JP2005238025A - Fuel reforming catalyst and fuel reforming system using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel reforming catalyst which exhibits excellent reforming effect even at a low temperature and gives a reformed gas having a low CO concentration, a low CH<SB>4</SB>concentration, and a high H<SB>2</SB>concentration. <P>SOLUTION: The fuel reforming catalyst is prepared by supporting a metal with different oxidation states on a carrier. Desirably, the catalyst is characterized in that the metal contains zero-valent cobalt and divalent cobalt oxide. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fuel reforming catalyst, and more particularly to a fuel reforming catalyst in which metals having different oxidation states are supported on a carrier.

  A method for reforming hydrocarbons such as methane and gasoline and alcohols such as methanol to generate hydrogen has already been industrially used. In general, the reforming reaction includes steam reforming and partial oxidation reforming represented by the following formula, and autothermal reforming combining steam reforming and partial oxidation reforming.

  However, it is generally necessary to set the reforming temperature to 700 to 900 ° C. in order to reform hydrocarbons, and then included in the heat exchanger for lowering the temperature of the reformed gas, or reformed gas. It is necessary to install many devices such as high temperature shift and low temperature shift reactors to reduce CO. For this reason, there are drawbacks such as an increase in the size of the fuel reforming apparatus and the hydrogen gas production apparatus, and an increase in startup time and startup energy.

  On the other hand, hydrocarbons used as reforming raw material gas are so-called fossil fuel resources such as oil and natural gas, and have a problem of generating carbon dioxide that promotes global warming. Methanol can also be used as a reforming raw material, and the reforming temperature is as low as 200 to 300 ° C., but has a drawback of high toxicity. Moreover, since it produces from a fossil fuel resource like a hydrocarbon, there exists a problem of generating the carbon dioxide which promotes global warming.

  On the other hand, since ethanol has low toxicity and is produced by photosynthesis, it can be produced using biomass resources such as plants as raw materials, and is considered as a renewable energy source. For these reasons, methods for reforming ethanol to generate hydrogen have been studied in recent years.

For example, there is a method for producing hydrogen gas that reforms ethanol using water vapor in the presence of oxygen (Patent Document 1). As the reforming catalyst, a reforming catalyst in which a mixture of nickel or nickel + copper is supported on α-alumina or silica, and reforming is performed at 700 ° C. in the examples.
Special table 2003-503295 gazette

However, a heating device or the like is required to increase the reforming temperature to 700 ° C., while a heat exchanger is also required to reduce the temperature of the reformed gas after reforming to 700 ° C. or lower. Furthermore, such reforming at high temperatures generates many by-products such as CH ₄ and CO, and it is necessary to install many devices such as a high-temperature shift and low-temperature shift reactor for reducing the CO concentration. . For this reason, disadvantages such as an increase in system size, start-up time, and start-up energy occur.

In addition, when a reforming reaction is performed in a low temperature region using a conventional catalyst, not only the reforming activity is bad, but also the CO ₄ concentration is low but the CH ₄ concentration is generally high. In some cases, the concentration of H ₂ contained in the gas was lowered.

In view of the above-mentioned present situation, the present invention provides a fuel reforming catalyst that is excellent in reforming effect even at low temperatures, can generate reformed gas with low CO concentration and CH ₄ concentration, and high H ₂ concentration. Objective.

  As a result of intensive studies to achieve the above problems, the present inventors have found that the above problems can be solved by a fuel reforming catalyst in which metals having different oxidation states are supported on a carrier.

The fuel reforming catalyst of the present invention has excellent reforming activity even at low temperatures. For this reason, an efficient reforming reaction can be performed even if the heat energy required for preheating the reforming raw material is small. In addition, since the shift ability is high, CO and CH ₄ by-products can be suppressed, and a high-concentration H ₂ -containing gas can be produced. Furthermore, the fuel reforming catalyst has excellent durability.

  Therefore, according to the present invention, it is possible to provide a fuel reforming catalyst that can exhibit an excellent reforming effect at low temperatures over a long period of time.

  The first of the present invention is a fuel reforming catalyst in which metals having different oxidation states are supported on a carrier.

  Conventionally, a reforming method using a nickel catalyst or the like is known as a method for producing a hydrogen-containing gas by reforming hydrocarbons or alcohols using a fuel reforming catalyst. There was a risk of CO, methane, etc. being a by-product.

