Concentration ratio measurement method and concentration ratio measurement device

Abstract

Disclosed is a concentration ratio measurement method for measuring the concentration ratio of a solution that contains toluene or methylcyclohexane, the concentration ratio measurement method comprising: a step for measuring the absorbance of the solution at a specific wavelength; and a step for calculating the concentration ratio t:m of the concentration t of the toluene to the concentration m of the methylcyclohexane on the basis of a calibration curve that is recorded in advance on the basis of the absorbance. The specific wavelength is at least one wavelength or wavelength range in the wavelength range of 1,120 nm to 1,140 nm inclusive, the wavelength range of 1,190 nm to 1,230 nm inclusive, the wavelength range of 1,620 nm to 1,680 nm inclusive, the wavelength range of 1,730 nm to 1,850 nm inclusive, the wavelength range of 1,800 nm to 2,050 nm inclusive, the wavelength range of 2,150 nm to 2,180 nm inclusive, and the wavelength range of 2,360 nm to 2,420 nm inclusive.

Description

Concentration ratio measuring method and concentration ratio measuring device

[0001] The present disclosure relates to a concentration ratio measurement method and a concentration ratio measurement device.

[0002] The use of hydrogen energy is being promoted as a decarbonized energy source. Hydrogen has a low energy density in gaseous form and is difficult to transport, so a technology known as the organic hydride system has been reported as a hydrogen storage and transportation technology, in which hydrogen is reacted with toluene to synthesize methylcyclohexane as a hydrogen storage medium, the methylcyclohexane is transported, and hydrogen is extracted from the methylcyclohexane by dehydrogenation (see, for example, Patent Document 1).

[0003] As a method for determining the concentration ratio of toluene to methylcyclohexane in a synthesis reaction or dehydrogenation reaction of methylcyclohexane, a method is known in which the reaction solution after synthesis is measured using a mass spectrometer such as gas chromatography to determine the concentrations of toluene and methylcyclohexane in the reaction solution, and the conversion rate is calculated from the concentrations of both (see, for example, Patent Document 2).

[0004] JP 2021-095329 A JP 2020-159743 A

[0005] However, in the conventional gas chromatography measurement method, the concentration of the component to be measured in the measurement sample must be sufficiently low, so the measurement sample must be sampled, sufficiently diluted with a solvent, and then submitted to a gas chromatography device. Therefore, although the conventional measurement method has high measurement accuracy, it is unable to measure concentrations over a wide concentration range in real time, and has problems in that it is difficult to automate.

[0006] An object of the present disclosure is to provide a concentration ratio measurement method and a concentration ratio measurement device that can measure the concentration ratio of a solution containing toluene or methylcyclohexane in real time over a wide concentration range.

[0007] As a means for solving the above-mentioned problems, a concentration ratio measurement method according to one embodiment of the present disclosure is a concentration ratio measurement method for measuring the concentration ratio of a solution containing toluene to methylcyclohexane, comprising the steps of: measuring the absorbance of the solution at a specific wavelength; and calculating, based on the absorbance and a pre-recorded calibration curve, the concentration ratio t:m of the toluene concentration t and the methylcyclohexane concentration m, wherein the specific wavelength is one or more wavelengths or wavelength ranges selected from the wavelength ranges of 1120 nm to 1140 nm, 1190 nm to 1230 nm, 1620 nm to 1680 nm, 1730 nm to 1850 nm, 1800 nm to 2050 nm, 2150 nm to 2180 nm, and 2360 nm to 2420 nm.

[0008] According to the present disclosure, it is possible to provide a concentration ratio measurement method and a concentration ratio measurement device that can measure the component concentrations of a solution containing toluene or methylcyclohexane in real time over a wide concentration range.

[0009] 9 is a schematic diagram showing an example of a concentration ratio measuring device in a first embodiment. It is a schematic diagram showing an example of a concentration ratio measuring device in a second embodiment. It is a schematic diagram showing another example of the concentration ratio measuring device in the first embodiment. It is a schematic diagram showing another example of the concentration ratio measuring device in the first embodiment. It is a flowchart showing an example of a concentration ratio measuring method in a seventh embodiment. It is a flowchart showing another example of a concentration ratio measuring method in the seventh embodiment. It is a graph showing the relationship between the concentration ratio of toluene and methylcyclohexane and the absorbance. It is a graph showing the relationship between the concentration ratio of toluene and methylcyclohexane, the absorbance, and the coefficient of determination. It is a graph showing the relationship between the absorbance and the coefficient of determination in a wavelength range with a wavelength width of 10 nm. It is a graph showing the relationship between the absorbance and the coefficient of determination in a wavelength range with a wavelength width of 20 nm. It is a graph showing the characteristics of an example of a bandpass filter for concentration ratio measurement in a fourth embodiment. It is a graph showing the characteristics of another ... wavelength range in which the coefficient of determination is 0.8 or less in the graph of FIG. 13 is a flowchart showing an example of a concentration ratio measurement method according to a thirteenth embodiment; FIG. 14 is a schematic diagram showing an example of a concentration ratio measurement device according to a thirteenth embodiment; FIG. 15 is a graph showing the characteristics of an example of a cutoff filter for measuring concentration ratios according to a fourth embodiment; FIG. 16 is a graph showing the characteristics of another example of a cutoff filter for measuring concentration ratios according to the fourth embodiment; FIG. 17 is a diagram showing an example of an organic hydride manufacturing apparatus having a concentration ratio measurement device according to the present embodiment; FIG. 18 is a graph showing the relationship between wavelength and absorbance for toluene, methylcyclohexane, water, and hydrogen; FIG. 19 is a graph showing the relationship between the concentration ratio of toluene and methylcyclohexane and the slope of absorbance; FIG. 19 is a flowchart showing an example of a concentration ratio measurement method according to a thirteenth embodiment;

[0010] Hereinafter, each embodiment will be described with reference to the accompanying drawings. In this specification and drawings, components having substantially the same functional configurations are designated by the same reference numerals, and redundant description will be omitted.

[0011] (Concentration ratio measurement method and concentration ratio measurement device) The concentration ratio measurement method of the present disclosure includes an absorbance measurement step and a concentration ratio calculation step, and further includes other steps such as a specific wavelength setting step and a calibration curve creation step as necessary. The concentration ratio measurement device of the present disclosure includes an absorbance measurement unit and a concentration ratio calculation unit, and further includes other components as necessary. Below, matters common to the concentration ratio measurement method and the concentration ratio measurement device will be described together.

[0012] - Synthesis reaction of methylcyclohexane and dehydrogenation reaction - First, the synthesis reaction of methylcyclohexane as a hydrogen storage material and the dehydrogenation reaction, which is the reaction to extract hydrogen, will be described. ６ H ５ CH ３ ) and hydrogen (H ２ ) to produce methylcyclohexane (C ６ H １１ CH ３ The reaction for synthesizing 2-(2-hydroxybenzoyl)-2-propanol (also referred to as hydrogenation reaction) is represented by the following reaction formula (1).

[0013] <Reaction formula (1)> C ６ H ５ CH ３ + 3H ２ → C ６ H １１ CH ３

[0014] The methylcyclohexane synthesis reaction can be carried out by known methods, such as reacting toluene with hydrogen; or synthesizing methylcyclohexane from water and toluene without using hydrogen gas by directly electrochemically reacting toluene. Once the hydrogenation reaction begins, the reaction system must usually be cooled because the hydrogenation reaction itself is exothermic. If the reaction temperature significantly exceeds the boiling point of methylcyclohexane (100.9°C) at atmospheric pressure, the synthesis efficiency of methylcyclohexane (hereinafter sometimes referred to as "conversion rate") decreases. Therefore, it is preferable to maintain the reaction temperature so that it does not rise too much, for example, by using a cooling device or a cooling water line. The reaction temperature is usually 80°C to 100°C, preferably 85°C to 98°C, and more preferably 85°C to 96°C.

[0015] The dehydrogenation reaction for extracting hydrogen from methylcyclohexane is represented by the following reaction formula (2), which is the reverse reaction of the above reaction formula (1). The dehydrogenation reaction can be carried out by a known method.

[0016] <Reaction formula (2)> C ６ H １１ CH ３ → C ６ H ５ CH ３ + 3H ２

[0017] The concentration ratio measurement method and concentration ratio measurement device can be suitably applied to measuring the concentration ratio of toluene to methylcyclohexane in a solution resulting from such a methylcyclohexane synthesis reaction or dehydrogenation reaction. The concentration ratio measurement method and concentration ratio measurement device can measure the concentration ratio over a wide concentration range from 0% to 100% by volume of methylcyclohexane without the dilution process required in the conventional gas chromatography measurement method, thereby enabling real-time measurement and automated measurement. By measuring the concentration ratio in the solution after the reaction, the conversion rate and dehydrogenation efficiency of methylcyclohexane in the resulting reaction solution can be easily evaluated over a wide concentration range. The ability to measure the concentration ratio in the solution during the reaction process in real time allows for optimization of the reaction apparatus and reaction conditions.

[0018] First Embodiment As shown in FIG. 1 , a concentration ratio measurement device 10 according to an embodiment of the present disclosure will be described using an example embodiment in which a concentration ratio measurement method is implemented to obtain the concentration ratio t:m between the toluene concentration t and the methylcyclohexane concentration m in a solution S flowing through a flow-through measurement cell 1a. The concentration ratio measurement device 10 includes an absorbance measurement unit 1 that measures the absorbance of the solution S at a specific wavelength, and a concentration ratio calculation unit 2 that calculates the concentration ratio t:m between the toluene concentration t and the methylcyclohexane concentration m in the solution S based on the measured absorbance and a pre-recorded calibration curve. The absorbance measurement unit 1 includes a flow-through measurement cell 1a through which the solution S flows, a light source 1b that irradiates the solution S flowing through the measurement cell 1a with a light beam L1, and an absorbance detector 1c that receives transmitted light L2 transmitted through the solution S. The device may further include a memory unit 5 that stores the calibration curve.

