Concentration ratio measuring method and concentration ratio measuring device

Abstract

To provide a concentration ratio measuring method that can measure, in real time, the component concentration of a toluene- or methylcyclohexane-containing solution within a wide concentration range.SOLUTION: A concentration ratio measuring method is to measure the concentration ratio of a solution containing toluene or methylcyclohexane, and includes the steps of: measuring absorbance at a specific wavelength of the solution; and on the basis of the absorbance, calculating the concentration ratio t:m between the concentration t of the toluene and the concentration m of the methylcyclohexane on the basis of a calibration curve recorded in advance. The specific wavelength is one or more wavelengths or wavelength regions in wavelength regions 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.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] The present disclosure relates to a concentration ratio measuring method and a concentration ratio measuring device. [Background technology]

[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, etc.).

[0003] As a method for determining the concentration ratio of toluene and methylcyclohexane in a synthesis reaction or a dehydrogenation reaction of methylcyclohexane, a method is known in which the reaction solution after synthesis is measured by 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, etc.). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-095329 [Patent Document 2] JP 2020-159743 A Summary of the Invention [Problem to be solved by the invention]

[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 presented to a gas chromatography device. Therefore, although the conventional measurement method has high measurement accuracy, it is difficult to measure the concentration in a wide concentration range in real time, and automation is difficult.

[0006] An object of the present disclosure is to provide a concentration ratio measuring method and a concentration ratio measuring device that are capable of measuring the concentration ratio of a solution containing toluene or methylcyclohexane in real time over a wide concentration range. [Means for solving the problem]

[0007] As a means for solving the above problems, a concentration ratio measurement method according to one embodiment of the present disclosure is a concentration ratio measurement method for measuring a 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 a concentration ratio t:m of the concentration t of the toluene to the concentration m of the methylcyclohexane based on the absorbance and a previously recorded calibration curve; 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. Effect of the Invention

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

[0009] [Figure 1] 1 is a schematic diagram showing an example of a concentration ratio measuring device in a first embodiment. [Diagram 2] FIG. 11 is a schematic diagram showing an example of a concentration ratio measuring device according to a second embodiment. [Diagram 3] 4 is a schematic diagram showing another example of the concentration ratio measuring device in the first embodiment. FIG. [Figure 4] 4 is a schematic diagram showing another example of the concentration ratio measuring device in the first embodiment. FIG. [Diagram 5] 4 is a schematic diagram showing another example of the concentration ratio measuring device in the first embodiment. FIG. [Figure 6] 13 is a flowchart showing an example of a concentration ratio measuring method in the seventh embodiment. [Figure 7] 13 is a flowchart showing another example of the concentration ratio measuring method in the seventh embodiment. [Figure 8] 1 is a graph showing the relationship between the concentration ratio of toluene to methylcyclohexane and absorbance. [Figure 9] 1 is a graph showing the relationship between the concentration ratio of toluene to methylcyclohexane, the absorbance, and the coefficient of determination. [Figure 10] 1 is a graph showing the relationship between absorbance and coefficient of determination in a wavelength range with a wavelength width of 10 nm. [Figure 11] 1 is a graph showing the relationship between absorbance and coefficient of determination in a wavelength range with a wavelength width of 20 nm. [Figure 12] 13 is a graph showing the characteristics of an example of a bandpass filter for measuring a concentration ratio in the fourth embodiment. [Figure 13] 13 is a graph showing characteristics of another example of the bandpass filter for measuring a concentration ratio in the fourth embodiment. [Figure 14] 13 is a graph showing characteristics of another example of the bandpass filter for measuring a concentration ratio in the fourth embodiment. [Figure 15] This is a graph showing the wavelength range in which the coefficient of determination is 0.8 or less in the graph of FIG. [Figure 16] 13 is a graph showing the characteristics of an example of a cutoff filter for measuring a concentration ratio in the fourth embodiment. [Figure 17] 13 is a graph showing characteristics of another example of the cutoff filter for measuring a concentration ratio in the fourth embodiment. [Figure 18] 1 is a diagram showing an example of an organic hydride manufacturing apparatus having a concentration ratio measuring device of the present embodiment. [Figure 19] 1 is a graph showing the relationship between wavelength and absorbance for toluene, methylcyclohexane, water, and hydrogen. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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

[0011] (Concentration ratio measuring method and concentration ratio measuring 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 measuring method and the concentration ratio measuring device will be described together.

