U.S. patent application number 11/664260 was filed with the patent office on 2008-12-18 for process for producing hydrorefined gas oil, hydrorefined gas oil, and gas oil composition.
Invention is credited to Hideshi Iki, Hirofumi Konno, Yukihiro Sugiura, Yuichi Tanaka.
Application Number | 20080308459 11/664260 |
Document ID | / |
Family ID | 36142629 |
Filed Date | 2008-12-18 |
United States Patent
Application |
20080308459 |
Kind Code |
A1 |
Iki; Hideshi ; et
al. |
December 18, 2008 |
Process for Producing Hydrorefined Gas Oil, Hydrorefined Gas Oil,
and Gas Oil Composition
Abstract
A process of the present invention for producing a hydrotreated
gas oil has a step for obtaining a product oil having a total
aromatic content of 3% by volume or less by hydrogenating a
hydrotreated oil including 95% by volume or more of fraction having
a boiling point range of 150-380.degree. C., a sulfur content of
2-15 ppm by mass, a total aromatic content of 10-25% by volume, and
a naphthene of 20-60% by volume in the presence of a hydrogenation
catalyst; and a step for obtaining, by hydrogenating the
above-described product oil in the presence of a hydrogenation
catalyst containing a crystalline molecular sieve component, a
product oil satisfying the conditions that the content of petroleum
fraction having a boiling point range of lower than 150.degree. C.
is 16% by volume or less, and the sum of the total aromatic content
and the total naphthene content is 80% or less relative to the sum
of these in the hydrotreated oil.
Inventors: |
Iki; Hideshi; (Kanagawa,
JP) ; Sugiura; Yukihiro; (Kanagawa, JP) ;
Tanaka; Yuichi; (Kanagawa, JP) ; Konno; Hirofumi;
(Kanagawa, JP) |
Correspondence
Address: |
FINNEGAN, HENDERSON, FARABOW, GARRETT & DUNNER;LLP
901 NEW YORK AVENUE, NW
WASHINGTON
DC
20001-4413
US
|
Family ID: |
36142629 |
Appl. No.: |
11/664260 |
Filed: |
September 30, 2005 |
PCT Filed: |
September 30, 2005 |
PCT NO: |
PCT/JP2005/018127 |
371 Date: |
February 28, 2008 |
Current U.S.
Class: |
208/144 |
Current CPC
Class: |
C10G 45/52 20130101;
C10G 2400/06 20130101; C10G 2300/301 20130101; C10G 2300/202
20130101; C10G 65/12 20130101 |
Class at
Publication: |
208/144 |
International
Class: |
C10G 45/00 20060101
C10G045/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 1, 2004 |
JP |
2004-290672 |
Claims
1. A process for producing a hydrotreated gas oil by carrying out
hydrotreating of a feed oil, comprising: a first step for obtaining
a first product oil having a total aromatic content of 3% by volume
or less, by using a hydrotreated oil including a petroleum fraction
of 95% by volume or more having a boiling point range of
150-380.degree. C., a sulfur content of 2-15 ppm by mass, a total
aromatic content of 10-25% by volume and a total naphthene content
of 20-60% by volume as a feed oil, and by carrying out
hydrotreating of the feed oil in the presence of a first
hydrogenation catalyst; and a second step for obtaining a second
product oil that satisfies the following conditions (1) and (2) by
carrying out hydrotreating of the first product oil in the presence
of a second hydrogenation catalyst containing a crystalline
molecular sieve component, (1) the content of petroleum fraction
having a boiling point range of lower than 150.degree. C. is 16% by
volume or less, and (2) the sum of the total aromatic content and
the total naphthene content is 80% or less relative to the sum of
the total aromatic content and the total naphthene content in the
feed oil.
2. A process for producing a hydrotreated gas oil according to
claim 1, wherein a polycyclic aromatic content in the feed oil is
1-7% by volume, and a polycyclic aromatic content in the second
product oil is 0.2% by volume of less.
3. A process for producing a hydrotreated gas oil according to
claim 1, wherein the sum of a polycyclic aromatic content and a
polycyclic naphthene content in the second product oil is 13% by
volume or less.
4. A process for producing a hydrotreated gas oil according to
claim 1, wherein: in the first step, the feed oil is subjecting to
hydrotreating under such reaction conditions as a reaction
temperature of 170-320.degree. C., a hydrogen partial pressure of
2-10 MPa, a liquid hourly space velocity of 0.1-4 h.sup.-1 and a
hydrogen/oil ratio of 250-800 NL/L; and in the second step, the
first product oil is subjected to hydrotreating under such reaction
conditions as a reaction temperature of 200-280.degree. C., a
hydrogen partial pressure of 2-10 MPa, a liquid hourly space
velocity of 0.1-2 h.sup.-1 and a hydrogen/oil ratio of 250-800
NL/L.
5. A process for producing a hydrotreated gas oil according to
claim 1, wherein both the first hydrogenation catalyst and the
second hydrogenation catalyst are composed of an active metal
supported on a porous support, and the active metal is at least one
kind of metal selected from the group consisting of group VIII
metals.
6. A process for producing a hydrotreated gas oil according to
claim 5, wherein the active metal is at least one kind of metal
selected from the group consisting of Rh, Ir, Pd and Pt.
7. A process for producing a hydrotreated gas oil according to
claim 1, wherein the support in the first hydrogenation catalyst
contains at least one kind of metal oxide selected from the group
consisting of titania, zirconia, boria and silica, and alumina.
8. A process for producing a hydrotreated gas oil according to
claim 1, wherein the crystalline molecular sieve component contains
silica and alumina, and has at least one kind of crystal structure
selected from the group consisting of a faujasite type, a beta
type, a mordenite type and a pentacyl type.
9. A hydrotreated gas oil that is obtained by the process for
producing the hydrotreated gas oil as described in claim 1, and
that has a sulfur content of 1 ppm by mass or less and a total
aromatic content of 3% by volume or less.
10. A gas oil composition comprising a hydrotreated gas oil that is
obtained by the process for producing the hydrotreated gas oil as
described in claim 1, and that has a sulfur content of 1 ppm by
mass or less and a total aromatic content of 3% by volume.
Description
TECHNICAL FIELD
[0001] The present invention relates to a process for producing a
hydrotreated gas oil, a hydrotreated gas oil, and a gas oil
composition.
BACKGROUND ART
[0002] Diesel engines are expected to serve a function in the
reduction of carbon-dioxide emissions as global warming prevention
measures because of a high energy efficiency thereof. On the other
hand, demands for cleaner diesel engine exhaust gas has been
tightened increasingly, and it is one of major challenges to remove
such harmful substances as fine particle contents referred to as
"particulate matter" and NOx. Of these, in order to remove the
particulate matter, the loading of an exhaust gas clean up system
such as a particulate removing filter is going to be promoted
increasingly.
[0003] However, it is indicated that, when a gas oil containing a
lot of sulfur content is used as fuel, the deterioration of such
exhaust gas clean up systems become significant. Responding to
this, for transportation trucks having long travel distances, in
particular, elongating the life of exhaust gas clean up systems to
a maximum extent is strongly expected. Thus, further reduction of
sulfur content in gas oil is indispensable. In addition, as the
largest cause of particulate matter generation, aromatic contents
in gas oil are indicated, and it is said that removing the aromatic
contents in gas oil is effective as fundamental measures for
reducing the particulate matter.
