PROCESS FOR PURIFICATION OF AN ORGANIC COMPOSITION

Abstract

Disclosed is a process for the purification of an organic composition (OC1) by adsorption using an assembly containing at least two adsorbers. The organic composition (OC1) comprising at least one alkane, at least one olefin and at least one compound containing oxygen and/or sulphur is fed into a first adsorber (A1) of the assembly in order to obtain an organic composition (OC2) comprising at least one alkane, at least one olefin and a reduced amount of at least one compound containing oxygen and/or sulphur compared to the respective amount in organic composition (OC1). Hydrogenation of the organic composition (OC2) provides a stream (S2) comprising at least one alkane and a reduced amount of at least one olefin compared to the respective amount in organic composition (OC2) obtained after feeding into the first adsorber (A1). A second adsorber (A2) of the assembly is regenerated by contact with stream (S2).

Claims

1-15. (canceled)

16: A process for purifying an organic composition (OC1) by adsorption using an assembly containing at least two adsorbers, the process comprising: a) purifying the organic composition (OC1) by feeding the organic composition (OC1) comprising at least one alkane or at least one olefin and at least one compound containing oxygen or sulphur into a first adsorber (A1) of the assembly in order to obtain an organic composition (OC2) comprising the at least one alkane, the at least one olefin and a reduced amount of the at least one compound containing oxygen or sulphur compared to the respective amount in the organic composition (OC1), b) hydrogenating at least a part of the organic composition (OC2) obtained in a) to obtain a stream (S2) comprising the at least one alkane and a reduced amount of the at least one olefin compared to the respective amount in the organic composition (OC2), c) regenerating a second adsorber (A2) of the assembly by contact with the stream (S2) obtained in b), wherein the purifying a) and the regenerating c) are performed in parallel.

17: The process according to claim 16, wherein i) the organic composition subjected to the hydrogenating b) comprises butane and butene, or ii) the organic composition subjected to the hydrogenating b) comprises ≦20 wt-ppm of at least one compound containing oxygen or sulphur, or iii) the stream (S2) comprises not more than 1000 wt-ppm olefin, or iv) the stream (S2) comprises at least 99 wt-% of at least one alkane, or v) the stream (S2) comprises ≦20 wt-ppm of at least one compound containing oxygen or sulphur, or vi) a load of the adsorber (A1) with the organic composition (OC1) in a) is 10 to 100 t/h, or vii) the organic composition (OC1) is fed into the adsorber (A1) in a) at a temperature of 25 to 40° C., or viii) the organic composition (OC1) is fed into the adsorber (A1) in a) at a pressure of 5 to 8 bar.

18: The process according to claim 17, wherein i) the organic composition subjected to the hydrogenating b) compromises at least 96 wt-% butane and not more than 4 wt-% butene, or ii) the stream (S2) compromises at least 99 wt-% of butane.

19: The process according to claim 16, wherein the organic composition (OC1) comprises at most 1000 wt-ppm of at least one compound containing oxygen or sulphur.

20: The process according to claim 16, wherein the organic composition (OC1) comprises butane and butene.

21: The process according to claim 16, wherein, in the organic composition (OC1), a weight ratio of the alkane to the olefin is 0.5:1 to 2:1.

22: The process according to claim 16, wherein the at least two adsorbers (A1) and (A2) are based on a molecular sieve or aluminium oxide, or the adsorbers adsorb compounds containing oxygen or sulphur out of the organic compositions.

23: The process according to claim 22, wherein the adsorbers adsorb ethers, alcohols, thiols, thioethers, sulfoxides, ketones, aldehydes, or a mixture thereof.

24: The process according to claim 16, wherein the purifying a) and the regenerating c) are performed for the same period of time.

25: The process according to claim 24, wherein the period of time ranges from 12 to 48 h.

26: The process according to claim 16, wherein the regenerating c) comprises at least one of c1) to c6): c1) converting the stream (S2) from a liquid phase into a gaseous phase, c2) heating the adsorber by contact with the stream (S2), which is gaseous, wherein the gaseous stream (S2) is condensed within the adsorber to obtain a condensate, c3) heating the adsorber by contact with the stream (S2), which is gaseous, up to a temperature of 230 to 270° C. without any condensation of the gaseous stream (S2) within the adsorber, c4) regenerating the adsorber at a temperature of 230 to 270° C. by contact with the stream (S2), which is gaseous, c5) cooling the adsorber by contact with the stream (S2), which is gaseous, to a temperature of 80° C. to 120° C., and c6) cooling the adsorber by contact with the stream (S2), which is liquid, obtained in b) to a temperature of below 80° C.