[0012] -Methylcyclohexane synthesis and dehydrogenation reaction- First, the synthesis reaction of methylcyclohexane as a hydrogen storage medium and the dehydrogenation reaction for extracting hydrogen will be described. Toluene (C 6 H 5 CH 3 ) and hydrogen (H 2 ) as a hydrogen storage medium. 6 H 11 CH 3 The reaction for synthesizing 2-(2-methylphenyl)propanediol (also called 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 synthesis reaction of methylcyclohexane can be carried out by a known method, and examples of such methods include a method of reacting toluene with hydrogen; and a method of synthesizing methylcyclohexane from water and toluene without passing through hydrogen gas by directly subjecting toluene to an electrochemical reaction. Once the hydrogenation reaction is started, the reaction system usually needs to be cooled since the hydrogenation reaction itself is an exothermic reaction. If the reaction temperature significantly exceeds 100.9°C, the boiling point of methylcyclohexane under 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 measuring method and the concentration ratio measuring device can be suitably applied to the measurement of the concentration ratio of toluene to methylcyclohexane in a solution resulting from such a synthesis reaction or dehydrogenation reaction of methylcyclohexane. According to the concentration ratio measurement method and concentration ratio measurement device, the concentration ratio can be measured over a wide concentration range from 0 volume % to 100 volume % methylcyclohexane without the need for a dilution process that is required in the conventional measurement method using gas chromatography. This makes it possible to perform real-time measurement and to automate the 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 concentration ratio can be measured in real time in the solution during the reaction process, which allows the optimization of the reaction apparatus and reaction conditions.

[0018] [First embodiment] As shown in FIG. 1, a concentration ratio measuring device 10 according to one embodiment of the present disclosure will be described taking as an example an embodiment in which a concentration ratio measuring method is implemented to obtain the concentration ratio t:m between the concentration t of toluene and the concentration m of methylcyclohexane in a solution S flowing through a flow-through type measurement cell 1a. The concentration ratio measuring device 10 has an absorbance measuring unit 1 that measures the absorbance of the solution S at a specific wavelength, and a concentration ratio calculating unit 2 that calculates the concentration ratio t:m between the concentration t of toluene and the concentration m of methylcyclohexane in the solution S based on the measured absorbance and a prerecorded calibration curve. The absorbance measuring unit 1 has a flow-through type 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 that has passed through the solution S. The absorbance measuring unit 1 may further have a memory unit 5 that stores the calibration curve.

[0019] Here, the light ray L1 includes light of specific wavelengths which are one or more wavelengths or wavelength ranges in the near-infrared wavelength range 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. The absorbance detector 1c receives the transmitted light L2 and detects and measures the absorbance at a specific wavelength based on the optical path length D.

[0020] The concentration ratio calculation unit 2 and the storage unit 5 may be a single device equipped with an operation unit and a display unit, and may further be equipped with 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 largely dependent on the temperature of the solution. In addition, 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 measure the absorbance accurately, the temperature of the solution S flowing through the measurement cell 1a may be converted to a constant temperature by, for example, arranging 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 the flow-through type measurement cell 1a is continuously measured, but is not limited to this embodiment. As shown in FIG. 2, the second embodiment of the concentration ratio measuring device 20 may be an embodiment that implements a batch-type concentration ratio measuring method in which a light beam L1 is transmitted to a solution S sampled in a fractional measurement cell 1a' and transmitted light L2 that has passed through the solution S is received.

[0023] In addition, the concentration ratio measuring device 20 shown in Figure 2 can appropriately adopt a configuration similar to that of the concentration ratio measuring device 10 shown in Figure 1, except that it has a fractional type measurement cell 1a' instead of the flow-through type 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 to methylcyclohexane that is the subject of measurement 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 of the toluene concentration t and the methylcyclohexane concentration m may be any concentration ratio, and in either case, the measurement can be performed suitably.

[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, in terms of volume ratio to the total amount of the solution, preferably 95% by volume or more, more preferably 98% by volume or more, and even more preferably 99% by volume or more.

[0026] The other components are not particularly limited and can be appropriately selected depending on the purpose. Examples of the other components 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 measuring step is a step of measuring the absorbance of the solution at a specific wavelength, and can be suitably performed by the absorbance measuring unit. The absorbance measurement unit is a unit that measures the absorbance of the solution at a specific wavelength, and specifically, it preferably 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 may further have a lens, a spectrometer, 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 the coefficient of determination is close to 1, and a good correlation is obtained between the concentration ratio t:m of the concentration t of toluene and the concentration m of methylcyclohexane, and the absorbance. Therefore, by measuring the absorbance of the solution at a 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 from 0 volume % to 100 volume % methylcyclohexane, and also to measure the concentration ratio in real time without pretreatment of the solution.

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

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

[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); continuous light such as halogen lamps; and the like.

[0033] <<Lens>> The lenses can be arranged at various positions on the optical path to converge or collimate light, such as light irradiated from a light source, light irradiated onto a measurement cell, light transmitted through a measurement cell, and light input to an absorbance detector.

[0034] <<Spectrometer>> The spectrometer is not particularly limited and can be appropriately selected depending on the purpose as long as it transmits light of a specific wavelength. Examples of the spectrometer include an optical filter, a prism, and a diffraction grating. These may be used alone or in combination of two or more. Examples of the optical filter include a bandpass filter that transmits a specific monochromatic light or a plurality of wavelength ranges, a longpass filter that transmits wavelengths longer than the cut-on wavelength, a shortpass filter that transmits wavelengths shorter than the cut-off wavelength, a cut-off filter that does not transmit a specific monochromatic light or a plurality of wavelength ranges, a colored glass filter, and a dichroic filter. Moreover, as the spectrometer, a combination of a variable optical filter capable of changing the transmission wavelength range and a variable optical attenuator can also be suitably used.

