U.S. patent application number 12/912025 was filed with the patent office on 2011-04-28 for method of hydrotreating feeds from renewable sources with indirect heating using a catalyst based on molybdenum.
This patent application is currently assigned to IFP Energies nouvelles. Invention is credited to Laurent Bournay, Thierry Chapus, Antoine Daudin, Wilfried Weiss.
Application Number | 20110094149 12/912025 |
Document ID | / |
Family ID | 42229261 |
Filed Date | 2011-04-28 |
United States Patent
Application |
20110094149 |
Kind Code |
A1 |
Weiss; Wilfried ; et
al. |
April 28, 2011 |
METHOD OF HYDROTREATING FEEDS FROM RENEWABLE SOURCES WITH INDIRECT
HEATING USING A CATALYST BASED ON MOLYBDENUM
Abstract
The invention describes a method of treating feeds from
renewable sources comprising a hydrotreatment stage comprising at
least two catalytic zones in which the entry stream comprising said
feed mixed with at least a part of a hydrotreated liquid effluent
from stage b) is introduced into the first catalytic zone at a
temperature comprised between 150 and 260.degree. C., and the
effluent from the first catalytic zone is then introduced, mixed
with at least a part of a hydrotreated liquid effluent from stage
b) and preheated, into the following catalytic zone or zones at a
temperature comprised between 260 and 320.degree. C., and a stage
of separation of the effluent from the hydrotreatment stage
permitting the separation of a gaseous effluent and a hydrotreated
liquid effluent of which at least a part is recycled at the top of
each catalytic zone, said method using, in at least the catalytic
zone or zones following the first, a bulk or supported catalyst
comprising an active phase constituted by a sulphidized group VIB
element, the group VIB element being molybdenum.
Inventors: |
Weiss; Wilfried; (Lyon,
FR) ; Bournay; Laurent; (Chaussan, FR) ;
Chapus; Thierry; (Lyon, FR) ; Daudin; Antoine;
(Corbas, FR) |
Assignee: |
IFP Energies nouvelles
Rueil-Malmaison Cedex
FR
|
Family ID: |
42229261 |
Appl. No.: |
12/912025 |
Filed: |
October 26, 2010 |
Current U.S.
Class: |
44/308 ;
44/307 |
Current CPC
Class: |
C10G 2300/1014 20130101;
C10G 65/04 20130101; C10G 2300/4081 20130101; C10G 2300/1018
20130101; C10G 2300/4006 20130101; C10G 3/48 20130101; Y02P 30/20
20151101; C10G 3/46 20130101; C10G 3/50 20130101 |
Class at
Publication: |
44/308 ;
44/307 |
International
Class: |
C10L 1/188 20060101
C10L001/188 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 27, 2009 |
FR |
09/05.160 |
Claims
1. Method of treating feeds from renewable sources comprising: a
hydrotreatment stage a) comprising at least two catalytic zones in
which the entry stream comprising said feed mixed with at least a
part of a hydrotreated liquid effluent from stage b) and a
hydrogen-rich gas is introduced into the first catalytic zone at a
temperature comprised between 150 and 260.degree. C., and in which
the effluent from the first catalytic zone is then introduced,
mixed with at least a part of the hydrotreated liquid effluent from
stage b), and preheated, into the following catalytic zone or zones
at a temperature comprised between 260 and 320.degree. C., a stage
b) of separation of the effluent from the hydrotreatment stage a)
permitting the separation of a gaseous effluent and a hydrotreated
liquid effluent of which at least a part is recycled at the top of
each catalytic zone of stage a), said method using, in at least the
catalytic zone or zones following the first of the hydrotreatment
stage a), a supported or bulk catalyst comprising an active phase
constituted by a sulphidized group VIB element, the group VIB
element being molybdenum.
2. Method according to claim 1 in which the entry stream is
introduced into the first catalytic zone at a temperature comprised
between 180 and 210.degree. C.
3. Method according to claim 1 in which said hydrotreated liquid
effluent from the separation stage b) is either cooled, or
preheated, before being recycled at the top of the first catalytic
zone of the hydrotreatment stage a).
4. Method according to claim 1 in which the catalyst used in the
first catalytic zone of the hydrotreatment stage a) is a catalyst
comprising at least one group VIII metal chosen from nickel and
cobalt and/or at least one group VIB metal chosen from molybdenum
and tungsten, alone or mixed and a support chosen from the group
formed by alumina, silica, the silica-aluminas, magnesia, clays and
the mixtures of at least two of these minerals.
5. Method according to claim 1 in which the catalyst used in the
first catalytic zone of the hydrotreatment stage a) is a supported
or bulk catalyst comprising an active phase constituted by a
sulphidized group VIB element, the group VIB element being
molybdenum.
6. Method according to claim 5 in which said supported catalyst
comprises a doping element chosen from phosphorus, boron and
silicon, deposited on the support.
7. Method according to claim 1 in which the hydrotreatment stage a)
comprises two catalytic zones.
8. Method according to claim 1 in which said effluent from the
first catalytic zone is then introduced, mixed with at least a part
of the hydrotreated liquid effluent from stage b) and preheated,
into the following catalytic zone called second catalytic zone, at
a temperature greater than 300.degree. C.
9. Method according to claim 1 in which the catalyst used in the
second catalytic zone of the hydrotreatment stage a) is identical
to that used in the first catalytic zone of stage a).
10. Method according to claim 1 in which the overall recycle rate
is comprised between 1 and 5.
11. Method according to claim 1 in which at least a part of the
non-recycled hydrotreated liquid effluent then undergoes a
hydroisomerization stage in the presence of a selective
hydroisomerization catalyst.
12. Method according to claim 11 in which the hydroisomerization
catalyst comprises at least one group VIII metal and/or at least
one group VIB metal as hydrodehydrogenating function and at least
one molecular sieve or an amorphous mineral support as
hydroisomerizing function.
13. Method according to claim 11 in which said molecular sieve is a
10 MR one-dimensional ZBM-30 zeolite molecular sieve synthesized
with the organic structuring agent triethylenetetramine.
14. Method according to claim 11 in which the hydroisomerization
stage operates at a temperature comprised between 150 and
500.degree. C., at a pressure comprised between 1 MPa and 10 MPa,
at an hourly space velocity advantageously comprised between 0.1
h.sup.-1 and 10 h.sup.-1, at a hydrogen flow rate such that the
hydrogen/hydrocarbons volume ratio is advantageously comprised
between 70 and 1000 Nm.sup.3/m.sup.3 of feed.
15. Method according to claim 1 in which the feeds from renewable
sources are chosen from oils and fats of vegetable or animal
origin, or mixtures of such feeds, containing triglycerides and/or
free fatty acids and/or esters, said vegetable oils being able to
be raw or refined, totally or in part, and from the plants: colza,
sunflower, soya, palm, cabbage palm, olive, coconut, and jatropha.
Description
FIELD OF THE INVENTION
[0001] The international context of the years 2005-2010 is marked
firstly by the rapid growth in the demand for fuels, in particular
gas oil bases in the European Community, and then by the extent of
the problems linked with global warming and the emission of
greenhouse gases. The result is a desire to reduce energy
dependency vis-a-vis raw materials of fossil origin and the
reduction of emissions of CO.sub.2. In this context, the search for
new feeds from renewable sources that can easily be integrated into
the traditional refining and fuel production process plays an
increasingly important part.
[0002] For this reason, the integration into the refining process
of new products of vegetable origin, from the conversion of
lignocellulosic biomass or from the production of vegetable oils or
animal fats, has attracted a great deal more interest in recent
years due to the increase in the cost of fossil materials.
Similarly, traditional biofuels (principally ethanol or methyl
esters of vegetable oils) have come to be considered a genuine
supplement to petroleum bases in fuel pools.
[0003] The strong demand for gas oil and kerosene fuels, coupled
with the extent of the concerns associated with the environment,
increases the interest in using feeds from renewable sources. Among
these feeds, there may be cited for example vegetable oils (for use
in food or not) or those from algae, animal fats or used frying
oils, raw or pre-treated, as well as mixtures of such feeds.
[0004] These feeds essentially contain chemical structures of
triglyceride type that a person skilled in the art also knows under
the name fatty acid triesters as well as free fatty acids and the
hydrocarbon chains which constitute these molecules are essentially
linear and have a number of unsaturations per chain generally
comprised between 0 and 3 but which can be higher in particular for
oils from algae. Vegetable oils and other feeds of renewable origin
also comprise various impurities and in particular compounds
containing heteroatoms such as nitrogen, and elements such as Na,
Ca, P, Mg.
[0005] The very high molecular weight (more than 600 g/mol) of the
triglycerides and the high viscosity of the considered feeds mean
that their use, direct or mixed in gas oils, poses problems for
modern engines of HDI type (compatibility with very high-pressure
injection pumps, problem of clogging of injectors, uncontrolled
combustion, low yields, emissions of toxic non-burned residues).
However, the hydrocarbon chains which constitute the triglycerides
are essentially linear and their length (number of carbon atoms) is
compatible with the hydrocarbons present in the gas oils. It is
therefore necessary to convert these feeds in order to obtain a gas
oil base of good quality and/or a kerosene cut meeting the
specifications in force, after mixing or addition of additives
known to a person skilled in the art. For diesel, the final fuel
must conform to standard EN590, and for kerosene it must meet the
specifications described in IATA (International Air Transport
Association) Guidance Material for Aviation Turbine Fuel
Specifications such as the standard ASTM D1655.
[0006] The hydrotreatment of vegetable oils uses complex reactions
which are favoured by a hydrogenating catalytic system. These
reactions comprise in particular: [0007] hydrogenation of
unsaturations, [0008] deoxygenation according to two reaction
pathways: [0009] hydrodeoxygenation: elimination of oxygen by
consumption of hydrogen and leading to formation of water [0010]
decarboxylation/decarboxylation: elimination of oxygen by formation
of carbon monoxide and dioxide: CO and CO.sub.2 [0011]
hydrodenitrogenation: elimination of nitrogen by formation of
NH.sub.3.
[0012] Sulphide catalysts are known to be active vis-a-vis
hydrotreatment reactions: hydrodesulphurization,
hydrodenitrogenation, hydrodeoxygenation and
hydrodemetallization.
