Catalysis Science & Technology最新文献

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.

In this study, a one-step co-electrodeposition method was employed to successfully introduce Bi into the NiSe system, resulting in the synthesis of a Ni₃Bi₂Se₂ bifunctional catalyst with an amorphous wrinkled nanosphere structure. This catalyst demonstrates exceptional electrocatalytic activity for both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), requiring low overpotentials of only 33 mV and 277 mV, respectively, at a current density of 10 mA cm⁻², along with remarkable stability over 120 hours. In the alkaline electrolyte, the overall water splitting reaction driven by this catalyst achieves a current density of 10 mA cm⁻² at a low cell voltage of 1.64 V. Theoretical calculations reveal that the incorporation of Bi significantly optimizes the Gibbs free energy (ΔG) of adsorption for H₂O molecules and reaction intermediates on the active sites of the metal selenide. Specifically, for the HER, the introduction of Bi brings the ΔG(H*) on Se sites close to zero, aligning with the Sabatier principle; for the OER, Bi doping effectively reduces the energy barrier of the rate-determining step (*O + OH⁻ → *OOH + e⁻), thereby accelerating the reaction kinetics. This study demonstrates that the doping strategy significantly enhances the electrochemical performance of transition metal compounds, providing new theoretical insights and practical approaches for designing highly efficient water-splitting catalysts.

Organoboron compounds are fundamental building blocks in organic synthesis, and recent advances in boron-migration reactions have attracted significant attention. However, carbonylative transformations featuring a 1,2-boron shift remain largely unexplored, with limited strategies available for the incorporation of exogenous carbonyl groups. We report an unprecedented 1,2-boron migratory carbonylation enabled by visible-light photoredox catalysis, in which carbon monoxide (CO) serves as an abundant and convenient C1 source to trap translocated alkyl radicals generated after 1,2-boron migration. The methodology provides an efficient and streamlined approach to synthesize structurally complex and diversely functionalized β-boryl thioesters under mild conditions. Notably, this reaction enables a functional-group translocation within a single molecule, allowing for the positional exchange between a carbonyl and a boryl group via sequential CO₂ extrusion, 1,2-boron migration, and CO insertion.

The selective conversion of biomass-derived 5-hydroxymethylfurfural (HMF) to 1,6-hexanediol (1,6-HDO) is a promising pathway for sustainable production of chemicals from renewable feedstock. Here, we report the catalytic performance of various supported platinum catalysts, including monometallic Pt nanoparticles on different supports (CeO₂, MgO, hydrotalcite, and hydroxyapatite) and bimetallic (PtPd, PtCo, PtRu, and PtRe) nanoparticles supported on hydroxyapatite for this reaction under batch reaction conditions. Among the monometallic catalysts, Pt supported on hydroxyapatite (Pt/HAP) demonstrated the highest selectivity (30%) for 1,6-HDO at 85% HMF conversion. This superior performance is attributed to the amphoteric properties of the hydroxyapatite support. Notably, the incorporation of Ru as a second metal in the Pt nanoparticles significantly improved catalytic efficiency. The bimetallic PtRu/HAP catalyst achieved an impressive selectivity of 62% for 1,6-HDO at 85% conversion. Characterization by X-ray Photoelectron Spectroscopy (XPS) and Electron Microscopy revealed that the addition of Ru to Pt nanoparticles resulted in smaller bimetallic nanoparticle sizes compared to monometallic Pt nanoparticles, contributing to the enhanced 1,6-HDO selectivity observed for the bimetallic system. The effects of reaction temperature and pressure on 1,6-hexanediol selectivity were also studied. Additionally, the acidity and basicity of the hydroxyapatite supported catalyst were analysed using the surface Ca/P ratio as well the CO₂ and NH₃ TPD data. The results show that the PtRu/HAP catalyst has optimal acidic site density and least basic sites compared to the monometallic catalysts. This unique combination of acidic and basic surface properties, together with the synergistic effects of the finely dispersed smaller bimetallic PtRu nanoparticles, makes this material one of the most active catalysts for the selective hydrogenolysis of HMF to 1,6-HDO.

We devised an electro-assisted method utilizing Fe_xN_yC catalysts for low-temperature NH₃-SCR. Compared to traditional heating methods, electric heating significantly reduced the T₉₀ of NO_x conversion for the Fe₃N_1.5C catalyst from 160 °C to 120 °C. Under electro-assisted conditions, the applied current facilitates the migration of bulk phase lattice oxygen to the catalyst surface, promoting the oxidation of NH₃ species adsorbed on the catalyst surface and thereby promoting the NH₃-SCR reaction.

The easily accessible and robust [(Salen*)Co^III(OAc)] complex (1) was applied as a unimolecular initiator and moderator for the bulk ring-opening polymerization (ROP) of ε-caprolactone (CL) and bio-based L-lactide (LLA), producing the corresponding biodegradable polyesters, polycaprolactone (PCL) and poly(L-lactide) (PLLA), with relatively good control. The high tolerance of the cobalt(III) complex 1 towards protic additives, such as alcohols, allowed performing the polymerization reactions under immortal conditions, using methanol or benzyl alcohol as transfer agents. Such an approach allows using catalytic amounts of metal (vs. polymer chains) and fine tuning both the polyester chain length (monomer/alcohol ratio) and the nature of the chain end (alcohol). Taking advantage of the living character of the ROP process mediated by complex 1, a well-defined PCL-b-PLLA copolymer could be synthesized in bulk under immortal conditions.