Note: Descriptions are shown in the official language in which they were submitted.
` 1 16 3 ~ 2 1 28761CA
TITANIUM IMPREGNATED SILICA-CHROMIUM CATALYSTS
Cross Reference to Related Application
This is a divisional of copending application Serial No.
364,387, filed November 10, 1980.
Background of the Invention
This invention relates to silica supported chromium catalysts
containing titanium.
Supported chromium oxide catalysts have been used for many
years in the polymerization of olefins to solid polymers. One widely
used method of producing such catalysts involves precipitating a silica
hydrogel, impregnating the hydrogel with an aqueous solution of a
chromium compound and drying. Such procedure gives a silica which
inherently has sufficient strength to resist severe shrinkage of the
pores during simple drying techniques such as oven drying, tray drying,
spray drying or drying under a heat lamp. Such catalyst is simple and
inexpensive to produce and gives outstanding results in solution
polymerization of olefins to give normally solid polymer.
There is an economic advantage in some instances to producing
olefin polymers in a slurry as opposed to a solution system. However,
certain control operations which are easily carried out in the solution
process are considerably more difficult in the particle-form or slurry
process. For instance in the solution process, control of the molecular
weight can be effected by changing the temperature, with lower molecular
weight thigher melt flow) being obtained at the higher temperature.
However, in the slurry process, this technique is inherently limited
since any ef~ort to increase the melt flow to any appreciable extent by
increasing the temperature causes the polymer to go into solution and
thus destroys the slurry process.
It is known that titanium affects the polymerization activity
of silica supported chromium catalysts in a way that is of special
importance in slurry polymerizations. However, when titanium is
,~k,
q~,
, ~
, . ~ , . , :
.. ~ . ., . . . . ~
t 1~6~ ~
coprecipitated with the silica, it produces a hydrogel which does not have
sufficient strength to resist serious collapse of the pores during simple
drying such as spray drying. Similarly, in accordance with the prior art,
if an aqueous solution of a titanium compound is added to the dried silica,
the pores are damaged. Accordingly, in order to take full advantage of
the improvement which can be imparted to the melt index capability through
the use of titanium in accordance with the prior art, the titanium had to
be coprecipitated with the silica and the resulting hydrogel (cogel) dried
by a more expensive azeotrope distillation or washing with a liquid oxygen-
containing water soluble organic compound~
S _ ary of the Invention
It is an object of this invention to provide a titanium-
containing silica supported chromium catalyst which can be dried in a
conventional manner and yet which exhibits the characteristics associated
with azeotrope dried titanium-silica coprecipitated catalysts.
It is a further object of this invention to provide a catalyst
suitable for use in slurry polymerization systems; and
It is yet a further object of this invention to provide an
improved olefin polymerization process.
There are two embodiments to this invention. In accordance with
the first embodiment, silica hydrogel is prepared and dried in the presence
of a pore preserving agent after which a titanium compound is anhydrously
incorporated therewith.
In accordance with the second embodiment of this invention, a
silica hydrogel or a silica xerogel is impregnated with an aqueous organic
acid solution of a substituted or unsubstituted titanium acetylacetonate.
Description of the Preferred Embodiments
Embodiment 1
In accordance with embodiment 1, a silica hydrogel containing
a pore preserving agent is dried and thereafter the titanium compound is
introduced in an anhydrous manner. The silica hydrogel can be prepared
in a conventional manner, for instance, by contacting an aqueous acid
solution with an aqueous solution of an alkali metal silicate as disclosed
in Witt, U. S. 3,900,457, issued August 19, 1975. Preferably, the alkali
metal silicate is added to the acid.
Prior to drying, the hydrogel must contain a pore preserving
agent. The silica pore structure preserving agents can be selected from
among organic silicon compounds, e.g., triarylsilanols, described in
,, .,.~ i -
.
