Winterization of Vegetable Oil Blends for Biodiesel Fuels and Correlation Based on Initial Saturated Fatty Acid Constituents

Winterization is a simple method to remove saturated fatty acid contents in biodiesel fuels for improving their cold flow properties. In this work, biodiesel fuels with different initial long-chain (C16 and above) saturated fatty acid constituents (S_i) were prepared from blends of palm, canola, and corn oils. The prepared biodiesels were treated at various winterization temperatures (T_w) to investigate the effect of T_w and S_i on the final saturated fatty acid constituents (S_w) of the winterized biodiesel fuel. Optical microscopy showed that ball-like crystals formed with fluid regions at moderate cooling rates (-6 °C/h) could allow solid-liquid separation by filtration. A saturated fatty acid reduction ratio, R_s, defined as (S_i - S_w)/S_i × 100, was used with the experimental results on large samples (ca. 600 mL) to develop a correlation for winterization temperature as T_w (°C) = 0.659 S_i (wt%) - 0.104 R_s (wt%) - 10.197. The correlation can provide estimation of the required winterization temperature for reducing a specified ratio of fatty acids in a biodiesel fuel that mainly contains long-chain fatty acids from the initial saturated fatty acid constituents. When used with literature relationships for cold filter plugging point (CFPP) and S_w, estimation of the CFPP of winterized biodiesel fuels is possible without requiring actual winterization treatment.