Synthesis of Nickel and Zinc-Doped Aluminogallate Nanocomposite Spinels with the Hydrothermal Method and Wet Atomization for NO Reduction

The levels of nitrogen oxides (NO_x = NO + NO₂) released from both portable and standing combustion devices are on the increase, which contributes to serious environmental problems such as global warming and air pollution. The selective catalytic reduction (SCR) of NO_x by hydrocarbons (HCs) is very effective, so there have been many studies of the performance of various catalysts for HC-SCR. In this study, Ga₂O₃–Al₂O₃–NiO–ZnO (GANZ) nanocomposite metal oxides were tested as catalysts for NO_x reduction by C₂H₄. The spinel metal oxide powders were prepared with the hydrothermal reaction method. Aluminum, gadolinium, nickel, zinc nitrate, and ammonium carbonate salts are highly water soluble and were used in these syntheses. The hydrothermally synthesized powders were then processed with wet atomization to obtain highly dispersed fine particles. Finally, the spinel powders were tested in NO_x reductions performed in the presence of high levels of oxygen and at a high space velocity, which are demanding conditions since most reported catalysts are not active in this environment. The synthesized product is an uncontaminated spinel phase of GANZ and was found to exhibit high catalytic activity even in the presence of 10 % H₂O vapor and SO₂ at a high space velocity. GANZ catalysts were also synthesized with the co-precipitation and sol–gel methods for comparison.