Evaluation method and evaluation device

Abstract

To provide an evaluation method that makes it possible to evaluate in real time a reaction state in a hydrogenation reaction and dehydrogenation reaction of a toluene or methylcyclohexane-containing solution.SOLUTION: The evaluation method is for evaluating a reaction state in a hydrogenation reaction and a dehydrogenation reaction of a toluene or methylcyclohexane-containing solution. The evaluation method includes the steps of: measuring an absorbance AT0 of the solution at a specific wavelength at time T0 and an absorbance AT1 of the solution at the wavelengths after T1 hours has elapsed; and determining whether the reaction state is hydrogenation, an equilibrium state, or dehydrogenation on the basis of a calculated absorbance difference ΔA.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present disclosure relates to an evaluation method and an evaluation 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] On the other hand, from the viewpoint of monitoring the synthesis of methylcyclohexane and the extraction of hydrogen and optimizing the conditions thereof, it is required to evaluate whether the reversible reaction is in the state of a hydrogenation reaction or a dehydrogenation reaction when the synthesis reaction or the dehydrogenation reaction of methylcyclohexane progresses.

[0007] An object of the present disclosure is to provide an evaluation method and evaluation device capable of evaluating in real time the reaction state in the hydrogenation reaction and dehydrogenation reaction of a toluene- or methylcyclohexane-containing solution. [Means for solving the problem]

[0008] As a means for solving the above problems, an evaluation method according to one embodiment of the present disclosure is a method for evaluating a reaction state in a hydrogenation reaction and a dehydrogenation reaction of a solution containing toluene to methylcyclohexane, the method comprising the steps of: The absorbance A of the solution at a specific wavelength at time T T0 and, The absorbance A of the solution at the specific wavelength after the lapse of time T1 T1 and measuring Based on the absorbance difference ΔA calculated by the following formula (i),

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[0009] According to the present disclosure, it is possible to provide an evaluation method and evaluation device capable of evaluating in real time the reaction state in the hydrogenation reaction and dehydrogenation reaction of a toluene- or methylcyclohexane-containing solution. [Brief description of the drawings]

[0010] [Figure 1] 1 is a graph showing the relationship between the concentration ratio of toluene to methylcyclohexane and absorbance in the range of 1000 nm to 2500 nm. [Diagram 2] 1 is a graph showing the relationship between the concentration ratio of toluene to methylcyclohexane, the absorbance, and the coefficient of determination. [Diagram 3] 1 is a graph showing the relationship between the concentration ratio of toluene to methylcyclohexane and the slope of absorbance. [Figure 4] 4 is a flowchart showing an example of an evaluation method in the first embodiment. [Diagram 5] 13 is a flowchart showing an example of an evaluation method according to the second embodiment. [Figure 6] FIG. 13 is a schematic diagram illustrating an example of an evaluation device according to a third embodiment. [Figure 7]FIG. 13 is a schematic diagram illustrating an example of an evaluation device according to a fourth embodiment. [Figure 8] FIG. 13 is a schematic diagram showing another example of the evaluation device in the third embodiment. [Figure 9] FIG. 13 is a schematic diagram showing another example of the evaluation device in the third embodiment. [Figure 10] FIG. 13 is a schematic diagram showing another example of the evaluation device in the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] 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.

[0012] (Evaluation method and evaluation device) The evaluation method of the present disclosure includes an absorbance measurement step and an evaluation step, and preferably includes a concentration ratio calculation step, and further includes other steps such as a wavelength setting step and a calibration curve creation step as necessary. The evaluation device of the present disclosure includes an absorbance measurement unit and an evaluation unit, and preferably includes a concentration ratio calculation unit, and further includes other components as necessary. Below, matters common to the evaluation method and the evaluation device will be described together.

[0013] -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 (C6H5CH3) and hydrogen (H2) are reacted to produce methylcyclohexane (C6H 11 The reaction to synthesize CH3) (also called hydrogen addition reaction) is represented by the following reaction formula (1).

[0014] <Reaction formula (1)> C6H5CH3+ 3H2→ C6H 11CH3

[0015] 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.

[0016] 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.

