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NGV.' 25,- 1945'- " "
Filed sept. 22, A1942
\Q .
Patentedy Nov. 26, 1946
_ 2,411,320l
oF cA'rALY's'rs
Á .
_'Kenneth D. Ashley, Noroton,_a_nd ‘Alphons v0.
Jaeger, Greenwich, Conn., a‘ssìg‘nors’to' Ameri- <
can 'Cyanam'id Company, >New York, N. Y.,- a
Corporation-@Maine 'Y
’ .i
~ 'e
applicati@ september 22„1942', serial No; `459,262 ,_ _
‘catalysts in the quantities commensurate _with
This invention relates 'to- the manufacture of
f catalysts, and more particularly tothe manufac- _ _ the _extent of the~petroleumiridi1stry.'1;
Ordinary silica gel is` preciuitated by
ture of gel-type catalysts containing oxides or `
'relatively strong solutions _of alkali metal Aisili
catès with relatively .conc_entrate'df- mineral 4acids
_ hydrous oxides of'metals of .the third and fourth v
_ groups of the periodic system. While the princi#
ples of the invention may be >applied _to- the pro~ __ t to _produce a colloidalsolu'tion of silicic’aCid. and
duction of gel-type catalysts for> any `_’purpose, _ ` . the'same procedure is employedf for the'man'ufac
"tureof aluminagel and other'hydrousoxide gels
, they are particularly useful in themanufacture
"used as adsorberits.V `In _all _cases _theconçentra
of cracking catalysts, dehydration catalysts and
dehydrogenation catalysts of any desired parti
Ations are such'thatthe entire reaction" mixture
soonj sets'to ,a'hydrogeL and _this'hydrogel is
cle size, such as those employed for the catalytic ` washed with hot ’water to'removejthe' _free acid
dehydrogenation or cracking of petroleum >frac- n
_and mostof the waterf-fsolublè salts, _Howeven it.
tions fory the production of butadiene or of high
is impossible to reinovethë'augaii metal "sans from
octane gasoline and those used for dehydrating
by _this method to‘_`_„the extent neces
glycols such as 1,4-,_2,4- or_2,3-butylene glycols to
saryjfor catalytic purposes, and >therefore these
An important class of gel-type catalystsin wide
commercial use for dehydrogenation and-crack
ing reactions are silica catalystsprepared by pre
cipitating hydrated silica from waterglass solu
tions.- Alumina-silica, aluminaètitanium-'oxide
" . salts `have been* _removed ji‘rfo'rn- the freshly precipl- ‘
tated silic'ic_'__acidfg€l _by repeated filtration and
washingl" This filas 'provento be avtedious and
_expensive procedure, _for the'iiltration rate of
aqueous suspensions of ordinary gelatinous silica
_isy extremely slow. "Moreoventhe alkallmetal
ionsare adsorbed so 4'strongly vbythe continuous
> silica and alumina-zirconium. oxide-silica cata- 1
lystsare produced by precipitating solutions con
coating of gelatinous silica on afllter that large
taining aluminum or mixtures of 'alumina' with 25 quantities of Wash Water are necessary for their
zirconium or titanium on a precipitated silica hy
removal, and the slow rate of penetration of the
drogel. Representative catalysts of the first class
‘ _ vvash 'Waterthrough alilter cloth coated with a
are described in U. S. Patents Nos. 2,285,314 and
' layer of'gelatin‘ous silica has increased still fur
2,287,917. It is a principal object ofthe present "f . therthedifliculties encountered inA operating this
f invention to provide -an improved-method’for the
_process ona largev scale.
We have’discovered that an aqueous suspension
_of hydr'ou's oxides consisting oforcontainlng ge
manufacture of catalysts of these _classes,«which
yprocess is especially adapted to the large scale '
manufacture ofv gel-type catalysts of'high efli
l latinous'jhydrat'ed silica can be pretreated in such
ciency. In their broader aspects, however, some
of the features of the present invention are ap
_ ‘f a manner as to'iacilitate the _filtration and wash
ing' thereof without impairing vthe, activity of. gels
plicable to the `manufacture of any gel-'type cata- _' 'v produced when the hydrated silica is dried and
" calcined. The most important feature of our'pre
_ treatment is referred to _hereinafter as a fioccu
-` _ lation step _and the silica sc_treated is referred
lyst consisting'of cr comprising active silica.'
Gel-type catalysts containing .active vsilica
should be substantially free from alkaliv metal
to' a‘s _floccul'ated _s_i1ica,'but it should> beunder
"stood that these terms referto the condition and
position. Such catalysts should also be of'rela _ _'behavio'rÍ'of A' the silica __or'_.other _hydrated metal
compounds and >other Water-soluble salts that
might act as a flux in the iinishedcatalyst com
tively uniforml particle size, with a ¿minimum
_ " _'oxide' duringjthe._dewatering'and Washing thereof
amount ofñnesnThe'present invention 1s rpar-
which catalysts are substantially free from corn- _ '
pounds ofalkali metals and are of relatively uni- ’
ject"r the vaqueous _suspensionsr containing' gelat
inou's hydrated silica to -a conditioning procedure
which does not materially change the density.
appearance or degree of dispersion rof the hy
form particle size. A principal advantage of the
invention resides in the fact’thatgel-type lcata
lysts having these desirable properties can vbe pre
pared from such cheap and readily available -rna- "
terials> as sodium> and iwtassiurn> silicates by the
method thereof, which "method is especially
adapted for large scale manufacture of cracking
ratlher than to' any noticeable'ch'ange in the aque
ous suspensions‘afterthe 'ñocculating agent has
`_ been added._ I__lrlpl‘acticing our- invention wer sub
ticularly directed to methods forthe preparation
of gel-type catalysts containing `active silica,
‘Ídrated vsilica particle‘sin'the aqueous slurry, but
,'which _'so modiñes these „particles“ that they >form
_' a relatively thick',_porous‘iilter‘cake'of good me
" chanical strength' instead ofthe 'ordinary thin,
55 slushy filter ’cakes- that are obtained when ordi
nary gelatinous silica suspensions are filtered.
We believe that the water-dispersible adhesive
point it may be stated that except where other
wise noted all the tanks subsequent to tank I
colloids hereinafter referred to as fiocculating
agents operate to modify in some way the electric
charge on the hydrated silica particles in sus
or redisperse gels that have settled or been fioc
pension, but the advantages 0f our invention are
are equipped with agitators which move very
slowly, so that there is no tendency to break up
not limited by this theory of operation and the
suflicient additional water to reduce the SiO:
to other causes.
The flocculating agents which modify the ge
latinous silica particles in the manner described
In the tank 3 sufficient additional acid «
is added to bring the pH to about 'LOZ-’7.8 and
results obtained may be due partly or even wholly
content to 3.8%.
After suitable retention in the correction tank
3 the gelatinous hydrated silica slurry resulting
are preferably added to the aqueous gelatinous '
from the acid addition and dilution is passed to a
silica suspension after the suspension has been
blending and aging tank 4, wherein it may be
aged for a period of time, although definite im
aged under slow agitation for any suitable time.
provements are noted when the aging step has 15 Aging of the slurry appears to increase the aver
been omitted. We have found that aging ap
age particle size of the silica suspension either by
pears to aid materially in obtaining a relatively
agglomeration of the smaller particles or by their
thick and porous filter cake; in fact, we have
adhesion to larger sized particles. It will be
noted some improvements in the filtration and
noted that tanks 3 and 4 are both provided with
washing of slurries of gelatinous hydrated silica 20 side outlets, which permit the retention of about
which had been aged for 1-2 hours, but to which
25% of the aged suspension from a preceding
no ñocculating agentwas added. Our invention
batch to function as a nucleus for particle size
in its broader aspects therefore includes the com
bined steps of aging followed by filtration as one
The aged slurry is vpassed t0 tank 5, which is a
of its important features.
