAu was calculated. Energy-dispersive X-ray (EDX) spectroscopy gave information about the spatial distribution of the ZnPc throughout the whole porous structure. NpAu and ZnPc are both absorbing light in the visible region, therefore, the heterogeneous hybrid systems were studied as photocatalysts for photooxidations using molecular oxygen. By irradiation of the hybrid system, singlet oxygen is formed, which was quantified using the photooxidation of 1,3-diphenylisobenzofuran (DPBF) as a selective singlet oxygen quencher. The illuminated surface area of the npAu-ZnPc hybrid system and the coverage of the ZnPc were optimized. The synergistic effect between the plasmon resonance of npAu and the photosensitizer ZnPc was shown by selective irradiation and excitation of only the phthalocyanine, the plasmon resonance of the npAu support and both absorption bands simultaneously, resulting in an enhanced photooxidation activity by nearly an order of magnitude. Full article
(This article belongs to the Special Issue Porous Materials for Photocatalysis and Energy)
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13 pages, 3461 KiB  
Article
Ni(II)-Aroylhydrazone Complexes as Catalyst Precursors Towards Efficient Solvent-Free Nitroaldol Condensation Reaction
by Manas Sutradhar, Tannistha Roy Barman, Armando J. L. Pombeiro and Luísa M.D.R.S. Martins
Catalysts 2019, 9(6), 554; https://doi.org/10.3390/catal9060554 - 20 Jun 2019
Cited by 12 | Viewed by 4614
Abstract
The aroylhydrazone Schiff bases 2-hydroxy-(2-hydroxybenzylidene)benzohydrazide and (2,3-dihydroxybenzylidene)-2-hydroxybenzohydrazide have been used to synthesize the bi- and tri-nuclear Ni(II) complexes [Ni2(L1)2(MeOH)4] (1) and [Ni3(HL2)2(CH3OH)8]· (NO [...] Read more.
The aroylhydrazone Schiff bases 2-hydroxy-(2-hydroxybenzylidene)benzohydrazide and (2,3-dihydroxybenzylidene)-2-hydroxybenzohydrazide have been used to synthesize the bi- and tri-nuclear Ni(II) complexes [Ni2(L1)2(MeOH)4] (1) and [Ni3(HL2)2(CH3OH)8]· (NO3)2 (2). Both complexes have been characterized by elemental analysis, spectroscopic techniques [IR spectroscopy and electrospray ionization-mass spectrometry (ESI-MS)], and single-crystal X-ray crystallography. The coordination behavior of the two ligands is different in the complexes: The ligand exhibits the keto form in 2, while coordination through enol form was found in 1. Herein, the catalytic activity of 1 and 2 has been compared with the nitroaldol condensation reaction under various conditions. Complex 2 exhibits the highest activity towards solvent-free conditions. Full article
(This article belongs to the Special Issue Recent Advances in Homogeneous Catalysis)
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22 pages, 4562 KiB  
Article
Wet Peroxide Oxidation of Chlorobenzenes Catalyzed by Goethite and Promoted by Hydroxylamine
by David Lorenzo, Carmen M. Dominguez, Arturo Romero and Aurora Santos
Catalysts 2019, 9(6), 553; https://doi.org/10.3390/catal9060553 - 20 Jun 2019
Cited by 18 | Viewed by 4452
Abstract
In this work, the abatement of several chlorobenzenes commonly found as pollutants in the aqueous phase has been carried out by catalytic wet peroxide oxidation using goethite as the catalyst and hydroxylamine as the promotor. Spiked water with monochlorobenzene and different positional isomers [...] Read more.
