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Amphiphilic magnetic nano-materials preparation and application of

Author: CuiXinAi
Tutor: HuDaoDao
School: Shaanxi Normal University
Course: Chemical processes
Keywords: ultra-deep desulfurization biphase catalytic oxidation magnetic silica naonoparticles polyoxometates
CLC: TB383.1
Type: Master's thesis
Year: 2008
Downloads: 225
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Abstract


Recently,the study of biphasic catalysis has attracted wide interest.Although different biphasic catalyses have been widely studied,it is still important to construct universal method for biphasic catalysis in that the systems of biphasic catalysis reactions possess certain differences and extensive application.A new protocol was proposed to construct a structural microreactor used in ultra-deep desulfurization of fuel oil by H2O2 oxidation,which is based on:(1)ultra-deep desulfurization of fuel oil by H2O2 oxidation is a typical biphasic catalysis;(2)ultra-deep desulfurization was requested internationally extensively because of environmental protection purposes;(3)using H2O2 as oxidiant in ultra-deep desulfurization of fuel oil was widely focused on.The purpose of constructing of the structural microreactor is to overcome some defects in biphasic catalysis.The structural microreactor can overcome the difficulties in the process of separation and recovery of the catalysts of the emulsion-based biphasic catalysis.To achieve the goal,two novel composite microspheres were synthesized by ion exchange reaction between H3PW12O40 and two hydrophobic quaternary ammonium groups loaded on the MSN.According to the objects above mentioned,the main contents of this research include two aspects are as follows:1.PWO/AEM/MSN and PWO/AcrH+/MSN composite microspheres were prepared using the magnetic silica nanoparticles(MSN) as the carrier.(1)Magnetic silica nanospheres were synthesized by a water-in-oil microemulsion technique(toluene/H2O/CTAB).Fe2+and Fe3+ with NH3·H2O co-precipitate inside the emulsion droplets gave magnetite precipitates.The TEOS was added slowly to the mixture,again under a nitrogen atmosphere.Follow that the catalyzed hydrolysis/condensation of the TEOS at the water/oil interface was happened because of the high pH.The morphology and composition of MSN were characterized by the HR-TEM,EDX,XRD and VSM,respectively.It was demonstrated that the magnetic silica nanoparticles possess a core-shell structure with the core of magnetite Fe3O4 phase and a shell of silica.The global Particles obtained had diameters about 40 nm.The synthesized iron oxide nanoparticles display strong magnetization,high specific surface area,and desirable superparamagnetic properties which are essential as the prime criterion as a magnetic carrier.(2)PWO/AEM/MSN and PWO/AcrH+/MSN composite microreactors were prepared by following method.Firstly,using post-synthetic grafting method to covalenfly link organosilane species with surface silanol groups,two different hydrophobic quaternary ammoniums were immobilized onto MSN surface.We obtained AEM/MSN and AcrH+/MSN.Secondly, PWO/AEM/MSN and PWO/AcrH+/MSN were constructed by ion-exchange between quaternary ammoniums loaded on the surface of MSN and H3PW12O40.The morphologies and compositions of the two microreactors were characterized by Optical Contact Angle Measuring Device,Scanning Electron Microscopy(SEM),EDX,Thermogravimetric Analysis(TGA),Fouier Transform Infrared Spectroscopy(FT-IR),respectively.The results indicate that phosphotungstic acid had been immobilized on MSN surface successfully through two prepared process.And we can tailor the surface hydrophobic/hydrophilic properties and PWO content of two composite microreactors via adjusting the density of the immobilized quaternary ammoniums.2.For a model reaction run,dibenzothiophene(DBT) was dissolved in decahydronaphthalene. 30%H2O2 as oxidant and PWO/AEM/MSN or PWO/AcrH+/MSN two composite microspheres as catalyst,the DBT was oxidated into the corresponding sulfone.Then the mixture was extracted by acetonitrile and water.In the system using PWO/AEM/MSN as microreactor,according to difference between dosages of AEM mobilized on composite material(PWO/AEM/MSN),two methods were used to introduce H2O2 onto the surface of magnetic microreactors.The results indicate that the composite material used as microreactor has excellent performences in ultra-deep desulfurization,whatever method was used.In the system using PWO/AcrH+/MSN as microreactor,the results indicate that the microreactor is efficient on DBT oxidation.Meanwhile,the microreactors were recycled under a magnetic field but no organic solvent involved.From above results,the microreactors constructed meet the purpose proposed.

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