25 flocculating apparatus in which the silica is fioc
A number,` of important advantages are ob
culated to a condition in which it is ready Afor
tained by preconditioning pulps or slurries of ge
_ filtering and washing to remove the water-soluble
latinous hydrated silica in the manner described
alkali metal salts.> The slurry in tank 5 is first
above, prior to the dewatering thereof. We have
brought to a pH of 5-6 by the addition of suitable
found that inorganic salts such as sodium sul 30 amounts of sulfuric acid or other mineral acid
fate, sodium nitrate, sodium chloride and the
aftell which a flocculating agent is added. . Rep
like can be more rapidly and completely removed
resentative adhesive colloids that we have used
from a ñocculated silica slurry by washing as
with success for this purpose are glue, gelatin,
well as by filtration, and the silica can therefore
gluten and gluten-containing materials such as
be dewatered by any suitable procedure; More
wheatv flour 'and the like. These and similar
over, flocculation of the hydrated silica also re
flocculating agents are preferably added as solu
suits in a final dried product of much greater
tions or suspensions in water and are employed
uniformity in partidle size, as compared with the
inv amounts of 0.001% to 0.1%. based on the
irregular size of the particles obtained by drying
weight of the slurry.
hydro'gels of silica or silica and alumina obtained 40 The flocculating agent is distributed uniformly
~by the ordinary methods heretofore employed.
Our invention in its broader aspects therefore in
cludes the dewatering and washing of ilocculated
silica by any suitable method including filtra
tion, settling and decantation, thickening and the
The application of these discoveries to an im
proved method for the manufacture of gel-type
catalysts suitable for use in hydrocarbon crack
ing and conversion reactions will be illustrated
by the following description of a preferred
method of catalyst manufacture with reference
to the accompanying drawing. This drawing is
a flow sheet in which the details of our preferred
process are diagrammatically illustrated by tanks,
Afilters and flow lines, but it should be understood
that the invention in its broader aspects is not>
limited thereto.
In carrying out Àthe process illustrated in the
' throughout the hydrated silica suspension in tank
,5 by means of slow agitation, The resulting floc
culated suspension is then pumped to the distrib
`utor box B, which is a wooden box of relatively
large cross-sectional? area provided with one or
more vertical partitions ‘I and adapted to main
tain the silica in a fiocculated condition while
supplying a steady fiowof slurry to the filter Il.
This may be an ordinary filter press or any other
known type of filter, but is preferably a rotary
-filter of the vacuum drum type provided with fine
Water sprays for continuous washing of the fil
ter cake, in order to aid in the separation of
salts of alkali metals and other undesirable ma
terials‘from the silica.
. On the `filter 8 the silica can be Washed free
from the major part of its Water-soluble impur
ities by wash water which may be acidified with
a little sulfuric or hydrochloric acid, the filtra
drawing wefirst prepare a dilute solution of so 60 tion and washing being greatly aided by the floc
dium or potassium silicate in a mixing tank I,
culation of the silica in the tank 5. In large scale
which is provided with a suitable high-speed >im»
operation the wash water from this and other
pelÀlor-type or turbine type agitator 2 to obtain
, similar washing steps of the process is preferably
uniform mixing of the charge. The diluted
regenerated for reuse by contact with a cation
water glass solution is neutralized with sulfuric,
exchange resin such as sulfonated coal, which re
hydrochloric, nitric or other mineral acid to a pH
moves the sodium ions and regenerates free sul
of about 7.4-7.8, after which the agitation is con-furic acid or hydrochloric acid in the solution.
tinued for about 1/2 hour. The amounts and
The washed ñlter cake is then discharged into a
strength of the reagents are such that the solu
repulper 9, which is an enamel-lined vessel ñt
tion contains about 5% S102.
70 ted with a horizontal agitator I0 which may be
After the preliminary acidification the con
a relatively high speed agitator. In the repulper
tents of tank I are discharged into tank 3, which
the filter cake is again dispersed in water to form
is a correction tank equipped with a suitable
a uniform slurry for further treatment.
agitator and of a size suillcient to permit a reten
In the preparation of catalysts or catalyst car
tion of the charge for about '75 minutes. At this 75 riers consisting essentially of silica the slurry
' lsuitable type, such as a-hotair or steam heated
Il to a fiocculating and adjusting tank'IZ where- ' ` drier. ' By this means-we'may remove `rasfmuch
' from the repulper >9 may be passed Vthro'ughlline ~
* as 40 to 60% ofthe water inthe filter cake, _after
in the silica may be aged and flocculated >by the
‘which Lthe dryingïof the partially- dried gel may.
