Note: Descriptions are shown in the official language in which they were submitted.
2123630
MILD HYDROCRACKING OF HEAVY HYDROCARBON
FEEDSTOCKS EMPLOYING SILICA-ALUMINA CATALYSTS
(D~ 92,031-F)
BACKGROUND OF THE INVENTION
s 1. Field of the Invention
This invention relates to a process for mild
hydrocracking of heavy oils. More particularly, this
invention relates to a catalytic process for converting
heavy oils boiling above 650 F., such as vacuum gas
~0
oil (VGO) and VG0 containing a high proportion of vacuum
resid (VR) to lighter distillate produc~s boiling at
or below 650 F.
In the mild hydrocracking process of this
invention a sulfur- and metal-containing hydrocarbon
feedstock, such as residua containing heavy oils, is
contacted at an elevated temperature with hydrogen and
a catalyst composition comprising a specified amount of
3 Group VIII metal, such as an oxide of nickel or
cobalt, a specified amount of an oxide of molybdenum
and, optionally, a specified amount of an oxide of
phosphorus, such lS phosphorus pentoxide supported on
-- 1 --
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a porous silica-containing alumina support. In the
catalytic mild hydrocracking process of this invention
the sulfur- and metal-containing hydrocarbon feed
is contacted with hydrogen and the catalyst, which has
a specified pore size distribution, in a manner such
that a substantially higher conversion of the 1000 F.+
fraction of the hydrocarbon feed to the 1000 F.-
lighter products is achieved over that obtained with the
use of prior art hydroprocessing catalysts while at
the same time high levels of sediment formation are
avoided.
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2 Prior Art
U.S. Patent No. 4,941,964, incorporated herein by
reference, discloses a process for the hydrotreatment
of a sulfur- and metal-containing hydrocarbon feed which
comprises contacting the feed with hydrogen and a
- catalyst in a manner such that the catalyst is maintained
at isothermal conditions and is exposed to a uniform
quality of feed. The catalyst has a composition
comprising 3.0 - S.0 wt. % of an oxide of a Group VIII
metal, 14.5 - 24.0 wt. % of an oxide of a Group VIB
metal and 0 - 2.0 wt. % of an oxide of phosphorus
supported on a porous alumina support, and the catalyst
is further characterized by having a total surface
area of 150 - 210 m /g and a total pore volume (TPV)
f 0.50 - 0.75 cclg with a pore diameter distribution
such that micropores having diameters of 100 - 160A
constitute 70 - 85 % of the total pore volume of the
catalyst and macropores having diameters of greater
than 250A constitute 5.5 - 22.0 % of the total pore
volume of the catalyst.
U.S. Patent No. 4,670,132 (Arias, et al.)
discloses a catalyst preparation and a catalyst
composition useful in the hydroconversion of heavy oils,
the catalyst comprising a high iron content bauxite
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with the addition of one or more of the following
promoters: phosphorus, molybdenum, cobalt, nickel or
tungsten. The bauxite catalysts typically contain
25 - 35 wt. % aluminum. The catalysts have certain
characteristic features for the elemental components
(including aluminum and where present, molybdenum)
when the pellet exteriors are examined in the fresh
oxide state using X-ray photoelectron spectroscopy (XPS).
For those catalysts which contain molybdenum, the
surface Mo/Al atomic ratios on the pellet exteriors
are in the range of 0.03 to 0.09.
U.S. Patent No. 4,652,545 (Lindsley, et al.)
discloses a catalyst composition useful in the hydro-
conversion of heavy oils, the catalyst containing
150.5 - 5 % Ni or Co and 1.8 - 18 % Mo (calculated as
the oxides) on a porous alumina support, such as
alumina containing a minor amount of silica, having
15 - 30 % of the Ni or Co in an acid extractable form,
and further characterized by having a TPV of
0.5 - 1.5 cc/g with a pore diameter distribution such
that (i) at least 70 % TPV is in pores having 80 - 120A
diameters, (ii) less than 0.03 cc/g of TPV (6 % TPV)
is in pores having diameters of less than 80A and
(iii) 0.05 - 0.1 cc/g of TPV (3 - 20 % TPV) is in pores
--4--
212~630
having diameters of greater than 120A. Lindsley, et al.
is distinguished from the instant invention in that
although it teaches that having a proportion of nickel
or cobalt contained in its catalyst in an acid
extractable form is advantageous in terms of heavy oil
hydroconversion. Lindsley, et al. does not teach or
suggest that catalysts which have a prescribed
molybdenum gradient are advantageous in terms of heavy
oil hydroconversion.
U.S. Patent No. 4,588,709 (hlorales, et al.)
discloses a catalyst preparation and a catalyst
composition useful in the hydroconversion of heavy
oils, the catalyst comprising S - 30 wt. % of a
, Group VIB element (e.g., molybdenum) and 1 - S wt. %
lS
of a Group VIII element (e.g., nickel). ~lorales, et al.
indicate that the finished catalysts have average
pore diameters of lS0 to 300 Angstroms. The catalysts
have certain characteristic features for the active
components (Mo and Ni) when the pellet exteriors are
examined in a sulfided state using X-ray photoelectron
spectroscopy (XPS). Mora-les ('709) requires a large
average pore diameter (lS0 to 300 Angstroms) and
hlorales ('709) requires certain characteristic XPS
features of the pellet exteriors after presulfiding.