[0004] Petroleum-based gas oil fraction usually contains sulfur of
1-3% by mass in an unrefined state, and is used as a gas oil stocks
after having been subjected to hydrodesulfurization. Other gas oil
stocks include hydrodesulfurized kerosine fraction, and cracked gas
oil obtained from a fluidized catalytic cracker or hydrocracker
unit, and gas oil products are obtained after mixing these gas oil
stocks. Among sulfur compounds existing in a gas oil fraction which
have been hydrodesulfurized with a hydrodesulfurization catalyst,
dibenzothiophene derivatives having plural methyl groups as a
substituent as represented by 4,6-dimethyldibenzothiophene have a
very poor reactivity. Therefore, even in the case of
hydrodesulfurization to a high depth, such compounds tend to remain
in the gas oil fraction.
[0005] Accordingly, in order to proceed with desulfurization of gas
oil fraction down to such a further low sulfur content as 1 ppm by
mass or lower while using conventional techniques, it is necessary
to employ a very high hydrogen partial pressure, or extremely long
contact time, that is, a very large reaction tower volume.
[0006] Further, unrefined petroleum-based gas oil fraction usually
contains aromatic contents of 20-40% by volume. In the
hydrogenation reaction of the aromatic components, there exists
such restriction of chemical equilibrium that, in general, the
equilibrium shifts to the generation of aromatic compounds on
higher temperature sides, and to the generation of cyclic saturated
hydrocarbons (naphthene) being hydrogenated products of aromatic
rings on lower temperature sides, respectively. Accordingly, in
order to accelerate the hydrogenation of aromatic compounds for the
purpose of reducing the aromatic content in gas oil fraction, a low
reaction temperature is advantageous from the viewpoint of the
chemical equilibrium. But, at relatively low reaction temperatures,
since the reaction rate of the aromatic hydrogenation reaction is
insufficient, reaction conditions other than reaction temperature
and a catalyst are required for compensating that.
[0007] Further, the hydrodesulfurization reaction is eventually a
reaction to cleave a carbon-sulfur bond, and the cleavage reaction
is accelerated at a higher temperature. Consequently, in
conventional techniques, when the reaction condition is set on a
lower temperature side in order to accelerate the hydrogenation of
aromatic compounds, the desulfurization activity is insufficient,
and, as the result, it is very difficult to satisfy both the ultra
low sulfur content and low aromatic content.
[0008] Incidentally, in diesel engines, gas oil is blown to air
having been compressed to be high temperatures to ignite and
combust. But, when combustion does not occur normally at the timing
of blowing the gas oil, knocking may occur. Therefore, gas oil must
have such property as an excellent ignitionability. The cetane
number is an index showing flammability, and gas oil having a
higher value of the cetane number is more excellent in the
ignitionability. Accordingly, the improvement of the cetane number
of gas oil is one of the important challenges for aiming to the
high efficiency of diesel engines. In general, it is said that
aromatic compounds and naphthene compounds have a low cetane number
and paraffin compounds (chain saturated hydrocarbon) have a high
cetane number. Therefore, in order to heighten the cetane number,
it is necessary to proceed with hydrogenation of aromatic compounds
and conversion of naphthene to paraffin.
[0009] However, the conversion of naphthene to paraffin is
accompanied, usually, with a cracking reaction, therefore
lightening of a product oil as compared with the feed oil is
inevitable, to lead to the substantial yield reduction of gas oil
fraction. As described above, expected are means for proceeding
effectively with hydrogenation reaction and conversion reaction to
paraffin while inhibiting undesirable cracking reaction.
[0010] Under such background, for a process for producing a diesel
gas oil with a small sulfur content and aromatic content, there is
proposed a production technique in which a desulfurization process
(first step) and an aromatic hydrogenation process (second step)
using zeolite or clay mineral as a catalyst are combined (see
Patent Document 1 and 2). However, even production processes as
described in these Patent Documents do not exert a sufficient
effect of decreasing both the sulfur content and aromatic content.
Specifically, even with such production processes as described in
these Patent Documents, it is difficult to achieve simultaneously
such a very high desulfurization and aromatics-removing levels as a
sulfur content of 1 ppm by mass or less and an aromatic content of
1% by volume or less. In such conventional production processes,
when the operation severity in the first step is raised, it becomes
difficult to continue economically the operation in the first step
for satisfactory period of time. Further, the rise of the reaction
temperature in the first step results in the increase in the
aromatics content in the product oil in the first step and hinders
removing of aromatics in the second step. Furthermore, there is the
above-described equilibrium restriction on aromatics in the second
step, therefore there are limitations on increasing the operation
severity such as the rise of the reaction temperature etc.
[0011] On the other hand, there is disclosed such a process as
treating gas oil fraction by a gas/liquid countercurrent flow type
process using a catalyst of Pt supported on USY (Ultra Stable Y
zeolite) as a technique of converting naphthene to paraffin in
Patent Document 3. However, in order to proceed with conversion of
naphthene to paraffin, a high reaction temperature is required, and
along with the increase in the severity of the reaction condition
as the result of the raised reaction temperature, the yield of the
generating gas oil fraction tends to decrease.
Patent Document 1: JP-A-7-155610
Patent Document 2: JP-A-8-283747
Patent Document 3: JP-T-2003-502478
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0012] The present invention was achieved with the view of the
above-described circumstances, and aims to provide a process for
producing a hydrotreated gas oil capable of producing such gas oil
excellent in both environmental properties and combustion
properties that has a sulfur content of 1 ppm by mass or less and a
total aromatic content of 3% by volume or less, and that further
has a high cetane number, with sufficient efficiency and
reliability without setting special operating conditions and
equipment investment. Further, the present invention also aims to
provide a hydrotreated gas oil that is obtained by the above
process for producing a hydrotreated gas oil, and a gas oil
composition containing the hydrotreated gas oil.
Means for Solving the Problems
[0013] The present invention provides a process for producing a
hydrotreated gas oil by carrying out the hydrotreating of a feed
oil, including a first step for obtaining a first product oil
having a total aromatic content of 3% by volume or less by using a
hydrotreated oil including a petroleum fraction of 95% by volume or
more having a boiling point range of 150-380.degree. C., a sulfur
content of 2-15 ppm by mass, a total aromatic content of 10-25% by
volume and a total naphthene content of 20-60% by volume as a feed
oil, and by carrying out hydrotreating of the feed oil in the
presence of a first hydrogenation catalyst; and a second step for
obtaining a second product oil that satisfies the following
conditions (1) and (2): (1) the content of petroleum fraction
having a boiling point range of lower than 150.degree. C. is 16% by
volume or less, and (2) the sum of the total aromatic content and
the total naphthene content is 80% or less relative to the sum of
the total aromatic content and the total naphthene content in the
feed oil, by carrying out hydrotreating of the first product oil in
the presence of a second hydrogenation catalyst containing a
crystalline molecular sieve component.
[0014] The process for producing a hydrotreated gas oil according
to the present invention uses the petroleum fraction satisfying
simultaneously the respective properties as a feed oil, carries
out, in a first step, hydrotreating of the feed oil so as to obtain
a first product oil having the above properties, and, further in a
second step, carries out hydrotreating of the first product oil so
that a second product oil to be obtained satisfies simultaneously
the above conditions with the use of the above specified catalyst.
As the result of these multiple actions, it becomes possible, for
the first time, to produce such a gas oil excellent in both
environmental properties and combustion properties that has a
sulfur content of 1 ppm by mass or less and a total aromatic
content of 3% by volume or less, and that has further a high cetane
number with a sufficient efficiency and reliability, without
setting special operation conditions and equipment investment, that
is, by using a conventional apparatus.