27: The process according to claim 16, further comprising: d) prior to c), at least partially removing the organic composition (OC1) or the organic composition (OC2) which is passed through the second adsorber (A2) during its operation mode.

28: The process according to claim 27, wherein the regenerating c) comprises: c1) converting the stream (S2) from a liquid phase into a gaseous phase, c2) subsequently heating the adsorber by contact with the gaseous stream (S2), wherein the gaseous stream (S2) is condensed within the adsorber to obtain a condensate, c3) subsequently heating the adsorber by contact with the gaseous stream (S2) up to a temperature of 230 to 270° C. without any condensation of the gaseous stream (S2) within the adsorber, c4) subsequently regenerating the adsorber at a temperature of 230 to 270° C. by contact with the gaseous stream (S2), c5) subsequently cooling the adsorber by contact with the gaseous stream (S2) to a temperature of 80° C. to 120° C., and c6) subsequently cooling the adsorber by contact with the liquid stream (S2) obtained in b) to a temperature of below 80° C.

29: The process according to claim 28, wherein the condensate obtained in c2) contains the stream (S2) and a residue of the organic composition (OC1) or the organic composition (OC2) which is not removed from the second adsorber (A2) during the removing d), and the condensate is optionally collected in a device to pass the collected condensate through an adsorber during its operation mode.

30: The process according to claim 26, wherein the regenerating c) comprises the converting c1), in which the conversion is carried out by employing at least one evaporator or at least one superheater or at least one flash vessel.

31: The process according to claim 16, further comprising: e) prior to b), carrying out an oligomerization of the organic composition (OC2), in which at least one of the olefins is at least partially oligomerized, thereby obtaining an organic composition (OC3) comprising an reduced amount of the at least one olefin and an increased amount of the at least one oligomerized olefin compared to the respective amounts in the organic composition (OC2); wherein the organic composition (OC3) rather than (OC2) is used afterwards.

32: The process according to claim 31, wherein the oligomerization is a dimerization.

33: The process according to claim 32, wherein the at least one olefin is butene, which is at least partially dimerized to octene.

34: The process according to claim 31, further comprising: f) prior to b) and after e), distilling the organic composition (OC3) in a distillation column (D1) to obtain (i) an organic composition (OC4) from an upper part of the distillation column (D1), wherein the organic composition (OC4) comprises the at least one alkane, the at least one olefin and an reduced amount of the at least one oligomerized olefin compared to the respective amount in the organic composition (OC3); and (ii) a stream (S3) from a lower part of the distillation column (D1), wherein the stream (S3) comprises at least 80% by weight of the at least one oligomerized olefin in the organic composition (OC3), wherein the organic composition (OC4) rather than (OC3) is used afterwards.

35: The process according to claim 34, further comprising: g) prior to b), distilling the organic composition (OC2), or optionally the organic composition (OC3), or optionally the organic composition (OC4), in a distillation column (D2) to obtain (i) an organic composition (OC2a) from an upper part of the distillation column (D2), wherein the organic composition (OC2a) comprises the at least one alkane and an reduced amount of the at least one olefin compared to the respective amount in (OC2), or (OC3), or (OC4); and (ii) a stream (S4) from a lower part of the distillation column (D2), wherein the stream (S4) comprises at least 80% by weight of the olefins present in (OC2), or (OC3), or (OC4), wherein the organic composition (OC2a) rather than (OC2), or (OC3), or (OC4) is used afterwards.

36: The process according to claim 35, wherein the distilling f) is performed prior to the distilling g).

37: The process according to claim 35, wherein the distillation column (D1) or the distillation column (D2) removes iso-butane, and the organic composition fed into (D1) or (D2) comprises butane or butene.

Description

[0026] The invention is specified in more detail as follows:

[0027] The invention relates to a process for the purification of an organic composition (OC1) by adsorption using an assembly containing at least two adsorbers comprising the following steps a) to c):

[0028] Within the context of the present invention, the term “adsorber” comprises the adsorbent as well as the device in which the adsorbent is embedded in. Instead of the term “adsorbent” the expression “adsorber material” may be used. The term adsorber may be used equivalently for adsorbent, even if a certain statement actually refers only to the adsorbent but not to the device in which the adsorbent is embedded in.

[0029] The adsorbers can be employed for the adsorption of compounds containing oxygen and/or sulphur out of organic compositions. Preferably, the adsorbers can be employed for the adsorption of ethers, alcohols, thiols, thioethers, sulfoxides, ketones, aldehydes or mixtures thereof.

[0030] Any adsorbent known to the person skilled in the art being appropriate for performing the adsorption of compounds containing oxygen and/or sulphur out of organic compositions may be applied.

