U.S. patent application number 13/808843 was filed with the patent office on 2013-07-18 for hydrocarbon feedstock average molecular weight increase.
This patent application is currently assigned to TOTAL RAFFINAGE MARKETING. The applicant listed for this patent is Delphine Minoux, Cyril Revault. Invention is credited to Delphine Minoux, Cyril Revault.
Application Number | 20130180884 13/808843 |
Document ID | / |
Family ID | 43302414 |
Filed Date | 2013-07-18 |
United States Patent
Application |
20130180884 |
Kind Code |
A1 |
Minoux; Delphine ; et
al. |
July 18, 2013 |
HYDROCARBON FEEDSTOCK AVERAGE MOLECULAR WEIGHT INCREASE
Abstract
The invention deals with hydrocarbon feedstock molecular weight
increase via olefin oligomerization and/or olefin alkylation onto
aromatic rings. Addition of a purification section allows improved
unit working time and lower maintenance.
Inventors: |
Minoux; Delphine; (Nivelles,
BE) ; Revault; Cyril; (Sainte-Adresse, FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Minoux; Delphine
Revault; Cyril |
Nivelles
Sainte-Adresse |
|
BE
FR |
|
|
Assignee: |
TOTAL RAFFINAGE MARKETING
Puteaux
FR
|
Family ID: |
43302414 |
Appl. No.: |
13/808843 |
Filed: |
July 7, 2011 |
PCT Filed: |
July 7, 2011 |
PCT NO: |
PCT/EP2011/061464 |
371 Date: |
March 22, 2013 |
Current U.S.
Class: |
208/57 |
Current CPC
Class: |
C10G 25/05 20130101;
C10G 2300/1088 20130101; C10G 2300/202 20130101; C10G 29/205
20130101; C10G 2300/104 20130101; B01J 20/18 20130101; B01J 20/3408
20130101; B01J 2220/56 20130101; B01J 29/40 20130101; C10G
2300/4081 20130101; B01J 20/186 20130101; C10G 2400/04 20130101;
C07C 2/00 20130101; C10G 45/32 20130101; B01J 20/226 20130101; C10G
69/123 20130101; C10G 2300/301 20130101; B01J 20/08 20130101; C10G
69/126 20130101; B01J 2220/42 20130101; C10G 2300/1096 20130101;
C10G 2300/201 20130101; C10G 50/00 20130101 |
Class at
Publication: |
208/57 |
International
Class: |
C10G 69/12 20060101
C10G069/12 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 8, 2010 |
EP |
10305759.2 |
Claims
1. A method for the treatment of an olefin containing hydrocarbon
feedstock, wherein said feedstock successively undergoes (i)
selective hydrogenation, (ii) treatment on adsorbent to obtain at
least one nitrogen depleted fraction, (iv) at least one middle
distillate generation via (iv-a) oligomerization of said nitrogen
depleted fraction and/or (iv-b) alkylation of said nitrogen
depleted fraction.
2. A method according to claim 1, wherein (v) at least one
unreacted material is separated from said at least one middle
distillate.
3. A method according to claim 2, wherein said at least one
unreacted material is recycled at step (iv) for at least one middle
distillate generation.
4. A method according to claim 1, wherein selectively hydrogenated
feedstock of step (i) is split into at least two of LCCS, MCCS,
HCCS and fuel gas prior to treatment of at least one of the
foregoing on adsorbent.
5. A method according to claim 1, wherein said feedstock
successively undergoes (i) selective hydrogenation, (ii) splitting
into a light cut (LCCS) and a heavier cut (HCCS or mixed
MCCS/HCCS), (iii) LCCS treatment on adsorbent to obtain a nitrogen
depleted LCCS, (iv) a first middle distillate generation via (iv-a)
oligomerization of said nitrogen depleted LCCS and/or (iv-b)
alkylation of said nitrogen depleted LCCS.
6. A method according to claim 5, wherein (vi) said first middle
distillate is further alkylated with a gasoline cut to produce a
second middle distillate.
7. A method according to claim 6, wherein (vii) a second unreacted
material is separated from said second middle distillate.
8. A method according to claim 7, wherein said second unreacted
material is recycled at step (vii) for said second middle
distillate generation.
9. A method for the treatment of an olefin containing hydrocarbon
feedstock according to claim 1, wherein said feedstock successively
undergoes (i) selective hydrogenation, (ii) splitting into a light
cut (LCCS) and a heavier cut (HCCS or mixed MCCS/HCCS), (iii) said
LCCS and said HCCS or mixed MCCS/HCCS separate treatment on
adsorbent so as to remove nitrogen compounds, to obtain nitrogen
depleted LCCS and nitrogen depleted HCCS or mixed MCCS/HCCS, (iv) a
third middle distillate generation via (iv-a) oligomerization
and/or (iv-b) alkylation of said nitrogen depleted LCCS combined
with said nitrogen depleted HCCS or mixed MCCS/HCCS.
10. A method according to claim 9, wherein a gasoline cut is
separated from said third middle distillate.
11. A method for the treatment of an olefin containing hydrocarbon
feedstock according to claim 1, wherein said feedstock successively
undergoes (i) selective hydrogenation, (ii) splitting into a light
cut (LCCS) and a heavier cut (HCCS or mixed MCCS/HCCS), (iii) said
LCCS and said HCCS or mixed MCCS/HCCS separate treatment on
adsorbent so as to remove nitrogen compounds, to obtain nitrogen
depleted LCCS and nitrogen depleted HCCS or mixed MCCS/HCCS, (iv-a)
a fourth middle distillate generation via oligomerization of said
nitrogen depleted LCCS, (iv-b) a fifth middle distillate generation
via alkylation of said nitrogen depleted HCCS or mixed
MCCS/HCCS.
12. A method according to claim 11, wherein unreacted olefins are
separated from said fourth middle distillate.
13. A method according to claim 12, wherein unreacted olefins are
recycled at step (iv-a) for fourth middle distillate
generation.