[0019] Here, the light beam L1 includes light of specific wavelengths, which are one or more wavelengths or wavelength ranges in the near-infrared wavelength range of 1120 nm to 1140 nm, 1190 nm to 1230 nm, 1620 nm to 1680 nm, 1730 nm to 1850 nm, 1800 nm to 2050 nm, 2150 nm to 2180 nm, and 2360 nm to 2420 nm. The absorbance detector 1c receives the transmitted light L2 and detects and measures the absorbance at the specific wavelengths based on the optical path length D.

[0020] The concentration ratio calculation unit 2 and the storage unit 5 may be a single device that also includes an operation unit and a display unit, and may further include a control unit that controls the operation of the absorbance measurement unit. The concentration ratio calculation unit 2 and the storage unit 5 may be incorporated into a single computer. The absorbance measurement unit 1 may be a single device, and the absorbance measurement unit 1 and the concentration ratio calculation unit 2 may be connected to each other via wire or wirelessly.

[0021] The absorbance may be highly dependent on the temperature of the solution. Furthermore, when a solution in the reaction process of the synthesis reaction or dehydrogenation reaction of methylcyclohexane flows through the measurement cell 1a, the temperature of the solution in the reaction process may be as high as 80°C or higher. Therefore, in order to accurately measure the absorbance, the temperature of the solution S flowing through the measurement cell 1a may be kept constant by, for example, placing a heat exchanger upstream of the measurement cell 1a. The constant temperature is not particularly limited and can be appropriately selected depending on the purpose, as long as a stable absorbance can be obtained, and may be, for example, about 25°C.

[0022] [Second Embodiment] The concentration ratio measuring device 10 in the first embodiment is an embodiment in which the absorbance of the solution S flowing through a flow-through type measurement cell 1a is continuously measured, but the present invention is not limited to this embodiment. As shown in Fig. 2, a concentration ratio measuring device 20 in the second embodiment may be an embodiment in which a batch-type concentration ratio measuring method is performed in which a light beam L1 is transmitted to the solution S sampled in a preparative type measurement cell 1a' and transmitted light L2 transmitted through the solution S is received.

[0023] The concentration ratio measuring device 20 shown in Fig. 2 can appropriately adopt a configuration similar to that of the concentration ratio measuring device 10 shown in Fig. 1, except that it has a preparative measurement cell 1a' instead of the flow-through measurement cell 1a. Here, the method for sampling the solution S into the preparative measurement cell 1a' is not particularly limited, and may be performed manually or automatically.

[0024] <Solution> The solution containing toluene or methylcyclohexane that is the measurement target is a solution containing at least one of toluene and methylcyclohexane, and may be a solution containing either toluene or methylcyclohexane, or may contain both toluene and methylcyclohexane, and the concentration ratio t:m between the concentration t of toluene and the concentration m of methylcyclohexane may be any concentration ratio, and measurement can be performed suitably in either case.

[0025] The solution contains at least one of toluene and methylcyclohexane, and may further contain other components as necessary, but preferably consists essentially of at least one of toluene and methylcyclohexane. The content of at least one of toluene and methylcyclohexane in the solution is preferably 95% by volume or more, more preferably 98% by volume or more, and even more preferably 99% by volume or more, in terms of volume ratio to the total amount of the solution.

[0026] The other components are not particularly limited and can be appropriately selected depending on the purpose. Examples include by-products such as benzene and methane; and components derived from catalysts and reaction equipment in the synthesis reaction and dehydrogenation reaction of methylcyclohexane.

[0027] <Absorbance measurement step and absorbance measurement unit> The absorbance measurement step is a step of measuring the absorbance of the solution at a specific wavelength, and can be suitably performed by the absorbance measurement unit. The absorbance measurement unit is a unit that measures the absorbance of the solution at a specific wavelength, and specifically, it preferably includes a measurement cell, a light source that irradiates the solution contained in the measurement cell with light of a specific wavelength, and an absorbance detector that measures the absorbance of light transmitted through the solution, and further includes a lens, a spectroscope, an optical fiber, etc. as necessary.

[0028] The specific wavelengths are one or more wavelengths or wavelength ranges in the wavelength ranges of 1120 nm or more and 1140 nm or less, 1190 nm or more and 1230 nm or less, 1620 nm or more and 1680 nm or less, 1730 nm or more and 1850 nm or less, 1800 nm or more and 2050 nm or less, 2150 nm or more and 2180 nm or less, and 2360 nm or more and 2420 nm or less.

[0029] As will be apparent from the examples shown below, the specific wavelength is a wavelength or wavelength range in which a good correlation is obtained between the absorbance and the concentration ratio t:m, where t is the concentration of toluene and m is the concentration of methylcyclohexane, and the coefficient of determination is close to 1. Therefore, by measuring the absorbance of the solution at the specific wavelength and calculating the concentration ratio t:m based on this, it is possible to measure the concentration ratio over a wide concentration range of methylcyclohexane from 0% to 100% by volume, and also to measure the concentration ratio in real time without pretreatment of the solution.

[0030] In addition, if the solution contains other components that affect the absorbance of the solution at wavelengths specific to those components, a concentration ratio measurement method with high measurement accuracy can be implemented by setting the specific wavelength so as not to include wavelengths specific to those components.

[0031] <<Measurement Cell>> The measurement cell is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include flow-through measurement cells, preparative measurement cells, etc. The material of the light transmitting portion of the measurement cell can be appropriately selected depending on the specific wavelength, solution composition, etc., and examples thereof include quartz glass, etc.

[0032] <<Light Source>> The light source is not particularly limited and can be appropriately selected depending on the purpose as long as it has a specific wavelength. Examples of the light source include monochromatic light sources such as laser light and light-emitting diodes (LEDs); and continuous light such as halogen lamps.

[0033] <<Lens>> The lens can be placed at each position on the optical path to converge or collimate light such as light irradiated from the light source, light irradiated onto the measurement cell, transmitted light that has passed through the measurement cell, and light input to the absorbance detector.

[0034] <<Spectrometer>> The spectrometer is not particularly limited and can be appropriately selected depending on the purpose as long as it transmits specific wavelengths. Examples include optical filters, prisms, diffraction gratings, etc. These may be used alone or in combination of two or more types. Examples of the optical filter include bandpass filters that transmit specific monochromatic light or multiple wavelength ranges, longpass filters that transmit wavelengths longer than the cut-on wavelength, shortpass filters that transmit wavelengths shorter than the cut-off wavelength, cutoff filters that do not transmit specific monochromatic light or multiple wavelength ranges, colored glass filters, dichroic filters, etc. Furthermore, a combination of a variable optical filter that can change the transmission wavelength range and a variable optical attenuator can also be suitably used as the spectrometer.

[0035] <<Optical Fiber>> The concentration ratio measuring device may use an optical fiber between the light source and the measurement cell, or between the measurement cell and the absorbance detector, in order to efficiently transmit light such as light irradiated from the light source to the measurement cell and transmitted light that passes through the measurement cell and is input to the absorbance detector.

[0036] <<Absorbance Detector>> The absorbance detector is not particularly limited and can be appropriately selected depending on the purpose as long as it can detect a specific wavelength, and examples thereof include optical semiconductors (photocells), photomultipliers, etc. The absorbance detector can measure the absorbance of the solution at a specific wavelength by converting transmitted light into an electrical signal.

[0037] As the third to sixth embodiments, a concentration ratio measurement method and a concentration ratio measurement device having a suitable combination of a light source and a spectroscope will be described. These embodiments can be applied to, for example, both the concentration ratio measurement device 10 shown in FIG. 1 and the concentration ratio measurement device 20 shown in FIG. 2.

[0038] [Third embodiment] The third embodiment is an embodiment in which a concentration ratio measuring device is used in combination with a light source that irradiates monochromatic light of a specific wavelength and a spectroscope such as a bandpass filter that transmits the monochromatic light of the specific wavelength, and a concentration ratio measuring method is carried out using the concentration ratio measuring device.

[0039] In any of the third to sixth embodiments, the spectroscope may be a pre-spectroscope provided on the optical path between the light source and the measurement cell (see FIGS. 3 and 4), or a post-spectroscope provided on the optical path between the measurement cell and the absorbance detector (see FIG. 5). In the pre-spectroscope type, the spectroscope may be provided after the light source as shown in FIG. 3, or before the measurement cell as shown in FIG. 4. In the third embodiment, the position at which the spectroscope is provided can be selected as appropriate, but it is preferable to provide it after the light source or before the measurement cell as shown in FIGS. 3 and 4.

[0040] According to the third embodiment, by measuring absorbance based on monochromatic light of a specific wavelength and calculating the concentration ratio, a monochromatic light absorbance measuring device can be used, thereby simplifying the measurement and calculation.

[0041] [Fourth embodiment: concentration ratio measuring device and concentration ratio measuring filter] The fourth embodiment is an embodiment of a concentration ratio measuring device that uses a light source that irradiates continuous light in combination with a spectroscope such as a bandpass filter, cutoff filter, or tunable optical filter that transmits specific wavelengths in a wavelength range wider than that of monochromatic light or in multiple wavelength ranges, and a concentration ratio measuring method that uses the concentration ratio measuring device.

[0042] The bandpass filter is not particularly limited as long as it transmits specific wavelengths and can be appropriately selected depending on the purpose. However, it is preferable that the bandpass filter transmits at least one wavelength range selected from the wavelength ranges of 1121 nm or more and 1140 nm or less, 1204 nm or more and 1223 nm or less, 1620 nm or more and 1639 nm or less, 1747 nm or more and 1766 nm or less, 1831 nm or more and 1850 nm or less, 2150 nm or more and 2169 nm or less, and 2360 nm or more and 2379 nm or less shown in Table 5 below, and it is more preferable that the bandpass filter transmits two or more wavelength ranges.

