Methods for the production of isobutylene, methods for the production of methacrylic acid, and methods for the production of methyl methacrylate.

Abstract

DEPCT66 Methods have been established for the production of isobutylene, which is produced from... Isobutanol exhibits high selectivity while suppressing the decline in conversion rates. Isobutanol under pressure in the method for the production of isobutylene according to this invention, A feed gas containing isobutanol is exposed to a catalyst to produce isobutylene. From isobutanol, the method involves exposing a raw gas containing isobutanol to contact. The catalyst operates at a linear velocity of 1.20 cm / s or more under a pressure of 120. Kilopascals or more in terms of absolute pressure to produce isobutylene from... Isobutanol -----------------------------------------------------------

Description

Methods for producing isobutylene, method for producing methacrylic acid, and method for producing methyl methacrylate

[0001] The present invention relates to a method for producing isobutylene, a method for producing methacrylic acid, and a method for producing methyl methacrylate. This application claims priority based on Japanese Patent Application No. 2020-064207, filed on March 31, 2020, the contents of which are incorporated herein by reference.

[0002] Isobutylene is an important chemical raw material that is converted into ethyl tert-butyl ether, paraxylene, methyl methacrylate, etc. For example, methyl methacrylate can be produced by subjecting isobutylene or tert-butyl alcohol, which is a hydrate of isobutylene, to gas-phase catalytic oxidation to obtain methacrylic acid, which is then esterified with methanol.

[0003] As a method for producing isobutylene, for example, a method is known in which isobutanol is brought into contact with a catalyst such as alumina under pressure to dehydrate the isobutanol to produce isobutylene (for example, Patent Document 1).

[0004] International Publication No. 2015 / 170686

[0005] In order to industrially produce isobutylene by dehydration of isobutanol, it is desirable to react isobutanol at a high conversion rate to produce isobutylene at a high selectivity. However, it has been found that when isobutanol is dehydrated under pressure, the selectivity to isobutylene may be improved, but the conversion of isobutanol tends to decrease.

[0006] Therefore, an object of the present invention is to provide a method for producing isobutylene from isobutanol with high selectivity while suppressing a decrease in the conversion rate of isobutanol under pressure, as well as a method for producing methacrylic acid and a method for producing methyl methacrylate that utilize the method for producing isobutylene.

[0007] The present invention has the following aspects. [1] A method for producing isobutylene by contacting a feed gas containing isobutanol with a catalyst to produce isobutylene from isobutanol, wherein the feed gas containing isobutanol is contacted with the catalyst at a linear velocity of 1.20 cm / s or more under an absolute pressure of 120 kPa or more. [2] The method for producing isobutylene according to [1], wherein the concentration of isobutanol contained in the feed gas containing isobutanol is 15% by volume or more and 100% by volume or less. [3] The method for producing isobutylene according to [1] or [2], wherein the particle size of the catalyst is 700 μm or more and 10,000 μm or less. [4] The method for producing isobutylene according to any one of [1] to [3], wherein the catalyst contains alumina. [5] A method for producing methacrylic acid, comprising producing isobutylene by the method for producing isobutylene according to any one of [1] to [4], and then producing methacrylic acid from the resulting isobutylene. [6] A method for producing methacrylic acid, comprising producing isobutylene by the method for producing isobutylene according to any one of [1] to [4], obtaining tert-butyl alcohol from the isobutylene, and then producing methacrylic acid from the obtained tert-butyl alcohol. [7] A method for producing methyl methacrylate, comprising producing methacrylic acid by the method for producing methacrylic acid according to [5] or [6], and producing methyl methacrylate from the obtained methacrylic acid and methanol.

[0008] According to the present invention, there is provided a method for producing isobutylene from isobutanol with high selectivity while suppressing a decrease in the conversion rate of isobutanol under pressure. According to the present invention, there are provided a method for producing methacrylic acid and a method for producing methyl methacrylate using the method for producing isobutylene of the present invention.

[0009] 1 is a graph showing the measurement results of the isobutanol conversion rate in a reference example. FIG. 2 is a graph showing the measurement results of the isobutanol conversion rate and the selectivity of isobutylene in the C4 gas in Examples 1 to 3 and Comparative Example 1. FIG. 3 is a graph showing the measurement results of the isobutanol conversion rate and the selectivity of isobutylene in the C4 gas in Examples 4 to 6 and Comparative Example 2. FIG. 4 is a graph showing the measurement results of the isobutanol conversion rate and the selectivity of isobutylene in the C4 gas in Examples 7 to 9 and Comparative Example 3. FIG. 5 is a graph showing the measurement results of the isobutanol conversion rate and the selectivity of isobutylene in the C4 gas in Examples 10 to 13 and Comparative Example 4. FIG. 6 is a graph showing the measurement results of the isobutanol conversion rate and the selectivity of isobutylene in the C4 gas in Examples 14 to 19. FIG. 7 is a graph showing the measurement results of the isobutylene selectivity in the C4 gas in Examples 20 and 21.

[0010] [Isobutylene Production Method] In the isobutylene production method of the present invention, isobutylene is produced from isobutanol by contacting a raw material gas containing isobutanol with a catalyst. For example, the raw material gas containing isobutanol can be contacted with the catalyst by supplying the raw material gas containing isobutanol to a reactor filled with a catalyst to form a catalyst layer. The type of isobutanol dehydration is not particularly limited, and for example, a fixed bed or a fluidized bed can be used.

