Modeling Combustions: The ab initio Treatment of the O(\(^3\) P) + CH\(_3\) OH Reaction
In this work we tackle the problem of dealing in an ab initio fashion with the description of the $$\begin{aligned} \mathrm{O(^3P) + CH_3OH \rightarrow OH + CH_2OH } \end{aligned}$$reaction that is one of the most important elementary processes involved i
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Department of Chemistry, Biology and Biotechnologies, University of Perugia, via Elce di Sotto, 8, 06123 Perugia, Italy [email protected] Laboratoire de Chimie et Physique Quantiques Universit´e Paul Sabatier - Bat., 3R1b4 118 route de Narbonne, 31400 Toulouse, France
Abstract. In this work we tackle the problem of dealing in an ab initio fashion with the description of the O(3 P) + CH3 OH → OH + CH2 OH reaction that is one of the most important elementary processes involved in the methanol oxidation. In particular, we carried out the following computational steps: 1. calculate the electronic structure of the O + CH3 OH system 2. fit to a pseudo triatomic LEPS (London Eyring Polanyi Sato) the collinear reaction channel leading to the production of OH 3. calculate the dynamical properties of the process using quantum techniques For the purpose of ab initio computing the electronic structure of the O(3 P) + CH3 OH system we used various computational programs based on DFT techniques (to characterize the stationary points and work out harmonic vibrational frequencies) and CCSD(T) level of theory (to refine the energy of the stationary points, calculate the exoergicity of the considered channel and estimate the height of the barrier to reaction). For the purpose of computing quantum reactive scattering state specific probabilities on the proposed LEPS potential energy surface, the Multi Configuration Time Dependent Hartree method was used.
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Introduction
Among bio-alcohols CH3 OH, methanol, is considered a very promising alternative fuel. In fact, it can be used in modern internal combustion engines as well as in fuel cells thanks to a catalytic electrolytic chemical process. In last years, several experiments and theoretical calculations [1–4] were carried out in order to evaluate its combustion properties, such as those important for the environment like heat release, CO2 emission and efficiency as fuel. Moreover, thanks to the fact that methanol is the simplest alcohol, the determination of its oxidation mechanism provides a reasonable basis for improving data available c Springer International Publishing Switzerland 2016 O. Gervasi et al. (Eds.): ICCSA 2016, Part I, LNCS 9786, pp. 71–83, 2016. DOI: 10.1007/978-3-319-42085-1 6
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for larger ones. Information derived from various kinetics studies [2,5] converge on a mechanism composed of different elementary processes, of which the most important ones are: O(3 P) + CH3 OH → OH + CH2 OH → OH + CH3 O
(1) (2)
→ HO2 + CH3
(3)
Process (1) is exoergic and exhibits a small energy barrier, process (2) is slightly endoergic (almost thermoneutral) and process (3) is endoergic with an energy barrier so large to make its investigation irrelevant. Experimental and theoretical findings [1,2] agree on the fact that process (1) is dominant over process (2) at low temperature while the latter becomes increasingly more important as temperature rises. Yet, the study of process (1) represents a real challenge from the theoretical point of view due to the fact th
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