JP2007099528A - Method for producing high purity hydrogen - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new method for producing high purity hydrogen by which high purity hydrogen can be obtained with high energy efficiency and with a high hydrogen recovery percentage over a long time. <P>SOLUTION: The method for producing high purity hydrogen includes: carrying out a dehydrogenation reaction of hydrogenated derivatives of aromatic hydrocarbons in a dehydrogenation reactor vessel 2; and purifying gas generated by the dehydrogenation reaction with a hydrogen separation member 5 based on Pd-Cu, wherein the hydrogen separation member 5 is operated at a first temperature of 150 to <350°C, and (I) when the operation of the hydrogen separation member 5 is stopped, the hydrogen separation member 5 is heated to a second temperature which is at least 300°C and higher than the first temperature and then the operation of the hydrogen separation member 5 is stopped, or (II) when the hydrogen recovery percentage in the hydrogen separation member 5 lowers, the temperature of the hydrogen separation member 5 is increased to a second temperature which is at least 300°C and higher than the first temperature, the temperature of the hydrogen separation member 5 is then lowered to a first temperature of 150 to <350°C, and the operation is continued. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing high-purity hydrogen by dehydrogenating an aromatic hydrocarbon hydride and purifying a product gas obtained by the dehydrogenation reaction using a hydrogen separation membrane. Thus, the present invention relates to a method for producing high-purity hydrogen capable of obtaining high-purity hydrogen with a high hydrogen recovery rate over a long period of time.

  In recent years, hydrogen has been considered promising as a new energy source due to environmental problems and energy problems. For example, development of hydrogen automobiles using hydrogen directly as fuel or fuel cells using hydrogen has been promoted. Although the fuel cell is small, it has high power generation efficiency. In addition, the fuel cell does not generate noise and vibration, and has excellent advantages such as the ability to use waste heat.

  On the other hand, in using hydrogen as an energy source, it is essential to supply hydrogen as a fuel safely and stably. In contrast, a method of supplying hydrogen directly as compressed hydrogen or liquid hydrogen, a method of storing and supplying hydrogen using hydrogen storage materials such as hydrogen storage alloys and carbon nanotubes, and steam reforming methanol and hydrocarbons to generate hydrogen. Various methods such as a supplying method have been proposed.

  As a hydrogen supply method similar to these, in recent years, the hydrogen storage rate is high, and it is possible to reuse by repeatedly storing and supplying hydrogen. A method for supplying hydrogen has attracted attention.

  In such a method for producing hydrogen by a dehydrogenation reaction using a hydride of an aromatic hydrocarbon, the reaction mixture after the dehydrogenation reaction usually contains unreacted aromatic hydrocarbons in addition to hydrogen gas. Since hydrides, aromatic hydrocarbons generated by dehydrogenation reaction, and by-products are included, hydrogen gas is separated from the reaction mixture by gas-liquid separation after the dehydrogenation reaction, and the purity of hydrogen is further increased. Therefore, a method for purifying hydrogen gas using pressure swing adsorption (PSA) or a hydrogen separation membrane has been proposed (see Patent Document 1 and Patent Document 2).

  Furthermore, a method using a membrane reactor type dehydrogenation reactor has been proposed as a method for obtaining high purity hydrogen by directly passing the gas phase after the dehydrogenation reaction through a hydrogen separation membrane. These are intended to perform a dehydrogenation reaction at a relatively low temperature. For example, from a method in which nitrogen gas coexists to lower the hydrogen partial pressure to facilitate the dehydrogenation reaction (see Patent Document 3) or from a hydrogen separation membrane. A method of increasing the efficiency of hydrogen recovery by reducing the pressure on the outlet side (see Non-Patent Document 1) has been proposed.

  Furthermore, the present inventors also produce high-purity hydrogen with a high hydrogen recovery rate compared with the existing technology (hydrogen recovery rate 70-85%) by PSA using a reactor equipped with a hydrogen separation membrane. Specifically, it succeeded in producing high-purity hydrogen of 99.999% or more efficiently by utilizing the heat and reaction pressure of the reaction product and with a high hydrogen recovery rate of 95% or more. (See Japanese Patent Application No. 2005-49017).

JP 2004-197705 A JP 2004-39351 A JP 2004-59336 A Catal Today, Vol.82, No.1, 119-125 (2003)

  By the way, in order to increase energy efficiency in the production of high purity hydrogen, it is preferable to operate the hydrogen separation membrane at a temperature as low as possible. Also, in alloys used for hydrogen separation membranes, the higher the operating temperature, the more likely the particle growth due to recrystallization occurs, and the membrane strength decreases and the hydrogen permeation performance deteriorates. It is necessary to operate the membrane. However, if the hydrogen separation membrane is operated at a low temperature for a long period of time, the hydrogen recovery rate in the hydrogen separation membrane gradually decreases during the operation, or the hydrogen recovery rate at the next start-up can be reduced with a simple shutdown method. There is a problem that decreases.