[0011] In the present invention, a feed gas containing isobutanol is contacted with a catalyst at a linear velocity of 1.20 cm / s or more, and the isobutanol is dehydrated under an absolute pressure of 120 kPa or more. This makes it possible to produce isobutylene with high selectivity while suppressing a decrease in isobutanol conversion under pressure. The factors that enable isobutylene to be produced with high selectivity while suppressing a decrease in conversion under pressure in the present invention are thought to be as follows.

[0012] When isobutanol is dehydrated under a pressure of 120 kPa or more, the selectivity to isobutylene increases, but the conversion of isobutanol tends to decrease. This is thought to be because, when a feed gas containing isobutanol is brought into contact with a catalyst under pressure, the feed gas used in the present invention is less likely to come into contact with the catalyst due to the influence of a boundary film on the catalyst surface.

[0013] In contrast, by setting the linear velocity of the raw material gas to 1.20 cm / s or more, the raw material gas is less affected by the boundary film on the catalyst surface when it is brought into contact with the catalyst, and it is thought that the conversion rate of isobutanol is improved.

[0014] The linear velocity of the raw material gas contacted with the catalyst is 1.20 cm / s or more, preferably 1.40 cm / s or more, more preferably 1.60 cm / s or more, even more preferably 1.80 cm / s or more, particularly preferably 2.00 cm / s or more, particularly preferably 2.20 cm / s or more, and most preferably 2.40 cm / s or more. If the linear velocity of the raw material gas is equal to or greater than the lower limit, the decrease in the conversion rate of isobutanol under pressure can be suppressed, and the selectivity for isobutylene can be improved. On the other hand, for the reasons mentioned above, if the linear velocity of the raw material gas is equal to or greater than the lower limit, the conversion rate tends to be improved, so the upper limit of the linear velocity is not particularly limited. For example, the linear velocity of the raw material gas can be 5000 cm / s or less.

[0015] The pressure in the dehydration of isobutanol is, as an absolute pressure, 120 kPa or more, preferably 150 kPa or more, more preferably 170 kPa or more, even more preferably 190 kPa or more, and particularly preferably 210 kPa or more. 230 kPa or more is especially preferred. If the pressure in the dehydration is equal to or higher than the lower limit, the selectivity of isobutylene is improved. The pressure in the dehydration of isobutanol is preferably 100,000 kPa or less, more preferably 50,000 kPa or less, even more preferably 10,000 kPa or less, particularly preferably 5,000 kPa or less, particularly preferably 2,500 kPa or less, and most preferably 1,000 kPa or less. The upper and lower limits can be combined arbitrarily. For example, the pressure in the dehydration of isobutanol is preferably 120 kPa to 100,000 kPa, more preferably 150 kPa to 50,000 kPa, even more preferably 170 kPa to 10,000 kPa, even more preferably 190 kPa to 5,000 kPa, particularly preferably 210 kPa to 2,500 kPa, and particularly preferably 230 kPa to 1,000 kPa. If the pressure in the dehydration of isobutanol is equal to or less than the upper limit, the amount of isobutanol supplied necessary to bring the linear velocity of the raw material gas contacting the catalyst to 1.20 cm / s or more can be reduced, thereby preventing the process from becoming bloated. The pressure in the dehydration is a value measured with a pressure sensor installed at a position where the influence of pressure loss can be ignored relative to the pressure at the inlet of the reactor.

[0016] The reaction temperature in the dehydration of isobutanol is preferably 390°C or lower, more preferably 380°C or lower, even more preferably 370°C or lower, particularly preferably 360°C or lower, and most preferably 350°C or lower. If the reaction temperature is equal to or lower than the upper limit of the above range, the isomerization reaction is easily suppressed, and the selectivity to isobutylene is improved. The reaction temperature in the dehydration of isobutanol is preferably 240°C or higher, more preferably 250°C or higher, even more preferably 260°C or higher, particularly preferably 270°C or higher, and most preferably 280°C or higher. If the reaction temperature is equal to or higher than the lower limit of the above range, the amount of catalyst used and the amount of raw material gas supplied can be reduced, which is advantageous in terms of cost and productivity. The above upper and lower limits can be combined arbitrarily. For example, the reaction temperature in the dehydration of isobutanol is preferably 240°C or higher and 390°C or lower, more preferably 250°C or higher and 380°C or lower, even more preferably 260°C or higher and 370°C or lower, particularly preferably 270°C or higher and 360°C or lower, and particularly preferably 280°C or higher and 350°C or lower.

[0017] The lowest temperature among the temperatures of the catalyst layer in the reactor that can be confirmed after the reaction has reached a steady state is taken as the reaction temperature. Therefore, if there is temperature variation in the catalyst layer, it is preferable to increase the number of measurement points or measure the temperature continuously in the catalyst packing direction. The method for controlling the reaction temperature is not particularly limited, and known methods can be used.

[0018] The isobutanol used as the starting material is not particularly limited, and from the viewpoint of environmental protection, it may be isobutanol derived from biomass. "Biomass-derived isobutanol" refers to isobutanol purified from organic compounds obtained through a fermentation process using fermentable sugars from biomass, or isobutanol obtained by a process including at least one of catalytic chemical conversion and thermochemical conversion of biomass. Biomass can be broadly divided into that derived from resource crops and that derived from waste. Examples of biomass derived from resource crops include food crops, wood, and flowers, and unused parts of these crops can also be used. Examples of biomass derived from waste include food waste, sewage sludge, livestock manure, and waste paper.

