The crystallization behavior of metakaolin (Al₂Si₂O₇) at 25–100°C in solutions of sodium hydroxide and sodium silicate with different concentrations was studied, and the conditions for its conversion into finely divided, high-crystallinity zeolites of types A and X were determined. On the basis of the product zeolites and kaolin, procedures were developed for the preparation of pelleted, binder-free materials as polycrystalline accretions of zeolites A and X, which do not rank below pelleted zeolites obtained from synthetic feedstock.

The second part of the review presents the results of research on SAPO-11 and SAPO-41 molecular sieves over the last three decades, with particular emphasis on methods to control the acid properties, morphology, and secondary porous characteristics of these molecular sieves, as well as on the catalytic applications of SAPO-11 and SAPO-41 for hydroisomerization of C₁₆₊ n-paraffins. The paper discusses the current understanding of the acid site formation mechanisms in SAPO-11 and SAPO-41, as well as methods for control over the strength and concentration of the acid sites and the morphology and dispersion of the crystals. Recent advances in the synthesis of SAPO-11 and SAPO-41 with a hierarchical porous structure are described, namely the use of pore-forming templates, crystal growth modifiers, and post-synthetic treatment techniques; the pros and cons of different synthesis methods are analyzed. The report also presents the catalytic properties of bifunctional catalytic systems based on SAPO-11 and SAPO-41, including hierarchical structures, in C₁₆₊ n-paraffin hydroisomerization. Prospective uses of bifunctional catalytic systems based on SAPO-11 and SAPO-41 for hydroisomerization of base oils are described. Finally, the paper formulates the remaining fundamental problems of SAPO-11 and SAPO-41 synthesis, as well as the prospects for the utilization of these materials as components of high-performance catalysts in the oil refining and petrochemical industries.

The formation of silicoaluminophosphate gels using boehmite, Al isopropoxide, and di-n-propylamine as a template of silicoaluminophosphate gels as well as their subsequent crystallization into SAPO-11 molecular sieves was studied in detail using X-ray fluorescence spectroscopy (XRF), powder X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and N₂ adsorption–desorption methods. The effect of the chemical and phase composition of silicoaluminophosphate gels on the physicochemical properties of SAPO-11 molecular sieves was shown. The secondary structural units that the AEL lattice is composed of were found to be formed at the initial stage of preparation involving aluminum isopropoxide. Several approaches to control their morphology and secondary porous structure are also proposed.

The laws governing the crystallization of metakaolin to ultrafine zeolite Y in a sodium silicate solution have been studied. Using the resulting zeolite, kaolin, and the additive polyvinyl alcohol, procedures for synthesizing binder-free granular zeolites Y with different silica ratios and properties superior to the known counterparts have been developed.

The review presents an analysis of the distinctive features of the structure and synthesis of silicoaluminophosphate molecular sieves such as SAPO-11 and SAPO-41. Various crystallization types are described and compared, including dry-gel conversion (DGC), solvent-free crystallization, hydrothermal crystallization, solvothermal crystallization, and crystallization in ionic liquids. The crystallization mechanisms are discussed.