Screening method for catalysts used in olefin hydration reactions

Abstract

To provide a simple screening method for a heteropolyacid-supported catalyst suitable for producing alcohol by olefin hydration.SOLUTION: A screening method for an olefin hydration catalyst includes: heating a catalyst with heteropolyacid supported on a carrier; and analyzing the heated catalyst by infrared spectroscopy to select a catalyst with an absorption band of 2200 cm-1.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for screening a catalyst for olefin hydration reaction based on infrared spectroscopic measurement in a catalyst in which a heteropoly acid is supported on a carrier, and a method for producing an alcohol by olefin hydration reaction using the catalyst.

Background Art

[0002] It is well known that a corresponding alcohol can be produced by subjecting a lower olefin to a hydration reaction in the gas phase. In this reaction, it is also well known that a supported catalyst in which a heteropoly acid or its salt is supported on a carrier is useful (Patent Documents 1 and 2).

[0003] In Non-Patent Document 1, in the hydration reaction of propylene using a phosphotungstic acid catalyst supported on silica, it is considered that hydroxonium ions (H3O + , H5O2 + ) are the active species of the hydration reaction. However, the correlation between hydroxonium ions and the olefin hydration reaction has not actually been investigated.

[0004] In Non-Patent Document 2, after adsorbing benzonitrile to a silicotungstic acid catalyst supported on silica, temperature-programmed desorption measurement is performed to systematically evaluate the acidic properties of the catalyst at various supported amounts. However, the correlation between the temperature-programmed desorption measurement results of benzonitrile and the olefin hydration reaction has not been investigated.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Non-Patent Documents

[0006] [Non-Patent Document 1] Applied Catalysis A: General, vol. 256, p.225-242 (2003). [Non-Patent Document 2] The Journal of Physical Chemistry C, Vol. 115, pp. 14762-14769 (2011). [Overview of the project] [Problems that the invention aims to solve]

[0007] The object of this invention is to provide a simple screening method for heteropoly acid-supported catalysts suitable for producing alcohols by the hydration reaction of olefins. [Means for solving the problem]

[0008] In heteropoly acid-supported catalysts, protonated water of crystals (H3O) in the heteropoly acid + H5O2 + ) may significantly affect the activity of the olefin hydration reaction. As a result of diligent research, the inventors heat-treated a catalyst in which a heteropoly acid was supported on a carrier under vacuum, and measured the catalyst after heat treatment by infrared spectroscopy, finding that 2200 cm⁻¹ -1 By selecting catalysts that exhibit the presence of a specific absorption band as useful catalysts, we discovered that catalysts active in the hydration reaction of olefins can be easily screened, thus completing the present invention.

[0009] In other words, the present invention relates to the following [1] to [7]. [1] A catalyst supported by a heteropoly acid was heat-treated, and the catalyst after heat treatment was measured by infrared spectroscopy, at 2200 cm⁻¹. -1 A method for screening catalysts for the hydration reaction of olefins, comprising selecting a catalyst in which an absorption band exists. [2] The catalyst screening method according to [1], wherein the temperature of the heat treatment is 100 to 200°C. [3] A method for screening catalysts according to [1] or [2], wherein the heat treatment time is 0.5 to 3 hours. [4] A method for screening catalysts according to any one of the following [1] to [3], wherein the heteropoly acid is silicic acid or phosphotungstic acid. [5] A method for screening a catalyst according to any one of [1] to [4], wherein the support is silica. [6] A method for screening a catalyst according to any one of [1] to [5], wherein the olefin is an olefin having 2 to 5 carbon atoms. [7] A method for producing alcohol by hydration reaction of an olefin, comprising the steps of screening a catalyst by any of the screening methods described in [1] to [5], and producing an alcohol by reacting an olefin with water using the catalyst screened in the first step. [Effects of the Invention]

[0010] According to the present invention, a heteropoly acid-supported catalyst suitable for producing alcohol by the hydration reaction of olefins can be efficiently selected. [Brief explanation of the drawing]

[0011] [Figure 1] These are the FT-IR spectra of heteropoly acid-supported catalysts A to I measured in the examples. [Figure 2] These are the FT-IR spectra obtained when 1-butene was reacted with heteropoly acid-supported catalysts A to I, as measured in the examples. [Modes for carrying out the invention]

[0012] The following describes preferred embodiments of the present invention, but it should be understood that the present invention is not limited to these forms and can be applied in various ways within its spirit and scope.

