Ethanol‐Based Biodiesel Production From Cottonseed Oil via Water‐Tolerant Thermally Induced Noncatalytic Transesterification

Biodiesel is a renewable fuel that replaces petro‐diesel in the transportation sector and supports efforts to resolve anthropogenic global warming. However, the use of methanol in biodiesel production lowers its sustainability because methanol is being produced from natural gas. The use of biomass‐derived ethanol in biodiesel production offers a more sustainable basis. Despite the environmental advantages of ethanol, its residual water content limits its practical application in conventional base‐catalyzed processes. This study proposes a thermally induced noncatalytic process for ethanol‐based biodiesel production. In this process, thermal energy induces the cleavage of ester bonds in triglycerides, generating fatty acid intermediates that subsequently react with ethanol to form fatty acid ethyl esters (FAEEs). Meanwhile, the confinement effect provided by a porous material enhances interfacial contact between the immiscible reactants and accelerates the reaction without externally applied pressure. Cottonseed (23.8 wt.% of oil content) was used as a biodiesel feedstock. Due to the steric hindrance caused by ethanol’s larger molecular size, conventional base‐catalyzed transesterification yielded 14.2 wt.% biodiesel at 70°C for 120 min. In contrast, thermally induced noncatalytic transesterification produced up to 88.1 wt.% biodiesel at 380°C in 1 min. With increasing water content, the FAEE yield decreased to 76.9 wt.% at 10 wt.% water, while a relatively high yield of 85.4 wt.% was maintained at 4 wt.% water, corresponding to 96 wt.% ethanol. These results suggest the potential of utilizing water‐containing ethanol as the alcohol feedstock for transesterification. Moreover, the use of FAEE produced through the noncatalytic transesterification of cottonseed oil was estimated to mitigate carbon dioxide (CO ₂ ) emissions by 1.16 g g _seed ⁻¹ . Accordingly, the application of thermally induced noncatalytic process for ethanol‐based biodiesel production would strengthen the shift toward sustainable transport systems.