Biodiesel Product Quality Challenges: Gaylord Palm Resort and Convention Center, Orlando Florida, February 4, 2008
Overview Introduction Product Quality Challenges Manufacturing Storage Conclusion.
Biodiesel is a novel fuel
Made from renewable sources Vegetable Oil Animal Fat Used Grease
Mining Utilities Emergency Systems Local Terminals Biodiesel and its blends power diesel engines Biodiesel can be handled nearly like a petroleum diesel and Fueling Telecommunications Agriculture Biodiesel is being evaluated as a fuel feed stock for critical turbine engines. Industrial Fleets Aviation Rail Marine
Biodiesel is good for the environment It is very biodegradable, Exhaust emissions from biodiesel are lower in CO & CO2, particulates, soot, and hydrocarbons
Biodiesel is good for our national security and economy Domestically produced feedstocks reduce the need to import foreign crude oil, Domestic production of biodiesel reinvests into our domestic and local economies,
Are there Quality Issues? There certainly are Unlike petroleum based diesel fuel, biodiesel is made from a perishable food source, Once certain product deterioration processes begin they are irreversible, Biodiesel product quality problems can go unnoticed for some time before creating operational issues,
MANUFACTURING
Production Process Biodiesel Transesterification Process vs. Petroleum Diesel Separation Process
Transesterification Comparison Soy Animal Fat Used Grease + (Catalyst NaOH / KOH) FAME* + Glycerin + Byproducts *Vegetable oils will contain natural antioxidants Source: Understanding Biodiesel Fuel Quality and Performance
Two Purification Processes Wet Method: B100 is purified by spraying a fine water mist over the fuel and impurities are removed as the water droplets settle to the bottom of the tank, The advantage is that some natural antioxidants remain with the B100 to provide temporary protection against peroxide formation, Disadvantage is the additional water results in increased cost, production time and B100 with high water content (>1000ppm) Distillation Method: B100 is purified from the unwanted by-products by distillation, The advantage is that the B100 is a much purer product The disadvantage is that the natural antioxidants do not carry over with the B100 and the product immediately begins peroxide formation,
Desired Products - Soy FAME (FAME Carbon Lengths C8-C22) C16:0 Saturated Molecules C18:0 C18:1 Unsaturated Molecules C18:2 C18:3
Undesired Reaction Byproducts Free Fatty Acids Glycerin Methanol NaOH / KOH Process Catalyst Monoglyceride & Diglyceride
Potential Product Quality Issues Characteristic Free Glycerin Mono- & diglycerides Free Fatty Acid Effect Failure Mode Corrodes non-ferrous metals, soaks cellulose filters, sediments on moving parts and lacquering Filter clogging and Injector Coking Issues similar to glycerin Causes swelling of some elastomers, nitrile rubbers to soften, swell or harden and crack Provides electrolytes and hastens the corrosion of zinc, Salts of organic acids, Organic compounds formed Fuel Leakage Corrosion of FIE, Filter Plugging Sediment on parts Methanol Carryover Corrodes aluminum & zinc, Corrosion of FIE Low flash point Process Catalysts Potassium and sodium compounds solid particles Blocked Nozzles Source: Diesel Fuel Injection Equipment Manufacturers Common Position Statement
Oxidative Instability Saturated oils, fats and FAME: Have poor cold temperature characteristics, However, tend to be more stable against oxidative degradation formation, Unsaturated oils, fats and FAME : Have a better cold weather characteristics, However, have a greater propensity to undergo oxidative degradation more readily,
Storage Issues
Storage Issues Decades ago it was discovered that stored oils and fats would degrade (rancid) when exposed to oxygen. This was eventually solved by the use of antioxidants, Oils and fats will undergo degradation in the presence of certain oxygen species, metals and acids to produce peroxides and hydroperoxides, The rate of degradation depends on the number of double bonds per molecule and their relative location, Biodiesel is made from a variety of oils, fats and greases,
Reactive Sites C16:0 Least Reactive Saturated Molecules C18:0 C18:1 Reactive Sites (Allylic Site) Unsaturated Molecules C18:2 More Reactive (Bis-Allylic Site) C18:3 Most Reactive (Bis-Allylic Site)
Reaction Sites H H H H C C C H H Methyl Carbon H H Allylic Carbon Saturated products tend to be more stable reducing radical formation, Unsaturated products tend to be less stable. The double bond makes it easier for allylic carbons to lose the hydrogen to form a radical. H H Bis - Allylic Carbon
Peroxide Formation Initiation + X H H H + XH Radical Propagation + H H H O--O Peroxide Radical + -- -- H + O2 H O--OH H Hydroperoxide Termination (a) (b) H H O--O + H-Antioxidant + + H -- -- (c) H H H H + Antioxidant Stable Product Stable Product O--O
Various Biodiesel Feedstocks Weight Percent of Fatty Acids in Fat and Oil Feedstocks
Storage B100, B20 & B5 Studies suggest that B100 can be exposed to oxidation degradation immediately after production: Wet purification will carry over some of the natural antioxidants providing short term protection to B100, Distillation purification does not carry over the natural antioxidants from B100, therefore no short term protection. Non-vegetable based B100 do not contain natural antioxidants thus possess no short term protection.
