Catalysts

10 pages, 3068 KiB

Open AccessArticle

The Effect of Transition Metal Substitution in the Perovskite-Type Oxides on the Physicochemical Properties and the Catalytic Performance in Diesel Soot Oxidation

by Liliya V. Yafarova, Grigory V. Mamontov, Irina V. Chislova, Oleg I. Silyukov and Irina A. Zvereva

Catalysts 2021, 11(10), 1256; https://doi.org/10.3390/catal11101256 - 19 Oct 2021

Cited by 6 | Viewed by 2167

Abstract

The paper is focused on the Fe for Co substitution effect on the redox and catalytic properties in the perovskite structure of GdFeO₃. The solid oxides with the composition GdFe_1−xCo_xO₃ (x = 0; 0.2; 0.5; 0.8; [...] Read more.

The paper is focused on the Fe for Co substitution effect on the redox and catalytic properties in the perovskite structure of GdFeO₃. The solid oxides with the composition GdFe_1−xCo_xO₃ (x = 0; 0.2; 0.5; 0.8; 1) were obtained by the sol-gel method and characterized by various methods: X-ray diffraction (XRD), temperature-programmed reduction (H₂-TPR), N₂ sorption, temperature-programmed desorption of oxygen (TPD-O₂), simultaneous thermal analysis (STA), and X-ray photoelectron spectroscopy (XPS). The H₂-TPR results showed that an increase in the cobalt content in the GdFe_1−xCo_xO₃ (x = 0; 0.2; 0.5; 0.8; 1) leads to a decrease in the reduction temperature. Using the TPD-O₂ and STA methods, the lattice oxygen mobility is increasing in the course of the substitution of Fe for Co. Thus, the Fe substitution in the perovskite leads to an improvement in the oxygen reaction ability. Experiments on the soot oxidation reveal that catalytic oxidation ability increases in the series: GdFe_0.5Co_0.5O₃ ˂ GdFe_0.2Co_0.8O₃ ˂ GdCoO₃, which is in good correlation with the increasing oxygen mobility according to H2-TPR, TPD-O_2, and STA results. The soot oxidation over GdFeO₃ and GdFe_0.8Co_0.2O₃ is not in this range due to the impurities of iron oxides and higher specific surface area. Full article

(This article belongs to the Special Issue Smart Nanomaterials for Catalytic Environment, Energy, and Sustainability)

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16 pages, 2347 KiB

Open AccessFeature PaperArticle

Underground Upgrading of the Heavy Crude Oil in Content-Saturated Sandstone with Aquathermolysis in the Presence of an Iron Based Catalyst

by Sergey A. Sitnov, Irek I. Mukhamatdinov, Dmitry A. Feoktistov, Yaroslav V. Onishchenko, Vladislav A. Sudakov, Marat I. Amerkhanov and Alexey V. Vakhin

Catalysts 2021, 11(10), 1255; https://doi.org/10.3390/catal11101255 - 19 Oct 2021

Cited by 8 | Viewed by 2024

Abstract

Increasing the efficiency of thermal recovery methods is an important and relevant task. This study is devoted to reducing heavy components (resins and asphaltenes) and quality improvement of heavy oil by catalytic hydrothermal treatment. The object of this study is a bituminous sandstone [...] Read more.

Increasing the efficiency of thermal recovery methods is an important and relevant task. This study is devoted to reducing heavy components (resins and asphaltenes) and quality improvement of heavy oil by catalytic hydrothermal treatment. The object of this study is a bituminous sandstone sample from the Ashal’cha reservoir. The catalytic (iron tallate) hydrothermal simulation was carried out under reservoir conditions (200 °C, 30 bar). The composition and physicochemical characteristics of the products were studied using elemental and SARA analysis, MALDI, GC-MS, FT-IR. Moreover, the extracted rock is analyzed in XRD and DSA (Drop Shape Analyzer). The introduction of catalyst in combination with a hydrogen donor reduces the content of resins by 22.0%wt. with an increase in the share of saturated hydrocarbons by 27%wt. The destructive hydrogenation leads to a decrease in the sulfur content of upgrading products. This is crucial for the oil reservoirs of the Tatarstan Republic, as their crude oils are characterized by high sulfur content. According to the wettability data, the hydrophilicity of the rock surface increases due to inhibition of the coke formation after the introduction of the catalytic complex. Thus, the oil recovery factor can be increased due to the alteration of the oil-wetting properties of reservoir rocks. Full article

(This article belongs to the Special Issue Catalysis in Aquathermolysis of Heavy Oil)

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3 pages, 171 KiB

Open AccessEditorial

Catalytic Conversion of Lignins for Valuable Chemicals

by Valery E. Tarabanko

Catalysts 2021, 11(10), 1254; https://doi.org/10.3390/catal11101254 - 18 Oct 2021

Cited by 4 | Viewed by 1357

Abstract

Modern civilization is moving from fossil sources of raw materials and, consequently, energy to renewable resources: plant raw materials and solar and wind energy [...] Full article

(This article belongs to the Special Issue Catalytic Conversion of Lignins for Valuable Chemicals)

12 pages, 3070 KiB

Open AccessArticle

Facile Preparation of Carbon Nitride-ZnO Hybrid Adsorbent for CO₂ Capture: The Significant Role of Amine Source to Metal Oxide Ratio

by Siti Aishah Anuar, Khairul Naim Ahmad, Ahmed Al-Amiery, Mohd Shahbudin Masdar and Wan Nor Roslam Wan Isahak

Catalysts 2021, 11(10), 1253; https://doi.org/10.3390/catal11101253 - 18 Oct 2021

Cited by 3 | Viewed by 1734

Abstract

The presence of CO₂ in gaseous fuel and feedstock stream of chemical reaction was always considered undesirable. High CO₂ content will decrease quality and heating value of gaseous fuel, such as biohydrogen, which needs a practical approach to remove it. Thus, [...] Read more.

The presence of CO₂ in gaseous fuel and feedstock stream of chemical reaction was always considered undesirable. High CO₂ content will decrease quality and heating value of gaseous fuel, such as biohydrogen, which needs a practical approach to remove it. Thus, this work aims to introduce the first C₃N₄-metal oxide hybrid for the CO₂ cleaning application from a mixture of CO₂-H₂ gas. The samples were tested for their chemical and physical properties, using field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), physical adsorption analysis (BET), fourier-transform infrared (FTIR), x-ray diffraction (XRD), and x-ray photoelectron spectroscopy (XPS). The CO₂ capacity test was carried out by means of a breakthrough test at 1 atm and 25° C using air as a desorption system. Among the samples, amine/metal oxide mass ratio of 2:1 (CNHP500-2(2-1)) showed the best performance of 26.9 wt. % (6.11 mmol/g), with a stable capacity over 6 consecutive cycles. The hybrid sample also showed 3 times better performance than the raw C₃N₄. In addition, it was observed that the hydrothermal C₃N₄ synthesis method demonstrated improved chemical properties and adsorption performance than the conventional dry pyrolysis method. In summary, the performance of hybrid samples depends on the different interactive factors of surface area, pore size and distribution, basicity, concentration of amine precursors, ratio of amines precursors to metal oxide, and framework stability. Full article

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21 pages, 11457 KiB

Open AccessArticle

Combustion-Synthesized Porous CuO-CeO₂-SiO₂ Composites as Solid Catalysts for the Alkenylation of C(sp³)-H Bonds Adjacent to a Heteroatom via Cross-Dehydrogenative Coupling

by Ha V. Le, Vy B. Nguyen, Hai H. Pham, Khoa D. Nguyen, Phuoc H. Ho, Philippe Trens and Francesco Di Renzo

Catalysts 2021, 11(10), 1252; https://doi.org/10.3390/catal11101252 - 18 Oct 2021

Cited by 1 | Viewed by 1956

Abstract

A series of mixed oxides of CuO, CeO₂, and SiO₂ were prepared by gel combustion and employed for the first time as efficient solid catalysts in a solvent-less liquid-phase cross-dehydrogenative coupling. The facile one-pot catalyst synthesis resulted in highly porous [...] Read more.

