Introduction to Biodiesel Fuel Lab Manual, Lab Reports of Chemistry

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Lab Manual

Introduction to Biodiesel Fuel

K. Walz, K. Cadwell,

A. Hoffman, and P. Morschauser

May, 2014

Version 6.

Lab Manual Contents

• ASTM Biodiesel Fuel Specifications - D6751
• Biodiesel Test Lab Student Data Sheet
• Titration of Used Oil Feedstocks
• Pensky Martens Flash Point Test
• Cloud Point Test
• Shell Cup Viscosity Test
• Copper Corrosion Test
• Rancimat Oxidative Stability Test
• 3/27 Glyceride Intermediate Test
• pHLIP Test
• Centrifuge Water and Sediment Test
• Sandy Brae Water Test
• Cold Soak Filtration Test
• Conradson Carbon Residue Test
• Paradigm Sensor Impedance Spectroscopy Test
• WI Biodiesel Production and Retail Station Lists
• WI Small Scale Biofuel Producer Program
• DOE Alternative Fuel Comparison Chart

Biodiesel Lab Test Data Sheet

Property

Test Method Apparatus/Procedure units limits

measured value result

Water content D2709 (^) Sandy Brae Test Kit % vol .050 max (^) or failpass

Water/Sediment D2709 Centrifuge % vol SeparationLayer? yes or no (^) or failpass

Carbon Residue (10 g sample) D4530^ Conradson flame test^ % mass^ .050 max^

pass or fail

FlashPoint, closed cup D^

Pensky Martens Flash Cup

o (^) C 130 min pass or fail Kinematic Viscosity (at 40 o^ C)

D445 (^) Shell Viscosity CupsViscometer^ mm^

(^2) /sec (cStokes) 1.9-6.^

pass or fail

Oxidative Stability (at 110 o^ C) EN 14112^ Rancimat^ hrs^ 3 hrs min.^

pass or fail

Copper Strip Corrosion D130^ Copper strips and heater^ class^ No 3. max^

pass or fail

Glyceride Intermediates 3-27 Test^ Solubility in methanol^ NA

Cloudy Emulsion or Insoluble liquid

yes or no (^) or failpass

Free and Total glycerin pHLip^ pHLip assay^ NA^

Haze or emulsion yes or no^

pass or fail

FFA (pH) pHLip pHLip assay NA (^) indicatoryellow yes or no (^) or failpass

Residual Catalyst (pH) pHLip^ pHLip assay^ NA^

purple indicator yes or no^

pass or fail

Specific gravity D1250 hygrometer NA report NA

Cloud Point D2500 cloud point bath o^ C report NA

Cold Soak Filtration D7501^ Vacuum Filtration^ seconds^

360 sec max

Pass or fail Total Glycerin (TG) (^) Ispec Q100D

Paradigm Sensor Impedance Spectormeter

% mass 0.25%max or fail^ pass

% Methanol (MT) EN Ispec Q

Paradigm Sensor Impedance Spectormeter

% mass 0.20%max or fail^ pass

Acid Number (AN) (^) Ispec Q100D

Paradigm Sensor Impedance Spectormeter

mg KOH/ g fuel 0.50 max^

pass or fail

Fatty Acid Determination of Used Oil Feedstocks

for Biodiesel Production

Background: Biodiesel fuel is made by mixing vegetable oil (triglycerides) with methyl alcohol (aka methanol) in the presence of a basic catalyst (KOH). This produces glycerol (a byproduct) and fatty acid methyl esters (the biodiesel fuel).

O H

O H

O H

O R

O H 3 C

O

O

R

O

O

R

O

O

R

CH 3 O H

KO H

triglyceride (^) methanol glycerol fatty acid methyl ester

3 3

BASIC BIODIESEL RECIPE FOR VIRGIN VEGETABLE OIL

Catalyst Mixture: 20 g of KOH per gallon of oil ( recommended by Josh Tickell, known to be too little ) 26 g of KOH per gallon of oil ( recommended by Piedmont Biofuels ) 36 g of KOH per gallon of oil ( recommended by Jon Van Gerpen , known to be excess )

Reaction Mixture: 1 gallon of methanol/KOH catalyst for every 5 gallons of oil Reaction Temp: Recommend between 55 and 60 o^ C (methanol BP = 64.7 o^ C) Reaction should take from 60 to 120 min at 60 o^ C, Depending on feedstock quality (van Gerpen et al.)

