Tuesday, November 6, 2007 - 8:30 AM
199a

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

Jing Fang, Department of Chemical and Petroleum Engineering, University of Kansas, Rm. 4132 Learned Hall, 1530 W. 15th, Lawrence, KS 66045, Debangshu Guha, Washington University, Campus Box 1198, One Brookings Drive, Saint Louis, MO 63130, Jon Tunge, Department of Chemistry, University of Kansas, 1251 Wescoe Hall Drive, Malott Hall, Room 4033, Lawrence, KS 66045, Milorad P. Dudukovic, Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, St. Louis, MO 63130, P.A. Ramachandran, 3Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, Box 1198, One Brookings Drive, Saint Louis, MO 63130, and Bala Subramaniam, Center for Environmentally Beneficial Catalysis/Chemical Engineering, University of Kansas, 1501 Wakarusa Dr., Suite A-110, Lawrence, KS 66047.

 

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).

 

 


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