U.S. patent application number 14/369432 was filed with the patent office on 2015-06-25 for process for hydrotreating a hydrocarbon oil.
This patent application is currently assigned to SHELL OIL COMPANY. The applicant listed for this patent is SHELL OIL COMPANY. Invention is credited to Edmundo Steven Van Doesburg.
Application Number | 20150175909 14/369432 |
Document ID | / |
Family ID | 47470014 |
Filed Date | 2015-06-25 |
United States Patent
Application |
20150175909 |
Kind Code |
A1 |
Van Doesburg; Edmundo
Steven |
June 25, 2015 |
PROCESS FOR HYDROTREATING A HYDROCARBON OIL
Abstract
A process or hydrotreating a hydrocarbon oil that employs a
first reactor and a second reactor. The hydrocarbon oil is
hydrotreated in the first reactor with a first hydrotreating
catalyst in the presence of a first stream of hydrogen-containing
gas to obtain a first effluent. The first effluent is separated
using a stripping column to provide a hydrotreated hydrocarbon oil
and used hydrogen-containing gas. A second stream of
hydrogen-containing gas is heated within a section of a heating
device arranged upstream of the first reactor to obtain a stream of
heated hydrogen-containing gas. The stream of heated
hydrogen-containing gas is contacted in the second reactor in the
presence of at least part of the hydrotreated hydrocarbon oil with
a second hydrotreating catalyst to obtain a second effluent which
comprises a further hydrotreated hydrocarbon oil.
Inventors: |
Van Doesburg; Edmundo Steven;
(Amsterdam, NL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SHELL OIL COMPANY |
Houston |
TX |
US |
|
|
Assignee: |
SHELL OIL COMPANY
Houston
TX
|
Family ID: |
47470014 |
Appl. No.: |
14/369432 |
Filed: |
December 27, 2012 |
PCT Filed: |
December 27, 2012 |
PCT NO: |
PCT/EP2012/076966 |
371 Date: |
June 27, 2014 |
Current U.S.
Class: |
208/89 |
Current CPC
Class: |
C10G 65/043 20130101;
C10G 65/02 20130101; C10G 2300/4031 20130101 |
International
Class: |
C10G 65/02 20060101
C10G065/02 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 29, 2011 |
EP |
11195994.6 |
Claims
1. A process for hydrotreating a hydrocarbon oil employing at least
a first reactor and a second reactor, which process comprises: (i)
providing a first stream of hydrogen-containing gas; (ii)
hydrotreating the hydrocarbon oil in the first reactor with a first
hydrotreating catalyst in the presence of the first stream of
hydrogen-containing gas as provided in step (i) to obtain a first
effluent; (iii) separating the first effluent as obtained in step
(ii) into a hydrotreated hydrocarbon oil and used
hydrogen-containing gas using a stripping column employing a
hydrogen-containing gas as stripping gas; (iv) providing a second
stream of hydrogen-containing gas which is heated within a section
of a heating device which is arranged upstream of the first reactor
to obtain a stream of heated hydrogen-containing gas; and (v)
contacting in the second reactor at least part of the stream of
heated hydrogen-containing gas as obtained in step (iv), optionally
in the presence of at least part of the hydrotreated hydrocarbon
oil as obtained in step (iii), with a second hydrotreating catalyst
to obtain a stream of used hydrogen-containing gas, and a second
effluent which comprises a further hydrotreated hydrocarbon oil
when hydrotreated hydrocarbon oil as obtained in step (iii) is also
present.
2. A process according to claim 1, wherein the first stream of
hydrogen-containing gas and the second stream of
hydrogen-containing gas are derived from the same source of clean
hydrogen-containing gas.
3. A process according to claim 1, wherein the hydrocarbon oil to
be hydrotreated is a gas oil which contains at least 75% by weight
of hydrocarbons boiling in the range of from 150 to 400.degree.
C.
4. A process according to claim 1, in which the hydrotreating
conditions in steps (ii) and (v) comprise a temperature ranging
from 250 to 480.degree. C., a pressure from 10 to 150 bar, and a
weight hourly space velocity of from 0.1 to 10 hr.sup.-1.
5. A process according to claim 1, wherein the second stream of
hydrogen-containing gas contains less than 0.1% by volume of
hydrogen sulphide.
6. A process according to claim 1, wherein the first effluent as
obtained in step (ii) is passed to a gas-liquid separator before
using the stripping column.
7. A process according to claim 1, wherein the used
hydrogen-containing gas as obtained in step (iii) is cleaned and
used again in step (v), and optionally in step (ii).
