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2. Cyclic dipeptides: catalyst/promoter-free, rapid and environmentally benign cyclization of free amino acidsElectronic supplementary information (ESI) available: Supplementary information including experimental procedures along with MW graphs for all the compounds studied, 1H, 13C NMR, ESI-MS data, elemental analysis, melting points, optical rotation, single crystal X-ray data collection procedure, tables containing crystallographic details of (1, 9, 11–13, bond length, bond angles, dihedral angles and hydrogen bonding interactions), CCDCs 783550–783553contain the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre viawww.ccdc.cam.ac.uk/data_request/cif. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c1gc15043j
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Nonappa, Ahonen, Kari, Lahtinen, Manu, and Kolehmainen, Erkki
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CYCLIC peptides , *SUSTAINABLE chemistry , *CATALYSTS , *RING formation (Chemistry) , *AMINO acids , *GREENHOUSE gases , *MOLECULAR self-assembly - Abstract
“The best catalyst is no catalyst.” With growing public concern over global warming and the amount of greenhouse gases, it is important to reduce the amount of chemicals and eliminate waste, to obtain better results in a simple, selective, safe, and environmentally benign fashion compared to conventional tedious chemical synthesis. Herein, we disclose an environmentally benign, rapid, catalyst/promoter/coupling reagent-free cyclization procedure of free amino acids to furnish exclusively cyclic dipeptides (2,5-diketopiperazines, DKPs) in excellent or even quantitative yield, along with their solid state self-assembling properties. This process is extremely simple and highly efficient with little or no traditional synthetic skills and without any chromatographic purification. Synthesis of structurally diverse DKPs has been achieved with a dramatic decrease in the reaction time, the amount/number of solvents used, a significant increase in the yield and nearly complete elimination of waste. As a result, this is an excellent example for the environmentally benign, clean and green chemistry concept. The most exciting outcome of our investigation is an unusual case of chiral self-recognition encountered upon the cyclization of rac-pipecolic acid, which resulted in the formation of the meso-product exclusively. [ABSTRACT FROM AUTHOR]
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- 2011
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3. High entropy materials: potential catalysts for electrochemical water splitting.
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Zhong Wang, Xinjia Tan, Ziyu Ye, Shiyu Chen, Guojian Li, Qiang Wang, and Shuang Yuan
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CATALYSTS ,HYDROGEN evolution reactions ,OXYGEN evolution reactions ,ENTROPY ,DENSITY functional theory ,PHOTOCATHODES - Abstract
High entropy materials (HEM) have been attracting much attention as emerging catalysts for electrochemical water splitting. HEM catalysts have unique properties such as an interesting cocktail effect, broad design space, customizable electronic structure, and excellent entropy stabilization effect compared with single-digit catalysts. This paper provides a comprehensive overview of the use of HEM as a catalyst for hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and water splitting. HEM design strategies including phase structure modulation, defect engineering, electrode configuration engineering, and computational aids are discussed to develop HEM catalysts with high performance and stability. In particular, the importance of density functional theory, high-throughput screening techniques, and machine learning for the discovery and design of HEM catalysts is emphasized. Finally, the challenges and imminent difficulties are prospected, and the corresponding strategies to deal with these challenges are put forward to promote the development of HEM catalysts in the field of electrochemical water splitting. [ABSTRACT FROM AUTHOR]
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- 2024
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4. Temperature-responsive Zn-based catalysts for efficient catalytic conversion of biomass-derived carbohydrates to ethyl lactate.
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Wang, Jiangang, Wang, Jinghua, Liu, Yifan, Liu, Tihang, Pang, Zhaobin, Cui, Hongyou, Zhang, Yuan, and Song, Feng
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CARBOHYDRATES ,CATALYST poisoning ,CATALYSTS ,LACTATES ,LACTIC acid ,POLYLACTIC acid ,SUCROSE - Abstract
Chemical catalytic conversion of biomass-derived sugars to lactic acid has attracted considerable attention due to the cheap, abundant and renewable nature of biomass and its huge potential application in the synthesis of biocompatible and biodegradable polylactic acid resins. However, this route is still a huge challenge in view of the transformation efficiency. This paper reports a series of Zn-based catalysts, which are facile and cheap to prepare and highly efficient for the conversion of biomass-derived carbohydrates to ethyl lactate (EL). The microstructure, active site composition and surface properties were characterized by TEM, HRTEM, XRD, NH
3 -TPD, CO2 -TPD, Py-IR, and XPS. The catalytic performance of catalysts in the conversion of biomass-derived carbohydrates to ethyl lactate (EL) and the effect of water content were investigated. It was found that the Zn species played a decisive role in regulating the strengths of the acidic and basic sites to match the rate of each reaction in the tandem reactions. The basic sites are beneficial for isomerization and retro-aldol condensation, while the temperature-responsive released H+ protons are responsible for the dehydration of triose to methylglyoxal, a rate-determining step in the conversion of triose to EL. Addition of a small amount of water could enhance the release of the protons and thus accelerate the dehydration reaction, but excessive water would favor the formation of humins. Using ZnSi-2 as a catalyst under optimal conditions, yields as high as 74.5% of EL from glucose, 81.0% from fructose, 70.9% from mannose, and 80.3% from sucrose could be achieved with tens of times higher productivity than the previously reported values in the literature. DFT calculations revealed that Zn(OEt)Cl, Zn(OH)Cl, and Zn(OH)(OEt) were probably the active components. In addition, the stability of the catalyst as well as the deactivation and regeneration was also studied. The findings in this research provide new insights into the exploration of efficient catalysts for biomass conversion to value-added chemicals. [ABSTRACT FROM AUTHOR]- Published
- 2023
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5. Enhanced nitrate reduction via the Ag–Cu–P catalyst for sustainable ammonia generation under ambient conditions.
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Wen, Xinwei, Zhao, Yue, Fan, Puyang, Wu, Jiajie, Xiong, Kai, Liu, Chang, Qu, Qing, and Li, Lei
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DRINKING water standards ,DENITRIFICATION ,ELECTRONIC modulation ,CATALYSTS ,ACTIVATION energy ,CHEMICAL industry ,AMMONIA - Abstract
The production of ammonia under ambient conditions has been a long-standing challenge for the chemical industry. The electroreduction of nitrate presents a promising solution for nitrate wastewater treatment and decentralized ammonia production. However, traditional Ag-based catalysts suffer from nitrate-to-nitrite conversion, leading to toxicity concerns and hampering ammonia preparation. In this study, we synthesized an innovative Ag–Cu–P catalyst that effectively tunes the d-band centre and electronic structure. The catalyst exhibited a remarkable NH
4 + yield rate of 566.30 μmol cm−2 h−1 at −0.3 V (vs. RHE), reducing nitrite content to below the drinking water standard. Characterization results revealed a distinctive fern leaf-like morphology, providing an expanded active surface area. The challenge of facile nitrate conversion to nitrite on Ag-based catalysts has been addressed through the implementation of electronic structure modulation in this work. Theoretical calculations confirmed the substantial reduction in the energy barrier by modulating the d-band centre and electronic structure, facilitating the conversion of nitrite to ammonia. The regulation and analysis of d-band centres yielded valuable insights for catalyst material design. Meanwhile, direct evidence for potential intermediates has also been presented through in situ spectroscopy. These findings hold significant potential for practical applications, such as enhanced wastewater treatment and decentralized ammonia production, and provide support in the pressing need for sustainable ammonia synthesis under ambient conditions. [ABSTRACT FROM AUTHOR]- Published
- 2024
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6. Dehydration in water: solid-supported lipases as green catalysts for esterification.
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Thomas, Rohan M., Lopez Lemus, Monica S., Ganesh, Krithika, Obbard, David B., Sivashanmugam, Karthikeyan, Sambasivam, Ganesh, Yang Yang, and Lipshutz, Bruce H.
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ESTERIFICATION ,LIPASES ,CATALYSTS ,TECHNOLOGICAL innovations ,BIOCATALYSIS ,ACID catalysts ,DEHYDRATION - Abstract
Catalytic esterification in water has been achieved with the aid of a commercially available polymer-supported lipase, Novozym-435. Remarkably, this well-known biocatalyst demonstrates significant activity towards esterification using just water as the reaction medium. This methodology features representative esterifications of complex acids and alcohols, in the presence of unprotected amines. The work disclosed leading to esters typically requires only two equivalents of alcohol, although conversion for water-soluble alcohols appears to require increased loadings. Recycling of both the aqueous medium and catalyst are documented, highlighting the potential of this new technology, especially using directed evolution on the enzyme involved. Pharmaceutically relevant compounds are efficiently esterified (e.g., Ibuprofen, Tolmetin, and Ticagrelor) and multi-step, one-pot chemoenzymatic sequences can be performed to demonstrate the robustness of this catalytic aqueous system. [ABSTRACT FROM AUTHOR]
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- 2024
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7. Efficient hydrodeoxygenation of lignin-derived phenolic compounds under acid-free conditions over carbon-supported NiMo catalysts.
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Shan Jiang, Riyang Shu, Anqi Wang, Zhuoli Deng, Yuhong Xiao, Jiajin Li, Qingwei Meng, and Qian Zhang
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PHENOLS ,SUSTAINABLE chemistry ,LIGNINS ,SCISSION (Chemistry) ,CATALYSTS ,LIQUID hydrocarbons ,LIGNANS - Abstract
High-quality liquid biofuels can be produced from renewable lignin-derived phenolic compounds through an efficient hydrodeoxygenation (HDO) process in which the traditional catalysts usually include metal sites and acid sites that catalyze the hydrogenation and deoxygenation procedures respectively. This work presents a novel acid-free Ni
x Moy N/C catalyst from the perspective of green chemistry providing a new pathway for HDO of lignin-derived phenolic compounds that involves hydrogenation deoxygenation and hydrogenolysis at the same time. A series of NixMoyN/C catalysts were prepared by varying the Ni :Mo molar ratio among which the Ni1 Mo3 N/C catalyst showed the best HDO performance. Guaiacol could be completely converted at 260 °C after 4 h with 95.8% cyclohexane selectivity. In addition a small amount of benzene could be obtained as a valuable fuel additive by-product by altering the conventional HDO reaction path. By shortening the reaction time benzene could be obtained as an intermediate product with a relative high selectivity. Based on the characterizations using XRD BET SEM TEM XPS H2 -TPD and EPR, the results demonstrate that the multiple active components of the Ni1 Mo3 N/C catalyst allow it to efficiently catalyze the hydrogen activation and C--O bond cleavage even under acid-free conditions. The existence of the active phases of Ni Ni2 Mo3 N and β-Mo2 C as well as the interaction between Ni and Mo metals together contributed toward efficient HDO performance. Not only for the various phenolic model compounds the feasibility of Ni1Mo3N/C catalysts for upgrading raw lignin oil was also demonstrated with the hydrocarbon content increasing from 5.7% to 88.4%. Notably arenes accounted for 18.2% of the hydrocarbon products which confirmed the occurrence of hydrogenolysis in the catalytic process. This work provides a novel route for the conversion of lignin-derived phenolic compounds to produce high-quality hydrocarbon liquid biofuels especially the direct production of arene components. [ABSTRACT FROM AUTHOR]- Published
- 2024
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8. Producing hexamethylenediamine from caprolactam via 6-aminocapronitrile: a green production technology of the monomer of nylon-66.
