Catalyst for producing isobutylene, and method for producing isobutylene

Abstract

The present invention pertains to: a catalyst for producing isobutylene, the catalyst containing γ-alumina and at least type of one metal sulfate selected among from iron and zinc; or a catalyst for producing isobutylene, the catalyst containing γ-alumina and tungsten trioxide.

Description

Catalyst for isobutylene production, and method for producing isobutylene

[0001] This invention relates to a catalyst for isobutylene production and a method for producing isobutylene.

[0002] Isobutylene is one of the important chemical raw materials that can be converted into ethyl tert-butyl ether (ETBE), paraxylene, methyl methacrylate (MMA) monomer, and others. Of these, MMA monomer, for example, is a highly valuable substance as a raw material for polymethyl methacrylate, which is useful as a transparent resin.

[0003] Isobutylene, used as a raw material for MMA monomers, is produced from petroleum. Isobutylene can be obtained, for example, by fractional distillation of butadiene from the C4 fraction obtained by naphtha cracking, extraction of isobutylene from the fractional distillation residue (spent BB) as tert-butanol by acid-catalyzed hydration, and dehydration. Another method involves synthesizing methyl tert-butyl ether from isobutylene and methanol in spent BB, and then decomposing it. Given concerns about petroleum depletion, there is a need for the development of petroleum-independent methods for producing isobutylene.

[0004] Furthermore, carbon dioxide, which is produced when petroleum is burned, is considered a cause of global warming. Therefore, biorefinery technology is attracting global attention as a technology for producing energy and chemicals from biomass, a renewable resource. A biorefinery refers to a plant or technology that produces synthesis gas, sugars such as glucose, and aromatic compounds such as lignin through gasification, saccharification, and extraction of various types of biomass, and then produces energy and chemicals by converting these into various forms. It is known that isobutanol, a C4 compound similar to isobutylene, can be obtained using such biorefinery technology. Isobutylene can also be produced by dehydrating isobutanol (see, for example, Patent Documents 1 and 2).

[0005] Japanese Patent Publication No. 4-247043 International Publication No. 2021 / 200689

[0006] Patent Document 1 discloses a method for producing olefins such as isobutylene by dehydrating lower alcohols such as isobutanol, in which γ-alumina with added silica is used as a dehydration catalyst. However, the isobutanol yield is not always sufficient.

[0007] Patent Document 2 discloses a method for producing isobutylene by dehydrating isobutanol, in which alumina containing metals such as Mn, Fe, Co, Ni, Cu, and Zn is used as a dehydration catalyst, and the dehydration reaction is carried out at 340°C, resulting in a high selectivity for isobutylene in the C4 gas of the reaction product. However, from the viewpoint of reducing environmental impact, there is a need to obtain a higher isobutylene yield at a lower reaction temperature.

[0008] The present invention has been made in view of the above circumstances, and aims to provide a catalyst for isobutylene production that can show a high isobutylene yield at a low reaction temperature, and a method for producing isobutylene using the catalyst.

[0009] The present invention includes the following embodiments: [1] A catalyst for isobutylene production comprising γ-alumina and at least one metal sulfate selected from iron or zinc. [2] The catalyst according to [1], wherein the ratio of iron or zinc to the total amount of Al, O and the constituent elements of the metal sulfate on the surface, as determined by measuring the surface of the catalyst according to energy-dispersive X-ray spectroscopy, is 15% by mass or more and 45% by mass or less. [3] A catalyst for isobutylene production comprising γ-alumina and tungsten trioxide. [4] The catalyst according to [3], wherein the ratio of W to the total amount of Al, O and W on the surface, as determined by measuring the surface of the catalyst according to energy-dispersive X-ray spectroscopy, is 2% by mass or more and 55% by mass or less. [5] A method for producing isobutylene, comprising producing isobutylene using the catalyst according to any one of [1] to [4]. [6] A method for producing isobutylene according to [5], wherein isobutanol and the catalyst are reacted at a temperature of 250°C or higher and less than 340°C.

[0010] The present invention provides a catalyst for producing isobutylene that can exhibit a high isobutylene yield at a low reaction temperature, and a method for producing isobutylene using the catalyst.

[0011] Embodiments of the present invention will be described in detail below.

[0012] (Catalyst) The first catalyst of this embodiment is a catalyst used to produce isobutylene. The catalyst of this embodiment comprises γ-alumina and at least one metal sulfate selected from iron or zinc. The second catalyst of this embodiment comprises γ-alumina and tungsten trioxide.

