Catalysts

15 pages, 3699 KiB

Open AccessArticle

Biochar Derived from Palm Waste Supported Greenly Synthesized MnO₂ Nanoparticles as a Novel Adsorbent for Wastewater Treatment

by Amel Taha and Samah Daffalla

Catalysts 2023, 13(2), 451; https://doi.org/10.3390/catal13020451 - 20 Feb 2023

Cited by 2 | Viewed by 1706

Abstract

Water pollution with dye effluents from different industries is a broadly established environmental and health problem that needs serious attention. In this study, making use of Acacia nilotica seed extract, greenly synthesized MnO₂ nanoparticles were loaded on the surface of biochar derived [...] Read more.

Water pollution with dye effluents from different industries is a broadly established environmental and health problem that needs serious attention. In this study, making use of Acacia nilotica seed extract, greenly synthesized MnO₂ nanoparticles were loaded on the surface of biochar derived from palm waste (MnO₂/PF), with specific surface areas of 70.97 m²/g. Batch experiments were adopted, aiming to evaluate the performance of palm fronds, biochar, and the MnO₂/PF adsorbents in methyl orange (MO) removal from an aqueous solution. The feedstock and synthesized biochars were comprehensively characterized using XRD, SEM-EDX, FTIR, and BET surface area techniques. Moreover, the influences of the modification of palm fronds, initial dye concentrations, pH, and adsorbent dosage on MO uptake were examined. The results demonstrated that MnO₂/PF biochar nanocomposite led to an increase in the removal efficiency by 6 and 1.5 times more than those of palm fronds and biochar, respectively. In addition, it was found that the second-order kinetic model presented the kinetic adsorption very well. This paper demonstrates that the depositing of greenly synthesized MnO₂ nanoparticles on the date palm waste biochar forms a novel adsorbent (MnO₂/PF) for the removal of MO from aqueous solutions. Furthermore, this adsorbent was easy to synthesize under moderate conditions without the need for chemical capping agents, and would thus be cost-effective and eco-friendly. Full article

(This article belongs to the Special Issue Nanocatalysts for the Degradation of Refractory Pollutants)

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18 pages, 4774 KiB

Open AccessArticle

Alkali and Alkaline Earth Metals (K, Ca, Sr) Promoted Cu/SiO₂ Catalyst for Hydrogenation of Methyl Acetate to Ethanol

by Muhammad Naeem Younis, Zhiheng Ren, Chunshan Li, Erqiang Wang and Jie Li

Catalysts 2023, 13(2), 450; https://doi.org/10.3390/catal13020450 - 20 Feb 2023

Cited by 1 | Viewed by 1744

Abstract

The advancing effects of various alkali and alkaline earth metals (inclusive of K, Ca, and Sr) modified Cu/SiO₂ catalysts, prepared with a modified precipitation-gel method, were investigated for the production of ethanol via hydrogenation of methyl acetate. Our results showed that Sr-doped [...] Read more.

The advancing effects of various alkali and alkaline earth metals (inclusive of K, Ca, and Sr) modified Cu/SiO₂ catalysts, prepared with a modified precipitation-gel method, were investigated for the production of ethanol via hydrogenation of methyl acetate. Our results showed that Sr-doped catalysts exhibited the best and most consistent results during catalytic tests. A series of techniques, including X-ray diffraction technique, Raman spectroscopy, N₂ adsorption/desorption, N₂O titration method, FTIR spectroscopy, and H₂ temperature, programmed desorption and reduction (TPD and TPR), and X-ray Photoelectron Spectroscopy, which was used to check the detailed characterization of Sr modification in the catalyst and its structural impacts on the properties of the catalyst. These results demonstrated that the addition of 5%Sr could strengthen the intrinsic stability of the catalyst by formulating the appropriate ratio of Cu⁺/(Cu⁰ + Cu⁺) to facilitate catalytic outcome improvement. The addition of 5%Sr-30%Cu/SiO₂ under the most favorable conditions, resulting in the peak conversion of MA (95%) and ethanol selectivity (96%), indicates its magnificent catalytic stabilizing effects. Furthermore, the best performing catalyst was compared and tested under various conditions (LHSV and temperatures) and a 300 h long life run. Full article

(This article belongs to the Section Catalytic Reaction Engineering)

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26 pages, 13065 KiB

Open AccessFeature PaperArticle

Synthesis of Activated Porous Carbon from Red Dragon Fruit Peel Waste for Highly Active Catalytic Reduction in Toxic Organic Dyes

by Pitchaimani Veerakumar, Shih-Tung Hung, Pei-Qi Hung and Veeraraghavan Vishnu Priya

Catalysts 2023, 13(2), 449; https://doi.org/10.3390/catal13020449 - 20 Feb 2023

Cited by 2 | Viewed by 1998

Abstract

In this study, an alternative precursor for production of biomass-derived activated carbon was introduced using dragon fruit (Hylocereus costaricensis) peels. Chemical activators such as FeCl₃, MgCl_2, ZnCl₂ were used in the thermal carbonization process to convert carbon [...] Read more.

In this study, an alternative precursor for production of biomass-derived activated carbon was introduced using dragon fruit (Hylocereus costaricensis) peels. Chemical activators such as FeCl₃, MgCl_2, ZnCl₂ were used in the thermal carbonization process to convert carbon into porous carbon (PC). However, heteroatom-doped PC catalysts including N-, B-, and P-doped carbon catalysts in the field of dye removal is highly desirable. Several approaches (XRD, FE-SEM/TEM, XPS, FT-IR, EDS, and elemental mapping) were employed to examine the surface morphology, surface properties, and elemental composition of the PC catalyst. The catalytic activity of metal-free PC catalyst was demonstrated for methylene blue (MB), crystal violet (CV), and Nile blue (NB) in a mild environment The corresponding rate constant (k_app) values were estimated as 0.2473, 0.3248, and 0.3056 min⁻¹, respectively, for MB, CV, and NB, which were significantly greater than those of numerous reports. It exhibited the best catalytic activity and recyclability. Moreover, the approach proposed here could create new opportunities for the remediation of organic dyes in lakes and industrial wastewater. Full article

(This article belongs to the Special Issue Memorial Issue Dedicated to Prof. King-Chuen Lin: Palladium-Based Nanocomposites for Photocatalysts, Sensors, and Energy Storage)

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25 pages, 3973 KiB

Open AccessFeature PaperArticle

CO₂ Methanation over Nickel Catalysts: Support Effects Investigated through Specific Activity and Operando IR Spectroscopy Measurements

by Vigni V. González-Rangulan, Inés Reyero, Fernando Bimbela, Francisca Romero-Sarria, Marco Daturi and Luis M. Gandía

Catalysts 2023, 13(2), 448; https://doi.org/10.3390/catal13020448 - 20 Feb 2023

Cited by 9 | Viewed by 3367

Abstract

Renewed interest in CO₂ methanation is due to its role within the framework of the Power-to-Methane processes. While the use of nickel-based catalysts for CO₂ methanation is well stablished, the support is being subjected to thorough research due to its complex [...] Read more.