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Geng, Kaiyu, Li, Hui, Zhang, Dianzi, Yu, Baowei, Hu, Hongqin, Geng, Jiao, Wu, Youting, and Hu, Xingbang
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HEXAMETHYLENEDIAMINE ,CAPROLACTAM ,MONOMERS ,HYDROGENATION ,CATALYSTS - Abstract
Hexamethylenediamine (HMDA), a crucial precursor of nylon-66, can be synthesized from caprolactam (CPL) via a two-step route involving CPL ammoniation and 6-aminocapronitrile (ACN) hydrogenation. Based on theoretical calculations and experimental screening, mesoporous alumina was selected which served as a highly active and cost-efficient catalyst for CPL ammoniation, catalysing the ring-opening of amides by C–N bond breakage and subsequent amide dehydration to nitrile. A 57.9% CPL conversion and 98.3% ACN selectivity were achieved at 320 °C with stability over 480 hours. The subsequent hydrogenation of ACN using the commercial RANEY® Ni catalyst yielded 100% HMDA, requiring milder conditions and half the hydrogen compared to adiponitrile processes. Overall, this research highlights a green HMDA production pathway, employing CPL as a feedstock. [ABSTRACT FROM AUTHOR]
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- 2024
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9. A simple continuous reaction for the synthesis of quinoline compounds.
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Song, Suhong, Dai, Yuyu, Hong, Yunyang, Li, Xiaoqing, and Yan, Xinhuan
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HYDROGEN transfer reactions ,QUINOLINE ,CATALYSTS ,SUSTAINABLE chemistry ,NITROAROMATIC compounds ,RUTHENIUM catalysts - Abstract
In this paper, 2-methylquinoline compounds were synthesized continuously from nitroarenes and the ethanol/water system by a simple hydrogen transfer reaction in the presence of the Ru–Fe/γ-Al
2 O3 catalyst. This new simple synthesis reaction was heterogeneous and continuous. At the same time, green solvents were used, and strong acids, oxidants, and other environmentally harmful substances were not added, which conformed to the principles of green chemistry. Through the impregnation method, the nanocatalysts with a smaller particle size and uniform dispersion were obtained on the γ-Al2 O3 particles (1–2 mm) and had good activity. The effects of the alcohol water volume ratio, pressure, flow rate and Ru–Fe mass ratios on the yields of 2-methylquinoline compounds in the reaction were investigated. The reaction can proceed smoothly for nitroarenes with different substituents, and a moderate to good yield (46%–88%) was obtained. [ABSTRACT FROM AUTHOR]- Published
- 2022
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10. Base-free aerobic oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid over a Fe single-atom catalyst.
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Hameed, Sohaib, Liu, Wengang, Yu, Zhounan, Pang, Jifeng, Luo, Wenhao, and Wang, Aiqin
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ADIPIC acid ,CATALYTIC oxidation ,CATALYSTS ,TEREPHTHALIC acid ,CATALYTIC activity ,ALCOHOL oxidation ,OXIDATION - Abstract
2,5-Furandicarboxylic acid (FDCA) is one of the most promising biodegradable substitutes for fossil-derived terephthalic acid (PTA) and adipic acid. The production of FDCA from biomass-derived 5-hydroxymethylfurfural (HMF) is significant and has attracted great attention. However, the major challenge lies in the development of a non-precious metal-based catalyst system without employing a homogeneous base. Herein, we successfully prepared an atomically dispersed Fe–N–C/γ-Al
2 O3 catalyst, which affords superior catalytic performance in terms of activity and stability with a FDCA yield of 99.8% and reusability of five recycle times in the catalytic oxidation of HMF to FDCA under base-free mild conditions. Based on controlled experiments and complementary characterization studies, we found that the atomically dispersed medium-spin Fe–N5 active sites together with the surface acidic/basic sites of alumina synergistically enhanced the catalytic activity and selectivity towards FDCA under base-free conditions. Our process eliminates the employment of expensive oxidants and corrosive bases, leading to economic and green biomass transformations. [ABSTRACT FROM AUTHOR]- Published
- 2024
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11. Green synthesis of a magnesium single-atom catalyst from Spinacia oleracea chlorophyll extracts for sustainable electrocatalytic nitrate reduction to ammonia.
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Kumar, Kanhai, Tripathi, Pragyan, Raj, Gokul, Kalyan, Dova, Gorle, Demudu Babu, Mohan, Nikhil George, Makineni, Surendra Kumar, Ramanujam, Kothandaraman, Singh, Abhishek Kumar, and Nanda, Karuna Kar
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DENITRIFICATION ,SPINACH ,METAL catalysts ,CATALYSTS ,MAGNESIUM ,CARRIER density ,CHLOROPHYLL ,AMMONIA - Abstract
Single atom-based catalysts (SACs), due to their exceptional electrocatalytic behavior, have been explored for numerous applications such as the oxygen reduction reaction, thermo-catalytic CO
2 reduction, and other catalytic activities. Ammonia is one of the most used chemical compounds, and its electrochemical synthesis is a promising alternative as it is simple and cost-effective and shows selective tunability towards the synthesis. Utilizing single-atom electrocatalysts with comparatively low metal mass loading yet exceptional activity could be a better approach to maximize ammonia production. Herein, we report a practically viable magnesium SAC (MgNx C) for the promising reduction of nitrate to ammonia. The catalyst was prepared using green leaf extracts of Spinacia oleracea via simple one-step pyrolysis. We optimized their synthesis temperature to scrutinize the effect of SAC formation and their variation on the catalysis efficacy. The MgNx C650 catalyst, anchored on a defective graphitic matrix, exhibits the best-optimized potential of −0.58 V vs. RHE, a faradaic efficiency of 81.5 ± 2.9% and a yield rate of 392.5 ± 41.2 μmol h−1 mg−1 cat. with excellent repeatability. A comprehensive study of the nature of the heterojunction formed at the reactive interface of MgNx C catalysts was carried out by Mott–Schottky analysis to probe the band structure of the intrinsically induced metal–semiconductor junction in the MgNx C catalysts, followed by the analysis of parameters like flat band potential and carrier density correlation. DFT is employed to optimize the most stable reactive site and various reaction pathways for favorable nitrate reduction reaction with probable reaction intermediates were explored. Collectively, our work demonstrates a simple, cost-effective, and convenient way to synthesize SACs. Moreover, it provides clear evidence that chlorophyll moieties can be used as a template to prepare metal catalysts singly anchored on the graphitic carbon matrix. [ABSTRACT FROM AUTHOR]- Published
- 2024
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12. Yeast-derived N, P co-doped porous green carbon materials as metal-free catalysts for selective hydrogenation of chloronitrobenzene.
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Wang, Xiaohua, Zhao, Hongfan, Zhou, Yebin, Yin, Chunyu, He, Wei, Feng, Feng, Wang, Fengli, Lu, Chunshan, and Li, Xiaonian
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CARBON-based materials ,DOPING agents (Chemistry) ,NITROGEN ,HYDROGENATION ,DENSITY functional theory ,CATALYSTS - Abstract
Biomass provides a promising source of carbon for obtaining environment-friendly carbon materials, but obtaining heteroatom-doped carbon materials (HDCMs) from biomass directly by a green method still remains challenging. This study successfully synthesized nitrogen and phosphorus co-doped porous carbon materials (Y-NPC) by the simple in situ pyrolysis of renewable yeast mixed with water from 800 to 950 °C. Various characterization methods show that nitrogen and phosphorus are doped into the carbon skeleton and mainly exist in the forms of graphite-N, pyridine-N, C–P, P–N, and P–O states. The catalyst Y-NPC-900 °C with a 3D hierarchical porous structure and high P–N content exhibited superior nitro hydrogenation performance and reaction stability using molecular hydrogen and hydrazine hydrate as hydrogen sources under mild conditions. Density functional theory (DFT) calculations and experiments attributed the exceptional catalytic performance to hydrogen activation and the good adsorption ability of substrates over N, P co-doped carbon (NPC). Therefore, this research proposes an eco-friendly and simple synthesis strategy for in situ N, P co-doping metal-free carbon catalysts derived from biomass, showing the significance of N, P co-doping and single N- or P-monodoping in the charge distribution of carbon materials. [ABSTRACT FROM AUTHOR]
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- 2024
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13. Electrochemical direct α-amidation and α-pyrazolation of N-alkoxy- and N-aryloxycarbonyl pyrrolidines.
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Wang, Zhuang, Liu, Yuxiu, Song, Hongjian, and Wang, Qingmin
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AMIDATION ,FUNCTIONAL groups ,PYRAZOLES ,AMIDES ,OXIDIZING agents ,CATALYSTS - Abstract
We have developed a straightforward electrochemical protocol for direct α-amidation and α-pyrazolation of N-alkoxy- and N-aryloxycarbonyl pyrrolidines with amides or pyrazoles. Unlike previously reported methods, this protocol does not require pre-prepared amidation reagents, thereby shortening the synthesis route and boosting atom economy. Various functional groups are tolerated, and the reaction proceeds at room temperature in only 2.5 h without assistance from chemical oxidants or catalysts. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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14. Cold plasma activated Ni0/Ni2+ interface catalysts for efficient electrocatalytic methane oxidation to low-carbon alcohols.
