KR20120090028A - Process for making higher olefins - Google Patents

Abstract

Processes for producing higher olefins are disclosed by oligomerizing lower olefins such as ethylene to higher olefins using catalytic distillation conditions. At the same time and interdependently, the lower olefins are oligomerized into higher olefins by a catalyst, which is separated and recovered as a liquid.

Description

PROCESS FOR MAKING HIGHER OLEFINS}

The present invention relates to the preparation of higher olefins by oligomerization of lower olefins, in particular to the oligomerization of ethylene, with simultaneous separation of the higher olefins using catalytic distillation conditions. In contrast to the prior art, the process is operated without the need for adding solvent.

Several catalysis processes have been developed to oligomerize olefins into higher olefins, and in particular to oligomerize ethylene into a series of higher olefins (C ₂ H ₄ ) n (Equation 1).

The higher olefins thus formed at first are typically terminal (alpha) olefins, ie olefins having a single double bond at the first carbon atom. Terminal olefins may then be isomerized to one or more internal olefins, ie olefins having double bonds at the carbon atoms therein. However, usually terminal olefins have higher commercial utility and value than internal olefins. For example, it is desirable to use terminal olefins in combination with ethylene to form partially branched polyolefin comonomers, biodegradable detergents, lubricants, or plasticizers.

It is therefore desirable to operate the catalytic reaction of this process under conditions where the isomerization reaction is minimized and thus higher selectivity to terminal olefins is ensured. Operation at low temperatures minimizes the speed of the isomerization reaction. However, it is also desirable to have a high reaction rate. Operation of the process at high temperatures provides higher reaction rates than low temperatures. However, this requires a high reactor pressure to allow high olefin concentrations in the liquid phase.

There are three main commercial processes currently being used for oligomerization of olefins, each of which has a relatively high level of complexity and efficiencies below the desired efficiency. Both Chevron and Ethyl Corporation use Ziegler type catalysts in homogeneous catalyst systems. Shell Higher Olefins Process (SHOP) uses a complex of nickel as a catalyst. Each of these systems uses solvents and catalysts in a liquid phase reactor necessarily equipped with an intermediate cooler. The mixture in the product stream is then purified in a series of separation columns.

Solid state catalysis processes used in slurry reactor systems are easier to separate catalyst from the reaction mixture but present some challenges. There is strong adsorption of the product on the catalyst surface as well as on the reactants. In addition, with the formation of internal olefins, there is a negative thermodynamic effect on the selectivity for the desired terminal olefin product at high reaction temperatures. There is a need for more active catalysts. Each of these factors must be overcome, including catalyst degradation (inactivation) by decomposition and formation of isomerization products.

Some of the potential beneficial changes that can be made to improve the oligomerization process, including the use of milder conditions, thereby maximizing selectivity and enhancing yield and production rates by developing more active and selective catalysts There is evidence.

Among the many catalysts known to catalyze the oligomerization of olefins, including, for example, finely divided nickel supported on sulfated alumina, as described in French Patent 2641 477, registered in 1990, It has been found that highly acidic heterogeneous catalysts are particularly active in the dimerization of propylene. The Ni / sulphated Al ₂ O ₃ catalyst used in '477 is active at room temperature for dimerization of propylene in a slurry with an inert hydrocarbon solvent. Furthermore, "Oligomerization of Ethylene in a Slurry Reactor with Nickel / Sulfonated Alumina Catalysts" Ind. Eng. Chem. As described by Zhang et al. In Res., 36, 3433-3438 (1997), the disclosure of which is incorporated herein by reference, a similar catalyst comprising Ni / sulfonated non-porous Al ₂ O ₃ (commercially available) Possible ALON) has been shown to be active in oligomerization of ethylene.

Some further processes for oligomerization of olefins are described in patents and publications. Among these there is a specification of a catalyst system for oligomerization of ethylene using either homogeneous or heterogeneous catalysts. However, in contrast to the process of the present invention, all prior art features are the use of the solvents necessary to carry out the process. Examples of other prior art that distinguish this invention and such include: Krug et al. US Patent 6,841,711; Gildert et al. U.S. Patent 6,274,783, Vora et al. U.S. Patent 6,025,53 and Townsend et al. U.S. Patent 6,004,256.

