U.S. patent application number 10/042248 was filed with the patent office on 2002-11-28 for high octane number gasolines and their production using a process associating hydro-isomerzation and separation.
This patent application is currently assigned to Institut Francais du Petrole. Invention is credited to Clause, Olivier, Durand, Jean-Pierre, Hotier, Gerard, Jullian, Sophie, Ragil, Karine.
Application Number | 20020175109 10/042248 |
Document ID | / |
Family ID | 9513846 |
Filed Date | 2002-11-28 |
United States Patent
Application |
20020175109 |
Kind Code |
A1 |
Ragil, Karine ; et
al. |
November 28, 2002 |
High octane number gasolines and their production using a process
associating hydro-isomerzation and separation
Abstract
The invention provides a high octane number gasoline pool
comprises at least 2% of di-branched paraffins containing 7 carbon
atoms, and a process for producing this gasoline pool by
hydro-isomerising a feed constituted by a C5 to C8 cut which
comprises at least one hydro-isomerisation section and at least one
separation section, in which the hydro-isomerisation section
comprises at least one reactor. The separation section comprises at
least one unit and produces at least two streams: a first stream
which is rich in di- and tri-branched paraffins, and possibly in
naphthenes and aromatic compounds which is sent to the gasoline
pool; and in a first version of the process, a second stream is
produced which is rich in straight-chain and mono-branched
paraffins which is recycled to the inlet of the hydro-isomerisation
section, while in a second version of the process, a second flux is
produced which is rich in straight-chain paraffins which is
recycled to the inlet of a first hydro-isomerisation section and a
third stream is produced which is rich in mono-branched paraffins
which is recycled to the inlet of a second hydro-isomerisation
section.
Inventors: |
Ragil, Karine; (Rueil
Malmaison, FR) ; Jullian, Sophie; (Rueil Malmaison,
FR) ; Durand, Jean-Pierre; (La Celle Saint Cloud,
FR) ; Hotier, Gerard; (Chaponost, FR) ;
Clause, Olivier; (Chatou, FR) |
Correspondence
Address: |
MILLEN, WHITE, ZELANO & BRANIGAN, P.C.
2200 CLARENDON BLVD.
SUITE 1400
ARLINGTON
VA
22201
US
|
Assignee: |
Institut Francais du
Petrole
4, avenue de Bois-Preau
Rueil-Malmaison
FR
F-92500
|
Family ID: |
9513846 |
Appl. No.: |
10/042248 |
Filed: |
January 11, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10042248 |
Jan 11, 2002 |
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09517071 |
Mar 1, 2000 |
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6338791 |
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09517071 |
Mar 1, 2000 |
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09199482 |
Nov 25, 1998 |
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Current U.S.
Class: |
208/63 ; 208/133;
208/15; 208/16; 208/62 |
Current CPC
Class: |
C10G 45/58 20130101;
C10L 1/06 20130101 |
Class at
Publication: |
208/63 ; 208/62;
208/133; 208/15; 208/16 |
International
Class: |
C10G 035/00; C10L
001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 25, 1997 |
FR |
97/14.891 |
Claims
1. A high octane number gasoline pool comprising a base from
hydro-isomerisation of a C5 to C8 cut and comprising at least 2% of
di-branched paraffins containing 7 carbon atoms.
2. A gasoline pool according to claim 1, in which the content of
di-branched paraffins containing 7 carbon atoms is at least 3%.
3. A gasoline pool according to claim 1, in which the content of
di-branched paraffins containing 7 carbon atoms is at least
4.5%.
4. A gasoline pool according to any one of claims 1 to 3, in which
the base from hydro-isomerisation originates from
hydro-isomerisation of a C5 -C8 cut.
5. A gasoline pool according to any one of claims 1 to 3, in which
the base from hydro-isomerisation originates from
hydro-isomerisation of a C6 -C8 cut.
6. A process for producing a gasoline stock by hydro-isomerisation
of a feed constituted by a C5 to C8 cut, comprising at least one
hydro-isomerisation section and at least one separation section, in
which the hydro-isomerisation section comprises at least one
reactor, and the separation section comprises at least one unit and
produces at least two streams: a first stream which is rich in di-
and tri-branched paraffins, and possibly in naphthenes and aromatic
compounds which is sent to the gasoline pool; and a second stream
which is rich in straight-chain paraffins and mono-branched
paraffins which is recycled to the inlet to the hydro-isomerisation
section.
7. A process for producing a gasoline stock by hydro-isomerisation
of a feed constituted by a C5 to C8 cut, comprising at least two
hydro-isomerisation section and at least one separation section, in
which the separation section produces three streams: a first stream
which is rich in di and tri-branched paraffins, and possibly in
naphthenes and aromatic compounds which is sent to the gasoline
pool; a second stream which is rich in straight-chain paraffins
which is recycled to the inlet to the first hydro-isomerisation
section; and a third stream which is rich in mono-branched
paraffins which is recycled to the inlet to the second
hydro-isomerisation section.
8. A process according to claim 7, in which all of the effluent
from the first hydro-isomerisation section traverses the second
section.
9. A process according to claim 8, in which the separation section
is located downstream of the hydro-isomerisation sections, the feed
is mixed with the straight-chain paraffins recycled from the
separation section, the resulting mixture is sent to the first
hydro-isomerisation section, the effluent leaving the first
hydro-isomerisation section is mixed with the stream which is rich
in mono-branched paraffins from the separation section, then the
mixture is sent to the second hydro-isomerisation section, and the
effluent from the latter section is sent to the separation
section.
10. A process according to claim 8, in which the separation section
is located upstream of the hydro-isomerisation sections, the feed
is mixed with the stream from the second hydro-isomerisation
section, the resulting mixture is sent to the separation section,
the effluent which is rich in straight-chain paraffins is sent to
the first hydro-isomerisation section, the stream which is rich in
mono-branched paraffins from the separation section is added to the
effluent from the first hydro-isomerisation section, and the
ensemble is sent to the second hydro-isomerisation section.
11. A process according to claim 7, in which the effluents from the
hydro-isomerisation sections are sent to at least one separation
section.
12. A process according to any one of claims 6 to 11, in which the
separation section is constituted by at least two distinct units to
carry out two different types of separation.
13. A process according to any one of claims 6 to 12, in which the
separation section comprises one or more sections operating by
adsorption.
14. A process according to any one of claims 6 to 12, in which the
separation section comprises one or more sections operating by
permeation.
15. A process according to any one of claims 6 to 12, in which the
separation section comprises at least one unit operating by
adsorption and at least one unit operating by permeation.
16. A process according to any one of claims 6 to 15, in which at
least one light fraction is separated by distillation upstream or
downstream of the hydro-isomerisation and/or separation
sections.
17. A process according to any one of claims 6 to 15, in which the
feed contains the C5 cut and at least one deisopentaniser and/or at
least one depentaniser are located upstream or downstream of the
hydro-isomerisation and/or separation sections.
18. A process according to any one of claims 6 to 15, in which the
feed contains a C6 cut but contains no C5, and at least one
deisohexaniser is located upstream or downstream of the
hydro-isomerisation and/or separation sections.
19. A process according to any one of claims 16 to 18, in which the
light fraction or the isopentane and/or the pentane and/or a
mixture of the two, or the hexane, act as an eluent or a flushing
gas for the adsorption or permeation separation processes
respectively.
20. A process according to any one of claims 6 to 18, in which
butane and/or isobutane is used as an eluent or a flushing gas for
the adsorption or permeation separation processes respectively.
21. A process according to claim 17, in which the isopentane is
sent to the gasoline pool.
22. A process according to any one of claims 6 to 21; in which the
feed comprises at least 12 mole % of hydrocarbons containing at
least 7 carbon atoms.
23. A process according to any one of claims 6 to 21, in which the
feed comprises at least 15 mole % of hydrocarbons containing at
least 7 carbon atoms.
24. A process according to any one of claims 6 to 23, in which
hydro-isomerisation is carried out at temperatures in the range
25.degree. C. to 450.degree. C., at a pressure in the range 0.01 to
7 MPa, at a space velocity, measured in kg of feed per kg of
catalyst per hour, in the range 0.5 to 2, and with an
H2/hydrocarbons molar ratio in the range 0.01 to 50.
25. A process according to any one of claims 6 to 24, in which
separation is carried out at temperatures in the range 50.degree.
C. to 450.degree. C. and at a pressure in the range 0.01 to 7 MPa.
Description
[0001] The invention relates to a high octane number gasoline pool
comprising at least 2% by weight, preferably at least 3% by weight,
and more preferably at least 4.5% by weight, of C7 di-branched
paraffins, i.e., di-branched paraffins containing 7 carbon atoms.
As a preferred example, such a gasoline pool can be obtained by
incorporating into said pool a gasoline stock from
hydro-isomerisation of a feed constituted by a C5-C8 cut or any cut
between C5 and C8, i.e., a cut comprising hydrocarbons containing 5
to 8 carbon atoms, such as C5-C8, C6-C8, C7-C8, C7, C8, etc. . . .
The invention also relates to processes for producing such a
gasoline stock and thus such a pool. This invention is an
improvement over conventional refining schemes as it proposes
upgrading light C5 to C8 cuts comprising paraffinic, naphthenic,
aromatic and olefinic hydrocarbons, by hydro-isomerisation and
recycling of low octane number paraffins, i.e., straight-chain and
mono-branched paraffins. Hydro-isomerisation of light C5 to C8 cuts
can be carried out in the gas, liquid or mixed liquid-gas phase in
one or more reactors where the catalyst is used in a fixed bed.
Normal and mono-branched paraffins can be recycled in the liquid or
gas phase using a separation process involving adsorption or
permeation using respectively one or more adsorbents, or one or
more permeation steps.
