LOW-TEMPERATURE SYNTHESIS OF HYDRATED ZINCO(BERYLLO)-PHOSPHATE AND ARSENATE MOLECULAR-SIEVES

ALUMINOSILICATE (zeolite) molecular sieves, both natural and synthetic, have been studied extensively because of their utility in commercial processes such as petroleum cracking, water treatment and gas absorption 1-3. Although aluminium and silicon may be replaced by a variety of other tetrahedrally coordinated elements, there are few examples of molecular sieves that contain neither aluminium nor silicon: several gallophosphates are known 4,5, and cacoxenite, a basic ferric oxyphosphate, occurs naturally 6. Recently, two new beryllophosphate minerals have been identified 7,8: tiptopite, isotypic with cancrinite, and pahasapaite (Li, Ca beryllophosphate), which has the structure of zeolite RHO. Harvey and Meier 9 have prepared five new beryllophosphates, with structures analogous to RHO (Li), gismondine (Na), edingtonite (K), pollucite (Cs), and a new structure, BPH, that has no aluminosilicate analogue. Here we describe the preparation of new families of hydrated zincophosphates/arsenates and beryllophosphates/arsenates with structures that are also related to zeolitic aluminosilicates. These materials may be prepared from gels over a much wider range of pH and at much lower temperatures than are possible for aluminophosphates, perhaps because of the greater solubility of the framework elements: analogues of hydrosodalite and zeolites RHO, Li-A(BW) and X are easily prepared at pH values ranging from 2 to 12 and between 4 and 100-degrees-C. Growth of crystals adequate for X-ray structural analyses seems to be easier than is the case for aluminosilicate/phosphate materials.