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Bio-DEE Synthesis and Dehydrogenation Coupling of Bio-Ethanol to Bio-Butanol over Multicomponent Mixed Metal Oxide Catalysts -
Immobilization of an Iridium(I)-NHC-Phosphine Catalyst for Hydrogenation Reactions under Batch and Flow Conditions -
The Effect of Atomic Layer Deposited Overcoat on Co-Pt-Si/γ-Al2O3 Fischer–Tropsch Catalyst -
Iridium(NHC)-Catalyzed Sustainable Transfer Hydrogenation of CO2 and Inorganic Carbonates
Journal Description
Catalysts
Catalysts
is a peer-reviewed open access journal of catalysts and catalyzed reactions published monthly online by MDPI. The Swiss Chemical Society (SCS) and Romanian Catalysis Society (RCS) are partners of Catalysts journal and its members receive a discount on the article processing charge.
- Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
- High Visibility: indexed within Scopus, SCIE (Web of Science), Inspec, CAPlus / SciFinder, CAB Abstracts, and many other databases.
- Journal Rank: JCR - Q2 (Chemistry, Physical) / CiteScore - Q2 (Physical and Theoretical Chemistry)
- Rapid Publication: manuscripts are peer-reviewed and a first decision provided to authors approximately 11.4 days after submission; acceptance to publication is undertaken in 2.7 days (median values for papers published in this journal in the first half of 2021).
- Recognition of Reviewers: reviewers who provide timely, thorough peer-review reports receive vouchers entitling them to a discount on the APC of their next publication in any MDPI journal, in appreciation of the work done.
Impact Factor:
4.146 (2020)
;
5-Year Impact Factor:
4.399 (2020)
Latest Articles
Biochar Nanoparticles over TiO2 Nanotube Arrays: A Green Co-Catalyst to Boost the Photocatalytic Degradation of Organic Pollutants
Catalysts 2021, 11(9), 1048; https://doi.org/10.3390/catal11091048 - 29 Aug 2021
Abstract
Biochar nanoparticles (BC NPs), produced by low temperature pyrolysis (350 °C) of microalgae (Nannochloropsis sp.) and nutshells, are proposed as low-cost and sustainable co-catalysts to promote the photocatalytic activity of TiO2 nanotube (NT) arrays towards the degradation of methylene blue (MB)
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Biochar nanoparticles (BC NPs), produced by low temperature pyrolysis (350 °C) of microalgae (Nannochloropsis sp.) and nutshells, are proposed as low-cost and sustainable co-catalysts to promote the photocatalytic activity of TiO2 nanotube (NT) arrays towards the degradation of methylene blue (MB) used as an organic pollutant model molecule. BC NPs (size < 25 nm) were obtained by treating bulk BC (i.e., biomass after pyrolysis) by sonication–centrifugation cycles in a water solution. The filtered BC NPs dispersion was deposited by simple drop-casting on the TiO2 NT support. The BC loading was varied by performing multiple depositions. Photocatalytic experiments under UV light (365 nm) revealed that the decoration with BC NPs significantly improves the TiO2 photoactivity. Such enhancement is mainly influenced by the amount of BC deposited; upon optimizing the BC deposition conditions, the rate of photocatalytic degradation of MB increases approximately three times with respect to bare TiO2, almost irrespective of the nature of the raw material. The greater photocatalytic activity of BC-TiO2 can be attributed to the synergistic combination of reactant/product adsorption and catalytic degradation of the adsorbed organic pollutant, as well as an improved charge carrier separation and electron transfer.
Full article
(This article belongs to the Special Issue Innovative and Practical Trends in Photocatalytic Degradation of Environmental Pollutants)
Open AccessArticle
Stable Mixed Fe-Mn Oxides Supported on ZrO2 Oxygen Carriers for Practical Utilization in CLC Processes
by
and
Catalysts 2021, 11(9), 1047; https://doi.org/10.3390/catal11091047 - 29 Aug 2021
Abstract
The objective of the research was to prepare Fe-based materials for use as oxygen carriers (OCs) and investigate their reactivity in terms of their applicability to energy systems. The performance of ZrO2 supported Fe-Mn oxide oxygen carriers with hydrogen/air in an innovative
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The objective of the research was to prepare Fe-based materials for use as oxygen carriers (OCs) and investigate their reactivity in terms of their applicability to energy systems. The performance of ZrO2 supported Fe-Mn oxide oxygen carriers with hydrogen/air in an innovative combustion technology known as chemical looping combustion (CLC) was analyzed. The influence of manganese addition (15–30 wt.%) on reactivity and other physical properties of oxygen carriers was discussed. Thermogravimetric analyses (TGA) were conducted to evaluate their performance. Multi-cycle tests were conducted in TGA with oxygen carriers utilizing gaseous fuel. The effect of redox cycle number and temperature on stability and oxygen transport capacity and redox reaction rate were also evaluated. Physical-chemical analysis such as phase composition was investigated by XRD, while morphology by SEM-EDS and surface area analyses were investigated by the BET method. For screening purposes, the reduction and oxidation were carried out from 800 °C to 1000 °C. Three-cycle TGA tests at the selected temperature range indicated that all novel oxygen carriers exhibited stable chemical looping combustion performance, apart from the reference material, i.e., Fe/Zr oxide. A stable reactivity of bimetallic OCs, together with complete H2 combustion without signs of FeMn/Zr oxide agglomeration, were proved. Oxidation reaction was significantly faster than the reduction reaction for all oxygen carriers. Furthermore, the obtained data indicated that the materials have a low cost of production, with superior reactivity towards hydrogen and air, making them perfect matching carriers for industrial applications for power generation.
