JP2008031306A - Desulfurization process for hydrocarbon fuel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a desulfurization process using a desulfurization agent capable of keeping a desulfurization effect for a long period of time on desulfurization of a hydrocarbon fuel containing carbonyl sulfide in a state mixed with a minute amount of methanol or further with moisture of a minute amount. <P>SOLUTION: On desulfurizing the hydrocarbon fuel containing carbonyl sulfide and methanol, the desulfurization process of the hydrocarbon fuel comprises using a zeolite family desulfurizing agent which contains silver at least and also a ratio of SiO<SB>2</SB>/Al<SB>2</SB>O<SB>3</SB>in the zeolite being 2-3, and the desulfurizing agent whose surface area of the desulfurizing agent being more than 300 m<SP>2</SP>/g. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for desulfurizing a hydrocarbon fuel containing carbonyl sulfide and methanol. Furthermore, the present invention relates to a fuel cell system using a hydrocarbon fuel containing carbonyl sulfide and methanol as a raw fuel.

In a fuel cell system, in particular, a polymer electrolyte fuel cell (PEFC), which has recently developed significantly, in the process of obtaining hydrogen from a hydrocarbon-based raw fuel, first, sulfur contained in the raw fuel can be removed to a very low level. In addition, catalytic reaction steps such as reforming in the latter stage, water gas shift, and CO selective oxidation are essential for normal and long-term operation. For this reason, many fuel cell systems include a desulfurization section for removing sulfur contained in the raw fuel by adsorption or hydrocracking. Hydrodesulfurization catalysts and sulfur adsorbents are used as the types of desulfurization agents and catalysts used. Among them, sulfur can be removed to an extremely low level under mild conditions at normal pressure and relatively low temperature close to room temperature. Zeolite-based desulfurization agents loaded with silver or copper by ion exchange are industrially useful, such as domestic fuel cell systems using low-boiling hydrocarbons such as natural gas and LP gas (liquefied petroleum gas) as raw fuel (See, for example, Patent Documents 1 to 5 and Non-Patent Document 1).
JP 2001-286753 A JP 2001-305123 A JP 2004-168648 A JP 2004-277747 A Japanese Patent Laid-Open No. 2-73877 “Journal of the Chemical Society of Japan”, 1981, Vol. 12, p. 1945-1950

However, in some hydrocarbon fuels, a trace amount of methanol may be added as necessary. For example, in LP gas, methanol may be added to prevent freezing of mixed water, particularly in winter. It has been found that the performance of the zeolitic desulfurizing agent decreases when a hydrocarbon fuel to which methanol is added is used. This tendency is particularly remarkable when the temperature is low. In this way, when methanol coexists, the phenomenon that the desulfurization performance decreases at a low temperature is not preferable because it impairs the durability of the fuel cell system, and even if methanol is added, a desulfurization agent having a high desulfurization performance in a low temperature region is undesirable. It was desired.
On the other hand, Patent Document 1 discloses that high performance desulfurization performance can be obtained when water is mixed in a hydrocarbon fuel by supporting silver on a hydrophobic zeolite. However, the present inventors have found that the desulfurization agent described in Patent Document 1 shows only limited performance under the use conditions in which the hydrocarbon fuel contains methanol.
Therefore, development of a desulfurization agent that does not deteriorate the performance even under use conditions including methanol has been demanded. In addition, there has been a demand for the development of a desulfurization agent that does not deteriorate the performance even when a hydrocarbon-based fuel containing methanol and further containing 1 ppm by mass or more of water is used.

Furthermore, if hydrocarbon fuel contains carbonyl sulfide as a sulfur component, it cannot be removed only with a zeolite desulfurization agent, and a desulfurization agent is required to remove carbonyl sulfide before or after the zeolite desulfurization agent. Thus, the volume of the desulfurization apparatus is increased because the number of stages is two or more. Furthermore, when methanol is added, a carbonyl sulfide desulfurization agent that is usually used in multiple stages such as Ni, Cu, and Zn cannot be used because the performance is extremely lowered, particularly under conditions of low temperature. Therefore, development of a desulfurizing agent that removes carbonyl sulfide with one type of desulfurizing agent such as a zeolite-based desulfurizing agent has been desired for downsizing of the desulfurization apparatus and desulfurization of carbonyl sulfide (see, for example, Patent Documents 6 to 7). .
International Publication No. 2004/058927 Pamphlet JP 2005-68337 A

  The present invention provides a desulfurization effect for hydrocarbon fuels in which a trace amount of methanol is mixed in a hydrocarbon fuel containing a trace amount of carbonyl sulfide as a sulfur component, or a trace amount of moisture is further mixed. An object of the present invention is to provide a desulfurization method using a desulfurizing agent that can be maintained for a long period of time.

