METHOD FOR OLIGOMERIZATION OF ETHYLENE

Abstract

The present invention relates to a method for the oligomerization of ethylene, and more specifically, to a method for the preparation of mainly ethylene oligomers of C.sub.10 or higher, which comprises obtaining mainly ethylene oligomers of C.sub.4 or higher by performing a first oligomerization of an ethylene gas using a Ni-containing mesoporous catalyst, followed by a second oligomerization using an ion exchange resin, etc. The method for the preparation of ethylene oligomers according to the present invention can produce C.sub.8-16 ethylene oligomers in high yield without inducing inactivation of a catalyst, compared to the conventional technology of ethylene oligomerization by a one-step process.

Claims

1. A method for oligomerization of ethylene, comprising: a first step of obtaining a first mixed gas containing an ethylene oligomer from a first mixed gas containing C.sub.2H.sub.4, in which C.sub.2H.sub.4 is converted at a temperature between 150° C. and 250° C. using a first catalyst; a second step of separating the first mixed gas containing an ethylene oligomer into a second mixed gas containing unconverted C.sub.2H.sub.4 and a mixed liquid containing an ethylene oligomer by cooling; a third step of obtaining a mixed liquid containing a C.sub.6-16 ethylene oligomer from the mixed liquid containing an ethylene oligomer separated in the second step using a second catalyst; and a fourth step of separating the mixed liquid containing a C.sub.6-16 ethylene oligomer into a mixed gas containing a C.sub.6/C.sub.7 ethylene oligomer and a mixed liquid containing a C.sub.8-16 ethylene oligomer by distillation at a temperature between 90° C. or higher and below 121° C.

2. The method of claim 1, wherein the first mixed gas containing C.sub.2H.sub.4 in the first step is produced by ethanol dehydration of bioethanol.

3. The method of claim 1, wherein the first mixed gas containing C.sub.2H.sub.4 in the first step comprises the second mixed gas containing C.sub.2H.sub.4 separated from the second step.

4. The method of claim 1, wherein the first catalyst in the first step is a Ni-containing mesoporous catalyst in which a nickel compound is supported in a mesoporous carrier containing silica and alumina in a Si/Al molar ratio between 0.3 and 50.

5. The method of claim 4, wherein the mesoporous carrier is amorphous silica-alumina; a nano-sized zeolite or nanosponge-type zeolite; micro-sized, nano-sized, or polymer-coated and acid-treated SBA-15; or MCM-41.

6. The method of claim 4, wherein the nickel content of the Ni-containing mesoporous catalyst is between 0.5 wt % and 3 wt % based on the weight of the porous carrier.

7. The method of claim 4, wherein the Ni/Al molar ratio in a catalyst may be in the range of 0.1 to 0.5.

8. The method of claim 1, wherein the first step is performed at a temperature of 150° C. to 250° C.

9. The method of claim 1, wherein the first step is performed in a pressure between 0.1 MPa and 3 MPa.

10. The method of claim 1, wherein the second step comprises a step of separating the first mixed gas containing an ethylene oligomer into a mixed liquid containing an ethylene oligomer of C.sub.4 or higher and the second mixed gas containing unconverted C.sub.2H.sub.4 by cooling to room temperature or below.

11. The method of claim 1, wherein the second catalyst in the third step is an Amberlyst-35 ion exchange resin-type Bronsted solid acid catalyst or a Lewis solid acid catalyst, in which aluminum is substituted in the mesoporous material selected from the group consisted of H-beta zeolite, SBA-15 and MCM-41.

12. The method of claim 1, wherein the third step is performed at a temperature between 50° C. and 150° C. and in a pressure between 0.1 MPa and 5 MPa.

13. The method of claim 1, wherein the fourth step is performed at a temperature ranging from 90° C. or higher to lower than 121° C. and at an atmospheric pressure.

14. The method of claim 1, wherein the mixed gas containing a C.sub.6/C.sub.7 ethylene oligomer separated from the fourth step is recycled in the second step after the gas is concentrated to a temperature of 50° C. or below thereby being converted into a liquid.

