Biodiesel Production

Biodiesel can virtually be prepared from any type of vegetable oil or animal fat. The primary constituent of vegetable oil is triglyceride — a long-chain hydro-carbon. Catalyzing triglyceride using anhydrous methyl alcohol in the presence of a strong base (sodium hydroxide) yields large amounts of biodiesel and a small amount of glycerin as by-product.

Methodology

Titration Testing

The free fatty acids present in vegetable oils must be neutralized. The amount of free acids present varies depending on the type of oil used and condition of place. Proper testing ahead of time is very critical.

  • Dissolve 1.0 g   of NaOH in one liter of distilled water.
  • Dissolve one 1.0 g of sample vegetable oil in 10 ml of anhydrous isopropyl alcohol in a conical flask.
  • Add a few drops of phenolphthalein indicator.
  • Titrate against NaOH solution taken in a burette till the color becomes pale pink.
  • The volume of NaOH required to neutralize free fatty acid (A) is noted.
  • Usually 3.5 g of NaOH per liter of triglyceride oil is required as a catalyst.
  • Total catalyst required is [5+ A] g per litre.

Depending on the free fatty acid (FFA) content of oil, conversion of any vegetable oil into biodiesel can be carried out using the following methods.

  1. Single Base Method
  2. Two step Acid-Base Method

Method 1: Single Base Method or Alkaline Transesterification

Alkaline transesterification process is carried out for oils having low FFA content (below 2%)

  • Add one liter oil into a round bottomed three neck flask, fitted with a condenser, thermometer and methanol dozer
  • Heat the vegetable oil to about 60° C.
  • Prepare sodium methoxide by dissolving required amount of sodium hydroxide (as per titration test) in 250ml methanol
  • Add sodium methoxide to the preheated oil and keep constantly mixing the contents for 1.0-1.5 hrs using a mechanical stirrer.
  • Allow the mixture to settle for about 1-2 hrs in a separating funnel.
  • Drain out glycerin that settles at the bottom as a thick, cloudy liquid.
  • The translucent liquid that remains on top is methyl ester or biodiesel.

Method 2: Two step Acid-Base Method

This is a two-stage procedure involving an acid esterification in the first-stage and transesterification using an alkaline (base) in the second-stage. This method and its proportions are based on the projected highest free fatty acid (FFA) content (more than 2%).

First stage (Acid Esterification)

  • This stage uses acid-based esterification to process out existing free fatty acids (FFA’s) in the feedstock, allowing more thorough transesterification during the second stage.
  • Measure the volume of oil/fats to be processed (preferably in liters). Record this information for use later on. Heat the oil to 55° C. Make sure that any solid fats that might have been present have melted completely.
  • Measure out the methanol at a ratio of 100 ml of methanol per liter of oil/fats. 1ml of sulphuric acid is mixed with methanol carefully and added to the pre-heated oil.
  • Mix the contents continuously. Maintain the temperature at 55° C for an hour, then stop heating with stirring, and allow settling down in a separating funnel.
  • The top layer rich in acid and methanol is separated and bottom layer is used for transesterification process.
  • Carry out titration test to find the amount of NaOH required

Acid-Esterification

 

 

 

 

 

 

 

 

Second Stage (Alkaline Transesterification)

  • Add one liter oil into a three neck fitted with condenser, thermometer and methanol dozer
  • Heat the vegetable oil to about 60° C.
  • Prepare sodium methoxide by dissolving required amount of sodium hydroxide (as per titration test) in 150 ml methanol
  • Add sodium methoxide to the preheated oil and constantly mix the contents for 1.0-1.5 hrs using mechanical stirrer.
  • Allow the mixture to settle for about 1-2 hrs in a separating funnel.
  • Drain out glycerin that settles at the bottom as a thick, cloudy liquid.
  • Translucent liquid that remains on top is methyl ester or biodiesel.

Alkaline

 

 

 

 

 

 

 

Washing Biodiesel

Washing of biodiesel is necessary to remove the soluble components using hot water. Hot water is sprayed on top of the biodiesel. Then, it is allowed to settle down and waste water is drained off. The washing is carried out 3-4 times to get pure biodiesel.

Biodiesel Biodiesel23

 

 

 

 

 

 

 

 

Drying Biodiesel

Drying can also be accomplished (more aggressively) by heating the now-washed fuel to approximately 110° C in an open container until there is no more steam rising from the fuel, which should be a clear. This heating process will also drive off any traces of remaining alcohol as well. Once allowed to cool to room temperatures, it can be pumped directly into vehicles, or into storage containers.

Drying-Biodiesel