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U.S. Patent No. 4,579,649 (Morales, et al.)
discloses a catalyst preparation and a catalyst
composition useful in the hydroconversion of heavy
oils, the catalyst containing a Group VIB element
(e.g., molybdenum), a Group VIII element (e.g., nickel)
and phosphorus oxide on a porous alumina support.
The catalyst has certain characteristic features for
the three active components (Mo, Ni and P) where the
pellet exteriors are examined in a sulfided state
using X-ray photoelectron spectroscopy (XPS).
Morales ('649) requires certain characteristic XPS
features of the pellet exteriors after presulfiding
whereas the catalyst of the instant invention
requires a specified molybdenum gradient as determined
by measuring the molybdenum/aluminum atomic ratios by
XPS for catalyst pellet exteriors and the pellets in
a crushed form as measured on the fresh catalysts in
an oxide state.
U.S. Patent No. 4,520,128 (~Sorales, et al.)
discloses a catalyst preparation and a catalyst
composition useful in the hydroconversion of heavy
oils, the catalyst containing 5 - 30 wt. % of a
Group VIB element (e.g., molybdenum), 0.1 - 8.0 wt. %
of a Group VIII element (e.g., nickel) and 5 - 30 wt. %
-6-
2l23~3a
of a phosphorus oxide on a porous alumina support. The
finished catalysts of Morales ('128) have mean pore
diameters of 145 to 154 Angstroms. The catalyst has
certain characteristic features for the three active
components (Mo, Ni and P) when the pellet exteriors
are examined in a sulfided state using X-ray photo-
electron spectroscopy (XPS). The catalyst of
Morales requires a high phosphorus oxide content.
U.S. Patent No. 5,047,142 (Sherwood, Jr., et al.)
discloses a process of hydroprocessing a sulfur- and
metal-containing hydrocarbon feed which comprises
contacting said feed with hydrogen and a catalyst in a
manner such that the catalyst is maintained at
isothermal conditions and is exposed to a uniform
quality of feed, where said catalyst has a composition
comprising l.0 - 5.0 wt. % of an oxide of nickel or
cobalt and 10.0 - 25.0 wt. % of an oxide of molybdenum,
all supported on a porous alumina support in such a
manner that the molybdenum gradient of the catalyst
has a value of less than 6.0> 15 - 30 % of the nickel
or cobalt is in an acid extractable form, and said
catalyst is further characterized by having a total
surface area of 150 - 210 m2/g> a total pore volume of
0.50 - 0.75 cc/g> and a pore size distribution such
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~ 2123630
that pores having diameters of less than lOOA
constitute less than 25.0 %, pores having diameters
of 100 - 160A constitute 70.0 - 85.0 ~ and pores
having diameters of greater than 250A constitute
1.0 - 15.0 % of the total pore volume of said catalyst.
U.S. Patent No. 4,886,582 (Simpson) discloses a
catalyst comprising at least one metal hydrogenating
component comprising Group VIB, such as molybdenum,
or Group VIII metal, such as nickel, on a porous
refractory oxide, such as lithia-alumina, silica-
alumina, etc., said composition comprising less than
15 wt. % of said metal hydrogenation component
calculated as the trioxide, and having a pore size
distribution where at least 75 % of the total pore
volume is in pores of diameters from about 20
Angstroms below the pore mode diameter to about 20
Angstroms above the pore mode diameter, less than
10 % of the total pore volume is in pores of diameters
less than 60 Angstroms and greater than 3 % to less
than 10 % of the total pore volume is in pores greater
than 110 Angstroms and the pore mode diameter is
in the range of about 70 to about 90 Angstroms.
U.S. Patent No. 4,846,961 (Robinson, et al.)
discloses a hydroprocessing catalyst containing nickel,
--8--
- ~123630
phosphorus and about 19 to about 21.5 wt. % of
molybdenum (MoO3) components on a porous refractory
oxide such as silica-alumina. The catalyst has a
narrow pore size distribution wherein at least 75 %
of the pore volume is in pores of diameters from about
50 to about 110 Angstroms, at least 10 % of the pore
volume in pores of diameters less than 70 Angstroms and
at least 60 % of the pore volume in pores of diameters
within about 20 Angstroms above or below the average
pore diameter. The catalyst is employed to hydroprocess
a hydrocarbon oil, especially those oils containing
sulfur and nitrogen components.
U.S. Patent No. 4,686,030 (Ward, et al.)
discloses a mild hydrocracking process using a catalyst
containing at least one active hydrogenation metal
component supported on an amorphous porous refractory
oxide such as silica-alumina wherein the catalyst has
a narrow pore size distribution including at least
75 % of the total pore volume in pores of diameters
from about S0 to about 130 Angstroms. Preferably, the
catalyst has at least about 60 % of the pore volume
in pores of diameter within about 20 Angstroms above or
below a mode pore diameter in the range from about
55 to about 100 Angstroms. In one embodiment, a vacuum
_ g _
2123630
gas hydrocarbon oil is mildly hydrocracked, with
simultaneous desulfurization and denitrogenation, by
contact with the catalyst under mild hydrocracking
conditions correlated so as to convert about 10 to
about 50 Vol % of the oil fraction boiling above 700 F.
to hydrocarbon products boiling at or below about
700 F. In other embodiments, the hydrocarbon oil may
be desulfurized and denitrogenated either prior to or
following the mild hydrocracking.
