Dr. Manhua Mandy Lin, Principal Investigator, DOE Grant No. DE-FG02-05ER84321

In the U.S., the production of 4.6 billion pounds of Nylon-6 and Nylon-6,6 starts with the liquid-phase oxidation of 3.5 billion pounds of cyclohexane to cyclohexanone/cyclohexanol, and the subsequent oxidation of the latter to adipic acid with HNO₃.  The liquid-phase cyclohexane oxidation, which operates at only 4-10% cyclohexane conversion, is the “least efficient” industrial process, and wastes trillions of Btu of energy by repeatedly recycling 90-96% of the 3.5 billion pounds of cyclohexane feedstock.  Just as alarming, the subsequent HNO₃ process generates a billion pounds of pollutants, N₂O and NOx.  This project will demonstrate a gas-phase catalytic process, using only air as the oxidant, which has high potential to efficiently oxidize cyclohexane to cyclohexanone and adipic acid in one-step.  At the same time, more than ten trillion Btu of energy released from the exothermic reaction will be captured, the use of toxic/corrosive reagents will be eliminated, as will the generation and treatment of all the harmful pollutants involved in conventional liquid phase processes.

Commercial Applications and Other Benefits:  The gas-phase catalytic production of cyclohexanone and cyclohexanol via one-step selective oxidation of cyclohexane being developed in this project has the potential to replace the current conventional processes for cyclohexanone production via liquid-phase cyclohexane oxidation (followed by oxidation with HNO₃ to adipic acid) with the following major benefits: (1) economic – by replacing the “least efficient” liquid-phase process with a efficient gas-phase process; (2) enery savings – by capturing more than ten trillion Btu per year of energy gained from the exothermic high temperature gas-phase process; (3) safety – by eliminating the use, consumption, and recycling of billion pounds of toxic and corrosive reagents including HNO₃ and boric acid; and (4) environmental – by eliminating the generation of a billion pounds of harmful air pollutants, such as N₂O and NOx.

The Phase I research of this project focused on the development of an effective catalyst for the efficient and selective conversion of cyclohexane to cyclohexanone and cyclohexanol, starting with the preparation of metal oxide-based lead catalysts, followed by compositional and structural modifications guided by rational and computer-assisted designs.  The Phase II research will further the development of the catalytic process that will significantly increase productivity, reduce energy consumption, and eliminate byproduct waste streams for the gas-phase production of cyclohexanone and cyclohexanol from cyclohexane.