chemical reaction

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Fatty!acid!methyl!esters!(FAME)!are!the!main!components!of!biodiesel.!!They!are!the! result!of!the!transesterification!of!vegetable!oils!(triglyceride!or!TG)!with!methanol! using!an!alkali!or!acid!as!a!catalyst.!The!overall!reaction!is:! !

!" + 3!"# → 3!!!!!! + !"!! ! ! !!!!!(1)! !

Triglyceride!+!Alcohol!→!Methyl!Esters!+!Glycerol! !

This!reaction!can!be!broken!down!into!three!steps:! !

!" + !"#! ⇄ !" + !!!!!!! ! ! !!!!!!!!(2)! !

!" + !"#! ⇄ !" + !!!!!!! ! ! !!!!!!!!(3)! !

!" + !"#! ⇄ !" + !!!!!!! ! ! !!!!!!!!!(4)! !

Where! DG! and! MG! are! diglycerides! and! monoglycerides,! respectively.! It! can! be! observed! from! (1)! that! the! required! stoichiometric! ratio! of! alcohol! to! TG! is! 3:1.! However,! since! the! set! of! reactions! are! reversible,! excess! alcohol! is! used! to! maximize!ester!yield.!

! The! data! shown! below! was! obtained! in! a! batch! reactor! using! soybean! oil! and! methanol! (6:1! ratio! of! alcohol! to! TG)! in! attempt! to! model! the! hydrolysis! of! TG,! presented! by! equation! (2).! Concentrations! were! measured! at! different! points! in! time!for!three!temperatures:!25,!40!and!60˚C.!! ! a) Evaluate! the! data! and! formulate! a! rate! law.! ! Calculate! the! specific! rate!

constants!and!order!of!reaction.! ! b) Calculate!the!activation!energy!and!preTexponential!factor.! ! c) The!data!presented!made!use!of!ultrasonic!mixing.!Literature!suggests!that!the!

apparent! specific! rate! constant!of! the!pseudoTreaction! (kTG’)! at!60˚C! is!0.036! (wt%!minT1)!when!traditional!mixing!is!used.!Did!the!ultrasonic!mixing!affect! the!apparent!specific!rate?!If!so,!what!may!this!be!attributed!to?! !

University of New Brunswick ChE 4101 Fall 2015 Chemical Reaction Engineering

Dr.$William$Cook$$$&$ office:!!!!!!ET230C! phone:!!!!!452T6318! e)mail:[email protected]!

Mr.$Francis$Lang$ C121!

453T3556! [email protected]!

Assignment$#2! Due:!4:30pm,!Thursday!October!15th!

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Table$1.$$Experimental$Data$for$triglyceride$transesterfication.$

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25°C% 40°C% 60°C% Concentration%TG%

(wt%)% Time% (min)%

Concentration%TG% (wt%)%

Time% (min)%

Concentration%TG% (wt%)%

Time% (min)%

66.7% 0% 42.5% 0% 73.7% 0% 49.4% 1% 11.0% 2% 5.8% 2% 25.8% 3% 7.0% 3% 2.7% 3% 13.5% 5% 4.3% 5% 2.5% 5% 11.0% 8% 3.0% 7% 1.2% 8% 5.5% 17% 2.7% 8% 0.9% 10.5% 3.3% 28% 1.5% 15% % % 2.6% 35% % % % % !

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