Investigation of the Deactivation Phenomena Occurring in the Cyclohexane Photocatalytic Oxidative Dehydrogenation on MoOx/TiO2 through Gas Phase and in situ DRIFTS Analyses

Abstract

Abstract:In this work, the results of gas phase cyclohexane photocatalytic oxidative dehydrogenation on MoO x /SO 4 /TiO 2 catalysts with DRIFTS analysis are presented. Analysis of products in the gas-phase discharge of a fixed bed photoreactor was coupled with in situ monitoring of the photocatalyst surface during irradiation with an IR probe. An interaction between cyclohexane and surface sulfates was found by DRIFTS analysis in the absence of UV irradiation, showing evidence of the formation of an organo-sulfur compound. In particular, in the absence of irradiation, sulfate species initiate a redox reaction through hydrogen abstraction of cyclohexane and formation of sulfate (IV) species. In previous studies, it was concluded that reduction of the sulfate (IV) species via hydrogen abstraction during UV irradiation may produce gas phase SO 2 and thereby loss of surface sulfur species. Gas phase analysis showed that the presence of MoO x species, at same sulfate loading, changes the selectivity of the photoreaction, promoting the formation of benzene. The amount of surface sulfate influenced benzene yield, which decreases when the sulfate coverage is lower. During irradiation, a strong deactivation was observed due to the poisoning of the surface by carbon deposits strongly adsorbed on catalyst surface.

New Trends in Oxidative Functionalization of Carbon–Hydrogen Bonds: A Review

“…In recent decades, traditional methods of stimulating catalyzed reactions (heating) new methods were added: photochemical initiation [67][68][69][70][71][72], microwave heating [73], electrocatalytic [74], and sonochemical [75] transformations.…”

Nanostructured N-doped TiO2 coated on glass spheres for the photocatalytic removal of organic dyes under UV or visible light irradiation

“…However, the main deficiency for the practical applications of TiO 2 is limited by its large band-gap (3.2 eV), meaning that it can be only active under the UV light irradiation [16][17][18][19][20][21]. The main research objectives are to increase the photocatalytic performances of TiO 2 through the doping of its crystalline structure with non-metal ions that reduces the http://dx.doi.org/10.1016/j.apcatb.2015.01.039 0926-3373/© 2015 Elsevier B.V. All rights reserved.…”

Synthesis of NaOH-Modified TiOF2 and Its Enhanced Visible Light Photocatalytic Performance on RhB

“…The peak around 3379 cm −1 and the broad band centered around 3212 cm −1 were due to the free and bonding O-H stretching vibration of Ti−OH, respectively [27,28]. The peak at 1620 cm −1 was due to the O-H bending vibration of Ti−OH [16,22,[29][30][31][32][33]. The broad band centered around 3212 cm −1 in NaOH-modified TiOF 2 becomes broader than that in TiOF 2 , meaning that more O-H bonds or associated O-H appeared in NaOH-modified TiOF 2 .…”