As a result of intensive studies to solve the above-mentioned problems, the present inventors used a zeolite-based desulfurizing agent containing at least silver as a desulfurizing agent in desulfurizing a hydrocarbon-based fuel containing carbonyl sulfide and methanol. and ranges _SiO 2 / _Al 2 _{O 3} ratio of the zeolite is 2-3, by the surface area used desulfurizing agent is 300 meters ² / g or more, found that the problem can be solved, and completed the present invention Has been reached.

That is, the present invention provides a zeolitic desulfurizing agent containing at least silver as a desulfurizing agent for desulfurizing a hydrocarbon fuel containing carbonyl sulfide and methanol, and the SiO ₂ / Al ₂ O ₃ ratio of the zeolite. And a desulfurization agent having a surface area of 300 m ² / g or more is used.

The present invention also relates to the above hydrocarbon-based fuel desulfurization method, wherein the reaction temperature is 100 ° C. or lower.
The present invention also relates to the above hydrocarbon fuel desulfurization method, wherein the concentration of methanol in the hydrocarbon fuel is 1 mass ppm or more.
The present invention also relates to the above hydrocarbon fuel desulfurization method, wherein the concentration of carbonyl sulfide in the hydrocarbon fuel is 0.1 mass ppm or more.
The present invention also relates to the above hydrocarbon fuel desulfurization method, wherein the hydrocarbon fuel contains 1 ppm by mass or more of water.

The present invention also relates to the above hydrocarbon fuel desulfurization method, wherein the zeolite is a faujasite type zeolite.
The present invention also relates to the above hydrocarbon fuel desulfurization method, wherein the hydrocarbon fuel is LP gas.

The present invention also relates to the aforementioned hydrocarbon fuel desulfurization method, wherein the zeolitic desulfurization agent is obtained by ion-exchange-supporting silver on zeolite.
The present invention also relates to the above hydrocarbon fuel desulfurization method, wherein the zeolite desulfurization agent is obtained by molding silver and then supporting silver.
The present invention also relates to the above hydrocarbon fuel desulfurization method, wherein the zeolitic desulfurization agent is obtained by performing a drying treatment at 80 ° C. or higher and 180 ° C. or lower after silver ion exchange.

The present invention also relates to a hydrogen production apparatus for a fuel cell system using the hydrocarbon-based fuel desulfurization method described above.
Furthermore, the present invention relates to a fuel cell system comprising the hydrogen production apparatus described above.

  By the desulfurization method of the present invention, desulfurization is performed in a state where a trace amount of carbonyl sulfide and a trace amount of methanol are mixed in the hydrocarbon fuel, preferably in a state where a trace amount of carbonyl sulfide, a trace amount of methanol and a trace amount of water are mixed. The performance of the agent can be maintained over a long period of time.

Hereinafter, the present invention will be described in more detail.
The hydrocarbon fuel used as the raw fuel in the present invention is a hydrocarbon fuel containing carbonyl sulfide and methanol. Examples of the hydrocarbon fuel include natural gas, LP gas, naphtha, gasoline, kerosene and the like. Among these, a fuel that is a gas at normal temperature and pressure, such as natural gas or LP gas, is preferable, and LP gas is more preferable.

In the case of LP gas, in addition to the components added to natural gas, lower mercaptans such as methyl mercaptan, ethyl mercaptan and propyl mercaptan, lower sulfides such as dimethyl sulfide, and carbonyl sulfide originally included in the LP gas production process And disulfides in which mercaptans are oxidatively coupled.
The sulfur concentration of LP gas is usually about 0.1 to 10 ppm by mass. However, when collecting gas from LP gas cylinders, it is known that the sulfur concentration varies depending on the remaining amount of cylinders. In some cases, it may exceed 100 ppm by mass in a short period.
In addition, naphtha and kerosene with a high average molecular weight are liquid at room temperature, so there is no need to add an odorant, but the concentration of sulfur contained in the raw material is high, and the types of sulfur compounds contained are higher in molecular weight. It reaches. In addition to mercaptans and sulfides, sulfur compounds include thiophenes, substituted thiophenes, benzothiophenes, and the like, and the sulfur content ranges from several ppm to several tens of ppm.