Renewed interest in CO₂ methanation is due to its role within the framework of the Power-to-Methane processes. While the use of nickel-based catalysts for CO₂ methanation is well stablished, the support is being subjected to thorough research due to its complex effects. The objective of this work was the study of the influence of the support with a series of catalysts supported on alumina, ceria, ceria–zirconia, and titania. Catalysts’ performance has been kinetically and spectroscopically evaluated over a wide range of temperatures (150–500 °C). The main results have shown remarkable differences among the catalysts as concerns Ni dispersion, metallic precursor reducibility, basic properties, and catalytic activity. Operando infrared spectroscopy measurements have evidenced the presence of almost the same type of adsorbed species during the course of the reaction, but with different relative intensities. The results indicate that using as support of Ni a reducible metal oxide that is capable of developing the basicity associated with medium-strength basic sites and a suitable balance between metallic sites and centers linked to the support leads to high CO₂ methanation activity. In addition, the results obtained by operando FTIR spectroscopy suggest that CO₂ methanation follows the formate pathway over the catalysts under consideration. Full article

(This article belongs to the Topic Materials and Catalysts for Pollutants and CO₂ Capture and Transformation)

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14 pages, 2630 KiB

Open AccessArticle

Removal of Safranin O from Water by UV/TiO₂/IO₃⁻ Advanced Oxidation Process: Parametric Study and Impact of Inorganic Ions and Humic Acid

by Meriem Bendjama, Oualid Hamdaoui, Hamza Ferkous and Abdulaziz Alghyamah

Catalysts 2023, 13(2), 447; https://doi.org/10.3390/catal13020447 - 19 Feb 2023

Cited by 1 | Viewed by 1194

Abstract

In the present paper, the influence of iodate (IO₃⁻) ions on the photocatalytic process using titanium dioxide (UV/TiO₂) was systematically examined. The innovative studied system (UV/TiO₂/IO₃⁻) demonstrated high performance in the elimination of [...] Read more.

In the present paper, the influence of iodate (IO₃⁻) ions on the photocatalytic process using titanium dioxide (UV/TiO₂) was systematically examined. The innovative studied system (UV/TiO₂/IO₃⁻) demonstrated high performance in the elimination of safranin O (SO), a model dye, from water due to the implication of iodine radicals (IO₃^•, IO₂^•, IO^•, etc.). The degradation was assessed by monitoring the change in initial substrate concentration (5–30 mg∙L⁻¹), TiO₂ loading (0.01–3 g∙L⁻¹), IO₃⁻ concentration, liquid temperature, and initial pH. Further enhancement of oxyanion amount was beneficial for the initial rate of degradation (r₀) over the range 0.1–50 mM, such that r₀ rose from 0.724 to 1.12 mg∙L⁻¹∙min⁻¹. However, a concentration of 100 mM IO₃⁻ slowed the removal kinetics. Low pH values were found to be favorable for pollutant removal. Furthermore, a variety of inorganic and organic substances was employed to clarify the effect of the UV/TiO₂/IO₃⁻ process in natural waters. The findings revealed a negative impact of chloride excess in seawater and a decline in SO degradation in mineral water as a result of HCO₃⁻ presence at more than 1 mM. At high concentrations of natural organic matter, the heterogeneity and the strong adsorption of humic acid on the TiO₂ surface were found to be harmful for SO decay. Full article

(This article belongs to the Special Issue Catalytic and Ultrasonic-Assisted Catalytic Processes for Environment Remediation: Water, Air and Soil)

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13 pages, 3038 KiB

Open AccessArticle

Three-Dimensionally Printed Zero-Valent Copper with Hierarchically Porous Structures as an Efficient Fenton-like Catalyst for Enhanced Degradation of Tetracycline

by Sheng Guo, Meng Chen, Yao Huang, Yu Wei, Jawad Ali, Chao Cai and Qingsong Wei

Catalysts 2023, 13(2), 446; https://doi.org/10.3390/catal13020446 - 19 Feb 2023

Cited by 4 | Viewed by 1410

Abstract

Three-dimensionally printed materials show great performance and reliable stability in the removal of refractory organic pollutants in Fenton-like reactions. In this work, hierarchically porous zero-valent copper (3DHP-ZVC) was designed and fabricated via 3D printing and applied as a catalyst for the degradation of [...] Read more.

Three-dimensionally printed materials show great performance and reliable stability in the removal of refractory organic pollutants in Fenton-like reactions. In this work, hierarchically porous zero-valent copper (3DHP-ZVC) was designed and fabricated via 3D printing and applied as a catalyst for the degradation of tetracycline (TC) through heterogeneous Fenton-like processes. It was found that the 3DHP-ZVC/H₂O₂ system could decompose over 93.2% of TC within 60 min, which is much superior to the homogeneous Cu²⁺/H₂O₂ system under similar conditions. The leaching concentration of Cu²⁺ ions in the 3DHP-ZVC/H₂O₂ system is 2.14 times lower than that in the Cu powder/H₂O₂ system in a neutral environment, which could be ascribed to the unique hierarchically porous structure of 3DHP-ZVC. Furthermore, 3DHP-ZVC exhibited compelling stability in 20 consecutive cycles. The effects of co-existing inorganic anions, adaptability, and pH resistance on the degradation of TC were also investigated. A series of experiments and characterizations revealed that Cu⁰ and superoxide radicals as reducing agents could facilitate the cycling of Cu(II)/Cu(I), thus enhancing the generation of hydroxyl radicals to degrade TC. This study provides new insights into employing promising 3D printing technology to develop high-reactivity, stable, and recycling-friendly components for wastewater treatment. Full article

(This article belongs to the Special Issue Nanocatalysts for the Degradation of Refractory Pollutants)

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13 pages, 2587 KiB

Open AccessArticle

Palladium Nanoparticles Incorporated Fumed Silica as an Efficient Catalyst for Nitroarenes Reduction via Thermal and Microwave Heating

by Afaf Y. Khormi, Badria M. Al-Shehri, Fatimah A. M. Al-Zahrani, Mohamed S. Hamdy, Amr Fouda and Mohamed R. Shaaban

Catalysts 2023, 13(2), 445; https://doi.org/10.3390/catal13020445 - 19 Feb 2023

Cited by 2 | Viewed by 1820

Abstract

The reduction of nitroarenes to arylamines is a synthetically important transformation both in the laboratory and in industry. Herein, Palladium (Pd) nanoparticles were synthesized via incorporation with mesoporous fumed silica material by doping technique. Water was used as a solvent and the as-synthetized [...] Read more.

The reduction of nitroarenes to arylamines is a synthetically important transformation both in the laboratory and in industry. Herein, Palladium (Pd) nanoparticles were synthesized via incorporation with mesoporous fumed silica material by doping technique. Water was used as a solvent and the as-synthetized material was reduced by using NaBH₄ to ensure the total transformation of PdO into Pd nanoparticles. The synthesized sample was characterized by using inductively coupled plasma (ICP) elemental analysis, X-ray powder diffraction (XRD), N₂ sorption measurement, scanning electron microscope (SEM), energy-dispersive spectroscopy (EDX), and transmission electron microscopy (TEM). Data showed that the Pd nanoparticles were successfully synthesized and supported on the mesoporous silica with an average size in the ranges of 10–20 nm, with an irregular shape. The purity of the synthesized sample was confirmed by EDX analysis which exhibits the presence of Si, O, and Pd. The catalytic activity of the prepared sample was evaluated in the heterogeneous reduction of nitroarenes to aromatic amines. Reduction reaction was monitored by Shimadzu GC-17A gas chromatography (GC, Japan) equipped with flam ionization detector and RTX-5 column, 30 m × 0.25 mm, 1-μm film thickness. Helium was used as carrier gas at flow rate 0.6 mL/min. Interestingly, the green hydrogenation of nitroarenes to primary amine compounds was achieved in an aqueous solution with high efficiency and in a short time; moreover, the reusability of heterogeneous Pd-SiO₂ was performed for four repeated cycles with more than 88% of efficiency at the fourth run. Finally, the heterogeneity of catalysis with high reliability and eco-friendly processes is a super new trend of nitroarenes reduction in the industry and economic scales. Full article

(This article belongs to the Special Issue Nanomaterials for Photocatalysis II)

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11 pages, 3273 KiB

Open AccessFeature PaperArticle

Novel Copper-Based Catalytic Systems for Atom Transfer Radical Polymerization of Acrylonitrile

by Ivan D. Grishin, Elizaveta I. Zueva, Yulia S. Pronina and Dmitry F. Grishin

Catalysts 2023, 13(2), 444; https://doi.org/10.3390/catal13020444 - 18 Feb 2023

Viewed by 1520

Abstract

Atom Transfer Radical Polymerization (ATRP) is an effective catalytic process leading to well-defined polymers with desired properties. This process based on reversible deactivation of propagating chains has a lower rate in comparison with conventional radical polymerization, especially in the case of obtaining polymers [...] Read more.

