MicrokineticModeling of BioalcoholDehydration in H-FAU, H ... · MicrokineticModeling of...

Microkinetic Modeling of Bioalcohol Dehydration in H-FAU, H-MOR, H-ZSM-5 and H-ZSM-22

Zeolites

Methusalem, Advisory Board Meeting, June 24, 2013

1http://www.lct.ugent.be

LaboratoryLaboratoryLaboratoryLaboratory forforforfor

Chemical Chemical Chemical Chemical TechnologyTechnologyTechnologyTechnology

C.M. Nguyen, K. Alexopoulos, M.-F. Reyniers, G.B. Marin


2

Overview

• Introduction

• Alcohol adsorption

• Alcohol dehydration

• Conclusions


3

Bioalcohols to hydrocarbons as a green route

van der Borght et al.,i–SUP, Bruges, Belgium, May 6, 2012.


4

Different temperatures = different product distributions

Ethanol

dehydration

Taarning et al.,Energy Environ. Sci., 4 (2011) 793

H-ZSM-5


5

Different zeolites = different product distributions

H-SAPO-34

MTO

H-ZSM-5

MTG

H-FER

Olefins

Gasoline

Haw et al., Acc. Chem. Res. 36 (2003) 317


6

Zeolite Models: 1 acid site per unit cell

12-MR

12-MR

H-F

AU

H-M

OR

H-Z

SM

-22

H-Z

SM

-5

10-MR 10-MR

Si/Al = 47 Si/Al = 95

Si/Al = 95 Si/Al = 35


7

Process optimization utilizes microkinetic modeling

Marin and Yablonsky, Kinetics of Chemical Reactions: Decoding Complexity, Wiley-VCH, 2011


8

C1-C4 alcohol adsorption thermodynamics

Nguyen et al., Europacat X, Glasgow, August 28, 2011


9

Nature of ROH-ZeOH complexes

PHYSISORPTION PHYSISORPTIONCHEMISORPTION

�Nature of ROH-ZeOH has remained unclear fromexp. data [1&2].�Molecular dynamics (MD) simulations for CH3OH-Zeolite [3]:

�Hzeolite strongly fluctuates midway between BAS and CH3OH.�Chemisorbed fraction increases with decreasing zeolite pore size.

[1] Mirth et al. J. Chem. Soc. Faraday Trans. 86, 3039 (1990). [2]Zamaraev andThomas, Advanced inCatalysis 41, 335 (1996). [3]Payneet al.J. Am. Chem. Soc. 121, 3292 (1999).

0

500

1000

1500

2000

2500

3000

0 50 100 150 200 250 300

Ra

dia

l d

istr

ibu

tio

n

fun

ctio

n,

g(r

)

distance, r (pm)

O-H1

O-H2


10

Ab initio MD simulation: NVT, 500K

H1H2O

50

100

150

200

250

1 2 3 4 5 6

O-H

dis

tan

ce (

pm

)

time (ps)

O-H1

O-H2

0.5

1

1.5

2

2.5

2000 2500 3000 3500

ab

sorb

an

ce (

a.u

.)

frequency (cm-1)


11

IR spectrum

Chem.

Phys.

ν(O-H) / ZeOH

ν(C-H)

ν(O-H)

Bonn et al. Chem. Phys. Letts. 278 (1997) 213 Nguyen et al. Phys. Chem. Chem. Phys. 12 (2010) 9481

-0.1

-0.05

0

0.05

0.1

3100 3300 3500 3700

ΔA

bso

rba

nce

(a

.u.)

frequency (cm-1)


12

Rotation along O…H bond

ν(O-H)

ν(O-H)

Bonn et al. Chem. Phys. Letts. 1997 (278) 213


13

Eads: theory vs experiment

experimenttheory

H-ZSM-5

Nguyen et al. Phys. Chem. Chem. Phys. 12 (2010) 9481 Lee et al. J. Phys. Chem. B 101 (1997) 381


14

Influence of carbon number

Nguyen et al. Phys. Chem. Chem. Phys. 12, 9481 (2010)

∆H0ads = αNC + β

α = -12 kJ mol-1 per C

-160

-140

-120

-100

1 2 3 4

∆E

ads

/ kJ

mol

-1

Carbon number

β = -100 kJ mol-1 per C

Phys. (H-ZSM-5, Straight)

Chem. (H-ZSM-5, Straight)


15

Influence of zeolite topology

-180

-155

-130

-105

-80

1 2 3 4

ΔH

0a

ds/

kJ

mo

l-1

Carbon number

H-FAU

H-MOR (12-MR)

H-ZSM-5 (Straight)

H-ZSM-5 (Zigzag)

H-ZSM-22


16

Influence of branching level

Nguyenet al. J. Phys. Chem. C 115 (2011) 8658.

