Deposition of sulfur from H2S on porous adsorbents and effect on their mercury adsorption capacity

The deposition of elemental sulfur on porous adsorbents (commercial pre-sulfurised activated carbons and alumina, an HY zeolite and a selenised adsorbent) has been observed when the adsorbents are exposed to a gaseous stream containing hydrogen sul®de and oxygen. The sulfur deposition from H2S is more marked for the activated carbons and the alumina, it is substantially decreased when zeolite is used, and is practically insigni®cant for the selenium-based adsorbent. For the pre-sulfurised activated carbons, further sulfur deposition is initially bene®cial in terms of increasing their mercury chemisorbing capacity but, subsequently, the structural properties are a€ected and this results in a drastic reduction in adsorption capacity. Further sulfur deposition on the pre-sulfurised alumina seems immediately to compromise its capacity to chemisorb mercury. The selenium-based adsorbent shows problems with detachment of the ®ne mercuric selenide powder from the matrix. Sulfur deposition on the initially unsulfurised zeolite improves its mercury adsorption capability. The initially sulfur-free zeolite could be a promising adsorbent for the treatment of this speci®c type of gas stream. In fact, after a moderate level of maintaining its required structural properties for a relatively long period. # 1999 CNR. Published by Elsevier Science Ltd. All rights reserved.sulfur deposition from oxidation of hydrogen sul®de, it can simultaneously chemisorb the mercury vapours by reaction with the sulfur itself while, unlike the activated carbons and alumina,