METHOD AND APPARATUS FOR PRODUCING HYDROCARBONS

Abstract

A method for producing hydrocarbons is proposed wherein a catalysis product stream (b) rich in n-butane, isobutane, 1-butene, 2-butene, isobutene and hydrocarbons with more than four and/or less than four carbon atoms is produced in a catalysis unit (1), using one or more catalyst feed streams containing oxygenates and/or olefins (a) and wherein additionally a steam cracking product stream (h) is produced in a steam cracking unit (2) using one or more steam cracking feed streams (g, r, s). It is provided that using the catalysis product stream (b) a skeletal isomerisation feed stream (f, q) poor in 1-butene, 2-butene and isobutene and containing at least isobutane is produced, in which the isobutane is at least predominantly reacted by skeletal isomerisation to form n-butane, and which is subsequently used at least partly as the, or one of the, steam cracking feed streams (g, r). The invention also relates to an apparatus (100, 200).

Claims

1. Method for producing hydrocarbons, wherein a catalysis product stream (b) rich in n-butane, isobutane, 1-butene, 2-butene, isobutene and hydrocarbons with more than four and/or less than four carbon atoms is produced in a catalysis unit (1), using one or more catalyst feed streams containing oxygenates and/or olefins (a), and wherein additionally a steam cracking product stream (h) is produced in a steam cracking unit (2) using one or more steam cracking feed streams (g, r, s), characterised in that using the catalysis product stream (b) a skeletal isomerisation feed stream (f, q) poor in 1-butene, 2-butene and isobutene and containing at least isobutane is produced, in which the isobutane is at least predominantly reacted by skeletal isomerisation to form n-butane, and which is subsequently used at least partly as the, or one of the, steam cracking feed streams (g, r).

2. Method according to claim 1, wherein, using at least part of the catalysis product stream (b), a separation feed stream is formed from which the hydrocarbons with more than four and/or less than four carbon atoms are at least predominantly separated off, to obtain a separation discharge stream (e) rich in n-butane, isobutane, 1-butene, 2-butene and isobutene.

3. Method according to claim 2, wherein, using at least part of the separation discharge stream (e), a hydrogenation feed stream is formed in which the 1-butene, 2-butene and isobutene are reacted at least predominantly by hydrogenation, to form n-butane and isobutane, thereby producing a hydrogenation discharge stream, at least part of the hydrogenation discharge stream being used in the formation of the skeletal isomerisation feed stream (f).

4. Method according to claim 2, wherein, using at least part of the separation discharge stream (e), a distillation feed stream (o) is formed, from which the n-butane and 2-butene are at least predominantly separated off, thereby forming a distillation discharge stream (p) which is poor in n-butane and 2-butene.

5. Method according to claim 4, wherein, using at least part of the separation discharge stream (e), a hydroisomerisation feed stream is formed in which the 1-butene is reacted at least predominantly by hydroisomerisation to form 2-butene, thereby producing a hydroisomerisation discharge stream, at least part of the hydroisomerisation discharge stream being used in the formation of the distillation feed stream (o).

6. Method according to claim 4 or 5, wherein, using at least part of the distillation discharge stream (p), a hydrogenation feed stream is formed wherein at least the isobutene is reacted at least predominantly by hydrogenation to form isobutane, thereby producing a hydrogenation discharge stream, at least part of the hydrogenation discharge stream being used in the formation of the skeletal isomerisation feed stream (q).

7. Method according to one of claims 4 to 6, wherein, using at least part of the n-butane and 2-butene separated from the distillation feed stream (o), a stream is formed which is used as a further steam cracking feed stream (s).

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

9. Method according to claim 8, wherein, using at least part of the steam cracking product stream (h), a residual stream (n) which is poor in butadiene and hydrocarbons with more than four and/or less than four carbon atoms is obtained, which is at least partly used in the production of the skeletal isomerisation feed stream (f, q).

10. Apparatus (100, 200) for the production of hydrocarbons, having a catalysis unit (1) which is configured to produce a catalysis product stream (b) rich in n-butane, isobutane, 1-butene, 2-butene, isobutene and hydrocarbons with more than four and/or less than four carbon atoms, using one or more catalyst feed streams containing oxygenates and/or olefins (a), and having a steam cracking unit (2) which is configured to produce a steam cracking product stream (h), using one or more steam cracking feed streams (g, r, s), characterised by means which are configured to produce a skeletal isomerisation feed stream (f, q) poor in 1-butene, 2-butene and isobutene and containing at least isobutane, using the catalysis product stream (b), to react the isobutane therein at least predominantly by skeletal isomerisation to form n-butane, and then to use the latter at least partly as the, or one of the, steam cracking feed streams (g, r).

11. Apparatus (100, 200) according to claim 10, which comprises means configured for carrying out a method according to one of claims 1 to 9.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0059] FIG. 1 shows an apparatus according to one embodiment of the invention, in schematic representation.

[0060] FIG. 2 shows an apparatus according to one embodiment of the invention, in schematic representation.

EMBODIMENTS OF THE INVENTION

[0061] 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, 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.

[0062] In FIG. 1 an apparatus according to one embodiment of the invention is shown schematically in simplified view and is generally designated 100.

[0063] 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, not shown here.

