Search Results (45)

From the sedimentary rock moler, a specific fraction of diatomaceous earth suitable for fluidized-bed applications was isolated. Three heterogeneous catalysts were prepared by wet impregnation: Cu@diatomaceous-earth, Co₃O₄@diatomaceous-earth, and NiO@diatomaceous-earth. The new materials were characterized by XRD, SEM, BET, and ICP-OES analyses, and their minimum fluidization velocities were experimentally determined. The catalytic performance of the fluidized beds was evaluated in the conversion of formic acid and methanol to hydrogen. Cu@DE exhibited the highest hydrogen production, reaching 94% during formic acid decomposition at 377 °C and 96% during methanol conversion at 400 °C. The use of NiO@DE bed for methanol conversion allows for a reduction in the conversion temperature with a slightly lower hydrogen efficiency, 92% at 332 °C. For the first time, a combined FTIR–GC–PDHID analytical approach was applied for comprehensive identification of the process products. A method enabling the analysis of infrared-active species using Fourier-transform infrared spectroscopy was developed, while infrared-inactive hydrogen was separated on a chromatographic column and quantified using a Pulsed Discharge Helium Ionization Detector. Furthermore, a rapid sequential hydrogen-analysis procedure was established, allowing evaluation at a frequency of 0.05 Hz. The calculated TOF and GHSV values confirm the competitive performance of the Cu@DE fluidized-bed catalyst relative to previously reported fluidized-bed and fixed-bed reactor systems. Full article

In this study, catalytic wet oxidation of highly concentrated antibiotic-containing pharmaceutical wastewater was investigated under mild operating conditions (200–280 °C, 2.0~6.0 MPa) using a CuCe/Al₂O₃catalyst, synthesized via the co-impregnation method. The physicochemical properties of the catalyst were characterized by SEM-EDS, TEM, XPS. The catalytic performance results demonstrated that the CuCe/Al₂O₃ catalyst exhibited optimal catalytic activity, achieving a chemical oxygen demand (COD) removal efficiency of 86.3% under the following conditions: reaction temperature 280 °C, reaction time 60 min, initial oxygen pressure 1.2 MPa, and catalyst dosage 5.0 g/L. The superior catalytic performance was attributed to the synergistic effect between Cu and Ce species as well as their excellent dispersion on the support. Kinetic analysis revealed that the oxidation process proceeded via two sequential reaction steps and followed an apparent first-order kinetic model. Overall, this catalytic wet oxidation process offers an efficient pretreatment strategy for highly concentrated pharmaceutical wastewater containing antibiotics. Full article

The need for a transition to a low-carbon economy has led to the growing demand for hydrogen as a clean energy source. Hence, ethanol steam reforming (ESR) is one of the promising technological pathways for hydrogen production. Ethanol, which is the major feedstock, can be obtained from abundant biomass. However, one of the major drawbacks is catalyst deactivation due to the high temperature requirement to start the reaction. This study therefore focused on employing a response surface approach to optimize the operating conditions (reaction temperature, steam-to-ethanol ratio and catalyst amount) of ethanol steam reforming over an Iridium-promoted Ni/MCM-41 catalyst. The Iridium-promoted Ni/MCM-41 catalyst was synthesized using the sequential wet impregnation method and characterized using field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), N₂ physisorption analysis, and X-ray diffraction (XRD). A central composite experiment design (CCD) was employed to study the effect of the variables on the hydrogen production from the ESR. The catalytic efficacy was ascertained by evaluating the H₂ yield under varied experimental conditions provided by the CCD. The characterization of the catalyst revealed well-dispersed Ir and Ni nanoparticles on a mesoporous MCM-41 support. Catalytic evaluations indicate that the H₂ yield was most influenced by the reaction temperature (correlation coefficient of 0.68), followed by the catalyst amount (correlation coefficient of 0.34) and steam-to-ethanol ratio (correlation coefficient of 0.28). A maximum H₂ yield of 5.82 mol/mol ethanol was obtained at 798.11 °C, a steam-to-ethanol ratio of 3.40, and 1.25 g of catalyst. These findings underscore the importance of Ir-promoted Ni/MCM-41 catalyst for efficient H₂ production, highlighting the reaction temperature as a critical parameter for process optimization. Full article

