Experiment 3: Biodiesel Production from Unused and Waste Vegetable Oil Objectives: 1. To determine acid value of the waste vegetable oil 2. To calculate the amount of NaOH needed for transesterifcation of waste vegetable oil. 3. To produce biodiesel from unused and waste vegetable oil by basecatalyed transesterifcation process. Introduction !iodiesel is an alternative to petroleum-based diesel fuel. "t is a renewable form of fuel manufactured from natural oils# such as soybeans or animal fat. !iodiesel fuel is used in diesel engines and and provides a cleaner burning alternative to petroleum diesels. $s a renewable resource# another advantage of biodiesel is that it can be manufactured domestically. !iodiesel fuel is created through a process called transesterifcation. Transesteri% Transesteri%cation cation is the process process of of transforming transforming one type type of ester into into another type of ester. "n this e&periment you will synthesie biodiesel fuel 'methylesters( from vegetable oil 'triglyceride)triester of glycerol( via a base-catalyed transesteri%cation reaction. This process process begins begins with vegetable vegetable oil. The process process uses sodium sodium hydro&ide 'NaOH( as a catalyst and an e&cess of alcohol 'methanol( to convert vegetable oil to biodiesel. The oil is either pure oil# referred referred to as unused vegetable oil '*O(# ta+en directly from plants such as palm oil or corn# or from waste vegetable oil ',*O(# the leftover oil after coo+ing. The amount of methanol needed is around 2-22 of oil volume. The reaction steps are as follows/ 1. NaOH reacts reacts with methanol methanol in an acid-base acid-base reaction. reaction. The The product product of this reaction is the very strong base sodium metho&ide and water. 2. The sodium sodium metho&ide metho&ide attac+s attac+s the three three carbonyl carbonyl carbons carbons of the vegetable oil. The overall result is the 0crac+ing0 of the triglyceride. 3. The elimination elimination of the the glycerol glycerol bac+bone bac+bone leads to the the formation formation of the three methyl esters 'the biodiesel( and glycerol. The general general reaction reaction is shown below below//
1
Triglyceride '*O(
ethanol
lycerol 3 molecule s metyl ester
"f the biodiesel is removed from the mi&ture# glycerol and unreacted NaOH and methanol remain. The glycerol is a valuable by-product used to ma+e soap and other s+in care products. The transesteri%cation reaction is sensitive to the presence of free fatty acids which are the result of vegetable oil degradation during coo+ing process. $s a result# waste vegetable oil tends to have higher levels of free fatty acids than unused vegetable oil which can slow or stop the transesteri%cation reaction. The same chemical that is used to catalye the reaction# NaOH# can also neutralie the free fatty acids. nough sodium hydro&ide will be needed to neutralie any free fatty acids in the oil# in addition to the amount of sodium hydro&ide that is used as a catalyst. The levels of free fatty acids can be determined through titration. $ titration is a way of determining the concentration of a substance by adding to it a standard reagent of +nown concentration until we see an e4ect# often a color change. "n our case the dissolved substance is the free fatty acids# the reagent of +nown concentration is the sodium hydro&ide# and the e4ect is color change 'from clear to bright pin+(# which indicates a speci%c change in pH. How does a color change relate to pH level and the presence of free fatty acids5 This titration uses a common pH indicator# phenolphthalein. The compound is colorless in acidic solution and pin+ish in basic pH. ,hen enough sodium hydro&ide is added to the solution to change the pH to basic# it will turn pin+. This indicates that we have neutralied the free fatty acids. aterials 6odium hydro&ide 'NaOH ( # anhydrous .1 NaOH solution .1 $cetic acid High purity '788 ( methanol 9nused vegetable oil ' palm oil( and waste coo+ing oil "sopropyl alcohol :henolphthalein indicator raduated cyclinder !urette 1 ml icropipettes and tips ;lamp stamp ;onical
!ea+er 6eparation funnel ;entrifuge and centrifuge tubes Hot plate agnetic stirrer 6afety goggles and gloves Thermometer 6ample containers =istilled water
P!"# I $ %etermine t&e acid value of used vegetable oil 'WVO( •
HYPOTHESIS: Predict which type o oil, unused or waste (used), has ore ree atty acids! "hy!
Procedure 1. >abel two bea+er as ?*O@ 'unused vegetable oil( and ?,;O@ 'waste vegetable oil(. 2. Aill the burette with .1 NaOH solution. 3. :our 2 m> of isopropyl alcohol into a graduated cylinder. $dd 1 m> of the isopropyl alcohol to the each bea+er labeled ?*O@ and ?,*O.@ B. $dd 1 m> of the unused vegetable oil sample the bea+er labeled ?*O@ containing the isopropyl alcohol. =escribe the appearance of the liCuid. D. $dd 1 m> of the waste vegetable oil sample to the bea+er labeled ?,*O@ containing the isopropyl alcohol. =escribe the appearance of the liCuid D. ently swirl the contents of the bea+er for 1 seconds. =escribe the appearance of the liCuid. E. $dd D F> of the :henolphthalein indicator solution to each ?*O@ and ?,*O@ bea+ers containing oil)isopropyl alcohol mi&ture. ently swirl the contents of the bea+er for 1 seconds. =escribe the appearance of the liCuid. G. ead and record the initial volume of .1 NaOH solution in the burette. !e sure to be precise with your measurement and record the data below/ "nitial)starting volume of .1 NaOH solution in burette / IIIIIIIIIIIIIII m> J. ;arefully position the burette directly over the *O bea+er. ;arefully add one '1( drop of the NaOH solution from the burette into the bea+er by turning the burette stopcoc+. =O TH"6 6>O,>K and ;$A9>>K. Only add ON =O: at a time. 8. 6wirl the bea+er and observe any color changes after adding the NaOH to the bea+er. 1. Leep adding the NaOH solution ;$A9>>K until the solution turns bright pin+ and remains that color for at least 1D seconds. Kou have reached at the titration end point. 3
11. ecord the remaining amount of NaOH in the burette in Table 1. 12. epeat the titration 'step G-1( and record your data in Table 1. et an average volume of .1 NaOH added to the ?*O@ bea+er from your titration. 13. epeat the titration 'step G-1( for ?,*O@ bea+er# twice)duplicate and record the remaining amount of NaOH in the burette in Table 2. ;alculate the average volume of .1 NaOH added to the ?,*O@ bea+er from your titration.
