WO2021202278A1 - Produit anti-encrassement et procédé - Google Patents

Produit anti-encrassement et procédé Download PDF

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Publication number
WO2021202278A1
WO2021202278A1 PCT/US2021/024348 US2021024348W WO2021202278A1 WO 2021202278 A1 WO2021202278 A1 WO 2021202278A1 US 2021024348 W US2021024348 W US 2021024348W WO 2021202278 A1 WO2021202278 A1 WO 2021202278A1
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Prior art keywords
antifoulant
ethylene
compressor
hyper
preheater
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PCT/US2021/024348
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English (en)
Inventor
Sean W. Ewart
Sarat Munjal
Henk Hagen
Alexandra E. FRANKEL
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Dow Global Technologies Llc
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Publication of WO2021202278A1 publication Critical patent/WO2021202278A1/fr

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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F110/00—Homopolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
    • C08F110/02—Ethene
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F2400/00—Characteristics for processes of polymerization
    • C08F2400/04—High pressure, i.e. P > 50 MPa, 500 bars or 7250 psi

Definitions

  • LDPE low density polyethylene
  • the process includes introducing an antifoulant into an ethylene feed of a reactor system.
  • the reactor system includes the ethylene feed, a hyper-compressor, a preheater and a polymerization reactor.
  • the ethylene feed is located upstream of the hyper-compressor.
  • the antifoulant consists of an inhibitor and optionally a solvent.
  • the process includes introducing the antifoulant into the ethylene feed upstream of the hyper-compressor.
  • the process further includes adding a free radical initiator to the polymerization reactor.
  • the process further includes polymerizing the ethylene in the polymerization reactor under high pressure free-radical polymerization conditions, and forming an ethylene-based polymer.
  • FIG. 1 is a schematic representation of a flow scheme for a reactor system in accordance with an embodiment of the present disclosure.
  • FIG. 2 is a schematic representation of the equipment used to replicate the operating conditions for the hyper-compressor and preheater in a large-scale industrial LDPE reactor system and, the equipment in FIG. 2 used to generate the comparative sample and the inventive examples.
  • FIG. 3 shows two photographs of the level of fouling in accordance with comparative sample 1.
  • FIG. 4 shows two photographs of the level of fouling for inventive example 1.
  • FIG. 5 shows two photographs of the level of fouling for inventive example 2.
  • FIG. 6 shows two photographs of the level of fouling for inventive example 3.
  • FIG. 7 shows two photographs of the level of fouling for inventive example 7.
  • the numerical ranges disclosed herein include all values from, and including, the lower and upper value.
  • ranges containing explicit values e.g., from 1 or 2, or 3 to 5, or 6, or 7
  • any subrange between any two explicit values is included (e.g., the range 1-7 above includes subranges of from 1 to 2; from 2 to 6; from 5 to 7; from 3 to 7; from 5 to 6; etc.).
  • blend refers to a mixture of two or more polymers.
  • a blend may or may not be miscible (not phase separated at molecular level).
  • a blend may or may not be phase separated.
  • a blend may or may not contain one or more domain configurations, as determined from transmission electron spectroscopy, light scattering, x-ray scattering, and other methods known in the art.
  • the blend may be effected by physically mixing the two or more polymers on the macro level (for example, melt blending resins or compounding), or the micro level (for example, simultaneous forming within the same reactor.
  • composition refers to a mixture of materials which comprise the composition, as well as reaction products and decomposition products formed from the materials of the composition.
  • compositions claimed through use of the term “comprising” may include any additional additive, adjuvant, or compound, whether polymeric or otherwise, unless stated to the contrary.
  • the term “consisting essentially of” excludes from the scope of any succeeding recitation any other component, step, or procedure, excepting those that are not essential to operability.
  • the term “consisting of” excludes any component, step, or procedure not specifically delineated or listed.
  • ethylene-based polymer refers to a polymer that includes, in polymerized form, more than 50 wt%, or a majority amount, of ethylene, based on the weight of the polymer, and, optionally, may include at least one comonomer or other molecule.
