Reactions

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

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 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

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

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

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

The synthesis of natural and unconventional compounds with carbohydrate structures is of great interest to glycochemists due to their vital biological roles. In recent years, there has been significant progress in developing direct and indirect synthetic strategies for constructing sugar moieties. Among these methods, the Prins reaction, employing homoallylic alcohols and carbonyl compounds, has proven invaluable for directly creating sugar skeletons. This review discusses approaches for crafting carbohydrate frameworks using the Prins reaction, utilizing both carbohydrate and non-carbohydrate starting materials. Full article

This study investigates the electrochemical conversion of methane to methanol using fuel-cell-type reactors with palladium- and lanthanum-based catalysts supported on antimony-doped tin oxide (ATO). The combination of these elements demonstrated promising characteristics for selective methanol production. Transmission electron microscopy (TEM) analysis revealed the impact of lanthanum addition on palladium nanoparticles, influencing size distribution and clusters. Polarization curves and power density plots highlighted the Pd₅₀La₅₀/ATO catalyst, indicating an optimal palladium/lanthanum ratio for methanol optimization. FTIR analysis confirmed the presence of methanol in the reaction products, while the methanol production rate showcased the superior performance of the Pd₅₀La₅₀/ATO catalyst compared to other compositions. The synergistic effects between lanthanum’s water activation capability and the carbophilic nature of PdO emerged as crucial factors for the catalyst’s success. Full article

Fast high-temperature gas-phase reactions occurring in the limited space of the arc cavity in the submerged arc welding (SAW) process limit the study of specific gas-phase behaviours. A low-temperature experimental method is applied to investigate gas-phase reactions in the reaction of oxy-fluoride slag with Al-Fe-Ni metal powders. The presence of nano-strands in the slag cavities confirms the vaporisation and re-condensation of gasses. Ti is the main element in nano-strands, although some nano-strands also contain Al-Mg-Si-Na oxy-fluoride. Nano-strand end-caps contain Mn-Fe-Si fluoride, and some contain Ni. The Ni in nano-strand end-caps is sourced from the added Ni powder and indicates gas-phase transfer. The Ti in the nano-strands is sourced from the flux. Themochemistry calculations identify KAlF₄, TiF₃, NaAlF₄, SiF₄, AlF₃, SiF₃, and Na in the gas phase. Increased Al reaction results in decreased TiF₃ in the gas phase, likely due to the displacement of Ti from TiF₃, resulting in the gas-phase transfer of Ti from the flux. Comparative diffusion flux calculations support Ti nano-strand formation via the vaporisation of TiF₃ and the re-condensation of Ti. The low-temperature simulation experiment applied here can be used to study the gas reaction behaviour in the reaction of oxy-fluoride flux with metal powders. Full article

Biorefineries play a critical role in addressing current global sustainability challenges by converting renewable biomass into valuable products such as biofuels, biochemicals, and bioenergy. The necessity of biorefineries has increased due to the growing demand for eco-friendly alternatives to fossil fuels, mitigating climate change, and reducing environmental impact. Utilizing agricultural byproducts, forest residues, and municipal waste, biorefineries harness feedstock through techniques such as pretreatment, anaerobic digestion, and thermochemical transformation, alongside advanced methods including electrochemical processes, hydrogenation of bio-derived substances, and the implementation of complex biocatalysts within biomass-oriented biorefineries. These processes enhance the efficiency of bioenergy production by breaking down complex biomass into simpler components. The current capacity of biorefineries is expanding globally, with increasing interest in advanced technologies such as gasification, fermentation, and enzymatic conversion. While biorefineries offer significant potential for reducing waste and promoting a circular economy, challenges such as scalability and cost efficiency remain. Future trends include integrating new biotechnological advances and optimizing resource recovery systems to improve yield, profitability, and sustainability in the bioeconomy. Full article

In this work, we have developed a method for synthesizing new 8-substituted triazolo[5,1-b]purines using diacetoxyiodobenzene as an oxidizing agent with good yields (59–67%). The advantages of this approach include mild reaction conditions and removing the need to use transition metals. Based on the results obtained, a plausible reaction pathway was proposed. The developed approach opens new possibilities for the preparation of previously inaccessible condensed purine derivatives, which are of interest for the development of biomolecules with a variety of pharmacological applications. The structures of the compounds were confirmed by the data of ¹H, ¹³C NMR spectroscopy, IR spectroscopy, and an elemental analysis. Full article

