Catalysts

35 pages, 8152 KiB

Open AccessFeature PaperEditor’s ChoiceReview

The Role of Alkali and Alkaline Earth Metals in the CO₂ Methanation Reaction and the Combined Capture and Methanation of CO₂

by Anastasios I. Tsiotsias, Nikolaos D. Charisiou, Ioannis V. Yentekakis and Maria A. Goula

Catalysts 2020, 10(7), 812; https://doi.org/10.3390/catal10070812 - 21 Jul 2020

Cited by 106 | Viewed by 12803

Abstract

CO₂ methanation has great potential for the better utilization of existing carbon resources via the transformation of spent carbon (CO₂) to synthetic natural gas (CH₄). Alkali and alkaline earth metals can serve both as promoters for methanation catalysts [...] Read more.

CO₂ methanation has great potential for the better utilization of existing carbon resources via the transformation of spent carbon (CO₂) to synthetic natural gas (CH₄). Alkali and alkaline earth metals can serve both as promoters for methanation catalysts and as adsorbent phases upon the combined capture and methanation of CO₂. Their promotion effect during methanation of carbon dioxide mainly relies on their ability to generate new basic sites on the surface of metal oxide supports that favour CO₂ chemisorption and activation. However, suppression of methanation activity can also occur under certain conditions. Regarding the combined CO₂ capture and methanation process, the development of novel dual-function materials (DFMs) that incorporate both adsorption and methanation functions has opened a new pathway towards the utilization of carbon dioxide emitted from point sources. The sorption and catalytically active phases on these types of materials are crucial parameters influencing their performance and stability and thus, great efforts have been undertaken for their optimization. In this review, we present some of the most recent works on the development of alkali and alkaline earth metal promoted CO₂ methanation catalysts, as well as DFMs for the combined capture and methanation of CO₂. Full article

(This article belongs to the Special Issue Catalysis for Energy Production)

► Show Figures

Graphical abstract

13 pages, 3940 KiB

Open AccessArticle

Effect of Calcination Temperature on Structural Properties and Catalytic Performance of Novel Amorphous NiP/Hβ Catalyst for n-Hexane Isomerization

by Jinshe Chen, Lijun Zhu, Yuzhi Xiang and Daohong Xia

Catalysts 2020, 10(7), 811; https://doi.org/10.3390/catal10070811 - 21 Jul 2020

Cited by 19 | Viewed by 3165

Abstract

To study how calcination temperature influences the structural properties and catalytic performance of a novel amorphous NiP/Hβ catalyst, amorphous NiP/Hβ catalysts calcined at different temperatures were prepared for n-hexane isomerization. The optimum calcination temperature was determined, and the effect of calcination temperature on [...] Read more.

To study how calcination temperature influences the structural properties and catalytic performance of a novel amorphous NiP/Hβ catalyst, amorphous NiP/Hβ catalysts calcined at different temperatures were prepared for n-hexane isomerization. The optimum calcination temperature was determined, and the effect of calcination temperature on the structural properties of the catalysts was investigated using different characterization methods, such as XRD, TPD and so on. It was found that the optimum calcination temperature was 200 °C. Simultaneously, the amorphous NiP/Hβ catalyst showed good application potential as a non-noble metal catalyst. Calcination temperatures from 100 to 400 °C had almost no effect on pore properties. Meanwhile, the acid properties of the amorphous NiP/Hβ catalyst were affected very little by calcination temperature. By increasing calcination temperature, the dispersion state of amorphous NiP became worse at 300 °C, and then the structure of NiP changed from an amorphous structure into a crystalline structure at 400 °C. In addition, the catalyst became more difficult to reduce with the increase in calcination temperature. Combined with the results of n-hexane isomerization catalyzed by different samples, the mechanism by which calcination temperature affects n-hexane isomerization over catalyst was revealed. It was shown that for the amorphous NiP/Hβ catalyst, calcination temperature influences the catalytic performance mainly by affecting the dispersion degree and structure of active components. Full article

► Show Figures

Figure 1

18 pages, 3204 KiB

Open AccessFeature PaperArticle

Co-Immobilization and Co-Localization of Oxidases and Catalases: Catalase from Bordetella Pertussis Fused with the Zbasic Domain

by Paz García-García, Javier Rocha-Martin, Jose M. Guisan and Gloria Fernandez-Lorente

Catalysts 2020, 10(7), 810; https://doi.org/10.3390/catal10070810 - 21 Jul 2020

Cited by 7 | Viewed by 2822

Abstract

Oxidases catalyze selective oxidations by using molecular oxygen as an oxidizing agent. This process promotes the release of hydrogen peroxide, an undesirable byproduct. The instantaneous elimination of hydrogen peroxide can be achieved by co-immobilization and co-localization of the oxidase and an auxiliary catalase [...] Read more.

Oxidases catalyze selective oxidations by using molecular oxygen as an oxidizing agent. This process promotes the release of hydrogen peroxide, an undesirable byproduct. The instantaneous elimination of hydrogen peroxide can be achieved by co-immobilization and co-localization of the oxidase and an auxiliary catalase inside the porous structure of solid support. In this paper, we proposed that catalase from Bordetella pertussis fused with a small domain (Zbasic) as an excellent auxiliary enzyme. The enzyme had a specific activity of 23 U/mg, and this was almost six-fold higher than the one of the commercially available catalases from bovine liver. The Zbasic domain was fused to the four amino termini of this tetrameric enzyme. Two domains were close in one hemisphere of the enzyme molecule, and the other two were close in the opposite hemisphere. In this way, each hemisphere contained 24 residues with a positive charge that was very useful for the purification of the enzyme via cationic exchange chromatography. In addition to this, each hemisphere contained 10 Lys residues that were very useful for a rapid and intense multipoint covalent attachment on highly activated glyoxyl supports. In fact, 190 mg of the enzyme was immobilized on one gram of glyoxyl-10% agarose gel. The ratio catalase/oxidase able to instantaneously remove more than 93% of the released hydrogen peroxide was around 5–6 mg of catalase per mg of oxidase. Thirty milligrams of amine oxidase and 160 mg of catalase were co-immobilized and co-localized per gram of glyoxyl-agarose 10BCL (10% beads cross-linked) support. This biocatalyst eliminated biogenic amines (putrescine) 80-fold faster than a biocatalyst of the same oxidase co-localized with the commercial catalase from bovine liver. Full article

(This article belongs to the Special Issue Application of Immobilized Enzyme as Catalysts in Chemical Synthesis)

► Show Figures

Figure 1

16 pages, 1978 KiB

Open AccessArticle

Valorization of Corn Seed Oil Acid Degumming Waste for Phospholipids Preparation by Phospholipase D-Mediated Processes

by Chiara Allegretti, Andrea Bono, Paola D’Arrigo, Francesca Denuccio, Davide De Simeis, Giuseppe Di Lecce, Stefano Serra, Davide Tessaro and Mariacristina Viola

Catalysts 2020, 10(7), 809; https://doi.org/10.3390/catal10070809 - 21 Jul 2020

Cited by 6 | Viewed by 3926

Abstract

This work focused on the phospholipase D-mediated treatment of the waste residue coming from acid degumming, which constitutes the second part of the degumming step in the crude corn edible oil refining process. This industrial process produces a complex by-product (called gum), a [...] Read more.