A series of mixed oxides of CuO, CeO₂, and SiO₂ were prepared by gel combustion and employed for the first time as efficient solid catalysts in a solvent-less liquid-phase cross-dehydrogenative coupling. The facile one-pot catalyst synthesis resulted in highly porous materials presenting large specific surface areas and strong metal–support interactions. The interaction with highly dispersed CeO₂ enhanced the redox properties of the CuO species. The CuO-CeO₂-SiO₂ composites exhibited excellent catalytic performance for the selective coupling between 1,1-diphenylethylene and tetrahydrofuran with a yield up to 85% of 2-(2,2-diphenylvinyl)-tetrahydrofuran in the presence of di-tert-butyl peroxide (DTPB) and KI. Albeit both CuO and CeO₂ species are proved to be responsible for the catalytic conversion, a great synergistic improvement in the catalytic activity was obtained by extended contact between the oxide phases by high porosity in comparison with the reactions using individual Cu or Ce catalysts. The activity of the composite catalyst was shown to be highly stable after five successive reaction cycles. Furthermore, the study scope was extended to the synthesis of different derivatives via composite-catalyzed coupling of C(sp²)-H with C(sp³-H) adjacent to a heteroatom. The good yields recorded proved the general validity of this composite for the cross-dehydrogenative coupling reaction rarely performed on solid catalysts. Full article

(This article belongs to the Special Issue Advances in Catalytic Coupling Reactions)

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17 pages, 2189 KiB

Open AccessReview

Apiose-Relevant Glycosidases

by Elena Karnišová Potocká, Mária Mastihubová and Vladimír Mastihuba

Catalysts 2021, 11(10), 1251; https://doi.org/10.3390/catal11101251 - 18 Oct 2021

Cited by 7 | Viewed by 2568

Abstract

Apiose is a branched pentose naturally occurring either as a component of the plant cell wall polysaccharides or as a sugar moiety present in numerous plant secondary metabolites such as flavonoid and phenylethanoid glycosides, substrates in plant defense systems or as glycosylated aroma [...] Read more.

Apiose is a branched pentose naturally occurring either as a component of the plant cell wall polysaccharides or as a sugar moiety present in numerous plant secondary metabolites such as flavonoid and phenylethanoid glycosides, substrates in plant defense systems or as glycosylated aroma precursors. The enzymes catalyzing hydrolysis of such apiosylated substances (mainly glycosidases specific towards apiose or acuminose) have promising applications not only in hydrolysis (flavor development), but potentially also in the synthesis of apiosides and apioglucosides with pharmaceutical relevance. This review summarizes the actual knowledge of glycosidases recognizing apiose and their potential application in biocatalysis. Full article

(This article belongs to the Special Issue New Potential Applications of Enzymes in Biocatalysis and Next Challenges for a Green Chemistry)

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13 pages, 2589 KiB

Open AccessArticle

Facile and Rapid Synthesis of Durable SSZ-13 Catalyst Using Choline Chloride Template for Methanol-to-Olefins Reaction

by Xiongchao Lin, Sasha Yang, Xiaojia Li, Caihong Wang and Yonggang Wang

Catalysts 2021, 11(10), 1250; https://doi.org/10.3390/catal11101250 - 18 Oct 2021

Cited by 2 | Viewed by 1812

Abstract

In the current study, a facile and rapid synthesis approach for a SSZ-13 catalyst using choline chloride (CC) as a template was proposed, and the catalytic performance for the methanol-to-olefins (MTO) reaction was examined. With a proper amount of CC addition (i.e., m(CC)/m(SiO [...] Read more.

In the current study, a facile and rapid synthesis approach for a SSZ-13 catalyst using choline chloride (CC) as a template was proposed, and the catalytic performance for the methanol-to-olefins (MTO) reaction was examined. With a proper amount of CC addition (i.e., m(CC)/m(SiO₂) = 0.14), uniform and homogeneously distributed cubic SSZ-13 crystals were obtained within 4 h with lower aggregation. The synthesized catalyst demonstrated excellent porous features with a total specific surface area and mesopore volume of 641.71 m²·g⁻¹ and 0.04 cm³·g⁻¹, respectively. The optimized strong and weak acid sites on SSZ-13 were obtained by regulating the m(CC)/m(SiO₂) ratio. The less strong acid sites and a larger amount of weak acid sites in the synthesized catalyst were conducive to the catalytic performance of the MTO reaction under a lower reaction temperature (450 °C). The appropriate acidity and well-developed pore structure of synthesized SSZ-13 could also slow down the carbon deposition rate and, thus, significantly improve the catalytic lifetime of the catalyst. The methanol conversion rate and initial selectivity of light olefin using the synthesized catalyst could maintain over 95% and 50%, respectively, and a lifetime of 172 min was achieved. Although the low olefin selectivity of the synthesized SSZ-13 catalyst was slightly lower than that of the purchased one, its desirable features were thought to have good potential for industrial application. Full article

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37 pages, 19142 KiB

Open AccessFeature PaperReview

Organocatalysis: A Tool of Choice for the Enantioselective Nucleophilic Dearomatization of Electron-Deficient Six-Membered Ring Azaarenium Salts

by Claire Segovia, Pierre-Antoine Nocquet, Vincent Levacher, Jean-François Brière and Sylvain Oudeyer

Catalysts 2021, 11(10), 1249; https://doi.org/10.3390/catal11101249 - 18 Oct 2021

Cited by 6 | Viewed by 3143

Abstract

Nucleophilic dearomatization of azaarenium salts is a powerful strategy to access 3D scaffolds of interest from easily accessible planar aromatic azaarene compounds. Moreover, this approach yields complex dihydroazaarenes by allowing the functionalization of the scaffold simultaneously to the dearomatization step. On the other [...] Read more.

