Reactions

In this study, methyl/^tbutyl salicylate-bearing zirconium complexes (C1–C8) were prepared by the reaction of zirconium (IV) propoxide/butoxide with salicylic acid, 3-methylsalicylic acid, 4-methylsalicylic acid, and 3,5-di-tert-butylsalicylic acid in alcohols, respectively. All these complexes (C1–C8) were characterized by ¹H NMR, ¹³C NMR, FTIR, mass spectroscopy (MS), elemental, and thermogravimetric analyses (TGA). These complexes were utilized as catalysts in the ring-opening polymerization (ROP) of Ɛ-caprolactone and were very effective. Polycaprolactone (PCL) was characterized by ¹H-NMR, ¹³C NMR, and gel permeation chromatography (GPC). In this study, perhaps for the first time, the effects of electron-donating substituents (Me and ^tBu) on Ɛ-caprolactone polymerization reactions on salicylate ligands linked to zirconium atoms were investigated. Full article

Edible oils are one of the renewable sources that enable the possibility of producing biodiesel sustainably. The transesterification of canola oil with methanol using cesium-modified phosphotungstic acid (Cs_2.5H_0.5PW₁₂O₄₀) as a heterogeneous catalyst was studied. Reaction conditions, specifically reaction time, catalyst loading, and the ratio of methanol to canola oil, were systematically explored. The canola oil conversion reached 55% at room temperature after 24 h. The reusability tests showed that the conversion of canola oil to biodiesel was maintained. Full article

N-alkylated C₂-symmetric amino acid amide derivatives were shown to catalyse the Michael addition of 2-hydroxy-1,4-napthoquinone to β-nitrostyrene, achieving a maximum ee of 44%. The corresponding trifluoroacetic acid salts also catalysed the aldol reaction between 4-nitrobenzaldehyde and hydroxyacetone, leading to the formation of predominantly syn-aldol products in up to 55% ee. Aspects of the solvent dependence of the aldol reaction and the H-bonding of the catalyst were investigated. Full article

The present review is a comprehensive update of the synthesis of monocyclic β-lactams via cycloaddition reactions. According to the IUPAC definition of cycloaddition, both elementary and stepwise processes (formal cycloadditions) have been considered. The years 2019–2022 are covered by the cited literature. The focus of the review is on synthetic aspects with emphasis on the structural scope, reaction conditions, mechanistic aspects, and selectivity results. Selected significant data related to biological activities and synthetic applications are also highlighted. Full article

The aim of this work was to develop a kinetic model based on the power law to describe the evolution of glycerol conversion and product distribution in the crude glycerol (G) acetylation reaction with acetic acid (AA) without the use of a catalyst. For this purpose, experimental tests were carried out with analytical glycerol under different reaction conditions (T = 80–160 °C, AA/G = 1–9 molar ratio, t = 0.25–2 h). The results showed the formation of mono- (MAG), di- (DAG) and tri- (TAG) acetylglycerols, liquid products with multiple applications in the chemical industry. From these results, a kinetic model based on the power law was implemented, which could acceptably estimate the experimental concentrations with an average relative error of 14.9%. Then, crude glycerol samples from different biodiesel industries were characterized by identifying and quantifying the impurities present in them (H₂O, CH₃OH, NaOH, NaCOOH, MONG and NaCl), and employed as reactants in the reaction tests. Given the significant differences observed in the glycerol conversion values compared to those obtained with analytical glycerol, further reaction tests were conducted to elucidate the effect of each impurity over the glycerol conversion. In these tests, the different impurities were added individually, maintaining the same concentration range as that of the crude glycerol samples. From the results obtained, global activity factors were introduced, which allowed us to modify the kinetic model to estimate glycerol conversions in the crude glycerol samples with an average relative error of 7%. It is hoped that this kinetic model will be a powerful tool useful for designing reactors on an industrial scale. Full article

Calcium molybdate (CaMoO₄) is of significant interest due to its unique properties and numerous industrial applications, such as catalysis, electrochemistry, and optoelectronics. In this study, we developed an economical and environmentally friendly method to synthesize calcium molybdate from Moroccan phosphogypsum (PG) industrial waste and sodium molybdate, all at room temperature. Comprehensive analysis through X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Raman vibrational spectroscopy, and scanning electron microscopy (SEM) revealed the high purity of the synthesized calcium molybdate, with particle sizes of only 12 nm. Additionally, optical characteristics were studied using ultraviolet-visible spectroscopy (UV-vis), which showed an optical band gap of Egap = 3.96 eV for CaMoO₄. These results confirm the successful synthesis of calcium molybdate nanoparticles from Moroccan phosphogypsum, demonstrating an effective pathway to valorize this industrial waste into a valuable material. This approach contributes to environmental sustainability by reducing dependence on rare chemicals while offering innovative solutions for the industry’s sustainable development. Full article

