Porous Support Materials Research Articles

Synthesis and characterization of SO42-/KCC-1 catalyst as an alternative candidate for simultaneous esterification and transesterification reactions

Sulfate-impregnated acid catalysts can be used to replace conventional homogeneous base catalysts which are very dangerous, corrosive and environmentally unfriendly. Sulfate impregnation on porous support material will increase the surface area of the catalyst. The use of KCC-1 as a supporting material can produce catalysts with excellent properties. The method used in this research is the hydrothermal method for the synthesis of KCC-1 and the direct impregnation method for the synthesis of SO42-/KCC-1. Characterization of the resulting material using X-ray diffraction (XRD), FTIR spectrometer, and low temperature emission scanning electron microscope (SEM). The characterization results showed that the synthesis of KCC-1 and SO42-/KCC-1 had been successfully carried out. This is evidenced by the formation of amorphous silica, the presence of peaks of silica and sulfate groups, and scanning electron microscope images showing nano-sized materials.©2021 JNSMR UIN Walisongo. All rights reserved.

Chromatographic characterization of a silica hydride-based amide stationary phase.

An amide phase based on a porous silica hydride support material is tested for retention characteristics in both the reversed-phase and aqueous normal-phase modes. A series of retention maps (capacity factor vs. mobile phase composition) were obtained using reference standards of varying analyte sizes, functionalities, and polarities. An assessment of the specific column selectivity is made and classes of compounds are identified that show high potential for effective retention, resolution, and efficiency when using amide functionalized silica hydride columns for reversed-phase and aqueous-normal phase separation. Several practical applications are presented that illustrate the capabilities of this particular column format.

Fatty amines/oxidized multi-walled carbon nanotubes phase change composites with enhanced thermal properties

The development of phase change composites with both high latent heat and better thermal conductivity is of great importance for thermal energy or solar energy storage applications. Here, three kinds of oxidized multi-walled carbon nanotubes (p-MWCNTs, a-MWCNTs and c-MWCNTs) prepared though multiple oxidations with different oxygen contents were used as porous support materials for construction of phase change composites, in which two kinds of fatty amines (FAs), e.g. tetradecylamine (TDA) and octadecylamine (ODA), were employed as organic phase change materials (PCMs). The thermal conductivity of FAs/oxidized-MWCNTs phase change composites increased with the increase of the oxygen content of oxidized-MWCNTs. As a kind of novel phase change composites, FAs/c-MWCNTs have excellent thermal stability and energy storage density (latent heat up to 273.8 kJ kg−1 for ODA/3%c-MWCNTs), which can compete or superior to those conventional organic PCMs-based (paraffin, PEG, etc.) composites. Benefiting from the merits mentioned above, the FAs/c-MWCNTs phase change composites may have great potentials for real energy-saving applications.

Alginate-chitosan Hydrogel Patch with Beta-glucan Nanoemulsion for Antibacterial Applications

Natural polymer materials have high biocompatibility and are not toxic because they can decompose into metabolites in the body; thus, they are widely used as medical polymer materials as well as porous support materials. As a biopolymer, alginate has a negative charge; in contrast, chitosan has a positive charge. Therefore, when the two substances are mixed, they form a relatively stable structure by ionic bonding. Beta-glucan is known to contribute to material stability and have high skin penetration, skin moisturizing and soothing effects, and burn and wound healing effects. In this study, antimicrobial activity was assessed by preparing alginate-chitosan hydrogel patches containing beta-glucan nanoemulsions. This could contribute to the development of wound dressings with antibacterial properties.

General Synthesis of Secondary Alkylamines by Reductive Alkylation of Nitriles by Aldehydes and Ketones.