8. A process according to claim 1, wherein step (v) is carried out
in the presence of at least part of the hydrotreated hydrocarbon
oil as obtained in step (iii).
9. A process according to claim 1, wherein the hydrogen-containing
gas that is being used as stripping gas in step (iii) has a
temperature of from 250 to 480.degree. C.
10. A process according to claim 1, wherein the used
hydrogen-containing gas as obtained in step (v) is used as
stripping gas in step (iii).
11. A process according to claim 1, wherein the first hydrotreating
catalyst in step (ii) is a hydrodesulphurization catalyst and the
second hydrotreating catalyst in step (v) is a hydrodewaxing
catalyst.
12. A process according to claim 11, wherein the
hydrodesulphurization catalyst as used in step (ii) comprises one
or more metals from Group VB, VIB and VIII of the Periodic Table of
the Elements, on a solid carrier.
13. A process according to claim 11, wherein the hydrodewaxing
catalyst as used in step (v) comprises as catalytically active
metal one or more noble metals from Group VIII of the Periodic
Table of the Elements on a solid carrier.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a process for hydrotreating
a hydrocarbon oil employing at least a first and a second
reactor.
BACKGROUND OF THE INVENTION
[0002] Processes for hydrotreating hydrocarbon oils are well known.
Also processes that employ two or more reactors have been described
in the literature.
[0003] Processes for reducing the amount of sulphur or nitrogen
containing compounds and aromatics, are in general called
hydrotreating processes. These processes can be further divided
into processes which are especially directed at saturation of
unsaturated compounds such as aromatics and olefins, in which case
they are called hydrogenation processes, and processes which are
especially directed at reducing the amount of sulphur containing
compounds and often at the same time also of nitrogen containing
compounds, in which case they are called hydrodesulphurisation
processes. There are also processes which are specifically directed
at reducing the amount of nitrogen containing compounds and in
which only a relatively small amount of sulphur-containing
compounds are removed. These are called hydrodenitrogenation
processes. With the expression hydrodesulphurisation processes,
which is used hereinafter, processes are meant which are directed
at removal of sulphur-containing compounds and optionally an amount
of nitrogen. Processes wherein linear waxy hydrocarbons are
isomerised to branched alkanes are referred to as
hydroisomerisation or as hydrodewaxing processes. These processes
can be applied to middle distillates so that the pour point is
reduced. Alternatively, the process can be applied to lubricating
oils to enhance the viscosity index.
[0004] A hydrotreating process using two reactors in series has
been described in WO 2011/006952 A2. It describes a hydrotreating
process in which process a combination of a hydrocarbon oil and a
hydrogen-containing gas is passed through a first furnace and the
heated combination is contacted with a hydrotreating catalyst in
first reactor vessel. The effluent of this contact is separated
into partly hydrotreated hydrocarbon oil and contaminated
hydrogen-containing gas. The separation is carried out in a
stripping column using hydrogen as stripping gas. The partly
hydrotreated hydrocarbon oil is passed through a second furnace and
the heated oil is contacted in a second reactor vessel with a
hydrotreating catalyst in the presence of a hydrogen-containing
gas. The product of this step is separated into a hydrotreated
hydrocarbon oil and used hydrogen-containing gas, which
hydrotreated hydrocarbon oil can be recovered as product, and which
used hydrogen-containing gas is recycled to the stripping
column.
[0005] Since product properties demand change during the year in
the sense that cold flow properties of the product are less
stringent during summer than the other months of the year, it is
desirable to have a flexible hydrotreating process in which the
first and second hydrotreating steps can attractively be decoupled.
Such decoupling would allow the use of the first reactor vessel
only during summer and the integration of the two reactor vessels
during the remaining part of the year. A major difficulty is,
however, the start-up of the second hydrotreating step once the two
hydrotreating steps need to be integrated again because the second
reactor vessel can easily be damaged during the start-up process.
Object of the present invention is to provide a process which
facilitates the coupling of the two reactor vessels in an
attractive manner, whilst enhancing the economics of the integrated
process.
