Note: Descriptions are shown in the official language in which they were submitted.
~157~2
PRQCESS AND APPA~ATUS FOR T~IE DEMETALLIZATION OF A H~DROCARBON OIL
The invention relates to a process for the demetalliza-tion of a
hydrocarbon oil by passing said oil together with hydrogen over one or
more fixed beds of a demetallization catalyst.
When refining hydrocarbon oils, such as mineral oils and in
particular petroleum, the light products are usually first removed by
distillation at atmospheric pressure, subsequently heavier fractions
are separated off by means of vacuum distillation and the remaining
residue (short residue) is deasphalted, in which process deasphalted
vacuum residue of a mineral oil (also referred to as DAO below) and
asphalt are obtained. The heavier fractions obtained in the vacuum
distillation (also referred to as vacuum distillate fractions) and the
residual fractions, in particular DAO, can be used as heavy fuel or
as feedstock for catalytic cracking. In order -to discharge the smallest
possible quantity of sulphur compounds into the atmosphere during the
combustion of heavy fuel, it is necessar-y that the sulphur content of
oils to be used as heavy fuel should be as low as possible. To this
end the sulphur is very suitably removed with catalysts suitable
therefor in the presence of hydrogen. Said catalysts are deactivated
rapidly if the fraction to be desulphurized contains a considerable
quan-tity of metal.
If the DAO and/or vacuum distillate fractions are to be used as
feed for a catalytic cracking reaction~ the metal conten-t and the
tendency to coke deposition of the feed -to be used must be as low as
possible in order to prevent rapid deactivation of the cracking catalyst.
In order to meet the requirements set for the metal content, at
least part of -the metals, which occur in larger quantities in residual
fractions than in the vacuum distillate fractions, must therefore in
many cases be removed both from vacuum distillate fractions and from
residual fractions (by which are meant fractions which have remained
behind as residue in the vacuum distillation of a mineral oil or have
been obtained from such a residue, for example short residue, DAO,
asphalt). Said metals consist for the greater part of nickel and
vanadium, which may occur in considerable quantities in mineral oils.
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Removal of me-tals, which need not be complete, is referred to as
demetallization in the present application.
The usual catalysts for catalytic hydrodesulphuriza-tion are not
resistant to quan-tities of metals in -the feed in excess of about 20
ppmw, since in the case of larger quantities of metal unaccep-table
pressure drop across the catalyst occurs after a relatively short time.
For this reason hydrocarbon oils having a metal content higher than
about 20 ppm canno-t be desulphurized with said catalysts in an
economically justified manner.
~0 In a number of cases it is therefore aclvisable that prior to
desulphurization a hydrocarbon oil to be desulphurized should be
demetallized -to a metal content below about 20 ppm, and this applies in
particular to residual fractions, since the latter usually have metal
contents which are considerab]y higher than 20 ppm.
~5 For the deme-tallization o~ hydrocarbon oils in the presence of
hydrogen (hydrodemetallization) specific ca-talysts exist which posess a
high activi-ty for demetallization but only a low capacity ~or
desulphurization. Consecuently, the hydrocarbon oil obtained in the
demetallization will in many cases still have to be desulphurized, in
order to obtain the desired demetallized and desulphurized hydrocarbon
oils. The hydrodesulphurization is very suitably carried out by ~eans of
catalysts suitable therefore which as stated above, are not resistant to
quantities of metal in the feed of about 20 ppm or more.
If no special measures are taken, demetallization catalysts have a
relatively short life, since after a relatively short -time, as a result
of the cluantities of metals and coke which originate ~rom the
hydrocarbon oil and have been deposited on the catalyst, the ca-talyst is
deactivated and such a high pressure drop across the demetallization
catalyst occurs that said catalyst cannot be used further and must be
removed and/or regenera-ted.
It is possible to use a -fresh cluantity of dematallization catalyst
which is contained, for example, in a different parallel-
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connected reactor than the deactiva-ted catalyst and to regenerate
and/or remove the deactivated deme-tallization catalyst.
