METHOD AND APPARATUS FOR PRODUCING HYDROCARBONS

Abstract

A method for preparing hydrocarbons is proposed, which comprises, in a catalysis unit (1) using one or more catalysis feed streams (a) containing oxygenates and/or olefins, producing a catalysis product stream (b) containing n-butane, isobutane, 1-butene, 2-butene, isobutene and hydrocarbons with more than four and/or less than four carbon atoms, and which further comprises producing a steam cracking product stream (s) in a steam cracking unit (2) using one or more steam cracking feed streams (g, n, l, r). It is provided that at least the great majority of the hydrocarbons with more than four and/or less than four carbon atoms and the isobutene is eliminated from the catalysis product stream (b) or a part thereof, whereby a stream (g, n) containing at least 5 percent by mole 1-butene and/or 2-butene is formed, and in that this stream (g, n) containing at least 5 percent by mole 1-butene and/or 2-butene or one or more streams (l, r) derived therefrom is or are used as the steam cracking feed stream or streams (g, n, l, r). The invention also relates to a corresponding apparatus (100, 200, 300).

Claims

1. Method for preparing hydrocarbons, which comprises, in a catalysis unit (1) using one or more catalysis feed streams (a) containing oxygenates and/or olefins, producing a catalysis product stream (b) containing n-butane, isobutane, 1-butene, 2-butene, isobutene and hydrocarbons with more than four and/or less than four carbon atoms, and which further comprises producing a steam cracking product stream (s) in a steam cracking unit (2) using one or more steam cracking feed streams (g, n, l, r), characterised in that at least the great majority of the hydrocarbons with more than four and/or less than four carbon atoms and the isobutene is eliminated from the catalysis product stream (b) or a part thereof, whereby a stream (g, n) containing at least 5 percent by mole 1-butene and/or 2-butene is formed, and in that this stream (g, n) containing at least 5 percent by mole 1-butene and/or 2-butene, or one or more streams (l, r) derived therefrom, is or are used as the steam cracking feed stream or streams (g, n, l, r).

2. Method according to claim 1, wherein initially the great majority of the hydrocarbons with more than four and/or less than four carbon atoms are separated off, leaving a C4 partial stream (c), and subsequently the great majority of the isobutene is eliminated from the C4 partial stream (c).

3. Method according to claim 2, wherein the elimination of the great majority of the isobutene comprises at least partially reacting the isobutene and separating off at least part of the reaction product thus formed.

4. Method according to claim 3, wherein at least part of a stream (g) that remains after the elimination of the great majority of the isobutene is used as the, or one of the, steam cracking feed streams (g).

5. Method according to claim 2, wherein the elimination of the great majority of the isobutene comprises the distillative separation thereof.

6. Method according to claim 5, wherein, before the distillative separation of the great majority of the isobutene, the great majority of the 1-butene contained in the C4 partial stream (c) is isomerised to form 2-butene.

7. Method according to one of claims 2 to 6, wherein a stream (n, r) predominantly containing n-butane and 2-butene is formed from at least part of a stream (g, h) that remains after the elimination of the great majority of the isobutene and is used as the steam cracking feed stream (n, r) or one of the steam cracking feed streams (n, r).

8. Method according to one of claims 2 to 7, wherein a stream (l) is formed which predominantly contains isobutane and is used as the steam cracking feed stream (n, r) or one of the steam cracking feed streams (n, r).

9. Method according to one of claims 2 to 8, wherein the steam cracking product stream (s) contains hydrocarbons with four carbon atoms, including butadiene, as well as hydrocarbons with more than four and/or less than four carbon atoms.

10. Method according to claim 9, wherein the great majority of the butadiene and of the hydrocarbons with more than four and/or less than four carbon atoms are separated from the steam cracking product stream (s), thereby producing a residual stream (x) low in butadiene, which predominantly contains hydrocarbons with four carbon atoms.

11. Method according to one of claims 2 to 10, wherein at least a part of the residual stream low in butadiene is combined with at least a part of the C4 partial stream (c).

12. Apparatus (100, 200, 300) for the production of hydrocarbons, having a catalysis unit (1) which is set up so as to produce, using one or more catalysis feed streams (a) containing oxygenates and/or olefins, a catalysis product stream (b) containing n-butane, isobutane, 1-butene, 2-butene, isobutene and hydrocarbons with more than four and/or less than four carbon atoms, and having a steam cracking unit (2) which is set up to produce a steam cracking product stream (s), using one or more steam cracking feed streams (g, n, l, r), characterised in that means are provided which are set up to eliminate, from the catalysis product stream (b) or a part thereof, at least the great majority of the hydrocarbons with more than four and/or less than four carbon atoms and the isobutene, whereby a stream (g, n) containing at least 5 percent by mole 1-butene and/or 2-butene is formed, and in that means are provided which are set up to use this stream (g, n) containing at least 5 percent by mole 1-butene and/or 2-butene, or one or more streams (l, r) derived therefrom, as the steam cracking feed stream or streams (g, n, l, r).

