Making Biodiesel from used cooking oil | A transesterification process

Summary

In this video, the process of creating biodiesel from used cooking oil is demonstrated. The experiment requires materials like cooking oil, ethyl alcohol, and sodium hydroxide. First, sodium hydroxide is dissolved in ethyl alcohol, producing sodium methoxide. After heating the oil to 60°C, the mixture is added to the oil, and after 30 minutes of stirring, biodiesel and glycerol are formed. After allowing the mixture to sit for 24 hours, the biodiesel is separated and tested for ignition. The experiment concludes with a successful ignition test, confirming the creation of biodiesel from waste oil.

Takeaways

• 😀 The experiment requires 200 ml of used cooking oil, 50 ml of ethyl alcohol (at least 70%), and 1 gram of sodium hydroxide.
• 😀 The process begins by dissolving sodium hydroxide into ethyl alcohol, creating sodium methoxide through an acid-base reaction.
• 😀 The oil is heated under low heat for 7 to 8 minutes, aiming for a temperature of about 60°C.
• 😀 Biodiesel production involves a transesterification reaction, where triglycerides (in the oil) are converted into biodiesel and glycerol.
• 😀 Sodium methoxide acts as a nucleophile, attacking the carbonyl carbons in the oil to create a highly unstable intermediate.
• 😀 After mixing sodium methoxide with the heated oil, the mixture is stirred continuously for 30 minutes.
• 😀 After 30 minutes, the reaction mixture is allowed to stand for 24 hours to allow the separation of biodiesel and glycerol.
• 😀 Glycerol sinks to the bottom of the mixture, while biodiesel remains at the top, forming a lighter yellow layer.
• 😀 Biodiesel is separated from glycerol by decanting it into a new container without including glycerol.
• 😀 A qualitative test for biodiesel is performed by dipping a cloth strip into both used cooking oil and biodiesel to check for ignition. Biodiesel ignites in 5 seconds, while the used oil does not.

Q & A

What materials are required to make biodiesel from used cooking oil?

You need 200 ml of used cooking oil, 50 ml of ethyl alcohol (at least 70% concentration), and a gram of sodium hydroxide.

What is the first step in making biodiesel from used cooking oil?

The first step is to dissolve the sodium hydroxide into the ethyl alcohol, ensuring all solid particles are dissolved.

What is the reaction that occurs when sodium hydroxide is dissolved in ethyl alcohol?

An acid-base reaction occurs, producing water and sodium methoxide, a very strong base.

Why is heating the oil to 60 degrees Celsius important in this experiment?

Heating the oil to around 60 degrees Celsius ensures that the transesterification reaction can take place effectively.

How did the person conducting the experiment determine when the oil reached 60 degrees Celsius?

Since the experimenter didn’t have a thermometer, they asked classmates about the time range for the oil to reach 60°C.

What is the transesterification reaction, and how is it involved in making biodiesel?

Transesterification is the process of converting a triglyceride (oil) into biodiesel. It involves the nucleophilic attack of sodium methoxide on the carbonyl carbon of the triglyceride, creating biodiesel and glycerol.

How long should the mixture be stirred after adding the sodium hydroxide-ethyl alcohol mixture to the oil?

The mixture should be stirred continuously for about 30 minutes.

What observable change occurs during the reaction process?

The color of the mixture changes, indicating that the transesterification reaction is taking place.

How is biodiesel separated from glycerol after the reaction has completed?

The biodiesel is separated from the glycerol by decanting it into a separate container, being careful not to include any glycerol.

What is the final test to confirm the biodiesel’s success in the experiment?

A strip of cloth is dipped in both the biodiesel and used cooking oil. The cloth dipped in biodiesel should ignite within five seconds, while the used cooking oil should not.