Molecular sieve abstract
Method for impregnating a Group VIII metal on a molecular sieve-binder
extrudate wherein the binder comprises a low acidity refractory
oxide binder material, which is essentially free of alumina, by
a) contacting the molecular sieve-binder extrudate with an aqueous
solution of a corresponding Group VIII metal nitrate salt having
a pH of below 8 wherein the molar ratio between the Group VIII
metal cations in the solution and the number of sorption sites present
in the extrudate is equal to or larger than 1 and b) drying the
molecular sieve-binder extrudate obtained from step a).
Molecular sieve claims
We claim:
1. A method for impregnating a Group VIII metal on a molecular
sieve-binder extrudate wherein the binder comprises a low acidity
refractory oxide binder material, which is essentially free of alumina,
comprising: a) contacting the molecular sieve-binder extrudate with
an aqueous solution of a corresponding Group VIII metal nitrate
salt having a pH of below 8 wherein the molar ratio between the
Group VIII metal cations in the solution and the number of sorption
sites present in the extrudate is equal to or larger than 1 and
b) drying the molecular sieve-binder extrudate obtained from step
a).
2. The method of claim 1 wherein the molar ratio between the Group
VIII metal cations and the number of sorption sites is between 1
and 20.
3. The method of claim 1 wherein the number of sorption sites in
the molecular sieve-binder extrudate is reduced prior to the impregnation
of the Group VIII metal by means of a dealumination treatment.
4. The method of claim 3 wherein the dealumination treatment comprises
contacting the molecular sieve or molecular sieve-binder extrudate
with a solution of ammonium hexafluoro silicate.
5. The method of claim 1 wherein the Group VIII metal is Ni, Pt,
and/or Pd.
6. The method of claim 1 wherein the Group VIII metal nitrate salt
is Ni(NO.sub.3).sub.2 Pt(NH.sub.3).sub.4(NO.sub.3).sub.2 or Pd(NH.sub.3).sub.4(NO.sub.3).sub.2.
7. The method of claim 1 wherein the molecular sieve is of the
MFI, TON, MTT or MTW type.
8. The method of claim 1 wherein the binder is silica.
9. The method of claim 1 wherein step a) is performed with an aqueous
solution of the corresponding Group VIII metal nitrate salt having
a pH in the range from 3.5 to 7.
10. The method of claim 1 wherein step a) is performed in the essential
absence of ammonium ions.
11. The method of claim 1 wherein step a) is performed by pore
volume impregnation.
12. The method of claim 1 wherein step b)is performed according
to an accelerated drying profile having a duration of less than
90 minutes, in which the temperature is increased from room temperature
up to more than 200.degree. C.
13. The method of claim 1 wherein the molecular sieve is in its
H-form before impregnation.
14. A hydrocarbon conversion process comprising contacting the
hydrocarbon with a catalyst containing the molecular sieve-binder
extrudate produced by the method of claim 1 wherein the molar ratio
of the Group VIII metal cations present in the extrudate and the
number of sorption sites present in the extrudate is between 1 and
20.
15. A dewaxing process comprising contacting a hydrocarbon feed
with a catalyst containing the molecular sieve-binder extrudate
produced by the method of claim 1 wherein the molar ratio of the
Group VIII metal cations present in the extruder and the number
of caption sites present in the extruder is between 1 and 20.
Molecular sieve description
[0001] The invention relates to a method for impregnating a Group
VIII metal on a molecular sieve-binder extrudate.
[0002] PCT patent publication No. WO-A-9641849 describes an impregnation
of platinum or palladium on a dealuminated silica-bound ZSM-5 with
an aqueous solution of tetramine platinum hydroxide or tetramine
palladium hydroxide. The impregnation of the silica-bound ZSM-5
was followed by drying for 2 hours at 120.degree. C. and calcined
for 2 hours at 300.degree. C. Thereafter the catalyst was activated
by reduction of the platinum or palladium.