The development of C−N bond formation reactions is highly desirable due to their importance in biology and chemistry. Recent progress in 3d metal catalysis is indicative of unique selectivity patterns that may permit solving challenges of chemical synthesis. We report here on a catalytic C−N bond formation reaction—the reductive alkylation of nitriles. Aldehydes or ketones and nitriles, all abundantly available and low‐cost starting materials, undergo a reductive coupling to form secondary alkylamines and inexpensive hydrogen is used as the reducing agent. The reaction has a very broad scope and many functional groups, including hydrogenation‐sensitive examples, are tolerated. We developed a novel cobalt catalyst, which is nanostructured, reusable, and easy to handle. The key seems the earth‐abundant metal in combination with a porous support material, N‐doped SiC, synthesized from acrylonitrile and a commercially available polycarbosilane.

Research progress of mesoporous silica-based composite phase change materials

Increasing concerns surrounding the rising global energy demand has forced humans to look for alternative energy sources such as the development and utilization of natural gas and nuclear energy, or to increase the efficiency of energy use, thereby optimizing the use of energy. Improving energy efficiency is an effective method that can quickly and efficiently reduce the energy demand and supply gap. Furthermore, developing new technologies for energy storage and energy saving is an effective way to solve the energy crisis, which is of great significance for the sustainable development of energy. Latent heat storage has become a popular research topic owing to its large energy storage density and small temperature changes during energy storage and its excellent thermal stability and high safety. Currently, phase-change materials have been widely used in solar heating systems, air conditioning systems, thermally regulated textiles, energy-efficient building construction, temperature-controlled greenhouses and other fields. The development of phase-change energy storage technology is significant for promoting the development of alternative energy sources and improving energy efficiency. However, phase change materials are prone to liquid leakage during the solid-liquid phase transition, which limits their application. To solve this problem, researchers have started introducing porous support materials to phase-change materials. Porous support materials have attracted extensive research attention in recent years owing to their outstanding properties such as high specific surface area, large pore volume, and low density. Porous support materials can absorb phase-change materials in their pores through the physical adsorption phenomena such as capillary action and interfacial tension, and thereby gradually develop into important substrates for phase-change material encapsulation. Inorganic materials are used as carriers for phase change energy storage materials. Compared with organic carrier materials, inorganic carrier materials have higher mechanical strength, flame retardancy and thermal conductivity, which can reduce the production cost of phase-change energy storage materials, and have a high research value. Mesoporous silica materials have good physical and chemical stability, biocompatibility, flame retardancy, low toxicity, corrosion resistance, controllable size, adjustable surface morphology and high specific surface area. They can comprehensively improve the performance of various aspects of phase change composites and broaden the application space of phase change energy storage materials. In this review, the effects of pore size, pore structure, and pore surface properties on the crystallization behavior of phase change materials in mesoporous silica carriers developed in recent years were comprehensively analyzed, and prospects of research methods for heat storage efficiency were explored.

Salt‐recrystallization preparation of metal organic framework derived porous carbon support for highly‐efficient proton exchange membrane fuel cell

We report a novel porous and high-specific surface area carbon support material (C-framework) for PEMFC by the salt-recrystallization-fixing HKUST-1 template. We believe this will be a universal method to convert high-temperature unstable MOF materials, such as HKUST-1. NaCl crystals serve as completely closed nanoreactors, which facilitate graphitization and structure inheritance. Electrochemical evaluation showed that the C-framework loaded with Pt nanoparticles exhibits high ORR activity and excellent electrochemical performance in acidic electrolytes. The PEMFC performance reached a maximum power density of 780 mW/cm2 under the H2/air testing condition in ultra-low Pt loading (cathode 0.1 mg/cm2).

Rapid analysis of polycyclic aromatic hydrocarbons.

Polycyclic aromatic hydrocarbons are a continuing environmental and health concern. The analytical methods developed to analyze this class of compounds have relied on reversed phase liquid chromatography and are often on the order of tens of minutes. Reduction in analysis times through the application of sub-2 μm fully porous and superficially porous support materials can increase the throughput of these LC separations. Herein, we demonstrate similar selectivity between a fully porous 1.8 μm and a 2.7 μm superficially porous material. Separations were individually developed with in silico modeling for a given flow rate determined by the fully porous column's backpressure requirements. Since the 2.7 μm superficially porous materials inherently require less backpressure to achieve similar levels of efficiency as the 1.8 μm fully porous materials, a marked increase in throughput is possible with elevated flow rates. Good resolution for a standard 16-component sample mixture is demonstrated in a sub-minute separation.

