The Preparation And Characterization Of Composite Microspheres Of Core-shell Structures With Potential Catalytic Oxidation

Abstract: Recently, the study of design and application about microreactor are more and more. The characteristic of microreactor that chemical reaction is restricted in micro-/nano-size space makes it have extensive application, especially in liquid/liquid biphasic catalytic reaction, it will have important application perspective. At the same time, much attention has been focused on the environmental problems. Very stringent environmental regulations limit the sulfur levels in fuel oils (Sulfur-free gasoline will be forced to be put into use all over the European Union by 2011). However, it is very difficult to decrease the sulfur content from several thousands ppm to a few ppm with traditional strategies. A lot of new desulfurization methods appeared one after the other, such as adsorption, extraction, oxidation and bioprocesses. Selective catalytic oxidation combined with extraction is one of the most promising ultra-deep desulfurization methods and one of the typical biphasic catalytic reactions. So, it is necessary to construct new biphasic catalysic microreaction.The main advantage of composite materials prepared using polymeric microgel as microreactor is that employing the effect of space confinement of template and regulation can easily control the hybridization between template and precursor in size as well as the surface morphology of composite microspheres. According to the essential theory of H₂O₂ catalytic oxidation deep dusulfurization, this research mainly focuses on the preparation and characterization of microreactor with activity of potential catalytic oxidation. Based on the idea mentioned above, the research in this thesis includes the following three parts.(1) A novel polymeric microgels with core-shell structure or like-beehive sructure of P(AM-MAA-VP) were successfully prepared via reversible suspended polymerization using N-vinyl-2-pyrrolidinone (VP), acrylamide (AM) and methacrylic acid (MAA) as monomers, N, N'-methylenebisacrylamide (BA) as cross-linker, ammonium persulfate (APS) as initiator, N, N, N', N'-tetramethylethylenediamine (TMEDA) as promoter. The morphology and structure of polymer microgels were characterized by SEM, EDX and FT-IR. We studied in detail the effect of VP, BA, APS, TMEDA on the morphology and structure ofmicrogel.(2) The P(AM-MAA-VP)/SiO₂ composite microspheres with core-shell structure were prepared via nanosilica sol absorbed by the microgels, electrostatic interaction between SiO₂ nanoparticles and the positively modified microgels and in-situ deposition at gas-solid interface, respectively. The morphology and structure of composite microspheres were characterized by SEM, TEM and FT-IR. The crystal structure and element composition were characterized by XRD and EDX. The experimental results indicate that the morphological and structural difference of the composite microspheres prepared by the three methods are mainly that the difference of nanosilica size and deformation of composite microspheres. This difference is explained by the difference of swelling behavior of template microspheres via different method and the difference of formation mechanism of silica. Additionally, these methods have use for reference meaning for expected composite materials via changing template composition and precursor.(3) Using P(AM-MAA-VP)/SiO₂ as templates, the P(AM-MAA-VP)/SiO₂/AEM amphiphilic composite microspheres were obtained via restricted in-situ deposition AEM on microsphere surface. The loading quality of AEM and the surface morphology of composite microspheres were effectively controlled by regulating dosage of AEM, vapour pressure and template morphology and so on.P(AM-MAA-VP)/SiO₂/AEM/W₂ composite microreactors with potential catalytic activity were obtained via ions exchange between Cl^- of P(AM-MAA-VP)/SiO₂/AEM microsphere surface and [{W(=O)(O₂)₂(H₂O)}₂(μ-o)]^2-. The loading quality of catalysis and surface morphology of composite microspheres were effectively controlleded by adjusting the dosage and adding manner of K₂ [{W(=O)(O₂)₂(H₂O)}₂(μ-o)]·2H₂O. It was demonstrated that the loading quality of catalysis increased with increasing the dosage of K₂[{W(=O)(O₂)₂(H₂O)}₂(μ-o)]·2H₂O; but if the dosage of K₂[{W(=O)(O₂)₂ (H₂O)}₂(μ-o)]·2H₂O was too much, the loading quality of catalysis decreased. This kind of structural multifunction microsphere materials has universial use for reference for biphasic catalytic reaction.