U.S. patent application number 10/455819 was filed with the patent office on 2004-03-04 for process for hydrocracking into a stage of hydrocarbon feedstocks.
Invention is credited to Benazzi, Eric, Bourges, Patrick, Cseri, Tivadar, Dulot, Hugues, Gueret, Christophe.
Application Number | 20040040888 10/455819 |
Document ID | / |
Family ID | 29559052 |
Filed Date | 2004-03-04 |
United States Patent
Application |
20040040888 |
Kind Code |
A1 |
Benazzi, Eric ; et
al. |
March 4, 2004 |
Process for hydrocracking into a stage of hydrocarbon
feedstocks
Abstract
This invention relates to an improved process for hydrocracking
into a stage of hydrocarbon feedstocks, using in a first reaction
zone a pretreatment catalyst that exhibits a low acidity according
to a standard activity test and an amorphous acid catalyst for
hydrocracking that is free of zeolite in a second reaction zone
that is located downstream from the first. The objective of the
process is essentially the production of middle distillates, i.e.,
fractions with an initial boiling point of at least 150.degree. C.
and a final boiling point that goes just up to the initial boiling
point of the residue, for example less than 340.degree. C., or else
370.degree. C. and optionally oil bases.
Inventors: |
Benazzi, Eric; (Chatou,
FR) ; Bourges, Patrick; (Rueil Malmaison, FR)
; Gueret, Christophe; (St Romain en Gal, FR) ;
Cseri, Tivadar; (Courbevoie, FR) ; Dulot, Hugues;
(Evry, FR) |
Correspondence
Address: |
MILLEN, WHITE, ZELANO & BRANIGAN, P.C.
2200 CLARENDON BLVD.
SUITE 1400
ARLINGTON
VA
22201
US
|
Family ID: |
29559052 |
Appl. No.: |
10/455819 |
Filed: |
June 6, 2003 |
Current U.S.
Class: |
208/89 ; 208/109;
208/111.3; 208/111.35 |
Current CPC
Class: |
C10G 65/12 20130101 |
Class at
Publication: |
208/089 ;
208/109; 208/111.3; 208/111.35 |
International
Class: |
C10G 065/12 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 6, 2002 |
FR |
02/07.046 |
Claims
1. Process for hydrocracking that comprises the following
successive stages: A hydrorefining stage in which the feedstock is
brought into contact with at least one hydrorefining catalyst that
exhibits in the standard activity test a conversion rate of the
methylcyclohexane that is less than 10% by mass; A hydrocracking
stage in which at least a portion of the effluent that is obtained
from the hydrocracking stage is brought into contact with at least
one non-zeolitic hydrocracking catalyst that in the standard
activity test exhibits a conversion rate of methylcyclohexane that
is higher than 10% by mass:
2. Process according to claim 1, in which the hydrocracking
catalyst contains 10-95% by weight of silica.
3. Process according to one of the preceding claims, in which the
hydrocracking catalyst comprises a substrate that is selected from
the group that is formed by the silica-aluminas, the titanium
silica-alumina-oxide compositions, the zirconia
silica-alumina-oxide compositions, and their mixtures with a
binder.
4. Process according to one of the preceding claims, in which the
hydrocracking catalyst comprises: 0-20% by weight of at least one
promoter element that is selected from the group that is formed by
boron, phosphorus and silicon; 0-20% by weight of at least one
element of group VIIA; 0-20% by weight of at least one element of
group VIIB; 0-60% by weight of at least one element of group VB;
5-40% by weight of at least one metal of group VIB and at least one
metal of group VIII that is not noble (expressed in oxide).
5. Process according to one of the preceding claims, in which all
of the effluent that is obtained from the hydrorefining zone is
sent into the hydrocracking zone.
6. Process according to one of the preceding claims, in which the
proportion of the hydrorefining catalytic volume represents 10-60%
of the total catalytic volume.
7. Process according to one of the preceding claims in which the
hydrotreatment catalyst does not contain silica.
8. Process according to one of claims 1 to 6, in which the
hydrotreatment catalyst contains silicon as a promoter element that
is deposited on the matrix, whereby its silica content is less than
10% by weight.
9. Process according to one of the preceding claims, in which the
feedstock contains at least 20% by volume of compounds that boil
above 340.degree. C.; it exhibits a nitrogen content that is higher
than 500 ppm and a sulfur content of between 0.01 and 5% by weight.
Description
[0001] This invention relates to a so-called improved process for
hydrocracking into a stage of hydrocarbon feedstocks, comprising a
first stage that is carried out in a first reaction zone with a
hydrotreatment catalyst that exhibits a low acidity according to a
standard activity test and a last stage that is carried out in a
second reaction zone that is downstream from the first, with an
amorphous acid catalyst for hydrocracking that is free of
zeolite.
[0002] The objective of the process is essentially the production
of middle distillates, i.e., fractions with an initial boiling
point of at least 150.degree. C. and a final boiling point that
goes just up to the initial boiling point of the residue, for
example less than 340.degree. C. or else 370.degree. C. and
optionally oil bases (residue).
[0003] Prior Art
[0004] The hydrocracking of heavy petroleum fractions is a very
important refining process that makes it possible to produce, from
excess heavy feedstocks that cannot be readily upgraded, lighter
fractions such as gasolines, jet fuels and light gas oils that the
refiner seeks to adapt his production to the structure of the
demand. Some hydrocracking processes make it possible also to
obtain a strongly purified residue that can provide excellent bases
for oils. Relative to the catalytic cracking, the advantage of
catalytic hydrocracking is to provide middle distillates, jet fuels
and gas oils, of very good quality. Conversely, the gasoline that
is produced exhibits an octane number that is much lower than the
one that is obtained from the catalytic cracking.