  However, in the present invention, by making the fuel reforming catalyst act, the selectivity of the reforming reaction is improved even at a low temperature of 300 to 500 ° C., and as a result, by-product such as methane is suppressed and efficient hydrogen content is achieved. It has been found that gas can be produced.

  As the metal used in the fuel reforming catalyst of the present invention, an optimal metal may be used as appropriate according to the reforming method. Preferably, at least one of nickel, cobalt, platinum, rhodium, palladium and ruthenium is used. Is mentioned. Of these, cobalt is preferred because of its excellent steam reforming activity.

  When cobalt is used as the metal having a different oxidation state in the fuel reforming catalyst, it is preferable that zero-valent cobalt and divalent cobalt oxide are supported on the carrier. Thereby, not only high catalytic activity at a low temperature is obtained, but also the durability of the fuel reforming catalyst can be greatly improved. In the present application, the oxidation state of the metal in the fuel reforming catalyst can be analyzed from a spectrum obtained by X-ray diffraction (XRD).

  The metal content in the fuel reforming catalyst is 2 to 20% by mass, more preferably 5 to 10% by mass per catalyst in terms of metal. If it is this range, a metal will be disperse | distributed uniformly on a support | carrier and, as a result, high catalyst activity can be ensured. When the metal is cobalt, the ratio of zero-valent cobalt to divalent cobalt oxide is 1: 5 to 5: 1, preferably 1: 2 to 2: 1. By this. A fuel reforming catalyst having high steam reforming activity, methanation suppressing ability and durability can be obtained.

  In addition, although the effective electrode area which an electrochemical reaction progresses increases so that the average particle diameter of the said metal is small, the phenomenon in which activity falls rather is actually seen when a catalyst particle diameter becomes small too much. Therefore, the average particle diameter of the catalyst metal is preferably 1 to 15 nm, more preferably 2 to 10 nm. The “average particle diameter” of the metal in the present application can be measured by the crystallite diameter obtained from the half width of the diffraction peak of the metal in X-ray diffraction or the average value of the particle diameter of the metal examined from a transmission electron microscope image. .

  Next, as the carrier used in the fuel reforming catalyst of the present invention, an optimal one may be used according to the reforming method, but preferably zinc oxide, magnesium oxide, tin oxide, bismuth oxide, oxidation Examples thereof include at least one of lead, cadmium oxide, alumina, silica, zirconia, and ceria. Among these, alumina is preferable because of its high ability to activate water.

The carrier preferably has a BET specific surface area of 10 to 200 m ² / g, more preferably 50 to 150 m ² / g.

  Examples of the method for producing the fuel reforming catalyst of the present invention include a method in which a desired metal is first supported on a carrier, calcined in an air atmosphere at a predetermined temperature, and further calcined in a reducing atmosphere. This makes it possible to vary the oxidation state of the metal supported on the carrier.

  Although there is no particular limitation on loading the metal on the support, for example, an impregnation method in which the support is dispersed and impregnated in a solution containing a desired metal can be mentioned. In addition to the impregnation method, various known techniques such as a coprecipitation method and a competitive adsorption method may be used.

  The metal supply source is not particularly limited, and compounds containing these widely can be used. Examples of such compounds include nitrates, chlorides, ammine complexes, sulfates, acetates, and carbonyl complexes of the above metals, which can be appropriately selected depending on the type and pH of the solvent in which these are dissolved. Among these, nitrates, carbonates, oxides, hydroxides and the like are preferable for industrial use. Moreover, water, alcohol, acetone, etc. are mentioned as a solvent which melt | dissolves the said compound.

  Next, the carrier carrying the desired metal is fired in an air atmosphere at 400 to 550 ° C., more preferably 500 to 530 ° C., and then in a reducing atmosphere at 350 to 400 ° C., more preferably 360 to 390 ° C. Bake with. As a result, as shown in FIG. 1, fuel reforming catalysts having different oxidation states of the metals supported on the carrier can be obtained. If the reduction temperature is less than 350 ° C., it is insufficient to change the oxidation state. If the reduction temperature exceeds 400 ° C., the reduction reaction proceeds too much, and all the metals on the support may be metalized to reduce the catalytic activity. Not desirable.

  The fuel reforming catalyst of the present invention may be in an irregular shape such as powder or granule, and it is preferable to use the fuel reforming catalyst supported on a honeycomb monolith, porous ceramics or the like. When honeycomb monoliths, porous ceramics, etc. are used, the catalyst filling part of the fuel reformer can be easily filled with the catalyst, and the air permeability of the raw material gas and the reformed gas can be secured by the honeycomb structure and the porous structure. It is. Further, when the raw material gas is supplied, the catalyst can be prevented from being heated and calcined, and the catalyst life and the catalytic activity can be improved.