[0002] In one version of the process, the process comprises at
least one hydro-isomerisation section and at least one separation
section. The hydro-isomerisation section comprises at least one
reactor. The separation section (composed of one or more units)
produces two streams, a first stream rich in di- and tri-branched
paraffins, and possibly in naphthenes and aromatic compounds, which
constitutes a high octane number gasoline stock and which is sent
to the gasoline pool, and a second stream which is rich in
straight-chain and mono-branched paraffins and which is recycled to
the inlet to the hydro-isomerisation section. When separating by
adsorption, this version of the process, optimised for feeds
containing more than 12 mole %, preferably more than 15 mole % of
C7+ (i.e., hydrocarbons containing at least 7 carbon atoms) uses an
adsorbable eluent to completely or at least partially regenerate
the adsorbent.
[0003] In a second version of the process, the process comprises at
least two hydro-isomerisation section and at least one separation
section. The separation section (composed of one or more units)
produces three streams: a first stream which is rich in di- and
tri-branched paraffins, and possibly in naphthenes and aromatics
which constitutes a high octane number gasoline stock and is sent
to the gasoline pool, a second stream which is rich in
straight-chain paraffins which is recycled to the inlet of the
first hydro-isomerisation section, and a third stream which is rich
in mono-branched paraffins which is recycled to the inlet of the
second section. Two implementations of this version of the process
are preferred: in the first, all of the effluent from the first
hydro-isomerisation section traverses the second section, and in
the second the effluents from the hydro-isomerisation sections are
sent to the separation section or sections.
[0004] Carrying out the process enables:
[0005] the amount of total aromatic compounds in a conventional
gasoline pool to be reduced by 3% to 12% by weight, depending on
the composition of the pool and in particular depending on the
reformed gasoline fraction and the hydro-isomerisation gasoline
introduced;
[0006] the amount of benzene in the gasoline pool to be
significantly reduced;
[0007] the severity of the operation of the associated catalytic
reforming units to be reduced.
PRIOR ART
[0008] Increasing environmental constraints have resulted in the
removal of lead compounds from gasolines, effectively in the United
States and Japan and becoming general in Europe. Aromatic
compounds, the main constituents of reformed gasolines, and
isoparaffins produced by aliphatic alkylation or isomerisation of
light gasolines initially compensated for the octane number loss
resulting from removing lead from gasoline. Subsequently,
oxygen-containing compounds such as methyl tertiobutyl ether (MFBE)
or ethyl tertiobutyl ether (ETBE) were introduced into the
gasolines. More recently, the known toxicity of compounds such as
aromatic compounds, in particular benzene, olefins and
sulphur-containing compounds, as well as the desire to reduce the
vapour pressure of the gasolines, led the United States to produce
reformulated gasolines. As an example, the maximum amounts of
olefins, aromatic compounds and benzene in gasoline distributed in
California in 1996 were respectively 6% by volume, 25% by volume,
and 1% by volume. Regulations are less severe in Europe, but
nevertheless there is a clear tendency to reduce the maximum
benzene, aromatic compound and olefin amounts in gasoline which is
produced and sold to a similar level.
[0009] Gasoline pools contain a plurality of components. The major
components are reformed gasoline, which normally comprises between
60% and 80% by volume of aromatic compounds, and FCC gasolines
which typically contain 35% by volume of aromatic compounds but
provide the majority of olefinic and sulphur-containing compounds
present in the gasoline pools. The other components can be
alkylates, with neither aromatic compounds nor olefinic compounds,
light gasolines which may or may not be isomerised, which contain
no unsaturated compounds, oxygen-containing compounds such as MTBE,
and butanes. Provided that the aromatic compound content is not
reduced below 35-40% by volume, the contribution of reformates to
gasoline pools remains high, typically 40% by volume. In contrast,
increased severity as regards the maximum admissible amount of
aromatic compounds to 20-25% by volume will result in a reduction
in the use of reforming, and as a result the need to upgrade C7-C10
straight run cuts by routes other than reforming.
[0010] Thus the production of multi-branched isomers from
low-branched heptanes and octanes contained in naphthas, instead of
producing toluene and xylenes from those compounds, appears to be
an extremely promising route. This justifies the search for high
performance catalytic systems for isomerising heptanes (also termed
hydro-isomerisation when carried out in the presence of hydrogen),
octanes and more generally C5-C8 cuts and intermediate cuts, and
the search for processes for selectively recycling low octane
number compounds which are straight-chain and mono-branched
paraffins to the isomerisation (hydro-isomerisation) step.
Regarding the catalytic systems, a compromise has to be found
between isomerisation proper and acid cracking or hydrogenolysis,
which produces light C1-C4 hydrocarbons which drop the overall
yields. Thus the more branched the paraffin, the more easily it
isomerises but also the greater is its tendency to crack. This
justifies the search for more selective catalysts, and for
processes which are arranged to supply different
hydro-isomerisation sections with streams which are rich in
straight-chain or mono-branched paraffins. The catalytic systems
described in the literature use bifunctional catalysts such as
Pt/zeolite b (Martens et al., J. Catal., 1995, 159, 323), Pt/SAPO-5
or Pt/SAPO-11 (Campelo et al., J. Chem. Soc., Faraday Trans., 1995,
91, 1551), massive or SiC supported mono-functional oxycarbide
catalysts (Ledoux et al., Ind. Eng. Chem. Res., 1994, 33, 1957),
mono-functional acid systems such as chlorinated aluminas (Travers
et al, Rev. Inst. Fr. Petr., 1991, 46, 89), sulphated zirconias
(Iglesia et al., J. Catal., 1993, 144, 238) or some heteropolyacids
(Vedrine et al., Catal. Lett., 1995, 34, 223).
[0011] Adsorption and permeation separation techniques are
particularly suitable for separating straight-chain, mono- and
multi-branched paraffins. Processes for separation by conventional
adsorption can be based on PSA (pressure swing adsorption), TSA
(temperature swing adsorption), chromatography (elution
chromatography or simulated counter-current chromatography, for
example). They can also result from a combination of the above.
Such processes all involve bringing a liquid or gaseous mixture
into contact with a fixed bed of adsorbent to eliminate certain
constituents of the mixture which may be adsorbed. Desorption can
be carried out by various means. Thus the common characteristic of
PSA is to regenerate the bed by depressurisation and in certain
cases by low pressure flushing. PSA type processes are described in
U.S. Pat. No. 3,430,418 by Wagner or in the more general work by
Yang ("Gas Separation by Adsorption Processes", Butterworths, US,
1987). In general, PSA type processes are operated sequentially
using all of the adsorption beds in alternation. Such PSA
techniques have been very successful in the natural gas industry,
for separating compounds of air, for producing solvents, and in
various refining sectors.
[0012] TSA processes use temperature as the driving force for
desorption and were the first to have been developed for
adsorption. The bed to be regenerated is heated by circulating a
pre-heated gas, in a closed or an open loop, in a direction which
is the reverse of that of adsorption. A number of variations ("Gas
Separation by Adsorption Processes", Butterworths, US, 1987) are
used depending on local constraints and on the nature of the gas
employed. The technique is generally used in purification processes
(drying, desulphuration of gas and liquids, purification of natural
gas: U.S. Pat. No. 4,770,676).
[0013] Liquid or gas phase chromatography is a highly effective
separation technique because a very large number of theoretical
plates is used (BE 891 522, Seko M., Miyake J., Inada K.: Ind. Eng.
Chem. Prod. Res. Develop., 1979, 18, 263). It can thus exploit
relatively low adsorption selectivities and accomplish difficult
separations. Such processes are competed with by simulated moving
bed or simulated counter current continuous processes. The latter
have been greatly developed in the petroleum industry (U.S. Pat.
No. 3,636,121 and U.S. Pat. No. 3,997,620).
[0014] Regeneration of the adsorbent uses the technique of
displacement by a desorbent which can optionally be capable of
being separated by distilling the extract and the raffinate.
[0015] The use of adsorption processes in the gasoline production
area is well known and a number of patents refer to it, based on
geometrical (U.S. Pat. No. 5,233,120, BE 891 522, FR-A-2 688 213)
and diffusional (U.S. Pat. No. 5,055,633 and U.S. Pat. No.
5,055,634) selectivities. Such processes, however, all pertain to
the light C5-C6 fraction with the aim of improving the octane
number. U.S. Pat. No. 5,055,633 and U.S. Pat. No. 5,055,634 concern
processes for separating and producing isopentane with a stream
which is rich in di-branched paraffins from a light C5-C6 cut
containing at least 10% of isopentane. C5-C6 centred cuts can
sometimes contain small quantities of paraffins containing seven or
more carbon atoms. However, the processes claimed in those patents
all pertain to less than 10 mole % of such C7+ compounds.
[0016] The advantage of permeation separation techniques over
adsorption techniques is that they are continuous and, as a result,
relatively simple to carry out. Further, they are recognised for
their modularity and compactness. Over the past ten years they have
taken their place beside adsorption and gas separation techniques,
for example for recovering hydrogen from refining gas,
decarbonating natural gas, producing inerting nitrogen ("Handbook
of Industrial Membranes", Elsevier Science Publishers, UK, 1995).
Their use in separating isomeric hydrocarbons is rendered possible
because of the recent advances in techniques for synthesising
materials and more particularly in the inorganic material synthesis
field where zeolite crystals can now be grown in the form of a thin
continuous supported or self supported layer. International patent
application WO 96/01687 describes a method for synthesising a
supported zeolite membrane and its applications, in particular
separating a mixture of normal and iso pentane. A further method
for synthesising a supported zeolite membrane adapted for
separating straight-chain alkanes from a mixture of more branched
hydrocarbons is described in International patent WO 93/19840.
[0017] The permeabilities of straight-chain and branched
hydrocarbons have been reported in the literature for films of self
supported zeolite or zeolite deposited on supports of different
natures.
