Indian Journal of Chemistry Vol. 42A, August 2003, pp. 1840-1S49 Influence of sulphate content on the physico-chemical properties and catalytic activity of some sulphated zirconia systems Suja Haridas, C S Deepa, K Sreeja Rani & S Sugunan* Department of Applied Chemistry, Cochin University of Science and Technology, Kochi 682022. Kerala. India Received 1 August 2002; revised 25 June 2003 The present work a systematic examination of the effect of sulphate content on the physico-chemical propertie!> and catalytic activity of sulphated zirconia and iron promoted sulphated zirconia systems. Sulphate content is estimated by EDX analysis. The amount of sulphate incorporated has been found to influence the surface area, crystal structure and the acid strength distribution. Ammonia TPD and adsorption studies using perylene have enabled the determination of surface acidic properties. The results are supported by the thermodesorption studies using pyridine and 2,6-dimethylpyridine. The catalytic activity towards benzoylatioll reaction has been correlated with the surface acidity of the systems. Hydrous zirconium oxide, when modified by anions like sulphate, has been reported to form highly acidic or superacidic catalyst depending on the treatment conditions 1-3. The type of precursor and precipitating agent. solution pH, sulphating agent employed, method of impregnation, calcination temperature etc. play a crucial role in deciding the final properties 4.7. A major shortcoming of this category of catalysts is the rapid deactivation due to coke formation at high temperatures. Modification with various transition metal ions has been reported to alter the properties of the system depending on the nature of the lOn . d 89 Incorporate '. The present investigation sets out to study the effect of calcination temperature and sulphate content on the physico-<.:hemical properties and catalytic activity of sulphated zirconia systems and to estimate the influence of Fe(lll) as promoter. Materials and Methods Cafal,vsf preparation Hydrous zirconium oxide was prepared by the hydrolysis of zirconyl nitrate, ZrO(N0 3h (CDH Ltd) with !: I ammonia at 80°C and at a pH 10. The precipitate was filtered, washed and dried overnight at 120"C. Sulphated zirconia samples were obtained by impregnating hydrous zirconium oxide with the requisite amount of IN H 2S04 solution. Wet- impregnation was carried out by stirring zirconium hydroxide with the modifier solution for 4 hours and then evaporating the solution under continued stirring. Iron promoted sulphated zirconia was prepared from zirconium hydroxide by single step impregnation using ferric nitrate solution and requisite amount of IN H2S04 solution. The iron loading in the samples was kept to 2%. The samples were designated based on the amount of H 1S04 solution (2.5. 5.0, 7.5 and I () ml) used per gram of hydrous zirconium oxide. The samples after overnight drying at 120"C were calcined at the required temperature for 3 hours. Prior 10 the characterisation and catalytic activiry tests, the samples were activated at the corresponding calcination temperature for half an hour. Catal,vst characterisatioll Surface area and pore volume were measured by BET method in a Micromeritics Gemini surface area analyser by nitrogen adsorption at liquid nitrogen temperature (P/Po range 0.1-0.9). The crystallinity 01 the samples was determined by the powder XRD method in an X-ray diffractometer (Rigaku D-Max C X-Ray Diffractometer) using a Ni filtered ClI-K radiation (1..=1.5406 A). Thermal stability was examined using a Shimadzu thermogravimelric analyser (TGA-50) in nitrogen atmosphere at a heating rate of 20°C/min. IR spectra of the samp\('" were recorded in a Shimadzu spectrophotometer (DR 8001). Selected samples were subjected to La-'L'r Raman spectroscopic analysis (Dilor-Jobin spectrophotometer). The sulphate content was obtained by EDX analysis (Stereoscan 4-1-0 Cambridge, UK).