MXPA97005174A - Procedure for the obtaining of debuted oligomers from ac butanos - Google Patents

Abstract

The present invention relates to a process for the preparation of butene oligomers from field butanes, characterized in that (a) in a dehydrogenation step the n- and iso-butanes contained in the field butanes are dehydrogenated and (b) ) the dehydrogenation mixture is oligomerized in an oligomerization step

Description

PROCEDURE FOR THE OBTAINING OF BUTYAN OLIGOMERS FROM FIELD BUTANES \ The invention relates to a process for the preparation of butene oligomers, which are valuable starting substances for softening alcohols, from field butanes. The preferred butene oligomers are isomeric octenes, which are dimethyl butenes and which, therefore, are also called dibutenes. A dibutene of particular demand is di-n-butene. Therefore, the invention also relates to a process in which di-n-butene is removed from dibutene. Finally, the invention relates to a process which, in addition to higher oligomers of butene, results in an exclusively di-n-butene as dibutene. Dibutene is an isomeric mixture that is formed, in addition to higher oligomers of butene, by the dimerization and / or co-dimerization of butenes, that is, of n-butene and / or isobutene, in the oligomerization of butenes. Di-n-butene is referred to as the product of the dimerization of n-butene, ie, 1-butene and / or 2-butene. The basic components of di-n-butene are 3-methyl-2-heptene, 3, 4-dimeti1-2-hexene and, to a lesser extent, n-octenes. Di-iso-butene is the isomeric mixture obtained by the dimerization of iso-butene. Di-iso-butene contains more branched molecules than dibutene, and this, in turn, is more branched than di-n-butene.

Dibutene, di-n-butene and di-isobutene are starting materials for the preparation of isomeric nonanols by hydroformylation and hydrogenation of the Cg aldehydes obtained in this way. The esters of these nonanoles, particularly the phthalic acid ester, are softeners that are produced in significant volumes and are used mainly for polyvinyl chloride. The di-n-butene nonanoles are, to a greater extent, straight chain than the nanoanes of dibutene, which, in turn, are less branched than the nonanoles of di-iso-butene. The esters of di-n-butene nonanoles, due to their structure to a greater extent of straight chain, have advantages of technical application with respect to the esters of other nonanoles based on dibutene and di-iso-butene and are particularly demanded . Butenes can be obtained for the dimerization, for example, of cutting C4 of thermal decomposers by steam or FC decomposers. In general, it is processed by first dissociating 1,3-butadiene by selective washing, for example with N-methylpyrrolidone. Iso-butene is a desired and particularly valuable component of C4 cutting, since it can be chemically transformed to desired products, for example with iso-butane to high octane isooctane or with methanol to methyl tertiary butyl ether (MTBE), which Gasoline additive improves its octane rating. After the reaction of the iso-butene, the n-butenes remain, as well as n- and iso-butane. The part of the n-butenes in the products of the dissociation of the steam thermal decomposer or of the decomposer FC is, however, proportionally low, namely in the range of about 10% by weight, based on the main target product, ethylene . A steam thermal decomposer with the respectable capacity of 600,000 t / year of ethylene therefore provides only about 60,000 t / year of n-butenes. It could increase its amount (and that of the iso-butenes), dehydrogenating about 15'000 t / year of n- and iso-butane, which are produced in addition to the n-butenes. However, it is not recommended, since dehydrogenation facilities require high investment costs and, for such a small capacity, they are not profitable. As mentioned, iso-butene is a decomposition product with a high demand and, therefore, it is not usually available for oligomerization. The amount of n-butenes produced directly by a steam thermal decomposer or an FC decomposer is not enough to produce enough dibutene for a nonanol facility, whose capacity is so great that it could compete economically with the large existing facilities for the production of softening alcohols. important, as 2-ethylhexanol. Therefore, n-butenes from various thermal decomposers should be collected by steam or FC decomposers and oligoed together to meet the need for dibutenes from a large nonanol facility. But there is the objection that the transport of liquefied gases is expensive, not ultimately because of the expensive security measures required. Therefore, it would be desirable to be able to make available butenes in a single place without transport for long distances, in the amounts necessary for the oligomerization, as required for the operation of a large facility for the production of nonanoles, for example, with a capacity from 200'000 to 800'000 t / year. It would also be desirable to have a process for obtaining butene oligomers in which the valuable di-n-butene can be separated from the dibutene. Finally, it would be desirable if the process could be controlled in such a way that, in addition to the higher butene oligomers, only di-n-butene or di-iso-butene is obtained as dibutene. The method according to the invention is illustrated in more detail by means of the block diagram of the attached figure, in which the variants A, B, C and D described below are shown in more detail, with their obligatory and optional steps. Field butane 1 is assigned as flow to variants A, B and C, alternative flow ib belongs to variants D and E.

