Note: Descriptions are shown in the official language in which they were submitted.
..
1 -
~~8g3~4
T 6146
PROCESS FOR UPGRADING A HYDROCARBONACEOUS FEEDSTOCK
The present invention relates to a process for upgrading a
hydrocarbonaceous feedstock substantially boiling in the gasoline
range.
One of the main objects in nowaday s oil refining is to
produce gasolines fulfilling the increasing environmental demands
on product quality and having a high octane number.
This means for gasoline that the octane specification has now
to be established without lead-containing additives, less
aromatics, in particular benzene, less olefins and lower gasoline
vapour pressure.
Object of the present invention is to provide a process for
the preparation of gasolines fulfilling both the increasing
environmental demands on product quality and the high octane
requirement.
It has now been found that gasolines can be produced having a
high octane number and a reduced aromatics content, in particular
benzene, when use is made of an upgrading process comprising a
specific sequence of process steps.
Accordingly, the present invention relates to a process for
upgrading a hydrocarbonaceous feedstock substantially boiling in
the gasoline range, which process comprises:
a) subjecting the feedstock to a separation treatment wherein
normal paraffins and optionally mono-isoparaffins are
separated from di-isoparaffins;
b) recovering therefrom a first separation effluent stream
comprising normal paraffins and optionally mono-isoparaffins
and a second separation effluent stream comprising
di-isoparaffins;
c) separating at least part of the second separation effluent
stream into a light fraction comprising hydrocarbons of the
208324
_ 2 _
C6-C10 range and a heavy fraction comprising C8 and greater
hydrocarbons;
and
d) subjecting at least part of the heavy fraction comprising C8
and greater hydrocarbons to a reforming step to produce a
reformate.
In this way a direct octane enhancement of the resultant
gasoline blending pool is established whilst a substantial
reduction of aromatics content, in particular of the benzene
content, is realized. In refineries with restriction on production
of gasoline due to octane and/or capacity limitations, this octane
enhancement can permit increased gasoline production. Moreover, it
is established that the amount of gas make and the production of
hydrocarbons having a low octane rating can substantially be
reduced in the reforming step.
The hydrocarbonaceous feedstock substantially boiling in the
gasoline range can suitably be obtained by distillation of crude
oil or from catalytic cracking although it may be obtained by other
cracking processes such as thermal cracking, delayed coking,
visbreaking and flexicoking. Such gasoline feedstocks usually
contain unacceptable levels of sulphur and nitrogen and benefit
from a hydrotreatment before they are subjected to the process
according to the present invention. While the full gasoline boiling
range fraction may be included in the feedstock, it may be
preferred to employ as feedstock a cut thereof substantially
boiling in the range of 70 to 220 °C. Suitably, the
hydrocarbonaceous feedstock consists essentially of a hydrocarbon
mixture substantially boiling in. the gasoline range.
Zn step a) the separation treatment can suitably be
established by passing the feedstock to a separation zone
comprising a shape-selective separatory molecular sieve having a
pore size of 4.5 x 4.5 A or smaller and being shaped to permit
adsorption of normal paraffins in a selective manner vis-à-vis
mono-isoparaf~ins, di-isoparaffins, other mufti-branched paraffins,
cyclic paraffins and aromatic hydrocarbons. In this way the normal
~a8~3~4
3 -
paraffins can selectively be separated from mono-isoparaffins and
di-isoparaffins. Subsequently, the first separation effluent stream
comprising substantially normal paraffins can be recovered and at
least part of the second separation effluent stream comprising
di-isoparaffins can be subjected to the separation treatment in
step c). Suitably, at least part of the first separation effluent
stream can be co-processed in step d). At least part of this
separation effluent stream can also suitably be used as a preferred
chemical feedstock. For instance, as a feedstock for a highly
selective cyclization process.