  • ethylene monomer refers to a chemical unit having two carbon atoms with a double bond therebetween, and each carbon bonded to two hydrogen atoms, wherein the chemical unit polymerizes with other such chemical units to form an ethylene-based polymer composition.
  • fouling refers to the deposition (temporary or permanent) of a pre polymer layer (or a polymer layer) onto the surface of a component in a polymerization reactor system or other apparatus used in a polymerization reactor system (such as an LDPE reactor system, for example).
  • a layer of pre-polymer (or polymer) of this nature in the hyper compressor (or on the check valves of the hyper-compressor) can negatively affect the total ethylene throughput into the reactor.
  • a layer of pre-polymer (or polymer) of this nature in the preheater or in the polymerization reactor can impact the overall heat transfer coefficient in one or more components of the reactor system used to produce LDPE, thus reducing the production rate of the polymer.
  • hydrocarbon-based molecule refers to a chemical component that has only carbon atoms and hydrogen atoms.
  • low density polyethylene refers to an ethylene-based polymer having a density from 0.909 g/cc to less than 0.940 g/cc, or from 0.917 g/cc to 0.9B0 g/cc, and long chain branches with a broad molecular weight distribution (MWD greater than 3.0). LDPE is distinct from linear low density polyethylene.
  • linear low density polyethylene refers to a linear ethylene/a-olefin copolymer containing heterogeneous short-chain branching distribution comprising units derived from ethylene and units derived from at least one C 3 -Ci 0 a-olefin, or C -C 8 a-olefin comonomer.
  • LLDPE is characterized by little, if any, long chain branching, in contrast to conventional LDPE which has long chain branching.
  • LLDPE has a density from 0.910 g/cc to less than 0.940 g/cc.
  • Nonlimiting examples of LLDPE include TUFLINTM linear low density polyethylene resins (available from The Dow Chemical Company), DOWLEXTM polyethylene resins (available from the Dow Chemical Company), and MARLEXTM polyethylene (available from Chevron Phillips).
  • molecular oxygen refers to a diatomic molecule that consists of two oxygen atoms covalently bonded to each other. Molecular oxygen is interchangeably referred to as elemental oxygen, or O2.
  • sources for molecular oxygen include air ( ⁇ 21 vol% molecular oxygen), 0 2 gas, liquid 0 2 , and blends of 0 2 in other inert gases such as nitrogen, N 2 , for example. Oxygen may be added as a gas stream or pre dissolved in a solvent.
  • polymer or a "polymeric material,” as used herein, refers to a compound prepared by polymerizing monomers, whether of the same or a different type, that in polymerized form provide the multiple and/or repeating "units" or "mer units” that make up a polymer.
  • the generic term polymer thus embraces the term homopolymer, usually employed to refer to polymers prepared from only one type of monomer, and the term copolymer, usually employed to refer to polymers prepared from at least two types of monomers. It also embraces all forms of copolymer, e.g., random, block, etc.
  • ethylene/a-olefin polymer and "propylene/a-olefin polymer” are indicative of copolymer as described above prepared from polymerizing ethylene or propylene respectively and one or more additional, polymerizable a- olefin monomer.
  • a polymer is often referred to as being "made of” one or more specified monomers, "based on” a specified monomer or monomer type, "containing” a specified monomer content, or the like, in this context the term “monomer” is understood to be referring to the polymerized remnant of the specified monomer and not to the unpolymerized species.
  • polymers herein are referred to has being based on “units” that are the polymerized form of a corresponding monomer.
  • melt index refers to the measure of how easily a thermoplastic polymer flows when in a melted state. Melt index, or , is measured in accordance by ASTM D 12S8, Condition 190°C/2.16 kg, and is reported in grams eluted per 10 minutes (g/10 min). The 110 is measured in accordance with ASTM D 12S8, Condition 190°C/10 kg, and is reported in grams eluted per 10 minutes (g/10 min).
  • the process includes introducing an antifoulant into an ethylene feed of a reactor system.
  • the reactor system includes the ethylene feed, a hyper-compressor, a preheater and a polymerization reactor.