[0043] These wavelength ranges can be classified into two groups: a T group whose absorbance increases with increasing toluene concentration, and an M group whose absorbance increases with increasing methylcyclohexane concentration. The T group consists of three wavelength ranges: 1121 nm to 1140 nm, 1620 nm to 1639 nm, and 2150 nm to 2169 nm (see FIG. 13). The M group consists of four wavelength ranges: 1204 nm to 1223 nm, 1747 nm to 1766 nm, 1831 nm to 1850 nm, and 2360 nm to 2379 nm (see FIG. 14).

[0044] Specifically, the bandpass filters shown in any of Figures 12 to 14, which have the characteristic of transmitting three or four wavelength ranges shown in Table 5 below, can be particularly suitably used as concentration ratio measurement filters for measuring the concentration ratios of solutions containing toluene to methylcyclohexane. For example, by locating the spectrometer 3 at the position shown in Figures 3 and 4, that is, on the optical path between the light source 1b and the measurement cell 1a, it is possible to measure absorbance only in wavelength ranges where there is a good linear relationship between absorbance and concentration ratio. Specifically, continuous light can be incident from a light source such as a tungsten lamp, and the limitation on transmitted wavelengths is relaxed, thereby increasing the amount of light and enabling stable measurement of concentration ratios.

[0045] The cutoff filter is not particularly limited as long as it transmits specific wavelengths and can be appropriately selected depending on the purpose. However, it is preferable that the cutoff filter does not transmit at least one wavelength range among the wavelength ranges of 1160 nm or more and 1166 nm or less, 1272 nm or more and 1368 nm or less, 1519 nm or more and 1593 nm or less, 1694 nm or more and 1707 nm or less, 2086 nm or more and 2090 nm or less, 2274 nm or more and 2284 nm or less, and 2444 nm or more and 2476 nm or less shown in Table 6 below, it is more preferable that the cutoff filter does not transmit two or more wavelength ranges, and it is even more preferable that the cutoff filter does not transmit all wavelength ranges.

[0046] 16 and 17, which have the property of blocking the seven wavelength ranges A to G shown in Table 6 below and Fig. 15, can be particularly suitably used as a concentration ratio measurement filter for measuring the concentration ratio of a solution containing toluene or methylcyclohexane. For example, by locating the spectrometer 3 at the position shown in Figs. 3 and 4, that is, on the optical path between the light source 1b and the measurement cell 1a, wavelength ranges with poor linearity are not input to the absorbance detector, making it possible to measure the concentration ratio with good linearity.

[0047] The position at which the spectroscope is provided can be selected as appropriate, but it is preferable to provide it after the light source or before the measurement cell as shown in FIGS.

[0048] According to the fourth embodiment, the absorbance is measured based on a specific wavelength in a wide wavelength range or a plurality of wavelength ranges, and the concentration ratio is calculated, thereby making it possible to measure the concentration ratio with high accuracy.

[0049] [Fifth Embodiment] The fifth embodiment is an embodiment of a concentration ratio measurement device that uses a light source that irradiates continuous light and a spectroscope that transmits monochromatic light of a specific wavelength using a tunable optical filter that can change the transmission wavelength range, and a concentration ratio measurement method that uses the concentration ratio measurement device. Examples of the tunable optical filter include a Fabry-Perot interference filter. The spectroscope can be located at any appropriate position, but it is preferably located before the absorbance detector, as shown in FIG. 5 .

[0050] [Sixth Embodiment] The sixth embodiment is an embodiment of a concentration ratio measuring device that uses a light source that irradiates continuous light in combination with a monochromator that extracts monochromatic light of a specific wavelength as a spectroscope, and a concentration ratio measuring method that uses the concentration ratio measuring device. The monochromator is a spectroscope that has a mechanism for extracting light of a specific wavelength from an exit slit from light dispersed by a dispersive element such as a prism or a diffraction grating. The position of the spectroscope can be selected as appropriate, but it is preferably installed after the light source as shown in Figure 3.

[0051] <Concentration Ratio Calculation Step and Concentration Ratio Calculation Unit> The concentration ratio calculation step is a step of calculating a concentration ratio t:m between the concentration t of the toluene and the concentration m of the methylcyclohexane based on the absorbance and a prerecorded calibration curve, and can be suitably performed by the concentration ratio calculation unit. The concentration ratio calculation unit is a unit that calculates the concentration ratio t:m between the concentration t of the toluene and the concentration m of the methylcyclohexane based on the absorbance and a prerecorded calibration curve, and can be, for example, a computer having stored therein a program for calculating the concentration ratio based on equations (1) and (2) described below.

[0052] [Seventh Embodiment: Concentration Ratio Measurement Method Based on One Wavelength] An embodiment of the concentration ratio measurement method will be described below. The concentration ratio measurement method in the seventh embodiment can be suitably implemented by any of the concentration ratio measurement devices 10, 20, 30, 40, and 50 shown in Figures 1 to 5, but will be described representatively with reference to Figure 1. The concentration ratio measurement device 10 calculates the concentration ratio of toluene and methylcyclohexane in the solution S based on the absorbance of transmitted light L2 that has passed through the solution S when a light beam L1 from a light source 1b is irradiated onto the solution S, and the optical path length D. The concentration ratio measurement method includes an absorbance measurement step and a concentration ratio calculation step, and may further include a specific wavelength setting step of setting a specific wavelength and a calibration curve creation step, as necessary.

[0053] <Specific Wavelength Setting Step> In the specific wavelength setting step, specific wavelengths are set as one or more wavelengths or wavelength ranges in the wavelength ranges of 1120 nm or more and 1140 nm or less, 1190 nm or more and 1230 nm or less, 1620 nm or more and 1680 nm or less, 1730 nm or more and 1850 nm or less, 1800 nm or more and 2050 nm or less, 2150 nm or more and 2180 nm or less, and 2360 nm or more and 2420 nm or less.

[0054] There are no particular restrictions on the method for setting the specific wavelength, and any known method can be appropriately selected depending on the purpose. Examples include a method for setting a light source capable of irradiating monochromatic light of a specific wavelength in the concentration ratio measuring device of the third embodiment; a method for setting a spectrometer such as a bandpass filter or cutoff filter that transmits specific wavelengths in a wide wavelength range or multiple wavelength ranges in the concentration ratio measuring device of the fourth embodiment; a method for setting the transmission wavelength of a tunable optical filter to monochromatic light of a specific wavelength in the concentration ratio measuring device of the fifth embodiment; a method for setting the wavelength of a monochromator to monochromatic light of a specific wavelength in the concentration ratio measuring device of the sixth embodiment; and a method for specifying the specific wavelength to be used for calculation in the concentration ratio calculation unit.

[0055] <Calibration Curve Creation Step> In the calibration curve creation step, standard solutions having stepwise concentration ratios, where the concentration ratio t:m between the concentration t of toluene and the concentration m of methylcyclohexane is clear, are prepared in advance, and the absorbance at a desired or set specific wavelength is measured to create a calibration curve showing a linear relationship between the concentration ratio and the absorbance.

[0056] The method for preparing a calibration curve is not particularly limited, and any known method can be appropriately selected depending on the purpose. For example, a calibration curve can be prepared by the method described in the Examples below and shown in FIG. 8. The prepared calibration curve can be stored in a memory unit. Examples of the stepwise concentration ratios in the standard solution include the concentration ratio t:m (volume ratio) of toluene concentration t to methylcyclohexane concentration m, which are 0:100, 10:90, 30:70, 50:50, 70:30, 90:10, and 100:0, respectively.

[0057] <Absorbance measurement step> In the absorbance measurement step, the absorbance at a specific wavelength of the solution to be measured (i.e., the concentration ratio is unknown) is measured. In the seventh embodiment, the specific wavelength is one wavelength. The method for measuring absorbance is not particularly limited, and a known method can be appropriately selected depending on the purpose. Specifically, as shown in Figures 6 and 7, the measurement can be performed by the following steps 1-1 to 1-3. Step 1-1: Measure the transmitted light T at a specific wavelength of a blank measurement cell containing no solution. ０ Step 1-2: Measure the amount of light T transmitted through the measurement cell containing the solution at a specific wavelength. Step 1-3: Measure the transmittance T / T ０ and the absorbance A at a specific wavelength is calculated based on the following formula (1):

[0058] T ０ : Transmitted light of blank at specific wavelength T: Transmitted light of solution at specific wavelength A: Absorbance at specific wavelength

[0059] <Concentration Ratio Calculation Step> In the concentration ratio calculation step, the concentration ratio t:m between the concentration t of the toluene and the concentration m of the methylcyclohexane is calculated based on the absorbance determined in the absorbance measurement step and a pre-recorded calibration curve. The method for calculating the concentration ratio t:m is not particularly limited, and a known method can be appropriately selected depending on the purpose. Specifically, the concentration ratio t:m can be calculated based on the calibration curve and the following formula (2).

[0060] A(λ １ ): Specific wavelength λ １ Absorbance at [A.U.] α Ｔ (λ １ ): λ １ Molar absorption coefficient of toluene in [L mol －１ ・cm －１ ] α Ｍ (λ １ ): λ １ Molar absorption coefficient of methylcyclohexane in [L mol －１ ・cm －１ ] D: Optical path length [cm] c Ｔ : Molar concentration of toluene [mol L －１ ] c Ｍ : Molar concentration of methylcyclohexane [mol L －１ ] t: Concentration ratio (volume ratio) of toluene in the solution m: Concentration ratio (volume ratio) of methylcyclohexane in the solution Where, t + m = 1

[0061] Here, in the fourth embodiment, in the case where a bandpass filter is used, the concentration ratio t:m can be calculated by adding up all the absorbances in the wavelength range that can be transmitted through the bandpass filter. By using all wavelengths in the wavelength range in the near-infrared region with a coefficient of determination of 0.99 or more, the amount of light that reaches the light receiving element of the absorbance measuring instrument can be increased, and therefore, measurements with a good S / N ratio become possible. Specifically, A(λ ｉ ) and then measure the sum of A(λ ｉ ), and the concentration ratio t:m can be calculated by finding t based on the following equation (3), in which all the variables except t are known.

