Selective oligomerization reaction process of ethylene

Abstract

The present invention relates to a commercial reaction process for the selective oligomerization reaction of ethylene, and a method for efficiently removing reaction heat to be generated in a reaction and regulating the temperature of the reactor and, more specifically, to an oligomerization reaction process of ethylene by circulating a liquid mixture in the reactor, separating unreacted ethylene from this circulation flow by an apparatus for separating unreacted ethylene from the circulation flow, and then cooling the remaining mixture and reintroducing it to the reactor, thereby removing the reaction heat in the reactor and allowing temperature control.

Claims

1. A method of preparing an ethylene oligomer product comprising: a) oligomerizing ethylene in a reaction solvent in the presence of a catalyst in an ethylene oligomerization reactor to produce a first liquid effluent comprising the ethylene oligomer product; b) passing the first liquid effluent into a gas-liquid separator to obtain a first gaseous mixture comprising unreacted ethylene and a second liquid mixture comprising the reaction solvent, the ethylene oligomer product, an oligomer byproduct, the catalyst, and a polyethylene byproduct; c) cooling the second liquid mixture in a first cooler to a lower temperature than the ethylene oligomerization reaction temperature, and recycling the cooled second liquid mixture into a first inlet of the oligomerization reactor; and d) cooling the first gaseous mixture in a second cooler and recycling the cooled first gaseous mixture into a second inlet of the oligomerization reactor; wherein the oligomer byproduct is an ethylene oligomer byproduct being a liquid phase at room temperature, and wherein the polyethylene byproduct is present in a solid state at room temperature.

2. The method of claim 1, wherein the ethylene oligomer product is an ethylene trimer and an ethylene tetramer.

3. The method of claim 1, wherein the oligomerization reactor has a temperature of 30 to 170 C. and a pressure of 1 to 100 bar, and the gas-liquid separator has a temperature of 0 to 150 C. and a pressure of 0.1 to 50 bar.

4. The method of claim 1, wherein the cooling in c) and d) is carried out at a temperature of 70 to 40 C.

5. The method of claim 1, wherein the first liquid effluent is transferred to the gas-liquid separator by pressure difference between the oligomerization reactor and the gas-liquid separator or a flow rate control transfer apparatus.

6. The method of claim 1, wherein c) includes separating and removing polyethylene byproduct from the second liquid mixture layer, and cooling a remaining liquid mixture to be circulated to the oligomerization reactor.

7. The method of claim 1, further comprising: separating from the first gaseous mixture in a first fractionation column a third liquid mixture comprising ethylene oligomer product, oligomer byproduct and reaction solvent.

8. The method of claim 1, further comprising: e) cooling a gaseous effluent from the oligomerization reactor and transferring the cooled gaseous effluent to a second fractionation column to separate a third gaseous mixture comprising unreacted ethylene and reaction solvent and a fourth liquid mixture comprising ethylene oligomer product and oligomer byproduct; and f) cooling the third gaseous mixture and recycling the cooled third gaseous mixture to the oligomerization reactor, and transferring the fourth liquid mixture layer to a rear end separation process.

9. The method of claim 8, wherein the cooling in e) and f) is carried out at a temperature of 70 to 40 C.

10. The method of claim 1, wherein the catalyst of a) is a chromium-based organo metalic compound catalyst system produced by a reaction of (1) a chromium compound; (2) a ligand including a pyrrole-based compound or one or more compounds selected from the group consisting of backbone structures of R.sub.1PCCPR.sub.2 and R.sub.3PNPR.sub.4; and (3) a cocatalyst (wherein R.sub.1 to R.sub.4 are independently of one another substituted or unsubstituted hydrocarbyl, or substituted or unsubstituted heterohydrocarbyl).

Description

DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a schematic illustration of a process according to a method of preparing an oligomer from ethylene of the present invention.

(2) FIG. 2 is a schematic illustration of a process according to a method of preparing an oligomer from ethylene of the present invention.

(3) FIG. 3 is a schematic illustration of a process according to a method of preparing an oligomer from ethylene of the present invention.

(4) FIG. 4 is a schematic illustration of a process according to a method of preparing an oligomer from ethylene of the present invention.

