2007 Annual Meeting

(199a) Homogeneous Olefin Hydroformylation By Transition Metal Complexes In CO2-Expanded Media: Solvent Effects And Kinetics

Authors

Fang, J. - Presenter, Univ. Kansas
Subramaniam, B. - Presenter, Center for Environmentally Beneficial Catalysis, University of Kansas
Guha, D. - Presenter, Washington University
Tunge, J. - Presenter, Univ. Kansas
Ramachandran, P. - Presenter, Washington University in St. Louis


 

Intensified 1-octene hydroformylation in CO2-expanded
liquids (CXLs)
were reported at relatively mild conditions (~40 bar and 60°C) with the
turnover frequency (~300 h-1) and linear aldehyde selectivity (~90%)
exceeding those obtained with conventional media [1]. The reaction is catalyzed by
triphenylphosphine modified Rh(acac)(CO)2 at  a feed CO:H2 molar ratio = 1 and
1-octene/Rh molar ratio = 2168.

 In order to
probe the fundamental transport and reaction rate processes, we acquired
intrinsic conversion and selectivity data in neat solvents (such as 1-octene,
toluene and methanol) and in CXLs using a 50-cm3 high-pressure
autoclave reactor equipped with an in
situ
attenuated total reflectance (ATR) IR probe (Mettler Toledo Inc.).
Intrinsic kinetic parameters are regressed from the temporal ReactIR
concentration profiles by using orthogonal distance regression technique
(Netlib Libraries) based on the kinetic scheme presented by Evans et al
[2] and Nair et al [3]. The predicted rate constants for the key catalytic
steps of catalyst hydrogenation (k1), olefin insertion, nonanal
formation, catalyst deactivation and octene isomerization are of similar order
of magnitude in neat solvent and CXL media. Further, an induction period is
observed in neat octene because of kinetic limitations, which is not observed
in CXL media [4]. This is attributed to the reduced hydrogen solubility in neat
octene. The lack of significant variation in the kinetic constants in the two
media indicates that the regressed constants are intrinsic for 1-octene
hydroformylation kinetics. The effects of CXLs involving toluene and methanol
are under investigation and these results will also be presented.

 

References

1.       
Jin,
H., Ghosh, A., Tunge, J.A. and B. Subramaniam, B. AIChE Journal 52, 2575 (2006).

2.       
Evans,
D., Osborn, J.A. and Wilkinson, G. Journal
of Chemical Society (A): Inorganic, Physical and Theoretical
3133 (1968).

3.       
Nair,
V.S., Mathew, S.P., Chaudhari, R.V. J. Mol. Cat. A: Chemical
143, 99 (1999).

4.      
Guha, D., Jin, H., Dudukovic, M.P., Ramachandran, P.A.and
Subramaniam, B. Chemical Engineering
Science
(in press).