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Researchers Develop Novel Au Catalyst for Hydroformylation

A research team from the Shanghai Advanced Research Institute (SARI) of the Chinese Academy of Sciences designed a zeolite-encaged Au single-atom catalyst with Au1-O-SiOX motifs, which shows remarkable catalytic activity and selectivity towards propene hydroformylation.

　　As one of the largest-volume industrial chemical processes today, hydroformylation converts olefins, H2 and CO into aldehydes and related products more than 10 million tons annually.
　　Although Au exhibits good ability towards olefins activation, H2 dissociation and CO bonding, it is conventionally considered inactive for hydroformylation due to its intrinsic inertness.
　　Now, a research team led by Profs. WANG Hui and SUN Yuhan from the Shanghai Advanced Research Institute (SARI) of the Chinese Academy of Sciences designed a zeolite-encaged Au single-atom catalyst with Au1-O-SiOX motifs, which shows remarkable catalytic activity and selectivity towards propene hydroformylation.
　　The study was published in Chem Catalysis on July 13.
　　Preliminary performance evaluation of impregnated Au on zeolite demonstrates that sub-nanometer Au clusters exhibit higher activity than nanoparticles in hydroformylation. Inspired by this, the confinement effect of zeolite is utilized to regulate the particle size of Au. Nanoparticles/sub-nanoclusters and atomically dispersed Au species within zeolite can be unambiguously observed through high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM).
　　The Au1@S-1 catalyst shows a total 3,794 μmol butyraldehyde and noticeable stability after 5 cycles, which is about one order of magnitude more active than Au nanoparticles and is even comparable to Rh-based catalysts.
　　Detailed characterizations and theoretical calculations indicate that the isolated Au atoms within the zeolite matrix are stabilized via oxygen bridge bonds. The formed Au1-O-SiOX motifs render maximum active site density and high structural stability, which are identified as the real active sites for efficient hydroformylation.
　　This work makes conventionally inactive Au efficient alternative for hydroformylation by reasonably tailoring the size, contact structure and electronic environment of active metals on specific reactions.
　　Structural modeling and performance comparison of Au-based catalysts (Image by SARI)
　　

2022-07-14 more+

Scientists Reveal Gas Nanobubbles Accelerate Solid-liquid-gas Reaction

A research group reported a real-time observation of the accelerated solid-liquid-gas etching progress of gold nanorods by introducing gas nanobubbles and revealed the underlying microscopic mechanism dependent on liquid layer thickness.

Solid–liquid–gas reactions are encountered in various natural phenomenon and industrial applications, such as hydrogen–oxygen fuel cell reactions, heterogeneous catalysis, metal corrosion in ambient environments, etc.
　　However, due to the absence of quantitative analysis of the reaction dynamics and an understanding of gas transport mechanism at the solid–liquid–gas interface, a comprehensive understanding of gas transport in liquid and following reactions at the triple-phase interfaces remains unclear.
　　Motivated by this challenge, Prof. CHEN Jige at Shanghai Advanced Research Institute (SARI) of the Chinese Academy of Sciences, collaborated with Prof. FANG Haiping at East China University of Science and Technology, Prof. Sun Litao at Southeast University, and Prof. ZHENG Haimei at Lawrence Berkeley National Laboratory, reported a real-time observation of the accelerated solid-liquid-gas etching progress of gold nanorods by introducing gas nanobubbles and revealed the underlying microscopic mechanism dependent on liquid layer thickness. The results were published in the latest Nature Materials.
　　In this work, the real-time observation of the accelerated etching of gold nanorods with oxygen nanobubbles in aqueous hydrobromic acid is given by using liquid-cell transmission electron microscopy (TEM). It is found that when an oxygen nanobubble is close to a nanorod below the critical distance (~1 nm), the local etching rate is significantly enhanced by over one order of magnitude. Molecular dynamics simulation results reveal that the strong attractive van der Waals interaction between the gold nanorod and oxygen molecules governs oxygen transport through the thin liquid layer and thus leads to enhanced etching rate.
　　The finding of a critical distance for etching acceleration between nanobubbles and gold nanorods leads to dramatical different physics picture, which is different from the conventional view that a more rapid reaction of nanobubbles toward the solid relates to a more rapid reaction. This study sheds light on the rational design of solid–liquid–gas reactions for enhanced activities and provides a promising approach to modify the solid–liquid–gas reaction rate. Moreover, it shows that liquid-cell TEM provides an observational and mechanistic understanding of the triple-phase reaction at relevant temporal and distance scales, which offers great potential for addressing many fundamental issues where nanoscale gas and liquid states are involved.Accelerated gold nanorods etching by introducing oxygen nanobubbles (Image by SARI)

2022-07-11 more+

Novel Silver Hollow Fiber Boosts CO2 Electroreduction

A research team led by Prof. WEI Wei and CHEN Wei reported a hierarchical micro/nanostructured silver hollow fiber electrode that reduces CO2 to CO with CO2 conversions exceeding 54% at a high space velocity of 31000 mL？gcat-1？h-1 under ambient conditions, maintaining stable large current densities (~1.26 A？cm-2) and high CO faradaic efficiencies (~93%). The results were published in the latest Nature Communications.

