Journal of Porous Materials最新文献

Propylene is an essential chemical feedstock, which needs efficient and stable production technology to meet its increasing industrial demand. In this work, the Pt–Sn/MgAl₂O₄ catalysts fabricated via the incipient wetness impregnation method were used for propane dehydrogenation to propylene (PDH). The effect of Sn on reaction performance was investigated to determine the optimal loading amount. The characterization results from XRD, N₂ physisorption, TEM, H₂-TPR, NH₃-TPD, and TGA elucidated the physicochemical characteristic evolution with varied Sn content in the catalysts. The Pt0.3Sn/MgAl₂O₄ achieved the best propane conversion of 40.9% and propylene selectivity of 82.5% at 600 °C. Sn addition promoted Pt dispersion, enhanced metal-support interactions, and inhibited the side reactions. The MgAl₂O₄ support could suppress the coke formation and maintain propylene selectivity. This work demonstrates the Pt–Sn/MgAl₂O₄ catalysts are effective and durable for PDH to meet propylene demand.

Amine-grafted adsorbents are promising CO₂ adsorbents; however, the excessive addition of an amino silane coupling agent during their synthesis increases their production cost. Thus, using low amounts of silane, we synthesized 3-aminopropyltrimethoxysilane (APTMS)-grafted SBA-15 mesoporous silica and evaluated its CO₂ adsorption performance. APTMS-grafted SBA-15 samples were prepared using either impregnation or heating–filtration method (grafting). The obtained samples were characterized by X-ray diffraction spectroscopy, transmission electron microscopy, N₂ adsorption/desorption, scanning electron microscopy, magic-angle spinning nuclear magnetic resonance, and elemental analysis. The results revealed that the micropores of SBA-15 were preferentially blocked, and APTMS increasingly occupied the mesopores with increasing amine loading. The CO₂-adsorption performance of the adsorbents was measured by thermogravimetric analysis under dry conditions. Both synthesis methods achieved high amine immobilization efficiency (78.3–92.2%), as estimated from the amount of silane coupling agents used in the synthesis and that immobilized on the support. The adsorbents prepared by the two methods adsorbed similar amounts of CO₂ of approximately 0.5 mmol g^− 1 in 400 ppm CO₂ and ~ 1.0 mmol g^− 1 in 5 vol% CO₂. The adsorption amounts attained in this study are comparable to those of previously reported silane-coupling-agent-modified adsorbents that were prepared with more silane. In contrast, the adsorption rate of the samples was affected by the synthesis method, even with similar amine loadings. Nonetheless, the results revealed that even with a low amount of the silane coupling agent, high-performance amine-grafted CO₂ adsorbents could be synthesized.

Porous silicon (PSi) has received a lot of attention in nanotechnology research in recent years for its potential use as sensing layers in sensor application. However, there have been relatively limited studies concerning the effect of varying contact gaps and bias voltages on the humidity sensor based on PSi. In this work, the nanostructure PSi layer was synthesized via the anodization method and fabricated at different annealing temperatures of 250 ℃, 450 ℃, 650 ℃, and 850 ℃. Subsequently, the four samples were deposited with varying gold (Au) contact gaps of 3.5 mm, 4.5 mm, 7.5 mm, and 8.5 mm. The morphological and structural characteristics of the PSi layer were characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. The PSi-based humidity sensors with varied Au contact gaps were evaluated in a humidity chamber at 40–90% relative humidity (RH) levels with different bias voltages of 2 V, 5 V, and 10 V. The optimized fabricated PSi device was evaluated for its electrical behaviour using I-V measurement under various operating temperatures ranging from 25 °C to 100 °C. The findings showed that the enhanced PSi structure of the 450 °C annealed sensor produced the highest sensitivity performance of 18.4705 µA/%RH with stable output at a contact gap of 4.5 mm and a bias voltage of 10 V. The sensor exhibited a high surface area to volume ratio, which facilitated efficient interactions between surface active sites and water molecules, resulting in a highly sensitive humidity sensor.

