Method for producing isobutene, catalyst for producing isobutene, and system for producing isobutene

Abstract

To provide a method for generating isobutene, for use in isomerizing normal butene to isobutene, in which the generation of by-products can be minimized, and a high yield of isobutene can be achieved.SOLUTION: A method for generating isobutene includes the step of isomerizing normal butene to isobutene. In the isomerizing step, the normal butene is brought into contact with a basic catalyst. It is preferable that the reaction temperature in the isomerizing step should range 25°C to 249°C.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a method for producing isobutene, a catalyst for producing isobutene, and a system for producing isobutene. [Background technology]

[0002] Efforts aimed at mitigating or reducing the impact of climate change have been ongoing for some time now, and research and development into reducing carbon dioxide emissions has been conducted to achieve this goal. For example, there is known technology that captures carbon dioxide from exhaust gases and the atmosphere and electrochemically reduces it to obtain valuable materials. The above technology is a promising technology that has the potential to achieve carbon neutrality.

[0003] Ethylene is produced by electrochemical reduction of carbon dioxide. Olefins such as 1-butene are produced by polymerizing ethylene in the presence of a polymerizing catalyst. Meanwhile, isobutene, which is a structural isomer of normal butene including 1-butene, is an industrially important hydrocarbon and has various applications as a synthetic intermediate. For example, MTBE and ETBE, which are used as gasoline additives, are obtained by addition reaction of isobutene with methanol or ethanol. In addition, isooctane, which is added to gasoline, is obtained by dimerizing and alkylating isobutene. Therefore, a technology related to a catalyst that promotes the isomerization reaction of normal butene to isobutene has been proposed (for example, see Non-Patent Document 1). [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Journal of Catalysis 167, 273-278(1997) Summary of the Invention [Problem to be solved by the invention]

[0005] Non-Patent Document 1 shows that a high yield of isobutene can be obtained by isomerizing normal butene to isobutene in the presence of a zeolite catalyst such as an FER type catalyst. On the other hand, in the isomerization reaction disclosed in Non-Patent Document 1, by-products having 3 or 5 carbon atoms are generated at a considerable rate. Therefore, it is difficult to separate and recover unreacted normal butene after the isomerization reaction. Even if unreacted normal butene can be separated and recovered, the yield of isobutene cannot be increased to a predetermined level or higher because of the generation of by-products. For the above reasons, a technology for further improving the yield of isobutene in a method for isomerizing normal butene to isobutene has been desired.

[0006] The present invention has been made in view of the above, and an object of the present invention is to provide a method for producing isobutene, which can minimize the production of by-products and obtain a high yield of isobutene in a method for isomerizing normal butene to isobutene. [Means for solving the problem]

[0007] (1) The present invention relates to a method for producing isobutene, comprising an isomerization step of isomerizing normal butene to isobutene, in which the normal butene is contacted with a basic catalyst in the isomerization step.

[0008] According to the invention of (1), a method for producing isobutene can be provided which can minimize the production of by-products and obtain a high yield of isobutene.

[0009] (2) The method for producing isobutene according to (1), wherein the reaction temperature in the isomerization step is within the range of 25 to 249° C.

[0010] According to the invention (2), a higher yield of isobutene can be obtained and the cost of the isomerization step can be reduced.

[0011] (3) The method for producing isobutene according to (1) or (2), wherein the basic catalyst is either a solid base catalyst or a catalyst in which a basic metal is supported on a solid base catalyst or a solid acid catalyst, the solid acid catalyst is zeolite, and the solid base catalyst is alumina.

[0012] According to the invention of (3), a method for producing isobutene can be provided that can minimize the production of by-products and obtain a higher yield of isobutene.

[0013] (4) The method for producing isobutene according to (3), wherein the basic metal is at least one of an alkali metal and an alkaline earth metal.

[0014] According to the invention (4), a method for producing isobutene can be provided that can obtain a higher yield of isobutene.

[0015] (5) The present invention also relates to a catalyst for producing isobutene, which promotes an isomerization reaction for producing isobutene by isomerizing normal butene, and which is any one of a solid base catalyst and a catalyst in which a basic metal is supported on a solid base catalyst or a solid acid catalyst.

[0016] According to the invention of (5), a catalyst for producing isobutene can be provided which can minimize the production of by-products and can provide a high yield of isobutene.