According to the above, the invention is a process for the preparation of butene oligomers from field butanes, in which (a) in a dehydrogenation step 2, the n- and iso-butanes contained in the butanes are dehydrogenated. field butans 1 and (b) the dehydrogenation mixture 1 is oligomerized in an oligomerization step 8 to an oligomerization mixture 9. In the following, this process is referred to as variant A. In a preferred embodiment, hereinafter referred to as variant B, from the oligomers 11 remaining after the separation of the residual gases 12 from the oligomerization mixture 9, the dibutene 14 is separated. From the dibutene 14, in another preferred embodiment, hereinafter referred to as variant C, di-n-butene can be separated. 17. In addition, in another preferred embodiment, hereinafter referred to as variant D, the process is controlled in such a way that, in addition to higher butene oligomers, di-n-butene is formed exclusively, separating n-butane 22 by fractional distillation of the butane field 1, if necessary previously hydrogenated, isomerizing the remaining iso-butane 23 in an isomerization step 24 to a mixture of n-butane and iso-butane, separating the n-butane by fractionated tilation of the isomerization mixture 25 and bringing it together with the n-butane 22 separated directly from the butane field 1, to the dehydrogenation step 2 and realizing the remaining iso-butane 23 to the isomerization stage 24. Finally, in a Variant E the process can be controlled in such a way that, in addition to higher oligomers of butene, di-iso-butene is formed exclusively, separating iso-butane 22a by fractional distillation of field butane 1, if necessary hydrogenated isomerizing the remaining n-butane 23a in an isomerization step 24 to a mixture of n-butane and iso-butane, separating the iso-butane by fractional distillation, from the isomerization mixture 25 and bringing it together with the iso-butane 22a separated directly from the field butane 1, to the dehydrogenation step 2 and feeding the remaining n-butane 23a to the isomerization stage 24. The process according to 1 invention with its variant s A to E is characterized by high flexibility. According to the needs of the market, it is therefore possible, if desired, to obtain exclusively di-n-butene, dibutene, di-n-butene and other dikenes together or exclusively di-iso-butene, even when the latter will seldom be the desired main product. As field butanes, it is called the C4 fraction of the "wet" parts of the natural gas as well as the gases that accompany the oil, which, by cooling to approximately -30 ° C, are separated from the gases in liquid form. By distillation at low temperatures, butanes are obtained from them, whose composition varies depending on the place, but which, in general, contain approx. 30% iso-butane and 65% n-butane. Other components are, usually, approx. 2% hydrocarbons with less than 4 carbon atoms and approx. 3% hydrocarbons with more than 4 carbon atoms. The field butanes, without dissociation, can be used as a matter in thermal decomposers by steam or as additives for gasoline. They can be dissociated by fractional distillation in n-butane and iso-butane. Iso-butane is used, for example, in important amounts for the production of propylene oxide by co-oxidation of propylene and iso-butane, and as an alkylating agent, with which n-butene is alkylated, or else, iso- butene to iso-octane, which, due to its high octane rating, can be seen as an additive for gasoline. In contrast, n-butane found less significant applications. It serves, for example, as butane gas for heating purposes or, in comparatively small quantities, it is used for the preparation of polymers or copolymers or of anhydrous maleic acid by atmospheric oxidation. Previously, n-butane, through the n-butene stage, was also dehydrogenated to 1,3-butadiene, but now this process is no longer profitable. As iso-butane is the most desired component of field butane, n-butane is isomerized on a large scale to iso-butane (see, for example, RA Pogliano et al., Dehydrogenation-Based Ether Production, 1996 Petrochemical Review, De itt & Company, Houston Texas, Butamer procedure, page 6; as well as S.T. Baas, F. Nierlich et al., Production of Ethers from Field Butanes and Refinery Streams, AIChE Summer Meeting, 1990, San Diego, California, page 11). Therefore, it was not part of the technique's tendency to develop a procedure that had as objective, in variants A, B and C and even directly, the use of n-butane in the field gas, from which they produce, through the intermediate di-n-butene stage, the preferred nonanoles. It goes even against the trend of the technique when, in variant D, the iso-butane normally so demanded is isomerized to n-butane.

