A process for preparing ethylene polymers including the step of polymerizing ethylene or copolymerizing ethylene and one or more comonomers at a temperature from 100° C. to 350° C. and a pressure of from 110 MPa to 350 MPa in a continuously operated tubular polymerization reactor, thereby yielding a reaction mixture, wherein the tubular polymerization reactor has a reactor cooling jacket for removing the heat of the reaction and a pressure control valve, the reaction mixture leaves the reactor through the pressure control valve, the reaction mixture then passes a post-reactor cooler equipped with a post-reactor cooling jacket, the reactor cooling jacket is provided with a reactor coolant having an inlet temperature and the post-reactor cooling jacket is provided with a post-reactor coolant having an inlet temperature, and the inlet temperature of the post-reactor coolant is independently controlled from the inlet temperature of the reactant coolant.

A process for preparing ethylene polymers including the step of polymerizing ethylene or copolymerizing ethylene and one or more comonomers at a temperature from 100° C. to 350° C. and a pressure of from 110 MPa to 350 MPa in a continuously operated tubular polymerization reactor, thereby yielding a reaction mixture, wherein the tubular polymerization reactor has a reactor cooling jacket for removing the heat of the reaction and a pressure control valve, the reaction mixture leaves the reactor through the pressure control valve, the reaction mixture then passes a post-reactor cooler equipped with a post-reactor cooling jacket, the reactor cooling jacket is provided with a reactor coolant having an inlet temperature and the post-reactor cooling jacket is provided with a post-reactor coolant having an inlet temperature, and the inlet temperature of the post-reactor coolant is independently controlled from the inlet temperature of the reactant coolant.

A process for preparing ethylene polymers including the step of polymerizing ethylene or copolymerizing ethylene and one or more comonomers at a temperature from 100° C. to 350° C. and a pressure of from 110 MPa to 350 MPa in a continuously operated tubular polymerization reactor, thereby yielding a reaction mixture, wherein the tubular polymerization reactor has a reactor cooling jacket for removing the heat of the reaction and a pressure control valve, the reaction mixture leaves the reactor through the pressure control valve, the reaction mixture then passes a post-reactor cooler equipped with a post-reactor cooling jacket, the reactor cooling jacket is provided with a reactor coolant having an inlet temperature and the post-reactor cooling jacket is provided with a post-reactor coolant having an inlet temperature, and the inlet temperature of the post-reactor coolant is independently controlled from the inlet temperature of the reactant coolant.

Embodiments of a method for reducing unreacted ethylene monomer in a low density polyethylene (LDPE) polymerization process comprises: delivering a monomer feedstock comprising ethylene monomer to a compressor system to produce a pressurized feedstock having a pressure of at least 2000 bar; passing the pressurized feedstock to at least one free radical polymerization reactor to produce a reactor effluent comprising the LDPE and unreacted ethylene monomer; and delivering the reactor effluent to a separation system comprising a first separation vessel, a second separation vessel, and a third separation vessel in series, the third separation vessel having an operating pressure of less than or equal to 0.05 bar, wherein the third separation vessel produces a separation product comprising LDPE and less than or equal to 50 ppm of the unreacted ethylene monomer, wherein there is no stripping agent added upstream of the third separation vessel.

Embodiments of a method for reducing unreacted ethylene monomer in a low density polyethylene (LDPE) polymerization process comprises: delivering a monomer feedstock comprising ethylene monomer to a compressor system to produce a pressurized feedstock having a pressure of at least 2000 bar; passing the pressurized feedstock to at least one free radical polymerization reactor to produce a reactor effluent comprising the LDPE and unreacted ethylene monomer; and delivering the reactor effluent to a separation system comprising a first separation vessel, a second separation vessel, and a third separation vessel in series, the third separation vessel having an operating pressure of less than or equal to 0.05 bar, wherein the third separation vessel produces a separation product comprising LDPE and less than or equal to 50 ppm of the unreacted ethylene monomer, wherein there is no stripping agent added upstream of the third separation vessel.

Embodiments of a method for reducing unreacted ethylene monomer in a low density polyethylene (LDPE) polymerization process comprises: delivering a monomer feedstock comprising ethylene monomer to a compressor system to produce a pressurized feedstock having a pressure of at least 2000 bar; passing the pressurized feedstock to at least one free radical polymerization reactor to produce a reactor effluent comprising the LDPE and unreacted ethylene monomer; and delivering the reactor effluent to a separation system comprising a first separation vessel, a second separation vessel, and a third separation vessel in series, the third separation vessel having an operating pressure of less than or equal to 0.05 bar, wherein the third separation vessel produces a separation product comprising LDPE and less than or equal to 50 ppm of the unreacted ethylene monomer, wherein there is no stripping agent added upstream of the third separation vessel.

A method of preparing a catalyst support comprising contacting an acid-soluble titanium-containing compound with an acid to form a first mixture; contacting the first mixture with an alkali metal silicate to form a hydrogel which has a silica content of from about 18 wt. % to about 35 wt. % based on the total weight of the hydrogel; contacting the hydrogel with an alkaline solution to form an aged hydrogel; washing the aged hydrogel to form a washed hydrogel; and drying the washed hydrogel to produce a titanium-containing-silica support wherein the support has a pore volume equal to or greater than about 1.4 cm.sup.3/g.

A method of preparing a catalyst support comprising contacting an acid-soluble titanium-containing compound with an acid to form a first mixture; contacting the first mixture with an alkali metal silicate to form a hydrogel which has a silica content of from about 18 wt. % to about 35 wt. % based on the total weight of the hydrogel; contacting the hydrogel with an alkaline solution to form an aged hydrogel; washing the aged hydrogel to form a washed hydrogel; and drying the washed hydrogel to produce a titanium-containing-silica support wherein the support has a pore volume equal to or greater than about 1.4 cm.sup.3/g.

A method of preparing a catalyst support comprising contacting an acid-soluble titanium-containing compound with an acid to form a first mixture; contacting the first mixture with an alkali metal silicate to form a hydrogel which has a silica content of from about 18 wt. % to about 35 wt. % based on the total weight of the hydrogel; contacting the hydrogel with an alkaline solution to form an aged hydrogel; washing the aged hydrogel to form a washed hydrogel; and drying the washed hydrogel to produce a titanium-containing-silica support wherein the support has a pore volume equal to or greater than about 1.4 cm.sup.3/g.

The present invention relates to a method for preparing a catalyst, and in particular provides a method for preparing a catalyst suitable for the polymerisation of ethylene and/or propylene, said catalyst comprising a compound of yttrium, neodymium or scandium supported on a silica support, and wherein the method comprises: a) Treating a silica support by heating at a temperature of at least 550° C., b) Contacting the treated silica support with a complex of the following formula: D.sub.mMX.sup.1X.sup.2R wherein M is selected from Y, Sc and Nd, R is a hydrocarbyl group, X.sup.1 and X.sup.2 are anionic groups, D is a neutral donor group, and m is 0 or greater.