Suitably, the process according to the present invention is
carried out in such a way that in step a) both the normal paraffins
and mono-isoparaffins are separated from the di-isoparaffins. The
separation treatment can suitably be established by passing the
hydrocarbonaceous feedstock to a separation zone comprising a
shape-selective separatory molecular sieve having a pore size
intermediate 5.5 x 5.5 to 4.5 x 4.5 A but excluding 4.5 x 4.5 A,
the pore size being sufficient to permit entry of normal paraffins
and mono-isoparaffins but restrictive to prohibit entry of
di-isoparaffins, other multi-branched paraffins, cyclic paraffins
and aromatic hydrocarbons. In this way the normal paraffins and
mono-isoparaffins can selectively be separated from the
di-isoparaffins. Subsequently, the first separation effluent stream
comprising both normal paraffins and mono-isoparaffins can be
recovered and at least part of the second separation effluent
stream comprising di-isoparaffins can be subjected to the
separation treatment in step c). Suitably, at least part of this
first separation effluent stream can be co-processed in step d). At
least part of this separation effluent stream can also suitably be
used as a preferred chemical feedstock as indicated hereinbefore.
Suitably, in step a) the normal paraffins are firstly
separated from the mono-isoparaffins and di-isoparaffins, whereas
the mono-isoparaffins are subsequently separated from the
di-isoparaffins. To this end use can be made of a multiple select
adsorbent molecular sieve system having particular separatory
2~~~324
- 4 -
qualities. Preferably, the multiple separatory sieve system to be
used comprises a first molecular sieve having a pore size of
4.5 x 4.5 A or smaller and being shaped to permit adsorption of
normal paraffins in a selective manner vis-à-vis mono-isoparaffins,
di-isoparaffins, other multi-branched paraffins, cyclic paraffins
and aromatic hydrocarbons and a second molecular sieve having a
pore size intermediate 5.5 x 5.5 to 4.5 x 4.5 A, but excluding
4.5 x 4.5 A, being selected to permit adsorption of mono-
isoparaffins (and any remaining normal paraffins) in deference to
di-isoparaffins and other multi-branched paraffins, cyclic
paraffins and aromatic hydrocarbons. In operation, the hydro-
carbonaceous feedstock is firstly passed to a first separation zone
comprising the first shape-selective separatory molecular sieve as
defined hereinabove to produce the first separation effluent stream
comprising the normal paraffins and the second separation effluent
stream comprising both mono- and di-isoparaffins. The latter
hydrocarbon effluent stream is subsequently passed to a second
separation zone comprising the second shape-selective separatory
molecular sieve as described hereinabove. Subsequently, a third
separation effluent stream comprising mono-isoparaffins can be
recovered and at least part of a fourth separation effluent stream
comprising di-isoparaffins can be separated into a light and a
heavy fraction in step c).
Suitably, at least part of the first and/or third separation
effluent streams can be co-processed in step d). At least part of
these streams can also suitbly be used as a preferred chemical
feedstock as indicated hereinbefore.
The multiple select adsorbent molecular sieve system as
described hereinabove comprises at least two molecular staves.
These can be arranged in separate vessels, or they can be arranged
in a stacked flow schema within one vessel.
The first molecular sieve can be a calcium 5 A zeolite or any
other sieve of similar pore dimensions, i.e. pore dimensions of 4.5
x 4.5 A. It is not necessary to size the first sieve to~adsorb all
of the normal paraffins, but it is preferred so that the second
- 20f~~3~~
-5-
molecular sieve does not have to function as a normal paraffin
adsorption sieve,
The second sieve to be applied in a multiple select adsorbent
molecular sieve system is exemplified by a molecular sieve which
has eight and ten member rings and pore dimensions intermediate
5.5 x 5.5 and 4.5 x 4.5 A, but excluding 4.5 x 4.5 A.
The preferred second molecular sieve of this invention is
exemplified by a ferrierite molecular sieve. It is preferred that
the ferrierite sieve be present in a hydrogen form, but it alter-
natively can be exchanged with a cation of an alkali metal, or
alkaline earth metal or transition metal cation. The molecular
sieves of this invention include ferrierite and other analogous
shape-selective materials with pore openings intermediate in
dimensions to those of the calcium 5 A zeolite and 2SM-5. Other
examples of crystalline sieves include aluminophosphates,
silicoaluminophosphates, and borosilicates.
