Catalytic Reaction Engineering...Alkylation of aromatics Halogenation of aromatics Sulphonation of...

CatalyticReaction Engineering

Yongdan Li

Nov-Dec, 2018

Professor of Industrial ChemistryDepartment of Chemical and Metallurgical EngineeringSchool of Chemical TechnologyAalto UniversityEmail: [email protected] 1, E404

1

Kinetics of Homogeneously Catalyzed Reactions

LEC 3

2

Part 2-1 Homogeneously Catalyzed Reactions

Homogeneous catalysis

Types:

Acid/base catalysis by homogeneous acids/bases

Organometallic catalysis (transition metal complexes)

Significant applications:

Alkylation

Polymerization

Fine and specialty chemical synthesis

Hydroformylation

3


The reactant molecules directly contact with the catalyst molecules

reactant molecule catalyst molecule product molecule

External diffusion

Internal diffusion

In the homogeneous catalytic process,

there are not external and internal

diffusions

4


Molecular diffusion

Forced convection

Diffusion and convection allows the molecules to mix

5

Part 2-2 Kinetics of Reactions

Elementary reaction – Mass interaction law

The reactants are converted directly into the products in one step

aA + bB cC + dD CAa=R CB

bk

is the order of the reactiona+b is the rate constantk

A I1 P

A I1 could be an elementary reaction

I1 P could be an elementary reaction

According to the reaction mechanism

Non-elementary reactions

6


Pseudo-steady state hypothesis

How to simplify rate equations?

PIA 211

0r1I 1/RR 11

Quasi-equilibrium hypothesis

7


Some reaction steps are assumed to be slow and some others fast

Slow steps determine reaction rate and fast steps are assumed to be

in equilibrium


8



CPBI2.

PICA1.

21

11

2

CP

BI22CP2BI22

1

PI

CA11PI1CA11

K

cccckRcckcckR

K

cccckRcckcckR

2

121

11

11

1. Reaction steps are elementary reactions:

First step is assumed fast and second one is slow

9


3. This is substituted in the rate equation of second reaction step:

21

PP

BA

P

C12

2

CP

P

CBA122

KK

cccc

c

cKk

K

cc

c

cccKkR 21

1

2

2. Fast step in equilibrium

1

1

11

P

CA1I

CA

PI

1c

ccKc

cc

ccK

According to Quasi-equilibrium hypothesis

4. Slow steps determine reaction rate R=R210


Pseudo-steady state hypothesis

CPBI2.

PICA1.

21

11

1. Generation rates of instable intermediates are assumed to be 0

B2P1

PC2CA1

I

PC2BI2PI1CA1I

ckck

cckcckc

0cck1cck1cck1cck1r

1

2

1

21111

11


2. This is substituted in the rate equation of second or first reaction step

3. Equation is simplified:

2

1

2

PC2

B2P1

P2A1

CB22 cckckck

ckckcckR

R=R1=R1=R2

B2P1

21

PP

BAC21

B2P1

PPC21CBA21

2ckck

KK

ccccckk

ckck

ccckkccckkR

1

21

1

21

R=R1=

12


4. Assuming k-1cP1>>k2cB the same equation is obtained as using quasi-

equilibrium hypothesis

21

PP

BA

P

C122

KK

cccc

c

cKkRR 21

1

B2P1

21

PP

BAC21

B2P1

PPC21CBA21

2ckck

KK

ccccckk

ckck

ccckkccckkR

1

21

1

21

13

HPBAH2.

AHHA1.

OHPHOHP3.

PBA2.

OHAOHAH1.

2

2

General mechanism

Part 2-3 Catalysis by Acid or Base

14

Several reactions in organic chemistry catalyzed by acid or base


Electrophilic substitution

Alkylation of aromatics Halogenation of aromatics Sulphonation of aromatics

Nitrification of aromatics

Overall reaction

15


Ethyl

carbonium

Aromatic

carbonium

Ethyl

benzene

First step : Carbonium formation

Second step : Electrophilic substitution

16


Nucleophilic substitution

Haloalkanes produce alcohols

Overall reaction

Reaction mechanism

17


Electrophilic addition

Alkenes produce haloalkanes, esters and alcohols

Bromonium ion

Overall reaction

Reaction mechanism

18


Nucleophilic addition

Alkynes produce alkyl ethers or alkyl esters

Methyl vinyl ether

Methoxy negative ion

Methyl vinyl ether carbanion

Overall reaction

First step : Methoxy negative ion formation

Second step : Nucleophilic addition

19


Carboniums

Several types of intermediates

Formation steps

Intermediates of the electrophilic attacking

Ethyl carboniumAromatic carbonium Benzyl carbonium

20


Carbanions

Several types of intermediates

Strong base

Strong base

Formation steps

Intermediates of the nucleophilic attacking

Acetylenyl carbanion Ethyl acetate carbanion Methyl vinyl ether carbanion

Strong base

21

Kinetics of reactions catalyzed by acid or base

CR

H

R'

