Special Issue "Design of Heterogeneous Catalysts and Adsorbents"

A special issue of Catalysts (ISSN 2073-4344).

Deadline for manuscript submissions: closed (31 October 2020) | Viewed by 15114

Special Issue Editors

Prof. Dr. Thomas Turek
E-Mail Website
Guest Editor
Institute of Chemical and Electrochemical Process Engineering, Clausthal University of Technology, Leibnizstr 17, D-38678 Clausthal Zellerfeld, Germany
Interests: heterogeneous catalysts; adsorbents; gas-diffusion electrodes; reactor modeling; electrochemical cells
Prof. Dr. Dieter Bathen
E-Mail Website
Guest Editor
University Duisburg Essen, Lehrstuhl Therm Verfahrenstech, Lotharstr 1, D-47057 Duisburg, Germany
Interests: Adsorption, Diffusion, Air Pollution Control, Hazardous Chemicals
Prof. Dr. Gregor Dionys Wehinger
E-Mail Website
Guest Editor
Clausthal University of Technology, Institute of Chemical and Electrochemical Process Engineering, Leibnizstr 17, D-38678 Clausthal Zellerfeld, Germany
Interests: transport phenomena in chemical and electrochemical reactors; computational fluid dynamics (CFD) for reaction engineering; fixed-bed reactors; 3D printing
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Special Issue Information

Dear Colleagues,

Heterogeneous catalysts and adsorbents are tailor-made materials with many common requirements. Typically, they consist of porous structures to accommodate the highest possible surface area for adsorption and/or (electro-)catalytic transformation. Obviously, a high surface area corresponds to small particles and pore sizes, resulting in diffusion limitations with an often strongly negative influence on the effective catalytic activity, product selectivity, or dynamics of sorption processes. In addition to the inner structure of heterogeneous catalysts and adsorbents, their outer shape also plays an important role in their overall performance. Since the external geometry is relevant for reactor-specific aspects, such as pressure drop as well as external mass and heat transfer properties, it becomes evident that the design of heterogeneous catalysts and adsorbents is a challenging task requiring deep understanding of the occurring processes on multiple scales.

In this context, we invite you to submit your recent achievements—both theoretical and experimental—to this Special Issue as original research articles or reviews. Contributions on the development of new porous materials, characterization of pore structures, tailoring of pore sizes and pellet or electrode shapes, novel preparation methods for porous solids, or smart catalyst and adsorbent geometries for the improvement of reactor performance are greatly welcomed.


Prof. Dr. Thomas Turek
Prof. Dr. Dieter Bathen
Prof. Dr. Gregor Dionys Wehinger
Guest Editors

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Catalysts is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2200 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • heterogeneous catalysts
  • adsorbents
  • electrodes
  • catalyst design
  • catalyst preparation
  • pore size distribution
  • pellet shapes
  • pressure drop
  • structured catalysts

Published Papers (6 papers)