[0015] In the process of the present invention for producing a
hydrotreated gas oil, it is preferred that a polycyclic aromatic
content in a feed oil is 1-7% by volume and a polycyclic aromatic
content in a second product oil is 0.2% by volume or less. This can
give an effect of the present invention more effectively, and,
additionally, makes it possible to inhibit further an equipment
investment. The "polycyclic" herein means both condensed rings and
ring aggregates.
[0016] In the process of the present invention for producing a
hydrotreated gas oil, preferably a sum of the polycyclic aromatic
content and a polycyclic naphthene content in the second product
oil is 13% by volume or less. This improves further a cetane number
of the hydrotreated gas oil to be obtained, and can give further
satisfactory fuel properties.
[0017] In the process of the present invention for producing a
hydrotreated gas oil, it is preferred to carry out the
hydrotreating of the feed oil in the first step under such reaction
conditions as a reaction temperature of 170-320.degree. C., a
hydrogen partial pressure of 2-10 MPa, a liquid hourly space
velocity of 0.1-4 h.sup.-1 and a hydrogen/oil ratio of 250-800
NL/L; and to carry out the hydrotreating of the first product oil
in the second step under such reaction conditions as a reaction
temperature of 200-280.degree. C., a hydrogen partial pressure of
2-10 MPa, a liquid hourly space velocity of 0.1-2 h.sup.-1 and a
hydrogen/oil ratio of 250-800 NL/L. This makes it possible to
obtain more easily the first product oil or the hydrotreated gas
oil having intended properties. Furthermore, it becomes possible to
inhibit further the shortening of the catalyst life and too much
equipment investment.
[0018] In the process of the present invention for producing a
hydrotreated gas oil, it is preferred that both the first
hydrogenation catalyst and the second hydrogenation catalyst are
composed of an active metal supported on a porous support, and that
the metal is at least one kind of metal selected from the group
consisting of group VIII metals. Such catalyst can exert a
desulfurization activity, an aromatic hydrogenation activity, an
activity of converting naphthene to paraffin, and the like for
achieving the purpose and effect of the present invention with a
further improved balance. From the same viewpoint, in the process
of the present invention for producing a hydrotreated gas oil,
preferably the active metal is at least one kind of metal selected
from the group consisting of Rh, Ir, Pd and Pt.
[0019] In the process of the present invention for producing a
hydrotreated gas oil, preferably the support for the first
hydrogenation catalyst contains at least one kind of metal oxide
selected from the group consisting of titania, zirconia, boria and
silica, and alumina. By adopting the first hydrogenation catalyst
provided with such support, it is possible to synthesize the first
product oil for obtaining the hydrotreated gas oil having intended
properties with a higher selectivity and yield.
[0020] In the process of the present invention for producing a
hydrotreated gas oil, preferably the crystalline molecular sieve
component contains silica and alumina, and has at least one kind of
crystal structure selected from the group consisting of the
faujasite type, the beta type, the mordenite type and the pentacyl
type. The second hydrogenation catalyst that contains such
crystalline molecular sieve component can exert a desulfurization
activity, an aromatic hydrogenation activity, an activity for
converting naphthene to paraffin, and the like, in particular the
activity for converting naphthene to paraffin for achieving the
purpose and effect of the present invention with a higher
effectiveness and reliability.
[0021] The present invention provides a hydrotreated gas oil that
can be obtained by the above-described process for producing the
hydrotreated gas oil, and that has a sulfur content of 1 ppm by
mass or less and a total aromatic content of 3% by volume or
less.
[0022] The present invention provide a gas oil composition
containing the hydrotreated gas oil that can be obtained by the
above-described process for producing the hydrotreated gas oil, and
that has a sulfur content of 1 ppm by mass or less and a total
aromatic content of 3% by volume or less.
EFFECT OF THE INVENTION
[0023] According to the present invention, it is possible to
provide a process for producing such hydrotreated gas oil excellent
in both environmental properties and combustion properties that has
a sulfur content of 1 ppm by mass or less and a total aromatic
content of 3% by volume or less, and that, further, has a high
cetane number, with a sufficient efficiency and reliability without
setting special operation conditions and equipment investment.
BEST MODES FOR CARRYING OUT THE INVENTION
[0024] Hereinafter, preferred embodiments of the present invention
are described in detail.
[0025] The process of the present invention for producing a
hydrotreated gas oil is a process for producing a hydrotreated gas
oil by carrying out the hydrotreating of a feed oil, wherein the
process has a first step for obtaining a first product oil having a
total aromatic content of 3% by volume or less by using
hydrotreated oil including a petroleum fraction of 95% by volume or
more having a boiling point range of 150-380.degree. C., a sulfur
content of 2-15 ppm by mass, a total aromatic content of 10-25% by
volume and a total naphthene content of 20-60% by volume as a feed
oil, and by carrying out hydrotreating of the feed oil in the
presence of a first hydrogenation catalyst; and a second step for
obtaining a second product oil that satisfies the following
conditions (1) and (2): (1) the content of petroleum fraction
having a boiling point range of lower than 150.degree. C. is 16% by
volume or less, and (2) the sum of the total aromatic content and
the total naphthene content is 80% or less relative to the sum of
the total aromatic content and the total naphthene content in the
feed oil, by carrying out the hydrotreating of the first product
oil in the presence of a second hydrogenation catalyst containing a
crystalline molecular sieve component.
[0026] (Feed Oil)
[0027] A hydrotreated oil used as the feed oil in the present
invention contains a petroleum fraction of 95% by volume or more
having a boiling point range of 150-380.degree. C., a sulfur
content of 2-15 ppm by mass, a total aromatic content of 10-25% by
volume, and a total naphthene content of 20-60% by volume.
[0028] Here, the term "boiling point range" herein means one that
is measured according to the method as described in JIS-K-2254
"Petroleum products--Determination of distillation characteristics"
or ASTM-D86. The term "sulfur content" herein means the mass
content of sulfur on the basis of a total gas oil volume, which is
measured according to the method as described in JIS-K-2541 "Crude
oil and petroleum products-Determination of sulfur content" or
ASTM-D5453.
[0029] Further, the terms "total aromatic content" and "polycyclic
aromatic content," which is described later, herein mean the
content that is calculated from the volume percentage (% by volume)
of respective aromatic contents to be measured according to the
method as described in Journal of the Japan Petroleum Institute
JPI-5S-49-97 "Petroleum products-Determination of hydrocarbon
types-High performance liquid chromatography" published by The
Japan Petroleum Institute. The terms "total naphthene content" and
"olefin content," which is described later, herein mean the content
that is measured according to the method as described in
ASTM-D2786-91 "Standard Test Method for Hydrocarbon Types Analysis
of Gas-Oil Saturates Fraction by High Ionizing Voltage Mass
Spectrometry."
[0030] When a feed oil contains a petroleum fraction of 95% by
volume or less having a boiling point range of 150-380.degree. C.,
it is meant that it contains light fraction having a boiling point
of lower than 150.degree. C. or heavy fraction having a boiling
point of above 380.degree. C. in a greater volume. The increase in
light fraction may lead to the increase in a LPG production volume,
and the increase in the heavy fraction may lead to an insufficient
progress of the hydrogenation reaction or the conversion reaction
of polycyclic aromatics, to tend to result in, for example, the
occurrence of the necessity for providing new equipment. This is
the same for a case where a feed oil that has not been subjected to
hydrotreating processing is used.
