The active phase in cobalt-based Fischer-Tropsch synthesis

Fischer-Tropsch synthesis (FTS) is an industrial catalytic process that converts a mixture of CO and hydrogen into long-chain hydrocarbons. These products are used as clean transportation fuels and chemical building blocks. The solid catalysts used in the process are complex multi-component systems. Therefore, unambiguously determining the catalytically active phase under reaction conditions remains challenging and thus a topic of debate. The active phase in cobalt-based FTS, including the reaction pathways it catalyzes, has been of industrial and academic interest for many years. It provides direct ways to control the output of the process. The delineation between an active and inactive phase is often unclear, as different phases (i.e., cobalt oxide, carbide, and metal) have different catalytic behavior. This review focuses on cobalt-based FTS materials, with a special focus on the industrially applied cobalt/TiO2 system. The various cobalt phases are reviewed and discussed with respect to the most recent literature

Correlating the Morphological Evolution of Individual Catalyst Particles to the Kinetic Behavior of Metallocene-Based Ethylene Polymerization Catalysts

Kinetics-based differences in the early stage fragmentation of two structurally analogous silica-supported hafnocene- and zirconocene-based catalysts were observed during gas-phase ethylene polymerization at low pressures. A combination of focused ion beam-scanning electron microscopy (FIB-SEM) and nanoscale infrared photoinduced force microscopy (IR PiFM) revealed notable differences in the distribution of the support, polymer, and composite phases between the two catalyst materials. By means of time-resolved probe molecule infrared spectroscopy, correlations between this divergence in morphology and the kinetic behavior of the catalysts' active sites were established. The rate of polymer formation, a property that is inherently related to a catalyst's kinetics and the applied reaction conditions, ultimately governs mass transfer and thus the degree of homogeneity achieved during support fragmentation. In the absence of strong mass transfer limitations, a layer-by-layer mechanism dominates at the level of the individual catalyst support domains under the given experimental conditions

The active phase in cobalt-based Fischer-Tropsch synthesis

Fischer-Tropsch synthesis (FTS) is an industrial catalytic process that converts a mixture of CO and hydrogen into long-chain hydrocarbons. These products are used as clean transportation fuels and chemical building blocks. The solid catalysts used in the process are complex multi-component systems. Therefore, unambiguously determining the catalytically active phase under reaction conditions remains challenging and thus a topic of debate. The active phase in cobalt-based FTS, including the reaction pathways it catalyzes, has been of industrial and academic interest for many years. It provides direct ways to control the output of the process. The delineation between an active and inactive phase is often unclear, as different phases (i.e., cobalt oxide, carbide, and metal) have different catalytic behavior. This review focuses on cobalt-based FTS materials, with a special focus on the industrially applied cobalt/TiO2 system. The various cobalt phases are reviewed and discussed with respect to the most recent literature

Using Biomass Gasification Mineral Residue as Catalyst to Produce Light Olefins from CO, CO2, and H2 Mixtures

Invited for this month's cover is the group of Bert Weckhuysen at Utrecht University. The image shows how iron nanoparticles in a biomass gasification residue can convert CO, CO 2 , and H 2 mixtures into light olefins. The Research Article itself is available at 10.1002/cssc.202200436

Using Biomass Gasification Mineral Residue as Catalyst to Produce Light Olefins from CO, CO2, and H2 Mixtures

Gasification is a process to transform solids, such as agricultural and municipal waste, into gaseous feedstock for making transportation fuels. The so-called coarse solid residue (CSR) that remains after this conversion process is currently discarded as a process solid residue. In the context of transitioning from a linear to a circular society, the feasibility of using the solid process residue from waste gasification as a solid catalyst for light olefin production from CO, CO2, and H2 mixtures was investigated. This CSR-derived catalyst converted biomass-derived syngas, a H2-poor mixture of CO, CO2, H2, and N2, into methane (57 %) and C2–C4 olefins (43 %) at 450 °C and 20 bar. The main active ingredient of CSR was Fe, and it was discovered with operando X-ray diffraction that metallic Fe, present after pre-reduction in H2, transformed into an Fe carbide phase under reaction conditions. The increased formation of Fe carbides correlated with an increase in CO conversion and olefin selectivity. The presence of alkali elements, such as Na and K, in CSR-derived catalyst increased olefin production as well

Correction to “Correlating the Morphological Evolution of Individual Catalyst Particles to the Kinetic Behavior of Metallocene-Based Ethylene Polymerization Catalysts”

