(446d) Mesoporous Zeolites Produced By Solid Crystallization and Their Hydrogenation Properties

Hydrogenation of aromatics is one of the most important unit operations in modern oil-refinery and coal liquefaction industries. The produced cycloalkane can significantly increase the cetane number of fuel, improve its combustion performance, and enhance its thermal stability even in some critical environments. Some recent studies found that when supported on acidic materials such as USY or Beta zeolites, noble metal catalyst such as platinum (Pt) showed much improved catalytic activity and sulfur tolerance in deep hydrogenation of aromatics. However, the sole microporosity of these zeolites often makes these reactions less effective when bulky aromatic hydrocarbons such as naphthalene (a major compound of light cycle oil or coal tar) are involved due to the significant mass transfer limitation.

Here we investigate the naphthalene hydrogenation performance over platinum loaded on new mesoporous zeolites (Meso-ZSM-5). A new solid-state crystallization approach is developed to synthesize mesoporous zeolites at ambient pressure without addition of water or other solvents. The adjacent nanocrystals are packed and eventually joined into a large monolithic zeolite, creating many regular inter-lattice space to serve as mesoporous pathways for better mass transport and acidic site utilization. The hydrogenation was performed between 150-280°C with a hydrogen pressure of 2-8 MPa. Compared to the hydrogenation over Pt/microporous ZSM-5 and Pt/Al2O3, Pt/Meso-ZSM-5 shows better conversion and high selectivity in the absence and presence of dibenzothiophene (DBT). It excellent catalytic performance and sulfur tolerance is further tailored with the acidity and mesoporous structure of Meso-ZSM-5.