scholarly journals Unraveling the Activity of Iron Carbide Clusters Embedded in Silica for Thermocatalytic Conversion of Methane

2020 ◽  
Author(s):  
Gopal K. Dixit ◽  
Manish Kumar ◽  
Ankita Katiyar ◽  
Antonius P. J. Jansen ◽  
Alexander van Bavel ◽  
...  
Keyword(s):  
Partial Pressure ◽  
Density Functional ◽  
High Selectivity ◽  
Iron Carbide ◽  
Methyl Radical ◽  
Reaction Conditions ◽  
Silica Substrate ◽  
Rate Determining Step ◽  
Conversion Of Methane ◽  
Thermocatalytic Conversion

<p>Isolated Fe-sites on silica substrate have recently been reported for direct and non-oxidative</p> <p>conversion of gaseous methane with high selectivity. The activated catalyst was proposed to be</p> <p>FeC2 cluster embedded in silica. Using a combination of density-functional theoretic methods</p> <p>and micro-kinetic modeling, we show that under the same reaction conditions (1223 K , 1 atm)</p> <p>FeC2 sites convert to FeC3 and the latter is instead responsible for the observed activity. We</p> <p>investigate the detailed mechanism of conversion of methane to methyl radical and hydrogen</p> <p>on FeC3@SiO2 under different conditions of methane partial pressure. We find that methyl</p> <p>radical evolution is the rate-determining step for the overall conversion. Our calculations also</p> <p>indicate that the conversion of embedded FeC3 to FeC4 competes with methyl radical evolution</p> <p>from the active catalyst. However, due to the higher stability of FeC3 sites, we anticipate that</p> <p>formation of higher carbides can be inhibited by controlling the hydrogen partial pressure.</p>

scholarly journals Unraveling the Activity of Iron Carbide Clusters Embedded in Silica for Thermocatalytic Conversion of Methane

2020 ◽  
Author(s):  
Gopal K. Dixit ◽  
Manish Kumar ◽  
Ankita Katiyar ◽  
Antonius P. J. Jansen ◽  
Alexander van Bavel ◽  
...  
Keyword(s):  
Partial Pressure ◽  
Density Functional ◽  
High Selectivity ◽  
Iron Carbide ◽  
Methyl Radical ◽  
Reaction Conditions ◽  
Silica Substrate ◽  
Rate Determining Step ◽  
Conversion Of Methane ◽  
Thermocatalytic Conversion

<p>Isolated Fe-sites on silica substrate have recently been reported for direct and non-oxidative</p> <p>conversion of gaseous methane with high selectivity. The activated catalyst was proposed to be</p> <p>FeC2 cluster embedded in silica. Using a combination of density-functional theoretic methods</p> <p>and micro-kinetic modeling, we show that under the same reaction conditions (1223 K , 1 atm)</p> <p>FeC2 sites convert to FeC3 and the latter is instead responsible for the observed activity. We</p> <p>investigate the detailed mechanism of conversion of methane to methyl radical and hydrogen</p> <p>on FeC3@SiO2 under different conditions of methane partial pressure. We find that methyl</p> <p>radical evolution is the rate-determining step for the overall conversion. Our calculations also</p> <p>indicate that the conversion of embedded FeC3 to FeC4 competes with methyl radical evolution</p> <p>from the active catalyst. However, due to the higher stability of FeC3 sites, we anticipate that</p> <p>formation of higher carbides can be inhibited by controlling the hydrogen partial pressure.</p>

Unraveling the activity of iron carbide clusters embedded in silica for thermocatalytic conversion of methane

2021 ◽  
Author(s):  
Gopal Krishna Dixit ◽  
Manish Kumar ◽  
Ankita Katiyar ◽  
Antonius P.J. Jansen ◽  
Sander van Bavel ◽  
...  
Keyword(s):  
High Selectivity ◽  
Iron Carbide ◽  
Silica Substrate ◽  
Conversion Of Methane ◽  
Fe Sites ◽  
Thermocatalytic Conversion

Isolated Fe-sites on silica substrate have recently been reported for direct and non-oxidative conversionof gaseous methane with high selectivity. The activated catalyst was proposed to be FeC2 clusterembedded in silica....

