ert 208/4 reaction engineering: bioreaction in bioreactors by; mrs haf iza bint i shu kor ert 208/4...
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ERT 208/4 REACTION ENGINEERING: Bioreaction in Bioreactors
By; Mrs Hafiza Binti Shukor
ERT 208/4 REACTION ENGINEERINGSEM 2 (2009/2010)
ERT 208/4 REACTION ENGINEERINGSEM 2 (2009/2010)
Students should be able Students should be able to; to;
APPLY pseudo-steady-state hypothesis (PSSH) in gas-phase reactions and in order to DEVELOP rate laws.
DESCRIBE reaction mechanism, chain reaction & reaction pathways utilizing biomolecular reaction (yeast fermentation)
ERT 208/4 REACTION ENGINEERINGSEM 2 (2009/2010)
Common form of the RATE LAW
n
AA kCr
If n=not interger number? Eg,The rate law for the decomposition of acetaldehyde
2
3
33 CHOCHCHOCH kCr
•homogeneous reaction,
•Reaction involving active intermediate
If n=1 (interger), reaction was 1 order
HIIH 222 232
2231
H
HI
HI Ckk
CCkkr
Reaction Order cannot de defined(polynomial fuction)
NON ELEMTARY REACTION
No direct correspondence between reaction order & stoichiometry
Reaction Order are described only for limiting values of reactant and/or product conc.
COCHCHOCH 43
ERT 208/4 REACTION ENGINEERINGSEM 2 (2009/2010)
Fundamentals of Nonelementary Reaction•For Gas-Phase Decomposition of azomethane, AZO
AZON Cr 2
EXPERIMENTAL OBSERVATIONS SHOWS ;
1st order at;•high conc•pressure >1atm
262223 NHCNCH
AZON Cr 2
2
2nd order at;•Low conc•Pressure < 50mmHg
ERT 208/4 REACTION ENGINEERINGSEM 2 (2009/2010)
Fundamentals of Nonelementary Reaction…cont…•Active Intermediates change in reaction order can be explained by the theory developed by Lindemann
‘ an active molecule,
results from collision or interaction between
molecules’
*]@[223 ANCH
ERT 208/4 REACTION ENGINEERINGSEM 2 (2009/2010)
Fundamentals of Nonelementary Reaction…cont…
*2232231
223223 NCHNCHNCHNCH k
•Lindemann Theory the decomposition of intermediate does not occur instantaneously after internal activation of the molecule …rather, there is a time lag although infinitesimally small during which the species remains activated.•Other types of active intermediates that can be formed are;a)Free radicals (one @ > unpaired electrons like H)b)Ionic internidiates (eg. Carbonium ion)c)Enzymes substrate complexes
MAMA k *1
ERT 208/4 REACTION ENGINEERINGSEM 2 (2009/2010)
Fundamentals of Nonelementary Reaction…cont…
*2232231
223223 NCHNCHNCHNCH k
2 reaction path that active intermediate may follow;
AZOAZO Ckr 2
1* 223 NCHAZO where.,
2232232
223223 * NCHNCHNCHNCH k
2623
223 * NHCNCH k
*2* AZOAZOAZO CCkr
*3* AZOAZO Ckr
Activated molecule become deactivated through collision with another molecule
where.,
Activated molecule decomposes spontaneously to form ethane & nitrogen
ERT 208/4 REACTION ENGINEERINGSEM 2 (2009/2010)
Fundamentals of Nonelementary Reaction…cont… The overall reaction is NON
ELEMENTARY consist of sequence of ELEMENTARY reactions
262223 NHCNCH
*2232231
223223 NCHNCHNCHNCH k
2232232
223223 * NCHNCHNCHNCH k
2623
223 * NHCNCH k
Nitrogen & Ethane only form from 3rd equation. The net rate of formation of nitrogen is;
*32 AZON Ckr
2 AZO molecules collide & the kinetic energy of one AZO molecule is transferred to internal rotational & vibrational energies of the other AZO molecule & it becomes activated & highly reactive.
1.
2.
3.
