Catalysts

23 pages, 26116 KiB

Open AccessReview

Ionic Liquid/Deep Eutectic Solvent-Mediated Ni-Based Catalysts and Their Application in Water Splitting Electrocatalysis

by Chenyun Zhang, Te Bai, Yefan Sun, Bingwei Xin and Shengnan Zhang

Catalysts 2022, 12(8), 928; https://doi.org/10.3390/catal12080928 - 22 Aug 2022

Cited by 7 | Viewed by 2127

Abstract

Nickel-based electrocatalysts have been widely used to catalyze electrocatalytic water splitting. In order to obtain high-performance nickel-based electrocatalysts, using ionic liquids and deep eutectic solvents mediated their preparation has received increasing attention. Firstly, ionic liquids and deep eutectic solvents can act as media [...] Read more.

Nickel-based electrocatalysts have been widely used to catalyze electrocatalytic water splitting. In order to obtain high-performance nickel-based electrocatalysts, using ionic liquids and deep eutectic solvents mediated their preparation has received increasing attention. Firstly, ionic liquids and deep eutectic solvents can act as media and templates for the preparation of Ni-based nanomaterials with novel structures and excellent catalytic activity. Secondly, ionic liquids and deep eutectic solvents can be employed as reactants to participate the synthesis of catalysts. Their participation not only increase the catalytic performance, but also simplify the reaction system, improve reproducibility, reduce emissions, and achieve atomic economy. On the basis of the work of our group, this review gives a detailed description of the impressive progress made concerning ionic liquids and deep eutectic solvents in the preparation of nickel-based electrocatalysts according to their roles. We also point out the challenges and opportunities in the field. Full article

(This article belongs to the Special Issue Advances in Transition Metal Catalysis)

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12 pages, 2826 KiB

Open AccessArticle

The Effect of Arsenic on the Photocatalytic Removal of Methyl Tet Butyl Ether (MTBE) Using Fe₂O₃/MgO Catalyst, Modeling, and Process Optimization

by Akbar Mehdizadeh, Zahra Derakhshan, Fariba Abbasi, Mohammad Reza Samaei, Mohammad Ali Baghapour, Mohammad Hoseini, Eder Claudio Lima and Muhammad Bilal

Catalysts 2022, 12(8), 927; https://doi.org/10.3390/catal12080927 - 22 Aug 2022

Cited by 5 | Viewed by 1483

Abstract

MTBE is an aliphatic matter successfully removed from contaminated water by an advanced oxidation process. Additionally, arsenic is a toxic metalloid that is detected in some water supplies, such as in Iran. Concerning the oxidation potential of arsenic in an aqueous solution, it [...] Read more.

MTBE is an aliphatic matter successfully removed from contaminated water by an advanced oxidation process. Additionally, arsenic is a toxic metalloid that is detected in some water supplies, such as in Iran. Concerning the oxidation potential of arsenic in an aqueous solution, it is expected that its interference in the photocatalytic removal of organic matter includes MTBE. Nevertheless, there is a lack of observation of this effect. In this study, the effect of arsenic on the photocatalytic removal of MTBE using an Fe₂O₃/MgO catalyst under UV radiation was investigated. Using an experimental design, modeling, and optimizing operational parameters, such as the arsenic and MTBE concentrations, catalyst dosage, pH, and reaction time, were studied. The synthesized nanocatalyst had a uniform and spherical morphological structure and contained 33.06% Fe₂O₃ and 45.06% MgO. The results indicate that the best model is related to the quadratic (p-value < 0.0001, R² = 0.97) and that the effect of the MTBE concentration is greater than the others. The highest removal efficiency was taken in an initial concentration of 37.5 mg/L MTBE, 1.58 mg/L Fe₂O₃/MgO, pH 5, and a reaction time of 21.41 min without any As. The removal efficiency was negatively correlated with the initial MTBE concentration and pH, but it was positively associated with the Fe₂O₃/MgO dosage and reaction time. Finally, the presence of arsenic decreased the removal efficiency remarkably (90.90% As = 0.25 μg/L and 61% As = 500 μg/L). Consequently, MTBE was removed by the photocatalytic process caused by Fe₂O₃/MgO, but the presence of arsenic was introduced as a limiting factor. Therefore, pretreatment for the removal of arsenic and more details of this interference effect are suggested. Full article

(This article belongs to the Special Issue Catalytic Processes for Water and Wastewater Treatment)

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14 pages, 6193 KiB

Open AccessArticle

High-Temperature Reaction Mechanism of Molybdenum Metal in Direct Coal Liquefaction Residue

by Chunling Wu, Linge Ma, Yufei Zhu, Xuqiang Guo, Yongli Wu, Zhen Wu, Xian Zhang and Lihua Hou

Catalysts 2022, 12(8), 926; https://doi.org/10.3390/catal12080926 - 21 Aug 2022

Cited by 5 | Viewed by 1907

Abstract

In this paper, the extraction residue of direct coal liquefaction residue-DCLR_(ER) was used as raw material. The high-temperature reaction mechanism of Mo compound in DCLR_(ER) was investigated using a synchronous thermal analyzer and the Factsage database. The high temperature reaction of [...] Read more.

In this paper, the extraction residue of direct coal liquefaction residue-DCLR_(ER) was used as raw material. The high-temperature reaction mechanism of Mo compound in DCLR_(ER) was investigated using a synchronous thermal analyzer and the Factsage database. The high temperature reaction of DCLR_(ER)-MoO₃ in an oxygen atmosphere consists of pyrolysis of organic components at 400–600 °C, molybdenum trioxide sublimation at 747–1200 °C, and a stable stage at 600–747 °C. The thermal reaction process of the DCLR_(ER)-MoS₂ system in the oxygen atmosphere involves the pyrolysis of unreacted coal and asphaltene, the oxidation of molybdenum sulfide at 349–606/666 °C, the diffusion of MoO₃ at 606/666–85 °C, and the sublimation reaction process of MoO₃ at 854–1200 °C. The results show that the lower heating rate can promote the oxidation of the Mo compound and the sublimation of molybdenum trioxide. On the other hand, the oxides of aluminum, calcium, and iron in DCLR_(ER) can inhibit the oxidative pyrolysis efficiency of the DCLR_(ER)-MoS₂ system. Full article

(This article belongs to the Section Catalytic Reaction Engineering)

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10 pages, 1670 KiB

Open AccessArticle

Integrated CO₂ Capture and Hydrogenation to Produce Formate in Aqueous Amine Solutions Using Pd-Based Catalyst

by Lichun Li, Xiangcan Chen, Chu Yao and Meng Xu

Catalysts 2022, 12(8), 925; https://doi.org/10.3390/catal12080925 - 21 Aug 2022

Cited by 3 | Viewed by 2044

Abstract

Integrated CO₂ capture and hydrogenation to produce formate offers a sustainable approach for reducing carbon dioxide emissions and producing liquid hydrogen carriers (formate) simultaneously. In the current study, three different types of aqueous amine solutions including monoethanolamine (MEA), diethanolamine (DEA) and triethanolamine [...] Read more.