Full article
(This article belongs to the Special Issue Catalysts in Environmental and Climate Protection)
Open AccessArticle
The Catalysis Effect of Na and Point Defect on NO Heterogeneous Adsorption on Carbon during High-Sodium Zhundong Coal Reburning: Structures, Interactions and Thermodynamic Characteristics
Catalysts 2021, 11(9), 1046; https://doi.org/10.3390/catal11091046 - 29 Aug 2021
Abstract
The reburning process in a furnace, a key way to reduce NOx emissions, is a heterogeneous reaction during coal combustion, in which the heterogeneous adsorption is dominant. Zhundong coal with a high content of alkali metal can enhance the reburning process. In
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The reburning process in a furnace, a key way to reduce NOx emissions, is a heterogeneous reaction during coal combustion, in which the heterogeneous adsorption is dominant. Zhundong coal with a high content of alkali metal can enhance the reburning process. In this paper, the influence of sodium and a defect on NO heterogeneous adsorption was studied by the density functional theory, and the thermodynamic characteristic was also analyzed. The results indicate that the binding energy for NO adsorption on the pristine graphene surface (graphene-NO), Na-decorated pristine graphene surface (graphene-Na-NO), defect graphene surface (gsv-NO) and Na-decorated defect graphene (gsv-Na-NO) is −5.86, −137.12, −48.94 and −74.85 kJ/mol, respectively, and that the heterogeneous adsorption is an exothermic reaction. Furthermore, except for covalent bonds of C and N, C and O for gsv-NO, other interactions are a closed-shell one, based on the analysis of AIM, ELF and IGM. The area of electron localization for NO is graphene-Na-NO > gsv-Na-NO > gsv-NO > graphene-NO. The dispersion interaction is the main interaction force between NO and the pristine graphene surface. The δg index for the atom pairs about N–C and O–C on the pristine graphene surface is also the smallest. The density of spikes at graphene-Na-NO is bigger than that at gsv-Na-NO. Moreover, the thermodynamics characteristic showed that the reaction equilibrium constant of graphene-NO is less than those on the other surfaces under the same temperature. Thus, NO on the pristine graphene surface is the most difficult to adsorb, but the presence of sodium and a defect structure can promote its adsorption.
Full article
(This article belongs to the Special Issue Catalytic Reaction for High-Temperature and Low-Emission Combustion Technologies)
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Open AccessArticle
A Titania-Supported Polyoxometalate and Au Cocatalyst for Efficient Photocatalytic Environmental Remediation
Catalysts 2021, 11(9), 1045; https://doi.org/10.3390/catal11091045 - 28 Aug 2021
Abstract
Photocatalysis has been considered an effective method for environmental purification and pollutant removal, with many experiments having being performed. The sustainable development of environmentally friendly materials that can photocatalytically oxidize and degrade contaminants is widely studied. Here, we report the results of the
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Photocatalysis has been considered an effective method for environmental purification and pollutant removal, with many experiments having being performed. The sustainable development of environmentally friendly materials that can photocatalytically oxidize and degrade contaminants is widely studied. Here, we report the results of the photocatalytic oxidation of contaminants (over 99% conversion of the contaminants was achieved) on a tri-component photocatalyst by the simultaneous decoration of Au nanoparticles and a new type of Sn-substituted Keggin structure polyoxometalate (POM) on a TiO2 semiconductor (denoted as AuPT). The light absorption and the electron–hole pair separation capacity of TiO2 was significantly ameliorated on AuPT. The synergistic effect of the Au resonance energy transfer (RET) course and the POM redox transformation can be advantageous to the efficient transmission of photogenerated electrons and holes in a way that achieves efficient photocatalytic oxidation of contaminants.
