Oxidative Stability of 20% Soy-based Biodiesel (B20) in Ultra-low Sulfur Diesel Anfeng Wang, Brad Clark, Haiying Tang, Kapila Wadumesthrige, Manhoe Kim, Steven O. Salley, and K. Y. Simon Ng Department of Chemical Engineering Wayne State University, Detroit, MI /13/2007

Motivation  Significant increase in Biodiesel production and usage in U.S.  Oxidative Stability and Cold Flow Problem  No ASTM specification for biodiesel blends

Effects of Poor Oxidative Stability Biodiesel  Viscosity increase  Acidity increase  Peroxide value increase  Gum formation Oxidation Damage to fuel delivery system and engine/transmission:  Filter plugging  Injector choking  Corrosion  Hardening of rubber components  Fusion of moving components  Engine deposits

Objectives  Establish the relationship between biodiesel composition and its oxidation, lubricity and other properties.  Investigate the oxidation behavior of individual FAME in ULSD, and to understand the effects of ULSD.  Explore approaches to enhance the oxidative stability of biodiesel.  Study the effect of metal ions on the oxidative stability of biodiesel.

Biodiesel blends collected from Michigan retailers  26 biodiesel blends  1 B2  6 B5  1 B10  19 B20  12 ULSD MID MICHIGAN (WJRT) - (02/05/07) -- School districts forced to replace bus fuel Bio- diesel fuels can turn to gel in freezing weather…

B2B5B10B20 Biodiesel Quality Survey – Measured FAME Blending Level

>38 hrs No BD was present B5B10B20 Biodiesel Quality Survey – Induction period

>38 hrs, No BD was present Biodiesel Quality Survey - Induction period vs. measured blending levels

Summary (Quality Survey)  Most of the biodiesel collected are soybean oil-based.  Over 55% of B20 samples contain less than 13% FAME.  Over 50% of B20 samples with IP < 6 hours.  TAN, viscosity, IP, CP/PP/CFPP vary significantly among B20 samples (data not shown).

Unit (%wt)C14:0C16:0C16:1C18:0C18:1C18:2C18:3C20:0C22:1 Soy Cotton- seed Poultry fat Yellow grease Rapeseed (Hi Oleic) Rapeseed (Hi Erucic) Corn trace Tallow FAME compositions of biodiesel from various feedstocks Bottom half: from J. Van Gerpen, et al., Biodiesel Production Technology, 2004

Induction period for pure FAMEs ? C18: hr C18: hr C18:3 Should be <0.1hr C18:3 in ULSD (20%) 0.13 hr C16:0 >60 hr C18:0 >60 hr C18:3 C18:2 C18:1

B100: 3.55 hr B20: 11.6 hr Induction periods for B100 and B20 with different contents of C18:3  The biodiesel was prepared from pure FAMEs purchased from NuChek Prep.  Since no natural antioxidants are present, the IP for both B100 and B20 was noticeably lower than the B100 derived from vegetable oil.  Certification ULSD was used to prepare B20. C16:015.89% C18:05.64% C18:128.81% C18:249.67% Base composition Soy-based B100 from a major producer in the USA

Conc (%)C18:1C18:2C18: > > 60 hr IP for pure FAMEs in certification ULSD Induction periods for pure FAMEs in ULSD

S012 S011 S017 S009 S hr 5.74 hr 0.99 hr 3.44 hr 5.67 hr B20 samples after Rancimat test All samples were from local stations in Southeast Michigan Station ID IP (110  C) 21 hrs14.5 hrs Time in heating blocks at 110  C Note: It takes a few hours for the heating blocks to cool down to room temperature.

Station 12Station 17 As isTop* Bottom* As isTop* Bottom* C16:0 1.46%3.47% 1.74% 1.60%2.85%0.93% C16:1 0.00%0.62% 0.09% 0.00%0.24%0.06% C18:0 0.55%1.11% 0.51% 0.56%1.15%0.17% C18:1 2.77%2.28% 1.73% 2.95%2.37%1.29% C18:2 7.80%6.72% 0.51% 8.24%3.25%0.31% C18:3 0.95%0.42% 0.00% 1.09%0.20%0.09% SUM13.52%14.63%4.59%14.43%10.06%2.85% FAME composition profiles Unit: weight % * After Rancimat tests

Free radical from oxidation Rearrangement C18:3 Free radical from oxidation Rearrangement C18:2 Free radical Polymer  Dimers, trimers, tetramers, and so on are also likely to be present. Mechanism of the formation of viscous phase Highly prone to oxidation J. A. Waynick, Characterization of biodiesel oxidation and oxidation products,2005.

20% in ULSD after Rancimat 18:118:318:2 Time at 110  C: 18 hours  After oxidation at 110  C for 18 hours (air flow: 10 liters/hour), phase separation was observed for 18:2 and 18:3 (20% vol) in ULSD, but not for 18:1.  Noticeable color change was observed for 18:2 and 18:3, but not for 18:1.  Phase separation was not observed for pure components in the absence of ULSD.  The bottom phase does not dissolve in ULSD and n-heptane.  The bottom phase was very viscous, and GC analyses indirectly indicated that they had high molecular weight. Pure FAMEs in ULSD after Rancimat test

Summary (Pure FAMEs)  C18:3 has the lowest IP at 110  C (0.13 hr), while the IP for C18:2 and C18:1 are 1.15 and 2.55 hr, respectively. C18:3 also showed the lowest IP while blended with ULSD.  For biodiesel made from pure FAMEs, IP dropped to 0.3 hr when C18:3 content reached 1%. However, when blended with ULSD at 20% level, no significant drop in IP was seen even when C18:3 content was 4% (~ 3hr).  Phase separation was observed when biodiesel blends were oxidized for a few hours on Rancimat (110  C). The bottom viscous liquid does not mix with ULSD and n-heptane, and has lower biodiesel content than the top light phase.  High-molecular weight species were believed to be present in the bottom phase, which resulted from radical polymerization of unsaturated FAMEs.

