[0001] The present invention relates to a process for producing propylene and
to a corresponding installation according to the preambles of the independent
claims.
BACKGROUND OF THE INVENTION
10
[0002] The production of propylene (propene) is described in the specialist
literature, for example in the article "Propylene" in Ullmann's Encyclopedia of
Industrial Chemistry, ed. 2012. Propylene is conventionally produced by
steam-cracking hydrocarbon feedstocks and by conversion processes in the
15 course of refinery processes. In the latter processes, propylene is not
necessarily formed in the desired quantity and only as one of several
components in a mixture with further compounds. Other processes for
producing propylene are also known, but are not satisfactory in all cases, for
example in terms of efficiency and yield.
20
[0003] An increasing demand for propylene ("propylene gap"), which requires
the provision of corresponding selective methods, is predicted for the future.
At the same time, it is necessary to reduce or completely prevent carbon
dioxide emissions. As a potential starting compound, on the other hand, large
25 amounts of methane are available, which are currently only fed to a material
utilization in a very limited manner and are predominantly burned. In addition,
appreciable amounts of ethane are often present in corresponding natural gas
fractions.
30 [0004] The object of the present invention is to provide an improved method,
in particular in view of these aspects, for producing propylene.
2
DISCLOSURE OF THE INVENTION
[0005] Against this background, the present invention proposes a process for
producing propylene and a corresponding installation having the respective
5 features of the independent claims. Preferred embodiments of the present
invention are the subject matter of the dependent claims and of the following
description.
[0006] In principle, in addition to the aforementioned steam cracking methods,
10 a plurality of different methods exist for converting hydrocarbons and related
compounds into one another, some of which will be mentioned below by way
of example.
[0007] For example, the conversion of paraffins to olefins of identical chain
15 length by oxidative dehydrogenation (ODH, also referred to as ODHE in the
case of ethane) is known. Typically, a carboxylic acid of identical chain length
is also formed as a coupling product in ODH, i.e. acetic acid in ODHE.
However, ethylene can also be produced by the oxidative coupling of methane
(OCM). Via a chain extension, for example by the hydroformylation described
20 below, it is also possible to arrive at propylene starting from the ethylene
formed in the oxidative dehydrogenation of ethane.
[0008] The production of propylene from propane by dehydrogenation (PDH)
is also known and represents a commercially available and established
25 process. The same also applies to the production of propylene from ethylene
by olefin metathesis. This process requires 2-butene as an additional reagent.
[0009] Lastly, so-called methane-to-olefins or methane-to-propylenes (MTO,
MTP) processes exist in which synthesis gas is first produced from methane
30 and the synthesis gas is then reacted to give olefins, such as ethylene and
propylene. Corresponding processes can be operated on the basis of
3
methane, but also on the basis of other hydrocarbons or carbon-containing
starting materials, such as coal or biomass.
[0010] Steam reforming and dry reforming as well as modifications thereof,
5 including a downstream water gas shift for adjusting the ratio of hydrogen to
carbon monoxide, are likewise known as individual technologies.
[0011] For synthesis gas production, partial oxidation (POX), in particular with
a higher proportion of carbon monoxide, is also known. Synthesis gases can
10 also be produced by gasification of various feedstocks (coal, oil, waste, in
particular plastic waste, etc.).
[0012] The hydroformylation already mentioned above in conjunction with the
oxidative dehydrogenation of ethane represents a further technology which is
15 used in particular for the production of so-called oxo compounds. Propylene is
typically converted in the hydroformylation, but higher hydrocarbons, in
particular hydrocarbons having six to eleven carbon atoms, or ethylene can
also be used. Various processes for hydrogenating aldehydes and
dehydrogenating alcohols (in particular ethanol and propanol) are likewise
20 known.
[0013] For example, for the production of propylene, as mentioned, a
hydroformylation can be used after an oxidative dehydrogenation of ethane. In
the product stream of the oxidative dehydrogenation, certain fractions of
25 carbon monoxide and especially unconverted ethane are present, inter alia. In
particular, the high proportion of ethane in the range from 25 to 70 mole
percent, in particular from 30 to 50 mole percent, leads to a significant dilution
and significantly influences the partial pressures in the hydroformylation.
Furthermore, carbon dioxide is formed in the oxidative dehydrogenation of
30 ethane and must be separated off and, as necessary, treated separately. Dry
reforming can be used for this purpose, for example. A significant integration
of the purification and decomposition steps has not been known until now and
4
the method steps taken into consideration hitherto are limited to the special
case of an oxidative dehydrogenation of ethane and the use of a product
stream which is not yet purified and the utilization of the by-product carbon
dioxide in dry reforming.