addition of a flocculating agent if` desired." In -
be completed‘iin a ycalcinerhof the rotary kiln
preparing mixed catalysts containing'the active
type. Alternatively, the` drying maybe carried
silica together with , other >catalytically, active
" vout in one or more rotary' kilns, and such a cal
ciner is illustrated on the drawing.
metal oxides and/or hydrogels the silica-slurry is
ñrstpassed to one of the two tanks*I3,an`d,I4.„~ A
T_he’calciner is preferably direct-'firedin a fire
solution ofaluminum sulfate or ‘other salt of the 7
desired metal'is then added tothe slurry suspen 10 box 25 and sufficient capacity is provídedvto 'heat
the catalyst to'temperatures of `1500o F. before it
sion after which sufficient ammonia is added as
` is discharged.' The dried' material is then ground
- in a. grinder 26 to «io-mesh size and is obtained
ammonium hydroxide to precipitate the hydrated
metal oxide from its salts. Thus, for‘example,
as a product containing >not more'than’0105%
' in the preparation o'f a silica-'alumina’catalyst of
~ the type described in U. S. Patent No. 2,285,314 al A1`5` fNaz'O and little or> n_o FezOa'orother undesirable
solution of aluminum sulfate `in kwater 'is added to '
the slurry of silica in the tank I3 under continu-`rv
The' following'specific examples are given to
Íshow the 'results obtained by the process of ourv
ous agitation during one-halfïhour after which
invention and also tovlllustrate the importance
8%r aqua ammonia‘is added during 10-20 min
' utes to bring the'pI'li'to’4.5-5.7.y In the prepara- „ r20 of certain features of .thisprocesa' `
tion of modified catalysts a small amount of zir
conium or titanium sulfate may also ‘be added .
Inpracticing the foregoing process. according
and precipitated. By'employing thel tanks I3
and I4 in parallel it is possible, of course, tohan
.gto oneembodiment’thereof, 4.36 tons ofsodium
die a second batch of the semi-purified silica `25' silicate in the form- 4ofvv commercial‘waterglass
f `was added to .thevmix'ingtank I, together with
while the alumina or >other polyvalent metal is
18.54 tons of water, and ,after completing- the
being added‘to and precipitated in the first batch,
dilutionl 2.2 tons 'of `24.9% sulfuric acid were
added. After agitatlng for one-half hour the
and any number of tanks may be employed in'thls
vmanner in large scale operation.-
After the addition and precipitation of alumina4 -30 'resulting slurry was passedthrough the correc
tion‘and aging tanks 3 and"l,"as=previously de
. -or other metal salts in`v the tanks I3 or Iloth‘e're- "
scribed, and 0.015% ‘of’ glue was added in the
>sulting slurry is introduced intol the aging- and
ñocculation tank I5, Glue, gelatin or other` suit
able flocculating agent may be> added in approx
imately the rsame quantities that were used inthe
-fiocculating tank 5l' After suitable >floccul'ation
,the solids were then filteredioff on the filter 8
’ and washed ‘with‘30.9 tons ofwaterïcontaining".
sufficient sulfuric acid toïreduce'the pH of 4the
wash water to 2.8. The washed filter’ _cake was
repulped with 9.6 tons of water` in therepulper
“land run into tank I3, where a solution-*of 0.8
Vtank 5 if desired, but'this'is- 'not usually neces- _‘;
, sary since the hydrated aluminum oxide makesv
the slurry much easier tolñlter. In the tankflä
»the slurry is preferably adjusted to ‘L5-6% sol
ton of> aluminum sulfatedin "1.16y tons of >water
ids by the addition of water -if' necessary,"andv
lwas added.
