Seite - 207 - in Advanced Chemical Kinetics
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Looking atTable 1 and Figure 9, one can note that there is a large difference inCTAG andυ
decaybetweenbothreactions,whatreflects in theconversionrate (XTAG).Theuncertaintybars
calculated for the velocity are disclosed to determine the accuracy of the study [33]. The
behaviourobserved in the reactionwith0.2%KOHand200 rpmpresents a slowdecay in the
concentration ofTAG in the first 10minof reaction,which is expected for reactions inwhich
mechanism exchange occurs. That region on the graphics of Figure 9 (first 10 minutes of
reaction) is inwhich the rate of consumption and conversion rate are slow, and it occursdue
to the lowmiscibility between alcohol and oil. Thus, as the methyl ester is produced, the
chemical reaction starts to control the kinetics of the reaction and, therefore, a large jump
between10and20minof reaction isobserved.After20minof reaction, it is clearlynoticeable
that there is stability between the conversion values and propagation velocity. This result
indicates that the ultrasound can determine the maximum point of conversion even in the
presenceof secondarysubstances (by-products).
Ontheotherhand,whenthereactionwith1.5%KOHand200rpmisonfocus,yet inFigure9, it
isobservedanexpressiveconsumptionofTAGinthefirst10minofreaction.After that time, the
stability in thevalues of the conversion aswell as in thepropagationvelocity is evident.Reac-
tions likethat, inwhichthereisarapidconversion, theregioncontrolledbymasstransfercanbe
consideredinsignificant.Here, it isobservedthat forreactionswith200rpmstirring, theincrease
incatalystconcentrationnotonlyacceleratesthetransesterificationprocessbutalso increasesthe
finalconversionaswell,andconsequentlydecreasestheremainingTAGinthereactionmedium.
Letuscheck if thesamewilloccuranalysing theresultspresented inTable2andFigure10, in
which the rotationspeedwas increased to520rpm.
For the reactionwith0.2%ofKOHand520 rpmof stirring, it isnoticeable that there is a slow
decrease in theTAGconcentration in the first 10min and stability of thevalues after 20min.
On the other hand, the reaction with 1.5% of KOH and 520 rpm reaches the maximum
conversion as fast as 5 min after the reaction had begun. In the sameway as observed in
Figure 9, the mass transfer controls the start of the reaction for the reaction with 0.2% of
catalyst, independently of the rotational speed employed.With the increase ofKOHconcen-
trationby7.5 times, there is a300%decrease in reaction time for the reactionwith520 rpmof
0.2%and520rpm 1.5%and520rpm
Time[min] XTAG [%] CTAG [molL 1] υ [ms 1] XTAG [%] CTAG [molL 1] υ [ms 1]
0 0 0.83 1426.8 0 0.83 1421.3
1 0.3 0.81 1342.9 52.8 0.65 1363.2
5 5.5 0.78 1353.0 85.9 0.12 1358.8
10 8.7 0.76 1354.0 87.7 0.10 1357.6
20 78.6 0.22 1357.3 88.7 0.09 1356.3
40 82.1 0.18 1360.0 89.1 0.09 1356.9
Table 2. Results for reactions at 520 rpm. Ultrasound as a Metrological Tool for Monitoring Transesterification Kinetics
http://dx.doi.org/10.5772/intechopen.70501 207
zurück zum
Buch Advanced Chemical Kinetics"
Advanced Chemical Kinetics
- Titel
- Advanced Chemical Kinetics
- Autor
- Muhammad Akhyar Farrukh
- Herausgeber
- InTech
- Ort
- Rijeka
- Datum
- 2018
- Sprache
- englisch
- Lizenz
- CC BY 4.0
- ISBN
- 978-953-51-3816-7
- Abmessungen
- 18.0 x 26.0 cm
- Seiten
- 226
- Schlagwörter
- Engineering and Technology, Chemistry, Physical Chemistry, Chemical Kinetics
- Kategorien
- Naturwissenschaften Chemie