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Reactions, Volume 3, Issue 4 (December 2022) – 11 articles

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14 pages, 3693 KiB  
Article
Study of the Synthetic Approach Influence in Ni/CeO2-Based Catalysts for Methane Dry Reforming
by Marco Pizzolato, Giulia Da Pian, Elena Ghedini, Alessandro Di Michele, Federica Menegazzo, Giuseppe Cruciani and Michela Signoretto
Reactions 2022, 3(4), 634-647; https://doi.org/10.3390/reactions3040043 - 16 Dec 2022
Cited by 1 | Viewed by 1338
Abstract
This study focuses on the synthetic approach influence in morphostructural features and catalytic performances for Ni/CeO2 catalysts. Incipient wetness impregnation, coprecipitation and nitrate combustion were studied as catalyst preparation approaches, and the materials were then tested at 700 °C for methane dry [...] Read more.
This study focuses on the synthetic approach influence in morphostructural features and catalytic performances for Ni/CeO2 catalysts. Incipient wetness impregnation, coprecipitation and nitrate combustion were studied as catalyst preparation approaches, and the materials were then tested at 700 °C for methane dry reforming (MDR). The morphostructural properties of the materials were deeply studied using several techniques, such as temperature programmed reduction (TPR), to investigate reducibility and support-metal interaction, N2 physisorption to evaluate the porosity and the surface area, scanning electron microscopy (SEM) and X-ray diffraction (XRD) to estimate Ni dispersion, and temperature programmed oxidation (TPO) to identify the type and amount of coke formed on catalysts’ surface after reaction. From the data obtained, coprecipitation turned out to be the most suitable technique for this application because this catalyst was able to reach 70% of CO2 conversion and 30% methane conversion, with an H2 yield of 15% and 30% yield of CO at the end of the 30 h test. Moreover, it was also the catalyst with the highest metal dispersion, the strongest interaction with the support, and the lowest coke deposition. Full article
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9 pages, 2049 KiB  
Article
Three-Component Condensation of β-Ketonitriles, 4-Fluorobenzaldehyde, and Secondary Cyclic Amines
by Dmitry V. Osipov, Kirill S. Korzhenko and Vitaly A. Osyanin
Reactions 2022, 3(4), 625-633; https://doi.org/10.3390/reactions3040042 - 12 Dec 2022
Viewed by 2040
Abstract
A new three-component condensation of β-ketonitriles, 4-fluorobenzaldehyde, and secondary cyclic amines was developed. A possible reaction mechanism has been proposed including Knoevenagel condensation followed by aromatic nucleophilic substitution. It was found that in the case of 3-oxopropanenitrile bearing the 6-amino-1,3-dimethyluracil moiety, the reaction [...] Read more.
A new three-component condensation of β-ketonitriles, 4-fluorobenzaldehyde, and secondary cyclic amines was developed. A possible reaction mechanism has been proposed including Knoevenagel condensation followed by aromatic nucleophilic substitution. It was found that in the case of 3-oxopropanenitrile bearing the 6-amino-1,3-dimethyluracil moiety, the reaction is not accompanied by fluorine substitution in the Knoevenagel adduct, and the Michael addition of a secondary amine occurs followed by oxidation. Full article
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10 pages, 1675 KiB  
Article
Synthesis and Characterization of Multiple Functionalized Cyclohexanone Using Diels–Alder Reaction of α-Nitrocinnamate
by Takumi Hamada, Kento Iwai and Nagatoshi Nishiwaki
Reactions 2022, 3(4), 615-624; https://doi.org/10.3390/reactions3040041 - 02 Dec 2022
Cited by 1 | Viewed by 1363
Abstract
A systematic study of the Diels–Alder reaction of α-nitrocinnamate was performed. The reaction of p-substituted α-nitrocinnamate with 2,3-dimethyl-1,3-butadienes smoothly proceeded regardless of the p-substituent, which was either an electron-donating or -withdrawing group. A control reaction revealed that α-nitrocinnamate isomerized during the [...] Read more.
