Biodiesel Production
Biodiesel is the most common biofuel in Europe. It is produced from oils or fats using transesterification and is a liquid similar in composition to mineral diesel. Its chemical name is fatty acid methyl (or ethyl) ester (FAME). Oils are mixed with sodium hydroxide and methanol (or ethanol) and the chemical reaction produces biodiesel (FAME) and glycerol. 1 part glycerol is produced for every 10 parts biodiesel.
Biodiesel is made by chemically altering an organic oil (typically vegetable oil) through a process called "transesterification". Essentially, the process thins down the oil to allow it to run in an unmodified diesel engine.
In organic chemistry, transesterification is the process of exchanging the alkoxy group of an ester compound by another alcohol. These reactions are often catalyzed by the addition of an acid or base.
Transesterification: alcohol + ester → different alcohol + different ester
Production Process
Biodiesel is the most common biofuel in Europe. It is produced from oils or fats using transesterification and is a liquid similar in composition to mineral diesel. Its chemical name is fatty acid methyl (or ethyl) ester (FAME). Oils are mixed with sodium hydroxide and methanol (or ethanol) and the chemical reaction produces biodiesel (FAME) and glycerol. 1 part glycerol is produced for every 10 parts biodiesel.
Biodiesel is made by chemically altering an organic oil (typically vegetable oil) through a process called "transesterification". Essentially, the process thins down the oil to allow it to run in an unmodified diesel engine.
In organic chemistry, transesterification is the process of exchanging the alkoxy group of an ester compound by another alcohol. These reactions are often catalyzed by the addition of an acid or base.
Transesterification: alcohol + ester → different alcohol + different ester
Production Process
Filtering and Heating
Oil is filtered to remove dirt, and other non-oil material. Water is removed because its presence causes the triglycerides to hydrolyze to give salts of the fatty acids instead of undergoing transesterification to give biodiesel.
This is often accomplished by heating the filtered oil to approximately 120 °C. At this point, dissolved or suspended water will boil off. A sample of the cleaned oil is titrated against a standard solution of base in order to determine the concentration of free fatty acids (RCOOH) present in the waste vegetable oil sample. The quantity of base required to neutralize the acid is then calculated.
Transesterification
While adding the base, a slight excess is factored in to provide the catalyst for the transesterification.
The calculated quantity of base (usually sodium hydroxide) is added slowly to the alcohol and it is stirred until it dissolves. Sufficient alcohol is added to make up three full equivalents of the triglyceride, and an excess is added to drive the reaction to completion.
The solution of sodium hydroxide in the alcohol is then added to a warm solution of the waste oil, and the mixture is heated (typically 50 °C) for several hours (4 to 8 typically) to allow the transesterification to proceed.
Used oil (straight vegetable oil) recycling requires titration. We do a titration to find out how much free fatty acid is present and to find out how much to compensate for it by adding more lye so there's some left for the desired biodiesel reaction.The biodiesel reaction needs alkaline lye (NaOH) or KOH, as a catalyst (methanol and vegetable oil wont' react to make biodiesel by themselves) Waste oil contains free fatty acids (FFA), and the free fatty acids will with lye to make soap before the lye has a chance to participate in making biodiesel.
Washing
There are a number of water-soluble impurities left in biodiesel after the reaction and initial settling is complete.. Biodiesel should be washed to remove the excess catalyst, alcohol and other impurities.When Biodiesel is first made it is quite caustic with a pH of between 8.0 and 9.0.
Washing with plain water is sufficient to wash out all remaining catalyst, bringing the pH down to near neutral territory. Since Biodiesel has a lower specific gravity than water, the water will sink to the bottom and the Biodiesel will remain over the water.
In the first wash, the water will turn almost totally white. This is because a form of soap is created when water comes in contact with the catalyst in the Biodiesel. It should clear up as the soap washes out with sub sequent washings.
Oil is filtered to remove dirt, and other non-oil material. Water is removed because its presence causes the triglycerides to hydrolyze to give salts of the fatty acids instead of undergoing transesterification to give biodiesel.
This is often accomplished by heating the filtered oil to approximately 120 °C. At this point, dissolved or suspended water will boil off. A sample of the cleaned oil is titrated against a standard solution of base in order to determine the concentration of free fatty acids (RCOOH) present in the waste vegetable oil sample. The quantity of base required to neutralize the acid is then calculated.
Transesterification
While adding the base, a slight excess is factored in to provide the catalyst for the transesterification.
The calculated quantity of base (usually sodium hydroxide) is added slowly to the alcohol and it is stirred until it dissolves. Sufficient alcohol is added to make up three full equivalents of the triglyceride, and an excess is added to drive the reaction to completion.
The solution of sodium hydroxide in the alcohol is then added to a warm solution of the waste oil, and the mixture is heated (typically 50 °C) for several hours (4 to 8 typically) to allow the transesterification to proceed.
Used oil (straight vegetable oil) recycling requires titration. We do a titration to find out how much free fatty acid is present and to find out how much to compensate for it by adding more lye so there's some left for the desired biodiesel reaction.The biodiesel reaction needs alkaline lye (NaOH) or KOH, as a catalyst (methanol and vegetable oil wont' react to make biodiesel by themselves) Waste oil contains free fatty acids (FFA), and the free fatty acids will with lye to make soap before the lye has a chance to participate in making biodiesel.
Washing
There are a number of water-soluble impurities left in biodiesel after the reaction and initial settling is complete.. Biodiesel should be washed to remove the excess catalyst, alcohol and other impurities.When Biodiesel is first made it is quite caustic with a pH of between 8.0 and 9.0.
Washing with plain water is sufficient to wash out all remaining catalyst, bringing the pH down to near neutral territory. Since Biodiesel has a lower specific gravity than water, the water will sink to the bottom and the Biodiesel will remain over the water.
In the first wash, the water will turn almost totally white. This is because a form of soap is created when water comes in contact with the catalyst in the Biodiesel. It should clear up as the soap washes out with sub sequent washings.
No comments:
Post a Comment