JP2017012992A - Dehydrogenation catalyst for hydrocarbon, hydrogen production system and hydrogen production method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dehydrogenation catalyst for hydrocarbon having excellent dehydrogenation activity.SOLUTION: There is provided a dehydration catalyst 1 for hydrocarbon, comprising a carrier including AlO, and Pt carried on the carrier. When the spectrum of the characteristic X rays of Pt along a direct line a located on the cross section CS of the dehydration catalyst 1 and also vertical to the surface S of the dehydration catalyst 1 is measured using an electron ray microanalyzer, the spectrum has a peak on the surface S side of the dehydration catalyst 1, and provided that the half-value width of the peak is W μm and the carried amount of Pt per the unit volume of the dehydration catalyst 1 is C g/mL, C/W satisfies 1.3×10to 3.5×10.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a hydrocarbon dehydrogenation catalyst, a hydrogen production system, and a hydrogen production method.

  In recent years, it is expected that a fuel cell using hydrogen with a small environmental load as a fuel will be used as a power source of an automobile or the like. In the process of transporting, storing and supplying hydrogen, for example, naphthenic hydrocarbons (cyclic hydrocarbons) are used. For example, in a hydrogen production facility, naphthenic hydrocarbons are generated by hydrogenation of aromatic hydrocarbons. This naphthenic hydrocarbon is transported to a hydrogen consumption area or stored in the consumption area. In the consumption area, hydrogen and aromatic hydrocarbons are generated by dehydrogenation of naphthenic hydrocarbons. This hydrogen is supplied to the fuel cell. Naphthenic hydrocarbons are liquid at room temperature, have a smaller volume than hydrogen gas, are less reactive than hydrogen gas, and are safe. Therefore, naphthenic hydrocarbons are more suitable for transportation and storage than hydrogen gas.

  As a dehydrogenation catalyst for naphthenic hydrocarbons, a catalyst in which a platinum-rhenium bimetal is supported on an alumina carrier is known (see Non-Patent Document 1 below).

R. W. Coughlin, K.M. Kawakami, Akram Hasan, Journal of Catalysis, Vol. 88, 150-162 (1984).

  An object of the present invention is to provide a hydrocarbon dehydrogenation catalyst having excellent dehydrogenation activity, a hydrogen production system and a hydrogen production method using the dehydrogenation catalyst.

A dehydrogenation catalyst according to one aspect of the present invention is a dehydrogenation catalyst for hydrocarbons, comprising a support containing Al ₂ O ₃ and Pt supported on the support, on the cross section of the dehydrogenation catalyst. When the characteristic X-ray spectrum of Pt along a straight line located and perpendicular to the surface of the dehydrogenation catalyst was measured using an electron beam microanalyzer, the spectrum had a peak on the surface side of the dehydrogenation catalyst. When the half-value width is W μm and the supported amount of Pt per unit volume of the dehydrogenation catalyst is Cg / mL, C / W is 1.3 × 10 ^{−4 to} 3.5 × 10 ⁻⁴ g / mL · μm.

  In the dehydrogenation catalyst according to one aspect of the present invention, W may be 12 to 20 μm.

  In the dehydrogenation catalyst according to one aspect of the present invention, Pt may be supported on the support by a method of immersing the support in a solution containing Pt.

  A hydrogen production system according to one aspect of the present invention includes a dehydrogenation reactor that includes the dehydrogenation catalyst and generates hydrogen by dehydrogenation of a hydrocarbon using the dehydrogenation catalyst.

  A method for producing hydrogen according to one aspect of the present invention includes a step of generating hydrogen by dehydrogenating a hydrocarbon using the dehydrogenation catalyst.

  In the method for producing hydrogen according to one aspect of the present invention, the hydrocarbon may be a naphthenic hydrocarbon.

  ADVANTAGE OF THE INVENTION According to this invention, the dehydrogenation catalyst for hydrocarbons which has the outstanding dehydrogenation activity, the manufacturing system of hydrogen using the said dehydrogenation catalyst, and the manufacturing method of hydrogen can be provided.

(A) in FIG. 1 is a diagram showing a columnar dehydrogenation catalyst according to an embodiment of the present invention. (B) in FIG. 1 is a diagram showing a spherical dehydrogenation catalyst according to an embodiment of the present invention. (A) in FIG. 2 is a schematic diagram of a part of a cross section of a dehydrogenation catalyst according to an embodiment of the present invention. (B) in FIG. 2 shows the characteristic X-ray spectrum of Pt measured on the cross section of the dehydrogenation catalyst according to one embodiment of the present invention. FIG. 3 is a schematic view showing an embodiment of the hydrogen production system according to the present invention. (A) in FIG. 4 is a secondary electron image of a cross section of the dehydrogenation catalyst according to Example 3. (B) in FIG. 4 is an enlarged view of the region I in (a) in FIG. (C) in FIG. 4 is a reflected electron image of a cross section of the dehydrogenation catalyst according to Example 3. (D) in FIG. 4 is an enlarged view of region II in (c) in FIG. (A), (b), (c), (d), and (e) in FIG. 5 are cross-sectional images of the dehydrogenation catalyst according to Example 3 taken by an electron beam microanalyzer (EPMA). , The location where the characteristic X-ray spectrum of Pt was measured is shown. (F), (g), (h), (i), and (j) in FIG. 5 show the characteristic X-ray spectra of Pt measured on the cross section of the dehydrogenation catalyst according to Example 3. (A) in FIG. 6 is a characteristic X-ray spectrum of Pt measured on the cross section of the dehydrogenation catalyst according to Example 3. (B) in FIG. 6 is a spectrum obtained by baseline correction of the spectrum shown in (a) in FIG. FIG. 7 shows the relationship between the C / W (unit: g / mL · μm) and the conversion rate rc (unit:%) of each of the dehydrogenation catalysts according to Examples and Comparative Examples. FIG. 8 shows the relationship between the half-value width W (unit: μm) and the conversion rc (unit:%) of each of the dehydrogenation catalysts according to Examples and Comparative Examples.

  Hereinafter, preferred embodiments of the present invention will be described. In the drawings, the same components are denoted by the same reference numerals. However, the present invention is not limited to the following embodiment.

(Dehydrogenation catalyst for hydrocarbons)
The dehydrogenation catalyst according to the present embodiment is used for hydrocarbon dehydrogenation. The dehydrogenation catalyst includes a support containing Al ₂ O ₃ (aluminum oxide) and Pt (platinum) supported on the support. As will be described below, the dehydrogenation catalyst according to the present embodiment is characterized by the characteristic X-ray spectrum of Pt measured in the cross section and the supported amount of Pt. The characteristic X-ray spectrum of Pt is measured by an electron beam microanalyzer (EPMA). Hereinafter, the characteristic X-ray spectrum of Pt is also simply referred to as “spectrum”. Hereinafter, the details of spectrum-based dehydrogenation catalyst characterization will be described with reference to FIGS. 1 and 2.

  As shown to (a) in FIG. 1, the dehydrogenation catalyst 1 which concerns on this embodiment may be cylindrical. As shown in FIG. 1 (b), the modified example of the dehydrogenation catalyst 1 according to the present embodiment may be spherical. The shape of the entire dehydrogenation catalyst 1 is not particularly limited.

  (A) in FIG. 2 is a partially enlarged view of a cross-section CS of the dehydrogenation catalyst 1 according to (a) or (b) in FIG. That is, the cross section CS indicated by (a) in FIG. 2 may be the cross section CS of the columnar dehydrogenation catalyst 1 indicated by (a) in FIG. Alternatively, the cross section CS indicated by (a) in FIG. 2 may be the cross section CS of the spherical dehydrogenation catalyst 1 indicated by (b) in FIG. As shown in FIG. 2A, the cross section CS of the dehydrogenation catalyst 1 is a cross section perpendicular to the surface S of the dehydrogenation catalyst 1. Needless to say, the cross-section CS of the dehydrogenation catalyst 1 is a surface formed by cutting the dehydrogenation catalyst 1 and is different from the surface S (outer surface) of the dehydrogenation catalyst 1. When the surface S of the dehydrogenation catalyst 1 is a curved surface, the cross section CS perpendicular to the surface S is perpendicular to a plane (tangential plane S ′) that is in contact with the surface S of the dehydrogenation catalyst 1 and It may be a plane passing through the contact point p between the surface S and the tangent plane S ′. The surface S that the tangent plane S ′ contacts may be cylindrical as shown in FIG. The surface S with which the tangent plane S ′ contacts may be a spherical surface as shown in FIG. The shape of the surface S of the dehydrogenation catalyst 1 is not limited to the shape shown in FIG. For example, the surface S of the dehydrogenation catalyst 1 may be a flat surface.

