Biodiesel Chemistry: Before and After the Process
Before discussing the specifics of biodiesel chemistry, we should first know some general information about the subject. Knowledge about organic chemistry will definitely be helpful because this field is related to the chemistry of organic compounds. Biodiesel are made of compounds that contain the element of carbon and such are organic compounds.
After knowing what branch of chemistry to use, we know proceed to the element itself. Biodiesel is made up of mono alkyl esters developed from renewable sources of lipids, i.e. animal fats or vegetable oils. Esters are compounds made up of bonded organic acid and alcohol. The latter substance is an organic compound which contains hydroxyl compounds. Biodiesel composition is made up of long fatty acids than contain carboxyl, a functional COOH group. These acids constitute sole chains of 12 up to 24 carbons per group of COOH.
If vegetable oil is used to produce biodiesel fuels, then we have to know its composition. This ingredient constitutes glycerol or glycerine, a kind of alcohol, attached to long chain of fatty acids esters or triglycerides. The ratio of these substances will be three long chains of fatty acids is to one triglyceride.
Biodiesel manufactured from various oils will comprise different quantities and kinds of fatty acid chains. This is the reason why biodiesel manufactured from canola oil will not have the alike chemical properties of biodiesel created from soybean oil. For example, palm oil has a melting point of -10C while soybean oil melts at -16C. Palm oil which has 45% C16 palmitic acid will melt at 35C.
Biodiesel undergoes the trasesterification. This process is conducted during batch processes. If the vegetable oil is used, it has to be filtered then heated to eliminate water substances. Bumping occurs during this process. Then, a strong base (typically sodium hydroxide) is then combined with alcohol substances (either methanol or ethanol) are added to the oil. The reaction of Catalyst (NaOH) with Methanol will result to CH3OH + NaOH ¨ CH3O-Na + H2O where CH3O-Na exists as the anion CH3O- and the cation Na+. The alcohol will be a nucleophile and is deprotinated. It will bout the ester groups in the glycerides, then transporting the, to form esters and glycerol.
When waste oil is used, esterification is done. Here, the carboxylic acids will react with the alcohol if a catalytic quantity of mineral acid is present. This will result to ester compounds. Once the carbonyl oxygen is protonized, the carbon will undoubtedly be attacked by frailer alcohol nucleophile. The next step involves determining the rate. As soon as this is done, alcohol oxygen will attack the carbonyl carbon and thus forming a tetrahedral intermediate. After this is done, the proton transfer begins which will release water molecules. And finally, the proton catalyst is now rejuvenated. To grasp the chemistry of biodiesel, you must really understand its raw composition and what the process does to its chemical characteristics and biodiesel properties.
The length of the carbon chain and the presence of double bonds affect the chemical behavior of oils and fats. This affects the chemistry of biodiesel. Fats have fewer double bonds and thus harden when there is a low room temperature. As an effect, straighter chains are produces. Oils have more double bonds which lead to a liquid state. To solidify oils, hydrogenating is done.
The biodiesel chemical formula is a combination of alkyl C12-C22 Fatty Acid Methyl Esters. Its Molecular weight is ~292(q). As to biodiesel chemical composition, carbon, hydrogen and oxygen weigh 77 grams, 12 grams and 11 grams. Its density at 60‹ F is 11g. The most common forms of biodiesel are Ethyl Stearate and Methyl Linoleate. The chemical formula for Methyl Linolaeate is C19H34O2 and for Ethyl Stearate is C20H40O2. Biodieselsf oxidative stability and melting point are a major concern. It is difficult to use palm oil in cold seasons because it solidifies.
It has been mentioned that blending biodiesel with conventional fuels can greatly increase its benefits. It can also rearrange its chemistry. Mixing fuels can reduce carbon monoxide, hydrocarbons and particulate matter. This means as the chemical composition of biodiesel changes, its effects also varies. Before making a biodiesel fuel, you have to know everything about the biodiesel formula. This is done to know the safety precautions to be done.