Method of recovering unreacted ethylene in ethylene oligomerization process
Provided is a method of recovering unreacted ethylene in an ethylene oligomerization process and reusing the ethylene as a raw material, and more particularly, to a method of recovering unreacted ethylene with an increased recovery rate of reuse. When the method of the present invention is used, most of unreacted ethylene may be dissolved in a solvent to be recovered without loss, and a low boiling point reaction product which is not dissolved in the solvent is removed to prevent an unreacted product from being concentrated in a reactor.
1. A method of recovering unreacted ethylene in an ethylene oligomerization process, the method comprising:
in the ethylene oligomerization process,
mixing a first recovery stream comprising the unreacted ethylene and a low boiling point reaction product separated in a second separation device in a latter stage of a reactor with a solvent introduced to a reaction raw material;
transferring the mixture to a first separation device, wherein an oligomerization catalyst introduced to a reaction raw material is introduced to the first separation device;
separating the mixture into a first upper effluent comprising the low boiling point reaction product and a first lower effluent comprising the ethylene and the solvent in the first separation device;
transferring the first lower effluent in the first separation device to the reactor and performing an ethylene oligomerization reaction; and
transferring a first reactant reacted in the reactor to the second separation device and recovering the first recovery stream comprising the unreacted ethylene and the low boiling point reaction product as a second upper effluent and separating a reactant comprising C4 or higher olefin oligomers and the solvent as a second lower effluent.
2. The method of recovering unreacted ethylene of claim 1 , wherein the ethylene introduced to a reaction raw material is introduced to the first separation device or the reactor.
3. The method of recovering unreacted ethylene of claim 1 , wherein the low boiling point reaction product comprises any one or more selected from methane, ethane, carbon monoxide (CO), nitrogen (N 2 ), hydrogen (H 2 ), and oxygen (O 2 ).
4. The method of recovering unreacted ethylene of claim 1 , wherein the first separation device and the second separation device are any one selected from a flash drum and a distillation column or a combination thereof, respectively.
5. The method of recovering unreacted ethylene of claim 1 , wherein the solvent introduced to a reaction raw material is any one selected from toluene, benzene, ethylbenzene, cumene, xylene, hexane, octane, cyclohexane, methyl cyclohexane, diethyl ether, and tetrahydrofuran, or a mixed solvent of two or more thereof.
6. The method of recovering unreacted ethylene of claim 1 , wherein a content of the solvent introduced to a reaction raw material satisfies the following Relation 1:
0.02
≤
W
e
/
W
s
≤
1.0
[
Relation
1
]
wherein W e is a content of unreacted ethylene in the first recovery stream, and W s is a content of the solvent introduced to a reaction raw material.
7. The method of recovering unreacted ethylene of claim 1 , wherein operation conditions of the first separation device are performed under conditions satisfying the following Relations 2 and 3:
0.0005
≤
RS
1
/
(
RS
1
+
W
S
)
×
100
≤
5
[
Relation
2
]
2
≤
RS
e
/
(
RS
e
+
W
S
)
×
100
≤
60
[
Relation
3
]
wherein RS 1 is a content of the low boiling point reaction product dissolved in the solvent in the first separation device, Rs e is a content of the unreacted ethylene dissolved in the solvent in the first separation device, and W s is a content of the solvent introduced to the reaction raw material.
8. The method of recovering unreacted ethylene of claim 7 , wherein the operation conditions of the first separation device are performed under conditions satisfying the following Relations 4 and 5:
RS
1
/
R
1
×
100
≤
90
[
Relation
4
]
95
≤
RS
e
/
R
e
×
100
[
Relation
5
]
wherein RS 1 is a content of the low boiling point reaction product dissolved in the solvent in the first separation device and R 1 is a content of the low boiling point reaction product in the first recovery stream, and
RS e is a content of the unreacted ethylene dissolved in the solvent in the first separation device and R e is a content of the unreacted ethylene in the first recovery stream.
9. The method of recovering unreacted ethylene of claim 1 , wherein the operation conditions of the first separation device are performed under conditions satisfying a relative volatility of the low boiling point reaction product to the unreacted ethylene of 1.5 to 35.0.