  Accordingly, an object of the present invention is to provide a novel method for producing high-purity hydrogen, which is high in energy efficiency and capable of obtaining high-purity hydrogen with a high hydrogen recovery rate over a long period of time.

  The inventors of the present invention conducted a sincere study on the operating conditions of the apparatus in the method for purifying a product gas mainly composed of hydrogen produced by the dehydrogenation reaction of an aromatic hydrocarbon hydride. When operating at a low temperature (first temperature) of less than 350 ° C., the film is heated to a second temperature that is 300 ° C. or higher and higher than the first temperature during operation or at the end of operation. It has been found that high-purity hydrogen can be produced at a high recovery rate after heat treatment during operation or at the next start-up. In particular, when the temperature of the hydrogen separation membrane is 150 ° C. to 200 ° C., the hydrogen permeation performance of the hydrogen separation membrane decreases and the hydrogen recovery rate decreases in a short time, but according to the method of the present invention, high hydrogen recovery is achieved. The rate can be maintained, and efficient operation becomes possible. Furthermore, the film is subjected to a heat treatment at a second temperature that is 300 ° C. or higher and higher than the first temperature in a hydrogen atmosphere at the end of the operation, so that a high hydrogen content can be obtained without special post-treatment. It has been found that the operation can be continued with a recovery rate, and the present invention has been completed. That is, this invention relates to the manufacturing method of the high purity hydrogen shown to following 1-7.

1. Production of high-purity hydrogen in which dehydrogenation of aromatic hydrocarbon hydride is performed in a dehydrogenation reactor, and the gas produced by the dehydrogenation reaction is purified using a hydrogen separation membrane containing Pd-Cu as a main component In the method
Operating the hydrogen separation membrane at a first temperature of 150 ° C. or higher and lower than 350 ° C .;
When stopping the operation of the hydrogen separation membrane, the hydrogen separation membrane is heated to a second temperature higher than 300 ° C. and higher than the first temperature, and then the operation of the hydrogen separation membrane is stopped. A method for producing high purity hydrogen.

2. Said 1st temperature is 150 degreeC or more and less than 300 degreeC, The manufacturing method of the high purity hydrogen of said 1 characterized by the above-mentioned.

3. Said 2nd temperature is 300 degreeC or more and 450 degrees C or less, The manufacturing method of the high purity hydrogen of said 1 characterized by the above-mentioned.

4). Production of high-purity hydrogen in which dehydrogenation of aromatic hydrocarbon hydride is performed in a dehydrogenation reactor, and the gas produced by the dehydrogenation reaction is purified using a hydrogen separation membrane containing Pd-Cu as a main component In the method
Operating the hydrogen separation membrane at a first temperature of 150 ° C. or higher and lower than 350 ° C .;
When the hydrogen recovery rate in the hydrogen separation membrane decreases, the temperature of the hydrogen separation membrane is raised to a second temperature that is 300 ° C. or higher and higher than the first temperature, and then the hydrogen separation membrane A method for producing high-purity hydrogen, wherein the operation is continued by lowering the temperature to a first temperature of 150 ° C. or higher and lower than 350 ° C.

5. When the hydrogen recovery rate in the hydrogen separation membrane decreases to less than 85%, the temperature of the hydrogen separation membrane is raised to a second temperature that is 300 ° C. or higher and higher than the first temperature. 5. The method for producing high-purity hydrogen as described in 4 above.

6). 5. The method for producing high-purity hydrogen according to 4 above, wherein the first temperature is 150 ° C. or higher and lower than 300 ° C.

7). 5. The method for producing high-purity hydrogen according to 4 above, wherein the second temperature is 300 ° C. or higher and 450 ° C. or lower.

  According to the method for producing high-purity hydrogen using the hydrogen separation membrane of the present invention, 150 ° C. or higher and 350 ° C. is obtained by utilizing the dehydrogenation reaction of the hydride of aromatic hydrocarbons with a simple facility with fewer incidental facilities. High purity hydrogen having a purity of 99.99% or more can be produced continuously or intermittently while maintaining a high hydrogen recovery rate of 85% or more at a low hydrogen separation membrane temperature (first temperature) of less than 1%. In addition, when the operation is stopped, the hydrogen recovery rate is reduced at the next start-up by heat-treating the hydrogen separation membrane at a second temperature higher than 300 ° C. and higher than the first temperature in a hydrogen atmosphere. Therefore, hydrogen having a purity of 99.99% or more can be produced stably and continuously.

  A preferred embodiment of the present invention will be specifically described below with reference to FIG. However, the present invention is not limited to the form shown in FIG.