[0013] A screening method for a catalyst for olefin hydration reaction in one embodiment includes at least the following (1) heat treatment step and (2) selection step. (1) Heat treatment step A step of heat-treating a catalyst in which a heteropolyacid is supported on a carrier under vacuum (2) Selection step Measuring the heat-treated catalyst by infrared spectroscopy, and selecting a catalyst having an absorption band at 2200 cm -1 A step of selecting a catalyst having an absorption band at 2200 cm

[0014] A catalyst having an absorption band at 2200 cm -1 attributed to protonated water of crystallization is considered to exhibit high activity in the olefin hydration reaction. In the present disclosure, the "absorption band at 2200 cm -1 " means an absorption band having an absorption peak at a wave number of 2100 cm -1 ~2300 cm -1 .

[0015] [Catalyst for olefin hydration reaction] The object of the screening method is a catalyst in which one or more kinds of heteropolyacids are supported on a carrier.

[0016] A heteropolyacid is composed of a central element and peripheral elements bonded to oxygen. The central element is usually silicon or phosphorus, but can be any one selected from a variety of elements in Groups 1 to 17 of the periodic table of elements. Specifically, for example, cupric ion; divalent beryllium, zinc, cobalt or nickel ion; trivalent boron, aluminum, gallium, iron, cerium, arsenic, antimony, phosphorus, bismuth or chromium ion; tetravalent silicon, germanium, tin, titanium, zirconium, vanadium, sulfur, tellurium, manganese, nickel, thorium, hafnium, cerium ion and other rare earth ions; pentavalent phosphorus, arsenic, vanadium, antimony ion; hexavalent tellurium ion; and heptavalent iodine ion, etc. can be mentioned, but it is not limited thereto. Further, specific examples of the peripheral elements include tungsten, molybdenum, vanadium, niobium, tantalum, etc., but are not limited thereto.

[0017] Such heteropoly acids are known as "polyoxoanions," "polyoxometallic salts," or "metal oxide clusters." Some well-known anion structures are named after researchers in this field, such as the Keggin, Wells-Dawson, and Anderson-Evans-Perloff structures. For more details, see "The Chemistry of Polyacids" (edited by the Chemical Society of Japan, Quarterly Review of Chemistry No. 20, 1993). Heteropoly acids usually have high molecular weights, for example, in the range of 700 to 8500, and include not only monomers but also dimeric complexes.

[0018] Particularly preferred examples of heteropoly acids that can be used as catalysts include: Silicate tungstic acid H4[SiW 12 O 40 ]·xH2O Phosphate tungstic acid H3[PW 12 O 40 ]·xH2O Phosphorus molybdate H3[PMo 12 O 40 ]·xH2O SiMolybdate H4[SiMo 12 O 40 ]·xH2O Tungstic acid H 4+n [SiV n W 12-n O 40 ]·xH2O Lymphatic tungstic acid H 3+n [PV n W 12-n O 40 ]·xH2O Lymphanodomolybdate H 3+n [PV n Mo 12-n O 40 ]·xH2O H23 kaevanadomolybdate 4+n [SiV n Mo 12-nO 40 ]·xH2O SiMolybdenum tungstic acid H4[SiMo n W 12 -nO 40 ]·xH2O Phosphorus-molybdenum tungstic acid H3[PMo n W 12 -nO 40 ]·xH2O (In the formula, n is an integer between 1 and 11, and x is an integer greater than or equal to 1.) These are some examples, but the list is not limited to these.

[0019] The heteropoly acid is preferably silicic acid, phosphotungstic acid, phosphomolybdic acid, silicic acid, silicanodungstic acid, or phosphonodungstic acid, and more preferably silicic acid or phosphotungstic acid.

