Dear Sarah

Thanks for your answer, volume ratio means how much oil and alcohol , please give example

fatty acids are having more fatty acids, every fatty acids have different molecular weight. Fatty acids molecular weight is high compared to methanol. i dont under stand the concept of molar ratio of oil to methanol. generally, the people are using 20% of alcohol for per litre of oil. 6 mole of alcohol gives around 180 ml of alcohol. but how 1 mole of oil how much amount of oil in ml.

Dear Sarah

Thanks for your answers i will be follow that formulas and verify that. and then i will discuss you

Dear Baskar,

It is very simple to calculate the average molecular weight of oil...first get your oil analyzed by GC. From the Fatty acid composition in % you can calculate av. mol. wt. of oil. (by sum of (% of Fatty acid * mol. wt. of fatty acid). Hence, from the averagre molecular weight u can get moles of oil for your amount of oil (in grams) as suggested by Sarah.

and for oil:methanol ratio multiply the moles of oil with the factor of ratio.

Suppose if u want to use 1:6 ratio and av. mol. wt. of ur oil is 800 and ur batch size is for 100 ml oil.

First 100/800 = 0.125 moles of oil.

Now, as u want 1:6 oil : methanol ratio, moles of methanol = 0.125 * 6 = 0.75 moles

Therefore, wt of methanol = 0.75 * 32.04 = 24.03 g.

& volume of methanol = 24.03 / 0.79 (density of methanol) = 30.41 ml

Hope, this example will help you.

Regards,

Krunal

I am Agree with Krunal Shah.... He is 100% right

Dear Krunal

Thanks for your answers i understood i will follow up that

Baskar, Are your through now..?

Guess this will help

V in liters - Oil volume

M in liters (V x 0.2) - Methanol volume

L in g ( (V x 3.5) - Lye (NaOH)

The calculations of 1:6 1:30 etc. are a product of biodiesel being a two way reaction. In reality, it only takes 1:3 molar ratio of oil:methanol to produce biodiesel. However, if you put in 1:3 ratio you'll end up with a large amount of unreacted material so commercially you usually do 1:6 (twice as much methanol as needed). You end up with a large volume of unreacted methanol in your product, which needs to be recaptured to preserve production economics. A 1:12 or 1:30 ratio is usually used in laboratory settings where economics don't matter and you are instead going after purity. Higher ratios push the reaction toward higher % completion at a faster rate. You shouldn't do a reaction any lower than 1:6 molar ratio.

Mwt of vegetable oil is 900g/mol , Mwt of methanol is 32.04 g/mol

Suppose you started your reaction with10g oil how much methanol you should take to keep your molar ratio (6:1)methanol:oil

Firstly convert all masses into moles

10 g oil X1mol/900=.0111 mol Oil

So how much methanol should take to to get 6 molar?

Answer is 2gm 

2gmX1mol/32.04=0.0625

Step 2 . To calculatethe molar ratio

0.0625/0.0111= (6/1)

That is exactly what we need

So add 2 gm methanol to each 10gm oil  to get (6:1) molar ratio

Hope this could help 

 Follow this calculations, i use this method. is this same you were talking about ?

Density of rubber seed oil = 0.886 g/ml 

Therefore moles of oil used = 180 ml x 0.886 g/ml x 1 mole/898 g = 0.1775 mole

Volume of MeOH used = 45 ml

Molar weight of MeOH =32.04 g/mol

Density of MeOH = 0.792 g/ml

Therefore moles of MeOH used = 45 ml x 0.792 g/ml x 1 mole/32.04 g = 1.112 moles

Molar ratio, MeOH/Oil = 1.112/0.1775 = 6.2: 1

But volume ratio, MeOH/Oil = 45 ml/180 ml = 0.25

Following this method you can do reverse calculation for estimation of amount of methanol.

If I want to know the molecular weight of waste cooking oil. How can I do it?

I studied more research articles, they have mentioned the molar ratio of oil to alcohol i.e 6:1, 8:1. 10:1. 12: 1. 14:1. I would like to know about that calculation. The percentage ratio of the catalyst. I referred some books, they mentioned by calculating the three fatty acid in oil and alcohol but the oil is having more number of fatty acids around 2 - 4. Some oils have different fatty acids present also.