Search Results (117)

This study investigates the effects of samarium (Sm) promotion on the catalytic activity of 5 weight percent Ni catalysts for partial oxidation of methane (POM)-based hydrogen production supported on a Si-Al mixed oxide (10SiO₂+90Al₂O₃) system. Several 5% Ni-based catalysts supported on silica–alumina was used to test the POM at 600 °C. Sm additions ranged from 0 to 2 wt.%. Impregnation was used to create these catalysts, which were then calcined at 500 °C and examined using BET, H₂-TPR, XRD, FTIR, TEM, Raman spectroscopy, and TGA methods. Methane conversion (57.85%) and hydrogen yield (56.89%) were greatly increased with an ideal Sm loading of 1 wt.%, indicating increased catalytic activity and stability. According to catalytic tests, 1 wt.% Sm produced high CH₄ conversion and H₂ production, as well as enhanced stability and resistance to carbon deposition. Nitrogen physisorption demonstrated a progressive decrease in pore volume and surface area with the addition of Sm, while maintaining mesoporosity. At moderate Sm loadings, H₂-TPR and XRD analyses showed changes in crystallinity and increased NiO reducibility. Sm incorporation into the support and its impact on the ordering of carbon species were indicated by FTIR and Raman spectra. The optimal conditions to maximize H₂ yield were successfully identified through optimization of the best catalyst, and there was good agreement between the theoretical predictions (87.563%) and actual results (88.39%). This displays how successfully the optimization approach achieves the intended outcome. Overall, this study demonstrates that the performance and durability of Ni-based catalysts for generating syngas through POM are greatly enhanced by the addition of a moderate amount of Sm, particularly 1 wt.%. Full article

Porous artificial reef materials made of cement used in the offshore area can repair and improve the ecological environment and enrich fishery resources. In this study, quartz sand was used as the aggregate, high-alumina cement as the cementing agent, and crushed particles of waste tires as the modifier to prepare porous cement–polymer composites. Through orthogonal tests, the effects of the aggregate particle size, the ratio of aggregate to cement, the rubber particle size, and the rubber ratio on the strength and permeability of the porous cement–polymer composites were studied. The significant degrees of different influencing factors were analyzed, and an appropriate configuration scheme for the porous cement–polymer composites was proposed. The experimental results show that the quantity of rubber particles added and the particle size of the rubber particles have a relatively large impact on the properties of the porous cement–polymer composites. Through response surface tests, the interactive effects of various factors in the porous cement–polymer composites on the compressive strength and permeability of the material were verified. The microstructure of the porous cement–polymer composites was observed by SEM. The differences in the microstructure and internal structure between the specimens with a low rubber content and large rubber particle size and those with a high rubber content and small rubber particle size were analyzed, and the influence mechanism of the differences in the microstructure and internal structure on the strength and permeability was proposed. Full article

Traditional β-eucryptite (LiAlSiO₄) is renowned for its unique characteristics of low thermal expansion and high temperature thermal stability, making it an ideal material for precision instruments and aerospace applications. In this study, β-eucryptite was fabricated into an aerogel structure through the sol–gel process and supercritical drying method and using alumina sol as a cost-effective precursor. The synthesized β-eucryptite aerogel demonstrated unique properties including a negative thermal expansion coefficient (−7.85 × 10⁻⁶ K⁻¹), low density (0.60 g/cm³), and high specific surface area (18.1 m²/g). X-ray diffraction (XRD) and transmission electron microscopy (TEM) mutually corroborated the crystalline structure of β-eucryptite, with XRD confirming the phase purity and TEM imaging revealing well-defined crystal lattice characteristics. Combined nitrogen adsorption–desorption analysis and scanning electron microscopy observations supported the hierarchical porous microstructure, with SEM visualizing interconnected nanoporous networks and nitrogen sorption data verifying the porosity. The negative thermal expansion behavior was directly linked to the β-eucryptite crystal structure, as collectively validated by thermal expansion measurements. Additionally, Fourier transform infrared spectroscopy (FTIR) independently confirmed the aluminosilicate framework structure through characteristic vibrational modes. This research shows the innovation in the synthesis of β-eucryptite aerogel, especially its application potential in precision instruments and building materials that need low thermal expansion and high stability, and the use of aluminum sol as an aluminum source has simplified the preparation steps and reduced production costs. Full article