[0005] Hydrocracking is a process that draws its flexibility from
three main elements that are the operating conditions that are
used, the types of catalysts that are used, and the fact that the
hydrocracking of hydrocarbon feedstocks can be carried out in one
or more stages.
[0006] The catalysts that are used in hydrocracking are all of the
bifunctional type that combines an acid function with a
hydrogenating function. The acid function is provided by
large-surface substrates (150 to 800 m.sup.2.g.sup.-1 generally)
that exhibit a superficial acidity, such as halogenated aluminas
(chlorinated or fluorinated in particular), combinations of boron
oxides and aluminum oxides, amorphous silica-aluminas and zeolites.
The hydrogenating function is provided either by one or more metals
of group VIII of the periodic table, such as iron, cobalt, nickel,
ruthenium, rhodium, palladium, osmium, iridium and platinum, or by
a combination of at least one metal of group VIB of the periodic
table such as molybdenum and tungsten and at least one metal of
group VIII.
[0007] The equilibrium between the acid and hydrogenating functions
is a basic parameter that governs the activity and the selectivity
of the catalyst. A weak acid function and a strong hydrogenating
function provide low-activity catalysts that work at a generally
high temperature (greater than or equal to 390.degree. C.) and at a
low feed volumetric flow rate (the VVH that is expressed by volume
of feedstock to be treated per unit of volume of catalyst and per
hour is generally less than or equal to 2) but equipped with a very
good selectivity of middle distillates. Conversely, a strong acid
function and a weak hydrogenating function provide active catalysts
that exhibit less advantageous selectivities of middle distillates.
The search for a suitable catalyst will therefore be centered on a
judicious selection of each of the functions to adjust the
activity/selectivity pair of the catalyst.
[0008] Thus, one of the great advantages of hydrocracking is to
exhibit a great flexibility at various levels: flexibility at the
level of the catalysts that are used that provides a flexibility of
feedstocks to be treated and at the level of the products that are
obtained. An easy parameter to control is the acidity of the
substrate of the catalyst.
[0009] The conventional hydrocracking catalysts can use weakly
acidic substrates, such as amorphous silica-aluminas, for example.
These systems are more particularly used to produce middle
distillates of very good quality and also, when their acidity is
very low, oil bases.
[0010] In the sparingly acidic substrates, the family of amorphous
silica-aluminas is found. A portion of the catalysts of the
hydrocracking market are based on amorphous silica-alumina that is
combined either with a metal from group VIII or, preferably when
the contents of organic compounds that contain sulfur and nitrogen
of the feedstock to be treated exceed 0.5% by weight, with a
combination of metal sulfides from groups VIB and VIII. These
systems have a very good selectivity of middle distillates, and the
products that are formed are of good quality. These catalysts, for
the less acidic among them, can also produce lubricating bases. The
drawback of all of these catalytic systems based on an amorphous
substrate is, as has been said, their low activity.
[0011] The catalysts that comprise a zeolite, for example an
FAU-structural-type Y zeolite, exhibit a catalytic activity that is
higher than that of the amorphous silica-aluminas, but exhibit
selectivities of light products that are higher.
[0012] In the processes where the hydrocracking catalyst is
zeolitic, it is necessary to pretreat the feedstock on a
hydrotreatment catalyst to eliminate the organic nitrogen that
inhibits the activity of the zeolite.
[0013] On the other hand, the amorphous hydrocracking catalysts
(without a zeolite) readily support the presence of organic
nitrogen and consequently prior hydrotreatment to remove the
heteroatoms is not used. Thus, these so-called "one stage"
processes of the prior art do not comprise hydrotreatment upstream
from the hydrocracking since the hydrotreatment takes place on the
hydrocracking catalyst.
[0014] However, the research work carried out by the applicant led
him to discover that, surprisingly enough, in a process of
hydrocracking into a stage that uses an amorphous hydrocracking
catalyst, a conversion of the hydrocarbon feedstock, a selectivity
of middle distillates (kerosene+gas oil) and a cycle time, higher
than with the processes in a known stage in the prior art, can be
obtained provided that a reaction zone that comprises a
hydrorefining catalyst that exhibits a low acidity is introduced
upstream from the amorphous hydrocracking catalyst. The addition of
this volume of hydrorefining catalyst is carried out without
increasing the overall catalytic volume nor reducing the flow rate
of the feedstock that is to be treated. Therefore, the improvements
that are described above are obtained at a constant feed volumetric
flow rate (VVH expressed by volume of feedstock to be treated per
unit of volume of the catalyst and per hour) relative to the
processes of the prior art using only an acidic amorphous catalyst
for hydrocracking.
Detailed Description of the Invention
[0015] The invention describes a process of hydrocracking,
hydrocarbon feedstocks (for example called process "in one stage")
for the production of middle distillates and optionally oil bases
that comprise at least a first reaction zone that includes
hydrorefining, and at least a second reaction zone , in which the
hydrocracking of the effluent that is obtained from the first
reaction zone is carried out.
[0016] More specifically, the invention is a hydrocracking process
that comprises the following stages:
[0017] A hydrorefining stage in which the feedstock is brought into
contact with at least one hydrorefining catalyst that exhibits in
the standard activity test a conversion rate of the
methylcyclohexane that is less than 10% by mass;
[0018] A hydrocracking stage in which at least a portion of the
effluent that is obtained from the hydrorefining stage is brought
into contact with at least one non-zeolitic hydrocracking catalyst
that in the standard activity test exhibits a conversion rate of
the methylcyclohexane that is higher than 10% by mass.