[0013] Numerous works of the literature mention their potential for
deoxygenation reactions used for the catalytic conversion of
bio-liquid (from oil products or lignocellulose) to fuel. In
particular, Senol et al (Applied Catalysis A: General vol. 326,
2007, pp. 236-244) studied the conversion of model molecules of
ester type representing the hydrophilic (ester group) and
lipophilic (alkyl chain) function of the triglycerides present in
vegetable oils in the presence of CoMo or NiMo/Al2O3 sulphide
catalysts.
[0014] Unlike reduced metal-based catalysts, the use of solids
based on sulphides of transition metals permits the production of
paraffins from molecules of ester type according to two reaction
pathways: hydrodeoxygenation and
decarboxylation/decarboxylation.
[0015] The hydrogenation of unsaturations (carbon-carbon double
bonds) is strongly exothermic and the increase in temperature
resulting from the release of heat of the saturation reactions of
the double bonds permits thermal levels to be reached where the
rates of the deoxygenation/decarbonylation reactions start to be
significant. Hydrodeoxygenation and decarboxylation/decarbonylation
are also exothermic reactions. Hydrodenitrogenation is a more
difficult reaction, requiring more severe temperature conditions
than hydrodeoxygenation and decarboxylation/decarbonylation.
However, hydrodenitrogenation is generally necessary, as
nitrogenous compounds are generally poisons of the
hydroisomerization catalysts generally used downstream from a
method of hydrotreating feeds from renewable sources. Thus, because
of the strongly exothermic nature of the set of reactions used,
control of the temperature of the reaction medium proves to be very
important, as too high a level of the temperatures favours: [0016]
the self-sustainment, even the runaway, of reactions due to the
effect of thermal acceleration of kinetics, [0017] undesirable
secondary reactions, such as for example polymerization, coking of
the catalysts or also cracking reactions.
[0018] Patent application EP 1 741 768 describes a method
comprising a stage of hydrotreatment of vegetable oil containing
more than 5 wt. % of free fatty acids in which the hydrotreated
product is recycled, as diluent of the fresh feed, so as to control
the exothermic nature of the reactions and to operate at reduced
temperature. The hydrotreatment stage operates at a temperature
comprised between 200 and 400.degree. C. and at a liquid recycle
rate comprised between 5 and 30 in order to limit the formation of
polymers which cause blockages in the preheating section and which
reduce the activity and the life of the catalyst. This solution
leads to an extra cost for equipment and utilities consumption, due
to the surplus of hydraulic capacity brought about by the high
liquid recycle rate. The hydrotreatment stage is then followed by a
hydroisomerization stage in order to improve the low-temperature
properties of the linear paraffins obtained. The hydrotreatment
stage in which the feed is simultaneously deoxygenated and
desulphidized is advantageously used in a reactor comprising at
least one catalytic bed and the hydrotreated product is recycled
and mixed with the fresh feed, at the same time, at the top of the
first catalytic bed and in the form of cooling quench liquid, also
mixed with the fresh feed and a stream of hydrogen at the top of
every other catalytic bed. This principle permits operation at
reduced temperature at the top of every other catalytic bed
following the first.
[0019] The present invention provides an improvement of this
principle, by proposing a hydrotreatment method scheme, permitting,
through the use of a liquid recycle at the entrance to each
catalytic zone, a precise control of temperatures, an improved
control of the exothermic nature and the different reactions taking
place in the different catalytic zones.
[0020] One of the aims of the present invention is thus to control
the progress and the exothermic nature of the reactions in the
different reaction zones used, while still ensuring the supply of
heat necessary for start-up and control of the different reactions
and in particular the hydrodenitrogenation requiring operating
conditions at specific temperatures.
[0021] Another aim of the present invention is to provide a method
intended to maximize the yield of gas oil and/or kerosene, by
seeking to promote the hydrodeoxygenation mechanism with a choice
of catalysts and of operating conditions while still seeking to
limit the consumption of hydrogen to what is strictly necessary,
and in particular that which would result from unwanted reactions,
such as methanation.
[0022] Another aim of the present invention is to provide a method
intended to convert feeds from renewable sources to n-paraffins by
hydrotreatment under pressure of hydrogen, the n-paraffins thus
obtained then being hydroisomerized in a dedicated downstream unit,
so as to obtain a good compromise between the cetane
characteristics and the low-temperature properties, in order to
produce a high-quality base that can be incorporated in the gas oil
pool as well as a kerosene cut that meets the specifications.
[0023] The present invention therefore relates to a hydrotreatment
method scheme permitting simultaneously a precise control of the
reaction temperatures used in the different catalytic zones and the
indirect heating of the system, by using a liquid recycle at the
entrance to each catalytic zone, while still aiming to direct
selectivity in favour of hydrodeoxygenation and ensuring the
hydrodenitrogenation of the feeds described above.
[0024] More precisely, the invention relates to a method of
treating feeds from renewable sources comprising: [0025] a
hydrotreatment stage a) comprising at least two catalytic zones in
which the entry stream comprising said feed mixed with at least a
part of a hydrotreated liquid effluent from stage b) and a
hydrogen-rich gas is introduced into the first catalytic zone at a
temperature comprised between 150 and 260.degree. C., and in which
the effluent from the first catalytic zone is then introduced,
mixed with at least a part of a hydrotreated liquid effluent from
stage b), and preheated, in the following catalytic zone or zones
at a temperature comprised between 260 and 320.degree. C., [0026] a
stage b) of separation of the effluent from the hydrotreatment
stage a) permitting the separation of a gaseous effluent and a
hydrotreated liquid effluent of which at least a part is recycled
at the top of each catalytic zone of stage a), said method using,
in at least the catalytic zone or zones following the first of the
hydrotreatment stage a), a supported or bulk catalyst comprising an
active phase constituted by a sulphidized group VIB element, the
group VIB element being molybdenum.
[0027] We therefore discovered that the use of a particular
catalyst in the hydrotreatment stage a) of the method according to
the invention permitted the reaction scheme according to the
hydrodeoxygenation route (HDO) to be very strongly favoured, the
effect of which is to very noticeably reduce the production of CO
and of CO.sub.2. In particular, according to a preferred
embodiment, the use of this sequence, using in the first catalytic
zone of the hydrotreatment stage a) a particular hydrodeoxygenation
catalyst favouring the HDO route followed by at least one second
catalytic zone using a catalyst according to the invention, makes
it possible, because of the absence of CO and CO.sub.2 formed in
the first catalytic zone, and compared with a use on a standard
hydrotreatment catalyst: [0028] to avoid corrosion phenomena, which
makes it easier to use the already existing refining units. In
fact, the presence of CO and of CO.sub.2 would mean using
corrosion-resistant materials, which are more costly, and possibly
substantially modifying the existing refinery units and therefore
increasing the level of investments required. [0029] to improve the
fuel, gas oil and kerosene base yield, since the excellent
selectivity for the hydrodeoxygenation route (HDO) permits the
formation of paraffins having the same number of carbon atoms as
the chains of fatty acids present in the feeds from renewable
sources. [0030] to reduce the size of the recycle gas purification
section. In fact, in the presence of formed CO and CO.sub.2, it
would be advisable on the one hand to increase the size of the
section for washing with amines to ensure the purification of the
recycle gas, so as to eliminate the H.sub.2S but also the CO.sub.2
and on the other hand to provide a methanation or Water Gas Shift
section in order to eliminate the CO that cannot be treated by
washing with amines.
DESCRIPTION OF THE INVENTION
[0031] The present invention relates to a method of treating feeds
from renewable sources, for conversion into gas oil and/or kerosene
fuel bases.
[0032] The feeds from renewable sources used in the present
invention are advantageously chosen from oils and fats of vegetable
or animal origin, or from mixtures of such feeds, containing
triglycerides and/or free fatty acids and/or esters. The vegetable
oils can advantageously be raw or refined, totally or in part, and
from the following plants: colza, sunflower, soya, palm, cabbage
palm, olive, coconut, jatropha, this list not being limitative.
Oils from algae or fish are also suitable. Animal fats are
advantageously chosen from lard or fats composed of residues from
the food industry or from the catering industry.
[0033] These feeds essentially contain chemical structures of
triglycerides type that a person skilled in the art also knows by
the names fatty acid triesters as well as free fatty acids. A fatty
acid triester is thus composed of three chains of fatty acids.
These chains of fatty acids in the form of triesters or in the form
of free fatty acids each have a number of unsaturations per chain,
also called number of carbon-carbon double bonds per chain,
generally comprised between 0 and 3 but which can be higher in
particular for oils from algae which can have 5 to 6 unsaturations
per chain.
[0034] The molecules present in the feeds from renewable sources
used in the present invention therefore have a number of
unsaturations, expressed per molecule of triglyceride,
advantageously comprised between 0 and 18. In these feeds, the
degree of unsaturation, expressed in number of unsaturations per
hydrocarbon fatty chain, is advantageously comprised between 0 and
6.
[0035] The feeds from renewable sources generally also contain
various impurities and in particular hetero atoms such as nitrogen.
The nitrogen contents of vegetable oils are generally comprised
between 1 ppm and 100 ppm by weight approximately, according to
their nature. They can amount to up to 1 wt. % of individual
feeds.
[0036] The presence of unsaturations, i.e. of carbon-carbon double
bonds, on the hydrocarbon chains constituting the free fatty acids
as on those constituting the triglycerides makes said feed
thermally unstable. Moreover, the hydrogenation of these
unsaturations is strongly exothermic.
[0037] The treatment method according to the invention used must be
both particularly flexible, in order to be able to process very
different feeds in terms of unsaturations such as soya and palm
oils for example or else oils of animal origin or from algae as
defined above, and to permit the reaction of hydrogenation of the
unsaturations to be started at as low as possible a temperature,
avoiding heating in contact with a wall which would cause hot spots
in said feed, which would lead to the formation of gums and cause
fouling and an increase in the pressure drop of the catalyst bed or
beds.
Stage a)
[0038] According to the method according to the invention, the
entry stream comprising said feed mixed with at least a part of the
hydrotreated liquid effluent from stage b) and a hydrogen-rich gas
is introduced into the first catalytic zone at a temperature
comprised between 150 and 260.degree. C., preferably at a
temperature comprised between 180 and 230.degree. C., preferably
comprised between 180 and 220.degree. C., even more preferably
comprised between 180 and 210.degree. C., and even more preferably
at a temperature equal to 200.degree. C. according to the
hydrotreatment stage a).
