How to make BIODIESEL (part 2)

1/Titration

-Before you are able to process the vegetable oil into biodiesel you have got to know first how much methanol and catalyst you need. As far as methanol is concerned you may always assume about 200-220 ml methanol per litre of oil. The percentage of NaOH is variable. If new vegetable oil is processed, then you will require 5 g per litre of oil to substitute all glycerol by methanol. If waste oil is used then the same amount of catalyst will be required plus a certain amount to neutralize the free fatty acids that are present in the oil. To this end you will have to determine by way of a test, called titration, how many of these free fatty acids (FFAs) are present in your oil.

*What do you need?

• 10 ml isopropyl alcohol, 99%*
• Oil (heated to 45º C)
• Phenolphtaleine-solution (0,2%-0,4%)*
• Catalyst (NaOH, KOH)*
• Distilled water
• Some glass saucers
• Some hypodermic syringes to enable dosing the right amount.*
• a pair of scales preferably accurate to 0.1 or 0.01 g.

2/The procedure is as follows

-Dissolve 1 g of catalyst in 1 liter of distilled water, this solution is the titrant. NaOH is very difficult to dissolve. This can best be done by putting for instance 50 ml distilled water into a transparent bottle, adding the gramme of NaOH, closing the bottle and shaking it as long as it takes to see no visible grains and pouring this back into the distilled water.
-This solution is suitable to carry out titrations in the following weeks. In order to reduce the chance of errors, you may consider dissolving 3 g of catalyst in 3 liters of distilled water. An error of for example 0.2 g has less effect that way than in the case of 1 liter. Cork the bottle and keep it well. Take care when weighing the grains of NaOH that you do not leave the packaging open. The grains are very quickly to attract water and will not be fit for use anymore. The photo on the right shows how the grains look when they are subjected to a few minutes of oxygen.

• Pour 10 ml Isopropyl Alcohol in a glass cup or saucer.

• Heat a bit of the oil to be tested to a temperature of 45º C , mix 1 ml of it with the alcohol and mix well, it will get a yellowish colour.

• The amount of alcohol does not require much precision, but it is important that you should measure out exactly 1 ml of oil. An old trick is to suck in a bubble of air first into the hypodermic and then the oil, this way you are able to read more precisely.

• Add 2-3 drops of PH-indicator solution (phenolphthalein).

-Start carefully to add the water with the catalyst, keep swinging the cup. The fluid will colour to a light pink, but will turn yellow again if you keep swinging. When the oil with alcohol remains pink for a period of 30 s, you stop adding the solution. Make a note of how many ml of solution you have used and repeat the whole procedure once or twice in order to make sure you have titrated correctly.

-When you have a PH-meter at your disposal you can use it instead of the phenolphtaleine-solution. When the fluid has reached a PH-value of 8.5, then you have added enough NaOH-solution.
That's all !!!!

-If you need less than 3 ml of the solution then you most probably have laid your hands on very good oil, 3-6 ml means that the oil is suitable to turn it into biodiesel. 6 ml or more implies a poor quality, but the oil may still be suitable for the production of biodiesel. Take care when titrating that you should use each instrument for only 1 agent. We advise to label all hypodermics, pipettes and other tools in order to avoid mistakes.

3/Test batch

-Irrespective of the titration results, it is advisable to first process one litter of oil, before turning to the production of bigger amounts. Should you have made a mistake somewhere than this will appear now, this way you avoid that you may have to throw away maybe 100+ litres of oil because you made a mistake in titration.
-Fortunately, one litre of test diesel is easy to make. You start with heating 1 litre of oil to 45°C, preferably in a jar or bottle that can be corked. In the meanwhile you mix 220 ml of methanol with the amount of catalyst you determined in titration. Put this in a glass jar or bottle that can be corked well. This mix is called methoxide.

4/How much NaOH?

-In processing new oil you use 5 g of NaOH per litre of oil.
-In processing waste oil you take 5 g +1 g for each ml of catalyst solution you needed for titration. If 4 ml solution was needed, for example then you use : 5+4=9 g of NaOH
-Mix the methoxide until of the catalyst is dissolved. The chemical reaction will make the fluid to get hot. When all grains of NaOH have been dissolved, you carefully add the heated oil. Subsequently you shake or mix it all during 10 to 15 minutes.Leave the oil to rest. In less than an hour already you will see a separation between biodiesel and glycerine

5/Good or not good?

-The test has been successful if you see a distinct dividing line between the biodiesel and the glycerine, the amount of glycerine should be about 10% of the total content.
If less than 10% glycerine forms, then you probably have used too little catalyst, carry out a new test with 0.5 – 1 g more of catalyst.

-If you see a clear layer of soap between the biodiesel and the glycerine, then you probably have used too much of catalyst. Carry out a new test with 0.5 - 1 g less of catalyst.
If you see lumps in the biodiesel, then you have bad oil or the titration was incorrect. Carry out a new titration and make a new test batch from it. If you see lumps again, then you better should not use this oil.

-Leave the biodiesel to rest for 12-24 hours. Dark coloured, somewhat viscous glycerine will have formed at the bottom of the jar, with a distinct dividing line with the pale fluid above it. The colour of biodiesel varies and depends on the type of oil that was used, but is mostly palish yellow. The diesel can be clear, but this is not required per se, it may be very turbid as well. Not to worry. Eventually it will become clear, but there is no reason to wait.

***Warning: Methanol, Methoxide (Methanol/catalyst-mix), and NaOH are dangerous chemicals. Before use always read the safety regulations provided and follow the instructions on the packaging. Always work in a well-aired room and always wear personal means of protection, such as a suitable face mask, gloves and face protection when working with these materials.