JPWO2016136678A1 - Base material for fuel reforming catalyst and fuel reforming catalyst using the same - Google Patents

Abstract

New fuel reforming that ensures sufficient contact frequency and contact time between gas and catalytically active components, is easy to handle, has high temperature rise characteristics, and does not pulverize catalyst pellets. A catalyst base material is proposed. A fuel reforming catalyst base material for supporting an active component of a fuel reforming catalyst, having a gas inflow surface, a gas outflow surface, and a peripheral side surface, and non-extending from the gas inflow surface to the gas outflow surface The present invention proposes a base material for a fuel reforming catalyst having a large number of pores that are linearly branched and communicated, and the porosity of the pores is 66 to 99%. is there.

Description

  The present invention relates to a fuel reforming catalyst capable of promoting a steam reforming reaction for reforming a hydrocarbon-containing fuel gas to obtain hydrogen, and in particular, a fuel reforming catalyst base for supporting a catalytically active component. Regarding materials.

  A fuel cell is a cell that converts chemical energy into electrical energy by electrochemically reacting hydrogen and oxygen, and as a hydrogen source, hydrogen obtained by reforming city gas or the like is used. Yes. City gas is a gaseous fuel mainly composed of natural gas, and typically contains 87 vol% or more of methane.

In such a steam reforming reaction that reforms city gas to obtain hydrogen, steam is added to hydrocarbon (C _n H _m ), which is the main component of city gas, and the fuel reforming catalyst is used to A reaction for generating hydrogen (H ₂ ) through a chemical reaction as represented by formula (1) proceeds as a main reaction. In addition, since carbon monoxide (CO) obtained by the reaction of the formula (1) is bonded to a large amount of water vapor, a reaction for generating hydrogen further proceeds by the water gas shift reaction (see the formula (2)). .

_{(1) ··· C n H m} + nH 2 O → nCO + (m / 2 + n) H 2
(2) ... CO + H ₂ O → CO ₂ + H ₂

  As a reforming catalyst used for such a steam reforming reaction, for example, a hydrocarbon steam formed by supporting zirconium oxide and ruthenium component with zirconia sol as a precursor on aluminum oxide containing alkaline earth metal aluminate. A reforming catalyst is disclosed (Patent Document 1).

  In Patent Document 2, at least one active ingredient selected from the group consisting of ruthenium and rhodium is at least one second selected from the group consisting of a first oxide of cerium oxide and aluminum oxide and zirconium oxide. There is disclosed a fuel reforming catalyst supported on a support containing the above oxide.

  Patent Document 3 discloses a steam reforming catalyst in which an alumina carrier contains a noble metal component containing at least one of ruthenium, rhodium and platinum and a rare earth metal.

  Patent Document 4 discloses a carrier containing a composite oxide in which ceria and alumina are both dispersed on a nanoscale, and at least one kind belonging to Groups 8 to 10 of the long-period periodic table carried on the carrier. A steam reforming catalyst containing a metal element is disclosed.

Patent Document 5 discloses a fuel reforming catalyst in which a fuel reforming catalyst is supported on a honeycomb monolith support, and the fuel reforming catalyst includes all or part of exhaust gas and reformed gas containing hydrogen from the fuel. Is a fuel reforming catalyst that produces zirconium oxide (ZrO ₂ ), lanthanum oxide (La ₂ O ₃ ), cerium oxide (CeO ₂ ), aluminum oxide (Al ₂ O ₃ ), and magnesium oxide (MgO). At least one metal oxide selected from the group, at least one metal component selected from the group consisting of platinum (Pt), rhodium (Rh), palladium (Pd) and nickel (Ni), and silicon oxide containing (SiO _2), the silicon oxide, the surface of the catalyst containing the metal oxide and the metal component, the average primary particle size is dispersed as particles with 4nm~20nm Fuel reforming catalyst, wherein Rukoto is disclosed.

  Patent Document 6 discloses a fuel reforming catalyst used in a fuel reforming system that generates a reformed gas containing hydrogen by reacting a gas containing water vapor and carbon dioxide with a fuel, and has barium on the surface of alumina particles. A compound of at least one element selected from the group consisting of strontium and calcium is formed, and at least one type selected from the group consisting of rhodium, platinum, iridium, palladium, ruthenium and nickel is formed on the surface of the compound. There is disclosed a fuel reforming catalyst in which a catalyst component is supported.

