Highly Ordered Mesoporous Fe₂O₃–ZrO₂ Bimetal Oxides for an Enhanced CO Hydrogenation Activity to Hydrocarbons with Their Structural Stability

Abstract

Highly ordered mesoporous Fe2O3–ZrO2 mixed bimetal oxides (FeZr) without any additional chemical promoters were first applied to produce the value-added hydrocarbons by CO hydrogenation through Fischer–Tropsch synthesis (FTS) reaction of syngas. To enhance a catalytic activity and structural stability, an irreducible ZrO2 as a structural promoter was incorporated in the ordered mesoporous Fe2O3 structures with a different Zr/Fe molar ratio from 0 to 1 prepared by using a hard template of KIT-6. When an optimal amount of zirconia (Zr/Fe molar ratio = 0.25) was incorporated in the ordered mesoporous Fe2O3 frameworks, the catalytic activity was significantly improved and almost 10 times higher than the mesoporous monometallic Fe2O3. The highly ordered mesoporous structures were stably preserved even under reductive FTS reaction conditions. The ordered mesoporous FeZr catalysts showed a higher C5+ selectivity even at a higher CO conversion above 80%. This improved catalytic activity and stability on the optimized FeZr catalyst were mainly attributed to the facile formation of active iron carbide species such as the stable χ-Fe5C2 with insignificant structural collapses through a formation of strongly interacted iron nanoparticles with the ZrO2 structural promoter with a suppressed inactive coke deposition in the highly ordered FeZr mesopores.

Ordered Mesoporous Co3O4−Al2O3 Binary Metal Oxides for CO Hydrogenation to Hydrocarbons: Synergy Effects of Phosphorus Modifier for an Enhanced Catalytic Activity and Stability

“…A regular mesopore size of 5 nm on all the fresh P/m-CoAl was originated from the wall thickness of the hard-template of KIT-6, and a small peak intensity appeared at~14 nm in size was mainly attributed to the inter-particular pores, which was attributed to the partially disintegrated structures of the m-CoAl. [13][14][15][16][17]26] The significantly reduced surface area and pore volume as well as slightly increased average pore diameter on the fresh P/m-CoAl at a higher phosphorous content could be possibly attributed to the preferential deposition of phosphorous species on the outer surfaces of the m-CoAl, which can form the much denser SiO 2like AlPO 4 phases. [19][20][21][22][23][24] The ordered mesoporous structures of the P/m-CoAl were also verified by a small-angle X-ray scattering (SAXS) analysis, and the SAXS peaks are displayed in supplementary Figure S2.…”

“…However, the direct applications of those ordered mesoporous transition metal oxides were so difficult for FTS reaction because of their intrinsically unstable structures by an easy phase transformation from cobalt oxides to metallic states. [6,[12][13][14] Based on our previous works, [14][15][16][17][18] the highly ordered mesoporous metal oxides structures were successfully preserved under a reductive FTS reaction condition by introducing irreducible metal oxide pillaring materials such as alumina or zirconia or by preparing binary mixed metal oxides incorporated with those irreducible metal oxides. These structural stabilities were mainly attributed to the partial formation of thermally stable spinel-type metal aluminates at an optimal molar ratio of M/Co = 0.25 (M = Al or Zr).…”

“…[20,21] The advantages of phosphorus incorporation on the Co/Al 2 O 3 were also reported to increase the thermal stability of active metallic cobalt nanoparticles by adjusting metalsupport interactions through a possible formation of the thermally stable spinel-type CoAl 2 O 4 phases and by enhancing the reducibility of cobalt oxide nanoparticles. [19][20][21][22][23][24] In the present study, the effects of phosphorus-modified highly ordered mesoporous Co 3 O 4 À Al 2 O 3 binary metal oxides (P/m-CoAl) during FTS reaction were investigated in terms of their structural durability [13][14][15][16][17][18]25] and outermost surface property changes to explain different catalytic activity and stability, which were not precisely reported till now as far as we know. The synergy effects of an optimal phosphorous content on the P/m-CoAl were explained by elucidating the possible phase transformations of cobalt and aluminum species as well as their positive contributions to the robust structural stability of the ordered mesoporous Co 3 O 4 À Al 2 O 3 metal oxide structures.…”

LPG Direct Synthesis from Syngas over a Cu/ZnO/ZrO2/Al2O3@H‐β Zeolite Capsule Catalyst Prepared by a Facile Physical Method

“…LPG can be essentially synthesized from syngas via two fundamental pathways; one is the traditional Fischer‐Tropsch (F−T) process and, two is the Methanol to Hydrocarbon (MTH) also known as the multi‐stage process . The F−T process follows the Anderson‐Schulz‐Flory (ASF) rule, where a wide range of hydrocarbons with different chain lengths are distributed .…”

Effect of Ca Promoter on the Structure and Catalytic Behavior of FeK/Al2O3 Catalyst in Fischer‐Tropsch Synthesis

“…The activity, selectivity and stability are strongly affected by promoters in terms of electronic and structural modification. [9,10] Metal oxides (i. e. ZrO 2 , TiO 2 ) are usually considered as structural promoters to disperse and stabilize Fe species, [11,12] while alkali metals (e. g. K, Na) and several non-metal elements (e. g. N, S) always function as electronic promoters because of the electron donation to iron that facilitates CO dissociation and suppresses CÀ C coupling. [13][14][15][16] Dual promoters usually function synergistically in literatures.…”