Preparation and properties of piperazine silicate (EU-19) and a silica polymorph (EU-20)

The hydrothermal crystallisation of a piperazine (pipz) silicate (EU-19) from the reaction mixture (p– 2y)pipz–yM2CO3–20SiO2–wH2O (p= 15, 20, or 25; y= 0–2.5; w= 250 or 1 000; M = Na, K, or Cs) at 120 and 150 °C is described. Dependent on w, plate-like or lath-like morphologies are observed. The chemical and physical properties of EU-19 are those of a layer structured material. On calcination the EU-19 crystals are pseudomorphically converted into a thermally stable silica polymorph (EU-20).