Accurate knowledge of the phase equilibria of CO 2 -expanded hydroformylation reaction mixtures is essential to rational process design and development. Vapor-liquid equilibria of the following systems were measured in a variable-volume view cell at temperatures ranging from (313.15 to 353.15) K and pressures up to 9 MPa: CO + 1-octene, CO 2 + 1-octene, CO + 1-octene + CO 2 , CO + nonanal, CO 2 + nonanal, CO + nonanal + CO 2 , H 2 + 1-octene, H 2 + 1-octene + CO 2 , H 2 + nonanal, and H 2 + nonanal + CO 2 . The measured solubilities of CO and H 2 in the liquid phases were consistent with literature values. The presence of CO 2 was found to enhance the solubilities of both CO and H 2 in the liquid phase. The enhancement factor is up to 1.54 for carbon monoxide and 1.82 for hydrogen. The Peng-Robinson equation of state (PR EoS) with van der Waals mixing rules and binary interaction parameters modeled the VLE data adequately, with much better fits for the 1-octene systems compared to the more polar nonanal systems.

A novel process for continuous hydroformylation in CO2‐expanded liquids (CXLs) is demonstrated using bulky phosphite ligands that are effectively retained in the stirred reactor by a nanofiltration membrane. The reactor is operated at 50°C with a syngas pressure of 0.6 MPa to avoid CO inhibition of reaction rate and selectivity. The nanofiltration pressure is provided by ∼3.2 MPa CO2 that expands the hydroformylation mixture and increases the H2/CO ratio in the CXL phase resulting in enhanced turnover frequency (∼340 h−1), aldehydes selectivity (>90%) and high regioselectivity (n/i ∼8) at nearly steady operation. The use of pressurized CO2 also reduces the viscosity in the CXL phase, thereby improving the mass‐transfer properties. Constant permeate flux is maintained during the 50 h run with Rh leakage being less than 0.5 ppm. This technology concept has potential applications in homogeneous catalytic processes to improve resource utilization and catalyst containment for practical viability. © 2013 American Institute of Chemical Engineers AIChE J, 59: 4287–4296, 2013

Environmental impacts and economics associated with a potentially greener, Rh-catalyzed, 1-octene hydroformylation process in CO 2 -expanded liquid (CXL) medium are quantitatively assessed against a conventional Cocatalyzed process. The economic analysis shows a more than 30% lower capital investment for the CXL process compared to the conventional Co-catalyzed process of similar capacity. This is due to the higher reaction and catalyst recovery efficiencies at milder reaction temperature and pressures (compared to the conventional process) used in the CXL process. The total production cost (TPC) associated with the CXL process is lower than the conventional process when the Rh makeup rate is lower than 0.94% (of the total amount of Rh in the reactor) per hour at the current Rh price ($20,800/ lb). This translates to an economic viability criterion of ($makeup Rh/$TPC) being 0.042 or less. Life cycle analysis (LCA) was performed using GaBi software and an EIO-LCA method based on plant scale simulation of both the conventional and continuous CXL processes to produce 150 kton/year of nonanal. Gate-to-gate LCA projections show that the CXL process is environmentally friendlier than the conventional process in most impact categories such as ecotoxicity, greenhouse gas emissions, and smog formation. Predicted emissions for the conventional process are of the same order of magnitude as those reported from an actual plant of similar capacity. Cradle-to-gate environmental impacts are 1 to 2 orders of magnitude greater than the gate-to-gate impacts with energy usage for the production of raw materials being the major source of adverse environmental impacts. The EIO-LCA results agree with the GaBi analysis. Our results show that the environmental performance of the CXL process can be further improved with lower solvent usage, thus also providing valuable guidance for process optimization.

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The use of n-butane expanded liquids (BXLs) as reaction media to enhance Co-catalyzed hydroformylation of 1-octene has been successfully demonstrated.