Integrated CO₂ capture and hydrogenation to produce formate offers a sustainable approach for reducing carbon dioxide emissions and producing liquid hydrogen carriers (formate) simultaneously. In the current study, three different types of aqueous amine solutions including monoethanolamine (MEA), diethanolamine (DEA) and triethanolamine (TEA) were investigated as CO₂-capturing and hydrogenation agents in the presence of a Pd/NAC catalyst. The effect of amine structures on the CO₂ absorption products and formate yield was investigated thoroughly. It was found that the formate product was successfully produced in the presence of all three aqueous amine solutions, with tertiary amine TEA accounting for the highest formate yield under the same CO₂ loadings. This is due to the fact that primary and secondary amine moieties in MEA and DEA are responsible for the formation of CO₂ adducts of carbamate and bicarbonate, whereas the tertiary amine moiety in TEA is responsible for the formation of hydrogenation-favorable bicarbonate as the solo CO₂ absorption product. A high yield of formate of 82.6% was achieved when hydrogenating 3 M TEA with 0.3 mol CO₂/mol amine solution in the presence of a Pd/NAC catalyst. In addition, the physio-chemical properties of the Pd/NAC catalyst analyzed using TEM, XRD and XPS characterization were applied to rationalize the superior catalytic performance of the catalyst. The reaction mechanism of integrated CO₂ capture and hydrogenation to produce formate in aqueous amine solutions over Pd/NAC catalyst was proposed as well. Full article

(This article belongs to the Special Issue Catalysts with New Formulations/Structures: Synthesis and Applications)

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12 pages, 13625 KiB

Open AccessArticle

A Reusable FeCl₃∙6H₂O/Cationic 2,2′-Bipyridyl Catalytic System for Reduction of Nitroarenes in Water

by Tsai-Yu Hung, Wen-Sheng Peng, Jing-Wen Tang and Fu-Yu Tsai

Catalysts 2022, 12(8), 924; https://doi.org/10.3390/catal12080924 - 21 Aug 2022

Cited by 2 | Viewed by 1732

Abstract

The association of a commercially-available iron (III) chloride hexahydrate (FeCl₃∙6H₂O) with cationic 2,2′-bipyridyl in water was proven to be an operationally simple and reusable catalytic system for the highly-selective reduction of nitroarenes to anilines. This procedure was conducted under [...] Read more.

The association of a commercially-available iron (III) chloride hexahydrate (FeCl₃∙6H₂O) with cationic 2,2′-bipyridyl in water was proven to be an operationally simple and reusable catalytic system for the highly-selective reduction of nitroarenes to anilines. This procedure was conducted under air using 1–2 mol% of catalyst in the presence of nitroarenes and 4 equiv of hydrazine monohydrate (H₂NNH₂∙H₂O) in neat water at 100 °C for 12 h, and provided high to excellent yields of aniline derivatives. After separation of the aqueous catalytic system from the organic product, the residual aqueous solution could be applied for subsequent reuse, without any catalyst retreatment or regeneration, for several runs with only a slight decrease in activity, proving this process eco-friendly. Full article

(This article belongs to the Special Issue Catalysis in Green Chemistry and Organic Synthesis)

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24 pages, 2120 KiB

Open AccessReview

Olive Mill Wastewater Remediation: From Conventional Approaches to Photocatalytic Processes by Easily Recoverable Materials

by Melissa G. Galloni, Elena Ferrara, Ermelinda Falletta and Claudia L. Bianchi

Catalysts 2022, 12(8), 923; https://doi.org/10.3390/catal12080923 - 21 Aug 2022

Cited by 15 | Viewed by 2950

Abstract

Olive oil production in Mediterranean countries represents a crucial market, especially for Spain, Italy, and Greece. However, although this sector plays a significant role in the European economy, it also leads to dramatic environmental consequences. Waste generated from olive oil production processes can [...] Read more.

Olive oil production in Mediterranean countries represents a crucial market, especially for Spain, Italy, and Greece. However, although this sector plays a significant role in the European economy, it also leads to dramatic environmental consequences. Waste generated from olive oil production processes can be divided into solid waste and olive mill wastewaters (OMWW). These latter are characterized by high levels of organic compounds (i.e., polyphenols) that have been efficiently removed because of their hazardous environmental effects. Over the years, in this regard, several strategies have been primarily investigated, but all of them are characterized by advantages and weaknesses, which need to be overcome. Moreover, in recent years, each country has developed national legislation to regulate this type of waste, in line with the EU legislation. In this scenario, the present review provides an insight into the different methods used for treating olive mill wastewaters paying particular attention to the recent advances related to the development of more efficient photocatalytic approaches. In this regard, the most advanced photocatalysts should also be easily recoverable and considered valid alternatives to the currently used conventional systems. In this context, the optimization of innovative systems is today’s object of hard work by the research community due to the profound potential they can offer in real applications. This review provides an overview of OMWW treatment methods, highlighting advantages and disadvantages and discussing the still unresolved critical issues. Full article

(This article belongs to the Special Issue Light-Assisted Catalysis in Water and Indoor Air Cleaning: Challenges and Perspectives)

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15 pages, 2484 KiB

Open AccessReview

Chemocatalytic Conversion of Lignocellulosic Biomass to Ethanol: A Mini-Review

by Zhenggang Gong, Xianqing Lv, Junhui Yang, Xiaolin Luo and Li Shuai

Catalysts 2022, 12(8), 922; https://doi.org/10.3390/catal12080922 - 21 Aug 2022

Cited by 3 | Viewed by 2552

Abstract

Ethanol has been widely used as a clean fuel, solvent, and hydrogen carrier. Currently, ethanol is generally produced through fermentation of starch- and sugarcane-derived sugars (e.g., glucose and sucrose) or ethylene hydration. Its production from abundant and inexpensive lignocellulosic biomass would facilitate the [...] Read more.

Ethanol has been widely used as a clean fuel, solvent, and hydrogen carrier. Currently, ethanol is generally produced through fermentation of starch- and sugarcane-derived sugars (e.g., glucose and sucrose) or ethylene hydration. Its production from abundant and inexpensive lignocellulosic biomass would facilitate the development of green and sustainable society. Biomass-derived carbohydrates and syngas can serve as important feedstocks for ethanol synthesis via biological and chemical pathways. Nevertheless, the biological pathway for producing ethanol through biomass-derived glucose fermentation has the disadvantages of long production period and carbon loss. These issues can be effectively mitigated by chemocatalytic methods, which can readily convert biomass to ethanol in high yields and high atomic efficiency. In this article, we review the recent advances in chemocatalytic conversion of lignocellulosic biomass to ethanol, with a focus on analyzing the mechanism of chemocatalytic pathways and discussing the issues related to these methods. We hope this mini-review can provide new insights into the development of direct ethanol synthesis from renewable lignocellulosic biomass. Full article

(This article belongs to the Special Issue Catalytic Conversion of Cellulose and Lignin)

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12 pages, 2978 KiB

Open AccessArticle

Development of New Amphiphilic Catalytic Steam Additives for Hydrothermal Enhanced Oil Recovery Techniques

by Firdavs Aliev, Amirjon Ali Akhunov, Oybek Mirzaev and Alexey Vakhin

Catalysts 2022, 12(8), 921; https://doi.org/10.3390/catal12080921 - 20 Aug 2022

Cited by 8 | Viewed by 1420

Abstract

In this paper, we propose the synthesis of green amphiphilic catalysts based on two metals: Ni and Al. The amphiphilic characteristics of the obtained catalyst were provided by alkylbenzenesulfonic acid (ABSA). The end product was thoroughly characterized by the FTIR analysis method. The [...] Read more.