14. A method according to claim 11, wherein fourth middle
distillate is alkylated with nitrogen depleted HCCS or mixed
MCCS/HCCS and an aromatic containing stream at step (iv-b) to
produce said fifth middle distillate.
15. A method according to claim 14, wherein unreacted material is
separated from said fifth middle distillate.
16. A method according to claim 15, wherein unreacted material is
recycled at step (iv-b).
17. A method according to claim 1, wherein said adsorbent comprises
one or more of molecular sieves, acidic ion-exchange resins,
acid-treated clays, activated aluminas, spent FCC catalysts, MOF
(Metal-Organic Framework), ASA, NiMo, and catalysts guard beds.
18. A method according to claim 1, wherein said adsorbent is loaded
into a purification section located in a guard bed capacity, which
guard bed capacity is operated on a swing cycle with two or three
beds, and wherein, respectively, one or two beds in series, are
being used on stream for contaminant removal, while the remaining
one is on regeneration.
Description
[0001] Hydrocarbon feedstock average molecular weight increase. The
instant invention discloses a method for the conversion of low
boiling point olefin containing hydrocarbon feedstock into higher
boiling point cuts via olefin oligomerization and/or olefin
alkylation onto aromatic moieties.
[0002] More specifically, the processed hydrocarbon load has an
initial boiling point that is set between butanes to hexanes
boiling points (included) and a final boiling point equal to or
below 165.degree. C.
[0003] Refineries of today have to adapt to a continuously evolving
and fluctuating market, requiring always more flexibility. It is
especially the case with the gasoline/middle distillates markets,
which have largely evolved during the years: a shift in product
focus from gasoline to middle distillates is being observed in the
current and future European market demands.
[0004] Middle distillates comprise from 10 to 20 carbon atoms and
present a boiling range from 145.degree. C. to 350.degree. C.
[0005] To respond to the above-mentioned disequilibrium, a nice way
of readjusting the gasoline/diesel balance according to the market
needs consists in upgrading at least part of the gasoline into
middle distillates (jet, diesel).
[0006] In a typical refinery today, most of the C4-C8 molecules end
up in the gasoline-pool. It is important to note that only around
5% of these molecules were initially present in the crude oil as
delivered, while cracking during refinery processing creates the
rest. About 50% of the C4's and 40% of the C5's that are produced
during Fluidized Catalytic Cracking (FCC) are olefinic in nature.
Currently the C4 olefins are used as feed for the alkylation and
etherification units to create gasoline components with high octane
and the higher olefins are generally directly blended into the
gasoline pool.
[0007] In that context, a convenient solution that allows a renewed
equilibrium between gasoline and distillates would be to convert
unsaturated molecules (olefins and/or aromatics) contained in the
gasoline feed into heavier molecules lying in the middle distillate
range (i.e. diesel and kerosene) by selective oligomerization
and/or alkylation of these unsaturated molecules.
[0008] The present invention relates to a process for the
manufacture of higher molecular weight organic molecules from a
stream of lower molecular weight molecules which contain
contaminants brought in by the feedstock.
[0009] Oligomerization of olefinic streams is largely documented
and is a widely used commercial process, but is subject to
limitations.
[0010] Typically, oligomerization processes involve contacting
lower olefins (typically mixtures of propylene and butenes) coming
from Fluid Catalytic Cracker (FCC) and/or steam crackers with a
solid acid catalyst, such as Solid Phosphoric acid (SPA) catalyst,
crystalline molecular sieve, acidic ion exchange resin or amorphous
acid material (silico-alumina).
[0011] With SPA catalyst, the pressure drop over the catalytic
bed(s) increases gradually due to coking, swelling of the catalyst,
and is therefore the limiting factor of a run duration, the unit
being shutdown once the maximum allowable pressure drop has been
reached.
[0012] With crystalline molecular sieve, acidic ion exchange resin
or amorphous acidic material (silico-alumina), the limiting factor
is usually no more the pressure drop along the catalytic bed but
the reactor run length which is determined by the catalytic
performances (shutdown when the catalytic activity has dropped to
an unacceptably low level). The performances of such catalyst are
therefore sensitive to poisons contained in the feedstock, which
may considerably affect the cycle length.
[0013] Certain impurities such as sulfur containing contaminants
and basic nitrogen have an adverse effect in the useful lifetime of
the catalyst.
[0014] Among the sulfur containing contaminants, low molecular
weight sulfur species are especially troublesome, as described in
US 2008/0039669, i.e. aliphatic thiols, sulfides and disulfides.
For example dimethyl-, diethyl-, and ethyl-methyl-sulphides,
n-propane thiol, 1-butane thiol and 1,1-methylethyl thiol,
ethyl-methyl- and dimethyl-disulphides, and
tetrahydrothiophene.
[0015] Among the basic nitrogen contaminants, we can distinguish:
[0016] The strong organic Bronsted bases (characterized by at least
one hydrogen atom bound to the nitrogen atom, and being proton
acceptors), such as amines and amides, contribute to negatively
affect the catalyst performances. [0017] The other organic nitrogen
compounds, called Lewis bases, have free electron pair on the
nitrogen atom such as nitriles, morpholines or N-Methyl
pyrrolidone. Though much weaker bases as compared to the Bronsted
bases, they strongly deactivate the catalyst. The detrimental
effect of such impurities has been discussed in US patent
application publication 2008/0312484.
[0018] In some specific cases, the purity of the olefinic stream is
not an issue:
[0019] It is the case when the stream involves very pure
Fisher-Tropsch (FT) derived olefins (US2008/0257783 or
WO2006/091986)
[0020] It is also the case in the fully integrated system MTG
(Methanol-to-Gasoline) where olefinic streams are produced from the
Methanol-To-Olefin process and oligomerized through the so-called
MOGD process (Mobil Olefin to Gasoline and Distillate). The MOGD
process, proposed by Mobil (U.S. Pat. No. 4,150,062; U.S. Pat. No.
4,227,992; U.S. Pat. No. 4,482,772; U.S. Pat. No. 4,506,106; U.S.