Nonaqueous flow batteries hold promise given their high cell voltage and energy density, but their performance is often plagued by the crossover of redox compounds. In this study, we used permselective lithium superionic conducting (LiSICON) ceramic membranes to enable reliable long-term use of organic redox molecules in nonaqueous flow cells. With different solvents on each side, enhanced cell voltages were obtained for a flow battery using viologen-based negolyte and TEMPO-based posolyte molecules. The thermoplastic assembly of the LiSICON membrane realized leakless cell sealing, thus overcoming the mechanical brittleness challenge. As a result, stable cycling was achieved in the flow cells, which showed good capacity retention over an extended test time. Full article

Carbon nanotubes (CNTs) are cylindrical-shaped materials composed of hexagonally arranged hybridized carbon atoms with versatility in synthesis methods and diverse applications. This review is focused on the fabrication, physicochemical and spectroscopic characterization, and industrial applications of CNTs. This review discusses some promising synthesis methods for the preparation of CNTs such as catalytic chemical vapor deposition, arc discharge, and laser ablation. A comparative discussion is made between these synthesis methods in terms of strengths, opportunities and challenges. Furthermore, functionalization and purification of CNTs’ surface leading to improved functionality has also been highlighted in this article. Finally, the analytical techniques employed to shed light on the physicochemical and morphological properties of CNTs are described. Full article

The first hydrogenation of most metal hydrides is a lengthy process that usually requires high pressure and temperature. This, in turn, significantly increases the production cost of metal hydrides. In this paper, the low temperature hydride-forming LaNi5 was selected to investigate the mechanism of first hydrogenation. For the first time, the effect of particle size, temperature and pressure on the incubation time were studied. We found that the first hydrogenation of LaNi₅ follows an Arrhenius process, with an activation energy of E_A = 78 ± 4 kJ/mol H₂. We also found that the pre-exponential factor depends on the applied pressure. Full article

Poultry litter was converted to biochar by torrefaction and to hydrochar by hydrothermal carbonisation. Many parameters were measured for the resulting chars, to investigate the effects of the production method and production temperature. SEM showed the presence of large quantities of crystalline material on the surface of the biochars. The elemental composition of some crystals was determined as 35% K and 31% Cl. This was confirmed as sylvite (KCl) crystals, which explains the high levels of water-extractable potassium in the biochar and may also be important in germination inhibition. Biochars almost totally inhibited germination, whilst hydrochars decreased germination. Although germination occurred on hydrochar, root growth was severely inhibited. Consequently, the germination index may be better to determine total phytotoxicity as it measures both effects and could be used as a bioassay for chars used as soil amendments. Washing removed germination inhibition in a low-temperature char (350 °C), possibly by removing KCl; however, root toxicity remained. There were very low levels of heavy metals, suggesting they are not the source of toxicity. In biochars, pore mean size decreased with temperature from 350 °C to 600 °C, due to changes in pore size distribution. The mean pore size was measured directly using SEM. The merits of this method are discussed. Low-temperature biochars seem best suited for fuel as they have a high calorific value, high hydrophobicity, a low ash content and a high yield. Higher temperatures are better for soil amendment and sequestration applications with a smaller mean pore size, higher surface area, and higher pH. Full article

Among the different polyoxometalate compounds, Keggin heteropolyacids have been extensively used as catalysts in several acid-catalyzed reactions, due to their strong strength of Bronsted acidity. These metal–oxygen clusters have a highly versatile structure that allows their conversion to derivatives, which are catalysts that are much more efficient than their precursors, with a greater catalytic activity in a plethora of reactions of industrial interest. Particularly, due to the inevitable exhaustion of fossil sources, reactions to valorize biomass have attracted significant attention, since it is a precious renewable raw material that can provide fine chemicals or fuels, minimizing our dependence on petroproducts. Biorefinery processes can produce platform molecules to achieve this goal. In this review, the recent advances achieved in the development of routes to converting biomass feedstocks to levulinic acid and furfural, which are valuable ingredients in biorefinery processes, using Keggin heteropolyacid catalysts were assessed. Full article

