Methanol production method

Abstract

The present invention provides a methanol production method in which the stability of a catalyst over time is excellent. The methanol production method according to one embodiment comprises a step for obtaining methanol by bringing a starting gas containing carbon monoxide and hydrogen into contact with a catalyst. The catalyst: 1) contains copper and zinc and has a molar ratio of zinc to copper (Zn / Cu) of 0.3 to 0.45; and 2) has an alkali metal content of 0 to 0.05 mass%.

Description

[Technical Field]

[0001] The present invention relates to a method for producing methanol, which comprises a step of contacting a feed gas containing carbon oxides and hydrogen with a catalyst. [Background technology]

[0002] Methanol is an important industrial basic raw material. Therefore, there has been a demand for a more efficient production process for reasons such as energy conservation and economic efficiency. The general methanol synthesis process uses carbon oxide derived from synthesis gas, which is a carbon source, and hydrogen as the main raw materials. It is known that this synthesis process uses a catalyst consisting of copper and zinc oxide (Cu-ZnO catalyst).

[0003] The reaction of synthesizing methanol from carbon dioxide and hydrogen is known to involve the simultaneous occurrence of the following elementary reactions and their reverse reactions, and proceeds under the influence of chemical equilibrium. CO2+3H2→ CH3OH+H2O CO+H2O → CO2+H2 CO+2H2→ CH3OH

[0004] As a catalyst for promoting the methanol synthesis reaction, for example, Patent Document 1 discloses a catalyst having a molar ratio of zinc to copper of 0.5 to 0.7. According to the same document, the catalyst may have an alkali metal content of 0 to 0.2 mol %. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2013 / 183577 Brochure Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the conventionally known methods for producing methanol, the catalyst life is not necessarily satisfactory, and there has been a demand for a method for producing methanol with better catalyst stability.

[0007] An object of one aspect of the present invention is to provide a method for producing methanol in which the catalyst has high stability over time. [Means for solving the problem]

[0008] The present invention includes the following configurations. <1> 1. A method for producing methanol, comprising: a step of contacting a feed gas containing carbon oxides and hydrogen with a catalyst to obtain methanol, The catalyst is 1) 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 is 0 to 0.05% by mass. 1. A method for producing methanol comprising the steps of: <2> The raw material gas contains water. <1> The method for producing methanol according to claim 1. <3> the alkali metal is sodium; <1> or <2> The method for producing methanol according to claim 1. <4> the content of the sodium in the catalyst is 0.01 to 0.05% by mass; <3> The method for producing methanol according to claim 1. [Effects of the Invention]

[0009] According to one aspect of the present invention, there is provided a method for producing methanol in which the catalyst has high stability over time. DETAILED DESCRIPTION OF THE INVENTION

[0010] An embodiment of the present invention will be described below, but the present invention is not limited thereto. The present invention is not limited to the configurations described below, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. In this specification, unless otherwise specified, "A to B" representing a numerical range means "greater than or equal to A and less than or equal to B."

[0011] [Method for producing methanol] A method for producing methanol according to one embodiment of the present invention includes a step of contacting a feed gas containing carbon oxides and hydrogen with a catalyst containing copper and zinc to obtain methanol. As described below, this catalyst has a specific composition and exhibits excellent stability over time. Therefore, the production method according to one embodiment of the present invention enables stable production over an extended period of time.

[0012] The reaction conditions in this step can be, for example, a reaction temperature of 150 to 300°C and a reaction pressure (gauge pressure) of 0.5 to 10 MPa-G. In the production method according to one embodiment of the present invention, carbon monoxide is usually a by-product. However, depending on the reaction conditions, carbon monoxide may become the main product.

[0013] Examples of reactors used in this step include fixed-bed reactors. Also, reactors having a condensation surface and capable of condensing the produced high-boiling components, including methanol and water, within the reactor are preferably used.

[0014] [Source gas] The raw material gas contains carbon oxide and hydrogen. The carbon oxide is at least one of carbon monoxide and carbon dioxide. When both carbon monoxide and carbon dioxide are used as the carbon oxide, they may be contained in any ratio.

