Calcined Ni—Al layered double hydroxide as a catalyst for total oxidation of volatile organic compounds: Effect of precursor crystallinity

The effect of hydrothermal treatment on properties (crystallinity, porous structure, reducibility, acidity, basicity, and catalytic activity and selectivity in toluene and ethanol total oxidation) of Ni—Al layered double hydroxide precursors and related mixed oxides was examined. The hydrothermal treatment increased considerably both the content of crystalline phase and LDH crystallite size. On the other hand, only a slight effect of the precursor hydrothermal treatment on crystallinity of the related Ni—Al mixed oxides obtained by calcination at 450°C was observed. The reducibility of NiO particles appeared to be hindered considerably compared to the reducibility of pure NiO. Catalytic activity of the Ni—Al mixed oxides prepared from the precursors hydrothermally treated for a short time (4 h) was the highest. The highest amount of acetaldehyde formed during the total oxidation of ethanol, i.e. the worst selectivity was found for the calcined Ni—Al LDH without hydrothermal treatment. Presented at the 33rd International Conference of the Slovak Society of Chemical Engineering, Tatranské Matliare, 22–26 May 2006.