  As materials constituting the honeycomb monolith, ceramic honeycomb (ceramics, 400 cells to 3000 cells, diameter 35 mmφ), metal honeycomb, metal foam (Ni-Cr, 20 pores / inch to 50 pores / inch, diameter 100 mmφ) and / or ceramic foam (Ceramics, 9 pores / inch to 30 pores / inch, diameter 75 mmφ), offset fins, etc., any of which may be used. Cera honeycomb, metal foam, and Cera foam are preferable because they are excellent in pressure loss and easy in coating technology. In order to ensure air permeability and catalytic activity, the cell width is preferably 0.01 to 10 mm, and the number of cells per liter is preferably 100 to 10,000.

  The catalyst may be supported on the honeycomb monolith, for example, by pulverizing the fuel reforming catalyst, thereafter preparing a slurry, impregnating or applying the slurry to the honeycomb monolith, and then firing the honeycomb monolith. In this case, various known techniques such as reducing the solution concentration and increasing the number of impregnations may be used as appropriate in order to infiltrate and carry the components deeply into the pores.

  The pulverization method for pulverizing the fuel reforming catalyst is not particularly limited. Preferably, the aqueous slurry containing these is wet pulverized to prepare an average particle size of 2 to 3 μm. An apparatus that can be used for pulverization is not particularly limited, and a commercially available ball-type vibration mill or the like can be used, and a desired particle size is obtained by adjusting the ball diameter, pulverization time, amplitude, and vibration frequency.

  The amount of catalyst supported on the honeycomb monolith may be appropriately determined so as to obtain a desired hydrogen generation amount in consideration of the supply amount of the reforming raw material.

  Next, examples of the material constituting the porous ceramic include magnesia, alumina, nickel oxide, cobalt oxide, nickel, cordierite, and the like, and are not particularly limited. In the porous ceramics, alumina powder or the like often enters the porous part at the time of production, and this impedes catalyst loading. Therefore, pretreatment such as washing may be performed to remove this.

  The catalyst may be supported on the porous ceramics by using a method of impregnating or applying the prepared slurry as in the above-described honeycomb monolith. Further, the present invention is not limited to this, and the pulverized fuel reforming catalyst may be used by filling porous ceramics.

  Examples of reforming raw materials used in the fuel reforming catalyst of the present invention include hydrocarbon compounds and alcohols. Examples of the hydrocarbon compound include light hydrocarbons such as methane, propane, butane, heptane, and hexane, and petroleum hydrocarbons such as gasoline, kerosene, and naphtha. Moreover, as alcohol, C1-C3 alcohol, Especially preferably, it is preferable for modification | reformation of methanol and ethanol, especially ethanol. Use of alcohol having 4 or more carbon atoms is disadvantageous because excessive energy may be required when gasifying the reforming raw material. On the other hand, ethanol is easy to gasify, is not particularly toxic in itself, and is preferable from the viewpoint of environmental conservation because it can be obtained from biomass. According to the fuel reforming catalyst of the present invention, ethanol that can be generated from biomass is preferably used as a raw material, and by-product such as methane as a global warming gas can be suppressed to generate a reformed gas having a high hydrogen concentration. it can.

  The fuel reforming catalyst of the present invention is suitable for any reforming of partial reforming, steam reforming, and autothermal. Since ethanol is a liquid at normal temperature and water is also a liquid at normal temperature, both can be mixed at an arbitrary ratio. For this reason, when the reforming raw material is ethanol, ethanol and water can be mixed and stored in the raw material tank, and efficient reforming can be performed without providing a separate water supply means. For this reason, the fuel reforming catalyst of the present invention is particularly suitable for steam reforming using ethanol. The reaction when ethanol is steam reformed is shown below.

  Since the steam reforming described above is an endothermic reaction, it is necessary to supply the amount of heat necessary for the reforming reaction at the time of startup. Therefore, when the temperature of the supplied steam is raised as a heat medium, the activity may be deteriorated due to oxidation of the catalyst. Further, even when the combustion exhaust gas in the combustion section of the reformer is used as a heat medium, oxidation may occur due to oxygen in the combustion exhaust gas, leading to deterioration of the activity of the catalyst.

