MXPA00005351A - Process for separating linear internal olefins from branched internal olefins - Google Patents

Abstract

A process for separating linear internal olefins from branched internal olefins. There is provided a process for converting a feedstock of linear internal olefins and branched internal olefins to a primarily linear internal olefin composition having a lower concentration of branched internal olefins than present in the feedstock, by:a) contacting the feedstock with a linear polyaromatic, optionally substituted, compound under conditions effective to form a linear polyaromatic compound-linear internal olefin adduct;b) separating the linear polyaromatic compound-linear internal olefin adduct from the reaction mixture;c) dissociating the linear polyaromatic compound-linear internal olefin adduct to form linear polyaromatic compound and a linear internal olefin composition;and optionally d) separating the linear polyaromatic compound formed in step c) from a linear internal olefin composition.

Description

PROCESS FOR THE SEPARATION OF INTERNAL LINEAR OLEFINS FROM BRANCHED INTERNAL OLEFINS FIELD OF THE INVENTION. The present invention relates to a process for separating linear internal olefins from branched internal olefins.

BACKGROUND OF THE INVENTION. Many industrial processes produce olefins which are mixtures of linear internal olefins and branched alpha olefins. Olefins are often used in the manufacture of polymers or as drilling mud additives, or as intermediates for the production of oil additives and detergents. According to each particular application, the manufacture of a linear internal olefin composition having the highest possible purity can be considered convenient. For example, detergents made from linear internal olefins are more biodegradable than detergents derived from many streams of olefins manufactured in the form of REF: 120403 industrial containing branched internal olefins. While on the one hand pure linear internal olefin species with a limited number of carbon atoms can be manufactured or produced in small quantities at a high cost, it was found that it would be especially advisable to economically provide large quantities of purified linear internal olefins of raw material presenting a mixture of linear internal olefins and branched internal olefins. Separating and isolating linear internal olefins from branched internal olefins is not an easy task, especially when these species have similar or identical molecular weights or numbers of carbon atoms. Conventional distillation methods are unsuitable for separating species of this type that have boiling points so closely related. The problem of separation is further aggravated since linear internal olefin species not only need to be separated from the branched internal olefins, but also from everything that is present in the mixture of basic material, such as, for example, saturated hydrocarbons. US Pat. No. 4,946,560 described a process for the separation of internal olefins from alpha olefins by contacting a basic material with anthracene to form an olefin adduct, separating the adduct from the basic material, dissociating the anthracene adduct. linear alpha olefin through heat to produce anthracene and an olefin composition enriched in alpha olefin, and separating anthracene from alpha olefin. However, it was found convenient to produce an olefin stream that is rich in linear internal olefins.

BRIEF DESCRIPTION OF THE INVENTION The present invention relates to a process for separating linear internal olefins from branched internal olefins. In particular, a process is provided for converting a basic material, comprising linear internal olefins and branched internal olefins to a lower concentration of branched internal olefins than is present in the basic material, the process comprises: a) it is placed in contacting the basic material with a linear polyaromatic compound, optionally substituted, under conditions effective to form an adduct of linear polyaromatic compound - linear internal olefin; b) the linear polyaromatic linear olefin-linear adduct, and optionally also the unreacted linear polyaromatic compound, is removed from the reaction mixture; c) the linear polyaromatic compound-linear internal define adduct is dissociated to form a linear polyaromatic compound and a linear internal olefin composition, and optionally, d) the linear polyaromatic compound formed in step c) of the composition is separated of linear internal olefin.