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2123630
SUMMARY OF THE INVENTION
The instant invention is a process of mild
hydrocracking of a sulfur- and metal-containing
hydrocarbon feedstock having a substantial proportion
of components boiling below about 1000 F., such as
residue, vacuum gas oils, etc., which comprises
contacting the feedstock at an elevated temperature
and at a pressure of less than 1500 psig with hydrogen
and a catalyst which comprises about 2.0 to about 6.0
wt. %, preferably about 2.5 to about 3.5 wt. % of an
oxide of a Group VIII metal, preferably nickel or
cobalt; about 12.0 to about 25.0 wt. %, preferably
about 12.0 to about 18.0 wt. % of an oxide of
molybdenum; about 0 to about 3.0 wt. %, preferably
about 0 to about 2.0 wt. % of an oxide of phosphorus,
preferably P205, all supported on a porous silica-
alumina support containing about 4.0 to about 30.0
wt. %, preferably about 4.0 to about 25.0 wt. %, based
on the weight of the support, of silica. The molybdenum
gradient of the catalyst ranges from about 1 to about
10, preferably from about 1 to about 6. This invention
also related to the catalyst employed in the described
process.
2123630
In one embodiment of this invention in which
the catalyst is prepared using a silica-alumina support
containing about 10 to about 25 wt. % of silica, the
catalyst has a total pore volume in the range of about
0.75 to about 0.92 cc/g, and a surface area in the
range of about 150 to about 250 m2/g. The pore volume
distribution as determined by mercury porosimetry
consists of about 25 to about 40 % of the pore volume
in pores with diameters greater than 250 A, about 30 to
about S0 % of the pore volume in pores having diameters
greater than 160A, about S0 to about 70 % of the pore
volume in pores with diameters less than 160A, and
about 20 to about 40 % of the pore volume in pores
having diameters less than lOOA. The pore mode of
the catalyst as determined by the BET method is in the
range of 80 - 120A. The preferred pore volume
distribution as determined by mercury porosimetry
consists about 28 to about 35 % of the pore volume
in pores with diameters greater than 250A, about 35 to
about 45 % of the pore volume in pores having
diameters greater than 160A, about 55 to about 65 %
of the pore volume in pores with diameters less than
160A, and about 24 to about 32 % of the pore volume
in pores having diameters less than lOOA. The pore
mode of the catalyst as determined by the BET method
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is in the range of about 80 to about 120A.
In a second embodiment of this invention in
which the catalyst is prepared using a silica-alumina
support containing about 4 to about 10 % of silica,
the catalyst has a total pore volume in the range of
about 0.60 to about 0.80 cc/g~and a surface area in the
range of about 150 to about 250 m /g. The pore volume
distribution consists about 5 to about 15 % of the
pore volume in pores with diameters greater than 250A,
about 10 to about 35 % of the pore volume in pores
having diameters greater than 160A, about 65 to about
85 % of the pore volume in pores with diameters less
than 160A, and about 0 to about 20 % of the pore
volume in pores having diameters less than lOOA. The
pore mode of the catalyst is in the range of about
100 to about 140A. The preferred pore volume
distribution consists about 10 to about 15 % of the
pore volume in pores with diameters greater than 250A,
about 20 to about 30 % of the pore volume in pores
having diameters greater than 160A, about 70 to about
80 % of the pore volume in pores with diameters less
than 160A, and 0 to about 10 % of the pore volume in
pores having diameters less than lOOA. The pore mode
of the catalyst is in the range of about 100 to about
140A.
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- 2123630
The use of the catalysts of this invention not
only provides a hydrocarbon conversion advantage but
also maintains the sediment-make at a level similar
to the conventional bimodal alumina based catalysts.
The instant invention is much improved over the prior
art catalysts in terms of sediment formation and reactor
unit operability.
The operating conditions for the process of the
instant invention are such as to yield about a 10 to
about a 60 vol % conversion of the hydrocarbon
feedstock boiling at 650 F.+ to hydrocarbon products
boiling at 650 F.-.
The residuum feedstocks may be contacted with
hydrogen and the catalyst utilizing a wide variety of
reactor types. Preferred means for achieving such
contact include contacting the feed with hydrogen and
the prescribed catalyst in a fixed bed hydrotreater,
in a single continuous-stirred-tank reactor or single
ebullated-bed reactor, or in a series of 2 - 5
continuous-stirred-tank or ebullated-bed reactors,
with ebullated-bed reactors being particularly preferred.
The process of the instant invention is particularly
effective in achieving high conversion rates of
1000 F.l to 1000 F.- fractions while maintaining
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2123630
desirable levels of 650 F.+ conversion, sediment make
and HDS activity compared to the results obtained
with the use of conventional bimodal alumina-based
catalysts.
