Ultralow Content of Chromium Species in Zeolite for Efficient Catalytic Propane Dehydrogenation

Abstract

Supported chromia catalysts have been commercially used in propane dehydrogenation, which relies on Cr loading at weight fractions of up to 20 wt %. This leads to problems in managing spent catalysts with a high content of toxic chromium species. These catalysts also rapidly deactivate within 10–15 min, requiring frequent regeneration in each cycle. To overcome these problems, we developed a siliceous MFI zeolite with an ultralow Cr content (e.g., 0.09 wt %) that exhibits high activity and durability for propane dehydrogenation. A mechanism study revealed that the chromic hydroxyl species readily dissociated the C–H bonds, accelerating the rapid desorption of propylene products and resulting in a slow deactivation rate. Therefore, the catalyst lifetime can be prolonged to more than 30 days under mild operating conditions (525 °C).