[0019] First Reaction Zone
[0020] Very varied feedstocks can be treated by the process
according to the invention and generally they contain at least 20%
by volume and often at least 80% by volume of compounds that boil
above 340.degree. C.
[0021] The feedstock can form part of, for example, LCO (light
cycle oil), atmospheric distillates, vacuum distillates, for
example, gas oil that is obtained from direct distillation of crude
or conversion units such as the FCC, the coker, or the visbreaking,
as well as feedstocks that are obtained from units for extracting
aromatic compounds from lubricating oil bases or obtained from
solvent dewaxing of lubricating oil bases, or else distillates that
are obtained by desulfurization or hydroconversion of RAT
(atmospheric residues) and/or RSV (vacuum residues) or else the
feedstock can be a desasphalted oil, or else any mixture of the
feedstocks cited above. The list above is not limiting. The
feedstocks preferably have a boiling point T5 that is higher than
340.degree. C., and better yet higher than 370.degree. C., i.e.,
that 95% of the compounds that are present in the feedstock have a
boiling point that is higher than 340.degree. C., and better yet
higher than 370.degree. C.
[0022] The nitrogen content of the hydrocarbon feedstocks that are
treated in the process according to the invention is usually higher
than 500 ppm and preferably between 500 and 5000 ppm by weight,
more preferably between 700 and 4000 ppm by weight and even more
preferably between 1000 and 4000 ppm. Generally, the sulfur content
is between 0.01 and 5% by weight, more generally between 0.2 and
4%. These feedstocks exhibit very low olefin contents.
[0023] In the first reaction zone, the feedstock undergoes at least
one hydrorefining cycle (hydrodesulfurization, hydrodenitration,
hydrogenation of aromatic compounds).
[0024] Standard catalysts can be used that contain at least one
amorphous substrate and at least one hydro-dehydrogenating element
(generally at least one non-noble element of groups VIB and VIII,
and most often at least one element of group VIB and at least one
non-noble element of group VIII).
[0025] Very advantageously, in the hydrocracking process according
to the invention, the feedstock that is to be treated is brought
into contact in the presence of hydrogen with a hydrorefining
catalyst that comprises at least one matrix, at least one
hydro-dehydrogenating element that is selected from the group that
is formed by the elements of group VIB and the non-noble group VIII
of the periodic table, optionally at least one promoter element
that is deposited on the catalyst and selected from the group that
is formed by phosphorus, boron and silicon, optionally at least one
element of group VIIA (chlorine, fluorine are preferred) and
optionally at least one element of group VIIB (manganese is
preferred), and optionally at least one element of group VB
(niobium is preferred).
[0026] The hydrorefining catalysts that are used do not contain
zeolite and exhibit a low acidity that is measured by a standard
activity test (TSA).
[0027] We will now define this test and specify what is meant by
low acidity.
[0028] The object of the standard activity test is to measure the
activity of catalysts (such as those of hydrorefining described
above) in the conversion of methylcyclohexane under the following
operating conditions:
[0029] The catalyst is sulfurized in advance under a pressure of 60
bar, at 350.degree. C. with a so-called reaction mixture that
comprises 0.5% by mass of aniline, 1.5% by mass of dimethyl
disulfide and 98% by mass of methylcyclohexane, for 4 hours. Then,
always under the same reaction flow by adding hydrogen, and under
the following reaction conditions: pressure of 60 bar, volumetric
flow rate VVh of 1 h.sup.-1, H2/reaction mixture ratio (described
above): 1000 Nl of hydrogen/l of liquid reaction mixture (Nl=normal
liters), the temperature is gradually brought to a reaction
temperature of 380.degree. C.
[0030] Under these operating conditions, a catalyst is considered
as exhibiting a low acidity and can therefore be used in the first
reaction zone if it leads to a conversion rate of methylcyclohexane
that is less than 10% by mass and preferably less than 5%.
[0031] The conversion of the methylcyclohexane reagent is defined
as the transformation of the latter into isomerization products
with 7 carbon atoms, such as, for example, the
dimethylcyclopentanes, into ring-opening products and into cracking
products. The conversion of methyl cyclohexane, as defined,
therefore takes into account all of the different products of
methyl cyclohexane. Obtaining all of these products requires the
presence of a more or less strong acid function on the
catalyst.
[0032] The hydrorefining catalysts that are used generally contain
less than 10% by weight, and preferably at most 5% by weight, of
silica. In addition, this silica is preferably brought by doping.
The silicon promoter element is then primarily located on the
matrix and can be characterized by the Castaing microprobe or
another method as described later with the hydrocracking
catalyst.
[0033] The preferred catalysts do not contain silica.
[0034] This catalyst preferably contains boron and/or silicon
and/or phosphorus as a promoter element. The contents of boron,
silicon and phosphorus are then 0.1-20%, preferably 0.1-15%, even
more advantageously 0.1-10%.
[0035] The matrices that can be used alone or in a mixture are by
way of nonlimiting example alumina, halogenated alumina, clays
(selected, for example, from among the 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.
[0036] The role of hydro-dehydrogenating function is preferably
filled by at least one metal or metal compound from group VIII that
is non-noble and VIB, preferably selected from among molybdenum,
tungsten, nickel and cobalt. This role is preferably ensured by the
combination of at least one element of group VIII (Ni, Co) with at
least one element of group VIB (Mo, W).
[0037] This catalyst can advantageously contain phosphorus;
actually, it is known in the prior art that this compound provides
two advantages to hydrorefining catalysts: a facility for
preparation in particular during the impregnation of nickel and
molybdenum solutions and a better hydrogenation activity.
