Method for producing propylene

Abstract

To provide a method for producing propylene, the method enabling propylene to be produced from ethanol at high yield and enabling suppression of generation of by-products.SOLUTION: A method for producing propylene is provided, in which propylene is obtained by bringing ethanol and a catalyst into contact with each other in a reactor. In the method, the catalyst contains zirconium and calcium, and a calcium content is equal to or more than 0.01 mass% and equal to or less than 3.3 mass%. The catalyst has crystalline structure and the structure contains at least one selected from the group consisting of tetragonal and cubic crystalline structures, and a molar ratio of calcium to zirconium (Ca / Zr) in the surface of the catalyst is equal to or more than 0.001 and equal to or less than 0.269.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for producing propylene.

Background Art

[0002] In recent years, due to concerns about climate change and the depletion and price increase of fossil resources, technologies for producing basic chemicals from sustainable raw materials have been demanded. Propylene is one of the typical basic chemicals and is widely used as a raw material for chemicals such as acrylic acid and cumene and as a raw material for resins such as polypropylene. Ethanol can be produced from biomass and is one of the sustainable raw materials. Therefore, as one of the methods for producing basic chemicals from sustainable raw materials, a method for producing propylene from ethanol has been studied.

[0003] For example, Patent Document 1 discloses a method for producing propylene in which a metal compound selected from the group consisting of metals of Group 1 elements, metals of Group 2 elements, and metals of rare earth elements is supported on zirconium oxide and fired at 650°C or higher, and the resulting catalyst is contacted with ethanol.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] When producing propylene using ethanol as a raw material and using a conventional porous oxide catalyst, there has been a problem that many by-products such as olefins and alkanes with a large number of carbon atoms are likely to be produced. Furthermore, when using a solid oxide catalyst such as zirconium oxide, although the by-production of olefins and alkanes with a large number of carbon atoms is suppressed, acetone and the like are by-produced, and the yield of propylene is not sufficient. Therefore, there has been a demand for a catalyst and a production method that can suppress the generation of by-products as described above and improve the yield of propylene. Accordingly, an object of the present disclosure is to provide a method for producing propylene that can produce propylene in a high yield from ethanol and can also suppress the generation of by-products.

Means for Solving the Problems

[0006] As a result of intensive studies to solve the above problems, the present inventors have found that the above problems can be solved by producing propylene using a specific catalyst containing calcium and zirconium, and have completed the invention.

[0007] That is, according to one aspect of the present disclosure, there is provided a method for producing propylene, comprising contacting ethanol with a catalyst in a reactor to obtain propylene, wherein the catalyst contains zirconium and calcium, the content of calcium is 0.01% by mass or more and 3.3% by mass or less, the catalyst has a crystal structure, the crystal structure contains at least one selected from the group consisting of a tetragonal crystal and a cubic crystal, and the molar ratio of calcium to zirconium (Ca / Zr) on the catalyst surface is 0.001 or more and 0.269 or less.

Advantages of the Invention

[0008] According to one aspect of the present disclosure, it is possible to provide a method for producing propylene that can produce propylene in a high yield from ethanol and can also suppress the generation of by-products.

Mode for Carrying Out the Invention

[0009] The present disclosure relates to a method for producing propylene by bringing ethanol into contact with a catalyst in a reactor to obtain propylene, wherein the catalyst contains zirconium and calcium, the calcium content is 0.01% by mass or more and 3.3% by mass or less, the catalyst has a crystal structure, and the crystal structure contains at least one selected from the group consisting of tetragonal and cubic crystals, and the molar ratio of calcium to zirconium (Ca / Zr) on the catalyst surface is 0.001 or more and 0.269 or less. The present disclosure will be described in detail below.

[0010] [Method for Producing Propylene] The method for producing propylene of the present disclosure is a method for producing propylene by bringing ethanol into contact with a catalyst in a reactor to obtain propylene, wherein the catalyst contains zirconium and calcium, the calcium content is 0.01% by mass or more and 3.3% by mass or less, the catalyst has a crystal structure, and the crystal structure contains at least one selected from the group consisting of tetragonal and cubic crystals, and the molar ratio of calcium to zirconium (Ca / Zr) on the catalyst surface is 0.001 or more and 0.269 or less. According to the method for producing propylene of the present disclosure, propylene can be produced in a high yield from ethanol, and the generation of by-products can also be suppressed.

