Ultradispersed catalysts significantly enhance rates of reaction and mass transfer by virtue of their extended and easy accessible surface. These attractive features were exploited in this study to effectively capture H2S(g) from an oil phase by ultradispersed sorbents. Sorption of H2S(g) from oil phases finds application for scavenging H2S(g) forming during heavy oil extraction and upgrading. This preliminary investigation Simulated heavy oil by (w/o) microemulsions having 1-methyl-naphthalene; a high boiling point hydrocarbon, as the continuous phase. H2S(g) was bubbled through the microemulsions which contained the ultradispersed sorbents. The type and origin of sorbent were investigated by comparing in situ prepared FeOOH and commercial alpha-Fe2O3 nanoparticles as well as aqueous FeCl3 and NaOH solutions dispersed in the (w/o) microemulsions. The in situ prepared FeOOH nanoparticles captured H2S(g) in a chemically inactive form and displayed the highest sorption rate and capacity. Temperature retarded the performance of FeOOH particles, while mixing hall no significant effect. (C) 2009 Elsevier Inc. All rights reserved.