Presentation on theme: "Biodiesel and Soap Week 3 Collection and Analysis of Biodiesel."— Presentation transcript:
Biodiesel and Soap Week 3 Collection and Analysis of Biodiesel
Getting biodiesel Siphon off the biodiesel May be contaminated with Soap Un-reacted acid Wash with water until Allow to separate Measure pH of water Repeat until pH ~7 Collect biodiesel Dry biodiesel
Analytical Techniques % yield Calorimetry Viscometry Single temp or as a function of temperature Freezing point FTIR Volatility analysis Thin layer chromatography GC-MS
% Yield Product yield Mass of biodiesel produced as a percentage of mass of oil used Good for comparing yield from different methods
Calorimetry Burn biodiesel and used heat given off to raise the temperature of water (NOT BOIL). Monitor the starting temp and final temperature of water Biodiesel + O 2 CO 2 + H 2 O + heat Heat given off will be used to heat q water (J) = m (g) * C (J/g.K) * ΔT (K)
Calorimetry How does this work? This is a quick and dirty method - good for comparison but not research grade Get a can Add known weigh to water to the can Can also make use of density of water and measure volume Weigh biodiesel into a crucible (use crucible which is already black- do not use pristine ones). Place a wick in oil Place can over crucible Set biodiesel alight while monitoring the change in temperature of the water. Ideally don’t want > 60C Calculate J/g or J/mg of C for water is J/(g.K)
Volatility Heat the sample to see if volatile impurity is lost Ethanol Water? Will have oven set to 75 C for this (Felizardo et al., Waste Management 26 (2006) 487–494) Don’t want to use Bunsen (flames)
FTIR Look for presence (or absence of functional groups) Good way to compare reactants and products Different biodiesel Know how to use the FTIR instrument
Viscometry Will use Varnish Viscometer Tubes flat bottom with graduation lines at 27, 100 and 108mm from the outside bottom Approximate I.D.=10.74 ± mm, length=114 mm How do you use Fill to 2 nd line Turn up side down and allow liquid to completely settle Turn right side up and note the bubble time which is the time bubble rises from the bottom-line (27) to the middle line (100). The length of time, in seconds, required for an air bubble to pass from the 27mm to 100mm score mark, a distance of 73mm, is approximately equal to the viscosity of the liquid in "Stoke" units; alternatively, viscosity may be expressed in "Bubble Seconds." It is important to note that the position of the air bubble in relation to the 27mm score should be similar at the end of the test on the 100mm score.
Thin Layer Chromatography (TLC) A good way to check for impurities How many different compounds are in a sample Very small quantities of the samples is placed on the special TLC plates The plate is put in a container with a solvent or solvent mixture The solvent runs up the plate and will separate the different kinds of molecules based on polarity differences and size differences
Chromatography Two types which essentially uses the same principles Thin Layer Chromatography Gas Chromatography
Thin Layer Chromatography (TLC) There are two phases a stationary phase (a solid, or a liquid supported on a solid) and a mobile phase (a liquid or a gas). The mobile phase flows through the stationary phase and carries the components of the mixture with it. Different components travel at different rates. The stationary phase in this case is silica gel coated on a thin piece of rigid plastic The mobile phase in this case is a mixture of solvents hexane and ethyl acetate in a 80:20 ratio (v/v)
Thin Layer Chromatography (TLC) How does it work? Get a cut piece of TLC plate Mark a line (in pencil at the ¼ inch from the bottom) Place a small dots of the biodiesel and oils on the line. There should be sufficient space between the dots When the sample is dry, place the plate in a shallow layer of solvent in a covered beaker. Make sure that the solvent level is below the line. As the solvent moves up the plate, different components will move at different rates. When the solvent reaches the top, remove the plate from the solvent. Place the plate in an iodine chamber and allow the color to develop Mark the various spots on the plate Calculate the Rf value for each component Rf = distance traveled by component distance traveled by solvent Ionic compounds will be more tightly held by the plate and will have a lower Rf value.
What is going on? The sample is first dissolved in the mobile phase The compounds present will then tend to get carried up the chromatography plate as the solvent continues to move upwards. How fast the compounds get carried up the plate depends on two things: The solubility of the component which is dependent o the Inter molecular Forces between the compound and the mobile phase. How much the compound sticks to the stationary phase is dependent on the IMF the compound and the silica gel. A compound which can form H-bonds ( N-H, O-H), will tend to stick to the stationary phase and will have lower Rf values
Gas Chromatography (GC- MS) Separates components of samples based on their boiling point or volatility. This tends to be far more effective than TLC The sample is injected on a column and a carrier gas (N 2 ) is passed over the column while the column is being heated. The more volatile compounds will be eluted (washed off the column) first. Mobile phase is called carrier gas is N 2 The compounds are identified by mass spectroscopy. To see how this works visit the web site at: http :// http :// http :// The settings we will be using is optimized for examining acids and their esters.
Prep of sample for GC-MS Each lab group may submit up to 5 samples for analysis by GC-MS You first need to make a 1:100 dilution of your sample in methanol (not water) You will be provided with 10 ml volumetric flasks for this. Place ~2 mL of diluted sample in labeled vial Close vials tightly and place in vial holder