Catalysis Letters最新文献

Developing high-efficiency, high-stability, and low-cost deoxygenation and hydrocracking catalysts could be considered one of the most significant breakthroughs in catalytic hydroprocessing. The present study utilized aluminophosphate (AlPO₄-18), a zeolite-like molecular sieve, as catalyst support for producing carbon-coated β-Mo₂C, Ni₃C, and WC nanoparticles. The synthesis used an incipient wetness impregnation followed by a temperature-programmed reduction-carburization approach which involved cracking a hydrocarbon gas, propane, in a hydrogen environment. The synthesis parameters were a 1:7 propane/hydrogen reductive-carburizing gas stream, 15 wt.% metal loading, an 800 °C carburization temperature ramped-up at a heating rate of 10 °C min⁻¹, a 2-h holding time, and a 1-h holding time in hydrogen. The synthesized catalysts were characterized using thermogravimetry mass spectroscopy/temperature-programmed oxidation (TPO TG-MS), nitrogen physisorption at 77 K, X-ray diffraction (XRD), and transmission electron microscopy/energy-dispersive X-ray spectroscopy (TEM EDS). TPO TG-MS, nitrogen physisorption, TEM, and XRD characterization results proved that atomic carbon was successfully incorporated into the lattice interstitials, resulting in thermally stable, well-dispersed, crystalline and mesoporous β-Mo₂C/AlPO₄-18, Ni₃C/AlPO₄-18, and WC/AlPO₄-18 nanoparticles. XRD analysis showed structural evolution during reduction-carburization, with average crystallite sizes of metal-containing particles of 8.2–9.22, 6.64–8.50, and 6.03–7.56 nm for β-Mo₂C/AlPO₄-18, Ni₃C/AlPO₄-18, and WC/AlPO₄-18, respectively. These values did not significantly deviate from high-resolution TEM analysis. The surface areas of the nanoparticles were categorized in decreasing order as WC/AlPO₄-18 > Ni₃C/AlPO₄-18 > β-Mo₂C/AlPO₄-18, with values of 193.79, 169.05, and 66.57 m² g⁻¹, respectively. In conclusion, these carbon-coated metal carbide nanoparticles with excellent thermal, structural, microscopic, and textural properties can be viable alternatives to noble metal catalysts for producing bio-jet fuel using the hydroprocessing pathway.

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Titanosilicate-supported Au-cluster catalysts can be used to selectively synthesize propylene oxide from propylene using O₂ and H₂. However, the details of the catalytic reaction mechanism have not yet been elucidated. Thus, the reaction mechanism was investigated using density functional theory calculations. The calculation results revealed that active Ti-OOH forms on the surface Ti site, which is active as an oxidant and acts as an anchorage site for Au nanoclusters. The rate-determining step of propylene oxide synthesis on Au/titanosilicate is O insertion into propylene, with an activation energy of 1.37 eV. The propylene involved in this reaction is activated by adsorption on Au nanoclusters. Moreover, it was also found that the formation of Ti-OOH on Au/titanosilicate requires an activation energy of 0.48 eV, while it is barrierless on Au/anatase-TiO₂. However, the decomposition energy of Ti-OOH on Au/titanosilicate is −0.16 eV, which is smaller than that on Au/anatase-TiO₂ (−1.12 eV). The results indicate that Ti-OOH decomposes more readily on Au/titanosilicate than on Au/anatase-TiO₂ but is easily regenerated because the reaction energy is significantly smaller than that on Au/anatase-TiO₂. Therefore, these calculations are qualitatively in good agreement with the experimental results for Au/titanosilicate, which exhibited high catalytic activity at high temperatures.

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A series of Co–M (M = Mn, Ce, Cu) bimetallic oxide catalysts were prepared by a modified solvent pyroalcoholysis method, and the performance in the catalytic oxidation of toluene was investigated. The experimental results showed that the conversion rate of the as-prepared Co₁Cu₁ catalyst performed a 50% conversion (T₅₀) and 90% conversion (T₉₀) in toluene oxidation at 211 °C and 241 °C, respectively. A series of the characterization demonstrated that the performance improvement is attributable to the Co₁Cu₁ catalyst owning high Co³⁺ concentration (Co³⁺/Co²⁺ = 1.14), abundant surface adsorbed oxygen (O_ads/O = 67.33%), and excellent low temperature reducibility. Interestingly, these properties promoted the adsorption and deep oxidation of toluene molecules. Concurrently, the XRD and Raman characterizations verified that the spinel structure of Co₃O₄ is altered by Cu doping, producing high-valence surface active Co species and numerous lattice defects that increased the catalyst’s catalytic efficiency. This study showed that creating defect sites by metal doping is a useful strategy for improving Co₃O₄ spinel’s catalytic activity.

