Content of sulfates and their stability: Key factors determining the catalytic activity of sulfated zirconia catalysts

Two series of sulfated zirconia catalysts were synthesized from various precursors using mono- or multi-step sequence preparations under laboratory conditions. Their activities/seleetivities in the isomerization reaction of n-hexane were correlated to their textural, structural and morphological properties. The slightly higher activity of a commercially sulfated Zr(OH) 4 -based catalyst is in agreement with the differences in the content of SO 2- 4 ions and their thermal stability, textural and structural properties, i.e., crystallite size and possible imperfection of the incorporation of sulfate groups in the multi-step synthesis of the catalyst having a nitrate origin. The employment of H 2 as the carrier gas resulted in no catalytic activity, regardless of the catalyst precursor, preparation method and calcination temperature. When the isomerization reaction was performed under He, the relatively short life-times of all catalyst samples were caused by fast deactivation due to coking in the absence of H 2 .