This work focused on the phospholipase D-mediated treatment of the waste residue coming from acid degumming, which constitutes the second part of the degumming step in the crude corn edible oil refining process. This industrial process produces a complex by-product (called gum), a mixture containing phospholipids (PLs) whose composition depends on the nature of the oil source. This residue is usually disposed of with the consequential costs and environmental concerns. An efficient multistep protocol of physical separations of the PL-rich fraction from waste gums has been set up, including centrifugation, precipitation and solvent partitioning. This waste stream, which is thoroughly characterized after the concentration process, constitutes a renewable feedstock for the production of value-added PLs with modified polar head-exploiting phospholipase D-mediated biotransformations, which have been successfully performed on this complex natural mixture. The valorization of these waste gums through the production of high value PLs for targeted applications paves the way to a new alternative approach for their disposal, which could be of great interest from a circular economy perspective. Full article

(This article belongs to the Special Issue Lipases and Phospholipases in Biocatalysis)

► Show Figures

Graphical abstract

20 pages, 2025 KiB

Open AccessFeature PaperArticle

Direct Decomposition of NO over Co-Mn-Al Mixed Oxides: Effect of Ce and/or K Promoters

by Květa Jirátová, Kateřina Pacultová, Kateřina Karásková, Jana Balabánová, Martin Koštejn and Lucie Obalová

Catalysts 2020, 10(7), 808; https://doi.org/10.3390/catal10070808 - 20 Jul 2020

Cited by 5 | Viewed by 2785

Abstract

Co-Mn-Al mixed oxides promoted by potassium are known as active catalysts for the direct decomposition of nitric oxide (NO). In this study, the answer to the following question has been considered: does the presence of cerium in K-promoted Co-Mn-Al catalysts substantially affect the [...] Read more.

Co-Mn-Al mixed oxides promoted by potassium are known as active catalysts for the direct decomposition of nitric oxide (NO). In this study, the answer to the following question has been considered: does the presence of cerium in K-promoted Co-Mn-Al catalysts substantially affect the physical-chemical properties, activity, and stability in direct NO decomposition? The Co-Mn-Al, Co-Mn-Al-Ce, and Co-Mn-Al-Ce-K mixed oxide catalysts were prepared by the precipitation of corresponding metal nitrates with a solution of Na₂CO₃/NaOH, followed by the washing of the precipitate and calcination. Two other catalysts were prepared by impregnation of the Ce-containing catalysts with Co and Co+K nitrates. After calcination, the solids were characterized by chemical analysis, XRD, N₂ physisorption, FTIR, temperature-programmed reduction, CO₂ and O₂ desorption (H₂-TPR, CO₂-TPD, O₂-TPD), and X-ray photoelectron spectrometry (XPS). Cerium and especially potassium occurring in the catalysts affected the basicity, reducibility, and surface concentration of active components. Adding cerium itself did not contribute to the increase in catalytic activity, whereas the addition of cerium and potassium did. Catalytic activity in direct NO decomposition depended on combinations of both reducibility and the amount of stronger basic sites determined in the catalysts. Therefore, the increase in cobalt concentration itself in the Co-Mn-Al mixed oxide catalyst does not determine the achievement of high catalytic activity in direct NO decomposition. Full article

(This article belongs to the Special Issue Catalytic Decomposition of N2O and NO)

► Show Figures

Figure 1

11 pages, 3027 KiB

Open AccessArticle

In-Exchanged CHA Zeolites for Selective Dehydrogenation of Ethane: Characterization and Effect of Zeolite Framework Type

by Zen Maeno, Xiaopeng Wu, Shunsaku Yasumura, Takashi Toyao, Yasuharu Kanda and Ken-ichi Shimizu

Catalysts 2020, 10(7), 807; https://doi.org/10.3390/catal10070807 - 20 Jul 2020

Cited by 16 | Viewed by 4360

Abstract

In this study, the characterization of In-exchanged CHA zeolite (In-CHA (SiO₂/Al₂O₃ = 22.3)) was conducted by in-situ X-ray diffraction (XRD) and ammonia temperature-programmed desorption (NH₃-TPD). We also prepared other In-exchanged zeolites with different zeolite structures (In-MFI [...] Read more.

In this study, the characterization of In-exchanged CHA zeolite (In-CHA (SiO₂/Al₂O₃ = 22.3)) was conducted by in-situ X-ray diffraction (XRD) and ammonia temperature-programmed desorption (NH₃-TPD). We also prepared other In-exchanged zeolites with different zeolite structures (In-MFI (SiO₂/Al₂O₃ = 22.3), In-MOR (SiO₂/Al₂O₃ = 20), and In-BEA (SiO₂/Al₂O₃ = 25)) and different SiO₂/Al₂O₃ ratios (In-CHA(Al-rich) (SiO₂/Al₂O₃ = 13.7)). Their catalytic activities in nonoxidative ethane dehydrogenation were compared. Among the tested catalysts, In-CHA(Al-rich) provided the highest conversion. From kinetic experiments and in-situ Fourier transform infrared (FTIR) spectroscopy, [InH₂]⁺ ions are formed regardless of SiO₂/Al₂O₃ ratio, serving as the active sites. Full article

(This article belongs to the Special Issue Metal-Exchanged Zeolite Catalysts)

► Show Figures

Graphical abstract

27 pages, 7861 KiB

Open AccessFeature PaperArticle

An Eco-Friendly Fluidizable Fe_xO_y/CaO-γ-Al₂O₃ Catalyst for Tar Cracking during Biomass Gasification

by Cindy Torres, Samira Rostom and Hugo de Lasa

Catalysts 2020, 10(7), 806; https://doi.org/10.3390/catal10070806 - 20 Jul 2020

Cited by 18 | Viewed by 3985

Abstract

The present study deals with the development, characterization, and performance evaluation of an eco-friendly catalyst, using 2-methoxy-4-methylphenol (2M4MP) as a surrogate tar. The 2M4MP was selected due to its chemical functionalities and the fact that it is a good model compound to represent [...] Read more.

The present study deals with the development, characterization, and performance evaluation of an eco-friendly catalyst, using 2-methoxy-4-methylphenol (2M4MP) as a surrogate tar. The 2M4MP was selected due to its chemical functionalities and the fact that it is a good model compound to represent the tar formed during biomass low temperature gasification. The eco-friendly catalyst was prepared using the typical Fe and Ca minerals which are present in ash. These ash components were added to a fluidizable γ-Al₂O₃ support using a multistep incipient impregnation, yielding Fe oxides as an active phase and CaO as the promoter. The prepared catalyst displayed a 120 m²/g BET specific surface area, with few γ-Al₂O₃ bulk phase changes, as observed with XRD. TPD-NH₃ and pyridine FTIR allowed us to show the significant influence of CaO reduced support acidity. A TPR analysis provided evidence of catalyst stability during consecutive reduction–oxidation cycles. Furthermore, catalyst evaluation vis-à-vis catalytic steam 2M4MP gasification was performed using the fluidized CREC riser simulator. The obtained results confirm the high performance of the developed catalyst, with 2M4MP conversion being close to 100% and with selectivities of up to 98.6% for C1-C2 carbon-containing species, at 500 °C, with a 7.5 s reaction time and 1.5 g steam/g 2M4MP. These high tar conversions are promising efficiency indicators for alumina catalysts doped with Fe and Ca. In addition, the used catalyst particles could be blended with biochar to provide an integrated solid supplement that could return valuable mineral supplements to the soil. Full article

(This article belongs to the Special Issue Commemorative Issue in Honor of Professor Hugo de Lasa)

► Show Figures

Graphical abstract

17 pages, 3827 KiB

Open AccessArticle

Synthesis, Characterization, and Anti-Algal Activity of Molybdenum-Doped Metal Oxides

by Sondavid Nandanwar, Myung Won Lee, Shweta Borkar, Jeong Hyung Cho, Naresh H. Tarte and Hak Jun Kim

Catalysts 2020, 10(7), 805; https://doi.org/10.3390/catal10070805 - 20 Jul 2020

Cited by 5 | Viewed by 3521

Abstract

In this study, we attempted to synthesize visible light active nano-sized photocatalysts using metal oxides such as zinc oxide, zirconium oxide, tungsten oxide, and strontium titanium oxide with (MoCl₅)₂ as a dopant by the simple ball-milling method. Fourier-transform infrared spectroscopy [...] Read more.

