ADSORPTION AND SELECTIVE OXIDATION OF H2S ON ALUMINA POWDERS - IN-SITU UV-VIS STUDIES IN A DIFFERENTIAL REACTOR

In-situ UV-VIS spectroscopy in transmission and reflection mode as wel l as on-line GC and TPD MS were performed on pressed and powdered wafe rs made from industrial aluminas in different microreactor cells at 40 0 K. These investigations were carried out on activated samples using a continuous gas flow of He containing either H2S (1%) or SO2 (0.5%) o r H2S (1%) with SO2 (0.5%) or O-2 (0.5 and 5.0%). The adsorbed reactan ts lead to an absorption band at 290 nm (H2S and SO2). This absorption band could be attributed to chemisorbed species. Using a differential microreactor for transmission spectroscopy, a conversion of ca. 10% w as measured in the steady state and an attribution of the different vi sible absorption bands to S-2(2-) to S-4(2-) (H2S oxidation by O-2) an d S-3(2-) to S-x(2-) (modified Claus reaction, 2H(2)S+SO2 = (3/x)S-x+3 H(2)O) seems plausible. The species S-8(2-) may be responsible for the stationary conversion during the modified Claus reaction.