[0035] <<Optical fiber>> In order to efficiently transmit light such as light irradiated from a light source to a measurement cell and transmitted light passing through the measurement cell and input to an absorbance detector, 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.

[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. Examples of the absorbance detector include optical semiconductors (photocells) and photomultipliers. 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 measuring method and a concentration ratio measuring 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 measuring device 10 shown in FIG. 1 and the concentration ratio measuring device 20 shown in FIG.

[0038] [Third embodiment] The third embodiment is an embodiment of a concentration ratio measuring device that uses a combination of a light source that irradiates monochromatic light of a specific wavelength and a spectrometer such as a bandpass filter that transmits monochromatic light of a specific wavelength, and a concentration ratio measuring method that uses 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 Figures 3 to 4), or a post-spectroscope provided on the optical path between the measurement cell and the absorbance detector (see Figure 5). In the case of the pre-spectroscopic method, the spectrometer may be provided after the light source as shown in FIG. 3, or may be provided before the measurement cell as shown in FIG. In the third embodiment, the position at which the spectroscope is provided can be appropriately selected, but it is preferable to provide it behind the light source or before the measurement cell as shown in FIGS.

[0040] According to the third embodiment, the absorbance is measured based on monochromatic light having a specific wavelength, and the concentration ratio is calculated, so that a monochromatic light absorbance measuring device can be used, and the measurement and calculation can be simplified.

[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 combination of a light source that irradiates continuous light and a spectrometer such as a bandpass filter, a cutoff filter, or a 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 of the wavelength ranges of 1121 nm to 1140 nm, 1204 nm to 1223 nm, 1620 nm to 1639 nm, 1747 nm to 1766 nm, 1831 nm to 1850 nm, 2150 nm to 2169 nm, and 2360 nm to 2379 nm shown in Table 5 below, and it is more preferable that the bandpass filter transmits two or more wavelength ranges.

[0043] Here, these wavelength ranges can be classified into two groups; specifically, they can be classified into a T group of wavelength ranges in which the absorbance increases as the toluene concentration increases, and an M group of wavelength ranges in which the absorbance increases as the methylcyclohexane concentration increases. The wavelength ranges of group T are three wavelength ranges: 1121 nm or more and 1140 nm or less, 1620 nm or more and 1639 nm or less, and 2150 nm or more and 2169 nm or less (see FIG. 13). The wavelength ranges of group M are four wavelength ranges: 1204 nm or more and 1223 nm or less, 1747 nm or more and 1766 nm or less, 1831 nm or more and 1850 nm or less, and 2360 nm or more and 2379 nm or less (see FIG. 14).

[0044] Specifically, a bandpass filter shown in any one of Figures 12 to 14, which has the characteristic of transmitting three or four wavelength ranges shown in Table 5 below, 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 Figures 3 and 4, that is, by locating the spectrometer on the optical path between the light source 1b and the measurement cell 1a, it is possible to measure the absorbance only in the wavelength range where there is a good linear relationship between the absorbance and the concentration ratio. Specifically, continuous light can be incident from a light source such as a tungsten lamp, and the limitation on the transmitted wavelength is relaxed, so that the amount of light increases and it becomes possible to measure the concentration ratio stably.

[0045] The cutoff filter is not particularly limited as long as it transmits a specific wavelength and can be appropriately selected depending on the purpose. However, it is preferable that the cutoff filter does not transmit at least one of 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 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] Specifically, a cutoff filter shown in any one of Figures 16 to 17, which has the property of not transmitting the seven wavelength ranges A to G shown in Table 6 below and Figure 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 positioning the spectrometer 3 as shown in Figures 3 and 4, that is, by having the spectrometer 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 concentration ratios with good linearity.

[0047] The position at which the spectroscope is provided can be appropriately selected, but it is preferable to provide it behind 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 a concentration ratio measuring device that uses a light source that irradiates continuous light in combination with a spectrometer that transmits monochromatic light of a specific wavelength using a tunable optical filter that can change the transmission wavelength range, and an embodiment that performs a concentration ratio measuring method using the concentration ratio measuring device. The tunable optical filter may be, for example, a Fabry-Perot interference filter. The position where the spectrometer is provided can be appropriately selected, but it is preferable to provide it in front of the absorbance detector as shown in FIG.

[0050] [Sixth embodiment] The sixth embodiment is 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 spectrometer, and an embodiment that implements a concentration ratio measuring method using the concentration ratio measuring device. The monochromator is a spectroscope having 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 where the spectroscope is provided can be appropriately selected, but it is preferable to provide it behind the light source as shown in FIG.