Influence of Local Environments in Pores of Different Size on the Catalytic Liquid-Phase Oxidation of d-Glucose by Au Nanoparticles Supported on Nanoporous Carbon

Inorganic nanoparticles (NPs) dispersed on the surface of porous support materials play a dominant role in heterogeneous catalysis. Especially in liquid-phase catalysis, support materials may lead to nanoconfinement of solvent molecules, and the solute and can thus influence their local concentration and structure. This further affects the surface coverage of nanoparticles with reactants and other species, but these influences remain poorly understood—in particular under experimental conditions. Nanoconfinement effects are of particular importance in reactions such as liquid-phase oxidation with oxygen, i.e., when one reactant is a gas that has to be dissolved before reaching the NP surface. The significant influence of the pore structure of carbon materials on the catalytic activity of gold nanoparticles (AuNPs) with nearly similar size (4.1–4.7 nm) is demonstrated in this study. Experimental results on the oxidation of d-glucose with molecular oxygen in aqueous solution show that the “apparent catalytic activity” of AuNPs is a function of the carbon pore size and geometry. The architecture of the carbon pore size is determining the local concentration of reactants. Nanoconfinement of water in carbon nanopores can lead to enhanced solubility of reactants and therefore to their higher local concentration in proximity to the catalytically active sites. In contrast to purely microporous carbon support with the less wettable internal surface without any detectable catalytic activity, AuNPs supported on mesoporous carbons show a much higher metal time yield between 3.8 and 60.6 molGlc min–1 molAu–1, depending on volume and geometry of the mesopores.

Sustainability in Catalytic Cyclohexane Oxidation: The Contribution of Porous Support Materials

The development of green and sustainable protocols for synthetic routes is a growing area of research in chemistry worldwide. The development of sustainable processes and products through innovative catalytic materials and technologies, that allow a better use of resources, is undoubtedly a very important issue facing research chemists today. Environmentally and economically advanced catalytic processes for selective alkane oxidations reactions, as is the case of cyclohexane oxidation, are now focused on catalysts’ stability and their reuse, intending to overcome the drawbacks posed by current homogeneous systems. The aim of this short review is to highlight recent contributions in heterogeneous catalysis regarding porous support materials to be applied to cyclohexane oxidation reaction. Different classes of porous materials are covered, from carbon nanomaterials to zeolites, mesoporous silicas, and metal organic frameworks. The role performed by the materials to be used as supports towards an enhancement of the activity/selectivity of the catalytic materials and the ability of recycling and reuse in consecutive catalytic cycles is highlighted.

Solvent and pH-stable poly(2,5-benzimidazole) (ABPBI) based UF membranes: Preparation and characterizations

Poly(2,5-benzimidazole), commonly known as ABPBI, is an excellent thermo-chemically stable polymer that is widely evaluated as a proton exchange membrane material in a fuel cell. Its niche intrinsic characteristics could be highly useful in the membrane preparation for various separation applications, especially under harsher environments. To gain insights towards this feasibility, ABPBI based supported membranes were prepared by phase inversion method. Effects of the nonwoven porous support material (polypropylene/polyester), non-solvent (water/0.5 N NaOH) and polymer concentration (6 or 4 wt%) on the membrane properties (water flux, rejection and porosity) were investigated. The stability of these membranes towards common organic solvents, concentrated acid (25 N H2SO4), base (2.5 N NaOH) and an autoclave condition was analyzed. ABPBI membrane showed a pore collapse after drying. In order to avoid this, the glycerol treatment was not only found to be suitable but also repeatable, without significant deviations in the water flux.

