Optimizing cold-flow properties and oxidation stability of B40 biodiesel blend with turpentine oil and ethanol: Experimental and quantum chemical approach

This study investigates the effectiveness of turpentine oil and ethanol as cold-flow improvers (CFIs), synergizing as antioxidants for ternary B40 biodiesel blend. Utilizing the response surface methodology (RSM), the effects of these CFIs on the ternary blend, including cloud point (CP), cold filter plugging point (CFPP), filter blocking tendency (FBT), precipitation, and oxidation stability, were comprehensively evaluated. The analysis of variance (ANOVA) presented that a linear model best describes the impact of CFIs on CP, whereas quadratic models more accurately represent CFPP, FBT, and oxidation stability. The results also demonstrate that 2FI was identified as the most suitable model for describing precipitation responses. The optimal concentrations of turpentine oil and ethanol were determined to be 10 % v/v and 0.5 % v/v, respectively, resulting in predicted values for CP, CFPP, FBT, precipitation, and oxidation stability of 10.4 °C, 9.0 °C, 1.31, 9.09 mg/100 mL, and 225 minutes, respectively. Theoretical insights from density functional theory (DFT) calculations confirmed that the primary interaction controlling wax formation in biodiesel blends is the strong hydrogen bonding between monostearin and pinene, a major component of turpentine oil, which effectively disrupts wax crystallization. This study presents a novel approach to enhancing B40 biodiesel cold-flow properties and maintaining its oxidation stability by utilizing the synergistic effects of turpentine oil and ethanol to optimize B40 biodiesel formulation.