Pat. No. 4,543,435) and developed between the seventies' and
eighties', in fact used ZSM-5 zeolite as catalyst. The products
obtained from the reaction of butenes are trimers and tetramers,
characterized by a low branching degree. The gas oil fraction
however is lower than that of the jet fuel fraction and
consequently, even if this process offers good quality gas oil
(cetane number>50), it is more interesting for the production of
jet fuel than gas oil. In US20040254413 patent application,
ExxonMobil pursued the Mobil development and introduced the new
generation of MOGD. This invention uses two or more zeolite
catalysts. Examples of zeolite catalysts include a first catalyst
containing ZSM-5, and a second catalyst containing a 10-ring
molecular sieve, including but not limited to, ZSM-22, ZSM-23,
ZSM35, ZSM-48, and mixtures thereof. The ZSM-5 can be unmodified,
phosphorous modified, steam modified having a micropore volume
reduced to not less than 50% of that of the unsteamed ZSM-5, or
various mixtures thereof.
[0021] ZSM-5 stands for Zeolite Sieve of Molecular porosity (or
Zeolite Socony Mobil)-5, (structure type MFI-Mordenite Framework
Inverted). ZSM-5 is an aluminosilicate zeolite mineral belonging to
the pentasil family of zeolites. Its chemical formula is
Na.sub.nAl.sub.nSi.sub.96-nO.sub.192.16H.sub.2O (0<n<27).
[0022] In a similar manner, Lurgi AG, Germany (WO2006/076942), has
developed the Methanol to Synfuels (MTS) process, which is in
principle similar to the MOGD process. The Lurgi route is a
combination of simplified Lurgi MTP technology with COD technology
from Sued Chemie (US5063187). This process produces gasoline (RON
80) and diesel (Cetane .about.55) in the ratio of approximately
1:4. Disclosed is a method for the production of synthetic fuels,
wherein, in a first step, a gas mixture consisting of methanol
and/or dimethyl ether and/or another oxygenate and water vapor is
reacted at temperatures of 300-600.degree. C. in order to form
olefins with, preferably, 2-8 carbon atoms. In a second step, the
olefin mixture thus obtained is oligomerized at an elevated
pressure to form higher olefins with predominantly more than 5,
preferably 10-20 carbon atoms. According to said method, a) the
production of olefins in the first step is carried out in the
presence of a gas flow which essentially consists of saturated
hydrocarbons which are separated from the product flow of the
second step and returned to the first step, and (b) the production
of olefins is carried out in the second step in the presence of a
flow of water vapor which is separated from the product flow of the
first step and returned to the first step.
[0023] Above-discussed methods are hardly developable in the
context of gasoline upgrading into distillates: Commonly available
olefinic feedstocks cause rapid deactivation of existing
oligomerization catalysts, due to the presence of contaminants in
the feed, which is a critical issue.
[0024] Catalytic cracking, usually fluid catalytic cracking (FCC),
is a suitable source of cracked naphthas. Thermal cracking
processes such as coking may also be used to produce usable feeds
such as coker naphtha, pyrolysis gasoline, and other thermally
cracked naphthas.
[0025] The process may be operated with a part of, or the entire
gasoline fraction, obtained from a catalytic or thermal cracking
step.
[0026] In case of alkylation reactions, the co-feed comprises a
light fraction, boiling within the gasoline boiling range which is
relatively rich in aromatics. A suitable refinery source for the
light fraction is a reformate fraction. The reformate co-feeds
usually contain very low amounts of sulfur as they have usually
been subjected to desulfurization prior to reforming.
[0027] To cope with the contaminants issue, different techniques
have been proposed:
[0028] A first technique consists in contacting the nitrogen and
sulfur contaminated feedstock either with a hydrotreating catalyst
at oxidized state (U.S. Pat. No. 6,884,916-Exxon) or with a metal
oxide catalyst (U.S. Pat. No. 7,253,330) in the absence of
hydrogen, ahead of the oligomerization section, thus limiting
catalyst deactivation. The pretreatment is believed to convert
small sulfur compounds into larger sulfur species, then into more
sterically hindered molecules, no more entering the catalyst pores,
and limiting catalyst deactivation.
[0029] Another convenient way (U.S. Pat. No. 7,186,874-Exxon) is to
mitigate the adverse effect of the sulfur compounds on catalyst
activity by appropriately adjusting the operating conditions of the
process by, for example, temperature rising.
[0030] Removal of nitriles and other organic nitrogen-containing
Lewis bases from the oligomerization feed may be achieved by a
washing step with water (WO2007/104385--Exxon). Removal of basic
nitrogen and sulfur-containing organic compounds by scrubbing with
contaminant removal washes such as caustic, methyl-ethyl-amine
(MEA), or other amines or aqueous washing liquids, is discussed in
WO 2006/094010 (Exxon). This method allows contaminants to stand at
acceptable levels (10-20 ppmwt S, trace levels for N) and therefore
to limit catalyst deactivation prior to oligomerization and
alkylation reactions.
[0031] Sorption techniques are also reported for nitrogen
components removal from the feed. US2005/0137442 (UOP) discloses
the use of molecular sieves catalysts (such as Y-zeolite) to remove
the nitrogen-based contaminants present in an olefinic stream to be
alkylated. Specificity of US2005/0137442 (UOP) lies in operating
conditions: adsorption is conducted at a temperature of at least
120.degree. C. to increase the nitriles adsorption capacity of the
sorbent in the presence of water.
[0032] Purification section using molecular sieves is also reported
in EP1433835 (IFP), where shaped MOR catalyst having a Si/Al atomic
ratio of 45 allows decreasing nitrogen content from 10 ppmwt to 0.2
ppmwt. US2008/0312484 (Exxon) shown that such a low nitrogen
concentration can be tolerated in olefin-containing hydrocarbon
feeds loaded in oligomerization sections.
[0033] WO2006/067305 (IFP) discloses a process for producing
propylene from C4/C5 cut (from steam cracking or catalytic
cracking). Prior to the steps of so-called
"oligomerization/cracking", the following purification sequence is
used to remove contaminants: a selective hydrogenation is used to
convert the dienes and acetylenic compounds into mono-olefins, then
drying and desulfurization steps are performed by the use of
different sorbents (3A, 13X molecular sieves).
