Development of a Greener Hydroformylation Process Guided by Quantitative Sustainability Assessments

Abstract

Environmental impacts and economics associated with a potentially greener, Rh-catalyzed, 1-octene hydroformylation process in CO2-expanded liquid (CXL) medium are quantitatively assessed against a conventional Co-catalyzed 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.