WO2022158473A1

WO2022158473A1 - Fuel reforming catalyst, fuel reforming method, and fuel reforming device

Info

Publication number: WO2022158473A1
Application number: PCT/JP2022/001721
Authority: WO
Inventors: 紘一郎本田; 裕基中山
Original assignee: エヌ・イーケムキャット株式会社
Priority date: 2021-01-20
Filing date: 2022-01-19
Publication date: 2022-07-28
Also published as: JPWO2022158473A1

Abstract

[Problem] To provide a fuel reforming catalyst having excellent reforming activity and excellent durability against deterioration factors such as catalyst poisoning. [Solution] This fuel reforming catalyst for reforming a hydrocarbon-containing fuel into a hydrogen-containing synthesis gas comprises: a catalyst component containing a platinum group metal element and a promoter component; and a carrier for supporting the catalyst component and the promoter component, wherein the promoter component contains at least one element selected from the group consisting of scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, barium, nickel and strontium.

Description

Fuel reforming catalyst, fuel reforming method and fuel reformer

Cross-reference to related applications

This application claims priority based on Japanese Patent Application No. 2021-7352 filed on January 20, 2021 and Japanese Patent Application No. 2021-7363 filed on January 20, 2021. , the entire disclosures of which are incorporated herein by reference.

TECHNICAL FIELD The present invention relates to a fuel reforming catalyst, and more particularly, a fuel reforming catalyst, a fuel reforming method, and a fuel reforming method for reforming a fuel containing hydrocarbons with steam to reform a synthesis gas containing hydrogen. Concerning quality equipment.

In an internal combustion engine, an exhaust gas recirculation (EGR) system is known that takes in part of the exhaust gas after combustion and reintakes it in order to reduce nitrogen oxides and improve fuel efficiency. In recent years, a fuel reforming engine system in which a heat exchange type fuel reformer and a fuel supply means (fuel injection valve) are combined with an EGR system, and a part of the fuel is passed through the fuel reformer and then burned in the cylinder. is proposed. A fuel reforming engine system has the advantage of greatly improved thermal efficiency compared to a conventional EGR system. This utilizes H ₂ O (water vapor) contained in the exhaust gas from the internal combustion engine and the heat of the exhaust gas to generate hydrogen and carbon monoxide from a portion of the fuel through a steam reforming reaction. It improves thermal efficiency by supplying it together with fuel to the internal combustion engine. The heat of the exhaust gas is used for the endothermic reaction of the steam reforming reaction.

In such a fuel reforming engine system, since the size of the fuel reformer is limited, active species used in the steam reforming reaction include rhodium (Rh), platinum (Pt), palladium (Pd), ), ruthenium (Ru), iridium (Ir), and other highly active platinum group metals are used as reforming catalysts. For example, Patent Document 1 discloses the formula: A′ _1-x A″ _x B′ _1-y B″ _y O ₃ (wherein A′ is lanthanum (La) and/or cerium (Ce), A " is at least one of lanthanum, calcium (Ca), samarium (Sm), cerium, strontium (Sr), barium (Ba), and praseodymium (Pr), and B' is cobalt (Co), iron (Fe), At least one of manganese (Mn) and gadolinium (Gd), and B″ is ruthenium (Ru) and rhodium (Rh).) is used as a fuel reforming catalyst. is proposed.

In addition, Patent Document 2 proposes a steam reforming catalyst in which Ru and Ir and/or Rh are carried on a carrier whose main component is alumina.

In addition, Patent Document 3 discloses that at least one active ingredient A selected from Pt, Pd, Ir, Rh and Ru, molybdenum (Mo), vanadium (V), tungsten (W), chromium (Cr) and rhenium (Re) , Co, Ce, and Fe, an oxide thereof, an alloy thereof, or a mixture thereof.

Further, in Patent Document 4, a composite oxide support containing alumina (Al ₂ O ₃ ), ceria (CeO ₂ ), zirconia (ZrO ₂ ), and a rare earth oxide other than ceria supports a platinum group metal. In the catalyst system, a steam reforming catalyst is proposed in which the surface composition of aluminum in the composite oxide support is 1.5 times or more the aluminum composition of the entire support.

