Process for the production of butadiene

[0001] The invention relates to improved processes for producing butadiene

Processes for producing butadiene from C4 raw materials that contain a significant amount of isobutene and / or isobutane, and n-butene (s) and / or n-butane (s) are described.

Butadiene is produced by dehydrogenation of n-butenes, using oxidative dehydrogenation, after highly efficient separation of isobutene (plus optionally isobutane) from all n-butenes (plus optionally n-butane) by using a tower for a combination of butene isomerization and distillation. The process involves the conversion of 1-butene to 2-butenes in order to obtain a substantially complete separation of iso and normal compounds. Processes can be supplemented by additional isomerization and / or dehydrogenation steps for overhead and bottom tower product streams and additional raw material streams.

Background Art [0002] Butadiene is a universal raw material used in the production of many synthetic rubbers, polymer resins and chemical semi-finished products. The greatest use of butadiene is in the production of styrene1 butadiene rubber and polybutadiene rubber, which are mainly used for the production of tires. Butadiene is also one of the components used in the production of acrylonitrile - butadiene - styrene polymer, latex - styrene - butadiene copolymer, block - styrene - butadiene copolymers and nitrile rubbers.

[0003] There is an increasing demand for butadiene, caused by an increase in the demand for tires, as well as a reduction in the production of natural rubber. It is expected that the global consumption of butadiene will increase by an average of 2% per year.

[0004] The main source of butadiene is the by-product of steam cracking of petroleum and diesel oil to obtain ethylene and propylene. Steam cracking is a process in which hydrocarbon molecules are exposed to very high temperature steam, which breaks them down into smaller particles. Separation of butadiene from other products of this process usually involves extractive distillation.

[0005] Other potential sources for the production of butadiene include the processing of raw materials containing butene and butane compounds, and mixtures thereof. Isobutene is used to produce tert-butyl methyl ether (MTBE). However, the market for MTBE is decreasing, especially in the US. Therefore, a relatively large supply of isobutene appears. Streams of various four-carbon raw materials represent alternative substrates for butadiene production. Unfortunately, no industrial processes have been developed or developed leading to effective conversion and selectivity of butadiene from these raw materials, especially when they contain a significant amount of isobutene and / or isobutane.

[0006] Various butene isomerization processes are disclosed in US Patent Nos. US 3,531,545; 4,312,745; 5,157,194; and 6,743,958. The processes described in these patents relate to butene isomerization rather than butadiene production. In the article by Newman, "Process for butadiene manufacture by catalytic oxydehydrogenation of butenes", Journal of Industrial and Engineering Chemistry (1970), 42-47, a process using catalytic oxidative dehydrogenation of butenes was disclosed. U.S. Patent No. 3,764,632 discloses an oxidative dehydrogenation process where butane-1 or butane-2 is converted to butadiene in high yield using various oxide catalysts. US Patent No. US 7,488,858 discloses a process for producing butadiene from nbutane in a two-stage process, wherein the second stage is the oxidative dehydrogenation of butane to butadiene.

[0007] "Reverse" isomerization of isobutene to n-butenes is known from Japanese Patent Applications JP 2004-009136 and 2004-009138, and articles by Gon Seo et al., "The Reversible Skeletal Isomerization between n-Butenes and iso- Butene over Solid Acid Catalysts ”, Catalysis Today 44 (1998) 215-222, and Lucia M. Petkovic and Gustavo Larsen, "Linear Butenes from Isobutene over H-Ferrierite: In Situ Studies Using an Oscillating Balance Reactor", J. of Catalysis 191, 1-11 (2000). These processes are not directed at obtaining butadiene.

[0008] US Patent No. US 6,743,958 to Commereuc et al. discloses an integrated process comprising separate steps of: 1 / selective hydrogenation of butadiene with isomerization of 1-butene to 2-butenes; 2 / skeletal ("reverse") isomerization of isobutene to n-butenes, and 3 / metathesis of the fraction enriched in 2-butene with ethylene. US Patent No. US 5,157,194 to Rahmim et al. discloses a method of converting highly n-olefin hydrocarbon raw materials to products enriched in isoolefins using a catalytic composition containing the microcrystalline ZSM-22.

[0009] Japanese patent application JP 2004-009136 isomerizes isobutene to n-butenes using ferrierite or γ-alumina. Isomerization of isobutene to n-butenes using γ-alumina with the addition of water is known from Japanese Patent Application No. JP 2004-009138. U.S. Patents AP No. US 6,242,661 and US No. 6,849,773 to Podrebarac et al. describe the use of a combination of butene isomerization and tower distillation reactions to convert 1-butene to 2-butenes with fractionation to separate isobutene (and isobutane) from 2-butenes (and n-butane).

[0010] All of the above references are generally directed to isomerization reactions or the use of metathesis products. None of the references describes the dehydrogenation of compounds with four carbon (C4) atoms, such as n-butenes to butadiene.

[0011] In Hydrocarbon Processing, Nov. 1978, p. 131-136 by Petro Tex describes the oxidative dehydrogenation of n-butenes to butadiene. However, this heading does not describe isomerization of butene, "reverse" isomerization, or methods of reducing or eliminating the harmful effects of isobutene by removing it. In addition, this entry does not describe the transformation of undesirable isobutene into additional processable productive n-butenes and the achievement of additional production of butadiene by the addition of isobutene conversion. In addition, the oxidative dehydrogenation process described in this article is very expensive due to the use of very large amounts of steam to dilute the mixture and to limit the increase in reaction temperature in the adiabatic granular bed reactor.

