Method for producing methanol

Abstract

The present invention provides a method for producing methanol with a catalyst having high temporal stability. The method for producing methanol in one embodiment of the present invention comprises the following steps: a raw material gas containing carbon oxides and hydrogen is brought into contact with a catalyst to obtain methanol; with respect to the catalyst, 1) the catalyst contains copper and zinc, and the molar ratio of zinc to copper (Zn / Cu) is 0.3 to 0.45; 2) the content of alkali metal in the catalyst is 0 mass % to 0.05 mass %.

Description

Technical Field

[0001] The present invention relates to a method for producing methanol, comprising the step of bringing a raw material gas containing carbon oxides and hydrogen into contact with a catalyst. Background Art

[0002] Methanol is an important basic raw material in industry. Therefore, for reasons such as energy saving and economic efficiency, the production process is required to be highly efficient. In a conventional methanol synthesis process, carbon oxides and hydrogen from synthesis gas as a carbon source are used as main raw materials. It is known that a catalyst containing copper and zinc oxide (Cu-ZnO catalyst) is used in this synthesis process.

[0003] Regarding the reaction of synthesizing methanol from carbon oxides and hydrogen, it is known that the following basic reaction and its reverse reaction occur simultaneously and proceed simultaneously under the influence of chemical equilibrium.

[0004] CO2+3H2→CH3OH+H2O

[0005] CO+H2O→CO2+H2

[0006] CO + 2H2 → CH3OH

[0007] As a catalyst for promoting methanol synthesis reaction, a catalyst having a molar ratio of zinc to copper of 0.5 to 0.7 is disclosed in Patent Document 1. According to the document, the alkali metal content of the catalyst can be 0 mol % to 0.2 mol %.

[0008] Prior art literature

[0009] Patent Literature

[0010] Patent Document 1: International Publication No. 2013 / 183577 Summary of the invention

[0011] Problems to be solved by the invention

[0012] However, in conventionally known methods for producing methanol, the life of the catalyst is not always satisfactory, and there is a demand for a method for producing methanol with better catalyst stability.

[0013] An object of one embodiment of the present invention is to provide a method for producing methanol having a catalyst with high temporal stability.

[0014] Means used to solve problems

[0015] The present invention includes the following configurations.

[0016] <1>

[0017] A method for producing methanol, comprising: bringing a raw material gas containing carbon oxides and hydrogen into contact with a catalyst to obtain methanol, characterized in that:

[0018] 1) The catalyst contains copper and zinc, and the molar ratio of zinc to copper (Zn / Cu) is 0.3 to 0.45;

[0019] 2) The alkali metal content of the catalyst is 0% by mass to 0.05% by mass.

[0020] <2>

[0021] The method for producing methanol according to <1>, wherein the raw material gas contains water.

[0022] <3>

[0023] The method for producing methanol according to <1> or <2>, wherein the alkali metal is sodium.

[0024] <4>

[0025] The method for producing methanol according to <3>, wherein a content of the sodium in the catalyst is 0.01% by mass to 0.05% by mass.

[0026] Effects of the Invention

[0027] According to one embodiment of the present invention, there is provided a method for producing methanol in which the catalyst has high temporal stability. DETAILED DESCRIPTION

[0028] An embodiment of the present invention is described below, but the present invention is not limited thereto. The present invention is not limited to the various structures described below, and various changes can be made within the scope indicated in the claims. The embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. It should be noted that in this specification, unless otherwise specified, "A to B" indicating a numerical range means "above A and below B".

[0029] [Method for producing methanol]

[0030] A method for producing methanol according to an embodiment of the present invention comprises: a step of obtaining methanol by contacting a raw material gas containing carbon oxides and hydrogen with a catalyst containing copper and zinc. As described later, the catalyst has a specific composition and excellent stability over time. Therefore, according to the production method according to an embodiment of the present invention, it is possible to produce stably for a long time.

[0031] The reaction conditions in this step can be set, for example, to a reaction temperature of 150° C. to 300° C. and a reaction pressure (gauge pressure) of 0.5 MPa-G to 10 MPa-G. In the production method of one embodiment of the present invention, carbon monoxide is usually produced as a byproduct. However, depending on the reaction conditions, carbon monoxide may sometimes become a main product.