[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 a concentration ratio t:m between the concentration t of toluene and the concentration m of methylcyclohexane based on the absorbance and a prerecorded calibration curve, and examples of the concentration ratio calculation unit include a computer having a program stored therein that calculates 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 measuring method will be described below. The concentration ratio measuring method in the seventh embodiment can be suitably carried out by any of the concentration ratio measuring devices 10, 20, 30, 40, and 50 shown in FIGS. 1 to 5, but will be described representatively with reference to FIG. The concentration ratio measuring device 10 calculates the concentration ratio of toluene and methylcyclohexane in the solution S based on the absorbance of transmitted light L2 transmitted 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 measuring method includes an absorbance measuring step and a concentration ratio calculating step, and may further include a specific wavelength setting step of setting a specific wavelength and a calibration curve creating step of creating a calibration curve, as necessary.

[0053] <Specific wavelength setting process> In the specific wavelength setting process, specific wavelengths are set to be 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] The method of setting a specific wavelength is not particularly limited, and a known method can be appropriately selected depending on the purpose, and examples thereof include a method of 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 of setting a spectrometer such as a bandpass filter or cutoff filter that transmits a specific wavelength in a wide wavelength range or multiple wavelength ranges in the concentration ratio measuring device of the fourth embodiment; a method of setting the transmission wavelength of a variable optical filter to monochromatic light of a specific wavelength in the concentration ratio measuring device of the fifth embodiment; a method of 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 of specifying a specific wavelength to be used for calculation in a concentration ratio calculation unit.

[0055] <Calibration curve creation process> In the calibration curve creation process, standard solutions having a graded concentration ratio, in which 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 creating a calibration curve is not particularly limited and a known method can be appropriately selected depending on the purpose, and for example, a calibration curve can be created by the method described in the Examples below and shown in Figure 8. Furthermore, the created calibration curve can be stored in a memory unit. Examples of the graded concentration ratios in the standard solution include the concentration ratios t:m (volume ratio) of the concentration t of toluene to the concentration m of methylcyclohexane, which are 0:100, 10:90, 30:70, 50:50, 70:30, 90:10, and 100:0, respectively.

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

[0058]

number

[0059] <Concentration ratio calculation process> In the concentration ratio calculation step, a concentration ratio t:m between the concentration t of the toluene and the concentration m of the methylcyclohexane is calculated based on the absorbance obtained in the absorbance measurement step and a prerecorded calibration curve. The method for calculating the concentration ratio t:m is not particularly limited and any 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]

number

[0061] Here, in the fourth embodiment, in an aspect using a bandpass filter, the concentration ratio t:m can be calculated by adding up all absorbances in the wavelength range that can transmit the bandpass filter. By using all wavelengths in the near-infrared range with a coefficient of determination of 0.99 or more, the amount of light that reaches the light receiving element of the absorbance meter can be increased, and therefore measurement with a good S / N ratio becomes possible. Specifically, A(λ i ) and then measure the sum of A(λ i ), and the concentration ratio t:m can be calculated by determining t based on the following equation (3), in which all factors except for t are known.

[0062]

number

[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, and 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 concentration ratio measurement method of the eighth embodiment is an embodiment in which the specific wavelength is 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. In order to obtain the concentration ratio, the absorbance at any wavelength at a specific wavelength where the linearity between the concentration ratio and the absorbance is excellent may be measured as shown in the seventh embodiment. However, by measuring the absorbance at two or more wavelengths or wavelength ranges and using the average absorbance as shown in the eighth embodiment, a more stable and accurate measurement can be realized.

[0065] A 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 ) was measured, and the average absorbance A meanNext, in the seventh embodiment, A(λ 1 ) to A mean By substituting the above, the concentration ratio can be calculated.

[0066] The specific wavelength is λ 1 From λ 2 If the wavelength range is 1, the average digital or analog absorbance A mean In the seventh embodiment, A(λ 1 ) to A mean By substituting the above, the concentration ratio can be calculated. 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 thereof include a digital method in which the average absorbance is determined by integrating and averaging the absorbance for each wavelength measured with a predetermined wavelength resolution for a specific wavelength in a set wavelength range; and a method in which light in a specific wavelength range is irradiated using an optical filter such as a bandpass filter, the transmitted light is collected, and the absorbance in that wavelength range is determined in an analog manner.

[0067] In an eighth embodiment, the specific wavelengths are two or more wavelengths or wavelength ranges, i.e., two or more wavelengths or wavelength ranges in the seven 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. The wavelength range is not particularly limited as long as it is 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 2 below) and can be appropriately selected depending on the purpose. The wavelength width Δλ of the wavelength range is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof 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 suitably. Alternatively, the average absorbance may be calculated 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 described above may be used.

[0068] As is apparent from the examples, Figures 10 to 11, and Table 3 described later, the coefficient of determination is improved for the average absorbance compared to the absorbance measured at one wavelength, and therefore a measurement with higher linearity can be performed. In addition, the total amount of transmitted light increases, the effects of measurement errors of wavelength and transmitted light can be reduced, and the S / N ratio is improved. Therefore, according to the concentration ratio measuring method of the eighth embodiment, it is possible to measure the concentration ratio more stably and with higher accuracy.

