[0001] The present invention relates to a process for the conversion of a hydrocarbonaceous
feedstock, and is particularly concerned with the production of olefins from hydrocarbonaceous
feedstocks.
[0002] There is considerable interest in the production of olefins, especially lower olefins
such as ethylene and propylene, from hydrocarbonaceous materials, in view of the importance
of such olefins as starting materials for the preparation of further more complex
chemical products.
[0003] It is known to convert hydrocarbonaceous feedstocks, such as light distillates, to
products rich in lower olefins, especially ethylene and propylene, by high temperature
steam cracking. The typical product slate obtained in such steam cracking processes
is not entirely suited to the needs of the chemical industry in that it represents
a comparatively low overall conversion to lower olefins, with a relatively high methane
production level and a high ratio of ethylene to propylene. GB-A-513545 discloses
polymerization of C₂₋₅ olefins obtained as a gasoline distillate, to produce liquid
products including gasoline. An ethylene fraction is thermally polymerized and a fraction
containing C₃ to C₅ olefins and butane is catalytically polymerized.
[0004] There have recently been developed alternative processes for the production of lower
olefins, for example as described in copending EP-A-0 347 003, EP-A-0 372 632 and
EP-A-0 385 538., from a wide range of hydrocarbonaceous feedstocks. Those processes
have been found to give surprisingly high yields of lower olefins, low amounts of
methane and a low ratio of ethylene to propylene and C₄ olefins when compared with
conventional steam cracking.
[0005] Ethylene and propylene are valuable starting materials for many chemical processes,
while C₄ olefins can find use as a starting material for alkylation and/or oligomerization
procedures in order to produce high octane gasoline and/or middle distillates. Isobutene
can be usefully converted to methyl t-butyl ether. However, in order to meet fluctuating
demand for production of C₂, C₃ and C₄ olefins, there is a need to provide a process
with a flexible product slate of lower olefins.
[0006] Accordingly, the present invention provides a process for the conversion of a hydrocarbonaceous
feedstock comprising the following steps:
(i) contacting the feedstock with a solid cracking catalyst at a temperature of at
least 400 °C during less than 10 seconds,
(ii) separating a fraction comprising one or more C₂ to C₆ olefins from the effluent
from step (i),
(iii)contacting at least a portion of said C₂ to C₆ olefin-comprising fraction with
an oligomerization catalyst under oligomerization conditions of a temperature from
150-330 °C, a pressure from 1-100 bar and a space velocity from 0.1-10 kg olefins
feed/kg catalyst.hour, and
(iv) recycling at least a portion of the effluent from step (iii) to step (i).
[0007] The term "lower olefins" is intended primarily to include ethylene, propylene, butene
and i-butene, but may extend to other olefins having up to 6 carbon atoms.
[0008] The feedstock is contacted with the solid cracking catalyst in step (i) for less
than 10 seconds. Suitably, the minimum contact time is 0.1 second. Very good results
are obtainable with a process in which the feedstock is contacted with the solid cracking
catalyst during 0.2 to 6 seconds.
[0009] The temperature during the reaction is relatively high. However, the combination
of high temperature and short contact time allows a high conversion of olefins in
step (i). A preferred temperature range is 480 to 900 °C, more preferably 500 to 750
°C.
[0010] The solid cracking catalyst preferably comprises at least one zeolite with a pore
diameter of from 0.3 to 0.7 nm, preferably 0.5 to 0.7 nm. The catalyst suitably further
comprises a refractory oxide that serves as binder material. Suitable refractory oxides
include alumina, silica, silica-alumina, magnesia, titania, zirconia and mixtures
thereof. Alumina is especially preferred. The weight ratio of refractory oxide and
zeolite suitably ranges from 10:90 to 90:10, preferably from 50:50 to 85:15. The catalyst
may also comprise further zeolites with a pore diameter above 0.7 nm. Suitable examples
of such zeolites include the faujasite-type zeolites, zeolite beta, zeolite omega
and in particular zeolite X and Y. The zeolitic catalyst preferably comprises as zeolite
substantially only zeolites with a pore diameter of from 0.3 to 0.7 nm.