[0003] A disadvantage of the impregnation method described in PCT
patent publication No. WO-A-9641849 is the long drying time. The
use of shorter drying times results in a less favourable distribution
of the platinum or palladium on the silica-bound ZSM-5. It is generally
known that a better distribution is possible when the molecular
sieve is transformed before impregnation from its H-form to a NH.sub.4-form.
By an "NH.sub.4-form" is understood that (part of) the
H+ ions in the molecular sieve are exchanged for ammonium-ions.
[0004] An example of the transformation of a molecular sieve in
a NH.sub.4-form before impregnation is described in US patent publication
U.S. Pat. No. 5397454. This patent publication describes the impregnation
of SSZ-32 zeolite powder with palladium. Before impregnation the
zeolite was subjected to a sequence of 4 NH.sub.4NO.sub.3-ion exchanges.
Hereafter it was slurried into an aqueous solution of NH.sub.4OH.
Then a tetramine palladium nitrate solution, of which the pH was
adjusted to 9.5 with NH.sub.4OH, was added slowly.
[0005] A disadvantage of this method is the long processing time
for impregnation. It would be advantageous if the extrudate with
the molecular sieve in its H-form could be used directly in the
process of impregnating a molecular sieve-binder extrudate.
[0006] The object of the present invention is to provide a method
for impregnating a Group VIII metal on a molecular sieve-binder
extrudate, which allows a short drying time and results in a good
distribution. Short drying times are desirable when a catalyst is
prepared on a commercial scale.
[0007] This object has been achieved when the following steps are
used for impregnating a Group VIII metal on a molecular sieve-binder
extrudate wherein the binder comprises a low acidity refractory
oxide binder material, which is essentially free of alumina. In
particular it relates to a method for impregnating a Group VIII
metal on such a molecular sieve-binder extrudate by ion exchange
with an aqueous solution of a Group VIII metal salt. Such steps
comprise:
[0008] a) contacting the molecular sieve-binder extrudate with
an aqueous solution of a corresponding Group VIII metal nitrate
salt having a pH of below 8 wherein the molar ratio between the
Group VIII metal cations in the solution and the number of sorption
sites present in the extrudate is equal to or larger than 1 and
[0009] b) drying the molecular sieve-binder extrudate obtained
from step a).
[0010] It has been found that with the process according to the
invention a good group VIII metal distribution is obtained, while
short drying times are possible. A further advantage is that the
molecular sieve or molecular sieve-binder extrudate can be directly
used in its H-form without the need to first transform the molecular
sieve in a NH.sub.4-form.
[0011] The choice of molecular sieve is not essential for obtaining
the advantages of the invention, namely good distribution and short
drying times. Examples of molecular sieves include metallosilicates,
metallophosphates and silica metallophosphates. Possible metallo
components in the framework of these molecular sieves include metals
such as Al, Fe, B, Ga or Ti or combinations of these metals. Preferred
molecular sieves are aluminosilicates, alumino phosphates and silica
aluminium phosphates, such as SAPO-11 SAPO-31 and SAPO-41. Especially
preferred molecular sieves are aluminosilicates, further referred
to as zeolites. Examples of suitable zeolites include ZSM-4 (Omega),
ZSM-5 ZSM-11 ZSM12 ZSM-22 ZSM-23 ZSM-35 ZSM-48 ZSM-50 Beta,
X,Y and L as well as ferrierite and mordenite and isotypic framework
structures thereof. When the catalyst, resulting after impregnation
of the molecular sieve-binder extrudate, is to be used for catalytic
dewaxing purposes, the preferred zeolite crystallites suitably have
pores with a maximum diameter in the range of from 0.35 to 0.80
nm. Preferred zeolite crystallites include MFI-type zeolites having
pores with diameters of 0.55 and 0.56 nm, such as ZSM-5 and silicalite,
offretite having pores with diameters of approximately 0.68 nm and
zeolites of the ferrierite group having pores with diameter of 0.54
nm, such as ZSM-35 and ferrierite. Another preferred class of zeolite
crystallites include TON-type zeolites. Examples of TON-type zeolite
crystallites are ZSM-22 Theta-1 and Nu-10 as described in U.S.
