Accelerating syngas-to-aromatic conversion via spontaneously monodispersed Fe in ZnCr2O4 spinel

Abstract

Spontaneous monodispersion of reducible active species (e.g., Fe, Co) and their stabilization in reductive atmospheres remain a key challenge in catalytic syngas chemistry. In this study, we present a series of catalysts including spontaneously monodispersed and enriched Fe on ZnCr2O4. Deep investigation shows remarkable performance in the syngas-to-aromatic reaction only when monodispersed Fe coupled with a H-ZSM-5 zeolite. Monodispersed Fe increases the turnover frequency from 0.14 to 0.48 s−1 without sacrificing the record high selectivity of total aromatics (80–90%) at a single pass. The increased activity is ascribed to more efficient activation of CO and H2 at oxygen vacancy nearest to the isolated Fe site and the prevention of carbide formation. Atomic precise characterization and theoretical calculations shed light on the origin and implications of spontaneous Fe monodispersion, which provide guidance to the design of next-generation catalyst for upgrading small molecules to synthetic fuels and chemicals.

A perspective of COx conversion to aromatics

“…These findings suggested that the d-band electrons of metals could be tuned while preserving the catalyst structure, resulting in effective regulation of reaction activity primarily controlled by the metal oxide side. A similar approach was adopted by Wei et al , 25 introducing appropriate amounts of F–T metals, such as Fe and Co, into spinel-type ZnCr 2 O 4 to significantly improve CO conversion without sacrificing total aromatic selectivity, as depicted in Fig. 2(b).…”

Effect of CO2 Co-Feeding on the Stabilization of Atomically Dispersed Iron Species over MgAl2O4 During Ethane Dehydrogenation Reactions

“…30 Monodispersed Fe species were obtained over ZnCr 2 O 4 spinel that restricted the formation of Fe x C y during syngas-to-aromatic reactions. 31 In this work, the sheet-like MgAl 2 O 4 spinel loaded with atomically dispersed Fe 3+ species was prepared via a simple impregnation method. However, these monodispersed Fe species were easy to migrate and agglomerate under the high reaction temperature (650 °C).…”

“…Given that 100% isolated Fe 3+ species in Fe/3Mg7Al were demonstrated in the 57 Fe Mossbauer spectra, and the comparison of the imaginary part of FT-EXAFS spectra (Figure S6), this signal is likely attributed to the Fe−Al scattering in Fe/3Mg7Al. 31,38 In addition, the wavelet transform (WT) EXAFS contour plots of Fe 2 O 3 is exhibited in Figure 2c, the signals at ca. 3.8 and 6.1 Å −1 are assigned to Fe−O and Fe−Fe path, respectively.…”

“…Pt nanoparticles in range of 1–3 nm supported on cuboctahedral MgAl 2 O 4 spinel material remain stable during high-temperature (800 °C) oxidative treatment for 1 week . Monodispersed Fe species were obtained over ZnCr 2 O 4 spinel that restricted the formation of Fe x C y during syngas-to-aromatic reactions …”

High-yield production of aromatics over CuFeO2/hierarchical HZSM-5 via CO2 Fischer–Tropsch synthesis

“…11–13 Aromatics, as some of the most important basic chemicals, are widely used for the production of polymers, plastics, paints, packaging, and films. 14–17 With the rapid shortage of fossil resources, the conventional production of aromatics from petroleum cracking cannot meet the rapidly increasing market demand. Thus, the production of aromatics with high yields via the non-fossil route of CO 2 hydrogenation using renewable hydrogen sources is significantly attractive for mitigating the CO 2 emissions and realizing carbon neutrality.…”