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

This article focuses on the H 2 S adsorption from normal heptane (nC 7 ) as synthetic natural gas liquids (NGL) using ZnO, SiO 2 and zeolite 13X in static mode. Results of the isotherm and kinetics of the investigated adsorbents for H 2 S adsorption under ambient condition showed that ZnO had the highest H 2 S adsorption capacity between 260 and 700 mgH 2 S.g -1 in the initial concentration range of 2500 and 7500 ppmH 2 S with an equilibrium time of less than 30 minutes. Additionally, the ZnO selectivity was greater than 3.16. In continued, H 2 S removal from nC 7 with ZnO was examined in dynamic mode. The H 2 S 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, H 2 S/CO 2 mixture (i.e., 1000 ppmH 2 S + 1000 ppmCO 2 ) caused the H 2 S breakthrough time to increase approximately by 1.11-fold. Alternatively, the ZnO regeneration conditions with hot stagnant air were optimized at different initial H 2 S concentrations (1000 ~ 3000 ppmH 2 S) using the Box-Behnken design. For instance, ZnO contaminated with 1000 ppmH 2 S was regenerated with an efficiency of more than 98 % for 160 minutes at 285 °C.