Nucleophilic dearomatization of azaarenium salts is a powerful strategy to access 3D scaffolds of interest from easily accessible planar aromatic azaarene compounds. Moreover, this approach yields complex dihydroazaarenes by allowing the functionalization of the scaffold simultaneously to the dearomatization step. On the other side, organocatalysis is nowadays recognized as one of the pillars of the asymmetric catalysis field of research and is well-known to afford a high level of enantioselectivity for a myriad of transformations thanks to well-organized transition states resulting from low-energy interactions (electrostatic and/or H-bonding interactions…). Consequently, in the last fifteen years, organocatalysis has met great success in nucleophilic dearomatization of azaarenium salts. This review summarizes the work achieved up to date in the field of organocatalyzed nucleophilic dearomatization of azaarenium salts (mainly pyridinium, quinolinium, quinolinium and acridinium salts). A classification by organocatalytic mode of activation will be disclosed by shedding light on their related advantages and drawbacks. The versatility of the dearomatization approach will also be demonstrated by discussing several chemical transformations of the resulting dihydroazaarenes towards the synthesis of structurally complex compounds. Full article

(This article belongs to the Special Issue Organocatalytic Asymmetric Synthesis or Transformation of Heterocycles)

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11 pages, 1876 KiB

Open AccessArticle

Hot Spots of Phytoene Desaturase from Rhodobacter sphaeroides Influencing the Desaturation of Phytoene

by Bo Hyun Choi, Sung Hui Kim and Pyung Cheon Lee

Catalysts 2021, 11(10), 1248; https://doi.org/10.3390/catal11101248 - 18 Oct 2021

Cited by 1 | Viewed by 2382

Abstract

Phytoene desaturase (CrtI, E.C. 1.3.99.31) shows variable desaturation activity, thereby introducing different numbers of conjugated double bonds (CDB) into the substrate phytoene. In particular, Rhodobacter sphaeroides CrtI is known to introduce additional 6 CDBs into the phytoene with 3 CDBs, generating neurosporene with [...] Read more.

Phytoene desaturase (CrtI, E.C. 1.3.99.31) shows variable desaturation activity, thereby introducing different numbers of conjugated double bonds (CDB) into the substrate phytoene. In particular, Rhodobacter sphaeroides CrtI is known to introduce additional 6 CDBs into the phytoene with 3 CDBs, generating neurosporene with 9 CDBs. Although in-depth studies have been conducted on the function and phylogenetic evolution of CrtI, little information exists on its range of CDB-introducing capabilities. We investigated the relationship between the structure and CDB-introducing capability of CrtI. CrtI of R. sphaeroides KCTC 12085 was randomly mutagenized to produce carotenoids of different CDBs (neurosporene for 9 CDBs, lycopene for 11 CDBs, and 3,4-didehydrolycopene for 13 CDBs). From six CrtI mutants producing different ratios of neurosporene/lycopene/3,4-didehydrolycopene, three amino acids (Leu163, Ala171, and Ile454) were identified that significantly determined carotenoid profiles. While the L163P mutation was responsible for producing neurosporene as a major carotenoid, A171P and I454T produced lycopene as the major product. Finally, according to the in silico model, the mutated amino acids are gathered in the membrane-binding domain of CrtI, which could distantly influence the FAD binding region and consequently the degree of desaturation in phytoene. Full article

(This article belongs to the Special Issue Enzyme Catalysis, Biotransformation and Bioeconomy)

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17 pages, 4509 KiB

Open AccessFeature PaperArticle

Calcium Hydroxyapatite: A Highly Stable and Selective Solid Catalyst for Glycerol Polymerization

by Negisa Ebadipour, Sébastien Paul, Benjamin Katryniok and Franck Dumeignil

Catalysts 2021, 11(10), 1247; https://doi.org/10.3390/catal11101247 - 17 Oct 2021

Cited by 11 | Viewed by 1848

Abstract

Calcium-based catalysts are of high interest for glycerol polymerization due to their high catalytic activity and large availability. However, their poor stability under reaction conditions is an issue. In the present study, we investigated the stability and catalytic activity of Ca-hydroxyapatites (HAps) as [...] Read more.

Calcium-based catalysts are of high interest for glycerol polymerization due to their high catalytic activity and large availability. However, their poor stability under reaction conditions is an issue. In the present study, we investigated the stability and catalytic activity of Ca-hydroxyapatites (HAps) as one of the most abundant Ca-source in nature. A stochiometric, Ca-deficient and Ca-rich HAps were synthesized and tested as catalysts in the glycerol polymerization reaction. Deficient and stochiometric HAps exhibited a remarkable 100% selectivity to triglycerol at 15% of glycerol conversion at 245 °C after 8 h of reaction in the presence of 0.5 mol.% of catalyst. Moreover, under the same reaction conditions, Ca-rich HAp showed a high selectivity (88%) to di- and triglycerol at a glycerol conversion of 27%. Most importantly, these catalysts were unexpectedly stable towards leaching under the reaction conditions based on the ICP-OES results. However, based on the catalytic tests and characterization analysis performed by XRD, XPS, IR, TGA-DSC and ICP-OES, we found that HAps can be deactivated by the presence of the reaction products themselves, i.e., water and polymers. Full article

(This article belongs to the Special Issue Catalytic Valorization of Glycerol: Strategies and Perspectives)

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13 pages, 2045 KiB

Open AccessFeature PaperArticle

Pt Electrocatalyst Prepared by Hydrothermal Reduction onto the Gas Diffusion Layer for High-Temperature Formic Acid and Ethanol Fuel PEMFC

by Rayane da Silva Cardoso, Bruna Sartório de Castro, Sophya de Andrade Dias, Maria Clara H. Clemente, Sílvia C. L. Dias, José A. Dias, Rudy Crisafulli, José J. Linares and Gesley A. Veloso Martins

Catalysts 2021, 11(10), 1246; https://doi.org/10.3390/catal11101246 - 17 Oct 2021

Cited by 3 | Viewed by 2211

Abstract

An alternative method for the preparation of PEMFC electrodes is presented in this work based on the direct deposition of Pt particles onto the gas diffusion layer (Pt@GDL) by hydrothermal reduction of the H₂PtCl₆ precursor from formic acid, ethylene glycol, [...] Read more.

An alternative method for the preparation of PEMFC electrodes is presented in this work based on the direct deposition of Pt particles onto the gas diffusion layer (Pt@GDL) by hydrothermal reduction of the H₂PtCl₆ precursor from formic acid, ethylene glycol, and ethanol reductive solutions. There is a successful anchorage of Pt particles via the formation of Pt crystal aggregates. The influence of the reducing agent concentration and temperature was studied to analyze their influence on the size, morphology, and distribution of the Pt particles on the gas GDL. The prepared Pt@GDL was tested for formic acid and ethanol high-temperature H₃PO₄-doped PEMFC. The Pt@GDL prepared in the formic acid reductive atmosphere presented the best performance associated with the formation of smaller Pt crystals and a more homogeneous dispersion of the Pt particles. For formic acid and ethanol-fed high-temperature PEMFC using a H₃PO₄-doped polybenzimidazole membrane as the solid electrolyte, maximum power densities of 0.025 and 0.007 W cm⁻² were drawn at 200 °C, respectively. Full article

(This article belongs to the Special Issue Novel Catalyst Materials for Low-Temperature Fuel Cells and Electrolyzers)

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13 pages, 3465 KiB

Open AccessFeature PaperArticle

Dehydroisomerisation of α-Pinene and Limonene to p-Cymene over Silica-Supported ZnO in the Gas Phase

by Aliyah Alsharif, Natalie Smith, Elena F. Kozhevnikova and Ivan V. Kozhevnikov

Catalysts 2021, 11(10), 1245; https://doi.org/10.3390/catal11101245 - 16 Oct 2021

Cited by 8 | Viewed by 2565

Abstract

Silica-supported zinc oxide possessing acid and dehydrogenation functions is an efficient, noble-metal-free bifunctional catalyst for the environment-friendly synthesis of p-Cymene from renewable monoterpene feedstock by gas-phase dehydroisomerisation of α-pinene and limonene in a fixed-bed reactor. The reaction involves acid-catalysed terpene isomerisation to p-menthadienes [...] Read more.

