UNIVERSITI TEKNOLOGI MARA FAKULTY OF CHEMICAL ENGINEERING PROCESS ENGINEERING LABORATORY 2 (CPE553)
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NAME GROUP E"PERIM ENT DATE PROG$CO DE SUBMIT TO N %
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MOHAMAD AZRUL SOFI BIN MOHD TAHAR (201392991) EH2!1! (GROUP1) LAB 3 # CSTR !0L
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2 OCTOBER 2015 EH2!1
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MDM LIM YING PEI T&'
1 Abstract 2 Introduction 3 Objectives 4 Theory 5 Procedures/Methodoloy " A##aratus $ %esults & 'alculation ( )iscussion 1! 'onclusion 11 %eco* eco** *endat ndatio ions ns 12 %e+erences 13 A##endices TOTAL
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ABSTRACT The conversion of reactant into product is very important in the chemical process. Reactors is used to convert the reactant into product. Reactors are very important in chemical processes. Furthermore the design of the reactors will determine the result of the product and it is very important to the success of the production. Meanwhile, in this experiment sodium hydroxide and ethyl acetate react in continuous stirred tank reactor. They are fed into the reactor at equimolar flowrate. The conversion achieve at different retention time is determined by measured the conductivity value of outlet stream. t the lowest flowrate, the retention time is highest. !o the result shows that the conversion is increased as the residence time increases. "ur ob#ectives in this experiment are to carry out the saponification reaction between sodium hydroxide and ethyl acetate in plug flow reactor, to determine the reaction rate constant and the rate of reaction of the saponification process. First of all, the equipment is set up before started the experiment. From the result, the rate of reaction and the value of reaction rate constant is calculated. t $.%$ &'min flowrate is ($.$$ M )%s)%, for the $.%* &'min reaction rate constant is +.- M )%s)%, for the $.-$ &'min reaction rate constant is +%./ M )%s)%, for the $.-* &'min reaction rate constant is -/. M )%s)%, and for the $.+$ &'min reaction rate constant is -0.$$ M )%s)%. 1owever, we also can to determine the rate of reaction for this process. fter that, we are plotted a graph of conversion factor against residence time. From the graph plotted, the conversion factor is directly proportional to the residence time. The conversion factor increases so the residence time also increases.
INTRODUCTION 2n a continuous)flow stirred)tank reactor 34!TR5 , reactants and products are continuously added and withdrawn. 2n practice, mechanical or hydraulic agitation is required to achieve uniform composition and temperature, a choice strongly influenced by process considerations. The 4!TR is the ideali6ed opposite of the well)stirred batch and tubular plug)flow reactors. nalysis of selected combinations of these reactor types can be useful in quantitatively evaluating more complex gas), liquid), and solid)flow behaviors. 7ecause the compositions of mixtures leaving a 4!TR are those within the reactor, the reaction driving forces, usually the reactant concentrations, are necessarily low. Therefore, except for reaction orders 6ero) and negative, a 4!TR requires the largest volume of the reactor types to obtain desired conversions. 1owever, the low driving force makes possible better control of rapid exothermic and endothermic reactions. 8hen high conversions of reactants are needed, several 4!TRs in series can be used. 9qually good results can be obtained by dividing a single vessel into compartments while minimi6ing back)mixing and short)circuiting. The larger the number of 4!TR stages, the closer the performance approaches that of a tubular plug)flow reactor. 4ontinuous)flow stirred)tank reactors in series are simpler and easier to design for isothermal operation than are tubular reactors. Reactions with narrow operating temperature ranges or those requiring close control of reactant concentrations for optimum selectivity benefit from series arrangements. 2f severe heat)transfer requirements are imposed, heating or cooling 6ones can be incorporated within or external to the 4!TR. For example, impellers or centrally mounted draft tubes circulate liquid upward, then downward through vertical heat)exchanger tubes. 2n a similar fashion, reactor contents can be recycled through external heat exchangers. 7y studying the saponification reaction of ethyl acetate and sodium hydroxide to form sodium acetate in a batch and in a continuous stirred tank reactor, we can evaluate the rate data needed to design a production scale reactor. stirred tank reactor 3!TR5 may be operated either as a batch reactor or as a steady state flow reactor 34!TR5. The key or main feature of this reactor is that mixing is complete so that properties such as temperature and concentration of the reaction mixture are uniform in all
parts of the vessel. Material balance of a general chemical reaction described below.The conservation principle requires that the mass of species in an element of reactor volume d: obeys the following statement; 3Rate of into volume element5 ) 3rate of out of volume element5 < 3rate of produced within volume element5 = 3rate of accumulated within vol. element5
THEORY mathematical model to predict ideal transient concentration in a 4!TR is developed by using principles of a simple material balance. From the material balance, the ideal residence time distribution is derived. 2n order to create the experimental model, a negative step input method is utili6ed. This process is used instead of the positive step method due to the difficulty of keeping an initial tracer concentration in the feed stream.