Problem: When vegetable oil is used for cooking purposes (especially for frozen foods), some of the triglyceride oil molecules break down to create free fatty acids (FFAs). The FFAs lower the pH of the oil, and unfortunately will neutralize the basic catalyst (KOH) that is normally added to speed the reaction up.

+ H 2 O ------------- > 3

heat

Free Fatty Acids (FFAs)

Solution: By doing a titration test before processing the fuel, we can measure the concentration of FFAs in the used cooking oil. We will then add additional extra KOH to our reaction to account for the neutralization of the FFAs.

OH

OH

OH

O R

O H 3 C

O

O

R

O

O

R

O

O

R

CH 3 OH

KOH

triglyceride (^) methanol glycerol fatty acid methyl ester

3 3 HO

O

R

Pensky-Martens Closed Cup Flash Point Test

A fuel’s flashpoint is the minimum temperature at which there is a sufficient concentration of evaporated fuel vapor for combustion to propagate after an ignition source (spark or flame) has been introduced. The concentration of fuel vapor is directly related to the fuel’s vapor pressure, which in turn is dependent on temperature (see figure 1 below). Different fuels require different vapor concentrations to initiate combustion, thus flash point varies significantly between fuels (see Figure 2). In fact, the flash point differences between gasoline and diesel fuels are integral factors in the function of spark ignition versus compression ignition engines.

Figure 1. Vapor Pressure as a function of temperature for ethanol and biodiesel fuel.

Figure 2. Flashpoints of several common fuels. Fuels marked with * indicate this value is the minimum allowed by ASTM. Fuel Flashpoint (°C) Flashpoint (°F) Gasoline -43* -45* Acetone -18 0 Methanol 10 50 Ethanol 12 54 Isopropanol 12 54 Octane 13 55 Butanol 35 95 #1 (winter) diesel 38* 100* #2 (summer) diesel 52* 126* #4 (marine) diesel 55* 131* #6 bunker fuel 66* 151* Methyl stearate 110 230 Methyl laurate 113 235 Biodiesel 130* 266* Cetane 135 275 Methyl oleate 180 356 Methyl linoleate 186 367 Canola oil 192 378

The Department of Transportation uses flashpoint to determine shipping and safety regulations. The DOT classifies substances as either flammable or combustible using the following criteria:

Flashpoint (°C) Boiling Point (°C) Flammable Class IA < 22.8°C < 37.8°C Class 1B < 22.8°C > 37.8°C Class IC 22.8°C - 37.8°C N/A

Combustible II 37.8°C - 60°C N/A IIIA 60°C - 93°C N/A IIIB > 93°C N/A

Your instructor will assign you and you lab partner(s) a fuel sample)to measure the flashpoint. Data may be combined to obtain class averages and to draw comparisons.

1. Inspect the flash point tester to ensure sample test cup is clean, the fluke digital thermometer is in place, and propane supply is turned on.

2. Making sure test cup and specimen are at least 18°C (32°F) below the expected flash point. Fill the test cup between 50% and 85% full with the fuel sample, place lid on cup and set cup inside the stove, making sure grooves are properly aligned.

3. Adjust the valve screw on the burner block starting with it all the way closed, then open it only 1/10 of a turn. Using the lighter provided light the test flame and adjust the screw if necessary to attain a flame size of ~ 1/8 inches in diameter (use the bead on the burner block for comparison).

4. Your instructor will suggest a preheat temperature and heat rate setting for your sample. Using the variable heat rate dial, adjust the rate assigned to you (either 25, 50, 75 or 100).

5. Stir sample using the mechanism on the top of the flash point instrument. WEAR A GLOVE DURING THIS PROCESS. The top sections of the instrument will get very hot to the touch.

6. Stop stirring (do this each time you apply the test flame). Lower the flame for half a second, leave it for 1 second, and then quickly raise the flame back to the test position.

7. Test the flashpoint at 5 o^ C temperature intervals as the sample heats. Stir between each test.

8. Record the flash point for your fuel. The sample is deemed to have flashed when “a large flame appears and instantaneously propagates itself over the entire surface of the test specimen ". You should see a flash, which sometimes is accompanied by a whoosh or popping noise as well.

