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Mechanism/Kinetic Modeling Study of Catalytic Reactions
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Mechanism/Kinetic Modeling Study of Catalytic Reactions

A special issue of Catalysts (ISSN 2073-4344). This special issue belongs to the section "Computational Catalysis".

Deadline for manuscript submissions: closed (15 January 2023) | Viewed by 30654

Special Issue Editors

Prof. Dr. Maria Jaworska

E-Mail Website
Guest Editor
Institute of Chemistry, University of Silesia in Katowice, Katowice, Poland
Interests: theoretical chemistry; reaction mechanisms modeling; enzymatic catalytic reactions; photochemistry
Dr. Piotr Lodowski

E-Mail Website
Guest Editor
Institute of Chemistry, University of Silesia in Katowice, Katowice, Poland
Interests: theoretical chemistry; reaction mechanisms modeling; enzymatic catalytic reactions; photochemistry

Special Issue Information

Dear Colleagues,

Catalytical reactions are of fundamental importance in industry and biochemical systems. The knowledge of catalytic reaction mechanisms is crucial in understanding the functioning of catalysts equally in homogeneous, heterogeneous, and enzymatic catalysis. In many technological or biological processes, the specific reaction mechanisms are not fully understood and are still widely discussed. The knowledge of reaction mechanisms can help to design better catalysts or effective drugs. Experimental kinetic research and simulations of catalytic reaction dynamics are crucial for understanding their mechanisms and comprehension of the observed reaction efficiencies. The use of advanced experimental techniques and modern theoretical methods is applied to elucidate catalytic mechanisms.

This Special Issue is devoted to the mechanisms and kinetics of homogeneous, heterogeneous, and enzymatic catalytic reactions. Articles focused on research with both experimental and computational methods are welcome. Short communications are also encouraged.

Prof. Dr. Maria Jaworska
Dr. Piotr Lodowski
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Catalysts is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • catalytic reaction mechanisms
  • catalytic reaction kinetics
  • homogeneous catalysis
  • heterogeneous catalysis
  • enzymatic catalysis
  • experimental methods
  • theoretical methods

Published Papers (17 papers)

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Research

18 pages, 3739 KiB  
Article
Insights into the Three-Component Coupling Reactions of Aldehydes, Alkynes, and Amines Catalyzed by N-heterocyclic Carbene Silver: A DFT Study
by Chenggen Zhang, Shuyuan Yu, Fei Wang, Jian Cao, Xinru Liang, Fuping Wang, Huimin Zheng, Yaning Zhang, Mengyao Yang and Boyu Zhao
Catalysts 2023, 13(4), 646; https://0-doi-org.brum.beds.ac.uk/10.3390/catal13040646 - 23 Mar 2023
Viewed by 1503
Abstract
Density functional theory (DFT) was used to investigate the three-component coupling reactions of aldehydes, alkynes, and amines (A3 coupling) using N-heterocyclic carbene silver as the catalyst. This study reveals that the addition reaction between the catalyst N-heterocyclic carbene silver and phenylacetylene (PAE) forms [...] Read more.
Density functional theory (DFT) was used to investigate the three-component coupling reactions of aldehydes, alkynes, and amines (A3 coupling) using N-heterocyclic carbene silver as the catalyst. This study reveals that the addition reaction between the catalyst N-heterocyclic carbene silver and phenylacetylene (PAE) forms Ag_PAE. Subsequently, one hydrogen atom of the Ag_PAE migrates to the nitrogen atom of the Amine. Thereafter, the amine aldehyde condensation reaction generates a molecule of water and an imine ion with (Path one) or without (Path two) another amine catalyst. Path one has a lower reaction barrier than Path two. Subsequently, the imine ion reacts with silver phenylacetylide to generate the A3 coupling reaction product propargylamine (PPA). Furthermore, the triple bond and −N3 group in PPA undergo a cycloaddition reaction and generate the final product (PR). The entire reaction is strongly exothermic, and, therefore, the reaction is easy to conduct. Moreover, conceptual density functional theory calculations confirm the reaction mechanism. Investigating the mechanism of these reactions will be helpful for understanding and developing new synthesis strategies for similar functional compounds. Full article
(This article belongs to the Special Issue Mechanism/Kinetic Modeling Study of Catalytic Reactions)
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23 pages, 8051 KiB  
Article
CO Oxidation Reaction by Platinum Clusters on the Surface of Multiwalled Carbon Nanotubes: Experimental and Theoretical Study of Kinetics in a Wide Range of O2/CO Ratios
by Elena Lashina, Elena Slavinskaya, Lidiya Kibis, Andrey Stadnichenko, Olga Stonkus, Daniil Zhuravlev, Andrey Zadesenets, Sergey Korenev, Olga Podyacheva and Andrei Boronin
Catalysts 2023, 13(3), 568; https://0-doi-org.brum.beds.ac.uk/10.3390/catal13030568 - 10 Mar 2023
Cited by 1 | Viewed by 1378
Abstract
This work presents a systematic study of the kinetic aspects of CO oxidation reaction catalyzed by platinum nanoparticles (NPs) supported on the surface of multiwalled carbon nanotubes (MWCNTs). The investigation presented is closely related to the actual practical task of air purification in [...] Read more.