  • the ethylene feed is located upstream of the hyper-compressor.
  • the antifoulant consists of an inhibitor (or a mixture of one or more inhibitors) and optionally a solvent; the antifoulant introduced into the ethylene feed upstream of the hyper-compressor.
  • the process includes adding a free radical initiator to the polymerization reactor and polymerizing the ethylene in the polymerization reactor under high pressure free-radical polymerization conditions.
  • the process includes forming an ethylene-based polymer.
  • the process includes introducing an antifoulant into an ethylene feed of a polymerization reactor system.
  • a "reactor system,” as used herein, refers to the components and devices used to polymerize one or more olefin monomers.
  • the reactor system includes a hyper-compressor, a preheater, and a polymerization reactor in fluid communication with each other.
  • the polymerization reactor is one or more high pressure polymerization reactors.
  • suitable high pressure polymerization reactors include an autoclave reactor, a tubular reactor, or a combination of an autoclave reactor in operative communication with a tubular reactor.
  • the reactor system includes an ethylene feed, a hyper-compressor, a preheater, and a polymerization reactor, each component in fluid communication with, or otherwise in operative communication with, each other.
  • a "hyper-compressor,” as used herein, is a compressor that pressurizes one or more ethylene feeds to a pressure of at least 100 MPa.
  • the ethylene feed is located upstream of the hyper-compressor.
  • the reactor system Moving through the reactor system in an upstream to downstream direction, the reactor system includes (i) the ethylene feed in fluid communication with (ii) the hyper-compressor, the hyper-compressor in fluid communication with (iii) the preheater, and the preheater in fluid communication with (iv) the polymerization reactor.
  • the pre-heater heats the polymerization reactor contents prior to injection of the free-radical initiator.
  • the reactor system may include other components in addition to these components.
  • FIG. 1 shows an embodiment of a flow scheme for the present reactor system.
  • Ethylene monomer is introduced into the reactor system as one or more ethylene feeds.
  • the ethylene monomer may be (i) a feed (1) of fresh ethylene, (ii) a feed (18) of recycle ethylene, or (iii) a combination of (i) and (ii), namely, a combined ethylene feed (3) composed of both fresh ethylene feed (1) and recycle ethylene feed (18).
  • Recycle ethylene feed (18) is ethylene monomer separated from the polymerization reaction mixture by way of a high pressure separator ("HPS" in FIG. 1).
  • HPS high pressure separator
  • Ethylene feed (1), (18), and/or (3) feed ethylene monomer to a hyper- compressor ("Hyper Compressor” in FIG. 1).
  • the hyper-compressor pressurizes the ethylene feed(s) to a level sufficient to feed the polymerization reactor ("Reactor” in FIG. 1) and produce high pressure free-radical polymerization conditions.
  • the preheater (“Preheater” in Fig. 1) receives the output from the hyper-compressor and heats this output to a temperature for high pressure free radical polymerization, or a temperature from 130°C to 170°C.
  • the polymerization reactor receives the output from the preheater and increases the temperature from 250 to 360°C; polymerization occurs in the polymerization reactor at a temperature from 250°C to 360°C.
  • high pressure free-radical polymerization conditions refers to the environment in a polymerization reactor (autoclave reactor and/or tubular reactor) with (i) a pressure of at least 100 MPa (1000 Bar), (ii) a temperature from 150°C to 360°C, and (iii) the presence of a free-radical initiator.
  • the fresh ethylene feed (1) is compressed together with the outlet of a booster compressor ("Booster” in FIG. 1), by a primary compressor ("Primary” in FIG. 1) to produce ethylene feed (2).
  • Booster booster compressor
  • Primary Primary compressor
  • ethylene feed (2) is combined with recycle ethylene stream (18) to form combined ethylene feed (3), and distributed over the suction inlets of the hyper-compressor ("Hyper-compressor" in FIG. 1).
  • the process includes introducing an antifoulant into the ethylene feed of the reactor system.