Various forms of alumina have attracted considerable attention for their ability to remove anionic dyes from wastewater, attributed to their high specific surface area, and environmental safety. In this study, a series of modified alumina materials were synthesized for the first time using the reverse precipitation method with dual aluminum sources and without template agent to explore their applicability in various scenarios, including adsorption processes and regeneration cycles. The results revealed that non-modified alumina exhibited superior adsorption properties, while silicon-modified alumina demonstrated exceptional thermal stability during high temperature calcination. For silicon-modified alumina, the replacement of some Al–OH groups with silicon resulted in the formation of a protective silicon layer on the alumina surface, which delayed the sintering process. The pseudo-second-order kinetic model and Langmuir model were utilized to fit the experimental data. Furthermore, the adsorption and regeneration properties of silicon-modified alumina were investigated, revealing a maximum equilibrium adsorption capacity of 822.6 mg/g for Congo Red using non-modified alumina. Notably, the non-modified alumina demonstrated a 40.6% increase in its adsorption capacity compared to its initial capacity after six regeneration cycles at 1000 °C. Full article

The present study aims to investigate a Pd catalyst on a complex multi-oxide medium-entropy support interlayer La₂O₃-CeO₂-ZrO₂-Al₂O₃ and its possible use as catalysts for methane abatement applications. The low-temperature N₂-adsorption, XRD, TEM, XPS, TPD, and TPR techniques were used to characterize the catalyst. The palladium deposition on the supports leads to the formation of PdO. After the catalytic tests, the metal-Pd phase was observed. The complete oxidation of methane on Pd/La-Ce-Zr-Al catalyst takes place at temperatures above 250 °C, and in the presence of water vapor, the reaction temperature increases to about 70 °C. The careful choice of constituent oxides provides a balance between structural stability and flexibility. The alumina and lanthanum oxide ensure the high specific surface area, while the simultaneous presence of zirconia and ceria leads to the formation of a mixed-oxide phase able to interact with palladium ions by incorporating and de-incorporating them at different conditions. The mechanism of Mars–van Kerevelen was considered as the most probable for the reaction of complete methane oxidation. The possibility of the practical application of Pd-modified La-Ce-Zr-Al catalyst is evaluated. The use of a mix of multiple rare and abundant oxides makes the proposed catalyst a cost-effective alternative. Full article

The thermal decomposition of hydrogen peroxide (H₂O₂) as a promising green propellant was performed over free-noble metallic-based catalysts deposited on abundant supports. A 30% (w/w) H₂O₂ liquid was decomposed over 1 wt.% of copper-based catalysts deposited on three different supports: γ-alumina, graphite and monocrystal clay. In this research work, the catalytic performance of the thermal decomposition of H₂O₂ was carried out by measuring the differential pressure (ΔP) versus time at initial constant temperatures and, for the first time, by the DTA-TG technique and by the DIP-MS technique at atmospheric pressure. The obtained preliminary results showed that copper deposited on alumina and on graphite are promising catalysts for the decomposition of the H₂O₂ liquid propellant. Moreover, the natural clay can be valorized on the thermal decomposition of H₂O₂ due to its high resistivity and high surface area. The N₂-physisorption technique and scanning electron microscopy technique were used to characterize the effect of the texture properties on the decomposition and to understand the morphological characteristics of the catalyst. Full article

This study shows how important the coordination of Al³⁺ ions in the silver support is for the overall activity in soot combustion. Five silver catalysts with a silver content of 14.7 wt.% were prepared using the following supports: α-Al₂O₃, which has only octahedrally coordinated Al³⁺, θ-Al₂O₃, which has both octahedrally and tetrahedrally coordinated Al³⁺, and zeolites, which contain only tetrahedrally coordinated Al³⁺: 10X, 13X, and 5A. The analysis of the diffraction patterns showed that silver on the surface of catalysts made with the first four supports was mainly in the metallic form, except for Ag/5A in which there was a lack of reflections from Ag⁰ in the XRD pattern. Nevertheless, the difference in the activity of the support and the catalyst as well as the EDX results indicate the presence of silver on the catalyst. The SEM-EDX analysis showed that the silver dispersion strongly depends on the support and that even the zeolites with large silver particles on the surface have silver evenly distributed across the surface. The activity of the catalysts decreased in the following series: Ag/Al 1200 > Ag/5A ≈ Ag/13X > Ag/10X ≈ Ag/Al 550. Time-of-Flight Secondary Ion Mass Spectrometry was used to delve into the reason why the catalyst with the low-surface area α-Al₂O₃ support yielded a better catalyst than that obtained using the high-surface area alumina support and showed that different ratios of secondary ions were emitted from the two surfaces. Full article