Full article
(This article belongs to the Special Issue High-Efficiency Solar Photocatalytic Materials and Technical Applications)
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Open AccessArticle
SuFEx-Click Approach for the Synthesis of Soluble Polymer-Bound MacMillan Catalysts for the Asymmetric Diels–Alder Reaction
Catalysts 2021, 11(9), 1044; https://doi.org/10.3390/catal11091044 - 28 Aug 2021
Abstract
Novel polymeric MacMillan catalysts were prepared from modified chiral imidazolidin-4-one monomers via sulfur(VI) fluoride exchange chemistry. The resulting polysulfates containing chiral imidazolidin-4-one units could be employed as polymeric organocatalysts for the asymmetric Diels–Alder reaction. With the use of these polysulfate catalysts, sufficient catalytic
[...] Read more.
Novel polymeric MacMillan catalysts were prepared from modified chiral imidazolidin-4-one monomers via sulfur(VI) fluoride exchange chemistry. The resulting polysulfates containing chiral imidazolidin-4-one units could be employed as polymeric organocatalysts for the asymmetric Diels–Alder reaction. With the use of these polysulfate catalysts, sufficient catalytic activity and enantioselectivity were obtained, which were similar to those obtained by monomeric catalysts in a homogeneous catalytic reaction. In addition, the polysulfate catalysts could be recovered and reused five times without a considerable loss of activity and selectivity.
Full article
(This article belongs to the Section Catalysis in Organic and Polymer Chemistry)
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Open AccessEditorial
Special Issue on “Green Catalysts: Application to Waste and Groundwater Treatment”
by
and
Catalysts 2021, 11(9), 1043; https://doi.org/10.3390/catal11091043 - 28 Aug 2021
Abstract
Water and soil pollution are among the most critical global problems due to population growth, industrial development, and associated resource consumption [...]
Full article
(This article belongs to the Special Issue Green Catalysts: Application to Waste and Groundwater Treatment)
Open AccessArticle
Mutation of Key Residues in β-Glycosidase LXYL-P1-2 for Improved Activity
Catalysts 2021, 11(9), 1042; https://doi.org/10.3390/catal11091042 - 28 Aug 2021
Abstract
The β-glycosidase LXYL-P1-2 identified from Lentinula edodes can be used to hydrolyze 7-β-xylosyl-10-deacetyltaxol (XDT) into 10-deacetyltaxol (DT) for the semi-synthesis of Taxol. Recent success in obtaining the high-resolution X-ray crystal of LXYL-P1-2 and resolving its three-dimensional structure has enabled us to perform molecular
[...] Read more.
The β-glycosidase LXYL-P1-2 identified from Lentinula edodes can be used to hydrolyze 7-β-xylosyl-10-deacetyltaxol (XDT) into 10-deacetyltaxol (DT) for the semi-synthesis of Taxol. Recent success in obtaining the high-resolution X-ray crystal of LXYL-P1-2 and resolving its three-dimensional structure has enabled us to perform molecular docking of LXYL-P1-2 with substrate XDT and investigate the roles of the three noncatalytic amino acid residues located around the active cavity in LXYL-P1-2. Site-directed mutagenesis results demonstrated that Tyr268 and Ser466 were essential for maintaining the β-glycosidase activity, and the L220G mutation exhibited a positive effect on increasing activity by enlarging the channel that facilitates the entrance of the substrate XDT into the active cavity. Moreover, introducing L220G mutation into the other LXYL-P1-2 mutant further increased the enzyme activity, and the β-d-xylosidase activity of the mutant EP2-L220G was nearly two times higher than that of LXYL-P1-2. Thus, the recombinant yeast GS115-EP2-L220G can be used for efficiently biocatalyzing XDT to DT for the semi-synthesis of Taxol. Our study provides not only the prospective candidate strain for industrial production, but also a theoretical basis for exploring the key amino acid residues in LXYL-P1-2.