[0017] (6) The catalyst for producing isobutene according to (5), wherein the solid acid catalyst is zeolite and the solid base catalyst is alumina.

[0018] According to the invention (6), a catalyst for producing isobutene can be provided which can provide a higher yield of isobutene.

[0019] (7) The catalyst for producing isobutene according to (5) or (6), wherein the basic metal is at least one of an alkali metal and an alkaline earth metal.

[0020] According to the invention (7), a method for producing isobutene can be provided that can obtain a higher yield of isobutene.

[0021] (8) The present invention also relates to an isobutene production system including an electrolysis device that produces ethylene by electrolyzing carbon dioxide, a dimerization device that produces normal butene by dimerizing the ethylene, and an isomerization device that produces isobutene by isomerizing the normal butene, wherein the isomerization device includes a catalyst with which the normal butene comes into contact, and the catalyst is a basic catalyst.

[0022] According to the invention of (8), it is possible to recover carbon dioxide from exhaust gas or the atmosphere and produce isobutene, which is an industrially important hydrocarbon, thereby contributing to the achievement of carbon neutrality. In addition, in the isomerization reaction for producing isobutene by isomerizing normal butene to isobutene, it is possible to provide an isobutene production system that can minimize the production of by-products and obtain a high yield of isobutene.

[0023] (9) The isobutene production system according to (8), further comprising a hydration reaction apparatus, which separates the normal butene from a mixture containing the normal butene and the isobutene produced in the isomerization apparatus, and the normal butene separated by the hydration reaction apparatus is returned to the isomerization apparatus.

[0024] According to the invention (9), the yield of isobutene in the isomerization unit of the isobutene production system can be theoretically made close to 100%. [Brief description of the drawings]

[0025] [Figure 1] FIG. 1 is a block diagram showing a configuration of an isobutene production system according to one embodiment of the present invention. [Diagram 2] 1 is a graph showing isobutene yields for each type of catalyst. [Diagram 3]1 is a graph showing the relationship between the amount of base and catalyst activity (isobutene yield). [Figure 4] 1 is a graph showing the relationship between the Na2O concentration and the isobutene yield when Na is added to a solid acid catalyst. [Diagram 5] 1 is a graph showing the relationship between the amount of Na2O added and the isobutene yield when Na is added to a solid base catalyst. [Figure 6] 1 is a graph showing the relationship between the amount of MOx added and the isobutene yield when various metals are added to a solid acid catalyst. [Figure 7] 1 is a graph showing the relationship between the amount of base and catalytic activity (isobutene yield) when various metals are added to a solid acid catalyst. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] <Catalyst for isobutene production> The catalyst for producing isobutene according to the present embodiment is a catalyst for promoting an isomerization reaction of normal butene to isobutene. In this specification, normal butene refers to an equilibrium mixture in which the structural isomers 1-butene, cis-2-butene, and trans-2-butene exist in equilibrium.

[0027] The catalyst for producing isobutene according to this embodiment is a basic catalyst. By using a basic catalyst as a catalyst for producing isobutene, not only can a preferable yield of isobutene be obtained, but also the reaction temperature can be lowered, so that the cost required for producing isobutene can be reduced. In this embodiment, the basic catalyst means any one of a solid base catalyst, or a catalyst in which a basic metal is supported on a solid base catalyst or a solid acid catalyst.

[0028] Examples of the solid base catalyst include alumina. The alumina is not particularly limited, and examples thereof include alumina having a crystal phase of α, γ, δ, η, θ, etc. The above alumina can be used alone or in combination of two or more. The above alumina may be activated alumina that has been made porous. The activated alumina can be obtained, for example, by a known method of dehydrating a hydrate. The above alumina may be a commercially available product. The shape of the alumina can be granular, powder, etc.

[0029] In addition to alumina, other solid base catalysts include magnesium oxide (MgO) and cerium oxide (CeO 2 ) and other metal oxides.

[0030] By supporting a basic metal, which will be described later, on the solid acid catalyst, it can be used as the basic catalyst according to this embodiment. An example of the solid acid catalyst is zeolite. The zeolite is not particularly limited, and examples thereof include FER type zeolite (ferrierite), MFI type zeolite (ZSM-5), MOR type zeolite (mordenite), FAU type zeolite (Y type zeolite), BEA type zeolite (beta type zeolite), CHA type zeolite (chabazite), and the like. The above zeolites can be used alone or in combination of two or more kinds. In addition to zeolites, silicon dioxide (SiO 2 ) can also be used.