This work presents a systematic study of the kinetic aspects of CO oxidation reaction catalyzed by platinum nanoparticles (NPs) supported on the surface of multiwalled carbon nanotubes (MWCNTs). The investigation presented is closely related to the actual practical task of air purification in enclosed spaces. Therefore, the catalytic reaction was carried out in the presence of an excess of oxygen (5 vol.%) and over a wide range of CO concentrations from 50 ppm to 1600 ppm. For the catalyst characterization, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) were applied. Kinetic modelling based on the Langmuir–Hinshelwood and Mars-van Krevelen mechanisms was taken as a basis, using the results obtained on Pt foil. Simulation of CO oxidation reaction on platinum NPs at temperatures above 90 °C was carried out using a kinetic model describing the reaction mechanism on bulk platinum. The description of the kinetics of CO oxidation reaction on Pt NPs over the entire temperature range, including the low temperatures down to −40 °C, required the introduction of the steps characterizing an additional concerted mechanism related to CO-assisted O2 dissociation. Using the presented model, some predictions of the kinetic behaviour of the system were made. Full article
(This article belongs to the Special Issue Mechanism/Kinetic Modeling Study of Catalytic Reactions)
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15 pages, 2717 KiB  
Article
Modeling of a Two-Bed Reactor for Low-Temperature Removal of Nitrogen Oxides in Nitric Acid Production
by Nadezhda Vernikovskaya, Yuliya Ivanova, Artem Sheboltasov, Victor Chumachenko and Lyubov Isupova
Catalysts 2023, 13(3), 535; https://0-doi-org.brum.beds.ac.uk/10.3390/catal13030535 - 06 Mar 2023
Cited by 1 | Viewed by 1412
Abstract
In this study, the modeling of the low-temperature catalytic abatement of NOX and N2O from tail gases in a weak nitric acid plant utilizing a single-pressure 0.716 MPa system was performed. A one-reactor concept assumes that in the first bed, [...] Read more.
In this study, the modeling of the low-temperature catalytic abatement of NOX and N2O from tail gases in a weak nitric acid plant utilizing a single-pressure 0.716 MPa system was performed. A one-reactor concept assumes that in the first bed, NOX is reduced by ammonia on a commercial vanadia–alumina catalyst, and in the second bed, N2O is decomposed on a proprietary nickel–cobalt catalyst. The kinetics of N2O decomposition on a Cs/Ni0.1Co2.9O4 catalyst was experimentally studied in an isothermal flow reactor. The reaction rate constants were determined by varying the residence time and temperature; these data formed the basis for modeling kinetics and heat and mass transport in an adiabatic reactor in which the low-temperature mitigation of nitrogen oxides occurred. Taking into account the given spatial limitations inside the reactor and the allowable temperatures, the layer heights were evaluated to ensure a residual NOX and N2O content of less than 50 ppm. Catalyst loading using layers in a commercial reactor was estimated for the tail-gas flow rates of 46,040–58,670 m3/h. Simulations showed that the optimum inlet temperature was 260 °C; in this case, the NOX and N2O conversion targets were achieved in the range of 46,040–58,670 m3/h while adhering to catalyst bed height and outlet temperature limitations. Full article
(This article belongs to the Special Issue Mechanism/Kinetic Modeling Study of Catalytic Reactions)
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18 pages, 12586 KiB  
Article
Effect of C3-Alcohol Impurities on Alumina-Catalyzed Bioethanol Dehydration to Ethylene: Experimental Study and Reactor Modeling
by Elena V. Ovchinnikova, Sardana P. Banzaraktsaeva, Maria A. Kovgan and Victor A. Chumachenko
Catalysts 2023, 13(3), 509; https://0-doi-org.brum.beds.ac.uk/10.3390/catal13030509 - 01 Mar 2023
Viewed by 1420
Abstract
The impact of feedstock impurities on catalytic process is among the crucial issues for processing real raw materials. A real and model 92%-bioethanol contaminated with 0.03–0.3% mol 1-propanol or 2-propanol were used to make ethylene on a proprietary alumina catalyst in isothermal flow [...] Read more.