[0017] <Reaction formula (2)> C6H 11 CH3 → C6H5CH3+ 3H2

[0018] These hydrogenation and dehydrogenation reactions of toluene and methylcyclohexane are reversible reactions, and therefore methylcyclohexane can function as a useful hydrogen storage medium. When the synthesis reaction of methylcyclohexane progresses and the concentration ratio or conversion rate of methylcyclohexane becomes high, for example, 95% by volume or more, the reaction approaches an equilibrium state. Conventional measurement methods could not measure in real time, and therefore could not evaluate the reaction state in real time. Therefore, it was difficult to optimize reaction conditions such as temperature and hydrogen supply.

[0019] The evaluation method and the evaluation device are capable of evaluating the reaction state in real time in the hydrogenation and dehydrogenation reactions of such a solution containing toluene or methylcyclohexane. According to the evaluation method and the evaluation device, it is possible to measure the concentration-dependent absorbance of toluene and methylcyclohexane in a wide concentration range from 0 volume % to 100 volume % methylcyclohexane without performing a dilution process that is required in the measurement method using gas chromatography of the conventional technology. This makes it possible to evaluate the reaction state in real time and measure the concentration ratio as necessary, thereby enabling automated evaluation and measurement. Therefore, based on the evaluation results of the reaction state, it is possible to provide information for optimizing reaction conditions such as temperature and hydrogen supply, and making decisions such as whether to further proceed with the reaction or to terminate the reaction.

[0020] Moreover, the evaluation method according to the second embodiment can be suitably applied to the measurement of the concentration ratio of toluene to methylcyclohexane in a solution of a synthesis reaction or a dehydrogenation reaction of methylcyclohexane. 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.

[0021] <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.

[0022] 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.

[0023] 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.

[0024] [First embodiment] <Absorbance measurement step and absorbance measurement unit> The absorbance measurement 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. T1 and can be suitably carried out by the absorbance measuring unit. 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, the measurement unit preferably has a measurement cell, a light source which irradiates the solution contained in the measurement cell with light of a specific wavelength, and an absorbance detector which measures the absorbance of the transmitted light which has passed through the solution, and further has a lens, a spectroscope, an optical fiber, etc., as necessary.

[0025] -Specific wavelength- The specific wavelength is one wavelength or a wavelength range 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.

[0026] FIG. 1 is a graph showing the relationship between the concentration ratio of toluene to methylcyclohexane and absorbance in the range of 1000 nm to 2500 nm. FIG. 2 is a graph showing the relationship between the concentration ratio of toluene to methylcyclohexane, the absorbance, and the coefficient of determination, and is a graph in which the relationship between the coefficient of determination is superimposed on the graph of FIG. In Figures 1 and 2, the vertical axis indicates absorbance, and the horizontal axis indicates wavelength. Solutions (represented as T00M100, T10M90, T30M70, T50M50, T70M30, and T100M00 in Figures 1 and 2) were prepared so that the concentration ratio t:m of the toluene concentration t and the methylcyclohexane concentration m was 0:100, 10:90, 30:70, 50:50, 70:30, 90:10, and 100:0, respectively, in terms of molar concentration [mol / L], and the absorbance of each solution was measured at wavelengths of 1000 [nm] to 2500 [nm]. In Fig. 2, each value in the legend indicates the concentration (volume ratio) of toluene, and the thick line indicates the coefficient of determination R 2 (Correlation coefficient R squared: R 2 ) and the right vertical axis shows the coefficient of determination.

[0027] As is apparent from FIGS. 1 and 2 and the examples shown below, the specific wavelength is a wavelength or wavelength range where the coefficient of determination is close to 1, and where 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-dependent absorbance and concentration ratio of toluene and methylcyclohexane over a wide concentration range from 0 volume % to 100 volume % methylcyclohexane, and it is also possible to measure the concentration-dependent absorbance and concentration ratio of toluene and methylcyclohexane in real time without pretreatment of the solution.

[0028] <Evaluation process and evaluation section> 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.

number

[0029] 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 following formula (i) and the evaluation criterion, and examples of the evaluation unit include a computer that stores a program for evaluating the reaction state based on formula (i) and the evaluation criterion.

