Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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T 5309
PROCESS ~OR THE ~ONVERSION OF A HYDROCARBONACEO~S FEEDSTOCK
Th~ present inv~ntion r~laeQs to a proce;~ for the conv~rsion
of a hydrocarbonacao~s aedstock and is particul~rly concsrnet wlth
the upgrading o~ cartain feedstocks.
US 4,171,257 tescribes a process for upgrading a hydro-
carbonacaous e~dstock by contacting tha feedstock wi~h a ZSM-5
crystalline alu~inosilicae~ caealyst at a pressure belo~ 14 bar, a
temperature of 260 to 427 ~C and a space v810city of 0. 1 to 15
l/l.h. The feedseock, axemplifLed as gas oil having a boiling poine
range of 230 to 437 C, must con~ain less than 5 ppmw of
nitrogen-cnntainin~ co~pounds, calculated as nitrogen. The upgraded
product incl~des olafinic hydrocarbons, such as propena ~nd
butenes.
The production of olafins is d~sirabl~ as their resctivity
renders eham suitabl~ or conv~rsion to further products, in
contrast to th~ low value lower paraffins. Ho~aver, the above
described process has the drawback thae ehe Initial feed~tock ~ust
have been severely denitrifiad in order to avoid rapid catalyst
deactivation.
I~ has surprisingly been found that a comparaei~ely hi~h yield
of olefins can be obtained, under less stringent csnditions as
ra~ards ni~rogen content, using certain z~olit~c catalys~s, at high
te~peratur~ with a short fe~dstock r~ idenc~ Ci~Q. Furtharmor~
has be~n ~urpris~ngly found that th~ convarsion is ~u~t~bl3 for
haavy hydrocarbon feedstocks and an upgsaded product rich in lower
ol~fins can be-obtain~d therefro~.
Accordingly, th~ pr~sent invention provid~s a proc~ss or the
conv2rsion ~f a hydrotreated and~or hydrocrack~d h~avy hytro-
carbonaceous feedstock, whlch process comprises contaceing the
feedstock with a zeolitic catalyst co~pri3ing a z~olitc with a por3
3~3~
diameter of 0.4 to 0.7 nm a~ a temperature of greater than 480 C
and a pressure of up to 10 bar during less than 10 seconds.
The feedstock is contacted with the ~eolitic catalyst for less
than 10 seconds. Suitably, the minimum contact time is 0.1 second.
Very good results are obtainable with a process in which ths
feedseock is contacted with the zeolitic catalyst during 1 to 6
seconds.
The temperature during the reaction is relatively high.
However, the combination of high temperature and short residence
time allows a high conversion to olefins. A preferrçd temperature
range is 480 to 900 C, more preferably 500 to 750 C.
The æeolitic catalyst comprises a zeolite with a pore diame~er
of from 0.4 ~o 0.7 nm. The catalys~ suitably further comprises a
refractory oxide that serves as binder material. Suitable
rafractory oxides include alumina, silica, silica-alumina,
magnesia, titania, zirconia and mixtures thereof. Alu~ina is
espacially preferred. The weight ratio of refractory oxide and
zeolite suitably ranges from 10:90 to 90:10, preferably from 50:50
to 85:}S. The catalyst may comprise further zeolites with a pore
diameter above 0.7 nm. Suitable examples of such zeolites include
the fau~asite-type zeolites, zeolite beta, 7eolite omega and in
particular zeolite X and Y. The zeolit$c catalyst preferably
comprises as æeolite substantially only zeolites with a pore
diameter of from 0.4 to 0.7 nm.
The term zeolite in this specification is not to be regarded
as comprising only crystalline aluminium silicates. The term slso
includes crystalline silica (silicalite), silicoaluminophosphates
~SAP0), chromosilicates, gallium silicates, iron silica~es,
aluminlum phosphates (ALP0), titaniu~ al~minosilicate~ (TAS0),
boron silicates, titanium aluminophosphates (TAP0) and iron
aluminosilicates.
