JP6217441B2 - Method for producing isoprene - Google Patents

Description

  The present invention relates to a method for producing isoprene by dehydrogenating isoamylene.

  Isoprene which is a main raw material such as synthetic rubber can be obtained, for example, by extractive distillation of isoprene contained in a C5 fraction discharged from an ethylene cracker at an ethylene center.

  In the process of extractive distillation of isoprene contained in the C5 fraction, cyclopentadiene is removed from the C5 fraction by dimerization (to form dicyclopentadiene), and then light components such as pentane and pentenes, and pentadienes ( Heavy components such as dicyclopentadiene and 1,3-pentadiene) and acetylenes are removed by two distillation columns, and diolefins (including 1,3-pentadiene) and After removing the remaining acetylenes, the residue is distilled, whereby isoprene can be efficiently obtained from the bottom of the column.

  At this time, a residue is obtained as an extraction residual oil when isoprene is extracted by extractive distillation, but the residue is returned to the ethylene center and used mainly as a raw material for gasoline bases and ethylene crackers. . On the other hand, in such a residue, isoamylene (2-methyl-1-butene, 2-methyl-2-butene, 3-methyl-1-butene) is contained, and isoamylene is dehydrogenated. However, it is not used as a raw material for isoprene synthesis, but as described above, it is returned to the ethylene center and consumed as a raw material for gasoline bases and ethylene crackers. is there. This is thought to be due to the low yield of isoprene in the method of obtaining isoprene by dehydrogenating isoamylene.

  For example, Patent Document 1 discloses that propylene and isobutene can be disproportionated, isoamylene is separated from the disproportionated stream, and the separated isoamylene can be converted to isoprene by dehydrogenation. However, this Patent Document 1 does not disclose the catalyst used for dehydrogenating isoamylene, the dehydrogenation reaction conditions, and the like. Therefore, in the technique described in Patent Document 1, It was difficult to produce isoprene with high yield using isoamylene as a raw material.

  On the other hand, Patent Document 2 discloses a technique for producing a cyclic ketone from a second cyclic alcohol using a catalyst containing zinc oxide and calcium carbonate. Patent Document 3 discloses a technique for producing formaldehyde from methanol using a catalyst comprising zinc oxide and / or indium oxide and silica. However, the techniques of Patent Documents 2 and 3 are techniques for oxidizing alcohol to obtain ketones and aldehydes, and the isoamylene dehydrogenation reaction described above is completely different from the target compound and reaction mechanism. Therefore, the characteristics required for the catalyst to be used are also different.

U.S. Pat. No. 4,091,046 Japanese Patent No. 3901220 Japanese Patent Publication No. 6-2698

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a method capable of producing isoprene in a high yield when producing isoprene by dehydrogenating isoamylene. And

  As a result of diligent research to achieve the above object, the inventors of the present invention, when producing isoprene by dehydrogenating isoamylene, mainly performed zinc oxide in an inert gas atmosphere. By carrying out using a solid catalyst contained as a component, it was found that isoprene can be produced in a high yield, and the present invention has been completed.

  That is, according to the present invention, a method for producing isoprene by dehydrogenating isoamylene, wherein the dehydrogenation reaction is performed using a solid catalyst containing zinc oxide as a main component in an inert gas atmosphere. A method for producing isoprene is provided.

In the production method of the present invention, it is preferable to dry the solid catalyst containing zinc oxide as a main component before the dehydrogenation reaction.
In the manufacturing method of this invention, it is preferable that the temperature in the case of the said dehydrogenation reaction is 500-620 degreeC.

  According to the present invention, when isoprene is produced by dehydrogenating isoamylene, isoprene can be produced with a high yield.

The production method of the present invention is a method for producing isoprene by dehydrogenating isoamylene, wherein the dehydrogenation reaction is performed using a solid catalyst containing zinc oxide as a main component in an inert gas atmosphere. A method for producing isoprene.
“Containing zinc oxide as a main component” means containing 50% by weight or more of zinc oxide.

  The isoamylene used for the dehydrogenation reaction in the present invention is a carbonization selected from 2-methyl-1-butene, 2-methyl-2-butene, and 3-methyl-1-butene, which are branched hydrocarbons having 5 carbon atoms. A hydrogen compound or a mixture of two or more thereof.

