Fe-MOF Materials as Precursors for the Catalytic Dehydrogenation of Isobutane

We investigate the use of a series of iron-based metal-organic frameworks as precursors for the manufacturing of isobutane dehydrogenation catalysts. Both the as-prepared and spent catalysts were characterized by PXRD, XPS, PDF, ICP-OES, and CHNS+O to determine the physicochemical properties of the materials and the active phases responsible for the catalytic activity. In contrast to the previous literature, our results indicate that (i) the formation of metallic Fe under reaction conditions results in secondary cracking and coke formation; (ii) the formation of iron carbide only contributes to coke formation; and (iii) the stabilization of the Fe²⁺species is paramount to achieve stable and selective catalysts. In this sense, promotion with potassium and incorporation of titanium improve the catalytic performance. While potassium is well known to improve the selectivity in iron-catalyzed dehydrogenation reactions, the unprecedented effect of titanium in the stabilization of a nanometric titanomaghemite phase, even under reductive reaction conditions, results in a moderately active and highly selective catalyst for several hours on stream with a remarkable resistance to coke formation.