Gold Catalysts on Y-Doped Ceria Supports for Complete Benzene Oxidation

Lyuba Ilieva,Wojciech Lisowski,Leonarda Liotta,Gabriel Munteanu,Petya Petrova,Janusz Sobczak,Zbigniew Kaszkur,Tatyana Tabakova

doi:10.3390/catal6070099

Abstract

Gold (3 wt. %) catalysts on Y-doped (1, 2.5, 5 and 7.5 wt. % Y2O3) ceria supports prepared by coprecipitation (CP) or impregnation (IM) were studied in complete benzene oxidation (CBO). A low-extent Y modification was chosen to avoid ordering of oxygen vacancies. The samples were characterized by XRD, TGA, XPS and TPR techniques. A positive role of air pretreatment at 350 °C as compared to 200 °C was established for all Y-containing catalysts and it was explained by cleaning the active sites from carbonates. The oxygen supply cannot be considered as a limiting step for benzene oxidation except for the high 7.5%-doped samples, as suggested by TGA and TPR data. On the basis of XPS results of fresh and used in CBO catalysts, the presence of cationic gold species does not seem important for high CBO activity. The gold catalyst on an IM support with 1% Y-doping exhibited the best performance. A 100% benzene conversion was achieved only over this catalyst and Au/ceria, while it was not reached even at 300 °C over all other studied catalysts. Gold and ceria particle agglomeration or coke formation should be excluded as a possible reason, and the most probable explanation could be associated with the importance of the benzene activation stage.

Highlights

Catalytic oxidation is considered one of the most promising technologies for the abatement of volatile organic compounds (VOCs) as hazardous and toxic air pollutants
The catalytic activity data in complete benzene oxidation (CBO) are expressed as the temperature dependence of the benzene conversion degree
In relation to the unresolved question about the role of the state of the gold, these results revealed that the cationic gold species cannot be supposed as important for high CBO activity

Summary

Introduction

Catalytic oxidation is considered one of the most promising technologies for the abatement of volatile organic compounds (VOCs) as hazardous and toxic air pollutants. In a recent review by Scire and Liotta ([1] and references therein), gold-based catalysts were suggested as promising candidates for the total oxidation of VOCs. The influence of different factors, such as the nature and the properties of the support, the gold particle size and shape, the electronic state of the gold, the preparation method and the pretreatment conditions of catalysts, have been discussed in details. A high activity could be expected for the readily reducible metal oxide supports. In this regard, ceria is a very appropriate support for gold

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