| There is a great demand for the removal of N-containing compounds (NCCs) in liquid fuels. Adsorptive denitrogenation using solid materials from fuels are considered to be one of the most attractive and challenging alternative for its advantages such as it can be conducted under milder conditions and its lower cost. Metal-organic frameworks (MOFs) are crystalline solids with extended network structures. They are comprised by linking metal cations or metal clusters and organic ligands via coordinative bonds. These materials are well known for their high specific surface area, huge porosity and easy modification, giving rise to their wide applications including gas adsorption/storage, liquid phase separation of chemicals, drug delivery, magnetism, catalysis, luminescence, and so on. The relative works were carried out just under this background.The paper mainly includes two parts:1. The adsorptive denitrogenation over three metal-organic frameworks (MIL-96(Al), MIL-53(Al) and MIL-101(Cr)) from fuels was studied by batch adsorption experiments. The pseudo-second-order kinetic model and Langmuir equation can be used to describe kinetics and thermal dynamics of the adsorption process, respectively. The influence of aromatics and sulfides in the adsorptive denitrogenation process over MIL-101(Cr) was studied by the introduction of toluene and benzothiophene to the model fuel. The denitrogenation of commercial diesel and gasoline and the regeneration ability of MIL-101(Cr) were also performed. The experiment results show that metal-organic frameworks present a good performance in the adsorption of NCCs from the liquid fuel, especially for the MIL-101(Cr) that contains Lewis acid sites. The interaction between MIL-101(Cr) and the NCCs is mainly based on the acid-base interaction, which is proved by the kinetics and thermal dynamics of the adsorption process. Furthermore, pore size and shape play a big role in the adsorptions over MIL-53(Al) and MIL-96(Al). The thermodynamic functions show that the adsorption of NCCs over MIL-101(Cr) is a spontaneous, entropy decreased and exothermic process. Meanwhile, the adsorptions of basic NCCs (pyridine and quinoline) present higher absolute values of the enthalpy change than that of the neutral ones (pyrrole and indole). The introduction of toluene has a greater influence to the adsorption of quinoline than that of indole. The selectivity factors of quinoline and indole over benzothiophene are10.05and5.13when MIL-101(Cr) was used as adsorbent, respectively. More than85%of the total N-content can be removed from commercial diesel and gasoline using MIL-101(Cr) with an adsorbent dosage of20g/L at room temperature. The used adsorbent can be regenerated by washing it with ethanol.2. Sulfoacid functionalized MIL-101(Cr)(S-MIL-101(Cr)) can be obtained by the sulfonation reaction of MIL-101(Cr), triflic anhydride and sulfuric acid. Different amount of sulfonic groups on the framework can be obtained by changing the molar ratio of MIL-101(Cr), triflic anhydride and sulfuric acid. The sulfated samples were characterized by XRD, FT-IR, nitrogen physical adsorption/desorption and acid-base potentiometric titration. The adsorptive denitrogenation of model fuel by different S-MIL-101(Cr) samples was performed by batch adsorption experiments. The experiment results indicate that the S-MIL-101(Cr) can strengthen the interactions between the NCCs and the sulfated samples. The sample obtained by the reaction with a molar ratio of MIL-101(Cr):H2SO4:Tf2O=1:3:4.5has the largest adsorption capacities for quinoline and indole. When compared to the bare MIL-101(Cr). this material can enhance the maximum adsorption capacities (Qo) by12.2%and6.3%for quinoline and indole, respectively. |
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