The impact of feedstock impurities on catalytic process is among the crucial issues for processing real raw materials. A real and model 92%-bioethanol contaminated with 0.03–0.3% mol 1-propanol or 2-propanol were used to make ethylene on a proprietary alumina catalyst in isothermal flow reactor. We proposed a formal kinetic model to describe the impure bioethanol conversion to ethylene and byproducts and used it to evaluate the multi-tubular reactor (MTR) for 60 KTPA ethylene production. The simulated data agree well with experimental results. Under reaction-controlled conditions, C3-alcohols strongly suppress the formation of by-products and ethylene-from-ethanol, and slightly inhibit the formation of ethylene-via-ether. It is the suppression of the ethylene-via-ether route that causes a decrease in ethanol conversion. The predominant formation of ethylene-via-ether results in an increased ethylene yield but doubling the catalyst load is required to achieve conversion as for pure feedstock. 2-Propanol has a stronger effect on dehydration than 1-propanol. Diffusion inside the grain’s levels out the effect of C3-alcohols on the process in MTR, giving an ethylene yield as high as ~98% while dehydrating a contaminated 92% ethanol. However, impurities dilute ethanol and generate propylene (which contaminates target product), and these worsen feedstock consumption and ethylene productivity in MTR. Full article
(This article belongs to the Special Issue Mechanism/Kinetic Modeling Study of Catalytic Reactions)
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13 pages, 2269 KiB  
Article
New Ni(II)-Ni(II) Dinuclear Complex, a Resting State of the (α-diimine)NiBr2/AlMe3 Catalyst System for Ethylene Polymerization
by Igor E. Soshnikov, Nina V. Semikolenova, Anna A. Bryliakova, Artem A. Antonov, Konstantin P. Bryliakov and Evgenii P. Talsi
Catalysts 2023, 13(2), 333; https://0-doi-org.brum.beds.ac.uk/10.3390/catal13020333 - 02 Feb 2023
Cited by 1 | Viewed by 1768
Abstract
A novel room-temperature stable diamagnetic nickel complex 2 was detected upon activation of Brookhart-type ethylene polymerization pre-catalyst LNiBr2 (1, L = 1,4-bis-2,4,6-trimethylphenyl-2,3-dimethyl-1,4-diazabuta-1,3-diene) with AlMe3. Using in situ 1H, 2H, and 13C NMR spectroscopy, as well [...] Read more.
A novel room-temperature stable diamagnetic nickel complex 2 was detected upon activation of Brookhart-type ethylene polymerization pre-catalyst LNiBr2 (1, L = 1,4-bis-2,4,6-trimethylphenyl-2,3-dimethyl-1,4-diazabuta-1,3-diene) with AlMe3. Using in situ 1H, 2H, and 13C NMR spectroscopy, as well as DFT calculations, this species has been identified as an antiferromagnetically coupled homodinuclear complex [LNiII(μ-Me)(μ-CH2)NiIIL]+Br−. Its behavior in the reaction solution is characteristic of the resting state of nickel catalyzed ethylene polymerization. Full article
(This article belongs to the Special Issue Mechanism/Kinetic Modeling Study of Catalytic Reactions)
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16 pages, 5144 KiB  
Article
Modeling and Optimization of Geraniol ((2E)-3,7-Dimethyl-2,6-Octadiene-l-ol) Transformation Process Using Response Surface Methodology (RSM)
by Anna Fajdek-Bieda, Andrzej Perec and Aleksandra Radomska-Zalas
Catalysts 2023, 13(2), 320; https://0-doi-org.brum.beds.ac.uk/10.3390/catal13020320 - 01 Feb 2023
Cited by 1 | Viewed by 1097
Abstract
This paper presents the modeling of the geraniol transformation process using response surface methodology (RSM). It uses a combination of both statistical and mathematical modeling methods to study the relationships occurring between several explanatory variables and one or more response variables. Interactions occurring [...] Read more.
