Hydrogen cyanide production method

Abstract

To provide a manufacturing method of hydrogen cyanide, that is capable of lowering temperature of a heat medium used more than before, and of suppressing heat medium cost and equipment cost.SOLUTION: A manufacturing method of hydrogen cyanide comprises a step (A) of conducting reaction in a vapor phase while supplying methanol and oxygen to a reaction vessel in the presence of a catalyst containing oxide of molybdenum; and a step (B) of conducting ammoxidation reaction in a vapor phase while supplying methanol, oxygen and ammonia to the reaction vessel, after the step (A). The step (A) and the step (B) are performed in a flow type.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing hydrogen cyanide. [Background technology]

[0002] Nitrile compounds are useful compounds for pharmaceutical and agrochemical intermediates, as well as for raw materials of functional resins, dyes, and pigments. The most inexpensive method for producing these compounds is the vapor-phase ammoxidation of organic compounds having alkyl groups. Various ammoxidation catalysts have been investigated, and numerous improvements have been proposed. Hydrogen cyanide is an important compound used in the production of many fine and specialty chemicals and is also produced by ammoxidation, for example, using methanol, ammonia, and air as feedstocks in a catalytic fluidized bed reactor. There have been various reports on catalysts used in the ammoxidation of methanol. For example, Patent Document 1 proposes a method for producing hydrogen cyanide using a molybdenum-bismuth (Mo-Bi) catalyst as a composite oxide catalyst, and Patent Document 2 proposes a method for producing hydrogen cyanide using a catalyst made by calcining a metal oxide containing iron-antimony (Fe-Sb). Furthermore, Patent Document 3 proposes a method for producing hydrogen cyanide using a catalyst whose main components are manganese (Mn) and phosphorus (P), and Patent Document 4 proposes a method for producing hydrogen cyanide using a catalyst whose main components are vanadium (V) and phosphorus (P). The ammoxidation of methanol is carried out at high temperatures of 400°C or higher in all cases. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-97017 [Patent Document 2] Japanese Patent Application Publication No. 10-251012 [Patent Document 3] Special Publication No. 2010-531290 [Patent Document 4] Japanese Patent Application Publication No. 7-206427 Summary of the Invention [Problem to be solved by the invention]

[0004] Typically, vapor-phase ammoxidation of hydrocarbons requires high reaction temperatures. Methanol ammoxidation is carried out at high temperatures of 400°C or higher. Therefore, the reaction vessel must be heated to 400°C or higher using a heat transfer medium before the reaction begins. Therefore, the heat transfer medium used in the early stages of ammoxidation must be a special one that can be heated to temperatures of 400°C or higher. This increases equipment costs.

[0005] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a method for producing hydrogen cyanide that can lower the temperature of the heat medium used compared to conventional methods, thereby reducing the heat medium costs and equipment costs. [Means for solving the problem]

[0006] As a result of extensive research into solving the above problems, the present inventors have found that the above problems can be solved by the following invention.

[0007] That is, the present invention relates to the following: [1] A method for producing hydrogen cyanide, comprising: step (A) of reacting methanol and oxygen in a gas phase while supplying them to a reactor in the presence of a catalyst containing a molybdenum oxide; and step (B) of, subsequent to step (A), carrying out an ammoxidation reaction in the gas phase while supplying methanol, oxygen, and ammonia to the reactor, wherein steps (A) and (B) are carried out in a flow system. [2] The method for producing hydrogen cyanide according to [1] above, wherein the catalyst containing an oxide of molybdenum contains at least one element selected from tin, titanium, and zirconium. [3] The method for producing hydrogen cyanide according to the above [1] or [2], wherein the reaction initiation temperature in the step (A) is 200 to 300°C, and the reaction temperature of the ammoxidation reaction in the step (B) is 270 to 600°C. [4] The method for producing hydrogen cyanide according to [3] above, wherein in the step (A), the reaction between the methanol and oxygen is initiated in a heated state using a heat medium. [5] The method for producing hydrogen cyanide according to any one of the above [1] to [3], wherein the gas phase reactions in the step (A) and the step (B) are carried out in a fixed-bed flow reactor. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a method for producing hydrogen cyanide in which the temperature of the heat medium used can be lowered compared to conventional methods, thereby reducing the costs of the heat medium and the equipment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, the present invention will be described in detail with reference to an embodiment. <Method of producing hydrogen cyanide> The method for producing hydrogen cyanide of the present embodiment includes: step (A) of reacting methanol and oxygen in a gas phase while supplying them to a reactor in the presence of a catalyst containing a molybdenum oxide; and step (B) of, subsequent to step (A), carrying out an ammoxidation reaction in the gas phase while supplying methanol, oxygen, and ammonia to the reactor, wherein steps (A) and (B) are carried out in a flow system.