[0031] Preferred adsorbents are, for example, molecular sieves with a pore diameter of 4 to 15 Å. Further, molecular sieves applicable are crystalline, natural aluminia silicates, like layer lattice silicates or synthetic molecular sieves. Furthermore, commercially available molecular sieves as sold by the Bayer AG, Dow, Union Carbide, Laporte or Mobil may be used. These molecular sieves can be, for example, zeolithes of the A-, X- and Y-type. Moreover, synthetic molecular sieves comprise silicium and aluminium as main components, whereby other atoms as side-components such as lanthanides like gallium, indium and lanthanum or other elements like nickel, cobalt, copper, zinc or silver may be useful. These can be introduced into the zeolithe for example by means of an ion-exchange with exchangeable cations.

[0032] Likewise, synthetic zeolithes can be employed, in which other atoms like boron or phosphorus are incorporated in the layer by co-precipitation.

[0033] Further suitable adsorbents are aluminium phosphate, silicium dioxide, kieselgur, titanium dioxide, zirconium dioxide, polymeric adsorbents and mixtures thereof.

[0034] The most preferred adsorbent is aluminium oxide, commercially available for example as Selexsorb CDL from BASF.

[0035] Preferably the at least two adsorbers (A1) and (A2) are based on a molecular sieve or aluminium oxide, preferably aluminium oxide and/or the adsorbers can be employed for the adsorption of compounds containing oxygen and/or sulphur out of organic compositions, preferably the adsorbers can be employed for the adsorption of ethers, alcohols, thiols, thioethers, sulfoxides, ketones, aldehydes or mixtures thereof.

[0036] In step a) the organic composition (OC1) comprising at least one alkane and/or at least one olefin and at least one compound containing oxygen and/or sulphur is fed into a first adsorber (A1) of the assembly in order to obtain an organic composition (OC2) comprising at least one alkane, at least one olefin and a reduced amount of at least one compound containing oxygen and/or sulphur compared to the respective amount in organic composition (OC1).

[0037] Preferably the alkane contains 1 to 14, more preferably 3 to 10, most preferably 4 to 6 carbon atoms in its longest chain.

[0038] The at least one alkane can be, for example, linear, branched and/or cyclic and is selected from the group: methane, ethane, propane, butane, pentane, hexane, heptane, octane, nonane and decane. Preferably the at least one alkane is butane.

[0039] In the context of the present invention, if not stated otherwise, it is not differentiated between the different isomers of a certain alkane. For example, the term butane may refer to n-butane and/or isobutane.

[0040] The organic compositions, within this invention, may comprise in a specific embodiment one or more further alkanes different from butane, which may be selected from the same alkanes as specified above.

[0041] Preferably the organic composition (OC1) comprises butane and butene.

[0042] Preferably the organic composition (OC1) comprises at most 1000 wt-ppm, more preferably at most 300 wt-ppm, most preferably at most 200 wt-ppm of at least one compound containing oxygen and/or sulphur.

[0043] The organic composition (OC1) preferably comprises at least 15 wt-ppm of at least one compound containing oxygen and/or sulphur.

[0044] Preferably organic composition (OC1) comprises not more than 250 wt-ppm 1,2-dimethoxyethane (DME), not more than 150 wt-ppm methyl tertiary butyl ether (MTBE), not more than 50 wt-ppm acetone, not more than 50 wt-ppm methanol and/or not more than 50 wt-ppm methyl mercaptane.

[0045] The at least one olefin may comprise at least one linear, branched, cyclic monoolefin and/or at least one linear, branched, cyclic olefin containing more than one olefinic double bond. Preferably the olefin has 2 to 14, more preferably 3 to 10, most preferably 4 to 6 carbon atoms in its longest carbon chain.

[0046] If more than one stereoisomer of an olefin exists, e.g. the corresponding cis- and trans-isomer, these isomers are, in the context of the present invention, regarded as equivalent. Further, it is not differentiated between constitutional isomers of monoolefins. For example, the term butene may comprise the constitutional isomers 1-butene and/or 2-butene as well as 2-butene the corresponding cis- and/or trans-stereoisomer.

[0047] Monoolefins can be, for example, selected from the group: ethene, propene, butene pentene, hexene, heptene, octene, nonene and decene. Preferably, the olefin is butene.

[0048] If at least one olefin containing more than one olefinic double bond is present, this olefin is preferably a diene, more preferably butadiene.

[0049] The organic compositions comprising at least one olefin may comprise in a specific embodiment one or more further olefins different from butene which may be selected from the same olefins as specified above.