In this work, the abatement of several chlorobenzenes commonly found as pollutants in the aqueous phase has been carried out by catalytic wet peroxide oxidation using goethite as the catalyst and hydroxylamine as the promotor. Spiked water with monochlorobenzene and different positional isomers of dichlorobenzene, trichlorobenzene, and tetrachlorobenzene, at concentrations ranging from 0.4 to 16.9 mg L−1 was treated. Runs were carried out batch-way, at room conditions, without headspace. The heterogeneous catalyst was commercial goethite, with a specific surface area (SBET) of 10.24 m2 g−1 and a total iron content of 57.3 wt%. Iron acts as a catalyst of hydrogen peroxide decomposition to hydroxyl radicals. Hydroxylamine (in a range from 0 to 4.9 mM) was added to enhance the iron redox cycle from Fe (III) to Fe (II), remarkably increasing the radical production rate and therefore, the conversion of chlorobenzenes. Iron was stable (not leached to the aqueous phase) even at the lowest pH tested (pH = 1). The effect of pH (from 2 to 7), hydrogen peroxide (from 1 to 10 times the stoichiometric dosage), hydroxylamine, and catalyst concentration (from 0.25 to 1 g/L) was studied. Pollutant removal increased with hydroxylamine and hydrogen peroxide concentration. An operating conditions study demonstrated that the higher the hydroxylamine and hydrogen peroxide concentrations, the higher the removal of pollutants. The optimal pH value and catalyst concentration was 3 and 0.5 g L−1, respectively. Operating with 2.4 mM of hydroxylamine and 10 times the stoichiometric H2O2 amount, a chlorobenzenes conversion of 90% was achieved in 2.5 h. Additionally, no toxic byproducts were obtained. Full article
(This article belongs to the Special Issue Trends in Catalytic Wet Peroxide Oxidation Processes)
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0 pages, 141 KiB  
Retraction
RETRACTED: Raja et al. Transient Operation: A Catalytic Chemoselective Hydrogenation of 2-Methyl-3-Butyn-2-ol via a Cooperative Pd and Radiofrequency Heating Directed Kinetic Resolution. Catalysts 2019, 9, 283
by Catalysts Editorial Office
Catalysts 2019, 9(6), 552; https://doi.org/10.3390/catal9060552 - 19 Jun 2019
Viewed by 3317
Abstract
We have been made aware that figures, tables, experimental data, and a whole paragraph in the results and discussion section of this article [...] Full article
12 pages, 2617 KiB  
Article
Investigation of C1 + C1 Coupling Reactions in Cobalt-Catalyzed Fischer-Tropsch Synthesis by a Combined DFT and Kinetic Isotope Study
by Yanying Qi, Jia Yang, Anders Holmen and De Chen
Catalysts 2019, 9(6), 551; https://doi.org/10.3390/catal9060551 - 19 Jun 2019
Cited by 17 | Viewed by 4359
Abstract
Understanding the chain growth mechanism is of vital importance for the development of catalysts with enhanced selectivity towards long-chain products in cobalt-catalyzed Fischer-Tropsch synthesis. Herein, we discriminate various C1 + C1 coupling reactions by theoretical calculations and kinetic isotope experiments. CH [...] Read more.
Understanding the chain growth mechanism is of vital importance for the development of catalysts with enhanced selectivity towards long-chain products in cobalt-catalyzed Fischer-Tropsch synthesis. Herein, we discriminate various C1 + C1 coupling reactions by theoretical calculations and kinetic isotope experiments. CHx(x=0−3), CO, HCO, COH, and HCOH are considered as the chain growth monomer respectively, and 24 possible coupling reactions are first investigated by theoretical calculations. Eight possible C1 + C1 coupling reactions are suggested to be energetically favorable because of the relative low reaction barriers. Moreover, five pathways are excluded where the C1 monomers show low thermodynamic stability. Effective chain propagation rates are calculated by deconvoluting from reaction rates of products, and an inverse kinetic isotope effect of the C1 + C1 coupling reaction is observed. The theoretical kinetic isotope effect of CO + CH2 is inverse, which is consistent with the experimental observation. Thus, the CO + CH2 pathway, owing to the relatively lower barrier, the high thermodynamic stability, and the inverse kinetic isotope effect, is suggested to be a favorable pathway. Full article
(This article belongs to the Special Issue Iron and Cobalt Catalysts)
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21 pages, 5694 KiB  
Article
Effect of Metal Loading in Unpromoted and Promoted CoMo/Al2O3–TiO2 Catalysts for the Hydrodeoxygenation of Phenol
by J. Andrés Tavizón-Pozos, Carlos E. Santolalla-Vargas, Omar U. Valdés-Martínez and José Antonio de los Reyes Heredia
Catalysts 2019, 9(6), 550; https://doi.org/10.3390/catal9060550 - 19 Jun 2019
Cited by 11 | Viewed by 4844
Abstract
This paper reports the effects of changes in the supported active phase concentration over titania containing mixed oxides catalysts for hydrodeoxygenation (HDO). Mo and CoMo supported on sol–gel Al2O3–TiO2 (Al/Ti = 2) were synthetized and tested for the [...] Read more.
This paper reports the effects of changes in the supported active phase concentration over titania containing mixed oxides catalysts for hydrodeoxygenation (HDO). Mo and CoMo supported on sol–gel Al2O3–TiO2 (Al/Ti = 2) were synthetized and tested for the HDO of phenol in a batch reactor at 5.5 MPa, 593 K, and 100 ppm S. Characterization results showed that the increase in Mo loading led to an increase in the amount of oxide Mo species with octahedral coordination (MoOh), which produced more active sites and augmented the catalytic activity. The study of the change of Co concentration allowed prototypes of the oxide species and their relationship with the CoMo/AT2 activity to be described. Catalysts were tested at four different Co/(Co + Mo) ratios. The results presented a correlation between the available fraction of CoOh and the catalytic performance. At low CoOh fractions (Co/(Co + Mo) = 0.1), Co could not promote all MoS2 slabs and metallic sites from this latter phase performed the reaction. Also, at high Co/(Co + Mo) ratios (0.3 and 0.4), there was a loss of Co species. The Co/(Co + Mo) = 0.2 ratio presented an optimum amount of available CoOh and catalytic activity since the XPS results indicated a higher concentration of the CoMoS phase than at a higher ratio. Full article
(This article belongs to the Special Issue Catalysis for Global Development. Contributions around the Iberoamerican Federation of Catalysis)
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7 pages, 3715 KiB  
Communication
Effect of Structure-Controlled Ruthenium Oxide by Nanocasting in Electrocatalytic Oxygen and Chlorine Evolution Reactions in Acidic Conditions
by Jisu Han, Hyung Jun An, Tae-Wan Kim, Kwan-Young Lee, Hyung Ju Kim, Youngmin Kim and Ho-Jeong Chae
Catalysts 2019, 9(6), 549; https://doi.org/10.3390/catal9060549 - 19 Jun 2019
Cited by 14 | Viewed by 5063
Abstract
RuO2 has been used for various applications because of its good catalytic properties. To further improve its electrocatalytic properties, we used a nanocasting technique. By using this technique, we obtained structure-controlled (SC) RuO2 with a high surface area and an ordered [...] Read more.
