TW201500277A - Method for producing hydrogen - Google Patents

Abstract

The present invention is a method for producing hydrogen by allowing a partial oxidation reaction and decomposition reaction of methanol to proceed in order to generate hydrogen, wherein it is possible to extend catalyst service life and to stably produce hydrogen over the long term. The method for producing hydrogen includes a starting material gas preparation step (s1) and a hydrogen generation step (s2). In the starting material gas preparation step (s1), a starting material gas containing methanol, water, and oxygen and adjusted to a predetermined reactable temperature is prepared. In the hydrogen generation step (s2), the starting material gas that has been adjusted to the reactable temperature is caused to flow through the inside of a reactor (2A) that is filled with a particulate catalyst, causing contact with the catalyst, and thereby allowing a partial oxidation reaction and decomposition reaction of methanol to proceed, generation hydrogen. In the hydrogen generation step (s2), the highest temperature of the catalyst surface contacting the starting material gas is controlled to be no greater than 300 DEG C by means of controlling the flow rate of starting material gas flowing within the reactor (2A).

Description

Hydrogen manufacturing method

The present invention relates to a method of producing hydrogen. More specifically, it relates to a method for producing hydrogen by reacting methanol with water and oxygen in the presence of a catalyst.

Methanol is an energy source that is easy to transport or store and is used as a raw material for generating hydrogen on site. As a method of producing hydrogen gas from methanol, a steam reforming method and a partial oxidation-steam reforming reaction method are generally known.

The steam reforming process is a process for producing hydrogen by contacting methanol vapor with water vapor in the presence of a catalyst. Since the steam reforming system is accompanied by a relatively large endothermic reaction, there is a disadvantage that the load of the heat supply system such as a heat exchanger is large, and the start-up takes time.

On the other hand, the partial oxidation-steam reforming method is a method in which methanol vapor is brought into contact with water vapor and oxygen in the presence of a catalyst to produce hydrogen. Since the partial oxidation-steam reforming reaction system partially oxidizes methanol (partial oxidation reaction) to generate carbon dioxide and hydrogen, the heat generated by reforming the water vapor by contacting the methanol vapor with the water vapor is Since it is modified into an endothermic reaction between carbon dioxide and hydrogen (decomposition reaction of methanol), there is an advantage that the load of the heat supply system such as a heat exchanger can be reduced.

However, in the partial oxidation-steam reforming reaction method, the partial oxidation reaction as the exothermic reaction and the steam reforming reaction (decomposition reaction) as the endothermic reaction are not simultaneously performed, and the steam reforming reaction (decomposition reaction) is relative to Partial oxidation reaction proceeds slightly slowly because This has the disadvantage that it is difficult to control the temperature in the reactor.

In this case, in the reactor in which the raw material gas containing methanol, water, and oxygen is supplied and filled with the catalyst, the reaction speed is faster in the upstream side of the flow direction of the raw material gas. In the partial oxidation reaction, a steam reforming reaction (decomposition reaction) in which the reaction rate is slow is performed in a portion on the downstream side in the flow direction of the raw material gas. As a result, the catalyst present in the reactor on the upstream side in the flow direction of the source gas is affected by the partial oxidation reaction accompanying the heat generation to become a high temperature. Thus, the catalyst which becomes a high temperature is melted and deteriorated, and the activity is lowered.

In the method for producing hydrogen using the partial oxidation-steam reforming reaction method, various methods for solving the above problems have been proposed.

For example, Patent Document 1 discloses a method for producing a hydrogen by a partial oxidation-steam reforming reaction method, which uses a catalyst in which copper oxide is supported on alumina, and temporarily stops being a part accompanying heat release. The oxygen-containing oxygen-containing gas of the raw material of the oxidation reaction is supplied to the reactor.

Further, Patent Document 2 discloses a method for producing a method for producing hydrogen by a partial oxidation-steam reforming reaction method, which accelerates the upstream side of the flow direction of the material gas in the reactor mainly performing the partial oxidation reaction with the exotherm. The flow rate of the raw material gas.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] International Publication WO2012/105355

[Patent Document 2] Japanese Patent Laid-Open No. Hei 11-92102

However, in the methods disclosed in Patent Documents 1 and 2, the difference in the reaction speed of the partial oxidation reaction accompanying the exotherm and the water vapor reforming reaction (decomposition reaction) accompanying the endothermic reaction is not sufficiently small, and the partial oxidation of the reaction rate is fast. Reaction of the flow of the raw material gas in the reactor The portion on the upstream side in the direction is carried out, and the decomposition reaction in which the reaction rate is slow is carried out in the portion on the downstream side in the flow direction of the material gas in the reactor.

For example, Patent Document 2 discloses that the temperature distribution of the reactor gas having a metal honeycomb structure can be controlled to 250 to 300 ° C by increasing the flow rate of the material gas on the upstream side in the flow direction of the material gas in the reactor. This temperature is only the external temperature of the metal honeycomb composed of a metal having a high thermal conductivity. It is preferable that the difference in the reaction rate between the partial oxidation reaction and the decomposition reaction is not sufficiently small, and the method disclosed in Patent Document 2 exists in the upstream side of the flow direction of the material gas in the reactor in which the partial oxidation reaction with the exotherm is performed. The surface temperature of the portion of the catalyst becomes a temperature higher than 300 ° C higher than the temperature of the metal honeycomb having high thermal conductivity.

