Pathways of photocatalytic gas phase destruction of HD simulant 2-chloroethyl ethyl sulfide

Photocatalytic oxidation of HD simulant, 2-chloroethyl ethyl sulfide (CEES), was studied in a specially designed coil and flow photocatalytic reactor by means of GC-MS and FTIR techniques. TiO2 Hombikat UV 100 photocatalyst was deactivated after a few hours of operation, which was signaled by the appearance of incomplete oxidation products in the reactor effluent and accumulation of incomplete oxidation products on the TiO2 surface. Complete reactivation of the photocatalyst was achieved by washing the photocatalyst with water. Compared to diethyl sulfide, CEES showed lower reactivity in photocatalytic oxidation and was accumulated on the TiO2 surface after catalyst deactivation. Without UV irradiation, hydrolysis of CEES proceeded on the TiO2 surface. Major gaseous products of CEES incomplete photocatalytic oxidation are acetaldehyde, chloroacetaldehyde, SO2, diethyl disulfide, and chloroethylene. Surface products extracted from the TiO2 surface with acetonitrile and water include mainly 2-chloroethyl ethyl sulfoxide and ethanesulfinic and ethanesulfonic acids, as well as diethyl di-, tri-, and tetrasulfides mono and disubstituted in the beta position with a chlorine or hydroxyl group. While surface monodentate sulfates can be removed upon washing, surface bidentate species stayed on the surface and possibly contribute to the permanent catalyst deactivation. (C) 2003 Elsevier Inc. All rights reserved.