Summary of the Invention

It is an object of the present invention to provide a process for oligomerization of lower olefins, in particular oligomerization of ethylene, without the use of additional solvents and thus without the need to separate higher olefin products from fluids such as hydrocarbon solvents. This process is operated under catalytic distillation conditions such that the product higher olefins are in liquid form, so that the product is easily separated from the reaction mixture as a liquid.

According to the present invention, through catalyzed oligomerization of lower olefins, where n is an integer from 2 to 5 and in particular oligomerization of ethylene, higher olefins of the formula CnH ₂ n where n is an integer greater than 2, A process is provided for the simultaneous separation of higher olefins as a liquid using, for example, catalytic distillation conditions in a catalytic distillation column. No additional solvent is needed. The process can be continued, where the higher olefins are predominantly liquid and the ethylene is operated at such temperatures and pressures, both in gas and in the dissolved phase, to form a solution with the liquid higher olefins. Suitable catalysts include the homogeneous and heterogeneous catalysts described above and, for example, catalysts comprising nickel dispersed on a non-porous alumina support are highly active and have good selectivity for terminal olefins at low temperatures. For example, the catalyst described above known as ALON has been found to be useful.

If the catalyst is a solid, it is called heterogeneous (gas-solid or liquid solid). If a solid or liquid catalyst is dissolved in the liquid reaction mixture, only one phase (liquid) is present, thus called homogeneous catalyst.

For a more complete understanding of the invention and its further objects and advantages, reference is made to the following description in conjunction with the accompanying drawings.
1 is a schematic of catalytic distillation for co- oligomerization of ethylene and separation of higher olefins.
2 shows the first profile of composition and temperature from modeling of the process of ethylene oligomerization using a catalytic distillation column. P = 40 atm, RR = 12, D / F = 0.45, RXN in step 3, equilibrium conversion = 0.05, total conversion of ethylene = 54.36%. Step 1 is at the top of the column.
3 shows a second profile of composition and temperature from modeling of the process of ethylene oligomerization using a catalytic distillation column. P = 40 atm, RR = 12, D / F = 0.45, RXN in step 3, equilibrium conversion = 0.05, total conversion of ethylene = 44.03%.
4 shows a third profile of composition and temperature from modeling of the process of ethylene oligomerization using a catalytic distillation column. P = 40 atm, RR = 12, D / F-0.45, RXN in step 3, equilibrium conversion = 0.05, total conversion of ethylene = 44.03%.
5 shows a fourth profile of composition and temperature from modeling of the process of ethylene oligomerization using a catalytic distillation column. P = 40 atm, RR = 15, D / F = 0.35, RXN = step 3, equilibrium conversion = 0.10, total conversion of ethylene = 61.27%.
6 shows a fifth profile of composition and temperature from modeling of the process of ethylene oligomerization using a catalytic distillation column. P = 40 atm, RR = 79, D / F = 0.05, RXN = Step 3, equilibrium conversion = 0.50, total conversion of ethylene = 96.88%.
7 shows a sixth profile of composition and temperature from modeling of the process of ethylene oligomerization using a catalytic distillation column. P = 40 atm, RR = 79, D / F = 0.05, RXN = Step 3, equilibrium conversion rate = 0.50; Total conversion of ethylene = 96.88%

DETAILED DESCRIPTION OF THE INVENTION

The following description includes data obtained through laboratory experiments and simulations using ASPEN PLUS.

Referring to FIG. 1, equipment 10 having a catalytic distillation column 12 is provided in this process. Column 12 has an upper first portion 14, an intermediate second portion 16 and a lower third portion 18. A condenser 20 is provided to the first portion 14 for the condensation of the condensable components of the gas phase reaction mixture 27 for the return to the first portion 14 of their column 12 as a liquid. Reboiler 22 has a third portion of column 12 for evaporation of the more volatile components of the liquid reaction mixture 28 collected therein for return as volatiles to third portion 18 of column 12. Provided in part 18.

