Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Heavy feed HPC process using a mixture of catalysts
The present invention relates to a process for hydroprocessing a heavy
hydrocarbon oil, in particular a process in which a mixture of two catalysts
is
used to obtain advantageous effects in the hydroprocessing of heavy
hydrocarbon oils. The present invention also relates to a mixture of catalysts
suitable for use in such a process.
More particularly, the present invention relates to a process suitable for the
hydroprocessing of heavy hydrocarbon oils containing ~ a large amount of
impurities such as sulfur, metals, and asphaltene to effect
hydrodesulfurisation
(HDS), hydrodemetallisation (HDM), asphaltene reduction (HDAsp) and/or
conversion into lighter products-, while limiting the amount of sediment
produced. The feed may also contain other contaminants such as Conradson
carbon residue (CCR) and nitrogen, and carbon residue reduction (HDCCR)
and hydrodenitrification (HDN) may also be desired processes.
Hydrocarbon oils containing 50 wt.% or more of components with a boiling point
of 538°C or higher are called heavy hydrocarbon oils. These include
atmospheric residue (AR) and vacuum residue (VR), which are produced in
petroleum refining. It is desired to remove impurities such as sulfur from
these
heavy hydrocarbon oils by hydroprocessing, and to convert them into lighter
oils, which have a higher economic value.
The hydroprocessing of heavy hydrocarbon oils is done in ebullating bed
operation or in fixed bed operation.
For ebullating bed operation, various catalysts have been proposed. Generally,
these catalysts are capable of efficiently removing sulfur, Conradson carbon
residue (CCR), various metals, nitrogen and/or asphaltenes. However, it was
found that the decomposition of asphaltenes, an aggregate of condensed
CONFIRMATION COPY
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aromatic compounds which is in good balance with the rest of the feedstock, is
generally accompanied by the formation of sediment and sludge.
Sediment can be determined by the Shell hot filtration solid test (SHFST).
(see
Van Kerkvoort et al., J. Inst Pet., 37, I pp. 596-604 (1951)). Its ordinary
content
is said to be about 0.19 to 1 wt.% in product with a boiling point of
340°C or
higher collected from the bottom of a flash drum.
Sediment formed during hydroprocessing operations may settle and deposit in
such apparatuses as heat exchangers and reactors, and because it threatens to
close off the passage, it can seriously hamper the operation of these
apparatuses. Especially in the hydroprocessing of heavy hydrocarbon feeds
containing large amounts of vacuum residue, sediment formation is an
important factor, and there is therefore need for a process for effecting
efficient
contaminant removal in combination with low sediment formation and high
conversion.
US 5,100,855 describes a catalyst mixture for effecting hydrodemetallisation,
hydrodesulphurisation, hydrodenitrogenation and hydroconversion of an
asphaltene-containing feedstock, wherein one catalyst is a relatively small-
pore
catalyst and the other possesses a relatively large amount of macropore
volume. The catalyst mixture is preferably applied in an ebullating bed. The
first
catalyst has less than 0.10 ml/g of pore volume in pores with a diameter above
200 A, less than 0.02 ml/g in pores with a diameter above 800 ,~, and a
maximum average mesopore diameter of 130 A. The second catalyst has more
than 0.07 mllg of pore volume in pores with a diameter of greater than 800 A.
US 6,086,749 describes a process and catalyst system for use in a moving bed,
wherein a mixture of two types of catalysts is used, each designed for a
different function such as hydrodemetallisation and hydrodenitrogenation,
respectively. At least one of the catalysts preferably has at least 75% of its
pore
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volume in pores with a diameter of 100-300 ,4, and less than 20% of its pore
volume in pores with a diameter below 100 A.
The object of the present invention is to provide an effective process for the
hydroprocessing of a heavy hydrocarbon oil containing a large. amount of
impurities such as sulfur, Conradson carbon residue, metals, nitrogen, and
asphaltene, especially a heavy oil containing 80% or more vacuum residue
fractions, for adequately removing the impurities. 1n addition to efiFicient
contaminant removal, the process should show low sediment formation, high
asphaltene removal, and high conversion. Further, it should possess high
flexibility.
On the basis of diligent research, a process was invented for the
hydroprocessing of heavy hydrocarbon oils, wherein a heavy oil is contacted
with a mixture of two different hydrotreating catalysts, both catalysts
meeting
specific repuirements as to surface area, pore volume, and pore size
distribution. The first catalyst is specifically designed to decrease the
impurities
in the heavy hydrocarbon oil. In particular, it achieves demetallisation and
efficient asphaltene removal, which is effective in preventing asphaltene
precipitation. The second catalyst is tailored to effect advanced
desulfurisation
and hydrogenation reactions while inhibiting sediment formation due to
asphaltene precipitation, to allow stable operation.
The use of a mixture of the two different catalysts leads to a synergistic
effect
resulting in a process showing stable operation, high contaminant removal and
conversion activity, and low sediment formation, this in combination with
great
. flexibility in operation.