[0010] [Process (A)] In step (A), methanol and oxygen are supplied to a reactor in the presence of a catalyst containing molybdenum oxide and reacted in a gas phase. This reaction is an exothermic reaction and is represented by the following formula (1): CH3OH+O2→HCHO+H2O (1) The reactor is heated by the heat of reaction generated in the reaction, and the temperature of the reactor rises to a temperature at which the subsequent reaction in step (B) can proceed. This allows the temperature of the heat medium used in the initial stage of the reaction to be lower than in the past. Therefore, in this embodiment, there is no need to use a special heat medium that can be used at high temperatures, such as molten salt. This makes it possible to produce hydrogen cyanide at low cost. Once the temperature of the reactor has risen to a temperature at which the reaction in step (B) can proceed, the temperature in step (B) is maintained by the heat of reaction, so normal control can be carried out and there is no need to perform step (A) again.

[0011] In step (A), the use of a catalyst containing a molybdenum oxide allows the reaction represented by formula (1) to be carried out efficiently. A known ammoxidation catalyst containing a molybdenum oxide can be used as the catalyst. The catalyst may contain at least one element selected from tin, titanium, and zirconium (hereinafter also referred to as element A). When the catalyst contains element A, the ratio of molybdenum to element A [molybdenum / element A] is preferably 0.1 to 1.0, more preferably 0.1 to 0.7, and even more preferably 0.2 to 0.5, in terms of lowering the reaction temperature. The ratio of molybdenum to element A can be determined by measuring the contents of molybdenum and element A contained in the catalyst using an X-ray fluorescence analyzer. Specifically, the ratio can be measured by the method described in the examples.

[0012] The catalyst can be produced by a known complex polymerization method, for example, as disclosed in JP-A-6-115934. The complex polymerization method uses a metal salt as a raw material for the metal complex, an oxycarboxylic acid that functions as a ligand, and a polyol for forming the complex polymer. For example, the raw material for the molybdenum oxide used in this embodiment is not particularly limited as long as it is completely soluble in a solvent, and the oxide may be used as is, or various compounds that can easily be converted into an oxide may be used. As raw materials for molybdenum oxide, heteropoly acids such as molybdenum trioxide, molybdic silicate, and molybdophosphoric acid, and molybdenum compounds that can be easily converted into oxides such as ammonium molybdate (para)tetrahydrate are preferably used, with ammonium molybdate (para)tetrahydrate being particularly preferred. Preferred hydroxycarboxylic acids include citric acid, tartaric acid, oxalic acid, malic acid, tartronic acid, glyceric acid, hydroxybutyric acid, hydroacrylic acid, lactic acid, glycolic acid, etc. Of these, citric acid is particularly preferred. Preferred polyols include ethylene glycol, propylene glycol, trimethylene glycol, 1,4-butanediol, etc. Among these, ethylene glycol is particularly preferred.

[0013] The metal complex obtained by reacting a molybdenum oxide raw material with an oxycarboxylic acid is polymerized with a polyol in a solvent to form a complex polymer, which is then calcined in an oxygen gas atmosphere. The solvent is not particularly limited, but water or an alcohol is preferred. The firing is carried out at 300 to 800°C for 1 to 10 hours while passing a gas containing oxygen gas through the firing. The firing temperature is preferably 400 to 650°C, and more preferably 450 to 600°C. There are no restrictions on the gas containing oxygen gas, but air is preferred. Pre-firing may be carried out prior to the firing.

[0014] In this embodiment, steps (A) and (B) are carried out in the same reactor in a flow-through manner. In step (A), the temperature of the reactor is raised by the heat of reaction generated by oxidizing methanol, thereby ensuring the reaction temperature required for the subsequent ammoxidation of methanol in step (B). Therefore, a reactor with a large heat storage capacity is preferred. The material of the reactor depends on the type of raw material and the reaction conditions, but generally, stainless steel such as SUS316; nickel, Inconel (registered trademark), Monel, Hastelloy (registered trademark) C, or other nickel-containing metals are used.

[0015] A fixed-bed flow reactor is preferably used as the reactor. Any known gas reaction vessel can be used as this fixed-bed flow reactor without any particular restrictions. The fixed-bed flow reactor is composed of a gas supply and a reactor filled with a catalyst. The reactor is heated from the outside by a heat medium. The gasified methanol and oxygen gas in the gas supply vessel are introduced into a reactor heated by a heat medium, and the mixed gas containing the methanol gas and the oxygen gas comes into contact with a catalyst and reacts continuously in the gas phase.

