One-step non-templating synthesis of hybrid zeolite catalyst for Knoevenagel condensation at room temperature efficiently

Abstract

From the view of energy saving and environment protection, green catalysis has become one of the most important goals of chemists, including both the green preparation of catalyst and the highly efficient catalysis under mild reaction condition. Herein, N,N-dimethylaminopropyl-functionalized hybrid zeolite is firstly synthesized by one-step non-templating method, which is characterized by powder X-ray diffraction, Fourier-transform IR, thermogravimetric analysis, element analysis, scanning electron microscope, water contact angle measurements, inductively coupled plasma atomic emission spectrometry, and N₂ adsorption–desorption measurements. The functionalized hybrid zeolite can be directly used as base catalyst without any post modification and achieve high yields of corresponding products in the Knoevenagel condensation of benzaldehyde (or substituted benzaldehyde) with ethyl cyanoacetate at room temperature by using ethanol as solvent. By the comparison with other zeolite catalysts, the unique and excellent catalytic properties of N,N-dimethylaminopropyl-functionalized hybrid zeolite was ascribed to not only the synergic effect of basic property and hydrophobic/lipophilicity of the organic groups, but also the easier accessibility of bulky substrate molecules with highly exposed catalytic active sites over the solid catalyst. The recycling and control experiments show that it owes excellent reusable stability.