Design and Application of Industrial Catalysts for Hydrocracking of PAHs: Catalytic Technology and Metal–Acid Intimacy

The NiMo/(alumina + zeolite Y) bifunctional catalysts have been industrially used in the hydrocracking processes of heavy oil. However, constructing an effective catalyst based on the current industrial process by truly controlling the proximity between metal and acid sites for selective ring-opening of polycyclic aromatic hydrocarbons (PAHs) remains highly challenging because high-loaded non-noble metals, such as NiMo, are used in industrial catalysts. In this paper, four series of catalysts (NiMo/A+Y-SM ( Cat micro ), NiMo/A+Y ( Cat nano-1 ), NiMo/(A+Y) ( Cat nano-2 ), and NiMo/Y+A-SM ( Cat atom )) were designed with distinguishable proximities (micrometer, nanometer, and atomic levels) between the non-noble NiMo metals and acid sites for exploring the effect of proximity between the non-noble metals NiMo and acid sites on the selective ring-opening of PAHs in the hydrocracking of tetralin and hydrotreated light cycle oil (HDT-LCO). As a result, the proximity at a micrometer scale of Cat micro, despite having the highest concentration of strong Brønsted acid sites (BAS) and superior hydrogenation capability, exhibits the lowest catalytic activity and yield of benzene, toluene, and xylene (BTX), because the excessive separation distance between the two types of active sites causes the metal and acid sites to function independently in hydrocracking. Conversely, the catalytic performance of Cat atom and Cat nano-2 catalysts is inferior to that of Cat nano-1 . The Cat nano-1 with enhanced metal dispersion and increased BAS density is advantageous for further cracking of intermediates by the Haag–Dessau nonclassical cracking, leading to higher activity and BTX yield, as well as achieving effective collaboration between metal and acid sites in the tetralin hydrocracking. Moreover, Cat nano-1 also demonstrated excellent catalytic performance in realistic HDT-LCO hydrocracking using an industrial pilot installation. This study provides a practical basis for the preparation of highly effective industrial hydrocracking catalysts.