SUMMARY OF THE INVENTION
[0006] Accordingly, the present invention provides a process for
hydrotreating a hydrocarbon oil employing at least a first reactor
and a second reactor, which process comprises:
(i) providing a first stream of hydrogen-containing gas; (ii)
hydrotreating the hydrocarbon oil in the first reactor with a first
hydrotreating catalyst in the presence of the first stream of
hydrogen-containing gas as provided in step (i) to obtain a first
effluent; (iii) separating the first effluent as obtained in step
(ii) into a hydrotreated hydrocarbon oil and used
hydrogen-containing gas using a stripping column employing a
hydrogen-containing gas as stripping gas; (iv) providing a second
stream of hydrogen-containing gas which is heated within a section
of a heating device which is arranged upstream of the first reactor
to obtain a stream of heated hydrogen-containing gas; and (v)
contacting in the second reactor at least part of the stream of
heated hydrogen-containing gas as obtained in step (iv), optionally
in the presence of at least part of the hydrotreated hydrocarbon
oil as obtained in step (iii), with a second hydrotreating catalyst
to obtain a stream of used hydrogen-containing gas, and a second
effluent which comprises a further hydrotreated hydrocarbon oil
when hydrotreated hydrocarbon oil as obtained in step (iii) is also
present.
DETAILED DESCRIPTION OF THE INVENTION
[0007] In accordance with the present invention the second stream
of clean hydrogen-containing gas is heated within a section of a
heating device which is arranged upstream of the first reactor to
obtain a stream of heated clean hydrogen-containing gas.
[0008] Suitably, the first stream of hydrogen-containing and/or the
hydrocarbon oil are heated within the same heating device before
the heated combination is passed to the first reactor. In a
particular embodiment of the present invention the first stream of
hydrogen-containing and the hydrocarbon oil are combined and heated
within a lower section of the heating device before the heated
combination is passed to the first reactor, whereas the second
stream of hydrogen-containing gas is heated in an upper section of
the heating device. In this way, the economics of the integrated
process are considerably improved since a separate second furnace
upstream the second reactor vessel is no longer required, whereas
at the same time the use of such a heating device allows the
warming-up of the second hydrogen-containing gas in a highly
controlled and flexible manner once the operation of the second
reactor needs to be integrated again with operation of the first
reactor after it has been decoupled during the summer.
[0009] The present invention includes the warming-up phase of the
second reactor. During said phase the second stream of heated
hydrogen-containing gas is passed to the second reactor which
allows the second reactor to warm-up and to become pressurized in a
controlled manner. Once the second reactor has been heated to the
desired temperature it can be pressurized. An additional advantage
of the present process is that during the warming-up of the second
reactor the hydrotreating catalyst inside the second reactor can
suitably be reduced by means of the second stream of heated
hydrogen-containing gas before the second reactor is integrated
again in operation with the first reactor. Suitably, such a
warming-up process the temperature in the reactor is gradually
increased. The increase in temperature can suitably be in the range
of from 5-40.degree. C./hour. Once a temperature is reached in the
range of from 240-350.degree. C., the second hydrotreating catalyst
can suitably be reduced for a period of time of 4-16 hours,
preferably 6-10 hours, before the operation of the second reactor
is integrated again with the operation of the first reactor.
Another advantage of the present process is that the second stream
of heated hydrogen-containing gas can suitably be used to strip off
hydrocarbon oil which is present on the second hydrotreating
catalyst before the second reactor is decoupled or at least part of
the second hydrotreating catalyst is replaced.
[0010] In accordance with the present invention the first stream of
clean hydrogen-containing gas and the second stream of
hydrogen-containing gas are preferably derived from the same source
of clean hydrogen-containing gas. During the period that the second
reactor cannot be pressurised, the spare compressor might be used
to circulate the stream of hydrogen-containing gas.
[0011] In general it will be advantageous to hydrotreat a
hydrocarbon oil of which a major amount, for example more than 70%
by weight, suitably more than 80% by weight and preferably more
than 90% by weight, is in the liquid phase at the process
conditions prevailing in the first reactor. Hydrocarbon oils that
can suitably be hydrotreated according to the present invention are
kerosene fractions, gas oil fractions and lubricating oils.
Especially a gas oil fraction can very suitably be subjected to the
present invention, as the environmental constraints on gas oils are
tightening. A suitable gas oil would be one of which a major
portion of the hydrocarbons, e.g. at least 75% by weight boils in
the range of from 150 to 400.degree. C. A suitable lubricating oil
contains at least 95% by weight of hydrocarbons boiling in the
range of from 320 to 600.degree. C.