[0019] For example, the raw material can be evaporated in an evaporator and supplied to the reactor as a raw material gas. The evaporator is not particularly limited, and examples thereof include a jacket type, a natural circulation horizontal tube type, a natural circulation immersed tube type, a natural circulation vertical short tube type, a vertical long tube ascending film type, a horizontal tube descending film type, a forced circulation horizontal tube type, a forced circulation vertical tube type, and a coil type.

[0020] In the raw material gas, the isobutanol concentration can be adjusted by diluting isobutanol with a diluent gas. The raw material gas may be a gas consisting of only isobutanol. The diluent gas may be any gas that does not affect the dehydration of isobutanol, and examples thereof include nitrogen, helium, neon, krypton, xenon, radon, argon, methane, ethane, propane, butane, isobutane, carbon monoxide, carbon dioxide, nitric oxide, nitrogen dioxide, nitrous oxide, dinitrogen trioxide, dinitrogen tetroxide, dinitrogen pentoxide, and water vapor. Oxygen or hydrogen may also be used as the diluent gas as long as it does not affect the dehydration of isobutanol. The raw material gas may contain one or more diluent gases. The raw material gas may contain moisture.

[0021] The isobutanol concentration in the feed gas is preferably 15.0% by volume or more, more preferably 20% by volume or more, even more preferably 30% by volume or more, particularly preferably 40% by volume or more, particularly preferably 50% by volume or more, and most preferably 55% by volume or more, based on the total volume of the feed gas. If the isobutanol concentration is equal to or higher than the lower limit, the isomerization reaction is easily suppressed, and the selectivity for isobutylene is improved. Furthermore, the reactor can be easily downsized, reducing equipment costs and the energy costs required for isobutylene recovery can also be reduced. There is no particular upper limit, and the upper limit is 100% by volume or less.

[0022] The catalyst used for the dehydration of isobutanol is not particularly limited as long as it is a catalyst capable of dehydrating isobutanol, and examples thereof include dehydration catalysts, among which acid catalysts are preferred. Examples of acid catalysts include alumina, silica alumina, zeolite, solid phosphoric acid, and titania. The catalyst preferably contains alumina because it has a high selectivity for isobutylene. In the present invention, the alumina catalyst means a catalyst in which the ratio of alumina to the total mass of the catalyst is 90 mass% or more. One type of catalyst may be used alone, or two or more types may be used in combination.

[0023] The crystalline form of the alumina used in the present invention is not particularly limited. Examples include α-alumina, β-alumina, γ-alumina, σ-alumina, θ-alumina, δ-alumina, and alumina hydrate. In particular, a catalyst containing γ-alumina is preferred from the viewpoints of activity and selectivity. Alumina of these crystalline forms may be used alone or in combination of two or more types. When two or more types are used in combination, aluminas with different crystalline forms may be used, or may be in a mixed-phase crystalline state.

[0024] The alumina used in the catalyst of the present invention can be easily produced by known methods, including, for example, thermal decomposition, precipitation, deposition, kneading, or a combination of these methods. Examples of raw materials for alumina include nitrates, acetates, alkoxides, sulfates, chlorides, alkali aluminates, alum, and other materials that produce alumina or alumina hydrate upon heating or hydrolysis. Examples of alkalis used in hydrolysis include caustic alkalis, alkali carbonates, aqueous ammonia, and ammonium carbonate. The alumina used in the catalyst of the present invention may be molded before use, if necessary.

[0025] The alumina catalyst used in the present invention may contain a compound other than alumina. From the viewpoint of high selectivity for isobutylene, the content of alumina in the catalyst is preferably 95.0 mass% or more, more preferably 97.0 mass% or more, still more preferably 98.0 mass% or more, particularly preferably 99.0 mass% or more, and most preferably 99.5 mass% or more, based on the total mass of the catalyst.

[0026] Examples of compounds other than alumina include SiO ２ and Na ２ Examples include O.

[0027] SiO in alumina catalyst ２ The content of SiO in alumina is preferably 1.0 mass% or less, more preferably 0.75 mass% or less, even more preferably 0.50 mass% or less, even more preferably 0.40 mass% or less, particularly preferably 0.30 mass% or less, and particularly preferably 0.20 mass% or less, based on the total mass of the catalyst. ２ may not be included.

[0028] Na in alumina catalyst ２ The content of O is preferably 0.20 mass% or less, more preferably 0.15 mass% or less, even more preferably 0.10 mass% or less, even more preferably 0.075 mass% or less, particularly preferably 0.050 mass% or less, and particularly preferably 0.025 mass% or less, based on the total mass of the catalyst. ２ O may not be included.

[0029] Alumina and SiO in the catalyst ２ and Na ２ The O content is measured by inductively coupled plasma atomic emission spectroscopy (ICP-AES), for example, using an Optima 8300 ICP-OES Spectrometer manufactured by Perkin Elmer.

[0030] In order to easily obtain sufficient activity, the BET specific surface area of ​​the catalyst is 40.0 m ２ / g or more is preferable, and 50.0m ２ / g or more is more preferable, and 60.0m ２ / g or more is more preferable, and 70.0m ２ / g or more is particularly preferred, and 80.0m ２ The upper limit of the BET specific surface area of ​​alumina is not particularly limited, but it is preferably 350 m ２ The BET specific surface area of ​​the catalyst is preferably N ２This is a value calculated from an adsorption / desorption isotherm, and can be measured using, for example, Tristar 3000 (product name, manufactured by Shimadzu Corporation).