The microwave-assisted 1,3-dipolar cycloaddition reaction of several aldoximes and dimethyl-2-methylene glutarate in the presence of diacetoxyiodobenzene as an oxidant produced four new isoxazoline-derived dimethyl carboxylates. Saponification followed by acidification of the latter yielded novel isoxazoline dicarboxylic acids in reasonable to high yields. The structures of these novel compounds were characterized by IR, ¹H-NMR, ¹³C-NMR, and HRMS spectroscopy. Their biological activities disclosed higher inhibition of the growth of E. coli organisms by the aromatic compounds than by the aliphatic derivatives, demonstrating their potential in antibiotics research. Full article

In this paper, we report a highly regioselective 1,3-dipolar cycloaddition (1,3-DC) reaction of nitrilimines with thioaurone derivatives that afforded the hitherto unreported spiropyrazolines. Spectroscopic and spectrometric data were utilized to confirm the structure of all products and elucidate the reaction’s regiochemistry. A mechanistic study was performed within the Molecular Electron Density Theory (MEDT) at the B3LYP/6-311G(d,p) computational level to explain the regioselectivity observed. The electron localization function (ELF) topological analysis confirms the carbenoid-type (cb-type) mechanism of the cycloaddition reactions between nitrilimines and thioaurones. The intermolecular interactions between reagents in this reaction account for the regioselectivity observed experimentally. Full article

The present study demonstrated an improvement in both 1-heptene conversion and mono-heptyltoluene selectivity. It simultaneously depicted the isomerization reactions of 1-heptene and toluene alkylation over Y zeolite catalysts having a Si/Al of 3.5 and a surface area of 817 m²/g. The physical properties of the fresh zeolite catalyst were characterized using XRD, FTIR, XRF, TPD, and N₂ adsorption–desorption spectroscopy. The experimental part was carried out in a 100 mL glass flask connected to a reflux condenser at different reaction temperatures ranging from 70 to 90 °C, toluene:1-heptene ratios of 3–8, and catalyst weights of 0.25–0.4 g. The highest conversion of ~96% was obtained at the highest toluene:1-heptene ratio (i.e., 8:1), 0.25 g of zeolite Y, at 180 min of reaction time and under a reaction temperature of 90 °C. However, the selectivity of 2-heptyltoluene reached its highest value of ~25% under these conditions. Likewise, the kinetic modeling developed in this study helped describe the proposed reaction mechanism by linking the experimental results with the predicted results. The kinetic parameters were determined by nonlinear regression analysis using the MATLAB^® package genetic algorithm. The ordinary differential equations were integrated with respect to time using the fourth-order Runge–Kutta method, and the resulting mole fractions were fitted against the experimental data. The mean relative error (MRE) values were calculated from the experimental and predicted results, which showed a reasonable agreement with the average MRE being ~11.7%. The calculated activation energies showed that the reaction rate follows the following order: coking (55.9–362.7 kJ/mol) > alkylation (73.1–332.1 kJ/mol) > isomerization (69.3–120.2 kJ/mol), indicating that isomerization reactions are the fastest compared to other reactions. A residual activity deactivation model was developed to measure the deactivation kinetic parameters, and the deactivation energy value obtained was about 48.2 kJ/mol. Full article

The species Yarrowia lipolytica is an aerobic yeast that produces different lipase isoforms, including extracellular, intracellular, and membrane-bound ones. The immobilization of lipases, such as those from Y. lipolytica, increases enzyme stability and lowers operational costs, through its reuse. The characterization of those biocatalysts is highly important to orientate their technological applications. The present work aims to obtain different Y. lipolytica lipases, through fermentation and immobilization techniques, and to evaluate the ester synthesis and hydrolysis activity of these biocatalysts in comparison to a commercial lipase produced by Candida rugosa and test them for phytosterol ester production. High immobilization yield was achieved by microencapsulating Y. lipolytica lipase extract on magnetic nanoparticles (>99.7%). However, immobilization significantly reduced their activity (more than 90%). Lipases from Y. lipolytica showed greater 4-nitrophenyl laurate synthesis in relation to the lipase from C. rugosa. However, C. rugosa lipase was still the best biocatalyst for β-sitosterol oleate synthesis, with a conversion of more than 99%. Y. lipolytica lipases can be good catalysts for ester hydrolysis reactions, even for ester synthesis, but are not good catalysts specifically for phytosterol esters synthesis. Full article

