Determination of the 14 C content in biodiesel. A method improving the detection sensitivity by decolorizing the biogenic materials in biofuels

Transcription

1 Determination of the 14 C content in biodiesel. A method improving the detection sensitivity by decolorizing the biogenic materials in biofuels M. Stomp-Smit, J. ter Wiel, R. Edler 2009 PerkinElmer

2 LSC for 14 C samples of biogenic origin 14 C of biogenic origin History Available Methods Sample Preparation for removal of Color Measurements with Biodiesel 2

3 LSC for 14 C samples of biogenic origin 14 C measurements of biogenic origin a.) Historically mainly carbon dating b.) Differentiation between fossil alcohol and alcohol from fermentation in wine and spirits Interest in biogenic 14 C increased with the increased interest in the reduction of the emissions of the fossil greenhouse gas CO 2 3

4 4 Regulations Important steps for 14 C measurements of biogenic samples a.) Kyoto protocol December 1997 (binding obligations on participating countries to reduce the emission of greenhouse gases in general) b.) Farm Security and Rural Investment Act in 2002 c.) Directive 2003/30/EC of the European Parliament in 2003 (exact definition of minimum amounts of biogenic additives to fuel) d.) Federal Biobased Products Preferred Procurement Program (FB4P). In 7 CFR ASTM 6866 is used to determine the amount of biogenic 14 C e.) CEN/TR 15591/EN in 2006 describes the determination of 14 C in solid recycled fuel. f.) DIN (2013?) determination of HVO in fuel

5 Importance of routine measurements Why are measurements so important a.) Only one out of 10 samples passed the specifications that the United States Department of Defense required for blends that contain 20% biodiesel (C. M. Reddy et al.) b.) Tax difference between fossil and biogenic fuel components in many countries 5 C. M. Reddy, J. A. DeMello, C. A. Carmichael, E. E. Peacock, L. Xu, J. S. Arey; Determination of Biodiesel Blending Percentages Using Natural Abundance Radiocarbon Analysis: Testing the Accuracy of Retail Biodiesel Blends, Environ. Sci. Technol. 42, 2476 (2008).

6 Methods for 14 C determination in biogenic materials Method Merit Drawback Direct LSC Analysis Method A: CO2 & LSC Method B: AMS/IRMS Method C: Benzene Synthesis & LSC Minimal, fast sample preparation, good sensitivity, lower costs per evaluation, high instrument availability, LSC is the most widely used method for 14C determination Less sample preparation than in Method C, lower costs per evaluation, high instrument availability worldwide High sensitivity, precise High sensitivity, precise, high instrument availability worldwide Not in accordance with ASTM standard D which discusses methods A, B and C Small sample activity due to limited uptake capacity of Carbo-Sorb E, not sensitive for lowest 14 C concentrations High cost, mostly for cases in dispute or less than 10% carbon by weight Slow sample preparation, small capacity, new benzene synthesizers hard to acquire, benzene carcinogenic 6

7 Direct Method for 14 C determination in biogenic materials The direct method for 14 C determination is preferred for liquid samples such as wine, alcohol and fuels due to simplicity of this method. The direct measurement of biodiesel based on FAME was problematic so far, due to heavy color quench in most biodiesel samples containing more than 10%. Biodiesel. (R. Kristof, J. K. Logar) 7 R. Kristof, J. K. Logar; Quenching Parameter in the Measurement of Biodiesel by Liquid Scintillation Counting, LSC 2010, Advances in Liquid Scintillation Spectrometry, Proceedings of the 2010 International Liquid Scintillation Conference, Paris, France, 6-10 September 2010, P. Cassette (Editor), page 35 (2011).

8 The Basic Liquid Scintillation Process The Scintillation Process radioactive molecule b solvent molecule fluor molecule hn photomultiplier tube Physical Quench Chemical Quench Dipol-Dipol interaction Light nm Molecule collisions Color Quench Light primary scintillator nm Light secondary sctintillator nm Unfortunately chemical quench and colour Quench have different influence on the counting efficiency and correction cannot be done with a simple quench for chemical quench. 8

9 Direct measurement of Biodiesel For our investigations we used a Biodiesel sample from Biovalue in Eemshaven, Netherlands. The Biodiesel sample was produced from rapeseed (brassica napus) which originated from all over the world. All raw materials contained a strong yellow to brown colour. 10% Biodiesel sample in 6 ml glass vial 9

10 Efficiency (%) Direct measurement of Biodiesel 100 Efficiency versus tsie C14 Quench Set C14 yellow Dye tsie A pure biodiesel sample with a tsie of 94 corrected with a chemical quench curve results in too high efficiencies and consequently in too low activities. 10