This paper presents the modeling of the geraniol transformation process using response surface methodology (RSM). It uses a combination of both statistical and mathematical modeling methods to study the relationships occurring between several explanatory variables and one or more response variables. Interactions occurring between process variables are studied using statistical techniques. In this paper, the influence of the most important process parameters, such as temperature 20–110 °C, catalyst concentration (mironecuton) 1.0–5.0 (wt.%), and reaction time 0.25–2 (h), is presented. The response functions were the conversion of geraniol (GA), the selectivity of conversion to thumbergol (TH), and the selectivity of conversion to 6,11-dimethyl-2,6,10-dodecatriene-1-ol (DMC). In addition, the effects of all control parameters on each of the response parameters were presented in the form of second-order polynomials. Attempts were made to identify process conditions that would allow high values of the process function. Full article
(This article belongs to the Special Issue Mechanism/Kinetic Modeling Study of Catalytic Reactions)
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19 pages, 7797 KiB  
Article
Molecular Dynamics Simulations for the Michaelis Complex of Ectoine Synthase (EctC)
by Justyna Andrys-Olek, Johann Heider and Tomasz Borowski
Catalysts 2023, 13(1), 124; https://0-doi-org.brum.beds.ac.uk/10.3390/catal13010124 - 06 Jan 2023
Cited by 1 | Viewed by 1510
Abstract
Ectoine is a chemical chaperone synthesised and used by bacteria to defend against osmotic stress. Although it has already gained attention from the pharmaceutical and cosmetic industries, thanks to its hydrating and cell-protecting properties, the reaction mechanism of its final synthesis step is [...] Read more.
Ectoine is a chemical chaperone synthesised and used by bacteria to defend against osmotic stress. Although it has already gained attention from the pharmaceutical and cosmetic industries, thanks to its hydrating and cell-protecting properties, the reaction mechanism of its final synthesis step is still not fully understood. The ultimate step of ectoine biosynthesis is catalysed by the ectoine synthase enzyme (EctC), which requires an iron ion for substrate binding and overall enzymatic activity. Even though a crystal structure for Paenibacillus lautus EctC—substrate complex is available (PDB: 5ONN), it is not very informative with respect to the geometry of the active site because: (1) the crystal was obtained at a pH value far from the enzyme’s pH optimum, (2) the electron density at the Fe position is weak, and (3) the Fe-ligand distances are too long. To fill this gap, in this work we have used classical molecular dynamics simulations to model the enzyme-substrate (N-gamma-acetyl-L-2,4-diaminobutyric acid) complex of Paenibacillus lautus EctC (PlEctC). Since PlEctC is a homodimeric protein, MD simulations were carried out for a dimer with various plausible occupancies by the substrate and for two plausible coordination geometries around the catalytic Fe ion: tetrahedral and octahedral. MD results revealed that the presence of the ligand has a stabilising effect on the protein structure, most notably on a short helix 112–118, which flanks the entrance to the active site. The most important amino acids for substrate binding are Trp21, Arg25, Asn38, Thr40, and Tyr52, which were also identified in the crystal structure. Importantly, the substrate can easily adopt a conformation suitable for the progress of the catalytic reaction, and it does so spontaneously for the octahedral 6-coordinate geometry of the iron cofactor or with a low energy penalty (ca. 3 kcal/mol) in the case of 4-coordinate tetrahedral geometry. Simulations for different substrate occupancy states did not reveal any signs of cooperativity between the two monomers. Full article
(This article belongs to the Special Issue Mechanism/Kinetic Modeling Study of Catalytic Reactions)
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15 pages, 2791 KiB  
Article
Energy Basics of Catalytic Hydrodesulfurization of Diesel Fuels
by Daria Petrova, Valentina Lyubimenko, Evgenii Ivanov, Pavel Gushchin and Ivan Kolesnikov
Catalysts 2022, 12(11), 1301; https://0-doi-org.brum.beds.ac.uk/10.3390/catal12111301 - 24 Oct 2022
Cited by 9 | Viewed by 2934
Abstract
Currently, Euro 5 (no more than 10 ppm sulfur content) and Euro 6 (less than 10 ppm sulfur content) diesel motor fuels are produced worldwide. High-quality diesel fuels are produced by removing sulfur compounds using a hydrodesulfurization process. This article is devoted to [...] Read more.