  Patent Document 7 relates to a ceramic porous body having macroporous communication holes. A slurry in which ceramic powder is dispersed in an aqueous solution of a water-soluble polymer that can be gelled is gelled, frozen, thawed, dried, and sintered. A method for producing a ceramic porous body using a ceramic powder of 0.01 μm to 5 μm, and a structure of ice crystals developed by freezing water released from a polymer in gelation and freezing of a slurry A frozen body having a structure is formed and held without being destroyed in the thawing, drying, and sintering processes, and has macroporous communication holes of 10 μm to 300 μm, and the porosity is 72% to 99%. A method for producing a ceramic porous body characterized by producing the ceramic porous body is disclosed.

Japanese Patent Laid-Open No. 5-220397 JP 2006-247451 A JP 2009-254929 A JP 2010-207782 A JP 2013-144266 A JP 2014-30778 A JP 2008-201636 A

  When a fuel gas containing hydrocarbons is reformed using a fuel reforming catalyst, the reaction proceeds instantaneously when the exhaust gas and catalytically active components come into contact with each other, like a catalyst for automobile exhaust gas. Since it is not a reaction, it has a feature that the catalytic reaction does not proceed unless the gas and the fuel reforming catalyst are in contact with each other for a sufficient time as compared with a catalyst for automobile exhaust gas. Therefore, in a fuel reformer using a fuel reforming catalyst, it is necessary to sufficiently ensure the number of contact times and the contact time between the gas and the catalytically active component.

Therefore, conventionally, a fuel reformer in which a pellet-like fuel reforming catalyst is filled in a gas reaction tube has been used in order to ensure a sufficient number of times and a contact time between the gas and the catalytically active component.
However, since such a fuel reformer has to be filled with a large number of catalyst pellets in the reaction tube, it is not only inconvenient in handling (handling property) but also has a high temperature rise due to few contacts between the catalysts. In addition, the catalyst pellets rub against each other and pulverize. In addition, there is a problem that it is difficult to reduce the size because the carrying amount is limited.

  In the present invention, the fuel reforming catalyst substrate for supporting the catalytically active component is convenient in handling (handling property), has a high temperature rise property, and pulverizes the catalyst pellets. No new fuel reforming catalyst substrate is proposed, which can be miniaturized and yet can sufficiently secure the contact frequency and contact time between the gas and the catalytically active component. It is what.

  The present invention has a gas inflow surface, a gas outflow surface and a peripheral side surface, and has a large number of non-linearly branched and communicating from the gas inflow surface to the gas outflow surface, and The present invention proposes a base material for a fuel reforming catalyst characterized in that the porosity of the pores is 66 to 99%.

The fuel reforming catalyst base material proposed by the present invention can constitute a fuel reforming catalyst by supporting the active component of the fuel reforming catalyst on the base material. Compared to the reformer packed in the reaction tube, the temperature rise is excellent, the handling property (handling property) is convenient, the catalyst pellets do not rub against each other, and it is compact. It is also possible to advance the process.
In addition, it has a large number of non-linear, branched and communicating pores extending from the gas inflow surface to the gas outflow surface, and the porosity of the fine pores is 66 to 99%, thereby allowing gas diffusion. Since the path is complicated, the back pressure can be sufficiently increased, and the number of contact times and contact time between the gas and the catalytically active component can be sufficiently ensured, so that the steam reforming performance can be enhanced.

It is the block diagram which showed the outline of the fuel reforming evaluation apparatus used in the gas reforming evaluation test of an Example. It is the image photograph obtained by scanning the cross section parallel to a length direction with the X-ray CT scanner about the fuel reforming catalyst D produced in the Example. Similarly, the fuel reforming catalyst D produced in the example is an image photograph obtained by scanning a cross section perpendicular to the length direction with an X-ray CT scanner at a predetermined distance from the gas inflow surface. It is the image photograph scanned in the position (position 1 of FIG. 2) 1 mm away in the length direction of the base material. Similarly, it is an image photograph scanned with an X-ray CT scanner at a position (position 2 in FIG. 2) separated from the gas inflow surface by 7.5 mm in the length direction of the base material. It is the image photograph similarly scanned with the X-ray CT scanner in the position (position 3 of FIG. 2) 15 mm away from the gas inflow surface in the length direction of the base material. Similarly, it is an image photograph scanned with an X-ray CT scanner at a position 22.5 mm away from the gas inflow surface in the length direction of the substrate (position 4 in FIG. 2). Similarly, it is an image photograph scanned with an X-ray CT scanner at a position 29 mm away from the gas inflow surface in the length direction of the substrate (position 5 in FIG. 2).

  Next, the present invention will be described based on an embodiment. However, the present invention is not limited to the embodiment described below.