[0030] FIG. 3 is a graph showing the relationship between the concentration ratio of toluene to methylcyclohexane and the absorbance, and is a graph showing the relationship by superimposing the slope on the graph of FIG. In FIG. 3, each numerical value in the legend indicates the concentration (volume ratio) of toluene, the thick line indicates the slope of the relationship between the toluene concentration and the absorbance, and the vertical axis on the right side indicates the slope.

[0031] As shown in FIG. 3, 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) The 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 concentration of toluene and the absorbance exceeds 0, and (2) 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, in which the slope of the relationship between the concentration of toluene and the absorbance is less than 0.

[0032] As shown in Table 1 below, the reaction state can be evaluated depending on the wavelength range to which the specific wavelength corresponds and whether the absorbance difference ΔA is ΔA<0, ΔA=0, or ΔA>0.

[0033] [Table 1]

[0034] There is no particular limitation on the time point T0, and any time point can be set appropriately depending on the purpose. The predetermined time at time T1 after the predetermined time has elapsed is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include one minute, one second, and one millisecond. The absorbance may be measured at two or more points, and may be measured continuously at the specified time interval (see, for example, Table 2) or discontinuously at a desired time interval. In either case, the reaction state can be evaluated based on the absorbance difference ΔA between any two points in time. For example, absorbances at each time point measured continuously at intervals of 1 millisecond or the like can be thinned out at an appropriate sampling interval and used for evaluation (see, for example, Table 3). The sampling interval can be appropriately selected by optimizing the time course of the chemical reaction and the sampling interval for absorbance measurement. Although it is conceivable that the chemical reaction may fluctuate, measurements with little variance in data are possible even if the chemical reaction fluctuates.

[0035] [Table 2]

[0036] [Table 3]

[0037] 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 ratios at time points T0 and T1 after calculating the concentration ratio from the absorbance based on the concentration ratio calculation process described below.

[0038] FIG. 4 shows a flowchart illustrating an example of the evaluation method according to the first embodiment. First, the absorbance A of the solution at a specific wavelength at time T0 T0 (Step S1-1), and then the absorbance A of the solution at a specific wavelength at time T1 after a predetermined time has elapsed is measured. T1 is measured (step S1-2). The absorbance difference ΔA is calculated based on the formula (i) (step S2-1), and it is determined whether the slope of the toluene concentration and the absorbance at a specific wavelength is greater than 0 or less than 0 (step S2-2). The reaction state is evaluated based on the calculated ΔA and the judgment criteria (step S2-3 or step S2-4).

[0039] It is preferable that the evaluation step and the evaluation unit further evaluate that the degree of progress of the reaction is high when the absolute value of the absorbance difference ΔA is equal to or greater than a predetermined value. Since the absolute value of the absorbance difference ΔA depends on the concentration ratio of toluene and methylcyclohexane from time T0 to T1, if the absolute value is equal to or greater than a predetermined value, it can be determined that the reaction continues to proceed after T1, and if 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. In addition, when evaluation is performed using two or more absorbance differences ΔA with different sampling intervals, the progress of the reaction may be evaluated based on the value ΔA / (T1-T0) obtained by dividing the absorbance difference ΔA by the sampling interval (T1-T0).

[0040] Specifically, in the synthesis of methylcyclohexane, i.e., in the case of a hydrogenation reaction, it is necessary to stop the supply of hydrogen at some point during the reaction. The timing can be determined by evaluating the reaction state in real time using the above evaluation method. In addition, information on the hydrogenation rate can be obtained from the absolute value of the absorbance difference ΔA. Based on this, the reaction conditions of the entire reaction system can be optimized.

[0041] [Second embodiment] The evaluation method as a second embodiment further includes a concentration ratio calculation step.The evaluation device as a second embodiment further includes a concentration ratio calculation unit.

[0042] <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. The absorbance is absorbance A T0 , and absorbance A T1 The absorbance may be measured at any time.

[0043] In addition, when the solution contains other components that affect the absorbance of the solution at wavelengths specific to the other components, the concentration ratio can be measured with high measurement accuracy by setting the specific wavelength so as not to include the wavelengths specific to the other components.