1 ll636`~1
U. S. 4,190,457, issued ~ebruary 26, 1980; oxygen-containing organic
compounds selected from among polyhydric alcohols, mono- and dialkyl
ethers of ethylene glycol and poly(alkylene)glycol as disclosed in
McDaniel, U. S. 4,169,926, issued October 2, 1979, and surfactants.
U. S. 4,169,926 also idscloses suitable anionic, cationic and nonionic
surfactants. This patent also discloses combinations of the oxygen-
containing organic compounds with a normally liquid hydrocarbon, e.g~,
n-heptane, kerosene, and, optionally, a surfactant, which are also
suitable pore preserving agents. The nonionic surfactants are preferred.
Said organic silicon compounds have the structure
RnSiA4 n
wherein n is an integer of 2 or 3, and wherein each R is a saturated or
unsaturated hydrocarbon group wherein each R can be the same or different
and wherein A is selected from the group consisting of hydroxy radicals,
halides and alkoxy radicals in which the alkyl group therein contains
from 1 to about 10 carbon atoms.
Preferably, R is selected from the group consisting of alkyl
radicals of from 4 to about 12 carbon atoms, alicyclic radicals of from
4 to about 12 carbon atoms, aryl radicals of from 6 to about 24 carbon
atoms, and hydrocarbyl-substituted aryl radicals such as alkylaryl and
cycloalkylaryl of from 6 to about 24 carbon atoms.
The pore preserving agents can also include certain inorganic
and organic acids used at a specific level of pH. Specifically the
hydrogel is contacted with an inorganic or organic acid in an amount
sufficient to impart to the mixture a pH ranging generally from about O
to about 3.5, more specifically from about O to 3. About ~.2 or below
is presently believed to be preferred.
Inorganic acids employable are those which are water soluble,
sufficiently ionized to produce the pH level required in the hydrogels,
and do not have a deleterious effect on the silica or in the end use
application. Specific but nonlimiting acids can be selected from among
hydrochloric acid, hydrobromic acid, hydriodic acid, nitric acid,
sulfamic acid, sulfuric acid, orthophosphoric acid and iodic acid.
Organic acids generally employable in this invention are those
which exhibit the same requirements as the inorganic acids. Specific but
nonlimiting examples include acetic acid, formic acid, tartaric acid,
citric acid, maleic acid, malic acid, malonic acid, succinic acid,
- ~
. ' ~ ' ' ' .
~1~3~2~
gluconic acid, diglycolic acid, ascorbic acid, cyclopentane tetra-
carbo~ylic acid, and benzenesulfonic acid.
In general, those organic acids meeting the requirements of
water solubility, stability, acid strength, nondeleterious action as
described before also have pK values of about 4.76 or less as disclosed
in Lange's Handbook of Chemistry, 11th Edition (1973), Tables 5-7, 5-8.
In other words their acid strength is equal to or greater than that of
acetic acid.
Acids such as sulfuric acid and hydrochloric acid are generally
preferred, however, because of their ready availability, relatively low
cost, great acid strength, and efficacy in the process.
Specific examples of preferred pore preserving agents are a
polysiloxane-polyoxyalkylene copolymer, a polyethoxylated sorbitol
monolaurate, and a polyethoxylated t-octyl phenol.
The pore preserving agent can be incorporated in one of the
ingredients used to make the silica hydrogel, however, it is preferably
incorporated into the hydrogel after the washing step since this avoids
loss of the agent during the washing step.
The hydrogel containing the pore preserving agent is then
conventionally dried using an air oven, spray drying, tray drying, vacuum
oven drying or drying under a heat lamp, for instance. Conventional drying
temperatures of room temperature to 425C or higher can be used to thus
remove free water and produce a xerogel. With spray drying the incoming
air can be up to 425C although the catalyst does not get that hot.
The titanium compound is then incorporated under anhydrous
conditions into the xerogel. This can be done by utilizing a nonaqueous
solution of a titanium compound such as a titanium alkoxide, generally at
an elevated temperature, to deposit the titanium compound. Alternatively,
any desired titanium compound can simply be added to the xerogel during
the first part of the activation (calcining) step in a fluidized bed.
The titanation can also be separately effected at about 100 to about 200C
in a fluidized bed, if desired.
~ urther with respect to the pore preserving agent, when the
pore preserving agent is an oxygen-containing organic compound, the
weight ratio of oxygen-containing organic compound to hydrogel employed
in making the catalyst can range from about 5:1 to about 0.5:1.
.
~,:
.
1 1f~3~2 1
When both an oxygen-containing organic compound and a normally
liquid hydrocarbon are employed with the hydrogel, the weight ratio of
hydrocarbon to organic compound can vary from about 20:1 to about 0.5:1.
When employing one or more surfactants with the hydrocarbonl
oxygen-containing organic compound, generally about 0.1 to about 5
weight percent surfactant is used based on the weight of hydrocarbon/
oxygen-containing organic compound.
When a surfactant or an organic silicon compound of said U. S.
4,190,457 is employed as the silica pore structure preserving agent, the
weight ratio of hydrogel to surfactant or organic silicon compound can
range from about 20:1 to about 500:1, preferably from about 40:1 to
about 100:1.
Sufficient treating time is allotted to obtain contact of the
various added components with the hydrogel or dried gel. Generally,
times ranging from about 30 seconds to about 10 hours, preferably 15
minutes to 120 minutes are adequate. The treated hydrogel is then dried
as described above to remoYe the liquids and the composite is then
activated at an elevated temperature.
The activation can be carried out in a conventional manner by
calcining at an elevated temperature, generally from about 400C to
1100C in a dry atmosphere containing oxygen, generally in air. The
resulting catalyst contains at least a portion of the chromium in the
hexavalent state. Alternatively, the catalyst can be activated in
accordance with the reduction/reoxidation procedures disclosed in
McDaniel and Welch, U. S. 4,151,122, which issued April 24, 1979. Use
of this activation technique further enhances the capability to produce
high melt index polymers exhibiting superior stress crack resistance.
Embodiment 2
In this embodiment, a silica is impregnated with an aqueous
titanium-containing composition prepared as described hereinbelow from
a titanium compound of the following structural formula:
\C/ ~
" \C - R
I
0 -~Ti 0
/ ~ \ R'
R - ~ B
~ CH - ~
, ", . .. . .. . .
1 1636'~1
where the R and R' groups are the same or different and are selected
from 1-7 carbon atom alkyl radicals. When all of the R groups are
methyl and the R' is isopropyl the compound is diisopropoxy titanium
acetylacetonate. The preferred titanium components are the acetyl-
acetonates, i.e., where R is methyl most preferably those where R'
is isopropyl or butyl.
If desired, a pore preserving agent as described in embodiment
1 can be used in the hydrogel to further enhance the beneficial qualities
of the catalyst and such is preferred. That is, for instance, an alkali
metal silicate can be added to an acid to precipitate a silica hydrogel
which is then washed and impregnated with a water soluble chromium
compound and thereafter dired in a conventional manner such as spray
drying, tray drying, oven drying or drying with a heat lamp as described
in embodiment 1. Thereafter, the thus formed xerogel is impregnated with
the aqueous titanium composition. Alternatively the aqueous titanium
composition can be combined with the hydrogel before drying, again either
with or without a pore preserving agent in the hydrogel, after which the
hydrogel is dried and activated as described in embodiment 1.
It is essential in accordance with Embodiment 2 that the
titanium compound first be mixed with an anhydrous or at least
essentially water free organic acid and thereafter diluted with water.