[0020] There are no particular restrictions on the method of synthesizing such heteropoly acids, and any method may be used. For example, heteropoly acids can be obtained by heating an acidic aqueous solution (pH 1 to pH 2) containing a salt of molybdic acid or tungstic acid and a simple oxyacid of a heteroatom or a salt thereof. Heteropoly acid compounds can be isolated, for example, by crystallization separation as metal salts from the resulting heteropoly acid aqueous solution. Specific examples of heteropoly acid production are described on page 1413 of "New Experimental Chemistry Course 8: Synthesis of Inorganic Compounds (III)" (edited by the Chemical Society of Japan, published by Maruzen Co., Ltd., August 20, 1984, 3rd edition), but the method is not limited to this. The structure of the synthesized heteropoly acid can be confirmed by chemical analysis, as well as by X-ray diffraction, UV or IR spectroscopy.

[0021] Specific examples of carriers include silica, alumina, titania, zirconia, silica-alumina, zeolite, and activated carbon. Silica is preferred as the carrier.

[0022] In one embodiment, the loading of a heteropoly acid onto a carrier includes, in this order, a step of absorbing (impregnating) the carrier with an aqueous solution of the heteropoly acid (heteropoly acid aqueous solution) and a step of drying the carrier impregnated with the heteropoly acid aqueous solution under specific drying conditions (drying step). Other steps (for example, an air-drying step, a transfer step from the impregnation device to the drying device, etc.) may be included between the impregnation step and the drying step, but it is preferable that these two steps be performed consecutively.

[0023] [(1) Heat treatment process] The heat treatment process involves heat-treating the catalyst, on which the heteropoly acid is supported, to remove excess moisture such as adsorbed water from the support. While the heat treatment method is not particularly limited, it is preferable to heat-treat the catalyst in the cell of an infrared spectrophotometer to suppress the re-adsorption of moisture to the catalyst. Furthermore, it is preferable to perform the heat treatment under reduced pressure to efficiently remove adsorbed water and other substances. Therefore, it is desirable that the infrared spectrophotometer be a device capable of heating, cooling, and reducing the pressure of the cell containing the sample for measurement.

[0024] In the heat treatment process, there is an appropriate range of temperature and time for the heat treatment, from the perspective of removing excess moisture from the catalyst.

[0025] The heat treatment temperature is preferably 100 to 200°C, more preferably 120 to 180°C, and even more preferably 140 to 160°C. If the heat treatment temperature is 100°C or higher, moisture is sufficiently removed. If the heat treatment temperature is 200°C or lower, partial decomposition of heteropoly acids is suppressed.

[0026] The heat treatment time is preferably 0.5 to 3 hours, more preferably 0.7 to 2 hours, and even more preferably 0.8 to 1.5 hours. If the heat treatment time is 0.5 hours or longer, sufficient moisture is removed. If the heat treatment time is 3 hours or less, energy consumption for heating can be suppressed.

[0027] The pressure used when performing heat treatment under reduced pressure is not particularly limited, but it is preferable to be close to a vacuum. Specifically, the heat treatment pressure is preferably 0.5 Pa or less.

[0028] [(2) Selection process] In the selection step, the catalyst after heat treatment is measured by infrared spectroscopy to obtain an infrared absorption spectrum. From the viewpoint of sensitivity and resolution, Fourier transform infrared spectroscopy (FT-IR) is preferred for the infrared spectroscopy measurement. The 2200 cm⁻¹ spectrum is attributed to protonated crystalline water. -1 The presence or absence of an absorption band is checked, and if this absorption band is present, it is determined that the catalyst is active in the hydration reaction of olefins, and this catalyst is selected. There are no particular restrictions on the measurement method using FT-IR, but in order to prevent contamination with water, a method that can measure using only the catalyst without using diluents such as KBr is preferred. Examples include the permeation method using a disk formed from only the catalyst, and the diffuse reflectance method and total internal reflection (ATR) method using only the catalyst powder.

