Catalysis Science & Technology最新文献

Chromium complexes supported by alkyl-bridged PCCP ligands (Ph₂PCH(R¹)-C(R²)PPh₂) demonstrate exceptional catalytic activity and selectivity in ethylene tri-/tetramerization reactions. To elucidate the influence of PCCP ligand geometry on catalytic performance, a series of bisphosphine ligands featuring five- to eight-membered cycloalkane bridges were systematically synthesized. Notably, the catalytic behavior is profoundly dependent on the ring size of the cycloalkane bridge. As the bridge cycloalkane increases in ring size, the chromium complexes exhibit a 3.4 fold enhancement in activity (from 813 kg g⁻¹ Cr per h for the five-membered ring to 2891 kg g⁻¹ Cr per h for the eight-membered variant) alongside a progressive improvement in α-olefin selectivity (total selectivity of 1-C₆ and 1-C₈ from 76.5% to 90.3%). Concurrently, polyethylene formation is dramatically suppressed (from 38.6% to 0.14%). Under optimal conditions, complex bearing ligand 4 achieves a peak activity of 3120 kg g⁻¹ Cr per h with 48.9% 1-C₈ selectivity, 89.9% α-olefin selectivity, and near-complete suppression of polymer. Structural analysis reveals a critical correlation between the ligand backbone dihedral angle and catalytic performance: smaller dihedral angles correlate with higher activity, underscoring the pivotal role of ligand structure in tuning reactivity.

The extensive use of plastics has resulted in severe environmental pollution, making the valorization of plastic waste not only a strategy for value recovery but also an effective approach to mitigate its environmental impact. Consequently, this topic has become a focal point of research in industry and academia. Pyrolysis is a key step in the carbon resource conversion of plastic waste, facilitating the degradation of complex polymeric materials into high value products such as alkanes, olefins, and BTX. This review summarizes recent advancements in plastic pyrolysis technologies, as a focus on scientific challenges and technological breakthroughs in this domain. Through a systematic analysis, the study examines the pyrolysis mechanisms and current research status of the most widely used plastics, exploring the critical factors influencing the pyrolysis process including reaction conditions, such as temperature, residence time, and catalyst dosage, and the reactor design which has a significant role in improving the pyrolysis efficiency and product selection. This review provides a summary of commonly used catalyst types, with emphasis on the exceptional performance of zeolite based catalysts and their metal modified productions. Research indicates that zeolite catalysts, owing to their strong acidity and stable pore structures, markedly enhance the activity and selectivity of pyrolysis reactions. Other catalysts such as FCC catalysts, clay catalysts and metal oxides have shown promising catalytic performance under certain conditions, offering potential for the industrial applicability of plastic pyrolysis technologies. However, plastic waste pyrolysis research remains a challenge, including regulation of reaction pathways for co-pyrolysis of multi-component plastics, reducing catalyst deactivation, and optimization of energy efficiency. These challenges not only limit further promotion of pyrolysis technologies but also demand more fundamental scientific research and engineering advances. Finally, we conclude with future research directions, with suggestions for theoretical guidance and technology support for plastic waste pyrolysis development and industrial applications.

High-efficiency, robust and low-cost electrocatalysts for the oxygen reduction reaction (ORR) are at the heart of new energy conversion and storage devices. Recently, atomically dispersed metal electrocatalysts (metal–nitrogen–carbon, M–N–C) for the ORR have received great attention. Herein, this review presents recent advances in the noble metal-free atomically dispersed metal electrocatalysts toward the ORR. Specifically, we first introduce the different mechanisms of 2e⁻ and 4e⁻ ORR on the catalyst. Then, the classification and corresponding recent advances in M–N–C electrocatalysts are reviewed, including metal coordination configuration (like the structure and coordination of N in M–N₄, heteroatom substitution, heteroatom doping in carbon skeleton and axial coordination), modulation of the second atom in diatomic catalysts, and the effect of metal nanoparticles/clusters in M–N–C catalysts. In parallel, the synthesis strategy, structure, electrochemical properties and reaction mechanism are highlighted. Finally, an outlook on the current advances and challenges and the potential of the M–N–C-based electrocatalysts towards 2e⁻ and 4e⁻ ORR are discussed.

In this study, we disclose a Zn(II)-catalysed metal-ligand cooperative approach that converts renewable primary alcohols into highly substituted N-heterocycles via acceptor-less dehydrogenation. A well-defined Zn(II) complex, C1, supported by the NNN pincer ligand (E)-2-((2-(pyridin-2-yl)hydrazineylidene)methyl)pyridine (L1), was prepared and characterized by IR, UV-vis, ¹H and ¹³C NMR spectroscopy, HRMS, and single-crystal X-ray diffraction. Complex C1 efficiently promotes a one-pot, three-component synthesis of 1,3,5-trisubstituted-pyrazolines from aromatic primary alcohols, aromatic ketones, and phenylhydrazine. The scope of C1 was further demonstrated in the multicomponent construction of 2,4,5,6-tetrasubstituted pyrimidines from primary alcohols, challenging cyclic ketones, and various amidine hydrochlorides, as well as in the dehydrogenative coupling of 2-aminobenzyl alcohol with aromatic ketones to furnish quinolines. Overall, 30 pyrazolines, 42 pyrimidines, and 27 quinolines were obtained in good yields. Control experiments, HRMS study, and DFT calculations collectively support a reaction pathway in which alcohol dehydrogenation proceeds through a metal–ligand cooperative mechanism.

PdZn_β alloy catalysts have attracted extensive attention in the methanol steam reforming (MSR) reaction due to their superior thermal stability compared to Cu-based catalysts, which are prone to sintering. However, conventional supported PdZn catalysts typically require a high Pd loading (e.g., Pd/ZnO, >5.0 wt%) to achieve the desired MSR performance, limiting their practical applications. In this work, we explore a ZnTiO₃ perovskite as a support and a zinc source to achieve the controlled synthesis of the PdZn_β alloy at low Pd loadings. The 0.1 wt% Pd/ZnTiO₃ catalyst achieves excellent reactivity and CO₂ selectivity (>96%) across a wide temperature range (up to 400 °C). This performance is attributed to the enhanced synergy between the small PdZn_β particles and the ZnTiO₃ support, which enhances methanol dehydrogenation and water dissociation, respectively. The catalyst also shows exceptional thermal stability over 50 hours at 350 °C with minimal loss in activity or selectivity, while pure ZnTiO₃ deactivates significantly. The advanced Pd/ZnTiO₃ catalysts with ultra-low Pd loading demonstrate superior potential over other metal oxides for efficient and stable hydrogen production in mobile applications, which typically need to operate at high reaction temperatures.

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.