JPH08301799A - Control of dehydrogenation reaction with near infrared rays - Google Patents

Abstract

PURPOSE: To enable the synthesis of styrene monomer of a constant composition and high purity, as the change in the composition of the reaction mixture can be promptly reflected on the operation of the reactor and the operation of the distillation column can be stabilized in the following purification process. CONSTITUTION: In the process where styrene monomer is synthesized by dehydrogenation of ethylbenzene, the reaction mixture at the outlet of the reactor is monitored through near-infrared absorption spectroscopy to effect the component analysis and one, two or more among the ratio of steam to ethylbenzene fed into the reactor and the heat fed to the reactor are varied based on the analytical results to keep the composition of the reaction mixture constant at the outlet of the reactor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a reaction for obtaining a styrene monomer by a dehydrogenation reaction of ethylbenzene, which is a typical apparatus in the chemical industry.

[0002]

2. Description of the Related Art The conventional operation management of a reactor has been to analyze the composition at the outlet of the reactor as needed or at any time in order to maintain a desired liquid composition of the reactant at the outlet of the reactor. I was going. However, this results in a large time delay and an increase in the amount of work because a sample is taken from the device for analysis.

Since production is continued when a time delay occurs, if the measurement result is out of specification, product loss occurs, and if the out-of-specification reaction solution is sent to the purification step, the distillation column is operated. The conditions are not constant, and in some cases the plant becomes unstable, making it impossible to continue operation. For this reason, as a method of eliminating the time delay, for convenience, the temperature inside the reactor is monitored, and the change in temperature is used as a change in the reaction state, which is used as a guide for operation management. Alone, it is not possible to achieve the high level of operation required in recent years.

The high level operation referred to here is an operation in which there is almost no difference between the composition of the reaction solution, which is a management target, and the actual composition, and the operation of the distillation column is stable in the purification step of the next step. Say. In recent years, as a means to operate at a high level, online analytical equipment has been introduced into the distillation column to minimize the time delay of analysis so that people can judge from the analysis value or the device can automatically judge and control. The technology used is adopted.

However, the feature of this technique is that the sampling of the usual gas chromatographic analysis is only performed automatically, and the analysis time of the on-line analytical instrument is not shortened at all, and it is more rapid. There was a demand for a simple online real-time analysis method. On the other hand, near-infrared analysis has been known as a new method for online real-time analysis. This analytical method was originally used for the measurement of proteins such as cereals, but recently, it has been used for a method for optimizing or automating the operation of a petrochemical plant, and has begun to attract attention.

For example, by analyzing the hydrocarbons supplied to the cracking furnace by using an infrared analysis photometer as disclosed in Japanese Unexamined Patent Publication No. 2-28293,
A method of controlling the yield of (di) olefins such as ethylene, propylene, etc. as a function of the analysis is disclosed. This technique analyzes the supplied hydrocarbons online and in real time, and controls the reaction conditions according to changes in the composition of the feed liquid.

However, in a general method for controlling a synthetic reaction, even if the reaction conditions are changed from the analytical values of the composition of the raw material and the feed solution as described above, the composition at the outlet of the reactor is accurately controlled to the target value. It is difficult to do so, and since the concentration of the site to be controlled varies greatly, a new control method has been demanded.

[0008]

An object of the present invention is to analyze the composition of a reaction solution in a reactor without delay.
It is an object of the present invention to provide a method of operating a reactor for synthesizing styrene monomer by a high level of dehydrogenation reaction, which can control the reactor and stabilize the operation of a distillation column in a subsequent step.

[0009]

Means for Solving the Problems As a result of intensive studies, the inventors of the present invention were able to analyze the composition by transmitting near-infrared rays directly to the reaction solution at the outlet of the reactor and measuring the spectrum. The inventors have found that the operation management of the reactor can be performed with high accuracy without time delay, and the present invention has been completed based on this finding.

That is, the present invention is a method for operating a reactor for synthesizing a styrene monomer by a dehydrogenation reaction of ethylbenzene, in which the reaction product at the outlet of the reactor is subjected to composition analysis by near-infrared spectrum, and the obtained measurement value is obtained. Is a method for controlling a dehydrogenation reaction by near-infrared radiation, characterized in that the ratio of steam and ethylbenzene supplied to the reactor or the amount of heat supplied to the reactor is changed and controlled by using.