Silica-supported zinc oxide possessing acid and dehydrogenation functions is an efficient, noble-metal-free bifunctional catalyst for the environment-friendly synthesis of p-Cymene from renewable monoterpene feedstock by gas-phase dehydroisomerisation of α-pinene and limonene in a fixed-bed reactor. The reaction involves acid-catalysed terpene isomerisation to p-menthadienes followed by dehydrogenation to form p-Cymene. Dehydroisomerisation of α-pinene produces p-Cymene with 90% yield at 100% conversion at 370 °C and WHSV = 0.01–0.020 h⁻¹. The reaction with limonene gives a 100% p-Cymene yield at 325 °C and WHSV = 0.080 h⁻¹. ZnO/SiO₂ catalyst shows stable performance for over 70 h without co-feeding hydrogen. Full article

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12 pages, 2271 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Facile Surfactant-Assisted Synthesis of BiVO₄ Nanoparticulate Films for Solar Water Splitting

by Laura Montañés, Camilo A. Mesa, Ana Gutiérrez-Blanco, Christian Robles, Beatriz Julián-López and Sixto Giménez

Catalysts 2021, 11(10), 1244; https://doi.org/10.3390/catal11101244 - 15 Oct 2021

Cited by 1 | Viewed by 2535

Abstract

Bismuth vanadate (BiVO₄), which has attractive applicability as a photoactive material, presents applications that range from catalysis to water treatment upon visible light irradiation. In this study, we develop a simple synthesis of < 200 nm monoclinic BiVO₄ nanoparticles, which [...] Read more.

Bismuth vanadate (BiVO₄), which has attractive applicability as a photoactive material, presents applications that range from catalysis to water treatment upon visible light irradiation. In this study, we develop a simple synthesis of < 200 nm monoclinic BiVO₄ nanoparticles, which were further deposited on transparent conductive substrates by spin coating and calcination, obtaining nanostructured films. The obtained nanostructured BiVO₄ photoanodes were tested for water oxidation, leading to promising photocurrents exhibiting competitive onset potentials (~0.3 V vs. RHE). These nanoparticulate BiVO₄ photoanodes represent a novel class of highly potential materials for the design of efficient photoelectrochemical devices. Full article

(This article belongs to the Special Issue Photoelectrochemical and Photocatalytic Materials for Fuel Production)

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17 pages, 3272 KiB

Open AccessArticle

Photocatalytic Degradation of Antibiotics by Superparamagnetic Iron Oxide Nanoparticles. Tetracycline Case

by Sunday Joseph Olusegun, Gonzalo Larrea, Magdalena Osial, Krystyna Jackowska and Pawel Krysinski

Catalysts 2021, 11(10), 1243; https://doi.org/10.3390/catal11101243 - 15 Oct 2021

Cited by 38 | Viewed by 3144

Abstract

The challenges associated with the uncontrolled presence of antibiotics such as tetracycline in the environment have necessitated their removal through different techniques. Tetracycline is hard to degrade in living organisms and can even be converted to more toxic substances. In view of this, [...] Read more.

The challenges associated with the uncontrolled presence of antibiotics such as tetracycline in the environment have necessitated their removal through different techniques. Tetracycline is hard to degrade in living organisms and can even be converted to more toxic substances. In view of this, we synthesized iron oxide nanoparticles with good magnetization (70 emu g⁻¹) and 15 nm particle size for the adsorption and photocatalytic degradation of tetracycline. Characterization carried out on the synthesized iron oxides revealed a bandgap of 1.83 eV and an isoelectric point at pH 6.8. The results also showed that the pH of the solution does not directly influence the adsorption of tetracycline. The adsorption isotherm was consistent with the model proposed by Langmuir, having 97 mg g⁻¹ adsorption capacity. Combined with the superparamagnetic behavior, this capacity is advantageous for the magnetic extraction of tetracycline from wastewater. The mechanisms of adsorption were proposed to be hydrogen bonding and n-π interactions. Photocatalytic degradation studies showed that approximately 40% of tetracycline degraded within 60 min of irradiation time with UV/vis light. The kinetics of photodegradation of tetracycline followed the pseudo-first-order mechanism, proceeding through hydroxyl radicals generated under illumination. Moreover, the photogenerated hydrogen peroxide could lead to heterogeneous photo-Fenton processes on the surface of iron oxide nanoparticles, additionally generating hydroxyl and hydroperoxyl radicals and facilitating photodegradation of tetracycline. Full article

(This article belongs to the Special Issue Environmental Catalysis for Water Remediation)

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3 pages, 161 KiB

Open AccessEditorial

Catalysts and Processes for H₂S Conversion to Sulfur

by Daniela Barba

Catalysts 2021, 11(10), 1242; https://doi.org/10.3390/catal11101242 - 15 Oct 2021

Cited by 2 | Viewed by 1537

Abstract

Hydrogen sulfide is one of the main waste products of the petrochemical industry; it is produced by the catalytic hydrodesulfurization processes (HDS) of the hydrocarbon feedstocks, and it is a byproduct from the sweetening of sour natural gas and from the upgrading of [...] Read more.

Hydrogen sulfide is one of the main waste products of the petrochemical industry; it is produced by the catalytic hydrodesulfurization processes (HDS) of the hydrocarbon feedstocks, and it is a byproduct from the sweetening of sour natural gas and from the upgrading of heavy oils, bitumen, and coals [...] Full article

(This article belongs to the Special Issue Catalysts and Processes for H₂S Conversion to Sulfur)

12 pages, 39636 KiB

Open AccessCommunication

Cobalt Boride/g-C₃N₄ Nanosheets-Assisted Electrocatalytic Oxidation of 5-Hydroxymethylfurfural into 2,5-Furandicarboxylic Acid

by Mohammed A. Suliman, Chanbasha Basheer and Wasif Farooq

Catalysts 2021, 11(10), 1241; https://doi.org/10.3390/catal11101241 - 15 Oct 2021

Cited by 4 | Viewed by 2235

Abstract

The electrochemical production of 2,5-furandicarboxylic acid (FDCA) from 5-(hydroxymethyl)furfural (HMF) is receiving growing attention. The FDCA-based polyethylene 2,5-furan dicarboxylate (PEF) polymer is a green candidate for substituting polyethylene terephthalate. This work demonstrated a highly efficient CoB/g-C₃N₄ nanosheet on the surface [...] Read more.