[0044] FIG. 5 shows a flowchart illustrating an example of the evaluation method according to the second embodiment. Following step S1-2, step S3 is carried out to calculate the concentration ratio t:m of toluene to methylcyclohexane based on formula (2), and the rest is the same as the flowchart shown in FIG. The order in which step S3 is performed is arbitrary, and step S3 can be performed at any time after step S1-1 or step S1-2.

[0045] [Third embodiment] As shown in FIG. 6, an evaluation device 10 according to an embodiment of the present disclosure will be described taking as an example an embodiment for 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 type measurement cell 1a. The evaluation device 10 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 2 that calculates an absorbance difference ΔA and evaluates the reaction state based on the evaluation criteria, and a concentration ratio calculation unit 3 that calculates the concentration ratio t:m of the toluene concentration t and the methylcyclohexane concentration m of the solution S based on a calibration curve recorded in advance, based on the measured absorbance, as necessary. The absorbance measurement unit 1 includes 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 device may further include a memory unit 5 that stores the calibration curve.

[0046] 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 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.

[0047] The evaluation unit 2, the concentration ratio calculation unit 3, 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 evaluation unit 2, the concentration ratio calculation unit 3, 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.

[0048] 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.

[0049] [Fourth embodiment] The evaluation device 10 in the third 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 the present invention is not limited to this embodiment. As shown in FIG. 7, an embodiment may be adopted in which a batch-type evaluation method is implemented in which a light beam L1 is transmitted to a solution S sampled in a fractional measurement cell 1a′ and transmitted light L2 transmitted through the solution S is received, as in the evaluation device 20 in the fourth embodiment.

[0050] The evaluation device 20 shown in FIG. 7 may have the same configuration as the evaluation device 10 shown in FIG. 6, except that it has a fractional 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.

[0051] <<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 measuring cell through which light passes can be appropriately selected depending on the specific wavelength, solution composition, etc., and examples thereof include quartz glass.

[0052] <<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.

[0053] <<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.

[0054] <<Spectrometer>> The spectrometer is not particularly limited and can be appropriately selected depending on the purpose as long as it transmits 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.

[0055] <<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 evaluation device may use an optical fiber between the light source and the measurement cell, or between the measurement cell and the absorbance detector.

[0056] <<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.

[0057] As the fifth to eighth embodiments, an evaluation method and an evaluation device having a suitable combination of a light source and a spectroscope will be described. The fifth to eighth embodiments can be applied to, for example, either the evaluation device 10 shown in FIG. 6 or the evaluation device 20 shown in FIG.

[0058] [Fifth embodiment] The fifth embodiment is an evaluation device that uses a light source that irradiates monochromatic light of a specific wavelength in combination with a spectroscope such as a bandpass filter that transmits the monochromatic light of a specific wavelength, and an evaluation method that uses the evaluation device.

[0059] In any of the fifth to eighth embodiments, the spectroscope may be a pre-spectroscope provided on the optical path between the light source and the measurement cell (see Figures 8 to 9), or a post-spectroscope provided on the optical path between the measurement cell and the absorbance detector (see Figure 10). In the case of the pre-spectroscopic method, the spectrometer 4 may be provided after the light source as shown in FIG. 8, or may be provided before the measurement cell as shown in FIG. In the fifth embodiment, the position at which the spectroscope 4 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.

[0060] 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.

[0061] [Sixth embodiment: Evaluation device] The sixth embodiment is an evaluation device that uses a light source that irradiates continuous light in combination with a spectrometer such as a bandpass filter or a cutoff filter that transmits specific wavelengths in a wavelength range wider than that of monochromatic light, and an evaluation method that uses the evaluation device.

[0062] According to the sixth embodiment, the absorbance can be measured based on a specific wavelength in a wide wavelength range, and the reaction state can be evaluated in real time, thereby enabling a highly accurate evaluation to be performed.

[0063] [Seventh embodiment] The seventh embodiment is an evaluation 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 evaluation method that uses the evaluation device. The position where the spectrometer 4 is provided can be appropriately selected, but it is preferable to provide it in front of the absorbance detector as shown in FIG.

[0064] [Eighth embodiment] The eighth embodiment is an evaluation 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 an evaluation method that uses the evaluation 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.

