Influences of synthesis conditions on the content of framework Cu species in Cu-AlPO<Subscript>4</Subscript>-5 molecular sieve

Summary

Copper substituted aluminophosphate molecular sieves with type 5, Cu-AlPO<Subscript>4</Subscript>-5, were hydrothermally synthesized. The influences of Cu<Superscript>2+</Superscript> concentration in the original gel, Et<Subscript>3</Subscript>N/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> molar ratio and different template on the content of Cu species in the framework were investigated by H<Subscript>2</Subscript>-TPR. The results showed that increasing the Cu<Superscript>2+</Superscript> concentration in the gel could not result in the formation of framework Cu species, but only increase the amount of extra-framework CuO clusters. The formation of the framework Cu species was observed when tertiary amines such as C<Subscript>6</Subscript>H<Subscript>11</Subscript>NH<Subscript>2</Subscript>, Pr<Subscript>3</Subscript>N and Et<Subscript>3</Subscript>N were used as templates, but failed with quaternary ammonium TPABr. For Et<Subscript>3</Subscript>N, the amount of the framework Cu species increased with the increment of Et<Subscript>3</Subscript>N/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> ratio until Et<Subscript>3</Subscript>N/Al<Subscript>2</Subscript>O<Subscript>3 </Subscript>= 1.40. It is inferred that Cu<Superscript>2+</Superscript> can be incorporated into the framework when the hydrolysis and polycondensation rates of Cu<Superscript>2+</Superscript> are slowed down and match those of Al- and P-containing species.