Journal of Catalysis最新文献

Identifying the parameters influencing the selectivity of products is prominently significant for fabricating efficient catalysts. However, little progress has been made in describing the regulation rule of CH₄ selectivity toward the CO₂ methanation reaction, which is considered a vital process for CO₂ emission and conversion. Herein, we disclosed the integral role of the electronegativity of M atoms in Ni-MO_x supported catalysts to producing CH₄ molecules, which the satisfactory catalytic performance stemmed from the regulated ability to capture CO₂ molecules and CO intermediates. More importantly, alongside the extensively studied descriptor of particle size, we uncovered a strong correlation between the electronegativity of M atom and CH₄ selectivity, in which the CO/CO₂ adsorption capacity upon the Ni/NiO_x/MO_x interfaces exhibited a volcanic trend based on the electronegativity of M atoms in MO_x supports. The screened Ni-Y₂O₃ composite catalysts demonstrated excellent CO₂ methanation performance, suggesting the powerful practicability of the electronegativity of M atoms in MO_x supports as a descriptor. These findings not only shed fundamental insight into the reaction pathway but also paved the way for the rational design of Ni-based catalysts based on the simple descriptor of electronegativity.

A 2D Mn-based MOF ([Mn₄(PDI)₂(DMF)₇(H₂O)]_n (MOF 1)) (H₄PDI = 5,5′-(1,3,6,8-tetraoxo-1,3,6,8-tetrahydrobenzo[lmn][3,8]phenanthroline-2,7-diyl)diisophthalic acid) was synthesized. Visible light excited Mn-PDI unit in MOF 1 oxidizes NaSO₂CF₃ to generate CF₃ radical and enables MOF 1 to exhibit activity for trifluoromethylation of (hetero)arenes under visible light. The unusual stability of MOF 1 in the trifluoromethylation reactions can be attributed to its unique structure, which prevents it from corrosion by acid byproduct. The peeling of MOF 1 to ultrathin nanosheets or partial oxidation of Mn(II) to Mn(III) in MOF 1 led to MOL 1 and NB 1 with significant improved activity for trifluoromethylation reactions, demonstrating the important role of composition and morphology of a catalyst on its performance. The light initiated trifluoromethylation reactions over these Mn-based MOFs was applied to a variety of substrates. This study provides an efficient strategy for synthesis of trifluoromethylated compounds and highlights the potential of MOFs in light initiated organic syntheses.

Measured chlorine coverages over Ag/α-Al₂O₃ catalysts with varying Ag weight loadings (1.3–35 wt%) and different Ag particle size distributions when parsed in terms of Cl coverages over particles of varying size constituted in the distribution reveal that Ag particles of size below ∼30 nm are covered in more than 1 monolayer (ML) of chlorine in presence of 3.5 ppm C₂H₅Cl. These assessments of Cl coverages were made possible by correlating the cumulative Cl coverage to the lognormal surface area distribution of 22 Ag/α-Al₂O₃ samples using a single exponential decay function. Fully chlorided small Ag particles exhibit low rates of epoxidation and only large Ag particles which exhibit sub-monolayer Cl coverages catalyze ethylene epoxidation with high ethylene oxide (EO) rates and selectivity. The Ag particle size dependence of Cl coverages plausibly explains why ≥ 100 nm Ag particles are typical in promoted Ag/α-Al₂O₃ ethylene epoxidation catalysts.

