Conventional propylene hydroformylation to produce butyraldehyde requires polymer grade propylene as feedstock.1
High purity propylene is obtained by energy intensive separation from propane/propylene mixtures. If propane/propylene mixtures can be used effectively as feed, process economics would be significantly enhanced. Previously, we had reported preliminary results on the beneficial effects of propane expanded liquids (with propylene/propane mixtures instead of polymer grade propylene as feed) for propylene hydroformylation with Rhodium-based catalysts. At sufficiently high pressures (>10 bar), the pressurized propane/propylene mixture forms a gas-expanded liquid phase that promotes regio-selective hydroformylation of propylene with homogenous Rh complex.2
In this talk, we report hydroformylation of propene in propane expanded solvents in the kinetic regime in a semi batch stainless steel reactor at 70−90 °C and 6−18 bar overpressure in 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate (NX-795), toluene and n-
butanol solvent with rhodium based complexes (Rh/TPP, Rh/ CHDPP, Rh/TPPA and Rh/BIPHEPHOS). The n/i
ratio and TOF achieved during Rh/BIPHEPHOS catalyzed hydroformylation in propane-expanded solvents is comparable with conventional processes in neat solvent. By tuning the propane/propylene partial pressure, the n/i
ratio in propane-expanded solvents could be enhanced by 30% in Rh-catalyzed reaction with mono-phosphine ligands while maintaining a reaction rate comparable to that without propane addition. Vapor−liquid equilibria of the reaction system were also measured in a variable-volume view cell at temperatures ranging from (343.15 to 363.15) K and pressures up to 20 Bar. The measured solubilities of CO and H2
in the liquid phases were consistent with literature values.3
The presence of propane was found to enhance the solubilities of both CO and H2
in the liquid phase. The enhancement factor is up to 1.56 for carbon monoxide and 1.91 for hydrogen. Based on experimentally recorded kinetic data, a kinetic model was developed to explain the effects of propane-expanded solvent on the observed rate and selectivity.
1.Krokoszinski, R., Hammon, U., & Todd, K. (2005). U.S. Patent No. 6,864,391. Washington, DC: U.S. Patent and Trademark Office.
2. Liu, D., Xie Z., Chaudhari, R.V., Subramaniam, B. Enhanced Hydroformylation of Propylene in Propane-Expanded Liquids with Rh-Based Complexes, 2015 AIChE annual meeting. Salt Lake City, UT
3. Nair, V. S., Mathew, S. P., & Chaudhari, R. V. (1999). Kinetics of hydroformylation of styrene using homogeneous rhodium complex catalyst. Journal of Molecular Catalysis A: Chemical, 143(1), 99-110.