[0012] In US Patent Nos. 3,668,147; 4,547,615; and 7,034,195 describes the general production of butadiene. US Patent No. US 7,034,195 to Schindler et al. discloses an integrated process for obtaining butadiene from n-butane by (1) feeding n-butane to the first dehydrogenation zone, autothermal (i.e. with some exothermic oxygen reaction, e.g. combustion, to balance thermal requirements, but not as a direct oxidation dehydrogenation reaction) conversion of nbutane into 1-butene, 2-butenes and optionally butadiene, (2) feeding the first gas stream to the second dehydrogenation zone, where oxidative processing of 1-butene and 2 takes place - butadiene butans.

[0013] US Patent No. US 4,547,615 to Yamamoto et al. describes the oxidative dehydrogenation of monoolefins to conjugated C4 + diolefins with a mixture of metal oxides with primary metals such as Mo, Bi, Cr, Ni, etc. US Patent No. US 3,668,147 to Yoshino et al. describes several reactions, including the production of butadiene with a mixture of metal oxides, primarily Fe / Sb / V or Mo or W / Te, etc.

[0014] The above references, however, do not describe industrial processes allowing the efficient and selective production of butadiene from four-carbon raw materials that contain significant amounts of isobutene and / or isobutane. The processes for producing butadiene from such raw materials must take into account, among other problems, the unnecessary presence of isobutene in the dehydrogenation step into butadiene, and the almost identical volatility of isobutene and 1-butene, which makes it essentially impossible to separate them by standard distillation. Of the four butene compounds (cis-2-butene, trans-2-butene, 1-butene and isobutene), isobutene does not significantly form butadiene by dehydrogenation, and during oxidative dehydrogenation it shows reactivity towards direct combustion and the formation of certain amounts of undesirable oxidized and other by-products. It also increases the oxygen consumption and deactivates the catalyst. Consequently, it is not recommended that a significant amount of isobutene be present in the dehydrogenation stream. When the content of isobutene in raw materials is significant, it should be separated from n-butenes and n-butane.

[0015] The complete separation of isobutene from all n-butenes by distillation is however very difficult. In particular, isobutene and 1-butene are considered to be "simultaneously boiling" because their boiling points of about - 6⁰C at atmospheric pressure, differ by less than 1 ⁰C.

The boiling point of 2-butenes is 1-4 ⁰C. Therefore, elimination

1-butene by isomerization to 2-butenes allows better separation of isobutene from n-butenes by distillation according to the processes according to the present invention.

[0016] In addition to the advantage of excluding isobutene from the feed stream directed to the nC4 dehydrogenation system, an additional benefit can be obtained by converting isobutene to n-butenes by "reverse" isomerization to supplement the feed to the nC4 dehydrogenation system. Isomerization of isobutene / n-butene has historically been directed towards the production of isobutene due to the demand for MTBE. Since n6 butenes are typically not marketed, there was little encouragement to study the "reverse" conversion of isobutene to n-butenes.

[0017] Isobutane also does not form butadiene by direct dehydrogenation, although it is not harmful because it does not react significantly to form undesirable by-products. On the other hand, an additional amount of butadiene can be obtained from isobutane if it is dehydrogenated to isobutene, which will then be subjected to the "reverse" isomerization described above to form an additional amount of n-butenes, possibly convertible into butadiene. According to the invention, a plant for the dehydrogenation of isobutane to isobutene can therefore be added for this purpose.

[0018] Another dehydrogenation unit for converting n-butane to n-butenes and some butadiene may also be added to the plant carrying out the complete process of the invention.

[0019] Although many industrial processes for the production of butadiene have been investigated, none of them feeds C4 feedstock with a significant proportion of isobutene and / or isobutane. Therefore, there is still an unmet need to develop an economical and efficient process for the industrial production of butadiene from such raw materials.

Summary of the Invention [0020] The invention relates to methods for producing butadiene according to claims 1 and 11. Optional or secondary features are defined in the dependent claims.

[0021] Isobutene removal is accomplished using a combination of butene isomerization and tower distillation reactions. During the isomerization reaction in the tower, 1-butene to 2-butenes are converted with the separation of isobutene from 2-butenes by fractionation. A certain amount of isobutane accompanies the isobutene in the tower overhead product, while n-butane is found in bottom effluent along with 2-butyrates. The conversion of 1-butene to 2-butenes prevents the passage of 1-butene to the overhead product, which allows it to be transferred in a productive form to the bottom effluent, where it is used to produce butadiene in the absence of isobutene. An example of combining butene isomerization and tower distillation reactions is the "CDdeIB®" system according to CDTECH, part of their CDHydro® Technologies, described in US Patent Nos. US 6,242,661 and 6,849,773, cited above. As catalyst for the isomerization reaction of n-butenes in the tower, preferably a catalyst containing 0.3 - 0.4% palladium on alumina is used.

[0022] The overhead product from the combination of butene isomerization and tower distillation reactions (CDdeIB®) mainly contains isobutene and / or isobutane together with only a small amount of n-butenes. The bottom product from the combination of butene isomerization and tower distillation mainly contains 2-butenes and some nbutane, with only a small amount of isobutene.

