Biodiesel and Related Technologies
Biodiesel is a mono alkyl ester compound
which is a result of transesterification reaction
between vegetable or animal oil (which is a
triglyceride organic compound) and alcohol
with acid or base as catalyst. The output of this
reaction is ester, as well as glycerol. There are
2 main reactions that create methyl ester,
namely transesterification and esterification
reactions.
1) Transesterification is the most
commonly used process in methyl ester
production. Triglyceride is transformed into ester through reaction with excessive amount
of alcohol, with alkaline solution as catalyst, such as sodium hydroxide, and potassium
hydroxide. This process takes place under the condition that free fatty acid has to be removed
from oil (the quantity of free fatty acid should not exceed 1%). At present, there are
a number of technological development of biodiesel such as;
Basic production process,
Transesterification by continuous deglycerolization process,
Transesterification by lipase enzyme,
Supercritical methanol transesterification,
Transesterification by microwave,
Transesterification by solid catalysts,
2) Esterification is a reaction between fatty acid and alcohol, with sulfuric acid
as catalyst. A process which combined esterification and transesterification under a single
production process has been developed. It is called two-stage process, which can be applied
with any materials with high fatty acid. In the first stage, free fatty acid is used in esterification.
Then the acid is removed and neutralized. In the second stage, a subsequent reaction
of transesterification with alkaline catalyst takes place. Moreover, there is a development
of solid catalysts, including lipase enzyme, to replace sulfuric acid catalyst which caused
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erosion problems for the production system. Furthermore, other than the 2 reactions
mentioned above, sophisticated technologies for biodiesel production have been developed,
including using algae to produce fuel and hydrogenated biodiesel (using hydrogen gas to
transform triglyceride and fatty acid as fuel).
As for biodiesel, the potential materials for producing biodiesel include oil palm,
Jatrophacurcas, coconut, used vegetable oil. The material with highest potential is palm oil.
Jatrophacurcas.
Plantation is expensive and attractive to farmers. There is also a high cost of biodiesel
production. Coconuts have issues of high volatility in price and high cost of collecting materials.
Used vegetable oil is so limited in quantity that it is insignificant.
Technologies used in each process of biodiesel production from various materials are
illustrated in Figure 20. Current technologies and technologies under development are both
presented. The technologies that use transesterification reaction include those that use
catalyst, such as conventional process (base/acid catalyst), continuous deglycerolization,
lipase-catalysis, and microwave, and those that do not use catalyst, namely supercritical
methanol. As for esterification reaction, there are batch and continuous reactions. Once raw
materials has gone through reaction, the output compounds from the chemical reaction are
divided into 2 parts, namely raw methyl/ethyl ester which will be purified to meet biodiesel
standards, including separation of residue alcohol for recycle, and raw glycerol which is
a by-product and can be purified and marketed.