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Zhang, Qiang, Li, Wei, Peng, Junyi, Xue, Lian, and He, Ge
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LOW temperature plasmas ,ALCOHOL oxidation ,TRANSITION metal nitrides ,COUPLING reactions (Chemistry) ,METHANE ,CATALYSTS - Abstract
The field of converting methane into valuable products using renewable energy sources under ambient conditions is both appealing and highly demanding. The inherent inertness of methane (CH
4 ) necessitates the selective breaking of its first C–H bond while avoiding excessive oxidation, in order to transform CH4 into high-value products. Herein we present a novel approach for creating a highly concentrated Ni0 /Ni2+ -on-Cu interface using an O2 cold plasma in situ method to enhance the activity and stability of the CH4 OR to low-carbon alcohol. The Cu@Ni–NiO electrocatalyst exhibits excellent performance for the CH4 OR to low-carbon alcohol, showcasing a high faradaic efficiency (FE) of 86.7%, an impressive low-carbon alcohol yield of 1215.2 μmol g−1 h−1 , remarkable durability (66 h) and a notable C2 H5 OH selectivity of 59.8% at 1.9 V vs. RHE. The ATRSEIRAS spectroscopy and DFT calculations further reveal that the synergistic effect of the Ni0 /Ni2+ -on-Cu interface can enhance the *O and *CH2 generation on Ni0 , and the *CH2 spillover from Ni0 to Ni2+ atoms can also improve the C–C coupling reaction. Additionally, the in situ treatment with O2 cold plasma can enhance the formation of NiO, leading to a high concentration of the Ni0 /Ni2+ -on-Cu interface, which effectively prevents the oxidation of Ni0 during the CH4 OR process. Furthermore, we developed a general oxidation strategy for the direct synthesis of transition metal nitrides by O2 cold plasma treatment of Ni0 . Compared with the previous methods used for the preparation of NiO, the Ni-based metal oxide synthesis method offers several advantages, including simplicity and practicality, low cost, high throughput, pollution-free nature, low energy consumption and the capability to prepare metal oxides with controllable coordination number of the O atom. This work provides new insights into the highly efficient CH4 OR process and presents an innovative, cost-effective method for preparing electrocatalysts. [ABSTRACT FROM AUTHOR]- Published
- 2024
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15. NiCoP@CoNi-LDH/SSM as a multifunctional catalyst for high-efficiency water splitting and ultra-long-life rechargeable zinc-air batteries.
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Juan Jian, Zhuo Wang, Yu Qiao, Shuang Gao, Meiting Wang, Limin Chang, Hairui Wang, and Ping Nie
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LAYERED double hydroxides ,ENERGY conversion ,CATALYSTS ,PHOSPHATE coating ,SOLAR cells ,LOW voltage systems ,PHOTOVOLTAIC power systems - Abstract
The design and development of self-supporting multifunctional catalysts for efficient water splitting and long-life rechargeable zinc-air batteries (ZABs) is of great significance for energy conversion. Different from previously reported metal layered double hydroxides (LDHs) grown on metal phosphides, herein, we synthesize a CoNi-LDH precursor with a larger exposed surface area on a stainless-steel mesh (SSM), followed by direct surface phosphating to form NiCoP@CoNi-LDH. The obtained NiCoP@CoNi-LDH/SSM demonstrated enhanced HER, OER and ORR properties compared to the CoNi-LDH/SSM precursor, and comparable to or even superior to those of commercial catalysts. Moreover, when applied as the aircathode of a ZAB, it can continue to operate for a long lifetime of more than 1500 h during charge and recharge testing at a current density of 10 mA cm
−2 , with a low voltage gap of only 0.81 V before 900 h. Additionally, the assembled ZAB can efficiently drive a two-electrode water-splitting experiment. The acquired voltage is only 1.579 V when the output current density is 10 mA cm−2 , which is much lower than that of the CoNi-LDH/SSM precursor (1.719 V), or even the commercial Pt/C/SSM∥RuO2 /SSM (1.626 V) electrode pair. After deeply analyzing the insight into the influence of the surface phosphating, we confirmed that both the generated NiCoP@CoNi-LDH heterojunction and the formed NiCoP nanoneedle enhanced the inherent multifunctional properties of NiCoP@CoNi-LDH/SSM. This work provides a superior trifunctional catalyst, and we believe that it will advance a novel idea for the design of efficient multifunctional nanomaterials. [ABSTRACT FROM AUTHOR]- Published
- 2024
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16. Selective hydrogenolysis of furfural to 1,2-pentanediol over a Pt–Fe/MT catalyst under mild conditions.
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Chen Cao, Weixiang Guan, Qiaoyun Liu, Lin Li, Yang Su, Fei Liu, Aiqin Wang, and Tao Zhang
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FURFURAL ,HYDROGENOLYSIS ,BIMETALLIC catalysts ,SUSTAINABILITY ,CATALYSTS ,CHARGE exchange ,TRANSFER hydrogenation - Abstract
Furfural is a large-volume and widely available biomass-derived platform compound, and its transformation into valuable pentanediols is important for the sustainable production of bio-based polymers. Herein, we report a new catalyst system composed of Pt–Fe bimetallic nanoparticles highly dispersed on a commercial magnesium titanate (MT) support. HAADF-STEM, CO-DRIFTS and XPS characterization studies revealed that Pt was in the metallic state with a particle size of 1–2 nm, while Fe existed as Fe
2+ and was decorated on the Pt particles. The electron transfer from Fe to Pt weakened the hydrogenation activity of the furan ring and meanwhile promoted selective ring-opening to 1,2-pentanediol (1,2-PeD). Reaction kinetics studies revealed the reaction rate with respect to hydrogen pressure was close to zero order, which allowed the reaction to proceed at a hydrogen pressure as low as 0.1 MPa. Under mild conditions of 140 °C and 0.1 MPa, the 0.1Pt0.05Fe/MT catalyst offered by far the highest production rate of 178 mol 1,2-PeD per mol Pt per hour, and the Pt–Fe bimetallic catalyst was stable during 200 h of time-on-stream, showing great potential for practical applications. [ABSTRACT FROM AUTHOR]- Published
- 2024
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17. Progress in batch preparation of single-atom catalysts and application in sustainable synthesis of fine chemicals.
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Hu, Yifan, Li, Hongxuan, Li, Zesheng, Li, Bolin, Wang, Shaoyu, Yao, Yuancheng, and Yu, Changlin
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CHEMICAL synthesis ,GAS migration ,CATALYSTS ,CATALYTIC activity ,COORDINATION polymers ,BALL mills ,RESEARCH teams - Abstract
In 2011, Zhang's research team, in cooperation with Li and Liu, reported the Pt
1 /FeOx atomically dispersed catalysts for the first time in the world, and based on this, proposed the concept of "single-atom catalysts". Single-atom catalysts (SACs) have a wide range of industrial application prospects in the catalytic synthesis of fine chemicals due to their high atomic utilization rate and special catalytic activity. With the deepening of the research, the preparation methods of SACs emerge in an endless stream, but it is still an urgent problem to realize the industrial production of highly stable SACs prepared in small batches (gram level) or even in large batches (kilogram level). In this review paper, several typical solvent-free green synthetic strategies (e.g., ball milling, physical mixing, gas migration, and pyrolyzing coordination polymers (including MOFs)) for the batch preparation of SACs are introduced. And typical catalytic application of SACs in green synthesis of fine chemicals by means of oxidation reaction, hydrogenation reaction, coupling reaction and other reactions are also introduced. This is the first review paper focusing on the mass preparation techniques of SACs and their applications in fine chemicals production. [ABSTRACT FROM AUTHOR]- Published
- 2021
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18. Dual -functional carbon-based solid acid-induced hydrothermal conversion of biomass saccharides: catalyst rational design and kinetic analysis.
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Xiong, Shanshan, Luo, Chao, Yu, Zhihao, Ji, Na, Zhu, Lingjun, and Wang, Shurong
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FURFURAL ,ACID catalysts ,CATALYSTS ,SACCHARIDES ,BIOMASS conversion ,ACTIVATION energy ,ENERGY conversion ,THERMAL stability - Abstract
The isomerization–dehydration cascade conversion on the saccharide platform is a pivotal route for biomass valorization, although it exhibits a specific reaction complexity that makes achieving an efficient conversion a highly technical challenge. The rational design of novel versatile solid acids is deemed to be the key to improving the cascade catalytic performance. In this paper, a dual-functional carbon-based solid acid catalyst (DFCSA) with tunable Brønsted/Lewis acid sites was developed for the cascade conversion of saccharides. The combined modification of H
3 PO4 and HNO3 on the carbon substrate contributed to the grafting of protonated moieties with a reasonably porous structure. With the aid of AlPO4 , which has an orthorhombic crystal structure, the newly developed catalyst was able to achieve good performance for the subsequent hydrothermal conversion. Under optimal conditions, glucose and xylose were transformed with high product yields: 38.2 mol% levulinic acid and 69.7 mol% furfural, respectively. In addition, the catalyst displayed excellent hydrothermal stability, with only a slight degradation in activity after 10 cycles, which was ascribed mainly to the high thermal stability of AlPO4 and the firm grafting of the surface functional groups. As shown by the kinetic analysis, the DFSCA catalyst had a higher conversion rate and lower activation energy in the cascade conversion of xylose than that of glucose, leading to a better yield of furfural. [ABSTRACT FROM AUTHOR]- Published
- 2021
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19. An atomically dispersed Co catalyst for efficient oxidative fabrication of benzoheterocycles under ambient oxygen conditions.
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Chen, Jia-Yue, Li, Ke-Ming, Sun, Yu-Xuan, Xiao, Yao, Guo, Feng-Shuo, Huang, Yao-Bing, and Lu, Qiang
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BENZOXAZOLES ,HETEROCYCLIC compounds synthesis ,HETEROGENEOUS catalysts ,CATALYSTS ,BENZOTHIAZOLE - Abstract
The highly efficient synthesis of benzoxazole, benzothiazole and benzimidazole has attracted much attention due to their superior biological activities. However, developing environmentally friendly and poisoning-resistant catalysts in heterogeneous catalytic systems remains a critical challenge. Herein, an atomically dispersed Co
1 /NC catalyst was fabricated by facile pyrolysis of a zeolitic imidazolate framework (ZnCo-ZIF). The Co1 /NC catalyst exhibited excellent oxidation catalysis, sulfur-resistance and reusability performance. The mass specific activity (MSA) of Co1 /NC was up to 42.0 mol2-PBO molCo −1 h−1 , much higher than that of the Co/NC nano-catalyst (15.6 mol2-PBO molCo −1 h−1 ). Mechanism studies showed that O2 was activated by atomically dispersed Co active species to form1 O2 and ˙O2 − , which were responsible for the dehydrogenation of the key imine intermediates to produce 2-phenylbenzoxazole (2-PBO). The current work represents a novel feasible strategy for the synthesis of bioactive heterocyclic compounds using efficient, stable and green heterogeneous catalysts. [ABSTRACT FROM AUTHOR]- Published
- 2024
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20. Chemical valorisation of biomass derived furanics and carboxylic acids over niobium-based catalysts.
