Abstract:
Processes for transitioning among polymerization catalyst systems, preferably catalyst systems that are incompatible with each other. In particular, the processes relate to transitioning from olefin polymerizations utilizing metallocene catalyst systems to olefin polymerizations utilizing traditional Ziegler-Natta catalyst systems.
Abstract:
This invention relates to processes for transitioning among polymerization catalyst systems, preferably catalyst systems, which are incompatible with each other. Particularly, the invention relates to processes for transitioning among olefin polymerization reactions utilizing Ziegler-Natta catalyst systems, metallocene catalyst systems and chromium-based catalyst systems.
Abstract:
Catalyst systems and methods for making and using the same are provided. The catalyst system can include a catalyst compound having (1) at least one cyclopentadienyl ligand and at least one heteroatom ligand; (2) two non-bridged cyclopentadienyl ligands; or (3) two or more heteroatom ligands. The catalyst system further comprise a support comprising fluorinated silica. The support may be essentially free of alumina. The catalyst system further comprises an aluminoxane, preferably methylaluminoxane, modified methylaluminoxane, or a combination thereof.
Abstract:
Catalysts and methods for making and using the same are provided. The method for fabricating a catalyst may includes contacting a supported catalyst with a monomer under conditions that reduce an overall charge of the catalyst to less than about 75% of an initial charge of the catalyst. A method for polymerization may include introducing a pre-polymerized catalyst and one or more olefins into a gas phase fluidized bed reactor, operating the reactor at conditions sufficient to produce a polyolefin, wherein the polymerization is carried out in the substantial absence of any continuity additives.
Abstract:
A continuous gas phase circulating bed reactor, including: a riser for contacting a catalyst and a first gas composition comprising an olefin to form a polyolefin under fast-fluidization regime or a dilute-phase pneumatic conveying regime conditions; a downer for contacting the catalyst and a second gas composition comprising an olefin to form additional polyolefin under fast fluidization regime or a dilute-phase pneumatic conveying regime conditions; and a transport section for conveying at least a portion of the catalyst, polyolefin, and additional polyolefin from the downer to the riser. Also disclosed is a polymerization process using such a circulating bed reactor.