Nitrogen-Incorporated SAPO-11 Molecular Sieve: Synthesis, Characterization, and Properties

Abstract

Nitrogen-incorporated SAPO-11 molecular sieves were synthesized by a secondary synthesis technique at low nitridation temperature (400 °C) with a starting material of SAPO-11 zeolite doped with 2 wt % Ru. The obtained powder samples showed high activity in Knoevenagel condensation, which acts as a probing reaction for base catalysis. The changes in structure of the nitrogen-incorporated samples were investigated by means of 27Al-MAS NMR and 31P-MAS NMR spectra, X-ray diffraction, and BET surface area measurements. It was found that nitrogen-containing species had incorporated into the framework of SAPO-11 zeolite, in which some N atoms directly bonded to Al and P atoms and formed AlN4, AlN2O2, and PN4 groups. These species with terminal −NH2 groups on the surface together were responsible for the basicity of nitrogen-incorporated SAPO-11 zeolite.