[0064] In the embodiment shown a catalysis product stream b is produced in the catalysis unit 1. It is fed as a separation feed stream to a separating unit 3, in which a stream e depleted in hydrocarbons with more than four and/or less than four carbon atoms or rich in hydrocarbons with four carbon atoms, referred to here as the separation discharge stream, is obtained from the catalysis product stream b. The streams separated off, here designated c and d, may for example comprise hydrocarbons with five or more and/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 obtained as products.

[0065] In the embodiment shown, the separation discharge stream e is combined with another stream n described hereinafter, referred to here as a residual stream, thereby producing a hydrogenation feed stream which is fed to a hydrogenation unit 4. In the hydrogenation unit 4, preferably all the unsaturated hydrocarbons of streams e and n are reacted to form corresponding saturated hydrocarbons. However, partial hydrogenation is also possible. In the hydrogenation unit 4 a stream is obtained which is designated the hydrogenation discharge stream.

[0066] Whereas the separation discharge stream e in the embodiment shown typically still contains all the hydrocarbons with four carbon atoms which are produced in the catalysis unit 1, or originate from the catalysis feed stream(s) a and have not been reacted in the catalysis unit 1, particularly n-butane, isobutane, 1-butene, 2-butene and isobutene, the hydrogenation discharge stream still contains only, or predominantly, the corresponding saturated hydrocarbons, i.e. n-butane and isobutane.

[0067] In the embodiment shown the hydrogenation discharge stream is fed as a skeletal isomerisation feed stream f to an isomerisation unit 5 in which the isobutane contained in the skeletal isomerisation feed stream f is reacted to form n-butane. A skeletal isomerisation discharge stream obtained in the skeletal isomerisation unit 5 therefore predominantly or exclusively contains n-butane and is fed into the steam cracking unit 2 as a steam cracking feed stream g.

[0068] The steam cracking feed stream g, i.e. essentially pure n-butane, for example, is processed in the steam cracking unit 2 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 h 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 steam cracking product stream h is fed into a further separating unit 6, in which, initially, by separating off hydrocarbons with more than four and/or less than four carbon atoms, as illustrated here by the streams i and k, a stream I is obtained which predominantly contains hydrocarbons with four carbon atoms, including butadiene. In the embodiment shown the stream I is fed into a butadiene separating unit 7, where the butadiene present is predominantly separated off and discharged from the apparatus as a stream m. A remaining residual stream, here designated n, which is low in butadiene can be combined with the above-mentioned hydrogenation feed stream or the separation discharge stream e which forms it and fed into the hydrogenation unit 4.

[0069] 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.

[0070] However, irrespective of the cracking severity, there is a tendency for a larger amount of butadiene to be produced only when the feed used still contains unsaturated components, namely 1-butene and/or 2-butene, in particular (which is not the case in the example of the apparatus 100 in the form of the steam cracking feed stream g). If a larger amount of butadiene is required, an apparatus 200 according to FIG. 2 may be used.

[0071] FIG. 2 schematically shows an apparatus according to another embodiment of the invention, generally designated 200.

[0072] In the apparatus 200, a separation discharge stream e from the separating unit 3 is optionally supplied to a hydroisomerisation unit 8. To do this, a combined stream, also referred to here as a hydroisomerisation feed stream, may be formed from the separation discharge stream e and the above-mentioned residual stream n low in butadiene. Instead of being fed into the hydroisomerisation unit 8 the separation discharge stream e and the residual stream n may also be fed directly into a distillation unit 9 in the form of a distillation feed stream o, which means that the hydroisomerisation unit 8 is optional. If a hydroisomerisation unit 8 is used, the 1-butene contained in the hydroisomerisation feed stream or the separation discharge stream e and the residual stream n is reacted therein to form 2-butene, which is contained in a corresponding hydroisomerisation discharge stream or the distillation feed stream o formed therefrom. As already explained, this assists with distillative separation in the distillation unit 9.

[0073] In the distillation unit 9, a distillation discharge stream p is obtained from the distillation feed stream o by separating off butane and 2-butene, or the major part thereof, in the form of the stream s. If there is no hydroisomerisation unit 8 the distillation discharge stream p contains 1-butene, but otherwise it does not. In addition, the distillation discharge stream p contains isobutene and isobutane. The distillation discharge stream p is supplied as hydrogenation feed stream to a hydrogenation unit, designated 4 here, as in FIG. 1. In the hydrogenation unit, 1-butene is reacted to 1-butane, if present in the hydrogenation feed stream p, and additionally isobutene is reacted to form isobutane. A hydrogenation discharge stream obtained in the hydrogenation unit 4 therefore contains either a mixture of essentially n-butane and isobutane or essentially pure isobutane. The hydrogenation discharge stream is then fed as a skeletal isomerisation feed stream q to a skeletal isomerisation unit, which is also designated 5 here. Once again, a substantially pure n-butane stream is obtained as the skeletal isomerisation discharge stream and is fed, as the steam cracking feed stream r, to the steam cracking unit 2.

[0074] In the distillation unit 9 a stream essentially containing butane and 2-butene is also obtained, as described, which can also be supplied as a (further) steam cracking feed stream s to a steam cracking unit, and can be fed into the same or a different cracking furnace from the steam cracking feed stream r.

[0075] Regarding the streams a to d and h to n and the units 1 to 3 and 6 and 7, reference is made to the foregoing remarks on FIG. 1.