Catalysis Letters最新文献

The impacts of PbCl₂ and PbO on Mn–Co catalysts were investigated and compared in the context of low-temperature CO oxidation. The poisoned catalysts were synthesized by impregnating fresh catalysts with aqueous solutions of PbCl₂ and Pb(NO₃)₂, respectively. The activity of the Mn–Co catalyst would be reduced by both Pb species, and PbO was more effective in poisoning it compared to PbCl₂. The Pb species led to a reduction in specific surface area and pore volume. Furthermore, the presence of Pb species decreased the concentrations of Mn³⁺, Co³⁺, and surface lattice oxygen species. In addition, the presence of Pb species led to a decrease in the reducibility, thereby impeding the adsorption activation process of CO as well as the redox cycle. Moreover, the oxidation of CO on the MC catalyst followed the Mars-van Krevelen (MvK) mechanism. CO reacted with Co³⁺ to form the CO–Co³⁺ species. Subsequently, CO–Co³⁺ species reacted with lattice oxygen to generate carbonate species and create oxygen vacancies. The carbonate is further decomposed into CO₂. The presence of Pb inhibited the adsorption of CO and reduced the generation of active intermediates. Besides, the introduction of Pb inhibited the decomposition of carbonate, leading to its accumulation on the catalyst surface, which blocked the active sites and oxygen vacancies.

The catalytic performance of phosphotungstic acid (WPA) hydrates and derived mixed oxide catalysts (0-WPA, D-WPA, Bronze) for vapor-phase dehydration of ethylene glycol to acetaldehyde was systematically investigated through controlled pyrolysis in the 300–700 °C temperature range. Experimental results demonstrated that the 0-WPA catalyst, a low-temperature pyrolyzed product with a Keggin structure, exhibited optimal catalytic performance under reaction conditions of 380 °C, a space velocity of 7.5 h⁻¹, and atmospheric pressure. The reaction achieved a glycol conversion rate of 91.2% and an acetaldehyde selectivity of 88.9%, with stability tests lasting 80 h. This performance significantly surpassed both the D-WPA catalyst featuring an exposed phosphotungstic acid structure and the Bronze catalyst characterized by an amorphous metal oxide structure. Multiple characterizations (XRD, Raman, XPS) revealed that the unique polyoxometalate cluster topology in the Keggin structure effectively optimized both surface oxygen vacancy concentration and electron mobility. The distinctive Brønsted–Lewis acid synergy facilitates preferential C–O bond cleavage through optimized dehydration pathways, thereby enhancing catalytic efficiency. This study provides fundamental insights into the structure-activity relationships of polyoxometalate catalysts in alcohol dehydration reactions, establishing a theoretical framework for rational design of high-performance catalytic systems for conversion of ethylene glycol to acetaldehyde.

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To enhance the UV transmittance of coal-derived ethylene glycol affected by unsaturated impurities, we designed Cu–Ni/γ-Al₂O₃ catalysts by precisely adjusting the Cu/Ni ratios to regulate Brønsted/Lewis acid distribution on γ-Al₂O₃ supports. Systematic characterization (XRD, H₂-TPR, and NH₃-TPD) revealed that the 1.6Cu18Ni/γ-Al₂O₃ catalyst possesses a uniform mesoporous structure (10 nm pore size, 95 m² g⁻¹ surface area) and an optimal Brønsted-to-Lewis acid ratio (0.23). This unique acidity conferred exceptional liquid-phase hydrogenation activity for unsaturated compounds, achieving UV transmittance improvements from 29%/42%/94% to 75%/92%/99% at 220/275/350 nm, meeting polyester-grade specifications. Mechanistic studies indicate that moderate Brønsted acidity selectively activates C=O/C=C bonds, while the synergistic effect of the Cu–Ni alloy can improve the hydrogenation kinetics of the single-metal system. This work establishes a design paradigm for high-efficiency catalysts through acid site engineering on support surfaces.

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This figure shows an intuitive process diagram and detailed XRD images

AuPd nanoalloys are shown to offer significantly enhanced catalytic performance for both the direct synthesis of hydrogen peroxide (H₂O₂) and the in-situ oxidative degradation of phenol. Under conditions where limited phenol conversion is observed using commercial H₂O₂, the bimetallic Au–Pd system facilitates efficient in-situ generation of H₂O₂ and associated reactive oxygen species (ROS), enabling phenol conversion rates exceeding 70%. By optimizing key reaction parameters, near-complete phenol degradation was achieved, alongside the effective breakdown of intermediate phenolic by-products. Notably, unlike earlier reported systems, the optimized 0.5%Au-0.5%Pd/TiO₂ catalyst exhibited excellent stability, maintaining consistent performance over 50 h of continuous operation, highlighting the potential to apply the in-situ approach for long-term application in advanced water treatment processes.

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Selective catalytic reduction (SCR) using ammonia (NH₃) effectively reduces NOx from industrial flue gases but faces deactivation by alkali/sulfur compounds, particularly sodium sulfate (Na₂SO₄) from high-sodium coal combustion. Na₂SO₄ deactivates commercial V₂O₅-WO₃/TiO₂ catalysts by reducing acidity, redox properties, and blocking sites. This work developed a novel Fe₂O₃-MoO₃/TiO¬₂-HY (Fe_xMT_yHY_z) catalyst. Fe_1.5MT₃HY_5.5 (15 wt% Fe₂O₃, 30 wt% MoO₃ supported on TiO₂, with HY as the balance) exhibits exceptional resistance to alkali/sulfur poisoning, maintaining > 90% NOx conversion at 310–380 °C after Na₂SO₄ doping. This resilience stems from synergistic effects: MoO₃ layered structure and the HY zeolite porosity preferentially capture Na⁺ via ion exchange, while MoO₃ activates surface sulfates to mitigate active site blockage. Fe_1.5MT₃HY_5.5 demonstrates high potential as an efficient SCR catalyst for flue gases containing Na⁺ and SO₂⁴⁻.

