Abderrahim Bouaid

To mitigate the environmental footprint of the aviation sector, this study proposes an integrated cascading biorefinery scheme to produce Sustainable Aviation Fuel (SAF) precursor bloodstock via enzymatic transesterification of coconut oil. Utilizing a synergistic binary alcohol system (ethanol-butanol) and the liquid lipase Eversa Transform 2.0, a strategic molecular reconfiguration of fatty acid esters was achieved. Optimization through Response Surface Methodology (RSM) identified critical parameters—5% catalyst loading, total binary alcohol-to-oil molar ratio of 7:1 (specifically comprised of a 2.5:4.5:1 ethanol/butanol/coconut oil matrix), and an operation temperature of 57.5 °C—yielding a 97% conversion efficiency. A sequential vacuum fractional distillation process was implemented to partition the ethyl-butyl esters into high-value streams. Notably, the light distillate fraction, characterized by a specific carbon chain distribution (C6: 27.2%, C8: 52.5%, C10: 6%, and C12: 13.6%), perfectly aligns with the molecular window of aviation kerosene. This fraction exhibits excellent cold-flow properties, viscosity, and volatility profiles, positioning it as an ideal high-performance SAF precursor blendstock to increase the renewable content of current aviation fuels. Simultaneously, the remaining C16–C18 residue serves as a high-density energy source for internal refinery processes, while C8–C14 species are recovered as high-purity chemical feedstocks. This circular model maximizes carbon atom economy and economic viability by cogenerating high added-value biochemicals alongside jet-grade blendstocks. These findings provide a scalable, enzymatic framework for the next generation of decarbonized aviation fuels.

In this paper, batch stirred-tank alcoholysis reactions of used and refined sunflower oils were performed with n-octyl, myristyl, cetyl, oleyl, and stearyl alcohols using immobilized lipases Novozym 435 and Lipozyme IM as catalysts. Alcohol conversions ranged from 74% to 94%, with slight differences between used frying sunflower oil and refined sunflower oil. The resulting wax esters were purified via stepwise column chromatography. The different regioselectivity of the biocatalysts led to distinct reaction pathways, and Novozym 435 proved to be the most effective enzyme, providing higher conversions and no detectable by-products. This study demonstrates the valorization of waste frying oils into high-value wax esters through enzymatic alcoholysis, comparing two industrially relevant immobilized lipases and achieving high conversion across multiple long-chain alcohols. The results highlight a sustainable alternative to conventional chemical catalysis and extend biocatalytic applications beyond traditional biodiesel production. By incorporating waste lipids into value-added products, the overall sustainability and circularity of the system are improved, contributing to green and sustainable chemistry.

A novel and cost-effective heterogeneous catalyst for glycerol carbonate production through transesterification was developed by impregnating smectite clay with K₂CO₃. Comprehensive structural and chemical analyses, including X-ray diffraction Analysis (XRD), Scanning Electron Microscopy (SEM)-Electron Dispersion Spectroscopy (EDS), Fourier Transform Infrared Spectroscopy (FTIR), and Brunauer-Emmett-Teller (BET) surface area analysis measurements, were employed to characterize the catalysts. Among the various catalysts prepared, the one impregnated with 40 wt% K₂CO₃ on smectite and calcined at 550 °C exhibited the highest catalytic activity, primarily due to its superior basicity. To enhance the efficiency of the transesterification process, several reaction parameters were optimized, including the molar ratio between propylene carbonate and glycerol reactor loading of the catalyst and reaction temperature. The highest glycerol carbonate conversion rate, approximately 77.13% ± 1.2%, was achieved using the best catalyst under the following optimal conditions: 2 wt% reactor loading, 110 °C reaction temperature, 2:1 propylene carbonate to glycerol molar ratio, and 6h reaction duration. Furthermore, both the raw clay and the best calcined K₂CO₃-impregnated catalysts demonstrated remarkable stability, maintaining their high activity for up to four consecutive reaction cycles. Finally, a kinetic analysis was performed using kinetic data from several runs employing raw clay and the most active K₂CO₃-modified clay at different temperatures, observing that a simple reversible second-order potential kinetic model of the quasi-homogeneous type fits perfectly to such data in diverse temperature ranges.

The use of non‐edible oils for energy production is attracting increasing attention, with a particular focus on those oils that can be produced from plants growing in non‐arable areas. Among the possible alternatives, oils with high free fatty acid content, such as jatropha, have shown great potential. The optimization of jatropha oil in the presence of a bio‐based alcohol (butanol) was investigated for the production of biodiesel using a commercial enzyme (Eversa from Novozymes). The optimization was conducted by changing the reaction temperature and the amount of catalyst, with a 6:1 butanol/oil molar ratio, while the reaction time was set to 60 min. The optimal result was found at the highest reaction temperature (42 °C) and the highest catalyst amount (9.79%), with a biodiesel yield of 83%. A second optimization was conducted, allowing the time to run for up to 8 h. Here the final biodiesel produced was in line with the EU14214 standards, fulfilling all the requirements with the exception of the requirement for oxidation stability. In addition to fulfilling most of the EU14214 standards, the cost of this new enzyme is lower than that of other commercial alternatives. Results show that biodiesel produced using butanol as alcohol in the transesterification process improved cold flow properties in terms of cloud point (CP), pour point (PP), and cold filter plugging point (CFPP). © 2021 The Authors. Biofuels, Bioproducts and Biorefining published by Society of Industrial Chemistry and John Wiley & Sons Ltd.

An innovative biorefinery approach has been applied to evaluate jojoba oil (JO) in high value‐added products. It consists of enzymatic transesterification using short (1‐propanol, 1‐butanol), medium linear (1‐octanol), and branched (2‐ethylhexanol) chain alcohols. The proposed biorefinery approach uses an integrated process for the production of jojobyl alcohol (JA) mixtures (11‐eicosenol, 13‐docosenol and 15‐tetracosenol) as products that can be used in pharmaceutical applications. The remaining fraction of fatty acid alkyl esters (FAAE) has a wide range of industrial uses and could be used as a promising alternative to conventional fuels, as it complies with EN14214, the European Biodiesel Norm. The separation of JA from FAAE was carried out by crystallization using a binary mixture of hexane and diethyl ether. After the separation step, the main properties of FAAE were determined. The results showed that the cold flow properties and oxidation stability of the FAAE fraction, obtained as co‐product during the process, have been improved with respect to transesterified JO. The use of 2‐ethylhexanol as an alcohol in the transesterification reaction increases the amount of the most valuable fraction containing JAs. In vitro cell viability was measured in HEK293T cells using the tetrazolium dye reduction (MTT) assay. The results showed that this oily liquid mixture of JA components (cis‐11‐eicosenol, cis‐13‐docosenol, and cis‐15‐tetracosenol) had a cytotoxic effect at concentrations of 10 and 100 μmol L⁻¹ and no cytotoxic activity at 1 μmol L⁻¹. The concentration of 1 μmol L⁻¹ does not, therefore, modify the cell viability, does not produce toxic effects in the tested cells and could be used as a therapeutic compound. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd