Note: Descriptions are shown in the official language in which they were submitted.
PCI'I LJS93/02104
WO 93/1?968
1
FREPARATiON OF STABILIZED ALUNiiNA ~IAVINO EN~iANCEI~
RESISTANCE TO LOSS OF SURFACE AREA AT HI(~HI TEMPERATtI'RES
BACI~GRO~ OF TIIE INVENTION
1 Field of the Invention
S The present invention relates to a process for producing alumina which can
be
converted to catalyst supports exhibiting enhanced resistance to loss of
surface area
when subjected to high teanperatures.
2. I~~c~°it~ti~n of the Bhckg_round
One ~f the key requirements of a catalyst support or substrate such as alumina
(A10,) is high suxface area. Increased surface area allows for deposition of
the
catalytically active species, enhances reactivity between the catalydcally
active species
and the reactants and; in general, makes for a mare efficient catalyst
support. In the
case o~ catalyst supports'of alumina used in catalytic c~OVerters for
automobiles, i.e.
auto~atalyst supports, high surface area is particularly desirable because of
short
residence times betweed reactants and catalytic species, the desire xo
minimize the
size ~f the catalytic con~rerter and hence the need for a high efficiency
catalyst.
A particular problem with autocatalyst sup~rts involves the high temperatures
to which the supports are subjected. Nigh temperatures deleteriously effect
the
structut'al integrity of the catalyst support , resulting in a loss ~f surface
area. In
effect; the elevated temperatures cause the catalyst to c~llapse on itself.
It is known that stabiloizers such as oxides of barium and the lan~anide
series
of elegnents can stabilize aut~catalysts an the sense that the loss of
structural integrity
of the - support is retarded. In' particulaf, oxides \of barium, lanthanum or
other
lanthanide elements have bin used in alumina based auto~talyst supports as
heat
stabilizers: .
CVO 93t1796~ PCT/iJS93/02104
2
SZJ1V~IAI~Y ~F ThIE INDENTION
It is therefore an object of the present invention to provide a process for
producing stabilized alumina which can be used in catalyst supports and other
structural substrates requiring high surface area.
Still another object of the present invention is to provide a catalyst support
exhibiting enhanced resistance to structural degradation at high temperatures.
The above and other objects of the present invention will become apparent
from the description given herein and the appended claims.
According to the process of the present invention, a stabilized alumina of
enhanced resistance tci high temperature surface area loss is prepared by
forming a
gel of a boehmite alumina, the boehnnite alumina being obtained by
hydrothermally
~ treating an aqueous mixture of a precursor boehmite alumina having a pl~i of
from
about 5 to about 9 for a period of time sufficient to convert the greater
portion of the
precursor boehmite alumana to a colloidal s~l. 'The gel is subjected to
working, i.e.
by using ' ~ suf~cien2 shearing force for a sufficient period of time to
produce a
w~rkerl boehnnite alumin~ and increase the pore volume by at least 30 percent
and the
median p~re radius by at least 2U percent. A stabilizer is added to the
boehrnite
alurrsina, the stabilizer being an oxide of a metal such as buriurn or a metal
included
in the lanthazaide aeries of metals ~r a compound of such metals which
converts to an
2~ oxide at elevated temperatures. Mixtures ~f such stabilizers can be
employed if
desired; the arnount of the stabilizer used being sufficient to decrease loss
of porosity
of a e~lcined ahamina pr~duced frown the worked alumin~.
In an optimal embodiment of the inven~a~n, the stabilizer can be added to a
calcin~! product obtained by calcining the worked (sheared) boehanite alumina.
_ .._ . .... .. _.._ .... . ~. . : _, ..... . .,. ... :. ~F ... : . . ..~....
. ,.. , .
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CA 02131795 2003-02-10
.i
DETAILED DESCRIP'I'I~N OF TI-IF I'Rh.FERRED EMBODIMENT
T'he aluminas which can be treated according to the process of the present
invention are boehmite aluwinas which leave L~~oru hydrotherlnally treated
under
conditions to convent tile gru~att:r portion crf tHc 1»~olornito alumina to a
colloidal see,
the thus hydrothermall}' treated aluminas loaning tl~e starting material
boehmite
alumina for use in the process of the prcaent invention. 'l'he boehmite
alumina which
is hydrothermally treated, hr,reinafter referred to as precursor boehmite
alumina, is
preferably, although nc:~t n~~essarilv, cabtc~ioecll by thG° Hydrolysis
of an aluminum
alkoxide in the well known tGrshiorr. 'The aluminum alkoxide (trialkoxide) can
be
produced, in the well known manner, by reacting a low molecular weight
alcohol, a
linear or branched chain, with an all.rminuln-bearily material. Such alunainum-
bearing materials include pure ali.utninua~a and rloixecl allu~y scrap.
Typical methods for
preparing stlCl7 altrrllrnum alkoxides arc: shown, Fox example, in U.S. Patent
No.
4,242,271. 'The aluminum alkoxide can be 11y<lrolyzed the well known manner,
such
as by the process tau~,lat in tJ.;~. 1'atwt No, 4,202.,b7(). Especially
preferred are
aluminas obtained from the hydrolysis of aluminum alkoxides derived from
Ziegler
Chemistry in the well known manner. \Whilc: the prei~rred feedstoclc used as
the
precursor alumina is an alumina slurry, particulurl~ a slurry produced by the
hydrolysis of aluminum alkoxides, it will Oe rocc°~gni:red that
aluminas from other
sources can be formed into slurries and hydrotHermally treated to produce the
precursor alumina.
The starting material bochlnite alumina used in the process of the present
invention can be obtained tl~,corclin~ tc.a the process disclosed and claimed
in U.S.
Patent No. 4,676,928. Basically, the process clisclosccl in U.S. Patent I\To.
4,676,928
involves taking a precursor boehmite altlmina, forming the precursor ?lamina
into an
aqueous slurry or mixture, tire pl-I bt~in~ in the range ol' f"rom about 5 to
about 9, and
there hating the aqueous slushy of the prc~:trrs<>r illunkiva at elevated
temperatures,
generally about 70°C or grearter, For a sufficient period oI" time to
convert the greater
portion of the precursor hoehrnlte alucnina to a c:.olloidal see.
In using the process cliselo''ecl in lJ.'~. 1'tvton~ 110. 4,Ei7Ci,92'8 to form
the
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..,_....~ . .. ,.,~ , y ~~.. .
~i . ., f.., .
~Y~ 93/1796 PCTIL1~931~21t14
4
'1~ ~. 3 ~'~ ~ ~
starting material boehmite alumina used in the present process, a colloidal
sol can be
employed. Alternately, a colloidal sol which has been dried to form a dried
powder
can be formed into an aqueous dispersion and used. In either event, the
alumina
content will range from about 15 to about 55 percent-by-weight calculated as
Ah~,,
depending on whether or not a gelling agent is employed. In cases where a
gelling
agent is empl~yed, the gel will normally contain from about 15 to about 25
percent-
by-weight AIZ~,. In the absence of a gelling agent, the gel will generally
contain
from about 35 to about 55 percent-by-weight A120,.
Generally the process is conducted by forming an aqueous slurry or
dispersion; either as the sol as described above, or by dispersing a dried sol
in an
aqueous medium. Once the slurry of the starting material boehmite alumina has
been
formed, it must be gelled or thickened to increase the viscosity prior to
being worked.
The term "gel" ~s used herein refers to a suspension, colloidal in nature, in
which
shearing stresses below a certain mite value fail to produce permanent
deformation.
~;~Iling of the aluanina slurry can be carried out simply by concentrating the
slurry
by the removal of water to firm a viscous gel of increased alumina content.
Additic~n~ily, or ~Itematively; the gelling ~f the dispersion can be carved
out by the
addition of gelling,age~ts. Such gelling agents are generally water-soluble
compounds
which are well known by those skilled in the art to be compounds which will de-
stabilize aqueous colloidal ystems. Ton-limiting examples of such gelling
agents
include minerr~ll acids such ~s nitric acid, hydrochloric acid, etc., organic
acids such
as formic acid, acetic acid; etc. ~ polyvalent metat salts, etc. For example,
water-
soluble salts of certain polyvalent metals such ~s the nitrates, chlorides,
acetates,
sulfates, etc:, of metals such as aluminum, iron, magnesium, manganese, etc.
can be
used. i~'hen employed, such gelling agents will be added in an amount
sufficient to
increase the viscosity to the desired degree, i.e. until a gel is formed,
amounts of
fr~rrc~ about 0. I t~ about 50 percent-by-weight based on the weight of
alumina in the
gel being generally used.
It is generally necessary, when viseosifying the alumina dispersion, whether
such be accomplished by concentrating the dispersion and/or the addition of
gelling
agents, to add sufficient acid to maintain the gelled alumina in a flowable
condition.
Generally speaking; monobasic acids such as nitric acid, hydrochloric acid,
formic
WO 93/1796 ~ ~ ~ ~ ~ ~ PGT/US93/021~~
S
acid, acetic acid, and so forth can be employed. The amount of acid added
should
be kept to a minimum; consistent with achieving desired gelling, as increased
acid
decreases porosity.
Worlting or shearing of the gel to the desired extent can be accomplished in
S a variety of equipment and under widely varying conditions. In general, any
apparatus which is capable of imparting high shear to viscous systems
can be
employed. Ikon-limiting examples of apparatus which can be used to
carry out the
working or shearing step include plastic melt viscometers, mullers
commonly used
for mixing paste-like materials, Briers fot preparing high viscosity
pastes and gels and
the like. Parameters such ' as shear rate, shear time, temperature,
etc. will vary
depending upon the concentration of alumina in the gel, the type
of gelling agent
employed; the type of precursor boehmite employed and-the type of
hydrothermal
treatment applied to the precursor alumina to obtain the staring
material boehmite
used in the process of the present invention. In general; conditions
of high shearing,
1S high concentration of alun~ina in the gel and minimu~in acid
concentration
are
preferred. 'Femperatuee can vary. widely as from arnmbient to about
100C. In
general, the gel will be subjected to a sufficient shearing force;
for a sufficient period
of time to increase the pore volume by at least 30 ~ and the median
,pore radius by
at least 20% over' that of the alumina in the unworked gel: Such
increase in porosity
parameters can be determined by techniques well kmown to these skilled
in the art.
It can be shown by transmission electron microscopy (TEIIrL) that
'ordinary
boehmite which. has not been treated according to the process o~
U:S. Patent No.
4,676,928; exists in floe form of extensive aggregates of individual
crystallites of
relatively small size, i.e. less than about 50~ in thickness (020
plane): Such aluminas
exhibit extensive'aggregation of the crystallites, i.e. microgels'
Aluminas which have
been"preparing according to the process of tLS. Patent rlo. 4,6T6,928,
as seen by
'i'El~, also exist -as aggregates but unlike ordinary boehrriite
the microgels are made
up ~f stacks of plate-like crystallites which are generally highly
oriented: iWhen the
latter type of alumina starting material is treated according o the
process of the
print inrrention, and again as can be observed by TEM microscopy;
the orientted,
stacks of crystallites become much more randomly oriented or de~aggldmerated
resulting in a more open structure of the aggregates; i.e: increased
porosity. Thus,
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...,..... .. , :...r,. .......... ~.. .,~".~ ...f.:;..
WO 93/ 179b8 PCT/1JS93/021 U4
~~ ;~"~ ~~J
6
to achieve the unexpected increase in porosity using the process
of the present
invention, it is necessary to employ a starting material alumina
which has been
prepared . in accordance with the process of U.S. Fatent No.
4, 676,928 or an
equivalent wherein the alumina exists essentially as microgels
comprising stacks of
plate-like crystallites. Such staring material aluminas can
be characterized as being
comprised of microgels which are comprised of numerous, associated
stacked
crystallites on the order of from about 50 to about 150 nm in
diameter, the individual
crystallite size being on the order of from about 50 to about
150~e in thickness (020
plane).
'The process of the present invention includes the addition
of a stabilizer to a
boehanite alumina r~rhich has been worked, i.e: sheared; as
described above. The
w term "stabilizer" or "stabilization", as used herein- and
with reference to the alumina
obtained by tlve process described above, refers to a compound
or process which acts
to decrease or retard Ioss of surface area when the alumina,
calcined to AI=03, is
subjected to elevated temperatures; i.e: I000C or greater, generally
1200C or .
greater. The stabilir.er can be an oxide of barium; an oxide
of a lanthanide metal
such as lanthanum; cerium, etc:; a compound of barium which
is converted to an
oxide upon heating at an elevated temperature or a; compound
of a lanthanide metal
which is converted to an oxide at an elevated temperate~re.
Especially preferred
stabilisers aa~e oxides or barium or lanthanum; or x compound
of barium or lanthanum
which is converted to an oxide upon heating at an elevated temperature.
In the more
preferred method; a compound of barium or a lanthanide metal
which can be
converted to the oxide 'is used rather than the oxide thereof.
This permits the
stabilizer to be incorpdrated in the form of an aqueous solution
or dispersion ensuring
more' unit;~rm distribution of the stabilizer thrbnghbut the
alumina.
The stabilizer may be added at various points in the process.
For examgle,
the stabiliser can,be added to the boehmite alumina prior to
gelling, during the gelling
or after the boehmite alurnina is sheared. Thus; the stabilizer
can be added to the
>aoehanite aluanina. prior to the boehmite alumina being worked
or after the boehmite
alumina i5 worked: For example; the worked boehmite alumina
can be dried and the
stabilizer added to the dried; worked beohmite alumina. In an
alternative embodiment
~f the present invention; the worked boehmite alumina can be
dried and calcined to
~Vf,~ 93/17968 ~ ~ ~ ~ "~ ~ C~ PCl'/US93/02104
7
produce a calcined product, i.e. Al=O,, and the stabilizer added to the
calcined
product. The stabilizer will be added in an amount sufficient to decrease loss
of
porosity of a calcined alumina which is subjected to elevated temperatures. In
general, the amount of the stabilizer added will be such as to provide a
stabilizer
content of from about 0.5 to about 20 weight percent based on AlzO, whether in
the
boehmite alumina or in the calcined product.
It is believed that the unexpected stability of alumina prepared according to
the process of the present invention results from the fact that the starting
material
boehmite is comprised of aggregations of individual pseudoboehmite
crystallites, the
crystallites being of a generally larger size, i.e. from about 50 to about 150
A in
thickness (020 plan); than the conventional boehmite aluminas wherein the
individual
crystallites are generally about 50 r~ and smaller in thickness (020 plan).
Further, in
the staring material baehmite used in the process of the present invention the
individual crystallites are plate-like structures which are generally arranged
in an
~rdered, stacked configuration as can be seen by transmission electron
microscopy
(;~~). den such an aluanina is subjected to working as by shearing, the
individual
drystallites become more randomly distributed; i.e. the stacks of crystallites
are
disoriented leaving voids or pores, i.e. greater porcssity and highdr surface
area. This
porosity provides for a reactive; accessible surface yielding higher catalytic
activity.
'fhe incorporation of a stabilizer enhances the structural integrity of the
alumina in
the sense that when subjected td high temperature; the surface area remains,
i.e. the
alui~nirta does not collapse upon itself: Thus, to achieve the unexpected,
stabilized
surface area retention using the process ~f the present inventian, it is
necessary to
employ, as a starting material alumina; a boehmite alumina which has been
prepared
in accordance with the precess of U.S: Patent h3o. 4;6'7,325 or an equivalent
wherein the alumina exists essentially as microgels comprising stacks of plate-
like
crystallites. Such starting material aluminas can be characterized as being
comprised
' ~f mierogels vrhich are comprised of numerous, associated stacked
crystallites on the
order of from about 50 t~ about 150 nm in diameter; the individual crystallite
size
being, ~s not~i; ~n the order of from about 50 to about 150 in thickness (020
plan).
~e press of the present invention can be used t~ make catalyst supports
which retain a high surface area, i.e. about 50 mZ/g or greater upon
ealcination at
1~V(~ 93117968 P(.'C/US93/02104
8
1200°C for three hours.
To more fully illustrate the present invention, the following non-limiting
examples are presented. The DISP~L~ aluminas used in the following examples
are
boehmite aluminas marketed by Vista Chemical Company and made in accordance
with the teachings of tl.S. Patent No. 4,676,928. In all cases surface area
was
obtained by the mufti-point SET method.
Exarra Ire 1
A series of samples were prepared by adding a predetermined amount of a
62.8 percent-by-weight lanthanum nitrate hexahydrate solution to a
predetermined
amount of DISP~L~ 120 alumina sol or DISPA.L~ 180 alumina powder. The
addition of th$ lhnthanuan solution resulted in gelation of the alumina sol.
'The
aluminallanthanum mixture was then worked on a Haake Torque Itlaeometer. The
material was then removed from the rheometer/mixer, dried over night at
70°C, and
then fired at 1200°C for three hours. The firing temperature and time
were selected
to mimic the conditions- that cause loss of surface area azid porosity
collapse, i.e.
conditions a catalyst would experience during use at elevated temperatures
such as in
a catalytic c~nverter. High surface areas, i.e: about 50 m2lg or greater,
following
such treatment at 1200°G are indicative of a highly stable catalyst
which would retain
high' surface area and provide improved catalytic activity for longer
lifetimes under
high temperature extremes. The results are shown in Table 1 below. Sample 1 is
a
contrtsl sample ~rhich was not work~l best contained stabilizer.
:1 ~.;;y>:,
. '. ,..; . ,... r ~ ... . . ,
~ri'.'...,~,.,. ,.'W:':. ..' ...... ,', , ...'.'.'... ":.. :...n. ;F.;. :
~.'~;.'.:., .~_..,....~y.~ ..:,~.... .... -... v.~.~... .....,.....".-., .
..,....'~ ..w~~ .' .:.
'W~ 9311?968 ~ ~~ ~ PCT/US93/02~04
9
v
Q
v co co w o r v~ m
a N titu1 ~i'tf1 t1!lf1
~~.1
ea
v-
J
N
ye O O O O O O
oat 1 O N N rt O O
ri N N rt rt rt
co
o a o 0 0 0
~ o--t~ ,-ara co m
~. ' O- 0. ~.
N N N
'
X
~ ~ ~ ~ ~ .-~to
N N, N N N I~ N
~ v ' v ' o o a
O ' a s
~ t~ (n ~ (~ ~
_
J
'
~ ~ ~ ~ ' ' ~.
R
. .
~
N
0 ~ ~ I ~ ti1O
a d~ 1G
o
~ ~ ~ Q O .
~ O
...
~
1 d C7 0 O ~ ~ 1
f
I
a
v~o N N N N N
r1 N fag <J'In W tv
W~ 93/17968 PCT/US93/02104
_ ~ ~. 3 ~.'~ '~
As can be seen from the data in Table l, samples prepared in accordance with
the process of the present invention wherein the alumina is worked, i.e.
sheared, and
contains a stabilizer; exhibit high surface area retention, i.e. generally
greater than
about 50 m~/g even after being subjected to a temperature of 1200°C for
three hours.
S This is to be contrasted with Sample i in which an unworked alumina
containing
stabilizer showed a surface area markedly less than 50 mZlg after being heated
to
1200 ° C for three hours:
Examples 2-4 which follow demonstrate that retention of high surface area of
calcined products is not achieved with conventional boehmite aluminas. In the
10 examples, the CATAPAL~ aluminas used are conventional aluminas marketed by
Vista Chemical Company which have not been prepared in accordance with the
process of U:S: Patent No. 4,676;928.
~~ple Z
IS 100 g of CATAPAL A~ alumina and 452_ g deionized water were placed in
a Balcex-Perkins Muller and sheared for 20 pninutes: The resulting material
was dried
at 6fi°C and calcined three h~urs as 1200°C. The surface area on
the ealcined
product was determined' to be 5.8 m~lg.
ample 3
g of CATAPAL A~ alumina; 32 g deionized water and 2.42 g lanthanum
nitrate solution (6I .1 wt: % lanthanum nitrate) were mixed f4r 10 minutes and
dried
at 66°C. 'The resulting powder was calcined three hours at
120Q°C. The resulting
caleined product was found to have a surface area of 26:1 m2/g.
.-..r
..;..r 7~ ....,
..,r... . .
S I .
. .:1.,, t
>< ~~.:., i.r.:i~.:
F' aF ... . . . , . . r . .
u.. I. . x . . . . . . . ... . .. , . .
°STA:..,..::f. .h....'~.,.,. ....,..,........... .._,.. .....4 ~.,..u.
. ....a... n... .. .. . ,. .....~. ..... ~ r r. ~ ....... ...t, . . , o. , . .
..
~~3~ 795
WO 93/ l 7968 PCT/US93/02t Q4
11
Example 4
700 g CATAPAL A~ alumina, 452 g deionized water and 69.79 lanthanum
nitrate solution (61.1 wt. % Lanthanum nitrate) were placed in a Baker-Perkins
MuIIer
and sheared for 20 minutes. The resulting material was dried at 66°C
and calcined
three hours at 1200°C. The calcined product was found to have a surface
area of
42.5 mZ/g.
As can be seen from a comphrrison of the surface area of the calcined products
~btained in Examples 2-4, although both working and stabilizing result in a
calcined
product which retains surface area as contrasted with a CATAPAL Am alurnina
which
has not been worked and/or stabilized, the surface area remains below about 50
mz/g.
~ In this regard, a CATAPAL A~ alumina which has not been worked (sheared) or
stabilized has a surface area of 4.7 mZ/g after calcining for three hours at
1200°C.
IS The following examples (5-8) demonstrate that when an alumina such as that
prepared according to U:S. Patent No. 4;6'76;928 is employed; the combination
of
working and stabilizing 'results in an end product which retains a surface
area of
greater than about 50 m2/g even when calcined at 1200°C for three
hours.
Example 5
A sample of DISPAL~ I8N4-80 alumina p~wcter was calcined three hours at
12Q0°C and found to have a surface area of 4.7 m=Ig.
700 g I?ISPAL~ I8N4-80 alumina and 452 ~ deionized watex were placed in
a Baker-Perkins Muller and sheared for 2d minutes. The resulting material was
dried
at 66°C and calcined three hours at 1200°C. The calcined
material was found to
have a surface area of 9.1 m=/g:
~0 ~Z
I00 g DISPAL~' 18N4-80 alumina, 100 g deioniaed water and 2.69 g
Ianthanum nitrate solutit~n (61.1 wt: % lanthanum nitrate) were mixed for 10
minutes
i~VO 93/17968 PCTI~l1S93/~2104
12
and dried at 66°C. The resulting powder was calcined three hours as
1200°C. The
calcined material was found to hare a surface area of 35.4 m~/g.
Exapn~fe 8
S ?00 g DISPAL~ 18114-80 alumina452 g deionized water and ?5.24
lanthanum nitrate solution (61.1 wt. % lanthanum nitrate) were placed in a
Faker-
Perkin MuIIer and shred for 20 minutes. The resulting material was dried at
66°C
and calcined three hours at 1200°C. The resulting calcined material was
found to
have a surface area of 52:9 m2lg.
,~s ~ be seen from a comparison of Examples 5-8, the combination of
working and stabilizing (Example 8) DISPILI,,~ alumina, i.e. aluminas prepared
in
accordance with the teaching of U.S. Patent Ido. 4,6?6,928, results in a
dramatic
increase in retained surface area of the final, t<xalcined product, i.e. a
surface area of
15 greater khan 50 m~/g is obtained even after the material has bin subjected
to a
~mpera~re ~f 1200 ° C for three hours:
~ I
IOO g of DI~PAI:~ 18N4-20 alumina and 4.54 g barium acetate powder were
20 mixed for 10 minutes and dr~ect at 66°C. ~'he resulting powder was
calcined three
h~urs at 1200°C: The c~lcined material was found to have a surface area
of 63 m2/g.
~~~~~0
?00 ~ of DISPEI.h,~' l8IvT4-80 alumina, 602 g deionized water, and 103.64 g
25 barium acetate pov~rder v~ere placedk in a ~aker~Perkins lVluller arid
sheaared for 20
minutes. The rcsultir~g gel was dried at 66°C and calcined three hours
at 1200°C.
The calcined material was f~und t~ have a surface area of ?2.1 mZ/g.
.Ass can be seen from E~mples 9 end 1~the combination ~f stabilization with
30 a barium containing mat~ri~I and 'working pmvades a marked iracrea~ in
retained
surface area (compare the surface -area of the calcined material from Examples
9 and
with the surface area of the calcined materials in Examples 5-?). Although, as
can
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,... .. ...r, "... ,., . .. .... . .. ..
PCI'/US93/021 i~~
WO 93/17968
13
be seen from Example 9, the presence of barium stabilization alone gives a
surface
area of greater than 50 Mm'/g, barium presents certain toxicity problems not
presented by the use of lanthanum. However, it can be seen that the use of
both
barium stabilization and working gives sharply increased retained surface area
(note
Example 10).
Examule 11
100 g CATAPAL A~ alumina, 500 g deionized water, and 12.59 g barium
acetate powder was mixed for 15 minutes and dried at 66°C. The
resulting powder
was calGined three hours as 1200°C: The calcined material had a surface
area of
43:4 m=/g.
Exa~n~nle 12_
7pp g C,~'TAPAL~ A alumina, 452 g deionized water, and 88.13 g barium
acetate powder were placed' in a Baker-Perkins Muller and sheared for 20
minutes.
,hhe resulting gel was dried ar 66°C and calcin~d three hours at
1200°C. The
calcined material was found to have a surface area of 45.8 m~/g.