[0012] The hydrotreating process can be a hydrofinishing process in
which the hydrocarbon oil is marginally changed, it may be a
hydrocracking process in which the average number of carbon atoms
in the oil molecules is reduced, it may be a hydrodemetallisation
process in which metal components are removed from the hydrocarbon
oil, it may be a hydrogenation process in which unsaturated
hydrocarbons are hydrogenated and saturated, it may be a
hydrodewaxing process in which straight chain molecules are
isomerised, or it may be a hydrodesulphurisation process in which
sulphur compounds are removed from the feedstock. It has been found
that the present process is particularly useful when the
hydrocarbon oil comprises sulphur compounds and the hydrotreating
conditions comprise hydrodesulphurisation conditions. The process
is also very advantageous in the treatment of sulphur-containing
hydrocarbon oils that contain so-called refractory sulphur
compounds, i.e., dibenzothiophene compounds.
[0013] The hydrotreating conditions that can be applied in the
process of the present invention are not critical and can be
adjusted to the type of conversion to which the hydrocarbon oil is
being subjected. Generally, the hydrotreating conditions in steps
(ii) and (v) comprise a temperature ranging from 250 to 480.degree.
C., preferably from 320 to 400.degree. C., a pressure from 10 to
150 bar, preferably 20 to 90 bar, and a weight hourly space
velocity of from 0.1 to 10 hr.sup.-1, preferably from 0.4 to 4
hr.sup.-1. The skilled person will be able to adapt the conditions
in accordance with the type of feedstock and the desired
hydrotreatment.
[0014] Preferably, the second stream of hydrogen-containing gas as
provided in step (iv) contains less than 0.1% by volume of hydrogen
sulphide.
[0015] The hydrotreating catalyst in step (ii) is suitably a
hydrodesulphurization catalyst and the hydrotreating catalyst in
step (v) is suitably a hydrodewaxing catalyst
[0016] Suitably, the hydrodesulphurization catalyst as used in step
(ii) comprises one or more metals from Group VB, VIB and VIII of
the Periodic Table of the Elements, on a solid carrier.
[0017] Suitably, the hydrodewaxing catalyst as used in step (v)
comprises as catalytically active metal one or more noble metals
from Group VIII of the Periodic Table of the Elements on a solid
carrier.
[0018] Suitable catalysts comprise at least one Group VB, VIB
and/or VIII metal of the Periodic Table of the Elements on a
suitable carrier. Examples of suitable metals include cobalt,
nickel, molybdenum and tungsten, but also noble metals may be used
such as palladium or platinum. Especially when the hydrocarbon oil
comprises sulphur, the catalyst suitably contains a carrier and at
least one Group VIB and a Group VIII metal. Whereas these metals
can be present in the form of their oxides, it is preferred to use
the metals in the form of their sulphides. Since the catalyst may
normally be produced in their oxidic form the catalysts may
subsequently be subjected to a pre-sulphiding treatment which can
be carried out ex situ, but is conducted preferably in-situ, in
particular under circumstances that resemble the actual
conversion.
[0019] The metals are suitably combined on a carrier. The carrier
may be an amorphous refractory oxide, such as silica, alumina or
silica alumina. Also other oxides, such as zirconia, titania or
germania can be used. For hydrodewaxing processes, crystalline
aluminosilicates, such as zeolite beta, ZSM-5, mordenite,
ferrierite, ZSM-11, ZSM-12, ZSM-23 and other medium pore zeolites,
can be used. When the hydrotreating conditions entail
hydrocracking, the catalyst may advantageously comprise a different
zeolite. Suitable zeolites are of the faujasite type, such as
zeolite X or Y, in particular ultra-stable zeolite Y. Other,
preferably large pore, zeolites are also possible. The zeolites are
generally combined with an amorphous binder, such as alumina. The
metals are suitably combined with the catalyst by impregnation,
soaking, co-mulling, kneading or, additionally in the case of
zeolites, by ion exchange. It is evident that the skilled person
will know what catalysts are suitable and how such catalysts can be
prepared.
[0020] The first and second hydrotreating catalysts can be present
in the respective reactor in one or more beds.
[0021] Suitably, at least part of the stream of used
hydrogen-containing gas as obtained in step (v) can be used as
stripping gas in step (iii).
[0022] Also gaseous hydrocarbons that may have been formed in the
second hydrotreating reactor may be used in the stripping action.
Moreover, since the stream of used hydrogen-containing gas as
obtained in step (v) emerges from the second hydrotreating reactor,
it may become available at hydrotreating conditions, which entails
elevated temperature. The stream of used hydrogen-containing gas at
such elevated temperature will facilitate the stripping action
further and will improve the heat recovery from the used
hydrogen-containing gas.
[0023] Suitably, both the first and second stream of
hydrocarbon-containing gas comprise a clean hydrogen-containing
gas. By "clean hydrogen-containing gas" is understood a gas that
contains less than 0.1% vol of hydrogen sulphide, based on the
total volume of the gas, preferably less than 0.01% vol, more
preferably less than 20 ppmv, and most preferably less than 5 ppmv.
