Regulation of the Properties of the Hierarchical Porous Structure of Alumophosphate Molecular Sieves AEL by Reaction Gels Prepared with Different Templates

Microporous alumophosphate molecular sieves AlPO₄-n are promising materials for use in catalysis, gas adsorption, and gas separation. However, AlPO₄-n faces problems such as diffusion limitations that lead to a deterioration in mass transfer. To solve this problem, we studied the crystallization of alumophosphate reaction gels prepared using aluminum isopropoxide and various secondary amines as templates, including diethyl-, di-n-propyl-, diisopropyl-, and di-n-butylamines. Using X-ray diffraction, Ramon spectroscopy, and STEM methods, it has been demonstrated that the reaction gels prepared using DPA, DIPA, and DBA are amorphous xerogels consisting of 5-10 nm nanoparticles. The reaction gel prepared with DEA is a combination of a layered phase and an amorphous aluminophosphate. It has been shown that the use of aluminum iso-propoxide allows the production of AlPO₄-11 in the form of 2-4 µm aggregates consisting of primary AlPO₄-11 nanocrystals. The template was found to exert a significant effect upon both the characteristics of the porous structure and the size of AlPO-11 nanocrystals. A template is proposed for the synthesis of hierarchical AlPO₄-11 with a maximum volume of mesopores. The morphology and crystal size of AlPO₄-11 were found to strongly influence its adsorption properties in the adsorption of octane.