Catalysis Letters最新文献

This work explored the possibility of doping MnO₂ structure simultaneously by cationic (Na⁺, Mg²⁺ or K⁺) and nitrogen species during its synthesis through gliding arc plasma route. Therefore, NaMnO₄, Mg(MnO₄)₂ or KMnO₄ precursor has been precipitated via plasmachemical reduction thanks to NO⋅ and NO₂⁻ respectively being short and long-lived species generated in plasma plume (gas phase) and plasma post-discharge (liquid phase). Physicochemical characterizations revealed nanostructured NaN–MnO₂, MgN–MnO₂ and KN–MnO₂ respectively with specific surface areas of 36, 110 and 116 m²/g, nitrogen atomic loading at surface of 0.6, 1.0 and 1.5%, and band gap values of 1.20, 1.30 and 1.45 eV. The three precursors with different cationic species allowed different nitrogen loading for their respective plasma-synthesized MnO₂, which led to the different values of band gap energy. An increase of the N-loading induced an increase of band gap energy and enlarged the absorption capability of MnO₂ from visible light to the UV region. Solar photocatalytic removal of TY revealed bleaching degrees of 53, 97 and 94% respectively for NaN–MnO₂, MgN–MnO₂ and KN–MnO₂ materials. This enlargement, together with the increased specific surface area of the plasma-synthesized N–MnO₂, led synergistically to an enhancement of its photocatalytic activity. This work highlights the usefulness of the synthesis via glidarc plasma, without any additional reagent, of MnO₂, as allowing cationic species insertion in their structure, and simultaneously their doping with different N-loading, so leading to different crystalline structures, and photocatalytic activities.

Graphical Abstract

In this work, we report a method of obtaining and characterizing (Fe, Pb) co-doped titanium oxide nanoparticles to study the influence of Fe³⁺ and Pb²⁺ doping on the photocatalytic and antimicrobial properties of TiO₂. The presence of dopant elements can provide electronic changes by promoting a decrease in the band gap or creating intra-band gap states, thereby allowing greater absorption under visible light irradiation and potentially increasing the efficiency for developing photocatalytic and antimicrobial applications. Therefore, co-doped Ti_1−x−yFe_xPb_yO₂ (x and y = 0, 0.01, 0.03, 0.07 mol) powders were successfully obtained in a single step by the sonochemical method (SM). The structural, morphological and optical properties were evaluated using X-ray diffraction (XRD), transmission electron microscopy (TEM), Field Emission Gun—Scanning Electron Microscopy (SEM-FEG) and UV–Visible spectroscopy (UV–Vis) techniques. The results showed the successful formation of the anatase phase of (Fe, Pb) co-doped TiO₂ by the SM with nanometric particles of irregular morphology. The photoluminescence exhibited low intensity for the co-doped samples, indicating a decrease in the recombination rate of the e−/h + electronic pair, which contributes to the photocatalytic efficiency. Optical measurements revealed a decrease in the band gap, providing possible energetic activation of these semiconductors by sunlight. The photocatalytic activity was estimated through the methylene blue dye (MB) degradation when exposed to UV light and Sunlight, and revealed that the type of radiation used to activate the photocatalysts influences the catalytic activity: T1F (Ti_0.99Fe_0.01O₂) and T1P (Ti_0.99Pb_0.01O₂) samples degraded the dye by 50% and 65% under UV light for 120 min, respectively, while the degradation under Solar irradiation was 98% and 99%, respectively. Antimicrobial properties were also investigated by agar diffusion method against E. coli (gram-negative) and S. aureus (gram-positive) bacteria and showed positive results of (Fe, Pb) co-doped TiO₂ samples compared to pure TiO₂. Accordingly, the results indicate that the co-doping of TiO₂ with Fe³⁺ and Pb²⁺ influences its potential application as photocatalysts and antimicrobial agents.

Graphical Abstract

Herein, Ag/TiO₂ NH₃-SCO catalyst was prepared by impregnation-rotary evaporation method with different calcination temperature and Ag loading content. The results of performance evaluation and characterization showed that the 10 wt% Ag/TiO₂ catalyst calcined at 500 °C showed the best comprehensive performance, with T₉₉ reaching 175 °C and N₂ selectivity reaching 80% at high temperatures. High-temperature calcination will lead to a significant decline in catalyst activity, accompanied by the transformation of TiO₂ from anatase to rutile phase and the obvious change and loss of Ag active sites, which greatly reduces the NH₃ adsorption and redox ability, but it can still maintain a high N₂ selectivity due to unchanged reaction mechanism. In addition, with the increase of Ag loading, excess Ag on Ag/TiO₂ will form metal clusters due to the lack of sufficient anchor points, which helps to improve NH₃-SCO activity. However, excessive Ag loading will reduce the specific surface area and acidic sites, and the Ag species on the catalyst surface will also change to the form of larger particles of Ag₂O, which will lead to the decline of catalytic performance.