5
[0014] Propylene can also be produced in principle starting from a component
mixture which, in addition to ethylene, also contains considerable proportions
of methane, carbon monoxide and carbon dioxide and optionally also
hydrogen and ethane, and which can be provided, for example, by an oxidative
10 coupling of methane. Here too, the further processing can comprise a
hydroformylation. Here too, however, there is a significant dilution of the
reactants which significantly influence the partial pressures in the
hydroformylation. A typical ethylene content in a product mixture from the
oxidative coupling of methane is basically rather at the lower end of a range of
15 from 5 to 60 mole percent. The hydroformylation is preferably performed at
high pressure, and in particular methane acts here as an inert medium which
negatively influences the partial pressures of the reactants ethylene, carbon
monoxide and hydrogen. Moreover, the comparatively high dilution also has a
negative effect on the size of the apparatuses and thus makes the investment
20 and operating costs more expensive. Corresponding disadvantages can also
occur, for example, in principle by the formation of carbon dioxide when a shift
reaction for converting carbon monoxide into hydrogen is undertaken.
[0015] Accordingly, US Pat. No. 10,519,087 B2 also describes a method in
25 which a feedstock stream from an oxidative coupling of methane is used, and
thus contains, as explained, as well as ethylene, significant amounts of other
components, in particular light and/or inert components, which then have to be
conducted through the hydroformylation. Reference is made to the
disadvantages just explained.
30
[0016] The above-mentioned methods all use a crude gas stream which, in
addition to the components carbon monoxide, hydrogen and ethylene, also
5
contains further components. A corresponding crude gas stream does not
necessarily contain the correct composition for the subsequent method steps
and can typically also contain inert components such as methane, ethane and
optionally carbon dioxide, but also disruptive compounds, such as acetylene,
5 oxygenates, etc. Therefore, a not inconsiderable purification and separation
outlay is typically required in such methods.
FEATURES AND ADVANTAGES OF THE INVENTION
10 [0017] The present invention creates a method which makes it possible to
contribute to covering the increasing demand for propylene mentioned at the
outset, in particular also in relation to ethylene. In particular, it allows an
integration of methane or other low-cost carbon sources into the petrochemical
value chain in an advantageous manner compared to the prior art and the
15 explained methods likewise possible in principle. This makes it possible, in
particular, to utilize previously unused accompanying gases from petroleum
and natural gas production or also from gasification of waste, in particular
plastic waste. This can lead to a significant reduction in the carbon dioxide
footprint of (petro)chemical installations.
20
[0018] Existing technologies such as steam cracking, methane-to-olefin or
methane-to-propylene methods always produce ethylene and propylene only
in a certain ratio, which can only be adjusted to a limited extent depending on
the feedstock by adapting the process parameters (e.g. temperature,
25 residence time, etc.). Here, the present invention allows significant
improvements and allows a targeted adjustment or focusing on a target olefin
such as propylene.
[0019] Olefin metathesis, which allows flexible conversion of ethylene into
30 propylene, proceeds nowadays from the olefins ethylene and 2-butene, which
are converted to propylene. This is in principle an equilibrium reaction, and this
technology was originally developed for the reverse reaction, i.e. of propylene
6
to ethylene and butene. The 2-butene required can be obtained, for example,
from the selective dimerization of ethylene or as a fraction from the production
of linear α-olefins, likewise based on the oligomerization of ethylene. It is
likewise possible to use 1-butene, which can be isomerized. Likewise, the use
5 of higher internal linear olefins is also known, in which case corresponding
reaction cascades ultimately always give propylene as the target product.
[0020] Although the technology of olefin metathesis can be regarded as being
mature and established, it remains a major disadvantage that only high-quality
10 and high-cost reagents are used. Olefin metathesis therefore usually serves in
particular to enable flexible balancing of ethylene and propylene production
and demand at a specific location or system. In contrast to olefin metathesis,
the present invention is advantageous because it can proceed from simple,
inexpensive starting products such as customary feeds for a steam cracking
15 method and methane.
[0021] Apart from so-called MTO or MTP methods (value chain: methane,
synthesis gas, methanol, propylene), no direct route from methane or natural
gas to propylene existed hitherto. By way of example, the Lurgi MTP method
20 can be cited, however, it produces approximately 20-30% of gasoline-like
compounds as a low-value by-product. The present invention avoids this.
[0022] In contrast to conventional methods, in the context of the present
invention, significantly smaller amounts of carbon dioxide are produced, on the
25 one hand due to the reduced firing, since this is not necessary or is only
necessary to a lesser extent, in contrast to endothermic processes such as
(pure) steam cracking and propane dehydrogenation, and on the other hand
since no carbon dioxide is formed as a by-product, for example as in oxidative
dehydrogenation.