Examples of clean hydrogen-containing gas may include fresh make-up
hydrogen, prepared by e.g., steam reforming, or a contaminated
hydrogen-containing gas that has been subjected to a cleaning
treatment, e.g., with an amine. Such contaminated gas may originate
from the present process, but also contaminated hydrogen-containing
gas from different sources or processes may be subjected to
cleaning and subsequent use in the present process. The amount of
hydrogen in clean hydrogen-containing gas is preferably at least
95% vol, more preferably at least 97% vol, based on the total clean
hydrogen-containing gas.
[0024] In a first embodiment the hydrogen-containing gas that is
used in step (ii) in the first reactor is clean hydrogen-containing
gas. This ensures that the amount of gas that needs to be fed into
the first reactor can be minimised. Such gas may suitably be
obtained from purification of contaminated hydrogen-containing gas,
e.g., such contaminated gas that becomes available in the present
process.
[0025] In a preferred embodiment the effluent from the first
reactor is passed to a gas-liquid separator before using the
stripping column. The gaseous phase in the effluent typically
contains large amounts, such as 0.5 to 5.0% vol, based on the total
volume of the gaseous phase, of contaminants such as hydrogen
sulphide. This phase is therefore withdrawn as contaminated
hydrogen-containing gas in the gas-liquid separator and may
preferably be passed to a purification section, such as an amine
scrubber. The liquid phase comprising partly hydrotreated
hydrocarbon oil is withdrawn from the gas-liquid separator and
passed to the stripping column. The stripping column is operated
with at least part of the stream of used hydrogen-containing gas as
obtained in step (v) from the second reactor. The combination of
the stream of used hydrogen-containing gas and stripped gas as
obtained in step (iii) can be fed to the first reactor as
hydrogen-containing gas. It is clear that in such an embodiment the
first effluent is passed to a gas-liquid separator before using the
stripping column. The majority of the contaminants will have been
removed in the gas liquid separator.
[0026] It will be understood that in the hydrotreatment processes
in steps (ii) and (v) hydrogen will be consumed. Generally, the
hydrogen consumption for the hydrotreatment steps is not critical
for the process and depends on the type of hydrocarbon oil that is
being processed. Suitably, the hydrogen consumption in each of the
reactors under hydrotreatment conditions ranges from 0.1 to 2.5%
wt, based on the weight of the hydrocarbon oil for the first
reactor and on the weight of the partly hydrotreated hydrocarbon
oil for the second reactor. The hydrogen consumed in the first and
second reactor is suitably being supplemented for at least 80% by
addition of clean hydrogen-containing gas to the second reactor. In
this way the amount of gas that gets contaminated with significant
amounts of contaminants in the first reactor is minimised. Further
minimisation can suitably be achieved by supplementing at least
90%, more preferably substantially 100% of the hydrogen consumed in
the first and second reactor, with clean hydrogen-containing gas to
the second reactor.
[0027] The first effluent from the first reactor contains partly
hydrotreated hydrocarbon oil. In step (iii) this partly
hydrotreated hydrocarbon oil is separated from contaminated
hydrogen-containing gas. In an advantageous embodiment the
hydrocarbon oil to be treated is a gas oil that typically contains
sulphur compounds. In the first reactor these sulphur compounds are
converted to hydrogen sulphide, which contaminates the
hydrogen-containing gas. In accordance with the process of the
present invention the contaminated hydrogen-containing gas is
separated in step (iii) from the partly hydrotreated hydrocarbon
oil in a stripping column. In the stripping process a
hydrogen-containing gas, preferably at least part of the stream of
used hydrogen-containing gas as recovered from step (v), is being
used as stripping gas. The contaminated hydrogen-containing gas
thus obtained in the stripping column is suitably cleaned and used
again as clean hydrogen-containing gas in step (v), and optionally
in step (ii).
[0028] The treatment of contaminated hydrogen-containing gases,
especially when contaminated with hydrogen sulphide and other
sulphur compounds, such as carbon disulphide or carbon oxysulphide,
is well known. A suitable way to remove these contaminants has been
briefly described in EP-A 611 816, and is by amine scrubbing.
Therefore, the contaminated hydrogen-containing gas is preferably
cleaned by treating with an amine.
[0029] In such situations the contaminated hydrogen-containing gas
is suitably contacted with an aqueous amine solution. The aqueous
solution comprises one or more amine compounds Suitable amine
compounds are primary, secondary and tertiary amines. Preferably,
the amines comprise at least one hydroxyalkyl moiety. The alkyl
group in such moiety suitably comprises from 1 to 4 carbon atoms.