[0069] [Ninth embodiment: Concentration ratio measurement method based on two specific wavelengths] In the concentration ratio measurement method of the ninth embodiment, the 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 following formula (12), which is the concentration ratio t:m of the toluene concentration t to the methylcyclohexane concentration m.

[0070] In a ninth embodiment, the specific wavelengths are two wavelengths, i.e., 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 is T (λ 1 ), and AT (λ 2 ) and the absorbance A of methylcyclohexane M (λ 1 ), and A M (λ 2 From the measurement results and the following formulas (4) to (9), the molar absorption coefficients of toluene and methylcyclohexane at each wavelength are calculated.

[0072]

number

[0073]

number

[0074]

number

[0075]

number

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

[0077]

number

[0078]

number

[0079]

number

[0080]

number

[0081] Equations (10) and (11) can be expressed as equation (12), which is a determinant. If we find the inverse matrix of equation (12) and apply it to the left of both sides, we get equation (13).

[0082]

number

[0083]

number

[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 It is. Looking at the right side of equation (13), it can be seen 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 previously obtained absorption coefficients of toluene and methylcyclohexane 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 It can be seen that it is possible to find From this result, the concentration ratio t:m of the toluene concentration t and the methylcyclohexane concentration m is c 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 dependency] The concentration ratio measurement method of the tenth embodiment is an embodiment based on a wavelength range with small wavelength dependency. Note that, except that it is based on a wavelength range with small wavelength dependency, it can be carried out 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, that is, 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 has wavelength dependency. The smaller this wavelength dependency, the more stable the measurement. If the wavelength dependency is large, the change in absorbance will be large for a small change in the measurement wavelength, and if there is any fluctuation in the measurement wavelength, the reproducibility will deteriorate. This means that the error sensitivity is high, which is one of the factors that cause unstable measurements. Therefore, from the viewpoint of reducing errors resulting from fluctuations in the measured wavelength and performing accurate measurements, it is advisable to select a wavelength range with small wavelength dependency (good flatness). As is clear from Table 4 in the Examples described below, it is preferable 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. According to the concentration ratio measuring method of the tenth embodiment, errors resulting from fluctuations in the measurement wavelength can be reduced, and highly accurate measurements can be performed.

[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, and can be carried out in the same manner as the seventh to ninth embodiments, except that it is based on a wavelength range with high absorbance sensitivity. 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 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, 2150 nm or more and 2180 nm or less, and 2360 nm or more and 2420 nm or less.

[0088] While the smaller the wavelength dependency, the more stable the measurement, the concentration ratio of toluene and methylcyclohexane changes depending on the progress of the hydrogenation / dehydrogenation reaction of toluene and methylcyclohexane. Therefore, in order to know the direction of the change (hydrogenation or dehydrogenation) and the dynamics of the change, it is best to measure the absorbance in a wavelength range with as high absorbance sensitivity as possible. Specifically, as will be apparent from Table 4 in the Examples described later, it is preferable to select a wavelength range of 1620 nm or more and 1680 nm or less, a wavelength range of 2150 nm or more and 2180 nm or less, and a wavelength range of 2360 nm or more and 2420 nm or less, in which the magnitude of the absorbance slope |a|>0.5. According to the concentration ratio measuring method of the eleventh embodiment, it is possible to perform measurements with high sensitivity to changes in concentration ratio.

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

[0090] [Twelfth embodiment: Concentration ratio measurement method excluding cases where water or hydrogen gas is mixed into the solution] The concentration ratio measuring method of the twelfth embodiment is an embodiment in which the concentration ratio of toluene and methylcyclohexane is measured, excluding the case where by-products such as water or hydrogen gas are mixed into the solution. Note that, except for excluding the case where water or hydrogen gas is mixed into the solution, the method can be carried out in the same manner as the first to eleventh embodiments.

[0091] The concentration ratio measuring device of the twelfth embodiment is an embodiment of a concentration ratio measuring device that measures the concentration ratio of a solution containing toluene to methylcyclohexane, excluding the case where water or hydrogen gas is mixed into the solution. Note that, except for excluding the case where water or hydrogen gas is mixed into the solution, it 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 Fig. 18. The organic hydride manufacturing apparatus 100 shown in Fig. 18 has 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 type measurement cell 1a connected to a pipe 71, and the concentration ratio measurement device 30, 40, or 50 shown in Figs. 3 to 5 may be used instead of the concentration ratio measurement device 10 shown in Fig. 1.