The aluminophosphate, silicoaluminophosphate and borosilicate
molecular sieves which can be used as a second molecular sieve will
have a pore opening intermediate between 5.5 x 5.5 and 4.5 x 4.5 A,
but excluding 4.5 x 4.5 A.
It is feasible that the molecular sieve comprises a large pore
zeolite that has been ion exchanged with canons to diminish the
effective pore size of the sieve to within the aforementioned range
of dimensions.
When applying a multiple select adsorbent molecular sieve
system the sequence of the sieves, whether in discrete vessels or
in a stacked variety, is very important. If the sieves are
interchanged the process loses effectiveness because the larger
sieve will rapidly fill with normal paraffins, prohibiting the
efficient adsorption of mono-isoparaffins.
The respective sieves in a multiple select adsorbent molecular
sieve system should be arranged in a process sequence to first
provide adequate adsorption of the normal paraffin hydrocarbons,
and then, adsorption of the mono-isoparaffins. Each of these
respective sieves can be provided with a common desorbent stream or
- 288324
each sieve may have its own desorbent stream. The desorbent is
preferably a gaseous material such as a hydrogen gas stream.
Alternatively, the normal paraffins can firstly be separated
from the mono-isoparaffins and di-isoparaffins using a molecular
sieve as described hereinbefore, whereafter the second separation
effluent stream comprising mono-isoparaffins and di-isoparaffins is
separated in step c) into a light fraction comprising hydrocarbons
of the C6-C10 range and a heavy fraction comprising C8 and greater
hydrocarbons. Subsequently, the heavy fraction obtained can be
subjected to a separation treatment as described hereinbefore
wherein mono-isoparaffins are separated from di-isoparaffins.
Thereafter, a third separation stream comprising mono-isoparaffins
can be recovered and at least part of a fourth separation effluent
stream comprising di-isoparaffins can be subjected to the reforming
step. At least part of the streams comprising normal or
di-isoparaffins can be co-processed in step d), or applied as a
preferred chemical feedstock as indicated hereinbefore.
The light and heavy fraction in step c) can suitably be
obtained by distillation.
In a preferred embodiment of the processes according to the
present invention as described hereinbefore, at least part of the
reformats is subjected to a separation treatment wherein normal
paraffins and optionally mono-isoparaffins are separated from
di-isoparaffins, and whereby a first hydrocarbon product stream
comprising normal paraffins is recovered and a second hydrocarbon
product stream comprising di-isoparaffins is recovered.
In this way upstream the reforming step the initially present
normal paraffins and optionally mono-isoparaffins are separated
from di-isoparaffins, whereas downstream the reforming step normal
paraffins and optionally mono-isoparaffins, which were still
present in the separation effluent stream comprising
di-isoparaffins together with those Which have been produced in the
reforming step, are separated from di-isoparaffins,
The separation treatment downstream the reforming step can
suitably be established by passing at least part of the reformats
~~~u~2~
_,-
to a separation zone comprising a shape-selective separatory
molecular sieve having a pore size of 4.5 x 4.5 A or smaller and
being shaped to permit adsorption of normal paraffins in a
selective manner vis-à-vis mono-isoparaffins, di-isoparaffins,
other multi-branched paraffins, cyclic paraffins and aromatic
hydrocarbons. In this way the normal paraffins can selectively be
separated from :nono-isoparaffins and di-isoparaffins. At least part
of the first hydrocarbon product stream comprising substantially
normal paraffins thus obtained can suitably be used as a preferred
chemical feedstock as indicated hereinbefore. In another suitable
embodiment of the process according to the present invention at
least part of this stream is co-processed in step d).