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Antunes, Margarida M., Skrodczky, Kai, Cabanelas, Pedro S., Pinna, Nicola, Russo, Patrícia A., and Valente, Anabela A.
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CARBOXYLIC acids ,BIOMASS chemicals ,VALERIC acid ,CATALYSTS ,FURFURAL ,NIOBIUM oxide - Abstract
Furfural is an industrial renewable platform chemical, which can be converted to useful furanics such as α-angelica lactone, carboxylic acids such as levulinic acid and valeric acid, or to higher carbon content products via condensation routes for producing drop-in fuel replacements and chemicals with diverse applications. These important conversion processes may be carried out in selective fashions, although they require adequate catalysts. They were successfully carried out using versatile, stable silica-wrapped niobium oxide nanostructured catalysts. For example, α-angelica lactone was converted in an integrated fashion to ethyl levulinate in 90% yield, and the esterification of levulinic and valeric acids gave ethyl levulinate in quantitative yield and ethyl valerate in 90% yield, respectively, at 140 °C. Catalytic, mechanistic and kinetic modelling studies shed light on the influence of the materials properties on the catalytic performances. These catalysts outperformed pure Nb
2 O5 , as well as hydrothermally synthesized composites consisting of Nb2 O5 nanoparticles embedded in a mesoporous siliceous matrix. [ABSTRACT FROM AUTHOR]- Published
- 2024
- Full Text
- View/download PDF
21. Catalytic self-transfer hydrogenolysis of lignin over Ni/C catalysts.
- Author
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Mei, Xuelei, Liu, Huizhen, Wu, Haihong, Wu, Wei, Zheng, Bingxiao, Liu, Yani, Zheng, Xinrui, Wang, Yaqin, Han, Wanying, and Han, Buxing
- Subjects
HYDROGENOLYSIS ,LIGNANS ,LIGNINS ,LIGNIN structure ,CATALYSTS ,METAL-organic frameworks ,MONOMERS - Abstract
Lignin is composed of phenylpropyl alcohol through the C–O and C–C bonds, where β-O-4 accounts for the majority. Self-transfer hydrogenolysis (STH) is a promising method to produce valuable chemicals and fuels from lignin by cleaving the β-O-4 bond without exogenous hydrogen, but all the reported work used noble metal-based catalysts. In this work, a highly efficient Ni/C catalyst was derived from a Ni-containing metal–organic framework (Ni-MOF), and its self-transfer hydrogenolysis performance towards ether bonds in lignin model compounds was evaluated using 2-phenoxy-1-phenylethanol as a model compound in detail. It was found that the catalyst pyrolyzed under a nitrogen atmosphere at 500 °C (Ni-NDC-500) was very efficient for the reaction. Moreover, it could also catalyze the reaction of native lignin into monomers effectively without exogenous hydrogen. In addition, Ni-NDC-500 was recycled three times without an obvious reduction of the activity. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
22. A highly efficient and sustainable catalyst system for terminal epoxy-carboxylic acid ring opening reactions.
- Author
-
Ramspoth, Tizian-Frank, Flapper, Jitte, van den Berg, Keimpe J., Feringa, Ben L., and Harutyunyan, Syuzanna R.
- Subjects
CARBOXYLIC acids ,IRON clusters ,CATALYSTS ,MATERIALS science ,IRON ,ENERGY consumption ,EPOXY coatings - Abstract
The nucleophilic ring opening of epoxides by carboxylic acids is an indispensable transformation for materials science and coating technologies. Due to this industrial significance, improvements in operational energy consumption and catalyst sustainability are highly desirable for this transformation. Herein, an efficient, environmentally benign and non-toxic halide free cooperative catalyst system based on an iron(III) benzoate complex and guanidinium carbonate is reported. The novel catalyst system shows improved activity over onium halide catalysts under neat conditions and in several solvents, including anisole and
n BuOAc. Detailed mechanistic studies using FeCl3 /DMAP as a catalyst revealed the importance of a carboxylate bridged cationic trinuclear μ3 -oxo iron cluster and guanidinium carbonate or DMAP as a carboxylate reservoir due to its superior activity. [ABSTRACT FROM AUTHOR]- Published
- 2024
- Full Text
- View/download PDF
23. Tailoring the molecular weight of isosorbide-derived polycarbonates via regulating the H-bond donor/acceptor ability of task-specific ionic liquid catalysts.
- Author
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Qian, Wei, Ma, Xifei, Fu, Mengqian, Chen, Minggong, Yang, Zhonglian, Su, Qian, and Cheng, Weiguo
- Subjects
MOLECULAR weights ,POLYCARBONATES ,CATALYSTS ,IONIC liquids ,CATALYTIC activity ,CATALYST structure ,MICROBIAL exopolysaccharides - Abstract
The biorenewable carbohydrate-derived rigid building block of isosorbide (ISB) has demonstrated potential in high-performance polymer materials; however, a controllable eco-friendly preparation technology is not yet available. For this purpose, a sustainable strategy to synthesize ISB-based polycarbonate (PIC) has been established by adopting the CO
2 -based compound dimethyl carbonate (DMC) as a monomer and ionic liquids (ILs) as metal-free catalysts. The molecular weight of PICs can be readily controlled by varying the cation structure of IL catalysts. Control experiments, density functional theory (DFT) calculations, and Kamlet–Taft solvent parameters indicated that the H-bond donor/acceptor (HBD/HBA) ability of IL catalysts played a dominant role in regulating catalytic activity. PIC molecular weight can be modulated by modifying the inherent difference in reactivity of endo-OH and exo-OH in ISB, wherein the chain length or substituent group of cations can regulate the HBD/HBA ability of IL catalysts and anions can specifically activate the carbonyl carbon of DMC. The experimental results revealed that a task-specific [Pmim][OAc] catalyst exhibited the highest catalytic activity, which is attributed to its significant role in considerably lowering the disparity in reactivity between endo-OH and exo-OH. For this DMC route, the [Pmim][OAc] catalyst offered a PIC with the highest molecular weight of 57 200 g mol−1 reported to date. Furthermore, a well-supported polymerization mechanism was proposed, in which [Rmim][OAc]'s anion–cation synergistically catalyzed ISB and DMC to prepare PIC. Our findings offer a clear pathway for designing efficient metal-free catalysts to enable the sustainable synthesis of high molecular weight PICs, thus expediting the industrialization of the DMC route. [ABSTRACT FROM AUTHOR]- Published
- 2024
- Full Text
- View/download PDF
24. Recycling spent LiNi1−x−yCoxMnyO2 cathodes to efficient catalysts for the oxygen evolution reaction.
- Author
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Chen, Mingfei, Zhou, Yixin, Wang, Li, Xue, Gang, Guo, Jiashuo, and Wang, Yaping
- Subjects
OXYGEN evolution reactions ,CATHODES ,CATALYSTS ,OXALIC acid ,ALKALINE solutions - Abstract
The wide application of lithium-ion batteries (LIBs) for electric vehicles forebodes a future decommissioning tide of spent LIBs. Therefore, the recycling of spent LIBs has garnered significant attention, primarily due to the scarcity of resources and the detrimental effects of environmental pollution. However, traditional recycling technologies such as pyrometallurgy and hydrometallurgy methods are limited by their high energy consumption, high pollution, and complicated separation processes. Herein, we propose a novel and general approach to convert a series of spent LiNi
1−x−y Cox Mny O2 (NCM) cathodes into Ni–Co–Mn hydroxide (NCM-OH) catalysts for the oxygen evolution reaction (OER) using deep eutectic solvents to extract valuable metals, followed by an in situ precipitation process using oxalic acid and a final self-templating process in an alkaline solution. The NCM-OH catalyst obtained from the spent LiNi0.33 Co0.33 Mn0.33 O2 cathode is found to possess a nanoflake-assembled microrod structure with a large surface area (385.8 m2 g−1 ) and high porosity, which is endowed with abundant active sites and gas channels for the electrocatalytic reaction and mass transfer process. As a result, the NCM-OH catalyst for the oxygen evolution reaction exhibits a low overpotential of 273 mV at a current density of 10 mA cm−2 with a Tafel slope of 50.46 mV dec−1 as well as satisfactory stability. The effect of the composition on the catalytic performance is also evaluated by comparing different Ni1−x−y Cox Mny hydroxide catalysts derived from commercially prevailing spent cathodes. This work provides a promising strategy for recycling spent LIBs into electrocatalyst materials for the OER. [ABSTRACT FROM AUTHOR]- Published
- 2024
- Full Text
- View/download PDF
25. Hydrodeoxygenation of guaiacol over physically mixed Co/TiO2 and WO3/TiO2 catalysts.
- Author
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Kim, Hyungjoo, Lim, Yong Hyun, Park, Jae Hyun, Ha, Jeong-Myeong, and Kim, Do Heui
- Subjects
CATALYST poisoning ,CATALYSTS ,TRANSITION metal catalysts ,GUAIACOL ,RAMAN spectroscopy - Abstract
To replace the noble metals used in hydrodeoxygenation (HDO) catalysts, guaiacol HDO was conducted using various transition metal-loaded catalysts. Co/TiO
2 was highly active for guaiacol HDO, enabling a more economic removal of the methoxy groups compared to the Ru/TiO2 catalyst, resulting in superior cyclohexanol selectivity. When a WO3 promoter was added to the Co catalyst to enhance its oxygen removal ability, the conversion of guaiacol was severely reduced because the co-impregnated WOx species decreased the number of exposed Co sites. To avoid this phenomenon, Co and WO3 were isolated by physically mixing Co/TiO2 and WO3 /TiO2 , where 100% conversion and oxygen removal could be achieved under 10 bar H2 at 250 °C. The cause of the catalyst deactivation was systematically investigated by magnetic separation of the physical mixture of the catalysts after the reaction, followed by a series of characterization studies. Temperature-programmed-oxidation mass spectroscopy and Raman spectroscopy revealed that the deposition of carbonaceous species was the main contributor to the deactivation of WO3 /TiO2 , and the catalytic activity could be successfully recovered by simple calcination at 400 °C. This study provides insights into the development of economical and efficient physically mixed HDO catalysts using transition metals, and contributes to the understanding of the deactivation and regeneration of physically mixed HDO catalysts. [ABSTRACT FROM AUTHOR]- Published
- 2024
- Full Text
- View/download PDF
26. Engineering built-in electric fields in oxygen-deficient MnO-CeO2@Cs catalysts: enhanced performance and kinetics for the oxygen reduction reaction in aqueous/flexible zinc–air batteries.