[0013] <γ-Alumina> In this specification, "alumina" means aluminum oxide (Al ２ O ３ ) is the case. "γ" refers to the crystalline form. The γ-alumina contained in the catalyst of this embodiment may be used alone, or two or more types may be used in combination with other crystalline forms of alumina, as long as the effects of the invention are not impaired. When two or more types are used in combination, different crystalline forms of alumina may be mixed, or a multiphase crystalline state may be taken. Different crystalline forms of alumina may be, for example, transition alumina with crystalline forms such as σ, θ, δ, κ, etc., or transition alumina containing alumina hydrate. In this embodiment, it is preferable to use γ-alumina alone.

[0014] The γ-alumina contained in the catalyst of this embodiment may contain impurities to the extent that they do not impair the effects of the invention. Examples of impurities include sodium oxide (Na). ２ O), iron(III) oxide (Fe ２ O ３ ), silicon dioxide (SiO ２), and the like. From the viewpoint of improving the isobutanol conversion rate, the purity of γ-alumina contained in the catalyst of the present embodiment is preferably 90% by mass or more, more preferably 95% by mass or more, and still more preferably 97% by mass or more. The purity of γ-alumina can be measured, for example, by ICP emission spectroscopy (ICP-AES). As the ICP emission spectrometer, for example, Optima 8300 ICP-OES Spectrometer manufactured by Perkin Elmer can be used.

[0015] Pores are formed in γ-alumina. Pores are fine voids. Pores are classified into micropores, mesopores and macropores according to pore size. Pores with a diameter of less than 2 nm are called micropores, pores with a diameter of 2 nm or more and less than 50 nm are called mesopores, and pores with a diameter of 50 nm or more are called macropores. The pore diameter of γ-alumina contained in the catalyst of the present embodiment is preferably 2 nm or more and less than 50 nm, more preferably 3 nm or more and 30 nm or less, and still more preferably 5 nm or more and 20 nm or less. The pore diameter of γ-alumina can be calculated from a gas adsorption-desorption isotherm, and can be measured, for example, using a multi-sample high-performance specific surface area / pore size distribution analyzer, 3Flex-2MP (product name, manufactured by Micromeritics, U.S.A.).

[0016] The pore volume of γ-alumina contained in the catalyst of the present embodiment is 0.01 cm ３ / g or more and 1 cm ３ / g or less, preferably 0.02 cm ３ / g or more and 0.9 cm ３ / g or less, more preferably 0.30 cm ３ / g or more and 0.80 cm ３ / g or less, and still more preferably. The upper limit and lower limit of the above range can be combined arbitrarily. The pore volume of γ-alumina can be calculated from a gas adsorption-desorption isotherm, and can be measured, for example, using a multi-sample high-performance specific surface area / pore size distribution analyzer, 3Flex-2MP (product name, manufactured by Micromeritics, U.S.A.).

[0017] The BET specific surface area of γ-alumina contained in the catalyst of the present embodiment is 50 m ２ / g or more and 500 m ２ / g or less, preferably 100 m ２ / g or more and 400 m ２ / g or less, more preferably 150 m ２ / g or more and 300 m ２ / g or less is even more preferable. The upper limit and lower limit of the above ranges can be combined arbitrarily. The specific surface area of γ-alumina can be calculated from gas adsorption-desorption isotherms, and can be measured, for example, using a multi-sample high-performance specific surface area / pore distribution measuring apparatus, 3Flex-2MP (product name, manufactured by Micromeritics Inc., U.S.A.).

[0018] The γ-alumina contained in the catalyst of the present embodiment may be in powder form or may be a spherical molded article. The average particle diameter of primary particles of powdery γ-alumina may be 5 µm or more and 200 µm or less, may be 10 µm or more and 150 µm or less, or may be 20 µm or more and 100 µm or less. The upper limit and lower limit of the above ranges can be combined arbitrarily. The particle diameter of γ-alumina in the form of a spherical molded article may be 0.5 mm or more and 20 mm or less, may be 1 mm or more and 15 mm or less, or may be 2 mm or more and 10 mm or less. The upper limit and lower limit of the above ranges can be combined arbitrarily. The particle diameter of γ-alumina can be measured, for example, using a laser diffraction particle size distribution analyzer, Partica LA-960V2 (product name, manufactured by Horiba, Ltd.).

[0019] The γ-alumina contained in the catalyst of the present embodiment may be one produced by a known method. Known methods include, for example, the Bayer process using bauxite as a raw material, the thermal decomposition method for ammonium alum, the underwater spark discharge method for aluminum, the vapor phase oxidation method, and the hydrolysis method for aluminum alkoxide.

