U.S. patent application number 10/781849 was filed with the patent office on 2004-11-18 for process of hydrocracking in two stages using an amorphous catalyst based on platinum and palladium.
Invention is credited to Benazzi, Eric, Bourges, Patrick, Euzen, Patrick.
Application Number | 20040226860 10/781849 |
Document ID | / |
Family ID | 32799519 |
Filed Date | 2004-11-18 |
United States Patent
Application |
20040226860 |
Kind Code |
A1 |
Bourges, Patrick ; et
al. |
November 18, 2004 |
Process of hydrocracking in two stages using an amorphous catalyst
based on platinum and palladium
Abstract
Hydrocracking process for the conversion of a hydrocarbon
feedstock that comprises a hydrorefining stage, in which the
feedstock is brought into contact with the hydrogen in the presence
of a hydrorefining catalyst at a temperature T1, a separation stage
in which at least a portion of the converted products that are
formed during the hydrorefining stage and a fraction that comprises
the unconverted products are separated, and a hydrocracking stage
in which the fraction that comprises the unconverted products is at
least in part brought into contact with hydrogen in the presence of
an amorphous hydrocracking catalyst that comprises a substrate,
palladium and platinum, at a temperature T2 that is less than T1,
whereby the difference between T1 and T2 is between 5 and
50.degree. C., preferably between 10 and 40.degree. C., and more
preferably between 15 and 30.degree. C.
Inventors: |
Bourges, Patrick; (Nanterre,
FR) ; Benazzi, Eric; (Chatou, FR) ; Euzen,
Patrick; (Paris, FR) |
Correspondence
Address: |
MILLEN, WHITE, ZELANO & BRANIGAN, P.C.
2200 CLARENDON BLVD.
SUITE 1400
ARLINGTON
VA
22201
US
|
Family ID: |
32799519 |
Appl. No.: |
10/781849 |
Filed: |
February 20, 2004 |
Current U.S.
Class: |
208/89 ;
208/111.35 |
Current CPC
Class: |
B01J 35/1042 20130101;
C10G 65/12 20130101; B01J 27/1856 20130101; B01J 21/12 20130101;
B01J 21/08 20130101; B01J 35/1019 20130101; C10G 47/14 20130101;
B01J 35/1038 20130101; B01J 35/10 20130101; C10G 55/06 20130101;
B01J 35/1061 20130101; B01J 23/44 20130101; C10G 45/12 20130101;
C10G 45/08 20130101; C10G 45/54 20130101; C10G 45/50 20130101 |
Class at
Publication: |
208/089 ;
208/111.35 |
International
Class: |
C10G 047/00; C10G
065/12 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 21, 2003 |
FR |
03/02.200 |
Claims
1. Hydrocracking process for the production of middle distillates
by conversion of a hydrocarbon feedstock that has a nitrogen
content of more than 500 ppm by weight, characterized in that it
comprises: a hydrorefining stage in which the feedstock is brought
into contact with the hydrogen in the presence of a hydrorefining
catalyst, at a temperature T1, and an effluent that comprises
converted products and unconverted products is recovered,
optionally a separation stage in which at least a portion of the
converted products formed during the hydrorefining stage and a
fraction that comprises the unconverted products are separated, and
a hydrocracking stage, in which the unconverted products are, at
least in part, brought into contact with the hydrogen, in the
presence of an amorphous hydrocracking catalyst that comprises a
substrate, palladium and platinum, at a temperature T2 that is less
than T1, whereby the difference between T1 and T2 is between 5 and
50.degree. C.
2. Process according to the claim, wherein the difference between
T1 and T2 is between 15 and 30.degree. C.
3. Process according to any of claims 1 and 2, wherein the
hydrorefining catalyst also comprises at least one dopant that is
deposited on said catalyst and selected from the group that is
formed by phosphorus, boron and silicon.
4. Process according to any of claims 1 to 3, wherein the
hydrorefining stage is carried out at a temperature T1 that ranges
from 330 to 420.degree. C.
5. Process according to any of claims 1 to 4, wherein the fraction
that is subjected to a hydrocracking stage essentially consists of
products that have a boiling point of more than 340.degree. C.
6. Process according to any of claims 1 to 5, wherein the organic
nitrogen content of the portion of the fraction that comprises
unconverted products that is subjected to the hydrocracking stage
is less than 10 ppm by weight, and the organic sulfur content of
the portion of the fraction that comprises the unconverted products
that is subjected to the hydrocracking stage is less than 100 ppm
by weight.
7. Process according to any of claims 1 to 6, wherein the H2S
content of the portion of the fraction that comprises the
unconverted products that is subjected to the hydrocracking stage
is less than 100 ppm by weight, and the NH3 content of the portion
of the fraction that comprises the unconverted products that is
subjected to the hydrocracking stage is less than 100 ppm by
weight.
8. Process according to any of claims 1 to 7, wherein the substrate
of the hydrocracking catalyst is an amorphous silica-alumina.
9. Process according to claim 8, wherein the substrate of the
hydrocracking catalyst comprises: an amount that is more than 10%
by weight and less than or equal to 80% by weight of silica
(SiO.sub.2), a mean pore diameter, measured by mercury porosimetry,
encompassed between 20 and 140 .ANG., a total pore volume, measured
by mercury porosimetry, encompassed between 0.1 ml/g and 0.6 ml/g,
a total pore volume, measured by nitrogen porosimetry, encompassed
between 0.1 ml/g and 0.6 ml/g, a BET specific surface area
encompassed between 150 and 500 m.sup.2/g, a pore volume, measured
by mercury porosimetry, encompassed in the pores with a diameter of
more than 140 .ANG., of less than 0.1 ml/g, a pore volume, measured
by mercury porosimetry, encompassed in the pores with a diameter of
more than 160 .ANG., of less than 0.1 ml/g, a pore volume, measured
by mercury porosimetry, encompassed in the pores with a diameter of
more than 200 .ANG., of less than 0.1 ml/g, a pore volume, measured
by mercury porosimetry, encompassed in the pores with a diameter of
more than 500 .ANG., of less than 0.01 ml/g, a pore distribution
such that the ratio between volume V2, measured by mercury
porosimetry, encompassed between D.sub.mean-30 .ANG. and
D.sub.mean+30 .ANG. to the total mercury volume is more than
0.6-volume V3, measured by mercury porosimetry, encompassed in the
pores with a diameter of more than D.sub.mean+30 .ANG. is less than
0.1 ml/g,-volume V6, measured by mercury porosimetry, encompassed
in the pores with a diameter of more than D.sub.mean+15 .ANG. is
less than 0.2 ml/g, an X diffraction diagram that contains at least
the main lines that are characteristic of at least one of the
transition aluminas contained in the group that consists of the
rho, chi, eta, gamma, kappa, theta and delta aluminas.
10. Process according to claim 8, wherein the substrate of the
hydrocracking catalyst has the following characteristics: a content
by weight of silica SiO.sub.2 of between 10 and 60%, an Na content
of less than 300 ppm by weight, a total pore volume of between 0.5
and 1.2 ml/g that is measured by mercury porosimetry, a specific
surface area of more than 200 m.sup.2/g, and a porosity that is
defined as follows: iii) a volume of mesopores whose diameter is
between 40 .ANG. and 150 .ANG., and whose mean diameter varies
between 80 and 120 .ANG. representing between 30 and 80% of the
total pore volume that is defined above, iv) a volume of
macropores, whose diameter is more than 500 .ANG. and, preferably,
between 1,000 .ANG. and 10,000 .ANG., represents between 20 and 80%
of the total pore volume.
11. Process according to any of claims 1 to 10, wherein the
hydrocracking stage is carried out at a temperature T2 that is
encompassed between 300 and 400.degree. C.
Description
[0001] This invention relates to the field of hydrocracking
hydrocarbon-containing feedstocks for the purpose of producing
middle distillates, and more particularly gas oil.
