Temperature program adsorption of hydrogen sulfide by NaOH-impregnated activated carbons for hot fuel gas purification

Natural gas, biogas and synthesis gas from coal gasification contain hydrogen sulfide (H₂S) that is toxic and strong odorous for human. It is high corrosive for engine. Among various methods for H₂S removal, the adsorption by activated carbon is known as an efficient process for low concentration H₂S removal. Moreover, activated carbon is not only inexpensive but also produces from agricultural waste in Thailand. The objective of this work is for upgrading the commercial-grade activated carbon by sodium hydroxide (NaOH) impregnation and the combination of steam activation and NaOH impregnation. The aim of upgrading is to improve the performance of H₂S removal from fuel gases. The commercial and NaOH-impregnated activated carbons were tested by the temperature program adsorption of H₂S at 30°C and 550°C. The results showed that the adsorption capacities of the NaOH-impregnated activated carbons are significantly higher than the commercial activated carbon (in the range of 2-21 times higher depending on the temperature of adsorption). At high temperature of adsorption, the adsorption capacity of the NaOH-impregnated activated carbon was 30.10 mg of H₂S per gram of activated carbon. It can be concluded that the upgraded activated carbons is applicable for hot fuel gas purification. The concentration of H₂S comes out at the outlet gas after treatment by the upgraded materials was almost 0 ppmv, which is safe for utilizing in fuel cell system and power engine.