The influence of NHsub.4NOsub.3 and NHsub.4ClOsub.4 on the porous texture and structure development of activated carbons produced from a non-porous polymeric precursor synthesized from furfuryl ...alcohol has been studied. The non-doped counterparts were prepared and studied for comparison purposes. NHsub.4NOsub.3 and NHsub.4ClOsub.4-doped polymers were carbonized under Nsub.2 atmosphere at 600 °C, followed by COsub.2 activation at 1000 °C and the obtained carbon materials and activated carbons were thoroughly characterized. The porosity characterization data have shown that NHsub.4NOsub.3-derived ACs present the highest specific surface area (up to 1523 msup.2/g in the experimental conditions studied), and the resulting porosity distributions are strongly dependent on the activation conditions. Thus, 1 h activation is optimum for the microporosity development, whereas larger activation times lead to micropores enlargement and conversion into mesopores. The type of doping salts used also has a substantial impact on the surface chemical composition, i.e., C=O groups. Moreover, NHsub.4NOsub.3 and NHsub.4ClOsub.4 constitute good sources of nitrogen. The type and contribution of nitrogen species are dependent on the preparation conditions. Quaternary nitrogen only appears in doped samples prepared by carbonization and pyrrolic, pyrydinic, and nitrogen oxide groups appear in the NHsub.4NOsub.3 -series. NHsub.4NOsub.3 incorporation has led to optimized materials towards COsub.2 and Csub.2Hsub.4 sorption with just 1 h activation time.
Polymers based on 2-(acetoacetoxy)ethyl methacrylate, charged with iron or sodium, were thermally heated at 150 °C. Both polymers were studied and characterized by SEM, TEM, STEM microscopy and SAEDF ...techniques. The morphological investigation revealed that, upon heating, both polymers were endowed with microholes, sometimes perfectly ordered, whose dimensions varied from 4–5 nm to approximately 500 nm. In the case of an Fe-containing copolymer, unexpectedly, iron did not fill in the cavities, thus implying that it was “dispersed” in the polymeric matrix. Electronic microdiffraction documented that both polymers exhibited a proto-crystallinity, likely induced by thermal heating.
Membrane technology is considered an innovative and promising approach due to its flexibility and low energy consumption. In this work, a comprehensive 3D-CFD model of the Hollow-Fiber Membrane ...Contactor (HFMC) system for COsub.2 capture into aqueous MEA solution, considering a counter-current fluid flow, was developed and validated with experimental data. Two different flow arrangements were considered for the gas mixture and liquid solution inside the HFMC module. The simulation results showed that the COsub.2 absorption efficiency was considerably higher when the gas mixture was channeled through the membranes and the liquid phase flowed externally between the membranes, across a wide range of gas and liquid flow rates. Sensitivity studies were performed in order to determine the optimal COsub.2 capture process parameters under different operating conditions (flow rates/flow velocities and concentrations) and HFMC geometrical characteristics (e.g., porosity, diameter, and thickness of membranes). It was found that increasing the membrane radius, while maintaining a constant thickness, positively influenced the efficiency of COsub.2 absorption due to the higher mass transfer area and residence time. Conversely, higher membrane thickness resulted in higher mass transfer resistance. The optimal membrane thickness was also investigated for various inner fiber diameters, resulting in a thickness of 0.2 mm as optimal for a fiber inner radius of 0.225 mm. Additionally, a significant improvement in COsub.2 capture efficiency was observed when increasing membrane porosity to values below 0.2, at which point the increase dampened considerably. The best HFMC configuration involved a combination of low porosity, moderate thickness, and large fiber inner diameter, with gas flow occurring within the fiber membranes.
Application of Covalent Organic Frameworks Inácio, Diogo; Pinto, Ana Lucia; Paninho, Ana B ...
Nanomaterials (Basel, Switzerland),
03/2023, Letnik:
13, Številka:
7
Journal Article
Recenzirano
Five Covalent Organic Frameworks (COFs) were synthesized and applied to Dye-Sensitized Solar Cells (DSSCs) as dyes and additives. These porous nanomaterials are based on cheap, abundant commercially ...available ionic dyes (thionin acetate RIO-43, Bismarck brown Y RIO-55 and pararosaniline hydrochloride RIO-70), and antibiotics (dapsone RIO-60) are used as building blocks. The reticular innovative organic framework RIO-60 is the most promising dye for DSSCs. It possesses a short-circuit current density (Jsub.sc) of 1.00 mA/cmsup.2, an open-circuit voltage (Vsub.oc) of 329 mV, a fill factor (FF) of 0.59, and a cell efficiency (η) of 0.19%. These values are higher than those previously reported for COFs in similar devices. This first approach using the RIO family provides a good perspective on its application in DSSCs as a dye or photoanode dye enhancer, helping to increase the cell's lifespan.
The aim of this research work was to develop a new, low-cost and low-energy-consuming preparation route for highly porous silica systems. The precursor gel systems were synthesized by sol-gel ...chemistry. The starting materials were TEOS and water glass in the sol-gel syntheses. The effect of the chemical composition, the catalysis, the pH, and the additives were investigated on the structure and porosity of the cryogels. The gel systems were treated by freeze-drying process to obtain porous cryogel silica products. The cryogel systems possess hierarchical structures. The conditions of the freeze-drying process were also studied to increase the porosity. Small angle X-ray measurements, scanning electron microscope technique, and infrared spectroscopy were applied for the investigation of gel and cryogel systems.