  Isoamylene used in the present invention is, for example, separated by extractive distillation from at least a portion of isoprene from a C5 fraction mainly composed of hydrocarbons having 5 carbon atoms, which is by-produced when pyrolyzing naphtha to produce ethylene. After that, what is contained in the residue obtained as the extraction residual oil may be used. In addition, the residue obtained as the extraction residual oil of such isoprene is 2-methyl-1-butene, 2-methyl-2-butene, and 3-methyl-1-butene constituting the isoamylene used in the present invention. In addition to the above, for example, linear hydrocarbons having 5 carbon atoms such as n-pentane, 1-pentene, and 2-pentene are also included. Therefore, in the present invention, when isoamylene contained in such a residue is used and this is subjected to a dehydrogenation reaction, when isoprene is obtained, 2-methyl-1-butene constituting isoamylene is formed. In addition to 2-methyl-2-butene and 3-methyl-1-butene, for example, containing a straight-chain hydrocarbon having 5 carbon atoms such as n-pentane, 1-pentene and 2-pentene Will be used. However, if the content ratio of components other than 2-methyl-1-butene, 2-methyl-2-butene, and 3-methyl-1-butene constituting isoamylene is too high, the production efficiency of isoprene decreases. In such a case, as a pretreatment, a separation membrane or the like is used as a pretreatment to separate straight hydrocarbons having 5 carbon atoms, and isoamylene in the residue is removed. The constituent 2-methyl-1-butene, 2-methyl-2-butene, and 3-methyl-1-butene may be concentrated.

  In the case of using isoamylene contained in such a residue, 2-methyl-1-butene, 2-methyl-2-butene, which constitutes isoamylene in the residue used for the dehydrogenation reaction, The total content of 3-methyl-1-butene is preferably 10 to 100% by weight, more preferably 20 to 100% by weight, and particularly preferably 50 to 100% by weight. Moreover, the ratio of 2-methyl-1-butene, 2-methyl-2-butene, and 3-methyl-1-butene constituting isoamylene is not particularly limited. For example, the ratio in the residue used It depends on.

  The solid catalyst used in the production method of the present invention is a solid catalyst containing zinc oxide (ZnO) as a main component. The solid catalyst used in the present invention is not particularly limited as long as it contains zinc oxide as a main component, but may be composed only of zinc oxide (that is, 100% by weight of zinc oxide). Alternatively, it may contain components other than zinc oxide. Examples of components other than zinc oxide include aluminum oxide, calcium oxide, silicon dioxide, magnesium oxide, and inevitable components such as water.

  When the solid catalyst used in the production method of the present invention contains a component other than zinc oxide, the content ratio of zinc oxide in the solid catalyst is preferably 65% by weight or more, more preferably 80% by weight. % Or more, more preferably 85% by weight or more. If the content ratio of zinc oxide is too low, it may be difficult to produce isoprene in a high yield.

  As described above, as the solid catalyst used in the production method of the present invention, those containing only zinc oxide and those containing components other than zinc oxide can be used. Among these, other than zinc oxide, It is preferable to use those containing components, and in particular, it is preferable to use those containing zinc oxide as a main component and containing aluminum oxide and calcium oxide from the viewpoint that the yield of isoprene in the dehydrogenation reaction can be further increased. preferable. In the case where a solid catalyst containing zinc oxide as a main component and containing aluminum oxide and calcium oxide is used, the content ratio of zinc oxide is preferably 65 to 97% by weight, more preferably 80 to 97% by weight, oxidation The content of aluminum is preferably 1 to 10% by weight, more preferably 1 to 5% by weight, and the content of calcium oxide is preferably 2 to 10% by weight, more preferably 2 to 5% by weight. The total content of the components excluding the zinc oxide, the aluminum oxide and the calcium oxide is preferably 15% by weight or less, more preferably 10% by weight or less.

  In addition, the shape of the solid catalyst used in the present invention is not particularly limited, and is generally a pellet shape, a spherical shape, a cylindrical shape, a ring shape, or the like. Furthermore, the particle size of the solid catalyst is not particularly limited, and an optimal value may be selected depending on the inner diameter of the reaction tube used for the dehydrogenation reaction, but from the viewpoint of efficiently proceeding with the dehydrogenation reaction, Preferably it is 0.5-20 mm, More preferably, it is 0.8-10 mm. Moreover, as a solid catalyst, you may use what was adjusted to the desired average particle diameter by crushing beforehand and classifying.

  The production method of the solid catalyst used in the production method of the present invention is not particularly limited. For example, a zinc-containing compound such as basic zinc carbonate, zinc oxalate, and zinc hydroxide is used as needed. And a calcium-containing compound, a method of thermal decomposition, a method of calcining at a dehydration temperature, and the like.

  The dehydrogenation reaction in the present invention can be performed, for example, by introducing isoamylene to be dehydrogenated in a gaseous state into the reaction tube filled with the above-described solid catalyst in an inert gas atmosphere.