[0034] Thus, state of the art processes do not use untreated
refinery streams for oligomerization/alkylation but rather pure
streams (such as ex-FT or ex-MTO olefins). As such, existing
commercial solutions cannot give satisfactory results for untreated
refinery streams to be valorized.
[0035] It has now been found an improved route to process untreated
refinery streams (such as FCC, coker . . . ) into an
oligomerization/alkylation reaction.
[0036] A first object of the invention concerns a method for the
treatment of an olefin containing hydrocarbon feedstock, wherein
said feedstock successively undergoes (i) selective hydrogenation,
(ii) treatment on adsorbent to obtain at least one nitrogen
depleted fraction, (iv) at least one middle distillate generation
via (iv-a) oligomerization of said nitrogen depleted fraction
and/or (iv-b) alkylation of said nitrogen depleted fraction.
[0037] A first step consists in selective hydrogenation of
di-olefins into mono-olefins to avoid gum formation in downstream
catalyst, allowing at the same time conversion of low molecular
weight sulfur containing molecules (aliphatic thiols, sulfides or
disulfides being especially troublesome) into heavier molecular
weight sulfur containing molecules.
[0038] Preferably, the resulting stream is then fractionated in a
splitter in a light cut (LCCS gasoline), and a heavier cut (HCCS or
mixed MCCS/HCCS)
[0039] A further step consists in removing from the obtained LCCS
gasoline cut (or from unfractionated selectively hydrogenated
feedstock) the residual light N and S compounds by the use of
different sorbents (alone or in combination, such as 3A/13X
molecular sieves) before entering the oligomerization/alkylation
section.
[0040] Once purified in such a purification section, the olefinic
stream can then be valorized into middle distillates by
oligomerization and/or alkylation as represented on FIGS. 3 to
8.
[0041] It has been found that oligomerization and/or alkylation
catalyst lifetime is tremendously increased using this method. An
hypothesis to explain improvement in catalyst lifetime in operation
could be that the allegedly most detrimental sulfur containing
compounds (S compounds) (such as aliphatic thiols, sulfides and
disulfides: for example, dimethyl-, diethyl-, and
ethyl-methyl-sulphides, n-propane thiol, 1-butane thiol and
1,1-methylethyl thiol, ethylmethyl- and dimethyl-disulphides) are
converted within the selective hydrogenation unit by direct
reaction of light sulfur containing molecules (e.g. here
above-mentioned S compounds) with olefins or thiophenic compounds,
thus leading to the formation of heavier S molecules, no more
present in the LCCS cut issued from the splitter section.
[0042] Though thiophenic ring containing molecules are still
present in the LCCS cut, they do not interact significantly with
the acid sites of the oligomerization/alkylation catalyst.
[0043] The allegedly most detrimental nitrogen containing compounds
(N molecules), if not converted into heavier N molecules in a
similar manner as S molecules, are removed in the purification
section by adsorption on sorbents. It is advantageous to use
molecular sieves (3A, 13X, HY . . . ), Acidic ion-exchange resins,
Acid-treated clays, Activated aluminas such as SAS-351, MOF (Metal
Organic Frameworks), amorphous alumina-silica (ASA), Spent FCC
catalysts either alone or in combination.
[0044] Advantageously, the method of the invention comprises a
further step wherein (v) at least one unreacted material is
separated from said at least one middle distillate.
[0045] Advantageously, said at least one unreacted material is
recycled at step (iv) for at least one middle distillate
generation.
[0046] In the method of the invention, selectively hydrogenated
feedstock may be splitted into at least two of LCCS (Light
Catalytic Cracked Stream), MCCS (Middle Catalytic Cracked Stream),
HCCS (Heavy Catalytic Cracked Stream) and fuel gas prior to
treatment of at least one of the foregoing on adsorbent.
[0047] The alkylation of said at least one nitrogen depleted
fraction is advantageously performed in presence of an aromatic
containing hydrocarbon feedstock.
[0048] In a first embodiment of the above described method, said
feedstock successively undergoes (i) selective hydrogenation, (ii)
splitting into a light cut (LCCS) and a heavier cut (HCCS or mixed
MCCS/HCCS), (iii) LCCS treatment on adsorbent to obtain a nitrogen
depleted LCCS, (iv) a first middle distillate generation via (iv-a)
oligomerization of said nitrogen depleted LCCS and/or (iv-b)
alkylation of said nitrogen depleted LCCS.
[0049] Preferably, alkylation is performed in presence of an
aromatic containing stream.
[0050] Advantageously, the method of the invention comprises a
further step (v) wherein a first unreacted material is separated
from said first middle distillate.
[0051] Advantageously, said first unreacted material is recycled at
step (iv) for first middle distillate generation.
[0052] The method may also comprise another step (vi) wherein said
first middle distillate is further alkylated with a gasoline cut to
produce a second middle distillate.
[0053] Preferably, (vii) a second unreacted material is then
separated from said second middle distillate and more particularly,
said second unreacted material is recycled at step (vii) for said
second middle distillate generation.
[0054] In a second embodiment of the above described method, said
feedstock successively undergoes (i) selective hydrogenation, (ii)
splitting into a light cut (LCCS) and a heavier cut (HCCS or mixed
MCCS/HCCS), (iii) said LCCS and said HCCS or mixed MCCS/HCCS
separate treatment on adsorbent so as to remove nitrogen compounds,
to obtain nitrogen depleted LCCS and nitrogen depleted HCCS or
mixed MCCS/HCCS, (iv) a third middle distillate generation via
(iv-a) oligomerization and/or (iv-b) alkylation of said nitrogen
depleted LCCS combined with said nitrogen depleted HCCS or mixed
MCCS/HCCS.
[0055] A third unreacted material may be separated from said third
middle distillate. A gasoline cut may also be separated from said
third middle distillate. Preferably, said third unreacted material
is recycled at step (iv) for said third middle distillate
generation.
