Abstract

A series of Ru-based mono and bimetallic materials were prepared and evaluated in the catalytic oxidation of chlorobenzene. Among the different Ru-based catalysts, 1Ru/TiO2(P25) was the most active catalyst and contributed the lowest complete oxidation temperature, suggesting that commercial P25 TiO2 was the best support for Ru catalysts. After ceria oxides were introduced into the Ru catalytic system, the catalytic activity of 1Ru-5Ce/TiO2(Rutile) dramatically improved and that of P25 supported catalysts was decreased. Comparing the chlorobenzene consumption rates for 1Ru/TiO2 and 1Ru-5Ce/TiO2 at 280 °C, it could be concluded that monometallic Ru catalytic system was appropriate for P25 support, and the Ru-Ce bimetallic catalytic system was suitable for the rutile TiO2 support. At 280 °C, for 1Ru-5Ce/TiO2(Rutile) and 1Ru-5Ce/TiO2(P25), the chlorobenzene conversion was stabilized at approximately 91% and 86%, respectively. According to the physicochemical properties of the catalysts as characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), and Hydrogen temperature programmed reduction (H2-TPR), it can be concluded that (a) electrophilic Oads species play an important role in VOCs oxidation; (b) abundant RuO2 nanoparticles on the surface of 1Ru-5Ce/TiO2(Rutile) result in higher catalytic activity and stability; and (c) dispersion is not the major factor for the catalytic activity, rather the unique structure greatly facilitated the catalytic activity and stability.

Highlights

  • Reducing volatile organic compounds (VOCs) emissions has been a major challenge for manufacturers and researchers [1,2]

  • 1Ru/TiO2 (P25) contributed the lowest complete oxidation temperature at 280 ◦ C, revealing that commercial P25 TiO2 was the best support for Ru catalysts in chlorobenzene oxidation, and it was believed that the rutile phase played an important role in the P25 support due to the similar interplanar lattice spacings for RuO2 and rutile (110) of TiO2

  • After ceria oxides were introduced into the Ru catalytic system, the T90 of 1Ru-5Ce/TiO2 (Rutile), 1Ru-5Ce/TiO2 (P25), and 1Ru-5Ce/TiO2 (Anatase) were 279, 283, and 290 ◦ C, respectively, revealing that the support crystal phase plays an important role in Ru-catalyzed chlorobenzene oxidation

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Summary

Introduction

Reducing volatile organic compounds (VOCs) emissions has been a major challenge for manufacturers and researchers [1,2]. Many strategies have been developed for CVOC abatement, including incineration, catalytic oxidation, and adsorption-based techniques [7,8,9]. Among the Ru-based catalysts, Ru/TiO2 was recognized as the most promising catalyst in chlorine-containing oxidation reactions, such as the deacon reaction and CVOC oxidation. Bimetallic catalysts commonly show higher catalytic activity, selectivity, and anti-poisoning ability than monometallic materials due to the synergistic effect [49,55,56,57,58,59,60,61,62]. It is of great interest to study the bimetallic catalysts Ru-Ce/TiO2 (anatase, rutile, and P25) for CVOC oxidation.

Catalytic Oxidation of Chlorobenzene
Catalyst Characterization
Representative
In Situ FTIR Studies and Reaction Mechanism
Catalyst
Catalytic Evaluation
Conclusions
Full Text
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