[0065] [Ninth embodiment: Evaluation method based on one specific wavelength] Hereinafter, an embodiment of the evaluation method according to the type of specific wavelength to be measured will be described. The evaluation method in the ninth embodiment can be suitably carried out by any of the evaluation devices 10, 20, 30, 40, and 50 shown in FIGS. 6 to 10, but will be described representatively with reference to FIG. The evaluation 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 the solution S is irradiated with light L1 from the light source 1b and the optical path length D. The evaluation method includes an absorbance measuring step, an evaluation step, and a concentration ratio calculating step, and may further include a wavelength setting step and a calibration curve creating step, as necessary.

[0066] <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.

[0067] The method of setting a specific wavelength is not particularly limited, and a publicly 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 evaluation device of the fifth 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 evaluation device of the sixth embodiment; a method of setting the transmission wavelength of a tunable optical filter to monochromatic light of a specific wavelength in the evaluation device of the seventh embodiment; a method of setting the wavelength of a monochromator to monochromatic light of a specific wavelength in the evaluation device of the eighth embodiment; and a method of specifying a specific wavelength to be used for calculation in a concentration ratio calculation unit.

[0068] <Calibration curve creation process> In the calibration curve creation process, standard solutions having a graded concentration ratio, in which the concentration ratio t:m of toluene and the concentration m of methylcyclohexane is clear, are prepared in advance, and the desired or set specific wavelength λ S The absorbance at each concentration is measured, and a calibration curve showing linearity between the concentration ratio and the absorbance is prepared.

[0069] 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 1. Furthermore, the created calibration curve can be stored in a memory unit. Examples of the stepwise 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.

[0070] <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, the absorbance can be measured by the following steps A to C. Step A: The amount of transmitted light T0 at a specific wavelength of a blank measurement cell containing no solution is measured. Step B: The amount of light T transmitted through a measuring cell containing the solution at a specific wavelength is measured. Step C: Calculate the absorbance A at a specific wavelength based on the transmittance T / T0 and the following formula (1).

[0071]

number

[0072] <Evaluation process> In the evaluation step, the absorbance A of the solution at a specific wavelength at time T0 is T0 and the absorbance A of the solution at the specific wavelength after T1 time has elapsed. T1 The reaction state is evaluated based on the absorbance difference ΔA calculated by the formula (i) and the evaluation criterion.

[0073] <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).

[0074]

number

[0075] [Tenth embodiment: Evaluation method based on two or more wavelengths or wavelength ranges] The evaluation method of the tenth 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 evaluation method can be carried out in the same manner as the ninth embodiment. In order to evaluate the reaction state, 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 ninth embodiment, but a more stable and accurate evaluation can be realized by measuring the absorbance at two or more wavelengths or wavelength ranges and using the average absorbance as shown in the tenth embodiment.

[0076] The specific wavelength is two or more wavelengths λ1,...λ n (n is an integer of 2 or more), the resulting absorbances A(λ1), A(λ n ) was measured, and the average absorbance A mean Then, in the ninth embodiment, A in formula (i) is obtained. T0 , and A T1 , the average absorbance A T0mean , and A T1mean By substituting A(λ1) in Eq. (2), the reaction state can be evaluated. mean By substituting the above, the concentration ratio can be calculated.

[0077] If the specific wavelength is in the wavelength range from λ1 to λ2, the average digital or analog absorbance A in that wavelength range is mean In the ninth embodiment, the average absorbance A mean By substituting the above, the reaction state can be evaluated and the concentration ratio can be obtained. Average absorbance A mean The method for determining the absorbance can be appropriately selected depending on the specifications of the evaluation 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.

[0078] In a tenth 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 5 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, 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.

[0079] Compared to the absorbance measured at one wavelength, the average absorbance improves the coefficient of determination, and therefore allows for more linear measurements. In addition, the total amount of transmitted light increases, reducing the effects of measurement errors of wavelength and transmitted light, and improving the S / N ratio. Therefore, according to the evaluation method of the tenth embodiment, it is possible to evaluate the reaction state more stably and with higher accuracy.