Furthermore, Patent Document 5 proposes a steam reforming catalyst in which rhodium, which is an active metal species, is supported on a ceria-zirconia-alumina composite oxide support, and discloses that steam reforming of E20 gasoline was performed. there is

Patent Document 1: JP-A-2001-224963 Patent Document 2: JP-A-2008-55252 Patent Document 3: JP-A-2008-149313 Patent Document 4: JP-A-2016-165712 Patent Document 5: JP-A-2008-149313 2018-143988 publication

In general, materials used in durable consumer goods such as automobiles are required to be practical so that performance does not deteriorate over a long period of 10 to 15 years. The above-described fuel reforming catalyst also needs to maintain excellent performance in a high-temperature environment or in a severe environment in which catalyst-poisoning components such as fuel-derived sulfur coexist. However, although the reforming fuel catalysts described in Patent Documents 1 to 5 are useful as active species for generating hydrogen and carbon monoxide from steam and hydrocarbons, there is still room for improvement in reforming reactivity. There is In addition, from the viewpoint of practical use, the durability against catalyst poisoning components such as sulfur and catalyst deterioration factors due to deposition of carbon produced by side reactions is insufficient.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide a fuel reforming catalyst that has excellent reforming activity and excellent durability against deterioration factors such as catalyst poisoning. Another object of the present invention is to provide a fuel reforming method and a fuel reforming engine system using a fuel reforming catalyst.

As a result of extensive research to achieve the above object, the present inventors have found that instead of using a conventionally used platinum group compound such as rhodium alone as a metal active species of a reforming fuel catalyst, platinum group The present inventors have noticed that the coexistence of a compound and a co-catalyst component such as a rare earth compound as a metal active species significantly improves the reforming activity as compared with a conventional single platinum group catalyst. Surprisingly, they have found that stable reforming activity is maintained for a long period of time even in the presence of sulfur, which is a catalyst poison of platinum group catalysts. That is, the gist of the present invention is as follows.

[1] A fuel reforming catalyst for reforming a fuel containing hydrocarbons into a synthesis gas containing hydrogen,
a catalyst component and a co-catalyst component containing a platinum group metal element;
a carrier that supports the catalyst component and the co-catalyst component;
with
A fuel reforming catalyst, wherein the promoter component comprises at least one element selected from the group consisting of scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, barium, nickel, and strontium.
[2] to [1], wherein the promoter component contains at least one element selected from the group consisting of scandium, yttrium, lanthanum, praseodymium, neodymium, promethium, samarium, europium, barium, nickel, and strontium; The fuel reforming catalyst described.
[3] The fuel reforming catalyst according to [1] or [2], wherein the promoter component is supported in an amount of 50 parts by mass or more and 1000 parts by mass or less with respect to 100 parts by mass of the catalyst component. .
[4] The fuel reforming catalyst according to any one of [1] to [3], wherein the carrier is made of a porous material.
[5] The fuel reforming catalyst according to any one of [1] to [4], wherein the fuel contains 50% by mass or more of hydrocarbons having 2 to 12 carbon atoms.
[6] The fuel reforming catalyst according to any one of [1] to [5], wherein the platinum group metal element contains rhodium and platinum.
[7] The fuel reforming catalyst according to any one of [1] to [6], wherein the fuel is automotive fuel.
[8] A fuel reforming method using the fuel reforming catalyst according to any one of [1] to [7],
A method comprising contacting a fuel comprising a sulfur component and hydrocarbons with said fuel reforming catalyst in the presence of steam to produce hydrogen and carbon monoxide.
[9] Some or all of the fuel containing hydrocarbons is converted into hydrogen and carbon monoxide by the post-combustion exhaust gas from the internal combustion engine and the fuel reforming catalyst according to any one of [1] to [7]. A fuel reforming engine system comprising reforming and adding the resulting hydrogen and carbon monoxide to a fuel supplied to an internal combustion engine.

According to the present invention, it is possible to realize a fuel reforming catalyst that has high reforming activity at low temperatures (about 400°C to 600°C) and has excellent durability against deterioration factors such as catalyst poisoning. In addition, by using the fuel reforming catalyst according to the present invention, fuel can be efficiently reformed even at low temperatures (about 400° C. to 600° C.), and fuel containing sulfur components can also be efficiently reformed. becomes possible.

<Fuel reforming catalyst>
A fuel reforming catalyst according to one embodiment of the present invention is a fuel reforming catalyst for reforming a fuel containing hydrocarbons into a synthesis gas containing hydrogen, and comprises a catalyst component containing a platinum group metal element and an assistant. It comprises a catalyst component and a carrier supporting the catalyst component and the co-catalyst component. Hereinafter, in this specification, the catalyst component and the co-catalyst component supported on the carrier may be collectively referred to as "catalyst active species". A member holding a fuel reforming catalyst (that is, a catalyst comprising a catalyst component, a co-catalyst component, and a carrier supporting both components) is sometimes called a "base material".

[Catalyst component]
The catalyst component used in the fuel reforming catalyst according to the invention comprises a platinum group metal element. Examples of platinum group metal elements include ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), and platinum (Pt). From the viewpoint of activity, Ru, Rh, Pd and Pt are preferred, and Rh and Pt are more preferred. These elements may be used alone or in combination of two or more.

