Transformer insulating oils undergo progressive degradation due to oxidation, accumulation of aging byproducts, and contamination by metallic particles. Proper regeneration of these oils is crucial to extend transformer lifespan and reduce environmental impact. This study investigates the performance of locally activated Algerian adsorbents (Illite and Maghnite) compared to commercial adsorbents (activated Bauxite and Sepiolite) for the regeneration of degraded transformer oils. The materials were evaluated for their adsorption efficiency toward acids, water, and oxidation products, as well as their ability to restore key electrical and thermal properties. Activated Illite and Maghnite demonstrated performance comparable to commercial adsorbents, significantly reducing the acid number from 0.23 to 0.01 mg KOH/g. Illite exhibited superior reusability, maintaining regeneration efficiency over 300 cycles. Additionally, sulfur compounds were reduced from 344 to 40 ppm. Treated oils achieved a breakdown voltage of 78 kV and a dielectric dissipation factor of 0.995, closely matching new oil standards. Computational fluid dynamics (CFD) simulations were employed to assess Illite's behavior in industrial-scale oil treatment, supporting its effectiveness as a substitute for Bauxite. The results highlight Illite's potential as a viable, sustainable, and locally available alternative for transformer oil recycling. Nevertheless, challenges related to large-scale implementation, including material availability, cost, and process integration, remain and warrant further investigation. This study contributes to the development of environmentally responsible and economically competitive solutions for the regeneration of insulating oils using natural adsorbents.
تهدف هذه الدراسة إلى تحليل تطور الإيرادات الضريبية البيئية في خمس دول أوروبية خلال الفترة 2010–2023، مع التركيز على مسارها القيمي ونسبتها إلى الناتج المحلي الإجمالي. رغم الاهتمام المتزايد بالضرائب البيئية في أوروبا، لم تتناول الدراسات السابقة بشكل كافٍ تحليل تطور هذه الإيرادات ونسبتها من الناتج على مدى فترة طويلة، مما يبرر هذه الدراسة لفهم دورها ضمن السياسات المالية والنمو المستدام. اعتمدت الدراسة أسلوباً وصفيّاً تحليلياً، وأظهرت النتائج ارتفاعاً مطرداً في قيمة الإيرادات، مقابل استقرار أو انخفاض نسبي في حصتها من الناتج المحلي الإجمالي، بما يعكس انسجامها مع أهداف النمو المستدام. تصنيفات JEL : H23 – Q56
Asphaltene aggregation and deposition pose major challenges in crude oil transport and processing. While extensive experimental studies have explored mitigation strategies, nanomaterials—particularly carbon nanotubes (CNTs)—have emerged as promising inhibitors due to their ability to adsorb asphaltenes and limit their clustering. However, experimental approaches provide limited insight into molecular-scale mechanisms. To address this, molecular dynamics (MD) simulations were performed to investigate interactions between model asphaltenes and CNTs in a toluene/heptane solvent. Five systems were studied: pristine CNTs and CNTs functionalized with carbamoyl (CONH2), methylcarbamoyl (CONHCH3), hydroxymethyl (CH2OH), and carboxylate (COO⁻) groups. Intermolecular interactions and aggregation behavior were analyzed using radial distribution functions (RDF), solvent-accessible surface area (SASA), cluster analysis, hydrogen bonding, and interaction energy decomposition (van der Waals and electrostatic contributions). Results show that CNTs significantly modify asphaltene aggregation, with carboxyl-functionalized CNTs exhibiting the strongest inhibition effect. This performance correlates with enhanced specific interactions between functional groups and asphaltene molecules, leading to reduced aggregation. Geometry optimizations and vibrational frequency calculations of toluene, heptane, the model asphaltene molecule, and the pristine carbon nanotube were performed using the Gaussian software package. These calculations were carried out within the framework of density functional theory (DFT) using the B3LYP functional and the 6-31G(d,p) basis set. The optimized structures obtained were subsequently used to construct the initial configurations for the molecular dynamics simulations and to derive Mulliken atomic charges for force-field parameterization. All-atom molecular dynamics simulations were performed using GROMACS 2023.3 and the OPLS-AA force field. After energy minimization using the steepest descent algorithm, the systems were equilibrated under NVT and NPT ensembles at 298.15 K and 1 bar. Production simulations were subsequently carried out for 150 ns using periodic boundary conditions and a 2 fs integration time step. Temperature and pressure were controlled using the velocity-rescaling thermostat and the Berendsen barostat, respectively. Long-range electrostatic interactions were treated using the Particle Mesh Ewald (PME) method, while bond constraints were maintained using the LINCS algorithm.
The linear optical properties, nonlinear optical properties, and reactivity of various phenols were studied, calculated, and analyzed in detail using quantum chemical calculations. Linear (dipole moment, mean polarizability, polarizability anisotropy) and nonlinear optical properties (total first hyperpolarizability, electric-field-induced second harmonic generation, hyper-Rayleigh scattering hyperpolarizability, and the depolarization ratio) were computed by employing five DFT functionals (B3LYP, PBE0, CAM-B3LYP, ωB97X-D, and M05-2X) in conjunction with the 6311+G** basis set. The differences in (hyper)polarizability as a consequence of phenol structures were consistent among functionals, facilitating the deduction of structure–property relationships. Among the selected phenols, eugenol showed the maximum mean polarizability and polarizability anisotropy of 132.66 and 74.54 a.u., respectively. The β// amplitude was 1.5 to 11 times more than other phenols. A high total first hyperpolarizability βtot up to 640.37 a.u. and a low energy gap Δε less than 3.69 eV were obtained. The βtot amplitude of eugenol is nearly 15 times higher than that reported for urea and almost five times higher than that reported for p-nitroaniline. Hence, we believe that the current investigation would further interest researchers in exploring these phenols in nonlinear optical (NLO) materials.
The chemical versatility of vanillin makes it an attractive candidate for the functionalization of aromatic compounds with potential applications in materials science and pharmaceuticals. This study highlights an unconventional reactivity pattern at a rarely explored site on vanillin's aromatic ring, driven by electronic effects of the hydroxyl and methoxy substituents. Within this context, we report in this work the synthesis of two novel vanillinderived compounds: 3-(5,6-dihydro-[1,3]dithiolo[4,5-b][1,4]dithiin-2-yl)-4-hydroxy-5-methoxybenzaldehyde (I) and 3-(4,5-bis(methylthio)-1,3-dithiol-2-yl)-4-hydroxy-5-methoxybenzaldehyde (II), through the reaction of vanillin with 4,5-ethylenedithio-1,3-dithiole-2-thione (A) and 4,5-bis(methylthio)-1,3-dithiole-2-thione (B). Focusing on an unconventional reactivity pattern near the phenolic hydroxyl group, computational studies using density functional theory (DFT) provided insights into the reaction mechanisms and effectively explained the experimental results. Structural characterization via single-crystal X-ray diffraction and Hirshfeld surface analyses revealed significant non-covalent interactions, including sulfur-sulfur (S & ctdot;S) contacts and hydrogen bonding, which contribute to the supramolecular architecture of these compounds. Preliminary biological assessments demonstrated promising antimicrobial, antioxidant, and anti-inflammatory activities, highlighting the bioactive potential of the synthesized compounds. The combination of structural novelty and biological efficacy suggests that these vanillin derivatives could serve as functional materials in therapeutic and conductive applications. This work not only expands the scope of vanillin chemistry but also opens avenues for further exploration in both synthetic chemistry and bioactive material design.