Figure 1 in the original paper shows d-acetonitrile molecules with four bonds between the N and C atoms. This has been corrected here. new figure to demonstrate a direct correlation between the point spectra and IR maps that were recorded on the given particle cross-section. The main text was adapted as follows: Point spectra, recorded of PE- (i.e., A1 and B1 in Figure 5) and silica-rich regions (i.e., A2 and B2 in Figure 5) as well as reference materials (Figures S10.S12), further helped to assign the imaged phases. A correction to the Supporting Information, section S4.B, was made to reflect that all data were recorded in PiF and not PiFM mode: Atomic force microscopy (AFM) topography images, IR maps and IR point spectra were recorded in dynamic noncontact PiF mode (60 accumulations, 500 ms pixel dwell time, 1 cm.1 spectral resolution) using NCHR Au-coated cantilevers (force constant: 40 N/m). The iFM labels in Figures S7.S9 (Supporting Information) were changed to PiF. Furthermore, the methodology for recording an IR map at a specific wavenumber was described in more detail, both in the Supporting Information and in the main text: Prior to acquiring an IR map at a specific wavenumber, a preliminary low-resolution scan was performed. A point spectrum was then taken in the mapped area to determine the wavenumber of the targeted vibrational band (i.e., the wavenumber at which the band has its maximum intensity). The IR PiFM maps were recorded in noncontact mode26 (amplitude ratio set point of 80%, attractive van der Waals force regime; Table S3) at characteristic wavenumbers for the Si.O stretching vibration46,47 (maps recorded at single wavenumbers in the range of 1050.1030 cm.1, (Si.O), Figure 4) and the symmetric C.H bending vibration of the methylene group37.39 (maps recorded at single wavenumbers in the range of 1472.1460 cm-1, (C.H), Figure 4)

Influence of Metal-Alkyls on Early-Stage Ethylene Polymerization over a Cr/SiO2 Phillips Catalyst: A Bulk Characterization and X-ray Chemical Imaging Study

The Cr/SiO2 Phillips catalyst has taken a central role in ethylene polymerization since its invention in 1953. The uniqueness of this catalyst is related to its ability to produce broad molecular weight distribution (MWD) PE materials as well as that no co-catalysts are required to attain activity. Nonetheless, co-catalysts in the form of metal-alkyls can be added for scavenging poisons, enhancing catalyst activity, reducing the induction period, and tailoring polymer characteristics. The activation mechanism and related polymerization mechanism remain elusive, despite extensive industrial and academic research. Here, we show that by varying the type and amount of metal-alkyl co-catalyst, we can tailor polymer properties around a single Cr/SiO2 Phillips catalyst formulation. Furthermore, we show that these different polymer properties exist in the early stages of polymerization. We have used conventional polymer characterization techniques, such as size exclusion chromatography (SEC) and 13C NMR, for studying the metal-alkyl co-catalyst effect on short-chain branching (SCB), long-chain branching (LCB) and molecular weight distribution (MWD) at the bulk scale. In addition, scanning transmission X-ray microscopy (STXM) was used as a synchrotron technique to study the PE formation in the early stages: allowing us to investigate the produced type of early-stage PE within one particle cross-section with high energy resolution and nanometer scale spatial resolution

Influence of Metal-Alkyls on Early-Stage Ethylene Polymerization over a Cr/SiO2 Phillips Catalyst: A Bulk Characterization and X-ray Chemical Imaging Study.

The Cr/SiO2 Phillips catalyst has taken a central role in ethylene polymerization since its invention in 1953. The uniqueness of this catalyst is related to its ability to produce broad molecular weight distribution (MWD) PE materials as well as that no co-catalysts are required to attain activity. Nonetheless, co-catalysts in the form of metal-alkyls can be added for scavenging poisons, enhancing catalyst activity, reducing the induction period, and tailoring polymer characteristics. The activation mechanism and related polymerization mechanism remain elusive, despite extensive industrial and academic research. Here, we show that by varying the type and amount of metal-alkyl co-catalyst, we can tailor polymer properties around a single Cr/SiO2 Phillips catalyst formulation. Furthermore, we show that these different polymer properties exist in the early stages of polymerization. We have used conventional polymer characterization techniques, such as size exclusion chromatography (SEC) and 13 C NMR, for studying the metal-alkyl co-catalyst effect on short-chain branching (SCB), long-chain branching (LCB) and molecular weight distribution (MWD) at the bulk scale. In addition, scanning transmission X-ray microscopy (STXM) was used as a synchrotron technique to study the PE formation in the early stages: allowing us to investigate the produced type of early-stage PE within one particle cross-section with high energy resolution and nanometer scale spatial resolution

Using Biomass Gasification Mineral Residue as Catalyst to Produce Light Olefins from CO, CO2, and H2 Mixtures

Invited for this month's cover is the group of Bert Weckhuysen at Utrecht University. The image shows how iron nanoparticles in a biomass gasification residue can convert CO, CO 2 , and H 2 mixtures into light olefins. The Research Article itself is available at 10.1002/cssc.202200436

Using Biomass Gasification Mineral Residue as Catalyst to Produce Light Olefins from CO, CO2, and H2 Mixtures

Gasification is a process to transform solids, such as agricultural and municipal waste, into gaseous feedstock for making transportation fuels. The so-called coarse solid residue (CSR) that remains after this conversion process is currently discarded as a process solid residue. In the context of transitioning from a linear to a circular society, the feasibility of using the solid process residue from waste gasification as a solid catalyst for light olefin production from CO, CO2, and H2 mixtures was investigated. This CSR-derived catalyst converted biomass-derived syngas, a H2-poor mixture of CO, CO2, H2, and N2, into methane (57 %) and C2–C4 olefins (43 %) at 450 °C and 20 bar. The main active ingredient of CSR was Fe, and it was discovered with operando X-ray diffraction that metallic Fe, present after pre-reduction in H2, transformed into an Fe carbide phase under reaction conditions. The increased formation of Fe carbides correlated with an increase in CO conversion and olefin selectivity. The presence of alkali elements, such as Na and K, in CSR-derived catalyst increased olefin production as well