DETAILED DESCRIPTION OF MAIN ELEMENTS

(5) 1: reactor 2: gas-liquid separator 3: first fractionation column 4: second fractionation column 11: first liquid mixture layer transfer flow 12: second liquid mixture layer transfer flow 13: discharge flow 14: second liquid mixture layer circulation flow 15: circulation pump 16: cooler 17: first gaseous mixture transfer flow 21: reaction solvent inlet flow 22: ethylene inlet flow 23: catalyst inlet flow 31: second gaseous mixture circulation flow 41: gaseous layer transfer flow 42: fourth liquid mixture layer transfer flow 43: third gaseous mixture circulation flow

BEST MODE

(6) Hereinafter, the method of preparing an oligomer from ethylene according to the present invention will be described in detail with reference to accompanying drawings. The exemplary embodiments and drawings to be provided below are provided by way of example so that the idea of the present invention may be sufficiently transferred to a person skilled in the art to which the present invention pertains. In addition, technical terms and scientific terms used in the present specification have the general meaning understood by a person skilled in the art unless otherwise defined, and a description for the known function and configuration obscuring the present invention will be omitted in the following description.

(7) Throughout this disclosure, the term polyethylene byproduct refers to a high molecular weight polyethylene polymer byproduct present in a solid state at a room temperature of 20 to 30 C. among the products produced from the present invention, and the term oligomer byproduct refers to an ethylene oligomer byproduct being a liquid phase at room temperature, except for the ethylene trimer and the ethylene tetramer produced from the present invention.

(8) In addition, throughout this disclosure, substituted refers to in a compound or a structure forming a compound, a hydrogen atom bonded to a carbon atom being substituted with one or more substituents selected from the group consisting of a halogen atom, a nitro group, a hydroxyl group, C1-C7 alkyl, C1-C7 alkoxy, C1-C7 alkylcarbonyl, C1-C7 alkoxycarbonyl, a formyl group (CHO) and the like.

(9) The present invention relates to a method of removing reaction heat produced in the oligomerization reaction and controlling temperature of the reactor, in a selective oligomerization reaction process of ethylene, and specifically, a method of preparing an oligomer from ethylene includes: a) oligomerizing ethylene in a reaction solvent in the presence of a catalyst in an ethylene oligomerization reactor; b) separating a first liquid mixture layer including an ethylene oligomer product in the oligomerization reactor of step a) into a first gaseous mixture, and a second liquid mixture layer in a gas-liquid separator; c) cooling the second liquid mixture layer separated from the gas-liquid separator to a lower temperature than an oligomerization reaction temperature of step a) to remove reaction heat produced in step a) and be circulated to the oligomerization reactor; and d) cooling the first gaseous mixture of step b) to be circulated to the oligomerization reactor.

(10) The ethylene oligomer product which is the material to be prepared by the preparation method may be an ethylene trimer and an ethylene tetramer, and more preferably 1-hexene and 1-octene which are commercially useful, but not limited thereto.

(11) The method of preparing an oligomer from ethylene of the present invention may be carried out in a continuous stirred tank reactor (CSTR) or a semi-batch reactor (SBR), but not limited thereto.

(12) In the present invention, the oligomerization reactor in which oligomerization proceeds in step a) may have a temperature of 30 to 170 C., preferably 50 to 120 C., more preferably 60 to 90 C., and a pressure of 1 to 100 bar, preferably 15 to 80 bar, more preferably 30 to 60 bar. The temperature condition of the oligomerization reactor is not particularly limited thereto, but it is preferred to satisfy the range, since the amount of unnecessary polyethylene byproduct produced from the present invention may be minimized, thereby minimizing the possibility of fouling in the reactor and plugging of the reactor outlet and the transfer tube which are process defects being the cause of the polyethylene byproduct. In addition, the pressure condition of the oligomerization reactor is also not particularly limited, but it is preferred to satisfy the range, since an appropriate level of ethylene may be dissolved in a liquid form in a reaction solvent present in the oligomerization reactor, and the oligomerization reaction of ethylene may proceed at a rapid rate.

(13) In the present invention, a liquid layer including an ethylene oligomer product composed of an ethylene trimer and an ethylene tetramer (hereinafter, referred to as a first liquid mixture layer) in the oligomerization reactor may be produced by step a), and the first liquid mixture layer may be separated into a first gaseous mixture and a second liquid mixture layer in a gas-liquid separator in step b), wherein the separated first gaseous mixture may include unreacted ethylene, a small amount of the ethylene oligomer product, a small amount of the reaction solvent and a small amount of the oligomer byproduct, and the second liquid mixture layer may include the reaction solvent, the ethylene oligomer product, 1-hexene and 1-oxtene, the oligomer byproduct, the catalyst, the polyethylene byproduct and a small amount of the unseparated unreacted ethylene.

