Theoretical Study on the Gas-Phase Reaction Mechanism Between Rhodium Monoxide and Methane for Methanol Production

The gas-phase reaction mechanism between methane and rhodium monoxide for the formation of methanol, syngas. formaldehyde, water, and methyl radical have been studied in detail oil the doublet and quartet state potential energy surfaces at the CCSD(T)/6-311+G(2d 2p), SDD/B3LYP/6-311+G(2d, 2p), SDD level. Over the 300-1100 K temperature range the branching ratio for the Rh (F-4) + CH3OH channel is 97.5-100%. whereas the branching ratio for the D-CH2ORh + H-2 channel is 0.0-2.5%, and tire branching ratio for the D-CH2ORh + H-2 channel is so small to be ruled Out. The minimum energy reaction pathway for the main product methanol formation involving two spin inversions prefers to both start and terminate on file ground quartet state, where the around doublet intermediate CH3RhOH is energetically preferred. and its formation rate constant over the 300-1100 K temperature range is fitted by k(CH3RhOH) = 7.03 x 10(6) exp(-69.484/RT) dm(3) mol(-1) s(-1). On the other hand, the main products shall be Rh + CH3OH in the reactions of RhO + CH4. CH2ORh + H-2, Rh + CO +2H(2), and RhCH2 + H2O whereas the Main Products shall be CH2ORh + H-2 in file reaction of Rh + CH,OH. Meanwhile, the doublet intermediates H2RhOCH2 and CH3RhOH are predicted to be energetically favored in the reactions of Rh + CH3OH and CH2ORh + H-2 and in the reaction of RhCH2 + H2O, respectively. (C) 2009 Wiley Periodicals, Inc. J Comput Chem 31: 938-953. 2010