[0020] <Metal Sulfate> The first catalyst of the present embodiment contains γ-alumina and at least one metal sulfate selected from iron and zinc.

[0021] The metal sulfate contained in the catalyst of the present embodiment may be contained in the surface layer of γ-alumina, may be contained in a form substituted for a part of aluminum in the crystal structure of γ-alumina, or may be a combination of these; however, from the viewpoint of improving the isobutylene yield, the metal sulfate is preferably contained in the surface layer of γ-alumina. The "surface layer" means the region within 5 µm from the surface of γ-alumina.

[0022] [Measurement of Metal Sulfate Content] The content of the metal sulfate in the first catalyst of the present embodiment can be measured on the surface of the first catalyst by the following measurement method using an energy dispersive X-ray spectrometer (EDX), specifically Rayny EDX-700 (product name, manufactured by Shimadzu Corporation). The content of the metal sulfate in the first catalyst of the present embodiment is defined as the ratio of the metal relative to the total amount of aluminum (Al), oxygen (O) and the constituent elements of the metal sulfate (iron (Fe), zinc (Zn), sulfur (S), oxygen (O)) on the surface of the first catalyst obtained as a result of the measurement.

[0023] (Measurement Method) Under a vacuum atmosphere, select a voltage of 5 to 50 kV, a current of 1 to 1000 µA, and a collimator from the range of φ1 to 10 mm, perform measurement in the channel range from Na to U, and obtain the result through processing and calculation by the fundamental parameter (FP) method. The voltage and current can be adjusted within the above ranges according to the type of the element to be measured for the purpose of improving peak sensitivity. The collimator diameter can be adjusted within the above ranges according to the state (size, particle size distribution, etc.) of the sample to be measured for the purpose of improving peak sensitivity. The measurement sample may be put into a dedicated sample container without pretreatment for measurement, or may be preliminarily pulverized with a mill or the like, then pressure-molded, and then put into a dedicated sample container for measurement.

[0024] The ratio of iron or zinc contained on the surface of the first catalyst of the present embodiment is preferably 15% by mass or more and 45% by mass or less, more preferably 18% by mass or more and 40% by mass or less, relative to the total amount of Al, O and the constituent elements of the metal sulfate contained on the surface of the catalyst.

[0025] The proportion of aluminum contained on the surface of the first catalyst in this embodiment is preferably 5% by mass or more and 30% by mass or less, and more preferably 10% by mass or more and 28% by mass or less, based on the total amount of constituent elements of Al, O, and metal sulfate contained on the surface of the first catalyst.

[0026] The proportion of sulfur contained on the surface of the first catalyst in this embodiment is preferably 5% by mass or more and 30% by mass or less, and more preferably 10% by mass or more and 25% by mass or less, based on the total amount of Al, O, and metal sulfate constituent elements contained on the surface of the first catalyst.

[0027] If the proportions of iron or zinc, aluminum and sulfur contained on the surface of γ-alumina are above the lower limit of the preferred range, the isobutanol conversion rate and isobutylene yield are improved. If the proportions of iron or zinc, aluminum and sulfur contained on the surface of γ-alumina are below the upper limit of the preferred range, the isobutylene selectivity and isobutylene yield are improved. The upper and lower limits of the range can be combined arbitrarily.

[0028] <Tungsten Trioxide> The second catalyst of this embodiment comprises γ-alumina and tungsten trioxide.

[0029] The form in which tungsten trioxide is contained in the second catalyst of this embodiment is not particularly limited. It may be contained in the surface layer of γ-alumina, or it may be contained in a form that replaces a part of the aluminum in the crystalline structure of γ-alumina, or a combination of these. However, from the viewpoint of improving the isobutylene yield, it is preferable that it is contained in the surface layer of γ-alumina. "Surface layer" means within 5 μm from the surface of γ-alumina.

[0030] The tungsten trioxide content of the second catalyst in this embodiment is the ratio of tungsten (W) to the total amount of aluminum (Al), oxygen (O), and tungsten (W) on the surface of the second catalyst, obtained from the same measurement results as for the metal sulfate content of the first catalyst in this embodiment described above.

[0031] The proportion of tungsten contained on the surface of the second catalyst in this embodiment is preferably 2% by mass or more and 55% by mass or less, and more preferably 5% by mass or more and 50% by mass or less, relative to the total amount of Al, O, and W contained on the surface of the catalyst.

[0032] The proportion of aluminum contained on the surface of the second catalyst in this embodiment is preferably 5% by mass or more and 50% by mass or less, and more preferably 8% by mass or more and 45% by mass or less, relative to the total amount of Al, O, and W contained on the surface of the catalyst.