[0031] A sulfur content in the feed oil for use in the present
invention is 2-15 ppm by mass, preferably 3-10 ppm by mass, more
preferably 4-9 ppm by mass. The sulfur content in the feed oil of
more than 15 ppm by mass tends to lower the activity of a
hydrogenation catalyst not to allow the desulfurization reaction
and aromatic hydrogenation reaction to proceed sufficiently. The
sulfur content in the feed oil of less than 2 ppm by mass tends to
lower the reaction temperature necessary for removing the sulfur
component not to allow the aromatic hydrogenation reaction and the
conversion reaction of naphthene to paraffin to proceed
sufficiently.
[0032] In the feed oil used for the present invention, usually,
there exist naphthene being a cyclic saturated hydrocarbon
component, paraffin being a noncyclic saturated hydrocarbon
component and olefin being an unsaturated hydrocarbon component, in
addition to an aromatic component. Among these, the total aromatic
content in the feed oil used for the present invention is 10-25% by
volume, preferably 11-21% by volume. The total aromatic content in
a feed oil of more than 25% by volume tends to require a long
contact time, that is, a too much reaction tower volume in order to
reduce the total aromatic content to 3% by volume or less in the
first step, thereby resulting in the necessity for new equipment
investment or too much equipment investment. On the other hand, the
total aromatic content in a feed oil of less than 10% by volume
tends to increase the operation cost and decrease the economic
advantage of the present invention, because the necessity for
setting more severe operation conditions necessary for aromatic
hydrogenation than operation conditions necessary for the
desulfurization is increased.
[0033] Further, regarding the composition of aromatics in the feed
oil used for the present invention, a polycyclic aromatic content
is preferably 1-7% by volume relative to the feed oil, more
preferably 1.5-5% by volume. The polycyclic aromatic content in a
feed oil of more than 7% by volume tends to require too much
equipment investment in order to achieve an intended polycyclic
aromatic content in a product oil; and less than 1% by volume tends
to make it difficult to obtain effectively the effect according to
the present invention.
[0034] The total naphthene content in the feed oil used for the
present invention is within a range of 20-60% by volume, more
preferably 25-45% by volume. In case where the total naphthene
content in a feed oil is less than 20% by volume, it is meant that
a lot of paraffin having a high cetane number are contained
originally, which results in the decrease in the improvement degree
of the cetane number by the conversion of naphthene to paraffin to
reduce the advantage of the present invention. On the other hand,
the total naphthene content in a feed oil of more than 60% by
volume tends to increase the total volume of aromatic component and
naphthene component in the feed oil. As described above, the
hydrogenation reaction of aromatic compounds is also an equilibrium
reaction with naphthene, therefore the increase in the total volume
of aromatic component and naphthene component may result in the
increase in the aromatic component in the product oil due to the
chemical equilibrium not to allow a sufficient effect on the
reduction of the aromatic component to be obtained.
[0035] The olefin content in the feed oil is preferably 1% by
volume or less. The olefin content of more than 1% by volume tends
to occlude the catalyst layer filled up with the first
hydrogenation catalyst in the first step due to such reaction as
polymerization in the reaction tower.
[0036] As the feed oil, a hydrotreated petroleum-based hydrocarbons
having the above-described properties are sufficient, and it may be
a mixture of petroleum fractions having been fractionized from
plural apparatuses. For example, it may be an oil that is obtained
by subjecting a straight-run oil having the prescribed boiling
point range that has been fractionized from an atmospheric
distillation apparatus to desulfurization processing in a
hydrodesulfurization apparatus. In this case, as a feed oil, a
petroleum fraction, which is obtained by mixing petroleum fraction
having a prescribed boiling point range that can be obtained from a
hydrocracking apparatus, a residual oil direct desulfurization
apparatus, a fluid catalytic cracking apparatus or like with the
above-described straight-run oil and then by subjecting the mixed
oil to hydrodesulfurization, may be used. Or, as a kind of a feed
oil, a petroleum fraction having a prescribed boiling point range,
which is obtained by hydrocracking a vacuum gas oil fraction
obtained from a vacuum distillation apparatus in a hydrocracking
apparatus, may be used. Further, as a feed oil, an oil, which is
obtained by subjecting separately each of kerosine fraction and gas
oil fraction from respective apparatuses to hydrotreating and then
mixing these so as to have a prescribed boiling point range, may be
used; or an oil, which is obtained by mixing product oils obtained
from respective hydrotreating apparatuses, may be used.
[0037] For hydrodesulfurization conditions for obtaining the feed
oil, conditions used for processing using a usual
hydrodesulfurization apparatus in petroleum refining are
sufficient. That is, preferably hydrodesulfurization processing is
carried out under such conditions as a reaction temperature of
250-380.degree. C., a hydrogen partial pressure of 2-8 MPa, a
liquid hourly space velocity (LHSV) of 0.3-10.0 h.sup.-1, and a
hydrogen/oil ratio of 100-500 NL/L. As a catalyst to be provided to
the hydrodesulfurization apparatus, such common
hydrodesulfurization catalyst can be used that is composed of an
active metal supported on a support. That is, as an active metal
species, usually, sulfide of group VIA metals and group VIII metals
(e.g., Co--Mo, Ni--Mo, Ni--Co--Mo, Ni--W) can be used. As a
support, porous inorganic oxide having alumina as a main component
can be used.
[0038] Hydrocracking conditions for obtaining the feed oil can be
the one used for processing using a common hydrocracking apparatus
in petroleum refining. That is, preferably the hydrocracking
treatment is carried out under such conditions as a reaction
temperature of 300-450.degree. C., a hydrogen partial pressure of
5-18 MPa, a liquid hourly space velocity (LHSV) of 0.1-8.0
h.sup.-1, a hydrogen/oil ratio of 300-2000 NL/L. As a catalyst to
be provided to the hydrocracking apparatus, a common hydrocracking
catalyst composed of an active metal supported on a support can be
used. That is, as the active metal species, usually sulfide of
group VIA metals and group VIII metals (e.g., Co--Mo, Ni--Mo,
Ni--Co--Mo, Ni--W) may be used. As a support, a material containing
such solid acid as inorganic complex oxide or zeolite may be
used.
[0039] Or, for a catalyst for obtaining the feed oil, the
aforementioned hydrodesulfurization catalyst and hydrocracking
catalyst may be used in combination. Incidentally, reaction
conditions and kinds of catalysts as described above that are
adopted in hydrotreating for obtaining the feed oil are not
particularly limited provided that properties of a feed oil to be
obtained satisfy the above conditions.
[0040] In these hydrodesulfurization processing and hydrocracking
processing, the constitution of respective apparatuses or an
apparatus groups composed by combining the two is not particularly
limited, but it is desirable to remove hydrogen sulfide as far as
possible from the product to be obtained by these hydrotreatings,
using a gas-liquid separation tower or prescribed hydrogen sulfide
removing equipment. For example, in common desulfurization
apparatuses for gas oil or kerosene, it is preferred to separate
hydrogen sulfide being a gas component from a fraction from a
reaction tower for hydrodesulfurization using a gas-liquid
separation tower. In case where the liquid fraction obtained by
removing the gas component in this way is used as a feed oil, a
very little amount of hydrogen sulfide is contained in the feed
oil, therefore it is more suitable as the feed oil for the present
invention. Even in case where hydrogen sulfide coexists in a feed
oil, in the production process of the present invention, it is
possible to achieve the purpose and advantage of the present
invention by setting appropriate hydrotreating conditions.