[0038] In a preferred catalyst, the total content by mass of metal
oxides of groups VI and VIII is most often between 5 and 60% and
preferably between 7 and 50%, 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 preferably between 20
and 1.25 and even more preferably between 10 and 2. The content by
mass of phosphorus oxide P.sub.2O.sub.5 will be less than 15% and
preferably 10%.
[0039] Another preferred catalyst that contains boron and/or
silicon (and preferably boron and silicon) generally contains in %
by weight relative to the total mass of the catalyst at least one
metal that is selected from the following groups and with the
following contents:
[0040] 3 to 40%, preferably 3 to 35%, and even more preferably 3 to
30% of at least one metal of group VIB and optionally
[0041] 0 to 30%, preferably 0 to 25%, and even more preferably 0 to
20% of at least one metal of group VIII,
[0042] whereby the catalyst also contains at least one substrate
that is selected from the following groups with the following
contents:
[0043] 0 to 99%, advantageously 0.1 to 99%, preferably 10 to 98%,
and even more preferably 15 to 95% of at least one amorphous or
poorly crystallized matrix,
[0044] whereby said catalyst is characterized in that it also
contains
[0045] 0.1 to 20%, preferably 0.1 to 15% and even more preferably
0.1 to 10% of boron and/or 0.1 to 15%, preferably 0.1 to less than
10% and even more preferably 0.1 to 5% by weight of silicon,
[0046] and optionally
[0047] 0 to 20%, preferably 0.1 to 15%, and even more preferably
0.1 to 10% of phosphorus,
[0048] and optionally also
[0049] 0 to 20%, preferably 0.1 to 15%, and even more preferably
0.1 to 10% of at least one element that is selected from the group
VIIA, preferably fluorine.
[0050] In general, the formulas that have the following atomic
ratios are preferred:
[0051] a group VIII metal/group VIB metals atomic ratio of between
0 and 1,
[0052] a B/group VIB metals atomic ratio of between 0.01 and 3,
[0053] an Si/group VIB metals atomic ratio of between 0.01 and
1.5,
[0054] a P/group VIB metals atomic ratio of between 0.01 and 1,
[0055] a group VIIA element/group VIB metals atomic ratio of
between 0.01 and 2.
[0056] The preferred catalysts are the NiMo and/or NiW catalysts on
alumina, also the NiMo and/or NiW catalysts on alumina doped with
at least one element included in the group of atoms formed by
phosphorus, boron, silicon and fluorine.
[0057] In general, the hydrorefining catalyst contains:
[0058] 5-40% by weight of at least one non-noble element of groups
VIB and VIII (% oxide),
[0059] 0-20% of at least one promoter element that is selected from
among phosphorus, boron, (% oxide), preferably between 0.1-10% and
even more preferably between 0.1 and 5% by weight; 0 to less than
10% by weight of promoter silicon, preferably 0.1-5%;
advantageously boron and/or silicon are present, and optionally
phosphorus.
[0060] 0-20% of at least one element of group VIIB (manganese, for
example)
[0061] 0-20% of at least one element of group VIIA (fluorine,
chlorine, for example)
[0062] 0-60% of at least one element of group VB (niobium, for
example)
[0063] 0.1-95% of at least one matrix, and preferably alumina.
[0064] The catalysts that are described above are generally used to
ensure the hydrorefining that is also called hydrotreatment.
[0065] Prior to the injection of the feedstock, the catalysts that
are used in the process according to this invention are preferably
subjected in advance to a sulfurization treatment that makes it
possible to transform, at least in part, metallic radicals into
sulfide before they are brought into contact with the feedstock
that is 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.
[0066] A standard sulfurization method that is well known to one
skilled in the art consists in heating in the presence of hydrogen
sulfide (pure or, for example, under a stream of a
hydrogen/hydrogen sulfide mixture) to a temperature of between 150
and 800.degree. C., preferably between 250 and 600.degree. C.,
generally in a flushed-bed reaction zone.
[0067] In the first reaction zone of the process, the feedstock is
brought into contact, in the presence of hydrogen, with at least
one catalyst as described above, at a temperature of between 330
and 450.degree. C., preferably 360-420.degree. C., under a pressure
that is higher than 7.5, preferably higher than 8.2 MPa, preferably
higher than 9.0 MPa, and even more preferably higher than 11.0 MPa
and lower than 20 MPa, whereby the volumetric flow rate is between
0.1 and 6 h.sup.-1, preferably 0.2-3 h.sup.-1, and the amount of
hydrogen that is introduced is such that the liter of
hydrogen/liter of hydrocarbon volumetric ratio is between 100 and
2000 l/l. Under these conditions, the conversion into products
boiling below 340.degree. C. (and even below 370.degree. C.) is
most often less than 30% by weight, usually less than 20% and even
15%. A conversion in this stage is not desired.
[0068] In the first reaction zone of the process according to the
invention, a significant reduction of the content of organic
nitrogen-containing and sulfur-containing compounds and of
condensed polycyclic aromatic hydrocarbons is obtained. Under these
conditions, at least a portion of the nitrogen-containing and
sulfur-containing organic products of the feedstock are also
transformed into H.sub.2S and into NH.sub.3.
[0069] The operating conditions under which this hydrorefining is
carried out are such that the organic nitrogen content of the
feedstock that is obtained from this hydrorefining and that is then
admitted to the hydrocracking catalyst bed is less than 200 ppm by
weight and preferably less than 100 ppm by weight and even more
preferably less than 80 ppm by weight.
[0070] The effluent that is obtained from this first reaction zone
is at least in part, and preferably completely, introduced into the
second reaction zone of the process according to the invention. An
intermediate separation of the gases can be carried out.
