Precipitate Formation above the Cloud Point in Soy-, Cottonseed-, and Poultry Fat-based Biodiesel Blends Haiying Tang, Steve O. Salley, and K. Y. Simon Ng National Biofuels Energy Laborotory NextEnergy/Wayne State University Detroit, MI Present to International Congress on Biodiesel: The Science and The Technologies November 7, 2007

Precipitates formation in biodiesel blend may have serious implications. –Clog fuel filter for diesel engine fuel delivery system. –Formed deposits on engine parts such as injectors and other critical fuel system. Cold Flow Properties: a current issue with biodiesel

Cold –flow properties: traditional petroleum wax precipitation –Cloud point (CP, ASTM 2500): at which crystallization begins. –Pour point (PP, ASTM 97): at which the fuel no longer pour. –Cold filter plugging point (CFPP, ASTM 6371): at which fuel starts to plug a fuel filter. Total insoluble: High temperature in the presence of oxygen – ASTM D 2274 (Accelerated Method): Oxidation Stability of Distillate Fuel ( 95 º C for 16 h). –ASTM D 4625: Storage Stability of Middle Distillate, Petroleum ( 43 º C for selected periods up to 24 weeks). ASTM Test Methods

The effects of biodiesel on cold-flow fuel properties when blended with ULSD have not been fully elucidated; Few studies on the effect of biodiesel blends on the amount of precipitate formation under low temperature storage. Critical Issues

Investigate the effect of blend levels on the precipitate formation at low temperature storage; Understand the mechanism of precipitate formation; Correlate the relationship between CP,PP, and CFPP and precipitate formation; Investigate the nature of precipitates. Objectives

Samples: –Soybean-, Cottonseed-, and Poultry fat- based biodiesel, and certification #2 ULSD –ULSD, B2, B5, B10, B20, B50, B70, and B100 –300 ml Storage Temperature and Time –-15 º C –4 º C –23 º C (Control) –24 hours Filter –Vacuum pump: 20 inHg (~68 Kpa) –0.7  m glass filter medium Experimental

Physical Appearance ( at 23 ºC for 24 hours ) SBO-based Biodiesel ULSD B5B10 B20B50B70 B100 B2

Physical Appearance (at 4 ºC for 24 hours) ULSD B2 ULSD B5 B10 B20 B50B70B100 SBO-based Biodiesel

Physical Appearance (at -15ºC for 24 hours) ULSDB5 B10 B20B50 B70B100 B2

Optical images of precipitates from B20 SBO-based biodiesel 5X20X

Precipitates are observed above cloud point for biodiesel blends –Storage temperature –Storage time –Blending levels –Feedstock Precipitates above Cloud Point

Time to filter Vs. Temperature

Precipitate Mass Vs. Temperature Significant mass of “new” precipitate at 4 ºC; Above the cloud point precipitate” is very different in nature as compared to the normal wax-crystal like precipitate formed below cloud point.

Precipitate Mass Vs. Time Different mechanisms for the precipitate formation; For B20, the relatively fast appearance of precipitate can be attributed to the solvency effect.

Precipitate Mass Vs. Feedstock CSO- and PF- based biodiesel had lower precipitate levels than the SBO-based biodiesel; The difference may be attributed to the presence of unsaturation FAME and minor components.

FAME Composition FAME composition (wt) % FASBOCSOPF C14:00.00%0.76%1.04% C16:014.10%24.74%21.82% C16:10.70%0.37%3.71% C18:05.15%2.68%7.61% C18:125.29%18.45%36.59% C18:248.70%52.99%27.02% C18:36.08%0.00%1.78% ∑SFA (%) ∑UFA (%)

Cloud point, Pour point, and CFPP The CFPP may indicate relative extent of the precipitate formation at low temperature.

Nature of Precipitates  Possibility  Stetyl glycosides;  Monoglycerides, diglycerides, triglycerides of total glycerin;  Dimers, trimers, tetramers of oxidative products;  Solvency effect when blend with ULSD.

Nature of Precipitates: FTIR Spectrum SBO-B100 SBO-B20 CSO-B100 CSO-B50 Standard Sterol Glucosides -OH -CH 2 C-O-C -COO

Nature of Precipitates: CG-FID Chromatogram CSO-B100 SBO-B100 Standard Sterol Glucosides SBO-B100 Internal Standard Three kinds of sterol glucosides

Nature of Precipitates: CG-FID Chromatogram Standard Glycerides PF-B100

Further Results Oxidative Biodiesel Blends Distillated SBO-B20 After cols soak test, no precipitates is observed on distilled or oxidized B100, or even on B20; Distillated B100 doesn't include sterol glycosides; The nature of “the above cloud point precipitate” formation is different from the oxidized insoluble observed from high temperature stability test of biodiesel.

Conclusions Storage temperature, storage time, biodiesel blend level, and feedstock affect the mass of precipitate formed; Solvency of ULSD has a significant influence on precipitates formation; Precipitates from SBO- and CSO-based biodiesel are due to sterol glucosides. However, the precipitates from PF-based biodiesel can be attributed to glycerides.

Acknowledgement Financial support from the Department of Energy (Grant # DE FG36-05GO85005) and Michigan ’ s 21st Century Job Fund is gratefully acknowledged.