In the present invention, near infrared light means visible light (400 to
700 nm) and mid-infrared rays (2,500-10000n)
It is light with a wavelength in the middle of m). As a characteristic of near-infrared light, the spectrum of wavelengths in this range is remarkably smaller than the number of peaks of the spectrum in the mid-infrared region because absorption occurs due to overtones of absorption and coupling vibrations occurring in the mid-infrared region. In addition, the change in absorbance per unit concentration change in the absorption spectrum of near infrared is 1/10 to 1/1000 compared with that of mid infrared.

The analysis principle will be described below by taking the absorption spectrum of near infrared rays as an example, but the reflection spectrum, the internal scattering spectrum and the transmission spectrum have the same basic principle. Light in a predetermined wavelength range of near infrared rays is applied to the substance to be measured, the absorbance is measured, and a calibration curve is obtained from the relationship between the concentration and the absorbance.
Further, in many cases, the characteristics of each spectrum are emphasized by performing the second derivative conversion of the continuous absorption spectrum with respect to the wavelength, which enables analysis with higher accuracy.

In the analysis, the peak unique to the component in the first derivative or the second derivative of the pure substance spectrum, which is the target component of the substance to be measured, is called the attribution wavelength, and a calibration curve is prepared at this wavelength. When there is no attribution wavelength, multivariate regression using several hundred wavelengths is used. There are generally three types of methods for collecting near infrared rays from a sample of a substance to be measured to obtain a spectrum. That is, there are a reflection method of irradiating light on a substance to be measured and collecting its reflected light, a transmission method of collecting transmitted light of a sample, and a combined method of transmission and internal scattering.

The transmission method can be widely applied to a film having a high transparency and a solution having a high degree of scattering, or a paste, a slurry or a suspension. The combined method of transmission and internal scattering gives clear spectra for clear, slightly scattered liquids, suspensions or gels. The method for detecting light by reflection method is most suitable for opaque powder, high-concentration substances, and movable solids.

In the case of reflection-based light detection, the light from the light source is first passed through a diffraction grating to disperse it, and then its energy is delivered to the sample. For each scan, the energy reflected from the sample is collected and detected by the probe, and the data is sent to the instrument. In the transmission method and the combined method of transmission and internal scattering, the reference spectrum for reference is subtracted from the sample spectrum in which the sample is transmitted, and the spectrum after the calculation is introduced into the diffraction grating to perform spectrum dispersion and detection.

In the analysis using near infrared rays, multiple components can be measured simultaneously and at high speed in about one minute. It is also possible for the operator to monitor the analysis result and reflect it to the operation manually, but not only that, the analyzer is directly connected to the controller and the analysis result is automatically reflected in the control of the reactor. Is also possible. The dehydrogenation reaction of ethylbenzene as referred to in the present invention means a reaction in which preheated ethylbenzene and steam are mixed and supplied to a reactor and a styrene monomer is synthesized by the dehydrogenation reaction. The catalyst used at this time is generally a fixed bed obtained by adding an alkali metal catalyst to iron oxide.

The reactor used in the dehydrogenation reaction is roughly classified into an isothermal type reactor and an adiabatic type reactor. Since the dehydrogenation reaction is an endothermic reaction, it is necessary to supply heat from the outside, but the amount of heat is held in ethylbenzene and steam supplied to the reactor and supplied to the reactor. There is an isothermal reactor in which heat supplied to the reactor is not only dependent on the raw materials and steam that are supplied to the reactor, but also indirectly through heat exchange, for example, combustion gas supplies heat to the reactor itself. The present invention is not subject to any restriction whether it is an adiabatic reactor or an isothermal reactor, and either reactor may be used.

Here, the control means that when the concentration of styrene monomer at the outlet of the reactor is lower than the control concentration, or when the reaction yield is low, the ratio of steam to ethylbenzene, which is a raw material, is increased, or it is supplied to the reactor. It refers to changes in reaction conditions such as increasing the amount of heat used. The control of the composition of the reactant is performed by the operator looking at the result of the composition analysis, and the amount of the combustion gas that is an indirect heat supply from the outside or the temperature of the combustion gas, or the temperature of the raw material, ethylbenzene, or the raw material. Change the reaction conditions such as the ratio of steam to ethylbenzene.

That is, when the concentration of the styrene monomer at the outlet of the reactor is lower than the control concentration or when the reaction yield is low, the amount of combustion gas that is an indirect heat supply from the outside is increased, or the amount of combustion gas is increased. The reaction conditions are changed to increase the concentration of the styrene monomer in the reaction solution by raising the temperature, or raising the temperature of the raw material ethylbenzene or raising the ratio of steam to the raw material ethylbenzene.

