- Unexpected, Latent Radical Reaction of Methane Propagated by Trifluoromethyl Radicals
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Thorough mechanistic studies and DFT calculations revealed a background radical pathway latent in metal-catalyzed oxidation reactions of methane at low temperatures. Use of hydrogen peroxide with TFAA generated a trifluoromethyl radical (?CF3), which in turn reacted with methane gas to selectively yield acetic acid. It was found that the methyl carbon of the product was derived from methane, while the carbonyl carbon was derived from TFAA. Computational studies also support these findings, revealing the reaction cycle to be energetically favorable.
- Zargari, Nima,Winter, Pierre,Liang, Yong,Lee, Joo Ho,Cooksy, Andrew,Houk,Jung, Kyung Woon
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- Efficient synthesis of acetic acid via Rh catalyzed methanol hydrocarboxylation with CO2 and H2 under milder conditions
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Acetic acid is an important bulk chemical and synthesis of acetic acid via methanol hydrocarboxylation with CO2 and H2 is a very promising route. In this work, we studied the reaction over a number of catalytic systems. It was found that Rh2(CO)4Cl2 with 4-methylimidazole (4-MI) as the ligand was very efficient in the presence of LiCl and LiI. Acetic acid began to form at 150°C. The TOF was as high as 26.2 h-1 and the yield of acetic acid could reach 81.8% at 180°C. The catalytic system had obvious advantages, such as simplicity, high activity and selectivity, milder reaction conditions, and less corrosiveness. The excellent cooperation of CO and Cl- in Rh2(CO)4Cl2, suitable basicity and aromaticity of the ligand 4-MI, and the hydrogen bonding ability of Cl- were crucial for the outstanding performance of the catalytic system. The control experiments showed that the reaction did not proceed via the CO pathway.
- Cui, Meng,Qian, Qingli,Zhang, Jingjing,Chen, Chunjun,Han, Buxing
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- Synthesis of acetic acid from CO2, CH3I and H2using a water-soluble electron storage catalyst
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This paper reports a possible mechanism of acetic acid formation from CO2, CH3I and H2in aqueous media and the central role played by a water-soluble Rh-based electron storage catalyst. In addition to water-solubility, we also report the crystal structures of two presumed intermediates. These findings together reveal (1) the advantage of water, not only as a green solvent, but also as a reactive Lewis base to extract H+from H2, (2) the role of the metal (Rh) centre as a point for storing electrons from H2and (3) the importance of an electron-withdrawing ligand (quaterpyridine, qpy) that supports electron storage.
- Yatabe, Takeshi,Kamitakahara, Kazuki,Higashijima, Kaede,Ando, Tatsuya,Matsumoto, Takahiro,Yoon, Ki-Seok,Enomoto, Takao,Ogo, Seiji
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supporting information
p. 4772 - 4774
(2021/05/25)
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- Carbon Dioxide to Methanol: The Aqueous Catalytic Way at Room Temperature
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Carbon dioxide may constitute a source of chemicals and fuels if efficient and renewable processes are developed that directly utilize it as feedstock. Two of its reduction products are formic acid and methanol, which have also been proposed as liquid organic chemical carriers in sustainable hydrogen storage. Here we report that both the hydrogenation of carbon dioxide to formic acid and the disproportionation of formic acid into methanol can be realized at ambient temperature and in aqueous, acidic solution, with an iridium catalyst. The formic acid yield is maximized in water without additives, while acidification results in complete (98 %) and selective (96 %) formic acid disproportionation into methanol. These promising features in combination with the low reaction temperatures and the absence of organic solvents and additives are relevant for a sustainable hydrogen/methanol economy.
- Sordakis, Katerina,Tsurusaki, Akihiro,Iguchi, Masayuki,Kawanami, Hajime,Himeda, Yuichiro,Laurenczy, Gábor
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supporting information
p. 15605 - 15608
(2016/10/25)
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- Catalytic conversion of glucose into alkanediols over nickel-based catalysts: A mechanism study
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The conversion of isotope-labeled glucose (d-1-13C-glucose) into alkanediols was carried out in a batch reactor over a Ni-MgO-ZnO catalyst to reveal the C-C cleavage mechanisms. The unique role of the MgO-ZnO support was highlighted by 13C NMR and GC-MS analysis qualitatively and the MgO-ZnO favored isomerization of glucose to fructose. 13C NMR, GC-MS and HPLC analysis demonstrated that the C1 position of ethylene glycol, the C1 and C3 positions of 1,2-propanediol and the C1 position of glycerin were labeled with 13C, which is attributed to a C-C cleavage at d-1-13C-glucose's corresponding positions through retro-aldol condensation. A hydrogenolysis followed by hydrogenation pathway was proposed for glucose converted into alkanediols at 493 K with 6.0 MPa of H2 pressure over Ni based catalysts.
