Topics in Catalysis最新文献

The present investigation highlights the photodegradation of inorganic dyes from textile wastewater, which is prevalently poisonous and harmful to the entire population. To address this issue, we explored environmentally friendly, chemical-free methods, which in turn demonstrated an efficient, cost-effective approach to environmental remediation. In this context, SnO₂ nanoparticles (SnO₂ NPs) are synthesized using pomelo fruit peel waste, optimizing the green route. The present research shows the effect of green synthesised SnO₂ NPs in methylene blue dye degradation using photocatalysis under UV radiations. The green SnO₂ NPs have vast surface area, strong photocatalytic activity, and efficient reusability up to 2 cycles after treatment. The present investigation uses pomelo fruit peel waste as a reducing agent, which has not previously been claimed to be responsible for the synthesis of SnO₂ NPs. It degrades the high concentration (30ppm) of methylene blue dye up to 67% using a low amount of catalyst (1.25 g/L MB dye solution) in just 25 min. The size of green synthesized SnO₂ NPs is also very small, and the band gap energy is narrow as compared to previous research, i.e. 2.79 eV, which is favourable for photocatalysis. The SnO₂ NPs were characterized using various techniques, including UV-Vis spectrophotometer (UV-Vis), Fluorescence spectrophotometer (photoluminescence), X-ray diffraction (XRD), Field emission electron microscopy (FESEM), Energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared (FTIR), High-resolution transmission electron microscopy (HRTEM) and Dynamic light scattering (DLS). The size of the nanoparticles was found to be approximately 9 nm using the Debye Scherrer formula and 5 nm using the Williamson-Hall method. The photocatalytic activity of SnO₂ NPs against the degradation of the cationic dye methylene blue (MB) and textile dye was evaluated under a UV lamp (15/30 W mercury lamp). The textile effluent dye degradation efficiency and antimicrobial efficiency of green synthesized SnO₂ NP were also tested for collected industrial wastewater samples. The work demonstrates that green SnO₂ NPs could serve as a promising photocatalyst for the degradation of industrial effluent and contribute to green chemistry and environmental sustainability.

This study investigated the impact of calcination temperature on the structural properties of CuAl catalyst which was found to be a robust nano-structured catalyst calcined directly without ramping at 400 °C and performed exceedingly well for aqueous phase hydrogenolysis of glycerol. Various samples of CuAl catalysts were prepared by co-precipitation at Cu: Al molar ratio 1:1 and were calcined at different temperatures (300–1000 °C). The obtained catalysts were reduced at 200 °C before their activity testing for glycerol hydrogenolysis reaction. To correlate the structure-activity, the catalysts were thoroughly characterized by XRD, XPS, BET, TEM, H₂-TPR, NH₃-TPD, and pyridine FTIR. It was observed that with an increase in calcination temperature from 300 to 700 °C, the glycerol conversion also increased from 47 to 55% with 93% selectivity to 1,2-PDO. The better performance of these catalysts was mainly related to the predominant presence of Brønsted acid sites, an appropriate ratio of the Cu⁰ to CuAl₂O₄ + CuO (0.33) and CuAl₂O₄ to CuO phases (0.35), the existence of Cu₂O phase and the smaller Cu⁰ particle size. It was shown that altering the ramping rate for the calcination temperature of 400 °C impacted the catalytic activity. The CuAl-400 (DC) (direct calcined) catalyst exhibited a maximum glycerol conversion of 60%.

At low temperature and pressure (20 ^o C and 1 atm), the oxidation of 1,2-dichlorobenzene using ozone and metal (Mn, Ni, V, and Fe) supported on TiO₂ catalysts was investigated in this study. The metal loaded on TiO₂ catalysts were prepared using the wet impregnation method and characterized using FT-IR, XRD, SEM-EDX, BET, TEM, and ICP-OES techniques. 1,2-dichlorobenzene was oxidized for 24 h and the sample aliquots were collected after 3, 6, 9, 12, 15, 18, and 24 h of ozonation. The ozonation products were identified using GC-MS and FT-IR techniques and the identified products were 3,4-dichloro-2,5-furandione (DHF) and mucochloric acid (MCA). The 2.5% Fe/TiO₂ was found to be the most active catalyst with a percentage conversion of 73% after 24 h of ozonation. Among the identified products, MCA recorded the highest percentage selectivity after 24 h of ozonation in all the metal-supported TiO₂ catalyzed ozonation reactions. The highest percentage of selectivity towards the formation of the main product was 97%.

