Hydrolysis of carbonyl sulfide over modified Al2O3 by platinum and barium in a packed-bed reactor

Abstract

The integrated gasification combined cycle (IGCC) has been applied as an alternative technology for power plant due to the higher thermal efficiency than that of conventional pulverized coal-fired technology. However, syngas produced from coal gasification in IGCC is usually contaminated with carbonyl sulfide (COS). Therefore, it is necessary to be treated before being utilized in gas turbine or chemicals production. In this paper, catalytic treatment of COS by hydrolysis over alumina-supported platinum (Pt/Al2O3) catalysts was investigated. COS was hydrolyzed and converted to hydrogen sulfide (H2S) in a packed-bed reactor under flue-gas in a temperature range of 150–250 °C, and Weight Hourly Space Velocity (WHSV) of 7,000 hr−1. The optimal Pt/Al2O3 catalysts were determined by varying active Pt metal (0.1–1.0 wt%) loadings and barium promoter (1–5 wt%) loadings. The prepared catalysts were characterized by X-ray diffraction (XRD), N2 adsorption and desorption, and Scanning Electron Microscopy with Energy Dispersive X-ray spectroscopy (SEM/EDX). It was found that the activity of Al2O3 drastically dropped from 90 to 10% after 510 min time on stream. The addition of Pt and Ba onto Al2O3 could stabilize the catalytic activity. The 0.5%Pt/5.0%Ba/Al2O3 catalyst provided the best performance in COS hydrolysis. The complete COS conversion was achieved with 0.5%Pt/5.0%Ba/Al2O3 in all initial concentrations, and the lifespan of the catalyst was prolonged. A kinetic model of this reaction was also purposed. Sulfur poisoning and carbon deposition on the catalyst surface caused the catalyst deactivation.