Pat. No. 5336478 EP-A-57049 and EP-A-65400. A further preferred
class of zeolite crystallites are of the MTW-type. Examples of molecular
sieve crystallites having the MTW-type topology are ZSM-12 Nu-13
TEA-silicate, TPZ-3 TPZ-12 VS-12 and Theta-3 as for example described
in U.S. Pat. No. 3832449 EP-A-513118 EP-A-59059 and EP-A-162719.
A next preferred class of zeolite crystallites are of the MTT-type.
Examples of zeolite crystallites having the MTT-type topology are
ZSM-23 SSZ-32 ISI-4 KZ-1 EU-1 EU-4 and EU-13 as for example
described U.S. Pat. No. 4076842 U.S. Pat. No. 4619820 EP-A-522196
EP-A-108486 and EP-A-42226.
[0012] The primary crystallite size of the molecular sieve can
vary within a wide range of 0.001 mm to 5 mm. For catalytic dewaxing
purposes the crystallite size of the zeolite may suitably be as
high as 100 micron. Preferably small crystallites are used in order
to achieve an optimum catalytic activity. Preferably crystallites
smaller than 10 micron and more preferably smaller than 1 micron
are used.
[0013] The binder of the molecular sieve-binder extrudate comprises
a low acidity refractory oxide binder material, which is essentially
free of alumina. Suitable binder materials, then, include low acidity
refractory oxides such as silica, zirconia, titanium dioxide, germanium
dioxide, boria and mixtures of two or more of these. The most preferred
binder, however, is silica. The binder may occur naturally or may
be in the form of gelatinous precipitates, sols or gels. The binder
may also be present as a mixture of those. Preferred extrudates
are those prepared by the method described in U.S. Pat. No. 5053374.
[0014] The weight ratio of the molecular sieve and the binder can
be anywhere between 5:95 and 95:5. Lower molecular sieve content
may in some cases be advantageous for achieving a higher selectivity
and higher molecular sieve content is to be preferred when a higher
activity is desired.
[0015] After extrusion the molecular sieve-binder extrudate is
dried for a time in the range of 15 minutes to 24 hours, more preferably
from 1 to 3 hours, at a temperature in the range from 10 to 350.degree.
C., more preferably from 120 to 150.degree. C. Thereafter the catalyst
composition is subjected to calcining under normal conditions, suitably
at a temperature of between 400 to 900.degree. C. by heating in
air for 1 to 48 preferably 1 to 10 hours.
[0016] Step a) of the method of the invention comprises contacting
the molecular sieve-binder extrudate with an aqueous solution of
a corresponding Group VIII metal nitrate salt having a pH of below
8 wherein the molar ratio between the Group VIII metal cations
in the solution and the number of sorption sites present in the
extrudate is equal to or larger than 1. Preferably the molar ratio
between the Group VIII metal cations and the number of sorption
sites is between 1 and 20. A sorption site is a site where theoretically
one Group VIII cation can be adsorbed. Calculation of the number
of sorption sites per gram extrudate can be done as follows. An
extrudate has a fixed value of moles H+ per gram extrudate. The
number of moles H+ per gram extrudate is determined by means of
NH.sub.3-temperature programmed desorption (TPD) as is described
in Zeolites, 19:288-396 1997. The molar number of sorption sites
according to the present invention is the number of moles H+ per
gram extrudate divided by the valency of the cation to be impregnated.
The molar ratio between the Group VIII metal cations and the number
of sorption sites is thus defined as the number of moles of the
Group VIII metal cation divided by the molar number of sorption
sites as defined above. It is to be understood that after impregnation,
the resulting catalyst (containing the modified molecular sieve-binder
extrudate) may, and normally will, contain more Group VIII metals
than the amount of which would be expected when the number of sorption
sites is taken into account. Preferably the final catalyst has a
molar ratio of Group VIII metal cations present in the extrudate
and the number of sorption sites present in the extrudate equal
to the ratio defined above.
