Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Incorrect rate for HO2+OH=H2O+O2 in primaryH2O2 library #647

Open
rwest opened this issue Mar 29, 2024 · 0 comments
Open

Incorrect rate for HO2+OH=H2O+O2 in primaryH2O2 library #647

rwest opened this issue Mar 29, 2024 · 0 comments

Comments

@rwest
Copy link
Member

rwest commented Mar 29, 2024

label = "OH + HO2 <=> H2O + O2",

entry(
    index = 17,
    label = "OH + HO2 <=> H2O + O2",
    kinetics = Arrhenius(A=(2.14e+06, 'cm^3/(mol*s)', '*|/', 2), n=1.65, Ea = (2180, 'cal/mol'), Tmin=(200, 'K'),
                         Tmax=(2500, 'K')),
    shortDesc = u"""[Konnov2019]""",
    longDesc = u"""Konnov (2019) https://doi.org/10.1016/j.combustflame.2019.01.032, Table 1, Reaction 7""",
)

This reaction is for the triplet O2 channel, but the rate taken from the Konnov paper is for the singlet O2 channel.

From Konnov:

Reaction between OH and HO2 radicals is usually included in kinetic mechanisms as OH + HO2 = H2O + O2. At low temperatures typical for atmospheric chemistry, formation of clusters with water may affect the rate of this reaction [30], which, however, is considered negligible for combustion. Role of recombination channel OH + HO2 + M = HOOOH + M was analyzed by Badenes et al. [31] and found irrelevant at all conditions and pressures up to 400 atm. Recent rate constant measurements at room temperature [32] were attributed to reaction OH + HO2 = H2O + O2 and found in good agreement with previous measurements of, e.g., Keyser [33]. Reaction between OH and HO2 radicals can take place also on singlet potential energy surface forming singlet O2(a¹Δg):
(7)OH + HO2 = H2O + O2 (1Δ)
It was therefore included in the Konnov [3] mechanism with the rate constant calculated by Gonzalez et al. [34] aiming at analysis of possible role of ozone and reactions of excited species O(1D), OH(2Σ+), and O2(a¹Δg), in hydrogen combustion. Recently, Monge-Palacios and Sarathy [35] repeated ab initio calculations of this reaction at higher level of theory. Their rate constant for the triplet channel is within a factor of two of the rate constant derived by Hong et al. [36] and implemented in the previous [3] and present models, with expression proposed by Burke et al. [37], and with the rates obtained during optimization of hydrogen [4] and syngas [2] mechanisms as illustrated in Fig. S1 of the Supplemental material. The rate constant for the singlet channel, however, was found [35] several orders of magnitude higher than that of Gonzalez et al. [34] as shown in Fig. S2 of the Supplemental material. Nevertheless Monge-Palacios and Sarathy [35] did not find an impact of this reaction on thermal combustion of hydrogen; small difference was seen only in the calculated burning velocities of the mixtures seeded with O3 . This new rate constant of reaction (7) is adopted in the present mechanism.

The paper has a zip of the mechanism as supplementary material and their actual rate for the triplet channel is

HO2+OH=H2O+O2                  7.000E+12      0.0     -1093.0 
    DUPLICATE
HO2+OH=H2O+O2                  4.500E+14      0.0     10930.0 
    DUPLICATE

the file also includes this singlet channel as

HO2+OH=H2O+O2X                 2.140E+06      1.65     2180.0 

if we want to add singlet O2 we could do, but at least we should use the correct rate for the triplet O2.

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Projects
None yet
Development

No branches or pull requests

2 participants