  • the antifoulant consists of (i) an inhibitor (or one or more inhibitors), (ii) optionally a solvent (or one or more solvents), and (iii) optional additives (or one or more additives).
  • the antifoulant consists of only one component (inhibitor), or consists of only two components (inhibitor and solvent), or consists of only three components (inhibitor, solvent and additive).
  • the antifoulant consists of one component, namely, the inhibitor (or one or more than one inhibitors).
  • the antifoulant consists of two and only two components, namely, the inhibitor (or one or more than one inhibitor), and the solvent (or one or more than one solvent).
  • the antifoulant excludes, or otherwise avoids, molecular oxygen.
  • the inhibitor is the sole component of the antifoulant and the inhibitor is added neat to the ethylene feed.
  • the neat inhibitor can be a solid (particulate material, or a powder) or a liquid.
  • the antifoulant consists only of the inhibitor, the inhibitor is a liquid, the neat inhibitor liquid added into the ethylene feed.
  • the inhibitor is dispersed in, or is otherwise dissolved in, the solvent.
  • Nonlimiting examples of suitable inhibitor include phenothiazine, (2, 2,6,6- Tetramethylpiperidin-l-yl)oxyl (TEMPO), derivatives of TEMPO, monomethyl ether hydroquinone (MEHQ), butylated hydroxytoluene (BHT) and combinations thereof--each to the exclusion of molecular oxygen.
  • TEMPO (2, 2,6,6- Tetramethylpiperidin-l-yl)oxyl
  • MEHQ monomethyl ether hydroquinone
  • BHT butylated hydroxytoluene
  • the solvent system can be a single solvent or a mixture of two or more solvents.
  • suitable solvent for the solvent system include aliphatic C3-C6 hydrocarbon (propane, butane, pentane, hexane), olefinic C3-C6 hydrocarbon (propylene, butene, pentene, hexene), Ci-C 6 ketone (acetone, methyl ethyl ketone), Ci-C 6 aldehyde, Ci- C 6 alcohol (methanol, ethanol, propanol, butanol, pentanol, hexanol), and combinations thereof.
  • the process includes dispersing, or otherwise dissolving, the inhibitor into the solvent prior to, or before, the introduction of the antifoulant into the ethylene feed.
  • the process includes (prior to the introduction of the antifoulant into the ethylene feed) dispersing, an inhibitor selected from phenothiazine (PTZ), (2,2,6,6-tetramethylpiperidin-l-yl)oxyl (TEMPO), a derivative of TEMPO, monomethyl ether hydroquinone (MEHQ), butylated hydroxytoluene (BHT) and combinations thereof, into a solvent selected from aliphatic C3-C6 hydrocarbon, olefinic C3-C6 hydrocarbon, C1-C6 ketone, Ci-C 6 aldehyde, C1-C6 alcohol, and combinations thereof, and forming the antifoulant.
  • the antifoulant is introduced into one, some, or all of the following ethylene feeds: ethylene feed
  • the point at which antifoulant addition occurs is upstream of the hyper-compressor. Since the antifoulant is introduced upstream of the hyper-compressor (and the hyper-compressor is upstream of the preheater), the point at which the antifoulant addition occurs is upstream of the preheater. Since the antifoulant is introduced upstream of the preheater (and the preheater is upstream of the polymerization reactor), the point at which antifoulant addition occurs is upstream of the polymerization reactor.
  • the process includes introducing the antifoulant into the fresh ethylene feed (1).
  • the process includes introducing the antifoulant into the ethylene feed (2).
  • the process includes introducing the antifoulant into the combined ethylene feed (3).
  • the process includes introducing the antifoulant into the recycle ethylene feed (18).
  • the reactor system includes one or more antifoulant inlets in fluid communication with the respective one or more ethylene feeds.
  • the antifoulant inlet is in direct fluid communication with the ethylene feed.
  • direct fluid communication refers to a configuration whereby a first structure (i.e., the antifoulant inlet) is in immediate fluid communication with a second structure (i.e., the ethylene feed) such that no intervening third structure is located between the first structure and the second structure.