[0031] The catalyst particle size is preferably 700 μm or more and 10,000 μm or less, more preferably 800 μm or more and 9,500 μm or less, and most preferably 1,000 μm or more and 9,000 μm or less. When the catalyst particle size is sized using a sieve or the like, the particle size is defined as the size of the sieve openings. In the case of a molded catalyst, for example, in the case of cylindrical pellets, the particle size is defined as the diameter. If the particle size is too small, the pressure loss in the catalyst layer packed in the reactor increases, resulting in increased equipment costs and energy costs for circulating the reaction gas. In addition, if the particle size is too large, the catalyst effectiveness coefficient decreases, leading to a decrease in activity per catalyst mass and a decrease in isobutylene selectivity.

[0032] [Method for producing methacrylic acid] The method for producing methacrylic acid of the present invention is a method for producing methacrylic acid using isobutylene produced by the method for producing isobutylene of the present invention. Examples include the following method (A) and method (B). According to method (A) and method (B), methacrylic acid can be produced from isobutylene with high selectivity.

[0033] (A) It comprises a step (a1) of producing isobutylene by the isobutylene production method of the present invention, and a step (a2) of producing methacrylic acid by vapor phase oxidation of isobutylene. (B) It comprises a step (b1) of producing isobutylene by the isobutylene production method of the present invention, a step (b2) of producing tert-butyl alcohol by hydrating isobutylene, and a step (b3) of producing methacrylic acid by vapor phase oxidation of tert-butyl alcohol produced by hydrating isobutylene.

[0034] The hydration of isobutylene in step (b2) can be carried out by a known method. Examples of the acid catalyst used for the hydration of isobutylene include ion exchange resins and heteropolyacids. Strongly acidic cation exchange resins are preferred as the acid catalyst because they can produce tert-butyl alcohol in a high yield.

[0035] The gas-phase oxidation of isobutylene in step (a2) or the gas-phase oxidation of tert-butyl alcohol in step (b3) may be carried out in one stage or two stages. Two-stage gas-phase oxidation is preferred because it results in a high selectivity for methacrylic acid.

[0036] When the gas-phase oxidation is carried out in two stages, it is preferable to use a catalyst for the first stage oxidation in the first gas-phase oxidation (first stage oxidation). The catalyst used may be a known catalyst. A catalyst containing at least molybdenum and bismuth is preferred.

[0037] As such a catalyst, a catalyst having a composition represented by formula (1) is preferred. １２ Bi ａ１ Fe ａ２ M ａ３ X ａ４ Y ａ５ Z ａ６ O ａ７ ... (1) where, in formula (1), Mo, Bi, Fe, and O represent molybdenum, bismuth, iron, and oxygen, respectively. M represents at least one element selected from the group consisting of cobalt and nickel. X represents at least one element selected from the group consisting of chromium, lead, manganese, calcium, magnesium, niobium, silver, barium, tin, tantalum, and zinc. Y represents at least one element selected from the group consisting of phosphorus, boron, sulfur, selenium, tellurium, cerium, tungsten, antimony, and titanium. Z represents at least one element selected from the group consisting of lithium, sodium, potassium, rubidium, cesium, and thallium. a1 to a7 represent the atomic ratio of each element, and a1, a2, a3, a4, a5, a6, and a7 represent the atomic ratio of each element to Mo12 atoms, where a1 = 0.01 to 3, a2 = 0.01 to 5, a3 = 1.0 to 12, a4 = 0 to 8.0, a5 = 0 to 5.0, and a6 = 0.001 to 2.0, and a7 is the atomic ratio of oxygen required to satisfy the valence of each component.

[0038] The first-stage oxidation can be carried out in a fixed bed. The form of the catalyst layer for the first-stage oxidation is not particularly limited, and may be an undiluted layer containing only the catalyst for the first-stage oxidation, or a diluted layer further containing an inert carrier. The catalyst layer for the first-stage oxidation may be a single layer or a mixed layer consisting of multiple layers.

[0039] The concentration of isobutylene or tert-butyl alcohol in the feed gas for the first oxidation stage is preferably 1.0% by volume or more, and more preferably 3.0% by volume or more. The concentration of isobutylene or tert-butyl alcohol in the feed gas for the first oxidation stage is preferably 20.0% by volume or less, and more preferably 10.0% by volume or less. The above upper and lower limits can be combined arbitrarily. For example, the concentration of isobutylene or tert-butyl alcohol in the feed gas for the first oxidation stage is preferably 1.0% by volume or more and 20.0% by volume or less, more preferably 3.0% by volume or more and 20.0% by volume or less, and even more preferably 3.0% by volume or more and 10.0% by volume or less.

[0040] Although it is economical to use air as the molecular oxygen source for the first oxidation step, air enriched with pure oxygen can also be used if necessary. The molar ratio (volume ratio) of isobutylene or tert-butyl alcohol to molecular oxygen in the reaction gas is preferably in the range of 1:0.1 to 1:5, more preferably 1:0.5 to 1:3.

[0041] It is economical to use the reaction gas diluted with an inert gas such as nitrogen or carbon dioxide, water vapor, or the like in addition to isobutylene or tert-butyl alcohol and molecular oxygen.