The exact role of the organic acid is not known with certainty. It is
not simply a matter of solubilizing the titanium compound (which is
insoluble in water) since it does not work to dissolve the titanium
component in other solvents such as acetone since a precipitate forms
when such a mixture is diluted with water. By essentially water free
organic acid is meant one having less than 5 percent water, preferably
less than 1 percent. The volume ratio of essentially water free organic
acid to titanium acetylacetonate must be greater than 0.5:1. Preferably
it is from 1:1 to 1~:1 more preferably about 2:1. The amount of acid
can be greater than 10:1 if desired so far as operability is concerned,
but generally a smaller amount is desired for practical reasons. The
amount must be greater than 0.5:1, howeverJ since the invention does
not operate satisfactorily with only one part acid for two parts of the
titanium compound. The acid can be added to the titanium component or
vlce versa.
After the organic acid and titanium compound have been mixed,
the resulting titanium-containing composition is diluted with water to
~ .,, . ~, ., ~ , . .
.
1 ~636'~1
give the aqueous titanium-containing composition. Preferably, a ratio
of water:titanium-containing composition of about 7:3 is used although
the ratio can be from about 1:1 to as much as 10:1 or greater. The
water can be added to the composition or vice versa. When the aqueous
titanium-containing composition is used to impregnate a xero~el, the
thus-impregnated xerogel can then be directly activated as in embodiment
1 or the water removed by simple evaporation and the dry composite
activated.
In all embodiments, the chromium component of the catalyst can
be coprecipitated with the silica or added by means of an anhydrous
solution of a chromium compound soluble in nonaqueous solvents such as
hydrocarbons to the xerogel but preferably the chromium is introduced by
means of incorporating an aqueous solution of a water soluble chromium
compound with the hydrogel. This is preferably done after the hydrogel
is washed with water to remove alkali metal ions. The water soluble
chromium compound can be selected from among chromium acetate, chromic
nitrate, chromic sulfate, chromous sulfate, chromium trioxide, ammonium
chromate, and other soluble chromium compounds. Chromium acetate and
CrO3 are preferred.
The amount of chromium compound employed in making the catalyst
is sufficient to provide from about 0.001 to about 10 weight percent,
preferably 0.1 to 5 weight percent chromium based on the weight of the
activated catalyst.
The amount of titanium compound employed in making the catalyst
is sufficient to provide from about 0.1 to 10, preferably 1.5 to 5.5
weight percent titanium based on the weight of the activated catalyst.
The catalyst of this invention resembles coprecipitated silica-
titanium catalyst in pore volume, in chromium content, and in the
titanium content although the process for making the catalyst is
substantially simplified and substantially less expensive.
The catalyst of this invention can be used to polymerize at
least one mono~l-olefin containing 2 to 8 carbon atoms per molecule.
The invention is of particular applicability in producing ethylene
homopolymers and copolymers from mixtures of ethylene and one or more
comonomer selected from l-olefins containing 3 to 8 carbon atoms per
molecule. Exemplary comonomers include aliphatic 1-olefins such as
propylene, 1-butene, l-hexene, and higher l-olefins and conjugated or
nonconjugated diolefins, such as 1,3-butadiene, isoprene, piperylene,
,.~, . ,.,,. ~. ~
1 1~3~`21
2,3-dimethyl-1,3-butadiene, 1,4-pentadiene, 1,7-hexadiene, and mixtures
thereof. Ethylene copolymers preferably constitute at least about 90,
more preferably g5 to 99 mole percent polymerized ethylene units.
Ethylene, propylene, 1-butene, and l-hexene are especially preferred.
The polymers can be prepared from the catalyst of this
invention by solution polymerization, slurry polymerization, and gas
phase polymerization technique using conventional equipment and
contacting processes. However, the catalyst of this invention is
particularly suitable in slurry polymerizations for the production of
hiBh melt index polymers in the absence of molecular weight modifiers,
such as hydrogen. The slurry process is generally carried out in an
inert diluent such as a paraffin, aromatic or cycloparaffin hydrocarbon.
For predominantly ethylene polymers, a temperature of about 66 to 110C
is employed. Hydrogen or other molecular weight modifiers can be used,
of course, if desired. Also conventional cocatalysts and adjuvants and
activators can be utilized, if desired.
Examples
Example I
This exemplifies embodiment 1 of the invention.
Hydrogel containing about 20 weight percent solids was prepared
by introducing an alkali metal silicate into an acid. The hydrogel was
admixed with sufficient aqueous chromium trioxide solution to provide 1
weight percent chromium based on the dry composite.
A series of catalysts was prepared from a conventionally spray
dried composite formed by admixing a portion of a hydrogel with
sufficient aqueous chromium(III) acetate solution to provide 1 weight
percent chromium based on the dry composite and 2 volume percent based
on the hydrogel of a liquid nonionic surfactant described as a poly-
ethoxylated t-octylphenol, commercially available from Alcolac, Inc.,
Baltimore, MD under the trademark Siponic F-300.
Individual portions of the spray dried composite were slurried
in about 50 mL of dry n-hexane and a specified amount of n-hexane
solution of titanium tetraisopropoxide containing 16 g titanium/100 ml
solution was added and mixed with the slurry. The solvent was evaporated
off by utilizing a hot plate and the product was converted into an active
catalyst by heating it for 5 hours at 649C with dry air in a fluidized
bed (Runs 1-6).
,.
. " , , , ,, , ~ , ,
' : . ` '
~ ' , '
1 1636~1
. g
Individual portions of the spray dried composite containing a
specified amount of titanium tetraisopropoxide added to a hexane slurry
of the composite and dried as described earlier in this example were
activated sequentially in a carbon monoxide atmosphere and an air
atmosphere under fluid bed conditions. Each sample was fluidized in dry
C0 at 815C for 3 hours, the activator was flushed with nitrogen to
remove the CO as the temperature was lowered to 705C, and then fluidi-
zation with dry air at 705C was continued for 2 hours. The activated
10 catalyst was recovered and stored as before pending the polymerization
testing (Runs 7-12).
Other individual portions of the spray dried composite were
fluidized in the activator with dry nitrogen at about 200 to 300C for
1 hour as a specified amount of titanium tetraisopropoxide was dripped
into the fluidized bed. The titanium addition required about 10 minutes.
The temperature was increased to about 55ûC in the nitrogen stream, the
nitrogen was cut off and dry air substituted and the temperature raised
to 650C over a 30 minute period and held at 650C for 5 hours. The
activated catalysts were recovered and stored in a dry atmosphere until
20 needed for polymerization testing (Runs 13-16.
A portion of each activated catalyst was used in ethylene
particle form polymer by conducting the polymerization at 107C in the
presence of 567 g of isobutane as diluent and ethylene at a nominal
reactor pressure of 3.9 MPa for a time sufficient to produce about
3000 g polymer per g catalyst. Polymer was recovered and melt index
was determined as described before. Each MI value was corrected to a
common productivity level of 3000 g polymer per g catalyst so that a
valie comparison of the values could be made. The catalyst weight and
titanium level of each catalyst employed and the results obtained are
30 given in Table IA, IB and IC. The calculated percent melt index
improvement values are based on the melt index of the respective
control run values.
' ~ - .- ' ~.
,~ .
,
0 1 1fii3
c c e e e
o o o o o
~ Q J
E ~1 C e ~ s G
~; g e ~ ~ e e
u ~ ~1 ~ ~ ~
IHI U~ ~ G~ C~ ,~
x~
~ .. ~ ~ 3, ,_
c c ~ e 6 `'~ o o ~D o o .:
~ ~ V U
o~ ~ 1~
C~ .-
~ X~
. e x el o ,i i , i ,.