This study investigates the influence of isomorphous substitution of Aluminum by V, Zr, La, and Ni in Beta zeolite frameworks used as supports for Ni-based dry reforming of methane catalysts. The research focuses on how the nature of the incorporated metal affects catalytic activity and long-term stability. Catalysts were synthesized using both co-impregnation and sequential impregnation strategies. Physicochemical characterization—including gas adsorption, X-ray diffraction, transmission electron microscopy, and H₂ temperature-programmed reduction—revealed distinct structural roles for each metal. Results indicate that V primarily occupies T-vacancy sites within the dealuminated Beta framework, whereas Ni resides as charge-compensating extra-framework species or highly dispersed NiO clusters. Zr and La tend to form highly dispersed oxide species or occupy enlarged silanol nests. Notably, the addition of La₂O₃ was found to significantly enhance the long-term stability of the catalysts during the dry reforming of methane process. V-modified catalysts exhibited the highest activity but suffered from low stability; conversely, Zr incorporation offered the best overall performance, balancing high activity with enhanced stability, achieving 85% CO₂ and 75% CH₄ conversion, with no detectable carbon deposition after 98 h on stream. Full article

Polycyclic aromatic hydrocarbons (PAHs) are highly toxic pollutants in marine ecosystems, necessitating efficient remediation. This study synthesized magnesium phthalocyanine (MgPc) and its modified derivatives, magnesium azaphthalocyanine (NMgPc) and methyl-substituted magnesium azaphthalocyanine (MeNMgPc), as visible-light-driven photocatalysts for PAH degradation. To enhance efficiency and recoverability, these photosensitizers were immobilized onto coconut shell activated carbon (AC) via multiple ultrasonic impregnation. Characterizations (UV-Vis, SEM, EDAX, BET) confirmed successful active component deposition; nitrogen substitution and peripheral methyl groups synergistically tuned the electronic structure and suppressed aggregation. Under xenon lamp irradiation, the MeNMgPc/C composite exhibited superior activity, degrading 90.55% of naphthalene. Box-Behnken response surface optimization identified optimal conditions (13.18 g/L dosage, 20 A, 2.28 h), yielding 96.67% experimental removal and adhering to pseudo-first-order kinetics. Mechanistic studies via electron spin resonance identified hydroxyl (•OH) and superoxide radicals (O₂^•−) as primary reactive species. GC-MS analysis elucidated a sequential phenanthrene ring-opening pathway, progressing to ultimate mineralization into CO₂. Consequently, MeNMgPc/C presents a highly efficient, recoverable photocatalytic platform for marine PAH remediation. Full article

Glued-laminated timber (GLT) and cross-laminated timber (CLT) panels are increasingly used as exposed structural elements in representative buildings. These structures are often part of public-use areas, which require the application of restrictive fire-safety measures without significantly affecting the color of exposed wooden surfaces during the service life of these building elements. The effect of fire-retardant treatments on the color of Scots pine (Pinus sylvestris L.) wood was evaluated using five impregnation agents with different active substances. Changes in gloss and color characteristics—lightness (L*), green-red coordinate (a*), and blue-and-yellow coordinate (b*)—were measured sequentially directly after impregnation, after exposure to variable humidity conditions and after exposure to UV radiation. The total color difference (ΔE*) ranged from 2.82 to 17.76 after impregnation and increased to 6.31–20.71 after aging, indicating a risk of aesthetic deterioration of fire-retardant-treated wood surfaces under typical service conditions for timber structures in representative buildings. The most pronounced color changes were observed for the fire retardant containing potassium and copper compounds (FR4) and the combination of 2-aminoethanol with boric acid (FR5). Full article

To increase printing speed and quality, a route consisting of using two sequential coextruders to form impregnated fiber immediately before feeding it to the printer. Such an approach, aimed at allowing the use of the most common industrial 12K carbon fibers for additive manufacturing, prevents damage to composite fibers during transportation, storage, and loading. An elaborate system was used to prepare carbon fibers impregnated with polypropylene, ethylene vinyl acetate, and their blends. The used scheme allows the production of composite fibers containing from 60 to 80 wt. % of carbon fibers. It was found that the elastic modulus of the composite fibers is close to those for raw carbon fibers and does not depend on the used polymer. It shows that the used carbon fiber path in the polymer melt and two sequential calibrating nozzles result in a high degree of orientation of the elementary filaments in the fiber at impregnation and maintain the elastic properties of the carbon fiber in the resulting composite. The tensile strength of the composite fibers depends on the polymer content in the composite fiber; the highest tensile strength was observed for fibers impregnated with ethylene vinyl acetate when increasing the coextrusion temperature up to 220 °C, which results in a composite fiber with a polymer content of 30 wt. %. A decrease in the polymer content in composite fibers results in a decrease in strength. Full article