Examples of zeolites that may be used in the process o~ the
invention and that ha~e a pore diameter of 0.4 to 0.7 nm, include
SAP0-4 and SAP0-11, which are described in US-A-4,440,871, ALP0-11,
described in US-A-4,310,440, TAP0-11, described in US-A-4,500,651,
3~0
TAS0-45, described in EP-A-229,295, boron silicates, described in
e.g. US-A-4,254,297, aluminium silicates like erionite, ferrierite
theta and the ZSM-type zeolites such as ZC.M-5, ZSM-ll, ZSM-12,
ZSM-35, ZSM-23, and ZSM-38. Preferably the æeolite ls selected from
the group consisting of crystalline me~al silicates having a ZSM-5
structure, ferrierite, erionite and mixtures theraof. Sultable
examples of crystalline metal silicates with ZSM-5 structure are
aluminium, galli~, iron, scand1um, rhodium and/or scandlum
silicatas as described in e.g. GB-B-2,110,559.
During the preparation of the zeolites usually a significant
amount of alkali metal oxide is present in the prepared zeolite.
Preferably the amount of alkali metal is removed by methods known
in the art, such as ion xchange, optionally followed by
calcination, to yield the zeolite in its hydrogen form. Preferably
the zeolite used in the present process is substantially in its
hydrogen form.
Olefin production is facilitated by the absence of hydrogen or
a hydrogen donor. Hence, the present process is advantageously
carried out in ~he absence of added hytrogen and/or ~taam. It i9,
of course, possible that during the reaction some small molecules,
such as hydrogen molecules are formed. However, this ~mount is
usually negligible and will be less than 0.5 ~wt of the product.
The pressure in the present process can be varied within wide
ranges. It is, however, preferred that the pressure is such that at
the prevailing temperature th~ feedstock is substantially in its
gaseous phase. Then it is easier to achieve the short contact times
envisagsd. Hence, the pressure is preferably relatively low. This
is the ~ore advantageous qince no expansive compressors and
high-pressure vessels and other equipment are necessary. Pressures
up to 10 bar can be employed. Subatmospheric pressures are
possible, but not preferred. The ~ini~um pressure is suitably 1
bar. It is economically advantsgeous to operate at atmospheric
pressure.
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The catalyst/feedscock weight ratio ~ay vary widely, for
example up eo 200 kg of catalyst per kg of faetstock. Prefasably,
the caealyst/fesdscock ~eighe ratio is fro~ 2 to 200.
The process according to the pres~nt ~nvention may bo carried
out in a fixed bed. However, this would i~ply ehae extramely high
space veLocities be required eo attain ~he short contac~ times
envisa~ed. Therefore, ~h2 pres~nt process 1~ preferably carrisd out
in a moving bed. The bed of catalyse may ~ove upwards or downwards.
When the bed moves upwards a process similar to a fluidized
catalytic cracking process i5 vbtained. Prefarably, the process ls
carr$ed out in a downwardly ~oving bed.
During the process some coke for~s on the catalyst. Thercfore,
it i9 advantageous to regen~rato the catalyst. Preferably the
catalyst is regenerated by sub~ecting i~, ~ftar having bean
contacted with the faedstock, to a traa~m~nt with an oxidizing gas,
such as air. A continuous regeneraeion, si~ilar to the regene~ation
carried out in a fluidized ca~alytic cracking proceis, is
~specially prefsrred.
The coke formation does not occur at a very high raee. ~ance,
it would be posslbla to arranga or a proc~ss in which the
- residence ti~ of the catalyse part$cles in a reaction zone, e.g.
moving bed, is longer than the r~sidence time of the feedstock in
th~ reaceion zone. Of cours~ the contact ti~e between eedstock ant
catalys~ should be less than L0 second~. The contact time generally
corrasponds with the residence time of ths feedstock. Suitably the
rasidenca time of the cstalyst is from 1 to 20 times t~ residenco
time of the feedstoc~.
She feedstock which i3 to ba convsrted i~ the present process
comprises hydrotreated and/or hydrocracked hydrocarbons,
preferably, though not n~ces~arily, hea~y feedstocXs.