I/We Claim:
1. Process (100, 200, 300) for producing propylene in which a first material
stream (1) is provided using a steam cracking method (10) and one or more
5 fractionations (10a, 10b, 90a) and is rich in ethylene, in which a second
material stream (2) containing carbon monoxide and hydrogen is provided
using a synthesis gas production method (20), in which at least a part of the
ethylene from the first material stream (1) is reacted with at least a part of the
carbon monoxide and the hydrogen from the second material stream (2) to
10 form propanal using a hydroformylation (30) to obtain a third material stream
(3), and in which at least a part of the propanal in the third material stream (3)
is converted to propylene, wherein the ethylene is provided by means of the
steam cracking method (10) in a first component mixture, wherein the
propylene is provided in a second component mixture.
15
2. Process (100, 200, 300) according to claim 1, wherein at least a part of
the first component mixture is subjected to a first fractionation (10a, 10b) to
obtain the first material stream, and wherein at least a part of the second
component mixture is subjected to one or more fractionation steps of the first
20 fractionation (10a, 10b) or a second fractionation (90a) to obtain a pure
propylene stream (19).
3. Process (100, 200, 300) according to one of the preceding claims, in
which the reaction of at least a part of the propanal to form the propylene
25 comprises a hydrogenation (50) to give propanol and a dehydrogenation (60)
to give propylene to obtain the second product mixture.
4. Process (100, 200, 300) according to claim 3, in which the third material
stream (3) contains unreacted ethylene, hydrogen and carbon monoxide as
30 light components, wherein the light components are transferred in a separation
(40) at least in part into a fourth material stream (4).
32
5. Process (100, 200, 300) according to claim 4, in which the separation
(40) of at least a part of the light components is carried out before the
hydrogenation (50) or between the hydrogenation (50) and the
dehydrogenation (60).
5
6. Process (100, 200, 300) according to claim 4 or 5, in which at least a
part of the fourth material stream (4) is returned into the process (100, 200,
300) as a recycle stream (5) upstream of the hydroformylation (30).
10 7. Process (100, 200, 300) according to claim 5, in which the return of at
least a part of the fourth material stream (4) comprises a post-compression.
8. Process (100, 200, 300) according to claim 6, in which a part of the
fourth material stream (4) is returned to the synthesis gas production method
15 (20).
9. Process (100, 200, 300) according to one of the preceding claims 6 or
7, in which the separation (40) of at least a part of the light components
comprises an adsorptive separation, an adsorptive separation, a membrane
20 separation, a separation by distillation and/or a phase separation.
10. Process (100, 200, 300) according to one of the preceding claims 3 to
8, in which a hydrogen stream (8) containing hydrogen is fed into the
hydrogenation and is provided using a separate hydrogen source and/or is
25 obtained using the synthesis gas production method (20) and/or using the
steam cracking method (10) and is separated using a hydrogen removal (70).
11. Process (100, 200, 300) according to one of the preceding claims 3 to
9, in which a product stream (10) containing water, propylene and secondary
30 components is formed in the dehydrogenation (60) and is subjected to a water
removal (80) to obtain the partial stream (12) containing propylene and also
the secondary components and depleted of water.
33
12. Process (100, 200, 300) according to claim 11, in which the partial
stream (12) or a subsequent stream formed therefrom in a trace removal (90)
is subjected at least partly as the second component mixture to the first or
5 second fractionation (10a, 10b, 90a).
13. Process (100, 200, 300) according to one of the preceding claims, in
which carbon dioxide is fed into the synthesis gas production method (20).
10 14. Process (100, 200, 300) according to one of the preceding claims, in
which electrical heating is performed in the steam cracking method (10) and/or
in the synthesis gas production method (20), and in which methane formed in
the steam cracking method (10) is fed into the synthesis gas production
method (20).
15
15. Process (100, 200, 300) according to one of the preceding claims, in
which one or more pumps, one or more compressors and/or one or more
turbines are used that are at least partially electrically driven.
20 16. Process (100, 200, 300) according to one of the preceding claims, in
which the first material stream (10) is formed using a tail-end hydrogenation
and contains hydrogen.
17. Process (100, 200, 300) according to one of the preceding claims, in
25 which the olefin efficiency factor and/or monomer efficiency is at least 100%,
in particular at least 115%, 125% or 130%, and up to 150%.
18. Installation for the production of propylene, with a steam cracking
device and one or more fractionations (10a, 10b, 90a), which is configured to
30 carry out a steam cracking method (10) and to provide an ethylene-containing
first material stream (1), with a synthesis gas producing device which is
configured to carry out a synthesis gas production method (20) and to provide
34
a second material stream (2) containing carbon monoxide and hydrogen, and
with a hydroformylation device which is configured to react at least a part of
the ethylene from the first material stream (1) with at least a part of the carbon
monoxide and of the hydrogen from the second material stream (2) to form
5 propanal using a hydroformylation (30) to obtain a third material stream (3),
wherein the installation is configured to provide the ethylene by means of the
steam cracking method (10) in a first component mixture, to react at least a
part of the propanal in the third material stream (3) to form the propylene and
in the process to provide a second component mixture containing the
10 propylene.