[0002] The hydrocracking of heavy petroleum fractions is a very
important refining process that makes it possible to produce
lighter fractions from excess heavy feedstocks that cannot be
readily upgraded. In some cases, these processes can also produce a
highly purified residue that can provide excellent bases for
oils.
[0003] Certain hydrocracking processes, often described as "once
through" processes, comprise a preliminary hydrotreatment stage
with a limited conversion of light fractions, making it possible to
transform the nitrogen-containing and sulfur-containing organic
compounds. These types of processes generally do not comprise an
intermediate separation between hydrotreatment and
hydrocracking.
[0004] Other hydrocracking processes comprise a preliminary
hydrorefining stage that makes it possible to convert between 20
and 60% of the feedstock, a stage of separation for recovering
unconverted products, and a hydrocracking stage. These processes
are often described as two-stage processes.
[0005] International Patent Application WO 99/47625 describes a
process for converting a hydrocarbon feedstock into a product that
has a lower mean molecular weight. This process comprises a
hydrocracking stage that is used with a catalyst based on a
cracking component and a hydrogenation component, whereby the
latter comprises palladium and platinum in a molar ratio that
varies between 10:1 and 1:10.
[0006] The implementation of such a process generally involves the
use of a hydrocracking catalyst that comprises a zeolite, which
makes it possible to produce gases, gasolines and middle
distillates with high conversion levels, but contrary to a mediocre
selectivity of middle distillates.
[0007] A process was found for the production of middle distillates
that makes it possible to reconcile a strong conversion with a high
selectivity level of middle distillates under operating conditions
that are favorable to an increase in the cycle time of catalysts
and to the production of gas oils and kerosene of excellent
quality.
[0008] A gas oil of excellent quality is defined as a gas oil that
has:
[0009] a sulfur content that is less than 50 ppm, preferably less
than 30 ppm, and more preferably less than 10 ppm,
[0010] a cetane number that is higher than 51, preferably higher
than 55,
[0011] a content of polyaromatic compounds that is less than 11% by
weight, preferably less than 5% by weight, and more preferably less
than 2% by weight, and
[0012] a content of aromatic compounds that is less than 15% by
weight, preferably less than 10% by weight.
[0013] A kerosene of excellent quality is defined as a kerosene
whose smoke point is higher than 20 mm, preferably higher than 25
mm.
[0014] This invention therefore relates to a hydrocracking process
for the conversion of a hydrocarbon feedstock that comprises:
[0015] a hydrorefining stage in which the feedstock is brought into
contact with the hydrogen in the presence of a hydrorefining
catalyst, at a temperature T1, and an effluent that comprises
converted products and unconverted products is recovered,
optionally a separation stage in which at least a portion of the
converted products formed during the hydrorefining stage and a
fraction that comprises the unconverted products are separated,
and
[0016] a hydrocracking stage, in which the unconverted products
(therefore optionally at least a portion of the fraction that
contains said products that are obtained from the separation) are,
at least in part, brought into contact with the hydrogen, in the
presence of an amorphous hydrocracking catalyst that comprises a
substrate, palladium and platinum, at a temperature T2 that is less
than T1, whereby the difference between T1 and T2 is between 5 and
50.degree. C., preferably between 10 and 40.degree. C., and more
preferably between 15 and 30.degree. C.
[0017] Very varied feedstocks can be treated by the process of the
invention. Generally, these feedstocks contain at least 20% by
volume, and often at least 80% by volume, of compounds that have a
boiling point above 340.degree. C.
[0018] Preferably, 95% of the compounds that are present in the
feedstock have a boiling point of higher than 340.degree. C., and
more preferably, 95% of the compounds that are present in the
feedstock have a boiling point that is higher than 370.degree.
C.
[0019] The nitrogen content of the treated hydrocarbon-containing
feedstocks in the process according to the invention is generally
higher than 500 ppm by weight, preferably between 500 and 5,000 ppm
by weight, more preferably between 700 and 4,000 ppm by weight, and
even more preferably between 1,000 and 3,000 ppm by weight.
[0020] The sulfur content of these hydrocarbon-containing
feedstocks is preferably between 0.01 and 5% by weight, and more
preferably between 0.2 and 4% by weight.
[0021] According to the process of the invention, the feedstock is
subjected, in a first reaction zone, to at least one hydrorefining
stage, during which it is brought into contact with the hydrogen in
the presence of a hydrorefining catalyst. During this hydrorefining
stage, the feedstock generally undergoes hydrodesulfurization,
hydrodenitration, as well as a conversion of a portion of the
latter into conversion products such as gases, gasolines and middle
distillates.
[0022] The hydrorefining catalysts can be selected from among the
catalysts that are commonly used in this field.
[0023] The hydrorefining catalyst can preferably comprise a matrix,
at least one hydro-dehydrogenating element that is selected from
the group that is formed by the elements of group VIB and group
VIII of the periodic table.
[0024] The matrix can consist of compounds that are used alone or
in a mixture, such as alumina, halogenated alumina, silica,
silica-alumina, clays (selected from, for example, natural clays
such as kaolin or bentonite), magnesia, titanium oxide, boron
oxide, zirconia, aluminum phosphates, titanium phosphates,
zirconium phosphates, carbon, and aluminates. It is preferred to
use matrices that contain alumina, in all of these forms that are
known to one skilled in the art, and even more preferably aluminas,
for example gamma-alumina.
[0025] The hydro-dehydrogenating element can be selected from the
group that is formed by the elements of group VIB and non-noble
element of group VIII of the periodic table. The
hydro-dehydrogenating element is preferably selected from the group
that is formed by molybdenum, tungsten, nickel and cobalt. More
preferably, the hydro-dehydrogenating element comprises at least
one element of group VIB and at least one non-noble element of
group VIII. This hydro-dehydrogenating element can comprise, for
example, a combination of at least one element of group VIII (Ni,
Co) with at least one element of group VIB (Mo, W).
[0026] The hydrorefining catalyst preferably also comprises at
least one dopant that is deposited on said catalyst and is selected
from the group that is formed by phosphorus, boron and silicon. In
particular, the hydrorefining catalyst can comprise, as dopants,
boron and/or silicon, with optionally, in addition, phosphorus. The
contents of boron, silicon and phosphorus are generally between 0.1
and 20%, preferably 0.1 and 15%, and more preferably between
0.1-10%.
[0027] The hydrorefining catalyst can advantageously comprise
phosphorus. This compound provides, i.a., two main advantages to
the hydrorefining catalyst, whereby a first advantage is a greater
facility of preparation of said catalyst during in particular the
impregnation of the hydro-dehydrogenating element, for example from
solutions based on nickel and molybdenum. A second advantage
provided by this compound is an increase in the hydrogenation
activity of the catalyst.
[0028] The hydrorefining catalyst can also-comprise at least one
element of the group VIIA (chlorine and fluorine are preferred)
and/or at least one element of group VIIB (manganese is preferred),
and optionally at least one element of group VB (niobium is
preferred).
[0029] In a preferred hydrorefining catalyst, the total
concentration of metal oxides of groups VIB and VIII is between 5
and 40% by weight, preferably between 7 and 30% by weight, and the
ratio by weight that is expressed in terms of metal oxide between
group VIB metal (or metals) vs. group VIII metal (or metals) is
between 20 and 1.25, preferably between 10 and 2. The concentration
of phosphorus oxide P.sub.2O.sub.5 can be less than 15% by weight,
preferably less than 10% by weight.