On the contrary, when the concentration of the styrene monomer at the outlet of the reactor is higher than the control concentration or the reaction yield is high, the amount of combustion gas, which is indirect heat supply from the outside, is reduced, or Or the temperature of the raw material ethylbenzene is lowered, or the ratio of steam to the raw material ethylbenzene is lowered to lower the concentration of the styrene monomer in the reaction solution.

The type of reaction used in the present invention is not particularly limited, and the case of the dehydrogenation reaction of a fixed bed has been described so far, but the present invention can be applied to a fluidized bed. Does not limit the Also, the reaction pressure of the reaction is not particularly limited although the desirable pressure range is shown below, and the present invention is not limited to any of the reduced pressure reaction, the pressure reaction and the normal pressure reaction. Not a thing. The aspect of the composition to be measured is not limited to the present invention at all, and may be liquid or gas.

The temperature and pressure of the hydrocarbon to be measured do not limit the composition analysis by the near infrared ray dehydrogenation reaction control method of the present invention, and are not affected by the chemical characteristics of the hydrocarbon. Is -10 ° C to 300 ° C, 0
It is desirable that the substance to be measured be maintained within the range of ~ 70 kg / cm ² G, more preferably 0 ° C to 50 ° C, 0 to 20 kg / c.
m ² G. In the temperature range outside of this temperature range and pressure range, the measurement generally becomes difficult due to the problem of the durability of the sealing material for packing used in the probe of the near infrared ray measuring device. Therefore, generally, the reaction solution of the dehydrogenation reaction is cooled to the above temperature range and the composition analysis of the present invention is performed.

In the present invention, the supply amount of combustion gas, which is an indirect heat supply from the outside, the temperature of the combustion gas, the temperature of ethylbenzene as a raw material, or the ratio of steam to ethylbenzene as a raw material, is within the range of change. Is not intended to limit. The wavelength range of near-infrared rays is 700 nm to 2500 nm, but when the spectrum is taken, the specific peak of the substance varies depending on the target substance to be measured. It is not limited.

For example, in the case of polystyrene, 1100n
A specific peak appears around m to 2500 nm.
11 for the reaction product of the dehydrogenation reaction of ethylbenzene
A specific peak appears around 00 nm to 1900 nm. Specifically, with ethylbenzene, 1614n
m, 2026 nm, 1656 nm, 2070 nm, and a plurality of wavelengths, and it is preferable to quantify the composition using these.

[0025]

EXAMPLES The present invention will be described in more detail below with reference to examples.

[0026]

Example 1 An isothermal reactor was used for the synthesis of styrene monomer (ST) by the dehydrogenation reaction of ethylbenzene. The initial set values of the reaction conditions are that the temperature of ethylbenzene (EB) supplied to the reactor is 560 ° C, the combustion gas (F
G) temperature is 700 ° C., reactor inlet pressure is 1.0 Kg /
cm2G, LHSV (space velocity of the catalyst layer) is 0.5 (1
/ Hr), and the ratio (weight / weight) of steam to ethylbenzene supplied to the reactor (hereinafter abbreviated as water ratio) is 0.8.

A near-infrared spectrophotometer was installed on the line extending from the cooler at the outlet of the reactor to analyze the condensed reaction solution. Since the analysis was online and the analysis time was short, it could be analyzed in about 1 minute, and the analysis result was able to be promptly reflected in the operation management of the reactor. Therefore, the deviation from the control standard of the reaction solution composition at the outlet of the reactor can be constantly monitored, and when the composition of the reaction solution deviates from the standard, it is possible to recover an appropriate composition without wasting time. there were.

The composition analysis results of the reaction product show that the concentration of the styrene monomer is lower than the control value. Therefore, the water ratio is 1%, the temperature of ethylbenzene is 1 ° C., and the temperature of the combustion gas is 2 in three times. ℃ up. Table 1 shows the analysis results of the reaction solution by near-infrared radiation, the time required for the analysis, the method for changing the reaction conditions, the time until the composition of the controlled reaction solution is restored, and the spectrum type (in the table, TOL Refers to toluene).

As described above, the rapid control makes it possible to obtain a styrene monomer having a high purity because the composition of the reaction product does not fluctuate, the distillation separation in the purification step is easy.