Electrification has become increasingly common in aerospace due to climate change concerns. After successful applications in general aviation aircraft, electrification is now addressing subregional (up to 19 passengers) and regional aircraft (around 80 passengers). Megawatt-class electric motors are needed both to drive propellers and to act as high-power generators in hybrid–electric propulsion systems. Power levels for this class of aircraft require a proper design of heat management systems capable of dissipating a much higher quantity of heat than that dissipated by traditional cooling systems. The technical solution here explored is based on the addition into a diathermic base liquid of nanoparticles, which can increase (by up to 30%) the thermal conductivity of the refrigerant, also providing large surface area enhancing the heat transfer capacity of base liquids. The Italian Aerospace Research Centre (CIRA), as part of the European research initiative Optimised Electric Network Architectures and Systems for More-Electric Aircraft (ORCHESTRA), developed a thermal management system (TMS) based on impinging jets technology for a 1 MW electric motor. In this work, a numerical verification of the possibility for nanofluids to improve the heat exchange efficiency of a submerged oil impinging jets TMS designed to directly cool the inner components of a 1 MW motor is conducted. Investigations aimed to analyse two nanoparticle types (alumina and graphite) added to diathermic oil with concentrations between 1% and 5% by volume. The application of nanofluids significantly increases final thermal conductivity with respect to conventional coolants, a 60% improvement in heat transfer at a fixed mass flow rate is achieved. Electric motor maximum temperatures are approximately 10% lower than those achieved with solely diathermic oil. This result is significant as a safety margin is needed in all cases where a sudden increase in power occurs. Full article

Human growth hormone (hGH) is a polypeptide hormone that is synthesized and secreted by the anterior pituitary gland, whose excess is linked to acromegaly-causing pituitary adenomas while deficiencies are linked to disorders including short stature and Turner’s syndrome. This study investigates the real-time biosensing of hGH using a microfluidic optical biosensor based on reflectometric interferometry Fourier spectroscopy (RIFTS). The biosensing platform is based on a monolayer of nanoporous anodic alumina (NAA) fabricated following the two-step anodization method to produce pore sizes between 30 and 35 nm. The sensitivity of the nanostructure is improved by increasing the effective surface area by widening the pores to about 45 nm. NAA structures are then functionalized to make them selective to hGH. The sensing performance of the system shows a linear detection range from 12.5 µg/mL to 100 µg/mL with a detection limit of 10.6 µg/mL. This biosensing platform demonstrates the capability to detect high concentrations of human growth hormone using a cost-effective, fast, and portable biosensing system. Full article