However~ this method, has the drawback that ~or the regeneration
and/or removal from the reactor o~ the deactiYated demetallizati`on
5 catalyst this reactor must be opened or at least the hydrogen present
therein must be replaced by air. On a site where a number o~ reactors
are located in which hydrotreatments at high pressure and temperature
are carried out, it is, ~or sa~ety reasons, undesirable to shut down
one o~ the reactors separately and replace the hyarogen therein by an
oxygen-containing gas. The aim will be to close down the whole plant
simultaneousl~ for the regeneration andlor remoYal of the demetalliza-
tion catalyst.
The invention provides a process ~or the hydrodemetallization
o~ a hydrocarbon o;l~ in which process the time during which~a
J5 demetallization catalyst can be used without it being necessary to
be removed and/or regenerated, is prolonged considerably.
Accordingly, the invention relates to process ~or the
demetallization o~ a hydrocarbon oil by passing said oil together
with hydrogen over one~or more ~ixed beds o~ a demetallization
catalyst, which process is characterized in that whenever that
catalyst portion which is first contacted with the hydrocarbon oil
is deactivated the point o~ supply o~ the hydrocarbon oil is moved
downstream, at least part of the original supply o~ hydrogen belng
main-tained over the~entire catalyst.
It is essential that at least part of the hydrogen stream
should be maintained over the entire catalyst. A~ter the supply~ o~
the hydrocarbon oil to be demetallized has been movea to a point
located further downstream, a quantit~ o~ oil învariably remains
present on the deactivatea part o~ the catalyst. This oil may
exhibit undesired decomposi:tion reactions with heat production, as
a result o~ which local oYerheating o~ the deactivated catalyst
may occur. By maintaining a hydrogen stream over the entire catalyst
such reactions are largely suppressed and if they nevertheless occur,
removal o~ the ieat produce is ensurea.
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In addition -to the hydrogen s-tream maintained over the en-tire
catalyst it is as a matter of course, possible to introduce hydrogen in
one or more downstream places if desired. The moment when -the catalys-t
portion which is first contacted with the oil to be deme-tallized is
considered deactiva-ted, is determined by the pressure drop occurring
across the catalyst. Depending on the conditions a not excessive
pressure drop may be permitted before the supply of hydrocarbon oil is
removed. When under the prevailing conditions the period of time
elapsing between the supply of hydrocarbon oil to a certain part of the
catalyst and the deactivation thereof has become known, it is of course
also possible on the basis of said period to move -the supply of
hydrocarbon oil to a point located further down-stream a short time
before the pressure drop across the catalyst becomes unacceptable.
Any hydrocarbon oil to be demetalli~ed can serve as feed for the
15 process according to the invention. As examples may be mentioned crude
oil, oil from which the volatile products are removed (topped crude
oil), oil from which light products are removed by distillation at
atmospheric pressure (so-called long residue), shale oils, oils obtained
from tar sands. Preference is given to residual fractions, as defined
20 above
Deme-tallization catalysts are known; they usually consist of oxidic
carriers on which one or more metals with hydrogenation activity (or
compounds of said metals) are optionally deposited. In the process
according to the invention use is very suitably made of catalysts of the
25 type described in the Dutch patent application 7309387. Said catalysts
contain one or more metals with hydrogenation activity on a carrier and
fulfil the following requirements:
1~ p/d ~ 3.5 - Q.02 v, in which p represents the specific average
pore diameter in nm, d represents the specific average par-ticle
diameter in mm and v is the percentage of the total pore volume
consisting of pores having a diameter above 100 nm,
2) the total pore vol~e is above 0.40 ml/g,
3) v is below 50 and
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4) the specific surface area is above 100 m !g;
in case -the catalyst has such a p and d that the quotient p/d
is higher than 3.5-0.02 v, but at most 10-0.~5 v, the catalyst
must fulfil the following additional requirements:
a¦ the nitrogen pore volume is above Q.60 ml/g,
b) -the speeific surface area is above 150 m /g and
cl p is above 5 nm.
The values to be used for p, d, v, the total pore volume, the
nitrogen pore ~olume and the specific surface area must be deter-
mined as descrihed in -the Dutch patent application 7309387.
The catalyst contains Yery suitably, metals with hydrogenation
activity selected from the group consisting of nickel, eobalt,
molybdenum, vanadium and tungsten, and particular preference is
given to catalysts which contain at least one metal o~ the group
15 consisting of nickel and cobalt and at least one metal of the group
eonsisting of molybdenum, vanadium and tungsten.