Variant A The field butanes are first dehydrogenated in the dehydrogenation step 2. Dehydrogenation is a co-dehydrogenation. It is noteworthy that the dehydrogenation of field butanes, which are a mixture of components with different dehydrogenation behavior, is achieved so well. The process conditions correspond to a large extent to those known for n- and iso-butane or other lower hydrocarbons. So, S.T. Bakas, F. Nierlich et al., Loe. cit., pages 12 et seq., describe the Oleflex process, which is generally suitable for the production of light olefins and with which, for example, it is possible to dehydrogenate isobutane with a selectivity of 91 to 93% to iso- buteno Other related publications are those of G.C. Sturtevant et al., Oleflex - Selective Production of Light Olefins, 1988 UOP Technology Conference, as well as EP 0 149 698. Conveniently, dehydrogenation is carried out in the gas phase in solidified or fluidized catalysts, for example chromium oxide (III) ) or, advantageously, in platinum catalysts with aluminum oxide or zeolites as carriers. The dehydrogenation generally takes place at temperatures of 400 to 800 ° C, advantageously 550 to 650 ° C. Work is usually carried out at atmospheric pressure or at slightly elevated pressure up to 3 bar. The residence time in the catalytic layer is, depending on the catalyst, the temperature and degree of reaction desired, in general between 1 and 60 minutes. The flow is correspondingly, usually, between 0.6 and 36 kg 3 of butane field per m catalyst and hour. It is convenient to carry out the dehydrogenation only until the dehydrogenation mixture 3 remains unchanged approx. 50% of the n- and iso-butane. At higher temperatures higher degrees of reaction could be achieved. However, decomposition reactions that lower the yield and, due to the deposit of coke, reduce the life of the dehydrogenation catalyst take place to a greater extent. The optimum combination of the reaction conditions leading to the desired degree of reaction, such as catalyst type, temperature and residence time, can be easily determined by orientation tests. The dehydrogenation mixture 3 usually contains 90 to 95% by weight of C4 hydrocarbons and also hydrogen, as well as low and high boiling portions, which come partly from field butane 1 and partly were formed in the dehydrogenation step. 2. It is conveniently cleaned before oligomerization. In a first cleaning step (not shown in the figure) fraction C and high boiling portions are condensed. The condensate is distilled under pressure, with hydrocarbons of less than 4 dissolved carbon atoms condensed first. Of the bottom residue, the C4 hydrocarbons are obtained as the main product in another distillation and the comparatively small amount of hydrocarbons with more than 4 carbon atoms as the residue. The C4 hydrocarbons generally contain, according to the degree of transformation, small amounts, for example 0.01 to 5% by volume, of 1,3-butadiene. It is advisable to remove this component, because even in clearly smaller amounts, it can damage the oligomerization catalyst. A suitable process is the selective hydrogenation 4, which, in addition, raises the part of the desired n-butene. A suitable procedure has been described, for example, by F. Nierlich et al. In Erdol & Kohle, Erdgas, Petrochemie, 1986, pages 73 et seq. It is carried out in the liquid phase with hydrogen completely dissolved in stoichiometric amounts. Suitable hydrogenation catalysts are, for example, nickel and particularly palladium on a carrier, for example 0.3% by weight of palladium on activated carbon or, preferably, on aluminum oxide. A small amount of carbon monoxide in the ppm range promotes the hydrogenation selectivity of the 1, 3-butadiene to monoolefin and causes the formation of polymers, contrary to the so-called "green oil", which deactivate the catalyst. The process generally works at room temperature or at an elevated temperature up to about 60 ° C. and under high pressures, which move conveniently in the range of up to 20 bar. The 1,3-butadiene content in the C4 cut of the dehydrogenation mixture is thus reduced to values of less than 1 ppm. It is also convenient, before the oligomerization step through the cleaning step 6, to bring fraction C of the dehydrogenation mixture 5 almost completely liberated from 1,3-butadiene to a molecular sieve in which other substances are removed harmful to the oligomerization catalyst, thereby increasing its life even more. Among these harmful substances are compounds of oxygen and sulfur. This procedure has been described by F. Nierlich et al. In EP-Bl 0 395 857. A molecular sieve with a pore diameter of 4 to 15 Angstrom, advantageously 7 to 13 Angstrom, is conveniently employed. In some cases it is convenient for industrial reasons to run the dehydrogenation mixture consecutively by molecular sieves of