[0031] By supporting a basic metal on the solid acid catalyst, the solid acid catalyst functions as a basic catalyst. Examples of basic metals include alkali metals and alkaline earth metals. Examples of alkali metals include Li, Na, K, Rb, Cs, and Fr, and examples of alkaline earth metals include Ca, Sr, Ba, Ra, Be, and Mg. In addition to the above, the basic metal may be Zn, Zr, W, La, and the like. The basic metal may be supported in the form of a compound such as an oxide or nitrate. It is preferable that the basic metal is a metal having a larger period number and a smaller group number in the periodic table, that is, a metal having a higher basicity.

[0032] The basic metal may be supported on the solid base catalyst. Although the solid base catalyst functions as a basic catalyst even when the basic metal is not supported on the solid base catalyst, the function as a basic catalyst can be further improved by supporting a basic metal on the solid base catalyst.

[0033] The method for supporting the basic metal on the solid acid catalyst or solid base catalyst is not particularly limited, and the basic metal can be supported by a known method such as an impregnation method. The impregnation method is not particularly limited, and for example, an evaporation to dryness method can be used in which a solution of a basic metal compound such as a nitrate is impregnated into the solid acid catalyst or solid base catalyst, and then the catalyst is dried by heating to evaporate the solvent, and then the catalyst is fired. In addition to the above, an adsorption method, a spray method, etc. can also be used as the impregnation method. When the solid acid catalyst or solid base catalyst is a porous body, the basic metal is supported in its pores. When the solid acid catalyst or solid base catalyst is not a porous body, the basic metal may be supported on its outer surface.

[0034] The amount of the basic metal supported is not particularly limited, but when supported on a solid acid catalyst, it can be 0.01 to 10 mass% based on the weight of the catalyst. The amount supported is preferably 0.07 to 10 mass%, more preferably 0.1 to 10 mass%, and even more preferably 1.0 to 10 mass%. The amount supported can be 10 mass% or more.

[0035] The basic catalyst is CO 2 The basic site determined by -TPD is preferably 0.1 mmol / g or more, more preferably 0.2 mmol / g or more. 2 -TPD is an acid probe molecule, carbon dioxide (CO 2 A known method can be applied in which the amount of basic sites is determined by adsorbing 1,2-diphenyl ether (A) onto a basic catalyst and measuring the desorbed gas.

[0036] <Method of producing isobutene> The method for producing isobutene according to the present embodiment includes an isomerization step in which normal butene, which is a raw material, is brought into contact with the basic catalyst, which is a catalyst for promoting an isomerization reaction. The isomerization reaction of normal butene in the isomerization step is represented by the following formula (1).

[0037] [ka] Formula (1)

[0038] In the above formula (1), normal butene is described as 1-butene for convenience, but normal butene is actually an equilibrium mixture in which 1-butene, cis-2-butene, and trans-2-butene exist in equilibrium. "i-butene" in the above formula (1) means isobutene. "Unreactive n-butene" in the above formula (1) means normal butene that is unreacted and not isomerized by the isomerization reaction. In the above formula (1), isobutene and normal butene are described as products, but in addition to the above products, trace amounts of by-products may be generated by the isomerization reaction shown in the above formula (1).

[0039] In the isomerization step, the reaction temperature is preferably within a range of 25 to 249° C. The reaction temperature is more preferably 25 to 200° C., further preferably 25 to 150° C., and most preferably 25 to 100° C. By using the basic catalyst according to this embodiment, the temperature of the isomerization step can be lowered, and not only can the cost required for the isomerization step be reduced, but also a more preferable isobutene yield can be obtained by lowering the reaction temperature.

[0040] In the isomerization process, the hourly space velocity (GHSV) of the raw gas containing normal butene is 20,000 to 80,000 ml g -1 h -1 The contact time (W / F) is preferably 0.0008 to 0.0031 g min ml -1 It is preferable that the conversion ratio of normal butene is increased by the above-mentioned formula (2).

[0041] Normal butene conversion rate (%) = ((amount of normal butene in the raw gas) - (amount of normal butene in the product gas)) / (amount of normal butene in the raw gas) x 100 (2)

[0042] The selectivity of isobutene is represented by the following formula (3), and the yield of isobutene is represented by the following formula (4).

