Elucidating deactivation of titania-supported cobalt Fischer-Tropsch catalysts under simulated high conversion conditions

The study of titania-supported cobalt nanoparticles is relevant for industrial Fischer-Tropsch synthesis (FTS). Herein, we report about various deactivation pathways of cobalt supported on P25 titania (cobalt loading 2–8 wt%) under simulated high conversion conditions using in situ Mössbauer spectroscopy. A fraction of metallic cobalt was...

Revealing Active Sites and Reaction Pathways in Methane Non-Oxidative Coupling over Iron-Containing Zeolites

Non-oxidative coupling of methane is a promising route to obtain ethylene directly from natural gas. We synthesized siliceous [Fe]zeolites with MFI and CHA topologies and found that they display high selectivity (>90 % for MFI and >99 % for CHA) to ethylene and ethane among gas-phase products. Deactivated [Fe]zeolites can be regenerated...

Sintering and carbidization under simulated high conversion on a cobalt-based Fischer-Tropsch catalyst; manganese oxide as a structural promotor

The commercial application of cobalt-based Fischer-Tropsch synthesis (FTS) suffers from catalyst deactivation. One of the main deactivation mechanisms under industrial conditions is sintering. In this work, we explored the role of manganese oxide as a structural promoter against sintering in a carbon nanofiber supported cobalt model catalyst....

Isotopic Exchange Study on the Kinetics of Fe Carburization and the Mechanism of the Fischer-Tropsch Reaction

The kinetics of the transformation of metallic Fe to the active Fe carbide phase at the start of the Fischer-Tropsch (FT) reaction were studied. The diffusion rates of C atoms going in or out of the lattice were determined using 13C-labeled synthesis gas in combination with measurements of the transient 12C and 13C contents in the carbide by...

The role of H₂ in Fe carburization by CO in Fischer-Tropsch catalysts

The formation of Fe-carbide phases is relevant to the synthesis of Fischer-Tropsch synthesis catalysts. We investigated the carburization of Raney Fe as a model catalyst using spectroscopic and temperature-programmed techniques. IR spectroscopy shows that CO dissociation already occurs at −150 °C, while C diffusion into metallic Fe requires...

Stability of Colloidal Iron Oxide Nanoparticles on Titania and Silica Support

Using model catalysts with well-defined particle sizes and morphologies to elucidate questions regarding catalytic activity and stability has gained more interest, particularly utilizing colloidally prepared metal(oxide) particles. Here, colloidally synthesized iron oxide nanoparticles (FexOy-NPs, size ∼7 nm) on either a titania (FexOy/TiO2)...

Co-Aromatization of Furan and Methanol over ZSM-5 - A Pathway to Bio-Aromatics

Aromatization of furan and substituted furans over zeolite catalysts is a promising reaction to convert cellulose-derived compounds into valuable aromatic hydrocarbons and light olefins. A lack of understanding of the reaction mechanism however hinders further development of this process. Here, we propose the reaction mechanism, underlying...

Electronic Structure Analysis of the Diels-Alder Cycloaddition Catalyzed by Alkali-Exchanged Faujasites

The Diels-Alder cycloaddition (DAC) reaction is a commonly employed reaction for the formation of C-C bonds. DAC catalysis can be achieved by using Lewis acids and via reactant confinement in aqueous nanocages. Low-silica alkali-exchanged faujasite catalysts combine these two factors in one material. They can be used in the tandem DAC...

Isolated fe sites in metal organic frameworks catalyze the direct conversion of methane to methanol

Hybrid materials bearing organic and inorganic motifs have been extensively discussed as playgrounds for the implementation of atomically resolved inorganic sites within a confined environment, with an exciting similarity to enzymes. Here, we present the successful design of a site-isolated mixed-metal metal organic framework (MOF) that...

Engineering of Transition Metal Catalysts Confined in Zeolites

Transition metal-zeolite composites are versatile catalytic materials for a wide range of industrial and lab-scale processes. Significant advances in fabrication and characterization of well-defined metal centers confined in zeolite matrixes have greatly expanded the library of available materials and, accordingly, their catalytic utility. In...

Catalytic (de)hydrogenation promoted by non-precious metals-Co, Fe and Mn: Recent advances in an emerging field

Catalytic hydrogenation and dehydrogenation reactions form the core of the modern chemical industry. This vast class of reactions is found in any part of chemical synthesis starting from the milligram-scale exploratory organic chemistry to the multi-ton base chemicals production. Noble metal catalysis has long been the key driving force in...

Tracking Local Mechanical Impact in Heterogeneous Polymers with Direct Optical Imaging

Structural heterogeneity defines the properties of many functional polymers and it is often crucial for their performance and ability to withstand mechanical impact. Such heterogeneity, however, poses a tremendous challenge for characterization of these materials and limits our ability to design them rationally. Herein we present a practical...

An Active Alkali-Exchanged Faujasite Catalyst for p-Xylene Production via the One-Pot Diels-Alder Cycloaddition/Dehydration Reaction of 2,5-Dimethylfuran with Ethylene

The one-pot Diels-Alder cycloaddition (DAC)/dehydration (D) tandem reaction between 2,5-dimethylfuran and ethylene is a potent pathway toward biomass-derived p-xylene. In this work, we present a cheap and active low-silica potassium-exchanged faujasite (KY, Si/Al = 2.6) catalyst. Catalyst optimization was guided by a computational study of...

Origin of enhanced Brønsted acidity of NiF-modified synthetic mica-montmorillonite clay

The Brønsted acidity of synthetic mica-montmorillonite (SMM) clay was studied by periodic DFT calculations. Different structural models were compared to determine the Brønsted acidity of protons of the SMM clay based on (i) isomorphous substitution of Si⁴⁺ by Al³⁺ in the tetrahedral silicate layer and additional NiF...

Synthesis of stable and low-Co2 selective Ɛ-iron carbide Fischer-Tropsch catalysts