various pore sizes. The process can be carried out in the gaseous, liquid or liquid-gas phase. According to the above, the pressure is generally 1 to 200 bar. It is conveniently worked at room temperature or at elevated temperatures until 2002C. The chemical nature of molecular sieves is less important than their physical constitution, that is, in particular the size of the pores. It is therefore possible to use the most diverse molecular sieves, both crystalline and natural aluminum silicates, for example sheet silicates in layers, as well as synthetic molecular sieves, for example those with zeolite structure. Zeolites of type A, X and Y can be obtained, inter alia, from Bayer AG, Dow Chemical Co., Union Carbide Corporation, Laporte Industries Ltd. and Mobil Oil Co. For the process, those molecular sieves are also suitable. they contain in addition to aluminum and silicon also other atoms incorporated by exchange of cations, such as gallium, indium or lanthanum, as well as nickel, cobalt, copper, zinc or silver. Also suitable are zeolites in which, in addition to aluminum and silicon, other atoms, such as boron or phosphorus, were incorporated into the grid by mixed precipitation. As already stated, the selective hydrogenation stage 4 and the cleaning step 6 with a molecular sieve are optional, advantageous measures for the process according to the invention. In principle, its sequence can be any, but the sequence shown in the figure is preferred. The dehydrogenation mixture 7, if appropriate treated in the manner described, is carried to the oligomerization step 8, which is an essential part of the process according to the invention. Oligomerization is a co-oligomerization of n-butenes and iso-butenes that is carried out in a manner known per se, for example, F. Nierlich has described in Oligomerization for Better Gasoline, Hydrocarbon Processing, 1992, pages 45 et seq. , or F. Nierlich et al. in the aforementioned EP-Bl 0 395 857. Work is generally carried out in the liquid phase and, for example, a system composed of nickel octoate (II), sodium chloride, and the like is used as a homogeneous catalyst. ethylaluminum and a free fatty acid (DE-PS 28 55 423), or one of the numerous known catalysts, arranged solid or suspended in the oligomerization mixture, based on nickel and silicon is preferably used. The catalysts often contain additional aluminum. Thus, DD-PS 160 037 discloses obtaining a precipitation catalyst containing nickel and aluminum on silicon oxide as a carrier material. Other usable catalysts are obtained by exchanging the positively charged particles located on the surface of the carrier materials, like protons or sodium ions, by nickel ions. The above is achieved with the most diverse carrier materials, such as aluminum amorphous silicate (R. Espinoza et al., Appl. Kat., 31 (1987), pages 259-266.; crystalline aluminum silicate (DE-PS 20 29 624); zeolites of the type ZSM (NL-PS 8 500 459); a zeolite X (DE-PS 23 47 235); X and Y zeolites (A. Barth et al., Z. Anorg, Allg. Chem. 521, (1985), pages 207-214); and a mordenite (EP-A 0 233 302). The co-oligomerization is conveniently carried out, according to the catalyst, at 20 to 2002 C and under pressures of 1 to 100 bar. The reaction time (or contact time) is generally 5 to 60 minutes. The parameters of the process, in particular the type of catalyst, the temperature and the contact time, are coordinated in such a way that the desired degree of oligomerization is achieved. In the case of nonanoles as the desired target product, it is primarily a dimerization. For this, of course, the reaction can not be carried out in its entire volume, but convenient transformations of 30 to 70% per shift are sought. Optimal combinations of the process parameters can be determined without difficulty by orientation tests. From the oligomerization mixture 9, the waste gas 12 is separated in the separation stage 10 and fed back to the dehydrogenation stage 2. If a catalyst of the type of the aforementioned liquid catalysts was used in the oligomerization stage 8, the gas was used. Residual 12 must be cleaned beforehand to protect the dehydrogenation catalyst. The oligomerization mixture is first treated with water to extract the catalyst components. The separated waste gas 12 is then dried with a suitable molecular sieve, other secondary components also being separated. The variously unsaturated compounds, such as budes, are then removed by selective hydrogenation, for example with palladium catalysts, and, finally, the waste gas 12 thus cleaned is brought to dehydrogenation stage 2. These measures for cleaning the gas residual 12 are not necessary if a solid oligomerization catalyst is used. The oligomers 11 that remain after removing the waste gas 12, are suitable for their branched components as an additive for gasoline to improve their octane.

