# Transforming Petrochemical Processes: Cutting-Edge Advances in Kaolin Catalyst Fabrication
## 1 Introduction
However, its natural acidity and surface area are lower compared to smectites, palygorskite, and sepiolite, which is attributed to the limited substitution in the kaolin layer [12]. Consequently, enhancing the acidity of kaolin requires the incorporation of specific components into its structure [13]. Figure 1: Schematic structure of the kaolin minerals. Figure extracted from [PERSON] et al. (2023) [4]. Reproduced with the permission of Elsevier. Research indicates that acid-treated kaolin can improve catalytic efficacy, increase specific surface area, and introduce new acid sites on the surface of the material. This characteristic makes kaolin suitable for various chemical processes, such as enhancing the production of aromatic compounds and improving deoxidation activity [14; 15]. Moreover, kaolin has gained prominence in the petrochemical sector as a catalyst and precursor for many significant industrial processes [16]. As mentioned before, the modification of kaolin-introducing acid sites is a crucial methodology for its use in catalytic cracking reactions, in which kaolin-based catalysts are used to break down large hydrocarbon molecules into more valuable light olefins like ethylene and propylene. In the context of petrochemical applications, kaolin has been extensively studied for its role in producing zeolites and mesoporous materials. Zeolites synthesized from kaolin exhibit excellent thermal stability, acidity, and pore structure, making them effective catalysts for a wide range of chemical reactions. These properties are particularly beneficial in fluid catalytic cracking units, in which zeolite-based catalysts derived from kaolin help optimize the conversion of heavy crude oil into lighter, more valuable products [17]. Moreover, kaolin's ability to improve the mechanical strength and thermal stability of catalysts further underscores its importance in the petrochemical industry. The incorporation of kaolin into catalyst formulations enhances their resistance to sintering and deactivation, thereby extending the catalyst's operational life and efficiency. This durability is essential in high-temperature processes, such as hydrocracking and catalytic reforming, in which maintaining catalyst performance over prolonged periods is critical [18]. In addition to its catalytic applications, kaolin also plays a significant role in the production of proppants used in hydraulic fracturing [19; 20]. Proppants are materials injected into shale formations to keep the fractures open, allowing for the extraction of oil and gas. Kaolin-based proppants offer high strength and conductivity, ensuring efficient resource recovery and reducing the environmental impact of drilling operations. Recent research has also explored the potential of kaolin in environmental applications related to the petrochemical industry. Modified kaolin has been investigated for its capacity to adsorb and remove pollutants from wastewater, including heavy metals and organic contaminants [21; 22]. This application not only helps mitigate the environmental footprint of petrochemical processes but also contributes to sustainable industrial practices. As research and technology continue to advance, the significance of kaolin in the petrochemical sector is expected to grow, driving innovation and efficiency in this critical industry. Figure 2 shows a bibliometric analysis that highlights how interest in kaolin-based materials in general (columns), and kaolin applied in the catalysis field in particular (line), as a research topic has grown in recent years. Herein, a comprehensive overview of kaolin is provided, exploring the physicochemical properties of kaolin that make it suitable for catalysis in the petrochemical industry. The review comprises six sections, as follows: it begins with an introduction (Section 1), followed by a geological perspective on the classification of kaolin based on its origin in Section 2. Section 3 discusses worldwide kaolin clay production, demand patterns, and market trends.