Study On Synthesis, Modification And Performance Of SO₄^2-/ZrO₂ Solid Superacid For Refining Trace Olefins From Aromatics

SO42-/ZrO2 (SZ) was synthesized and first tested for removal of olefins from aromatics in this paper. SZ exhibited high catalytic activity and efficient recoverability in the purification of aromatics, which showed great superiority in comparison with active clay and USY zeolite. Clay is the most common industrially-used material to remove olefins, and zeolites such as USY is considered as the most promising alternative to commercial clay. Variable preparation parameters were studied and optimized, including precipitants, terminal pH during precipitation, calcination temperature and time, the category and concentration of impregnating solution. A series of synthesized catalyst samples were characterized by XRD, TG-DTG, FTIR, N2 adsorption analysis,13C NMR and FTIR pyridine adsorption (py-IR). The optimum precursor for synthesizing SZ was precipitated by ammonium hydroxide with a terminal pH value over 9.5. The final catalyst impregnated with 2.0 mol/L sulfuric acid and calcined at 650?, performed optimally for the purification of aromatics. SZ exhibited promising reusability, keeping the olefin conversion over 80%for 8 hours even after five catalytic uses. Base on the optimal conditions for SO4-2/ZrO2 preparation, appropriate iron oxide was doped into SZ for further modification, which optimized products distribution of raw aromatic materials as well as improved the catalytic activity. The incorporation of Fe2O3 increased the specific surface area, purified the tetragonal phase of ZrO2 and enhanced the superacidity. The conversion of olefin was over 84% after the purification process was catalyzed by Fe2O3(5wt%)-SO42-/ZrO2 for 12h. With the modification of Fe2O3, a preferable composite solid superacid catalyst Fe2O3-SO42-/ZrO2 was finally synthesized for the purification of aromatics.