[0071] Second Reaction Zone
[0072] The operating conditions that are used in the reactor or
reactors that are located downstream from the first reaction zone
of the process according to the invention are: a temperature that
is higher than 200.degree. C., often between 250-480.degree. C.,
advantageously between 320 and 450.degree. C., preferably between
330 and 425.degree. C., under a pressure of between 3 MPa and 20
MPa, preferably higher than 7.5, preferably higher than 8.2 MPa,
preferably higher than 9.0 MPa, or else higher than 11.0 MPa and
less than 20 MPa, whereby the volumetric flow rate is between 0.1
and 20 h.sup.-1, and preferably 0.1-6 h.sup.-1, preferably 0.2-3
h.sup.-1, and the amount of hydrogen that is introduced is such
that the liter of hydrogen/liter of hydrocarbon volumetric ratio is
between 80 and 5000 l/l and most often between 100 and 2000 l/l.
Under these conditions, the overall conversion of the process is
generally at least 50% by weight and preferably at least 60% when
the objective is to obtain middle distillates.
[0073] The process according to the invention is very
advantageously operable within 3 ranges of pressure making it
possible to obtain different yields and different qualities of
products.
[0074] It is thus possible to work at low total pressures,
generally of at most 7.0 MPa, or high pressures, generally of at
least 11 MPa, or within the intermediate range of moderate
pressures that are higher than 7 MPa and less than 11 MPa,
generally of between 8.2-11 MPa.
[0075] Thus, in an advantageous way, within the ranges of low
pressures and primarily within ranges of moderate pressures, higher
conversion levels are achieved than with single hydrocracking
catalysts.
[0076] This increase (it is the same at high pressures) is obtained
only from the conversion provided by hydrotreatment (which is
actually fairly low) but primarily from modification of the
feedstock.
[0077] These operating conditions that are used in the second
reaction zone of the process according to the invention make it
possible to achieve conversions per pass into products that have
boiling points of less than 340.degree. C. and, better, less than
370.degree. C., greater than 30% by weight and even more preferably
between 40 and 95% by weight.
[0078] The second reaction zone comprises at least one reactor that
contains at least one amorphous catalyst bed of hydrocracking. The
hydrocracking catalysts that are used in the hydrocracking
processes are all of the bifunctional type combining an acid
function with a hydrogenating function. The acid function is
provided by large-surface substrates (generally 150 to 800
m.sup.2.g.sup.-1) that exhibit a superficial acidity, such as the
halogenated aluminas (chlorinated or fluorinated in particular),
combinations of boron oxides and aluminum oxides, combinations of
titanium oxide, silicon oxide and aluminum oxide, combinations of
zirconium oxides, aluminum oxides and silicon oxides, amorphous
silica-aluminas, halogenated silica-aluminas (chlorinated or
fluorinated in particular). These oxides or combinations of
amorphous oxides can be obtained by any of the synthesis methods
that are known to one skilled in the art.
[0079] The hydrogenating function is provided either by one or more
metals of group VIII of the periodic table or by a combination of
at least one metal of group VIB of the periodic table and at least
one metal of group VIII.
[0080] Said catalyst comprises at least one amorphous acid function
such as a silica-alumina, and at least one hydro-dehydrogenating
function, optionally at least one matrix. Optionally, it can also
contain at least one element that is selected from among boron,
phosphorus and silicon, at least one element of group VIIA
(chlorine, fluorine, for example), at least one element of group
VIIB (manganese, for example), and at least one element of group VB
(niobium, for example).
[0081] According to a preferred method according to the invention,
the hydrorefining catalyst and the hydrocracking catalyst are
placed in separate reactors. In another method, they are placed in
the same reactor but in separate beds, and the entire hydrotreated
effluent moves on to hydrocracking.
[0082] In all of the cases, the reactor or reactors that contain
the hydrorefining catalyst is (are) upstream from the reactor or
reactors containing the hydrocracking catalyst. In other words, the
hydrocracking catalyst comes from a hydrorefining catalyst with a
lower acidity than the hydrocracking catalyst.
[0083] Amorphous Catalyst
[0084] The non-zeolitic hydrocracking catalyst contains an
amorphous acid function, generally a silica-alumina. It also
contains a hydro-dehydrogenating function and optionally a matrix.
It can also optionally contain at least one promoter element
(boron, phosphorus and/or silicon); their content is generally
0-20%, preferably at least 0.1%, advantageously 0.1-15% or else
0.1-10% or 0.1-5%. It optionally contains at least one element of
group VIIA (chlorine, fluorine) whose content is generally 0-20%,
preferably at least 0.1%, advantageously 0.1-15% or else 0.1-10%;
fluorine is preferred. It can also contain at least one element of
group VIIB (manganese, for example), and at least one element of
group VB (niobium, for example). The element content of group VIIB
is 0-20%, preferably at least 0.1%. The element content by weight
of group VB is 0-60%, preferably at least 0.1%.
[0085] The content by weight of silica of said silica-alumina is
between 10 and 95% and preferably between 20 and 90% and even more
preferably between 30 and 90%. These silica-aluminas can be
prepared by any of the methods that are known to one skilled in the
art such as, for example, the methods of cogelation,
coprecipitation, . . ..
[0086] The amorphous acid function can also be ensured by ternary
mixtures of oxides such as titanium silica-alumina-oxide
compositions or else zirconia silica-alumina-oxide compositions.
The silica-alumina substrates, or titanium silica-alumina-oxide
substrates or else zirconia silica-alumina-oxide substrates are
prepared by all of the methods that are known to one skilled in the
art such as the methods of cogelation, coprecipitation, . . ..