The main goal of this work was to determine the role of copper in bimetallic nickel–copper BEA zeolite catalysts prepared by sequential impregnation and co-impregnation, as well as defining the influence of the method of impregnation on the catalytic activity of the described catalysts. The all-prepared samples were tested in hydrocracking reactions with rapeseed oil as a feedstock. The physicochemical properties of the catalytic materials were determined using H₂-TPR, TPD-NH₃, XRD, BET, and SEM-EDS techniques. The reaction products were analyzed using chromatographic techniques (HPLC and GC-MS). The bimetallic systems obtained post-impregnation exhibited lower conversions of rapeseed oil than catalysts synthesized by co-impregnation. For all bimetallic catalysts, oil conversion was higher than for the monometallic copper BEA zeolite catalyst. This indicates that nickel is responsible for better oil conversion. The highest oil conversion (92.7%) was noted for the co-impregnated 5%Ni-5%Cu_BEA zeolite catalyst. For all tested catalysts, the highest selectivity was noted for the gasoil fraction. However, the presence of copper in bimetallic Cu-Ni_BEA zeolite catalysts led to increased selectivity towards gasoline and kerosene compared to the monometallic nickel BEA zeolite catalyst. Full article

Catalytic dry reforming of ethanol offers a sustainable pathway for syngas and hydrogen production through CO₂ utilization, though its efficiency depends heavily on the strategic synthesis of catalysts and the optimization of reaction parameters. This study employs Box–Behnken Design (BBD) and Response Surface Methodology (RSM) to optimize hydrogen yield from CO₂ reforming of ethanol over a Yttrium-promoted Ni-Co/MCM-41 catalyst. The catalyst was synthesized using sequential wet impregnation method and characterized for its physicochemical properties. The catalyst was tested in fixed-bed reactor using experimental data obtained from BBD considering the effects of temperature (550–700 °C), ethanol flowrate (0.5–1 mL/min) and CO₂ flowrate (15–30 mL/min) on the hydrogen yield. The experimental conditions were optimized using RSM quadratic model. The characterization revealed that the ordered mesoporous nature of the MCM-41 is maintained providing a high surface area of 597.75 m²/g for the catalyst. The addition of Yttrium as a promoter facilitates the formation of well crystallized nanoparticles. Maximum hydrogen yield of 85.09% was obtained at 700 °C, 20.393 mL/min and 0.877 mL/min for temperature, CO₂ and ethanol flowrate, respectively. The predicted hydrogen yield obtained is strongly correlated with the actual values as indicated by R² of 0.9570. Full article

Recently, research has increasingly focused on the introduction of non-precious metals and developing highly stable carriers to enhance catalyst performance. In this study, we successfully synthesized copper (Cu)-modified biochar catalysts utilizing a sequential approach involving enzymatic treatment, liquid impregnation, and activation processes, which effectively enhanced the dispersion and introduction efficiency of Cu onto the biochar, thereby reducing the requisite Cu loading while maintaining high catalytic activity. The experimental results showed that the toluene degradation of 10%Cu@BCL was three times higher than that of unmodified activated carbon (AC) at 290 °C. A more uniform distribution of Cu was obtained by the enzymatic and activation treatments, optimizing the catalyst’s structural properties and reducing the amount of Cu on the biochar. Moreover, the transformation between various oxidation states of Cu (from Cu⁰/Cu(I) to Cu(II)) facilitated the electron transfer during the degradation of toluene. To further understand the catalytic mechanisms, density functional theory (DFT) calculations were employed to elucidate the interactions between toluene molecules and the Cu-modified biochar surface. These findings reveal that the strategic modification of biochar as a carrier not only enhances the dispersion and stability of active metal species but contributes to improved catalytic performance, thereby enhancing its degradation efficiency for VOCs in high-temperature conditions. Full article

A double-layer core–shell photocatalytic coating was engineered on carbon fibers (CFb) derived from bamboo pulp precursors, employing a sequential process involving seed pre-loading, solvothermal treatment, and impregnation. XRD, SEM, and SEM-EDS analyses revealed that g-C₃N₄ and Bi₂O₃ nanosheets were co-assembled on the carbon fiber skeleton, and 50 nm MoS₂ particles were successfully loaded, resulting in the fabrication of MoS₂/g-C₃N₄/Bi₂O₃/CFb photocatalytic fibers. UV–vis spectroscopy, transient photocurrent response, and EIS tests demonstrated that the introduction of narrow-bandgap visible-light photocatalysts (g-C₃N₄ and MoS₂) enhanced light absorption and improved the separation and migration efficiency of photogenerated electron hole pairs. Photocatalytic degradation experiments of MB showed that MoS₂/g-C₃N₄/Bi₂O₃/CFb significantly outperformed g-C₃N₄/Bi₂O₃/CFb and Bi₂O₃/CFb, achieving a degradation efficiency of 92% within 60 min. Band structure calculations and analysis confirmed the formation of Z-scheme heterojunctions between g-C₃N₄ and Bi₂O₃, as well as between MoS₂ and Bi₂O₃. This dual Z-scheme heterojunction endowed MoS₂/g-C₃N₄/Bi₂O₃/CFb with enhanced redox capabilities, providing a novel strategy for developing efficient photocatalytic materials. Full article