Catalysts containing niekel and vanadium are particularly suitable.
~he metals are preferably present as their oxides or sulphides.
Alumina and silica-alumina are very suitable as carriers.
20 Preference is given to carriers completely or substantially
completely consisting o~ silica.
Yery suitable catalysts for -the hydrodemetallization according
to the invention are those described in the Dutch patent
application 7316396. Said catalysts eontain 0.1-15 parts by weight
of the metal combination nickel-vanadium per ~00 parts by weight
of a silica carrier and have a loss on ignition, determined under
standard conditions, of less than 0. 5% by weight.
Catalysta as described in the Dutch patent application 7412155
are also very suitable. The latter catalysts ~ulfil the above-
mentioned requirements and are obtained by the nodulizing technique;they have a pore volume, present in pores having a diameter above
50 nm, of at least 0. 2 ml/g.
If the hydrocarbon oil to be demetallized has a high metal
eontent, it is also possible to use as eatalyst silica on whieh
35 no metals with hydrogenation aetivity have been deposited, as
described in the Dutch patent applieation 7607552.
t~7~
The process according to the invention is carried out under
conditions which are usual for hydrodeme-tallization. The hydrocarbon oil
to be demetalliæed (which in most cases is for at least 80 vol.% in the
liquid phase) together with hydrogen is very suitably passed in downward
direction over the ca-talyst at a temperature between 300 and 450C
~preferably between 350 and 425C), a total pressure between 75 and 250
bar (preferably between 100 and 200 bar), a hydrogen partial pressure
between 35 and 120 bar (preferably between 50 and 100 bar~, a space
velocity of 0.~-25 parts by volume of fresh feed per part by volume of
10 catalyst per hour and a hydrogen/feed ratio of 100-2000 (preferably 200-
1500) Nl of H2/kg of feed.
The hydrogen required for the hydrodeme-tallization may be a
hydrogen containing gas s-tream, such as a reformer off-gas stream, or a
mainly pure hydrogen. The hydrogen-containing gases preferably contain
35 at least 60% by volume of hydrogen.
The demetallization catalyst may be present in one fixed bed, but
is preferabl~ present in several serially connected fixed beds. The
fixed beds can be located in one or more reactors. The size of the
catalyst beds is very suitably so chosen that the supply point of
20 hydrocarbon oil to be demetallized is in all cases moved to a place
between two catalyst beds.
After the furthest downstream portion of the catalyst is also
deactivated7 the catalyst must be taken out of service and can be
regenerated and~or removed. During regeneration the coke deposits and
25 the metal deposits (which in many cases mainly consist of vanadium and
to a lesser e~tent of nickell must be at least partly removed. The
regeneration is ver~ suitably carried out b~ the methods described in
the Dutch patent applications 75~1993, 7703181 and 7703380. In these
methods, the deactivated catalyst is extracted with an aqueous solution
30 Of a mineral acid (for example sulphuric acid~, which extraction is very
suitably preceded by a treatment with a reducing agent or is carried out
in the presence of a reducing agent. Sulphur dioxide is very suitable as
reducing agen-t.
In order to remove also the coke and sulphur deposits it is
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advisable, before -the extraction with an aqueous solution of a mineral
acid (and the optional trea-tment with a reducing agent), to subject the
deactivated catalys-t to a treatment with steam, and/or an oxygen-
containing gas such as air, and/or with a mixture of steam and air, at a
temperature above 250 C at atmospheric or a higher pressure.
If the carrier of -the ca-talys-t is resistant to an aqueous solu-tion
of mineral acid (i.e. consists of~ for example, silica) the ca-talyst can
be reused after removal of the coke, sulphur and metals, op-tionally
after application O-r the abovementioned metals wi-th hydrogena-tion
activity.
If the carrier is not resistant to an aqueous solution of a m;neral
acid (i.e. consists, for example, of alumina) regeneration in the above-
mentioned manner is impossible. In that case it is also possible,
however, to carry out the treatment with mineral acid in order to
recover the metals deposited from the hydrocarbon oil. Said metals can
of course also be recovered from the extract obtained in the treatment
with an aqueous mineral acid solution of deactivated catalys-ts, the
carriers of which are resis-tan-t to a treatment of this type.
