Kinetics and Mechanisms of hydrogenation of DMO

Li Siming2012.9.8

10~20 目 20~40 目 40~60 目 60~70 目空速 (g/gcat.

h)0.5 1.0 0.5 1.0

XDMO 97.1% 99.0% 100% 100%

SEG 82.4% 93.8% 91.0% 93.9%

C. Perego, S. Peratello, Catalysis Today 1999, 52, 133-145.

Internal Diffusion Effects

obs p2*

eff,i i

r Lηφ =

D C eff,i p

εD = D

τ

P K B,iD D D

1 1 1 K p

i

TD d

M48.5

nj

j=B i i ij

y

D y D2,

1 1

1

iji j

i j

TD

M MP V V

13 23 2

21 13 3

1 10 1 1

当 2ηφ小于 0.1(0.15) 时，可认为无内扩散影响。

C. Perego, S. Peratello, Catalysis Today 1999, 52, 133-145.

External Diffusion Effects

0 )obs

gs *g s i i

rCa =

k a (C C

, 1/3 ReB ig D

Dk = Sc J

R

0.82 0.386

1 0.765 0.365)

Re ReDJ = (θ

当 gsCa小于 0.05 时，可认为无外扩散影响。

CH3O C C OCH3 + H2

O OCu/SiO2

CH3O C C OCH3

O OH

H(A)

Cu/SiO2 H2C CH2 + H2

OH OH

CH3 CH2OH + H2O

(E)

(EG)

Cu/SiO2

CH3O C CH2 + H2

OH OH

H2C CH2 + CH3OH

OH OH

Cu/SiO2CH3O C CH2 + CH3OH

O OH

CH3O C C OCH3 + H2

O OH

H (MG) (ME)

CH3O C CH2

OH

(B)

Cu/SiO2CH3O C CH2 + H2

O OH OH

H

Pathway of DMO hydrogenation

H2 + 2# 2H #

DMO * + 2 H# A* + 2# (1)

A* + 2H# + * MG* + 2# + ME* (2)

B* + 2H# + * EG* + ME* + 2# (4)

EG* + 2H# Et* + H2O + 2# (5)

EG* EG + *

ME* ME + *

Et* Et + *

DMO + * DMO *

MG* + 2H# B* +2 # (3)

#, *: Different active site( MG* MG + * )

Ester un-dissociative adsorption

Hydrogen dissociatively adsorb on the active site:

Hydrogen un-dissociatively adsorb on the active site:

Hydrogen un-dissociative adsorption

2H H H vK p

This way is similar to hydrogen dissociative.

The rate control step may be Hydrogen adsorption, surface(1~4) or ester adsorption.

2(1 )H HK pUsing (1+KHpH) instead of in the rate expression.

When the rate is is determined by the un-dissociative adsorption of hydrogen, the rate expression is:

2 2H aH H v dH Hr k p k

C

O

R1 OR2

dissociatively adsorbsR1C*O + R2O*+ 2*

R1C*O

R2O*

hydrogenation and desorbR1CH2OH + *

R2OH + *hydrogenation and desorb

Ester Dissociative adsorption

Pathway of ester dissociative adsorptionH2 + 2# 2H #

EG* + 2H# Et* + H2O + 2# (7)

EG* EG + *

Et* Et + *

MG + 2* HOCH2C*O +OCH3 * (4)

MG* MG + * (3)

CH3OOCC*O + 3H# CH3OOCC*H2OH (MG) + 3# (2)

HOCH2C*O +3H# HOCH2C*H2OH + 3# (5)

OCH3 * + H# ME* + # (6)

ME* ME + *

#, *: Different active site

DMO + 2* CH3OOCC*O +OCH3 * (1)A B

C

The most possible pathwayH2 + 2# 2H #

CH3OOCC*O + H# CH3OOCC*OH + # (1)

EG* + 2H# Et* + H2O + 2#

EG* EG + *

Et* Et + *

DMO + 2* CH3OOCC*O +OCH3 * (9)

MG + 2* HOCH2C*O +OCH3 * (8)

MG* MG + * (7)

CH3OOCC*OH + H# CH3OOCC*HOH + # (2)

CH3OOCC*HOH + H# CH3OOCC*H2OH(MG) + # (3)

HOCH2C*O +H# HOCH2C*OH + # (4)

HOCH2C*OH +H# HOCH2C*HOH + # (5)

HOCH2C*HOH +H# HOCH2C*H2OH + # (6)

OCH3 * + H# ME* + # (10)

ME* ME + *

#, *: Different active site

Summary of model of DMO hydrogenation

DMO dissociative adsorption

DMO molecular adsorption

H2

molecular adsorption

H2

dissociative adsorption

Control step

① DMO adsorption ② H2 adsorption

③ Surface reaction 7 kinds

① ester adsorption

② H2 adsorption ③ Surface reaction 4 kinds

④adsorption/desorption of intermediate-MG

① ester adsorption

② H2 adsorption

③ Surface reaction 4 kinds

23 kind

s

8 月 25 日评价 8 月 27 日评价

0.5h-1 1.0h-1 0.5h-1 1.0h-1

XDMO （ % ） 100 97.0 100 /

SEG （ % ） 97.85 33.84 47.37 /

SMG （ % ） 1.06 65.7 51.52 /

SEt （ % ） 0.84 0.30 0.36 /

表 1 25/27 日催化剂评价表

表 2 设备维修前下催化剂评价表

XDMO （ % ） SEG （ % ） 0.5h-1 100 91.0

1.0h-1 100 93.9

Catalytic performance

0

20

40

60

80

100

120

0 1 2 3 4 5LHSV/ h-1

DMO

/EG(

MG,E

t)

%转

化率

选择

性

X dmoS EGS MGS Et

Catalytic performance on No.3 reactor

Work plan

1.Finish the work about elimination of External/ Internal Diffusion effects

2. Measure the intrinsic reaction rate and select the most possible model.

①. Reaction rate and adsorption equilibrium constant must higher than > 0;

② Activation energy can not be below zero.

③ Reaction rate constant and adsorption equilibrium constant must satisfy th

e Arrhenius and Van’t Hoff equation;

④ A close correlation with experiment data.

3. Think about further verification of mechanism after kinetics experiment.

Key Laboratory for Green Chemical Technology of Ministry of Education

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