Process design critically depends on the characterization of fuels and their kinetics under process conditions. This study steps beyond the fundamental methods of thermogravimetry to modulated (MTGA) and Hi-Res™ (high resolution) techniques to (1) add characterization detail and (2) increase the utility of thermal analysis data. Modulated TGA methods overlay sinusoidal functions on the heating rates to determine activation energy as a function of temperature with time. Under devolatilization conditions, Hi-Res™ TGA maintains a constant mass loss with time and temperature. These two methods, run independently or overlaid, offer additional analysis in which multiple samples at different heating rates are run to different final temperatures. Advanced methods allow researchers to use fewer samples by conducting fewer runs, targeting practical experimental designs, and quantifying errors easier. The parameters of the studies included here vary the heating rate at 10, 30, and 50 °C/min; vary gas-phase oxygen for pyrolysis or combustion conditions; and particle size ranges of 100–125 µm, 400–425 µm, and 600–630 µm. The two biomass fuels used in the studies are pinewood from Northern Sweden and wheat straw. The influence of torrefaction is also included at temperatures of 220, 250, and 280 °C. Apparent activation energy results align with the previous MTGA data in that combustion conditions yield higher values than pyrolysis conditions—200–250 kJ/mol and 175–225 kJ/mol for pine and wheat combustion, respectively, depending on pre-treatment. Results show the dependence of these parameters upon one another from a traditional thermal analysis approach, e.g., the Ozawa-Flynn-Wall method, as well as MTGA and Hi-Res™ thermogravimetric investigations to show future directions for thermal analysis techniques. Full article

This study combines theoretical modeling and experimental validation to explore anaerobic digestion comprehensively. Developing a computational model is crucial for accurately simulating a digester’s performance, considering various feedstocks and operational parameters. The main objective was to adapt the anaerobic digestion model 1 (ADM1) simulation code to align with the laboratory-scale anaerobic digestion reactor’s specifications, especially regarding the liquid–gas transfer process. Within this computational framework, users may define model parameters and elucidate processes occurring in compartments reflecting the physical design. The model accurately predicts total concentrations of chemical oxygen demand (COD) as well as the produced biogas, with an average difference of less than 10% between experimental and simulated data. This consistency underscores the reliability and effectiveness of the adapted model in capturing anaerobic digestion nuances under specified conditions. Full article

C-H borylation is a powerful strategy for the construction of C-B bonds due to the synthetic versatility of C-B bonds. Various transition metals affect the powerful functionalization of C-H bonds, of which Ir is the most common. Substrate-directed methods have enabled directed Ir-catalyzed C-H borylation at the ortho position. Amongst the powerful directing groups in Ir-catalyzed C-H borylation are N-containing carbocyclic systems. This review covers substrate-directed Ir-catalyzed ortho-C-H borylation of aromatic C(sp2)-H bonds in N-containing carbocyclic compounds, such as anilines, amides, benzyl amines, hydrazones, and triazines. Full article

Approximate models are a fast and most often precise tool for determining the effectiveness factor for heterogeneous catalysis processes that are realized in the real world. They are also frequently applied as robust transient models describing the work of a single catalyst pellet or as a part of a more complex model, for example, a reactor model, where mass balances for the gas phase and solid phase are necessary. So far, approximate models for diffusion and reaction processes have been presented for processes described by a single balance equation. In the present work, approximate models without the mentioned limitation are presented and discussed. In addition, simple rules are shown for the development of other complex approximate models without tedious derivation in the complex domain. The formulas considered in this work are typical long-time approximations of the transient process. The accuracy is good, especially in the range of small and intermediate Thiele modulus values. Full article

The treatment of wastewater worldwide generates substantial quantities of sewage sludge (SS), prompting concerns about its environmental impact. Various approaches have been explored for SS reuse, with energy production emerging as a viable solution. This study focuses on harnessing energy from domestic wastewater treatment (WWT) sewage sludge through plasma gasification. Effective syngas production hinges on precise equipment design which, in turn, depends on the detailed feedstock used for characterization. Key components of plasma gasification include the plasma torch, reactor, heat exchanger, scrubber, and cyclone, enabling the generation of inert slag for landfill disposal and to ensure clean syngas. Designing these components entails considerations of sludge composition, calorific power, thermal conductivity, ash diameter, and fusibility properties, among other parameters. Accordingly, this work entails the development of an experimental setup for the plasma gasification of sewage sludge, taking into account a comprehensive sludge characterization. The experimental findings reveal that domestic WWT sewage sludge with 40% humidity exhibits a low thermal conductivity of approximately 0.392 W/mK and a calorific value of LHV = 20.78 MJ/kg. Also, the relatively low ash content (17%) renders this raw material advantageous for plasma gasification processes. The integration of a detailed sludge characterization into the equipment design lays the foundation for efficient syngas production. This study aims to contribute to advancing sustainable waste-to-energy technologies, namely plasma gasification, by leveraging sewage sludge as a valuable resource for syngas production. Full article

