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Bert M Weckhuysen - One of the best experts on this subject based on the ideXlab platform.
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matrix effects in a fluid catalytic cracking Catalyst Particle influence on structure acidity and accessibility
Chemistry: A European Journal, 2020Co-Authors: Marjolein E Z Velthoen, Alessandra Lucini Paioni, Iris E Teune, Marc Baldus, Bert M WeckhuysenAbstract:Matrix effects in a fluid catalytic cracking (FCC) Catalyst have been studied in terms of structure, accessibility, and acidity. An extensive characterization study into the structural and acidic properties of a FCC Catalyst, its individual components (i.e., zeolite H-Y, binder (boehmite/silica) and kaolin clay), and two model FCC Catalyst samples containing only two components (i.e., zeolite-binder and binder-clay) was performed at relevant conditions. This allowed the drawing of conclusions about the role of each individual component, describing their mutual physicochemical interactions, establishing structure-acidity relationships, and determining matrix effects in FCC Catalyst materials. This has been made possible by using a wide variety of characterization techniques, including temperature-programmed desorption of ammonia, infrared spectroscopy in combination with CO as probe molecule, transmission electron microscopy, X-ray diffraction, Ar physisorption, and advanced nuclear magnetic resonance. By doing so it was, for example, revealed that a freshly prepared spray-dried FCC Catalyst appears as a physical mixture of its individual components, but under typical riser reactor conditions, the interaction between zeolite H-Y and binder material is significant and mobile aluminum migrates and inserts from the binder into the defects of the zeolite framework, thereby creating additional Bronsted acid sites and restoring the framework structure.
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correlated x ray ptychography and fluorescence nano tomography on the fragmentation behavior of an individual Catalyst Particle during the early stages of olefin polymerization
Journal of the American Chemical Society, 2020Co-Authors: Koen W Bossers, Florian Meirer, Nic Friederichs, Roozbeh Valadian, Silvia Zanoni, Remy Peter Theresia Smeets, Jan Garrevoet, Bert M WeckhuysenAbstract:A combination of X-ray ptychography and X-ray fluorescence tomography (XRF) has been used to study the fragmentation behavior of an individual Ziegler-Natta Catalyst Particle, ∼40 μm in diameter, in the early stages of propylene polymerization with submicron spatial resolution. The electron density signal obtained from X-ray ptychography gives the composite phases of the Ziegler-Natta Catalyst Particle fragments and isotactic polypropylene, while 3-D XRF visualizes multiple isolated clusters, rich in Ti, of several microns in size. The radial distribution of Ti species throughout the polymer-Catalyst composite Particle shows that the continuous bisection fragmentation model is the main contributor to the fragmentation pathway of the Catalyst Particle as a whole. Furthermore, within the largest Ti clusters the fragmentation pathway was found to occur through both the continuous bisection and layer-by-layer models. The fragmentation behavior of polyolefin Catalysts was for the first time visualized in 3-D by directly imaging and correlating the distribution of the Ti species to the polymer-Catalyst composite phase.
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operando monitoring of temperature and active species at the single Catalyst Particle level
Nature Catalysis, 2019Co-Authors: Thomas Hartman, Robin G Geitenbeek, Gareth T Whiting, Bert M WeckhuysenAbstract:The development of improved Catalysts requires insights into the relationship between catalytic activity and Catalyst structure, including the underlying reaction mechanism. Here, we demonstrate a unique set of Catalyst extrudate sensors that allow for the simultaneous detection of local temperature by luminescence thermometry, and of surface species by shell-isolated nanoParticle-enhanced Raman spectroscopy. This sensing approach was applied to the characterization of direct conversion of syngas into hydrocarbons and C2+ oxygenates over supported Rh and RhFe Catalysts. Luminescence thermometry demonstrated a mismatch between the set temperature and the local Catalyst temperature, with variations up to 40 °C. Furthermore, by investigating the surface species on varying extrudate and Catalyst compositions, we identified tilted carbonyl species on the Rh/SiO2 interface that are probable precursors for the hydrogen-assisted CO dissociation. The implementation of extrudate Catalyst sensors as a characterization tool provides a unique approach towards the further understanding of the relevant parameters in catalysis. Multi-modal approaches to simultaneously characterize different aspects of a reaction in situ are not readily accessible. Here, Catalyst extrudates equipped with both luminescence thermometry and Raman spectroscopy sensors are introduced, providing an in-depth picture for the conversion of syngas on a supported rhodium Catalyst.