[0029] [Method for producing alcohol by hydration reaction of olefins] Alcohols can be obtained by supplying water and an olefin to a reactor and carrying out a hydration reaction in the gas phase using a catalyst in which a heteropoly acid is supported on a support (hereinafter, in this disclosure, this may be simply referred to as "catalyst for olefin hydration reaction").

[0030] A specific example of the alcohol production reaction by the hydration reaction of olefins is shown in equation (1). [ka] (In the formula, R 1 ~R 4 Each of these independently represents either a hydrogen atom or an alkyl group.

[0031] The olefins that can be used in the hydration reaction of olefins using a catalyst for olefin hydration are not particularly limited, but olefins having 2 to 5 carbon atoms are preferred. Preferred olefins having 2 to 5 carbon atoms include ethylene, propylene, 1-butene, isobutene, pentene, or mixtures of two or more thereof, and more preferably ethylene and 1-butene. There are no restrictions on the ratio of olefin to water used, but because the reaction rate is highly dependent on the concentration of the olefin, and because the energy cost of the alcohol production process increases when the water concentration is high, the molar ratio of olefin to water is preferably water / olefin = 0.01 to 2.0, and more preferably water / olefin = 0.1 to 1.0.

[0032] There are no restrictions on the type of olefin hydration reaction using an olefin hydration catalyst; any reaction type can be used. Preferred types include fixed-bed, fluidized-bed, and suspension-bed reactions, from the viewpoint of ease of separation from the catalyst and reaction efficiency, with the fixed-bed reaction being the most preferable as it requires the least energy for separation from the catalyst.

[0033] When using a fixed-bed system, the gas space velocity is not particularly limited, but from the viewpoint of energy and reaction efficiency, it is preferably 500 to 15,000 / hr, more preferably 1,000 to 10,000 / hr. If the gas space velocity is 500 / hr or higher, the amount of catalyst used can be effectively reduced, and if it is 15,000 / hr or lower, the amount of gas circulation can be reduced, so alcohol can be produced more efficiently within the above range.

[0034] There are no restrictions on the reaction pressure in the hydration reaction of olefins using a catalyst for olefin hydration. Since the hydration reaction of olefins is a reaction in which the number of molecules decreases, it is generally advantageous to carry it out at high pressure. The reaction pressure is preferably 0.5 to 7.0 MPaG, and more preferably 1.5 to 4.0 MPaG. "G" means gauge pressure. If the reaction pressure is 0.5 MPaG or higher, a sufficient reaction rate can be obtained, and if it is 7.0 MPaG or lower, the costs related to the installation of equipment for preventing olefin condensation and evaporation, equipment for high-pressure gas safety measures, and energy can be further reduced.

[0035] The reaction temperature for the hydration reaction of olefins using a catalyst for olefin hydration is not particularly limited and can be carried out at a wide range of temperatures. A preferred reaction temperature is 100 to 550°C, more preferably 150 to 350°C, considering the thermal stability of the heteropoly acid and the temperature at which water, one of the raw materials, does not condense.

[0036] The hydration reaction of olefins using a catalyst for olefin hydration is an equilibrium reaction, and the conversion rate of the olefin is at most the equilibrium conversion rate. For example, the equilibrium conversion rate in the production of ethanol by hydrated ethylene is calculated to be 7.5% at a temperature of 200°C and a pressure of 2.0 MPaG. Therefore, in the production of alcohol by hydrated olefins, the maximum conversion rate is determined by the equilibrium conversion rate, and as seen in the example of ethylene, the hydration reaction of olefins tends to have a low equilibrium conversion rate. Industrially, there is a strong demand to carry out the hydration reaction of olefins with high efficiency under mild conditions.

[0037] In olefin hydration reactions using catalysts for olefin hydration, olefin loss can be reduced by recycling unreacted olefins back into the reactor. There are no restrictions on the method of recycling unreacted olefins back into the reactor; they may be isolated and recycled from the process fluid coming out of the reactor, or they may be recycled together with other inert components. Typically, industrial-grade ethylene often contains very small amounts of ethane. Therefore, when recycling unreacted ethylene back into the reactor using ethylene containing ethane, it is desirable to purge a portion of the recovered ethylene gas from the system to prevent ethane concentration and accumulation.