[0080] [Eleventh embodiment: Evaluation method based on wavelength range with high sensitivity] The evaluation method of the eleventh embodiment is an embodiment based on a wavelength range with high wavelength dependency, 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 sensitivity. The specific wavelengths in the eleventh embodiment are one or more wavelengths or wavelength ranges in the wavelength range with high sensitivity, i.e., one or more wavelengths or wavelength ranges in the wavelength ranges of 1620 nm to 1680 nm, 2150 nm to 2180 nm, and 2360 nm to 2420 nm.

[0081] 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 the wavelength range with the greatest sensitivity. Specifically, 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. According to the evaluation method of the eleventh embodiment, evaluation with high sensitivity to changes in concentration ratio can be performed.

[0082] As in the eleventh embodiment, the measurement wavelength can be changed depending on the purpose. In other words, when monitoring concentration ratios, measurements are 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, when checking the direction or dynamics of a reaction, or checking minute changes in the conversion rate in the final stage of a reaction, measurements are 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). EXAMPLES

[0083] 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.

[0084] 1 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. 1, 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].

[0085] It can be seen from FIG. 1 that the absorbance exhibits a specific value for each wavelength depending on a given concentration ratio (volume %) of toluene and methylcyclohexane.

[0086] Next, in order to evaluate the correlation between the absorbance and the concentration ratio t:m shown in FIG. 1, the coefficient of determination between the absorbance and the concentration ratio t:m was calculated and shown in FIG. 2, which is superimposed on the graph of FIG. FIG. 2 is a graph showing the relationship between the concentration ratio of toluene to methylcyclohexane, the absorbance, and the coefficient of determination. In Figure 2, the bold 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 Figure 1.

[0087] In FIG. 2, the coefficient of determination indicates the linearity between absorbance and the concentration ratio t:m. The coefficient of determination R2 is 0≦R 2 The value is ≦1, and the closer it is to 1, the more linear the relationship is.

[0088] Toluene concentration c T The relationship between and absorbance is expressed by the following equation (2).

[0089]

number

[0090] 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. 2 shows a graph showing the strength of the relationship between toluene concentration t and absorbance A(λ) as a coefficient of determination. As can be seen from Figure 2, in the wavelength range of 1100[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 4, when the absorbance of 0[AU] to 2.6[AU] is expressed as transmittance T / T0, it is equivalent to a change of 100[%] to 0.25[%].

[0091] [Table 4]

[0092] The relationship between absorbance and transmittance is given by the following formula (1).

number

[0093] From Figure 2 and Table 4, 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 when the wavelength is 1.3 [AU] or more. This is equivalent to a transmittance T / T0 of 89.1% or more and 5.0% or less.

[0094] From these results, it was found that there is an optimal wavelength range for determining the concentration-dependent change between the toluene concentration t and the methylcyclohexane concentration m, and the concentration ratio t:m, as shown in Table 5. It was also found that the reaction state can be evaluated and the concentration ratio can be accurately determined by measuring the absorbance of the solution using a specific wavelength that is one or more wavelengths or wavelength ranges in the wavelength ranges shown in Table 2. It was confirmed that it is not necessary to measure absorbance in all wavelength ranges, but rather that the reaction state can be evaluated and the concentration ratio can be calculated by measuring absorbance at one of the most suitable wavelength ranges shown in Table 5.

[0095] [Table 5]

[0096] FIG. 3 is a graph showing the relationship between the concentration ratio of toluene to methylcyclohexane and the absorbance, and is a graph showing the relationship by superimposing the slope on the graph of FIG. In FIG. 3, each numerical value in the legend indicates the concentration (volume ratio) of toluene, the thick line indicates the magnitude of the slope |a| between the toluene concentration and the absorbance, and the vertical axis on the right side indicates the slope.

[0097] Here, from FIG. 3 and Table 1, since the slope is based on the toluene concentration, (1) in the wavelength regions of 1120 nm to 1140 nm, 1620 nm to 1680 nm, and 2150 nm to 2180 nm, where the slope of the relationship between the toluene concentration and the absorbance is greater than 0, ΔA<0, ΔA=0, and ΔA>0 indicate dehydrogenation, equilibrium, and hydrogenation, respectively, and (2) in the wavelength regions of 1190 nm to 1230 nm, 1730 nm to 1850 nm, 1800 nm to 2050 nm, and 2360 nm to 2420 nm, where the slope of the relationship between the toluene concentration and the absorbance is less than 0, ΔA<0, ΔA=0, and ΔA>0 indicate hydrogenation, equilibrium, and dehydrogenation, respectively.

