Preparation and purification of Biodiesel

synthesised from Vanaspati

Sumit Kumar Kar(09MS029),Sourav Kumar Sahoo(09MS032),Debtanu Chakraborty(09MS031),Anirban Mukherjee(09MS004)

November 24, 2010

Figure 1: Fatty acid portion varies between C12 to C18.Fat is deposited in theadipose tissue in the form of Triacylglycerides it is a efficient way of storingfatty acids

Figure 2: Transesterification reaction of triglyceride to FAME (fatty acid methylester).

0.1 Introduction to Biodiesel

Vegetable oils and their derivatives (ethyl esters,propyl esters,methyl esters)are commonly referred to as biodiesels and are prominent candidates as al-ternative diesel fuels . Biodiesel can be produced from plant oils best sourceis Jatropa . Biodiesel is a renewable fuel and carbon dioxide produced fromthe burning of the biodiesel is recycled into the next crop through the car-bon cycle .Besides being a renewable and domestic resource, biodiesel reducesmost emissions while engine performance and fuel economy are nearly identi-cal compared to conventional fuels. Several problems, however,remain, whichinclude economics, combustion, some emissions, lube oil contamination, andlow-temperature properties.

0.2 Theory

Biodiesel can be produced from vegetable oils through transesterification pro-cess . Vegetable oils essentially are Triglycerides which is three fatty acids with aglycerol backbone . Triacylglcerides with methanol in the presence of the NaOH

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catalyst forms three methyl esters and Glycerol is produced as a byproduct .The reaction is known as Transesterfication . The reaction occurs in three stepsin the first step of the reaction NaoH reacts with methanol forming a strongbase Sodium Methoxide(NaOCH3) . In the second step Sodium Methoxideacts as a nucleophile and attacks a carbonyl carbon of the vegetable oil formingtetrahedral intermediate . In the third step the Methyl Esters separate fromGlycerol backbone this is known as Cracking . These Methyl Esters composethe Biodiesel . For Methyl Ester with 2n(varies generally from 14 to 20) carbonatoms:Methyl Ester(2n Carbon atoms)+ 3n

2 − 1 O2 ⇒ nCO2+nH2O+Energy

0.3 Procedure

0.3.1 Preparation of Sodium Methoxide

1→ 50 ml 99 percent pure MeOH is taken in a 300 ml Beaker and placed in afume hood.2→ 0.503 gms of Na Metal is taken in a solvent. And it is also placed in thefume hood.3→ From their small amount of Na metal is taken with a spatula and added tothe 300 ml Beaker containing MeoH . We wait for a few seconds to allow theHydrogen gas to liberate.Again a little Na Metal is added to the MeOH andwait for a few seconds.In these way the whole 0.503 gm Na Metal is added tothe 300 ml Beaker.

0.3.2 Addition of Vegetable Oil to NaOMe

1→ Vanaspati ghee is heated at around 80oC initially till it liquifies com-pletely.Then it is allowed to cool down to 40oC .Then 250 ml is measuredusing a measuring cylinder and transferred to the reaction beaker containingNaOMe.Now the beaker is covered with a butter paper.2→ Now the reaction mixture is stirred for 30 to 40 mins then we wait foranother 20 to 30 minutes till dense layer glycerol collects in the bottom andMethyl esters is collected on the top.

0.3.3 Purification

1.The entire mixture is transferred to a 500 ml separating funnel and allowedto stand for 10 mins.The Glycerol layer formed in the bottom of the separatingfunnel was collected in a beaker.2.Then 100 ml water is added to the separating funnel and cork is fitted andseparating is shaken properly and allowed to stand for 15 minutes.3.After 15 minutes the aqueous layer formed at the bottom of the separatingfunnel was separated out leaving the top layer intact.4.The above step was followed one more time but this time along with water 50ml dimethyl ether was added and slowly shaked with the cork open.5.The separating funnel was allowed to stand for 15 minutes to allow the for-mation of the aqueous and the organic layer.

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6.The Aqueous layer was again separated out.Then the organic layer was col-lected in a beaker.7.To remove any moisture present in the organic layer around 10 gms of Na2SO4

was added to the beaker.After few minutes when the solution cleared the liquidpart was separated out,kept to open overnight tom remove the volatile dimethylether.

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