Production of biodiesel from vegetable oils

University essay from KTH/Skolan för kemivetenskap (CHE)

Author: Boris Ramos; [2012]

Keywords: Biodiesel; Corn oil; Ethanol; Methanol; Palm oil;

Abstract:

The production of biodiesel using vegetables oils is studied.

Palm oil and its use for production of biodiesel have been focused. Palm tree is very productive and one of the most profitable for biodiesel production. Among the oilseed crops palm tree produce more oil per hectare. Palm oil has a good availability and a competitive price. The production of palm oil at the industrial plantation level has caused environmental damage. The Roundtable on Sustainable Palm Oil has established principles and criteria in order to certify a sustainable cultivation of the palm oil.

The experimental work involves the production of biodiesel using corn oil. Ethanol and methanol are used as alcohols. Sodium and potassium hydroxides are selected as catalyst.

The ratio alcohol to oil is the most important parameter in the production of biodiesel.  An excess of alcohol is required to drive the reaction to the right.  In the experiments with ethanol the yield of biodiesel increased with the ratio ethanol/oil achieving the highest yield at a molar ratio ethanol/oil: 7.78. In the experiments with methanol, using 0.9 g NaOH and 1 hour reaction time the highest yield was obtained with  a molar ratio methanol:oil = 9. Using KOH as catalyst and 2 hour reaction time a very good yield is already obtained with a molar ratio methanol:oil = 4.5

The amount of catalyst is another studied parameter. In the experiments with ethanol, the amount of 0.8 mg NaOH and 1.2 mg KOH for 200 ml corn oil (0.22 mol) is enough in order to obtain a good yield. An increase of the amount of catalyst does not produce an increase of the yield of biodiesel. In experiments with methanol, using the lowest tested amount catalyst (0.85 g KOH and 0.23 g NaOH) a good yield of biodiesel is obtained.

The effects of the reaction time, rate of mixing and the reaction temperature were studied in the experiments with methanol. The yield of biodiesel increased when the reaction time is increased from 1 to 2 hours. The yield of produced biodiesel increased from 90% to 94% when the rate of mixing was increased from 500 to 1500 rpm. Often the transesterification is carried out at a temperature near the boiling point of alcohol. The highest yield was obtained at 60 oC with KOH and at 55 oC using NaOH but already at 40 oC a good yield was obtained (89%).

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