Full article
(This article belongs to the Special Issue Enzyme Catalysis, Biotransformation and Bioeconomy)
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Open AccessFeature PaperArticle
Activity of Ag/CeZrO2, Ag+K/CeZrO2, and Ag-Au+K/CeZrO2 Systems for Lean Burn Exhaust Clean-Up
by
, , , , , , , , and
Catalysts 2021, 11(9), 1041; https://doi.org/10.3390/catal11091041 (registering DOI) - 28 Aug 2021
Abstract
Herein, the activity of Ag and bimetallic Au-Ag catalysts, supported over Ce0.85Zr0.15O2 (CZ), was investigated in a complex stream, whose components included CO, C3H8, NO, O2, and, optionally,
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Herein, the activity of Ag and bimetallic Au-Ag catalysts, supported over Ce0.85Zr0.15O2 (CZ), was investigated in a complex stream, whose components included CO, C3H8, NO, O2, and, optionally, an injection of water vapor. In such a stream, three of the possible reactions that can occur are CO oxidation, propane combustion, and NO oxidation. The aim of these studies was to explore whether silver, due to its strong affinity to oxygen, will counteract the stabilization of oxygen by potassium. The effect of the presence of potassium ions on the activity of the monometallic silver catalysts is beneficial in the complex stream without water vapor in all three studied reactions, although it is negligible in the model CO stream. It has been shown that water vapor strongly suppresses the activity of the Ag+K/CZ catalyst, much more so than that of the Ag/CZ catalyst. The second purpose of the work was to determine whether the negative effect of potassium ions on the activity of nanogold catalyst can be countered by the addition of silver. Studies in a model stream for CO oxidation have shown that, for a catalyst preloaded with gold, the effect of potassium is nulled by silver, and the activity of AuAg + 0.15 at%K/CZ and AuAg + 0.30 at%K/CZ is the same as that of the monometallic Au catalyst. Conversely, when the reaction is carried out in a complex stream, containing CO, C3H8, NO, O2, and water vapor, the presence of water vapor leads to higher CO conversion as well as increased NO2 formation and slightly suppresses the C3H8 combustion.
Full article
(This article belongs to the Special Issue Women in Catalysts)
Open AccessArticle
Glycerol Valorization over ZrO2-Supported Copper Nanoparticles Catalysts Prepared by Chemical Reduction Method
Catalysts 2021, 11(9), 1040; https://doi.org/10.3390/catal11091040 - 28 Aug 2021
Abstract
Copper nanoparticles (NPs) and ZrO2-supported copper NPs (Cu NPs/ZrO2) were synthesized via a chemical reduction method applying different pH (4, 7 and 9) and evaluated in a glycerol dehydration reaction. Copper NPs were characterized with transmission electron microscopy (TEM)
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Copper nanoparticles (NPs) and ZrO2-supported copper NPs (Cu NPs/ZrO2) were synthesized via a chemical reduction method applying different pH (4, 7 and 9) and evaluated in a glycerol dehydration reaction. Copper NPs were characterized with transmission electron microscopy (TEM) and UV–vis spectroscopy. Transmission electron microcopy (TEM) results revealed a homogeneous distribution of copper NPs. A hypsochromic shift was identified with UV–vis spectroscopy as the pH of the synthesis increased from pH = 4 to pH = 9. Zirconia-supported copper NPs catalysts were characterized using N2 physisorption, X-ray diffraction (XRD), TEM, X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (TPR), temperature-programmed desorption of ammonia (NH3-TPD) and N2O chemisorption. The presence of ZrO2 in the chemical reduction method confirmed the dispersion of the copper nanoparticles. X-ray diffraction indicated only the presence of tetragonal zirconia patterns in the catalysts. XPS identified the Cu/Zr surface atomic ratio of the catalysts. TPR patterns showed two main peaks for the Cu NPS/ZrO2 pH = 9 catalyst; the first peak between 125 and 180 °C (region I) was ascribed to more dispersed copper species, and the second one between 180 and 250 °C (region II) was assigned to bulk CuO. The catalysts prepared at pH = 4 and pH = 7 only revealed reduction at lower temperatures (region I). Copper dispersion was determined by N2O chemisorption. With NH3-TPD it was found that Cu NPs/ZrO2 pH = 9 exhibited the highest total quantity of acidic sites and the highest apparent kinetic constant, with a value of 0.004 min−1. The different pH applied to the synthesis media of the copper nanoparticles determined the resultant copper dispersion on the ZrO2 support, providing active domains for glycerol conversion.
Full article
(This article belongs to the Special Issue Metallic Nanoparticles and Metal-Mediated Synthesis in Catalysis)
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Open AccessReview
A Review on Metal Ions Modified TiO2 for Photocatalytic Degradation of Organic Pollutants
by
, , , , , and
Catalysts 2021, 11(9), 1039; https://doi.org/10.3390/catal11091039 - 27 Aug 2021
Abstract
TiO2 is a semiconductor material with high chemical stability and low toxicity. It is widely used in the fields of catalysis, sensing, hydrogen production, optics and optoelectronics. However, TiO2 photocatalyst is sensitive to ultraviolet (UV) light; this is why its photocatalytic
[...] Read more.
