Catalysis Science & Technology最新文献

Oxygen defects in Ni–CeO₂ catalysts play an important role in CO₂ methanation. Herein, efforts are centered on enhancing the concentration of oxygen defects by tuning the Ni–CeO₂ catalyst morphology to enhance methane productivity. A relationship between oxygen defect concentration, the structure of Ni–CeO₂ catalysts and catalytic performance for CO₂ methanation is established through a combination of catalyst characterization (scanning transmission electron microscopy (STEM), temperature programmed reduction (H₂-TPR), H₂ pulse chemisorption, X-ray diffraction, in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and Raman spectroscopy) and kinetic studies. Raman studies indicated that (i) inverse Ni–CeO₂ catalyst structures, along with (ii) incorporation of low amounts (<1 wt%) of aliovalent, rare-earth metal dopants, such as Pr, enhanced the formation of oxygen defects, consequently leading to high methane productivity. In situ DRIFTS studies showed that CO₂ methanation over Ni–CeO₂ inverse catalysts with the best catalytic performance followed a formate reaction pathway.

The hydrodeoxygenation (HDO) of biomass by a vapor-phase catalyst plays a crucial role in the development of renewable energy resources. While the catalysts for HDO are not satisfactory in terms of both selectivity and stability. The poor stability is due to the need for acid centers that can cause carbon deposition. TiO₂ modified with P was used as a support to improve the selectivity and stability. It was found that the content of surface acid on the catalysts exhibited a volcano-shaped curve in relation to increasing P content. The conversion of m-cresol over 5%Ru/TiO₂–3.5%P is up to 60%, while the conversion of m-cresol over 5%Ru/TiO₂ is only 0.3% under the same conditions. In addition, the activity over 5%Ru/TiO₂–3.5%P remains stable over 100 hours due to the presence of a suitable acid center, which is not observed over other supports, such as Nb₂O₅, Al₂O₃, TiO₂, CeO₂, and so on. As revealed by CO-TPD, TEM and XPS, the encapsulation of Ru by TiO₂ was eliminated after the TiO₂ was modified with P. It was demonstrated by changing the order of catalyst modification and the way of catalyst reduction that the introduction of Brønsted acid on the catalysts improves the selectivity for toluene, and the increase of catalytic activity is caused by more exposed Ru sites and the introduction of Brønsted acid. The findings of this study may provide a new approach to the appropriate control of the metal and support interface.

Achieving a future sustainable carbon-neutral society requires the development of efficient systems for the chemical conversion of solar light energy to CO₂-free fuels such as H₂ as alternatives to fossil fuel. In this case, water splitting driven by solar energy is one of the most promising approaches for sustainable H₂ production. However, the critical bottleneck in establishing efficient water splitting systems is the sluggish oxygen evolution reaction (OER) with high overpotentials (η_{O 2}). Thus, the development of highly efficient OER electrocatalysts to minimize η_{O 2} and thus attain efficient water splitting is a challenging key task. Recently, there has been prominent progress in the development of efficient Ni-based electrocatalysts with extremely low η_{O 2}. Herein, the aspects and mechanisms of state-of-the-art Ni-based OER electrocatalysts reported in the last three years from 2020 to 2023 are reviewed. Furthermore, we discuss the perspectives to develop efficient Ni-based OER electrocatalysts based on the comprehensive understanding of the catalysts introduced in this review.

C₂–C₄ shorter olefins, particularly ethylene and propylene, are crucial building blocks in modern petrochemical, polymer, and chemical industries. However, their predominant sourcing from fossil resources raises concerns due to increased awareness of carbon emissions and diminishing petroleum reserves. Therefore, a necessary shift towards sustainable resources is underway. The zeolite-catalyzed methanol-to-olefin (MTO) process, particularly over 8-MR zeolite/zeo-type materials, has gained industrial prominence in this context. If methanol strictly originated from renewable sources, then the MTO process would actively promote the “methanol economy”. Despite the advantages of zeolite/zeo-type materials, they encounter deactivation due to the accumulation of coke precursors, limiting their lifetime. While achieving high olefin selectivity in the MTO process is not challenging, improving the catalytic lifetime without compromising preferential olefin selectivity is crucial. To achieve this objective, various surface modification approaches, such as dealumination through acid etching, steaming, and constructing bifunctional catalytic systems, are applied to numerous 8-MR zeolite/zeo-type materials, including industrially operational MTO catalysts. Combining catalytic studies with advanced characterization methods, including under operando conditions, has enhanced MTO process efficiency by mitigating the formation of coke precursors. Ultimately, this study contributes to a deeper understanding of zeolite-catalyzed MTO processes, paving the way for more efficient and sustainable production of low-carbon olefins.

