Unraveling the Role of Zinc on Bimetallic Fe₅C₂–ZnO Catalysts for Highly Selective Carbon Dioxide Hydrogenation to High Carbon α-Olefins

Abstract

In this work, Fe−Zn catalysts were prepared, characterized, and examined for the synthesis of linear high carbon α-olefins (LAOs; C ≥ 4) directly from CO 2 hydrogenation. The relationship of performance and structure has been established to unravel the role of ZnO in bimetallic Fe 5 C 2 −ZnO catalysts. A Fe2Zn1 catalyst showed high selectivity to C 2 −C 7 olefins (a selectivity of 57.8% in gas phase) after 200 h of time-on-stream and total C 4+ olefins selectivity in liquid products of 81.9% with 85.9% LAOs in C 4+ alkenes at a CO 2 conversion of 35.0%. The dominant mechanism of deactivation was ascribed to phase transformation from FeC x to FeO x in comparison with Fe 2 O 3 and Fe5Zn1. Zn and Na were proved to migrate onto the surface during the activation process. The interaction between Zn and Na could suppress the oxidation of FeC x by H 2 O and CO 2 . This study revealed the deactivation mechanism and stabilization effects of Zn on the active phase of FeC x during CO 2 hydrogenation.

Ternary Fe–Zn–Al Spinel Catalyst for CO2 Hydrogenation to Linear α-Olefins: Synergy Effects between Al and Zn

“…488 kOe for A site and 456 kOe for B site). 33,51 This happens because of the replacement of Fe 2+ by Zn 2+ and Fe 3+ by Al 3+ and a similar variation has been observed on the spinel system Zn x Co 1−x Fe 2−x Al x O 4 . 52 The XPS results of the spent catalysts are shown in Figure 4a, and the binding energies (BE) of the detected peaks and the surface atomic concentrations are given in Table S6.…”

“…32 Recently, by studying the phase transformation during activation and reaction, our group revealed the stabilization effects of Zn on the active phase of Fe x C during CO 2 hydrogenation. 33 At present, however, studies on the effect of different additives on Fe-based catalysts are mostly isolated even though multiple combinations of mix additives have been employed in industrial catalysts. 34,35 Xu et al recently unveiled a subtle synergy between Na and Mn in Fe-based catalysts in CO 2 hydrogenation as Na mediates the strong interaction between Fe and Mn.…”

Dynamic structural evolution of iron catalysts involving competitive oxidation and carburization during CO 2 hydrogenation

“…That is, the ability to catalyze C 2+ production ranks as Fe 5 C 2 > Fe 3 C >> Fe 3 O 4 . Density functional theory (DFT) investigations showed that CO 2 activation is more facile on Fe 5 C 2 and Fe 3 C than on Fe 3 O 4 (45,46), and Han and colleagues (27,39) found that the transition of Fe 5 C 2 to Fe 3 O 4 causes the deactivation in CO 2 hydrogenation. From the comparison on the performance over model catalysts and Fe NPs with different TOS (Fig.…”

Potassium as a Versatile Promoter to Tailor the Distribution of the Olefins in CO2 Hydrogenation over Iron‐Based Catalyst

“…), hydrogenating CO 2 via thermo-catalysis can not only mitigate CO 2 emissions, but also effective in providing valuable organic chemicals. [5,6] Significant progress has been made in the selective catalytic hydrogenation of CO 2 into C 2 + hydrocarbons (e. g., olefins, [7][8][9][10][11][12] isoparaffins, [13] and aromatics [14][15][16][17][18] and oxygenates (e. g., methanol [19,20] and ethanol [21] ). Among these products, olefins are basic feedstocks for the production of various important commodities.…”