W.R. Grace & Co.-Conn.

A gas-phase polymerization process is disclosed for producing polypropylene random copolymers with excellent reactor operability and/or particle morphology. The polypropylene random copolymer is produced while maintaining the partial pressure of the propylene monomer within controlled limits based upon the amount of comonomer present and the operating temperature.

A Ziegler-Natta catalyst composition is disclosed. The catalyst composition is formed from a procatalyst containing a magnesium moiety and a titanium moiety. At least one internal electron donor is incorporated into the procatalyst. During a titanation procedure in conjunction with the internal electron donor, a titanium extractant is used to remove or deactivate low activity or atactic titanium active sites.

A gas-phase process for producing a polypropylene random copolymer in a fluidized bed reactor is provided. The process comprises feeding a fluidizing medium into a reactor vessel containing a bed of catalytically active polyolefin particles. In one embodiment, the fluidizing medium comprises propylene gas, C2 and/or C4-C8 α-olefin comonomers, hydrogen, and an inert gas. The momentum flux of the fluidizing medium, defined as is 7.0 N/m 2 or greater and the condensing level of the reactor cycle gas when entering the reactor is less than 25 wt. %. In the above equation, ρ g is the density of the fluidizing medium and SGV is the superficial gas velocity of the fluidizing medium. ( SGV [ m s ] ) 2 * ρ g [ kg m 3 ]

Olefin catalyst systems comprising silica supports are provided. For example, in one embodiment, the olefin polymerization catalyst system comprises a silica support, a catalyst precursor compound, and an activator. The silica support comprises a plurality of silica gel particles. Each particle comprises a rigid network of amorphous silica. The particles are spherical, single gel particles that have an average aspect ratio of about 1.2 or less, an average pore volume of from about 1.4 ml/g to about 3 ml/g, an average surface area from about 200 m2/g to about 950 m 2 /g, and a median particle size from about 4 μm to about 100 μm.

A process of preparing a solid catalyst component for the production of polypropylene includes a) dissolving a halide-containing magnesium compound in a mixture, the mixture including an epoxy compound, an organic phosphorus compound, and a hydrocarbon solvent to form a homogenous solution; b) treating the homogenous solution with an organosilicon compound during or after the dissolving step; c) treating the homogenous solution with a first titanium compound in the presence of a first non-phthalate electron donor, and an organosilicon compound, to form a solid precipitate; and d) treating the solid precipitate with a second titanium compound in the presence of a second non-phthalate electron donor to form the solid catalyst component, where the process is free of carboxylic acids and anhydrides.

A process for increasing a settled bulk density of a granular polyolefin polymer includes feeding a catalyst stream into a gas phase polymerization reactor, the catalyst stream comprising catalyst particles, optionally in slurry form by suspending in a mineral oil and/or other hydrocarbon liquid, contained in a carrier fluid; feeding a support gas into the gas phase polymerization reactor together with the catalyst stream entering the reactor, the support gas being fed into the gas phase reactor at a velocity; forming polyolefin particles in the gas phase polymerization reactor through contact with the catalyst particles and a monomer and optionally one or more comonomers; and determining a settled bulk density of the granular polyolefin particles, and, based on the settled bulk density, selectively increasing or decreasing the velocity of the support gas in order to maintain the settled bulk density above a preset limit.

A process of producing a spherical catalyst component for use in producing polyolefin polymers includes dissolving a magnesium halide compound in a solvent to form a homogeneous solution, the solvent comprising an alcohol; and treating the homogeneous solution with a titanium compound in the presence of a surfactant, a supportive electron donor, and an internal electron donor to form a solid catalyst component comprising a magnesium halide compound base incorporating a titanium unit, the supportive electron donor, and the internal electron donor; wherein the catalyst component comprises particles having a substantially spherical shape and a D 50 from about 3 μm to about 150 μm.

Catalyst systems for polymerization of mixtures comprising an olefin include a selectivity control agent comprising at least one silicon-containing compound containing at least one C1-C10 alkoxy group bonded to a silicon atom and an amount of one or more agent compounds. The agent compound comprises C2-C13 mono- or polycarboxylic esters of aliphatic C2-C7 carboxylic acids and inertly substituted derivatives thereof. One or more polymerization catalysts may also be present. A polymerization process includes contacting an olefin or a mixture of the olefin and one or more copolymerizable comonomers under polymerization conditions with the catalyst composition.

Disclosed are catalyst compositions having an internal electron donor which includes a 3,6-di-substituted-1,2-phenylene aromatic diester. Ziegler-Natta catalyst compositions containing the present catalyst compositions exhibit very high hydrogen response, high activity, high selectivity and produce propylene-based olefins with high melt flow rate.

A Ziegler-Natta catalyst composition is disclosed. The catalyst composition includes an internal electron donor with improved polymerization kinetics, a long lifetime, improved stereoselectivity and/or improved hydrogen response.