 The majority of biodiesel produced in the USA are from soybean oil (>85%), and other feedstocks include recycled cooking oil, animal fats, yellow grease, cottonseed oil.  Survey performed in 2004 lead by McCormick (NREL) indicated that only 1 out of 27 B100 on the market met the EN standard (6 hrs) regarding oxidative stability. Over 85% of B100 with IP less than 2 hours.  Induction period keeps decreasing with time, and the current recommended storage time is 6 months. Facts Strategies  Partial hydrogenation  Distillation  Antioxidant treatment Why study antioxidants on biodiesel Higher production costs Worse oxidative stability Poorer cold flow properties

B100B20 Soy Soy Cottonseed Poultry fat Yellow grease Ratios of IP (B20)/IP (B100) Oxidative stability of B100 and B20  IP for Soy-1 and Soy-2 was obtained on 11/30/06 and 4/25/07 on the same batch of biodiesel (produced in August, 2006). It was stored in steel container at room temperature with exposure to atmosphere.  IP for cottonseed oil-based B100 was 6.57 hrs eighty days ago. ASTM EN IP for B100 and B20 at 110  C

Oxidative stability of B100 and B20 w/ antioxidants B100: 1000 PPM B20: 200 PPM  Soy-based B100 was from a major producer in the USA  Certification ULSD was used to prepare B Ratios of IP(B20)/IP(B100) Induction period (hr)

Induction period of soy-based B100 EN ASTM D6751 Induction period (hr) B100 was from a major producer in the USA

EN ASTM D6751 Induction period (hr) Induction period of soy-based B100 B100 was from a small local producer in Michigan, which failed the glycerin test (ASTM 6584)

BeforeAfter C14:00.00% C16:014.10%16.02% C16:10.70%0.56% C18:05.15%5.37% C18:125.29%26.51% C18:248.70%46.31% C18:36.08%5.23% C20:00.00% C22:10.00% BeforeAfter IP °C) * Acid # (mg KOH/g) Viscosity (cSt, 40 C) Cloud point (° C) 34 Pour point (° C) -30 CFPP (° C) -30 HFRR (B2) (um)* Vacuum distillation of soy-based B100 Note: IP for B100 made from pure components with the same composition profile is only 0.13 hours at 110  C.

Antioxidants on the distilled soy B100 Induction period (hr) EN ASTM D6751

Induction period of poultry fat-based B100 ASTM D6751 Induction Period (hrs) EN 14214

Induction Period (hrs) EN Induction period of cottonseed oil-based B100

Ionol BF200: mixture of Mono-, Di-, and Tri- tert-butylphenol  -(+)-Tocopherol Chemical structures of antioxidants

Summary 2  The IP for B20 is between 2.40 to 3.65 times the IP for the corresponding B100.  Synthetic antioxidants can enhance the oxidative stability of both B100 and B20, while adding tocopherol marginally improve the IP.  The efficacy of each antioxidant differs for biodiesel made from different feedstock, even for soy-based biodiesel made by different producers.  Vacuum distillation worsens oxidative stability, cold flow properties and lubricity, but lowers the acid number and viscosity.  The long-term stability of biodiesel with or without antioxidants are ongoing.

What are the effects of catalytic metals on the oxidative stability of B100? What are the common industrial metals that need to be tested? How is the rate of oxidation influenced by metals? How do changes in feedstock affect sensitivity to metals? How should the effect of metals be reported?

Method Group IV transition metals selected: V, Cr, Mn, Fe, Co, Ni, Cu and Zn Metals added as nitrate or chloride salts dissolved in MeOH Oxidative stability was determined by Rancimat®. B100 from soy and cottonseed oil were tested Given the variables of different metals at different concentrations and different feedstock, Δ % IP was selected as the means to report the effects observed

Δ % IP = Δ % IP

Response to a metal may vary in different feedstock

Response to a metal may be similar in different feedstock

Highly active metal -78 Δ% IP at 2 ppm Cu in soy based biodiesel

Less active metal -34 Δ % IP at 100 ppm Ni in soy based biodiesel

|Δ IP| < 20% Soy (ppm) 0.6 i 0.05 e 0.3 e 20 i 0.5 i 50 i 0.01 e 2 i metal V Cr Mn Fe Co Ni Cu Zn |Δ IP| < 20% Cotton (ppm) 0.05 e 0.08 e 0.2 e 15 i 0.05 i 5 i 0.04 i 4 i Limits of 20% reduction of IP for biodiesel for the group IV transition metals i: interpolatede: extrapolated

Summary 4 All group IV transition metals tested showed catalytic activity (V, Cr, Mn, Fe, Co, Ni, Cu and Zn) The activity of these metals varies with concentration and feedstock (cottonseed or soy oil) Neither feedstock is clearly superior in terms of its ability to resist the catalytic effect of these metals