General Mole Balance Equation
Assumptions
%5 !teady state therefore -5 8ell mixed therefore r is the same throughout the reactor
Rearranging the generation
2n terms of conversion
The reaction to be studied is the saponification reaction of ethyl acetate 9t3c5 and sodium hydroxide >a"1. !ince this is a second order of reaction, the rate of reaction depends on both of these reactants. The reaction will be carried out using equimolar feeds of both the reactants with same initial concentrations. The reaction equation is? >a"1 < 9t 3c5 @>a3c5 < 9t"1 or
<
7
@ 4 <
A
For a second order equimolar reaction with the same initial concentration 34 " = 47o5, the rate law is? 2
−r a=k C A C B= k C A
−r A=
V CSTR F A 0 X
Thus, the volume of the reactor is ? Ao −¿ C A C ¿ ¿ F 0 ¿ F A 0 X V CSTR = =¿ 2 k C A
For equimolar feed rate, the reaction constant is ? Ao −¿ C A C ¿ ¿ ¿ k =¿
The residence time of a chemical reactor or vessel is a description of the time that different fluid elements spend inside the reactor is given by?
Residence time , τ =
V CSTR F 0
This equation gives the concentration of species i in the outlet stream at any time t . The residence)time distribution function, 93t5, is given;
7y substituting this equation
into above equation and solving, we obtain the following expression which describes the amount of time a tracer spends in the reactor;
The ideal cumulative concentration distribution, F3t5, is also practical when evaluating the residence time distribution, providing the percent of material that has a RTA of time t or less
7y definition, 93t5 = )dF3t5'dt for a negative step input. Therefore, by differentiating 9q. (, we obtain the residence)time distribution function for a non)ideal 4!TR.
OBECTI!ES %. To carry out a saponification reaction between sodium hydroxide,>a"1 and ethyl acetate 9t3c5 in a 4!TR -. To determine the reaction rate constant of sodium hydroxide,>a"1 and ethyl acetate 9t3c5 +. To determine the effect of residence time on the conversion in a 4!TR.
A""ARATUS %. laboratory scale of 4ontinuous !tirred Tank Reactor $litre -. conductivity meter +. *$ m& 7eakers . -*$ m& 4onical Flasks *. burette (. retort stand. 0. !odium 1ydroxide . 9thyl acetate /. 1ydrochloric acid %$. Bhenolphtalein %%. Aeioni6ed water
"ROCEDURE a# "reparation o$ Cali%ration Cur&e %. % liter of sodium acetate, >a3c5 $.%M and % liter of sodium hydroxide, >a"1 $.%M are prepared. -. The following list of solution are mixed together into %$$m& of deionised water to determine the conductivity and >a"1 concentration for each conversion values. a5 $C conversion ; %$$m& >a"1 b5 -*C conversion ; 0*m& >a"1 < -*m& >a3c5 c5 *$C conversion ; *$m& >a"1 < *$m& >a3c5 d5 0*C conversion ; -*m& >a"1 < 0*m& >a3c5 e5 %$$Cconversion ; %$$ m& >a3c5 +. The value of conductivity for each conversion is recorded. . The graph of the calibration curve of conductivity versus conversion is plotted. The slope and y)axis intercept is determined.
%# Bac' Titration "roce(ures $or manual Con&ersion Determination %. $.%M >a"1 solution is filled into a burette. -. $.-*M 14l is measured at %$m& in a flask. +. From the experiment, a *$m& sample is obtained and immediately added to the 14l in the flask to quench the saponification reaction. . Then, a few drops of phenolphtalein were fadded into the mixture *. The mixture is titrated with >a"1 solution from the burette until the mixture was neutrali6ed. The amount of >a"1 titrated recorded.
c# E$$ect o$ Resi(ence Time on t)e Reaction in a CSTR %. Deneral start)up procedures is performed. -. Bumps B% and B- are switched on simulteneously and the valves :* and :%$ are opened to obtain the hishest possible flow rate into reactor. +. The >a"1 and 9t3c5 solutions were allowed to enter the reactor until it is #ust about to overflow. . For the valves :* and :%$ are read#usted to give a flowrate about $.%&'min. *. The stirrer M% were switched on and the speed were setted to about -$$ rpm. (. The conductivity value at 3E2)$%5 is started to monitor until they did not change over the time to ensure that the reactor reached the steady state. 0. The sampling valve :%- is opened and a *$m& sample collected. back titration procedure is carried out to manually determine the concentration of >a"1 in the reactor and extent of conversion. . The experiment is repeated from step to 0 for different residence time by increasing the feed flow rates of >a"1 and 9t 3c5 to about $.%*, $.-$, $.-* and $.+$ ml'min. Make sure that both was the same.
