# 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
#### 7.4.1 Fluid Catalytic Cracking (FCC)
Additionally, due to environmental regulations, the crystalline silica content in kaolin has become an important consideration, despite its typically low concentration in the clay. Minimizing crystalline silica presence is now more critical than ever due to recent regulatory changes. Advancements in this field were addressed, since the enhancement of FCC catalysts with modified kaolinite introduces porosity into the catalyst structure, which can significantly improve cracking activity, leading to the production of high-octane gasoline and increased yields of lower olefins such as butylene and propylene [181]. [PERSON] et al. developed a novel porous mullite through the calcination of kaolinite at 1200 \({}^{\circ}\)C [174]. Their findings indicated that the synthesized mullite exhibited resistance to attrition due to the formation of strong inter-crystalline bonds. The mullite was impregnated with chloroplatinic acid using the incipient wetness method, and the resulting catalyst was employed in FCC units for CO oxidation. Regarding binder based on kaolin materials, it is worth mentioning that the in situ type of FCC catalyst preparation, as introduced by [PERSON] [182], eliminates the need for an added binder. The process begins by forming kaolin microspheres. Initially, these clay particles exhibit weak binding after spray drying, leading to breakdown if slurried in water. However, high-temperature calcination significantly enhances their attrition resistance and maintains their microspherical shape. This is crucial for the subsequent in situ crystallization step in a caustic solution, which further hardens the microspheres and facilitates the formation of intrastructural NaY zeolite. The high-temperature environment promotes the reaction of surface hydroxyls on the clay platelets, eliminating water and creating oxygen-bridged bonds between particles. During crystallization, substantial silica removal from the particles results in macropores that are subsequently filled by growing intrastructural zeolite, yielding significant porosity in the 30 to 100 A range. The remaining matrix, now richer in alumina due to silica removal, exhibits notable acidity and high surface area, making it an effective matrix for bottom cracking. However, the large surface area and exposure to contaminant metals within the clay can lead to increased coke and gas production. Retaining some silica, as suggested by [PERSON] [170], mitigates this undesired activity by reducing the overall surface area. Recent advancements involving metakaolin and seed technology have further decreased porosity and surface area, thereby enhancing the catalyst's performance [183]. Subsequent studies introduced by [PERSON] et al. showed the preparation of phosphorus-modified kaolinite blended with ZSM-5 zeolites [184]. This catalyst blend, containing 40 wt% ZSM-5 and approximately 2.3-2.5 wt% phosphorus, demonstrated good attrition resistance and was utilized in the cracking of Joliet sour heavy gas oil in a fixed-fluidized bed unit. The blend showed a marked improvement in the yields of butylene and propylene compared to the base catalyst, corroborating findings from earlier studies [185]. In the last two decades, FCC catalysts synthesized from kaolin-derived zeolites have been extensively studied due to their potential to enhance catalytic activity, selectivity, and resistance to deactivation [186]. Below, a summary will present key findings from various studies conducted between 2001 and 2023, highlighting the advancements in FCC catalyst performance attributed to different synthesis and modification techniques of kaolin-based zeolites. Initially, [PERSON] et al. developed the synthesis and characterization of zeolite-containing microspheres and FCC catalysts based on Ukrainian kaolin, revealing that variations in synthesis conditions notably affect the micro- and mesoporous of the samples [187]. This work established that the sodium cations in the zeolite act as weak Lewis acid sites, impacting ammonia retention and thus influencing catalytic activity.