[0039] Before mixing with a part of the hydrotreated liquid
effluent and optionally before mixing with a hydrogen-rich gas, the
feed reaches ambient temperature or optionally a higher
temperature, comprised between 50.degree. C. and 150.degree. C., by
a preheating operation with an exchanger or a furnace at the moment
when the temperature of the wall is low enough not to form
gums.
[0040] At least a part of the hydrotreated liquid effluent from
stage b) can advantageously be either cooled, or preheated, before
being recycled at the top of the first catalytic zone of the
hydrotreatment stage a), according to the temperature and the flow
rate of feed and hydrogen, such that the temperature of the entry
stream, comprising said feed mixed with at least a part of said
hydrotreated liquid effluent and a hydrogen-rich gas, is comprised
between 180 and 230.degree. C., preferably comprised between 180
and 220.degree. C. and even more preferably comprised between 180
and 210.degree. C. and even more preferably at a temperature equal
to 200.degree. C.
[0041] In the case where at least a part of the hydrotreated liquid
effluent from the separation stage b) is preheated before being
recycled at the top of the first catalytic zone of the
hydrotreatment stage a), said effluent optionally passes into at
least one exchanger and/or at least one furnace before being
recycled at the top of the first catalytic zone of the
hydrotreatment stage a), so as to adjust the temperature of said
hydrotreated and recycled liquid effluent.
[0042] In the case where at least a part of the hydrotreated liquid
effluent from the separation stage b) is cooled before being
recycled upstream from the first catalytic zone of the
hydrotreatment stage a), said effluent optionally passes into at
least one exchanger and/or at least one cooling tower before being
recycled upstream from the first catalytic zone of the
hydrotreatment stage a), so as to adjust the temperature of said
hydrotreated and recycled liquid effluent.
[0043] The use of the recycling upstream from the first catalytic
zone of at least a part of the hydrotreated and separated liquid
effluent from stage b) which can be either cooled or preheated, if
necessary, or kept at the same temperature as at the exit from the
separation stage b), therefore permits the temperature of the
stream entering said first catalytic zone to be adjusted as
required. Thus, the increase in the temperature of the feed is
caused by mixing with a hotter liquid, and not by contact with a
heated wall. In the case where the hydrotreated liquid effluent is
preheated, this permits the increased temperatures to be locally
limited. In fact during a heating in a heat exchanger or in a
furnace, to reach a given reference temperature T, the temperature
on the hot side must necessarily be greater than T in order to
carry out the heat transfer economically. It is well known to a
person skilled in the art that the heat flow through a wall depends
firstly on the difference in temperature on either side of said
wall and on the exchange surface. A small difference in temperature
between the cold side and the hot side will mean, for a given
quantity of exchanged heat, a larger exchange surface. As a result,
the temperature of the wall in contact with the cold fluid is
higher than the desired temperature commonly called skin
temperature. A heating by direct mixing with a hot fluid thus
permits the skin temperature effect to be avoided and thus the
zones of high temperature to be limited. This type of heating by
mixing with an inert hot liquid therefore permits the undesirable
reactions described above to be limited, and the temperature at
which the stream enters the first catalytic zone of stage a) to be
adjusted so as to start the reaction of hydrogenation of the
unsaturations, preferably at as low as possible a temperature,
while still controlling the exothermic nature of these reactions by
a dilution effect of the reactive species.
[0044] The energy needed for the reaction and more precisely the
adjustment of the minimum temperature necessary for the activation
of the saturation reactions of the double bonds is therefore
principally reached by mixing, upstream from a first catalytic
zone, said feed from a renewable source and a hydrogen-rich gas,
with a recycling of the hydrotreated liquid effluent from the
separation stage b), having optionally undergone a temperature
adjustment and preferably having been preheated or cooled.
[0045] According to the invention, a stream of hydrogen-rich gas is
mixed with said fresh feed and/or with a part of the hydrotreated
liquid effluent, preferably upstream from the first catalytic zone.
The stream of hydrogen-rich gas can advantageously come from a
supply of hydrogen and/or from the recycling of the gaseous
effluent from the separation stage b), the gaseous effluent
containing a hydrogen-rich gas having previously undergone one or
more intermediate purification treatments before being recycled and
mixed with the feed and/or with a part of the hydrotreated liquid
effluent.
[0046] Upstream from the first catalytic zone, the hydrogen-rich
gaseous stream can advantageously be heated or cooled, according to
the case.
[0047] Thus, the stream of hydrogen-rich gas can advantageously be
preheated or cooled, before mixing with a part of the hydrotreated
liquid effluent and/or with the feed or after mixing with a part of
said hydrotreated liquid effluent and/or with the feed, so as to
adjust the entry temperature of the stream entering the first
catalytic zone.
[0048] Thus, the temperature conditions used at the entrance to the
first catalytic zone of stage a) of the method according to the
invention permit the reaction of hydrogenation of the unsaturations
to be started while still controlling the exothermic nature of
these reactions, such that the variation in temperature between the
entry stream, comprising said feed mixed with at least a part of
the hydrotreated liquid effluent from stage b) and a hydrogen-rich
gas, and the effluent leaving the first reaction zone is
advantageously limited to between 50 to 60.degree. C. Thus, the
effluent leaves the first catalytic zone at a temperature
advantageously comprised between 200 and 320.degree. C., preferably
comprised between 230 and 290.degree. C., very preferably comprised
between 230 and 280.degree. C. and more preferably comprised
between 230 and 270.degree. C. and even more preferably the
temperature does not exceed 260.degree. C.
[0049] This principle thus permits operation at reduced temperature
at the top of the first catalytic zone and therefore overall
lowering of the average temperature level of the reaction zone,
which favours the hydrogenolysis reactions and therefore the yield
of gas oil and/or kerosene base.
[0050] The degree of hydrogenation of the unsaturations of the
triglycerides of the feed at the exit from the first catalytic
zone, i.e. the saturation of said feed thus obtained is monitored
by measuring the iodine index according to standard NF ISO 3961.
The degree of hydrogenation of the unsaturations of said feed is
advantageously comprised between 70 and 80 mol % i.e. 80% of the
number of unsaturations present in the initial feed are
saturated.
[0051] The heat released by the saturation of the double bonds
permits the raising of the temperature of the reaction medium and
the starting of the deoxygenation reactions by the
hydrodeoxygenation and decarboxylation/decarbonylation mechanisms
in said first catalytic zone.
[0052] The degree of deoxygenation in molar percentage is monitored
by measuring the oxygen concentration by elementary analysis.
[0053] In the first catalytic zone, the operating conditions used
permit a degree of deoxygenation comprised between 30 and 50% and
preferably between 35 and 40 mol % to be reached, i.e. that 30 to
50 mol % of the oxygen present is converted.
[0054] According to the invention, a hydrotreatment stage a)
comprises at least two catalytic zones and preferably stage a)
comprises two catalytic zones.
[0055] The hydrotreatment catalyst used in the first catalytic zone
of stage a) of the method according to the invention advantageously
contains a hydro-dehydrogenating function comprising at least one
group VIII metal and/or at least one group VIB metal and a support
chosen from the group formed by alumina, silica, the
silica-aluminas, magnesia, clays and mixtures of at least two of
these minerals. Said support can also advantageously contain other
compounds and for example oxides chosen from the group formed by
boron oxide, zirconia, titanium oxide, phosphoric anhydride. The
support is preferably constituted by alumina and very preferably by
.eta., .delta. or .gamma. alumina.
[0056] Preferably, said catalyst advantageously comprises at least
one group VIII metal chosen from nickel and cobalt and at least one
group VIB metal chosen from molybdenum and tungsten, alone or
mixed.
[0057] Said catalyst used in the first catalytic zone of stage a)
of the method according to the invention can also advantageously
contain at least one doping element chosen from phosphorus and
boron. This element can advantageously be introduced into the
matrix or preferably be deposited on the support. Silicon can also
advantageously be deposited on the support, alone or with
phosphorus and/or boron and/or fluorine.
[0058] The oxide content by weight of said doping element is
advantageously less than 20% and preferably less than 10% and is
customarily advantageously at least 0.001%.
[0059] The metals of the catalysts used in the first catalytic zone
of stage a) of the method according to the invention are
advantageously sulphidized metals or metallic phases.
[0060] In the case where the metals are sulphidized, the
sulphidation methods are the standard methods, known to a person
skilled in the art.
[0061] Another preferred catalyst used in the first catalytic zone
of stage a) of the method is a supported or bulk catalyst
comprising an active phase constituted by a sulphidized group VIB
element, the group VIB element being molybdenum.
[0062] Said catalyst can advantageously be supported. In the case
where said catalyst is supported, it advantageously comprises an
amorphous mineral support preferably chosen from the group formed
by alumina, silica, the silica-aluminas, magnesia, clays and
mixtures of at least two of these minerals and preferably said
support is alumina. Said support can also advantageously contain
other compounds such as for example oxides chosen from the group
formed by boron oxide, zirconia and titanium oxide.
[0063] Preferably, the amorphous mineral support is constituted
only by alumina and very preferably only by .eta., .delta. or
.gamma. alumina. Thus, in this preferred embodiment, said support
contains no other compound and is constituted 100% by alumina.
[0064] In the case where said preferred catalyst is in supported
form, the group VIB element content is advantageously comprised
between 15% and 35 wt. % oxide of the group VIB element relative to
the total weight of the catalyst, preferably comprised between 17
and 35 wt. % and very preferably between 20 and 32 wt. %.
[0065] Preferably, and in the case where said catalyst is in
supported form, said catalyst also comprises at least one doping
element chosen from phosphorus, fluorine, silicon and boron and
preferably the doping element is phosphorus, in order to achieve a
high level of conversion while still maintaining a reaction
selectivity for the hydrodeoxygenation route. Preferably, and in
the case where said catalyst is in supported form, said doping
element is advantageously deposited on the support. Silicon can
also advantageously be deposited on the support, alone or with
phosphorus and/or boron and/or fluorine.
[0066] It is known to a person skilled in the art that these
elements have indirect effects on catalytic activity: a better
dispersion of the sulphidized active phase and an increase in the
acidity of the catalyst favouring hydrotreatment reactions (Sun et
al, Catalysis Today 86 (2003) 173).
[0067] In the case where said catalyst is in supported form, the
doping element content, said doping element preferably being
phosphorus, is advantageously strictly greater than 0.5% and less
than 8 wt. % of oxide P.sub.2O.sub.5 relative to the total weight
of the catalyst and preferably greater than 1% and less than 8% and
very preferably greater than 3% and less than 8 wt. %.
[0068] A more preferred catalyst that can be used in the first
catalytic zone of the hydrotreatment stage a) is a supported
catalyst containing an active phase constituted by a sulphidized
group VIB element, the group VIB element being molybdenum and an
amorphous mineral support constituted by alumina alone, said
catalyst having a group VIB element content comprised between 20
and 32 wt. % oxide of said group VIB element relative to the total
weight of the catalyst and also comprising a doping element chosen
from phosphorus, boron and silicon, deposited on said support.
[0069] In the case of the use of a supported catalyst, the
hydrogenating function can be introduced on said catalyst by any
method known to a person skilled in the art such as for example
comixing, dry impregnation etc.
[0070] Said catalyst used in the first catalytic zone of the
hydrotreatment stage a) of the method according to the invention
can alternatively be bulk, in this case said catalyst does not
contain a support.
[0071] In the case where said catalyst is in bulk form the group
VIB element content is advantageously comprised between 92 and 100
wt. % of oxide of the group VIB element relative to the total
weight of the catalyst, preferably greater than 92% and strictly
less than 99.5 wt. %, preferably comprised between 92 and 99 wt. %
and very preferably comprised between 92 and 97 wt. %.
[0072] The catalyst used in the first catalytic zone of the method
according to the invention, in the case where said catalyst is in
bulk form, can also advantageously contain at least one doping
element chosen from phosphorus, fluorine, silicon and boron and
preferably the doping element is phosphorus, in order to achieve a
high level of conversion while still maintaining a reaction
selectivity for the hydrodeoxygenation route.
[0073] In the case where said catalyst is in bulk form, said doping
element is advantageously deposited on the active phase.
[0074] In the case where said catalyst is in bulk form, the doping
element content, said doping element preferably being phosphorus,
is advantageously strictly greater than 0.5% and less than 8 wt. %
of oxide P.sub.2O.sub.5 relative to the total weight of the
catalyst and preferably greater than 1% and less than 8% and very
preferably greater than 3% and less than 8 wt. %.
[0075] In the case where said catalyst is in bulk form, it is
obtained using any synthesis methods known to a person skilled in
the art such as the direct sulphidation of oxide precursors and the
thermal decomposition of metallic thiosalt.
[0076] The use of such a preferred catalyst permits a very high
selectivity to be achieved for the hydrodeoxygenation reactions and
permits the decarboxylation/decarbonylation reactions to be limited
and thus the drawbacks created by the formation of carbon oxides to
be limited.
[0077] The hydrodeoxygenation reaction leads to the formation of
water by consumption of hydrogen and to the formation of
hydrocarbons with a carbon number equal to that of the initial
chains of fatty acids. The effluent from the hydrodeoxygenation
comprises even-numbered hydrocarbon compounds, such as C14 to C24
hydrocarbons and are in a large majority compared with odd-numbered
hydrocarbon compounds, such as C15 to C23, obtained by
decarbonylation/decarboxylation reactions.
[0078] The selectivity for the hydrodeoxygenation route is
demonstrated and is defined by measuring the ratio of the number of
mols of even-numbered paraffins in the 150.degree. C.+ cut to the
total number of mols of paraffins in the 150.degree. C.+ cut.
[0079] HDO selectivity (%)=100.times.(number of mols of
even-numbered paraffins in the 150.degree. C.+ cut)/[number of mols
of even-numbered paraffins in the 150.degree. C.+ cut+ number of
mols of odd-numbered paraffins in the 150.degree. C.+ cut].
[0080] The number of moles of even-numbered paraffins in the
150.degree. C.+ cut and the number of mols of odd-numbered
paraffins in the 150.degree. C.+ cut permitting access to
selectivity for the hydrodeoxygenation route are obtained by gas
chromatography analysis of the liquid effluents having a reaction
that can be utilized in fuel. The technique of measurement by gas
chromatography analysis is a method known to a person skilled in
the art.
[0081] In the first catalytic zone of the hydrotreatment stage a)
of the method according to the invention, the selectivity for the
hydrodeoxygenation route is advantageously greater than 80%.
[0082] Thus, the selectivity for the
decarboxylation/decarbonylation route which is demonstrated is
defined by measuring the ratio of the number of mols of
odd-numbered paraffins in the 150.degree. C.+ cut to the total
number of mols of paraffins in the 150.degree. C.+ cut. i.e.:
[0083] DCO selectivity (%)=100.times.(number of mols of
odd-numbered paraffins in the 150.degree. C.+ cut)/[number of mols
of even-numbered paraffins in the 150.degree. C.+ cut+number of
mols of odd-numbered paraffins in the 150.degree. C.+ cut] is
advantageously less than 20%.
[0084] In the preferred embodiment where the catalyst used in the
first catalytic zone of stage a) of the method according to the
invention is a supported or bulk catalyst comprising an active
phase constituted by a sulphidized group VIB element, the group VIB
element being molybdenum, the selectivity for the
hydrodeoxygenation route is advantageously greater than 95% and
preferably greater than 99%.
[0085] Thus, in this case, the selectivity for the
decarboxylation/decarbonylation route is advantageously less than
5% and preferably less than 1%.
[0086] The reactions in the first catalytic zone of the
hydrotreatment stage a) are advantageously carried out at a
pressure comprised between 1 MPa and 10 MPa, preferably between 3
MPa and 10 MPa and even more preferably between 3 MPa and 6 MPa, at
an hourly space velocity comprised between 0.1 h.sup.-4 and 10
h.sup.-1 and preferably between 0.2 and 5 h.sup.-1. The stream
entering the first catalytic zone, comprising said feed mixed with
at least a part of a hydrotreated liquid effluent from stage b) and
a hydrogen-rich gas, is brought into contact with the catalyst in
the presence of hydrogen. The quantity of hydrogen mixed with the
feed or with the hydrotreated effluent or with the mixture of the
two at the entrance to the first catalytic zone is such that the
hydrogen/feed ratio is comprised between 200 and 2000 Nm.sup.3 of
hydrogen/m.sup.3 of feed, preferably comprised between 200 and 1800
and very preferably between 500 and 1600 Nm.sup.3 of
hydrogen/m.sup.3 of feed.
[0087] The feeds from renewable sources generally also contain
various impurities and in particular heteroatoms such as nitrogen.
The nitrogen contents encountered are comprised between 1 and 100
ppm by weight for vegetable oils, but can reach 1 wt. % in
particular in feeds such as certain animal fats.
[0088] However, nitrogen is a poison of the hydroisomerization
catalysts optionally used downstream from the treatment method
according to the invention with the aim of obtaining a gas oil base
of good quality and/or a kerosene cut conforming to the
specifications.
[0089] One way of removing the nitrogen is to carry out a
hydrodenitrogenation reaction in order to convert the
nitrogen-containing molecules to ammonia that can be easily
eliminated.
[0090] The temperature level reached after the saturation of the
double bonds and the deoxygenation, which was deliberately limited
as stated above; is not sufficient to permit
hydrodenitrogenation.
[0091] However, hydrodenitrogenation is a reaction characterized by
relatively slow kinetics, which necessitates high temperature
levels in order to achieve a quasi-total conversion, for reasonable
residence times, and therefore more severe conditions than
hydrodeoxygenation and decarboxylation/decarbonylation.
[0092] The temperature level necessary for hydrodenitrogenation is
provided, according to the invention, by injecting at least a part
of a hydrotreated liquid effluent, preheated beforehand through at
least one exchanger and/or through at least one furnace or any
other heating method known to a person skilled in the art such as
for example microwaves, in the catalytic zone or zones following
the first.
[0093] According to the method according to the invention, the
effluent from the first catalytic zone is then introduced, mixed
with at least a part of a hydrotreated liquid effluent from stage
b) and preheated, into the following catalytic zone or zones and
preferably into the following catalytic zone called second
catalytic zone, at a temperature comprised between 260 and
320.degree. C., preferably at a temperature comprised between 280
and 320.degree. C. and even more preferably at a temperature
greater than 300.degree. C., according to the hydrotreatment stage
a).
[0094] At least a part of the hydrotreated liquid effluent from
stage b) is therefore preheated beforehand by optional passage
through at least one exchanger and/or at least one furnace or any
other heating means known to a person skilled in the art, before
being recycled at the top of each catalytic zone of the
hydrotreatment stage a) following the first catalytic zone, so as
to adjust the temperature of said hydrotreated and recycled liquid
effluent and to bring about the mixture of the effluent from the
first catalytic zone with at least a part of said hydrotreated
liquid effluent at temperature conditions favouring the
hydrodenitrogenation reaction.
[0095] The recycling of at least a part of the hydrotreated liquid
effluent, preheated beforehand, at the top of each catalytic zone
of the hydrotreatment stage a) following the first catalytic zone
therefore permits the indirect heating of the effluent from the
first catalytic zone and the adjustment of the temperature at the
entrance to the following catalytic zones to a temperature
comprised between 260 and 320.degree. C., so as to have temperature
conditions favouring the hydrodenitrogenation reaction and carry
out the deoxygenation of the partially deoxygenated effluent.
[0096] Another heating stream is advantageously constituted by a
hydrogen-rich gaseous effluent from the hydrogen supply and/or the
gaseous effluent from the separation stage b). At least a part of
this hydrogen-rich gaseous effluent from the hydrogen supply and/or
the gaseous effluent from the separation stage b) is advantageously
injected mixed with at least a part of the hydrotreated liquid
effluent from stage b) or separately, at the top of each catalytic
zone of stage a) following the first catalytic zone and preferably
at the top of the second catalytic zone. The hydrogen-rich gaseous
stream can therefore advantageously be preheated mixed with at
least a part of the hydrotreated liquid effluent or preheated
separately before mixing preferably by optional passage through at
least one exchanger and/or at least one furnace or any other
heating means known to a person skilled in the art. Thanks to the
different heating streams, the temperature conditions used in the
catalytic zones following the first are more favourable to the
hydrodenitrogenation kinetics than the temperature conditions used
in the first catalytic zone and also permit a majority of the
deoxygenation reactions to be carried out.