[0033] When the proportions of tungsten and aluminum contained on the catalyst surface are above the lower limit of the preferred range, the isobutanol conversion rate and isobutylene yield are improved. When the proportions of tungsten and aluminum contained on the catalyst surface are below the upper limit of the preferred range, the isobutylene selectivity and isobutylene yield are improved. The upper and lower limits of the range can be combined in any way.

[0034] <Optional Components> The first catalyst of this embodiment may contain tungsten, tungsten oxides, hydrates, or salts, to the extent that it does not impair the effects of the present invention. The second catalyst of this embodiment may contain iron, zinc, hydrates, oxides, or salts thereof, to the extent that it does not impair the effects of the present invention.

[0035] The catalyst of this embodiment may contain metal sulfates of iron or zinc, or metal components other than tungsten trioxide, as long as the effects of the present invention are not impaired. Optional components include, for example, titanium, vanadium, chromium, manganese, cobalt, nickel, copper, gallium, zirconium, niobium, molybdenum, technetium, ruthenium, rhodium, palladium, silver, cadmium, indium, tin, hafnium, tantalum, rhenium, osmium, iridium, platinum, gold, mercury, thallium, lead, their hydrates, oxides, or salts.

[0036] The content of the optional component contained on the surface of the catalyst is preferably 0% to 5% by mass, more preferably 0% to 3% by mass, and even more preferably 0% to 1% by mass, relative to the total amount of constituent elements contained on the surface of the catalyst. The upper and lower limits of the above range can be combined arbitrarily.

[0037] <Method for Manufacturing the Catalyst> The method for manufacturing the catalyst in this embodiment is not particularly limited and can be manufactured by following known processes. Examples of known methods include impregnation, kneading, and precipitation. The impregnation method is preferred for manufacturing the catalyst in this embodiment.

[0038] One example of a method for producing the catalyst of this embodiment is to immerse γ-alumina in a solution containing a metal sulfate or a complex aqueous solution containing tungsten trioxide, impregnate the pores of the γ-alumina with the solution containing the metal sulfate or the complex aqueous solution containing tungsten trioxide, and then dry and calcine it.

[0039] The solvent used to dissolve the metal sulfate is not particularly limited as long as it can dissolve the metal sulfate, and examples include distilled water or deionized water. The concentration of the metal sulfate in the metal sulfate solution is preferably 50% by mass or less, more preferably 30% by mass or less, and even more preferably 20% by mass or less. When the concentration of the metal sulfate is 50% by mass or less, the metal sulfate is uniformly dispersed on the γ-alumina surface, and the catalytic activity is improved.

[0040] A complex aqueous solution containing tungsten trioxide can be obtained by dissolving tungsten trioxide in water together with carboxylic acids such as oxalic acid, succinic acid, glutaric acid, and tartaric acid. The concentration of tungsten trioxide in the complex aqueous solution is preferably 50% by mass or less, more preferably 30% by mass or less, and even more preferably 20% by mass or less. When the concentration of tungsten trioxide is 50% by mass or less, the metal sulfate is uniformly dispersed on the γ-alumina surface, improving catalytic activity.

[0041] In the first catalyst manufacturing method of this embodiment, the amount of metal sulfate solution added can be adjusted by the mass of metal sulfate in the metal sulfate solution. The mass of metal sulfate in the metal sulfate solution is preferably 5% to 50% by mass, more preferably 7% to 45% by mass, and even more preferably 10% to 40% by mass, relative to the mass of γ-alumina. The upper and lower limits of the above range can be arbitrarily combined. If the mass of metal sulfate is above the lower limit of the above preferred range, the isobutanol conversion rate and isobutylene yield are improved. If the amount of metal sulfate added is below the upper limit of the above preferred range, the isobutylene selectivity and isobutylene yield are improved.

[0042] In the method for producing the second catalyst of this embodiment, the amount of the complex aqueous solution in which the tungsten trioxide solution is dissolved can be adjusted by the mass of tungsten trioxide in the complex aqueous solution. The mass of tungsten trioxide in the complex aqueous solution is preferably 5% to 50% by mass, more preferably 7% to 45% by mass, and even more preferably 10% to 40% by mass, relative to the mass of γ-alumina. The upper and lower limits of the above range can be arbitrarily combined. If the mass of tungsten trioxide is above the lower limit of the above preferred range, the isobutanol conversion rate and isobutylene yield are improved. If the amount of tungsten trioxide added is below the upper limit of the above preferred range, the isobutylene selectivity and isobutylene yield are improved.