The constituent parts of systems where radiation-catalytic processes occur usually differ in terms of mass and electron density, structural characteristics, electro-physical and chemical properties. Therefore, interaction between phases in any form has a sharp effect on the direction and parameters of the processes in individual components. The resulting X-ray diffraction pattern was mainly determined by the atomic plane (ε), the intensity of the obtained peaks, the corresponding syngony of the sample, the lattice size, density, lattice constants, and the distance between the phase groups. The X-ray diffraction data were processed using the Full prof program. Full-profile processing of NaNO₃ X-ray diffraction data showed that the initial sample has a triclinic structure. The scientific component of the article is of interest be- cause it touches upon the issues of structural transformations of NaNO₃ under the action of gamma radiation. The radiation- heterogeneous processes of water decomposition NaNO₃ have been studied. The kinetics of buildup of molecular hydrogen in the radiolysis processes of water decomposition has been examined. Hydrogen generation by water splitting is reported in NaNO₃ + H₂O_abs., NaNO₃ + H₂O_flu. systems using gamma radiation and 300 K temperature. This indicates that in the case of finding NaNO₃ in the volume of water, there is an effective transfer of energy from the solid phase to water molecules. The presence of the second slow stage of radiolysis on the kinetic curves indicates that there is a diffusion-hindered stage of heterogeneous radiolysis of water in the presence of nanoparticles at 300 K.

We report in this article, the Dysprosium doping effects on microstructure and mechanical properties of nanoporous metallic gold, synthesized by electrochemical dealloying of Ag₇₀Au₃₀ and Ag₇₀Au₂₉Dy₁ alloys. It is shown that these dealloyed nanoporous metallic materials exhibit the mean ligament diameter in a length scale of 5–10 nm. The variation of ligament diameter in pure and Dysprosium doped nanoporous Au with annealing temperature influences their mechanical properties. Higher microhardness value has been obtained around 10 nm ligament diameter on both pure and Dysprosium doped nanoporous gold. The maximum values of Vickers hardness H_V obtained from the analysis of indentation diagonals with applied load are close to the H_V value reported for bulk gold. Since the nanoporous metallic materials behave in a way like compressible sponge materials, we used the well-known density scaling equation for the determination of ligament yield strength of pure and Dysprosium doped nanoporous gold with ligament diameter. The results obtained have been finally compared with literature reports.

Abstract

Recently, the direct ink writing (DIW) of hierarchical porous copper ((Cu)) (HP- ({text{Cu}}) ) for lithium metal battery applications has attracted significant attention. To achieve this, (Cu) ink with ideal rheological properties and high particle loading is necessary. However, to date, no work focusing on systematic (Cu) ink development with (Cu) particle loading more than 95 (wt%) has been reported. Hence, in the present work, a novel (Cu) ink with a particle loading of more than 95 (wt%,) and polylactic acid (PLA) as a binder has been developed. The rheological behavior of the (Cu) ink with different amounts of (Cu) loading i.e. 93, 95 and 97 (wt%) respectively were investigated. Moreover, the modelling using the Herschel-Bulkey equation was done to establish the rheology. All the prepared inks showed viscoelastic and shear thinning behaviour. Moreover, the ink having 97 (wt%) (Cu) loading exhibited optimum rheology with a shear elastic modulus of around ({10}^{5} Pa) in the linear viscoelastic area. Subsequently, DIW using the prepared (Cu) inks followed by sintering was performed. The morphological study of the 3D printed (Cu) green samples and sintered samples was performed and it was found that the variation in (Cu) particle loading significantly affected the density and volumetric shrinkage. Finally, an HP- ({text{Cu}}) sample having a pore size less than 200 (mu m) was fabricated using DIW and sintering to validate the efficacy of the developed (Cu) ink. Proper interparticle bonding between the (Cu) particles was observed indicating that the developed ink is suitable for the fabrication of complex (Cu) parts for lithium metal battery application.