[0062] A(λ ｉ ): Specific wavelength λ ｉ Absorbance at [A.U.] α Ｔ (λ ｉ ): λ ｉ Molar absorption coefficient of toluene in [L mol －１ ・cm －１ ] α Ｍ (λ ｉ ): λ ｉ Molar absorption coefficient of methylcyclohexane in [L mol －１ ・cm －１ ] D: Optical path length [cm] c Ｔ : Molar concentration of toluene [mol L －１ ] c Ｍ : Molar concentration of methylcyclohexane [mol L －１ ] t: Concentration ratio (volume ratio) of toluene in the solution m=1-t: Concentration ratio (volume ratio) of methylcyclohexane in the solution n: Number of wavelength ranges

[0063] As shown in FIG. 6, steps 1-1 to 1-3 may be performed as an absorbance measurement step, and step 2 may be performed as a concentration ratio calculation step, or as shown in FIG. 7, step 0 may be further performed before step 1-1 as an arbitrary specific wavelength setting step.

[0064] Eighth Embodiment: Concentration Ratio Measurement Method Based on Two or More Wavelengths or Wavelength Ranges The eighth embodiment of the concentration ratio measurement method is an embodiment in which the specific wavelengths are two or more wavelengths or wavelength ranges. Except for being based on two or more wavelengths or wavelength ranges, the method can be carried out in the same manner as the seventh embodiment. To determine the concentration ratio, the absorbance at any wavelength among specific wavelengths at which the linearity between the concentration ratio and the absorbance is excellent may be measured as in the seventh embodiment. However, as in the eighth embodiment, by measuring the absorbance at two or more wavelengths or wavelength ranges and using the average absorbance, a more stable and accurate measurement can be achieved.

[0065] The specific wavelength is two or more wavelengths λ １ , ...λ ｎ(n is an integer of 2 or more), the resulting absorbance A(λ １ ), ...A(λ ｎ ) were measured, and the average absorbance A ｍｅａｎ Next, in the seventh embodiment, A(λ １ ) to A ｍｅａｎ The concentration ratio can be calculated by substituting

[0066] The specific wavelength is λ １ From λ ２ In the case where the wavelength range is ｍｅａｎ In the seventh embodiment, A(λ １ ) to A ｍｅａｎ The concentration ratio can be calculated by substituting the average absorbance A ｍｅａｎ The method for determining the absorbance can be appropriately selected depending on the specifications of the concentration ratio measuring device used, and examples include a digital method in which the average absorbance is determined by integrating and averaging the absorbance for each wavelength measured at a predetermined wavelength resolution for a specific wavelength in a set wavelength range; and a method in which an optical filter such as a bandpass filter is used to irradiate light in a specific wavelength range, receive the transmitted light collectively, and determine the absorbance in that wavelength range in an analog manner.

[0067] In the eighth embodiment, the specific wavelengths are two or more wavelengths or wavelength ranges, i.e., two or more wavelengths or wavelength ranges among the seven wavelength ranges of 1120 nm to 1140 nm, 1190 nm to 1230 nm, 1620 nm to 1680 nm, 1730 nm to 1850 nm, 1800 nm to 2050 nm, 2150 nm to 2180 nm, and 2360 nm to 2420 nm. The wavelength ranges are not particularly limited and can be appropriately selected depending on the purpose, as long as they are within the range of any of the seven wavelength ranges (i.e., wavelength ranges with a coefficient of determination close to 1 shown in Table 6 below). The wavelength width Δλ of the wavelength ranges is not particularly limited and can be appropriately selected depending on the purpose, and examples include 5 nm, 10 nm, and 20 nm. Many commercially available optical filters have a half-width of 10 nm or 20 nm, and these filters can be used preferably. Alternatively, the average absorbance may be determined in an analog manner using an optical filter having an arbitrary half-width or a variable optical filter capable of changing the transmission wavelength range, or the digital method may be used.

[0068] As is clear from the examples, FIGS. 10 and 11, and Table 6 described below, the coefficient of determination is improved for average absorbance compared to absorbance measured at a single wavelength, and therefore measurements with higher linearity can be performed. Furthermore, the total amount of transmitted light increases, reducing the effects of wavelength and transmitted light measurement errors, and improving the S / N ratio. Therefore, the concentration ratio measurement method of the eighth embodiment enables more stable and accurate measurement of concentration ratios.

[0069] [Ninth embodiment: Concentration ratio measurement method based on two specific wavelengths] In addition, in the concentration ratio measurement method of the ninth embodiment, a first specific wavelength λ １ , and a second specific wavelength λ ２ are selected, and the absorbance of the solution at each wavelength is measured. The molar absorbance of toluene and the molar absorbance of methylcyclohexane at each wavelength can be calculated based on the molar absorbance of toluene and the molar absorbance of methylcyclohexane at each wavelength, and the following formula (12):

[0070] In the ninth embodiment, the specific wavelengths are two wavelengths, namely, two different wavelengths in the wavelength ranges of 1120 nm to 1140 nm, 1190 nm to 1230 nm, 1620 nm to 1680 nm, 1730 nm to 1850 nm, 1800 nm to 2050 nm, 2150 nm to 2180 nm, and 2360 nm to 2420 nm.

[0071] First, the wavelength λ １ , and λ ２ At each wavelength, the absorbance A of toluene Ｔ (λ １ ), and A Ｔ (λ ２ ) and the absorbance A of methylcyclohexane Ｍ (λ １ ), and A Ｍ (λ ２ The molar absorption coefficients of toluene and methylcyclohexane at each wavelength are calculated from the measurement results and the following equations (4) to (9).

[0072] α Ｔ (λ １ ): λ １ Molar absorption coefficient of toluene in [L mol －１ ・cm －１ ] A Ｔ (λ １ ): λ １ Absorbance of toluene at [A.U.] c Ｔ : Molar concentration of toluene [mol L －１ ] D: Optical path length [cm]

[0073] α Ｔ (λ ２ ): λ ２ Molar absorption coefficient of toluene in [L mol －１ ・cm －１ ] A Ｔ (λ ２ ): λ ２ Absorbance of toluene at [A.U.] c Ｔ : Molar concentration of toluene [mol L －１] D: Optical path length [cm]

[0074] α Ｍ (λ １ ): λ １ Molar absorption coefficient of methylcyclohexane in [L mol －１ ・cm －１ ] A Ｍ (λ １ ): λ １ Absorbance of methylcyclohexane at [A.U.] c Ｍ : Molar concentration of methylcyclohexane [mol L －１ ] D: Optical path length [cm]

[0075] α Ｍ (λ ２ ): λ ２ Molar absorption coefficient of methylcyclohexane in [L mol －１ ・cm －１ ] A Ｍ (λ ２ ): λ ２ Absorbance of methylcyclohexane at [A.U.] c Ｍ : Molar concentration of methylcyclohexane [mol L －１ ] D: Optical path length [cm]

[0076] wavelength λ １ , and λ ２ The absorbance of can be expressed by equations (8) to (11).

[0077] T ０ (λ １ ): λ １ The transmitted light T(λ １ ): λ １ The transmitted light A (λ １ ): λ １ Absorbance at

[0078] T ０ (λ ２ ): λ ２ The transmitted light T(λ ２ ): λ２ The transmitted light A (λ ２ ): λ ２ Absorbance at

[0079]

[0080]

[0081] Equations (10) and (11) can be expressed as equation (12), which is a determinant. If the inverse matrix of equation (12) is found and applied to the left of both sides, equation (13) is obtained.

[0082]

[0083]

[0084] The left side of equation (12) is the desired molar concentration of toluene, t × c Ｔ and the molar concentration of methylcyclohexane m × c Ｍ Looking at the right side of equation (13), we can see that it is expressed only by the absorption coefficient of toluene, the absorption coefficient of methylcyclohexane, the absorbance of the solution, and the optical path length. From this, the absorbance A(λ) of the solution at two specific wavelengths can be calculated based on the absorption coefficient of toluene and the absorption coefficient of methylcyclohexane that were previously calculated, and equation (13). １ ), and A(λ ２ ) to determine the molar concentration of toluene, t × c Ｔ and the molar concentration of methylcyclohexane m × c Ｍ From this result, it is possible to calculate the concentration ratio t:m between the concentration t of toluene and the concentration m of the methylcyclohexane. Ｔ , c Ｍ It can be calculated using the value of

[0085] [Tenth Embodiment: Concentration Ratio Measurement Method Based on Wavelength Range with Small Wavelength Dependence] The concentration ratio measurement method of the tenth embodiment is an embodiment based on a wavelength range with small wavelength dependency. Note that, except for being based on a wavelength range with small wavelength dependency, it can be implemented in the same manner as the seventh to ninth embodiments. The specific wavelengths in the tenth embodiment are one or more wavelengths or wavelength ranges in a wavelength range with small wavelength dependency, i.e., one or more wavelengths or wavelength ranges in the wavelength ranges of 1730 nm to 1850 nm and 1800 nm to 2050 nm.

[0086] Absorbance is wavelength-dependent. The smaller this wavelength dependence, the more stable the measurement. If the wavelength dependence is large, the change in absorbance will be large with a small change in the measurement wavelength, and fluctuations in the measurement wavelength will degrade reproducibility. This results in high error sensitivity, which is one of the factors that cause unstable measurements. Therefore, from the perspective of reducing errors caused by fluctuations in the measurement wavelength and performing accurate measurements, it is advisable to select a wavelength range with low wavelength dependence (good flatness). As is clear from Table 7 in the Examples section described below, it is preferable to select a wavelength range from 1730 nm to 1850 nm and a wavelength range from 1800 nm to 2050 nm. According to the concentration ratio measurement method of the tenth embodiment, errors caused by fluctuations in the measurement wavelength can be reduced, allowing for accurate measurements.