In this study, we attempted to synthesize visible light active nano-sized photocatalysts using metal oxides such as zinc oxide, zirconium oxide, tungsten oxide, and strontium titanium oxide with (MoCl₅)₂ as a dopant by the simple ball-milling method. Fourier-transform infrared spectroscopy data confirmed the presence of M-O-Mo linkage (M = Zn, Zr, W, and SrTi) in all the molybdenum-doped metal oxides (MoMOs), but only MoZnO inhibited the growth of the bloom-forming Microcystis aeruginosa under visible light in a concentration-dependent manner up to 10 mg/L. Further, structural characterization of MoZnO using FESEM and XRD exhibited the formation of typical hexagonal wurtzite nanocrystals of approximately 4 nm. Hydroxyl radical (·OH), reactive oxygen species (ROS), and lipid peroxidation assays revealed ·OH generated by MoZnO under the visible light seemed to cause peroxidation of the lipid membrane of M. aeruginosa, which led to an upsurge of intracellular ROS and consequently introduced the agglomeration of cyanobacteria. These results demonstrated that nano-sized MoZnO photocatalyst can be easily synthesized in a cost-effective ball-mill method and utilized for biological applications such as the reduction of harmful algal blooms. Further, our study implies that a simple ball-milling method can provide an easy, green, and scalable route for the synthesis of visible light active doped metal oxides. Full article

(This article belongs to the Section Photocatalysis)

► Show Figures

Graphical abstract

33 pages, 2256 KiB

Open AccessReview

Impact of Titanium Dioxide (TiO₂) Modification on Its Application to Pollution Treatment—A Review

by Ruixiang Li, Tian Li and Qixing Zhou

Catalysts 2020, 10(7), 804; https://doi.org/10.3390/catal10070804 - 20 Jul 2020

Cited by 176 | Viewed by 20750

Abstract

A high-efficiency method to deal with pollutants must be found because environmental problems are becoming more serious. Photocatalytic oxidation technology as the environmentally-friendly treatment method can completely oxidate organic pollutants into pollution-free small-molecule inorganic substances without causing secondary pollution. As a widely used [...] Read more.

A high-efficiency method to deal with pollutants must be found because environmental problems are becoming more serious. Photocatalytic oxidation technology as the environmentally-friendly treatment method can completely oxidate organic pollutants into pollution-free small-molecule inorganic substances without causing secondary pollution. As a widely used photocatalyst, titanium dioxide (TiO₂) can greatly improve the degradation efficiency of pollutants, but several problems are noted in its practical application. TiO₂ modified by different materials has received extensive attention in the field of photocatalysis because of its excellent physical and chemical properties compared with pure TiO₂. In this review, we discuss the use of different materials for TiO₂ modification, highlighting recent developments in the synthesis and application of TiO₂ composites using different materials. Materials discussed in the article can be divided into nonmetallic and metallic. Mechanisms of how to improve catalytic performance of TiO₂ after modification are discussed, and the future development of modified TiO₂ is prospected. Full article

(This article belongs to the Special Issue Advances in Photocatalytic Wastewater Purification)

► Show Figures

Figure 1

16 pages, 3258 KiB

Open AccessArticle

The Influence of a Surface Treatment of Metallic Titanium on the Photocatalytic Properties of TiO₂ Nanotubes Grown by Anodic Oxidation

by Živa Marinko, Luka Suhadolnik, Zoran Samardžija, Janez Kovač and Miran Čeh

Catalysts 2020, 10(7), 803; https://doi.org/10.3390/catal10070803 - 19 Jul 2020

Cited by 2 | Viewed by 3235

Abstract

Titanium dioxide (TiO₂) nanotubes obtained by the anodic oxidation of titanium metal foils can be used for the photocatalytic degradation of organic pollutants. The aim of our study was to determine the influence of the titanium foil’s surface treatment on the [...] Read more.

Titanium dioxide (TiO₂) nanotubes obtained by the anodic oxidation of titanium metal foils can be used for the photocatalytic degradation of organic pollutants. The aim of our study was to determine the influence of the titanium foil’s surface treatment on the final morphology of the TiO₂ nanotubes and their photocatalytic activity. In our experiments, we used two different titanium foils that were electropolished or untreated prior to the anodic oxidation. The morphologies of the starting titanium foils and the resulting TiO₂ nanotube layers were investigated and the photocatalytic activities measured by the decomposition of caffeine under UV irradiation. Our results showed that electropolishing of the starting foils produced a more uniform and smoother TiO₂ nanotubes surface. In contrast, the TiO₂ nanotube surfaces from untreated titanium foils mimic the initial surface roughness of the titanium foil. A comparison of the photocatalytic properties of the TiO₂ nanotube layers obtained from the untreated and electropolished titanium foils showed that electropolishing does not necessarily improve the photocatalytic properties of the resulting TiO₂ nanotube layer. It was found that the determining factors influencing the photocatalytic activity are the chemical impurities (Ti-nitride) on the surface of the titanium foils and the surface roughness of the TiO₂ nanotube layer. The highest photocatalytic activity was achieved with the anodized untreated foil with the minimal presence of Ti-nitride and a relatively high roughness of the TiO₂ nanotubes. Full article

(This article belongs to the Special Issue Environmental Catalysis in Advanced Oxidation Processes)

► Show Figures

Graphical abstract

13 pages, 6767 KiB

Open AccessArticle

A Pd/MnO₂ Electrocatalyst for Nitrogen Reduction to Ammonia under Ambient Conditions

by Chang Sun, Yingxin Mu and Yuxin Wang

Catalysts 2020, 10(7), 802; https://doi.org/10.3390/catal10070802 - 19 Jul 2020

Cited by 8 | Viewed by 3218

Abstract

Electrochemical ammonia synthesis, which is an alternative approach to the Haber–Bosch process, has attracted the attention of researchers because of its advantages including mild working conditions, environmental protection, and simple process. However, the biggest problem in this field is the lack of high-performance [...] Read more.

Electrochemical ammonia synthesis, which is an alternative approach to the Haber–Bosch process, has attracted the attention of researchers because of its advantages including mild working conditions, environmental protection, and simple process. However, the biggest problem in this field is the lack of high-performance catalysts. Here, we report high-efficiency electroreduction of N₂ to NH₃ on γ-MnO₂-supported Pd nanoparticles (Pd/γ-MnO₂) under ambient conditions, which exhibits excellent catalytic activity with an NH₃ yield rate of 19.72 μg·mg⁻¹_Pd h⁻¹ and a Faradaic efficiency of 8.4% at −0.05 V vs. the reversible hydrogen electrode (RHE). X-ray diffraction (XRD) and transmission electron microscopy (TEM) characterization shows that Pd nanoparticles are homogeneously dispersed on the γ-MnO₂. Pd/γ-MnO₂ outperforms other catalysts including Pd/C and γ-MnO₂ because of its synergistic catalytic effect between Pd and Mn. Full article

(This article belongs to the Section Electrocatalysis)

► Show Figures

Graphical abstract

16 pages, 2555 KiB

Open AccessArticle

Fast Microwave Synthesis of Gold-Doped TiO₂ Assisted by Modified Cyclodextrins for Photocatalytic Degradation of Dye and Hydrogen Production

by Cécile Machut, Nicolas Kania, Bastien Léger, Frédéric Wyrwalski, Sébastien Noël, Ahmed Addad, Eric Monflier and Anne Ponchel

Catalysts 2020, 10(7), 801; https://doi.org/10.3390/catal10070801 - 18 Jul 2020

Cited by 11 | Viewed by 3748

Abstract

A convenient and fast microwave synthesis of gold-doped titanium dioxide materials was developed with the aid of commercially available and common cyclodextrin derivatives, acting both as reducing and stabilizing agents. Anatase titanium oxide was synthesized from titanium chloride by microwave heating without calcination. [...] Read more.