[0030] In another hydrorefining catalyst that comprises boron
and/or silicon, preferably boron and silicon, said catalyst
generally comprises, in % by weight relative to the total mass of
said catalyst,
[0031] from 1 to 99%, preferably from 10 to 98%, and more
preferably from 15 to 95% of at least one matrix,
[0032] from 3 to 60%, preferably from 3 to 45%, and more preferably
from 3 to 30% of at least one metal of group VIB,
[0033] optionally from 0 to 30%, preferably from 0 to 25%, and more
preferably from 0 to 20% of at least one metal of group VIII,
[0034] from 0.1 to 20%, preferably from 0.1 to 15%, and more
preferably
[0035] from 0.1 to 10% of boron and/or 0.1 to 20%, preferably from
0.1 to 15%, and more preferably from 0.1 to 10% of silicon,
[0036] optionally from 0 to 20%, preferably from 0.1 to 15%, and
more preferably from 0.1 to 10% of phosphorus, and
[0037] optionally from 0 to 20%, preferably from 0.1 to 15%, and
more preferably from 0.1 to 10% of at least one element that is
selected from group VIIA, for example fluorine.
[0038] In another hydrorefining catalyst, said catalyst
comprises:
[0039] between 1 and 95% by weight (% oxide) of at least one
matrix, preferably alumina,
[0040] between 5 and 40% by weight (% oxide) of at least one
non-noble element of groups VIB and VIII,
[0041] between 0 and 20%, preferably between 0.1 and 20% by weight
(% oxide) of at least one promoter element that is selected from
among phosphorus, boron, and silicon,
[0042] between 0 and 20% by weight (% oxide) of at least one
element of group VIIB (manganese, for example),
[0043] between 0 and 20% by weight (% oxide) of at least one
element of group VIIA (fluorine, chlorine, for example), and
[0044] between 0 and 60% by weight (% oxide) of at least one
element of group VB (niobium, for example).
[0045] In a general way, hydrorefining catalysts that have the
following atomic ratios are preferred:
[0046] an atomic ratio of group VIII metals/group VIB metals
ranging from 0 to 1,
[0047] an atomic ratio of B/group VIB metals ranging from 0.01 to
3,
[0048] an atomic ratio of Si/group VIB metals ranging from 0.01 to
1.5,
[0049] an atomic ratio of P/group VIB metals ranging from 0.01 to
1, and
[0050] an atomic ratio of group VIIA elements/group VIB metals
ranging from 0.01 to 2.
[0051] The particularly preferred hydrorefining catalysts are the
NiMo and/or NiW catalysts on alumina, also the NiMo and/or NiW
catalysts on alumina that is doped with at least one element that
is included in the group of atoms formed by phosphorus, boron,
silicon and fluorine.
[0052] The hydrorefining catalysts that are described above are
therefore used during the hydrorefining stage, often called a
hydrotreatment stage.
[0053] The hydrorefining catalyst is preferably subjected in
advance to a sulfurization treatment that makes it possible to
transform, at least in part, the metal sulfide radicals before
contact with the feedstock to be treated. This treatment of
activation by sulfurization is well known to one skilled in the art
and can be carried out by any method that is already described in
the literature or in-situ, i.e., in the reactor, or ex-situ.
[0054] The operating conditions that are used during the
hydrorefining stage preferably can be defined as follows:
[0055] a temperature T1 ranging from 330 to 420.degree. C.,
preferably from 350 to 410.degree. C., more preferably from 360 to
400.degree. C., and even more preferably from 370 to 390.degree.
C.;
[0056] a pressure that is higher than 7.5 MPa, preferably higher
than 8.2 MPa, more preferably higher than 9.0 MPa, and even more
preferably higher than 11.0 MPa and less than 20 MPa;
[0057] a volumetric flow rate ranging from 0.1 to 6 h.sup.-1,
preferably from 0.2 to 3 h.sup.-1;
[0058] an amount of hydrogen that is introduced with a volumetric
ratio of liter of hydrogen by liter of hydrocarbons ranging from
100 and 2,000 l/l.
[0059] During the hydrorefining stage of the process of the
invention, the contents of organic nitrogen-containing compounds,
organic sulfur-containing compounds and condensed polycyclic
aromatic hydrocarbons are generally reduced. A large portion of the
nitrogen-containing and sulfur-containing organic products of the
feedstock is found transformed into H2S and NH3.
[0060] The operating conditions of the hydrorefining stage are
preferably established such that the organic nitrogen content of
the feedstock that is obtained from this hydrorefining is less than
10 ppm by weight, preferably less than 5 ppm.
[0061] The operating conditions of the hydrorefining stage are
preferably established so as to obtain a level of conversion of the
feedstock into compounds whose boiling point is less than
340.degree. C. or, even better, less than 370.degree. C.,
encompassed between 10 and 50%, preferably between 20 and 40%.
[0062] According to the process of this invention, the effluent
that is recovered during the hydrorefining stage is subjected to a
separation stage in which at least a portion of the converted
products formed during the hydrorefining stage and a fraction that
comprises the unconverted products are separated.
[0063] The effluent of this hydrorefining stage can be sent into a
separation means, such as, for example, a separator tank, so as to
eliminate the ammonia and the hydrogen sulfide that are produced
during the hydrorefining stage. The hydrocarbon-containing
effluent, obtained from this separation, can undergo an atmospheric
distillation. This distillation can be complemented, in some cases,
by a vacuum distillation. The purpose of the distillation is to
carry out the separation between the converted products, i.e.,
generally having boiling points of less than 340.degree. C.,
preferably less than 370.degree. C., and a fraction, generally
liquid, that comprises unconverted products.
[0064] It is advantageously possible to distill at atmospheric
pressure to obtain several converted products, such as, for
example, gasolines, kerosene, and gas oil, as well as unconverted
products that have an initial boiling point of higher than
340.degree. C. or else higher than 370.degree. C.
[0065] According to the process of this invention, the fraction
that comprises the unconverted products is, at least in part,
subjected to a hydrocracking stage.
[0066] The fraction that is subjected to a hydrocracking stage
preferably essentially consists of products that have a boiling
point that is higher than 340.degree. C., preferably higher than
370.degree. C.
[0067] This fraction that is subjected to the hydrocracking stage
generally has very low contents of organic sulfur, organic
nitrogen, hydrogen sulfide and ammonia. Organic sulfur and organic
nitrogen are defined as the sulfur and the nitrogen that are
included in organic compounds.
[0068] The organic nitrogen content of the portion of the fraction
that comprises the unconverted products subjected to the
hydrocracking stage is preferably less than 10 ppm by weight, more
preferably less than 5 ppm by weight.
[0069] The organic sulfur content of the portion of the fraction
that comprises the unconverted products subjected to the
hydrocracking stage is preferably less than 100 ppm by weight, more
preferably less than 20 ppm by weight.
[0070] The H.sub.2S content of the portion of the fraction that
comprises the unconverted products subjected to the hydrocracking
stage is preferably less than 100 ppm by weight, more preferably
less than 10 ppm by weight, and even more preferably less than 5
ppm by weight.
[0071] The NH.sub.3 content of the portion of the fraction that
comprises the unconverted products subjected to the hydrocracking
stage is preferably less than 100 ppm by weight, more preferably
less than 10 ppm by weight and even more preferably less than 5 ppm
by weight.
[0072] According to the process of the invention, the hydrocracking
stage is carried out by contact with hydrogen in the presence of a
hydrocracking catalyst.
[0073] The hydrogen that is used during the hydrocracking stage
generally has a hydrogen sulfide content of less than 100 ppm,
preferably less than 10 ppm, more preferably less than 5 ppm, and
an ammonia content that is less than 50 ppm, preferably less than
10 ppm, more preferably less than 5 ppm.
[0074] According to the process of the invention, the hydrocracking
catalyst exhibits an amorphous or non-zeolitic nature. The
hydrocracking catalyst generally comprises at least one amorphous
acidic substrate and at least one noble metal-type
hydro-dehydrogenating function.
[0075] The substrates generally have large surface areas that can
range from 150 to 800 m.sup.2g.sup.-1 and exhibit a surface
acidity. They can be selected from among the halogenated aluminas
(in particular chlorinated or fluorinated aluminas), the boron and
aluminum oxide combinations, the titanium, silicon and aluminum
oxide combinations, the zirconium, aluminum and silicon oxide
combinations, the amorphous silica-aluminas, and the halogenated
silica-aluminas (chlorinated or fluorinated silica-aluminas in
particular). These oxides or combinations of amorphous oxides can
be obtained by any methods of synthesis that are known to one
skilled in the art. Preferably, the substrate of the hydrocracking
catalyst is an amorphous silica-alumina.