[0038] In olefin hydration reactions using catalysts for olefin hydration, the resulting alcohol may dehydrate, producing ether compounds as by-products. For example, when ethanol is obtained by hydrating ethylene, diethyl ether is produced as a by-product. This diethyl ether is thought to be produced by a dehydration reaction from two molecules of ethanol, and when ethanol is produced by the hydration of ethylene, it significantly reduces the reaction yield. However, by recycling the by-product diethyl ether back into the reactor, the diethyl ether can be converted back into ethanol, allowing for extremely efficient production of ethanol from ethylene. There are no particular restrictions on the method of recycling the by-product ether compounds back into the reactor, but examples include isolating the ether compounds from the components distilled from the reactor and recycling them back into the reactor, or recycling them back into the reactor as a gaseous component together with unreacted olefins.

[0039] The formation of alcohols through the hydration reaction of olefins can be confirmed using FT-IR. Infrared spectroscopy at 2200 cm² -1 When an olefin is introduced into a cell containing a heteropoly acid-supported catalyst with an absorption band present, and the FT-IR spectrum is measured, protonated water of crystal (H3O + H5O2 + ) belongs to 2200cm -1The absorption band decreases as the reaction progresses. At the same time, an absorption band corresponding to the alcohol species adsorbed on the catalyst appears. For example, 1700-1800 cm⁻¹ -1 A broad absorption band can be observed, which is attributed to the OH stretching vibration of the alcohol interacting with the catalyst. [Examples]

[0040] The present invention will be further described with reference to the following embodiments, but the present invention is not limited to these embodiments.

[0041] [IR Spectrum Measurement] The IR spectrum was measured by transmission using a Fourier transform infrared spectrophotometer (FT / IR-4100; manufactured by JASCO Corporation). The measurement conditions were a wavenumber resolution of 4 cm. -1 The number of cumulative measurements was set to 64. An MCT (mercury-cadmium-tellurium compound) detector was used as the detector. The infrared spectrophotometer is equipped with a cell for housing the sample to be measured, and this cell can be heated by a heater, cooled by liquid nitrogen, and depressurized by a vacuum line.

[0042] [Preparation of silica support (mesoporous silica SBA-15)] Pluronic(registered trademark) P123(HO(CH2CH2O)) 20 (CH2CH(CH3)O) 70 (CH2CH2O) 20 5.0 g of H (manufactured by Sigma-Aldrich) was dissolved in 17.0 g of 12 M hydrochloric acid and 183 g of water. The resulting solution was heated to 40°C, and 10.4 g of tetraethoxysilane was added. The solution was held at 40°C for 20 hours, and then aged at 100°C for 20 hours. The precipitated white powder was filtered off and washed with ethanol. The washed white powder was dried at 100°C and then calcined at 500°C for 10 hours to obtain SBA-15.

[0043] [Preparation of catalyst] (Preparation of Catalyst A) Commercially available Keggin-type tungstic acid 24-hydrate (H4SiW 12 O 400.20 g of 24H2O (Nippon Inorganic Chemical Industry Co., Ltd.) was dissolved in 30 g of water. 0.80 g of SBA-15 was added to the resulting solution and stirred well, then the water was removed at 100°C. The resulting solid powder was dried at 150°C for 4 hours to obtain catalyst A.

[0044] (Preparation of catalysts B to E) Catalysts B through E were obtained by repeating the same procedure as for catalyst A, except that the amounts of silicatungstic acid and SBA-15 used were changed as shown in Table 1.

[0045] (Preparation of catalyst F) Catalyst F was obtained by repeating the same procedure as for the preparation of catalyst A, except that the amount of silicatungstic acid used was 0.10 g and SBA-15 was replaced with 0.90 g of hydrophilic fumed silica (AEROSIL® 200; manufactured by Evonik).