  In the present invention, when performing the dehydrogenation reaction, it is preferable to perform a drying treatment on the solid catalyst in advance in order to remove the water contained in the solid catalyst. By performing the drying treatment on the solid catalyst in advance, the amount of water contained in the solid catalyst can be reduced, and thereby the yield of isoprene in the dehydrogenation reaction can be further increased.

Although it does not specifically limit as drying process conditions, While supplying dry gas, such as nitrogen gas and dry air, Preferably the method of heating to 100-600 degreeC, More preferably, 400-550 degreeC etc. are mentioned. In this case, the drying gas supply rate (the value obtained by dividing the total flow rate of the drying gas per hour by the filling volume of the solid catalyst (based on the empty cylinder), hereinafter referred to as “GHSV”) is not particularly limited. but preferably 200～2000H ^-1, more preferably 500~1500h ^-1. The drying time is not particularly limited, but is preferably 10 minutes to 2 hours, more preferably 15 minutes to 1 hour. The amount of water contained in the solid catalyst after the drying treatment is not particularly limited, but is preferably 2% by weight or less, more preferably 1% by weight or less.

  In the production method of the present invention, as a method for introducing isoamylene into a reaction tube filled with a solid catalyst in an inert gas atmosphere in a gaseous state, a temperature at which each component contained in isoamylene vaporizes (for example, 180 to 220 ° C.) and isoamylene is heated and introduced into a reaction tube filled with a solid catalyst together with a sweep gas (for example, nitrogen gas) made of an inert gas.

The space velocity when introducing the gas containing isoamylene and inert gas into the reaction tube filled with the solid catalyst (the total flow rate per hour of the gas containing isoamylene and inert gas is determined based on the solid catalyst filling volume (cylinder standard). The value divided by), hereinafter referred to as “GHSV”) is not particularly limited, but is preferably 330 to 2000 h ⁻¹ , more preferably 600 to 1600 h ⁻¹ .

  Moreover, the temperature at the time of making it dehydrogenate becomes like this. Preferably it is 500-620 degreeC, More preferably, it is 530-600 degreeC, More preferably, it is 540-570 degreeC. In the present invention, by using a solid catalyst containing zinc oxide as a main component as a catalyst for the dehydrogenation reaction, the dehydrogenation reaction can proceed with high efficiency at a relatively low temperature as described above. Therefore, the energy consumption due to heating can be kept low, and the production efficiency of isoprene can be increased. Further, by performing the dehydrogenation reaction at a relatively low temperature as described above, the cracking reaction can be suppressed, and thereby, the unreacted product can be reused as a raw material for obtaining isoprene. On the other hand, if the temperature during the dehydrogenation reaction is too high, the cracking reaction becomes remarkable, and it tends to be difficult to reuse the unreacted material as a raw material for obtaining isoprene.

  The pressure of the dehydrogenation reaction is a gauge pressure, and the upper limit is preferably 0.05 MPa, more preferably 0.01 MPa, and the lower the pressure, the more desirable. Since the dehydrogenation reaction is an equilibrium reaction that generates hydrogen and isoprene from isoamylene, the lower the pressure, the higher the yield of isoprene. On the other hand, the lower limit is not particularly limited, but is a gauge pressure, preferably 0 MPa, from the viewpoint of production cost.

  The reaction tube used for the dehydrogenation reaction is not particularly limited, but the inner diameter is preferably 6 to 100 mm, more preferably 10 to 70 mm, and the length of the reaction tube is preferably 0.15 to 2.5 m, More preferably, it is 0.2-2.0 m.

  According to the production method of the present invention, a solid catalyst containing zinc oxide as a main component is used as a dehydrogenation reaction catalyst, and the dehydrogenation reaction is performed in an inert gas atmosphere. Can be manufactured. In particular, according to the present invention, by using a solid catalyst containing zinc oxide as a main component as a catalyst for the dehydrogenation reaction, the conversion to isoprene is suppressed while keeping the conversion reaction to hydrocarbon compounds other than isoprene low. Thus, isoprene can be produced very well. That is, for example, when the conversion rate to hydrocarbon compounds other than isoprene such as 1-pentene and 2-pentene is high, such 1-pentene and 2-pentene are reused as raw materials for obtaining isoprene. As a result, the yield of isoprene is greatly deteriorated. On the other hand, according to the production method of the present invention, since the conversion rate to hydrocarbon compounds other than isoprene such as 1-pentene and 2-pentene can be kept low, such a problem is effective. Can be solved.