[0023] The bottom product is then fed to one or more dehydrogenation reactors to convert 2-butenes and, if necessary, nbutane to butadiene. An oxidative dehydrogenation system is used to convert n-butenes to butadiene. If the bottom product contains a significant amount of n-butane, or n-butane is supplied in a separate stream, an additional dehydrogenation plant can be added to convert it to n-butene by methods known in the art, such as (i) by dehydrogenation oxidative using the CATADIENE® process according to Lummus, (ii) by dehydrogenation processes, including oxidative "autothermal" dehydrogenation (in which oxygen is typically added to burn some compounds, e.g. a hydrocarbon or preferably hydrogen produced in a dehydrogenation reaction in an amount sufficient to generate heat to meet the heat requirements of the endothermic dehydrogenation reaction which is the principal reaction; or (iii) by its own dehydrogenation. In all these cases in connection with the present invention, the dehydrogenation of n-butane is used to produce primarily n-butenes, which are then used in final dehydrogenation plants to obtain butadiene. Therefore, there are two reaction stages from n-butane to n-butenes and to butadiene rather than a one-step transition directly from n-butane to butadiene. Depending on the amount of n-butane and other conditions, the n-butane dehydrogenation system may be located downstream of the n-butene oxidative dehydrogenation plant or upstream of the C4S effluent from the n-butene oxidative dehydrogenation plant after removal of butadiene and each of the recycle streams.

[0024] The CATADIENE® process can be carried out as a single reaction step in which a partial conversion of n-butane to n-butenes takes place, and a partial subsequent conversion to butadiene, wherein the effluents of n-butane and nbutene are recycled after separation of the butadiene product. However, due to the requirement of high recovery and total costs, it is more economical to use a two-stage system, even with CATADIENE®, and feed the n-butenes obtained in it to the oxidative dehydrogenation process of the invention.

[0025] As yet another option, and depending on the amount of n-butane and other factors, an additional dehydrogenation plant to convert n-butane to n-butenes or butadiene may be omitted as preceding this part of the butadiene production process.

[0026] The overhead product from the combination of butene isomerization and tower distillation mainly contains isobutene and optionally isobutane, and some "light" components. This product stream is fed to a "reverse" isomerization plant in which the isobutene is partially converted to nbuten, producing a mixed butene stream. This stream is directed back to the tower for a combination of butene isomerization and distillation reactions to convert the newly formed 1-butene to 2-butenes and recover all freshly formed 2-butenes in the product from the bottom of the tower, as described above. The conversion of isobutene and recycling of its products in this way increases the overall efficiency of the process and reduces or eliminates the rejection of isobutene distillate.

[0027] In the presence of a significant amount of isobutane, it enters the overhead product from the tower for a combination of butene isomerization and distillation reactions. In one solution, a dehydrogenation plant can be introduced to convert isobutane to isobutene by methods known to experts, e.g. by non-oxidative dehydrogenation using the CATOFIN® process according to Lummus, or other types of dehydrogenation processes. This increases the isobutane content of the tower top product, which can be taken away, if needed or transferred to a "reverse" isomerization installation, as described above, in which the isobutene is processed into n-butenes The obtained n-butene mixture can be fed to a combination of butene isomerization and tower distillation, where 1-butene is processed into 2-butenes, 2-butenes are recovered in the bottom product from the tower, and n-butenes are then converted to butadiene in an oxidative dehydrogenation plant for n-butenes.

[0028] As stated above, both the oxidative dehydrogenation plant for n-butenes, as well as the possibly used dehydrogenation plant for nbutane can use recycle streams. Furthermore, the recycle streams and / or the leachate stream from one plant can be fed to the other. Similarly, the recycle streams and / or the effluent stream from the dehydrogenation plant can be recycled to the tower for a combination of butene isomerization and distillation reactions.

[0029] Butadiene and other effluent compounds can be recovered separately from the effluent of each dehydrogenation plant, optionally common recovery systems are used. Depending on the composition of the leachate streams, they can be fed far in the production line, e.g. to the installation of butadiene extraction for the primary C4 stream from its source (steam cracking, fluidized catalytic cracking).

[0030] One of the advantages of the invention is the economical and efficient process configuration, using the minimum number of steps to obtain a high degree of conversion and selectivity of butadiene from the C4 raw material mixture, which contains a significant amount of isobutene and / or isobutane. This advantage is only shown in a few non-limiting examples, and the additional benefits and advantages will become apparent to experts from the description below.

Brief Description of the Drawings [0031] Figure 1 is a diagram illustrating one embodiment of the invention in which butadiene is produced by the oxidative dehydrogenation of n-butenes at the bottom of the tower for a combination of butene isomerization and distillation which is fed with a feed material in the form of a C4 olefin mixture containing a significant amount of isobutene as well as n-butene (s).

Figure 2 is a diagram illustrating another embodiment of the invention in which butadiene is produced by oxidative dehydrogenation of n-butenes at the bottom of the tower for a combination of butene isomerization and distillation which is fed with the material fed as a mixture of C4 olefins together with nbutane.

Figure 3 is a diagram illustrating another embodiment of the invention in which a separate stream of n-butane is fed to a dehydrogenation plant for the conversion of n-butanes to n-butenes. Alternatively, a separate nC4 stream may be fed first to the oxidation dehydrogenation plant for n-butenes, especially if it contains a significant amount of n-butenes.