Lactic acid (LA) is an essential chemical that produces high-value-added products across various industries. However, its traditional production via sugar fermentation raises environmental concerns, highlighting the need for alternative, biomass-based production methods. This study investigates the production of LA from hydroxyacetone (HA) oxidation using a Cu/ZrO₂ catalyst prepared by the incipient impregnation method. The catalyst was characterized through several techniques such as ICP-MS, SEM-EDS, N₂-physisorption, XRD, XPS, H₂-TPR, N₂O chemisorption, NH₃-TPD, CO₂-TPD, Pyridine FT-IR, and TPO analyses, revealing well-dispersed copper species in the zirconia’s tetragonal phase, imparting distinctive redox and acid-base properties. In this contribution, we progressively assessed some reaction parameters and established conditions, including a temperature of 120 °C, a specific HA concentration, and an HA-to-catalyst ratio, to boost the lactic acid performance. Moreover, computational chemistry calculations of Gibbs free energy on model intramolecular and intermolecular Cannizzaro-type reactions demonstrated a distinct preference for lactic acid formation over pyruvic acid, offering valuable insights into the reaction mechanism and spontaneity.

Graphical Abstract

Herein, we reported the synthesis of molybdenum (Mo) doped tungsten trioxide (Mo@WO₃) by employing simple strategies. The physicochemical properties of the synthesized WO₃ and Mo@WO₃ samples were analyzed by powder X-ray diffraction method to examine the phase purity and formation of the proposed materials. The surface structural characteristics of the prepared samples were examined on scanning electron microscope whereas composition and elements have been authenticated by utilizing energy dispersive X-ray spectroscopy. We also adopted X-ray photoelectron spectroscopy to further confirm the presence of Mo in the prepared Mo@WO₃ sample. Subsequently, glassy carbon electrode (GC) has been modified using the electrocatalyst (WO₃ or Mo@WO₃) for the determination of 2,4,6-TNP. Voltammetry methods such as cyclic voltammetry and differential pulse voltammetry were used to examine the sensing ability of the fabricated electrode (Mo@WO₃/GC). The detection limit of 0.3 µM and sensitivity of 3.41 µA.µM⁻¹.cm⁻² were obtained using Ni@WO₃/GC as the sensor for the determination of 2,4,6-TNP. The proposed electrode i.e. Mo@WO₃/GC also exhibits decent selectivity and stability for the sensing of 2,4,6-TNP.

Anion sensing represents a significant challenge in modern day due to the essential roles that anion play in environmental, biological, and industrial processes. Developing effective and selective sensors for anion is crucial for chemical analysis, and environmental monitoring. Here, we report density functional theory (DFT) and time dependent-density functional theory (TD-DFT) calculations to investigate the cyanide anion sensing mechanism of the Dicyanovinyl-substituted Benzofurazan derivative (C1). Thermodynamic parameters, such as free-energy and binding-energy change revealed the feasibility of cyanide anion addition to the molecule C1. Frontier molecular orbital (FMO) analysis indicated the absence of intramolecular charge transfer (ICT) in C1, however, upon cyanide addition (C1CN), the shift in electron density suggests the presence of ICT. Furthermore, natural bond orbital (NBO) analysis identifies the atom C15 as the optimal site for anion addition. This work provides detailed insights into the sensing mechanism of C1 molecule, highlighting its potential as a selective sensor for cyanide anions.

Water pollution has increased in recent years with pharmaceutical pollutants, such as tetracycline pollution. This pollutant has a harmful effect on the environment, water resources, agriculture, and drinking water for humans, animals, and agriculture. This research aims to use some nano oxides (vanadium pentoxide and nickel oxide) as an adsorbent material to remove this pollutant from water. The thermal method (reflex) was used to prepare vanadium pentoxide and the Sol–Gel method was used to prepare nickel oxide. The prepared oxides were calcined at 500 °C and then characterized by several methods, including UV/Visible, FTIR, XRD, SEM, and AFM. These prepared oxides were used to remove tetracycline from aqueous solution, and these prepared nano oxides showed variation in their removal efficiency (%R and qt), depending on the type of nano and its calcination temperature. Vanadium pentoxide ranked first in removal in both cases (as prepared and calcination), and the first case (as prepared) was considered the best, so it was adopted for optimal working conditions in terms of the best weight of the adsorbent material (nano), the highest concentration of the pollutant (tetracycline), the highest concentration of the detector (permanganate), the fastest stirring speed, and the best stirring time. Isotherm calculations were also performed using Langmuir and Freundlich equations.

