Effect of H2S poisoning on the i.-r.-spectrum of CO and COS adsorbed on alumina-supported platinum
Abstract
An i.-r. investigation has been conducted to determine the effect of H2S poisoning on CO- and COS-covered γ-alumina-supported platinum surfaces. The chemisorption of CO on a “clean” surface resulted in the formation of a sharp band at 2080 cm–1. Adsorption of H2S on a CO-covered surface drastically decreased the intensity of the 2080 cm–1 band, and produced a weak band at 2170 cm–1. Adsorption of CO on an H2S-poisoned platinum surface showed bands at 2170, 2080, and 2060 cm–1. The 2170 cm–1 band disappears with evacuation; it is attributed to CO weakly adsorbed on sulphur-poisoned sites.
COS adsorption on platinum resulted in the formation of bands at 2080, 2050, 1995, 1950 and 1920 cm–1. The 2080 cm–1 band is due to the decomposition of COS on platinum at room temperature. The three bands at 2050, 1995 and 1950 cm–1 disappeared with evacuation and are presumably due to the weakly chemisorbed COS on “clean” or sulphur-poisoned platinum sites. The chemisorption of CO on a COS-covered surface results in the decrease of intensity of the 1920 cm–1 band. Addition of H2S to a COS-covered surface caused a more rapid disappearance of the 1920 cm–1 band than the 2080 cm–1 band. The formation of the 1920 cm–1 band is attributed to the CO stretching of the chemisorbed COS molecule on a “clean” platinum site.