- Highly efficient vanadium-catalyzed transformation of CH4 and CO to acetic acid
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(Matrix presented) The VO(acac)2 (acac = 2,4-pentanedionato) catalyst in the presence of K2S2O8 and CF3COOH has been found to efficiently transform methane and CO to acetic acid selectively. The reaction of methane (5 atm) with CO (20 atm) at 80°C for 20 h gives acetic acid in 93% yield based on methane. Other vanadium compounds such as V2O3, V2O5, and NaVO3 and various vanadium-containing heteropolyacids such as H5PV2-MO10O40, H4PVW11O40, and H5SiVW11O40 also work as catalysts.
- Taniguchi, Yuki,Hayashida, Taizo,Shibasaki, Hiroyasu,Piao, Dongguo,Kitamura, Tsugio,Yamaji, Teizo,Fujiwara, Yuzo
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Read Online
- Low-Temperature Reverse Water–Gas Shift Process and Transformation of Renewable Carbon Resources to Value-Added Chemicals
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The use of CO2 instead of toxic CO in the production of important chemicals has attracted widespread interest, and the reverse water–gas shift reaction (RWGSR) is the key step for this kind of processes. Although the thermodynamic limitations are overcome by the reaction of CO with other compounds, the temperature of most reactions involving RWGSR is usually very high owing to the inertness of CO2. Herein, it was found that Ru3(CO)12 could catalyze the RWGSR in the ionic liquid HMimBF4 without ligand or promoter, and CO could be produced at 80 °C, which was much lower than the temperatures reported to date. Detailed studies showed that the BF4 ? in the ionic liquid played a crucial role in the low-temperature RWGSR. Based on the low-temperature RWGSR, three important routes to transform CO2 into valuable chemicals were developed, including synthesis of xanthone from CO2 and diaryl ethers, synthesis of phenol and acetic acid from CO2 and anisole, and production of acetic acid from CO2 and lignin. The reactions could occur at temperature as low as 80 °C, and low-temperature RWGSR was essential for the reactions under mild conditions. The strategy opens the way to produce value-added chemicals by using CO2 and H2 as feedstocks under low temperature.
- Shen, Xiaojun,Meng, Qinglei,Dong, Minghua,Xiang, Junfeng,Li, Shaopeng,Liu, Huizhen,Han, Buxing
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p. 5149 - 5156
(2019/11/26)
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- Real-Time Interrogation of Aspirin Reactivity, Biochemistry, and Biodistribution by Hyperpolarized Magnetic Resonance Spectroscopy
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Hyperpolarized magnetic resonance spectroscopy enables quantitative, non-radioactive, real-time measurement of imaging probe biodistribution and metabolism in vivo. Here, we investigate and report on the development and characterization of hyperpolarized acetylsalicylic acid (aspirin) and its use as a nuclear magnetic resonance (NMR) probe. Aspirin derivatives were synthesized with single- and double-13C labels and hyperpolarized by dynamic nuclear polarization with 4.7 % and 3 % polarization, respectively. The longitudinal relaxation constants (T1) for the labeled acetyl and carboxyl carbonyls were approximately 30 seconds, supporting in vivo imaging and spectroscopy applications. In vitro hydrolysis, transacetylation, and albumin binding of hyperpolarized aspirin were readily monitored in real time by 13C-NMR spectroscopy. Hyperpolarized, double-labeled aspirin was well tolerated in mice and could be observed by both 13C-MR imaging and 13C-NMR spectroscopy in vivo.
- Zacharias, Niki M.,Ornelas, Argentina,Lee, Jaehyuk,Hu, Jingzhe,Davis, Jennifer S.,Uddin, Nasir,Pudakalakatti, Shivanand,Menter, David G.,Karam, Jose A.,Wood, Christopher G.,Hawk, Ernest T.,Kopetz, Scott,Vilar, Eduardo,Bhattacharya, Pratip K.,Millward, Steven W.
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p. 4179 - 4183
(2019/02/25)
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- A straightforward implementation of in situ solution electrochemical 13C NMR spectroscopy for studying reactions on commercial electrocatalysts: Ethanol oxidation
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Identifying and quantifying electrocatalytic-reaction-generated solution species, be they reaction intermediates or products, are highly desirable in terms of understanding the associated reaction mechanisms. We report herein a straightforward implementation of in situ solution electrochemical 13C NMR spectroscopy for the first time that enables in situ studies of reactions on commercial fuel-cell electrocatalysts (Pt and PtRu blacks). Using ethanol oxidation reaction (EOR) as a working example, we discovered that (1) the complete oxidation of ethanol to CO2 only took place dominantly at the very beginning of a potentiostatic chronoamperometric (CA) measurement and (2) the PtRu had a much higher activity in catalysing oxygen insertion reaction that leads to acetic acid.