[0097] The degree of deoxygenation in molar percentage is monitored
by measuring the oxygen concentration by elementary analysis.
[0098] In the catalytic zone or zones following the first catalytic
zone, the operating conditions used permit a degree of
deoxygenation greater than 60% and preferably greater than 90% to
be achieved, i.e. an overall rate of deoxygenation (by HDO and DCO
combined) over all the zones referred to of between 80 and 100% and
preferably between 95 and 100%, and permit a nitrogen content of
the hydrotreated effluent of less than 5 ppm, preferably less than
2 ppm and very preferably, less than 1 ppm to be achieved at the
end of the catalytic zone or zones following the first catalytic
zone and preferably the second catalytic zone, the nitrogen content
being measured according to the standard ASTM D4629-2002.
[0099] According to the invention, the hydrotreatment catalyst used
in the catalytic zone or zones following the first catalytic zone
of the hydrotreatment stage a) of the method according to the
invention and preferably the second catalytic zone is a supported
or bulk catalyst comprising an active phase constituted by a
sulphidized group VIB element, the group VIB element being
molybdenum.
[0100] Said catalyst can advantageously be supported. In the case
where said catalyst is supported, it advantageously comprises an
amorphous mineral support preferably chosen from the group formed
by alumina, silica, the silica-aluminas, magnesia, clays and
mixtures of at least two of these minerals and preferably said
support is alumina. Said support can also advantageously contain
other compounds such as for example oxides chosen from the group
formed by boron oxide, zirconia and titanium oxide.
[0101] Preferably, the amorphous mineral support is constituted
only by alumina and very preferably only by .eta., .delta. or
.gamma. alumina. Thus, in this preferred embodiment, said support
contains no other compound and is constituted 100% by alumina.
[0102] In the case where said preferred catalyst is in supported
form, the group VIB element content is advantageously comprised
between 15% and 35 wt. % of oxide of the group VIB element relative
to the total weight of the catalyst, preferably comprised between
17 and 35 wt. % and very preferably between 20 and 32 wt. %.
[0103] Preferably, and in the case where said catalyst is in
supported form, said catalyst also comprises at least one doping
element chosen from phosphorus, fluorine, silicon and boron and
preferably the doping element is phosphorus, in order to achieve a
high level of conversion while still maintaining a reaction
selectivity for the hydrodeoxygenation route. Preferably, and in
the case where said catalyst is in supported form, said doping
element is advantageously deposited on the support. Silicon can
also advantageously be deposited on the support, alone or with
phosphorus and/or boron and/or fluorine.
[0104] It is known to a person skilled in the art that these
elements have indirect effects on catalytic activity: a better
dispersion of the sulphidized active phase and an increase in the
acidity of the catalyst favouring hydrotreatment reactions (Sun et
al, Catalysis Today 86 (2003) 173).
[0105] In the case where said catalyst is in supported form, the
doping element content, said doping element preferably being
phosphorus, is advantageously strictly greater than 0.5% and less
than 8 wt. % of oxide P.sub.2O.sub.5 relative to the total weight
of the catalyst and preferably greater than 1% and less than 8% and
very preferably greater than 3% and less than 8 wt. %.
[0106] A more preferred catalyst that can be used in the second
catalytic zone of the hydrotreatment stage a) is a supported
catalyst containing an active phase constituted by a sulphidized
group VIB element, the group VIB element being molybdenum and an
amorphous mineral support constituted by alumina alone, said
catalyst having a group VIB element content comprised between 20
and 32 wt. % oxide of said group VIB element relative to the total
weight of the catalyst and also comprising a doping element chosen
from phosphorus, boron and silicon, deposited on said support.
[0107] In the case of the use of a supported catalyst, the
hydrogenating function can be introduced on said catalyst by any
method known to a person skilled in the art such as for example
comixing, dry impregnation etc.
[0108] According to the invention, said catalyst used in the second
catalytic zone of the hydrotreatment stage a) of the method
according to the invention can alternatively be bulk, in this case
said catalyst does not contain a support.
[0109] In the case where said catalyst is in bulk form the group
VIB element content is advantageously comprised between 92 and 100
wt. % of oxide of the group VIB element relative to the total
weight of the catalyst, preferably greater than 92% and strictly
less than 99.5 wt. %, preferably comprised between 92 and 99 wt. %
and very preferably comprised between 92 and 97 wt. %.
[0110] The catalyst used in the second catalytic zone of the method
according to the invention, in the case where said catalyst is in
bulk form, can also advantageously contain at least one doping
element chosen from phosphorus, fluorine, silicon and boron and
preferably the doping element is phosphorus, in order to achieve a
high level of conversion while still maintaining a reaction
selectivity for the hydrodeoxygenation route.
[0111] In the case where said catalyst is in bulk form, said doping
element is advantageously deposited on the active phase.
[0112] In the case where said catalyst is in bulk form, the doping
element content, said doping element preferably being phosphorus,
is advantageously strictly greater than 0.5% and less than 8 wt. %
of oxide P.sub.2O.sub.5 relative to the total weight of the
catalyst and preferably greater than 1% and less than 8% and very
preferably greater than 3% and less than 8 wt. %.
[0113] In the case where said catalyst is in bulk form, it is
obtained using any synthesis methods known to a person skilled in
the art such as the direct sulphidation of oxide precursors and the
thermal decomposition of metallic thiosalt.
[0114] The catalyst used in the second catalytic zone of the
hydrotreatment stage a) is preferably identical to that used in the
first catalytic zone of stage a).
[0115] The use of such a preferred catalyst permits a very high
selectivity for the hydrodeoxygenation reactions to be achieved in
the second catalytic zone of the hydrotreatment stage a) of the
method according to the invention and permits the
decarboxylation/decarbonylation reactions to be limited and thus
the drawbacks created by the formation of carbon oxides to be
limited.
[0116] In the second catalytic zone of the hydrotreatment stage a)
of the method according to the invention, the selectivity for the
hydrodeoxygenation route is advantageously greater than 95% and
preferably greater than 99%.
[0117] Thus, in this case, the selectivity for the
decarboxylation/decarbonylation route is advantageously less than
5% and preferably less than 1%.
[0118] According to the invention, the metals of the catalysts used
in the second catalytic zone of stage a) of the method according to
the invention are sulphidized metals, the sulphidation methods are
the standard methods, known to a person skilled in the art.
[0119] The reactions in the catalytic zone or zones following the
first catalytic zone are advantageously carried out at a pressure
comprised between 1 MPa and 10 MPa, preferably between 3 MPa and 10
MPa and even more preferably between 3 MPa and 6 MPa, at an hourly
space velocity comprised between 0.1 h.sup.-1 and 10 h.sup.-1 and
preferably between 0.2 and 5 h.sup.-1. The total quantity of
hydrogen mixed at the entrance to the second catalytic zone with
the effluent from the first zone or with the part of the
hydrotreated liquid effluent or with the mixture of the two is such
that the hydrogen/hydrocarbons ratio entering the catalytic zone or
zones following the first is comprised between 200 and 2000
Nm.sup.3 of hydrogen/m.sup.3 of feed, preferably comprised between
200 and 1800 and very preferably between 500 and 1600 Nm.sup.3 of
hydrogen/m.sup.3 of feed. To achieve these conditions a stream of
hydrogen-rich gas is mixed with the stream upstream from the second
catalytic zone. The stream of hydrogen-rich gas can advantageously
come from a hydrogen supply and/or the recycling of the gaseous
effluent from the separation stage b), the gaseous effluent
containing a hydrogen-rich gas having previously undergone one or
more intermediate purification treatments before being recycled and
mixed.
[0120] Moreover, the minimization of the streams at the entrance to
the catalytic zone or zones following the first limits the dilution
of the nitrogen-containing compounds. The minimization of the
liquid recycling therefore favours the hydrodenitrogenation
kinetics, since these are a function of the concentration of
nitrogen-containing compounds. It is therefore beneficial to
minimize the hydrotreated liquid recycle.
[0121] The overall recycle rate of the method according to the
invention is defined by the ratio of the mass flow rate of total
recycled hydrotreated product in kilograms to the mass flow rate of
fresh feed in kilograms.
[0122] The overall recycle rate of the method according to the
invention is advantageously comprised between 1 and 5 and
preferably between 0.5 and 4, preferably between 0.5 and 3 and very
preferably strictly less than 3.
[0123] The use of low overall recycle rates is permitted due to an
advantageous use of the heats of reaction, combined with as low as
possible a temperature at the entrance to each catalytic zone. The
minimization of the hydraulic flow rate in the first catalytic zone
leads to significantly reduced investment costs and operating
costs.
[0124] Moreover, the minimization of the recycle rate in the unit,
leading to a smaller dilution of the nitrogen-containing compounds,
combined with a high temperature permitted due to the supply of a
hot stream at the entrance to the second catalytic zone, leads to
higher hydrodenitrogenation kinetics and therefore permits an
optimized quantity of catalyst.
[0125] The control of the temperature and the rate of recycling of
hot or very hot liquid at the entrance to each catalytic zone
ensures the flexibility of the method by supplying the heat
necessary to start up the reactions while still controlling the
increase in temperature. In fact, a part of the energy released by
the reactions carried out will serve to heat both the feed and the
recycle. The result is a smaller increase in temperature. The
control of the increase in temperature of the reaction medium
permits the kinetics of the reactions, themselves exothermic, to be
influenced. This permits the risks of runaway to be limited for an
operation in complete safety and permits the desired conversion to
be achieved in each catalytic zone.
[0126] Preferably, the different catalytic zones of the
hydrotreatment stage a) are situated in one or more reactors and
preferably in a single reactor.
[0127] In the case where they are situated in a single reactor, the
different catalytic zones are constituted by several catalytic
beds, optionally separated by liquid or gaseous quench zones.
[0128] Preferably, stage a) comprises two catalytic zones situated
in one or in two reactors. The first catalytic zone is
advantageously a hydrogenation zone in which the majority of the
double bonds are hydrogenated and the heat released by the
hydrogenation reaction is advantageously used to start the
deoxygenation reactions and the second catalytic zone is
advantageously a deoxygenation (decarboxylation and
hydrodeoxygenation) and hydrodenitrogenation zone in which the
majority of the deoxygenation and hydrodenitrogenation reactions
take place.