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integrated transmission electron and single molecule fluorescence microscopy correlates reactivity with ultrastructure in a single Catalyst Particle
Angewandte Chemie, 2018Co-Authors: Frank C Hendriks, Florian Meirer, Samanbir Kalirai, Eelco T C Vogt, Sajjad Mohammadian, Zoran Ristanovic, Pieter C A Bruijnincx, Hans C Gerritsen, Bert M WeckhuysenAbstract:Establishing structure–activity relationships in complex, hierarchically structured nanomaterials, such as fluid catalytic cracking (FCC) Catalysts, requires characterization with complementary, correlated analysis techniques. An integrated setup has been developed to perform transmission electron microscopy (TEM) and single-molecule fluorescence (SMF) microscopy on such nanostructured samples. Correlated structure–reactivity information was obtained for 100 nm thin, microtomed sections of a single FCC Catalyst Particle using this novel SMF-TEM high-resolution combination. High reactivity in a thiophene oligomerization probe reaction correlated well with TEM-derived zeolite locations, while matrix components, such as clay and amorphous binder material, were found not to display activity. Differences in fluorescence intensity were also observed within and between distinct zeolite aggregate domains, indicating that not all zeolite domains are equally active.
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single molecule fluorescence microscopy reveals local diffusion coefficients in the pore network of an individual Catalyst Particle
Journal of the American Chemical Society, 2017Co-Authors: Frank C Hendriks, Florian Meirer, Eelco T C Vogt, Zoran Ristanovic, Pieter C A Bruijnincx, Alexey V Kubarev, Maarten B J Roeffaers, Bert M WeckhuysenAbstract:We used single-molecule fluorescence microscopy to study self-diffusion of a feedstock-like probe molecule with nanometer accuracy in the macropores of a micrometer-sized, real-life fluid catalytic cracking (FCC) Particle. Movies of single fluorescent molecules allowed their movement through the pore network to be reconstructed. The observed tracks were classified into three different states by machine learning and all found to be distributed homogeneously over the Particle. Most probe molecules (88%) were immobile, with the molecule most likely being physisorbed or trapped; the remainder was either mobile (8%), with the molecule moving inside the macropores, or showed hybrid behavior (4%). Mobile tracks had an average diffusion coefficient of D = 8 × 10–14 ± 1 × 10–13 m2 s–1, with the standard deviation thought to be related to the large range of pore sizes found in FCC Particles. The developed methodology can be used to evaluate, quantify and map heterogeneities in diffusional properties within complex ...
Florian Meirer - One of the best experts on this subject based on the ideXlab platform.
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correlated x ray ptychography and fluorescence nano tomography on the fragmentation behavior of an individual Catalyst Particle during the early stages of olefin polymerization
Journal of the American Chemical Society, 2020Co-Authors: Koen W Bossers, Florian Meirer, Nic Friederichs, Roozbeh Valadian, Silvia Zanoni, Remy Peter Theresia Smeets, Jan Garrevoet, Bert M WeckhuysenAbstract:A combination of X-ray ptychography and X-ray fluorescence tomography (XRF) has been used to study the fragmentation behavior of an individual Ziegler-Natta Catalyst Particle, ∼40 μm in diameter, in the early stages of propylene polymerization with submicron spatial resolution. The electron density signal obtained from X-ray ptychography gives the composite phases of the Ziegler-Natta Catalyst Particle fragments and isotactic polypropylene, while 3-D XRF visualizes multiple isolated clusters, rich in Ti, of several microns in size. The radial distribution of Ti species throughout the polymer-Catalyst composite Particle shows that the continuous bisection fragmentation model is the main contributor to the fragmentation pathway of the Catalyst Particle as a whole. Furthermore, within the largest Ti clusters the fragmentation pathway was found to occur through both the continuous bisection and layer-by-layer models. The fragmentation behavior of polyolefin Catalysts was for the first time visualized in 3-D by directly imaging and correlating the distribution of the Ti species to the polymer-Catalyst composite phase.