[0018] As an example, Tsikoyiannis, J. G. and Haag, W. O., in
Zeolite 1992, 12, 126-30, observed a permeability ratio of 17.2 for
normal C6 (nC6) with respect to isoC6 (iC6) on a self supported
ZSM-5 film.
[0019] Permeability measurements in pure gases on a membrane
composed of silicalite crystals on a porous steel support have
shown that the nC4 stream is larger than the iC4 stream (Geus, E.
R.; Van Bekkum, H.; Bakker, W. J. W.; Moulijn, J. A. Microporous
Mater. 1993, 1, 131-47). For these same gases the ratio of
permeabilities (nC4/iC4) is 18 at 30.degree. C. and 31 at
185.degree. C. with a membrane constituted by ZSM-5 zeolite on a
porous alumina support. Regarding the separation of
nC6/2,2-dimethylbutane, a selectivity of 122 was measured with a
silicalite membrane on a porous glass support (Meriaudeau P.;
Thangaraj A.; Naccache C; Microporous Mater, 1995, 4, 213-19).
SUMMARY OF THE INVENTION
[0020] The invention provides a high octane number gasoline pool in
which the total content of di-branched C7 paraffin content is at
least 2% by weight, preferably at least 3% by weight, more
preferably at least 4.5% by weight. Such di-branched C7 paraffins
are, for example, represented by 2,2; 2,3; 2,4; and
3,3-dimethylpentane. These dimethylpentanes are collectively known
as DMC5. A detailed study of the composition of commercial
gasolines containing up to 30% of alkylate has demonstrated that
the di-branched C7 paraffin content in such gasolines never exceeds
1.75% by weight.
[0021] It is possible to obtain a gasoline pool of the invention by
incorporating into said pool a high octane number gasoline stock
from hydro-isomerisation of C5 to C8 cuts such as C5-C8, C6-C8,
C7-C8, C7, C8, etc. . . .
[0022] In a further aspect, the invention provides processes for
producing such a gasoline stock and thus such a pool. The processes
of the invention are aimed at modifying the landscape of gasoline
production by reducing the aromatic compound content while keeping
the octane number high. This can be accomplished by sending a feed
constituted by a C5-C8 cut (for example straight run) or any
intermediate cut between C5 and C8, such as C5-C8, C6-C8, C7-C8,
C7, C8, etc. . . . , not to the reforming and C5-C6 paraffin
hydro-isomerisation units but to at least one hydro-isomerisation
section which converts the straight-chain paraffins (nCx, x=5 to 8)
to branched paraffins and possibly mono-branched paraffins (monoCx)
to di- and tri-branched paraffins (diCx or triCx).
[0023] It is appropriate at this juncture to summarise the research
octane numbers (RON) and the motor octane numbers (MON) of
different hydrocarbon compounds (see Table I).
1TABLE 1 Paraffin nC8 nC7 monoC7 monoC6 diC6 diC5 triC4 triC5 RON
<0 0 21-27 42-52 55-76 80-93 112 100-109 MON <0 0 23-39 23-39
56-82 84-95 101 96-100
[0024] As Table 1 shows, conversion of the different paraffins of
this cut must be as efficient as possible towards highly branched
compounds. Since the hydro-isomerisation reaction is
thermodynamically limited, it is necessary to separate and recycle
to the hydro-isomerisation section in order to obtain a conversion
which is as efficient as possible.
[0025] More precisely, the invention provides a process for
producing a high octane number gasoline stock which can form part
of the composition of a gasoline pool comprising at least 2% by
weight, preferably at least 3% by weight, and more preferably at
least 4.5% by weight, of di-branched C7 paraffins such as
dimethylpentanes (DMC5) and a small amount of aromatic compounds by
associating at least one hydro-isomerisation section comprising at
least one hydro-isomerisation section and at least one second
section accomplishing separation by adsorption or by permeation, in
one or more units, recycling the straight chain and mono-branched
paraffins to said hydro-isomerisation section. This association has
other characteristics which will be detailed in the remainder of
the text.
[0026] For all versions of the process of the invention, the normal
and mono-branched paraffins are recycled in the liquid or gas phase
using adsorption or permeation separation processes. The adsorption
separation processes used may be PSA (pressure swing adsorption),
TSA (temperature swing adsorption), chromatography (elution
chromatography or simulated counter current chromatography, for
example) or it can be a combination of these methods. The
separation section can use one or more molecular sieves. When
separation is accomplished by permeation, the isomerate (i.e., the
effluent from the hydro-isomerisation section) can be separated
using a gas permeation or pervaporation technique. In all versions
of the process of the invention, the separation section(s) can be
located upstream or downstream of the hydro-isomerisation
section(s). when the feed to the process includes a C5 cut, the
straight-chain and mono-branched paraffin recycling process can
include at least one deisopentaniser and/or at least one
depentaniser located upstream or downstream of the
hydro-isomerisation sections and/or separation sections. The
isopentane is preferably eliminated since it is not isomerised to a
more branched compound under the operating conditions for the
hydro-isomerisation section. Isopentane, pentane or a mixture of
these two as separated can act as an eluent or the flushing gas for
the adsorption or permeation separation processes respectively.
When the cuts contain no C5 but contain C6 compounds, the process
can comprise at least one deisohexaniser upstream or downstream of
the hydro-isomerisation and separation sections. In general, it may
be important to prepare one or more light fractions by distilling
the feed, to act as an eluent or flushing gas for the adsorption or
permeation separation processes respectively.
[0027] A preferred version of the process of the invention
comprises a hydro-isomerisation section and a separation section.
The hydro-isomerisation section comprises at least one reactor. The
separation section produces two streams: a first stream which is
rich in di- and tri-branched paraffins, and possibly in naphthenes
and aromatic compounds which constitute a high octane number
gasoline stock and which is sent to the gasoline pool; and a second
stream which is rich in straight-chain and mono-branched paraffins
which is recycled to the hydro-isomerisation section inlet. This
version of the process, optimised for feeds containing more than 12
mole %, preferably more than 15 mole %, of C7+, uses (for
adsorption separation) an adsorbable eluent to completely
regenerate or at least partially regenerate the adsorbent. This
eluent can be isopentane, n-pentane or isohexane previously
extracted from the feed.
[0028] In a second preferred version of the process of the
invention, the hydro-isomerisation reaction is carried out in at
least two distinct sections. A process for separating into three
streams is carried out in at least one section comprising one or
more units to produce three effluents, respectively rich in
straight-chain paraffins, in mono-branched paraffins and in di- and
tri-branched paraffins, and possibly in naphthenes and aromatic
compounds. The effluents which are rich in straight-chain and
mono-branched paraffins are separately recycled, to one and to the
other of the hydro-isomerisation sections or to two sections and/or
two reactors which are different if there are more than two. The
effluent which is rich in di- and tri-branched paraffins, and
possibly in naphthenes and aromatic compounds, which constitutes a
high octane number gasoline stock, is sent to the gasoline pool.
The advantages of such a configuration are many-fold. It enables at
least two reactors to be operated at different temperatures and
different HSVs to minimise cracking of di- and tri-branched
paraffins, which is particularly important for the cuts under
consideration.
[0029] In a first implementation of this second version of the
process, all of the effluent leaving the first hydro-isomerisation
section is sent to the second hydro-isomerisation section. In a
second implementation, the effluents from the hydro-isomerisation
sections are sent to the separation section or sections. The
process is thus optimised by the arrangement of the separation and
hydro-isomerisation sections, since it can avoid mixing the high
octane number streams with the low octane number feed.
DETAILED DESCRIPTION OF THE INVENTION
[0030] With regard to reducing the amount of aromatic compounds in
gasolines, the feed treated in the process of the invention
originates from a C5-C8 cut or any intermediate cuts (such as
C5-C7, C6-C8, C6-C7, C7-C8, C7, C8 . . . ) from atmospheric
distillation, from a reforming unit (light reformate) or from a
conversion unit (naphtha hydrocracking, for example). In the
remainder of the text, this set of possible feeds will be
designated by the term "C5-C8 cuts and intermediate cuts".
[0031] It is mainly composed of straight-chain, mono-branched and
multi-branched paraffins, naphthenic compounds such as
dimethylcyclopentanes, aromatic compounds such as benzene or
toluene and possibly olefinic compounds. The term "multi-branched
paraffins" includes all paraffins with a degree of branching of two
or more.
[0032] The feed introduced into the process of the invention
comprises at least one alkane which will be isomerised to form at
least one product with a higher degree of branching. The feed can
contain normal pentane, 2-methylbutane, neopentane, normal hexane,
2-methylpentane, 3-methylpentane, 2,2-dimethylbutane,
2,3-dimethylbutane, normal heptane, 2-methylhexane, 3-methylhexane,
2,2-dimethylpentane, 3,3-dimethylpentane, 2,3-dimethylpentane,
2,4-dimethylpentane, 2,2,3-trimethylbutane, normal octane,
2-methylheptane, 3-methylheptane, 4-methylheptane,
2,2-dimethylhexane, 3,3-dimethylhexane, 2,3-dimethylhexane,
3,4-dimethylhexane, 2,4-dimethylhexane, 2,5-dimethylhexane,
2,2,3-trimethylpentane, 2,3,3-trimethylpentane, and
2,3,4-trimethylpentane. When the feed originates from C5-C8 cuts
and/or intermediate cuts obtained after atmospheric distillation,
it can also contain cyclic alkanes such as dimethylcyclopentanes,
aromatic hydrocarbons (such as benzene, toluene, xylenes) and other
C9+ hydrocarbons (i.e., hydrocarbons containing at least 9 carbon
atoms) in small quantities. The feeds constituted by C5-C8 cuts and
intermediate cuts from reformates can also contain olefinic
hydrocarbons, in particular when the reforming units are operated
at low pressure.