The second part 16 of column 12 comprises a catalyst bed 24 having an oligomerization catalyst 26 therein. Experimental testing has shown that the catalyst 26 is preferably an acidic catalyst. The catalyst is considered acidic if it consumes a significant amount of base during the titration. For example, nickel sulfate / alumina (ALON) will consume NH ₃ during the titration experiment. This finding is described by Espinoza et al. "Catalytic Oligomerization of Ethylene on Nickel-Exchanged Amorphous Silica-Alumina: Effect of Acid Strength of Support [Catalytic Oligomerization of Ethylene over Nickel-exchanged Amorphous Silica-alumina: Effect of the Acid] Strength of the Support] "Appl. Catal. 29, 295 (1987).

One preferred catalyst 26 comprises nickel (Ni), for example the commercial product ALON, which is well dispersed and supported on a non-porous alumina support. The inventors have found that the mild conditions (about -10) for oligomerization of substantially pure ethylene as a feed 30 (see below) when such a catalyst is operated at about 40-50 atmospheric pressure, for example. It has been found that it has a highly active Ni moiety that allows the oligomerization process to be carried out under < RTI ID = 0.0 > Preferred surface acidity is achieved through surface sulfation. Since ALON only has an outer surface and the reaction product is a large molecule, the desorption of the reaction product is improved (less adsorbed on the catalyst surface), resulting in higher reaction rates and improved catalyst stability.

In a second embodiment of equipment 10 (not shown), there are a plurality of catalyst beds 24 at different heights in column 12. When one or more catalyst beds 24 are present, there is no temperature gradient in column 12 and the relative concentration of feed (eg ethylene) 30 in column 12 is more easily controllable.

No additional solvent is required at all in the reaction mixture.

The oligomerization reaction of this process was found to occur in catalyst bed 24 (Equation 1 above). When the temperature and pressure at which ethylene 30 is primarily a liquid are sufficiently high (critical temperature-boiling point-8.9 ° C. for ethylene), and acid catalyst 26 comprises Ni supported on non-porous alumina. , The contact between the product 36 and ethylene 30 promotes the desorption of the product 36. Liquid ethylene 30 dissolves the higher olefins 36 adsorbed at the catalytic surface active site, thus minimizing the reaction of further catalysts. As a result, the formation of olefin isomers or other by-products is minimized, thereby enhancing the selectivity for the desired terminal linear olefins (alpha-olefins).

Feed 30 is more volatile than product 36. When the process is operated at sufficiently high temperatures and pressures, the product 36 is mainly in the liquid phase 28. Preferably, feed 30 is supplied as a liquid, which is present in the gas and liquid in equilibrium in the refluxing reaction mixture.

We will now summarize the process of using ethylene as an example of a feed 30. Ethylene feed 30 is substantially pure ethylene, 99.9% ethylene comprising 0.1% ethane, such as generally used for making polyethylene, or mixtures rich in ethylene, for example, generally about 80.5% ethylene, 18.2% It may be selected from an unfractionated industrial ethylene stream comprising ethane and 1.3% acetylene. Optionally, acetylene can be removed or converted before feeding to the oligomerization reactor. Those skilled in the art will understand that the reaction parameters for feeding the lower olefin feed in liquid form at its boiling point will vary somewhat for different compositions of the ethylene-rich feed mixture. For example, when feed 30 comprises the above unfractionated industrial ethylene stream, the mixture flashes between 16 ° C. and 17.5 ° C. at 50 atm. It will also be appreciated that when the low olefin feed composition comprises C3, C4, C5, and the like, the temperature and pressure required to provide the feed in the required liquid form will be different, i.e. different boiling points.