The process according to the invention is a process for hydroprocessing a
heavy hydrocarbon oil, comprising contacting a heavy hydrocarbon oil in the
presence of hydrogen with a mixture of hydroprocessing catalyst I and
hydroprocessing catalyst II, wherein
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~ catalyst I comprises a Group V1B metal component and optionally a Group
VIII metal component on a porous inorganic carrier, said catalyst having a
specific surface area of at least 100 m2/g, a total pore volume of at least
0.55 ml/g, at least 50% of the total pore volume in pores with a diameter of
at least 20 nm (200 ,4), and 10-30% of the total pore volume in pores with a
diameter of at least 200 nm (2000 A) and
~ catalyst II comprises a Group VIB metal component and optionally a Group
VIII metal component on a porous inorganic carrier, said catalyst having a
specific surface area of at least 100 m2/g, a total pore volume of at least
0.55 ml/g, at (east 75% of the total pore volume in pores with a diameter of
10-120 nm (100-1200 A), 0-2% of the total pore volume in pores with a
diameter of at least 400 nm (4000 A), and 0-1 % of the total pore volume in
pores with a diameter of at least 1000 nm (10000 A).
The present invention also pertains to a mixture of catalysts suitable for use
in
such a process, wherein the catalyst mixture comprises catalysts I and II
defined above.
The catalysts used in the process according to the invention comprise
catalytic
2o materials on a porous carrier. The catalytic materials present on the
catalysts
used in the process according to the invention comprise a Group VIB metal and
optionally a Group VIII metal of the Periodic Table of Elements applied by
Chemical Abstract Services (CAS system). It is preferred for a Group Vlll
metal
to ~be present on the catalysts used in the process according to the
invention.
The Group Vlll metal used in this invention is at least one selected from
nickel,
cobalt, and iron. In view of performance and economy, cobalt and nickel are
preferred. Nickel is especially preferred. As the Group VIB metals which can
be
used, molybdenum, tungsten, and chromium may be mentioned, but in view of
performance and economy,. molybdenum is preferred. The combination of
molybdenum and nickel is particularly preferred for the catalytic materials of
the
catalyst according to the invention.
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Based on the weight (100 wt.°l°) ofi the fiinal catalysfi, the
amounts of the
respective catalytic materials used in the catalysts used in the process
according to the invention are as follows.
5
The catalysts generally comprise 4-30 wt.% of Group VIB metal, calculated as
trioxide, preferably 7-20 wt.%, more preferably 8-16 wt.°I°. if
less than 4 wt.% is
used, the activity of the catalyst is generally less than optimal. On the
other
hand, ifi more than 16 wt.%, in particular more than 20 wt.% is used, the
catalytic performance is generally not improved further. Optimum activity is
obtained when the Group VI metal content is selected to be within the cited
preferred ranges.
As indicated above, it is preferred fior the catalysts to comprise a Group
Vlll
metal component. If applied, this component is preferably present in an amount
of 0.5-6 wt.%, more preferably 1-5 wt.%, of Group VIII metal, calculated as
oxide. If the amount is less than 0.5 wt.%, the activity of the catalysts is
less
than optimal. If 'more than 6 wt.% is present, the catalyst performance will
not
be improved further.
2o The total pore volume of catalyst I and catalyst II is at least 0.55 ml/g,
preferably
at least 0.6 ml/g. It is preferred for it to be at most 1.0 ml/g, more
preferably at
most 0.9 ml/g. The determination of the total pore volume and the pore size
distribution is effected via mercury penetration at a contact angle of
140° with a
surface tension ofi 480 dynes/cm, using, for example, a mercury porosimeter
Autopore II (trade name) produced by Micrometrics.
Catalyst I has a specific surface area of at least 100 m2/g. For the catalyst
to
meet the required pore size distribution ranges, it is preferred fior it to
have a
surface area of 100-180 m2lg, preferably 150-170 m2/g. If the surfiace area is
less than 100 m2/g, the catalytic activity will be too low. In the present
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specification the surface area is determined in accordance with the BET method
based on N2 adsorption.
Catalyst I has at least 50% of the total pore volume in pores with a diameter
of
at least 20 nm (200 A), preferably at least 60%. The percentage of pore volume
in this range is preferably at most 80%. If the percentage of pore volume in
this
range is below 50%, the catalytic performance, especially the asphaltene
cracking activity, will decrease. As a result thereof, sediment formation will
increase. The carrier of catalyst I preferably shows at least 43% of pore
volume
in this range, more preferably at least 47%. The percentage of pore volume in
this range for the carrier preferably is at most 75%, more preferably at most
70%.
Catalyst I has 10-30% of the total pore volume in pores with a diameter of at
least 200 nm (2000 A), preferably 15-25%. If the percentage of pores in this
range is too low, the asphaltene removal capacity in the bottom of the reactor
will decrease, therewith increasing sediment formation. If the percentage of
pores in this range is too high, the mechanical strength of the catalyst will
decrease, possibly to a value which may be unacceptable for commercial
operation.
To improve catalyst strength and activity, Catalyst I preferably has 0-5% of
the
total pore volume in pores with a diameter above 1000 nm (10000 A), more
preferably 0-1 %.
Especially when the feedstock contains a large amount of vacuum residue, that
is, if the percentage of the feed boiling above 538°C is at least 70%,
more'
preferably at least 80%, it is preferred for Catalyst I to have a %PV(10-120
nm)
(%PV(100-1200 A)) of less than 85%, preferably less than 82%, still more
preferably less than 80%. If the percentage of pore volume present in this
range
becomes too high, the percentage of pore volume in pores with a diameter
above 200 nm (2000 A) will decrease, and the residue cracking rate may be
insufficient.
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It is preferred for Catalyst I to have less than 0.2 ml/g of pore volume in
pores
with a diameter of 50-150 nm (500 to 1,500 A). If more than 0.2 ml/g of pore
volume is present in this range, the relative percentage of pore volume
present
in pores with a diameter below 30 nm (300 A) will decrease, and the catalytic
performance may decline. Additionally, since pores with a diameter below 30
nm (300 A) are liable to closing by very heavy feedstock components, it is
feared that the life of the catalyst may be shortened if the amount of pore
volume present in this range is relatively too small.
Additionally, it is preferred for Catalyst I to have less than 25% of its pore
volume in pores with a diameter of 10 nm (100 A) or less, more preferably less
than 17%, still more preferably less than 10%. If the percentage of pore
volume
present in this range is above this value, sediment formation may increase due
to increased hydrogenation of the non-asphaltenic feed constituents.
Catalyst I is based on a porous inorganic oxide carrier which generally
comprises the conventional oxides, e.g., alumina, silica, silica-alumina,
alumina
with silica-alumina dispersed therein, silica-coated alumina, magnesia,
zirconia,
boric, and titanic, as well as mixtures of these oxides. It is preferred for
the
carrier to consist for at least 80% of alumina, more preferably at least 90%,
still
more preferably at least 95%. A carrier consisting essentially of alumina is
preferred, the wording "consisting essentially ofi' being intended to mean
that
minor amounts of other components may be present, as long as they do not
detrimentally affect the catalytic activity of the catalyst. An example of a
suitable
catalyst I is the catalyst described in WO 01/100541.
Catalyst II has a specific surface area of at least 100 m2/g, preferably at
least
130 m2/g. If the surface area is below 100 m2/g, the catalytic activity will
be
insufficient.
Catalyst II will have at least 75% of the total pore volume in pores with a
diameter of 10-120 nm (100-1200 A), preferably at least 78%. If the percentage
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of pore volume in this range is insufficient, the hydrocracking and
hydrodesulfurisation activity of the catalyst will be insufficient. Catalyst
II has 0-
2% of the total pore volume in pores with a diameter of at least 400 nm
(4000 A), and 0-1 % of the total pore volume in pores with a diameter of at
least
1000 nm (10000 A). If these requirements are not met, the stability of the
hydrodesulfurisation and hydrocracking activity of Catalyst II cannot be
guaranteed.
Catalyst II has a %PV(>2000 A) which is less than that of catalyst I.
Preferably,
it is less than 10%, more preferably it is less than 5 %, still more
preferably it is
less than 3%.
Additionally, it is preferred for Catalyst II to have less than 25% of its
pore
volume in pores with a diameter of 10 nm (100 A) or less, more preferably less
than 17%, still more preferably less than 10%. If the percentage of pore
volume
present in this range is above this value, sediment formation may increase due
to increased hydrogenation of the non-asphaltenic feed constituents.
Catalyst II is also based on a porous inorganic oxide carrier which generally
comprises the conventional oxides, e.g., alumina, silica, silica-alumina,
alumina
with silica-alumina dispersed therein, silica-coated alumina, magnesia,
~irconia,
boria, and titania, as well as mixtures of these oxides. It is preferred for
the
carrier to consist for at least 70 wt.% of alumina, more preferably at least
88
wt.%, with the balance being made up of silica.
We have developed two specific embodiments of catalyst II, which were found
to be particularly suitable for use in the process according to the invention.
The first specific embodiment, further indicated as Catalyst Ila, has a
surface
area of at least 100 m2/g. It is preferably between 100 and 180 m2/g, more
preferably between 150 and 170 m2/g. It has at least 75% of the total pore
volume in pores with a diameter of 10-120 nm (100-1200 A), preferably at least
85%, more preferably at least 87%. Catalyst Ila preferably has a %PV(>200 A
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of at least 50%, preferably 60-80%, a %PV(>1000 A) of at least 5%, preferably
5-30%, more preferably 8-25%.
