# Transforming Petrochemical Processes: Cutting-Edge Advances in Kaolin Catalyst Fabrication
## 7 Kaolin in Petrochemical Catalysis: From Fundamentals to Innovations
### Kaolin-Driven Catalysis in Petrochemical Processes
#### 7.4.3 Methanol-to-Olefin (MTO) Catalytic Reaction for Olefin Production
In the same year, other work [220] demonstrated the synthesis of macroporous SAPO-34 microspheres (MAMISAPO-34) using 2 \(\upmu\)m polystyrene spheres as a template. These microspheres, which were formed by mixing cubic SAPO-34 with kaolin, silica sol, and aluminum phosphate sol, were spray-dried and then treated hydrothermally and calcined. Compared to non-macroporous SAPO-34 (NOMISAPO-34), MAMISAPO-34 had higher crystallinity and stronger acid sites. In methanol-to-olefin (MTO) reactions, MAMISAPO-34 exhibited better catalytic performance due to its greater crystallinity. Years later, [PERSON] et al. [221] used \(\upbeta\)-cyclodextrintrin (\(\upbeta\)-CD) as a crystal growth inhibitor during the synthesis of SAPO-34 from metakaolin, leading to smaller crystal sizes and better silicon dispersion. The catalyst with \(\upbeta\)-CD showed a significantly extended active period in MTO reactions, remaining active for 610 min, compared to 280 min for the sample synthesized without \(\upbeta\)-CD, indicating enhanced catalytic performance and prolonged lifetime. Several authors have studied the synthesis of hierarchical mesoporous SAPOs with mild acidity to solve the problem of rapid deactivation [222, 223]. Then, [PERSON] et al. [224] reported a novel strategy that involved synthesizing hierarchical SAPO-34@kaolin composites by thermally treating kaolin microspheres and rearranging the active silicon and aluminum species with an external phosphorus source. This method, which was co-templated by CTAB and TPOAC, produced SAPO-34 with a small crystal size and hierarchical micro mesoporous structure. The resultant composites exhibited a 20% increase in selectivity to ethylene and propylene and a remarkably prolonged catalyst lifespan, from 50 to 200 min, in MTO reactions. In another approach, a low-cost and efficient MTO catalyst was synthesized via dry gel conversion (DGC) using TEAOH as the structure-directing agent and TEA and H\({}_{2}\)O vapors [225]. The process yielded nano-SAPO-34 with good pore connectivity and high activity. The prepared microsphere catalysts showed a 14% extension in catalyst lifetime and a 1.55% increase in selectivity for C\({}_{2}\) and C\({}_{3}\) olefins, which are suitable for industrial applications due to their slow carbon deposition rate and high activity utilization ratio. Over the following 5 years, [PERSON] and colleagues have progressively refined the synthesis and characterization of SAPO-34 catalysts for the methanol-to-olefins (MTO) reaction, focusing on enhancing their physicochemical properties, catalytic performance, and mechanical strength. In their initial research, [PERSON] et al. investigated the impact of various ion exchange methods on the assembly of nanostructured kaolin-SAPO-34 catalysts using silica sol as a binder [226]. These catalysts, which were prepared by spray drying, exhibited typical SAPO-34 and kaolinite phases. It was found that using resin as an ion exchange agent resulted in smoother and larger particles. The optimized catalyst demonstrated excellent activity, maintaining nearly 22 h of activity during MTO reactions in a fluidized bed reactor. In subsequent work, the team focused on preparing fluidizable catalysts suitable for fluidized bed reactors by treating kaolin with inorganic acids to enhance its activity [227]. The acid-treated kaolin increased the intensity of acid sites, improving the conversion of methanol to light olefins and reducing the induction period. However, higher reaction rates in the fluidized bed led to faster deactivation due to uniform coke formation. Further studies examined the performance of SAPO-34 catalysts with different particle sizes prepared via spray drying [228]. The smallest particle size resulted in larger and more spherical particles with rapid product diffusion, reducing the formation of heavier byproducts. The optimal catalyst maintained activity for nearly 5 h in a fluidized bed reactor and exhibited lower coking rates and longer lifetimes. Exploring spray drying methods, [PERSON] et al.