EP-4735485-A1 - OLEFIN POLYMERIZATION PROCESS

Abstract

The present invention relates to an olefin polymerization process comprising polymerization of at least one olefin monomer in one or more polymerization reactors. An object of the present invention is to recover unreacted components from the polymer powder leaving the reactor of an olefin polymerization process. Another object of the present invention is to reduce the amount of dissolved monomers with higher molecular weight to prevent issues with fouling and lump formation in subsequent purging operations.

Inventors

• Delsman, Erik René
• JACOB, Kiran Abraham

Assignees

• SABIC Global Technologies B.V.

Dates

Publication Date

20260506

Application Date

20240620

Claims (4)

1. 1. A process for polymerization of olefins, such as propylene, ethylene and 1 - hexene, in the presence of a catalyst system in a reactor comprising an agitated bed for forming polymer particles, a plurality of liquid feed ports, and a plurality of gas feed ports, wherein the process comprises the steps of: - recovering a reactor off-gas comprising H2, olefins from the reactor, - feeding the reactor off-gas to a condenser to form a gas-liquid mixture, - feeding the gas-liquid mixture to a separator to obtain a first gas stream comprising H2, ethylene and propylene and a first liquid stream comprising H2, ethylene, propylene and 1 -hexene, wherein fresh propylene is further fed to the separator and/or added to the first liquid stream, - feeding the catalyst system to the reactor through a port arranged on the top side of the reactor, - feeding a H2 poor quench liquid comprising propylene a H2 rich quench liquid comprising H2, ethylene and propylene and 1 -hexene to the reactor through the liquid feed ports, - feeding a H2 poor bottom gas comprising fresh propylene and a H2 rich bottom gas comprising H2, ethylene and propylene through the gas feed ports, - collecting the polymer particles formed in the agitated bed from the reactor, - feeding fresh ethylene and fresh C4-C8 olefin to the reactor, wherein the step of collecting the polymer particles formed in the agitated bed from the reactor comprises a step of contacting the stream of polymer particles with a stripping gas thereby forming a stream of polymer particles having a C4-C8 olefins content that is lower than the C4-C8 olefins content of the stream of polymer particles formed in the agitated bed from the reactor, -compressing and recycling the stripping gas to the reactor, wherein the stripping gas is chosen from the group of vaporized propylene and ethylene.
2. 2. A process according to claim 1 , wherein after the step of contacting the stream of polymer particles formed in the agitated bed from the reactor with a stripping gas the C4-C8 olefins content of the stream of polymer particles thus obtained is reduced with at least 20 wt.%, preferably at least 40 wt.%, more preferably 50 wt.%, compared to the C4-C8 olefins content of the stream of polymer particles formed in the agitated bed.
3. 3. A process according to any one or more of the preceding claims, wherein the stripping gas is contacted in a counter-current flow with the polymer particles formed in the agitated bed from the reactor.
4. 4. A process according to any one or more of the preceding claims, wherein the temperature during the step of contacting with the stripping gas is in a range of 50 - 70 °C.

Description

Title: Olefin polymerization process Description: The present invention relates to an olefin polymerization process comprising polymerization of olefin monomer(s) in one or more polymerization reactors. Processes for vapor-phase polymerization of monomers in a vapor-phase, quench-cooled reactor vessel are known in the art. Polyolefins, such as polyethylene and polypropylene, may be prepared by particle form polymerization, also referred to as slurry polymerization. In this technique, a monomer feed may be polymerized in a reaction zone in the presence of a catalyst and optionally, a solvent (also known as a diluent) to produce a polymerization effluent containing a slurry of polymer solids in a liquid medium comprising unreacted hydrocarbon monomer and optionally, solvent. In order to recover the polymer solids from the slurry, the polymerization effluent may be withdrawn from the reactor and the polymer solids may be separated from the liquid medium. Typical polymer recovery and separation systems include subjecting the polymerization effluent to a reduction in pressure so that the liquid medium may vaporize leaving concentrated polymer solids. The vaporized liquid medium may exit at an upper portion of a flash tank, while the polymer solids may be recovered through a lower portion of the flash tank. The vaporized liquid medium can then be recycled back to the reaction zone. WO 2017/102303 in the name of the present applicant relates to an olefin polymerization process comprising polymerization of at least one olefin monomer in one or more polymerization reactors wherein the polymerization process is carried out in an apparatus comprising one or more reactor vessels to which olefin monomer and catalyst components can be added and which contain an agitated bed of forming polymer particles, means for removing a stream comprising polymer particles from the reactor, means for removing a gas-liquid stream comprising unreacted olefin monomers from the reactor, means for withdrawing a liquid recycle stream from the gas-liquid stream, means for recycle a gas-liquid stream to the reactor, wherein the process further comprises the steps of withdrawing a gaseous stream from the stream comprising polymer particles, contacting a liquid recycle stream with the gaseous stream thereby forming a mixture, withdrawing a liquid stream from the mixture and recycling a vapor stream from the mixture to the polymerization reactor. US Patent No. 4,921 ,919 relates to a method and apparatus for minimizing the formation of polymer agglomerates or lumps in a reactor used in the gas-phase polymerization of polypropylene. In operation of vapor-phase polymerization processes using vapor-phase, quench-cooled reactor vessels such processes and apparatus, particles of polymer are formed around solid catalyst particles. The horizontally disposed reactor vessel typically has recycled propylene gas introduced into the bottom thereof together with hydrogen gas. Then, liquid propylene, as a quench liquid, is injected into the reactor from the top of the reactor. The hydrogen is provided for molecular weight control. Agitators inside the vessel stir the contents of the vessel. At a so-called upstream end of the vessel a catalyst system comprising a catalyst injected at one point into the top of the vessel, and a cocatalyst plus modifier injected at a point adjacent the point of injection of the catalyst, is injected into the top of the vessel. Solid polypropylene powder is created in the vessel and is withdrawn from the downstream end thereof. EP 1 853 635 relates to a process for the polymerization of ethylene in which the ethylene is polymerized in the presence of a catalyst in a gas-phase reactor to form polymer particles and reaction gas comprising propane and unpolymerized ethylene is circulated to remove the heat of polymerization, wherein the polymer particles are discharged continuously or discontinuously from the reactor, the polymer particles are separated from the major part of the concomitantly discharged gas and the polymer particles are degassed, the gas is freed of entrained fine particles, the gas is separated from a low-boiling fraction comprising in a first separation stage, a propane fraction is separated off in a second separation stage and this propane fraction is used for degassing the polymer particles discharged from the reactor. EP 2 083 020 relates to a process for the recovery of unreacted monomers from a polyolefin polymerization process, comprising the steps of recovering a fluid stream generated by the separation of the polyolefin product from the polymerization fluid comprising unreacted monomers and optionally comonomers, contacting said fluid stream in an absorption zone with a scrub liquid, thereby absorbing at least a portion of the unreacted monomers in said scrub liquid; and withdrawing from said absorption zone a vapor overhead comprising light gas and an absorber bottoms scrub liquid comprising said unr