A PROCESS AND A MULTI-STAGE REACTOR ASSEMBLY FOR THE PRODUCTION OF POLYOLEFINS

Abstract

A process for the production of polyolefins comprising: feeding a slurry comprising at least one polymerization catalyst, at least one carrier liquid, first olefin monomer(s) and optionally at least one first comonomer into at least one loop reactor; polymerizing the first olefin monomer(s) and optionally the at least one first comonomer yielding a first polyolefin; withdrawing the first polyolefin from the loop reactor; feeding the first polyolefin to a gas-solids olefin polymerization reactor, wherein the gas-solids olefin polymerization reactor comprises: a top zone; a middle zone, which comprises a top end in direct contact with said top zone and which is located below said top zone, the middle zone having a generally cylindrical shape; and a bottom zone, which is in direct contact with a bottom end of the middle zone and which is located below the middle zone; introducing a fluidization gas stream into the bottom zone of the gas-solids olefin polymerization reactor; polymerizing second olefin monomer(s) and optionally at least one second comonomer in the presence of the polymerization catalyst and the first polyolefin to a second polyolefin in a dense phase formed by particles of said second polyolefin suspended in an upwards flowing stream of the fluidization gas in the middle zone; introducing a jet gas stream through one or more jet gas feeding ports in a jet gas feeding area of the middle zone at the dense phase in the middle zone of the gas-solids olefin polymerization reactor; withdrawing the second polyolefin from the gas-solids olefin polymerization reactor.

Claims

1. A process for the production of polyolefins comprising: a) feeding a slurry comprising at least one polymerization catalyst, at least one carrier liquid, first olefin monomer(s) and optionally at least one first comonomer into at least one loop reactor; b) polymerizing the first olefin monomer(s) and optionally the at least one first comonomer yielding a first polyolefin; c) withdrawing the first polyolefin from the loop reactor; d) feeding the first polyolefin to a gas-solids olefin polymerization reactor, wherein the gas-solids olefin polymerization reactor comprises: a top zone (1); a middle zone (2), which comprises a top end in direct contact with said top zone and which is located below said top zone (1), the middle zone (2) having a generally cylindrical shape; and a bottom zone (3), which is in direct contact with a bottom end of the middle zone (2) and which is located below the middle zone (2); e) introducing a fluidization gas stream (6, FG) into the bottom zone (3) of the gas-solids olefin polymerization reactor; f) polymerizing second olefin monomer(s) and optionally at least one second comonomer in the presence of the polymerization catalyst and the first polyolefin to a second polyolefin in a dense phase (4) formed by particles of said second polyolefin suspended in an upwards flowing stream of the fluidization gas in the middle zone (2); g) introducing a jet gas stream (8, JG) through one or more jet gas feeding ports (5) in a jet gas feeding area of the middle zone (2) at the dense phase (4) in the middle zone (2) of the gas-solids olefin polymerization reactor; h) withdrawing the second polyolefin from the gas-solids olefin polymerization reactor; wherein the jet gas stream (JG) fed through at least one of the one or more jet gas feeding ports (5) is provided by a flash pipe (FP) from the loop reactor.

2. The process according to claim 1, wherein the fluidization gas is removed from the top zone (1) of the gas-solids olefin polymerization reactor and at least a part of the fluidization gas is introduced into the jet gas stream (8) and into the fluidization gas stream (6).

3. (canceled)

