Hydrochloric acid oxidation catalyst and method for producing chlorine

Abstract

This hydrochloric acid oxidation catalyst oxidizes hydrochloric acid. The hydrochloric acid oxidation catalyst includes: a carrier; and copper, an alkali metal, and a rare-earth metal, which are carried on the carrier. The differential value of a spectrum obtained through differential thermal analysis of the hydrochloric acid oxidation catalyst is 0.035 μV / sec or less relative to a baseline.

Description

[Technical Field]

[0001] The present invention relates to a hydrochloric acid oxidation catalyst and a method for producing chlorine, and more particularly to a hydrochloric acid oxidation catalyst for oxidizing hydrochloric acid and a method for producing chlorine using the same. [Background technology]

[0002] Conventionally, a hydrochloric acid oxidation catalyst has been used to oxidize hydrochloric acid with oxygen to obtain chlorine.

[0003] For example, a hydrochloric acid oxidation catalyst in which copper, potassium, and samarium are dispersed in silica has been proposed (see, for example, Patent Document 1 below). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] WO2009 / 041384 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the hydrochloric acid oxidation catalyst described in Patent Document 1 has the drawback that its catalytic activity is significantly reduced over long-term use, resulting in a decrease in the yield of chlorine.

[0006] The present invention provides a hydrochloric acid oxidation catalyst and a method for producing chlorine, which can suppress a decrease in catalytic activity and a decrease in chlorine yield even with long-term use. [Means for solving the problem]

[0007] The present invention (1) is a hydrochloric acid oxidation catalyst for oxidizing hydrochloric acid, comprising a support and copper, an alkali metal, and a rare earth element supported on the support, wherein the hydrochloric acid oxidation catalyst is subjected to differential thermal analysis under the following measurement conditions, and the derivative of the spectrum obtained is 0.035 μV / sec or less relative to a baseline in the range of 290 to 400°C.

[0008] Measurement conditions Reference material: α-alumina Atmosphere: Nitrogen (200 mL / min) Sample amount: 10 mg Heating rate: 15°C / sec Data sampling time: 2 seconds

[0009] The present invention (2) includes the hydrochloric acid oxidation catalyst according to (1), which has an average pore diameter (4V / A) determined by the BET method using a nitrogen adsorption method of 5 nm or more and 30 nm or less.

[0010] The present invention (3) includes the hydrochloric acid oxidation catalyst according to (1) or (2), wherein the support contains alumina.

[0011] The present invention (4) includes a method for producing chlorine, which comprises contacting hydrochloric acid with oxygen in the presence of the hydrochloric acid oxidation catalyst according to (1) or (2).

[0012] The present invention (5) includes the method for producing chlorine according to (4), in which the hydrochloric acid oxidation catalyst is used as a fixed-bed catalyst. [Effects of the Invention]

[0013] The hydrochloric acid oxidation catalyst and the method for producing chlorine of the present invention can suppress the decrease in catalytic activity and the decrease in chlorine yield even after long-term use. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a graph showing the relationship between the temperature and the differential value of the spectrum obtained by differential thermal analysis of the catalyst of Example 1. [Figure 2] FIG. 2 is a graph showing the relationship between the temperature and the differential value of the spectrum obtained by differential thermal analysis of the catalyst of Example 2. [Figure 3] FIG. 3 is a graph showing the relationship between the temperature and the differential value of the spectrum obtained by differential thermal analysis of the catalyst of Comparative Example 1. [Figure 4]FIG. 4 shows a schematic cross-sectional view of a fixed-bed catalytic reactor in the use example and the comparative use example. DETAILED DESCRIPTION OF THE INVENTION

[0015] [Hydrochloric acid oxidation catalyst] The hydrochloric acid oxidation catalyst of the present invention is a catalyst for oxidizing hydrochloric acid. Hereinafter, the hydrochloric acid oxidation catalyst will be simply referred to as the catalyst.

[0016] [Catalyst properties] The catalyst is in the form of particles. That is, the catalyst is made up of a large number of particles. Note that the term "particulate" includes "particles" and "granules." The shape and size of the particles are not limited.