  Hereinafter, although this invention is demonstrated based on a more detailed Example, this invention is not limited to these Examples. In the following, “part” and “%” are based on weight unless otherwise specified. Moreover, the test and evaluation followed the following.

Example 1
(Catalyst drying process)
Zinc oxide catalyst pellets (height 8.5 mm, diameter 4.6 mm, zinc oxide: 88%, aluminum oxide: 4%, calcium oxide: 3%, other components including water: 5%) were crushed in a mortar, By sieving, zinc oxide catalyst particles were obtained by separating particles having a particle size of 850 μm to 2 mm. A jacketed stainless steel reaction tube (length: 250 mm, inner diameter: 23.2 mm) was charged with 14.1 ml of the obtained zinc oxide catalyst particles, and nitrogen was introduced at a supply rate of GHSV = 1000 h ^−1. After starting and raising the temperature of the reaction tube to 450 ° C., a drying treatment was performed at 450 ° C. for 20 minutes under introduction of nitrogen. The amount of water contained in the solid catalyst after the drying treatment was 0.1% by weight or less.

(Dehydrogenation of 2-methyl-2-butene)
A stainless steel vaporizing tube (length: 250 mm, heated at 180 ° C. with 2-methyl-2-butene at a feed pump of 1.7 mmol / min and nitrogen as a sweep gas at 11.6 mmol / min, respectively. The inner diameter is 23.2 mm) and 2-methyl-2-butene is vaporized to form a mixed gas of 2-methyl-2-butene and nitrogen, and this mixed gas is heated to 550 ° C. (drying treatment) To a stainless steel reaction tube filled with zinc oxide catalyst particles (length: 250 mm, inner diameter: 23.2 mm)), feed rate: GHSV = 1265 h ⁻¹ , reaction pressure 0.01 MPa or less at gauge pressure By introducing the 2-methyl-2-butene, the dehydrogenation reaction was performed. And the gas after the dehydrogenation reaction obtained from the reaction tube outlet gas is cooled with a heat exchange type cooler, and in the gas state, a gas chromatograph with a thermal conductivity detector (manufactured by Shimadzu Corporation) and hydrogen flame ions Analysis is performed using a gas chromatograph with a detector (manufactured by Shimadzu Corporation), and the composition ratio (molar fraction) of the components contained in the gas after the dehydrogenation reaction is determined from the area ratio of each component obtained by each gas chromatograph. Rate). In obtaining the composition ratio, a calibration curve of (molar amount / peak area) of each component constituting nitrogen, the raw material, and the dehydrogenated product was prepared in advance. And from the obtained composition ratio, according to the following formula (1), the raw material conversion rate, the isoprene yield according to the following formula (2), and the isoprene selectivity according to the following formula (3) were obtained, respectively. The results are shown in Table 1.
Raw material conversion rate (mol%) = 100 × (raw material mole amount before reaction−raw material mole amount after reaction) / raw material mole amount before reaction (1)
Isoprene yield (mol%) = 100 × (mol amount of isoprene produced / mol amount of raw material before reaction) (2)
Isoprene selectivity (mol%) = 100 × (isoprene yield / raw material conversion) (3)

  In this example, in the analysis by the gas chromatograph equipped with the thermal conductivity detector, SHIN CARBON ST 50/80 (6.0 m × 3.0 mm, manufactured by Shinwa Kako Co., Ltd.) was used as the packed column, and the sample injection amount : 1.5 mL, injection temperature: 150 ° C., detector temperature: 200 ° C., carrier gas: argon, and carrier gas flow rate: 40 ml / min, heating is started under conditions of oven temperature: 40 ° C., and held for 12 minutes Then, the temperature was raised to 200 ° C. at a rate of 10 ° C./min and held for 12 minutes. The gas chromatograph with a thermal conductivity detector was used for analyzing inorganic gases.

  Moreover, in the analysis by a gas chromatograph equipped with a flame ion detector, HP-1 (60 m × 0.25 μm × 1.00 μm, manufactured by Agilent Technologies) was used as a capillary, sample injection amount: 1.0 mL, split ratio : 1/50, injection temperature: 140 ° C., detector temperature: 260 ° C., carrier gas: helium, carrier gas flow rate: 56.3 ml / min, heating is started under the conditions of oven temperature: 40 ° C., 15 This was carried out by holding for 5 minutes, then raising the temperature to 250 ° C. at a rate of 20 ° C./min and holding for 5 minutes. In addition, the gas chromatograph with a flame ion detector was used for analyzing carbon compounds.