Graphical Abstract

The catalytic oxidation of CO is a significant process for environmental and human health protection. The CuMnO_x (hopcalite) catalyst is a good candidate for the CO oxidation reaction, owing to advantages such as low cost and good catalytic activity at low temperature. In this study, a combination of reactive force field molecular dynamic simulations and density functional theory calculations was employed to investigate the CO oxidation reaction catalyzed by CuMnO_x. We examined the effect of three factors (oxygen content of CuMnO_x catalyst, pressure, and free O₂ concentration) on enhancing the CO conversion. The CuMnO₄ catalyst exhibited superior performance in the CO oxidation reaction. The main oxygen source of the oxidation product (CO₂) was found to be the lattice oxygen atoms of the CuMnO_x catalyst. The energy barrier of the oxidation reaction between CO and the lattice oxygens was relatively low, showing that this reaction was kinetically favored. The present results provide microscopic insight into the CO oxidation reaction catalyzed by CuMnO_x, which is expected to elucidate the corresponding mechanism and thus guide the design of highly active catalysts.

Graphical Abstract

Poly(triazine imide) is a non-metal semiconductor material with remarkable photocatalytic properties, which was successfully employed for selective photoreactions. Currently, pristine forms of semiconductors are inefficient and rarely used as such. Instead, various composites are being composed on their base in search of more efficient means for photo-activated processes, such as hydrogen evolution, pollution remediation and selective photoreactions. In pursuit of a more efficient photoactive material catalyzing selective photooxidation of an alcohol to an aldehyde, we screened various compositions of PTI and hematite obtained in hydrothermal conditions. Although conversion rates exhibited by the best sample of the composites did not exceed those of pristine PTI, selectivity of the process was improved to 98% at the conversion rate of 99%.

Graphical Abstract

New SCR catalysts based on Mn supported on simple or mixed aerogel oxides (Mn/ZrO₂, Mn/CeO₂-ZrO₂ and Mn/CeO₂-ZrO₂-SO₄²⁻) were prepared for selective catalytic reduction of nitrogen oxide by ammonia (NO-SCR by NH₃). One step sol gel method followed by supercritical drying process were used for elaborating the catalytic supports, however, Mn species were incorporated into aerogels via impregnation method. Structural, textural, acidic and redox properties of samples were studied using XRD; BET and porosity measurements; NH₃-TPD and H₂-TPR techniques. The results revealed that Mn/ZrO₂ and Mn/CeO₂-ZrO₂ solids develop mesoporous texture, good crystallinity of zirconia tetragonal phase and nano-sized particles but exhibit a poor NO-SCR activity. The addition of SO₄²⁻ induces a disorder in ZrO₂ structure but it generates very active strong acid sites for the high temperature NO reduction. 100% NO conversion into N₂ was achieved above 400 °C over the new Mn/CeO₂-ZrO₂-SO₄²⁻ catalytic system.

Graphical Abstract

Direct synthesis of liquid fuel (C₅₊ hydrocarbons) through CO₂ hydrogenation has attracted considerable interest. However, it is plagued by high selectivity of C₁ by-products (CO and CH₄) and low reaction activity. Herein, we report that Na-FeZn catalysts promoted by a combination of metal additives and investigate their synergistic effect in the catalytic CO₂ hydrogenation reaction. The CO₂ conversion is high to 40.6% with the 68.3% C₅₊ selectivity. The characteristic results reveal the specific surface area has a great influence on the catalytic performance. Furthermore, the synergistic effect of Mn in the catalyst enhances CO₂ adsorption while weakening H₂ adsorption, thus remarkably promoting the carbon chain growth and limiting the production of C₁ products. This study offers a promising approach to modulating the metal electronic environment and improving carbon efficiency for CO₂ hydrogenation reactions.

Graphical Abstract

We present a simple NaFeZnMn-S nanocatalyst that can effectively catalyze CO₂ hydrogenation to C₅₊ hydrocarbons. The selectivity towards C₅₊ hydrocarbons is as high as 68.3% at 40.6% CO₂ conversion.