(14) In the present invention, when the first liquid mixture layer is transferred from the oligomerization reactor to the gas-liquid separator, it may be transferred by pressure difference between the oligomerization reactor and the gas-liquid separator, or by a flow rate control transfer apparatus being present between the oligomerization reactor and the gas-liquid separator, but not particularly limited thereto.

(15) In the present invention, the gas-liquid separator carrying out the separation of the first liquid mixture layer in step b) may use any one separating apparatus selected from the group consisting of a tank type, a column type having a separating end, and a flash drum type, and the gas-liquid separator may include a stirrer for stirring the first liquid mixture layer to be introduced.

(16) The temperature and the pressure of the gas-liquid separator used in the present invention may be in a range lower than the temperature and pressure conditions of the oligomerization reactor, specifically the gas-liquid separator may have a temperature of 0 to 150 C., preferably 15 to 100 C., more preferably 25 to 70 C., and a pressure of 0.1 to 50 bar, preferably 0.5 to 45 bar, more preferably 1 to 30 bar. The temperature and pressure conditions of the gas-liquid separator are not particularly limited, but it is preferred to satisfy the range, since the evaporation reaction of the unreacted ethylene present in the first liquid mixture layer is activated, so that the separation reaction of the first gaseous mixture and the second liquid mixture layer may be effectively carried out. The first gaseous mixture produced from the separation of the first liquid mixture layer may be eluted through an outlet present in an upper portion of the gas-liquid separator, and the second liquid mixture layer may be eluted through an outlet present in a lower portion of the gas-liquid separator.

(17) The second liquid mixture layer separated in step b) of the present invention may be eluted from the gas-liquid separator to be recirculated to the oligomerization reactor in step c). Here, the above step c) of the present invention may include separating polyethylene byproduct from the second liquid mixture layer and cooling the remaining liquid mixture to be circulated to the oligomerization reactor, and the separation step may be carried out by a filter or a centrifuge, however, the present invention is not particularly limited thereto. By removing the solid polyethylene byproduct from the oligomerization reaction circulation flow in the above separation step, the possibility of occurrence of fouling in the reactor and plugging of the reactor outlet and the transfer tube, caused by the polyethylene byproduct reintroduced to the oligomerization reactor may be minimized. In addition, the liquid mixture from which the polyethylene byproduct is separated by the separation step may be cooled to a lower temperature than the temperature of the oligomerization reactor of the present invention by the cooling apparatus to be circulated to the oligomerization reactor.

(18) In the present invention, the cooling in step c) may be carried out at a temperature of 70 to 40 C., preferably of 40 to 30 C. The cooling temperature condition of the separated liquid mixture is not particularly limited, but it is most preferred to satisfy the above range, since the reaction heat in the oligomerization reactor may be effectively removed by introducing the cooled liquid mixture to the oligomerization reactor, which allows the temperature control of the oligomerization reactor, thereby minimizing the production possibility of the polyethylene byproduct in a solid state caused by abrupt temperature change of the reactor.

(19) In addition, in the present invention, the above step d) may further include a separation step of eluting and transferring the first gaseous mixture from the gas-liquid separator to be separated into a second gaseous mixture including unreacted ethylene, a small amount of the ethylene oligomer product, a small amount of the oligomer byproduct and a small amount of the reaction solvent; and a third liquid mixture layer including a small amount of the unreacted ethylene, the ethylene oligomer product, the oligomer byproduct and the reaction solvent, in a first fractionation column, before cooling (hereinafter, referred to as the separation step in step d)). The first fractionation column may have a temperature of 5 to 50 C., preferably of 10 to 25 C., and a pressure of 0 to 10 bar. The temperature and pressure conditions of the first fractionation column are not particularly limited, but it is preferred to satisfy the range, since the separation reaction of the second gaseous mixture and the third liquid mixture layer from the first gaseous mixture may be effectively carried out. The second gaseous mixture produced from the separation of the first gaseous mixture may be eluted through an outlet present in an upper portion of the first fractionation column, and the third liquid mixture layer may be eluted through an outlet present in a lower portion of the first fractionation column. By the elution, the third liquid mixture layer may be transferred to a rear end separation process, and by the rear end separation process, the ethylene trimer and the ethylene tetramer which are the ethylene oligomer product of the present invention may be obtained in a separate form. The rear end separation process of the present invention may be any process as long as it is used for separating the components of a liquid mixture, and preferably may include distillation by a distillation apparatus, but not particularly limited thereto.