4. A multi-stage reactor assembly for the production of polyolefins comprising a) at least one loop reactor, comprising: at least one inlet for feeding a slurry comprising at least one polymerization catalyst, at least one carrier liquid, first monomer(s) and optionally at least one first comonomer; at least one outlet for withdrawing the first polyolefin produced in the loop reactor; and b) at least one gas-solids olefin polymerization reactor comprising: a top zone (1); a middle zone (2), which comprises a top end in direct contact with said top zone (2) and which is located below said top zone (1), the middle zone (2) having a generally cylindrical shape; and a bottom zone (3), which is in direct contact with a bottom end of the middle zone (2) and which is located below said middle zone (2); one or more jet gas feeding ports (5) located in a jet gas feeding area of the middle zone (2); a first line (6) for feeding a fluidization gas stream (FG) into the bottom zone (3) of the gas-solids olefin polymerization reactor, a second line (7) for withdrawing a stream comprising fluidization gas from the top zone (1) of the gas-solids olefin polymerization reactor, a third line (8) for introducing a jet gas stream (JG) into the middle zone (2) of the gas-solids olefin polymerization reactor via the one or more feeding ports (5), an inlet (9) connected to the outlet of the at least one loop reactor, for feeding catalyst, polyolefin, monomer and optionally comonomer; and an outlet (10) for withdrawing the second polyolefin produced in the gas-solids olefin polymerization reactor; one or more flash pipe feeding ports (14) located in a jet gas feeding area of the middle zone (2); and a sixth line (15) for introducing a flash pipe gas stream (FP) into the bottom zone (2) of the gas-solids olefin polymerization reactor via the one or more flash pipe feeding ports (14).

5. (canceled)

6. The process of claim 1, wherein the carry-over of particles of the polyolefin of the olefin monomer(s) into the second stream withdrawn from the top zone of the gas-solids olefin polymerization reactor is reduced.

7. The process of claim 1, wherein, the split between the first polyolefin produced in the loop reactor and the second polyolefin produced in the gas-solids olefin polymerization reactor is adjusted.

8. The process of claim 1, wherein the bulk density of the dense phase is increased during polymerization.

9. The process of claim 2, wherein the carry-over of particles of the polyolefin of the olefin monomer(s) into the second stream withdrawn from the top zone of the gas-solids olefin polymerization reactor is reduced.

10. The process of claim 3, wherein the carry-over of particles of the polyolefin of the olefin monomer(s) into the second stream withdrawn from the top zone of the gas-solids olefin polymerization reactor is reduced.

11. The process of claim 4, wherein the carry-over of particles of the polyolefin of the olefin monomer(s) into the second stream withdrawn from the top zone of the gas-solids olefin polymerization reactor is reduced.

12. The process of claim 5, wherein the carry-over of particles of the polyolefin of the olefin monomer(s) into the second stream withdrawn from the top zone of the gas-solids olefin polymerization reactor is reduced.

13. The process of claim 2, wherein the split between the first polyolefin produced in the loop reactor and the second polyolefin produced in the gas-solids olefin polymerization reactor is adjusted.

14. The process of claim 3, wherein the split between the first polyolefin produced in the loop reactor and the second polyolefin produced in the gas-solids olefin polymerization reactor is adjusted.

15. The process of claim 4, wherein the split between the first polyolefin produced in the loop reactor and the second polyolefin produced in the gas-solids olefin polymerization reactor is adjusted.

16. The process of claim 5, wherein the split between the first polyolefin produced in the loop reactor and the second polyolefin produced in the gas-solids olefin polymerization reactor is adjusted.

17. The process of claim 2, wherein the bulk density of the dense phase is increased during polymerization.

18. The process of claim 3, wherein the bulk density of the dense phase is increased during polymerization.

19. The process of claim 1, wherein the loop reactor is a loop reactor for polymerizing polypropylene.

Description

SHORT DESCRIPTION OF THE FIGURES

[0125] FIG. 1 shows a gas-solids olefin polymerization reactor as known from the prior art.

[0126] FIG. 2 shows gas-solids olefin polymerization reactors of a multi-stage reactor assembly according to the present invention having jet injection capabilities.

[0127] FIG. 3 shows a gas-solids olefin polymerization reactor of a multi-stage reactor assembly according to the present invention having jet injection capabilities connected to a flash pipe from a preceding polymerization reactor.

[0128] FIG. 4 shows the catalyst activity profile of the catalyst used in CE1 and IE1

[0129] FIG. 5 shows the catalyst activity profile of the catalyst used in CE2 and IE2

DETAILED DESCRIPTION OF THE FIGURES

[0130] FIG. 1 shows a gas-solids olefin polymerization reactor as typically used. Typical hydrodynamic patterns are depicted. Gas bubbles generated by the distribution plate move preferably in the center of the reactor upwards.