A convenient and fast microwave synthesis of gold-doped titanium dioxide materials was developed with the aid of commercially available and common cyclodextrin derivatives, acting both as reducing and stabilizing agents. Anatase titanium oxide was synthesized from titanium chloride by microwave heating without calcination. Then, the resulting titanium oxide was decorated by gold nanoparticles thanks to a microwave-assisted reduction of HAuCl₄ by cyclodextrin in alkaline conditions. The materials were fully characterized by UV-Vis spectroscopy, X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM), and N₂ adsorption-desorption measurements, while the metal content was determined by Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). The efficiency of the TiO₂@Au materials was evaluated with respect to two different photocatalytic reactions, such as dye degradation and hydrogen evolution from water. Full article

(This article belongs to the Special Issue Materials and Processes for Photocatalytic and (Photo)Electrocatalytic Removal of Bio-Refractory Pollutants and Emerging Contaminants from Waters)

► Show Figures

Graphical abstract

49 pages, 10500 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Synthesis of Biodegradable Polymers: A Review on the Use of Schiff-Base Metal Complexes as Catalysts for the Ring Opening Polymerization (ROP) of Cyclic Esters

by Orlando Santoro, Xin Zhang and Carl Redshaw

Catalysts 2020, 10(7), 800; https://doi.org/10.3390/catal10070800 - 18 Jul 2020

Cited by 85 | Viewed by 8386

Abstract

This review describes the recent advances (from 2008 onwards) in the use of Schiff-base metal complexes as catalysts for the ring opening polymerization (ROP) of cyclic esters. The synthesis and structure of the metal complexes, as well as all aspects concerning the polymerization [...] Read more.

This review describes the recent advances (from 2008 onwards) in the use of Schiff-base metal complexes as catalysts for the ring opening polymerization (ROP) of cyclic esters. The synthesis and structure of the metal complexes, as well as all aspects concerning the polymerization process and the characteristics of the polymers formed, will be discussed. Full article

(This article belongs to the Special Issue Catalysis in Plastics for the 21st Century)

► Show Figures

Graphical abstract

13 pages, 7372 KiB

Open AccessArticle

MOF-Derived CuPt/NC Electrocatalyst for Oxygen Reduction Reaction

by Rehan Anwar, Naseem Iqbal, Saadia Hanif, Tayyaba Noor, Xuan Shi, Neelam Zaman, Daarain Haider, Syed Aun M. Rizvi and A. M. Kannan

Catalysts 2020, 10(7), 799; https://doi.org/10.3390/catal10070799 - 17 Jul 2020

Cited by 33 | Viewed by 4541

Abstract

Metal-organic frameworks (MOFs) have been at the center stage of material science in the recent past because of their structural properties and wide applications in catalysis. MOFs have also been used as hard templates for the preparation of catalysts. In this study, highly [...] Read more.

Metal-organic frameworks (MOFs) have been at the center stage of material science in the recent past because of their structural properties and wide applications in catalysis. MOFs have also been used as hard templates for the preparation of catalysts. In this study, highly active CuPt/NC electrocatalyst was synthesized by pyrolyzing Cu-tpa MOF along with Pt precursor under flowing Ar-H₂ atmosphere. The catalyst was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and X-ray powder diffraction (XRD). Rotating disk electrode study was performed to determine the oxygen reduction reaction (ORR) activity for CuPt/NC in 0.1 M HClO₄ at different revolutions per minute (400, 800, 1200, and 1600) and it was also compared with commercial Pt/C catalyst. Further the ORR performance was evaluated by K-L plots and Tafel slope. CuPt/NC shows excellent ORR performance with onset potential of 0.9 V (vs. RHE), which is comparable with commercial Pt/C. The ORR activity of CuPt/NC is demonstrated as an efficient electrocatalyst for fuel cell. Full article

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

► Show Figures

Graphical abstract

17 pages, 2752 KiB

Open AccessFeature PaperArticle

Enantioselective Transesterification of Allyl Alcohols with (E)-4-Arylbut-3-en-2-ol Motif by Immobilized Lecitase™ Ultra

by Aleksandra Leśniarek, Anna Chojnacka, Radosław Drozd, Magdalena Szymańska and Witold Gładkowski

Catalysts 2020, 10(7), 798; https://doi.org/10.3390/catal10070798 - 17 Jul 2020

Cited by 2 | Viewed by 2527

Abstract

Lecitase™ Ultra was immobilized on four different supports and tested for the first time as the biocatalyst in the kinetic resolution of racemic allyl alcohols with the (E)-4-arylbut-3-en-2-ol system in the process of transesterification. The most effective biocatalyst turned out to [...] Read more.

Lecitase™ Ultra was immobilized on four different supports and tested for the first time as the biocatalyst in the kinetic resolution of racemic allyl alcohols with the (E)-4-arylbut-3-en-2-ol system in the process of transesterification. The most effective biocatalyst turned out to be the enzyme immobilized on agarose activated with cyanogen bromide (LU-CNBr). The best results (E > 200, ee_s and ee_p = 95–99%) were obtained for (E)-4-phenylbut-3-en-2-ol and its analog with a 2,5-dimethylphenyl ring whereas the lowest ee of kinetic resolution products (90%) was achieved for the substrate with a 4-methoxyphenyl substituent. For all substrates, (R)-enantiomers were esterified faster than their (S)-antipodes. The results showed that LU-CNBr is a versatile biocatalyst, showing high activity and enantioselectivity in a wide range of organic solvents in the presence of commonly used acyl donors. High operational stability of LU-CNBr allows it to be reused in three subsequent reaction cycles without negative effects on the efficiency and enantioselectivity of transesterification. This biocatalyst can become attractive to the commercial lipases in the process of the kinetic resolution of allyl alcohols. Full article

(This article belongs to the Special Issue Lipases and Phospholipases in Biocatalysis)

► Show Figures

Graphical abstract

25 pages, 6371 KiB

Open AccessFeature PaperArticle

Numerical Investigation of Ventilation Air Methane Catalytic Combustion in Circular Straight and Helical Coil Channels with Twisted Tape Insert in Catalytic-Monolith Reactors

by Benitta A. Chaedir, Jundika C. Kurnia, Lianjun Chen, Lishuai Jiang and Agus P. Sasmito

Catalysts 2020, 10(7), 797; https://doi.org/10.3390/catal10070797 - 17 Jul 2020

Cited by 6 | Viewed by 2809

Abstract

In a catalytic combustion of ventilation air methane, one of the key factors determining the reactor performance is the geometry of the reactor. It should be designed to provide maximum energy conversion at minimum catalyst usage and operating cost. This numerical study is [...] Read more.

