# 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)
A patent reported by [PERSON] [174] employing similar technology necessitates the use of both metakaolin and high-temperature-calcined kaolin, along with seeds, to achieve crystallinities approaching 60% within the microsphere. By adjusting the crystallization time and the clay-type ratio, the extent of crystal formation can be modulated. Regardless of the specific conditions, the unconverted portion of the microsphere serves as a stable matrix that binds the zeolite and aids in cracking molecules that are too large to enter the zeolite supercage. Zeolite Y synthesis can also begin with the acid treatment of metakaolin to remove alumina [175]. After removing enough alumina, the kaolin is combined with a caustic solution, left to age, and then crystallized to form pure zeolite Y crystals. The aluminum removal is crucial to achieving the appropriate soda-silica-alumina ratio necessary for zeolite Y formation. The calcination of kaolin to metakaolin is essential to activate the alumina within the clay. The calcination temperature and the quality and consistency of the clay source are critical factors. However, this method is not currently used in commercial practice. In 2007, [PERSON] et al. [171] dealuminated metakaolin with an inorganic acid to synthesize X zeolite, increasing the Si/Al ratio to the desired value without using sodium silicate, as reported by [PERSON] et al. They achieved 57% faujasite zeolite, consisting of 34% X zeolite and 23% Y zeolite. This result is attributed to the similar synthesis conditions for both zeolites, such as the Si/Al ratio, the pH value, aging, the reaction temperature, and time. However, longer aging periods have been shown to increase the purity and crystallinity of Y zeolite. [PERSON] et al. [176] explained that a higher percentage of Y zeolite could be achieved with extended aging periods, suggesting that [PERSON] et al. could have generated a higher yield if they had increased the aging time. Recently, [PERSON] et al. [177] synthesized NaY zeolite from potassium-rich Nigerian kaolinite clay, focusing on the effects of the metakaolinization temperature and aging on potassium's role in zeolitization. Optimal conditions included calcination at 900 \({}^{\circ}\)C for 6 h, followed by aging for 8 days and synthesis at 95 \({}^{\circ}\)C for 72 h. Potassium was found to hinder NaY formation, affecting nucleation, crystal morphology, and stability. The NaY zeolite produced had a cubic shape, an ion exchange capacity of 4.72-4.94 meq/g, and a specific surface area of 672 m\({}^{2}\)/g, maintaining stability up to 600 \({}^{\circ}\)C. This indicates that potassium's presence significantly impacts the synthesis and quality of NaY zeolite. Based on that, the most important mineral currently used in the manufacture of carriers for FCC catalysts is kaolin. Kaolin's largest use is in catalyst substrates for the catalytic cracking of petroleum. Because many catalysts are used at high temperatures and pressures, the refractory character of kaolin is appropriate for these applications. The purity of kaolin is critical in petroleum cracking operations, thus a processed kaolin with low levels of iron, titanium, alkali, and alkaline earth compounds is preferred [6]. Kaolin's conversion to a zeolite in the preparation of cracking catalyst supports increases the surface area of the catalyst exposed in the reaction, enhancing its effectiveness. The low cost, high purity, and platelet shape of kaolin promote the formation of good pore structures, ease of acid leaching, and ease of conversion to zeolite [162]. The transformation of kaolin to zeolite not only augments the catalytic activity but also improves the mechanical strength and thermal stability of the catalysts, which are essential properties for enduring the rigorous conditions of FCC units.