Reactions

19 pages, 6227 KiB

Open AccessArticle

Comparative Study of Greener Alkene Epoxidation Using a Polymer-Supported Mo(VI) Complex: Performance Evaluation and Optimisation via Response Surface Methodology

by Md Masud Rana Bhuiyan and Basudeb Saha

Reactions 2025, 6(2), 22; https://doi.org/10.3390/reactions6020022 - 24 Mar 2025

Abstract

A heterogeneous polybenzimidazole-supported Mo(VI) catalyst and tert-butyl hydroperoxide (TBHP) as an oxidising reagent have been utilised to establish a more environmentally friendly and greener alkene epoxidation process. A polybenzimidazole-supported Mo(VI) complex (PBI.Mo) has been prepared, characterised and evaluated successfully. The stability and [...] Read more.

A heterogeneous polybenzimidazole-supported Mo(VI) catalyst and tert-butyl hydroperoxide (TBHP) as an oxidising reagent have been utilised to establish a more environmentally friendly and greener alkene epoxidation process. A polybenzimidazole-supported Mo(VI) complex (PBI.Mo) has been prepared, characterised and evaluated successfully. The stability and catalytic activity of the produced catalyst have been evaluated for the epoxidation of 1,7-octadiene and 1,5-hexadiene in a jacketed stirred batch reactor to assess its performance towards these alkenes. The suitability and efficiency of the catalyst have been compared by studying the effect of reaction temperature, feed mole ratio of alkene to TBHP, catalyst loading, and reaction time on the yield of 1,2-epoxy-5-hexene and 1,2-epoxy-7-octene. Response surface methodology (RSM) using Box–Behnken Design (BBD) has been employed to design experimental runs and study the catalytic performance of the PBI.Mo catalyst for all batch experimental results. A quadratic regression model has been developed representing an empirical relationship between reaction variables and response, which is the yield of epoxides. The numerical optimisation technique concluded that the maximum yield that can be reached is 66.22% for 1,7-octadiene and 64.2% for 1,5-hexadiene. The reactivity of alkenes was observed to follow the sequence 1,5-hexadiene > 1,7-octadiene. The findings of this study confirm that the optimal reaction conditions vary between the two reactions, indicating differences in catalytic performance for each alkene. Full article

(This article belongs to the Special Issue Feature Papers in Reactions in 2025)

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17 pages, 4491 KiB

Open AccessArticle

CASPT2 Study of the Unimolecular Reactions of Nitromethane—A Look at the Roaming Reactions in the Decomposition of Nitromethane: An Exergonic Route at High Temperatures

by Juan Soto

Reactions 2025, 6(1), 21; https://doi.org/10.3390/reactions6010021 - 12 Mar 2025

Abstract

In this work, we studied the main decomposition reactions on the ground state of nitromethane (CH₃NO₂) with the CASPT2 approach. The energetics of the main elementary reactions of the title molecule have been analyzed on the basis of Gibbs [...] Read more.

In this work, we studied the main decomposition reactions on the ground state of nitromethane (CH₃NO₂) with the CASPT2 approach. The energetics of the main elementary reactions of the title molecule have been analyzed on the basis of Gibbs free energies obtained from standard expressions of statistical thermodynamics. In addition, we describe a mapping method (orthogonalized 3D representation) for the potential energy surfaces (PESs) by defining an orthonormal basis consisting of two

R^{n}

orthonormal vectors (n, internal degrees of freedom) that allows us to obtain a set of ordered points in the plane (vector subspace) spanned by such a basis. Geometries and harmonic frequencies of all species and orthogonalized 3D representations of the PESs have been computed with the CASPT2 approach. It is found that all of the analyzed kinetically controlled reactions of nitromethane are endergonic. For such a class of reactions, the dissociation of nitromethane into CH₃ and NO₂ is the process with the lower activation energy barrier (ΔG); that is, the C-N bond cleavage is the most favorable process. In contrast, there exists a dynamically controlled process that evolves through a roaming reaction mechanism and is an exergonic reaction at high temperatures: CH₃NO₂ → [CH₃^…NO₂]* → [CH₃ONO]* → CH₃O + NO. The above assertions are supported by CASPT2 mappings of the potential energy surfaces (PESs) and classical trajectories obtained by “on-the fly” CASSCF molecular dynamics calculations. Full article

(This article belongs to the Special Issue Feature Papers in Reactions in 2025)

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22 pages, 2652 KiB

Open AccessArticle

Design and Synthesis of 7-(N-Aryl Pyrrolidinyl) Indoles as Potential DCAF15 Binders

by Ravi Devarajappa, Scarlett Kiyeleko, Sofiane Hocine, Victor Cosson, Remi Calandrino, Timea Baló, Jayson Alves Bordelo, Sébastien Triboulet, Laure Caruana, Laurence Klipfel, Sandrine Calis, András Herner and Stephen Hanessian

Reactions 2025, 6(1), 20; https://doi.org/10.3390/reactions6010020 - 7 Mar 2025

Abstract

We describe the design and synthesis of a series of 7-(N-aryl pyrrolidinyl) indoles and oxo-analogs as isosteric mimics of the DCAF15 binder E7820, a well-known member of aryl sulfonamides known as SPLAMs. The functionalization of C-7 in indoles was achieved by metal-catalyzed CH-activation [...] Read more.