[0050] The organic composition (OC1) may comprise at least 20 wt-% of the at least one olefin, preferably butene and/or at least 20 wt-% of the at least one alkane, preferably butane.

[0051] Preferably in the organic composition (OC1) the ratio of alkane to olefin is 0.5:1 to 2:1 [weight-%:weight-%].

[0052] The organic composition (OC2) preferably comprises not more than 20 wt-ppm of compounds containing oxygen and/or sulphur.

[0053] Preferably the load of the adsorber (A1) with organic composition (OC1) in step a) is 10 to 100 t/h, more preferably 30 to 80 t/h, most preferably 45 to 65 t/h.

[0054] Preferably the organic composition (OC1) is fed into the adsorber (A1) in step a) at a temperature of 25 to 40° C.

[0055] Preferably the organic composition (OC1) is fed into the adsorber (A1) in step a) at a pressure of 5 to 8 bar.

[0056] In step b) at least a part of the organic composition (OC2) obtained in step a) is hydrogenated to obtain a stream (S2) comprising at least one alkane and a reduced amount of at least one olefin compared to the respective amount in organic composition (OC2).

[0057] The hydrogenation may be carried out by any appropriate method known to the person skilled in the art.

[0058] Useful may be a catalyzed hydrogenation using at least a catalyst and a hydrogen source.

[0059] Preferably, the catalyst comprises d-block elements, more preferably, for example, Pd, Pt, Ru, Ir, Rh, Cu, Ni or Co, most preferably Pd, Ni, Pt or Rh, in particular preferably Pd or Ni.

[0060] The hydrogenation can be performed using H.sub.2-gas and/or as catalytic transfer hydrogenation, employing for example ammonium formate, silyl hydrides, NaBH.sub.4, cyclohexene or alcohols like methanol and propanol as hydrogen source. Preferably, the hydrogenation is carried out using H.sub.2-gas as hydrogen source.

[0061] The hydrogen source and the solvent may be identical, for example, in the case of alcohols like methanol.

[0062] Any solvent known to the person skilled in the art being appropriate for performing the hydrogenation may be employed.

[0063] In general polar-protic, polar-nonprotic and/or unpolar solvents can be employed, for example methanol, ethanol, propanol, isopropanol, tetrahydrofurane or toluene.

[0064] Alternatively, the hydrogenation can be carried out without using any solvent.

[0065] In a preferred embodiment, the hydrogenation is carried out without the use of any solvent and with H.sub.2-gas as hydrogen source.

[0066] Any reactor known to the person skilled in the art being appropriate for performing the hydrogenation may be employed.

[0067] Preferably a trickle bed reactor is employed for performing the hydrogenation.

[0068] Preferably the stream (S2) comprises not more than 1000 wt-ppm olefin, more preferably not more than 500 wt-ppm olefin, most preferably not more than 100 wt-ppm olefin, preferably the olefin is butene.

[0069] Preferably the stream (S2) comprises at least 99 wt-% of at least one alkane, more preferably at least 99.5 wt-% of at least one alkane, most preferably at least 99.9 wt-% of at least one alkane, preferably the alkane is butane.

[0070] Preferably the stream (S2) comprises ≦20 wt-ppm, more preferably ≦5 wt-ppm, most preferably ≦1 wt-ppm of at least one compound containing oxygen and/or sulphur.

[0071] The respective organic composition subjected to hydrogenation in step b) preferably comprises butane and butene, more preferably at least 96 wt-% butane and not more than 4 wt-% butene.

[0072] The respective organic composition subjected to hydrogenation in step b) preferably comprises ≦20 wt-ppm, more preferably ≦5 wt-ppm, most preferably ≦1 wt-ppm of at least one compound containing oxygen and/or sulphur.

[0073] In step c) a second adsorber (A2) of the assembly is regenerated by contact with stream (S2) obtained in step b),

[0074] wherein the purification employing the first adsorber (A1) of the assembly according to step a) and the regeneration of the second adsorber (A2) of the assembly according to step c) are run in parallel.

[0075] Regeneration, in the context of the present invention, means desorption and removal of adsorbed compounds containing oxygen and/or sulphur from the adsorber, in particular from the adsorbent in the adsorber. Regeneration of the adsorber may also comprise additional measures/steps necessary, for example, for preparation of the regeneration medium, the adsorber itself for regeneration or for enabling the adsorber after finished regeneration to be operated again for adsorption of compounds containing oxygen and/or sulphur out of organic compositions.

[0076] Consequently, an adsorber, within this invention, can at least be operated in the modes of operation: operation mode or regeneration mode.

