Oxidative decarboxylation of fatty acids represents a promising hydrogen-free route for hydrocarbon production, yet catalytic systems operating under moderate aerobic conditions with kinetic and mechanistic validation remain limited. In this study, a biomimetic Mn–Cu catalytic system was evaluated for the oxidative decarboxylation of lauric acid at 110–150 °C under continuous air flow. Reaction performance was assessed through CO₂ evolution as a kinetically relevant indicator of carboxyl-group cleavage, enabling real-time evaluation of decarboxylation activity. The Mn–Cu system exhibited substantially higher catalytic activity than the corresponding monometallic Mn- and Cu-based systems, indicating cooperative interactions between the two metal components. Kinetic analysis showed that the reaction proceeded under an oxygen-coupled regime without an observable induction period. The initial CO₂ formation rate under air reached 0.1863 mmol min⁻¹, approximately 9.3 times higher than that under N₂, confirming the essential role of oxygen in sustaining catalytic turnover. Radical trapping experiments using butylated hydroxytoluene (BHT) resulted in concentration-dependent inhibition of CO₂ formation, reaching up to 73.3%, supporting the involvement of radical species in the decarboxylation pathway. GC–MS analysis confirmed hydrocarbon formation, with C11 compounds as the dominant fraction, consistent with lauric acid decarboxylation. A plausible Mn–Cu-assisted oxygen-coupled pathway is proposed, in which Cu contributes to oxygen activation while Mn facilitates carboxylate oxidation through electron-transfer processes. However, specific Cu–oxygen species, Mn oxidation states, and radical intermediates were not directly identified. Overall, these findings provide coherent kinetic and mechanistic evidence for Mn–Cu-assisted oxidative decarboxylation under moderate aerobic conditions. Copyright © 2027 by Authors, Published by BCREC Publishing Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).
Free α-amylase is readily inactivated at high temperatures and cannot be recovered after starch hydrolysis, which limits its industrial use. Hybrid supports can combine the advantages of their components, but a chitosan–silica gel 60 hybrid has not been reported for Aspergillus fumigatus α-amylase. This study aimed to compare the catalytic properties, thermal inactivation kinetics, and reusability of A. fumigatus α-amylase immobilized on silica gel 60, chitosan, and a chitosan–silica gel 60 hybrid. The enzyme was purified by (30–90)% ammonium sulfate fractionation and dialysis, increasing its specific activity from 702.23 to 3449.43 U/mg (4.9-fold). The hybrid, synthesized with glutaraldehyde as a cross-linker, showed the FT-IR bands of both components with wavenumber shifts, indicating their interaction. The enzyme was immobilized by physical adsorption at an optimum binding pH of 5.0 on all matrices. Immobilization raised the optimum temperature from 50 to 55 °C, increased KM from 3.48 to 4.62–5.80 mg mL−1, and decreased Vmax from 12.97 to 2.72–3.73 μmol mL−1 min−1. After 80 min at 60 °C, the purified enzyme retained 24.8% of its activity, whereas the enzyme immobilized on silica gel 60, chitosan, and the hybrid retained 77.3, 55.1, and 81.1%, respectively. The enzyme–hybrid had the longest half-life (260.85 min; a 6.5-fold increase), the highest free energy of inactivation (109.62 kJ mol−1), and the highest residual activity after six reuse cycles (57%). The chitosan–silica gel 60 hybrid is therefore a more effective support than either of its components for stabilizing and reusing α-amylase.
