MOF-Derived Iron Catalysts for Nonoxidative Propane Dehydrogenation

The dehydrogenation of light alkanes, sourced from cracking of traditional petrochemical feedstocks and from emerging shale gas, represents an attractive route to alkenes (ethene, propene, and butenes), which are the building blocks for valuable polymers and chemicals. Carbon-supported iron catalysts formed from pyrolysis of Fe-containing metal-organic frameworks (MOFs; Fe-BTC) are investigated here for propane dehydrogenation. The temperature of pyrolysis is found to influence the iron phase (oxide, metal, and carbide) and surface area of the material, but the high-temperature reduction and reaction conditions needed for propane dehydrogenation (500-600 °C) result in a metallic iron phase that is shown to be active and selective for propene formation, though differential isoconversion data indicate that the pyrolysis temperature affects the selectivity to propene. X-ray absorption spectroscopy and X-ray diffraction are utilized to investigate the catalyst state both pre- and post-reduction and reaction. This work demonstrates how using MOFs as precursors may allow the synthesis of useful and perhaps unique catalyst structures that can be designed to obtain desired rates and product selectivities of hydrocarbon processes.