Process for production of higher linear internal olefins from butene

Abstract

A process for production of higher linear internal olefins from 1- and 2-butene feedstocks in one or a series of sequential catalytic reactive distillation columns containing olefin disproportionation and olefin isomerization catalysts.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] There are no other related applications.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT.

[0002] This research was not federally sponsored.

BACKGROUND OF THE INVENTION

[0003] The present invention relates to the production of valuable higher linear olefins from low value butenes via a catalytic disproportionation reaction in a catalytic distillation reactor.

[0004] Catalytic disproportionation, transalkylation or metathesis technology refers to the technology, which, in alkenes, exchanges the alkyl groups on both sides of the double bond with another alkene. For example, propylene can be reacted to make ethylene and 2-butene. Typically, the alkene products contain both higher and lower carbon number chains. One of the earlier examples of the prior art is described in the U.S. Pat. No. 3,261, 879 (1966) regarding the reaction of propylene mentioned above. This is easily accomplished as the reactions are reversible and proceed to equilibrium, thus if starting with butene and ethylene the reaction will proceed to about 50% conversion to propylene, while starting at propylene, the reaction will proceed to about 50% conversion to ethylene and butene. Most of the prior art describes single reactant phase reactions in a fixed bed, a fluidized bed or a moving bed where the equilibrium limits the conversion to desired alkene. Longer residence times in such systems lead to isomerization and other by-product reactions. U.S. Pat. No. 3,463,827 (1969); U.S. Pat No. 3,448,163 (1969); U.S. Pat. No. 3,641,189 (1972); U.S. Pat. No. 3,676,520 (1972) all describe processes of disproportionation of alkenes where a Group VIB metal carbonyl catalyst associated with alumina or a rhenium heptoxide on alumina, or rhenium heptoxide on alumina with mixtures of other metals. These processes, in part, discuss the reaction of 1-butene to give ethylene and 3-hexene. Although the theoretical conversion of 1-butene to ethylene and 3-hexene is about 50%, none of the references sited above were able to approach even the theoretical conversion with high selectivity to these desired products. Some systems attempted to use high temperature to drive to higher conversion, but with considerable detriment to the selectivity of the reaction because of the increased isomerization rates as well as consecutive reactions of the reaction products.

[0005] U.S. Pat. No. 4,709,115 (1987) teaches of improving the selectivity and conversion of the reactions of 1- and 2-butene to ethylene, propylene, 2-pentene and 3-hexene by using a reactive distillation column, which uses rhenium oxide catalyst impregnated on alumina both as a catalyst and a distillation substrate to facilitate phase transfer. In this reactive distillation system the conversion is improved to 85-93% and the combined yield to ethylene and 3-hexene (or ethylene, propylene (light ends) and 2-pentene, 3-hexene (heavy ends) is improved to 79.5-89%. This result is obtained because the light reaction products are removed from the liquid phase immediately and thus push the equilibrium to the heavy products. Also, this invention claims the ability to achieve high reaction rates at moderate (50-130° C.) temperatures. However, the products of this reaction are commercially insignificant, because ethylene and propylene are in general less valuable than 1-butene. 2-Pentene and 3-hexene, comprising most of the product weight, do not have valuable commercial outlets. Thus this art does use plentiful and low value feedstocks, but does not make desirable range linear internal olefin products.