The catalyst heated to a temperature exceeding 300 ° C is sintered to deteriorate, thereby lowering the activity. That is, in the methods disclosed in Patent Documents 1 and 2, the catalyst lifetime is short, and hydrogen cannot be stably produced for a long period of time.

An object of the present invention is to provide a method for producing a hydrogen which is capable of prolonging the life of a catalyst by performing a partial oxidation reaction and a decomposition reaction of methanol to generate hydrogen, and which can stably produce hydrogen for a long period of time.

The present invention relates to a method for producing hydrogen, comprising: a temperature adjustment step of preliminarily adjusting a material gas containing methanol, water, and oxygen to a predetermined reaction temperature; and a hydrogen generation step of adjusting the above to a raw material gas having a reaction temperature flows through a reactor filled with a particulate catalyst to be in contact with a catalyst, thereby performing a partial oxidation reaction and a decomposition reaction of methanol to generate hydrogen; and in the hydrogen generation step, By controlling the flow rate of the material gas flowing through the reactor, the maximum temperature of the catalyst surface in contact with the raw material gas during the partial oxidation reaction and the decomposition reaction of methanol is controlled to 300 ° C or lower.

Further, in the method for producing hydrogen according to the present invention, it is preferable that the raw material gas is controlled so that the linear velocity of the material gas flowing through the reactor is 0.01 to 0.2 (Nm/s) in the hydrogen generation step. flow.

Further, in the method for producing hydrogen according to the present invention, it is preferable that the flow rate of the material gas is controlled so that the space velocity of the material gas flowing through the reactor is 200 to 1500 (/h) in the hydrogen generation step. .

Further, in the method for producing hydrogen according to the present invention, it is preferred that the catalyst is a catalyst in which a copper compound is supported on alumina.

According to the present invention, a method for producing hydrogen includes a temperature adjustment step and a hydrogen generation step. In the temperature adjustment step, the material gas containing methanol, water, and oxygen is previously adjusted to a predetermined reaction temperature. In the hydrogen generation step, the material gas adjusted to the reaction temperature is passed through a reactor filled with a particulate catalyst to be in contact with the catalyst. When the raw material gas is brought into contact with the catalyst, a partial oxidation reaction based on methanol and oxygen and a decomposition reaction based on methanol and water are performed.

In the method for producing hydrogen according to the present invention, the raw material gas is controlled by controlling the flow rate of the material gas flowing through the reactor in the hydrogen generation step of performing the partial oxidation reaction with the exotherm and the decomposition reaction with the endothermic reaction. The maximum temperature of the contact catalyst surface is controlled to be below 300 °C.

There is a close relationship between the reaction rate of the partial oxidation reaction and the decomposition reaction and the maximum temperature of the catalyst surface. When the reaction rate difference is small, the maximum temperature of the catalyst surface can be controlled to 300 ° C or less.

In this case, a part of the oxidation reaction in which the reaction rate is high in the reactor upstream of the flow direction of the raw material gas is generally carried out in the reactor filled with the catalyst in which the raw material gas flows, in the reactor. A portion of the downstream side of the flow direction of the gas undergoes a decomposition reaction having a slow reaction rate. For the reaction phenomenon, the hydrogen system of the present invention In the manufacturing method, by controlling the flow rate of the material gas flowing through the reactor, the reaction speed difference between the partial oxidation reaction and the decomposition reaction is reduced, and the partial oxidation of the raw material gas in the same portion of the reactor is performed. Reaction and decomposition reactions. As a result, it is possible to suppress a portion of the catalyst surface that is excessively temperature-increased by the influence of the partial oxidation reaction accompanying the heat generation on the catalyst charged in the reactor, thereby controlling the maximum temperature of the catalyst surface to 300 ° C or less. . Therefore, according to the method for producing hydrogen of the present invention, deterioration of the catalyst can be suppressed to prolong the life of the catalyst, and hydrogen can be stably produced over a long period of time.

Further, according to the present invention, in the hydrogen generation step, the flow rate of the material gas is controlled so that the linear velocity of the material gas flowing through the reactor becomes 0.01 to 0.2 (Nm/s). By thus controlling the flow rate of the material gas flowing through the reactor, the reaction speed difference between the partial oxidation reaction and the decomposition reaction can be surely reduced, and the flow direction of the material gas can be partially performed in substantially the same portion of the reactor. Oxidation reaction and decomposition reaction. As a result, the maximum temperature of the catalyst surface can be more reliably controlled to 300 ° C or less, so that the catalyst life can be prolonged, and hydrogen can be stably produced over a long period of time.

Further, according to the present invention, in the hydrogen generation step, the material gas is controlled such that the linear velocity of the material gas flowing through the reactor is 0.01 to 0.2 (Nm/s) and the space velocity is 200 to 1500 (/h). Traffic. By thus controlling the flow rate of the material gas flowing through the reactor, the reaction speed difference between the partial oxidation reaction and the decomposition reaction can be surely reduced, and the flow direction of the material gas can be partially performed in substantially the same portion of the reactor. Oxidation reaction and decomposition reaction. As a result, the maximum temperature of the catalyst surface can be more reliably controlled to 300 ° C or less, so that the catalyst life can be prolonged, and hydrogen can be stably produced over a long period of time.