Sulfonyl Radical Triggered Selective Iodosulfonylation and Bicycli-zations of 1,6-Dienes

2021 ◽  
Author(s):  
Shi-Ping Wu ◽  
Dong-Kai Wang ◽  
Qing-Qing Kang ◽  
Guo-Ping Ge ◽  
Hongxing Zheng ◽  
...  
Keyword(s):  
Functional Group ◽  
High Selectivity ◽  
Reaction Conditions ◽  
First Time

A novel sulfonyl radical triggered selective iodosulfonylation and bicyclizations of 1,6-dienes has been described for the first time. High selectivity and efficiency, mild reaction conditions, excellent functional group compatibility, and...

scholarly journals Understanding the reaction mechanism of the regioselective piperidinolysis of aryl 1-(2,4-dinitronaphthyl) ethers in DMSO: Kinetic and DFT studies

2021 ◽  
Vol 46 ◽  
pp. 146867832110274
Author(s):  
Yasmen M Moghazy ◽  
Nagwa MM Hamada ◽  
Magda F Fathalla ◽  
Yasser R Elmarassi ◽  
Ezzat A Hamed ◽  
...  
Keyword(s):  
Carbon Atom ◽  
Density Functional ◽  
Function Analysis ◽  
Density Functional Theory Method ◽  
Activation Parameters ◽  
Kinetic Studies ◽  
Nucleophilic Attack ◽  
Common Mechanism ◽  
Slow Step ◽  
Rate Determining Step

Reactions of aryl 1-(2,4-dinitronaphthyl) ethers with piperidine in dimethyl sulfoxide at 25oC resulted in substitution of the aryloxy group at the ipso carbon atom. The reaction was measured spectrophotochemically and the kinetic studies suggested that the titled reaction is accurately third order. The mechanism is began by fast nucleophilic attack of piperidine on C1 to form zwitterion intermediate (I) followed by deprotonation of zwitterion intermediate (I) to the Meisenheimer ion (II) in a slow step, that is, SB catalysis. The regular variation of activation parameters suggested that the reaction proceeded through a common mechanism. The Hammett equation using reaction constant σo values and Brønsted coefficient value showed that the reaction is poorly dependent on aryloxy substituent and the reaction was significantly associative and Meisenheimer intermediate-like. The mechanism of piperidinolysis has been theoretically investigated using density functional theory method using B3LYP/6-311G(d,p) computational level. The combination between experimental and computational studies predicts what mechanism is followed either through uncatalyzed or catalyzed reaction pathways, that is, SB and SB-GA. The global parameters of the reactants, the proposed activated complexes, and the local Fukui function analysis explained that C1 carbon atom is the most electrophilic center of ether. Also, kinetics and theoretical calculation of activation energies indicated that the mechanism of the piperidinolysis passed through a two-step mechanism and the proton transfer process was the rate determining step.

scholarly journals Reaction Mechanism for Methane-to-Methanol in Cu-SSZ-13: First-Principles Study of the Z2[Cu2O] and Z2[Cu2OH] Motifs

Catalysts ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 17
Author(s):  
Unni Engedahl ◽  
Adam A. Arvidsson ◽  
Henrik Grönbeck ◽  
Anders Hellman
Keyword(s):  
Liquid Fuel ◽  
Density Functional ◽  
Reaction Pathway ◽  
Direct Conversion ◽  
Reaction Conditions ◽  
Oxidation Of Methane ◽  
Small Pore ◽  
Desorption Step ◽  
Solution Gas ◽  
Stable Motif