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The development and design of high-performance catalysts for selective hydrogenation of phenol to high value-added cyclohexanol is challenging. A series of hollow carbon coated Ni nanoreactor catalysts (Ni@HCS-T) were synthesized, adjusting carbonization temperature to investigate the effect of chemical microenvironment on the performance of selective hydrogenation of phenol. The results confirmed the carbonization temperature can regulate the degree of carbon skeleton defects and hydroxyl functional group content on the catalysts. The optimum catalyst (Ni@HCS-800) catalyzed phenol conversion of 99.54% and cyclohexanol selectivity of 98.53% at 120 ℃, 2 h and 1 MPa H₂ under the carbonization at 800 ℃. The Ni@HCS-800 catalyst is rich in defective structures which, together with neighbouring hydroxyl groups, significantly enhance substrate adsorption. Meanwhile, the abundant defects reasonably modulate the interfacial charge transfer behavior, resulting in a significantly enhanced degree of electron transfer between the metal Ni and carrier, enhancing the interaction between carbon carrier and metal. The Ni@HCS-800 catalyst showed the activation energy E_a of 46.05 kJ⋅mol⁻¹ and remained stable performance after five cycles. In addition, the catalyst could effectively catalyze the conversion of a variety of lignin derivatives, showing wide applicability.

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Sustainable catalyst synthesis offers a fundamental development via utilizing plants reducing the dependency on synthetic chemicals and minimizing environmental impact. This study presents a sustainable approach to catalysis through the synthesis of MnO2 using oak bark as a precursor. The catalyst synthesis was characterized using various analytical techniques including Fourier Transform Infrared Spectroscopy (FT-IR), X-ray Diffraction (XRD), Scanning Electron Microscopy with Energy Dispersive X-ray Spectroscopy (SEM–EDX), and High-Performance Liquid Chromatography (HPLC). FT-IR analysis confirmed the chemical structure and functional groups peak observed at 1709 cm⁻¹ is indicative of the stretching vibration of conjugated alkenes' C–C bonds. XRD revealed the crystalline nature and phase purity, confirming the formation of MnO₂. HPLC analysis demonstrated the catalytic activity of MnO2 catalyst organic transformations derived from oak bark includes polyphenolic compounds such as gallic acid (RT 9.2 min; C₇H₆O₅), condensed tannins like proanthocyanidin (RT 21.7 min; C₃₁H₂₈O₁₂), quercetin derivatives such as quercetin-3-O-glucoside (RT 32.2 min; C₂₁H₂₀O₁₂), and flavonoids such as kaempferol (RT 35.3 min; C₁₅H₁₀O₆). This study emphasizes the feasibility and effectiveness of using natural sources like oak bark for synthesizing eco-friendly catalysis with promising applications in green chemistry.

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The legal obligation to swiftly adopt renewable energies has been increased because of the continuous usage of fossil fuels. In this perspective, biomass serves as a pillar to improve the current conditions over different heterogeneous catalysts due to their known advantages. This work is focused on the synthesis of a novel catalyst comprising mono lacunary phosphotungstate and zeolite HY. The catalyst was characterized by number of physicochemical techniques and evaluation of the activity of catalyst for the esterification of most promising bio platforms, levulinic acid and succinic acid to produce fuel additives. After a detailed optimization of both reactions, remarkable conversions of levulinic acid (77%) and succinic acid (96%) with turnover numbers of 2749 and 3427 respectively, were obtained. The order of the reaction and activation energy for the said reactions were calculated in the kinetic study. The sustainable nature of the catalyst was confirmed via regeneration and viability towards other bio-based molecules which enhances its industrial importance.