13. Apparatus (100, 200, 300) according to claim 12, having means which are arranged to carry out a method according to one of claims 1 to 11.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0054] FIG. 1 shows an apparatus according to one embodiment of the invention, in schematic representation.

[0055] FIG. 2 shows an apparatus according to one embodiment of the invention, in schematic representation.

[0056] FIG. 3 shows an apparatus according to one embodiment of the invention, in schematic representation.

EMBODIMENTS OF THE INVENTION

[0057] The Figures show corresponding elements with identical reference numerals and are not repeatedly explained, in the interests of clarity. The streams shown in the respective Figures are given identical reference numerals when they have essentially the same or a comparable composition and irrespective of any differences in volume flows. In all the Figures, a catalysis unit is designated 1 and a steam cracking unit is designated 2.

[0058] In FIG. 1 an apparatus according to one embodiment of the invention is shown schematically in simplified view and is generally designated 100.

[0059] One or more catalysis feed streams, here designated a, containing oxygenates and/or olefins are supplied to the catalysis unit 1. As already mentioned, the catalysis unit 1 may comprise one or more reactors which are operated with a zeolite catalyst. The catalysis unit may additionally be supplied with further streams, in this case the stream e, as explained below.

[0060] In the embodiment shown a catalysis product stream b is produced in the catalysis unit 1. It is fed to a separating unit 3, in which a stream c depleted in hydrocarbons with more than four and/or less than four carbon atoms or rich in hydrocarbons with four carbon atoms, i.e. a C4 stream, is obtained from the catalysis product stream b. The streams separated off, here designated y and z, may for example comprise hydrocarbons with five or more or hydrocarbons with three or less carbon atoms, or other such fractions. Streams of this kind may also be processed in a corresponding apparatus and/or recovered as products.

[0061] In the embodiment shown the C4 stream c is supplied to a reaction unit 4 in which isobutene contained in the C4 stream c is reacted, for example, with methanol, which is supplied in the form of a stream d, to produce methyl-tent-butyl ether. Methyl-tent-butyl ether or another reaction product with a different compound supplied in the form of the stream d can be drawn off as stream e. As indicated by a dashed arrow, optionally at least some of the corresponding products can be removed from the apparatus as stream f. The remainder of the stream e or the whole of the stream e can be fed into the catalysis unit 1 again and thus used as a recycle stream.

[0062] A C4 stream, thus freed from isobutene and now designated g, is fed into the steam cracking unit 2 and processed there in one or more cracking furnaces, optionally also together with further streams which are fed into the same or different cracking furnaces. A steam cracking product stream s is obtained which, as already explained, contains hydrocarbons with four carbon atoms, including butadiene, as well as hydrocarbons with more than four and/or less than four carbon atoms. This stream, here designated s, is fed into a further separating unit 5, in which, initially, by separating off hydrocarbons with more than four and/or less than four carbon atoms, as illustrated here by the streams t and u, a stream v is obtained which predominantly contains hydrocarbons with four carbon atoms, including butadiene. In the embodiment shown the stream v is fed into a butadiene separating unit 6, where the butadiene present is predominantly separated off and discharged from the apparatus as a stream w. A remaining residual stream, here designated x, which is low in butadiene can be combined with the above-mentioned C4 partial stream c and fed into the reaction unit 4.

[0063] Depending on the desired result, severe cracking (to maximise ethylene) or mild cracking (to maximise propylene) can be carried out in the steam cracking unit 2. However, irrespective of the cracking severity, there is a tendency for a larger amount of butadiene to be produced, as the feed used in the form of the stream g still contains unsaturated components, namely 1-butene and 2-butene. If an increased amount of butadiene is not wanted, the steam cracking feed stream or streams may be hydrogenated beforehand. In this way, a yield of propylene or ethylene may be increased further. (Partial) hydrogenation and/or hydroisomerisation, which may also be provided, may furthermore be used to hydrogenate any polyunsaturated components still present and to react 1-butene to form 2-butene, which in turn promotes the production of butadiene. All the processes taken together have the advantage that the isobutene which is unsuitable for cracking in the steam cracking unit 2 is eliminated, but all the other components, particularly n-butene, are still available for the cracking.

[0064] FIG. 2 schematically shows an apparatus according to another embodiment of the invention, generally designated 200.