Activated AZO* is deactivated through collision with another AZO
Activated AZO* is widely vibrating, spontaneously decomposes into ethane & nitrogen
ERT 208/4 REACTION ENGINEERINGSEM 2 (2009/2010)
Fundamentals of Nonelementary Reaction…cont…
3*2*1** AZOAZOAZOAZO rrrr
AZOAZO Ckr 2
11*
*22* AZOAZOAZO CCkr
*33* AZOAZO Ckr
Where,
Rate of formation of active intermediate = sum of the rates of formation of all reaction
*3*2
2
1* AZOAZOAZOAZOAZO CkCCkCkr
To express CAZO* in term of MEASURABLE CONC, we have to use STEADY STATE HYPOTHESIS (PSSH)
The concentration of the active intermediate, AZO* is very difficult to measure because it is highly reactive and very short lived about 10-9 s
ERT 208/4 REACTION ENGINEERINGSEM 2 (2009/2010)
Pseudo-Steady-State Hypothesis (PSSH)..
0*r
Its not possible to eliminate the concentration of active intermediate Active intermediate molecule has a very short lifetime because of its high reactivity (large specific reaction rates). Have to consider it present at very low concentrations
The rate of formation = is assumed to be equal to its rate of disappearance.As a results, the net rate of formation of the active intermediate r* is ZERO
Pseudo-Steady-State approximation
*32 AZON Ckr
*3*2
2
1* AZOAZOAZOAZOAZO CkCCkCkr
Rate of formation of product, nitrogen;
Rate of formation of AZO*;
Using PSSH; 0* AZOr
0*3*2
2
1* AZOAZOAZOAZOAZO CkCCkCkr
ERT 208/4 REACTION ENGINEERINGSEM 2 (2009/2010)
Pseudo-Steady-State Hypothesis (PSSH)cont..
The final form of rate law
AZO
AZO
AZO
AZOAZOAZO
AZOAZOAZOAZO
AZOAZOAZOAZOAZO
Ckk
CkC
kCkCCk
CkCCkCk
CkCCkCkr
23
2
1*
32*
2
1
*3*2
2
1
*3*2
2
1*
0)(
0
0
AZO
AZO
N
AZON
Ckk
Ckkr
Ckr
23
2
31
2
*32
At low conc azomethane;
At high conc azomethane;
32 kCk AZO
32 kCk AZO
AZON Ckr 2
12
AZOAZON kCCk
kkr
2
31
2
1st order
2nd order
ERT 208/4 REACTION ENGINEERINGSEM 2 (2009/2010)
Pseudo-Steady-State Hypothesis (PSSH)cont..
productscollisionAA __*
Rules of Thumb For Development of Mechanism1. Species having the conc(s) appearing in the denominator of the rate law probably collide with the active intermediate.
2. If a constant in the denominator, one of the reaction steps is probably the spontaneous decomposition of the active intermediate.3. Species having the conc(s) appearing in the numerator of the rate law probably produce the active intermediate in one of the reaction step
productsiondecompositA __*
productsotherAtreac __*tan
ERT 208/4 REACTION ENGINEERINGSEM 2 (2009/2010)
Pseudo-Steady-State Hypothesis (PSSH)cont..
productscollisionAA __*
Exercise 1;Mechanism For Azomethane????
productsiondecompositA __*
productsotherAtreac __*tan
ERT 208/4 REACTION ENGINEERINGSEM 2 (2009/2010)
Pseudo-Steady-State Hypothesis (PSSH)cont..
productscollisionAA __*
Mechanism For Azomethane
productsiondecompositA __*
productsotherAtreac __*tan
AZOAZOAZOAZO *
262* NHCAZO
AZOAZOAZOAZO *
Ans;
ERT 208/4 REACTION ENGINEERINGSEM 2 (2009/2010)
Pseudo-Steady-State Hypothesis (PSSH)cont..Exercise 2; By assuming the main product for the reaction below is ethane, write down the final form equation for rate of formation for ethane. 262223 NHCNCH
AZO
AZO
HC
AZOHC
Ckk
Ckkr
Ckr
23
2
31
62
*362
Ans;
ERT 208/4 REACTION ENGINEERINGSEM 2 (2009/2010)
Pseudo-Steady-State Hypothesis (PSSH)cont..