9. Turn the temperature dial down to zero and allow the instrument to cool. Only remove and clean test cup once the temperature have decreased to safe handing temperatures of less than 55°C (130°F). If yours is the last sample that will be tested for the day, turn off the propane tank.

10. The instructor may assist you in the use of compressed air to cool the flashpoint apparatus.

Shell Cup Viscosity Test

Viscosity is an important factor in determining the suitability of biodiesel for use in engines. If the fuel viscosity is too high, the injection pump will not be able to supply sufficient fuel into the cylinder. If the viscosity is too low, it may provide insufficient lubrication for fuel pumps and injectors and in extreme cases, may cause fuel injector nozzles to leak/drip.

High viscosity may be caused by: a) Presence of unreacted feedstock oil and/or monoglyceride and diglyceride intermediates in the biodiesel fuel (symptomatic of an incomplete transesterfication process).

b) Presence of glycerol byproduct in the biodiesel fuel (symptomatic of incomplete separation).

Low viscosity may be caused by: a) Presence of methanol in the biodiesel fuel. Note that this will also be indicated by a low fuel flashpoint (symptomatic of an incomplete washing process).

b) Presence of water in the biodiesel fuel. Note that this will also be indicated by the centrifuge water and sediment test (symptomatic of an incomplete drying process).

There are two types of viscosity: kinematic viscosity measures the resistance of a liquid to flowing under gravity and has units of mm^2 /s or centiStokes; dynamic viscosity is the ratio of the applied shear stress to the rate of shear of a material and has units of mPa·s or centiPoise. The kinematic and dynamic viscosity of a fluid are related by its density. The density of biodiesel is about 0.88 g/cm^3.

kinematic viscosity (in centiStokes) = dynamic viscosity (in centiPoise) ÷ density (in g/cm^3 ) 1 centiPoise = 1cP = 1 mPa·s and 1 centiStoke = 1cS = 1 mm^2 /s

The tables below list the kinematic viscosity (in cS) of several pure liquids and common fuels.

The viscometer you will be using measures the dynamic viscosity of fluids, but the ASTM 6751 standard for B100 (pure biodiesel) specifies a kinematic viscosity in the range of 1.9 – 6.0 cS at 40°C (104°F). You will measure the dynamic viscosity of your biodiesel and use the equation above or the attached table to convert its dynamic viscosity value to a kinematic viscosity value.

Pure Liquids Viscosity ethanol 1. hexadecane 2. soy oil 35. palm oil 47. rapeseed oil 54. lard 62. glycerol 176.

Fuel Min Max #1 Diesel 1.3 2. #2 Diesel 1.9 4. #4 Diesel NA 29. Biodiesel (B100) 1.9 6.

Materials & Equipment: Shell Viscosity Cups #1&3 Digital Thermometer Temperature Bath

Procedure:

1. Set up a water incubator bath to warm your feedstock and biodiesel samples. Place the probe tip of the digital thermometer into the sample liquid to be tested. The temperature should read between 38°C and 42 °C. If it does not, slightly adjust the bath setting and wait a few minutes for the temperature to change.
2. When the liquid is in the desired temperature range, remove the thermometer from the sample cup. Use the Shell cups to measure the drain time for the liquids to be sampled. The Shell cups must be immersed in ~120 mL of liquid so that the cup is completely filled. Stop the timer when the line of fluid draining from the cup first breaks. If instructed, repeat this measure 2 or 3 times and calculate an average.
3. Use the calibration curves provided for each of the Shell Cups to determine the viscosity of each liquid in centiPoise (cP). Mark points and label the drain times for each of the liquids tested on the graphs provided.

Feedstock Dynamic viscosity: _________ cP Kinematic Viscosity:________ cS

Biodiesel Dynamic viscosity: _________ cP Kinematic Viscosity:________ cS

4. Calculate the kinematic viscosity of each liguid in centistokes. OR use the table below to find the nearest dynamic viscosity value to the one you measured and read across to find the corresponding kinematic viscosity value and record it above. Note the density of biodiesel is ~ 0.88 g/cm^3

Dynamic viscosity (in cP) ÷ density (in g/cm^3 ) = Kinematic viscosity (in cS or mm^2 /s

5. Is the kinematic viscosity of your biodiesel within the ASTM specification of 1.9 – 6.0 cS? If not, what processing conditions might have caused your fuel to be off-spec?