Variant B In the distillation step 13, the oligomers 11 are separated into dibutenes 14, as well as trimers 15, that is, isomeric dodecenes and even higher oligomers, the main fraction of the desired dibutenes 14 being composed. The dodecenes 15 can be hydroformylated, the hydroformylation products can be hydrogenated and the tridecanols thus obtained can be oxethylated, whereby valuable raw washing materials are obtained. The dibutenes 14 are directly suitable as starting material for the preparation of nonanol.

Variant C When the special characteristics of the nonanoles from di-n-butene are important, the dibutenes 14 are separated in the stage of fine distillation 16 in di-n-butene 17 and the rest of the dibutenes 18, as molecules more branched, easier boiling, which can also be used to obtain nonanoles or add to gasoline. This procedure is a better alternative to the variant in which, from the co-hydrogenation mixture 7, by distillation, n- and iso-butene are separated and these isomers are oligomerized separately. This variant would require two separate oligomerization steps, which would be much more expensive and also more complicated in the operation than only a co-oligomerization stage 8, although higher, in conjunction with a fine distillation stage 16.

Variant D This variant is chosen when it is desired to obtain exclusively di-n-butene as dibutene. If the Ib butane contains olefinically unsaturated components, it is advantageously brought first to a hydrogenation step 19, because these components can be a problem later for the isomerization of the iso-butane. The hydrogenation is carried out in a manner known per se, as, for example, they describe K.H. Walter and colleagues in The Hüls Process for Selective Hydrogenation of Butadiene in Crude C4 * s, Development and Technical Application, DGKM-Tagung, Kassel, November 1993. Therefore, the liquid phase is conveniently worked and, depending on the catalyst, a ambient temperature or elevated temperature up to 90ac and under a pressure of 4 to 20 bar, the partial pressure of hydrogen being from 1 to 15 bar. The usual catalysts are used for the hydrogenation of olefins, for example, 0.3% palladium on aluminum oxide. The hydrogenated field butanes are brought to the separation stage 21. This is basically composed of an active column, in which n-butane 22 and iso-butane 23 are fractionated by distillation. The column is operated in the usual manner, conveniently under a pressure of 4 to 7 bar. The hydrocarbons having more than 4 carbon atoms remain as bottom residue, the n-butane 22 is sucked into the side stream and taken together with the waste gas 12 to dehydrogenation 2, and the boiling isobutane 23 at 2ose lower, together with lighter ends, to the isomerization stage 24, in which iso-butane is converted into maximum n-butane up to an equilibrium, which, according to the temperature, is between 40 to 55% of n-butane and 45 to 60% iso-butane. The isomerization of n- and iso-butane is a known reaction, although usually with the aim of obtaining iso-butane (see, for example, HW Grote, Oil and Gas Journal, 56 (13), pages 73 et seq. (1958)). In general, the gas phase is worked, suitably at a temperature of 150 to 230 ° C, under a pressure of 14 to 30 bar and with a platinum catalyst on aluminum oxide as a carrier, whose selectivity can be further improved by providing it with a chlorine compound, such as hydrocarbon tetrachlor. Advantageously, a small amount of hydrogen is added to counteract a dehydrogenation. The selectivity of the isomerization of n-butane is high, the decomposition to smaller fractions only takes place in insignificant amounts (approximately 2%). The isomerization mixture should be separated into the isomers. The above is conveniently carried out in column 21 of itself existing, from which n-butane reaches the dehydrogenation step 2, which, unlike the variants A, B and C, is not a dehydrogenation step. In the rest of the development, variant D corresponds to the other variants. In the oligomerization step 8 a co-oligomerization takes place again, since the n-butene of the dehydrogenation step 2 is a mixture of 1-butene and 2-butene. The fine distillation step 16 can be eliminated, since the dibutene 14 is already di-n-butene.

