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

Abstract

Two series of sulfated zirconia catalysts were synthesized from various precursors using mono- or multi-step sequence preparations under laboratory conditions. Their activities/selectivities 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 SO2-4 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 H2 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 H2.