Effect of ammonia and water molecule on OH + CH3OH reaction under tropospheric condition

Ali, Mohamad Akbar; Balaganesh, M.; Al-Odail, Faisal A.; Lin, King‐Chuen

doi:10.1038/s41598-021-90640-6

Cited by 13 publications

(41 citation statements)

References 34 publications

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“…The oxidation of CH 4 in the stratosphere is an important source of water vapor in this region. Over the last few years, many experimental and theoretical studies have been conducted on the catalytic effect of a single water molecule on many important atmospheric reactions, such as [20][21][22][23][24][25][26][27][28][29][30][31][32]. Experimental measurements on some of the reactions, i.e., OH + CH 3 OH (+H 2 O) [20] and OH + CH 3 CHO (+H 2 O)] [22], have been performed.…”

Section: Introductionmentioning

confidence: 99%

Effect of Water and Formic Acid on ·OH + CH4 Reaction: An Ab Initio/DFT Study

Ali

Muthiah

2022

Catalysts

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In this work, we used ab initio/DFT method coupled with statistical rate theory to answer the question of whether or not formic acid (HCOOH) and water molecules can catalyze the most important atmospheric and combustion prototype reaction, i.e., ·OH (OH radical) + CH4. The potential energy surface for ·OH + CH4 and ·OH + CH4 (+X) (X = HCOOH, H2O) reactions were calculated using the combination of hybrid-density functional theory and coupled-cluster theory with Pople basis set [(CCSD(T)/ 6-311++G(3df,3pd)//M06-2X/6-311++G(3df,3pd)]. The results of this study show that the catalytic effect of HCOOH (FA) and water molecules on the ·OH +CH4 reaction has a major impact when the concentration of FA and H2O is not included. In this situation the rate constants for the CH4 + HO···HCOOH (3 × 10−9 cm3 molecule−1 s−1) reaction is ~105 times and for CH4 + H2O···HO reaction (3 × 10−14 cm3 molecule−1 s−1 at 300 K) is ~20 times higher than ·OH +CH4 (~6 × 10−15 cm3 molecule−1 s−1). However, the total effective rate constants, which include the concentration of both species in the kinetic calculation has no effect under atmospheric condition. As a result, the total effective reaction rate constants are smaller. The rate constants when taking the account of the FA and water for CH4 + HO···HCOOH (4.1 × 10−22 cm3 molecule−1 s−1) is at least seven orders magnitude and for the CH4 + H2O···HO (7.6 × 10−17 cm3 molecule−1 s−1) is two orders magnitude smaller than ·OH +CH4 reaction. These results are also consistent with previous experimental and theoretical studies on similar reaction systems. This study helps to understand how FA and water molecules change the reaction kinetic under atmospheric conditions for ·OH +CH4 reaction.

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Section: Introductionmentioning

confidence: 99%

Effect of Water and Formic Acid on ·OH + CH4 Reaction: An Ab Initio/DFT Study

Ali

Muthiah

2022

Catalysts

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“…The optimized parameters of RC-c, Ints-c, TSs-c and PC-c are given in Table S1. As suggested in the previous work [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37], the possibilities of molecular collisions between O 2 , • CH 3 and CO 2 are very unlikely, therefore, we believe that • CH 3 and O 2 collide first to form an RC complex, and this complex collides with CO 2 to form a threemolecular complex, i.e., RC-c. Based on our previous knowledge and the previous studies, we believe that the RC is more important (negative energy…”

Section: Reaction Pathways Formentioning

confidence: 62%

“…The vibrational mode, which corresponds to the Hindered Rotor (HR), was treated as HR approximation in the densum-input file. To further improve the accuracy of energy, the single-point energy calculations were performed at CCSD(T)/6-311++G(3df,3pd) [designated CC-p] level [28][29][30][31][32][33]. The RCCSD(T) method was used for closed-shell species, such as CH 2 O and H 2 O, CO 2 , and for all open-shell species the UCCSD(T) method was used.…”

Section: Electronic-structure Calculationsmentioning

confidence: 99%

“…Our results show that the rate constants, without including the concentration of CO 2 , are higher than the • CH 3 + 3 O 2 reaction in the temperature range of 500 to 1500 K. In general, the rate constants of the CO 2 -catalyzed reaction are higher than the • CH 3 + 3 O 2 reaction in the entire temperature range (see Figure 5). As discussed in our previous studies [26][27][28][29][30][31][32] under pseudo-first-order conditions, the relative equilibrium concentrations strongly depend on the concentration of the excess CO 2 , and the correct equation to calculate the effective rate constant is k e f f c…”

Section: Rate Constantsmentioning

confidence: 99%

“…They also suggested that the chemical kinetic analysis for the effect of CO 2 on CH 3 + O 2 reaction is underway. Therefore, in this study, we have re-investigated the effect of CO 2 on the • CH 3 + 3 O 2 reaction using a similar level of theory in combination with an advanced statistical-rate theory, to understand the chemical kinetic behavior for the effect of CO [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36]. All of these studies indicate that a single H 2 O molecule makes complexes, transition states and post complexes thermodynamically more stable than a water free-reaction, due to the formation of more hydrogen-bonded species.…”