  Therefore, when the catalyst activity reaches a predetermined degree of deterioration due to oxidation during the reaction, the fuel reforming catalyst of the present invention can be regenerated by performing a reduction treatment. Thereby, the metal on a support | carrier can be made into a desired oxidation state, and catalyst activity can be recovered | restored.

The degree of deterioration of the catalyst activity can be detected, for example, by temperature, and is defined as the time when the temperature in the reforming reactor filled with the catalyst has increased by 10 to 50 ° C. during the reforming reaction. This is because the steam reforming of ethanol or the like is an endothermic reaction, and therefore the temperature in the reforming reactor increases as the catalyst deteriorates and the endothermic amount due to the reforming reaction decreases. The degree of deterioration can be detected not only by such temperature detection but also by CO concentration, ethanol concentration, hydrogen concentration, CO ₂ concentration, H ₂ O concentration, gas flow rate, and the like.

The reduction treatment is preferably performed at 350 to 400 ° C., preferably 360 to 390 ° C., in contact with hydrogen, carbon monoxide, preferably hydrogen. If the reduction temperature is less than 350 ° C., it may be insufficient to change the oxidation state. If the reduction temperature exceeds 400 ° C., the reduction reaction may proceed too much, and all of the metal on the support may be metalized to lower the catalytic activity. and so on.
This is not desirable because there is a risk of excessive reduction.

  The time for performing the reduction treatment may be appropriately determined in consideration of the amount of fuel reforming catalyst, the size, the flow rate of the reducing gas, etc. so that the catalytic activity is restored to a desired value, but it is about 10 minutes to 1 hour. It is enough to do.

  Further, the metal in the fuel reforming catalyst may be reduced by the hydrogen gas contained in the reformed gas, resulting in deterioration of catalyst activity. Therefore, when the catalytic activity reaches a predetermined degree of deterioration due to reduction during the reaction, the fuel reforming catalyst can be regenerated by performing the oxidation treatment first and then performing the reduction treatment. Also by such a method, the metal on the support can be brought into a desired oxidation state, and the catalytic activity can be increased again.

The degree of deterioration of the catalyst activity at this time can be detected in the same manner as described above, and is detected by at least one of temperature, CO concentration, ethanol concentration, hydrogen concentration, CO ₂ concentration, H ₂ O concentration, gas flow rate, and the like. The oxidation treatment is preferably performed at 400 to 550 ° C., preferably 500 to 530 ° C., in contact with an oxygen-containing gas such as air. If the oxidation treatment temperature is less than 400 ° C., the treatment time may be unnecessarily prolonged. If the oxidation treatment temperature exceeds 550 ° C., the metal may be sintered and the catalyst activity may be reduced.

  The time for performing the oxidation treatment may be performed until the reduced and deteriorated metal recovers to a desired oxidation state such as CoO, and is appropriately determined in consideration of the amount and size of the fuel reforming catalyst, the flow rate of the oxygen-containing gas, and the like. It suffices to carry out for about 10 minutes to 1 hour.

  The reduction treatment performed after the oxidation treatment may be performed in the same manner as described above.

  Thus, it is preferable to perform the regeneration process described above according to the deterioration state of the fuel reforming catalyst such as deterioration due to oxidation or deterioration due to reduction. The deterioration state of the fuel reforming catalyst can be detected by a known method such as X-ray diffraction.

  The activity of the fuel reforming catalyst recovered by performing such regeneration treatment can be recovered to the same level as the initial activity and can be maintained over a long period of time as shown in the examples described later. . In a conventional fuel reforming catalyst, when deterioration occurs, the catalyst is replaced at an appropriate stage. However, by using the fuel reforming catalyst of the present invention, it is possible to reduce the cost, labor, time and the like required for catalyst replacement by repeating the reforming reaction and the regeneration process.

  The fuel reforming catalyst of the present invention has various excellent properties as described above. Therefore, if this is used in a fuel reforming system, not only is it excellent in energy efficiency and durability, but it is possible to suppress by-products such as methane, which is a global warming gas. Therefore, it is possible to provide a fuel reforming system that is also excellent in environmental safety. Hereinafter, the fuel reforming system of the present invention will be described.

  The fuel reforming system of the present invention includes a reforming reactor having the above-described fuel reforming catalyst, and a carbon monoxide shift reaction that reduces carbon monoxide contained in the exhaust gas from the reforming reactor by a water gas shift reaction. A carbon monoxide selective reactor for removing carbon monoxide contained in the exhaust gas from the carbon monoxide shift reactor, and a fuel cell.

