Preparation Of Well-Dispersed Catalysits For Diesel Hydrodesulfurization By In-Situ Crystallization

Hydrodesulfurization is one of the most widely used processes that can handle FCC diesel with reasonable recovery of clean fractions and acceptable cost, in which activity of catalysts plays a crucial role in guaranteeing good performance. Several methods had been proposed to improve the activity of catalysts, among which the increase of active component’s dispersive was considered as an effective approach to improve the activity of catalysts.While y-Al2O3is playing an important role in modern hydrorefining industry for its suitable intrinsic acidities, mechanical properties, and pore size distribution, much attention is being paid to the development of novel preparation methods from γ-Al2O3. Although significant progress has been made on preparation methods, the preparation of well-dispersed NiO-MoO3desulfurization catalysts by calcination from LDHs(Layered Double Hydroxides)/γ-Al2O3composites, remains an untouched area, to which the present investigation is addressed.A series of TAMA (terephthalate)-Ni-Al-LDHs/γ-Al2O3composites were synthesized by in-situ crystallization. XRD analyses showed that the (003) peak of TAMA-Ni-Al-LDHs/y-Al2O3shifts to6.2°due to the introduction of TAMA. The influence of process factors including pH, crystallization time and crystallization temperature has also been studied. The recommended conditions are:pH=10-11for24h at55℃.A series of MMA (molybdate anion)-Ni-Al-LDHs/y-Al2O3composites were synthesized by ion-exchange from TAMA-Ni-Al-LDHs/γ-Al2O3. It also follows from the XRD analyses that the replacement of TAMA by MMA has little effect on the crystal structures.Well diesel desulfurization catalysts were made from MMA-Ni-Al-LDHs/γ-Al2O3by calcination, and their catalytic performance for hydrodesulfurization were assessed in a fixed-bed reactor. The desulfurization efficiency was95.3%for Shengli FCC diesel, and95.7%for Daqing FCC diesel.In this thesis it has been shown that composites with high area are obtained. Well-disperesed catalysts prepared by calcination show excellent desufurization properties for Shengli FCC diesel and Daing FCC diesel. The successful synthesis of MMA-Ni-Al-LDHs/y-Al2O3throws a light on the preparation of well-dispersed catalysts for diesel deep hydrodesulfurization.