Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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- This invention relates to an improved hydroconversion catalyst
wherein the improvement is attributed to particular physical charac-
teristics of the alumina-based catalyst, and to hydroconversion
processes employing it,such as hydrogenation, hydrodemetallization,
hydrodesulphurization and hydrodenitrogenation.
It is well known to purify mineral oils, such as crude oil,
petroleum fract~ns, shale oils, coal tar distillates,petroleum
residues and the like with hydrogen in the presence of a catalyst.
Typically the catalyst i~ deployed in the hydroconversion zone in
one or more fixed beds. Often these beds are supported or retained
at their inlet or outlet, or both by materials which are inert to
the reaction, in order to facilitate even distribution o~ the
feedstock, that is, to prevent or reduce channelling through the
catalyst bed; and to trap undesirable materials in the feedstock
Yuch as corroæion products and other particulate matter as may be
present in the feedstock, in order to prevent such undesirable
material from pluggine or otherwise deactivating the catalyst bed.
The inert materials, which conventionally are in the form of pellets
or spheres, typically must be resistant to crushing under the
weight of catalyst beds which in an uprieht reactor may have depths
of 15 m or more.
; In many large hydroconversion reactors such as employed in
petroleum refining, the inerts will occupy a substantial portion
of the reaction zone, e.g., up to 15 to 20% or more of the reaction
zone volume. Further, many hydroconversion processes often employ
high pressures up to several hundreds kg/cm requiring e~pensive
pressure reactors. Accordingly, the use of inerts adds to the capitaI
expense of a hydroconversion process both for the reactors which
must be oversized to accommodate the inerts and for the costs of
the inerts which do not contribute in any significant manner to
desired hydroconversion of the feedstock. In addition, it would be
highly desirable to increase the efficacy of existing hydroconversion
processes by replncing the volume of inerts in the renction zone
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with an active catalyst capable not only of performing the functions
of the inert material, but of enhancing the desired conversion process
as well. Thus, the development of a catalyst which would make it
possible to carry out hydrotreatment at greater efficiency and lower
cost was desired.
According to the invention there is provided an improved hydro-
conversion spherical catalyst consisting essentially of alumina,
optionally containing up to 6% by weight of silica, as support, and
from 2 to 20% by weight of a Group VI-B metal and from 0.5 to 10%
by weight of Group VIII metal each in the form of metals or their
oxides or sulphides and having a diameter greater than 6 mm, a
surf&ce area above 200 m /gm and a crush strength above 31.7 kg.
The invention further provides a process for use of the catalyst
which comprises passing mineral oil feedstock and a hydrogen containing
gas through a reaction zone at elevated temperature and pressure and
recovering the hydroconverted oil from the reaction zone.
The spherical alumina-based supports for the catalyst according
to the invention are preferably gamma- or eta-~1umina. They may be
prepared according to known processes in sizes from about 6 to
about 30 mm. Generally, the use of spherical particles less than
6 mm tends to plug more readily and be less ef~'ective in distributing
feed across the initial contact layer of catalyst, whereas the use
of spherical particles having diameters above about 25-30 mm results
in catalysts having significantly lower activity. Preferred are
particles having diameters above 9 mm and particularly above 13 mm.
Preferably, the catalysts of the invention employed as mixtures
of particles having a size ratio in the range of from about 1.5 : 1
to about 3 : 1. Thus, for example, the support materials may comprise
mixtures of particles having diameters from about 6 to 9 ~m to about
8 to 25 mm. A particularly preferred cat~lyst comprises mixtures
of particles having diameters in the range of from about 6 to about
13 mm. The term "spherical" herein refers to particles having both
a true rounded shape and those generally spheroidal particles which
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do not pass perfectly rounded configurations. Procedures for preparing
these particles are known in the art and are not part of the present
invention.
The support is further characterized by a surface area greater
than 200 square metres per gra~ and preferably above 250 square
metres per gram and which may extend up to 600 square metres per
gram or more. Catalysts prepared from a~umina having a surface area
of less than 200 square metres per gram generally ha~e poorer
activity when employed in the present hydroconversion process in
comparison to catalysts in which the alumina-based support initially
is characterized by a surface area in substantial excess of 200
square metres per gram. The term "surface area" as used herein
designates the surface area as determined by the adsorption of
nitrogen according to the method of Brunnauer et al., Journal of
the American Chemical Society 60, 309 et. seq. (1938).
The alumina-based support is preferably all alumina but may
contain minor amounts, i.e., up to 6% by weight of silica. The
silica may be incorporated into the alumina prior to shaping, but
preferably is applied as a surface coating to the preformed alumina,
e.g., with sodium silicate, according to procedures well known in
in the art. Preferred as catalyst supports are spherical aluminas
having crush strenethsabove 36.3 kg and particularly preferred
are supports having crush strengths above 40.8 ke.
