Thermocatalytic Conversion of Ethanol to Acetone: Effect of Heating Method on Selectivity and Conversion

The widespread usage of fossil fuels to supply heat to industrial processes contributes to 8% of the United States’ energy-related carbon dioxide emissions. Induction heating (IH) has emerged as an alternative method to supply heating for industrial processes. By using alternating electric currents to produce oscillating magnetic fields, IH heats conductive, ferromagnetic, and ferrimagnetic materials with high efficiency. If powered by renewable energy, this electrified heating is virtually emissions-free. Additionally, IH has been demonstrated to improve catalyst activity in chemical reactions compared to conventional heating (CH), and its application in the synthesis of acetone from ethanol is of interest to the chemical industry. Acetone is a vital industrial solvent, and its versatile chemistry renders it an essential precursor for chemicals, especially plastics. Since acetone is typically produced from petroleum-derived chemicals through the cumene process, it is desirable to use more sustainable feedstocks to minimize the environmental impacts of its production. To this end, acetone can be synthesized from water and biomass-derived ethanol above 350°C with a Fe₂O₃-ZnO catalyst. In this study, the effect of induction heating on the selectivity and conversion of the thermocatalytic ethanol-to-acetone reaction was investigated. The Fe₂O₃-ZnO catalyst was synthesized, and it was characterized via XRD. The catalyst was placed in a packed-bed reactor, into which a gaseous mixture of ethanol, water, and nitrogen was fed. Time-on-stream and temperature-sweep experiments were performed using a copper solenoid for IH and a furnace for CH. The reaction products were analyzed via gas chromatography. Although both heating methods exhibited similar selectivity and deactivation trends in time-on-stream experiments, temperature-sweep experiments revealed high ethanol conversion and acetone selectivity with IH at lower temperatures than CH. As a result of the alternating magnetic field, IH causes both the stainless steel susceptor beads and ferrimagnetic catalyst to generate heat within the catalyst bed. This internal heat generation enhances heat transfer compared to CH, which heats the reactor externally. The benefits of improved heat transfer, reduced process temperature, and electrified heating demonstrate the capability of IH to decarbonize the chemical industry. Future works will probe the effects of magnetic fields, such as those produced in induction heating, on the activity of ferrimagnetic catalyst sites.