[0056] In a third embodiment of the invention, said feedstock
successively undergoes (i) selective hydrogenation, (ii) splitting
into a light cut (LCCS) and a heavier cut (HCCS or mixed
MCCS/HCCS), (iii) said LCCS and said HCCS or mixed MCCS/HCCS
separate treatment on adsorbent so as to remove nitrogen compounds,
to obtain nitrogen depleted LCCS and nitrogen depleted HCCS or
mixed MCCS/HCCS, (iv-a) a fourth middle distillate generation via
oligomerization of said nitrogen depleted LCCS, (iv-b) a fifth
middle distillate generation via alkylation of said nitrogen
depleted HCCS or mixed MCCS/HCCS.
[0057] Preferably, alkylation is performed in presence of an
aromatic containing stream.
[0058] Unreacted olefins are advantageously separated from said
fourth middle distillate. For example, said unreacted olefins are
recycled at step (iv-a) for fourth middle distillate
generation.
[0059] Fourth middle distillate may also be alkylated with nitrogen
depleted HCCS or mixed MCCS/HCCS and said aromatic containing
stream at step (iv-b) to produce said fifth middle distillate.
Advantageously, unreacted material is then separated from said
fifth middle distillate, and preferably, said unreacted material is
recycled at step (iv-b).
[0060] In any of the embodiments of the invention, said adsorbent
comprises one or more of molecular sieves, acidic ion-exchange
resins, acid-treated clays, activated aluminas, spent FCC
catalysts, MOF (Metal-Organic Framework), ASA, NiMo, and catalysts
guard beds.
[0061] Preferably, the adsorbent is selected among, or is a
combination of one or more of 13X molecular sieve, ASA, NiMo, and
MOF.
[0062] Advantageously, adsorbent used in any method of the
invention is loaded into a purification section located in a guard
bed capacity.
[0063] With regards to purification section, a guard bed reactor
may be operated on a swing cycle with two beds, one bed being used
on stream for contaminant removal and the other on regeneration in
the conventional manner. If desired, a three-bed guard bed system
may be used on a swing cycle with the two beds used in series for
contaminants removal and the third bed in regeneration. With the
three-bed guard bed system used to achieve low contaminant levels
by the two-stage series sorption, the beds will pass sequentially
through a three-step cycle of regeneration. A three-bed guard bed
system allows better use of guard bed sorption capacity since
non-used sorbent sent in regeneration is lowered, if not
eliminated. Typically, a three-bed guard bed system may be operated
as follows: Step 1: feedstock flows into first then second guard
bed, third one being isolated and under regeneration. Step 2: once
first guard bed is saturated in impurities, the latter is isolated
and regenerated, and feedstock now flows into second then third
guard beds. Step 3: once second guard bed is saturated in
impurities, the latter is isolated and regenerated, and feedstock
now flows into third then first guard beds. Step 4: go to step
1.
[0064] A plural reactor system may be employed with inter-reactor
cooling for oligomerization/alkylation, whereby exothermal reaction
can be carefully controlled to prevent excessive temperature above
the normal moderate range.
[0065] The oligomerization/alkylation reactor can be of isothermal
or adiabatic fixed bed type or a series of such reactors or a
moving bed reactor. The oligomerization/alkylation may be performed
continuously in a fixed bed reactor configuration using a series of
parallel "swing" reactors. Herein used catalysts have been found to
be stable enough. This enables the oligomerization/alkylation
process to be performed continuously in two parallel "swing"
reactors wherein, when one or two reactors are in operation, the
other reactor is undergoing catalyst regeneration. Catalysts of the
invention may be regenerated. Regeneration may be done several
times.
[0066] An object of the present invention is to convert olefins
containing stream into heavier hydrocarbons enriched distillate,
employing a continuous multi-stage catalytic technique. A plural
reactor system may be employed with inter-reactor cooling, whereby
the exothermal reaction can be carefully controlled to prevent
excessive temperature above the normal moderate range. Preferably,
the maximum temperature differential across only one reactor does
not exceed 75.degree. C. Optionally, the pressure differential
between the two stages can be utilized in an intermediate flashing
separation step.
[0067] The following types of acid catalysts can be used in
oligomerization and/or alkylation:
[0068] Amorphous or crystalline alumosilicate or
silicaalumophosphate in H-form, optionally containing alkali,
alkali-earth, transition or rare-earth elements, selected from the
group:
[0069] MFI (e.g. ZSM-5, silicalite-1, boralite C, TS-1), MEL
(Si/Al>25) (e.g. ZSM-11, silicalite-2, boralite D, TS-2,
SSZ-46), ASA (amorphous silica-alumina), MSA (mesoporous
silica-alumina), FER (e.g. Ferrierite, FU-9, ZSM-35), MTT (e.g.
ZSM-23), MWW (e.g. MCM-22, PSH-3, ITQ-1, MCM-49), TON (e.g. ZSM-22,
Theta-1, NU-10), EUO (e.g. ZSM-50, EU-1), ZSM-48, MFS (e.g.
ZSM-57), MTW, MAZ, SAPO-11, SAPO-5, FAU (e.g. USY), LTL, BETA, MOR,
SAPO-40, SAPO-37, SAPO-41, MCM-41, MCM-48 and a family of
microporous materials consisting of silicon, aluminum, oxygen and
optionally boron, Al.sub.2O.sub.3, and mixtures thereof.
[0070] Amorphous alumosilicates or silicaalumophosphates in H-form
optionally modified by addition of halogens (Fluorine preferred)
such as MSA (mesoporous silica-alumina) can also be used.
[0071] Above-mentioned catalysts can be subjected to an additional
treatment before use, including ion exchange, modification with
metals such as alkali, alkali-earth and rare earth metals,
steaming, treatment in an alkaline medium, acid treatment or other
dealumination methods, phosphatation, surface passivation by silica
deposition or combination thereof.