[0015] The molar ratio of hydrogen to carbon oxide in the feed gas is not particularly limited and may be any. The feed gas may contain components other than carbon oxide and hydrogen as long as the amount does not affect the production of methanol. Examples of such components include third components such as nitrogen and impurities such as by-products associated with the production of carbon oxide.

[0016] The feed gas may further contain water. In the production of methanol, it is generally considered preferable to have a feed gas with as little water as possible. However, according to the production method of one embodiment of the present invention, the catalyst stability is maintained even when a feed gas containing a certain amount of water is used.

[0017] 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. 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, 90 kPa or less, 80 kPa or less, 70 kPa or less, 60 kPa or less, or 50 kPa or less.

[0018] Carbon oxide, hydrogen and steam may be introduced into the reactor separately, or may be introduced into the reactor as a mixed gas of any combination.

[0019] 〔catalyst〕 The catalyst for methanol production used in one embodiment of the present invention is a catalyst containing copper and zinc. The copper may be in the form of copper oxide (CuO) or elemental copper (Cu). The components of the catalyst are not limited to the above components and may contain other elements.

[0020] The molar ratio of zinc to copper (Zn / Cu) in the catalyst is 0.30 to 0.45, preferably 0.30 to 0.40. If the molar ratio is too small, aggregation of Cu crystals may occur easily, resulting in a rapid decrease in activity. If the molar ratio is too large, the amount of Cu, the active component, will decrease, which may result in a decrease in activity.

[0021] The catalyst may also contain an alkali metal. The lower limit of the alkali metal content in the catalyst is 0% by mass or more, 0.001% by mass or more, 0.01% by mass or more, or 0.015% by mass or more. The upper limit of the alkali metal content in the catalyst is 0.05% by mass or less, 0.04% by mass or less, or 0.03% by mass or less. If the alkali metal content is too high, aggregation of Cu crystals may occur more easily, which may lead to a rapid decrease in activity. The alkali metal content in the catalyst may be 0% by mass.

[0022] Examples of alkali metals include Na, K and Rb. In one embodiment, the alkali metal is Na.

[0023] [Method for producing catalyst] The method for producing the catalyst for methanol production used in one embodiment of the present invention is not particularly limited, and may be a known method. For example, the catalyst can be produced by precipitating an aqueous acidic salt solution of each metal element constituting the catalyst with a precipitant, followed by drying and calcining (see JP 2010-194421 A).

[0024] [Use of catalyst] In the production method according to one embodiment of the present invention, the catalyst may be used as it is, or may be reduced with a reducing gas (hydrogen, a mixed gas of hydrogen and nitrogen, a gas containing carbon monoxide, etc.) before use. For example, when the catalyst is a CuO-ZnO catalyst, one preferred embodiment is to bring the CuO-ZnO catalyst into contact with a gas containing hydrogen to convert it into a reduced Cu-ZnO catalyst, and then contact it with the raw material gas.

[0025] When the catalyst is packed into the reactor, it may be mixed with various diluents that are inert to the raw material gas and reaction products. Examples of diluents include copper, alumina, zirconia, quartz, glass, and silicon carbide. The shape of the diluent may be granular, spherical, cylindrical, or amorphous. When copper is used as a diluent, this copper is not included in the calculation of the Zn / Cu molar ratio of the catalyst. [Example]

[0026] EXAMPLES The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0027] The residual activity rate in the examples and comparative examples is a value defined by the following formula: The residual activity rate is an index showing the decrease in activity of a catalyst over time, and a higher rate indicates that the catalyst has a more suppressed decrease in activity over time. Residual activity rate (%) = [carbon dioxide conversion rate 15 hours after the start of reaction] / [carbon dioxide conversion rate 2 hours after the start of reaction] × 100

[0028] Example 1 2 g of CuO-ZnO catalyst (Zn / Cu molar ratio: 0.35, sodium content: 0.03 mass%), which had been sieved to a particle size of 0.5 mm to 1.7 mm, was mixed with copper granules (0.8 to 2 mm) to make a total volume of 3 mL. This mixture was packed into a stainless steel single-tube fixed-bed reactor (inner diameter: 12 mm). Next, hydrogen (7 NmL / min) and argon (133 NmL / min) were circulated through the reactor, and the catalyst layer temperature was raised to 150°C. Thereafter, the catalyst was heated at a rate of 1°C / min. 150℃ The temperature was raised from 0°C to 300°C and then held at 300°C for 2 hours.