<Fuel reforming catalyst>
A fuel reforming catalyst (referred to as “the present fuel reforming catalyst”) according to an example of an embodiment of the present invention has a configuration in which a catalytically active composition is supported on a base material (referred to as “the present base material”). It is a thing.
This fuel reforming catalyst can be used as a catalyst in various apparatuses related to the steam reforming reaction. For example, it can be used in hydrogen plants such as refineries, hydrogen production apparatuses for fuel cells in stationary distributed power sources, and other apparatuses.

<Base material>
The base material of the fuel reforming catalyst, that is, the base material, has a gas inflow surface, a gas outflow surface, and a peripheral side surface, and extends from the gas inflow surface to the gas outflow surface in a nonlinear and branched manner. The base material is characterized by having a large number of pores and a porosity of 66 to 99%.
However, it is not necessary that all the pores of the base material are pores that are non-linearly connected in a branched manner. Some of the pores may be non-communication pores that are linear, not branched, or blocked inside the substrate.

  The substrate may have any form as long as it has a gas inflow surface, a gas outflow surface, and a peripheral side surface. For example, arbitrary forms, such as columnar shape, prismatic shape, and plate shape, may be sufficient.

  The base material has a large number of pores that are non-linearly connected in a branched manner, and part or all of the base material communicates from the gas inflow surface to the gas outflow surface. It is preferable to have the characteristic which exhibits.

  The porosity of the base material, that is, the porosity due to the pores, is preferably 66% or more from the viewpoint of further increasing the contact area and the number of times of contact with the gas flowing through the base material, and in particular, 75%. More preferably, it is more preferably 85% or more. On the other hand, if the porosity is too high, the contact area and the number of times of contact tend to decrease conversely, so 99% or less is preferable.

In this base material, the average median pore diameter of the whole base material in the logarithmic differential pore size distribution measured by a mercury intrusion porosimeter increases the contact area and the number of times of contact, and evenly mixes gas and moisture to increase the catalytic activity. From a viewpoint of making it favorable, it is preferable that it is 25 micrometers-140 micrometers.
The “average median pore diameter of the entire substrate” means an average value of values obtained by measuring the 50% diameter at a plurality of locations, for example, 15 locations spaced at appropriate intervals in the length direction of the substrate. Here, the 50% diameter is defined as a value obtained when the cumulative pore volume is 50% in the logarithmic differential pore diameter distribution (vertical axis: cumulative pore volume, horizontal axis: pore diameter) measured by a mercury intrusion porosimeter. It means the pore diameter (the same applies to the 50% diameter described later).

In particular, a fuel cell used in a high SV region in which a space velocity (referred to as “SV” or “SV value”) obtained by dividing the flow rate of the fuel gas by the catalyst volume is 5000 or more, for example, a fuel used for a high temperature fuel cell. Regarding the base material for the reforming catalyst, the average median pore diameter (50% diameter) of the base material is 55 μm or more or 140 μm or less, particularly from the viewpoint of improving the catalytic activity by uniformly mixing gas and moisture. It is more preferable that
On the other hand, for a fuel cell used in a low SV region where the SV value is less than 5000, for example, a fuel reforming catalyst substrate used in a low temperature fuel cell, the average median pore diameter (50% diameter) of this substrate is In particular, from the viewpoint of further increasing the contact area and the number of contacts, it is more preferably 25 μm to 60 μm.

  In this substrate, the average median pore diameter (50% diameter) in the logarithmic differential pore diameter distribution measured by a mercury intrusion porosimeter is more preferably 25 μm to 140 μm in both the gas inflow portion and the gas outflow portion. .

Moreover, in this base material, it is preferable that the average median pore diameter in a gas outflow part is smaller than the average median pore diameter in a gas inflow part from a viewpoint of raising back pressure.
More specifically, the difference between the average median pore diameter in the gas inflow part and the average median pore diameter in the gas outflow part is preferably 0.5 μm or more.

In particular, regarding a fuel cell used in a high SV region having an SV value of 5000 or more, for example, a fuel reforming catalyst base material used in a high-temperature fuel cell, the gas and moisture are reacted uniformly to provide good catalytic activity. In view of the above, the difference between the average median pore diameter in the gas inflow portion and the average median pore diameter in the gas outflow portion is preferably 20 μm to 110 μm, and more preferably 50 μm or more.
On the other hand, with respect to a fuel cell used in a low SV region having an SV value of less than 5000, for example, a fuel reforming catalyst substrate used in a low-temperature fuel cell, from the viewpoint of further increasing the contact area and the number of contacts, the gas inflow portion The difference between the average median pore diameter in and the average median pore diameter in the gas outflow portion is preferably 0.5 μm to 85 μm, and more preferably 40 μm or less.