　　The electrochemical conversion of CO2 into carbon-based fuels and valuable feedstocks by renewable electricity is an attractive strategy for addressing CO2 abatement and renewable energy consumption, which is of great significance for achieving the goal of carbon neutralization.
　　CO is the important component of syngas (a mixture of CO and H2), which can be directly converted into various value-added chemicals via well-developed industrial processes such as Fischer-Tropsch synthesis, methanol synthesis, etc. Therefore, CO2 electroreduction to CO is considered one of the most promising routes to obtain cost-competitive products. However, highly efficient CO2 conversion with high space velocity under mild conditions remains a challenge.
　　Motivated by such challenge, a research team led by Prof. WEI Wei and CHEN Wei reported a hierarchical micro/nanostructured silver hollow fiber electrode that reduces CO2 to CO with CO2 conversions exceeding 54% at a high space velocity of 31,000 mL · gcat-1 · h-1 under ambient conditions, maintaining stable large current densities (~1.26 A·cm-2) and high CO faradaic efficiencies (~93%). The results were published in the latest Nature Communications.
　　The reported hollow fiber electrode with hierarchical micro/nanostructures composed of only metallic silver (Ag) for electroreducing CO2 to CO. Such a porous hollow-fiber Ag electrode acting as a CO2 disperser not only enhances three-phase interface reactions but also guides mass transfers during electrolysis. Electrochemical results and time-resolved operando Raman spectra demonstrate that enhanced three-phase interface reactions and oriented mass transfers synergistically boost CO production.
　　This result provides new opportunities for heightening three-phase interface reactions and mass transfer kinetics simultaneously. In addition, it demonstrates that activated Ag HF can be an ideal industrial electrode with excellent durability, representing an encouraging headway in CO2 electroreduction that may lead to scalable applications.
　　Schematic illustration of hollow fiber electrode for boosting CO2 reduction to CO (Image by SARI)
　　

2022-06-02 more+

Tandem Catalysis Improve Selective Oxidation of Methane to Oxygenates

a research team led by Prof. SUN Yuhan and Prof. ZHONG Liangshu at Shanghai Advanced Research Institute (SARI) of the Chinese Academy of Sciences reported a ZSM-5 (Z-5) supported PdCu catalyst for selective oxidation of CH4 to oxygenates using O2 in the presence of H2. The as-obtained PdCu/Z-5 catalyst exhibited a high oxygenates yield of 1178 mmol/gPd/h with oxygenates selectivity of 95% at 120 °C. The research results were published in the latest issue of Angew. Chem. Int. Ed.

　　Direct conversion of methane to oxygenates has attracted numerous research interests from both industrial and academics. However, selective oxidation of methane to value-added chemicals with both high catalytic activity and selectivity under mild conditions still remains a great challenge.
　　Firstly, selective oxidation of CH4 to oxygenates with O2 or O2/H2 suffers from low catalytic activity and low oxygenates selectivity, due to the low activity of oxygen and the overoxidation of the oxygenates. Secondly, the high loading (1~5 wt%) of noble metals for supported catalysts used for methane conversion leads to high cost, which is not business-friendly.
　　Inspired by these challenges, a research team led by Prof. SUN Yuhan and Prof. ZHONG Liangshu at Shanghai Advanced Research Institute (SARI) of the Chinese Academy of Sciences reported a ZSM-5 (Z-5) supported PdCu catalyst for selective oxidation of CH4 to oxygenates using O2 in the presence of H2. The as-obtained PdCu/Z-5 catalyst exhibited a high oxygenates yield of 1178 mmol/gPd/h with oxygenates selectivity of 95% at 120 °C. The research results were published in the latest issue of Angew. Chem. Int. Ed.
　　Based on a combination of control experiments and electron paramagnetic resonance as well as in situ spectroscopic techniques, researchers found that PdO nanoparticles facilitated in situ generation of H2O2, while Cu single atoms not only accelerated the generation of abundant ·OH from H2O2 decomposition, but also enabled the homolytic cleavage of CH4 by ·OH to ·CH3. Subsequently, the ·OH reacted quickly with the ·CH3 to form CH3OH with high selectivity.
　　These findings may provide valuable insights into selective oxidation of methane to oxygenates, which may also shed light on other highly efficient and low-price catalysts for the selective activation of C-H bonds in light alkanes.
　　Product yield and oxygenates selectivity for selective oxidation of CH4 with O2 and H2. (Image by SARI)
　　

2022-04-14 more+

Researchers Propose Direct Convertion of Methane to Acetic Acid with Ultrahigh Selectivity over Fe Binuclear Sites

Direct conversion of methane to chemicals at mild conditions is regarded as the “Holy Grail” reaction in catalysis science, which has attracted numerous research interests from both industrial and academics. Inspired by these challenges, a research team led by Prof. Yuhan Sun and Prof. Liangshu Zhong at Shanghai Advanced Research Institute (SARI) of the Chinese Academy of Sciences reported the direct conversion of methane to acetic acid (CH3COOH) with ultrahigh selectivity in oxygenated products by direct coupling of CH4, CO and H2O2 over ZSM-5 supported Fe binuclear sites under 30 °C. The research results were published in Chem.