1-BuOH i-BuOH

2-BuOH t-BuOH


17

Zeolite-catalyzed alcohol conversion to fuels and chemicals

Alcohols

Ethers

Olefins

Aromatics

ValidationGoal: Simulate the influence

of reaction conditions and zeolite framework on product distribution

H-FAU H-ZSM-5

H-MOR H-ZSM-22

Method:

T, P, W/F, %H2OReactor

simulation

Reaction network

Thermo-dynamics


18

Ab-initio based microkinetic modeling

Validation

Reactor simulation

Reaction network

Thermo-dynamics


19


Reactor simulation

Reaction network

Thermo-dynamics

Validation


20

Desorption profile of adsorbed ethanol in H-MOR

Kondo et al. J. Phys. Chem. C 114 (2010) 20107

H-MORStatic IR cell reactorNo DEE is observed


21

Ethanol dehydration in a flow reactor at 368 – 398 K

[1] Chiang & Bhan, J. Catal. 271(2010) 251

12-MR

Turn

over

freq

uenc

yDifferential flow reactor

0.05 bar ethanol

Ethene is observed only in 8-MR side pocket of H-MOR [1].8-MR side pockets prevent formation of bulky ethanol dimers [1].

M 1

AlO O

H

AlO O

HO

H

M 2

AlO O

H

OH

AlO O

CH2H

AlO O

H

AlO O

H

OAl

O

H

OH5C2 H

O

H

C2H5

OAl

O

H

OH

O

H

C2H5

D1 D2

OAl

O

H5C2 O

H

C2H5

DEE*

Ethene*

(1)

(3)

(7)

(4)

(2)(5)

(6)

(8)

(9)

Ethoxide

+ H2O(g)

- H2O(g)

+ H2O(g)

- H2O(g)

+ C2H4(g)- C2H4(g)

+ DEE(g) - DEE(g)

+ C2H5OH(g)

- C2H5OH(g)

- C2H5OH(g)+ C2H5OH(g)

+ C2H4(g)

- C2H4(g)

OAl

O

H

O

H

C2H5

- C2

H 5OH (g

)

+ C 2

H 5O

H (g)

(11)

(12)

(10)

C1


22

Reaction network of ethanol dehydration


23


Reactor simulation

Reaction network

Thermo-dynamics

Validation


24

Dispersion – corrected pbc[DFT-D]

( )∑ ∑=∈

−−

−=L Lji

ijD

ij

ji

D LrfLr

ccsE

0,6

666

2

DDFTDDFT EEE +=−

� VASP 4.6

� Plane wave basis set & Projector Augmented Wave method

� GGA PBE-D2 implementation for zeolites [1,2].

� Brillouin zone sampling restricted to the Γ point.

� Convergence criteria: Ecutoff = 600 eV, ∆ESCF = 10-6 eV,Max force = 0.02 eV/Å

� CI-NEB for transition state location [3]

� Statistical thermodynamics & PHVA – MBH [4][1] Grimme J. Comput. Chem. 27 (2006) 1787 [2] Kresse et al. J. Phys. Rev. B 48 (1993) 13115[3] Henkelman et al. J. Chem. Phys. 13 (2000) 9978 [4] De Moor et al. J. Chem. Theory Comput. 7 (2011) 1090


25

Monomolecular pathway (300 K)


26

Bimolecular pathway (300 K)


27


Reactor simulation

Reaction network

Thermo-dynamics

Validation

(1) C2H5OH(g) + * ↔ M1

(2) M1 ↔ M2

(3) M2 ↔ Ethoxy + H2O(g)