15. A method of preparing jet-class fuel, comprising hydrogenating C.sub.8-16 ethylene oligomer prepared by the method of claim 1.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0039] FIG. 1 shows a reaction mechanism and a reaction flow with respect to the preparation of jet fuel from ethanol.

[0040] FIG. 2 shows a flowchart illustrating the method of ethylene oligomerization according to an exemplary embodiment of the present invention.

[0041] FIG. 3 shows a graph illustrating the ethylene conversion according to time and the change in oligomer selectivity in the first step of Example 1.

[0042] FIG. 4 shows a graph illustrating the results of product analysis after the reaction for 24 hours in the second step of Example 1.

[0043] FIG. 5 shows a graph illustrating the results of product analysis after the reaction for 24 hours in the second step of Example 2.

[0044] FIG. 6 shows a graph illustrating the ethylene conversion according to time and the change in oligomer selectivity in the first step of Example 3.

[0045] FIG. 7 shows a graph illustrating the results of product analysis after the reaction for 24 hours in the second step of Example 3.

[0046] FIG. 8 shows graphs illustrating the ethylene conversion according to time and the change in selectivity on oligomers of C.sub.10 or higher in the liquid-phase product of Example 4.

[0047] FIGS. 9 and 10 show graphs illustrating the 1-hexene conversion according to time and the change in selectivity on oligomers of C.sub.10 or higher in the liquid-phase product of Example 5, respectively.

[0048] FIG. 11 shows graphs illustrating the 1-hexene conversion according to time and the change in selectivity on oligomers of C.sub.10 or higher in the liquid-phase product of Example 6.

[0049] FIG. 12 shows a graph illustrating the ethylene conversion according to time and the change in oligomer selectivity of Comparative Example 1.

DETAILED DESCRIPTION OF THE INVENTION

[0050] Hereinafter, the present invention will be described in more detail with reference to the following Examples. However, these Examples are for illustrative purposes only and the invention is not intended to be limited by these Examples.

EXAMPLE 1

Ethylene Oligomerization using Ni-SBA-15 Catalyst and Amberlyst-35 Catalyst

[0051] A fixed-bed reactor was filled with Ni-SBA-15 (Si/Al molar ratio=5, 1 g) and pretreated in an atmospheric pressure at 550° C. while flowing a nitrogen gas thereto at 60 mL/min for 8 hours. Then, the reactor was maintained at a temperature of 200° C. and at a pressure of 10 bar. Subsequently, the reaction was performed while flowing ethylene thereto at 8 mL/min (the first step). During the reaction for 200 hours in the above conditions, the catalytic activity was continuously maintained at a high level of 98% or above without a change in ethylene conversion. As shown in FIG. 3, it was confirmed that the product distribution was in the order of C.sub.4>C.sub.6>C.sub.8>C.sub.10, and the yield of the oligomers of C.sub.10 or higher was lower than 10%.

[0052] The gas product obtained in the first step was cooled to 5° C. to separate the liquid product therefrom.

[0053] The liquid product obtained from the first step in an amount of 10 g was mixed with 0.5 g of the Amberlyst-35 ion exchange resin, and the reactor was maintained at a temperature of 100° C. and at a pressure of 30 bar. As shown in FIG. 4, as a result of the product analysis of the 24 hour-reaction, the percentage of C.sub.4 components was significantly decreased while the percentages of C.sub.8 and C.sub.10 components were significantly increased instead. In particular, the percentage of the components of C.sub.10 or higher was increased from 8% before the reaction to 45% after the reaction.

[0054] The resulting product was distilled at 90° C. in an atmospheric pressure to obtain a gas product and a liquid product.

EXAMPLE 2

Ethylene Oligomerization using Ni-SBA-15 Catalyst and H-beta Zeolite Catalyst

[0055] Ethylene oligomerization was performed in the same manner as in Example 1, except that the liquid product obtained in the first step was mixed with H-beta zeolite (0.5 g) instead of Amberlyst-35 ion exchange resin and then the reactor was maintained at a temperature of 200° C. and at a pressure of 30 bar.