  In a fuel reforming system using ethanol or the like as a raw material, first, the raw material is reformed in a reforming reactor filled with a fuel reforming catalyst to generate a reformed gas containing hydrogen and carbon monoxide. Next, the reformed gas is supplied to a carbon monoxide shift reactor, and the carbon monoxide contained in the reformed gas is reduced by a water gas shift reaction. Next, the carbon monoxide is supplied to a carbon monoxide selective reactor having a catalyst layer for removing carbon monoxide contained in the outlet gas of the carbon monoxide shift reactor to reduce carbon monoxide, and high purity hydrogen gas is supplied to the fuel cell. To supply.

  The fuel reforming system of the present invention is suitable for any reforming of partial reforming, steam reforming, and autothermal. Therefore, an oxygen supply means, a water supply means, etc. may be provided according to the reforming raw material and the reforming method, and further, a heater, a preheater, etc. may be provided as necessary.

  FIG. 2 shows a schematic diagram of a fuel reforming system which is an example of a preferred embodiment of the present invention. In the fuel reforming system 100, 1 is an evaporator, 2 is a reforming reactor, 3 is a heat exchanger, 4 is a CO shift reactor, 5 is a CO selective reactor, 6 is a fuel cell, 7 is a raw material tank, 8 Indicates a pump.

  The raw material is supplied from the raw material tank 7 to the evaporator 1 through the raw material supply pipe. In the case of the steam reforming of ethanol, ethanol and water may be mixed in a predetermined ratio in the raw material tank 7, and the ethanol tank and the water tank are separately provided and a predetermined ratio is obtained by joining the pipes. May be mixed.

  The raw material is heated in advance by a heat exchanger 3 as a heat source up to a predetermined temperature, supplied to the evaporator 1, and boiled / vaporized. The raw material gas obtained by mixing the ethanol and water vapor obtained in the evaporator 1 is supplied to the reforming reactor 2 through a predetermined pipe. Since the raw material gas has a predetermined temperature, a steam reforming reaction takes place in the reforming reactor 2 using this heat.

The mixing ratio of water and ethanol is preferably 1: 1 to 20: 1 by mole ratio, more preferably 3: 1 to 10: 1. Further, S / C ratio may be any _{0.5~10, O} 2 / C ratio may be a 0-1. In addition, as for the supply amount of a raw material, SV is 1,000-300,000h- ¹ with respect to a catalyst filling part. However, the higher the space velocity, the shorter the catalyst contact time and the lower the conversion rate. Further, if the S / C is low, the H ₂ concentration may inevitably be low. Further, the lower the O ₂ / C, the better because the H ₂ concentration increases. However, since the reaction heat of the partial oxidation reaction with oxygen decreases, the conversion rate may decrease.

  As the reaction system, a continuous flow system in which the raw material is continuously brought into contact with the catalyst is preferably used. The pressure is 0.1 to 1 MPa · G, preferably 0.1 to 0.15 MPa · G. The reforming reaction temperature is 200 to 600 ° C, more preferably 350 to 450 ° C. In order to adjust to such a temperature, in addition to a method of preheating the raw material in advance by a heating device such as the heat exchanger 3, a method of heating only the reforming reactor may be used. When the temperature is lower than 200 ° C., vaporization of the raw materials and water components becomes insufficient. On the other hand, when the temperature exceeds 600 ° C., the catalyst may be deactivated.

  Conventionally, steam reforming of ethanol has been performed at 600 to 800 ° C. In contrast, in the present application, the modification can be performed at a low temperature of 200 to 600 ° C. Therefore, it is possible to reduce the size of the system, the startup time, and the startup energy.

  Next, the reformed gas obtained from the reforming reactor 2 may be supplied as fuel for the fuel cell as it is. Further, it can be used as a raw material for chemical industry in addition to the fuel cell. In particular, among fuel cells, molten carbonate fuel cells and solid oxide fuel cells, which are classified as high-temperature operation types, can use carbon monoxide and hydrocarbons as fuels in addition to hydrogen. The hydrogen-containing gas obtained from the reforming reactor 2 may be used directly.