The reverse water–gas shift (RWGS) reaction has tremendous practical significance for solving energy shortage problems. However, its harsh reaction conditions inevitably lead to the sintering of an active metal, which results in the loss of interface sites. Therefore, the construction of efficient and stable catalysts with uniform interfaces for the RWGS reaction is a persisting challenge. In this work, sintered Cu species were applied to fabricate an inverse Y₂O₃/Cu catalyst with a notable RWGS reaction performance. This inverse Y₂O₃/Cu catalyst sustained a high CO₂ conversion (45.6%) for up to 100 h at 600 °C (GHSV = 400 000 mL g_cat⁻¹ h⁻¹), exceeding the CO₂ conversion of a conventional Cu/Y₂O₃ catalyst (24.4% for up to 40 h). The CO₂ and H₂ adsorption and activation ability of the inverse Y₂O₃/Cu catalyst were greatly optimized, which strikingly accelerated the catalytic reaction. Y₂O₃/CuO_x/Cu interfaces constructed using the sintered Cu species promoted the metal–support interaction of the inverse Y₂O₃/Cu catalyst to achieve excellent catalytic stability. This strategy of using sintering Cu species to construct a stable interface provides new insights into the study of efficient and stable catalytic materials in the RWGS reaction.

The mechanism of Ru(ii)-catalyzed gem-hydrogenation of 1,3-enynes was studied with the aid of DFT calculations. The origins of cyclization selectivity involved in the two Ru(ii)-catalyzed hydrogenative cyclization reactions, where reaction A bears an –OMe group and reaction B bears an –OSiMe₃ group, were explored explicitly. For reaction A, the thermodynamically unfavorable chair-to-twist boat isomerization is found to be involved in the process of forming a five-membered carbocycle product (P′), thus leading to the formation of the preferred five-membered heterocycle product (P). In contrast, for reaction B, the low electronegativity of the silicon atom in –OSiMe₃ makes the proton transfer from the methyl group to the carbene atom more difficult to form a six-membered heterocycle product (P1′), thus leading to the preferred five-membered carbocycle product (P1). Additionally, the influence of a series of heteroatoms on the cyclization selectivity was predicted theoretically (reaction A with –XMe (X = O, S, Se and Te) and reaction B with –OYMe₃ (X = C, Si, Ge and Sn)).

Methanol steam reforming (MSR) is a convenient method for in situ hydrogen production and broadens hydrogen energy application. Identifying the intrinsic activity of Cu-based catalysts for MSR and developing more efficient catalysts is a significant topic for applying in situ hydrogen production. Here, we developed a series of copper catalysts supported by Al₂O₃ with varying copper contents. The highest hydrogen production rate of 147.6 μmol g⁻¹ s⁻¹ was obtained over 10Cu/Al₂O₃ at 250 °C, exceeding most copper-based metallic oxide catalysts. Quasi in situ XPS and CO DRIFTS revealed the variation trend of copper's electronic state in mCu/Al₂O₃ catalysts, where m is the copper loading (in weight percentage). Meanwhile, intermediate formate species adsorbed on the interfacial site at 1602 cm⁻¹ were detected by in situ DRIFTS. This formate species (HCOO–CuAl) dissociated faster to CO₂ and H₂ than those adsorbed on Al₂O₃ (HCOO–Al). The inverse Al₂O₃/Cu catalyst further confirmed that the Cu–Al₂O₃ interfaces play a crucial role in MSR. This work defines the copper–oxide interface as the main active site in MSR and guides the construction of high-performance catalysts.