Figure 4 is a diagram illustrating a solution according to the invention in which all or part of a second feed stream containing nbutenes is fed directly to an oxidative dehydrogenation plant.

Figure 5 is a diagram illustrating a further embodiment of the invention in which butadiene is produced by oxidative dehydrogenation of n-butenes at the bottom of the tower for a combination of butene isomerization and distillation which is fed with feed material containing both C4 olefin mixtures.

Detailed description of the invention [0032] The present invention relates to improved processes for the production of butadiene from C4 type raw material, which contains a significant amount of isobutene and / or isobutane, by oxidative dehydrogenation after prior separation of isobutene without loss of 1-butene, which is a valuable raw material. The feed stream with the content of the C4 olefin mixture is fed to the tower for a combination of butene isomerization and distillation reactions, where processing of 1-butene to 2-butenes and separation of isobutene from 2-butenes by distillation takes place.

[0033] Figure 1 illustrates one embodiment of the invention in which butadiene is produced from the feed stream of the C4 olefin mixture (10). The feed stream of the C4 olefin mixture generally contains isobutene, 1-butene and 2-butenes, in any proportions. Isobutene and 1-butene have very similar boiling points and are usually referred to as "simultaneously boiling." The boiling point for both of these compounds is about - 6⁰C at atmospheric pressure. Separating them only by distillation is very difficult. On the other hand, 2-butenes have a boiling point of about 1-4⁰C. To use this difference with respect to isobutene, 1-butene is isomerized to 2-butenes in a tower for a combination of butene isomerization and distillation (15), which allows separation of isobutene from all n-butenes by distillation and increases process efficiency and selectivity .

[0034] The feed stream (10) with the content of the C4 olefin mixture is fed to the tower for a combination of butene isomerization and distillation reactions (15), where the processing of 1-butene from the raw material stream to 2-butenes takes place. An example of a combination of butene isomerization and tower distillation is the CDdeIB® system according to CDTECH, part of their CDHydro® technology

Technologies. The 2-butenes in the mixture are separated from isobutene and 1-butene residues by distillation. The overhead product stream (12) from the tower for the combination of butene isomerization and distillation (15) contains essentially all of the isobutene from the feed stream, along with small amounts of n-butenes. Typically, the overhead product stream contains 5% or less by weight of nC4 compounds (n-butane plus n-butenes). The bottom product (22) from the tower for the combination of butene isomerization and distillation (15) contains essentially 2-butenes, and only small amounts of 1-butene or isobutene. Typically, the bottom stream contains 1% or less by weight of iC4S (isobutane plus isobuten) and 1-5% or less by weight of 1-butene.

[0035] The tower for the combination of butene isomerization and distillation (15) contains a catalyst. It can be selected from any of the catalysts known in the olefin isomerization industry. In some embodiments, the catalyst is Pd palladium. In a particular embodiment, 0.3 - 0.4% by weight of Pd on alumina is used.

[0036] Typically, the tower for the combination of butene isomerization and distillation (15) operates at a pressure between 344 and 758 kPa (50 and 100 psig). The overhead product stream leaves the tower for a combination of butene isomerization and distillation (15) at a temperature of 27 to 82⁰C (80 and 180 ⁰F), and the bottom stream from the tower for the combination of butene isomerization and tower distillation (15) has a temperature of 38 to 121 ⁰C (100 and 250 ⁰F). The heat for the distillation process can come from any source known to experts, such as the use of a reboiler.

[0037] The overhead product stream (12) is typically condensed in a deflaterator (17), and some is usually recycled to the tower for a combination of butene isomerization and distillation (15) as reflux (14) in a ratio of 0.5 to 33. If necessary, the net part of the peak stream (16), i.e. the overhead stream (12) reduced by the reflux stream (14), can be removed from the factory as waste, for storage or further processing, via a pipe (18). It should be understood that the conduit (18) may represent a single conduit or several different conduits, possibly of different composition.

[0038] Optionally, a portion of the net peak stream (20) can be further processed and recycled to the tower for a combination of butene isomerization and distillation (15). In this embodiment, a portion of the net peak stream is fed through a conduit (40) to the plant for "reverse" isomerization (45) to convert isobutene to n-butenes to form a stream of a mixture of C4 compounds. The installation for "reverse" isomerization can be of any type known to experts. Part or all of the product from the "reverse" isomerization plant (45) is fed through a conduit (44) back to the tower for a combination of butene isomerization and distillation (15). Optionally, part of the product from the installation for 'reverse' isomerization (45) may be given for other purposes via a conduit (46), which may represent several conduits for different purposes, and part of the effluent from the installation for 'reverse' isomerization (45) may be recycled through the pipe (42) to the feed stream (42) to the installation for "reverse" isomerization.

[0039] A portion of the bottom product stream (22) from the tower for the combination of butene isomerization and tower distillation (15), containing 2-butenes, is typically reheated in a reboiler heat exchanger (21) and fed (24) back to the tower . Part of the net bottom stream ((bottom stream (22) minus the part recycled to the tower (24)) can be removed from the factory for storage or further processing (26). Part or all of the net stream from below is fed through a conduit (70) to the charge (72) for the oxidative dehydrogenation plant (75) to convert 2-butenes to butadiene. The oxidative dehydrogenation plant (75) can be of any type known to experts for the conversion of olefins to dienes.