In the present invention, the “gas inflow portion” refers to a portion having a length from the inflow surface of the base material to 33% of the total length of the base material in the length direction of the base material. The part of the length of the base material from the outflow surface of the base material to 33% of the total length of the base material.
The “average median pore diameter in the gas inflow portion” means an average value of values obtained by measuring 50% diameters at a plurality of locations, for example, 5 locations, at appropriate intervals in the length direction in the gas inflow portion of the base material. is there.
The “average median pore diameter in the gas outflow portion” means an average value of values obtained by measuring 50% diameters at a plurality of locations, for example, 5 locations, at appropriate intervals in the length direction in the gas outflow portion of the base material. is there.

The mercury intrusion porosimeter uses the large surface tension of mercury to apply pressure to the measurement object to infiltrate mercury, and calculate the pore size and logarithmic differential pore size distribution from the pressure at that time and the amount of mercury injected. It is a device to measure. Therefore, the target pores are only open pores (pores communicating with the outside), and closed pores (independent pores) are not included in the target.
The “pore diameter” means the diameter of the bottom surface when the pore is approximated to a cylinder, and is calculated by the following equation.
dr = -4σcos θ / p (σ: surface tension, θ: contact angle, p: pressure)
In this equation, the surface tension of mercury is known, and the contact angle indicates a unique value for each apparatus. Therefore, the pore diameter can be calculated from the pressure of the injected mercury. Further, the median pore diameter can be calculated from the calculation result.

Since the base material has pores as described above, it is preferable that the back pressure is 8 kPa or more from the viewpoint of sufficiently ensuring the number of times of contact between the gas and the catalytically active component and the contact time. Among them, it is preferably 10 kPa or more, and particularly preferably 12 kPa or more. At this time, the upper limit of the back pressure is not particularly limited. The upper limit of the back pressure is typically about 40 kPa, particularly about 20 kPa.
The back pressure is an indicator of the difficulty of flow when the gas flowing in from the gas inflow surface flows out from the gas outflow surface, that is, an index of resistance, and thus indicates the complexity of the shape of the pores. Such back pressure can be adjusted to a desired value by designing the porosity of the base material, the median pore diameter, the difference in pore diameter between the inflow portion and the outflow portion, the seal area on the peripheral side surface, the composition of the seal material, and the like. .

  As a result of having such pores as described above, the present substrate can have a compressive strength (MPa) in the length direction of the substrate of 30 or less, particularly 20 or less, and more preferably 3 or less. At this time, the lower limit value of the compressive strength (MPa) is not particularly limited. The lower limit of the compressive strength (MPa) is typically about 0.3.

The base material having the pores as described above can be produced by, for example, a gelation freezing method. However, it is not limited to the gelation freezing method.
The gelation freezing method is a method for producing a porous body through gelation and freezing of a slurry. For example, a gel is produced from a small amount of ceramic powder, a large amount of moisture, and a polymer resin capable of retaining this moisture. When frozen, ice serving as a pore source is formed in the gel, and when this is dried, the ice is removed and fired, a high porosity ceramic porous body having fine pores can be produced.

  The base material preferably has a structure in which a part or all of the peripheral side surface is sealed, that is, covered. Among them, an area of 50% or more of the peripheral side surface, of which 80% or more of the area, of which 90% or more of the area, among them, a structure in which all of them are sealed, that is, coated to prevent gas leakage is provided. Is preferred.

  At this time, the sealing method is arbitrary as long as the gas flowing in from the gas inflow surface flows out from the gas outflow surface without leaking out from the peripheral side surface. For example, a sealing material made of an organic or inorganic binder or the like can be applied to the peripheral side surface for sealing, or the peripheral side surface can be covered with a sheet and sealed, or other sealing methods can be employed.

Such a sealing material or sheet is preferably aligned with the thermal expansion coefficient of the base material from the viewpoint of peelability. Specifically, it is preferable to use a material whose difference from the coefficient of thermal expansion of the substrate is 2 × 10 ⁻⁶ (/ K) or less.
The sealing material is preferably an inorganic binder, particularly an inorganic binder containing an inorganic material of the same material as the base material, from the viewpoint of improving the peel strength.