[0041] (First Step)
[0042] In the first step of the present invention, in the presence
of the first hydrogenation catalyst, the feed oil is subjected to
hydrotreating to give the first product oil having the total
aromatic content of 3% by volume or less.
[0043] The first hydrogenation catalyst for use in the first step
is preferably one composed of at least one kind of metal selected
from the group consisting of the group VIII metals as an active
metal supported on a porous support.
[0044] For the support for the first hydrogenation catalyst,
preferred is one containing at least one kind of metal oxide
selected from the group consisting of titania, zirconia, boria and
silica, and alumina. For respective components for constituting the
support, the above-described components can be combined, and, from
the viewpoint of the sulfur resistance of the catalyst,
silica-alumina, titania-alumina, boria-alumina, zirconia-alumina,
titania-zirconia-alumina, silica-boria-alumina,
silica-zirconia-alumina, silica-titania-alumina and
silica-titania-zirconia-alumina are preferred, silica-alumina,
boria-alumina, zirconia-alumina, titania-zirconia-alumina,
silica-boria-alumina, silica-zirconia-alumina and
silica-titania-alumina are more preferred, and silica-alumina and
silica-zirconia-alumina are further preferred.
[0045] The component ratio between alumina and other component in
the support is not particularly limited, but the alumina content is
preferably 90% by mass or less on the basis of the total support
mass, more preferably 60% by mass or less, further preferably 40%
by mass or less. The lower limit of the alumina content is not
particularly limited, but is preferably 20% by mass or more on the
basis of the total support mass. More than 90% by mass of alumina
tends to make the sulfur resistance of the catalyst insufficient,
and, less than 20% by mass of alumina tends to lower the
formability of the catalyst to make the industrial production
thereof difficult.
[0046] The preparation processes of the support is not particularly
limited, and the support is prepared, for example, as given bellow.
Firstly, in order to obtain the support, there is prepared such an
"alumina precursor" as an alumina gel-containing liquid, boehmite
powder, an alumina suspension or kneaded product that is obtained
by conventional methods. Next, in order to introduce a metal oxide
other than the alumina, an aqueous or organic solvent solution of
an acetate, chloride, nitrate, sulfate, naphthenate or various
coordinate compounds of the metal is compounded to the alumina
precursor by such a method as addition or coprecipitation. Among
these, the use of a nitrate, acetate or chloride is preferred, and
the use of a nitrate or acetate is further preferred. According to
need, the compounded product is kneaded, dried, molded or calcined
to give a support. The metal oxide for modifying a support may be
introduced by, for example, impregnating an aqueous or organic
solvent solution of an acetate, chloride, nitrate, sulfate,
naphthate or various coordinate compounds of the metal after
calcining the support.
[0047] Or, the support may be prepared by preparing once such a
complex oxide or complex hydroxide as silica-alumina,
silica-zirconia, alumina-titania, silica-titania, or alumina-boria,
and then adding the above-described alumina gel being a precursor
of the metal oxide, a gel or suitable solution of another hydroxide
to the complex oxide or the like followed by the kneading or the
like. In case where the molding is carried out, such a shape can be
molded by extrusion molding as an approximate cylinder having an
approximately circular cross-section, or a tetralobal-shaped rod
having a tetralobal-shaped cross section.
[0048] The reaction conditions of the first step in the present
invention are preferably a reaction temperature of 170-320.degree.
C., a hydrogen partial pressure of 2-10 MPa, a liquid hourly space
velocity (LHSV) of 0.1-4 h.sup.-1 and a hydrogen/oil ratio of
250-800 NL/L, more preferably a reaction temperature of
180-305.degree. C., a hydrogen partial pressure of 4-8 MPa, a
liquid hourly space velocity (LHSV) of 1.0-3.0 h.sup.-1 and a
hydrogen/oil ratio of 300-700 NL/L.
[0049] A lower reaction temperature is advantageous for
hydrogenation reaction, but a reaction temperature of lower than
170.degree. C. tends not to allow the desulfurization reaction to
progress easily. A reaction temperature of higher than 320.degree.
C. tends to shorten the catalyst life and increase the aromatic
content due to the advantage for the generation of aromatics in the
chemical equilibrium. For both the hydrogen partial pressure and
hydrogen/oil ratio, generally a higher value tends to accelerate
both the desulfurization reaction and hydrogenation reaction. The
hydrogen partial pressure and hydrogen/oil ratio of less than the
above-described lower limit tend not to allow the desulfurization
reaction and aromatics hydrogenation reaction to progress easily.
On the other hand, the hydrogen partial pressure and hydrogen/oil
ratio of more than the above-described upper limit tend to require
too much equipment investment. A lower liquid hourly space velocity
(LHSV) tends to be advantageous for the desulfurization reaction
and hydrogenation reaction. However, the liquid hourly space
velocity of less than 0.1 h.sup.-1 tends to require a very great
reaction tower volume and require too much equipment investment. On
the other hand, the liquid hourly space velocity of more than 4
h.sup.-1 tends not to allow the desulfurization and aromatics
hydrogenation reaction, and, in addition, the naphthene conversion
reaction to progress sufficiently.
[0050] In the first step, the reaction conditions are so regulated
that the total aromatic content in the first product oil to be
obtained is 3% by volume or less, preferably 1% by volume or less.
The total aromatic content in the first product oil of more than 3%
by volume tends not to allow the conversion reaction of naphthene
to paraffin in the second step to progress easily, thereby making
it difficult to give a gas oil having excellent environmental
properties and a high cetane number.
[0051] The olefin content in the first product oil is preferably 1%
by volume or less. The olefin content of more than 1% by volume
tends to occlude the catalyst layer filled with the second
hydrogenation catalyst in the second step due to such reaction as
polymerization in the reaction tower.
[0052] (Second Step)
[0053] In the second step of the present invention, the first
product oil is subjected to hydrotreating in the presence of the
second hydrogenation catalyst containing a crystalline molecular
sieve component to give the second product oil that satisfy the
above-described conditions (1) and (2) simultaneously. Here, the
"crystalline molecular sieve component" herein means a solid
crystal having a molecular sieve function.
[0054] The second hydrogenation catalyst for use in the second step
is not particularly limited only when it contains a crystalline
molecular sieve component. As the crystalline molecular sieve
component, for example, zeolite can be mentioned. As components
constituting the crystal skeleton of zeolite, in addition to
silica, alumina, titania, boria, gallium etc. can be mentioned.
Among these, zeolite including silica and alumina, that is,
aluminosilicate is preferred. As the crystal structure of zeolite,
for example, a faujasite type, a beta type, a mordenite type, and a
pentacyl type can be mentioned.
[0055] For the crystalline molecular sieve component in the present
invention, in order to obtain stably an intended crystal structure,
one in which the alumina content is regulated in accordance with
the stoichiometric mixture ratio of feed materials, or one having
been subjected to a prescribed hydrothermal processing and/or acid
processing can be used. From the viewpoint of proceeding more
efficiently with the conversion of naphthene to paraffin, the
crystalline molecular sieve component is preferably faujasite
zeolite or beta zeolite, more preferably faujasite zeolite.