As transportation continues to increase world-wide, there is a need for more efficient utilization of fossil fuel. One possibility is direct conversion of the solution gas bi-product CH4 into an energy-rich, easily usable liquid fuel such as CH3OH. However, new catalytic materials to facilitate the methane-to-methanol reaction are needed. Using density functional calculations, the partial oxidation of methane is investigated over the small-pore copper-exchanged zeolite SSZ-13. The reaction pathway is identified and the energy landscape elucidated over the proposed motifs Z2[Cu2O] and Z2[Cu2OH]. It is shown that the Z2[Cu2O] motif has an exergonic reaction path, provided water is added as a solvent for the desorption step. However, a micro-kinetic model shows that neither Z2[Cu2O] nor Z2[Cu2OH] has any notable activity under the reaction conditions. These findings highlight the importance of the detailed structure of the active site and that the most stable motif is not necessarily the most active.

scholarly journals Ring-Opening Copolymerization of Cyclohexene Oxide and Cyclic Anhydrides Catalyzed by Bimetallic Scorpionate Zinc Catalysts

Polymers ◽  
2021 ◽  
Vol 13 (10) ◽  
pp. 1651
Author(s):  
Felipe de la Cruz-Martínez ◽  
Marc Martínez de Sarasa Buchaca ◽  
Almudena del Campo-Balguerías ◽  
Juan Fernández-Baeza ◽  
Luis F. Sánchez-Barba ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Reaction Mechanism ◽  
Catalytic System ◽  
Phthalic Anhydride ◽  
Ring Opening ◽  
High Selectivity ◽  
Zinc Complexes ◽  
Cyclohexene Oxide ◽  
Reaction Conditions ◽  
Cyclic Anhydrides

The catalytic activity and high selectivity reported by bimetallic heteroscorpionate acetate zinc complexes in ring-opening copolymerization (ROCOP) reactions involving CO2 as substrate encouraged us to expand their use as catalysts for ROCOP of cyclohexene oxide (CHO) and cyclic anhydrides. Among the catalysts tested for the ROCOP of CHO and phthalic anhydride at different reaction conditions, the most active catalytic system was the combination of complex 3 with bis(triphenylphosphine)iminium as cocatalyst in toluene at 80 °C. Once the optimal catalytic system was determined, the scope in terms of other cyclic anhydrides was broadened. The catalytic system was capable of copolymerizing selectively and efficiently CHO with phthalic, maleic, succinic and naphthalic anhydrides to afford the corresponding polyester materials. The polyesters obtained were characterized by spectroscopic, spectrometric, and calorimetric techniques. Finally, the reaction mechanism of the catalytic system was proposed based on stoichiometric reactions.

Research Progress on Photocatalytic Activation of Methane to Methanol

2021 ◽  
Author(s):  
Yu dong Tian ◽  
Lingyu Piao ◽  
Xiaobo Chen
Keyword(s):  
Thermodynamic Equilibrium ◽  
Research Progress ◽  
Conversion Of Methane ◽  
Thermocatalytic Conversion

The conversion of methane (CH4) to methanol (CH3OH) has attracted much attention in catalysis. However, the traditional thermocatalytic conversion of CH4 to CH3OH is largely restricted by the thermodynamic equilibrium...

scholarly journals Theoretical insight on the treatment of β-hexachlorocyclohexane waste through alkaline dehydrochlorination

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Alicia Bescós ◽  
Clara I. Herrerías ◽  
Zoel Hormigón ◽  
José Antonio Mayoral ◽  
Luis Salvatella
Keyword(s):  
Density Functional ◽  
Kinetic Studies ◽  
Alkaline Treatment ◽  
Functional Study ◽  
Reaction Intermediates ◽  
Preferential Formation ◽  
Reaction Intermediate ◽  
Rate Determining Step ◽  
Dehydrochlorination Reaction ◽  
Theoretical Results