As can be seen from the data in Examples 11 and 12, while the addition of
stabilizer and working on a cmnventional boehmite alumina, i.e. an alurnina
not made
in accordance with the teaching of U.S. Patent No. 4;676;928, results in
increased,
retained surface area, the retained surface area is substantially less than ~0
m~lg.
F13
600 g ~I~PAL~ 18N4-25 alumina sot and 24.90 g aluminum nitrate solution
(50 wt. % aluminum nitrate; 50 wt. l deion~zed water) were minced to form an
alumina gel. The gel was sheared on a Haa% Torque Rheameter for 10 minutes at
60°C, 110 rpm. The AIZU, content of the sheared gel was 26.8 perront.
53.0 g of
ih~ sheared gel, 2.6 g barium acotate powder, and $0:0 g deionized water were
mixed
for 10 miinutes and dried at ~°C. The resulting powder was calcined
three hours at
1200°C. The calcined material was found to:have a surface area of 67.8
hi /g:
.~x~~tr~?,i;d k x...~' ;l 1 at~;.:~ ~ Y i.f.l. 5i ~ ". ~ ._ ,')~ a .. ., .. .
.~ ~' . ,. . .. ,'., w,~4 ..
W~ 93117968 ~CT/US93/~2104
14
~~~~.r~ t.~'~
Exam~nle 14
55.7 g of the sheared gel of Example 13 were dried at 66°C. The
resulting
dried gel (18 g), 2.77 g barium acetate powder and 80.0 g deionized water were
mixed for 10 minutes and dried at 66°C. The resulting powder was
calcined three
hours at 1200°C. The calcined material.viias found to have a surface
area of 68.7
malg: -
lExhrnole 15
52.24 g of the sheared gel of Example l3 were dried at 66°C. The dried
gel
was calcined two hours at 250°C followed by 24 hours at 600°C.
The resulting
material ~rhs mixed for 10 minutes with 2.59 g barium acetate powder and 20.0
g
deionized water. The slurry vvas dried at 66°C and the resulting powder
calcined
thr~ hours at 120Q°C. The calcined material was found to have a surface
area of
70.6 m2/g.
Exam~le ~b
53.0 g of the sheared gel of Example 13, 1.84 g lanthanum nitrate solution
(61.1 wt: % lanthanum nitrate), ~d 80.0 g dei~nized water were mixed for 10
minutes and dried at 66°C: The resulting powder has calcined three
hours at
1200°C. The calcined material was found to have a surface area 6f 50.2
m2/g.
Dle l7
55.75 g of the sheared gel of Example 13 were dried at 66°C. The
resulting
dried gel ( 18 g), 1.94 g lanthanum nitrate soluti6n, and 80.0 g deionized
water were
~ mixes fir 10 minutes and dried at 66°C. The resulting powder was
calcined three
hours at 1200°C. 'The cca~llcined material was found to nave a surface
area of 47.7
m2/g,
52.24 g of the shred gel of Example 13 were dried at °C. The resulting
d~~ gel w~: ~eia~ ,~,~ hours at 25Q°C, followed by 24 hours at
600°C. The
resulting material was rnix~d for 10 minutes with 1:82 g lanthanum nitrate
solution
W~ 93/17968 ~ ~ ~ ~ '~ ~ ~ PCT/US93/a2104
(61.1 wt. % lanthanum nitrate) and 20.0 g deionized water. The slurry was
dried at
66°C and the resulting powder calcined three hours at 1200°C.
The calcined material
was found to have a surface area of 52.2 m'Ig.
5 As can be seen from a comparison of Examples 13-18, the combination of
working (shearing) and the use of a stabilizer results in an alumina which,
after
calcining at 1200°C for three hours, in general, retains a surface area
of greater than
about SO m2lg. As can be seen from these examples, best results are obtained
in
terms ~f retained surface area when the worked or sheared gel is first dried
and
10 calcined and the stabilizer then added to the calcined material. Compare,
for
exaanple, the retained surface area obtained by the procedure of Examples IS
and 18.
In general, however, the data in Examples I3-18, as well as the other
examples,
demanstrate that the stabilizer can be added after the gel has been worked,
after the
gel has been worked and dried, after the gel has been worked, dried and
calcined,
15 and the ieetained surface area still remains above about 50 ma/g.
~~ foregoing c~iscl~sure and description of the invention is illustrative and
explanatory thereof, and various changes in the method steps may be made
within the
scope of the appended claims without departing from the spirit of the
invention.