Further, according to the present invention, as a catalyst filled in the reactor, a catalyst in which a copper-based compound is supported on alumina is used. This catalyst is excellent in terms of suppressing the decrease in catalytic activity. However, the alumina constituting the catalyst has a function of generating dimethyl ether from methanol at a high temperature of more than 300 °C. That is, when it is used in a catalyst in which a copper-based compound is supported on alumina, if the surface temperature of the catalyst exceeds 300 ° C, dimethylation from methanol is carried out. The reaction of ether reduces the amount of methanol used to form hydrogen, resulting in a decrease in the yield of hydrogen. In the method for producing hydrogen according to the present invention, the flow rate of the material gas flowing through the reactor is controlled, and the maximum temperature of the catalyst surface is controlled to 300 ° C or less, so that even if it is used for alumina loading The catalyst having a copper compound can also suppress the reaction for producing dimethyl ether from methanol, and as a result, the hydrogen production yield can be maintained at a high yield.

1‧‧‧Material Gas Preparation Department

2‧‧‧Reaction gas generation department

2A‧‧‧Reactor

2B‧‧‧Protection tube

2C‧‧‧Cold and heat medium circulation pipe

3‧‧‧Hydrogen separation unit

4‧‧‧Hot Department

5‧‧‧ pump

6‧‧‧1st piping

7a‧‧‧1st valve

7b‧‧‧2nd valve

8‧‧‧ heat exchanger

9‧‧‧ Gas Burning Department

10‧‧‧2nd piping

11‧‧‧3rd piping

12‧‧‧4th piping

13‧‧‧3rd valve

14‧‧‧5th piping

15‧‧‧6th piping

16‧‧‧7th piping

17‧‧‧ Hydrogen storage tank

18‧‧‧8th piping

100‧‧‧Hydrogen manufacturing equipment

The objects, features, and advantages of the invention will be apparent from the description and appended claims.

Fig. 1 is a flow chart showing a method of producing hydrogen according to an embodiment of the present invention.

Fig. 2 is a schematic view showing the configuration of a hydrogen producing apparatus 100 for realizing the method for producing hydrogen according to the present invention.

FIG. 3 is a view showing an enlarged configuration of the reaction gas generating unit 2.

Fig. 4 is a graph showing the relationship between the distance from the upstream end portion in the flow direction of the material gas in the reactor and the surface temperature of the catalyst.

Figure 5 is a graph showing the relationship between the linear velocity of the material gas and the maximum temperature of the catalyst surface in the reactor.

Figure 6 is a graph showing the relationship between the temperature of the material gas immediately before flowing into the reactor and the maximum temperature of the catalyst surface in the reactor.

Preferred embodiments of the present invention will be described in detail below with reference to the drawings.

Fig. 1 is a flow chart showing a method of producing hydrogen according to an embodiment of the present invention. Fig. 2 is a schematic view showing the configuration of a hydrogen producing apparatus 100 for realizing the method for producing hydrogen according to the present invention. FIG. 3 is a view showing an enlarged configuration of the reaction gas generating unit 2.

The method for producing hydrogen according to the present embodiment is a method for producing hydrogen by reacting methanol with water and oxygen in the presence of a catalyst, and is carried out using the hydrogen production apparatus 100 shown in Figs. The hydrogen production apparatus 100 includes a raw material gas preparation unit 1 and a reaction gas having a reactor 2A. The body generating unit 2, the hydrogen gas separating unit 3, and the heat retaining unit 4.

The method for producing hydrogen according to the present embodiment includes a raw material gas preparation step s1, a hydrogen generation step s2, a hydrogen separation step s3, and a residual gas combustion step s4.

The raw material gas preparation step s1 is a step of preparing a raw material gas which is previously adjusted to a predetermined reaction temperature and contains at least methanol, water and oxygen, and is carried out by the raw material gas preparation unit 1. The raw material gas preparation step s1 includes a vaporization step s11 and an oxygen-containing gas mixing step s12.

In the vaporization step s11 of the raw material gas preparation step s1, a mixed gas containing methanol vapor and water vapor is produced by vaporizing methanol and water. As shown in FIG. 2, methanol and water are sent from the pump 5 to the material gas preparation unit 1 via the first pipe 6, for example. The first pipe 6 is provided with a first valve 7a and a second valve 7b that open or close the flow path of the first pipe 6. In the state in which the first valve 7a and the second valve 7b are opened, the methanol and the water are supplied from the pump 5 to the material gas preparation unit 1 in the first pipe 6 and supplied to the material gas preparation unit 1.

A heat exchanger 8 may be disposed between the pump 5 and the material gas preparation unit 1 as needed. When the heat exchanger 8 is disposed, the methanol and the water can be heated by heat exchange with the reaction gas obtained in the reaction gas generating unit 2 described below by the heat exchanger 8, and the reaction gas generating unit 2 obtains the heat. The reaction gas can be cooled by heat exchange with methanol and water. Thereby, methanol and water are heated in advance before the liquid is supplied to the raw material gas preparation unit 1, so that methanol and water can be efficiently vaporized.

The amount of water per 1 mol of methanol is preferably 1.2 mol or more, more preferably 1.5 mol, from the viewpoint of efficiently generating hydrogen gas and reducing the residual amount of carbon monoxide gas to increase the yield of hydrogen gas. Above the ear. Further, even if the amount of water becomes excessive, the yield of hydrogen hardly increases, and it is preferably 2.5 m or less from the viewpoint of reducing the amount of water having a large latent heat of vaporization and improving energy efficiency. It is below 2.0 m.