[0043] Isobutene selectivity (%) = (amount of isobutene in the product gas) / (amount of normal butene in the feed gas) × 100 (3)

[0044] Isobutene yield (%) = (isobutene selectivity (%)) × (normal butene conversion (%)) ÷ 100 (4)

[0045] The method for producing isobutene according to the present embodiment may include a process other than the isomerization process. 2The method may further include a step of preparing a raw material gas by diluting the product gas with a gas at a predetermined dilution ratio. The method may also include a step of separating unreacted normal butene from the product gas, and may further include a step of reusing the separated normal butene as a raw material gas. The method for producing isobutene according to the present embodiment can minimize the production of by-products, and therefore can easily separate unreacted normal butene from the product gas. Furthermore, by reusing the normal butene separated from the product gas as a raw material gas, the theoretical yield of isobutene can be improved to nearly 100%.

[0046] The step of separating unreacted normal butene from the product gas can be achieved, for example, by a hydration reaction (water addition reaction) shown in the following formula (5).

[0047] [ka] Formula (5)

[0048] By the hydration reaction in the above formula (5), only isobutene can be converted into TBA (tert-butyl alcohol), which is liquid or solid at room temperature, so that normal butene, which is gaseous at room temperature, can be easily separated from the above-mentioned product gas. As a specific method, for example, a known method can be used, such as a method of using an aqueous solution containing a heteropolyacid having at least one element selected from Mo, W, and V as a condensed coordination element and reacting at a temperature of less than 100°C. Note that TBA can be effectively utilized by converting it into isooctane by known dimerization and hydrogenation techniques. This is because isooctane can be used as a gasoline base material, etc.

[0049] <Isobutene generation system> As shown in FIG. 1, an isobutene production system 1 according to this embodiment includes an electrolysis device 10, a dimerization device 20, an isomerization device 30, a hydration reaction device 40, and flow paths F1 to F4 connecting the devices together.

[0050] The electrolysis device 10 is a device for producing carbon dioxide (CO 2 ) is electrochemically reduced to ethylene (C 2 H 4 The electrolysis device 10 reduces carbon dioxide using an electrolysis cell that reduces carbon dioxide. An example of the electrolysis cell is an electrolysis cell that has at least a cathode and an anode. The cathode electrochemically reduces carbon dioxide to produce ethylene (C 2 H 4 The anode oxidizes hydroxide ions to produce oxygen. The ethylene (C) produced by the electrolysis device 10 is 2 H 4 ) is supplied to the dimerization device 20 via flow path F1.

[0051] Carbon dioxide (CO 2 The source of ) is not particularly limited, and may be one that is separated and recovered from the air, or one that is separated and recovered from exhaust gas discharged from a combustion facility such as a boiler.

[0052] The dimerizer 20 is a dimerizer that receives ethylene (C 2 H 4 ) is dimerized to produce normal butene (nC 4 H 8 The dimerization apparatus 20 has a reactor 21 and a cooling separator 22. The dimerization apparatus 20 is an apparatus for producing normal butene (nC 4 H 8 ) can be produced, for example, in a yield of 80% or more.

[0053] The reactor 21 is, for example, a reactor for producing normal butene (nC) by carrying out a polymerization reaction of ethylene in the presence of an olefin polymerization catalyst. 4 H 8 The olefin polymerization catalyst is, for example, a solid acid catalyst using silica alumina or zeolite as a carrier, a transition metal complex compound, etc. An example of the metal atom supported on the carrier is Ni.

[0054] The cooling separator 22 separates the product gas after the polymerization reaction in the reactor 21 into gas and liquid. The boiling point of the olefins contained in the product gas increases with the increase in the carbon number. Therefore, the temperature of the cooling separator 22 is adjusted to 100° C. 4 H 8 ) and lower than the boiling point of other olefins with 6 or more carbon atoms, 4 H 8 The normal butene (nC) separated by the cooling separator 22 can be easily separated into gas and liquid. 4 H 8 ) is supplied to the isomerization unit 30 via flow path F2. Other olefins having 6 or more carbon atoms separated by the cooling separator 22 are separated and discharged as a liquid fraction.