' kept under slow .agitationuntil the hydrated
The alum K‘was' then precipitated
by the addition of 1.87` tons of k8,%’§l\I_IH4.OH solu
washing. It is thenpassed' to the -ñlter I6, which , ' tion and the resulting> slurry wasr flocculated in
vthe tank I5 by the addition oit-0.015%v of‘glu'eas
is a rotary filter similar to the'filter `8,~ and the
flocculated solids are separatedfrom the accom 45 before., AAfter the following'filtrationstep the
alumina-silica mixture is ready for filtration and
-cake on the'filter I6 was washed- with 25.5 tons
'panying salt solution and washed with acidifled .
vof water containing sufficient sulfuric acid to
reduce its pH to 2.5-¿3 and repulped in 12.9 tons
The same
kof dilute lacid
In order to reduce still further‘the content ofl
alkali metal salts, ammonium salts, and otherl '
undesirable water-soluble material from the sil 50 and waterwere used ony the filter I8 and re
ica-alumina mixture, the filter cake is‘again' pref, . "Apulper 20, but 21.9`tons ofl'purewater were used
erably reslurried in water-,in 'a second Vrepulper ` " to Wash the filter cake onj'the filter [22. YAfter '
1 thei'calci’nation 1.26 tons of an oil-cracking cat
I'I and again filtered on la rotary filter I8, with or
alyst were `obtained which contained 90% SiOz
>and"10% A1203 in a highly active condition'. ,
`> Example 2f. ..
without reflocculation and aging in tank I9 de
pending on the condition of the solids .at this
-> point. rI‘he filter cake »from 'the' filter I8 may
then be reslurried once more in the repulper 20
.if desired, brought to a vsolids content of 5%.and
a pI-I of. 4.3-5.0 in’ the tank 2I kand filtered on the
- v52.5 pounds of water and 12.5pounds lof 41°
~ Bé.- commercial` sodium silicate containing- 28.5%
rotary filter 22 which is washed with water to 60
remove the remaining water-Soluble impurities.
The filter cake is then removed at approximate
ly 10% solids onto a belt conveyor 23, which dis
charges it into a calciner 24.
Because of the 'large quantities of water `re
tained by gelatinous hydrated silica or silica-alu
mina mixtures a relatively large drier or calciner
is necessary. In some cases, however, we havev
SiO:y and 8.9% of NazO are run into a mixing tank> f
corresponding to the mixing tank I _on the draw
. ing. 6.5 pounds of 25% sulfuric acid were addedv
wlth the agitator 2 vat sufficiently high speed to
keep the material moving away from the edges
of the tankwhen the mixture became thick.
After 30 minutes the resulting mixture was
transferred to a tank corresponding to the floc
culating tank 5 provided‘with a slow-moving,>v
gate-typeV agitator. v24 pounds ofv waterwere
found that the purified gelatinous filter cake can
be advantageously dried and calcined by a plu 70 added along with 0.1-0.3 pounds-of 25% sulfurick
acid .to reduce the pH to 6.8-'7.8. The mixture
y drying stages. Thus„` for example, we
was allowedïto age for 2 hours, the pH was re’
may-subject the wet filter cake to hot air or other
duced to 5.5'by the addition of further quantities
drying ~’gases by vsupporting iton- a belt or other
of sulfuric acid and a water-solution of glue was
conveying mechanism which is passed continu
ously or vintermittently through a drier of any 75 added equivalent -to 0.015% of glue on the weight f y
of the slurry. After completing the fiocculation
a rotary filter such as an Oliver filter. vAbout
but a .three hour period was necessary to filter
the resulting suspension and only a small amount
of wash water could be passed through the filter
20 minutes were required for the filtration and
oí the hydrated silica the fioc was dewatered on
the filter cake Was 0.75 inch thick.