[0011] The term zeolite in this specification is not to be regarded as comprising only crystalline
aluminium silicates. The term also includes crystalline silica (silicalite), silicoaluminophosphates
(SAPO), chromosilicates, gallium silicates, iron silicates, aluminium phosphates (ALPO),
titanium aluminosilicates (TASO), boron silicates, titanium aluminophosphates (TAPO)
and iron aluminosilicates.
[0012] Examples of zeolites that may be used in the process of the invention and that have
a pore diameter of 0.3 to 0.7 nm, include SAPO-4 and SAPO-11, which are described
in US-A-4,440,871, ALPO-11, described in US-A-4,310,440, TAPO-11, described in US-A-4,500,651,
TASO-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 ZSM-5, ZSM-11, ZSM-12, ZSM-35, ZSM-23, and ZSM-38. Preferably the zeolite is selected
from the group consisting of crystalline metal silicates having a ZSM-5 structure,
ferrierite, erionite and mixtures thereof. Suitable examples of crystalline metal
silicates with ZSM-5 structure are aluminium, gallium, iron, rhodium and/or scandium
silicates as described in e.g. GB-B-2,110,559.
[0013] 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 exchange, 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.
[0014] The pressure in step (i) of the present process can be varied within wide ranges.
It is, however, preferred that the pressure is such that at the prevailing temperature
the feedstock is substantially in its gaseous phase or brought thereinto by contact
with the catalyst. Then it is easier to achieve the short contact times envisaged.
Hence, the pressure is preferably relatively low. This can be advantageous since no
expensive compressors and high-pressure vessels and other equipment are necessary.
A suitable pressure range is from 1 to 10 bar. Subatmospheric pressures are possible,
but not preferred. It can be economically advantageous to operate at atmospheric pressure.
Other gaseous materials may be present during the conversion such as steam and/or
nitrogen.
[0015] Step (i) is carried out preferably in a moving bed. The bed of catalyst, preferably
fluidized may also move upwards or downwards. When the bed moves upwards a process
somewhat similar to fluidized catalytic cracking process is obtained.
[0016] During the process some coke forms on the catalyst. Therefore, it is advantageous
to regenerate the catalyst. Preferably the catalyst is regenerated by subjecting it,
after having been contacted with the feedstock, to a treatment with an oxidizing gas,
such as air. A continuous regeneration, similar to the regeneration carried out in
a fluidized catalytic cracking process, is especially preferred.
[0017] If the coke formation does not occur at too high a rate, it would be possible to
arrange for a process in which the residence time of the catalyst particles in a reaction
zone, is longer than the residence time of the feedstock in the reaction zone. Of
course the contact time between feedstock and catalyst should be less than 10 seconds.
The contact time generally corresponds with the residence time of the feedstock. Suitably
the residence time of the catalyst is from 1 to 20 times the residence time of the
feedstock.
[0018] The catalyst/feedstock weight ratio in step (i) may vary widely, for example up to
200 kg of catalyst per kg of feedstock including recycled material. Preferably, the
catalyst/feedstock weight ratio is from 20 to 100:1.
[0019] The feedstock which is to be converted in the process of the present invention can
vary within a wide boiling range. Examples of suitable feedstocks are relatively light
petroleum fractions such as feedstocks comprising C₃₋₄ hydrocarbons (e.g. LPG), naphtha,
gasoline fractions and kerosine fractions. Heavier feedstocks may comprise, for example,
vacuum distillates, long residues, deasphalted residual oils and atmospheric distillates,
for example gas oils and vacuum gas oils.
[0020] One example of a suitable feedstock has been found to comprise hydrotreated and/or
hydrocracked hydrocarbons, preferably, though not necessarily, heavy feedstocks. Suitable
feedstocks of this type may be obtained by hydrotreating and/or hydrocracking heavy
flashed distillate fractions from long residue or deasphalted oils obtained from short
residue.
