Synthesis of 1,3-butadiene from ethanol/acetaldehyde over ZrO2-MgO-SiO2 catalyst: The thermodynamics and reaction kinetics analysis

The catalytic conversion of ethanol into 1,3-butadiene has once again attracted widely attention. However, the kinetics of 1,3-butadiene synthesis from ethanol are rarely reported. In this work, the kinetics of 1,3-butadiene synthesis from ethanol and acetaldehyde over ZrO2-MgO-SiO2 catalyst developed by our research group were studied. The study was carried out in an isothermal integral reactor at temperatures of 573-613 K with various space velocity. The kinetics of two main side reactions, dehydration of ethanol to ethylene and ether, were also measured. It was assumed that the aldol condensation rate determining step followed the Langmuir-Hinshelwood mechanism and the Eley-Rideal mechanism respectively, from which the corresponding kinetics models were derived. The results showed that the aldol condensation step followed the Langmuir-Hinshelwood mechanism over ZrO2-MgO-SiO2 catalyst, and the activation energy was calculated to be 54.6 kJ/mol. The obtained kinetics models were verified under the conditions of different ethanol/acetaldehyde molar ratio. The discrepancy between calculated outlet flow rates of key components and the experimental values was within +/- 16%, indicating the validity of the obtained kinetics models. The research results can provide some theoretical guidance for the reactor design of 1,3-butadiene synthesis from ethanol.