[0072] The amount of alkali, alkali-earth, transition or rare-earth
elements is in the range 0.05-10 wt %, preferably from 0.1 to 5 wt
%, more preferably from 0.2 to 3 wt % (wt % stands for weight
percent).
[0073] Preferred alkali, alkali-earth or rare-earth elements are
selected among Na, K, Mg, Ca, Ba, Sr, La, Ce, and mixtures
thereof.
[0074] Above-mentioned catalysts may be additionally doped with
further metals. In this respect, and according to another
embodiment of the invention, Me-catalysts (Me=metal) containing at
least 0.1 wt % are used. Preferably, the metal is selected from the
group of Zn, Mn, Co, Ni, Ga, Fe, Ti, Zr, Ge, Sn, Cr, and mixtures
thereof.
[0075] Those atoms can be inserted into the tetrahedral framework
through a [MeO.sub.2] tetrahedral unit. Incorporation of the metal
component is typically accomplished during synthesis of the
molecular sieve. However, post-synthesis ion exchange or
impregnation can also be used. In post-synthesis exchange, the
metal component will be introduced as a cation on ion-exchange
positions at an open surface of the molecular sieve, but not into
the framework itself.
[0076] The selected materials could be subjected to a different
treatment before use in the reaction, including introduction of
phosphorous, ion exchange, modification with alkali, alkali-earth
or rare earth metals, steaming, acid treatment or other
dealumination methods, surface passivation by silica deposition or
combination thereof.
[0077] The catalyst can be a blend of materials as depicted above,
and/or can be further combined with other materials that provide
additional hardness or catalytic activity to the finished catalyst
product (binder, matrix).
[0078] The method of the invention permits to treat a feedstock
issued from FCC, coker, flexi-coker, visbreaker, steam cracker,
hydrocracker, for example from DHC (distillate hydrocracker) or MHC
(mild hydrocracker) hydrocracker, preferably from FCC or coker.
[0079] For example, the feedstock may be issued from a Prime-G
1.sup.st stage unit. Particularly, the feedstock may be a LCCS cut
corresponding to the low boiling point fraction of a LCN treated on
a Prime-G 1.sup.st stage unit.
[0080] The final boiling point of the feedstock may be below
200.degree. C., preferably below 165.degree. C.
[0081] The initial boiling point of the feedstock may be above
-50.degree. C., preferably above 0.degree. C., more preferably
above +25.degree. C.
[0082] The invention is now described with reference to appended
FIGS. 1-8, which depict different non-limitative methods for the
preparation of middle distillate cuts starting from olefin
containing lighter cuts, e.g. ex-FCC, ex-coker or ex-DHC gasoline
cuts.
[0083] FIG. 1 is a graph showing olefin conversion (% wt) as a
function of TOS (Time Of Stream) when no purification section is
used. (See example 1 for details)
[0084] FIG. 2 shows olefin conversion rate (% wt) as a function of
TOS when a purification section is used. (See example 2 for
details)
[0085] FIG. 3 represents an oligomerization method using a
purification section and optionally a recycle of unreacted
stream.
[0086] FIG. 4 shows an oligomerization and alkylation process
scheme using a purification section and optionally a recycle of
unreacted stream.
[0087] FIG. 5 illustrates another alkylation method using a
purification section and optionally a recycle of unreacted olefin
and aromatic streams.
[0088] FIG. 6 represents another oligomerization and alkylation
process using a purification section and optionally a recycle of
unreacted olefin and aromatic streams.
[0089] FIG. 7 shows a one-pot oligomerization and alkylation scheme
using a purification section and optionally a recycle of unreacted
olefin stream.
[0090] FIG. 8 represents an oligomerization and alkylation scheme
of full olefin containing refinery stream using a purification
section and optionally a recycle of unreacted olefin and aromatic
streams.
[0091] FIG. 3 represents an oligomerization method using a
purification section and optionally a recycle of unreacted
stream.
[0092] The untreated refinery stream 310 is fed to a Selective
Hydrogenation Unit (SHU) 31. The dedienized refinery stream 311
thus obtained is fed to a splitter 32 wherein it is separated in
fuel gas 312, LCCS 313 (FBP=60.degree. C. to 100.degree. C.) and
HCCS 314 (Boiling point cut ranges from 60-170.degree. C. to
100-170.degree. C.).
[0093] In the present application, FBP stands for Final Boiling
Point and IBP stands for Initial Boiling Point.
[0094] LCCS 313 is then fed to a purification unit 33 for removal
of nitrogen by adsorption on sorbents.
[0095] The purified LCCS stream 315 obtained is fed to an
oligomerization unit 34, the obtained products being separated in a
further splitter 35 into a gasoline 316, aromatics 317 and middle
distillate 318.
[0096] The part of the gasoline 316, consisting of unreacted
olefins, may optionally be recycled back into the oligomerization
unit 34 via the line 319.
[0097] FIG. 4 shows an oligomerization and alkylation process
scheme using a purification section and optionally a recycle of
unreacted stream.
[0098] The untreated refinery stream 410 (for example LCN (Light
Cracked Naphtha)) is fed to a Selective Hydrogenation Unit, SHU 41.
The dedienized refinery stream 411 thus obtained is purified in a
purification units 42 for removal of nitrogen by adsorption on
sorbents.
[0099] The purified stream 412 is fed to an oligomerization unit
43. Optionally, an aromatic stream 413 may be co-fed with stream
412.
[0100] The effluents issued from the oligomerization unit 43 are
separated in a splitter 44 into gasoline 415 and middle distillates
416.
[0101] The part of the gasoline 415, consisting of unreacted
material, may optionally be recycled back into the oligomerization
unit 43 via the line 414.
[0102] FIG. 5 shows an alkylation process scheme using a
purification section and a recycle of unreacted olefin and aromatic
streams.
[0103] The untreated refinery stream 510 is fed to a Selective
Hydrogenation Unit (SHU) 51. The dedienized refinery stream 511
thus obtained is fed to a first splitter 52 wherein it is separated
in LCCS 512 (FBP=60.degree. C. to 100.degree. C.) and M/HCCS 513
(Boiling point cut ranges from 60-170.degree. C. to 100-170.degree.