RuO2 has been used for various applications because of its good catalytic properties. To further improve its electrocatalytic properties, we used a nanocasting technique. By using this technique, we obtained structure-controlled (SC) RuO2 with a high surface area and an ordered porous structure, which created enhanced electrocatalytic properties over commercial RuO2 nanoparticles for both oxygen and chlorine evolution reactions. Full article
(This article belongs to the Special Issue Catalytic Properties of Nanostructured Electrodic Materials)
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16 pages, 4859 KiB  
Article
Computational Investigation of Nickel-Mediated B–H Activation and Regioselective Cage B–C(sp2) Coupling of o-Carborane
by Wei-Hua Mu, Wen-Zhu Liu, Rui-Jiao Cheng, Li-Juan Dou, Pin Liu and Qiang Hao
Catalysts 2019, 9(6), 548; https://doi.org/10.3390/catal9060548 - 18 Jun 2019
Cited by 3 | Viewed by 3879
Abstract
Density functional theory (DFT) methods including LC-ωPBE, CAM-B3LYP, B3LYP, and B3LYP-D3, combined with double Zeta all-electron DZVP basis set, have been employed to conduct computational investigations on nickel-mediated reaction of o-carboranylzirconacycle, n-hexene, and 2-bromophenyltrimethylsilylacetylene in toluene solution. A multistep mechanism leading [...] Read more.
Density functional theory (DFT) methods including LC-ωPBE, CAM-B3LYP, B3LYP, and B3LYP-D3, combined with double Zeta all-electron DZVP basis set, have been employed to conduct computational investigations on nickel-mediated reaction of o-carboranylzirconacycle, n-hexene, and 2-bromophenyltrimethylsilylacetylene in toluene solution. A multistep mechanism leading to the C,C,B-substituted carborane-fused tricyclics, including (1) sequential insertion of alkene and alkyne into Ni–C bonds; (2) double 1,2-migration of the TMS group; (3) B–H activation assisted by Cs2CO3 additive; and (4) reduction cage B–C (sp2) coupling, was proposed. Among these steps, the B–H activation of o-carborane was located as rate-determining step (RDS). With assistance of Cs2CO3 additive (replaced by K2CO3 in simulation), the RDS free-energy barrier at PCM-LC-ωPBE/DZVP level was calculated to be 23.1–23.9 kcal·mol−1, transferring to a half-life of 3.9–15.1 h at 298 K. The predicted half-life coincides well with 80% experimental yields of C,C,B-substituted carborane-fused tricyclics after 12 h. Kinetic data obtained by employing LC-ωPBE method also reproduced the experimental diastereoselective ratio well. Various B–H activation pathways with and without Cs2CO3 additive were taken into consideration, which illustrates Cs2CO3 as an essential guarantee for smooth occurrence of this reaction at room temperature. Full article
(This article belongs to the Special Issue Ni-Containing Catalysts)
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11 pages, 884 KiB  
Article
Developing Multicompartment Biopolymer Hydrogel Beads for Tandem Chemoenzymatic One-Pot Process
by Jan Pauly, Harald Gröger and Anant V. Patel
Catalysts 2019, 9(6), 547; https://doi.org/10.3390/catal9060547 - 18 Jun 2019
Cited by 13 | Viewed by 5289
Abstract
Chemoenzymatic processes have been gaining interest to implement sustainable reaction steps or even create new synthetic routes. In this study, we combined Grubbs’ second-generation catalyst with pig liver esterase and conducted a chemoenzymatic one-pot process in a tandem mode. To address sustainability, we [...] Read more.