Stage b)
[0129] According to stage b) of the method according to the
invention, the effluent from the hydrotreatment stage a) undergoes
a stage permitting the separation of a gaseous effluent and a
hydrotreated liquid effluent of which at least a part is recycled
at the top of each catalytic zone of stage a).
[0130] The gaseous effluent contains mostly hydrogen, carbon
monoxide and dioxide, light hydrocarbons with 1 to 5 carbon atoms
and water vapour. The aim of this stage is therefore to separate
the gases from the liquid, and in particular to recover the
hydrogen-rich gases and at least one hydrotreated liquid effluent
very preferably having a nitrogen content of less than 1 ppm by
weight.
[0131] At least a part of the hydrogen-rich gaseous effluent from
the separation stage b) which has preferably undergone a
purification treatment with the aim of deconcentrating the
impurities from the reactions present in the gaseous effluent at
the moment of the separation stage b) can advantageously be
injected either mixed with at least a part of the hydrotreated
liquid effluent from stage b) or separately, at the top of each
catalytic zone of stage a).
[0132] The separation stage can advantageously be implemented by
any method known to a person skilled in the art such as for example
the combination of one or more high- and/or low-pressure
separators, and/or distillation and/or high- and/or low-pressure
stripping stages.
[0133] The hydrotreated liquid effluent is essentially constituted
by n-paraffins which can be incorporated in the gas oil pool and/or
the kerosene pool. So as to improve the low-temperature properties
of this hydrotreated liquid effluent, a hydroisomerization stage is
necessary to convert the n-paraffins into branched paraffins having
better low-temperature properties.
[0134] At least a part, and preferably all, of the non-recycled
hydrotreated liquid effluent then undergoes an optional
hydroisomerization stage in the presence of a selective
hydroisomerization catalyst.
[0135] The hydroisomerization stage is advantageously carried out
in a separate reactor. The hydroisomerization catalysts used are
advantageously of bifunctional types, i.e. they have a
hydro/dehydrogenating function and a hydroisomerizing function.
[0136] The hydroisomerization catalyst advantageously comprises at
least one group VIII metal and/or at least one group VIB metal as
hydrodehydrogenating function and at least one molecular sieve or
an amorphous mineral support as hydroisomerizing function.
[0137] The hydroisomerization catalyst advantageously comprises
either at least one group VIII precious metal preferably chosen
from platinum or palladium, active in their reduced form, or at
least one group VIB metal, preferably chosen from molybdenum or
tungsten, in combination with at least one group VIII base metal,
preferably chosen from nickel and cobalt, used preferably in their
sulphidized form.
[0138] In the case where the hydroisomerization catalyst comprises
at least one group VIII precious metal, the total precious metal
content of the hydroisomerization catalyst used in stage c) of the
method according to the invention is advantageously comprised
between 0.01 and 5 wt. % relative to the finished catalyst,
preferably between 0.1 and 4 wt. % and very preferably between 0.2
and 2 wt. %.
[0139] Preferably, the hydroisomerization catalyst comprises
platinum or palladium and preferably the hydroisomerization
catalyst comprises platinum.
[0140] In the case where the hydroisomerization catalyst comprises
at least one group VIB metal in combination with at least one group
VIII base metal, the group VIB metal content of the
hydroisomerization catalyst used in stage c) of the method
according to the invention is advantageously comprised, in oxide
equivalent, between 5 and 40 wt. % relative to the finished
catalyst, preferably between 10 and 35 wt. % and very preferably
between 15 and 30 wt. % and the group VIII metal content of said
catalyst is advantageously comprised, in oxide equivalent, between
0.5 and 10 wt % relative to the finished catalyst, preferably
between 1 and 8 wt. % and very preferably between 1.5 and 6 wt.
%.
[0141] The metallic hydro/dehydrogenating function can
advantageously be introduced on said catalyst by any method known
to a person skilled in the art, such as for example comixing, dry
impregnation, exchange impregnation.
[0142] According to a preferred embodiment, said hydroisomerization
catalyst comprises at least one amorphous mineral support as
hydroisomerizing function, said one amorphous mineral support being
chosen from the silica-aluminas and silicated aluminas and
preferably the silica-aluminas.
[0143] A preferred hydroisomerization catalyst comprises an active
phase based on nickel and tungsten and an amorphous silica-alumina
mineral support, said catalyst being preferably in sulphide
form.
[0144] According to another preferred embodiment, said
hydroisomerization catalyst comprises at least one molecular sieve,
preferably at least one zeolite molecular sieve and more preferably
at least one 10 MR one-dimensional zeolite molecular sieve as
hydroisomerizing function.
[0145] Zeolite molecular sieves are defined in the classification
"Atlas of Zeolite Structure Types", W. M Meier, D. H. Olson and Ch.
Baerlocher, 5th revised edition, 2001, Elsevier to which the
present application also refers. The zeolites are classified there
according to the size of their pore or channel openings.
[0146] 10 MR one-dimensional zeolite molecular sieves have pores or
channels of which the opening is defined by a ring with 10 oxygen
atoms (10 MR opening). The channels of the zeolite molecular sieve
having a 10 MR opening are advantageously non-interconnected
one-dimensional channels which open directly onto the outside of
said zeolite. The 10 MR one-dimensional zeolite molecular sieves
present in said hydroisomerization catalyst advantageously comprise
silicon and at least one element T chosen from the group formed by
aluminum, iron, gallium, phosphorus and boron, preferably aluminum.
The Si/Al ratios of the zeolites described above are advantageously
those obtained during synthesis or obtained after post-synthesis
dealuminating treatments well known to a person skilled in the art,
such as and non-limitatively hydrothermal treatments followed or
not by acid attacks or also direct acid attacks by solutions of
mineral or organic acids. Preferably, they are practically totally,
in acid form, i.e. the atomic ratio between the monovalent
compensation cation (for example sodium) and the element T inserted
into the crystal lattice of the solid is advantageously less than
0.1, preferably less than 0.05 and very preferably less than 0.01.
Thus, the zeolites included in the composition of said selective
hydroisomerization catalyst are advantageously calcined and
exchanged by at least one treatment with a solution of at least one
ammonium salt so as to obtain the ammonium form of the zeolites
which once calcined lead to the acid form of said zeolites.
[0147] Said 10 MR one-dimensional zeolite molecular sieve of said
hydroisomerization catalyst is advantageously chosen from the
zeolite molecular sieves of structural type TON, such as NU-10,
FER, such as ferrierite, EUO, chosen from EU-1 and ZSM-50, used
alone or mixed, or the zeolite molecular sieves ZSM-48, ZBM-30,
IZM-1, COK-7, EU-2 and EU-11, used alone or mixed.
[0148] Preferably, said 10 MR one-dimensional zeolite molecular
sieve is chosen from the ZSM-48, ZBM-30, IZM-1 and COK-7 zeolite
molecular sieves, used alone or mixed. Even more preferably, said
10 MR one-dimensional zeolite molecular sieve is chosen from the
zeolite molecular sieves ZSM-48 and ZBM-30, used alone or
mixed.
[0149] Very preferably, said 10 MR one-dimensional zeolite
molecular sieve is ZBM-30 and even more preferably, said 10 MR
one-dimensional zeolite molecular sieve is ZBM-30 synthesized with
the organic structurizing agent triethylenetetramine.
[0150] Zeolite ZBM-30 is described in patent EP-A-46 504, and
zeolite COK-7 is described in patent applications EP 1 702 888 A1
or FR 2 882 744 A1.
[0151] Zeolite IZM-1 is described in patent application FR-A-2 911
866 and zeolite ZSM 48 is described in Schlenker, J. L. Rohrbaugh,
W. J., Chu, P., Valyocsik, E. W. and Kokotailo, G. T. Title: The
framework topology of ZSM-48: a high silica zeolite. Reference:
Zeolites, 5, 355-358 (1985) Material "ZSM-48".
[0152] The zeolites of structural type TON are described in the
work "Atlas of Zeolite Structure Types", W. M. Meier, D. H. Olson
and Ch. Baerlocher, 5th Revised edition, 2001, Elsevier.
[0153] The zeolite of structural type TON is described in the work
"Atlas of Zeolite Structure Types" cited above and, with respect to
zeolite NU-10, in patents EP-65400 and EP-77624.
[0154] The zeolite of structural type FER is described in the work
"Atlas of Zeolite Structure Types" cited above.
[0155] The content of 10 MR one-dimensional zeolite molecular sieve
is advantageously comprised between 5 and 95 wt. %, preferably
between 10 and 90 wt. %, more preferably between 15 and 85 wt. %
and very preferably between 20 and 80 wt. % relative to the
finished catalyst.
[0156] Preferably, said hydroisomerization catalyst also comprises
a binder constituted by a porous mineral matrix. Said binder can
advantageously be used during the stage of shaping said
hydroisomerization catalyst.
[0157] Preferably, the shaping is carried out with a binder
constituted by a matrix containing alumina, in all its forms known
to a person skilled in the art, and very preferably with a matrix
containing gamma alumina.
[0158] The hydroisomerization catalysts obtained are formed as
grains of various shapes and sizes. They are generally used in the
form of cylindrical extrudates or multilobed extrudates such as
bilobed, trilobed, multilobed of straight or twisted shape, but can
optionally be manufactured and used in the form of pulverized
powders, tablets, rings, spheres, wheels. Techniques other than
extrusion, such as tableting or particle coating, can
advantageously be used.
[0159] In the case where the hydroisomerization catalyst contains
at least one precious metal, the precious metal content of said
hydroisomerization catalyst must advantageously be reduced. One of
the preferred methods for carrying out the reduction of the metal
is treatment under hydrogen at a temperature comprised between
150.degree. C. and 650.degree. C. and a total pressure comprised
between 1 and 250 bar. For example, a reduction consists of a
plateau at 150.degree. C. for two hours then a temperature rise to
450.degree. C. at a rate of 1.degree. C./min then a plateau of two
hours at 450.degree. C.; throughout this reduction stage, the
hydrogen flow rate is 1000 normal m.sup.3 hydrogen/m.sup.3 catalyst
with the total pressure maintained constant at 1 bar. Any method of
reduction ex-situ can advantageously be envisaged.