[0006] U.S. Pat. No. 5,243,120 (1993) as well as other U.S. patents (U.S. Pat. Nos. 3,786,112; 5,043,520; 4,996,386; and 4,180,524) all describe methods of improving yields of medium-range olefins by reacting a high carbon number chain olefin with a low carbon-number chain olefin by affecting simultaneous disproportionation and isomerization of the olefins. Most of the subject matter of these patents refers to the production of detergent-range linear internal (C10-C16) olefins from a feedstock of light (C4-C8) and heavy (C18-C20+) alpha-olefins. Some variation of these processes is a part of current commercial linear alcohols process. These patents advise that physical mixtures of olefin disproportionation catalyst (such as rhenium oxide) and an olefin (double bond) isomerization catalyst (such as potassium on alumina) are able to effectively simultaneously isomerize the double bond initially located in a primary position to a deep internal position and to disproportionate the light olefins with the heavy olefins, thus making a high yield of intermediate olefins. Without isomerization, the mixture would tend to make ethylene and very heavy olefin. The process is conducted in a fixed bed reactor. The disadvantage of this process is that it has to use high-value light alpha-olefins and high-value heavy alpha-olefins to produce intermediate olefins of similar value. Thus this art produces some of the high-value higher olefins, but at the expense of consuming other high-value olefins and does not utilize low value feedstocks.

BRIEF SUMMARY OF THE INVENTION

[0007] This invention is a process for production of high-value higher olefins from low-value mixed 1- and 2-butene streams via olefin disproportionation in one or in more than one sequential catalytic distillation reactors. The reactor has several catalyst beds in a sequence. The various catalyst beds are: olefin disproportionation catalyst bed, including molybdenum, tungsten, rhenium elements, compounds and mixtures thereof, optionally including cobalt; olefin isomerization catalyst bed, including sodium, potassium, rubidium, cesium elements, compounds and mixtures thereof; and a bed consisting of a physical mixture of olefin disproportionation and olefin isomerization catalysts. The products of this reaction system are ethylene, propylene and some 2-butene (overhead product) and C5-C20 and higher linear internal olefins (bottoms product). This invention improves the art of disproportionation of alkyls by devising a high-yield method of producing a desirably broad range of high-value linear internal olefins from low-value 1-and 2-butenes.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0008] FIG. 1. Linear Internal Olefins Process.

[0009] This drawing depicts a process consisting of several stages of physically separate reactive distillation columns.

DETAILED DESCRIPTION OF THE INVENTION

[0010] Olefins, which can serve as feedstocks to this process, are acyclic alkenes with at least two carbon atoms. Alkenes having 3 to 30 carbon atoms and mixtures of such are preferred. More specifically, mixtures of 1- and 2-butenes are the best feedstocks.

[0011] The reactor or reactors include known olefin disproportionation catalysts, such as molybdenum, tungsten and rhenium metals and their oxides, optionally including cobalt, supported on porous substrate. For the purposes of the present invention the preferred disproportionation catalyst is that containing tungsten or rhenium oxides on a porous alumina or silica-containing support. The preferred substrate is the catalytic grade gamma-alumina or silica-alumina.

[0012] Also, the reactor or reactors include known olefin isomerization catalysts, consisting of sodium, potassium, rubidium, cesium and mixtures thereof. These metals are impregnated on alumina or silica-containing porous substrate. It is preferred to calcine these impregnated metals to oxides. Further, gamma-alumina or silica-alumina is the preferred substrate for this catalyst.

[0013] The disproportionation catalyst mixture can be prepared by any of the conventional methods, including dry-mixing, impregnation or co-precipitation. One of the methods, which can be used is the impregnation of the alumina with a solution containing aqueous salts of rhenium or rhenium oxide and/or tungsten or tungsten oxide. Alumina support can be in a form of conventional dumped distillation packing, such as saddles, rings, spheres to enhance mass transfer during fractionation. After impregnation, the catalyst should be calcined at 300° C. to 700° C. in a flow of air and/or nitrogen to activate the catalyst. The disproportionation catalyst typically contains 5 to 20% by weight rhenium or 5 to 35% tungsten.

[0014] The olefin isomerization catalyst can be prepared by impregnating an alumina support with an alkali metal such as sodium, potassium, rubidium or cesium. For impregnation various salts and compounds of these metals can be used. For example, carbonates, chelates, hydroxides, alkoxylates and other compounds can be used as long as they can be decomposed to leave some form of metal oxides or aluminates on the surface. The preferred metals for this process are potassium carbonates or potassium carboxylates. After impregnation, the catalyst is calcined at 400° C. to 800° C. in the presence of air flow to activate the catalyst. Preferably, calcination temperature should be between 500° C. and 700° C. The content of an alkali metal on the alumina should be from 5 to 20% by weight.