[0011] [Ethanol] The ethanol used in the method for producing propylene of the present disclosure is not particularly limited, but preferably, ethanol derived from biomass (bioethanol) is used. By bringing bioethanol into contact with the catalyst of the present disclosure, propylene can be produced without increasing the carbon dioxide concentration in the environment, unlike ethanol obtained from fossil fuels.

[0012] [Catalyst] The catalyst used in the method for producing propylene of the present disclosure contains zirconium and calcium, the calcium content is 0.01% by mass or more and 3.3% by mass or less, has a crystal structure, and the crystal structure contains at least one selected from the group consisting of tetragonal and cubic crystals, and the molar ratio of calcium to zirconium (Ca / Zr) on the catalyst surface is 0.001 or more and 0.269 or less. By using the catalyst in the method for producing propylene of the present disclosure, propylene can be produced from ethanol in a high yield, and the generation of by-products can also be suppressed. The reason why such an effect can be exhibited is not clear, but it is considered as follows. It is considered that the inclusion of calcium suppresses the acid during the reaction and suppresses the by-production of ethylene as a by-product. Furthermore, by suppressing the calcium content to a low range, the reaction from acetone as an intermediate to propylene can be promoted, and the generation of impurities can be reduced. In particular, reducing the calcium ratio on the catalyst surface that directly contributes to the reaction is considered to be extremely effective in reducing impurities. Furthermore, having a tetragonal or cubic crystal is considered to increase the active part and improve the propylene yield.

[0013] The catalyst contains calcium. The calcium contained in the catalyst is preferably present in a state of being a composite oxide with zirconium oxide (ZrO 2 ). The calcium content is 0.01% by mass or more and 3.3% by mass or less, preferably 0.01% by mass or more and 3.0% by mass or less, more preferably 0.01% by mass or more and 2.8% by mass or less, still more preferably 0.1% by mass or more and 2.3% by mass or less, even more preferably 0.1% by mass or more and 1.8% by mass or less, even more preferably 0.1% by mass or more and 1.3% by mass or less, even more preferably 0.1% by mass or more and 0.8% by mass or less, even more preferably 0.1% by mass or more and 0.5% by mass or less, and even more preferably 0.2% by mass or more and 0.5% by mass or less with respect to the total amount of the catalyst. When the calcium content is within the above range, the propylene yield can be improved while particularly reducing the generation of impurities. The calcium content of the catalyst can be measured by ICP emission spectrometry, specifically, it can be measured by the method described in the examples.

[0014] The catalyst has a crystal structure and contains at least one selected from the group consisting of tetragonal and cubic crystal structures, preferably contains a tetragonal crystal structure, and more preferably contains a tetragonal and a cubic crystal structure. The catalyst may have a crystal structure other than tetragonal and cubic crystal structures, and monoclinic crystal is preferred as the crystal structure other than tetragonal and cubic crystal structures. It is preferable that the crystal structure of the catalyst further contains a monoclinic crystal. The total content of the tetragonal and cubic crystal structures of the catalyst is preferably 5% or more, more preferably 10% or more, still more preferably 15% or more. There is no upper limit as long as it is 100% or less, but preferably 99% or less. When the catalyst has the above crystal structure, the propylene yield is improved. This is considered to be because there are many surface oxygen vacancies which are important active sites. The above crystal structure can be confirmed by XRD measurement, specifically, it can be confirmed by the method described in the examples.

[0015] The catalyst contains zirconium, and both zirconium and calcium are contained on the catalyst surface. The molar ratio of calcium to zirconium (Ca / Zr) on the catalyst surface is 0.001 or more and 0.269 or less, preferably 0.010 or more and 0.269 or less, more preferably 0.010 or more and 0.266 or less, still more preferably 0.010 or more and 0.250 or less, even more preferably 0.050 or more and 0.200 or less, even more preferably 0.050 or more and 0.150 or less, and even more preferably 0.080 or more and 0.150 or less. When the molar ratio of calcium to zirconium on the catalyst surface is within the above range, the propylene yield can be improved while particularly reducing the generation of impurities. This molar ratio is in terms of metal. That is, the molar ratio is the ratio of the number of moles of calcium (element) contained in the surface of the catalyst to the number of moles of zirconium (element) contained in the surface of the catalyst. The molar ratio of calcium to zirconium on the catalyst surface can be calculated from the XPS measurement results, specifically, it can be calculated by the method described in the examples.