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Research

Article
Energetic Characterization of Faujasite Zeolites Using a Sensor Gas Calorimeter
Catalysts 2021, 11(1), 98; https://doi.org/10.3390/catal11010098 - 12 Jan 2021
Cited by 5 | Viewed by 1536
Abstract
In addition to the adsorption mechanism, the heat released during exothermic adsorption influences the chemical reactions that follow during heterogeneous catalysis. Both steps depend on the structure and surface chemistry of the catalyst. An example of a typical catalyst is the faujasite zeolite. [...] Read more.
In addition to the adsorption mechanism, the heat released during exothermic adsorption influences the chemical reactions that follow during heterogeneous catalysis. Both steps depend on the structure and surface chemistry of the catalyst. An example of a typical catalyst is the faujasite zeolite. For faujasite zeolites, the influence of the Si/Al ratio and the number of Na+ and Ca2+ cations on the heat of adsorption was therefore investigated in a systematic study. A comparison between a NaX (Sodium type X faujasite) and a NaY (Sodium type Y faujasite) zeolite reveals that a higher Si/Al ratio and therefore a smaller number of the cations in faujasite zeolites leads to lower loadings and heats. The exchange of Na+ cations for Ca2+ cations also has an influence on the adsorption process. Loadings and heats first decrease slightly at a low degree of exchange and increase significantly with higher calcium contents. If stronger interactions are required for heterogeneous catalysis, then the CaNaX zeolites must have a degree of exchange above 53%. The energetic contributions show that the highest-quality adsorption sites III and III’ make a contribution to the load-dependent heat of adsorption, which is about 1.4 times (site III) and about 1.8 times (site III’) larger than that of adsorption site II. Full article
(This article belongs to the Special Issue Design of Heterogeneous Catalysts and Adsorbents)
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Article
Iron Based Core-Shell Structures as Versatile Materials: Magnetic Support and Solid Catalyst
Catalysts 2021, 11(1), 72; https://doi.org/10.3390/catal11010072 - 07 Jan 2021
Cited by 6 | Viewed by 2233
Abstract
Core-shell materials are promising functional materials for fundamental research and industrial application, as their properties can be adapted for specific applications. In particular, particles featuring iron or iron oxide as core material are relevant since they combine magnetic and catalytic properties. The addition [...] Read more.
Core-shell materials are promising functional materials for fundamental research and industrial application, as their properties can be adapted for specific applications. In particular, particles featuring iron or iron oxide as core material are relevant since they combine magnetic and catalytic properties. The addition of an SiO2 shell around the core particles introduces additional design aspects, such as a pore structure and surface functionalization. Herein, we describe the synthesis and application of iron-based core-shell nanoparticles for two different fields of research that is heterogeneous catalysis and water purification. The iron-based core shell materials were characterized by transmission electron microscopy, as well as N2-physisorption, X-ray diffraction, and vibrating-sample magnetometer measurements in order to correlate their properties with the performance in the target applications. Investigations of these materials in CO2 hydrogenation and water purification show their versatility and applicability in different fields of research and application, after suitable individual functionalization of the core-shell precursor. For design and application of magnetically separable particles, the SiO2 shell is surface-functionalized with an ionic liquid in order to bind water pollutants selectively. The core requires no functionalization, as it provides suitable magnetic properties in the as-made state. For catalytic application in synthesis gas reactions, the SiO2-stabilized core nanoparticles are reductively functionalized to provide the catalytically active metallic iron sites. Therefore, [email protected]2 core-shell nanostructures are shown to provide platform materials for various fields of application, after a specific functionalization. Full article
(This article belongs to the Special Issue Design of Heterogeneous Catalysts and Adsorbents)
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Article
Porosity and Structure of Hierarchically Porous Ni/Al2O3 Catalysts for CO2 Methanation
Catalysts 2020, 10(12), 1471; https://doi.org/10.3390/catal10121471 - 16 Dec 2020
Cited by 20 | Viewed by 4046
Abstract
CO2 methanation is often performed on Ni/Al2O3 catalysts, which can suffer from mass transport limitations and, therefore, decreased efficiency. Here we show the application of a hierarchically porous Ni/Al2O3 catalyst for methanation of CO2. [...] Read more.
CO2 methanation is often performed on Ni/Al2O3 catalysts, which can suffer from mass transport limitations and, therefore, decreased efficiency. Here we show the application of a hierarchically porous Ni/Al2O3 catalyst for methanation of CO2. The material has a well-defined and connected meso- and macropore structure with a total porosity of 78%. The pore structure was thoroughly studied with conventional methods, i.e., N2 sorption, Hg porosimetry, and He pycnometry, and advanced imaging techniques, i.e., electron tomography and ptychographic X-ray computed tomography. Tomography can quantify the pore system in a manner that is not possible using conventional porosimetry. Macrokinetic simulations were performed based on the measures obtained by porosity analysis. These show the potential benefit of enhanced mass-transfer properties of the hierarchical pore system compared to a pure mesoporous catalyst at industrially relevant conditions. Besides the investigation of the pore system, the catalyst was studied by Rietveld refinement, diffuse reflectance ultraviolet-visible (DRUV/vis) spectroscopy, and H2-temperature programmed reduction (TPR), showing a high reduction temperature required for activation due to structural incorporation of Ni into the transition alumina. The reduced hierarchically porous Ni/Al2O3 catalyst is highly active in CO2 methanation, showing comparable conversion and selectivity for CH4 to an industrial reference catalyst. Full article
(This article belongs to the Special Issue Design of Heterogeneous Catalysts and Adsorbents)
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Article