[0017] The catalyst has pores. The average pore diameter (4V / A) determined by the BET method using the nitrogen adsorption method is, for example, 1 nm or more, preferably 5 nm or more, and for example, 100 nm or less, preferably 30 nm or less. If the average pore diameter (4V / A) is equal to or greater than the above-mentioned lower limit, the diffusion and movement of reactants and products can be prevented from slowing down. If the average pore diameter (4V / A) is equal to or less than the above-mentioned upper limit, the diffusion can be accelerated while preventing a decrease in the frequency of arrival at the catalyst surface. Details of the BET method using the nitrogen adsorption method will be described in the Examples below.

[0018] [Carrier, copper, alkali metal, rare earth element] The catalyst comprises a support and copper, an alkali metal and a rare earth element (active components).

[0019] [Carrier] The support maintains the shape of the catalyst. The support has the same average pore diameter as the above-mentioned catalyst. Examples of support materials include alumina, silica-alumina, titania, and zirconia. The support preferably contains alumina from the viewpoint of extending the catalyst life. Specific examples of such supports include alumina and silica-alumina. The proportion of alumina in the silica-alumina is, for example, 1% by mass or more, preferably 5% by mass or more, and 75% by mass or less, preferably 45% by mass or less, and more preferably 25% by mass or less.

[0020] If the support contains alumina, the interaction between the alumina and the active component can suppress the dissipation (volatilization) of the active component even when the catalyst is used for a long period of time. This can extend the catalyst life. The dissipation (volatilization) of the active component is presumed to be due to the melting of the active component, which is solid at 23°C and 101,325 Pa (room temperature and pressure), at high operating temperatures (including the range of 290 to 400°C). The melting is observed using DDTA, which will be described later.

[0021] A more preferred example of the support material is alumina.

[0022] On the other hand, silica may be unsuitable as a carrier material from the viewpoint of extending the catalyst life as described above. If the carrier material is silica, the interaction between the silica and the active component tends to be significantly weak, and the dissipation (volatilization) of the active component may not be suppressed. Therefore, the melting of the active component may be clearly observed by DDTA even at 290 to 400°C (see Comparative Example 1, Figure 3).

[0023] [Active ingredient] Copper, alkali metals, and rare earth elements are the active components of the catalyst and are dispersed (supported) on a carrier. Copper, alkali metals, and rare earth elements exist in a solid state on the surface of the carrier. The copper, alkali metals, and rare earth elements, and their combinations, are described in detail, for example, in WO2009 / 041384.

[0024] Examples of alkali metals include lithium, sodium, potassium, rubidium, cesium, and francium, and preferably potassium.

[0025] The rare earth elements include 17 types, including scandium, yttrium, and lanthanoids (15 types), preferably lanthanoids, more preferably praseodymium, neodymium, lanthanum, europium, and samarium, and even more preferably samarium.

[0026] The respective proportions of copper, alkali metals, and rare earth elements in the catalyst are, for example, 1% by mass or more and 25% by mass or less. The total proportion of copper, alkali metals, and rare earth elements in the catalyst is, for example, 5% by mass or more and 50% by mass or less. The mass proportion of alkali metals relative to 100 parts by mass of copper is, for example, 20 parts by mass or more, preferably 30 parts by mass or more, and for example, 200 parts by mass or less, preferably 180 parts by mass or less. The mass proportion of rare earth elements relative to 100 parts by mass of copper is, for example, 20 parts by mass or more, preferably 30 parts by mass or more, and for example, 350 parts by mass or less, preferably 300 parts by mass or less. When the mass ratio of the rare earth element to 100 parts by mass of copper is equal to or less than the upper limit, the durability of the catalyst can be improved.

[0027] [Differential values ​​of the spectrum in differential thermal analysis of catalyst] The differential value of the spectrum obtained by differential thermal analysis of the catalyst is 0.035 μV / sec or less relative to the baseline in the range of 290 to 400°C.

[0028] If the differential value exceeds 0.035 μV / sec, the dissipation (volatilization) of the active component described above cannot be suppressed during long-term use of the catalyst, and the decrease in chlorine yield cannot be suppressed. In particular, when the catalyst is used in a fixed bed, the movement of hot spots cannot be suppressed during long-term use of the catalyst, and as a result, the decrease in chlorine yield cannot be suppressed.

[0029] As shown in Fig. 4, the hot spot is a high temperature point that occurs due to catalytic activity in the hydrochloric acid oxidation reaction in a catalyst region 4 formed in a fixed-bed catalytic reactor 1 in which a catalyst 3 is provided as a fixed bed. The catalyst region 4 is aligned with the flow direction of chlorine and oxygen.