[0033] The amount of paraffins (P) essentially depends on the
origin of the feed, i.e., on its paraffinic or naphthenic and
aromatic character, sometimes measured using the parameter N+A (the
sum of the amount of naphthenes (N) and the amount of aromatic
compounds (A)), also its initial point, i.e., the amount of C5 and
C6 in the feed. In hydrocracking naphthas, which are rich in
naphthenic compounds, or light reformates, which are rich in
aromatic compounds, the amount of paraffins in the feed will
generally be low, of the order of 30% by weight. In straight run
C5-C8 cuts and intermediate cuts (such as C5-C7, C6-C8, C6-C7,
C7-C8 . . . ), the amount of paraffins varies between 30% and 80%
by weight, with an average value of 55-60% by weight. The octane
gain using the hydro-isomerisation process described in this patent
will be higher as the amount of paraffins in the feed is
increased.
[0034] For a C5-C8 feed or a feed composed of intermediate cuts
from atmospheric distillation, obtained from the head of a naphtha
splitter, for example, the heavy fraction corresponding to the
naphtha can supply a catalytic reforming section. In this case,
installation of a hydro-isomerisation section for these cuts will
reduce the amount of feed in the reforming section, which could
continue to treat the heavy C8+ naphtha fraction.
[0035] The hydro-isomerisation effluent can contain the same types
of hydrocarbons as those described above, but their respective
proportions in the mixture leads to higher RON and MON octane
numbers than those of the feed.
[0036] The feed which is rich in paraffins containing 5 to 8 carbon
atoms generally has a low octane number and the process of the
invention has the advantage of increasing its octane number without
increasing the aromatic compound content. In order to carry this
out, a minimum of two sections should be used: the
hydro-isomerisation section and the separation section. Several
versions and implementations of the process are possible depending
on the number and arrangement of the different hydro-isomerisation
or separation sections and the different recycles.
[0037] For all versions and implementations of the process of the
invention, the normal and mono-branched paraffins are recycled in
the liquid or gas phase using adsorption or permeation separation
processes. The adsorption separation processes used can be PSA
(pressure swing adsorption), TSA (temperature swing adsorption),
chromatography (elution chromatography or simulated counter current
chromatography, for example) or it can be a combination of these
methods. The separation section can use one or more molecular
sieves. When separation is accomplished by permeation, a gas
permeation or pervaporation technique can be used. In all versions
of the process of the invention, the separation sections can be
located upstream or downstream of the hydro-isomerisation
section.
[0038] In a first preferred version of the process (FIGS. 1A and 1B
for variations 1a and 1b), the hydro-isomerisation section (2)
comprises at least one reactor. The separation section (4),
constituted by at least one unit, produces two streams: a first
high octane number stream which is rich in di- and tri-branched
paraffins, and possibly in naphthenes and aromatic compounds
(stream 8 for variation 1a and 18 for variation 1b), which
constitutes a high octane number gasoline stock and can be sent to
the gasoline pool; and a second stream which is rich in
straight-chain and mono-branched paraffins which is recycled (7 for
variation 1a and 9 for variation 1b), to the inlet to
hydro-isomerisation section (2). In variation 1a, the
hydro-isomerisation section 2 precedes separation section 4, while
this is reversed in variation 1b. As a result in variation 1a, only
straight-chain and mono-branched paraffins are recycled to the
hydro-isomerisation section (stream 7). In variation 1b, all of
effluent 10 from the hydro-isomerisation section 2 is recycled to
separation section 4. The effluent thus contains straight-chain,
mono-branched and multi-branched paraffins. The operating
conditions for this variation of the p, described below, are
selected with the aim of optimising the process for feeds
containing more than 12 mole %, preferably more than 15 mole %, of
C7+. They are particularly selected to minimise cracking of di and
tri-branched paraffins containing more than 7 carbon atoms.
Further, when the feed for the process includes a C5 cut, the
straight-chain and mono-branched paraffin recycling process can
optionally include a deisopentaniser, located upstream or
downstream of the hydro-isomerisation and/or separation sections.
In particular, it can be placed in feed 1 between the separation
and hydro-isomerisation sections (streams 6 and 9) or in the
recycled streams 7 and 10. The isopentane is preferably eliminated
since it is not isomerised to a more branched compound under the
operating conditions of the hydro-isomerisation section.
[0039] It may also be interesting to add a depentaniser or to
combine a depentaniser and a deisopentaniser in at least one of
streams 1, 6, 9, 7 or 10. The ispoentane, pentane or a mixture of
these two extracted from the feed can optionally act as an eluent
or flushing gas for the adsorption or permeation separation
processes respectively. The isopentane can also optionally be sent
directly to the gasoline pool due to its good octane number.
[0040] In the same manner, when the cut contains no C5 but contains
C6 compounds, a deisohexaniser can optionally be placed in at least
one of streams 1, 6, 7, 9 or 10 (FIGS. 1A and 1B). The recovered
isohexane can act as an eluent or a flushing gas for the adsorption
and permeation separation processes respectively. The isohexane is
preferably not sent to the gasoline pool as its octane number is
too low and it must thus be separated from high octane number
streams 8 or 18 (FIGS. 1A and 1B). This use of a portion of the
feed in the separation section constitutes very good integration
for the process.
[0041] In general, it may be of interest to distil the feed into
one or more light fractions which can act as an eluent or flushing
gas for the adsorption or permeation separation processes
respectively. However, this section can also use other compounds.
In particular, light paraffins such as butane and isobutane can
advantageously be used, as they are readily separated from heavier
paraffins by distilling.
[0042] Finally, when the separation section is located upstream of
the hydro-isomerisation section (variation 1b), the quantity of
naphthenic and aromatic compounds traversing the
hydro-isomerisation section is lower than in the reverse
configuration (variation 1a). This limits saturation of the
aromatic compounds contained in the C5 to C8 cut and thus reduces
the hydrogen consumption in the hydro-isomerisation section.
Further, in variation 1b, the volumes of the streams traversing the
hydro-isomerisation section are lower with respect to variation 1a,
enabling the size of this section to be reduced, minimising the
quantity of catalyst required.
[0043] In a second preferred version of the process (FIGS. 2.1A,
2.1B, 2.2A,-2.2B, 2.2E, 2.2D respectively for variations 2.1a and
b; 2.2a, b, c and d in implementations 2.1 and 2.2), the
hydro-isomerisation reaction is carried out in at least two
distinct sections, comprising at least one reactor (sections 2 and
3). A process for separation into at least three streams is carried
out in at least one separation section (sections 4 and possibly 5),
comprising at least one unit, to produce three streams: a first
stream which is rich in di and tri-branched paraffins, and possibly
in naphthenes and aromatic compounds; a second stream which is rich
in straight-chain paraffins; and a third stream which is rich in
mono-branched paraffins. The effluent which is rich in
straight-chain paraffins is recycled to the hydro-isomerisation
section 2 and the effluent which is rich in mono-branched paraffins
is recycled to the hydro-isomerisation section 3.
[0044] In a first implementation (FIGS. 2.1A and 2.1B) of the
second version of the process, all of the effluent leaving the
first hydro-isomerisation section 2 is sent to the second
hydro-isomerisation section 3. This implementation includes two
variations in which the separation section, composed of one or
optionally more units, is located downstream (FIG. 2.1A) or
upstream (FIG. 2.1B) of the hydro-isomerisation section.
[0045] In variation 2.1a (FIG. 2.1A), fresh feed (stream 1)
containing straight-chain, mono-branched and multi-branched
paraffins, also naphthenic compounds and aromatic compounds, is
mixed with a recycle of straight-chain paraffins from the
separation section 4 (stream 10). The resulting mixture 33 is sent
to the first hydro-isomerisation section 2 which converts a portion
of the straight-chain paraffins to mono-branched paraffins and a
portion of the mono-branched paraffins to multi-branched paraffins.
The effluent (stream 6) leaving hydro-isomerisation section 2 is
mixed with the recycle 9, which is rich in mono-branched paraffins
and originates from separation section 4, then the mixture is sent
to the hydro-isomerisation section 3. The effluent 7 from section 3
is sent to separation section 4. In section 4, a process for
separation into three streams is carried out to produce three
effluents which are rich in either straight-chain paraffins (10),
mono-branched paraffins (9) or multi-branched paraffins, naphthenic
compounds and aromatic compounds (8). Effluent 8 (FIG. 2.1A), which
is rich in multi-branched paraffins and in naphthenic and aromatic
compounds, has a high octane number, and constitutes a high octane
number gasoline stock and can be sent to the gasoline pool. This
process leads to the production of a high octane number gasoline
which is rich in multi-branched paraffins.
[0046] In variation 2.1b (FIG. 2.1B), fresh feed (stream 1)
containing straight-chain, mono-branched and multi-branched
paraffins, naphthenes and aromatic compounds, is mixed with stream
14 from hydro-isomerisation section 3, then the resulting mixture
23 is sent to separation section 4. A process for separating into
three streams is carried out to produce three effluents which are
rich in either straight-chain paraffins (11), in mono-branched
paraffins (12), or in multi-branched paraffins, naphthenic and
aromatic compounds (18). The effluent 11 which is rich in
straight-chain paraffins is sent to the hydro-isomerisation section
2. The effluent 18 which is rich in multi-branched paraffins and in
naphthenic and aromatic compounds has a high octane number.
Effluent 18 (FIG. 2.1B) thus constitutes a high octane number
gasoline stock and can be sent to the gasoline pool.
Hydro-isomerisation section 2 converts a portion of the
straight-chain paraffins to mono-branched paraffins and to
multi-branched paraffins. The stream which is rich in mono-branched
paraffins (12) from separation section 4 is added to the effluent
(13) from section 2. This is sent to the second hydro-isomerisation
section 3 (FIG. 2.1B).
