Synthesis And Characterization Of Pillared Interlayer Compounds And Their Applications In Diesel Deep Hydrodesulfurization

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. Co-Mo, Ni-Mo and Ni-W are generally used as the active components in hydrodesulfurization catalysts. Therefore, development of novel preparation methods and novel supports are the focus of the present investigations.While y-A12O3is 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-MoO3desulfurization 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/y-Al2O3composites are synthesized by in-situ crystallization using ammonia as the precipitator. On the basis of this, a series of Mo7O246"-Ni-Al-LDHs/y-Al2O3composites were synthesized by ion-exchange from TAMA-Ni-Al-LDHs/y-Al2O3and NiO-MoO3/y-Al2O3catalysts are prepared by the subsequent calcination. The content of NiO (above10%) indicated that ammonia is not an appropriate precipitator for the preparation of NiO-MoO3/y-Al2O3catalysts.Because urea hydrolysis occurs and releases OH" at temperature higher than60℃. This process makes the mixing and the reaction of urea with Ni2+in the solution separate as well as controllable, finally leading to the controllable precipitation of Ni species on the support. Just with this idea, urea was employed as the precipitator to synthesize TAMA-Ni-Al-LDHs/y-Al2O3composites by in-situ crystallization. The results of N2adsorption indicate that the surface area of TAMA-Ni-Al-LDHs/y-Al2O3composites is305m2/g, much higher than that of y-Al2O3(250m2/g), and the pore volume of the composite (0.71cm3/g) was higher than that of y-Al2O3(0.5cm3/g). The influence of process factors including pH, crystallization time and crystallization temperature has also been studied. The recommended conditions are as follows:crystallization temperature is80℃for more than18h,[urea]/[Ni2+]=3, and [NH4NH3]/[Ni2+]≥1. A series of Mo7O246--Ni-Al-LDHs/γ-Al2O3composites are synthesized by ion-exchange from TAMA-Ni-Al-LDHs/γ-Al2O3composites. NiO-MoO3/y-Al2O3catalysts are prepared by calcinations of Mo7O246--Ni-Al-LDHs/y-Al2O3. SEM images showed that the active components are well dispersed on the carriers and the clusters of NiO-MoO3are separated by y-Al2O3. Moreover, many "rim-edge" active phases are present on the catalysts. The catalytic performance of this catalyst for hydrodesulfurization is assessed in a fixed-bed reactor for828h. The result shows that the desulfurization percentage maintains at99.5%.In this thesis it has been shown that Mo7O246"-Ni-Al-LDHs/γ-Al2O3composites are obtained using urea as the precipitator. Well-disperesed catalysts prepared by the subsequent calcination showed excellent desufurization properties for Dagang FCC diesel. This result throws a light on the industrial preparation and application of NiO-MoO3catalysts for diesel deep hydrodesulfurization.