N . ~ 111
E-l 0~ J~ u
~: ~ ~ O O O O O O
O ~)V s- c-~ ~ ~ ~ cn
oo E tr~
E v
C
s o O
. o ~ u~ O O ~ e
3 c~
.~ ~ U o o o I" o o
~ ~ o
C~
C~ ~ .,, _
: E~ O ~ ~ ~ ~ ~
3 . ~ ,.
zl ~ ~ ~ ~ ~ `D S
~ ~ ,
o
'
' ' ' ~
: ' ' : ' `~ `' . . ',
1 ~36~1
11
.` C C C C C
O L~
E ~I c c c c c
cl ~- ~ ~ J 0
c~ C ~
. o c C c c ~c
oC
x
; C ;~ ~ E ~
c ~ ~ ~_
. ~, ~ ~ o I o o o o o
u -~ 4 ,~
~,~ E o c~ E O
c~ O ~ Xl
r~
o ~ ~ ,~
I 0 ~
6; ~O:E: ~ O
C 2 ~ _~
0al ~ a .
E~ ~ q ,~ :~ ~'
6 ~ ~ ~ oC
~ _ O O O O O O
c~
o ~ ~ ~ c~ _I o ~u~
C --I ~ el C~
~ o u ~o ~
~ o~- ~ o
~ 3 ~1
C c, u
~- 0 ~ oo
~ E _l ~ ot~c~ ~ .. -
E~ ~ o~ oo ~
C
- ~
~- u~ o u~ o c ~n C
3 c~ o
u~ ~o u~
. o o oo o o
L~ . . ,. , .
~ ~ t~ o C
~ ~- ~ ~
3: o
Z ,~
O
:::
:~
j
:: , "
:
: . ~ ~ : - ` -
~: ~
:
.
3~1
1~
- o~l c c c
o o o
o ~ ....
C C 'C
V ~ ~
~C oc ~ C ~
V ~ ~ ~
3!~1 0 ~ ~ ~
X
0 Q~ _~
E ~
0 ~ C ~ _
I &o ~5
¢ ~ ~ -~ 8
^ :~`
;o X
~ 0 U`~
O ~ ~ ~ ~ ~ r~ CD
C
^ ~C
H O ~
N Cl ~ U
~C ~ ~C O O O O
_I ~ ~1 ~ ~1
O 0 U 0 ~ O . ~ ~1
C~ '~;1 ~ tr~ ~ ~
3 3 o o
G~
C d
~J 0
E~ :~ 0 04 o a~
P~ ~ C~
O
~ U~ O A~ o C
J~ Ot O O C~ O
~ ~1 . . .
~ a O
3~
~ e: ~
~ ~ ~ ~ ~ ~ U~
'~ O
.
,
; ~,
':
,
.
~'~ ' .~' ' ` ` ,
:
.: .
,
1 1636~1
Inspection of the results given in Tables IA, IB, IC shows that
titanation of the dry silica-chromium compound composite can be
accomplished either with a hydrocarbon solution of the titanium compound
by impregnation or with neat addition of the titanium compound to the
fluidized bed during the preliminary phase of the activation cycle given
the catalyst. Active catalysts are formed which exhibit modest to
markedly superior melt index capabilities compared to the control
catalysts. When catalysts prepared according to the invention are
sequentially activated in carbon monoxide and air, then their melt index
capability is even more substantially improved, particularly when the
titanium content of the catalysts range from about 2 to about 5 weight
percent.
Example II
This exemplifies embodiment 2 of the invention.
A series of catalysts was prepared by admixing 12.7 g portions
of a dry, commercially available silica-chromium oxide polymerization
catalyst containing 1 weight percent chromium as the oxide with the
components, when employed, described below. Each sample was dried
overnight in a vacuum oven at 100C, then activated in a fluidized bed
with dry air at 760C for 5 hours. No pore preserving agents were used.
Catalyst 1, control; no titanium compound added.