  The method for measuring the characteristic X-ray spectrum of Pt using EPMA is, for example, as follows. As shown to (a) in FIG. 2, the cross section CS of the dehydrogenation catalyst 1 is exposed. An electron beam is irradiated along a straight line a located on the cross section CS of the dehydrogenation catalyst 1 and perpendicular to the surface S of the dehydrogenation catalyst 1. That is, the cross section CS of the dehydrogenation catalyst 1 may be scanned with the electron beam along the straight line a. A characteristic X-ray of Pt is emitted from the portion irradiated with the electron beam. This characteristic X-ray is continuously detected along the straight line a. By such a measuring method, a characteristic X-ray spectrum of Pt shown in FIG. 2B is obtained. The horizontal axis of the spectrum indicated by (b) in FIG. 2 may coincide with the straight line a indicated by (a) in FIG. The horizontal axis of the spectrum is, for example, the distance D (unit: μm) from the origin 0 on the straight line a. The origin 0 on the horizontal axis may be a position where electron beam irradiation (detection of characteristic X-rays) is started. The origin 0 on the horizontal axis may be located outside the dehydrogenation catalyst 1 or may be located on the center side of the cross section CS of the dehydrogenation catalyst 1. The cross section CS may be scanned with an electron beam from the outside of the dehydrogenation catalyst 1 toward the center side of the cross section CS. The cross section CS may be scanned with an electron beam from the center side of the cross section CS of the dehydrogenation catalyst 1 toward the outside. The vertical axis of the spectrum indicated by (b) in FIG. 2 indicates the intensity I (unit: cps) of the detected characteristic X-ray of Pt.

  The acceleration voltage of the electron beam may be 25 kV, for example. The electron beam irradiation current may be, for example, 137 nA. The step size of the electron beam may be 0.5 μm / step, for example. The irradiation time of the electron beam may be 20 msec / step.

  The energy of the characteristic X-ray of Pt is specific to the Pt element. For example, the characteristic X-rays of Pt detected by EPMA may be Lα rays. The stronger the intensity I (unit: cps) of the detected characteristic X-ray of Pt, the greater the number of Pt atoms present at the site emitting characteristic X-rays. Therefore, the characteristic X-ray spectrum of Pt indicated by (b) in FIG. 2 shows the distribution of the Pt element along the straight line a located on the cross section CS of the dehydrogenation catalyst 1.

As is clear from the relative positional relationship between (a) and (b) in FIG. 2, the characteristic X-ray spectrum of Pt has a peak on the surface S side of the dehydrogenation catalyst 1. In other words, the dehydrogenation catalyst 1 has a region where the amount of Pt existing is maximized on the surface S side. That is, the characteristic X-ray peak located near the surface S of the dehydrogenation catalyst 1 indicates that Pt is localized near the surface S of the dehydrogenation catalyst 1. As shown in FIG. 2B, the half-value width of the peak of the characteristic X-ray of the Pt element is defined as W (unit: μm). The amount of Pt supported per unit volume of the dehydrogenation catalyst 1 is defined as C (unit: g / mL). In the dehydrogenation catalyst 1 according to the present embodiment, C / W is 1.3 × 10 ^{−4 to} 3.5 × 10 ⁻⁴ g / mL · μm. The dehydrogenation catalyst 1 having C / W in the above range has an excellent dehydrogenation activity as compared with a conventional dehydrogenation catalyst. The reason will be described below.

  It is considered that hydrocarbon dehydrogenation (dehydrogenation reaction) by the dehydrogenation catalyst 1 proceeds, for example, through the following route. First, the hydrocarbon comes into contact with the dehydrogenation catalyst 1 in a reducing atmosphere. Next, Pt, which is an active site, pulls at least a pair of hydrogen atoms from the hydrocarbon, thereby generating a hydrogen molecule and an unsaturated hydrocarbon. Such activity of the dehydrogenation catalyst 1 that promotes dehydrogenation of hydrocarbons is referred to as dehydrogenation activity.

The dehydrogenation activity is evaluated based on the conversion rate Rc of hydrocarbon. A high conversion rate Rc per unit volume of the dehydrogenation catalyst 1 means that the dehydrogenation activity of the dehydrogenation catalyst 1 is high. The conversion rate Rc is defined by the following formula (1), for example.
Rc (unit:%) = (M ₂ / M ₁ ) × 100 = {M ₂ / (M ₂ + M ₃ )} × 100 (1)
In formula (1), M ₁ is the number of moles of hydrocarbons supplied to the reaction vessel in which the dehydrogenation catalyst 1 is disposed. M ₂ is the number of moles of unsaturated hydrocarbons contained in the product of the dehydrogenation reaction. In other words, M ₂ is the number of moles of unsaturated hydrocarbons produced by hydrocarbon dehydrogenation. M ₃ is the number of moles of the raw material (hydrocarbon not dehydrogenated) remaining after the dehydrogenation reaction.

  The relationship between the excellent dehydrogenation activity of the dehydrogenation catalyst 1 and C / W is estimated as follows.

In the hydrocarbon dehydrogenation reaction, the reaction rate is more dominant than the diffusion rate of hydrocarbons into the catalyst. Therefore, the hydrocarbon comes into contact with the active metal Pt in the vicinity of the surface S of the dehydrogenation catalyst 1 before the hydrocarbon diffuses into the catalyst, and the dehydrogenation reaction proceeds. Therefore, Pt located deep inside the dehydrogenation catalyst 1 is unlikely to come into contact with hydrocarbons and hardly contributes to the dehydrogenation reaction. A large half-value width W means that Pt is distributed over a wide region extending from the surface S to the inside of the dehydrogenation catalyst 1. That is, the large half width W means that Pt exists not only on the surface S of the dehydrogenation catalyst 1 but also deep inside the dehydrogenation catalyst 1. Therefore, the larger the half width W, the smaller the Pt density (for example, Pt particle density) in the vicinity of the surface S of the dehydrogenation catalyst 1. That is, the smaller the C / W, the smaller the Pt density in the vicinity of the surface S of the dehydrogenation catalyst 1. As a result, the amount of Pt that can contribute to the dehydrogenation reaction decreases, and the dehydrogenation activity becomes insufficient. When the half width W is too small, the interval between Pt (for example, the interval between Pt particles) is too small on the surface S side of the dehydrogenation catalyst 1. That is, the larger the C / W, the higher the density of Pt in the vicinity of the surface S of the dehydrogenation catalyst 1 (for example, the density of Pt particles). As a result, Pt easily aggregates in the vicinity of the surface S of the dehydrogenation catalyst 1, and the surface area of active Pt is reduced. That is, the active points of the dehydrogenation catalyst 1 are reduced. As a result, the hydrocarbon does not sufficiently contact Pt and the dehydrogenation activity becomes insufficient. When C / W is 1.3 × 10 ⁻⁴ g / mL · μm or more, there is little Pt that is located deep in the dehydrogenation catalyst 1 and does not contribute to the dehydrogenation reaction. Moreover, when C / W is 3.5 × 10 ⁻⁴ g / mL · μm or less, Pt localized in the vicinity of the surface S of the dehydrogenation catalyst 1 is adequately dispersed so that hydrocarbons come into contact with each other. The surface area of Pt is ensured. Therefore, when C / W is 1.3 × 10 ^{−4 to} 3.5 × 10 ⁻⁴ g / mL · μm, dehydrogenation of hydrocarbons efficiently proceeds near the surface S of the dehydrogenation catalyst 1. To do. That is, excellent dehydrogenation activity is realized.