Currently, Euro 5 (no more than 10 ppm sulfur content) and Euro 6 (less than 10 ppm sulfur content) diesel motor fuels are produced worldwide. High-quality diesel fuels are produced by removing sulfur compounds using a hydrodesulfurization process. This article is devoted to the study of hydrodesulfurization of diesel fuel containing 120 ppm of sulfur compounds in the presence of an Al-Ni-Mo-O catalyst with a 98% diesel fuel purification rate. According to the Langmuir–Hinshelwood–Panchenkov theory, a kinetic model of the process is developed with the calculation of the theoretical change in the entropy and enthalpy of the activation of the hydrodesulfurization process. The mathematical model, for the first time, takes into account the influence of the pressure of substances involved in the process on the transformation of sulfur-containing compounds. A mechanism for diesel fuel hydrotreating from sulfur-containing compounds is formulated using a generalized quantum-chemical principle. The hydrodesulfurization mechanism includes nine stages. The formulated mechanism and developed mathematical model of hydrotreating fully describe the reaction of the hydrodesulfurization of diesel fuel and show the possibility of regulating and controlling this industrially important process. Full article
(This article belongs to the Special Issue Mechanism/Kinetic Modeling Study of Catalytic Reactions)
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14 pages, 25454 KiB  
Article
Propane Dehydrogenation on Co-N-C/SiO2 Catalyst: The Role of Single-Atom Active Sites
by Aleksey N. Chernov, Vladimir I. Sobolev, Evgeny Yu. Gerasimov and Konstantin Yu. Koltunov
Catalysts 2022, 12(10), 1262; https://0-doi-org.brum.beds.ac.uk/10.3390/catal12101262 - 17 Oct 2022
Cited by 6 | Viewed by 2301
Abstract
Recently, significant attention has been drawn to carbon materials containing cobalt coordinated to nitrogen, as the promising inexpensive catalysts of a wide range of applications. Given that non-oxidative propane dehydrogenation to propylene (PDH) is also becoming increasingly important, we present the results on [...] Read more.
Recently, significant attention has been drawn to carbon materials containing cobalt coordinated to nitrogen, as the promising inexpensive catalysts of a wide range of applications. Given that non-oxidative propane dehydrogenation to propylene (PDH) is also becoming increasingly important, we present the results on PDH over Co-N-C/SiO2 composites. The latter were prepared by pyrolysis of silicone gel enriched with Co(II) salt and triethanolamine. According to XRD, HRTEM and XPS characterizations, the resulting materials consist of metallic cobalt nanoparticles of about 5 to 10 nm size and subnano-sized cobalt species (cobalt single atom sites coordinated to nitrogen/carbon), which are uniformly distributed in mesoporous silica of high specific surface area (up to 500 m2 g−1). The composites demonstrated significant catalytic activity in PDH, which was examined under typical reaction conditions (600 °C, 1 atm) using a fixed bed flow reactor. The subnano-sized Co centers proved to be the real active catalytic sites responsible for the target reaction, while carbon deposition induced by Co nanoparticles provided the catalyst deactivation. It is shown that the catalyst can be reactivated by the treatment with oxygen, which, in addition, notably increases selectivity to propylene (up to 98%) and enhances the catalyst stability in the next operation cycle. This remarkable change in catalytic behavior is shown to be due to the dramatic structural modification of the catalyst upon high-temperature oxidation. Full article
(This article belongs to the Special Issue Mechanism/Kinetic Modeling Study of Catalytic Reactions)
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14 pages, 2902 KiB  
Article
N-Heterocyclic Molecules as Potential Liquid Organic Hydrogen Carriers: Reaction Routes and Dehydrogenation Efficacy
by Sergey A. Stepanenko, Danil M. Shivtsov, Anton P. Koskin, Igor P. Koskin, Roman G. Kukushkin, Petr M. Yeletsky and Vadim A. Yakovlev
Catalysts 2022, 12(10), 1260; https://0-doi-org.brum.beds.ac.uk/10.3390/catal12101260 - 17 Oct 2022
Cited by 10 | Viewed by 2119
Abstract
This study is focused on the development of liquid organic hydrogen carriers (LOHC) based on N-heterocyclic compounds. These LOHC-substrates are attractive for their lower hydrogen extraction temperature compared to cycloalkanes, which is caused by the low enthalpy of the dehydrogenation reaction of the [...] Read more.