[0016] In step (A), the reaction initiation temperature is preferably 200 to 300° C., more preferably 200 to 270° C., even more preferably 210 to 250° C., and still more preferably 210 to 240° C. The reaction initiation temperature can be appropriately adjusted by a heat medium.

[0017] Examples of the heat medium include silicone oil, high-pressure water, ionic liquid, sand bath, etc. Among them, silicone oil is preferred from the viewpoints of ease of handling, heat removal / uniform heating, and heat resistance. The temperature of the heat medium is preferably 200 to 300° C., more preferably 200 to 270° C., even more preferably 210 to 250° C., and still more preferably 210 to 240° C. When the temperature of the heat medium is 200° C. or higher, the reaction can proceed, and when the temperature is 300° C. or lower, side reactions due to an increase in reaction temperature can be suppressed. The temperature of the heat medium can be appropriately adjusted by adjusting the temperature setting of the heater for the heat medium.

[0018] The feed composition of methanol and oxygen gas [O2 / CH3OH] is preferably 0.5 to 10.0, more preferably 0.5 to 2.0, and even more preferably 1.0 to 1.2, in molar ratio. When the feed composition of methanol and oxygen gas [O2 / CH3OH] is 0.5 or more, the reaction can be maintained without deactivating the catalyst, and when it is 10.0 or less, excessive oxidation can be suppressed.

[0019] The mixed gas containing methanol and oxygen gas may contain gases other than ammonia as long as they are inert to the reaction. If ammonia is mixed into the mixed gas containing methanol and oxygen gas in step (A), the ammonia may competitively inhibit the adsorption of methanol onto the catalyst surface, lowering the reaction temperature and potentially making it difficult for ammoxidation to proceed in the subsequent step (B). Examples of gases other than ammonia contained in the mixed gas include nitrogen gas, carbon dioxide, and inert gases such as helium and argon. Of these, nitrogen gas is preferred from the viewpoints of cost and safety.

[0020] The linear velocity (LV) of the mixed gas is usually 0.25 to 5.2 m / min, preferably 0.5 to 2.0 m / min. The reaction in step (A) varies depending on the operating conditions, but is usually carried out for 30 to 60 minutes before step (B). The by-product gases containing oxygen gas and unreacted methanol gas may be rendered harmless by a predetermined method and discharged to the outside of the system, or a part or all of the by-product gases may be reused as a mixed gas to be introduced into the reactor.

[0021] During the step (A), the temperature of the catalyst packed in the reactor (catalyst layer temperature) is measured. The measurement can be performed by moving a thermocouple up and down inside an interior tube attached to the reactor. When the catalyst layer temperature in the reactor reaches 250 to 430°C and stabilizes, it is preferable to end the step (A) and proceed to the step (B) immediately. The temperature of the catalyst layer in the reactor at the time of proceeding to step (B) is preferably 260 to 370° C., more preferably 270 to 330° C. If the catalyst layer temperature is 250° C. or higher, the ammoxidation reaction in the subsequent step (B) can proceed sufficiently, and if it is 430° C. or lower, side reactions can be suppressed. The catalyst layer temperature can be appropriately adjusted depending on the type of catalyst, the amount of catalyst, and the inner diameter of the reactor.

[0022] [Process (B)] In step (B), subsequent to step (A), an ammoxidation reaction is carried out in a gas phase while supplying methanol, oxygen, and ammonia to the reactor. Ammonia is further introduced from the gas supply device into the reactor heated in the step (A), and the raw material mixed gas containing methanol, oxygen gas, and ammonia is brought into contact with the catalyst to continuously carry out an ammoxidation reaction in the gas phase. The ammoxidation reaction is initiated under the catalyst layer temperature conditions achieved by the reaction in step (A). When the reaction in step (B) is carried out, the reaction temperature (catalyst layer temperature) rises above the reaction temperature in step (A) due to the heat of reaction from ammoxidation. The reaction temperature for ammoxidation is preferably 270 to 600°C, more preferably 300 to 600°C, even more preferably 320 to 500°C, and still more preferably 320 to 450°C. When the reaction temperature for ammoxidation is 270°C or higher, the reaction can be maintained, and when it is 600°C or lower, sublimation of molybdenum and side reactions can be suppressed.

