Screening activated carbons produced from recycled petroleum coke for acid gas separation

Abstract

Activated carbons derived from petroleum coke (petcoke) have the potential to (a) help reduce sulfur dioxide emissions through desulfurization, (b) help reduce carbon dioxide and (c) utilize a common waste product. Herein we present results for the selective adsorption of H2S and CO2 from a synthetic sour gas mixture using 7 activated carbons, four derived from petcoke and three obtained commercially. The petcoke activated with sodium hydroxide (P_Na) showed an H2S/CH4 selectivity up to SH₂S/CH₄ = 152 in temperature swing adsorption experiments. The H2S/CH4 selectivity was observed to be inversely proportional to the BET apparent surface area and directly proportional to the oxygen content of the activated carbons. H2S/CH4 and H2S/CO2 selectivity for P_Na was found to increase with increasing temperature. The P_Na activated carbon maintained a high H2S selectivity (SH₂S/CH₄ > 50 and SH₂S/CO₂ > 20) after regeneration at temperatures of T = 423 – 723 K. Pure component CH4, CO2, and H2S adsorption isotherms at T = 288.15 K, 298.15 K and 308.15 K were collected and used to estimate the multi-component adsorption. The results of these studies indicate that the petcoke activated carbons are viable materials for separating H2S and CO2 from sour natural gas streams or biogas.

Keywords

• H2S adsorption
• Petroleum coke
• Activated carbon
• Waste material