JP2008207986A - Method for producing hydrogen - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing hydrogen by which the deterioration of the catalytic activity can be suppressed when hydrogen is generated by the dehydrogenation of a hydrogenated aromatic compound, the life and reliability of a catalyst can be enhanced, and hydrogen can be produced inexpensively. <P>SOLUTION: The method for producing hydrogen comprises dehydrogenating a hydrogenated aromatic compound A (except following hydrogenated compound B allowed to coexist) in the presence of the hydrogenated compound B of a polycyclic aromatic compound in which at least one benzene ring is condensed with a naphthalene skeleton and/or substituted on the naphthalene skeleton and a catalyst. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing hydrogen by dehydrogenating a hydrogenated aromatic compound such as decalin.

  Use of hydrogen gas generated by dehydrogenation of hydrogenated aromatic compounds typified by cyclohexane and decalin as a fuel hydrogen supply source for automobiles and home and office fuel cells is being studied. . For example, Non-Patent Document 1 discloses that in a hydrogenation reactor at a factory site, naphthalene is reacted with hydrogen gas to obtain a hydrogenated product containing decalin as a main component. Carry it to a retail store or a gasoline retailer / stand, generate naphthalene and hydrogen from decalin using the dehydrogenation reactor at the destination, supply the obtained hydrogen to automobiles, etc. It discusses the technology and system for transportation to the hydrogenation reactor. Furthermore, in the reforming reaction for obtaining an aromatic compound from a naphthenic hydrocarbon, it is pointed out that a decrease in activity due to carbon deposited on the catalyst surface is a serious problem. It is described that the superheated liquid film catalytic reaction is effective as a reaction method for solving this.

  Patent Document 1 discloses a monocyclic aromatic compound such as benzene, toluene, xylene and mesitylene, a bicyclic aromatic compound such as naphthalene and methylnaphthalene, and a tricyclic aroma such as anthracene as a hydrogen gas storage and transport medium. A hydrogen storage / supply system that uses a group compound and performs a dehydrogenation reaction by a so-called superheated liquid film method to obtain hydrogen is disclosed. Example 1 describes that the dehydrogenation conversion rate of cyclohexane to benzene progressed at 25% using a platinum catalyst supported on a silica / alumina support by the superheated liquid film method. On the other hand, in the case of a normal gas phase catalytic reaction using a conventional fixed bed gas phase flow reactor, the conversion rate of cyclohexane with the same catalyst is 1.6% (Comparative Example 1), In the liquid-phase suspension catalyst method using a conventional stationary autoclave, the conversion rate of cyclohexane is only 0.8% using the same catalyst (Comparative Example 2).

  Patent Document 2 describes an apparatus for dehydrogenating decalin by a superheated liquid film method to generate hydrogen and separating generated naphthalene and hydrogen. In addition, carbon-supported platinum catalysts and carbon-supported platinum-rhenium composite metal catalysts have been disclosed as decalin dehydrogenation catalysts using the apparatus [0027]. Further, although the surface temperature of the catalyst is 200 to 500 ° C., preferably 200 to 350 ° C. [0037, 0057], nothing is described about pressure or catalyst life.

  Patent Document 3 includes a hydrogen storage / supply system similar to Patent Document 1 that uses an aromatic compound similar to Patent Document 1 as a hydrogen gas storage and transport medium, and nickel, palladium, platinum, rhodium, and the like as preferred catalysts. And the preferred dehydrogenation / hydrogenation reaction conditions are described as follows: a temperature of 50 to 500 ° C. and a hydrogen partial pressure of 0.1 to 50 atm. For the dehydrogenation reaction, a low pressure side within the partial pressure range is preferred. [0069]. And Example 1 similar to Example 1 of patent document 1 is described. This document does not describe anything about the catalyst life of the supported catalyst.

  In Patent Document 4, hydrogen is removed by gas-phase dehydrogenation of naphthenic hydrocarbon under the conditions that the average temperature of the catalyst layer is 270 to 500 ° C., the pressure is normal pressure to 2 MPa, and the liquid space velocity is 0.5 to 10. A method of manufacturing is described. Example 13 describes that a reduction in the conversion rate of methylcyclohexane was not observed even after 500 hours of continuous operation using a platinum / aluminum oxide catalyst.

