Silica-supported isolated gallium sites as highly active, selective and stable propane dehydrogenation catalysts

Single-site gallium centers on the surface of silica are prepared via grafting of Ga(OSi(OtBu)3)3(THF) on SiO2-700 followed by a thermolysis step. The resulting surface species corresponds to well-defined tetra-coordinate gallium single-sites, ([triple bond, length as m-dashSiO)3Ga(XOSitriple bond, length as m-dash)] (X = -H or triple bond, length as m-dashSi) according to IR, X-ray absorption near-edge structure and extended X-ray absorption fine structure analysis. These gallium sites show high activity, selectivity and stability for propane dehydrogenation with an initial turnover frequency of 20 per h per gallium center, propylene selectivity of ≥93% and remarkable stability over 20 h. The stability of the catalyst probably results from site-isolation of the active site on a non-reducible support such as silica, diminishing facile reduction typical of Ga2O3-based catalysts.