  • the process includes introducing the antifoulant into the antifoulant inlet and into the ethylene feed.
  • the reactor system includes an antifoulant inlet la in direct fluid communication with ethylene feed (1), and/or an antifoulant inlet 2a in direct fluid communication with ethylene feed (2), and/or an antifoulant inlet 3a in direct fluid communication with combined ethylene feed (3), and/or an antifoulant inlet 18a in direct fluid communication with recycle ethylene feed (18).
  • the antifoulant consists of only neat liquid inhibitor, the neat liquid inhibitor introduced into the antifoulant inlet la and/or 2a, and/or 3a, and/or 18a.
  • the antifoulant inlet Since the antifoulant inlet is located upstream of the hyper-compressor, the point at which the antifoulant inlet introduces antifoulant into the ethylene feed is upstream of the hyper-compressor, and the antifoulant inlet is also upstream of the preheater, and the antifoulant inlet is also upstream of the polymerization reactor.
  • the process includes introducing the antifoulant into the antifoulant inlet (la) and directly into fresh ethylene feed (1).
  • the process includes introducing the antifoulant into the antifoulant inlet (2a) and directly into ethylene feed (2).
  • the process includes introducing the antifoulant into the antifoulant inlet (3a) and directly into combined ethylene feed (3).
  • the process includes introducing the antifoulant into the antifoulant inlet (18a) and directly into the recycle ethylene feed (18).
  • one or more chain transfer agents are fed to the hyper compressor for introduction into the polymerization reactor to control molecular weight of the resultant ethylene-based polymer.
  • suitable CTAs include propylene, isobutane, n-butane, 1-butene, methyl ethyl ketone, acetone, ethyl acetate, propionaldehyde, ISOPAR (ExxonMobil Chemical Co.), and isopropanol, and combinations thereof.
  • the amount of CTA used in the process is from 0.01 weight percent to 10 weight percent, or from 0.01 weight percent to 5 weight percent, or from 0.1 weight percent to 1.0 weight percent, or from 0.1 weight percent to 0.5 weight percent, or from 0.01 weight percent to 0.1 weight percent of the total reaction mixture.
  • the solvent for the antifoulant is the CTA for the high pressure free-radical polymerization. Consequently, the addition of the CTA occurs simultaneously with, or substantially simultaneously with, the introduction of the antifoulant into the ethylene feed.
  • the present process includes introducing the CTA (as the solvent for the inhibitor, the CTA a component of the antifoulant) with the antifoulant into the ethylene feed, the introduction of the CTA occurring upstream of the hyper-compressor.
  • the reaction system includes CTA stream (4) and/or recycle CTA stream (5).
  • the CTA stream 4 and/or the CTA recycle stream (5) can, in principle, be freely distributed over the main compression streams fed and/or distributed over the side stream (8) and front stream (9).
  • CTA stream (4) and/or CTA recycle stream (5) can be fed in the inlet(s), interstage(s), outlet(s) of the hyper-compressor and/or inlet(s) of the reaction zones in the polymerization reactor.
  • the CTA stream (4) and/or the recycle CTA stream (5) operate in conjunction with the antifoulant feed to provide the proper amount of CTA to the reaction system.
  • the CTA stream (4) and/or recycle CTA stream (5) are the sole sources of CTA for the reactor system.
  • the reactor system includes a branching agent stream (6) and/or a polymerizable comonomer stream (7).
  • the branching agent feed (6) and/or the polymerizable comonomer stream (7) can, in principle, be freely distributed over the main compression streams fed and/or distributed over the side stream (8) and/or front stream (9).
  • Branching agent stream (6) and/or polymerizable comonomer stream (7) can be fed in the inlet(s), interstage(s), outlet(s) of the hyper-compressor, individual ethylene feed streams to the reactor or directly into the reaction zones.
  • the discharge temperature of the hyper-compressor is from 60°C to 110°C.
  • the preheater heats the ethylene feed (and other feeds) received from the hyper-compressor to a temperature from 130°C to 170°C.