Further, the liquid temperature of the methanol and the water to be supplied to the raw material gas preparation unit 1 is not particularly limited, and may be normal temperature or a temperature higher than normal temperature, but it is preferable from the viewpoint of improving the productivity of hydrogen gas. To be as high as possible. The upper limit of the above liquid temperature from the viewpoint of improving energy efficiency The temperature is preferably below the boiling point of methanol.

Further, methanol and water do not necessarily have to be heated and vaporized at the same time, and vaporization of methanol and vaporization of water may be carried out separately, or methanol may be mixed with water, and the mixture may be vaporized.

The raw material gas preparation unit 1 is, for example, a metal tube having a spiral shape as shown in FIG. 1 , but is not limited to this example. The metal used for the metal pipe is, for example, stainless steel, and copper, brass, or the like is preferable in terms of excellent thermal conductivity. The raw material gas preparation unit 1 is disposed in the container-shaped heat retention unit 4 in order to efficiently transfer heat generated by burning the following residual gas in the gas combustion unit 9.

In the raw material gas preparation unit 1, a mixed gas system containing methanol vapor and water vapor obtained by vaporization of methanol and water flows through the second pipe 10, and is supplied to the reaction gas generating unit 2.

In the present embodiment, oxygen as a raw material for generating hydrogen gas is used in the form of an oxygen-containing gas. Examples of the oxygen-containing gas include air, oxygen, and the like, and a mixed fluid of an inert gas such as nitrogen or argon, and oxygen. However, the inert gas which is separable from hydrogen is not limited to this example.

In the oxygen-containing gas mixing step s12 of the raw material gas preparation step s1, a mixed gas containing methanol vapor and water vapor flowing in the second pipe 10 is mixed with an oxygen-containing gas to prepare a raw material containing at least methanol, water and oxygen. gas. Further, since the heat capacity of the oxygen-containing gas is smaller than that of methanol and water, heating may not be performed particularly, and heating may be performed as needed.

Further, from the viewpoint of reducing the residual amount of unreacted methanol, the amount of oxygen contained in the oxygen-containing gas per 1 mole of methanol is preferably 0.05 mol or more, more preferably 0.08 mol or more. It is preferable to prevent the reaction temperature from becoming high due to the reaction between the hydrogen gas generated from the methanol and the supplied oxygen, and to prevent the generated hydrogen from being consumed by the reaction with oxygen, preferably 0.20 mol or less, more preferably 0.15. Moel below.

The oxygen-containing gas is supplied to the reaction gas generating unit 2 via the third pipe 11 provided with the third valve 13 . The oxygen-containing system flows in the third pipe 11 while the third valve 13 is opened, and Air is supplied to the reaction gas generating unit 2.

The second pipe 10 through which the mixed gas containing methanol vapor and water vapor flows, and the third pipe 11 through which the oxygen-containing gas flows are connected to the fourth pipe 12, and the fourth pipe 12 is connected to the reaction of the reaction gas generating unit 2. 2A. The mixed gas flowing in the second pipe 10 and the oxygen-containing gas flowing in the third pipe 11 are mixed in the fourth pipe 12, thereby preparing a material gas containing at least methanol, water, and oxygen. The raw material gas system thus prepared flows through the fourth pipe 12 and is supplied to the reactor 2A.

In the hydrogen generation step s2, the raw material gas flowing in the fourth pipe 12 and supplied to the reactor 2A of the reaction gas generating unit 2 is subjected to a partial oxidation reaction and a decomposition reaction of methanol in the presence of a catalyst to generate a reaction containing hydrogen. The step of the gas is carried out by the reaction gas generating unit 2. In the present embodiment, the reaction gas generating unit 2 is disposed in the heat retaining portion 4. By disposing the reaction gas generating unit 2 in the heat retaining portion 4 in this manner, heat generated by burning the residual gas in the gas burning portion 9 provided in the heat retaining portion 4 can be used to suppress the methanol caused by the endothermic heat. The temperature of the decomposition reaction is lowered, and hydrogen gas is efficiently generated.

The raw material gas system supplied to the reaction gas generating unit 2 via the fourth pipe 12 is previously adjusted to a predetermined reaction temperature before flowing into the reactor 2A. The temperature of the material gas is adjusted to the reaction temperature before the temperature (the inlet temperature of the reactor 2A) immediately before flowing into the reactor 2A. From the viewpoint of promoting the partial oxidation reaction of methanol and reducing the residual amount of unreacted methanol, the temperature of the material gas immediately before flowing into the reactor 2A is preferably 200 ° C or higher, more preferably 220 ° C or higher. From the viewpoint of the heat resistance temperature of the medium, it is preferably 300 ° C or lower, more preferably 260 ° C or lower.

A catalyst layer is formed by filling a catalyst in a particle form in the reactor 2A. The catalyst is a catalyst in which a copper-based compound is supported on alumina. Specific examples include a catalyst in which copper is supported on copper, and a catalyst in which copper and zinc oxide are supported on alumina.