[0040] The oxidative dehydrogenation plant (75) comprises a catalyst. Any catalyst can be used to convert olefins to dienes. Particularly suitable catalysts for the oxidative dehydrogenation of n-butenes to 1,3-butadiene are generally based on Mo-Bi oxide blend systems. Their preparation is described, for example, in US Patent AP: US 3,911,039 (Mo12BiFe3Co4,5Ni2,5Sn0,5K0,1Ox),

US 4,424,141 (Mo12BiFe3Co4,5Ni2,5P0,5K0,1Ox),

US 4,547,615 (Mo12BiFe0,1Ni8ZrCr3K0,2Ox),

US 7,034,195 (Mo12Bi0,6Fe3Co7Cr0,5Si1,6K0.08Ox),

US 4,423,281 (Mo12BiCr3Ni8Li2Pb0,5Ox), and

US 4,336,409 (Mo12BiCr3Ni6P0,5Cd2FeOx). Preferred catalyst systems for the process of the invention are described, for example, in US Patent Nos. US 3,911,039 (Mo12BiFe3Co4,5Ni2,5Sn0,5K0,1Ox) and US 7,034,195 (Mo12Bi0,6Fe3Co7Cr0,5Si1,6K0,00Ox).

[0041] The oxidative dehydrogenation plant (75) preferably operates at a pressure of 0 to 689 kPa (0 to 100 psig), and at a temperature of 288 to 454 ⁰C (550 to 850 ⁰F). The butadiene obtained in the oxidative dehydrogenation plant (75) is separated from other effluent components by methods known to experts, e.g. by extractive distillation. Any nbutene residue and other compounds that can be used for recycling, e.g. n-butane and other non-reactive paraffins as reaction diluents can be recycled to the oxidative dehydrogenation plant (75). Nbutene residues can be recycled via the conduit (74) to connect to the charge to the oxidation dehydrogenation plant (75) in the feed stream (72), or via the conduit (78) to connect to the feed stream to the tower for a combination of isomerization and distillation reactions (15) . By-products and unreacted compounds, etc. they are removed from the system through a drain line (80), which may be one or several lines, possibly with different compositions. Recycling through the conduit (78) to the tower for a combination of isomerization and distillation reactions (15), instead of to or in addition to the conduit (74), can be another route to remove iC4 and lighter compounds that could accompany the desired recycle components. If both (74) and (78) are used, they may contain streams of different compositions. The butadiene product is fed through a conduit (82) for storage or further processing.

[0042] In another embodiment of the invention shown in Fig. 2, butadiene is produced from the feed stream (10) containing n-butane together with the C4 olefin mixture. The feed stream may also contain isobutane. The input stream (10) is fed to the tower for a combination of isomerization and distillation reactions (15), of the type described above. Butene-1 from the input stream is processed to 2-butenes in an isomerization reaction on a catalyst inside the tower. The overhead product stream (12) from the combination of isomerization and distillation reactions (15) contains essentially all isobutene from the input stream plus isobutene from other sources, and only small n-butenes and n-butane. Typically, the overhead product contains% or less by weight of C 4 (n-butane plus n-butenes). The bottom product (22) from the tower for the combination of isomerization and distillation reactions (15) consists essentially of 2-butenes and n-butane, with only small amounts of 1-butene or isobutene. Typically, the bottom tower product contains 1% or less by weight of iC4 (isobutene plus isobutene), and 1-5% or less by weight of 1-butene.

[0043] Part of the overhead stream is usually recycled to the tower for the combination of isomerization and distillation reactions (15) as return (14). Part of the net peak stream (16), i.e. the peak stream (12) minus the return stream (14), can be discharged from the factory as waste, to a warehouse or for further processing via a pipe (18).

Optionally, all or part of the net overhead stream (20) can be further processed and recycled to the tower for a combination of isomerization and distillation reactions (15) as described above, as follows. Part of the net peak stream (20) to be recycled is fed through a conduit (40) to the "reverse" isomerization plant (45) to convert isobutene to n-butenes. Part or all of the product from the "reverse" isomerization plant (45) can be fed via a conduit (44) back to the tower for a combination of isomerization and distillation reactions (15). If desired, part of the product from the "reverse" isomerization plant can be directed to other applications via the conduit (46), and part of the effluent from the "reverse" isomerization plant (45) can be recycled to the input stream (40) to the " reverse "isomerization through the conduit (42).

[0044] The bottom product (22) from the tower for the combination of isomerization and distillation reactions (15) contains 2-butenes and n-butane. Part of this product is typically heated in a reboiler exchanger (21) and fed back to the tower (15) via a pipe (24). Part of the product from below can be taken away from the factory for storage or further processing via a pipe (26). Part or all of the product from the bottom of the net can be fed through a conduit (50) to the charge (54) for the first dehydrogenation plant (55), which partially converts n-butane to n-butenes. Optionally, the dehydrogenation plant (55) can be configured to also process nbutenes to butadiene. The first dehydrogenation plant (55) may contain a CATADIENE ® reactor. In this case, its product would normally contain a significant amount of butadiene, but the CATADIENE® installation can be run under conditions that maximize the formation of n-butenes and minimize the formation of butadiene. In this mode of operation, you can call it CATOFIN ® installation, or keep the name of the (slow) CATADIENE ® installation. At least some of the n-butenes obtained in the n-butane dehydrogenation reactor (55) are fed via a conduit (54) to the oxidation dehydrogenation reactor (75) of the type described above, where the n-butenes are converted to butadiene.