[0047] The advantages of the configurations of variations 2.1a and
2.1b are many-fold. These configurations enable two
hydro-isomerisation sections 2 and 3 to be operated at different
temperatures and different HSVs so as to minimise cracking of
di-branched and tri-branched paraffins, which is particularly
important for the cuts under consideration. Further, they enable
the quantity of catalyst in section 2 to be minimised by recycling
only straight-chain paraffins to this section, enabling a higher
temperature to be used. In contrast, section 3, mainly supplied
with mono-branched paraffins, operates at a lower temperature which
improves the yield of di and tri-branched paraffins because of the
more favourable thermodynamic equilibrium under these conditions,
while limiting cracking of multi-branched paraffins, not encouraged
at low temperatures.
[0048] When the separation section, composed of one or more units,
is located upstream of the hydro-isomerisation section (variation
2.1b), the quantity of naphthenic and aromatic compounds traversing
the hydro-isomerisation section is lower than in the reverse
configuration (variation 2.1a). This limits saturation of the
aromatic compounds contained in the C5-C8 cut or in the
intermediate cuts, thus reducing the hydrogen consumption in the
process.
[0049] When the feed includes a C5 cut, the process of the
invention in its implementation 2.1 (variations 2.1a and 2.1b) can
optionally comprise a deisopentaniser located upstream or
downstream of the hydro-isomerisation and/or separation sections.
In particular, the deisopentaniser can be placed in stream 1
(feed), between the two hydro-isomerisation sections (stream 6 FIG.
2.1A and stream 13 FIG. 2.1B), or after the hydro-isomerisation
section (stream 7 or 14), after the separation section in the
mono-branched paraffin rich stream (stream 9 or 12). Preferably,
the isopentane can optionally be eliminated since it is not
isomerised to a higher degree of branching under the operating
conditions of the hydro-isomerisation section. The isopentane can
optionally be used as an eluent or a flushing gas for the
adsorption or permeation separation processes respectively. It can
also optionally be sent directly to the gasoline pool because of
its good octane number. It may be of interest to place a
depentaniser in at least one of streams 1, 6, 7, 10 (FIG. 2.1A) or
1, 11, 13 or 14 (FIG. 2.1B). A combination of a deisopentaniser and
a depentaniser is also possible. The pentane or mixture of pentane
and isopentane thus separated can optionally be used as an eluent
or a flushing gas for the adsorption or permeation separation
processes respectively. In the latter case, the pentane cannot be
sent to the gasoline pool because of its low octane number. As a
result it has to be separated from high octane number streams 8 and
18.
[0050] In the same manner, when the cut contains no C5 but contains
C6, a deisohexaniser can optionally be placed in at least one of
streams 1, 6, 7 or 9 for variation 2.1a (FIGS. 2.1A) and 1, 13, 14
and 12 for variation 2.1b (FIG. 2.1B). The recovered isohexane can
act as an eluent or a flushing gas respectively for the adsorption
and permeation separation processes. The isohexane cannot, however,
be sent to the gasoline pool as its octane number is too low and it
must thus be separated from high octane number streams 8 or 18
(FIGS. 2.1A and 2.1B).
[0051] In general, it may be of interest to prepare the feed by
distillation into one or more light fractions, which can act as an
eluent or a flushing gas for the adsorption or permeation
separation processes respectively.
[0052] These uses for a portion of the feed in the separation
section constitute very good integration for the process. However,
this section can also use other compounds. In particular, light
paraffins such as butane and isobutane are of interest as they can
readily be separated from heavier paraffins by distilling.
[0053] In a second implementation (2.2) of version 2 of the process
of the invention, the effluents from the hydro-isomerisation
sections 2 and 3 are sent to one or more separation sections 4 and
5. This implementation can be split into four variations 2.2a,
2.2b, 2.2c, 2.2d. Variations 2.2a and 2.2b (FIGS. 2.2A and 2.2B)
correspond to the case where the process comprises at least two
separation sections which can carry out two different types of
separation. In variations 2.2c and 2.2d (FIGS. 2.2C and 2.2D), the
separation section can be constituted by one or more units.
Variations 2,2a, 2.2b, 2.2c and 2.2d optimise the arrangement of
separation and hydro-isomerisation sections as they prevent the
high octane number streams from mixing with the low octane number
feed.
[0054] Variation 2.2a comprises the following steps:
[0055] The fresh feed (stream 1, FIG. 2,2A) containing
straight-chain, mono-branched and multi-branched paraffins,
naphthenic compounds and aromatic compounds, is mixed with an
effluent 9 which is rich in straight-chain paraffins from
separation section 4, then the resulting mixture 33 is sent to
hydro-isomerisation section 2 which converts a portion of the
straight-chain paraffins to mono-branched paraffins and a portion
of the mono-branched paraffins to multi-branched paraffins. The
ensemble leaving hydro-isomerisation section 2 is sent to
separation section 4. Separation section 4 produces two effluents
which are respectively rich in straight-chain paraffins (9) and in
mono-branched and multi-branched paraffins, naphthenic compounds
and aromatic compounds (7). Effluent 7 is mixed with stream 12
which is rich in mono-branched paraffins from separation section 5,
then sent to hydro-isomerisation section 3. The hydro-isomerisation
section 3 converts a portion of the mono-branched paraffins to
multi-branched paraffins. The ensemble (stream 11) leaving
hydro-isomerisation section 3 is sent to separation section 5. In
that section a process is carried out which separates it into two
streams to produce two effluents, one rich in mono-branched
paraffins (12) and the other rich in multi-branched paraffins (8).
Effluent 8 (FIG. 2.2A), which is rich in di and tri-branched
paraffins and in naphthenic and aromatic compounds, has a high
octane number, and constitutes a high octane number gasoline stock
and can be sent to the gasoline pool.
[0056] Variation 2.2b differs from variation 2.2a in that the
separation sections 4 and 5 (FIG. 2.2B) are placed upstream of
hydro-isomerisation sections 2 and 3. In this configuration, feed 1
is mixed with effluent 17 from hydro-isomerisation section 2, then
the resulting mixture is sent to separation section 4. That section
produces two streams, respectively rich in straight-chain paraffins
(16) and in mono-branched and multi-branched paraffins (13).
[0057] Stream 16 is sent to the hydro-isomerisation section 2 to
produce effluent 17. Effluent 13 is mixed with stream 15 from
hydro-isomerisation section 3, then the mixture is sent to
separation section 5. That section produces two effluents, one rich
in mono-branched paraffins 14, which is sent to the
hydro-isomerisation section 3, the other rich in multi-branched
paraffins, naphthenic compounds and aromatic compounds 18, which
has a high octane number and constitutes a high octane number
gasoline stock. Effluent 18 (FIG. 2.2B) can thus be sent to the
gasoline pool.
[0058] In variation 2.2c (FIG. 2.2C), the separation section 4 is
constituted by one or more units, and is located between two
hydro-isomerisation sections (2 and 3). In this configuration, feed
1 is mixed with the straight-chain paraffin rich effluent from
separation section 4, and the resulting mixture 33 is sent to
hydro-isomerisation section 2. This produces an effluent 19 with a
higher octane number than that of the feed. This effluent 19 is
mixed with effluent 22 from hydro-isomerisation section 3, then the
ensemble is sent to separation section 4. This section produces
three streams 20, 21 and 28. Stream 21, which is rich in
mono-branched paraffins, is sent to hydro-isomerisation section 3
which converts these paraffins into higher branched paraffins.
Stream 28, which is rich in multi-branched paraffins, naphthenic
compounds and aromatic compounds, has a high octane number and
constitutes a high octane number gasoline stock. Effluent 28 (FIG.
2.2C) can thus be sent to the gasoline pool.
[0059] In variation 2.2d (FIG. 2.2D), the separation section which
is constituted by one or more units, is placed upstream of the two
hydro-isomerisation sections. In this configuration, feed 1 is
mixed with recycled streams 25 and 27 from hydro-isomerisation
sections 2 and 3 respectively. The resulting stream 23 is sent to
separation section 4. This produces three effluents 24, 26 and 38.
Stream 24, which is rich in straight-chain paraffins, is sent to
hydro-isomerisation section 2 which converts these paraffins into
higher branched paraffins. Stream 26, which is rich in
mono-branched paraffins, is sent to the hydro-isomerisation section
3 which also converts these paraffins into branched paraffins.
Stream 38, which is rich in multi-branched paraffins, aromatic
compounds and naphthenic compounds, has a high octane number and
constitutes a high octane number gasoline stock. Effluent 38 (FIG.
2.2D) can thus be sent to the gasoline pool.
[0060] The advantages of implementation 2.2 are many-fold. As for
implementation 2.1, it enables the sections and/or the
hydro-isomerisation reactor or reactors to be operated at different
temperatures and different HSVs so as to minimise cracking of di
and tri-branched paraffins. Further, it can minimise the quantity
of catalyst by recycling only straight-chain paraffins to the
hydro-isomerisation reactors 2 which enables a higher temperature
to be used and thus minimises the quantity of catalyst in this
section. The hydro-isomerisation reactor section 3, mainly supplied
with mono-branched paraffins for variations 2,2b, c and d and with
mono and multi-branched paraffins for variation 2.2a, operate at a
lower temperature which improves the yield of di and tri-branched
paraffins because of the more favourable thermodynamic equilibrium
under these conditions, while limiting cracking of multi-branched
paraffins, which is not favoured at low temperatures. This
configuration (with the exception of variation 2.2d) can also avoid
mixing high octane number streams with low octane number streams.
Thus the recycling streams 9 (FIG. 2.2A) and 20 (FIG. 2.2C) which
are rich in straight-chain paraffins are mixed with feed 1. Stream
12 which is rich in mono-branched paraffins is mixed with stream 7
which is rich in mono-branched and multi-branched paraffins.
Finally, streams 15 and 22 from hydro-isomerisation sections 3 are
respectively mixed with streams 13 and 19 with octane numbers which
are higher than that of the feed.