CO

H+ OH - C C

O -

H

R

R'C - C

O

H

R

R'+ H2O

C CO -

H

R

R'C

H R''

O

+CR

R'

CO

H

CH

R''

O -

CR

R'

CO

H

CH

R''

O -

O

H H+

CR

R'

CO

H

CH

R''

OH+ OH -

A I1 W

I1 B I2

I2 W C

OH

OH


Aldol condensations 22

Reaction steps as elementary reactions

3

OHPWI33OHP3WI33

2

I

BI22I2BI22

1

WI

OHA11WI1OHA11

K

cccckRcckcckR

K

ccckRckcckR

K

cccckRcckcckR

22

2

121

1

1


K1=k1/k-1 K2=k2/k-2 K3=k3/k-3

A+OH- I1+W (1) I1+B I2 (2) I2+W C+OH- (3)

23

Let’s assume

0RRr

0RRr

32I

21I

2

1

1cKk

kc

k

KKk

K

ccccKKk

R

W2

2

3B

1

213

PBAOH213


R1=R2=R3

= =

(K=K1K2K3)R=R1=R2=R3

Get cI1and cI2

cI1and cI2

24

Let’s assume

First step and third step is assumed to be fast

Second reaction step is slow

2

I

BI2I2BI22K

ccckRckcckRR 2

121

W

OHA1I

OHA

WI

1c

ccKc

cc

ccK

1

1 W3

OHPI

WI

OHP3

cK

ccc

cc

ccK

2

2

After substitution in the rate equation of the second step

K

ccc

c

cKkR PBA

W

OH12 K=k2K1K2K3


R=R2

cI1and cI2

25

QE vs. PSS hypothesis

If k1 and k3 are large (2. step RDS), second term of denominator prevails in

the PSS rate equation (the same equation is obtained as with QE hypothesis):

K

ccc

c

cKkR

cKk

k

K

ccccKKk

R

1cKk

kc

k

KKk

K

ccccKKk

R

PBA

W

OH12

W2

2

3

PBAOH213

W2

2

3B

1

213

PBAOH213

PSS hypothesis

QE hypothesis


26

If k1 and k2 are large (3. step RDS), third term of denominator (+1) prevails

in the PSS rate equation (the same equation is obtained as with QE

hypothesis):

K

ccccKKkR

1cKk

kc

k

KKk

K

ccccKKk

R PBAOH213

W2

2

3B

1

213

PBAOH213

PSS hypothesis QE hypothesis


27

Part 2-4 Catalysis by Transition Metal Complex

Metal atom(s) or ion(s) : d-block transition elements

A neutral molecule with one ormore electron pairs

Ligands :

Metal complexes contain metal atom(s) or ion(s) and ligands that are bundled

into one entity through coordination bond(s), and the entity can be identified as

a unit.

Metal complexes

H2O NH3 CO

Negatively charged ions (anions)

A molecule or multi-atomic ionwith π bonding electrons

OH- Cl- CN-

PPh3

28

Part 2-4 Catalysis by Transition Metal Complexes

Metal complexes

Ligands can have one or more donor atoms and can coordinate through either

one or more of those donor atoms

Examples：nitrite (NO2-)

Cyanide (CN-), cyanate (CNO-) and thiocyanate (NCS-) ions

[ ]- [ ]- [ ]-

29


Metal complexes

Coordination number : The number of ligands binding with one metal atom

or ion

23)Ag(NH

Coordination number 2


3HgI

Pt(PPh3)3

lower oxidation state ions such as Pt(0), Ag(I) and Hg(I) complexes exhibit a

lower coordination number

Plane triangle

Linear

30


Metal complexes


2

4NiCl

[AuBr4]-

[Zn(NH3)4]2+


[Cu(H2O)5]2+

2

5SbCl

Fe(CO)5

[Ni(CN)5]2-

Tetrahedron Plane square

Square pyramidal Trigonal bipyramidal 31


Metal complexes


3

6Fe(CN)

Coordination number 7, 8 and 9 ……

These coordination numbers are mainly observed in lanthanide and actinide

(with f electrons) complexes

Octahedron

32


Metal complexes

3 4 3 3 3[Pt(PPh ) ] [Pt(PPh ) ] PPh

The coordination number can change.