Examples of combining two or more platinum group elements are not particularly limited, but a combination of two or more platinum group elements with excellent oxidation activity, a combination of two or more platinum group elements with excellent reduction activity, and platinum with excellent oxidation activity. A combination of a group element and a platinum group element having excellent reduction activity can be mentioned. Among these, a combination of a platinum group element having excellent oxidation activity and a platinum group element having excellent reduction activity is preferable as one aspect of the synergistic effect. Specifically, the combination of Pd and Rh, the combination of Pt and Rh, and the combination of Ru and Rh are preferred, and among these, the combination of Pt and Rh is more preferred. By such a combination, in addition to the steam reforming reactivity, the exhaust gas purification performance, especially the light-off performance tends to be further improved.

When the catalyst component contains Rh and a platinum group metal element other than Rh, the ratio is not particularly limited, but the platinum group metal element other than Rh is usually 1 part by mass or more, preferably 5 parts by mass, per 100 parts by mass of Rh. Above, it is more preferably 10 parts by mass or more, while the upper limit is usually 500 parts by mass or less, preferably 300 parts by mass or less, more preferably 200 parts by mass or less. When the ratio is within the above range, the performance as a fuel reforming catalyst is improved, and deactivation by poisoning substances such as sulfur can be suppressed.

[Co-catalyst component]
The fuel reforming catalyst according to the present invention is characterized by containing, as catalytically active species, a promoter component selected from specific elements in addition to the catalyst component selected from the platinum group metal elements described above. In the present invention, in addition to the platinum group metal element that has been conventionally used as a catalytically active species of a fuel reforming catalyst, by coexisting a specific element described later as a metal active species (promoter component), conventional platinum Remarkably improved reforming activity compared to a single platinum group catalyst, and surprisingly, it maintains stable reforming activity for a long period of time even in the presence of sulfur, which is a catalyst poison for platinum group catalysts. be able to. Although the reason for this is not clear, it is considered as follows.

That is, by using together the catalyst component selected from the platinum group metal elements and the co-catalyst component selected from the specific elements, the co-catalyst component exerts an electronic interaction with the catalyst component, and the catalyst component (platinum group element) is likely to act. As a specific example, when the catalyst component is Rh, Rh is likely to be reduced by the co-catalyst component, and the catalytic activity is considered to be improved compared to the case where Rh alone is used as the catalyst component. In addition, although examples (Ce—Zr particles, etc.) in which the co-catalyst component has a carrier structure are also known, in the present invention, the presence of the co-catalyst component and the co-catalyst component on the surface of the carrier allows the co-catalyst component acts as acid and base sites on the carrier, and acts as a buffer for carbon deposition, which tends to progress at acid sites, and sulfur poisoning, which tends to progress at basic sites, and improves the durability of the catalyst component.
In particular, the above-mentioned specific element as a co-catalyst component exhibits the properties of both acids and bases in addition to favorable electronic interaction with the catalyst component. there is

Examples of co-catalyst components that can be used in combination with the above-described platinum group metal element catalyst components include scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), and neodymium (Nd). , Promethium (Pm), Samarium (Sm), Europium (Eu), Gadolinium (Gd), Terbium (Tb), Dysprosium (Dy), Holmium (Ho), Erbium (Er), Thulium (tm), Ytterbium (Yb) , rare earth elements such as lutetium (Lu); alkaline earth metals such as barium (Ba) and strontium (Sr); and Group 10 elements such as nickel (Ni). Selected from the group consisting of Sc, Y, La, Ce, Pr, Nd, Pm, Ba, Ni, and Sr from the viewpoint of the ability to generate hydrogen generated by and the resistance to deactivation by the sulfur content contained in the fuel. At least one element is used as a promoter component. These elements may be used alone, or two or more of them may be used in combination.

Among the above promoter component elements, Sc, Y, La, Pr, Nd, and Pm are more preferable, and Nd is particularly preferable, from the viewpoint of hydrogen generating ability and deactivation resistance due to sulfur content. Although cerium is preferable for catalytic activity, long-term durability is a problem depending on the type of fuel (especially when even a small amount of sulfur is contained).

The ratio of the catalyst component and the co-catalyst component is not particularly limited, but the co-catalyst component is usually 10 parts by mass or more, preferably 50 parts by mass or more, more preferably 100 parts by mass or more with respect to 100 parts by mass of the catalyst component. , the upper limit is usually 2000 parts by mass or less, preferably 1000 parts by mass or less. When the ratio of both is within the above range, the catalytic activity (fuel reforming ability) of the catalyst component selected from platinum group metal elements is improved, and deactivation by poisoning substances such as sulfur can be suppressed.
In addition, when a plurality of elements are included as the catalyst component and the co-catalyst component, the blending ratio means the total sum.

