Polymerization process

Claim 2

A process for polymerizing ethylene or a mixture of ethylene and one or more other 1-olefins or 1,3-diolefins comprising contacting a titanium modified heat activated catalyst comprising chromium oxide and a difficulty reducible inorganic oxide support material wherein at least part of the chromium is present in a valency state suitable for polymerization with a first liquid hydrocarbon and then contacting the monomeric material or materials with said catalyst in the presence of a second different liquid hydrocarbon diluent.

Claim 3

A process as claimed in claim 1 wherein the titanium compound used in the titanium modification of said catalyst is selected from those represented by the formulae (a) (R') n Ti (OR') m ; (b) (RO) m Ti (OR') n ; (c) TiX 4 ; (d) TiO 2 ; (e) titanium acetyl acetonate compounds; and (f) alkanolamine titanates, whereon m is 1, 2, 3 or 4; n is 0, 1, 2 or 3; m + n = 4; the R group(s) are selected from alkyl, aryl, cycloalkyl and combinations thereof, each group having 1 to 12 carbon atoms; R' is selected from the group consisting of R, cyclopentadienyl and alkenyl, each group having 1-12 carbon atoms; X is halogen and wherein when more than one R (or R') group occurs in the titanium compound the groups are the same or different.

Claim 4

A process as claimed in claim 1 wherein the titanium compound used in the titanium modification of said catalyst has the formula (RO 4 Ti.

Claim 5

A process as claimed in claim 3 wherein the titanium compound is tetraisopropyltitanate.

Claim 6

A process as claimed in claim 2 wherein the quantity of titanium compound employed is in the range 2.0 to 6.0% based on the weight of the catalyst support material.

Claim 7

A process as claimed in claim 1 wherein during the preparation of the said titanium modified catalyst, the titanium compound is incorporated after the chromium had been added.

Claim 8

A process as claimed in claim 1 wherein ethylene is the sole monomer.

Claim 9

A process as claimed in claim 1 wherein the first liquid hydrocarbon is selected from the group consisting of straight and branched chain paraffinic, cycloparaffinic, olefinically unsaturated and aromatic hydrocarbons having at least 5 carbon atoms per molecule.

Claim 10

A process as claimed in claim 8 wherein the first liquid hydrocarbon is n-hexane or cyclohexane.

Claim 11

A process as claimed in claim 1 wherein the second liquid hydrocarbon diluent is isopentane, n-pentane or isobutane.

Claim 12

A process as claimed in claim 1 wherein the polymerisation is conducted in the presence of hydrogen gas.

Claim 13

A process as claimed in claim 9 wherein the second liquid hydrocarbon diluent is isopentane, n-pentane or isobutane.