|Materials for Titration|
- conical beaker 100 ml
- measuring cylinder 1 liter
- burettes 30 ml
- pipettes 5 ml
- test tubes 5 ml
- test tube stand
- burette stand
- bottles 200 cc
- pH paper
- weigh scale 100 gm
- round bottom flask 2 liters
- heating mantle
- Potassium Hydroxide
- isopropyl alcohol
- distilled water
- phenolphthalein solution
- laboratory chemicals
Reagent: Dissolve 1 gram of KOH in 1 liter of distilled or de-ionized water (0.1% KOH solution).
Basic titration : In a smaller beaker, dissolve 1 ml of dewatered oil in 10 ml of pure isopropyl alcohol. Warm the beaker gently by standing it in hot water, stir until all the oil dissolves in the alcohol and the mixture turns clear. Add 2 drops of phenolphthalein solution to get end point.
Using a burette, add 0.1% KOH solution, drop by drop to the oil alcohol phenolphthalein solution, stirring all the time, until the solution stays pink (magenta) for 10 seconds. To the number of milliliters of 0.1% KOH solution you used, add 5. This is the number of grams of KOH you will need per liter of oil.
Test batches : The first few times you do this process, it is a good practice to first try out your KOH amounts on a 1 liter batch. This works really well and you do not need to heat up the oil too much, just enough so it will spin well. Start by mixing up the exact quantity of KOH and 200 ml of methanol. First make sure that vessels used are dry. Forming the exothermal potassium methoxide polar molecule will heat up the vessel a bit. Keep mixing until all the KOH has been dissolved.
Pre-heat 1 liter of Used Cooking oil or acid oil to 48 to 54oC, in 2 liter round bottom flask and heat by heating mantle. Add the potassium methoxide prepared, to oil. Install the condenser on top of round bottom flask. Make certain all your weights and volumes are precise. If you are unsure of the titration result then use 5.0 grams of KOH per liter of oil. Smaller batches need only be run for about 15 to 20 minutes. The solution can be poured from the vessel into another container right after switching off heating and cooling. Settling takes some time to complete.
It is good to do a few batches with varying amounts of KOH recorded, so later when checking results one can choose the KOH quantity that did the best job. When too much KOH is used the result can be a troublesome gel that is tough to do anything with. When not enough KOH is used the reaction does not go far enough so some unreacted oil will be mixed with the biodiesel and glycerine. This will form three levels with biodiesel on top above unreacted oil with glycerine on the bottom. If there is too much water in the oil, it will form soaps and settle right above the glycerine forming a fourth level in the container. This layer is not too easy to separate from the unreacted oil and glycerine layers.
Settling and Separation : Allow the solution to settle and cool for at least eight hours, preferably longer. The methyl esters (Biodiesel) will be floating on top while the denser glycerine will have congealed on the bottom of the container forming a hard gelatinous mass.
Glycerine Layer: It typically contains a mixture of glycerine, methanol, water, inorganic salts (catalyst residue) free fatty acids, unreacted mono-, di-, and triglycerides, methyl esters, and a variety of other matter organic non-glycerol in varying quantities. The glycerine from oil is brown and usually turns to a solid below about 38oC. The excess methanol can be recovered for reuse when boiled off, if you run the vapors through a condenser.
Soap residue: Suspended in the Biodiesel will also be some soapy residues. These are the result of K+ ions from the KOH reacting with water created when the methanol bonds with the ester chains along with any water that was suspended in the oil. The reaction produces more than the usual amount of soap if KOH comes into contact with water before KOH has a chance to react with the oil. In this case the excess water should have been boiled off first.
The part of the process where it is vital to keep all water out of the reaction, is when making the potassium methoxide. Keep the vessels where KOH comes in contact with, as dry as possible. The chances of a good clean splitting of ester from glycerine with little soap by-product are much better on a warm dry summer day than on a damp winter day.
Equipments required in laboratory for testing BioDiesel:
- Soxhlet Apparatus for determination of oil content in seed / cake
- Analytical Balance
- Gas Chromatography for oil and biodiesel
- Carl Fischer Titrator for moisture
- pH Meter
- Copper Corrosion test strips
- Kinematic Viscocity apparatus
- Oil Testing centrifuge for testing sediments
- Cloud and Pour point apparatus
- Flash point apparatus