Decomposition of Furan on Pd(111)

Periodic density functional theory calculations (GGA-PBE) have been performed to investigate the mechanism for the decomposition of furan up to CO formation on the Pd(111) surface. At 1/9 ML coverage, furan adsorbs with its molecular plane parallel to the surface in several states with nearly identical adsorption energies of -1.0 eV. The decomposition of furan begins with the opening of the ring at the C-O position with an activation barrier of = 0.82 eV, which yields a C4H4O aldehyde species that rapidly loses the alpha H to form C4H3O ( = 0.40 eV). C4H3O further dehydrogenates at the delta position to form C4H2O ( = 0.83 eV), before the alpha-I-2 C-C bond dissociates ( = 1.08 eV) to form CO. Each step is the lowest-barrier dissociation step in the respective species. A simple kinetic analysis suggests that furan decomposition begins at 240-270 K and is mostly complete by 320 K, in close agreement with previous experiments. It is suggested that the C4H2O intermediate delays the decarbonylation step up to 350 K.