  In the method for producing high-purity hydrogen according to the present invention, the aromatic hydrocarbon hydride is pumped up from a tank 1 for storing the aromatic hydrocarbon hydride as a raw material by a pump or the like, and is supplied to the dehydrogenation reactor 2 after preheating. Thus, it is preferable to perform a dehydrogenation reaction. Here, the preheating of the aromatic hydrocarbon hydride is preferably performed by the heat exchanger 3, and the heat generated by burning the fuel with the burner 4 can be used as the heat source. In addition, although not shown in the figure, pre-heating of the aromatic hydrocarbon hydride is high-purity hydrogen after permeating the hydrogen separation membrane 5 and extracting the hydrogen for recycling, or a gas-liquid separator without permeating the hydrogen separation membrane 5 A gas flowing to 6 can also be used as a heat source. In addition, the preheating of the aromatic hydrocarbon hydride may be performed by combining two or three of the heat sources described above, and in this case, a plurality of heat exchangers may be used in combination.

  If sufficient heat exchange cannot be performed by the heat exchanger 3 at the time of starting the hydrogen production facility, the output of the burner 4 or the like is adjusted, and the temperatures of the dehydrogenation reactor 2 and the hydrogen separation membrane 5 are set to dehydrogenation reaction and By making the temperature sufficient for membrane separation, the start-up time can be shortened. At the time of startup, in order to prolong the catalyst life, it is desirable to supply hydrogen supplemented separately to the animal pressure device or the like to the dehydrogenation reactor 2 until the flow rate of hydrogen for recycling becomes sufficient, although not shown. Note that after the operation is started and the flow rate of hydrogen for recycling becomes sufficient, the hydrogen at the outlet of the hydrogen separation membrane 5 may be circulated to the inlet of the dehydrogenation reactor 2.

  Examples of hydrides of aromatic hydrocarbons used in the present invention include cyclohexanes and decalins, but those having substituents are preferred from the viewpoint of safety and ease of handling of aromatic hydrocarbons generated after dehydrogenation reaction, It is preferable to use alkylcyclohexane such as methylcyclohexane, ethylcyclohexane, dimethylcyclohexane, diethylcyclohexane and trimethylcyclohexane, alkyldecalin such as methyldecalin, ethyldecalin, dimethyldecalin and diethyldecalin, and mixtures thereof. Note that the temperatures of the dehydrogenation reactor 2 and the hydrogen separation membrane 5 are desirably equal to or higher than the boiling point of the aromatic hydrocarbon to be handled.

  The dehydrogenation reactor 2 used in the present invention is filled with a catalyst, and an aromatic hydrocarbon hydride is supplied to cause a dehydrogenation reaction. Here, as a supply method to the dehydrogenation reactor 2, either a method of supplying an aromatic hydrocarbon hydride as a liquid or a method of supplying it as a preheated gas can be used. It is preferable to supply the gas to the bed reactor.

  In addition, as a dehydrogenation reaction catalyst charged in the dehydrogenation reactor 2, at least one metal selected from the group consisting of platinum, ruthenium, palladium, rhodium, tin, rhenium, and germanium is supported on a porous carrier. The average pore diameter is preferably selected as appropriate depending on the type of the aromatic hydrocarbon hydride supplied to the dehydrogenation reactor 2. That is, a catalyst having an average pore diameter of 40 to 80 mm is particularly preferred when using one-ring cyclohexanes, and a catalyst having an average pore diameter of 65 to 130 mm is particularly preferred when using two-ring decalins. It is preferable to select them, and it is preferable that the volume of pores having a preferable pore diameter is 50% or more of the total pore volume.

In order to control the average pore diameter and pore volume ratio of the dehydrogenation reaction catalyst, it is preferable to use Al ₂ O ₃ or SiO ₂ as the catalyst support, and each may be used alone or at an appropriate ratio. You may use combining both. When the aromatic hydrocarbon hydride is a mixture of one ring and two rings, a catalyst having a preferable average pore diameter may be mixed and used depending on the composition.

  Further, the metal loading in the dehydrogenation reaction catalyst is preferably in the range of 0.001 to 10% by mass, and more preferably in the range of 0.01 to 5% by mass. If the metal loading is less than 0.001% by mass, the dehydrogenation reaction cannot be sufficiently progressed. On the other hand, even if the metal is loaded exceeding 10% by mass, an effect commensurate with the increase in the amount of metal cannot be obtained. .

The dehydrogenation reaction carried out in the present invention is carried out in the presence of the above-mentioned catalyst for dehydrogenation reaction, LHSV: 0.5-4 hr ⁻¹ , reaction temperature: 100-500 ° C., preferably 250 ° C.-450 ° C., reaction pressure: normal pressure It is carried out by circulating hydrogen at ˜2 MPa. The hydrogen flow rate is preferably in the range of 0.01 to 10 in terms of hydrogen / aromatic hydrocarbon hydride molar ratio. When hydrogen is circulated and the dehydrogenation reaction is performed, side reactions can be suppressed compared to when hydrogen is not circulated, and not only hydrogen can be produced efficiently, but also the oil recovered after the dehydrogenation reaction is hydrogenated again. Thus, impurities contained in the reuse as an aromatic hydrocarbon hydride can be reduced. Furthermore, in order to produce hydrogen efficiently, it is preferable to select reaction conditions so that the conversion rate is 85% or more.