[0032] As an example of the reactor used in this step, a fixed bed reactor can be cited. In addition, it is also preferable to use a reactor having a condensation surface and capable of condensing high boiling components including generated methanol and water in the reactor.

[0033] [Raw material gas]

[0034] The raw material gas contains carbon oxides and hydrogen. Carbon oxides refer to at least one of carbon monoxide and carbon dioxide. When both carbon monoxide and carbon dioxide are used as carbon oxides, they may be contained in any ratio.

[0035] The molar ratio of hydrogen to carbon oxide in the raw gas is not particularly limited and can be any molar ratio. The raw gas may also contain components other than carbon oxide and hydrogen as long as it does not affect the production of methanol. Examples of such components include third components such as nitrogen, impurities such as by-products accompanying the production of carbon oxides, and the like.

[0036] The raw gas may also contain water. Originally, in the production of methanol, the less water in the raw gas, the better. However, according to the production method of one embodiment of the present invention, even if a raw gas containing a certain amount of water is used, the stability of the catalyst can be maintained.

[0037] The lower limit of the partial pressure of water vapor at the inlet of the reactor is 0.05 kPa or more, 0.5 kPa or more, 5 kPa or more, 10 kPa or more, 20 kPa or more, 30 kPa or more, 40 kPa or more, or 45 kPa or more. In addition, the upper limit of the partial pressure of water vapor at the inlet of the reactor is 300 kPa or less, 200 kPa or less, 150 kPa or less, 100 kPa or less, 90 kPa or less, 80 kPa or less, 70 kPa or less, 60 kPa or less, or 50 kPa or less.

[0038] The carbon dioxide, hydrogen and water vapor may be introduced into the reactor separately or in the form of a mixed gas in any combination.

[0039] [catalyst]

[0040] The catalyst for methanol production used in one embodiment of the present invention is a catalyst containing copper and zinc. Copper may be in the form of copper oxide (CuO) or in the form of a single substance (Cu). The constituent components of the catalyst are not limited to the above components, and may also contain other elements.

[0041] The molar ratio of zinc to copper in the catalyst (Zn / Cu) is 0.30 to 0.45, preferably 0.30 to 0.40. When the molar ratio is too small, it is easy to cause the aggregation of Cu crystals, and sometimes the activity decreases faster. When the molar ratio is too large, the amount of Cu as an active component decreases, so the activity sometimes decreases.

[0042] In addition, the catalyst may also contain an alkali metal. The lower limit of the content of the alkali metal in the catalyst is more than 0 mass %, more than 0.001 mass %, more than 0.01 mass % or more than 0.015 mass %. The upper limit of the alkali metal content in the catalyst is less than 0.05 mass %, less than 0.04 mass % or less than 0.03 mass %. When the alkali metal content is too much, it is easy to cause the aggregation of Cu crystals, and sometimes the activity decreases faster. The alkali metal content in the catalyst can be 0 mass %.

[0043] Examples of alkali metals include Na, K and Rb. In one embodiment, the alkali metal is Na.

[0044] [Method for producing catalyst]

[0045] The method for producing the methanol production catalyst used in one embodiment of the present invention is not particularly limited and may be a known method. For example, the catalyst may be produced by precipitating an acidic salt solution of each metal element constituting the catalyst using a precipitant, followed by drying and calcining (see Japanese Patent Application Laid-Open No. 2010-194421).

[0046] [Use of catalyst]

[0047] In the manufacturing method of one embodiment of the present invention, the above-mentioned catalyst can be used directly in the present invention, or it can be used after being reduced by a reducing gas (hydrogen, a mixed gas of hydrogen and nitrogen, a gas containing carbon monoxide, etc.). For example, when the catalyst is a CuO-ZnO catalyst, as one of the preferred methods, the CuO-ZnO catalyst can be contacted with a gas containing hydrogen to change it into a Cu-ZnO catalyst in a reduced state, and then contacted with the raw material gas.