CHAIN REACTIONS
Initiation……….
Propagation / Chain Transfer……….
Termination……….
Formation of an active intermediate
Interaction of an active intermediate with the reactant/product to produce another active intermediateDeactivation of the active intermediate
ERT 208/4 REACTION ENGINEERINGSEM 2 (2009/2010)
EXAMPLE 1; PSSH Applied to Thermal Cracking of Ethane (Gas-Phase Reaction)The thermal decomposition of ethane to ethylene, methane, butane and hydrogen is believed to proceed in the following sequence;Initiation;
Propagation ;
Termination ;
362_1
62 2CHHC HCk
5242
623 HCCHHCCH k
HHCHC k42
352
2524
62 HHCHCH k
1045
522 HCHC k
62_11
6262_162_1
_ HC
HCHC
kkLets
HCkr
623262_2 HCCHkr HC
52342_3 HCkr HC
62462_4 HCHkr HC
52_55
2
5252_552_5
_ HC
HCHC
kkLet
HCkr
ERT 208/4 REACTION ENGINEERINGSEM 2 (2009/2010)
EXAMPLE 1; PSSH Applied to Thermal Cracking of Ethane ….conta)Use PSSH to derive a rate law for the RATE OF FORMATION OF ETHYLENE & RATE OF DISAPPEARANCE OF ETHANE….
HHCHC k42
352 52342_3 HCkr HC
Solutions……
Rate of formation of ethylene (Reaction 3) is,
Active intermediates :
52HC
3CH
H
The net of reactions are:
0:5255245235225252 HCHCHCHCHC rrrrrHC
02:622621323133 HCHCCHCHCH rrrrrCH
0:62442343 HCHCHHH rrrrrH
ERT 208/4 REACTION ENGINEERINGSEM 2 (2009/2010)
EXAMPLE 1; PSSH Applied to Thermal Cracking of Ethane ….cont
From reaction stoichiometry, we have;
Then,
0:5255245235225252 HCHCHCHCHC rrrrrHC
622522 HCHC rr 423523 HCHC rr
624524 HCHC rr
0:5256244236225252 HCHCHCHCHC rrrrrHC
0:5256244236225252 HCHCHCHCHC rrrrrHC
02:622621323133 HCHCCHCHCH rrrrrCH
0:62442343 HCHCHHH rrrrrH
Finally got
ERT 208/4 REACTION ENGINEERINGSEM 2 (2009/2010)
EXAMPLE 1; PSSH Applied to Thermal Cracking of Ethane ….cont
From substituting the concentrations into the elementary equation gives;
Where,
02:622621323133 HCHCCHCHCH rrrrrCH
Solving for the conc of the free radical ,
02622621
HCHC rr
02 6232621 HCCHkHCk 6262_162_1 HCkr HCHC
623262_2 HCCHkr HC 3CH
2
13
2
k
kCH
ERT 208/4 REACTION ENGINEERINGSEM 2 (2009/2010)
EXAMPLE 1; PSSH Applied to Thermal Cracking of Ethane ….cont
Adding this 2 equations…..
0:5256244236225252 HCHCHCHCHC rrrrrHC
0:62442343 HCHCHHH rrrrrH
get… 0
525622 HCHC rr
Substituting for conc in the rate laws…..
623262_2 HCCHkr HC
25252_552_5 HCkr HCHC
02
5256232 HCkHCCHk where…
ERT 208/4 REACTION ENGINEERINGSEM 2 (2009/2010)
EXAMPLE 1; PSSH Applied to Thermal Cracking of Ethane ….cont
PSSH solution…..