[0043] In the catalyst manufacturing method of this embodiment, the drying temperature and time are not particularly limited and may be, for example, 6 to 48 hours at a temperature of room temperature or higher and 120°C or lower. Drying may be carried out under normal pressure, reduced pressure, or under vacuum. In the catalyst manufacturing method of this embodiment, the calcination temperature may be, for example, 300°C or higher and 700°C or 400°C or higher and 600°C or lower. In the catalyst manufacturing method of this embodiment, the calcination time may be, for example, 1 to 5 hours.

[0044] The catalyst manufacturing method of this embodiment may optionally include a molding process. Examples of molding processes include spray granulation, compression molding, and extrusion molding. The molded catalyst may also be pulverized to form a powder.

[0045] The catalyst of this embodiment described above contains γ-alumina and at least one metal sulfate selected from iron or zinc, or tungsten trioxide. With the catalyst of this embodiment, isobutylene can be produced at a low reaction temperature with a high isobutylene yield. The reason for this effect is not clear, but it is presumed to be as follows: The metal sulfate and tungsten trioxide form strong acidic sites on the surface of γ-alumina, contributing to improved reactivity. An acidic site refers to a point on a solid surface that exhibits acidic properties. Furthermore, because the metal sulfate and tungsten trioxide have high thermal decomposition temperatures, they can maintain stable acidic sites. For this reason, in the catalyst of this embodiment, the oxidative dehydration reaction of isobutanol on the catalyst surface is promoted, isobutylene is efficiently produced, and a high isobutylene yield can be observed.

[0046] (Method for producing isobutylene) The method for producing isobutylene in this embodiment is a method of dehydrating isobutanol in the presence of the catalyst of this embodiment described above.

[0047] The isobutanol used in the method for producing isobutylene in this embodiment is not particularly limited, and known isobutanol may be used. From the viewpoint of environmental impact, it is preferable to use isobutanol produced using a biorefinery as the isobutanol used in the method for producing isobutylene in this embodiment.

[0048] The method for producing isobutylene in this embodiment may include a vaporization step of isobutanol (i), a dehydration reaction step of vaporized isobutanol (ii), and a gas-liquid separation step of the product (iii).

[0049] <Step (i)> The method for producing isobutylene according to this embodiment may include a step (i) of vaporizing isobutanol. The method for vaporizing isobutanol is not particularly limited, and for example, a method of heating isobutanol at or above its boiling point (108°C) can be used.

[0050] The vaporization of isobutanol may be carried out inside the reaction vessel of the subsequent dehydration reaction step (ii) or outside the reaction vessel. One method of carrying out the vaporization outside the reaction vessel is to heat the vaporized isobutanol in a container connected to the reaction vessel by a flow channel, and then introduce the vaporized isobutanol into the reaction vessel.

[0051] The vaporized isobutanol may be mixed with an inert gas, provided that it does not affect the dehydration reaction of the isobutanol. Examples of inert gases include nitrogen, helium, argon, methane, ethane, propane, butane, isobutane, and carbon monoxide. The inert gas may be liquid before supply and vaporize under the conditions of isobutanol vaporization. Examples of such substances include pentane, hexane, heptane, cyclopentane, cyclohexane, benzene, and toluene. The amount of inert gas used is preferably 1 to 2 parts isobutanol per part inertan.

[0052] <Step (ii)> The method for producing isobutylene according to this embodiment may include a dehydration reaction step (ii) of vaporized isobutanol. As an example of the dehydration reaction of isobutanol, a method may be used in which vaporized isobutanol is brought into contact with a catalyst filled in a fixed-bed reaction vessel.

[0053] In step (ii), the conditions for contacting the vaporized isobutanol with the catalyst in the fixed-bed reaction vessel can be set, for example, by the WHSV value. The WHSV value is the flow rate (cm³) of the fluid in contact with the catalyst per unit time relative to the mass of the catalyst. ３ WHSV is a value representing the ratio of mass equivalent values ​​(w / min), and can be calculated using the following formula: WHSV = Q × 60 / W(hr －１ Q = Mass equivalent of the fluid flow rate (g / min) W = Mass of the catalyst (g)

[0054] The WHSV value in process (ii) is 1hr －１ More than 30 hours －１ The following is acceptable, 2 hours －１ Over 20 hours －１ The following is preferable, 3hr －１ The above is for 15 hours. －１ The following are preferable.