[0093] The electrolytic cell 60 has an anode chamber 61, an anode electrode 62, an electrolyte membrane 63, a cathode electrode 64, a cathode chamber 65, and a power supply unit 66. The electrolytic cell 60 hydrogenates toluene by electrochemical reduction reaction to generate methylcyclohexane (MCH), which is an organic hydride. Here, after water is electrolyzed, hydrogen ions directly reduce toluene, and MCH is directly generated, basically without going through a process of generating hydrogen. Specifically, water in the anode chamber 61 is oxidized by the anode electrode 62, and hydrogen ions are generated. The generated hydrogen ions pass through the electrolyte membrane 63 and move to the cathode electrode 64 side. Toluene supplied from the tank 70 to the cathode chamber 65 reacts with the transferred hydrogen ions to generate MCH. The generated MCH and non-hydrogenated toluene are then returned to the cathode liquid supply tank 70 via the pump 75. By repeating this cycle, most of the toluene is eventually converted to MCH.

[0094] On the other hand, as a side reaction, hydrogen ions that could not react with toluene at the cathode become hydrogen. Also, a part of the water in the anode chamber 61 passes through the electrolyte membrane 63 and moves to the cathode electrode 64 side. As a result, like toluene and MCH, water and hydrogen also circulate through the cathode liquid supply tank 70 and the 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, so cases where water or hydrogen gas is mixed into the solution S are excluded from the measurement target.

[0096] As long as the solution S contains water and / or hydrogen and can be excluded from the measurement target, the detection method is not particularly limited and can be appropriately used depending on the purpose. 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 (for example, 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 the case can be excluded from the measurement of the concentration ratio of toluene and methylcyclohexane.

[0097] As for hydrogen, the absorbance of hydrogen is very small in the wavelength range of 1500 nm or more and 1900 nm or less, including the wavelength range shown in Figure 19, and may be considered to be substantially zero, and is smaller than the absorbance of a solution containing toluene to methylcyclohexane at any wavelength. Therefore, when the absorbance is less than the minimum absorbance of a solution containing toluene to 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 cases where solution S contains water and / or hydrogen from consideration and measuring the concentration ratio of toluene and methylcyclohexane when solution S contains substantially only toluene or methylcyclohexane, it is possible to realize highly accurate measurement of the concentration ratio while eliminating the influence of the mixed water and hydrogen. EXAMPLES

[0099] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0100] 8 is a graph showing the relationship between the concentration ratio of toluene and 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 indicates absorbance, and the horizontal axis indicates wavelength. Solutions (represented as T00M100, T10M90, T30M70, T50M50, T70M30, and T100M00 in Fig. 8) were prepared so that the concentration ratio t:m of the concentration t of toluene to the concentration m of methylcyclohexane was 0:100, 10:90, 30:70, 50:50, 70:30, 90:10, and 100:0, respectively, in terms of volume [L], and the absorbance of each solution was measured at wavelengths of 1000 [nm] to 2500 [nm].

[0101] It can be seen from FIG. 8 that the absorbance exhibits a specific value for each wavelength depending on a given concentration ratio (volume ratio) of toluene and methylcyclohexane.

[0102] Next, in order to evaluate the correlation between the absorbance and the concentration ratio t:m shown in FIG. 8, the coefficient of determination between the absorbance and the concentration ratio t:m was calculated and shown as FIG. 9, superimposed on the graph of FIG. FIG. 9 is a graph showing the relationship between the concentration ratio, absorbance, and coefficient of determination for each wavelength of toluene and methylcyclohexane. In Fig. 9, each value in the legend indicates the concentration of toluene (molar concentration ratio), and the thick line indicates the coefficient of determination R 2 (Correlation coefficient R squared: R 2 ) and the right vertical axis indicates the coefficient of determination. Other legends are the same as in Fig. 8.

[0103] In FIG. 9, the coefficient of determination indicates the linearity between the absorbance and the concentration ratio t:m. 2 , 0≦R 2 The value is ≦1, and the closer it is to 1, the more linear the relationship is.

[0104] Concentration of toluene c T The relationship between and absorbance is expressed by the following equation (2).

[0105]

number

[0106] A(λ 1 ): Specific wavelength λ 1 Absorbance at [AU] α T (λ 1 ): λ 1 Molar absorptivity of toluene in [L mol -1 ·cm -1 ] α M (λ 1 ): λ 1 Molar absorptivity 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 of toluene in the solution (volume ratio) m: Concentration ratio (volume ratio) of methylcyclohexane in the solution where t+m=1

[0107] Here, according to the reaction formulas (1) and (2) above, the hydrogenation / dehydrogenation reaction of toluene and methylcyclohexane is an equimolar reaction, and therefore the concentration ratio can be expressed as t:m=t:1-t. By substituting into equation (2), the absorbance A(λ) of the solution can be expressed as a linear equation in terms of the toluene concentration t. FIG. 9 shows a graph showing the strength of the relationship between the toluene concentration t and the absorbance A(λ) as a coefficient of determination. As can be seen from FIG. 9, in the wavelength range of 1000 [nm] to 2500 [nm], the absorbance value varies between 0 [AU] and 2.6 [AU]. Referring to the correspondence between absorbance and transmittance shown in Table 1, the absorbance of 0 [AU] to 2.6 [AU] is expressed as the transmittance T / T 0Expressed as such, this is equivalent to a change from 100[%] to 0.25[%].

