Identifying the things you will need

Titrating: The first step in preparing your larger chemicals for production.

The titration is a necessary stage in order to know the quantity Sodium Hydroxide, NaOH (caustic soda) to be added to your methanol.Bio diesel from used cooking oil requires a titration before every batch is made. With fresh oil, however, this step is unnecessary.

An understanding between the two types of oil, fresh and used, will help to make this step clearer.

New cooking oil:Fresh cooking oil has a glycerin backbone and three fatty acid chains that are connected to this backbone. These components make up a total vegetable oil molecule, also known as a triglyceride molecule. When oil is fresh, glycerin and fatty acids are stable.To make bio diesel with fresh oil, all that is required is:1 litre of oil, 20% methanol by volume, and 3.5 grams of caustic soda

The 3.5g of NaOH is sufficient to split the glycerin backbone away from the fatty acid chains and allow the methanol to reconnect with these chains. Essentially the methanol pretends to be glycerin.

Used cooking oil:In used cooking oil however, once heat is applied to cooking oil, the bond between glycerin and fatty acids are partially broken, leaving partial free fatty acids (FFAs) in the vegetable oil.

Not all of the vegetable oil molecules are destroyed this way however, thus in used cooking oil there will still exist some fresh vegetable oil molecules. In other words, there are still many stable bonds that exist even in used oil and it is from these stable bonds that we make bio diesel.

These stable vegetable oil molecules will follow the same rule as with fresh cooking oil: 3.5g NaOH and 20% methanol by volume will convert 1 litre of oil to bio diesel.

But, because these stable molecules exist alongside broken vegetable oil molecules and FFAs, the NaOH will be attracted first to the FFAs in the oil before it has a chance to work with the stable molecules to produce bio diesel. (NaOH is an alkaline and the FFAs are acids. The two are naturally attracted to each other and will neutralize each other)

Because of this, an excess of NaOH must be added to used cooking oil, in order to: 1) allow the FFAs to be neutralized, and 2) ensure that 3.5 grams of NaOH is left behind to convert our 1 litre of stable vege oil molecules to bio diesel.

In other words 3.5g NaOH, PLUS excess NaOH, will convert used oil to biodiesel

Calculating this excess NaOH is the point of titrating our oil.

By not performing this titration, it is possible that insufficient NaOH can be added and as a result, FFA’s as well as monoglycerides and diglycerides will exist in partially made bio diesel, resulting in damage to engines.

What is needed:Just as the titration allows us to prepare the chemicals for bio diesel production, there are certain chemicals that have to be prepared for the titration. These are:

An indicator The solute The titrant

The indicator. The indicator indicates by colour, the “end point” of the titration, or the point at which all the FFA’s have been neutralized, leaving only stable molecules for conversion. The indicator changes from yellow, when the oil is acidic, to pink, when most of the acidity is neutralized. A good indicator that can be home made is one made using 1 part tumeric to 5 parts alcohol.

The solute is the sample you wish to perform the titration on. It is always 1ml of vegetable oil, dissolved in 10ml of pure alcohol.

The titrant. The titrant is a solution made up of 1 gram of NaOH, dissolved in 1 litre of distilled water. The NaOH is dissolved in water for a number of reasons. The first is because NaOH in solid form will not react well, and the second, because the quantities used in the titration are too small to be measured in solid form, whereas in dissolved form, tiny measured droplets containing even smaller quantities of NaOH can be used to provide accuracy.

The titrant is added slowly, in very small quantities, to our test sample being titrated. The more titrant added, the more FFAs are neutralized and the solution turns more from yellow to pink.

By adding 1 gram of NaOH to 1 litre of water, we actually have an accurate tool for measuring small quantities of the NaOH dissolved in it. If we took half of the volume of water, 500ml, we would also have half the amount of NaOH we added, in otherwords, 0.5g NaOH. If we took a quarter of the water, 250ml, we would have one quarter the NaOH, 0.250g.

Let us say for example that in our titration, instead of adding our titrant slowly, we simply dumped 4ml of our titrant into our solute, and the solute immediately turned pink.We could say that 4ml of the titrant was sufficient to neutralize the FFAs in our sample. However, it is possible it was really only 2.7ml that was needed, but we did not test accurately enough to determine that.

What is done therefore, is to add the titrant slowly, about 0.1ml drops at a time. As mentioned above, every time we take a known volume of water out of our water/NaOH solution, we are also taking out a known amount of NaOH. So if we add drops of 0.1ml of water, we are also taking 0.001g of NaOH in each drop.

By adding such small quantities slowly, we can determine the exact moment and amount of NaOH that will change the solution from yellow to pink , thus neutralizing the FFAs.

Once the FFAs are neutralized, from yellow to pink, we take note of how much of the titrant was used for this colour change to occur. If it took ten 0.1ml drops of the titrant (1ml), we add 1 gram to the 3.5 grams we already know about. It the titration took twenty 0.1ml drops (2ml) we add 2 grams to our 3.5 grams. And so on.

Step 1: Prepare the indicator. Measure 1 part tumeric to 5 parts alcohol. A measuring spoon works best. Wait for all the tumeric to settle to the bottom of vial before using. The alcohol should be yellow and not cloudy.

Step 2: Prepare the titrant. Using an accurate scale, weigh 1 gram of NaOH. Dissolve the NaOH into 1 litre of distilled water.

Step 3: Prepare the solute. Step 3.1: Measure 10ml of pure alcohol. (This is not the same as surgical

or rubbing alcohol.)

Step 3.2: Neutralize the acidity of the alcohol. As alcohol ages, it becomes slightly acidic. This can give inaccurate readings. To neutralize, add one to two small drops of the indicator to the alcohol and afterwards, add, slowly, measured drops of the titrant to the alcohol until it goes from yellow to pink.

Step 3.3: Add to the neutralized alcohol, 1ml of the vegetable oil sample. Mix thoroughly. The sample will turn from pink back to yellow again.

Step 4: Once the solute is ready, begin adding slowly, and counting, 0.1ml drops of the titrant to the solute. The solute will require stirring or mixing while adding the titrant. Continue adding until the solute can remain pink for a pprox. 30 seconds.

Step 5: Record the amount of the titrant that was added to the solute.

Step 6: Repeat steps 4 and 5 three more times. Step 7: Perform final calculations.

E.g. Let us say that we added 1.2ml of titrant in the first trial, 1.4ml in the second trial and 1.2ml again in the third trial. The average here is 1.3ml. Therefore we know that 1.3ml or 1.3 EXTRA grams is required to neutralize JUST the FFAs in 1 litre of our oil sample.

We add 1.3 to our 3.5 grams (the amount needed for our stable vege oil molecules) to have a total of 4.8 grams that would be needed to neutralize the FFAs AND convert the stable oil to bio diesel.

Step 8: Determine how many litres of oil you will be processing. Step 9: Multiply the number of litres of oil to be converted, by the amount of

NaOH needed to convert 1 litre. For e.g., assuming that we were making 40 gallons. So 40 gallons x 3.78 = 151.2 litres. 4.8g x 151.2 = 725.76g of NaOH.

Preparing the Methoxide

Once the methanol (20% of the total volume of vegetable oil to be processed) is ready, the NaOH must be added and mixed thoroughly until dissolved.