[0042] The reaction temperature of the first-stage oxidation is preferably 200°C or higher and 450°C or lower, more preferably 250°C or higher and 400°C or lower. The contact time between isobutylene and molecular oxygen in the first-stage oxidation is preferably 0.5 seconds or higher, more preferably 1.0 second or higher. The contact time between isobutylene and molecular oxygen in the first-stage oxidation is preferably 10.0 seconds or lower, more preferably 6.0 seconds or lower. The above upper and lower limits can be arbitrarily combined. For example, the contact time between isobutylene and molecular oxygen in the first-stage oxidation is preferably 0.5 seconds or higher and 10.0 seconds or lower, more preferably 0.5 seconds or higher and 6.0 seconds or lower, and even more preferably 1.0 seconds or higher and 6.0 seconds or lower.

[0043] The first oxidation step produces methacrolein and methacrylic acid, which is converted to methacrylic acid in the second gas-phase oxidation step (second oxidation step).

[0044] The catalyst used in the second-stage oxidation may be a known catalyst, preferably a catalyst containing at least molybdenum and phosphorus.

[0045] As such a catalyst, a catalyst having a composition represented by formula (2) is preferred. ａ８ Mo ａ９ V ａ１０ Cu ａ１１ A ａ１２ E ａ１３ Ga １４ O ａ１５ ... (2) In formula (2), P, Mo, V, Cu, and O represent phosphorus, molybdenum, vanadium, copper, and oxygen, respectively. A represents at least one element selected from the group consisting of antimony, bismuth, arsenic, germanium, zirconium, tellurium, silver, selenium, silicon, tungsten, and boron. E represents at least one element selected from the group consisting of potassium, rubidium, cesium, thallium, magnesium, and barium. G represents at least one element selected from the group consisting of iron, zinc, chromium, calcium, strontium, tantalum, cobalt, nickel, manganese, titanium, tin, lead, niobium, indium, sulfur, palladium, gallium, cerium, and lanthanum. a8 to a15 represent the atomic ratio of each element, and when a9 = 12, a8 = 0.5 to 3, a10 = 0.01 to 3, a11 = 0.01 to 2, a12 = 0 to 3, preferably 0.01 to 3, a13 = 0.01 to 3, a14 = 0 to 4, and a15 is the atomic ratio of oxygen necessary to satisfy the valence of each element.

[0046] The second-stage oxidation can be carried out in a fixed bed. The catalyst layer for the second-stage oxidation is not particularly limited, and may be an undiluted layer containing only the catalyst for the second-stage oxidation, or a diluted layer containing an inert carrier. The catalyst layer for the second-stage oxidation may be a single layer or a mixed layer consisting of multiple layers.

[0047] The concentration of methacrolein in the reaction gas of the second-stage oxidation is not limited and can be set to any concentration, but is preferably 1.0 vol% or more, more preferably 3.0 vol% or more. Furthermore, the concentration of methacrolein in the reaction gas of the second-stage oxidation is preferably 20.0 vol% or less, more preferably 10.0 vol% or less. The above upper and lower limits can be arbitrarily combined. For example, the concentration of methacrolein in the reaction gas of the second-stage oxidation is preferably 1.0 vol% or more and 20.0 vol% or less, more preferably 1.0 vol% or more and 10.0 vol% or less, and even more preferably 3.0 vol% or more and 10.0 vol% or less.

[0048] It is economical to use air as the molecular oxygen source for the second-stage oxidation, but air enriched with pure oxygen can also be used if necessary. The concentration of molecular oxygen in the reaction gas of the second-stage oxidation is preferably 0.5 mol or more, more preferably 1.0 mol or more, per 1.0 mol of methacrolein. Furthermore, the concentration of molecular oxygen in the reaction gas of the second-stage oxidation is preferably 4.0 mol or less, more preferably 3.0 mol or less, per 1.0 mol of methacrolein. The above upper and lower limits can be arbitrarily combined. For example, the concentration of molecular oxygen in the second-stage oxidation is preferably 0.5 mol or more and 4.0 mol or less, more preferably 1.0 mol or more and 4.0 mol or less, even more preferably 1.0 mol or more and 3.0 mol or less, per 1.0 mol of methacrolein.

[0049] The reaction gas for the second oxidation may contain water (water vapor) in addition to methacrolein and molecular oxygen.

[0050] The reaction gas for the second oxidation step may contain small amounts of impurities such as lower saturated aldehydes, but it is preferable that the amount of impurities be as small as possible. The reaction gas for the second oxidation step may also contain inert gases such as nitrogen and carbon dioxide.

[0051] The reaction pressure of the second-stage oxidation can be set in the range from atmospheric pressure to several hundred kPaG. The reaction temperature of the second-stage oxidation is preferably 230°C or higher, more preferably 250°C or higher. The reaction temperature of the second-stage oxidation is preferably 450°C or lower, more preferably 400°C or lower. The above upper and lower limits can be combined arbitrarily. For example, the reaction temperature of the second-stage oxidation is preferably 230°C or higher and 400°C or lower, more preferably 250°C or higher and 450°C or lower, and even more preferably 250°C or higher and 400°C or lower.

[0052] [Method for producing methyl methacrylate] The method for producing methyl methacrylate of the present invention is a method for producing methyl methacrylate using the methacrylic acid of the present invention. The method for producing methyl methacrylate of the present invention includes a step of producing the methacrylic acid of the present invention and a step of producing methyl methacrylate by esterifying the methacrylic acid with methanol. According to the method of the present invention, methyl methacrylate can be produced from isobutylene with high selectivity.