[0030]

Comparative Example 1 A styrene monomer was synthesized in the same manner as in Example 1 except that the reaction solution was not analyzed by a near infrared spectrophotometer. The reaction solution was sampled every time it was necessary to confirm whether the reaction conditions were appropriate, and the sample was analyzed by gas chromatography. Depending on the sampling time and the analysis time, there was an average time delay of 60 to 90 minutes before the actual change of the operating conditions, and rapid control was not possible.

The composition analysis results of the reaction product show that the concentration of the styrene monomer is lower than the control value. Therefore, the water ratio, the temperature of ethylbenzene, and the temperature of the combustion gas were changed. Repeat these operations 3 times, finally increase the water ratio by 1%,
The temperature of ethylbenzene was increased by 1 ° C and the temperature of combustion gas was increased by 2 ° C. Since the analysis is not automatic, it is not possible to constantly monitor the concentration, and operation management is very rough, and operation is performed with a deviation from the control concentration occurring between analyzes. ing.

Table 2 shows the results of analysis of the reaction liquid at the outlet of the reactor by gas chromatography, the time required for the analysis, the method of changing the manipulated variable, and the time until the composition of the controlled reaction liquid is recovered.

[0033]

Example 2 The set values of the initial reaction conditions were set such that the temperature of ethylbenzene supplied to the reactor was 600 ° C., the combustion gas (F
G) temperature is 740 ° C., reactor inlet pressure is 0.7 Kg /
cm2G, LHSV (space velocity of the catalyst layer) is 0.7 (1
/ Hr) and the water ratio (wt / wt) are 1.0,
A styrene monomer was synthesized in the same manner as in Example 1.

The analysis results were promptly reflected in the operation management of the reactor. The deviation from the control standard of the composition of the reaction solution at the outlet of the reactor could be constantly monitored, and when the composition of the reaction solution deviated from the standard, it was possible to recover to an appropriate composition without waste in time. Looking at the composition analysis results of the reactants, the concentration of styrene monomer is higher than the control value, so the water ratio is 1%, the temperature of ethylbenzene is 1 ° C, the temperature of the combustion gas is 2 ° C. I went down.

Table 1 shows the analysis results of the near infrared rays of the reaction solution, the time required for the analysis, the method for changing the reaction conditions, the time until the composition of the controlled reaction solution is recovered, and the type of spectrum. As described above, the rapid control makes it possible to obtain a styrene monomer having a high purity because the composition of the reaction product does not fluctuate and thus the distillation separation in the purification step is easy.

[0036]

Comparative Example 2 A styrene monomer was synthesized in the same manner as in Example 2 except that the reaction solution was not analyzed by a near infrared spectrophotometer. The reaction solution was sampled every time it was necessary to confirm that the reaction conditions were appropriate values, and analyzed by gas chromatography.

There was a delay of 60 to 90 minutes on the average until the operating conditions were actually changed due to the sampling time and analysis time, and rapid control could not be performed. The composition analysis results of the reaction product show that the styrene monomer concentration is higher than the control value, so the water ratio, the temperature of ethylbenzene, and the temperature of the combustion gas were changed. Repeat these operations twice, and finally,
The water ratio was decreased by 1%, the temperature of ethylbenzene was decreased by 1 ° C, and the temperature of combustion gas was decreased by 2 ° C.

Since the analysis is not automatic, it is not possible to constantly monitor the concentration, and the operation control is very rough, so that there is a gap between the control concentration and the operation during the operation. became. In addition, it took 150 minutes to sample and complete the operation. Results of analysis by gas chromatography of the reaction liquid at the outlet of the reactor and the time required for analysis, a method for changing the manipulated variable,
Table 2 shows the time required to recover the composition of the controlled reaction solution.

[0039]

Example 3 With respect to the set values of the initial reaction conditions, the temperature of ethylbenzene supplied to the reactor was 580 ° C., the temperature of combustion gas was 710 ° C., and the inlet pressure of the reactor was 0.6 kg / cm 2.
G, LHSV (space velocity of catalyst layer) is 0.4 (1 / H
r), styrene monomer was synthesized in the same manner as in Example 1 except that the water ratio (wt / wt) supplied to the reactor was 0.9.

A near-infrared spectroscopic analyzer was installed on the line extending from the cooler at the outlet of the reactor to analyze the condensed reaction liquid. The analysis was promptly reflected in the operation management of the reactor. The deviation from the control standard of the composition of the reaction solution at the outlet of the reactor could be constantly monitored, and when the composition of the reaction solution deviated from the standard, it was possible to recover to an appropriate composition without waste in time.