[0108] [Table 1]

[0109] The relationship between absorbance and transmittance is given by the following formula (1).

number

[0110] As shown in Figure 9 and Table 1, due to the dynamic characteristics of the sensor and filter, the linearity characteristics decrease when the absorbance A is 0.05 [AU] or less or 1.3 [AU] or more. This is because the transmittance T / T 0 Expressed as 89.1% or more and 5.0% or less.

[0111] 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 2, and that the concentration ratio can be accurately determined by measuring the absorbance of a solution using a specific wavelength that is one or more wavelengths or a wavelength range in the wavelength range shown in Table 2. It was confirmed that it is not necessary to measure absorbance in all wavelength ranges, but rather that it is possible to measure absorbance at one of the most suitable wavelength ranges shown in Table 2 and calculate the concentration ratio.

[0112] [Table 2]

[0113] Next, a method for measuring the concentration ratio when the wavelength range is a specific wavelength will be described. Figure 10 is a graph showing the relationship between absorbance and coefficient of determination in a 10 nm wavelength range. The average absorbance was calculated for each of the seven wavelength ranges with excellent linearity shown in Table 2, each with a continuous wavelength range of 10 nm, and the wavelength range with the largest coefficient of determination was shown.

[0114] Specifically, in the same manner as in the embodiment shown in Fig. 8, absorbance was measured in the wavelength range of 1100 [nm] to 2500 [nm] with a wavelength resolution of 1 [nm]. Next, all of the continuous wavelength ranges with a wavelength width of 10 nm were set within the seven wavelength ranges with excellent linearity shown in Table 2. For example, within the wavelength range of 1120 nm to 1140 nm, 12 wavelength ranges with a wavelength width of 10 nm can be set at 1 nm intervals, such as 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 band, the absorbance for 10 samples (10 wavelengths) was integrated, the average absorbance was calculated, and the concentration ratio was calculated based on the average absorbance.

[0115] In Fig. 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 value of the arithmetic average of the determination coefficients calculated from the average absorbance of each series in a wavelength range of 10 [nm] within the wavelength range shown in Table 2, and the vertical axis on the right indicates the determination coefficient. In Fig. 10, the dotted lines with a wavelength range of 10 [nm] indicate the wavelength range (horizontal axis) where the arithmetic average of the determination coefficients is maximum, and the average absorbance (vertical axis on the left).

[0116] An example shown in FIG. 11 was carried out in the same manner as in FIG. 10, except that the wavelength band having a wavelength width of 10 nm was changed to a wavelength band having a wavelength width of 20 nm. Figure 11 is a graph showing the relationship between absorbance and coefficient of determination in a 20 nm wavelength range. The average absorbance was calculated for each of the seven wavelength ranges with excellent linearity shown in Table 2, each with a continuous wavelength range of 20 nm, and the wavelength range with the largest coefficient of determination was shown.

[0117] Table 3 shows the wavelength ranges of 10 nm or 20 nm in which the coefficient of determination is maximized, and the maximum value of the coefficient of determination, obtained from FIGS. 10-11 and Table 3 shown below, by measuring the average absorbance in the wavelength range, the coefficient of determination is improved (or, when the maximum value of the coefficient of determination for one original wavelength is 1, the coefficient of determination is 0.999 or more), and therefore, a measurement with high linearity can be performed. Furthermore, by measuring absorbance in the wavelength range, the total amount of transmitted light increases, the influence of measurement errors of wavelength and transmitted light can be reduced, and the S / N ratio is improved. Therefore, it was found that the concentration ratio measurement method based on the wavelength range enables more stable and more accurate measurement of the concentration ratio.

[0118] Among the wavelength ranges in Table 3, the wavelength ranges of 1751 [nm] to 1760 [nm] and 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.

[0119] [Table 3]

[0120] In addition, Table 4 shows the wavelength dependency (flatness) of absorbance and the magnitude of the slope |a| in each of the seven wavelength ranges.

[0121] <Wavelength dependence of absorbance (flatness)> The wavelength dependence (flatness) of absorbance is shown in FIG. 8 and Table 2. The wavelength dependence of absorbance of toluene, ΔA T (λ) / Δλ, and wavelength dependence of absorbance of methylcyclohexane ΔA M The (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 3. Here, A T (λ) is the absorbance of toluene [AU], and AM (λ) indicates the absorbance [AU] 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, ~|ΔA M (λ) / Δλ|≦0.009 is satisfied, and the wavelength dependence of absorbance is not small. 〇:|ΔA T (λ) / Δλ|<0.009 and |ΔA M (λ) / Δλ|<0.009, and the wavelength dependence of absorbance is small.