[0131] These bubbles in the center create a cylindrical hydrodynamic pattern, in which the inner parts of the cylinder move upwards, while the outer parts move downwards. In the lower part of the reactor, where the centralizing of the bubbles has not happened yet, the above-described pattern induces another hydrodynamic pattern, which acts counter wise. As a result, there is a calm zone, in which the solid-gas mixture is not moving very rapidly. In this zone, wall sheeting can occur. Furthermore, as a result of solid entrainment into the disengaging zone, sheeting can also occur further upstream of the reactor middle zone.

[0132] FIG. 2 shows the first preferred embodiment of the process according to the present invention in a gas-solids olefin polymerization reactor.

Reference Signs

[0133] 1 top zone (disengaging zone) [0134] 2 middle zone [0135] 3 bottom zone [0136] 4 fluidized bed (dense zone) [0137] 5 jet gas feeding port(s) [0138] 6 first line (fluidization gas (FG) input) [0139] 7 second line (fluidization gas output) [0140] 8 third line (jet gas (JG) input) [0141] 9 feeding port for polymerization catalyst [0142] 10 polymer withdrawal [0143] 11 fluidization grid [0144] 12 fourth line connecting the third line (8) and the second line (7) [0145] 13 fifth line connecting the third line (8) and the first line (6)

Description of FIG. 2

[0146] FIG. 2 shows the first preferred embodiment of the gas-solids olefin polymerization reactor system as implemented in the multi-stage reactor assembly of the present invention and as used in the process of the present invention. The gas-solids olefin polymerization comprises a top zone (1), a middle zone (2) and a bottom zone (3). The first stream of fluidization gas (6) enters the gas-solids olefin polymerization reactor through the bottom zone (3) and flows upwards, thereby passing a fluidization grid (11) and entering the middle zone (2). Due to the substantially cylindrical shape of the middle zone (2) the gas velocity is constant so that the fluidized bed (4) is established after the fluidization grid (11) in the middle zone (2). Due to the conical shape of the top zone (1) the gas entering the top zone (1) expands so that the gas disengages from the polyolefin product of the polymerization reaction so that the fluidized bed (4) is confined in the middle zone (2) and the lower part of the top zone (1). The polymerization catalyst together with optional polyolefin powder polymerized in previous polymerization stage(s) is introduced into the gas-solids olefin polymerization reactor through at least on feeding port (9) directly into the fluidized bed (4). The polyolefin product of the polymerization process is withdrawn from the gas-solids olefin polymerization reactor through outlet (10). The fluidized gas is withdrawn from the top zone (1) as second stream of fluidization gas (7).

[0147] In a particularly preferred embodiment of the invention, the solids-gas reactor according to the present invention (FIG. 2b) further comprises a fourth line (12) connecting the second line (7) and the third line (8) as well as a fifth line (13) connecting the third line (8) and the first line (6). Hence, in this embodiment at least part of the fluidization gas leaving the reactor from the top zone is recycled and reintroduced into the reactor either as fluidization gas or jet gas. The advantage of such an arrangement is that lower amounts of fluidization gas is needed and the overall process is less energy consuming as at least part of the heat as removed with the fluidization gas from the reactor is reintroduced at the bottom or via the jet gas feeds reducing the amount of energy needed to bring the gas streams to the temperature as needed for the reaction on the reactor.

[0148] FIG. 3 shows another embodiment of the process according to the present invention in a gas-solids olefin polymerization reactor.

