Catalysis Science & Technology最新文献

Noble metal catalysts exhibit high efficiency and stability in CO removal, but their high loading of noble metals led to elevated costs, limiting industrial applications. This study selected three representative noble metals (Pt, Au, Ru) to investigate the CO reaction mechanisms on low-loading noble metal catalysts and the effects of SO₂/H₂O on CO oxidation. Catalysts with 0.1 wt% metal loading were synthesized via the impregnation method using conventional TiO₂ as the support, denoted as 0.1Pt/Ti, 0.1Au/Ti and 0.1Ru/Ti. Among them, 0.1Pt/Ti achieved complete CO conversion at 270 °C and maintained 100% conversion over 46 h of continuous operation at 250 °C in the presence of SO₂ and H₂O. In situ DRIFTS indicated that the CO reaction over all catalysts followed the Mars–van Krevelen (MvK) mechanism. However, both Langmuir–Hinshelwood (L–H) and MvK pathways coexisted on 0.1Pt/Ti, with the L–H mechanism being dominant. DFT calculations revealed that CO also exhibited a higher adsorption preference for the 0.1Pt/Ti catalyst, which was identified as the primary reason for its superior performance.

This study develops a hierarchical calcium oxide (CaO) catalyst, designated as CaO(I), synthesized via the impregnation of a calcium acetate precursor onto porous hollow rape pollen templates. The catalyst demonstrates exceptional efficacy in glycerol-free biodiesel production through the tri-component transesterification of rapeseed oil with methyl acetate and methanol. Under optimized conditions (60 °C, 2 h reaction time, 1 : 1 : 8 oil/methyl acetate/methanol molar ratio), CaO(I) achieves a near-quantitative fatty acid methyl ester (FAME) yield of 99.72%. Comprehensive characterization (SEM, XRD, N₂-physisorption, FT-IR, TG, and CO₂-TPD) confirms that CaO(I) possesses a well-defined hierarchical pore structure with superior textural properties—including enhanced basic site density (14.6161 mmol g⁻¹) and BET surface area (34.8607 m² g⁻¹, versus 4.8 m² g⁻¹ for commercial CaO)—attributed to high active-phase dispersion and favorable pore architecture. Parameter optimization reveals 700 °C as the optimal calcination temperature, and it is observed that the precursor concentration critically influences the catalytic performance. The catalyst maintains robust reusability over multiple cycles with negligible activity loss. This novel templating approach leverages sustainable biomass resources to simultaneously address glycerol surplus issues in conventional biodiesel synthesis and enhance catalytic efficiency, establishing an environmentally conscious pathway for high-performance biofuel production.

The efficient reduction of CO₂ is significant for achieving carbon neutrality and renewable fuel synthesis. However, CO₂ thermostatic systems are limited by energy utilization efficiency, while high-temperature electrocatalysis is limited by the need for inlet preheating of the material. Considering the existence of high-grade thermal energy at the outlet of thermostatic CO₂ not utilized, the article proposes a combined thermal–electrocatalytic CO₂ reduction system, which can utilize high-temperature products of thermostatic CO₂ reduction for further electrocatalytic co-electrolysis of H₂O as well as CO₂, and at the same time solves the problems of lower efficiency of thermostatic reduction as well as the need of pre-heating for electrocatalytic reduction. Mathematical models of the two subsystems were developed, and thermodynamic analyses were performed. The results show that the efficiency of the thermostatic reduction part could be optimized by designing the reaction parameters, and the maximum efficiency could reach 25.42%, while the electrolytic efficiency of the electrocatalytic part could reach 99.21%. The electrocatalytic efficiency of the coupled system can be increased by 24.84% to 95.80%. And when the two systems are coupled to catalyze CO₂, the overall efficiency of the system can be increased by 29.00%.