  Even if the supported amount C of Pt in the dehydrogenation catalyst 1 according to this embodiment is the same as the supported amount of Pt in a conventional dehydrogenation catalyst whose C / W is not in the above range, the dehydrogenation according to this embodiment is performed. The catalyst 1 has dehydrogenation activity superior to that of conventional dehydrogenation catalysts. In other words, in this embodiment, even if the amount of Pt supported C is smaller than that of the conventional dehydrogenation catalyst, it is possible to have a catalytic activity equivalent to that of the conventional dehydrogenation catalyst. Therefore, in this embodiment, it is possible to reduce the amount C of the expensive Pt supported without sacrificing the dehydrogenation activity.

From the viewpoint of further improving the dehydrogenation activity, C / W may be 1.4 × 10 ^{−4 to} 3.1 × 10 ⁻⁴ g / mL · μm. C / W may be 1.4 × 10 ^{−4 to} 2.8 × 10 ⁻⁴ g / mL · μm.

  The half width W may be 10 to 21 μm, may be 12 to 20 μm, and may be. When the half-value width W is in the above range, the ratio of Pt that can contribute to the reaction tends to be high, and the conversion rate tends to be improved.

  The half width W can be calculated by the following method, for example. First, in the cross section CS of the dehydrogenation catalyst 1, arbitrary N points are selected from the region on the surface S side of the dehydrogenation catalyst 1. The spectrum of the characteristic X-ray of Pt is measured at the selected N locations to obtain N spectra. Next, each spectrum is analyzed by the following procedure. First, a region indicated by A in FIG. 2B (a region where Pt is assumed not to exist) is regarded as a baseline. A standard deviation σ of the intensity I of the characteristic X-ray at the baseline is calculated. Next, the spectrum is corrected by subtracting 3σ from the intensity I of the characteristic X-ray of the spectrum. This correction is called baseline correction. In the spectrum after correction, the half width of the peak is obtained. The half width of the peak is, for example, the distance (peak width) between two points where the intensity of the characteristic X-ray is half that of the peak top and located on both sides of the peak top. N spectra are analyzed by the above procedure to obtain N half widths. Of the N half widths, an average value of the remaining (N−2) half widths excluding the maximum value and the minimum value is obtained. This average value is defined as a half width W. When N is 3, the remaining half width (intermediate value) of the three half widths excluding the maximum and minimum values may be used for calculating C / W. The number of data N (N is an integer) for calculating the half-value width W may be, for example, 3 to 10, or 5.

The support may consist only of Al ₂ O ₃ . The type of Al ₂ O ₃ is not limited, but specific examples of Al ₂ O ₃ include α-alumina, δ-alumina, θ-alumina, γ-alumina, and alumite. Although the specific surface area of aluminum oxide is not particularly limited, it falls within the range of about 100 to 500 m ² / g.

  The carrier may further contain a metal element belonging to Group 3 of the long periodic table (hereinafter simply referred to as “Group 3 metal”).

  The Group 3 metal may be at least one selected from the group consisting of scandium (Sc), yttrium (Y), lanthanoid and actinoid. Examples of the lanthanoid include lanthanum (La) and cerium (Ce). Of these Group 3 metals, Ce is most preferred.

The Group 3 metal may be contained in the carrier as a simple metal. The Group 3 metal may be contained in the support as an oxide. Further, the Group 3 metal may be present as a composite oxide with Al ₂ O ₃ . The carrier may be composed only of a composite oxide of Al ₂ O ₃ and a Group 3 metal. Group 3 metal may be contained within the _Al 2 _{O 3,} it may be supported on the surface of the _Al 2 _{O 3.} If the third group metal is supported on the surface of the Al ₂ O _3, the Al ₂ O ₃ of the third group metal supported "carrier".

When the support contains a Group 3 metal, Pt is less likely to be supported inside the support as compared to the case where the support is made of only Al ₂ O ₃ . In other words, when the support contains a Group 3 metal, the peak half-value width W tends to be smaller than when the support is made of only Al ₂ O ₃ .

  Moreover, when a support | carrier contains a group 3 metal, there exists a tendency for dehydrogenation activity to improve more easily. When a Group 3 metal is added to the support, Pt acting as an active site on the catalyst surface increases due to its physical, electronic or chemical action, or the function of Pt as an active site increases. Therefore, the present inventors consider that such an effect can be obtained. In addition, the present inventors consider that one of the specific reasons that the above-described effect can be obtained when the support contains a Group 3 metal is as follows.

When the Group 3 metal is supported on the surface of the support, a part of oxygen constituting Al ₂ O ₃ or the oxide of the Group 3 metal is desorbed from the support in a reducing atmosphere, and the lattice has many lattice defects. Is formed. Pt is fixed to the carrier by fitting Pt into the lattice defect. As a result, Pt becomes more highly dispersed by heating during the dehydrogenation reaction, and movement and aggregation of Pt on the support surface are further suppressed. That is, by supporting the Group 3 metal on the surface of the support, the surface area of Pt during the dehydrogenation reaction is further increased and the aggregation of Pt is further suppressed as compared with the conventional dehydrogenation catalyst. Thereby, dehydrogenation activity and durability improve more. Such an effect is remarkable when the Group 3 metal is Ce. The formation of lattice defects caused by the Group 3 metal is, for example, observing the chemical shift of the peak derived from the Group 3 metal constituting the oxide in the X-ray photoelectron spectroscopy (XPS) spectrum of the dehydrogenation catalyst 1. Can be confirmed.

  When the support contains a Group 3 metal, the aggregation of Pt during the dehydrogenation reaction is further suppressed as compared with the case where the support does not contain a Group 3 metal. Therefore, the deactivation over time associated with the dehydrogenation reaction is more easily suppressed, and the high dehydrogenation activity is easily maintained for a longer period.

  However, even if the carrier does not contain a Group 3 metal, the dehydrogenation catalyst 1 has an excellent dehydrogenation activity.

The content of the Group 3 metal in the support is not particularly limited, but may be 0.1 to 5.0% by mass with respect to the mass of the entire support in terms of Group 3 metal oxide. The mass of the entire support includes the mass of the Group 3 metal oxide. When the content of the Group 3 metal is not less than the above lower limit value, the platinum surface area is further increased, and the dehydrogenation activity tends to be further improved. When the content of the Group 3 metal is not more than the above upper limit value, it is easy to increase the platinum surface area while maintaining the mechanical strength of the dehydrogenation catalyst 1. Further, when the content of the Group 3 metal is not more than the above upper limit value, the carrier can be easily molded in the production process. When the content of the Group 3 metal greatly exceeds the above upper limit value, the performance of the support tends to deteriorate, and the platinum surface area tends to decrease. However, even if the content of the Group 3 metal is outside the above numerical range, the effect of the present invention is achieved. For example, the content of the Group 3 metal in the support may be greater than 0 parts by mass and 20 parts by mass or less based on 100 parts by mass of Al ₂ O _{3 in} terms of Group 3 metal oxides. The content of the Group 3 metal in the support may be greater than 0 parts by mass and 10 parts by mass or less with respect to 100 parts by mass of Al ₂ O _{3 in} terms of Group 3 metal oxides. The content of the Group 3 metal in the support may be 0.3 to 5.0 parts by mass with respect to 100 parts by mass of Al ₂ O _{3 in} terms of Group 3 metal oxide, and 2.0 to It may be 3.0 parts by mass. When the content of Group 3 metal in the support is 2.0 to 3.0 parts by mass with respect to 100 parts by mass of Al ₂ O _{3 in} terms of Group 3 metal oxide, the platinum surface area is particularly increased. And the dehydrogenation activity tends to be further improved.