The carbon paste was boosted with a nanocomposite of ZIF-8 and ZnO nanoparticles and used for the fabrication of a modified electrode named ZIF-8, ZnONP/CPE. Then, a thin film of poly L-cysteine was electrodeposited on its surface. The synthesized nanomaterials and modified electrode were characterized by utilizing scanning electron microscopy, FT-IR, and X-ray diffraction techniques. The electrochemical behavior of morphine was studied using fabricated electrodes by cyclic and differential pulse voltammetry methods. Evaluating the pH effect on morphine oxidation at ZIF-8, ZnONP/CPE revealed a two electrons-one proton reaction. Based on Tafel slope the electron transfer coefficient equal to 0.6 was obtained. The diffusion coefficient of 1.75 × 10^− 5 cm²/s was calculated for morphine by applying Cottrell’s relation on the chronoamperogarms current. The optimized electrochemical parameters resulted in the outstanding performance of the developed sensor for detecting morphine, encompassing a broad linear range from 9 nM to 250 µM and achieving a low detection limit of 1 nM.

The unprecedented growth in economy and industry caused the rapid increase of CO₂ emission which impacts health and environment. The climate change and global warming are remarkable challenges calling for urgent need to mitigate CO₂ concentration in the atmosphere. The conversion of CO₂ into carbon-based fuel (methane) is the promising approach to pursue the goal of mitigation. The extensive studies of nickel-based catalysts in CO₂ methanation are due to the obvious superiorities such as the tremendous activity, availability, and low price. The nickel silicate (NiSil) nanotubes catalysts synthesized by solvothermal method and different loadings of Co species (0.25–1.0 wt%) were deposited by chemical deposition under sonication treatment. Various techniques such as XRD, TEM, FT-IR, DRUV-vis, XPS and N₂ physisorption were used to investigate the physicochemical properties of the catalysts. The results from the measurements confirmed the successful preparation of the Co deposited NiSil catalysts with the required physicochemical properties. Among the synthesized catalysts, 0.5Co–NiSil catalyst offered the highest CO₂ methanation activity, mainly due to the high surface area, pore volume, easy reducibility, and lower particle size. In addition, time on stream analysis revealed that the Co deposited NiSil catalysts exhibited considerable stability (48 h) without losing catalytic activity.

Increasingly stricter regulations for vehicle emissions require more competitive exhaust emission control systems. Three-way catalysis is a major up-to-date emission control technology, though the activity could be limited during the cold start as well as steady state operation including the three regimes: rich (λ<1), lean (λ>1), and stoichiometric (λ=1). Periodic rich/lean switching emerges as a promising strategy to address this challenge. In this work, we investigate the influence of the switching process, using a fixed lambda air-to-fuel ratio amplitude of λ = 1±0.02 (0.5 Hz), on pollutant conversion from 100 to 400 °C, under a complex matrix including nitrogen monoxide (NO), carbon monoxide (CO), hydrogen (H₂), and hydrocarbons (C₁-C₅), simulating the typical car exhaust gas. Moreover, two catalysts were tested: one homogeneously coated with Pd, and another zone-coated with Pd, both containing the same total amount of Pd, in order to identify the effect of the catalyst zone-coating and rationalize the use of increasingly scarce platinum group metals. Simple binary pollutant oxidation reactions were also performed to determine the reactivity of individual pollutant gases. Interestingly, NO, CH₄ and C₅H₁₂ displayed highest conversions during the switching regime compared to steady-state periods, attributed to the beneficial balance between active site poisoning/regeneration during the rich/lean regimes respectively. The zone-coated catalyst showed an overall higher activity under the full gas mixture that could be explained by a slightly higher Pd content, more effective Pd-support interactions, exothermic effect or the better OSC properties.