In Situ Formation of Metal Carbide Catalysts

Abstract

Metal carbide catalysts are essential to many widely used chemical processes. Fischer‐Tropsch synthesis, methane dehydroaromatization and biomass conversion catalysts are typically prepared in situ from a metal oxide precursor with a carbon‐containing gas. The reduction process of the metal oxide affects the final catalyst, as does the carburization gas mixture and metal promoters. By looking at materials that are carburized in situ, new insights can be gained about catalyst activation, fuel processing, and deactivation stages. The main focuses of this Review are iron carbide, molybdenum carbide and nickel carbide; analyzing catalyst synthesis methods, reduction steps, in situ carburization and improvements to the native processes. By combining years of research on these catalysts, trends and similarities are observed that can be used to improve current catalytic studies.

Effect of a potassium promoter on the Fischer–Tropsch synthesis of light olefins over iron carbide catalysts encapsulated in graphene-like carbon

“…Then, by carburization of CO during the reduction and further in the initial reaction period, it is transformed into a complex mixture of iron carbides including ε-Fe 2 C, χ-Fe 5 C 2 , θ-Fe 3 C, etc. 47 The reduction and activation progress is as follows: 10,48,49 In this study, a fraction of cementite Fe 3 C was directly obtained via a facile in situ synthesis method (Fig. 1a).…”

Synthesis of Iron-Carbide Nanoparticles: Identification of the Active Phase and Mechanism of Fe-Based Fischer–Tropsch Synthesis

“…[1][2] Despite the extensive exploration of Fe-based catalysts over the past 90 years, its active phases and reaction mechanisms are still in controversial. 3 The typical iron catalysts, usually produced from thermal reduction and successive activation of iron oxide precursors, contain different phases including metals, oxides and carbides produced during the pretreatment of the catalysts by carbon-containing gases such as CO. [4][5][6][7][8][9][10] The phase evolution of the iron catalysts during FTS reaction is even more complicated, and in most cases, a mixture of different phases was resulted during the FTS reaction. [11][12][13][14][15] To address this issue, various types of metal or metal carbides were prepared.…”

Molybdenum carbide and oxycarbide from carbon-supported MoO3 nanosheets: phase evolution and DRM catalytic activity assessed by TEM and in situ XANES/XRD methods

“…Since the 1970s reports on the noble-metal-like catalytic activity of Mo 2 C 1 and WC, 2 transition metal carbides have remained in the focus of the catalysis community. [3][4][5][6][7][8][9][10][11] For instance, molybdenum carbide has been studied as a catalyst for various heterogeneous reactions including methane reforming, 12,13 methane dehydroaromatization, 14,15 water gas shift, [16][17][18] and deoxygenation reactions. [19][20][21][22] The dry reforming of methane (DRM, eqn (1)) is a particularly relevant reaction because it allows producing synthesis gas from the two main greenhouse gases, CH 4 and CO 2 , although it requires high temperatures for reaching high conversions (typically, 800°C and above).…”