Mechanisms involved in the formation and growth of Al–Cu–Ni hydrotalcite-like precipitates using the ureahydrolysis scheme

Abstract

Urea hydrolysis was used to generate carbonate and hydroxide anions required to coprecipitate Al–Cu–Ni hydrotalcite-like compounds (HTlcs) as the precursors for alumina supported Cu–Ni catalysts. The factors influencing the urea hydrolysis and the morphology of the precipitates are discussed. It was found that the ratio of urea to metal salts (PTR), reaction time and temperature are three important parameters in the synthesis of HTlcs using urea hydrolysis. Among these, PTR and temperature are the most important factors in the formation of monodisperse precipitates. The results also indicate that the pH curves of precipitation tests are the best indicators of precipitation sequences. A reaction scheme for the formation of the Al–Cu–Ni HTl structure was also predicted.