The composition analysis result of the reaction product shows that the concentration of styrene monomer is lower than the control value.
The water ratio was increased by 1%, the temperature of ethylbenzene was increased by 1 ° C, and the temperature of combustion gas was increased by 2 ° C. Table 1 shows the results of analysis of the reaction solution by near-infrared radiation, the time required for the analysis, the method for changing the reaction conditions, the time until the composition of the controlled reaction solution is restored, and the type of spectrum.

As described above, the rapid control makes it possible to obtain a styrene monomer having a high purity, in which the composition of the reaction product does not fluctuate, the distillation separation in the purification step is easy, and the purity is high.

[0043]

Comparative Example 3 A styrene monomer was synthesized in the same manner as in Example 3 except that the reaction solution was not analyzed by a near infrared spectrophotometer. The reaction solution was sampled every time it was necessary to confirm that the reaction conditions were appropriate values, and analyzed by gas chromatography. The average time delay is 60 minutes until the operating conditions are actually changed between the sampling time and the analysis time.
There was 90 minutes, and quick control could not be performed.

The composition analysis results of the reaction product show that the concentration of the styrene monomer is lower than the control value. Therefore, the water ratio, the temperature of ethylbenzene, and the temperature of the combustion gas were changed. These operations were carried out once, the water ratio was increased by 1%, the temperature of ethylbenzene was increased by 1 ° C, and the temperature of the combustion gas was increased by 2 ° C. Since the analysis is not automatic, it is not possible to constantly monitor the concentration, and operation management is very rough, and the operation was performed with a deviation from the control concentration occurring between the analyzes. It took 70 minutes.

Table 2 shows the results of analysis of the reaction liquid at the outlet of the reactor by gas chromatography, the time required for the analysis, the method of changing the manipulated variable, and the time until the composition of the controlled reaction liquid is recovered.

[0046]

Example 4 An adiabatic reactor was used for the synthesis of styrene monomer by the dehydrogenation reaction of ethylbenzene. The initial setting values of the reaction conditions are as follows: the temperature of ethylbenzene supplied to the reactor is 610 ° C., the temperature of the combustion gas is 740 ° C., the reactor inlet pressure is 0.4 Kg / cm 2 G, and the LHSV (space velocity of the catalyst layer) is 0. 0.6 (1 / Hr), and the water ratio (wt / wt) supplied to the reactor is 1.2.

A near-infrared spectrophotometer was installed on the line extending from the cooler at the outlet of the reactor to analyze the condensed reaction solution. Since the analysis was online and the analysis time was short, it could be analyzed in about 1 minute, and the analysis result was able to be promptly reflected in the operation management of the reactor. Therefore, the deviation from the control standard of the reaction solution composition at the outlet of the reactor can be constantly monitored, and when the composition of the reaction solution deviates from the standard, it is possible to recover an appropriate composition without wasting time. there were.

The composition analysis result of the reaction product showed that the concentration of the styrene monomer was higher than the control value. Therefore, the operation was divided into 3 times to reduce the water ratio by 1% and the temperature of ethylbenzene by 1 ° C. Table 1 shows the analysis results of the reaction solution by near infrared rays, the time required for the analysis, the method of changing the reaction conditions, the time until the composition of the controlled reaction solution is recovered, and the type of spectrum.

As described above, the rapid control makes it possible to obtain a styrene monomer having a high purity because the composition of the reaction product is less likely to change, and the separation by distillation in the purification step is easy.

[0050]

[Comparative Example 4] A styrene monomer was synthesized in the same manner as in Example 4 except that the reaction solution was not analyzed by a near infrared spectrophotometer. The reaction solution was sampled every time it was necessary to confirm that the reaction conditions were appropriate values, and analyzed by gas chromatography. The average time delay is 60 minutes before the operating conditions are actually changed with the sampling time and analysis time.
There was 90 minutes, and quick control could not be performed.

The composition analysis results of the reaction product show that the concentration of the styrene monomer is higher than the control value. Therefore, the water ratio and the temperature of ethylbenzene were changed. These operations were repeated 3 times, and finally the water ratio was reduced by 1% and the temperature of ethylbenzene was reduced by 1%. Since the analysis is not automatic, it is not possible to constantly monitor the concentration, and operation management is very rough, and the operation was performed with a deviation from the control concentration occurring between the analyzes. The time required was 210 minutes.