[0023] In order to improve the reaction rate, the concentration of methanol in the raw material mixed gas in step (B) is preferably 1 to 15 mol %, more preferably 5 to 15 mol %, and even more preferably 5 to 12 mol %. The amount of oxygen gas used, in terms of the molar ratio to methanol [O2 / CH3OH], is preferably 1 to 10, more preferably 1 to 6, and even more preferably 1 to 4. When the amount of oxygen gas used is within the above range, the reaction can be maintained without reducing the catalyst. The amount of ammonia used, in terms of the molar ratio to methanol [NH3 / CH3OH], is preferably 0.5 to 3.0, more preferably 0.6 to 2.5, and even more preferably 0.8 to 2.0. When the amount of ammonia used is within the above range, the ammoxidation reaction can be maintained.

[0024] The contact time between the raw material mixed gas and the catalyst is preferably 0.1 to 25 seconds, more preferably 0.1 to 10 seconds. The gas hourly space velocity (SV) is preferably 1,000 to 20,000 Hr. -1More preferably, 2000 to 9000 hours -1 is. The ammoxidation reaction can be carried out under normal pressure, elevated pressure, or reduced pressure, but is preferably carried out within a range of normal pressure to 300 kPaG (gauge pressure).

[0025] The reaction product can be collected, for example, by washing the reaction product gas with a solvent such as water and collecting it. The collected reaction product can be purified by a known method such as distillation to obtain the target product, hydrogen cyanide. [Example]

[0026] The present invention will now be described in detail with reference to examples, but the present invention is not limited to these examples in any way.

[0027] [Catalyst production] <Catalyst 1> 9.93 g of ethylene glycol (Fujifilm Wako Pure Chemical Corporation), 0.71 g of ammonium molybdate (para)tetrahydrate (Fujifilm Wako Pure Chemical Corporation), 7.68 g of citric acid (Kanto Chemical Co., Ltd.), and 25 ml of water were placed in a silica-alumina container and heated with stirring at 60 °C until dissolved. After cooling to room temperature (25 °C), 3.62 g of tin chloride dihydrate (Kanto Chemical Co., Ltd.) was added and heated with stirring at 100 °C until dissolved. The molybdenum metal content was 20 mol% of the total metals, and the molar ratio of total metals to citric acid and ethylene glycol was 1 / 2 / 8. The mixture was then heated at 150 °C until a viscous polymer-like solid was formed. The heating temperature was gradually increased to 350 °C, and the polymer was carbonized to obtain a catalyst precursor. The obtained catalyst precursor was heated in a muffle furnace in an air atmosphere from room temperature (25°C) to 500°C over 50 minutes, and then calcined at 500°C for 6 hours to prepare an ammoxidation catalyst. The catalyst was then crushed in a mortar to prepare Catalyst 1 (molybdenum-tin catalyst). The molar ratio of molybdenum to tin was 0.35.

[0028] <Catalyst 2> Catalyst 2 (molybdenum-titanium catalyst) was prepared in the same manner as catalyst 1, except that 4.7 g of titanium chloride (Fujifilm Wako Pure Chemical Industries, Ltd.) was used instead of tin chloride dihydrate. The molar ratio of molybdenum to titanium was 0.23.

[0029] <Catalyst 3> Catalyst 3 (molybdenum-zirconium catalyst) was prepared in the same manner as Catalyst 1, except that 3.7 g of zirconium chloride (Fujifilm Wako Pure Chemical Industries, Ltd.) was used instead of tin chloride dihydrate. The molar ratio of molybdenum to zirconium was 0.25.

[0030] [Catalyst analysis] The catalysts 1 to 3 were analyzed for composition by the fundamental parameter (FP) method using an XRF (X-ray fluorescence analyzer) (Rigaku Corporation, product name: RIGAKU ZSX PrimusIV X-ray fluorescence analyzer), and the molybdenum metal content [mol%] relative to total metals and the content [mol%] of element A were calculated. The specific surface areas of catalysts 1 to 3 were also measured by the BET single-point method using nitrogen adsorption using a specific surface area analyzer (Microtrac-Bell Corporation, product name: BELSORP MINI II). The results are shown in Table 1 below.

[0031] [Table 1]

[0032] [Production of hydrogen cyanide] In the following examples and comparative examples, an atmospheric pressure fixed-bed flow reactor was used as the reactor. The reactor tube was a stainless steel tube with an outer diameter of 19.1 mm and a length of 27.0 mm, with a stainless steel tube with an outer diameter of 3.0 mm fixed inside so that the reaction temperature in the catalyst layer could be measured. The reactor tube was heated externally in a silicone oil bath. The results obtained in Examples 1 to 3 are shown in Table 2.