We describe the design and synthesis of a series of 7-(N-aryl pyrrolidinyl) indoles and oxo-analogs as isosteric mimics of the DCAF15 binder E7820, a well-known member of aryl sulfonamides known as SPLAMs. The functionalization of C-7 in indoles was achieved by metal-catalyzed CH-activation with unexpected results. Binding assays revealed the pyrrolidine N-aryl carboxylic acid analog to be as equally active as E7820. Full article

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14 pages, 2872 KiB

Open AccessArticle

Silicotungstate- or Phosphotungstate-Catalyzed Glycerol Esterification with Acetic Acid: A Comparison of Zinc and Tin Salts

by Marcio Jose da Silva, Cesar Macedo Oliveira, Pedro Henrique da Silva Andrade and Neide Paloma Gonçalves Lopes

Reactions 2025, 6(1), 19; https://doi.org/10.3390/reactions6010019 - 7 Mar 2025

Abstract

In this work, tin and zinc salts of silicotungstic and phosphotungstic acids were synthesized, characterized, and tested as catalysts for esterification reactions of glycerol with acetic acid (HOAc) to produce glycerol esters such as monoacetyl glycerol (MAG), which are used as additives in [...] Read more.

In this work, tin and zinc salts of silicotungstic and phosphotungstic acids were synthesized, characterized, and tested as catalysts for esterification reactions of glycerol with acetic acid (HOAc) to produce glycerol esters such as monoacetyl glycerol (MAG), which are used as additives in the pharmaceutical and food industries and in the manufacturing of explosives, or, in the case of di- or triacetyl glycerol (DAG and TAG), green bioadditives for diesel or gasoline. The activity of metal-exchanged salts (Zn, Sn) in H₃PW₁₂O₄₀ and H₄SiW₁₂O₄₀ heteropolyacids was evaluated in esterification reactions at room temperature. Among the catalysts tested, Sn_2/3PW₁₂O₄₀ was the most active and selective toward the glycerol esters. The process’s selectivity can be controlled by changes to reaction conditions. The maximum selectivitiesy of DAG and TAG were 60% and 30%, respectively, using a 1:3 molar ratio of glycerol/HOAc and a Sn_3/2PW₁₂O₄₀/673 K catalyst load of 0.4 mol%. Under these conditions, a glycerol conversion rate of 95% was observed and selectivity towards DAG and TAG was observed at 60% and 30%, respectively. The results were achieved after an 8 h reaction at a temperature of 333 K. The Sn_3/2PW₁₂O₄₀/673 K catalyst demonstrated the highest efficiency, which was attributed to its higher degree of acidity. Full article

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16 pages, 3458 KiB

Open AccessArticle

Organic Dye Photodegradation Using Niobium-Alkali Perovskite Photocatalysts: The Effect of the Alkali

by Mirtha Z. L. L. Ribeiro, Igor F. Gomes, Edher Z. Herrera, Alexandre Mello, Marília O. Guimarães, Patrícia A. Carneiro, Débora C. M. Rodrigues, Wanderlã L. Scopel, Rodrigo G. Amorim and Mauro C. Ribeiro

Reactions 2025, 6(1), 18; https://doi.org/10.3390/reactions6010018 - 4 Mar 2025

Abstract

This study combines experimental and density functional theory (DFT) to evaluate the influence of alkaline cation characteristics on the electronic structure and photodegradation efficacy of organic dyes in MNbO₃ (M = Na, K) perovskites. The X-ray Photoelectron Spectroscopy (XPS) and X-ray Absorption [...] Read more.

This study combines experimental and density functional theory (DFT) to evaluate the influence of alkaline cation characteristics on the electronic structure and photodegradation efficacy of organic dyes in MNbO₃ (M = Na, K) perovskites. The X-ray Photoelectron Spectroscopy (XPS) and X-ray Absorption Near Edge Spectroscopy (XANES) spectra at the Nb edge of the Perovskites were employed to characterize its chemical and structural properties. The DFT calculations were carried out to simulate XANES spectra as well as the structural and electrical properties of KNbO₃ and NaNbO₃. Our results show that the simulated and experimental XANES spectra are similar, indicating that the computational simulations were able to capture the local structure of the niobate samples. In addition, a photocatalytic experiment was conducted to benchmark the methylene blue consumption efficiency between different niobates. The findings demonstrated that KNbO₃ is more efficient than NaNbO₃ for methylene blue UV photocatalytic degradation, which is associated with their electronic properties. This arises as a direct result of the variably deformed NbO₆ octahedra resulting from the different alkali used. Our findings facilitate the advancement of stable and abundantly available photocatalysts, which may be employed for energy-intensive processes such as the mineralization of organic water pollutants and hydrogen production by water splitting. Full article