[0061] In variations 2.2b and 2.2d (FIGS. 2.2B and 2.2D), the
disposition of separation sections 4 and possibly 5 with respect to
the hydro-isomerisation sections 2 and 3 is such that the quantity
of naphthenic and aromatic compounds traversing the
hydro-isomerisation section is lower than in variation 2.2a. This
limits saturation of the aromatic compounds contained in the C5-C8
cut or in the intermediate cuts resulting in a lower hydrogen
consumption for the process. Similarly, in variation 2.2c, the
disposition of the separation section 4 with respect to the
hydro-isomerisation section 3 enables the hydrogen consumption in
the latter to be reduced.
[0062] As in the case of implementation 2.1, when the feed includes
a C5 cut, the process of implementation 2.2 can optionally comprise
a deisopentaniser located upstream or downstream of the separation
and hydro-isomerisation sections. In particular, the
deisopentaniser can be placed in feed stream 1, in any one of
streams 1, 6, 7, 10, 11, 12 (FIG. 2.2A), in any one of streams 1,
13, 14, 15, 17 (FIG. 2,2B), in any one of streams 19, 21, 22 (FIG.
2.2C) and in any one of streams 23, 25, 26 or 27 (FIG. 2.2D). It
may also be of interest to place a depentaniser in any one of
streams 1, 6 or 9 (FIG. 2.2A) or 1, 16 or 17 (FIG. 2,2B), 1, 19 or
20 (FIG. 2,2C) or 1, 23, 24, or 25 (FIG. 2,2D). A combination of a
deisopentaniser and a depentaniser is also possible. The
isopentane, pentane or mixture of pentane and isopentane thus
separated can optionally act as an eluent or a flushing gas for the
adsorption or permeation separation processes respectively. In the
latter case, the pentane is preferably not sent to the gasoline
pool because of its low octane number. As a result, it is
preferably separated from high octane number streams 8, 18, 28 and
38 (FIGS. 2.1A and 2.1B). In contrast, the isopentane is preferably
sent to the gasoline pool with streams 8, 18, 28 and 38 because of
its good octane number.
[0063] As for implementation 2.1, when the cut contains no C5 but
contains C6, a deisohexaniser can optionally be placed on any one
of streams 1, 6, 7, 10, 11 or 12 (FIG. 2.2A), or 1, 13, 14, 15 or
17 (FIG. 2.2B), 19, 21 or 22 for 2.2c and 23, 25, 26 or 27 (FIG.
2.2D). The isohexane recovered can act as an eluent or a flushing
gas for the adsorption or permeation separation processes
respectively. The isohexane is preferably not sent to the gasoline
pool because of its low octane number. It is preferably separated
from high octane number streams 8, 18, 28 and 38 (FIGS. 2,2A, 2,2B,
2,2C and 2,2D). This use of a portion of the feed in the separation
section constitutes very good integration of the process. However,
this section can also use other compounds as an eluent or a
flushing gas for the adsorption or permeation separation processes
respectively. In particular, light paraffins such as butane and
isobutane are of interest as they can readily be separated from
heavier paraffins by distillation.
[0064] For each of these variations and implementations, the
hydro-isomerisation section is composed of at least one
hydro-isomerisation section containing, for example, a catalyst
from the family of bifunctional catalysts such as catalysts based
on platinum or a sulphide phase on an acid support (chlorinated
alumina, a zeolite such as mordenite, SAPO, Y zeolite, b zeolite)
or from the family of mono-functional acid catalysts such as
chlorinated aluminas, sulphated zirconias with or without platinum
and promoter, heteropolyacids based on phosphorous and tungsten,
molybdenum oxycarbides and oxynitrides which are normally ranked
among the mono-functional catalysts with metallic character. They
function in a range of temperatures between 25.degree. C., for the
most acidic (heteropolyanions, supported acids) and 450.degree. C.,
for bi-functional catalysts or molybdenum oxycarbides. The
chlorinated aluminas are preferably used between 80.degree. C. and
110.degree. C. and platinum based catalysts on a support containing
zeolite are used between 260.degree. C. and 350.degree. C. The
operating pressure is in the range 0.01 to 0.7 MPa, and depends on
the C5-C6 concentration in the feed, the operating temperature and
the H2/HC molar ratio. The space velocity, measured in kg of feed
per kg of catalyst per hour, is in the range 0.5 to 2. The
H2/hydrocarbons molar ratio is generally in the range 0.01 to 50,
depending on the type of catalyst used and its resistance to coking
at the operating temperatures. With low H2/HC ratios, for example
H2/HC=0.06, it is not necessary to recycle the hydrogen, thus
saving a separator drum and a hydrogen recycle compressor.
[0065] The hydro-isomerisation section can comprise one or more
reactors disposed in series or in parallel which can, for example,
contain one or more of the catalysts mentioned above. As an
example, for variations 1a and 1b (FIGS. 1A and 1B), the
hydro-isomerisation section 2 comprises at least one reactor, but
can comprise two reactors or more disposed in series or in
parallel. For variations 2.1a and b (FIGS. 2.1A and 2.1B), and
2.2a, b, c and d (FIGS. 2.2A, 2.2B, 2.2C, 2.2D), the
hydro-isomerisation sections 2 and 3 can optionally comprise two
reactors each, for example, optionally containing two different
catalysts. Sections 2 and 3 can optionally also each comprise a
plurality of reactors in series and/or in parallel, with different
catalysts depending on the reactors.
[0066] Similarly, each separation section can be constituted by one
or more units which can carry out overall separation into two or
three effluents which are rich in straight-chain, mono and
multi-branched paraffins, naphthenic compounds and aromatic
compounds. Thus each of separation sections 4 and/or 5 of any one
of variations 2.1a or 2.2a, b, c or d, comprise at least one
separation unit which can be substituted by two or more separation
units, disposed in series or in parallel.
[0067] When separating by adsorption, the section comprises at
least one adsorption bed. This adsorber will, for example, be
filled with a natural or synthetic adsorbent which can separate
straight-chain, mono and multi-branched paraffins on the basis of
geometrical, diffusional or thermodynamic differences.
[0068] A large number of adsorbent materials can carry out this
type of separation. Among them are carbon, activated clay, silica
gel, and activated alumina molecular sieves and crystalline
molecular sieves. These latter have a uniform pore size and for
this reason are particularly suitable for separation. Such
molecular sieves include the different forms of
silicoaluminophosphates and aluminophosphates described in U.S.
Pat. No. 4,444,871, U.S. Pat. No. 4,310,440 and U.S. Pat. No.
4,567,027 as well as zeolitic molecular sieves. These, in their
calcined form, can be represented by the chemical formula
M.sub.2/nO: Al.sub.2O.sub.3: xSiO.sub.2: yH.sub.2O where M is a
cation, x is in the range 2 to infinity, y is in the range 2 to 10
and n is the valency of the cation. For our purposes, microporous
molecular sieves with an effective pore diameter of slightly more
than 5 .ANG. (1 .ANG.=10.sup.-10 m) are preferred. The term
"effective pore diameter" is a conventional term in the art. It is
used to functionally define the size of a pore in terms of the size
of molecule which can enter the pore. It does not define the actual
dimension of the pore as that is often difficult to determine since
the pore is usually irregular in shape (i.e., non circular). D. W.
Breck discusses the effective pore diameter in his book entitled
"Zeolite Molecular Sieves", John Wiley and Sons, New York, 1974),
pages 633 to 641.
[0069] Preferred microporous molecular sieves are those with
elliptical pore cross sections with dimensions in the range 5.0
.ANG. to 5.5 .ANG. (5.0 to 5.5.times.10.sup.-10 m) along the minor
axis and about 5.5 to 6.0 .ANG. along the major axis. An adsorbent
with these characteristics, and thus particularly suitable for the
present invention, is silicalite. The term "silicalite" includes
here both silicopolymorphs described in U.S. Pat. No. 4,061,724 and
F silicalite described in U.S. Pat. No. 4,073,865. Other adsorbents
with the same characteristics and thus which are particularly
suitable for our application are ZSM-5, ZSM-11, ZSM-48 and numerous
other analogous crystalline aluminosilicates. ZSM-5 and ZSM-11 are
described in U.S. Pat. No. 3,702,886, RE 29 948 and U.S. Pat. No.
3,709,979. The amount of silica in these adsorbents can vary.
Adsorbents which are the most suitable for this type of separation
are those with high silica contents. The Si/Al molar ratio should
preferably be at least 10 and more preferably over 100.
[0070] A further type of adsorbent which is particularly suitable
for our application contains elliptical cross section pores with
dimensions in the range 4.5 .ANG. to 5.5 .ANG.. This type of
adsorbent has been described in U.S. Pat. No. 4,717,748, for
example, as being a tectosilicate with a pore size intermediate
between that of pores of a calcium 5A sieve and the pores of ZSM-5.
Preferred adsorbents from this family include ZSM-23 described in
U.S. Pat. No. 4,076,872 and ferrierite described in U.S. Pat. No.
4,016,425 and U.S. Pat. No. 4,251,499.
[0071] The operating conditions for separation depend on its
implementation and on the adsorbent under consideration. They are
generally in the temperature range 50.degree. C. to 450.degree. C.,
and in the pressure range 0.01 MPa to 7 MPa. More precisely, if
separation is carried out in the liquid phase, the separation
conditions are generally: a temperature of 50.degree. C. to
200.degree. C. and a pressure of 0.1 MPa to 5 MPa. If said
separation is carried out in the gas phase, these conditions are
generally: a temperature of 150.degree. C. to 450.degree. C. and a
pressure of 0.01 MPa to 7 MPa.
[0072] When the separation technique is permeation, the membrane
used can be in the form of hollow fibres, bundles of tubes, or a
stack of plates. Such configurations are known in the art and
ensure homogeneous distribution of the fluid to be separated over
all of the membrane surface, maintaining the pressure difference
from one side to the other of the membrane, and recovering the
fluid which has permeated separately from that which has not
permeated. The selective layer can be formed from one of the
adsorbent materials described above providing that it can form a
uniform surface delimiting a section in which at least a portion of
the feed can circulate, and a section in which at least a portion
of the fluid which has permeated circulates.
