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

Catalysts

Vincenzo Vaiano²  Diana Sannino²  Ana Rita Almeida¹  Guido Mul¹ 

[1] Faculty of Science & Technology, University of Twente, PO Box 217, Meander 225, 7500 AE, Enschede, The Netherlands; E-Mails:;Department of Industrial Engineering, University of Salerno, Via Giovanni Paolo II, 132; 84084, Fisciano, SA, Italy; E-Mails:

关键词: cyclohexane;    gas phase analysis;    DRIFTS analysis;    deactivation;   

DOI  :  10.3390/catal3040978

来源: mdpi

【 摘 要 】

In this work, the results of gas phase cyclohexane photocatalytic oxidative dehydrogenation on MoO_x/SO₄/TiO₂ 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 SO₂ 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.

【 授权许可】

CC BY   
© 2013 by the authors; licensee MDPI, Basel, Switzerland.