C.).
[0104] LCCS 512 is then fed to a purification unit 53 for removal
of nitrogen by adsorption on sorbents.
[0105] The purified LCCS stream 514 obtained is fed to an
alkilation unit 54, the obtained products being separated in a
further splitter 55 into a gasoline 516, aromatics 517 and middle
distillates 518.
[0106] The part of the gasoline 516, consisting of unreacted
olefins, may optionally be recycled back into the alkylation unit
54 via the line 519 as well as the part of unreacted aromatic 517
via line 520.
[0107] An aromatic containing stream (e.g. reformate), may also be
added to the feed of alkylation unit 54 via line 515.
[0108] FIG. 6 shows an oligomerization and alkylation process
scheme using a purification section and optionally a recycle of
unreacted olefin and aromatic streams.
[0109] The untreated refinery stream 610 is fed to a Selective
Hydrogenation Unit, SHU 61. The dedienized refinery stream 611 thus
obtained is separated in a first splitter 62 into a LCCS 612
(FBP=60.degree. C. to 100.degree. C.) and a M/HCCS 613 (Boiling
point cut ranges from 60-170.degree. C. to 100-170.degree. C.).
[0110] LCCS 612 is then purified in a purification unit 63 for
removal of nitrogen by adsorption on sorbents.
[0111] The purified stream 614 is fed to an oligomerization unit
64.
[0112] The effluents issued from the oligomerization unit 64 are
separated in another splitter 65 into a stream 616 of oligomers and
unreacted olefins, a part of which may optionally be recycle
upstream of oligomerization unit 64 via line 615, and into a stream
of (light) middle distillates 617.
[0113] Middle distillates 617 are fed to an alkylation unit 66
which is also fed with a (light) gasoline cut 618. Effluents issued
from the alkylation unit 66 are separated in a third splitter 67
into a (heavier) gasoline cut 620, a part of which may be recycled
back upstream of alkylation unit 66 via line 619, and into a
(heavier) middle distillate 621.
[0114] FIG. 7 shows a one pot oligomerization and alkylation
process scheme using a purification section and optionally a
recycle of unreacted olefin stream.
[0115] The untreated refinery stream 710 is fed to a Selective
Hydrogenation Unit, SHU 71. The dedienized refinery stream 711 thus
obtained is separated in a first splitter 72 into a LCCS 712
(FBP=60.degree. C. to 100.degree. C.) and a M/HCCS 713 (Boiling
point cut ranges from 60-170.degree. C. to 100-170.degree. C.).
[0116] LCCS 712 is then purified in a dedicated purification unit
73 and M/HCCS 713 is purified in another dedicated purification
unit 73', for removal of nitrogen by adsorption on sorbents.
[0117] The purified streams 714 and 718 issued respectively from
purification units 73 and 73', are fed to a combined
oligo-alkylation unit 74.
[0118] The effluents issued from the oligo-alkylation unit 74 are
separated in a further splitter 75 into a stream 716 of middle
distillates, a part of which may optionally be recycled upstream of
oligo-alkylation unit 74 via line 715, and into a gasoline cut
717.
[0119] FIG. 8 shows an oligomerization and alkylation process
scheme of a full olefin containing refinery stream, this process
using a purification section and optionally a recycle of unreacted
olefin and aromatic streams.
[0120] The untreated refinery stream 810 is fed to a Selective
Hydrogenation Unit, SHU 81. The dedienized refinery stream 811 thus
obtained is separated in a first splitter 82 into a LCCS 812
(FBP=60.degree. C. to 100.degree. C.) and a M/HCCS 813 (Boiling
point cut ranges from 60-170.degree. C. to 100-170.degree. C.).
[0121] LCCS 812 is then purified in a purification unit 83 on
sorbents and M/HCCS 813 is purified in a different purification
unit 83', for removal of nitrogen by adsorption on sorbents.
[0122] The purified LCCS stream 814 is fed to an oligomerization
unit 84. The effluents issued from the oligomerization unit 84 are
separated in another splitter 85 into a stream 817 of (light)
gasoline cut and a stream 815 of oligomers. The part of unreacted
olefins 816 of the stream 817 may be recycled upstream of
oligomerization unit 84.
[0123] The purified M/HCCS 813 is fed to an alkylation unit 86,
preferably with an aromatic containing stream 818. The stream 815
of oligomers issued from splitter 85 is also fed to the alkylation
unit 86 The effluents issued from the alkylation unit 86 are
separated in a further splitter 87 into a stream 820 of middle
distillates and a stream 821 of a (heavier) gasoline cut. The part
of unreacted material 819 of the stream 821 may be recycled
upstream of alkylation unit 86.
EXAMPLES
[0124] In the following examples, the gasoline cut feedstock is a
LCCS cut (Light Catalytic Cracked Stream) corresponding to the low
boiling point fraction of a LCN (Light Cracked Naphtha) treated on
a Prime-G 1st stage unit (Prime-G is a naphtha selective
hydrogenation technology marketed by Axens, which hydrogenates most
reactive alkenes, mainly di-olefines, in particular conjugated
dienes (e.g. buta-1,3-diene into but-1-ene) and eventually
isomerizes n-olefines (end-chain double bond, e.g. n-hex-1-ene)
into sec-olefines (internalized double bond, e.g. n-hex-2-ene), so
as to get rid of the di-olefins (by selective hydrogenation) and of
the low molecular weight sulfur containing molecules by conversion
into heavier ones).
[0125] Unless otherwise specified, % are weight %.
[0126] Characteristics of the gasoline cut are reported below in
table 1.