Reference Signs

[0149] The reference signs 1-13 are identical to FIG. 2. [0150] 14 flash pipe jet gas feeding port(s) [0151] 15 sixth line connecting a flash pipe (FB) to reactor via feeding port(s) 14. [0152] FP flash pipe from a preceding polymerization reactor

Description of FIG. 3

[0153] As can be seen in FIGS. 3a-c, in this preferred embodiment of the present invention, either the whole jet gas injection system is completely replaced by a solids-gas stream derived from a flash pipe (FP, 5, 8; FIG. 3a) or at least one jet stream is derived from a flash pipe (FP, 14, 15, FIG. 3b-c) in addition to the jet stream as already described in the embodiments of FIG. 2 (JG, 5, 8; FIG. 2a-b). Further combinations can be implemented, e.g. a reactor assembly having flash pipe jet gas input and fluidization gas recirculation without the jet gas injection as described in the embodiments of FIG. 2 (i.e. line 8 via port(s) 5).

[0154] The stream derived from a flash pipe of a preceding polymerization reaction, preferably a polymerization reactor for the polymerization of polypropylene, most preferably a loop polymerization reactor for the polymerization of polypropylene, has a very high energy (momentum). Hence, the resulting jet gas stream has also much higher energy than the jet gas stream as provided by the fluidization gas. The technical effect of such an embodiment is that the hydrodynamic pattern as found in typical gas-solids olefin polymerization reactors (i.e. without jet gas injection) can be more efficiently destroyed yielding an increase in bulk density at reduced solids carry-over.

Examples

[0155] Preparation of Catalyst A

[0156] First, 0.1 mol of MgCl.sub.2×3 EtOH was suspended under inert conditions in 250 ml of decane in a reactor at atmospheric pressure. The solution was cooled to the temperature of −15° C. and 300 ml of cold TiCl.sub.4 was added while maintaining the temperature at said level. Then, the temperature of the slurry was increased slowly to 20° C. At this temperature, 0.02 mol of dioctylphthalate (DOP) was added to the slurry. After the addition of the phthalate, the temperature was raised to 135° C. during 90 minutes and the slurry was allowed to stand for 60 minutes. Then, another 300 ml of TiCl.sub.4 was added and the temperature was kept at 135° C. for 120 minutes. After this, the catalyst was filtered from the liquid and washed six times with 300 ml heptane at 80° C. Then, the solid catalyst component was filtered and dried.

[0157] Catalyst A and its preparation concept is described in general e.g. in EP 0 491 566, EP 0 591 224 and EP 0 586 390.

[0158] Preparation of Catalyst B

[0159] Raw Materials (Catalyst B) [0160] TiCl.sub.4 (CAS 7550-45-90) [0161] 20% solution in toluene of butyl ethyl magnesium (Mg(Bu)(Et)), provided by Crompton [0162] 2-ethylhexanol, provided by Merck Chemicals [0163] 3-Butoxy-2-propanol, provided by Sigma-Aldrich [0164] bis(2-ethylhexyl)citraconate, provided by Contract Chemicals [0165] Viscoplex® 1-254, provided by Evonik [0166] Heptane, provided by Chevron

[0167] Preparation of Mg Complex (Catalyst B)

[0168] 3.4 l of 2-ethylhexanol and 810 ml of propylene glycol butyl monoether (in a molar ratio 4/1) were added to a 20 l reactor. Then 7.8 l of a 20% solution in toluene of BEM (butyl ethyl magnesium) provided by Crompton GmbH was slowly added to the well stirred alcohol mixture. During the addition the temperature was kept at 10° C. After addition the temperature of the reaction mixture was raised to 60° C. and mixing was continued at this temperature for 30 minutes. Finally, after cooling to room temperature the obtained Mg-alkoxide was transferred to storage vessel.

[0169] 21.2 g of Mg-alkoxide as prepared above was mixed with 4.0 ml bis(2-ethylhexyl) citraconate for 5 min. After mixing the obtained Mg complex was used immediately in the preparation of catalyst component.

[0170] Preparation of Catalyst Component (Catalyst B)

[0171] 19.5 ml titanium tetrachloride was placed in a 300 ml reactor equipped with a mechanical stirrer at 25° C. Mixing speed was adjusted to 170 rpm. 26.0 g of Mg-complex as prepared above was added within 30 minutes keeping the temperature at 25° C. 3.0 ml of Viscoplex 1-254 and 24.0 ml of heptane were added to form an emulsion. Mixing was continued for 30 minutes at 25° C. Then the reactor temperature was raised to 90° C. within 30 minutes. The reaction mixture was stirred for further 30 minutes at 90° C. Afterwards stirring was stopped and the reaction mixture was allowed to settle for 15 minutes at 90° C.

