The transformation of zeolite A and X into nitrate cancrinite under low temperature hydrothermal reaction conditions

摘要

Investigations on the hydrothermal crystallisation of nitrate enclathrated cancrinite werernperformed using the alkaline transformation of zeolites A and X at a temperature of 353 K.rnDiluted (2-molar) and concentrated (16-molar) NaOH-solutions were inserted, mixed withrnhigh amounts of sodium nitrate as a structure directing agent. The conversion of the zeolitesrninto nitrate enclathrated cancrinite was followed in the early stage of the reactions for times uprnto 48 hours by X-ray-powder diffraction and IR- spectroscopy.rnA fast and total transformation of zeolite X into pure phase cancrinite could be stated in mostrnof the experiments, independent of the alkalinity. In contrast the conversion of zeolite A underrnlow alkaline conditions was slow and accompanied by a sodalite-cancrinite cocrystallisationrnas well as the formation of an intermediate phase between both structure types. The resultsrnindicate a more kinetically controlled reaction mechanism for zeolite A transformation underrnthese conditions.