[0016] The molar ratio of calcium to zirconium (Ca / Zr) in the catalyst is preferably from 0.001 / 1 to 0.4 / 1, more preferably from 0.005 / 1 to 0.15 / 1, still more preferably from 0.005 / 1 to 0.10 / 1, even more preferably from 0.005 / 1 to 0.08 / 1, even more preferably from 0.005 / 1 to 0.06 / 1, even more preferably from 0.005 / 1 to 0.05 / 1, even more preferably from 0.005 / 1 to 0.04 / 1, even more preferably from 0.005 / 1 to 0.03 / 1, even more preferably from 0.005 / 1 to 0.02 / 1, even more preferably from 0.008 / 1 to 0.02 / 1. This molar ratio is in terms of metal. That is, the molar ratio is the ratio of the number of moles of calcium (element) contained in the whole catalyst to the number of moles of zirconium (element) contained in the whole catalyst. In the production of the catalyst, the use ratio of the calcium compound and the zirconium compound can be adjusted to obtain the target molar ratio. By using a catalyst in which the molar ratio of calcium to zirconium in the catalyst is within the above range, the crystal structure changes from monoclinic to tetragonal or cubic, and it is considered that the surface oxygen vacancies increase, so the activity increases and propylene can be obtained in a high yield. Furthermore, since the amount of calcium does not exist in excess, it is considered that the reaction is not inhibited and propylene can be obtained in a high yield. As described above, by using a catalyst in which the molar ratio of calcium to zirconium in the catalyst is within the above range, propylene can be produced from ethanol in a high yield, and the generation of by-products can also be suppressed. Also, the molar ratio of calcium to zirconium (Ca / Zr) in the catalyst can be determined by ICP emission spectrometry.

[0017] The BET specific surface area of the catalyst is preferably 10 to 150 m 2 / g, more preferably 15 to 100 m 2 / g, still more preferably 40 to 95 m 2 / g, even more preferably 40 to 90 m 2 / g, even more preferably 40 to 85 m 2 / g, even more preferably 40 to 70 m 2 / g. By using a catalyst with a BET specific surface area within the above range, propylene can be produced from ethanol in a high yield, and the generation of by-products can also be suppressed.

[0018] From the above, the catalyst used in the method for producing propylene according to the present disclosure preferably contains zirconium and calcium, the calcium content is 0.01% by mass or more and 3.3% by mass or less, has a crystal structure, and the crystal structure contains at least one selected from the group consisting of tetragonal crystal and cubic crystal, contains zirconium, and the molar ratio of calcium to zirconium (Ca / Zr) on the catalyst surface is 0.001 or more and 0.269 or less. It is a catalyst for propylene production. Therefore, the catalyst for propylene production is preferably a catalyst for propylene production used in a method for producing propylene by contacting with ethanol. The catalyst for propylene production is more preferably a catalyst for propylene production used in a method for producing propylene by contacting ethanol in a reactor.

[0019] The catalyst may be produced by any method. Preferred production methods of the catalyst include coprecipitation method, sol-gel method, hydrothermal synthesis method, solvothermal method, ion exchange method, and impregnation method. That is, the catalyst used in the production method of the present invention is preferably a catalyst obtained by coprecipitation method, sol-gel method, hydrothermal synthesis method, solvothermal method, ion exchange method, or impregnation method. Among these production methods, coprecipitation method, sol-gel method, hydrothermal synthesis method, and solvothermal method are more preferred, and coprecipitation method, sol-gel method, and hydrothermal synthesis method are even more preferred. As a method for producing a catalyst by coprecipitation, it is preferable to mix a zirconium salt solution and a calcium salt solution, add a base to obtain a zirconium-calcium composite, and then perform a firing treatment to oxidize it to obtain a zirconium-calcium composite oxide.