Rising greenhouse gas concentrations are causing climatic change that threatens ecosystem sustainability. This study investigated the impact of silica incorporation into alumina-supported nickel catalysts for the partial oxidation of methane (POM), a crucial process for syngas production. The investigation also focuses on the impact of using different calcination temperatures. The catalysts were synthesized using the impregnation method and structurally characterized with BET, TPR, FTIR, UV, XRD, TGA, Raman, and TEM analysis techniques. These characterization techniques revealed that increasing the silica content reduced the surface area and weakened the interaction between nickel and the support. The calcination temperature significantly influenced catalyst properties, affecting pore structure, nickel reducibility, and the formation of nickel aluminates and silicates. Activity tests of synthesized catalysts were performed in a packed-bed reactor at 600 °C with a 24 mL/min gas flow rate. The catalyst composition of 5Ni/10Si + 90Al demonstrated the highest activity, achieving optimal performance at lower calcination temperatures. This catalyst generates a greater concentration of active sites, primarily due to nickel oxide (NiO), which creates these sites through both mild and strong interactions. The degree of graphitization is notably lowest for the 5Ni/10Si + 90Al composition. This catalyst achieved an impressive hydrogen yield of approximately 54%, with an H₂/CO ratio of 3.4 over a streaming period of up to 240 min. When the silica loading exceeds 10 wt.%, the interaction between the metal and the support weakens, resulting in a significant decrease in surface area and, subsequently, lower catalytic activity. The 5Ni/10Si + 90Al catalyst, which was prepared with calcination temperatures above 500 °C, has very few active sites during the Partial Oxidation of Methane (POM) reaction at a reaction temperature of 600 °C. This catalyst also exhibits a high degree of crystallinity, which leads to reduced exposure of the active sites. As a result, incorporating higher weight percentages of silica into the 5Ni/xSi + (100 − x) Al catalysts results in decreased activity. When the silica loading exceeds 10 wt.%, the interaction between the metal and the support weakens, resulting in a significant decrease in surface area and, subsequently, lower catalytic activity. The 5Ni/10Si + 90Al catalyst, which was prepared with calcination temperatures above 500 °C, has very few active sites during the POM reaction at a reaction temperature of 600 °C. This catalyst also exhibits a high degree of crystallinity, which leads to reduced exposure of the active sites. As a result, incorporating higher wt.% of silica into the 5Ni/xSi + (100 − x) Al catalysts results in decreased activity. These findings highlight the complex interplay between silica content, calcination temperature, and catalyst properties, significantly influencing catalytic performance in POM. Full article

COx-free H₂, along with uniform carbon nanotubes, can be achieved together in high yield by CH₄ decomposition. It only needs a proper catalyst and reaction condition. Herein, Fe-based catalyst dispersed over titania-incorporated-alumina (Fe/Ti-Al), with the promotional addition of lanthanides, like CeO₂ and La₂O₃, over it, is investigated for a methane decomposition reaction at 800 °C with GHSV 6 L/(g·h) in a fixed-bed reactor. The catalysts are characterized by temperature-programmed reduction (TPR), powder X-ray diffraction (XRD), Raman spectroscopy, and transmission electron microscopy (TEM). The promoted catalysts are facilitated with higher surface area and enhanced dispersion and concentration of active sites, resulting in higher H₂ and carbon yields than unpromoted catalysts. Ceria-promoted 20Fe/Ti-Al catalyst had the highest concentration of active sites and always attained the highest activity in the initial hours. The 20Fe-2.5Ce/Ti-Al catalyst attains >90% CH₄ conversion, >80% H₂-yield, and 92% carbon yield up to 480 min time on stream. The carbon nanotube over this catalyst is highly uniform, consistent, and has the highest degree of crystallinity. The supremacy of ceria-promoted catalyst attained >90% CH₄ conversion even after the second cycle of regeneration studies (against 87% in lanthanum-promoted catalyst), up to 240 min time on stream. This study plots the path of achieving catalytic and carbon excellence over Fe-based catalysts through CH₄ decomposition. Full article

Preeclampsia is a pregnancy-specific hypertensive syndrome recognized as the leading cause of maternal and fetal morbidity worldwide. Early diagnosis is crucial for mitigating its adverse effects, and recent investigations have identified endoglin as a potential biomarker for this purpose. Here, we present the development of a hybrid biosensor platform for the ultrasensitive detection of endoglin, aimed at enabling the early diagnosis of preeclampsia. This platform integrates the high surface area properties of nanoporous anodic alumina (NAA) with the unique optical characteristics of gold nanoclusters (AuNCs) to achieve enhanced detection capabilities. The NAA surface functionalized to promote attachment of AuNCs, which then was functionalized with specific antibodies to confer selectivity towards endoglin. Photoluminescence (PL) analysis of the biosensor demonstrated a linear detection range of 10–50 ng/mL, with a detection limit of 5.4 ng/mL and a sensitivity of 0.004 a.u./(ng/mL). This proof-of-concept study suggests that the NAA-AuNCs-based biosensing platform holds significant potential for the development of ultrasensitive, portable, and cost-effective diagnostic tools for preeclampsia, offering a promising avenue for advancing prenatal care. Full article