[0087] The content by weight of silica of said ternary oxides is
between 10 and 90% and preferably between 20 and 90% and even more
preferably between 30 and 85%. These ternary oxides can be prepared
by any of the methods that are known to one skilled in the art,
such as, for example, the methods of cogelation, coprecipitation, .
. ..
[0088] The role of hydro-dehydrogenating function for the
hydrocracking catalyst that comprises at least one acid function,
as defined above, is preferably filled by at least one non-noble
metal or metal compound of group VIII and of group VIB preferably
selected from among molybdenum, tungsten, nickel and cobalt. This
role is preferably ensured by the combination of at least one
element of group VIII (Ni) with at least one element of group VIB
(Mo, W), whereby the total content by weight of said metals is
generally 5-40%.
[0089] Advantageous amorphous catalysts for hydrocracking are the
NiMo and/or NiW catalysts on silica-alumina or on titanium
silica-alumina-oxide or else on zirconia silica-alumina-oxide.
These catalysts can be prepared by any of the methods that are
known to one skilled in the art.
[0090] The catalysts that are described above and that are used in
the second reaction zone are characterized in that they do not
contain zeolite and exhibit a higher acidity than that of catalysts
that are used in the first reaction zone upstream. Their acidity is
measured by the standard activity test (TSA) that is described
above.
[0091] Under these operating conditions, a catalyst is considered
as exhibiting a sufficient acidity to be used in the second
reaction zone if it results in a methylcyclohexane conversion rate
that is higher than 10% by mass and preferably higher than 15%.
[0092] The substrate on which the metals are deposited can consist
of silica-aluminas or ternary oxides as defined in the paragraphs
above or result from mixing said silica-aluminas or ternary oxides
with a binder such as alumina (Al.sub.2O), clays, and any mixture
of binders cited above. The preferred binder is 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 catalyst is such that it makes it possible
to obtain a level of acidity as described in the standard activity
test (TSA) in the preceding paragraph. The substrate, defined as
the mixing of a binder and at least one acid function that is
selected from the group that is formed by the silica-aluminas, the
ternary oxides such as the titanium silixa-alumina oxides and the
zirconia silica-alumina-oxides, most often comprises a content by
weight of silica of at least 10% and preferably higher than 20% and
less than 95%, or, better, 90%.
[0093] The catalysts whose substrate consists only of silica
alumina or ternary oxides without any binder are preferred,
however; they contain 10-95% by weight of silica.
[0094] The substrate can be prepared by shaping silica-alumina or
ternary oxides with or without a 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 by 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.
[0095] The catalysts that comprise at least one silica-alumina or a
ternary oxide as described above in the patent, a hydrogenating
function that is generally ensured preferably by at least one metal
that is selected from the group that is formed by the metals of
group VIB and group VIII of the periodic table, also preferably
comprise at least one element that is selected from the group that
is formed by boron, silicon and phosphorus. The catalyst optionally
contains at least one element of group VIIA, preferably chlorine
and fluorine, and also optionally at least one element of group
VIIB.
[0096] Boron, silicon, and/or phosphorus are preferably located on
silica-alumina, ternary oxide and/or the substrate in the case
where a binder was used for shaping the silica-alumina or ternary
oxide used.
[0097] The promoter element that is introduced, and in particular
silicon, is primarily located on the silica-alumina and/or the
substrate and can be characterized by techniques such as the
Castaing microprobe (distribution profile of various elements),
transmission electron microscopy combined with an X analysis of the
components of catalysts, or else by combining distribution mapping
of the elements that are present in the catalyst by electronic
microprobe.
[0098] The metals of group VIB and group VIII of the catalyst of
this invention can be present completely or partially in metallic
form and/or oxide form and/or sulfide form.
[0099] In the case where the acid phase is an amorphous
silica-alumina, a usable catalyst, for example, comprises at least
one hydro-dehydrogenating element (preferably deposited on the
substrate) and a substrate that comprises (or preferably consists
of) at least one silica-alumina, whereby said silica-alumina has
the following characteristics:
[0100] 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,
[0101] An Na content that is less than 300 ppm by weight and
preferably less than 200 ppm by weight,
[0102] A total pore volume of between 0.5 and 1.2 ml/g that is
measured by mercury porosimetry,
[0103] Whereby the porosity of said silica-alumina is as
follows:
[0104] i/ The volume of mesopores whose diameter is between 40
.ANG. and 150 .ANG., and whose mean diameter varies between 80 and
120 .ANG. represents between 30 and 80% of the total pore volume
defined above and preferably between 40 and 70%.
[0105] ii/ The volume of macropores, whose diameter is larger than
500 .ANG., and preferably between 1000 .ANG. and 10,000 .ANG.,
represents between 20 and 80% of the total pore volume and
preferably between 30 and 60% of the total pore volume, and even
more preferably the volume of the macropores represents at least
35% of the total pore volume.
[0106] A specific surface area that is larger than 200 m.sup.2/g
and preferably larger than 250 m.sup.2/g.
[0107] In the case where the catalyst above is used in
hydrocracking, a catalyst for hydrotreatment that contains Ni, Mo
and P and alumina, or Ni, Mo, phosphorus, alumina and silicon will
be preferred; whereby the latter will be brought as a dopant.
[0108] Prior to the injection of the hydrocarbon effluent in the
second reaction zone of the process according to this invention,
the catalyst is subjected to a sulfurization treatment that makes
it possible to transform, at least in part, the metallic radicals
into sulfide before they are brought into contact with the
feedstock that is 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.
[0109] A standard sulfurization method that is well known to one
skilled in the art consists in heating in the presence of hydrogen
sulfide (pure or, for example, under a stream of a
hydrogen/hydrogen sulfide mixture), to a temperature of between 150
and 800.degree. C., preferably between 250 and 600.degree. C.,
generally in a flushed-bed reaction zone.