The material of this base material is arbitrary. For example, refractory materials such as ceramics and metal materials can be used.
Ceramic substrates include refractory ceramic materials such as cordierite, alumina, zirconia, cordierite-alpha alumina, silicon nitride, zircon mullite, alumina-silica magnesia, zircon silicate, sillimanite, magnesium silicate, Examples of the main material include zircon, petalite, alpha alumina, and aluminosilicates.
Examples of the metal substrate include refractory metals such as stainless steel or other suitable corrosion-resistant alloys based on iron.

<Fuel reforming catalyst composition>
The catalytically active composition in the present fuel reforming catalyst (referred to as “the present fuel reforming catalyst composition”) only needs to contain catalytically active species, and if necessary, an inorganic porous carrier, a promoter component, and the like. May be included.

(Catalytically active species)
The catalytically active species is preferably a noble metal belonging to the platinum group. Examples include ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), platinum (Pt), nickel (Ni), and one or more of these. Is preferably included as a catalytically active species.
In the present fuel reforming catalyst, the use of the above-mentioned base material increases the geometric surface area, increasing the number of contact times and the contact area between the gas and the catalytically active component. Can be significantly reduced.
Such catalytically active species are preferably contained in the fuel reforming catalyst composition in an amount of 1 to 100 g / L in view of the catalytic activity.

(Inorganic porous carrier)
The fuel reforming catalyst composition may contain an inorganic porous carrier.
Examples of the inorganic porous carrier include those made of alumina, silica, silica alumina, cordierite, stainless steel, or the like.
Such an inorganic porous carrier is preferably contained in the fuel reforming catalyst composition in an amount of 10 to 200 g / L.

(Cocatalyst)
The fuel reforming catalyst composition may contain CeO ₂ , ZrO ₂ or the like as a co-catalyst.
The cocatalyst is preferably contained in the fuel reforming catalyst composition in an amount of 1 to 50 g / L.

(Other ingredients)
In addition, the fuel reforming catalyst composition may contain, for example, Fe ₂ O ₃ , SiO ₂ , Na ₂ O, La ₂ O ₃ , BaCO _3, etc., which are known for improving the heat resistance of the carrier. it can.

<Manufacturing method>
The fuel reforming catalyst can be manufactured as follows.
For example, the fuel reforming catalyst composition is mixed and agitated with a binder and water to form a slurry, and the resulting slurry is applied to the base material and fired to form a catalyst layer on the surface of the base material. A method can be mentioned.
In addition, after preparing the base material, the base material is immersed in a solution containing the fuel reforming catalyst composition, the catalytically active component is supported on the base material, and this is fired to form the base material surface. A method of forming a catalyst layer can also be mentioned.
Alternatively, a fuel reforming catalyst in which the base material and the catalyst layer are integrated can be obtained by kneading the fuel reforming catalyst composition at the time of manufacturing the base material.
However, any known method can be adopted as a method for producing the fuel reforming catalyst, and the method is not limited to the above example.

  In any of the production methods, the catalyst layer may be a single layer or a multilayer of two or more layers.

It is also possible to adjust the porosity and back pressure of the fuel reforming catalyst by adjusting the amount of the fuel reforming catalyst composition supported on the substrate.
At this time, the porosity of the fuel reforming catalyst, that is, the fuel reforming catalyst composition supported on the base material, is 66 to 99% as in the case of the base material. It is preferable from the viewpoint of improving the quality performance.

<Explanation of words>
In the present specification, when expressed as “X to Y” (X and Y are arbitrary numbers), unless otherwise specified, “X is preferably greater than X” or “preferably Y”. It also includes the meaning of “smaller”.
In addition, when expressed as “X or more” (X is an arbitrary number) or “Y or less” (Y is an arbitrary number), it is “preferably greater than X” or “preferably less than Y”. Includes intentions.

  Hereinafter, the present invention will be described in more detail based on examples.

[Method for measuring physical properties]
Various physical property values of the base materials and catalysts obtained in the following examples were measured as follows.

<Measurement of porosity>
The porosity of the substrate (sample) was measured using the Archimedes method.

<Measurement of median pore diameter>
The measurement of the logarithmic differential pore size distribution is a method of measuring the pore size distribution by changing the pressure applied to mercury and measuring the amount of mercury that has entered the pores at that time.
The conditions under which mercury can enter the pores can be expressed by PD = −4σCOSθ from the balance of force, where the pressure P, the pore diameter D, and the contact angle and surface tension of mercury are θ and σ, respectively. At this time, if the contact angle and the surface tension are constants, the pressure P and the pore diameter D through which mercury can enter at that time are inversely proportional. For this reason, the pressure P and the amount of liquid V entering at that time are measured while changing the pressure, and the horizontal axis P of the obtained PV curve is directly replaced by the pore diameter from this equation, and the pore diameter distribution and The median pore diameter was determined.