The mass ratio of copper (Cu) to aluminum oxide (Al ₂ O ₃ ) from the viewpoint of sufficiently exerting the catalytic activity of copper (Cu) as an additive [copper (Cu) / alumina (Al ₂ O) ₃ )] is preferably 0.1 or more, and is preferably 1 or less from the viewpoint of imparting sufficient mechanical strength to the added copper (Cu) and improving catalyst activity.

Commercially available catalysts in which copper is supported on copper or a catalyst in which copper and zinc oxide are supported on alumina are present in a state in which copper is copper oxide. Since the catalyst activity is not displayed in this state, it is preferably used for reduction to make it copper. As a method of reducing copper oxide, for example, a method of bringing a catalyst containing copper oxide into contact with a reducing gas is mentioned, but the present invention is not limited to this method. Examples of the reducing gas include hydrogen gas, a mixed gas of hydrogen gas and an inert gas such as nitrogen gas or argon gas, and the like.

From the viewpoint of reducing the pressure loss of the catalyst layer, the particle size of the catalyst supporting the copper in the alumina or the catalyst supporting the copper and the zinc oxide in the alumina is preferably 1 mm or more, more preferably From 3 mm or more, from the viewpoint of improving the contact efficiency between the catalyst and methanol vapor, water vapor, and oxygen-containing gas, it is preferably 20 mm or less, more preferably 10 mm or less. Further, it is preferable that the amount of the copper-carrying catalyst supported on the alumina or the catalyst supporting the copper and the zinc oxide in the alumina is preferably 35 ml per 1 g/min of the methanol fed to the raw material gas preparation unit 1. the above.

The reactor 2A is a cylindrical body having a circular cross-sectional shape, and is formed by filling a catalyst into the cylindrical body to form a columnar catalyst layer. Further, the reactor 2A may be formed by combining two tubular bodies of a circular cross-sectional shape into a concentric shape, and filling a catalyst with a gap between the cylindrical bodies to form a cylindrical catalyst layer. That is, the reactor 2A is formed in a cylindrical shape, and a catalyst is filled in the internal space thereof. Further, the reactor 2A has the same inner diameter of the one end portion in the axial direction and the other end portion, and has a length extending in the axial direction longer than the inner diameter.

Further, the reactor 2A in which the catalyst layer is formed by filling the catalyst is inserted into a cylindrical protective tube 2B extending from one end of the axial direction to the other end along the axis, and the protective tube 2B can be inserted for measuring contact A temperature measuring member for the surface temperature of the medium. The temperature measuring member is movable within the protective tube 2B along the axis of the reactor 2A. Thereby, the catalyst filled in the reactor 2A can be measured over the entire area in the reactor 2A from one end to the other end in the axial direction. surface temperature. The temperature measured by the temperature measuring member moving inside the protective tube 2B is different from the surface temperature of the outside of the reactor 2A, and is the temperature of the catalyst surface filled in the reactor 2A.

Further, the reactor 2A may be provided with a cold heat medium flow pipe 2C for use in a flow path for adjusting the temperature of the catalyst surface or a flow path through which the heat medium flows. Furthermore, the cold heat medium flow pipe 2C does not necessarily have to be provided.

Further, the reactor 2A is preferably formed such that the catalyst layer formed in the internal space has an effective area (m ² )/length (m) extending in the axial direction of 0.017 or more and 0.025 or less. Here, the effective area is the area obtained by subtracting the area of the protective tube 2B or the cold heat medium flow tube 2C from the total area of the surface of the catalyst layer perpendicular to the axis.

From the viewpoint of efficiently reforming methanol to hydrogen, the surface temperature (maximum temperature) of the catalyst filled in the reactor 2A is preferably 250 ° C or more, thereby preventing deterioration of the catalyst and suppressing reaction by-products. From the viewpoint of formation and suppression of the reaction between hydrogen and oxygen, it is preferably 300 ° C or lower. Further, the pressure in the reactor 2A is not particularly limited, but is usually preferably 0.2 to 1.5 MPa in terms of gauge pressure.

When the raw material gas adjusted to the reaction temperature and containing at least methanol, water, and oxygen is supplied to the reaction gas generating unit 2 via the fourth pipe 12, the raw material gas is in the reactor 2A from the one end in the axial direction toward the other end along the axis. flow. When the raw material gas flows in the reactor 2A and comes into contact with the catalyst as described above, a partial oxidation reaction represented by the following formula (1) in which methanol is partially oxidized to generate hydrogen and carbon dioxide, and methanol is decomposed into carbon monoxide and hydrogen. The decomposition reaction represented by the following formula (2) and the decomposition reaction (water vapor reforming reaction) represented by the following formula (3) in which methanol is decomposed into carbon dioxide and hydrogen.

CH ₃ OH+1/2O ₂ →CO ₂ +2H ₂ (1)

CH ₃ OH→CO+2H ₂ (2)

CH ₃ OH+H ₂ O→CO ₂ +3H ₂ (3)

Furthermore, the partial oxidation reaction represented by the formula (1) is an exothermic reaction, and the formulas (2) and (3) are The decomposition reaction shown is an endothermic reaction.