The amount of the above-described catalytically active species supported is not particularly limited, and may be appropriately supported according to the desired design conditions, cost requirements, etc., but it is 0.05 mass per 100 parts by mass of the support in terms of metal. It is preferably from 0.1 part to 20 parts by mass, and more preferably from 0.1 part by mass to 15 parts by mass. If the supported amount of the catalytically active species is small, there is a tendency that sufficient catalytic activity cannot be obtained in the steam reforming reaction of the fuel composed of hydrocarbons. There is a tendency that the catalytic activity per unit amount of active species does not improve. Considering both catalyst performance and cost, the amount of supported catalytically active species is more preferably 0.4 parts by mass or more and 8 parts by mass or less with respect to 100 parts by mass of the carrier.

The catalytically active species (catalyst component and co-catalyst component) supported on the carrier are preferably supported in the form of particles. In this case, the particle diameter of the catalytically active species is preferably 1 to 100 nm, more preferably 2 to 50 nm, from the viewpoint of catalytic activity. If the particle size of the catalytically active species is too small, it tends to become an oxide state that does not exhibit catalytic activity. Activity tends to decrease.

In order to make the catalytically active species have a predetermined particle size as described above, for example, a catalyst component supply source (for example, platinum group metal nitrate or acetate) and a promoter component supply source (for example , Nitrate or acetate of the above-described predetermined element), impregnating the support with a predetermined amount of the solution, and then calcining the support to support the catalyst on the support. , the particle diameter of the catalyst particles can be adjusted by controlling the concentration of the solution (concentration of catalytically active species), the impregnation amount of the solution, and the calcination conditions (temperature and time).

The fuel reforming catalyst according to the present invention has the above-described catalytically active species supported on a carrier, but may contain other components other than the catalytically active species. However, in the fuel reforming catalyst excluding the carrier, the ratio of the catalytically active species is preferably 70% by mass or more, more preferably 90% by mass or more, and particularly 95% by mass or more (100% by mass including).

[Carrier]
The carrier for supporting the catalytically active species described above is not particularly limited, and known carriers can be used, but inorganic oxides can be preferably used from the viewpoint of durability. Examples include alumina (Al ₂ O ₃ ) such as α, γ, δ, θ, zirconia (ZrO ₂ ), titania (TiO ₂ ), silica (SiO ₂ ), and ceria (CeO ₂ ). These may be used singly or in combination of two or more, or may be composite oxides thereof. Among these, alumina is preferably used from the viewpoint of durability.

The carrier used in the fuel reforming catalyst of the present invention is preferably a porous body. The porous body may have a BET specific surface area of 30 m ² /g to 600 m ² /g. In order to obtain a porous body, a carrier is produced by a conventionally known method as described later. For example, a slurry is prepared by kneading a catalytically active species component, a carrier component, a binder, a pore-forming agent, a solvent, etc., using a ball mill or the like, and after molding into a desired shape, drying and firing are carried out to obtain a pore-forming agent and a slurry. The binder is removed and pores are formed in the carrier.

When the carrier is made of a porous material, the average pore diameter is preferably 0.5 nm or more and 100 nm or less, more preferably 1 nm or more and 50 nm or less, from the viewpoint of diffusion of the fuel gas and contact with the catalyst. More preferably, the thickness is 2 nm or more and 10 nm or less. This is because if the pore diameter in the carrier is too large, the number of times of contact with the catalyst is reduced and the reaction is difficult to proceed, and if the pore diameter is too small, the fuel gas is difficult to diffuse and the reaction is similarly difficult to proceed. In the present specification, the average pore size is determined by measuring the pore size of 10 arbitrarily selected individual carriers using a nitrogen adsorption type pore distribution meter or the like, and calculating the average value of these 10 pore sizes. can be obtained by

[Base material]
Although the fuel reforming catalyst of the present invention can be used alone, it may be held on a suitable substrate. The base material is not particularly limited, and known ones can be used. For example, as a support, alumina, silica, mullite (alumina-silica), cordierite, cordierite-alpha alumina, zircon mullite, alumina-silica magnesia, zircon silicate, sillimanite, magnesium silicate, zircon, petalite ( ceramics such as platinum, aluminosilicates, aluminum titanate, silicon carbide, silicon nitride, and metal materials such as refractory metals such as stainless steel and corrosion-resistant alloys such as iron-based ferritic stainless steel. . The above inorganic or metallic materials may be used singly or in combination of two or more. Among these, alumina, silica, mullite, cordierite, stainless steel, and silicon carbide are preferred, and cordierite, stainless steel, and silicon carbide are more preferred. In this case, preferably 80% by mass or more, more preferably 90% by mass or more, and particularly preferably 99% by mass or more (including 100% by mass) of the entire substrate is made of the above material. .

Moreover, the base material may contain other components with the above-described material as a main component. For example, Fe ₂ O ₃ , SiO ₂ , Na ₂ O, etc., which are known to improve the heat resistance of the carrier, may be added to the above materials.

