Deactivation of Activated Alumina Adsorbents Used for H2S Removal from Olefin-containing Streams

An oligomer produced from unsaturated and reactive components (green oil) is formed when hydrogen sulfide (H2S) is removed from the exhaust stream of the methyl tert-butyl ether (MTBE) plant. A remedy to minimize this contaminant formation is using adsorbents with low reactivity toward the olefinic precursors. Here, the green oil formation on the surface of different types of commercial alumina is studied. Results confirm that the regular commercially activated alumina has low H2S adsorption capacity. Still, the alumina alkalized with 3.98 wt.% of Na2O has a breakthrough time of more than 29 h and stable performance in a cyclic operation. Moreover, the promoted alumina with a wide pore diameter (about 9 nm) and low surface area (about 215 m2/g) is less susceptible to deactivation by forming green oil. It is supposed that the capillary condensation of C3/C4 unsaturated compounds and acidic sites of the alumina intensify the oligomerization inside the pores of an adsorbent.