[0053] For example, methacrylic acid produced by the production method of the present invention is recovered by extraction, distillation, or the like, and esterified with methanol in the presence of an acid catalyst. A catalyst is preferably used for the esterification. The catalyst used is preferably an acid catalyst, and for example, sulfuric acid or an ion exchange resin can be used. The ion exchange resin is preferably a strongly acidic cation exchange resin. Specific examples of strongly acidic cation exchange resins include Diaion (registered trademark), PK216, RCP12H (manufactured by Mitsubishi Chemical Corporation), Lewatit (registered trademark), K2431 (manufactured by Bayer), and Amberlyst (registered trademark) 15WET (manufactured by Rohm and Haas Japan). These may be used alone or in combination of two or more.

[0054] The flow direction of the reaction fluid in the esterification may be either vertically upward or vertically downward and can be selected appropriately. When the ion exchange resin used as the acid catalyst for the esterification swells significantly, the flow direction of the reaction fluid is preferably vertically upward. When the reaction fluid forms a heterogeneous phase, the flow direction of the reaction fluid is preferably vertically downward.

[0055] When esterification is carried out in a fixed-bed reactor filled with an ion exchange resin, the amount of the raw material containing methacrylic acid and methanol passed through is preferably 0.10 times or more, more preferably 0.20 times or more, in terms of mass ratio relative to the amount of ion exchange resin. Furthermore, the amount of the raw material passed through is preferably 10.0 times or less, more preferably 5.0 times or less, in terms of mass ratio relative to the amount of ion exchange resin. The above upper and lower limits can be arbitrarily combined. For example, the amount of the raw material passed through is preferably 0.10 times or more and 10.0 times or less, more preferably 0.20 times or more and 10.0 times or less, and even more preferably 0.20 times or more and 5.0 times or less, in terms of mass ratio relative to the amount of ion exchange resin.

[0056] When a strongly acidic cation exchange resin is used as the acid catalyst, the esterification reaction temperature is preferably 40°C or higher and 130°C or lower. If the reaction temperature is 40°C or higher, the reaction rate is high and esterification can be carried out efficiently. If the reaction temperature is 130°C or lower, the deterioration rate of the ion exchange resin is low and esterification can be carried out continuously for a long period of time. The esterification reaction temperature can be appropriately determined to an optimum temperature from the viewpoint of chemical equilibrium.

[0057] From the viewpoint of chemical equilibrium, the raw material composition can simplify the recovery and purification processes by increasing the concentration of either methacrylic acid or methanol and increasing the conversion rate of the raw material with a lower concentration.

[0058] The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following descriptions.

[0059] The raw material gas and the products were analyzed by gas chromatography. The conversion rate of isobutanol and the selectivity of each product are defined as follows: Isobutanol conversion (%) = (b / a) x 100 C4 gas selectivity (%) = (j / b) x 100 Diisobutyl ether selectivity (%) = (h / b) x 2 x 100 Isobutyraldehyde selectivity (%) = (i / b) x 100 Isobutylene selectivity in C4 gas (%) = (c / j) x 100 Isobutane selectivity in C4 gas (%) = (d / j) x 100 1-butene selectivity in C4 gas (%) = (e / j) x 100 Trans-2-butene selectivity in C4 gas (%) = (f / j) x 100 Cis-2-butene selectivity in C4 gas (%) = (g / j) x 100 a: Number of moles of isobutanol supplied b: Number of moles of isobutanol reacted c: Number of moles of isobutylene produced d: number of moles of isobutane produced e: number of moles of 1-butene produced f: number of moles of trans-2-butene produced g: number of moles of cis-2-butene produced h: number of moles of diisobutyl ether produced i: number of moles of isobutyraldehyde produced j: number of moles of C4 gas (isobutene, isobutane, 1-butene, trans-2-butene, cis-2-butene) produced

[0060] The mass hourly space velocity (WHSV) of the raw gas is defined as follows: WHSV(h －１ ) = W1 / W2 (3) where W1 is the amount of isobutanol supplied per unit time (g / h), and W2 is the amount of catalyst used (g).

[0061] The flow rate and linear velocity of the raw material gas supplied to the catalyst layer are defined as follows. The raw material gas flow rate (L / h) below is the total flow rate of a mixed gas consisting of isobutanol as the raw material and a diluent gas. Raw material gas flow rate (L / h) = raw material gas flow rate measured under standard conditions (NL / h) × 101.3 (kPa) / reaction pressure (kPa) × reaction temperature (K) / 273 (K) Linear velocity of raw material gas (cm / s) = raw material gas flow rate (L / h) × 1000 / 3600 ÷ cross-sectional area of ​​reaction tube (cm ２ )

[0062] [Reference Example] A dehydration catalyst (cylindrical pellet-shaped alumina crushed bodies formed to a diameter of 3.0 mm, alumina containing γ-alumina phase as the main crystalline phase, particle diameter: 800 to 1190 μm, BET specific surface area: 243 m) was placed in a vertical tubular reaction tube having an inner diameter of 0.75 cm and a length of 40 cm. ２ / g, Na ２ O content: less than 0.0500 mass%, SiO ２ A catalyst layer was formed by filling the reactor with 0.192 g of 1,2-dimethyl-2,4-trimethylsilyl ether (content: less than 0.100 mass%, hereinafter referred to as "catalyst A"). For the reactor, the set temperature of the electric furnace for the reaction tube was adjusted so that the catalyst layer temperature was at a predetermined temperature. The reaction pressure was also adjusted using a back-pressure valve so that the reaction pressure was at a predetermined pressure. Next, isobutanol (manufactured by Nacalai Tesque, Inc., water content measured by the Karl Fischer method: 411 ppm) was introduced into a vaporizer heated at 200°C at 0.263 ml / min using a double plunger pump and evaporated. Nitrogen gas as a diluent gas was supplied into the vaporizer at a flow rate of 16 ml / min (standard conditions) using a mass flow meter and then supplied to the reactor together with the evaporated isobutanol. The isobutanol concentration in the raw material gas supplied to the catalyst layer was 79.9 vol%, and the temperature of the catalyst layer during the reaction (reaction temperature) was 340°C.

