Precipitation above cloud point in palm oil based biodiesel during production and storage

Precipitation of a white solid in palm oil based biodiesel (PO-B100) can be found even in PO-B100 that contains minor contaminants (i.e. mono-, di- and triglycerides) within the limitation according to EN-14214 and Thailand’s regulation. To identify compounds causing this precipitation, the precipitates collected at the temperature near cloud point and at room temperature were characterized using a gas chromatograph-flame ionization detector, gas chromatograph-mass spectrometry and fourier transform-infrared. The result indicated that the compounds causing the precipitation were steryl glucosides, not glycerides, regardless of temperature. Therefore, effect of steryl glucosides on precipitation time was further investigated using PO-B100s with different amounts of steryl glucosides, mono-, di- and triglycerides. The result revealed that precipitation time of the PO-B100 with high concentration of steryl glucosides was much less than the one without steryl glucosides and decreasing steryl glucosides concentration to 20 ppm significantly improved storage stability of PO-B100. In addition, the precipitation time was not influenced by concentration of mono-, di- and triglycerides.