Preferably, the process according to the present invention is
carried out in such a way that downstream the reforming step both
the normal paraffins and mono-isoparaffins are separated from the
di-isoparaffins. To this end at least part of the reformate can be
passed to a separation zone comprising a shape-selective separatory
molecular sieve having a pore size intermediate 5.5 x 5.5 to 4.5 x
4.5 A but excluding 4.5 x 4.5 A, the pore size being sufficient to
permit entry of normal paraffins and mono-isoparaffins but
restrictive to prohibit entry of di-isoparaffins, other
multi-branched paraffins, cyclic paraffins and aromatic paraffins.
In this way the normal paraffins and mono-isoparaffins can
selectively be separated from the di-isoparaffins. Subsequently, a
first hydrocarbon product stream comprising both normal paraffins
and mono-isoparaffins can be recovered and a second product stream
comprising di-isoparaffins can be recovered. The separation
treatments upstream and downstream the reforming step can suitably
be carried out in the same separation zone.
Suitably, at least part of the first hydrocarbon product
stream can be applied as a preferred chemical feedstock as
indicated hereinbefore, or co-processed in step d).
Preferably, in the second separation treatment the normal
paraffins are firstly separated from the mono-isoparaffins and the
di-isoparaffins, whereas the mono-isoparaffins are subsequently
208~~~~
_ .
separated from the di-isoparaffins. To this end use can be made of
a multiple select adsorbent molecular sieve system as described
hereinbefore. In this way a first hydrocarbon product stream
comprising normal paraffins and a second hydrocarbon product stream
comprising mono-isoparaffins can be selectively separated from a
third hydrocarbon product stream comprising di-isoparaffins. At
least part of the first and/or second hydrocarbon product stream
can suitably be applied as a preferred chemical feedstock as
indicated hereinbefore, or co-processed in step d).
The application of a multiple select adsorbent molecular sieve
system both upstream and downstream of the reforming step is very
attractive since it offers product flexibility together with
product quality. Suitably, at least part of the reformats obtained
is passed to a hydrogenation unit before being subjected to any of
the separation treatments described hereinbefore.
Suitably, at least part of the reformats obtained is
separated, for instance by distillation, into a gaseous fraction, a
light fraction comprising C5-C6 hydrocarbons and a gasoline
fraction. At least part of the light fraction can be introduced
with another light refinery hydrocarbon stream comprising CS-C6
hydrocarbons into an isomerization unit. The isomerate so obtained
can subsequently be passed to the gasoline blending pool.
The gasoline fraction obtained can subsequently directly be
passed to the gasoline blending pool or it can be subjected to a
separation treatment wherein normal paraffins and optionally
mono-isoparaffins are separated from di-isoparaffins as described
hereinbefore.
At least part of the light fraction obtained in step c) can
directly be passed to the gasoline blending pool. In a preferred
embodiment of the present invention at least part of the light
fraction obtained in step c) is co-processed with the reformats and
subjected to a separation treatment as described hereinbefore
wherein normal and optionally mono-isoparaffins are separated from
di-isoparaffins. Alternatively, the light fraction obtained in step
c) can directly be subjected to the separation treatment downstream
2~883~4
- 9 -
the reforming step wherein mono-isoparaffins are separated from
di-isoparaffins.
The light and heavy fraction in step e) can suitably be
obtained by distillation.
At least part of one or more of the separation effluent
streams comprising normal paraffins and/or mono-isoparaffins can
suitably be co-processed with the heavy fraction in step d).
Suitably, butane can be added to to the gasoline obtained in
the gasoline blending pool in order to obtain an overall gasoline
having the maximum allowable RVP (Reid Vapour Pressure)
specification.
Suitably, at least part of the gasoline fraction obtained
downstream the reforming step can be separated, for instance by
means of distillation, into a light gasoline fraction comprising
hydrocarbons of the C6-C10 range and a heavy gasoline fraction
comprising Ca and greater hydrocarbons. At least part of the light
gasoline fraction obtained can suitably be subjected to a
separation treatment as described hereinbefore wherein normal
paraffins and optionally mono-isoparaffins are separated from
di-isoparaffins. At least part of the heavy gasoline fraction
obtained can directly be passed to the gasoline blending pool.