In the present invention, a hydrocarbon-based fuel containing a carbonyl sulfide as a sulfur compound is used. The content of carbonyl sulfide is usually 0.1 mass ppm or more, for example, 0.1 to 20 mass ppm, preferably 0.2 to 15 mass ppm, more preferably 0.5 to 10 mass ppm.
In addition, although there is no restriction | limiting in particular about content of sulfur compounds other than carbonyl sulfide, it is preferable that it is 100 mass ppm or less, and it is the range of 0.01-100 mass ppm normally.

  In the present invention, a hydrocarbon-based fuel in which methanol is mixed in addition to carbonyl sulfide is used. The content of methanol is usually 1 ppm by mass or more, for example, 1 to 10,000 ppm by mass, preferably 10 to 5,000 ppm by mass, and more preferably 100 to 2,000 ppm by mass. Particularly in the case of LP gas, methanol is usually added artificially for the purpose of preventing inconveniences such as freezing of mixed water, particularly in winter, and clogging of piping and switching regulators. Usually, this methanol is added in an amount of 100 to 5,000 mass ppm, preferably 300 to 2,500 mass ppm, with respect to the liquid LP gas in the cylinder. In the case of a system in which LP gas is extracted as a liquid and vaporized outside the cylinder, the methanol concentration in the hydrocarbon-based fuel introduced into the fuel cell system becomes equal to the methanol concentration in the liquid LP gas.

  On the other hand, when the LP gas vaporized in the cylinder is introduced into the fuel cell system, the methanol concentration in the vaporized LP gas does not necessarily match the concentration in the liquid LP gas, but usually 1 to 10,000 masses. LP gas having a methanol concentration of about ppm, preferably about 10 to 5,000 mass ppm, more preferably about 100 to 2,000 mass ppm is introduced into the fuel cell system.

The desulfurizing agent used in the present invention is a zeolitic desulfurizing agent containing at least silver. As the zeolite used here, various zeolites such as A type and faujasite type can be used, and among them, the faujasite type is preferably used.
As the zeolite, one having a specific SiO ₂ / Al ₂ O ₃ ratio (molar ratio) is used. That is, it is necessary that the SiO ₂ / Al ₂ O ₃ ratio is in the range of 2 to 3, preferably 2.2 to 3, more preferably 2.3 to 3. When the SiO ₂ / Al ₂ O ₃ ratio is greater than 3, an adverse effect is observed on the desulfurization agent life under the use conditions of the present invention, and sufficient desulfurization performance cannot be obtained. On the other hand, when the SiO ₂ / Al ₂ O ₃ ratio is smaller than 2, it is not preferable because a sufficient desulfurizing agent life cannot be obtained.

The surface area of the desulfurizing agent needs to be 300 m ² / g or more, and preferably 320 m ² / g or more. When the surface area is lower than 300 m ² / g, the desulfurization performance is not sufficient, which is not preferable.

  The supported amount of silver is preferably 10 to 30% by mass, more preferably 15 to 25% by mass, based on the total amount of the desulfurizing agent. When the supported amount is less than 10% by mass, the desulfurization performance is not sufficient, and when it is more than 30% by mass, the desulfurization performance corresponding to the addition amount of silver is not exhibited, which is not preferable.

  As a method for supporting silver, an ion exchange method is preferably used. As the zeolite used for ion exchange, various types such as sodium type, ammonium type, and hydrogen type can be used, and the sodium type is most preferably used. On the other hand, silver is usually prepared as a cation dissolved in water. Specific examples thereof include an aqueous solution of silver nitrate and silver perchlorate, an aqueous solution of silver ammine complex ion, and the like, and an aqueous silver nitrate solution is most preferably used. The density | concentration of the aqueous solution containing silver ion is 0.5-10 mass% normally as a density | concentration of silver, Preferably it is the range of 1-5 mass%.