A systematic study of the Diels–Alder reaction of α-nitrocinnamate was performed. The reaction of p-substituted α-nitrocinnamate with 2,3-dimethyl-1,3-butadienes smoothly proceeded regardless of the p-substituent, which was either an electron-donating or -withdrawing group. A control reaction revealed that α-nitrocinnamate isomerized during the reaction. Danishefsly’s diene (1-methoxy-3-trimethylsiloxy-1,3-butadiene) facilitated cycloaddition under mild conditions to afford a cycloadduct without the alternation of the diastereomeric ratio. Moreover, the desilylation of the cycloadduct furnished multiple functionalized cyclohexanones. Full article
(This article belongs to the Special Issue Cycloaddition Reactions at the Beginning of the Second Millennium)
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13 pages, 7405 KiB  
Article
Selective O-alkylation of Phenol Using Dimethyl Ether
by Mane Samruddhi, Akash Bhatkar, Marimuthu Prabu, Siva Prasad Mekala, Pranjal Gogoi, Gourab Mohapatra and Raja Thirumalaiswamy
Reactions 2022, 3(4), 602-614; https://doi.org/10.3390/reactions3040040 - 17 Nov 2022
Viewed by 3026
Abstract
Anisole is a straw-colored aromatic compound mainly used in making solvents, flavoring agents, perfumes, fuel additives, and in the synthesis industries. Anisole, also known as methoxybenzene, is synthesized from sodium phenoxide or phenol using various methylating agents. The use of dimethyl ether (DME) [...] Read more.
Anisole is a straw-colored aromatic compound mainly used in making solvents, flavoring agents, perfumes, fuel additives, and in the synthesis industries. Anisole, also known as methoxybenzene, is synthesized from sodium phenoxide or phenol using various methylating agents. The use of dimethyl ether (DME) as an alkylating agent is seldom reported in the literature. Herein, we have synthesized anisole through the O-alkylation process of phenol and DME to obtain zero discharge from this process. The thermodynamic equilibrium for the reaction of phenol and DME is simulated by using Aspen HYSYS (Hyprotech and Systems). The O-alkylation of phenol has been investigated using phosphotungstic acid (PTA) over γ-Al2O3 with appropriate acidity. Active metal loadings of various percentages were studied and the conversion was optimized at 46.57% with a selectivity of 88.22% at a temperature of 280 °C. The liquid products from the continuously stirred reactor were analyzed with liquid G.C. and the conversion and selectivity were calculated. A comparison of the O-alkylation and C-alkylation of phenol at different temperatures, reactant ratios, residence times, and recyclability was explored, as well as the impact of these factors on the yield of the desired anisole. The catalyst was characterized by XRD, BET, HR-TEM, FE-SEM, elemental mapping, XPS, and DRIFT studies. Full article
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13 pages, 2776 KiB  
Article
Hydrolytic Oxidation of Cellobiose Using Catalysts Containing Noble Metals
by Oleg Manaenkov, Olga Kislitsa, Ekaterina Ratkevich, Yuriy Kosivtsov, Valentin Sapunov and Valentina Matveeva
Reactions 2022, 3(4), 589-601; https://doi.org/10.3390/reactions3040039 - 16 Nov 2022
Cited by 2 | Viewed by 1402
Abstract
Studies of the processes of the hydrolytic oxidation of disaccharides are the first step towards the development of technologies for the direct conversion of plant polysaccharides, primarily cellulose, into aldonic and aldaric acids, which are widely used in chemical synthesis and various industries. [...] Read more.