In response to the challenges of equipment corrosion and environmental pollution associated with the homogeneous catalytic production of crotonaldehyde via acetaldehyde aldol condensation, this work focused on the synthesis of Zr-β zeolites with Lewis acidity. The crotonaldehyde selectivity was significantly improved by tailoring the acidic properties of the zeolites. A comparative study of three distinct Lewis acid sites identified isolated framework tetra-coordinated Zr sites as the most efficient catalytic centers, which were successfully constructed using hydrothermal synthesis and liquid-phase incorporation methods. Zr-β zeolites synthesized via liquid-phase incorporation demonstrated higher conversion and selectivity owing to larger pore size, greater total Lewis acidity and a higher proportion of weak and medium Lewis acid sites. These properties were further optimized by adjusting the precursor and solvent during the synthesis process. In situ DRIFTS analysis revealed that the Lewis acid sites activated the α-H of acetaldehyde, forming carbanion intermediates essential for the enolization and subsequent aldol condensation. The main by-product, methyl cyclopentenone, was found to originate from the Prins reaction of sorbaldehyde formed through excessive aldol condensation, which was mediated by Brønsted acid sites. To suppress this side reaction, the zeolites were modified with alkali cations (Na⁺, K⁺) to selectively passivate the Brønsted acid sites while enhancing the Lewis acidity significantly. This strategy effectively reduced by-product formation and ultimately achieved a crotonaldehyde selectivity of 94.7%.

Alkali metals are effective promoters in heterogeneous catalysis, enhancing the catalytic performance. Research over the past few decades has elucidated their promoting mechanisms. This review synthesizes the latest surface science and theoretical advances in alkali metal-doped acetylene hydrochlorination catalysts, focusing on structure–activity relationships and catalytic mechanisms for catalyst optimization. Finally, we critically examine the key challenges and future opportunities in this dynamic field.

Methanol has great potential as a liquid organic hydrogen carrier (LOHC) and serves as a key feedstock for formaldehyde synthesis via the Formox (250–400 °C) and BASF (600–720 °C) processes. Developing low-temperature methods for methanol dehydrogenation has therefore significant practical interest. Herein, we present a thermo-assisted photocatalytic (TAPC) strategy for methanol dehydrogenation, enabling CO_x-free H₂ and HCHO production in equimolar amounts at a low thermal input (105 °C). Fluoride-etched TiO₂ microspheres (F-TMS) were synthesized, loaded with Au single atoms, fully characterized, and employed as catalysts. The TAPC methanol dehydrogenation was conducted in a continuous-flow reactor, with key parameters (Au loading, temperature, methanol concentration, and light intensity) optimized. A minimal Au loading (0.1 wt%) confined within F-TMS was sufficient to achieve the highest H₂ evolution rate at 105 °C, with no CO or CO₂ detected. Increasing the temperature above 105 °C led to undesirable byproducts (CO, CO₂, CH₄), emphasizing the need for an optimized low-temperature window. No thermocatalytic activity was observed at 105 °C, confirming the essential role of light, further supported by a linear increase in H₂ production rate with light intensity. Water played a crucial role in enhancing hydrogen production, either by providing a rich source of hydrogen ions or by facilitating the generation of ˙OH radicals. The introduction of Au single atoms reduced the apparent activation energy by half, greatly enhancing the kinetics of the methanol dehydrogenation reaction. The gas-phase TAPC process outperformed liquid-phase traditional photocatalysis in both activity and selectivity. Compared to the benchmark TiO₂ P25 photocatalyst, F-TMS exhibited 2.6-fold higher TAPC activity. These findings demonstrate that low-temperature TAPC methanol dehydrogenation over Au/F-TMS offers an efficient and selective route for CO_x-free hydrogen and HCHO production.

One of the main drawbacks of acid-based heterogeneous catalytic processes involving hydrocarbons is coke formation. Still, research on shaped catalysts remains limited. The main objective of this study was to gain insight into the catalyst deactivation in the methanol-to-hydrocarbon (MTH) reaction. Diffraction and absorption computed tomography experiments were performed on spray dried, hollow semi-spherically shaped ZSM-5/alumina catalysts of approximately 250 microns in size. The catalysts were employed in the MTH reaction at two different pressures, resulting in varying degrees of coking. Absorption tomography (0.027 μm³ per voxel) revealed the structural features and sponginess of the shaped catalysts. These are not perfect spheres; they rather have openings as they burst during the spray drying process. Further, high resolution powder X-ray diffraction computed tomography slices (0.125 μm³ per voxel) were analyzed by parametric Rietveld refinement. The analysis showed that the catalyst and binder overall are rather homogeneously spatially distributed within each sphere, but bubbles and agglomerates of a single phase are frequent. In addition, it is demonstrated that there were no coking gradients across the sphere wall at both partial and full deactivation. This indicates that the binder and the catalyst shape and size were suitable for the reaction conditions. Indeed, the catalyst lifetime was almost doubled relative to the pure, powdered zeolite catalyst. A series of catalysts with varying degrees of deactivation have been fully characterized ex situ, suggesting significant spillover of coke from the zeolite to the alumina matrix. These findings demonstrate the need for greater efforts to understand the formulation of shaped catalyst objects, where the matrix should not only hold the components together but also support and enhance the overall catalytic process.

