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, Volume:
13, Issue:
7
Journal Article
Peer reviewed
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.
As key performance indicators, the water absorption and mechanical strength of ceramics are highly associated with sintering temperature. Lower sintering temperatures, although favorable for energy ...saving in ceramics production, normally render the densification degree and water absorption of as-prepared ceramics to largely decline and increase, respectively. In the present work, 0.5 wt.% MnOsub.2, serving as an additive, was mixed with aluminosilicate ceramics using mechanical stirring at room temperature, achieving a flexural strength of 58.36 MPa and water absorption of 0.05% and lowering the sintering temperature by 50 °C concurrently. On the basis of the results of TG-DSC, XRD, MIP, and XPS, etc., we speculate that the MnOsub.2 additive promoted the elimination of water vapor in the ceramic bodies, effectively suppressing the generation of pores in the sintering process and facilitating the densification of ceramics at a lower temperature. This is probably because the MnOsub.2 transformed into a liquid phase in the sintering process flows into the gap between grains, which removed the gas inside pores and filled the pores, suppressing the generation of pores and the abnormal growth of grains. This study demonstrated a facile and economical method to reduce the porosity and enhance the densification degree in the practical production of aluminosilicate ceramics.
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