| The supercritical impregnation process is innovative and promising technology to produce composite micro-particles, which is used to produce supported metallocene catalyst selecting polycarbonate (PC) as carrier, titanocene dichloride (Cp2TiCl2) as catalyst, and SC-CO2 as solute in this article.Metallocene catalysts have a great deal of advantages, such as high activity, narrow molecular weight distribution, and the outstanding catalytic capacity of copolymerization. Except these advantages, there are still several problems, such as the difficulty in controlling polymer morphology with soluble homogeneous catalysts, the inability to be used in continuous slurry and fluidized-bed gas-phase processes, significant reactor fouling, and the very large amount of MAO needed to achieve maximum metallocene catalytic activity, are needed to be solved if metallocene catalysts would be used widely in industry. Although immobilizing metallocene complexes on an inorganic support can solve these problems to a certain extent, the surface properties of supports strongly influence the behavior of its supporting catalysts, and immobilization often depresses catalyst activities at some extent. Moreover, the carriers influence the processing properties of polymer for their containment in polymer as additional ash. Recently, metallocenes with organic or polymer materials as the carrier, are of great interests in industry and academic research, because polymer-supported metallocenes can offer the following advantages: easy preparation and low cost; preserving fairly high activity and the features such as single-site, narrow co-monomer and molecular-weight distribution, and high ability to incorporate co-monomers with unsupported metallocenes; lower inorganic residues in polymer products in comparison with inorganic supports such as SiO2, Al2O3, MgCl2; capacity of controlling the morphology of the polymer to reduce the possibility of reactor fouling, and the adaptation to slurry and gas phase process.Firstly, the solubility of PC in chloroform and the mixture of chloroform and ethanol were measured respectively, which are necessary for explaining the possibility of making PC micro-particles using liquid anti-solvent crystallization. The mean particle diameter of PC micro-particles prepared is ranged between 266~712 nm under different conditions with narrow particle size distributions. BET analysis shows that PC micro-particles preparedhave specific surface area of 36~51 m2/g.The effect of feed rate, concentration of solution, temperature, etc on PC micro-particle size were investigated in experiments and it was found that increasing in feed rate; controlling volume ratio of solution to anti-solvent and solution concentration to a certain extent; and decreasing in the crystallization temperature could reduce the size of PC micro-particles.Then, Combining the supercritical fluid technology with conventional impregnation to make the supported metallocene catalyst, because supercritical fluid has some unique characteristics, such as the solve power large changed along with temperature and pressure small change; the sudden depressurization causing the dissolved matter to precipitate completely and the supercritical fluid turned to gas and get lost immediately; making the polymer swell etc. Through the characterizations of the transmission electronic microscope (TEM), scanning electronic microscope (SEM), the electron diffraction analysis and energy dispersive X-ray spectrometry (EDS), it is evident that the processed PC micro-particles are coated with nano Cp2TiCl2 and the carrier PC taking the role of dispersing and sustaining the catalyst micro-particles. There is no extra chemical bond existing comparing the FTIR spectra of the supported metallocene catalyst with the unprocessed catalyst and carrier.Afterward, ethylene slurry polymerization was catalyzed by the obtained Cp2TiCl2-PC, which showed a highly active catalyst for polymerization, producing polyethylene with activity of 105~106 g/(molTihr). The influence of the...
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