from
2/1
623
5
252
HCCHk
kHC
52HC
02
5256232 HCkHCCHk
where…
Solving for gives us,
2/1
62
52
2152
2
HCkk
kkHC
2
13
2
k
kCH
2/1
62
5
152
2
HCk
kHC
ERT 208/4 REACTION ENGINEERINGSEM 2 (2009/2010)
EXAMPLE 1; PSSH Applied to Thermal Cracking of Ethane ….cont
52HC
where…
Substituting for in equation
yields the rate of formation of ethylene;
2/1
62
2/1
5
1352342
2HC
k
kkHCkr HC
52342_3 HCkr HC
2/1
62
5
152
2
HCk
kHC
ERT 208/4 REACTION ENGINEERINGSEM 2 (2009/2010)
EXAMPLE 1; PSSH Applied to Thermal Cracking of Ethane ….cont
H
where…
Next, we write the net rate of formation in In terms of concentration,
0:62442343 HCHCHHH rrrrrH
0:62442343 HCHCHHH rrrrrH
0624423 HCHC rr 52342_3 HCkr HC
62462_4 HCHkr HC 0624523 HCHkHCk
Using eq to substitute for gives the
conc of the hydrogen radical
2/1
62
5
152
2
HCk
kHC 52HC
02
624
2/1
62
5
13
HCHkHCk
kk
ERT 208/4 REACTION ENGINEERINGSEM 2 (2009/2010)
EXAMPLE 1; PSSH Applied to Thermal Cracking of Ethane ….contfrom
02
624
2/1
62
5
13
HCHkHCk
kk
02
624
2/1
62
5
31
HCHkHCk
kk
2/1
62
2/1
5
1
4
3 2
HC
k
k
k
kH
ERT 208/4 REACTION ENGINEERINGSEM 2 (2009/2010)
EXAMPLE 1; PSSH Applied to Thermal Cracking of Ethane ….cont
Rate of disappearance of ethane is
6262_162_1 HCkr HCHC
623262_2 HCCHkr HC
62462_4 HCHkr HC
62462326262_162HCHkHCCHkHCkr HCHC
Where,
ERT 208/4 REACTION ENGINEERINGSEM 2 (2009/2010)
EXAMPLE 1; PSSH Applied to Thermal Cracking of Ethane ….cont
Substituting for the concentration of free radicals, the rate law of disappearance of ethane is….
2/1
62
2/1
5
13621162
22 HC
k
kkHCkkr HC
2/1
62
2/1
5
1
4
3 2
HC
k
k
k
kH
2
13
2
k
kCH
62
2/1
62
2/1
5
1
4
3462
2
126262_162
22HCHC
k
k
k
kkHC
k
kkHCkr HCHC
62462326262_162HCHkHCCHkHCkr HCHC
Where,
ERT 208/4 REACTION ENGINEERINGSEM 2 (2009/2010)
Conclusions
Reaction that not follow elementary rate law (NON ELEMENTARY involve a number of reaction steps, each of which is ELEMENTARY
After finding net rates of reaction for each species, we use PSSH to derive a rate law of the reaction.
PSSH not only can be used in gas-phase reaction, but also can be used in biological reactions (enzymatic reactions).
ERT 208/4 REACTION ENGINEERINGSEM 2 (2009/2010)
BIOLOGICAL REACTIONS
•BIOREACTORS
Lab Scale Bioreactor
Industrial Scale Bioreactor
ERT 208/4 REACTION ENGINEERINGSEM 2 (2009/2010)
Fermentation Process
ERT 208/4 REACTION ENGINEERINGSEM 2 (2009/2010)
Major Functions of a Bioreactor
1) Provide operation free from contamination;
2) Maintain a specific temperature;
3) Provide adequate mixing and aeration;
4) Control the pH of the culture;
5) Allow monitoring and/or control of dissolved oxygen;
6) Allow feeding of nutrient solutions and reagents;
7) Provide access points for inoculation and sampling;
8) Minimize liquid loss from the vessel;
9) Facilitate the growth of a wide range of organisms.
Ref;(Allman A.R., 1999: Fermentation Microbiology and Biotechnology)
ERT 208/4 REACTION ENGINEERINGSEM 2 (2009/2010)
Biotechnological Processes Of Growing Microorganisms In A
Bioreactor1)Batch culture: microorganisms are inoculated into a
fixed volume of medium and as growth takes place nutrients are consumed and products of growth (biomass, metabolites) accumulate.