The method of ion exchange is not particularly limited, but usually the above-mentioned zeolite is added to the above solution containing cationic silver, and it is usually 0 to 90 ° C., preferably 20 to 70 ° C. for 1 hour to The ion exchange treatment is performed for several hours, preferably with stirring.
After ion exchange, solids are separated by means such as filtration, washed with water, etc., and then dried at a temperature of 80 ° C. or higher and 180 ° C. or lower, more preferably 85 ° C. or higher and 150 ° C. or lower. This ion exchange treatment can be repeated. A temperature lower than 80 ° C. is not preferable because drying is insufficient. Moreover, when higher than 180 degreeC, since aggregation of a metal is accelerated | stimulated, it is unpreferable. After the drying process, it is preferable not to perform the baking treatment for the sake of simplification of the manufacturing process. By such a method, the target silver ion exchange zeolite can be obtained.

  Zeolite supporting silver produced by the above method is made of alumina, silica, clay mineral, etc., or a precursor thereof as an appropriate binder, extrusion molding, tableting molding, rolling granulation, spray drying. And it can be molded and used by a usual method such as firing as necessary.

  In addition, it is also preferable to pre-mold zeolite and apply the above ion exchange method thereafter. According to the results examined by the present inventors, when a small amount of methanol is mixed in a hydrocarbon fuel, it is generally better to use a desulfurizing agent obtained by ion exchange after molding. Was found. Therefore, in the present invention, a method of ion exchange after molding is more preferably employed.

  The silver ion exchange zeolite thus produced is a hydrocarbon fuel containing carbonyl sulfide as a sulfur compound, preferably a fuel that is a gas at normal temperature and pressure, such as natural gas or LP gas, more preferably LP gas. It can be suitably used for the removal of contained sulfur compounds. Under desulfurization conditions, it is usually preferable that the hydrocarbon fuel is in a vaporized state. The desulfurization temperature is selected in the range of −50 ° C. to 100 ° C., preferably −20 ° C. to 80 ° C. When the temperature is higher than 100 ° C., the deterioration of silver is accelerated under the condition containing methanol, and when the temperature is lower than −50 ° C., sufficient activity is not exhibited, which is not preferable.

When using a fuel which is gaseous at normal temperature and pressure, such as natural gas or LP gas, GHSV is 10~100,000h ^-1, preferably chosen between 100~10,000h ^-1. When GHSV is lower than 10 h ⁻¹ , the desulfurization performance is sufficient, but since the desulfurizing agent is used more than necessary, the desulfurizer becomes excessively unfavorable. On the other hand, if GHSV is greater than 100,000 h ⁻¹ , sufficient desulfurization performance cannot be obtained. In addition, liquid fuel can also be used, and in that case, it is used in the range of 0.1 to 1,000 h ⁻¹ as WHSV.
The working pressure is usually selected in the range of normal pressure to 1 MPa (gauge pressure, the same shall apply hereinafter), preferably normal pressure to 0.5 MPa, more preferably normal pressure to 0.2 MPa. Most preferably, it can be implemented.

  In the desulfurization method of the present invention, the zeolitic desulfurizing agent is usually used by being filled in a desulfurizer installed in a flow reaction tube. The flow-type reaction tube may be of any known type and shape, and may be provided with, for example, a temperature control function, a pressure control function, or the like, or may not be provided. In addition, when the desulfurization agent is insufficient in desulfurization, another desulfurization agent can be disposed in the subsequent stage. Examples of the desulfurizing agent that can be used at that time include desulfurizing agents including at least one selected from nickel, chromium, manganese, cobalt, copper, silver, zinc, and iron, and those including nickel are preferable.

  The desulfurization method of this invention can be used in the desulfurization part of the hydrogen production apparatus for fuel cell systems. Hydrogen production equipment usually uses a desulfurization unit that removes sulfur from hydrocarbon-based fuel, a reforming unit that decomposes hydrocarbon-based fuel in the presence of steam and oxygen if necessary, and hydrogen generated in the reforming unit. Selective oxidation that converts carbon monoxide mixed into carbon dioxide and hydrogen by reaction with water vapor, and selective oxidation that selectively converts carbon monoxide remaining in the shift portion to carbon dioxide by reaction with oxygen It consists of parts. Alternatively, an apparatus for obtaining pure hydrogen can be assembled by arranging a membrane separation hydrogen purification apparatus using a palladium membrane or the like in the reforming section or the shift section. As described above, any known configuration can be used for the hydrogen production apparatus of the present invention. However, it is preferable that the desulfurization unit using the desulfurization method of the present invention is disposed upstream of the reforming unit.