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Photocatalytic reforming of plastic pollutants into renewable hydrogen fuel and value-added hydrocarbons represents a promising environmental remediation strategy. However, conventional approaches for polyethylene terephthalate (PET) degradation require energy-intensive pre-hydrolysis under harsh conditions (≥ 10 M NaOH, > 60 °C), which accelerate catalyst deactivation and secondary pollution. Herein, a low-temperature wet-chemical method prepare a series of AZCS/MXene photocatalysts were successfully synthetic for hydrogen product integrated with degradation of polyethylene terephthalate (PET). Owing to the amorphous ZnCdS breaking long-range atomic order that induce dipole moments and generate strong electric fields within the particles which facilitates charge separation and transfer. The Ti₃C₂T_x MXene provide the enhanced separation ability of photocarriers. Here, the best photocatalytic hydrogen of AZCS@M₆ evolution activity (1845.65 µmol g⁻¹ h⁻¹) and the selective generation of high value chemicals: (i) Formate (164.77 µmol), (ii) Glyoxal (807.70 µmol), (iii) Acetate (272.8 µmol). This work offers new solutions to energy problem and microplastic pollution under mild conditions (1 M NaOH, 40 °C).

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In this work, niobium-doped phosphomolybdic acids with the general formulae H_3+nPMo_12-nNb_nO₄₀ (n = 0, 1, 2, and 3) were prepared, characterized, and evaluated as catalysts in the acetalization of the β-citronellal with alcohols. The impact of niobium load on the structural and catalytic properties of phosphomolybdic acids was assessed. Among the niobium-substituted phosphomolybdic acids, the H₄PMo₁₁Nb₁O₄₀ acid was the most active and selective toward the methyl acetal β-citronellal, achieving a TON 196, TOF of 0.11 mmol/s, and 98% yield after 30 min reaction. The effects of main reaction variables, such as time, temperature, catalyst load, type of alcohol, and niobium load, on the conversion and selectivity of the reactions were assessed. The highest activity of H₄PMo₁₁Nb₁O₄₀ was attributed to the adequate proportion of H⁺ and Nb⁵⁺ cations. The H₄PMo₁₁Nb₁O₄₀ catalyst was easily recovered and reused without loss of activity.

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β-citronellal applications

The Ni-Re/TiO₂ catalyst was synthesized via the impregnation method, exhibiting exceptional catalytic performance in the hydrogenation of dimethyl oxalate (DMO) to methyl glycolate (MG). With low Ni and Re loadings (2.5Ni0.5Re/TiO₂), the catalyst achieved 94% DMO conversion and 96% MG selectivity, maintaining impressive stability for over 200 h, highlighting its potential for industrial applications. Characterization studies demonstrated that Re doping promotes strong electronic interactions between Ni and Re, stabilizing and enhancing the dispersion of Ni nanoparticles, which facilitates H₂ activation. Concurrently, the presence of ReOx species introduces abundant Lewis acid sites, which enhance the adsorption and activation of C = O groups, thus facilitating DMO adsorption and dissociation. The superior catalytic performance arises from the synergistic interactions between ReOx and Ni species, providing valuable insights into the development of low-loading, high-activity catalysts for DMO hydrogenation.

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This work reports the synthesis and photocatalytic evaluation of an Ag/ZnO nanocomposite for efficient degradation of phenol under solar irradiation. The photocatalyst was prepared by impregnating ZnO with AgNO₃, followed by reduction in pure hydrogen gas at 450 °C. This process resulted in the simultaneous formation of metallic silver (Ag⁰) and silver oxide (Ag₂O), incorporating both Ag⁰ and Ag¹⁺ species on the ZnO surface. X-ray photoelectron spectroscopy (XPS) confirmed the coexistence of Ag⁰ and Ag₂O at the Ag–ZnO interface, indicating that strong metal–support interactions and Fermi level alignment facilitated partial oxidation of Ag⁰ into Ag⁺, even under reducing conditions. The photocatalytic activity of the composite was significantly enhanced compared to pure ZnO, achieving ~ 98% phenol degradation within 3 h of solar exposure. This improvement is attributed to the synergistic effects of Ag⁰ and Ag₂O: Ag⁰ induces localized surface plasmon resonance (LSPR), while Ag₂O acts as an electron mediator, suppressing charge recombination and extending light absorption into the visible region. These findings highlight the critical role of controlled silver oxidation states, tailored via hydrogen treatment, in designing efficient photocatalysts for solar-driven environmental remediation.

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Methanation is an important technological process producing synthetic natural gas. This study compares five preparation methods for Ni/Al₂O₃ catalysts and discusses their impact on the formation of Ni active sites and their methanation activity. Conventional wet impregnation was evaluated alongside methods involving microwave-assisted deposition (MC), ultrasonic waves (UT), and pH-adjusted methods such as ammonia evaporation (AE) and deposition precipitation (DP). These techniques primarily influenced the size of Ni active sites as well as their reducibility and stability. The stability of NiO/Ni species after reduction and methanation was described. Their performance of prepared Ni/Al₂O₃ was assessed in CO₂ methanation within a temperature range of 250–490 °C under a low gauge pressure of 0.2 MPa. The highest methane yield of 42% was obtained with the MC catalyst; however, a high reaction temperature of 449 °C was needed. On the other hand, both DP and AE catalysts outperformed all tested catalysts in the catalyst productivity. This was due to the smaller Ni/NiO particles and their higher thermal stability.

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