Studies of the processes of the hydrolytic oxidation of disaccharides are the first step towards the development of technologies for the direct conversion of plant polysaccharides, primarily cellulose, into aldonic and aldaric acids, which are widely used in chemical synthesis and various industries. In this study, heterogeneous catalysts based on a porous matrix of hypercrosslinked polystyrene (HPS) and noble metals (Pt, Au, Ru, and Pd) were proposed for the hydrolytic oxidation of cellobiose to gluconic and glucaric acids. The catalysts were characterized using low-temperature nitrogen adsorption, hydrogen chemisorption, electron microscopy, and other methods. In particular, it was shown that the Pt-containing catalyst contained, on average, six times more active centers on the surface, which made it more promising for use in this reaction. At a temperature of 145 °C, an O2 pressure of 5 bars, and a substrate/catalyst weight ratio of 4/1, the yields of gluconic and glucaric acids reached 21.6 and 63.4%, respectively. Based on the data obtained, the mathematical model of the cellobiose hydrolytic oxidation kinetics in the presence of 3% Pt/HPS MN270 was developed, and the parameter estimation was carried out. The formal description of the kinetics of cellobiose hydrolytic oxidation was obtained. Full article
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13 pages, 1849 KiB  
Article
Decomposition of Heavy Diesel SCR Urea Fluid Adsorbed in Cu/HZSM-5 SCR Catalysts Studied by FTIR Spectroscopy at Ambient Conditions
by Christiaan Tempelman, Brahim el Arkoubi, Jochem Spaan, Ronny Slevani and Volkan Degirmenci
Reactions 2022, 3(4), 576-588; https://doi.org/10.3390/reactions3040038 - 11 Nov 2022
Viewed by 1304
Abstract
A method is presented to study the decomposition of urea deposited on Cu/HZSM-5 SCR catalysts and therewith the ability of the Cu/HZSM-5 SCR catalyst to be regenerated when being overdosed with SCR urea fluids during operation. This straightforward laboratory method could speed up [...] Read more.
A method is presented to study the decomposition of urea deposited on Cu/HZSM-5 SCR catalysts and therewith the ability of the Cu/HZSM-5 SCR catalyst to be regenerated when being overdosed with SCR urea fluids during operation. This straightforward laboratory method could speed up calibration of exhaust gas aftertreatment systems. As an example, the removal of adsorbed urea to the SCR substrate due to dosage malfunction is studied. To study the removal of adsorbed urea on the catalyst substrate, FTIR experiments have been conducted to investigate the state of the catalyst. Besides Cu/HZSM-5 also HZSM-5 and CuOx were studied as model compounds to provide more inside on the processes occurring at the Cu/HZSM-5 surface upon urea decomposition. To simulate exposure of the SCR catalyst to overdosing of the urea solution, samples were impregnated with a 32 wt% urea solution, which correlates to that of commercial heavy duty diesel urea solutions. After impregnation, the samples were heated at various temperatures in the 133–400 °C temperature region, typically the operation window of a SCR catalyst. After heating, the samples were cooled to room temperature and measured in FTIR. The obtained spectra were compared with various literature reports to correlate the observed absorption bands to urea, urea related compounds and decomposition compounds. The concentration of these adsorbed species decreases at increased thermolysis temperature and is no longer visible at temperatures >250 °C. Extended heat treatment at 200 °C revealed only minor loss of adsorbents after 6 h and were still observable in the FTIR spectra after 24 h. Urea derived adsorbents were completely removed when simulating catalyst regeneration under SCR operation conditions under continuous air flow with a humidity of 10% and at elevated temperatures (400 °C). Full article
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23 pages, 3789 KiB  
Article
Preliminary Studies on the Electrochemical Conversion of Liquefied Forest Biomass
by Tiago Silva, José Condeço and Diogo M. F. Santos
Reactions 2022, 3(4), 553-575; https://doi.org/10.3390/reactions3040037 - 31 Oct 2022
Cited by 2 | Viewed by 1560
Abstract
Bio-oils produced from three different biomass sources, namely cork, pinewood, and olive stones, are evaluated concerning their suitability and prospects of including their electrochemical transformations in a biorefinery scenario for the production of added-value compounds. Different types and concentrations of electrolytes (e.g., H [...] Read more.
