Kinetic modeling of propene hydroformylation with Rh/TPP and Rh/CHDPP catalysts

Hydroformylation of propene to isobutyraldehyde and n-butyraldehyde was studied in the kinetic regime in a semibatch stainless steel reactor at 70-115 °C and 1 - 15 bar overpressure in 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate solvent with rhodium/cyclohexyl diphenylphosphine (Rh/CHDPP) and rhodium/triph-enylphosphine (Rh/TPP) catalysts. The influence of process parameters such as Rh concentration (50-250 ppm), ligand mass fraction (0-10 wt %), H₂-to-CO ratio, and stirring power was investigated and the influence of solvent concentration was studied by using mixtures of valeraldehyde and 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate as solvent. The solubility of propene, H₂, and CO in 2,2,4-trimethyl-1,3- pentanediol monoisobutyrate was measured in the same reactor. Rh/CHDPP showed lower normal/isometric aldehyde ratio (n/i) than Rh/TPP. The rate was temperature and pressure dependent, while the Rh concentration or syngas composition did not have any significant impact. The n/i ratio was always independent of the conversion, but dependent on the ligand concentration: higher ligand concentration promoted isobutyraldehyde formation. Based on experimentally recorded kinetic data, a stoichiometric scheme was proposed and parameters of power-law rate models were determined by using nonlinear regression analysis. The experimental system was described as a perfectly mixed gas-liquid reactor. As showed by sensitivity analysis, the kinetic parameters were well identified and physically reasonable and they were in accordance with qualitative observations. The kinetic models with a degree of explanation of more than 0.9 described the formation of the products with satisfying accuracy.