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11 pages, 1316 KiB

Open AccessCommunication

Palladium-Catalyzed α-Arylation of Esters: Synthesis of the Tetrahydroisoquinoline Ring

by Georgeta Serban and Faïza Diaba

Reactions 2025, 6(1), 17; https://doi.org/10.3390/reactions6010017 - 1 Mar 2025

Abstract

The palladium-catalyzed cross-coupling reaction used for carbon–carbon bond formation is one of the most commonly applied reactions in modern organic synthesis. In this work, a concise strategy was developed for constructing the tetrahydroisoquinoline core, a key structural motif found in many biologically active [...] Read more.

The palladium-catalyzed cross-coupling reaction used for carbon–carbon bond formation is one of the most commonly applied reactions in modern organic synthesis. In this work, a concise strategy was developed for constructing the tetrahydroisoquinoline core, a key structural motif found in many biologically active compounds. This method involves the palladium-catalyzed intramolecular coupling of aryl iodides with ester enolates generated in the presence of K₃PO₄ as a base, resulting in the formation of the tetrahydroisoquinoline ring with an exceptionally high yield of 84%. Full article

(This article belongs to the Special Issue Feature Papers in Reactions in 2025)

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12 pages, 664 KiB

Open AccessArticle

A Fast and Efficient Response Surface Approach for the Optimization of the Gas-Phase Hydrogenation of Carbon Dioxide on Nickel-Based Catalysts

by Mirosław K. Szukiewicz, Natalia Patulska and Elżbieta Chmiel-Szukiewicz

Reactions 2025, 6(1), 16; https://doi.org/10.3390/reactions6010016 - 15 Feb 2025

Abstract

In this study, the application of the response surface method was used to determine the best reaction conditions of the gas-phase hydrogenation of carbon dioxide on a commercial nickel-based catalyst. The procedural goals included the choice and tests of the robustness of the [...] Read more.

In this study, the application of the response surface method was used to determine the best reaction conditions of the gas-phase hydrogenation of carbon dioxide on a commercial nickel-based catalyst. The procedural goals included the choice and tests of the robustness of the statistical method that could improve the achievement of the goal of the process, first of all by reducing the number of necessary experiments. The outcome goal for the process under consideration was the optimization of reaction conditions for mild reaction conditions and the stoichiometric deficiency of hydrogen; these reaction conditions are rarely presented in the literature (despite their potential advantages). Both goals were achieved with a successful result. To find optimal reaction conditions, only 36 experiments were carried out. This is a very good result, taking into account the insufficient information in the literature, which means that it is a difficult task to deduce the region of the highest carbon dioxide conversion. The maximum carbon dioxide conversion was obtained for a temperature of 318 °C and a ratio of molar fluxes of H₂ to CO₂ equal to 3.5. It should be emphasized that this result was confirmed experimentally. Full article

(This article belongs to the Special Issue Feature Papers in Reactions in 2024)

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9 pages, 1196 KiB

Open AccessArticle

A Rapid and Green Method for the Preparation of Solketal Carbonate from Glycerol

by Sanjib Kumar Karmee, Sreedhar Gundekari, Louis C. Muller and Ajinkya Hable

Reactions 2025, 6(1), 15; https://doi.org/10.3390/reactions6010015 - 13 Feb 2025

Abstract

Glycerol is a biogenic waste that is generated in both the biodiesel and oleo-chemical industries. The value addition of surplus glycerol is of utmost importance for making these industries economically profitable. In line with this, glycerol is converted into glycerol carbonate, a potential [...] Read more.

Glycerol is a biogenic waste that is generated in both the biodiesel and oleo-chemical industries. The value addition of surplus glycerol is of utmost importance for making these industries economically profitable. In line with this, glycerol is converted into glycerol carbonate, a potential candidate for the industrial production of polymers and biobased non-isocyanate polyurethanes. In addition, glycerol can also be converted into solketal, which is the protected form of glycerol with a primary hydroxyl functional group. In this contribution, we developed a microwave-assisted solvent and catalyst-free method for converting solketal into solketal carbonate. Under conventional heating conditions, the reaction of solketal with dimethyl carbonate resulted in 70% solketal carbonate in 48 h. However, under microwave heating, 90% solketal carbonate was obtained in just 30 min. From the perspective of sustainability and green chemistry, biomass-derived heterogeneous catalysts are gaining importance. Therefore, in this project, several green catalysts, such as molecular sieves (MS, 4Å), Hβ-Zeolite, Montmorillonite K-10 clay, activated carbon from groundnut shell (Arachis hypogaea), biochar prepared from the pyrolysis of sawdust, and silica gel, were successfully used for the carbonyl transfer reaction. The obtained solketal carbonate was thoroughly characterized by ¹H NMR, ¹³C NMR, IR, and MS. The method presented here is facile, clean, and environmentally benign, as it eliminates the use of complicated procedures, toxic solvents, and toxic catalysts. Full article