The crush strength herein refers to the average value obtained
on at least 20 spherical particles by the following procedure:
A catalyst particle is placed between two parallel horizontal
plates, one stationary and one movable. A gradually increasing
force is applied to the movable plate perpendicular to the surface
of the plate until the catalyst particle breaks. That force in
kilograms which was applied at the instant the particle breaks,
is considered as the crush strength.
The catalyst according to this invention comprises a metal of
Group VI-B and a metal of Group VIII compounded with the alumina-based
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support. Accordingly, the catalyst may comprise at least one of
the metals chromium, molybdenum and tungsten in combination with
at least one of e.g. the metals iron, nickel, cobalt, platinum,
palladium and iridium. Of the Group VI-B metals, molybdenum is
most preferred. The final catalyst most suitably will contain
from 2 to 20 per cent by weight of Group VI-B metal. Of the
Group VIII metals, nickel and cobalt are preferred. ~he amount
of Group VIII metal in the final catalyst suitably will be in
the range of from 0.5 to 10 per cent by weight. Particularly
effective catalysts are obtained utilizing as Group VIII metal
nickel or cobalt. The weight ratio of Group VIII metal to
Group VI-B met~l is preferably from 0.20 : 1 to 0.55 : 1, with
a ratio of from 0.25 : 1 to 0.5 : 1 being preferred in particular.
The metal components can be composited with the alumina-based
spherical particles in any suitable manner. For example, the
particles can be impregnated by dipping or soaking utilizi~g
individual solutions of a suitable compound of a Group VI-B metal
and a suitable Group VIII metal compound, in any convenient
sequence. Alternatively, the metals may be composited with the
spherical alumina particles in a common solution containing suit-
able compounds of both a Group VI-B metal and a Group VIII metal.
Suitable compounds of Group VI-B metals include molybdic acid,
ammonium molybdate, ammonium para-molybdate, chromium acetate,
chromous chloride, = onium meta-tungstate and tungstic acid.
Compounds of Group VIII which are suitable include cobalt chloride,
cobalt carbonate, cobalt sulphate, cobalt nitrate, cobalt fluoride,
nickel nitrate, nic~el sulphate, nickel bromide, nickel acetate,
nickel formate, nickel carbonate, ferric nitrate, ferric formate,
ferric acetate, platinum chloride, chloroplatinic acid and pPl-
ladium chloride. The compositing may be facilitated by the use of
compositing aids, such as a~monium hydro~ide. After all the
catalytic components are present in the final catalyst composite,
the particles suitably are dried for a period of 1 to 20 hours at
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temperatures from about 90 to about 150C and calcined in an
oxidizing atmosphere such as air at temperatures from about 400
to 700 C for a period from about 1 to about 10 hours or more.
The finished catalyst is usually activated in the presence
of hydrogen preferably containing about 1-30 mol. per cent of
hydroeen sulphide at a temperature between 150 and 400C prior to
its use.
The finished catalyst is useful for effecting various mineral
oil conversion reactions, such as demetallization, desulphur-
ization, denitrogenation, hydrogenation and the like. Accordingly,
the process of the invention comprises passing mineral oil feed-
stock and a hydrogen-containing gas through a reæction zone con-
taining the catalyst of the invention at an elevated temperature of
100 to 500 C and a total pressure of 0.35 - 700 kg/cm2 and recover-
ing the hydroconverted oil from the reaction zone. The catalyst is
suitably employed at liquid hourly space velocities (L~SV) from
about 0.2 to about 12 1. feedstock/l. catalyst per hour and from
about 53 to 1780 1. of added hydrogen per 1. of feed. Particularly
preferred conditions are temperatures in the range of from about
250 to 475 C, total pressures from about 7 to about 350 kg/cm ~
uid hourly space velocities from about 0.4 to about 9 1. feed-
stock/l. catalyst per hour and 89 to 4~5 1. of added hydrogen per
1. of feed.
Owing to the unique combination of physical properties the
; 25 particularly preferred embodiment of the process of the invention
utilizes an upright reaction zone wherein ~e feedstock contacts
initially and/or finally catalyst according to the invention.