[0063] Reaction evaluation was initiated 5 minutes after the catalyst layer temperature and reaction pressure stabilized within ±0.5°C of the specified temperature and ±0.5 kPa of the specified pressure, respectively. After the reaction reached a steady state, gas was sampled from the reactor outlet, and isobutylene, isobutane, 1-butene, cis-2-butene, and trans-2-butene were quantified using gas chromatography (Shimadzu Corporation, GC-8A). Furthermore, the reaction gas discharged from the reactor outlet was trapped in ice-cooled acetonitrile, and unreacted isobutanol, diisobutyl ether, and isobutyraldehyde were quantified using gas chromatography (Shimadzu Corporation, GC-2014). A pressure gauge for measuring the reaction pressure was installed between the evaporator and the reactor inlet. It was confirmed that the pressure loss from the evaporator to the reactor inlet was negligibly small across all flow rate ranges under the conditions of Examples 1 to 19 and Comparative Examples 1 to 6, including this Reference Example. The measurement results of the isobutanol conversion rate, the selectivity of C4 gases (isobutylene, isobutane, 1-butene, cis-2-butene, trans-2-butene) in the product, and the selectivity of isobutylene in the C4 gas at each reaction pressure are shown in Table 1 and FIG. 1.

[0064]

[0065] As shown in Table 1 and FIG. 1, when the reaction pressure is high, the conversion rate of isobutyl alcohol tends to decrease.

[0066] [Example 1] A crushed alumina pellet (alumina consisting of γ, θ, and α-alumina crystal phases, particle size: 800 to 1190 μm, BET specific surface area: 105 m) formed into a cylindrical pellet shape (diameter: 3.00 m) was used as a dehydration catalyst. ２ / g, Na ２ O content: less than 0.0500 mass%, SiO ２A vertical tubular reactor with an inner diameter of 1.0 cm and a length of 40 cm was filled with 0.232 g of catalyst B (content: 0.160 mass%, hereinafter referred to as "catalyst B"). The reaction temperature and pressure were maintained at 340°C and 250 kPa, respectively. Next, a feed gas consisting of isobutanol (concentration in the feed gas: 49.8% by volume) and nitrogen was supplied to a fixed-bed reactor packed with 0.232 g of catalyst B at a linear velocity of 1.57 cm / s, and the isobutanol was contacted with alumina to obtain a product. The feed gas flow rate was 2.50 L / h, and the WHSV was 19.5 h. －１ The results of measuring the conversion of isobutanol, the selectivity of C4 gas in the product, and the selectivity of isobutylene in the C4 gas are shown in Table 2 and FIG.

[0067] [Examples 2 and 3 and Comparative Example 1] Products were obtained in the same manner as in Example 1, except that the reaction conditions were changed as shown in Table 2. The results of measuring the conversion of isobutanol, the selectivity of C4 gas in the product, and the selectivity of isobutylene in the C4 gas are shown in Table 2 and Figure 2.

[0068]

[0069] 2, under the same pressurized conditions, the higher the linear velocity of the feed gas, the higher the isobutanol conversion and isobutylene selectivity. In Examples 1 to 3, in which the linear velocity of the feed gas and the reaction pressure were appropriately controlled, isobutylene could be produced with high selectivity while suppressing a decrease in isobutanol conversion, as compared to Comparative Example 1.

[0070] Example 4 0.232 g of catalyst A was packed into a fixed-bed reactor and maintained at 340°C and 400 kPa. Next, a feed gas consisting of isobutanol (concentration in the feed gas: 80.3% by volume) and nitrogen was supplied to the fixed-bed reactor packed with 0.232 g of catalyst A at a linear velocity of 2.07 cm / s, and the isobutanol was brought into contact with alumina to obtain a product. The feed gas flow rate was 3.29 L / h, and the WHSV was 66.3 h. －１ The results of measuring the conversion of isobutanol, the selectivity of C4 gas in the product, and the selectivity of isobutylene in the C4 gas are shown in Table 3 and FIG.

[0071] [Examples 5 and 6 and Comparative Example 2] Products were obtained in the same manner as in Example 4, except that the reaction conditions were changed as shown in Table 3. The measurement results of the conversion of isobutanol, the selectivity of C4 gas in the product, and the selectivity of isobutylene in the C4 gas are shown in Table 3 and Figure 3.

[0072]

[0073] As shown in Table 3 and Figure 3, under the same pressurized conditions, the higher the linear velocity of the feed gas, the higher the isobutanol conversion and isobutylene selectivity. In Examples 4 to 6, in which the linear velocity of the feed gas and the reaction pressure were appropriately controlled, isobutylene could be produced with high selectivity while suppressing a decrease in isobutanol conversion, as compared to Comparative Example 2.