#able ) $ Volume of *+*), -aO. added to Unused Vegetable Oil 'VO( Titration #: nding volume of .1 NaOH solution in burette / IIIIIIIIIIIIIII m> "nitial)starting volume of .1 NaOH solution in burette / IIIIIIIIIIIIIII m> Total volume of .1 NaOH added to the bea+er / IIIIIIIIIIIIIIIIIIIII m> Titration $:
nding volume of .1 NaOH solution in burette / IIIIIIIIIIIIIII m> "nitial)starting volume of .1 NaOH solution in burette / IIIIIIIIIIIIIII m> Total volume of .1 NaOH added to the bea+er / IIIIIIIIIIIIIIIIIIIII m> !verage volume of *+*) -aO. added to t&e /VO0bea1er: 222222222222222222m
#able 4 $ Volume of *+*), -aO. added to Waste Vegetable Oil 'WVO( B
Titration #:
nding volume of .1 NaOH solution in burette / IIIIIIIIIIIIIII m> "nitial)starting volume of .1 NaOH solution in burette / IIIIIIIIIIIIIII m> Total volume of .1 NaOH added to the bea+er / IIIIIIIIIIIIIIIIIIIII m> Titration $:
nding volume of .1 NaOH solution in burette / IIIIIIIIIIIIIII m> "nitial)starting volume of .1 NaOH solution in burette / IIIIIIIIIIIIIII m> Total volume of .1 NaOH added to the bea+er / IIIIIIIIIIIIIIIIIIIII m> !verage volume of *+*) -aO. added to t&e /WVO0bea1er: 2222222222222222m
Muestion/ "hich oil has hi%her atty acid content! :revious research has determined that each milliliter NaOH solution used in the titration corresponds to a gram of NaOH needed to neutralie the free fatty acids in one liter of vegetable oil. Therefore# the acid value eCuals to the amount of NaOH solution added to the oil)isopropyl alcohol mi&ture. 1m> of .1 NaOH solution 1g NaOH)> of oil $cid value for your ,*O / IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIg NaOH)> of ,*O P!"# II $ %etermine t&e total amount of -aO. needed to ma1e biodiesel from 5our sample Transesteri%cation of unused vegetable oil reCuires four grams 'B g( of sodium hydro&ide for every liter of oil. However# since your samples were waste vegetable oil# we +now they contained a certain amount of additional free fatty acids. The acid value you calculated for waste vegetable oil allows us to determine how much additional sodium hydro&ide we will need D
in our reaction to neutralie the free fatty acids prior to the transesteri%cation process. Therefore# to get the total amount needed# you will need to add the amount of sodium hydro&ide needed to neutralie the amount of free fatty acids in your sample 'the $cid *alue number( to the amount of sodium hydro&ide needed for the transesteri%cation process 'B. g NaOH)liter of unused oil(. B. g)> NaOH IIIIIIIIIIIIIIIII IIIIIIIIIIIIII g NaOH)> of ,*O ';onstant value( ',*O acid value( '$mount NaOH to add to ma+e biodiesel from ,*O( P!"# III6 #ransesteri7cation of Unused and Used Vegetable Oil to Produce Biodiesel 1. >abel two 2D ml-bea+ers as ?*O@ and ?,*O@ 2. >abel two 2D ml-conical oil or .B g NaOH for every 1 m> of *O(. B. $dd 2 m> of methanol the ?*O metho&ide of 1 pure vegetable oil to about BP; 'measure the temperature using thermometer( in a 2D m> bea+er. ,arming the oil up is not necessary# but increases the reaction rate. J. ,hen all of the NaOH is dissolved# pour the 1 m> of oil into the ?*O metho&ide@ separatory funnel. The mi&ture will separate into two di4erent layers. The glycerol will fall to the E
bottom# and the crude methyl ester 'biodiesel( will of .1 acetic acid to the biodiesel# cap the tube# invert gently %ve times 'do not sha+e(# then centrifuge at 2 rpm for D minutes. =iscard the bottom# aCueous layer into the labeled waste container. epeat the e&traction step using 1 m> of distilled water. 12. ,eigh an empty D ml conical
8uestion: 1. ,hy it is necessary to wash and purify the crude biodiesel prior to using it as fuel5 2. =o you observe any product of side reaction at the end of transesteri%cation of used vegetable oil5 "f any# what are the side reaction and the unwanted product5 3. "n your opinion# is it practical to carry out transesteri%cation of waste vegetable oil5 =oes utiliation of waste vegetable oil save or add more cost in biodiesel production compare to unused vegetable oil5
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