Bifunctional Catalysis for the Conversion of Synthesis Gas to Olefins and Aromatics

Abstract

The conversion of synthesis gas (a mixture of hydrogen and carbon monoxide) to value‐added chemicals has attracted significant attention in the past few years. Strong emphasis has been placed on enabling a process that allows the production of short olefins from synthesis gas, which can be derived from coal, biomass, or natural gas. Here, we introduce bifunctional catalysis to tailor the selectivity towards aromatics next to olefins by combining an iron‐based Fischer–Tropsch to olefins catalyst with the acid function of a zeolite. Olefins were formed from synthesis gas on an iron‐based catalyst and partly converted to aromatics on the acid sites of the zeolite. Surprisingly, this aromatization did not follow the pathway of hydrogen transfer, whereby three paraffin molecules are produced for every aromatic molecule formed, which allowed us to obtain carbon selectivity towards chemicals (sum of lower olefins and aromatics) of 70–80 % at 1 bar reaction pressure. Increasing the partial pressure of hydrogen led to substantial hydrogenation of olefins towards paraffins.

Recent Advances in Direct Synthesis of Value‐Added Aromatic Chemicals from Syngas by Cascade Reactions over Bifunctional Catalysts

“…The degree of a carburization and reduction, however, strongly depends on the types of chemical promoters of the Fe‐based catalysts with zeolite acidic components, which can significantly influence syngas conversion and aromatic selectivity as well. [7,70a] It is worth noting that the reduced Fe species was not easily carburized into Fe carbide phases with the copresence of an acidic component, although the degree of reduction depends on the natures of transition metals and the reactivity of their oxygen species in the frameworks of zeolites . Weber et al[70a] have performed the Mössbauer spectroscopy to investigate the differences of the degree of carburization and reduction of iron oxides before and after the addition of chemical promoters, and HZSM‐5 to the Fe‐based catalysts.…”

“…[7,70a] It is worth noting that the reduced Fe species was not easily carburized into Fe carbide phases with the copresence of an acidic component, although the degree of reduction depends on the natures of transition metals and the reactivity of their oxygen species in the frameworks of zeolites . Weber et al[70a] have performed the Mössbauer spectroscopy to investigate the differences of the degree of carburization and reduction of iron oxides before and after the addition of chemical promoters, and HZSM‐5 to the Fe‐based catalysts. The presence of HZSM‐5 (denoted as Z, Si/Al = 15) and promoters with Fe species (FeP‐2Z, ratio of Fe to Z = 2) enhanced both the degree of carburization and reduction.…”

Attachment of Iron Oxide Nanoparticles to Carbon Nanotubes and the Consequences for Catalysis

“…Colloidal synthesis has been successfully appliedt oo btain well-defined model catalysts suitable for fundamentals tudies. [9][10][11][12][13] In addition, colloidal particles have been shown to be relatively stable and to have catalytic properties that are comparable to those of conventional catalysts, making them interesting model systemsf or fundamentals tudies on FTO. [7,8] FTO involves iron-based catalysts and is becoming increasingly important as an alternative to the traditional cracking of crude oil fractions for the production of lower olefins (C2-C4) and aromatics from syngas (CO/H 2 ).…”

Beyond Cars: Fischer‐Tropsch Synthesis for Non‐Automotive Applications

“…The direct conversion of syngas via conventional FT synthesis into aromatics is very challenging. Fabricating a bifunctional catalyst comprising F‐T component and an aromatization zeolite is one of efficient strategies to achieve such process …”