  Patent Document 5 uses a device in which a hydrogenation reaction device for hydrogenating an aromatic compound with a mixed gas containing hydrogen and a dehydrogenation reaction device for dehydrogenating the obtained hydrogenated aromatic compound are connected in series. , A method for selectively recovering hydrogen from the mixed gas is described. It is described that monocyclic compounds, bicyclic compounds, tricyclic compounds and mixtures thereof can be used as hydrogenated aromatic compounds [0027]. However, this document does not describe anything about the catalyst life.

JP 2001-110437 A JP 2002-255503 A JP 2001-198469 A JP 2004-203712 A Japanese Patent Laying-Open No. 2005-200254 ECO Industry Vol.7 No.8 P.29-35 (2002)

  In the hydrogen storage / supply system using a hydrogenated aromatic compound as a hydrogen storage and transport medium, the present invention has been a problem in the past when generating hydrogen in the dehydrogenation reaction step of the hydrogenated aromatic compound. Another object of the present invention is to provide a method for producing hydrogen that suppresses deterioration of catalyst activity, has a long life, is highly reliable, and is inexpensive.

  In carrying out the dehydrogenation reaction of the hydrogenated aromatic compound A (for example, decalin), the present inventor has obtained a hydride B of a polycyclic aromatic compound in which one or more benzene rings are condensed and / or substituted on the naphthalene skeleton. For example, by mixing perhydroanthracene) with hydrogenated aromatic compound A as a raw material, at least hydrogenated aromatic compound A and reaction products (for example, naphthalene and anthracene) present in the dehydrogenation reaction apparatus. It has been found that when a part of the catalyst is efficiently condensed, the activity deterioration of the dehydrogenation catalyst can be greatly suppressed, and the present invention as described below has been reached.

  The present invention relates to a hydride B of a polycyclic aromatic compound obtained by condensing and / or substituting one or more benzene rings with a naphthalene skeleton from a hydrogenated aromatic compound A (excluding the following hydride B coexisting). A method for producing hydrogen, wherein hydrogen is obtained by dehydrogenation in the presence.

  In the method for producing hydrogen of the present invention, the mixing ratio of the hydride B of the polycyclic aromatic compound is 0.1 to 0.1 of the total amount of the hydride B of the hydrogenated aromatic compound A and the polycyclic aromatic compound. It is preferably 20% by mass.

  In the method for producing hydrogen according to the present invention, the polycyclic aromatic compound is preferably at least one polycyclic aromatic hydrocarbon selected from anthracene, phenanthrene, pyrene, phenylnaphthalene, binaphthyl, phenylanthracene and phenylphenanthrene.

  In the method for producing hydrogen according to the present invention, the hydrogenated aromatic compound A is preferably at least one hydrogenated polycyclic alicyclic hydrocarbon selected from decalin, methyldecalin, tetralin and methyltetralin.

  In the method for producing hydrogen according to the present invention, the catalyst is preferably a supported catalyst of at least one noble metal selected from the group consisting of palladium, platinum, rhodium and iridium.

  According to the production method of the present invention, in the dehydrogenation reaction of a hydrogenated aromatic compound, deterioration of catalytic activity, which has been a problem in the past, can be suppressed, long life is reliable, and hydrogen gas is inexpensive. Can be manufactured.

Below, the manufacturing method of hydrogen by the dehydrogenation reaction of the hydrogenated aromatic compound A of this invention is demonstrated in detail.
In the present invention, a hydrogenated aromatic compound A (hereinafter also referred to as a raw material), which is a raw material for the dehydrogenation reaction, is a hydrogen of a polycyclic aromatic compound in which one or more benzene rings are condensed and / or substituted on a naphthalene skeleton. This is a method for producing hydrogen by performing a dehydrogenation reaction using a catalyst in the presence of a chemical compound B (hereinafter also referred to as an additive). The aromatic compound by-produced in the dehydrogenation reaction is cycled as a raw material for hydrogen production. That is, the hydrogenated aromatic compound A functions as a hydrogen supply source, and the by-produced aromatic compound functions as a hydrogen acceptor to constitute a hydrogen storage / supply system.