(4) Ethoxy ↔ Ethene*

(5) Ethene* ↔ Ethene(g) + *

(6) M1 + C2H5OH(g) ↔ D1

(7) D1 ↔ D2

(8) D2 ↔ DEE* + H2O(g)

(9) DEE* ↔ DEE(g) + *

(10) DEE* ↔ C1

(11) C1 ↔ M1 + Ethene(g)

(12) C1 ↔ Ethene*+ C2H5OH(g)


28

Reactor simulation

vib

B

B

B

B

qqwhere

Tk

E

q

q

h

Tk

Tk

G

h

Tkk

=

∆−=

∆−=

expexp‡0

‡‡

immobile surface species

where, F molar flow (mol/s),

W catalyst weight (kg) , Ct acid site concentration (mol H+/kg),

R turnover frequency, r reaction rate (molecules/site/s = mol/mol H+/s),

νji the stoichiometric coefficient of component i in the elementary step j

��∗ ��∗��

� 0

Plug flow reactor equations for each gas-phase

component i with QSSA for the surface species i*:

��

�

TST for reaction rate coefficients:

(apart from Ethene* where a 2D translation

and 1D rotation is assumed)


29


Reactor simulation

Reaction network

Thermo-dynamics

Validation


30

Experimental validation

0

20

40

60

80

100

0 10 20 30 40 50 60

Co

nv

ers

ion

/Se

lect

ivit

y

Ethanol pressure (kPa)

X (%) S-DEE (%) S-C2H4 (%)

T= 503 K

Wcat/FEtOH,0 = 6.5 kg s / mol

� Good agreement between theory (full lines) and experiment (points)

H-MOR

0

20

40

60

80

100

0 10 20 30 40 50 60

Co

nv

ers

ion

/Se

lect

ivit

y


X (%) S-DEE (%) S-C2H4 (%)


31


T= 503 K


� Better agreement between theory (full lines) and experiment (points),

if the activation energy for ethoxy formation is slightly increased (+2 kJ/mol)

H-MOR

(3) M2 ↔ Ethoxy + H2O(g)


32

Influence of reaction conditionsC2H4 yield (%)

450 460 470 480 490 500Temperature (K)

10

15

20

25

30

35

40

45

Eth

anol

pre

ssur

e (k

Pa)

0

2

4

6

8

10

12

14H-ZSM-5

More ethene at higher T and lower pEtOH


33

Is DEE a primary product?

T= 495 K, H-ZSM-5

YES

0

5

10

15

20

25

30

0 1 2 3 4

Co

nv

ers

ion

(%

)

site time (mol H+ s / mol EtOH0 )

H-ZSM-22

H-ZSM-5

H-MOR

H-FAU


34

Influence of zeolite topology

10-MR zeolites more reactive than 12-MR zeolites

10 kPa EtOH,

T= 473 K


35

Factors governing zeolite reactivity

Ea,D1 AD1 kD1/368 KH–FAU 154 5.1 1013 6.3 10–9 H–MOR (12–MR) 161 1.2 1015 1.6 10–8 H–ZSM–5 136 6.2 1013 3.1 10–6 H–ZSM–22 122 1.1 1014 5.2 10–4

Ea,D1

D1

DEE*

TSII


36

TS stabilization: Hydrogen bonds


37

TS stabilization: Electrostatic interactions

H-FAU H-MOR

H-ZSM-5 H-ZSM-22

Ele

ctro

stat

ic p

oten

tial /

eV

Electrostatic: H-FAU < H-MOR < H-ZSM-5 < H-ZSM-22


38

Stabilization factor, α

ΔΔΔΔEEEETSIITSIITSIITSII

TSII (H-FAU)

TSII (ZeOH)

D1 (H-FAU)

D1 (ZeOH)

ΔΔΔΔ((((ΔΔΔΔEEEEads,D1ads,D1ads,D1ads,D1))))

)( 1,Dads

TSII

E

E

∆∆∆=ααααα

H-FAU 0.0

H-MOR 0.4

H-ZSM-5 1.9

H-ZSM-22 3.1

E

H-FAU is the reference


39

Conclusions

• First principles microkinetic modeling provides predictive

guidance for the influence of catalyst’s characteristics and reaction

conditions on reactivity and product selectivity.