[0074] Example 7 0.132 g of catalyst A was packed into a fixed-bed reactor and maintained at 340°C and 200 kPa. Next, a feed gas consisting of isobutanol (concentration in the feed gas: 79.4% by volume) and nitrogen was supplied to the fixed-bed reactor packed with 0.132 g of catalyst A at a linear velocity of 4.57 cm / s, and the isobutanol was brought into contact with alumina to obtain a product. The feed gas flow rate was 7.27 L / h, and the WHSV was 127 h. －１ The results of measuring the conversion of isobutanol, the selectivity of C4 gas in the product, and the selectivity of isobutylene in the C4 gas are shown in Table 4 and FIG.

[0075] [Examples 8 and 9 and Comparative Example 3] Products were obtained in the same manner as in Example 7, except that the reaction conditions were changed as shown in Table 4. The measurement results of the conversion of isobutanol, the selectivity of C4 gas in the product, and the selectivity of isobutylene in the C4 gas are shown in Table 4 and Figure 4.

[0076]

[0077] As shown in Table 4 and FIG. 4 , in Examples 7 to 9 in which the linear velocity of the raw material gas and the reaction pressure were appropriately controlled at the same reaction temperature, isobutylene could be produced with a high selectivity while suppressing a decrease in the conversion rate of isobutanol, as compared to Comparative Example 3.

[0078] Example 10: 0.591 g of catalyst B was packed into a fixed-bed reactor and maintained at 340°C and 200 kPa. Next, a feed gas consisting of isobutanol (concentration in the feed gas: 80.1% by volume) and nitrogen was supplied to the fixed-bed reactor at a linear velocity of 4.53 cm / s, and the isobutanol was brought into contact with alumina to obtain a product. The feed gas flow rate was 7.21 L / h, and the WHSV was 28.4 h. －１ The results of measuring the conversion of isobutanol, the selectivity of C4 gas in the product, and the selectivity of isobutylene in the C4 gas are shown in Table 5 and FIG.

[0079] Examples 11 to 13 and Comparative Example 4 Products were obtained in the same manner as in Example 10, except that the reaction conditions were changed as shown in Table 5. The results of measuring the conversion of isobutanol, the selectivity of C4 gas in the product, and the selectivity of isobutylene in the C4 gas are shown in Table 5 and FIG.

[0080]

[0081] As shown in Table 5 and FIG. 5, in Examples 10 to 13 in which the linear velocity of the raw material gas and the reaction pressure were appropriately controlled, isobutylene could be produced with a high selectivity while suppressing a decrease in conversion rate, compared to Comparative Example 4.

[0082] Example 14: 0.903 g of catalyst B was packed into a fixed-bed reactor and maintained at 360°C and 450 kPa. Next, a feed gas consisting of isobutanol (concentration in the feed gas: 79.9% by volume) and nitrogen was supplied to the fixed-bed reactor packed with 0.903 g of catalyst B at a linear velocity of 1.57 cm / s, and the isobutanol was contacted with alumina to obtain a product. The feed gas flow rate was 2.50 L / h, and the WHSV was 14.0 h －１ The results of measuring the conversion of isobutanol, the selectivity of C4 gas in the product, and the selectivity of isobutylene in the C4 gas are shown in Table 6 and FIG.

[0083] Examples 15 to 19 Products were obtained in the same manner as in Example 14, except that the reaction conditions were changed as shown in Table 5. The measurement results of the isobutanol conversion, the selectivity of C4 gas in the product, and the selectivity of isobutylene in the C4 gas are shown in Table 6 and FIG.

[0084]

[0085] As shown in Table 6 and FIG. 6, the higher the reaction temperature, the higher the conversion rate, and the lower the reaction temperature, the higher the selectivity for isobutylene.

[0086] Examples 20 and 21 Products were obtained in the same manner as in Example 3, except that the reaction conditions were changed as shown in Table 7. The measurement results of the isobutanol conversion, the selectivity of C4 gas in the product, and the selectivity of isobutylene in the C4 gas are shown in Table 7 and FIG.

[0087]

[0088] As shown in Table 7 and FIG. 7, the higher the reaction temperature, the higher the conversion rate, and the lower the reaction temperature, the higher the selectivity for isobutylene.

Claims

DEPCT661. Method for the production of isobutylene, in which a feed gas containing isobutanol is exposed to a catalyst to produce isobutylene from isobutanol, the method comprises: exposure of a feed gas containing isobutanol to a catalyst at a linear velocity of 1.20 cm / s or more under a pressure of 120 kPa or more in terms of absolute pressure to produce isobutylene from isobutanol.

2. Method for the production of isobutylene according to claim 1, in which The concentration of isobutanol contained in the isobutanol-containing feed gas is 15% by volume or more and 100% by volume or less.

3. Methods for the production of isobutylene according to Reservation 1 or 2, where the catalyst has a particle diameter of 700 µm or more and 10,000 µm or less.

4. Methods for the production of isobutylene according to one of Reservations 1 through 3, where the catalyst is an alumina-containing catalyst. 5.Methods for the production of methacrylic acid, including: Production of methacrylic acid from isobutylene which is produced according to the methods for the production of isobutylene as specified in any of the claims 1 to 46. Methods for the production of methacrylic acid, including: Obtaining ter-butyl alcohol from isobutylene which is produced according to the methods for the production of isobutylene as specified in any of the claims 1 to 4, and subsequently producing methacrylic acid from the obtained ter-butyl alcohol.

7. Methods for the production of methyl methacrylate, including: Production of methyl methacrylate from methacrylic acid which is produced according to the methods for the production of methacrylic acid as specified in claim 5 or 6 and from methanol.