[0077] An adsorber, within this invention, is in operation mode, when a stream comprising an organic composition, comprising at least one alkane and/or at least one olefin and compounds containing oxygen and/or sulphur, preferably not being routed through the adsorber before, is fed into the adsorber and compounds containing oxygen and/or sulphur are adsorbed completely or at least partially from this stream on the adsorbent.

[0078] Preferably at least 50%, more preferably at least 80%, most preferably at least 97% of the compounds containing oxygen and/or sulphur are adsorbed from the stream comprising organic composition, according to the preceding paragraph.

[0079] An adsorber, within this invention, is in regeneration mode when measures to remove or measures related to the removal of adsorbed compounds containing oxygen and/or sulphur from the adsorbent are carried out or optionally the definition of the operation mode does not apply.

[0080] Preferably the time for regeneration and purification is equal, more preferably in the range of 12 to 48 h.

[0081] In a further embodiment the invention comprises at least one, of the following options i) to viii): [0082] i) the respective organic composition subjected to hydrogenation in step b) comprises butane and butene, preferably at least 96 wt-% butane and not more than 4 wt-% butene, and/or [0083] ii) the respective organic composition subjected to hydrogenation in step b) comprises ≦20 wt-ppm, preferably ≦5 wt-ppm, more preferably ≦1 wt-ppm of at least one compound containing oxygen and/or sulphur, and/or [0084] iii) the stream (S2) comprises not more than 1000 wt-ppm olefin, preferably not more than 500 wt-ppm olefin, most preferably not more than 100 wt-ppm olefin, preferably the olefin is butene, and/or [0085] iv) the stream (S2) comprises at least 99 wt-% of at least one alkane, preferably at least 99.5 wt-% of at least one alkane, most preferably at least 99.9 wt-% of at least one alkane, preferably the alkane is butane and/or [0086] v) the stream (S2) comprises ≦20-wt-ppm, preferably ≦5 wt-ppm, more preferably ≦1 wt-ppm of at least one compound containing oxygen and/or sulphur, and/or [0087] vi) the load of the adsorber (A1) with organic composition (OC1) in step a) is 10 to 100 t/h, preferably 30 to 80 t/h, more preferably 45 to 65 t/h and/or [0088] vii) the organic composition (OC1) is fed into the adsorber (A1) in step a) at a temperature of 25 to 40° C., and/or [0089] viii) the organic composition (OC1) is fed into the adsorber (A1) in step a) at a pressure of 5 to 8 bar.

[0090] Step c) of the process according to the present invention may comprise at least one of the following component steps c1) to c6): [0091] c1) converting stream (S2) from liquid into gaseous phase, [0092] c2) heating the adsorber by contact with the gaseous stream (S2), wherein the gaseous stream (S2) is condensed within the adsorber, [0093] c3) heating the adsorber by contact with the gaseous stream (S2) up to a temperature in the range of 230 to 270° C. without any condensation of the gaseous stream (S2) within the adsorber, [0094] c4) regeneration of the adsorber at a temperature in the range of 230 to 270° C. by contact with the gaseous stream (S2), [0095] c5) cooling of the adsorber by contact with the gaseous stream (S2) to a temperature in the range of 80° C. to 120° C., and/or [0096] c6) cooling of the adsorber by contact with the liquid stream (S2) obtained in step a) to a temperature below 80° C., preferably to a temperature in the range of 40 to 60° C.,

[0097] preferably step d) (as defined below) is carried out prior to step c) and step c) comprises the component steps c1), followed by c2), followed by c3), followed by c4), followed by c5) and followed by c6).

[0098] The conversion of liquid stream (S2) into gaseous phase in step c1) may be carried out by lowering the pressure and/or heating of the liquid stream (S2), preferably by employing at least one evaporator and/or at least one super-heater and/or at least one flash vessel.

[0099] In a preferred embodiment, liquid stream (S2), with a pressure of 5 to 80 bar, preferably of 10 to 50 bar, most preferably of 20 to 30 bar is, for the conversion according step c1), fed into a flash vessel, wherein the pressure of liquid stream (S2) is lowered to 4 to 16 bar, preferably to 7 to 13 bar, most preferably to 8 to 11 bar.

[0100] Lowering the pressure of liquid stream (S2), preferably in a flash vessel, compared to the pressure of liquid (S2) fed into the flash vessel, can result in conversion of at least a part of liquid stream (S2) into gaseous phase. Remaining liquid stream (S2) at lowered pressure may be converted into gaseous phase by use of at least one evaporator.

[0101] By lowering the pressure of liquid stream (S2), preferably in a flash vessel, compared to the pressure of liquid stream (S2) obtained in step a), 0 to 80%, preferably less than 10% of liquid stream (S2) may be converted into gaseous phase.

