Seite - 198 - in Advanced Chemical Kinetics

The competitiveness of companies forwhich the core business is theproductionof consumer goods is directly linked to their production process. Quality and productivity, once seen as dissociated elements, noware joined together, strongly impacting business competitiveness, improvingprocessperformance,productqualityandreducing costs. In thisway, the studyof the kinetics of chemical processes allows the optimization of the process, avoiding thewaste notonlyof rawmaterials, butalsoofenergyandtime [6]. Establishing thekinetics of a chemical reaction canbevery complexdependingon the chem- ical route.An in-depthstudyrequiresa seriesof experimentsandsimulations that canpredict when the reactionhas reached theoptimal state. For reactions inwhich the convertingmech- anism isnotwell established, severalkineticmodelsmaybeproposed, arising fromcountless reactionmonitoring techniques. Thus, the combination of techniques, well described in the literatureandeasilyaccessible, allowsamoreprecise conclusionof theobjectof study [6, 7]. To illustrate, letus takeoneof the chemical reactions responsible forbiodieselproduction, the transesterification reaction,disclosed inFigure1. Figure1discloses that anoil can reactwith a small chainalcohol in thepresenceof a catalyst and produce biodiesel. Biodiesel, also known as fatty acidmethyl ester (FAME), is nothing more thanamixtureofesters. The transesterificationreaction toproducebiodiesel is reversibleand, therefore,usuallyworks with excess of alcohol. A typical proportion is 6:1 (alcohol:oil) ratio, so that the equilibrium displacement is forced towards the conversionof biodiesel.However, the oil and alcohol are not miscible, establishing two phases. In this stage, when there are two phases within the mixture, one can say that themass transfer controls thekinetics of the reaction.Nevertheless, asbiodiesel (methyl ester) is formed, itworksasaco-solvent, facilitating themiscibility.Upon reaching thehomogeneity of the system, the chemical reaction starts to control the system.A reaction inwhichanexchangeofmechanismoccursmakesdifficult todefine thekineticsand, consequently, theestablishmentofoptimal reactionconditions [7–12]. Figure1. Transesterificationofvegetableoil forbiodieselproduction. Advanced Chemical Kinetics198