Liquid ethylene 30 is fed to the top 14 of the column through the inlet line 32 at a position above the top surface 34 of the catalyst bed 24. Ethylene 30 is oligomerized with a series of higher olefins CnH ₂ n 36 which is mixed with ethylene to form a liquid phase reaction mixture 28 which descends through the bottom surface 38 of the catalyst bed 24 Collected in the third part 18 of the column 12. Liquid ethylene 30 supplied via line 32 washes off liquid phase product 36 on the catalyst surface as liquid mixture 28. In this way ethylene 30 is continuously fed, reacts in catalyst bed 24 and descends as liquid mixture 28 with product 36.

As shown in FIG. 1, the position of the inlet line 32 is above the catalyst bed 24. Those skilled in the art will appreciate that the inlet line 32 may be located above, below or at any position within the vertical range of the catalyst bed 24. Furthermore, there may be one or more feed lines 32 located at different heights above column 12. Product distribution is influenced by the position of inlet line 32. The distribution of the product in the slate can be controlled controllably by modifying the position of the inlet line 32 and controlling the reflux rate and the reboiler efficiency. It should be particularly noted that line 42 is selectable. It is only necessary if impurities are present in the gas phase in the condenser.

Liquid product mixture 28 is removed via reboiler 22 from which more volatile components, in particular ethylene, return to column 12 as volatiles. The remaining part is liquid product 36 which is removed via line 40.

The rate of feed of ethylene 30, process operating conditions, and removal rate of the liquid product determine the composition of the product liquid removed from column 12. Preferably, the reaction is operated at high pressure, for example 40 atmospheres, in order to keep ethylene 30 at its boiling point. When the process is operated at 40-50 atmospheric pressure, it is operated at low temperatures, preferably from about -20 ° C to about 8 ° C, more preferably -10 ° C to 8 ° C. Under these conditions ethylene is mainly present as a liquid at its boiling point in the first part 14 of the column 12 and in the condensed bed 28 in the catalyst bed 24 and in the third part 18 of the column 12. ) As a solution with product (36). It is preferable to run the CD column at the highest possible temperature, where ethylene is liquid at its boiling point (both gas and liquid present). At the top of the column, there is no product and therefore it is preferred to operate at the boiling point of ethylene in this zone (about 8 ° C. at 50 atm). The temperature of the bed increases once the product is formed or when there are ingredients that boil at higher temperatures, such as ethane.

It is well known that industrial ethylene contains impurities, including ethane. Moreover, ethane or other light hydrocarbons can accumulate in the reaction mixture and, as they are volatile, can accumulate primarily in the first portion 14 of column 12. Thus, when operating in batch mode or when operating a continuous process continuously, it will sometimes be necessary to remove these volatiles 44. Streams containing undesirable volatiles 44 are removed via outlet line 42.

The new process for oligomerization of olefins and especially oligomerization of ethylene has the following beneficial properties. Several catalysts are active in oligomerization of ethylene, including homogeneous and heterogeneous catalysts. One preferred catalyst has a highly active Ni moiety that enables the oligomerization process under very mild conditions. Preferred surface acidity is achieved through surface sulfation. Such preferred catalysts include Ni, well dispersed and supported on a non-porous alumina support, thus facilitating product desorption and consequently minimizing isomer formation and thus selectivity for the desired terminal linear olefins (alpha-olefins). To strengthen. Both the liquid feed and the higher olefins formed through oligomerization of the feed also serve as liquid vehicles, without added solvent, thus promoting product desorption from the catalyst surface.

The use of catalytic distillation column 12 provides further advantages. The heat of the exothermic reaction is used to reduce the energy requirement in the distillation step (22 kcal / mol). There is no hot spot at all, thus eliminating the need for an inter-cooler. Solvents are not necessary because the liquid feed and product higher olefins 36 serve as solvents, only feed olefins are fed to the column. The resulting high reactant concentration results in low mass transfer resistance and high reaction rates. Details of the acidic Ni / Al ₂ O ₃ catalyst, described in Example 1 below, have excellent selectivity and stability. At least one fixed catalyst bed 24 is used as a reactor in the catalytic distillation column 12, and in order to separate the catalyst from the reaction mixture, in contrast to possible highly acidic homogeneous reactive distillation systems that can be used without solvents. There is no need to provide another column. Thus, this heterogeneous reaction is substantially similar to the liquid phase reaction used in some current commercial processes, but the catalyst and catalytic distillation processes described herein confer significant additional advantages.