[0102] Alternatively, liquid stream (S2) may be converted into gaseous phase, preferably with at least one evaporator, without prior lowering the pressure.

[0103] Within the present invention, an evaporator is a device which converts a liquid stream into gaseous phase by transfer of heat to the liquid stream.

[0104] It is also possible to use two or more evaporators through which stream (S2) may flow in series and/or in parallel.

[0105] Any evaporator known to the person skilled in the art being appropriate for performing the evaporation may be applied.

[0106] Examples for evaporators are electric evaporators and evaporators transferring heat by means of a heat transfer medium, like steam (gaseous water) or other gaseous media, hydrocarbons, oils or salts. Preferably, the evaporators are of the Kettle type.

[0107] The conversion of liquid stream (S2) into gaseous phase according to step c1) may also comprise super-heating.

[0108] Super-heating, in the context of the present invention, means further increasing the temperature of the already gaseous stream (S2), preferably by transfer of heat to the gaseous stream (S2).

[0109] Any super-heater known to the person skilled in the art being appropriate for the super-heating may be applied.

[0110] Super-heating may be performed with one or more super-heaters. When more than one super-heater is used, the super-heaters can be arranged in series and/or in parallel.

[0111] Examples for possible super-heaters are electric super-heaters and super-heaters transferring heat by means of a heat transfer medium, suitable gaseous media, hydrocarbons, oils or salts. Preferably, super-heaters are of the shell-and-tube type.

[0112] Evaporating and super-heating may be performed in different devices and/or be combined in at least one device capable to fulfill both functions, for instance a shell-and-tube heat exchanger stacked on top of a Kettle-type evaporator.

[0113] If evaporators and/or super-heaters based on a heat transfer medium are used, the same stream of heat transfer medium may be passed through only one evaporator or super-heater or through more than one evaporator or super-heater. The same stream of heat transfer medium can be used for evaporators or super-heaters or for evaporators and super-heaters.

[0114] The same type of heat transfer medium can be applied for all evaporators and/or super-heaters or different types of heat transfer media for each individual device or a group of evaporators and/or super-heaters may be used.

[0115] Dependent on the temperature actually required at a given time of the process, the heat transfer to the liquid or gaseous stream (S2) by the respective evaporators and/or super-heaters may be reduced, stopped completely and/or one or any number of evaporators and/or one or any number of super-heaters may be by-passed by stream (S2).

[0116] Preferably gaseous stream (S2) is passed through all super-heaters and heat transfer is reduced or stopped when lower temperatures for gaseous stream (S2) are required.

[0117] Preferably evaporators and/or super-heaters are by-passed if liquid stream (S2) is required.

[0118] Condensation, meaning conversion from gaseous into liquid phase, of the components comprised in stream (S2) in step c), in particular in step c2), usually takes place if at least one spot, meaning spacial element, inside the adsorber, being the adsorbent and/or the adsorber wall, has a temperature, which is below the dew point temperature of the respective components comprised in gaseous stream (S2), present at that spot.

[0119] The pressure in the adsorber (A1) and/or (A2), being in regeneration mode, is usually defined by the pressure of stream (S2) in the respective adsorber.

[0120] In another embodiment of the invention, the condensate obtained in step c2) contains the stream (S2) and the residue of the organic composition (OC1) and/or (OC2) which was not removed from the adsorber (A2) when carrying out draining step d), and the condensate is optionally collected in a device, preferably in a buffer vessel, in order to pass the collected condensate through an adsorber during its operation mode.

[0121] An additional draining step d), prior to carrying out step c) may be carried out in order to at least partially remove an organic composition (OC1) and/or (OC2) which was passed through the second adsorber during its operation mode.

[0122] Preferably at least 10%, more preferably at least 30%, most preferably at least 40% of the organic composition (OC1) and/or (OC2) is removed from the adsorber in the draining step d).

[0123] Prior to step b), an additional step e) may be carried out, comprising: [0124] e) oligomerization of organic composition (OC2), wherein at least one of the olefins is at least partially oligomerized, obtaining an organic composition (OC3) comprising an reduced amount of at least one olefin and an increased amount of at least one oligomerized olefin compared to the respective amounts in (OC2), with use of (OC3) rather than (OC2) in the subsequent steps,

[0125] preferably the oligomerization is a dimerization and more preferably butene is at least partially dimerized to octene.

[0126] Oligomerization, within the present invention, is defined as a catalyzed chemical reaction, in which at least two olefins are connected to an oligomerized olefin, with a higher molecular weight than each of the at least two olefins connected, over a newly formed single bond and wherein at least one double bond of the at least two olefins, per newly formed connecting single bond in the oligomerized olefin, is transformed into a single bond.