The electrochemical production of 2,5-furandicarboxylic acid (FDCA) from 5-(hydroxymethyl)furfural (HMF) is receiving growing attention. The FDCA-based polyethylene 2,5-furan dicarboxylate (PEF) polymer is a green candidate for substituting polyethylene terephthalate. This work demonstrated a highly efficient CoB/g-C₃N₄ nanosheet on the surface of the nickel foam as an electrode for the HMF electrooxidation reaction. Electrolysis at a constant potential combined with liquid chromatography showed the formation of FDCA with a yield of 97% with an excellent faradaic efficiency of near 95%. CoB/g-C₃N₄ achieved a current density of 20 mA cm⁻² for HMF oxidation in 1.0 M KOH with 10 mM HMF at 1.37 V vs. RHE before the competing oxygen evolution reaction. The electrocatalyst was effectively reused up to three times without compromising efficiency. This work demonstrates a cheap and active electrocatalyst material for the electrochemical formation of FDCA from HMF and gives perception into the reaction mechanism. Full article

(This article belongs to the Special Issue Organic-Inorganic Hybrid Catalysts for Energy Applications)

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10 pages, 2228 KiB

Open AccessArticle

Screening of Acetyl Donors and the Robust Enzymatic Synthesis of Acetyl-CoA by 10-Deacetylbaccatin III-10-β-O-acetyltransferase

by Bo-Yong Zhang, Hao Wang, Ting Gong, Tian-Jiao Chen, Jing-Jing Chen, Jin-Ling Yang and Ping Zhu

Catalysts 2021, 11(10), 1240; https://doi.org/10.3390/catal11101240 - 15 Oct 2021

Viewed by 1596

Abstract

Acetyl-CoA is the precursor of many bio-manufacturing products and is also the hub of the cellular metabolism of energy and substances. However, acetyl-CoA is not a bulk commodity and its application is hindered due to its high cost and low yield. In this [...] Read more.

Acetyl-CoA is the precursor of many bio-manufacturing products and is also the hub of the cellular metabolism of energy and substances. However, acetyl-CoA is not a bulk commodity and its application is hindered due to its high cost and low yield. In this study, we screened acetyl donor candidates and utilized 10-deacetylbaccatin III-10-β-O-acetyltransferase (DBAT) in the synthesis of acetyl-CoA with CoASH as the acetyl acceptor. Among the tested candidates, acetylsalicylic acid methyl ester was identified to be the best acetyl donor, followed by acetyl-trans-resveratrol, acetylsalicylic acid ethyl ester, acetylsalicylsalicylic acid, and 4-acetoxyacetanilide. The enzymatic reaction conditions were optimized and the maximum yield of acetyl-CoA reached 14.82 mg/mL, which is the highest yield among all reported approaches to date. Meanwhile, 4.22 mg/mL of the by-product salicylic acid methyl ester, which is another industrial material, was produced. Additionally, a preliminary purification process for acetyl-CoA was established, in which 40 mg acetyl-CoA (HPLC purity > 98%) was acquired from the finished 20 mL reaction system (feeding 46 mg CoASH and 34 mg ASME) with a recovery rate of 86%. Our study lays the foundation for the large-scale production of acetyl-CoA by an enzymatic approach and will promote its application in different fields. Full article

(This article belongs to the Special Issue Enzyme Catalysis, Biotransformation and Bioeconomy)

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41 pages, 3920 KiB

Open AccessFeature PaperReview

Carbon-Based Materials for Oxidative Desulfurization and Denitrogenation of Fuels: A Review

by Fernanda F. Roman, Jose L. Diaz de Tuesta, Adrián M. T. Silva, Joaquim L. Faria and Helder T. Gomes

Catalysts 2021, 11(10), 1239; https://doi.org/10.3390/catal11101239 - 15 Oct 2021

Cited by 19 | Viewed by 3643

Abstract

Sulfur (S) and nitrogen (N) are elements naturally found in petroleum-based fuels. S- and N-based compounds in liquid fuels are associated with a series of health and environmental issues. Thus, legislation has become stricter worldwide regarding their content and related emissions. Traditional treatment [...] Read more.

Sulfur (S) and nitrogen (N) are elements naturally found in petroleum-based fuels. S- and N-based compounds in liquid fuels are associated with a series of health and environmental issues. Thus, legislation has become stricter worldwide regarding their content and related emissions. Traditional treatment systems (namely hydrodesulfurization and hydrodenitrogenation) fail to achieve the desired levels of S and N contents in fuels without compromising combustion parameters. Thus, oxidative treatments (oxidative desulfurization–ODS, and oxidative denitrogenation-ODN) are emerging as alternatives to producing ultra-low-sulfur and nitrogen fuels. This paper presents a thorough review of ODS and ODN processes applying carbon-based materials, either in hybrid forms or as catalysts on their own. Focus is brought to the role of the carbonaceous structure in oxidative treatments. Furthermore, a special section related to the use of amphiphilic carbon-based catalysts, which have some advantages related to a closer interaction with the oily and aqueous phases, is discussed. Full article

(This article belongs to the Special Issue Catalysis and Carbon-Based Materials)

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16 pages, 5331 KiB

Open AccessFeature PaperArticle

Photocatalytic Degradation of Tetracycline in Aqueous Solution Using Copper Sulfide Nanoparticles

by Murendeni P. Ravele, Opeyemi A. Oyewo, Sam Ramaila, Lydia Mavuru and Damian C. Onwudiwe

Catalysts 2021, 11(10), 1238; https://doi.org/10.3390/catal11101238 - 14 Oct 2021

Cited by 9 | Viewed by 2492

Abstract

In this paper, spherical-shaped pure phase djurleite (Cu₃₁S₁₆) and roxbyite (Cu₇S₄) nanoparticles were prepared by a solvothermal decomposition of copper(II) dithiocarbamate complex in dodecanthiol (DDT). The reaction temperature was used to control the phases of [...] Read more.

In this paper, spherical-shaped pure phase djurleite (Cu₃₁S₁₆) and roxbyite (Cu₇S₄) nanoparticles were prepared by a solvothermal decomposition of copper(II) dithiocarbamate complex in dodecanthiol (DDT). The reaction temperature was used to control the phases of the samples, which were represented as Cu₃₁S₁₆ (120 °C), Cu₃₁S₁₆ (150 °C), Cu₇S₄ (220 °C), and Cu₇S₄ (250 °C) and were characterized by using X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM and TEM), and absorption spectroscopy. The samples were used as photocatalysts for the degradation of tetracycline (TC) under visible light irradiation. The results of the study showed that Cu₇S₄ (250 °C) exhibited the best activity in the reaction system with the TC degradation rate of up to 99% within 120 min of light exposure, while the Cu₃₁S₁₆ (120 °C) system was only 46.5% at the same reaction condition. In general, roxbyite Cu₇S₄ (250 °C) could be considered as a potential catalyst for the degradation of TC in solution. Full article

(This article belongs to the Special Issue Application of Photocatalysts in Environmental Chemistry)

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11 pages, 2374 KiB

Open AccessArticle

Tuning the Electronic Structure of CoO Nanowire Arrays by N-Doping for Efficient Hydrogen Evolution in Alkaline Solutions

by Maoqi Cao, Xiaofeng Li, Dingding Xiang, Dawang Wu, Sailan Sun, Hongjing Dai, Jun Luo and Hongtao Zou

Catalysts 2021, 11(10), 1237; https://doi.org/10.3390/catal11101237 - 14 Oct 2021

Cited by 4 | Viewed by 1915

Abstract

Electrochemical hydrogen evolution reactions (HER) have drawn tremendous interest for the scalable and sustainable conversion of renewable electricity to clear hydrogen fuel. However, the sluggish kinetics of the water dissociation step severely restricts the high production of hydrogen in alkaline media. Tuning the [...] Read more.