The demetallized hydrocarbon oil obtained in the process accord-
ing to the invention can be used for any desired purpose.The demetallization need of course not be complete and a quantity of
metal may still be present in -the demetallized product.
~ s stated above~ it is in many cases at-tractive to subject the
resultan-t demetallized hydrocarbon oil to a hydrodesulphurization
treatment and it is advantageous to carry out the deme-tallization
and desulphurization in one continuous treatment without intermediate
isolation and!or purification of the deme-tallized hydrocarbon oil
and of the hydrogen-containing gas becoming available from the final
reactor bed of demetallization catalyst.
For the hydrodesulphurization of heavy hydrocarbon fractions,
such as residual fractions, specific catalysts are known which can
be used for a long time without replacement or regeneration of -the
ca-talyst being necessary as a result of deposition of coke and
high-molecl1lar components (such as resins, polyaroma-tics and
asphaltenes) from the feed. Catalysts as described in the Dutch
paten-t application 7010427 are very sui-table. The particles of
said catalysts have a pore volume above 0.30 ml/g, of which pore
~1574:1~
volume less than 10% is present in pores having a diameter above ~00 nm,
and the catalyst ~articles have a speci~ic pore diameter expressed
in nm ~rom 7.5 x d-9 to 17 x d 9, in which d represents the spec;fic
particle diameter in ~.
Said catalysts very sui-tably contain a carrier on which one or more
metals chosen ~rom the group consisting of nickel, cobalt, tungsten and
molybdenum, and in particular one metal o~ the group consisting o~
nickel and cobalt and one metal o~ the group consisting o~ tungsten and
molybdenum, are deposited. Catalysts containing nickel or cobalt
10 together with molybdenum are particularly suitable. The metals are
preferably present as their oxides or sulphides. Very sui-table carriers
are silica, silica-alumina and in particular alumina.
The hydrodesulphurization is carried out under the usual conditions.
The demetallized hyclrocarbon oil to be desulphurized together wi-th the
hydrogencontaining gas obtained in the demetallization (to which extra
hydrogen is added, i~ desired~ is very suitably passed in downward
direction over the catalyst at a temperature between 350 and 475 C
(preferably between 385 and 4~5C), a total pressure between 75 and 250
bar (pre~erably between 100 and 225 bar), a hydrogen partial pressure
20 between 35 and 120 bar (preferably between 50 and 100 bar), a space
velocity o~ 0.1-25 (pre~erably 0.2-5~ parts by volume of ~eed per part
by volume o~ catalyst and a hydrogen/feed ratio o~ 150-2000 (preferably
250-1500) Nl o~ II2/kg o~ ~eed.
The desulphurization catalyst is very suitably contained in one or
25 more fixed beds which, i~ desired, are located in several serially
connected reactors.
When the demetalli~ation catalyst or the desulphurization catalyst
is deactivated, the whole plant is closed down and the demetallization
catalyst and desulphurization ca-talyst are both removed and/or
30 regenerated. For economic reasons the aim will be to choose the
quantities of demetallization catalyst and desulphurization catalyst in
such a manner tha-t both are deac-tivated about simu]taneously, since in
-that manner no or only a small portion o~ active catalyst is removed
and/or subjected to a regeneration process.
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The product ob-tained after the desulphurization is sepera-ted from
the hydrogen-containing gas in the usual manner; if desired, said
gas can be recycled -to the process after complete or partial
removal of H2S and any other impurities. ~ r~Jn~
The inven-tion also relates to an apparatus ~r~e~a-~ one
or more serially connected reac-tors each o which can be filled
with one or more fixed catalyst beds, the first bed of the first
reactor having an inlet for a gas and an inlet for a hydrocarbon
oil~ characterized in that one or more inlets for hydrocarbon
oil is/are present downs-tream, and that each hydrocarbon oil
inlet can be separa-tely connected or closed.