[0055] The reaction temperature (temperature in the fixed-bed reaction vessel) for the dehydration reaction of isobutanol in step (ii) is preferably 220°C to 360°C, more preferably 240°C to 340°C, even more preferably 250°C to 330°C, and particularly preferably 260°C to 320°C. The upper and lower limits of the above range can be arbitrarily combined. If the reaction temperature for the dehydration reaction of isobutanol is above the lower limit of the above range, the isobutanol conversion rate and isobutylene yield are improved. If the reaction temperature for the dehydration reaction of isobutanol is below the upper limit of the above range, the environmental burden is reduced.

[0056] The reaction pressure in step (ii) (pressure inside the fixed-bed reaction vessel) can be set to a pressure sufficient to stabilize the flow rate of vaporized isobutanol per unit time. The reaction pressure in step (ii) is preferably 0.5 MPa or less, more preferably 0.1 MPa or less, even more preferably 0.05 MPa or less, and particularly preferably under atmospheric pressure, using a gauge pressure with atmospheric pressure being 0 MPa.

[0057] <Step (iii)> The method for producing isobutylene according to this embodiment may include a gas-liquid separation step (iii) of the reaction product obtained in step (ii). As a gas-liquid separation method, for example, a method may be used in which the reaction product obtained in step (ii) is cooled to condense impurities such as unreacted isobutanol, oligomers, and leaving groups, and to separate them from the gaseous component containing isobutylene. The cooling temperature in step (iii) must be higher than the boiling point of the target product isobutylene, and is preferably -5°C to 10°C, and more preferably 0°C to 5°C.

[0058] The gaseous component of the reaction product separated in step (iii) contains not only the target product, isobutylene, but also by-products such as 1-butene, cis-2-butene, and trans-2-butene. The isobutylene contained in the gaseous component of the reaction product can be quantified, for example, by gas chromatography.

[0059] The method for producing isobutylene according to this embodiment, as described above, can produce a high isobutylene yield at a low reaction temperature because it uses the catalyst of this embodiment described above.

[0060] In another aspect, the present invention further encompasses the following embodiments.

[0061] [7] A method for producing isobutylene using a catalyst comprising γ-alumina and at least one metal sulfate selected from iron or zinc, wherein the amount of the metal sulfate is 5% by mass or more and 50% by mass or less with respect to the mass of the γ-alumina. [8] A method for producing isobutylene using a catalyst comprising γ-alumina and tungsten trioxide, wherein the amount of tungsten trioxide is 5% by mass or more and 50% by mass or less with respect to the mass of the γ-alumina. [9] The method for producing isobutylene according to [7] or [8], wherein isobutanol and the catalyst are reacted at a temperature of 250°C or more and less than 340°C.

[0062] The present invention will be described below with reference to examples, but the present invention is not limited to the following examples.

[0063] (Example 1) <Example of catalyst production> Iron sulfate heptahydrate (FeSO4) ４・ 7H ２ O) 1.9 g was dissolved in 10 g of deionized water, then 10 g of γ-alumina (JRC-ALO-6) was added under stirring and stirred for 3 hours, followed by sonication for 0.5 hours. After removing water from the reaction solution using an evaporator, it was dried at 100°C under vacuum for 24 hours. Next, it was calcined at 600°C for 4 hours to obtain a catalyst (10% by mass FeSO4) containing γ-alumina and iron sulfate. ４We obtained γ-alumina (JRC-ALO-6). The γ-alumina (JRC-ALO-6) used was degassed under vacuum at 250°C for 10 hours, and then measured using a high-performance multi-sample specific surface area / pore size distribution analyzer (Micromeristics, Inc., 3Flex-2MP) by nitrogen gas adsorption using a constant volume method. The results showed a peak pore size of 19.5 nm and a pore volume of 0.70 cm³. ３ The BET specific surface area is 199.7 m² / g. ２ It was / g.

[0064] <Example of Isobutylene Production> Isobutylene was produced under atmospheric pressure (0.1 MPa) using a fixed-bed reactor. A tubular stainless steel reactor with a diameter of 0.95 cm (3 / 8 inch) and a length of 20 cm was packed with quartz wool at the inlet, and then filled with 2.0 g of glass beads. The catalyst produced above (10% by mass FeSO4) ４ A catalyst layer, a mixture of 0.5 g of JRC-ALO-6 and 1.5 g of quartz sand, was packed into the glass bead layer and fixed in place with quartz wool to form a fixed-bed reactor. A heater for heating the catalyst bed, a thermocouple thermometer for measuring the internal temperature of the catalyst bed, and a thermocouple thermometer for controlling the reaction temperature for measuring the outer wall temperature of the fixed-bed reactor were installed around the outer circumference of the reactor. The heater output was controlled by these thermocouple thermometers. A preheater (a tubular stainless steel unit with a diameter of 0.95 cm (3 / 8 inch) and a length of 20 cm) filled with 5 g of glass beads was connected to the upstream side of the fixed-bed reactor. Using an HPLC pump, isobutanol was introduced at a rate of 0.042 mL (0.034 g) / min, and nitrogen gas was supplied at a rate of 20 mL / min while flowing into the preheater set to a temperature of 240°C to vaporize the isobutanol. Vaporized isobutanol was introduced into a fixed-bed reactor maintained at a temperature of 280°C. The reaction product that flowed out of the fixed-bed reactor was then introduced into a cooling vessel maintained at 0°C, where it was separated into gas and liquid to obtain isobutylene.