In a catalytic combustion of ventilation air methane, one of the key factors determining the reactor performance is the geometry of the reactor. It should be designed to provide maximum energy conversion at minimum catalyst usage and operating cost. This numerical study is conducted to investigate the catalytic combustion of ventilation air methane from a gassy underground mine in a circular straight and helical reactor channel with twisted tape insert. A three-dimensional computational fluid dynamics model which considers conservation of mass, momentum, energy, and species together with chemical reactions, and constitutive relations for species properties and reactions kinetics was developed and validated against the previously published data. The effect of several key factors affecting the catalytic combustion performance such as inlet Reynolds number, twisted tape ratio, and reactor length are evaluated to obtain the optimum reactor parameters. For evaluation purpose, the reaction performance of the studied reactors will be compared to the straight reactor without twisted tape which is set as a baseline. The results give a firm confirmation on the superior performance of the reactors with twisted tape insert as compared to those without. In addition, it is found that helical reactors generate higher net power as compared to their respective straight reactor counterpart despite having lower FoM due to larger catalyst area. Interestingly, the higher twisting ratio offers better performance in terms of net power as well as FoM. Overall, the results highlight the potential of twisted tape insert application in catalytic combustion. Full article

(This article belongs to the Special Issue Catalytic Reactors Design for Industrial Applications)

► Show Figures

Figure 1

14 pages, 4902 KiB

Open AccessArticle

Graphite–Metal Oxide Composites as Potential Anodic Catalysts for Microbial Fuel Cells

by Elitsa Chorbadzhiyska, Ivo Bardarov, Yolina Hubenova and Mario Mitov

Catalysts 2020, 10(7), 796; https://doi.org/10.3390/catal10070796 - 17 Jul 2020

Cited by 11 | Viewed by 3149

Abstract

In this study, graphite–metal oxide (Gr–MO) composites were produced and explored as potential anodic catalysts for microbial fuel cells. Fe₂O₃, Fe₃O₄, or Mn₃O₄ were used as a catalyst precursor. The morphology and [...] Read more.

In this study, graphite–metal oxide (Gr–MO) composites were produced and explored as potential anodic catalysts for microbial fuel cells. Fe₂O₃, Fe₃O₄, or Mn₃O₄ were used as a catalyst precursor. The morphology and structure of the fabricated materials were analyzed by scanning electron microscopy and X-ray diffraction, respectively, and their corrosion resistance was examined by linear voltammetry. The manufactured Gr–MO electrodes were tested at applied constant potential +0.2 V (vs. Ag/AgCl) in the presence of pure culture Pseudomonas putida 1046 used as a model biocatalyst. The obtained data showed that the applied poising resulted in a generation of anodic currents, which gradually increased during the long-term experiments, indicating a formation of electroactive biofilms on the electrode surfaces. All composite electrodes exhibited higher electrocatalytic activity compared to the non-modified graphite. The highest current density (ca. 100 mA.m⁻²), exceeding over eight-fold that with graphite, was achieved with Gr–Mn₃O₄. The additional analyses performed by cyclic voltammetry and electrochemical impedance spectroscopy supported the changes in the electrochemical activity and revealed substantial differences in the mechanism of current generation processes with the use of different catalysts. Full article

(This article belongs to the Special Issue Catalysts for Microbial Fuel Cells)

► Show Figures

Graphical abstract

10 pages, 3094 KiB

Open AccessArticle

Carbon Dioxide Reforming of Methane over Ni Supported SiO₂: Influence of the Preparation Method on the Resulting Structural Properties and Catalytic Activity

by Hua-Ping Ren, Shao-Peng Tian, Si-Yi Ding, Gui-Qiu Huang, Min Zhu, Qiang Ma, Wen-Qi Song, Yu-Zhen Zhao, Zongcheng Miao and Wei Wang

Catalysts 2020, 10(7), 795; https://doi.org/10.3390/catal10070795 - 17 Jul 2020

Cited by 9 | Viewed by 2464

Abstract

Ni-C/SiO₂ and Ni-G/SiO₂ catalysts were prepared by a complexed-impregnation method using citric acid and glycine as complexing agents, respectively. Ni/SiO₂ was also prepared by the conventional incipient impregnation method. All the catalysts were comparatively tested for carbon dioxide reforming of [...] Read more.

Ni-C/SiO₂ and Ni-G/SiO₂ catalysts were prepared by a complexed-impregnation method using citric acid and glycine as complexing agents, respectively. Ni/SiO₂ was also prepared by the conventional incipient impregnation method. All the catalysts were comparatively tested for carbon dioxide reforming of methane (CDR) at P = 1.0 atm, T = 750 °C, CO₂/CH₄ = 1.0, and GHSV = 60,000 mL·g⁻¹·h⁻¹. The results showed that Ni-C/SiO₂ and Ni-G/SiO₂ exhibited better CDR performance, especially regarding stability, than Ni/SiO₂. The conversions of CH₄ and CO₂ were kept constant above 82% and 87% after 20 h of reaction over Ni-C/SiO₂ and Ni-G/SiO₂ while they were decreased from 81% and 88% to 56% and 59%, respectively, over the Ni/SiO₂. The characterization results of the catalysts before and after the reaction showed that the particle size and the distribution of Ni, as well as the interactions between Ni and the support were significantly influenced by the preparation method. As a result, an excellent resistance to the coking deposition and the anti-sintering of Ni was obtained over the Ni-C/SiO₂ and Ni-G/SiO₂, leading to a highly active and stable CDR performance. Full article

► Show Figures

Figure 1

22 pages, 15307 KiB

Open AccessArticle

Bimetallic Substituted Ceria: An Alternative Approach to Ligand-Free Heck-Mizoroki Cross-Coupling Reactions

by Zanele P. Vundla and Holger B. Friedrich

Catalysts 2020, 10(7), 794; https://doi.org/10.3390/catal10070794 - 16 Jul 2020

Cited by 1 | Viewed by 2722

Abstract

This work describes Ce_0.89Zr_0.03Pd_0.08O_2-δ as a heterogeneous catalyst for Heck-Mizoroki reactions. The material was synthesised by urea-assisted solution combustion to give a zirconium-stabilised cerium fluorite structure, with a fraction of palladium incorporated into the host structure. [...] Read more.

This work describes Ce_0.89Zr_0.03Pd_0.08O_2-δ as a heterogeneous catalyst for Heck-Mizoroki reactions. The material was synthesised by urea-assisted solution combustion to give a zirconium-stabilised cerium fluorite structure, with a fraction of palladium incorporated into the host structure. Characterisation techniques included ICP-OES, P-XRD and electron microscopy. The catalyst illustrated a high TOF of 1860 h⁻¹ for the cross-coupling of iodobenzene with methyl acrylate, when trimethylamine (TEA) was used as a base and dimethylformamide (DMF) as the solvent at 130 °C. To establish the activity of coupling pairs, screening was limited to aryliodobenzenes, with various electronic properties, to determine the influence of aryliodobenzene electronic density on the trans product yield. Electron-donating substituents showed good yields, while electron-withdrawing groups had lower yields. Furthermore, various classes of electron-deficient olefins were screened to determine any effect on the trans product yield. Electron-deficient olefins showed higher yields with regard to the trans product than neutral styrene. Full article

(This article belongs to the Special Issue The Design and Development of Precious Metal Catalysts)

► Show Figures

Graphical abstract

14 pages, 2498 KiB

Open AccessArticle

H₂ Production from Catalytic Methane Decomposition Using Fe/x-ZrO₂ and Fe-Ni/(x-ZrO₂) (x = 0, La₂O₃, WO₃) Catalysts

by Fahad Al-Mubaddel, Samsudeen Kasim, Ahmed A. Ibrahim, Abdulrhman S. Al-Awadi, Anis H. Fakeeha and Ahmed S. Al-Fatesh

Catalysts 2020, 10(7), 793; https://doi.org/10.3390/catal10070793 - 16 Jul 2020

Cited by 18 | Viewed by 3112

Abstract

An environmentally-benign way of producing hydrogen is methane decomposition. This study focused on methane decomposition using Fe and Fe-Ni catalysts, which were dispersed over different supports by the wet-impregnation method. We observed the effect of modifying ZrO₂ with La₂O₃ [...] Read more.