In this work, a low-cost activated carbon derived from walnut shells (WSAC) was developed through pyrolysis coupled with chemical activation using ZnCl₂. The preparation process was statistically optimized using the Box–Behnken design (BBD) to assess the influence of impregnation ratio, carbonization time, and carbonization temperature on the textural properties of the material. The optimal conditions, predicted by Design Expert, corresponded to a carbonization temperature of 450 °C, a carbonization time of 90 min, and an impregnation ratio of 1:1 (w/w). Under these conditions, the WSAC achieved a high specific surface area of 873 m²/g and a total pore volume of 0.490 cm³/g, indicating a predominantly mesoporous structure. The physico-chemical properties of WSAC, including thermogravimetric analysis, crystalline structure, morphology, functional groups, and surface area, were investigated using various techniques such as TGA-DTG, SEM, XRD, FTIR, pHZPC, and BET analysis. The adsorption behavior of paracetamol (PCT) from aqueous solution was systematically evaluated as a model pharmaceutical contaminant. The effects of solution pH, temperature, initial concentration, and adsorbent dosage were investigated. The adsorption data were best described by the Langmuir isotherm, with a maximum monolayer adsorption capacity of 62.06 mg.g-1, while the kinetic results followed a pseudo-second-order model (R2 = 0.999). It was found that the adsorption mechanism involves hydrogen bonding and phi–phi interactions. Thermodynamic parameters revealed that the adsorption process is spontaneous and exothermic. These results show that WSACs can be an efficient adsorbent for the removal of PCT or other pharmaceutical pollutants from water. Copyright © 2027 by Authors, Published by BCREC Publishing Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).
Biodiesel’s cold flow properties, limited by the crystallisation of saturated and trans‑unsaturated fatty acid methyl esters (FAMEs), can be improved through skeletal isomerisation of unsaturated FAMEs to branched‑chain isomers. Zeolite‑β has shown promise for this reaction, but detailed characterisation of the complex isomer mixture remains challenging. This study investigates the isomerisation of methyl oleate over Zeolite‑β (H‑β) in a batch reactor at 200 °C and atmospheric pressure for 6 h, using 10 wt% catalyst. A conversion of 92.2% was achieved, confirming high catalyst activity. However, analysis by gas chromatography–mass spectrometry (GC–MS) with a polar BPX70 column revealed significant limitations: the product chromatogram showed extensive peak overlap, and the mass spectra of positional, geometric, and branched‑chain isomers were nearly identical, preventing reliable determination of selectivity and yield. The work highlights that conventional GC–MS is inadequate for full isomer speciation in such complex mixtures. Advanced techniques such as comprehensive two‑dimensional GC (GC×GC), silver‑ion chromatography, or high‑resolution mass spectrometry are required for accurate isomer identification. These findings establish a performance baseline for Zeolite‑β and delineate the analytical challenges that must be addressed to enable rational catalyst and process optimisation for improved biodiesel cold flow properties. Copyright © 2027 by Authors, Published by BCREC Publishing Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).
Rice husk (RH), an abundant agricultural residue, is a promising precursor for the production of carbon- and silica-based catalyst supports for upgrading lipid feedstocks. Previous studies have shown that RH-derived biochar and biosilica can serve as effective catalyst supports in reactions involving relatively small molecules; however, their application in the deoxygenation of lipid-derived molecules remains largely unexplored. In this study, RH was converted into three distinct supports, desilicated biochar (RH-C), KOH-activated desilicated biochar (RH-AC), and biosilica (RH-SiO₂), which were systematically compared as supports for Ni catalysts in the solvent-free deoxygenation of oleic acid. The supports and catalysts were characterized by BET, TEM, XRD, XPS, and TGA. Ni/RH-AC exhibited the highest surface area (809.8 m2.g-1) but lower mesopore volume than Ni-RH-C, while Ni/RH-SiO2 showed moderate surface area and minimal microporosity. XPS revealed minimal electronic perturbation of Ni supported on biochar, whereas biosilica induced electron withdrawal. All catalysts predominantly followed the decarboxylation/decarbonylation (deCOx) pathway, although Ni/RH-SiO2 also exhibited noticeable hydrodeoxygenation (HDO). Ni/RH-C achieved the highest conversion (96%), while Ni/RH-AC and Ni/RH-SiO2 achieved 76% and 72%, respectively. TGA/DSC analysis showed greater carbonaceous material deposition on Ni/RH-AC than on Ni/RH-C, with Ni/RH-SiO2 exhibiting the lowest coking. These findings reveal a clear structure-property-performance relationship, revealing that desilicated rice-husk biochar provides higher catalytic activity, whereas biosilica offers greater stability and lower susceptibility to coking. Moreover, excessive chemical activation after desilication appears unnecessary and may even be detrimental. Copyright © 2026 by Authors, Published by BCREC Publishing Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).