[0056] Among faujasite zeolite, the use of Y type zeolite as the
crystalline molecular sieve component for the present invention is
preferred, and the use of ultrastable Y type (hereinafter, referred
to as "USY") zeolite having been ultrastabilized by a hydrothermal
processing and/or acid processing is more preferred. In the USY
zeolite, in addition to such fine pore structure of 20 .ANG. or
less referred to as micropores that is owned by Y type zeolite
originally, new fine pores are formed within a range of 20-100
.ANG.. It is thought that this gives more effective progress of
conversion of naphthene to paraffin. For the hydrothermal
processing conditions for obtaining USY zeolite, publicly known
conditions can be adopted. In USY zeolite, the molar ration of
silica/alumina (molar ratio of silica relative to alumina;
hereinafter, referred to as a "silica/alumina ratio") is preferably
10-120, more preferably 15-70, further preferably 20-50. A
silica/alumina ratio of higher than 120 tends not to give good acid
properties (such as acid point, acid strength) of zeolite for the
conversion of naphthene to paraffin, thereby lowering the
conversion activity from naphthene. A silica/alumina ratio of lower
than 10 tends to result in strong acid properties and accelerate a
caulk generation reaction, thereby leading to rapid activity
lowering of the second hydrogenation catalyst.
[0057] As the crystalline molecular sieve component according to
the present invention, one that is molded by a tablet molding
process directly after the synthesis may be used, but the use of
one that is molded after being mixed with a binder component is
preferred. As the binder component, in addition to alumina as a
simple substance and silica as a simple substance, it may be any of
silica-alumina, titania-alumina, boria-alumina, zirconia-alumina,
titania-zirconia-alumina, silica-boria-alumina,
silica-zirconia-alumina, silica-titania-alumina or
silica-titania-zirconia-alumina, which is a support for the
hydrogenation catalyst for use in the first step.
[0058] The zeolite content in the second hydrogenation catalyst is
preferably 10% by mass or more, more preferably 30% by mass or
more, further preferably 50% by mass or more. The zeolite content
in the second hydrogenation catalyst of 10% by mass or less tends
to lower the naphthene conversion activity. The shape of a molded
catalyst is not particularly limited, and any of such shape as a
cylinder, macaroni type, or sphere can be selected.
[0059] As the second hydrogenation catalyst for use in the second
step, to the latter stage of the portion composed of the
hydrogenation catalyst containing the crystalline molecular sieve
component, a part composed of a hydrogenation catalyst not
containing the crystalline molecular sieve component may be
provided. For the part of the latter stage, the same catalyst as
that in the first step can be used. As a result of this, it is
possible to stabilize, by hydrogenation reaction or the like, such
compound as a radical product or a compound susceptive to oxidation
reaction due to an unstable structure thereof among products
obtained by the naphthene conversion reaction, to prevent sludge
(solid material) generation and coloring due to
oxidation/polycondensation of the obtained product.
[0060] The percentage of the second hydrogenation catalyst relative
to the total volume of the first hydrogenation catalyst and the
second hydrogenation catalyst is not particularly limited, but the
percentage of the hydrogenation catalyst containing the crystalline
molecular sieve component relative to the total volume of the first
hydrogenation catalyst and the second hydrogenation catalyst (a
hydrogenation catalyst that contains a crystalline molecular sieve
component and a hydrogenation catalyst that does not contain a
crystalline molecular sieve component) is preferably 30% by volume
or more, more preferably 40% by volume or more. The ratio of the
hydrogenation catalyst containing the crystalline molecular sieve
component of less than 30% by volume tends to lower the naphthene
conversion activity.
[0061] The second step in the present invention has such reaction
conditions as preferably a reaction temperature of 200-280.degree.
C., a hydrogen partial pressure of 2-10 MPa, a liquid hourly space
velocity (LHSV) of 0.1-2 h.sup.-1 and a hydrogen/oil ratio of
250-800 NL/L, more preferably a reaction temperature of
220-270.degree. C., a hydrogen partial pressure of 4-8 MPa, a
liquid hourly space velocity (LHSV) of 0.5-1.5 h.sup.-1 and a
hydrogen/oil ratio of 300-700 NL/L.
[0062] A lower reaction temperature is advantageous for the
hydrogenation reaction, but a reaction temperature of lower than
200.degree. C. tends to lower the naphthene conversion reaction
activity. On the other hand, a higher reaction temperature is
advantageous for the naphthene conversion reaction, but a reaction
temperature of higher than 280.degree. C. tends to increase the
yield of products having a boiling point of lower than 150.degree.
C. to reduce the yield of the intended gas oil fraction. A higher
hydrogen partial pressure and hydrogen/oil ratio, generally, tend
to accelerate both the hydrogenation reaction and naphthene
conversion reaction. A hydrogen partial pressure and hydrogen/oil
ratio lower than the above-described lower limit tend not to allow
the hydrogenation reaction and naphthene conversion reaction to
progress easily. On the other hand, a hydrogen partial pressure and
hydrogen/oil ratio of more than the above-described upper limit
tend to require too much equipment investment. A lower liquid
hourly space velocity (LHSV) tends to be advantageous for the
hydrogenation reaction and naphthene conversion reaction. However,
a liquid hourly space velocity of smaller than 0.5 h.sup.-1 tends
to require a very large reaction tower volume and too much
equipment investment. On the other hand, a liquid hourly space
velocity of greater than 1.5 h.sup.-1 tends not to allow the
hydrogenation reaction and naphthene conversion reaction to
progress easily.
[0063] In the second step, the reaction conditions are so regulated
that the second product oil to be obtained has light petroleum
fraction having a boiling point range of 150.degree. C. or lower in
16% by volume or less. More preferably the reaction conditions are
so regulated that the above-described light petroleum fraction
content is 12% by volume or less, further preferably 8% by volume
or less. A light petroleum fraction more than 16% by volume reduces
the yield of gas oil obtained from the second product oil, thereby
making it difficult to produce the gas oil with sufficient
efficiency.
[0064] Further, the reaction conditions are so regulated that the
second product oil to be obtained has the sum of the total aromatic
content and the total naphthene content of 80% or less, preferably
70% relative to the sum of the total aromatic content and the total
naphthene content in the above-described feed oil. The sum of the
total aromatic content and the total naphthene content of more than
80% relative to the sum of the total aromatic content and the total
naphthene content in the feed oil tends not to allow a gas oil that
has excellent environmental properties and a high cetane number to
be obtained easily.
[0065] According to the present invention, the total aromatic
content in the second product oil becomes 3% by volume or less, and
the content of 1% by volume or less is more preferred. The total
aromatic content of more than 3% by volume reduces the effect of
lowering the particulate matter in diesel exhaust gas, therefore it
becomes difficult to obtain gas oil having excellent environmental
properties and a high cetane number, and the purpose and advantage
of the present invention are not achieved.
[0066] The polycyclic aromatic content in the second product oil is
preferably 0.2% by volume or less, more preferably 0.1% by volume
or less. The polycyclic aromatic content of more than 0.2% by
volume tends to increase the particulate matter in diesel exhaust
gas.
[0067] Further, the sum of the polycyclic aromatic content and the
polycyclic naphthene content in the second product oil is
preferably 13% by volume or less, more preferably 10% by volume or
less. The sum of the polycyclic aromatic content and the polycyclic
naphthene content of more than 13% by volume tends to result in the
difficulty in improving the cetane number and not to allow good
fuel properties to be obtained easily.
[0068] The active metal to be supported in the first hydrogenation
catalyst and the second hydrogenation catalyst according to the
present invention is preferably at least one metal selected from
the group consisting of Fe, Co, Ni, Ru, Rh, Pd, Os, Ir and Pt
belonging to the group VIII metals, more preferably at least one
metal selected from the group consisting of Rh, Ir, Pd and Pt, from
the viewpoint of such desulfurization activity, aromatic
hydrogenation activity, activity of converting naphthene to
paraffin that enable the purpose and advantage of the present
invention to be achieved.
