Variable temperature FTIR study on the surface acidity of variously treated sulfated zirconias

The acidity of three related sulfated zirconias has been compared by IR spectroscopy using CO and H2 as probe molecules. The parent material (SZ) was obtained by calcination of a commercial sulfated zirconium hydroxide. The other two samples, SZ-WW and SZ-SO3, were obtained from SZ by water washing and by sulfation with gaseous SO3, respectively. The labile sulfate groups responsible for alkane activation and associated with an IR band at 1406 cm−1 are removed by water washing and increased by SO3-sulfation. No remarkable differences in the strength of either Lewis or Brønsted acid sites have been observed between SZ and SZ-SO3. Water washing strongly weakens Brønsted acidity but only slightly weakens Lewis acidity.