Formation of Platinum Sites on Layered Double Hydroxides Type Basic Supports: I. Effect of the Nature of the Interlayer Anion on the Structure Characteristics of the Layered Aluminum–Magnesium Hydroxide and the Formation of an Oxide Phase

摘要

A layered aluminum–magnesium hydroxide of the hydrotalcite type containing interlayer carbon-ate counterions (HT-CO_3) and activated hydrotalcite containing interlayer OH~– ions (HT-OH) were studied for the subsequent use as the precursors of supports for platinum catalysts. It was found that the nature of an interlayer anion in the composition of an aluminum–magnesium layered hydroxide is an important factor affecting both the formation of the oxide support and its texture characteristics. The replacement of the inter-layer CO_3~(2-) anion by OH~– resulted in changes in the structural parameters of the initial double hydroxide: a decrease in the interlayer distance with the retention of the Mg/Al ratio and an increase in the imperfection of the layered material. X-ray diffraction studies in the temperature range of 30–900°C showed that HT-OH is characterized by the ability to form low-temperature spinel at 375°C. As a result, two types of aluminum–magnesium oxide supports, which were characterized by different pore space organizations at the same Mg : Al ratio, were obtained from the given layered hydroxides.