pH control of the structure, composition, and catalytic activity of sulfated zirconia

We report a detailed study of structural and chemical transformations of amorphous hydrous zirconia into sulfated zirconia-based superacid catalysts. Precipitation pH is shown to be the key factor governing structure, composition and properties of amorphous sulfated zirconia gels and nanocrystalline sulfated zirconia. Increase in precipitation pH leads to substantial increase of surface fractal dimension (up to similar to 2.7) of amorphous sulfated zirconia gels, and consequently to increase in specific surface area (up to similar to 80 m(2)/g) and simultaneously to decrease in sulfate content and total acidity of zirconia catalysts. Complete conversion of hexene-1 over as synthesized sulfated zirconia catalysts was observed even under ambient conditions. (c) 2012 Elsevier Inc. All rights reserved.