[0073] The selective layer can be deposited on a permeable support
which provides the mechanical strength of the membrane so
constituted, as described in WO 96/01687 or WO 93/19840.
[0074] The selective layer is preferably formed by growing crystals
of zeolite from a microporous support as described in European
patents EP-A-0 778 075 and EP-A-0 778 076. In a preferred mode of
the invention, the membrane is constituted by a continuous layer of
silicalite crystals about 40 microns thick (1 micron=10.sup.-6 m),
bonded to an alpha alumina support with a 200 nm pore size.
[0075] The operating conditions will be selected so as to maintain
a chemical potential difference of the constituent(s) to be
separated over the whole membrane surface to encourage their
transfer through the membrane. The pressures either side of the
membrane must allow average differences of transmembrane partial
pressures of the constituents to be separated of 0.05 to 1 MPa.
[0076] To reduce the partial pressure of the constituents, it is
possible to use a flushing gas or to maintain the vacuum using a
vacuum pump at a pressure which, depending on the constituents, can
be from 100 Pa to 10.sup.4 Pa and to condense vapours at very low
temperatures, typically about -40.degree. C. Depending on the
hydrocarbons used, the temperatures should not exceed 200.degree.
C. to 400.degree. C. to limit cracking and/or coking of olefinic
and/or aromatic hydrocarbons in contact with the membrane. The rate
of feed circulation is preferably such that it flows
turbulently.
[0077] A pre-treatment consisting of desulphurisation and
denitrogenation of the feed upstream of the hydro-isomerisation
section is generally necessary. The effect of sulphur poisoning is
particularly marked when bi-functional catalysts are used, as it
results in an attenuation of the hydro-dehydrogenating function
provided by the metal which means that the temperatures have to be
increased to the detriment of the desired selectivity for C5-C8
compounds. Denitrogenation of the feed, particularly indispensable
for converted naphthas, is essentially justified by neutralisation
of the acid sites of the catalyst resulting from poisoning by
nitrogen-containing bases. In certain particular cases, such as
using sulphur- and nitrogen-depleted feeds (less than 100 ppm of
sulphur-containing compounds, less than 0.5 ppm of
nitrogen-containing compounds), and the use of thio and
azoresistant catalysts such as molybdenum oxycarbides,
pre-treatment of the feed is not indispensable. In other cases, in
addition to desulphuration and denitrogenation, the feed must also
be deoxygenated, consisting of eliminating traces of water, oxygen
and oxygen-containing compounds such as ethers. This case is
encountered, for example, when the catalyst is a chlorinated
alumina, with or without platinum, used at low temperature
(40.degree.-150.degree. C.). Pre-treatment of the feed (stream 1)
is generally carried out upstream of the
hydro-isomerisation+separation section group. However, in the
particular case of the sequence shown in FIG. 1b, pre-treatment can
be carried out downstream of the separation section and selectively
treat low octane number stream 9 intended to supply the
hydro-isomerisation section. Similarly, in variations 2.1b and
2.2b, these pre-treatments can respectively be carried out on any
one of streams 11 or 12 (FIG. 2.1B), 16 and 14 (FIG. 2.2B), or 24
and 26 (FIG. 2.2D).
[0078] Downstream of the hydro-isomerisation section, it is
generally advantageous to provide a feed stabilisation column to
limit the vapour tension of the isomerate to an acceptable value.
The vapour tension is controlled by eliminating a certain quantity
of volatile compounds, such as C1-C4, using techniques which are
well known to the skilled person. In the absence of hydrogen
recycling, hydrogen can be separated from the feed in the
stabilisation column. When proper operation of one of the
isomerisation catalysts used upstream requires the addition of a
chlorinated agent upstream of the hydro-isomerisation section, the
separation column can also eliminate the hydrogen chloride formed.
In this case, it is advantageous to mount a washing drum for gases
from the stabilisation step to limit discharge of acid gases to the
atmosphere.
[0079] As described above, the separation section can be located
upstream (FIGS. 1B, 2.1B, 2.2B, 2.2D) or downstream (FIGS. 1A,
2.1A, 2.2A, 2.2C) of the hydro-isomerisation section. In the first
case, the major portion of the naphthenic and aromatic compounds
avoid the hydro-isomerisation section, which has two important
consequences:
[0080] the volume of the hydro-isomerisation section is
smaller;
[0081] the aromatic compounds present in the feed are not
saturated, resulting in a lower hydrogen consumption in the process
and a smaller reduction in the octane number of the effluent.
[0082] In the second case (FIGS. 1A, 2.1A, 2.2A, 2.2C), the
aromatic and naphthenic compounds traverse all or a part of the
hydro-isomerisation section. It may thus be necessary to add a
reactor for saturating the aromatic compounds, immediately upstream
of the isomerisation section (if there is only one), or the first
isomerisation section (if there is more than one). The criterion
for adding a saturation reactor could, for example, be an aromatic
compound content in the feed of over 5% by weight.
[0083] As illustrated in FIGS. 2.1A, 2.1B, 2.2A, 2.2B, 2.2C and
2.2D, there could also be at least two hydro-isomerisation sections
2 and 3 with recycling of a stream which is rich in straight-chain
paraffins to the head of section 2 and recycling of a stream which
is rich in mono-branched paraffins to the head of section 3. Such
an arrangement enables the second section to be operated at a lower
temperature than the first, which reduces cracking of the mono and
multi-branched paraffins formed in the first section, in particular
cracking of tri-branched paraffins such as 2,2,4 trimethylpentane
which readily produces isobutane by acid cracking.
[0084] The following examples illustrate the importance of a
process for hydro-isomerisation of C5-C8 cuts or intermediate cuts
of the invention on the MON (motor octane number), the RON
(research octane number), the total aromatic compound content and
the benzene content for a variety of gasoline stocks with or
without hydro-isomerisation gasoline.
[0085] In the examples, DMC5 represents the dimethylpentanes, i.e.,
the sum of the concentrations by weight of 2,2; 2,3; 2,4 and 3,3
dimethylpentanes, C7 di-branched paraffins.
EXAMPLE 1
hydro-isomerisation of a straight run C7-C8 cut
[0086] Consider the properties of a premium grade type gasoline
pool constituted by a reformate, an FCC gasoline, an alkylate and
an oxygen-containing compound (MTBE). Table 1 summarises the
composition of the mixture by volume, the percentages by weight of
paraffins, total aromatic compounds, benzene, olefins, dimethylC5
(DMC5), motor octane numbers and research octane numbers. The
reformate, FCC gasoline and alkylate were effluents from existing
units. The feed for the reforming unit was a straight run naphtha
containing 0.18% by weight of benzene.
2TABLE 1 Ben- Ole- Vol Paraf Aromat zene fins DMC5 % wt % wt % wt %
wt % wt % RON MON Reformate 50 25.1 73.0 3.2 0.8 1.3 98.7 88 FCC 30
24.7 34.6 1.2 33.1 1.2 94.8 83.4 Alkylate 10 99.9 0 0 0.1 3.3 93.4
91.9 MTBE 10 0 0 0 0 0 117 102 Mixture 100 30.0 46.9 2.0 10.3 1.3
98.8 86.3
[0087] By way of comparison, consider a premium grade type gasoline
pool constituted by unchanged FCC gasoline, alkylate and MTBE
bases, in the same proportions, with a smaller proportion of
reformate, the complement being supplied by the effluent from a
C7-C8 hydro-isomerisation process in accordance with the invention.
to accomplish this, the C7-C11 feed from the reforming unit was
separated by distillation into a C7-C8 hydro-isomerisation feed and
a C9-C11 reforming feed. The composition of the reformate was
estimated using tools which are known to the skilled person
(correlative models, kinetic models, etc.). The composition of the
isomerate was as that obtained after the pilot tests on the C7-C8
feed mentioned above. The hydro-isomerisation process was that
represented in version 2, variation 2.1b of the invention (FIG.
2.1B). The separation section was placed upstream of the reaction
section. The aromatic and naphthenic compounds initially contained
in the feed were sent directly to the gasoline pool without
isomerisation or saturation of the aromatic compounds.
3TABLE 2 Ben- Ole- Vol Paraf Aromat zene fins DMC5 % wt % wt % wt %
wt % wt % RON MON Reformate 15 15.1 83.6 0.8 0.4 0 101.7 904 FCC 30
24.7 34.6 1.2 33.1 1.2 94.8 83.4 C7-C8 35 53.3 12.2 0.4 0 13.9 82.7
81.0 Hydro- isom alkylate 10 99.9 0 0 0.1 3.3 93.4 91.9 MTBE 10 0 0
0 0 0 117 102 Mixture 100 32.3 27.2 0.5 10.1 5.6 95.6 86.2
[0088] Introducing the hydro-isomerisation effluent from the C7-C8
cut obtained using the process of the invention reduced the total
aromatic compound content in the mixture by about 20% by weight.
The benzene content reduced from 2% to 0.5%, the residual benzene
coming from demethylation and deethylation of xylenes and A9+
aromatic compounds (i.e., aromatic compounds containing more than 9
carbon atoms) in the reforming step, also benzene present in the
distillation naphtha since the separation section was located
upstream of the hydro-isomerisation section. The research octane
number showed a reduction of 3.2 points while the motor octane
number remained unchanged. This latter point is one of the main
advantages of the C7-C8 cut hydro-isomerisation process of the
invention. The substantial reduction in aromatic compounds, in
particular of benzene in the mixture was not accompanied by a
reduction in the motor octane number.
