Study of the effect of the base, the silica and the niobium sources on the [Nb]-MCM-41 synthesized at room temperature

Abstract [Nb]-MCM-41 was synthesized at room temperature by varying the base (tetramethylammonium hydroxide or ammonium hydroxide), the silica source (tetraethyl orthosilicate or tetramethyl orthosilicate), the niobium source (ammonium niobium oxalate, NH 4 [NbO(C 2 O 4 ) 2 (H 2 O) 2 ] · 3H 2 O, or potassium niobate, K 8 Nb 6 O 19 ) and the order of addition of the niobium source (before or after the silica source). These variations were determinant in the amount of niobium incorporated into the framework and in the structural order of the [Nb]-MCM-41 obtained. Only one method led to the formation of [Nb]-MCM-41 with the desired characteristics and active in the epoxidation of cis -cyclooctene with tert -butyl hydroperoxide leading to 19% conversion and 95% selectivity for cyclooctene oxide after 10 h.