In the reforming step any conventional reforming catalyst can
be applied. Preferably, in the reforming step a catalyst is used
having a substantial (dehydro)cyclization activity. Exemplary of a
conventional reforming catalyst is a platinum-containing catalyst
platinum present in for instance a range of 0.005 wt~ to 10.0 wt8.
The catalytic metals associated with the reforming function are
preferably noble metals from Group VIII of the Periodic Table of
elements, such as platinum and palladium. The reforming catalyst
can be present per se or it may be mixed with a binder material.
It is well appreciated that the application of noble metal(s)-
containing reforming catalysts normally requires a pretreatment in
the form of a catalytic hydrotreatment of the feedstock to be
upgraded. In this way nitrogen-compounds and sulphur-compounds can
be removed from the feedstock which compounds would otherwise
10
reduce the performance of the reforming catalyst considerably.
The reforming step can suitably be carried out under
conventional reforming conditions. Typically the process is carried
out at a temperature from 450 to 550 °C and a pressure of 3 to
20 bar. The reaction section in which the reforming step is to be
performed can suitably be separated into several stages or
reactors.
The present invention will now be illustrated by means of the
following Example.
Example
A process according to the present invention is carried out in
accordance with the flow diagram as schematically shown in
Figure 1.
A hydrocarbonaceous feedstock substantially boiling in the
gasoline range and having properties as set out in Table 1 is
introduced via a line 1 into a distillation column 2 wherein the
feedstock is separated into a first light fraction comprising
hydrocarbons of the C5-C6 range and a heavy fraction comprising C6
and greater hydrocarbons. The light fraction is withdrawn via a
line 3 and introduced into an isomerization unit 4. The isomerate
effluent obtained therefrom is withdrawn via a line 5 and
introduced into the blending gasoline pool 6, whereas a gaseous
fraction is withdrawn via a Line 7. The heavy fraction is withdrawn
via a line 8, and passed to a separation zone 9 which contains two
molecular sieves 10 and 11.
Molecular sieve #1 (10) is a commercial zeolite having pore
size of from 4.5 to 4.5 A or smaller. Molecular sieve 11, referred
to as molecular sieve #2, has a pore size intermediate 5.5 x 5.5 to
4.5 x 4.5 A, but excludes 4.5 x 4.5 A.
The first molecular sieve 10 selectively adsorbs normal
paraffins in preference to mono-isopara~~ins, di-isoparaffins,
other multi-branched paraffins, cyclic paraffins and aromatic
hydrocarbons. A fraction comprising the normal paraffins is
withdrawn via a line 12. The separation effluent stream
substantially freed from normal paraf~ins is withdrawn via a
21~~4;~~~~
- 11 -
line 13 and contacted with molecular sieve #2 (11). In this
particular sieve, mono-isoparaffins are adsorbed while
di-isoparaffins and other multi-branched paraffins, cyclic
paraffins and aromatic hydrocarbons are passed through the sieve
without adsorption. A fraction comprising mono-isoparaffins is
withdrawn via a line 14, and the remaining separation effluent
(di-isoparaffins fraction) which is now substantially freed from
normal paraffins and mono-isoparaffins is withdrawn via a line 15.
Subsequently, the separation effluent comprising the di-iso-
paraffins is introduced into a distillation column 16 wherein the
effluent stream is separated into a light fraction comprising
hydrocarbons of the C6-C10 range, which is passed via a line 17 to
the gasoline blending pool 6, and a heavy fraction comprising C8
and greater hydrocarbons. The heavy fraction is withdrawn via a
line 18 and then introduced into a reforming reactor 19. The
reforming is carried out at a temperature of 498 °C, a pressure of
10.6 bar, a weight hourly space velocity of 1.8 kg/kg/hr and a
hydrogen/feed ratio of 510 N1/kg. The commercially available
reforming catalyst comprises platinum and tin on alumina. The
fractions withdrawn via the lines 12 and 14 are co-processed in the
reforming step. The reformate obtained is subsequently withdrawn
via a line 20 and introduced into a distillation column 21. In the
distillation column 21 the reformate is separated into a gaseous
fraction, a second light fraction comprising C5-C6 hydrocarbons and
a gasoline fraction. The gaseous fraction is withdrawn via a line
22, the second light fraction is co-processed with the first light
fraction comprising C5-C6 hydrocarbons via a line 23 and the
gasoline fraction is withdrawn via a line 24. Via the line 24 the
gasoline fraction is passed to a separation zone 25 containing
molecular sieves 26 and 27. Molecular sieve #3 (26) is a commercial
zeolite having pore size of from 4.5 to 4.5 A or smaller. Molecular
sieve 27, referred to as molecular sieve #4, has a pore size
intermediate 5.5 x 5.5 to 4.5 x 4.5 A, but excludes 4.5 x 4.5 A.
