Catalysis Letters最新文献

Reduction of nitric acid reaction (2NO + HNO₃ + 3CH₃OH → 3CH₃ONO + 2H₂O) can convert by-product nitric acid into raw material methyl nitrite in the coal to ethylene glycol (CTEG) technology. This not only realizes the efficient recycling of nitrogen resources but also plays a crucial role in mitigating environmental pollution. Despite being a promising catalyst, the Pd/C catalyst face challenges due to its high metal loading, substantial loss rate, and consequent issues of poor stability, presenting obstacles in meeting industrial requirements. To address this issue, a defect strategy has been employed to develop a low-loaded 0.3% Pd/NC catalyst with robust metal-support interaction, resulting in a significant enhancement of catalyst stability. Remarkably, even after undergoing five cycles, the catalyst maintains a high nitric acid conversion rate of 90%. This improved performance can be attributed to the strong metal-support interaction driven by electron transfer from the nitrogen-doped carbon (NC) substrate to the Pd nanoparticles evident in the Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and inductively coupled plasma (ICP) results. This interaction effectively suppresses the leaching of the active Pd nanoparticles, leading to significantly enhanced stability and a noticeable reduction in the loss rate. Raman spectrum and electron paramagnetic resonance (EPR) results can further reveal that the increase in the defect density lead to the strong metal-support interaction after nitrogen doping (pyridinic-N-dominated). These findings highlight the significant potential of the Pd/NC catalyst and its applicability in expediting the industrialization process of catalyst.

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A series of Ni-W bimetallic catalysts were prepared by Ni₂O₃ and WO₃ on porous materials and used in a fixed bed reactor for the hydrogenation of poly alpha-olefin base oil synthesis. The catalysts were characterized by N₂ adsorption–desorption, XRD, H₂-TPR, H₂-TPD, XPS, TEM and ICP-OES to investigate the catalytic activity and explore the possible deactivation mechanism. Under the optimal reaction conditions of 250℃, 4 MPa, LHSV = 3 h⁻¹ and H₂: PAO = 200, the Ni5W1/Clay catalyst with 5% nickel and 1% tungsten loading can make the hydrogenation conversion rate as high as 100%, and the catalyst deactivation is not obvious within 8 h. The addition of W led to the reduction of the metal particle size as well as the formation of more dispersed active sites, thus improve its catalytic activity.

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Using piezoelectric catalysis to convert CO₂ and water into fuels or chemicals with waste mechanical energy offers a solution to carbon emissions and energy deficits. The current challenges are the limited efficiency and unpredictable product selectivity. In this study, a novel heterojunction material was prepared by integrating α-Fe₂O₃ nanoparticles with ZnO microrods through a hydrothermal treatment of their mixture. Through careful optimization of the α-Fe₂O₃ content on ZnO surface, the CO₂ reduction rate transitioned from 8.5 μmol·h⁻¹·g⁻¹ (CH₄) and 32.9 μmol·h⁻¹·g⁻¹ (CHOOH) to 118.2 μmol·h⁻¹·g⁻¹ (CH₄) and 18.4 μmol·h⁻¹·g⁻¹ (CHOOH), leading to a substantial enhancement in CH₄ selectivity from 20.6% to 86.5%. Combining CO₂ temperature-programmed desorption, electrochemical analysis, and photoluminescence, it was found that α-Fe₂O₃ plays a crucial role in promoting charge separation and increasing CO₂ adsorption on the catalysts, resulting in a more effective and deeper reduction of CO₂ into CH₄. Our research outlines a strategic methodology for boosting CO₂ reduction efficiency and precisely tailoring the products from piezoelectric catalysis.