The shape of the substrate is not particularly limited, and various shapes such as spherical, cylindrical, bead, pellet, prismatic, tablet, needle, film, honeycomb monolith, etc. can be used depending on the application. can do. Among these, beads, pellets, and honeycomb monoliths are preferred. Therefore, it is particularly preferable that the substrate according to a preferred embodiment of the present invention is made of alumina, silica, mullite, cordierite, or stainless steel, and has a bead, pellet, or honeycomb monolith shape. I can say

When the shape of the substrate is bead or pellet, the average diameter of the substrate is preferably 0.5 mm or more and 10 mm or less, and 0.7 mm or more, from the viewpoint of handleability and fluidity in a container. It is more preferably 5 mm or less, and even more preferably 1 mm or more and 3 mm or less. Further, when the shape of the carrier is spherical, the average diameter (diameter) of the carrier is preferably 1 mm or more and 10 mm or less, and more preferably 1 mm or more and 5 mm or less, from the viewpoint of handling properties and fluidity in the container. is more preferred. The average diameter of the carrier is obtained by observing with an optical microscope or the like, measuring the major and minor diameters of 100 arbitrarily selected carriers (catalyst particles), and calculating the average of the major and minor diameters as the particle diameter. , can be obtained by calculating the average particle size of 100 individual particles.

<Method for producing fuel reforming catalyst>
The fuel reforming catalyst described above can be obtained by supporting a catalytically active species component (catalyst component and cocatalyst component) on a carrier. The supporting method is not particularly limited, and conventionally known methods can be applied. As an example, a carrier is impregnated with a mixed catalyst solution containing the nitrate or acetate of the above-described predetermined element, and then reduction or calcination is performed to precipitate catalytically active species components on the carrier in the form of particles. can be done. Alternatively, the catalyst component supply source is first impregnated into the carrier, and then the support is impregnated with the promoter component supply source, and then the two are supported by reduction or calcination. Conversely, the promoter component supply source is first impregnated. may be impregnated into the carrier, and then the catalyst component supply source may be impregnated into the carrier and then reduced or calcined to support both. After that, if necessary, a fuel reforming catalyst can be produced by performing treatments such as washing, calcination, and hydrogen reduction.

As a source of the catalytically active species component, the above platinum group metal element (catalyst component) or rare earth element or alkaline earth element (promoter component) acetate, carbonate, nitrate, ammonium salt, citrate, dinitro Diammine salts and the like or their complexes can be mentioned. For example, when the platinum group metal element is rhodium, rhodium (Rh) acetates, carbonates, nitrates, ammonium salts, citrates, dinitrodiamine salts, etc. or their of which nitrates are preferred. In addition, when the platinum group metal element is platinum, platinum (Pt) acetate, carbonate, nitrate, ammonium salt, citrate, dinitrodiamine salt, etc. or them from the viewpoint of ease of carrying and high dispersibility Among them, dinitrodiamine salts are preferred.

Further, when the fuel reforming catalyst of the present invention is used in a fuel reforming device for internal combustion engines, for example, it is preferable to use the fuel reforming catalyst in a state in which it is held in a substrate such as a honeycomb monolith. A method for manufacturing a fuel reforming honeycomb catalyst for an internal combustion engine using the fuel reforming catalyst of the present invention will be described below.

As an example, a metal salt of a catalyst component, a metal salt of a co-catalyst component, a carrier, and optionally a binder, a dispersant and a solvent are mixed to prepare a slurry solution, and the slurry solution is applied to a honeycomb monolith by a wash coating method or the like. A honeycomb catalyst holding the fuel reforming catalyst can be obtained by impregnating the substrate with the slurry solution and firing the substrate impregnated with the slurry solution.

The solvent for the slurry solution is not particularly limited, but examples include solvents such as water (preferably pure water such as ion-exchanged water and distilled water). Although the concentration of such a metal salt solution is not particularly limited, it is preferably 0.001 mol/L or more and 0.5 mol/L or less as ions of the metal salt.

The temperature at which the base material impregnated with the slurry solution is fired is not particularly limited, but is usually 200°C or higher and 800°C or lower. If the calcination temperature is too low, the supply source of the catalytically active species element will not be sufficiently thermally decomposed, making it difficult to enter a metal state exhibiting catalytic activity, which tends to lower the activity. On the other hand, if the calcination temperature is too high, the supported catalytically active species element tends to become coarse particles and the catalytic activity in the steam reforming reaction of the fuel composed of hydrocarbons tends to decrease.

The firing time can also be adjusted as appropriate, but it is usually preferably 0.1 hours or more and 100 hours or less. If the calcination time is too short, the source material of the catalytically active species element will not be sufficiently thermally decomposed, and it will be difficult to change to a metallic state that exhibits catalytic activity, so the activity tends to decrease. On the other hand, even if the firing time is longer than necessary, no effect can be obtained, and the cost and the production amount per unit time tend to decrease.