[0110] The proportion of catalytic volume of the catalyst with low
acidity that is present in the first reaction zone represents,
according to the cases of 10 to 60% of total catalytic volume,
preferably between 15 and 50% and even more preferably between 20
and 45% of the total catalytic volume.
[0111] Final Separation
[0112] The effluent at the outlet of the second reaction zone of
the hydrocracking process according to the invention is subjected
to a so-called final separation (for example by atmospheric
distillation optionally followed by a vacuum distillation) so as to
separate the gases (such as ammonia (NH.sub.3) and hydrogen sulfide
(H.sub.2S), as well as the other light gases that are present,
hydrogen and conversion products. . . ). At least one residual
liquid fraction that essentially contains products whose boiling
point is generally higher than 340.degree. C. and that can be at
least in part recycled upstream from the second reaction zone of
the process according to the invention, and preferably upstream
from the hydrocracking catalyst that is based on silica-alumina is
obtained in a facility for production of middle distillates.
[0113] The conversion into products that have boiling points of
less than 340.degree. C. or else less than 370.degree. C. is at
least 50% by weight.
[0114] The following examples illustrate the invention without,
however, limiting its scope.
EXAMPLE 1
Preparation of Catalysts
[0115] Hydrorefining catalyst C1 is obtained by dry impregnation of
a substrate A that consists of cubic gamma-alumina, in the form of
cylindrical extrudates with a diameter of 1.6 mm and that have a
surface area of 250 m2/g, a pore volume that is measured with
mercury of 0.60 ml/g, by an aqueous solution that contains nickel
salts, molybdenum salts and phosphoric acid. The nickel salt is
nickel nitrate Ni(NO.sub.3).sub.2.6H.sub.2O and that of molybdenum
is ammonium heptamolybdate
(NH.sub.4).sub.6Mo.sub.7O.sub.24.4H.sub.2O.
[0116] After maturation at ambient temperature in a water-saturated
atmosphere, the impregnated extrudates are dried at 120.degree. C.
and then calcined at 500.degree. C. in dry air. The final content
of MoO.sub.3 is 17.1%, and that of NiO is 3.7% by mass and that of
P.sub.2O.sub.5 is 4.1% by mass.
[0117] Substrate B is a 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 cc/g. The pore distribution is
bimodal. In the domain of mesopores, we observe a broad peak of
between 40 and 150 .ANG. with a dV/dD maximum toward 70 .ANG.. On
the substrate, macropores that have a size of greater than 500
.ANG. represent about 40% of the total pore volume.
[0118] Catalyst C2 is obtained by dry impregnation of substrate B
by an aqueous solution that contains tungsten and nickel salts. The
tungsten salt is ammonium metatungstate
(NH.sub.4).sub.6H.sub.2W.sub.12O.sub.40*4H- .sub.2O and that of
nickel is nickel nitrate Ni(NO.sub.3).sub.2*6H.sub.2O. 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 WO.sub.3 is 25% by weight. The final content of NiO is
3.5% by weight.
EXAMPLE 2
Standard Activity Test (TSA) on Catalysts C1 and C2
[0119] Catalysts C1 and C2 are subjected to a standard activity
test (TSA) as follows. The sulfurization stage of the catalysts is
carried out at a pressure of 60 bar, at 350.degree. C. with a
mixture that comprises 0.5% by mass of aniline, 1.5% by mass of
dimethyl disulfide and 98% by mass of methylcyclohexane, for 4
hours.
[0120] The catalyst is sulfurized in a fixed-bed reactor at a
pressure of 60 bar, at 350.degree. C. by means of a mixture that
comprises 0.5% by mass of aniline, 1.5% by mass of dimethyl
disulfide, and 98% by mass of methylcyclohexane for 4 hours. Then,
still in the same reaction stream and under the following operating
conditions: pressure of 60 bar, volumetric flow rate VVh of 1
h.sup.-1, H2/reaction mixture ratio (described above): 1000 Nl of
hydrogen/l of liquid reaction mixture (Nl=normal liters), the
temperature is brought gradually to 380.degree. C.
[0121] Under these conditions, catalyst C1 leads to a conversion of
methylcyclohexane of 6% by weight. It is therefore, as defined
above in the text, a catalyst that exhibits a low acidity.
[0122] Under the same operating conditions, catalyst C2 leads to a
conversion of methylcyclohexane of 18% by weight. It therefore
exhibits an acidity that is higher than that of C2.
[0123] The conversion of the methylcyclohexane reagent is defined
as the transformation of the latter into isomerization products
with 7 carbon atoms, such as, for example, the
dimethylcyclopentanes, into ring-opening products and into cracking
products. The conversion of methylcyclohexane, as defined,
therefore takes into account all of the different products of the
methylcyclohexane. Obtaining all of these products requires the
presence of a more or less strong acid function on the
catalyst.
EXAMPLE 3
Use According to the Invention
[0124] The catalysts whose preparations are described in Example 1
are used to carry out the hydrocracking of a vacuum distillate
whose main characteristics are provided below:
1 Type of feedstock Vacuum distillate Density at 15.degree. C.
0.941 Sulfur, % by weight 2.9 Nitrogen, ppm by weight 1400
Simulated Distillation DS: 0.5% p.degree. C. 399 DS: 10% p.degree.