  In the present invention, the deterioration of the activity of the dehydrogenation reaction catalyst is remarkably suppressed by mixing the additive. This is because at least part of the organic compound (raw material hydrogenated aromatic compound A, additive, product aromatic compound, additive dehydrogenation reaction product) present in the dehydrogenation reactor by the additive. It is inferred that this is due to the fact that the organic compound is efficiently condensed and present in the reaction apparatus in a liquid phase, and the organic compound adsorbed on the catalyst surface is washed away by the liquid organic compound. Note that “efficient” means that the additive condenses at a lower pressure than when no additive is present.

  Conventionally, the superheated liquid film method is excellent for the dehydrogenation reaction of hydrogenated aromatic compounds, and the liquid phase reaction has been considered disadvantageous. However, since the present hydrogen gas is present in the dehydrogenation reactor, the present inventor is very much able to condense the hydrogenated aromatic compound A such as decalin and the product aromatic compound such as naphthalene. Since a high pressure is required, it was difficult to proceed in the liquid phase under the reaction conditions in the conventional concretely proposed method, and it was assumed that the reaction was substantially carried out in the gas phase. And since it was a gas phase reaction, it was guessed that the catalyst surface was covered with carbonaceous matter within a short time, and the catalytic activity deteriorated. On the other hand, when the additive of the present invention is present, at least a part of the organic compound present in the dehydrogenation reaction apparatus is efficiently condensed to form a liquid phase in the reaction apparatus. Further, like the hydrogenated aromatic compound A, which is a raw material for the dehydrogenation reaction, the additive itself acts as a hydrogen storage medium / supply source in the dehydrogenation-hydrogenation cycle. The generation of hydrogen by the hydrogenated aromatic compound A and the by-product aromatic compound are not reduced.

In the present invention, the hydrogenated aromatic compound A that is a raw material for the dehydrogenation reaction may be a cyclohexene, even if it is a hydride of 1 to 3 rings such as cyclohexane, methylcyclohexane, decalin, methyldecalin, and perhydroanthracene. , Bicyclic hydrogenated polycyclic alicyclic hydrocarbons selected from decalin, methyldecalin, tetralin and methyltetralin, which may be partially hydrides of 1 to 2 rings such as methylcyclohexene, tetralin and methyltetralin Is preferred. These can be used alone or in combination of two or more.
However, it is preferable to remove as much as possible a compound that acts as a catalyst poison for the dehydrogenation catalyst, such as a sulfur compound. For example, in the case of a sulfur compound, it is preferably removed to 5 ppm or less, more preferably 0.5 ppm or less, and even more preferably 0.1 ppm or less. The sulfur compound can be removed by a known technique such as a hydrodesulfurization method or a Takahax method.

Next, the hydride B of the polycyclic aromatic compound of the present invention will be described.
In the present invention, the polycyclic aromatic compound as a precursor of the additive is a compound in which one or more benzene rings are condensed and / or substituted on a naphthalene skeleton, and anthracene, phenanthrene, pyrene, phenylnaphthalene, phenylanthracene. , At least one polycyclic aromatic hydrocarbon selected from binaphthyl and phenylphenanthrene. These compounds are compounds in which 3 to 4 benzene rings are condensed and / or substituted. The additive needs to have a higher boiling point than the hydrogenated aromatic compound A as a raw material. Furthermore, since the boiling point of a fully hydride and / or partial hydride of a polycyclic aromatic compound composed of 2 or less benzene rings is low, the hydrogenated aromatic compound A, which is a raw material for the dehydrogenation reaction, can be efficiently used. It cannot be condensed, which is not preferable. A fully hydride and / or a partial hydride of a polycyclic aromatic compound composed of 5 or more benzene rings is not preferable because the catalytic activity is lowered due to inhibition of adsorption of the additive itself on the catalyst surface.