The amount of supported catalytically active species can be measured with an ICP emission spectrometer. By appropriately adjusting the concentration and amount of each supply source impregnated in the carrier, the promoter component can be supported in an amount of 50 parts by mass or more and 1000 parts by mass or less with respect to 100 parts by mass of the catalyst component.

<Application of fuel reforming catalyst>
The fuel reforming catalyst according to the present invention can be used not only for EGR applications in internal combustion engines, but also as a single catalyst as it is, and can be used as a catalyst in various devices involved in steam reforming reactions. For example, it can be applied to a hydrogen plant such as an oil refinery, a hydrogen production device for a fuel cell in a stationary distributed power source, a hydrogen production device from natural gas, and the like.

<Fuel reforming method>
Hydrocarbons can be steam reformed by using the fuel reforming catalyst according to the present invention. That is, a hydrocarbon containing fuel can be contacted with a fuel reforming catalyst in the presence of water vapor to produce hydrogen and carbon monoxide.

In the fuel reforming method of the present invention, the fuel containing hydrocarbons and steam may be independently supplied to the reactor, or they may be mixed in advance and then supplied to the reactor.
When steam is supplied to the reactor, it is preferable to use a method of providing the reactor with the exhaust gas after combustion with hydrogen after reforming.

The hydrocarbons contained in the fuel are not particularly limited, and examples thereof include alkanes, alkenes, alkynes, aromatic compounds, alcohols, aldehydes, etc. Specifically, methane, Linear or branched saturated aliphatic hydrocarbons such as ethane, propane, butane, pentane, hexane, heptane, octane, nonane, and decane; alicyclic saturated hydrocarbons such as cyclohexane, methylcyclohexane, and cyclooctane; Alternatively, gaseous or liquid hydrocarbons having 2 to 12 carbon atoms such as polycyclic aromatic hydrocarbons are preferable, and hydrocarbons having 2 to 8 carbon atoms are more preferable. Among these, saturated aliphatic hydrocarbons are preferred, and 50% or more of the fuel is more preferably saturated aliphatic hydrocarbons.

In addition, as the fuel composed of hydrocarbons, biomass fuel composed of hydrocarbons such as ethanol, gasoline, diesel fuel (light oil), natural gas, hydrocarbon gas, and biodiesel can be used. Furthermore, when used as a fuel composed of hydrocarbons in internal combustion engines such as automobiles, for example, a mixed fuel of ethanol and gasoline can be used. As such a mixed fuel, since ethanol has a high octane number, by mixing gasoline with a low octane number (for example, in the range of 30 to 85) and ethanol, an octane number in the range of 80 to 100, which is equivalent to that of ordinary gasoline fuel, can be obtained. can be obtained, and can be suitably used as a fuel for internal combustion engines such as automobiles.

Among the fuels containing hydrocarbons, the fuel reforming method of the present invention is used from the viewpoint that it is liquid at normal temperature, is easy to handle, has high safety, has high affinity with water (steam), and is easy to obtain. , natural gas, methanol, ethanol and gasoline, and more preferably ethanol, gasoline and mixed fuels of ethanol and gasoline.

The mixing ratio of the fuel containing hydrocarbons and the water vapor contained in the exhaust gas is not particularly limited. For example, when the fuel containing hydrocarbons is ethanol, the molar ratio of water vapor to carbon (S/C) is preferably 0.2 to 10, more preferably 0.4 to 2. By using the fuel reforming catalyst of the present invention, fuel containing hydrocarbons can be reformed even under low S/C conditions where coking occurs.

The temperature of the reforming reaction is preferably 250-800°C, more preferably 350-700°C. According to the fuel reforming catalyst of the present invention, a fuel containing hydrocarbons can be reformed even at a low temperature of 400° C. or less, which has conventionally been difficult to steam reform a fuel containing hydrocarbons due to low catalytic activity. becomes possible. In addition, it is possible to maintain high activity even at a high temperature of 550° C. or higher, and it becomes possible to reform a fuel composed of hydrocarbons with steam.
In addition, by supplying the exhaust gas after combustion of the internal combustion engine to the reactor as a heat source, it becomes unnecessary to prepare a separate heat source, which is advantageous in terms of structure and cost.

Further, since the fuel reforming catalyst according to the present invention is excellent in resistance to sulfur poisoning, it can exhibit stable catalytic performance over a long period of time even when the fuel contains a sulfur component. Sulfur components contained in the fuel include, for example, S, S ²⁻ , SO, SO ₂ , SO ₃ , SO ₄ ²⁻ and compounds containing S. Main sources of sulfur components include contact with sulfur components contained in fuel and sulfur components contained in exhaust gas after fuel combustion.