The production of hydrocarbon-based biofuels has been the target of intense research worldwide. In this context, the core goal of the present work was to investigate the use of mesopore-rich activated carbons (ACs) as support for sulfided Mo-based catalysts intended for the hydroprocessing of lipidic feedstocks. The key motivations for the work were that, in comparison to traditional inorganic supports such as Al₂O₃, ACs are less propense to form coke, due to their lower acidity, and are highly resistant to hydrolysis, which is a very important aspect in the hydroprocessing of lipidic feedstocks because water is abundantly produced during the process. Furthermore, the porosity of ACs can be tailored to give rise to a high mesopore content, which is important for improving the access of bulky triglyceride molecules to metallic active sites located inside the pores network. A systematic study on the effects of the preparation conditions on the properties and performance of the obtained catalysts was carried out for the first time. The highest hydrodeoxygenation (HDO) activity was verified for the catalyst prepared through sequential deposition of Mo and Ni by wet impregnation. The prepared catalyst presented better performance for coconut oil HDO than an industrial sulfided NiMo/Al₂O₃ catalyst. Furthermore, it presented good stability, provided that the sulfidation degree was kept high. The obtained results evidenced that ACs have great potential to replace inorganic support in sulfided Mo-based catalysts. Full article

The selective hydrogenolysis of glycerol to 1,3-Propanediol (1,3-PDO) presents a sustainable approach, leveraging a bio-renewable feedstock and significantly enhancing the economic viability of biodiesel production. However, the limited selectivity toward 1,3-PDO in glycerol hydrogenolysis has hindered its widespread adoption on an industrial scale. In this work, we synthesized a series of Pt/WO₃–Al₂O₃ catalysts using a simple wetness sequential impregnation method. Comprehensive characterization and kinetic studies revealed that the surface tungsten content of the catalyst exerted a critical and multifaceted influence on the catalytic performances. Under optimal conditions, glycerol could be selectively converted to 1,3-PDO with a yield of 43% in a fixed-bed continuous flow reactor. Furthermore, a plausible reaction mechanism for glycerol hydrogenolysis was proposed based on the correlations between catalyst structure and catalytic performance. Full article

Real textile wastewater (RTWW) poses significant environmental challenges. RTWW typically contains high levels of organic compounds, such as dyes, as well as inorganic substances like salts. These contaminants can harm aquatic life when released into water bodies without appropriate treatment. RTWW was subjected to a series of sequential treatments: exchange resins for removing ions, advanced oxidation with bicarbonate-activated peroxide to degrade organic matter, and a biological treatment based on the Zahn–Wellens test to remove remaining chemical oxygen demand (COD) The advanced oxidation process based on the activation of H₂O₂ with NaHCO₃ (catalyzed with cobalt impregnated on a pillared clay, Co/Al–PILC)) was optimized using central composite design (CCD) and response surface methodology (RSM). After the process integration, reductions in ion concentrations, chemical oxygen demand (COD), and total organic carbon content (TOC) were achieved. Reduced hardness (99.94%) and ions (SO₄²⁻ and acid black 194 dye of 99.88 and 99.46%, respectively), COD (96.64%), and TOC (96.89%), guaranteeing complete treatment of RTWW, were achieved. Additionally, the biodegradability index of RTWW increased from 0.28 ± 0.01 to 0.90 ± 0.01, and phytotoxicity was reduced, going from a phytotoxic that inhibited the germination of lettuce seeds to a phytostimulant after biological treatment with activated sludge. Full article

With a rising interest in smart windows and optical displays, the utilization of metal oxides (MOs) has garnered significant attention owing to their high active sites, flexibility, and tunable electronic and optical properties. Despite these advantages, achieving precise tuning of optical properties in MOs-based quantum dots and their mass production remains a challenge. In this study, we present an easily scalable approach to generate WO₃ quantum dots with diverse sizes through sequential insertion/exfoliation processes in solvents with suitable surface tension. Additionally, we utilized the prepared WO₃ quantum dots in the fabrication of luminescent transparent wood via an impregnation process. These quantum dots manifested three distinct emitting colors: red, green, and blue. Through characterizations of the structural and optical properties of the WO₃ quantum dots, we verified that quantum dots with sizes around 30 nm, 50 nm, and 70 nm showcase a monoclinic crystal structure with oxygen-related defect sites. Notably, as the size of the WO₃ quantum dots decreased, the maximum emitting peak underwent a blue shift, with peaks observed at 407 nm (blue), 493 nm (green), and 676 nm (red) under excitation by a He-Cd laser (310 nm), respectively. Transparent woods infused with various WO₃ quantum dots exhibited luminescence in blue/white emitting colors. These results suggest substantial potential in diverse applications, such as building materials and optoelectronics. Full article