The average median pore diameter of the inflow portion and the outflow portion is obtained by dividing the base material (sample) into three equal parts along the length direction of the base material (the inflow portion, the central portion, and the outflow portion). The median pore diameter (50% diameter) is obtained from the pore distribution obtained by cutting out 5 points arbitrarily at 5 mm × 5 mm × 10 mmt for each of the portions and measuring with the following porosimeter for each of the 5 points. The average value of each part, that is, the average median pore diameter was calculated from the pore diameter (50% diameter).
The average median pore diameter in the central part was also determined in the same manner. That is, the median pore diameter (50% diameter) was determined from the pore distribution obtained by arbitrarily cutting out 5 points at 5 mm × 5 mm × 10 mmt for the central portion and measuring each of the 5 points with the following porosimeter. The average value of the central portion, that is, the average median pore diameter was calculated from the median pore diameter (50% diameter).
And the average median pore diameter of the whole base material computed and calculated | required the average value of the said average median pore diameter of the inflow part part, the center part, and the outflow part part.

  As a measuring apparatus, an automatic porosimeter “Autopore IV9520” manufactured by Shimadzu Corporation was used for measurement under the following conditions and procedures.

(Measurement condition)
Measurement environment: 25 ° C
Measurement cell: sample chamber volume 3 cm ³ , press-fit volume 0.39 cm ³
Measurement range: 0.0048 MPa to 255.106 MPa Measurement point: 131 points (dots are engraved at equal intervals when the pore diameter is taken logarithmically)
Press-fit volume: adjusted to be 25% or more and 80% or less.

(Low pressure parameter)
Exhaust pressure: 50 μmHg
Exhaust time: 5.0 min
Mercury injection pressure: 0.0034 MPa
Equilibrium time: 10 secs
(High pressure parameter)
Equilibrium time: 10 secs
(Mercury parameters)
Advancing contact angle: 130.0 degrees
Receding contact angle: 130.0 degrees
Surface tension: 485.0 mN / m (485.0 dynes / cm)
Mercury density: 13.5335 g / mL

(Measurement procedure)
(1) As described above, 5 mm × 5 mm × 10 mmt were arbitrarily cut out from the inflow portion, the center portion, and the outflow portion of the base material (sample), and measurement was performed.
(2) The measurement was performed at 46 points in the range of 0.0048 MPa to 0.2068 MPa at the low pressure part.
(3) 85 points were measured in the range of 0.2241 MPa to 255.1060 MPa at the high pressure part.
(4) The pore size distribution and the median pore size were calculated from the mercury injection pressure and the mercury injection amount.
In addition, said (2), (3), (4) was performed automatically with the software attached to the apparatus. Other conditions were in accordance with JIS R 1655: 2003.

<Measurement of back pressure>
The back pressure of the sealed alumina substrate produced in the example was measured as follows.
The base material made of seal alumina was cut into a diameter of 25.4 mmΦ × 30 mm, the N ₂ flow rate was made to flow 10 L / min, and the pressure difference between the gas inflow side and the gas outflow side was measured.

<Measurement of compressive strength>
The bending strength (MPa) in the length direction of the base material (sample) was measured according to JIS R 1601: 2008, using a bending tester (Shimadzu Corporation autograph, AG-20 kNplus).

[Preparation of base materials a to d]
Alumina powder (average particle size: 0.4 μm) and water are mixed to prepare a slurry so that the volume ratio of alumina to water is 20:80. Volume percent was added to gel the slurry. Next, the gelled slurry was put in a mold, and the mold was put in a freezer at −20 ° C. and frozen. Dry with a freeze dryer, degrease, and sinter at 1600 ° C for 3 hours using an electric furnace to produce a pre-processed sintered body (25.4 mmφ x 32 mmt). The base material a (cylindrical shape, diameter 25.4 mmφ × 30 mmt) was obtained.

On the other hand, alumina substrates b to d having the characteristics shown in Table 1 were obtained in the same manner as the production conditions for the alumina substrate a except that the ratio of the alumina powder to water was changed as follows. It was.
Alumina base material b: Volume ratio of alumina to water 15:85
Alumina substrate c: volume ratio of alumina to water 10:90
Alumina substrate d: volume ratio of alumina to water 5:95

  Each of the alumina base materials a to d has a gas inflow surface, a gas outflow surface, and a peripheral side surface, and a large number of non-linearly branched and communicating from the gas inflow surface to the gas outflow surface. It had a hole.