Chemoenzymatic processes have been gaining interest to implement sustainable reaction steps or even create new synthetic routes. In this study, we combined Grubbs’ second-generation catalyst with pig liver esterase and conducted a chemoenzymatic one-pot process in a tandem mode. To address sustainability, we encapsulated the catalysts in biopolymer hydrogel beads and conducted the reaction cascade in an aqueous medium. Unfortunately, conducting the process in tandem led to increased side product formation. We then created core-shell beads with catalysts located in different compartments, which notably enhanced the selectivity towards the desired product compared to homogeneously distributing both catalysts within the matrix. Finally, we designed a specific large-sized bead with a diameter of 13.5 mm to increase the diffusion route of the Grubbs’ catalyst-containing shell. This design forced the ring-closing metathesis to occur first before the substrate could diffuse into the pig liver esterase-containing core, thus enhancing the selectivity to 75%. This study contributes to addressing reaction-related issues by designing specific immobilisates for chemoenzymatic processes. Full article
(This article belongs to the Special Issue Combined Catalytic Systems for Organic Synthesis via Cascade and One-Pot Reactions)
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16 pages, 1427 KiB  
Article
Novel Combi-lipase Systems for Fatty Acid Ethyl Esters Production
by Esteban C. Toro, Diego F. Rodríguez, Nelson Morales, Lina M. García and César A. Godoy
Catalysts 2019, 9(6), 546; https://doi.org/10.3390/catal9060546 - 18 Jun 2019
Cited by 29 | Viewed by 4649
Abstract
Most Combi-lipases (CL) are based on mixtures of different lipases immobilized on different supports. The increased CL efficiency has been attributed solely to the complementary selectivity of lipases. However, the role of the immobilization support in CL or in co-immobilized systems (co [...] Read more.
Most Combi-lipases (CL) are based on mixtures of different lipases immobilized on different supports. The increased CL efficiency has been attributed solely to the complementary selectivity of lipases. However, the role of the immobilization support in CL or in co-immobilized systems (coCL) and the application of kinetic models to account CL composition effects, have not been assessed. In this work, commercial lipases from Thermomyces lunuginosus (TLL), Candida antarctica (CALB) and Rhizomocur miehei (RML) and supports as Lewatit®VPOC1600 (LW) and Purolite®ECR1604 (PU), were combined to produce new CL systems for the production of fatty acid ethyl esters (EE) which are the main component of ethylic biodiesel: Co-immobilization slightly altered palm olein EE yields with regard to that of equivalent CL systems, e.g., the best coCL of TLL and CALB in LW (89.5%) and the respective CL (81.8%). The support did affect CL behavior: (i) The best coCL of TLL and RML on LW produced 80.0% EE while on PU 76.4%; (ii) CL based on mixtures of the same enzyme, but immobilized on different supports (semiCL) show complementarity: The best TLL semiCL produced 86.1% EE while its constituents (LW) and (PU) produced individually 78.2 and 70.3%, respectively. The proposed model accounts adequately the EE production properties for CL systems based on TLL, CALB and LW. This work expands the tools to obtain new CL systems for EE production. Full article
(This article belongs to the Special Issue Biocatalysts: Design and Application)
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11 pages, 1544 KiB  
Article
Porosity Design of Shaped Zeolites for Improved Catalyst Lifetime in the Methanol-to-Hydrocarbons Reaction
by Rogéria Bingre, Renna Li, Qiang Wang, Patrick Nguyen, Thomas Onfroy and Benoît Louis
Catalysts 2019, 9(6), 545; https://doi.org/10.3390/catal9060545 - 18 Jun 2019
Cited by 9 | Viewed by 4871
Abstract
Additional porosity, such as meso- and macropores, was introduced in zeolite extrudates with the intention intuit of improving the effective diffusivity of the catalysts. The samples were characterized in depth by nitrogen adsorption-desorption, mercury intrusion porosimetry, ammonia temperature programmed desorption and adsorption of [...] Read more.
Additional porosity, such as meso- and macropores, was introduced in zeolite extrudates with the intention intuit of improving the effective diffusivity of the catalysts. The samples were characterized in depth by nitrogen adsorption-desorption, mercury intrusion porosimetry, ammonia temperature programmed desorption and adsorption of pyridine followed by infrared spectroscopy. The results revealed no significant change in the acidity but an increase of the pore volume. According to significant improvement in the effective diffusivity, the samples were tested in the methanol-to-hydrocarbons reaction. The catalytic stability was greatly enhanced with an increase in the pore volume, demonstrating a relation between effective diffusivity and resistance to deactivation by coke formation. Further experiments also revealed a higher toluene adsorption capacity and a raise in the breakthrough time over the most porous samples due to better accessibility of toluene molecules into the active sites of the zeolite. Full article
(This article belongs to the Section Catalytic Materials)
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13 pages, 3212 KiB  
Article
Insight on Single Cell Proton Exchange Membrane Fuel Cell Performance of Pt-Cu/C Cathode
by Marjan Bele, Matija Gatalo, Primož Jovanovič, Francisco Ruiz-Zepeda, Martin Šala, Ervin Šest, Nejc Hodnik, Stanko Hočevar, Irene Gatto, Ada Saccà, Antonino S. Aricò and Miran Gaberšček
Catalysts 2019, 9(6), 544; https://doi.org/10.3390/catal9060544 - 17 Jun 2019
Cited by 16 | Viewed by 5937
Abstract
The oxygen reduction reaction (ORR) properties of a proprietary PtCu3/C alloy electrocatalyst produced on a multi-gram scale are characterized by the conventional rotating disc electrode (RDE) method and by constructing a membrane electrode assembly (MEA) proton exchange membrane (PEM) single cell. [...] Read more.