An example of a hydrogen production apparatus will be described in more detail. The hydrogen production apparatus can include a desulfurization unit, a reforming unit, a shift unit, and a selective oxidation unit. The desulfurization part is as described above.
The reforming section can take any form of a steam reforming reaction or an autothermal reforming reaction. There is no restriction | limiting in particular as a reforming catalyst used in a reforming part, Arbitrary things can be suitably selected and used from the well-known thing conventionally known as a reforming catalyst of a hydrocarbon fuel. As such a reforming catalyst, for example, a suitable carrier carrying nickel or a noble metal such as ruthenium, rhodium or platinum can be used. The supported metal may be a single type or a combination of two or more types.

When employing a steam reforming reaction in the reforming section, the reaction temperature can be 450 ° C to 900 ° C, preferably 500 ° C to 850 ° C, and more preferably 550 ° C to 800 ° C. The amount of steam introduced into the reaction system is defined as the ratio of the number of moles of water molecules to the number of moles of carbon atoms contained in the feed hydrocarbon fuel (steam / carbon ratio), and this value is preferably 0.5-10. Preferably it is 1-7, More preferably, it is 2-5. The space velocity (WHSV) at this time can be expressed as A / B when the flow rate of the hydrocarbon fuel in the liquid state is A (kg / h) and the catalyst weight is B (kg), and this value is preferably It is set in the range of 0.05 to 20 h ⁻¹ , more preferably 0.1 to 10 h ⁻¹ , and still more preferably 0.2 to 5 h ⁻¹ .

  On the other hand, it is also possible to adopt an autothermal reforming reaction in which oxygen, preferably air, is introduced into the reforming section and the combustion reaction and the decomposition reaction proceed in the same reactor. The reaction is carried out in the presence of a metal catalyst, typically a Group VIII metal such as cobalt, iron, ruthenium, rhodium, iridium and platinum. The amount of steam introduced into the reaction system is preferably 0.3 to 10, more preferably 0.5 to 5, and still more preferably 1 to 3, as a steam / carbon ratio.

In autothermal reforming, oxygen is added to the raw material in addition to steam. The oxygen source may be pure oxygen, but in many cases air is used. Usually, oxygen is added to such an extent that it can generate an amount of heat that can balance the endothermic reaction associated with the steam reforming reaction, but the amount of addition is appropriately determined in relation to heat loss and external heating installed as necessary. The amount is preferably 0.05 to 1, more preferably 0.1 to 0.75, and even more preferably as a ratio of the number of moles of oxygen molecules to the number of moles of carbon atoms contained in the raw hydrocarbon fuel (oxygen / carbon ratio). Is 0.2 to 0.6. The reaction temperature of the autothermal reforming reaction is set in the range of 450 ° C. to 900 ° C., preferably 500 ° C. to 850 ° C., more preferably 550 ° C. to 800 ° C., as in the case of the steam reforming reaction. The space velocity (WHSV) at this time is preferably selected in the range of 0.1 to 30 h ⁻¹ , more preferably 0.5 to 20 h ⁻¹ , and still more preferably ¹ to 10 h ⁻¹ .
In any case, the pressure of the reforming reaction is not particularly limited, but is preferably in the range of atmospheric pressure to 2 MPa, more preferably atmospheric pressure to 0.5 MPa, and further preferably atmospheric pressure to 0.2 MPa.

  The reformed gas generated in the reformer includes carbon monoxide, carbon dioxide, methane, water vapor and the like in addition to hydrogen. Further, nitrogen is also contained when air is used as an oxygen source in the autothermal reforming. Shifting the process of converting carbon monoxide to water and carbon dioxide by reacting it with water in order to increase the hydrogen concentration and also to reduce the carbon monoxide concentration because carbon monoxide can be a catalyst poison. Part. Usually, the reaction proceeds in the presence of a catalyst, and a catalyst containing a noble metal such as a mixed oxide of Fe—Cr, a mixed oxide of Zn—Cu, platinum, ruthenium, and iridium is used. The mol% calculated excluding the above is preferably reduced to 2% by mass or less, more preferably 1% by mass or less, and further preferably 0.5% by mass or less. The shift reaction can also be carried out in two stages, and in this case, it is preferably composed of a high temperature shift reactor and a low temperature shift reactor.