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integrated transmission electron and single molecule fluorescence microscopy correlates reactivity with ultrastructure in a single Catalyst Particle
Angewandte Chemie, 2018Co-Authors: Frank C Hendriks, Florian Meirer, Samanbir Kalirai, Eelco T C Vogt, Sajjad Mohammadian, Zoran Ristanovic, Pieter C A Bruijnincx, Hans C Gerritsen, Bert M WeckhuysenAbstract:Establishing structure–activity relationships in complex, hierarchically structured nanomaterials, such as fluid catalytic cracking (FCC) Catalysts, requires characterization with complementary, correlated analysis techniques. An integrated setup has been developed to perform transmission electron microscopy (TEM) and single-molecule fluorescence (SMF) microscopy on such nanostructured samples. Correlated structure–reactivity information was obtained for 100 nm thin, microtomed sections of a single FCC Catalyst Particle using this novel SMF-TEM high-resolution combination. High reactivity in a thiophene oligomerization probe reaction correlated well with TEM-derived zeolite locations, while matrix components, such as clay and amorphous binder material, were found not to display activity. Differences in fluorescence intensity were also observed within and between distinct zeolite aggregate domains, indicating that not all zeolite domains are equally active.
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single molecule fluorescence microscopy reveals local diffusion coefficients in the pore network of an individual Catalyst Particle
Journal of the American Chemical Society, 2017Co-Authors: Frank C Hendriks, Florian Meirer, Eelco T C Vogt, Zoran Ristanovic, Pieter C A Bruijnincx, Alexey V Kubarev, Maarten B J Roeffaers, Bert M WeckhuysenAbstract:We used single-molecule fluorescence microscopy to study self-diffusion of a feedstock-like probe molecule with nanometer accuracy in the macropores of a micrometer-sized, real-life fluid catalytic cracking (FCC) Particle. Movies of single fluorescent molecules allowed their movement through the pore network to be reconstructed. The observed tracks were classified into three different states by machine learning and all found to be distributed homogeneously over the Particle. Most probe molecules (88%) were immobile, with the molecule most likely being physisorbed or trapped; the remainder was either mobile (8%), with the molecule moving inside the macropores, or showed hybrid behavior (4%). Mobile tracks had an average diffusion coefficient of D = 8 × 10–14 ± 1 × 10–13 m2 s–1, with the standard deviation thought to be related to the large range of pore sizes found in FCC Particles. The developed methodology can be used to evaluate, quantify and map heterogeneities in diffusional properties within complex ...
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relating structure and composition with accessibility of a single Catalyst Particle using correlative 3 dimensional micro spectroscopy
Nature Communications, 2016Co-Authors: Yijin Liu, Florian Meirer, Courtney M Krest, Samuel M Webb, Bert M WeckhuysenAbstract:To understand how hierarchically structured functional materials operate, analytical tools are needed that can reveal small structural and chemical details in large sample volumes. Often, a single method alone is not sufficient to get a complete picture of processes happening at multiple length scales. Here we present a correlative approach combining three-dimensional X-ray imaging techniques at different length scales for the analysis of metal poisoning of an individual Catalyst Particle. The correlative nature of the data allowed establishing a macro-pore network model that interprets metal accumulations as a resistance to mass transport and can, by tuning the effect of metal deposition, simulate the response of the network to a virtual ageing of the Catalyst Particle. The developed approach is generally applicable and provides an unprecedented view on dynamic changes in a material's pore space, which is an essential factor in the rational design of functional porous materials.
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fib sem tomography probes the mesoscale pore space of an individual catalytic cracking Particle
ACS Catalysis, 2016Co-Authors: D Matthijs A De Winter, Florian Meirer, Bert M WeckhuysenAbstract:The overall performance of a Catalyst Particle strongly depends on the ability of mass transport through its pore space. Characterizing the three-dimensional structure of the macro- and mesopore space of a Catalyst Particle and establishing a correlation with transport efficiency is an essential step toward designing highly effective Catalyst Particles. In this work, a generally applicable workflow is presented to characterize the transport efficiency of individual Catalyst Particles. The developed workflow involves a multiscale characterization approach making use of a focused ion beam-scanning electron microscope (FIB-SEM). SEM imaging is performed on cross sections of 10.000 μm2, visualizing a set of Catalyst Particles, while FIB-SEM tomography visualized the pore space of a large number of 8 μm3 cubes (subvolumes) of individual Catalyst Particles. Geometrical parameters (porosity, pore connectivity, and heterogeneity) of the material were used to generate large numbers of virtual 3D volumes resembling...
