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Fisher‐Tropsch Synthesis (FTS) is industrially used for converting a carbon‐containing feedstock, such as coal, natural gas, biomass, and municipal waste, via the production of synthesis gas (a mixture of CO+H2) into hydrocarbons. This review article focuses on Fe‐based FTS catalysis, thereby focusing on the process conditions available for steering the various carbon pathways from input CO and their associated reactions. We will also discuss the effects of alkali‐sulphur chemical promotion and the identification of the FTS reaction active Fe carbides, which are assigned with precise crystal structures and nomenclature. Each observed Fe carbide crystal structure is further assigned with corresponding Mössbauer Absorption Spectroscopy (MAS) hyperfine fields. The expected formation temperatures and experimental conditions for the identified Fe carbides encountered in FTS research, namely ϵ‐Fe3C, η‐Fe2C, χ‐Fe5C2, θ‐Fe3C and θ‐Fe7C3, are reviewed.

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Zeolite-based catalyst bodies are commonly employed in a range of important industrial processes. Depending on the binder and shaping method chosen, vast differences in the reactivity, selectivity and stability are obtained. Here, three highly complementary micro-spectroscopic techniques were employed to study zeolite ZSM-5-binder interactions in SiO2-, Al2O3-, SiO2 : Al2O3- (2 : 1 mix) and kaolinite-bound catalyst pellets. We establish how their preparation influences the zeolite-clay/binder interactions. Using thiophene as an acid-catalyzed staining reaction, light absorbing oligomers produced in each sample were followed. To our surprise, kaolinite decreased the overall reactivity of the sample due to the phase change of the binder, creating a hard impenetrable outer layer. Aluminum migration to the zeolite was observed when Al2O3 was selected as a binder, creating additional Brønsted acid sites, which favored the formation of ring-opened thiophene oligomers compared to the larger oligomer species produced when SiO2 was used as a binder. In the latter case, the interaction of the Si-OH groups in the binder with thiophene was revealed to have a large impact in creating such large oligomer species. Furthermore, the combination of a SiO2 : Al2O3 mix as a binder enhanced the reactivity, possibly due to the creation of additional Brønsted acid sites between the two binder components during pellet preparation. It is evident that, independent of the shaping method, the intimate contact between the zeolite and binder heavily impacts the reactivity and product selectivity, with the type of binder playing a vital role.

Fluid catalytic cracking (FCC) catalysts play a central role in the chemical conversion of crude oil fractions. Using scanning transmission X-ray microscopy (STXM) we investigate the chemistry of one fresh and two industrially deactivated (ECAT) FCC catalysts at the single zeolite domain level. Spectro-microscopic data at the Fe L3 , La M5 , and Al K X-ray absorption edges reveal differing levels of deposited Fe on the ECAT catalysts corresponding with an overall loss in tetrahedral Al within the zeolite domains. Using La as a localization marker, we have developed a novel methodology to map the changing Al distribution of single zeolite domains within real-life FCC catalysts. It was found that significant changes in the zeolite domain size distributions as well as the loss of Al from the zeolite framework occur. Furthermore, inter- and intraparticle heterogeneities in the dealumination process were observed, revealing the complex interplay between metal-mediated pore accessibility loss and zeolite dealumination.

In Fe-based Fischer-Tropsch Synthesis (FTS), the Fe carbides form under the carburizing H 2 : CO reaction atmosphere providing the active phases for hydrocarbon synthesis. H 2 reduced Fe (À NaÀ S)/α-Al 2 O 3 catalyst materials, with and without NaÀ S promotion, were carburized under CO at 240-440°C to form Fe carbides. X-ray Powder Diffractometry (XRPD) with Rietveld Quantitative Phase Analysis (R-QPA) and Mössbauer Absorption Spectroscopy (MAS) were used to identity and quantify the formed Fe carbide phases. The Fe carbides formed in order of increasing temperature are ɛ-Fe 3 C, η-Fe 2 C, χ-Fe 5 C 2 and θ-Fe 3 C. θ-Fe 7 C 3 and a distorted χ-Fe 5 C 2 phase are formed at 25 bar CO (340°C) from a Fe oxide precursor. Fe carbide formation was unaffected by NaÀ S addition, but it did increase Fe oxidation (� 290°C) and preferred formation of χ-Fe 5 C 2 over θ-Fe 3 C phase (� 390°C). The results unify the often ambiguous Fe carbide identification and nomenclature and specify the role of NaÀ S in the carburization process.

A Na−S promoted Fe-based Fischer−Tropsch synthesis (FTS) catalyst converts a H 2 /CO gas mixture into hydrocarbons with enriched C 2 −C 4 olefin content. Above 300 °C, the carbondepositing Boudouard reaction competes with the FTS reaction for CO as reactant. By making use of a combined in situ X-ray powder diffractometry (XRPD)/Raman spectroscopy setup, the simultaneous evolution of the Fe x O y /α-Fe/Fe x C phases and various formed carbon species has been monitored at 340 °C and 10 bar. CO carburized, Na−S promoted and unpromoted Fe(−Na−S)/α-Al 2 O 3 catalysts were investigated. The various Fe phases present were quantified with Rietveld quantitative phase analysis (R-QPA) from the in situ collected XRPD patterns. The observed D-and G-bands in the in situ Raman spectra were analyzed for their relative intensities, band widths, and positions and compared to reference carbon materials. It was found that amorphous carbon with C sp 3 and C sp 2 in chain-like ordering evolved toward carbon nanofiber-like structures during FTS. Na−S promotion and initial CO carburization at temperatures ≥340 °C led to an increased amount of cyclic sixfold C sp 2 species. Preliminary carbon deposits present in the catalysts decreased the initial fast increase of the Raman band intensities, while Na−S promotion increased Raman band intensity growth after the initial fast increase period. The carbon species evolution was unaffected by the presence of specific Fe carbides or by carbide-to-carbide transitions. Na−S promotion aided in the reduction of Fe 3 O 4 by (H 2 :)CO to carbon-depositing Fe carbides. The results obtained add to our further understanding on the role of Fe and carbon species during a high-temperature FTS reaction.

Due to the surge of natural gas production, feedstocks for chemicals shift towards lighter hydrocarbons, particularly methane. The success of a Gas-to-Chemicals process via synthesis gas (CO and H2) depends on the ability of catalysts to suppress methane and carbon dioxide formation. We designed a Co/Mn/Na/S catalyst, which gives rise to negligible Water-Gas-Shift activity and a hydrocarbon product spectrum deviating from the Anderson–Schulz–Flory distribution. At 240 °C and 1 bar, it shows a C2-C4 olefins selectivity of 54%. At 10 bar, it displays 30% and 59% selectivities towards lower olefins and fuels, respectively. The spent catalyst consists of 10 nm Co nanoparticles with hcp Co metal phase. We propose a synergistic effect of Na plus S, which act as electronic promoters on the Co surface, thus improving selectivities towards lower olefins and fuels while largely reducing methane and carbon dioxide formation.