The oxygen reduction reaction (ORR) properties of a proprietary PtCu3/C alloy electrocatalyst produced on a multi-gram scale are characterized by the conventional rotating disc electrode (RDE) method and by constructing a membrane electrode assembly (MEA) proton exchange membrane (PEM) single cell. The PtCu3 nanoparticles become porous, enriched in Pt on the surface, and exhibit a high RDE activity. The single cell electrochemical study reveals that, contrary to most advanced catalysts, the high ORR activity can be transferred from the RDE to the MEA. In the latter case, at 0.9VIRfree, a mass activity of 0.53 A/mgPt, at a Pt electrode loading of 0.2 mg/cm2, is achieved. However, at high current density, oxygen transport becomes limited. This is proven by the analysis of polarization curves and electrochemical impedance spectroscopy (EIS) data with a Kulikovsky (physical) model. These indicate that this limitation is caused by the non-optimal microporosity of our catalyst, which hinders the mass transport of oxygen during ORR. Based on our prospective results, one can realistically plan for further efforts to bridge the gap between the RDE and MEA measurements completely and achieve high power densities for Pt-alloy electrocatalysts. Full article
(This article belongs to the Special Issue Advances in Fuel Cell Catalyst)
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6 pages, 3492 KiB  
Correction
Correction: Chun S., et al. CO2 Microwave Plasma—Catalytic Reactor for Efficient Reforming of Methane to Syngas. Catalysts 2019, 9, 292
by Se Min Chun, Dong Hun Shin, Suk Hwal Ma, Geon Woo Yang and Yong Cheol Hong
Catalysts 2019, 9(6), 543; https://doi.org/10.3390/catal9060543 - 17 Jun 2019
Cited by 3 | Viewed by 2778
Abstract
The authors found that the gas sensor analyzer had a large amount of error, and the re-experiments were tested several times [...] Full article
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15 pages, 2706 KiB  
Article
Catalyst/Feedstock Ratio Effect on FCC Using Different Catalysts Samples
by Abdualkaber Alkhlel and Hugo de Lasa
Catalysts 2019, 9(6), 542; https://doi.org/10.3390/catal9060542 - 17 Jun 2019
Cited by 8 | Viewed by 6969
Abstract
The present study is a follow-up to a recent authors contribution which describes the effect of the C/O (catalyst/oil) ratio on catalytic cracking activity and catalyst deactivation. This study, while valuable, was limited to one fluidized catalytic cracking (FCC) catalyst. The aim of [...] Read more.
The present study is a follow-up to a recent authors contribution which describes the effect of the C/O (catalyst/oil) ratio on catalytic cracking activity and catalyst deactivation. This study, while valuable, was limited to one fluidized catalytic cracking (FCC) catalyst. The aim of the present study is to consider the C/O effect using three FCC catalysts with different activities and acidities. Catalysts were characterized in terms of crystallinity, total acidity, specific surface Area (SSA), temperature programmed ammonia desorption (NH3-TPD), and pyridine chemisorption. 1,3,5-TIPB (1,3,5-tri-isopropyl benzene) catalytic cracking runs were carried out in a bench-scale mini-fluidized batch unit CREC (chemical reactor engineering centre) riser simulator. All data were taken at 550 °C with a contact time of 7 s. Every experiment involved 0.2 g of 1,3,5-TIPB with the amount of catalyst changing in the 0.12–1 g range. The resulting 0.6–5 g oil/g cat ratios showed a consistent 1,3,5-TIPB conversion increasing first, then stabilizing, and finally decreasing modestly. On the other hand, coke formation and undesirable benzene selectivity always rose. Thus, the reported results show that catalyst density affects both catalyst coking and deactivation, displaying an optimum C/O ratio, achieving maximum hydrocarbon conversions in FCC units. Full article
(This article belongs to the Special Issue Catalyst Deactivation and Regeneration)
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16 pages, 3170 KiB  
Article
Oxidative Thermal Sintering and Redispersion of Rh Nanoparticles on Supports with High Oxygen Ion Lability
by Grammatiki Goula, Georgia Botzolaki, Amin Osatiashtiani, Christopher M. A. Parlett, Georgios Kyriakou, Richard M. Lambert and Ioannis V. Yentekakis
Catalysts 2019, 9(6), 541; https://doi.org/10.3390/catal9060541 - 17 Jun 2019
Cited by 48 | Viewed by 6856
Abstract
The thermal sintering under oxidative conditions of Rh nanoparticles supported on oxides characterized by very different oxygen storage capacities (OSC) and labilities was studied at 750 and 850 °C. Under sintering conditions, significant particle growth occurred for Rh/γ-Al2O3 (up to [...] Read more.