Feng Ding - One of the best experts on this subject based on the ideXlab platform.
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Catalyst Particle size dependent carbon nanotube cloning
'Elsevier BV', 2021Co-Authors: Feng DingAbstract:The single walled carbon nanotube (SWCNT) cloning or its seeded growth with a Catalyst Particle docked on one of its ends was proposed as the ultimate solution for chirality-specific SWCNT synthesis and, therefore, revealing the effect of Catalyst Particle size on the robustness of the SWCNT cloning is crucial for experimental designs. Through systematic atomic simulations, we have clearly demonstrated that the robustness of SWCNT cloning depends on both the chiral angle of the SWCNT and the ratio of the diameters between the SWCNT and the docked Catalyst Particle. The zigzag (ZZ) or near ZZ SWCNTs are highly sensitive to the size of the docked Catalyst Particle. A small change of the Catalyst Particle size could lead to a variation of the SWCNT's chirality. In contrast, armchair (AC) or near-AC SWCNTs are less sensitive to the size of the docked Catalyst Particle and able to maintain their original chiralities within ∼30% variation of the Catalyst Particle size. This study greatly deepens our understanding of SWCNT's growth mechanism and provides a quantitative guidance for SWCNT cloning.11Nsciescopu
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How a Solid Catalyst Determines the Chirality of the Single-Wall Carbon Nanotube Grown on It
2019Co-Authors: Xiao Wang, Feng DingAbstract:Although the growth of single-wall carbon nanotubes (SWCNTs) with a chirality selectivity up to 90% has been successfully achieved using solid Catalysts (Yang, F. Nature, 2014, 510, 522; Zhang, S.; Nature, 2017, 543, 234, etc.), the underlying mechanism that governs the chirality selection is far from clear. Here we propose a mechanism to understand how a solid Catalyst Particle determines the structure of the SWCNT grown on it. The mechanism has to satisfy three criteria: (i) thermodynamic selection of SWCNTs that possess a structural symmetry the same as that of the Catalyst surface; (ii) kinetic elimination of the achiral SWCNTs with extremely low growth rates; (iii) rough control over the Catalyst Particle size leads to SWCNTs with only one or a few dominant chiralities. Besides the deep understanding on the mechanisms of experimentally synthesized (12, 6) and (8, 4) SWCNTs, the preference growth of other SWCNTs of the (2n, n) family, such as the (10, 5) or (6, 3) SWCNTs, by using Catalyst surface with a 5- or 3-fold symmetry is predicted. Such a simple three-criteria mechanism deepens our understanding of the selective growth of SWCNTs and provides a guideline for Catalyst design for controlled SWCNT synthesis
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How a Solid Catalyst Determines the Chirality of the Single-Wall Carbon Nanotube Grown on It
AMER CHEMICAL SOC, 2019Co-Authors: Xiao Wang, Feng DingAbstract:Although the growth of single-wall carbon nanotubes (SWCNTs) with a chirality selectivity up to 90% has been successfully achieved using solid Catalysts (Yang, F. et al. Nature, 2014, 510, 522; Zhang, S.; et al. Nature, 2017, 543, 234, etc.), the underlying mechanism that governs the chirality selection is far from clear. Here we propose a mechanism to understand how a solid Catalyst Particle determines the structure of the SWCNT grown on it. The mechanism has to satisfy three criteria: (i) thermodynamic selection of SWCNTs that possess a structural symmetry the same as that of the Catalyst surface; (ii) kinetic elimination of the achiral SWCNTs with extremely low growth rates; (iii) rough control over the Catalyst Particle size leads to SWCNTs with only one or a few dominant chiralities. Besides the deep understanding on the mechanisms of experimentally synthesized (12, 6) and (8, 4) SWCNTs, the preference growth of other SWCNTs of the (2n, n) family, such as the (10, 5) or (6, 3) SWCNTs, by using Catalyst surface with a 5- or 3-fold symmetry is predicted. Such a simple three-criteria mechanism deepens our understanding of the selective growth of SWCNTs and provides a guideline for Catalyst design for controlled SWCNT synthesis. © 2019 American Chemical Societ
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dependence of swnt growth mechanism on temperature and Catalyst Particle size bulk versus surface diffusion
arXiv: Materials Science, 2006Co-Authors: Feng Ding, Arne Rosen, Kim BoltonAbstract:MD simulations reveal that many aspects of SWNT nucleation and growth from solid and liquid metal Particles are similar. In both cases graphitic islands lift off the cluster surface to form caps that grow into SWNTs. However, in contrast to liquid Particles, where C atoms primarily diffuse into the bulk of the cluster before adding to the growing SWNT, incorporation of C into SWNTs on solid Particles occurs predominantly via surface diffusion.