(This article belongs to the Special Issue Waste Biorefinery Technologies for Accelerating Sustainable Energy Processes)

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13 pages, 4681 KiB

Open AccessArticle

Eco-Friendly Synthesis of Cerium Oxide Nanoparticles from Lycium cooperi

by Jhonathan Castillo-Saenz, Jorge Salomón-Carlos, Ernesto Beltrán-Partida and Benjamín Valdez-Salas

Reactions 2025, 6(1), 14; https://doi.org/10.3390/reactions6010014 - 11 Feb 2025

Abstract

Cerium oxide nanoparticles (CeO₂-NPs) offer promising advantages in semiconductors and biomedical applications due to their optical, electrical, antioxidant, and antibacterial properties. However, the widely reported synthetic strategies for CeO₂-NPs demand toxic precursors and intermediary pollutants, representing a major limitation [...] Read more.

Cerium oxide nanoparticles (CeO₂-NPs) offer promising advantages in semiconductors and biomedical applications due to their optical, electrical, antioxidant, and antibacterial properties. However, the widely reported synthetic strategies for CeO₂-NPs demand toxic precursors and intermediary pollutants, representing a major limitation to CeO₂-NPs applications. Therefore, it is necessary to develop greener strategies that implicate ecological precursors to reduce the negative impact on the scalability of CeO₂-NPs. In this regard, we applied Lycium cooperi (L. cooperi) aqueous extracts as an unexplored potential green reducing agent for the eco-friendly synthesis of CeO₂-NPs. The L. cooperi extract showed the presence of alkaloids, flavonoids, cardiac glycosides, and carbohydrate-derived families, which were assessed for spherical monodispersed CeO₂-NPs under a rapid chemical reduction. Moreover, the elemental composition revealed Ce and O, indicating highly pure CeO₂-NPs characterized by an interplanar cubic crystalline structure. Furthermore, we detected the presence of stabilizing functional groups from L. cooperi, which, after a controlled annealing process, resulted in a band gap energy of 3.9 eV, which was optimal for the CeO₂-NPs. Thus, the results indicate that L. cooperi is an environmentally friendly synthesis method that can open a new route for CeO₂-NPs in biomedical and industrial applications. Full article

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18 pages, 1761 KiB

Open AccessArticle

Oxides for Pt Capture in the Ammonia Oxidation Process—A Screening Study

by Julie Hessevik, Cathinka S. Carlsen, Oskar K. Bestul, David Waller, Helmer Fjellvåg and Anja O. Sjåstad

Reactions 2025, 6(1), 13; https://doi.org/10.3390/reactions6010013 - 11 Feb 2025

Cited by 1

Abstract

Metallic Pd/Ni gauzes, located downstream of the Pt/Rh ammonia oxidation catalyst nets in the Ostwald process, is the current technology for capturing volatile gas phase platinum and rhodium species lost from the Pt/Rh combustion catalyst through evaporation. In this screening study, we explore [...] Read more.

Metallic Pd/Ni gauzes, located downstream of the Pt/Rh ammonia oxidation catalyst nets in the Ostwald process, is the current technology for capturing volatile gas phase platinum and rhodium species lost from the Pt/Rh combustion catalyst through evaporation. In this screening study, we explore four oxide families, ABO₃ perovskites, (ABO₃)_n(AO) Ruddlesden–Popper (RP) phases, AO rock salt, and A₂O₃ sesquioxide type oxides, as alternative materials for platinum capture. It was found that all the tested nickelates, LaNiO₃, NdNiO₃, La₂NiO₄, and La₄Ni₃O₁₀, captured platinum well and formed A₂NiPtO₆. In contrast, La_0.85Sr_0.15FeO₃, LaFeO₃, and LaCoO₃ did not capture platinum. CaO, SrO, and Nd₂O₃ formed low-dimensional platinates such as Ca_xPt₃O₄, Sr₄PtO₆, and a newly discovered neodymium platinate, Nd_10.67Pt₄O₂₄. Gd₂O₃ did not capture platinum in bench-scale experiments in dry air, but did, however, seem to capture platinum under pilot plant conditions, likely due to the co-capture of Co lost from the N₂O abatement catalyst. The catalytic activity of both oxides and platinum-containing products were studied, toward NO_x and N₂O decomposition. None of the oxides showed significant activity toward NO_x decomposition, and all showed activity toward N₂O decomposition, but to different extents. An overall assessment of the screened oxides with respect to potential use in industrial Ostwald conditions is provided. All tested oxides except CaO and SrO withstood industrial conditions. From our assessments, the nickelates and A₂O₃ (A = Nd, Gd) stand out as superior oxides for platinum capture. Full article