Table 2 shows the results of analysis of the reaction liquid at the outlet of the reactor by gas chromatography, the time required for the analysis, the method of changing the manipulated variable, and the time until the composition of the controlled reaction liquid is recovered.

[0053]

Example 5: Initial reaction conditions were set such that the temperature of ethylbenzene supplied to the reactor was 600 ° C., the temperature of combustion gas was 730 ° C., and the reactor inlet pressure was 0.4 Kg / cm 2 G.
LHSV (space velocity of the catalyst layer) is 0.5 (1 / Hr),
A styrene monomer was synthesized in the same manner as in Example 4 except that the water ratio (wt / wt) supplied to the reactor was 1.3.

A near-infrared spectrophotometer was installed on the line extending from the cooler at the outlet of the reactor, and the condensed reaction solution was analyzed by
Since the analysis time was short, the analysis could be completed in about 1 minute, and the analysis result was able to be promptly reflected in the operation management of the reactor. Therefore, it is possible to constantly monitor the deviation from the control standard of the reaction solution composition at the reactor outlet, and when the composition of the reaction solution deviates from the standard, it is possible to recover to an appropriate composition without waste in time. It was

The composition analysis result of the reaction product showed that the concentration of the styrene monomer was lower than the control value. Therefore, the operation was divided into two steps, the water ratio was increased by 2%, and the temperature of ethylbenzene was increased by 2 ° C. Table 1 shows the analysis results of the reaction solution by near infrared rays, the time required for the analysis, the method of changing the reaction conditions, the time until the composition of the controlled reaction solution is recovered, and the type of spectrum.

As described above, the rapid control makes it possible to obtain a highly pure styrene monomer in which the fluctuation of the composition of the reaction product is small and the distillation separation in the purification step is easy.

[0057]

[Comparative Example 5] A styrene monomer was synthesized in the same manner as in Example 4 except that the reaction solution was not analyzed by a near infrared spectrophotometer. In operation management, the reaction solution was sampled every time it was necessary to confirm that the reaction conditions were appropriate values, and analyzed by gas chromatography. The time delay was 60 to 90 minutes on average before actually changing the operating conditions, and rapid control could not be performed.

The composition analysis result of the reaction product showed that the concentration of the styrene monomer was lower than the control value. Therefore, the water ratio and the temperature of ethylbenzene were changed. These operations were repeated twice, and finally the water ratio was increased by 2% and the temperature of ethylbenzene was increased by 2 ° C. Since the analysis is not automatic, it is not possible to constantly monitor the concentration, and the operation management is very rough, and the operation was carried out with a gap between the control concentration and the analysis. The required time was 150 minutes.

Table 2 shows the results of analysis of the reaction liquid at the outlet of the reactor by gas chromatography, the time required for the analysis, the method of changing the reaction conditions, and the time until the composition of the controlled reaction liquid is recovered.

[0060]

Comparative Example 6 Under the same conditions as in Comparative Example 1, a near-infrared spectrophotometer was installed in the feed line of the reactor to analyze the feed liquid. The analysis result of the feed liquid was observed and reflected in the operation management of the reactor. The deviation from the control standard of the feed liquid composition at the reactor inlet is constantly monitored and the ratio of water supplied to the reactor or the amount of heat supplied to the reactor is changed to control the composition of the reaction liquid at the reactor outlet as a control value. It was evaluated whether or not.
However, the determination as to whether the composition of the reaction solution had a controlled concentration was carried out by gas chromatography measurement.

Looking at the composition of the raw material at the inlet of the reactor, the concentration of ethylbenzene is higher than the control value. Therefore, the operation was divided into three times, and finally the water ratio was increased by 2% and the temperature of ethylbenzene was increased to 2%. The temperature of the combustion gas was raised by 2 ° C. At this time, the concentration of the styrene monomer in the reaction solution was 38.0% by weight before the operation, but 40.
It was 0% by weight, and it did not recover up to the control concentration of 39.0% by weight.

Table 3 shows the analysis results of the reactor feed solution by near infrared rays, the method of changing the reaction conditions, the type of spectrum, and the analysis results of the reaction solution by gas chromatography analysis. The sensitivity of composition changes to changes in reaction conditions is
Compared to the liquid composition at the reactor inlet, the liquid composition at the outlet of the reactor is larger, and even if the composition at the reactor inlet is adjusted to the control value,
The composition at the outlet of the reactor was not constant and fluctuated, and the control concentration was not recovered even after three operations (requiring 60 minutes).