[0065] (Example 2) In the production of the catalyst, the amount of γ-alumina (JRC-ALO-6) added was determined to be the amount of iron sulfate (FeSO4) in the solution. ４Isobutylene was obtained in the same manner as in Example 1, except that the mass percentage of ) was 15% by mass relative to the mass of γ-alumina.

[0066] (Example 3) <Example of catalyst production> Oxalic acid dihydrate ((COOH) ２ ・2H ２ O) Dissolve 2.176 g in 100 g of deionized water, then tungstic acid (WO ３ ・H ２ O) 0.432 g was added and dissolved. After heating this solution to 70°C, 0.9 g of γ-alumina (JRC-ALO-6) was added under stirring and stirred at the same temperature for 3 hours. The amount of γ-alumina added was equal to the amount of tungsten trioxide (WO) in the solution. ３ The mass of the catalyst (40% by mass WO) was set to 40% by mass relative to the mass of γ-alumina. After removing water from the reaction solution using an evaporator, it was dried at 100°C under vacuum for 24 hours. Then, it was calcined at 550°C for 2 hours to obtain a catalyst (40% by mass WO) containing γ-alumina and tungsten trioxide. ３ We obtained JRC-ALO-6.

[0067] <Example of isobutylene production> Catalyst containing γ-alumina and iron sulfate (10% by mass FeSO ４ Replace the catalyst (JRC-ALO-6) with the catalyst prepared above (40% by mass WO ３ Isobutylene was obtained in the same manner as in Example 1, except that JRC-ALO-6 was used.

[0068] (Example 4) In the production of the catalyst, the amount of γ-alumina (JRC-ALO-6) added was determined to be the same as the amount of tungsten trioxide (WO) in the solution. ３ Isobutylene was obtained in the same manner as in Example 3, except that the mass of ) was set to 10% by mass relative to the mass of γ-alumina.

[0069] (Example 5) Isobutylene was obtained in the same manner as in Example 4, except that the temperature of the fixed-bed reactor was set to 320°C.

[0070] (Example 6) <Example of catalyst production> 6.0 g of 15 mol / L aqueous ammonia, 4.68 g of cetyltetraammonium bromide, and 4.68 g of urea were mixed and stirred. Then, 34.0 g of 0.002 mol / L aqueous aluminum nitrate was added over 2 hours at a temperature of 85°C with stirring. Next, the pH was adjusted to 8 with 0.1 mol / L aqueous ammonia, and after stirring for 0.5 hours, the precipitate was filtered off. After washing with deionized water, it was dried under reduced pressure. Next, it was calcined at a temperature of 500°C for 2 hours to obtain white solid γ-alumina (mesoA). Instead of γ-alumina (JRC-ALO-6), the γ-alumina (mesoA) produced above was used, and instead of iron sulfate heptahydrate, zinc sulfate (ZnSO4) was used. ４ Except for using ) and ensuring that the mass percentage of zinc sulfate in the solution was 10% by mass relative to the mass of γ-alumina, the same procedure as in Example 1 was used to produce a catalyst containing γ-alumina and zinc sulfate (10% by mass ZnSO4). ４ We obtained γ-alumina (mesoA). The manufactured γ-alumina (mesoA) was degassed under vacuum at 250°C for 10 hours, and then measured using a high-performance multi-sample specific surface area / pore distribution analyzer (Micromeristics, Inc., 3Flex-2MP) by nitrogen gas adsorption using a constant-volume method. The results showed a peak pore diameter of 5.2 nm and a pore volume of 0.33 cm³. ３ The BET specific surface area is 253.8 m² / g. ２ It was / g.

[0071] <Example of isobutylene production> Catalyst containing γ-alumina and iron sulfate (10% by mass FeSO ４ Replace the catalyst (JRC-ALO-6) with the catalyst prepared above (10% by mass of ZnSO4). ４ Isobutylene was obtained in the same manner as in Example 1, except that mesoA was used.