Spray-Dried Ni Catalysts with Tailored Properties for CO2 Methanation
Catalysts 2020, 10(12), 1410; https://doi.org/10.3390/catal10121410 - 02 Dec 2020
Cited by 9 | Viewed by 1674
Abstract
A catalyst production method that enables the independent tailoring of the structural properties of the catalyst, such as pore size, metal particle size, metal loading or surface area, allows to increase the efficiency of a catalytic process. Such tailoring can help to make [...] Read more.
A catalyst production method that enables the independent tailoring of the structural properties of the catalyst, such as pore size, metal particle size, metal loading or surface area, allows to increase the efficiency of a catalytic process. Such tailoring can help to make the valorization of CO2 into synthetic fuels on Ni catalysts competitive to conventional fossil fuel production. In this work, a new spray-drying method was used to produce Ni catalysts supported on SiO2 and Al2O3 nanoparticles with tunable properties. The influence of the primary particle size of the support, different metal loadings, and heat treatments were applied to investigate the potential to tailor the properties of catalysts. The catalysts were examined with physical and chemical characterization methods, including X-ray diffraction, temperature-programmed reduction, and chemisorption. A temperature-scanning technique was applied to screen the catalysts for CO2 methanation. With the spray-drying method presented here, well-organized porous spherical nanoparticles of highly dispersed NiO nanoparticles supported on silica with tunable properties were produced and characterized. Moreover, the pore size, metal particle size, and metal loading can be controlled independently, which allows to produce catalyst particles with the desired properties. Ni/SiO2 catalysts with surface areas of up to 40 m2 g−1 with Ni crystals in the range of 4 nm were produced, which exhibited a high activity for the CO2 methanation. Full article
(This article belongs to the Special Issue Design of Heterogeneous Catalysts and Adsorbents)
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Article
Analysis and Model-Based Description of the Total Process of Periodic Deactivation and Regeneration of a VOx Catalyst for Selective Dehydrogenation of Propane
Catalysts 2020, 10(12), 1374; https://doi.org/10.3390/catal10121374 - 25 Nov 2020
Cited by 3 | Viewed by 1463
Abstract
This study intends to provide insights into various aspects related to the reaction kinetics of the VOx catalyzed propane dehydrogenation including main and side reactions and, in particular, catalyst deactivation and regeneration, which can be hardly found in combination in current literature. [...] Read more.
This study intends to provide insights into various aspects related to the reaction kinetics of the VOx catalyzed propane dehydrogenation including main and side reactions and, in particular, catalyst deactivation and regeneration, which can be hardly found in combination in current literature. To kinetically describe the complex reaction network, a reduced model was fitted to lab scale experiments performed in a fixed bed reactor. Additionally, thermogravimetric analysis (TGA) was applied to investigate the coking behavior of the catalyst under defined conditions considering propane and propene as precursors for coke formation. Propene was identified to be the main coke precursor, which agrees with results of experiments using a segmented fixed bed reactor (FBR). A mechanistic multilayer-monolayer coke growth model was developed to mathematically describe the catalyst coking. Samples from long-term deactivation experiments in an FBR were used for regeneration experiments with oxygen to gasify the coke deposits in a TGA. A power law approach was able to describe the regeneration behavior well. Finally, the results of periodic experiments consisting of several deactivation and regeneration cycles verified the long-term stability of the catalyst and confirmed the validity of the derived and parametrized kinetic models for deactivation and regeneration, which will allow model-based process development and optimization. Full article
(This article belongs to the Special Issue Design of Heterogeneous Catalysts and Adsorbents)
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Article
CFD Simulations of Radiative Heat Transport in Open-Cell Foam Catalytic Reactors
Catalysts 2020, 10(6), 716; https://doi.org/10.3390/catal10060716 - 26 Jun 2020
Cited by 12 | Viewed by 3247
Abstract
The heat transport management in catalytic reactors is crucial for the overall reactor performance. For small-scale dynamically-operated reactors, open-cell foams have shown advantageous heat transport characteristics over conventional pellet catalyst carriers. To design efficient and safe foam reactors as well as to deploy [...] Read more.
The heat transport management in catalytic reactors is crucial for the overall reactor performance. For small-scale dynamically-operated reactors, open-cell foams have shown advantageous heat transport characteristics over conventional pellet catalyst carriers. To design efficient and safe foam reactors as well as to deploy reliable engineering models, a thorough understanding of the three heat transport mechanisms, i.e., conduction, convection, and thermal radiation, is needed. Whereas conduction and convection have been studied extensively, the contribution of thermal radiation to the overall heat transport in open-cell foam reactors requires further investigation. In this study, we simulated a conjugate heat transfer case of a µCT based foam reactor using OpenFOAM and verified the model against a commercial computational fluid dynamics (CFD) code (STAR-CCM+). We further explicitly quantified the deviation made when radiation is not considered. We studied the effect of the solid thermal conductivity, the superficial velocity and surface emissivities in ranges that are relevant for heterogeneous catalysis applications (solid thermal conductivities 1–200 W m−1 K−1; superficial velocities 0.1–0.5 m s−1; surface emissivities 0.1–1). Moreover, the temperature levels correspond to a range of exo- and endothermal reactions, such as CO2 methanation, dry reforming of methane, and methane steam reforming. We found a significant influence of radiation on heat flows (deviations up to 24%) and temperature increases (deviations up to 400 K) for elevated temperature levels, low superficial velocities, low solid thermal conductivities and high surface emissivities. Full article
(This article belongs to the Special Issue Design of Heterogeneous Catalysts and Adsorbents)
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