In this paper, we propose the synthesis of green amphiphilic catalysts based on two metals: Ni and Al. The amphiphilic characteristics of the obtained catalyst were provided by alkylbenzenesulfonic acid (ABSA). The end product was thoroughly characterized by the FTIR analysis method. The efficiency of both catalysts was tested by modeling the catalytic hydrothermal upgrading of heavy-oil samples from Ashal’cha field (Russia) in a high-pressure/high-temperature (HP/HT) reactor with a stirrer at a temperature of 250 °C. The physical and chemical properties of the heavy oils and their fractions were studied before and after the catalytic hydrothermal upgrading by analytical procedures such as SARA analysis, FTIR spectroscopy, GC–MS, elemental analysis, gas chromatography, etc. The results showed that both catalysts had a different influence on the viscosity-reduction degree. It was revealed that the contribution of Al ABSA to the viscosity reduction was the highest: more than 80% in contrast to the initial crude oil sample. The Al-based catalyst showed the best activity in hydrogenation and decarbonization, and hence the H/C ratio of the upgraded oil was at a maximum in the presence of Al ABSA. Full article

(This article belongs to the Special Issue Heterogeneous Catalysis in Enhanced Oil Recovery: Prospects and Challenges)

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15 pages, 6334 KiB

Open AccessArticle

Pd-Supported Co₃O₄/C Catalysts as Promising Electrocatalytic Materials for Oxygen Reduction Reaction

by Virginija Kepenienė, Raminta Stagniūnaitė, Sidra Rafique, Jūratė Vaičiūnienė, Vitalija Jasulaitiene, Vidas Pakštas, Zita Sukackienė, Rasa Vilkauskaite, Loreta Tamašauskaitė-Tamašiūnaitė and Eugenijus Norkus

Catalysts 2022, 12(8), 920; https://doi.org/10.3390/catal12080920 - 20 Aug 2022

Cited by 1 | Viewed by 1465

Abstract

This paper describes the activity of PdCo₃O₄/C obtained by wet impregnation towards the oxygen reduction reaction (ORR). For this purpose, the Co₃O₄/C substrate was synthesized using the microwave irradiation heating method with further annealing of [...] Read more.

This paper describes the activity of PdCo₃O₄/C obtained by wet impregnation towards the oxygen reduction reaction (ORR). For this purpose, the Co₃O₄/C substrate was synthesized using the microwave irradiation heating method with further annealing of the substrate at 400 °C for 3 h (Co₃O₄/C-T). Then, the initial Co₃O₄/C substrate was impregnated with palladium chloride (Pd-Cl₂-Co₃O₄/C), and then part of the obtained Pd-Cl₂-Co₃O₄/C catalyst was annealed at 400 °C for 3 h (PdOCo₃O₄/C). The electrocatalytic activity of the prepared catalysts was investigated for the oxygen reduction reaction in alkaline media and compared with the commercial Pt/C (Tanaka wt. 46.6% Pt) catalyst. It was found that the annealed PdOCo₃O₄/C catalyst showed the largest ORR current density value of −11.27 mA cm⁻² compared with Pd-Cl₂-Co₃O₄/C (−7.39 mA cm⁻²) and commercial Pt/C (−5.25 mA cm⁻²). Full article

(This article belongs to the Special Issue Catalytical Processes in Presence of 2D Nanomaterials)

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21 pages, 5799 KiB

Open AccessReview

Recent Advances in Metal-Based Molecular Photosensitizers for Artificial Photosynthesis

by Lei Wang

Catalysts 2022, 12(8), 919; https://doi.org/10.3390/catal12080919 - 19 Aug 2022

Cited by 2 | Viewed by 3030

Abstract

Artificial photosynthesis (AP) has been extensively applied in energy conversion and environment pollutants treatment. Considering the urgent demand for clean energy for human society, many researchers have endeavored to develop materials for AP. Among the materials for AP, photosensitizers play a critical role [...] Read more.

Artificial photosynthesis (AP) has been extensively applied in energy conversion and environment pollutants treatment. Considering the urgent demand for clean energy for human society, many researchers have endeavored to develop materials for AP. Among the materials for AP, photosensitizers play a critical role in light absorption and charge separation. Due to the fact of their excellent tunability and performance, metal-based complexes stand out from many photocatalysis photosensitizers. In this review, the evaluation parameters for photosensitizers are first summarized and then the recent developments in molecular photosensitizers based on transition metal complexes are presented. The photosensitizers in this review are divided into two categories: noble-metal-based and noble-metal-free complexes. The subcategories for each type of photosensitizer in this review are organized by element, focusing first on ruthenium, iridium, and rhenium and then on manganese, iron, and copper. Various examples of recently developed photosensitizers are also presented. Full article

(This article belongs to the Special Issue Chiral Nanomaterials and Their Photo(Electro)catalytic Applications)

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15 pages, 4895 KiB

Open AccessArticle

Catalytic Activity of Carbon Materials in the Oxidation of Minerals

by Aura Alejandra Burbano, Gabriel Gascó, Jorge Paz-Ferreiro and Ana Méndez

Catalysts 2022, 12(8), 918; https://doi.org/10.3390/catal12080918 - 19 Aug 2022

Cited by 2 | Viewed by 1305

Abstract

This study aims to advance the knowledge of using carbon materials as catalysts in the oxidation of chalcopyrite. For this, two different materials (a commercial activated carbon (CC) and commercial biochar (BC)) were added to chalcopyrite ore (CPY) at three weight ratios (1:1, [...] Read more.

This study aims to advance the knowledge of using carbon materials as catalysts in the oxidation of chalcopyrite. For this, two different materials (a commercial activated carbon (CC) and commercial biochar (BC)) were added to chalcopyrite ore (CPY) at three weight ratios (1:1, 1:0.5, and 1:0.25). Mixtures were treated with sulfuric/ferric solution for 96 h at 90 °C. Experimental results showed that extraction of copper from CPY was around 36%, increasing to higher than 90% with the addition of CC or BC at the proper ratio. The best result (99.1% Cu extraction) was obtained using a 1:1 ratio of CPY:CC. Analysis of solid residues shows that CC, with a high surface area, adsorbs sulfur onto its surface, limiting elemental sulfur formation. Additionally, the treatment of CPY in the CC’s presence transforms the chalcopyrite into CuS. Sulfur adsorption or CuS formation was not observed after the leaching of chalcopyrite with BC. However, the addition of BC to CPY at a ratio of 1:0.25 also increased the extraction of copper to 91.1%. Two carbon materials were oxidized after treatment with a sulfuric/ferric solution, and BC probably displayed catalytic properties in the leaching medium. Full article

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

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14 pages, 4899 KiB

Open AccessArticle

Determination of Chemical Kinetic Parameters for Adsorption and Desorption of NH₃ in Cu-Zeolite Used as a DeNO_x SCR Catalyst of Diesel Engines

by Yanghwa Kim, Ocktaeck Lim and Hongsuk Kim

Catalysts 2022, 12(8), 917; https://doi.org/10.3390/catal12080917 - 19 Aug 2022

Viewed by 1481

Abstract

Ammonia-based selective catalytic reduction is one of the most effective NO_x reduction technologies for diesel engines, but its low NO_x reduction efficiency under low-temperature conditions needs further improvement. Previous studies have broadened our understanding of the NH₃ adsorption and desorption [...] Read more.

