Hydrogen sulfide removal from normal heptane using zinc oxide, silicon dioxide and zeolite 13X: adsorption capacity, kinetics, selectivity, breakthrough and regeneration.

Abstract

This article focuses on the H2S adsorption from normal heptane (nC7) as synthetic natural gas liquids (NGL) using ZnO, SiO2 and zeolite 13X in static mode. Results of the isotherm and kinetics of the investigated adsorbents for H2S adsorption under ambient condition showed that ZnO had the highest H2S adsorption capacity between 260 and 700 mgH2S.g-1 in the initial concentration range of 2500 and 7500 ppmH2S with an equilibrium time of less than 30 minutes. Additionally, the ZnO selectivity was greater than 3.16. In continued, H2S removal from nC7 with ZnO was examined in dynamic mode. The H2S breakthrough time for ZnO reduced from 210 to 25 minutes as weight hourly space velocity (WHSV) was increased from 5 to 20 h-1 at 30 bar. Also, the breakthrough time at 30 bar was about 2.5 times greater than that at atmospheric pressure. Furthermore, H2S/CO2 mixture (i.e., 1000 ppmH2S + 1000 ppmCO2) caused the H2S breakthrough time to increase approximately by 1.11-fold. Alternatively, the ZnO regeneration conditions with hot stagnant air were optimized at different initial H2S concentrations (1000 ~ 3000 ppmH2S) using the Box-Behnken design. For instance, ZnO contaminated with 1000 ppmH2S was regenerated with an efficiency of more than 98 % for 160 minutes at 285 °C.