Bio-oils produced from three different biomass sources, namely cork, pinewood, and olive stones, are evaluated concerning their suitability and prospects of including their electrochemical transformations in a biorefinery scenario for the production of added-value compounds. Different types and concentrations of electrolytes (e.g., H2SO4, KOH) are added to the bio-oils to increase the samples’ initially low ionic conductivity. The samples prepared by mixing bio-oil with 2 M KOH aqueous solution (50 vol.%) lead to a stable and homogeneous bio-oil alkaline emulsion suitable for electrochemical studies. The bio-oil samples are characterized by physicochemical methods (e.g., density, viscosity, conductivity), followed by analyzing their electrochemical behavior by voltammetric and chronoamperometric studies. The organics electrooxidation and the hydrogen evolution reaction in the bio-oils are assessed using Pt electrodes. Single- and two-compartment cell laboratory bio-oil electrolyzers are assembled using nickel plate electrodes. Electrolysis is carried out at 2.5 V for 24 h. Attenuated Total Reflection-Fourier-Transform Infrared Spectroscopy and Mass Spectrometry are applied to identify possible changes in the bio-oil samples’ chemical structure during the electrolysis experiments. Comparing the analyses of the bio-oil samples subjected to electrolysis with the blank samples demonstrates that bulk electrolysis significantly changes the bio-oil composition. The bio-oil obtained from cork biomass shows the most promising results, but further studies are required to understand the nature of the actual changes. Full article
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16 pages, 5113 KiB  
Article
Greener and Efficient Epoxidation of 1,5-Hexadiene with tert-Butyl Hydroperoxide (TBHP) as an Oxidising Reagent in the Presence of Polybenzimidazole Supported Mo(VI) Catalyst
by Md Masud Rana Bhuiyan, Misbahu Ladan Mohammed and Basudeb Saha
Reactions 2022, 3(4), 537-552; https://doi.org/10.3390/reactions3040036 - 21 Oct 2022
Cited by 1 | Viewed by 1605
Abstract
Alkene epoxidation with TBHP as an oxidising reagent using heterogeneous Mo(VI) catalyst is an environmentally friendly process since it eliminates acid waste and chlorinated by-products often associated with the conventional industrial method that uses stoichiometric peracid such as peracetic acid and m-chloroperbenzoic acid. [...] Read more.
Alkene epoxidation with TBHP as an oxidising reagent using heterogeneous Mo(VI) catalyst is an environmentally friendly process since it eliminates acid waste and chlorinated by-products often associated with the conventional industrial method that uses stoichiometric peracid such as peracetic acid and m-chloroperbenzoic acid. Polybenzimidazole supported Mo(VI) complex, i.e., PBI.Mo has been successfully prepared, characterised and assessed for the epoxidation of 1,5-hexadiene in the presence of tert-butyl hydroperoxide (TBHP) as an oxidising reagent. A quadratic polynomial model has been developed, demonstrating the yield of 1,2-epoxy-5-hexene in four independent variables. The effects of different parameters such as reaction temperature, feed mole ratio of 1,5-hexadiene to TBHP, catalyst loading, and reaction time were studied. Response surface methodology (RSM) using Box-Behnken Design (BBD) was employed to study the interaction effect of different variables on the reaction response. This study presents the optimization of 1,5-hexadiene epoxidation in a batch reactor using TBHP as an oxidant and a polymer-supported Mo(VI) catalyst. Full article
(This article belongs to the Special Issue Feature Papers in Reactions in 2022)
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12 pages, 1798 KiB  
Article
Measuring Kinetics in Flow Using Isoperibolic Flow Calorimetry
by Timothy Aljoscha Frede, Moritz Greive and Norbert Kockmann
Reactions 2022, 3(4), 525-536; https://doi.org/10.3390/reactions3040035 - 12 Oct 2022
Cited by 4 | Viewed by 2150
Abstract
Continuous flow calorimeters are a promising tool in process development and safety engineering, particularly for flow chemistry applications. An isoperibolic flow calorimeter is presented for the characterization of exothermic reactions. The calorimeter is adapted to commercially available plate microreactors made of glass and [...] Read more.
