The storage stability issue of Biodiesel and the additives solution. Long - Term Storage of Fuels Seminar Israeli Institute of Energy and Environment

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1 The storage stability issue of Biodiesel and the additives solution Long - Term Storage of Fuels Seminar Israeli Institute of Energy and Environment Tel Aviv, 3 of December 2008

2 An Introduction Biodiesel, as many other organic materials, is susceptible to oxidation upon exposure to air. The oxidation process ultimately affects fuel quality. An oxidative stability specification was included in the European and American biodiesel standards (EN14214 and ASTM D6751).

3 An Introduction Primary oxidation occurs by a free radicals process, which consist of initiation, propagation and termination reactions. Initiation RH + I R + IH Propagation R + O 2 ROO ROO + RH ROOH + R Termination R + R RR ROO + R ROOR

4 Fatty Acid Distribution O palmitic acid 16:0 C O O stearic acid 18:0 oleic acid 18:1 linoleic acid 18:2 linoleneic acid 18: C O C O C O C O O O O

5 An Introduction The CH 2 positions allylic or bis allylic to the double bonds in the fatty acid chains are those more susceptible to oxidation. The autoxidation of unsaturated fatty compounds proceeds at different rates depending on the number and position of the double bonds (18:1/18:2/18:3 ~ 1/40/100) E.g.: methyl linolenate (C18:3)

6 An Introduction Secondary oxidation: Decomposition of the fatty ester peroxides into: Aldehydes Alcohols Formic Acid Shorter fatty acids

7 An Introduction Secondary oxidation: Vinyl polymerization also has been proposed as a possible secondary oxidation reaction Oligomers formed through this path do not exceed trimeric or tetrameric forms

8 Oxidation consequences Long-term Storage Increase of oligomers, polymers and other secondary oxidation compounds Formation of GUMS, SLUDGE, INSOLUBLE DEPOSIT Increase of acidity, viscosity

9 Methods: Iodine Value I 2 value grams I 2 that react with double bonds in 100 gram of biodiesel High I 2 value lower stability to oxidation Limit: it only measures the amount of double bonds The oxidation rate (1:40:100) is not taken into account

10 Methods: Total Acid Number The acids content not only affect the biodiesel current quality but also its tendency to be oxidized (potential quality) In fact acids can increase the rate of oxidation of the biodiesel Acids may be already present in the biodiesel just after its production Presence of free fatty acids in the oil Biodiesel production process or may form as a consequence of oxidation reactions

11 Methods: Oxidation Stability Index (OSI) Accelerated aging Air is passed through an heated biodiesel sample (110 C) Then is sent through a flask with distilled water Water conductivity proportional to oxidation rate Metrohm Rancimat Oxidation products (formic acid) are more volatile than biodiesel. The air fluxed moves them into water raising its conductivity.

12 Methods: Oxidation Stability Index (OSI)

13 Aging effect Total Acid Number Polymer Content Quiescent aging 6 weeks, 50 C, closed bottles (no air replenishment) Agitated aging ASTM D h at 95 C with O 2 fluxing

14 Aging effect on OSI B100 B20 Quiescent aging 6 weeks, 50 C, closed bottles (no air replenishment) Agitated aging ASTM D h at 95 C with O 2 fluxing

15 TAN-Polymer content correlation TAN and Polymer content showed in several studies a very good correlation. Here is an example:

16 OSI TAN Polymer content OSI have good correlation with both TAN and Polymer content after aging:

17 EN OSI > 6h Iodine number > 120 gi 2 /100g Total Acid Number < 0,5 mg KOH/g

18 ASTM D6751 OSI > 3h Iodine number Not Included Total Acid Number < 0,5 mg KOH/g

19 Worldwide Fuel Charter The World wide Fuel Charter is the Engine Companies point of view on fuels quality characteristics The WWFC for mineral fuels arrived to the 4 edition It is under preparation also a specific document for biodiesel

20 Worldwide Fuel Charter

21 Factors affecting stability Biodiesel fatty acid distribution Natural antioxidants content Free Fatty Acids Metal content Biodiesel Characteristics Pre- and Post- treatments

22 Fatty Acid Distribution

23 OSI of Different Biodiesel 12 >12h Rancimat, hrs Soybean Sunflower Rapeseed Canola Jatropha Palm UFO Induction Period range

24 Antioxidants Natural: tocopherols (α, β, γ, δ) most of them removed during the process of biodiesel production Synthetic: retardants (and hydroperoxide decomposers) mainly phenolic type (and amine type) different products than in mineral fuels similar action (AH: highly labile hydrogen)

25 Synthetic The typical synthetic antioxidants used for vegetable oils are effective also in the biodiesel BHT BHA TBHQ The not alimentary use of biodiesel permits to apply also antioxidants normally banned for vegetable oils: Propyl Gallate Amines

26 Synthetic - BHT BHT is a well known and widely recognized antioxidant for vegetable oils and biodiesel. BHT was the first antioxidant to be used in biodiesel. Limits: BHT is solid at ambient temperature. It is used as a powder or diluted in a proper solvent. During the years other, more efficient, products came to the market.

27 Synthetic - BHT Delta Rancimat, hrs 4 3,5 3 2,5 2 1,5 1 0,5 0 Soybean Sunflower Rapeseed Jatropha Palm Dosage rate 250 ppm 500 ppm

28 Development of new products The market requested the development of new products Cost optimization Lower dosage rates and treatment costs More critical raw materials to be treated Better handling BHT has low efficiency on most the critical biodiesel from used frying oils and highly unsaturated vegetable oils Liquid stabilizers Stable at low temperatures

29 Chimec Developments Delta Rancimat, hrs 4 3,5 3 2,5 2 1,5 1 0,5 0 Soybean Sunflower Rapeseed Jatropha Palm Dosage rate 50 ppm 100 ppm

30 Chimec Developments Rancimat, hrs RME/SME Blends Additive 1 100% RME 75:25 50:50 25:75 100% Soy Dosage rate 0 ppm 50 ppm 100 ppm

31 Rancimat, hrs Biodiesel Oxidation Chimec Developments Biodiesel from Used Frying Oils Dosage rate BHT Additive 1 Additive 2

32 Stability During Storage As we saw the stability to oxidation is not a stable characteristic It normally decreases with time (aging) and the decrease rate strongly depends on the storage conditions Also biodiesel treated with antioxidants are susceptible to a decrease of their stability with time The best antioxidants, anyhow, are also able to slow down the stability losses during typical storage conditions

33 Stability During Storage RME Stored in the dark with seldom air replenishment 10 Induction period (h) Time 0 1 Month 3 Months Blank Additive 1 BHT

34 Stability During Storage SME Stored in the dark with seldom air replenishment Induction period (h) 8 7,5 7 6,5 6 5,5 5 4,5 4 3,5 3 Time 0 1 Month 3 Months Blank Additive 1 BHT

35 Thank you for your attention Stefano Tortora CHIMEC SpA Fuel Additives Technological Unit