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The quest for highly active and efficient ligands in coordination polymer-based catalytic applications is paramount. The new porous cross-linked polymer manganese composites, which featured a benzimidazole-pyrimidine backbone, were designed, synthesized and fully characterized through several modern means. The resulting manganese composites revealed good catalytic activity in the selective synthesis of bisindolylmethane derivatives with high selectivity. Furthermore, the porous cross-linked polymer matrix composites displayed impressive recyclability, demonstrating their economic and environmental merits, with mechanistic studies shedding light on these transformative processes.

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The new porous cross-linked polymer manganese composites, which featured a benzimidazole-pyrimidine backbone. The resulting manganese composites revealed good catalytic activity in the selective synthesis of bisindolylmethane derivatives with high selectivity. Furthermore, the porous cross-linked polymer matrix composites displayed impressive recyclability, demonstrating their economic and environmental merits, with mechanistic studies shedding light on these transformative processes.

Owing to the intrinsic nature of the uniformed topologies and ultrasmall Zr₆ nodes of Zr-MOFs, herein, we employed Zr-MOFs (UiO-66 and UiO-67), as opposed to the support of traditional ZrO₂, to prepare the Pd catalysts for toluene degradation. Compared with the catalysts of Pd/UiO-66 and Pd/ZrO₂, Pd/UiO-67 catalyst boosted an excellence catalytic performance for toluene degradation, giving the lowest T_90% value of 235 °C with long-term stability. With the assisting of the cavity confinement of Zr-MOFs, Pd nanoparticles are prone to be encapsulated in the 3D frameworks of Zr-MOFs, and the bigger micropores of UiO-67 are more conducive to the formation of larger Pd nanoparticles. The in situ FT-IR results further declared that although the active sites are partly sacrificed due to the larger Pd nanoparticles formed in UiO-67, the stable adsorbed toluene on Pd/UiO-67 boosted the quick degradation of toluene in the reaction interval even without undergoing intermediate processes of benzoate and benzaldehyde.

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UiO-66, UiO-67 and ZrO₂ were employed to prepare the Pd catalysts for toluene degradation, Pd/UiO-67 catalyst boosted an excellence catalytic performance with long-term stability.

Particle size is critical in determining the catalytic behavior of noble metal catalysts. It is a significant interest for the rational design of clearly defined catalyst materials to research on noble metal nanoparticles. Herein, a facile prepared method for the Pt/TiO₂ catalysts can not only potentially benefit the reuse of industrial catalysts, but also help to reduce the cost of VOC catalytic oxidation. In this work, the calcination of Pt/TiO₂ catalyst under N₂ atmosphere achieves the redispersion of large Pt particles into small ones (~ 1.4 nm). The Pt/TiO₂-400 catalyst (calcinated at 400 °C) with smaller Pt particles and higher concentration of active sites has superior catalytic activity and stability of toluene oxidation, contributing to the strong metal-support interaction, the larger effective metal surface area, the excellent low-temperature reducibility, abundant amounts of Pt⁰ species and adsorbed oxygen species. This work provides a facile method for metal redispersion of the catalysts, maintaining high activity and excellent stability.

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Transition metal-based mixed metal oxides (MMOs) are nexus nanomaterials that garner significant interest from scientists because of their unique magnetic, electronic, optical and catalytic properties that can easily be tailored by varying their composition and structure. Although MMOs hold significant potential in multifunctional applications, but they are plagued by certain challenges such as identifying the appropriate method for synthesis, complications in controlling the surface area and the oxidation states of the constituent transition metals, while also ensuring the homogenous distribution of the constituent metal ions. Therefore, the present work aims to study the formation of homogenous and porous zinc-copper-nickel mixed metal oxide (ZnCuNi-MMO) by performing calcination of ZnCuNi-LDH at 350 °C. The obtained ZnCuNi-MMO was characterized using PXRD, SEM–EDX and BET techniques. Thereafter, ZnCuNi-MMO was applied as a heterogeneous catalyst for the hydrogenation of p-nitroaniline (p-NA) and catalytic reduction of methyl orange (MO) dye. The pollutant degradation characteristics were assessed using time-dependent UV–Visible absorption spectroscopy showing advanced efficient behavior of ZnCuNi-MMO towards the hydrogenation of p-NA (96.98%) and reduction of MO (95.58%). The catalyst exhibited fast reaction rates (0.402 min⁻¹ for hydrogenation of p-NA and 0.471 min⁻¹ for catalytic reduction of MO) and kinetics analysis of the experimental data was found to be coherent with the pseudo-first order model, thereby implying that the catalysis proceeded through the Langmuir–Hinshelwood mechanism. Thus the obtained experimental results highlight the utility and viability of synthesized MMO as an efficacious and sustainable catalytic material.