Usually, in the reactor 2A filled with the catalyst through which the raw material gas flows, a partial oxidation reaction in which the reaction rate is fast in the upstream side (one end side in the axial direction) of the flow direction of the raw material gas is performed in the flow direction of the raw material gas. A portion of the downstream side (the other end side in the axial direction) undergoes a decomposition reaction having a slow reaction rate. As a result, the catalyst in the portion on the upstream side in the flow direction of the source gas in the reactor 2A is affected by the partial oxidation reaction accompanying the heat generation, and becomes a high temperature exceeding 300 °C. The catalyst heated to a temperature exceeding 300 ° C is sintered and deteriorated, and the activity is lowered to become a shorter catalyst life.

Further, when it is used in a catalyst in which a copper-based compound is supported on alumina, when the temperature of the surface of the catalyst is higher than 300 ° C, alumina functions as a methanol dehydration catalyst, and the following formula is carried out ( 4) The dimethyl ether formation reaction indicated.

2CH ₃ OH→CH ₃ OCH ₃ +H ₂ O...(4)

When the formation reaction of dimethyl ether represented by the formula (4) is carried out, the partial oxidation reaction represented by the formula (1) and the amount of hydrogen generated by the decomposition reaction represented by the formulas (2) and (3) are reduced. And cause instability of the device. The details are explained below, and the remaining part of the gas when the high-purity hydrogen is separated from the reaction gas is burned in the gas combustion unit 9, and the heat generated by the combustion is utilized in the raw material gas preparation unit 1, but the dimethyl is formed. The ether makes the heat of combustion different, causing instability of the device.

In order to solve the problem of the high temperature of the surface temperature of the catalyst as described above, in the hydrogen generation step s2 in the method for producing hydrogen according to the present embodiment, the active layer/edge is formed in the catalyst layer formed in the internal space. The reactor 2A, which is set to have a length in the axial direction of 0.017 to 0.025, controls the maximum temperature of the catalyst surface contacted by the material gas to 300 ° C by controlling the flow rate of the material gas flowing in the reactor 2A. the following. More specifically, in the hydrogen generation step s2, the flow rate of the material gas flowing in the reactor 2A is controlled so that the linear velocity of the material gas flowing in the reactor 2A is 0.01 to 0.2 (Nm/s). Further preferably, in the hydrogen generating step s2, the raw material gas flowing in the reactor 2A The linear velocity of the body is 0.01 to 0.2 (Nm/s) and the space velocity of the material gas is 200 to 1500 (/h), and the flow rate of the material gas flowing in the reactor 2A is controlled.

The flow rate of the material gas flowing in the reactor 2A can be controlled by adjusting the flow rate of the liquid flow of methanol and water flowing through the first pipe 6 and the flow rate of the oxygen-containing gas flowing through the third pipe 11.

In the method for producing hydrogen according to the present embodiment, the reaction rate of the partial oxidation reaction and the decomposition reaction is reduced by controlling the flow rate of the material gas flowing in the reactor 2A, and the flow direction of the material gas is in the reactor 2A. The partial oxidation reaction and the decomposition reaction are carried out in substantially the same portion. As a result, the heat generated in the partial oxidation reaction accompanying the exotherm is consumed in the decomposition reaction accompanying the endothermic reaction, so that the catalyst filled in the reactor 2A can be suppressed from being strongly affected only by the partial oxidation reaction accompanying the exotherm. The portion where the temperature rises excessively is generated, so that the maximum temperature of the catalyst surface can be controlled to be 300 ° C or less. Therefore, according to the method for producing hydrogen of the present embodiment, the life of the catalyst can be extended, and hydrogen can be stably produced over a long period of time.

Further, in the method for producing hydrogen according to the present embodiment, the flow rate of the material gas flowing in the reactor 2A is controlled, and the maximum temperature of the catalyst surface is controlled to 300 ° C or lower. The catalyst of the compound can also inhibit the reaction of producing dimethyl ether from methanol, and as a result, the hydrogen production yield can be maintained at a high yield.

The reaction gas generated by the partial oxidation reaction and the decomposition reaction of methanol in the reactor 2A contains, in addition to hydrogen, an impurity gas such as unreacted methanol vapor, carbon dioxide gas, carbon monoxide gas, water vapor or dimethyl ether. The reaction gas system generated in the reactor 2A is supplied to the hydrogen separation unit 3 via the fifth pipe 14 and the sixth pipe 15 .

A heat exchanger 8 is disposed between the fifth pipe 14 and the sixth pipe 15 . In the heat exchanger 8, the reaction gas generated in the reactor 2A is heat-exchanged with methanol and water of the raw material, whereby the methanol and water can be efficiently heated, and the reaction gas is carried out by using methanol and water. Heat exchange can be performed efficiently.

The hydrogen separation step s3 is a step of separating the hydrogen gas from the impurity gas from the reaction gas supplied to the hydrogen separation unit 3 via the fifth pipe 14 and the sixth pipe 15, and is carried out by the hydrogen separation unit 3.

As the hydrogen separation unit 3, for example, an adsorption tower filled with an adsorbent or the like can be mentioned. Although only one adsorption tower can be used, from the viewpoint of efficiently producing high-purity hydrogen, for example, it is preferable to use a plurality of two to five.

In the case of removing carbon dioxide, methanol, dimethyl ether or the like as the adsorbent, a carbon-based adsorbent or the like may be mentioned. When carbon monoxide is removed, a zeolite or the like may be mentioned, and when water vapor or the like is removed, Listed alumina and the like. Usually, it is removed by adsorbing an impurity gas such as steam of unreacted methanol, carbon dioxide gas, carbon monoxide gas, water vapor or dimethyl ether, and these adsorbents are mixed and used.