- Tan, Zhichao,Miao, Gai,Liu, Chang,Luo, Hu,Bao, Liwei,Kong, Lingzhao,Sun, Yuhan
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p. 62747 - 62753
(2016/07/13)
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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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- The metabolic and biochemical impact of glucose 6-sulfonate (sulfoquinovose), a dietary sugar, on carbohydrate metabolism
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Increased activity of the main carbohydrate pathways (glycolysis, pentose phosphate, and hexosamine biosynthetic pathways) is one of the hallmarks of metabolic diseases such as cancer. Sulfoquinovosyl diacylglycerol is a sulfoglycolipid found in the human
- Sacoman, Juliana L.,Badish, Lauren N.,Sharkey, Thomas D.,Hollingsworth, Rawle I.
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p. 21 - 29,9
(2012/12/12)
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- The metabolic and biochemical impact of glucose 6-sulfonate (sulfoquinovose), a dietary sugar, on carbohydrate metabolism
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Increased activity of the main carbohydrate pathways (glycolysis, pentose phosphate, and hexosamine biosynthetic pathways) is one of the hallmarks of metabolic diseases such as cancer. Sulfoquinovosyl diacylglycerol is a sulfoglycolipid found in the human
- Sacoman, Juliana L.,Badish, Lauren N.,Sharkey, Thomas D.,Hollingsworth, Rawle I.
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- Study of the Beckmann rearrangement of acetophenone oxime over porous solids by means of solid state NMR spectroscopy
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The Beckmann rearrangement of acetophenone oxime using zeolite H-beta and silicalite-N as catalysts has been investigated by means of 15N and 13C solid state NMR spectroscopy in combination with theoretical calculations. The results obtained show that the oxime is N-protonated at room temperature on the acid sites of zeolite H-beta. At reaction temperatures of 423 K or above, the two isomeric amides, acetanilide and N-methyl benzamide (NMB) are formed, and interact with the Bronsted acid sites of zeolite H-beta through hydrogen bonds. The presence of residual water hydrolyzes the two amides, while larger amounts inhibit the formation of NMB and cause the total hydrolysis of the acetanilide. Over siliceous zeolite silicalite-N, containing silanol nests as active sites, the oxime is adsorbed through hydrogen bonds and only acetanilide is formed at reaction temperatures of 423 K or above. In the presence of water, the reaction starts at 473 K, still being very selective up to 573 K, and the amide is partially hydrolyzed only above this temperature. the Owner Societies 2009.
- Fernandez, Ana Belen,Lezcano-Gonzalez, Ines,Boronat, Mercedes,Blasco, Teresa,Corma, Avelino
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experimental part
p. 5134 - 5141
(2011/06/21)
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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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- 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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p. 557 - 559
(2008/02/11)
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- Skeletal Rearrangements Preceding CO Loss from Metastable Phenoxymethylene Ions Derived from Phenoxyacetic Acid and Anisole
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The loss of CHO2(.) from the molecular ion of phenoxyacetic acid and the expulsion of an H(.) atom from ionized anisole lead to phenoxymethylene ions, which fragment predominantly by CO loss on the microsecond time-scale.Carbon-13 labelling reveals that ca. 90percent of the CO molecules expelled from the metastable ions derived from phenoxyacetic acid incorporate the carbon atom from the 1-position of the phenyl group of the parent compound, whereas the residual CO molecules contain one of the other carbon atoms of the aromatic ring.The 2-fluoro- and 2-methylphenoxymethylene ions derived from the appropriate aryloxyacetic acids behave similarly, i.e. the carbon atom of the methylene group of the parent compound is not incorporated in the expelled CO molecules.In contrast, ca. 45percent of the CO molecules eliminated from the metastable phenoxymethylene ions formed from ionized anisole contain the carbon atom of the methyl group, while the remaining part contains the carbon atom from the 1-position of the phenyl ring of the parent compound.This result is taken as evidence for the occurrence of a skeletal rearrangement of the anisole molecular ion leading to an interchange between the carbon atom of the methyl group and the carbon atom at the 1-position of the ring.The elimination of CO from the metastable ions generated from either phenoxyacetic acid or anisole gives rise to a composite metastable peak.Conclusive evidence as to the formation of (+) isomers other than the phenoxymethylene ion is not obtained, indicating that the composite metastable peak is a result of two competing reactions both leading to CO loss.Possible mechanisms of these reactions are discussed together with the mechanism of the skeletal rearrangement of the molecular ion of anisole prior to H(.) loss.
- Molenaar-Langeveld, Tineke A.,Ingemann, Steen,Nibbering, Nico M. M.
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p. 1167 - 1178
(2007/10/02)
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