11 Direct measurement of Biodiesel For the comparison of calculated and theoretical DPM values we made the following assumptions: 1.) Biodiesel consists of 100% erucic acid 2.) Biodiesel density of 0.86 g/ml 3.) Modern carbon activity of 14 DPM/g carbon for biogenic material in 2010 O HO Erucic acid, monounsaturated omega-9 fatty acid C 22 H 42 O 2, molecular mass = g/mol 11

12 Purification of 10% biodiesel in heptane Initially we used a 10% biodiesel sample in heptane for ease of use. Measurements were done in Ultima Gold F with a Tri-Carb 2550TR/AB in 6 ml Pico glass vials, 3 ml sample, 3 ml Ultima Gold F in the open 14 C window from kev, counting time 60 minutes. Silicagel 60 Cycle1 CPM tsie % Eff. % Lum. Heptane 12, ,1 1 Fuel 36, ,1 1 10% Biodiesel 15, ,1 11 (yellow) purified 14, ,9 1 Aluminum oxide 90 Cycle2 CPM tsie % Eff. % Lum. Heptane 12, ,1 1 Fuel 37, ,1 0 10% Biodiesel 14, ,1 1 (yellow) purified 13, ,0 0 1 cm 12

13 Purification of 10% biodiesel in heptane CPM tsie %Eff. %Lum. Original 16, ,7 1 Fraction 1 13, ,1 1 Fraction 2 15, ,9 1 Fraction 3 16, ,1 1 Fraction 4 16, ,1 1 Fraction 5 16, ,8 1 Fraction 6 16, ,1 1 10% biodiesel 1 st, 2 nd and 3 rd fraction

14 Efficiency (%) Measurement of diluted biodiesel with Quantulus 1220 Accurate biodiesel measurements without removal of color require color correction Sample µl yellow dye SQP CPM 14 C Eff ,0 8087,5 89, ,4 8027,3 88, ,7 7562,1 83, ,3 7052,2 77, ,0 6464,3 71, ,9 5769,2 63, ,6 4807,1 53, ,8 3403,4 37, ,0 2293,8 25, ,9 1353,5 14, ,5 788,4 8, ,9 457,6 5, ,8 303,2 3, Yellow dye solution in Ultima Gold F Poly. (Yellow dye solution in Ultima Gold F) y = -0,0004x 2 + 0,7644x - 310,93 R² = 0,9861 Quench Curve SQP Yellow dye: 20 mg dimethyl azobenzene in 100 ml Ultima Gold F All standards contained 9075 DPM +/- 1%

15 Measurement of diluted biodiesel with Quantulus 1220 Sample mg biodiesel SQP Ch CPM - blank 14 C Eff. % dpm dpm/g biodiesel dpm/g carbon Measurement of different amounts of biodiesel in 10 ml Ultima Gold F in the open 14 C window (channel )

16 Purification of undiluted biodiesel Slightly different procedure: 50 g biodiesel were stirred with 3 g of aluminum oxide and 300 mg of charcoal for two hours at 50 C. Two different column preparations: Test 1: Only 10 g of aluminum oxide inside the glass column. Test 2: Column filled with 10 g of aluminum oxide and 2.5 g silica gel on top. CPM tsie DPM Theory Heptane 11, Original 20,2 94,7 20,4 23,5 Test 1,1 33, ,4 23,5 Test 1,2 32, ,6 23,5 Test 2,1 33, ,6 23,5 Test 2,2* 32, ,8 21,95 CPM tsie DPM % Eff. Heptane ,5 Original ,87 Test 1, ,3 Test 1, ,5 Test 2, ,1 Test 2,2* ,8 * The fraction Test 2,2 only contained 2 g of biodiesel, other samples contained 2.15 g biodiesel

17 Sensitivity for the measurement of undiluted biodiesel g k 1 k E V 1 b R 0 1 t0 1 t m Bq/L Sensitivity for colored biodiesel (120 min): 33.8 Bq/L Sensitivity for colorless biodiesel (120 min): 14.4 Bq/L Increasing the sample volume and optimizing the energy window allows sensitivities below 1 Bq/L in 120 minutes counting time on a Quantulus.

18 Purification of undiluted biodiesel Problem background correction: A major problem in colored samples is the determination of background. Colored samples require a quench dependent background correction. SQP (E) CPM Channel net CPM channel Blank (heptane) 839 0,597 75,7 0 1 g biodiesel 490 0,365 #?? Eff% DPM DPM calculated 1 g purified 829 8,657 8,060 75,5 10,69 10, mg biodiesel 713 1,235 0,638 62,6 1,180 1,097 Measurements done in a Quantulus 1220 in 20 ml plastic vials using 10 ml Ultima Gold F

19 Summary Colorless biodiesel Colored biodiesel Normal chemical quench curve results in accurate data. Simple hydrocarbons can be used as a background source. High sensitivity Untreated biodiesel samples require color correction. Quench dependent background correction required. Limited sensitivity 19

20 Finish Thank you for your attention!!! Ronald Edler Specialist Radiometric Detection Mobile: +49 (0)