- Author
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Wang, Lixia, Hu, Xinran, Li, Huatong, Huang, Zhiyang, Huang, Jia, Isimjan, Tayirjan Taylor, and Yang, Xiulin
- Subjects
ELECTRIC fields ,ENERGY conversion ,POWER density ,CHARGE exchange ,CATALYSTS ,ELECTROCATALYSTS - Abstract
Deliberate engineering of built-in electric fields (BEFs) can facilitate electron transfer and promote asymmetrical charge distribution, thereby regulating the adsorption/desorption of reaction intermediates. Herein, an oxygen-deficiency-rich MnO-CeO
2 is synthetized supported on a carbon sphere (MnO-CeO2 @Cs), adeptly crafted with a prominent work function difference (ΔΦ) and robust BEF, targeting the electrocatalytic oxygen reduction reaction (ORR). Empirical and theoretical results substantiate that the BEF triggers interfacial charge redistribution, fine-tuning the adsorption energy of oxygen intermediates and hastening reaction kinetics. Consequently, the MnO-CeO2 @Cs showcases commendable performance (E1/2 = 0.80 V and jL = 5.5 mA cm−2 ), outshining its single-component counterparts. Impressively, the MnO-CeO2 @Cs-based zinc–air batteries (ZABs) boast an exemplary power density of 202.7 mW cm−2 and enduring stability of 297 h. Additionally, the solid-state ZAB commands a peak power density of 67.4 mW cm−2 , underscoring its potential in flexible ZAB applications. This work delineates a strategic avenue to harness interfacial charge redistribution, aiming to enhance the catalytic performance and longevity of energy conversion/storage apparatuses. [ABSTRACT FROM AUTHOR]- Published
- 2024
- Full Text
- View/download PDF
27. Modular synthesis of spirocyclic carbonates: unravelling the synergistic interplay of electronic and electrostatic sites on phenolic catalyst.
- Author
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Dabas, Shilpa, Patel, Brijesh, Mehra, Sanjay, Barik, Manas, Murugan, Prabhahar, Kumar, Arvind, and Subramanian, Saravanan
- Subjects
CATALYSTS ,CARBONATES ,CARBON dioxide ,OXINDOLES ,SPIRO compounds - Abstract
The enhancement of 3D character in chemical scaffolds has become an unavoidable space and a key component for diverse applications. Herein, we report a simple phenol-derived catalyst with synergistic involvement of electronic and electrostatic sites to access spirocyclic carbonates from spiroepoxy oxindoles and carbon dioxide. The metal-free and co-catalyst free catalytic system demonstrates excellent activity in synthesizing diverse spirocyclic carbonates with good conversions (up to 99%) under ambient reaction conditions. Volumetric and NMR investigations enabled the synergistic role of the key chemical functionalities in the catalyst and elucidated the probable reaction mechanism. The calculated values of different green metrics revealed the suitability and practical applicability of the catalytic system. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
28. Selective production of bio-based para-xylene over an FeOx-modified Pd/Al2O3 catalyst.
- Author
-
Xiao, Yuxue, Meng, Qingwei, Pan, Xiaoli, Zhang, Chao, Fu, Zaihui, and Li, Changzhi
- Subjects
CATALYSTS ,METAL catalysts ,ELECTRON density ,PRECIOUS metals ,DECARBONYLATION ,POLYETHYLENE terephthalate - Abstract
para-Xylene (PX) is a basic building block of polyethylene terephthalate, which is currently produced from petroleum resources. Developing a renewable route to PX is highly desirable to address both economic and environmental concerns. Several attempts used noble metal catalysts, e.g. Pd/Al
2 O3 , to synthesize PX from biomass-derived 4-methyl-3-cyclohexene-1-carboxaldehyde (4-MCHCA), but suffered from a severe decarbonylation reaction, resulting in toluene as the main product. In this paper, we report an FeOx modification strategy to suppress the decarbonylation reaction on a Pd/Al2 O3 catalyst, leading to a drastic shift in selectivity towards PX with a yield up to 81% via a cascade dehydroaromatization–hydrodeoxygenation (DHA–HDO) pathway. Characterization and control experiments revealed that the electron density of Pd sites decreased in an FeOx -modified Pd/Al2 O3 catalyst compared to Pd/Al2 O3 , thus tuning the preferential adsorption mode of the substrate from η2 -(C,O), the key transition state of the decarbonylation reaction, to the η1 -(O) mode that favors the hydrodeoxygenation process. Notably, this designed catalyst is highly stable and is readily applicable in the selective synthesis of a broad range of desired aromatic chemicals via the same DHA–HDO pathway from cyclohex-3-enecarbaldehyde derivatives. Overall, this work develops a controllable catalyst modification strategy that tailors an efficient catalyst for petroleum-independent bio-PX synthesis. [ABSTRACT FROM AUTHOR]- Published
- 2020
- Full Text
- View/download PDF
29. Iron-catalysed 1,2-acyl migration of tertiary α-azido ketones and 2-azido-1,3-dicarbonyl compounds.
- Author
-
Yang, Tonghao, Lin, Yajun, Yang, Chaoqun, and Yu, Wei
- Subjects
KETONES ,BENZENE ,IRON compounds ,CATALYSTS - Abstract
Iron-catalysed 1,2-acyl migration of tertiary α-azido ketones and 2-azido-1,3-dicarbonyl compounds provides a simple and atom-economical approach toward enamides and isoquinolones. This paper reports two catalyst systems for these transformations which employ iron(II) complexes [Fe(dpbz)]Br
2 (dpbz = 1,2-bis(diphenylphosphino)benzene) and FeBr2 /Et3 N, respectively. [Fe(dpbz)]Br2 was found to be highly effective at converting 2-azido-2,3-dihydro-1H-inden-1-ones to isoquinolones. The reagent combination of FeBr2 /Et3 N, on the other hand, exhibited a broader catalytic scope, owing to the beneficial effect of Et3 N. This latter catalyst system enables 2-azido-2-methyl-1,3-dicarbonyl compounds to be converted to the corresponding enamides under mild conditions in good yields. [ABSTRACT FROM AUTHOR]- Published
- 2019
- Full Text
- View/download PDF
30. Organocatalytic Friedel–Crafts arylation of aldehydes with indoles utilizing N-heterocyclic iod(az)olium salts as halogen-bonding catalysts.
- Author
-
Galathri, Eirini M., Kuczmera, Thomas J., Nachtsheim, Boris J., and Kokotos, Christoforos G.
- Subjects
INDOLE compounds ,ARYLATION ,ALDEHYDES ,CATALYSTS ,SALTS ,INDOLE - Abstract
The Friedel–Crafts arylation is among the most known organic reactions, usually being promoted by a Lewis acid, that have been employed for the synthesis of bis-indolyl methanes. Herein, we report a mild, inexpensive, green and organocatalytic protocol for the promotion of a Friedel–Crafts-type reaction between indoles and aldehydes, where N-heterocyclic iod(az)olium salts are utilized as halogen-bonding catalysts, leading to the double addition of the indole motif. A variety of aliphatic and aromatic aldehydes were converted into diarylmethanes in good to high yields, while the scope of indoles was also investigated. Water was employed as the solvent, while the reaction time was short. The reaction mechanism was also studied. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
31. A comparative study of palladium-gold and palladium-tin catalysts in the direct synthesis of H2O2.
- Author
-
Kovačič, Dávid, Lewis, Richard J., Crombie, Caitlin M., Morgan, David J., Davies, Thomas E., López-Martín, Ángeles, Qin, Tian, Allen, Christopher S., Edwards, Jennifer. K., Chen, Liwei, Skjøth-Rasmussen, Martin Skov, Liu, Xi, and Hutchings, Graham J.
- Subjects
CATALYST synthesis ,SCRAP metals ,COMPARATIVE studies ,CATALYSTS ,DISPERSION (Chemistry) - Abstract
Herein we evaluate the promotive effect of Au and Sn incorporation into supported Pd nanoparticles for the direct synthesis of H
2 O2 from molecular H2 and O2 . The introduction of both secondary metal modifiers was found to result in a significant enhancement in catalytic performance, although, in the case of the PdSn system, it was identified that relatively large quantities of the secondary metal were required to rival the activity observed over optimal Au-containing formulations, with the 0.25%Pd–2.25%Sn/TiO2 catalyst offering comparable H2 O2 synthesis rates to the optimised 0.25%Pd–0.25%Au/TiO2 formulation. The introduction of Sn was found to considerably improve Pd dispersion, correlating with an improvement in selective H2 utilisation. Notably, the optimal PdSn catalyst identified in this work achieves superior H2 O2 selectivities compared to the PdAu analogue and is able to rival the performance of state-of-the-art materials. [ABSTRACT FROM AUTHOR]- Published
- 2023
- Full Text
- View/download PDF
32. The quantitative conversion of polyethylene terephthalate (PET) and Coca-Cola bottles to p-xylene over Co-based catalysts with tailored activities for deoxygenation and hydrogenation.
- Author
-
Shao, Yuewen, Fan, Mengjiao, Sun, Kai, Gao, Guoming, Li, Chao, Li, Dianqiang, Jiang, Yuchen, Zhang, Lijun, Zhang, Shu, and Hu, Xun
- Subjects
POLYETHYLENE terephthalate ,HYDROGENATION ,DEOXYGENATION ,P-Xylene ,CATALYSTS ,SCISSION (Chemistry) - Abstract
The selective depolymerization of PET plastics to p-xylene (xylene) is very challenging owing to the full deoxygenation of the terephthalic acid monomer and the retainment of the benzene ring through saturation. In this study, the modification of Co–Al catalysts by introducing a second metal (Fe, Cu, Ni, or Zn) was conducted to tailor the activity of the cobalt species for the conversion of PET to xylene. The results indicated that the CoFe alloy in the Co–Fe–Al catalyst weakened the adsorption/activation of H
2 , achieving xylene yields of >99.0% from PET. Co–Fe–Al suppressed the ring hydrogenation of the benzene ring, while Co–Al and Co–Ni–Al catalyzed the hydrogenation of the benzene ring and cleavage of the C–C bond in the intermediates. Benzene ring-containing intermediates showed a high affinity for Co–Ni–Al and Co–Al, facilitating their hydrogenation. Co–Fe–Al could preferably adsorb and activate the oxygen-containing functionalities of the intermediates for the deoxygenation reactions. The hydrogenolysis reaction of C–OH in intermediates, like 1,4-benzenedimethanol (Ea : 137.8 kJ mol−1 ), was the rate-determining step, while the hydrogenation of the carboxylic intermediates was much easier. [ABSTRACT FROM AUTHOR]- Published
- 2023
- Full Text
- View/download PDF
33. New conformationally flexible and recyclable aryl iodine catalysts from an inexpensive chiral source for asymmetric oxidations.