TABLE-US-00001 TABLE 1 Characteristics of the LCCS cut used in the
examples Unit Value Density at 15.degree. C. g/mL 0.6518 Sulfur ppm
wt 24 Total nitrogen ppm 12.6 Diene value UOP 326 g iodine/100 g
0.11 Bromine Number g bromine/100 g 140.8 ASTM D1159 Reid Vapor
Pressure kPa 125.5 ASTM D5191 Sulfur speciation
Methyl-ethyl-sulfide ppm wt 2 Thiophene ppm wt 22 ASTM D86
T.degree. C. at IBP .degree. C. 27.6 T.degree. C. at 5% vol
.degree. C. 31 T.degree. C. at 50% vol .degree. C. 38 T.degree. C.
at 95% vol .degree. C. 55 T.degree. C. at FBP .degree. C. 63.6
Chemical species C4 % wt 6.80 C5 % wt 45.44 C6 % wt 10.65 Total
olefins % wt 62.89 iC5 % wt 21.35
[0127] The olefinic conversion is expressed in % wt as:
100.times.(olefin IN-olefin OUT)/olefin IN
[0128] 100 mL of ZSM-5 based catalyst diluted with 100 mL of inert
material (SiC 0.21 mm) have been loaded in a fixed bed tubular
reactor of 18 mm inner diameter. Before testing, catalyst has been
activated at 400.degree. C. (60.degree. C./h) under 160 NL/h
Nitrogen during 2 hours. Temperature has then been decreased down
to 40.degree. C. before starting the testing program.
Example 1 (Comparative Example)
Oligomerization without Purification Section
[0129] The LCCS cut is directly oligomerized on a ZSM-5 based
catalyst (80% wt alumina-20% wt ZSM-5) in the following operating
conditions: at 55 barg, with a LHSV (liquid hour space velocity) of
1 h.sup.-1, once through, temperature has been increased from
180.degree. C., to 220.degree. C., up to 250.degree. C.
[0130] Olefin conversion (% wt) data as a function of TOS when no
purification section is used is shown at FIG. 1.
[0131] Though the contaminants level is low (24 ppmwt S, 12 ppmwt
N), the deactivation of the catalyst is significantly pronounced as
represented in the FIG. 1: for instance at 220.degree. C., a loss
of 28% wt olefin conversion is observed within 59 hours. Table 2
below gathers the product characteristics obtained for samples
withdrawn at different times of stream (TOS).
TABLE-US-00002 TABLE 2 Product distribution and density of the
effluents recovered at different TOS when no purification section
is used 180.degree. C. 220.degree. C. 250.degree. C. TOS (h) 16.3
31 51 75 116 147 IBP-165 96.2 83.2 85.5 90.9 81 94.2 165-245 2.2
12.3 10.3 5.8 14.6 3.7 245-350 0 0 0 0 2.7 0 350- 0 0 0 0 0 0 FBP
FBP (.degree. C.) 194 266 263 196 272 194 Density 0.6642 0.6899
0.6847 0.675 0.6924 0.6652 at 15.degree. C. (g/mL)
[0132] This example clearly stresses the need for a process
sequence in which catalyst lifetime can be improved.
Example 2
Oligomerization with Purification Section
[0133] The LCCS cut is first purified on a set of two molecular
sieves: 3A followed by 13X, before being oligomerized on the ZSM-5
based catalyst (80% wt alumina-20% wt ZSM-5) used for example 1.
The following operating conditions were chosen: 55 barg, a LHSV
(liquid hour space velocity) of 1 h.sup.-1, once through, and
temperature has been increased from 180.degree. C., to 220.degree.
C., up to 250.degree. C.
[0134] As observed on FIG. 2, the catalyst deactivation has been
largely limited thanks to the use of a purification section.
[0135] The product distribution as well as the density of the
effluent recovered is reported in table 3 below. The following
abbreviations are used:
[0136] WABT=Weight Average Boiling Point.
[0137] Barg=bar gauge, i.e. absolute pressure minus atmospheric
pressure. 1 barg=2 bar absolute (or 2 bara) when referred to a
complete vacuum, and when atmospheric pressure is 1 bar.
[0138] Analyses of the LCCS purified on molecular sieves have been
achieved and reveal that: [0139] The breakthrough of sulfur
compounds (mainly thiophenic) is quickly reached (after only 2 days
of run, the same sulfur content is obtained at the outlet of the
molecular sieves) [0140] Nitrogen containing species are
successfully retained on the purification section (the N content is
found below 0.5 ppmwt). The comparison of the results obtained in
presence and in absence of a purification section (FIGS. 1&2)
clearly underlines the beneficial effect of the use of a
purification section prior to acid catalyzed reactions (such as
oligomerization, alkylation . . . ). The larger impact of small
nitrogen containing molecules compared to aromatic sulfur
containing molecules (e.g. thiophene) on catalyst deactivation is
also clearly stressed here.
[0141] Boiling points are given at ambient pressure, unless
otherwise specified,
TABLE-US-00003 TABLE 3 Product distribution (%) and density of the
effluents recovered at different TOS when a purification section is
used. Pressure in operation 55 barg TOS (h) 16 31.5 55.5 79.5 103.5
127.5 151.5 WABT 182.2 182.2 202.9 202.8 202.7 198.5 199.6
(.degree. C.) IBP-165 76.7 76.6 65.8 66.3 66.5 69.3 69.5 165-245 17
17 21.3 21.3 21.1 20.5 20.5 245-350 3.6 3.1 10.4 10 10 8.9 8.7
350-FBP 0 0 0 0 0 0 0 FBP (.degree. C.) 271 269 329 326 326 320 318
Density at 0.7036 0.7033 0.716 0.7156 0.7153 0.713 0.7128
15.degree. C. (g/mL) Pressure in operation 25 barg 55 barg TOS (h)
175.5 223.5 247.5 271.5 295.5 343.5 WABT (.degree. C.) 203.5 200.2
200.2 200.1 199.4 223.1 IBP-165 67.8 70.7 71.5 71.7 71.5 60 165-245
20.7 20.1 19.5 19.4 20.2 23 245-350 9.6 8.2 7.6 7.2 6.8 14.2
350-FBP 0 0 0 0 0 1 FBP (.degree. C.) 323 319 317 316 316 360
Density at 0.7141 0.7106 0.7099 0.7093 0.7104 0.7184 15.degree. C.
(g/mL)
* * * * *