Atom Transfer Radical Polymerization (ATRP) is an effective catalytic process leading to well-defined polymers with desired properties. This process based on reversible deactivation of propagating chains has a lower rate in comparison with conventional radical polymerization, especially in the case of obtaining polymers with high molecular weights. Thus, the increase of the rate of this process with preserving control over molecular weight distribution is a challenging task. In this work, novel catalytic systems for Activators Generated by Electron Transfer (AGET) ATRP of acrylonitrile based on copper (II) bromide complexes were proposed. It was found that Rochelle salt (potassium sodium tartrate tetrahydrate) may be used as a reducing agent for regeneration of copper-based catalysts to increase the rate of the process. The provided UV-vis spectroscopy experiments have confirmed the reducing ability of tartaric anion. It was found that the use tandem catalytic system based on two copper complexes with different ligands also increases the polymerization rate. The performed experiments allowed us to develop a catalytic system for rapidly obtaining polyacrylonitrile polymers with desired molecular weights exceeding 100 kDa. Full article

(This article belongs to the Section Catalysis in Organic and Polymer Chemistry)

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19 pages, 3527 KiB

Open AccessArticle

Interaction of Jania rubens Polyphenolic Extract as an Antidiabetic Agent with α-Amylase, Lipase, and Trypsin: In Vitro Evaluations and In Silico Studies

by Asmaa Nabil-Adam, Mohamed L. Ashour, Tamer M. Tamer, Mohamed A. Shreadah and Mohamed A. Hassan

Catalysts 2023, 13(2), 443; https://doi.org/10.3390/catal13020443 - 18 Feb 2023

Cited by 10 | Viewed by 2455

Abstract

Jania rubens red seaweed has various bioactive compounds that can be used for several medicinal and pharmaceutical applications. In this study, we investigate the antidiabetic, anti-inflammatory, and antioxidant competency of Jania rubens polyphenolic extract (JRPE) by assessing their interactions with α-amylase, lipase, and [...] Read more.

Jania rubens red seaweed has various bioactive compounds that can be used for several medicinal and pharmaceutical applications. In this study, we investigate the antidiabetic, anti-inflammatory, and antioxidant competency of Jania rubens polyphenolic extract (JRPE) by assessing their interactions with α-amylase, lipase, and trypsin enzymes. HPLC analysis revealed the dominance of twelve polyphenolic compounds. We performed computational analysis using α-amylase, lipase, and trypsin as target proteins for the polyphenols to explore their activities based on their predicted modes of binding sites following molecular modeling analysis. The molecular docking analysis demonstrated a good affinity score with a noticeable affinity to polyphenolic compositions of Jania rubens. The compounds with the highest affinity score for α-amylase (PDB: 4W93) were kaempferol, quercetin, and chlorogenic acid, with −8.4, −8.8 and −8 kcal/mol, respectively. Similarly, lipase (PDB: 1LPB) demonstrated high docking scores of −7.1, −7.4, and −7.2 kcal/mol for kaempferol, quercetin, and chlorogenic acid, respectively. Furthermore, for trypsin (PDB: 4DOQ) results, kaempferol, quercetin, and chlorogenic acid docking scores were −7.2, −7.2, and −7.1 kcal/mol, respectively. The docking findings were verified using in vitro evaluations, manifesting comparable results. Overall, these findings enlighten that the JRPE has antidiabetic, anti-inflammatory, and antioxidant properties using different diabetics’ enzymes that could be further studied using in vivo investigations for diabetes treatment. Full article

(This article belongs to the Special Issue Enzymes in Biomedical, Cosmetic and Food Application)

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10 pages, 3156 KiB

Open AccessFeature PaperArticle

Selective CO₂ Fixation to Styrene Oxide by Ta-Substitution of Lindqvist-Type [(Ta,Nb)₆O₁₉]⁸⁻ Clusters

by Vorakit Chudatemiya, Mio Tsukada, Hiroki Nagakari, Soichi Kikkawa, Jun Hirayama, Naoki Nakatani, Takafumi Yamamoto and Seiji Yamazoe

Catalysts 2023, 13(2), 442; https://doi.org/10.3390/catal13020442 - 18 Feb 2023

Cited by 1 | Viewed by 1441

Abstract

Metal oxide clusters composed of group 5 metal ions, such as Nb and Ta, exhibit catalytic activities for CO₂ fixation to styrene oxide (SO) due to the highly negative natural bonding charge of the terminal O atoms that could work [...] Read more.

Metal oxide clusters composed of group 5 metal ions, such as Nb and Ta, exhibit catalytic activities for CO₂ fixation to styrene oxide (SO) due to the highly negative natural bonding charge of the terminal O atoms that could work as CO₂ activation sites. In this study, tetrabutylammonium (TBA) salts of [Ta_xNb_6−xO₁₉]⁸⁻ (TBA-Ta_xNb_6−x, x = 0–6) were prepared and Ta-substitution effect on the catalytic properties of TBA-Ta_xNb_6−x for CO₂ fixation to SO was investigated. We found that TBA-Ta₁Nb₅ shows the highest styrene carbonate (SC) selectivity (95%) among TBA-Ta_xNb_6−x, although the SO conversion monotonously increases with the incremental Ta substitution amount. The CO₂ fixation to SO under various conditions and in situ X-ray absorption fine structure measurements reveal that CO₂ is activated on both terminal O sites coordinated to the Ta (terminal O_Ta) and Nb (terminal O_Nb) sites, whereas the activation of SO proceeds on the terminal O_Ta and/or bridge O sites that are connected to Ta. Density functional theory (DFT) calculations reveal that the terminal O_Ta of TBA-Ta₁Nb₅ preferentially adsorbs CO₂ compared with other O_Nb base sites. We conclude that the selective CO₂ activation at terminal O_Ta of TBA-Ta₁Nb₅ without SO activation is a crucial factor for high SC selectivity in the CO₂ fixation to SO. Full article

(This article belongs to the Special Issue Nanostructured Materials and Nanoparticles as Efficient Catalysts: Design and Mechanism)

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14 pages, 2856 KiB

Open AccessEditor’s ChoiceArticle

Role of N-Terminal Extensional Long α-Helix in the Arylesterase from Lacticaseibacillus rhamnosus GG on Catalysis and Stability

by Bin-Chun Li, Tongtong Guo, Xue Li, Xueting Hou and Guo-Bin Ding

Catalysts 2023, 13(2), 441; https://doi.org/10.3390/catal13020441 - 18 Feb 2023

Viewed by 1059

Abstract

In the α/β hydrolases superfamily, the extra module modulated enzymatic activity, substrate specificity, and stability. The functional role of N-terminal extensional long α-helix (Ala2-Glu29, designated as NEL-helix) acting as the extra module in the arylesterase LggEst from Lacticaseibacillus rhamnosus GG had been systemically [...] Read more.