  • the ethylene monomer with antifoulant flows into, or otherwise enters into, the polymerization reactor ("Reactor" in FIG. 1).
  • the process includes adding a free radical initiator to the polymerization reactor and polymerizing the ethylene in the polymerization reactor under high pressure free-radical polymerization conditions to form an ethylene-based polymer.
  • the free radical initiator is added directly to one or more reaction zones of the polymerization reactor.
  • the free radical initiator is introduced into the polymerization reactor by way of side stream (8).
  • suitable free radical initiator include organic peroxides, cyclic peroxides, diacyl peroxides, dialkyl peroxides, hydroperoxides, peroxycarbonates, peroxydicarbonates, peroxyesters, peroxyketals, t-butyl peroxy pivalate, di-t-butyl peroxide, t-butyl peroxy acetate and t-butyl peroxy-2-hexanoate, and combinations thereof.
  • the free radical initiator includes at least one peroxide group incorporated in a ring structure.
  • free radical initiators with a peroxide group incorporated in a ring structure include TRIGONOX 301 (3,6,9-triethyl-3,6,9-trimethyl-l,4,7-triperoxonaan) and TRIGONOX 311 (3,3,5,7,7-pentamethyl-l,2,4-trioxepane), both available from Akzo Nobel, and HMCH-4-AL (3,3,6,6,9,9-hexamethyl-l,2,4,5-tetroxonane) available from United Initiators.
  • the organic peroxy initiators are used in an amount from 0.001 wt% to 0.2 wt%, based upon the weight of polymerizable monomers.
  • the high pressure free-radical polymerization occurs in a tubular reactor having multiple reactor zones (from three to six reactor zones).
  • the maximum temperature in each reactor zone is from 150°C to 360°C, or from 170°C to 350°C, or from 200°C to 340°C.
  • the pressure in each reactor zone is from 100 MPa to 380 MPa, or from 110 MPa to 340 MPa, or from 110 MPa to 300 MPa.
  • Pre-polymerization is the premature polymerization of the ethylene (and optional branching agent and/or optional polymerizable comonomer) in the hyper-compressor and/or in the preheater.
  • the pre-polymer formed in the hyper-compressor (also in the interstage cooler), and in the preheater is high-density (0.930-0.965 g/cc) high molecular weight (150,000-500,000 g/mol) polymer which phase separates and forms a solid deposit, thus interfering with operation of the hyper-compressor and reducing the heat transfer in interstage cooler(s) and in the preheater.
  • the process includes reducing, or otherwise preventing, with the antifoulant, pre-polymerization (or pre-polymer composed of the ethylene and/or optional branching agent and/or optional polymerizable comonomer) in the hyper-compressor and/or in the preheater.
  • Applicant developed a fouling rating scale with a rating of "1" being highly fouled (comparative sample 1 having a “1” rating of highly fouled as shown in FIG.3) and a rating of "5" being completely clean (inventive examples 1-2 and 4 each having a rating of "5" completely clean as shown in FIGs. 4-5).
  • the process includes introducing the antifoulant into the ethylene feed to form an ethylene feed containing from 0.01 mol ppm to 5 mol ppm inhibitor, or from 0.05 mol ppm to 3mol ppm inhibitor, or from 0.07 mol ppm to 2 mol ppm inhibitor, or from 0.1 mol ppm to 1.0 mol ppm inhibitor; the process further including reducing, or otherwise preventing ("preventing" being fouling rating 3-5, or 5), pre-polymerization (or formation of pre-polymer) in the hyper-compressor and/or in the preheater.
  • the process includes adding a polymerizable comonomer to the polymerization reactor by way of polymerizable comonomer stream (7) and forming an ethylene copolymer.
  • suitable polymerizable comonomers include one or more C3-C20 a-olefin comonomers, acrylate, (meth)acrylic acid, (meth)acrylic ester, carbon monoxide, maleic anhydride, vinyl acetate, vinyl propionate, mono esters of maleic acid, diesters of maleic acid, vinyl trialkoxysilane, vinyl trialkyl silane, and any combination thereof.