  The gas produced by the dehydrogenation reaction is mainly composed of hydrogen, but in addition to this, unreacted aromatic hydrocarbon hydride, aromatic hydrocarbons produced by the dehydrogenation reaction, methane, ethane produced by side reactions, etc. It may contain lower hydrocarbons, alkylcyclopentane produced by side reactions, and the like. However, carbon monoxide contained in the reaction product gas when hydrogen is produced by a reforming reaction of city gas, kerosene, naphtha, etc. is not included in the dehydrogenation reaction product gas of the aromatic hydrocarbon hydride. .

  In the method for producing high-purity hydrogen according to the present invention, hydrogen heated immediately after the dehydrogenation reaction to a relatively low temperature (first temperature) of 150 ° C. or higher and lower than 350 ° C., preferably 150 ° C. or higher and lower than 300 ° C. The separation membrane 5 is used to obtain high-purity hydrogen having a purity of 99.99% or higher. In the method for producing high-purity hydrogen according to the present invention, purification is performed without gas-liquid separation using the hydrogen separation membrane 5 heated to 150 ° C. or higher and lower than 350 ° C. by heat energy from the gas phase immediately after the dehydrogenation reaction. The energy efficiency is higher than that of the conventional technique that requires cooling and reheating of the dehydrogenation reaction product gas and the method of operating the hydrogen separation membrane 5 at a high temperature.

  In general, the lower the temperature of the hydrogen separation membrane 5, the lower the hydrogen permeation performance of the hydrogen separation membrane 5 and the lower the hydrogen recovery rate. However, by increasing the pressure, a hydrogen recovery rate of 85% or more can be achieved even at about 150 ° C. Can be maintained. In methanol reforming and steam reforming that are used in existing technologies, the generated gas contains carbon monoxide, and the carbon monoxide is strongly adsorbed on the surface of the hydrogen separation membrane, resulting in a significant reduction in hydrogen permeation performance. However, in the method of the present invention, it was necessary to set the temperature of the hydrogen separation membrane to 350 ° C. or more. In the method of the present invention, hydrogen and aromatic hydrocarbon hydride as a raw material and aromatic carbon produced by dehydrogenation reaction were used as the generated gas. Since only hydrocarbons generated by hydrogen and side reactions are included, even when the temperature of the hydrogen separation membrane 5 is 150 ° C. or higher and lower than 350 ° C., the hydrogen separation membrane 5 exhibits high hydrogen permeation performance.

  The hydrogen separation membrane (hydrogen permeable membrane) 5 used in the present invention is a membrane containing Pd—Cu as a main component. The Pd—Cu film can be produced, for example, by the method described in US Pat. No. 3,439,474.

  When producing high-purity hydrogen having a purity of 99.99% or more from the gas produced by the dehydrogenation reaction through the hydrogen separation membrane 5 described above, if the temperature of the hydrogen separation membrane 5 is low, a high input / output differential pressure is obtained. When the temperature of the membrane 5 is high, hydrogen can be separated at a high recovery rate of 85% or more with a low input / output differential pressure. For example, when the temperature of the hydrogen separation membrane 5 is 150 ° C., the hydrogen recovery rate of 85% or more can be secured by setting the input / output differential pressure of the hydrogen separation membrane 5 to 0.5 MPa or more. Note that the higher the temperature of the hydrogen separation membrane 5, the higher the hydrogen recovery rate. However, at 350 ° C. or higher, recrystallization of metal particles on the surface of the Pd—Cu film is promoted, and large grain boundaries are likely to be generated on the surface. If the inlet / outlet differential pressure of the separation membrane 5 is increased, it may break, and if it exceeds 450 ° C., the Pd—Cu membrane is deteriorated by heating for a long time, resulting in a decrease in mechanical strength or a reaction product. May decompose on the membrane surface and cause carbon deposition, resulting in a significant decrease in the hydrogen recovery rate. Therefore, it is desirable to operate the hydrogen separation membrane 5 at the lowest possible temperature.

  However, depending on the pressure in the system, when the temperature of the hydrogen separation membrane 5 is less than 150 ° C., the hydrocarbons used as a raw material are in a liquid phase, and the surface of the hydrogen separation membrane is covered with a liquid film. Hydrogen, which is a phase, cannot be adsorbed on the metal surface, resulting in extremely low hydrogen permeation performance. Even when hydrocarbons can exist in the gas phase, it is sufficient if the temperature of the hydrogen separation membrane 5 is too low. The hydrogen permeation performance is not exhibited, and even if the differential pressure is increased, the target hydrogen recovery rate of 85% cannot be maintained. Therefore, in order to produce hydrogen efficiently, the pressure difference and temperature of the membrane are controlled so that the hydrogen recovered through the hydrogen separation membrane is 85% or more of the hydrogen in the dehydrogenation reaction product gas. It is preferable.