Suitable feedstock~ arR obtainad by hydrotrQaeing and/or hydro-
cracking he~vy flashed d~tillat~ iraceio~ fro~ long r~sidu~ or
d~sphaltad oLls o'otainet irom short rosL~u~. Th~ fe~d~tock i~
suitably fraceLonated to ~amove lower boiling fractions aft~r
2g~ 0
hydrotreating and/or hydrocracking and prior to contacting with the
zeolitic catalyst in accordance with the invention.
The product obtained by the process of the invention is
op~ionally fractionated to yield an olefin-rich gas fraction, a
gasoline fraction and a bottom fraction, all or part of which is
optionally recycled to the feedstock upstream of the hydrotreating
snd/or hydrocracking unit. In this way, high conversion of the
heavy deasphalted oil or heavy flashed distillate feedstock to more
valuable olefin-rich gas is obtained.
Therefore, in accordance with a fureher aspect of the
in~ention, there is provided a process for ehe con~ersion of a
hydrocarbonaceous feedstock comprising hydrotreating and/or
hydrocracking said feedstock in the presence of a suitable
catalyst, contacting at least a part of the hydrotreated and/or
hydrocracked product with a zeolitic catalyst comprising a zsolite
with a pore diameter of 0.4 to 0.7 nm at a temperature of greater
than 480 C and a pressure of up to 10 bar during less than 10
seconds, fractionating the resulting converted material and
recycling a heavier fraction to said hydrotreating and/or
hydrocracking step.
The said hydrotreating step is known in the art and may be
carried out at known conditions. Suitable conditions includs a
temperature of 150 to 400 C, a hydrogen (partial) prsssure of 30
to 150 bar, a space velocity of n . s to 4.0 kg/l.h and a
hydrogen/feedstock ratio of 100 to 2000 Nl/kg. Suitable hydro-
treating catalysts comprise nickel, cobalt, tungsten, molybdenum,
platinu~, palladium or mixtures thereof on a carrier, such as
alu~ina, silica-alumina, silica, zirconia, zeolites and the like.
The catalyst may further comprise fluorine, phosphorus and/or
boron. The temperature, gas rate and space velocity can be selected
by the person skilled in the are, suitably from the range given
above.
Hydrocracking is also known in the art and may be carried out
under known conditions, such as over a hydrocracking catalyst at a
temperature of 300 to 450 C, a hydrogen (partial) pressure of 50
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to 200 bar, a space velocity of 0.5 to 2.0 kg/l.catalyst.h and a
H2/mineral oil fraction ratio of 500 to 2000 Nl/kg. The hydro-
cracking catalyst can be selected from any hydrocracking catalyst
known in the art. Suitably the hydrocracking catalyst co~prises a
carrier and at least one hydrogenating metal or a co~pound thereof,
which carrier has been selected from the group con.sisting of
silica, alumina, silica-alumina and the faujasite-type 2eolites.
The most preferred faujasiee-type zeolite is zeolite Y. The most
preferred hydrogenating metals are nickel, cobalt, tungsten and
molybdenum and mixtures thereof, but platinum and/or palladium may
also be used. The catalyst may further comprise fluorine and/or
phosphorus and/or boron. When nickel, cobalt, molybdenum and/or
tungsten are used as hydrogenating me~al, they are pref~rably
present in the form of their sulphides.
One of the advantages of the present invention over the
process according to US 4,171,257 re~ des in the fact that a
feedstock with a nitrogen content graater than 5 ppmw may be used
with substantially no effect on the caealyst activity. Suitable
Peedstocks may have a nitrogen content oi more than 10 ppmw,
calculated as nitrogen. The feedstoc'~ may a~en have a nitrogen
content of 1000 ppmw or more, calculacad as nitrogen.
The invention will now be furtnar dsscribed with reference to
the following examples and the accom?anying drawing:
EXAMPLE 1
The ieedstock in ehis exa~ple was a hydrotreated Arabian light
deasphalted oil having the following properties:
IBP, C 453
50 ~wt 591
67 ~wt 620
density 70/4 0.B532 kgjl
sulphur232 ppmw
nitrogen12 ppmw
The DAO feedstock was upgraded in a downflow reactor by
passing it downwards co-currently with a flow of catalyse
particles. The catalyst comprised ZSM-5 in an alumina ~atrix
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~weight ratio ZS~ 5/alu~ina 1:3). The experiment was carriad out at
atmospheric pressure. Further process conditions and the results of
the experiment are given in Table 1 below.