[0076] The substrate can consist of pure silica-alumina or result
from the mixing, with said silica-alumina, of a binder such as
silica (SiO2), alumina (Al2O3), clays, titanium oxide (TiO2), boron
oxide (B2O3) and zirconia (ZrO2) and any mixture with the binders
cited above. The preferred binders are silica and alumina and, even
more preferably, alumina in all of these forms that are known to
one skilled in the art, for example gamma-alumina. The content by
weight of binder in the substrate of the catalyst can be between 0
and 40% by weight, preferably between 1 and 40% by weight, and more
preferably between 5% and 20% by weight. This has the result that
the content by weight of silica-alumina is generally between
60-100% by weight. However, the catalysts whose substrate consists
only of silica-alumina without any binder are preferred.
[0077] The substrate can be prepared by shaping silica-alumina with
or without the presence of binder by any technique that is known to
one skilled in the art. The shaping can be carried out by, for
example, extrusion, pelletizing, the drop (oil-drop) coagulation
method, turntable granulation or any other method that is well
known to one skilled in the art. At least one calcination can be
carried out after any of the stages of the preparation; it is
usually carried out in air at a temperature of at least 150.degree.
C., preferably at least 300.degree. C.
[0078] The catalyst substrates can exhibit a certain number of
characteristics.
[0079] Among the characteristics that are used below, the B.E.T.
specific surface area is determined by adsorption of nitrogen
according to ASTM Standard D3663-78 established from the
BRUNAUER-EMMETT-TELLER method described in the periodical "The
Journal of American Society," 60, 309, (1938).
[0080] Relative to the measurements of volumes, they are generally
carried out by mercury porosimeter intrusion according to ASTM
Standard D4284-83 at a maximum pressure of 4,000 bar, using a
surface tension of 484 dyne/cm and a contact angle for the
amorphous silica-alumina substrates of 140.degree.. The mercury
mean diameter, D.sub.mean, is defined as being a diameter such that
all the pores of a size smaller than this diameter constitute 50%
of the pore volume (VHg) in an interval of between 36 .ANG. and
1,000 .ANG.. So as to obtain better precision, the value of the
mercury volume in ml/g that is provided in the text below
corresponds to the value of the total mercury volume in ml/g that
is measured in the sample less the value of the mercury volume in
ml/g that is measured in the same sample for a pressure that
corresponds to 30 psi (about 2 bar). So as to better characterize
the pore distribution, the following mercury pore distribution
criteria are defined: volume V1 corresponds to the volume that is
contained in the pores whose diameter is less than the mean
diameter less 30 .ANG.. Volume V2 corresponds to the volume that is
contained in the pores with a diameter that is larger than the mean
diameter less 30 .ANG. and less than the mean diameter plus 30
.ANG.. Volume V3 corresponds to the volume that is contained in the
pores with a diameter that is larger than the mean diameter plus 30
.ANG.. Volume V4 corresponds to the volume that is contained in the
pores whose diameter is less than the mean diameter less 15 .ANG..
Volume V5 corresponds to the volume that is contained in the pores
with a diameter that is larger than the mean diameter less 15 .ANG.
and less than the mean diameter plus 15 .ANG.. Volume V6
corresponds to the volume that is contained in the pores with a
diameter that is larger than the mean diameter plus 15 .ANG..
[0081] Below, the pore distribution that was measured by nitrogen
adsorption was determined by the Barrett-Joyner-Halenda (BJH)
model. The nitrogen adsorption-desorption isotherm according to the
BJH model is described in the periodical "The Journal of American
Society," 73, 373 (1951) written by E. P. Barrett, L. G. Joyner and
P. P. Halenda. In the following presentation of the invention,
nitrogen adsorption volume is defined as the volume that is
measured for P/PO=0.99, pressure for which it is accepted that
nitrogen has filled all the pores. The nitrogen desorption mean
diameter is defined as being a diameter such that all the pores
that are smaller than this diameter constitute 50% of pore volume
(Vp) measured on the desorption branch of the nitrogen isotherm.
Adsorption surface area is defined as the surface area that is
measured on the branch of the adsorption isotherm. Reference will
be made to, for example, the article of A. Lecloux, "Mmoires Socit
Royale des Sciences de Lige, 6.sup.th Series, Part I, Volume 4, pp.
169-209 (1971)."
[0082] The sodium content has been measured by atomic absorption
spectrometry.
[0083] In the following presentation, the x-ray analysis is carried
out on powder with a Philips PW 1830 diffractometer that operates
by reflection and is equipped with a rear monochromator by using
the CoKalpha radiation (.lambda.K.sub.a1=1.7890 .ANG., .lambda.
K.sub.a2=1.793 .ANG., intensity ratio K.sub.a1/K.sub.a2=0.5). For
the X diffraction diagram of the gamma-alumina, reference will be
made to the ICDD data base, form 10-0425. In particular, the two
most intense peaks are located at a position that corresponds to
one d encompassed between 1.39 and 1.40 .ANG. and one d encompassed
between 1.97 .ANG. to 2.00 .ANG.. d is called the interreticular
distance that is derived from the angular position by using Bragg's
equation (2 d .sub.(hkl)*sin (.theta.)=.eta.*.lambda.)
Gamma-alumina is defined in the text below, i.a., as, for example,
an alumina contained in the group that consists of cubic
gamma-aluminas, pseudo-cubic gamma-aluminas, tetragonal
gamma-aluminas, poorly or slightly crystallized gamma-aluminas,
large-surface-area gamma-aluminas, low-surface-area gamma-aluminas,
gamma-aluminas that are obtained from coarse boehmite,
gamma-aluminas that are obtained from crystallized boehmite,
gamma-aluminas that are obtained from boehmite that is slightly or
poorly crystallized, gamma-aluminas that are obtained from a
mixture of crystallized boehmite and an amorphous gel,
gamma-aluminas that are obtained from an amorphous gel, and
gamma-aluminas evolving toward delta-aluminas. For the positions of
diffraction peaks of eta-, delta- and theta-aluminas, it is
possible to refer to the article by B. C. Lippens and J. J.
Steggerda in Physical and Chemical Aspects of Adsorbents and
Catalysts, E. G. Linsen (Ed.), Academic Press, London. 1970, pp.
171-211.
[0084] Finally, in the following presentation, the analyses by RMS
MAS are carried out on a spectrometer of the Bruker Company such as
MSL 400, with a 4 mm probe. The speed of rotation of the samples is
on the order of 11 kHz. Potentially, the NMR of the aluminum makes
it possible to distinguish three types of aluminum whose chemical
displacements are presented below:
[0085] between 100 and 40 ppm, tetra-coordinated-type aluminum,
denoted as Al.sub.IV,
[0086] between 40 and 20 ppm, penta-coordinated-type aluminum,
denoted as Al.sub.V,
[0087] between 20 and -100 ppm, hexa-coordinated-type aluminum,
denoted as Al.sub.VI.
[0088] The aluminum atom is a quadripolar core. Under certain
analysis conditions (weak radiofrequency fields: 30 kHz,
low-impulse angle: .pi./2 and water-saturated sample), the NMR
technique of magic angle rotation (MAS) is a quantitative
technique. The decomposition of the NMR MAS spectra makes it
possible to gain access directly to the amount of different
radicals. The spectrum is locked in chemical displacement relative
to a 1 M solution of aluminum nitrate. The aluminum signal is at
zero ppm. We chose to integrate the signals between 100 and 20 ppm
for the Al.sub.IV and Al.sub.V, which corresponds to area 1, and
between 20 and -100 ppm for Al.sub.VI, which corresponds to area 2.
In the following presentation of the invention, proportion of
octahedral Al.sub.VI is defined as the following ratio: area
2/(area 1+area 2).