[0160] In the hydroisomerization zone, the feed is contacted, in
the presence of hydrogen, with said hydroisomerization catalyst, at
operating temperatures and pressures advantageously permitting
hydroisomerization of the non-converting feed to be carried out.
This means that the hydroisomerization is carried out with a
conversion of the 150.degree. C..sup.+ fraction to 150.degree.
C..sup.- fraction of less than 20 wt. %, preferably less than 10
wt. % and very preferably less than 5 wt. %.
[0161] Thus, the optional hydroisomerization stage operates at a
temperature comprised between 150 and 500.degree. C., preferably
between 150.degree. C. and 450.degree. C., and very preferably
between 200 and 450.degree. C., at a pressure comprised between 1
MPa and 10 MPa, preferably between 2 MPa and 10 MPa and very
preferably between 1 MPa and 9 MPa, at an hourly space velocity
advantageously comprised between 0.1 h.sup.-1 and 10 h.sup.-1,
preferably between 0.2 and 7 h.sup.-1 and very preferably between
0.5 and 5 h.sup.-1, at a hydrogen flow rate such that the
hydrogen/hydrocarbons volume ratio is advantageously comprised
between 70 and 1000 Nm.sup.3/m.sup.3 of feed, between 100 and 1000
normal m.sup.3 of hydrogen per m.sup.3 of feed and preferably
between 150 and 1000 normal m.sup.3 of hydrogen per m.sup.3 of
feed.
[0162] Preferably, the optional hydroisomerization stage operates
in co-current.
[0163] The hydroisomerized effluent is then advantageously
subjected at least partly, and preferably wholly, to one or more
separations. The aim of this stage is to separate the gases from
the liquid, and in particular to recover the hydrogen-rich gases
that may also contain light fractions such as the C.sub.1-C.sub.4
cut, at least one gas oil (250.degree. C.+ cut) and kerosene
(150-250.degree. C. cut) cut of good quality and a naphtha cut. The
use made of the naphtha cut is not the subject of the present
invention, but this cut can advantageously be sent to a steam
cracking or catalytic reforming unit.
[0164] The products, gas oil and kerosene bases, obtained according
to the method according to the invention and in particular after
hydroisomerization have excellent characteristics.
[0165] The gas oil base obtained after mixing with a petroleum gas
oil from a renewable feed such as coal or lignocellulosic biomass,
and/or with an additive, is of excellent quality: [0166] its
sulphur content is less than 10 ppm by weight. [0167] its total
aromatics content is less than 5 wt. %, and the polyaromatics
content less than 2 wt. %. [0168] the cetane number is excellent,
greater than 55. [0169] the density is less than 840 kg/m.sup.3,
more often greater than 820 kg/m.sup.3. [0170] its kinematic
viscosity at 40.degree. C. is 2 to 8 mm.sup.2/s. [0171] its
low-temperature stability properties are compatible with the
standards in force, with a cold filter plugging point below
-15.degree. C. and a cloud point below -5.degree. C.
[0172] The kerosene cut obtained after mixing with a petroleum
kerosene from a renewable feed such as coal or lignocellulosic
biomass and/or with an additive has the following characteristics:
[0173] a density comprised between 775 and 840 kg/m.sup.3 [0174] a
viscosity at -20.degree. C. of less than 8 mm.sup.2/s [0175] a
crystal disappearance point below -47.degree. C. [0176] a flash
point above 38.degree. C. [0177] a smoke point above 25 mm.
BRIEF DESCRIPTION OF THE FIGURES
[0178] FIG. 1 illustrates a non-limitative preferred embodiment of
the method according to the invention in which stage a) comprises
two catalytic zones situated in two reactors.
[0179] The fresh feed (1) is introduced mixed with a part of the
hydrotreated liquid effluent (14) from the separation zone (60) via
the pipe (3). Hydrogen-rich gas is mixed via the pipe (17) with the
fresh feed. The hydrogen-rich gas (17) comes from a hydrogen supply
(2) and gaseous effluent from the separation zone (60) via the pipe
(8), the gaseous effluent having previously undergone one or more
intermediate purification treatments before being mixed with the
fresh feed and recycled feed via the pipe (15).
[0180] Upstream from the first catalytic zone (30), the fresh feed,
mixed with a hydrogen-rich gaseous stream, is also mixed via the
pipe (14) with at least a part of the hydrotreated effluent from
the separator (60) via the pipe (11) so as to obtain the sought
temperature at the entrance to the first catalytic zone (30).
[0181] The effluent (4) from the first catalytic zone (30) is then
mixed with a hydrogen-rich gas via the pipe (19) and at least a
part of the hydrotreated liquid effluent via the pipe (13). The
hydrogen-rich gas (19) is obtained by heating the stream (18) from
a hydrogen source in a furnace (80). The hydrotreated effluent (13)
is obtained by heating the stream (12) from the separator (60) in a
furnace (70) in order to adjust the temperature of the mixture in
the pipe (5) at the entrance to the second catalytic zone (40).
[0182] The effluent from the second catalytic zone (40) via the
pipe (6) then undergoes a separation stage in the separator (60) in
order to obtain a hydrotreated liquid effluent (10) and a gaseous
effluent (8). The gaseous effluent (8) is a hydrogen-rich gas of
which a part is treated before being recycled upstream from the two
catalytic zones (30) and (40). The stream (10) is constituted for
the most part by a hydrotreated product which is divided into two
streams, the stream (11) which is recycled upstream from the two
catalytic zones after having been optionally preheated or not and
the stream (20) which is sent directly into a hydroisomerization
unit not shown in FIG. 1.
[0183] The following example illustrates the invention without,
however, limiting its scope.
EXAMPLE
[0184] Soya oil is constituted for the most part by triglycerides
each molecule of which comprises on average approximately 4.7
double bonds. This figure is an average of the number of
unsaturations present per molecule of triglycerides and obtained
from the typical fatty acids composition of the oil. This figure is
defined as the ratio between the total number of unsaturations and
the number of molecules of triglycerides.
[0185] Palm oil is constituted for the most part by triglycerides
each molecule of which comprises on average approximately 2.1
double bonds. This difference in the number of double bonds or
unsaturations manifests itself in very different heats of reaction.
These two oils constitute excellent examples for illustrating the
thermal flexibility of the method.
[0186] 50 L/h of soya oil of density 920 kg/m.sup.3 having a
nitrogen content equal to 23 ppm by weight is introduced into a
first adiabatic reactor, loaded with 31 L of a hydrotreatment
catalyst constituting the first catalytic zone.
[0187] The principal characteristics of the soya oil and palm oil
feeds used in the method according to the invention are listed in
Table 1.
TABLE-US-00001 TABLE 1 soya oil palm oil Properties of the feed
Elementary analysis S [ppm by wt] 4 3 N [ppm by wt] 73 15 P [ppm by
wt] 10 10 H [wt. %] 11.4 11.9 O [wt. %] 11.0 11.3 Composition in
fatty acids (%) 12:0 0.10 0.25 14:0 0.10 1.07 16:0 10.28 44.21 16:1
0.15 17:1 18:0 3.73 4.45 18:1 22.98 39.89 18:2 54.13 9.62 18:3 8.67
0.37 Hydrotreated effluent properties Elementary analysis S [ppm by
wt] <0.3 <0.3 N [ppm by wt] <0.4 <0.4 P [ppm by wt]
<1 <1 O [wt. %] <0.2 <0.2
[0188] The feed, initially at ambient temperature, is introduced
into said first catalytic zone mixed with a part of the
hydrotreated liquid effluent from the separation stage b), said
effluent having an exit temperature of 322.degree. C. for the soya
oil and a temperature of 328.degree. C. for the palm oil, and a
hydrogen-rich gas, the mixture of hydrotreated effluent and
hydrogen-rich gas being cooled beforehand in an exchanger at a
temperature of 230.degree. C. in the case of a soya oil feed and
260.degree. C. in the case of a palm oil feed.
[0189] 1000 Nm.sup.3 of hydrogen/m.sup.3 of feed are introduced
into the first reactor mixed beforehand with the hydrotreated
effluent. The flow rate of the hydrotreated effluent introduced
into the first catalytic zone is equal to 125 L/h in the case of
the soya oil and 50 L/h in the case of the palm oil.
[0190] Thus, the stream entering the first catalytic zone,
constituted by said feed mixed with a part of the hydrotreated
liquid effluent from stage b) and a hydrogen-rich gas, is
introduced into said first catalytic zone at a temperature of
200.degree. C. for the soya oil and for the palm oil.
[0191] The catalyst used in first catalytic zone of the
hydrotreatment stage a) is a sulphidized MoP/alumina catalyst
comprising 25.3 wt. % of MoO.sub.3 and 6.1 wt. % of P.sub.2O.sub.5,
supported on a gamma alumina.
[0192] The supported catalysts are prepared by dry impregnation of
the oxide precursors in solution then sulphidized in-situ, at a
temperature of 350.degree. C., prior to the test using a
direct-distillation gas oil feed with 2 wt. % dimethyldisulphide
(DMDS) added.
[0193] After sulphidation in situ in the pressurized unit, the feed
from a renewable source constituted by soya oil or palm oil
described in Table 1 is passed into the reactor. In order to keep
the catalyst in a sulphidized state, 50 ppm by weight of sulphur in
the form of DMDS is added to the feed. In the reaction conditions,
the DMDS is totally decomposed to form methane and H.sub.2S.
[0194] The method of preparation of the catalysts does not limit
the scope of the invention.
[0195] In the first catalytic zone, the pressure is kept at 5 MPa,
the hourly space velocity is 1.6 h.sup.-1 and the total quantity of
hydrogen is such that the hydrogen/feed ratio is 1000
Nm.sup.3/h/m.sup.3.
[0196] The operating conditions and more particularly the
temperature of 200.degree. C. of the stream entering the first
catalytic zone permit the hydrogenation of the majority of the
unsaturations of the feed at reduced temperature and the heat
released by this reaction permits the starting of the feed
deoxygenation reactions.
[0197] As the hydrogenation reactions are exothermic, the
temperature at the exit from the first catalytic zone is
258.degree. C. in the case of the soya oil and 258.degree. C. in
the case of the palm oil.