[0087] [Eleventh Embodiment: Concentration Ratio Measurement Method Based on Wavelength Range with High Absorbance Sensitivity] The concentration ratio measurement method of the eleventh embodiment is an embodiment based on a wavelength range with high absorbance sensitivity. Note that, except for being based on a wavelength range with high absorbance sensitivity, it can be implemented in the same manner as the seventh to ninth embodiments. The specific wavelengths in the eleventh embodiment are one or more wavelengths or wavelength ranges in the wavelength range with high absorbance sensitivity, i.e., one or more wavelengths or wavelength ranges in the wavelength ranges of 1120 nm to 1140 nm, 1190 nm to 1230 nm, 1620 nm to 1680 nm, 2150 nm to 2180 nm, and 2360 nm to 2420 nm.

[0088] While the smaller the wavelength dependence, the more stable the measurement, the concentration ratio of toluene to methylcyclohexane changes depending on the progress of the hydrogenation / dehydrogenation reaction of toluene and methylcyclohexane. Therefore, to determine the direction of the change (hydrogenation or dehydrogenation) and the dynamics of the change, it is advisable to measure the absorbance in a wavelength range with as high absorbance sensitivity as possible. Specifically, as is clear from Table 7 in the Examples section described later, it is preferable to select a wavelength range of 1620 nm to 1680 nm, a wavelength range of 2150 nm to 2180 nm, and a wavelength range of 2360 nm to 2420 nm, where the magnitude of the absorbance slope |a| is greater than 0.5. The concentration ratio measurement method of the eleventh embodiment enables measurements with high sensitivity to changes in the concentration ratio.

[0089] As in the tenth and eleventh embodiments, the measurement wavelength can be changed depending on the purpose. That is, for applications such as monitoring the concentration ratio, measurements can be made in a wavelength range in which the coefficient of determination is close to 1 and the wavelength dependency of absorbance is small (good flatness). On the other hand, when checking the direction and dynamics of the reaction or checking minute changes in the conversion rate in the final stage of the reaction, measurements can be made in a wavelength range in which the sensitivity of absorbance to the concentration ratio is high (the absolute value |a| of the slope a is large).

[0090] [Twelfth Embodiment: Concentration Ratio Measurement Method Excluding Cases Where Water or Hydrogen Gas is Contaminated in the Solution] The concentration ratio measurement method of the twelfth embodiment is an embodiment of a concentration ratio measurement method that measures the concentration ratio of toluene and methylcyclohexane, excluding cases where by-product water or hydrogen gas is contaminated in the solution. Note that, except for excluding cases where water or hydrogen gas is contaminated in the solution, the method can be carried out in the same manner as the first to eleventh embodiments.

[0091] The concentration ratio measurement device of the twelfth embodiment is an embodiment of a concentration ratio measurement device that measures the concentration ratio of a solution containing toluene or methylcyclohexane, excluding cases where water or hydrogen gas is mixed into the solution. Note that, except for excluding cases where water or hydrogen gas is mixed into the solution, the concentration ratio measurement device can be implemented in the same manner as the first to eleventh embodiments.

[0092] An example of an organic hydride manufacturing apparatus having the concentration ratio measurement device of this embodiment is shown in Figure 18. The organic hydride manufacturing apparatus 100 shown in Figure 18 includes a concentration ratio measurement device 10, an electrolytic cell 60, a cathode liquid supply tank 70, pipes 71 to 73, and a pump 75. In this embodiment, the concentration ratio measurement device 10 is an embodiment that continuously measures the absorbance of a solution S flowing through a flow-through measurement cell 1a connected to the pipe 71, and the concentration ratio measurement devices 30, 40, or 50 shown in Figures 3 to 5 may be used instead of the concentration ratio measurement device 10 shown in Figure 1.

[0093] The electrolytic cell 60 includes an anode chamber 61, an anode electrode 62, an electrolyte membrane 63, a cathode electrode 64, a cathode chamber 65, and a power supply 66. The electrolytic cell 60 hydrogenates toluene through an electrochemical reduction reaction to produce methylcyclohexane (MCH), an organic hydride. After water is electrolyzed, hydrogen ions directly reduce toluene to produce MCH, essentially without a hydrogen generation process. Specifically, water in the anode chamber 61 is oxidized at the anode electrode 62 to produce hydrogen ions. The generated hydrogen ions pass through the electrolyte membrane 63 and migrate to the cathode electrode 64. Toluene supplied from the tank 70 to the cathode chamber 65 reacts with the migrated hydrogen ions to produce MCH. The generated MCH and unhydrogenated toluene are then returned to the cathode fluid supply tank 70 via a pump 75. By repeating this cycle, most of the toluene is eventually converted to MCH.

[0094] Meanwhile, as a side reaction, hydrogen ions that could not react with toluene at the cathode are converted into hydrogen. Also, some of the water in the anode chamber 61 passes through the electrolyte membrane 63 and moves toward the cathode electrode 64. As a result, like toluene and MCH, water and hydrogen also circulate through the cathode solution supply tank 70 and electrolytic tank 60 of the organic hydride manufacturing apparatus 100.

[0095] 19 is a graph showing the relationship between wavelength and absorbance for toluene, methylcyclohexane, water, and hydrogen. If water or hydrogen gas is mixed into the solution S flowing through the flow-through measurement cell 1a in the concentration ratio measurement device 10, the concentration ratio of toluene and methylcyclohexane cannot be measured correctly. Therefore, cases in which water or hydrogen gas is mixed into the solution S are excluded from the measurement target.

[0096] The detection method is not particularly limited and can be appropriately selected depending on the purpose, as long as it can detect cases where the solution S contains water and / or hydrogen and exclude such cases from the measurement targets. Specifically, with regard to water, when an absorbance exceeding the maximum absorbance of a solution containing toluene or methylcyclohexane is detected in a wavelength range where the absorbance of toluene and MCH is low (e.g., one or more wavelengths or wavelength bands of 1500 nm to 1650 nm and / or 1750 nm to 1900 nm), it can be determined that the solution S contains water, and such cases can be excluded from the measurement of the concentration ratios of toluene and methylcyclohexane.

[0097] With regard to hydrogen, the absorbance of hydrogen is very small and can be considered to be substantially zero in the wavelength range of 1500 nm or more and 1900 nm or less, which includes the wavelength range shown in Fig. 19, and is smaller than the absorbance of a solution containing toluene or methylcyclohexane at any wavelength. Therefore, when the absorbance is less than the minimum absorbance of a solution containing toluene or methylcyclohexane at one or more wavelengths or wavelength ranges of 1500 nm or more and 1900 nm or less, it can be determined that solution S contains hydrogen, and such a case can be excluded from the measurement of the concentration ratio of toluene and methylcyclohexane.

[0098] As described above, by excluding from consideration cases where the solution S contains water and / or hydrogen and measuring the concentration ratio of toluene and methylcyclohexane when the solution S contains substantially only toluene or methylcyclohexane, it is possible to realize highly accurate measurement of the concentration ratio while excluding the influence of the mixed water and hydrogen.

[0099] [Thirteenth embodiment: embodiment for evaluating reaction state in real time] The concentration ratio measurement method of the thirteenth embodiment includes an absorbance measurement step and an evaluation step, and preferably includes a concentration ratio calculation step, and further includes other steps as necessary, such as a wavelength setting step, a calibration curve creation step, etc. The concentration ratio measurement device of the thirteenth embodiment preferably includes an absorbance measurement unit and an evaluation unit, and includes a concentration ratio calculation unit, and further includes other components as necessary.

[0100] In the synthesis reaction of methylcyclohexane according to the above-mentioned reaction formula (1), as the synthesis reaction progresses and the concentration ratio or conversion rate of methylcyclohexane increases, for example, to 95% by volume or higher, the reaction approaches an equilibrium state. Conventional measurement methods are unable to measure in real time, and therefore are unable to evaluate the reaction state in real time. This makes it difficult to optimize reaction conditions such as temperature and hydrogen supply.

[0101] The concentration ratio measurement method and concentration ratio measurement device of the thirteenth embodiment can evaluate the reaction state in real time during the hydrogenation and dehydrogenation reactions of such toluene- or methylcyclohexane-containing solutions. The concentration ratio measurement method and concentration ratio measurement device of the thirteenth embodiment can measure the concentration-dependent absorbance of toluene and methylcyclohexane over a wide concentration range from 0% to 100% by volume of methylcyclohexane without the dilution process required in the conventional gas chromatography measurement method. This enables real-time evaluation of the reaction state and measurement of the concentration ratio as needed, enabling automated evaluation and measurement. Therefore, based on the evaluation results of the reaction state, reaction conditions such as temperature and hydrogen supply can be optimized to further advance the reaction or to provide information for making decisions such as terminating the reaction.

[0102] <Absorbance Measuring Step and Absorbance Measuring Unit> The absorbance measuring step is performed by measuring the absorbance A of the solution at a specific wavelength at time T0. Ｔ０ and the absorbance A of the solution at the specific wavelength at time T1 after a predetermined time has elapsed. Ｔ１and the absorbance measurement unit measures the absorbance A of the solution at a specific wavelength at time T0. Ｔ０ and the absorbance A of the solution at the specific wavelength at time T1 after a predetermined time has elapsed. Ｔ１ Specifically, it is preferable that the measurement device has a measurement cell, a light source that irradiates the solution contained in the measurement cell with light of a specific wavelength, and an absorbance detector that measures the absorbance of the transmitted light that has passed through the solution, and further has a lens, a spectroscope, an optical fiber, etc., as necessary.