33


Insert reaction

Ln—M—R Ln—M—C—C—R

—— CC

Several key reactions in coordination catalysis

Bonds that can be inserted by a molecule : M-C, M-H, M-X, M-N

Molecules : CO, CO2, SO2 , H

Insert directly

First coordinate and then insert

34


Addition reaction and elimination reaction

The difficulty of addition and the reaction rate are related to the type of the

central atom and ligand.

Rh

CO

PPh3

PPh3

Cl

+ CH3I Rh

CO

PPh3

PPh3

Cl

CH3

I

M=Ir(I) The reaction is irreversibleM=Rh(I) The reaction is reversible

IrCO

PPh3

PPh3

Cl

+ CH3I Ir

CO

PPh3

PPh3

Cl

CH3

I

35


a

b

The higher the positive charge density of the central atom, the easier the

formation of the M-H bond.

β-H transfer reaction

36


Rearrange reaction

Ln-M-CH2-CH=CH2 Ln-M-

σ bond π bond

Substitution reaction

[Fe(CN)6]4-(aq) + H2O (aq) [Fe(CN)5(H2O)]

4-(aq) + CN-(aq)

37


The oldest (Otto Roehlen, 1938) and most significant (largest production

volumes) homogeneously catalysed process.

normal butyraldehyde

Hydroformylation

iso butyraldehyde

main product

38


Hydroformylation

Depending on the environment (pressure, temperature), different forms of

the complex with different properties can exist

Most common catalyst:

rhodium - tri-phenyl phosphine

complex (Rh-TPP)

Rh-TPP complexe

39


Rh

T P P

H

O C

T P P

Rh

T P P

H

O C

T P P

Rh

H

C ( O ) C H 2 C H 2 R

T P P

T P P H

C O

7 RCH 2 CH 2 CHO

8

CO CO

1

D

2 R

Rh

H

T P P

T P P

R

3

Rh

T P P

C H 2 C H 2 R

O C

T P P

CO 4

Rh

T P P

T P P H

C O

C O

5

Rh

C O

C ( O ) C H 2 C H 2 R

T P P

T P P

R A

Rh

C O T P P

T P P H

C O

R

Rh

T P P

T P P C H 2 C H 2 R

C O

C O

H 2 6

O C

Mechanistic model for kinetics of propene hydroformylation with Rh catalyst. AIChE J., 58: 2192–2201. 40


Ethylene oxidation

C2H4 + O2[PdCl4]

2-

CH3CHO

Pd (II) and ethylene form complexes

1K2

4 2 4 3 2 4[PdCl ] C H [PdCl (C H )] Cl fast

2

1 4 2 4K [[PdCl ] ][C H ][A][Cl ]

1 2

4 2 4

[A][Cl ]K

[[PdCl ] ][C H ]

A

CuCl2 HCl

Step 1

41


2K

3 2 4 2 2 2 2 4[PdCl (C H )] H O trans [PdCl (H O)(C H )] Cl

Cl- and H+ fall off

fast

fast3K

2 2 2 4 2 2 4(trans )[PdCl (H O)(C H )] (trans )[PdCl (OH)(C H )] H

2K [A][B][Cl ]

2

[B][Cl ]K

[A]

A B

3

[C][H ]K

[B]

B C

3K [B][C][H ]

Step 2

Step 3

42


2

4 2 41 2 3 2

[[PdCl ] ][C H ]C=K K K

[H ][Cl ]

2

1 4 2 4K [[PdCl ] ][C H ][A][Cl ]

2K [A][B][Cl ]

3K [B][C][H ]

43


Change structure

slow

fast

4k

2 2 4 2 2 2slow(trans )[PdCl (OH)(C H )] (cis )[Cl Pd(CH CH )(OH)]

fast

2 2 2 3(cis )[Cl Pd(CH CH )(OH)] CH CHO Pd(0) H 2Cl

C D

D

Catalysis regeneration

2 2CuCl 0.5O 2HCl 2CuCl H O k6

2

2 4Pd 2CuCl 2Cl [PdCl ] 2CuCl

k5 fast

fast

Step 4

Step 5

Step 6

Step 7

44


2

4 2 44 1 2 3 2

[[PdCl ] ][C H ]R k K K K

[H ][Cl ]