TiO2 is a semiconductor material with high chemical stability and low toxicity. It is widely used in the fields of catalysis, sensing, hydrogen production, optics and optoelectronics. However, TiO2 photocatalyst is sensitive to ultraviolet (UV) light; this is why its photocatalytic activity and quantum efficiency are reduced. To enhance the photocatalytic efficiency in the visible light range as well as to increase the number of the active sites on the crystal surface or inhibit the recombination rate of photogenerated electron–hole pairs electrons, various metal ions were used to modify TiO2. This review paper comprehensively summarizes the latest progress on the modification of TiO2 photocatalyst by a variety of metal ions. Lastly, the future prospects of the modification of TiO2 as a photocatalyst are proposed.
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(This article belongs to the Special Issue Application of TiO2 Nanotube in Electrocatalysis/Photocatalysis)
Open AccessArticle
From Cell-Free Protein Synthesis to Whole-Cell Biotransformation: Screening and Identification of Novel α‑Ketoglutarate-Dependent Dioxygenases for Preparative-Scale Synthesis of Hydroxy-l-Lysine
Catalysts 2021, 11(9), 1038; https://doi.org/10.3390/catal11091038 - 27 Aug 2021
Abstract
The selective hydroxylation of non-activated C-H bonds is still a challenging reaction in chemistry. Non-heme Fe2+/α-ketoglutarate-dependent dioxygenases are remarkable biocatalysts for the activation of C-H-bonds, catalyzing mainly hydroxylations. The discovery of new Fe2+/α-ketoglutarate-dependent dioxygenases with suitable reactivity for biotechnological
[...] Read more.
The selective hydroxylation of non-activated C-H bonds is still a challenging reaction in chemistry. Non-heme Fe2+/α-ketoglutarate-dependent dioxygenases are remarkable biocatalysts for the activation of C-H-bonds, catalyzing mainly hydroxylations. The discovery of new Fe2+/α-ketoglutarate-dependent dioxygenases with suitable reactivity for biotechnological applications is therefore highly relevant to expand the limited range of enzymes described so far. In this study, we performed a protein BLAST to identify homologous enzymes to already described lysine dioxygenases (KDOs). Six novel and yet uncharacterized proteins were selected and synthesized by cell-free protein synthesis (CFPS). The subsequent in vitro screening of the selected homologs revealed activity towards the hydroxylation of l-lysine (Lys) into hydroxy-l-lysine (Hyl), which is a versatile chiral building block. With respect to biotechnological application, Escherichia coli whole-cell biocatalysts were developed and characterized in small-scale biotransformations. As the whole-cell biocatalyst expressing the gene coding for the KDO from Photorhabdus luminescens showed the highest specific activity of 8.6 ± 0.6 U gCDW−1, it was selected for the preparative synthesis of Hyl. Multi-gram scale product concentrations were achieved providing a good starting point for further bioprocess development for Hyl production. A systematic approach was established to screen and identify novel Fe2+/α-ketoglutarate-dependent dioxygenases, covering the entire pathway from gene to product, which contributes to accelerating the development of bioprocesses for the production of value-added chemicals.
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(This article belongs to the Special Issue 10th Anniversary of Catalysts: Biocatalysis in Analysis and Synthesis—Past, Present and Future)
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Open AccessArticle
Optimized Synthesis Routes of MnOx-ZrO2 Hybrid Catalysts for Improved Toluene Combustion
Catalysts 2021, 11(9), 1037; https://doi.org/10.3390/catal11091037 - 27 Aug 2021
Abstract
In this contribution, the three Mn-Zr catalysts with MnxZr1−xO2 hybrid phase were synthesized by two-step precipitation route (TP), conventional coprecipitation method (CP) and ball milling process (MP). The components, textural and redox properties of the Mn-Zr hybrid catalysts
[...] Read more.
In this contribution, the three Mn-Zr catalysts with MnxZr1−xO2 hybrid phase were synthesized by two-step precipitation route (TP), conventional coprecipitation method (CP) and ball milling process (MP). The components, textural and redox properties of the Mn-Zr hybrid catalysts were studied via XRD, BET, XPS, HR-TEM, H2-TPR. Regarding the variation of synthesis routes, the TP and CP routes offer a more obvious advantage in the adjustment of the concentration of MnxZr1−xO2 solid solution compared to the MP process, which directly commands the content of Mn4+ and oxygen vacancy and lattice oxygen, and thereby leads to the enhanced mobility of reactive oxygen species and catalytic activity for toluene combustion. Moreover, the TP-Mn2Zr3 catalyst with the enriched exposure content of 51.4% for the defective (111) lattice plane of MnxZr1−xO2 exhibited higher catalytic activity and thermal stability for toluene oxidation than that of the CP-Mn2Zr3 sample with a value of 49.3%. This new observation will provide a new perspective on the design of bimetal catalysts with a higher VOCs combustion abatement.
