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Sterol Glucosides in Biodiesel

Haiying Tang, Steven O. Salley, and K. Y. Simon Ng National Biofuels Energy Laboratory NextEnergy/Wayne State University Detroit, MI 48202. Sterol Glucosides in Biodiesel. Outline. Chemical structure and physical properties of sterol glucosides

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Sterol Glucosides in Biodiesel

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  1. Haiying Tang, Steven O. Salley, and K. Y. Simon Ng National Biofuels Energy Laboratory NextEnergy/Wayne State University Detroit, MI 48202 Sterol Glucosides in Biodiesel

  2. Outline • Chemical structure and physical properties of sterol glucosides • Precipitates formation above cloud point in Soy-, Cottonseed-, and Poultry Fat-based Biodiesel Blends • “Filter-Blocking Tendency ” test and cold soak filtration • Analysis method • Typical processing technique for oil refining • Possible techniques to remove sterol glucosides • Conclusion

  3. Plants Sterols • Free sterols • Sterol esters • Sterol glucosides • Acylated sterol glucosides

  4. Sterol composition in seed oil(mg/kg) Data From Gunston ed al, The lipid handbook, 1994

  5. Chemical Structure of Sterols • Phytosterols mainly include campesterol, β-sitosterol, stigmasterol, Δ5-avenasterol, Δ7-stigmastenol, and brassicasterol.

  6. What is Sterol Glucoside in Biodiesel? • Sterol Glycosides occurs naturally in vegetable oils, mainly as soluble fatty acid esters ; • Usually, the acyl sterol glycosides at concentrations are two to ten fold greater than those of the non-acylated forms; • Hydrolyzed during transesterification process and become insoluble. • β-sitosterol glucoside is the most typical sterol glucoside. β-sitosterol glucosides

  7. Biodiesel Reaction- Base Transesterification 100 lbs of oil +10 lbs methanol 100 lbs of biodiesel +10 lbs of glycerol

  8. Physical Properties of Free Sterol Glucosides • Powdery solid, melting point 283-287°C • Limited solubility in most organic solvents except pyridine, chloroform/methanol (2:1) • Soluble in fresh biodiesel.

  9. Typical Concentration of SG in Biodiesel (ppm) Data from1Ringwald SC. Biodiesel characterization in the QC environment; 2 Pfalzgraf et al , Identification of sterol glucosides in biodiesel and their effect on filterability.

  10. Precipitates Formation above Cloud Point in Soy-, Cottonseed-, and Poultry Fat-based Biodiesel Blends

  11. Cold Flow Properties: a current issue with biodiesel • Precipitatesformation in biodiesel blends may have serious implications. • Clogging of fuel filters. • Formation of deposits on engine parts such as injectors and other critical fuel system components.

  12. ASTM Test Methods • 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 will 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 ºC for 16 h). • ASTM D 4625: Storage Stability of Middle Distillate, Petroleum (43 ºC for selected periods up to 24 weeks).

  13. Experimental • Samples: • SBO-, CSO-, and PF- based biodiesel • ULSD, B2, B5, B10, B20, B50, B70, and B100 • 300 mL volume • Storage Temperature and Time • -15 ºC for 24 hr • 4 ºC for 24 hr • 23 ºC for 24 hr (Control) • Allow to come to room temperature without external heating • Filter • Vacuum pump: ~68 kpa • 0.7 mm glass fiber filter Filtration system from ASTM D4625-04

  14. Physical Appearance (at 23 ºC for 24 hours ) SBO-based Biodiesel ULSD B2 B5 B10 B100 B20 B50 B70

  15. Physical Appearance (at 4 ºC for 24 hours) SBO-based Biodiesel ULSD ULSD ULSD B2 B10 B5 B20 B50 B70 B100

  16. Physical Appearance (at -15ºC for 24 hours) B10 ULSD B2 B5 B70 B100 B20 B50

  17. Optical Images of Precipitates 50X 200X Taken from B20 SBO-based biodiesel

  18. Time to Filter Vs. Temperature SBO-based biodiesel

  19. Insolubles Mass Vs. Temperature • No significant mass of “new” insolubles as result of blending at 23 ºC ; • Significant effect at 4 ºC; • Above the cloud pointinsolubles are very different in nature as compared to the normal wax-crystal like insolubles formed below cloud point.

  20. Insolubles Mass Vs. Time • Different mechanisms for the insolubles formation from B20 and B100; • For B20, the relatively fast appearance of insolubles can be attributed to a solvency effect. B100 B20

  21. Insolubles Mass Vs. Feedstock • CSO- and PF- based biodiesel had lower insolubles levels than the SBO-based biodiesel; • The difference may be attributed to the presence of naturally occurring levels of sterol glucosides in the feedstocks.

  22. Cloud Point, Pour Point, and Cold Filter Plugging Point • The CFPP may indicate relative extent of the insolubles formation at low temperature.

  23. Nature of Insolubles • Possibilities • Sterol glucosides: Soluble within vegetable oil; however, hydrolyzed during transesterification process and become insoluble. • Monoglycerides, diglycerides, triglycerides of total glycerin; • Dimers, trimers, tetramers of oxidative products; • Solvency effect when blended with ULSD.