  In the method for producing high-purity hydrogen according to the present invention, the hydrogen separation membrane 5 is operated at a first temperature of 150 ° C. or higher and lower than 350 ° C., preferably 150 ° C. or higher and lower than 300 ° C. After the supply of the raw material from is stopped, the temperature of the hydrogen separation membrane 5 is adjusted to a heat source such as the burner 4 to 300 ° C. or higher, preferably 300 ° C. to 450 ° C. and higher than the first temperature. After heating to the second temperature, the burner 4 and the like are stopped and the operation is terminated. Although the cooling time from the heating stop varies greatly depending on the outside air temperature and the amount of the heat insulating material, the surface temperature of the hydrogen separation membrane 5 becomes less than 100 ° C. in about 10 to 30 minutes.

  When shutting down the operation, although not shown, the inside of the system is purged with nitrogen for safety, or in order to sufficiently dry the catalyst and the hydrogen separation membrane, although not shown, replenished hydrogen is circulated to the animal pressure device or the like. It is also possible. In the method of the present invention, unlike the case of using a hydrogen separation membrane having a single Pd composition, hydrogen embrittlement of Pd does not occur even when the temperature is lowered from a high temperature of 300 ° C. or higher to a normal temperature in a hydrogen atmosphere. Immediately without going through complicated procedures, the temperature can be lowered while hydrogen gas is present in the system. In the case of a hydrogen separation membrane having a single Pd composition, if the temperature of the hydrogen separation membrane is lowered without performing a nitrogen purge, hydrogen enters the inside of the Pd metal, and the mechanical strength of the hydrogen separation membrane decreases in a short period of time. To do.

  When the temperature of the hydrogen separation membrane 5 is set to a first temperature of 150 ° C. or higher and lower than 350 ° C., preferably 150 ° C. or higher and lower than 300 ° C., and the operation is continued for a long time, the hydrogen recovery rate is monitored, or The membrane temperature is temporarily 300 ° C. or higher, preferably 300 ° C. to 450 ° C., and a second temperature higher than the first temperature every time when the hydrogen permeation performance examined in advance decreases. The reaction temperature of the dehydrogenation reaction is increased, or the burner 4 is simply set so that the film temperature is 300 ° C. or higher, preferably 300 ° C. to 450 ° C. and higher than the first temperature. After adjusting the output, etc., and confirming that the recovery to the predetermined hydrogen recovery rate has been made, or after increasing the film temperature for a recoverable time examined in advance, the original lower film temperature (first temperature) Return to the operating conditions at By, it is possible to continue the operation. In general, the hydrogen permeability increases in proportion to the temperature and differential pressure of the hydrogen separation membrane. However, when the hydrogen separation membrane is exposed to a temperature of 350 ° C. or higher, the recrystallization of the hydrogen separation membrane is promoted as described above, and the hydrogen recovery rate in the hydrogen separation membrane 5 gradually decreases, Operation at a low temperature of 150 ° C. or higher and lower than 350 ° C. becomes difficult. In that case, while taking into account the life of the hydrogen separation membrane, operation is performed at a temperature of 350 ° C. or higher that can maintain a high hydrogen recovery rate. The lifetime of the separation membrane 5 is determined.

  In general, the optimum operating temperature of the hydrogen separation membrane 5 differs depending on the raw material used for the dehydrogenation reaction. Here, the optimum operating temperature is the maximum hydrogen permeation temperature at which the permeation performance and the membrane temperature maintain a proportional relationship, but in many cases, the lowest membrane with a hydrogen recovery rate of about 90 to 95%. Indicates temperature. This optimum membrane operating temperature is presumed to be related to the temperature at which the aromatic component generated by dehydrogenation to the hydrogen separation membrane is adsorbed to the membrane and the boiling point of the product oil and feedstock. For example, among the aromatic compounds, benzene without a substituent (cyclohexane as the raw material) has the strongest adsorption power to the film surface at the same temperature, and the more the substituents and the longer the side chain of the substituent, the more the membrane The adsorption power to the surface is weakened, and it is possible to operate for a long time at a lower film temperature. Further, as already described, under the condition that the liquid phase is obtained when operating at a high pressure, the membrane surface is covered with the liquid film, and the hydrogen recovery rate is greatly reduced. Accordingly, the first temperature and the second temperature vary depending on the type of raw material to be subjected to the dehydrogenation reaction, and are preferably equal to or higher than the boiling points of the raw material and the product at the reaction pressure. The operating conditions that exceed the hydrogen recovery rate determined in consideration of the type, economic efficiency, energy efficiency, etc. are desired. The first temperature is 150 ° C. or higher and lower than 350 ° C., and the second temperature is 300 ° C. or higher. The first temperature and the second temperature usually have a difference of about 50 ° C. to 100 ° C. When an aromatic compound having a weak adsorption force to the membrane surface is produced, the membrane performance can be sufficiently recovered by setting the second temperature to about 300 ° C. In this case, the first temperature is set to 150 to By setting the temperature to about 200 ° C., a sufficient hydrogen recovery rate can be obtained. However, when the second temperature is higher than 450 ° C., the mechanical strength of the Pd—Cu alloy is lowered when treated at a high temperature for a long time, and the hydrocarbons in contact with the film react on the film surface. 450 ° C or lower is preferable because it may cause wake-up carbides on the membrane surface and impede permeation, but there is no particular problem as long as the feedstock oil is not circulated in a short time, and the operating pressure is around normal pressure. If so, the problem of mechanical strength can also be avoided.