[0089] The dimethylpentane content (DMC5 in the Table) increased
substantially on introducing the C7-C8 hydro-isomerisation
gasoline, from 1.3% to 5.6% by weight. In a "standard" gasoline
pool containing no C7-C8 hydro-isomerisation gasoline stock, the
major portion of the DMC5s originate from the alkylate. As a
result, gasoline pools containing the most DMC5 are pools which are
the richest in alkylates. However, an examination of the
composition of commercial gasolines containing up to 30% of
alkylate has shown that the DMC5 content in these gasolines never
exceeded 1.75% by weight.
EXAMPLE 2
hydro-isomerisation of a straight run C5-C8 cut
[0090] Consider the properties of a premium grade type gasoline
pool constituted by the following bases: a reformate, an FCC
gasoline, an alkylate, an oxygen-containing compound and a C5-C6
hydro-isomerisation gasoline. The reformate, FCC gasoline and
alkylate were identical to those of Example 1. Table 3 summarises
the properties of the mixture with the proportions by volume of
each constituent.
4TABLE 3 Ben- Ole- Vol Paraf Aromat zene fins DMC5 % wt % wt % wt %
wt % wt % RON MON Reformate 38 25.1 73.0 3.2 0.8 1.3 98.7 88 C5C6
12 84.0 0.1 0.1 0 0 83.1 81.7 hydro- isom FCC 30 24.7 34.6 1.2 33.1
1.2 94.8 83.4 Alkylate 10 99.9 0 0 0.1 3.3 93.4 91.9 MTBE 10 0 0 0
0 0 117 102 Mixture 100 38.1 38.2 1.6 10.2 1.2 97.4 86.2
[0091] By way of comparison, consider a premium grade type gasoline
pool constituted by unchanged FCC gasoline, alkylate and MTBE
bases, in the same proportions, with a smaller proportion of
reformate. The C5-C8 cut was treated using the hydro-isomerisation
process of the invention (variation 2.1b, FIG. 2.1B) which replaced
the C5-C6 hydro-isomerisation unit described above. The composition
of the isomerate was as that obtained after the pilot tests on the
C5-C8 feed mentioned above. The separation section was upstream of
the reaction section. The aromatic and naphthenic compounds
initially contained in the feed were sent directly to the gasoline
pool without isomerisation or saturation of the aromatic
compounds.
5TABLE 4 Ben- Ole- Vol Paraf Aromat zene fins DMC5 % wt % wt % wt %
wt % wt % RON MON Reformate 11.4 18.3 80.2 0.8 0.3 0 101.8 90.1
C5C8 38.6 61.7 10.5 2.3 0 12.6 85.6 84.0 hydro- isom FCC 30 24.7
34.6 1.2 33.1 1.2 94.8 83.4 Alkylate 10 99.9 0 0 0.1 3.3 93.4 91.9
MTBE 10 0 0 0 0 0 117 102 Mixture 100 43.3 23.6 1.3 10.0 5.6 94.1
87.1
[0092] Now consider a mixture identical to the above, except for
the hydro-isomerisation. In this example, the C5 cut (normal
pentane, isopentane) contained in the straight run gasoline was
sent directly to the gasoline pool without being isomerised. This
could be achieved either by installing a depentaniser upstream of
the hydro-isomerisation step, or by removing the C5 during
atmospheric distillation or by removing the C5 from the head of a
naphtha splitter. Only the C6-C8 cut was isomerised.
6TABLE 5 Ben- Ole- Vol Paraf Aromat zene fins DMC5 % wt % wt % wt %
wt % wt % RON MON Reformate 11.4 18.3 80.20 0.8 0.3 0 101.8 90.1 C5
cut 6 100 0 0 0 0 80.9 79.5 C6C8 32.6 47.9 14.3 3.2 0 14.9 83.6
82.0 hydro- isom FCC 30 24.7 34.6 1.2 33.1 1.2 94.8 83.4 Alkylate
10 99.9 0 0 0.1 3.3 93.4 91.9 MTBE 10 0 0 0 0 0 117 102 Mixture 100
41.1 24.2 1.5 10.0 5.6 93.2 86.2
[0093] In the cases illustrated in Tables 4 and 5, it can be seen
that introducing C5-C8 or C6-C8 hydro-isomerisation gasoline
resulted in a significant increase in MON over the composition of
Table 3 which contained a gasoline from hydro-isomerisation of a
C5-C6 cut. The quantity of benzene in the gasoline pool reduced by
0.3% while the total aromatic compound concentration was reduced by
14.6%, which is considerable. Sending the C5 cut directly to the
gasoline pool without hydro-isomerisation was accompanied by a
reduction of 0.9 in RON and MON with respect to the case where all
of the C5 -C7 cut was hydro-isomerised. As a result, installing a
depentaniser upstream of the hydro-isomerisation step or extracting
the C5 cut from the head of the naphtha splitter caused a
substantial reduction in the size of the hydro-isomerisation
section at the cost of a modest drop in octane number.
[0094] Further, it can be seen that in comparison with Table 1,
introducing C5 -C8 or C6-C8 hydro-isomerisation gasoline is
accompanied by a substantial increase in the DMC5 content in the
premium grade gasoline pool.
EXAMPLE 3
hydro-isomerisation of a C5 -C7 cut including a light reformate
[0095] 1. Hydro-isomerisation of a light reformate cut at
85.degree. C. and addition of a c5-C6 hydro-isomerisation gasoline
(identical to that reported in Table 3, 18% of normal paraffins).
In this case we consider a hydro-isomerisation process in
accordance with variation 2.1b, i.e., separating the aromatic
compounds upstream of the hydro-isomerisation section. These
aromatic compounds were sent to the gasoline pool without being
saturated.
[0096] Consider a gasoline pool constituted by FCC gasoline and
alkylate already described in the preceding examples, also heavy
reformate (initial point 80.degree. C.; end point 220.degree. C.)
and light reformate+light gasoline hydro-isomerised using the
process of the invention (the aromatic compounds being extracted
upstream of the isomerisation section).
7TABLE 6 Ar- Ben- Ole- Vol Paraf omat zene fins Oxyg % wt % wt % wt
% wt % wt % RON MON Reformate 32 12.2 82.0 0 0.3 0 101.3 90.7
80-220.degree. C. Light 6 67.6 22.6 22.0 4.6 0 91.8 85.2 reformate
C5C6 12 84.0 0.1 0.1 0 0 83.1 81.7 hydro- isom FCC 30 24.7 34.6 1.2
33.1 0 94.8 83.4 Alkylate 10 99.9 0 0 0.1 0 93.4 91.9 MTBE 10 0 0 0
0 100 117 102 Mixture 100 38.1 38.0 1.7 10.3 10 98.0 86.7
[0097] Compared with the gasoline the composition of which was
described in Table 3, which did not involve isomerisation of a
light reformate, the aromatic compound content did not
substantially vary but the RON increased by 0.6 and the MON
increased by 0.5.
[0098] 2. Hydro-isomerisation of a light reformate cut at
105.degree. C. (half of the toluene from the reformate was in this
cut) and addition of a C5 -C6 hydro-isomerisation gasoline
(identical to that of Table 3).
8TABLE 7 Ar- Ben- Ole- Vol Paraf omat zene fins Oxyg % wt % wt % wt
% wt % wt % RON MON Reformate 26 7.7 90.5 0 0.2 0 105.8 94.8
105-220.degree. C. Hydro- 12 58.5 37.4 10.1 2.0 0 94.3 86.3 isom
reformate IP 105.degree. C. C5C6 12 84.0 0.1 0.1 0 0 83.1 81.7
hydro- isom FCC 30 24.7 34.6 1.2 33.1 0 94.8 83.4 Alkylate 10 99.9
0 0 0.1 0 93.4 91.9 MTBE 10 0 0 0 0 100 117 102 Mixture 100 37.7
38.4 1.6 10.2 10 98.7 87.3
[0099] Compared with the gasoline described in Table 3, which did
not involve isomerisation of a light reformate, the aromatic
compound content did not substantially vary but the RON increased
by 1.3 and the MON increased by 1.1. This gain, when compared with
Table 6, is the consequence of isomerisation of the C7 paraffins of
the raffinate.
[0100] 3. Hydro-isomerisation of a light reformate cut at
105.degree. C. then saturation and addition of a C5 -C6
hydro-isomerisation gasoline (identical to that shown in Table
3).
9TABLE 8 Ar- Ben- Ole- Vol Paraf omat zene fins Oxyg % wt % wt % wt
% wt % wt % RON MON Reformate 26 7.7 90.5 0 0.2 0 105.8 94.8
105-220.degree. C. Hydro- 12 58.7 0 0 2.0 0 79.6 94.8 isom
reformate IP 105.degree. C. saturation C5C6 12 84.0 0.1 0.1 0 0
83.1 81.7 hydro- isom FCC 30 24.7 34.6 1.2 33.1 0 94.8 83.4
Alkylate 10 99.9 0 0 0.1 0 93.4 91.9 MTBE 10 0 0 0 0 100 117 102
Mixture 100 37.7 33.9 0.48 10.2 10 97.5 86.9
[0101] Compared with the preceding example, the aromatic compounds
contained in the light reformate were saturated to naphthenic
compounds. This could be accomplished by adding an aromatic
compound hydrogenation section at the head of the
hydro-isomerisation section. By comparison with table 7, the
aromatic compound content reduced by 4.5% but the RON reduced by
1.2 and the MON by 0.4.
[0102] When compared with Table 3, i.e., with no
hydro-isomerisation of the C5 -C7 light reformate, the aromatic
compounds reduced by 4.3% by weight, then the benzene content
reduced to 1.1% by weight, the RON did not change (+0.1) and the
MON increased by 0.7. Hydro-isornerisation of the light C5 -C7
reformate with saturation of the aromatic compounds contained in
the light reformate thus reduced the benzene content to below 0.8%
by weight, which corresponds to the most severe of current
regulations in the world (California), with no loss of RON, with a
gain in MON, and a reduction in the total aromatic compounds
content.
* * * * *