The support may contain components other than Al ₂ O ₃ and Group 3 metals. Other components may be, for example, TiO ₂ and SiO ₂ . These other components may exist as a composite oxide with Al ₂ O ₃ . The carrier may be composed only of a complex oxide of Al ₂ O ₃ and the other components.

When the support contains a Group 3 metal or the above-mentioned other components, the content of Al ₂ O _{3 in} the support is, for example, 50 to 99.5% by mass or 80 to 99.5% by mass based on the total mass of the support. %. When the content of Al ₂ O ₃ is in the above range, the dehydrogenation activity tends to be further improved.

  The shape of the carrier is not particularly limited. The carrier may be molded or molded. The carrier may be spherical or columnar, for example. The cross section of the columnar carrier (the cross section CS of the dehydrogenation catalyst 1) may be circular, trilobal, or tetralobal. The support may be plate-shaped or honeycomb-shaped.

  The major axis (for example, diameter) of the carrier is not particularly limited, but may be 1 to 4 mm. When the major axis of the carrier is not less than the above lower limit value, excellent mechanical strength is easily obtained. When the major axis of the support is not more than the above upper limit value, the geometric surface area of the dehydrogenation catalyst 1 does not become too small, and C / W can be easily adjusted to a desired range. For the same reason, the major axis of the carrier may be 1.15 to 1.59 mm.

  Pt may be supported on the carrier as a large number of atoms, clusters or fine particles. The particle diameter of the Pt fine particles supported on the carrier is not particularly limited, but may be, for example, 10 nm or less, and may be, for example, 1.6 to 2.1 nm. In this embodiment, Pt is supported substantially on the entire surface of the carrier, but a portion where Pt is not supported may exist on the surface of the carrier. When Pt is supported on the entire surface of the support, better dehydrogenation activity is easily obtained.

The supported amount C of Pt in the dehydrogenation catalyst 1 may be 6.0 × 10 ^{−4 to} 7.0 × 10 ⁻³ g / mL based on the total volume of the dehydrogenation catalyst 1. When the supported amount C of Pt is not less than the above lower limit value, the dehydrogenation activity tends to be further improved. Further, when the supported amount C of Pt exceeds the above upper limit value, the degree of improvement in the catalyst activity accompanying the increase in the supported amount of Pt becomes moderate. Since the price of Pt is very high, the amount C of Pt supported is limited for practical use of the dehydrogenation catalyst 1. For the same reason, the supported amount C may be 2.8 × 10 ^{−3 to} 3.4 × 10 ⁻³ g / mL.

  Only Pt may be supported on the carrier. Other metal components other than Pt may be supported on the carrier. The other metal component may be a Group VIII element of the short periodic table (Group 8 to 10 element of the long periodic table) (except Pt). Group VIII elements of the short periodic table are Fe (iron), Ru (ruthenium), Os (osmium), Co (cobalt), Rh (rhodium), Ir (iridium), Ni (nickel) and Pd (palladium). It may be at least one selected from the group consisting of When other metal components are supported on the support, Pt may be supported on the support as a single metal, or may be supported on the support as an alloy with other metal components.

  The shape of the dehydrogenation catalyst 1 may be the same as the shape of the carrier described above. The major axis of the dehydrogenation catalyst 1 (size of the dehydrogenation catalyst 1) may be approximately the same as the major axis of the carrier (size of the carrier) described above.

(Method for producing dehydrogenation catalyst 1)
The dehydrogenation catalyst 1 according to this embodiment includes, for example, a step of obtaining a support containing Al ₂ O ₃ (first step) and a step of supporting Pt on the obtained support (second step) as follows. And manufactured by a method comprising:

[First step]
The support containing Al ₂ O ₃ can be produced by a known method. Commercially available Al ₂ O ₃ may be used as the carrier.

When the support contains a Group 3 metal, the support is, for example, a mixture having a porous structure by mixing a Group 3 metal compound with Al ₂ O ₃ or a precursor thereof before having a stable porous structure. Can be obtained by a method of forming Examples of such a method include a kneading method, a sol-gel method, and a coprecipitation method.

  As the Group 3 metal compound, for example, nitrate, sulfate, carbonate, acetate, phosphate, oxalate, borate, chloride, alkoxide, acetylacetonate, or the like may be used.

The support may be obtained by physically mixing Al ₂ O ₃ and a Group 3 metal oxide. The Group 3 metal may be added to the support by molding a mixture of the Al ₂ O ₃ raw material powder and the Group 3 metal compound and firing the molded body. For example, boehmite, which is a raw material of γ-alumina, may be used as the raw material powder of Al ₂ O ₃ . The firing temperature in this case may be a temperature at which pyrolysis of the Group 3 metal compound proceeds and γ-alumina is generated by sintering of boehmite. Such a firing temperature is, for example, about 300 to 600 ° C.

The carrier may be produced by the following method. First, a kneaded product is prepared by kneading pseudoboehmite aluminum hydroxide, a Group 3 metal nitrate aqueous solution, and dilute nitric acid. Next, pellets are produced by extrusion molding of the kneaded product. The obtained pellet is fired to prepare a carrier. By producing the carrier by such a method, the Group 3 metal is easily dispersed in the carrier. In the dehydrogenation catalyst 1 produced using such a carrier, the platinum surface area tends to be large, and high dehydrogenation activity is likely to be obtained. Hydroxides of pseudoboehmite state aluminum, for example, represented by the composition formula of AlOOH or _{Al 2 O 3 · H 2 O} . The kneaded product is also called a dough. What is necessary is just to adjust pH of a kneaded material to 3-7. By adjusting the pH, the kneaded product has an appropriate viscosity, and the kneaded product is easily molded. The pH of the kneaded product varies depending on the amount of nitric acid added. You may adjust pH of a kneaded material by adding ammonia water to a kneaded material.

When the support is a support in which a Group 3 metal is supported on Al ₂ O ₃ , the support supports, for example, a porous Al ₂ O ₃ solution containing the Group 3 metal (for example, an aqueous solution). It can be produced by a method. The solution containing a Group 3 metal can be prepared, for example, by dissolving a Group 3 metal compound in a solvent. Examples of a method for supporting a solution containing a Group 3 metal on Al ₂ O ₃ include an impregnation method (incipient wetness method or a pore filling method), an adsorption method, an immersion method (chemical adsorption method), an evaporation and drying method, and a spraying method. Method, ion exchange method, liquid phase reduction method and the like. By these methods, a Group 3 metal salt is deposited on the surface of Al ₂ O ₃ . The amount of the Group 3 metal supported may be adjusted depending on the concentration of the Group 3 metal compound in the solution containing the Group 3 metal or the amount of the solution containing the Group 3 metal.

By salts of the Group III metal to decompose the salt by firing Al ₂ O ₃ deposited, a Group 3 metal is supported on Al ₂ O _3. The firing temperature may be any temperature at which the thermal decomposition of the salt proceeds, for example, about 300 to 600 ° C.

  The carrier before firing or after firing may be formed or molded into a predetermined shape.

[Second step]
In the second step, Pt is supported on the carrier obtained in the first step. The second step may include a step of supporting a solution containing Pt (Pt solution) on the carrier obtained in the first step. The method for supporting the Pt solution is an impregnation method (incipient wetness method or pore filling method), an adsorption method, an immersion method (chemical adsorption method), an evaporation to dryness method, a spray method, an ion exchange method, a liquid phase reduction method, or the like. It may be. When the method for supporting the Pt solution is an immersion method (chemical adsorption method), the Pt solution tends to be uniformly supported on the entire surface of the carrier. Therefore, when the immersion method (chemical adsorption method) is used, the half width W of the peak does not become too large, and it becomes easy to adjust C / W to a desired range.

  A method for supporting a Pt solution on a carrier by an immersion method (chemical adsorption method) will be described in more detail.

  The dipping method (chemical adsorption method) is a loading method different from the impregnation method. In the immersion method (chemical adsorption method), the Pt solution is supported on the carrier by immersing the carrier in the Pt solution. The Pt solution can be prepared, for example, by dissolving a Pt compound in a solvent. The compound of Pt is not particularly limited, but is required to be soluble in a liquid solvent. The compound of Pt may be nitrate, sulfate, carbonate, acetate, phosphate, oxalate, borate, chloride, alkoxide, acetylacetonate, and the like.