[0020] <Production conditions of propylene> The method for producing propylene of the present disclosure is a method of bringing ethanol and a catalyst into contact in a reactor to obtain propylene. In the method for producing propylene of the present disclosure, the method of bringing ethanol and the catalyst into contact is not particularly limited, but ethanol may simply be introduced into a reactor filled with the catalyst. Examples of the reactor include a fixed-bed reactor, a fluidized-bed reactor, a batch reactor, a semi-batch reactor, etc. From the viewpoint of propylene productivity, a fixed-bed reactor or a fluidized-bed reactor is preferable, and a fixed-bed reactor is more preferable.

[0021] The state of ethanol as a raw material is not particularly limited, but from the viewpoint of enhancing the production efficiency of propylene and facilitating the reaction, it is preferably a gas during the reaction. In addition, when bringing gaseous ethanol into contact with the catalyst in the reactor, ethanol may be supplied into the reactor in combination with other components. Examples of other components include water, reaction intermediates, carrier gases, etc. Among these, at least one selected from the group consisting of water and reaction intermediates is preferable, and water is more preferable. Acetone is preferable as the reaction intermediate. When the final product contains acetone, it is preferable to recycle the acetone as the reaction intermediate. By recycling acetone, the yield of propylene from ethanol as the raw material can be finally improved. Water is preferably supplied as water vapor, which is gaseous water, during the reaction. Therefore, it is preferable to supply ethanol into the reactor in combination with water, and it is more preferable to supply ethanol into the reactor in combination with water and acetone. The molar ratio of water to ethanol [water / ethanol] when supplied into the reactor is preferably from 20 / 80 to 80 / 20, more preferably from 30 / 70 to 70 / 30, and still more preferably from 40 / 60 to 60 / 40. When the mass ratio of water to ethanol is within the above range, it is preferable because the formation of ethylene can be suppressed. The molar ratio of acetone to ethanol [acetone / ethanol] when supplied into the reactor is preferably from 0 / 100 to 60 / 40, more preferably from 1 / 99 to 20 / 80, and still more preferably from 3 / 97 to 10 / 90. When the mass ratio of acetone to ethanol is within the above range, it is preferable because the reaction of ethanol to the intermediate is promoted and the by-production of by-products is suppressed. Examples of the carrier gas include nitrogen, hydrogen, carbon monoxide, carbon dioxide, etc. Among these, nitrogen, which is an inert carrier gas, is preferable.

[0022] The reaction temperature in the method for producing propylene of the present disclosure is not particularly limited, but is preferably from 300 to 700 °C, more preferably from 350 to 600 °C, and still more preferably from 400 to 500 °C. By reacting within this temperature range, the yield of propylene can be improved.

Examples

[0023] Next, the present disclosure will be described in more detail with reference to examples, but the technology of the present disclosure is not limited by these examples.

[0024] The analysis methods and evaluation methods of the catalysts obtained in the production of the catalysts shown in the examples and comparative examples are as follows. (1) Calcium content in the catalyst Using an ICP emission spectrometer Agilent 5100 (manufactured by Agilent Technologies), the amount of calcium was quantified and the calcium content was calculated. The measurement wavelength of calcium (Ca) in ICP emission spectroscopy was set to 396.847 nm.

[0025] (2) Crystal Structure of Catalyst The total content of tetragonal and cubic crystals in the catalysts used in the examples and comparative examples was determined as follows by X-ray diffraction (XRD measurement). X-ray diffraction (XRD measurement) was performed using an X-ray diffractometer MiniFlex 600 (manufactured by Rigaku Corporation). The measurement was carried out using CuKα radiation under the conditions of a tube voltage of 40 kV, a tube current of 40 mA, and a measurement speed of 5 degrees / min. In the X-ray diffraction pattern, when a monoclinic crystal structure is present, peaks with peak tops at diffraction angles 2θ = 27.90 - 28.40° and 2θ = 31.20 - 31.70°, which are diffraction patterns derived from monoclinic ZrO 2 are detected. When a tetragonal or cubic crystal structure is present, a peak with a peak top at a diffraction angle 2θ = 29.95 - 30.45°, which is a diffraction pattern derived from tetragonal or cubic CaO-ZrO 2 composite oxide, is detected. In addition, the total content of tetragonal and cubic crystals in the present invention was defined by the following formula. Content of tetragonal and cubic crystals = (Peak intensity of peak at diffraction angle 2θ = 29.95 - 30.45°) × 100 / (Peak intensity of peak at diffraction angle 29.95 - 30.45° + Peak intensity of peak at diffraction angle 27.90 - 28.40°)