Catalyst Ila preferably is based on an alumina carrier. As the alumina carrier
in
this embodiment, a carrier consisting essentially of alumina is preferred, the
wording "consisting essentially of being intended to mean that minor amounts
of other components may be present, as long as they do not detrimentally
affect
the catalytic activity of the catalyst.
However, if it is necessary to improve catalyst strength and/or carrier
acidity, the
carrier can contain at least one material selected, for example, from oxides
of
silicon, titanium, zirconium, boron, zinc, phosphorus, alkali metals and
alkaline
earth metals, zeolite, and clay minerals. These material are preferably
present
in an amount of less than 5 wt.%, based on the weight of the completed
catalyst, preferably less than 2.5 wt.%, more preferably less than 1.5' wt.%,
still
more preferably less than 0.5 wt.%. Suitable catalysts meeting the
requirements
of catalyst Ila are described in WO 02/053286.
The second specific embodiment, further indicated as Catalyst Ilb, has a
surface area of at least 150 m2/g, preferably 185-250 m2/g. It has at least
75%
of the total pore volume in pores with a diameter of 10-120 nm (100-1200 A),
preferably at least 78%. It may be preferred for catalyst Ilb to have less
than
50% of its pore volume present in pores with a diameter of above 20.0 A, more
preferably less than 40%.
Catalyst Ilb is preferably based on a carrier comprising at least 3.5 wt.% of
silica, calculated on the weight of the final catalyst, more preferably 3.5-30
wt.%, still more preferably 4-12 wt.%, even more preferably 4.5-10 wt.%. The
presence of at least 3.5 wt.% of silica has been found to increase the
performance of Catalyst Ilb. The balance of the carrier of. catalyst Ilb is
generally made up of alumina, optionally containing other refractory oxides,
such as titanic, zirconia, etc. It is preferred that the balance of the
carrier of
catalyst Ilb is made up of at least 90% of alumina, more preferably at least
95%.
It is preferred for the carrier of the catalyst of the invention to consist
essentially
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of silica and alumina, the wording "consists essentially of being intended to
mean that minor amounts of other components may be present,.as long as they
do not detrimentally affect the catalytic activity of the catalyst. .
It may also be preferred for Catalyst Ilb to comprise a Group IA metal
5 component. Sodium and potassium may be mentioned as suitable materials.
Sodium is preferred for reasons of performance and economy. The amount of
Group IA metal is 0.1-2 wt.%, preferably 0.2-1 wt.%, more preferably 0.1-0.5
wt.%, calculated as oxide.
10 If less than 0.1 wt.% is present, the desired effect will not be obtained.
If more
than 2 wt.%, is present, or sometimes more than 1 wt.%, the activity of the
catalyst will be adversely affected.
It may additionally be preferred for catalyst Ilb to comprise a compound of
Group VA, more in particular one or more compounds selected from
phosphorus, arsenic, antimony, and bismuth. Phosphorus is preferred. The
compound in this case preferably is present in an amount of 0.05-3 wt.%, more
preferably 0.1-2 wt.%., still more preferably 0.1-1 wt.%, calculated as P2Qs.
A particularly preferred embodiment of catalyst Ilb comprises the combination
of
silica and a Group IA metal component, in particular sodium, as described
above.
Another particularly preferred embodiment of catalyst Ilb comprises the
combination of silica and phosphorus as described above.
Still another particularly preferred embodiment of catalyst Ilb comprises the
combination of silica, Group IA metal component, in particular sodium, and
phosphorus as described above.
Optionally, catalyst II of the present invention comprises a mixture of
catalysts
Ila and Ilb. If a mixture of catalyst Ila and catalyst Ilb is used, it is
preferred for
catalyst Ila to have at least 50% of its pore volume in pores with a diameter
above 200 A, more preferably 60-80%, while for catalyst Ilb it is preferred to
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have less than 50% of its pore volume present in pores with a diameter of
above 200 A, more preferably less than 40%.
If this requirement is met, catalyst Ila will show good asphaltene cracking
properties and low sediment formation and catalyst Ilb will show good
hydrodesulfurisation activity and good hydrogenation activity, and the
combination will lead to very good results.
If a mixture of catalysts Ila and Ilb is applied, the mixture has to comprise
at
least 1 wt.% of catalyst Ilb, calculated on the total amount of catalysts Ila
and
Ilb, preferably at least 10 wt.%. The mixture preferably comprises up to 50
wt.%
of catalyst Ilb, preferably up to 30 wt.%.
If this requirement is met, the hydrogenation activity of the total amount of
catalyst II will be well-balanced, and low sediment formation can easily be
obtained.
If catalyst II comprises a mixture of catalysts Ila and Ilb, it is
particularly
preferred for catalyst Ilb to comprise a compound of Group VA, more in
particular one or more compounds selected from phosphorus, arsenic,
antimony, and bismuth, more in part phosphorus, as described above.
