Catalyst for isobutylene production, and method for producing isobutylene

Abstract

To provide a catalyst for isobutylene production that can exhibit a high isobutylene yield at a low reaction temperature, and a method for producing isobutylene using the catalyst. [Solution] A catalyst for isobutylene production is used, comprising γ-alumina and at least one metal sulfate selected from iron or zinc, or a catalyst for isobutylene production comprising γ-alumina and tungsten trioxide.

Description

[Technical Field]

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

[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 to develop 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 by 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). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 4-247043 [Patent Document 2] International Publication No. 2021 / 200689 [Overview of the Initiative] [Problems that the invention aims to solve]

[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. [Means for solving the problem]

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

[0010] According to the present invention, there are provided a catalyst for isobutylene production that can exhibit a high isobutylene yield at a low reaction temperature, and a method for producing isobutylene using the catalyst. Modes for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present invention will be described in detail.

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

[0013] <γ-alumina> As used in the present specification, "alumina" refers to aluminum oxide (Al₂O₃). "γ" refers to a crystal form. The γ-alumina contained in the catalyst of the present embodiment may be used alone, or two or more types may be used in combination with alumina of other crystal forms within a range that does not impair the effects of the invention. When two or more types are used in combination, aluminas of different crystal forms may be mixed, or a mixed-phase crystal state may be adopted. The aluminas of different crystal forms may be, for example, transition aluminas with crystal forms such as σ, θ, δ, κ, or those containing alumina hydrate in the transition alumina. The γ-alumina of the present embodiment is preferably used as γ-alumina alone.

[0014] The γ-alumina contained in the catalyst of the present embodiment may contain impurities within a range that does not impair the effects of the invention. Examples of the impurities include sodium oxide (Na₂O), iron(III) oxide (Fe₂O₃), silicon dioxide (SiO₂), and the like. From the viewpoint of improving the isobutanol conversion rate, the purity of the 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 even more preferably 97% by mass or more. The purity of γ-alumina can be measured, for example, by ICP optical emission spectrometry (ICP-AES). As the ICP optical emission spectrometer, for example, Optima 8300 ICP-OES Spectrometer manufactured by Perkin Elmer Co., Ltd. can be used.

[0015] Pores are formed in γ-alumina. The pores refer to fine voids. The pores are classified into micropores, mesopores and macropores according to the pore size. Pores with a diameter of less than 2 nm are referred to as micropores, pores with a diameter of 2 nm or more and less than 50 nm are referred to as mesopores, and pores with a diameter of 50 nm or more are referred to as macropores. The pore diameter of the 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 even 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 using, for example, a multi-sample high-performance specific surface area / pore distribution analyzer, 3Flex-2MP (product name, manufactured by Micromeritics Instrument Corp., USA).

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

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

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

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

[0020] <Metal sulfates> The first catalyst of this embodiment comprises γ-alumina and at least one metal sulfate selected from iron or zinc.

[0021] The metal sulfate contained in the catalyst of this embodiment may be contained in the surface layer of γ-alumina, in a form where it substitutes for a portion of the aluminum in the crystalline structure of γ-alumina, or in a combination thereof. 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.

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

[0023] (Measurement method) Under a vacuum atmosphere, the voltage is measured from 5 to 50 kV, the current from 1 to 1000 μV, the collimator is selected from a range of φ1 to 10 mm, and the channel is measured in the range of Na to U. The results are then calculated using the fundamental parameter (FP) method. The voltage and current can be adjusted within the above range to increase peak sensitivity, depending on the type of element being measured. The collimator diameter can be adjusted within the above range to increase peak sensitivity, depending on the condition of the sample being measured (size, particle size distribution, etc.). The sample may be measured by placing it in a dedicated sample container without any pretreatment, or it may be ground in advance using a mill or similar device, then pressure-molded and placed in a dedicated sample container for measurement.

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

[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 thereof. 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 ingredients> 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, their hydrates, oxides, or salts, 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 in any way.

[0037] <Method for manufacturing a catalyst> The method for producing the catalyst of this embodiment is not particularly limited and can be produced by following known processes. Examples of known methods include impregnation, kneading, and precipitation. The impregnation method is preferred for producing the catalyst of 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 production 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 room temperature or above 120°C. Drying may be carried out at atmospheric pressure, under reduced pressure, or under vacuum. In the catalyst manufacturing method of this embodiment, the calcination temperature may be, for example, 300°C to 700°C, or 400°C to 600°C. In the catalyst manufacturing method of this embodiment, the calcination time may be, for example, 1 hour or more and 5 hours or less.

[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. According to 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 entirely clear, but it can be speculated as follows: Metal sulfates and tungsten trioxide form strong acidic sites on the surface of γ-alumina, contributing to improved reactivity. Acidic sites refer to points on a solid surface that exhibit acidic properties. Furthermore, because metal sulfates and tungsten trioxide have high thermal decomposition temperatures, they can maintain stable acidic sites. Therefore, in the catalyst of this embodiment, the oxidative dehydration reaction of isobutanol on the catalyst surface is promoted, efficiently generating isobutylene and resulting in a high isobutylene yield.

[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] <Process (i)> The method for producing isobutylene in this embodiment may include a vaporization step (i) of isobutanol. The method for vaporizing isobutanol is not particularly limited, and examples include heating at or above the boiling point of isobutanol (108°C).

[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 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 vaporization conditions of isobutanol. Examples of such substances include pentane, hexane, heptane, cyclopentane, cyclohexane, benzene, and toluene. The amount of the inert gas used is preferably 1 to 2 parts per part isobutanol.

