Kinetics of 4-Methoxybenzyl Alcohol Oxidation in Aqueous Solution in a Fixed Bed Photocatalytic Reactor

Abstract

The photocatalytic oxidation of 4-methoxybenzyl alcohol in water was performed in a fixed bed continuous annular reactor by using a home-prepared TiO2 catalyst supported on Pyrex glass beads. The investigation was aimed to modeling the complex kinetics of the photoprocess which occurs through two parallel pathways: (i) partial oxidation to the corresponding aldehyde and (ii) total oxidation to CO2 and H2O. On these grounds, the influence of liquid flow rate, inlet concentrations of alcohol and oxygen, catalyst amount, and irradiation power on the photoreactivity were studied. A kinetic model like that of Langmuir-Hinshelwood satisfactorily fitted the experimental results and allowed determination of the values of model parameters. It was found that all these parameters are positively affected by an increase of radiant energy absorbed by the catalyst. All the reactivity results indicate that the partial oxidation pathway is favored by the low flux of absorbed photons and by low oxygen coverage on the TiO2 surface; opposite conditions favor the mineralization pathway

Titania Photocatalysts for Selective Oxidations in Water

“…[19] The partial oxidation of benzyl alcohol (BA), 4-methoxybenzyl alcohol (MBA), 4-methylbenzyl alcohol (MeBA), and 4-nitrobenzyl alcohol (NBA) to the corresponding aldehydes was achieved with both home-prepared and commercial TiO 2 samples, and the influence of the substituent group on the reaction rate was studied. [19][20][21][22][23][24][25][26][27][28] The selective oxidation of glycerol, a polyhydroxylated alcohol, in water was also investigated to check whether or not the oxidation mechanism is a characteristic of the alcohol-catalyst couple. [29] Polymorphic TiO 2 catalysts, that is, catalysts featuring the anatase, rutile, and brookite phases, were prepared in our laboratory and tested in photocatalytic oxidation reactions.…”

Enhancing selectivity in photocatalytic formation of p-anisaldehyde in aqueous suspension under solar light irradiation via TiO2 N-doping

“…15,16 Only recently, photocatalytic partial oxidation of aromatic alcohols to the corresponding aldehydes has been carried out under near-UV radiation in aqueous suspensions of home-prepared (HP) anatase, [17][18][19] brookite 20,21 and rutile TiO 2 [22][23][24] in laboratory batch reactors and also in continuous reactors. 25,26 In those conditions HP photocatalysts showed selectivity values for aldehyde production far higher than those of commercial TiO 2 ones.…”

Selective Oxidation of Benzyl Alcohol in the Aqueous Phase by TiO2‐Based Photocatalysts: A Review

“…Meanwhile, Palmisano and his group synthesized home-prepared TiO 2 (HP) at room temperature with low crystallinity for both anatase and rutile. The HP photocatalysts displayed a high hydroxyl group density on the surface for promoting the desorption of aldehydes [34][35][36][37][38][39][40][41][42]. The mixture phase of anatase and brookite phases (TiO 2 -SG) decreases the pore volume and increases the surface area, which is beneficial for the availability of reactive sites and light adsorption.…”