212363~
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The decreasing demand for heavy fuel oils has
caused refiners to seek ways to convert heavier
hydrocarbon feedstocks to lighter products of more
value. To increase mid-distillate production, the
refiner has several process options. They include
hydrocracking, fluid catalytic cracking, and coking,
which all require heavy investments in the refineries.
Because of such high costs, refiners are continually
searching for conversion processes which may be
utilized in existing units. An additional option
available to refiners is to employ a mild hydrocracking
(MHC) process. MHC process is an evolution of the VG0
hydrodesulfuTization (HDS) process. The main feedstock
for this MHC process is VG0 but other types of heavy
gas oils, such as coking gas oils and deasphalted oils,
can be used.
The major advantage of MHC is that it can be
carried out within the operating constraints of
existing VG0 hydrotreaters. The typical conditions
for the MHC process are: Temperature: 720 - 780 F.,
Hydrogen Pressure: 600 - 1200 psig, H2/Oil Ratio:
1000 - 2000 SCF/BBL, Space Velocity: 0.4 - 1.5
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2123630
Vol/Vol/Hr. In contrast, true high conversion
hydrocracking units are operated at these conditions:
Temperature: 700 - 900 F., Hydrogen Pressure:
1800 - 3000 psig, H2/Oil Ratio: 1400 - 6000 SCF/BBL,
Space Velocity: 0.3 - 1.5 Vol/Vol/Hr. The major
difference between the two processes is the hydrogen
pressure.
The products obtained from the MHC process are
low sulfur fuel oil (60 - 80 %) and middle distillate
(20 - 40 %). This hydrotreated fuel oil is also an
excellent feed for catalytic cracking because of its
higher hydrogen content and lower nitrogen content
compared to the original feed. The quality of diesel
cut produced by MHC is usually close to diesel oil
specifications for the cetane index, and so can be
added to the diesel pool.
The switch from a HDS mode to a MHC mode can
be achieved in different ways, assuming that the
refiner is equipped to recover the surplus of the
middle distillate fraction. One way to increase
middle distillate production from a unit loaded with
HDS catalyst is to increase the operating temperature.
Using a conventional hydrotreating catalyst, the ~IHC
process typically converts about 10 to 30 Vol % of
2123~30
,
hydrocarbon feedstock boiling above 650 F. (650 F.+)
to middle distillate oils boiling at or below 650 F.
(650 F.-).
Another way to increase the middle distillate
production is to change, at least partly, a HDS
catalyst on a nonacidic alumina support to a slightly
acidic catalyst. Catalysts of higher activity are
still being sought. The higher the activity of the
catalyst, the lower the temperature required to obtain
a product of given sulfur, nitrogen or metal content
in any given boiling range. For the VG0 containing
a high proportion of residuum, an HDS catalyst usually
gives less than 10 Vol % conversion of the 650 F.
fraction. The conversion of resid components
boiling above 1000 F. (1000 F.+) into products boiling
at or below 1000 F. (1000 F.-) with the known
alumina-based hydrotreating catalysts is achieved
primarily by thermal cracking reactions.
A particular difficulty which arises in resid
2~
hydroprocessing units employing the currently known
catalysts is the formation of insoluble carbonaceous
substances (also called sediment) when the conversion
is high (above 50 Vol %). High sediment may cause
plugging of reactor or downstream units, such as a
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212~630
fractionation unit. The higher the conversion level
for a given feedstock, the greater the amount of
sediment formed. This problem is more acute at a low
hydrogen pressure and high reaction temperature.
The process of the instant invention employs a
catalyst composition comprising about 2.0 - 6.0,
preferably 2.5 - 3.5 wt. % of an oxide of a Group VIII
metal, preferably nickel or cobalt, most preferably
NiO, about 12.0 to about 25.0 wt. %, preferably about
12.0 to about 18.0 wt. % of an oxide of molybdenum,
most preferably MoO3 and about O to about 3.0,
preferably O to about 2.0 wt. % of an oxide of
phosphorus, preferably P205 all supported on a porous
silica-alumina support containing about 4.0 to about
30.0 wt. %, preferably about 4.0 to about 25.0 wt. %,
based on the weight of the support, of silica. Most
preferably, the support is gamma alumina. Groups
VIII, as referred to herein, is Groups VIII of the
Periodic Table of Elements. The Periodic Table of
Elements referred to herein is found on the inside
cover of the CRC Handbook of Chemistry and Physics,
55th Ed. (1974-75). Other oxide compounds which may be
found in such a catalyst composition include S04
(present in less than 0.8 wt. %), and Na20 (present in
-19-
2123630
less than 0.1 wt. %). The above-described silica-
alumina support may be purchased or prepared by methods
well known to those skilled in the art.