[0052] <Process (ii)> The method for producing isobutylene in 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 packed 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 This value represents the ratio of the mass equivalent values ​​(per minute), and can be calculated using the following formula. WHSV = Q × 60 / W(hr) -1) Q = Mass equivalent value of fluid flow rate (g / min) W = Mass of catalyst (g)

[0054] The WHSV value in process (ii) is 1hr -1 More than 30hr -1 The following is acceptable, 2 hours -1 Over 20 hours -1 The following is preferable, 3hr -1 Over 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 combined arbitrarily. 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 will improve. If the reaction temperature for the dehydration reaction of isobutanol is below the upper limit of the above range, the environmental burden will decrease.

[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 as 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). Examples of gas-liquid separation methods include cooling the reaction product obtained in step (ii) to condense impurities such as unreacted isobutanol, oligomers, and leaving groups, and separating them from the gaseous component containing isobutylene. The cooling temperature in step (iii) must be higher than the boiling point of the target substance, 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, comprising 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 relative to the mass of γ-alumina. [9] A method for producing isobutylene according to [7] or [8], comprising reacting isobutanol with the catalyst at a temperature of 250°C or higher and less than 340°C. [Examples]

[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) <Examples of catalyst manufacturing> Iron sulfate heptahydrate (FeSO 4· 1.9 g of (7H2O) 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 the water from the reaction solution using an evaporator, the mixture 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 / JRC-ALO-6) containing γ-alumina and iron sulfate. 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 diameter of 19.5 nm and a pore volume of 0.70 cm³. 3 The specific surface area of ​​BET is 199.7 m² / g. 2 It was / g.

[0064] <Example of isobutylene production> Isobutylene was produced using a fixed-bed reactor under atmospheric pressure (0.1 MPa). 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 on the inlet side, and then filled with 2.0 g of glass beads. A catalyst layer, made by mixing 0.5 g of the catalyst prepared above (10% by mass FeSO4 / JRC-ALO-6) with 1.5 g of quartz sand, was packed in contact with the glass bead layer, and then fixed in place with quartz wool to form a fixed-bed reactor. The fixed-bed reactor is equipped with 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 temperature of the outer wall of the fixed-bed reactor. The heater output is controlled using 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 supplied with nitrogen gas at a rate of 20 mL / min into a preheater set to 240°C to vaporize the isobutanol. The vaporized isobutanol was then introduced into a fixed-bed reactor controlled to 280°C. Next, the reaction product effluent from the fixed-bed reactor was 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 preparation of the catalyst, isobutylene was obtained in the same manner as in Example 1, except that the amount of γ-alumina (JRC-ALO-6) added was such that the mass percentage of iron sulfate (FeSO4) in the solution was 15% by mass relative to the mass of γ-alumina.

[0066] (Example 3) <Examples of catalyst manufacturing> 2.176 g of oxalic acid dihydrate ((COOH)2·2H2O) was dissolved in 100 g of deionized water, and then 0.432 g of tungstic acid (WO3·H2O) 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 the mixture was stirred at the same temperature for 3 hours. The amount of γ-alumina added was such that the mass of tungsten trioxide (WO3) in the solution was 40% by mass relative to the mass of γ-alumina. After removing the water from the reaction mixture using an evaporator, the mixture 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 WO3 / JRC-ALO-6) containing γ-alumina and tungsten trioxide.

[0067] <Example of isobutylene production> Isobutylene was obtained in the same manner as in Example 1, except that the catalyst prepared above (40% WO3 / JRC-ALO-6) was used instead of the catalyst containing γ-alumina and iron sulfate (10% FeSO4 / JRC-ALO-6).

[0068] (Example 4) In the preparation of the catalyst, isobutylene was obtained in the same manner as in Example 3, except that the amount of γ-alumina (JRC-ALO-6) added was such that the mass of tungsten trioxide (WO3) in the solution was 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) <Examples of catalyst manufacturing> 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. Then, it was calcined at a temperature of 500°C for 2 hours to obtain white solid γ-alumina (mesoA). A catalyst containing γ-alumina and zinc sulfate (10% by mass ZnSO4 / mesoA) was obtained in the same manner as in Example 1, except that γ-alumina (mesoA) prepared as described above was used instead of γ-alumina (JRC-ALO-6), zinc sulfate (ZnSO4) was used instead of iron sulfate heptahydrate, and the mass percentage of zinc sulfate in the solution was 10% by mass relative to the mass of γ-alumina. 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 size 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 specific surface area of ​​BET is 253.8 m² / g. 2 It was / g.

[0071] <Example of isobutylene production> Isobutylene was obtained in the same manner as in Example 1, except that the catalyst prepared above (10% ZnSO4 / mesoA) was used instead of the catalyst containing γ-alumina and iron sulfate (10% FeSO4 / JRC-ALO-6).

[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) Isobutylene was produced in the same manner as in Example 1, except that γ-alumina (JRC-ALO-6) was used instead of a catalyst containing γ-alumina and iron sulfate (10% by mass FeSO4 / 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 method described below. The results are shown in Table 1 as "Composition of catalyst surface (mass%)".

[0075] (Measurement method) Measurement equipment: Energy-dispersive X-ray spectrometer (EDX), Rayny EDX-700 (product name, manufactured by Shimadzu Corporation) Measurement conditions: • Collimator: 10mm • Atmosphere: Vacuum Channel: NaU Voltage: 50kV ·Current: 100μV • Compound form: Metal (Sensitivity coefficients were referenced for "sysmetal") • 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 described 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 1-7 and the Comparative Examples.

[0078] [Table 1]

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

[0080] [Table 2]

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

Claims

1. A catalyst for producing isobutylene, 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.

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