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Manganese oxide loaded on activated alumina beads (MnO_x/AABs) was prepared by one-pot hydrothermal method and applied to activate periodate (PI) towards the degradation of Rhodamine B (RhB) and other organic dyes. The catalyst was first characterized by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy (XPS) and N₂ sorption. Subsequently, the effects of catalyst dosage, oxidant dosage, initial pH as well as co-existing inorganic anion and humic acid on the performance of the MnO_x/AABs/PI system were studied. Under optimum conditions (catalyst dosage = 15 beads, PI dosage = 0.2 g/L), the removal efficiency of 50 mg/L RhB reached 99.4%, with a total organic carbon removal efficiency of 51.0%. The removal efficiencies of several other organic dyes were in the range of 70%-95.1%. The leached amount of Mn was measured to be 0.027 mg/L. Mechanism studies revealed that ¹O_2, IO₃^⋅ and O₂^⋅− were identified to be responsible in this reaction system, and ¹O₂ played a decisive role. In addition, IO₄⁻ was converted to IO₃⁻ without other toxic products during the degradation process. Reusability test in both the batch and continuous modes showed that the catalyst could be efficiency regenerated by calcination. Combining the results of liquid chromatography-mass spectrometry (LC–MS) and density functional theory calculations, the possible degradation pathway of RhB was proposed. Finally, toxicity evaluation of the degradation products of RhB was performed by theoretical calculations as well as experimental tests with Vigna radiata.

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In this work, the performance of a series of noble metal catalysts supported on the SBA-16 mesoporous matrix was studied. Its activity was measured in catalytic hydrotreating (HDT) reactions, such as tetralin hydrogenation in a batch reactor. The results were adjusted with a pseudo first order equation and then, the most active catalysts were tested in a continuous flow reactor under industrial-like conditions. Noble metal catalysts were synthesized, mainly monometallic iridium and bimetallic iridium-platinum and iridium-palladium supported SBA-16. The support was also modified with aluminum to provide Bronsted and Lewis acidity to the catalysts. All the catalysts were characterized by FTIR, XRD, NMR, N₂ isotherms, H₂ chemisorption, TPR and XPS to be able to relate the activity with the nature of the catalyst. The catalyst modified with 0.5 wt% of Ir, 0.5 wt% of Pt and 3 wt% of Al supported over SBA-16 matrix was the most active in tetralin hydrogenation to decalins in a Batch reactor, achieving the higher kinetic constant of 0.012 min⁻¹ and 90% of conversion to fully hydrogenated decalins at 120 min of reaction time. This catalyst also was the most active in the hydrogenation of tetralin using a continuous flow reactor obtaining the highest kinetic constant of all the catalysts tested with a value of 0.152 mol/h g cat. and achieving 90% of conversion to decalins at W/F = 150. Its greater activity was explained in terms of greater hydrogenating capacity, better dispersion of the active species, and greater resistance to deactivation thanks to the protective effect of the bimetallic alloy formed in synergy with a greater acidity of the aluminum-modified support. In this work, optimization has been achieved in the synthesis of an active, selective, contaminant-resistant catalyst with great stability. Very good results were obtained in a continuous process under conditions like to industrial ones.

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Ru/HAP catalyst with high-dispersion is prepared by a novel homogeneous deposition precipitation method (DPU). As compared to the conventional impregnation method (IM), the catalytic oxidation performance for toluene and DCM are much higher for DPU-sample with higher activity and good stability in humid air. Characterizations reveal that DPU-sample has a larger surface area with mesoporous structure, keeping smaller Ru particle size and uniform distribution on HAP, which is favorable for the exposure of active sites. The preparation and reaction conditions were also systematically studied, showing that 0.5 Ru/HAP(500)-DPU sample is a promising catalyst for VOC and CVOC removal.

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The Ru/HAP (DPU) is a promising broad-spectrum catalyst for VOC and CVOC removal.

A novel helical polymer (compound poly-1₂₀₀) containing side chains of L-leucine was synthesized. This chiral L-leucine polymer catalyst exhibited excellent catalytic activity and stereoselectivity in Aldol reaction. Poly-1₂₀₀ catalyzed Aldol reaction of cyclopentanone and 4-nitrobenzaldehyde in saturated brine solution with a high enantiomeric excess (ee) value of up to 99% and a diastereomeric selectivity (dr) value of 58/42. Furthermore, the chiral polymer catalyst could be recycled three times in the asymmetric Aldol reaction without significant loss of catalytic activity.

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