Page - 210 - in Advanced Chemical Kinetics

Thus, an economic analysis is necessary to evaluate towhat extent an increaseof the rotation used,orof the catalyst concentration, to thedetrimentof the reduction in the reaction time, is economically feasible.But theuseofultrasoundasatool formonitoringchemicalreactionshas beenshowntobeefficient [33]. 6.Final remarks Ultrasound is widely used formore than a century for diagnosis applications. The state of the technology is vast on applications for non-destructive testing andbiomedical equipment. Theuseofultrasoundinchemistry ismorecommonasatool toacceleratereactionsorenhance theperformanceof establishedmethods.However, the technology isnot sowidelydeveloped andspreadaroundregardingtheuseofultrasoundasamonitoringtool forchemicalreactions. As a tool, ultrasound is remarkably simple to use.Nevertheless, onemust be aware that the apparent straightforwardnessundercovers a complexphysical process that takesplace in the generation, propagations, reflection and reception of ultrasound in both the transmit/receive and pulse/echo approaches. Unless an experiment is carefully designed, carried out, and analysed, theoutcomeofanyultrasonicproposedmethodcouldbeofno technicalusefulness. In thepresent chapter, the use of anultrasoundpulse/echo schemewasvalidated as amoni- toringprocedureof the transesterificationkineticsof soybeanoil intobiodiesel.Thesensibility of themethodwas good enough to compare different catalyst concentrations (0.2 and 1.5%) anddifferent rotational speedofmechanical stirring (200 and520 rpm). The comparisonwas done using as gold standard the gas chromatography and 1HRMN. The validation leads to quite interestingoutcomes. Figure 12. Variation of (a) TAG concentration, (b) propagation velocity and (c) TAG conversion for the reactionswith 1.5%(w/w)ofKOH. Advanced Chemical Kinetics210