Kinetics and Mechanisms of hydrogenation of DMO

1
Kinetics and Mechanisms of hydrogenation of DMO
Li Siming 2012.7.15
2
Mechanisms of ester hydrogenation
M. Mokhtar et al. Only Cu0 acts as the
active sites in ester hydrogenation
E.K. Poels et al. Cu0 dissociatively
adsorbs H2, Cu stabilizes the methoxy
and the acyl species
A.Y. Yin et.al. Cu may function as
electrophilic or Lewis acid sites to
polarize the CO bond via
the electron lone pair on oxygen.
M. A. Kohler et al. The kinetics of the
reaction were well described by a L-H
model in which
dissociatively adsorbed dimethyl succinate
reacts with
adsorbed molecular hydrogen.
M. Mokhtar, C. Ohlinger, J. H. Schlander, T.
Turek, Chemical Engineering Technology 2001,
24, 423-426. E. K. Poels, D. S. Brands, Applied
Catalysis A General 2000, 191, 83-96. A. Yin, X.
Guo, W.-L. Dai, K. Fan, The Journal of Physical
Chemistry C 2009, 113, 11003-11013. M. A. Kohler,
M. S. Wainwright, D. L. Trimm, N. W. Cant, Ind.
Eng. Chem. Res. 1987, 26, 652-656.
3
J. A. Dumesic1 et al . The rate of
reduction of n-alkyl acetates is determined
by the
dissociative adsorption of these molecules and

by the surface hydrogenation of surface acyl
species
Dumesic1 et al .. Journal of Catalysis 2000.
193 1628 .
4
B. Ju et al. The dissociative
adsorption of Buthylbutyrate would be involved
in the elementary steps
for the hydrogenolysis reaction.
The rate-determining step involves dissociative
adsorption of butyl butyrate.
I. B. Ju, W. Jeon, M.-J. Park, Y.-W. Suh, D. J.
Suh, C.-H. Lee, Applied Catalysis A General
2010, 387, 100-106.
5
Mechanisms of hydrogenation
S. Sitthisa et al. molecular
adsorption of furfural (FAL?? ), furfuryl
alcohol (FOL??),
and 2-methyl furan (MF)
Dissociative adsorption of hydrogen
Surface reaction is the rate-determining step.
Crotonaldehyde(???) adsorbed on Cu sites
with hydrogen spilled over from Cu0 sites.
Hydrogenation of an intermediate species as the
rate-determining step .
A. Dandekar et al.
S. Sitthisa, T. Sooknoi, Y.
Ma, P. B. Balbuena, D. E. Resasco, Journal of
Catalysis 2011, 277, 1-13. A. Dandekar, R. T. K.
Baker, M. A. Vannice, Journal of Catalysis 1999,
183, 131-154.
6
Mechanisms of DMO hydrogenation
DMO dissociatively adsorb on the catalyst via
cleavage of CO bond The reaction mainly proceeds
along Route (2), only small amounts of (B) will
react along Route (1) Dissociative adsorption is
slower than hydrogenation. MG will
dissociatively adsorb on the active site of the
catalyst.
S. G. Hui, B. Zhang, S. H. Zhang, W. Li, J. Nat.
Gas Chem. 2012, 21, 753-758.
7
Model of DMO hydrogenation
Hydrogenation of DMO is a consecutive reaction.
It involves
Assumptions

1. The mechanism of DMO to MG is similar to that of
   MG to EG.

1. The activation energy of adsorption and
   desorption is independent of coverage rate
   (Langmuir homogeneous adsorption)

3. The control step is surface reaction,
adsorption of reactants.
8
Previous work
Figure 1. The correlation of Yields of EG with
surface Cu0/(Cu0 Cu)
At first, the catalyst has only one active
site, Cu0 H2 is activated, the reactant is
adsorbed through the hydroxyl group and cleaved.
Cu0 activates H2 , Cu species adsorbs DMO.
9
(No Transcript)
10
(No Transcript)
11
??????????????? ?????????/?????? ?????????
12
?????????,? ??????????? ??????????? ??????????? ?
??,??????? ???????
13
??????????????? ???????????/????/ ???????????????
?????
14
(No Transcript)
15
(No Transcript)
16
(No Transcript)
17
(No Transcript)
18
(No Transcript)
19

• ??
• FAL, FOL,MF????
• ??????
• ????????
• ??????

20
LH??
21
-?H 11.9 kcal/mol
Vant Hoff ??
22
(No Transcript)
23
(No Transcript)
24
Adsorption of furfural on Cu(1 1 1)
25
???? ???
????
????
??
26
(No Transcript)
27
(No Transcript)
28
(No Transcript)
29
Work plan

• 1. Choose conformable condition to make sure
  the catalyst have high activity
• 2. Finish the work about elimination of
  External/ Internal Diffusion effects
• 3. Measure the intrinsic reaction rate and
  select the most possible model.