[0015] The reactive distillation column or columns used in this process is a distillation column or columns of the following construction (See FIG. 1): the uppermost several stages of the column consists of structured low-temperature packing. The packing immediately above and/or below the feed point consists of olefin disproportionation catalyst arranged in one or several beds. Preferably, the olefin disproportionation catalyst is used in one bed immediately below the feed and in one bed immediately above the feed. The lowermost internals of the column consist of one to several beds of olefin disproportionation and olefin isomerization catalyst either physically mixed in a single bed, or arranged in alternating series of beds. The preferred method is to either physically mix the two catalysts or alternate shallow beds. Preferably, the method of alternation is isomerization/disproportionation/isomerization/disproportionation, etc. Also, the column may be separated into different physical units as the practical considerations of the unit size, optimum cost and better vapor and liquid equilibria dictates. For example, the initial reaction of 1- and 2-butene to make 2-pentene and 3-hexene over disproportionation catalyst without the presence of isomerization catalyst may be done in a separate reactive distillation column. Also, due to the limitations of vapor-liquid equilibrium, the successively higher linear internal olefins may be achieved in separate reactive distillation columns operating at successively lower pressure and higher temperature to achieve the vaporization of the successively heavier products. Also, the separation of ethylene and propylene may be done in a separate unit to reduce the temperature range handled in a single piece of equipment.

[0016] The process temperature in the column will depend on the feedstock olefin and the desired product distribution. In general, the temperature range will be between −30° C. overhead and 300° C. bottoms temperatures. Preferably, the temperatures will range between 0° C. and 200° C. The pressure in the column will also depend on the feedstock olefin and the desired extent of reaction as well as the required process temperature to achieve the desired conversion and selectivity. The pressure in the column can be 0 to 500 psia and more preferably, from 0 to 150 psia.

[0017] Three simultaneous unit operations are carried out in the reactive distillation reactor. They are: olefin disproportionation, olefin isomerization and fractionation. Feed, containing 1- and 2-butene, undergoes disproportionation in the olefin disproportionation beds located near the feed point. Depending on the feed composition, the likely products are 3-hexene, 2-pentene, ethylene and propylene. Ethylene and propylene are fractionated overhead where they are recovered. 3-hexene and 2-pentene descend lower in the column until they reach the beds containing both isomerization and disproportionation catalysts. Alternatively, in a multiple column scheme, 3-hexene and 2-pentene are collected off the bottoms of the column and fed to the next column which is packed with a mixture of both disproportionation and isomerization catalyst. In these beds 3-hexene is isomerized to a thermodynamic equilibrium mixture of 1-, 2- and 3-hexene. Subsequent disproportionation reactions of 2-hexene with itself or with 2-pentene make 4-octene or 3-heptene. These species, in turn, are isomerized partially to 2- and 3-octene, which go on to make, in part, 6-dodecene, 5-undecene and 5-decene. Some of this is accomplished in the same physical reactive distillation column, while for best results the mixture with the average composition of between heptene and octene can be removed and fed to a subsequent reactive distillation column. The advantage of the reactive distillation scheme is that at any point in the reactor the light species are flashed off thus preventing the recombination of the products back to the reactants. The fractionation of the lights concentrates the heavies and assures the building of the longer molecules in the lower beds of the column. The butene will be bottled up in the column and mostly reacted to either to lights or to heavies, while some is distilled overhead and, if it is warranted, recycled. Pentene, as well, not being a desirable product, will be reacted to extinction in the reactive distillation columns. Alternatively, unreacted butene and pentene may be dropped out of the bottoms of the column when a particularly light product distribution is desired. Depending on the vapor liquid equilibrium present in the reactive distillation column, the bottoms product will consist of a range of products in a bell-curve, Poisson or modified or skewed bell-curve or Poisson distribution.

