ChemCatChem最新文献

Cu/ZnO/ZrO₂ (CZZ) catalysts outperform conventional Cu/ZnO/Al₂O₃ (CZA) materials in methanol synthesis. Building on recent findings that CZA catalysts enable hydrogen release from the oxygen-containing LOHC compound dicyclohexylmethanol (H14-BP) below 200°C, this study investigates structure-activity correlations with CZZ catalysts in the partial dehydrogenation of H14-BP as a model reaction. CZZ materials were produced by continuous co-precipitation with subsequent batch suspension ageing. A ZrO₂ content between 4 and 8 mol% increased the specific surface area and catalytic activity. Zn-rich materials with elevated aurichalcite [(Cu,Zn)₅(OH)₆(CO₃)₂] content in the catalyst precursor achieved higher activity despite a reduced specific surface area. Ageing at 70°C promoted aurichalcite formation and improved performance, whereas higher temperatures reduced the specific surface area. An initial pH value of 6.7 enhanced Zn uptake during ageing and increased dehydrogenation productivity by 45% compared to pH 7.1. High catalyst productivity correlated with aurichalcite contents up to 98% and small crystallite sizes. Overall, CZZ outperformed CZA catalysts in the partial dehydrogenation of H14-BP, with the aurichalcite phase playing a crucial role. Our results demonstrate the potential of this material class for selective dehydrogenation reactions and enable targeted further development based on the correlation between material-specific properties and catalytic activity.

Herein, we present a concept for CO₂-assisted direct aqueous-phase hydrogenation of sodium acetate to ethanol, offering a salt-tolerant approach that circumvents energy-intensive acidification and simplifies biomass valorization. The reaction was performed over highly dispersed Pt on the CoAlPt (CAP) catalyst, which improves H₂ activation and drives hydrogen spillover, thereby increasing the reactive surface hydrogen species while mitigating excessively strong H adsorption that suppresses activity under alkaline conditions. The CAP catalyst achieved 90.88% ethanol selectivity with a productivity of 3.63 mmol·g⁻¹·h⁻¹ at 180°C without CO₂ addition. Introducing CO₂ (0.1 MPa) increased ethanol productivity to 4.92 mmol·g⁻¹·h⁻¹ by converting OH⁻ to HCO₃⁻ and shifting acetate speciation toward molecular acetic acid, which is more readily hydrogenated. The results obtained in this concept study highlight the potential of using CO₂ as a promoter for direct acetate hydrogenation towards a sustainable strategy for converting acetate-rich aqueous streams to ethanol and other value-added products.

The Front Cover illustrates the rich diversity of the MXene family, highlighting the pivotal role of X-ray techniques in elucidating the structures and compositions for MXene-based photocatalysts. These methods facilitate the understanding of MXene chemistry, guiding the development of efficient MXene-based photocatalysts. More information can be found in the Review by A. Kurenkova and A. Saraev (DOI: 10.1002/cctc.202501411).

Sustainable hydrogen production via low-temperature water electrolysis is key to advancing the hydrogen economy, with polymer electrolyte membrane water electrolysis (PEM-WE) as a central technology. However, sluggish oxygen evolution reaction (OER) kinetics at the anode limit PEM-WE efficiency. Iridium-based catalysts remain the benchmark due to their balance of activity and stability under harsh conditions, though iridium scarcity necessitates designs with reduced Ir content. Here, we report a highly active and stable OER catalyst based on TaO_x–IrO₂ nanoparticles synthesized via a reverse microemulsion method and calcined at 800°C. Encapsulation in silica nanoreactors enabled precise control over particle size and crystallinity during thermal treatment. The TaO_x–IrO₂ catalyst achieves a mass activity of 619 ± 93 mA mg_Ir⁻¹ at 1.55 V_RHE, outperforming commercial IrO₂ by a factor of 2.5 and bare IrO₂ synthesized under identical conditions. While TaO_x is electrochemically inactive, it shows exceptional dissolution resistance. The intrinsic stability of TaO_x–IrO₂, expressed via the S-number, exceeds that of commercial IrO₂ and matches bare IrO₂ calcined at 600°C. These results highlight TaO_x–IrO₂ as a promising OER catalyst, combining enhanced activity with notable stability, and support the development of durable, efficient catalysts for PEM-WE.