  However, CO contained in the reformed gas may contribute to catalyst deterioration. Therefore, the reformed gas is a CO shift reactor 4 in which water vapor is added to reduce the carbon monoxide concentration by a shift reaction, or a small amount of oxygen is added to reduce the carbon monoxide concentration by a selective oxidation reaction of carbon monoxide. It is desirable to connect the CO selective reactor 5 to be connected by a predetermined pipe and reduce the carbon monoxide concentration through these.

  The shift catalyst charged in the CO shift reactor 4 may be a conventionally known catalyst such as a Pt-based, Cu-based, Fe-based, or Cu-ZnO-based catalyst. Conventionally known CO removal catalysts such as Pt-based and Ru-based catalysts can be used. The carbon monoxide concentration can be reduced to about 1% by the CO shift reaction, and can be reduced to 100 ppm or less by the carbon monoxide selective oxidation reaction. The exhaust gas from the CO shift reactor 4 may be cooled in advance by a cooling unit or the like and then supplied to the CO selective reactor 5 to improve the carbon monoxide removal efficiency. In addition, impurities can be removed by using a cryogenic separation method, a PAS method, a hydrogen storage alloy, a palladium membrane diffusion method, or the like to obtain a high purity hydrogen gas.

  In this way, the fuel gas having a reduced CO concentration and containing high-purity hydrogen gas is supplied to the fuel cell 6 through a predetermined pipe, and can be used as a drive energy source for the moving body. The type of the fuel cell is not particularly limited, but a polymer electrolyte fuel cell or the like is preferably used from the viewpoints of practicality and safety. A solid polymer fuel cell is configured by sandwiching a solid polymer electrolyte membrane selectively permeable to hydrogen ions between an anode and a cathode, and by an electrochemical reaction of fuel gas and oxidant gas supplied at the anode and cathode. An electromotive force is generated and generated.

  When catalyst activity deteriorates in the fuel reforming system described above, the reforming performance can be recovered without performing catalyst replacement by performing the above-described catalyst regeneration operation. FIG. 3 is a schematic diagram showing an example of a preferred embodiment of a fuel reforming system further provided with a catalyst regeneration operation.

  In the fuel reforming system of FIG. 3, a temperature sensor 10 for detecting the temperature in the reforming reactor 2 and a regeneration gas generator 9 are disposed in the reforming reactor 2.

  In a fuel reforming system, as the reforming reaction proceeds, the reforming rate gradually decreases with time, and the endothermic amount of the reforming reaction decreases, thereby increasing the catalyst temperature, that is, the temperature in the reforming reactor. Therefore, it is preferable to temporarily stop the supply of the fuel gas and perform the catalyst regeneration operation when the temperature in the reforming reactor is raised to a predetermined temperature by measuring with a catalyst temperature sensor.

  The catalyst regeneration operation is performed according to the following procedure. The deterioration state of the fuel reforming catalyst can be detected by a known method such as X-ray diffraction. Therefore, it is preferable to perform the catalyst regeneration operation according to the deterioration state of the metal such as reduction deterioration or oxidation deterioration.

  First, when the fuel reforming catalyst in the reforming reactor deteriorates due to oxidation, the fuel reforming reaction is stopped and the reduction process is performed. The reduction process is performed by sending a reducing gas such as hydrogen or carbon monoxide from the regeneration gas generator 9 to the reforming reactor 2. The regeneration gas generator 9 is not particularly limited as long as it can supply a reducing gas or the like, and a hydrogen generator by water electrolysis, discharge reforming, or the like may be installed. Further, the reducing gas supply means is not limited to that using the regeneration gas generator, and may be means such as supplying hydrogen by fuel reforming or supplying from a separately provided hydrogen tank. There is no particular limitation. Moreover, since a heat capacity of a certain level or more is required for the reduction treatment, the temperature in the reforming reactor is preferably 350 to 400 ° C, particularly 360 to 390 ° C. In addition, if the space velocity is too high, the supply of the reducing gas may cause metal sintering, and if it is too slow, it takes a long time for the regeneration operation. Good. The time for performing the reduction treatment may be appropriately determined in consideration of the amount of fuel reforming catalyst, the size, the flow rate of the reducing gas, and the like, but it is sufficient that the time is about 10 minutes to 1 hour. By performing such a reduction treatment, the metal in the fuel reforming catalyst becomes a desired oxidation state, and high catalytic activity can be recovered. Thereafter, the catalyst regeneration operation may be stopped and the fuel reforming reaction may be restarted.