The thermal sintering under oxidative conditions of Rh nanoparticles supported on oxides characterized by very different oxygen storage capacities (OSC) and labilities was studied at 750 and 850 °C. Under sintering conditions, significant particle growth occurred for Rh/γ-Al2O3 (up to 120% at 850 °C). In striking contrast, Rh/ACZ (alumina–ceria–zirconia) and Rh/CZ (ceria–zirconia) exhibited marked resistance to sintering, and even moderate (ca. −10% at 850 °C) to pronounced (ca. −60% at 850 °C) redispersion of the Rh. A model is proposed based on a double-layer description of metal–support interactions assigned to back-spillover of labile oxygen ions onto the Rh particles, accompanied by trapping of atomic Rh by the resulting surface oxygen vacancies. This model accounts for the observed resistance to sintering and actual redispersion of Rh, consistent with both alternative sintering mechanisms, namely Ostwald ripening (OR) or particle migration and coalescence (PMC). Full article
(This article belongs to the Special Issue Nanomaterials in Catalysis Applications)
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13 pages, 2369 KiB  
Article
Catalytic Activity of Nickel and Ruthenium–Nickel Catalysts Supported on SiO2, ZrO2, Al2O3, and MgAl2O4 in a Dry Reforming Process
by Izabela Wysocka, Jan Hupka and Andrzej Rogala
Catalysts 2019, 9(6), 540; https://doi.org/10.3390/catal9060540 - 17 Jun 2019
Cited by 40 | Viewed by 5778
Abstract
Dry reforming of methane (DRM) is an eco-friendly method of syngas production due to the utilization of two main greenhouse gases—methane and carbon dioxide. An industrial application of methane dry reforming requires the use of a catalyst with high activity, stability over a [...] Read more.
Dry reforming of methane (DRM) is an eco-friendly method of syngas production due to the utilization of two main greenhouse gases—methane and carbon dioxide. An industrial application of methane dry reforming requires the use of a catalyst with high activity, stability over a long time, and the ability to catalyze a reaction, leading to the needed a hydrogen/carbon monoxide ratio. Thus, the aim of the study was to investigate the effect of support and noble metal particles on catalytic activity, stability, and selectivity in the dry reforming process. Ni and Ni–Ru based catalysts were prepared via impregnation and precipitation methods on SiO2, ZrO2, Al2O3, and MgAl2O4 supports. The obtained catalysts were characterized using X-ray diffractometry (XRD), inductively coupled plasma optical emission spectrometry (ICP-OES), Brunauer–Emmett–Teller (BET) specific surface area, and elemental carbon-hydrogen-nitrogen-sulphur analysis (CHNS) techniques. The catalytic activity was investigated in the carbon dioxide reforming of a methane process at 800 °C. Catalysts supported on commercial Al2O3 and spinel MgAl2O4 exhibited the highest activity and stability under DRM conditions. The obtained results clearly indicate that differences in catalytic activity result from the dispersion, size of an active metal (AM), and interactions of the AM with the support. It was also found that the addition of ruthenium particles enhanced the methane conversion and shifted the H2/CO ratio to lower values. Full article
(This article belongs to the Section Catalytic Materials)
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12 pages, 3154 KiB  
Article
Evaluation on the Methane Production Potential of Wood Waste Pretreated with NaOH and Co-Digested with Pig Manure
by Renfei Li, Wenbing Tan, Xinyu Zhao, Qiuling Dang, Qidao Song, Beidou Xi and Xiaohui Zhang
Catalysts 2019, 9(6), 539; https://doi.org/10.3390/catal9060539 - 17 Jun 2019
Cited by 22 | Viewed by 6154
Abstract
Wood waste generated during the tree felling and processing is a rich, green, and renewable lignocellulosic biomass. However, an effective method to apply wood waste in anaerobic digestion is lacking. The high carbon to nitrogen (C/N) ratio and rich lignin content of wood [...] Read more.