The separation of hydrogen is carried out using a pressure swing adsorption device (PSA, Pressure Swing Adsorption). More specifically, it can be carried out, for example, according to the separation method described in JP-A-2004-66125.

The high-purity hydrogen gas obtained in the hydrogen separation step s3 is stored in the hydrogen storage tank 17 via the seventh pipe 16, but for example, when the high-purity hydrogen gas obtained is rapidly used in the field, the hydrogen storage tank is not necessarily required. 17.

On the other hand, the impurity gas adsorbed and removed by the hydrogen separation unit 3 is, for example, after the production of the hydrogen gas is stopped, and the inside of the hydrogen separation unit 3 is deaerated, whereby the residual gas remaining in the hydrogen separation unit 3 can be recovered. The residual gas contains hydrogen gas in addition to the impurity gas. The residual gas system is supplied to the gas combustion unit 9 disposed in the heat retention unit 4 via the eighth pipe 18 .

The residual gas combustion step s4 is a step of burning the residual gas by the gas combustion unit 9. In the present embodiment, the residual gas is not treated as a waste gas or burned, and as described above, the gas combustion unit 9 disposed in the heat retention unit 4 performs combustion to effectively use the residual gas.

If it is used to make the combustion heat generated when the residual gas is burned, add methanol and water. By heat, methanol vapor and water vapor can be efficiently produced. In addition, the heat at the time of the decomposition reaction of the endothermic methanol represented by the above formulas (2) and (3) can be supplied by the combustion heat of the residual gas, so that hydrogen gas can be efficiently generated.

When the residual gas is burned, it is preferred to use a catalyst. Among the catalysts, a platinum catalyst is preferred in terms of high catalytic activity and excellent heat resistance. The platinum catalyst is preferably one in which a carrier having a honeycomb structure is loaded with platinum. Metal honeycombs, ceramic honeycombs can be used. The platinum catalyst may be platinum particles, or may be a carrier supported on a carrier such as alumina particles. Examples of the catalyst for burning the residual gas include noble metals such as palladium, rhodium, and silver, and compounds of the metals.

When the residual gas is burned, it is preferred to use air in order to burn the residual gas. The amount of air is not particularly limited as long as it is an amount sufficient to sufficiently burn the hydrogen contained in the residual gas. The heating temperature of the methanol vapor and the water vapor as the reaction gas used for the combustion heat generated when the residual gas is burned is preferably from the viewpoint of reducing the residual amount of unreacted methanol and increasing the amount of generated hydrogen gas. From 250 ° C or more, from the viewpoint of suppressing deterioration of the catalyst, it is preferably 600 ° C or lower.

[Examples]

Hereinafter, the present invention will be described in detail based on examples, but the present invention is not limited to the examples.

(Example 1)

In a cylindrical SUS304 reactor having a length of 1000 mm and an inner diameter of 154.4 mm and a protective tube for temperature measurement, which is extended in the axial direction, is filled with a catalyst supporting copper oxide and zinc oxide supported on alumina. (manufactured by Mitsubishi Gas Chemical, MGC-MH1, particle size: 3 mm), nitrogen gas containing 4 vol% of hydrogen was introduced into the reactor at about 21 Nm ³ /h for about 10 hours to reduce copper oxide. The effective area (m ² ) / length (m) extending in the axial direction of the reactor was 0.019.

Feed methanol and water to the raw materials at a flow rate of 218.5 g/min and 184.7 g/min, respectively. The gas preparation unit vaporizes the same in the raw material gas preparation unit to obtain a mixed gas containing methanol vapor and water vapor. The mixed gas was mixed with air (oxygen-containing gas) flowing at a flow rate of 68 L/min in a standard state (NTP, Normal Temperature and Pressure) to prepare a raw material gas, and the raw material gas was introduced into the reactor. Further, the temperature of the material gas (inlet temperature of the reactor) immediately before flowing into the reactor was controlled to 240 °C. At this time, the water/methanol molar ratio was 1.5/1, and the oxygen/methanol molar ratio was 0.09/1. Further, the material gas had a linear velocity (LV) of 0.2 (Nm/s), a space velocity (SV) of 1230 (/h), and a gauge pressure in the reactor of 0.8 MPa.

(Example 2)

The reaction was carried out in the same manner as in Example 1 except that the linear velocity of the material gas was 0.04 (Nm/s) and the space velocity was 250 (/h).

(Comparative Example 1)

The reaction was carried out in the same manner as in Example 1 except that the linear velocity of the material gas was 1.6 (Nm/s) and the space velocity was 1700 (/h).

(Comparative Example 2)

The reaction was carried out in the same manner as in Example 1 except that the linear velocity of the material gas was 0.4 (Nm/s) and the space velocity was 425 (/h).

<evaluation result>

In the above-described Examples 1 and 2 and Comparative Examples 1 and 2, in order to sufficiently stabilize the apparatus, the distribution of the surface temperature of the catalyst filled in the reactor was repeated after repeating the operation for 7 hours for 7 hours. The amount of methanol reacted, the amount of hydrogen in the gas after the reaction, and the amount of dimethyl ether (DME) gas were investigated. The amount of hydrogen and the amount of DME gas in the gas after the reaction were investigated by analyzing the reaction gas discharged from the reactor by gas chromatography.

