Effect of pre-adsorbed sulfur on CH_x(x = 1-3) formation from synthesis gas reaction over Cu(111) surface

摘要

The presence of small amounts of sulfur in the syngas produced from fossil derived fuels is a major reason for deactivation of Cu-based catalysts. The formation of the key intermediates CHx(x = 1-3) in the ethanol synthesis from syngas on sulfur covered Cu(1 1 1) surfaces is studied based on density functional theory. The results show that the adsorption energies of most surface species are heavily reduced after a sulfur atom pre-adsorbed on Cu (1 1 1) surface compared with clean Cu(1 1 1) except for CO, CH2O and CHOH, and the variation of the adsorption energies is not obvious with increasing sulfur coverage from 1/16 to 3/16 ML. When sulfur coverage is gradually increased, the adsorption energies of CO and CHOH have a downward and risen trend, respectively, while CH2O hardly changes due to its physical adsorption. The reaction activity of CHx(x = 1-3) formation is seriously inhibited with sulfur added to the system. The presence of sulfur does not change the optimal reaction pathways and rate-limiting steps of CH formation, but changes the rate-limiting steps of CH2 formation and the optimal reaction pathways of CH3 formation. The dominant CHx(x = 1-3) species are CH2 and CH3 at 1/16 ML sulfur coverage, and only CH3 is the most favored CHx(x = 1-3) monomer when increasing sulfur coverage up to 2/16 and 3/16 ML. Our results provide the detailed insight into the sulfur effect on the CHx(x = 1-3) formation on Cu surface.