Investigation on the Insertion Channel in the S(³P) + H₂ Reaction

Abstract

To reexamine the possibility of the spin-forbidden, molecular-elimination mechanism of the thermal decomposition of H 2 S, H 2 S + M f S( 3 P) + H 2 + M (1), recently indicated by experimental and theoretical studies, as well as to examine the cause of discrepancies of its rate constants among recent works, the reverse insertion channel of the S( 3 P) + H 2 reaction, S( 3 P) + H 2 + M f H 2 S + M (-1), has been investigated. The experiments have been conducted with an excimer-laser photolysis (248 nm) in a shock tube at a lower temperature range, 900-1050 K, and a higher pressure range up to 4 atm, than previous studies, where the insertion process (-1) was estimated to be dominant over the simple hydrogen-atom-transfer reaction, S( 3 P) + H 2 f H + HS (2). The decay rate of S( 3 P) atoms has been measured by using an atomic resonance absorption spectrometry technique. The measured rate constant agreed well with the extrapolation of the previous measurements for reaction 2, showing that the recombination channel (-1) is still minor at these experimental conditions. The upper limit of the rate constant for reaction 1 derived in the present study was shown to be consistent with the theoretical rate constant calculated by the Troe's formula with the ab initio threshold energy for the intersystem crossing and with reasonable weak collision factors derived from the rate constant for reaction 1 reported by Shiina et al. [J.

Systematically reduced chemical mechanisms for sulfur oxidation and pyrolysis

“…The rates for reactions (4) and (38) have been determined experimentally by Shiina et al [47]. The rate used for reaction (27) originates from a study by Tsuchiya et al [48].…”

An Exploratory Flow Reactor Study of H2S Oxidation at 30–100 Bar

“…The medium to high-temperature chemistry of H 2 S has received attention due to its importance in combustion, in the Claus process, and as a potential hydrogen source [1,2]. The H/S system has been investigated for both H 2 S pyrolysis and H 2 sulfidation [3][4][5][6][7][8][9][10]. Despite some remaining uncertainties, available experimental results are described satisfactorily by a detailed reaction mechanism [8].…”

Dynamical properties of S(3P) + HD reaction on 13A″state and their quantum wavepacket calculation

“…The two triplet PESs ( 3 A ′ and 3 A ″) cross the singlet 1 A ′ one in the reactant channel because of the influences of the spin‐orbit coupling and intersystem crossing. This effect is mentioned in investigating the spin‐forbidden thermal decomposition of by Olschewski et al and Shiina group . Based on the spin‐orbit matrix calculated by themselves and the singlet Ho PES, Maiti et al undertook nonadiabatic dynamics studies of reaction using a QCT surface‐hopping method.…”

“…This effect is mentioned in investigating the spin-forbidden thermal decomposition of H 2 S by Olschewski et al [15] and Shiina group. [16,17] Based on the spin-orbit matrix calculated by themselves and the singlet Ho PES, Maiti et al [18] undertook nonadiabatic dynamics studies of Sð 3 P; 1 DÞ1H 2 reaction using a QCT surface-hopping method. Their results show that the spin-orbit interaction has an important effect on the Sð 3 PÞ1H 2 reaction, leading to the possibility for the reaction on 3 A 00 PES to occur without surmounting the triplet barrier.…”