Copper Strip Corrosion Test

Sulfur and other acidic/basic compounds in diesel fuels can have corrosive action on various metals (especially copper and brass which are often used in fuel line systems and). The copper strip test measures the relative corrosiveness of a fuel sample.

Excessive copper corrosion may be caused by:

a) Presence of sulfur compounds in the fuel (possibly for biodiesel blends with petroleum).

b) Presence of residual KOH catalyst in the biodiesel fuel (symptomatic of an incomplete neutralization/washing process).

c) Presence of free fatty acids in the biodiesel fuel (symptomatic of aged fuel that has oxidized).

d) Presence of water in the biodiesel fuel. Note that this will also be indicated by the centrifuge water and sediment test (symptomatic of an incomplete drying process).

Materials & Equipment: Copper strip (3” x ½” x 1/16”) Steel wool and ethanol to clean copper surface Constant temperature bath/block (50 oC) Reaction vessel with biodiesel fuel

Procedure:

1. Clean the surface of the copper strip by polishing with steel wool. Use ethanol to help remove any oil deposits from your fingers. Verify the clean surface with a white cotton swab before proceeding.
2. Preheat a constant temperature bath/block to receive the sample chamber at 50 oC.
3. Immerse the copper strip in the sample chamber, seal and heat for 3 hours.
4. After 4 hours, remove the copper strips from the sample chamber. Clean the strip with ethanol and classify according to the following descriptions:

Slight Tarnish 1 a. Light orange, almost the same as freshly polished strip b. dark orange Moderate Tarnish 2 a. Claret red b. Lavendar c. Multicolored with lavender, blue, or silver overlaid on claret red d. Silvery e. Brassy or gold Dark Tarnish 3 a. Magenta Overcast on Brassy Strip b. Multicolored with red and green showing (peacock), but not gray Corrosion 4 a. Transparent black, grey, or brown with peacock green barely showing b. Graphite or lusterless black c. Glossy or jet black

Rancimat Oxidative Stability Test

Over time, fuels can degrade by reaction with oxygen from the air. The rate at which biodiesel oxidizes depends on both the feedstock and processing conditions used to make the fuel. The oxidation process typically occurs over time scales of weeks to months, and is accelerated by factors such as aeration, light, and temperature. In some cases, the oxidation process may be slowed/inhibited through use of fuel additives (e.g. antioxidants, preservatives, etc.). The Rancimat oxidative stability test measures the rate at which biodiesel fuel decomposes when subjected to elevated temperatures and vigorous aeration. These conditions allow for a rapid measure of fuel stability that has been shown to correlate to the slower oxidative process that occurs under normal storage conditions.

Preparing the Instrument Do this step a few days before the measurement is to be made:

1. Regenerate the intake air molecular sieve by removing the canister and heating it in a drying oven at 140– 180 oC for 48 hours.
2. Inspect the intake air filter and replace if necessary.

Cleaning the Instrument The cleanness of instruments and accessories is an absolute necessity for achieving reliable, reproducible and correct analytical results. Even minute contamination can catalytically accelerate the oxidative decomposition and lead to completely false results.

1. Check whether the openings for the glass reaction tubes are clean and empty. Blow out any dust in the openings with nitrogen.
2. Clean conductivity measuring vessels several times with alcohol and distilled water (do not use acetone!).
3. Rinse the measuring vessel cover complete with electrodes several times with distilled water. If necessary, remove the protective ring for better access to the electrodes.
4. Rinse the connection tubing between reaction tube and measuring vessel several times with distilled water and alcohol or acetone.
5. It is recommended to use new glass reaction tubes and air tubes for each determination.
6. Used and not too strongly contaminated reaction tubes and air tubes can be cleaned by immersion in boiling RBS solution or a similar laboratory flushing agent for 1 h. They must then be thoroughly rinsed with distilled water and acetone.
7. Remove the air tube from the reaction tube cover and rinse it several times with distilled water and acetone. Dry the cover at 80°C in a drying oven. 8. Note: Reaction tubes and tube covers which have not been dried properly can contaminate the sample with water and falsify the results.

