# 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
#### 7.4.6. Isomerization  
Catalytic isomerization is a vital process in the petrochemical industry that is essential for converting linear hydrocarbons into branched isomers, thereby improving the octane rating of gasoline. This process addresses the demand for high-performance fuels by preventing engine knocking and enhancing fuel efficiency. The isomerization reaction typically involves the rearrangement of straight-chain alkanes, such as normal butane (n-C4H10) and normal pentane (n-C5H12), into their branched counterparts, isobutane (i-C4H10) and isopentane (i-C5H12), which possess higher octane numbers [161]. This transformation is crucial for producing high-octane gasoline, which is essential for the efficient operation of modern internal combustion engines [251]. In the petrochemical industry, the importance of isomerization extends beyond gasoline production. It also plays a role in the production of high-quality jet fuels and lubricants. The ability to tailor the properties of hydrocarbons through isomerization is crucial for meeting specific performance standards and regulatory requirements. This process usually takes place in the presence of hydrogen to suppress coke formation and enhance catalyst longevity. The reaction conditions typically involve moderate temperatures and pressures, with hydrogen acting as a protective agent for the catalyst. Catalysts play a fundamental role in isomerization processes. Commonly used catalysts include bifunctional materials that contain both acidic and metallic sites [252]. Platinum (Pt) or palladium (Pd) dispersed on acidic supports, such as zeolites or chlorinated alumina, are frequently employed [253]. The acidic sites facilitate the protonation of alkanes, leading to carbocation intermediates, while the metallic sites aid in hydrogenation and dehydrogenation steps, ensuring the overall stability of the reaction. The isomerization mechanism involves several steps, as follows [254]:  
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2. Protonation of alkanes: The acidic sites of the catalyst protonate the alkane, forming a carbocation. 3. Carbocation rearrangement: The carbocation undergoes a rearrangement to form a more stable, branched isomer. 4. Deprotonation: The branched carbocation is deprotonated to yield the branched alkane. 5. Hydrogenation/Dehydrogenation: Metallic sites facilitate the addition or removal of hydrogen atoms, stabilizing the reaction intermediates and products. The use of kaolin-based catalysts in isomerization offers several advantages, such as cost-effectiveness, environmental sustainability, and enhanced performance, since modifications, such as acid treatment and metal impregnation, can significantly boost the catalytic activity and selectivity of kaolin-based catalysts. Several studies have explored the use of kaolin-based catalysts for isomerization, revealing significant advancements in catalyst preparation and performance. In 2007, [PERSON] et al. [255] investigated the preparation of solid acid catalysts from metakaolin. By treating natural kaolin at high temperatures to produce metakaolin and subsequently acid-treating it, the authors obtained materials with distinct catalytic properties. The acid-treated metakaolin, particularly the sample treated at 850 \({}^{\circ}\)C (MK8), exhibited a high surface area and density of acid sites, making it highly effective for the isomerization of 1-butene. This study highlighted the potential of metakaolin as catalyst support with tailored acidity and porosity for isomerization reactions. Building on this foundation, [PERSON] et al. (2018) [256] synthesized Pt-containing catalysts using halloysite aluminosilicate nanotubes (multilayer aluminosilicate nanotubes formed by rolling kaolin layers) and ZSM-5 zeolite. These catalysts were evaluated for xylene isomerization under elevated hydrogen pressure.