19-03-2020 дата публикации
Номер: US20200087430A1
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Catalyst preparation systems and methods for preparing reduced chromium catalysts are disclosed, and can comprise irradiating a supported chromium catalyst containing hexavalent chromium with a light beam having a wavelength within the UV-visible light spectrum. Such reduced chromium catalysts have improved catalytic activity compared to chromium catalysts reduced by other means. The use of the reduced chromium catalyst in polymerization reactor systems and olefin polymerization processes also is disclosed, resulting in polymers with a higher melt index. 1. A method for reducing a chromium catalyst for olefin polymerization , the method comprising:irradiating a reductant comprising a C—H bond and a supported chromium catalyst comprising chromium in the hexavalent oxidation state with a light beam at a wavelength in the UV-visible spectrum to reduce at least a portion of the supported chromium catalyst to form a reduced chromium catalyst.2. The method of claim 1 , wherein:the reductant comprises ethylene, 1-butene, 1-hexene, 1-octene, methane, ethane, propane, isobutane, n-pentane, isopentane, n-hexane, tetrafluoroethane, cyclohexane, adamantane, decalin, benzene, toluene, or any combination thereof; andthe supported chromium catalyst comprises a solid oxide selected from silica, alumina, silica-alumina, silica-coated alumina, aluminum phosphate, aluminophosphate, heteropolytungstate, titania, zirconia, magnesia, boria, zinc oxide, silica-titania, silica-zirconia, alumina-titania, alumina-zirconia, zinc-aluminate, alumina-boria, silica-boria, aluminophosphate-silica, titania-zirconia, or any combination thereof.3. The method of claim 1 , wherein the supported chromium catalyst comprises chromium/silica claim 1 , chromium/silica-titania claim 1 , chromium/silica-titania-magnesia claim 1 , chromium/silica-alumina claim 1 , chromium/silica-coated alumina claim 1 , chromium/aluminophosphate claim 1 , or any combination thereof.4. The method of claim 1 , wherein the ...
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