Gas Phase Catalytic Oxidation of Cyclohexane to Cyclohexanone and Cyclohexanol

In the U.S., the annual production of 4.6 billion pounds of nylon starts with the liquid-phase oxidation of 3.5 billion pounds of cyclohexane to KA-oil (a mixture of cyclohexanone and cyclohexanol) and the subsequent oxidation of the latter to adipic acid with HNO3. The liquid-phase cyclohexane process, which operates at only 4-10% cyclohexane conversion, is the ¿least efficient¿ industrial process, and wastes trillions of Btu of energy in the repeated recycling of 90-96% of the 3.5 billion pounds of unreacted cyclohexane. This project will develop an effective metal-oxide-based catalyst for the efficient conversion of cyclohexane to KA-oil in a gas-phase process. A gas-phase catalytic process would greatly enhance KA-oil productivity while capturing ~7 trillion Btu/yr of energy released in the exothermic reaction. Phase I proved the feasibility of producing cyclohexanone via cyclohexane gas-phase oxidation with air as the oxidant. Several lead catalysts were discovered that met and exceeded the targets of 20% cyclohexane conversion and 20% cyclohexanone selectivity. Phase II will seek to achieve one-pass 30% cyclohexane conversion and 50-60 % KA-oil selectivity by: (1) conducting studies to understand and minimize the undesirable cyclohexane oxidation pathways, and to enhance KA-oil production; (2) enhancing the catalytic performance of the lead catalysts through the optimization of catalyst composition and preparation methods; and (3) conducting an economic analysis to compare the new process to existing commercial processes. Commercial Applications and other Benefits as described by the awardee: The gas-phase cyclohexane catalytic oxidation process should replace current conventional cyclohexane liquid-phase processes for the production of KA-oil, the key intermediates for the production of 4.6 billion lb/yr of nylon in the U.S. The advantages of the gas-phase process include: (1) improved productivity, (2) significant reduction of energy consumption, (3) the capture for use of at least 7 trillion Btu/yr of energy from the exothermic high temperature gas-phase process; (4) the elimination of the need to use and recycle billions lb/yr of boric acid; and (5) the elimination of massive amounts of acidic aqueous waste streams.