<Fuel reforming engine system>
The EGR system, which uses gasoline as a fuel and exhaust gas from an internal combustion engine as a steam and heat source, has a simple reformer structure and is advantageous in terms of cost, but the amount of contact between the fuel reforming catalyst and the sulfur content also increases. , the problem of reduced catalyst life tends to occur.
In contrast, the fuel reforming method using the fuel reforming catalyst according to the present invention can improve the thermal efficiency by combining it with the EGR system. For example, by using the steam contained in the post-combustion exhaust gas from an internal combustion engine, the fuel containing hydrocarbons is brought into contact with the fuel reforming catalyst according to the present invention in the presence of steam, thereby partially or entirely converting the fuel. By reforming into hydrogen and carbon monoxide and adding the obtained hydrogen and carbon monoxide to the fuel supplied to the internal combustion engine, the thermal efficiency of the engine can be improved.

The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[Example 1]
γ-alumina powder (average particle size: 28 μm, BET specific surface area: 141 m ² /g) was impregnated with an aqueous solution of neodymium nitrate and dried. Next, γ-alumina powder impregnated with an aqueous solution of neodymium nitrate (approximately 25 wt% in terms of Nd ₂ O ₃ ) was impregnated with an aqueous solution of rhodium nitrate (approximately 7 wt% in terms of Rh). After baking for 30 minutes, a rhodium-neodymium-supported alumina precursor was obtained. When the amount of each element carried was measured by an ICP emission spectrometer, it was 0.8% by mass of rhodium and 4.0% by mass of neodymium.
Nitric acid and water are added to the obtained rhodium-neodymium-supported alumina powder to adjust the pH to 4 to 5, and then wet pulverized with a ball mill until the particle size (D90) is 12 μm or less, and the catalyst-supported alumina powder is obtained. A slurry solution was prepared.

After filling 50 mg of powdered solid matter obtained by drying the obtained slurry solution into a reaction tube, the temperature of the reaction tube was raised to 600 ° C., and carbonization was performed in the reaction tube to simulate a mixed gas of regular gasoline and the atmosphere. A raw material gas containing hydrogen (O ₂ : 0.5 vol%, iso-octane: 0.045 vol%, Ar: 5 vol%, H ₂ O: 1 vol%, He: balance (S/C = 3.5)) The gas was supplied for 5 minutes at a flow rate of 300 cc/min for reaction. The components of the gas that passed through the reaction tube were analyzed using a mass spectrometer, and the amount of hydrogen generated by reforming the raw material gas was evaluated. The amount of hydrogen generated is relative to the amount of hydrogen generated by the same operation using a reaction tube filled with powder obtained in the same manner as in Example 1 except that only rhodium was used as a catalytically active species. value. The measured hydrogen generation amount was as shown in Table 1 below.

[Comparative Example 1]
A catalyst-supporting alumina powder was prepared in the same manner as in Example 1, except that the γ-alumina powder was not impregnated with the aqueous solution of neodymium nitrate, and the reaction tube was filled with the powder to measure the amount of hydrogen generated. The evaluation results were as shown in Table 1 below.

[Examples 2 to 9]
Catalyst-supported alumina powder was prepared in the same manner as in Example 1 except that the neodymium nitrate aqueous solution was changed to the metal nitrate aqueous solution shown in Table 1 and the supported amount was as shown in Table 1, and the reaction tube was filled with hydrogen generation amount. was measured. The catalyst components, co-catalyst support amount, and hydrogen generation amount of each catalyst were as shown in Table 1 below.

[Examples 10-12]
γ-alumina powder (average particle size: 28 μm, BET specific surface area: 141 m ² /g) was impregnated with an aqueous solution of neodymium nitrate (approximately 25 wt % in terms of Nd ₂ O ₃ ) and dried. Next, the γ-alumina powder impregnated with the neodymium nitrate aqueous solution was impregnated with a platinum salt solution (manufactured by NECC, product name: A-solt) and dried. Subsequently, the γ-alumina powder impregnated with the platinum salt aqueous solution was impregnated with the rhodium nitrate aqueous solution described above and dried in the same manner as in Example 1 to prepare a catalyst-supporting alumina powder, which was filled in a reaction tube to generate hydrogen. Quantitative measurements were made. The catalyst components, co-catalyst support amount, and hydrogen generation amount of each catalyst were as shown in Table 1 below.

