One-step synthesized Cu-containing Silicalite-1 zeolite using Cu-NTA complex for the selective ammoxidation reaction

Abstract

A one-pot synthesis strategy for the Cu-containing Silicalite-1 (Cu@S-1-N) zeolite with Cu⁺ anchored in silanol nests was initially presented via using nitrilotriacetic acid (H₃NTA) as a ligand. Introducing H₃NTA guaranteed the formation of a copper-chelate in the form of [Cu(NTA)₂]^2- in the precursor solution, whose un-coordinated carboxylate ion may condensate with silicate during the crystallization process, leading to the innumerable highly active and stable Cu⁺ species in the final Cu@S-1-N zeolite. In the model benzaldehyde ammoxidation reaction, the highly dispersed and electron-deficient Cu⁺ species in the Cu@S-1-N catalyst was more active and stable than the Cu²⁺ species in the Cu/S-1-N catalyst prepared by the incipient wetness impregnation method. The Cu⁺ species preferentially chemisorbed benzaldehyde, activating its carbonyl carbon for nucleophilic attack by the amino group from the decomposition of ammonium carbonate and subsequent toward the benzonitrile formation.