[0045] The butadiene obtained in the first dehydrogenation plant (55) can be separated and fed through a conduit (60) to the butadiene product conduit (84). Hydrogen can also be separated and removed as a byproduct through the conduit (62) for external or internal use. Water can be condensed, separated and removed through a pipe (62). Some n-butenes can be removed by (62) if it is needed for a purpose other than conversion to butadiene. It should be understood that the conduit (62) may represent a single conduit or several different conduits. with possibly different stream compositions, for removing certain products, by-products or unreacted input components. Residues of n-butane and other compounds can be separated and recycled via a conduit (56) to the first dehydrogenation plant (55). Alternatively or additionally, a portion of the remaining n-butane can be recycled by connecting it to the input stream (10) to the tower for a combination of isomerization and distillation reactions (15) via the conduit (58), especially when there are some iC4 compounds or lighter to be removed this way . In another embodiment, a portion of the remaining nbutane is fed through a conduit (64), together with or separately from nbutenes, to a second oxidative dehydrogenation plant (75).

[0046] In a further embodiment, part or all of the effluent from the first oxidative dehydrogenation plant can be fed, without separating the by-products and n-butane, as described above, directly via a conduit (64) to the second oxidative dehydrogenation plant (75) if it is preferable to separate them between these installations. As an additional option, both methods can be used. This means that a portion of the entire effluent from the first oxidative dehydrogenation plant can be fed directly through the conduit (64) to the second oxidative dehydrogenation plant, while the other part can be separated before the n-butenes from this part are also fed by conduit (64) to the second oxidative dehydrogenation plant (75).

[0047] In the above-described solutions, in the first oxidative dehydrogenation plant (55), the dehydrogenation of n-butane from the bottom tower product to n-butenes takes place, while in the second oxidative dehydrogenation (n-butenes) plant (75), n- butenes to butadiene by oxidative dehydrogenation. In other process solutions shown in Fig. 2 which are especially useful when there is a significant amount of n-butenes in the bottom product from the tower, the order described above is reversed, and at least part of the bottom product from the tower for the combination of isomerization and distillation reactions (15) is fed through a conduit (70) to dehydrogenate first the n-butenes in the first oxidative dehydrogenation plant (55), and then sending the n-butane part of the effluent from the oxidation dehydrogenation plant of n-butenes (75) through the conduit (76) for the dehydrogenation plant of the n-butane (55) and / or optionally via the conduit (78) to the tower for a combination of isomerization and distillation reactions (15). In this solution, the feed (72) for the oxidative dehydrogenation plant of n-butenes (75) is a combination of a direct bottom product from the tower for a combination of isomerisation and distillation reactions (15) fed through a conduit (70) with nbutene streams (64) from the dehydrogenation plant n-butane (55). The total input to the oxidative dehydrogenation plant of n-butenes (75) may also contain return (74) from its own effluent.

[0048] Alternatively, the first part of the bottom product from the tower for the combination of isomerization reactions and the distillation tower (15) can be fed through a conduit (50) for the dehydrogenation plant of n-butane (55), and the second part of the bottom product from the tower for the combination of isomerization reactions and distillation (15) can be fed through a conduit (70) to the oxidative dehydrogenation plant for n-butenes (75). [0049] In yet another embodiment (not shown in Fig. 2, but with the same configuration as shown in fig. 1), the n-butane dehydrogenation plant (55) and the production of butadiene corresponding to the conversion of n-butane content can be completely omitted, and only the n-butene oxidative dehydrogenation plant (75) can be used to process n-butenes to butadiene, while n-butane is removed via a conduit (80).

[0050] Although not shown in Fig. 2, separation of butadiene in the effluent from the two dehydrogenation plants (55) and (75) can be done in a common butadiene separation system (e.g. extraction). If desired, one or more return streams or leachate can be fed much earlier, e.g. to a butadiene extraction plant for the primary stream C4 from its source (steam cracking, fluidized catalytic cracking).

[0051] In another embodiment of the invention, shown in Fig. 3, the first feed stream (10) containing the C4 olefin mixture is fed to the tower for a combination of isomerization and distillation reactions (15) of the type described above, and the second feed stream (52), containing n-butane and substantially free of isobutene, is fed through pipe (54) for nbutane dehydrogenation installation (55). As described above, in the tower for the combination of isomerization and distillation reactions (15), 1-butene from the first feed stream is converted into 2-butenes. The 2-butenes in the mixture are separated from isobutene and the remaining 1-butene by distillation. The overhead product (12) from the isomerization and distillation reaction combination tower (15) contains essentially all isobutene, plus all isobutene from the first feed stream, with only small amounts of n-butenes. The overhead product is cooled in a radiator (12). The bottom product (22) from the isomerisation and distillation combination tower (15) contains essentially 2-butenes, plus all the n-butane that may be present in the first feed stream, with only a small amount of 1-butene or isobutene.