As indicated above, the present invention is directed to a mixture of catalyst
I
and catalyst II and its use in the hydroprocessing of heavy hydrocarbon feeds.
In the context of the present invention, the term mixture is intended to refer
to a
catalyst system wherein, when the catalyst has been brought into the unit,
both
the top half of the catalyst volume and the bottom half of the catalyst volume
contain at least 1 % of both types of catalyst. The term mixture is not
intended to
refer to a catalyst system wherein the feed is first contacted with one type
of
catalyst and then with the other type of catalyst. The term catalyst volume is
intended to refer to the volume of catalyst comprising both catalyst I and
catalyst II. Optional following layers or units comprising other catalyst
types are
not included therein.
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It is preferred for the mixture in the context of the present invention to be
such
that if the catalyst volume is horizontally divided into four parts of equal
volume,
each part contains at least 1 % of both types of catalyst. It is even more
preferred for the mixture in the context of the present invention to be such
that if
the catalyst volume is horizontally divided into ten parts of equal volume,
each
part contains at least 1 % of both types of catalyst.
In the above definitions, at least 1% of both types of catalyst should be
present
in the indicated section, preferably at least 5%, more preferably at least
10%.
Obviously it is not intended for, e.g., the right-hand half of the unit to be
filled
with one type of catalyst while the left-hand half of the unit is filled with
another
type of catalyst. Accordingly, the word mixture as applied in the present
invention also requires that both the right-hand side and the left hand side
of the
catalyst volume contain at least 1% of both types of catalyst. Preferably, if
the
catalyst volume is vertically divided into four parts of equal volume, each
part
contains at least 1 % of both types of catalyst. More preferably, if the
catalyst
volume is vertically divided into ten parts of equal volume, each part
contains at
least 1 % of both types of catalyst. In the definitions in this paragraph, at
least
1 % of both types of catalyst should be present in the indicated section,
2o preferably at least 5%, more preferably at least 10%.
There are various ways in which a catalyst mixture can be obtained.
The first one, which is inherent to ebullating bed operation and preferred for
fixed bed operation, is a random mixture of the two types of catalyst
particles.
With regard to ebullating bed operation it should be noted that the word
random
includes natural segregation taking place in the unit due to differences in
density between the catalyst particles.
A further method applicable to fixed bed units would be to apply the two types
of
catalysts in (thin) alternating layers.
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An additional method would be to sock-load the unit with socks of the two
types
of catalysts, wherein each sock contains one type of catalyst, but wherein the
combination of socks results in a mixture of catalysts as defined above.
Overall, the mixture of catalysts I and II generally comprises 2-98 wt.% of
catalyst I and 2-98 wt.% of catalyst II. Preferably, the mixture comprises 10-
90
wt.% of catalyst I, more preferably 20-80 wt.% of catalyst I, still more
preferably
30-70 wt.% of catalyst I. The mixture preferably comprises 10-90 wt.% of
catalyst II, more preferably 20-80 wt.% of catalyst II, still more preferably
30-70
wt.% of catalyst II.
The catalyst particles can have the shapes and dimensions common to the art.
Thus, the particles may be spherical, cylindrical, or polylobal and their
diameter
may range from 0.5 to 10 mm. Particles with a diameter of 0.5-3 mm, preferably
0.7-1.2 mm, for example 0.9-1 mm, and a length of 2-10 mm, for example 2.5-
4.5 mm, are preferred. For use in fixed bed operation polylobal particles are
preferred, because they lead to a reduced pressure drop in
hydrodemetallisation operations. Cylindrical particles are preferred for use
in
ebullating bed operations.
The carrier to be used in the catalysts to be used in the process according to
the invention can be prepared by processes known in the art.
A typical production process for a carrier comprising alumina is
coprecipitation
of sodium aluminate and aluminium sulfate. The resulting gel is dried,
extruded,
and calcined, to obtain an alumina-containing carrier. Optionally, other
components such as silica may be added before, during, or after precipitation.
By way of example, a process for preparing an alumina gel will be described
below. First, a tank containing tap water or warm water is charged with an
alkali
solution of sodium aluminate, aluminium hydroxide or sodium hydroxide, etc.,
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and an acidic aluminium solution of aluminium sulfate or aluminium nitrate,
etc.
is added for mixing.
The hydrogen ion concentration (pH) of the mixed solution changes with the
progression of the reaction. It is preferable that when the addition of the
acidic
aluminium solution is completed, the pH is 7 to 9, and that during mixing, the
temperature is 60 to 75°C. The mixture is then kept at that temperature
for, in
general, 0.5-1.5 hours, preferably for 40-80 minutes.
By way of a further example, a process for preparing a silica-containing
alumina
gel is described below. First, an alkali solution such as sodium aluminate,
ammonium hydroxide or sodium hydroxide is fed into a tank containing tap
water or hot water, an acid solution of an aluminium source, e.g., aluminium
sulfate or aluminium nitrate, is added, and the resulting mixture is mixed.