[0017] The above mentioned ratio can be achieved in every way known
in the art. For example such a ratio can be achieved by using a
high amount or a high concentration of Group VIII metal nitrate
salt in an aqueous solution to such an extent that the above mentioned
ratio is obtained.
[0018] In a preferred embodiment the above mentioned ratio is obtained
by reducing the number of sorption sites in the molecular sieve
or molecular sieve-binder extrudate before contacting the molecular
sieve-binder extrudate with the solution in step a). The number
of sorption sites in the molecular sieve or molecular sieve-binder
extrudate can be reduced by reducing the number of acid sites of
the molecular sieve crystallites. A reduction of the number of acid
sites can be achieved by methods known in the art, for example by
subjecting the molecular sieve-binder extrudate to a hydrothermal
treatment, for example by steaming the particles at a temperature
of between 400 and 900.degree. C.
[0019] If the molecular sieve-binder extrudate contains aluminosilicates
as a molecular sieve, it has been found advantageous to subject
the molecular sieve or molecular sieve-binder extrudate to a dealumination
treatment prior to impregnation with the group VIII metal according
to the method of the invention. Dealumination results in a reduction
of the number of alumina moieties present in the aluminosilicate
and hence in a reduction of the mole percentage of acid sites and
hence in the number of sorption sites. Dealumination can be attained
by methods known in the art. Particularly useful methods are those,
wherein the dealumination selectively occurs, or anyhow is claimed
to occur selectively, at the surface of the crystallites of the
molecular sieve.
[0020] Examples of dealumination processes are described in WO-A-9641849.
Preferably dealumination is performed by a process in which the
molecular sieve or the molecular sieve-binder extrudate is contacted
with an aqueous solution of a fluorosilicate salt wherein the fluorosilicate
salt is represented by the formula:
(A).sub.2/bSiF.sub.6
[0021] wherein `A` is a metallic or non-metallic cation other than
H+ having the valence `b`. Examples of cations `b` are alkylammonium,
NH.sub.4.sup.+, Mg.sup.++, Li.sup.+, Na.sup.+, K.sup.+, Ba.sup.++,
Cd.sup.++, Cu.sup.+, Ca.sup.++, Cs.sup.+, Fe.sup.++, Co.sup.++,
Pb.sup.++, Mn.sup.++, Rb.sup.+, Ag.sup.+, Sr.sup.++, Tl.sup.+, and
Zn.sup.++. Preferably `A` is the ammonium cation. The molecular
sieve or molecular sieve-binder extrudate material may be contacted
with the fluorosilicate salt in an amount of at least 0.0075 moles
per 100 grams of the molecular sieve or molecular sieve-binder extrudate
material. The pH is suitably between 3 and 7. An example of the
above described dealumination process is described in U.S. Pat.
No. 5157191.
[0022] The method according to the invention can suitably be used
for impregnation of any Group VIII metal, for example Pt, Pd, Ni,
Ru and Co. The corresponding Group VIII metal nitrate salt can be
a simple salt, such as for example Ni(NO.sub.3).sub.2 or a complex
salt, such as for example Pt(NH.sub.3).sub.4(NO.sub.3).sub.2 Pd(NH.sub.3).sub.4(NO.sub.3).-
sub.2 Pt(NH.sub.3).sub.6(NO.sub.3).sub.4 or Pd(NH.sub.3).sub.6(NO.sub.3).-
sub.4. For catalytic dewaxing purposes, salts of Pt, Pd, Ni, and
mixtures thereof are preferred, and Pt is especially preferred.
Preferred Group VIII metal nitrate salts for catalytic dewaxing
are Ni(NO.sub.3).sub.2 Pt(NH.sub.3).sub.4(NO.sub.3).sub.2 and Pd
(NH.sub.3).sub.4(NO.sub.3).sub.- 2.
[0023] The total amount platinum, palladium or nickel, impregnated
on the molecular sieve-binder extrudate, is suitably lower than
10% by weight calculated as element and based on total weight of
molecular sieve-binder extrudate, and preferably is in the range
of from 0.01 to 5.0% by weight, more preferably from 0.1 to 1.0%
by weight.