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(This article belongs to the Special Issue Heterogeneous Catalysis and Advanced Oxidation Processes (AOP) for Environmental Protection (VOCs Oxidation, Air and Water Purification))
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Open AccessArticle
Momentum Transfer in Short-Channel Structures of Hexagonal Channel Cross-Section Shape: Experiments vs. CFD
Catalysts 2021, 11(9), 1036; https://doi.org/10.3390/catal11091036 - 27 Aug 2021
Abstract
Short-channel structures are promising catalyst carriers because it is easy to control the heat/mass transfer and fluid flow characteristics by changing their lengths. In this work, the flow resistance of hexagonal structures was investigated experimentally and numerically. The structure tested (6 mm long)
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Short-channel structures are promising catalyst carriers because it is easy to control the heat/mass transfer and fluid flow characteristics by changing their lengths. In this work, the flow resistance of hexagonal structures was investigated experimentally and numerically. The structure tested (6 mm long) was manufactured from AISI 316 steel using the selective laser melting technique. Due to some differences between theoretical approaches and practical results, two types of computational models were applied to analyze the pressure distribution in a short hexagonal duct. It was shown that although experimental results agree with some theoretical solutions, the channel wall thickness should not be omitted from the overall flow resistance. A comparison of short structures differing in channel length with widely used long monoliths was performed as well.
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(This article belongs to the Special Issue Modern Catalytic Reactor: From Active Center to Application Tests)
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Open AccessArticle
Photocatalytic Degradation of Rhodamine B and Methylene Orange Using TiO2-ZrO2 as Nanocomposite
by
, , , and
Catalysts 2021, 11(9), 1035; https://doi.org/10.3390/catal11091035 - 27 Aug 2021
Abstract
The present research reports the synthesis of ZrO2-doped TiO2 photocatalysts at different ZrO2 contents (1, 3 and 5% wt.) synthesized by the sol–gel method. The samples were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction,
[...] Read more.
The present research reports the synthesis of ZrO2-doped TiO2 photocatalysts at different ZrO2 contents (1, 3 and 5% wt.) synthesized by the sol–gel method. The samples were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction, attenuated total reflectance-Fourier transform infrared, ultraviolet–visible, X-ray photoelectron spectroscopy and N2 adsorption–desorption analysis. The photocatalytic activity of the ZrO2-doped TiO2 was investigated against the dyes methyl orange and rhodamine B through mineralization studies. The ZrO2-doped TiO2 samples presented a semiglobular-ovoid agglomerate shape around 500–800 nm. The samples presented high crystallinity of the TiO2 anatase phase, XPS suggested the formation of Zr–O–Ti bonds and the samples were classified as mesoporous materials with slight changes in the optical features in comparison with pure TiO2. Our study shows that the ZrO2-doped TiO2 composites exhibited a higher photocatalytic activity than just utilizing the synthetized TiO2 and a commercial P25. The different degradation behaviors are attributed to differences in the textural properties, and to the different optical absorptions of the samples due to structural defects created by the level of doping of Zr4+ ions into the TiO2 lattice. Reaction kinetics parameters were calculated by the Langmuir–Hinshelwood model, and a third run cycle of the ZrO2-doped TiO2 at 1% wt. achieved a photocatalytic degradation of 78.1 and 75.5% for RhB and MO, respectively.
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(This article belongs to the Special Issue Application of Photocatalysts in Environmental Chemistry)
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Open AccessArticle
Comparison between Artificial Neural Network and Rigorous Mathematical Model in Simulation of Industrial Heavy Naphtha Reforming Process
Catalysts 2021, 11(9), 1034; https://doi.org/10.3390/catal11091034 - 26 Aug 2021
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In this study, an artificial neural network (ANN) model was developed and compared with a rigorous mathematical model (RMM) to estimate the performance of an industrial heavy naphtha reforming process. The ANN model, represented by a multilayer feed forward neural network (MFFNN), had
[...] Read more.