Self-Supported Hierarchical Porous Metallic Aerogels Synthesized Via Spontaneous Methods As High Performance Electrocatalysts

Metal nanomaterials are one major class of enablers for clean technology. For example, they play vital roles as electrocatalysts in fuel cells and electrochemical sensors. Despite great efforts from world-wide, the commercialization of metal electrocatalysts based devices still meet critical challenges including high cost, insufficient activity, and low durability. Therefore, it is of great interests to explore the factors that influence the electrocatalytic activity and durability of the metallic electrocatalysts, and to develop simple strategies to generate high performance metallic electrocatalysts. We have developed facile spontaneous methods including one-step spontaneous gelation method in combination with galvanic replacement reaction and fabricated a series of self supported metallic aerogels with extended metal backbone nanostructures of nanowire or nanotubular networks and very high surface area and large porosity.[1-5] In addition, supported metal nanostructure have been also obtained and self-assembled on electrodes.[6,7] These materials were utilized as high performance electrocatalysts in fuel cell anode and cathode reactions and in electrochemical sensors. Our results show that porous structure, metal composition and support material have great influences on the electrocatalytic activity of metal nanomaterials. Acknowledgements The authors acknowledge the financial supports from the 100Top Talents Program - Sun Yat-sen University (P.R. China), theEuropean Commission (Brussels) for the Marie Curie Research Fel-lowship for Transfer of Knowledge (No. MTKD-CT-2006-042637)and from the Finnish Cultural Foundation. Financial supportsfrom the Alexander von Humboldt Foundation and the EuropeanResearch Council (ERC-2013-AdG AEROCAT) a gratefully acknowl-edged. References W. Liu, A.-K. Herrmann, D. Geiger, L. Borchardt, F. Simon, S. Kaskel, N. Gaponik and A. Eychmüller, Angew. Chem. Int. Ed. 51, 5743 -5747 (2012).A. Eychmüller, W. Liu, J. Yuan, N. Gaponik, A.-K. Herrmann, T. J. Schmidt, P. Rodriguez, A. Rabis, A. Foelske-Schmitz, R. Kötz, European Patent EP000002690693(A1) (2014)W. Liu, P. Rodriguez, L. Borchardt, A. Foelske, J. Yuan, A.-K. Herrmann, D. Geiger, Z. Zheng, S. Kaskel, T. J. Schmidt, and A. Eychmüller, Angew. Chem. Int. Ed. 52, 9849 -9852 (2013).W. Liu, A.-K. Herrmann, N. C. Bigall, P. Rodriguez, D. Wen, M. Oezaslan, T. J. Schmidt, N. Gaponik, A. Eychmüller, Acc. Chem. Res. 48, 154-162 (2015).W. Liu, D. Haubold, B. Rutkowski, M. Oschatz, R. Hübner, M. Werheid, C. Ziegler, L. Sonntag, S. Liu, Z. Zheng, A.-K. Herrmann, D. Geiger, B. Terlan, T. Gemming, L. Borchardt, S. Kaskel, A.Czyrska-Filemonowicz, and A. Eychmüller, Chem. Mater. 28, 6477-6483 (2016).W. Liu, E. Repo, M. Heikkilä, M. Leskelä, M. Sillanpää, Nanotechnology 21, 395604 (2010).W. Liu, K. Hiekel, R. Hübner, H. Sun, A. Ferancova, M. Sillanpää, Sens. Actuators B: Chem. 255, 1325-1334 (2018). Figure 1

Durabilty of Pt-Based Alloy Nanoparticles Supported on Functionalized Carbon Materials for the ORR – Tuning the Interaction between Particles and Support Material