[0055] The isomerization apparatus 30 is a reactor for isomerizing normal butene (nC 4 H 8 ) to isobutene (iC 4 H 8 The isomerization unit 30 is an apparatus for producing normal butene (nC). The isomerization unit 30 has the above-mentioned basic catalyst. The basic catalyst is, for example, packed in a catalyst layer of a fixed bed reactor included in the isomerization unit 30. 4 H 8 ) is distributed, the normal butene (nC 4 H 8 The isomerization unit 30 also includes a catalyst that is capable of reacting with normal butene (nC 4 H 8 ) to N 2 A dilution device for diluting the gas to a predetermined dilution ratio may be provided. 4 H 8 The fixed bed reactor may be equipped with known devices capable of adjusting the flow rate of the gas containing isobutene (iC), as well as the temperature and pressure of the fixed bed reactor. 4 H 8 ) and unreacted normal butene (nC4 H 8 ) is supplied to the hydration reactor 40 via flow path F3.

[0056] The hydration reactor 40 is a reactor for hydration of isobutene (iC 4 H 8 ) and unreacted normal butene (nC 4 H 8 ) from a mixture containing unreacted normal butene (nC 4 H 8 The hydration reactor 40 separates isobutene (iC 4 H 8 ) is converted to TBA (tert-butyl alcohol) by hydration reaction, and normal butene (nC 4 H 8 The TBA (tert-butyl alcohol) separated by the hydration reactor 40 is converted to isooctane or the like by existing technology and used. The unreacted normal butene (nC 4 H 8 ) is returned to the isomerization apparatus 30 via a flow path F4 serving as a return flow path. The flow path F4 may be connected to the middle of the flow path F2, or may be connected to the isomerization apparatus 30.

[0057] The isobutene production system 1 having the above-mentioned configuration has the following effects. Since the isobutene production system 1 has the isomerization device 30 having a basic catalyst, the target substance is isobutene (iC 4 H 8 ) can be obtained in a high yield and the production of by-products can be suppressed to an almost limit. In addition, the isobutene production system 1 can also be used to convert isobutene (iC 4 H 8 ) and unreacted normal butene (nC 4 H 8 The reaction system further includes a hydration reactor 40 for separating a mixture of unreacted normal butene (nC 4 H8 ) to the isomerization apparatus 30. This allows the ratio of isobutene (iC) to normal butene (raw material) in the isomerization apparatus 30 to be reduced. 4 H 8 Theoretically, the yield of the product can be close to 100%.

[0058] In addition, the isobutene production system 1 is capable of recovering carbon dioxide from exhaust gas or the atmosphere to produce isobutene, an industrially important hydrocarbon, and therefore contributes to achieving carbon neutrality.

[0059] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above-mentioned embodiments, and the present invention includes modifications and improvements within the scope of the present invention that can achieve the object of the present invention.

[0060] In the above embodiment, the isobutene production system 1 has been described as being directly connected between the devices via the flow paths F1 to F4. This is not limited to the above. Each device may store the product in a storage tank such as a cylinder, and the storage tank may be transported to supply the product to other devices. EXAMPLES

[0061] The present invention will be described in detail below using examples, but the present invention is not limited to these examples.

[0062] [Relationship between type of basic catalyst and isobutene yield] Using each catalyst shown in Table 1 below, normal butene (nC 4 H 8 ): 15ml / min, N 2 The reaction gas was passed through at a flow rate of 50 ml / min to carry out the isomerization reaction under the following reaction conditions: temperature: 200° C., pressure: 0.1 MPa, reaction time: 40 min, and catalyst amount: 0.2 g.

[0063] [Table 1]

[0064] The catalyst No. 2 in Table 1 was prepared by the following procedure: Aluminum nitrate nonahydrate, TEOS, and urea were precipitated by the homogeneous precipitation method (10 equivalents of urea, aging at 80°C for 48 hours), and the resulting fine powder was calcined at 700°C for 6 hours to prepare the catalyst.

[0065] <Gas Chromatography> The product gases generated by the isomerization reaction using each catalyst shown in Table 1 were quantitatively analyzed by gas chromatography. The measurement conditions for gas chromatography are as follows.