Abstract

In this article, the suitability of utilization of porous lumen structure of Halloysite (Hal) nanoclay has been studied elaborately. To utilize the lumen structure for membrane development, the effect of temperature, pressure and time on the porous lumen feature and subsequent use of the clay in pristine form as a membrane coating material for separation purposes at specified temperatures shows the importance of this study. The present study investigates structural changes in Halloysite nanoclay's inherent porous tubular morphology. Membranes are prepared by coating clay-alumina porous support tube with Halloysite sol under pressure and temperature of 100 and 160 °C for 24, 48 and 64 h, respectively. XRD and FTIR reveal that the tubular structure remains intact under experimental conditions. In contrast, the morphology of pristine Hal powder treated at the specified temperature and under in situ developed autogenous pressure shows a significant textural change in the nanotubular morphology observed from FESEM. At 100 °C, lumen porosity remains intact, but at 160 °C, under higher pressure, lumen mouth sealing, conjoining and coalescence of the halloysite nanotubes (HNT) result. In addition, for both temperatures under existing operating pressure, the effect of 24 h time duration on morphology is less. For practical viability, a preliminary study for dye removal is carried out with H1 membrane coating, which shows promising %rejection values. This study on powders and membrane coatings might thus help to assign new application fields, such as membrane-based separation utilizing the porous nature of HNT by controlling different process parameters.

Zeolites synthesis using a combination of tetraethylammonium hydroxide (TEAOH) and 1,6-diaminohexane (DAH) as organic structure-directing agents (OSDAs) has been studied in order to understand how they acted during the synthesis. This combination can crystallize four zeolites: beta, ZSM-12, ZSM-48, and silicalite-1. TEAOH is found to direct the synthesis of beta, and ZSM-12 zeolites, whereas DAH directs the synthesis of ZSM-48 zeolite. On the other hand, the two organic components are found to have a cooperative role in the crystallization process of silicalite-1, with greater templating ability for TEAOH compared to DAH. The use of a supplementary organic component does not affect the degree of filling of the primary OSDA in the structure or the morphology of the obtained zeolites. The carbon dioxide (CO₂) adsorption capacity of the zeolites obtained was evaluated at a temperature of 293 K in a pressure range of 0 to 1 atm. The relationship between the surface properties of the zeolites and their adsorption behavior was studied. Beta zeolite had the highest adsorption capacity with 2.9 mmol/g, while ZSM-48 zeolite had the lowest adsorption capacity with only 0.7 mmol/g.

In general, hierarchical zeolite synthesis will produce waste, which will cause many problems for environmental pollution. The waste that comes from the synthesis of zeolites, such as the use of hazardous chemicals from the use of many solvents, additional templates, silica sources used, and other precursors that are not environmentally friendly. One solution to the problem is to use bio-based templates. The advantage of using this bio-based template is that it is environmentally friendly, reduces dependence on hazardous chemicals, and supports sustainability for bio-based templates such as carbohydrates, chitin, and others. The use of the previously mentioned templates in zeolite synthesis can produce hierarchical pores, high crystallinity, and catalytic properties that are not inferior to conventional zeolites obtained, and more cost-effective. The efforts are expected to fulfill the principles of green chemistry, which prioritizes the environment to provide better prospects for the synthesis of hierarchical zeolites in the future.

Rodlike ZSM-5 zeolite microspheres (R-Z5) were synthesized via a seed induced hydrothermal method with S-1 seeds in the presence of β-cyclodextrin (CD). The synthesized ZSM-5 zeolites were characterized with XRD, SEM, N₂ adsorption and desorption, NH₃-TPD, the catalytic performance of R-Z5 catalysts was studied for the methanol to propylene (MTP) reaction. The effects of the ratio of CD/SiO₂ on the morphologies and textural properties of the products were discussed in detail. A possible formation process of R-Z5 was proposed. The results showed that CD played a key role in the preparation of R-Z5, which could be ascribed to the amphipathy of CD for the formation of rodlike ZSM-5 crystals. Compared with the conventional seed induced method, R-Z5 zeolites possessed the larger BET surface area and mesopore volumes and the more moderate acidic sites. Moreover, the synthesized R-Z5 catalysts exhibited excellent conversion activity (64 h) and propylene selectivity (41.35%) in the primary catalytic performance of MTP reaction.