After the outbreak of COVID-19, the severe threat to the entire biological environment caused by the extensive use of chloroquine phosphate (CQ) continues. In this paper, a new sol–gel method was used to inject highly active Co into the PrSmMnO₃ matrix structure to prepare a novel perovskite composite catalyst PrSmCo_0.8Mn_0.2O₃ with stable properties, and was used to efficiently activate monopersulfate (PMS) to produce high concentration of ¹O₂ and degrade CQ. The CQ degradation rate of 40 mg L⁻¹ within 80 min was 97.3%, and excellent performance was maintained after 5 cycles. The fixed variable method found that the PrSmCo_0.8Mn_0.2O₃/PMS system still has high efficiency and adaptability in complex water bodies. Through quenching experiments and electron paramagnetic resonance spectroscopy (EPR), we explored the PrSmCo_0.8Mn_0.2O₃/PMS system. PMS is efficiently adsorbed on highly active Co, forming a high-entropy mixed interface, which promotes the decomposition of PMS and generates a large amount of ⋅O₂⁻ radicals. At the same time, Co–Mn synergistically and efficiently utilizes excess electrons and ⋅O₂⁻ radicals in the solution to produce high concentrations of ¹O₂ through disproportionation reactions, promoting the degradation of CQ. It provides new insights into the application of perovskite oxides in medical wastewater treatment.

Graphical Abstract

This study aimed to synthesize the emollient ester hexyl oleate by enzymatic catalysis using lipase G from Penicillium camemberti immobilized on the magnetic copolymer poly(styrene-co-triethylene glycol dimethacrylate) (STY-TEGDMA-M). For this, an experimental study was carried out on esterification reactions conducted in solvent-free medium, and the collected data were used to construct a mathematical model. The physical properties of the immobilized derivative were evaluated by scanning electron microscopy and Fourier-transform infrared spectroscopy. The results confirmed that lipase G was successfully immobilized onto the support, with a catalytic activity of 564.63 U g⁻¹. The biocatalyst showed optimum performance at 45 °C, reaching 82% conversion after 48 h of reaction. A chromatographic method was used to confirm the formation of hexyl oleate. A thermal stability assay was conducted, showing that the biocatalyst retained 87% of its initial activity after 4 h of incubation at 60 °C. Mathematical modeling was based on the ping-pong bi-bi kinetic mechanism. The best model was selected according to the lowest value of the corrected Akaike information criterion (AIC_C = 124.776). The model revealed equilibrium constant values (K_eq) ranging from 0.87 to 14.57, maximum rates of the forward reaction ranging from 0.088 to 0.090 mol L⁻¹ min⁻¹, and a maximum rate of the reverse reaction of 0.021 mol L⁻¹ min⁻¹.

Graphical Abstract

Construction of multi-interface contact step-scheme (S-scheme) photocatalyst is a promising pathway to achieve high-electron transfer efficiency for photodegradation estrone and congo red. In this paper, g-C₃N₄ is chosen as the main photocatalyst, CeO₂ nanosheet with the unique Ce⁴⁺ → Ce³⁺ conversion performance and Fe₃O₄-Reduced graphene oxide are loaded onto the g-C₃N₄ surface to bulid 2D-2D magnetic photocatalyst. The 2D–2D magnetic photocatalyst structure imparts reusability by magnetic retrieval and at the same time Fe₃O₄-Reduced graphene oxide acts as an efficient host for g-C₃N₄/CeO₂ composite photocatalyst. The photocatalytic performance is examined using etsrone and congo red. Photodegradation studies show the CeO₂/g-C₃N₄/ Fe₃O₄- Reduced graphene oxide a composite catalyst can degrade 71% of estrone, 92% of congo red and 89% phenanthrene, Free radical scavenger test shows superoxide and hydroxyl radical species play a major role in the degradation. Furthermore, it is demonstrated that the magnetic CeO₂/g-C₃N₄/ Fe₃O₄-Reduced graphene oxide possesses strong antibacterial properties against Proteus mirabilis and Escherichia coli. A three-factor-three-level Box–Behnken design (BBD) was selected to optimize three greatly influential parameters: light irradiation time (min), The quality of photocatalyst(mg) and pollution concentration(ppm) by response surface methodology. It is expected that CeO₂/g-C₃N₄/ Fe₃O₄- Reduced graphene oxide can be used as a 2D–2D magnetic photocatalyst for to achieve its valorization, which have very broad development prospects in the field of environmental remediation or catalysis.

Graphical Abstract