Photodecomposition of chloroform catalyzed by unmodified MCM-41 mesoporous silica.
Unactivated MCM-41 mesoporous silica catalyzes the photodecomposition of chloroform to phosgene and hydrogen chloride under near-UV (λ > 360 nm) irradiation. The rate of photodecomposition increases toward an asymptotic limit as the O(2) partial pressure is increased. Deuterochloroform does not decompose under the same experimental conditions. Low concentrations of both cyclohexane and ethanol quench the photodecomposition, whereas water, up to its solubility limit, does not. Dissolved tetraalkylammonium salts suppress photodecomposition. The data are consistent with a mechanism in which light absorption by an SiO(2) defect yields an electron-deficient oxygen atom, which then abstracts hydrogen from chloroform. The resulting CCl(3) radicals react with oxygen to form a peroxy radical that decomposes, eventually yielding phosgene and hydrogen chloride.
Department of Chemistry, Santa Clara University, Santa Clara, CA.
Laura A
LA
Peña
Alissa M
AM
Chan
Larissa R
LR
Cohen
Karen
K
Hou
Brent M
BM
Harvey
Patrick E
PE
Hoggard
D002384:Catalysis; D002725:Chloroform / Q000737:chemistry*; D055668:Photochemical Processes; D012822:Silicon Dioxide / Q000737:chemistry*; D014466:Ultraviolet Rays
C509968:MCM-41; D012822:Silicon Dioxide; D002725:Chloroform