Enhancing Kinetics of Carbonyl Sulfide Hydrolysis Using Pt-Supported Al2O3 Catalysts: First-Principles-Informed Energetic Span Analysis

Abstract

Catalytic hydrolysis is considered an effective strategy for treating carbonyl sulfide (COS)─a toxic sulfur-containing gas that causes problems to the environment and petrochemical industries. Al2O3-based materials are commonly used as catalysts for COS hydrolysis owing to their stability and cost effectiveness. However, they still suffer from sulfur poisoning leading to partial COS conversion after long time use. To improve their catalytic performances, herein, we computationally designed and studied the catalytic activity of the Pt-supported Al2O3 catalysts by means of density functional calculations. We mechanistically explored the COS hydrolysis on both bare and Pt-decorated surfaces to reveal the role of Pt catalysts in the reaction kinetics. We find that bare Al2O3 suffers from difficult C–S bond breaking as its barrier is relatively high. Pt facilitates C–S bond breaking where its barrier is reduced by more than half (1.34 to 0.60 eV). However, the Pt–Al2O3 catalyst could encounter sulfur poisoning as the sulfur-containing intermediates are rather stable. Such issues could be remedied by increasing the operating temperature to destabilize the intermediates and promote product desorption. The energetic span models reveal that the important states of bare and Pt–Al2O3 are indeed C–S bond breaking and product desorption corresponding to an energy span of 2.72 and 1.67 eV at 773 K, respectively─suggesting that Pt dramatically enhances the catalytic activity of Al2O3-based catalysts toward COS hydrolysis. The suggested operating temperatures are above 673 K to avoid sulfur poisoning. Our findings will be useful for the development of more efficient Al2O3-based catalysts for treating COS.