Masamitsu Kobayashi

Preparation of Aluminum Tetrametaphosphate in the Reaction of α -A12O3 or Al(OH)3 with NH4H2PO4

Conditions of formation for four types, A, B, C and D, of aluminum tetrametaphosphate, Al4(P4O12)3, were studied in the reaction of α -A12O3 or Al(OH)3 with NH4H2PO4.Type A is produced on heating α -A12O3 and NH4H2PO4 mixture above 750 C. Type B is easily obtained by heating α -A12O3 and NH4H2PO4 mixture at 500-550 C. Type C can be produced by heating α -A12O3 and NH4H2PO4 mixture at 600-700 C, but it is intermingled with type A or B. By heating 1-5% mixture of thus obtained type C in α -A12O3 and NH4H2PO4 at 525-575 C, pure type C is readily and reproducibly obtained. Type D is produced by heating a mixture of α -A12O3 and NH4H2PO4 in nitrogen stream or dry air at 500 C, while heating of this mixture in vacuum at 500-700 C gives type B as sole product. The type and yie1d of aluminum tetrametaphosphate formed greatly depend on the sort of aluminum compounds used as starting materials, molar ratio of the aluminum compounds and the phosphate, heating temperature and atmosphere.IR spectra and thermal transformation of aluminum tetrametaphosphate were also discussed.