In this study, an artificial neural network (ANN) model was developed and compared with a rigorous mathematical model (RMM) to estimate the performance of an industrial heavy naphtha reforming process. The ANN model, represented by a multilayer feed forward neural network (MFFNN), had (36-10-10-10-34) topology, while the RMM involved solving 34 ordinary differential equations (ODEs) (32 mass balance, 1 heat balance and 1 momentum balance) to predict compositions, temperature, and pressure distributions within the reforming process. All computations and predictions were performed using MATLAB® software version 2015a. The ANN topology had minimum MSE when the number of hidden layers, number of neurons in the hidden layer, and the number of training epochs were 3, 10, and 100,000, respectively. Extensive error analysis between the experimental data and the predicted values were conducted using the following error functions: coefficient of determination (R2), mean absolute error (MAE), mean relative error (MRE), and mean square error (MSE). The results revealed that the ANN (R2 = 0.9403, MAE = 0.0062) simulated the industrial heavy naphtha reforming process slightly better than the rigorous mathematical model (R2 = 0.9318, MAE = 0.007). Moreover, the computational time was obviously reduced from 120 s for the RMM to 18.3 s for the ANN. However, one disadvantage of the ANN model is that it cannot be used to predict the process performance in the internal points of reactors, while the RMM predicted the internal temperatures, pressures and weight fractions very well.
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Open AccessArticle
Heterogeneous Double Metal Cyanide Catalyzed Synthesis of Poly(ε-caprolactone) Polyols for the Preparation of Thermoplastic Elastomers
by
, , , , , , and
Catalysts 2021, 11(9), 1033; https://doi.org/10.3390/catal11091033 - 26 Aug 2021
Abstract
A series of polycaprolactones (PCLs) with molecular weights of 950–10,100 g mol−1 and Ð of 1.10–1.87 have been synthesized via one-pot, solvent-free ring-opening polymerization (ROP) of ε-caprolactone (CL) using a heterogeneous double metal cyanide (DMC) catalyst. Various initiators, such as polypropylene glycol,
[...] Read more.
A series of polycaprolactones (PCLs) with molecular weights of 950–10,100 g mol−1 and Ð of 1.10–1.87 have been synthesized via one-pot, solvent-free ring-opening polymerization (ROP) of ε-caprolactone (CL) using a heterogeneous double metal cyanide (DMC) catalyst. Various initiators, such as polypropylene glycol, ethylene glycol, propylene glycol, glycerol, and sorbitol, are employed to tune the number of hydroxyl end groups and properties of the resultant PCLs. Kinetic studies indicate that the DMC-catalyzed ROP of CL proceeds via a similar mechanism with the coordination polymerization. Branched PCLs copolymers are also synthesized via the DMC-catalyzed copolymerization of CL with glycidol. The α,ω-hydroxyl functionalized PCLs were successfully used as telechelic polymers to produce thermoplastic poly(ester-ester) and poly(ester-urethane) elastomers with well-balanced stress and strain properties.
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(This article belongs to the Special Issue Recent Advances in Polymerization Catalysis)
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Open AccessArticle
Role of PhOH and Tyrosine in Selective Oxidation of Hydrocarbons
Catalysts 2021, 11(9), 1032; https://doi.org/10.3390/catal11091032 - 26 Aug 2021
Abstract
Earlier, we established that nickel or iron heteroligand complexes, which include PhOH (nickel complexes) or tyrosine residue (nickel or iron complexes), are not only hydrocarbon oxidation catalysts (in the case of PhOH), but also simulate the active centers of enzymes (PhOH, tyrosine). The
[...] Read more.
Earlier, we established that nickel or iron heteroligand complexes, which include PhOH (nickel complexes) or tyrosine residue (nickel or iron complexes), are not only hydrocarbon oxidation catalysts (in the case of PhOH), but also simulate the active centers of enzymes (PhOH, tyrosine). The AFM method established the self-organization of nickel or iron heteroligand complexes, which included tyrosine residue or PhOH, into supramolecular structures on a modified silicon surface. Supramolecular structures were formed as a result of H-bonds and other non-covalent intermolecular interactions and, to a certain extent, reflected the structures involved in the mechanisms of reactions of homogeneous and enzymatic catalysis. Using the AFM method, we obtained evidence at the model level in favor of the involvement of the tyrosine fragment as one of the possible regulatory factors in the functioning of Ni(Fe)ARD dioxygenases or monooxygenases of the family of cytochrome P450. The principles of actions of these oxygenases were used to create highly efficient catalytic systems for the oxidation of hydrocarbons.