Example

Example 1. Activity of a catalyst comprising Ni supported on alumina.

"Oligomerization of Ethylene in Slurry Reactors Using Nickel / Sulfurized Alumina Catalysts" Ind. Eng. Chem. Res. 36, 3433-3438 (1997) to Zhang et al. The data reported by it was reproducible and showed that the catalyst is useful in the present invention under catalytic distillation conditions.

Zhang et al. Conducted a series of experiments using batch reactors and under mild operating conditions when heptane was used as a solvent. The catalyst Ni / ALON prepared as described by them appeared to be very active when used under the following operating conditions:

Reaction temperature: 278, 298, 308, 323 K

Pressure: 170.26 kPa.

Duration of run in the Parr reactor: 3 hours

n-heptane (solvent) charge: 120 mL

Stirring Speed: 450 rpm

Catalyst: 1.7 wt% Ni and 5.0 wt% SO ₄ ^2-

Catalyst charge: 0.2, 0.3, 0.4, 0.5 g

The catalyst is highly active for oligomerization. The process was found to have first-order kinetics for ethylene (Eq. 2) and an activation energy of 16.3 kJ / mol. Neither inter-particle or inter-particle resistance can be ignored with this catalyst. The combined resistance to external diffusion, internal diffusion and reaction is a control step, as shown in equation (3).

At low temperatures (<298 K) and close to atmospheric pressure, high selectivity to 1-butene and 1-hexene can be obtained when using n-heptane as solvent. Under this condition no obvious degradation (inactivation) occurred.

Example 2. Simulation of a process with different operating parameters.

The following data were obtained from a simulation using ASPEN PLUS® software. The design was based on a column with 20 equilibration steps. Simulation results show temperature and concentration profiles along the column. At the top of the column (step 1), it can be seen from the concentration profile that its composition is similar to the feed (mainly C2 =). At the bottom of the column (step 20), the product contains C4 = and C6 = and residue C2 =. It is assumed in the simulation that oligomerization produces only C4 = and C6 = at different fractions of equilibrium concentrations. The results for the product distribution are shown in Figures 2-6. FIG. 7 is another simulation run with only 10 equilibrium steps in the column, all other conditions being the same as those used in FIG. The temperature profile provides design data for selecting the reboiler and capacitor.

Those skilled in the art will appreciate that various types of apparatus can be used to present the catalyst in at least one catalyst bed of the catalytic distillation column.

2 to 7 show concentration and temperature profiles across column 12 using different sets of process operating parameters for oligomerization of ethylene to higher olefins. In each case, the reaction took place over catalyst 26 in catalyst bed 24.

Under each set of conditions, some ethylene is present in the third portion 18 of the column and the ethylene dissolved in the liquid phase 28 is returned from the reboiler 22 to the column 12 as a volatile. Happens quickly enough. The small amount of olefin product 36 present in the vapor phase in the first part 14 of column 12 is returned as liquid from the condenser 20.

It should be noted that the catalytic distillation column can be operated with a homogeneous catalyst. In this case the catalyst is mixed with feed ethylene and introduced at the top of the column.

Cited References

U.S. Patent Document

6,841,711 Krug et al. Process for making a lube base stock from a lower molecular weight feedstock in a catalytic distillation unit [Method for preparing a lubricant-based stock from a low molecular weight feedstock in a catalytic steamer]

6,274,783 Gildert et al. Catalytic distillation process for the production of C 8 alkanes

6,025,533 Vora et al. Oligomer production with catalytic distillation

6,004,256 Townsend et al. Catalytic distillation oligomerization of vinyl monomers to mke polymerizable vinyl monomer oligomers, uses approximately and methods for same [Catalytic distillation oligomerization of vinyl monomers for the production of polymerizable vinyl monomer oligomers, its use and methods thereof]

