In this article, we report the results of research the formation of silicoaluminophosphate gels under changing gel aging conditions and the influence of an aluminum source (boehmite), characterized by different properties. The samples of initial gels were characterized by XRF, X-ray diffraction, MAS NMR ²⁷Al and ³¹P, and scanning electron microscopy (SEM). Products of crystallization were characterized by XRF, X-ray diffraction, MAS NMR ²⁷Al and ³¹P, scanning electron microscopy (SEM), N₂-physical adsorption, and IR spectroscopy with pyridine adsorption. It has been established that the chemical and phase composition of aging gels and the products of further crystallization is conditioned by the size of the crystals and the porous structure of boehmite. Methods of management the morphology and secondary porous structure of SAPO-11, including the hierarchical porous structure, are proposed based on the use of boehmits characterized by different properties and changing the aging conditions of the initial gels. SAPO—based catalyst with a hierarchical porous structure showed excellent catalytic performance in dimerization of α-methylstyrene with a high degree of conversion and selectivity for linear isomers.

Among the most selective catalytic systems for the hydroisomerization of C₁₆₊ n-paraffins, catalytic systems based on SAPO-11 are quite promising. In order to increase the activity and selectivity of these bifunctional catalysts, it is necessary to reduce the diffusion restrictions for the reacting molecules and their products in the microporous structure of SAPO-11 by reducing the crystal size. To solve this problem, we have studied the influence of different templates (diethylamine, dipropylamine, diisopropylamine, and dibutylamine) on the physicochemical properties of reaction gels and SAPO-11 silicoaluminophosphates during their crystallization. Using XRD, SEM, and NMR techniques, we found that regardless of the template used, the reaction gel after the aging process at 90 °C is an AlPO₄·2H₂O hydroaluminophosphate. At the same time, the nature of the template affects the morphology and crystal sizes of the intermediate alumophosphate, AlPO₄·2H₂O, and the molecular sieves, SAPO-11. The acidic properties and the porous structure characteristics of SAPO-11 are also affected by the template. A template was proposed to enable the synthesis of nanoscale SAPO-11 crystals. The influence of the morphology and crystal size of SAPO-11 on the catalytic properties of a bifunctional catalyst based on SAPO-11 in the hydroisomerization of hexadecane was investigated.

The formation of intermediate phases during aging of the reaction gel composition 1.0Al₂O₃•1.0P₂O₅•1.5DPA•40H₂O and its subsequent crystallization into molecular sieves AlPO-11 and AlPO-41 was studied in this work. The initial gels and crystallization products were characterized by XRD; MAS NMR ²⁷Al and ³¹P; scanning electron microscopy (SEM); transmission electron microscopy (TEM); and N₂-physical adsorption. It has been found that the nature of the aluminum source used to prepare the gel has a significant effect on the properties of the resulting intermediate phases. It is shown that by changing the chemical and phase composition of the intermediate aluminophosphate, it is possible to control the morphology and characteristics of the secondary porous structure of the AlPO-11 molecular sieve. The formation of the intermediate phases with a layered structure opens the possibility to synthesize high-phase purity AlPO-41 at the di-n-propylamine/Al₂O₃ ratio = 1.5. The formation mechanisms of AlPO-11 and AlPO-41 are proposed depending on the phase composition of the intermediate phases.

A series of SAPO-11 and SAPO-41 molecular sieve samples were synthesized using two different aluminum sources. The physicochemical properties of the samples were characterized, and their catalytic performance was tested in hydroisomerization of n-hexadecane. The effects of the aluminum source on the morphology and size of SAPO-11 and SAPO-41 crystals were identified. Specifically, the SAPO-11 and SAPO-41 samples synthesized using aluminum isopropoxide were found to have a higher specific surface area and a higher mesopore volume than their counterparts prepared with boehmite as an aluminum source. It is further shown that SAPO-11 and SAPO-41 samples with similar acidity and similar porosity characteristics exhibit comparable catalytic performance in hydroisomerization of higher n-paraffins.