[0103] <Evaluation Step and Evaluation Unit> The evaluation step is a step of determining whether the reaction state is hydrogenation, an equilibrium state, or dehydrogenation based on the absorbance difference ΔA calculated by the following formula (i) and the following evaluation criteria, and can be suitably performed by the evaluation unit. [Evaluation Criteria] (1) The specific wavelength is one wavelength or wavelength range in the wavelength ranges of 1120 nm to 1140 nm, 1620 nm to 1680 nm, and 2150 nm to 2180 nm, and (1a) when the absorbance difference ΔA is greater than 0, it is evaluated as dehydrogenation, (1b) when the absorbance difference ΔA is 0, it is evaluated as equilibrium, or (1c) when the absorbance difference ΔA is less than 0, it is evaluated as hydrogenation; or (2) The specific wavelength is one wavelength or wavelength range in the wavelength ranges of 1190 nm to 1230 nm, 1730 nm to 1850 nm, 1800 nm to 2050 nm, and 2360 nm to 2420 nm, and (2a) when the absorbance difference ΔA is greater than 0, it is evaluated as hydrogenation. (2b) When the absorbance difference ΔA is 0, it is evaluated as being in an equilibrium state, or (2c) When the absorbance difference ΔA is less than 0, it is evaluated as being in dehydrogenation.

[0104] The evaluation unit is a unit that determines whether the reaction state is hydrogenation, an equilibrium state, or dehydrogenation based on the absorbance difference ΔA calculated by the formula (i) and the evaluation criteria, and may be, for example, a computer that stores a program for evaluating the reaction state based on the formula (i) and the evaluation criteria.

[0105] Fig. 20 is a graph showing the relationship between the concentration ratio of toluene to methylcyclohexane and the slope of absorbance, superimposed on the graph of Fig. 8. In Fig. 20, each numerical value in the legend indicates the toluene concentration (volume ratio), the thick line indicates the magnitude of the slope |a| between the toluene concentration and absorbance, and the vertical axis on the right indicates the slope.

[0106] 20, the seven wavelength ranges that can be used as specific wavelengths can be classified into the following (1) or (2) depending on the wavelength range: (1) Wavelength ranges of 1120 nm to 1140 nm, 1620 nm to 1680 nm, and 2150 nm to 2180 nm, in which the slope of the relationship between the toluene concentration and the absorbance exceeds 0; and (2) Wavelength ranges of 1190 nm to 1230 nm, 1730 nm to 1850 nm, 1800 nm to 2050 nm, and 2360 nm to 2420 nm, in which the slope of the relationship between the toluene concentration and the absorbance is less than 0.

[0107] As shown in Table 1 below, the reaction state can be evaluated depending on the wavelength range to which the specific wavelength falls and whether the absorbance difference ΔA is ΔA<0, ΔA=0, or ΔA>0.

[0108]

[0109] The time T0 is not particularly limited and can be set at any time point depending on the purpose. The predetermined time at time T1 after the predetermined time has elapsed is not particularly limited and can be selected appropriately depending on the purpose, for example, 1 minute, 1 second, 1 millisecond, etc. Furthermore, the time points at which the absorbance is measured may be two or more points, and may be continuously measured at the predetermined time intervals (see, for example, Table 2) or discontinuously measured at desired time intervals. In either case, the reaction state can be evaluated based on the absorbance difference ΔA between any two points. For example, absorbances measured continuously at each point, for example, at 1 millisecond intervals, can be thinned out at an appropriate sampling interval and used for evaluation (see, for example, Table 3). The sampling interval can be selected appropriately by optimizing the time course of the chemical reaction and the sampling interval for absorbance measurement. Although it is possible for the chemical reaction to fluctuate, measurements with little data variance can be obtained even with chemical reaction fluctuations.

[0110]

[0111]

[0112] Although an example of evaluation based on the difference in absorbance has been shown, the reaction state can also be evaluated using the difference in concentration ratio at time points T0 and T1 after calculating the concentration ratio from the absorbance based on the concentration ratio calculation process described below.

[0113] 21 is a flowchart showing an example of the evaluation method according to the thirteenth embodiment. First, the absorbance A of the solution at a specific wavelength at time T0 is calculated. Ｔ０ (Step S11-1), and then, the absorbance A of the solution at a specific wavelength at time T1 after a predetermined time has elapsed is measured. Ｔ１ (Step S11-2). Then, a step of calculating the concentration ratio t:m of toluene to methylcyclohexane based on formula (2) is carried out (Step S12). Note that the order in which Step S12 is carried out is arbitrary, and Step S12 can be carried out at any timing as long as it is after Step S11-1 or Step S11-2.

[0114] The absorbance difference ΔA is calculated based on formula (i) (step S13-1), and it is determined whether the slope of the relationship between the toluene concentration and the absorbance at a specific wavelength is greater than or less than 0 (step S13-2). The reaction state is evaluated based on the calculated ΔA and the criteria (step S13-3 or step S13-4).

[0115] The evaluation step and evaluation unit preferably further evaluate the degree of reaction progress as high when the absolute value of the absorbance difference ΔA is equal to or greater than a predetermined value. The absolute value of the absorbance difference ΔA depends on the concentration ratio of toluene to methylcyclohexane from time T0 to T1. Therefore, when the absolute value is equal to or greater than a predetermined value, it can be determined that the reaction continues to progress after T1. When the absolute value is less than the predetermined value, it can be determined that the reaction has settled down. The predetermined value is not particularly limited and can be appropriately selected depending on the purpose. Furthermore, when evaluation is performed using two or more absorbance differences ΔA with different sampling intervals, the degree of reaction progress may be evaluated based on the value ΔA / (T1-T0) obtained by dividing the absorbance difference ΔA by the sampling interval (T1-T0).

[0116] Specifically, in the case of the synthesis of methylcyclohexane, i.e., a hydrogenation reaction, it is necessary to stop the supply of hydrogen at some point during the reaction. By evaluating the reaction state in real time using the evaluation method described above, it is possible to determine the timing for stopping the supply of hydrogen. In addition, information on the hydrogenation rate can be obtained from the absolute value of the absorbance difference ΔA. Based on this, it is possible to optimize the reaction conditions of the entire reaction system.

[0117] The thirteenth embodiment will be described using the concentration ratio measurement device shown in FIG. 22 as an example. The concentration ratio measurement device 60 shown in FIG. 22 is an embodiment implementing an evaluation method for evaluating in real time the reaction state of a solution S containing toluene and methylcyclohexane flowing through a flow-through measurement cell 1a. The concentration ratio measurement device 60 includes an absorbance measurement unit 1 that measures the absorbance of the solution S at a specific wavelength at two points in time, an evaluation unit 4 that calculates the absorbance difference ΔA and evaluates the reaction state based on the evaluation criteria, and, if necessary, a concentration ratio calculation unit 2 that calculates the concentration ratio t:m of the toluene concentration t and the methylcyclohexane concentration m in the solution S based on the measured absorbance and a pre-recorded calibration curve. The absorbance measurement unit 1 includes a flow-through measurement cell 1a through which the solution S flows, a light source 1b that irradiates the solution S flowing through the measurement cell 1a with light beam L1, and an absorbance detector 1c that receives transmitted light L2 transmitted through the solution S. The device may further include a memory unit 5 that stores the calibration curve.

[0118] The evaluation unit 4, concentration ratio calculation unit 2, and storage unit 5 may be a single device that also includes an operation unit and a display unit, and may further include a control unit that controls the operation of the absorbance measurement unit. The evaluation unit 4, concentration ratio calculation unit 2, and storage unit 5 may be incorporated into a single computer. The absorbance measurement unit 1 may be a single device, and the absorbance measurement unit 1 and concentration ratio calculation unit 2 may be connected to each other via wire or wirelessly.

[0119] The concentration ratio measuring device 60 shown in Figure 22 can appropriately adopt a configuration similar to that of the concentration ratio measuring devices 10, 20, 30, 40, and 50 shown in Figures 1 to 5, except that it has an absorbance measuring unit 1 that measures the absorbance of the solution S at a specific wavelength at two points in time, and an evaluation unit 4 that calculates the absorbance difference ΔA and evaluates the reaction state based on the evaluation criteria.

[0120] The present invention will be described in more detail below based on examples, but the present invention is not limited to the following examples.

[0121] FIG. 8 is a graph showing the relationship between the concentration ratio of toluene to methylcyclohexane and absorbance. Specifically, it shows the absorbance of a solution in which toluene and methylcyclohexane are mixed at a predetermined concentration ratio at wavelengths of 1000 nm to 2500 nm. In FIG. 8, the vertical axis represents absorbance, and the horizontal axis represents wavelength. Solutions were prepared so that the concentration ratio t:m of toluene concentration t to methylcyclohexane concentration m was 0:100, 10:90, 30:70, 50:50, 70:30, 90:10, and 100:0, respectively, in terms of volume [L] (denoted as T00M100, T10M90, T30M70, T50M50, T70M30, and T100M00 in FIG. 8). The absorbance of each solution was measured at wavelengths of 1000 nm to 2500 nm.

[0122] It can be seen from FIG. 8 that the absorbance exhibits a specific value for each wavelength depending on a predetermined concentration ratio (volume ratio) of toluene and methylcyclohexane.

[0123] Next, in order to evaluate the correlation between the absorbance and the concentration ratio t:m shown in Figure 8, the coefficient of determination between the absorbance and the concentration ratio t:m was calculated and shown in Figure 9, which is superimposed on the graph of Figure 8. Figure 9 is a graph showing the relationship between the concentration ratio of toluene and methylcyclohexane at each wavelength, the absorbance, and the coefficient of determination. In Figure 9, each value in the legend indicates the concentration (molar concentration ratio) of toluene, and the thick line indicates the coefficient of determination R ２ (The square of the correlation coefficient R: R ２ ) and the right vertical axis indicates the coefficient of determination. Other legends are the same as in Figure 8.

[0124] In FIG. 9, the coefficient of determination indicates the linearity between the absorbance and the concentration ratio t:m. ２ is 0≦R ２ The value is ≦1, and the closer it is to 1, the more linear the relationship is.