  For example, in the polymer electrolyte fuel cell system, it is preferable to further reduce the carbon monoxide concentration. For this purpose, the outlet gas of the shift reactor is processed in the selective oxidation unit. In this step, a catalyst containing iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium, platinum, copper, silver, gold, or the like is used, and preferably 0.5 mol relative to the remaining number of moles of carbon monoxide. The carbon monoxide is selectively converted to carbon dioxide by adding 10 to 10 times mol, more preferably 0.7 to 5 times mol, and still more preferably 1 to 3 times mol, and the carbon monoxide concentration is preferably Is reduced to 10 mass ppm or less. In this case, the carbon monoxide concentration can be reduced by reacting with the coexisting hydrogen simultaneously with the oxidation of carbon monoxide to generate methane.

  In the fuel cell system of the present invention, hydrogen having a low carbon monoxide content thus obtained is introduced into the fuel cell and used for power generation. As the fuel cell, a known cell stack such as a solid polymer type (PEFC), a phosphoric acid type (PAFC), a solid oxide type (SOFC), a molten carbonate type (MCFC) can be used. A polymer type is used.

Next, a configuration of a polymer electrolyte fuel cell will be described as an embodiment of the fuel cell.
A polymer electrolyte fuel cell comprises an anode (fuel electrode), a cathode (air electrode), and a solid polymer electrolyte sandwiched between these electrodes. The reformer containing hydrogen obtained by the above reformer on the anode side. The gas is supplied after the carbon monoxide concentration is reduced through the shift reactor and the selective oxidation reactor, and an oxygen-containing gas such as air is supplied to the cathode side. On both the anode side and the cathode side, the supplied gas is introduced after appropriate humidification treatment if necessary.

  At this time, a reaction in which hydrogen gas becomes protons and emits electrons proceeds at the anode, and a reaction in which oxygen gas obtains electrons and protons to become water proceeds at the cathode. In order to promote these reactions, platinum black and a Pt catalyst or Pt-Ru alloy catalyst supported on activated carbon are used for the anode, and platinum black or a Pt catalyst supported on activated carbon is used for the cathode. In general, both the anode and cathode catalysts are formed into a porous catalyst layer together with polytetrafluoroethylene, a low molecular weight polymer electrolyte membrane material, activated carbon and the like as necessary.

  As solid polymer electrolytes, Nafion (Nafion, manufactured by DuPont), Gore (Gore, manufactured by Gore), Flemion (Flemion, manufactured by Asahi Glass), Aciplex (Aciplex, manufactured by Asahi Kasei), etc. A molecular electrolyte membrane can be used, and the porous catalyst layer is laminated on both sides thereof to form an MEA (Membrane Electrode Assembly). Further, the fuel cell is assembled by sandwiching the MEA with a separator having a gas supply function, a current collection function, particularly an important drainage function in the cathode, and the like made of a metal material, graphite, carbon composite or the like. The electric load is electrically connected to the anode and the cathode.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

(1) Production of catalyst by ion exchange of powdered zeolite (Method A)
An aqueous silver nitrate solution was prepared by adding 600 ml of distilled water to 30 g of silver nitrate. Next, the mixture was mixed with 50 g of NaX-type zeolite powder with SiO ₂ / Al ₂ O ₃ (molar ratio, the same shall apply hereinafter) = 2.5 with stirring, and ion exchange was performed. Then, it was washed with distilled water so as not to leave nitrate radicals. After washing, it was dried in air at 130 ° C. overnight. 5 g of an alumina binder was mixed with 30 g of the powdered silver exchanged zeolite after drying, and extrusion molding was performed at 1 mmφ to obtain a desulfurizing agent.
Similarly, a desulfurization agent was prepared using NaY type zeolite (SiO ₂ / Al ₂ O ₃ = 5.5) and USY type zeolite (SiO ₂ / Al ₂ O ₃ = 9).
Table 1 summarizes the prepared desulfurizing agents and the amounts of reagents used for ion exchange. Silver loading was determined by elemental analysis.