[0089] The packing density (DRT) of the substrates and catalysts
that can be used in the process according to the invention is
measured in the manner that is described in the work "Applied
Heterogeneous Catalysis" by J. F. Le Page, J. Cosyns, P. Courty, E.
Freund, J.-P. Franck, Y. Jacquin, B. Juguin, C. Marcilly, G.
Martino, J. Miguel, R. Montarnal, A. Sugier, H. Van Landeghem,
Technip. Paris, 1987. A graduated cylinder with acceptable
dimensions is filled with catalyst by successive additions; and
between each addition, the catalyst is packed by shaking the
cylinder until a constant volume is achieved. This measurement is
generally carried out on 1,000 cm.sup.3 of catalyst that is packed
into a cylinder whose height to diameter ratio is close to 5:1.
This measurement can preferably be made on automated devices such
as Autotap.RTM. that is marketed by Quantachrome.RTM..
[0090] The acidity of the catalyst substrate that can be used in
the process according to the invention is measured by infra-red
(IR) spectrometry. The IR spectra are recorded on a Nicolet
interferometer such as Nexus-670 under a resolution of 4 cm.sup.-1
with a Happ-Genzel-type apodization. The sample (20 mg) is pressed
in the form of a self-supported pellet, then is placed in an
in-situ analysis cell (25.degree. C. to 550.degree. C., furnace
offset from the IR beam, secondary vacuum of 10.sup.-6 mbar). The
diameter of the pellet is 16 mm.
[0091] The sample is pretreated in the following way to eliminate
the physisorbed water and to dehydroxylate partially the surface of
the catalyst to obtain a representative image of the acidity of the
catalyst in use:
[0092] increase in temperature from 25.degree. C. to 300.degree. C.
in 3 hours
[0093] plateau of 10 hours at 300.degree. C.
[0094] drop in temperature from 300.degree. C. to 25.degree. C. in
3 hours.
[0095] The basic probe (pyridine) is then adsorbed with saturating
pressure at 25.degree. C. and then thermo-desorbed according to the
following plateaus:
[0096] 25.degree. C. for 2 hours under secondary vacuum
[0097] 100.degree. C. for 1 hour under secondary vacuum
[0098] 200.degree. C. for 1 hour under secondary vacuum
[0099] 300.degree. C. for 1 hour under secondary vacuum.
[0100] A spectrum is recorded at 25.degree. C. at the end of the
pretreatment and at each desorption plateau in transmission mode
with an accumulation time of 100 s. The spectra are set to iso-mass
(i.e., assumed to be at iso-thickness) (20 mg exactly). The number
of Lewis sites is proportional to the surface area of the peak
whose maximum lies around 1450 cm.sup.-1, including any shoulder.
The number of Bronsted sites is proportional to the surface area of
the peak whose maximum is located toward 1545 cm.sup.-1. The ratio
of the number of Bronsted sites/number of Lewis sites is estimated
to be equal to the ratio of the surface areas of two peaks
described above. The surface area of peaks at 25.degree. C. is
generally used. This B/L ratio is generally calculated from the
spectrum that is recorded at 25.degree. C. at the end of the
pretreatment.
[0101] According to a first embodiment of this invention, the
substrate of the hydrocracking catalyst is a non-zeolitic substrate
with a silica-alumina base (i.e., that comprises silica and
alumina) that comprises the following characteristics:
[0102] a content by mass of silica (SiO.sub.2) that is more than 5%
by weight and less than or equal to 95% by weight, preferably
between 10 and 80% by weight, preferably a silica content that is
more than 20% by weight and less than 80% by weight, and even more
preferably more than 25% by weight and less than 75% by weight, and
the silica content is advantageously encompassed between 10 and 50%
by weight,
[0103] preferably a cationic impurity content that is less than
0.1% by weight, preferably less than 0.05% by weight, and even more
preferably less than 0.025% by weight. Cationic impurity content is
defined as the total alkaline content.
[0104] preferably an anionic impurity content that is less than 1%
by weight, preferably less than 0.5% by weight, and even more
preferably less than 0.1% by weight.
[0105] a mean pore diameter, measured by mercury porosimetry,
encompassed between 20 and 140 .ANG., preferably between 40 and 120
.ANG., and even more preferably between 50 and 100 .ANG.,
[0106] preferably a ratio between volume V2, measured by mercury
porosimetry, encompassed between D.sub.mean-30 .ANG. and
D.sub.mean+30 .ANG., to the total pore volume that is also measured
by mercury porosimetry, that is more than 0.6, preferably more than
0.7, and even more preferably more than 0.8,
[0107] preferably a volume V3 that is encompassed in the pores with
a diameter of more than D.sub.mean+30 .ANG., measured by mercury
porosimetry, that is less than 0.1 ml/g, preferably less than 0.06
ml/g, and even more preferably less than 0.04 ml/g, preferably a
ratio between volume V5 that is encompassed between D.sub.mean-15
.ANG. and D.sub.mean+15 .ANG., measured by mercury porosimetry, and
volume V2 that is encompassed between D.sub.mean-30 .ANG. and
D.sub.mean+30 .ANG., measured by mercury porosimetry, that is more
than 0.6, preferably more than 0.7, and even more preferably more
than 0.8,
[0108] preferably a volume V6 that is encompassed in the pores with
a diameter of more than D.sub.mean+15 .ANG., measured by mercury
porosimetry, that is less than 0.2 ml/g, preferably less than 0.1
ml/g, and even more preferably less than 0.05 ml/g,
[0109] a total pore volume, measured by mercury porosimetry,
encompassed between 0.1 ml/g and 0.6 ml/g, preferably encompassed
between 0.20 and 0.50 ml/g, and even more preferably more than 0.20
ml/g,
[0110] a total pore volume, measured by nitrogen porosimetry,
encompassed between 0.1 ml/g and 0.6 ml/g, preferably between 0.20
and 0.50 ml/g,
[0111] a BET specific surface area encompassed between 100 and 550
m.sup.2/g, preferably encompassed between 150 and 500
m.sup.2/g,
[0112] preferably an adsorption surface area such that the ratio
between the adsorption surface area and the BET surface area is
more than 0.5, preferably more than 0.65, and more preferably more
than 0.8,
[0113] a pore volume, measured by mercury porosimetry, encompassed
in the pores with a diameter of more than 140 .ANG., of less than
0.1 ml/g, preferably of less than 0.05 ml/g, and even more
preferably of less than 0.03 ml/g,
[0114] a pore volume, measured by mercury porosimetry, encompassed
in the pores with a diameter of more than 160 .ANG., of less than
0.1 ml/g, preferably of less than 0.05 ml/g, and even more
preferably of less than 0.025 ml/g,
[0115] a pore volume, measured by mercury porosimetry, encompassed
in the pores with a diameter of more than 200 .ANG., of less than
0.1 ml/g, preferably of less than 0.05 ml/g, and even more
preferably of less than 0.025 ml/g,
[0116] a pore volume, measured by mercury porosimetry, encompassed
in the pores with a diameter of more than 500 .ANG., of less than
0.01 ml/g,
[0117] an X diffraction diagram that contains at least the main
lines that are characteristic of at least one of the transition
aluminas contained in the group that consists of the rho, chi,
kappa, eta, gamma, theta and delta aluminas, and preferably
characterized in that it contains at least the main lines that are
characteristic of at least one of the transition aluminas contained
in the group that consists of the gamma, eta, theta and delta
alumina, and more preferably, characterized in that it contains at
least the main lines that are characteristic of the gamma-alumina
and eta-alumina, and even more preferably characterized in that it
contains the peaks at one d encompassed between 1.39 and 1.40 .ANG.
and the peaks at one d encompassed between 1.97 .ANG. and 2.00
.ANG..