Ammonia-based selective catalytic reduction is one of the most effective NO_x reduction technologies for diesel engines, but its low NO_x reduction efficiency under low-temperature conditions needs further improvement. Previous studies have broadened our understanding of the NH₃ adsorption and desorption that occurs in an SCR catalyst of Cu ion-exchanged zeolite. However, many studies conducted to data on the control of the NH₃ adsorption and desorption in SCR catalysts have considered a simple chemical reaction related to a single acid site. This study demonstrates a detailed process for determining the chemical kinetic parameters of the adsorption and desorption of NH₃ for different types of acid sites of a zeolite catalyst. The determined chemical kinetics parameters will be used for more effective control of the SCR system in future studies. Full article

(This article belongs to the Special Issue Catalytic Methods for Nitrogen Pollutants Conversion in Flue Gases)

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22 pages, 4742 KiB

Open AccessArticle

Effects of Potassium Loading over Iron–Silica Interaction, Phase Evolution and Catalytic Behavior of Precipitated Iron-Based Catalysts for Fischer-Tropsch Synthesis

by Hai Chang, Quan Lin, Meng Cheng, Kui Zhang, Bo Feng, Jiachun Chai, Yijun Lv and Zhuowu Men

Catalysts 2022, 12(8), 916; https://doi.org/10.3390/catal12080916 - 19 Aug 2022

Cited by 8 | Viewed by 2390

Abstract

Potassium (K) promoter and its loading contents were shown to have remarkable effects on the Fe–O–Si interaction of precipitated Fe/Cu/K/SiO₂ catalysts for low-temperature Fischer-Tropsch synthesis (FTS). With the increase in K content from 2.3% (100 g Fe based) up to 7% in [...] Read more.

Potassium (K) promoter and its loading contents were shown to have remarkable effects on the Fe–O–Si interaction of precipitated Fe/Cu/K/SiO₂ catalysts for low-temperature Fischer-Tropsch synthesis (FTS). With the increase in K content from 2.3% (100 g Fe based) up to 7% in the calcined precursors, Fe–O–Si interaction was weakened, as reflected by ATR/FTIR, H₂-TPR and XPS investigations. XRD results confirmed that the diffraction peak intensity from (510) facet of χ-Fe₅C₂ phase strengthened with increasing K loading, which indicates the crystallite size of χ-Fe₅C₂ increased with the increase in K contents either during the syngas reduction/carburization procedure or after FTS reaction. H₂-TPH results indicated that more reactive surface carbon (alpha-carbon) was obtained over the higher K samples pre-carburized by syngas. Raman spectra illustrated that a greater proportion of graphitic carbon was accumulated over the surface of spent samples with higher K loading. At the same time, ATR-FTIR, XRD and Mössbauer spectra (MES) characterization results showed that a relatively higher level of bulk phase Fayalite (Fe₂SiO₄) species was observed discernibly in the lowest K loading sample (2.3 K%) in this work. The catalytic evaluation results showed that the CO conversion, CO₂ selectivity and O/P (C₂–C₄) ratio increased progressively with the increasing K loading, whereas a monotonic decline in both CO conversion and O/P (C₂–C₄) ratio was observed on the highest K loading sample during c.a. 280 h of TOS. Full article

(This article belongs to the Special Issue Development of Novel Catalysts for Fischer–Tropsch Synthesis)

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12 pages, 1773 KiB

Open AccessArticle

Formation and Intramolecular Capture of α-Imino Gold Carbenoids in the Au(I)-Catalyzed [3 + 2] Reaction of Anthranils, 1,2,4-Oxadiazoles, and 4,5-Dihydro-1,2,4-Oxadiazoles with Ynamides

by Ioannis Stylianakis, Iraklis Litinas, Antonios Kolocouris and Carlos Silva López

Catalysts 2022, 12(8), 915; https://doi.org/10.3390/catal12080915 - 19 Aug 2022

Cited by 2 | Viewed by 1613

Abstract

α-Imino gold carbenoid species have been recognized as key intermediates in a plethora of processes involving gold-activated alkynes. Here, we explored the pathways of the Au(I)-catalyzed [3 + 2] reaction between the mild nucleophiles: anthranil, 1,2,4-oxadiazole, or 4,5-dihydro-1,2,4-oxadiazole, and an ynamide, PhC≡C-N(Ts)Me, proceeding [...] Read more.

α-Imino gold carbenoid species have been recognized as key intermediates in a plethora of processes involving gold-activated alkynes. Here, we explored the pathways of the Au(I)-catalyzed [3 + 2] reaction between the mild nucleophiles: anthranil, 1,2,4-oxadiazole, or 4,5-dihydro-1,2,4-oxadiazole, and an ynamide, PhC≡C-N(Ts)Me, proceeding via the formation of the aforementioned α-imino gold carbene intermediate which, after intramolecular capture, regioselectively produces 2-amino-3-phenyl-7-acyl indoles, N-acyl-5-aminoimidazoles, or N-alkyl-4-aminoimidazoles, respectively. In all cases, the regioselectivity of the substituents at 2, 3 in the 7-acyl-indole ring and 4, 5 in the substituted imidazole ring is decided at the first transition state, involving the attack of nitrogen on the C1 or C2 carbon of the activated ynamide. A subsequent and steep energy drop furnishes the key α-imino gold carbene. These features are more pronounced for anthranil and 4,5-dihydro-1,2,4-oxadiazole reactions. Strikingly, in the 4,5-dihydro-1,2,4-oxadiazole reaction the significant drop of energy is due to the formation of an unstable α-imino gold carbene, which after a spontaneous benzaldehyde elimination is converted to a stabilized one. Compared to anthranil, the reaction pathways for 1,2,4-oxadiazoles or 4,5-dihydro-1,2,4-oxadiazoles are found to be significantly more complex than anticipated in the original research. For instance, compared to the formation of a five-member ring from the α-imino gold carbene, one competitive route involves the formation of intermediates consisting of a four-member ring condensed with a three-member ring, which after a metathesis and ring expansion led to the imidazole ring. Full article

(This article belongs to the Section Computational Catalysis)

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8 pages, 1468 KiB

Open AccessArticle

Controllable Construction of IrCo Nanoclusters and the Performance for Water Electrolysis

by Fangqin Mao, Xiaojie Zhao, Ying Chang and Jingchun Jia

Catalysts 2022, 12(8), 914; https://doi.org/10.3390/catal12080914 - 19 Aug 2022

Cited by 2 | Viewed by 1530 | Correction

Abstract

Finding a suitable catalyst is an important research direction in hydrogen (H₂) production from water electrolysis. We report a synthetic method to obtain Ir_xCo/C clusters by polyol reduction. The catalyst is small in size and can be evenly distributed. [...] Read more.