This study focuses on the collection and UV characterization of the bio-oil phase from primary aerosols ejected from the liquid intermediate phase during the fast pyrolysis of biomass in a hot plate reactor. The effects of the reactor pressure and aerosol-collecting surface temperature on the bio-oil yield and characteristics were evaluated. The study found that lower reactor pressures and a lower temperature of the collecting surface significantly enhanced the aerosol yield (up to 85%). UV-fluorescence was employed to assess the influence of these parameters on the light-to-heavy compound ratio (monomers vs. oligomers). The heavy fraction of bio-oil from the hot plate reactor was predominantly composed of dimers and trimers (340–370 nm), similar to pyrolytic lignin and the heavy fraction of the bio-oil, which also showed peaks in this range. In contrast, pyrolysis oils from auger and fluidized bed reactors displayed two peaks in the UV spectrum, with a maximum around 300 nm, indicating that they are mainly composed of light monomeric compounds. The UV characterization of the primary aerosols and the comparison with the UV spectra of the bio-oil and its fractions (light and heavy fraction and pyrolignin) revealed similar UV prints, highlighting the importance of aerosol ejection in the final composition of bio-oil. Full article

Organic dyes such as methylene blue (MB) and rhodamine 6G (Rh 6G), when dissolved in water, pose a serious threat to the environment, humans, and aquatic life. In this study, we report the synthesis of Fe-doped ZnCuInS/ZnS core/shell quantum dots (FeZCIS/ZnS QDs) in aqueous solution by varying the iron concentrations (0%, 1%, 3%, 5%, 7%, and 10%) for the instant removal of these organic pollutants in contaminated water. The as-synthesized FeZCIS/ZnS QDs were negatively charged and spherical in shape with a diameter of 2.97 nm ± 0.73 nm. Furthermore, it showed improved quantum yield (QYs) compared to the undoped with an average lifetime of 37.15 ns (3% Fe-doped QDs). The undoped ZCIS/ZnS QDs showed percentage removal efficiency of 94.42% and 93.97% for MB and Rh 6G in contaminated deionized water, respectively, and 90.73% (MB) and 1.28% (Rh 6G), respectively, in contaminated rivers. However, the 3% FeZCIS/ZnS QDs showed a percentage removal efficiency of 99.94% and 95.79% for MB and Rh 6G in contaminated deionized water, respectively, and 91.42% and 11.11%, respectively, in rivers contaminated with the dyes. Increasing the concentration of the nanocatalyst to 4 mg/mL improved the removal efficiency of Rh 6G in contaminated rivers to 93.28% and 94.40% using ZCIS/ZnS QDs and FeZCIS/ZnS QDs, respectively. Full article

This study uses the application of Pinch analysis to optimize an integrated electrolyzer and methanation system, a promising approach for producing green hydrogen and synthetic natural gas (SNG). By leveraging renewable energy sources, such as wind and solar, electrolysis is used to produce hydrogen, which reacts with captured carbon dioxide in the methanation reactor to form methane. This process not only allows for efficient energy storage but also supports the reduction of greenhouse gas emissions. A key focus of this study is the optimization of thermal energy flows within the system, which has not been extensively addressed in the literature. Pinch analysis was applied to identify the critical Pinch point, which revealed the temperature at which the most efficient heat recovery could be achieved. The design of a tailored heat exchanger network led to significant improvements, including a 66.45% reduction in hot utility consumption and an 18.85% reduction in cold utility demand. Overall, the system achieved global energy savings of 31.02%. These results were compared with the existing literature, demonstrating that our approach offers comparable or superior utility savings while addressing challenges, such as the complexity of chemical reactions and system integration. This research highlights the potential for substantial operational cost reductions and increasing sustainability in industrial applications, contributing to the advancement of renewable energy technologies and the decarbonization of energy systems. Full article

Despite multiple advances in treatment and prevention, cancer remains one of the leading causes of death worldwide. Chemotherapy remains the most effective method for cancer treatment. However, commercial chemotherapeutic drugs have limited efficacy, severe side effects, and acquired resistance. Therefore, the scientific community has devoted a great effort to designing new, more effective, and cheaper drugs. In this sense, copper-catalyzed azide-alkyne cycloaddition reactions (CuAAC) provide 1,4-disubstituted 1H-1,2,3-triazoles in high yields without forming by-products. This reaction allows the easy, efficient, functional, ordered, rapid, selective, and specific joining of small molecules, giving rise to more complex molecules. The CuACC reaction simplifies the synthesis processes, accelerating the discovery of new chemotherapeutic agents by allowing the joining of commercial platinum drugs, slightly altering their structure, or creating new molecules with improved properties. This work shows the importance of CuAAC reactions in the search for new metallodrugs with possible anticancer activity. Full article