[0118] The NMR MAS spectra of the solid of .sup.27Al of such a
substrate show two clusters of separate peaks. A first type of
aluminum whose maximum resonates toward 10 ppm extends between -100
and 20 ppm. The position of the maximum suggests that these
radicals are essentially of Al.sub.VI type (octahedral). A second
type of minority aluminum whose maximum resonates toward 60 ppm
extends between 20 and 110 ppm. This cluster can be decomposed into
at least two radicals. The predominant radical of this cluster
would correspond to Al.sub.IV atoms (tetrahedral). For the
substrates of this embodiment of the invention, advantageously the
proportion of octahedral Al.sub.VI is more than 50%, preferably
more than 60%, and even more preferably more than 70%.
[0119] The substrate can comprise at least two silico-aluminum
zones, whereby said zones have Si/Al ratios that are less than or
greater than the overall Si/Al ratio that is determined by X
fluorescence. A substrate that has an overall Si/Al ratio that is
equal to 0.5 thus comprises, for example, two silico-aluminum
zones: one of the zones has an Si/Al ratio that is determined by
MET of less than 0.5, and the other zone has an Si/Al ratio that is
determined by MET of between 0.5 and 2.5.
[0120] The substrate can comprise a single silico-aluminum zone,
whereby said zone has an Si/Al ratio that is equal to the overall
Si/Al ratio that is determined by X fluorescence and is less than
2.3.
[0121] The acidity of the catalyst substrate that can be used in
the process according to the invention can advantageously be
measured, without restricting the scope of the invention, by IR
tracking of the thermodesorption of the pyridine. Generally, the
B/L ratio, as described above, of the substrate according to the
invention is between 0.05 and 1, preferably between 0.05 and 0.7,
very preferably between 0.06 and 0.3, and even more preferably
between 0.075 and 0.15.
[0122] The packing density of the substrates, after calcination, is
generally more than 0.65 g/cm.sup.3, preferably more than 0.72
g/cm.sup.3, very preferably more than 0.75 g/cm.sup.3, and even
more preferably more than 0.78 g/cm.sup.3.
[0123] The packing density of the catalysts that are obtained from
this substrate is generally more than 0.85 g/cm.sup.3, preferably
more than 0.95 g/cm.sup.3, very preferably more than 1.025
cm.sup.3/g, and even more preferably more than 1.1 g/cm.sup.3.
[0124] More specifically, this first embodiment of the invention
relates to a non-zeolitic substrate based on silica-alumina that
contains an amount that is more than 5% by weight and less than or
equal to 95% by weight of silica (SiO.sub.2), characterized by:
[0125] a mean pore diameter, measured by mercury porosimetry,
encompassed between 20 and 140 .ANG.,
[0126] a total pore volume, measured by mercury porosimetry,
encompassed between 0.1 ml/g and 0.6 ml/g,
[0127] a total pore volume, measured by nitrogen porosimetry,
encompassed between 0.1 ml/g and 0.6 ml/g,
[0128] a BET specific surface area encompassed between 100 and 550
m.sup.2/g,
[0129] a pore volume, measured by mercury porosimetry, encompassed
in the pores with a diameter of more than 140 .ANG., of less than
0.1 ml/g,
[0130] a pore volume, measured by mercury porosimetry, encompassed
in the pores with a diameter of more than 160 .ANG., of less than
0.1 ml/g,
[0131] a pore volume, measured by mercury porosimetry, encompassed
in the pores with a diameter of more than 200 .ANG., of less than
0.1 ml/g,
[0132] a pore volume, measured by mercury porosimetry, encompassed
in the pores with a diameter of more than 500 .ANG., of less than
0.01 ml/g,
[0133] an X diffraction diagram that contains at least the main
lines that are characteristic of at least one of the transition
aluminas contained in the group that consists of the rho, chi, eta,
gamma, kappa, theta and delta aluminas.
[0134] The teaching of the U.S. patent application of Ser. No.
10/696,561 is incorporated here as a reference.
[0135] According to a second embodiment of this invention, the
substrate of the hydrocracking catalyst comprises at least one
silica-alumina, whereby said silica-alumina comprises the following
characteristics:
[0136] a content by weight of silica SiO.sub.2 of between 10 and
60%, preferably between 20 and 60%, and even more preferably
between 30 and 50% by weight,
[0137] an Na content of less than 300 ppm by weight and preferably
less than 200 ppm by weight,
[0138] a total pore volume of between 0.5 and 1.2 ml/g that is
measured by mercury porosimetry,
[0139] a specific surface area of more than 200 m.sup.2/g and
preferably more than 250 m.sup.2/g, and
[0140] a porosity that is defined as follows:
[0141] i) a volume of mesopores whose diameter is between 40 .ANG.
and 150 .ANG., and whose mean diameter varies between 80 and 120
.ANG. representing between 30 and 80% of the total pore volume that
is defined above and preferably between 40 and 70%,
[0142] ii) a volume of macropores, whose diameter is more than 500
.ANG. and preferably between 1,000 .ANG. and 10,000 .ANG.,
represents between 20 and 80% of the total pore volume, preferably
between 30 and 60% of the total pore volume, and more preferably,
at least 35% of the total pore volume.
[0143] According to this invention, the amorphous hydrocracking
catalyst comprises palladium and platinum. These two compounds are
part of the hydro-dehydrogenating element of the hydrocracking
catalyst.
[0144] In addition to the palladium and the platinum, the
hydro-dehydrogenating element can comprise either one or more noble
metals of group VIII of the periodic table, or a combination of at
least one metal of group VIB of the periodic table and at least one
metal of group VIII.
[0145] The hydrocracking catalyst can comprise, in percentage by
weight relative to the total mass of the catalyst, 0.2 to 8% by
weight, preferably 0.3 to 5% by weight, and more preferably 0.4 to
2% by weight of noble metals of group VIII.
[0146] The hydrocracking catalyst can be subjected in advance to a
reduction treatment that makes it possible to transform, at least
in part, the noble metal oxides into reduced noble metals. One of
the preferred methods for carrying out the reduction of the
catalyst is a treatment under hydrogen at a temperature of between
150 and 650.degree. C. and at a total pressure of between 0.1 and
20 MPa. We also note that any ex-situ reduction method can be
suitable.
[0147] By way of example, a reduction can include holding at a
temperature of 150.degree. C. for 2 hours, followed by a rise in
temperature up to 350.degree. C. at a rate of 1.degree. C. per
minute, then holding at 350.degree. C. for 2 hours. During this
reduction treatment, the hydrogen flow rate can be 1,000 liters of
hydrogen per liter of catalyst.
[0148] According to an essential characteristic of the process of
the invention, the hydrocracking stage is implemented at a
temperature T2 that is less than hydrorefining temperature T1,
whereby the difference between T1 and T2 is between 5 and
50.degree. C., preferably between 10 and 40.degree. C., and more
preferably between 15 and 30.degree. C.
[0149] The operating conditions that are used during the
hydrocracking stage of the process according to the invention can
be:
[0150] a temperature T2 that is more than 200.degree. C.,
preferably between 250 and 420.degree. C., more preferably between
300 and 400.degree. C., even more preferably between 330 and
380.degree. C.;
[0151] a pressure of more than 7.5, preferably more than 8.2 MPa,
more preferably more than 9.0 MPa, and even more preferably more
than 11.0 MPa and less than 20 MPa;
[0152] a volumetric flow rate of between 0.1 and 20 h-1, preferably
between 0.1 and 6 h-1, and more preferably between 0.2 and
3h-1;
[0153] an amount of hydrogen that is introduced such that the
volumetric ratio of liters of hydrogen per liter of hydrocarbon is
between 80 and 5,000 l/l, preferably between 100 and 2,000 l/l.
[0154] These operating conditions that are used during the
hydrocracking stage can be established so as to reach one
conversion per pass into products that have a boiling point of less
than 340.degree. C. (and, even better, less than 370.degree. C.)
and more than 30% by weight, preferably between 40 and 95% by
weight.