In the α/β hydrolases superfamily, the extra module modulated enzymatic activity, substrate specificity, and stability. The functional role of N-terminal extensional long α-helix (Ala2-Glu29, designated as NEL-helix) acting as the extra module in the arylesterase LggEst from Lacticaseibacillus rhamnosus GG had been systemically investigated by deletion mutagenesis, biochemical characterization, and biophysical methods. The deletion of the NEL-helix did not change the overall structure of this arylesterase. The deletion of the NEL-helix led to the shifting of optimal pH into the acidity and the loss of thermophilic activity. The deletion of the NEL-helix produced a 10.6-fold drop in catalytic activity towards the best substrate pNPC10. NEL-Helix was crucial for the thermostability, chemical resistance, and organic solvents tolerance. The deletion of the NEL-helix did not change the overall rigidity of enzyme structure and only reduced the local rigidity of the active site. Sodium deoxycholate might partially replenish the loss of activity caused by the deletion of the NEL-helix. Our research further enriched the functional role of the extra module on catalysis and stability in the α/β hydrolase fold superfamily. Full article

(This article belongs to the Special Issue Advances in Enzyme Engineering, Biocatalysis and Biosynthesis)

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36 pages, 7985 KiB

Open AccessReview

Magnetic Nanomaterials as Catalysts for Syngas Production and Conversion

by Natarajan Chidhambaram, Samuel Jasmine Jecintha Kay, Saravanan Priyadharshini, Rajakantham Meenakshi, Pandurengan Sakthivel, Shanmugasundar Dhanbalan, Shajahan Shanavas, Sathish-Kumar Kamaraj and Arun Thirumurugan

Catalysts 2023, 13(2), 440; https://doi.org/10.3390/catal13020440 - 18 Feb 2023

Cited by 3 | Viewed by 2722

Abstract

The conversion of diverse non-petroleum carbon elements, such as coal, biomass, natural/shale gas, and even CO₂, into cleaner hydrocarbon fuels and useful chemicals relies heavily on syngas, which is a combination of CO and H₂. Syngas conversions, which have [...] Read more.

The conversion of diverse non-petroleum carbon elements, such as coal, biomass, natural/shale gas, and even CO₂, into cleaner hydrocarbon fuels and useful chemicals relies heavily on syngas, which is a combination of CO and H₂. Syngas conversions, which have been around for almost a century, will probably become even more important in the production of energy and chemicals due to the rising need for liquid fuels and chemical components derived from sources of carbon other than crude oil. Although a number of syngas-based technologies, including the production of methanol, Fischer–Tropsch (FT) synthesis, and carbonylation, have been industrialized, there is still a great need for new catalysts with enhanced activity and adjustable product selectivity. New novel materials or different combinations of materials have been investigated to utilize the synergistic effect of these materials in an effective way. Magnetic materials are among the materials with magnetic properties, which provide them with extra physical characteristics compared to other carbon-based or conventional materials. Moreover, the separation of magnetic materials after the completion of a specific application could be easily performed with a magnetic separation process. In this review, we discuss the synthesis processes of various magnetic nanomaterials and their composites, which could be utilized as catalysts for syngas production and conversion. It is reported that applying an external magnetic field could influence the outcomes of any applications of magnetic nanomaterials. Here, the possible influence of the magnetic characteristics of magnetic nanomaterials with an external magnetic field is also discussed. Full article

(This article belongs to the Special Issue Innovative Catalytic Materials for Environmental Remediation and Energy Applications)

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14 pages, 3592 KiB

Open AccessArticle

Green and Efficient Acquirement of Unsaturated Ether from Direct and Selective Hydrogenation Coupling Unsaturated Aldehyde with Alcohol by Bi-Functional Al-Ni-P Heterogeneous Catalysts

by Yan Xu, Huiqing Zeng, Dan Zhao, Shuhua Wang, Shunmin Ding and Chao Chen

Catalysts 2023, 13(2), 439; https://doi.org/10.3390/catal13020439 - 18 Feb 2023

Cited by 1 | Viewed by 1265

Abstract

In view of the industrial importance of high-grade unsaturated ether (UE) and the inconvenience of acquiring the compound, herein, a series of low-cost Al-Ni-P catalysts in robust AlPO₄/Ni₂P structure possessing novel bi-functional catalytic features (hydrogenation activation and acid catalysis) [...] Read more.

In view of the industrial importance of high-grade unsaturated ether (UE) and the inconvenience of acquiring the compound, herein, a series of low-cost Al-Ni-P catalysts in robust AlPO₄/Ni₂P structure possessing novel bi-functional catalytic features (hydrogenation activation and acid catalysis) were innovated, and testified to be efficient for directly synthesizing UE with a superior yield up to 97% from the selective hydrogenation coupling carbonyl of unsaturated aldehyde (cinnamaldehyde or citral) with C1–C5 primary or secondary alcohol under 0.1 MPa H₂ and 393 K. The integrated advantages of high efficiency, green manner and convenient operation of the present heterogeneous catalytic system gave the system potential for feasibly harvesting high-grade unsaturated ether in related fine chemical synthesis networks. Full article

(This article belongs to the Special Issue Exclusive Papers in Environmentally Friendly Catalysis in China)

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23 pages, 5166 KiB

Open AccessReview

Transition-Metal-Catalyzed C–C Bond Macrocyclization via Intramolecular C–H Bond Activation

by Xiao Wang, Ming-Zhu Lu and Teck-Peng Loh

Catalysts 2023, 13(2), 438; https://doi.org/10.3390/catal13020438 - 17 Feb 2023

Cited by 3 | Viewed by 1721

Abstract

Macrocycles are commonly synthesized via late-stage macrolactamization and macrolactonization. Strategies involving C–C bond macrocyclization have been reported, and examples include the transition-metal-catalyzed ring-closing metathesis and coupling reactions. In this mini-review, we summarize the recent progress in the direct synthesis of polyketide and polypeptide [...] Read more.

Macrocycles are commonly synthesized via late-stage macrolactamization and macrolactonization. Strategies involving C–C bond macrocyclization have been reported, and examples include the transition-metal-catalyzed ring-closing metathesis and coupling reactions. In this mini-review, we summarize the recent progress in the direct synthesis of polyketide and polypeptide macrocycles using a transition-metal-catalyzed C–H bond activation strategy. In the first part, rhodium-catalyzed alkene–alkene ring-closing coupling for polyketide synthesis is described. The second part summarizes the synthesis of polypeptide macrocycles. The activation of indolyl and aryl C(sp²)–H bonds followed by coupling with various coupling partners such as aryl halides, arylates, and alkynyl bromide is then documented. Moreover, transition-metal-catalyzed C–C bond macrocyclization reactions via alkyl C(sp³)–H bond activation are also included. We hope that this mini-review will inspire more researchers to explore new and broadly applicable strategies for C–C bond macrocyclization via intramolecular C–H activation. Full article

(This article belongs to the Special Issue Theme Issue in Memory to Prof. Jiro Tsuji (1927–2022))

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18 pages, 3805 KiB

Open AccessEditor’s ChoiceArticle

Ni₂P-Modified P-Doped Graphitic Carbon Nitride Hetero-Nanostructures for Efficient Photocatalytic Aqueous Cr(VI) Reduction

by Evangelos K. Andreou, Eirini D. Koutsouroubi, Ioannis Vamvasakis and Gerasimos S. Armatas

Catalysts 2023, 13(2), 437; https://doi.org/10.3390/catal13020437 - 17 Feb 2023

Cited by 4 | Viewed by 1820

Abstract

Targeting heterostructures with modulated electronic structures and efficient charge carrier separation and mobility is an effective strategy to improve photocatalytic performance. In this study, we report the synthesis of 2D/3D hybrid heterostructures comprising P-doped graphitic carbon nitride (g-C₃N₄) nanosheets [...] Read more.