[0069] Further, for the active metal of the hydrogenation catalyst,
plural metals may be selected and combined. Such combination as
Pt--Pd, Pt--Rh, Pt--Ir, Rh--Ir, Rh--Pd, Ir--Pd, Pt--Pd--Ir,
Pt--Rh--Ir, Pt--Rh--Pd or Rh--Ir--Pd can be adopted. Among these,
more preferred is Pt--Pd, Pt--Rh, Pt--Ir, Pt--Pd--Ir, Pt--Rh--Ir or
Pt--Rh--Pd, further preferred is Pt--Pd, Pt--Ir or Pt--Pd--Ir, and
especially preferred is Pt--Pd, from the viewpoint of such
desulfurization activity, aromatic hydrogenation activity, activity
of converting naphthene to paraffin that enable the purpose and
advantage of the present invention to be achieved.
[0070] Next, the active metals in the first hydrogenation catalyst
and the second hydrogenation catalyst according to the present
invention are described. The supported volume of these active
metals is not particularly limited, but is preferably 0.05-10% by
mass in the sum of the metal volumes relative to the entire
catalyst volume, more preferably 0.1-5% by mass, further preferably
0.15-3% by mass, from the viewpoint of such desulfurization
activity, aromatic hydrogenation activity, activity of converting
naphthene to paraffin that enable the purpose and advantage of the
present invention to be achieved.
[0071] For the supporting process of the active metal onto the
support, such supporting processes used for common hydrogenation
catalysts as an impregnation process and an ion exchange process
may be adopted, while using the aqueous solution, the water-soluble
organic solvent solution or the water-insoluble organic solvent
solution of an inorganic salt or complex compound of the active
metal, that is, carbonate, nitrate, sulfate, organic acid salt or
oxide thereof. In case where plural metals are to be supported,
they may be supported simultaneously using a mixed solution, or may
be supported sequentially using solutions of a single component.
The support processing of the active metal onto a support may be
carried out after the end of the entire preparation process of the
support, or may be carried out, after supporting the active metal
onto a suitable oxide, complex oxide or crystalline molecular sieve
in the intermediate process of the support preparation, by gel
blending, heating and compressing, kneading processes and the like,
but it is preferred to carry out the processing after the end of
the entire preparation process of the support. Then, by calcining
the product composed of the active metal that is impregnated and
supported on the support under intended conditions, the
hydrogenation catalyst according to the present invention can be
obtained.
[0072] The first hydrogenation catalyst and the second
hydrogenation catalyst according to the present invention are used
preferably after being subjected to a pre-reduction processing. The
pre-reduction processing is carried out, usually, by pouring a gas
containing hydrogen in a reaction tube (reaction tower) filled with
a hydrogenation catalyst, and giving heat at 200.degree. C. or
higher to the hydrogenation catalyst according to a prescribed
procedure. As a result, the supported active metal of the catalyst
is reduced, to allow the catalyst to exert more effectively the
hydrogenation activity and the naphthene conversion activity.
[0073] An apparatus for carrying out hydrotreating of the feed oil
in this way may have any constitution, and a reaction tower in
which the catalyst is filled may be single, or plural towers may be
combined. Further, for the purpose of reducing the hydrogen sulfide
concentration in the reaction tower, gas-liquid separation
equipment or other equipment for removing hydrogen sulfide may be
provided, or equipment for injecting additional hydrogen may be
provided to the former step of the reaction tower, or, in case
where plural reaction towers are provided serially, between the
plural reaction towers.
[0074] The reaction form of a hydrotreating apparatus for use in
the present invention may be a fixed bed system. That is, for
hydrogen, either countercurrent flow form or co-current flow form
relative to the feed oil may be usable, or, a combined form of a
countercurrent flow and co-current flow with plural reaction towers
may be usable. General forms are of down flow, and there is a
gas-liquid twin co-current flow form. The reaction tower may be
constituted of plural catalyst beds, and, between respective
catalyst beds, hydrogen gas may be injected for the purpose of
removing reaction heat or raising the hydrogen partial pressure
(quench hydrogen).
[0075] The hydrotreated gas oil as described above that is obtained
by the favorable embodiment of the present invention is one having
a sulfur content of 1 ppm by mass or less, and the total aromatic
content of 3% by volume or less. Further, the present inventors
confirmed that the cetane number of the hydrotreated gas oil can be
improved significantly relative to the feed oil, and that, for
example, the value increases by at least three points relative to
the feed oil before the refining. This is considered due to a fact
that the feed oil has been converted to such constitution as
containing a lot of hydrocarbon having a higher cetane number by
the conversion of naphthene to paraffin, as well as the
hydrogenation of aromatic contents. The cetane number is an index
representing combustion quality, and a larger value thereof gives
more excellent ignition properties and expectation for improving
the combustion efficiency in diesel engines.
[0076] Here, the "cetane number" herein is a cetane number that is
measured according to the method as described in JIS-K2280
"Determination of octane number, cetane number and calculation of
cetane index." Incidentally, increase and decrease in the cetane
number of petroleum fraction can be checked simply from the cetane
index that is calculated according to the calculation method of the
cetane index as described in JIS-K2280 "Determination of octane
number, cetane number and calculation of cetane index."
[0077] The gas oil that is obtained according to the favorable
embodiment of the present invention may be used singly as a diesel
gas oil, or it may be mixed with another base stock to produce a
gas oil composition to be used as a diesel gas oil. Another base
stock includes synthetic gas oil or synthetic kerosene that can be
obtained, while using so-called synthesis gas constituted of
hydrogen and carbon monoxide as a feed stock, via Fischer-Tropsch
reaction or the like. These synthetic kerosene and synthetic gas
oil scarcely contain aromatic component and contain saturated
hydrocarbon as a main component, and, usually, have a high cetane
number. For the production process of the synthetic gas, publicly
known processes can be used, and there is no particular
limitation.
[0078] The compounding ratio of synthetic gas oil in a gas oil
composition (diesel gas oil) is preferably 30% by volume or less,
more preferably 20% by volume or less, further preferably 10% by
volume or less. The compounding ratio of synthetic kerosene in a
gas oil composition is preferably 60% by volume or less, more
preferably 50% by volume or less, further preferably 40% by volume
or less. Thus, the favorable embodiments of the present invention
have been described, but the present invention is not limited to
these embodiments.
EXAMPLE
[0079] Hereinafter, the present invention is described in more
detail based on Example, but the present invention is not limited
to the Example.
[0080] (Preparation of Hydrogenation Catalyst)
[0081] After allowing an aqueous solution of sodium silicate
(concentration: 29% by mass, 2350 g) to gel under the condition of
pH 4, it was aged under the conditions of 60.degree. C., pH 7 for
two hours to give slurry. Next, the obtained slurry was added with
an aqueous solution containing zirconium sulfate (tetrahydrate, 350
g). Then, the slurry after the addition was regulated to pH 7 to
generate silica-zirconia complex hydroxide. The complex hydroxide
was aged at 60.degree. C. for 30 minutes, which was then added with
an aqueous solution containing aluminum sulfate (quatrodeca
hydrate, 420 g) to be regulated to pH 7 to generate slurry of
silica-zirconia-alumina complex hydroxide. The slurry of
silica-zirconia-alumina complex hydroxide was filtrated and washed,
and then moisture thereof was regulated by heating concentration.
