Reduction Behavior of Potassium-Promoted Iron Oxide under Mixed Steam/Hydrogen Atmospheres

Potassium-promoted iron oxide catalysts are used in large volume for the commercial ethylbenzene dehydrogenation to styrene process. Short-term deactivation of these catalysts, which is addressed by operating in excess steam, is thought to be caused due to reactive site loss through coking and/or reduction. However, the relative importance of the two mechanisms is not known. Presented are results concerning the reduction behavior of potassium-promoted iron oxide materials in the absence of carbon. Thermogravimetric experiments and X-ray diffraction analysis were used to examine the reduction behavior of potassium-promoted iron oxide materials. The reduction behavior was then compared with results from isothermal ethylbenzene dehydrogenation reactor studies under low steam-toethylbenzene operation. Potassium incorporation was found to stabilize the iron oxide against reduction apparently through the formation of KFeO2. Chromium addition improved the reduction resistance, which gave good qualitative agreement with the dehydrogenation reaction studies. In contrast, vanadium incorporation led to more significant reduction as well as poor stability in the dehydrogenation reaction.