In case of secondary and tertiary amines, the amine compounds
preferably comprise one or more alkyl and hydroxyalkyl groups each
with preferably from 1 to 4 carbon atoms. Suitable examples of
amine compounds include monoethanol amine, monomethanol amine,
monomethyl-ethanolamine, diethyl-monoethanolamine, diethanolamine,
triethanolamine, di-isopropanolamine, diethyleneglycol monoamine,
methyldiethanolamine and mixtures thereof. Other suitable compounds
are N,N'-di(hydroxyalkyl) piperazine,
N,N,N',N'-tetrakis(hydroxyalkyl)-1,6-hexanediamine, in which the
alkyl moiety may comprise from 1 to 4 carbon atoms.
[0030] The aqueous solution may also comprise physical solvents.
Suitable physical solvents include tetramethylene sulphone
(sulpholane) and derivatives, amides of aliphatic carboxylic acids,
N-alkyl pyrrolidone, in particular N-methyl pyrrolidine, N-alkyl
piperidones, in particular N-methyl piperidone, methanol, ethanol,
ethylene glycol, polyethylene glycols, mono- or
di(C.sub.1-C.sub.4)alkyl ethers of ethylene glycol or polyethylene
glycols, suitably having a molecular weight from 50 to 800, and
mixtures thereof.
[0031] The concentration of the amine compound in the aqueous
solution may vary within wide ranges. The skilled person will be
able to determine suitable concentrations without undue burden.
Advantageously, the aqueous solution comprises at least 15% wt of
water, from 10 to 65% wt, preferably from 30 to 55% wt of amine
compounds and from 0 to 40% wt of physical solvent, all percentages
based on the weight of water, amine compound and physical
solvent.
[0032] The conditions under which the contaminated
hydrogen-containing gas is being treated with an amine suitably
include a temperature of from 0 to 150.degree. C., preferably, from
10 to 60.degree. C., and a pressure of from 10 to 150 bar,
preferably from 35 to 120 bar.
[0033] The stripping gas in the stripping column comprises a
hydrogen-containing gas. Since at least part of the stripping gas
can suitably become available from the hydrotreatment reaction in
step (v), it becomes available at elevated temperature. Since the
elevated temperature has an improved stripping performance over the
stripping performance of cool gas and counteracts the cooling
effect of stripping, it is evidently clear that the present process
provides an additional advantage in that an improved stripping
action is being obtained. The hydrogen-containing gas that is being
used as stripping gas in step (iii) has advantageously a
temperature of from 250 to 480.degree. C., preferably from 320 to
400.degree. C.
[0034] A portion of or the entire partly hydrotreated hydrocarbon
oil is subjected to a further hydrotreatment in step (v). As
indicated above, the present process is especially advantageous
when the hydrocarbon oil to be treated is a gas oil. Therefore, it
is particularly preferred that the hydrotreating catalyst in step
(ii) is a hydrodesulphurisation catalyst and the hydrotreating
catalyst in step (v) is a hydrodewaxing catalyst. In such cases the
hydrodesulphurization catalyst suitably comprises an optionally
sulphided catalyst comprising one or more metals from Group V, VI
and VIII of the Periodic Table of the Elements, on a solid carrier.
As indicated earlier the solid carrier can be selected from any of
the refractory oxides described above. The hydrodesulphurisation
catalyst in particular may comprise one or more of the metals
nickel and cobalt, and one or more of the metals molybdenum and
tungsten. The catalyst may advantageously be sulphided as described
above.
[0035] The hydrodewaxing catalyst suitably comprises as
catalytically active metal one or more noble metals from Group
VIIII of the Periodic Table of the Elements on a solid carrier.
Preferably the noble metal is selected from the group consisting of
platinum, palladium, iridium and ruthenium. The carrier
advantageously comprises a zeolite as described above in
combination with a binder material. Suitable binder material
includes alumina, silica and silica-alumina. However, other
refractory oxides can also be used.
[0036] As indicated before, the present process can suitably be
used during the start-up period of the second reactor or just
before the second reactor is decoupled from the first reactor.