[0172] The solid material was washed with 100 ml of toluene, with of 30 ml of TiCl.sub.4, with 100 ml of toluene and two times with 60 ml of heptane. 1 ml of donor was added to the two first washings. Washings were made at 80° C. under stirring for 30 min with 170 rpm. After stirring was stopped the reaction mixture was allowed to settle for 20-30 minutes and followed by siphoning.

[0173] Afterwards stirring was stopped and the reaction mixture was allowed to settle for 10 minutes the temperature was decreased to 70° C. with subsequent siphoning, and followed by N.sub.2 sparging for 20 minutes to yield an air sensitive powder.

[0174] Catalyst B has a surface area measured by BET method below 5 m.sup.2/g, i.e. below the detection limit.

Comparative Example 1 (CE1)

[0175] A Ziegler Natta polypropylene (ZNPP) catalyst (Catalyst A) exhibiting a kinetic profile as shown in FIG. 4 was used. The catalyst was slurried in a carrier liquid, co-catalyst and donor, hydrogen, and propylene and subsequently fed into a pre-polymerizer.

[0176] The pre-polymerizer was operated at a pressure of 58 barg and a temperature of 30° C. The material introduced into the pre-polymerized had a mean residence time of 30 min. The produced pre-polymer was fed with additional propylene and hydrogen for molecular weight control to the slurry loop reactor.

[0177] The reaction took place in bulk propylene as a carrier liquid. The loop reactor was operated at a temperature of 80° C. and a pressure of 56 barg, whereby the slurry concentration was around 45 wt %.

[0178] Subsequently, the slurry from the loop reactor was fed directly to the first gas solid olefin polymerization reactor to produce further homopolypropylene. This reactor was operated at a temperature of 85° C. and a pressure of 22 barg.

[0179] After withdrawal from the first gas solid olefin polymerization reactor, the material was transferred to the second first gas solid olefin polymerization reactor to produce homopolymer/random copolymer.

[0180] The overall residence time in the gas solid olefin polymerization reactors connected in series was 2 h and 15 min. The production split was 51/49 (i.e., 51 wt % of the polymer was produced in the loop reactor and 49 wt % of the polymer was produced in first gas solid olefin polymerization reactors).

Inventive Example 1 (IE1)

[0181] In Inventive Example 1, the polymerization series described in Comparative Example 1 was repeated with the only difference being the introduction of jet gas in the first gas solid olefin polymerization reactors. While the fluidization bed volume and the production rate of the first gas solid olefin polymerization reactors was kept constant according to Comparative Example 1, the production split was 43.5/56.5 (i.e., 43.5 wt % of the polymer was produced in the loop reactor and 56.5 wt % of the polymer was produced in the gas solid olefin polymerization reactors).

Comparative Example 2 (CE2)

[0182] In Comparative Example 2, the polymerization series described in Comparative Example 1 was repeated with the only difference being the catalyst system used. In this example, a Ziegler Natta polypropylene (ZNPP) catalyst (Catalyst B) exhibiting a kinetic profile shown in FIG. 5 was used. The production split was 60/40 (i.e., 60 wt % of the polymer was produced in the loop reactor and 40 wt % of the polymer was produced in the gas solid olefin polymerization reactors).

Inventive Example 2 (IE2)

[0183] In Inventive Example 2, the polymerization series described in Comparative Example 2 was repeated with the only difference being the introduction of jet gas in the gas solid olefin polymerization reactors. While the fluidization bed volume and the production rate of the first gas solid olefin polymerization reactors was kept constant according to Comparative Example 2, the production split was 49.3/56.5 (i.e., 49.3 wt % of the polymer was produced in the loop reactor and 56.5 wt % of the polymer was produced in the gas solid olefin polymerization reactors).