Immobilization Of Ionic Liquids - Tungstate Peroxide Catalysts In Sulfide Oxidation Reactions

Study of sulfide oxidation reaction is attracting more and more attention.On the one hand, sulfoxide and sulfone, the products of sulfide oxidation, are important bioactive molecules.A lot of medicine, pesticides and other fine chemicals contained the basic structure of sulfoxide and sulfone. Sulfoxide and sulfone also are the key intermediates for construction of C-C bonds and have broad application in the synthesis of functional materials and in various molecular rearrangements. On the other hand, sulfide exists widely in diesel oil, petrol oil and some other kinds of fuel oil. It is the most main source of sulfur in fuel oil. The high-temperature combustion of fuel oil generates the SOx, leading to the acid rain and acid fog with causing harm to humans and environment pollution. The sulfur-containing compounds existing in fuel oil are oxidized into highly polar sulfone which can be removed via extracting by the polar solvent methanol, then the low sulfur content fuel oil is obtained, and this method is the oxidative desulfurization technology. Compared with other desulfurization technologies, the oxidative desulfurization is the most potential technique with the advantages of low cost and simple operation, and it has become an international research hotspot.Currently, a large number of volatile organic solvents, chemical oxidants and noble metal catalysts used in the chemical reactions polluted the environment seriously. Therefore, in the process of chemical reaction, the development of milder and cleaner technology has become the chemical workers’working emphasis. In sulfide oxidation reaction, H2O2as "green" oxidant receives much concern both at home and abroad. However, for most catalyst/H2O2systems which have been applied to sulfide oxidation reaction, they haven’t a simple way to synthesis the catalyst and suffer from the catalysts’high price and high toxicity. They also are on the defects of low selectivity and activity, and have the problem of appearance of sulfones in the synthesis of sulfoxide. When the peroxotungstate complexes were used as catalysts, the system of peroxotungstate and H2O2shows ideal activity in oxidation reaction. Morever, the peroxotungstate complexes possesses the features of cheap and low toxicity. But it is unease to realize the peroxotungstate catalysts’ recovery and reuse. Thus, it has been a focal of study to search for the catalytic oxidation systems which combine the advantages of high activity and high selectivity, so that the target product can be obtained in high yield.Herein, encouraged by our previous research, we synthesized two kinds of heterogeneous catalysts by exchanging with anion of ionic liquid in this work. One is a catalyst of peroxotungstate held in a ionic liquid(IL) brush (SiO2-BisILsC9H17[W2O3(O2)4]), another one is phosphotungstic acid held in a ionic liquid(IL) brush(Si02-BisILsC8H17[PW12O40]). Then, the catalysts were applied to sulfides oxidation reaction and oxidation desulfurition. The overview of this work with three respects is shown as follows:Part1:Summary of the research background and recent situation of sulfides oxidation reaction and oxidation desulfurition. First, summary the recent and important catalytic systems of metal and nonmetal using hydrogen peroxide as oxidant in sulfides oxidation reaction. Second, introduce the recent and important oxidation desulfurition projects which using hydrogen peroxide as oxidant.Part2:SiO2-BisILsC8H17[W2O3(O2)4] was synthesized using cheap silica as support, which was studied as catalyst in the selective oxidation of sulfides to sulfoxides or sulfones in neat water at room temperature. Using methyl phenyl sulfide as a prototypical reaction to optimize the reaction conditions, including the dosage of hydrogen peroxid and the catalyst. The experimental results show that when the ratio of catalyst, H2O2, and sulfide was1.5:120:100, sulfides were selectively converted to sulfoxides. When the ratio of catalyst, H2O2, and sulfide was2:280:100, sulfides were selectively converted to sulfone. Under the optimum conditions, the other9kinds of sulfides were easily and selectively converted to sulfoxides or sulfones in high yield. In the reactions, the catalyst has high efficiency and outstanding recyclability, and can be simplly isolated from product.Part3:SiO2-BisILsC8H17[PW12O40] was synthesized, which was studied as catalyst in the oxidation desulfurition reaction. Using hydrogen peroxide as oxidant, methanol as extractant, series factors which effect the extractve and oxidative desulfurization reactivity were investigated systematically, including the dosage of hydrogen peroxid and the catalyst, reaction temperature, the dosage and species of extractant and the amount of catalyst. Under the optimized conditions:10mL model fuel(sulfur content=1000vg/g approximately),1mL methanol, n(H2O2)/n(BT)=10, n(BT)/n(Catalyst)=2.5, reaction temperature=70℃, the desulfurization ratio by GC analysis reached100%for10h. Under the same conditions except reaction temperature and time, DBT in the model fuel can be removed completely for4h at50℃. In the reactions, the catalyst has high efficiency and outstanding recyclability with a greater ease of separation. We also brought forward a simple, convenient and green craft for the oxidative desulfurization technique.In summary, this thesis developed two environmentally-friendly methodologies of reactions, which are simple, efficient, easy isolation to get products with recyclable and cheap catalyst. Both of them use non-toxic and cheap hydrogen peroxide as oxidant. So, they have the advantages of safety and environmental protection. Especially for the synthesis of sulfoxides and sulfones, it is a "real" on-water procedure avoiding the use of any organic co-solvent or addictive. Thus it is in the requirements of green chemistry.