[0125] Toluene concentration c Ｔ The relationship between the absorbance and the luminance is expressed by the following formula (2).

[0126]

[0127] A(λ １ ): Specific wavelength λ１ Absorbance at [A.U.] α Ｔ (λ １ ): λ １ Molar absorption coefficient of toluene in [L mol －１ ・cm －１ ] α Ｍ (λ １ ): λ １ Molar absorption coefficient of methylcyclohexane in [L mol －１ ・cm －１ ] D: Optical path length [cm] c Ｔ : Molar concentration of toluene [mol L －１ ] c Ｍ : Molar concentration of methylcyclohexane [mol L －１ ] t: Concentration ratio (volume ratio) of toluene in the solution m: Concentration ratio (volume ratio) of methylcyclohexane in the solution Where, t + m = 1

[0128] Here, from the reaction formulas (1) and (2), since the hydrogenation / dehydrogenation reaction of toluene and methylcyclohexane is an equimolar reaction, the concentration ratio can be expressed as t:m = t:1-t. By substituting into formula (2), the absorbance A(λ) of the solution can be expressed as a linear equation of the toluene concentration t. Figure 9 shows a graph showing the strength of the relationship between the toluene concentration t and the absorbance A(λ) using the coefficient of determination. As can be seen from Figure 9, in the wavelength range of 1000 nm to 2500 nm, the absorbance value varies between 0 A.U. and 2.6 A.U. Referring to the correspondence between absorbance and transmittance shown in Table 4, the absorbance of 0 A.U. to 2.6 A.U. is expressed as the transmittance T / T. ０ This is equivalent to a change from 100% to 0.25%.

[0129]

[0130] The relationship between absorbance and transmittance is given by the following formula (1). T ０ : Transmitted light of blank at specific wavelength T: Transmitted light of solution at specific wavelength A: Absorbance at specific wavelength [A.U.]

[0131] 9 and Table 4, due to the dynamic characteristics of the sensor and filter, the linearity characteristics deteriorate at wavelengths where the absorbance A is 0.05 [A.U.] or less or 1.3 [A.U.] or more. This is due to the transmittance T / T ０ This is equal to 89.1% or more and 5.0% or less.

[0132] From these results, it was found that there is an optimal wavelength range for determining the concentration ratio t:m between the concentration t of toluene and the concentration m of methylcyclohexane, as shown in Table 5, and that the concentration ratio can be accurately determined by measuring the absorbance of a solution using one or more wavelengths or a specific wavelength range within the wavelength range shown in Table 5. It was confirmed that it is not necessary to measure the absorbance over all wavelength ranges, and that the concentration ratio can be calculated by measuring the absorbance at one wavelength within the most suitable wavelength range shown in Table 5.

[0133]

[0134] Next, a method for measuring concentration ratios when a wavelength range is a specific wavelength is described. Figure 10 is a graph showing the relationship between absorbance and coefficient of determination in a wavelength range with a wavelength width of 10 nm. Among the seven wavelength ranges with excellent linearity shown in Table 5, the average absorbance was calculated for each continuous wavelength range with a wavelength width of 10 nm, and the wavelength range with the largest coefficient of determination was shown.

[0135] Specifically, absorbance was measured at a wavelength resolution of 1 nm in the wavelength range of 1100 nm to 2500 nm, as in the example shown in Figure 8. Next, within the seven wavelength ranges with excellent linearity shown in Table 5, all consecutive wavelength ranges with a wavelength width of 10 nm were set. For example, within the wavelength range of 1120 nm to 1140 nm, 12 wavelength ranges with a wavelength width of 10 nm could be set, each at 1 nm intervals: 1120 nm to 1129 nm, 1121 nm to 1130 nm, 1122 nm to 1131 nm, ... 1131 nm to 1140 nm. Next, for each 10 nm-wide wavelength range, the absorbance for 10 wavelengths (10 wavelengths) was integrated to determine the average absorbance, and the concentration ratio was calculated based on the average absorbance.

[0136] In Figure 10, the series (1, 0.9, 0.7, 0.5, 0.3, 0.1, 0) indicates the concentration ratio t of toluene. The thick line indicates the maximum arithmetic average of the coefficients of determination calculated from the average absorbance of each series in a wavelength range of 10 [nm] within the wavelength range shown in Table 5, and the vertical axis on the right indicates the coefficient of determination. In Figure 10, the scattered lines with a wavelength range of 10 [nm] indicate the wavelength range (horizontal axis) where the arithmetic average of the coefficients of determination is maximum, and the average absorbance (vertical axis on the left).

[0137] The example shown in Figure 11 was carried out in the same manner as in Figure 10, except that the wavelength range with a wavelength width of 10 nm was changed to a wavelength range with a wavelength width of 20 nm. Figure 11 is a graph showing the relationship between absorbance and coefficient of determination in a wavelength range with a wavelength width of 20 nm. Within the seven wavelength ranges with excellent linearity shown in Table 5, the average absorbance was calculated for each continuous wavelength range with a wavelength width of 20 nm, and the wavelength range with the largest coefficient of determination was shown.

[0138] Table 6 shows the wavelength ranges with wavelength widths of 10 nm or 20 nm where the coefficient of determination is maximized, as well as the maximum value of the coefficient of determination, as obtained from Figures 10 and 11. As is clear from Figures 10 to 11 and Table 6 below, measuring the average absorbance over a wavelength range improves the coefficient of determination (or, if the maximum value of the coefficient of determination for the original single wavelength is 1, the coefficient of determination is 0.999 or greater), thereby enabling highly linear measurements. Furthermore, measuring absorbance over a wavelength range increases the total amount of transmitted light, reducing the effects of measurement errors in wavelength and transmitted light, and improving the S / N ratio. Therefore, it was found that a concentration ratio measurement method based on a wavelength range enables more stable and accurate measurement of concentration ratios.

[0139] In Table 6, the wavelength ranges of 1751 [nm] to 1760 [nm] or 1747 [nm] to 1766 [nm] showed the closest coefficient of determination to 1 and the most linear results, but since some variation is expected depending on the sensor and other optical systems, it is advisable to fine-tune and set the wavelength range appropriate for the system.

[0140]

[0141] Table 7 also shows the wavelength dependency (flatness) of absorbance and the magnitude of the slope |a| in each of the seven wavelength ranges.

[0142] <Wavelength Dependence (Flatness) of Absorbance> The wavelength dependence (flatness) of absorbance is shown in FIG. 8 and Table 5. Ｔ (λ) / Δλ, and wavelength dependence ΔA of absorbance of methylcyclohexane Ｍ (λ) / Δλ was calculated, and the wavelength dependency of absorbance was evaluated according to the following evaluation criteria. The evaluation results are shown in Table 6. Ｔ (λ) indicates the absorbance of toluene [A.U.], and A Ｍ (λ) indicates the absorbance [A.U.] of methylcyclohexane, and Δλ indicates the difference between the lower limit and the upper limit of each wavelength range. [Evaluation Criteria] △: |ΔA Ｔ (λ) / Δλ|≧0.009, to |ΔA Ｍ (λ) / Δλ|≦0.009 is satisfied, and the wavelength dependence of absorbance is not small. Ｔ (λ) / Δλ|<0.009 and |ΔA Ｍ (λ) / Δλ|<0.009 is satisfied, and the wavelength dependency of absorbance is small.

[0143] <Magnitude of absorbance gradient> The magnitude of the absorbance gradient |a| is the largest |a| within the wavelength range among the absolute values ​​of the coefficient (gradient) a of t when approximating the absorbance and the toluene concentration ratio to a linear equation shown in the following formula (14) in each of the seven wavelength ranges. A large |a| indicates high sensitivity of the absorbance to changes in toluene concentration. In particular, cases where |a| > 0.5 are indicated by "O".

[0144] A = a × t + b Equation (14) A: absorbance t: toluene concentration ratio a: t coefficient (slope) b: constant

[0145]

[0146] From the viewpoint of reducing errors in the measurement wavelength and performing measurements with high accuracy, it is preferable to measure absorbance in a wavelength range with small wavelength dependency (good flatness), and specifically, it has been found that it is good to select a wavelength range of 1730 nm or more and 1850 nm or less, and a wavelength range of 1800 nm or more and 2050 nm or less.

[0147] On the other hand, in order to know the direction of change in the reaction (hydrogenation or dehydrogenation) and the dynamics of the change, it is preferable to measure absorbance in a wavelength range with as high sensitivity as possible; specifically, it was found that it is good to select the wavelength ranges of 1620 nm or more and 1680 nm or less, 2150 nm or more and 2180 nm or less, and 2360 nm or more and 2420 nm or less.

[0148] From the results shown in Figures 9 to 11, the wavelength ranges in which the coefficient of determination is close to 1 and exceeds 0.99 are the wavelength ranges shown in Table 8 below. When absorbance is measured in these wavelength ranges, a good linear relationship is obtained between the absorbance and the concentration ratio of toluene and methylcyclohexane. Therefore, the bandpass filter shown in Figure 12 was fabricated, which has the characteristic of transmitting the seven wavelength ranges shown in Table 8. In addition, the bandpass filter shown in Figure 13 was fabricated, which has the characteristic of transmitting the wavelength range of group T, in which absorbance increases with increasing toluene concentration, and the bandpass filter shown in Figure 14 was fabricated, which has the characteristic of transmitting the wavelength range of group M, in which absorbance increases with increasing methylcyclohexane concentration. By using these bandpass filters, it is possible to measure absorbance only in wavelength ranges where there is a good linear relationship between absorbance and concentration.

[0149]

[0150] On the other hand, when the coefficient of determination is small, for example, when the absorbance is measured in a wavelength range where the coefficient of determination is less than 0.9 as shown in the wavelength ranges A to G in Table 9 and Figure 15, a good linear relationship cannot be obtained between the concentration ratio of toluene and methylcyclohexane and the absorbance. Therefore, cutoff filters shown in Figures 16 and 17 were fabricated, which have the property of not transmitting the seven wavelength ranges A to G shown in Table 9 and Figure 15. By using these cutoff filters, even if the absorbance is measured in a way that includes the wavelength ranges A to G by mistake, infrared light does not pass through the regions A to G, so that the concentration ratio can be measured with good linearity.

