Fe-Mo-oxide of spinel structure for methanol oxidation

Abstract: The aim of this master thesis was to investigate a Fe-Mo-oxide catalyst of spinel structure for methanol oxidation to produce formaldehyde and determine if the spinel could be an alternative to the commercial Formox catalyst used today. This included firstly, synthesising the catalyst to get more knowledge of the formation of the structure and secondly, determine the activity, selectivity to formaldehyde and stability of the catalyst. A literature review was performed and several synthesis methods to form a Fe/Mo spinel were found. The method that was most commonly used in previous work was precipitation in combination with H2-reduction and thus it was selected to use for synthesis in this project. Spray drying in combination with H2-reduction was also chosen to move forward with. The experimental part of the project focused on: synthesis of spinel catalyst, catalyst characterisation and activity and stability measurements. The catalyst synthesis included formation of precursors (precipitation or spray drying), which was prepared and performed before this project, and reduction by hydrogen. For the reduction experiments, some parameters were chosen to vary to learn more about at what conditions the spinel phase is favoured. All synthesised catalysts were characterised; to obtain the present phases in the catalyst an X-ray diffraction analysis was performed and to measure the specific surfaces a Brunauer-Emmett-Teller-analysis was executed. The results showed that it was more difficult to synthesise pure spinel phase when the Mo-content was high. After reduction and characterisation some catalysts were selected for activity and stability measurements. These measurements aimed to find the catalytic performance of the spinels and compare it to the commercial catalyst used in the process. The activity and ageing tests (stability measurements) were thus constructed to imitate the Formox process in terms of temperatures and reactor feed. Results from the activity tests showed that the selectivity to formaldehyde is lower than for the present Formox catalyst. The most promising spinel from the activity measurements was then used for stability measurements and this test showed better results; the formaldehyde selectivity increased over time. An inductively coupled plasma analysis was performed and it was found that all molybdenum was maintained from the ageing test which is a promising catalyst quality.