[0127] If not more than two olefins per oligomerized olefin were connected, for this reaction the term dimerization may be used.

[0128] It is not differentiated between constitutional and stereoisomers of the oligomerized olefins.

[0129] Preferably the at least one oligomerized olefin has a higher molecular weight, than the at least one olefin from organic compositions originating from and/or being fed into steps preceding step b).

[0130] Preferably the at least one oligomerized olefin is octene.

[0131] Preferably at least 10 wt-%, more preferably at least 20 wt-% of the at least one olefin of (OC2) is oligomerized.

[0132] The oligomerization according to step e) may be carried out [0133] i) with a catalyst comprising 10 bis 70 wt.-% NiO, 5 to 30 wt.-% TiO.sub.2 and/or ZrO.sub.2, 0 to 20 wt.-% AlO, 20 to 40 wt.-% SiO.sub.2 and 0.01 to 1 wt.-% of an alkali metal oxide, preferably the catalyst comprises at least 50 wt.-% NiO and 0 wt.-% Al and/or [0134] ii) at a pressure of 10 to 300 bar, preferably 10 to 50 bar, most preferably at pressure of 10 to <30 bar and/or [0135] iii) at a temperature of 20 to 280° C., preferably at a temperature of 30 to 130° C. and/or [0136] iv) adiabatically, without additional measures taken for cooling by means of an heat exchange medium and/or [0137] v) in a fixed bed process.

[0138] The organic composition (OC3) preferably comprises octene.

[0139] Organic composition (OC3) preferably comprises at least one alkane.

[0140] Organic composition (OC3) preferably comprises at least 5 wt.-% of octene.

[0141] The organic composition (OC3) preferably comprises not more than 5 wt.-ppm of compounds containing oxygen and/or sulphur.

[0142] In a preferred embodiment of the invention, [0143] i) the oligomerization according to step b) is a dimerization and/or [0144] ii) the olefin in the organic composition (OC2) is butene, which is at least partially dimerized to octene.

[0145] Preferably at least 10 wt-%, more preferably at least 20 wt-%, of the butene in the organic composition (OC2) is dimerized to octene.

[0146] In a further embodiment of the invention step e) and f) (as defined below) are carried out more than one time during the process.

[0147] In this embodiment, the oligomerized olefins are separated from the organic composition obtained comprising the application of step f) after finishing a step according to step e). In the following step e), the corresponding organic composition obtained from the upper part of the distillation column in step f) is reused instead of (OC2). In the respective next step following the last, step b) is carried out, whereby the organic composition corresponding to (OC3) is applied.

[0148] Preferably step e), in the embodiment as specified in the preceding paragraph, is carried out at least three times.

[0149] Prior to step b) and after step e) an additional step f) may be carried out, comprising [0150] f) distillation of organic composition (OC3) in a distillation column (D1), wherein [0151] i) an organic composition (OC4) is obtained from the upper part of (D1) and (OC4) comprises at least one alkane, at least one olefin and an reduced amount of at least one oligomerized olefin compared to the respective amount in (OC3), with the use of (OC4) rather than (OC3) in the subsequent steps, [0152] ii) a stream (S3) is obtained from the lower part of (D1) and (S3) comprises at least 80% by weight, preferably at least 95% by weight of the at least one oligomerized olefin present in organic composition (OC3).

[0153] The organic composition (OC4) may comprise at least 20 wt-% alkane, preferably butane, and less than 5 wt.-% oligomerized olefin, preferably octene.

[0154] Any distillation column known to the person skilled in the art being appropriate for performing the distillation in step f) and/or step g) (as defined below) may be employed.

[0155] Prior to step b) an additional step g) may be carried out, comprising [0156] g) distillation of organic composition (OC2), or optionally of organic composition (OC3) or optionally of organic composition (OC4) in a distillation column (D2), wherein [0157] i) an organic composition (OC2a) is obtained from the upper part of (D2) and (OC2a) comprises at least one alkane and an reduced amount of at least one olefin compared to the respective amount in (OC2), (OC3) or (OC4), with use of (OC2a) rather than (OC2), (OC3) or (OC4) in the subsequent steps, [0158] ii) a stream (S4) is obtained from the lower part of (D2) and (S3) comprises at least 80% by weight, preferably at least 90% by weight of the olefins present in (OC2), (OC3) or (OC4),

[0159] preferably step e) is carried out prior to step f), step f) is followed by step g) and step g) is followed by step b).