[0066] (Measurement conditions) Measuring device: GC-2014 (Shimadzu Corporation) Column: Rtx-1 (RESTEK, length 60 m, inner diameter 0.25 mm, film thickness 0.5 mm) Carrier gas: N 2 (Total flow rate 50ml / min, purge flow rate 3.0ml / min) Split ratio: 66.1 (column flow rate 0.70 ml / min) Injection: 250℃ Detection: 280℃ Analysis: 40°C for 10 min, then heat to 200°C at 20°C / min, then 200°C for 9.5 min (total 30 min)

[0067] Based on the analytical results obtained by the above gas chromatography, the yield of isobutene was calculated, and the results are shown in the following Table 2 and the graph in Figure 2. 4 H 8 " indicates the isobutene yield. As shown in Table 2 and FIG. 2, it is clear that a high isobutene yield can be obtained by using basic catalysts 5, 6, 7, 8, 9, 10, 11, 14, 16, and 17 (numbers indicate Catalyst. No. in Tables 1, 2, and FIG. 2).

[0068] [Table 2]

[0069] [Relationship between reaction temperature and isobutene yield] Ferrierite (Tosoh Corporation, 760HOA, FER (silica / alumina ratio of about 60)) and γ-alumina (JRC-ALO-6, Nikki Universal Corporation) were used as catalysts, and normal butene (nC 4 H 8 The reaction conditions were the same as those shown in Figure 2, except for the reaction temperature. The results are shown in Table 3. 4 H 8 " indicates the isobutene yield.

[0070] [Table 3]

[0071] As shown in Table 3, it is clear that the basic catalyst γ-alumina gives a higher isobutene yield than ferrierite and does not produce by-products, especially in the temperature range below 250° C. Furthermore, it is clear that the higher the temperature of ferrierite, the higher the isobutene yield, whereas the basic catalyst γ-alumina gives a higher isobutene yield at lower temperatures.

[0072] [Relationship between the amount of base in the catalyst and the isobutene yield 1] An isomerization reaction was carried out using γ-alumina, θ-alumina, silica magnesia, and zeolite, each of which has a different amount of base, to determine the relationship between the amount of base sites and the isobutene yield. The measurement of the isomerization reaction was carried out under the same conditions as in Figure 2. The amount of base sites was measured using CO 2The measurement was performed by FT-TPD. The measurement equipment used was a catalyst analyzer BELCAT B (manufactured by Microtrack BEL Co., Ltd.). The reaction conditions were as follows: 0.1 g of catalyst was packed into a quartz cell. As a pretreatment, the catalyst was heated at 500°C for 1 hour under a flow of He (30 ml / min), and then cooled to 50°C while flowing He. Then, the catalyst was analyzed by CO 2 (30ml / min) was passed for 1 hour, and CO 2 After the adsorption, He (30 ml / min) was passed through the sample at 50°C for 1 hour to measure the amount of physically adsorbed CO. 2 The temperature was then increased from 50°C to 800°C at a rate of 10°C / min under a flow of He (30 ml / min) and held at 800°C for 30 min. 2 The amount of base sites was determined by measuring the amount of base sites. The results are shown in Figure 3. As shown in Figure 3, it is clear that the isobutene yield tends to improve as the amount of base sites in the catalyst increases.

[0073] [Relationship between basic metal loading and isobutene yield 1] The basic metals (Na 2 The Y-type zeolite (shown as "◯" in FIG. 4) carrying Na, the Na-type zeolite "HSZ-320NAA" (manufactured by Tosoh Corporation) and "JRC-Z-HY4.8" (manufactured by Catalysts and Chemicals Industry Co., Ltd.) in Table 4 carrying Na 2 The isomerization reaction was carried out under the same conditions as in Figure 2 using a catalyst with added O (shown as "△" in Figure 4). 2 The relationship between the O content (wt%) and the isobutene yield was determined, and the results are shown in Table 4 below and FIG.

[0074] [Table 4]

[0075] As shown in Table 4 and FIG. 4, in the zeolite solid acid catalyst, the basic metal (Na 2 It is clear from the results that the higher the content of .O., the higher the isobutene yield.

[0076] [Relationship between basic metal loading and isobutene yield 2] The Na content of the γ-alumina catalyst JRC-ALO-6 (manufactured by Nikki Universal Co., Ltd.) and the catalysts in which different amounts of Na were supported on JRC-ALO-6 by the impregnation method were measured in the same manner as in Figure 4. 2 The relationship between the content (wt%) of O and the isobutene yield was determined. 3 After impregnation with the aqueous solution, the material was dried at 110°C for 12 hours and then calcined at 400°C for 3 hours. The results are shown in Table 5.