[0024] For the impregnation of the molecular sieve-binder extrudate
according to the method of the invention, use can be made of the
various techniques known in the art, such as for example circulating
solution impregnation and pore volume impregnation. Preferably pore
volume impregnation is used, which is a very time-efficient technique.
In this technique the volume of the solution containing the Group
VIII metal salt, which is contacted with the extrudate, is about
equal to the pore volume of the molecular sieve-binder extrudate
to be impregnated (see also Studies in Surface Science and Catalysis,
vol. 58 Introduction to zeolite science and practice, H. van Bekkum
et.al. Elsevier, 1991 page 503).
[0025] The concentration of the aqueous solution of Group VIII
metal salt used to achieve the required amount of metal distributed
on the molecular sieve-binder extrudate can vary within wide ranges
and effects the duration of the impregnation. The preferred concentration
of Group VIII metal salt is less than 20%. When using pore volume
impregnation, the concentration is preferably within the range of
0.02 to 10.0 by weight, most preferably from 0.2 to 2.0%. The molecular
sieve-binder extrudate is contacted with the solution for a time
effective to impregnate the Group VIII metal salt. The duration
of the impregnation suitably varies from 5 minutes to 24 hours,
more preferably varies from 5 minutes to 3 hours.
[0026] The aqueous solution used in step (a) has a pH of less than
8 preferably between 3.5 and 7. The aqueous solution may contain
ammonium ions provided the pH is within the claimed range. Preferably
ammonium-ions are essentially absent from the solution.
[0027] The temperature applied in step (a) is not critical and
can vary within a range of below room temperature up to about 100.degree.
C., more preferably within a range of 15 to 65.degree. C. Preferably
the impregnation is performed at room temperature for reasons of
convenience.
[0028] The pressure may vary within wide ranges and is not critical.
For reasons of convenience the impregnation according to step (a)
of the method of the invention is preferably conducted under atmospheric
pressures.
[0029] Other metals may optionally be present in the molecular
sieve or molecular sieve-silica extrudate, before impregnation with
the Group VIII metal nitrate salt according to the method of the
invention.
[0030] Step b) according to the method of the invention comprises
drying the molecular sieve-binder extrudate obtained from step a).
The in step a) modified molecular sieve-binder extrudate can suitably
be dried at temperatures ranging from room temperature to 350.degree.
C., according to any drying profile known in the art. In a preferred
embodiment the molecular sieve-binder extrudate is dried according
to an accelerated drying profile having a duration of less than
90 minutes, in which the temperature is increased from about room
temperature up to more than 200.degree. C., preferably up to more
than 250.degree. C. The drying profile can comprise a continuous,
linear or non-linear, increase of the temperature, or can comprise
stages in which the temperature is raised and stages in which the
temperature is maintained stable. For batch-wise processes a preferred
accelerated drying profile comprises the following steps: raising
the temperature at a rate in the range of 10.degree. C. to 20.degree.
C. per minute, to a temperature in the range of 150.degree. C. to
200.degree. C.; maintaining this temperature for an amount of time
in the range of 5 to 15 minutes; raising the temperature at a rate
in the range of 10.degree. C. to 40.degree. C. per minute, to a
temperature in the range of 250.degree. C. to 300.degree. C.; maintaining
this temperature for an amount of time in the range of 10 to 20
minutes; cooling down to room temperature. For continuous processes
a preferred accelerated drying profile comprises a continuous temperature
increase, wherein the increase can be gradually or wherein the rate
of temperature increase varies. The use of this accelerated drying
profile can decrease the drying time which is especially advantageous
when a catalyst is prepared on a commercial scale. As will become
clear from the examples, impregnation according to the method of
the invention allows one to use such an accelerated drying profile
while still obtaining a good distribution of the metal over the
molecular sieve-binder extrudate.
[0031] After drying, the molecular sieve-binder extrudate is optionally
calcined at a temperature between about 350.degree. C. and 500.degree.
C.