[Fabrication of fuel reforming catalysts (samples) A to D]
Al ₂ O ₃ powder 74.3 parts by weight, Al ₂ O ₃ sol 15 parts by weight, organic binder 0.7 part by weight, dispersant 0.5 part by weight, water 9.5 parts by weight were mixed, and Al ₂ O ₃ A paste was prepared.
Next, the Al ₂ O ₃ paste was applied to the side surfaces of the above-described alumina substrates a to d, and then dried with a dryer (100 ° C.) and baked at 1200 ° C. Furthermore, the said paste was apply | coated to the whole surface so that the said surrounding side surface might be set to 1 mm, and it sealed, and produced the sealing alumina base materials ad.
Adjust the concentration of the nitric acid Ru solution to a desired concentration, make the sealed alumina base materials ad absorb, dry at 80 ° C. overnight, and then baked at 500 ° C. in air for 3 hours. Fuel reforming catalysts (samples) A to D were prepared. At this time, the supported amount of Ru was 7.603 g / L.

(Steam reforming performance evaluation test 1)
Using the fuel reforming evaluation apparatus shown in FIG. 1, the steam reforming performance is evaluated by measuring the hydrogen concentration (H ₂ %) of the fuel reforming catalyst (sample) obtained in each of the examples and comparative examples. did.
As shown in FIG. 1, this fuel reforming evaluation apparatus comprises a gas mass flow controller 2 and a liquid mass flow controller, respectively, for city gas supplied from a cylinder as gaseous fuel 1 and pure water in a pure water tank 3. 4, the flow rate can be adjusted. The pure water passes through the vaporizer 6 in the electric furnace 5 and becomes water vapor, which is mixed with gaseous fuel in the fuel gas / water vapor mixing section 7 and sent to the reforming catalyst 9 sealed in a stainless steel container in the electric furnace 8. The gas reformed by the reforming catalyst 9 is exhausted through a bubbler 11.
A part of the exhaust gas is sucked by a pump built in a gas chromatograph (hereinafter referred to as “GC”) 13, and the reformed gas that has passed through the water removing device 12 is quantified by the GC 13. At this time, the hydrogen concentration (H ₂ %) relative to the total gas amount was measured and evaluated.

(Gas reforming evaluation test 1)
In the reformer, the fuel reforming catalysts (samples) A to D were fixed with glass tape, and the electric furnace 8 was controlled at 550 ° C. with the value measured by the thermocouple 10.
The ratio of the molar amount of water vapor to be supplied and the molar amount of the total carbon amount in the fuel gas (hereinafter referred to as “S / C ratio”) is 2.5, and 30 minutes have passed since the thermocouple 10 showed 550 ° C. The hydrogen concentration was measured and evaluated.
The flow rate was controlled so that SV was about 1000 h ⁻¹ and about 9000 h ⁻¹ .

(Discussion)
From such test results and various test results that the inventors have conducted so far, the porosity of the substrate is 66 to 99%, particularly 75% or more or 99% or less, and more preferably 85% or more or 99% or less. It can be considered preferable.
Regarding the fuel reforming catalyst (sample) A, since the porosity was as low as 64% and the back pressure was extremely high, the pressure sensor worked and the back pressure value and the hydrogen concentration could not be measured. It was.

[Production of base materials e to h]
In the production of the alumina base material a, the one having a freezing temperature of −30 ° C. and a sintered body thickness of 32 mm before processing was changed as follows, and the others were produced in the same manner as the alumina base material a. As a result, alumina base materials (samples) e to h having the characteristics shown in Table 2 were obtained.
The gelation freezing method is known to have different pore diameters in the length direction, and the pore diameter distribution can be changed by changing the thickness of the sintered body before processing. The thickness after processing was all evaluated to be 30 mmt.
-Alumina substrate e: freezing temperature -30 ° C, sintered body thickness 32 mm before processing
・ Alumina base material f: freezing temperature −35 ° C., sintered body thickness 32 mm before processing
・ Alumina substrate g: freezing temperature -20 ° C., sintered body thickness 37 mm before processing
・ Alumina substrate h: freezing temperature -20 ° C., sintered body thickness 42 mm before processing

  Each of the alumina base materials e to h has a gas inflow surface, a gas outflow surface, and a peripheral side surface, and a large number of non-linearly branched and communicating from the gas inflow surface to the gas outflow surface. It had a hole.

(Steam reforming performance evaluation test 2)
Fuel reforming catalysts (samples) E to H are prepared in the same manner as the fuel reforming catalysts (samples) A to D using the base materials e to h having different average median pore diameters of the entire base materials, and Together with the fuel reforming catalyst (sample) D, an evaluation test was performed in the same manner as the gas reforming evaluation test 1 described above.

