Effect of Promoters and Calcination Temperature on Surface and Acidity of Modified Zirconia

Abstract

The effect of sulfating agent concentration, calcination temperature, and Ni incorporation on commercial zirconia have been evaluated. Sulfation of commercial zirconia was prepared by wet impregnation with different amounts of sulfuric acid (0.2, 0.5 and 0.8 M) then calcined at 400, 500, 600, 700, 800 and 900°C for 4 h. Ni was incorporated by refluxing over sulfated zirconia, followed by calcination-reduction process. All samples were characterized by XRD, FTIR, ammonia sorption, SEM-EDX, TEM, and AAS. The presence of sulfate has been added to acidic strength of the sulfated zirconia, the more sulfuric acid were used the stronger the acidic property. There has been degradation of sulfate groups that was adrift in sulfated zirconia by calcination treatment above 600°C. The best physicochemical properties of sulfated zirconia were modification with 0.8 M sulfuric acid and on calcination at 400°C. The 0.8SZ-400 has exhibited the highest Brønsted acidic sites with total acidity of 1.71 mmol/g. The impregnation of Ni enhanced the Lewis acidic sites on the surface of the 0.8SZ-400 which NiSZ gave 2.71 mmol/g of total acidity. All prepared materials consisted of nearly spherical shape of nanocrystal with mostly aggregated particles.