(20) In the present invention, the first gaseous mixture of step d), or the second gaseous mixture including unreacted ethylene, a small amount of the ethylene oligomer product, a small amount of the oligomer byproduct and a small amount of the reaction solvent in a gaseous state, produced from the separation step in step d) may be cooled to a lower temperature than the temperature of the oligomerization reactor of the present invention by the cooling apparatus through cooling of step d) of the present invention to be circulated to the oligomerization reactor.

(21) In the present invention, the cooling in step d) may be carried out at a temperature of 70 to 40 C., preferably of 40 to 10 C. The cooling temperature condition of step d) is not particularly limited, but it is preferred to cool the first gaseous mixture or the second gaseous mixture to the above temperature range, since the operation energy cost of the gaseous mixture is low, and thus, economical, and the process may be simplified. The first gaseous mixture or the second gaseous mixture cooled in step d) of the present invention may be circulated into the reactor by a pressure apparatus, but not particularly limited thereto.

(22) In addition, the method of preparing an oligomer from ethylene of the present invention may further include e) cooling the gaseous layer in the oligomerization reactor of step a) and then transferring it to a second fractionation column to separate the gaseous layer into a third gaseous mixture including the unreacted ethylene and the reaction solvent in a gaseous state; and a fourth liquid mixture layer including the ethylene oligomer product, a small amount of the reaction solvent and the oligomer byproduct; and f) cooling the third gaseous mixture of step e) to be circulated to the oligomerization reactor, and transferring the fourth liquid mixture layer to a rear end separation process.

(23) The above steps e) and f) of the present invention may be carried out simultaneously with step b) of the present invention after step a), or after step d) of the present invention, but it not particularly limited thereto.

(24) In the present invention, the first liquid mixture layer including the ethylene oligomer product in the oligomerization reactor, and also the gaseous layer including a small amount of the ethylene oligomer product and the oligomer byproduct, the unreacted ethylene and the reaction solvent in a gaseous state may be produced by the ethylene oligomerization reaction of step a), and the gaseous layer may be eluted into the outlet present in the upper portion of the oligomerization reactor. The eluted gaseous layer may be cooled through step e), and then transferred to the second fractionation column to be separated into the third gaseous mixture and the fourth liquid mixture layer. In step e) of the present invention, the gaseous layer may be cooled to a temperature of 70 to 40 C., preferably 40 to 20 C., but not particularly limited thereto.

(25) In addition, the second fractionation column used in step e) of the present invention may have a temperature of 5 to 50 C., preferably of 10 to 25 C., and a pressure of 0 to 10 bar. The temperature and pressure conditions of the second fractionation column are not particularly limited, but it is preferred to satisfy the range, since the separation reaction of the third gaseous mixture and the fourth liquid mixture layer from the gaseous layer may be effectively carried out.

(26) The third gaseous mixture produced from the separation of the gaseous layer may be eluted through an outlet present in an upper portion of the second fractionation column, and the fourth liquid mixture layer may be eluted through an outlet present in a lower portion of the second fractionation column. By the elution, the fourth liquid mixture layer may be transferred to the rear end separation process of the present invention, and the ethylene trimer and the ethylene tetramer which are the ethylene oligomer product in the reaction circulation flow of the present invention may be obtained in a separate form thereby.

(27) In addition, the third gaseous mixture including unreacted ethylene and the reaction solvent in a gaseous state, produced from the separation step in step e) of the present invention may be cooled to a lower temperature than the temperature of the oligomerization reactor of the present invention by the cooling apparatus through step f) of the present invention to be circulated to the oligomerization reactor.

(28) In the present invention, the cooling in step f) may be carried out at a temperature of 70 to 40 C., preferably of 40 to 10 C. The cooling temperature condition of the separated third gaseous mixture is not particularly limited, but it is preferred to cool the third gaseous mixture to the above temperature range, since the operation energy cost of the third gaseous mixture is low, and thus, economical, and the process may be simplified. The third gaseous mixture cooled in step f) of the present invention may be circulated into the reactor by a pressure apparatus, but not particularly limited thereto.