RESU*TS Reactor &olume + & Concentration o$ NaOH in $ee( &essel + $.%M Concentration o$ Et,Ac# in $ee( &essel + $.%M
Temperature ,-C# .lo/rate o$ NaOH0 ,m*1min# .lo/rate o$ Et,Ac#0 ,m*1min#
+$.%
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+$.*
+$.(
+%.$
%$$
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0./-
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0.$$
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Total $lo/ rate o$ solutions0 .2 ,m*1min# Con(ucti&it30 ,4S1cm# Resi(ence time0 5 ,min# Con&ersion0 6 ,7#
Table % 9ffect of residence time tubular flow reactor
Solution mi8tures Con&ersion 7
29: M NaOH0 m*
29: M Et,Ac#0 m*
H ;O0 m*
Concentration
Con(ucti&it30
o$ NaO ,M#
mS1cm
$
%$$
$
%$$
$.$*$$
0.($$
-*
0*
-*
%$$
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*$
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$.$-*$
$.0$$
0*
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Table - Breparation of calibration curve
G-+12 %3 *%45)-/&%4 " 5/6 ')71)-+'8-) %3 -)+*'%31-2 31 3!-& 3!-" 3!-4
T)71)-+'8-)
3!-2 3! 2(-& 2(-" 2(-4 2(-2 $!
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5
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DISCUSSION To determine the conversion of the reaction of between sodium hydroxide 3>a"15 and ethyl acetate 39t3c55 at certain value of conductivity, the calibration curve is plotted. From the calibration curve, the conductivity of the sodium hydroxide solution varied linearly with concentration of sodium hydroxide. 8hen the molar concentration of >a"1 decreases, the conductivity is decrease. Aifferent value of conductivity will be given by both of them when mixture of different of moles is used. !odium hydroxide is used as a reactant while sodium acetate is produced as a product from this mixture. 9thyl acetate and ethanol are not electric conductor from that we can measured the concentration of unreacted >a"1 that remains solution that relate to conversion by used the conductivity of the mixture measurements. :olumetric flowrate is affect to the residence time so this experiment is conduct in different flowrate. 8hen the volumetric flowrate is increase so the conversion is increases too. Residence time is time that the fluid elements spend within reactor. More conversion reactant is occurred when the time of the reactant spend in is longer. !o the concentration of the reactant will decrease and the concentration of product will increase. Fluid entering the reactor at time t
will exit the reactor at time t < , where is the residence time of the reactor. The velocity of fluid moving inside the reactor is low at the low flowrate. The reactant will spend more time within the reactor when the velocity of fluid is lower. Furthermore, the electronic device on the reactor is used to determine the conversion based on the conductivity value. 7ack titration procedure is used to determine the conversion manually. From the calculation, the value of conversion that obtained is increase when the volumetric flowrate decrease. This proved the theory form the calibration curve from the first experiment. The experiment is successful conducted. Gnfortunately there are no calculations in this experiment due to the mistake with the instrument itself during the experiment is conducted. For the titration part not done successful because of the error in the reading of the samples obtained from the instrument.
CONC*USION From the experiment, the different volumetric flowrate is used and caused different conversion in the reaction between >a"1 and 9t3c5 which done in a continuous stirred tank reactor. s the flowrate decreases, the reaction rate constant, k for the second order of reaction is decreases. 2n order to achieve the ob#ectives of the experiment, the continuous stirred tank reactor is used. From the experiment, all the purposes are met and the results are recorded. From the results, it shows that as for each flow rates decrease from $.%$$ &'min to $.-/ &'min, the conversion of sodium hydroxide decrease from /.$ C to 0(.$ C. Meanwhile for the graph of conversion of sodium hydroxide versus residence time is plotted. 2t is shows that the conversion of sodium hydroxide is directly proportional to the residence time. s the conversion increase, the residence time increase as well. s all the purposes of this experiment is achieved, this experiment is considered as a successful.
RECOMMENDATION %. The general start)up must be done first to check the machine functining well. -. Rinsed the burette with sodium hydroxide after rinsed using the distilled water to prevent error. +. Blease make sure the solution that filled in the tank is correct solution and the amount is also correct. Aifferent substance reacts differently and lack of substance can damage the apparatus. . 9ye protection must be wear at all the time when handle with the sodium hydroxide. 7ecause sodium hydroxide is corrosive to flesh and can cause blindness. *. The device needs to be well maintenance in order to avoid it from malfunctioning during the experiment period like the one we are having in our session. (. To get a better result, only one person is needed to take care of the opening and closing of the valve and other person take care of the pump. This is because some valve needed to be opened or closed simultaneously.
RE.ERENCES nd %. Fogler, 1. !., H Elements of Chemical Reaction Engineering I, edition, Brentice 1all, %//-, >ew Jersey. -. Dilbert F.Froment and Kenneth 7.7ischoff., H4hemical Reactor nalysis and AesignIJohn 8iley L !ons, -nd 9dition, %//$. +. H4ontinuous !tirred Tank Reactor modelI, http;''en.wikipedia.org'wiki'plug)flow)reactor) model, accessed in "ctober -$%%. . &evenspiel ". Chemical Reaction Engineering . John 8iley L !ons, >ework, third edition, %///. *. http;''www.scribd.com'doc'0+0+*'cstr
A""ENDICES
Time ,min#
: ; > ? @ :2
Mem%rane ;
Mem%rane >
Mem%rane ?