　　Direct conversion of methane to chemicals at mild conditions is regarded as the “Holy Grail” reaction in catalysis science, which has attracted numerous research interests from both industrial and academics. Compared with traditional C1 products including CH3OH and HCOOH, conversion of methane to C2 products involving C-C coupling is more economic and challenging. In the previous studies for methane conversion to C2 products, the low catalytic activity and selectivity with the usage of noble metals are still far behind the industrial application.
　　Inspired by these challenges, a research team led by Prof. Yuhan Sun and Prof. Liangshu Zhong at Shanghai Advanced Research Institute (SARI) of the Chinese Academy of Sciences reported the direct conversion of methane to acetic acid (CH3COOH) with ultrahigh selectivity in oxygenated products by direct coupling of CH4, CO and H2O2 over ZSM-5 supported Fe binuclear sites under 30 °C. The research results were published in Chem entitled "Fe binuclear sites convert methane to acetic acid with ultrahigh selectivity”.
　　The ZSM-5 supported Fe binuclear sites can afford 89% total oxygenates selectivity with 66% being CH3COOH in oxygenated products at 30 °C. Particularly, 100% CH3COOH selectivity in oxygenated products can be obtained over Fe-BN/ZSM-5 by optimizing reaction conditions if the formed CO2 was not taken into consideration.
　　The unexpected ultrahigh selectivity towards CH3COOH was attributed to the unique Fe binuclear sites structure of [Fe(III)-(μO)2-Fe(III)-(OH)2] , which was evidenced by advanced spectroscopic techniques and density functional theory (DFT) calculations.
　　The unique structure of [Fe(III)-(μO)2-Fe(III)-(OH)2] also promoted the formation of CH3COOH by direct coupling of ·CH3 with CO* and OH*, compared with the oxidation of CH4 by OH* to form CH3OH, benefited the CH3COOH formation.
　　Large usage of precious metal catalysts, low oxygenates (sole product) yield and selectivity are the main challenges for methane direct conversion. The findings in this work may provide an efficient pathway and low-price catalysts for direct conversion of CH4 to CH3COOH with high yield and selectivity.
　　Catalytic performance and schematic illustration for methane conversion to acetic acid (Image by SARI)
　　Contact: ZHONG Liangshu
　　Shanghai Advanced Research Institute
　　zhongls@sari.ac.cn
　　

2022-03-09 more+

Bifunctional Catalysts Enable High para-Xylene Productivity in Syngas Conversion

Recently, a research group from Shanghai Advanced Research Institute (SARI) of the Chinese Academy of Sciences has fabricated bifunctional catalysts combining versatile zeolites and CoMnAl oxide.These catalysts exhibited high stability and high space-time yield of para-xylene under mild reaction conditions.

　　Aromatics, in particular benzene, toluene, and xylenes, are important basic chemicals for highly valuable chemicals and materials.
　　Direct conversion of syngas to aromatics (STA) has drawn much attention and the current reported process can be achieved using tandem catalysts through the methanol or olefin intermediates. However, the development of efficient catalysts with high catalytic activity, selectivity, and stability still remains challenging.
　　Recently, a research group from Shanghai Advanced Research Institute(SARI) of the Chinese Academy of Sciences has fabricated bifunctional catalysts combining versatile zeolites and CoMnAl oxide.
　　These catalysts exhibited high stability and high space-time yield of para-xylene under mild reaction conditions.
　　The study was published in Chem Catalysis on Feb. 14.
　　In order to produce a catalyst capable of converting syngas to aromatics selectively, the researchers first fabricated bifunctional catalysts containing a series of HZSM-5 zeolites and CoMnAl composite oxides (CMA).
　　The combined catalysts were tested in the STA reaction and the distribution of the aromatic products was tuned by modifying the HZSM-5 zeolite with a hollow nanostructure and a silicalite-1 layer grown epitaxially on the HZSM-5 crystals.
　　The results showed that the catalysts comprising CoMnAl catalysts and versatile HZSM-5@silicalite-1 zeolites achieved ultrahigh catalytic activity, selectivity, and stability under mild reaction conditions.
　　The CO conversion surpassed 70% under mild reaction conditions. The selectivity toward aromatics was higher than 63% and the para-xylene fraction of the aromatics produced reached 34.7%. In addition, the catalyst exhibited high stability, with no deactivation was observed over 726 h.
　　Furthermore, the researchers investigated the reaction mechanism and revealed that olefins and oxygen-containing aromatic compounds form were important intermediates inside HSZM-5 during the conversion of syngas to the aromatic products.
　　This study brings enlightenment for high-performance bifunctional catalyst for the direct conversion of syngas to value-added para-xylene. It also improves our understanding of the complex reaction network of syngas to aromatics, paving the way for designing highly active, selective, and stable catalysts for the synthesis of aromatics.
　　
　　Schematic diagram of the syngas to aromatics pathway on CoMnAl/HZSM-5 bifunctional catalysts (Image by SARI)
　　

2022-02-15 more+

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