This study is focused on the development of liquid organic hydrogen carriers (LOHC) based on N-heterocyclic compounds. These LOHC-substrates are attractive for their lower hydrogen extraction temperature compared to cycloalkanes, which is caused by the low enthalpy of the dehydrogenation reaction of the N-heterocyclic compounds. The low hydrogen extraction temperature, as well as the low volatility of the heterocycles, provide high purity hydrogen from the reaction. Under similar reaction conditions, the comparison of the efficacy of three promising heterocycles (1-methyl-octahydroindole (8HMI), tetradecahydrophenazine and decahydroquinoline) was carried out in the presence of palladium-containing catalysts. As a result, the advantages of using catalysts supported by alumina, and the high perspectivity of the 8MHI application as a LOHC-substrate, were shown. The dehydrogenation of 8HMI in the presence of 1 wt.% Pd/Al2O3 allowed for reaching a 100% yield in hydrogen under the conditions of the standard catalytic test (1 h, 240 °C). In order to study the high reactivity of 8HMI, thermodynamic dehydrogenation reaction profiles were computationally evaluated, which showed that 8HMI was the most energetically preferred in the field of hydrogen storage from the studied heterocyclic compounds. Full article
(This article belongs to the Special Issue Mechanism/Kinetic Modeling Study of Catalytic Reactions)
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13 pages, 1623 KiB  
Article
Formic Acid Production via One-Pot Hydrolysis-Oxidation of Starch over Quaternary Ammonium Salts of Vanadium-Containing Keggin-Type Heteropoly Acids
by Nikolay V. Gromov, Tatiana B. Medvedeva, Ivan A. Lukoyanov, Valentina N. Panchenko, Maria N. Timofeeva, Oxana P. Taran and Valentin N. Parmon
Catalysts 2022, 12(10), 1252; https://0-doi-org.brum.beds.ac.uk/10.3390/catal12101252 - 17 Oct 2022
Cited by 9 | Viewed by 1623
Abstract
Bifunctional solid acidic quaternary ammonium salts of Keggin-type vanadium-containing heteropoly acids, such as R3.5H0.5PVMo11O40 (R: (C2H5)4N, (C4H9)4N, (C6H13)4N), [...] Read more.
Bifunctional solid acidic quaternary ammonium salts of Keggin-type vanadium-containing heteropoly acids, such as R3.5H0.5PVMo11O40 (R: (C2H5)4N, (C4H9)4N, (C6H13)4N), and [(C4H9)4N]4.5H0.5SiW11VO40, are capable of one-pot hydrolysis-oxidationconversion (OxFA-processing) of starch to biogenic formic acid. The impact of the reaction conditions and catalyst type was revealed. The highest formic acid yield of 50% was achieved over the best [(C2H5)4N]3.5H0.5PVMo11O40 catalyst, which was active and stable in seven reaction cycles. The kinetic computational model, which described formic acid formation well, was proposed in the presence of the most active [(C2H5)4N]3.5H0.5PVMo11O40 catalyst. Full article
(This article belongs to the Special Issue Mechanism/Kinetic Modeling Study of Catalytic Reactions)
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16 pages, 2915 KiB  
Article
Effect of the Support on Rhenium Carbide in the Hydrodeoxygenation of Guaiacol as Lignin-Derived Model Compound
by Elodie Blanco, Ana Belén Dongil, Isaac Tyrone Ghampson and Néstor Escalona
Catalysts 2022, 12(10), 1229; https://0-doi-org.brum.beds.ac.uk/10.3390/catal12101229 - 13 Oct 2022
Cited by 2 | Viewed by 1415
Abstract
The effect of support on the formation of rhenium carbide in the hydrodeoxygenation (HDO) of guaiacol as a lignin-derived compound was evaluated. Catalysts were prepared by incipient wetness impregnation, carburized at 650 °C under a mixture 25/75 of ethylene/hydrogen, and characterized by XRD, [...] Read more.
The effect of support on the formation of rhenium carbide in the hydrodeoxygenation (HDO) of guaiacol as a lignin-derived compound was evaluated. Catalysts were prepared by incipient wetness impregnation, carburized at 650 °C under a mixture 25/75 of ethylene/hydrogen, and characterized by XRD, N2-physisorption, TPR, TPD of NH3 or isopropylamine (IPA), and XPS. The results have demonstrated that the support choice affects the carburization of rhenium. Indeed, over non-acidic support (e.g., SiO2), limited carburization of the metal was observed, while over ZrO2 and Al2O3, carburization of rhenium occurred, and different carbidic species were obtained depending on the surface and chemical identity of the support. The rhenium carbide species obtained over ZrO2 was the most active and selective toward benzene (22% at 98% of conversion). Full article
(This article belongs to the Special Issue Mechanism/Kinetic Modeling Study of Catalytic Reactions)
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13 pages, 27429 KiB  
Article
Density Functional Theory Study of the Regioselectivity in Copolymerization of bis-Styrenic Molecules with Propylene Using Zirconocene Catalyst
by Shu-Yuan Yu, Xiaoxia Peng, Fuping Wang, Jian Cao, Fei Wang and Cheng-Gen Zhang
Catalysts 2022, 12(9), 1039; https://0-doi-org.brum.beds.ac.uk/10.3390/catal12091039 - 13 Sep 2022
Cited by 3 | Viewed by 1296
Abstract
Density functional theory (DFT) was used to study the regioselectivity of the copolymerization of propylene and the bis-styrenic molecules (DVB and BVPE) using a zirconocene catalyst. This study reveals the following: when hydrogen is introduced to reactivate the catalyst on the vinyl [...] Read more.