Electrochemical hydrogen evolution reactions (HER) have drawn tremendous interest for the scalable and sustainable conversion of renewable electricity to clear hydrogen fuel. However, the sluggish kinetics of the water dissociation step severely restricts the high production of hydrogen in alkaline media. Tuning the electronic structure by doping is an effective method to boost water dissociation in alkaline solutions. In this study, N-doped CoO nanowire arrays (N-CoO) were designed and prepared using a simple method. X-ray diffraction (XRD), element mappings and X-ray photoelectron spectroscopy (XPS) demonstrated that N was successfully incorporated into the lattice of CoO. The XPS of Co 2p and O 1s suggested that the electronic structure of CoO was obviously modulated after the incorporation of N, which improved the adsorption and activation of water molecules. The energy barriers obtained from the Arrhenius relationship of the current density at different temperatures indicated that the N-CoO nanowire arrays accelerated the water dissociation in the HER process. As a result, the N-CoO nanowire arrays showed an excellent performance of HER in alkaline condition. At a current density of 10 mA cm⁻¹, the N-CoO nanowire arrays needed only a 123 mV potential, which was much lower than that of CoO (285 mV). This simple design strategy provides some new inspiration to promote water dissociation for HER in alkaline solutions at the atomic level. Full article

(This article belongs to the Special Issue Synthesis and Application of Metal Mixed Oxide Catalysts (MMOs Catalysts))

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9 pages, 893 KiB

Open AccessFeature PaperCommunication

Strategies for the Immobilization of Eversa^® Transform 2.0 Lipase and Application for Phospholipid Synthesis

by Bruno R. Facin, Ernestina G. Quinto, Alexsandra Valerio, Débora de Oliveira, Jose V. Oliveira and Gloria Fernandez-Lorente

Catalysts 2021, 11(10), 1236; https://doi.org/10.3390/catal11101236 - 14 Oct 2021

Cited by 3 | Viewed by 1856

Abstract

Eversa^® Transform 2.0 lipase (ET2) is a recent lipase formulation derived from the Thermomyces lanuginosus lipase cultivated on Aspergillus oryzae and specially designed for biodiesel production. Since it has not been available for a long time, research on the efficiency of this [...] Read more.

Eversa^® Transform 2.0 lipase (ET2) is a recent lipase formulation derived from the Thermomyces lanuginosus lipase cultivated on Aspergillus oryzae and specially designed for biodiesel production. Since it has not been available for a long time, research on the efficiency of this enzyme in other applications remains unexplored. Moreover, even though it has been launched as a free enzyme, its immobilization may extend the scope of ET2 applications. This work explored ET2 immobilization on octadecyl methacrylate beads (IB-ADS-3) and proved the efficiency of the derivatives for esterification of glycerophosphocholine (GPC) with oleic acid in anhydrous systems. ET2 immobilized via interfacial activation on commercial hydrophobic support Immobead IB-ADS-3 showed maximum enzyme loading of 160 mg/g (enzyme/support) and great stability for GPC esterification under 30% butanone and solvent-free systems. For reusability, yields above 63% were achieved after six reaction cycles for GPC esterification. Considering the very high enzyme loading and the number of reuses achieved, these results suggest a potential application of this immobilized biocatalyst for esterification reactions in anhydrous media. This study is expected to encourage the exploration of other approaches for this enzyme, thereby opening up several new possibilities. Full article

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11 pages, 32004 KiB

Open AccessFeature PaperArticle

Study of the Photoelectrochemical Properties of 1D ZnO Based Nanocomposites

by Bekbolat Seitov, Sherzod Kurbanbekov, Dina Bakranova, Nuriya Abdyldayeva and Nurlan Bakranov

Catalysts 2021, 11(10), 1235; https://doi.org/10.3390/catal11101235 - 13 Oct 2021

Cited by 1 | Viewed by 1831

Abstract

Exploitation of common elements as photocatalysts for conversion of photons to electricity stimulates the development of a green energy strategy. In this paper, methods for the preparation of active coatings based on ZnO/Ag/CdS, which are used in the photocatalytic oxidation reaction, are examined. [...] Read more.

Exploitation of common elements as photocatalysts for conversion of photons to electricity stimulates the development of a green energy strategy. In this paper, methods for the preparation of active coatings based on ZnO/Ag/CdS, which are used in the photocatalytic oxidation reaction, are examined. The physical and chemical properties of the resulting arrays were studied using optical spectrometers, an electron microscope, an X-ray diffractometer, and potentiostatic measurements and electrochemical impedance spectroscopy. The effectiveness of photocatalysts was calculated by the ability to liberate gas from aqueous solutions when exposed to light. The rate of degradation was indirectly measured with a conductometer. Full article

(This article belongs to the Special Issue Novel Semiconductors, Catalysts and Approaches for the Photoelectrochemical Water Splitting)

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19 pages, 47335 KiB

Open AccessFeature PaperArticle

Innovative Ag–TiO₂ Nanofibers with Excellent Photocatalytic and Antibacterial Actions

by Petronela Pascariu, Corneliu Cojocaru, Anton Airinei, Niculae Olaru, Irina Rosca, Emmanouel Koudoumas and Mirela Petruta Suchea

Catalysts 2021, 11(10), 1234; https://doi.org/10.3390/catal11101234 - 13 Oct 2021

Cited by 21 | Viewed by 2675

Abstract

Ag–TiO₂ nanostructures were prepared by electrospinning, followed by calcination at 400 °C, and their photocatalytic and antibacterial actions were studied. Morphological characterization revealed the presence of one-dimensional uniform Ag–TiO₂ nanostructured nanofibers, with a diameter from 65 to 100 nm, depending on [...] Read more.