Catalyst 2, invention; dry control catalyst was admixed with
38.1 ml of a solution formed by dissolving 10 ml (9.9 g) diisopropoxy
titanium acetylacetonate [Ti(ACAc)2] in 20 ml (21 g) of glacial acetic
acid (HAc) and then diluting with 70 ml of water. The water to HAc volume
ratio was then about 3.5 to 1. The amount of titanium compound added was
sufficient to provide 3 weight percent titanium based on the dry
composite.
Catalyst 3, invention; dry control catalyst was admixed with 19
ml of a solution formed by dissolving 10 ml of Ti(AcAc)2 in 20 ml of HAc
and then diluting with 20 ml of water. The water to HAc volume ratio was
then 1 to 1. The amount of titanium compound was sufficient to provide 3
weight percent titanium based on the dry composite.
Catalyst 4, invention; duplicate of catalyst 3 to indicate
reproducibility of the catalyst forming method.
Catalyst 5, control; dry catalyst was admixed with 38.1 ml of
a solution formed by dissolving 10 ml of Ti(ACAc)2 in 20 ml (16 g) of
methyl ethyl ketone (MEK) and then diluting with 70 ml of water. The
.~
1 16~21
14
water to MEK volume ratio was then about 3.5 to 1. The amount of titanium
compound added was sufficient to provide 3 weight percent titanium based
on the dry composite.
Samples of the activated catalysts were employed in ethylene
polymerization exactly as described in the first example. The catalyst
weights used and the results obtained are given in Table II. Calculated
percent melt index improvement is based on the melt index obtained in
control run 1.
, ~
1 16~621
\
D 8 8
U~ C C C U
:C O o o `_
E o v o
~: C ~ ~ ~ C
O 1:: 5 C O
U ~ ~ 1 U
CO ~o U'l
'JI~1 ' ~ `D a~ cs~
-
~ X C
C ~ ~ E ns
~ aJ ~o C ~ ~,
D~ U ~ ' I ~ O O ~
:~: ~ :1 o _I o o~ C
~ 0 - ' U ~ _~ o ~ :
c~ ?` P~ S: ~C~ ~
~ ~ C~. ~
o u ~ 01 ~ o o c~ o o
o :~-~ ~ C~
_I 0 C O o' o
~_ C ~ C C
O o ~ ~#
0 ~ ~ 1 V
,~ ~ o .
N ~ri~-
as ~-~ ~:~ 'J _ _
:~
~ C L~ $ ~ X Ul
O E-~0 0 c~ . o ~ ~ oo
_ S ~ ~ ~* ~ ~ 1
0 ~ O ~1
~0 ~ u c ~
V
C C 0
~- ~ ~
o o
~o co
. L~
0
e,~ r, ~ v
~ 0 ~C `D cn ~ O ~
_I r ~ O ~ ~ :~ 3 3
o ~c~
~ C c C
0 ~ ~
;~ a t~, c
E~ c~ 0
~1 C auJ
o ~o co r~ o 0
. ~ u~ O r~
3 O 0.
o ~a 111 v
~ 0
¢ ~ ~:
C o I ~ c~ o u
o
'~^-
.~ ~.,~"., " , . .. .
,
1 ~63~ ~1
16
The results in Table II show that a dry silica-chromium oxide
catalyst can be successfully aqueously titanated with a solution
consisting of diisopropoxy titanium acetylacetonate dissolved in a
glacial acetic acid water mixture. Catalysts recovered and activated
produce ethylene polymers having melt index values ranging from 14 to lOO
percent better (runs 2-4) than the untitanated control catalyst of run 1.
When methyl ethyl ketone is substituted for acetic acid in preparing the
catalyst the melt index results in control run 5 demonstrate no
improvement in melt index capability over the control catalyst of run 1.
It is believed similar good results would be obtained by
incorporating the aqueous titanium composition in the hydrogel and such
would be preferred for economic reasons.
While this invention has been described in detail for the
purpose of illustration, it is not to be construed as limited thereby but
is intended to cover all changes and modifications within the spirit and
scope thereof.
:
. .
.