In the last decades, proton exchange membrane fuel cells (PEMFC) have attracted large attention as promising renewable and clean technology for energy conversion. Designing nanomaterials with the aim to improve their electrocatalytic performance and long-term durability is still a critical challenge. Today´s PEMFC research has focused on Pt-based alloy nanoparticles combined with high surface area carbon materials due to its improved activity and stability for the ORR compared to pure Pt/C.[1,2,3] Although many studies have focused on the relations between the structural and chemical properties of the catalytically active metal nanoparticles and their catalytic ORR performance, the interactions of these nanoparticles with the carbon substrate have been rarely investigated up to date. In particular, the immobilization and stabilization of the nanoparticles on the support material have a strong influence on the long-term durability of the ORR catalysts. Therefore, one crucial point is the functionalization of the carbon support with hydroxide and carboxylate groups which seems to improve nucleation and dispersion of the Pt alloy nanoparticles; on the other hand, these oxygen-containing surface groups can accelerate the carbon corrosion associated with particle detachment during the potential cycling. Therefore, another strategy is the introduction of hetero-atoms as N-C-, C-B, C-F and C-S-bonds into the carbon framework improving their electrochemical oxidation resistance.[4,5,6,7]One target of this work is the stabilization of the carbon support material by functionalization to prevent carbon corrosion under the operating fuel cell conditions. We modified the morphology, structure and chemical properties of the porous carbon materials by using different methods such as acid treatment or thermal treatment in a reactive gas atmosphere. On the other hand, we optimized the design of Pt-based alloy (Pt-Ni, Pt-Co) nanoparticles supported on these functionalized porous carbon support materials. The properties and behavior of these materials are monitored by using high resolution transmission electron microscopy (HR-TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDX) and X-ray absorption spectroscopy (XAS). The electrochemical stability and durability of the catalysts were also investigated by applying various accelerated test protocols such as potential cycling between 0.5 - 1.0 (10.000 cycles), 0.5 - 1.5 (2000 cycles) and 1.0 - 1.5 V vs. RHE (2000 cycles). We monitored the electrochemically active surface area (ECSA) of the Pt and Pt alloy nanoparticles supported on these functionalized carbon materials during the runs to correlate its loss to the number of cycles, scan rate and potential range. Based on these results we evaluate the relationship between the carbon modification, size and chemical composition of the bimetallic nanoparticles, electrocatalytic properties and durability.Based on this study, we developed a model, describing the critical parameters to improve the interaction between the particles and the support material. This approach serves to enhance the catalytic properties and long-term durability of the ORR electrocatalysts for PEMFC applications.

A technique for lyopreservation of Clostridium ljungdahlii in a biocomposite matrix for CO absorption.

A system capable of biocatalytic conversion of distributed sources of single carbon gases such as carbon monoxide into hydrocarbons can be highly beneficial for developing commercially viable biotechnology applications in alternative energy. Several anaerobic bacterial strains can be used for such conversion. The anaerobic carbon monoxide-fixing bacteria Clostridium ljungdahlii OTA1 is a model CO assimilating microorganism that currently requires cryogenic temperature for storage of the viable strains. If these organisms can be stabilized and concentrated in thin films in advanced porous materials, it will enable development of high gas fraction, biocomposite absorbers with elevated carbon monoxide (CO) mass transfer rate, that require minimal power input and liquid, and demonstrate elevated substrate consumption rate compared to conventional suspended cell bioreactors. We report development of a technique for dry-stabilization of C. ljungdahlii OTA1 on a paper biocomposite. Bacterial samples coated onto paper were desiccated in the presence of trehalose using convective drying and stored at 4°C. Optimal dryness was ~1g H2O per gram of dry weight (gDW). CO uptake directly following biocomposite rehydration steadily increases over time indicating immediate cellular metabolic recovery. A high-resolution Raman microspectroscopic hyperspectral imaging technique was employed to spatially quantify the residual moisture content. We have demonstrated for the first time that convectively dried and stored C. ljungdahlii strains were stabilized in a desiccated state for over 38 days without a loss in CO absorbing reactivity. The Raman hyperspectral imaging technique described here is a non-invasive characterization tool to support development of dry-stabilization techniques for microorganisms on inexpensive porous support materials. The present study successfully extends and implements the principles of dry-stabilization for preservation of strictly anaerobic bacteria as an alternative to lyophilization or spray drying that could enable centralized biocomposite biocatalyst fabrication and decentralized bioprocessing of CO to liquid fuels or chemicals.