[0052] Part of the overhead product stream (12) is usually recycled to the tower for a combination of isomerization and distillation reactions (15) as return (14). Part of the net peak product may be removed from the factory through the pipe (s) (18) as waste, for storage or further treatment. Optionally, all or part of the net overhead product stream (20) may be further processed and recycled to the tower for a combination of isomerization and distillation reactions (15) as described above, as follows. The portion of the net peak product to be recycled is fed through a conduit (40) to the 'reverse' isomerization plant (45) to convert isobutene to n-butenes. Part or all of the product from the "reverse" isomerization plant (45) is fed through a conduit (44) back to the tower for a combination of isomerization and distillation reactions (15). Some or all of the product may be transferred for other purposes (46), and some of the effluent from the "reverse" isomerization (45) may be recycled (42) to the installation via the supply line (40).

[0053] The bottom product (22) from the tower for the combination of isomerization and distillation reactions (15) contains 2-butenes and all of the n-butane present. Part of the product from below is usually heated in a reboiler heat exchanger (21) and fed back to the tower (15) via a pipe (24). Part of the product from below can be removed from the factory (26) for storage or further processing. Part or all of the net product from the bottom of the tower for the combination of isomerization and distillation reactions (15) can be fed through the conduit (70) to the oxidative dehydrogenation plant (75) to convert 2-butenes to butadiene.

[0054] The second feed stream (52), containing n-butanes, can be fed through a conduit (54) to the first dehydrogenation plant (55), in which the partial conversion of n-butane to n-butenes takes place. Optionally, the first dehydrogenation plant (55) can be configured so that the conversion of n-butenes to butadiene also takes place there. The first dehydrogenation plant (55) may contain a CATADIENE ® reactor. In this case, its product would normally contain a significant amount of butadiene, but the CATADIENE® installation can be run under conditions that maximize the formation of n-butenes and minimize the formation of butadiene. In this mode of operation, it can be considered as a CATOFIN ® installation or the name of the (slow) CATADIENE ® installation can be maintained.

At least a portion of the product obtained in the nbutane dehydrogenation plant (55) is fed through the conduit (64), together with the product (70) net from the bottom of the plant for the combination of the isomerization reaction and distillation tower (15), in the total stream (72) to the reactor oxidative dehydrogenation (75), where n-butenes are converted to butadiene.

[0055] Drains from the dehydrogenation plant (55) and (75) may undergo alternative treatment processes as described above for the solutions shown in Fig. 2. The butadiene obtained in the first dehydrogenation plant (55) can be separated and fed through a conduit (60) to the butadiene product conduit (84). Hydrogen can also be separated and removed as a byproduct through the conduit (62) for external or internal use. Water can be condensed, separated and removed through a pipe (62). Some n-butenes can be removed (62) if it is needed for a purpose other than conversion to butadiene. It should be understood that the conduit (62) may represent a single conduit or several different conduits, possibly with different stream compositions, for removing n-butenes, by-products or unreacted input components. Residues of n-butane and other compounds can be separated and recycled via a conduit (56) to the first dehydrogenation plant (55). Alternatively or additionally, part of the remaining n-butane can be recycled by attaching it to the input stream (10) to the tower for the combination of the isomerization reaction and the distillation tower (15) through the conduit (58). In another embodiment, a portion of the remaining n-butane is fed through a conduit (64), together or separately from the n-butenes, to a second oxidative dehydrogenation plant (75).

[0056] In a further embodiment, part or all of the effluent from the first oxidative dehydrogenation plant can be fed, without separating the by-products and n-butane, as described above, directly via a conduit (64) to the second oxidative dehydrogenation plant (75) if it is preferable to separate them between these installations. As an additional option, both methods can be used. This means that part of the entire effluent from the first oxidative dehydrogenation plant can be fed directly through the conduit (64) to the second dehydrogenation plant (75), while the second part can be separated before the n-butenes from this part are also given through a conduit (64) to a second oxidative dehydrogenation plant (75).

[0057] In the above-described solutions, in the first oxidative dehydrogenation plant (55), the dehydrogenation of n-butane from the second feed stream (52) to n-butenes takes place, while in the second oxidative dehydrogenation (n-butenes) plant (75) conversion of n25 butenes to butadiene by oxidative dehydrogenation. In other process solutions shown in Fig. 4 which are especially useful when there is a significant amount of n-butenes in the second supply stream (52), the order described above is reversed, and at least part of the product of the second feed stream (52) is fed through a conduit (53) to a feed conduit (72) for an oxidative dehydrogenation plant (75) to dehydrogenate n-butenes from the stream (52) in an oxidative dehydrogenation plant (75) . and then the n-butane part of the effluent from the oxidation dehydrogenation plant of n-butenes (75) is sent through a conduit (76) to the n-butane dehydrogenation plant (55), as described above. In this solution, the feed to the installation for the oxidative dehydrogenation of n-butenes (75) can be a combination of a direct bottom product from the tower for a combination of isomerization and distillation reactions (15) fed through the conduit (70) with all or part of the second feed stream (52), as well as with n-butene streams (64) from the n-butane dehydrogenation plant (55). The total feed (72) for the oxidative dehydrogenation plant of n-butenes (75) may also contain return (74) from its own effluent as described above.

[0058] Alternatively, the first portion of the second feed stream (52) may be fed through a conduit (54) for the dehydrogenation plant of n-butane (55), and the second part of the second feed stream (52) may be fed through the conduit (72) to the installation Oxidative dehydrogenation of n-butenes (75). These two parts can have different compositions and can be considered as the second and third feed stream.