[0077] [Table 5]

[0078] [Relationship between basic metal loading and isobutene yield 3] As in Figure 4, the Na content of each catalyst was measured for alumina such as JRC-ALO-6 (manufactured by Nikki Universal Co., Ltd.) (shown as "◯" in Figure 5), which is γ-alumina, and catalysts in which different amounts of Na were supported on JRC-ALO-6 by the impregnation method (shown as "△" in Figure 5). 2 The relationship between the content (wt%) of O and the isobutene yield was determined. 3 After impregnation with the aqueous solution, the catalyst was dried at 110°C for 12 hours, and then calcined at 400°C for 3 hours. The results are shown in Figure 5. As shown in Table 5 and Figure 5, the alumina solid base catalyst had a high concentration of basic metal (Na 2 It is clear from the results that the higher the content of .O., the higher the isobutene yield.

[0079] [Relationship between added metal and isobutene yield 1] The zeolite CBV28014 (Zeolyst, ZSM-5 type, silica-alumina ratio 280) was loaded with Na, Mg, Zn, La, W, and Zr as additive metals in different amounts, and the relationship between the additive metal content (MOx equivalent, weight %) and the isobutene yield in each catalyst was determined in the same manner as in FIG. 4. The results are shown in FIG. 6. As shown in FIG. 6, it is clear that the isobutene yield improves as the additive metal content increases. In addition, as for the type of additive metal, Na had the highest effect of improving the isobutene yield per additive amount, followed by Mg. Therefore, it is clear that the use of an alkali metal or an alkaline earth metal as an additive metal can provide a high effect of improving the isobutene yield.

[0080] [Relationship between added metal and isobutene yield 2] Under the same conditions as in Figure 6, each metal shown in Table 6 was loaded onto CBV28014 in an amount of 0.7 mol% (equivalent to each metal atom) as the added metal, and the relationship between the type of added metal and the isobutene yield was determined in the same manner as in Figure 4. The results are shown in Table 6.

[0081] [Table 6]

[0082] From the results in Table 6, it is clear that a higher effect of improving the isobutene yield can be obtained by using, as an added metal, a metal having a larger period number and a smaller group number in the periodic table, that is, a metal having a higher basicity.

[0083] [Relationship between the amount of base in the catalyst and the isobutene yield 2] The amount of base sites of each catalyst with various metals added in Figure 6 was measured using CO 2 The results were obtained by TPD to determine the relationship between the amount of base sites and the yield of isobutene. The results are shown in Figure 7. As shown in Figure 7, there is a proportional relationship between the amount of base sites and the yield of isobutene, and it is clear that the yield of isobutene increases as the amount of base sites increases. [Explanation of symbols]

[0084] 1. Isobutene generation system 10 Electrolyzer 20 Dimerization device 30 Isomerization equipment 40 Hydration reactor

Claims

1. A method for producing isobutene, comprising an isomerization step of isomerizing normal butene to isobutene, In the isomerization step, the normal butene is contacted with a basic catalyst, the basic catalyst is either alumina or a catalyst in which at least one of an alkali metal and an alkaline earth metal is supported on alumina or zeolite; The method for producing isobutene, wherein the reaction temperature in the isomerization step is within the range of 25 to 150°C.

2. A catalyst for producing isobutene that promotes an isomerization reaction for producing isobutene by isomerizing normal butene, used in the isomerization reaction at temperatures in the range of 25 to 150° C., A catalyst for producing isobutene, which is either an alumina catalyst or a catalyst in which at least one of an alkali metal and an alkaline earth metal is supported on alumina or zeolite.

3. an electrolysis device for producing ethylene by electrolyzing carbon dioxide; a dimerization unit for dimerizing the ethylene to produce normal butene; an isomerization unit for isomerizing the normal butene to produce isobutene; The isomerization reaction temperature in the isomerization apparatus is within the range of 25 to 150° C., The isomerization unit includes a catalyst with which the normal butene is contacted, The catalyst is any one of alumina and a catalyst in which at least one of an alkali metal and an alkaline earth metal is supported on alumina or zeolite.

4. Further comprising a hydration reactor, The hydration reactor separates the normal butene from a mixture containing the normal butene and the isobutene produced in the isomerization reactor, The isobutene production system according to claim 3 , wherein the normal butene separated by the hydration reaction unit is returned to the isomerization unit.

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