[0037] Accordingly, the present invention also provides in one
embodiment a process for hydrotreating a hydrocarbon oil employing
at least a first reactor and a second reactor, which process
comprises:
(i) providing a first stream of hydrogen-containing gas; (ii)
hydrotreating the hydrocarbon oil in the first reactor with a first
hydrotreating catalyst in the presence of the first stream of
hydrogen-containing gas as provided in step (i) to obtain a first
effluent; (iii) separating the first effluent as obtained in step
(ii) into a hydrotreated hydrocarbon oil and used
hydrogen-containing gas using a stripping column employing a
hydrogen-containing gas as stripping gas; (iv) providing a second
stream of hydrogen-containing gas which is heated within a section
of a heating device which is arranged upstream of the first reactor
to obtain a stream of heated hydrogen-containing gas; and (v)
contacting in the second reactor at least part of the stream of
heated hydrogen-containing gas as obtained in step (iv) with a
second hydrotreating catalyst to obtain a stream of used
hydrogen-containing gas.
[0038] It will be appreciated that in such embodiments of (a)
starting-up the second reactor or (b) stripping hydrocarbon oil
from the second hydrotreating catalyst prior to decoupling the
second reactor no partly hydrotreated hydrocarbon oil will be
passed to the second reactor.
[0039] The present invention also provides a hydrotreating process
wherein the operation of the first and second reactors is
integrated.
[0040] Hence, the present invention also provides in a second
embodiment a process for hydrotreating a hydrocarbon oil employing
at least a first reactor and a second reactor, which process
comprises:
(i) providing a first stream of hydrogen-containing gas; (ii)
hydrotreating the hydrocarbon oil in the first reactor with a first
hydrotreating catalyst in the presence of the first stream of
hydrogen-containing gas as provided in step (i) to obtain a first
effluent; (iii) separating the first effluent as obtained in step
(ii) into a hydrotreated hydrocarbon oil and used
hydrogen-containing gas using a stripping column employing a
hydrogen-containing gas as stripping gas; (iv) providing a second
stream of hydrogen-containing gas which is heated within a section
of a heating device which is arranged upstream of the first reactor
to obtain a stream of heated hydrogen-containing gas; and (v)
contacting in the second reactor at least part of the stream of
heated hydrogen-containing gas as obtained in step (iv) in the
presence of at least part of the hydrotreated hydrocarbon oil as
obtained in step (iii), with a second hydrotreating catalyst to
obtain a stream of used hydrogen-containing gas, and a second
effluent which comprises a further hydrotreated hydrocarbon
oil.
[0041] In a step (vi) the second effluent of the hydrotreatment in
the second reactor can be recovered and separated into a
hydrotreated hydrocarbon oil and stream of used hydrogen-containing
gas. In accordance with the present invention in a step (vii) at
least part of the stream of used hydrogen-containing gas can be
transferred to step (iii) for use as stripping gas. Preferably, at
least 90% vol of the stream of used hydrogen-containing gas is
transferred to step (iii), more preferably at least 95% vol, and
most preferably, the entire volume of the stream of used
hydrogen-containing gas is transferred to step (iii).
[0042] The separation in step (vi) can be carried out in any
suitable way. A suitable method involves the use of separation
means inside the second reactor comprising a downwardly extending
plate having an opening between the lower edge of the plate and the
wall of the reactor. Preferably, a downwardly extending flange has
been provided at the lower edge of the plate. This is in accordance
with a similar plate that has been described in EP-A 611 861.
Alternatively, different separation trays can be used in the lower
part of the second reactor. In a further embodiment, the separation
of the effluent of the hydrotreatment in the second reactor is
performed in a separate gas-liquid separator, optionally with
additional heat integration. The effluent, before or after
separation, can suitably be used for heat exchange with the partly
hydrotreated hydrocarbon oil emerging from the stripping column.
This has the advantage that the effluent is cooled whilst the
partly hydrotreated hydrocarbon oil can be heated to the desired
hydrotreating temperature without the use of an additional furnace.
It will be evident that such represents a considerable economical
and heat-efficient advantage.
[0043] FIG. 1 shows a simplified flow scheme of the two embodiments
of the present invention.
[0044] FIG. 2 shows a simplified flow scheme of a further
embodiment of the present invention.