DETAILED DESCRIPTION OF THE INVENTION A linear internal olefin (s) is an olefin whose double bond is found anywhere along the carbon chain except at the terminal carbon atom. The linear internal olefin does not have any alkyl, aryl or alicyclic branching on any of the double-bonded carbon atoms or on any of the carbon atoms adjacent to the double-bonded carbon atoms. A branched internal olefin (s) is an olefin whose double bond is located anywhere along the carbon chain except at the terminal carbon atom. As used in the present invention, branched internal effine possesses one or more alkyls, aryls or alicyclic branches on one or more double bonding carbon atoms or on any carbon atom adjacent to a double bonding carbon atom. The olefins of basic material used in the process of the present invention comprise linear internal olefins and branched internal olefins. The basic material may optionally contain other types of olefins, aromatics, paraffins, and oxygenates. In general, the basic matter is produced by commercial processes such as the oligomerization of ethylene, followed by isomerization and molecular disproportionation. Otherwise, the basic material can be produced by the Fischer-Tropsch process, which commonly contains a significant amount of branched species as well as paraffins, aromatics, alcohols, ketones, acids, and other impurities. Another process for the production of internal olefins is the dimerization or oligomerization of propylene and higher olefins by means of conventional organometallic dimerization catalysts or molecular sieves such as ZSM or SAPO zeolites. The amount of branched internal olefins, linear internal olefins, and other optional ingredients present in the basic material is not particularly limited. In fact, the basic material can contain such a small amount of internal olefins as 1% by weight and up to 95% of internal olefins, based on the weight of all the ingredients of the basic material. However, the process of the present invention is particularly suitable for an industrial-scale production of a linear internal olefin stream. Accordingly, in a preferred embodiment of the present invention, the basic material to be treated according to the process of the present invention contains at least 50% by weight of internal defines and up to 95% by weight of internal olefins. In general, the basic material will contain from 5% by weight to 95% by weight of the linear internal olefins, but preferably from 25% by weight to 80% by weight of the linear internal olefins, based on the weight of all the ingredients of the basic matter. Often, the amount in particular will vary with the method of manufacturing the basic material, such as, for example, by oligomerization of the olefins or by the Fischer-Tropsch process. The amount of branched internal olefin in the basic material is generally between 1% by weight and 95% by weight based on the weight of the basic material stream, the amounts of which vary from 20% by weight to 75% by weight. weight, which are more common and more adequate to justify in economic terms, the separation procedure and obtain the desired product. Other ingredients that may be present in the basic material are alpha olefins, aromatics, paraffins, and oxygenates. Since the linear polyaromatic compound preferably forms an adduct with alpha olefins, which therefore interfere with the formation of a linear polyaromatic linear olefin-linear olefin adduct, it is preferred that the feed stream contains only minor amounts of alpha-olefin, such as example less than 5% by weight of alpha olefins, and more preferably 2% by weight or less, more preferably 0.5% by weight or less. In addition to the high olefins, the other ingredients may be present in the raw material in amounts ranging from 0 wt% to 50 wt%, based on the weight of the basic material. Commonly, the feed olefins will have an average number of carbon atoms ranging from 4 to 22, more preferably from about 6 to about 18. The physical properties required by the end use of the olefins, determine in part the quantities of suitable carbon atoms that must be isolated. The effins with numbers of carbon atoms greater than 22 and less than 6, can be used in the process of the present invention, but from a commercially practical point of view, the basic materials with amounts of carbon atoms varying between 6 and 18. , will be frequently used as such, as intermediates for derivatives, or oligomerized, for use in the field of detergents, plasticizers, lubricants to work the metal, and well drilling fluids.

