While taking reaction mixtures for synthesis of biodiesel, molar ratios of methanol and feedstock are taken. Can't the reactants be taken in stoichiometric proportions?
fatty acids have molar masses that vary from source to source, however, as they are triglycerides, each complete reaction between a fatty acid and alcohol will form three biodiesel molecules. Because each molecule of alcohol will react with each of the glycerides from fatty acid. Reaction: triglyceride + 3 alcohol = 3 biodiesel + glicerin.
Each triglyceride and its biodieses have an average molecular weight.
Example: soybean oil = 835g / mol and biodiesel 881 mol / g (sum of the three mol biodiesel).
The origin of the seed that produced the oil, the harvest of oil and other agricultural and environmental factors influence the average molecular weight of oil and biodiesel.
For these reasons, I use a standard (low reference) mean molecular mass to calculate the stoichiometric yield
See morrison and boyd organic chemistry 7th edition
The reason is probably that it is easier to calculate molar ratio in terms of weight percent rather than determining the molecular wright of the vegetable oil when you use stoichiometric relation.
fatty acids have molar masses that vary from source to source, however, as they are triglycerides, each complete reaction between a fatty acid and alcohol will form three biodiesel molecules. Because each molecule of alcohol will react with each of the glycerides from fatty acid. Reaction: triglyceride + 3 alcohol = 3 biodiesel + glicerin.
Each triglyceride and its biodieses have an average molecular weight.
Example: soybean oil = 835g / mol and biodiesel 881 mol / g (sum of the three mol biodiesel).
The origin of the seed that produced the oil, the harvest of oil and other agricultural and environmental factors influence the average molecular weight of oil and biodiesel.
For these reasons, I use a standard (low reference) mean molecular mass to calculate the stoichiometric yield
See morrison and boyd organic chemistry 7th edition
Dear Y. Sharma, the methanol has always to be supplied in excess, when compared with raw-material (triglycerides), otherwise, the conversion, the yield and the methyl esters content of transesterification reaction will be lower than the suitable ones. For that reason, we always use the reactants quantities in terms of molar ratios.
Dear Sharma, In my opinion, Puna is telling the truth. I agrre with Puna.
the simple reason is that chemists calculate in terms of molar matter, while engineers in terms of measurable means, like kg, t, later, etc. You will never meet operational instruction to add two time the stochiometric amount, but, to add x kg of methanol and y g of catalyst.
Biodiesel is methyl ester of any fatty oil. the best ratio of oil : methanol is 1:7 and catalyst dosages should be 1% of total weight of oil. glycerol formation takes place as side product which should be removed by simple decantation process. dosages of catalyst, reaction temperature as well as rpm plays an important role for good yield of biodiesel synthesis,
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