[0198] The degrees of hydrogenation of the unsaturations and the
degree of deoxygenation of the different feeds in the first
catalytic zone of the hydrotreatment stage a) are given in Table
1.
[0199] The effluent from the first catalytic zone is then sent into
a second catalytic zone situated in a second reactor loaded with 50
L of a hydrotreatment catalyst described below, mixed with the
hydrotreated effluent from the separation stage and hydrogen. 500
Nm.sup.3 of hydrogen/m.sup.3 of feed are introduced into the second
reactor mixed beforehand with the hydrotreated effluent. The flow
rate of the hydrotreated effluent introduced into the second
catalytic zone is equal to 22.5 L/h in the case of the soya oil and
12.5 L/h in the case of the palm oil.
[0200] The mixture of hydrotreated effluent and hydrogen going to
the second catalytic zone is preheated beforehand in a furnace to a
temperature of 427.degree. C. in the case of the soya oil and
429.degree. C. in the case of the palm oil.
[0201] The temperature of the stream entering the second catalytic
zone is therefore adjusted to 291.degree. C. in the case of the
palm oil and 293.degree. C. in the case of the soya oil.
[0202] The catalyst used in the second catalytic zone of the
hydrotreatment stage a) is identical to the catalyst used in the
first catalytic zone and is a sulphidized MoP/alumina catalyst
comprising 25.3 wt. % of MoO.sub.3 and 6.1 wt. % of P.sub.2O.sub.5
supported on a gamma alumina.
[0203] Said catalyst is prepared and sulphidized in the same way as
the catalyst used in the first catalytic zone.
[0204] In the second catalytic zone, the pressure is kept at 5 MPa,
the hourly space velocity is 1 h.sup.-1 and the total quantity of
hydrogen is such that the hydrogen/feed ratio is 500
Nm.sup.3/h/m.sup.3.
[0205] The temperature conditions used, namely an entry stream
temperature equal to 291.degree. C. in the case of the soya oil and
293.degree. C. in the case of the palm oil in the second catalytic
zone favour the hydrodenitrogenation kinetics and also permit the
deoxygenation reactions to be carried out in the majority of cases.
The exit temperature from the second catalytic zone of the
hydrotreated effluent is 322.degree. C. for the soya oil, and
328.degree. C. for the palm oil.
[0206] The degree of hydrogenation of the unsaturations, the degree
of deoxygenation and the nitrogen content of the effluent from the
second catalytic zone of the different feeds in the second
catalytic zone are given in Table 2. At the end of the
hydrotreatment stage a), the hydrogenation of the unsaturations is
total, and the nitrogen content is less than 0.4 ppm and the oxygen
content is less than 0.2%.
TABLE-US-00002 TABLE 2 operating conditions Soya Palm Total
pressure (MPa g) 5 5 overall H2/HC (Nm.sup.3/m.sup.3) 1500 1500
overall hsv (h - 1) 0.6 0.6 hsv zone 1 (h - 1) 1.6 1.6 hsv zone 2
(h - 1) 1 1 H2/HC zone 1 (Nm.sup.3/m.sup.3) 1000 1000 H2/HC zone 2
(Nm.sup.3/m.sup.3) 500 500 Overall recycle 2.95 1.25 Entry T zone 1
(.degree. C.) 200 200 Exit T zone 1 (.degree. C.) 258 258 Degree of
hydrogenation of the 73 73 unsaturations zone 1 (mol %) Degree of
deoxygenation zone 1 35 35 (mol %) HDO selectivity zone 1 99 99
Entry T zone 2 (.degree. C.) 291 293 Exit T zone 2 (.degree. C.)
322 328 Degree of hydrogenation of the 100 100 unsaturations zone 2
(mol %) Degree of deoxygenation zone 2 >97 >97 (mol %)
Nitrogen content zone 2 <0.4 <0.4 HDO selectivity zone 2 99
99
[0207] The hydrotreated effluents are then characterized. The
yields and the properties of the different cuts are listed in Table
3.
TABLE-US-00003 TABLE 3 Case of Case of Yield (wt. %/fresh feed)
soya oil palm oil Yield C.sub.1-C.sub.7 cut [wt. %] 5.1 5.2 Yield
150.degree. C. - cut [wt. %] 0 0 Yield 150.degree. C. + cut (gas
oil) 85.4 84.3 [wt. %]
[0208] The use of low overall recycle rates is permitted thanks to
an advantageous use of the heats of reaction, combined with as low
as possible a temperature at the entrance to each catalytic zone.
The minimization of the hydraulic flow rate in the first catalytic
zone leads to significantly reduced investment costs and operating
costs.
[0209] Moreover, the minimization of the recycle rate in the unit,
leading to a smaller dilution of the nitrogen-containing compounds,
combined with a high temperature permitted thanks to the supply of
a hot stream at the entrance to the second catalytic zone, leads to
higher hydrodenitrogenation kinetics and therefore permits an
optimized quantity of catalyst.
[0210] The proposed scheme therefore constitutes a flexible and
economical method of hydrotreating vegetable oils.
[0211] The effluent from the hydrotreatment stage is then separated
by means of a hydrogen stripping, in order to recover a gaseous
effluent and a hydrotreated liquid effluent of which at least a
part is recycled at the top of each catalytic zone of stage a) as
explained above.
[0212] In the case of the treatment of soya oil, 125 L/h of the
hydrotreated liquid effluent is recycled to the first catalytic
zone, and 22.5 L/h to the second catalytic zone. All of the
non-recycled hydrotreated liquid effluent is passed into a
hydroisomerization zone.
[0213] In the case of the treatment of palm oil, 50 L/h of the
hydrotreated liquid effluent is recycled to the first catalytic
zone, and 12.5 L/h to the second catalytic zone.
[0214] All of the non-recycled hydrotreated liquid effluent is
passed into a hydroisomerization zone.
[0215] The hydroisomerization catalyst is a catalyst containing a
precious metal and a 10 MR one-dimensional ZBM-30 zeolite. This
catalyst is obtained according to the procedure described below.
The ZBM-30 zeolite is synthesized according to BASF patent
EP-A-46504 with the organic structuring agent triethylenetetramine.
The crude ZBM-30 synthetic zeolite is subjected to a calcination at
550.degree. C. under a stream of dry air for 12 hours. The H-ZBM-30
zeolite (acid form) thus obtained has an Si/Al ratio of 45. The
zeolite is mixed with a type SB3 alumina gel supplied by the
company Condea-Sasol. The mixed paste is then extruded through a
die with a diameter of 1.4 mm. The extrudates thus obtained are
calcined at 500.degree. C. for 2 hours under air. The H-ZBM-30
content by weight is 20 wt. %. The supporting extrudates are then
subjected to a dry impregnation stage with an aqueous solution of
platinum salt Pt(NH.sub.3).sub.4.sup.2+, 2OH--, and then undergo a
maturation stage in a water soaker for 24 hours at ambient
temperature and are then calcined for two hours under dry air in a
fluidized bed at 500.degree. C. (temperature rise gradient
5.degree. C./min). The platinum content by weight of the finished
catalyst after calcination is 0.48%.
[0216] The operating conditions of the hydroisomerization stage are
described below: [0217] HSV (volume of feed/volume of
catalyst/hour)=h.sup.-1 [0218] total operating pressure: 5 MPa
[0219] hydrogen/feed ratio: 700 normal litres/litre
[0220] The temperature is adjusted so as to have a conversion of
less than 10 wt. % of the 150.degree. C..sup.+ fraction to
150.degree. C..sup.- fraction during the hydroisomerization. Before
the test, the catalyst undergoes a reduction stage under the
following operating conditions: [0221] hydrogen flow rate: 1600
normal litres per hour per litre of catalyst [0222] ambient
temperature rise 120.degree. C.: 10.degree. C./min [0223] plateau
for one hour at 120.degree. C. [0224] rise from 120.degree. C. to
450.degree. C. at 5.degree. C./min [0225] plateau for two hours at
450.degree. C. [0226] pressure: 0.1 MPa
[0227] The hydroisomerized effluent is then characterized. The fuel
yields and properties are listed in Tables 4, 5 and 6.
TABLE-US-00004 TABLE 4 yield of the hydroisomerization section (in
wt. % relative to the feed entering the hydroisomerization stage)
Yield (wt. %) Case of Case of soya oil palm oil C.sub.1-C.sub.4 cut
yield [wt. %] 1 1 150.degree. C. - cut (naphtha cut) yield [wt. %]
9.2 8.8 150.degree. C.-250.degree. C. cut (kerosene cut) yield 31.8
37.2 [wt. %] 250.degree. C. + cut (gas oil cut) yield [wt. %] 58
53
TABLE-US-00005 TABLE 5 characterization of the gas oil base
(250.degree. C. + cut) Case of Case of soya oil palm oil Cetane
number (ASTMD613) 80 75 Cold filter plugging point (.degree. C.)
-15 -20 Sulphur (ppm by wt) 1 1 Density (kg/m3) 790 785 Aromatics
content (wt. %) <0.2 <0.2
[0228] The density specification is obtained by mixing with a
petroleum gas oil of greater density.
TABLE-US-00006 TABLE 6 characterization of the kerosene cut
(150-250.degree. C. cut) Case of Case of soya oil palm oil Density
(kg/m.sup.3) 775 770 Smoke point (mm) 30 30 Viscosity (mm.sup.2/s)
at -20.degree. C. less than 8 6 5
[0229] The density, crystals disappearance point and flash point
specifications are obtained by mixing with a petroleum
kerosene.
[0230] The described sequence permits the production, from feeds of
renewable origin, of gas oil bases as well as a kerosene cut of
excellent quality, in terms of cetane number and low-temperature
properties in particular and also the limiting of the formation of
carbon oxide by using a catalyst favouring the hydrodeoxygenation
route.
[0231] 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 imitative of the remainder of the disclosure
in any way whatsoever.
[0232] The entire disclosures of all applications, patents and
publications, cited herein and of corresponding FR application Ser.
No. 09/05.160, filed Oct. 27, 2009, are incorporated by reference
herein.
[0233] From the foregoing description, one skilled in the art can
easily ascertain the essential characteristics of this invention
and, without departing from the spirit and scope thereof, can make
various changes and modifications of the invention to adapt it to
various usages and conditions.
* * * * *