Finding a suitable catalyst is an important research direction in hydrogen (H₂) production from water electrolysis. We report a synthetic method to obtain Ir_xCo/C clusters by polyol reduction. The catalyst is small in size and can be evenly distributed. The Ir₃Co/C cluster catalyst had very good activity under acidic conditions. The overpotential of the best-performing Ir₃Co/C cluster for the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) is only 290 mV and 91 mV when 10 mA cm⁻² and 100 mA cm⁻². The catalyst performance may be improved because of the synergistic effect and the small size of the prepared catalyst, which accelerates proton transfer. This approach offers a strategy to reduce costs while improving catalytic activity. Full article

(This article belongs to the Special Issue Advanced Nanomaterials for Electrocatalysis: Synthesis, Characterization and Application)

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17 pages, 6560 KiB

Open AccessArticle

Monolayer CoMoS Catalysts on Hierarchically Porous Alumina Spheres as Bifunctional Nanomaterials for Hydrodesulfurization and Energy Storage Applications

by Anabel D. Delgado, Lorena Álvarez-Contreras, Karen A. Beltrán, Noé Arjona, Minerva Guerra-Balcázar, José Béjar and Alfredo Aguilar-Elguezabal

Catalysts 2022, 12(8), 913; https://doi.org/10.3390/catal12080913 - 19 Aug 2022

Cited by 2 | Viewed by 1752

Abstract

In this work, CoMoS catalysts were synthesized onto porous alumina spheres obtained using Pluronic P-123 (PS) or urea (US) and used as bifunctional nanomaterials for two energy applications: hydrodesulfurization and energy storage. For the first application, the catalysts were assessed in a hydrodesulfurization [...] Read more.

In this work, CoMoS catalysts were synthesized onto porous alumina spheres obtained using Pluronic P-123 (PS) or urea (US) and used as bifunctional nanomaterials for two energy applications: hydrodesulfurization and energy storage. For the first application, the catalysts were assessed in a hydrodesulfurization reactor using two model sulfur molecules, dibenzothiophene and 4,6-dimethyl dibenzothiophene, as well as feeding a heavy oil fraction. The results indicated that the spheres obtained by Pluronic P-123 allowed a greater dispersion degree of MoS₂ slabs than US, indicating that the size and hierarchically porous structure of alumina spheres played a principal role as a booster of the HDS catalytic efficiency of DBT, 4,6 DMDBT and diesel fuel. Then, these catalysts were used for the electrocatalysis of the oxygen reduction and oxygen evolution reactions (ORR/OER), which take place in rechargeable Zn-air batteries. For the ORR, the CoMoS catalyst on PS in the presence of a conductive support (N-doped carbon nanotubes + graphene) displayed an overpotential of only 90 mV in comparison with Pt/C. Importantly, the chalcogenide enabled an increase in the stability, maintaining almost two times higher current retention than Pt/C for the ORR and IrO₂/C for the OER. These results suggest that expended chalcogenides from the hydrodesulfurization industry can have a second life as co-catalysts for renewable energy storage systems, enabling a circular economy. Full article

(This article belongs to the Section Catalytic Reaction Engineering)

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11 pages, 3430 KiB

Open AccessPerspective

Asymmetric Organocatalysis—A Powerful Technology Platform for Academia and Industry: Pregabalin as a Case Study

by Giuliana Giorgianni, Luca Bernardi, Francesco Fini, Fabio Pesciaioli, Francesco Secci and Armando Carlone

Catalysts 2022, 12(8), 912; https://doi.org/10.3390/catal12080912 - 18 Aug 2022

Cited by 1 | Viewed by 2960

Abstract

Enantioselective organocatalysis has quickly established itself as the third pillar of asymmetric catalysis. It is a powerful technology platform, and it has a tremendous impact in both academic and industrial settings. By focusing on pregabalin, as a case study, this Perspective aims to [...] Read more.

Enantioselective organocatalysis has quickly established itself as the third pillar of asymmetric catalysis. It is a powerful technology platform, and it has a tremendous impact in both academic and industrial settings. By focusing on pregabalin, as a case study, this Perspective aims to show how a process amenable to industry of a simple chiral molecule can be tackled in several different ways using organocatalysis. Full article

(This article belongs to the Special Issue Organocatalysis: Advances, Opportunity, and Challenges)

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30 pages, 15061 KiB

Open AccessReview

Copper-Catalyzed Reactions of Aryl Halides with N-Nucleophiles and Their Possible Application for Degradation of Halogenated Aromatic Contaminants

by Tomáš Weidlich, Martina Špryncová and Alexander Čegan

Catalysts 2022, 12(8), 911; https://doi.org/10.3390/catal12080911 - 18 Aug 2022

Cited by 7 | Viewed by 3946

Abstract

This review summarizes recent applications of copper or copper-based compounds as a nonprecious metal catalyst in N-nucleophiles-based dehalogenation (DH) reactions of halogenated aromatic compounds (Ar-Xs). Cu-catalyzed DH enables the production of corresponding nonhalogenated aromatic products (Ar-Nu), which are much more biodegradable and can [...] Read more.

This review summarizes recent applications of copper or copper-based compounds as a nonprecious metal catalyst in N-nucleophiles-based dehalogenation (DH) reactions of halogenated aromatic compounds (Ar-Xs). Cu-catalyzed DH enables the production of corresponding nonhalogenated aromatic products (Ar-Nu), which are much more biodegradable and can be mineralized during aerobic wastewater treatment or which are principally further applicable. Based on available knowledge, the developed Cu-based DH methods enable the utilization of amines for effective cleavage of aryl-halogen bonds in organic solvents or even in an aqueous solution. Full article

(This article belongs to the Special Issue Gold, Silver and Copper Catalysis)

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14 pages, 3884 KiB

Open AccessArticle

Hollow CuFe₂O₄/MgFe₂O₄ Heterojunction Boost Photocatalytic Oxidation Activity for Organic Pollutants

by Zhicheng Zhang, Wei Cai, Shaopeng Rong, Hongxia Qu and Huifang Xie

Catalysts 2022, 12(8), 910; https://doi.org/10.3390/catal12080910 - 18 Aug 2022

Cited by 7 | Viewed by 1590

Abstract

P-n heterojunction-structured CuFe₂O₄/MgFe₂O₄ hollow spheres with a diameter of 250 nm were synthesized using a template-free solvothermal method, and time-dependent morphological studies were carried out to investigate the hollow formation mechanism. The CuFe₂O₄ [...] Read more.

P-n heterojunction-structured CuFe₂O₄/MgFe₂O₄ hollow spheres with a diameter of 250 nm were synthesized using a template-free solvothermal method, and time-dependent morphological studies were carried out to investigate the hollow formation mechanism. The CuFe₂O₄/MgFe₂O₄ with a molar ratio of 1:2 (Cu:Mg) had the highest degradation efficiency with the model organic dye Acid Orange 7, with a degradation rate of 91.96% over 60 min. The synthesized CuFe₂O₄/MgFe₂O₄ nanocomposites were characterized by XRD, TEM, HRTEM, UV-vis spectroscopy, Mott–Schottky, and EIS. Due to the synthesis of the p-n heterojunction, CuFe₂O₄/MgFe₂O₄ has efficient photogenerated carriers, and the hollow structure has a higher specific surface area and stronger adsorption capacity, which is significantly better than that of CuFe₂O₄ and MgFe₂O₄ in terms of photocatalytic performance. The outstanding performance shows that the p-n heterostructure of CuFe₂O₄/MgFe₂O₄ has potential for application in wastewater degradation. Full article

(This article belongs to the Special Issue Advances in Catalytic Oxidation of Hydrocarbons and Volatile Organic Compounds (VOCs))

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15 pages, 4030 KiB

Open AccessFeature PaperReview

Levulinic Acid Is a Key Strategic Chemical from Biomass

by Amudhavalli Victor, Pankaj Sharma, Indra Neel Pulidindi and Aharon Gedanken

Catalysts 2022, 12(8), 909; https://doi.org/10.3390/catal12080909 - 18 Aug 2022

Cited by 7 | Viewed by 4749

Abstract

Levulinic acid (LA) is one of the top twelve chemicals listed by the US Department of Energy that can be derived from biomass. It serves as a building block and platform chemical for producing a variety of chemicals, fuels and materials which are [...] Read more.