Targeting heterostructures with modulated electronic structures and efficient charge carrier separation and mobility is an effective strategy to improve photocatalytic performance. In this study, we report the synthesis of 2D/3D hybrid heterostructures comprising P-doped graphitic carbon nitride (g-C₃N₄) nanosheets (ca. 50–60 nm in lateral size) and small-sized Ni₂P nanoparticles (ca. 10–12 nm in diameter) and demonstrate their prominent activity in the photocatalytic reduction of Cr(VI). Utilizing a combination of spectroscopic and electrochemical characterization techniques, we unveil the reasons behind the distinct photochemical performance of these materials. We show that Ni₂P modification and P doping of the g-C₃N₄ effectively improve the charge-carrier transportation and spatial separation through the interface of Ni₂P/P-doped g-C₃N₄ junctions. As a result, the catalyst containing 15 wt.% Ni₂P exhibits superior photocatalytic activity in the detoxification of Cr(VI)-contaminated effluents under UV-visible light illumination, presenting an apparent quantum yield (QY) of 12.5% at 410 nm, notably without the use of sacrificial additives. This study marks a forward step in understanding and fabricating cost-effective photocatalysts for photochemical applications. Full article

(This article belongs to the Special Issue Feature Papers in Environmental Catalysis)

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28 pages, 6740 KiB

Open AccessFeature PaperReview

Gold Complexes with Hydrophilic N-Heterocyclic Carbene Ligands and Their Contribution to Aqueous-Phase Catalysis

by Pascale Crochet and Victorio Cadierno

Catalysts 2023, 13(2), 436; https://doi.org/10.3390/catal13020436 - 17 Feb 2023

Viewed by 1715

Abstract

N-Heterocyclic carbenes (NHCs) are nowadays one of the most widely employed ligands in organometallic chemistry and homogeneous catalysis due to the inherent stability of the metal-carbene bond and the ease of modification of the backbone as well as the N-wingtips substituents [...] Read more.

N-Heterocyclic carbenes (NHCs) are nowadays one of the most widely employed ligands in organometallic chemistry and homogeneous catalysis due to the inherent stability of the metal-carbene bond and the ease of modification of the backbone as well as the N-wingtips substituents of these ligands. The functionalization of NHCs with hydrophilic groups offers the possibility of using NHC-metal complexes in aqueous catalysis, a hot topic within the Green Chemistry context due to the positive implications associated with the use of water as a reaction medium. In line with the enormous interest aroused by gold complexes in catalysis, significant efforts have been directed in the last years to the design and application of hydrophilic NHC-gold catalysts. This review is aimed to summarize the research in this area. The catalytic applications of water-soluble gold nanoparticles stabilized by hydrophilic NHCs are also covered. Full article

(This article belongs to the Special Issue Exclusive Review Papers in Catalysis in Organic and Polymer Chemistry)

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15 pages, 7192 KiB

Open AccessFeature PaperArticle

Mechanistic Studies into the Selective Production of 2,5-furandicarboxylic Acid from 2,5-bis(hydroxymethyl)furan Using Au-Pd Bimetallic Catalyst Supported on Nitrated Carbon Material

by Yiran Liu, Yao Chen, Wen Guan, Yu Cao, Fang Wang and Yunlei Zhang

Catalysts 2023, 13(2), 435; https://doi.org/10.3390/catal13020435 - 17 Feb 2023

Cited by 4 | Viewed by 1471

Abstract

Aerobic oxidation of bio-sourced 2,5-bis(hydroxymethyl)furan (BHMF) to 2, 5-furandicarboxylic acid (FDCA), a renewable and green alternative to petroleum-derived terephthalic acid (TPA), is of great significance in green chemicals production. Herein, hierarchical porous bowl-like nitrogen-rich (nitrated) carbon-supported bimetallic Au-Pd nanocatalysts (Au_mPd_n [...] Read more.

Aerobic oxidation of bio-sourced 2,5-bis(hydroxymethyl)furan (BHMF) to 2, 5-furandicarboxylic acid (FDCA), a renewable and green alternative to petroleum-derived terephthalic acid (TPA), is of great significance in green chemicals production. Herein, hierarchical porous bowl-like nitrogen-rich (nitrated) carbon-supported bimetallic Au-Pd nanocatalysts (Au_mPd_n/ N-BN_xC) with different nitrogen content and bimetal nanoparticle sizes were developed and employed for the highly efficient aerobic oxidation of BHMF to FDCA in sodium carbonate aqueous solution. The reaction pathway for catalytic oxidation of BHMF went through the steps of BHMF→HMF→HMFCA→FFCA→FDCA. Kinetics studies showed that the activation energies of BHMF, HMF, HMFCA, and FFCA were 58.1 kJ·moL⁻¹, 39.1 kJ·moL⁻¹, 129.2 kJ·moL⁻¹, and 56.3 kJ·moL⁻¹, respectively, indicating that the oxidation of intermediate HMFCA to FFCA was the rate-determining step. ESR tests proved that the active species was a superoxide radical. Owing to the synergy between the nitrogen-rich carbon support and bimetallic Au-Pd nanoparticles, the Au₁Pd₁/N-BN₂C nanocatalysts exhibited BHMF conversion of 100% and FDCA yield of 95.8% under optimal reaction conditions. Furthermore, the nanocatalysts showed good stability and reusability. This work provides a versatile strategy for the design of heterogeneous catalysts for the highly efficient production of FDCA from BHMF. Full article

(This article belongs to the Special Issue Catalytical Methods for the Production of Fine and Bulk Chemicals and Biomaterials from Biomass)

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19 pages, 6037 KiB

Open AccessArticle

Photocatalytic Degradation of Paracetamol under Simulated Sunlight by Four TiO₂ Commercial Powders: An Insight into the Performance of Two Sub-Micrometric Anatase and Rutile Powders and a Nanometric Brookite Powder

by Nicola Blangetti, Francesca S. Freyria, Maria Chiara Calviello, Nicoletta Ditaranto, Salvatore Guastella and Barbara Bonelli

Catalysts 2023, 13(2), 434; https://doi.org/10.3390/catal13020434 - 17 Feb 2023

Cited by 7 | Viewed by 1821

Abstract

The photocatalytic degradation of the emerging contaminant paracetamol in aqueous solution has been studied under 1 SUN (~1000 W m⁻²) in the presence of four commercial TiO₂ powders, namely sub-micrometric anatase and rutile, and nanometric brookite and P25 (the popular [...] Read more.

The photocatalytic degradation of the emerging contaminant paracetamol in aqueous solution has been studied under 1 SUN (~1000 W m⁻²) in the presence of four commercial TiO₂ powders, namely sub-micrometric anatase and rutile, and nanometric brookite and P25 (the popular anatase/rutile mixture used as a benchmark in most papers). The rutile powder showed low activity, whereas, interestingly, the anatase and the brookite powders outperformed P25 in terms of total paracetamol conversion to carboxylic acids, which, according to the literature, are the final products of its degradation. To explain such results, the physicochemical properties of the powders were studied by applying a multi-technique approach. Among the physicochemical properties usually affecting the photocatalytic performance of TiO₂, the presence of some surface impurities likely deriving from K₃PO₄ (used as crystallization agent) was found to significantly affect the percentage of paracetamol degradation obtained with the sub-micrometric anatase powder. To confirm the role of phosphate, a sample of anatase, obtained by a lab synthesis procedure and having a “clean” surface, was used as a control, though characterized by nanometric particles and higher surface area. The sample was less active than the commercial anatase, but it was more active after impregnation with K₃PO₄. Conversely, the presence of Cl at the surface of the rutile did not sizably affect the (overall poor) photocatalytic activity of the powder. The remarkable photocatalytic activity of the brookite nanometric powder was ascribed to a combination of several physicochemical properties, including its band structure and nanoparticles size. Full article

(This article belongs to the Special Issue TiO₂-Based Materials for (Photo)Catalysis II)

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17 pages, 13271 KiB

Open AccessArticle

Ionothermal Crystallization of SAPO-11 Using Novel Pyridinium Ionic Liquid and Its Catalytic Activity in Esterification of Levulinic Acid into Ethyl Levulinate

by Al Issa Jehad Moh’dFathi Mohammad, Vinithaa Saminathan, Zeinhom M. El-Bahy, Laure Michelin, Tau Chuan Ling and Eng-Poh Ng

Catalysts 2023, 13(2), 433; https://doi.org/10.3390/catal13020433 - 17 Feb 2023

Viewed by 1629

Abstract

A study using a novel pyridinium ionic liquid, namely 1-propylpyridinium bromide ([PPy]Br), to crystallize SAPO-11 under ionothermal conditions is reported. By carefully following the crystallization process, SAPO-11 can readily be crystallized in the presence of [PPy]Br, which serves as a synthesis solvent and [...] Read more.