[0155] The effluent that is recovered during the hydrocracking
stage is generally subjected to a so-called final separation stage
so as to separate the gases, such as ammonia, hydrogen sulfide,
hydrogen, as well as the other light gases of the effluent.
[0156] Following this final separation stage, an atmospheric
distillation can be implemented. In some cases, this atmospheric
distillation is completed by a vacuum distillation. The
distillation has as its object to carry out the separation between
the converted products, i.e., generally having boiling points of
less than 340.degree. C. (and, even better, less than 370.degree.
C.) and an unconverted liquid fraction.
[0157] It is advantageously possible to distill at atmospheric
pressure to obtain several converted fractions, such as, for
example, gasolines, kerosene, gas oil and an unconverted liquid
fraction having an initial boiling point that is more than
340.degree. C. or else more than 370.degree. C.
[0158] To improve the final separation, it is possible to add a
vacuum distillation. This will be the case, for example, for
distilling the diesel with better effectiveness.
[0159] The unconverted liquid fraction can be completely or
partially injected into the hydrocracking reactor so as to be
converted there.
[0160] Advantageously, the final separation is carried out with
separation stage means implemented between the hydrorefining and
hydrocracking stages when the latter comprise an atmospheric
distribution and optionally a vacuum distillation.
[0161] This process makes it possible to obtain levels of
conversion of the feedstock into products whose boiling point is
less than 370.degree. C., more than 70% and preferably more than
80%. This process also makes it possible to obtain high
selectivities of middle distillates and more especially of gas
oil.
[0162] The gas oil and the kerosene that are obtained exhibit
excellent qualities, i.e., a high cetane number and a low sulfur
content.
[0163] The examples below illustrate this invention without,
however, limiting its scope.
EXAMPLE 1
Preparation of a Hydrocracking Catalyst According to the Invention
(C1)
[0164] The preparation of substrate S1 according to the invention
is described below.
[0165] The silica-alumina gels are prepared by mixing soda silicate
and water, by sending this mixture into an ion exchange resin. A
solution of aluminum hexahydrate in water is added to the
decationized silica sol. So as to obtain a gel, ammonia is added,
then the precipitate is filtered, and washing is carried out with a
solution of water and concentrated ammonia until the conductivity
of the wash water is constant. The gel that is obtained from this
stage is mixed with Pural boehmite powder such that the final
composition of the mixed substrate of anhydrous product is, at this
stage of the synthesis, equal to 60% Al.sub.2O.sub.3-40% SiO.sub.2.
This suspension is passed into a colloidal mill in the presence of
nitric acid. The content of added nitric acid is adjusted such that
the percentage at the nitric acid mill outlet is 8% relative to the
mass of solid mixed oxide. This mixture is then filtered so as to
reduce the amount of water of the mixed cake. Then, the cake is
mixed in the presence of 10% nitric acid and then extruded. The
mixing is done in a Z-arm mixing machine. The extrusion is carried
out by passage of the paste through a die that is equipped with
orifices that are 1.4 mm in diameter. The extrudates that are thus
obtained are dried at 150.degree. C. and then calcined at
550.degree., and then calcined at 700.degree. C. in the presence of
water vapor.
[0166] The characteristics of the S1 substrate are as follows:
[0167] a composition of the silica-alumina substrate of 60.7%
Al.sub.2O.sub.3 and 39.3% SiO.sub.2;
[0168] a BET surface area of 258 m.sup.2/g;
[0169] a total pore volume, measured by nitrogen adsorption, of
0.47 ml/g;
[0170] a mean pore diameter, measured by mercury porosimetry, of 69
.ANG.;
[0171] a ratio between volume V2, measured by mercury porosimetry,
encompassed between D.sub.mean-30 .ANG. and D.sub.mean+30 .ANG. to
the total mercury volume of 0.89;
[0172] a volume V3, measured by mercury porosimetry, encompassed in
the pores with a diameter of more than D.sub.mean+30 .ANG. of 0.032
ml/g;
[0173] a volume V6, measured by mercury porosimetry, encompassed in
the pores with a diameter of more than D.sub.mean+15 .ANG. of 0.041
ml/g;
[0174] a ratio between the adsorption surface area and the BET
surface area of 0.83;
[0175] a pore volume, measured by mercury porosimetry, encompassed
in the pores with a diameter of more than 140 .ANG. of 0.012
ml/g;
[0176] a pore volume, measured by mercury porosimetry, encompassed
in the pores with a diameter of more than 160 .ANG. of 0.0082
ml/g;
[0177] a pore volume, measured by mercury porosimetry, encompassed
in the pores with a diameter of more than 200 .ANG. of 0.0063
ml/g;
[0178] a pore volume, measured by mercury porosimetry, encompassed
in the pores with a diameter of more than 500 .ANG. of 0.001
ml/g;
[0179] an X diffraction diagram that contains at least the gamma
characteristic main lines and the peaks at one d encompassed
between 1.39 and 1.40 .ANG. and the peaks at one d encompassed
between 1.97 .ANG. and 2.00 .ANG., whereby the X diffraction
diagram also contains the characteristic main lines of
gamma-alumina and in particular the peaks at one d encompassed
between 1.39 and 1.40 .ANG. and the peaks at one d encompassed
between 1.97 .ANG. and 2.00 .ANG.;
[0180] an atomic sodium content of 200+/-20 ppm;
[0181] an atomic sulfur content of 800 ppm; and
[0182] NMR MAS spectra of the solid of .sup.27Al of the catalysts
that show two clusters of separate peaks, a first type of aluminum
whose maximum resonates toward 10 ppm that extends between -100 and
20 ppm, the position of the maximum suggesting that these radicals
are essentially of Al.sub.VI type (octahedral), a second type of
minority aluminum whose maximum resonates toward 60 ppm and that
extends between 20 and 100 ppm, whereby this cluster can be
decomposed into at least two radicals, and the predominant radical
of this cluster would correspond to Al.sub.IV atoms (tetrahedral),
whereby the proportion of octahedral Al.sub.VI is 70%.
[0183] The catalyst contains a single silico-aluminum zone with an
Si/Al ratio that is determined by a MET microprobe of 0.63.
[0184] Catalyst C1 is obtained by impregnation in the dry state of
substrate S1 by an aqueous solution that contains platinum and
palladium salts. The platinum salt is hexachloroplatinic acid
H.sub.2PtCl.sub.6*6H.sub.2O, and the palladium salt is the
palladium nitrate Pd(NO.sub.3).sub.2. After maturation at ambient
temperature in a water-saturated atmosphere, the impregnated
extrudates are dried at 120.degree. C. for one night and then
calcined at 500.degree. C. under dry air. The final content of Pt
is 0.5% by weight. The final content of Pd is 1.0% by weight.
EXAMPLE 2
Preparation of a Hydrocracking Catalyst According to the Invention
(C2)
[0185] Substrate S2 is an amorphous silica-alumina that has a
chemical composition of 40% by weight of SiO.sub.2 and 60% by
weight of Al.sub.2O.sub.3. Its Si/Al molar ratio is 0.56. Its Na
content is on the order of 100-120 ppm by weight. It is in the form
of cylindrical extrudates with a diameter of 1.7 mm. Its specific
surface area is 320 m.sup.2/g. Its total pore volume, measured by
mercury porosimetry, is 0.83 ml/g. The pore distribution is
bimodal. In the field of mesopores, we observe a wide peak of
between 40 and 150 .ANG. with a dV/dD maximum toward 70 .ANG.. On
the substrate, macropores that are larger than 500 .ANG. in size
represent about 40% of the total pore volume.
[0186] Catalyst C2 is obtained by impregnation in the dry state of
substrate S2 by an aqueous solution that contains platinum and
palladium salts. The platinum salt is hexachloroplatinic acid
H.sub.2PtCl.sub.6*6H.sub.2O, and the palladium salt is the
palladium nitrate Pd(NO.sub.3).sub.2. After maturation at ambient
temperature in a water-saturated atmosphere, the impregnated
extrudates are dried at 120.degree. C. for one night and then
calcined at 500.degree. C. in dry air. The final content of Pt is
0.5% by weight. The final content of Pd is 1.0% by weight.
