The acidic properties of H-MeAlPO-5 (Me = Si, Ti, or Zr): A periodic density functional study

The relative strength for Brønsted acid sites of isomorphously substituted H-MeAlPO-5 molecular sieves (Me = Si, Ti, or Zr) is investigated using density functional theory employing periodic models. The results are consistent with the experimental observation and show that H-ZrAlPO-5 has the weakest Brønsted acid sites. Furthermore, the Brønsted acidity of H-MeAlPO-5 (Me = Si or Ti) is compared with that of H-MeAlPO-34 (Me = Si or Ti) [M. Elanany, K. Koyama, M. Kubo, P. Selvam, A. Miyamoto, Micropor. Mesopor. Mater. 71 (2004) 51].

Density functional theory calculations on periodic models of aluminophosphate molecular sieves shows the relative acidity order: H-SiAlPO-5 > H-TiAlPO-5 > H-ZrAlPO-5. Furthermore, the Brønsted acidity of H-MeAlPO-5 (Me = Si or Ti) is weaker than those of their H-MeAlPO-34 counterparts. Figure optionsDownload as PowerPoint slide