(2) Production of catalyst by ion exchange of zeolite after extrusion molding (Method B)
1 kg of alumina binder was mixed with 5 kg of powder of NaX-type zeolite (SiO ₂ / Al ₂ O ₃ = 2.5), and extrusion molded at 1 mmφ to produce an extruded molded product.
Similarly, an extruded product was prepared using NaY type zeolite (SiO ₂ / Al ₂ O ₃ = 5.5) and USY type zeolite (SiO ₂ / Al ₂ O ₃ = 9).
30 g of this extrusion-molded product was taken and mixed with a silver nitrate aqueous solution in which a predetermined amount of silver nitrate was dissolved in 300 ml of distilled water with stirring to perform ion exchange. Then, it was washed with distilled water so as not to leave nitrate radicals. After washing, it was dried in air at 130 ° C. overnight.
Table 2 shows the prepared desulfurizing agent and the amount of raw materials used for the preparation. Silver loading was determined by elemental analysis.

(3) Performance test of desulfurization agent 6 ml of the prepared desulfurization agent was charged into a flow-type reaction tube, and LP gas containing 1,000 mass ppm of methanol (sulfur concentration: 3 mass ppm, carbonyl sulfide concentration: 1 mass ppm, 2 Carbon sulfide concentration: 0.05 mass ppm) was circulated at normal pressure with GHSV = 9,000 h ⁻¹ . The sulfur concentration at the inlet and outlet of the reaction tube was measured by SCD (Sulfur Chemiluminescence Detector) gas chromatography. Since the LP gas used in this test contained some water, its amount was measured at any time during the period of this test, but it varied between 2 and 100 ppm by mass.

[Example 1]
The desulfurization agent NaX-A1 was tested by the above test method. At this time, the reaction temperature was 25 ° C. When the sulfur concentration of the outlet gas was measured 170 hours after the start of the experiment, it was below the detection limit (20 mass ppb).

[Examples 2-14 and Comparative Examples 1-12]
Similarly, the total sulfur concentration of the outlet gas after 170 hours was measured using each desulfurization agent, and the time for those exceeding the detection limit was recorded. The results are shown in Table 3.

By comparing Examples 1 to 3 and Comparative Examples 1 to 3, it can be seen that for the desulfurizing agent prepared by Method A, the one using NaX zeolite gives the best results. This is evident by comparing NaX-A3 / NaY-A2 / USY-A1 and NaX-A2 / NaY-A1 with approximately the same loading. Moreover, it has been confirmed that most of the sulfur compounds detected at the outlet of the desulfurizing agent are carbonyl sulfide, and it can be seen that carbonyl sulfide cannot be completely removed except for NaX zeolite.
By comparing Examples 4 to 6 and Comparative Examples 4 to 6, it can be seen that the desulfurization agent prepared by Method B uses NaX zeolite to give the best results. This is evident by comparing NaX-A3 / NaY-A2 / USY-A1 and NaX-A2 / NaY-A1 with approximately the same loading. Moreover, it has been confirmed that most of the sulfur compounds detected at the outlet of the desulfurizing agent are carbonyl sulfide, and it can be seen that carbonyl sulfide cannot be completely removed except for NaX zeolite.
Examples 7 to 12 show that the desulfurization agent of the present invention can be used in a wide temperature range.
By comparing Examples 2 and 5 and Comparative Examples 7 to 8, it can be confirmed that sulfur compounds such as carbonyl sulfide can be removed when the surface area of the NaX zeolite is 300 m ² / g or more.
By comparing Examples 13 to 14 and Comparative Examples 9 to 12, it can be confirmed that the NaX zeolite can remove sulfur compounds such as carbonyl sulfide even at a low temperature of 0 ° C.

