Crystal structure of a synthetic lithium zeolite

Abstract

The zeolite Li-A(BW) was first reported by Barrer and White (1951) and given the approximate formula, LiAlSiO4 · 2H2O. A recent examination of their specimens has resulted in the determination of the orthorhombic unit cell with a = 10.31, b = 8.18, c = 5.00 Å, and the proposal of a structure based on Pna 21. The x-ray analysis was based on 78 intensity data from powder, and refined to R = 0.13. The aluminosilicate framework consists of 4-, 6- and 8-membered rings, the 4-membered rings linking to form ribbons running lengthwise along the fibrous crystals, while the 8-membered rings enclose channels of about 3.2 Å free diameter running likewise. A column of water molecules is situated centrally in the channel adjacent to Li cations which are located each side of the 6-membered rings. Use is described in determining the space group and the ratio Al/(Si + Al), of a program which refines distances to prescribed values. Evidence of ordering of Si and Al atoms is also found. Li-A(BW) shows much similarity to bikitaite and cancrinite.