Ag–TiO₂ nanostructures were prepared by electrospinning, followed by calcination at 400 °C, and their photocatalytic and antibacterial actions were studied. Morphological characterization revealed the presence of one-dimensional uniform Ag–TiO₂ nanostructured nanofibers, with a diameter from 65 to 100 nm, depending on the Ag loading, composed of small crystals interconnected with each other. Structural characterization indicated that Ag was successfully integrated as small nanocrystals without affecting much of the TiO₂ crystal lattice. Moreover, the presence of nano Ag was found to contribute to reducing the band gap energy, which enables the activation by the absorption of visible light, while, at the same time, it delays the electron–hole recombination. Tests of their photocatalytic activity in methylene blue, amaranth, Congo red and orange II degradation revealed an increase by more than 20% in color removal efficiency at an almost double rate for the case of 0.1% Ag–TiO₂ nanofibers with respect to pure TiO₂. Moreover, the minimum inhibitory concentration was found as low as 2.5 mg/mL for E. coli and 5 mg/mL against S. aureus for the 5% Ag–TiO₂ nanofibers. In general, the Ag–TiO₂ nanostructured nanofibers were found to exhibit excellent structure and physical properties and to be suitable for efficient photocatalytic and antibacterial uses. Therefore, these can be suitable for further integration in various important applications. Full article

(This article belongs to the Special Issue Heterogeneous Photocatalysis: A Solution for a Greener Earth)

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17 pages, 6044 KiB

Open AccessArticle

Optimizing MgO Content for Boosting γ-Al₂O₃-Supported Ni Catalyst in Dry Reforming of Methane

by Abdulaziz Bagabas, Ahmed Sadeq Al-Fatesh, Samsudeen Olajide Kasim, Rasheed Arasheed, Ahmed Aidid Ibrahim, Rawan Ashamari, Khalid Anojaidi, Anis Hamza Fakeeha, Jehad K. Abu-Dahrieh and Ahmed Elhag Abasaeed

Catalysts 2021, 11(10), 1233; https://doi.org/10.3390/catal11101233 - 13 Oct 2021

Cited by 8 | Viewed by 1835

Abstract

The dry reforming of methane (DRM) process has attracted research interest because of its ability to mitigate the detrimental impacts of greenhouse gases such as methane (CH₄) and carbon dioxide (CO₂) and produce alcohols and clean fuel. In view [...] Read more.

The dry reforming of methane (DRM) process has attracted research interest because of its ability to mitigate the detrimental impacts of greenhouse gases such as methane (CH₄) and carbon dioxide (CO₂) and produce alcohols and clean fuel. In view of this importance of DRM, we disclosed the efficiency of a new nickel-based catalyst, which was promoted with magnesia (MgO) and supported over gamma-alumina (γ-Al₂O₃) doped with silica (SiO₂), toward DRM. The synthesized catalysts were characterized by H₂ temperature-programmed reduction (H₂-TPR), X-ray diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Thermogravimetric analysis (TGA), and Transmission electron microscopy (TEM) techniques. The effect of MgO weight percent loading (0.0, 1.0, 2.0, and 3.0 wt. %) was examined because the catalytic performance was found to be a function of this parameter. An optimum loading of 2.0 wt. % of MgO was obtained, where the conversion of CH₄ and CO₂ at 800 °C were 86% and 91%, respectively, while the syngas (H₂/CO) ratios relied on temperature and were in the range of 0.85 to 0.95. The TGA measurement of the best catalyst, which was operated over a 15-h reaction time, displayed negligible weight loss (<9.0 wt. %) due to carbon deposition, indicating the good resistance of our catalyst system to the deposition of carbon owing to the dopant and the modifier. TEM images showed the presence of multiwalled carbon nanotubes, confirming the TGA. Full article

(This article belongs to the Special Issue Catalytic Reforming of Light Hydrocarbons)

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18 pages, 6463 KiB

Open AccessArticle

Synthesis of Nano-ZnO/Diatomite Composite and Research on Photoelectric Application

by Beibei Yang, Xuefei Liu, Zixu Ma, Qian Wang and Junjiao Yang

Catalysts 2021, 11(10), 1232; https://doi.org/10.3390/catal11101232 - 13 Oct 2021

Cited by 4 | Viewed by 1737

Abstract

The key to the commercialization of sustainable energy conversion technologies is the development of high-performance catalysts. The discovery of a stable, efficient, and low-cost multi-function catalysts is the key. We used a simple green precipitation method to load nanozinc oxide particles onto a [...] Read more.

The key to the commercialization of sustainable energy conversion technologies is the development of high-performance catalysts. The discovery of a stable, efficient, and low-cost multi-function catalysts is the key. We used a simple green precipitation method to load nanozinc oxide particles onto a diatomite substrate. The ZnO is nano-sized. This precipitation method produces ZnO nanoparticles in situ on diatomite. The catalysts degraded 90% of Methylene blue solution and also degraded gaseous benzene and gaseous acetone. Not only can the catalysts be used for the organic degradation of wastewater, but it also has the potential to degrade volatile organic compounds. Photocatalytic efficiency is closely related to the generation and separation of photogenerated electrons and holes. The effective suppression of the recombination rate of photoliving carriers and thus improvement of the photocatalytic activity, has become a key research area. At present, photocatalysis is an effective technology to inhibit photogenerated carrier recombination, which is often studied in sewage treatment. Photoelectrochemical decomposition of water reduces the recombination of photogenerated electrons and holes by applying an external bias, thus improving the quantum efficiency for the complete mineralization of organic pollutants. The composite catalysts were used for oxygen and hydrogen extraction reactions, and a comparison of the catalysts with various loading ratios showed that the photoelectrochemical decomposition of water activity of the composite catalysts are due to pure ZnO, and the efficiency is highest when the loading ratio is 10%. This work provides new methods for the design and further optimization of the preparation of photoelectrochemical decomposition of water catalysts. Full article

(This article belongs to the Special Issue 10th Anniversary of Catalysts—Feature Papers in Photocatalysis)

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29 pages, 11709 KiB

Open AccessArticle

Catalytic Tar Conversion in Two Different Hot Syngas Cleaning Systems

by Grazyna Straczewski, Robert Mai, Uta Gerhards, Krassimir Garbev and Hans Leibold

Catalysts 2021, 11(10), 1231; https://doi.org/10.3390/catal11101231 - 13 Oct 2021

Cited by 3 | Viewed by 2764

Abstract

Tar in the product gas of biomass gasifiers reduces the efficiency of gasification processes and causes fouling of system components and pipework. Therefore, an efficient tar conversion in the product gas is a key step of effective and reliable syngas production. One of [...] Read more.

Tar in the product gas of biomass gasifiers reduces the efficiency of gasification processes and causes fouling of system components and pipework. Therefore, an efficient tar conversion in the product gas is a key step of effective and reliable syngas production. One of the most promising approaches is the catalytic decomposition of the tar species combined with hot syngas cleaning. The catalyst must be able to convert tar components in the synthesis gas at temperatures of around 700 °C downstream of the gasifier without preheating. A Ni-based doped catalyst with high activity in tar conversion was developed and characterized in detail. An appropriate composition of transition metals was applied to minimize catalyst coking. Precious metals (Pt, Pd, Rh, or a combination of two of them) were added to the catalyst in small quantities. Depending on the hot gas cleaning system used, both transition metals and precious metals were co-impregnated on pellets or on a ceramic filter material. In the case of a pelletized-type catalyst, the hot gas cleaning system revealed a conversion above 80% for 70 and 110 h. The catalyst composed of Ni, Fe, and Cr oxides, promoted with Pt and impregnated on a ceramic fiber filter composed of Al₂O₃(44%)/SiO₂(56%), was the most active catalyst for a compact cleaning system. This catalyst was catalytically active with a naphthalene conversion of around 93% over 95 h without catalyst deactivation. Full article

(This article belongs to the Special Issue Catalysts in Production of Clean Gasification Gas)

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21 pages, 2305 KiB

Open AccessFeature PaperArticle

Al₂O₃-Supported Transition Metals for Plasma-Catalytic NH₃ Synthesis in a DBD Plasma: Metal Activity and Insights into Mechanisms

by Yury Gorbanev, Yannick Engelmann, Kevin van’t Veer, Evgenii Vlasov, Callie Ndayirinde, Yanhui Yi, Sara Bals and Annemie Bogaerts

Catalysts 2021, 11(10), 1230; https://doi.org/10.3390/catal11101230 - 13 Oct 2021

Cited by 25 | Viewed by 3558

Abstract

N₂ fixation into NH₃ is one of the main processes in the chemical industry. Plasma catalysis is among the environmentally friendly alternatives to the industrial energy-intensive Haber-Bosch process. However, many questions remain open, such as the applicability of the conventional catalytic [...] Read more.