[0098] In addition, Table 6 shows the magnitude of the slope |a| in each of the seven wavelength ranges.

[0099] <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 to a linear equation in each of the seven wavelength ranges, as shown in the following equation (3). 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 "◯".

[0100] A=a×t+b formula (3) A: Absorbance t: Volume ratio of toluene a: t coefficient (slope) b: constant

[0101] [Table 6]

[0102] In order to know the direction of reaction change (hydrogenation or dehydrogenation) and the degree of reaction progress (dynamic 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.

[0103] 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]

[0104] 10, 20: Evaluation device 1: Absorbance measuring section 1a, 1a': Measuring cell 1b:Light source 1c: Absorbance detector 2: Evaluation section 3: Concentration ratio calculation section 4: Spectrometer 5: Storage section L1: Ray of light L2: Transmitted light S :Solution D: Optical path length

Claims

1. A method for evaluating a reaction state in a hydrogenation reaction and a dehydrogenation reaction of a solution containing toluene or methylcyclohexane, comprising the steps of: The absorbance A of the solution at a specific wavelength at time T Ｔ０ and, The absorbance A of the solution at the specific wavelength at time T1 after a predetermined time has elapsed Ｔ１ and measuring Based on the absorbance difference ΔA calculated by the following formula (i), [0010] (1) The specific wavelength is one wavelength or a 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 dehydrogenation; (1b) When the absorbance difference ΔA is 0, the equilibrium state is reached; 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 a 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 hydrogenation; (2b) When the absorbance difference ΔA is 0, the equilibrium state is reached; or (2c) An evaluation method, characterized in that when the absorbance difference ΔA is less than 0, it is evaluated as dehydrogenation.

2. 2. The evaluation method according to claim 1, wherein the degree of progress of the reaction is evaluated to be high when the absolute value of the absorbance difference ΔA is equal to or greater than a predetermined value.

3. 3. The evaluation method according to claim 1, wherein the specific wavelength is one wavelength or a wavelength range selected from the wavelength ranges of 1620 nm to 1680 nm, 2150 nm to 2180 nm, and 2360 nm to 2420 nm.

4. The absorbance A Ｔ０ Or A Ｔ１ 3. The evaluation method according to claim 1, further comprising a step of calculating a concentration ratio t:m of the concentration t of the toluene and the concentration m of the methylcyclohexane based on a previously recorded calibration curve.

5. An evaluation apparatus for evaluating a reaction state in a hydrogenation reaction and a dehydrogenation reaction of a solution containing toluene or methylcyclohexane, comprising: The absorbance A of the solution at a specific wavelength at time T Ｔ０ and, The absorbance A of the solution at the specific wavelength at time T1 after a predetermined time has elapsed Ｔ１ and an absorbance measurement unit for measuring the absorbance of the light; Based on the absorbance difference ΔA calculated by the following formula (i), [0025] (1) The specific wavelength is one wavelength or a 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 dehydrogenation; (1b) When the absorbance difference ΔA is 0, the equilibrium state is reached; 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 a 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 hydrogenation; (2b) When the absorbance difference ΔA is 0, the equilibrium state is reached; or (2c) an evaluation unit that evaluates that dehydrogenation has occurred when the absorbance difference ΔA is less than 0; An evaluation device comprising:

6. The evaluation device according to claim 5 , wherein the evaluation unit evaluates that the degree of progress of the reaction is high when the absolute value of the absorbance difference ΔA is equal to or greater than a predetermined value.

7. 7. The evaluation device according to claim 5, wherein the specific wavelength is one wavelength or a wavelength range selected from the wavelength ranges of 1620 nm to 1680 nm, 2150 nm to 2180 nm, and 2360 nm to 2420 nm.

8. The absorbance A Ｔ０ Or A Ｔ１ 7. The evaluation device according to claim 5, further comprising a concentration ratio calculation unit that calculates a concentration ratio t:m of the concentration t of the toluene and the concentration m of the methylcyclohexane based on a previously recorded calibration curve.

9. 7. The evaluation 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 transmitted light that has passed through the solution.

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