US patent application

2007/0123743 Al Ng et al. Composite catalyst for the selective oligomerization of lower alkenes and the production of high octane products

Foreign patent documents

French Patent 2641 477 C. Yves and C. Dominique "Process for the preparation and use, in the dimerisation of olefins, of a catalyst containing nickel, sulphur and alumina [dimerization of olefins of a catalyst containing nickel, sulfur and alumina Manufacturing and use in

Other literature

Q. Zhang, M. Kantcheva, LG. Dalla Lana, "Oligomerization of Ethylene in a Slurry Reactor Using a Nickel / Sulfated Alumina Catalyst [Oligomerization of Ethylene in Slurry Reactor with Nickel / Sulfated Alumina Catalyst]" Ind. Eng. Chem. Res. 36, 3433-3438 (1997).

R.L. Espinoza, R. Snel, CJ. Corf, CP. Nicolaide, "Catalytic Oligomerization of Ethylene over Nickel-exchanged Amorphous Silica-alumina: Effect of the Acid Strength of the Support Appl. Catal. 29, 295 (1987).

Claims (18)

Providing a feed composition comprising a lower olefin, wherein n is an integer from 2 to 5,
The feed composition is exposed to catalytic distillation conditions in a catalyst bed comprising an oligomerization catalyst having selectivity for the formation of terminal higher olefins, the temperature and pressure causing the feed composition to be in liquid form at its boiling point, Forming a liquid reaction mixture containing a higher olefin,
And
At the same time, separating the higher olefins from the reaction mixture by catalytic distillation and recovering the higher olefins as a liquid
Process for producing a linear higher olefin of the general formula C n H ₂ n wherein n is an integer greater than 2. The process of claim 1 wherein the catalyst is a heterogeneous catalyst or a homogeneous catalyst. The process of claim 2 wherein the catalyst is an acidic heterogeneous catalyst. 4. The process of claim 3, wherein the catalyst is nickel supported on sulfonated non-porous alumina. The process of claim 1 wherein the feed composition comprises ethylene. The process of claim 5, wherein the temperature is about −20 ° C. to about 8 ° C. and the pressure is 40 to 50 atmospheric pressure. The process of claim 1 wherein the feed composition comprises 99.9% ethylene and 0.1% ethane. The process of claim 1 wherein the feed composition comprises 80.5% ethylene, 18.2% ethane and 1.3% acetylene, the temperature is 16-17.5 ° C. and the pressure is 50 atmospheres. The process of claim 1, wherein the process is continuous. Providing a feed composition comprising a lower olefin, wherein n is an integer from 2 to 5,
Feeding said composition in its boiling point in liquid form into a catalytic distillation column having a lower olefin feed inlet and a higher olefin outlet and a catalyst bed containing an oligomerization catalyst having good selectivity for the formation of terminal higher olefins, ; The lower olefins are then oligomerized by reacting the lower olefins on the oligomerization catalyst to form a liquid reaction mixture containing the higher olefins,
At the same time, separating the reaction mixture by catalysis distillation in the column, causing the higher olefins to descend as a liquid in the column and recovering the higher olefins as a liquid deposit from the column.
Process for producing a linear higher olefin of the general formula C n H ₂ n wherein n is an integer greater than 2. The process of claim 10 wherein the catalytic distillation column is operated at pressures and temperatures such that the liquid reaction mixture contains the higher product olefins in the liquid phase and the lower olefins are present in both gas and liquid. 12. The process of claim 11, wherein the lower olefin is ethylene and the higher olefin is an oligomer of ethylene. 13. The process of claim 12, wherein the catalyst comprises an acidic heterogeneous catalyst. 13. The process of claim 12, wherein the catalyst is nickel supported on sulfonated non-porous alumina. The process of claim 14, wherein the temperature is about −20 ° C. to about 8 ° C. and the pressure is 40 to 50 atmospheric pressure. The process of claim 10 wherein the catalyst is a homogeneous catalyst. The process of claim 10 wherein the catalyst is a Ziegler type nickel complex. The process of claim 10, wherein the process is continuous.

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