Mononuclear gold species anchored on TS-1 framework as catalyst precursor for selective epoxidation of propylene

Deposition of gold on supports can produce catalytically active forms of gold as well as spectators, but previous understanding of the nature of active immobilized precursors is poor. By using synchrotron X-ray powder diffraction (SXRD) and X-ray absorption spectroscopy (XAS) techniques, we report a novel synthesis and structural elucidation of atomically dispersed gold species anchored to the internal surface of TS-1 as K+Au(OH)(2)Na+(O-f)(3) ("f" signifies the framework atoms of TS-1 in the formula.). It is found that the choice of alkali ions plays a crucial role in nucleation and stabilization of the atomic precursor. These anchored single Au upon controlled reduction in H-2 can form uniform gold clusters in direct contact with the TS-1 surface containing isolated Ti sites: their interface exhibits excellent specificity and stability towards epoxidation of propylene in H-2/O-2 due to synergetic effect. (C) 2018 Elsevier Inc. All rights reserved.