  High-purity hydrogen having a purity of 99.99% or more produced through the hydrogen separation membrane 5 can be used as a fuel for fuel cells such as a fuel cell vehicle or a stationary fuel cell. It is desirable to recycle to the reactor 2 and use it as circulating hydrogen necessary for the dehydrogenation reaction. The high-purity hydrogen is preferably preheated through the heat exchanger 3 before being introduced into the dehydrogenation reactor 2.

  The circulating hydrogen necessary for the dehydrogenation reaction includes hydrogen introduced from the outside, hydrogen contained in the unpurified gas of the reaction product gas exiting from the dehydrogenation reactor 2, and gas not permeated through the hydrogen separation membrane 5. However, if the purity of the hydrogen is low, the concentration of gas other than hydrogen will increase during recycling, and the advantages of performing the dehydrogenation reaction under the flow of hydrogen will be sufficiently obtained. Therefore, it is preferable to recycle the high-purity hydrogen having a purity of 99.99% or more obtained through the hydrogen separation membrane 5 to the dehydrogenation reactor 2.

  In the present invention, the gas recovered from the dehydrogenation reaction product gas without passing through the hydrogen separation membrane 5 is introduced into the gas-liquid separator 6, and the unreacted aromatic hydrocarbon hydride and the fragrance produced by the dehydrogenation reaction. It is preferably separated into a liquid such as a group hydrocarbon and an alkylcyclopentane generated by a side reaction, and hydrogen and other gases. Other gases in the gas include lower hydrocarbons generated by side reactions and liquid vapor that could not be separated. Here, hydrogen and other gas can be used as a raw material of the heat source by, for example, burning the dehydrogenation reactor 2 together with other fuel in the burner 4. On the other hand, the liquid containing unreacted aromatic hydrocarbon hydride, aromatic hydrocarbon generated by the dehydrogenation reaction and alkylcyclopentane generated by the side reaction is recovered in the recovered oil tank 7 and hydrogenated again to produce the aromatic. It can be reused as a group hydrocarbon hydride.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not restrict | limited at all by this Example.

(Reference Example 1)
As a dehydrogenation catalyst, 0.5% Pt / Al ₂ O ₃ catalyst (average pore diameter 72.9 kg, ratio of pore volume of 40 to 80 kg in the total pore volume 60 cm) 10 cm ³ was fixed bed flow reactor Filled. 99.99% methylcyclohexane (MCHX) was used as the hydride of the aromatic hydrocarbon, the catalyst layer temperature was 380 ° C., the reaction pressure was 0.9 MPa, the liquid space velocity (LHSV) = 2 hr ⁻¹ , the hydrogen / oil ratio (H _The dehydrogenation reaction was carried out under the conditions of ₂ / Oil) = 3 mol / mol. The outlet gas from the reactor was gas-liquid separated, and the composition of the product gas and recovered oil was analyzed by gas chromatography. After the dehydrogenation reaction conversion rate of 93%, after correction calculation (the amount of pure hydrogen gas introduced into the reactor was subtracted) E) Hydrogen in the evolved gas was 99.983% and methane was 0.01%.