AbstractThe occurrence of 4.8–7.2 million tons of hexachlorocyclohexane (HCH) isomers stocked in dumpsites around the world constitutes a huge environmental and economical challenge because of their toxicity and persistence. Alkaline treatment of an HCH mixture in a dehydrochlorination reaction is hampered by the low reactivity of the β-HCH isomer (HCl elimination unavoidably occurring through syn H–C–C–Cl arrangements). More intriguingly, the preferential formation of 1,2,4-trichlorobenzene in the β-HCH dehydrochlorination reaction (despite the larger thermodynamical stability of the 1,3,5-isomer) has remained unexplained up to now, though several kinetic studies had been reported. In this paper, we firstly show a detailed Density Functional study on all paths for the hydroxide anion-induced elimination of β-HCH through a three-stage reaction mechanism (involving two types of reaction intermediates). We have now demonstrated that the first reaction intermediate can follow several alternative paths, the preferred route involving abstraction of the most acidic allylic hydrogen which leads to a second reaction intermediate yielding only 1,2,4-trichlorobenzene as the final reaction product. Our theoretical results allow explaining the available experimental data on the β-HCH dehydrochlorination reaction (rate-determining step, regioselectivity, instability of some reaction intermediates).

scholarly journals Highly active and selective oxygen reduction to H2O2 on boron-doped carbon for high production rates

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yang Xia ◽  
Xunhua Zhao ◽  
Chuan Xia ◽  
Zhen-Yu Wu ◽  
Peng Zhu ◽  
...  
Keyword(s):  
Oxygen Reduction ◽  
Density Functional ◽  
High Selectivity ◽  
Density Functional Theory Calculations ◽  
Reduction Reaction ◽  
Production Rates ◽  
Practical Applications ◽  
Highly Active ◽  
Boron Doped ◽  
Oxidized Carbon

AbstractOxygen reduction reaction towards hydrogen peroxide (H2O2) provides a green alternative route for H2O2 production, but it lacks efficient catalysts to achieve high selectivity and activity simultaneously under industrial-relevant production rates. Here we report a boron-doped carbon (B-C) catalyst which can overcome this activity-selectivity dilemma. Compared to the state-of-the-art oxidized carbon catalyst, B-C catalyst presents enhanced activity (saving more than 210 mV overpotential) under industrial-relevant currents (up to 300 mA cm−2) while maintaining high H2O2 selectivity (85–90%). Density-functional theory calculations reveal that the boron dopant site is responsible for high H2O2 activity and selectivity due to low thermodynamic and kinetic barriers. Employed in our porous solid electrolyte reactor, the B-C catalyst demonstrates a direct and continuous generation of pure H2O2 solutions with high selectivity (up to 95%) and high H2O2 partial currents (up to ~400 mA cm−2), illustrating the catalyst’s great potential for practical applications in the future.

scholarly journals Phosphate-Catalyzed Succinimide Formation from an NGR-Containing Cyclic Peptide: A Novel Mechanism for Deammoniation of the Tetrahedral Intermediate

Molecules ◽  
2018 ◽  
Vol 23 (9) ◽  
pp. 2217 ◽  
Author(s):  
Ryota Kirikoshi ◽  
Noriyoshi Manabe ◽  
Ohgi Takahashi
Keyword(s):  
Conformational Changes ◽  
Density Functional ◽  
Cyclic Peptide ◽  
Density Functional Theory Method ◽  
Proton Exchange ◽  
Computational Method ◽  
Side Chain ◽  
Tetrahedral Intermediate ◽  
Rate Determining Step ◽  
Proton Source

Spontaneous deamidation in the Asn-Gly-Arg (NGR) motif that yields an isoAsp-Gly-Arg (isoDGR) sequence has recently attracted considerable attention because of the possibility of application to dual tumor targeting. It is well known that Asn deamidation reactions in peptide chains occur via the five-membered ring succinimide intermediate. Recently, we computationally showed by the B3LYP density functional theory method, that inorganic phosphate and the Arg side chain can catalyze the NGR deamidation using a cyclic peptide, c[CH2CO–NGRC]–NH2. In this previous study, the tetrahedral intermediate of the succinimide formation was assumed to be readily protonated at the nitrogen originating from the Asn side chain by the solvent water before the release of an NH3 molecule. In the present study, we found a new mechanism for the decomposition of the tetrahedral intermediate that does not require the protonation by an external proton source. The computational method is the same as in the previous study. In the new mechanism, the release of an NH3 molecule occurs after a proton exchange between the peptide and the phosphate and conformational changes. The rate-determining step of the overall reaction course is the previously reported first step, i.e., the cyclization to form the tetrahedral intermediate.

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