EXAMPLE 1

[0018] The first stage of the system to manufacture linear internal olefins from 1- and 2-butenes consists of a reactive distillation column packed with disproportionation catalyst only. The product of this stage, whether in-situ in the same physical vessel, or in a different physical vessel is a mixture of pentenes and hexenes. These pentenes and hexenes are then fed into the second stage, where there is both the transalkylation and isomerization catalyst is present as described above.

[0019] The reaction conditions were:

[0020] Overhead pressure: 30 psig; reboiler temperature: 300° F.

[0021] The composition of the bottoms of the reactive distillation in weight percent (wt %) was:

C4 8.15
C5 46.21
C6 26.92
C7 13.31
C8 1.69

EXAMPLE 2

[0022] The product from the first stage as described in Example 1 was introduced into the second stage at slightly different conditions. The conditions were:

[0023] Overhead pressure=20 psig, reboiler temperature=400° F. The second stage bottoms composition in wt % was:

C6  3.1
C7  18.3
C8  61.7
C9  13.2
C10 2.5
C11 1.1

EXAMPLE 3

[0024] The product from the first stage as described in Example 1 was introduced into the second stage at slightly different conditions. The conditions were:

[0025] Overhead pressure=20 psig, reboiler temperature=350° F. The second stage bottoms composition in wt % was:

C5 4.7
C6 38.5
C7 38.2
C8 18.6

EXAMPLE 4

[0026] The product from the second stage as described in Examples 1-3 was introduced into the third stage also containing layered transalkylation and isomerization catalysts. The conditions were:

[0027] Overhead pressure=10 psig, reboiler temperature=400° F. The third stage bottoms composition in wt % was:

C8  3.77
C9  20.16
C10 34.97
C11 25.1
C12 10.37
C13 3.87
C14 2.16
C15 0.59

EXAMPLE 5

[0028] The product from the second stage as described in Examples 1-3 was introduced into the third stage also containing layered transalkylation and isomerization catalysts. The conditions were:

[0029] Overhead pressure=10 psig, reboiler temperature=450° F. The third stage bottoms composition in wt % was:

C7  0.2
C8  1.9
C9  6.6
C10 16.4
C11 23.5
C12 21.4
C13 14.3
C14 8.2
C15 4.2
C16 2.0
C17 0.9
C18 0.4

[0030] The yield to heavy products (C6 and heavier) is thought to be in the range of 20% to 80% by weight, more preferably 50% to 75% by weight. Most preferably, the yield to heavy products will be about 70% by weight. The product distribution can be controlled by varying temperature and pressure in the columns.

Claims

1. A process for producing heavy linear internal olefins from 1- and 2-butene feedstocks in a reactive distillation column or in a set of reactive distillation columns employing disproportionation catalyst containing rhenium, tungsten or molybdenum elements and isomerization catalyst containing sodium, potassium, rubidium, cesium and mixtures thereof elements.

2. A process according to claim 1 wherein the disproportionation catalyst contains a rhenium compound impregnated on alumina support.

3. A process according to claim 1 wherein the isomerization catalyst contains a potassium compound impregnated on alumina.

4. A process according to claims 2 and 3 where the alumina is gamma-alumina.

5. A process according to claims 1 where the process consist of a number of successive stages, with the first stage containing only the disproportionation catalyst and the subsequent stages, numbered 1-10, more preferably 1-4, contain a mixture of disproportionation and isomerization catalysts operating at progressively lower pressures and same or higher temperatures.

6. A process according to claim 1 wherein the mixture of isomerization and disproportionation catalysts may be a physical mixture of these catalysts, alternating layers of catalysts or entire alternating beds.

7. A process according to claim 1 where in the first stage 1- and 2-butene are reacted in the disproportionation beds without the presence of isomerization catalyst to make ethylene, propylene and 2-pentene and 3-hexene at overhead column pressures of 0-200 psia, more preferably from 20 to 100 psia, and column reboiler temperatures from 100 to 500° F., more preferably from 200 to 400° F.