  Pt compounds are tetrachloroplatinic acid, potassium tetrachloroplatinate, ammonium tetrachloroplatinate, sodium tetrachloroplatinate, bis (acetylacetonato) platinum, diamminedichloroplatinum, dinitrodiammineplatinum, tetraammineplatinum dichloride, tetraammineplatinum. Hydrochloride, tetraammineplatinum nitrate, tetraammineplatinum acetate, tetraammineplatinum carbonate, tetraammineplatinum phosphate, hexaammineplatinum tetrachloride, hexaammineplatinum hydrochloride, hexaammineplatinum hydrochloride, bis (ethanolammonium) hexa It is at least one selected from the group consisting of hydroxoplatinum (IV), sodium hexahydroxoplatinum (IV), potassium hexahydroxoplatinum (IV), platinum nitrate and platinum sulfate. Good.

  In this embodiment, the Pt solution may be vigorously stirred when the carrier is immersed. By vigorously stirring the Pt solution, the number of contacts between the Pt ions in the solution and the carrier can be increased. As a result, the Pt solution is easily supported uniformly on the entire surface of the carrier, and the dehydrogenation catalyst 1 according to this embodiment is easily obtained.

  In the second step, the amount of Pt supported C can be adjusted by adjusting the concentration of Pt solution used for supporting Pt (the content of Pt in the solution).

In the dipping method, W may be controlled by adjusting the Pt loading speed (adsorption speed). However, W is not controlled only by adjusting the carrying speed of Pt. The Pt loading speed V (unit: mass% / min) is defined by the following formula (X).
V = [Pt] / T (X)
In the formula (X), T is a time (unit: minute) for immersing the carrier in the Pt solution. [Pt] is the amount of Pt supported on the carrier during time T, and is a relative amount (unit: mass%) when the supported amount of Pt in the dehydrogenation catalyst after completion is 100% by mass. is there.

  For example, the Pt loading speed V may be maintained at 5 to 6 mass% / min until the Pt loading reaches 80% of the desired loading. After the Pt loading amount reaches 80% of the desired loading amount, the Pt loading may be completed while adjusting the Pt loading speed V to 0.5 to 1.5 mass% / min. When the loading speed V of Pt is too small, it takes time to load a predetermined amount of Pt, and the production efficiency of the dehydrogenation catalyst tends to decrease. When the carrying speed V of Pt is too large, Pt carrying spots occur, and W spots tend to occur.

  The higher the temperature of the Pt solution, the easier it is for the Pt compound in the Pt solution to be adsorbed on the carrier, and the Pt loading rate V tends to increase. In other words, the lower the temperature of the Pt solution, the lower the Pt loading speed V tends to be. Further, the higher the concentration of the Pt solution, the higher the Pt loading speed V tends to be. On the other hand, the lower the concentration of the Pt solution, the smaller the Pt loading speed V tends to be. By adjusting the temperature or the concentration of the Pt solution, the Pt loading speed V can be freely controlled.

  Before the carrier is immersed in the Pt solution, water may be absorbed into the carrier. By making the carrier absorb water in advance, rapid adsorption of Pt on the carrier is suppressed. As a result, it becomes easy to control the carrying speed of Pt.

  The second step may include a sub-step of firing the carrier carrying the Pt solution. The Pt compound attached to the carrier is decomposed by firing. As a result, Pt is supported on the carrier, and the dehydrogenation catalyst 1 according to this embodiment is completed.

  The furnace used for firing the carrier carrying the Pt compound (precursor) may be, for example, a fixed furnace. In other words, the carrier in the container may be fired by putting a predetermined amount of the carrier into the baking container and raising the temperature in the furnace to the predetermined temperature without stirring the carrier in the container. The furnace used for baking may be a belt conveyor type furnace. The furnace used for firing may be a rotary furnace such as a rotary kiln. However, a stationary furnace or a belt conveyor type furnace is more suitable for producing the dehydrogenation catalyst 1 according to the present embodiment than a rotary furnace. A rotary furnace is generally used in the process of firing the carrier. In a rotary furnace, the carrier is fired while the carrier in the furnace is stirred by the rotation of the furnace. The rotation of the furnace causes friction between the surface of the carrier and the inner wall of the furnace. As a result, the surface of the carrier is scraped. Therefore, the supported Pt or Pt compound is detached from the surface of the carrier, and it is difficult to adjust the half width W of the peak. On the other hand, when a fixed type furnace or a belt conveyor type furnace is used, Pt is not easily detached from the carrier, and C / W can be easily adjusted to a desired range.

  The firing temperature may be a temperature at which decomposition of the Pt compound proceeds, and may be, for example, about 200 to 500 ° C. The temperature increase rate in baking may be 1-10 degree-C / min, for example. As the rate of temperature increase is higher, W tends to be smaller. W tends to increase as the heating rate decreases.

  Even when Pt is supported on the carrier by a method other than the immersion method (chemical adsorption method), the C / W can be adjusted to a desired range by bringing the Pt solution into uniform contact with the surface of the carrier. Is possible. For example, in the impregnation method, the carrier is put into a cylindrical container, and the carrier is impregnated with the Pt solution while rotating the container. Thereby, it becomes easy to carry Pt uniformly on the surface of the carrier.

C / W can be adjusted to the range of 1.4 × 10 ^{−4 to} 3.1 × 10 ⁻⁴ by loading Pt on the carrier by the above loading method.

  In the present embodiment, the second step may be repeated. That is, a cycle consisting of loading the Pt solution on the carrier and drying the carrier may be repeated. After repeating the cycle, the carrier may be fired once. For example, Pt may be supported on the support by the impregnation method, and then Pt may be supported again on the support by the impregnation method. This method is called a double impregnation method. By carrying Pt on the carrier a plurality of times, the dehydrogenation activity tends to be improved as compared with the case where the same amount of Pt is carried on the carrier all at once. The reason for this is not clear, but when Pt is supported on the support in multiple steps, the Pt solution can be supported more uniformly and without unevenness by reducing the concentration of the Pt solution used in each support step. It is presumed to be easy.

(Hydrogen production system and hydrogen production method)
In the present embodiment, hydrogen is produced using the hydrogen production system 100 shown in FIG. The hydrogen production system 100 is, for example, a hydrogen station for supplying hydrogen gas as fuel to a fuel cell vehicle.

  A hydrogen production system 100 according to this embodiment includes at least a dehydrogenation reactor 2, a gas-liquid separator 4, a hydrogen purification device 6, and a tank 16. The manufacturing system 100 may further include a high-pressure compressor 14. The dehydrogenation reactor 2 includes the dehydrogenation catalyst 1 according to the present embodiment, and generates hydrogen and organic compounds (such as unsaturated hydrocarbons) by dehydrogenation of hydrocarbons using the dehydrogenation catalyst 1. . That is, the method for producing hydrogen according to the present embodiment includes a step (dehydrogenation step) of generating hydrogen and an organic compound by dehydrogenation of hydrocarbons using the dehydrogenation catalyst 1 according to the present embodiment.

  The hydrocarbon may be, for example, a naphthenic hydrocarbon (cyclic hydrocarbon). The naphthenic hydrocarbon (cyclic hydrocarbon) may be at least one selected from the group consisting of cyclohexane, methylcyclohexane, dimethylcyclohexane, decalin, 1-methyldecalin, 2-methyldecalin and 2-ethyldecalin, for example. . These compounds are called organic hydrides.