Storage B100, B20 & B5 Oxidation Stability Index (Rancimat) studies have shown: B100 with an induction period <3hrs, will likely go out of specification for acid value and oxidation stability within 4 months with formation of free fatty acid (FFA) and insoluble deposits, Even B100 with an induction period >7hrs (from natural antioxidants), still could go out of specification for oxidation stability after approximately 4 months,
Storage B100, B20 & B5 Studies suggest that B100 should not be stored for more than several months (or shorter) unless treated with a synthetic antioxidant, (hindered phenolic compounds) Studies also suggests that B100 treated with an synthetic anti-oxidant and that demonstrate an induction period of >3hrs will, Produce a B5 that will remain stable for 12 months, Produce a B20 that should remain stable for 12 months,
Catalytic Effect of Metal Species Studies also indicate that FAME can undergo peroxide formation in the presence of metals, Certain metals can facilitate peroxide formation in FAME, For example copper appears to exert the greatest catalytic degradation affect on FAME products (Cu+2 + e- è Cu+3) This is why biodiesel and biodiesel blends should not come in contact with copper, yellow metals (copper alloys), zinc, etc.
Effects of Excess Water Traditionally, above ground and underground storage tanks contain a volume of free water on the bottom of the fuel storage tank which is drained seasonally, Generally, the greatest concern with water in petroleum fuel systems is corrosion and microbial growth which will lead to fuel degradation and microbially influenced corrosion (MIC), Unlike petroleum diesel, FAME products have a much greater propensity toward microbial degradation.
Various Biodeterioration Rates Biodiesel Metabolism EPA Standard 560/6-82-003, CO2 Evolution (%) Days Rape Ethyl Ester Rape Methyl Ester Soy Ethyl Ester Soy Methyl Ester Neat Rape Neat Soy #2 Diesel Dextrose 0 0 0 0 0 0 0 0.00 0.00 7 69.01 66.32 67.68 68.4 58.39 60.57 13.20 59.84 14 79.15 80.72 78.40 77.83 70.47 70.12 21.04 80.19 28 86.92 88.49 86.40 85.54 78.45 75.95 26.24* 87.79 * Reduce mineralization rate due in part to the need to oxidize the reduced hydrocarbon to the fatty acid
Biodeterioration of Biodiesel Product O CH3 O Microbial enzymatic attack of the terminal methyl group Fatty Acid Methyl Ester O Free Fatty Acid O- (+ CH3 ) Methyl Group
Biodegradation Order of Petroleum Fuels (Comparison Discussion) 1. Linear & branched hydrocarbons 2. Cyclic (Unsubstituted/Substituted) R 3. Aromatic & Polyaromatic
Biodeterioration Petroleum Product In its reduced form petroleum fuels slow to microbial degradation n-alkane [O2] OH 1 Alcohol [O2] Aldehyde [O2] Carboxylic Acid O O OH Oxidation of the petroleum product makes the material more available for microbial metabolism
Biodeterioration of FAME and Petroleum Diesel O O- Free Fatty Acid O O- (+ CH3 ) Methyl Group (+ H+ ) Proton Oxidized Petroleum Product
Conclusion
Putting Things Into Perspective (1900 2008), the petroleum industry has had a century to resolve many product quality issues dealing with: Manufacturing & Chemistry, Material compatibility, Long term storage, MIC, etc. 24 Biodiesel (4 Hours) 18 6 Petroleum Diesel (24 Hour) 12 (1990-2008), the biodiesel industry has had just 2 decades to address product quality issues involving: Manufacturing & Chemistry, Material compatibility, Long term storage, MIC, etc.
Manufacturing / Purchasing Considerations If manufacturing, B100 must meet ASTM Specifications (ASTM D67581- XX) to ensure consistent product quality especially regarding biodiesel blends, If purchasing B100, request a Certificate of Analysis (COA) to confirm product quality. Reject any B100 that fails to meet any of the ASTM Specification.
Long Term Use and Product Storage For long term storage (not defined), the user should consider monitoring several quality parameters of the blended fuel product to ensure product remains in specification such as Formation of insolubles, Peroxide Value (PV), Total Acid Number (TAN) Viscosity Ester Content Polymer Content, Microbial Contamination
Long Term Use and Product Storage Based on the surveillance results or the presence of excess free water present in the storage tank, the biodiesel and biodiesel blends may need to be treated with the appropriate additive(s) to minimize on-going degradation mechanisms: Anti-Oxidants Metal Deactivators Multifunctional Stabilizer Packages Microbicides!!!!
Long Term Use and Product Storage B100 Blends Antioxidants Antioxidants Microbicides!!!! Microbicides!!!! Metal Deactivator Multifunctional Stabilizers
Industry Support Is the national trade association representing the biodiesel industry as the coordinating body for research and development in the US. BQ-9000 helps companies improve their fuel testing and greatly reduce any chance of producing or distributing inadequate fuel. BQ-9000 is open to any biodiesel manufacturer, marketer or distributor of biodiesel and biodiesel blends in the United States and Canada.
Reference Sources
Industry Peer Groups ASTM D6751
THANK YOU. Edward W. English Fuel Quality Services, Inc. eenglish@fqsinc.com
References 1. 2. 3. 4. 5. T.W. Graham Solomons, Organic Chemistry,1976, pg. 755. John Chandler, Improving Cold Flow Performance of Biodiesel, ASTM Biodiesel Workshop, December 4, 2005. Gerhard Knothe and Robert O. Dunn, Dependence of Oil Stability Index of Fatty Compounds on Their Structure and Concentration and Presence of Metals, 2003. Empirical Study of the Stability of Biodiesel and Biodiesel Blends, NREL/TP-540-41619, May 2007. Characterization of Biodiesel Oxidation and Oxidation Products, CRC Project N. AVFL-2b, August 2005.