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Biodiesel is a methyl ester that is obtained by the chemical reaction of any vegetable oil and animal fat.
As you know, fat molecules consist of triglycerides or compounds of triatomic alcohol glycerol and three fatty acids. To obtain methyl ether, one unit of mass of methanol is added to 7 units of mass of vegetable oil (a ratio of 7:1 is obtained).
It is necessary to replace glycerol in glycerol esters with methanol (ethanol). This substitution is performed by a reaction between fat and alcohol to form methyl ether and precipitate glycerol, which is denser and insoluble in methyl ether. An acceptable reaction rate and degree of conversion can be obtained by raising the temperature, introducing excess alcohol, and using catalysts.
The chemical reaction produces the methyl ether that we need, as well as glycerine (95%), which is widely used in the pharmaceutical and paint industry. The resulting ether has a good Flammability due to the high cetane index. If for mineral diesel fuel the cetane index is 42-45, then the cetane index of biodiesel (methyl ether) is at least 51. This allows it to be used in diesel engines without other substances that stimulate ignition. It is because of this property that the methyl ether obtained from vegetable oils and fats was called biodiesel.
Vegetable oil (animal fat)
Biodiesel can be used in conventional internal combustion engines, either separately or mixed with conventional diesel fuel, without changing the engine design.