PARTIAL OXIDATION OF ISOBUTENE TO METHACROLEIN ON BIW/FECOMOK MIXED-OXIDE CATALYSTS

The partial oxidation of isobutene to methacrolein and methacrylic acid was studied on oxidic catalysts containing mainly a mixture of bismuth tungstate and iron cobalt potassium molybdate. The catalysts were prepared via different synthesis methods. The content of bismuth tungstate and iron cobalt potassium molybdate was varied. Catalyst shaping was done by extrusion. The kinetic measurements were performed by monitoring the gas-phase composition along the length of a fixed bed of catalyst. The reactor was treated as an isothermal plug-flow system. The network of parallel and consecutive reactions taking place in this system can be described by a simplified scheme. It is possible to predict the gas-phase composition prevailing in the reactor using five different kinetic parameters. In the temperature range 380 degrees C < theta < 420 degrees C grain selectivities as high as 85% combined with yields of methacrolein and methacrylic acid about 70% at 92% conversion were obtained on catalysts prepared via a slurry synthesis method and containing bismuth tungstate in the range between 20 and 70 wt%. Calculations based on the experimentally determined kinetic constants promise an increase in yield if the reactor containing catalysts of different composition is treated at non-uniform temperature. In the case of temperature structuring alone an increase of the methacrolein and methacrylic acid yield of about three points has been verified experimentally.