- Author
-
Zhou, Hai-Jie, Yao, Yi-Ping, Zhang, Tonghui, Chen, Biao, Wang, Xu, Zhao, Hang, Zeng, Jie, Chen, Jian-Ai, Xiao, Xiao, and Chen, Fen-Er
- Subjects
ORGANOCATALYSIS ,ORGANIC synthesis ,IODINE ,HYPERVALENCE (Theoretical chemistry) ,AMINO acid residues ,DERACEMIZATION ,CATALYSTS - Abstract
Despite the remarkable advances in the research field of asymmetric catalytic oxidation reactions via hypervalent iodines with simple procedures, high level of efficiency and stereoselectivity and the development of their highly scalable, environmentally benign, and sustainable protocols under the greener organocatalysis paradigm for further industrial translations remains a long-standing challenge in synthetic organic chemistry and process engineering over the past few decades. Herein, we design and synthesize a new library of conformationally flexible and recyclable aryl iodine catalysts by utilization of (i) industrial waste (chloramphenicol base) as the scaffold and (ii) inexpensive amino acid residue (threonine) as the chiral source. Our chiral aryl iodine(III) catalysts bearing H-bond donors and a tunable chiral pocket have been successfully applied in diverse, robust asymmetric oxidative transformations, e.g., dearomatization, spirolactonization, direct C(sp
2 )–H/C(sp3 )–H cross coupling, and fluoridation. Our processes feature a column isolation-free approach, easy-handling operation, and upscaling synthesis with the catalysts being facilely recycled, in particular via precipitation. [ABSTRACT FROM AUTHOR]- Published
- 2023
- Full Text
- View/download PDF
34. Bio-glycerol hydrodeoxygenation to propylene: advancing knowledge on Mo-based catalyst characteristics and reaction pathways under flow conditions.
- Author
-
Ioannidou, Georgia and Lemonidou, Angeliki A.
- Subjects
GLYCERIN ,PROPENE ,CATALYST testing ,CATALYSTS ,SURFACE reactions ,CARBON-black - Abstract
In this work, the reaction pathways of one-step glycerol hydrodeoxygenation in the gas phase are exploited under flow conditions over molybdena-based catalysts (8.7 wt% Mo/black carbon). Hydrodeoxygenation (HDO) experiments with possible reaction intermediates along with temperature-programmed surface reaction spectroscopy (TPSR) experiments demonstrated two possible reaction pathways. The major one involves propylene formation via hydrodeoxygenation of 2-propen-1-ol which is considered to be the main intermediate of the reaction. In the secondary route, propanal formed via 2-propen-1-ol isomerization is further converted to 1-propanol. XPS measurements in fresh-reduced and reduced-used catalysts revealed that molybdena exists as multivalent species mostly as Mo
5+ , Mo4+ and Mo3+ , the presence of which seems to be crucial for the desired pathway of successive HDOs towards propylene. TPSR tests using methanol as the probe molecule showed that redox and acid sites co-exist on the surface of reduced molybdena catalysts, and this bifunctionality is mostly served by the undercoordinated molybdena species. The long-term catalyst test at 280 °C and 60 bar pressure under glycerol hydrodeoxygenation conditions demonstrated that the catalyst remains stable in terms of activity and selectivity for the first 10 h with a gradual drop afterwards. Regeneration of the catalyst for a short time under hydrogen flow proved to be sufficient to fully recover the initial activity and product selectivity. [ABSTRACT FROM AUTHOR]- Published
- 2023
- Full Text
- View/download PDF
35. Recyclable iodine-catalyzed oxidative C–H chalcogenation of 1,1-diarylethenes in water: green synthesis of trisubstituted vinyl sulfides and selenides.
- Author
-
Mukherjee, Nilanjana and Chatterjee, Tanmay
- Subjects
DIVINYL sulfide ,SUSTAINABLE chemistry ,SELENIDES ,OXIDATIVE coupling ,IODINE ,MOLECULES ,CATALYSTS - Abstract
We disclose a metal-free, iodine-catalyzed oxidative C–H sulfenylation and selenation of alkenes, particularly 1,1-diarylethenes with diorganyl dichalcogenides in water for the cost-effective, highly atom-economical, and sustainable synthesis of valuable vinyl sulfides and selenides including some aggregation-induced-emission (AIE) active molecules. The transformation required only 10 mol% iodine as the catalyst and a very small amount of a green oxidant, H
2 O2 (0.3 equiv.), to afford the desired products in moderate to high yields of up to 96% under mild reaction conditions, i.e. 50 °C and an aerobic atmosphere. The products were further synthetically diversified to various novel classes of organic molecules. The notable advantages of this method over the previously developed ones for the C–H chalcogenation of 1,1-diarylalkenes are (a) a metal-free, energy-efficient, cost-effective and sustainable protocol for the synthesis of both vinyl sulfides and selenides, (b) use of inexpensive reagents such as iodine as the catalyst and H2 O2 as the green oxidant, (c) water as the green reaction medium and water as the only byproduct, (d) a straightforward scale-up process up to the gram scale without any compromise on the reaction outcome, (e) very clean reactions (100% conversion) in multiple cases to afford pure vinyl sulfides/selenides without the requirement of a huge organic-solvent consuming column chromatographic purification technique, and (f) excellent green chemistry metrics such as high atom economy (>96%), atom efficiency (≥87%), carbon efficiency (>88%), and reaction mass efficiency (≥81%), a very low E-factor (≤4.5 g waste per g product), here the byproduct is nothing but water, and a very high EcoScale score (≥82) which revealed that this method is excellent in the context of green chemistry. Moreover, the catalyst iodine could be recovered after the reaction and recycled without any compromise on the reaction outcome which makes the process highly sustainable. Mechanistic studies revealed a radical pathway for this transformation. [ABSTRACT FROM AUTHOR]- Published
- 2023
- Full Text
- View/download PDF
36. Contents list.
- Subjects
CATALYSTS ,ALCOHOL oxidation ,PALLADIUM compounds ,CHEMICAL processes ,CATALYSTS recycling ,MOLECULAR self-assembly ,PLASMA jets - Published
- 2022
- Full Text
- View/download PDF
37. Tailoring the catalytically active sites in Co-based catalysts for electrochemical methanol upgrading to produce formate.
- Author
-
Wang, Yameng, Yang, Xue, Wang, Kexin, Liu, Zimeng, Sun, Xiaoning, Chen, Jinyue, Liu, Shanshan, Sun, Xu, Xie, Junfeng, and Tang, Bo
- Subjects
OXIDATION of methanol ,COBALT catalysts ,STANDARD hydrogen electrode ,CATALYSTS ,SUSTAINABLE chemistry ,ELECTROSYNTHESIS ,METHANOL - Abstract
Electrochemical valorization of bulk chemicals to produce value-added fine chemicals is highly attractive and deemed to be a green and economic way to optimize traditional industrial synthesis. The electrochemical methanol upgrading (EMU) process which converts methanol to value-added formate exhibits an expectation of high profit and adherence to the tenets of green chemistry, and it has received substantial interest aimed at discovering highly efficient catalysts with satisfactory operational stability. In this work, focusing on enriching and activating the high-valence cobalt active sites, a hierarchically nanoporous nitrogen-doped carbon-supported Co/CoO hybrid catalyst grown on cobalt foam (Co–N–C/CoO/CF) was fabricated. The high porosity and conductive microchannels could synergistically enrich the local high-valence Co active sites and boost the in situ generation of such sites via an electrochemical pre-oxidation process. Benefitting from the synergy of multiple structural benefits, the Co–N–C/CoO/CF catalyst exhibits robust EMU performance. An ultralow potential of 1.309 V versus a reversible hydrogen electrode can be identified to drive a 50 mA cm
−2 EMU current density, and a high faradaic efficiency (FE) of 98.2% can be achieved. In addition, with the merits of high structural stability, excellent operational stability can be achieved for Co–N–C/CoO/CF with negligible degradation in either current density or FE for at least 120 h, making the catalyst the most stable catalyst to date for methanol-to-formate upgrading. Its high activity and excellent operational stability make the Co–N–C/CoO/CF catalyst a promising candidate for green and economic formate electrosynthesis via partial methanol electro-oxidation. [ABSTRACT FROM AUTHOR]- Published
- 2023
- Full Text
- View/download PDF
38. Efficient Fe3O4 nanoparticle catalysts for depolymerization of polyethylene terephthalate.
- Author
-
Jo, Yoonjeong, Kim, Eun Jeong, Kim, Jueun, and An, Kwangjin
- Subjects
POLYETHYLENE terephthalate ,NANOPARTICLES ,DEPOLYMERIZATION ,CATALYSTS ,TRACE metals ,SPINEL group ,ION exchange resins - Abstract
Polyethylene terephthalate (PET) can be recovered as high-purity bis(2-hydroxyethyl terephthalate) (BHET) monomer by glycolysis in the presence of Fe
3 O4 nanoparticles (NPs). In this study, Fe3 O4 NPs of various shapes, sizes, and surface areas were synthesized using different colloidal synthesis methods, and the conversion of PET glycolysis and BHET yield were compared. Spinel ferrite NPs, including Fe3 O4 , were synthesized using the coprecipitation (CP), thermal decomposition (TD), and the hydrothermal (H) methods. Among the NP catalysts, Fe3 O4 -CP exhibited the best glycolysis performance with a PET conversion of ∼100% and BHET yield of 93.5% at 195 °C for 2 h owing to its high surface area (146.6 m2 g−1 ). The larger the surface area and the better the dispersion, the higher the glycolysis activity. The glycolysis performance of the mixed spinel ferrite NPs was similar to that of the Fe3 O4 NPs, indicating that replacing Fe2+ in the Fe3 O4 NPs with other transition metals, M2+ , did not significantly change the glycolysis performance. BHET monomers produced from commercial waste PET bottles in large quantities contained trace amounts of metal contaminants, because PET production uses various metal-based additives and catalysts. Amberlite IRC-120, a cation-exchange resin, effectively removed metal impurities from BHET. This study provides an effective strategy for producing recycled PET (r-PET) by waste PET glycolysis. [ABSTRACT FROM AUTHOR]- Published
- 2023
- Full Text
- View/download PDF
39. MnBr(CO)5: a commercially available highly active catalyst for olefin hydrosilylation under ambient air and green conditions.