EXAMPLE 3
Evaluation of C1 and C2 Catalysts Under Conditions According to the
Invention
[0187] A vacuum distillate is subjected to a hydrorefining stage on
an HR448 catalyst that is marketed by Procatalyse, with a base of
nickel (3.3% by weight), molybdenum (16.5% by weight) supported on
alumina, in the presence of hydrogen, at a temperature of
385.degree. C. and at an hourly volumetric flow rate of 0.50
h.sup.-1. During this hydrorefining stage, the conversion into
products whose boiling point is less than 370.degree. C. is about
35% by weight.
[0188] The effluent that is produced during this hydrorefining
stage is subjected to a separation stage that makes it possible to
recover a 370.degree. C.+ fraction that is subjected to a
hydrocracking stage.
[0189] The physico-chemical characteristics of the 370+ fraction
that is subjected to the hydrocracking stage are described in Table
1:
1TABLE 1 Characteristics of the Fraction that is Subjected to the
Hydrocracking Stage. Density (20/4) 0.854 Organic Sulfur (ppm by
weight) 8 Organic Nitrogen (ppm by weight) 2 H2S (ppm by weight) 5
NH3 (ppm by weight) 4 Simulated Distillation Starting Point
325.degree. C. 5% Point 366.degree. C. 10% Point 384.degree. C. 50%
Point 449.degree. C. 90% Point 527.degree. C. End Point 591.degree.
C.
[0190] The fraction that is subjected to the hydrocracking stage is
introduced into a hydrocracking test unit that simulates the
operation of the second stage of a 2-stage hydrocracking process
that comprises a fixed-bed reactor with upward circulation of the
feedstock ("up flow") into which 50 ml of catalyst is
introduced.
[0191] Catalysts C1 and C2 are reduced in advance at 350.degree. C.
for 2 hours under a hydrogen flow rate of 50 l/h, under a total
pressure of 14 MPa. At the beginning of this reduction stage, the
temperature is increased to 350.degree. C. with a rate of
temperature rise of 1.degree. C. per minute.
[0192] Once the reduction is carried out, the fraction that is
described in Table 1 is then hydrocracked. The operating conditions
of this test simulating the second stage of the 2-stage
hydrocracking process are as follows:
2TABLE 2 Operating Conditions Total Pressure 14 MPa Catalyst 50 ml
Temperature 365-370-375.degree. C. Hydrogen Flow Rate 50 l/h
Feedstock Flow Rate 50 ml/h
[0193] The catalytic performance levels are expressed by the net
conversion into products that have a boiling point of less than
370.degree. C., by the coarse selectivity of middle distillate
(fraction 150-370.degree. C.) and by the ratio between the gas oil
yield and the kerosene yield in the middle distillate fraction.
They are expressed starting from the simulated distillation
results. These performance levels are determined at different
temperature levels of the test. For each temperature level, the
performance levels are measured on the catalyst after a
stabilization period, generally at least 72 hours, has elapsed.
[0194] Net conversion CN is provided by the following formula:
CN370.sup.-=[(% 370.sup.-.sub.effluents)-(%
370.sup.-.sub.feedstock)]/[100- -(% 370.sup.-.sub.feedstock)]
with:
[0195] % 370.sup.-.sub.effluents: content by mass of compounds that
have boiling points of less than 370.degree. C. in the effluents,
and
[0196] (% 370.sup.-.sub.feedstock: content by mass of compounds
that have boiling points of less than 370.degree. C. in the
feedstock.
[0197] Middle distillate coarse selectivity SB is obtained as
follows:
SB.sub.middle distillates=[(fraction(150.degree. C.-370.degree.
C.).sub.effluents)]/[(% 370.degree. C..sup.-.sub.effluents)]
[0198] The ratio between the gas oil yield and the kerosene yield
(gas oil/kerosene ratio) in the middle distillate fraction
corresponds to the ratio between the yield of the fraction
(250.degree. C.-370.degree. C.) of the effluent and the yield of
the fraction (150.degree. C.-250.degree. C.) of the effluent.
[0199] The catalytic performance levels that are obtained on the C1
and C2 catalysts are provided in Table 3 below.
3TABLE 3 Catalytic Results that are Obtained on Catalysts C1 and
C2. Gas Oil/Kerosene Middle Ratio (% by Temperature CN 370.degree.
C. - Distillate SB Weight/% by Catalyst (.degree. C.) (% by Weight)
(% by Weight) Weight) C1 360 60 77 1.4 C1 370 80 71 1.0 C1 375 90
68 0.7 C2 360 59 75 1.3 C2 370 78 70 0.9 C2 375 89 67 0.6
[0200] The C1 and C2 amorphous acid hydrocracking catalysts that
are used in the hydrocracking stage make it possible to obtain high
levels of conversion into products that have a boiling point less
than 370.degree. C. and high selectivities of middle distillates,
whereby they do so at a temperature levels such that the
temperature of the hydrocracking stage is less than the temperature
of the hydrorefining stage by 10 to 25.degree. C., whereby the
hydrorefining stage is carried out at 385.degree. C. in this
example.
[0201] The effluent that is obtained from the hydrocracking
undergoes a distillation so as to recover the kerosene fraction
(compounds that have boiling points of more than 150.degree. C. and
less than 250.degree. C.) and the gas oil fraction (compounds that
have boiling points of more than 250.degree. C. and less than
370.degree. C.). The kerosene and gas oil fractions are then
analyzed. The characteristics of these fractions are combined in
Table 4 regarding kerosene and in Table 5 regarding gas oil.
4TABLE 4 Characteristics of the Kerosene Fraction that is Obtained
Catalyst Smoke Point (mm) C1 27 C2 26
[0202]
5TABLE 5 Characteristics of the Gas Oil Fraction that is Obtained
Content of Content of Sulfur Content Aromatic Polyaromatic (ppm by
Engine Compounds Compounds Catalyst Weight) Cetane (% by Weight) (%
by Weight) C1 7 57 9.1 1.7 C2 8 56 9.3 1.9
[0203] The C1 and C2 amorphous acid hydrocracking catalysts of the
PtPd/silica-alumina type according to the invention, used in the
second hydrocracking stage of the hydrocracking process according
to the invention, make it possible to obtain kerosene and gas oil
fractions of excellent quality.
EXAMPLE 5
Evaluation of the C1 Catalyst Under Conditions that are not in
Accordance with the Invention
[0204] Catalyst C1 is evaluated under hydrocracking conditions.
[0205] The fraction that is subjected to the hydrocracking is
identical to the one that is described in Example 3 whose
characteristics are transferred into Table 1.
[0206] Before this fraction is injected, catalyst C1 undergoes a
reduction treatment under operating conditions that are identical
to the operating conditions of the reduction treatment described in
Example 3.
[0207] Once the reduction is made, the fraction that is described
in Table 1 can be treated. The operating conditions of this test,
not in accordance with the invention, are described in Table 8. The
temperature of the hydrocracking stage is equal to the temperature
of the hydrorefining stage, or 385.degree. C.
6TABLE 8 Operating Conditions Total Pressure 14 MPa Catalyst 50 ml
Temperature 385.degree. C. Hydrogen Flow Rate 50 l/h Feedstock Flow
Rate 50 ml/h
[0208] The catalytic performance levels that are obtained on
catalyst C1 under these operating conditions are provided in Table
9 below.
7TABLE 9 Catalytic Results that are Obtained on Catalyst C1. Gas
Oil/Kerosene Middle Ratio (% by Temperature CN 370.degree. -
Distillate SB Weight/% by Catalyst (.degree. C.) (% by Weight) (%
by Weight) Weight) C1 385 100 49 0.6
[0209] The conversion into products that have a boiling point of
less than 370.degree. C. is total, but the selectivity of middle
distillates (150-370.degree. C.) is very low.
* * * * *