[0029] A mixed gas consisting of 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 a temperature of 240°C and a gauge pressure of 0.80 MPa-G. 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. In this way, methanol was obtained.

[0030] The conversion rate of the raw material carbon dioxide 2 hours after the start of contact between the raw material gas and the catalyst was 7.7%. The conversion rate of the raw material carbon dioxide 15 hours after the start of contact between the raw material gas and the catalyst was 7.6%. Therefore, the residual activity rate was 99%. Thus, in Example 1, the conversion rate hardly decreased even after 15 hours had passed since the start of supplying the raw material gas.

[0031] Example 2 The same operation as in Example 1 was carried out, except that the sodium content of the CuO-ZnO catalyst used was 0.05% by mass. The conversion rate of the raw material carbon dioxide 2 hours after the start of contact between the raw material gas and the catalyst was 6.7%. The conversion rate of the raw material carbon dioxide 15 hours after the start of contact between the raw material gas and the catalyst was 5.6%. Therefore, the residual activity rate was 84%. Thus, in Example 2, a decrease in conversion rate was observed 15 hours after the start of supplying the raw material gas, but it was within an acceptable level.

[0032] Comparative Example 1 The same operation as in Example 1 was carried out, 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 material carbon dioxide was 5.3% 2 hours after the start of contact between the raw material gas and the catalyst. The conversion rate of the raw material carbon dioxide was 2.3% 15 hours after the start of contact between the raw material gas and the catalyst. Therefore, the residual activity rate was 43%. Thus, in Comparative Example 1, a significant drop in conversion rate was observed 15 hours after the start of feed gas supply.

[0033] Comparative Example 2 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 material carbon dioxide 2 hours after the start of contact between the raw material gas and the catalyst was 4.6%. The conversion rate of the raw material carbon dioxide 15 hours after the start of contact between the raw material gas and the catalyst was 3.4%. Therefore, the residual activity rate was 73%. As described above, in Comparative Example 2, the activity was low, and a significant drop in the conversion rate was observed 15 hours after the start of supplying the raw material gas.

[0034] Example 3 2 g of CuO-ZnO catalyst (Zn / Cu molar ratio: 0.35, sodium content: 0.03 mass%), which had been sieved to a particle size of 0.5 mm to 1.7 mm, was mixed with copper granules (0.8 to 2 mm) to make a total volume of 3 mL. This mixture was packed into a stainless steel single-tube fixed-bed reactor (inner diameter: 12 mm). Next, hydrogen (7 NmL / min) and argon (133 NmL / min) were circulated through the reactor, and the catalyst layer temperature was raised to 150°C. Thereafter, the catalyst was heated at a rate of 1°C / min. 150℃ The temperature was raised from 0°C to 300°C and then held at 300°C for 2 hours.

[0035] At a temperature of 240°C and a gauge pressure of 0.80 MPa-G, a mixed gas consisting of 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. Simultaneously, hydrogen gas at 7 NmL / min was bubbled through water at 25°C, and hydrogen gas containing water equivalent to the saturated water vapor pressure (water pressure 3 kPa) 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 0.08 kPa. In this way, methanol was obtained.

[0036] The conversion rate of the raw material carbon dioxide 2 hours after the start of contact between the raw material gas and the catalyst was 14.5%. The conversion rate of the raw material carbon dioxide 15 hours after the start of contact between the raw material gas and the catalyst was 14.2%. Therefore, the residual activity rate was 98%. Thus, in Example 3, the conversion rate hardly decreased even after 15 hours had passed since the start of supplying the raw material gas.

[0037] Example 4 The same operation as in Example 3 was carried out, 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 was 10.8% 2 hours after the start of contact between the raw gas and the catalyst. The conversion rate of the raw carbon dioxide was 10.3% 15 hours after the start of contact between the raw gas and the catalyst. Therefore, the residual activity rate was 96%. Thus, in Example 4, the conversion rate hardly decreased even after 15 hours had passed since the start of supplying the raw gas.

