Photon flux and wavelength effects on the selectivity and product yields of the photocatalytic air oxidation of neat cyclohexane on TiO(2) particles.
Product selectivity and yields of cyclohexanol and cyclohexanone formation in the photocatalytic air oxidation of cyclohexane on TiO(2) particles were determined as a function of the irradiation wavelength (254 < or = lambda/nm < or = 366) and the photon flux (0.3 < or = I(0)/neinstein cm(-2) s(-1) < or = 5.0). Photonic efficiencies for total monooxygenated products (cyclohexanol + cyclohexanone) ranged from 10 to 25% depending on photon energy and fluency. The cyclohexanol-to-cyclohexanone ratio linearly increases with the incident photon flux at each wavelength and varies more than a magnitude order -- from 3 to 32%-at the same incident photon fluency -- 5 neinstein cm(-2) s(-1) -- by changing the irradiation wavelength from 366 to 303 nm. Experimental evidence indicates that both spectral and intensity effects emerge as a consequence of the change in the frequency of photon absorption per particle. A mechanism is proposed which accounts for the origin of the selectivity changes.
Brusa
Marta A
MA
Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de Mar del Plata, B7602AYL Mar del Plata, Buenos Aires, Argentina.
Grela
Maria A
MA