[0048] When the catalyst is filled into the reactor, various diluents that are inactive to the raw gas and the reaction product may be mixed with the catalyst. As diluents, copper, aluminum oxide, zirconium oxide, quartz, glass, silicon carbide, etc. may be cited. The shape of the diluent may be granular, spherical, cylindrical, etc., irregular shapes, etc. When copper is used as the diluent, the copper is not included in the calculation of the Zn / Cu molar ratio of the catalyst.

[0049] Example

[0050] Hereinafter, the present invention will be described in further detail by way of Examples and Comparative Examples, but the present invention is not limited to these Examples.

[0051] The residual activity ratio in Examples and Comparative Examples is a value defined by the following formula: The residual activity ratio is an index showing the decrease in activity of a catalyst over time, and a higher value indicates a catalyst in which the decrease in activity over time is suppressed.

[0052] Residual activity rate (%) = [carbon dioxide conversion rate at 15 hours after the start of the reaction] / [carbon dioxide conversion rate at 2 hours after the start of the reaction] × 100

[0053] [Example 1]

[0054] 2g of CuO-ZnO catalyst (Zn / Cu molar ratio: 0.35, sodium content: 0.03% by mass) sieved to a particle size of 0.5mm to 1.7mm was mixed with copper particles (0.8mm to 2mm) to a total volume of 3mL. The mixture was filled into a stainless steel single-tube fixed bed reactor (inner diameter: 12mm). Next, hydrogen (7NmL (standard milliliters) / minute) and argon (133NmL / minute) were circulated in the reactor to raise the catalyst layer temperature to 150°C. Then, the temperature was raised from 150°C to 300°C at a heating rate of 1°C / minute, and then maintained at 300°C for 2 hours.

[0055] Under the conditions of a temperature of 240°C and a gauge pressure of 0.80 MPa-G, a mixed gas comprising carbon dioxide (24% by volume), hydrogen (72% by volume) and nitrogen (4% by volume) was supplied to the reactor at a flow rate of 250 NmL / min. At the same time, gasified water was supplied to the reactor at a flow rate of 0.01 g / min. At this time, the water vapor pressure at the reactor inlet was calculated to be 47 kPa. Methanol was obtained by such operation.

[0056] The conversion rate of the raw carbon dioxide 2 hours after the raw gas and the catalyst began to contact was 7.7%. The conversion rate of the raw carbon dioxide 15 hours after the raw gas and the catalyst began to contact was 7.6%. Therefore, the activity residual rate was 99%. It can be seen that in Example 1, even after 15 hours from the start of the supply of the raw gas, the conversion rate was almost not reduced.

[0057] [Example 2]

[0058] The same operation as in Example 1 was performed except that the sodium content of the CuO-ZnO catalyst used was 0.05 mass %. The conversion rate of the raw carbon dioxide 2 hours after the raw gas and the catalyst began to contact was 6.7%. The conversion rate of the raw carbon dioxide 15 hours after the raw gas and the catalyst began to contact was 5.6%. Therefore, the activity residual rate was 84%. It can be seen that in Example 2, the conversion rate decreased at the moment of 15 hours after the supply of the raw gas began, but it was to an acceptable degree.

[0059] [Comparative Example 1]

[0060] The same operation as in Example 1 was performed except that (i) the Zn / Cu molar ratio of the CuO-ZnO catalyst used was 0.34, (ii) the sodium content was 0.06 mass %, and (iii) the inner diameter of the reactor was 15.5 mm. The conversion rate of the raw carbon dioxide 2 hours after the raw gas and the catalyst began to contact was 5.3%. The conversion rate of the raw carbon dioxide 15 hours after the raw gas and the catalyst began to contact was 2.3%. Therefore, the active residual rate was 43%. It can be seen that in Comparative Example 1, the conversion rate was greatly reduced at the moment of 15 hours after the supply of the raw gas began.

[0061] [Comparative Example 2]

[0062] The same operation as in Example 1 was performed except that (i) the Zn / Cu molar ratio of the CuO-ZnO catalyst used was 0.17 and (ii) the sodium content was 0.02 mass %. The conversion rate of the raw carbon dioxide 2 hours after the raw gas and the catalyst began to contact was 4.6%. The conversion rate of the raw carbon dioxide 15 hours after the raw gas and the catalyst began to contact was 3.4%. Therefore, the activity residual rate was 73%. It can be seen that in Comparative Example 2, the activity was low and the conversion rate was greatly reduced after 15 hours from the start of the supply of the raw gas.