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molecular dynamics study of the Catalyst Particle size dependence on carbon nanotube growth
arXiv: Materials Science, 2006Co-Authors: Feng Ding, Arne Rosen, Kim BoltonAbstract:The molecular dynamics method, based on an empirical potential energy surface, was used to study the effect of Catalyst Particle size on the growth mechanism and structure of single-walled carbon nanotubes (SWNTs). The temperature for nanotube nucleation (800-1100 K), which occurs on the surface of the cluster, is similar to that used in Catalyst chemical vapor deposition experiments, and the growth mechanism, which is described within the vapor-liquid-solid model, is the same for all cluster sizes studied here (iron clusters containing between 10 and 200 atoms were simulated). Large Catalyst Particles, that contain at least 20 iron atoms, nucleate SWNTs and have a far better tubular structure than SWNTs nucleated from smaller clusters. In addition, the SWNTs that grow from the larger clusters have diameters that are similar to the cluster diameter, whereas the smaller clusters, which have diameters less than 0.5 nm, nucleate nanotubes that are approximately 0.6-0.7 nm in diameter. This is in agreement with the experimental observations that SWNT diameters are similar to the Catalyst Particle diameter, and that the narrowest free-standing SWNT is 0.6-0.7 nm.
L A Chernozatonskii - One of the best experts on this subject based on the ideXlab platform.
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correlation between metal Catalyst Particle size and carbon nanotube growth
Chemical Physics Letters, 2002Co-Authors: E F Kukovitsky, S G Lvov, N A Sainov, V A Shustov, L A ChernozatonskiiAbstract:Abstract The dependence of carbon nanotube diameters upon the size of nickel Catalyst Particles supported on amorphous carbon films was studied. Nanotubes were catalytically grown at different temperatures to elucidate the effect of temperature. The transformation of nanotube-growth mechanism takes place in the range 700–800 °C as evident from Particle size–nanotube diameter relations, tip Particles and nanotube morphologies. At low temperature (700 °C), the nanotube growth is conducted through solid tip Catalyst Particles. At 800 °C, nanotubes grow via liquid Catalyst Particles by extrusion mode. Low-temperature tube diameters reproduce essential features of original Particle size distribution. In contrast, high-temperature tubes exhibit universal Gauss-like diameter distribution irrespective of Catalyst Particle sizes.
Kim Olto - One of the best experts on this subject based on the ideXlab platform.
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molecular dynamics study of the Catalyst Particle size dependence on carbon nanotube growth
Journal of Chemical Physics, 2004Co-Authors: Arne Rose, Kim OltoAbstract:The molecular dynamics method, based on an empirical potential energy surface, was used to study the effect of Catalyst Particle size on the growth mechanism and structure of single-walled carbon nanotubes (SWNTs). The temperature for nanotube nucleation (800–1100 K), which occurs on the surface of the cluster, is similar to that used in Catalyst chemical vapor deposition experiments, and the growth mechanism, which is described within the vapor-liquid-solid model, is the same for all cluster sizes studied here (iron clusters containing between 10 and 200 atoms were simulated). Large Catalyst Particles, which contain at least 20 iron atoms, nucleate SWNTs that have a far better tubular structure than SWNTs nucleated from smaller clusters. In addition, the SWNTs that grow from the larger clusters have diameters that are similar to the cluster diameter, whereas the smaller clusters, which have diameters less than 0.5 nm, nucleate nanotubes that are ≈0.6–0.7 nm in diameter. This is in agreement with the expe...