[0032] The catalyst containing the molecular sieve-binder extrudate
may be activated before use, in any way known in the art, for example
by reducing of the Group VIII cation with hydrogen.
[0033] The catalyst resulting after the treatment of a molecular
sieve-binder extrudate according to the method of the invention
can be used in any hydrocarbon conversion reaction. Examples of
such hydrocarbon conversion reactions are hydrocracking, isomerization,
alkylation, hydrogenation, dehydrogenation, polymerization, reforming,
catalytic cracking and catalytic hydrocracking. The catalyst may
be suitably used in catalytic dewaxing. By catalytic dewaxing is
meant a process for decreasing the pour point of lubricating base
oil products by selectively converting the components of the oil
feed which impart a high pour point to products which do not impart
a high pour point. Products which impart a high pour point are compounds
having a high melting point. These compounds are referred to as
waxes. Wax compounds include for example high temperature melting
normal paraffins, iso-paraffins and mono-ringed compounds. The pour
point is preferably reduced by at least 10.degree. C. and more preferably
by at least 20.degree. C. Examples of such catalytic dewaxing processes
are described in the before mentioned PCT patent publication No.
9641849.
[0034] The catalyst can be used in the catalytic dewaxing of any
kind of hydrocarbon feed. Suitably the catalyst can be used in the
catalytic dewaxing of lubricants, base oil products, gas oils and
feeds having relatively high amounts of waxy compounds. Examples
of feeds with a high amount of waxy compounds are synthetic waxy
raffinates (Fischer-Tropsch waxy raffinates), hydrocracker bottom
fractions (hydrowax) and slack waxes obtained from the dewaxing
of hydroprocessed or solvent refined waxy distillates.
[0035] The method of the invention will now be illustrated by the
following non-limiting examples.
COMPARATIVE EXAMPLE A
[0036] ZSM-5/silica extrudate (30%/70% w/w, calcined at 800.degree.
C.) was treated with a 0.01 M aqueous ammonium hexafluorosilicate
(AHS) solution, washed, dried and calcined. The extrudate contained
0.048 H+ mmoles/gram extrudate. Hereafter 22.65 gram of the extrudate
was impregnated with about 0.7% w/w platinum by pore volume impregnation
in 5 minutes with 16.23 ml of a 5.0 M aqueous solution containing
2.79 gram of a tetramine platinum hydroxide (Pt(NH.sub.3).sub.4(OH).sub.2)-solution
(5.9% w/w Pt). The pH of the solution was >8. The impregnated
extrudate was not washed, but dried according to a slow drying profile
by; drying during 2 hours at 120.degree. C.; whereafter the temperature
was raised with 25.degree. C./minute to 190.degree. C. and held
stable during 1 hours; whereafter the temperature was raised again
with 50.degree. C./minute to a temperature of 300.degree. C. and
held stable during 1 hour. Hereafter the extrudate was cooled down
to room temperature. The 0.048 H+ mmoles/gram extrudate correspond
with 0.024 mmoles sorption sites for Pt 2+ cations. 22.65 gram extrudate
contains 0.54 mmoles sorption sites. From the above it can be calculated
that the solution contained 0.84 mmoles Pt2+ cations. Thus the molar
ratio between the Pt 2+ cations and the number of sorption sites
was 1.55. The obtained platinum distribution was examined visually
and was satisfactory.
COMPARATIVE EXAMPLE B
[0037] ZSM-5/silica extrudate (30%/70% w/w, calcined at 800.degree.
C.) was treated with 0.01 M AHS, washed, dried and calcined. The
extrudate contained 0.048 H+ mmoles/gram extrudate. Hereafter 29.15
gram of the extrudate was impregnated with about 0.7% platinum by
pore volume impregnation in 5 minutes with 20.96 ml of an aqueous
solution containing 3.59 gram of a tetramine platinum hydroxide
(Pt(NH.sub.3).sub.4(OH).sub.2- )-solution (5.9% w/w Pt). The pH
of the solution was >8. The extrudate was not washed but dried
by an accelerated drying profile; by raising the temperature with
15.degree. C./minute to 180.degree. C.; maintaining this temperature
for 10 minutes; raising the temperature again with 30.degree. C./minute
to 290.degree. C.; maintaining this temperature for 15 minutes.
