Silicoaluminophosphate Molecular Sieves SAPO-11 and SAPO-41: Synthesis, Properties, and Applications for Hydroisomerization of C16+ n-Paraffins. Part 2: Current State of Research on Methods to Control the Crystal Morphology, Dispersion, Acidic Properties, Secondary Porous Structure, and Catalytic Properties of SAPO-11 and SAPO-41 in Hydroisomerization of C16+ n-Paraffins (A Review)

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.