Continuous flow calorimeters are a promising tool in process development and safety engineering, particularly for flow chemistry applications. An isoperibolic flow calorimeter is presented for the characterization of exothermic reactions. The calorimeter is adapted to commercially available plate microreactors made of glass and uses Seebeck elements to quantify the heat of reaction. For automation of calibration procedures and calorimetric measurements, the device is connected to a lab automation system. Reaction enthalpy of exothermic reactions is determined via an energy balance of the entire calorimeter. Characterization of reaction kinetics is carried out via a local balancing of the individual Seebeck elements without changing the experimental setup, while using the previous measurements and additional ones at higher flow rates. The calorimeter and the associated measurement procedures were tested with the oxidation of sodium thiosulfate using hydrogen peroxide. Reaction enthalpy was determined to be 594.3 ± 0.7 kJ mol−1, which is within the range of literature values. Full article
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9 pages, 2271 KiB  
Article
Microwave-Assisted Synthesis of Tri-Substituted 1,3,5-Triazines from Metformin Using Benzotriazole Chemistry
by Siva S. Panda, Eyana Thomas and Ashley M. Pham
Reactions 2022, 3(4), 516-524; https://doi.org/10.3390/reactions3040034 - 04 Oct 2022
Cited by 2 | Viewed by 1552
Abstract
A simple, metal-free, cost-effective, and eco-friendly protocol for the preparation of trisubstituted 1,3,5 triazine from metformin using benzotriazole chemistry is reported. Short reaction time, large-scale synthesis, easy and quick isolation of the product, and excellent yield are the main advantages of this procedure. [...] Read more.
A simple, metal-free, cost-effective, and eco-friendly protocol for the preparation of trisubstituted 1,3,5 triazine from metformin using benzotriazole chemistry is reported. Short reaction time, large-scale synthesis, easy and quick isolation of the product, and excellent yield are the main advantages of this procedure. Furthermore, the use of benzotriazole chemistry results in a product free from metal traces. Our optimized reaction condition and methodology overcome the challenges of using a metal catalyst, such as a longer reaction time, lower yields, and expensive starting materials. Full article
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17 pages, 2314 KiB  
Article
Kinetic Modeling for the Gas-Phase Hydrogenation of the LOHC γ-Butyrolactone–1,4-Butanediol on a Copper-Zinc Catalyst
by Vincent Gautier, Isabelle Champon, Alban Chappaz and Isabelle Pitault
Reactions 2022, 3(4), 499-515; https://doi.org/10.3390/reactions3040033 - 26 Sep 2022
Cited by 1 | Viewed by 2619
Abstract
Liquid organic hydrogen carriers (LOHCs) are an interesting alternative for hydrogen storage as the method is based on the reversibility of hydrogenation and dehydrogenation reactions to produce liquid and safe components at room temperature. As hydrogen storage involves a large amount of hydrogen [...] Read more.
Liquid organic hydrogen carriers (LOHCs) are an interesting alternative for hydrogen storage as the method is based on the reversibility of hydrogenation and dehydrogenation reactions to produce liquid and safe components at room temperature. As hydrogen storage involves a large amount of hydrogen and pure compounds, the design of a three-phase reactor requires the study of gas and liquid-phase kinetics. The gas-phase hydrogenation kinetics of LOHC γ-butyrolactone/1,4-butanediol on a copper-zinc catalyst are investigated here. The experiments were performed with data, taken from the literature, in the temperature and pressure ranges 200–240 °C and 25–35 bar, respectively, for a H2/γ-butyrolactone molar ratio at the reactor inlet of about 90. The best kinetic law takes into account the thermodynamic chemical equilibrium, is based on the associative hydrogen adsorption and is able to simulate temperature and pressure effects. For this model, the confidence intervals are at most 28% for the pre-exponential factors and 4% for the activation energies. Finally, this model will be included in a larger reactor model in order to evaluate the selectivity of the reactions, which may differ depending on whether the reaction takes place in the liquid or gas phase. Full article
(This article belongs to the Special Issue Hydrogen Production and Storage, 2nd Edition)
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