2) Semi-continuous: fed batch-gradual addition of concentrated nutrients so that the culture volume and product amount are increased (e.g. industrial production of baker’s yeast);
Perfusion-addition of medium to the culture and withdrawal of an equal volume of used cell-free medium (e.g. animal cell cultivations).
3) Continuous: fresh medium is added to the bioreactor at the exponential phase of growth with a corresponding withdrawal of medium and cells. Cells will grow at a constant rate under a constant condition.
ERT 208/4 REACTION ENGINEERINGSEM 2 (2009/2010)
Biotechnological processes of growing microorganisms in a bioreactor
ERT 208/4 REACTION ENGINEERINGSEM 2 (2009/2010)
Batch Culture VS Continuous Culture
Continuous systems: limited to single cell
protein, ethanol productions, and some
forms of waste-water treatment processes.
Batch cultivation: the dominant form of
industrial usage due to its many
advantages.
Ref;(Smith J.E, 1998:
Biotechnology)
ERT 208/4 REACTION ENGINEERINGSEM 2 (2009/2010)
Advantages of Batch Culture VS Continuous Culture
1) Products may be required only in a small quantities at any given time.
2) Market needs may be intermittent.3) Shelf-life of certain products is short.4) High product concentration is required in broth for
optimizing downstream processes.5) Some metabolic products are produced only during the
stationary phase of the growth cycle.6) Instability of some production strains require their
regular renewal.7) Compared to continuous processes, the technical
requirements for batch culture is much easier.
ERT 208/4 REACTION ENGINEERINGSEM 2 (2009/2010)
Fermentation Technology
• What is it important to know the kinetics of the reaction in the fermenter?
ERT 208/4 REACTION ENGINEERINGSEM 2 (2009/2010)
Typical pattern of growth cycle during batch fermentation
I. Lag phaseII. Acceleration phaseIII. Exponential (logarithmic)
phase IV. Deceleration phaseV. Stationary phaseVI. Accelerated death phaseVII. Exponential death phaseVIII. Survival phase
From: EL-Mansi and Bryce (1999)Fermentation Microbiology and Biotechnology.
Cell Growth
ERT 208/4 REACTION ENGINEERINGSEM 2 (2009/2010)
Cell Growth...cont...
Lag Phase Exponential Growth Phase
Stationary Phase
Death Phase
•Little increase in cell conc.•Cell adjusting their new environment, synthesizing enzymes & ready to reproducing
•Cell are dividing at max rate•Cell able to use the nutrients most efficiently
•Cell reach a minimum biological space (lack of 1@> nutrients limits cell growth)•Net growth = 0•Fermentation product produce.
•Decrease in live cell conc occur.•Results of toxic by-product
ERT 208/4 REACTION ENGINEERINGSEM 2 (2009/2010)
Rate Laws
Rate law for the cell growth rate of new cells,
Cells + Substrate More Cells + Product
The most commonly used expression is the Monod equation for exponential growth;
cg Cr )./(__ 3 sdmgrategrowthcellrg
)(__ 1 srategrowthspecific
)/(_ 3dmgionconcentratcellCc
Where,
ERT 208/4 REACTION ENGINEERINGSEM 2 (2009/2010)
Rate Laws...cont...
Specific cell growth rate can be expressed as,
1
max ,
s
CK
C
ss
s
)(___max__ 1
max
sratereactiongrowthspecifica
)/(tan__ 3dmgtconsmonodtheK s
)/()( 3dmgionconcentratnutrientsubstrateCs
Where,
ERT 208/4 REACTION ENGINEERINGSEM 2 (2009/2010)
Rate Laws...cont...
Combine ,
1
max ,
s
CK
C
ss
s
Will get,
cg Cr and
ss
csg CK
CCr
max Monod equation for
bacterial cell growth rate
Parameter value for the E.coli growth on glucose.
Ks is small for a numb of different bacteria in which case the rate law reduce to,
1
max 3.1 h35 /102.2 dmmolXK s
cg Cr maxPlz refer ERT 104 Bioprocess Eng Principle
ERT 208/4 REACTION ENGINEERINGSEM 2 (2009/2010)
Thank You
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