# 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
#### 7.4.4 Desulfurization  
Catalytic deslufurization processes are crucial in the petrochemical industry due to the stringent environmental regulations and the need for cleaner fuels [18; 239]. These processes primarily involve the removal of sulfur compounds from petroleum fractions, which helpsreduce sulfur dioxide emissions during fuel combustion, thus minimizing air pollution and acid rain. Desulfurization typically includes hydrodesulfurization (HDS), in which sulfur compounds are converted into hydrogen sulfide (H\({}_{2}\)S) using hydrogen gas in the presence of a catalyst. This reaction generally occurs at elevated temperatures and pressures. The effectiveness of this process largely depends on the catalyst used, with traditional catalysts being based on molybdenum or tungsten, often supported on alumina. Recent advancements have focused on the use of kaolin-based catalysts due to their unique properties and cost-effectiveness. Kaolin, which is a natural clay, can be transformed into various catalytic forms, including zeolites, which offer high surface areas, appropriate acidity, and thermal stability. Kaolin-based catalysts are particularly advantageous in desulfurization due to their abundant availability, low cost, and versatility in modification. Its properties are essential for effective desulfurization as they enhance the interaction between sulfur compounds and the catalyst, leading to more efficient sulfur removal. They can be engineered to exhibit specific pore structures and acid sites, optimizing their performance for different desulfurization reactions. This adaptability not only improves the desulfurization efficiency but also extends the catalyst's lifespan and reduces operational costs. Various studies have explored the effectiveness of kaolin-based catalysts in desulfurization processes, highlighting their advantages and potential industrial applications. The first approach involved the synthesis of a ZSM-5, kaolin, and silica catalyst for the dehydro-sulfidation of gasoline [240]. This catalyst demonstrated a higher selectivity for converting ethyl mercaptan (EM) over n-octane, without the need for hydrogen addition, indicating its efficiency in EM conversion with an activation energy of 46.66 kJ/mol. Additionally, the catalytic EM dehydrodisulfidation led to higher EM conversions than n-octane, with product species identified during thermal experiments suggesting both intramolecular and intermolecular dehydrodisulfidation pathways. Further advancements were made with the synthesis of a multi-pore zeolite beta (MB) from kaolin, which served as a support for NiW catalysts in diesel hydrodesulfurization (HDS) [241]. The NiW/TiO\({}_{2}\)-Al\({}_{2}\)O\({}_{3}\)-MB catalyst achieved an impressive HDS conversion of 99.3%, compared to 97.5% for NiW/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\). This improvement was attributed to the optimal balance of Bronsted and Lewis acids and increased hydrogenation activity, with the incorporation of TiO\({}_{2}\) enhancing the catalytic performance further. In 2012, a study by [PERSON] et al. [242] developed a kaolin/Cu\({}_{2}\)O photocatalyst for photochemical oxidation extraction desulfurization of model fuel. The catalyst achieved a desulfurization rate of over 97% under optimal conditions, which included a 20% kaolin load ratio, 2 h reaction time, and 150 mL-min-1 oxygen volume. This demonstrated the effectiveness of combining photocatalysis with liquid-liquid extraction for sulfur removal. A notable development in 2020 by [PERSON] et al. [243] involved the preparation of a mesoporous kaolin carrier, which significantly increased its surface area from 16.6 m\({}^{2}\)/g to 303.4 m\({}^{2}\)/g. The resulting V\({}_{2}\)O\({}_{5}\)/mesoporous kaolin catalyst achieved nearly complete oxidative degradation of dibenzothiophene within 10 min. This rapid and efficient sulfur removal was due to the synergistic effects of mesoporous kaolin and well-dispersed V\({}_{2}\)O\({}_{5}\) nanoparticles, exposing more V\({}^{5+}\)/V\({}^{4+}\) Lewis acid sites.