[0021] The effluent from step (i) may be subjected to any suitable separation means dependent
on the composition of the effluent which will vary somewhat dependent on the feedstock
employed. However, in accordance with the invention, a fraction comprising one or
more lower olefins is separated from the effluent. The lower olefin-comprising fraction
suitably comprises one or more of ethylene, propylene, butene and isobutene and may
include other light olefinic and/or paraffinic products but is preferably free of
heavier products. The olefin-comprising fraction which is separated depends on the
product slate desired. Thus, for example, a fraction rich in C₄ olefins is separated,
if it is desired to produce a final product slate rich in C₂ and/or C₃ olefins. A
preferred lower olefin rich fraction will be rich in one or two of C₂, C₃ and C₄ olefins.
[0022] At least a portion of the olefin-comprising fraction is contacted with an oligomerization
catalyst under oligomerization conditions. It will be appreciated that any suitable
oligomerization process can be employed. Examples of such processes include those
employing solid catalysts such as ZSM-5 (e.g. US Patents 4,456,779 and 4,433,185)
and fluorided silica/alumina (Ind. Pet. Gaz. - Chim 1978, (501), p 13-20), hydrocarbon-soluble
catalysts such as a mixture of an organo-nickel compound and a hydrocarbyl aluminium
halide (e.g. US Patents 4,366,087 and 4,398,049) and heterogeneous catalyst systems
such as phosphoric acid on silica (C.L. Thomas, "Catal. Proc. and Proven Catalysts",
McGraw Hill, 1970, p 67-69).
[0023] A preferred catalyst employed in step (iii) of the process according to the invention
comprises at least one metal (Z) selected from the group consisting of metals from
Groups 1b, 2a, 2b, 3a, 4b, 5b, 6b and 8 of the Periodic Table of the Elements and
a crystalline trivalent metal (Q) silicate.
[0024] Reference is made to the Periodic Table of the Elements as published in the "Handbook
of Chemistry and Physics", 55th addition (1975), CRC Press, Ohio, USA.
[0025] Preferably, at least part of the amount, and most preferably the total amount, of
metal(s) Z has(have) been incorporated into the catalyst by means of ion exchange.
Preferably, the catalyst applied in step (iii) of the process according to the invention
is prepared by using a zeolite carrier material, including such zeolites as mordenite,
faujasite, omega, L, ZSM-5, -11, -12, -35, -23 and -38, ferrierite, erionite, theta,
beta and mixtures thereof. A preferred zeolite is mordenite (see for example EP-A-233382).
The carrier comprises exchangeable cations such as alkali metal-, hydrogen- and/or
preferably ammonium ions. The carrier material is suitably treated one or more times
with a solution of at least one metal salt such as an aqueous solution of a metal
nitrate or -acetate. The ion exchange treatment is suitably carried out at a temperature
from 0 °C up to the boiling temperature of the solution, and preferably at a temperature
from 20-100 °C.
[0026] The valency n of the metals Z can vary from +1 to +6. Preferably, however, at least
one of the metals Z in the catalyst is bivalent or trivalent, in which case the molar
ratio Z:Q is preferably greater than 0.5. Z is preferably selected from the group
consisting of the bivalent metals copper, zinc, cadmium, magnesium, calcium, strontium,
barium, titanium, vanadium, chromium, manganese, iron, cobalt and nickel. A particularly
preferred metal Z is nickel.
[0027] The trivalent metal Q which is present in the crystal structure of the preferred
metal silicate catalyst carrier used in step (iii) preferably comprises at least one
metal selected from the group consisting of aluminium, iron, gallium, rhodium, chromium
and scandium. Most preferably Q consists substantially of aluminium; the resulting
crystalline aluminium silicate preferably comprises a major part of mordenite and
most preferably consists substantially completely of mordenite.
[0028] The molar ratio silicon:Q in the catalyst is suitably in the range from 5:1 to 100:1
and preferably in the range from 7:1 to 30:1. This ratio is in most cases substantially
identical to the molar ratio Si:Q in the crystalline metal silicate employed as carrier
material, except when some of the metal Q has been removed from the crystal structure
during the catalyst preparation e.g. by means of acid leaching.
[0029] If desired (e.g. in order to increase the crushing strength of the catalyst particles),
the carrier material and/or the ready catalyst for either one of the steps of the
present process can be combined with a binder material such as refractory oxide(s),
clay and/or carbon. Suitable refractory oxides comprise alumina, silica, magnesia,
zirconia, titania and combinations thereof.
