Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Silicon containing or process of making
Reexamination Certificate
2000-04-25
2002-04-16
Wu, David W. (Department: 1713)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Silicon containing or process of making
C502S233000, C502S234000, C502S238000, C502S256000, C502S087000, C526S348000, C526S089000
Reexamination Certificate
active
06372685
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to silica powders and mixed silica-oxide powders and methods of preparing such powders for use as catalyst supports for polymerization processes.
BACKGROUND OF THE INVENTION
The use of amorphous gels and precipitates as support material for polymerization catalysts is known. For example, aluminophosphate gels and precipitates have often been used for such support materials. In some cases, the support was improved by incorporating silica into the aluminum phosphate support.
While aluminophosphates have long been known, along with their methods of preparation, such aluminophosphates have not as yet achieved commercial success. Part of this is believed to be that the prior art aluminophosphates lacked a combination of physical properties which have been found to characterize superior polymerization catalysts. It is the combination of a high macropore volume of at least 0.1 cc's per gram plus a fragmentation potential (to be defined below) of preferably 30 to 60 plus a preferred mesopore volume of 0.3 to 0.8 cc's per gram which particularly characterize the superior polymerization catalysts. In two prior inventions of Applicants (Pecoraro and Chan, U.S. patent application Ser. No. 08/742,794 U.S. Pat. No. 6,022,313; Auburn and Pecoraro, U.S. patent application Ser. No. 08/741,595 U.S. Pat. No. 5,869,587), which are incorporated herein by reference, a new aluminophosphate with both high macropore volume and a fragmentation potential about 30 was developed which was also both physically and thermally stable. It is believed that the presence of sheets of aluminophosphate in the microstructure results in the packing of the microstructures in such a way that a high macropore volume and a high fragmentation potential are achieved along with physical and thermal stability.
In another related invention by Applicants (U.S. application Ser. No. 08/961,825 U.S. Pat. No. 6,111,037, Auburn, Pecoraro and Chan), which is a continuation-in-part of Ser. Nos. 08/741,595 and 08/742,794 discussed above, and which is also incorporated by reference herein, a silica-modified, amorphous aluminophosphate composition which like the previous inventions exhibits a microstructure of sheets and exhibits spheres of silica-modified aluminophosphate as well.
The use of silica alone or the combination of silica with other oxides such as alumina or titania or vanadia to form such amorphous compositions for use as polymerization catalyst support material is also known. Previously, the microstructure of such supports primarily contained small particles. As a result of this small particle structure, it was difficult to tailor the materials over a wide range of pore sizes, distributions and volumes, and of acceptable fragmentation characteristics.
It would be desirable to find silica support materials which could be used over a wide range of pore sizes, distributions and volumes and of acceptable fragmentation characteristics.
The present invention has achieved such materials. The present invention has achieved high surface area, amorphous silicas which surprisingly form a continuous network matrix, rather than the typical small particles found in conventional amorphous silicas. Furthermore, the pore size and the distribution and volume of the pore size can be tailored over a wide range.
Surprisingly, also, the present invention achieves an amorphous SiO
2
base composition with a non-particulate, dense, network matrix and encapsulated less dense, non particulate regions with true macropores. In one embodiment, the present invention also comprises a sheet-like microstructure.
SUMMARY OF THE INVENTION
One object of the present invention is to provide an amorphous SiO
2
or mixed oxide silica base composition comprising:
(a) a non-particulate, dense, continuous network matrix; and
(b) encapsulated, less dense, non particulate regions with true macropores.
Another object of the present invention is to provide such an amorphous SiO
2
or mixed oxide silica base composition in which the gel matrix further comprises a sheetlike microstructure.
Still another object of-the present invention is to provide such an amorphous SiO
2
or mixed oxide silica base composition in which the composition has surface areas in a range of from 150 to 600 m
2
/gm.
Yet another object of the present invention is to provide such an amorphous SiO
2
or mixed oxide silica base composition in which the composition has a mean mesopore diameter in a range of from 60 to about 250 Å.
An additional object of the present invention is to provide such an amorphous SiO
2
or mixed oxide silica base composition in which the composition has a measured pore volume in a range of from about 0.5 to 1.5 cc/gm.
Still another object of the present invention is to provide such an amorphous SiO
2
or mixed oxide silica base composition in which the composition has a macropore volume of at most 0.5 cc/gm.
Yet another object of the present invention is to provide an amorphous mixed oxide silica base composition selected from the group consisting of silica alumina, silica titania, silica vanadia and silica zirconia.
An additional object of the present invention is to provide powders produced from such an amorphous SiO
2
or mixed oxide silica base composition.
A further object of the present invention is to provide such powders which are spray dried.
Yet a further object of the present invention is to provide such powders which are vacuum dried.
Still a further object of the present invention is to provide such spray dried powders having fragmentation potentials in a range of from about 20 to about 30.
Another object of the present invention is to provide a catalyst comprising such a SiO
2
base composition, the composition being impregnated with a catalytic amount of at least one transition metal-containing compound.
Yet another object of the present invention is to provide such a catalyst in which the at least one transition metal-containing compound is a chromium compound.
Still another object of the present invention is to provide such a catalyst in which the at least one transition metal-containing compound is present in an amount of 0.1 weight percent or greater based on the total catalyst weight.
An additional object of the present invention is to provide such a catalyst in which the at least one transition metal-containing compound is present in an amount in the range of from about 0.1 weight percent to about 10 weight percent.
Yet an additional object of the present invention is to provide a polymerization process comprising contacting such a catalyst with at least one alpha-olefin under polymerization conditions.
Still an additional object of the present invention is to provide a method for preparing a silica gel composition which is a precursor material for a silica powder material with a microstructure comprising a non-particulate, dense, continuous network matrix and encapsulated, less dense, non particulate regions with true macropores, the method comprising:
(a) forming a first aqueous solution comprising silica ions;
(b) forming a second aqueous solution capable of neutralizing said first aqueous solution; and
(c) contacting said first and second aqueous solutions in a mixer-reactor under mixing conditions to form the silica gel composition.
An additional object of the present invention is to provide an olefin polymerization catalyst prepared from a silica gel composition obtained by such a method.
Yet another object of the present invention is to provide such a method in which the first aqueous solution is an acidic solution comprising sodium silicate and acid and in which the second aqueous solution has a pH above 8.
Still an object of the present invention is to provide such a method in which the second aqueous solution is an ammonia based material selected from the group consisting of ammonium hydroxide; ammonium carbonate; ammonium bicarbonate and urea.
An additional object of the present invention is to provide such a method in which the first aqueous solution is a basic solution of sodiu
Auburn Pamela R.
Chan Ignatius Y.
Pecoraro Theresa A.
Whaley Darryl K.
Chevron Phillips Chemical Company LP
Choi Ling-Siu
Sun Hsiang-ning “Sean”
Wu David W.
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