4 4R R k [C]

Slowest step (step 4) determines the reaction rate

2

4 2 41 2 3 2


[H ][Cl ]

2

4 2 41 2 3 2


[H ][Cl ]

2

1 4 2 4K [[PdCl ] ][C H ][A][Cl ]

2K [A][B][Cl ]

3K [B][C][H ]

4 4R R k [C]

45

Part 2-5 Free Radical Reaction

Containing one or more single electron species called free radicals

Free radical

(Alkyl radicals) (Aryl radicals)

(Derivative radicals) (Halogen radicals )

46

Homolytic cleavage of bond

Formation of free radicals

C6H5 C

O

-O-O- O2C

O

C6H5C

070-80

C6H5C

O

. 2CO2C6H52 +.heart

heatingheart

hearthν

The ease of cleavage is directly related to the bond dissociation energy

The bonds with easy homolytic cleavage, such as :


C-N O-O C-I

benzoyl peroxide

47

Oxidation or reduction of single electron

Fe2+ + H2O2 Fe3+ HO+ ● + HO-


e-

48

Typical reactions of free radicals

Addition reaction

Transfer reaction R· + R'H R-H + R'·

R·+ R'· R-R'

heart

Termination reaction


Coupling

Disproportionation

49

The halogenation of hydrocarbons

The hydrogen atom in the saturated hydrocarbon molecule is replaced by a

halogen atom.

heartCH4 + Cl2 CH3Cl + HClhv, ( )

CH3Cl + Cl2 CH2Cl2 + HClhv

heartHCl

CH2Cl2 + Cl2 CHCl3 + HClhv heartHCl

hvCHCl3 + Cl2 CCl4 + HClheartHCl

heartHCl


50

Cl : Clhv

Cl. .Cl+

+ ..Cl CH4 HCl + CH3

..CH3 + Cl2 CH3Cl + Cl

+ Cl ..Cl Cl2

+CH3. CH3

. CH3CH3

+ .ClCH3. CH3Cl

Chain initiation

Chain propagation

Chain termination


51

Radical addition of alkene

Electrophilic addition

Radical addition


52

Chain initiation

Chain propagation

Initiator

More stable


53

Chain termination


54

Kinetics of free radical reaction

H2 + Br2 = 2HBr

1 Br2 2 Br ●k1

HBr + H 2 Br + H2

k2● ●


5 Br2k5

2Br ●

HBr + Br 3 H + Br2k3

● ●

4 H + HBr H2 + Br ● ●

k4

55


0C2kCCkCCkCCkC2kdt

dC 2Br.5

2HBr.2HBrH.4

2BrH.3

2Br1

Br.

0CCkCCkCCkdt

dCHBrH.4

2BrH.3

2HBr.2

.H

2Br

5

1Br. C

k

kC

HBr42

Br3

2Br

5

1

2H2

H.CkCk

Ck

kCk

C

Get and

56


The rate of reaction, in terms of the disappearance of H2

0CCkCCkCCkdt

dCHBrH.4

2BrH.3

2HBr.2

.H Because of

RH2 =RHBr=2RH2

We get =RHBr=2RH2

RHBr=2RH2=

HBr42

Br3

2Br

5

1

2H2

H.CkCk

Ck

kCk

C

HBrH.42

HBr.2 CCkCCk

2BrH.3 CCk

2Br

HBr

3

1

21

2Br

2H

21

5

12

C

C

k

k1

CCk

k2k

57

References

• Chemistry of Catalytic Processes

– Bruce Gates

• Kinetics of Gas Phase Reactions

– Guy-Marie Côme

58

Catalytic Reaction Engineering

Yongdan Li

Nov-Dec, 2018

Professor of Industrial ChemistryDepartment of Chemical and Metallurgical EngineeringSchool of Chemical TechnologyAalto UniversityEmail: [email protected] 1, E404

59

Catalytic Reaction Engineering...Alkylation of aromatics Halogenation of aromatics Sulphonation of...

Documents

Transcript of Catalytic Reaction Engineering...Alkylation of aromatics Halogenation of aromatics Sulphonation of...