Encapsulation of Bimetallic Metal Nanoparticles into Robust Zirconium-Based Metal-Organic Frameworks: Evaluation of the Catalytic Potential for Size-Selective Hydrogenation.

The realization of metal nanoparticles (NPs) with bimetallic character and distinct composition for specific catalytic applications is an intensively studied field. Due to the synergy between metals, most bimetallic particles exhibit unique properties that are hardly provided by the individual monometallic counterparts. However, as small-sized NPs possess high surface energy, agglomeration during catalytic reactions is favored. Sufficient stabilization can be achieved by confinement of NPs in porous support materials. In this sense, metal-organic frameworks (MOFs) in particular have gained a lot of attention during the last years; however, encapsulation of bimetallic species remains challenging. Herein, the exclusive embedding of preformed core-shell PdPt and RuPt NPs into chemically robust Zr-based MOFs is presented. Microstructural characterization manifests partial retention of the core-shell systems after successful encapsulation without harming the crystallinity of the microporous support. The resulting chemically robust NP@UiO-66 materials exhibit enhanced catalytic activity towards the liquid-phase hydrogenation of nitrobenzene, competitive with commercially used Pt on activated carbon, but with superior size-selectivity for sterically varied substrates.

Solid amine sorbents for CO2 capture by chemical adsorption: A review

Abstract Amines are well-known for their reversible reactions with CO 2 , which make them ideal for CO 2 capture from several gas streams, including flue gas. In this respect, selective CO 2 absorption by aqueous alkanolamines is the most mature technology but the process is energy intensive and has also corrosion problems. Both disadvantages can be diminished to a certain extent by chemical adsorption of CO 2 selectively. The most important element of the chemical adsorption of CO 2 involves the design and development of a suitable adsorbent which consist of a porous support onto which an amine is attached or immobilized. Such an adsorbent is often called as solid amine sorbent. This review covers solid amine-based studies which are developed and published in recent years. First, the review examines several different types of porous support materials, namely, three mesoporous silica (MCM-41, SBA-15 and KIT-6) and two polymeric supports (PMMA and PS) for CO 2 adsorption. Emphasis is given to the synthesis, modifications and characterizations -such as BET and PXRD data-of them. Amination of these supports to obtain a solid amine sorbent through impregnation or grafting is reviewed comparatively. Focus is given to the adsorption mechanisms, material characteristics, and synthesis methods which are discussed in detail. Significant amount of original data are also presented which makes this review unique. Finally, relevant CO 2 adsorption (or equilibrium) capacity data, and cyclic adsorption/desorption performance and stability of important classes of solid amine sorbents are critically reviewed. These include severa PEI or TEPA impregnated adsorbents and APTES-grafted systems.

The Correlative Approach of 3D Imaging Techniques, Simulation and Diffusion Experiments to Explore Transport Properties in Porous Otm Support Material

Solid state electrochemical energy devices such as batteries, fuel cells and oxygen transport membranes (OTMs) have the potential to revolutionize distributed low-carbon power supply. However, in order to accelerate their commercialization across a range of applications, a much improved understanding of the underlying material microstructure is required. In particular, the rate limiting step of an OTM membrane applied for syngas production is found in concentration losses caused by mass transport limitations. In this field, microstructural parameters, such as tortuosity, porosity and average pore diameter, play a vital role in characterising, comparing and evaluating porous materials. However, unlike the latter two parameters, tortuosity cannot be measured directly which is why different methods have been developed for this purpose. These differ considerably from each other in terms of calculation approach and data preparation techniques. Here, we utilise X-ray nano computed tomography (CT) techniques to reveal the complex microstructure and resolve geometric features affecting mass transport of tubular porous support layers of OTMs to examine the relationship between the pore structure and mass transport (Figure 1). This is achieved via image based tortuosity calculation methods: a fast marching computational technique and a Laplace solver using MATLAB is employed to examine the geometrical tortuosity, and StarCCM+ and COMSOL software packages are used to model the heat flux and effective transport parameters of the porous phase, respectively. In turn, the results are validated using diffusion cell experiments to evaluate the bulk transport properties of the same samples for different binary gas mixtures at different temperatures. Tortuosity is then extracted by applying equimolar and equimass diffusion models [1]. We conclude, that image based calculation methodologies arrive at lower tortuosity values in comparison to diffusion cell experiments (Figure 2). Even the widely used Bruggeman [2] and Maxwell relations prove to be unfit to estimate tortuosity values in the analysed microstructure. The observed difference may stem from Knudsen diffusion effects which are not accounted for in the entirety of tomography based modelling techniques. Secondly, tortuosity values extracted via diffusion cell experiments are a function of gas mixture, temperature and microstructural characteristics rather than a constant value. Consequently, care must be taken in applying purely continuum interpretations of diffusion processes in these complex porous media.