C. 422 DS: 50% p.degree. C. 494 DS: 90% p.degree. C. 566 DS: Final
point .degree. C. 619
[0125] In the case of use according to the process of the invention
by using a pilot unit that comprises two flow-through fixed-bed
reactors, the fluids circulate from bottom to top (up-flow). In the
first reactor (upstream) is placed hydrorefining catalyst C1 that
is described in Example 1, and in the second reactor (downstream)
is placed the amorphous hydrocracking catalyst C2 that is also
described in Example 1. The volume of catalyst C1 represents 1/3 of
the total catalytic volume (C1+C2) and the volume of catalyst C2
represents the 2/3 remaining.
[0126] The sulfurization of the catalyst is carried out at 120 bar
and at 350.degree. C. by means of a direct distillation gas oil
diluted with 2% by weight of DMDS.
[0127] After sulfurization, the catalytic test is carried out under
the following conditions:
2 Total pressure 14 MPa T = 400.degree. C. Overall VVH 0.7
h.sup.-1
[0128] The volumetric flow rate (VVh) is expressed relative to the
entire catalytic volume (catalysts C1+C2).
[0129] The catalytic performance levels are expressed by the net
conversion of products that have a boiling point of less than
370.degree. C., by the net selectivity of a middle distillate
fraction of 150-370.degree. C., and the ratio of gas oil
yield/kerosene yield in the middle distillate fraction. They are
expressed from the results of simultaneous distillation.
[0130] Net conversion CN is assumed to be equal to:
CN 370.degree. C.=[(% of 370.degree. C..sup.-.sub.effluents)-(% of
370.degree. C..sup.-.sub.feedstock)/[100-(% of 370.degree.
C..sub.feedstock)]
[0131] The net selectivity of middle distillate SN is assumed to be
equal to:
SN definition=[(fraction of 150-370.sub.effluents)=(fraction of
150-370.sub.fedstock)/[(% of 370.degree. C..sub.effluents)-(% of
370.degree. C..sup.-.sub.feedstock)]
[0132] The gas oil yield/kerosene yield (go./ker.ratio) in the
middle distillate fraction is assumed to be equal to:
Go./ker.ratio=yield of the fraction (250.degree. C.-370.degree. C.)
of the effluent/yield of the fraction (150.degree. C.-250.degree.
C.) in the effluent.
[0133] The catalytic performance levels that are obtained are
provided in Table 1 below.
EXAMPLE 4
Use Not in Accordance with the Invention
[0134] In this example, the amorphous hydrocracking catalyst C2 is
not used according to the invention. In this case, catalyst C2 is
used by itself. The sulfurization of the catalyst is carried out at
120 bars, at 350.degree. C. with a direct distillation gas oil that
is diluted with 2% by weight of DMDS.
[0135] After sulfurization, the catalytic test is carried out under
the following conditions:
3 Total pressure 14 MPa T = 400.degree. C. Overall VVH 0.7
h.sup.-1
[0136] The volumetric flow rate (VVh) is expressed relative to the
catalytic volume of catalyst C2.
[0137] The definitions of conversions, selectivities and
go./ker.ratio are equivalent to those that are described in Example
3.
[0138] The catalytic performance levels that are thus obtained are
provided in the tables below.
4TABLE 1 Catalytic Results CN 370.degree. C. Catalyst VVh
(h.sup.-1) T.degree. C. % by weight C1 + C2 0.7 400 59 C2 0.7 400
50
[0139]
5TABLE 2 Catalytic Results SN % by weight Middle Go./Ker. Ratio CN
370.degree. C. Distillate % by weight/% Catalyst VVh (h.sup.-1) %
by weight (DM) by weight C1 + C2 0.7 59 74 1.35 C2 0.7 59 70
1.28
[0140] The results that are noted in Table 1 demonstrate that, for
the same volumetric flow rate, amorphous hydrocracking catalyst C2
leads to a higher net conversion at iso temperature when it is used
according to the process of the invention, i.e., with a catalyst C1
with low acidity upstream, than when it is used by itself.
[0141] The results of Table 2 are obtained at the same volumetric
flow rate, and the reaction temperature was adjusted to obtain the
same net conversion in the cases.
[0142] The results that are noted in Table 2 demonstrate that for
the same volumetric flow rate and the same net conversion,
amorphous hydrocracking catalyst C2 leads to a higher DM
selectivity and a higher go./ker.ratio, when it is used according
to the process of the invention, i.e., with a catalyst C1 with low
acidity upstream, than when it is used by itself.
[0143] In other words, relative to a process that uses a volume V1
of a hydrocracking catalyst that is not preceded by a
hydrotreatment, the upstream installation of hydrocracking of a
volume V2 of a hydrotreatment catalyst makes it possible to
increase the overall conversion and selectivity of the process
while offering the possibility of reducing the volume of
hydrocracking catalyst, which is often the most expensive
catalyst.
[0144] Without further elaboration, it is believed that one skilled
in the art can, using the preceding description, utilize the
present invention to its fullest extent. The preceding preferred
specific embodiments are, therefore, to be construed as merely
illustrative, and not limitative of the remainder of the disclosure
in any way whatsoever.
[0145] In the foregoing and in the examples, all temperatures are
set forth uncorrected in degrees Celsius, and all parts and
percentages are by weight, unless otherwise indicated.
[0146] The entire disclosure of all applications, patents and
publications, cited herein and of corresponding French Application
No. 02/07,046, filed on Jun. 6, 2002, is incorporated by reference
herein.
[0147] The preceding examples can be repeated with similar success
by substituting the generically or specifically described reactants
and/or operating conditions of this invention for those used in the
preceding examples.
[0148] From the foregoing description, one skilled in the art can
easily ascertain the essential characteristics of this invention
and, without departing form the spirit and scope thereof, can make
various changes and modifications of the invention to adapt it to
various usages and conditions.
* * * * *