Density functional theory (DFT) was used to study the regioselectivity of the copolymerization of propylene and the bis-styrenic molecules (DVB and BVPE) using a zirconocene catalyst. This study reveals the following: when hydrogen is introduced to reactivate the catalyst on the vinyl bonds containing DVB or BVPE, the second vinyl bond is inserted into the polymer in a regio-irregular 1,2-way. (I) The 1,2-insertion mode forms more thermodynamically stable products. (II) The 2,1 insertion, DVB-PP1, or BVPE-PP1 needs to rotate 180° along the Zr-C1 bond to complete the process; thus, it is easier to accomplish the 1,2 insertion. (III) The analysis of the local electrophilicity/nucleophilicity index and the Fukui functions also indicate that the 1,2-insertion mode is the optimal insertion mode. Investigating the mechanism of this experimental phenomenon is important in the development of a functionalization strategy for polypropylene (PP) polymers. Full article
(This article belongs to the Special Issue Mechanism/Kinetic Modeling Study of Catalytic Reactions)
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10 pages, 565 KiB  
Article
Ethylene Polymerization over Supported Vanadium-Magnesium Catalysts with Different Vanadium Content: The Effect of Hydrogen on Molecular Weight Characteristics of the Produced Bimodal Polyethylene
by Tatiana Mikenas, Zenghui Zhao, Peng Guan, Mikhail Matsko, Vladimir Zakharov and Wei Wu
Catalysts 2022, 12(9), 985; https://0-doi-org.brum.beds.ac.uk/10.3390/catal12090985 - 01 Sep 2022
Viewed by 1252
Abstract
Data are presented on the activity of supported vanadium-magnesium catalysts (VMCs) with different vanadium content in ethylene polymerization and the molecular weight characteristics of the produced polyethylene. The VC1 catalyst, with a very low vanadium content (0.12 wt.%), showed a sixfold higher activity [...] Read more.
Data are presented on the activity of supported vanadium-magnesium catalysts (VMCs) with different vanadium content in ethylene polymerization and the molecular weight characteristics of the produced polyethylene. The VC1 catalyst, with a very low vanadium content (0.12 wt.%), showed a sixfold higher activity per unit weight of vanadium than the VC2 catalyst with a high-vanadium content (4.0 wt.%). Additionally, the total activity of VC2 (kg PE/g cat·h) was fivefold higher when compared to VC1. The introduction of hydrogen in polymerization leads to a considerable decrease in the activity of both catalysts. The polyethylene obtained in the presence of hydrogen over both catalysts has a broad bimodal molecular weight distribution (MWD) with a distinct shoulder in the high-molecular region (Mw ≥ 106 g/mol). Decomposition of the MWD curves of bimodal polyethylene into two fractions (high- and low-molecular fractions) made it possible to determine for the first time the ratio of the reaction rate constants of chain transfer with hydrogen (KtrH) and polymer chain propagation (Kp) for two groups of the VMC active sites producing low- and high-molecular fractions of bimodal polyethylene. Full article
(This article belongs to the Special Issue Mechanism/Kinetic Modeling Study of Catalytic Reactions)
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14 pages, 2405 KiB  
Article
Effect of Brønsted Acid on the Reactivity and Selectivity of the Oxoiron(V) Intermediates in C-H and C=C Oxidation Reactions
by Alexandra M. Zima, Oleg Y. Lyakin, Anna A. Bryliakova, Dmitrii E. Babushkin, Konstantin P. Bryliakov and Evgenii P. Talsi
Catalysts 2022, 12(9), 949; https://0-doi-org.brum.beds.ac.uk/10.3390/catal12090949 - 26 Aug 2022
Cited by 5 | Viewed by 1421
Abstract
The effect of HClO4 on the reactivity and selectivity of the catalyst systems 1,2/H2O2/AcOH, based on nonheme iron complexes of the PDP families, [(Me2OMePDP)FeIII(μ-OH)2FeIII(MeOMe2PDP)](OTf)4 [...] Read more.