(Reference Example 2)
25 cm ³ of the same catalyst as in Reference Example 1 was charged into a fixed bed flow reactor, and the reactor was heated to 390 ° C. in an electric furnace while flowing high-purity hydrogen (99.999%). 1 is flowed under the conditions of liquid hourly space velocity (LHSV) = 1 hr ⁻¹ , hydrogen / oil ratio (H ₂ /Oil)=1.35 mol / mol, and the reactor inlet gauge pressure becomes 0.75 MPa. The pressure was adjusted as follows. The temperature of the catalyst layer in a stable state with a constant amount of generated hydrogen is 352 ° C., and the composition of the outlet gas from the reactor at that time is hydrogen: toluene (TOL): MCHX: hydrocarbons other than TOL and MCHX = It was 80.06: 17.94: 1.77: 0.23 (vol%), and the conversion rate was 91%. This gas was selectively permeated through a Pd-40Cu membrane (hydrogen separation membrane) with a film thickness of 25 μm at 350 ° C. at a separation membrane inlet gauge pressure of 0.75 MPa and a separation membrane outlet gauge pressure of 0.0 MPa. After the time, the hydrogen purity was 99.999% or more, and the hydrogen recovery rate was 95.8%. In Examples 1 and 2 and Comparative Example 1 below, the purity of hydrogen recovered by the hydrogen separation membrane was 99.999% or higher, and no substance other than hydrogen was detected. The hydrogen recovery rate after 6 hours from the start of operation was 96.5%. Upon completion of the reaction, without replacing the inside with nitrogen or drying treatment, the flow of MCHX as a raw material was stopped, and the heat source of the reactor was immediately stopped to terminate the reactor and the film temperature (RUN 1-1). .

  Subsequently, when the above apparatus was started (RUN1-2) in the same manner as RUN1-1 on the next day, the hydrogen recovery rate after 1 hour of operation was 96.5%, and the hydrogen recovery rate after 6 hours of operation was 96. 0%. Next, a stop operation was performed in the same manner as RUN1-1, and RUN1-2 was terminated. Similarly, when the above apparatus was started (RUN1-3) under the same conditions the next day, the hydrogen recovery rate after 1 hour of operation was 96.2% and the hydrogen recovery rate after 6 hours was 96.5%. In the start / stop operation, the hydrogen recovery rate only fluctuates within ± 0.5%, and no decrease in the hydrogen recovery rate was observed during start / stop and continuous operation.

(Comparative Example 1)
25 cm ³ of the same catalyst as in Reference Example 1 was charged into a fixed bed flow reactor, the catalyst bed temperature was 352 ° C., the reactor inlet gauge pressure was 0.75 MPa, the liquid space velocity (LHSV) = 1 hr ⁻¹ , the hydrogen / oil ratio. When MCHX was dehydrogenated under the conditions of (H ₂ /Oil)=1.35 mol / mol, the conversion was 91% and the reactor outlet gas composition was almost the same as in Reference Example 2. This gas was selectively permeated through a Pd-40Cu membrane having a film thickness of 25 μm at 250 ° C. with a separation membrane inlet gauge pressure of 0.75 MPa and a separation membrane outlet gauge pressure of 0.0 MPa. As a result, hydrogen was recovered one hour after the start of operation. The rate was 89.0%, and the hydrogen recovery rate 6 hours after the start of operation was 88.0% (RUN2-1). At the end of the reaction, the raw material supply was cut off, and the system was dried while maintaining the membrane temperature at 250 ° C under a hydrogen flow for 60 minutes when no liquid was discharged from the reactor outlet, and the membrane temperature was further maintained at 250 ° C. Further, after completing the drying process for 60 minutes in a hydrogen atmosphere, the temperature of the film was slowly lowered to room temperature, and the apparatus was stopped.

  Subsequently, the above apparatus was started up under the same conditions the next day (RUN2-2). The hydrogen recovery rate after 1 hour of operation was 88.0%, and after 6 hours, it was 85.1%. When the system was stopped and terminated in the same manner as RUN2-1 and the above system was started up under the same conditions (RUN2-3) the next day, the hydrogen recovery rate after 1 hour of operation was 83.0%, 6 hours later The hydrogen recovery rate was 78.5%. Further, when the above apparatus was started up under the same conditions as RUN2-1 on the next day, the hydrogen recovery rate after 1 hour of operation was 78.0%, and the hydrogen recovery rate after 6 hours had decreased to 73.5%. (RUN2-4).

Example 1
25 cm ³ of the same catalyst as in Reference Example 1 was charged into a fixed bed flow type reactor, and started in the same manner as in Reference Example 2. The catalyst layer temperature was 352 ° C., the reactor inlet gauge pressure was 0.75 MPa, the liquid space velocity (LHSV ) = 1 hr ⁻¹ , hydrogen / oil ratio (H ₂ /Oil)=1.35 mol / mol, methylcyclohexane (MCHX) was dehydrogenated. The reaction conversion rate was 91%, which was the same as in the four experiments of Reference Example 2, and the reactor outlet gas composition was almost the same as in Reference Example 2. This gas was selectively permeated through a Pd-40Cu membrane having a film thickness of 25 μm at 250 ° C. with a separation membrane inlet gauge pressure of 0.75 MPa and a separation membrane outlet gauge pressure of 0.0 MPa. As a result, hydrogen was recovered one hour after the start of operation. The rate was 92.5%, and the hydrogen recovery rate 6 hours after the start of operation was 87.5% (RUN3-1). At the end of RUN3-1, the temperature of the hydrogen separation membrane was raised to 300 ° C. under a flow of hydrogen, and then immediately cooled to stop the operation. The next day, when the above apparatus was started up and operated under the same conditions as in RUN3-1, the hydrogen recovery rate after 1 hour of operation was restored to 89.0%, and hydrogen after 6 hours of operation was started. The recovery rate was also 88.0% (RUN3-2).