Catalyst Preparation
In preparing the catalyst the support containing
silica is impregnated with the requisite amounts of
the VIB metal oxide and Group VIII metal oxide and,
optionally, phosphorus oxide via conventional means
known to those skilled in the art to yield a finished
catalyst containing a Group VIII metal oxide in the
amount of 2.0 to about 6.0 wt. O, preferably about
2.5 to about 3.5 wt. %, molybdenum oxide in the amount
of 12.0 to about 25.0 wt. %, preferably 12.0 to about
18.0 wt. % and phosphorus oxide in the amount of
about 0 to about 3.0 wt. %, preferably 0 to about 0.1
wt. %-
The Group VIII metal may be iron, cobalt, or
nickel which is loaded on the support, for example, as
a 10 - 30 wt. ~, preferably about 15 wt. % of an
aqueous solution of metal nitrate. The preferred
metal of this group is nickel which may be employed
at about 16 wt. % aqueous solution of nickel nitrate
hexahydrate. Molybdenum may be loaded on the support
employing, for example, a 10 - 20 wt. %, preferably
-20-
-- 2123~30
about 15 wt. %, of an aqueous solution of ammonium
heptamolybdate (AHM). The phosphorus component, when
utilized, may be prepared from 85 % phosphoric acid.
The active metals and phosphorus may be loaded
onto the catalyst support via pore filling. Although
it is possible to load each metal separately, it is
preferred to impregnate simultaneously with the Group
VIII metal and molybdenum compounds, phosphoric acid,
as well as with stabilizers such as hydrogen peroxide
and citric acid (monohydrate), when employed. It is
preferred that the catalyst be impregnated by filling
95 - 105 %, for example, 97 % of the support pore
volume with the stabilized impregnating solution
containing the required amount of metals and citric
acid.
Finally, the impregnated support is oven-dried
and then directly calcined preferably at 1000 - 1150 F.
for about 20 minutes to 2 hours in flowing air.
A hydroconversion process, such as a mild
hydrocracking process, which preferentially removes
sulfur and nitrogen from the converted product stream
with components having boiling points less than 1000 F.
is desirable in those instances where there is less
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concern over the quality of the unconverted product
stream, but, rather, where the primary concern is the
quality of the distillate product from the
hydroconversion process. It is well known to those
skilled in the art that high heteroatom contents of
distillate hydroconversion products have an adverse
effect on fluid catalytic cracking of the heavier gas
oils (having a boiling point of about 650 F. to about
1000 F.) and that extensive hydrotreating of the
distillate streams would be required to meet the
strict mandated levels of heteroatoms in distillate
fuels. The demands placed upon catalyst compositions
make it difficult to employ a single catalyst in a
hydroconversion process, such as a mild hydrocracking
process, which will achieve effective levels of sulfur
and nitrogen removal from the converted product stream
having components with boiling points below 1000 F.
However, the catalyst employed in the process of the
instant invention is capable of achieving such results
because the prescribed catalyst has an optimized
micropore diameter to overcome the diffusion limitations
for hydrotreatment of the converted product molecules
but it also does not contain such large macropores
that would allow poisoning of the catalyst pellet
5 interior. As previously described, the catalyst also
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has a specified pore size distribution such that pores
with diameters less than 55A are minimized as these
pores are easily plugged with contaminants during
hydroprocessing.
Catalyst Examples SN-6599, 6600, 6601, 6616 and
6602, the properties of which are described in Table I
below, as well as Catalyst Examples SN-6922, 6923
and 6615, the properties of which are described in
Table II below, are catalysts prepared in the manner
set out above, which may be employed in the process of
this invention while the properlies of the Support
SN-6599X used in processing Catalyst SN-6599, Support
SN-6602X used in preparing Catalyst SN-6602 and Support
SN-6923X employed in preparing Catalyst SN-6923 are
described in Tables III and IV below. The catalysts
were prepared with a commercially available silica-
alumina support obtained from American Cyanamid and are
available in the form of extrudates in the diameter
range of 0.035 - 0.041 inch.
The silica content of the catalysts described
in Tables I and II is based on the weight of the catalyst
support.
2123~30
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- 24-
- 2123630
TABLE II
NiMo CATALYSTS ON SILICA-ALUMINA SUPPORTS
Catalyst SN-6922 SN-6923 SN-6615
Impreg. Sol'n. Ni-Mo Ni-Mo Ni-Mo
(Citric (Citric (Phos-
Acid) Acid) phoric
Acid)
SiO2 wt. % 16 16 16
P205 wt. % O 0 1.6
MoO3 wt. % 14.2 14.2 15.0
NiO wt. % 3.1 2.8 3.2
Total PV, % TPV 0.88 0.82 0.78
PV > 250A % TPV 28.4 31.7 33.3
PV > 160A % TPV 36.4 40.2 42.3
PV < 55A % TPV 2.2 1.9
PV < 160A % TPV 63.6 59.8 57.7
PV < lOOA % TPV 35.2 24.4 25.6
PV 100-160A 28.4 34.1 32.1
PM at (dv/dD) max A 93 110 88
PM (BET), A 98 109 84
Surf. Area, m /g 239 193 173
HDS-MAT, CO 5g, % 92 84 50
Metals Distribution by XPS Analysis
(Mo/Al)int 0.11 0.10 0.10
(Ni/Al)int 0.010 0.009 0.010
Mo Gradient 2.2 3.7 1.4
Ni Gradient 1.8 3.1 1.3
2123630
TABLE III
PROPERTIES OF SILICA-ALUMINA SUPPORTS
Catalyst
Support SN-6599X SN-6602X SN-6923X
Si02 wt; % 4 8 16
NH3 Desorbed, cc/g 11.8 10.6 11.1
Pore Yolume Distribution by Hg Porosimetry
TPV, cc/g 0.81 0.85 1.04
PV > 250A % TPV 8.6 11.8 24.0
PV > 160A % TPV 14.8 25.9 40.4
PV < 160A % TPV 85.2 75.3 59.6
PV < 100A % TPV 19.8 14.1 20.2
PV 100-160A % TPV 65.4 61.2 39.4
MPD (Vol), A 117 128 102
TSA (N2), m /g N/A 187 N/A
Note: The suffix X denotes the support for the catalyst
of the same number. The contact angle usecl in the
determination of Median Pore Mode by Volume
denoted as MPD (Vol) for the supports and the
finished catalysts was 140 and 130 degrees,
respectively.