[0030] The movement of the hot spot refers to the movement of the high temperature point described above downstream in the flow direction. The high temperature point is the part of the catalyst region 4 with the highest catalytic activity. The high temperature point in the initial stage of catalyst use is usually located approximately in the center of the catalyst region 4 in the flow direction. Due to this movement, the part that was the high temperature point in the initial stage of catalyst use loses catalytic activity and its temperature drops due to the dissipation (volatilization) of active components over a long period of catalyst use. With prolonged use of the catalyst, the high temperature point gradually shifts from the initial high temperature point downstream in the flow direction. Eventually, the high temperature point reaches the downstream end of the catalyst region 4 in the flow direction and stops moving thereafter. As a result, the catalytic activity of the entire catalyst region 4 significantly decreases. Therefore, suppressing the movement of the hot spot means that a significant decrease in the catalytic activity of the entire catalyst region 4 can be suppressed.

[0031] Furthermore, when the differential value exceeds 0.035 μV / sec, the spectrum in differential thermal analysis has a large melting peak, which is presumed to cause the dissipation (volatilization) of the active component, i.e., a significant decrease in the catalytic activity of the catalyst.

[0032] On the other hand, the differential value is preferably 0.030 μV / sec or less, more preferably 0.025 μV / sec or less, even more preferably 0.020 μV / sec or less, and particularly preferably 0.015 μV / sec or less. If the differential value is below the upper limit, the dissipation (volatilization) of the active component is sufficiently suppressed, and the decrease in chlorine yield can be reliably suppressed. Furthermore, when the catalyst is used in a fixed bed, the movement of hot spots can be further suppressed, and a significant decrease in catalytic activity can be suppressed.

[0033] The differential thermal analysis is carried out under the following measurement conditions. Measurement conditions Reference material: α-alumina Atmosphere: Nitrogen (200 mL / min) Sample amount: 10 mg Heating rate: 15°C / sec Data sampling time: 2 seconds

[0034] The differential value of the spectrum of the differential thermal analysis of the catalyst is obtained as the DDTA spectrum of the catalyst.

[0035] The baseline is a straight line connecting the average derivative (unit: μV / sec) of the spectrum from 290 to 300°C, which corresponds to 295°C, and the derivative (unit: μV / sec) of the spectrum from 390 to 400°C, which corresponds to 395°C (see Figures 1 to 3).

[0036] The differential value is the length from the above-mentioned baseline to the differential curve of the spectrum at 290 to 400°C.

[0037] In the present invention, this can also be expressed as the maximum differential value of the differential curve of the spectrum from the baseline at 290 to 400° C. being 0.035 μV / sec or less.

[0038] More preferably, the spectrum at 290 to 400° C. contains noise as in Examples 1 and 2 shown in FIGS. 1 and 2, but does not contain a clear peak as in Comparative Example 1 shown in FIG.

[0039] The maximum value of the above-mentioned differential value is obtained by the following steps [1] to [3]. Step [1]: Obtain a DDTA spectrum by differential thermal analysis of the catalyst described above. Step [2] Based on the DDTA spectrum, draw the baseline described above on the chart. Step [3] Identify the DDTA spectrum with the longest distance from the baseline and obtain that distance as the maximum value (μV / sec).

[0040] [Catalyst manufacturing method, oxidation of hydrochloric acid] Next, a method for producing the catalyst will be described.

[0041] First, the carrier and the active components (copper, alkali metal and rare earth element) are prepared.

[0042] The active ingredients are prepared as an active ingredient-containing aqueous solution containing compounds such as their chlorides, oxides, etc. The active ingredient-containing aqueous solution contains acidic water (specifically, hydrochloric acid aqueous solution), and the above-mentioned compounds are dissolved in the acidic water.

[0043] Thereafter, the carrier and the aqueous solution containing the active ingredient are blended, followed by heating and drying. Before heating, the atmosphere therein can be reduced in pressure, if necessary.

[0044] Thereafter, a granular catalyst is obtained in which the active component is dispersed on the support.

[0045] [Catalyst applications] The catalyst may be used in any of a batch system and a flow system (fixed bed, fluidized bed, moving bed), preferably in a flow system, and more preferably in a fixed bed.

[0046] The catalyst is packed, for example, in a fixed bed reactor.