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H₂ recycling between naphthalene, tetralin and decalin can be a promising application in chemical hydrogen storage, which is an important area for hydrogen fuel cell applications. Pt-based catalysts can be used in the dehydrogenation reaction for this purpose and support modification can effectively improve the catalytic performance. Effects of preparation method, Mg/Al molar ratio and metal composition on the Pt-based LDH-derived nanoplatelets catalysts for decalin dehydrogenation were systematically investigated in this work. The results out of this study indicated that the preparation method, Mg/Al molar ratio and metal composition exert significant effects on the microstructure and catalytic performance of the catalysts for decalin dehydrogenation. The Pt/MgAl-LDO catalyst with a Mg/Al molar ratio of 4 prepared by hydrothermal method yielded the largest specific surface area of 374 m²/g and the smallest average Pt particle size of 1.62 nm, which exhibited excellent H₂ production yield of 5.94 mol/g_Pt. These are mainly attributed to the sheet-like structure, large specific surface area and strong Pt-support interaction, leading to the superior Pt dispersion. This work provides a new approach for the preparation of low-cost and high-performance decalin dehydrogenation catalysts, which is of great significance for the application of liquid-phase organic hydride hydrogen storage technology.

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It was established that the surface functionality of nanoglobular carbon (NGC) can be effectively altered by treatment at temperatures of 573 – 1173 K in an inert atmosphere, without affecting the structure and morphology of the material as a whole. The destruction and loss of surface oxygen groups occurs as a result of this treatment, which is accompanied by a decrease in the concentration of paramagnetic centers. At a temperature of 1173 K, a restructuring and “smoothing” of the carbon surface apparently takes place, which is expressed by annealing of defects (sources of EPR signal). It was found that changes in the surface functionality of NGC affect the reducibility of supported palladium precursor and the formation of palladium nanoparticles, without causing changes in palladium dispersion state. The study of the obtained Pd/NGC catalysts in the practically important hydrogenation of 4-nitrobenzoic acid ethyl ester and furfural showed that thermal pre-treatment of the support affects the catalytic performance in these reactions. It is important that varying temperature of such pre-treatment over a fairly wide range, which has a significant impact on the functionality of the support surface, leads to only relatively small changes in the activity and selectivity of the resulting catalysts. In this regard, thermal pre-treatment of carbon support should be considered as an approach to fine tune the performance of carbon-supported palladium catalysts.

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A series of hollow VO_x/SiO₂ nanofiber catalysts (nV/S-f) with vanadium content ranging from 0.25 wt% to 4.0 wt% were prepared by electrospinning-calcination, and characterized by ICP-MS, XRD, N₂ adsorption–desorption, SEM, XPS, UV–Vis-DRS and H₂-TPR. Subsequently, the performance of these catalysts in the oxidative dehydrogenation of propane (ODHP) was evaluated. It was found that vanadium species with high dispersivity were obtained when the V content was less than 1.5 wt%. By comparison, 1.0V/S-f catalyst had the best catalytic performance, especially in terms of the propylene selectivity at high-temperature: ~ 77% at 550 °C and ~ 74% at 575 °C. In contrast to the conventional impregnation technique, the catalyst with one-dimensional nanostructure has more catalytic advantages.

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