The Synthesis Of Functioned Silica Beads And Performance Of Catalyze Knoevenagel Reaction

Mesoporous materials as the carrier of catalyst has been widely used in a large number of catalytic reaction, many researches about MCM-41 SBA-15 series of silica materials have been done, the recovery and reuse of catalysts are relatively complex. Moreover, the mesoporous channel is not enough for large molecules to get through, and make the activity limited by the pore diameter.To solve the limitation of mesoporous materials in macro-molecular reaction, at the same time the reuses of the catalysts, this paper prepared bigger mesoporous silica microspheres at room temperature using hard template as template, continued by using 3- ammonia propyl triethoxysilane as a coupling agent to amine-functionalize the silica microspheres, both of the samples was measured by FT-IR, thermo-gravimetric(TG), nitrogen adsorption/desorption, SEM and TEM characterization, the characterization results proved mesoporous silica beads about 30 nm pore diameter was successfully synthesized. In the process of amine functionalization, influence of the synthesis temperature, solvent type and the amount of silane-coupling agent were discussed. In order to study the catalytic performance of the amino-grafted silica beads, Knoevenagel condensation reaction of benzaldehyde and ethyl cyanoacetate was calculated. Experimental results showed that for Knoevenagel condensation reaction between benzaldehyde and ethyl cyanoacetate, functionalized silica microspheres showed a conversion rate of more than 90%, and could achieve enough conversion rate after four times recycles. Noted that those amino-functioned silica beads could remain morphology after reactions, so the catalysts precipitate in the bottom of the reactor and achieve a simple separation.In addition, we synthesized bi-functioned acid-base mesoporous silica microspheres, benzaldehyde dimethyl acetal and ethyl cyanoacetate was measured to study catalytic properties of bi-functionalized silica microspheres, using aluminum and iron as acid center, synthesis under different conditions was researched, as a result, aluminum-amine functionalized silica microspheres showed the highest conversion rate of 87.2%.