[0063] [Example 3]

[0064] 2g of CuO-ZnO catalyst (Zn / Cu molar ratio: 0.35, sodium content: 0.03% by mass) sieved to a particle size of 0.5mm to 1.7mm was mixed with copper particles (0.8mm to 2mm) to a total volume of 3mL. The mixture was filled into a stainless steel single-tube fixed bed reactor (inner diameter: 12mm). Next, hydrogen (7NmL / min) and argon (133NmL / min) were circulated in the reactor to raise the catalyst layer temperature to 150°C. Then, the temperature was raised from 150°C to 300°C at a heating rate of 1°C / min, and then maintained at 300°C for 2 hours.

[0065] Under the condition of temperature of 240 ℃ and gauge pressure of 0.80MPa-G, a mixed gas containing carbon dioxide (24 volume %), hydrogen (72 volume %) and nitrogen (4 volume %) is supplied to the reactor at a flow rate of 250NmL / min. At the same time, 7NmL / min of hydrogen is bubbled in water at 25 ℃, and hydrogen containing water at saturated water vapor pressure (water partial pressure 3kPa) is supplied to the reactor together with the mixed gas. At this time, the water vapor pressure at the reactor inlet is calculated to be 0.08kPa. Methanol is obtained by such operation.

[0066] The conversion rate of the raw carbon dioxide 2 hours after the raw gas and the catalyst began to contact was 14.5%. The conversion rate of the raw carbon dioxide 15 hours after the raw gas and the catalyst began to contact was 14.2%. Therefore, the activity residual rate was 98%. It can be seen that in Example 3, even after 15 hours from the start of the supply of the raw gas, the conversion rate was almost not reduced.

[0067] [Example 4]

[0068] The same operation as in Example 3 was performed except that (i) the Zn / Cu molar ratio of the CuO-ZnO catalyst used was 0.44 and (ii) the sodium content was 0.03 mass %. The conversion rate of the raw carbon dioxide 2 hours after the raw gas and the catalyst began to contact was 10.8%. The conversion rate of the raw carbon dioxide 15 hours after the raw gas and the catalyst began to contact was 10.3%. Therefore, the active residual rate was 96%. It can be seen that in Example 4, even after 15 hours from the start of the supply of the raw gas, the conversion rate was almost not reduced.

[0069] [Example 5]

[0070] A reactor having a condensation surface and capable of condensing high-boiling components including generated methanol and water in the reactor is used. The reactor has a structure having a stainless steel reactor body (inner diameter: 26 mm), a stainless steel punched metal inner cylinder (outer diameter: 15 mm, thickness: 0.5 mm) and a stainless steel cooling tube (outer diameter: 6 mm) in a concentric circle. 1.6 g of CuO-ZnO catalyst (Zn / Cu molar ratio: 0.35, sodium content: 0.03 mass%) sized to a particle size of 0.5 mm to 1.7 mm using a sieve is mixed with copper particles (0.8 mm to 2 mm) to a total of 18 mL. The mixture is filled between the above-mentioned reactor body and the inner cylinder. There is a cavity between the inner cylinder and the cooling tube, and the gas and condensed components can flow back and forth between the catalyst layer and the cooling tube.

[0071] Hydrogen (7 NmL / min) and argon (133 NmL / min) were circulated in the reactor to raise the catalyst layer temperature to 150° C. Then, the temperature was raised from 150° C. to 300° C. at a rate of 1° C. / min and then maintained at 300° C. for 2 hours.

[0072] Under the conditions of temperature: 240°C, cooling water temperature: 10°C, gauge pressure: 0.90MPa-G, a mixed gas containing carbon dioxide (24% by volume), hydrogen (72% by volume), and nitrogen (4% by volume) was supplied to the reactor at a flow rate of 50NmL / min. At the same time, vaporized water was supplied to the reactor at a flow rate of 0.01g / min. At this time, the water vapor pressure at the reactor inlet was calculated to be 196kPa. Methanol was obtained by such operation.