(This article belongs to the Special Issue Feature Papers in Reactions in 2024)

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18 pages, 5286 KiB

Open AccessArticle

Synthesis and Characterization of Tetrasubstituted Porphyrin Tin(IV) Complexes and Their Adsorption Properties over Tetracycline Antibiotics

by Hanifi Yaman, Mirza Talha Baig and Asgar Kayan

Reactions 2025, 6(1), 12; https://doi.org/10.3390/reactions6010012 - 6 Feb 2025

Abstract

New tetrasubstituted porphyrin tin complexes (5–14) were prepared in two different ways: In the first preparation procedure, tin porphyrin complexes were prepared by a direct reaction of butyltin trichloride and dibutyltin dichloride with tetra/tetrakis(4-X-phenyl)porphyrins (X = H, F, Cl, [...] Read more.

New tetrasubstituted porphyrin tin complexes (5–14) were prepared in two different ways: In the first preparation procedure, tin porphyrin complexes were prepared by a direct reaction of butyltin trichloride and dibutyltin dichloride with tetra/tetrakis(4-X-phenyl)porphyrins (X = H, F, Cl, Br, CF₃, CH₃O, and (CH₃)₂N). In the second procedure, the same tin porphyrin complexes were synthesized from the reaction of butyltin trichloride and dibutyltin dichloride with lithium porphyrinato derivatives. These novel tin complexes were characterized by elemental analysis, ¹H, ¹³C NMR, FTIR, UV-Vis spectroscopy, and mass spectrometry. Among these complexes, tin porphyrin containing methoxy group [Bu₂Sn(TMOPP)] was tested as an adsorbent to remove tetracycline antibiotics from wastewater. The TTC antibiotic removal efficiency (R%) of this complex was measured using UV-Vis spectroscopy. After 120 min of equilibration, the final R% and adsorption capacity (q_t) were measured at 60.15% and 18.10 mg/g, respectively. Full article

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19 pages, 2835 KiB

Open AccessArticle

Production of Lipase from Streptomyces spp. AM9-01 by Solid-State Fermentation of Residual Babassu Mesocarp and Immobilization in Accurel^® MP1000

by Aldo A. T. Junior, Tamires N. dos Anjos, Melissa L. E. Gutarra, Rodrigo P. do Nascimento and Ivaldo Itabaiana Jr.

Reactions 2025, 6(1), 11; https://doi.org/10.3390/reactions6010011 - 4 Feb 2025

Abstract

A wide range of agro-industrial waste has been generated due to higher demands for food and energy. New protocols for its valorization are urgent strategies for sustainable development. In this work, residual babassu mesocarp, a native plant from the north of Brazil, was [...] Read more.

A wide range of agro-industrial waste has been generated due to higher demands for food and energy. New protocols for its valorization are urgent strategies for sustainable development. In this work, residual babassu mesocarp, a native plant from the north of Brazil, was used as a matrix for producing lipases through solid-state fermentation (SSF) by actinobacterial strains. Initially, 121 strains were screened by rhodamine B and tributyrin methods, where strain Streptomyces spp. AM9-01 was the most promising. It was submitted to the SSF at 30 °C, where 84.8 ± 1.5 U·mL⁻¹ of hydrolytic activity (HA) was found in 48 h. Further studies at pH 7 increased lipase production, achieving 94.6 ± 1.6 U·mL⁻¹ of HA in 12 h. The enzymatic extract was immobilized in Accurel^® MP1000, where the biocatalyst Lip 10 showed 79.9 ± 1.5% immobilization efficiency, 4234 ± 24 U·g⁻¹ of HA, and activity retention of 55.4%. Lip10 was used to synthesize ethyl oleate, showing conversions of over 97% in 6 h of reaction, while the commercial biocatalysts TLIM^® and N435^® showed conversions of over 95% in just 8 h. In addition, Lip10 showed operational stability for eight consecutive cycles. Therefore, it was demonstrated that babassu mesocarp is a viable alternative for obtaining competitive biocatalysts containing lipases for industrial applications from SSF by actinobacteria, which have few reports in the literature and could be potential biocatalytic agents. Full article

(This article belongs to the Special Issue Waste Biorefinery Technologies for Accelerating Sustainable Energy Processes, 2nd Edition)

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19 pages, 4042 KiB

Open AccessArticle

Electrolysis of Liquefied Biomass for Sustainable Hydrogen and Organic Compound Production: A Biorefinery Approach

by Ana P. R. A. Ferreira, M. Margarida Mateus and Diogo M. F. Santos

Reactions 2025, 6(1), 10; https://doi.org/10.3390/reactions6010010 - 2 Feb 2025

Abstract

Liquefaction is an effective thermochemical process for converting lignocellulosic biomass into bio-oil, a hydrocarbon-rich resource. This study explores liquefied biomass electrolysis as a novel method to promote the electrocracking of organic molecules into value-added compounds while simultaneously producing hydrogen (H₂). Key [...] Read more.