[0026] (3) Molar Ratio of Calcium to Zirconium (Ca / Zr) on the Catalyst Surface The molar ratio of calcium to zirconium on the catalyst surface was calculated from the peak area ratio derived from the zirconium 3d orbital and calcium 2p orbital of the spectrum obtained by XPS measurement using an X-ray photoelectron spectrometer AXIS-ULTRA (manufactured by KRATOS ANALYTICAL). The specific method is shown below. The catalyst was placed on the measurement stage, installed at a predetermined position with a pressing plate, and introduced into the measurement chamber. The pressure inside the measurement chamber was 1×10 -8 ~1×10 -6It was controlled to Pa, a monochromatic Al source was used as the measurement line source, and the measurement was carried out under the conditions of an anode voltage of 15 kV and an emission of 10 mA. For the spectrum obtained in the above measurement, the background was subtracted by the Scherrer method, and the peak area was calculated. For the peak derived from the zirconium 3p orbital and the peak derived from the calcium 2p orbital, the peak areas were calculated by waveform separation.

[0027] (4) BET specific surface area of the catalyst The specific surface areas of the catalysts of the examples and comparative examples were measured by the BET method using a catalyst analyzer (BELSORP MAX X, manufactured by MicrotracBEL). As a pretreatment, 0.5 g of the catalyst pulverized into powder was heat-treated at 400 °C for 60 minutes while flowing He at a flow rate of 30 mL / min, and then the measurement was carried out.

[0028] (5) Molar ratio of calcium to zirconium (Ca / Zr) in the catalyst Using an ICP emission spectroscopic analyzer Agilent 5100 (manufactured by Agilent Technologies), the amounts of calcium and zirconium were quantified, and the molar ratio was calculated. The measurement wavelengths in ICP emission spectroscopy were 396.847 nm for calcium (Ca) and 343.823 nm for zirconium (Zr).

[0029] (6) Yields of propylene and by-products In the production of propylene shown in the examples and comparative examples, the gas discharged from the reaction tube outlet was analyzed by gas chromatography, and the yields of propylene and by-products (ethylene, acetone, COx, and other by-products) were determined by the following formula. Note that COx is carbon dioxide and carbon monoxide. Other by-products are mainly alkanes, alkenes having 4 to 6 carbon atoms, dienes having 4 to 6 carbon atoms, and aromatic hydrocarbons. (Yield of each product (mol%-C)) = (Number of moles of carbon in each product) / (Number of moles of carbon in the raw material compound used in the reaction) × 100

[0030] [Catalyst] The catalysts used in the examples and comparative examples are as follows. Catalyst 1: Calcium-zirconium catalyst, calcium content; 0.33 mass%, crystal structure; monoclinic, tetragonal and cubic, total content of tetragonal and cubic 19%, molar ratio of calcium to zirconium on the catalyst surface (Ca / Zr) 0.134, BET specific surface area; 47.7 m 2 / g, molar ratio of calcium to zirconium in the catalyst (Ca / Zr) 0.0107, produced by the coprecipitation method. Catalyst 2: Calcium-zirconium catalyst, calcium content; 1.6 mass%, crystal structure; monoclinic, tetragonal and cubic, total content of tetragonal and cubic 99.99%, molar ratio of calcium to zirconium on the catalyst surface (Ca / Zr) 0.206, BET specific surface area; 80.3 m 2 / g, molar ratio of calcium to zirconium in the catalyst (Ca / Zr) 0.0552, produced by the coprecipitation method. Catalyst 3: Calcium-zirconium catalyst, calcium content; 2.6 mass%, crystal structure; tetragonal and cubic, molar ratio of calcium to zirconium on the catalyst surface (Ca / Zr) 0.265, BET specific surface area; 92.8 m 2 / g, molar ratio of calcium to zirconium in the catalyst (Ca / Zr) 0.0911, produced by the coprecipitation method. Catalyst 4: Calcium-zirconium catalyst, calcium content; 3.5 mass%, crystal structure; tetragonal and cubic, molar ratio of calcium to zirconium on the catalyst surface (Ca / Zr) 0.260, BET specific surface area; 102.4 m 2 / g, molar ratio of calcium to zirconium in the catalyst (Ca / Zr) 0.119, produced by the coprecipitation method. Catalyst 5: Zirconium catalyst, calcium-free, crystal structure; monoclinic, BET specific surface area; 51.2 m 2 / g Catalyst 6: Calcium-zirconium catalyst, calcium content; 0.33 mass%, crystal structure; monoclinic, molar ratio of calcium to zirconium on the catalyst surface (Ca / Zr) 0.165, BET specific surface area; 48.9 m 2 / g, molar ratio of calcium to zirconium in the catalyst (Ca / Zr) 0.0107, produced by the impregnation method. Catalyst 7: Calcium-zirconium catalyst, calcium content: 4.0% by mass, crystal structure: monoclinic, tetragonal and cubic, total content of tetragonal and cubic: 18%, molar ratio of calcium to zirconium (Ca / Zr) on the catalyst surface: 0.270, BET specific surface area: 36.4 m 2 / g, molar ratio of calcium to zirconium (Ca / Zr) in the catalyst: 0.138, produced by the impregnation method.