TABLE 1
Process conditions:
Reactor temperature, C 531
Catalyst/oil ratio, g~g 4.3
Contact time, s 2.2
Product, ~w on feed
Cl 1.0
C2 1.2
C2 4.9
C3 2.0
C3 17.9
C4 2.1
C4 16.4
CS-221 C 26.3
221-~50 C 18.2
450 ~C+ 9.1
Coka 0.8
Conversion of 450 C+ feed, ~w 91
Fro~ the above results it will be seen that a high proportion
of the gaseous products was olefinically unsaturated and the
product contained a comparatively high proportion of midd}e
distillates.
EXA~IPLE 2
The feedstock in this example was a hydrocracked heavy flashed
distillate ha~ing the following properties:
IBP, C 330
50 3wt 432
FBP, C 620
fraction boiling below 370 C, ~wt 7,7
density 70/4 0.8157 kg/l
sulphur 20 ppmw
nitrogen 2 pp~w
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Tha ~xperiment was carried out as described in E~ample 1, but
using the process conditions described in Table 2 below to ~ive the
results given in Table 2.
TABLE 2
Process conditions:
Reactor temperature, C 579
Catalyst/oil ratio, g/~ 141
Contact time, s 1.7
Product, ~w on fead
Cl 1.6
C2 1.0
~2 14.7
C3 3.9
C3 37.3
C4 4.6
C4 18.8
G5-221 ~C 8.6
221-370 C 2.3
370 C~ 0.4
Coke 6.3
Conversion of 370 C~, ~w 99.6
EXAMPLE 3
This example employed as feedstock an Arabian heavy heavy
flashed distillate which, after initial hydrocracking, typically
had the proper~iec gi~en in Table 3 below.
The flashed distillate was treated in accordance with the
process illustrated in Fig. 1 as follows.
Feedstock W85 introduced on line 1, af er mixing with hydrogen
from line 2, to a hydrotreating/hydrocracking unit 3 operated at
90 bar hydrogen partial pressure at 400 C with a suitable
~i/Mo/alumina hytrotreating catalyst.
The hydrotreated product was fractionated in ~nit 4 into a
gaseous fraction 5, a naphtha fraction 6, a kerosine fraction 7, a
~as oil fraction 8 and a bottoms fraction 9. Under conditions as
described herein, bottoms fraction 9 was passed to a downflow
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reactor 10 as described in Example 1, containing catalyst as
described in Example 1 and provided with suitable regeneration
means from which coke can be removed in line 11 when necessary,
while gaseous and liquid product is saparated in fractionation unit
12 lnto a gaseous product 13, a gasoline product 14 and a bottoms
stream 15, which is recycled to ehe feedstock in line 1 for
re-processing.
Bottoms fraction 9 which is upgraded in reactor 10 comprises
about 69% by weight based on the initial feed in llne 1 when
fractionated in unit 12. The co~position of the fract$on obtalned
from unit 12 i5 given in Table 3 below:
TABLE 3
Hydrocracked feedstock
Refractive index, ~1.4720
W aromatics, ~ol/100 g
mono25
di 4
poly 3
Initial boiling point, C 340
50 ~wt 420
Final boiling point540
Product, ~w on feed
Gas (Cl 4) 31.5
H2 0.1
Cl 0.7
C2 0.8
C2 3.4
C3 1.4
C3 12.3
C4 1.5
C4 11.3
Gasoline (C5-221 C)18.5
Coke o.5
Recycle (221 C) 19
3 91`~
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It will be seen from the above results that the bottoms
component sepsrated from the ini~ial flashed distillate has yielded
a high proportion of olefinically unsaturated gaseous products and
gasoline while ehe recycling facility enables maxlmum upgrading to
S more valuable products.