[0065] In contrast to the apparatus 100 shown in FIG. 1, there is no reaction unit 4 provided here for reacting the isobutene, but an isomerisation unit is optionally provided, as illustrated in the form of a block 7 shown by dashed lines. The separating unit designated 3 in FIG. 1 is designated X here but may be of identical configuration. The isomerisation unit 7 is particularly set up for isomerising 1-butene contained in the stream c (and the stream x) to form 2-butene, in order to make subsequent distillation in a distillation unit 8 easier, as explained hereinbefore. The isomerisation unit 7 is particularly set up for hydroisomerisation. By means of the isomerisation in the isomerisation unit 7, preferably exclusively branched C4 components are separated off in the distillation unit 8. In the distillation unit 8 a stream i is obtained which predominantly contains isobutene and isobutane, but not the 1-butene which otherwise also goes over into a corresponding fraction or into the stream i, as this has been isomerised in the isomerisation unit 7. If no such isomerisation is carried out, 1-butene also goes over into the stream i. A further stream obtained in the distillation unit 8, here designated n, essentially contains butane and 2-butene, which are used as steam cracking feed stream and are fed into the steam cracking unit 2.

[0066] In the embodiment shown, the stream i is optionally treated in another distillation unit 9, where an isobutene stream k is produced from the stream i, or, if the stream i still contains 1-butene, a stream k containing isobutene and 1-butene is produced, which can be recycled into the catalysis unit. A stream l obtained in the further distillation unit 9 essentially contains isobutane and is supplied as a steam cracking feed stream to the steam cracking unit 2.

[0067] If the isomerisation unit 7 and the further distillation unit 9 are available in a corresponding apparatus, essentially all the C4-hydrocarbons of the stream c, apart from isobutene, can be fed into the steam cracking unit 2 and be profitably processed therein. As already mentioned, the isobutene can be recycled into the catalysis unit in the form of the stream k and/or be removed from a corresponding apparatus in the form of the stream m. There is a potential for further maximising the butadiene content in the stream s in the steam cracking unit, as butadiene tends to be formed in larger amounts from 2-butene. Regarding the streams s to x and the units 5 and 6 reference is made to the earlier explanations concerning FIG. 1.

[0068] FIG. 3 schematically shows an apparatus according to another embodiment of the invention, generally designated 300.

[0069] The apparatus 300 in FIG. 3 corresponds essentially to the apparatus 100 in FIG. 1, up to the reaction unit 4. However, an isobutene-depleted C4 hydrocarbon stream, here also designated g, is fed into a distillation unit which is basically comparable with the distillation unit in the apparatus 200 according to FIG. 2 and is therefore also designated 8 here.

[0070] In the distillation unit 8 a partial stream o which essentially contains isobutane and 1-butene is obtained from the isobutene-depleted C4 hydrogen stream g. It is fed into another distillation unit, which is also designated 9 here. In the further distillation unit 9 a stream p essentially containing 1-butene and a stream q essentially containing isobutane are produced from the stream o. The stream q, like a stream r, which is produced in the distillation unit 8 and predominantly contains butane and 2-butene, can be fed into the steam cracking unit 2 as a steam cracking feed stream. For the streams s to x and the units 5 and 6, reference is made to the foregoing explanations of FIG. 1.

[0071] Overall, in all the apparatus 100 to 300 shown, hydrocarbon streams with three or less carbon atoms from the separating units 3 or X and 5 can be further processed jointly. Corresponding paraffins separated from these fractions, particularly ethane and propane, can be recycled into the steam cracking unit 2. The same applies to corresponding streams with hydrocarbons having five or more carbon atoms. These may also be further processed jointly. Joint fractionation may be carried out and specific fractions may be recycled into the catalysis unit 1 and/or, optionally after hydrogenation, into the steam cracking unit 2. It should be emphasised that, in certain process variants, other fractions may also be processed, for example fractions that also contain C5, C6 and higher hydrocarbons.

[0072] Further embodiments of the present invention might also provide that the isobutene fraction separated off, which also contains 1-butene and isobutene, in particular, should be completely hydrogenated and fed into a steam cracking unit 2, if it is undesirable to feed any recycle streams into the catalysis unit 1. If, for example, recovery of 1-butene is desired, this is also possible by means of a combination of a corresponding reaction unit and subsequent distillation, as shown in FIG. 3. In every case, further feeds such as naphtha and/or ethane or propane may be fed into a steam cracking unit 2.

[0073] It should be emphasised that a particular advantage of the present invention arises from the fact that the streams obtained from the catalysis unit b or the streams c formed therefrom contain small amounts of dienes.