Oxidative Stability and Induction Times for

Peanut Oil at 130, 120, 110, and 100 C

Conductivity (uS/cm) versus time (hours)

Log-Linear Extrapolation of Oxidative Stability for Peanut oil

Temperature (C) versus Time (h)

I n d u c t i o n t i m e S t a b i l i t y t i m e

1. 0 2. 5 5. 0 7. 5 1 0. 0 1 2. 5

6

0

. 3^

μ^ S^

/ c^

m

h

P e a n u t o i l / D B G 2 3 0 7 P e a n u t o i l / D B G 2 3 0 7 P e a n u t o i l / D B G 2 3 0 7 P e a n u t o i l / D B G 2 3 0 7

1 0

2 0

3 0

4 0

5 0

6 0

7 0

8 0

9 0

1 0 0

1 1 0

1 2 0

1 3 0

1 4 0

1 0 1 1 0 2 1 0 3

° C

h

The “3/27” Glyceride Intermediate Test

(Mono, Di, and Triglyceride content)

1. For the glycerides test add 27 ml of methanol to a glass vial. Using a disposable beral pipette, add 3 ml of commercial biodiesel. Cap the vial to seal.
2. Shake vigorously for a minute, and allow the mixture to settle in a test tube rack.

Biodiesel that meets ASTM specs should dissolve in the methanol solvent resulting in a single phase of clear liquid. Biodiesel that is out of spec will result in a cloudy emulsion of glyceride and methyl ester droplets suspended in the methanol.

4. After 5 minutes observe the bottom of the vial.

Biodiesel that meets ASTM specs for free and total glycerol should remain dissolved in the methanol solvent as a single phase of clear liquid. After settling, biodiesel that is out of spec will typically exhibit an insoluble glyceride liquid layer at the bottom of the tube in addition to the cloudy emulsion suspended in the methanol.

For video footage, see http://www.youtube.com/watch?v=R3jGvefA4OI

5. Observe the interface between the two layers: is it smooth and “mirror-like” or does it appear that there is a middle layer present?
6. Interpret the quality of your biodiesel with respect to glycerin and catalyst contamination and acid number using the guidelines and photos below (excerpted from the manufacturer’s instructions).

High quality biodiesel is indicated by:

• Clear biodiesel layer
• Clear, “cherry red” indicator layer
• Smooth, “mirror-like” interface

A cloudy biodiesel layer combined with a clear, red indicator layer is characteristic of excess free or total glycerin or free fatty acids (in aged fuel). The glycerin/glycerides may also form a middle emulsion layer between the fuel and the indicator.

A cloudy lower layer is likely due to soap contamination. Soap may be formed by a combination of water, free fatty acids and catalyst.

A purple lower layer indicates a high pH. This results from residual alkaline catalyst (KOH, NaOH, etc.) in the fuel.

An orange or yellow lower layer indicates a low pH. This results either from high free fatty acid content of the feedstock or aging of the fuel.

Centrifuge Test for Water and Sediment

Water and sediment can cause problems with fuel line icing and filter plugging. In order to meet ASTM specifications, biodiesel must contain < 0.050% water and sediment by volume. Failure to meet this specification usually is attributable to poor separation processes during the biodiesel synthesis or washing stages.

Materials & Equipment: Centrifuge, Centrifuge tubes, biodiesel fuel

Procedure:

1. Check all of the slots available on the centrifuge and inspect for the presence of weights or stoppers in the bottom of the slots. It is critical to ensure that the centrifuge rotor is balanced.
2. Obtain two matched centrifuge tubes of similar manufacture (same shape, mass, etc.) Fill both tubes with equal quantities of biodiesel so that they contain an equal mass of fuel.
3. Place the tubes in centrifuge slots located directly opposite one another to maintain balance on the rotor.
4. Spin the samples at 800 rcf (relative centrifugal force) for a period of 10 minutes.
5. When the centrifuge has stopped, remove the tubes and report the % water and sediment.

Note: ASTM D2709 requires specialized centrifuge tubes to obtain the desired accuracy for this test. If performing the test to these standards, the taper bottom tubes must accommodate 100 mL fuel samples and be marked with graduations to the nearest 0.01 mL.