The pH of the mixture changes as the reaction progresses. Preferably, after
all
the acid aluminium compound solution has been added, the pH is 7 to 9. After
completion of the mixing an alumina hydrogel can be obtained. Then, an alkali
metal silicate such as a water glass or an organic silica solution is added as
silica source. To mix the silica source, it can be fed into the tank together
with
the acid aluminium compound solution or after the aluminium hydrogel has
been produced. The silica-containing alumina carrier can, for another example,
be produced by combining a silica source such as sodium silicate with an
alumina source such as sodium aluminate or aluminium sulfate, or by mixing an
alumina gel with a silica gel, followed by moulding, drying, and calcining.
The
carrier can also be produced by causing alumina to precipitate in the presence
of silica in order to form an aggregate mixture of silica and alumina.
Examples
of such processes are adding a sodium aluminate solution to a silica hydrogel
and increasing the pH by the addition of, e.g., sodium hydroxide to
precipitate
alumina, and coprecipitating sodium silicate with aluminium sulfate. A further
possibility is to immerse the alumina carrier, before or after calcination, in
an
impregnation solution comprising a silicon source dissolved therein.
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In a following stage, the gel is separated from the solution and a
commercially
used washing treatment, for example a washing treatment using tap water or
hot water, is carried out to remove impurities, mainly salts, from the gel.
Then, the gel is shaped into particles in a manner known in the art, e.g., by
way
5 of extrusion, beading or pelletising.
Finally, the shaped particles are dried and calcined. The drying is generally
carried out at a temperature from room temperature up to 200°C,
generally in
the presence of air. The calcining is generally carried out at a temperature
of
10 300 to 950°C, preferably 600 to 900°C, generally in the
presence of air, for a
period of 30 minutes to six hours. If so desired, the calcination may be
carried
out in the presence of steam to influence the crystal growth in the oxide.
By the above production process it is possible to obtain a carrier having
15 properties which will give a catalyst with the surface area, pore volume,
and
pore size distribution characteristics specified above. The surface area, pore
volume, and pore size distribution characteristics can be adjusted in a manner
known to the skilled person, for example by the addition during the mixing or
shaping stage of an acid, such as nitric acid, acetic acid or formic acid, or
other
compounds as moulding auxiliary, or by regulating the water content of the gel
by adding or removing water.
The carriers of the catalysts to be used in the process according to the
invention
have a specific surface area, pore volume, and pore size distribution of the
same order as those of the catalysts themselves. The carrier of catalyst I
preferably has a surface area of 100-200m2/g, more preferably 130-170 m2/g.
The total pore volume is preferably 0.5-1.2 ml/g, more preferably 0.7-1.1
ml/g.
The carrier of catalyst II preferably has a surface area of 180-300 m2/g, more
preferably 185-250 m2/g, and a pore volume of 0.5-1.0 ml/g, more preferably
0.6-0.9 ml/g.
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The Group VIB metal components, Group VIII metal components, and, where
appropriate, Group IA metal components and compounds of Group V such as
phosphorus, can be incorporated into the catalyst carrier in a conventional
manner, e.g., by impregnation and/or by incorporation into the support
material
before it is shaped into particles.
At this point in time it is considered preferred to first prepare the carrier
and
incorporate the catalytic materials into the carrier after it has been dried
and
calcined. The metal components can be incorporated into the catalyst
composition in the form of suitable precursors, preferably by impregnating the
catalyst with an acidic or basic impregnation solution comprising suitable
metal
precursors. For the Group VIB metals, ammonium heptamolybdate, ammonium
dimolybdate, and ammonium tungstenate may be mentioned as suitable
precursors. Other compounds, such as oxides, hydroxides, carbonates, nitrates,
chlorides, and organic acid salts, may also be used. For the Group VIII
metals,
suitable precursors include oxides, hydroxides, carbonates, nitrates,
chlorides,
and organic acid salts. Carbonates and nitrates are particularly suitable.
Suitable Group IA metal precursors include nitrates and carbonates. For
phosphorus, phosphoric acid may be used. The impregnation solution, if
applied, may contain other compounds the use of which is known in the art,
such as organic acids, e.g., citric acid, ammonia water, hydrogen peroxide
water, gluconic acid, tartaric acid, malic acid or EDTA (ethylenediamine
tetraacetic acid). It will be clear to the skilled person that there is a wide
range
of variations on this process. Thus, it is possible to apply a plurality of
impregnating stages, the impregnating solutions to be used containing one or
more of the component precursors that are to be deposited, or a portion
thereof.
Instead of impregnating techniques, dipping processes, spraying processes,
etc. can be used. In the case of multiple impregnation, dipping, etc., drying
and/or calcining may be carried out in between.
