Preparation of zeolite X with low levels of iron impurity from reaction mixtures containing triethanolamine

Virtually iron-free zeolite X can be prepared using readily available raw materials and normal laboratory techniques by the addition of 2,2′,2″-nitrilotriethanol (triethanolamine, TEA) to the reaction mixture prior to crystallization. The TEA chelates to Fe³⁺ in solution to reduce the quantity of iron which is incorporated in the a luminosilicate framework. Experiments have been performed in which controlled quantities of iron(III) sulfate were added to the fresh reaction mixture in order to verify this assertion. Samples which were prepared in the absence of TEA generally contained more than three times as much iron as did those prepared with TEA. The electron paramagnetic resonance (EPR) spectrum of a sample prepared from a mixture to which no iron was intentionally added, and which contained TEA, showed that the zeolite was effectively iron-free. The corresponding sample prepared without TEA gave strong EPR signals for octahedral Fe₂O₃ clusters and tetrahedral (framework substituted) iron.