Synthesis And Oxidative Desulfurization Performance Of Titanium Modified MIL-101(Cr) Structural Materials

MIL-101?Cr?,as a member of metal-organic framework materials?MOFs?,has attracted wide attention from researchers because of its large specific surface area,abundant pore structure and coordination of unsaturated metal centers.At present,the synthesis of the material is mainly carried out under the conditions of adding a solvent and HF,which inevitably brings about problems such as large amount of waste liquid,low utilization rate of the reactor,unfriendly environment,and high cost.Therefore,the synthesis of MIL-101?Cr?without solvent and HF conditions is expected,but previous studies have found that the organic ligands in MIL-101?Cr?synthesized under these conditions are easily nitrated,resulting in The material obtained is actually nitro-functionalized MIL-101?Cr?.Therefore,how to inhibit the nitrification of the ligand during the synthesis of MIL-101?Cr?under non-solvent conditions is a problem.In addition,oxidative desulfurization of fuel is regarded as one of the most promising deep desulfurization technologies.When MIL-101?Cr?structural material is used as an oxidative desulfurization catalyst,its catalytic efficiency is low due to lack of active sites.Aiming at the above problems,this thesis explored the method of inhibiting ligand nitration in the synthesis of MIL-101?Cr?under non-solvent conditions,and studied the oxidative desulfurization performance of titanium modified MIL-101?Cr?structural materials.The main contents are as follows:First,the nitration of the ligand was inhibited by adding chromium chloride as a common chromium source and pre-treating the precursor of the chromium source in the MIL-101?Cr?synthesis process under non-solvent conditions.Under this synthetic system,the effects of parameters such as pretreatment temperature,crystallization temperature and chromium chloride addition on the synthetic materials were investigated systematically.The experimental results showed that the ratio of chromium to ligand was 1.5,chromium nitrate and chlorination.The molar ratio of chromium is1:4,the pretreatment temperature is 130?,and the crystallization at 220?for 4 h can successfully inhibit the nitration of the ligand.The BET specific surface area?3109m²/g?and pore volume?1.86 cm³/g?of the obtained product,close to MIL-101?Cr?made by the conventional method..Secondly,in order to solve the problem of lack of oxidative desulfurization active sites in MIL-101?Cr?structural materials,titanium modification was prepared by introducing the titanium active center into the structure of MIL-101?Cr?by direct method and post-grafting method.MIL-101?Cr?structural material.The results show that the titanium-modified MIL-101?Cr?structural material synthesized by post-grafting method exhibits excellent oxidative desulfurization performance.With H₂O₂ as oxidant,the simulated oil can be used in the reaction time of 40 min at room temperature.The benzothiophene?DBT?is removed to more than 99%,and accordingly,the sulfur content in the simulated oil is reduced from 1000 ppm to less than 10 ppm.In addition,the regeneration of the MIL-101?Cr?structural material after titanium modification may be studied due to the fact that the product sulfone compound has strong polarity and the recycling ability of the catalyst is significantly reduced.And vacuum heat activation is an effective catalyst regeneration method,and the catalyst regenerated by this method can be recycled and maintain good catalytic oxidative desulfurization performance.