[0056] As shown in FIG. 5, as a result of the product analysis of the 24 hour-reaction, the percentage of C.sub.4 components was significantly decreased while the percentages of C.sub.8 and C.sub.10 components were significantly increased instead. In particular, the percentage of the components of C.sub.10 or higher was increased from 8% before the reaction to 42% after the reaction for 24 hours.

EXAMPLE 3

Ethylene Oligomerization using Ni/SIRAL 30 Catalyst and Amberlyst-35 Catalyst

[0057] After filling a fixed-bed reactor with Ni/SIRAL 30 (Si/Al molar ratio=0.3, 1 g), a reaction was performed in the same manner as in Example 1 while flowing ethylene thereto at 5 mL/min, and thereby the liquid product of the first step was obtained. In the above conditions, ethylene conversion was maintained at a high level of 98% or higher. As shown in FIG. 6, it was confirmed that the product distribution was in the order of C.sub.6 >C.sub.4>C.sub.8>C.sub.10, and the yield of the oligomers of C.sub.10 or higher was about 18%.

[0058] The gas product obtained in the first step was cooled to 5° C. to separate the liquid product therefrom.

[0059] The liquid product obtained from the first step in an amount of 10 g was mixed with 0.5 g of the Amberlyst-35 ion exchange resin, and a reaction was performed in the same manner as in Example 1. As shown in FIG. 7, as a result of the product analysis of the 24 hour-reaction, the percentage of C.sub.4 components was significantly decreased while the percentages of C.sub.8 and C.sub.10 components were significantly increased instead. In particular, the percentage of components of C.sub.10 or higher was significantly increased to about 48%.

[0060] The resulting product was distilled at 90° C. in an atmospheric pressure to obtain a gas product and a liquid product.

EXAMPLE 4

Ethylene Oligomerization using Ni/zeolite Catalyst

[0061] A fixed-bed reactor was filled with Ni-ZSM-5 and Ni-beta zeolites (Si/Al molar ratio=50, 0.2 g each) and pretreated in an atmospheric pressure at 550° C. while flowing a helium gas thereto at 20 mL/min for 8 hours. In particular, with respect to the zeolite catalysts used herein (ZSM-5 and beta zeolite), nickel was supported in an amount of about 1 wt % to a micro-sized (M-)-type zeolite and a nanosponge-type zeolite having mesoporous pores (MN-). Then, the reactor was cooled to 200° C. and the pressure of the entire reactor was adjusted to 35 bar using a back pressure regulator while flowing a helium gas thereto at 200 mL/min. Subsequently, a reaction was performed for about 900 minutes by injecting an argon gas, an inert gas, to the reactor at 10 mL/min while simultaneously flowing ethylene thereto at 6.6 mL/min (the first step). For the separation of the liquid product released after the reaction, a cooler (5° C.) was provided under the reactor. The liquid-phase and gas-phase products among the reaction products were collected at 3 hour intervals, subjected to gas chromatography mass analyzer for the analysis of each component, and ethylene conversion and selectivity on the oligomers of C.sub.10 or higher in the liquid-phase product were drawn and the results are shown in FIG. 9. As devices for the analysis, YL Instrument 6500 GC System equipped with a DHA capillary column (100 m, 0.25 mm, 0.5 μm) was used as the gas chromatography column.

[0062] As shown in FIG. 9, the catalyst provided as nano-sized particles having a nanosponge structure among the ZSM-5 zeolite containing about 1 wt % of nickel, exhibited excellent ethylene conversion and selectivity on oligomers of C.sub.10 or higher, whereas the catalyst provided as micro-sized particles exhibited slight ethylene conversion, although significantly lower than that of the catalyst provided as nano-sized particles, and the selectivity on the oligomers of C.sub.10 or higher was shown to be low to be less than 10%. These results suggest that the catalyst provided as micro-sized particles can induce the oligomerization reaction of ethylene but it only enables the production of about C.sub.4-6 hydrocarbons and has a difficulty in producing high-value added hydrocarbons of C.sub.10 or higher.

