Study On Olefin Polymerization Catalyzed By Zirconocene And Composite Support Ziegler-Natta Catalysts

The composition and structure of catalysts for olefin polymerization have large influence on the olefin polymerization behavior, and the morphology and structure of the resultant polyolefin. It is of great practical value and important theoretical significance to study the olefin polymerization behavior and the properties of the polyolefin prepared with special structural catalysts.In this paper, mesoporous molecular sieves (MCM-41 and SBA-15) with different pore diameters were synthesized by hydrothermal crystallization. Ethylene polymerization was carried out with MCM-41 or SBA-15 supported Cp₂ZrCl₂ catalysts under atmospheric pressure. The effects of pore diameter of molecular sieve on polymerization behavior, crystal property and morphology of the resultant polyethylene had been investigated. The results showed that the supported catalysts had high activity and the resultant polyethylene had nano-fiber morphology when the pore diameter of molecular sieve was 2.90nm and 5.64nm. The diameter of the nano-fibers increased with the increase of the pore diameter of the support. On the other hand, the resultant polyethylene had nano-sheet morphology when the pore diameter of molecular sieve was 1.4nm. Moreover, the results of DSC showed that the melting point of the polyethylene prepared with MCM-41 (d=2.90nm) supported catalyst was higher than that of the polyethylene prepared with SBA-15 (d=5.64nm) supported catalyst, which indicated that the pore diameter of the support could affect the extend of the polyethylene chains and obtain polyethylene with different crystallinity.In this paper, TiCl₄/MCM-41 catalytic system was prepared for ethylene polymerization. The influence of polymerization conditions on the morphology and crystal properties of the resultant polyethylene had been investigated. The results showed that the polyethylene prepared with TiCl₄/MCM-41 mainly had approximate spherical morphology in short polymerization time. But, with the increase of polymerization time, the nano-fibre could be obtained and the resultant polyethylene had high melting point. When the active sites on the exterior surface of MCM-41 were destroyed by the additional β-cyclodextrin, the nano-channels of MCM-41 could serve as nano-extruder and the polyethylene could be extruded from the channels to obtain nano-polyethylene fibres.Carbon nanotubes (CNTs) is a new kind of nano-materials with one-dimensional structure. In this work, ethylene polymerization was carried out with CNTs and open-end CNTs supported Cp₂ZrCl₂, respectively. The influence of polymerization conditions and the structure of CMTs on the ethylene polymerization behaviour and morphology of the resultant PE were investigated. The results showed that the CNTs-supported Cp₂ZrCl₂ had high polymerization activity. At T=50°C and [Al][Zr]=1000, the resultant polyethylene could enwrap on the surface of CNTs to obtain polyethylene fibres. But, with the increase of PE on the surface of CNTs, the fibres morphology disappeared and the resultant polyethylene presented floccules. However, the open-ended CNTs-supported catalyst had low polymerization activity and stable polymerization kinetics, andthe resultant polyethylene had sheet morphology.In this paper, propylene polymerization was carried out with MCM-41-supported rac-Et(Ind)₂ZrCl₂. The resultant polypropylene was characterized by the techniques of DSC and ¹³C-NMR. The results showed that the resultant PP had high melting point, high isotacticity and low crystallinity. Moreover, the PP in the channels of MCM-41 was uncrystalline and no melting peak existed in the curve of DSC. These results indicated that the channels of MCM-41 could not only make the PP chains extruded out of the channels arrangement regularly to obtain perfect crystal, but also prevented the crystal of the PP in the channels of MCM-41. However, in the presence of β-cyclodextrin, the morphology of the resultant PP is similar to the support of MCM-41. Moreover, the resultant PP had similar melting point to the PP prepared with the supported catalyst in the absence of β-cyclodextrin. But, the crystalinity of the PP prepared with the the supported catalyst in the presence of β-cyclodextrin decreased distinctly. The results indicated that the channels of MCM-41 could act as nano-reactor in propylene polymerization and the polypropylene extruded out of the channels could form perfect crystal.In this paper, (2-Ph-Ind)₂ZrCl₂ was synthesized and characterized. Propylene polymerization was carried out with the catalyst in the presence and absence of additional magnetic field. The results of ¹³C-NMR showed that the isotactic pentad content [mmmm] of the resultant polypropylene decreased in the presence of the magnetic field. But, the additional magnetic field had little effect on the propylene polymerization behavior and polymerization kinetics. According to the results of ¹³C-NMR and the chains propagation mechanism of the catalyst, we proposed a chain propagation model. After simulating the pentad intensities of the resultant polypropylene using the proposed model, it was found that the calculated results from the model could account for the experimental data very well.Low isotactic polypropylene was a new kind of polyolefin material, which had widely application in many fields. However, the polymerization activity of the traditional Z-N catalyst was low for synthesizing polypropylene. In this paper, one-pot ball-milling method was used to prepare the MnCl₂ (or AlCl₃) /MgCl₂ supported Z-N catalyst. The influences of polymerization conditions on polymerization activities had been investigated. The results showed that the best polymerization conditions were: MnCl₂/MgCl₂=0.05, Ti-loading amount=1 .2wt% , [Al]/[Ti]=40 and T=30℃. The maximal polymerization activity was 8500gPP/gTi.h. Furthermore, it was found that when AlCl₃/MgCl₂=0.1, Ti-loading amount= 1.2wt%, [Al]/[Ti]=60 and T= 30℃, the maximal polymerization activity could reach to 14000gPP/gTi.h. The installation for synthesizing polypropylene was designed and installed for industrial production.