[0045] FIG. 1 shows a line 1 via which a hydrocarbon oil is passed
trough a heat exchanger 2 and to which clean hydrogen-containing
gas is added via a line 3e, either upstream or downstream of heat
exchanger 2. The combination of hydrogen-containing gas and
hydrocarbon oil is passed through a lower section of a furnace 4
and the heated combination is passed via a line 5 to a first
hydrotreating reactor 6. The first hydrotreating reactor 6 has been
provided with three catalyst. Between subsequent beds a quench, for
instance clean hydrogen-containing gas, is added via lines 3c and
3d, respectively. In principle, the flow in the first and second
reactor can be upwards or downwards. It is preferred to pass the
hydrogen-containing gases and hydrocarbon oil or partly
hydrotreated hydrocarbon oil cocurrently through the reactor
vessels in a downflow direction. In this way the gas flow and the
liquid flow can be controlled in a reliable way. Further, reaction
temperatures may be more easily controlled. The effluent from the
first reactor is withdrawn via a line 7. The effluent is also
passed through heat exchanger 2 to preheat the hydrocarbon oil to
be treated, and subsequently passed to a stripping column 8. In the
stripping column stripping gas in the form of used
hydrogen-containing gas is fed into the lower part via a line 10
and the gaseous components in the effluent from line 7 together
with the stripping gas are withdrawn as contaminated
hydrogen-containing gas via a line 9. The contaminated
hydrogen-containing gas is treated in an amine absorption column 16
and purified, clean hydrogen-containing gas is recovered via a line
3. The line 3 is split into the line 3a that leads
hydrogen-containing gas to the hydrocarbon oil, a line 3b that
splits subsequently into lines 3c and 3d to provide the first
reactor 6 with additional hydrogen for reactor temperature control,
and the line 3e via which hydrogen-containing gas is heated in an
upper section of the furnace 4. The heated hydrogen-containing gas
so obtained is then via line 14 combined with the partly
hydrotreated hydrocarbon in line 11 and the combined streams so
obtained are then introduced into a second reactor 12 via line 23.
It is appreciated that whereas the amine absorption is shown in the
Figure as a single absorption column 16 the amine treatment unit
comprises absorption and desorption columns and, optionally, one or
more compressors. Further, the clean hydrogen-containing gas in the
line 3 may be subjected to heat exchange with one or more other
process streams, such as the contaminated hydrogen-containing gas
in the line 9 and/or the effluent from the first reactor in the
line 7. Stripped, partly hydrotreated hydrocarbon oil is discharged
from the stripping column 8 via a line 11, whereby during
integrated operation of the two reactors valve 17 is closed. The
partly hydrotreated hydrocarbon oil in the line 11 can be passed to
the second reactor 12. In accordance with the present invention at
least 80% of the hydrogen consumed in reactors 6 and 12 will be
added to reactor 12. It will be evident to the skilled person,
that, if desired, a portion of fresh make-up hydrogen, i.e. up to
20% of the hydrogen gas stream, can be supplemented with a stream
of hydrogen-containing gas from line 3. The treated hydrocarbon oil
from reactor 12 is separated into a gaseous and a liquid stream,
either inside the reactor with the aid of a special separation tray
13 or in a separate knock-out drum. The gaseous components, i.e.
used hydrogen-containing gas, is withdrawn from the reactor 12 via
the line 10, which passes the used hydrogen-containing gas to the
stripping column 8. Liquid hydrotreated hydrocarbon oil is
recovered via a line 15. The products in line 15 may be
fractionated in any known manner. During the start-up process of
reactor 2, just prior to the decoupling of reactor 12 when
hydrocarbon oil is stripped from the catalyst in reactor 12, or
when catalyst is to be replace in reactor 12, clean heated
hydrogen-containing gas is allowed to enter the reactor 12 via line
14, whereas the flow of partly hydrotreated hydrocarbon oil is no
longer allowed to pass to the reactor 12 by way of a closed valve
20, and partly hydrotreated hydrocarbon oil can be recovered via
line 21 via open valve 17. When the reactor 12 is completely
decoupled from reactor 6, also the flow of hydrogen to the reactor
12 via line 14 will be discontinued by means of closed valves 19
and 22, and the withdrawal of effluent from reactor 12 will be
stopped by way of closed valve 18. Further, at least part of the
hydrogen-containing gas may surpass the furnace 4 via line 21 and
valve 22 and can be combined with the heated hydrogen-containing
gas in line 14.
[0046] In a further embodiment of the invention, shown in FIG. 2, a
line 24 is added to circulate the stream of hydrogen-containing
gas. Valves 25 and 26 have been added. The line 3 is now split into
the line 3e that leads hydrogen-containing gas to the hydrocarbon
oil, a line 3b that splits subsequently into lines 3c and 3d to
provide the first reactor 6 with additional hydrogen for reactor
temperature control, and the line 3a via which hydrogen-containing
gas is heated in an upper section of the furnace 4. During the
period that the second reactor cannot be pressurised, the spare
compressor can be used to circulate the stream of
hydrogen-containing gas via line 24 and closing valves 25 and
26.
* * * * *