A mesoporous TiO2-Fe2O3 mixed oxide material (MTF-1E) with nanoscale porosity and a high BET surface area was synthesized using sodium dodecyl sulfate (SDS) as a structure-directing agent. The ...material was characterized by powder XRD, high-resolution TEM, N2 sorption, and NH3 temperature-programmed desorption studies. The catalyst shows an excellent regioselectivity for the ring-opening of epoxides with amines under solvent-free conditions at room temperature for the synthesis of a series of beta-amino alcohols. It also showed a very high catalytic efficiency for the synthesis of benzimidazole derivatives in water. The catalyst can be recovered easily from the reaction medium and reused six times without a significant decrease in its catalytic activity and selectivity.
A theoretical molecular simulation study of the encapsulation of gaseous SOsub.2 at different temperature conditions in a type II porous liquid is presented here. The system is composed of cage ...cryptophane-111 molecules that are dispersed in dichloromethane, and it is described using an atomistic modelling of molecular dynamics. Gaseous SOsub.2 tended to almost fully occupy cryptophane-111 cavities throughout the simulation. Calculations were performed at 300 K and 283 K, and some insights into the different adsorption found in each case were obtained. Simulations with different system sizes were also studied. An experimental-like approach was also employed by inserting a SOsub.2 bubble in the simulation box. Finally, an evaluation of the radial distribution function of cryptophane-111 and gaseous SOsub.2 was also performed. From the results obtained, the feasibility of a renewable separation and storage method for SOsub.2 using porous liquids is mentioned.
Silica aerogels or xerogels are renowned dried gels with low density, high surface area, higher porosity, and better thermal stability which makes it suitable for aerospace, light weight structures, ...thermal insulation, and hydrophobic coatings. But brittle behaviour, low mechanical strength, and high manufacturing cost restrict its usage. Recently, the addition of various fibres like glass or carbon fiber is one of the best reinforcement methods to minimize the brittle behaviour. Supercritical drying technique usually used to develop aerogel that is expensive and difficult to produce in bulk quantities. Higher cost obstacle can be tackled by applying ambient pressure drying technique to develop xerogel. But researcher observed cracks in samples prepared through the ambient pressure drying technique is still a major shortcoming. The aim of this study is to systematically analyze the influence of silica gel fiber reinforcement on silica xerogels, encompassing morphology, mechanics, thermal behaviour, compression test, and thermogravimetric characteristics. The research used a low-cost precursor named Tetraethyl orthosilicate to synthesize low-cost composite Silica xerogel and glass and carbon fiber added to provide strength and flexibility to the overall composite. Silica gel works as binder in strengthening the xerogel network. The investigation employs scanning electron microscopy (SEM) to examine the morphology of the composites, Fourier Transform Infrared (FTIR) analysis to affirm hydrophobic characteristics, compression tests to assess mechanical strength, and thermogravimetric tests to study weight loss under different conditions. SEM results reveals that glass fibers exhibit lower adhesion to the xerogel network compared to carbon fibers. FTIR analysis confirms the hydrophobicity of the composite silica xerogel. Compression tests showed that, under a 48% strain rate, the carbon fiber composite demonstrates superior compressive stress endurance. Thermogravimetric tests revealed a 1% lower weight loss for the carbon fiber composite compared to the glass fiber composite. This work concludes that glass and carbon fiber together with silica gel particles successfully facilitated in developing flexible, less costly, hydrophobic, and crack-free silica xerogel composites by APD. These advancements have the potential to drive innovations in material science and technology across diverse industries.
•Evaluation of the porosity of the HTTU annular packed bed.•Angular and radial variation in porosity for bottom near-wall region characterized.•Standard deviation and skewness of angular at each ...radial position calculated.•Variation of tangentially averaged porosity in axi-symmetric r-z plane shown.•Average porosity and standard deviation for 20 selected regions presented.
In this paper a comprehensive analysis of the porosity of the annular packed bed of the High Temperature Test Unit (HTTU) is presented. The annular packed bed is generated using a Discrete Element Method (DEM) approach. Semi-analytical methods are then used to analyse the porosity. The quality and representativity of the packed bed are established by evaluating the overlaps between spheres and spheres and walls and comparing the axial and radial variations in porosity with available experimental and numerical data. The angular and radial variation of selected sphere layers in the bottom near-wall region was studied revealing how the spheres in the axial layers and radial rings are staggered with respect to each other. The analysis of the radial variation in porosity also included the standard deviation and the skewness of the angular porosity at each radial position. An analysis of the radial porosity of the layers revealed that only first layer next to the bottom is markedly affected by the bottom wall. The interference between the oscillatory porosity variations perpendicular to the inner, outer, and bottom walls of the annular packed bed is demonstrated by the plot of the variation in porosity on an axi-symmetric r-z plane. The annular packed bed is also divided into 20 regions and the average porosity and the standard deviation of the porosity for each region in provided.
A series of ionic covalent triazine frameworks (CTFs) bearing charged groups were designed and prepared through ZnCl.sub.2-catalyzed cyclotrimerization of 1,3-bis(4-cyanophenyl)imidazolium chloride ...and tricyanobenzene as an auxiliary monomer. Pore properties of the ionic CTFs could be controlled by varying the proportion of monomer. The resulting ionic CTFs had high BET specific surface areas up to 1105 m.sup.2/g, high pore volumes up to 0.65 cm.sup.3/g, and high physicochemical stability. Among the four ionic CTFs, tCTF-Cl-3 exhibited the highest CO.sub.2 adsorption of 72.7 cm.sup.3/g and highest I.sub.2 capture capacity of 370 wt%. The incorporation of ionic functional groups, the existence of homogenous charge distribution, and the permanent porosity improved the capturing ability and affinity of the ionic CTFs for CO.sub.2 and I.sub.2. This methodology, based on the fine tuning of monomer ratio, can be utilized to obtain new insights into the preparation of functional ionic porous materials.
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