The additive may be a total hydride, a partial hydride, or a mixture thereof. The mixing ratio of the total hydride and the partial hydride is 0/100 to 100/0, preferably 25/75 to 100 / 0, more preferably 50/50 to 100/0.
Preferred hydrides B of polycyclic aromatic compounds are hydrides of condensed 3-4 ring aromatic hydrocarbons such as anthracene, phenanthrene, and pyrene. It is a hydride of aromatic hydrocarbon substituted with 1 to 2 rings. Specific examples of the additive include perhydroanthracene, perhydrobinaphthyl, perhydropyrene, and perhydrophenylanthracene.

The additive of the present invention may be used singly or as a mixture. The mixing ratio in a plurality of cases is arbitrary and is not limited at all. However, it is preferable to remove as much as possible a compound that acts as a catalyst poison for the dehydrogenation catalyst, such as a sulfur compound.
For example, in the case of a sulfur compound, it is preferably removed to 5 ppm or less, more preferably 0.5 ppm or less, and even more preferably 0.1 ppm or less. The sulfur compound can be removed by a known technique such as a hydrodesulfurization method or a Takahax method.

The use amount of the additive of the present invention is generally specified because the optimum amount is determined by the kind of additive, the kind of hydrogenated aromatic compound A which is a raw material for the dehydrogenation reaction, and the reaction conditions such as temperature and pressure. However, it is 0.1 to 20% by mass in 100% by mass of the total amount of the raw material hydrogenated aromatic compound A and the additive. For example, when the additive is perhydroanthracene and the raw material is decalin and the dehydrogenation reaction is performed at 380 ° C. and 3 MPa, the amount of perhydroanthracene is preferably 0.5 to 20% by mass, more preferably 2 to 15%. % By mass. Further, when the additive is perhydrobinaphthyl, the raw material is decalin, and the dehydrogenation reaction is performed at 350 ° C. and 4 MPa, the amount of perhydrobinaphthyl is preferably 0.1 to 15% by mass, more preferably 1 to 10% by mass. %.
The combination of raw materials and additives is not particularly limited. For example, the raw material is decalin, the additive is perhydroanthracene or perhydrobinaphthyl, the raw material is perhydroanthracene, and the additive is perhydropyrene or perhydrophenyl. A combination of anthracene, a half hydride in which the raw material is tetralin and an additive is binaphthyl is preferable.

  A known dehydrogenation catalyst can be used as the dehydrogenation catalyst of the present invention, and is not limited at all. For example, a dehydrogenation catalyst including at least one kind of metal selected from palladium, platinum, rhodium, iridium, ruthenium, osmium, molybdenum, rhenium, tungsten, vanadium, nickel, chromium, cobalt, and iron can be used. These metals can be used unsupported like nickel sponge, but are preferably supported on a catalyst carrier. Examples of the catalyst carrier include alumina, silica, zirconia, zeolite, titania, activated carbon, and diatomaceous earth. A catalyst in which a noble metal such as palladium, platinum, rhodium, iridium or the like is supported on alumina or activated carbon, which has high dehydrogenation activity and has established active metal recycling technology, is particularly preferable. In addition, a promoter component such as rhenium, tin, or lanthanum can be added to these supported noble metal catalysts. The loading amount of the active metal component is not limited, but is 0.01 to 20% by mass, preferably 0.05 to 15% by mass.

  The shape of the dehydrogenation catalyst is not limited in any way, and examples thereof include powder, granule, pellet, and honeycomb. Since the pressure loss of the catalyst layer is small, granular, pellet, and honeycomb shapes are particularly preferable. The method for supporting the active metal component on the carrier is not particularly limited, and examples thereof include an impregnation method, an ion exchange method, a dip coating method, and a CVD method.

  In the method for producing hydrogen of the present invention, a known catalytic reaction apparatus such as a fixed bed liquid phase reaction apparatus or a suspension reaction apparatus can be used, and is not limited at all. As the flow system of the raw material hydrogenated aromatic compound A mixed with the additive of the present invention or the hydrogen gas to be generated and the catalyst, either an upward flow or a downward flow can be employed. Moreover, it can also be set as the cocurrent flow which distribute | circulates the raw material which mixed the additive of this invention, and the hydrogen gas to produce | generate to the same direction, or can set it as a countercurrent which makes a raw material a downflow and makes hydrogen gas an upflow. Further, a hydrogen separation means such as a hydrogen separation membrane may be disposed in or behind the dehydrogenation reactor.

