Synthesis of novel hierarchically porous NiMo/ZSM-5-KIT-5 catalysts and their superior performance in hydrodenitrogenation of quinoline

Abstract

ZSM-5-KIT-5 (Zk) materials with different amounts of ZSM-5 emulsion were successfully synthesized by a nano self-assembly method, and were employed as supports to prepare hydrodenitrogenation catalysts. These supports and catalysts were characterized by a series of technical methods, including small and wide angle XRD, N₂ isothermal absorption–desorption, FT-IR, XPS, Raman and HRTEM. The characterization results of XRD and FT-IR demonstrated that the Zk materials possessed both a mesoporous structure and a MFI structure, indicating that ZSM-5 structure units were embedded into the framework of the KIT-5 material. With the usage of a ZSM-5 seed solution, the walls of the composite materials were gradually thickened, leading to slight decreases in the pore sizes, specific surface areas and volumes of the Zk materials. Furthermore, the addition of the ZSM-5 emulsion strengthened the acidic properties and produced more Brønsted acid sites. The performances of all the catalysts were evaluated for quinoline hydrodenitrogenation under the conditions of temperature ranging from 340–400 °C, a total of 4.0 MPa, a H₂/hydrocarbon ratio of 400 ml ml⁻¹ and a confined WHSV of 10 h⁻¹. Among all the catalysts, NiMo/Zk-3 showed the highest HDN efficiency (79.3%), the maximum k_HDN (3.47 × 10⁻⁴ mol g⁻¹ h⁻¹) and a high ratio of propylcyclohexane/propylbenzene (3.16), since it had open three dimensional channels (6.7 nm), a high specific surface area (393 m² g⁻¹) and volume (0.34 cm³ g⁻¹), the maximum degree of sulfidation (86.2%) and suitable stacking of MoS₂.