Levulinic acid (LA) is one of the top twelve chemicals listed by the US Department of Energy that can be derived from biomass. It serves as a building block and platform chemical for producing a variety of chemicals, fuels and materials which are currently produced in fossil based refineries. LA is a key strategic chemical, as fuel grade chemicals and plastic substitutes can be produced by its catalytic conversion. LA derivatisation to various product streams, such as alkyl levulinates via esterification, γ-valerolactone via hydrogenation and N-substituted pyrrolidones via reductive amination and many other transformations of commercial utility are possible owing to the two oxygen functionalities, namely, carbonyl and carboxyl groups, present within the same substrate. Various biomass feedstock, such as agricultural wastes, marine macroalgae, and fresh water microalgae were successfully converted to LA in high yields. Finding a substitute to mineral acid catalysts for the conversion of biomass to LA is a challenge. The use of an ultrasound technique facilitated the production of promising nano-solid acid catalysts including Ga salt of molybophosphoric acid and Ga deposited mordenite zeolite, with optimum amounts of Lewis and Bronsted acidities needed for the conversion of glucose to LA in high yields, being 56 and 59.9 wt.% respectively. Microwave irradiation technology was successfully utilized for the accelerated production of LA (53 wt.%) from glucose in a short duration of 6 min, making use of the unique synergistic catalytic activity of ZnBr₂ and HCl. 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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16 pages, 4260 KiB

Open AccessArticle

Crystalline Violet Wastewater Treatment by Low-Temperature Plasma Combined with Industrial Solid Waste Red Mud

by Weiwei Zhang, Haixia Wu, Yongjun Sun, Qu Wu, Jiliang Bi, Juncheng Jin, Minglong Fang and Zhiru Shi

Catalysts 2022, 12(8), 908; https://doi.org/10.3390/catal12080908 - 17 Aug 2022

Cited by 2 | Viewed by 1623

Abstract

Low-temperature plasma (LTP) technology has been successfully used to treat persistent organic pollutants in water. Efforts have been devoted to combine catalysts and LTP to improve the degradation efficiency of pollutants and energy utilization efficiency. Herein, industrial solid waste red mud as a [...] Read more.

Low-temperature plasma (LTP) technology has been successfully used to treat persistent organic pollutants in water. Efforts have been devoted to combine catalysts and LTP to improve the degradation efficiency of pollutants and energy utilization efficiency. Herein, industrial solid waste red mud as a novel catalyst was added to an LTP system to treat crystalline violet (CV) wastewater. The energy yield at 50% CV decomposition and TOC after a 30 min reaction by the plasma treatment, red mud adsorption, and red mud/plasma treatment were compared. The effects of the main operating parameters, such as red mud dosing amount, initial pH, discharge voltage, and initial concentration of CV, on the removal efficiency of CV were investigated. The best degradation of CV was achieved with a red mud dosage of 2 g, a neutral environment, and a discharge voltage of 22 kV. When the red mud was recycled three times, the removal efficiency decreased a little in the red mud/plasma system. Hydroxyl radical plays an important role in the treatment of CV. The red mud was characterized by BET, SEM, XRD, and FT-IR, and the structure of the red mud was not greatly affected after being used in the red mud/plasma system. Full article

(This article belongs to the Special Issue Plasma Catalytic Pollution Degradation: State of the Art and Future Directions)

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9 pages, 1834 KiB

Open AccessCommunication

The Shell Matters: Self-Organized CdS-ZnS/MnS-Core-Shell—Porphyrin-Polymer Nano-Assemblies for Photocatalysis

by Maximilian Wagner and Franziska Gröhn

Catalysts 2022, 12(8), 907; https://doi.org/10.3390/catal12080907 - 17 Aug 2022

Viewed by 1332

Abstract

A facile synthesis of catalytically tunable core-shell CdS-Zn_xMn_1-xS-nanoparticles in conjunction with poly(acrylic acid) (PAA) and porphyrin in an aqueous solution is described in the following: The shell composition of the inorganic nanoparticles is varied to tune the optical properties [...] Read more.

A facile synthesis of catalytically tunable core-shell CdS-Zn_xMn_1-xS-nanoparticles in conjunction with poly(acrylic acid) (PAA) and porphyrin in an aqueous solution is described in the following: The shell composition of the inorganic nanoparticles is varied to tune the optical properties and to optimize the catalytic activity. Further, the tetravalent cationic 5,10,15,20-tetrakis(4-trimethylammoniophenyl) porphyrin (TAPP) fulfills a triple functionality in the catalyst: as a photosensitizer, as an electrostatic linker connecting the nanoparticles and as a probe to investigate the surface composition of the II-VI semiconducting nanoparticles. Different nanoparticles with varying zinc sulfide/manganese sulfide shell ratios are tested with regard to their photocatalytic behavior by crocin bleaching. The results reveal that the shell composition can be a crucial key to optimize the catalytic activity, which can further be important in tuning the reactivity of related systems. Fundamentally, the stepwise multi-component self-assembly in an aqueous solution has been demonstrated to allow the tuning of optic and catalytic properties of core-shell nanoparticles, a general concept that may be widely applicable. Full article

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

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16 pages, 12821 KiB

Open AccessArticle

Modified Mn/ZSM-5 for Non-Thermal Plasma Mineralization of VOCs and DFT Simulation Using a Novel Y-Type ZSM-5 Model

by Su Liu, Jiabin Zhou, Dan Liu and Ke Du

Catalysts 2022, 12(8), 906; https://doi.org/10.3390/catal12080906 - 17 Aug 2022

Viewed by 1559

Abstract

Using a catalyst to mineralize volatile organic compounds (VOCs) in a Non-thermal Plasma (NTP) reactor is an effective method. In many kinds of catalysts for VOCs degradation, oxygen defect is a crucial factor affecting the catalytic activity. Three different methods (steaming, doping, plasma) [...] Read more.

