Optimal experimental design and kinetic modeling for the selective oxidation of methanol to formaldehyde using Fe-Mo catalysts

The selective oxidation of methanol to formaldehyde is a key industrial reaction for formalin production; however, optimizing its reaction conditions is challenging due to strong interactions among multiple operating variables and catalyst composition. In this study, an Fe–Mo mixed oxide catalyst was investigated for methanol oxidation using Response Surface Methodology (RSM) employing a Central Composite Design (CCD) to systematically optimize key process parameters. The effects of temperature, oxygen and methanol flow rates, Mo/Fe molar ratio, and time-on-stream were studied, and a quadratic model was developed to predict and maximize the reaction rate. The model showed good agreement with experimental data, with an overall R 2 of 0.9576, confirming the model’s reliability. Optimal conditions were determined as 350 °C, O 2 flow rate of 120 mL min − 1 , methanol flow rate of 2.5 mL h − 1 , Mo/Fe = 1.7, and time-on-stream = 1 h, yielding a maximum reaction rate of 1.25 mol g cat −1 s − 1 . Kinetic modeling using both the Power Law (PL) and Mars–van Krevelen (MVK) approaches provided activation energies ranging from 21 to 48 kJ mol − 1 , consistent with literature data, and provided experimentally determined kinetic parameters that offer practical insights into the reaction. These results demonstrate the effectiveness of RSM–CCD for multivariable process optimization and provide experimentally validated kinetic parameters for methanol oxidation over Fe–Mo catalysts.