The first molecular sieve 26 selectively adsorbs normal
paraffins in preference to mono-isoparaffins, di-isoparaffins,
208~32~
- 12 - ,
cyclic paraffins and aromatic hydrocarbons. A fraction comprising
the normal paraffins is withdrawn via a line 28. The separation
effluent stream substantially freed from normal paraffins is
withdrawn via a line 29 and contacted with molecular sieve #4 (27).
In this particular sieve, mono-isoparaffins are adsorbed while
di-isoparaffins and other multi-branched paraffins, cyclic
paraffins and aromatic hydrocarbons are passed through the sieve
without adsorption. The fraction comprising mono-isoparaffins is
withdrawn via a line 30, and the remaining separation effluent
(di-isoparaffins fraction) which is now substantially freed from
normal paraffins and mono-isoparaffins is withdrawn via a line 31
and introduced into the blending gasoline pool 6. The fractions
withdrawn via the lines 28 and 30 are co-processed in the reforming
step.
100pbw of the feedstock in line 1 yields the various
product
fractions
in
the
following
quantities:
17.7 pbwlight fraction (line 3)
82.3 pbwheavy fraction (line 8)
22.5 pbw
isomerate
fraction
(line
5)
2.2 pbw
gaseous
fraction
(line
7)
16.8 pbwnormal paraffins fraction (line 12)
65.5 pbwseparation effluent stream (line 13)
16.4 pbwmono-isoparaffins fraction (line 14)
49.1 pbwdi-isoparaffins fraction (line 15)
31.9 pbwlight fraction (line 17)
17.2 pbwheavy fraction (line 18) ,
52.2 pbwreformate fraction (line 20)
12.0 pbwgaseous fraction (line 22)
7.0 pbwlight fraction (line 23)
33.2 pbwgasoline fraction (line 24)
0.6 pbwnormal paraffins fraction (line 28)
32.6 pbwseparation effluent stream (line 29)
1.2 pbwmono-isoparaffins fraction (line 30)
31.4 pbwdi-isoparaffins fraction (line 31)
In
the
gasoline
blending
pool
6,
3.8
pbw
of
butane
has
been
added
~as~~~~
- 13 -
to the gasoline obtained via a line 32. In this way 89.6 pbw of an
overall gasoline is obtained having the maximum allowable RVP
specification.
The overall gasoline obtained in the blending gasoline pool 6
has the properties as set out in Table 2.
From Table 2 it is clear that a very attractive gasoline, in
terms of octane number and content of aromatics, in particular
benzene, can be produced by applying the present invention. In
conventional upgrading processes gasolines are obtained having a
considerable higher content of aromatics, in particular benzene.
2Q~3~2~:
- 14 -
m_t,_ ,
C (8wt) . 84.9
H (8wt) . 15.1
S (ppm) . 15
d (70/4) . 0.729
I.B.P. (°C, ASTM): 50
10~ wt rec. . 82
30$ " " . 100
50$ " " . 110
70$ " " . 128
908 " " . 149
F.B.P. . 183
RON . 55
naphthenes " . 34
aromatics " . 6
Table 2
Gasoline properties:
RON 95.0
total aromatics ($vol) 31.6
benzene (~vo1) 1.0
naphthenes (~vol) 25.9
RVP (kPa) 62