An environmentally-benign way of producing hydrogen is methane decomposition. This study focused on methane decomposition using Fe and Fe-Ni catalysts, which were dispersed over different supports by the wet-impregnation method. We observed the effect of modifying ZrO₂ with La₂O₃ and WO₃ in terms of H₂ yield and carbon deposits. The modification led to a higher H₂ yield in all cases and WO₃-modified support gave the highest yield of about 90% and was stable throughout the reaction period. The reaction conditions were at 1 atm, 800 °C, and 4000 mL(hg_cat)⁻¹ space velocity. Adding Ni to Fe/x-ZrO₂ gave a higher H₂ yield and stability for ZrO₂ and La₂O₃ + ZrO₂-supported catalysts whose prior performances and stabilities were very poor. Catalyst samples were analyzed by characterization techniques like X-ray diffraction (XRD), nitrogen physisorption, temperature-programmed reduction (TPR), thermo-gravimetric analysis (TGA), and Raman spectroscopy. The phases of iron and the supports were identified using XRD while the BET revealed a significant decrease in the specific surface areas of fresh catalysts relative to supports. A progressive change in Fe’s oxidation state from Fe³⁺ to Fe⁰ was observed from the H₂-TPR results. The carbon deposits on Fe/ZrO₂ and Fe/La₂O₃ + ZrO₂ are mainly amorphous, while Fe/WO₃ + ZrO₂ and Fe-Ni/x-ZrO₂ are characterized by graphitic carbon. Full article

(This article belongs to the Special Issue Metal Dispersed on Porous Supports as Catalysts for Methane-Related Reactions)

► Show Figures

Figure 1

17 pages, 4734 KiB

Open AccessArticle

Facile Synthesis of Tin Dioxide Nanoparticles for Photocatalytic Degradation of Congo Red Dye in Aqueous Solution

by Chih Ming Ma, Gui Bing Hong and Shang Chieh Lee

Catalysts 2020, 10(7), 792; https://doi.org/10.3390/catal10070792 - 16 Jul 2020

Cited by 38 | Viewed by 3886

Abstract

This research work reports an approach used to prepare a SnO₂ photocatalyst by precipitation and calcination pathways and describes an investigation of the effects of preparation parameters on SnO₂ yield. The SnO₂ photocatalyst was further used for the photocatalytic degradation [...] Read more.

This research work reports an approach used to prepare a SnO₂ photocatalyst by precipitation and calcination pathways and describes an investigation of the effects of preparation parameters on SnO₂ yield. The SnO₂ photocatalyst was further used for the photocatalytic degradation of Congo red (CR) dye, and the removal efficiency was optimized using response surface methodology. The results indicate that the SnO₂ photocatalyst yield was the highest in 0.05 M of the precursor, stannous chloride and 28 wt % ammonia as the precipitant, pH 10, at 30 °C. The transmission electron microscopy results of the SnO₂ photocatalyst illustrate that the average particle size was mainly around 30–50 nm and had a solid spherical shape. The X-ray diffraction results reveal that the prepared sample had a highly crystalline SnO₂ rutile crystal structure. The prediction and experimental results of the Response surface methodology (RSM) indicate that, when the reaction time was 97 min, the operating temperature was 47 °C, the photocatalyst dosage was 751 mg/L, and the optimal degradation rate of the CR dye was 100%. After five consecutive photodegradation reactions, the degradation rate remained at 100%. The results demonstrated that the SnO₂ photocatalyst prepared in this study possesses excellent reusability. Full article

(This article belongs to the Special Issue Electrocatalysis/Photocatalysis for CO₂ Conversion, H₂ Production, and Pollutant Removal)

► Show Figures

Figure 1

17 pages, 5153 KiB

Open AccessArticle

K₂O Doped Dolomite as Heterogeneous Catalyst for Fatty Acid Methyl Ester Production from Palm Oil

by Muhammad Yahaya, Irmawati Ramli, Ernee Noryana Muhamad, Nor Shafizah Ishak, Usman Idris Nda-Umar and Yun Hin Taufiq-Yap

Catalysts 2020, 10(7), 791; https://doi.org/10.3390/catal10070791 - 16 Jul 2020

Cited by 12 | Viewed by 4862

Abstract

Biodiesel obtained from palm oil over an environmentally friendly catalyst is highlydesirable. For that matter, dolomite, a natural material was used as a catalyst in this work, and this included potassium oxide (K₂O)-doped dolomite, 5 wt% K/D, 10 wt% K/D, 15 [...] Read more.

Biodiesel obtained from palm oil over an environmentally friendly catalyst is highlydesirable. For that matter, dolomite, a natural material was used as a catalyst in this work, and this included potassium oxide (K₂O)-doped dolomite, 5 wt% K/D, 10 wt% K/D, 15 wt% K/D, and 20 wt% K/D. X-ray diffraction analysis of dolomite revealed the CaO and MgO phases with high crystallinity, in which intensity reduced after doped with varying concentrations of K₂O. When the catalysts were evaluated, the K₂O-doped dolomite exhibited a better catalytic activity for palm oil transesterification. In the presence of K₂O, the methyl ester reached 98.7%, with the highest being displayed by 15 wt% K/D as compared to 87% over dolomite at reaction temperature of 60 °C, 12:1 methanol to palm oil ratio, 1 wt% catalyst amount and 1 h reaction time. SEM revealed that as more K₂O was doped on dolomite, the particles became more agglomerated, with a reduced BET surface area of 1.3 m²/g in 20 wt% K/D as opposed to homogeneously small-sized MgO and CaO particles in dolomite with a high BET surface area of 19.0 m²/g. However, the high activity of the doped catalyst was dictated by the high amount of basic site, as evidenced in TPD-CO₂ which showed an increase in the capacity of the basic site with an increased amount of K₂O. The catalyst was also reusable up to six times with a negligible decrease in activity due to K⁺ leaching. Full article

► Show Figures

Figure 1

25 pages, 9275 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

The Effect of Noble Metal (M: Ir, Pt, Pd) on M/Ce₂O₃-γ-Al₂O₃ Catalysts for Hydrogen Production via the Steam Reforming of Glycerol

by Nikolaos D. Charisiou, Georgios I. Siakavelas, Kyriakos N. Papageridis, Davide Motta, Nikolaos Dimitratos, Victor Sebastian, Kyriaki Polychronopoulou and Maria A. Goula

Catalysts 2020, 10(7), 790; https://doi.org/10.3390/catal10070790 - 15 Jul 2020

Cited by 20 | Viewed by 4027

Abstract

A promising route for the energetic valorisation of the main by-product of the biodiesel industry is the steam reforming of glycerol, as it can theoretically produce seven moles of H₂ for every mole of C₃H₈O₃. In [...] Read more.

A promising route for the energetic valorisation of the main by-product of the biodiesel industry is the steam reforming of glycerol, as it can theoretically produce seven moles of H₂ for every mole of C₃H₈O₃. In the work presented herein, CeO₂–Al₂O₃ was used as supporting material for Ir, Pd and Pt catalysts, which were prepared using the incipient wetness impregnation technique and characterized by employing N₂ adsorption–desorption, X-Ray Diffraction (XRD), Temperature Programmed Reduction (TPR), Temperature Programmed Desorption (TPD), X-ray Photoelectron Spectroscopy (XPS) and Transmission Electron Microscopy (TEM). The catalytic experiments aimed at identifying the effect of temperature on the total conversion of glycerol, on the conversion of glycerol to gaseous products, the selectivity towards the gaseous products (H₂, CO₂, CO, CH₄) and the determination of the H₂/CO and CO/CO₂ molar ratios. The main liquid effluents produced during the reaction were quantified. The results revealed that the Pt/CeAl catalyst was more selective towards H₂, which can be related to its increased number of Brønsted acid sites, which improved the hydrogenolysis and dehydrogenation–dehydration of condensable intermediates. The time-on-stream experiments, undertaken at low Water Glycerol Feed Ratios (WGFR), showed gradual deactivation for all catalysts. This is likely due to the dehydration reaction, which leads to the formation of unsaturated hydrocarbon species and eventually to carbon deposition. The weak metal–support interaction shown for the Ir/CeAl catalyst also led to pronounced sintering of the metallic particles. Full article

(This article belongs to the Special Issue The Design and Development of Precious Metal Catalysts)

► Show Figures

Figure 1

10 pages, 3548 KiB

Open AccessArticle

Microwave-Assisted Solvothermal Synthesis of Chalcogenide Composite Photocatalyst and Its Photocatalytic CO₂ Reduction Activity under Simulated Solar Light

by Gang-Juan Lee, Yu-Hong Hou, Hsin-Ting Huang, Wenmin Wang, Cong Lyu and Jerry J. Wu

Catalysts 2020, 10(7), 789; https://doi.org/10.3390/catal10070789 - 15 Jul 2020

Cited by 10 | Viewed by 2644

Abstract

A novel heterostructure consisting of Ru and Cu co-doped ZnS nanopowders (RCZS) into a MoS₂-graphene hybrid (MSG) is successfully prepared by the microwave-assisted solvothermal approach. RCZS nanopowders are fabricated on the surface of MSG, which produces a nanoscale interfacial between RCZS [...] Read more.