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(This article belongs to the Special Issue Catalytic Oxidation of Hydrocarbons)
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Open AccessFeature PaperArticle
Dynamic Pyrolysis Characteristics, Kinetics and Products Analysis of Waste Tire Catalytic Pyrolysis with Ni/Fe-ZSM-5 Catalysts Using TG-IR-GC/MS
Catalysts 2021, 11(9), 1031; https://doi.org/10.3390/catal11091031 - 26 Aug 2021
Abstract
Catalysts are usually used in the thermal conversion of waste tires to enhance the efficiency of the process and the quality of pyrolytic products. Recently, it has already been proved that Ni/Fe bimetallic catalysts had an effective catalytic effect on the thermal decomposition
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Catalysts are usually used in the thermal conversion of waste tires to enhance the efficiency of the process and the quality of pyrolytic products. Recently, it has already been proved that Ni/Fe bimetallic catalysts had an effective catalytic effect on the thermal decomposition of organic solid wastes. Herein, we employed a TG-IR-GC/MS system to investigate the kinetics and product analysis of waste tire catalytic pyrolysis using Ni/Fe bimetallic ZSM-5 as catalysts. Iso-conversional methods and master-plot methods were employed to estimate the activation energies and reaction model of waste tire catalytic pyrolysis. The results illustrated that the ZSM-5 loading with 7 wt.% Ni and 3 wt.% Fe had the best catalytic effect on decreasing the activation energies with a reduction of 13%. The determination of kinetic models showed that both non-catalyzed and catalyzed pyrolysis were fitted to a Fn model while the addition of a catalyst reduced the reaction order to varying degrees. Both FTIR and GC/MS results suggested that the metallic Ni-based catalyst had strong ability to transform alkenes into aromatic hydrocarbons. Ni/Fe bimetallic catalysts showed almost the same catalytic performance as the Ni metallic catalyst, which could reduce the cost of the catalyst. Thus, this study could deepen the understanding and provide a basic guideline of Ni/Fe bimetallic catalysts on the catalytic pyrolysis process of waste tires.
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(This article belongs to the Special Issue Catalytic Recycling of Waste)
Open AccessFeature PaperArticle
Extracting Turnover Frequencies of Electron Transfer in Heterogeneous Catalysis: A Study of IrO2-TiO2 Anatase for Water Oxidation Using Ce4+ Cations
Catalysts 2021, 11(9), 1030; https://doi.org/10.3390/catal11091030 - 26 Aug 2021
Abstract
Within the context of electron transfer during the catalytic water oxidation reaction, the Ir-based system is among the most active. The reaction, mimicking photosynthesis II, requires the use of an electron acceptor such the Ce4+ cation. This complex reaction, involving adsorbed water
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Within the context of electron transfer during the catalytic water oxidation reaction, the Ir-based system is among the most active. The reaction, mimicking photosynthesis II, requires the use of an electron acceptor such the Ce4+ cation. This complex reaction, involving adsorbed water at the interface of the metal cation and Ce4+, has mostly been studied in homogenous systems. To address the ambiguity regarding the gradual transformation of a homogenous system into a heterogeneous one, we prepared and studied a heterogeneous catalyst system composed of IrO2, with a mean particle size ranging from about 5 Å to 10 Å, dispersed on a TiO2 anatase support, with the objective of probing into the different parameters of the reaction, as well as the compositional changes and rates. The system was stable for many of the runs that were conducted (five consecutive runs with 0.18 M of Ce4+ showed the same reaction rate with TON > 56,000) and, equally importantly, was stable without induction periods. Extraction of the reaction rates from the set of catalysts, with an attempt to normalize them with respect to Ir loading and, therefore, to obtain turnover frequencies (TOF), was conducted. While, within reasonable deviations, the TOF numbers extracted from TPR and XPS Ir4f were close, those extracted from the particle shape (HR-STEM) were considerably larger. The difference indicates that bulk Ir atoms contribute to the electron transfer reaction, which may indicate that the reaction rate is dominated by the reorganization energy between the redox couples involved. Therefore, the normalization of reaction rates with surface atoms may lead to an overestimation of the site activity.
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(This article belongs to the Special Issue Commemorative Issue in Honor of Professor Gerhard Ertl on the Occasion of His 85th Birthday)
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Open AccessFeature PaperReview
Focus on Materials for Sulfur-Resistant Catalysts in the Reforming of Biofuels
Catalysts 2021, 11(9), 1029; https://doi.org/10.3390/catal11091029 - 26 Aug 2021
Abstract
The reforming of biofuels represents a promising technology for low carbon and renewable hydrogen production today. The core of the process is an active and stable catalyst, which can help to improve this technology and its efficiency. With this review, we aim to
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The reforming of biofuels represents a promising technology for low carbon and renewable hydrogen production today. The core of the process is an active and stable catalyst, which can help to improve this technology and its efficiency. With this review, we aim to survey the more relevant literature on heterogeneous catalysts for the reforming of biofuels with improved sulfur tolerance. The review is structured into four main sections. Following the introduction, the fundamental aspects of sulfur poisoning are discussed. In the third section, the basic principles of the reforming of biofuels are reported, and finally, in the fourth section—the core of the review—recent progresses in the development of sulfur resistant catalysts are discussed, distinguishing the role of the metal (noble and non-noble) from that of the support.
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(This article belongs to the Section Catalysis for Sustainable Energy)
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