Saturated monoglyceride effects on low-temperature performance of biodiesel blends

Abstract

The effect of saturated monoglyceride (SMG) content of four B100s on the cloud point (CP) of blends with four diesel fuels was examined. Detecting CP with a more sensitive light-scattering method allowed observation of an early (higher temperature) CP in blends containing approximately 0.01wt.% to 0.03wt.% SMG. Blend samples with SMG content in this range may be particularly prone to unexpected filter clogging above the measured CP. Results for a 140 blend sample matrix revealed that SMG content had a larger effect on CP than other blend properties. An increase of 0.01wt.% SMG in a biodiesel blend increased CP by as much as 4°C. At a constant SMG level, increasing biodiesel content lowered CP, as did increasing the diesel fuel aromatic content, by improving the solubility of SMG. This implies that lowering the SMG content of a B100 allows preparation of higher biodiesel content blends having the same or lower CP. Increasing the unsaturated monoglyceride-to-SMG ratio by blending in monoolein lowered CP, presumably because monoolein inhibits nucleation of SMG. In most blends with SMG content above 0.01wt.%, polymorphic phase transformation of crystallized SMG (converting from the metastable α-form to the less soluble, stable β-form) was observed.