Liquefaction is an effective thermochemical process for converting lignocellulosic biomass into bio-oil, a hydrocarbon-rich resource. This study explores liquefied biomass electrolysis as a novel method to promote the electrocracking of organic molecules into value-added compounds while simultaneously producing hydrogen (H₂). Key innovations include utilizing water from the liquefaction process as an electrolyte component to minimize industrial waste and incorporating carbon dioxide (CO₂) into the process to enhance decarbonization efforts and generate valuable byproducts. The electrolysis process was optimized by adding 2 M KOH, and voltammetric methods were employed to analyze the resulting emulsion. The experimental conditions, such as the temperature, anode material, current type, applied cell voltage, and CO₂ bubbling, were systematically evaluated. Direct current electrolysis at 70 °C using nickel electrodes produced 55 mL of H₂ gas with the highest Faradaic (43%) and energetic (39%) efficiency. On the other hand, pulsed electrolysis at room temperature generated a higher H₂ gas volume (102 mL) but was less efficient, showing 30% Faradaic and 11% energetic efficiency. FTIR analysis revealed no significant functional group changes in the electrolyte post-electrolysis. Additionally, the solid deposits formed at the anode had an ash content of 36%. This work demonstrates that electrocracking bio-oil is a clean, sustainable approach to H₂ production and the synthesis of valuable organic compounds, offering significant potential for biorefinery applications. Full article

(This article belongs to the Special Issue Waste Biorefinery Technologies for Accelerating Sustainable Energy Processes, 2nd Edition)

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14 pages, 1967 KiB

Open AccessArticle

Immobilization of Trametes versicolor Laccase by Interlinked Enzyme Aggregates with Improved pH Stability and Its Application in the Degradation of Bisphenol A

by Thaís Marques Uber, Vanesa de Oliveira Pateis, Vinícius Mateus Salvatori Cheute, Luís Felipe Oliva dos Santos, Amanda Rúbia de Figueiredo Trindade, Alex Graça Contato, José Rivaldo dos Santos Filho, Rúbia Carvalho Gomes Corrêa, Rafael Castoldi, Cristina Giatti Marques de Souza, Adelar Bracht and Rosane Marina Peralta

Reactions 2025, 6(1), 9; https://doi.org/10.3390/reactions6010009 - 22 Jan 2025

Abstract

Laccase from Trametes versicolor was immobilized via the formation of interlinking enzyme aggregates (CLEA). Its free and immobilized enzymes were characterized, and its efficiency was tested via the removal of bisphenol A (BPA) in aqueous solution. The resistances against thermal denaturation and pH [...] Read more.

Laccase from Trametes versicolor was immobilized via the formation of interlinking enzyme aggregates (CLEA). Its free and immobilized enzymes were characterized, and its efficiency was tested via the removal of bisphenol A (BPA) in aqueous solution. The resistances against thermal denaturation and pH variations were improved upon immobilization. Although the optimal pH of the enzyme was not modified by immobilization, the latter considerably increased its stability in the pH range of 2.0 to 8.0. The immobilized form was still 50% active after 6 months of storage, while the free form took 1 month to suffer a similar drop in activity. Both free and immobilized T. versicolor laccases were efficient in removing 200 µM BPA from aqueous solutions. The free laccase removed 79% and 92.9% of the compound during the first hour of reaction when 0.1 and 0.2 U were used, respectively. The immobilized form, on the other hand, removed 72% and 94.1% of 200 µM BPA during the first hour of reaction when 0.2 and 0.5 U were used, respectively. The immobilized enzyme allowed seven reuse cycles in the oxidation of ABTS and up to four cycles in the degradation of BPA. The results suggest that the laccase from T. versicolor may be useful in biological strategies aiming at degrading endocrine disruptors, such as BPA. Full article

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16 pages, 2571 KiB

Open AccessArticle

Effective One-Component Organocatalysts for Eco-Friendly Production of Cyclic Carbonates

by Enrique Francés-Poveda, Marta Navarro, Monserrat Beroíza-Duhart, Genesys L. Mahecha, Julio I. Urzúa, María Luisa Valenzuela, Felipe de la Cruz-Martínez, Oscar A. Douglas-Gallardo, Francisca Werlinger, Agustín Lara-Sánchez and Javier Martínez

Reactions 2025, 6(1), 8; https://doi.org/10.3390/reactions6010008 - 13 Jan 2025

Abstract

One-component or bifunctional organocatalysts are some of the most capable compounds to perform the synthesis of cyclic carbonates from epoxides and carbon dioxide (CO₂) since the presence of a co-catalyst is not required. In this study, we designed, synthesized, and evaluated [...] Read more.

