关键词: 费-托合成, 铁基费托合成催化剂, 铁碳物相, 金属有机骨架材料, Fe-MIL-100

Depletion of crude oil resources and environmental concerns have spurred worldwide interest in finding un-oil route for liquid fuels. Fischer-Tropsch synthesis is an effective progress for a wide spectrum of hydrocarbon chains from synthesis gas. The use of iron-based catalysts would be preferred in the industry. Here we present a strategy to produce highly dispersed active component embedded in a matrix of porous carbon. Through the carbonization of iron-containing metal-organic frameworks (Fe-MIL-100) at different temperature in N₂, four kinds of Fe@C catalysts were prepared. Glucose was used as additional carbon precursor for the synthesis catalyst samples to prevent particle agglomeration. Our strategy avoids the particle agglomeration in the weak metal-support interaction Fe@C catalysts during calcination, reduction and reaction. The structure and morphology of prepared catalysts were characterized by X-ray diffraction (XRD), N₂ physical adsorption, transmission electron microscopy (TEM), inductively coupled plasma-atomic emission spectrometer (ICP-AES). It is demonstrated that the iron loading, the particle size, and the Fe phase structure of Fe@C catalysts can be controlled by changing the carbonization temperature of Fe-MIL-100. With increasing the temperature, the iron loading and the particle size increase gradually. Depending on the carbonization temperature, the Fe₃O₄ phase is dominant at 400 and 500℃. The FeO and Fe phase appear at 600℃. The Fe₃C phase prevails at 700℃. The high dispersion of the metal phase and its encapsulation in a highly porous carbon matrix result in an unrivalled FTS activity. The spatial restriction created by encapsulation seems to minimize sintering and oxidation of the active Hägg carbide phase. When the reaction conditions were set at 260℃, 3 MPa, the space velocity of 8000 h^-1, the conversion of CO is up to 68%. The Fe time yield (FTY) of the Fe@C-500 catalyst were as high as 164 μmol_CO·g_Fe^-1·s^-1, which surpasses that of most F-T catalysts reported in the literature in middle-temperature Fischer-Tropsch synthesis.

Key words: Fischer-Tropsch synthesis, iron-based Fischer-Tropsch catalysts, iron carbide phases, metal organic frameworks, Fe-MIL-100