Aging of Iron Molybdate Oxide Catalysts during Partial Oxidation of Methanol to Formaldehyde

Inga Walzel1, Marcel A. Liauw1, and M. Estenfelder2. (1) RWTH Aachen, Institute of Technical and Macromolecular Chemistry, Worringerweg 1, Aachen, 52074, Germany, (2) Süd-Chemie AG, Waldheimer Str. 11, Bruckmühl, 83052, Germany

The optimization of the production of formaldehyde is very important because formaldehyde is a raw material for many industrial processes, i.e. resin production, disinfectant, and cosmetic production. The industrial production of formaldehyde is catalyzed either by silver or by iron molybdate catalysts.

The partial oxidation of methanol over an iron molybdate oxide catalyst takes place at 250 – 400°C. It is a two-step oxidation in gaseous state which involves oxidized and reduced catalyst. The usual oxide mixture has a Fe : Mo atomic ratio of 1.5 – 2.0. Small amounts of V2O5, CuO, Cr2O3, CoO, P2O5 can be used as promotor. The average lifetime of industrial iron molybdate catalysts is about 6 – 12 months. The major reason of deactivation is the loss of Mo from the catalyst surface. This causes segregation into different phases: MoO3 and Fe2(MoO4)3 which is accompanied by MoO3 sublimation.

For an optimization of the production of formaldehyde, an increased lifetime of the catalyst is necessary. To reach this goal, more knowledge on how the deactivation is working is required. Recent results of a corresponding study will be presented here.