[0047] To oxidize hydrochloric acid using a catalyst, for example, hydrochloric acid and oxygen are contacted in the above-mentioned reactor. When the catalyst is used in a fixed bed, the supply rates of hydrochloric acid and oxygen are not limited. Chlorine is produced by the oxidation of hydrochloric acid. Therefore, in the method for producing chlorine, hydrochloric acid and oxygen are contacted in the presence of a hydrochloric acid oxidation catalyst.

[0048] As a result, hydrochloric acid is oxidized by oxygen to produce chlorine (production of chlorine), with water being produced as a by-product.

[0049] [effect] The differential value of the spectrum obtained by differential thermal analysis of this catalyst under the above conditions is 0.035 μV / sec or less relative to the baseline in the range of 290 to 400°C. This means that the active components (copper, alkali metals, and rare earth elements) supported on the carrier are prevented from melting in the range of 290 to 400°C. Therefore, this catalyst can prevent a decrease in chlorine yield even with long-term use.

[0050] Furthermore, if the average pore diameter of the catalyst is 5 nm or more and 30 nm or less, a reaction field is formed in which reactants and products can easily diffuse and move, and a high chlorine yield can be obtained.

[0051] In this catalyst, if the carrier contains alumina, the interaction between the alumina and the active component can suppress the dissipation (volatilization) of the active component, thereby extending the catalyst life.

[0052] In particular, when the catalyst is used in a fixed bed, the movement of hot spots can be suppressed even with long-term use of the catalyst, and as a result, the decrease in chlorine yield can be suppressed.

[0053] [Variations] If necessary, the catalyst can be heated at a high temperature (pre-treated, calcined). Heating is carried out in the air or in a mixed gas atmosphere of oxygen and nitrogen. The heating temperature is, for example, 200°C or higher, preferably 300°C or higher, and, for example, 600°C or lower, preferably 500°C or lower. The heating time is, for example, 1 hour or higher, preferably 2 hours or higher, and, for example, 10 hours or lower, preferably 5 hours or lower. [Example]

[0054] The present invention will be described in further detail below with reference to examples and comparative examples, but the present invention is not limited thereto. Specific numerical values ​​of the blending ratios (content ratios), physical property values, parameters, etc. used in the following description can be replaced with the upper limit values ​​(numeric values ​​defined as "not more than" or "less than") or lower limit values ​​(numeric values ​​defined as "not less than" or "exceeding") of the corresponding blending ratios (content ratios), physical property values, parameters, etc. described in the above "Form for Carrying Out the Invention." Note that "parts" and "%" are based on mass unless otherwise specified.

[0055] Example 1 According to the formulation shown in Table 1, water, the active ingredient, and an aqueous hydrochloric acid solution were mixed to prepare an aqueous solution containing the active ingredient.

[0056] Thereafter, the aqueous solution containing the active component was mixed with a spherical alumina carrier according to the formulation shown in Table 1. The mixture was then depressurized, heated, dried, and cooled under the conditions shown in Table 2 to obtain a catalyst. The proportions (mass%) of the active components (copper, potassium, and samarium) in the catalyst are shown in Table 3.

[0057] Example 2 and Comparative Example 1 A catalyst was obtained by treating in the same manner as in Example 1, except that the proportion of the active component in the active component-containing aqueous solution and the type of carrier were changed so as to obtain the proportion of the active component shown in Table 3.

[0058] <Evaluation> The catalysts of Examples 1 and 2 and Comparative Example 1 were evaluated for the following items. The results are shown in Table 3.

[0059] (average pore diameter of catalyst) The average pore diameter (4V / A) of the catalyst was determined by the BET method using nitrogen adsorption. The catalyst was calcined in an electric furnace in air at 200°C for 3 hours before being loaded into the measurement container of the measurement device. The measurement device and measurement conditions are as follows:

[0060] Measuring device: BERSORP-max (manufactured by Microtrack Bell) Measurement conditions: Pretreatment: 30°C, 1kPa, 4 hours. Measurement temperature: -196°C

[0061] (Calculation of the maximum differential value of the spectrum in differential thermal analysis) The catalyst was subjected to differential thermal analysis, and the differential value of the spectrum obtained was calculated. In other words, the DDTA spectrum of the catalyst was obtained. The measurement device and measurement conditions are as follows:

[0062] Measurement equipment: TG-DTA TG8120 (Rigaku Corporation) Measurement conditions: Reference material: α-alumina Atmosphere: Nitrogen (200 mL / min) Sample amount: 10 mg Heating rate: 15°C / sec Data sampling time: 2 seconds

[0063] The DDTA spectrum of the catalyst of Example 1 is shown in Figure 1. The DDTA spectrum of the catalyst of Example 2 is shown in Figure 2. The DDTA spectrum of the catalyst of Comparative Example 1 is shown in Figure 3.

