Synthesis And Performance Study Of MIL-101Materials

Metal-organic frameworks are composed of secondary structural units formedby inorganic metal ions, and organic ligands, usually in the form of nitrogen orcarboxylic acid. They form three-dimensional network structures through strongchemical bond. MIL-101materials, especially the stability of MIL-101(Cr),possessing huge specific surface area, large window size, large pore volume andpore size, have been widely researched.Friedel-Crafts alkylation reaction is an important reaction in pharmaceuticalindustry and chemical industry. Traditional Friedel-Crafts alkylation reactioncatalysts are a series of homogeneous catalysts, like FeCl3, ZnCl2, anhydrous AlCl3,and H2SO4. The use of these homogeneous catalysts has many shortcomings, such asthe difficulty of separation of the catalysts from the reaction systerm, therebylimiting the reuse ability of the catalysts; catalysts going into the environment,leading to environmental pollution; catalysts having certain acidity, resulting in thecorrosion of equipment; the use of AlCl3requiring harsh reaction conditions,involving in high operating costs. So we need to find heterogeneous catalysts thatare environmentally friendly and have high catalytic activity.For the reaction of the benzylation of trimethylbenzene by benzyl chloride,MIL-101(Fe) showed excellent catalytic activity. The conversation of benzylchloride reached100%within5minutes. But MIL–101(Fe) was not stable, part ofthe structure collapsing after reaction, due to water vapor and HCl generated in thereaction system, so the reuse ability of the material was limited. MIL-101(Cr)showed no catalytic activity due to lack of active catalytic species.Aluminum-containing MIL-101(Cr) materials showed no catalytic activity due tothe active catalytic sites occupied by water molecules or other species.Iron-containing MIL-101(Cr)(Fe/MIL-101(Cr)) prepared by impregnationmethod, showed excellent catalytic activity for the reaction of the benzylation oftrimethylbenzene by benzyl chloride. The Fe/MIL-101(Cr) materials areheterogeneous catalysts, and the catalytic activity basically remained unchangedwith a small amount of water in the reaction system. The Fe/MIL-101(Cr) materialscan also be reused at least five times without decrease in catalytic activity, having acertain industrial application prospect.This paper made a preliminary study on using materials based on MIL-101(Cr)in adsorption desulfurization and oxidation desulfurization. We prepared a series ofMIL-101(Cr) containing Fe3+, Cu2+, and CuO by impregnation method. They were used in adsorption removal of dibenzothiophene (DBT) dissolved in model oil.Because the acidity of Lewis acid sites in the catalysts don’t match with thealkalinity of sulfur compounds, the adsorption effect was not ideal. In addition,TiO2-containing MIL-101was also prepared by impregnation method to be used inoxidative desulfurization of DBT. Due to the weak catalytic activity of amorphousTiO2, the effect was weak.