[0160] In a preferred embodiment of the process according to the present invention, distillation column (D1) and/or distillation column (D2) serve the purpose of removing iso-butane and the respective organic composition fed into (D1) and/or (D2) comprises butane and/or butene.

[0161] Preferably distillation in step g) is carried out at temperatures at the upper part of distillation column (D2) ranging from 50 to 90° C., more preferably from 60 to 80° C. and most preferably from 65 to 75° C. and/or temperatures at the lower part of the distillation column (D2) ranging from 60 to 110° C., more preferably from 70 to 100° C. and most preferably from 80 to 90° C.

[0162] Preferably distillation in step g) is carried out at pressures at the lower part of distillation column (D2) from 8 to 15 bar, more preferably from 9 to 13 bar and most preferably from 10 to 12 bar. The pressure drop over the entire column can be, for example 0.1 to 0.5 bar.

[0163] Preferred columns employed as distillation column (D2) may be both packed columns and/or columns having built-in column trays (tray columns) and/or columns comprising both packing and trays, beds of packing elements in parts of the column and appropriate internals (steel plates) in other parts. Preferably the tray column comprises 40 to 150, more preferably 80 to 120 trays.

[0164] Preferably the distillation column (D2) comprises at least 5, more preferably at least 10 theoretical plates. Preferably the distillation column comprises a total number of theoretical plates from 10 to 100, more preferably from 20 to 100, most preferably from 30 to 100 and in a particular preferred embodiment 40 to 70.

[0165] In preferred embodiment, the distillation column (D2) is divided into a stripping section and an enrichment section; preferably the stripping section comprises 25 to 40 theoretical plates and the enrichment section comprises 15 to 30 theoretical plates.

[0166] Organic composition (OC2a) comprises preferably at least 96 wt-% butane and not more than 4 wt-% butane.

FIGURES

[0167] FIG. 1 illustrates certain aspects of the invention. For the sake of clarity not all applicable components and embodiments are drawn in one and/or all figures. Embodiments shown in different figures may be combined with each other and do not exclude the incorporation of further components within the limits of the disclosure of the specification.

[0168] FIG. 1 illustrates the most basic assembly of the present invention. Organic composition (OC1) is fed into adsorber (A1), run in operation mode, in order to obtain an organic composition (OC2) comprising at least one alkane, at least one olefin and a reduced amount of at least one compound containing oxygen and/or sulphur compared to the respective amount in organic composition (OC1). At least a part of the organic composition (OC2) is subsequently fed into the hydrogenation reactor (HR) and a stream (S2) is obtained, which is fed into adsorber (A2) run in regeneration mode. After a regeneration/purification cycle is finished, the adsorbers are operated in the respective other mode. Organic composition (OC1) is fed into an adsorber only in operation mode, while stream (S2) is fed only into an adsorber in regeneration mode.

[0169] FIG. 2 shows a further embodiment of the invention, wherein organic composition (OC2) is fed into a oligomerization reactor (OR1) to obtain a stream (OC3) comprising an reduced amount of at least one olefin and an increased amount of at least one oligomerized olefin compared to the respective amounts in (OC2). Organic composition (OC3) is fed into the hydrogenation reactor (HR) instead of organic composition (OC2).

[0170] FIG. 3 demonstrates that the organic composition (OC2) may be subjected to a distillation in a distillation column (D2) to obtain from the upper part of (D2) an organic composition (OC2a) comprising at least one alkane and a reduced amount of at least one olefin compared to organic composition (OC2) as well as from the lower part of (D2) a stream (S4) comprising at least 80% by weight, preferably at least 90% by weight of the olefins present in organic composition (OC2). Organic composition (OC2a) is fed into hydrogenation reactor (HR) instead of organic composition (OC2).

[0171] FIG. 4 illustrates an extension of the embodiment, shown in FIG. 2. Instead being fed into the hydrogenation reactor (HR), organic composition (OC3) is passed through distillation column (D1) to obtain from the upper part of (D1) an organic composition (OC4) comprising at least one alkane, at least one olefin and a reduced amount of at least one oligomerized olefin compared to the respective amount in (OC3) and (OC2). Besides (OC4), from the lower part of (D1) a stream (S3) is obtained comprising at least 80% by weight, preferably at least 95% by weight of the at least one oligomerized olefin present in organic composition (OC3). (OC4) is fed into distillation column (D2) yielding from the upper part of (D2) organic composition (OC2a) comprising at least one alkane and a reduced amount of at least one olefin compared to organic composition (OC2), (OC3) or (OC4) and from the lower part of (D2) a stream (S4) comprising at least 80% by weight, preferably at least 90% by weight of the olefins present in (OC2), (OC3) or (OC4).