  • Nonlimiting examples of suitable C3-C20 a-olefin comonomers include one or more linear or branched C3-C12 a-olefin comonomers, or one or more linear or branched C -C 8 a- olefin comonomers such as propylene, 1-butene, 1 pentene, 4-methyl-l-pentene, 1-hexene, and 1-octene.
  • the antifoulant is void of, or otherwise excludes, a polymerizable comonomer.
  • the reaction mixture is depressurized and/or cooled in (10), and separated in the high pressure separator (HPS).
  • HPS high pressure separator
  • the high pressure separator separates the reaction mixture into an ethylene rich stream (15), containing minor amounts of waxes and/or entrained polymer, and a polymer rich stream (11), which is sent for further separation to the low pressure separator (LPS).
  • Ethylene stream (15) is cooled down and cleaned in stream (17).
  • Stream (16) is a purge stream to remove impurities and/or inerts.
  • the ethylene-based polymer separated in LPS is further processed in (12).
  • the ethylene removed in the LPS is fed to the booster compressor ("Booster" in FIG.
  • Booster booster compressor
  • the reactor system includes a lubricant feed for the hyper-compressor.
  • the lubricant oil may (or may not) contain an antioxidant. Some lubricant may leak into the compression chamber of the hyper-compressor and thus leak into the ethylene.
  • the present process advantageously adds antifoulant directly into the ethylene feed upstream of the hyper-compressor, avoiding the need to dissolve antifoulant in the lubricant oil.
  • the antifoulant upon addition to the ethylene feed is void of, or otherwise excludes, lubricant oil.
  • FIG. 2 shows a schematic representation of the equipment used to prepare the inventive examples and the comparative sample.
  • a S00 ml continuous polymerization reactor (CPR) is used to replicate the hyper-compressor and the preheater portions of an industrial-scale LDPE production system.
  • CPR continuous polymerization reactor
  • ethylene monomer is added at 7 Ib/hr.
  • propionaldehyde serving as both a chain transfer agent and the antifoulant solvent
  • the ethylene and propionaldehyde are then pressurized in the hyper-compressor to 30,000 psi (206800 kiloPascals (kPa)) through the use of a valve.
  • the CPR is heated to 140°C to replicate the temperatures in the hyper-compressor and in the preheater portion of an industrial-scale LDPE production system.
  • the ethylene and propionaldehyde are allowed to flow through the CPR reactor at 140°C for 18 hours to further replicate the hyper compressor and the preheater portions of an industrial-scale LDPE production system.
  • All pre-polymer formed is collected and weighed.
  • the CPR is opened and examined for the level of fouling (hereafter referred to as Process 1).
  • Processl is performed and an amount of inhibitor is dissolved in the propionaldehyde to form the anitfoulant.
  • the antifoulant is added simultaneously with the ethylene monomer to the reactor system.
  • Processl is performed seven separate times using four different antifoulants.

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Abstract

La présente divulgation concerne un procédé. Dans un mode de réalisation, le procédé comprend l'introduction d'un produit anti-encrassement dans une alimentation en éthylène d'un système de réacteur. Le système de réacteur comprend l'alimentation en éthylène, un hyper-compresseur, un préchauffeur et un réacteur de polymérisation. L'alimentation en éthylène est située en amont de l'hyper-compresseur. Le produit anti-encrassement est constitué d'un inhibiteur et éventuellement d'un solvant. Du fait que l'alimentation en éthylène est située en amont de l'hyper-compresseur, le procédé comprend l'introduction de l'agent anti-encrassement dans l'alimentation en éthylène en amont de l'hyper-compresseur. Le procédé comprend en outre l'ajout d'un initiateur de radicaux libres dans le réacteur de polymérisation. Le procédé comprend en outre la polymérisation de l'éthylène dans le réacteur de polymérisation dans des conditions de polymérisation par radicaux libres à haute pression, et la formation d'un polymère à base d'éthylène.
PCT/US2021/024348 2020-03-31 2021-03-26 Produit anti-encrassement et procédé WO2021202278A1 (fr)

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Citations (5)

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