[0046] (Preparation of catalysts G and H) Catalysts G and H were obtained by repeating the same procedure as for the preparation of catalyst F, except that the amounts of silicatungstic acid and AEROSIL (trademark) 200 used were changed as shown in Table 1.

[0047] (Preparation of Catalyst I) Catalyst I was obtained by repeating the same procedure as for the preparation of catalyst A, except that the amounts of silicatungstic acid and SBA-15 used were changed to 0.10 g and 0.90 g, respectively.

[0048] [Thermal treatment of catalysts and selection of catalysts using FT-IR] 40 mg each of catalysts A to I, applied at 400 kgf / cm² 2 The material was pressurized and formed into a disc with a diameter of 20 mm and a thickness of 0.5 mm. The formed disc was placed in the measurement cell of an infrared spectrophotometer connected to a vacuum line and heat-treated for 1 hour under a vacuum of 150°C (achievable vacuum of 0.1 Pa). Subsequently, the IR spectrum was measured at 150°C under the above conditions, and the result was 2200 cm⁻¹. -1 We checked for the presence or absence of absorption zones.

[0049] [1- Reaction with butene] The heat-treated disc in the measurement cell was cooled to -100°C under vacuum. 1-butene gas was introduced into the measurement cell at a pressure of 100 Pa. After approximately 1 minute, the measurement cell was evacuated to remove any 1-butene gas in the gas phase that was not adsorbed on the catalyst. Subsequently, the measurement cell was heated to -20°C at a rate of 3°C / min, and the IR spectrum was measured under the above conditions.

[0050] Figure 1 shows the IR spectra of each catalyst after heat treatment. In catalysts A to H, protonated water of crystals (H3O) + H5O2 + ) belongs to 2200cm -1 Since an absorption band was confirmed, these catalysts were selected based on the judgment that they would be useful for the hydration reaction of olefins. On the other hand, with catalyst I, the absorption band was 2200 cm². -1 Since no absorption band was observed, it was determined that catalyst I was not useful for the hydration reaction of olefins, and therefore catalyst I was not selected.

[0051] Figure 2 shows the IR difference spectrum (difference spectrum before and after 1-butene adsorption) when 1-butene was adsorbed onto the heat-treated catalyst at -100°C and then the temperature was raised to -20°C. Catalysts A-H showed 2200 cm⁻¹. -1 A reverse peak (valley) was observed nearby, at 2200cm. -1 It can be seen that the absorption zone has decreased. In addition, 1700-1800cm -1 A broad absorption band was observed, attributed to the OH stretching vibration of butanol interacting with the catalyst. This indicates that the hydration reaction of 1-butene proceeded, producing butanol. On the other hand, with catalyst I, the absorption band was 1700-1800 cm⁻¹. -1 No broad absorption band was observed, and the 1650 cm² is attributed to the 1-butene polymer. -1 An absorption band was identified. In other words, the hydration reaction of 1-butene was not observed to be progressing. Based on these results, after heat treatment, 2200 cm -1 It can be seen that catalysts for olefin hydration reactions can be screened by selecting catalysts that have an absorption band.

[0052] Table 1

Claims

1. A catalyst supported by a heteropoly acid was heat-treated, and the catalyst after heat treatment was measured by infrared spectroscopy at 2200 cm⁻¹. －１ A method for screening catalysts for the hydration reaction of olefins, comprising selecting a catalyst in which an absorption band exists, wherein the temperature of the heat treatment is 100 to 200°C.

2. The catalyst screening method according to claim 1, wherein the heat treatment time is 0.5 to 3 hours.

3. The catalyst screening method according to claim 1 or 2, wherein the heteropoly acid is silicic acid or phosphotungstic acid.

4. A method for screening a catalyst according to any one of claims 1 to 3, wherein the support is silica.

5. The catalyst screening method according to any one of claims 1 to 4, wherein the olefin is an olefin having 2 to 5 carbon atoms.

6. A method for producing alcohol by hydration reaction of an olefin, comprising the steps of: screening a catalyst by a screening method described in any one of claims 1 to 4; and producing an alcohol by reacting an olefin with water using the catalyst screened in the first step.

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