Thermolytic molecular precursor route to site-isolated vanadia-silica materials and their catalytic performance in methane selective oxidation

摘要

The thermolytic Molecular precursor (TMP) method was used to prepare site-isolated, high-surface area vanadia-silica (V/SBA15) materials of various V loadings via the grafting of two precursors, OV[OSi(O'Bu)(3)](3) (1) and OV(O'BLu)(3) (2). Spectroscopic analysis indicates that excellent synthetic control was established for the exclusive formation Of a pseudotetrahedral monovanadate (VO4) Structure on all catalyst surfaces. Another V/SBA 15 catalyst was prepared via conventional incipient wetness impregnation (WI) with aqueous NH4VO3. A spectroscopic investigation of this catalyst revealed the presence of monovanadate and polyvanadate species along with small domains Of V2O5. The TMP materials behave as single-site catalysts in the selective oxidation of methane to formaldehyde LIP to a V coverage of 0.47 V nm(-2) and demonstrate superior activity compared with the WI catalyst. A space-time yield of 5.84 kg(CH2O) kg(cat)(-1) h(-1) cat was observed. more than twice the highest value previously reported. (c) 2005 Elsevier Inc. All rights reserved.