Synthesis of formaldehyde from dimethyl ether on alumina-supported molybdenum oxide catalyst

- Selective oxidation of dimethyl-ether to formaldehyde.
- Supported molybdenum oxides provide high FA selectivities (70%).
- Significant catalyst deactivation but reaching steady state activity.
- Kinetic model based on Mars- Van Krevelen mechanism.

The selective oxidation of DME to formaldehyde over alumina-supported MoOx catalyst (prepared by dry impregnation) is studied in this work. The activity and stability of the catalyst were evaluated in a fixed-bed continuous reactor at different temperatures and reactant concentrations.The influence of the main operating conditions, (DME, O2, CO2 and CO feed concentrations; reaction temperature) on reaction rate and product selectivity was experimentally determined. Thus, DME conversion decreases on increasing DME feed concentration and increases on increasing O2 feed concentration. Formaldehyde selectivity remained almost unaffected. A reaction mechanism, based on a Mars-van-Krevelen redox cycle representing DME oxidation to formaldehyde was used as a basis to develop a kinetic model for the reaction. The resulting simplified model suggests power law dependences for the reaction rate of 0.2 for the O2 and 0.5 for the DME.

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