After the metals have been incorporated into the catalyst composition, it is
optionally dried, e.g., in air flow for about 0.5 to 16 hours at a temperature
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between room temperature and 200°C, and subsequently calcined,
generally in
air, for about 1 to 6 hours, preferably 1-3 hours at 200-800°C,
preferably 450
600°C. The drying is done to physically remove the deposited water. The
calcining is done to bring at least part, preferably all, of the metal
component
precursors to the oxide form.
It may be desirable to convert the catalyst, i.e., the Group VIB and Group
VIII
metal components present therein, into the sulfidic form prior to its use in
the
hydroprocessing of hydrocarbon feedstocks. This can be done in an otherwise
conventional manner, e.g., by contacting the catalyst in the reactor at
increasing
temperature with hydrogen and a sulfur-containing feedstock, or with a mixture
of hydrogen and hydrogen sulfide. Ex situ presulfiding is also possible.
The process of the present invention is particularly suitable for the
hydroprocessing of heavy hydrocarbon feeds. It is particularly suitable for
hydroprocessing heavy feedstocks of which at least 50 wt.%, preferably at
least
80 wt.%, boils above 538°C (1000°F) and which comprise at least
2 wt.% of
sulfur and at least 5 wt.% of Conradson carbon. The sulfur content of the
feedstock may be above 3 wt.%. Its Conradson carbon content may be above 8
wt.%, preferably above 10 wt.%. The feedstock may contain contaminant
metals, such as nickel and vanadium. Typically, these metals are present in an
amount of at least 20 wtppm, calculated on the total of Ni and V, more
particularly in an amount of at least 30 wtppm. The asphaltene content of the
feedstock is preferably between 3 and 15 wt.%, more preferably between 5 and
10 wt.%.
Suitable feedstocks include atmospheric residue, vacuum residue, residues
blended with gas oils, particularly vacuum gas oils, crudes, shale oils, tar
sand
oils, solvent deasphalted oil, coal liquefied oil, etc. Typically they are
atmospheric residue (AR), vacuum residue (VR), and mixtures thereof.
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The process according to the invention can be carried out in a fixed bed, in a
moving bed, or in an ebullated bed. Carrying out the process in an ebullating
bed is particularly preferred.
The process according to the invention can be carried out in a single reactor
or
in multiple reactors. If multiple reactors are used, the catalyst mixture used
in
the two reactors may be the same or different. If two reactors are used, one
may or may not one perform or more of intermediate phase separation,
stripping, Ha quenching, etc. between the two stages.
The process conditions for the process according to the invention may be as
follows. The temperature generally is 350-450°C, preferably 400-
440°C. The
pressure generally is 5-25 MPA, preferably 14-19 MPA. The liquid hourly space
velocity generally is 0.1-3 h-1, preferably 0.3-2 h-1. The hydrogen to feed
ratio
generally is 300-1,500 NI/I, preferably 600-1000 NI/I. The process is carried
out
in the liquid phase.
The invention will be elucidated below by way of the following examples,
though
it must not be deemed limited thereto or thereby.
Example 1
Preparation of Catalyst A
A sodium aluminate solution and an aluminium sulfate solution were
simultaneously added dropwise to a tank containing tap water, mixed at pH 8.5
at 77°C, and held for 70 minutes. The thus produced alumina hydrate gel
was
separated from the solution and washed with warm water, to remove the
impurities in the gel. Then, the gel was kneaded for about 20 minutes and
extruded as cylindrical particles having a diameter of 0.9 to 1 mm and a
length
of 3.5 mm. The extruded alumina particles were calcined at 800°C for 2
hours,
to obtain an alumina carrier.
100 g of the alumina carrier obtained as described above were immersed in 100
ml of a citric acid solution containing 17.5 g of ammonium molybdate
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tetrahydrate and 9.8 g of nickel nitrate hexahydrate at 25°C for 45
minutes, to
obtain a carrier loaded with metallic components.
Subsequently the loaded carrier was dried at 120°C for 30 minutes and
calcined
at 620°C for 1.5 hours, to complete a catalyst. The amounts of the
respective
components in the produced catalyst and the properties of the catalyst are
shown in Table 1. Catalyst A meets the requirements of Catalyst I of the
present
invention.
Preparation of Catalyst B
The preparation of Catalyst A was repeated, except for the following
modifications: In the carrier preparation, the temperature during the alumina
gel
formation was 65°C. The carrier calcination temperature was
900°C. In the
catalyst preparation the impregnation solution contained 16.4 g of ammonium
molybdate tetrahydrate, and the catalyst calcination temperature was
600°C.
The composition and properties of Catalyst B are given in Table 1. Catalyst B
meets the requirements of Catalyst II of the present invention.
Preparation of Catalyst C
To produce a silica-alumina carrier, a sodium aluminate solution was supplied
to a tank containing tap water, and an aluminium sulfate solution and a sodium
silicate solution were added and mixed. When the addition of the aluminium
sulfate solution was completed, the mixture had a pH of 8.5. The mixture was
kept at 64°C for 1.5 hours. By such mixing a silica-alumina gel was
produced.