  24. Distilled and Oxidized Biodiesel • After cold soak test, no insoluble was observed in distilled or oxidized B100, or even in B20; • Insolubles formation is due to minor component; • Insolubles formation is not due to oxidized product. • The nature of “the above cloud point insolubles” formation is different from the oxidized insolubles observed in the high temperature stability test of biodiesel; Distillated SBO-B20 Oxidative Biodiesel Blends

  25. Nature of Insolubles: FTIR Spectra -CH2 -CH2 -OH C-O-C Insolubles from SBO-B100 Insolubles from SBO-B20 Insolubles fromCSO-B100 Insolubles from CSO-B50 Standard Sterol Glucosides

  26. Nature of Insolubles: GC-FID Chromatograms Insolubles from CSO-B100 Insolubles from SBO-B100 Internal Standard Standard Sterol Glucosides Three kinds of Sterol Glucosides

  27. GC-FID Chromatogram (Continued) Precipitates from PF-B100 Standard Glycerides

  28. Summary 1 • Storage temperature, storage time, biodiesel blend level, and feedstock affect the mass of insolubles formed; • Solvency of ULSD has a significant influence on insolubles formation; • Insolubles from SBO- and CSO-based biodiesel are due to sterol glucosides. However, the insolubles from PF-based biodiesel can be attributed to glycerides.

  29. “Filter-Blocking Tendency ”Test • Tests • 300ml of fuel at 20ml/min • Filter • ASTM D2068/IP387 • 1.6 micron • Result calculated based on pressure and volume measured during the test.

  30. Effect of SG on FBT • Adding SG to biodiesel caused it to fail to the FBT test; • SG presence at high enough levels could potentially cause filter problems. Data from Lee et al. The role of sterol glucoside on filter plugging, Biodiesel Magazine 2007.

  31. Biodiesel Cold Soak Filtration • Storage temperature and time • 4 ºC (refrigerator) • 16 hours • Allow sample to come to the room temperature (23 ºC to 24 ºC ) • Filter • Vacuum pump: 22.5 inches Hg (~76.2 Kpa) • Whatman 47 mm GF/F, 0.7 mm.

  32. Biodiesel Cold Soak Filtration

  33. Different Feedstocks of Biodiesel

  34. Analysis of Sterol Glucosides • The presence of sterol glucosides in biodiesel residues has been confirmed using FTIR and GC-FID • Qualification will be evaluated by GC- FID, HPLC, and FTIR with purchased known standards

  35. Preliminary results :GC-FID Chromatograms sitosterol glucoside stigmasterol glucoside campesterol glucoside Precipitates from REG Precipitates from Nextdiesel Standard sterol glucosides

  36. Refining Water degumming Caustic refining Bleaching Deodorization Process of Crude Soybean Oil to Food-grade Oil • Chemical refining • Water degumming • Chemical neutralization • Bleaching • Deodorization • Physical refining • Acid degumming • Bleaching • Deodorization

  37. Conventional RBD Process Phosphoric acid NaOH Bleaching clays Steam vacuum CHEMICAL NEUTRALIZATION DEODORIZATION (Distillation) BLEACHING CRUDE OIL REFINED OIL WATERDEGUMMING Phospholipids and gums Free fatty acids Trace component Pigments Reduce portion of free sterols Reduce portion of free sterols Remove portion of SG

  38. Average Composition for Crude and Refined Soybean oil Data from Van Gerpen, J.; Biodiesel production technology, 2004

  39. Process techniques to remove SG • Filtering: removal of particulate from media with a steel screen, cartridge or filter paper • Effect of filter pore sizes • Effect of filter types • Cold filtering:holding the biodiesel at a lower temperature for desired time before the filtering process.  • Effects of cold filter temperature • Effect of storage time Particle

  40. Preliminary Results: Effect of temperature on removing particles with filtration • Cold filtration is better to remove particles than room temperature filtration

  41. Preliminary Results: Effect of storage time on removing particles with cold filtration (4 ºC ) • Longer storage time in cold soak test could more effective to remove particles in biodiesel.

  42. Adsorbent Untreated Biodiesel Finished product tank Filter Mix Tank Process techniques to remove SG(Con.) • Adsorbent treatment: • Removal of particulate with a porous pad or a “cake” of filter-aid-type materials • Diatomaceous earth (DE) • Magnesol • Carbon • Magnesium silicate • Act as deep filtration • Effect of concentration • Effect of incubation time • Effect of temperature

  43. SG content of biodiesel after incubation and filtering through DE Data from Lee et al. Processes of producing biodiesel and biodiesel produced therefrom; Patent application publication, 2007.

  44. Process techniques to remove SG (Con.) • Water degumming:a basic process to wash biodiesel product to remove contaminants • Effect of water ratio • Effect of mixing temperature • Vacuum distillation:an energy intensive technique for biodiesel processing • Effect of temperature • Effect of pressure

  45. Preliminary Result: GC-FID Chromatography Sterol glucosides SBO-biodiesel Glycerol Precipitates from SBO-biodiesel Distillated SBO-biodiesel

  46. Conclusions

  47. Future Work • Evaluate and develop processing strategies to reduce sterol glucosides content in biodiesel; • Develop a robust analytical method to determine the sterol glucosides content in biodiesel.

  48. Thanks! Questions?

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