[0031] [Production of Propylene] Examples 1 to 3 and Comparative Examples 1 to 4 A pressurized fixed-bed flow reactor was used. 5.0 g of the catalyst shown in Table 1 was filled into a reaction tube made of stainless steel (SUS316) with an inner diameter of 0.5 inches. While flowing nitrogen at a flow rate of 60 mL / min at 1.5 MPaG, a mixed aqueous solution of ethanol and acetone (ethanol:acetone:water = 47.5:2.5:50 (molar ratio)) was supplied to the reaction tube at a rate of 6 mL / h (as a liquid), and the reaction was carried out at 450°C. The gas discharged from the outlet of the reaction tube was analyzed by gas chromatography to determine the yield.

[0032]

Table 1

[0033] As shown in Table 1, it can be seen that by using the catalysts of the examples, propylene can be produced from ethanol in high yield. It can also be seen that the formation of by-products, particularly the formation of acetone and other by-products (alkanes and alkenes with 4 or more carbon atoms, etc.), can be suppressed. Thus, it can be seen that the catalyst obtained by the production method of the examples can produce propylene from ethanol in high yield and can also suppress the formation of by-products.

Claims

1. A method for producing propylene by bringing ethanol into contact with a catalyst in a reactor, comprising: the catalyst contains zirconium and calcium, and the calcium content is 0.01% by mass or more and 3.3% by mass or less; the catalyst has a crystal structure, and the crystal structure contains at least one selected from the group consisting of tetragonal crystal and cubic crystal; A method for producing propylene, wherein the molar ratio of calcium to zirconium (Ca / Zr) on the catalyst surface is 0.001 or more and 0.269 or less.

2. The method for producing propylene according to claim 1, wherein the reaction temperature is 300 to 700 °C.

3. The method for producing propylene according to claim 1 or 2, wherein ethanol is supplied into the reactor in combination with water.

4. The method for producing propylene according to claim 3, wherein ethanol is further supplied into the reactor in combination with acetone.

5. The method for producing propylene according to any one of claims 1 to 4, wherein the reactor is a fixed-bed reactor.

6. The method for producing propylene according to any one of claims 1 to 5, wherein the catalyst is a catalyst obtained by a coprecipitation method, a sol-gel method, a hydrothermal synthesis method, a solvothermal method, an ion exchange method, or an impregnation method.

7. The method for producing propylene according to any one of claims 1 to 6, wherein the molar ratio of calcium to zirconium (Ca / Zr) in the catalyst is 0.001 / 1 to 0.4 / 1.

8. The BET specific surface area of the catalyst is 10 to 150 m 2 / g, and the method for producing propylene according to any one of claims 1 to 7.

9. A catalyst for propylene production, which contains zirconium and calcium, and the calcium content is 0.01% by mass or more and 3.3% by mass or less; has a crystal structure, and the crystal structure contains at least one selected from the group consisting of tetragonal crystal and cubic crystal; and the molar ratio of calcium to zirconium (Ca / Zr) on the catalyst surface is 0.001 or more and 0.269 or less.

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