The invention will now be illus-trated with reference to the
following diagrammatic figure. Each of the reactors R1, R2 and R3
contains two ~ixed beds of demetallization catalyst (1, 2, 3, 4, 5
and 6~. Hydrogen is supplied to the bed 1 in reactor R1 through a
line 7, passes the beds 2, 3, 4, 5 and 6 consecutively and leaves
reactor R3 through a line 8 toge-ther with demetallized hydrocarbon
oil. Fresh hydrocarbon oil is supplied -through a line 9 and is
initially supplied to bed 1 via an open valve 10 and passes through
the beds 1, 2, 3, 4, 5 and 6 consecutively. ~alves 11, 12, 13, 14 and
15 are closed. After the demetallization catalyst in bed 1 is
deactivated, valve 11 is opened and valve 10 is closed. The hydro-
carbon oil to be demetallized is then supplied to bed 2 and passes
through the beds 2, 3, 4, 5 and 6 consecutively. When bed 2 is de-
activated, valve 12 is opened and valve ~1 is closed and the hydro-
carbon oil to be demetallized is supplied to bed 3. In a similar
manner the hydrocarbon oil to be demetallized is supplied to the
beds 4, 5, and 6 whenever the preceding bed is deactivated. After
bed 6 is also deactivated, the hydrocarbon oil and hydrogen streams
are interrup-ted and the catalyst in reactors R1, R2 and R3 is replaced
or regenerated. ln the figure -the resul-tan-t demetallized hydrocarbon
oil and -the hydrogen containing gas which become available -through
a line o from reactor R3 are passed without further purification
through the reactors R4 and R5, each containing two beds of a
desulphurization ca-ta~ys-t.
_ _ .... _ _ _ _ . . . .
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The desulphurized and demetallized hydrocarbon oil and the hydrogen-
containing gas becoming available from reactor R5 through a line 16
can be separated and purified by conventional methods. As regards
pressure, temperature and space velocity, conditions suitable for
demetallization are maintained in reactors R1, R2 and R3 and con-
ditions suitable for desulphurization are maintained in reactors R
and R5.
EX~PLE
In an apparatus as described in the figure, beds-1-6in the
reactors R1, R2 and R3 are filled with a demetallization catalyst.
Said catalyst contains o.6% by weight of nickel (as oxide) and 1.9%
by weight of vanadium (as oxide~ on silica as carrier, has a specific
average pore diameter of 13.6 nm, a specific average particle dia-
meter of 2.2 mm, a specific surface area of 262 m /g and a pore
volume of o.78 ml/g, of which pore volume 0.3% consists o~ pores
having a diameter above 100 nm. Before use the catalyst is sulphided
by passing over it a gasoil containing ~.6% by weight of sulphur, at
a space velocity of 1 kg/litre of catalyst/h, a temperature of 350 C
and a hydrogen pressure of 50 bar. The reactors R4 and R5 are filled
with a desulphurization catalyst. This catalyst contains 3.6% by
weight of nickel (as oxide~ and 8.9% by weight of molybdenum (as
oxide) on alumina as carrier, and has a specific average pore dia-
meter of 20.2 nm, a specific average particle diameter of 1.5 mm, a
specific surface area of ~83 m /g and a pore volume of o.54 ml/g, of
25 which less than 0.4% is present in pores h~ving a diameter above 100
nm. Before use this desulphurization ca-talyst is sulphided in the
same way as the demetallization catalyst.
A deasphalted vacuum residue of a mineral oil (DA0) containing
40 ppm of vanadium and 2.7~ by weigh-t o~ sulphur, is subsequently
30 passed through the reactors R1-R5 at a space velocity of 0.29 kg/l
o~ catalyst/h both ~or the demetal.lization catalyst and -the desulphur-
ization catalyst, at a temper-ature o~ 390 C, a hydrogen partial
pressure o~ 70 bar and a gas space velocity of 1000 Nl/kg of feed.
Whenever the pressure drop increases rapidly, the feed inlet is
moved -to the nex-t bed of demetallization catalyst, the hydrogen
stream being maintained over all the beds.
1 1 5 ~
1 1
The test is interrup-ted after unaccep-table pressure drop occurs
while the feed is being supplied to bed 6; this is 12,000 hours
after -the start of the test. The product obtained con-tains 1 ppm
of vanadium and 0.5% by weight of sulphur.
For the sake of comparison an experir~ent is carried ou-t
in which the feed inlet is not moved downstream. After only
2000 hours such a pressure drop occurs that the experiment must
be interrupted.
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