[0059] In yet another embodiment (not shown), the n-butane dehydrogenation plant (55) and the production of butadiene corresponding to the conversion of n-butane content can be completely omitted, and only the oxidative dehydrogenation plant of n-butenes (75) can be used for processing n-butenes to butadiene, the second feed stream (52) being fed directly to the oxidative dehydrogenation plant for n-butenes (75).

[0060] As described above, the separation of butadiene in the effluent from two dehydrogenation plants (55) and (75) can be done in a common butadiene separation system (e.g. extraction). If desired, one or more return streams or leachate can be fed much earlier, e.g. to a butadiene extraction plant for the primary stream C4 from its source (steam cracking, fluidized catalytic cracking).

[0061] In another embodiment of the invention, shown in Fig. 5, butadiene is produced from feed material containing both the butene mixture and the butane mixture. The feed stream with the C4 mixture is fed through a conduit (10) to a tower for a combination of isomerization and distillation reactions (15), where 1-butene is converted to 2-butenes, and isobutane and isobutene are separated from n-butane and 2-butenes. The part of the overhead product stream (12) containing isobutane and isobutene is typically recycled to the tower for the combination of isomerization and distillation reactions (15) as return (14) after cooling in the cooler (17). Part of the peak net stream (16), i.e. the peak stream (12) minus the return stream (14), can be removed from the factory as waste, for storage or further processing (18).

[0062] Optionally, all or part of the net overhead product stream (20) can be further processed and recycled to the tower for a combination of isomerization and distillation reactions (15). In this solution, both isobutane and isobutene in the net peak product stream are processed into compounds that can be converted to butadiene, and recycled by feeding through a conduit (30) a portion of the net peak stream (20) to a dehydrogenation plant such as like CATOFIN ®, which converts isobutane to isobutene. Part of the product from the dehydrogenation plant (35) can be discharged (32) and the other part can be recycled through the pipe (34) to the inlet (30) of the isobutane dehydrogenation plant (35). It should be understood that the conduit (32) may represent a single conduit or several different conduits, with possibly different stream compositions, for removing some products, by-products or unreacted feed components. [0063] At least a portion of the product (36) from the dehydrogenation plant (35) containing a significantly larger amount of isobutene is fed through a conduit (40) to the plant for "reverse" isomerization (45) in which the conversion of isobutene to n-butenes takes place. Part or all of the product from the "reverse" isomerization plant (45) is fed through a conduit (44) back to the tower for a combination of isomerization and distillation reactions (15). Part may be transferred to other applications (46), and part of the effluent from the "reverse" isomerization (45) may be returned (42) back to the system via the supply line (40).

[0064] The bottom tower product for the combination of isomerization and distillation reactions (15) contains 2-butenes and n-butane. It may alternatively be subjected to any of the processes described above. Also, the second (or third) feed stream (52) containing n-butane and / or n-butenes, and substantially free of isobutene, can be fed directly to the nbutane (55) dehydrogenation plant or the n-butene oxidative dehydrogenation plant (75) ), as described above for figure 3, using one of the alternative processes described above.

[0065] In a different embodiment, not forming part of the invention but using the process kit as shown in Fig. 5, feed stream (10) containing only a mixture of C4 paraffins (i.e. without significant content C4 =) is fed to the tower for a combination of isomerization and distillation reactions (15), where isobutane is separated from n-butane. Part of the overhead product stream (12) is typically recycled to the tower for a combination of isomerization and distillation reactions (15) as return (14) after cooling in the cooler (17). Part of the peak net stream (16), i.e. the peak stream (12) minus the return stream (14), can be removed from the factory as waste, for storage or further processing (18). In this solution, at least part of the net peak product (20) is converted into compounds that can be converted to butadiene and recycled to the tower for a combination of isomerization and distillation reactions (15). Part of the net peak product (20) is fed through a conduit (30) to a dehydrogenation plant (35) such as CATOFIN®, which converts isobutane to isobutene. At least a portion of the product (36) from the dehydrogenation plant (35), containing a significantly higher amount of isobutene, is fed through the conduit (40) to the "reverse" isomerization plant (45), in which the conversion of isobutene to nbutene takes place. At least a portion of the product from the "reverse" isomerization plant (45) is fed through a conduit (44) back to the tower for a combination of isomerization and distillation reactions (15). Since stream (44) now contains some isobutene, as well as n-butenes and some isobutane, the tower for the combination of isomerization and distillation reactions (15) works with a mixture of both mixed butanes and mixed butenes, as in previous solutions, and can be subjected to any alternative process solution from those described above.

[0066] The bottom tower product for the combination of isomerization and distillation reactions (15) contains 2-butenes and n-butane. It may alternatively be subjected to any of the processes described above.

[0067] The expert will recognize that many variations or changes can be made to the process described without departing from the scope of the invention. Therefore, the purpose of the above description of preferred solutions is to present the invention by way of example and not for the purpose of limitation.

[0068] Furthermore, when amounts, concentrations, or other values ​​or parameters are given either as a range, preferred range or list of upper preferred values ​​and lower preferred values, they should be understood as specific disclosure of all ranges formed from any pair of upper range boundaries or preferred values, either from any pair of lower ranges or preferred values, regardless of which ranges are disclosed separately. Unless otherwise specified, the purpose of this specification is to include extreme values, and any numbers or fractions in this range. The values ​​given are not intended to limit the scope of the invention to the values ​​specified when defining the range.