The effect of HClO4 on the reactivity and selectivity of the catalyst systems 1,2/H2O2/AcOH, based on nonheme iron complexes of the PDP families, [(Me2OMePDP)FeIII(μ-OH)2FeIII(MeOMe2PDP)](OTf)4 (1) and [(NMe2PDP)FeIII(μ-OH)2FeIII(NMe2PDP](OTf)4 (2), toward oxidation of benzylideneacetone (bna), adamantane (ada), and (3aR)-(+)-sclareolide (S) has been studied. Adding HClO4 (2–10 equiv. vs. Fe) has been found to result in the simultaneous improvement of the observed catalytic efficiency (i.e., product yields) and the oxidation regio- or enantioselectivity. At the same time, HClO4 causes a threefold increase of the second-order rate constant for the reaction of the key oxygen-transferring intermediate [(Me2OMePDP)FeV=O(OAc)]2+ (1a), with cyclohexane at −70 °C. The effect of strong Brønsted acid on the catalytic reactivity is discussed in terms of the reversible protonation of the Fe=O moiety of the parent perferryl intermediates. Full article
(This article belongs to the Special Issue Mechanism/Kinetic Modeling Study of Catalytic Reactions)
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18 pages, 3038 KiB  
Article
Mechanistic Insights into the Effect of Sulfur on the Selectivity of Cobalt-Catalyzed Fischer–Tropsch Synthesis: A DFT Study
by Yagmur Daga and Ali Can Kizilkaya
Catalysts 2022, 12(4), 425; https://0-doi-org.brum.beds.ac.uk/10.3390/catal12040425 - 10 Apr 2022
Cited by 3 | Viewed by 2342
Abstract
Sulfur is a common poison for cobalt-catalyzed Fischer–Tropsch Synthesis (FTS). Although its effects on catalytic activity are well documented, its effects on selectivity are controversial. Here, we investigated the effects of sulfur-covered cobalt surfaces on the selectivity of FTS using density functional theory [...] Read more.
Sulfur is a common poison for cobalt-catalyzed Fischer–Tropsch Synthesis (FTS). Although its effects on catalytic activity are well documented, its effects on selectivity are controversial. Here, we investigated the effects of sulfur-covered cobalt surfaces on the selectivity of FTS using density functional theory (DFT) calculations. Our results indicated that sulfur on the surface of Co(111) resulted in a significant decrease in the adsorption energies of CO, HCO and acetylene, while the binding of H and CH species were not significantly affected. These findings indicate that sulfur increased the surface H/CO coverage ratio while inhibiting the adsorption of carbon chains. The elementary reactions of H-assisted CO dissociation, carbon and oxygen hydrogenation and CH coupling were also investigated on both clean and sulfur-covered Co(111). The results indicated that sulfur decreased the activation barriers for carbon and oxygen hydrogenation, while increasing the barriers for CO dissociation and CH coupling. Combining the results on elementary reactions with the modification of adsorption energies, we concluded that the intrinsic effect of sulfur on the selectivity of cobalt-catalyzed FTS is to increase the selectivity to methane and saturated short-chain hydrocarbons, while decreasing the selectivity to olefins and long-chain hydrocarbons. Full article
(This article belongs to the Special Issue Mechanism/Kinetic Modeling Study of Catalytic Reactions)
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21 pages, 37607 KiB  
Article
Theoretical Studies of Acetyl-CoA Synthase Catalytic Mechanism
by Maria Jaworska and Piotr Lodowski
Catalysts 2022, 12(2), 195; https://0-doi-org.brum.beds.ac.uk/10.3390/catal12020195 - 04 Feb 2022
Cited by 3 | Viewed by 1820
Abstract
DFT calculations were performed for the A-cluster from the enzyme Acetyl-CoA synthase (ACS). The acid constants (pKa), reduction potentials, and pH-dependent reduction potential for the A-cluster with different oxidation states and ligands were calculated. Good agreement of the reduction potentials, dependent [...] Read more.
DFT calculations were performed for the A-cluster from the enzyme Acetyl-CoA synthase (ACS). The acid constants (pKa), reduction potentials, and pH-dependent reduction potential for the A-cluster with different oxidation states and ligands were calculated. Good agreement of the reduction potentials, dependent on pH in the experiment, was obtained. On the basis of the calculations, a mechanism for the methylation reaction involving two–electron reduction and protonation on the proximal nickel atom of the reduced A-cluster is proposed. Full article
(This article belongs to the Special Issue Mechanism/Kinetic Modeling Study of Catalytic Reactions)
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