EFFECT OF SODIUM ON THE ADSORPTION OF SO2 ON AL2O3 AND ON ITS REACTION WITH H2S

Citation
Abm. Saad et al., EFFECT OF SODIUM ON THE ADSORPTION OF SO2 ON AL2O3 AND ON ITS REACTION WITH H2S, Journal of physical chemistry, 99(13), 1995, pp. 4620-4625
Citations number
25
Categorie Soggetti
Chemistry Physical
ISSN journal
00223654
Volume
99
Issue
13
Year of publication
1995
Pages
4620 - 4625
Database
ISI
SICI code
0022-3654(1995)99:13<4620:EOSOTA>2.0.ZU;2-O
Abstract
The adsorption of SO2 on Al2O3 and on 3% sodium on Al2O3 preactivated at 350 and 600 degrees C has been studied by gravimetry, thermodesorpt ion, infrared spectroscopy, and Raman spectroscopy. The quantity of SO 2 adsorbed is greater on Na/Al2O3. A comparison of the results showed that physical adsorption occurs on weak basic O2- Or OH- sites. Chemis orption mainly arises from adsorption on basic sites through the forma tion of sulfite species (AlOSO2) which are characterized by an infrare d band near 1060 cm-l Other minor species such as disulfite or hydroge n sulfite were postulated in order to account for (1) a perturbation o f surface OH groups and (2) the constant quantity of chemisorbed speci es which form as a function of the temperature of activation. The sulf ite species were more stable on Na/Al2O3 than on Al2O3, and they were less reactive toward H2S. This is attributed to the greater basicity o f the 3% sodium-doped catalyst and accounts for the lower reactivity o f Na/Al2O3 relative to pure Al2O3. On either Al2O3 or Na/Al2O3, no sul fur was produced if gaseous SO2 was added to preadsorbed H2S. However, in the reverse sequence, 2H(2)S(g) + SO2(ads) --> (3/n)S-n + 2H(2)O, sulfur was detected via Raman spectroscopy.