The purification and removal of polar impurities in olefin feedstocks is crucial for downstream deep processing, and adsorption is the main method for deep purification of such impurities. This article takes dimethyl ether, a typical oxygen-containing compound impurity in MTOs, as a polar impurity molecule, and LTA and FAU topological zeolites as research objects. The influence of zeolite topology, morphology, skeleton silicon–aluminum (Si/Al) ratio, and ion type on the adsorption and removal of trace dimethyl ether was investigated by XRD, SEM, XRF, and nitrogen adsorption–desorption methods. The FAU topological zeolites show a better adsorption performance for dimethyl ether owing to their larger specific surface area and unobstructed pores compared with LTA zeolites. Among FAU topological zeolites, the NaX zeolite a with lower framework silica–alumina ratio has the highest adsorption capacity for dimethyl ether. Magnesium ion exchange on NaX zeolites (MgNaX) reduce the specific surface area and adsorption capacity of the NaX zeolite. However, after forming with alumina as a binder, the adsorption capacity of the MgNaX–Al₂O₃ adsorbent is about 13% higher than that of the NaX–Al₂O₃ adsorbent without Mg ion exchange. This may be due to the decomposition of residual organic Mg salts in the Mg ion exchange samples during high-temperature calcination, resulting in a larger specific surface area for the formed adsorbent. Further characterization of NH₃–TPD and CO₂–TPD shows that Mg ion exchange weakens the acid–base active sites on the adsorbent surface. The reduction in acid–base sites reduces the occurrence of side reactions such as polymerization and isomerization caused by the exothermic adsorption of olefins on adsorbents. Repeated adsorption data show that the formed adsorbent has excellent regeneration–adsorption performance. Full article

Several Cu and Ni-based catalysts were synthetized over Ce-based supports, either pure or mixed with different amounts of alumina (1:2 and 1:3 mol/mol). Different metal loadings (10–40 wt%) and preparation methods (wet impregnation, co-precipitation, and flame-spray pyrolysis—FSP) were compared for the oxidative steam reforming of methanol. Characterization of the catalysts has been performed, e.g., through XRD, BET, XPS, TPR, SEM, and EDX analyses. All the catalysts have been tested in a bench-scale continuous setup. The hydrogen yield and methanol conversion obtained have been correlated with the operating conditions, metal content, crystallinity of the catalyst particles, total surface area, and with the interaction of the metal with the support. A Cu loading of 20% wt/wt was optimal, while the presence of alumina was not beneficial, decreasing catalyst activity at low temperatures compared with catalysts supported on pure CeO₂. Ni-based catalysts were a possible alternative, but the activity towards the methanation reaction at relatively high temperatures decreased inevitably the hydrogen yield. Durability and deactivation tests showed that the best-performing catalyst, 20% wt. Cu/CeO₂ prepared through coprecipitation was stable for a long period of time. Full methanol conversion was achieved at 280 °C, and the highest yield of H₂ was ca. 80% at 340 °C, higher than the literature data. Full article

Pyocyanin is considered a maker of Pseudomonas aeruginosa (P. aeruginosa) infection. Pyocyanin is among the toxins released by the P. aeruginosa bacteria. Therefore, the development of a direct detection of PYO is crucial due to its importance. Among the different optical techniques, the Raman technique showed unique advantages because of its fingerprint data, no sample preparation, and high sensitivity besides its ease of use. Noble metal nanostructures were used to improve the Raman response based on the surface-enhanced Raman scattering (SERS) technique. Anodic metal oxide attracts much interest due to its unique morphology and applications. The porous metal structure provides a large surface area that could be used as a hard template for periodic nanostructure array fabrication. Porous shapes and sizes could be controlled by controlling the anodization parameters, including the anodization voltage, current, temperature, and time, besides the metal purity and the electrolyte type/concentration. The anodization of aluminum foil results in anodic aluminum oxide (AAO) formation with different roughness. Here, we will use the roughness as hotspot centers to enhance the Raman signals. Firstly, a thin film of gold was deposited to develop gold/alumina (Au/AAO) platforms and then applied as SERS-active surfaces. The morphology and roughness of the developed substrates were investigated using scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques. The Au/AAO substrates were used for monitoring pyocyanin secreted from Pseudomonas aeruginosa microorganisms based on the SERS technique. The results showed that the roughness degree affects the enhancement efficiency of this sensor. The high enhancement was obtained in the case of depositing a 30 nm layer of gold onto the second anodized substrates. The developed sensor showed high sensitivity toward pyocyanin with a limit of detection of 96 nM with a linear response over a dynamic range from 1 µM to 9 µM. Full article