CuO-Doped Catalyst Synthesized from Red Mud and Rice Husk Ash Using Urea-Nitrate Combustion Technique for p-Xylene Deep Oxidation

Abstract

To propose an effective CuO-doped catalyst fabricated from red mud and rice hush ash for deep oxidation and emphasize the relation between properties and activity of catalysts, in this work, 5 mass% CuO-doped materials fabricated from red mud and rice husk ash were synthesized using urea/nitrate combustion technique. Effect of urea/nitrate molar ratios on properties and activity of prepared material in p-xylene deep oxidation was also investigated. The obtained catalysts were characterized by several techniques such as X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET) surface area and Hydrogen Temperature Program Reduction (H₂-TPR). The results showed that the change in urea/nitrate ratio could reduce CuO crystallite size of catalyst and enhance its reducibility leading to an increase of catalyst’s oxidative activity. The 5 mass% CuO-doped material with nanoparticles of about 20 nm synthesized with urea/nitrate molar ratio of 2 showed the best activity in p-xylene deep oxidation at the temperature range of 275–400°C. The deep oxidation of p-xylene to CO₂ was almost complete at 400°C and WHSV of 12,000 mL·h⁻¹·g⁻¹. This study found an alternative, low-cost and friendly way for the exploitation of catalyst based on waste materials – red mud and rice husk ash. The modification of CuO-doped material by using urea as a fuel in the preparation is one of the most promising approaches, toward the development of effective VOCs oxidation. The cheap catalyst obtained in this work can be applied in the treatment of VOCs in polluted air.

Fig. 5 The activity of catalysts in p-xylene deep oxidation.