[0151]

[0152] The present invention is not limited to the configurations described in the above embodiments, but may be combined with other elements, etc. These aspects can be changed without departing from the spirit of the present invention, and can be appropriately determined depending on the application form.

[0153] This international application claims priority based on Japanese Patent Application No. 2023-126247 filed on August 2, 2023, priority based on Japanese Patent Application No. 2023-135124 filed on August 23, 2023, and priority based on Japanese Patent Application No. 2024-110064 filed on July 9, 2024. The entire contents of Japanese Patent Application Nos. 2023-126247, 2023-135124, and 2024-110064 are incorporated by reference into this international application.

[0154] 10, 20: Concentration ratio measuring device 1: Absorbance measuring section 1a, 1a': Measuring cell 1b: Light source 1c: Absorbance detector 2: Concentration ratio calculating section 3: Spectrometer 4: Evaluation section 5: Memory section L1: Light beam L2: Transmitted light S: Solution D: Optical path length 100: Organic hydride manufacturing apparatus 60: Electrolytic cell 70: Cathode liquid supply cell

Claims

1. A method for measuring the concentration ratio of a solution containing toluene or methylcyclohexane, comprising the steps of: measuring the absorbance of the solution at a specific wavelength; and calculating the concentration ratio t:m of the toluene concentration t and the methylcyclohexane concentration m based on the absorbance and a prerecorded calibration curve, wherein the specific wavelength is one or more wavelengths or wavelength ranges selected from the following wavelength ranges: 1,120 nm to 1,140 nm, 1,190 nm to 1,230 nm, 1620 nm to 1,680 nm, 1730 nm to 1,850 nm, 1800 nm to 2,050 nm, 2150 nm to 2,180 nm, and 2360 nm to 2,420 nm.

2. The concentration ratio measuring method according to claim 1, wherein the specific wavelengths are two or more wavelengths or wavelength ranges.

3. The concentration ratio measuring method according to claim 1, wherein the specific wavelength is one or more wavelengths or wavelength ranges in the wavelength ranges of 1120 nm to 1140 nm, 1190 nm to 1230 nm, 1730 nm to 1850 nm, and 1800 nm to 2050 nm.

4. The method for measuring a concentration ratio according to claim 1, further comprising a step of excluding cases where water or hydrogen gas is mixed into the solution from the measurement of the concentration ratio of the solution containing toluene or methylcyclohexane, wherein the cases where water or hydrogen gas is mixed into the solution are the following (1) or (2): (1) A case where the absorbance in one or more wavelengths in the wavelength range of 1500 nm to 1650 nm and / or 1750 nm to 1900 nm exceeds the maximum absorbance of the solution containing toluene or methylcyclohexane, and water is mixed into the solution; or (2) A case where the absorbance in one or more wavelengths in the wavelength range of 1500 nm to 1900 nm is less than the minimum absorbance of the solution containing toluene or methylcyclohexane, and hydrogen gas is mixed into the solution.

5. The method further includes a step of evaluating the reaction state in the hydrogenation and dehydrogenation reactions of the solution containing toluene to methylcyclohexane, wherein the step of measuring the absorbance comprises: Ｔ０ and the absorbance A of the solution at the specific wavelength at time T1 after a predetermined time has elapsed. Ｔ１ and the step of evaluating the reaction state includes measuring an absorbance difference ΔA calculated by the following formula (i): (1) the specific wavelength is one wavelength or wavelength range in the wavelength ranges of 1120 nm to 1140 nm, 1620 nm to 1680 nm, and 2150 nm to 2180 nm, and (1a) when the absorbance difference ΔA is greater than 0, it is evaluated as dehydrogenation, (1b) when the absorbance difference ΔA is 0, it is evaluated as equilibrium, or (1c) when the absorbance difference ΔA is less than 0, it is evaluated as hydrogenation; or (2) the specific wavelength is one wavelength or wavelength range in the wavelength ranges of 1190 nm to 1230 nm, 1730 nm to 1850 nm, 1800 nm to 2050 nm, and 2360 nm to 2420 nm, and (2a) when the absorbance difference ΔA is greater than 0, it is evaluated as hydrogenation, (2b) when the absorbance difference ΔA is 0, it is evaluated as equilibrium, or The concentration ratio measuring method according to claim 1, further comprising the step of: (2c) evaluating that dehydrogenation has occurred when the absorbance difference ΔA is less than 0.

6. A concentration ratio measuring method according to claim 5, wherein the degree of progress of the reaction is evaluated as being high when the absolute value of the absorbance difference ΔA is equal to or greater than a predetermined value.

7. A concentration ratio measuring method according to claim 5, wherein the specific wavelength is one wavelength or wavelength range within the wavelength ranges of 1620 nm to 1680 nm, 2150 nm to 2180 nm, and 2360 nm to 2420 nm.

8. A concentration ratio measuring device for measuring the concentration ratio of a solution containing toluene or methylcyclohexane, comprising: an absorbance measuring unit for measuring the absorbance at a specific wavelength of the solution; and a concentration ratio calculating unit for calculating the concentration ratio t:m of the toluene concentration t and the methylcyclohexane concentration m based on the absorbance and on a pre-recorded calibration curve, wherein the specific wavelength is one or more wavelengths or wavelength ranges selected from the following wavelength ranges: 1120 nm or more and 1140 nm or less, 1190 nm or more and 1230 nm or less, 1620 nm or more and 1680 nm or less, 1730 nm or more and 1850 nm or less, 1800 nm or more and 2050 nm or less, 2150 nm or more and 2180 nm or less, and 2360 nm or more and 2420 nm or less.

9. A concentration ratio measuring device as described in claim 8, wherein the absorbance measuring unit comprises a measurement cell, a light source which irradiates the solution contained in the measurement cell with light of the specific wavelength, and an absorbance detector which measures the absorbance of the transmitted light which has passed through the solution.

10. A concentration ratio measuring device as described in claim 9, wherein the absorbance measuring unit further has a spectroscope on the optical path between the light source and the measurement cell, and the spectroscope is a bandpass filter that transmits wavelengths in the ranges of 1121 nm to 1140 nm, 1620 nm to 1639 nm, and 2150 nm to 2169 nm.

11. A concentration ratio measuring device as described in claim 9, wherein the absorbance measuring unit further has a spectroscope on the optical path between the light source and the measurement cell, and the spectroscope is a bandpass filter that transmits wavelengths in the ranges of 1204 nm to 1223 nm, 1747 nm to 1766 nm, 1831 nm to 1850 nm, and 2360 nm to 2379 nm.

12. A concentration ratio measuring device as described in claim 9, wherein the absorbance measuring unit further has a spectroscope on the optical path between the light source and the measurement cell, and the spectroscope is a cutoff filter that does not transmit the wavelength ranges of 1160 nm to 1166 nm, 1272 nm to 1368 nm, 1519 nm to 1593 nm, 1694 nm to 1707 nm, 2086 nm to 2090 nm, 2274 nm to 2284 nm, and 2444 nm to 2476 nm.

13. A concentration ratio measuring device as described in claim 5, wherein cases in which water or hydrogen gas is mixed into the solution are excluded from the measurement of the concentration ratio of the solution containing toluene or methylcyclohexane, and cases in which water or hydrogen gas is mixed into the solution are (1) or (2) below. (1) The absorbance in one or more wavelengths in the wavelength range of 1500 nm to 1650 nm and / or 1750 nm to 1900 nm exceeds the maximum absorbance of the solution containing toluene or methylcyclohexane, and water is mixed into the solution. (2) The absorbance in one or more wavelengths in the wavelength range of 1500 nm to 1900 nm is less than the minimum absorbance of the solution containing toluene or methylcyclohexane, and hydrogen gas is mixed into the solution.

14. The present invention further includes an evaluation unit for evaluating a reaction state in a hydrogenation reaction and a dehydrogenation reaction of a solution containing toluene or methylcyclohexane, and the absorbance measurement unit measures the absorbance A of the solution at a specific wavelength at time T0. Ｔ０ and the absorbance A of the solution at the specific wavelength at time T1 after a predetermined time has elapsed. Ｔ１ and based on the absorbance difference ΔA calculated by the following formula (i), (1) the specific wavelength is one wavelength or wavelength range in the wavelength ranges of 1120 nm to 1140 nm, 1620 nm to 1680 nm, and 2150 nm to 2180 nm, and (1a) when the absorbance difference ΔA is greater than 0, it is evaluated as dehydrogenation, (1b) when the absorbance difference ΔA is 0, it is evaluated as equilibrium, or (1c) when the absorbance difference ΔA is less than 0, it is evaluated as hydrogenation; or (2) the specific wavelength is one wavelength or wavelength range in the wavelength ranges of 1190 nm to 1230 nm, 1730 nm to 1850 nm, 1800 nm to 2050 nm, and 2360 nm to 2420 nm, and (2a) when the absorbance difference ΔA is greater than 0, it is evaluated as hydrogenation, (2b) when the absorbance difference ΔA is 0, it is evaluated as equilibrium, or (2c) The concentration ratio measurement device according to claim 8, wherein when the absorbance difference ΔA is less than 0, it is evaluated as dehydrogenation.

15. The concentration ratio measuring device according to claim 14, wherein the evaluation unit evaluates the degree of progress of the reaction to be high when the absolute value of the absorbance difference ΔA is equal to or greater than a predetermined value.

16. The concentration ratio measuring device according to claim 14, wherein the specific wavelength is one wavelength or wavelength range within the wavelength ranges of 1620 nm to 1680 nm, 2150 nm to 2180 nm, and 2360 nm to 2420 nm.

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