The linear polyaromatic compound is used in the process of the present invention to form the adduct with the alpha olefins in the feed stream. Without being limited by theory, it is considered that the linear polyaromatic compound preferably forms an adduct with the linear internal olefins and, to a lesser extent, with the branched internal olefins. The preferential adduction of a linear polyaromatic compound to the linear internal olefin over the branched internal olefins may be due to the steric hindrance and / or the electronic effects of these latter olefins in a Diels-Alder reaction. As used in the present invention, the term "linear polyaromatic compound" refers to a linear polyaromatic compound having at least three molten aromatic rings, which may or may not be substituted and have similar adducing properties to those of the unsubstituted molecule, and mixtures thereof. Linearity should be extended to all three fused rings if a compound of three fused rings and at least four cyclic rings fused consecutively is used if a compound of four or more fused rings is used. The linear polyaromatic compound also refers to mixtures of compounds containing as one of its ingredients, the linear polyaromatic compound, including but not limited to, coal tars, anthracene oil, and any mixture of crude contain different fractions of naphthalene. The linear polyaromatic compound also includes the aromatic molecules linked together by means of a bridging group, such as for example a hydrocarbon chain, an ether linkage, or a ketone group containing a chain; as well as those containing a heteroatom that does not interfere with the separation of linear internal olefins from branched internal olefins. Non-limiting examples of the linear polyaromatic compound include anthracene, 2,3-benzanthracene, pentacene, and hexacene. Among the suitable examples of substituent atoms on linear substituted polyaromatic compounds, but without the enumeration being exhaustive, there is the lower alkyl, for example, methyl, ethyl, butyl; halo, for example, chlorine, bromine, fluorine; nitro; sulfate; sulfonyloxy; carboxyl; carbo-lower alkoxy, eg, carbomethoxy, carbethoxy; Not me; mono- and dialkylamino lower, for example, methylamino, dimethylamino, methylethylamino; amido; hydroxy; cyano; lower alkoxy, for example, methoxy; ethoxy; interior alkyanoyloxy, for example, acteoxy; monocyclic aryls, for example, phenyl, xylyl, toluyl, benzyl, etc. The special size of the substituent atoms, their quantity and their location, should be selected from those which are relatively inert under the reaction conditions and relatively small to avoid the steric hindrance of the Diels-Alder adduct formation. Linear polyaromatic compounds suitably substituted can be determined by means of routine experimentation. Examples of suitable linear polyaromatic compounds are 9,10-dimethylanthracene, 9,1-dichloroanthracene, 9-methylanthracene, 9-acetylanthracene. , 9- (methylaminomethyl) anthracene, 2-chloroanthracene, 2-ethyl-9, 10-dimethoxyanthracene, anthrarobin, and 9-anthryltrifluomethyl ketone. The preferred linear polyaromatic compounds are anthracene and 2,3-benzanthracene. The process of the present invention is basically a process consisting of three steps wherein (a) a linear polyaromatic compound is reacted with a basic material containing branched and linear internal olefins to form an adduct, (b) the adduct is separated of the reaction mixture, and (c) the adduct is dissociated to release the olefin and regenerate the linear polyaromatic compound. The reaction that forms the Diels-Alder adduct is carried out in a conventional manner and in a reaction zone. An example of a suitable reaction zone is a continuous stirred tank reactor where the olefin and the linear polyaromatic compound are added continuously in the stirring tank, the reaction mixture is continuously removed from the agitation tank. Otherwise, the reaction can be carried out in a batch reactor, where the olefin and the linear polyaromatic compound are loaded in an autoclave which is then heated to a reaction temperature sufficient to complete the reaction. Commonly, the reaction is carried out at temperatures ranging between 150 ° C and 290 ° C, preferably between 200 ° C and 280 ° C, and more preferably between 240 ° C and 265 ° C. The pressures are not decisive and commonly vary between atmospheric, approximately, and 10,000 kPa, approximately. The reaction can be carried out in the gaseous stage under the liquid stage or under vacuum or mixed gaseous-liquid stage, according to the volatility of the feed olefins, but generally in the liquid stage. The stoichiometric proportions or an excess of olefin or linear polyaromatic compound can be used in the formation of adducts, but a molar excess of olefin is preferred. The molar ratio of the olefin to the linear polyaromatic compound is greater than 0.5: 1 to 10: 1, more preferably 1.5: 1 to 7: 1. An inert solvent can be used to dissolve the feed olefins or the linear polyaromatic compound or both in the reactor. The preferred solvents are hydrocarbon solvents which are liquid at reaction temperatures and in which the olefins, the linear polyaromatic compound and the linear polyaromatic-olefin compound adducts are soluble. Illustrative examples of useful solvents include alkanes, such as pentane, iso-pentane, hexane, heptane, octane, nonane, etc.; cycloalkanes such as, for example, cyclopentane, cyclohexane, etc .; and aromatics such as benzene, toluene, ethylbenzene, diethylbenzene, etc. The amount of solvent to be used can vary widely without producing a deleterious effect on the reaction. However, in one embodiment of the present invention, the formation of the basic material and the adduct of linear linear polyaromatic-linear olefin compound is carried out in the absence of a solvent. It has been found that the absence of solvent does not significantly affect the amount of linear polyaromatic compound regenerated under equivalent reaction conditions, and that the concentration of linear internal olefins generated is substantially the same. Thus, in a preferred embodiment, the process of the present invention is carried out in the absence of solvent. After the formation of an adduct of linear polyaromatic-olefin compound, it is separated from the reaction mixture. The linear polyaromatic linear olefin-linear olefin adduct is separated from the reaction mixture by conventional means. Due to the high molecular weight and the structural difference between the linear polyaromatic compound - linear internal olefin adduct and the excess of the reaction mixture, conventional separation techniques are well suited for removing unreacted olefins from the polyaromatic compound adduct linear - linear internal olefin. For example, olefins that have not reacted can be removed from the top or in fractions by flash distillation or vacuum of the reaction mixture to leave the adduct of linear polyaromatic compound-linear internal olefin and the linear polyaromatic compound that did not react as liquid waste. Other non-reactive compounds can be distilled from the reaction mixture, such as unreacted olefins as well as paraffins, aromatics, alcohols, ketones, acids, and other impurities. Otherwise, the linear polyaromatic linear olefin-linear olefin adduct is separated by cooling the reaction mixture until the adduct is crystallized, followed by filtration or centrifugation to remove unreacted olefin. In most cases, the unreacted linear polyaromatic compound is separated with the linear polyaromatic linear olefin-linear olefin adduct. The rest of the reaction mixture can be used in other processes or applications since it will have an enriched internal olefin content above that of the basic material. The next step of the process of the present invention is the dissociation of the linear polyaromatic linear olefin-linear olefin adduct. The dissociation process can be completed by heating or pyrolyzing the linear polyaromatic compound-linear internal olefin compound recovered at a temperature of 250 ° C to 400 ° C, preferably 300 ° C to 350 ° C. This pyrolysis releases the linear internal olefins of the linear polyaromatic compound. Then, the linear polyaromatic compound is separated from the resulting mixture by conventional means, which can be carried out simultaneously with the pyrolysis operation, such as for example the vacuum or flash distillation of the linear internal olefins together with any other impurity pyrolysis temperatures, and removal of the linear polyaromatic compound as a residue from the dissociation zone of the adduct. Among other separation techniques, filtration and centrifugation are found. The linear polyaromatic compound can be recycled back into the reaction zone of the adduct. The separate linear internal olefin composition is enriched in the content of linear internal olefin over that of the basic material, and the concentration of branched internal olefins in the linear internal olefin composition is reduced over that of the basic material. While on the one hand most branched internal olefins will have separated from linear internal olefins, a small amount of branched internal olefins may be present in the linear internal olefin composition, together with other impurities. For many applications, the amount of branched internal olefins in the linear internal olefin composition after one pass through the process of the present invention is sufficiently small that only one pass through the process is necessary. However, if preferred, the linear internal olefin composition can be subjected to multiple passes through the additional reaction zone and the adduct dissociation reactors fed by the linear internal olefin composition produced in the previous pass, for further reduce the branched internal olefin content and further improve the linear internal olefin content. In a preferred embodiment, the method of the present invention is repeated more than once, more preferably, 2-4 times. The amount of branched internal olefins in the linear internal olefin composition is less than 3% by weight after subjecting the basic material to the process of the present invention. Preferably, the amount of branched internal olefins in the linear internal olefin composition is 2.5% by weight or less, more preferably 2.0% by weight or less, more preferably 1.5% by weight or less. With multiple passes, the content of branched internal olefins can be reduced in the linear internal olefin composition to 1.0 wt% or less, preferably up to 0.7 wt% or less, more preferably up to 0.5 wt% or less. The present invention will now be illustrated by means of the following examples and illustrative embodiments.