The evaluation results are shown in Fig. 4, Fig. 5, and Table 1. Fig. 4 is a graph showing the relationship between the distance from the upstream end portion in the flow direction of the material gas in the reactor and the surface temperature of the catalyst. Figure 5 is a graph showing the relationship between the linear velocity of the material gas and the maximum temperature of the catalyst surface in the reactor. Chart.

As shown in Fig. 4, the catalyst in the reactor in which the distance from the upstream end portion in the flow direction of the raw material gas is short is affected by the partial oxidation reaction of the methanol accompanying the exothermic heat. This phenomenon was produced in both Examples 1 and 2 and Comparative Examples 1 and 2, but the maximum temperature of the catalyst surface was largely different. Specifically, as shown in Table 1, the maximum temperature of the catalyst surface of Example 1 was 293 ° C, and the maximum temperature of the catalyst surface of Example 2 was 262 ° C. Thus, in Examples 1 and 2, the maximum temperature of the catalyst surface was 300 ° C or lower. On the other hand, the maximum temperature of the catalyst surface of Comparative Example 1 was 391 ° C, and the maximum temperature of the catalyst surface of Comparative Example 2 was 331 ° C. In Comparative Examples 1 and 2, the maximum temperature of the catalyst surface was over 300 ° C. The temperature.

The temperature of the catalyst surface can be controlled by the flow rate of the raw material gas in the reactor. In the first and second embodiments, the linear velocity of the raw material gas is in the range of 0.01 to 0.2 (Nm/s) and the space velocity. In the range of 200 to 1500 (/h), the flow rate of the material gas flowing in the reactor is controlled, so that the maximum temperature of the catalyst surface can be controlled to 300 ° C or lower.

Further, as is clear from the results shown in Table 1, it is understood that in Examples 1 and 2, it is possible to produce a reaction containing hydrogen which suppresses the generation of DME as a by-product after consuming all the raw materials methanol charged into the reactor. gas. Further, it is envisioned in the first and second embodiments, Since the maximum temperature of the surface of the catalyst is lower than 300 ° C, the life of the catalyst can be prolonged, and hydrogen can be stably produced over a long period of time.

On the other hand, in Comparative Examples 1 and 2, it was found that all of the raw material methanol charged into the reactor was consumed, but the dimethyl ether as a by-product increased as the reaction temperature increased. Further, in Comparative Examples 1 and 2, since the maximum temperature of the surface of the catalyst was in a high temperature state exceeding 300 ° C, the catalyst life was shortened.

[The effect of the temperature of the raw material gas before flowing into the reactor]

In order to confirm the influence of the temperature of the material gas immediately before flowing into the reactor, the following Examples 3 and 4 were examined on the basis of the above Example 2.

(Example 3)

The reaction was carried out in the same manner as in Example 2 except that the temperature of the material gas immediately before flowing into the reactor was controlled to 220 °C.

(Example 4)

The reaction was carried out in the same manner as in Example 2 except that the temperature of the material gas immediately before flowing into the reactor was controlled to 260 °C.

<evaluation result>

In the above Examples 2 to 4, in order to sufficiently stabilize the apparatus, the maximum temperature of the catalyst surface filled in the reactor was evaluated after repeating the operation 7 times for 7 hours. The evaluation results are shown in Fig. 6 and Table 2. Figure 6 is a graph showing the relationship between the temperature of the material gas immediately before flowing into the reactor and the maximum temperature of the catalyst surface in the reactor.

As is clear from the results shown in FIG. 6 and Table 2, it can be seen that the catalyst filled in the reactor can be controlled by controlling the temperature of the material gas immediately before flowing into the reactor to be in the range of 220 to 260 °C. The maximum temperature of the surface is controlled to be below 300 °C.

The present invention may be embodied in other various forms without departing from the spirit or essential characteristics thereof. Therefore, the above-described embodiments are merely illustrative in all respects, and the scope of the present invention is not limited by the scope of the specification. Further, all changes or modifications belonging to the scope of the patent application are within the scope of the invention.

Claims (4)

A method for producing hydrogen, comprising: a temperature adjustment step of preliminarily adjusting a material gas containing methanol, water, and oxygen to a predetermined reaction temperature; and a hydrogen generation step of adjusting the above to a reaction temperature The raw material gas flows into the reactor filled with the particulate catalyst to contact the catalyst, thereby performing partial oxidation reaction and decomposition reaction of methanol to generate hydrogen; and in the hydrogen generation step, by controlling the flow The flow rate of the material gas passing through the reactor is controlled so that the maximum temperature of the catalyst surface in contact with the raw material gas during the partial oxidation reaction and the decomposition reaction of methanol is controlled to 300 ° C or lower. The method for producing hydrogen according to claim 1, wherein in the hydrogen generating step, the flow rate of the material gas is controlled so that the linear velocity of the material gas flowing through the reactor is 0.01 to 0.2 (Nm/s). The method for producing hydrogen according to claim 2, wherein in the hydrogen generating step, the flow rate of the material gas is controlled so that the space velocity of the material gas flowing through the reactor is 200 to 1500 (/h). The method for producing hydrogen according to any one of claims 1 to 3, wherein the catalyst is a catalyst in which a copper compound is supported on alumina.