A novel heterostructure consisting of Ru and Cu co-doped ZnS nanopowders (RCZS) into a MoS₂-graphene hybrid (MSG) is successfully prepared by the microwave-assisted solvothermal approach. RCZS nanopowders are fabricated on the surface of MSG, which produces a nanoscale interfacial between RCZS and MSG. As the photo-excited electrons of RCZS can easily migrate to MoS₂ through graphene by hindering the electron and hole (e^– and h⁺) recombination, the photocatalytic activity could be improved by effective charge transfer. As RCZS are anchored onto the MSG, the photoluminescence intensity of the chalcogenide composite photocatalyst obviously decreases. In addition, a quaternary ruthenium and copper-based chalcogenide RCZS/MSG is able to improve the harvest and utilization of light. With the increase in the concentrations of Ru until 4 mol%, the band gap significantly decreases from 3.52 to 2.73 eV. At the same time, moderate modification by ruthenium can decrease the PL intensity compared to the pristine CZS/MSG sample, which indicates the enhancement of e^– and h⁺ separation by Ru addition. The photocatalytic activity of as-synthesized chalcogenide composite photocatalysts is evaluated by the photocatalytic carbon dioxide reduction. Optimized operation conditions for carbon dioxide reduction have been performed, including the concentration of NaOH solution, the amount of RCZS/MSG photocatalyst, and the content of co-doped ruthenium. The doping of ruthenium would efficiently improve the performance of the photocatalytic activity for carbon dioxide reduction. The optimal conditions, such as the concentration of 2 M NaOH and the 0.5RCZS/MSG dosage of 0.05 g L^–1, provide the maximum methane gas yield of 58.6 μmol h⁻¹ g^–1. Full article

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

► Show Figures

Figure 1

34 pages, 8026 KiB

Open AccessReview

Recent Advances in Noble Metal Catalysts for Hydrogen Production from Ammonia Borane

by Mengmeng Liu, Liu Zhou, Xianjin Luo, Chao Wan and Lixin Xu

Catalysts 2020, 10(7), 788; https://doi.org/10.3390/catal10070788 - 15 Jul 2020

Cited by 66 | Viewed by 9157

Abstract

Interest in chemical hydrogen storage has increased, because the supply of fossil fuels are limited and the harmful effects of burning fossil fuels on the environment have become a focus of public concern. Hydrogen, as one of the energy carriers, is useful for [...] Read more.

Interest in chemical hydrogen storage has increased, because the supply of fossil fuels are limited and the harmful effects of burning fossil fuels on the environment have become a focus of public concern. Hydrogen, as one of the energy carriers, is useful for the sustainable development. However, it is widely known that controlled storage and release of hydrogen are the biggest barriers in large-scale application of hydrogen energy. Ammonia borane (NH₃BH₃, AB) is deemed as one of the most promising hydrogen storage candidates on account of its high hydrogen to mass ratio and environmental benignity. Development of efficient catalysts to further improve the properties of chemical kinetics in the dehydrogenation of AB under appropriate conditions is of importance for the practical application of this system. In previous studies, a variety of noble metal catalysts and their supported metal catalysts (Pt, Pd, Au, Rh, etc.) have presented great properties in decomposing the chemical hydride to generate hydrogen, thus, promoting their application in dehydrogenation of AB is urgent. We analyzed the hydrolysis of AB from the mechanism of hydrogen release reaction to understand more deeply. Based on these characteristics, we aimed to summarize recent advances in the development of noble metal catalysts, which had excellent activity and stability for AB dehydrogenation, with prospect towards realization of efficient noble metal catalysts. Full article

(This article belongs to the Special Issue Catalysts for Sustainable Hydrogen Production: Preparation, Applications and Process Integration)

► Show Figures

Figure 1

11 pages, 2613 KiB

Open AccessFeature PaperArticle

The Use of Ion Liquids as a Trojan Horse Strategy in Enzyme-Catalyzed Biotransformation of (R,S)-Atenolol

by Adam Sikora, Joanna Chałupka and Michał Piotr Marszałł

Catalysts 2020, 10(7), 787; https://doi.org/10.3390/catal10070787 - 14 Jul 2020

Cited by 7 | Viewed by 2793

Abstract

The enzymatic method was used for the direct biotransformation of racemic atenolol. The catalytic activities of commercially available lipases from Candida rugosa were tested for the kinetic resolution of (R,S)-atenolol by enantioselective acetylation in various two-phase reaction media containing [...] Read more.

The enzymatic method was used for the direct biotransformation of racemic atenolol. The catalytic activities of commercially available lipases from Candida rugosa were tested for the kinetic resolution of (R,S)-atenolol by enantioselective acetylation in various two-phase reaction media containing ionic liquids. The composed catalytic system gave the possibility to easy separate substrates and products of the conducted enantioselective reaction and after specific procedure to reuse utilized enzymes in another catalytic cycle. Full article

(This article belongs to the Special Issue Enzyme-Catalyzed Biotransformations)

► Show Figures

Figure 1

24 pages, 6385 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Synthesis and Characterization of Metal Modified Catalysts for Decomposition of Ibuprofen from Aqueous Solutions

by Soudabeh Saeid, Matilda Kråkström, Pasi Tolvanen, Narendra Kumar, Kari Eränen, Markus Peurla, Jyri-Pekka Mikkola, Laurent Maël, Leif Kronberg, Patrik Eklund and Tapio Salmi

Catalysts 2020, 10(7), 786; https://doi.org/10.3390/catal10070786 - 14 Jul 2020

Cited by 14 | Viewed by 4121

Abstract

The presence of pharmaceuticals in surface water, drinking water, and wastewater has attracted significant concern because of the non-biodegradability, resistance, and toxicity of pharmaceutical compounds. The catalytic ozonation of an anti-inflammatory pharmaceutical, ibuprofen was investigated in this work. The reaction mixture was analyzed [...] Read more.