[Example 13]
In Example 1, by changing the impregnation amount of the solution to the carrier, a catalyst-supporting alumina powder with a catalyst-supporting amount of 1.33% by mass of rhodium and 4.0% by mass of neodymium was prepared, and the obtained rhodium- Nitric acid and water were added to the neodymium-supported alumina powder to adjust the pH to 4 to 5, followed by wet pulverization with a ball mill to an average particle size of 12 μm to prepare a slurry solution of the catalyst-supported alumina powder.
Next, a honeycomb base material made of cordierite (number of cells/mil thickness: 600 cpsi/3.5 mil) was prepared, and the end of the honeycomb base material was immersed in the slurry solution, and from the opposite end side of the honeycomb base material, Vacuum suction was applied to impregnate the substrate surface with the slurry solution (wash coat amount: 150 g/L).
The honeycomb base material impregnated with the slurry solution in this manner was dried at 150° C. and fired at 450° C. in an air atmosphere to obtain a catalyst-carrying honeycomb base material. The amount of catalyst supported on the catalyst-supported honeycomb substrate (amount of catalyst with respect to catalyst volume) was 2.0 g/L for Rh and 6.0 g/L for neodymium.

Gases simulating engine exhaust gas (CO: 0.71%, HC: 0.12%, NO: 0.03%, O ₂ : 0.69%, CO ₂ : 14%, H ₂ O: 14%, N ₂ : Balance, A/F = 14.7 with perturbation (perturbation O ₂ : 0.31%, CO: 63%), A/F ± 0.2 2 .5 Hz) and a gas simulating regular gasoline (C ₁₀ H ₂₂ : 0.362%, SO ₂ : 0.31%) was steam-reformed, and EGR was used in a regular gasoline vehicle. Under conditions simulating the environment (S/C=3.5, temperature 600° C., SV≈50000 h ⁻¹ ), the amount of hydrogen generated and the durability in the presence of poisoning substances were evaluated. The stage at which the reaction was stabilized after switching to the raw material gas was defined as 0 seconds, and the amount of hydrogen generated at 0 seconds was defined as 100, and the amount of hydrogen generated over time was evaluated.

[Comparative Example 2]
A catalyst-supporting honeycomb substrate was produced in the same manner as in Example 13 except that a catalyst-supporting alumina powder slurry with a catalyst-supporting amount of 2% by mass of rhodium was used, and the washcoat amount was 100 g/L. We evaluated the amount of hydrogen generated over time. The amounts of hydrogen generated in Example 13 and Comparative Example 2 at 0 seconds were almost the same.

As is clear from the evaluation results in Table 1, in a system filled with a supported catalyst (Examples 1 to 12) in which a specific promoter component is used in addition to a catalyst component made of a platinum group metal element, conventional platinum group Compared to a system filled with a supported catalyst (corresponding to Comparative Example 1) consisting only of metal elements, it can be seen that the amount of hydrogen generated is greater and the catalytic performance is improved.
In addition, as is clear from the evaluation results in Table 2, which simulates the case where the fuel reforming catalyst of the present invention is applied to a gasoline vehicle, a specific co-catalyst component was used in addition to the catalyst component composed of a platinum group metal element. Even when the supported catalyst (Example 13) is used for reforming a fuel containing sulfur, compared with a conventional supported catalyst (equivalent to Comparative Example 2) consisting only of a platinum group metal element, It can be seen that the decrease in the amount of hydrogen generated is gradual, and the durability against deterioration factors such as catalyst poisoning is excellent.

Claims

A fuel reforming catalyst for reforming a fuel containing hydrocarbons into a synthesis gas containing hydrogen,
a catalyst component and a co-catalyst component containing a platinum group metal element;
a carrier that supports the catalyst component and the co-catalyst component;
with
A fuel reforming catalyst, wherein the promoter component comprises at least one element selected from the group consisting of scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, barium, nickel, and strontium.
2. The fuel of claim 1, wherein the promoter component comprises at least one element selected from the group consisting of scandium, yttrium, lanthanum, praseodymium, neodymium, promethium, samarium, europium, barium, nickel, and strontium. reforming catalyst.
The fuel reforming catalyst according to claim 1 or 2, wherein the promoter component is supported in an amount of 50 parts by mass or more and 1000 parts by mass or less with respect to 100 parts by mass of the catalyst component.
The fuel reforming catalyst according to any one of claims 1 to 3, wherein the carrier is made of a porous material.
The fuel reforming catalyst according to any one of claims 1 to 4, wherein the fuel contains 50% by mass or more of hydrocarbons having 2 to 12 carbon atoms.
The fuel reforming catalyst according to any one of claims 1 to 5, wherein the platinum group metal elements include rhodium and platinum.
The fuel reforming catalyst according to any one of claims 1 to 6, wherein the fuel is automotive fuel.
A fuel reforming method using the fuel reforming catalyst according to any one of claims 1 to 7,
A method comprising contacting a fuel comprising a sulfur component and hydrocarbons with said fuel reforming catalyst in the presence of steam to produce hydrogen and carbon monoxide.
A part or all of a fuel containing hydrocarbons is reformed into hydrogen and carbon monoxide by using a post-combustion exhaust gas from an internal combustion engine and the fuel reforming catalyst according to any one of claims 1 to 7, and adding hydrogen and carbon monoxide obtained to a fuel supplied to an internal combustion engine.