Photooxidation of a Mustard Gas Simulant over Mixed-Oxide Photocatalyst:Site Poisoning by Oxidation Products and Reactivation

摘要

The photooxidation of 2-chloroethyl ethyl sulfide (2-CEES),a simulant for mustard gas,was studied using transmission IR spectroscopy on a mixed-oxide TiO2~SiO2 photocatalyst.Ultraviolet irradiation in the photon energy range from 2.1 to 5 eV was employed at a catalyst temperature of 200 K.Rapid photooxidation was observed by the loss of infrared intensity in the v(CH_x)stretching region,and concomitant infrared features of adsorbed oxidation products were observed to develop.The oxidation products,captured on the photocatalyst at 200 K,were found to block 2-CEES readsorption.Upon heating the poisoned photocatalyst to about 300 K,infrared measurements indicate that the adsorbed CO_2 oxidation product was desorbed.The capability for full readsorption of 2-CEES was achieved upon heating the poisoned photocatalyst to 397 K,and continued rapid photooxidation of the 2-CEES was then possible at about 1/3 the rate found for the fresh catalyst.Thus thermal treatment at 397 K of oxidation-product-poisoned TiO_2-SiO_2 material is able to partially restore the TiO_2-SiO_2 photooxidation activity.