  In the dehydrogenation step, hydrocarbons are supplied into the dehydrogenation reactor 2. In the dehydrogenation reactor 2, the dehydrogenation catalyst 1 according to the present embodiment is installed. The inside of the dehydrogenation reactor 2 is a reducing atmosphere. When the hydrocarbon comes into contact with the dehydrogenation catalyst 1 in the dehydrogenation reactor 2, a dehydrogenation reaction occurs and at least a pair of hydrogen atoms are extracted from the hydrocarbon. For example, when a naphthenic hydrocarbon is used as the hydrocarbon, a hydrogen molecule and an organic compound (unsaturated hydrocarbon) such as an aromatic hydrocarbon are generated. Thus, the dehydrogenation reaction is a gas phase reaction. In the dehydrogenation step, hydrogen may be supplied into the dehydrogenation reactor 2 together with the hydrocarbon. This tends to maintain the dehydrogenation activity for a longer period.

The conditions for the dehydrogenation reaction are not particularly limited. The reaction temperature may be 250-420 ° C. In order to adjust the reaction temperature to the above range, the temperature of the central portion of the catalyst layer in the dehydrogenation reactor 2 may be adjusted to the above range. The liquid hourly space velocity (LHSV) may be 0.2 to 4.0 h ⁻¹ . When hydrogen is supplied into the dehydrogenation reactor 2 together with the hydrocarbon, the hydrogen partial pressure may be 0.1 to 1.0 MPa. Further, the molar number _{n H} of hydrogen supplied to the dehydrogenation reactor 2, the ratio _n H / _{n C} of the moles _{n C} of supplying hydrocarbons to the dehydrogenation reactor 2 is 0.05. It may be zero.

  The product (hydrogen molecule and organic compound) of the dehydrogenation reaction is supplied from the dehydrogenation reactor 2 into the gas-liquid separator 4. The temperature in the gas-liquid separator 4 is not lower than the melting point of the organic compound and lower than the boiling point of the organic compound. Therefore, the hydrogen molecules in the gas-liquid separator 4 are gases, and the organic compounds in the gas-liquid separator 4 are liquids. That is, in the gas-liquid separator 4, the product of the dehydrogenation reaction is separated into hydrogen gas (gas phase, gas layer) and organic compound liquid (liquid phase, liquid layer). The gas phase (hydrogen-containing gas) in the gas-liquid separator 4 is supplied to the hydrogen purifier 6. The liquid phase (organic compound liquid) in the gas-liquid separator 4 is supplied to the tank 16. Note that vapor of an organic compound may be mixed in the gas phase. The partial pressure of the organic compound in the gas phase is at most about the saturated vapor pressure of the organic compound. On the other hand, organic hydride that has not been dehydrogenated may remain in the liquid phase.

  The hydrogen-containing gas supplied from the gas-liquid separator 4 to the hydrogen purification device 6 is purified in the hydrogen purification device 6. The hydrogen purifier 6 may include, for example, a separation membrane that selectively allows only hydrogen gas among hydrogen gas and organic compounds to permeate. The separation membrane is, for example, a metal membrane (such as a PbAg-based membrane, a PdCu-based membrane, or an Nb-based membrane), an inorganic membrane (such as a silica membrane, a zeolite membrane, or a carbon membrane), or a polymer membrane (a fluororesin membrane or polyimide). A membrane). The hydrogen gas permeates through the separation membrane, thereby increasing the purity of the hydrogen gas. On the other hand, organic compounds (such as unreacted organic hydride) in the hydrogen-containing gas cannot permeate the separation membrane. Therefore, the organic compound is separated from the hydrogen-containing gas, and high-purity hydrogen gas is purified. The purified high-purity hydrogen gas may be used as fuel for the fuel cell without passing through the high-pressure compressor 14, or may be used as fuel for the fuel cell after being compressed by the high-pressure compressor 14. Note that not only an organic compound but also a trace amount of hydrogen gas may not permeate the carbon film. Hydrogen gas that has not permeated the carbon membrane may be recovered together with the organic hydride and supplied as an off-gas into the dehydrogenation reactor 2. Alternatively, the organic compound that has not permeated the carbon film may be collected into the tank 16. The hydrogen purification apparatus 6 is not limited to an apparatus provided with a separation membrane. The hydrogen purifier 6 is selected from the group consisting of, for example, a pressure swing adsorption (PSA) method, a thermal swing adsorption (TSA) method (temperature swing adsorption method), a temperature pressure swing adsorption (TPSA) method, and a cryogenic separation method. An apparatus that performs at least one method may be used. These apparatuses may be used to purify the hydrogen-containing gas, supply the off-gas generated along with the purification into the dehydrogenation reactor 2, and supply the organic compound separated from the hydrogen-containing gas to the tank 16. A part of the purified hydrogen gas may be supplied to the dehydrogenation reactor 2 together with the organic hydride. Thereby, the dehydrogenation activity of the dehydrogenation catalyst 1 in the dehydrogenation reactor 2 is easily maintained.

  Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment.

  Hereinafter, although the content of the present invention is explained in detail using an example and a comparative example, the present invention is not limited to the following examples.

Example 1
[First step]
As a carrier, a molded body made of porous γ-alumina was prepared. The shape of the molded body was a columnar shape. The diameter of the molded body was about 1/16 inch (1 inch = about 25.4 mm).

[Second step]
The carrier was placed in a cylindrical container. An aqueous solution of bis (ethanolammonium) hexahydroxoplatinic acid was prepared. This aqueous solution was dropped onto the carrier in the container while rotating the container. That is, the platinum salt in the solution was supported on the support by an impregnation method (pore filling method). Subsequently, the support was dried at 100 ° C. overnight. The dried support was calcined in air at 330 ° C. for 2 hours to decompose bis (ethanolammonium) hexahydroxoplatinum. A muffle furnace was used for firing. In the second step, the concentration of the bis (ethanolammonium) hexahydroxoplatinic acid aqueous solution was adjusted so that the supported amount C of Pt in the dehydrogenation catalyst was 3.0 × 10 ⁻³ g / mL.

The dehydrogenation catalyst of Example 1 was produced through the above steps. The dehydrogenation catalyst of Example 1 includes a carrier made of γ-alumina and Pt supported on the carrier. The supported amount C of Pt per unit volume of the dehydrogenation catalyst was 3.0 × 10 ⁻³ g / mL.

(Example 2)
[First step]
A predetermined amount of water, an aqueous solution of cerium nitrate, and dilute nitric acid were added to the aluminum hydroxide powder in a pseudo boehmite state, and these were kneaded. Furthermore, the pH of the kneaded material was adjusted to about 3 to 7 by adding dilute nitric acid. A columnar shaped body was produced by extrusion molding of the kneaded product. The cross section of the molded body was a four-leaf shape. The diameter of the molded body was 1/22 inc. The molded body was dried at 100 to 150 ° C. for 2 hours. The dried compact was fired at 550 ° C. for 2 hours to obtain the carrier of Example 2. The support includes gamma alumina and Ce ₂ O ₃ . The content of Ce in the carrier was 2% by mass with respect to the mass of the whole carrier containing Ce ₂ O ₃ in terms of Ce oxide (Ce ₂ O ₃ ).

[Second step]
An aqueous solution of bis (ethanolammonium) hexahydroxoplatinum (IV) was prepared. While the aqueous solution was vigorously stirred in the container, the carrier obtained in the first step was immersed in the aqueous solution. That is, Pt was supported on the carrier by the chemical adsorption method. In the chemical adsorption method, the Pt loading rate was adjusted to 5 to 6 mass% / min until the Pt loading on the dehydrogenation catalyst reached 80% of the desired loading. Further, when the amount of Pt supported on the dehydrogenation catalyst reached 80% of the desired amount supported, the Pt loading rate was adjusted to 0.5 to 1.5 mass% / min. The carrier was then dried at 100 ° C. overnight. The dried support was calcined in air at 330 ° C. for 2 hours to decompose bis (ethanolammonium) hexahydroxoplatinum. A muffle furnace was used for firing. In the second step, the concentration of the bis (ethanolammonium) hexahydroxoplatinic acid aqueous solution was adjusted so that the supported amount C of platinum (Pt) in the dehydrogenation catalyst was 2.9 × 10 ⁻³ g / mL.