EXAMPLE To illustrate the concept of the present invention, several samples of internal olefins of six carbon atoms having different compositions were used as the basic material. Table 1 below establishes the composition of each sample of basic material. They were loaded in a Parr autoclave of 100 ml, purged three times with nitrogen and sealed, 0.054 moles of anthracene (samples 1-5), 0.022 moles of 2,3-benzanthracene (sample 6) or 0.022 moles of 1,2-benzanthracene (sample 7, to compare). The autoclave was placed in a dry box and 0.108 moles of a sample of basic material purged with nitrogen was added to the autoclave together with 10 ml of toluene purged with nitrogen in samples 1, 2, 6 and 7. The autoclave was sealed, removed from the dry box and placed in a heating jacket and heated to 255 ° C. The reaction time for samples 1, 2, 6 and 7 containing toluene solvent was three hours. The reaction time for samples 3-5 without solvent was one hour. During the heating, the contents of the autoclave were shaken, once the reaction was complete, the temperature of the autoclave was reduced to 20 ° C. The excess of basic define matter that did not react from the product mixture was distilled off. The remaining unconverted linear polyaromatic compound and the linear polyaromatic compound-linear adduct-linear adduct mixture were subjected to a temperature of 300 ° C to 350 ° C for about 0.5 hour, during which time the linear polyaromatic compound-olefin adduct linear internal was dissociated into a recyclable linear polyaromatic compound and the product of the internal olefin composition was enriched in the linear internal olefins with respect to the moles of the internal olefins in the basic material. This linear internal olefin composition was analyzed by gas chromatography. The results are shown in Table 1. The concentration of the species within the basic material and within the resulting linear internal olefin composition appears as percentages by weight. ÍABL S &PÓGÓN OF LINEAR AND BRANCHED INTERNAL OLEFINS * No adduct formation.

