HYDROFORMYLATION OF C3 AND C8 OLEFINS IN HYDROCARBON GAS-EXPANDED SOLVENTS
University of Kansas
Chemical & Petroleum Engineering
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Hydroformylation involves the addition of syngas to the double bond of an alkene yielding aldehydes used to produce basic building blocks for myriad consumer goods. Resource-efficient technologies that conserve feedstock and energy continue to be of interest to industry. It has been shown previously by our group that the use of CO2-expanded liquids significantly enhances the Rh-catalyzed 1-octene hydroformylation rate and selectivity. This dissertation extends this concept by employing light alkanes such as propane and n-butane as compressed solvents in propylene and 1-octene hydroformylation, respectively. Phase behavior measurements demonstrate that at identical H2 or CO fugacities in the vapor phase, the H2 and CO solubilities in either propane- or propylene-expanded solvents (PXLs) are greater than those in the corresponding neat solvents by as high as 76% at 70 °C and 1.5 MPa. The H2/CO ratio in PXLs is enhanced by simply increasing the propane partial pressure. In contrast, the H2/CO in the neat solvent at a given temperature is constant at all syngas partial pressures. For Rh/triphenylphosphine catalyzed propylene hydroformylation between 70 to 90°C and pressures up to 2.0 MPa, the n/i aldehyde ratio in PXL media is increased by up to 45% compared to conventional media. However, with Rh/BiPhePhos catalyst complexes, the n/i ratio and turnover frequency (TOF) in PXL media are comparable with those observed in conventional processes in neat solvent. Thus, refinery-grade propane/propylene mixtures, rather than polymer-grade propylene, can be used in industrial propylene hydroformylation obviating purification by distillation. Technoeconomic analyses show ~ 30% lower capital costs and ~ 20% lower utilities costs for the PXL process compared to the conventional process. The reduced material and energy consumption in the PXL process also lowers adverse environmental impacts (greenhouse gas emission, air pollutants emission, and toxic release) associated with the PXL process. For Co-catalyzed 1-octene hydroformylation at 180°C, the use of n-butane expanded liquids (BXLs) as reaction media was demonstrated. The results show that the TOF for alcohol formation was enhanced by more than 20% in BXL system with a 20% reduction in organic solvent usage. These results pave the way for the rational application of gas-expanded solvents in hydroformylations.
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