The dehydrogenation catalyst of Example 2 was produced through the above steps. The dehydrogenation catalyst of Example 2 includes a support containing γ-alumina and Ce ₂ O ₃ (cerium oxide), and Pt supported on the support. The supported amount C of Pt in Example 2 was 2.9 × 10 ⁻³ g / mL.

(Example 3)
In the second step of Example 3, the concentration of the bis (ethanolammonium) hexahydroxoplatinic acid aqueous solution was adjusted so that the supported amount C of Pt in the dehydrogenation catalyst was 2.8 × 10 ⁻³ g / mL. Moreover, in Example 3, the temperature increase rate in the furnace at the time of baking of a support | carrier was adjusted to the value smaller than Example 1 and 2. FIG. Except for these points, the dehydrogenation catalyst of Example 3 was produced in the same manner as in Example 2. The supported amount C of Pt in Example 3 was 2.8 × 10 ⁻³ g / mL.

Example 4
In the second step of Example 4, the concentration of the bis (ethanolammonium) hexahydroxoplatinic acid aqueous solution was adjusted so that the supported amount C of Pt in the dehydrogenation catalyst was 2.8 × 10 ⁻³ g / mL. In Example 4, the chemical adsorption method was performed at a Pt loading rate (adsorption rate) different from that in Example 3. Furthermore, in Example 4, the temperature rising rate in the furnace at the time of firing the carrier was adjusted to a value smaller than those in Examples 1 and 2. Except for these points, the dehydrogenation catalyst of Example 4 was produced in the same manner as in Example 2. The supported amount C of Pt in Example 4 was 2.8 × 10 ⁻³ g / mL.

(Example 5)
[First step]
In Example 5, the same carrier as in Example 2 was used.

[Second step]
The carrier was placed in a cylindrical container. An aqueous solution of bis (ethanolammonium) hexahydroxoplatinic acid was prepared. This aqueous solution was dropped onto the carrier in the container while rotating the container. That is, the platinum salt in the solution was supported on the support by the impregnation method. Subsequently, the support was dried at 100 ° C. overnight.

  The dried carrier was placed in a cylindrical container. An aqueous solution of bis (ethanolammonium) hexahydroxoplatinic acid was prepared. This aqueous solution was dropped onto the carrier in the container while rotating the container. That is, the platinum salt in the solution was supported on the support by the impregnation method. Subsequently, the support was dried at 90 ° C. overnight. The dried carrier was calcined in air at 330 ° C. after drying for 2 hours to decompose bis (ethanolammonium) hexahydroxoplatinum. A fixed bed furnace was used for firing. In Example 5, the temperature rising rate in the furnace at the time of firing the carrier was adjusted to a value smaller than in Examples 1 and 2.

As described above, in Example 5, the second step was performed twice. The concentration of the aqueous bis (ethanolammonium) hexahydroxoplatinic acid solution used in each second step was adjusted so that the supported amount C of Pt in the dehydrogenation catalyst was 2.9 × 10 ⁻³ g / mL.

The dehydrogenation catalyst of Example 5 was produced by the above process. The dehydrogenation catalyst of Example 5 includes a support containing γ-alumina and Ce ₂ O ₃ and Pt supported on the support. The supported amount C of Pt in Example 5 was 2.9 × 10 ⁻³ g / mL.

(Example 6)
In the first step of Example 6, the carrier was formed into a cylindrical shape. The diameter of the carrier was adjusted to 1/16 inch. Except for this point, the carrier of Example 6 was obtained in the same manner as in Example 2.

In the second step of Example 6, the concentration of the bis (ethanolammonium) hexahydroxoplatinic acid aqueous solution was adjusted so that the supported amount C of Pt in the dehydrogenation catalyst was 3.4 × 10 ⁻³ g / mL. Except for this point, Pt was supported on the carrier of Example 6 in the same manner as Example 2.

The dehydrogenation catalyst of Example 6 was produced by the above process. The supported amount C of Pt in Example 6 was 3.4 × 10 ⁻³ g / mL.

(Example 7)
In Example 7, the same carrier as in Example 2 was used. In the second step of Example 7, the concentration of the bis (ethanolammonium) hexahydroxoplatinic acid aqueous solution was adjusted so that the supported amount C of Pt in the dehydrogenation catalyst was 3.1 × 10 ⁻³ g / mL. Except for these points, the dehydrogenation catalyst of Example 7 was produced in the same manner as in Example 1. The supported amount C of Pt in Example 7 was 3.1 × 10 ⁻³ g / mL.

(Example 8)
In the second step of Example 8, the concentration of the bis (ethanolammonium) hexahydroxoplatinic acid aqueous solution was adjusted so that the supported amount C of Pt in the dehydrogenation catalyst was 3.1 × 10 ⁻³ g / mL. Moreover, in Example 8, the temperature rising rate in the furnace at the time of baking of a support | carrier was adjusted to the same value as Example 1. That is, in Example 8, the temperature rising rate in the furnace at the time of firing the carrier was adjusted to a value larger than that in Example 5. Except for this point, the dehydrogenation catalyst of Example 8 was produced in the same manner as in Example 5. The supported amount C of Pt in Example 8 was 3.1 × 10 ⁻³ g / mL.

(Comparative Example 1)
In the second step of Comparative Example 1, the concentration of the bis (ethanolammonium) hexahydroxoplatinic acid aqueous solution was adjusted so that the supported amount C of Pt in the dehydrogenation catalyst was 6.0 × 10 ⁻⁴ g / mL. Except for this point, the dehydrogenation catalyst of Comparative Example 1 was produced in the same manner as in Example 8. The supported amount C of Pt in Comparative Example 1 was 6.0 × 10 ⁻⁴ g / mL.

(Comparative Example 2)
In the second step of Comparative Example 2, the concentration of the bis (ethanolammonium) hexahydroxoplatinic acid aqueous solution was adjusted so that the supported amount C of Pt in the dehydrogenation catalyst was 1.7 × 10 ⁻³ g / mL. Except for this point, a dehydrogenation catalyst of Comparative Example 2 was obtained in the same manner as in Example 8. The supported amount C of Pt per unit volume of the dehydrogenation catalyst was 6.0 × 10 ⁻⁴ g / mL.

[Spectrum measurement]
The dehydrogenation catalyst of Example 3 was cut in a direction perpendicular to the surface of the dehydrogenation catalyst to expose a four-leaf shaped cross section. The cross section of the dehydrogenation catalyst was observed using EPMA. As the EPMA, JXA-8800R manufactured by JEOL Ltd. was used. FIG. 4 shows secondary electron images and backscattered electron images of a cross section of the photographed dehydrogenation catalyst. (A) in FIG. 4 is a secondary electron image of a cross section of the dehydrogenation catalyst of Example 3. (B) in FIG. 4 is an enlarged view of a region indicated by I in (a) in FIG. (C) in FIG. 4 is a reflected electron image of a cross section of the dehydrogenation catalyst. (D) in FIG. 4 is an enlarged view of a region indicated by II in (c) in FIG.

  The characteristic X-ray spectrum of Pt was measured on the cross section of the dehydrogenation catalyst. The EPMA was used for the spectrum measurement. The spectrum was measured according to the following procedure.

  First, arbitrary five places were selected from the area | region of the surface side of a dehydrogenation catalyst among the cross sections of a dehydrogenation catalyst. The selected five images are shown in (a), (b), (c), (d) and (e) in FIG. The cross section shown in FIG. 5A was scanned with an electron beam along a straight line located between the straight line b and the straight line c and parallel to the straight line b and the straight line c. By performing 40 scans along 40 straight lines parallel to the straight lines b and c, 40 spectra were obtained. Between the straight line b and the straight line c, the width | variety of the area | region scanned with the electron beam was 20 micrometers. The acceleration voltage of the electron beam was 25 kV. The irradiation current of the electron beam was 137 nA. The step size of the electron beam was 20 msec / step. The electron beam irradiation time was 0.5 μm / step. The width (spot diameter) of the irradiated electron beam was 0.5 μm. Pt characteristic X-ray spectra along the scanning direction were obtained by averaging the intensities of the 40 spectra. The obtained spectrum is shown in (f) of FIG.

