In-Situ Preparation And Characterization Of NiO-WO₃/γ-Al₂O₃Composites

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. Development of novel preparation methods and novel supports are the focus of the present investigations.While γ-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 y-Al2O3. Although significant progress has been made on preparation methods, the preparation of well-dispersed NiO-WO3desulfurization catalysts by calcination from LDHs(Layered Double Hydroxides)/y-Al2O3composites, remains an untouched area, to which the present investigation is addressed.In the present investigation, a series of LDHS/γ-Al2O3composites are synthesized by in-situ crystallization using urea as the precipitator. On the basis of this, a series of PW12O40-Ni-Al-LDHs/y-Al2O3composites were synthesized by ion-exchange from TAMA-Ni-Al-LDHs/y-Al2O3and NiO-WO3/γ-Al2O3composites are prepared by the subsequent calcination.In order to improve the content of WO3, We calcine TAMA-Ni-Al-LDHs/γ-Al2O3as carrier, NiO-WO3/γ-Al2O3composites are prepared by isopyknic impregnation. The results of SEM indicate that NiO-WO3/y-Al2O3disperse well. The results of N2adsorption indicate that the surface area of NiO-WO3/y-A12O3composites is226.1m2/g, and the pore volume of the composite is0.408cm3/g, the average diameter is6.523nm. The pore volume and the average diameter are lowwer than y-Al2O3, the surface area is larger than y-Al2O3.Because TAMA can’t be exchanged easily from the interlayers of LDHs, another composites N03--Ni-Al-LDHs/y-Al2O3were synthesized using ammonium as the precipitator. On the basis of this, a series of PW12O4O3--Ni-Al-LDHs/y-Al2O3composites were synthesized by ion-exchange, and NiO-WO3/γ-Al2O3catalysts are prepared by the subsequent calcination. The results of N2adsorption indicate that the surface area of NiO-WO3/y-Al2O3composites is214.4m2/g, and the pore volume of the composite is0.373cm3/g, the average diameter is6.587nm.In this thesis it has been shown that N03--Ni-Al-LDHs/y-Al203composites are obtained using ammonium as the precipitator. Well-disperesed NiO-WO3/y-Al2O3composites were prepared by the subsequent calcination. The content of WO3is high and adjustable through the process of ion-exchange. This result throws a light on the industrial preparation diesel deep hydrodesulfurization catalysts.