The invention relates to power cable polymer composition which comprises a thermoplastic polyethylene having a chlorine content which is less than X, wherein X is 10 ppm, a power cable, for example, a high voltage direct current (HV DC), a power cable polymer insulation, use of a polymer composition for producing a layer of a power cable, and a process for producing a power cable.

Supported chromium catalysts containing a solid oxide and 0.1 to 15 wt. % chromium, in which the solid oxide or the supported chromium catalyst has a particle size span from 0.5 to 1.4, less than 3 wt. % has a particle size greater than 100 μm, and less than 10 wt. % has a particle size less than 10 μm, can be contacted with an olefin monomer in a loop slurry reactor to produce an olefin polymer. Representative ethylene-based polymers produced using the chromium catalysts have a HLMI of 4 to 70 g/10 min, a density from 0.93 to 0.96 g/cm.sup.3, from 150 to 680 ppm solid oxide (such as silica), from 1.5 to 6.8 ppm chromium, and a film gel count of less than 15 catalyst particle gels per ft.sup.2 of 25 micron thick film and/or a gel count of less than or equal to 50 catalyst particles of greater than 100 μm per five grams of the ethylene polymer.

A bimodal polymer composition comprising a lower molecular weight homopolymer and a higher molecular weight copolymer wherein the bimodal polymer composition has a density of from about 0.930 gram per cubic centimeter (g/cc) to about 0.970 g/cc, a ratio of high load melt index:melt index of from about 10 to about 150 and an Environmental Stress Crack Resistance (ESCR) of from about 25 hours to about 300 hours when measured in accordance with ASTM D1693 or ASTM D2561. A chromium-catalyzed polymer composition comprising (i) a lower molecular weight homopolymer and (ii) a higher molecular weight copolymer, wherein the bimodal polymer composition has an Environmental Stress Crack Resistance (ESCR) of from about 25 hours to about 300 hours when measured in accordance with ASTM D1693 or ASTM D2561.

A bimodal polymer composition comprising a lower molecular weight homopolymer and a higher molecular weight copolymer wherein the bimodal polymer composition has a density of from about 0.930 gram per cubic centimeter (g/cc) to about 0.970 g/cc, a ratio of high load melt index:melt index of from about 10 to about 150 and an Environmental Stress Crack Resistance (ESCR) of from about 25 hours to about 300 hours when measured in accordance with ASTM D1693 or ASTM D2561. A chromium-catalyzed polymer composition comprising (i) a lower molecular weight homopolymer and (ii) a higher molecular weight copolymer, wherein the bimodal polymer composition has an Environmental Stress Crack Resistance (ESCR) of from about 25 hours to about 300 hours when measured in accordance with ASTM D1693 or ASTM D2561.

Disclosed herein is a method of preparing 1-octene at high activity and high selectivity while stably maintaining reaction activity by tetramerizing ethylene using a chromium-based catalyst system comprising a transition metal or a transition metal precursor, a cocatalyst, and a P—C—C—P backbone structure ligand represented by (R.sup.1)(R.sup.2)P—(R.sup.5)CHCH(R.sup.6)—P(R.sup.3)(R.sup.4).

A supported three-center catalyst, a preparation method and the use are provided. The catalyst comprises a porous inorganic carrier, an organic chromium active component, an inorganic chromium active component and an inorganic vanadium active component, and may further comprise a catalyst modifying component. A method involves, by means of one or more steps of dipping and drying or dipping, drying and high-temperature roasting procedures, respectively converting an organic chromium source, a chromium source, a vanadium source and a Q component into an organic chromium active component precursor, an inorganic chromium active component precursor, an inorganic vanadium active component precursor and a catalyst modifying component that are supported on the surface of the porous inorganic carrier, and then activating same with an organometallic cocatalyst or a polymerization monomer, so as to obtain the supported three-center catalyst.

A supported three-center catalyst, a preparation method and the use are provided. The catalyst comprises a porous inorganic carrier, an organic chromium active component, an inorganic chromium active component and an inorganic vanadium active component, and may further comprise a catalyst modifying component. A method involves, by means of one or more steps of dipping and drying or dipping, drying and high-temperature roasting procedures, respectively converting an organic chromium source, a chromium source, a vanadium source and a Q component into an organic chromium active component precursor, an inorganic chromium active component precursor, an inorganic vanadium active component precursor and a catalyst modifying component that are supported on the surface of the porous inorganic carrier, and then activating same with an organometallic cocatalyst or a polymerization monomer, so as to obtain the supported three-center catalyst.

A supported three-center catalyst, a preparation method and the use are provided. The catalyst comprises a porous inorganic carrier, an organic chromium active component, an inorganic chromium active component and an inorganic vanadium active component, and may further comprise a catalyst modifying component. A method involves, by means of one or more steps of dipping and drying or dipping, drying and high-temperature roasting procedures, respectively converting an organic chromium source, a chromium source, a vanadium source and a Q component into an organic chromium active component precursor, an inorganic chromium active component precursor, an inorganic vanadium active component precursor and a catalyst modifying component that are supported on the surface of the porous inorganic carrier, and then activating same with an organometallic cocatalyst or a polymerization monomer, so as to obtain the supported three-center catalyst.

Modified chromium-based catalyst compositions for olefin polymerization are disclosed. The modifiers prevent or reduce catalyst particle aggregation providing improved catalyst particle dispersion and consistent flow index response of the compositions in olefin polymerization.

Modified chromium-based catalyst compositions for olefin polymerization are disclosed. The modifiers prevent or reduce catalyst particle aggregation providing improved catalyst particle dispersion and consistent flow index response of the compositions in olefin polymerization.