[0038] Example 5 A reactor with a condensation surface was used, allowing the high-boiling components, including the produced methanol and water, to condense within the reactor. The reactor consisted of 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) arranged concentrically. 1.6 g of CuO-ZnO catalyst (Zn / Cu molar ratio: 0.35, sodium content: 0.03 mass%), sieved to a particle size of 0.5 mm to 1.7 mm, was mixed with copper granules (0.8 mm to 2 mm), and the total volume was adjusted to 18 mL. This mixture was packed between the reactor body and the inner cylinder. The space between the inner cylinder and the cooling tube was hollow, allowing gas and condensed components to move between the catalyst layer and the cooling tube.

[0039] Hydrogen (7 NmL / min) and argon (133 NmL / min) were circulated through the reactor, and the catalyst layer temperature was raised to 150°C. Thereafter, the temperature was raised at a rate of 1°C / min. 150℃ The temperature was raised from 0°C to 300°C and then held at 300°C for 2 hours.

[0040] A mixed gas consisting of carbon dioxide (24% by volume), hydrogen (72% by volume), and nitrogen (4% by volume) was supplied to the reactor at a flow rate of 50 NmL / min at a temperature of 240°C, a cooling water temperature of 10°C, and a gauge pressure of 0.90 MPa-G. 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 196 kPa. In this way, methanol was obtained.

[0041] The conversion rate of the raw material carbon dioxide 2 hours after the start of contact between the raw material gas and the catalyst was 43.6%. The conversion rate of the raw material carbon dioxide 15 hours after the start of contact between the raw material gas and the catalyst was 43.8%. Therefore, the residual activity rate was 100%. Thus, in Example 5, the conversion rate hardly decreased even after 15 hours had passed since the start of supplying the raw material gas.

[0042] Example 6 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%), which had been sieved to a particle size of 0.5 mm to 1.7 mm, was mixed with copper granules (0.8 to 2 mm) to make a total volume of 18 mL. This mixture was filled between the reactor body and the inner cylinder.

[0043] Hydrogen (7 NmL / min) and argon (133 NmL / min) were circulated through the reactor, and the catalyst layer temperature was raised to 150°C. Thereafter, the temperature was raised at a rate of 1°C / min. 150℃ The temperature was raised from 0°C to 300°C and then held at 300°C for 2 hours.

[0044] At a temperature of 240°C, a cooling water temperature of 10°C, and a gauge pressure of 0.90 MPa-G, a mixed gas consisting of 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 50 NmL / min. Simultaneously, hydrogen gas at 7 NmL / min was bubbled through water at 25°C, and hydrogen gas containing water equivalent to the saturated water vapor pressure (water pressure 3 kPa) 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 0.37 kPa. In this way, methanol was obtained.

[0045] The conversion rate of the raw material carbon dioxide was 34.2% two hours after the start of contact between the raw material gas and the catalyst. The conversion rate of the raw material carbon dioxide was 34.2% 15 hours after the start of contact between the raw material gas and the catalyst. Therefore, the residual activity rate was 100%. Thus, in Example 6, the conversion rate hardly decreased even after 15 hours had passed since the start of supplying the raw material gas.

[0046] [Table 1]

[0047] 〔result〕 The difference between Example 1 and Comparative Example 1 was that the sodium concentration in the catalyst in Comparative Example 1 exceeded 0.05 mass %. The difference between Example 1 and Comparative Example 2 was that the Zn / Cu molar ratio of the catalyst in Comparative Example 2 was less than 0.3. The production methods according to Comparative Examples 1 and 2 had significantly lower residual activity rates than the production method according to Example 1. On the other hand, even when production conditions that improved the conversion rate were adopted as in Examples 3 to 6, the production methods according to the examples maintained a sufficient residual activity rate. [Industrial Applicability]

[0048] The present invention can be used for producing methanol.

Claims

[Claim 1] 1. A method for producing methanol, comprising: a step of contacting a feed gas containing carbon oxides, hydrogen, and water with a catalyst to obtain methanol, The catalyst is 1) containing copper and zinc, the molar ratio of zinc to copper (Zn / Cu) being 0.3 to 0.45; 2) The sodium content is 0.01 to 0.04% by mass; 1. A method for producing methanol comprising the steps of:

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