Hereafter the extrudate was cooled down to room temperature. The
molar ratio between the Pt 2+ cations and the number of sorption
sites was 1.55. No distribution of the platinum was obtained since
the tetramine platinum hydroxide complex did not decompose.
EXAMPLE 1
[0038] ZSM-5/silica extrudate (30%/70% w/w, calcined at 800.degree.
C.) was treated with 0.01 M AHS, washed, dried and calcined. The
extrudate contained 0.048 H+ mmoles/gram extrudate. Hereafter 29.15
gram of the extrudate was impregnated with about 0.7% w/w platinum
by pore volume impregnation in 5 minutes with 20.96 ml of an aqueous
solution containing 6.82 gram of a tetramine platinum nitrate (Pt(NH.sub.3).sub.4(NO.sub.3).s-
ub.2-solution (2.99% w/w Pt) The pH of the solution was about 6.
The extrudate was not washed but dried and calcined by an accelerated
drying profile; by raising the temperature with 15.degree. C./minute
to 180.degree. C.; maintaining this temperature for 10 minutes;
raising the temperature again with 30.degree. C./minute to 290.degree.
C.; maintaining this temperature for 15 minutes. Hereafter the extrudate
was cooled down to room temperature. The molar ratio between the
Pt 2+ cations and the number of sorption sites was 1.49. A good
platinum distribution was obtained.
EXAMPLE 2
[0039] ZSM-5/silica extrudate (30%/70% w/w, calcined at 800.degree.
C.) was treated with an AHS solution, washed, dried and calcined.
The extrudate contained 0.048 H+ mmoles/gram extrudate. Hereafter
47.96 gram of the extrudate was impregnated with about 0.7% w/w
Nickel by pore volume impregnation in about 15 minutes with 30.74
ml of a aqueous solution containing 1.68 gram of a nickel nitrate
salt (Ni(NO.sub.3).sub.2.6H.sub.2O). The pH of the solution was
about 4. The extrudate was washed and dried and calcined by an accelerated
drying profile; by raising the temperature with 15.degree. C./minute
to 180.degree. C.; maintaining this temperature for 10 minutes;
raising the temperature again with 30.degree. C./minute to 300.degree.
C.; maintaining this temperature for 15 minutes. Hereafter the extrudate
was cooled down to room temperature. The molar ratio between the
Ni 2+ cations and the number of sorption sites present in the extrudate
was 5.0. A good nickel distribution was obtained.
[0040] A summary of the results obtained in the examples is given
in Table 1. In Comparative example A, a satisfactory distribution
result was obtained by using tetramine platinum hydroxide and a
slow drying profile. When an accelerated drying profile was used
instead of the slow drying profile, as illustrated in Comparative
example B, the tetramine platinum hydroxide complex was found not
to decompose. When this catalyst was subsequently activated in a
reductive atmosphere, a migration of Pt to the exterior of the catalyst
was observed, resulting in an unacceptable loss of performance.
Examples 1 and 2 show that an accelerated drying profile can be
used, while obtaining at the same time full decomposition of the
complex as well as a good distribution, when a Group VIII metal
nitrate complex is used according to the invention.
1TABLE 1 pH of ratio of Group Ex- Group VIII the Form of the VIII
metal peri- metal salt solu- molecular drying cations over Distribution
ment used tion sieve profile sorption sites result A Pt(NH.sub.3).sub.4(OH).sub-
.2 >8 H-form slow 1.55 satisfactory B Pt(NH.sub.3).sub.4(OH).sub-
.2 >8 H-form accelerated 1.55 the complex did not decompose 1
Pt(NH.sub.3).sub.4(NO.sub.3).sub.2 .+-.6 H-form accelerated 1.49
good 2 Ni(NO.sub.3).sub.2.6H.sub.2O .+-.4 H-form accelerated 5.0
good
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