N₂ fixation into NH₃ is one of the main processes in the chemical industry. Plasma catalysis is among the environmentally friendly alternatives to the industrial energy-intensive Haber-Bosch process. However, many questions remain open, such as the applicability of the conventional catalytic knowledge to plasma. In this work, we studied the performance of Al₂O₃-supported Fe, Ru, Co and Cu catalysts in plasma-catalytic NH₃ synthesis in a DBD reactor. We investigated the effects of different active metals, and different ratios of the feed gas components, on the concentration and production rate of NH₃, and the energy consumption of the plasma system. The results show that the trend of the metal activity (common for thermal catalysis) does not appear in the case of plasma catalysis: here, all metals exhibited similar performance. These findings are in good agreement with our recently published microkinetic model. This highlights the virtual independence of NH₃ production on the metal catalyst material, thus validating the model and indicating the potential contribution of radical adsorption and Eley-Rideal reactions to the plasma-catalytic mechanism of NH₃ synthesis. Full article

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12 pages, 3876 KiB

Open AccessArticle

Morphology and Catalytic Performance of MoS₂ Hydrothermally Synthesized at Various pH Values

by Seung-Jae Lee, Yang-Seung Son, Jin-Hoon Choi, Seong-Soo Kim and Sung-Youl Park

Catalysts 2021, 11(10), 1229; https://doi.org/10.3390/catal11101229 - 12 Oct 2021

Cited by 13 | Viewed by 2311

Abstract

Although preparation conditions are known to affect the morphology and catalytic performance of hydrothermally synthesized MoS₂, the influence of pH remains unclear. Herein, unsupported MoS₂ was prepared from ammonium tetrathiomolybdate (ATTM) by a hydrothermal reaction at various pH values under [...] Read more.

Although preparation conditions are known to affect the morphology and catalytic performance of hydrothermally synthesized MoS₂, the influence of pH remains unclear. Herein, unsupported MoS₂ was prepared from ammonium tetrathiomolybdate (ATTM) by a hydrothermal reaction at various pH values under a reaction pressure of 2 MPa. The physical and chemical properties of the MoS₂ samples were characterized, and the catalytic performance for CO methanation was examined. With increasing pH, the morphology of the MoS₂ particles transformed from aggregates of irregular grain-like particles to flower-like particles through the agglomeration of fine mesoporous nanoflakes. Hydrothermal synthesis at a pH of 9.5 increased the MoS₂ crystallinity by enhancing the stacking of the (0 0 2) lattice plane. The MoS₂ samples prepared at pH 7.0 and 9.5 showed increased CO conversion during methanation, which was associated with a low concentration of Mo⁵⁺ species and the presence of surface sulfate species. Thus, a high pH during catalyst preparation may promote the complete decomposition of ATTM to MoS₂ and the formation of sulfur vacancies, which can facilitate methanation. Full article

(This article belongs to the Special Issue New Horizons for Heterogeneous Catalysts)

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17 pages, 3993 KiB

Open AccessArticle

Influence of Bio-Based Surfactants on TiO₂ Thin Films as Photoanodes for Electro-Photocatalysis

by Fanny Duquet, Amr Ahmed Nada, Matthieu Rivallin, Florence Rouessac, Christina Villeneuve-Faure and Stéphanie Roualdes

Catalysts 2021, 11(10), 1228; https://doi.org/10.3390/catal11101228 - 12 Oct 2021

Cited by 5 | Viewed by 1587

Abstract

Photocatalytic water splitting into hydrogen is considered as one of the key solutions to the current demand for eco-responsible energy. To improve the efficiency and sustainability of this process, the development of a TiO₂-based photoanode by adding bio-sourced surfactants to the [...] Read more.

Photocatalytic water splitting into hydrogen is considered as one of the key solutions to the current demand for eco-responsible energy. To improve the efficiency and sustainability of this process, the development of a TiO₂-based photoanode by adding bio-sourced surfactants to the sol–gel preparation method has been considered. Three different polymeric biosurfactants (GB, GC, and BIO) have been tested, giving rise to three different materials being structurally and morphologically characterized by XRD, Rietveld refinement, BET, SEM, AFM, and XPS, which was completed by light absorption, photocatalytic (Pilkington test), electronic (EIS and C-AFM), and photoelectrochemical (cyclic voltammetry) measurements. Correlations between the structure/morphology of materials and their functional properties have been established. One specific surfactant has been proven as the most suitable to lead to materials with optimized photoelectrochemical performance in direct relation with their photocatalytic properties essentially controlled by their specific surface area. Full article

(This article belongs to the Special Issue Titanium Dioxide-Based Nanostructured Catalysts for Solar Energy Production and Storage)

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13 pages, 7676 KiB

Open AccessFeature PaperArticle

Ru-gC₃N₄ Catalyzed Hydrodebenzylation of Benzyl Protected Alcohol and Acid Groups Using Sodium Hypophosphite as a Hydrogen Source

by Sourav Chakraborty, Ashish Bahuguna and Yoel Sasson

Catalysts 2021, 11(10), 1227; https://doi.org/10.3390/catal11101227 - 12 Oct 2021

Cited by 1 | Viewed by 1923

Abstract

A straightforward process for hydrodebenzylation of benzyl protected acid and alcohol derivatives to the corresponding acids and alcohols using sodium hypophosphite in the presence of Ru-GCN catalyst is reported. The developed Ru-GCN catalyst is cost effective compared to other noble metal-based catalysts and [...] Read more.

A straightforward process for hydrodebenzylation of benzyl protected acid and alcohol derivatives to the corresponding acids and alcohols using sodium hypophosphite in the presence of Ru-GCN catalyst is reported. The developed Ru-GCN catalyst is cost effective compared to other noble metal-based catalysts and has been explored to exhibit excellent activity for catalytic hydrodebenzylation reactions under moderate reaction conditions. The non-corrosive sodium hypophosphite has been found as a better hydrogen donor compared to alkali metal formats in presence of Ru-GCN catalyst. The stated catalyst was characterized using several spectrometric and material characterization methods such as PXRD, IR, SEM, TEM, XPS, and TGA. The Ru-GCN catalyst corroborated good reusability and stability for multiple cycles. The catalyst preparation is facile and the developed process is simple and safe as it avoids use of high hydrogen pressure. The developed protocol can also be replicated on industrial scale on account of excellent recyclability and retained activity after multiple cycles and makes the process sustainable. Gram scale reaction was performed to verify the industrial potential of reported catalyst. Full article

(This article belongs to the Special Issue Advances in Graphitic Carbon Nitride-Based Catalysts)

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