Download - CRE L19 Catalyst Deactivation

8/13/2019 CRE L19 Catalyst Deactivation

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L -18 Catalyst Deactivation

Prof. K. K.Pant

Department of Chemical EngineeringIIT Delhi.

[email protected]
mailto:[email protected]:[email protected]


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Slow decay : Temperature time trajectory

Moderate decay: Moving bed reactorsRapid Decay: Straight through transport reactors

For and nthorder activity decay

and mthorder gas phase

Coupled differential eqns to be solved are

(MBR)


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Moving bed reactors


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Thermofer Catalytic crackin unit (Used for reactions with moderate decay)


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Combining activity equation with the mole balance equation:


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For a first order Decay


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Straight through Transport

Reactor (Circulating fludized bedreactor)

Used when deactivation is rapid.Used for production of gasoline

Catalyst pellet and feed enter

together and transported rapidly.Bulk density of the catalyst is low

compared to Moving bed.


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STTR : Used when coking is rapid.


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Mole balance

rA= brA

Or

Z= Height ,and U is velocity of catalyst


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Reading Assignment: Examples : 10.5 ,10.7, 10.8 Fogler


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a

1 R 1= ln +

T E Ta o

Temperature/Time Trajectories A control strategy involves maintaining a

constant conversion with catalyst decay byincreasing operating temperature.

develop a temperature/time trajectory to find Tt

relationship:

-rA (t=0,T0) = -rA (t= t,T) = a(t ,T)[-rA (t=0,T) ]

(For First order reaction ) k T a T,t = ko

E 1 1a -R T To

k e a = ko o


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Temperature/Time Trajectories

a

E1 1d -

R T Tda o n

r = - = k ed ddt

decay law is:

a

Ed- lnaE

da a n- = k e

ddt o

a

E

dn-Ea

= kdo

a

1 R 1= ln +

T E Ta o


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Temperature/Time Trajectories

1- n+ E Ead1-a

t =

k 1-n+ E Ead do

a

1 R 1= ln +T E T

a o

E 1 1a -R T T

oa = e

E -n E +Ea a 1 1d -

R T To1-e

=E

dk 1-n+d Eo a

a

a

Ed-n+E

a tda = -k dt1 0d

o

Ed-n 1

Ea


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THANK YOU