Then, the complex hydroxide after the moisture regulation was
extrusion molded, further dried in the air at 110.degree. C. for
one hour, and calcined at 550.degree. C. for three hours to give a
catalyst support (porous support). The obtained support had such
ratio of respective constituents as 20% by mass of alumina, 57% by
mass of silica, and 23% by mass of zirconia as oxide.
[0082] To the support, active metals were impregnated by a common
process using a mixed aqueous solution of tetraammine platinum (II)
chloride and tetraammine palladium (II) chloride, whose
concentration had been regulated so as to be a volume appropriate
to the water absorption percentage of the support. It was then
dried in the air at 110.degree. C. for one hour, calcined at
300.degree. C. for two hours to give the first hydrogenation
catalyst. The supported volume of platinum and palladium in the
first hydrogenation catalyst was 0.3% by mass and 0.5% by mass,
respectively, relative to the entire catalyst.
[0083] Next, a Y type zeolite having a silica/alumina ratio of 5
was stabilized by a publicly known ultra-stabilization processing
method, which was then subjected to acid processing with a 1 N
aqueous solution of nitric acid to give USY zeolite of a proton
type having a unit lattice length of 24.33 .ANG. and a
silica/alumina ratio of 30. The obtained USY zeolite (550 g) was
added to an aqueous solution of ammonium nitrate (concentration: 2
N, 3 L) and stirred at room temperature to be converted to the
ammonium type.
[0084] Next, the obtained ammonium type zeolite was added to a
mixed solution of tetraammine platinum (II) chloride and
tetraammine palladium (II) chloride whose concentration had been
regulated so as to be a volume appropriate to the water absorption
percentage of the support, which was stirred at 70.degree. C. to
allow the active metals to be supported by an ion exchange method.
The zeolite supporting the active metals was filtrated and
isolated, dried in the air at 110.degree. C. for one hour, and
calcined at 300.degree. C. for two hours. Then, the obtained
zeolite was kneaded with a commercially available alumina gel (by
Condea) and molded to give the second hydrogenation catalyst. The
supported volume of platinum and palladium in the second
hydrogenation catalyst was 0.3% by mass and 0.5% by mass,
respectively, relative to the entire catalyst. The ratio of the
zeolite and alumina was 70:30 by mass ratio.
Example 1
[0085] A first reaction tube (inner diameter: 20 mm) filled with
the first hydrogenation catalyst (20 mL) and a second reaction tube
(inner diameter: 20 mm) filled with the second hydrogenation
catalyst (20 mL) were attached in tandem to a fixed bed flow type
reactor (down flow), then a pre-reduction processing was carried
out under the conditions of hydrogen partial pressure of 5 MPa at
300.degree. C. for 5 hours as a preprocessing. Then, a feed oil,
whose properties are listed in Table 2, was conducted into the
reactor under the conditions as listed in Table 1 to carry out a
hydrotreating test. The feed oil was an oil obtained by subjecting
the fraction corresponding to gas oil that was obtained by
atmospheric distillation of feed oil originated in Middle East to
hydrotreating processing.
[0086] In Table 2, "IBP" means the initial boiling point as defined
in JIS-K-2254, and "EP" means the end point as defined in
JIS-K-2254. The "(total aromatic content+total naphthene content)
yield" means the percentage of the sum of the total aromatic
content and the total naphthene content in the second product oil
relative to the sum of the total aromatic content and the naphthene
content in the feed oil. The "gas oil yield" means the yield of the
fraction having a boiling point range of 150-380.degree. C. The
"light fraction yield" means the yield of fractions that are
lighter than the gas oil, that is, the yield of fractions having a
boiling point range of less than 150.degree. C.
TABLE-US-00001 TABLE 1 First Reaction temperature [.degree. C.] 220
step Hydrgen partial pressure [MPa] 5.0 Liquid hourly space
velocity [h.sup.-1] 2.0 Hydrogen/Oil ratio [NL/L] 400 Second
Reaction temperature [.degree. C.] 240 step Hydrgen partial
pressure [MPa] 5.0 Liquid hourly space velocity [h.sup.-1] 2.0
Hydrogen/Oil ratio [NL/L] 400
TABLE-US-00002 TABLE 2 Raw Second formed oil oil Example Comp. Ex.
1 Comp. Ex. 2 Density (15.degree. C.) [g/cm.sup.3] 0.8300 0.8090
0.7990 0.8065 IBP/EP [.degree. C.] 187/370 165/365 172/360 175/367
Sulfur content [ppm by mass] 8.0 0.5 1.5 0.3 Olefin content [% by
volume] 0.0 0.3 0.2 0.1 Total aromatic content [% by volume] 19.9
0.6 4.1 0.5 Total naphthene content [% by volume] 39.7 39.4 48.1
55.1 (Total aromatic content + total naphthene 59.6 40.0 52.2 55.6
content) [% by volume] (Total aromatic content + total naphthen 13
65.1 85.4 91.0 content) yield [%] Polycyclic aromatic content [% by
volume] 2.5 0.1 0.4 0.1 Polycyclic naphthene content [% by volume]
17.1 11.8 17.5 18.9 (Polycyclic aromatic content + polycyclic 19.6
11.9 17.9 19.0 naphthene content) [% by volume] Gas oil yield [% by
volume] -- 97.0 97.5 97.5 Light fraction yield [% by volume] -- 3.0
2.5 2.5 Cetane number 60.0 68.7 61.2 61.5
[0087] In the product oil (first product oil) distilled from the
first reaction tube filled with the first hydrogenation catalyst,
the total aromatic content was 0.8% by volume, the olefin content
was 0.1% by volume, and the sulfur content was 0.6 ppm by mass, on
the 10th day from the start of the hydrotreating test. Properties
of the second product oil on the 10th day from the start of the
hydrotreating test are listed in Table 2.
Comparative Example 1
[0088] A hydrotreating test was practiced in the same way as in
Example 1 except for changing the filling volume of the first
hydrogenation catalyst into the first reaction tube from 20 mL to 8
mL, and the liquid hourly space velocity in the first step from 2.0
h.sup.-1 to 5.0 h.sup.-1. In the product oil (first product oil)
distilled from the first reaction tube filled with the first
hydrogenation catalyst, the total aromatic content was 6.8% by
volume, the olefin content was 0.2% by volume, and the sulfur
content was 2.6 ppm by mass. Properties of the second product oil
on the 10th day from the start of the hydrotreating test are listed
in Table 2.
Comparative Example 2
[0089] A hydrotreating test was practiced in the same way as in
Example 1 except for changing the catalyst filled in the second
reaction tube (inner diameter: 20 mm) from the second hydrogenation
catalyst (20 mL) to the first hydrogenation catalyst (20 mL). In
the product oil (first product oil) distilled from the first
reaction tube filled with the first hydrogenation catalyst, the
total aromatic content was 0.8% by volume, the olefin content was
0.1% by volume, and the sulfur content was 0.6 ppm by mass.
Properties of the second product oil on the 10th day from the start
of the hydrotreating test are listed in Table 2.
INDUSTRIAL APPLICABILITY
[0090] According to the present invention, it is possible to
provide the process for producing a hydrotreated gas oil capable of
producing such gas oil excellent in both environmental properties
and combustion properties as having a sulfur content of 1 ppm by
mass or less and the total aromatic content of 3% by volume or
less, and further a high cetane number, with sufficient efficiency
and reliability without providing for special operation conditions
and equipment investment.
* * * * *