  The operating pressure of the dehydrogenation reactor is 0.5 MPa or more, preferably 0.8 MPa or more, more preferably 1.1 MPa or more, and 10 MPa or less, preferably 8 MPa or less. If it is less than 0.5 MPa, the ratio of the hydrogenated aromatic compound A and the aromatic compound as a product present as a gas is high, which is not preferable because the catalyst life is shortened. When the pressure exceeds 10 MPa, the reaction rate greatly decreases and is not economical, which is not preferable.

  The dehydrogenation reaction temperature is not limited because the optimum range varies depending on the raw material, the type of additive of the present invention, and the operating pressure, but is preferably 100 to 500 ° C. If it is less than 100 degreeC, reaction rate is slow and is not practical. If the temperature exceeds 500 ° C., the reaction rate is high, but carbon is deposited on the catalyst, and the catalyst life is shortened.

Hereinafter, the present invention will be specifically described by way of examples.
(Example 1)
A dehydrogenation reaction apparatus (straight pipe with an inner diameter of 27 mm), a dehydrogenation catalyst in which platinum is supported on a cylindrical metal honeycomb carrier (material: Fe—Cr—Al alloy) (amount supported per bulk volume of the carrier: 6 g / L) ) Filled two pieces.
A mixture in which dehydroline (trans isomer: cis isomer = 1: 1) was mixed with perhydroanthracene so as to be 10% by mass was continuously fed to the reactor at a flow rate of 9 g / h from the top, naphthalene, Reaction products such as anthracene were continuously withdrawn from the bottom of the reactor and hydrogen gas from the top of the reactor. A sheathed heater is wound around the outside of the reactor, and the dehydrogenation reaction temperature can be controlled by a thermocouple inserted almost at the center in the axial direction of the reactor. Continuous dehydration at 380 ° C. and a total pressure of 3 MPa for 500 hours. An elementary reaction was performed.

The decalin conversion rate was 62% 24 hours after the start of the reaction, 60% after 240 hours, 61% after 480 hours, and no decrease in activity was observed even after about 500 hours. Perhydroanthracene was also dehydrogenated almost quantitatively to anthracene. Further, hydrogen gas corresponding to the conversion rate of decalin was generated. The purity of the gas was 99% or more.
After completion of the reaction, the reactor was opened at room temperature, and 82 g of reaction product remained in the reactor. The dead space of the reactor in the catalyst-packed state was about 100 cm ³ . Since the reaction pressure is 3 MPa, the dead space under the reaction conditions is calculated to be about 3L. If all reaction products present in this dead space are in the gas phase, the number of moles is 0.13 mol. For convenience, assuming that the reaction product is a 9: 1 mixture of naphthalene and anthracene, 0.13 mol corresponds to 17 g of reaction product. Thus, it was clear that the liquid phase was present in a significant proportion under the reaction conditions.

(Example 2)
In Example 1, instead of 10% by mass of perhydroanthracene, dehydrogenation of decalin was performed in the same manner and under the same conditions as in Example 1 except that a mixture in which perhydrobinaphthyl was mixed with decalin to 8% by mass was used. The reaction was continued for 500 h. Similar to the perhydroanthracene of Example 1, perhydrobinaphthyl was almost quantitatively dehydrogenated to form binaphthyl. The decalin conversion rate was 63% after 24 hours from the start of the reaction, 64% after 240 hours, and 62% after 480 hours, and no decrease in activity was observed even after about 500 hours. The residual reaction product after completion of the reaction was 76 g, and it was clear that the liquid phase ratio was high under the reaction conditions.