[0063]

Comparative Example 7 Under the same conditions as in Comparative Example 1, a near-infrared spectrophotometer was installed in the feed line of the reactor to analyze the feed liquid. The analysis result of the feed liquid was observed and reflected in the operation management of the reactor. The deviation from the control standard of the feed liquid composition at the reactor inlet is constantly monitored, and the composition of the reaction liquid at the reactor outlet is adjusted to the control value by changing the ratio of water supplied to the reactor or the amount of heat supplied to the reactor. It was evaluated whether or not.
However, the determination as to whether the composition of the reaction solution had a controlled concentration was carried out by gas chromatography measurement.

Looking at the composition of the raw material at the inlet of the reactor, the concentration of ethylbenzene is higher than the control value. Therefore, the operation was divided into two steps, and finally the water ratio was reduced by 1% to reduce the temperature of ethylbenzene. The temperature of the combustion gas was lowered by 1 ° C. At this time, the concentration of the styrene monomer in the reaction solution was 38.5% by weight before the operation, but 38.
It was 0% by weight, and it did not recover up to the control concentration of 39.0% by weight.

Table 3 shows the analysis results of the reactor feed solution by near infrared rays, the method of changing the reaction conditions, the type of spectrum, and the analysis results of the reaction solution by gas chromatography analysis. The sensitivity of composition changes to changes in reaction conditions is
Compared to the liquid composition at the reactor inlet, the liquid composition at the outlet of the reactor is larger, and even if the composition at the reactor inlet is adjusted to the control value,
The composition at the outlet of the reactor is not constant and fluctuates, and the operation is repeated twice (5
Even if it took 0 minutes, the control concentration did not recover.

[0066]

Comparative Example 8 Under the same conditions as in Comparative Example 1, a near-infrared spectrophotometer was installed in the feed line of the reactor to analyze the feed liquid. The analysis result of the feed liquid was observed and reflected in the operation management of the reactor. The deviation from the control standard of the feed liquid composition at the reactor inlet is constantly monitored, and the composition of the reaction liquid at the reactor outlet is adjusted to the control value by changing the ratio of water supplied to the reactor or the amount of heat supplied to the reactor. It was evaluated whether or not.
However, the determination as to whether the composition of the reaction solution had a controlled concentration was carried out by gas chromatography measurement.

Looking at the composition of the raw material at the reactor inlet, since the concentration of ethylbenzene is higher than the control value, the operation is divided into two times and finally the water ratio is increased by 1% and the temperature of ethylbenzene is increased to 1%. The temperature of the combustion gas was raised by 1 ° C. At this time, the concentration of the styrene monomer in the reaction solution was 38.0% by weight before the operation, but was 3% even after the operation.
It was 8.5% by weight and did not recover up to the control concentration of 39.0% by weight.

Table 3 shows the results of the near-infrared analysis of the reactor feed solution, the method of changing the reaction conditions, the type of spectrum, and the results of the gas chromatography analysis of the reaction solution. The sensitivity of composition changes to changes in reaction conditions is
Compared to the liquid composition at the reactor inlet, the liquid composition at the outlet of the reactor is larger, and even if the composition at the reactor inlet is adjusted to the control value,
The composition at the outlet of the reactor was not constant and fluctuated.
Even if it took 0 minutes, the control concentration did not recover.

[0069]

[Table 1]

[0070]

[Table 2]

[0071]

[Table 3]

[0072]

INDUSTRIAL APPLICABILITY The reactor control method using near-infrared rays according to the present invention allows compositional analysis of a reaction solution to be performed online and quickly, so that a composition change can be performed more quickly in the operating conditions of the reactor than in the conventional method. Reflecting this, the composition of the reaction product can be kept constant, and the operation of the distillation column in the subsequent step can be stabilized.

Claims (1)

[Claims] 1. A method of operating a reactor for synthesizing a styrene monomer by a dehydrogenation reaction of ethylbenzene, wherein a composition of a reaction product at the outlet of the reactor is analyzed by a near infrared spectrum, and the measured value is transferred to the reactor. A method for controlling dehydrogenation reaction by near-infrared radiation, which comprises controlling the reaction by changing the ratio of steam to be supplied and ethylbenzene or the amount of heat supplied to the reactor.