Using a catalyst to mineralize volatile organic compounds (VOCs) in a Non-thermal Plasma (NTP) reactor is an effective method. In many kinds of catalysts for VOCs degradation, oxygen defect is a crucial factor affecting the catalytic activity. Three different methods (steaming, doping, plasma) were used to introduce possible oxygen defects into the Mn/ZSM-5 to prepare modified catalysts, which were evaluated in VOCs degradation activity using a Double Dielectric Barrier Discharge (DDBD) plasma device. Additionally, a novel Y-type ZSM-5 model was employed in the DFT simulation. The new Y-type ZSM-5 model used in this paper is a more realistic aperiodic model. It showed that introducing possible oxygen defects can substantially enhance degradation efficiency. Taking the catalyst with oxygen defects introduced by plasma as an example, the conversion (CO₂ selectivity) of the methanol, acetone, and toluene could reach 100% (100%), 97.7% (99.1%), 91.2% (93.9%), respectively, at an initial concentration of 2000 ppm and specific input energy of 9 kJ/L. The results demonstrated that modification could significantly enhance the activity of the catalyst in decomposing VOCs at room temperature using non-thermal plasma catalysis. Theoretical simulation of density functional theory (DFT) revealed that the adsorption of adsorbate on the catalyst becomes easier after possible oxygen defects are introduced. Full article

(This article belongs to the Special Issue Recent Progress of Catalysis in “Dual Carbon Targets”)

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19 pages, 4704 KiB

Open AccessFeature PaperReview

Single-Atom-Based Catalysts for Photocatalytic Water Splitting on TiO₂ Nanostructures

by Seyedsina Hejazi, Manuela S. Killian, Anca Mazare and Shiva Mohajernia

Catalysts 2022, 12(8), 905; https://doi.org/10.3390/catal12080905 - 17 Aug 2022

Cited by 10 | Viewed by 2949

Abstract

H₂ generation from photocatalytic water splitting is one of the most promising approaches to producing cost-effective and sustainable fuel. Nanostructured TiO₂ is a highly stable and efficient semiconductor photocatalyst for this purpose. The main drawback of TiO₂ as a photocatalyst [...] Read more.

H₂ generation from photocatalytic water splitting is one of the most promising approaches to producing cost-effective and sustainable fuel. Nanostructured TiO₂ is a highly stable and efficient semiconductor photocatalyst for this purpose. The main drawback of TiO₂ as a photocatalyst is the sluggish charge transfer on the surface of TiO₂ that can be tackled to a great extent by the use of platinum group materials (PGM) as co-catalysts. However, the scarcity and high cost of the PGMs is one of the issues that prevent the widespread use of TiO₂/PGM systems for photocatalytic H₂ generation. Single-atom catalysts which are currently the frontline in the catalysis field can be a favorable path to overcome the scarcity and further advance the use of noble metals. More importantly, single-atom (SA) catalysts simultaneously have the advantage of homogenous and heterogeneous catalysts. This mini-review specifically focuses on the single atom decoration of TiO₂ nanostructures for photocatalytic water splitting. The latest progress in fabrication, characterization, and application of single-atoms in photocatalytic H₂ generation on TiO₂ is reviewed. Full article

(This article belongs to the Special Issue Innovative Strategies for (Photo)Electrocatalytic Water Splitting and CO₂ Reduction)

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14 pages, 3800 KiB

Open AccessArticle

Chitin and Silk Fibroin Biopolymers Modified by Oxone: Efficient Heterogeneous Catalysts for Knoevenagel Reaction

by Fernando B. Neves, Lucas L. Zanin, Rayanne R. Pereira, José Otávio C. S. Júnior, Roseane Maria R. Costa, André L. M. Porto, Sérgio A. Yoshioka, Alex Nazaré de Oliveira, David E. Q. Jimenez and Irlon M. Ferreira

Catalysts 2022, 12(8), 904; https://doi.org/10.3390/catal12080904 - 17 Aug 2022

Cited by 2 | Viewed by 1684

Abstract

New materials from silk fibroin (FS-Ox) and chitin (CT-Ox) functionalized with Oxone^® salt were developed for application in the synthesis of Knoevenagel adducts. The experiments were performed using benzaldehyde derivatives, malononitrile, and a mixture of water and ethanol as green solvents. The [...] Read more.

New materials from silk fibroin (FS-Ox) and chitin (CT-Ox) functionalized with Oxone^® salt were developed for application in the synthesis of Knoevenagel adducts. The experiments were performed using benzaldehyde derivatives, malononitrile, and a mixture of water and ethanol as green solvents. The efficiency of conventional and microwave irradiation as heating sources for this reaction was also investigated. When the reactions were performed for 60 min under optimized conditions with conventional heating, twelve Knoevenagel adducts 2a–l were obtained, with good yields for both catalysts (CT-Ox 60–98% and FS-Ox 71–98%). When microwave irradiation was used, the reaction periods were reduced twelvefold, with the same Knoevenagel adducts with good CT-Ox (39–99%) and FS-Ox (35–99%) yields obtained in most cases. The reuse of these materials as catalysts in successive reactions was also evaluated, and CT-Ox FS-Ox were successfully used for 4 and 2 cycles, respectively. The results presented prove the efficiency of the CT-OxFS-Ox catalyst as a promising low-cost and reusable material with suitable catalytic properties to be applied in the aldol condensation reaction in a sustainable way. Full article

(This article belongs to the Topic Green and Sustainable Chemistry)

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7 pages, 1523 KiB

Open AccessCommunication

Revealing the Synergetic Effects between Reactants in Oxidative Coupling of Methane on Stepped MgO(100) Catalyst

by Xiaoying Sun, Yue Liu, Xinyu Li, Zhan Yu, Bo Li and Zhen Zhao

Catalysts 2022, 12(8), 903; https://doi.org/10.3390/catal12080903 - 17 Aug 2022

Viewed by 1266

Abstract

The oxidative coupling of methane (OCM) on MgO is often computationally explored via Mars-Krevelen (MvK) mechanism. However, the difficult desorption of CH₃ radical at stepped MgO surface shadow the feasibility of mechanism. In this work, density functional theory calculations are performed to [...] Read more.

The oxidative coupling of methane (OCM) on MgO is often computationally explored via Mars-Krevelen (MvK) mechanism. However, the difficult desorption of CH₃ radical at stepped MgO surface shadow the feasibility of mechanism. In this work, density functional theory calculations are performed to unravel the syngenetic effects between reactants which lead to a new Langmuir-Hinshelwood (L-H)-like mechanism. It was found that co-adsorption of reactants pave ways for CH₃ radical formation with negligible desorption energy. The role of oxygen molecule is not only to oxidize reduced surface but also decrease the reactivity of Mg-O site which facile CH₃ desorption. Electronic structure analysis indicated the distinct feature along pathway between MvK and L-H. The current work clearly indicated the importance of effective interactions between reactants and provided new insights on the reaction mechanism of OCM. Full article

(This article belongs to the Special Issue Computational Insights into Small Molecule Activation)

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13 pages, 3342 KiB

Open AccessArticle

Site and Structural Requirements for the Dehydra-Decyclization of Cyclic Ethers on ZrO₂

by Mengjie Fan, Yichen Ji, Ajibola Lawal, Omar A. Abdelrahman, Raymond J. Gorte and John M. Vohs

Catalysts 2022, 12(8), 902; https://doi.org/10.3390/catal12080902 - 17 Aug 2022

Cited by 3 | Viewed by 1594

Abstract

In this study, we examined the site and structural requirements for the dehydra-decyclization of cyclic ethers, tetrahydrofuran, and tetrahydropyran to produce conjugated dienes over ZrO₂-based catalysts, a reaction that could be an important step in the use of biomass-derived sugars as [...] Read more.