One-component or bifunctional organocatalysts are some of the most capable compounds to perform the synthesis of cyclic carbonates from epoxides and carbon dioxide (CO₂) since the presence of a co-catalyst is not required. In this study, we designed, synthesized, and evaluated five halogenated compounds as bifunctional organocatalysts for this catalytic transformation. Among them, 1,3-dimethylimidazolium iodide (1) exhibited the highest catalytic efficiency, enabling the synthesis of a broad range of monosubstituted cyclic carbonates with diverse functional groups under mild conditions (80 °C, 20 bar CO₂) within 1 h, using only 1 mol% catalyst loading. Remarkably, this organocatalyst also facilitated the synthesis of five internal cyclic carbonates and a carvone-derived exo-cyclic carbonate, which was obtained for the first time without the use of a metal catalyst, under more demanding conditions. A mechanistic proposal was developed through a combination of ¹H-NMR studies and density functional theory (DFT) simulations. Styrene oxide and cyclohexene oxide were used as model substrates to investigate the reaction pathway, which was computed using an optimized climbing-image nudged elastic band (CI-NEB) method. The results revealed the critical role of 1,3-dimethylimidazolium iodide in key reaction steps, particularly in facilitating the epoxy ring opening process. These findings highlight the potential use of bifunctional compounds as efficient and versatile catalysts for CO₂ valorization. Full article

(This article belongs to the Special Issue Cycloaddition Reactions at the Beginning of the Third Millennium)

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14 pages, 2820 KiB

Open AccessArticle

Obtaining Nanolignin from Green Coconut Shell and Fiber by the Acetosolv Method with Subsequent Ultrasonication

by Larissa Nascimento Lôbo, Rosana Reis de Lima Araújo, Francine Pimentel de Andrade, Renata Maria Rosas Garcia Almeida, Carlos Eduardo de Farias Silva, Jennifer Mclaine Duarte de Freitas, Johnnatan Duarte de Freitas, Mariana Barboza da Silva and Pedro Henrique Barcellos França

Reactions 2025, 6(1), 7; https://doi.org/10.3390/reactions6010007 - 11 Jan 2025

Abstract

This work aimed to extract nanolignin from green coconut husk and fiber using the acetosolv method, with the aim of transforming waste into high-value-added products and promoting sustainability and bioeconomy. The acetosolv pulping was carried out in two stages, varying temperature conditions and [...] Read more.

This work aimed to extract nanolignin from green coconut husk and fiber using the acetosolv method, with the aim of transforming waste into high-value-added products and promoting sustainability and bioeconomy. The acetosolv pulping was carried out in two stages, varying temperature conditions and the presence or absence of extractives. Lignin was obtained by precipitation and subsequently characterized through chemical and morphological analyses. The analyses of the primary components of the coconut husk and fiber demonstrated lignin, cellulose, and hemicellulose contents of 40%, 15.90%, and 15.86%, respectively. Then, nanolignin was produced through ultrasonication (850 W for 10 and 20 min). The characteristics of the obtained products were analyzed, considering the influence of two temperatures (100 °C and 120 °C) and the need for a pretreatment step (removal of extractives). The temperature variation between 100 °C and 120 °C, as well as the presence of extractives, did not significantly influence the lignin quality or extraction efficiency. The nanolignin produced under this condition was subjected to the DLS technique to determine the hydrodynamic diameter and polydispersity of the nanoparticles obtained, with an average diameter of 533.75 ± 15.12 nm after 20 min of ultrasonication. The purity of the lignin was confirmed by analyses such as the Klason lignin and ash content, which presented values of 78.82 ± 0.81% and 0.55 ± 0.26%, respectively. FTIR analyses revealed typical lignin characteristics, such as the presence of ketone groups, aromatic structures, and methoxylation, while thermograms confirmed the thermal stability of the lignin. Acetosolv pulping proved to be particularly interesting, preserving good quality lignin and allowing for partial recovery of the solvents used, promoting the sustainability and energy efficiency of the process. Full article

(This article belongs to the Special Issue Waste Biorefinery Technologies for Accelerating Sustainable Energy Processes)

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5 pages, 169 KiB

Open AccessOpinion

Changes in the Mechanism of the Fenton Reaction

by Mordechai L. Kremer

Reactions 2025, 6(1), 6; https://doi.org/10.3390/reactions6010006 - 8 Jan 2025

Cited by 1

Abstract

The kinetics of modified versions of the model of the Fenton reaction have been investigated. In these versions, radicals are produced by splitting FeO²⁺ (dissociation product of Fe²⁺ ozonide Fe²⁺O₃) into Fe³⁺ and OH^. The [...] Read more.