[0122] <Magnitude of absorbance gradient> The magnitude of the absorbance slope |a| is the largest |a| within the wavelength range among the absolute values ​​of the coefficient (slope) a of t when approximating the absorbance and the toluene concentration ratio in each of the seven wavelength ranges to a linear equation shown in the following equation (14). When |a| is large, it indicates that the sensitivity of absorbance to the change in toluene concentration is high. In particular, the case of |a|>0.5 is indicated by "◯".

[0123] A=a×t+b Equation (14) A: Absorbance t: Toluene concentration ratio a: t coefficient (slope) b: constant

[0124] [Table 4]

[0125] From the viewpoint of reducing measurement wavelength errors and performing accurate measurements, it is preferable to measure absorbance in a wavelength range with small wavelength dependency (good flatness); specifically, it has been found that it is good to select the wavelength ranges of 1730 nm or more and 1850 nm or less, and 1800 nm or more and 2050 nm or less.

[0126] On the other hand, in order to know the direction of reaction change (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.

[0127] From the results of 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 in Table 5 below, and when absorbance is measured in these wavelength ranges, a good linear relationship is obtained between the concentration ratio of toluene and methylcyclohexane and the absorbance. Therefore, we fabricated the bandpass filter shown in Figure 12, which has the characteristic of transmitting the seven wavelength ranges shown in Table 5. We also fabricated the bandpass filter shown in Figure 13, which has the characteristic of transmitting the wavelength range of group T, where absorbance increases as the toluene concentration increases, and the bandpass filter shown in Figure 14, which has the characteristic of transmitting the wavelength range of group M, where absorbance increases as the methylcyclohexane concentration increases. 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.

[0128] [Table 5]

[0129] On the other hand, the coefficient of determination is small. For example, when the absorbance is measured in a wavelength range where the coefficient of determination is <0.9 as shown in the wavelength ranges A to G in Table 6 and FIG. 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 created that have the property of not transmitting the seven wavelength ranges A to G shown in Table 6 and Figure 15. By using these cutoff filters, even if the absorbance is measured in a manner that mistakenly includes the wavelength ranges A to G, infrared light does not pass through the regions A to G, making it possible to measure the concentration ratio with good linearity.

[0130] [Table 6]

[0131] The present invention is not limited to the configurations shown in the above embodiments, combinations with other elements, etc. These points can be changed without departing from the spirit of the present invention, and can be appropriately determined according to the application form. [Explanation of symbols]

[0132] 10, 20: Concentration ratio measuring device 1: Absorbance measuring section 1a, 1a': Measuring cell 1b:Light source 1c: Absorbance detector 2:Concentration ratio calculation section 3: Spectrometer 5: Storage section L1: Ray of light L2: Transmitted light S :Solution D: Optical path length 100: Organic hydride production equipment 60: Electrolytic cell 70: Cathode liquid supply tank

Claims

1. A method for measuring a 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 a concentration ratio t:m of the concentration t of the toluene to the concentration m of the methylcyclohexane based on the absorbance and a previously recorded calibration curve, The concentration ratio measuring method according to the present invention, characterized in that the specific wavelength is 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.

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

3. 2. The concentration ratio measuring method according to claim 1, 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, 1730 nm to 1850 nm, and 1800 nm to 2050 nm.

4. The method further includes 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, 2. The method for measuring a concentration ratio according to claim 1, wherein the case in which water or hydrogen gas is mixed into the solution is the following (1) or (2). (1) When 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 at 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. A concentration ratio measuring device for measuring the concentration ratio of a solution containing toluene to methylcyclohexane, an absorbance measurement unit for measuring the absorbance of the solution at a specific wavelength; a concentration ratio calculation unit that calculates 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 previously recorded calibration curve; having The specific wavelength is 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.

6. 6. The concentration ratio measurement device according to claim 5, wherein the absorbance measurement unit comprises a measurement cell, a light source that irradiates the solution contained in the measurement cell with light of the specific wavelength, and an absorbance detector that measures the absorbance of the transmitted light that has passed through the solution.

7. The absorbance measurement unit further includes a spectroscope on an optical path between the light source and the measurement cell, 7. The concentration ratio measuring device according to claim 6, wherein the spectroscope is a bandpass filter that transmits wavelengths in the wavelength ranges of 1121 nm to 1140 nm, 1620 nm to 1639 nm, and 2150 nm to 2169 nm.

8. The absorbance measurement unit further includes a spectroscope on an optical path between the light source and the measurement cell, 7. The concentration ratio measuring device according to claim 6, wherein the spectroscope is a bandpass filter that transmits wavelengths in the following ranges: 1204 nm to 1223 nm, 1747 nm to 1766 nm, 1831 nm to 1850 nm, and 2360 nm to 2379 nm.

9. The absorbance measurement unit further includes a spectroscope on an optical path between the light source and the measurement cell, 7. The concentration ratio measuring device according to claim 6, wherein the spectrometer is a cutoff filter that does not transmit wavelengths in the following ranges: 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.

10. Cases where 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, 6. The concentration ratio measuring device according to claim 5, wherein the case where water or hydrogen gas is mixed into the solution is the following (1) or (2). (1) When 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 at 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.

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