The results indicate that in each sample according to the present invention, the amount of linear internal olefin was enriched in the product while on the other hand the amount of branched internal olefin was greatly reduced. In some cases, the amount of branched internal olefin was reduced by more than 80%, up to more than 90%, over the amount present in the basic material. Non-linear 1,2-benzanthracene was not effective. It is noted that in relation to this date, the best method known to the applicant, to implement said invention is that which is clear from the manufacture of the objects to which it refers. Having described the invention as above, the content of the following is claimed as property.

Claims (10)

1. A process for converting a feedstock comprising linear internal olefins and branched internal olefins, into a linear internal olefin composition having a lower molar concentration of branched internal olefins than is present in the feedstock, characterized in that: a) the feed charge is contacted with a linear polyaromatic compound, optionally substituted, under conditions effective to form an adduct of linear polyaromatic compound - linear internal olefin; b) linear linear olefin-linear olefin adduct is separated from the reaction mixture; c) the linear polyaromatic compound-linear internal olefin adduct is dissociated to form a linear polyaromatic compound and a linear internal olefin composition, and optionally, d) the linear polyaromatic compound formed in step c) of the composition is separated of linear internal olefin.

2. The process according to claim 1, characterized in that the linear polyaromatic compound is anthracene or a substituted anthracene.

3. The process according to claim 1, characterized in that the linear polyaromatic compound is 2, 3-benzanthracene or 2,3-substituted benzanthracene.

4. The process according to any one of claims 1-3, characterized in that the basic material is brought into contact with the linear polyaromatic compound at a temperature ranging from 150 ° C to 290 ° C.

5. The process according to any one of claims 1-4, characterized in that the molar ratio of the olefins of the feedstock to the linear polyaromatic compound varies from more than 0.5: 1 to 10: 1.

6. The process according to any one of claims 1-5, characterized in that the adduct of linear polyaromatic compound-linear internal olefin is dissociated by subjecting the adduct of linear polyaromatic compound-linear internal olefin at a temperature ranging from 250 ° C to 400 ° C.

7. The process according to any one of claims 1-6, characterized in that the separations of step b) and / or d) are carried out by vacuum or flash distillation.

8. The process according to any one of claims 1-7, characterized in that the separations of steps b) and / or d) are carried out by cooling, first followed by filtration or centrifugation.

9. The method according to any one of claims 1-8, characterized in that steps a) - c) are repeated more than once.

10. A method according to any one of claims 1-9, characterized in that the basic material is produced from a Fischer-Tropsch process. SUMMARY OF THE INVENTION Separation process of linear internal olefins of branched internal olefins. A process of conversion of basic material of linear internal olefins and branched internal olefins in a primary linear internal olefin composition having a lower concentration of branched internal olefins than those found in the basic material is provided, by which: a) the basic material is contacted with a linear polyaromatic compound, optionally substituted, under conditions effective to form an adduct of linear polyaromatic compound - linear internal olefin; b) the linear internal olefin-linear polyaromatic compound adduct is separated from the reaction mixture; c) Linear linear olefin-linear polyaromatic adduct is dissociated to form a linear polyaromatic compound and a linear internal olefin composition, and optionally, d) the linear polyaromatic compound formed in step c) of the linear internal olefin composition is separated.