(Discussion)
From the above examples and various test results conducted by the inventors so far, the average median pore diameter of the whole substrate is preferably 25 μm to 140 μm, and in particular, in the case of a high SV region, it may be 55 μm or more. More preferably, in the case of the low SV region, it can be considered that the thickness is preferably 60 μm or less.
Further, the difference between the average median pore diameter in the gas inflow portion and the average median pore diameter in the gas outflow portion is preferably 0.5 μm or more, and particularly in the high SV region, it is 20 μm to 110 μm. More preferably, it can be considered that 50 μm or more is even more preferable. On the other hand, in the case of a low SV region, 0.5 μm to 85 μm is more preferable, and 40 μm or less is more preferable. be able to.

  Further, a photograph of the fuel reforming catalyst (sample) D obtained by scanning a cross section parallel to the length direction (pixel resolution: 13.5 μm / pixel) using an X-ray CT scanner (SkyScan1272 / manufactured by Toyo Technica). As shown in FIG. 2, a cross section perpendicular to the length direction is scanned at five positions 1 mm, 7.5 mm, 15 mm, 22.5 mm, and 29 mm in the length direction from the gas inflow surface (pixel resolution 13. The photographs taken at 5 μm / pixel) are shown in FIGS. As can be seen from these images, it was confirmed that the median pore diameter became smaller from the gas inflow surface toward the gas outflow surface. That is, it was confirmed that the average median pore diameter in the gas outflow portion was smaller than the average median pore diameter in the gas inflow portion.

[Preparation of base materials i to k]
Using the alumina base material c obtained above, in the gas reforming evaluation test 1 in the area portions of 0%, 50%, 80% and 100% from the lower end of the peripheral side surface of the base material c, respectively. Sealed alumina substrates i to k were obtained in the same manner as the sealed alumina substrate c, except that the prepared Al ₂ O ₃ paste was applied and the peripheral side surface was sealed with a thickness of 1 mm.
Alumina substrate c: 100%
Alumina substrate i: 80%
Alumina substrate j: 50%
Alumina base material k: 0%

  Each of the alumina base materials i to k has a gas inflow surface, a gas outflow surface, and a peripheral side surface, and a large number of non-linearly branched and communicating from the gas inflow surface to the gas outflow surface. It had a hole.

(Steam reforming performance evaluation test 3)
Using the alumina base materials i to k, the fuel reforming catalysts (samples) I to K were prepared in the same manner as the fuel reforming catalysts (samples) A to D, and the above fuel reforming catalyst (sample) C and In addition, an evaluation test was conducted in the same manner as the gas reforming evaluation test 1 described above.

(Discussion)
From the above examples and the results of various tests conducted by the inventors so far, 50% or more of the peripheral side surface of the substrate, of which 80% or more, of which 90% or more, of which, all are sealed. It turned out to be preferable.

Claims (9)

  It has a gas inflow surface, a gas outflow surface, and a peripheral side surface, and has a large number of non-linearly branched pores communicating from the gas inflow surface to the gas outflow surface. A base material for a fuel reforming catalyst having a porosity of 66 to 99%.   2. The fuel reforming catalyst substrate according to claim 1, wherein an average median pore diameter of the whole substrate is 25 μm to 140 μm in a logarithmic differential pore diameter distribution measured by a mercury intrusion porosimeter.   3. The fuel reforming according to claim 1, wherein in the logarithmic differential pore size distribution measured by a mercury intrusion porosimeter, the average median pore size in the gas outflow portion is smaller than the average median pore size in the gas inflow portion. Catalyst substrate.   The base material for a fuel reforming catalyst according to claim 3, wherein the difference between the average median pore diameter in the gas inflow portion and the average median pore diameter in the gas outflow portion is 0.5 µm or more.   The base material for fuel reforming catalysts according to any one of claims 1 to 4, comprising a structure in which a part or the entire surface of the peripheral side surface of the base material is sealed.   The base material for a fuel reforming catalyst according to any one of claims 1 to 5, which is a base material produced by a gelation freezing method.   The base material for a fuel reforming catalyst according to any one of claims 1 to 6, wherein the back pressure is 8 kPa or more.   The base material for a fuel reforming catalyst according to any one of claims 1 to 7, wherein a compressive strength (MPa) in the length direction of the base material is 0.6 or more.   A fuel reforming catalyst comprising a base material for a fuel reforming catalyst according to any one of claims 1 to 8, wherein a fuel reforming catalyst active component is supported.