Pinacol-type rearrangement catalyzed by Zr-incorporated SBA-15

Highly ordered zirconium-incorporated SBA-15 materials, designated as Zr-SBA-15, with Zr/Si ratios up to 10.8 mol% were one-pot synthesized in a self-generated acidic environment. Zr was incorporated into the SBA-15 framework as isolated Zr species, and it also formed superficial zirconia clusters with two or more Zr centers on the pore walls when the Zr/Si ratio was higher than 3 mol%. The acid amounts of Zr-SBA-15 materials increased linearly with Zr loading, but the acidities were lower than those of commercially available HY and ZSM-5 zeolites. However, when used as the catalysts in liquid phase pinacol-type rearrangement, one-pot synthesized Zr-SBA-15 materials, especially those with superficial zirconia clusters, were the most efficient catalysts. The pinacolone yield of 2.7 g/g catal h and selectivity of 81% were achieved in 1 h over Zr-SBA-15 with a Zr/Si ratio of 10.8 mol%. Moreover, Zr-SBA-15 was also efficient in catalyzing the rearrangement of bulky 2,3-pinanediol to yield camphor as the major product through hydrogen migration. (C) 2009 Elsevier Inc. All rights reserved.