[0033] Example 1 The reaction tube was filled with 1.0 g of the catalyst 1 prepared above, and the flow rates of oxygen gas and nitrogen gas were adjusted. The gas was passed through a vaporizer heated to 200°C and then sent to the catalyst bed from the side of the reactor. The catalyst bed temperature at this time was 217°C, which was the reaction initiation temperature. After the temperature stabilized, methanol was passed through a vaporizer heated to 200°C and gasified, and additional methanol was sent to the catalyst bed. During this process, the reaction temperature rose due to the oxidation of methanol, and the catalyst bed temperature (methanol oxidation reaction temperature) reached 278°C. The total amount of gas supplied was 220 mL / min, with a feed composition (molar ratio) of CH3OH:O2:N2 = 1:1.2:6.7.

[0034] Next, after the temperature stabilized, ammonia gasified through a vaporizer heated to 200°C was added to a gas mixture containing oxygen gas, nitrogen gas, and methanol, and the resulting mixture was sent to the catalyst bed as a raw material gas mixture. The reaction temperature rose due to the ammoxidation of methanol, and the catalyst bed temperature (methanol ammoxidation reaction temperature) reached 426°C. The total amount of the raw material gas mixture was CH3OH:NH3:O2:N2 = 1:1.1:1.2:6.7 in molar ratio at 220 mL / min. The gas hourly space velocity (SV) was 4519 Hr -1 The contact time between the raw material mixed gas and the catalyst was 0.44 seconds. The reaction gas that passed through the reaction tube was trapped with an acidic aqueous solution of hydrochloric acid, and the gas that escaped through the trap was collected. The reaction gas was analyzed. 96.6% of the methanol added was converted into hydrogen cyanide. The yield of hydrogen cyanide was 52.3%.

[0035] Example 2 The reaction was carried out in the same manner as in Example 1, except that 1.0 g of catalyst 2 was used instead of catalyst 1, to obtain hydrogen cyanide (yield: 31.8%).

[0036] Example 3 The reaction was carried out in the same manner as in Example 1, except that 1.0 g of catalyst 3 was used instead of catalyst 1, to obtain hydrogen cyanide (yield: 22.5%).

[0037] (Comparative Example 1) A reaction tube was filled with 1.0 g of the catalyst 1 prepared above, and oxygen gas, nitrogen gas, and ammonia were each adjusted in flow rate and passed through a vaporizer heated to 200°C before being sent to the catalyst layer. The catalyst layer temperature at this time was 217°C, which was the reaction initiation temperature. Due to the presence of ammonia, the reaction between methanol and oxygen gas did not proceed, and the reaction temperature only rose to 220°C. It was determined that the ammoxidation reaction had not taken place, and the reaction was terminated. The total amount of gas supplied was 220 mL / min, and the feed composition (molar ratio) was CHOH:NH:O:N = 1:1.1:1.2:6.7. The gas hourly space velocity (SV) was 4519 Hr -1 The contact time between the raw material gas mixture and the catalyst was 0.44 seconds.

[0038] [Methanol conversion rate] The conversion rate of methanol was calculated from the following formula (1). Methanol conversion rate (%) = reacted methanol concentration (mol%) / supplied methanol concentration (mol%) × 100 (1)

[0039] [Yield of hydrogen cyanide] The yield of hydrogen cyanide (HCN) was calculated from the following formula (2). Hydrogen cyanide yield (%) = hydrogen cyanide concentration (mol%) produced / methanol concentration (mol%) supplied × 100 (2)

[0040] [Selectivity to hydrogen cyanide] The selectivity for hydrogen cyanide (HCN) was calculated from the following formula (3). Selectivity of hydrogen cyanide (%) = Yield of hydrogen cyanide (%) / Conversion of methanol (%) × 100 (3)

[0041] [Table 2]

Claims

1. a step (A) of reacting methanol and oxygen in a gas phase while supplying them to a reactor in the presence of a catalyst containing molybdenum oxide; Following the step (A), a step (B) is carried out in a gas phase while supplying methanol, oxygen, and ammonia to the reactor, A method for producing hydrogen cyanide, characterized in that the step (A) and the step (B) are carried out in a flow system.

2. 2. The method for producing hydrogen cyanide according to claim 1, wherein the catalyst containing an oxide of molybdenum contains at least one element selected from the group consisting of tin, titanium, and zirconium.

3. In the step (A), the reaction initiation temperature is 200 to 300°C, 3. The method for producing hydrogen cyanide according to claim 1, wherein the reaction temperature of the ammoxidation reaction in step (B) is 270 to 600°C.

4. 4. The method for producing hydrogen cyanide according to claim 3, wherein in the step (A), the reaction between the methanol and oxygen is initiated in a heated state using a heat medium.

5. The method for producing hydrogen cyanide according to any one of claims 1 to 3, wherein the gas-phase reactions in the step (A) and the step (B) are carried out in a fixed-bed flow-type reactor.

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