REDUCTION OF COPPER(II) WITH SUBSEQUENT DISPROPORTIONATION OF COPPER(I) DURING THE HYDROTHERMAL SYNTHESES OF MICROPOROUS SILICOALUMINIUM PHOSPHATES SAPO-5 AND SAPO-11

The hydrothermal synthesis of SAPO-5 in the presence of copper(II) wit h weak and strong coordinating anions has been investigated. At temper atures above 190 degrees C, it is shown that copper(II) is reduced by the amine templates to copper(I) which, in the absence of coordinating anions (e.g. Cl-), disproportionates to metallic copper. This reducti on/disproportionation in aqueous solutions by amines above this temper ature is the first substantiated observation. Further, we observe that calcining the as-synthesised copper(II)-containing SAPO-5 produces co pper(II) oxide mixed with SAPO-5, whereas for the corresponding SAPO-1 1 system copper(II) on extraframework positions has been previously re ported. The result for the SAPO-5 system is consistent with the presen ce of metallic copper crystallites in the as-synthesised material. The se results show that copper(II) cannot be incorporated into the SAPO-5 lattice to form CuSAPO-5 under the conditions prevailing in our synth esis.