  Further, when the fuel reforming catalyst in the reforming reactor deteriorates due to the reduction, the oxidation treatment is first performed and then the reduction treatment is performed. The oxidation treatment may be performed by supplying an oxygen-containing gas such as air into the reforming reactor using a compressor or the like. The reduction-degraded metal of the fuel reforming catalyst reacts with the supplied oxygen-containing gas and is regenerated, and the temperature in the reforming reactor rises due to the reaction heat at this time. Therefore, in order to bring the metal into a desired oxidation state, it is preferable to carry out while controlling at 400 to 550 ° C, particularly 500 to 530 ° C. The time for performing the oxidation treatment may be appropriately determined in consideration of the amount and size of the fuel reforming catalyst, the flow rate of the reducing gas, etc., but it is sufficient that the time is about 10 minutes to 1 hour.

  After performing the oxidation treatment, the reduction treatment is performed in the same manner as described above, whereby the metal in the fuel reforming catalyst becomes a desired oxidation state and high catalytic activity can be recovered. Can be resumed.

  Moreover, although the above-mentioned catalyst regeneration operation measures the catalyst deterioration based on the temperature in the reforming reactor, the measuring means is not particularly limited to this.

  Hereinafter, the present invention will be described based on examples. In addition, this invention is not limited only to these Examples. In the examples, “%” represents a mass percentage unless otherwise specified.

<Example 1>
(1) Preparation of fuel reforming catalyst Using a cobalt nitrate aqueous solution (30% by mass), cobalt was impregnated into alumina. The impregnation conditions were 4 hours at room temperature. Cobalt was supported on the carrier so as to be 10% by mass (cobalt conversion) in the total mass of the obtained catalyst. This was dried at 120 ° C. for 3 hours and then calcined in air at 500 ° C. for 3 hours.

  Next, in order to coat the fired product on the honeycomb carrier, water was added to about 200 g of the fired product and pulverized into a slurry.

The obtained slurry was applied to a cordierite honeycomb carrier (4 mil 400 cells) so that the supported amount of catalyst powder was 200 g / L, dried at 120 ° C., fired at 400 ° C., and then 375 in a hydrogen stream. A Co / Al ₂ O ₃ (375) catalyst was obtained by reduction treatment at 1 ° C. for 1 hour.

(2) Production of reformed gas Using a honeycomb carrier carrying a Co / Al ₂ O ₃ (375) catalyst, ethanol reforming was performed by a small fuel reformer.

An ethanol aqueous solution (ethanol: water = 1: 4 (molar ratio)) was placed in the raw material tank, supplied to the evaporator by a pump, and after gasification, it was introduced into the reforming reactor so that the ethanol space velocity was 5000 h ⁻¹ . . At this time, S / C = 2 and O ₂ /C=0.1 were set. The Co / Al ₂ O ₃ (375) catalyst size in the reforming reactor was 20 ml.

  When the reaction was started at a temperature of 400 ° C. in the reactor, the reaction proceeded stably and reformed gas was generated. Table 1 shows the result of analyzing the reformed gas obtained from the reactor after 1 hour by gas chromatography. Table 2 shows the change over time in the ethanol conversion obtained by analyzing and calculating the reformed gas obtained from the reactor using a gas chromatograph. The ethanol conversion was calculated based on the following formula.

<Comparative Example 1>
An aqueous nickel nitrate solution (30% by mass) was used to impregnate the alumina with nickel. The impregnation conditions were 4 hours at room temperature. Nickel was supported on the carrier so as to be 10% by mass (in terms of nickel) in the total mass of the resulting catalyst. This was dried at 120 ° C. for 3 hours and then calcined in air at 500 ° C. for 3 hours.

  Next, in order to coat the fired product on the honeycomb carrier, water was added to about 200 g of the fired product and pulverized into a slurry.

The obtained slurry was applied to a cordierite honeycomb carrier (4 mil, 400 cells) so that the supported amount of catalyst powder was 200 g / L, dried at 120 ° C., fired at 400 ° C., and then heated in a hydrogen stream. A reformed gas was produced in the same manner as in Example 1 except that a Ni / Al ₂ O ₃ catalyst was obtained by reduction treatment at 1 ° C. for 1 hour.

<Comparative example 2>
In Example 1 (1), except that Co / Al ₂ O ₃ (300) was prepared at a reduction treatment temperature in a hydrogen stream of 300 ° C., the reformed gas was Manufactured.

<Comparative Example 3>
In Example 1 (1), except that Co / Al ₂ O ₃ (500) was prepared at a reduction treatment temperature in a hydrogen stream of 500 ° C., the reformed gas was Manufactured.