• Alcohol adsorption strength increases with decreasing zeolite pore

size (indicative of primary driving vdW forces).

• Entropy-enthalpy compensation governs the shape-selectivity

effect of H-ZSM-5 on adsorption of butanol isomers.

• 10-MR zeolites are more reactive than 12-MR zeolites (more effectively stabilized TS by HB/Electrostatic interactions)


40

• Long Term Structural Methusalem Funding by the

Flemish Government – grant number BOF09/01M00409

• European Community’s Sixth Framework Programme

(contract nr 011730)

• Fund for Scientific Research (FWO) – Flanders

• Stevin Supercomputer Infrastructure of Ghent University

• Experimental data (H-MOR): Kristof Van der Borght

• Ab initio MD: Roger Rousseau, Mal-Soon Lee

Acknowledgements


41

Glossary

• Alcohol chemisorption: Upon chemisorption over the Brønsted acid site, the acid proton is completely transferred to the alcohol, leading to formation of a positively charged oxonium ion.

• Alcohol physisorption: An alcohol is physisorbed over the Brønsted acid site and is stabilized by strong hydrogen bonds with the zeolite. The acid proton is still attached to the zeolite.

• Electrostatic potential: evaluated from the interaction between a negative unit charge and the local charge density. This factor is critical in stabilizing positively charged adsorbed complexes and especially transition states in the zeolite.


42

Zeolites are promising catalysts for biorefinery processes

Fluidic Catalytic Cracking & Hydrocracking are based on Zeolites

Huber andCorma, Angew. Chem. Int. Ed. 46 (2007) 7184.Taarning et al., Energy Environ. Scie. 4 (2011) 793.


43

Influence of temperature

10 kPa EtOH, H-MOR

More ethene formation at higher T

0

5

10

15

20

0 2 4 6 8

Co

nv

ers

ion

(%

)

space time ( kg s / mol )

503 K

495 K

473 K

453 K0

20

40

60

80

100

0 2 4 6 8

C2

H4

(d

ash

ed

lin

es)

& D

EE

(fu

ll li

ne

s) s

ele

ctiv

ity

(%

)

space time ( kg s / mol )

0

2

4

6

8

10

12

0 2 4 6 8 10 12

C2

H4

(d

ash

ed

lin

es)

& D

EE

(fu

ll l

ine

s)

yie

ld (

%)

Conversion (%)

10 kPa EtOH 50 kPa EtOH

0

10

20

30

40

50

60

70

80

90

100

0 2 4 6 8 10 12

C2

H4

(d

ash

ed

lin

es)

& D

EE

(fu

ll l

ine

s)

sele

ctiv

ity

(%

)

Conversion (%)

10 kPa EtOH 50 kPa EtOH


44

Is DEE a primary product?

T= 495 K, H-MOR

YES

0

20

40

60

80

100

0 10 20 30 40 50 60

Co

nv

ers

ion

/Se

lect

ivit

y


X-sim (%)

S-DEE-sim (%)

S-E-sim (%)

X-exp (%)

S-DEE-exp (%)

S-E-exp (%)


45


T= 503 K


� Good agreement between theoretical (full lines) and experimental

(points) conversion

H-ZSM-5

0

20

40

60

80

100

0 10 20 30 40 50 60

Co

nv

ers

ion

/Se

lect

ivit

y


X-sim (%)

S-DEE-sim (%)

S-E-sim (%)

X-exp (%)

S-DEE-exp (%)

S-E-exp (%)


46


T= 503 K


� Better agreement between theory (full lines) and experiment (points)

by modifying the kinetics of reaction 10, i.e. k10-mod=10 k10, K10-mod=K10

H-ZSM-5

(10) DEE* ↔ C1


47

Experimental results

T= 503 K

Wcat/FEtOH,0 = 6.5 kg s / molH-ZSM-5

Kristof van der Borght , personal communication


48

Experimental results

Kristof van der Borght , personal communication

Ethanol

DEEEthylene

Higher hydrocarbons

Eff

lue

nt

com

po

siti

on

(%)

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