Wood waste generated during the tree felling and processing is a rich, green, and renewable lignocellulosic biomass. However, an effective method to apply wood waste in anaerobic digestion is lacking. The high carbon to nitrogen (C/N) ratio and rich lignin content of wood waste are the major limiting factors for high biogas production. NaOH pre-treatment for lignocellulosic biomass is a promising approach to weaken the adverse effect of complex crystalline cellulosic structure on biogas production in anaerobic digestion, and the synergistic integration of lignocellulosic biomass with low C/N ratio biomass in anaerobic digestion is a logical option to balance the excessive C/N ratio. Here, we assessed the improvement of methane production of wood waste in anaerobic digestion by NaOH pretreatment, co-digestion technique, and their combination. The results showed that the methane yield of the single digestion of wood waste was increased by 38.5% after NaOH pretreatment compared with the untreated wood waste. The methane production of the co-digestion of wood waste and pig manure was higher than that of the single digestion of wood waste and had nonsignificant difference with the single-digestion of pig manure. The methane yield of the co-digestion of wood waste pretreated with NaOH and pig manure was increased by 75.8% than that of the untreated wood waste. The findings indicated that wood waste as a sustainable biomass source has considerable potential to achieve high biogas production in anaerobic digestion. Full article
(This article belongs to the Special Issue Sustainable Catalytic Conversion of Biomass for the Production of Biofuels and Bioproducts)
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18 pages, 4250 KiB  
Article
Heterogeneous Bimetallic Cu–Ni Nanoparticle-Supported Catalysts in the Selective Oxidation of Benzyl Alcohol to Benzaldehyde
by Lili Liu, Xiaojing Zhou, Li Liu, Shuai Jiang, Yingjie Li, Luxia Guo, Shijuan Yan and Xishi Tai
Catalysts 2019, 9(6), 538; https://doi.org/10.3390/catal9060538 - 17 Jun 2019
Cited by 26 | Viewed by 5084
Abstract
Three bimetallic Cu–Ni nanoparticle-supported catalysts were synthesized by co-immobilization followed by H2 reduction. A chromium(III) terephthalate metal organic framework (MIL-101), titanium dioxide (TiO2), and carbon (C) with different properties (acidity and Brunauer–Emmett–Teller surface area) were selected as supports for studying [...] Read more.
Three bimetallic Cu–Ni nanoparticle-supported catalysts were synthesized by co-immobilization followed by H2 reduction. A chromium(III) terephthalate metal organic framework (MIL-101), titanium dioxide (TiO2), and carbon (C) with different properties (acidity and Brunauer–Emmett–Teller surface area) were selected as supports for studying the effect of the support nature on the catalytic activity and selectivity in the oxidation of benzyl alcohol. The physicochemical properties of the Cu–Ni-supported catalysts were characterized by XRD, NH3-TPD, nitrogen adsorption/desorption, TEM, EDS, XPS, and ICP-OES. Bimetallic Cu–Ni nanoparticles were highly dispersed on the support. The catalytic activities of CuNi/MIL-101, CuNi/TiO2, and CuNi/C were tested in the selective oxidation of benzyl alcohol to benzaldehyde in the presence of molecular oxygen under mild reaction conditions. The highest benzaldehyde yields were achieved with CuNi/TiO2, CuNi/MIL-101, and CuNi/C catalysts at 100 °C within 4 h under 5, 3, and 3 bar of O2, respectively. The bimetallic Cu–Ni-supported catalysts possessed two types of catalytic active sites: acid sites and bimetallic Cu–Ni nanoparticles. The CuNi/MIL-101 catalyst possessed a high number of acid sites and exhibited high yield during selective benzyl alcohol oxidation to benzaldehyde. Importantly, the catalysts exhibited a high functional group (electron-donating and electron-withdrawing groups) tolerance. Cu–Ni-supported catalysts with an Cu:Ni mole ratio of 1:1 exhibited the highest yield of 47% for the selective oxidation of benzyl alcohol to benzaldehyde. Reusability and leaching experiment results exhibited that CuNi/MIL-101 showed better stability than CuNi/TiO2 and CuNi/C catalysts due to the large porous cavities of MIL-101 support; these cavities can be used to trap bimetallic Cu–Ni nanoparticles and inhibit nanoparticle leaching. Full article
(This article belongs to the Special Issue Transition Metal Complexes as Catalysts in Organic Chemistry)
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18 pages, 3584 KiB  
Article
Valorization of Olive By-Products as Substrates for the Cultivation of Ganoderma lucidum and Pleurotus ostreatus Mushrooms with Enhanced Functional and Prebiotic Properties
by Georgios Koutrotsios, Marianna Patsou, Evdokia K. Mitsou, Georgios Bekiaris, Maria Kotsou, Petros A. Tarantilis, Vasiliki Pletsa, Adamantini Kyriacou and Georgios I. Zervakis
Catalysts 2019, 9(6), 537; https://doi.org/10.3390/catal9060537 - 16 Jun 2019
Cited by 47 | Viewed by 7632
Abstract
The successful management of olive by-products constitutes a major challenge due to their huge volume, high organic content, and toxicity. Olive-mill wastes (TPOMW) and olive pruning residues (OLPR) were evaluated as substrates for the cultivation of Ganoderma lucidum and Pleurotus ostreatus. Chemical [...] Read more.
