METHOD OF PREPARING A TITANIUM-MODIFIED CR/SILICA CATALYST
A method for making high-PV titanium-modified Cr/Silica (Cr/Ti/Silica) catalyst precursor, with PV>1.5 ml/g, comprising: providing a silica support, typically based on a desired porosity, purity, particle size and size distribution; providing a coating solution containing a Cr-containing compound, a Ti-containing compound, and a solvent; mixing the coating solution with the silica support to form a catalyst preparation mixture; and drying the catalyst preparation mixture to produce a Cr/Ti/Silica catalyst precursor. The Cr/Ti/Silica catalyst is surprisingly tolerant to the presence of water in the catalyst preparation mixture, as shown by it containing water in an H 2 O:Ti molar ratio ranging from 2-50 with negligible effect on the pore volume (PV) and the MI potential of the Cr/Ti/Silica catalyst precursor. A catalyst, such as an olefin polymerization catalyst, made by the method is also disclosed.
1 . A method for making titanium-modified Cr/Silica catalyst precursor, comprising:
providing a silica support;
providing a coating solution that contains:
a Cr-containing compound,
a Ti-containing compound selected from a Titanium acetylacetonate having the following formula: (RO)(R′O)Ti(CH 3 COCHCOCH 3 ) 2 , Titanium bis-(triethanolamine) diisopropoxide or a combination thereof, and
an organic containing solvent,
mixing the coating solution with the silica support to form a catalyst preparation mixture, wherein the catalyst preparation mixture contains water in an H 2 O:Ti molar ratio ranging from 2-50; and
drying the catalyst preparation mixture to produce a Cr/Ti/Silica catalyst precursor having:
a pore volume (PV) of at least 1.5 cc/g,
chromium in an amount ranging from 0.01-3 wt %, and
titanium in an amount ranging from 0.1 wt % to 8 wt %.
2 . The method of claim 1 , wherein the Cr/Ti/Silica catalyst precursor has a PV of at least 1.8 ml/g.
3 . The method of claim 1 , wherein the Cr/Ti/Silica catalyst precursor has a PV ranging from 1.8 to 2.8 ml/g.
4 . The method of claim 1 , wherein the catalyst preparation mixture contains water in an H 2 O:Ti molar ratio ranging from 4-40.
5 . The method of claim 4 , wherein the catalyst preparation mixture contains water in an H 2 O:Ti molar ratio ranges from 10-30.
6 . The method of claim 1 , wherein the Ti-containing compound comprises titanium acetylacetonate, wherein R=C 2 H 5 and R′=i-C 3 H 7 .
7 . The method of claim 1 , wherein the Ti-containing compound comprises titanium acetylacetonate, wherein R=R′=i-C 3 H 7 .
8 . The method of claim 1 , wherein the Cr compound is soluble in the solvent and can be converted to chromium oxide by calcining.
9 . The method of claim 8 , wherein the Cr compound comprises chromium nitrate, chromium acetate, ammonium chromate, tert-butyl chromate, or mixtures thereof.
10 . The method of claim 6 , wherein the Cr compound comprises basic chromium acetate (BCA) having the general formula (Cr x (OOCCH 3 ) y (OH) 3x-y ·nH 2 O.
11 . The method of claim 1 , wherein the organic containing solvent comprises at least one or more alcohols.
12 . The method of claim 11 , wherein the alcohol contains water in an amount of H 2 O:Ti molar ratio up to 30.
13 . The method of claim 1 , further comprising pyrolyzing the catalyst precursor under an inert atmosphere.
14 . The method of claim 13 , wherein said pyrolyzing is performed in an inert atmosphere at a temperature ranging from 400 to 700° C. to form a pyrolyzed catalyst precursor.
15 . The method of claim 14 , further comprising activating the catalyst precursor or the pyrolyzed catalyst precursor in an oxidizing atmosphere at temperatures ranging from about 400 to about 900° C. to convert the catalyst precursor or the pyrolyzed catalyst precursor to an activated catalyst.
16 . The method of claim 15 , wherein the activated catalyst comprises a titanium-modified Cr/Silica olefin polymerization catalyst.
17 . The method of claim 1 , wherein the silica support contains water in an amount of H 2 O:Ti molar ratio up to 45.
18 . The method of claim 1 , wherein mixing the coating solution with the silica support to form a catalyst preparation mixture is done via incipient wetness impregnation of the silica support with the coating solution.
19 . A titanium-modified Cr/Silica catalyst precursor made by the method of claim 1 .
20 . The titanium-modified Cr/Silica catalyst precursor of claim 19 , which has a pore volume (PV) of at least 1.5 ml/g.
21 . The titanium-modified Cr/Silica catalyst precursor of claim 19 , which has a pore volume (PV) of at least 1.8 ml/g.
22 . The titanium-modified Cr/Silica catalyst precursor of claim 19 , which a pore volume (PV) ranging from 1.8 to 2.8 ml/g.
23 . The titanium-modified Cr/Silica catalyst precursor of claim 19 , which is a precursor for a titanium-modified Cr/Silica olefin polymerization catalyst.