Carbon capture and utilization play an important role by converting CO₂ emissions to high value fuels and chemicals such as methanol. This work reports the modelling and simulation of the CCU to methanol using a bifunctional catalyst with amine sites for CO₂ capture and Pt sites to catalyze the reduction of intermediates to methanol. The bifunctional material exhibited high CO₂ capture capacity under post-combustion conditions at 50°C–70°C and promising methanol formation under dynamic experiments of sequential CO₂ capture and hydrogenation steps. CO₂ sorption experiments using TGA were employed to extract kinetics for the CO₂ capture. Steady-state CO₂ hydrogenation over the bifunctional material was used for the development of the hydrogenation kinetic model. The validation of the kinetic models coupled with a transient reactor model under dynamic conditions showed that the model can predict the transient formation of methanol. A parametric investigation under varying operation conditions highlighted the advantage of isothermal cycles at high temperature with respect to experimental time efficiency and maximized methanol formation rate compromised by the lower capture capacity. Further investigations in material development focusing on the facilitation of the methanol desorption from the pores would significantly improve the combined process and allow more time-efficient screening protocols.

The Cover Feature visualizes the biotechnological conversion of C₁ waste gases into biodegradable plastics. On the left, methane and CO₂ are released in industrial emissions. In the center, metabolically engineered bacteria fix these gases via synthetic pathways. At the bottom right, the process culminates in the biosynthesis of eco-friendly bioplastics, thus highlighting a sustainable approach to carbon valorization. More information can be found in the Review by Z. Mustafa and E. Y. Lee (DOI: 10.1002/cctc.202501314).

The transformation of CO₂ and green hydrogen into methanol presents a sustainable route for chemical and fuel production. Conventional methanol synthesis catalysts, such as Cu/ZnO/Al₂O₃, employ Al₂O₃ as a structural promoter, while Ga₂O₃ has recently emerged as a promising alternative. This study compares Cu-based catalysts supported on Al₂O₃ (CA) and Ga₂O₃ (CG), prepared via coprecipitation of layered double hydroxide precursors with identical molar Cu:M (M = Al or Ga) ratio of 70:30. Using in situ and operando X-ray absorption spectroscopy and X-ray powder diffraction, we investigate the structural and redox dynamics of Ga during activation and CO₂ hydrogenation. Gallium from its precursor state undergoes several phase transitions. At elevated temperatures, Ga exhibits redox activity, transitioning from Ga³⁺ to metallic Ga⁰ and forming Cu_xGa_y alloys at 480 °C, followed by de-alloying and re-oxidation at even higher temperatures. Our results suggest that the beneficial role of Ga reported in literature arises from metal-oxide interfacial effects rather than bulk alloying. Excess Ga₂O₃ leads to low conversion levels and pronounced deactivation compared to the Al₂O₃-supported Cu catalyst and thus should be prevented. These findings highlight the importance of controlling promoter loading and dynamic behavior in catalyst design to optimize activity, stability, and selectivity for CO₂-to-methanol conversion.

Carbohydrates have been considered as important renewable substrates which are readily available in large quantities from waste streams. During the last two decades, conversion of carbohydrates catalyzed by Lewis acids has been intensively investigated. This research activity has been mostly focused on the tin atoms embedded into zeolite framework, though it has not been limited to these materials. This review summarizes the recent results on conversion of saccharides addressing isomerization, epimerization, and retro-aldol cleavage reactions. Reaction networks and reaction mechanisms are considered, the dependencies of the catalytic performance on catalyst structure and reaction conditions are reviewed. Stability of the catalysts on stream is addressed.