- Author
-
Vivien, Anthony, Veyre, Laurent, Mirgalet, Raphaël, Camp, Clément, and Thieuleux, Chloé
- Subjects
ALKENES ,HYDROSILYLATION ,AIR conditioning ,CATALYSTS ,DIOLEFINS - Abstract
The catalytic hydrosilylation of alkenes is a major industrial reaction and a very efficient and atom-economical way to obtain functional organosilane compounds and cross-linked materials. Platinum-based catalysts are currently preferred in the industry despite the low availability and high cost of platinum but considerable efforts are being directed to replace Pt with non-noble metals. In this context, we developed a robust and highly active non-noble metal catalytic system using commercially available MnBr(CO)
5 . It was successfully employed in olefin hydrosilylation reactions using various functional olefins and industrially relevant silanes such as 1,1,1,3,5,5,5-heptamethyltrisiloxane (MDHM) and polymethylhydrosiloxanes (PMHS). This system tolerates unpurified substrates and can be used in green solvents (H2 O, anisole) under ambient air, selectively yielding the anti-Markovnikov hydrosilylated products (yields up to >99%) at 70 °C using 2 mol% catalyst. MnBr(CO)5 was also successfully employed for the synthesis of cross-linked materials using dienes, carbonyl and epoxide containing substrates with low Mn loadings (0.3 mol%) at 70 °C under ambient air. [ABSTRACT FROM AUTHOR]- Published
- 2023
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40. Reversal of methanation-oriented to RWGS-oriented Ni/SiO2 catalysts by the exsolution of Ni2+ confined in silicalite-1.
- Author
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Chia-Hung Chen, Hong-Kai Chen, Wei-Hsiang Huang, Chi-Liang Chen, Kittisak Choojun, Tawan Sooknoi, Hong-Kang Tian, and Yu-Chuan Lin
- Subjects
CATALYTIC hydrogenation ,CATALYST testing ,CATALYSTS ,DENSITY functional theory ,WATER-gas - Abstract
Investigation of catalytic hydrogenation of CO
2 to CO via the reverse water-gas shift (RWGS) was undertaken using Ni/SiO2 -based catalysts. Among the array of catalysts tested, the Ni/SiO2 catalyst derived from the reduction of silicalite-1-encapsulated, ligand-protected Ni2+ (Ni0.2 @S-1-red) exhibited promising performance. This catalyst demonstrated a CO2 conversion rate approaching the equilibrium conversion of RWGS, a selectivity for CO exceeding 99%, and a high space time yield of CO (9.7 mol gNi-1 h-1 ). The outcomes observed can be attributed to several factors, such as the highly dispersed Ni0 and Niδ+ species, as well as the presence of bridging oxygen of the Ni-O-Si structure, on which CO2 can be adsorbed moderately. The moderately bonded CO2 on Ni0.2 @S-1-red allows for the efficient desorption of its reduced intermediate, i.e. *CO, resulting in the generation of gaseous CO at a rapid rate, consequently preventing its deep hydrogenation to CH4 . Complementary Density Functional Theory (DFT) calculations were performed and revealed that CO molecules have poor adsorption and higher adsorption energy on the Ni@S-1 surface compared to the S-1 surface. This supports the rapid desorption of *CO and the observed high selectivity of CO. Moreover, the structure-activity correlation analysis further supports the claim of Ni0.2 @S-1-red as a promising RWGS catalyst. [ABSTRACT FROM AUTHOR]- Published
- 2023
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- View/download PDF
41. Machine learning-aided catalyst screening and multi-objective optimization for the indirect CO2 hydrogenation to methanol and ethylene glycol process.
- Author
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Yang, Qingchun, Fan, Yingjie, Zhou, Jianlong, Zhao, Lei, Dong, Yichun, Yu, Jianhua, and Zhang, Dawei
- Subjects
MACHINE learning ,ETHYLENE glycol ,HYDROGENATION ,PEARSON correlation (Statistics) ,METHANOL ,CATALYSTS ,CARBONATES - Abstract
Indirect CO
2 hydrogenation to methanol and ethylene glycol is a green, efficient, and economical technique for converting CO2 into high-value chemicals to address the intractable environmental crisis caused by CO2 emissions. However, traditional methods for screening and optimizing catalysts in this process mainly depend on experience and repeated 'trial-and-error' experiments, which are resource-, time- and cost-consuming tasks. Therefore, this study developed a machine learning framework for predicting the conversion ratio of ethylene carbonate and the yield of methanol and ethylene glycol from the indirect CO2 hydrogenation technology to accelerate the catalyst screening and optimization processes. The initial dataset was visualized by conducting principal component analysis and improved to ensure sufficient information variables for the machine learning model to distinguish between catalyst types. After comparing the optimized results of three algorithms, the neural network with two hidden layers is the core of the machine learning model of the indirect CO2 hydrogenation process. It was then further optimized by a feature engineering method coupled with feature importance analysis and the Pearson correlation matrix. It indicates that the optimized neural network model has higher performance, especially in predicting ethylene carbonate conversion and product yields. Compared with other input features, the space velocity and hydrogen/ester ratio are the two most important factors affecting the conversion ratio of ethylene carbonate and the yield of methanol and ethylene glycol. Based on the results of the feature importance analysis, a multi-objective optimization model with a genetic algorithm was employed to screen the most suitable catalyst. Compared with other catalysts, more efforts should be devoted to the optimized xMoOx –Cu/SiO2 catalyst for the industrialization of indirect CO2 hydrogenation technology after experimental verification. [ABSTRACT FROM AUTHOR]- Published
- 2023
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- View/download PDF
42. Vitreoscilla hemoglobin: a natural carbene transfer catalyst for diastereo- and enantioselective synthesis of nitrile-substituted cyclopropanes.
- Author
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Xie, Hanqing, Li, Fengxi, Xu, Yaning, Wang, Chunyu, Xu, Yuelin, Wu, Junhao, Li, Zhengqiang, Wang, Zhi, and Wang, Lei
- Subjects
CYCLOPROPANE derivatives ,HEMOGLOBINS ,TURNOVER frequency (Catalysis) ,HEMOPROTEINS ,ORGANIC synthesis ,CATALYSTS - Abstract
Hemoproteins have recently emerged as attractive biocatalysts for catalyzing carbene-mediated cyclopropanation, a synthetically valuable reaction not found in nature. In this study, we present a hemoglobin-catalyzed strategy for the highly stereoselective synthesis of nitrile-substituted cyclopropanes. This method offers efficiency and environmental friendliness by utilizing an asymmetric olefin cyclopropanation reaction catalyzed by wild-type Vitreoscilla hemoglobin in the presence of in situ generated diazoacetonitrile. A diverse range of nitrile-substituted cyclopropanes could be synthesized in water with exceptional stereoselectivity, achieving up to 99.9% de and ee and high turnover numbers of up to 3232. By employing this sustainable approach, not only can various chiral nitrile-substituted cyclopropanes be efficiently obtained, but also the practical application of hemoglobin in organic synthesis can be expanded. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
43. Harmonization of an incompatible aqueous aldol condensation/oxa-Michael addition/reduction cascade process over a core–shell-structured thermoresponsive catalyst.
- Author
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Su, Yu, Wang, Chengyi, Chen, Qipeng, Zhu, Yuanli, Deng, Shaomin, Yang, Shoujin, Jin, Ronghua, and Liu, Guohua
- Subjects
REVERSIBLE phase transitions ,RUTHENIUM catalysts ,TRANSFER hydrogenation ,CATALYSTS ,KINETIC resolution ,THERMORESPONSIVE polymers ,HYDROGELS ,MOLECULES - Abstract
The utilization of stimuli-responsive hydrogels as bifunctional catalysts for an aqueous sequential organic transformation to prepare chiral organic molecules is not only environmentally friendly, but also complements the synthetic limitations of mutually contradictory multistep reactions. However, finding a solution to the incompatible issue arising from complicated multicomponent cross-interactions in sequential transformations is a significant challenge. To address this issue, we have developed a core–shell-structured hydrogel as a site-isolated bifunctional catalyst. This catalyst features thermoresponsive poly(N-isopropylmethacrylamide) with a switching function via a reversible transition between its hydrogel and solution phases that perfectly matches a temperature-tuned base-catalyzed aldol condensation/oxa-Michael addition at 70 °C and the ruthenium-catalyzed dynamic kinetic resolution asymmetric transfer hydrogenation (DKR-ATH) process at 40 °C. As we envisioned, through the harmonization of the conflicting sequential reactions, this aldol condensation/oxa-Michael addition/DKR-ATH cascade process can be achieved by transitioning from being incompatible to compatible, enabling direct access to chiral chromanols with 1,3-positioned dual stereocenters from commercially available ortho-hydroxyl arylketones and aldehydes. Mechanistic investigations, which involve monitoring the cascade reaction and analyzing the deuterium-labeling experiments, reveal a domino-like aldol condensation/oxa-Michael addition/DKR-ATH sequential route comprising an initial aldol condensation/oxa-Michael addition followed by the subsequent DKR-ATH process. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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- View/download PDF
44. A bifunctional molecular catalyst built up of L-proline grafted polyoxometalate for one-pot three-component green synthesis of heterocycles.