Diverse studies have showed that the pesticides can cause important damages in ecosystem. Therefore, the development of bio pesticides through nanotechnology can increase efficacy and limit the negative impacts in the environmental that traditionally seen through the use of chemical pesticides. Nanoparticles obtained from plants’ extracts can be used for effective pest management as a combined formulation of metal and some other organic material present in the plants. In the present study, our evaluated biosynthesis of nanoparticles of copper used two plant extracts (Acacia cornigera and Annona purpurea), and the Taguchi method was adopted for the synthesis optimization of the following variables of biosynthesis: temperature, pH, extract concentration, and reaction times to maximize the insecticidal activity on Tribolium castaneum. Our results showed that the nanoparticles were successfully synthesized using Acacia cornigera and Anona purpurea extract under optimum conditions under Taguchi L 9 orthogonal design, where copper nanoparticles were obtained with a size of 63–153 nm for using A. cornigera extract, 87–193 nm for A. purpurea extract, and a zeta potential of 9.6 mV and −32.7 mV, respectively. The nanoparticles of copper from A. cornigera showed effective insecticidal activity against Tribolium castaneum, and 90% mortality compared to the 76.6% obtained from nanoparticles of copper from A. purpurea. The results suggest that Cu-nanoparticles derived from both plants could be used as a biocontrol agent of Tribolium castaneum, a pest of stored grain with great economic importance. Full article

Bioethanol, which is currently produced commercially from a growing variety of renewable biomass and waste sources, is an appealing feedstock for the production of fuels and chemicals. The literature clearly shows that bioethanol is a versatile building block to be used in biorefineries. The ethanol conversion using several catalysts with acidic, basic, and redox characteristics results in a diverse assortment of high-value bioproducts. High-acidity tungsten zirconia-based catalysts are stated to compete with traditional zeolitic catalysts and can be employed in the dehydration of ethanol to ethylene, but for a low reaction temperature acetic acid is formed, which causes corrosion issues. WO₃-ZrO₂ (W/Zr = 1, atomic) catalysts modified with MoO₃ were prepared by a sol-gel-like procedure and tested in a gas phase ethanol conversion in the presence of air. The citrate derived xerogels were annealed at 853 K for 12 h, allowing low surface area (<10 m²/g) materials with a Mo-W mixed-oxide-rich surface over tetragonal nanostructured zirconia. Catalysts with MoO3-loading produced mainly acetaldehyde, instead of ethylene, as a result of the high reducibility of Mo⁶⁺ when compared to W⁶⁺. During the reaction, the Mo⁶⁺ becomes partially reduced, but Mo⁶⁺/Mo⁵⁺ species are still active for methanol conversion with increased ethylene selectivity due to the high acidity of tetrahedral MO_X species formed during the reaction. Adding water to ethanol, to simulate bioethanol, only leads to a slight inhibition in ethanol conversion over the MoO₃/(WO₃-ZrO₂) catalysts. The results show that molybdenum oxide deposited on tungstated zirconia catalyst is active, with low sensitivity to water, for the valorization of bioethanol into high-value chemicals, such as ethylene and acetaldehyde, and whose selectivity can be tuned by changing the amount of MoO₃ that is loaded. The MoO₃/(WO₃-ZrO₂) catalysts prepared show catalytic behavior similar to that of noble metal-based catalysts reported in the literature for the dehydrogenation of bioethanol in high-value chemicals. Full article

Computer simulation is a crucial element in the design of chemical processes. Although numerous commercial software options are widely recognized, the expense associated with acquiring and sustaining valid software licenses can be prohibitive. In contrast, open-source software, being freely available, provides an opportunity for individuals to study, review, and modify simulation models. This accessibility fosters technology transfer and facilitates knowledge dissemination, benefiting both academic and industrial domains. In this study, a thermodynamic equilibrium steady-state analysis of steam methane reforming using a natural-gas-like intake fuel was conducted. An analytical method was developed on the Microsoft Excel platform, utilizing the material balance equations system. The obtained results were compared to numerical methods employing the free-of-charge chemical process simulation software COCO and DWSIM. The investigation explored the influence of temperature, pressure, and steam-to-carbon ratio to determine optimal operating conditions. The findings suggest that higher temperatures and lower pressures are highly favorable for this process, considering that the choice of steam-to-carbon ratio depends on the desired conversion, with a potential disadvantage of coke formation at lower values. Consistent results were obtained through both analytical and numerical methods. Notably, simulations performed using DWSIM showed a deviation of 6.42% on average compared to COCO values. However, it was observed that the analytical method tended to overestimate the results by an average of 3.01% when compared to the simulated results from COCO, highlighting the limitations of this analytical approach. Full article