Theoretical study on the gas‐phase reaction mechanism between nickel monoxide and methane for syngas production

Abstract

The comprehensive mechanism survey on the gas-phase reaction between nickel monoxide and methane for the formation of syngas, formaldehyde, methanol, water, and methyl radical has been investigated on the triplet and singlet state potential energy surfaces at the B3LYP/6-311++G(3df, 3pd)//B3LYP/6-311+G(2d, 2p) levels. The computation reveals that the singlet intermediate HNiOCH(3) is crucial for the syngas formation, whereas two kinds of important reaction intermediates, CH(3)NiOH and HNiOCH(3), locate on the deep well, while CH(3)NiOH is more energetically favorable than HNiOCH(3) on both the triplet and singlet states. The main products shall be syngas once HNiOCH(3) is created on the singlet state, whereas the main products shall be methyl radical if CH(3)NiOH is formed on both singlet and triplet states. For the formation of syngas, the minimal energy reaction pathway (MERP) is more energetically preferable to start on the lowest excited singlet state other than on the ground triplet state. Among the MERP for the formation of syngas, the rate-determining step (RDS) is the reaction step for the singlet intermediate HNiOCH(3) formation involving an oxidative addition of NiO molecule into the C-H bond of methane, with an energy barrier of 120.3 kJ mol(-1). The syngas formation would be more effective under higher temperature and photolysis reaction condition.

Theoretical study on the gas‐phase reaction mechanism between rhodium monoxide and methane for methanol production

“…For CH 4 ). 36 The geometric structure of CH 4 RhO is analogical to that of CH 4 MO (M 5 Zn, 16 Ni, 22,41 Pd, 22 Be, 24 Pt, 23 Mn, 38,40 and Fe 38,40 ). Alternatively, for CH 4 ORh, the complexation energy is calculated to be 1.7 and 2.9 kJ mol 21 relative to the corresponding reactants on the quartet and doublet states, respectively.…”

“…This oxidative addition reaction pathway is semblable to that in the system of NiO 1 CH 4 . 41 As shown in Figure 2, for this oxidative addition pathway, i.e., CH 4 RhO ? 1-TS1b ?…”

“…13,14,20 Lately, we have comprehensively investigated the gas-phase reaction mechanism of CH 4 with NiO for the formation of CO 1 2H 2 , HCHO, CH 3 OH, H 2 O, and CH 3 radical. 41 It is suggested that the main products would be syngas once HNiOCH 3 is created on the singlet state, whereas the main products would be methyl radical if CH 3 NiOH is formed on both singlet and triplet states. 41 Moreover, it is predicted that the syngas formation would be more effective under higher temperature and photolysis reaction conditions.…”

“…41 It is suggested that the main products would be syngas once HNiOCH 3 is created on the singlet state, whereas the main products would be methyl radical if CH 3 NiOH is formed on both singlet and triplet states. 41 Moreover, it is predicted that the syngas formation would be more effective under higher temperature and photolysis reaction conditions. 41 These theoretical studies have provided some valuable information concerning the reaction mechanism and energetics.…”

“…41 Moreover, it is predicted that the syngas formation would be more effective under higher temperature and photolysis reaction conditions. 41 These theoretical studies have provided some valuable information concerning the reaction mechanism and energetics.…”