- Author
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Dai, Guoyong, Li, Qi, Zang, Dejin, and Wei, Yongge
- Subjects
CATALYSTS ,CHEMICAL synthesis ,ORGANIC synthesis ,HETEROCYCLIC compounds ,ALCOHOL oxidation ,POLYOXOMETALATES ,PYRIDINE derivatives - Abstract
Both polyoxometalates (POMs) and organic small molecular catalysts show excellent performance in chemical synthesis. The incorporation of nanoscale POMs and organocatalysts allows the full expression of their respective merits and enables elusive reactions to be achieved in one catalytic system. However, the covalent combination of such two components has been rarely explored. Here, we have successfully designed and synthesized a bifunctional nanomolecular catalyst L -Pro-Mn-Anderson by grafting L -proline onto an Mn-Anderson POM for the first time, and catalytic experiments show that L -Pro-Mn-Anderson can realize the one-pot alcohol oxidation/three-component reaction to synthesize two types of heterocyclic compounds (5-aryl-pyrimido[4,5-b]quinoline-dione derivatives and pyrazolo[3,4-b] pyridine derivatives) in high yields up to 97%. The detailed characterization of the catalyst and the catalytic mechanism has shown that L -Pro-Mn-Anderson exhibits synergistic effects that combine both organic and inorganic catalytic functions, and the covalent linkage improves the overall redox activity of the molecular catalyst. This study opens up a new way for the design and application of covalently combined organic–inorganic molecular catalysts toward de novo organic synthesis. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
45. On the reduction of CO2 footprint via selective hydrodeoxygenation by ZnO–Ti3C2Tx catalyst under solvent-free conditions.
- Author
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Saini, Bhagirath, Krishnapriya, R., Yadav, Meena, Singhal, Rahul, and Sharma, Rakesh K.
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ESSENTIAL fatty acids ,LIQUID fuels ,CATALYST selectivity ,NICKEL phosphide ,CATALYSTS ,EDIBLE coatings ,CATALYSTS recycling - Abstract
Biomass-derived fatty acids are essential feedstock for producing liquid fuels and value-added chemicals with significantly low CO
2 footprints. Herein, Ti3 C2 Tx and ZnO–Ti3 C2 Tx catalysts were synthesized and demonstrated for the selective hydrodeoxygenation reaction (HDO) of methyl oleate (MO) as a model compound. The synthesized ZnO–Ti3 C2 Tx catalyst showed 100% conversion of MO with >90% selectivity for the HDO product (n-C18). In addition, the pure Ti3 C2 Tx demonstrated 100% conversion with a selectivity of 67% for n-C17 hydrocarbon via the decarboxylation route. The highest reduction of CO2 footprint is achieved at 280 °C and 30 bar H2 pressure under solvent-free conditions using ZnO–Ti3 C2 Tx . The catalyst is recyclable and reusable for five test cycles. The high catalytic selectivity of the ZnO–Ti3 C2 Tx catalyst towards HDO is attributed to the synergic effect of the Ti and ZnO active sites and the thermally stable structure. This study offers an efficient route for converting edible and non-edible vegetable oils to biofuels by controlling CO2 production. [ABSTRACT FROM AUTHOR]- Published
- 2023
- Full Text
- View/download PDF
46. Aerobic oxidation of alcohols using a slurry loop membrane reactor.
- Author
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Venezia, Baldassarre and Gavriilidis, Asterios
- Subjects
MEMBRANE reactors ,ALCOHOL oxidation ,SLURRY ,ALCOHOL ,CATALYSTS ,HYDROGENATION - Abstract
The use of molecular oxygen is unquestionably the green path to the selective oxidation of alcohols to aldehyde and ketones. However, this reaction class poses safety problems associated with mixing oxygen with organic substrates. Continuous membrane reactors offer an attractive solution, owing to their ability to keep the oxygen phase separated from the liquid substrate, while controlling the dosing of oxygen during reaction. In this work, we demonstrate a slurry loop membrane reactor for continuous oxidations as well as hydrogenations. The catalyst slurry was circulated around a loop, to which a saturator containing a flat Teflon AF-2400 membrane was connected, along with a crossflow filter to keep the catalyst particles within the loop. Under a recycle flowrate 100 times higher than the inlet, the residence time distribution was found to be comparable to that of an ideal CSTR. A remarkably high k
L a of 1.2 s−1 was achieved under a moderate specific power input of 2.4 kW m−3 during styrene hydrogenation. Continuous aerobic oxidations of various primary and secondary alcohols were carried out for 6–7 h at 90–120 °C and 2–6 bar, using a 1 wt% Au-Pd/TiO2 powder catalyst, leading to conversions between 17% and 75%. The reactor could also be operated in batch mode, achieving higher conversions, while scaled-up operations produced aldehyde yields of 0.4–19 g with only 88 mg of catalyst. Overall, the slurry loop membrane reactor provides significant advantages in terms of catalyst usage and process safety for aerobic oxidations. [ABSTRACT FROM AUTHOR]- Published
- 2023
- Full Text
- View/download PDF
47. Ultrafast and selective recycling of poly(p-dioxanone) to monomers by using Brønsted–Lewis acidic ionic liquids as solvents/catalysts.
- Author
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Zhang, Wei, Tian, Guo-Qiang, Wu, Gang, Chen, Si-Chong, and Wang, Yu-Zhong
- Subjects
POLYMERIZED ionic liquids ,MONOMERS ,CHEMICAL recycling ,IONIC liquids ,CHEMICAL structure ,CATALYSTS - Abstract
In recent years, chemical recycling to monomer (CRM) has emerged as an advanced strategy to deal with post-consumer plastics. However, because it usually takes a long time to react at a relatively high temperature, CRM suffers from side reactions and energy consumption issues. In this work, a Brønsted–Lewis acid ionic liquid/polyhydroxy-compound system ([Et
3 NH][ZnCl3 ]/pentaerythritol) was developed as a bifunctional reagent for dissolving poly(p-dioxanone) (PPDO) and highly efficiently catalysing its CRM. In situ addition of the polyhydroxy-compound significantly prevented the formation of byproduct, i.e., cyclic PPDO, by converting it back to depolymerizable linear PPDO. Therefore, both the CRM efficiency and selectivity were obviously improved. At 160 °C, PPDO was almost fully depolymerized to the PDO monomer in only 8 minutes with 99.9% GC purity of yield. Moreover, [Et3 NH][ZnCl3 ]/pentaerythritol could be reused at least 5 times without post-processing and its chemical structure and efficiency remained intact. According to the kinetic study, the activation energy of depolymerization was calculated to be 64.81 kJ mol−1 , half lower than the traditional method. Based on NMR titration, the catalytic mechanism was discussed. Importantly, according to the assessment of the energy economy factor, environmental factor, and environmental energy impact factor, the strategy developed in this work is better than all of the related works in greenness. [ABSTRACT FROM AUTHOR]- Published
- 2023
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- View/download PDF
48. Understanding the mechanism of enhanced alcoholysis of biomass carbohydrates to alkyl levulinates over bifunctional catalysts: does it resemble that in water?
- Author
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Zhang, Yuxuan, Ju, Zhaoyang, Chen, Xueli, Lyu, Qian, Mei, Jiaqi, Han, Lujia, Liu, Dong, and Xiao, Weihua
- Subjects
ALCOHOLYSIS ,CATALYTIC hydrolysis ,CARBOHYDRATES ,BIOMASS ,CATALYSTS - Abstract
The catalytic hydrolysis/alcoholysis of biomass carbohydrates into levulinic acid/levulinate esters (alkyl levulinates) as green biofuels and value-added chemicals holds great promise for achieving the goals of sustainable chemistry. Bifunctional catalysts with Brønsted- and Lewis-acidic sites have been widely reported to boost the efficiency of both processes. However, current understanding of the origin of the enhancement in alcoholic media is still in its infancy compared to that in aqueous media. Herein, we investigate the reaction process of glucose in methanol using a representative bifunctional catalyst (aluminum phosphotungstate) and its Brønsted-acid form (phosphotungstic acid), respectively. Isotopic labeling experiments were first applied to monitor the potential intermediates in glucose methanolysis. Coupling with mass spectrometric analysis and theoretical calculations, it has been revealed that Al
3+ ions may accelerate the rate-limiting step by inducing ring opening of the key intermediate, methyl- D -glucopyranoside (MDGP), to D -glucose dimethyl acetal, rather than the prevalent speculation of facilitating the isomerization of MDGP to methyl fructoside. These findings refresh and reinforce our knowledge of the mechanism behind catalytically producing alkyl levulinates from biomass carbohydrates and provide a basis for the rational design of superior catalysts for biomass valorization. [ABSTRACT FROM AUTHOR]- Published
- 2023
- Full Text
- View/download PDF
49. Electrochemical oxidation-induced benzylic C(sp3)–H functionalization towards the atom-economic synthesis of oxazole heterocycles.
- Author
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Yang, Na, Li, Anni, Gao, Hui, Liao, Li-Mei, Yang, Yu-Ping, Wang, Pei-Long, and Li, Hongji
- Subjects
HETEROCYCLIC compounds ,NITRILES ,ALKYNES ,OXIDIZING agents ,CATALYSTS ,RING formation (Chemistry) - Abstract
A unique electrochemical four-component reaction of terminal alkynes, (thio)xanthenes, nitriles, and water has been established in the absence of any catalyst or external oxidant. This electrochemical reaction features high atom economy and mild conditions, affording oxazole derivatives in moderate to good yields. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
50. Efficient CO2 conversion by biocompatible N-doped carbon nanosheets coupled with Ralstonia eutropha: synergistic interactions between microbial and inorganic catalysts.
- Author
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Yao, Jiani, Li, Youzhi, Xiu, Siyuan, Zheng, Shujie, Huang, Ying, Zhou, Zijing, Hou, Yang, Yang, Bin, Lei, Lecheng, and Li, Zhongjian
- Subjects
RALSTONIA eutropha ,DOPING agents (Chemistry) ,CATALYSTS ,NANOSTRUCTURED materials ,REACTIVE oxygen species ,HYDROGEN evolution reactions - Abstract
Electricity-to-chemical production from a hybrid microbial–inorganic catalytic system relies upon biocompatible and efficient catalysts for hydrogen evolution reactions (HERs). Herein, metal-free nitrogen-doped carbon nanosheets (NC) with no metal leaching and little generation of reactive oxygen species were synthesized to develop an efficient hybrid catalytic system for converting CO
2 to poly-β-hydroxybutyrate. A yield of 538 mg L−1 with an electricity-to-organic efficiency of 10.5% was obtained, which outcompetes most of the previous achievements. The coupling of NC with Ralstonia eutropha H16 reduced the HER overpotential by 200 mV. It was attributed to the doped N atoms facilitating the immobilization of bacteria on the catalysts to enhance hydrophilicity. Besides, the [NiFe]-hydrogenase from R. eutropha accelerates the desorption of H2 and may provide an effective HER catalytic center on the catalysts. This study reveals the synergistic interactions between metal-free catalysts and R. eutropha H16 to promote H2 production and CO2 conversion. [ABSTRACT FROM AUTHOR]- Published
- 2023
- Full Text
- View/download PDF
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