A study using a novel pyridinium ionic liquid, namely 1-propylpyridinium bromide ([PPy]Br), to crystallize SAPO-11 under ionothermal conditions is reported. By carefully following the crystallization process, SAPO-11 can readily be crystallized in the presence of [PPy]Br, which serves as a synthesis solvent and structure-directing agent, at 150 °C after 133 h of heating. The study also focuses on manipulating other synthesis parameters (e.g., crystallization temperature, phosphorous content, silicon amount and [PPy]Br concentration) and investigating their respective effects on the formation of SAPO-11. The crystallized SAPO-11 has an acidic nature and a high surface area. Under conductive instant heating conditions, the SAPO-11 catalyst is very active in the conversion of levulinic acid into ethyl levulinate; 93.4% conversion and 100% selectivity of ethyl levulinate are recorded at 180 °C after 30 min of reaction. This result is comparable to or even better than those of conventional homogeneous catalysts. Full article

(This article belongs to the Special Issue Ionic Liquids for Green Catalysis and Separation)

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10 pages, 2450 KiB

Open AccessFeature PaperArticle

Cationic Covalent Triazine Network: A Metal-Free Catalyst for Effective Acetylene Hydrochlorination

by Zhaobing Shen, Ping Xing, Ke Wen and Biao Jiang

Catalysts 2023, 13(2), 432; https://doi.org/10.3390/catal13020432 - 17 Feb 2023

Cited by 1 | Viewed by 1487

Abstract

Vinyl chloride, the monomer of polyvinyl chloride, is produced primarily via acetylene hydrochlorination catalyzed by environmentally toxic carbon-supported HgCl₂. Recently, nitrogen-doped carbon materials have been explored as metal-free catalysts to substitute toxic HgCl₂. Herein, we describe the development of [...] Read more.

Vinyl chloride, the monomer of polyvinyl chloride, is produced primarily via acetylene hydrochlorination catalyzed by environmentally toxic carbon-supported HgCl₂. Recently, nitrogen-doped carbon materials have been explored as metal-free catalysts to substitute toxic HgCl₂. Herein, we describe the development of a cationic covalent triazine network (cCTN, cCTN-700) that selectively catalyzes acetylene hydrochlorination. cCTN-700 exhibited excellent catalytic activity with initial acetylene conversion, reaching ~99% and a vinyl chloride selectivity of >98% at 200 °C during a 45 h test. X-ray photoelectron spectroscopy, temperature programmed desorption, and charge calculation results revealed that the active sites for the catalytic reaction were the carbon atoms bonded to the pyridinic N and positively charged nitrogen atoms (viologenic N⁺) of the viologen moieties in cCTN-700, similar to the active sites in Au-based catalysts but different from the those in previously reported nitrogen-doped carbon materials. This research focuses on using cationic covalent triazine polymers for selective acetylene hydrochlorination. Full article

(This article belongs to the Special Issue Catalytic and Functional Materials for Environment and Energy)

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13 pages, 1601 KiB

Open AccessEditor’s ChoiceArticle

Chlorobenzene Mineralization Using Plasma/Photocatalysis Hybrid Reactor: Exploiting the Synergistic Effect

by N’Zanon Aly KONE, Nacer Belkessa, Youcef Serhane, Sandotin Lassina Coulibaly, Mahamadou Kamagate, Lotfi Mouni, Sivachandiran Loganathan, Lacina Coulibaly, Abdelkrim Bouzaza, Abdeltif Amrane and Aymen Amine Assadi

Catalysts 2023, 13(2), 431; https://doi.org/10.3390/catal13020431 - 16 Feb 2023

Cited by 2 | Viewed by 1597

Abstract

Mineralization of gaseous chlorobenzene (major VOC from cement plants) was studied in a continuous reactor using three advanced oxidation processes: (i) photocatalysis, (ii) Dielectric Barrier Discharge (DBD) plasma and (iii) DBD/TiO₂-UV coupling. The work showed an overproduction of OH * and [...] Read more.

Mineralization of gaseous chlorobenzene (major VOC from cement plants) was studied in a continuous reactor using three advanced oxidation processes: (i) photocatalysis, (ii) Dielectric Barrier Discharge (DBD) plasma and (iii) DBD/TiO₂-UV coupling. The work showed an overproduction of OH * and O * radicals in the reaction medium due to the interaction of Cl * and O₃. A parametric study was carried out in order to determine the evolution of the removal efficiency as a function of the concentration, the flow rate and the applied voltage. Indeed, a variation of the flow rate from 0.25 to 1 m³/h resulted in a decrease in the degradation rate from 18 to 9%. Similarly, an increase in concentration from 13 to 100 mg/m³ resulted in a change in degradation rate from 18 to 4%. When the voltage was doubled from 6 to 12 kV, the degradation rate varied from 22 to 29 % (plasma) and from 53 to 75% (coupling) at 13 mg/m³. The evolution of CO_X and O₃ was monitored during the experiments. When the voltage was doubled, the selectivity increased from 28 to 37% in the plasma alone and from 48 to 62 % in the coupled process. In addition, at this same voltage range, the amount of ozone formed varied from 10 to 66 ppm in plasma and 3 to 29 ppm in coupling. This degradation performance can be linked to a synergistic effect, which resulted in an increase in the intensity of the electric field of plasma by the TiO₂ and the improvement in the performance of the catalyst following the bombardment of various high-energy particles of the plasma. Full article

(This article belongs to the Special Issue Catalysts for Air Pollution Control: Present and Future)

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18 pages, 8712 KiB

Open AccessArticle

Methane Dry Reforming over Ni/NiO Supported on Ce-, Zr-, and Al-Modified Y₂O₃ for Hydrogen Production

by Zijian Chen, Lei Mao, Xiuzhong Fang, Xianglan Xu, Junwei Xu and Xiang Wang

Catalysts 2023, 13(2), 430; https://doi.org/10.3390/catal13020430 - 16 Feb 2023

Cited by 2 | Viewed by 1492

Abstract

In this work, Ce, Zr, and Al are used to promote Y₂O₃ as supports for Ni/NiO, with the expectation to obtain more efficient catalysts for DRM reaction. XRD and Raman results have testified that all the three cations have been [...] Read more.

In this work, Ce, Zr, and Al are used to promote Y₂O₃ as supports for Ni/NiO, with the expectation to obtain more efficient catalysts for DRM reaction. XRD and Raman results have testified that all the three cations have been doped into the lattice of Y₂O₃ to form a solid solution structure, thus obtaining supports with decreased crystallinity and improved surface areas. As a result, all the modified catalysts display evidently improved reaction performance. The Ni–support interaction of the modified catalysts is enhanced in comparison with the unmodified catalyst, thus having improved Ni dispersion. Moreover, the modified catalysts have improved alkalinity, which is beneficial to activate CO₂ and enhance the activity. In addition, it is found that all the modified catalysts possess a richer amount of surface active oxygen species (O₂^δ− and O₂⁻), which is critical to eliminate carbon depositions. It is believed that the interaction of these factors is responsible for the enhanced DRM performance of the modified catalysts. In situ DRIFTS results have confirmed that the addition of the secondary metals can improve the DRM activity of the catalyst by accelerating the conversion of formate intermediate species. Full article

(This article belongs to the Special Issue Exclusive Papers in Environmentally Friendly Catalysis in China)

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25 pages, 2461 KiB

Open AccessReview

Emission Control of Toluene in Iron Ore Sintering Using Catalytic Oxidation Technology: A Critical Review

by Qiqi Shi, Dongrui Kang, Yuting Wang and Xiao Zhang

Catalysts 2023, 13(2), 429; https://doi.org/10.3390/catal13020429 - 16 Feb 2023

Cited by 1 | Viewed by 1279

Abstract

Iron ore sintering flue gas containing large amounts of volatile organic compounds (VOCs) can form secondary photochemical smog and organic aerosols, thus posing a serious threat to human health and the ecological environment. Catalytic combustion technology has been considered as one of the [...] Read more.