Acknowledged as an ideal method for in situ hydrogen generation, methanol steam reforming (MSR) requires high-performance catalysts to enhance production efficiency. Herein, we prepared a series of Zr-modified Cu-based catalysts by a coprecipitation method and conducted a systematic analysis of the impacts of structural variations on MSR performance. Extensive characterization reveals a strong dependence of the catalyst’s surface structure on Zr content. Introducing a moderate amount of Zr to the Cu/ZnO catalysts forms ZnZrO_x solid solution and increases Cu dispersion, forming more Cu-ZnZrO_x and Cu-ZnO interfacial sites with higher H₂ production rate. Further increases in Zr content enlarge Cu nanoparticles and multiply Cu-ZrO₂ interfacial sites. The optimal catalyst with a Zn/Zr molar ratio of 5, with the richest Cu-ZnO/Cu-ZnZrO_x interfacial sites, achieves the highest H₂ production rate of 117.4 ${\text{mmol}}_{{\text{H}}_{\text{2}}}{\text{g}}_{\text{cat}}^{\text{-1}}{\text{h}}^{\text{-1}}$ at 200 °C, which is 1.3 times and 6.8 times higher than those of Cu/ZnO and Cu/ZrO₂, respectively.

Aromatic diols play a pivotal role in various industries as crucial components of bulk feedstock and fine chemicals, particularly in pharmaceutical production. However, the complexity of the chemical reactions involved in their synthesis often poses challenges for achieving high yields and purity. This study introduces an alternative approach for the synthesis of 2,3-diphenylbutane-2,3-diol (DPB) and 2-phenylbutane-2,3-diol (PB) using niobium oxides as photocatalysts for C–C reductive coupling with acetophenone as the substrate. Niobium oxides were synthesized from commercially available niobic acid (HY-340) via calcination at various temperatures. The characterization data revealed the critical impact of thermal treatment on the acid-hydroxylated surface groups of niobic acid, which strongly influenced the photocatalytic performance. Therefore, niobic acid emerged as the most active photocatalyst, achieving yields of 32.0 % and 35.1 % for PB and DPB, respectively, after 2 h of UV irradiation. Control experiments were conducted in conjunction with electron paramagnetic resonance and electrochemical impedance measurements to elucidate the mechanistic pathways governing the formation of DPB and PB, and to shed light on the significant role played by the surface structure of niobic acid in influencing the photocatalytic performance. This study not only provides valuable insights into the synthesis of aromatic diols but also emphasizes the significance of tailoring the surface properties of niobium oxide catalysts to enhance reactivity in photochemical processes.

A new family of well-defined cobalt complexes (Co1–Co7) bearing N,N-bidentate chelate aldimine imidazolidine-2-imine/guanidine ancillary ligands were designed and successfully synthesized. All of the target metal complexes were structurally characterized by single-crystal X-ray diffraction analysis. It revealed that the Co atom adopted distorted tetrahedral coordination geometry and formed a unique six-membered chelate ring which exhibited structural distinctions with traditional N^N-based α-diimine and β-diimine Co complexes. In combination with a very low amount of Et₂AlCl (as low as 50 equiv.), these Co complexes exhibited high activity (up to 99 % yield within 6 hrs) and good thermal stability (up to 80 °C) in the coordination polymerizations of isoprene to afford cis-1,4/3,4-polyisoprenes with adjustable molecular weights M_n (25.9–138.4 kg/mol) and cis-1,4 contents (64.7–73.3 %). The different substituents on these Co catalysts also exerted influence on catalytic behaviors, chain microstructures, and polymer properties. This study represents the first example of imidazolidine-imine/guanidine analog ligated Cobalt complexes for the polymerization of isoprene.

One important way to increase the production of higher-margin products from less valuable unsaturated hydrocarbons is the widely used process of catalytic metathesis. Progress in the development of more advanced metathesis catalysts is hampered by obvious gaps in scientific knowledge about this process. This work is aimed at establishing the influence of physicochemical properties of Mo-containing lower olefins metathesis catalysts and developing methods for increasing their activity through promotion. A classic support for Mo-oxide metathesis catalyst was promoted with NH₄HF₂, (NH₄)₂SiF₆, H₃BO₃ additives. The synthesized systems were analyzed by a large set of methods. The catalytic properties of obtained systems were determined in the propylene metathesis reaction. It was shown that the proposed promotion leads to an increase in activity of the catalyst up to 8.5 times. It was shown that strong Brønsted acid sites play a decisive role in increasing activity. In addition, it has been experimentally proven that the formation of active centers occurs when the substrate interacts with Brønsted, but not Lewis acid sites on the surface of the catalyst. The discoveries obtained in this work can serve as the basis for the creation of a new generation highly active lower olefins metathesis catalysts.