(Example 2)
(Dehydrogenation of 2-methyl-1-butene)
A 2-hydrogen-1-butene was dehydrogenated in the same manner as in Example 1 except that 2-methyl-1-butene was used instead of 2-methyl-2-butene. The composition ratio of the components contained in the gas after the dehydrogenation reaction was determined. And from the obtained composition ratio, it carried out similarly to Example 1, and calculated | required the raw material conversion rate, the isoprene yield, and the isoprene selectivity, respectively. The results are shown in Table 1.

(Example 3)
(Dehydrogenation of 3-methyl-1-butene)
Instead of 2-methyl-2-butene, 3-methyl-1-butene was dehydrogenated in the same manner as in Example 1 except that 3-methyl-1-butene was used. The composition ratio of the components contained in the gas after the dehydrogenation reaction was determined. And from the obtained composition ratio, it carried out similarly to Example 1, and calculated | required the raw material conversion rate, the isoprene yield, and the isoprene selectivity, respectively. The results are shown in Table 1.

(Comparative Example 1)
(Catalyst drying process)
By crushing γ-alumina catalyst pellets (height 3.1 mm × diameter 3.1 mm, aluminum oxide (γ-alumina): 95%, other components including water: 5%) in a mortar and sifting, By separating particles having a particle size of 850 μm to 2 mm, γ-alumina catalyst particles were obtained. A jacketed stainless steel reaction tube (length: 250 mm, inner diameter: 23.2 mm) was charged with 14.1 ml of the obtained γ-alumina catalyst particles, and nitrogen was introduced at a supply rate of GHSV = 1000 h ^−1. After starting and raising the temperature of the reaction tube to 450 ° C., a drying treatment was performed at 450 ° C. for 20 minutes under introduction of nitrogen.

(Dehydrogenation of 2-methyl-2-butene)
The dehydrogenation reaction of 2-methyl-2-butene was carried out in the same manner as in Example 1 except that a stainless steel reaction tube filled with γ-alumina catalyst particles subjected to drying treatment was used as the reaction tube. Similarly, the composition ratio of the components contained in the gas after the dehydrogenation reaction was determined. And from the obtained composition ratio, it carried out similarly to Example 1, and calculated | required the raw material conversion rate, the isoprene yield, and the isoprene selectivity, respectively. The results are shown in Table 1.

From Table 1, when a solid catalyst containing zinc oxide as a main component is used as the catalyst for the dehydrogenation reaction and the dehydrogenation reaction is performed in an inert gas atmosphere, the isoprene selectivity in the conversion compound is In addition, the yield of isoprene was high (Examples 1 to 3). In particular, this tendency is the same when any of 2-methyl-2-butene, 2-methyl-1-butene, and 3-methyl-1-butene constituting isoamylene is used as a raw material. there were.
On the other hand, in Comparative Example 1 using the γ-alumina catalyst, the isoprene selectivity in the conversion compound was low and the isoprene yield was poor.
In this example, one compound selected from 2-methyl-2-butene, 2-methyl-1-butene, and 3-methyl-1-butene constituting isoamylene was used. The same results can be obtained by using what is contained in the residue obtained as an extraction residual oil after separating at least a portion of isoprene by extractive distillation from the C5 fraction containing the hydrocarbon of formula 5 as the main component. Is considered to be obtained.

  Table 2 shows the composition ratios of the components contained in the gas after the dehydrogenation reaction, obtained from the area ratios of the respective components obtained in each gas chromatograph in Example 1 and Comparative Example 1. From Table 2, in Comparative Example 1, in addition to the low proportion of isoprene, other than 3-methyl-1-butene, 2-methyl-1-butene and 2-methyl-1-butene constituting isoprene and isoamylene The ratio of this compound was high, and it was not suitable for reuse as a raw material for obtaining isoprene. On the other hand, in Example 1, in addition to the high proportion of isoprene, other than 3-methyl-1-butene, 2-methyl-1-butene, and 2-methyl-1-butene constituting isoprene and isoamylene. The ratio of these compounds was low and suitable for reuse. In Table 2, only the results of Example 1 and Comparative Example 1 were shown, but Examples 2 and 3 also had the same tendency as Example 1.

Claims (3)

A method for producing isoprene by dehydrogenating isoamylene,
A solid catalyst containing zinc oxide as a main component in an inert gas atmosphere and further containing at least one selected from aluminum oxide, calcium oxide, silicon dioxide, and magnesium oxide is used for the dehydrogenation reaction. A method for producing isoprene, characterized in that Wherein prior to performing the dehydrogenation reaction, method for producing isoprene of claim 1, characterized in that the drying process before Symbol solid body catalyst.   The method for producing isoprene according to claim 1 or 2, wherein a temperature during the dehydrogenation reaction is 500 to 620 ° C.