The Analysis of Biodiesel for Trace Metals and the Development of Certified Biodiesel Standards CRMMA Workshop Pittcon 2008 New Orleans, LA Author: Thomas Rettberg, Ph.D. VHG Labs, Inc. Manchester, NH USA
Energy alternative: biodiesel From an obscure beginning a decade ago, biodiesel has become one of the major topics related to energy in the last few years + New energy source + Not derived from fossil fuel + Cleaner burning and reduces CO 2 burden + Independent of middle east oil + Production residue can be used as rich food or protein source: oilseed cake 3.2 what is the net energy advantage for biodiesel today when the costs of all factors involved in production and distribution are taken into account.
Diesel D1 D2 D3 Distillate of crude oil & catalytically cracked C 9 to C 24 55% paraffins, 24% aromatic, 12% napthenes, olefins, etc. incl. S compounds Gasoline Distillate of crude oil & catalytically cracked C 7 to C 11, mostly C 8, paraffinic Biodiesel What fuels our vehicles, burners, machinery & ships? Product of chemical reaction (w/ catalyst) of plant or animal derived oils Mostly C 18 fuel, oxygenated, no S or N, olefinic Soy, canola/rapeseed, tallow, other oilseeds primary feedstocks
What is biodiesel? FAME: Fatty Acid Methyl Ester made from triglyceride (tg) Produced by a chemical reaction: NOT the tg oil itself Bnn refers to biodiesel concentration - B100 is neat biodiesel - B5 (5%) is the first gas pump concentration goal Oxygenated = complete combustion = lower particulates Inherently good lubricity for engines biological energy is Nearly the same energy output as diesel stored as a triglyceride Stearate Methyl ester
What biodiesel is not It is chemically dissimilar from ethanol Ethanol: Fermentation product Much greater volatility Neat, it combusts quite differently than gasoline Plant derived ethanol overall energy advantage not as good Yet, as a liquid energy source, biodiesel is analogous to E10 ethanol ( gasohol ), i.e. it is a green fuel supplement for diesel as ethanol is a green fuel supplement for gasoline.
How biodiesel is made Simple process reactors can create biodiesel, however larger reactors will become more prevalent Feedstock: plant or animal oils Catalyst: methoxides (NaOH or KOH & methanol) Process: 40-100 o C, water or dry wash, remove H 2 O and Methanol Testing: ASTM D6751, EN24114 Additives: Stabilizers can be added to final material CH 2 -O-COR CH 2 OH CH 2 -O-COR + 3CHO 3-3R-COOCH 3 + CH 2 OH CH 2 -O-COR formation of the methoxide: K(or Na)OH + CH 3 OH K(or Na) + OCH 3 - + H 2 O CH 2 OH
Concerns addressed by testing Efficiency of conversion of the oil Absence of methanol, water, glycerol Low metal contamination (Na, K, etc. from process, feedstock, or apparatus) Properties: cloud point, flash point, viscosity Absence of decomposition As it turns out, biodiesel is not as chemically stable as diesel fuels. Contamination plays a major role, especially metal contamination. Stability 6 mos. in tanks, 3 mos. if open to air and exposed to light. Heat increases reaction rates, therefore some seasonal & geographic influences. Oxidation & Hydrolysis are main routes to degradation ASTM D6751 and EN14214 were developed to test for and manage these issues
Range of testing in ASTM guideline ASTM method limits designed to ensure quality fuel Built from existing petroleum fuel methods June 2008 vote for implementation as a guideline (ASTM is not a regulating body)
ASTM 6751 Testing of Biodiesel for Metals ICP-AES is specified technique (ICP-MS has been used) P and S not typically referred to as metals, but P is included for ICP-AES - S is not part of ICP Test, but has been effectively measured by ICP-AES* - S is determined by combustion technique - XRF analysis, as is done for S in Diesel, has shown that matrix-matched standards are necessary to avoid bias in sulfur measurements Method is feedstock neutral
Certified Standards of Metals in B100 Made with organo-metallic raw materials Ligand moiety of o-m well suited for biodiesel Stability shown to be good - Heat age & freeze tests Purity refinement of blank biodiesel ICP-AES method typically performed by 1:5 or 1:10 dilution of B100 in clean kerosene - also can be run neat ICP-AES work done using PE Optima 4300 and Teledyne-Leeman Fuel Pro system
ICP-AES matrix effects-1 Shown: Measurement of a known B100 concentration using standards of petroleum oil matrix prepared in pure kerosene.
ICP-AES matrix effects-2 Shown: Measurement of a known B100 using petroleum oil matrix stock standards prepared in pure kerosene, w/o internal standard.
ICP-AES matrix effects-3 Shown: Measurement of a known B100 using petroleum oil matrix stock standards prepared in pure kerosene with Sc internal standard.
ICP-AES matrix effects-4 Shown: Matrix-matched calibrants (1:5 diln. in kerosene) along with data for non-matrix-matched determinations.
Physical matrix effects: sample nebulization Shown: photos of aerosol for different liquids, identical conditions B100 Aerosol density, droplet sizes vary and will interact differently with the plasma, affecting emission. kerosene di water Acetone
ICP-AES matrix effects: conclusions ICP-AES method requires standards in metallo-organic form While dilution at 1:5 or 1:10 is okay, detection limits suffer - d.l. may be adequate to verify D6751 compliance, but not to actually measure the true concentration Standards made in biodiesel matrix (matched) overcome bias in results Use of internal standards can otherwise help overcome matrix effects, but not as effectively
ICP-MS techniques for biodiesel ICP-MS has a substantial detection limit advantage over ICP-AES Newer types of commercial ICP-MS systems overcome interference issues of older systems with organic matrices VHG Labs evaluating ICP-MS for characterizing blank biodiesel levels (without digestion of samples)
Standards developed for biodiesel testing Certified standards in biodiesel Matrix Metals: Ca, Mg, Na, K, P Sulfur - 0, 5, 10, 15, 20, 200 ug/g multi-element - 500 ug/g single element (incl. Fe, Cu, Zn) - 0, 5, 10,15,20, 25 50, 100, 250 500 ug/g In stock for ASTM testing and in development using B100 Viscosity TAN Water (Karl Fisher) Cloud point Flash point
Direction of the industry Industry Sustainability of the industry is an over-arching issue high commodity prices driving a move away from food source feedstocks. Many oil sources being investigated, even including algae. 2007 Federal Energy bill guarantees a large need for biodiesel in upcoming years Testing of Biodiesel 6751 fully voted in this June 2008 (likely) B6 and B20 might likely will have stand-alone methods this year Stability parameter might be added, i.e. rancimat type test EN 24114 and ASTM 6751 being harmonized. A few differences regarding test methods exists, but not involving metals. Dilution in kero common practice may not suffice for ICP-AES