Variant E This variant is chosen when, exceptionally, only di-iso-butene is desired as dibutene. The arrangement of variant D is then used, but the iso-butane 22a of column 21 is brought into dehydrogenation step 2, where, again, as in variant D and unlike variants A, B and C , no co-dehydrogenation takes place. The n-butane 23a is taken from the column 21 to the isomerization stage 24 and there is isomerized to maximum iso-butane until equilibrium. This is separated from n-butane, again conveniently carried to column 21 and also to dehydrogenation step 2, while n-butane returns to the isomerization stage 24. In this way n-butane is completely transformed in iso-butane. The dehydrogenation mixture 3 is conveniently cleaned, as described in variant A. The oligomerization in the oligomerization step 8 is a homooligomerization, as only iso-butane is involved, and di-iso-butene is produced in the distillation step 13. . The fine distillation is also eliminated 16.

Claims (10)

NOVELTY OF THE INVENTION Having described the foregoing invention, the content of the following is claimed as property: CLAIMS

1. A process for obtaining butene oligomers from field butanes, characterized in that (a) in a dehydrogenation step the n- and iso-butanes contained in the field butanes are dehydrogenated and (b) the dehydrogenation mixture is oligomerized in an oligomerization step.

2. A process according to claim 1, characterized in that, between the dehydrogenation step and the oligomerization step, a selective hydrogenation step and / or a molecular sieve cleaning step is arranged in any sequence.

A process according to one of claims 1 or 2, characterized in that the waste gas is separated from the oligomerization mixture and fed back, if necessary after cleaning, to the dehydrogenation step.

4. A process according to claim 3, characterized in that the dibutene is separated from the remaining oligomers after removing the residual gas.

5. A process according to claim 4, characterized in that the dibutenes are separated in a step of fine distillation in di-n-butenes and remaining dibutenes.

6. A process according to one of claims 1 to 3, characterized in that di-n-butene is obtained exclusively, separating the n-butane by fractional distillation of the butane from the field, if necessary hydrogenated, isomerizing the remaining iso-butane. in a step of isomerization to a mixture of n-butane and iso-butane, separating the n-butane by fractional distillation, from the isomerization mixture and bringing it together with the n-butane separated directly from the field butane, to the step of dehydrogenation and re-feeding the remaining iso-butane to the isomerization stage.

7. A process according to one of claims 3, characterized in that di-iso-butene is obtained exclusively, separating the iso-butane by fractional distillation of the field butane, if necessary hydrogenated and bringing it to the dehydrogenation stage, isomerizing the remaining n-butane in an isomerization stage to a mixture of n-butane and iso-butane, separating the iso-butane by fractional distillation, from the isomerization mixture and bringing it together with the isobutane separated directly from the field butane, to the dehydrogenation step and re-feeding the remaining n-butane to the isomerization stage.

8. The use of the dibutenes, the di-n-butenes, the remaining dibutenes or the di-iso-butenes according to claims 4, 5 and 7 for the preparation of nonanoles, by hydroformylation and subsequent hydrogenation.

9. The use of the remaining dibutenes, di-n-butenes or dibutenes according to claims 4 and 5 for the preparation of nonanic acids, by hydroformylation and subsequent oxidation.

10. The use of dodecenes for obtaining raw materials for washing, by hydroformylation, hydrogenation of hydroformylation products and oxethylation of hydrogenation products.