Cu-impregnated alumina/silica bed materials for Chemical Looping Reforming of biomass gasification gas

Raw gas derived from low-temperature biomass gasification usually contains condensable hydrocarbons referred to as “tars” as well as other hydrocarbons such as ethylene and other olefins. Reforming of these compounds via Chemical Looping Reforming has been recently proposed. In this work Cu supported on four different Al2O3/SiO2-based porous support materials were investigated for reforming of ethylene. The investigated particles were manufactured by incipient wetness impregnation of the porous support with a copper nitrate solution followed by calcination, and then tested in a small-scale fluidized bed reactor at temperatures between 600°C and 850°C. The ethylene conversion was found to be strongly inhibited by the presence of aromatics in the gas. However, it was found that Cu supported on commercial PURALOX transition alumina catalyst exhibited superior properties, with high degrees of ethylene conversion achievable even in the presence of aromatic compounds. Under the experimental conditions in this work, up to 90% ethylene conversion was obtained at T=850°C in the presence of high concentrations of benzene. For the other prepared materials, the ethylene conversion was drastically reduced when monoaromatic compounds were present in the feed.

Influence of pore structure and impregnation–drying conditions on the solid distribution in porous support materials

ABSTRACTDeposition of solids within porous materials from a drying solution is an important phenomenon in numerous natural and industrial processes. A profound knowledge about influences of different parameters on the solid distribution in the material is required for an effective targeted impregnation process. Experimental investigations and simulations are used to study the influence of pore structure, drying conditions, and solute concentration on the solid distribution in porous support materials after impregnation and drying. It is found that low drying rates lead to strong solid accumulation at the material surface, whereas high drying rates reduce the solute transport to the surface and result in more uniform solid distributions. A small pore diameter and distribution width reduce solute migration during drying and lead to uniform solid distributions without being influenced by the drying conditions. A higher initial concentration of the impregnation solution causes pronounced surface accumulation, while low initial solute concentrations result in more uniform distributions. Fundamental effects during drying are captured in an existing pore network model by adaption of experimental pore structures and impregnation–drying conditions, resulting in a good general agreement of experiments with simulations.

The application of 3D imaging techniques, simulation and diffusion experiments to explore transport properties in porous oxygen transport membrane support materials

Tortuosity plays a vital role in diffusive mass transport through porous layers of electrochemical devices. However, tortuosity cannot be measured directly which is why different methods have been developed to determine the tortuosity of porous samples. These methods differ considerably from each other in terms of calculation approach and applied data sets.Here, we utilise advanced tomography techniques, simulation and diffusion cell experiments to calculate tortuosity of a porous support layer of an oxygen transport membrane (OTM). The results are then compared and the suitability of these different approaches is evaluated.We conclude, that image and simulation based methodologies arrive at lower tortuosity values in comparison to diffusion cell experiments; the difference, depending on the calculation method, can be close to a factor of two. The difference may stem from Knudsen diffusion effects which currently are not accounted for in the image based modelling techniques. Moreover, tortuosity values extracted via diffusion cell experiments are a function of gas mixture and temperature. As a result, one has to distinguish between geometric tortuosity and diffusive tortuosity used for quantifying the resistance of a structure to a flux.