[0073] The conversion rate of the raw carbon dioxide 2 hours after the raw gas and the catalyst began to contact was 43.6%. The conversion rate of the raw carbon dioxide 15 hours after the raw gas and the catalyst began to contact was 43.8%. Therefore, the activity residual rate was 100%. It can be seen that in Example 5, even after 15 hours from the start of the supply of the raw gas, the conversion rate was almost not reduced.

[0074] [Example 6]

[0075] The reactor used in Example 5 was used. 1.6 g of CuO-ZnO catalyst (Zn / Cu molar ratio: 0.35, sodium content: 0.03 mass%) sized to a particle size of 0.5 mm to 1.7 mm using a sieve was mixed with copper particles (0.8 mm to 2 mm) to a total of 18 mL. The mixture was filled between the reactor body and the inner cylinder.

[0076] Hydrogen (7 NmL / min) and argon (133 NmL / min) were circulated in the reactor to raise the catalyst layer temperature to 150° C. Then, the temperature was raised from 150° C. to 300° C. at a rate of 1° C. / min and then maintained at 300° C. for 2 hours.

[0077] Under the conditions of temperature: 240°C, cooling water temperature: 10°C, gauge pressure: 0.90MPa-G, a mixed gas containing carbon dioxide (12% by volume), carbon monoxide (16% by volume), hydrogen (68% by volume), and nitrogen (4% by volume) was supplied to the reactor at a flow rate of 50NmL / min. At the same time, 7NmL / min of hydrogen was bubbled in water at 25°C, and hydrogen containing water at saturated water vapor pressure (water partial pressure 3kPa) was supplied to the reactor together with the mixed gas. At this time, the water vapor pressure at the reactor inlet was calculated to be 0.37kPa. Methanol was obtained by such operation.

[0078] The conversion rate of the raw carbon dioxide 2 hours after the raw gas and the catalyst began to contact was 34.2%. The conversion rate of the raw carbon dioxide 15 hours after the raw gas and the catalyst began to contact was 34.2%. Therefore, the activity residual rate was 100%. It can be seen that in Example 6, even after 15 hours from the start of the supply of the raw gas, the conversion rate was almost not reduced.

[0079] Table 1

[0080] Zn / Cu molar ratio Na concentration Residual activity rate (%) Conversion rate after 2 hours (%) Conversion rate after 15 hours (%) Example 1 0.35 0.03 99 7.7 7.6 Example 2 0.35 0.05 84 6.7 5.6 Example 3 0.35 0.03 98 14.5 14.2 Example 4 0.44 0.03 96 10.8 10.3 Example 5 0.35 0.03 100 43.6 43.8 Example 6 0.35 0.03 100 34.2 34.2 Comparative Example 1 0.34 0.06 43 5.3 2.3 Comparative Example 2 0.17 0.02 73 4.6 3.4

[0081] [result]

[0082] The difference between Example 1 and Comparative Example 1 is that in Comparative Example 1, the sodium concentration in the catalyst is greater than 0.05 mass%. The difference between Example 1 and Comparative Example 2 is that in Comparative Example 2, the Zn / Cu molar ratio of the catalyst is less than 0.3. Compared with the production method of Example 1, the activity residual rate of the production methods of Comparative Examples 1 and 2 is significantly reduced. On the other hand, as shown in Examples 3 to 6, even when the production conditions that increase the conversion rate are adopted, the activity residual rate is fully maintained in the production methods of the Examples.

[0083] Industrial Applicability

[0084] The present invention can be used for the production of methanol.

Claims

1. A method for producing methanol, comprising: bringing a raw material gas containing carbon oxides, hydrogen and water into contact with a catalyst to obtain methanol, wherein: 1) The catalyst contains copper and zinc, and the molar ratio of zinc to copper (Zn / Cu) is 0.3 to 0.45, 2) The alkali metal content of the catalyst is 0.01 mass % to 0.04 mass %, and the alkali metal is sodium.

2. The method for producing methanol according to claim 1, wherein: The molar ratio of zinc to copper (Zn / Cu) is 0.30 to 0.40.