8. A process according to claim 1 where 3-hexene is isomerized by the isomerization catalyst contained in the isomerization/disproportionation beds of the second stage reactive distillation column to a mixture of 1-, 2-, and 3-hexenes. Subsequently, 1- and 2-hexenes and 2-pentene are disproportionated over the disproportionation catalyst partially to heavier species. The reactions and physical separations in this stage are taking place at the overhead pressure of 0-100 psia, and more preferably at the pressure of 10-50 psia, and column reboiler temperatures from 100 to 600° F., more preferably from 250 to 500° F. The bottoms products of this stage consists of a range of linear internal olefins C4 through C20, more exactly C4 through C15 including large concentrations of various isomers of hexene, heptene, octene and nonene. Ethylene, propylene and butene are the by-products distilled overhead.

9. A process according to claim 1 wherein heavier internal olefins from the bottoms of the second stage as described in claim 8, including such symmetrical isomer species as 3-hexene, 4-octene and 5-decene and heavier are isomerized over the isomerization catalyst to a random mixture of isomers. The resulting stream is disproportionated in the disproportionation beds of the reactive distillation column with itself and also with like species, such as other pentenes, hexenes, heptenes, etc. to give a range of linear internal olefin products from C4 to C20, preferably from C5 to C18, and ethylene, propylene and butene as the light by-products. The reaction is carried out at 0-100 psia overhead pressure, more preferably 5-50 psia, and 100-600° F. reboiler temperature, more preferably 250-550° F. reboiler temperature.

10. A process according to claims 1 wherein the bottoms stream from stage three as described in claim 9 or subsequent bottoms streams from this fourth or following sequential reactive distillation stages containing in part symmetrical linear internal olefins and other like species are isomerized to a random range of linear internal olefins and subsequently disproportionationed to progressively heavier and heavier products distilled as the bottoms of these reactive distillation columns. The reaction conditions in this fourth or subsequent stages are 0-100 psia overhead pressure, more preferably 0-30 psia and 100-600° F. reboiler temperature, preferably 300-550° F. The products are C5-C30 linear internal olefins, more preferably C8-C25 linear internal olefins, with ethylene, propylene and butene as by-products.

11. A process according to claims 7-10 wherein the process may have any number of stages from 1-20, preferably from 1-5, and produce any range of linear olefin products from C4-C30, preferably from C5-C25, and more preferably from C7-C20.

12. A process according to claim 1 where the subsequent stages may be in the same physical vessel, or in different distillation vessels.

13. A process according to claim 1 wherein the light species formed at each stage are flashed off and either distilled overhead or condensed in the upper stages and reacted with like molecules at that stage.

14. A process according to claims 1, and 7-10 wherein the operating temperatures of each stage may be between −30° C. at the top and 300° C. at the bottom bottoms.

15. A process according to claim 14 wherein the operating temperature may be between 0° C. at the top and 200° C. at the bottom.

16. A process according to claim 1 and claims 7-10 wherein the operating pressure may be between 0 and 500 psia.

17. A process according to claim 16 wherein the operating pressure may be between 5 and 100 psia.

18. A process according to claim 1 wherein the overall yield to heavy internal olefins by weight is 30% to 80%.

19. A process according to claim 18 where the yield to heavy olefins is about 70% by weight.

20. A process according to claim 2 where the rhenium compound is Re2O7.

21. A process according to claim 1 where the feedstock composition is 0% to 100% 1-butene, the balance being 2-butene.

22. A process according to claim 22 where the feedstock composition is at least 30% 1-butene.

23. A process according to claim 1 where the higher linear internal olefins are C5 through C30+ linear internal olefins.

24. A process according to claim 23 where the higher internal olefins are produced in a bell-curve or a Poisson distribution.

25. A process according to claim 24 where the higher internal olefins are produced in a modified bell-curve or Poisson distribution with distribution being skewed from a normal distribution.