[Example 15]
A fuel cell system using the desulfurization method of the present invention will be described. FIG. 1 is a schematic view showing an example of a fuel cell system of the present invention.
In FIG. 1, the fuel vaporized in the LP gas cylinder 3 flows into the desulfurizer 5 filled with NaX-B2 through the pressure reducing valve 4. At this time, the GHSV of the desulfurizer is set to 500 h- ¹ . The fuel desulfurized in the desulfurizer 5 is mixed with the water vapor produced from the water tank 1 via the water pump 2 and the vaporizer 6, and the reformer 7 filled with ₂ % by mass Ru / Al ₂ O ₃ as a catalyst. Is sent to. At this time, the steam / carbon ratio is set to 3.0. In addition, the space velocity of the distribution raw material is set to 0.5 h ⁻¹ for WHSV. The reformer reaction tube is heated by a burner 18 using fuel from the fuel tank and anode off gas as fuel, and is adjusted to 700 ° C.
The gas containing hydrogen and carbon monoxide produced in this way used a high-temperature shift reactor 9 using an iron-chromium-based catalyst, a low-temperature shift reactor 10 using a copper-zinc-based catalyst, and a ruthenium catalyst. By sequentially passing through the selective oxidation reactor 11, the carbon monoxide concentration is reduced to a level that does not affect the characteristics of the fuel cell.
The polymer electrolyte fuel cell 17 comprises an anode 12, a cathode 13, and a solid polymer electrolyte 14, and a fuel gas containing high-purity hydrogen obtained by the above method is provided on the anode side, and an air blower is provided on the cathode side. The air sent from 8 is introduced after appropriate humidification processing (a humidifier is not shown) if necessary. The electric load 15 is electrically connected to the anode and the cathode.
The anode off-gas is combusted in the burner 18 and used to warm the reforming tube, and then discharged. The cathode off gas is discharged from the exhaust port 16.
In the above test apparatus, operation was performed using LP gas containing 500 mass ppm of methanol, 10 mass ppm of water, and 2 mass ppm of carbonyl sulfide as fuel in the liquefied state in the LP gas cylinder. As a result of analyzing the gas at the anode inlet, it contained 72 vol% hydrogen (excluding water vapor).
During the test period (170 hours), the reformer operated normally and no decrease in the activity of the catalyst was observed. The fuel cell also operated normally and the electric load 15 was operated smoothly.

It is the schematic which shows an example of the fuel cell system of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Water tank 2 Water pump 3 LP gas cylinder 4 Pressure reducing valve 5 Desulfurizer 6 Vaporizer 7 Reformer 8 Air blower 9 High temperature shift reactor 10 Low temperature shift reactor 11 Selective oxidation reactor 12 Anode 13 Cathode 14 Solid polymer electrolyte 15 Electric load 16 Cathode off-gas outlet 17 Polymer electrolyte fuel cell 18 Burner

Claims (12)

When desulfurizing a hydrocarbon-based fuel containing carbonyl sulfide and methanol, the desulfurizing agent is a zeolite-based desulfurizing agent containing at least silver, and the zeolite has a SiO ₂ / Al ₂ O ₃ ratio of 2 to 3. A desulfurization method for hydrocarbon fuel, wherein a desulfurization agent having a surface area of 300 m ² / g or more is used.   The method for desulfurizing a hydrocarbon fuel according to claim 1, wherein the reaction temperature is 100 ° C or lower.   The method for desulfurizing a hydrocarbon fuel according to claim 1 or 2, wherein the concentration of methanol in the hydrocarbon fuel is 1 mass ppm or more.   The method for desulfurizing a hydrocarbon fuel according to any one of claims 1 to 3, wherein the concentration of carbonyl sulfide in the hydrocarbon fuel is 0.1 mass ppm or more.   The hydrocarbon-based fuel desulfurization method according to any one of claims 1 to 4, wherein the hydrocarbon-based fuel contains 1 mass ppm or more of water.   The method for desulfurizing a hydrocarbon fuel according to any one of claims 1 to 5, wherein the zeolite is a faujasite type zeolite.   The hydrocarbon-based fuel desulfurization method according to any one of claims 1 to 6, wherein the hydrocarbon-based fuel is LP gas.   The method for desulfurizing a hydrocarbon fuel according to any one of claims 1 to 7, wherein the zeolitic desulfurizing agent is obtained by ion-exchange-supporting silver on zeolite.   The method for desulfurizing a hydrocarbon fuel according to any one of claims 1 to 8, wherein the zeolitic desulfurizing agent is obtained by supporting silver after molding the zeolite.   The method for desulfurizing a hydrocarbon fuel according to any one of claims 1 to 9, wherein the zeolitic desulfurizing agent is obtained by performing a drying treatment at 80 ° C or higher and 180 ° C or lower after ion exchange of silver.   11. A hydrogen production apparatus for a fuel cell system, wherein the desulfurization method according to claim 1 is used.   A fuel cell system comprising the hydrogen production apparatus according to claim 11.

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