The growing demand for environmentally friendly hydrogen peroxide (H₂O₂) production has fueled extensive research into synthesis strategy for photocatalysis though the use of the sunlight. However, the current challenge lies in the efficient production of photocatalysts without relying on sacrificial agents in the atmospheric environment. In this study, we propose a breakthrough approach to synthesize N, S co-doped carbon dots (N, S-CDs) by utilizing disulfide bonds in discarded shuttlecock waste and demonstrate its impressive performance (2062.4 µM g^-1h⁻¹) for photocatalytic H₂O₂ production. The significance of the S-O functional groups in N, S-CDs is not limited to the structural elements, since it is not only the key adsorption site for oxygen, but also active site to promote electron transfer from the bulk phase to surface of N, S-CDs during the oxygen reduction reaction (ORR) process for photocatalytic H₂O₂ production. Furthermore, femtosecond transient absorption spectroscopy (fs-TA) indicates that the presence of the S-O moiety is effective in prolonging the electron lifetime, which effectively inhibit the recombination of electron-holes, thus greatly improving carriers’ utilization. These findings provide new insight for the design of biomass carbon-based photocatalysts, which have important implications for the industrial application of solar energy for the synthesis of H₂O₂.

Flower-like Al₂O₃ materials were successfully incorporated by TS-1 nanocrystals to synthesize Flower-like TS-1-Al₂O₃ (FTA) micro-mesoporous composite by a facile nano self-assembly method. FTA supported NiMo bimetallic catalysts (NiMo/FTA) were further constructed and applied to the hydrodesulfurization (HDS) reactions for dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT). FTA composites were constructed from flower-like pore structures stacked with nanosheets, which are conducive to the even load and dispersion of active species and the diffusion of macromolecular sulfur-containing compounds with relatively low resistance. The fabrication of TS-1 nanocrystals effectively enhanced the acidic sites, regulated the metal-support interaction, which could increase the stacking layer of MoS₂ slabs, and producing more NiMoS-II type active phase. NiMo/FTA-10 presented the excellent HDS conversion of DBT (99.3 %) and 4,6-DMDBT (93.2 %) at 10 h⁻¹, the highest reaction rate constant (2.6 × 10^-7 mol g⁻¹ s⁻¹) and turnover frequency values (6.7 × 10^-4 s⁻¹) for 4,6-DMDBT HDS reaction. Compared to the direct desulfurization route (DDS), hydrogenation route (HYD) and isomerization route (ISO) can effectively eliminate the steric hindrance of 4,6-DMDBT, which is more conducive to the HDS reaction.

Finding a better catalyst for the reduction of nitrogen to ammonia would be of considerable use to the chemical industry, allowing for cheaper and possibly decentralized ammonia production. One approach to find a better catalyst is to explore the element component space continuously via the use of high-entropy alloys, uncovering as of yet untested multi-element catalysts and reaction sites to optimize reaction activity. Utilizing DFT calculations and microkinetic modeling, we use the AuCoFeMoRu high-entropy alloy as a discovery platform for N₂ reduction catalysts. Testing both terrace and step sites, we find that high-entropy alloy terraces can reach as high activities as steps for the N₂ reduction reaction, due to their heterogeneous surface structure. We also find that high-entropy alloys are able to circumvent the scaling relations to an extent, due to the decoupling of the transition state and final state structure of the reaction. We discover several promising high-entropy alloy reaction sites, with a roughly twofold improvement in activity over the best monometallic surface. However, significantly larger gains in activity seem to still be fundamentally limited by the scaling relations.