Optimization of Oil-Sludge-Based Adsorbents for the Treatment of Toxic H₂S in Oilfield Gases: Preparation, Modification, Characterization, and Adsorption Mechanism

Abstract

The mitigation of toxic hydrogen sulfide (H2S) in oil field gas is crucial as a result of its significant health and environmental repercussions. This research developed an efficient H2S adsorbent using oil sludge, a hazardous waste of oil production, by adding the alkaline activator KOH before pyrolysis. The performance of the adsorbent was assessed with a fixed bed in humid gas conditions. The adsorption kinetics were characterized theoretically, and reaction pathways were subsequently proposed. Results showed that the adsorbent activated by KOH presented a higher desulfurization capacity than those activated by NaOH, Na2CO3, and K2CO3. The addition of KOH increased the volume of the mesopores and the content of surface active sites. However, an optimal KOH concentration emerged when assessing the desulfurization capacity concerning the mass of the adsorbent or activator. The kinetic investigations revealed that the H2S adsorption process obeyed the Langmuir model and was modulated by both external diffusion and internal diffusion. In addition, the role of KOH during the H2S adsorption process was identified through the analysis of desulfurization products on the deactivated adsorbent. As a result of being catalyzed by KOH, elemental sulfur was oxidized to high-valent sulfuric acid and neutralized to sulfate. This research provides innovative perspectives on devising economical oil-sludge-based adsorbents, facilitating the concurrent processing of oil field gas and oil sludge in oilfield operations.