-26-
- 2123630
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- 27-
- 2123630
The properties of two commercially available
hydroprocessing catalysts are set forth in Table V
below. All of these catalysts are available state of
the art catalysts sold for use in hydroprocessing resid
oils. Catalyst A, which is American Cyanamid HDS-1443B
catalyst, is referred to in this specification as the
standard reference catalyst.
Pore structure values set out in Tables I - V
were determined using Micrometrics Autopore 9220
Mercury Porosimetry Instrument. In the tables reference
to BET means values measured by the Brunauer-Emmett-
Teller Techniques.
- 2123630
TABLE V
ALUMINA BASED CATALYSTS AS CONTROL EXAMPLES
Catalyst A B
Impreg. Sol'n. Ni-Mo Ni-Mo
Mo03 wt. % 11.5-14.5 14.5-15.5
.~i0 wt. % 3.2-4.0 3.0-3.5
Pore Volume Distribution by Hg Porosimetry
Total PV, cc/g 0.74 0.64
PV > 250A % TPV 33.8 7.8
PV > 160A % TPV 37.8 17.2
PV < 160A % TPV 62.2 84.4
PV < 100A % TPV 58.1 9.4
PV 100-160A % TPV 4.1 75.1
PM at tdv/dD) max A 50 126
PM (BET), A 46 105
Surf. Area, m tg 314 194
HDS-MAT, C0 5g- % 73 88
Metals Distribution by XPS Analysis
( / )int 0.012
(Ni/Al)int 0.012 0.016
~o Gradient 1.2 3.1
Ni Gradient 1.6 1.0
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- 2123630
A preferred feature of the catalyst composition
of the instant invention is that the above-described
oxide of molybdenum, preferably MoO3, is distributed
on the above-described porous alumina support in such
a manner that the molybdenum gradient of the catalyst
has a value of about 1.0 to about 10.0~ As used in
this description and in the appended claims, the phrase
"molybdenum gradient" means that the ratio of a given
catalyst pellet exterior molybdenum/aluminum atomic
ratio to a given catalyst pellet interior molybdenum/
aluminum atomic ratio has a value of less than 6.0,
preferably 1.0 - 5.0, the atomic ratios being measured
by X-ray photoelectron spectroscopy (XPS), sometimes
referred to as Electron Spectroscopy for Chemical
Analysis (ESCA). It is theorized that the molybdenum
gradient is strongly affected by the impregnation of
molybdenum on the catalyst support and the subsequent
drying of the catalyst during its preparation. ESCA
data on both catalyst pellet exteriors and interiors
were obtained on an ESCALAB MKII instrument available
from V. G. Scientific Ltd., which uses a 1253.6
electron volt magnesium X-ray source. Atomic percentage
values were calculated from the peak areas of the
molybdenum 3p3/2 and aluminum 2p3/2 signals using the
sensitivity factors supplied by V. G. Scientific Ltd.
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2123630
The value of 74.7 electron volts for aluminum was used
as a reference binding energy.
To determine the molybdenum/aluminum atomic
ratio of a given catalyst pellet exterior for the
catalyst of the instant invention, the catalyst pellets
were stacked flat on a sample holder, and subjected to
ESCA analysis. For the catalyst of the instant
invention the molybdenum/aluminum atomic ratio of the
catalyst pellet éxterior is in the range of 0.12 - 0.75,
preferably 0.12 - 0.42. This exterior molybdenum/
aluminum atomic ratio is considerably greater than the
Mo/Al catalyst surface atomic ratio of 0.03 - 0.09
disclosed in U.S. Pat. No. 4,670,132.
To determine the molybdenum/aluminum atomic
ratio of a given catalyst pellet interior for the
catalyst of the instant invention, the catalyst pellets
were crushed into a powder, placed firmly in a sample
holder, and subjected to ESCA analysis. For the
catalyst of the instant invention, the molybdenum/
aluminum atomic ratio of the catalyst pellet interior
(i.e., the molybdenum/aluminum ratio of the powder,
which is assumed to be representative of the interior
portion of the pellet) is in the range of 0.08 - 0.15,
preferably 0.11 - 0.12.
