| Autor: |
Oemry F; Research Center for Quantum Physics, National Research and Innovation Agency, Kawasan Puspiptek Serpong, Tangerang Selatan, Banten, 15314, Indonesia. fere001@brin.go.id., Adilina IB; Research Center for Advanced Chemistry, National Research and Innovation Agency, Kawasan Puspiptek Serpong, Tangerang Selatan, Banten, 15314, Indonesia., Cahyanto WT; Department of Physics, Universitas Jenderal Soedirman, Jl. dr. Soeparno 61, Purwokerto, 53122, Indonesia., Rinaldi N; Research Center for Advanced Chemistry, National Research and Innovation Agency, Kawasan Puspiptek Serpong, Tangerang Selatan, Banten, 15314, Indonesia., Aulia F; Research Center for Advanced Chemistry, National Research and Innovation Agency, Kawasan Puspiptek Serpong, Tangerang Selatan, Banten, 15314, Indonesia., Jackson A; Scientific Computing Department, STFC Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire, OX11 0QX, UK., Parker SF; ISIS Neutron and Muon Source, STFC Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire, OX11 0QX, UK., Kroner AB; Diamond Light Source Ltd, Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0DE, UK., Shotton EJ; Diamond Light Source Ltd, Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0DE, UK. |
| Abstrakt: |
We report on intermediate (oxysulfides) and sulfided structures of NiMo supported on aluminium pillared clay (Al-PILC) during the catalyst activation process and the prefered guaiacol adsorption sites on the sulfided catalyst. In situ X-ray absorption fine structure (XAFS) together with density functional theory (DFT) calculations confirm the existence of ill-defined suboxides (MoO x , NiO x ) and the well-known subsulfides (Mo 2 S 9 , Ni 3 S 2 ) at the first stage which, at a later stage in the process, transform into MoS 2 with two edges, oxygen-decorated Mo and Ni with zero sulfur coverage. The freshly sulfided NiMoS 2 catalyst under sulfiding agents is mainly terminated by Mo-edge surface with 50% sulfur coverage (Mo-S50) with a disordered Ni-edge surface that can be assigned as NiMoS (1̄010). When exposed to an inert atmosphere such as He gas, the Mo and Ni edges evolved partially into new structures of Mo and Ni edges with zero sulfur coverage, labelled as Mo-Bare and Ni-Bare. Guaiacol is often used as a model compound for lignin and a series of calculations of guaiacol on the structural edges of a sulfided NiMoS 2 catalyst show relatively good agreement between the observed and calculated inelastic neutron scattering (INS) spectra for Mo-S50, Ni-Bare, and NiMoS (1̄010) where guaiacol weakly chemisorbed via oxygen atom of OH group. The results also confirm that guaiacol is physisorbed on the basal plane of NiMoS 2 in a horizontal (flat-lying) configuration via van der Waals interaction at a separation of about 3.25 Å. |