EXAMPLE 5

1-Hexene Oligomerization using Zeolite Catalyst

[0063] As a method for compensating the drawbacks of the one-step ethylene oligomerization in Example 4, a two-step oligomerization was performed. In this regard, 1-hexene was assigned as a model compound, and the two-step oligomerization was performed. For the zeolite catalyst, ZSM-5 and beta-zeolite having a Si/Al molar ratio of 50 were used, and solid acid catalysts in a micro-sized-type zeolite (M-), a nano-sized-type zeolite (N-) and a nanosponge-type zeolite having mesoporous pores (MN-) were used.

[0064] A fixed-bed reactor was filled with a zeolite catalyst (0.5 g), pretreated in the same manner as in Example 4, and the temperature and pressure of the reactor were adjusted. Then, the reaction was started while flowing a mixed solution of 1-hexene (95 wt %) and n-heptane (5 wt %) at a rate of 0.025 mL/min, in a weight/hour space velocity (WHSV) of 2 h.sup.−1, using an HPLC pump, and the reaction was continued for about 780 minutes. For the separation of the liquid product released after the reaction, a cooler (5° C.) was provided under the reactor. The liquid-phase product among the reaction products was collected at 3 hour intervals, analyzed in the same manner as in Example 4 using the same gas chromatography mass analyzer and column, and the results are shown in FIGS. 10 and 11.

[0065] The values of peak areas were drawn from the gas chromatogram obtained therefrom and were compared with the existing values obtained by quantification of the expected products. The values of the peak areas after the reaction were calculated by comparing with the existing values of the peak areas of the expected products based on the value of the n-heptane, which was not involved in the reaction, and thereby the conversion was measured and the selectivity on oligomers of C.sub.10 or higher was drawn based on the result. As shown in FIGS. 10 and 11, the micro-sized particles of ZSM-5 and beta-zeolites not only exhibited significantly low conversion of 1-hexene and selectivity on oligomers of C.sub.10 or higher compared to the nano-sized particles but also showed a further decrease in the conversion of 1-hexene and selectivity on oligomers of C.sub.10 or higher along with the increase of the reaction time and exhibited absolutely no activity at all after the lapse of 800 minutes of the reaction time. Meanwhile, in the case of the nano-sized particles, they showed significantly higher conversion of 1-hexene and selectivity on oligomers of C.sub.10 or higher compared to the micro-sized particles, and in particular, the particles having a nanosponge structure were shown to have even higher conversion of 1-hexene and selectivity on oligomers of C.sub.10 or higher. The result indicates that even a size reduction of the particle to a nano level can significantly improve the catalytic activity of olefin, e.g., 1-hexene, with regard to the oligomerization and selectivity on oligomers of C.sub.10 or higher, and furthermore, in a case when a sponge type microstructure is added thereto, a more significant effect can be provided.

EXAMPLE 6

1-Hexene Oligomerization using SBA-15 Catalyst

[0066] As a method for compensating the drawbacks of the one-step ethylene oligomerization, a two-step oligomerization was performed by assigning 1-hexene as a model compound in the same manner as in Example 5. As the SBA-15 catalyst, micro-sized and nano-sized (H-SBA-15, 400 nm) ones were used. For the purpose of lowering the process temperature, polymer coated and acid treated SBA-15 (H-PS/SBA-15), which was prepared by coating SBA-15 with a H-PS(polystyrene) followed by addition of acid center, was used.

