Solid Phase Transfer Catalyst Magnetic Nanometer Micro Reactor Building And Its Desulfurization

Recenly, to design new heterogeneous catalysts for diphase catalytic reaction became the research hotspot of the catalytic field. To prepare the immobilized-type phase transfer catalyst by immobilizing traditional phase transfer catalysts on the carrier is one of the important methods of preparation of heterogeneous catalysts. For an optimal heterogeneous catalytic material, first, it should have good mass transfer characteristics. Second, it should have suitable spacial domains to favor contact between reactants and catalytic active moieties. Third, it should possess an ability to be easily separated from reaction mixtures. The research of heterogeneous catalyst has not only important theoretical value, but also great significance for solving practical probles. Today, deep desulfurization of fuel oil has become a hotspot. Using hydrogen peroxide as an oxidant in the diphase catalytic system for deep desulfurization is considered to be the most promising desulfurization method. For preliminary studies of our group found that the larger-scale micro-reactor is not conducive to mass transfer. The stability and the uniformity of catalyst is not good. As the continuous part of previous work, a new method was proposed to prepare nano-magnetic micro-reactor immobilizing phosphotungstic acid (PTA)/quaternary ammonium salt (QAS) phase transfer on magnetic particles, aimed at solving the problem above. The research laid a foundation for designing high efficiency and easy seperation of heterogeneous catalysts.Based on the purpose above, three aspects are concluded in the thesis as follow:1. Preparation and characterization of magnetic silica nanoparticles (MSN). In a reverse microemulsion system, co-precipitation of Fe2+and Fe3+with ammonia in microemulsion droplets generated Fe3O4.The hydrolysis and condensation of TEOS then got the SiO2coating in the outer layer of the magnetic particles. The nanoparticle was characterized by TEM, XRD, EDX, FT-IR, VSM, respectively. The results show that the nanoparticles have a core/shell structure and the diameter is-20nm, with a uniform particle size, a large specific surface area and strong superparamagnetic.2. Preparation and characterization of MSN/QAS/PTA. The3-chloropropyl triethoxysilane (CPS) was immobilized on MSN surface by hydrolysis and condensation, N, N-dimethyl amine wih different chain length were introduced to MSN surface by Hoffman alkylation reaction, then PTA anion was immobilized on the surface by ion exchange. The prepared materials was charactered by TEM, EDX, TGA-DSC, FT-IR, VSM, optical video contact angle measurement, elemental analyze, XPS, respectively. The results showed that PTA/QAS has been immobilized on MSN surface sucessfully, the difference of chain length and the amount of CPS both had influence of surface properties on the nanoparticle.3. The catalytic performance study of MSN/QAS/PTA in deep desulfurization reaction. MSN/QAS/PTA was used as the catalyst, hydrogen peroxide as the oxidant, decalin/dibenzothiophene (DBT) solution as the fuel. GC-FID was used to detect the sulfur content. The results showed that:the catalyst had a higher catalytic efficiency and it can be seperated by the external magnetic field; the catalyst could be reused several times with constantly hith catalytic efficiency, and it could extract the polar reaction products out of the system; MSN/QAS/PTA with moderate chain length of QAS (12C), the suitable amount catalyst loadings, the quaternization reaction remperature, the method of H2O2introduced into the system, and the suitable amount of H2O2all had a large influence on the desulfurization efficiency.A new method had been proposed to construct the paramagnetic nanoparticle with phase transfer catalysis. This preparation protocol allows to easy control the modification reactions and the length of alkyl chain in tertiary amines. According to this protocol, the surface nature of this kind of catalytic nanoparticles is easily adjusted. The prepared nanoparticles with phase transfer catalysis and the paramagnetic function allow not only the high catalytic activity in the oxidation of DBT to corresponding sulfones by hydrogen peroxide but also the easy separation of the nanoparticles from medium by external magnetism. Additionally, the prepared nanoparticles can be reused for several times with almost constant activity. The preparation of the material may be significant to design catalytic materials used in oil/water diphase catalysis.