The filter
cake was washed with water containing a small
VExample 5
amount of hydrochloric acid by means of fine
sprays at the rate of 2.5-3 gallons of water per
pound of SiOz in the slurry. A sample of the
8.5% of 'NazO and 28.5% of SiOz was diluted with
12.5 lbs. of 41° Bé. sodium silicate containing
52.5 lbs. of pure water lin a mixer of the turbine
filter cake was then found to contain about 0.2% 10 type (see Chemical , Engineering Handbook,
p. 1288). 6.5 lbs. of 25% sulfuric acid were added
of sodium on the weight of the SiOz.
with vigorous agitation .during 20-30 minutes,
Enough Water was added to the filter cake to
afterlwhich the mixer was emptied and Washed
make 70 pounds of slurry. To this slurry was
added 2.3 pounds of aluminum sulfate contain
with 24 lbs. of Water containing 0.3-0.4 lb. of
of A1203 in the form of 5` pounds of an 15' 25% sulfuric acid. The Wash water was added
to the precipitated silica slurry and the mixture
solution. Ammonium hydroxide con
was aged for 1.5-2 hours at a pH of 7.0-7.3. A
15% of NH3 was then addedto bring
A Water solution of glue was then added in amounts
to 4.2-5.5. The mixture was ñltered,
the filter. cake was washed as before andvslurried " ' of (ml-0.02% of glue and the flocculated hydrous
silica was dewatered by filtration. A dried sample
with enough Water to bring the solids content
of the filter cake contained 0.22% sodium.
~ '
(SiOz plus A1203) to 4-6% and the mixture was
The filter cake was washed on the filter with
again filtered and washed. This filter cake was
an amount of wash water equal to the original
again reslurried in water and filtered land the
weight of the slurry, sludged up with a little
. filter cake was washed and thoroughly dewat
ered. It was then found to contain NazO equiva 25 water and aged for 12 hours. It was then diluted
with water to 4-6% solids, 5% being the preferred
lent to only 0.01% of the weight of solids in the
ing 17%
the pH
figure, 0.015% of glue was again added. and the
silica slurry was again filtered and the filter cake
washed with acidified water. The sodium con«
' Example 3
A gelatinous hydrated silica slurry was >pre 30 tent of a dried sample of the filter cake was 0.02%.
pared exactly as described in Example 2, but was
The aging, fiocculation,A filtration and washing
filtered Without the addition of glue. The filter
was repeated a third time,rbut in this case no
cake was very wet and soft and fell away from
acid was used inl the Wash Water. This re
the filter cloth when the Wash water .was ap->
duced the sodium content to 0.01%. The filter
plied. For this reason it was difficult to wash 35 cake was then calcined as described in Example l
the filter cake on a filter of .the Oliver type.
and the resulting pure *silica catalyst Was ground
to 4-6 mesh.`
Escdmple 4
It was well suited for use as a
dehydration catalystvfor the production of buta
720 parts by weight of 41° Bé. sodium silicate
diene from butylene glycols.
solution was dissolved in 2600 parts by weight `of 40
-What we claim is:
water and the solution was placed in a kettle
1. A method of preparing a silica-containing
equipped with an agitator having three paddles
catalyst which comprises the steps of neutralizing
ank aqueous alkali metal silicate solution by the
which was rotated at 100 R. P. M.
Acid was
addedin 40 minutesto bring the pH to 3, after
addition of an vacid to form an aqueous slurry of
which the pH slowly rose to 5.0.
gelatinous'silica containing alkali metal salts,
aging the slurry, adding glue to flocculate the
silica, and separating the alkali metal salts by
dewatering and washing.-
It Was neces
sary to add sufficient acid to lower the pH to
about 3 in order to neutralize the sodium in the
grains of the hydrous SiOz, since these grains
_vary in size from a .few microns to 1/8" in diame
2. A method of preparing a silica-containing
This slurry would not filter until the pH 50 catalyst which comprises the steps of neutralizing
was increased to 6.5. It then formed a %” cake
on the filter but very litle Wash water could be
an aqueous alkali metal silicate solution by the
Aaddition of an acid to.form an aqueous slurry of
passed through the cake.
gelatinous silicaV containing alkali metal salts,
After repeated at
tempted washings a sample analyzed 1.3% of
NazO, based on the SiOz content. After reslur
rying the filter cake in Water a second attempted
filtration on the Oliver type filter gave a filter
cake only 1/8” thick. The aluminum salt was
added to a slurry of this filter cake in water and
precipitated with ammonia in the usual manner,
aging the slurry, adding glue to flocculate the
silica, and. separating the alkali metal salts by
filtering off the fiocculated silica and washing the
ñlter cake.
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