Iron ore sintering flue gas containing large amounts of volatile organic compounds (VOCs) can form secondary photochemical smog and organic aerosols, thus posing a serious threat to human health and the ecological environment. Catalytic combustion technology has been considered as one of the most prospective strategies for VOC elimination. This paper focuses on a review of studies on catalytic removal of typical VOCs (toluene) on transition metal oxide catalysts in recent years, with advances in single metal oxides, multi-oxide composites, and supported metal oxide catalysts. Firstly, the catalytic activities of a series of catalysts for toluene degradation are evaluated and compared, leading to an analysis of the key catalytic indicators that significantly affect the efficiency of toluene degradation. Secondly, the reaction pathway and mechanism of toluene degradation are systematically introduced. Considering the site space and investment cost, the conversion of VOC pollutants to harmless substances using existing selective catalytic reduction (SCR) systems has been studied with considerable effort. Based on the current development of simultaneous multi-pollutant elimination technology, the interaction mechanism between the NH₃-SCR reaction and toluene catalytic oxidation on the surface is discussed in detail. Finally, views on the key scientific issues and the challenges faced, as well as an outlook for the future, are presented. This overview is expected to provide a guide for the design and industrial application of NO/VOC simultaneous removal catalysts. Full article

(This article belongs to the Special Issue Catalytic Purification of Pollutants and Catalytic Conversion of Solid Wastes)

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12 pages, 2806 KiB

Open AccessArticle

Catalyst Loading Controls Chemoselectivity: Unusual Effect in Rhodium(II) Carbene Insertion Reactions with Tetrahydrofuran

by Alexander Kazantsev, Ivan A. Rodionov, Olga Bakulina, Grigory Kantin, Dmitry Dar’in and Mikhail Krasavin

Catalysts 2023, 13(2), 428; https://doi.org/10.3390/catal13020428 - 16 Feb 2023

Cited by 1 | Viewed by 1162

Abstract

(E)-3-Arylidene-4-diazopyrrolidine-2,5-diones previously shown to yield two products in reactions with tetrahydrofuran mediated by rhodium carbenes—tetrahydrofur-2-yl-substituted product of C-H insertion and spirocyclic product of formal C-O insertion. Accidentally, it was noted that the ratio of the two products depends on the catalyst loading, [...] Read more.

(E)-3-Arylidene-4-diazopyrrolidine-2,5-diones previously shown to yield two products in reactions with tetrahydrofuran mediated by rhodium carbenes—tetrahydrofur-2-yl-substituted product of C-H insertion and spirocyclic product of formal C-O insertion. Accidentally, it was noted that the ratio of the two products depends on the catalyst loading, and the phenomenon was investigated in detail. It was found to be of preparative significance: by solely changing the catalyst loading from 0.01 mol% to 10 mol%, one can obtain sound yields of either of the two products. Mechanistic and kinetic interpretation of this new phenomenon has been proposed. Full article

(This article belongs to the Special Issue Catalysts in Energy Applications II)

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41 pages, 22568 KiB

Open AccessFeature PaperReview

Methane Combustion over the Porous Oxides and Supported Noble Metal Catalysts

by Hongxia Lin, Yuxi Liu, Jiguang Deng, Lin Jing and Hongxing Dai

Catalysts 2023, 13(2), 427; https://doi.org/10.3390/catal13020427 - 16 Feb 2023

Cited by 6 | Viewed by 2097

Abstract

Methane is the most stable hydrocarbon with a regular tetrahedral structure, which can be activated and oxidized above 1000 °C in conventional combustion. Catalytic oxidation is an effective way to eliminate lean methane under mild conditions, and the key issue is to develop [...] Read more.

Methane is the most stable hydrocarbon with a regular tetrahedral structure, which can be activated and oxidized above 1000 °C in conventional combustion. Catalytic oxidation is an effective way to eliminate lean methane under mild conditions, and the key issue is to develop the catalysts with high efficiencies, good stability, and high selectivities. Catalytic combustion of low-concentration methane can realize the light-off and deep conversion at low temperatures, thus achieving complete combustion with fewer byproducts below 500 °C. This review article summarizes the recent advances in preparation of ordered porous oxides and supported noble metal catalysts and their methane combustion applications. The results reveal that the superior performance (good hydrothermal stability and excellent moisture- or sulfur-resistant behavior) is associated with the well-ordered and developed three-dimensional porous structure, large surface area, ultrahigh component dispersion, fast mass transfer, low-temperature reducibility, reactant activation ability, and strong interaction between metal and support. In addition, the development trend of porous oxides for industrial applications in the future is also proposed. Full article

(This article belongs to the Special Issue Advances in Catalytic Oxidation of Methane and Carbon Monoxide, 2nd Edition)

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15 pages, 6497 KiB

Open AccessArticle

Layered Copper Hydroxide Salts as Catalyst for the “Click” Reaction and Their Application in Methyl Orange Photocatalytic Discoloration

by Rafael Marangoni, Rafael E. Carvalho, Monielly V. Machado, Vanessa B. Dos Santos, Sumbal Saba, Giancarlo V. Botteselle and Jamal Rafique

Catalysts 2023, 13(2), 426; https://doi.org/10.3390/catal13020426 - 16 Feb 2023

Cited by 3 | Viewed by 1834

Abstract

The 1,2,3-triazoles are an important class of organic compounds that are found in a variety of biologically active compounds. The most usual and efficient methodology to synthetize these compounds is the Copper-catalyzed Azide–Alkyne Cycloaddition (CuAAC), preferably by use of click chemistry principles. Therefore, [...] Read more.

The 1,2,3-triazoles are an important class of organic compounds that are found in a variety of biologically active compounds. The most usual and efficient methodology to synthetize these compounds is the Copper-catalyzed Azide–Alkyne Cycloaddition (CuAAC), preferably by use of click chemistry principles. Therefore, the development of simple, robust, easily accessible and efficient materials as catalysts for this kind of reaction is highly desirable. In this sense, layered hydroxide salts (LHS) emerge as an interesting alternative for the click reaction. Thus, we describe herein the preparation and characterization of copper (II) layered hydroxide salts and their application as catalysts for the CuAAC reaction under solvent-free conditions. This synthetic methodology of CuAAC reaction is attractive as it follows several concepts of green chemistry, such as being easy to perform, allowing purification without chromatographic column, the process forming no sub-products, affording the desired 1,2,3-traizoles in the specific 1,4-disubstituted position in high yield, and having a short reaction time. Moreover, the photocatalysis for the degradation of methyl orange was also highly efficient using the same catalyst. Full article

(This article belongs to the Special Issue Feature Papers in Catalysis in Organic and Polymer Chemistry)

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31 pages, 9945 KiB

Open AccessArticle

Impact of Geometric and Electronic Factors on Selective Hydro-Deoxygenation of Guaiacol by Surface-Rich Metal/Silica Catalysts

by Nils Kretzschmar, Oliver Busse and Markus Seifert

Catalysts 2023, 13(2), 425; https://doi.org/10.3390/catal13020425 - 16 Feb 2023

Cited by 2 | Viewed by 1597

Abstract

The selective production of hydrocarbons for the chemical industry from biogenic feedstock is a significant challenge when ensuring hydrocarbon and fuel supply, despite the heterogeneity of this feed. In this study, guaiacol, as a surrogate for complex lignin-based biomass resources, is converted by [...] Read more.