[0030] The molar ratio Z:Q in the ready catalyst is preferably from 0.1-1.5 and most preferably
from 0.2-1.2.
[0031] In an alternative preferred embodiment of the process according to the invention
the metal Z is identical with the metal Q and is incorporated in the crystal structure
of the silicate; most preferably gallium is the metal Q in the case where no additional
metal Z is present in the catalyst.
[0032] After loading of the carrier material with the metal(s) Z, the catalytically active
composition thus obtained is preferably dried and calcined before being employed as
catalyst in step (iii). Drying is suitably carried out at a temperature from 100-400
°C, and preferably from 110-300 °C, for a period of 1-24 hours; the calcination temperature
is suitably from 400-800 °C and preferably from 450-650 °C. The calcination treatment
is suitably carried out at (sub-)atmospheric or elevated pressure for a period of
0.1-24 hours, and preferably of 0.5-5 hours in air or in an inert (e.g. nitrogen)
atmosphere.
[0033] Step (iii) can be carried out in one or more fixed-, moving- and/or fluidized beds
or in a slurry-type of reactor; preferably, the process is carried out in a fixed
bed of catalyst particles such as extrudates, pellets or spheres passing sieve openings
having a width from 0.05-5 mm, and preferably from 0.1-2.5 mm.
[0034] Step (iii) is preferably carried out at a temperature from 180-300 °C, a pressure
from 10-50 bar and a space velocity from 0.2-5 kg olefin feed/kg catalyst.hour.
[0035] At least a portion of the effluent from step (iii) as described above is recycled
to step (i), suitably by combining it with the feed to step (i). It is not necessary
that the entire effluent from step (iii) be recycled to step (i). However in a preferred
mode of operation, substantially the entire C₂ and/or C₃ and/or C₄ olefin content
of the effluent from step (i) is subjected to oligomerization in step (iii) and substantially
the entire effluent from step (iii) is recycled to step (i), thus achieving ultimately
high conversion of the less desired lower olefin fraction to desired lower olefins.
[0036] The following example illustrates the invention, together with the accompanying Figure
which is a flow diagram of the process of the example.
EXAMPLE
[0037] The process according to the invention was carried out as shown diagrammatically
in the Figure using as initial feedstock a hydrocracked heavy flashed distillate supplied
on line 1 and having the properties described in Table 1 below.
[0038] The feedstock was treated in a downflow reactor 2 by passing it downwards co-currently
with a flow of catalyst particles. The catalyst comprised ZSM-5 in an alumina matrix
(weight ratio ZSM-5/alumina 1:3). The reaction was carried out at atmospheric pressure.
Further process conditions are given in Table 1.
![](https://data.epo.org/publication-server/image?imagePath=1993/10/DOC/EPNWB1/EP90200788NWB1/imgb0001)
[0039] The product from reactor 2 was separated by distillation in unit 3. The C₄⁺ olefin
fraction was withdrawn on line 4 while products including C₂ and C₃ olefins were withdrawn
on one or more lines 5. The C₄⁺ olefin stream was passed to oligomerization unit 6
comprising a bed of nickel/mordenite catalyst prepared by ion exchange of mordenite
in the ammonium form at a temperature of 100 °C with an aqueous solution containing
one mol nickel(II) acetate/litre. The resulting catalyst had a molar ratio of nickel:aluminium
of 1.5:1 after drying at a temperature of 120 °C.
[0040] The nickel mordenite catalyst was mixed with 20 %wt pseudo-boehmite as a binder,
1 %wt acetic acid as peptising agent and water such that the loss on ignition amounts
to 45%. After kneading the mixture was extruded into 1.5 mm extrudates and the catalyst
dried at 120 °C for two hours and successively calcined in air at 500 °C for two hours.
[0041] The reaction conditions were as follows:
- Reaction temperature, °C
- 483
- Total pressure, bar
- 30
- WHSV, hr⁻¹
- 0.5
[0042] The oligomerized product was recycled on line 7 to the feedstock 1 to the reactor
2.
