Comprehensive Gas Chromatography (GCxGC) Analysis of High-Ethanol Containing Motor Fuels

Transcription

1 Paper # Comprehensive Gas Chromatography (GCxGC) Analysis of High-Ethanol Containing Motor Fuels Elise K. Libby, John V. Seeley, Stacy K. Seeley Oakland University, Rochester, MI, USA James D. McCurry Agilent Technologies, Wilmington, DE, USA Chunxiao Wang Agilent Technologies, Shanghai, Peoples Republic of China Dalin Conference Page 1 June, 2007

2 Alternative/Renewable Fuels Program Fuel blends containing part petroleum products and part renewable products Biodiesel, Methanol gas, and E85 Renewable Fuel Standard Program (RFS) Established by the Environmental Protection Agency (EPA) Increase amount of renewable fuel to be blended with gasoline 7.5 billion gallons/year by 2012, instead of 4 billion in 2004 Page 2

3 E85 Fuel Ethanol for Automotive Spark Engines 85 vol% denatured ethanol, 15 vol% petroleum based gasoline Must meet ASTM Specification D5798: Fuel Ethanol (Ed75-Ed85) for Automotive Spark Engines Feedstock: Denatured fuel ethanol Distilled ethanol (primarily from corn) Meets ASTM specification D4806: Denatured Fuel Ethanol for Blending with Gasolines Acceptable denaturants natural gasoline, gasiline components, unleaded gasoline Other possible contaminants Methanol, isobutanol, propanol Fusel alcohols Byproducts from distillation process 1- and 2- propanol, butyl alcohol isomers, and amyl alcohol isomers. Stability enhancers Page 3

4 GC Methods to Meet E85 ASTM D5798 Requirements Properties Specification Test Method Ethanol and higher alcohols, min. (vol %) D5501 Methanol, max (vol %) 0.5 Not specified (D4815 or D5501?) C3-C6 Alcohols, max (vol%) 2 D4815 Hydrocarbons/aliphatic ethers (vol%) D4815 for ethers, hydrocarbons by difference Page 4

5 E85 GC Methods ASTM D5501 Test Method for the Determination of Ethanol Content of Denatured Fuel Ethanol Single column method used to separate ethanol from gasoline denaturant Uses 150 m x 0.25mm PDMS column with 45 minute temperature program Method Scope 93 to 97 mass percent ethanol 0.1 to 0.6 mass percent methanol Method scope does not match D5769 specification Page 5

6 E85 GC Methods ASTM D4815 Test Method for the Determination of MTBE, ETBE, TAME, DIPE, t-amyl Alcohol and C1-C5 Alcohols in Gasoline Dual column configuration with valve switching Polar column separates oxygenates from low boiling hydrocarbons Non-polar column resolves oxygenates Method Scope 0.1 to 20.0 mass percent aliphatic ethers 0.1 to 12.0 mass percent alcohols Large ethanol content (70 to 79 vol%) may affect final results Page 6

7 D5501 Analysis of E85 Gasoline Sample ethanol Ethanol - Methanol vol% 0.02 vol% methanol Min. D5501 suitable for ethanol and methanol analysis in E85 gasoline Page 7

8 D4815 Analysis of E85 Separation of Low Level Alcohols and Ethers from Olefins 0.1 vol% Oxygenates Standard MeOH EtOH i-proh t-buoh n-proh MTBE s-buoh DIPE i-buoh ETBE TAA DME (istd) n-buoh Benzene Gasoline Blank No Oxygenates Min. Page 8

9 D4815 Analysis of E85 Sample Low Level Alcohols and Ethers Methanol - n-proh - i-buoh - ETBE - TAA - Total vol% 0.03 vol% 0.02 vol% 0.02 vol% 0.03 vol% 0.11 vol% MeOH EtOH n-proh i-buoh ETBE TAA Problems with Oxygenate Analysis using D4815 Min. Co-elution with low-level olefins Outside of method scope of 0.1 mass% per compound Page 9

10 GCxGC Analysis of E85 Gasoline Non- Polar primary column DB-1: 40 m x 0.18 mm x 0.20 micrometer Polar Secondary columns DB- Wax and DB-210 Analysis of alcohols, but no ethers Single GC Analysis with 10 minute run time Two axes of separation Page 10

11 Flow Modulated GCxGC System H 2 Carrier Gas Constant Flow Mode 1 o flow = 1.0 cm 3 min -1 2 o flow = 20.0 cm 3 min -1 2 o Column split = 1:1 2 o Injection Period = 1.5 s 40.0 m x 0.18 μm DB μm film thickness Page 11

12 10- minute GCxGC Analysis of Reformulated Gasoline 12 wt% Ethanol Page 12

13 Comparison of Gasoline with E85 Gasoline E85 Diaromatics Alcohols DB-Wax Alkanes Aromatics Ethanol Alcohols DB-210 Diaromatics Alkanes Aromatics Page 13

14 Calibration Standard Containing Alcohols, Ethers and Reformulated Gasoline n-proh n-buoh Ethanol i-buoh Methanol 2-BuOH TAA i-proh t-buoh Ethers unresolved from hydrocarbons Page 14

15 Details of Total Analysis of E85 Using GCxGC 1-Propanol 3-Methyl-1-Butanol Ethanol 78.1 vol% Isobutanol 2-Methyl-1-Butanol n-proh 0.04 vol% i-buoh 0.03 vol% C5 Alcohols 0.15 vol% 1-Propanol Isobutanol 3-Methyl-1-Butanol & 2-Methyl-1-Butanol Hydrocarbons/ Alipahtic ethers vol% (by difference) Page 15

16 Conclusions GC Methods Cited by ASTM Specification Requires two analyses totaling 80 minutes D5501 suitable for ethanol (>70 vol%) and methanol (<0.5 vol%) D4815 not suitable due to large ethanol peak and poor separation of alcohols below 0.1 vol% GCxGC A single 10-minute run for complete analysis of ethanol and higher alcohols Cannot separate aliphatic ethers Ethers reported with hydrocarbons Methanol not seen below 0.1 vol% Page 16