The successful management of olive by-products constitutes a major challenge due to their huge volume, high organic content, and toxicity. Olive-mill wastes (TPOMW) and olive pruning residues (OLPR) were evaluated as substrates for the cultivation of Ganoderma lucidum and Pleurotus ostreatus. Chemical composition, glucans, total phenolic content, and antioxidant activity were measured in mushrooms, and their prebiotic potential was assessed by examining their effect on the growth of four intestinal bacteria. Several substrates based on olive by-products had a positive impact on P. ostreatus mushroom production, whereas only one performed adequately for G. lucidum. Increased ratios of OLPR to wheat-straw resulted in an increase of crude protein content in P. ostreatus fruit-bodies by up to 42%, while G. lucidum mushrooms from OLPR-based substrates exhibited an up to three-fold increase in α-glucan, or a significant enhancement of β-glucan content, when compared to beech sawdust (control). The mushrooms’ FTIR spectra confirmed the qualitative/quantitative differentiation detected by standard assays. In regard to prebiotic properties, mushrooms powder supported or even enhanced growth of both Lactobacillus acidophilus and L. gasseri after 24/48 h of incubation. In contrast, a strain-specific pattern was observed in bifidobacteria; mushrooms hindered Bifidobacterium bifidum growth, whereas they supported a similar-to-glucose growth for B. longum. Full article
(This article belongs to the Special Issue Environmental Biocatalysis: From Remediation to Waste Valorization)
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10 pages, 3577 KiB  
Communication
Cu Modified Pt Nanoflowers with Preferential (100) Surfaces for Selective Electroreduction of Nitrate
by Ting Chen, Yuxuan Li, Luyan Li, Yanjie Zhao, Shuhua Shi, Rongyan Jiang and Houyi Ma
Catalysts 2019, 9(6), 536; https://doi.org/10.3390/catal9060536 - 15 Jun 2019
Cited by 25 | Viewed by 4759
Abstract
Improving surface selectivity and maximizing electrode surface area are critical needs for the electroreduction of nitrate. Herein, preferential (100) oriented Pt nanoflowers with an extended surface area were prepared by potentiostatic deposition on carbon cloth (Pt NFs/CC), and then Cu atoms were adsorbed [...] Read more.
Improving surface selectivity and maximizing electrode surface area are critical needs for the electroreduction of nitrate. Herein, preferential (100) oriented Pt nanoflowers with an extended surface area were prepared by potentiostatic deposition on carbon cloth (Pt NFs/CC), and then Cu atoms were adsorbed on the Pt NFs (Cu/Pt NFs/CC) for application of nitrate electroreduction. The results reveal that Cu/Pt NFs/CC with 8.7% Cu coverage exhibits a high selectivity for nitrate electroreduction to N2 following two steps: Nitrate firstly converts into nitrite on Cu sites adsorbed on Pt NFs, then nitrite subsequently selective reduction and ammonia oxidation to N2 occur on the large exposed (100) terraces in Pt NFs. In addition, electrocatalytic activity and selectivity of nitrate reduction strongly rely on the Cu surface coverage on Pt NFs, the lower activity of nitrate reduction is displayed with increase of Cu coverage. Accordingly, the selective reduction of nitrate to N2 is feasible at such nanostructured Pt nanoflowers modified with Cu. Full article
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12 pages, 2493 KiB  
Article
Monitoring Enzymatic Hydroesterification of Low-Cost Feedstocks by Fourier Transform InfraRed Spectroscopy
by Mariana Cruz, Manuel Fonseca Almeida, Maria da Conceição Alvim-Ferraz and Joana Maia Dias
Catalysts 2019, 9(6), 535; https://doi.org/10.3390/catal9060535 - 15 Jun 2019
Cited by 16 | Viewed by 4838
Abstract
Enzymatic hydroesterification is a heterogeneous catalyzed process suitable for the conversion of low-cost feedstocks in biodiesel production, namely, because of its tolerance to high free fatty acid contents. The current study describes the use of Fourier transform infrared spectroscopy (FTIR) to monitor biodiesel [...] Read more.
Enzymatic hydroesterification is a heterogeneous catalyzed process suitable for the conversion of low-cost feedstocks in biodiesel production, namely, because of its tolerance to high free fatty acid contents. The current study describes the use of Fourier transform infrared spectroscopy (FTIR) to monitor biodiesel production using enzymatic hydroesterification and, as raw materials, acid oil from soapstock and olive pomace oil. Acid oil (~34 wt.% FFA) and olive pomace oil (~50 wt.% FFA) were first hydrolyzed (35 °C, 24 h, 200 rpm, 3 wt.% of lipase from Thermomyces lanuginosus, and 1:0.5 water:oil ratio, w:w), and then enzymatic esterification was performed (35 °C, 7 h, 200 rpm, 2 wt.% of lipase from Thermomyces lanuginosus, and 2:1 molar ratio of methanol to acid). FTIR analyses were conducted on the products using a Jasco FT/IR-4100 with a scanning range of 4000–650 cm−1 at 4 cm−1 spectral resolution and 54 scans. For free fatty acid (FFA) quantification, the C=O band at 1708 cm–1 was used, corresponding to the carboxylic acid, whereas for fatty acid methyl ester (FAME) quantification, the peak corresponding to C=O at 1746 cm−1 was considered, which corresponded to the ester. The results were calibrated using volumetric titration and gas chromatography analyses, concerning FFA and FAME quantification, respectively. The best conditions for analysis were determined, and a calibration method was established. FTIR has shown to be a simple, fast, and clean technique suitable to monitor hydroesterification of low-cost feedstocks. Full article
(This article belongs to the Special Issue Heterogeneous Catalysis in Biodiesel Production)
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