[0072] (Example 7) Isobutylene was obtained in the same manner as in Example 6, except that the temperature of the fixed-bed reactor was set to 300°C.

[0073] (Comparative Example) Catalyst containing γ-alumina and iron sulfate (10% by mass FeSO ４Isobutylene was produced in the same manner as in Example 1, except that γ-alumina (JRC-ALO-6) was used instead of (JRC-ALO-6).

[0074] [Measurement of Metal Sulfate Content] The proportions of Al, O, and constituent elements of metal sulfates (S, O, and Fe or Zn) contained on the surface of each catalyst obtained in Examples 1-2 and 6-7 were measured by the following method. The results are shown in Table 1 as "Composition of Catalyst Surface (mass%)".

[0075] (Measurement Method) Measurement device: Energy-dispersive X-ray spectrometer (EDX), Rayny EDX-700 (product name, manufactured by Shimadzu Corporation) Measurement conditions: ・Collimator: 10 mm ・Atmosphere: Vacuum ・Channel: Na-U ・Voltage: 50 kV ・Current: 100 μV ・Compound form: Metal (Sensitivity coefficient was referenced from "systemal") ・Processing calculation method: FP method

[0076] [Measurement of Tungsten Trioxide Content] The proportions of Al, O, and W contained on the surface of each catalyst obtained in Examples 3 to 5 were measured using the same method as in [Measurement of Metal Sulfate Content] above. The results are shown in Table 1 as "Composition of Catalyst Surface (mass%)".

[0077] Table 1 shows the raw materials, catalyst surface composition, and reaction temperature (fixed-bed reactor temperature) of each catalyst in Examples 1 to 7 and the Comparative Examples.

[0078]

[0079] (Evaluation) The gaseous and liquid components separated from the reaction products of each example were quantitatively analyzed using a GC-FID (GC-2014AF, Shimadzu Corporation). From the results of the quantitative analysis, the isobutanol conversion rate, isobutylene selectivity, and isobutylene yield were calculated using the following methods. The results are shown in Table 2. [Isobutanol conversion rate] = [Number of moles of isobutanol reacted] / [Number of moles of isobutanol flowed into the fixed-bed reactor] × 100 [Isobutylene selectivity] = [Number of moles of isobutylene produced] / [Total number of moles of reaction products] × 100 [Isobutylene yield] = [Isobutanol conversion rate] × [Isobutylene selectivity] / 100

[0080]

[0081] Examples 1 and 2, which used a catalyst containing γ-alumina (JRC-ALO-6) and iron sulfate, and Examples 3 to 5, which used a catalyst containing γ-alumina (JRC-ALO-6) and tungsten trioxide, showed improved isobutanol conversion rates and isobutylene yields compared to the comparative example using γ-alumina alone as a catalyst. Examples 6 and 7, which used a catalyst containing γ-alumina (mesoA) and zinc sulfate, showed very high isobutanol conversion rates and improved isobutylene yields compared to the comparative example using γ-alumina alone as a catalyst. In all examples, isobutylene could be produced in good yields at low reaction temperatures of 280°C to 320°C.

[0082] The present invention provides a catalyst for producing isobutylene that can exhibit a high isobutylene yield at a low reaction temperature, and a method for producing isobutylene using the catalyst.

[0083] Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. This application is based on Japanese Patent Application No. 2025-054978 filed on 28 March 2025, the contents of which are incorporated herein by reference.

Claims

1. A catalyst for isobutylene production comprising γ-alumina and at least one metal sulfate selected from iron or zinc.

2. The catalyst according to claim 1, wherein the value obtained by measuring the surface of the isobutylene production catalyst by energy-dispersive X-ray spectroscopy is such that the ratio of iron or zinc to the total amount of Al, O and the constituent elements of the metal sulfate on the surface is 15% by mass or more and 45% by mass or less.

3. A catalyst for isobutylene production, comprising γ-alumina and tungsten trioxide.

4. The catalyst according to claim 3, wherein the value obtained by measuring the surface of the isobutylene production catalyst by energy-dispersive X-ray spectroscopy is such that the ratio of W to the total amount of Al, O, and W on the surface is 2% by mass or more and 55% by mass or less.

5. A method for producing isobutylene, comprising producing isobutylene using the catalyst described in any one of claims 1 to 4.

6. A method for producing isobutylene according to claim 5, comprising reacting isobutanol with the catalyst at a temperature of 250°C or higher and less than 340°C.

Images