That is,the catalyst of the invention will substantially or
entirely replace the inert pellets, balls or spheres conventionally
employed, resulting in higher catalytic activity and conversion
efficiency. ~or many existing hydroconvexsion processes the
catalyst according to the invention will suitably replace only
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the inert material while retaining the catalyst heretofore employed
for hydrodesulphurization, hydrodenitrogenation, hydrocracking
and the like. That is, the catalyst according to the invention will
be disposed in layers having a depth from a few to a few fundred
centimetres above and/or below the conventionally employed
catalyst. This is particularly useful for processes emp~ing
highly packed small sized extrudates since the generally larger
spherical catalyst of the invention, owing to configuration, will
have a ereater void fraction for particulate retention. However,
the duration of satisfactory operation will generally be much
longer when employing the catalyst of the invention, than if
the inerts were replaced solely with, e.g., small-sized extrudates.
Unexpectedly, it has been found that for hydrogenation of highly
unsaturated feedstocks such as pyrollizates, e.g., distillates
from steam cracking of hydrocarbons, such as naphthas and gas
oils, the use of the instant catalysts in place of conventional
inertæ of like size results in significant reduction of polymeric
deposits within the reaction zone.
Accordingly, the enhanced activity of the reaction zone
employing the catalyst of the invention can be used to reduce the
operatine temperatures conventionally employed, thereby conserving
expensive fuel, or where equipment permits to increase throughput
for a given conversion level.
In order to illustrate the method of the present invention the
following examples are given.
EXAMPLE I
A mixture of alumina spheres obtained commercially and having a
; particle size in the ranee of from about 6 to 13 mm was impregnated
with a solution containing nickel nitrate hexahydrate and ammonium
dimolybdate in a mixture of aqua ammonia and water. The spheres were
separated from the solutDn, and dried at about 95C for one hour.
The dried composite spheres, which were calcined in air for about
one hour at about 500 C, were found to contain 1.8% by weight of
nickel and 5.4% by weight of molybdenum. The catalyst had a
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surface area of about 300 m /gm and a crush strength of about
37.3 kg.
About 10 cubic centimetres (8.3 grams) of the catalyst were
placed in a fixed bed upright tubular reactor. The catalyst was
sulphided by circulating hydrogen gas containing 5% by weight H2S
for 2 hours at about 204 C,for one hour at about 260C and finPlly
for 2 hours at about 371C. A mid-continent catalytically cracked
heavy gas oil was charged downflow through the bed in a once-
through operation at a liquid hourly space velocity of about 1O5
l. feedstock/l. catPlyst per hour and in admixture with recycle
hydrogen. The hydrogen was recycled to the reactor at the rate of
about 4.0 hydrogen to oil molar ratio. The feedstock had a 50%w
boiling point of about 350 C, an API gravity of 17.1 at 60 F,-
a carbon content of 88.o3% by weight, a hydrogen content of
10.51% by weight, a sulphur concentration of 1.37% by weight and
a nitrogen concentration of 87 parts ~r million. The feedstock
was preheated entering the catalyst bed at a temperature of about
343 C and a total pressure of 60 kg/cm . The catQlyst was found
to be effective for hydrogenation resulting in hydrogen con-
sumption of 55.4 l of hydrogen per l., the hydrotreated product
analyzed 0.59% by weight sulphur and 643 ppm nitrogen.
For purposes of comparison the above procedure was repeated
except that a portion of the unimpregnated alumina support was
used in place of the catalyst. No hydrogen consumption, de-
sulphurization or denitrogenation activity was found.
For further purposes of comparison, the above procedure was
again repeated except that the catalyst was replaced using com-
B mercially available inert spherical material available from Norton~
and having a particle size of about 6-8 mm and a crush strength
above 45.3 kg. This material too was found not to have any
significant hydroconversion effect. The results of the above tests
are summarized in the following Table:
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Hydroconversion Product Properties
Catalyst of the Support Inert
invention
Hydrogen consumed
l.H2/l. oil 55-4
Nitrogen, ppm 643 871 871
Sulphur, %w 0. 59 1.37 1.37
EXAMPLE II
The catalyst preparation procedure of Example I was repeated
except that in place of the nickel nitrate, cobalt nitrate hexa-
hydrate was used in the solution. The final catalyst spheres were
found to contain 1.8~w of cobalt, 5.4%w of molybdenum, had a
surface area of above about 300 m /gm and a crush strength of
about 41.2 kg-
The general procedure of Example I was repeated except the
feedstock was a straight-run gas oil h~ving an API gravity of 22.8
at 60 F, a carbon content of 85.24, a hydrogen content of 12.05, a
sulphur content of 2.57%w and a nitrogen content of 1300 ppm. The
reaction conditions included a temperature of about 371 c, a total
pressure of 56 kg/~m2, a hydrogen rate of 356 l. /l. and a liquid
hourly space velocity of 2.0 l. feedstock/l. catalyst per hour.
~he product ~8 found to coctsin 1.1% sulphur and 970 ppr nitrogen.