The sodium silicate concentration was set at 1.6 wt.% of the alumina gel
solution.
The silica-alumina gel was isolated by filtration and washed with hot water to
remove impurities from the gel. It was then extruded into cylindrical grains
with
a diameter of 0.9-1 mm and a length of 3.5 mm. The resulting particles were
dried in air at a temperature of 120°C for 16 hours and subsequently
calcined in
the presence of air for two hours at 800°C to obtain a silica-alumina
carrier. The
silica-content of the obtained carrier was 7 wt.%.
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One hundred grams of the thus obtained silica-alumina carrrer were
impregnated with 100 ml of an impregnation solution containing 16.4 g of
ammonium molybdate tetrahydrate, 9.8 g of nickel nitrate hexahydrate, 0.66
°g
of sodium nitrate, and 50 ml of 25% ammonia water. The impregnated carrier
5 was then dried at a temperature of 120°C for 30 minutes and calcined
in a kiln
for 1.5 hours at 540°C to produce a final catalyst. The composition and
properties of this catalyst are given in Table 1. Catalyst C meets the
requirements of Catalyst II of the present invention.
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Table 1: Catalyst composition and properties
Catal st Catal st A Catal st B Catal st C
carrier alumina alumina AI203 + 6%
Si02
Grou VIB wt.% 13.1 11.9 11.5
ox
Grou VIII wt.%2.0 2.0 2.1
ox
Grou IA wt.% 0 0 0.2
ox
surface area 161 147 214
m2l
total ore volume0.88 0.79 0.75
ml/
%PV >200 ~ 63 74 25
%PV >2000 /g, 24 1 1
%PV >100001~ 0.1 0 0
%PV 100-1200 74 89 80
~
%PV > 4000 16 1 0.3
~
%PV(< 100 ~) 0.4 ~ ~.4 I 14
~
Catalysts A through C were tested in various combinations in the
hydroprocessing of a heavy hydrocarbon feedstock. The feedstock used in
these examples was a Middle East petroleum consisting of 90 wt.% of vacuum
residue (VR) and 10 wt.% of atmospheric residue (AR). The composition and
properties of the feed are given in Table 2.
Table 2: Feedstock composition
Middle East etroleum R:AR =
90:10
Sulfur wt.% 4.9
Nitro en w m 3300
Metals - vanadium w m 109
Metals - nickel w m 46
Conradson Carbon residue wt.% 22.5
C7- insolubles wt.% 8.0
Vacuum residue wt.% 93
Densit /ml at 15C 1.0298
' Asphaltene fraction - matter insoluble in n-heptane
2 Fraction boiling above 538°C in accordance with ASTM D 5307
(distillation
gas chromatography)
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A mixture of at least two of Catalysts A through C were packed into a fixed
bed
reactor in the combinations given in Table 3 below. The catalyst bed contained
equal volume amounts of catalyst.
The feedstock was introduced into the unit in the liquid phase at a liquid
hourly
space velocity of 1.5 h-1, a pressure of 16.0 MPa, an average temperature of
427°C, with the ratio of supplied hydrogen to feedstock (H2/oil) being
kept at
800 NI/I.
The oil product produced by this process was collected and analysed to
calculate the amounts of sulfur (S), metals (vanadium + nickel) (M), and
asphaltene (Asp) removed by the process, as well as the 538°C+fraction.
The
relative volume activity values were obtained from the following formulae.
RVA = 100 * k (tested catalyst combination)! k (comparative catalyst
combination 2)
wherein for HDS
k = (LHSV/(0.7)) * (1/y°'' - 1/x°v)
and for HDM and asphaltene removal
k = LHSV * In (x/y)
with x being the content of S, M, or Asp in the feedstock, and y being the
content of S, M, or Asp in the product.
Table 3 below gives the tested catalyst combinations and the results obtained.
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Table 3
C. 1 C. 2 C. 3
Catalyst A A A
I
Catalyst g C g+C
II 50:50
RVA HDS 106 116 110
RVA HDM 117 106 106
RVA As 119 109 109
Cracking 41 42 41
rate
538C+ fraction
residue
wt.%
Sediment 0.1 0.09 0.22
Wt.%
C. C. C. C. C. C.
1 2 3
Catalyst ,4 B C
I
Catalyst ,4 B C
II
RVA HDS 102 100 129
RVA HDM 115 100 86
RVA As 116 100 72
Cracking 37 40 43
rate
538C+ fraction
residue
wt.%
Sediment 0.09 0.28 0.60
IA/t. %
~
' Sediment determined in accordance with the IP 375 method of the English
Institute of Petroleum
As can be seen from Table 3, the catalyst combinations according to the
invention show high activities in HDS, HDM, and asphaltene removal in
combination with a high residue cracking rate and low sediment formation.
