Effect of calcination temperature on structure, composition and properties of S2O82−/ZrO2 and its catalytic performance for removal of trace olefins from aromatics

Abstract

A solid superacid catalyst, S₂O₈²⁻/ZrO₂ (S₂Z), was synthesized by the immersion-precipitation method to remove olefins from aromatics; the effect of calcination temperature on the structure, chemical and phase composition and properties of persulfated zirconia were studied. A series of synthesized catalyst samples were characterized by TG-DTG, XRD, SEM, FTIR, FTIR pyridine adsorption (py-IR) and N₂ adsorption analysis. The characterization results revealed that the outstanding activity for removal trace olefins from aromatics is attributed to the interaction between sulfur species and ZrO₂, particularly the more covalent persulfate with tetragonal zirconia (t-ZrO₂), and the calcination temperature was shown to be the key factor in governing the phase composition of S₂Z. Py-IR analysis indicated that the high catalytic activity was well correlated with excellent acidity, primarily with the Lewis acidity of S₂Z. Different calcination temperatures influenced the amount of catalytically active t-ZrO₂, which was favorable to increasing the number of acid sites, improving surface properties and thus enhancing the catalytic activity. Moreover, the regeneration procedure did not change the structure and crystal form of the catalyst. The catalytic activity test revealed that S₂Z calcined at 650 °C was superiorly active and efficiently reusable to remove trace olefins and exhibits promising application prospects in industry.