<Example 2>
In the same manner as in Example 1, a Co / Al ₂ O ₃ (375) catalyst was installed on the honeycomb carrier, and ethanol reforming was performed using the fuel reformer shown in FIG.

An ethanol aqueous solution (ethanol: water = 1: 4 (molar ratio)) was placed in the raw material tank, supplied to the evaporator by a pump, and after gasification, it was introduced into the reforming reactor so that the ethanol space velocity was 5000 h ⁻¹ . . At this time, S / C = 2 and O ₂ /C=0.1 were set.

When the reaction was started at a temperature of 400 ° C. in the reactor, the reaction proceeded stably and a reformed gas was produced, but after 100 hours, the catalyst temperature rose by 20 ° C. due to a decrease in conversion. As a result of analysis by XRD diffraction of the catalyst, the catalyst was in a Co trivalent state and was oxidized and deteriorated. Therefore, once interrupted reforming reaction, after a 375 ° C. of hydrogen gas from the regeneration gas generator according to the reforming reactor to discharge the reforming was carried out by supplying 30 minutes recovery processing space velocity 1000h ^-1, modification When the reaction was started, reformed gas was generated again. Table 3 shows the results of changes over time when the generated reformed gas was analyzed with a gas chromatograph.

<Result>
When Example 1 was compared with each comparative example, by-product such as methane was suppressed in Example 1, and the hydrogen concentration showed a high value. Further, when Example 1 and Comparative Example 2 were compared, Example 1 showed a high hydrogen concentration because by-products such as ethylene were suppressed and the conversion rate was high. According to the present invention, by-products can be suppressed and a reformed gas containing hydrogen as a main component can be efficiently produced.

  When the change over time in the conversion rate of Example 1 and Comparative Example 3 was compared, Example 1 showed a stable conversion rate with almost no decrease in the conversion rate. According to the present invention, a reformed gas containing hydrogen as a main component can be produced stably.

  In Example 2, even when the conversion rate decreased, a high conversion rate was shown again by the regeneration treatment. According to the present invention, a reformed gas containing hydrogen as a main component could be produced continuously.

  The fuel reformer of the present invention can produce a high-concentration hydrogen-containing gas with few by-products, and is particularly useful as a hydrogen supply device.

The schematic diagram of a fuel reforming catalyst is shown. 1 is a schematic view of a fuel reforming system which is an example of an embodiment of the present invention. 1 is a schematic view of a fuel reforming system including a fuel reforming catalyst regeneration unit, which is an example of an embodiment of the present invention. FIG.

Explanation of symbols

1 ... Evaporator,
2 ... reforming reactor,
3 ... heat exchanger,
4 ... CO shift reactor,
5 ... CO selective reactor,
6 ... Fuel cell,
7 ... Raw material tank,
8 ... pump,
9 ... Regeneration gas generator,
10: Temperature sensor.

Claims (8)

  A fuel reforming catalyst in which metals having different oxidation states are supported on a carrier.   The fuel reforming catalyst according to claim 1, wherein the metal contains zero-valent cobalt and divalent cobalt oxide.   A fuel reforming catalyst in which the fuel reforming catalyst according to claim 1 or 2 is supported on a honeycomb monolith or porous ceramics.   The fuel reforming catalyst according to any one of claims 1 to 3, which is used for reforming ethanol.   A reforming reactor having the fuel reforming catalyst according to any one of claims 1 to 4, and a carbon monoxide shift reaction for reducing carbon monoxide contained in an exhaust gas from the reforming reactor by a water gas shift reaction. A fuel cell system comprising at least a reactor, a carbon monoxide selective reactor for removing carbon monoxide contained in exhaust gas from the carbon monoxide shift reactor, and a fuel cell.   A method for producing a fuel reforming catalyst, in which a metal is supported on a carrier, calcined in an air atmosphere at 400 to 550 ° C, and then calcined in a reducing atmosphere at 350 to 400 ° C.   The method for regenerating a fuel reforming catalyst according to claim 1, wherein the fuel reforming catalyst whose activity is reduced during the reaction is brought into contact with a reducing gas at 350 to 400 ° C.   The method for regenerating a fuel reforming catalyst according to claim 7, wherein the fuel reforming catalyst is brought into contact with an oxygen-containing gas at 400 to 550 ° C and then further brought into contact with a reducing gas at 350 to 400 ° C.

Images