Section: Introductionmentioning

confidence: 99%

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Catalytic Effect of CO2 and H2O Molecules on •CH3 + 3O2 Reaction

2022

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The methyl (•CH3) + 3O2 radical is an important reaction in both atmospheric and combustion processes. We investigated potential energy surfaces for the effect of CO2 and H2O molecules on a •CH3+ O2 system. The mechanism for three reaction systems, i.e., for •CH3 + 3O2, •CH3 + 3O2 (+CO2) and •CH3 + 3O2 (+H2O), were explored using ab initio/DFT methods [CCSD(T)//M062X/6-311++G(3df,3pd)] in combination with a Rice−Ramsperger−Kassel−Marcus (RRKM)/master-equation (ME) simulation between a temperature range of 500 to 1500 K and a pressure range of 0.0001 to 10 atm. When a CO2 and H2O molecule is introduced in a •CH3 + 3O2 reaction, the reactive complexes, intermediates, transition states and post complexes become thermodynamically more favorable. The calculated rate constant for the •CH3 + 3O2 (3 × 10−15 cm3 molecule−1 s−1 at 1000 K) is in good agreement with the previously reported experimentally measured values (~1 × 10−15 cm3 molecule−1 s−1 at 1000 K). The rate constant for the effect of CO2 (3 × 10−16 cm3 molecule−1 s−1 at 1000 K) and H2O (2 × 10−17 cm3 molecule−1 s−1 at 1000 K) is at least one–two-order magnitude smaller than the free reaction (3 × 10−15 cm3 molecule−1 s−1 at 1000 K). The effect of CO2 and H2O on •CH3 + 3O2 shows non-RRKM behavior, however, the effect on •CH3 + 3O2 shows RRKM behavior. Our results also demonstrate that a single CO2 and H2O molecule has the potential to accelerate a gas-phase reaction at temperature higher than >1300 K and slow the reaction at a lower temperature. The result is unique and observed for the first time.

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Theoretical kinetics analysis of the OH + CH₃OH hydrogen abstraction reaction using a full‐dimensional potential energy surface

Espinosa‐García

García-Chamorro

2023

Int J of Chemical Kinetics

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Based on an analytical full-dimensional potential energy surface (PES), named PES-2022, fitted to high-level ab initio calculations previously developed by our group and specifically developed to describe this polyatomic reactive process, an exhaustive kinetics analysis was performed in the temperature range 50-2000 K, that is, interstellar, atmospheric and combustion conditions. Using the competitive canonical unified theory with multidimensional tunneling corrections of small curvature, CCUS/SCT, and low-and high-pressure limit (LPL and HPL) models, in this wide temperature range we found that the overall rate constants increase with temperature at T > 300 K and T < 200 K, showing a V-shaped temperature dependence, reproducing the experimental evidence when the HPL model was used. The increase of the rate constant with temperature at low temperatures was due to the strong contribution of the tunneling factor. The title reaction evolves by two paths, H 2 O + CH 2 OH (R1) and H 2 O + CH 3 O (R2), and the branching ratio analysis showed that the R2 path was dominant at T < 200 K while the R1 path dominated at T > 300 K, with a turnover temperature of ∼260 K, in agreement with previous theoretical estimations. Three kinetics isotope effects (KIEs), 13 CH 3 OH, CH 3 18 OH, and CD 3 OH, were theoretically studied, reproducing the experimental evidence. The kinetics analysis in the present paper together with the dynamics study previously reported showed the capacity of the PES-2022 to understand this important chemical process.

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Effect of ammonia and water molecule on OH + CH3OH reaction under tropospheric condition

Cited by 13 publications

References 34 publications

Effect of Water and Formic Acid on ·OH + CH4 Reaction: An Ab Initio/DFT Study

Effect of Water and Formic Acid on ·OH + CH4 Reaction: An Ab Initio/DFT Study

Catalytic Effect of CO2 and H2O Molecules on •CH3 + 3O2 Reaction

Theoretical kinetics analysis of the OH + CH₃OH hydrogen abstraction reaction using a full‐dimensional potential energy surface

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Effect of ammonia and water molecule on OH + CH3OH reaction under tropospheric condition

Cited by 13 publications

References 34 publications

Effect of Water and Formic Acid on ·OH + CH4 Reaction: An Ab Initio/DFT Study

Effect of Water and Formic Acid on ·OH + CH4 Reaction: An Ab Initio/DFT Study

Catalytic Effect of CO2 and H2O Molecules on •CH3 + 3O2 Reaction

Theoretical kinetics analysis of the OH + CH3OH hydrogen abstraction reaction using a full‐dimensional potential energy surface

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Product

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Theoretical kinetics analysis of the OH + CH₃OH hydrogen abstraction reaction using a full‐dimensional potential energy surface