The selective production of hydrocarbons for the chemical industry from biogenic feedstock is a significant challenge when ensuring hydrocarbon and fuel supply, despite the heterogeneity of this feed. In this study, guaiacol, as a surrogate for complex lignin-based biomass resources, is converted by an inert silica carrier material with different d-metal impregnation (Mo, W, Re, Fe, Co, Ni, Cu, Pd, Ag) to reveal the reasons for different product selectivity to hydrogenated and deoxygenated hydrocarbon products. Hydrogen at 15 bar (gauge) and guaiacol are converted on metal/silica catalysts between 250 °C and 400 °C, while the physicochemical catalyst properties are characterized before and after catalytic tests. Volcano plots for the conversion, hydrogenation and deoxygenation products versus the d-band energy, surface atom distance and fouling properties reveal three groups of metals: (i) those that are less active and show high coking (Ag, α-Fe); (ii) those that show high activity for hydrogenation (β-Co, Ni, Pd) and, therefore, preferably yielded cyclohexane, cyclohexanol and 2-methoxycyclohexanol; (iii) those that preferably promote deoxygenation (Mo, W, Re, Cu) and, therefore, promoted the formation of phenol, benzene, anisole and catechol. The results are summarized in a pseudo van Krevelen diagram and interpreted as a complex interdependency from Sabatier’s principle of geometric correspondence of hexagonal metal surface for hydrogenation, electronic correspondence for the activation of hydrogen and electronic correspondence by oxophilicity for deoxygenation from the d-band center model. Full article

(This article belongs to the Special Issue Catalysis on Zeolites and Zeolite-Like Materials II)

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17 pages, 3769 KiB

Open AccessArticle

Pyrite Cinder as an Effective Fenton-like Catalyst for the Degradation of Reactive Azo Dye: Effects of Process Parameters and Complete Effluent Characterization

by Djurdja Kerkez, Milena Bečelić-Tomin, Vesna Gvoić, Aleksandra Kulić Mandić, Anita Leovac Maćerak, Dragana Tomašević Pilipović and Vesna Pešić

Catalysts 2023, 13(2), 424; https://doi.org/10.3390/catal13020424 - 16 Feb 2023

Cited by 2 | Viewed by 1591

Abstract

This research investigates the potential use of pyrite cinder (PC) as an efficient Fenton-like catalyst for the removal of the reactive azo dye Reactive Red 120 (RR120) from aqueous solutions. The characterization of its PC structure and composition confirmed its great potential to [...] Read more.

This research investigates the potential use of pyrite cinder (PC) as an efficient Fenton-like catalyst for the removal of the reactive azo dye Reactive Red 120 (RR120) from aqueous solutions. The characterization of its PC structure and composition confirmed its great potential to act as catalytic iron source in a heterogeneous Fenton system. Dye removal optimization was performed in terms of PC dosage (0.4–8 g/L), H₂O₂ concentration (2–25 mM), pH value (2–4.6), initial dye concentration (50–200 mg/L), and mixing time. The highest decolorization efficiency (92%) was achieved after a reaction time of 480 min under following conditions: RR120 = 50 mg/L, PC = 4 g/L, H₂O₂ = 10 mM, and pH = 3. After decolorization, an extensive analysis of the generated effluent was performed regarding metal leaching, mineralization, toxicity, and degradation product formation. The metal leaching indicated the necessity for a pH increase in order to remove the settled metal hydroxides. The mineralization efficiency was satisfactory, reaching 85% and 62% of the COD and TOC removal, respectively. The respirometry measurements and bioluminescence tests indicated the detoxification of the treated solution. The absorption spectra and GC/MS analysis confirmed the changes in the molecular structure in the form of the destruction of the azo bond, with a simpler aromatic and aliphatic intermediates formation. This study provides an effective method for removing azo dye in polluted water by employing waste tailings as alternative Fenton-like catalysts, while also using waste tailings as the secondary resource. Full article

(This article belongs to the Special Issue Trends and Advances in the Development of Waste-based Catalysts and Processes: Applications in Conventional & Intensified Processes)

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22 pages, 4701 KiB

Open AccessArticle

Photocatalytic Decomposition of Azo Dyes and Phenols Using Polymer Composites Containing Nanostructured Poly(Titanium Oxide) Doped with Gold or Silver Nanoparticles under Light Irradiation in a Wide Wavelength Range

by Evgeniia Salomatina, Pavel Shelud’ko, Vsevolod Kuz’michev and Larisa Smirnova

Catalysts 2023, 13(2), 423; https://doi.org/10.3390/catal13020423 - 16 Feb 2023

Cited by 2 | Viewed by 1351

Abstract

The photocatalytic properties of poly(titanium oxide) (PTO) dispersed in optically transparent polymeric matrices of different natures under the action of both UV and visible light on aqueous solutions of azo dyes and phenols were investigated. PTO in materials forms clusters of mixed polymorphic [...] Read more.

The photocatalytic properties of poly(titanium oxide) (PTO) dispersed in optically transparent polymeric matrices of different natures under the action of both UV and visible light on aqueous solutions of azo dyes and phenols were investigated. PTO in materials forms clusters of mixed polymorphic modification—anatase and rutile—with an average size ~12 nm. With a one-electron transition Ti⁴⁺ + e⁻ → Ti³⁺ accompanied by a reversible break of the Ti-O bond, the formation of electron-hole pairs and, consequently, active oxygen species occurs in PTO under UV irradiation. The PTO band gap in nanocomposites is 3.11–3.35 eV. Its doping with gold and silver nanoparticles with sizes from ~10 to ~30 nm reduces the PTO band gap by up to 2.11 eV, which leads to the operating wavelength range extension of the materials. It provides the enhancement of nanocomposites’ photocatalytic properties under UV irradiation and is the reason for their high activity under visible light action. It was found that azo dyes decompose by ~90% in this case. A phenol and para-nitrophenol conversion of 80–90% was proven at ~60 min upon their aqueous solutions’ visible-light irradiation at the nanocomposite concentration in a solution of 0.5 g/L. Full article

(This article belongs to the Special Issue Advances in the Synthesis and Applications of Transition/Noble Metal Oxide Photocatalysts)

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22 pages, 2728 KiB

Open AccessReview

Carbon Quantum Dots: Synthesis, Structure, Properties, and Catalytic Applications for Organic Synthesis

by Pradeep Kumar Yadav, Subhash Chandra, Vivek Kumar, Deepak Kumar and Syed Hadi Hasan

Catalysts 2023, 13(2), 422; https://doi.org/10.3390/catal13020422 - 16 Feb 2023

Cited by 21 | Viewed by 9621

Abstract

Carbon quantum dots (CQDs), also known as carbon dots (CDs), are novel zero-dimensional fluorescent carbon-based nanomaterials. CQDs have attracted enormous attention around the world because of their excellent optical properties as well as water solubility, biocompatibility, low toxicity, eco-friendliness, and simple synthesis routes. [...] Read more.

Carbon quantum dots (CQDs), also known as carbon dots (CDs), are novel zero-dimensional fluorescent carbon-based nanomaterials. CQDs have attracted enormous attention around the world because of their excellent optical properties as well as water solubility, biocompatibility, low toxicity, eco-friendliness, and simple synthesis routes. CQDs have numerous applications in bioimaging, biosensing, chemical sensing, nanomedicine, solar cells, drug delivery, and light-emitting diodes. In this review paper, the structure of CQDs, their physical and chemical properties, their synthesis approach, and their application as a catalyst in the synthesis of multisubstituted 4H pyran, in azide-alkyne cycloadditions, in the degradation of levofloxacin, in the selective oxidation of alcohols to aldehydes, in the removal of Rhodamine B, as H-bond catalysis in Aldol condensations, in cyclohexane oxidation, in intrinsic peroxidase-mimetic enzyme activity, in the selective oxidation of amines and alcohols, and in the ring opening of epoxides are discussed. Finally, we also discuss the future challenges in this research field. We hope this review paper will open a new channel for the application of CQDs as a catalyst in organic synthesis. Full article

(This article belongs to the Special Issue Catalytic Methods for the Synthesis of Carbon Nanodots and Their Applications)

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