In this study, we examined the site and structural requirements for the dehydra-decyclization of cyclic ethers, tetrahydrofuran, and tetrahydropyran to produce conjugated dienes over ZrO₂-based catalysts, a reaction that could be an important step in the use of biomass-derived sugars as a starting material to produce monomers for the plastics industry. To help identify the active sites for this reaction, studies were conducted in which ZrO₂ surfaces were decorated with Na. These studies showed that Na was effective at poisoning the activity for the ring opening of cyclic ethers, but much less so for the dehydration of the resulting adsorbed alkoxides. The studies of the activity of different types of ZrO₂ for the dehydra-decyclization reaction, including single crystals and ultra-thin films supported on MgAl₂O₄ and silica, also showed that the reaction was dependent on the local structure of the ZrO₂ surface. The insights these results provide for identifying the active sites on the ZrO₂ surface are discussed. Full article

(This article belongs to the Section Biomass Catalysis)

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10 pages, 2030 KiB

Open AccessCommunication

An Efficient Zr-ZSM-5-st Solid Acid Catalyst for the Polyol Esterification Reaction

by Huaigang Su, Ze Zong, Wenjing Lou, Qin Zhao, Xiaobo Wang, Xiang Feng, Yanxing Qi and Zhaoning Song

Catalysts 2022, 12(8), 901; https://doi.org/10.3390/catal12080901 - 16 Aug 2022

Cited by 2 | Viewed by 1769

Abstract

In this study, Zr active species were implanted into a ZSM-5 zeolite framework to form a solid acid catalyst through steam treatment and the liquid-solid isomorphous substitution process. The as-synthesized Zr-ZSM-5-st catalyst ensured excellent esterification of trimethylolpropane and fatty acids (FAs) to achieve [...] Read more.

In this study, Zr active species were implanted into a ZSM-5 zeolite framework to form a solid acid catalyst through steam treatment and the liquid-solid isomorphous substitution process. The as-synthesized Zr-ZSM-5-st catalyst ensured excellent esterification of trimethylolpropane and fatty acids (FAs) to achieve a polyol ester production yield of 94.41%. Combined with N₂ physisorption, X-ray diffraction, Fourier transform infrared spectroscopy, ultraviolet-visible spectroscopy, transmission electron microscopy mapping, X-ray photoelectron spectroscopy, NH₃ temperature-programmed desorption, and inductively coupled mass plasma spectroscopy were conducted. The results revealed that the excellent performance of Zr-ZSM-5-st catalyst could be attributed to the enhanced acidity and the developed surface area and pore structure. Full article

(This article belongs to the Topic Green and Sustainable Chemistry)

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22 pages, 7084 KiB

Open AccessArticle

Bifunctional Co₃O₄/ZSM-5 Mesoporous Catalysts for Biodiesel Production via Esterification of Unsaturated Omega-9 Oleic Acid

by Francisco Núñez, Lifang Chen, Jin An Wang, Sergio Ordin Flores, José Salmones, Ulises Arellano, Luis Enrique Noreña and Francisco Tzompantzi

Catalysts 2022, 12(8), 900; https://doi.org/10.3390/catal12080900 - 16 Aug 2022

Cited by 11 | Viewed by 1730

Abstract

In the present work, two sets of the Co/ZSM-5 mesoporous catalysts with different acidity and Co loadings varying from 1 to 5 and 10 wt% were prepared using mesoporous ZSM-5-A (Si/Al = 50) and ZSM-5-B (Si/Al = 150) as support. X-ray diffraction (XRD) [...] Read more.

In the present work, two sets of the Co/ZSM-5 mesoporous catalysts with different acidity and Co loadings varying from 1 to 5 and 10 wt% were prepared using mesoporous ZSM-5-A (Si/Al = 50) and ZSM-5-B (Si/Al = 150) as support. X-ray diffraction (XRD) analysis showed that the Co₃O₄ phase was formed in the surface of catalysts and the reducibility of Co₃O₄ nanoparticles on the ZSM-5-B was greater in comparison with that on the ZSM-5-A solid. In situ FTIR of pyridine adsorption characterization confirmed that all of the Co/ZSM-5 catalysts contained both Lewis (L) and Brønsted (B) acid sites, with a relatively balanced B/L ratio ranging from 0.61 to 1.94. Therefore, the Si/Al molar ratio in ZSM-5 affected both the surface acidity and the cobalt oxide reducibility. In the esterification of unsaturated omega-9 oleic acid with methanol, under the optimal reaction conditions (temperature 160 °C, catalyst concentration 2 g/L, methanol/oleic acid molar ratio 30, and reaction time 180 min), the biodiesel selectivity reached 95.1% over the most active 10 wt% Co/ZSM-5-B catalyst. The higher esterification activity of the Co/ZSM-5-B catalysts can be correlated with the greater amount of B and L acid sites, the balanced B/L ratio, and the higher reducibility of Co₃O₄ nanoparticles. The oleic acid esterification reaction followed the bifunctional mechanism of combining metal function (dispersed Co₃O₄ with a greater reducibility) with the acidity function (both B and L acid sites with a relative balanced B/L ratio) on the catalysts, which may help in providing a deep understanding of the esterification pathways and benefiting the design of novel bifunctional catalysts for biofuel production. Full article

(This article belongs to the Topic Nanomaterials and Catalysts for Clean Fuels and Sustainable Energy)

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16 pages, 3434 KiB

Open AccessArticle

Sorbent and Photocatalytic Potentials of Local Clays for the Removal of Organic Xenobiotic: Case of Crystal Violet

by Sadou Dalhatou, Mouhamadou Sali, Samuel Tetteh, Abdoulaye Boubakari, Bouba Talami, Hicham Zeghioud, Abdoulaye Kane, Atef El Jery, Aymen Amin Assadi and David Olubiyi Obada

Catalysts 2022, 12(8), 899; https://doi.org/10.3390/catal12080899 - 16 Aug 2022

Cited by 3 | Viewed by 1476

Abstract

Natural materials are widely used in the field of environmental remediation and are appreciated for their surface physical and chemical properties. Clay constitutes a typical example. In this work, we report the evaluation of sorbent and photocatalytic potentials of local clay of two [...] Read more.

Natural materials are widely used in the field of environmental remediation and are appreciated for their surface physical and chemical properties. Clay constitutes a typical example. In this work, we report the evaluation of sorbent and photocatalytic potentials of local clay of two irrigated rice field waters in the degradation of crystal violet. The structural, textural and compositional properties of the local clay were investigated by Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD) and X-ray Fluorescence (XRF) analysis. The analysis results showed that these materials were composed mainly of quartz and kaolinite. The efficiency of these adsorbents (Y. Clay and L. Clay) to eliminate crystal violet dye from aqueous medium was examined at different initial concentrations, pH, contact time, adsorbent dose and the possible interference of inorganic salts from fertilizers. Kinetic studies showed that the adsorption process was well described by the pseudo-second order model and the equilibrium modelling results fitted adequately to the Freundlich model. The maximum amount of uptake capacity achieved at pH 2.0 was 18.40 (mg·g⁻¹) and 20.40 (mg·g⁻¹), respectively, for Y. Clay and L. Clay. The evaluation of the photocatalytic potential showed that the raw clay samples do not show photocatalytic activities during the 30 min of exposure to UV light. On the other hand, their photocatalytic potential is manifested when loaded with titanium dioxide (TiO₂). Clays coupled with TiO₂ under UV light showed an improvement in the degradation of the crystal violet dye by 15%. The synergistic effects between the high photocatalytic activity of TiO₂ and the strong adsorption capacity of clays can be one promising technique for in situ remediation of contaminated soaked rice field. Full article

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

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