[0043] Table 2 below gives (A) the results obtained for the product stream 5 from unit 2
when recycling C₄ olefins from unit 2 via unit 6 as described above to give a ratio
of recycled product/fresh feed entering unit 2 of 0.23 and (B) comparative results
obtained for the product stream from unit 2 without recycle via unit 6.
![](https://data.epo.org/publication-server/image?imagePath=1993/10/DOC/EPNWB1/EP90200788NWB1/imgb0002)
[0044] It will be seen from the above results that, when operating in accordance with the
invention (Run A), enhanced C₂ and C₃ olefin yields are obtained when compared with
the comparative results (Run B), while still maintaining a high conversion to lower
olefin product.
1. A process for the conversion of a hydrocarbon-aceous feedstock comprising the following
steps:
(i) contacting the feedstock with a solid cracking catalyst at a temperature of at
least 400 °C during less than 10 seconds,
(ii) separating a fraction comprising one or more C₂ to C₆ olefins from the effluent
from step (i),
(iii)contacting at least a portion of said C₂ to C₆ olefin-comprising fraction with
an oligomerization catalyst under oligomerization conditions of a temperature of from
150 to 330 °C, a pressure of from 1 to 100 bar and a space velocity of from 0.1 to
10 kg olefins feed/kg catalyst.hour, and
(iv) recycling at least a portion of the effluent from step (iii) to step (i).
2. A process according to claim 1 wherein the solid cracking catalyst used in step (i)
comprises at least one zeolite having a pore diameter of 0.3 to 0.7 nm.
3. A process according to claim 2 wherein the at least one zeolite is selected from crystalline
metal silicates having a ZSM-5 structure, ferrierite, erionite and mixtures thereof.
4. A process according to any one of the preceding claims wherein the feedstock is contacted
in step (i) with a moving bed of solid cracking catalyst.
5. A process according to any one of the preceding claims wherein the feedstock is contacted
with the solid cracking catalyst in step (i) during 0.2 to 6 seconds.
6. A process according to any one of the preceding claims wherein the contacting temperature
in step (i) is from 500 to 750 °C.
7. A process according to any one of the preceding claims in which the catalyst/feedstock
weight ratio in step (i) is from 20 to 100:1.
8. A process according to any one of the preceding claims wherein the oligomerization
catalyst employed in step (iii) is a solid oligomerization catalyst comprising at
least one metal selected from metals from Groups 1b, 2a, 2b, 3a, 4b, 5b, 6b and 8
and a crystalline trivalent metal silicate.
9. A process according to claim 8 wherein the metal comprises nickel and the crystalline
silicate comprises mordenite.
1. Ein Verfahren zur Umwandlung eines kohlenwasserstoffhaltigen Ausgangsmaterials, umfassend
die folgenden Stufen:
(i) Kontaktieren des Ausgangsmaterials bei einer Temperatur von mindestens 400°C und
während weniger als 10 Sekunden mit einem festen Crackkatalysator,
(ii) Abtrennen einer Fraktion aus dem Abstrom der Stufe (i), welche ein oder mehrere
C₂- bis C₆-Olefine enthält,
(iii) Kontaktieren mindestens einer Teilmenge besagter C₂- bis C₆-Olefine enthaltenden
Fraktion mit einem Oligomerisierungskatalysator unter Oligomerisierungsbedingungen
bei einer Temperatur von 150 bis 330°C, einem Druck von 1 bis 100 bar und einer Raumgeschwindigkeit
von 0,1 bis 10 kg Olefinzuspeisung/kg Katalysator je Stunde und
(iv) Rückführung mindestens einer Teilmenge des Abstromes von Stufe (iii) in die Stufe
(i).
2. Ein Verfahren nach Anspruch 1, in welchem der in Stufe (i) eingesetzte feste Crackkatalysator
mindestens einen Zeolith mit einem Porendurchmesser von 0,3 bis 0,7 nm umfaßt.
3. Ein Verfahren nach Anspruch 2, in welchem der mindestens eine Zeolith ausgewählt ist
aus kristallinen Metallsilikaten mit einer ZSM-5-Struktur, Ferrierit, Erionit und
Mischungen davon.
