Effect of the Mg : Al ratio on borate (or silicate)itrate exchange in hydrotalcite

摘要

Layered double hydroxides (LDHs) have been prepared with interlayer nitrate and with different Mg:Al ratios. Solids with low Mg:Al ratios show larger basal spacings than those with larger Mg:Al ratios, consistent with tilting of the nitrate ions, respectively. Nitrate/tetraborate and nitrate/silicate anionic exchange has been achieved only for those samples with "tilted" nitrate. The precise nature of the interlayer species in the exchanged samples has been concluded from MAS-NMR IR results. The layered structure of the exchanged samples collapses at temperatures higher than those for the nitrate-containing precursors. (C) 2000 Academic Press. [References: 44]