The synergistic interaction between redox properties and acidity was crucial for achieving efficient catalytic oxidation of chlorinated volatile organic compounds (CVOCs). This study systematically investigated the influence of Pt content on the redox–acidity synergy by hydrothermally synthesizing a series of Pt–HSiW/CeO₂ catalysts with gradient Pt loadings (0.5–3.0 wt%). Comprehensive characterization revealed that Pt loading significantly modulated oxygen vacancy concentration, surface oxygen activity, and acid site distribution. The Cat-2.0 catalyst (2.0 wt% Pt) exhibited the highest Ce³⁺ fraction (29.8%), abundant surface adsorbed oxygen (71.7%), and the lowest oxygen desorption temperature, thereby demonstrating optimal catalytic performance for chlorobenzene. Although the total acidity of the catalyst decreased with increasing Pt loading, Cat-2.0 retained sufficient weak and medium-strong acidic sites, promoting C–Cl bond cleavage while inhibiting electrophilic chlorination. In situ DRIFTS and GC-MS analyses further confirmed that synergistic interactions between oxidative and acidic sites accelerated the conversion of chlorobenzene to phenol and benzoquinone, ultimately yielding CO₂ and H₂O.

Metal–support interaction (MSI) is a well-established strategy for tuning catalytic activity in thermal catalysis, yet its role in nonthermal plasma catalytic CO₂ methanation remains insufficiently explored. In this study, Ni/Ce_xZr_1−xO₂ catalysts were synthesized using Ce_xZr_1−xO₂ supports calcined at different temperatures to systematically modulate the MSI. A volcano-shaped correlation was observed between the catalytic activity and support calcination temperature in both thermal and plasma systems. The Ce_xZr_1−xO₂ support calcined at 600 °C having a moderate particle size, demonstrated the optimum MSI (i.e., promoting the facile formation of oxygen vacancies and stable interfacial anchoring of Ni particles) and thus the comparatively best catalytic performance under both conditions. Under the tested conditions, thermal CO₂ methanation exhibited superior activity compared to plasma-assisted reactions, e.g., the NCZ-600 catalyst achieved an 83% CH₄ yield at 350 °C versus 11.3% at 7.0 kV. These results underscore the critical role of the MSI in governing CO₂ methanation across distinct catalytic environments and highlight its potential as a unifying design principle for both thermal and plasma catalysis.

The catalytic activity of copper nanoparticles is known to be closely related to their redox behavior. However, in supported Cu-based catalysts, the interface between the metallic nanoparticles and the support can introduce catalytic properties that are instead associated with acidity. While this phenomenon has been reported in supports that are prone to form strong metal-support interactions (SMSI), such as titania, it remains less evident in covalent solids, like silica. In this study, we compare copper-silica catalysts in both their oxidized and reduced forms, synthesized via chemisorption hydrolysis, aerosol-assisted sol–gel, and incipient wetness impregnation, focusing on their structural-textural properties and acidity levels. Experimental results show that Lewis acidity is strongly related to the dispersion of the active phase. Acidic active sites effectively promote the acid-catalyzed styrene epoxide ring alcoholysis at low temperatures (60 °C) with selectivity exceeding 90%. They are also responsible for the acid-catalyzed formation of carbonaceous deposits under a gaseous ethylene stream at high temperatures (300 °C). The nature of this acidity is the basis for the rational design of active and stable Cu-based catalysts.