Biodiesel Investigation - How the concentration of Potassium Hydroxide solution would affect the yield of biodiesel when transesterified with a standard sample of vegetable oil .

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                11th May 2015

Biodiesel Experiment


‘Biodiesel is a clean burning renewable fuel made using natural vegetable oils and fats.1 Biodiesel is a revelation to chemists, engineers and environmentalists who are looking for more sustainable ways to make use of fuels. Since it is a natural and renewable fuel, it can be fitted in as a substitute for petroleum diesel, which is the substance conventionally used in automobile transport.

Biodiesel is normally utilised as a replacement for petroleum diesel fuel or can be blended together with petroleum diesel fuel in any ratio. Biodiesel is a biodegradable substance with a lower toxicity in comparison to petroleum diesel fuel and is preferred as it is safer to handle since there is little human risk involved in its handling. The use of biodiesel as a petroleum substitute reduces the degree of exhaust emission. Biodiesel are notorious for their easy use in terms of how they can easily be pumped and stored in existing engines without having to make major industrial alterations to the engines themselves. They are usually blended together with petroleum fuels in order to create the optimal usage in engines.

The output yield of biodiesel is I had never really heard of biodiesel until it was a topic covered in school. After finding out what biodiesel was, I looked into the IB chemistry syllabus to see what points it had on biodiesel and looked further into the applications of biodiesel as well as the process of transesterification and what is involved. My personal interest was sparked from my curiosity of how to obtain my own sample of biodiesel after I found out about its many uses. My high school chemistry department provided us with a set of materials and allowed us to investigate our own ways of obtaining biodiesels and I was keen to see what I could do with a sample of this versatile substance. I do feel as though this is an important experiment to engage in as scientists find biodiesels an extremely useful substance to use in machines and such. To try an experiment which involves looking at factors that can change the output of the product, would be a stepping stone to building a stronger understanding on the substance itself and how more of it can be obtained and perhaps what benefits it may serve.

The experiment conducted was intent on looking at a certain independent variable (the concentration) that would affect the yield of biodiesel produced in experiment. The research question for this is: How the concentration of Potassium Hydroxide solution would affect the yield of biodiesel when transesterified with a standard sample of vegetable oil.


To look at the scientific aspect of it, biodiesels are a form of methyl esters, an organic chain compound that has a set of properties. The experiment involves the reaction between vegetable oil and potassium hydroxide and methanol mixed together. The equation for the reaction of the transesterification is:

Vegetable Oil (l) + (3)HOCH3 + (NaOH catalyst) ——> C3H8O3 + 3-methyl ester

1 Biodiesel Basics


This valuable renewable fuel resource is not vegetable oil, but instead formed from the organic chain compound. It is 3-methyl ester and has the following chemical structure:

Fig. 1

The diagram on the left shows the transesterification process that forms two products (Glycerol and A 3-methyl ester). The experiment conducted involves potassium hydroxide as a catalyst instead of sodium hydroxide. Furthermore the biodiesel product of this varies from the other structured methyl ester that usually come in The other product is glycerol, which is commonly found in soaps. This is a standard example of transesterification however the experiment that is attempted involves different reactants. The diagram below shows the process for this experiment and the outcomes.

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The temperature of the oil mixed with the methanol mixture will be measured and the experiment consists of five different solutions of KOH + methanol that will each be reacted with the vegetable oil. A magnetic stirrer will be used in the process to get the reaction going and afterwards the finalised solution will be placed in a centrifugal and the process of centrifugation will separate the solution into glycerol and biodiesel. The biodiesel will then be extracted to give a reading on percentage yield.

The method was personally derived and many modifications were made to the ...

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