- Huang,Sorte,Sun,Tong
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p. 8086 - 8088
(2015/05/20)
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- Methane to acetic acid over Cu-exchanged zeolites: Mechanistic insights from a site-specific carbonylation reaction
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The selective low temperature oxidation of methane is an attractive yet challenging pathway to convert abundant natural gas into value added chemicals. Copper-exchanged ZSM-5 and mordenite (MOR) zeolites have received attention due to their ability to oxidize methane into methanol using molecular oxygen. In this work, the conversion of methane into acetic acid is demonstrated using Cu-MOR by coupling oxidation with carbonylation reactions. The carbonylation reaction, known to occur predominantly in the 8-membered ring (8MR) pockets of MOR, is used as a site-specific probe to gain insight into important mechanistic differences existing between Cu-MOR and Cu-ZSM-5 during methane oxidation. For the tandem reaction sequence, Cu-MOR generated drastically higher amounts of acetic acid when compared to Cu-ZSM-5 (22 vs 4 μmol/g). Preferential titration with sodium showed a direct correlation between the number of acid sites in the 8MR pockets in MOR and acetic acid yield, indicating that methoxy species present in the MOR side pockets undergo carbonylation. Coupled spectroscopic and reactivity measurements were used to identify the genesis of the oxidation sites and to validate the migration of methoxy species from the oxidation site to the carbonylation site. Our results indicate that the CuII-O-CuII sites previously associated with methane oxidation in both Cu-MOR and Cu-ZSM-5 are oxidation active but carbonylation inactive. In turn, combined UV-vis and EPR spectroscopic studies showed that a novel Cu2+ site is formed at Cu/Al 0.2 in MOR. These sites oxidize methane and promote the migration of the product to a Bronsted acid site in the 8MR to undergo carbonylation.
- Narsimhan, Karthik,Michaelis, Vladimir K.,Mathies, Guinevere,Gunther, William R.,Griffin, Robert G.,Romn-Leshkov, Yuriy
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supporting information
p. 1825 - 1832
(2015/03/04)
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- Mechanistic insight into the formation of acetic acid from the direct conversion of methane and carbon dioxide on zinc-modified H-ZSM-5 zeolite
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Methane and carbon dioxide are known greenhouse gases, and the conversion of these two C1-building blocks into useful fuels and chemicals is a subject of great importance. By solid-state NMR spectroscopy, we found that methane and carbon dioxide can be co-converted on a zinc-modified H-ZSM-5 zeolite (denoted as Zn/H-ZSM-5) to form acetic acid at a low temperature range of 523-773 K. Solid-state 13C and 1H MAS NMR investigation indicates that the unique nature of the bifunctional Zn/H-ZSM-5 catalyst is responsible for this highly selective transformation. The zinc sites efficiently activate CH4 to form zinc methyl species (-Zn-CH3), the Zn-C bond of which is further subject to the CO2 insertion to produce surface acetate species (-Zn-OOCCH3). Moreover, the Bronsted acid sites play an important role for the final formation of acetic acid by the proton transfer to the surface acetate species. The results disclosed herein may offer the new possibility for the efficient activation and selective transformation of methane at low temperatures through the co-conversion strategy. Also, the mechanistic understanding of this process will help to the rational design of robust catalytic systems for the practical conversion of greenhouse gases into useful chemicals.
- Wu, Jian-Feng,Yu, Si-Min,Wang, Wei David,Fan, Yan-Xin,Bai, Shi,Zhang, Chuan-Wei,Gao, Qiang,Huang, Jun,Wang, Wi
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supporting information
p. 13567 - 13573
(2013/09/24)
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- Fmoc-SPPS chemistry compatible approach for the generation of (glyco)peptide aryl thioesters
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A new approach is described for the general Fmoc-based solid-phase synthesis of (glyco)peptide aryl thioesters. A peptide alkyl oxoester obtained by standard Fmoc-based chain elongation undergoes an O-to-S acyl shift, and is followed by alkyl thioester exchanges with a large excess of aryl thiol, affording the corresponding peptide aryl thioester. The newly developed methodology is useful for the chemical synthesis of post-translationally modified proteins because of its compatibility with standard Fmoc-SPPS conditions. In addition, the peptide aryl thioesters are essential intermediates for chemical synthesis of proteins by kinetically controlled convergent strategy.
- Zheng, Ji-Shen,Xi, Wei-Xian,Wang, Feng-Liang,Li, Juan,Guo, Qing-Xiang
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scheme or table
p. 2655 - 2660
(2011/06/10)
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- Calcium-catalyzed selective and quantitative transformation of CH4 and CO into acetic acid
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93.8% conversion into acetic acid with 100% selectivity was achieved in the calcium-catalyzed carboxylation of methane [Eq. (a)]. In the catalyst system, CaCl2 is eventually converted into CaO·, which abstracts an H atom from methane. The resulting CH3· radical is trapped by CO, and CH3CO· is converted with trifluoroacetic acid into acetic acid via the mixed anhydride. TFA = trifluoroacetic acid, TFAA = trifluoroacetic anhydride.
- Asadullah, Mohammad,Kitamura, Tsugio,Fujiwara, Yuzo
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p. 2475 - 2478
(2007/10/03)
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- In situ NMR investigations of heterogeneous catalysis with samples prepared under standard reaction conditions
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Only 170 milliseconds are required to cool the catalyst bed by 150 K in the catalytic reactor shown on the right. Thus, NMR spectroscopic investigations can be carried out on products that are formed after very short contact times and under real catalysis conditions.
- Haw, James F.,Goguen, Patrick W.,Xu, Teng,Skloss, Timothy W.,Song, Weiguo,Wang, Zhike
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p. 948 - 949
(2007/10/03)
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- A Dynamic Equilibrium of Oxaphosphetanes
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The course of the Wittig reaction was investigated by rapid injection NMR spectroscopy.Rate constants for the formation of oxaphosphetanes were determined.A new dynamic equilibrium of oxaphosphetanes was observed for the first time.The solvent and substituent dependence of the new effect was investigated.By labeling various oxaphosphetanes with 13C and 17O the lithium salt dependence of the new equilibrium was shown.A lithium adduct of oxaphosphetanes under these conditions is proposed. - Key Words: Wittig reaction / Rapid injection NMR / Dynamic NMR / Oxaphosphetanes
- Geletneky, Christian,Foersterling, Frank-Holger,Bock, Willi,Berger, Stefan
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p. 2397 - 2402
(2007/10/02)
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