[0067] In the case of the H-SBA-15 catalyst, the catalyst (2 g) was filled into the fixed-bed reactor and then pretreated in the same manner as in Example 4, and the temperature and pressure of the reactor were adjusted. In the case of the H-PS/SBA-15 catalyst, the same amount of the catalyst (2 g) was filled into the fixed-bed reactor and then the reactor was heated at a rate of 5° C./min to 100° C. while flowing a helium gas at a rate of 50 mL/min thereto. After maintaining the reactor at 100° C. for 3 hours, the temperature was adjusted according to the reaction conditions. Then, the reaction was started while flowing a mixed solution of 1-hexene (95 wt %) and n-heptane (5 wt %) at a rate of 0.1 mL/min, in a weight/hour space velocity (WHSV) of 2 h.sup.−1, using an HPLC pump, and the reaction was continued for about 190 minutes. For the separation of the liquid product released after the reaction, a cooler (5° C.) was provided under the reactor. The product in liquid-phase among the reaction products was collected at 3 hour intervals, analyzed in the same manner as in Examples 4 and 5 using the same gas chromatography mass analyzer and column and calculated, and the results are shown in FIG. 12.

[0068] A 1-hexene oligomerization reaction was performed using a series of catalysts, which were prepared by coating micro-sized SBA-15 and SBA-15 of a size of 400 nm with polystyrene and activated by acid treatment, and a catalyst, which was prepared by acid treatment of SBA-15 itself which was not coated with a polymer. The conversion according to reaction time was calculated and the results are shown in FIG. 12. The reaction was performed not only at 100° C. but also at 200° C. by elevating the temperature, and the conversion and selectivity on the oligomers of C.sub.10 or higher were measured. As a result, it was confirmed that the 1-hexene oligomerization performed using SBA-15, the catalysts (micro-sized and a size of 400 nm) treated with an acid without polymer coating not only exhibited a significantly lower conversion at 100° C. compared to when the reaction was performed at 200° C., but also exhibited a decrease in conversion along with time. In contrast, when the reaction was performed using the SBA-15 catalyst, which was prepared according to the present invention by polystyrene coating followed by acid treatment, it was confirmed that the reaction performed even at 100° C. was shown to achieve conversion at a level similar to that performed at 200° C. This indicates that the use of the catalyst according to the present invention can exhibit the desired conversion of 1-hexene oligomerization without excessively increasing the temperature and thus confirms that the catalyst is an efficient catalyst from the energy aspect.

Comparative Example 1

Low-Temperature High-Pressure Ethylene Oligomerization using the Catalyst Ni-SBA-15 alone

[0069] A fixed-bed reactor was filled with Ni-SBA-15 (Si/Al molar ratio=5) 1 g and pretreated in an atmospheric pressure at 550° C. while flowing a nitrogen gas thereto at 60 mL/min for 8 hours. Then, the temperature of the reactor was maintained at 120° C. and the pressure of the reactor was maintained at 35 bar. Subsequently, the reaction was proceeded while flowing ethylene at a rate of 5 mL/min thereto.

[0070] When the ethylene oligomerization is performed in a high-pressure condition of 35 bar as in this experiment, the selectivity on oligomers of C.sub.10 or higher may increase.

[0071] However, in the above condition, desorption of the oligomers of C.sub.10 or higher on the surface of the catalyst may not readily occur and thus the catalyst may be inactivated.

[0072] As shown in FIG. 8, as a result of the reaction in the above condition, ethylene conversion was decreased from 30% at the initial stage with the increase of reaction time and further decreased to 5%, after 12 hours of the reaction.

[0073] Additionally, the C.sub.10 concentration was as high as 40% at the initial stage of the reaction but decreased to a level of 10% in 12 hours thereafter by the inactivation of the catalyst.

[0074] Accordingly, when the reaction is performed in a low-temperature high-pressure condition as in this experiment using the Ni-SBA-15 catalyst alone, ethylene conversion becomes low and the inactivation of the catalyst can rapidly occur and thus it is not possible to obtain the product with high C.sub.10 concentration on a stable basis.

[0075] From the results of the above experiments, it was confirmed that when the conversion of ethylene into oligomers is performed by a two-step process, it can produce C.sub.8-16 ethylene oligomers in high yield without inducing the inactivation of the catalyst.