(29) The catalyst of step a) which may be used in the method of preparing an oligomer from ethylene of the present invention may be an organo metalic compound catalyst system produced by a reaction of (1) a chromium compound; (2) ligand including a pyrrole-based compound or one or more compounds selected from the group consisting of backbone structures of R.sub.1PCCPR.sub.2 (hereinafter, referred to as PCCP) and R.sub.3PNPR.sub.4; and (3) a cocatalyst. Here, R.sub.1 to R.sub.4 may be independently of one another substituted or unsubstituted hydrocarbyl or substituted or unsubstituted heterohydrocarbyl, preferably independently of one another any one selected from the group consisting of phenyl, benzyl, naphthyl, anthracenyl, mesityl, xylyl, methyl, ethyl, ethylenyl, propyl, propenyl, propynyl, butyl, cyclohexyl, 4-methylcyclohexyl, 4-ethylcyclohexyl, 4-isopropylcyclohexyl, tolyl, xylyl, 4-methylphenyl, 4-ethylphenyl, 4-isopropylphenyl, 4-t-butylphenyl, 4-methoxyphenyl, 4-isopropoxyphenyl, cumyl, methoxy, ethoxy, phenoxy, tolyloxy, dimethylamino, thiomethyl, trimethylsylyl, dimetylhydrizyl, 2-methylcyclohexyl, 2-ethylcyclohexyl, 2-isopropylcyclohexyl, o-methylphenyl, o-ethylphenyl, o-isopropylphenyl, o-t-butylphenyl, o-methoxyphenyl, o-isopropoxyphenyl, biphenyl, naphthyl, anthracenyl and the like, but not limited thereto.

(30) In the present invention, the chromium-based organo metalic compound used as the catalyst may be a chromium-based organo metalic complex having chromium as a center metal, and coordinated with ligand compounds including one or more of nitrogen, oxygen, sulfur or phosphorus atoms having unshared electron pairs, and the compound may be produced by a combination of a cocatalyst activating the chromium complex in addition to the chromium complex. The chromium compound and the ligand which are the precursors of the complex may be used, respectively, in the reaction in place of the chromium organo metalic complex. The chromium compound used for producing the catalyst of the present invention may be one or more selected from the group consisting of chromium(III) (acetylacetonate).sub.3, chromium trichloride tristetrahydrofuran, chromium(III)2-ethylhexanoate and the like. In addition, the ligand used in the catalyst of the present invention may be preferably one or more selected from the group consisting of pyrrole, dialkylpyrrole, (phenyl).sub.2-PN(isopropyl)-P(phenyl).sub.2, (phenyl).sub.2-PCH(methyl)CH(methyl)-P(phenyl).sub.2, (o-methoxyphenyl).sub.2-PCH(methyl)CH(methyl)-P(o-methoxyphenyl).sub.2 and (p-methoxyphenyl).sub.2-PCH(methyl)CH(methyl)-P(p-methoxyphenyl).sub.2 and the like, but not limited thereto. The chromium-based organo metalic complex used in the present invention may be a compound synthesized by a reaction of the chromium compound and the ligand under an organic solvent, and most preferably chromium trichloride tristetrahydrofuran as the chromium compound, and bis-[(phenyl).sub.2-PCH(methyl)CH(methyl)-P(phenyl).sub.2chromium dichloride(-chloride)] synthesized by a reaction of (phenyl).sub.2-PCH(methyl)CH(methyl)-P(phenyl).sub.2 as the ligand, but not particularly limited thereto. The cocatalyst used in the catalyst of the present invention may be alkylaluminum or partially oxidized aluminoxane of alkylaluminum, and used differently depending on the kind of ligand. More specifically, in the case that the ligand used in the present invention is the pyrrole-based compound, alkylhalide-added alkylaluminum may be used as the cocatalyst, and in the case that the used ligand is one or more compounds selected from the group consisting of the backbone structures of R.sub.1PCCPR.sub.2 (hereinafter, referred to as PCCP) and R.sub.3PNPR.sub.4, aluminoxane may be used as the cocatalyst. Here, the aluminoxane may be preferably partially oxidized methylaluminoxane (MAO) of trimethylaluminum (AlMe.sub.3, TMA), or modified methylaluminoxane (MMAO) by partially oxidized triisobutylaluminum (Al(i-Bu).sub.3, TIBA) and TMA, but not limited thereto.