The kinetics of modified versions of the model of the Fenton reaction have been investigated. In these versions, radicals are produced by splitting FeO²⁺ (dissociation product of Fe²⁺ ozonide Fe²⁺O₃) into Fe³⁺ and OH^. The analysis shows that the revised models have the same shortcomings as the corresponding models of Haber and Weiss and of Barb et al. A nonradical model, based on an intact FeO²⁺ as an intermediate, accounted satisfactorily for the kinetics of the reaction under the same conditions. The amphoteric nature of FeO²⁺ to form FeOH³⁺ and HOFeO⁺ in reactions with H⁺ and OH⁻, respectively, extends its activity to a wide range of pH values. Full article

25 pages, 4952 KiB

Open AccessArticle

Influence of Oxygen Carrier on the Autothermicity of a Chemical-Looping Reforming Process for Hydrogen Production

by Juliana López van der Horst, Maria Florencia Volpe Giangiordano, Felipe Suarez, Federico M. Perez, Martín N. Gatti, Gerardo F. Santori and Francisco Pompeo

Reactions 2025, 6(1), 5; https://doi.org/10.3390/reactions6010005 - 4 Jan 2025

Abstract

The chemical-looping reforming (CLR) of methane for hydrogen production employs a solid oxygen carrier (OC) and combines endothermic and exothermic stages, allowing for potential autothermal operation. This study conducted a thermodynamic analysis using Gibbs free energy minimization and energy balances to assess the [...] Read more.

The chemical-looping reforming (CLR) of methane for hydrogen production employs a solid oxygen carrier (OC) and combines endothermic and exothermic stages, allowing for potential autothermal operation. This study conducted a thermodynamic analysis using Gibbs free energy minimization and energy balances to assess the behavior of WO₃, MnWO₄, and NiWO₄ as OCs in the CLR process. The effects of CH₄:OC ratios and reactor temperatures on equilibrium composition and the energy performance were examined. The results demonstrated that elevated reduction temperatures promote OC conversion and the formation of more reduced solid products. Molar ratios above stoichiometric prevent carbon formation, whereas stoichiometric ratios result in higher H₂ yield, achieving 98% at 1000 °C. However, these conditions do not support autothermal operation, which requires CH₄:OC molar ratios above stoichiometric. Additionally, lower oxidation temperatures are preferred regardless of the OC, due to the lower heat needed to preheat the air, which has a greater effect on the net heat. For the reduction temperature, its effect depends on the type of OC analyzed. The maximum H₂ yield obtained under autothermal operation was 88% for the three OCs, at 875 °C for MnWO₄ and 775 °C for both WO₃ and NiWO₄. Full article

(This article belongs to the Special Issue Hydrogen Production and Storage, 3rd Edition)

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16 pages, 3432 KiB

Open AccessArticle

Chemoselective Transfer Hydrogenation over MgO as the Catalyst: Acetylnaphthalenes, Diacylbenzenes, Acetophenone, Benzaldehyde, and Various Aliphatic Ketones as Hydrogen Acceptors

by Marek Gliński, Olga Dubinin, Klaudia Rostek and Patrycja Waniek

Reactions 2025, 6(1), 4; https://doi.org/10.3390/reactions6010004 - 4 Jan 2025

Abstract

Liquid and vapor phase transfer hydrogenation with 2-alkanols as hydrogen donors in the presence of MgO as a catalyst was studied. A series of dicarbonyl compounds as well as the equimolar mixtures of various monocarbonyl compounds were used as hydrogen acceptors in order [...] Read more.

Liquid and vapor phase transfer hydrogenation with 2-alkanols as hydrogen donors in the presence of MgO as a catalyst was studied. A series of dicarbonyl compounds as well as the equimolar mixtures of various monocarbonyl compounds were used as hydrogen acceptors in order to determine the chemoselectivity (ChS) in the reduction of their carbonyl groups. Thus, 1,4-diacetylbenzene was reduced to 1-(4-acetylphenyl)-1-ethanol with 89% ChS and 1,3-diacetyl-4,6-dimethylbenzene with 100% ChS. Mesitylene diacyl derivatives were unreactive in the studied reaction. CTH of an equimolar mixture of benzaldehyde and acetophenone gave benzyl alcohol and 1-PhEtOH with yields of 91 and 3%, respectively (97% ChS). An equimolar mixture of acetophenone and 6-undecanone underwent CTH with yields of the corresponding alcohols of 89 and 2%, respectively, with 98% ChS towards 1-PhEtOH. Significant differences in reactivity in CTH were reported for an equimolar mixture of regioisomeric 1- and 2-acetylnaphthalenes. The yields of the corresponding alcohols were 20 and 68% with a ChS of 77% towards 2-NphCH(OH)Me. In the case of CTH of 3-oxo-2,2-dimethylbutanal and 2,4-bis(spirocyclohexyl)-1,3-cyclobutanedione with 2-propanol, only the solvolysis of the substrates was observed. The products were methyl isopropyl ketone and isopropyl formate for the former diketone and 1-(cyclohexylcarbonyl)-1-(carboisopropoxy)cyclohexane for the latter. Full article

(This article belongs to the Special Issue Feature Papers in Reactions in 2024)

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