4. Ein Verfahren nach irgendeinem der vorhergehenden Ansprüche, in welchem das Ausgangsmaterial
in Stufe (i) mit einem Fließbett des festen Crackkatalysators kontaktiert wird.
5. Ein Verfahren nach irgendeinem der vorhergehenden Ansprüche, in welchem das Ausgangsmaterial
in Stufe (i) während 0,2 bis 6 Sekunden mit dem festen Crackkatalysator kontaktiert
wird.
6. Ein Verfahren nach irgendeinem der vorhergehenden Ansprüche, in welchem die Kontakttemperatur
in Stufe (i) im Bereich von 500 bis 750°C liegt.
7. Ein Verfahren nach irgendeinem der vorhergehenden Ansprüche, in welchem das Gewichtsverhältnis
von Katalysator zu Ausgangsmaterial in Stufe (i) im Bereich von 20:1 bis 100:1 liegt.
8. Ein Verfahren nach irgendeinem der vorhergehenden Ansprüche, bei welchem es sich bei
dem in der Stufe (iii) eingesetzten Oligomerisierungskatalysator um einen festen Oligomerisierungskatalysator
handelt, welcher mindestens ein Metall ausgewählt aus den Gruppen 1b, 2a, 2b, 3a,
4b, 5b, 6b und 8, sowie ein kristallines Silikat eines dreiwertigen Metalls enthält.
9. Ein Verfahren nach Anspruch 8, wobei das Metall Nickel ist und das kristalline Silikat
ein Mordenit ist.
1. Un procédé pour la conversion d'une charge hydrocarbonée comprenant les étapes suivantes
:
(1) mise en contact de la charge avec un catalyseur solide de craquage à une température
d'au moins 400°C pendant moins de 10 secondes,
(2) séparation d'une fraction comprenant une ou plusieurs oléfines de C₂ à C₆ à partir
de l'effluent de l'étape (1),
(3) mise en contact d'au moins une portion de la fraction contenant des oléfines de
C₂ à C₆ avec un catalyseur d'oligomérisation dans des conditions d'oligomérisation
comprenant une température de 150 à 330°C, une pression de 1 à 100 bars et une vitesse
spatiale de 0,1 à 10 kg de charge d'oléfines par kg de catalyseur et par heure, et
(4) recyclage d'au moins une portion de l'effluent de l'étape (3) à l'étape (1).
2. Un procédé selon la revendication 1, dans lequel le catalyseur solide de craquage
utilisé dans l'étape (1) comprend au moins une zéolite ayant un diamètre de pores
de 0,3 à 0,7 nm.
3. Un procédé selon la revendication 2, dans lequel ladite au moins une zéolite est choisie
parmi des silicates métalliques cristallins ayant une structure de ZSM-5, la ferriérite,
l'érionite et leurs mélanges.
4. Un procédé selon l'une quelconque des revendications précédentes, dans lequel la charge
est mise en contact dans l'étape (1) avec un lit mobile de catalyseur solide de craquage.
5. Un procédé selon l'une quelconque des revendications précédentes, dans lequel la charge
est mise en contact avec le catalyseur solide de craquage dans l'étape (1) pendant
0,2 à 6 secondes.
6. Un procédé selon l'une quelconque des revendications précédentes, dans lequel la température
de mise en contact dans l'étape (1) est comprise entre 500 et 750°C.
7. Un procédé selon l'une quelconque des revendications précédentes, dans lequel le rapport
en poids catalyseur/charge dans l'étape (1) est compris entre 20 et 100:1.
8. Un procédé selon l'une quelconque des revendications précédentes, dans lequel le
catalyseur d'oligomérisation utilisé dans l'étape (3) est un catalyseur solide d'oligomérisation
comprenant au moins un métal choisi parmi les métaux des groupes 1b, 2a, 2b, 3a, 4b,
5b, 6b et 8 et un silicate cristallin de métal trivalent.
9. Un procédé selon la revendication 8, dans lequel le métal comprend du nickel et le
silicate cristallin comprend de la mordénite.