The presence of pharmaceuticals in surface water, drinking water, and wastewater has attracted significant concern because of the non-biodegradability, resistance, and toxicity of pharmaceutical compounds. The catalytic ozonation of an anti-inflammatory pharmaceutical, ibuprofen was investigated in this work. The reaction mixture was analyzed and measured by high-performance liquid chromatography (HPLC). Liquid chromatography-mass spectrometry (LC-MS) was used for the quantification of by-products during the catalytic ozonation process. Ibuprofen was degraded by ozonation under optimized conditions within 1 h. However, some intermediate oxidation products were detected during the ibuprofen ozonation process that were more resistant than the parent compound. To optimize the process, nine heterogeneous catalysts were synthesized using different preparation methods and used with ozone to degrade the ibuprofen dissolved in aqueous solution. The aim of using several catalysts was to reveal the effect of various catalyst preparation methods on the degradation of ibuprofen as well as the formation and elimination of by-products. Furthermore, the goal was to reveal the influence of various support structures and different metals such as Pd-, Fe-, Ni-, metal particle size, and metal dispersion in ozone degradation. Most of the catalysts improved the elimination kinetics of the by-products. Among these catalysts, Cu-H-Beta-150-DP synthesized by the deposition–precipitation process showed the highest decomposition rate. The regenerated Cu-H-Beta-150-DP catalyst preserved the catalytic activity to that of the fresh catalyst. The catalyst characterization methods applied in this work included nitrogen adsorption–desorption, scanning electron microscopy, transmission electron microscopy, and Fourier-transform infrared spectroscopy. The large pore volume and small metal particle size contributed to the improved catalytic activity. Full article

(This article belongs to the Special Issue Microporous Zeolites and Related Nanoporous Materials: Synthesis, Characterization and Applications in Catalysis)

► Show Figures

Graphical abstract

21 pages, 11694 KiB

Open AccessArticle

Synthesis of Highly Selective and Stable Co-Cr/SAPO-34 Catalyst for the Catalytic Dehydration of Ethanol to Ethylene

by Peirong Niu, Xiao Ren, Deyuan Xiong, Shilei Ding, Yuanlin Li, Zhaozhou Wei and Xusong Chen

Catalysts 2020, 10(7), 785; https://doi.org/10.3390/catal10070785 - 14 Jul 2020

Cited by 13 | Viewed by 4204

Abstract

In this study, silicoaluminophosphate (SAPO)-34 and Me (Me = Cr, Co)-modified SAPO-34 were synthesized and used as catalysts to investigate the catalytic performance by means of a probe reaction from ethanol to ethylene. The metal oxides were loaded on the SAPO-34 support via [...] Read more.

In this study, silicoaluminophosphate (SAPO)-34 and Me (Me = Cr, Co)-modified SAPO-34 were synthesized and used as catalysts to investigate the catalytic performance by means of a probe reaction from ethanol to ethylene. The metal oxides were loaded on the SAPO-34 support via an impregnation method. The synthesized catalysts were characterized using XRD, SEM, EDX, FT-IR, NH₃-TPD, BET, and TGA techniques. Compared to SAPO-34, SAPO-34 doped with metal oxides showed the same chabazite (CHA) topology. The structure and properties of the catalyst were further optimized by varying the amount of Me. The experimental results showed that Co-Cr/SAPO-34 exhibited the best catalytic performance when the reaction temperature reached 400 °C at a weight hourly space velocity (WHSV) of 3.5 h⁻¹, for which the single-pass conversion of ethanol was determined as 99.15%, and the selectivity of ethylene was 99.4% at an optimum catalytic performance in the reaction of up to 600 min. In addition, Co-Cr/SAPO-34 exhibited better catalytic activity and anti-coking ability than pure SAPO-34, which was attributed to its enhanced pore structure and moderate acidity. It can also be concluded from the results of this experiment that the performance of the Co-Cr bimetal-supported catalyst is better than that of the Cr mono-metal catalyst. Full article

► Show Figures

Figure 1

15 pages, 3084 KiB

Open AccessArticle

Bi-Polymer Electrospun Nanofibers Embedding Ag₃PO₄/P25 Composite for Efficient Photocatalytic Degradation and Anti-Microbial Activity

by Zunaira Habib, Chang-Gu Lee, Qilin Li, Sher Jamal Khan, Nasir Mahmood Ahmad, Yousuf Jamal, Xiaochuan Huang and Hassan Javed

Catalysts 2020, 10(7), 784; https://doi.org/10.3390/catal10070784 - 14 Jul 2020

Cited by 6 | Viewed by 3788

Abstract

Using a bi-polymer system comprising of transparent poly(methyl methacrylate) (PMMA) and poly(vinyl pyrrolidone) (PVP), a visible light active Ag₃PO₄/P25 composite was immobilized into the mats of polymeric electrospun nanofibers. After nanofibers synthesis, sacrificial PVP was removed, leaving behind rough [...] Read more.

Using a bi-polymer system comprising of transparent poly(methyl methacrylate) (PMMA) and poly(vinyl pyrrolidone) (PVP), a visible light active Ag₃PO₄/P25 composite was immobilized into the mats of polymeric electrospun nanofibers. After nanofibers synthesis, sacrificial PVP was removed, leaving behind rough surface nanofibers with easy access to Ag₃PO₄/P25 composite. The remarkable photocatalytic efficiency was attained using a PMMA and Ag₃PO₄/P25 weight ratio of 1:0.6. Methyl orange (MO) was used to visualize pollutant removal and exhibited stable removal kinetics up to five consecutive cycles under simulated daylight. Also, these polymeric nanofibers (NFs) revealed an important role in the destruction of microorganisms (E. coli), signifying their potential in water purification. A thin film fibrous mat was also used in a small bench scale plug flow reactor (PFR) for polishing of synthetic secondary effluent and the effects of inorganic salts were studied upon photocatalytic degradation in terms of total organic carbon (TOC) and turbidity removal. Lower flow rate (5 mL/h) resulted in maximum TOC and turbidity removal rates of 86% and 50%, respectively. Accordingly, effective Ag₃PO₄/P25 immobilization into an ideal support material and selectivity towards target pollutants could both enhance the efficiency of photocatalytic process under solar radiations without massive energy input. Full article

(This article belongs to the Special Issue Nanomaterials for Photocatalytic Degradation of Organic Pollutants and Inactivation of Microorganisms)

► Show Figures

Graphical abstract

17 pages, 3579 KiB

Open AccessArticle

Improved SO₂ Tolerance of Cu-SAPO-18 by Ce-Doping in the Selective Catalytic Reduction of NO with NH₃

by Shuai Han, Qing Ye, Qi Gao and Hongxing Dai

Catalysts 2020, 10(7), 783; https://doi.org/10.3390/catal10070783 - 13 Jul 2020

Cited by 13 | Viewed by 2880

Abstract

The Ce-Cu-SAPO-18 catalysts were prepared using the ion exchange method. The impact of sulfur dioxide on catalytic performance of Ce-Cu-SAPO-18 for the selective catalytic reduction (SCR) of NO with NH₃ was examined. Detailed characterization of the fresh and sulfur-poisoning Cu-SAPO-18 and Ce-Cu-SAPO-18 [...] Read more.

The Ce-Cu-SAPO-18 catalysts were prepared using the ion exchange method. The impact of sulfur dioxide on catalytic performance of Ce-Cu-SAPO-18 for the selective catalytic reduction (SCR) of NO with NH₃ was examined. Detailed characterization of the fresh and sulfur-poisoning Cu-SAPO-18 and Ce-Cu-SAPO-18 samples was conducted. XRD and BET results show that SO₂ treatment of the Ce-doped Cu-SAPO-18 (Ce-Cu-SAPO-18-S) sample did not induce a remarkable change in structure, as compared with that of the fresh counterpart. According to in situ DRIFT, H₂-TPR, SEM, and EDS results, it is found that the sulfation species attached preferentially to the cerium species, rather than the isolated Cu²⁺ species. In particular, the TG/DSC results confirm that the sulfate species on the Ce-Cu-SAPO-18-S sample was easier to decompose than that on the Cu-SAPO-18-S sample. The catalytic active sites of Ce-Cu-SAPO-18 were less influenced after SO₂ treatment, as demonstrated by the TPR and XPS results. All of the above results show that the Ce-Cu-SAPO-18 sample exhibited better sulfur-resistant performance than the Cu-SAPO-18 sample. Full article

(This article belongs to the Special Issue DeNOx Systems and VOCs (Volatile Organic Compounds) for Pollution Abatement in Catalysis)

► Show Figures

Graphical abstract

Journal Menu

Journal Browser

Catalysts, Volume 10, Issue 7 (July 2020) – 93 articles

Further Information

Guidelines

MDPI Initiatives

Follow MDPI