-31-
2123630
The molybdenum/aluminum atomic ratios of the
total catalyst composition of the instant invention,
as determined by conventional means (i.e., Atomic
Absorption (AA) or Inductively Coupled Plasma (ICP)
spectroscopies) is in the range of 0.060 - 0.075,
preferably 0.062 - 0.071. To determine the total
catalyst composition molybdenum/aluminum atomic ratio,
catalyst pellets were ground to a powder and digested
in acid to form an ionic solution. The solution was
then measured by AA or ICP to determine Mo ion
concentration, which was then adjusted to ~loO3
concentration. Alumina (A1203) concentration was back-
calculated from the direct measurement of the
concentrations of the other components (e.g., Ni, Fe,
Na, S).
The HDS Microactivity Test ~HDS-~IAT) was used to
evaluate the intrinsic activity of catalysts in the
absence of diffusion and using a model sulfur compound
as a probe. The catalyst, ground to a 30 - 60 mesh
fraction, is presulfided at 750 F. with a 10 % H2S/H2
mixture for 2 hours. The presulfided catalyst is
exposed to a benzothiophene-containing feed at 550 F.
and flowing hydrogen for approximately four hours. Cuts
are taken periodically and analyzed by a gas
21236~0
chromatograph for the conversion of benzothiophene
to ethylbenzene. The results obtained with HDS-MAT
tests as well as the Mo and Ni gradients of the
catalysts described are shown in Tables I and II.
Catalyst Properties
Tables III and IV show the pore volume
distributions and surface areas of six silica-alumina
supports with silica contents varying from 4 to 16
wt. %. As the silica content was increased from 4 to
16 %, the total pore volume (TPV) and the macro-
porosity (PV>250A) increased, whereas the pore volumein the region of PV 100-160A decreased. The TPV of
the supports was in the range of 0.81 to 1.06 cc/g
and the macroporosity was varied from 0.07 to 0.34
cc/g. The pore volume of pores with diameters in the
range of 100-160A was varied from 0.24 to 0.56 cc/g or
32 to 72 % of the pore volume of pores having diameters
less than 250A. A comparison of the pore volume
distributions between the support and the finished
catalyst indicated that the pore volume in the region
of PV 100-160A was maintained essentially the same
after impregnation of active metals.
There is another unique feature of this type of
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2123630
silica-alumina in contrast to the conventional
silica-alumina used in the cracking and hydrocracking
catalysts. That is, the acidity of the supports,
shown in Table III as NH4 desorbed, does not depend on
the silica content. The method employed to
incorporate silica sol into the alumina gel is not
effective for enhancing the acidity function of the
support and the finished catalysts.
The properties of five silica-alumina based
NiMo catalysts are compared in Table I. Three kinds
of impregnation stabilizers, hydrogen peroxide, citric
acid and phosphoric acid, were used in the co-
impregnation of Ni and Mo onto the silica-alumina
supports. It is seen that the HDS-~IAT activity
decreases with increasing silica content. All of the
catalysts listed in Table I except the citric acid
stabilized SN-6616 show high Mo gradients. To improve
the HDS-MAT activity of Ni~o catalysts on silica-
alumina supports of 16 % silica, the calcination20
temperature was lowered to 1100 F. (in the cases of
SN-6922 and SN-6923). As seen in Table II, the HDS-MAT
activities of SN-6601 and SN-6923 are significantly
higher than SN-6601 and SN-6615. By contrast, the Mo
gradients of SN-6922 and SN-6923 are significantly lower
-34-
21236~0
-
than that of SN-6601. Therefore, the citric acid is
the most effective impregnation stabilizer to achieve
high dispersion of Mo and uniform laydown of Mo
across the catalyst extrudates.
BERTY REACTOR HYDROCRACKING
CATALYST EVALUATION
The Berty reactor, a type of continuous stirred
tank reactor (CSTR), was used to determine hydrocracking
activities of the catalysts of this invention in a
diffusion controlled regime at a low rate of
deactivation. The catalysts were presulfided and then
the reaction was carried out at a single space velocity
for 38 hours. The sample cuts were taken every 4 hours
and tested for boiling point distribution, Ni, V, S,
and sediment content. Using these data, conversions
for the 650 F.+ and 1000 F.+ fractions were determined.
The feedstock properties and the operating conditions
of the Berty reactor are listed in Table VI which
follows.
The hydrocracking activity was determined by
comparing the percentages of products in the 650 F.-
fraction and 1000~ F.- fraction when various catalysts
were evaluated under constant mild hydrocracking
conditions with the same feedstock. The conversions of
-35-
2123630
650 F.+ and 1000 F.+ were calculated by theequations below:
Y(F) - Y(P)
Conversion = X 1000 %
Y(F)
Y(F) denotes the volume percentage of the 650 F.+
or 1000 F.+ fraction in the feedstock.
Y(P) denotes the volume percentage of the 650 F.+
or 1000 F.+ fraction in the products.
The boiling point distribution of the total
product was determined using the ASTM D-2887 Method,
Simulated Distillation by Gas Chromatography. The
existent sediment content in the total product was
measured by using the IP 375/86 Method, Total Sediment
in Residual Fuels. The Total Sediment is the sum of
the insoluble organic and inorganic material which is
separated from the bulk of the residual fuel oil by
filtration through a filter medium, and which is also
insoluble in a predominantly paraffinic solvent.
-36-
2123630
TABLE VI
BERTY REACTOR OPERATING CONDITIONS
1. PRESULFIDING
Temperature 750 - 800 F.