  Table 1 summarizes the results of the start and stop experiments of Reference Example 2, Comparative Example 1, and Example 1.

(Example 2)
When 25 cm ³ of the same catalyst as in Reference Example 1 was charged into a fixed bed flow type reactor and started in the same manner as in Reference Example 2 and MCHX was dehydrogenated under the reaction conditions of Reference Example 2, the outlet gas from the reactor was The composition was the same as in Reference Example 2, and the conversion was 91%. When this gas was selectively permeated through a Pd-40Cu membrane having a film thickness of 25 μm at 250 ° C. with a separation membrane inlet gauge pressure of 0.75 MPa and a separation membrane outlet gauge pressure of 0.0 MPa, the hydrogen purity after 1 hour was 99 More than .999%, the hydrogen recovery rate was 89.3%. When the operation was continued for 6 hours at a membrane temperature of 250 ° C., the hydrogen recovery rate decreased to 82.5%. Immediately after measurement of the hydrogen recovery rate 6 hours after the start of operation, the membrane temperature was increased to 300 ° C. at 50 ° C./30 minutes, and immediately after reaching 300 ° C., the membrane temperature was immediately set to 250 ° C. The membrane temperature returned to 250 ° C. When the hydrogen recovery rate after 7 hours from the start of operation was measured again, the hydrogen recovery rate was recovered to 89.5%.

  From the above results, when the operation is stopped, the temperature of the hydrogen separation membrane is set to a second temperature that is 300 ° C. or higher and higher than the first temperature, or when the hydrogen recovery rate decreases during operation, the hydrogen separation membrane It can be seen that the recovery rate of hydrogen in the hydrogen separation membrane can be recovered by setting the temperature of the second temperature to 300 ° C. or higher and higher than the first temperature. Also, with this method, in steady operation, the temperature of the hydrogen separation membrane is less than 350 ° C., so that recrystallization of metal particles on the surface of the Pd—Cu membrane is not promoted, and the life of the hydrogen separation membrane is increased. Can be extended.

It is a schematic diagram which shows an example of the manufacturing apparatus suitable for the manufacturing method of the high purity hydrogen of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Aromatic hydrocarbon hydride tank 2 Dehydrogenation reactor 3 Heat exchanger 4 Burner 5 Hydrogen separation membrane 6 Gas-liquid separator 7 Recovery oil tank

Claims (7)

Production of high-purity hydrogen in which dehydrogenation of aromatic hydrocarbon hydride is performed in a dehydrogenation reactor, and the gas produced by the dehydrogenation reaction is purified using a hydrogen separation membrane containing Pd-Cu as a main component In the method
Operating the hydrogen separation membrane at a first temperature of 150 ° C. or higher and lower than 350 ° C .;
When stopping the operation of the hydrogen separation membrane, the hydrogen separation membrane is heated to a second temperature higher than 300 ° C. and higher than the first temperature, and then the operation of the hydrogen separation membrane is stopped. A method for producing high purity hydrogen.   The method for producing high-purity hydrogen according to claim 1, wherein the first temperature is 150 ° C or higher and lower than 300 ° C.   The method for producing high-purity hydrogen according to claim 1, wherein the second temperature is 300 ° C. or higher and 450 ° C. or lower. Production of high-purity hydrogen in which dehydrogenation of aromatic hydrocarbon hydride is performed in a dehydrogenation reactor, and the gas produced by the dehydrogenation reaction is purified using a hydrogen separation membrane containing Pd-Cu as a main component In the method
Operating the hydrogen separation membrane at a first temperature of 150 ° C. or higher and lower than 350 ° C .;
When the hydrogen recovery rate in the hydrogen separation membrane decreases, the temperature of the hydrogen separation membrane is raised to a second temperature that is 300 ° C. or higher and higher than the first temperature, and then the hydrogen separation membrane A method for producing high-purity hydrogen, wherein the operation is continued by lowering the temperature to a first temperature of 150 ° C. or higher and lower than 350 ° C.   When the hydrogen recovery rate in the hydrogen separation membrane decreases to less than 85%, the temperature of the hydrogen separation membrane is raised to a second temperature that is 300 ° C. or higher and higher than the first temperature. The method for producing high-purity hydrogen according to claim 4.   The method for producing high-purity hydrogen according to claim 4, wherein the first temperature is 150 ° C or higher and lower than 300 ° C. The method for producing high-purity hydrogen according to claim 4, wherein the second temperature is 300 ° C or higher and 450 ° C or lower.

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