(Example 3)
In Example 1, the same conditions and conditions as in Example 1 were used, except that 90% by mass of tetralin was used instead of 90% by mass of decalin and 10% by mass of binaphthyl hemihydride was used instead of 10% by mass of perhydroanthracene. The dehydrogenation reaction of tetralin was continuously performed for 500 hours. Binaphthyl hemihydride was almost quantitatively dehydrogenated to form binaphthyl. The tetralin conversion was 75% after 24 hours from the start of the reaction, 77% after 240 hours, and 77% after 480 hours, and no decrease in activity was observed even after about 500 hours. The residual reaction product after the reaction was 69 g, and it was clear that the liquid phase ratio was high under the reaction conditions.

Example 4
In Example 1, perhydroanthracene 94% by mass instead of decalin 90% by mass, and perhydropyrene 6% by mass in place of perhydroanthracene 10% by mass was used in the same manner and under the same conditions as in Example 1. The dehydrogenation reaction of hydroanthracene was carried out continuously for 500 hours. The added perhydropyrene was dehydrogenated to pyrene. The perhydroanthracene conversion rate was 56% after 24 hours from the start of the reaction, 54% after 240 hours, and 54% after 480 hours, and no decrease in activity was observed even after about 500 hours. The residual reaction product after completion of the reaction was 88 g, and it was clear that the liquid phase ratio was high under the reaction conditions.

(Comparative Example 1)
In Example 1, decalin was dehydrogenated continuously for 500 hours in the same manner and under the same conditions as in Example 1 except that 10% by mass of perhydroanthracene was not mixed with decalin (trans form: cis form = 1: 1). It was. The decalin conversion was 54% after 24 hours from the start of the reaction and 34% after 240 hours, and continued to decrease, so the reaction was stopped after 300 hours. The conversion rate of decalin immediately before stopping the reaction was 28%. The residual reaction product after stopping the reaction is only 15 g, and it is estimated that the reaction was substantially a gas phase reaction.

(Comparative Example 2)
In Example 1, decalin was dehydrogenated continuously for 500 hours under the same method and conditions as in Example 1 except that 10% by mass of tetralin was used instead of 10% by mass of perhydroanthracene. The decalin conversion rate was 53% after 24 hours from the start of the reaction and 35% after 240 hours, which was almost the same as that of Comparative Example 1 in which no additive was added. Therefore, the reaction was stopped after 300 hours. The residual reaction product after stopping the reaction is only 13 g, and it is estimated that the reaction was substantially a gas phase reaction. This is presumably because the raw material and the additive are hydrocarbons having the same number of carbon atoms, and thus were substantially equivalent to the state in which no additive was added.

When the dehydrogenation reaction of the hydrogenated aromatic compound A mixed with the additive of the present invention is performed using a high-pressure reactor, hydrogen gas can be obtained at a high pressure. Therefore, for example, in order to fill the hydrogen gas into a hydrogen cylinder of a fuel cell of an automobile, it is not necessary to provide a high-pressure filling facility in a gas station or the like, or at least it can be greatly simplified.
In addition, the hydrogen production method of the present invention is a method for storing hydrogen gas in which a hydrogenation reaction apparatus for hydrogenating an aromatic compound with hydrogen and a dehydrogenation reaction apparatus for dehydrogenating the obtained hydrogenated aromatic compound are connected. -It can also be applied to a dehydrogenation reaction process in a transportation system.

Claims (4)

  Dehydration of hydrogenated aromatic compound A (excluding hydride B described below) in the presence of a polycyclic aromatic compound hydride B and a catalyst in which one or more benzene rings are condensed and / or substituted on a naphthalene skeleton A method for producing hydrogen, comprising obtaining hydrogen.   The mixing ratio of the hydride B of the polycyclic aromatic compound is 0.1 to 20% by mass of the total amount of the hydride B of the hydrogenated aromatic compound A and the polycyclic aromatic compound. The method for producing hydrogen according to claim 1.   3. The polycyclic aromatic compound according to claim 1, wherein the polycyclic aromatic compound is at least one polycyclic aromatic hydrocarbon selected from anthracene, phenanthrene, pyrene, phenylnaphthalene, binaphthyl, phenylanthracene, and phenylphenanthrene. A method for producing hydrogen.   The hydrogenated aromatic compound A is at least one hydrogenated polycyclic alicyclic hydrocarbon selected from decalin, methyldecalin, tetralin, and methyltetralin. A method for producing hydrogen.