Pressure 40 Psig
Gas Mixture 10 Vol % H2S - 90 Vol % H2
Gas Flow 500 SCCM
Duration 2 Hr., 45 ~lin.
2. FEEDSTOCK
60 Vol % Desulfurized VG0
40 Vol % Ar M/H Vac. Resid
Boiling Point
Distribution IBP 444 F.
FBP 1371 F.
650 F.+89.2 Vol %
900 F.+45.6 Vol %
1000 F.+33.5 Vol %
Sulfur wt % 2.2
Ni Content, ppm 20
V Content, ppm 54
3. REACTION CONDITIONS
Temperature 805 F.
Pressure 1000 Psig
Hydrogen Feed Rate 300 SCCM
Liquid Feed Rate 82.5 CC/Hr
Liquid Holdup 125 CC
Catalyst Charge 36.9 Grams
2123630
Data listed in Table VII, which follows, show
the activity results achieved with Catalysts S~-6599,
6600, 6601 and 6616 of this invention compared to
the activities exhibited by Catalyst A (the reference
catalyst) and Catalyst B, which are both commercial
hydroprocessing catalysts, as determined in the Berty
Reactor tests.
The data presented in Table VII show that
Catalysts SN-6599, 6600, 6601 and 6616, catalysts of
this invention, have a substantially greater activity
for the 650 F.+ conversion`value than Catalyst A;
that Catalysts SN-6600 and 6616 exhibit a greater
activity for the 650 F.+ conversion than Ca~alyst B
while Catalyst SN-6601 has a 650 F.+ conversion value
about equal to Catalyst B and Catalyst SN-6599
exhibits a 650 F.+ conversion value somewhat less than
Catalyst B. Catalysts SN-6599, 6600, 6601 and 6616
all show a 1000 F.+ conversion value greater than
Catalysts A or B.
2~
-38-
2123~30
-
TABLE VII
BERTY RESID MILD HYDROCRAC~ING ACTIVITIES
Catalyst 650 F.+ 1000 F.+ IP HDM HDS
Conversion Conversion Sediment Act. Act.
Vol % Vol % ~ % %
A 29 78 0.7 80 69
B 45 83 0.9 60 71
* SN-6599 40 86 0.6 62 68
* SN-6600 48 91 0.6 81 72
* SN-6601 44 89 0.5 78 55
~ SN-6616 48 92 0.4 72 62
Run conditions: Temperature = 805 F., Pressure =
1000 psig, LHSV = 0.66, Hydrogen Flow
Rate = 300 scc/m, and the feedstock is
40 Vol % Arabian ~edium/Arabian Heavy
(65:35 Vol %) vacuum resid in
desulfurized vacuum gas oil.
* Catalyst of the instant invention.
-39-
2l2363o
Two commercial alumina-based hydroprocessing
catalysts, Catalyst A (i.e., Catalyst HDS-1443B)
and Catalyst B were used as the reference in the
evaluation for MHC activities. A comparison of
conversion advantages over Catalyst A which has a
bimodal pore structure is set out in the data presented
in Table VIII which follows.
-40-
2123630
TABLE VIII
BERTY RESID ~ILD HYDROCRACKING ACTIVITIES
Catalyst 650 F.+ 1000 F.+ IP
Conversion Conversion Sediment
Advantage Advantage Delta
Vol % Vol % %
A O O O
B +16 +5 +0.2
*SN-6599 +11 +8 -0.1
*SN-6600 +19 +13 -0.1
*SN-6601 +15 +11 -0.2
*SN-6616 +19 +14 -0.3
un conditions: Temperature = 805 F., Pressure = 1000
psig, LHSV = 0.66, Hydrogen Flow Rate =
300 scc/m, and the feedstock is 40 Vol %
Arabian Medium/Arabian Heavy (65:35
Vol %) vacuum resid in desulfurized
vacuum gas oil.
Catalyst of the instant invention.
2123630
The data presented in Table VIII show that
Catalysts SN-6599, 6600, 6601 and 6616, catalysts of
the instant invention, exhibit an increase of 11 to
19 Vol % in 650 F.+ conversion which corresponds to
a 37.9 to 65.5 % improvement in relative conversion
over that achieved with Catalyst A (i.e., the standard
base commercial catalyst). Catalysts SN-6599, 6600,
6601 and 6616 also gave an appreciable improvement in
the 1000 F.+ conversion ranging from 8 to 14 Vol %
which corresponds to a 10.3 to 17.9 % improvement over
that achieved with Catalyst A. The IP sediment make
of these same catalysts showed a decrease of 0.1 to
0.3 % over the sediment make of Catalyst A.
The results set out in Table VIII clearly
indicate that the silica-alumina based catalyst
substantially outperforms Catalyst A or B of the prior
art.
~lild hydrocracking of heavy oils containing
resids in the presence of the catalyst of this invention
comprising, for example, molybdenum oxide, nickel
oxide, and, optionally, phosphorus oxide on the silica-
alumina support having a specified pore size
distribution not only allows an increased production of
middle distillate and more effective conversion of resid
-42-
212:~630
feedstocks but also maintains the sediment make at a
low level or similar to that achieved with conventional
bimodal alumina-based catalysts.
-43-
