Adsorption and Photooxidation of CH₃CN on TiO₂

Abstract

The adsorption and photooxidation of CH3CN chemisorbed on TiO2 has been investigated using infrared spectroscopy. It was found that CH3CN forms an ice layer on TiO2 at 126K and above 126K CH3CN diffusion into TiO2 occurs. At 200K, the adsorption of CH3CN on both isolated Ti−OH groups and on the Ti4+ Lewis acid site was observed. Under UV irradiation (350 ± 50 nm; hυ = 3.10−4.13 eV), CH3CN was oxidized in the presence of O2 to form H2O, CO2, surface CO3 2- and an intermediate partially oxidized isocyanate species, NCO, which was identified by various isotopic experiments. Photooxidation of the CH3 moiety in adsorbed CH3CN occurs more readily does the CN moiety in CH3CN. Lattice oxygen of TiO2 was found to preferentially form adsorbed NCO, compared to oxygen from adsorbed O2. A mechanism of the formation of NCO species was postulated.

An EPR investigation of acetonitrile reactivity with superoxide radicals on polycrystalline TiO2

“…The CN -moiety renders it a particularly interesting molecule to examine, as it is representative of a number of toxic materials which are candidates for TiO 2 -based oxidation processes. However, to date, only a limited number of studies have appeared on the catalytic degradation of acetonitrile over TiO 2 either under dark conditions [6,7] or under UV irradiation [8][9][10][11][12][13][14][15].…”

“…The observation of the cyanogen moiety was considered as proof for the existence of the CN • radical, the latter being formed via a C-C bond breaking process. However, an IR study by Zhuang et al [11] later found that CH 3 CN was photooxidised over TiO 2 in the presence of oxygen to form H 2 O, CO 2 and surface CO 3 2-with an absorbed NCO intermediate. Additional information on the surface adsorption processes and surface products formed during photooxidation was also provided in a comprehensive study by Chuang et al [9].…”

Interaction of Acetonitrile with Oxygen on TiO2-supported Au Catalysts: FTIR–MS Study

“…It was demonstrated [11] that CH 3 CN adsorbed on Pt/SiO 2 could be -at least partly -hydrogenated. The formation of gaseous products and surface species in the UV irradiation of CH 3 CN adsorbed on TiO 2 has been studied in the presence [12] and in the absence [13] of oxygen.…”

Adsorption of acetonitrile and its reaction with oxygen on TiO2-supported Au — Rh bimetallic catalysts

“…It was found that CH 3 CN adsorbed on Pt/SiO 2 could be -at least partly -hydrogenated [14]. The UV irradiation of CH 3 CN adsorbed on TiO 2 in the presence of oxygen [15] led to the formation of H 2 O, CO 2 , surface CO 3 2-and surface isocyanate (NCO). The formation of surface CH 3 CONH 2 , η 2 (N,O)-CH 3 CONH, CH 3 COO (a) , HCOO (a) , NCO (a) and CN-containing species was observed, when the UV irradiation of CH 3 CN adsorbed on TiO 2 was performed in the absence of oxygen [16].…”