[0064] <Examples of use and comparative testing> Each of the catalysts of Examples 1 and 2 and Comparative Example 1 was brought into contact with hydrochloric acid and oxygen while being heated to produce chlorine.

[0065] Specifically, as shown in FIG. 4, a straight tube (an example of a reactor) 2 having a diameter of 1.6 cm was filled with 6 mL (apparent volume) of catalyst 3 to create a catalyst region 4. The length of the catalyst region 4 (the length in the direction in which the straight tube 2 extended) was 3 cm. In this way, a fixed-bed catalytic reactor 1 was produced, which included the straight tube 2, catalyst 3, thermocouple 6, and sheath tube 7. The thermocouple 6 can measure the temperature of the catalyst 3. The thermocouple 6 is movable in the vertical direction relative to the straight tube 2. The sheath tube 7 protects the thermocouple 6. The sheath tube 7 has a cylindrical shape with a bottom. The outer diameter of the sheath tube 7 is 0.4 mm. In the fixed-bed catalytic reactor 1, the catalyst region 4 was disposed at the center of the straight tube 2 in the longitudinal direction.

[0066] The fixed-bed catalytic reactor 1 is also provided with a heating furnace 5 that houses the catalyst region 4 therein. The heating furnace 5 is a temperature-controllable electric furnace. The heating furnace 5 is equipped with a program that raises the temperature inside the heating furnace 5 when the temperature of the catalyst 3 drops during use from the initial temperature set at the start of use so that the temperature of the catalyst 3 becomes the same as the initial temperature set at the start of use.

[0067] Hydrochloric acid and oxygen were each passed through the fixed-bed catalytic reactor 1 at a rate of 45 mL / min from the upper end to the lower end of the fixed-bed catalytic reactor 1. The temperature of the heating furnace 5 was set so that the temperature of the catalyst 3 would become the reaction temperature shown in Table 4.

[0068] The chlorine yields were then determined after 50 hours and after 1500 hours, respectively. The chlorine yields were determined based on the description in WO2009 / 041384.

[0069] <Evaluation of use cases and comparative use cases> The following items were evaluated for Use Examples 1 to 5 and Comparative Use Example 1. The results are shown in Table 4.

[0070] <Move hotspot> The presence or absence of movement of the hot spot below (downstream in the flow direction) and the distance of movement were determined by measuring the temperature distribution of the catalyst 3 by moving the thermocouple 6 vertically.

[0071] <Set temperature difference of the heating furnace> The difference between the furnace set temperature after 50 hours of use and after 1500 hours of use was determined.

[0072] A large difference means a large decrease in catalytic activity after 1500 hours of use.

[0073] [Table 1]

[0074] [Table 2]

[0075] [Table 3]

[0076] [Table 4]

[0077] The above invention is provided as an exemplary embodiment of the present invention, but it is merely an example and should not be interpreted as being limiting. Modifications of the present invention that are obvious to those skilled in the art are included in the scope of the following claims. [Industrial Applicability]

[0078] The hydrochloric acid oxidation catalyst is used in the production of chlorine. [Explanation of symbols]

[0079] 1. Fixed-bed catalytic reactor 3. Catalyst

Claims

1. a hydrochloric acid oxidation catalyst for oxidizing hydrochloric acid; a support made of alumina; copper, an alkali metal, and a rare earth element supported on the support; The average pore diameter (4V / A) determined by the BET method using a nitrogen adsorption method is 5 nm or more and less than 23 nm, The hydrochloric acid oxidation catalyst is subjected to differential thermal analysis under the following measurement conditions, and the derivative of the spectrum obtained is 0.035 μV / sec or less relative to the baseline in the range of 290 to 400° C. Measurement conditions Reference material: α-alumina Atmosphere: Nitrogen (200 mL / min) Sample amount: 10 mg Heating rate: 15°C / sec Data sampling time: 2 seconds

2. A method for producing chlorine, comprising contacting hydrochloric acid with oxygen in the presence of the hydrochloric acid oxidation catalyst according to claim 1.

3. 3. The method for producing chlorine according to claim 2, wherein the hydrochloric acid oxidation catalyst is used as a fixed bed catalyst.

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