  In the same way, the spectrum of the characteristic X-ray of Pt was measured on the cross sections shown in (b), (c), (d) and (e) in FIG. The spectrum measured in the cross section shown in (b) of FIG. 5 is shown in (g) of FIG. The spectrum measured in the cross section shown in (c) of FIG. 5 is shown in (h) of FIG. The spectrum measured in the cross section shown in (d) of FIG. 5 is shown in (i) of FIG. The spectrum measured in the cross section shown in (e) of FIG. 5 is shown in (j) of FIG.

[Spectrum analysis]
The characteristic X-ray spectrum of the obtained Pt was analyzed by the following procedure.

  The spectrum shown in (a) in FIG. 6 corresponds to the spectrum shown in (g) in FIG. However, the origin 0 of the horizontal axis shown in (a) in FIG. 6 does not necessarily match the origin 0 of the horizontal axis shown in (g) in FIG. First, a region indicated by A ′ in FIG. 6A is regarded as a baseline. A standard deviation σ of the intensity I of characteristic X-rays at the baseline was calculated. Next, the spectrum was corrected by subtracting 3σ from the intensity I of the characteristic X-ray of the spectrum. As a result, a corrected spectrum shown in FIG. 6B was obtained. The half width of the peak was obtained from the corrected spectrum.

  The spectrum shown in (f), (h), (i) and (j) in FIG. 5 was also analyzed by the same procedure as above. That is, five half widths were obtained from five spectra. Of the five half-value widths, an average value of three half-value widths excluding the maximum value and the minimum value was calculated. This average value was defined as the half width W of Example 3. The full width at half maximum of Example 3 was 17 μm.

The ratio C / W (g / mL · μm) of the loading amount C (g / mL) to the half width W (μm) was calculated. The ratio C / W of Example 3 was 1.6 × 10 ⁻⁴ (g / mL · μm).

  By analyzing the dehydrogenation catalysts of other Examples and Comparative Examples in the same manner as in Example 3, spectra of characteristic X-rays of Pt of other Examples and Comparative Examples were obtained. By analyzing the spectra of other examples and comparative examples in the same manner as in example 3, the full width at half maximum W and the ratio C / W of other examples and comparative examples were determined.

The full width at half maximum of Example 1 was 21 μm. The ratio C / W of Example 1 was 1.4 × 10 ⁻⁴ g / mL · μm.

The full width at half maximum W of Example 2 was 15 μm. The ratio C / W of Example 2 was 1.9 × 10 ⁻⁴ g / mL · μm.

The full width at half maximum of Example 4 was 20 μm. The ratio C / W of Example 4 was 1.4 × 10 ⁻⁴ g / mL · μm.

The full width at half maximum of Example 5 was 18 μm. The ratio C / W of Example 5 was 1.6 × 10 ⁻⁴ g / mL · μm.

The full width at half maximum of Example 6 was 12 μm. The ratio C / W of Example 6 was 2.8 × 10 ⁻⁴ g / mL · μm.

The half width W of Example 7 was 10 μm. The ratio C / W of Example 7 was 3.1 × 10 ⁻⁴ g / mL · μm.

The full width at half maximum of Example 8 was 10 μm. The ratio C / W of Example 8 was 3.1 × 10 ⁻⁴ g / mL · μm.

The full width at half maximum of Comparative Example 1 was 5 μm. The ratio C / W of Comparative Example 1 was 1.2 × 10 ⁻⁴ g / mL · μm.

The half width W of Comparative Example 2 was 4 μm. The ratio C / W of Comparative Example 2 was 4.3 × 10 ⁻⁴ g / mL · μm.

[Evaluation of dehydrogenation activity]
The dehydrogenation activity of the dehydrogenation catalysts of Examples 1 to 8 and Comparative Examples 1 and 2 was evaluated by the following method.

First, 0.5 mL of a dehydrogenation catalyst was charged into a fixed bed flow type reactor. Next, the temperature at the outlet of the catalyst layer was maintained at 300 ° C. while supplying a mixed gas of methylcyclohexane (hereinafter sometimes referred to as “MCH”) and hydrogen into the reactor. Thereby, the dehydrogenation reaction of MCH was continued in the reactor. In the mixed gas, the number of moles _{n H} hydrogen, the ratio _n H / _{n M} of the moles _{n M} of MCH was 0.7. The reaction pressure was 0.19 MPaG. The liquid space velocity (LHSV) of MCH fed into the reactor was maintained at 80 h- ¹ . When a predetermined time has elapsed from the start of the reaction, the gas discharged from the reactor was recovered and cooled to obtain a product oil.

The product oil was analyzed with a gas chromatograph-flame ionization detector (GC-FID). The conversion ratio rc of MCH at 300 ° C. was calculated from the ratio between the GC area (peak area) of MCH contained in the product oil and the GC area of toluene contained in the liquid. rc is defined by the following formula (2).
rc (unit:%) = (m ₂ / m ₁ ) × 100 = {m ₂ / (m ₂ + m ₃ )} × 100 (2)
In formula (2), m ₁ is the number of moles of methylcyclohexane supplied to the reaction vessel in which the dehydrogenation catalyst is arranged. m ₂ is the number of moles of toluene contained in the product of the dehydrogenation reaction. In other words, m ₂ is the number of moles of toluene produced by dehydrogenation of methylcyclohexane. m ₃ is the number of moles of methylcyclohexane (methylcyclohexane not dehydrogenated) remaining after the dehydrogenation reaction.

A high conversion rc means an excellent dehydrogenation activity. The conversion rc of each of the examples and comparative examples is shown in Table 1 below. FIG. 7 shows the relationship between C / W and conversion rate rc for each of the examples and comparative examples. FIG. 8 shows the relationship between the full width at half maximum W and the conversion rate rc in each of the examples and comparative examples. “E-0n” (n is a natural number) described in Table 1 and FIG. 7 means “× 10 ⁻ⁿ ”.

  Hydrogen gas produced by dehydrogenation of hydrocarbons using the dehydrogenation catalyst according to the present invention is used as fuel for fuel cell vehicles, for example.

  DESCRIPTION OF SYMBOLS 1 ... Dehydrogenation catalyst, S ... Surface, CS ... Cross section, a ... Straight line, 2 ... Dehydrogenation reactor, 4 ... Gas-liquid separator, 6 ... Hydrogen purification apparatus, 14 ... High-pressure compressor, 16 ... Tank, 100 ... Hydrogen Manufacturing system.

Claims (6)

A dehydrogenation catalyst for hydrocarbons,
A support containing Al ₂ O ₃ and Pt supported on the support,
When the spectrum of the characteristic X-ray of Pt along a straight line located on the cross section of the dehydrogenation catalyst and perpendicular to the surface of the dehydrogenation catalyst is measured using an electron beam microanalyzer,
The spectrum has a peak on the surface side of the dehydrogenation catalyst;
The peak half-value width is W μm,
When the supported amount of Pt per unit volume of the dehydrogenation catalyst is Cg / mL,
C / W is 1.3 × 10 ^{−4 to} 3.5 × 10 ⁻⁴ g / mL · μm,
Dehydrogenation catalyst for hydrocarbons. W is 12 to 20 μm,
The dehydrogenation catalyst according to claim 1. The Pt is supported on the carrier by a method of immersing the carrier in a solution containing the Pt.
The dehydrogenation catalyst according to claim 1 or 2. It has a dehydrogenation catalyst according to any one of claims 1 to 3, and comprises a dehydrogenation reactor that generates hydrogen by dehydrogenation of the hydrocarbon using the dehydrogenation catalyst.
Hydrogen production system. Comprising a step of generating hydrogen by dehydrogenation of a hydrocarbon using the dehydrogenation catalyst according to any one of claims 1 to 3.
A method for producing hydrogen. The hydrocarbon is a naphthenic hydrocarbon,
The method for producing hydrogen according to claim 5.