JP5275114B2 - Hydrocarbon desulfurization agent and production method thereof, hydrocarbon desulfurization method, and fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a desulfurizing agent for a hydrocarbon having desulfurization performance for removing a sulfur content in the hydrocarbon, especially in a kerosene to a low concentration about (about 20 mass ppb) even in non-copresence of hydrogen, excellent in durability and capable of simplifying a manufacturing step. <P>SOLUTION: The desulfurizing agent for the hydrocarbon includes 10-30 mass% of porous inorganic oxide making the whole mass of the desulfurizing agent as the reference, 3-40 mass% of zinc oxide and 45-75 mass% of nickel atom by nickel oxide conversion. A reduction degree of the nickel atom is 50-80%, and the hydrogen adsorption amount per unit mass of the desulfurizing agent is 3.5-4.6 ml/g. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a hydrocarbon desulfurization agent used for hydrocarbons, particularly a raw fuel such as a fuel cell, and a method for producing the same, and a method for producing a hydrocarbon desulfurization agent for a fuel cell system. The present invention also relates to a method for desulfurizing a hydrocarbon containing a sulfur compound using the desulfurizing agent, and further to a fuel cell system including a hydrocarbon desulfurization apparatus using the desulfurizing agent.

  In recent years, new energy technology has attracted attention due to environmental problems, and fuel cells are attracting attention as one of the new energy technologies. This fuel cell has a feature that high energy efficiency can be obtained because a free energy change caused by a fuel combustion reaction can be directly taken out as electric energy. In addition to the fact that it does not emit harmful substances, it is being developed for various uses. In particular, polymer electrolyte fuel cells are characterized by high power density, compactness, and operation at low temperatures.

  In general, as a fuel gas for a fuel cell, a gas containing hydrogen as a main component is used, but as a raw fuel for obtaining a fuel gas containing this hydrogen, hydrocarbons such as natural gas, LPG, naphtha, kerosene, Alternatively, alcohols such as methanol and ethanol, or ethers such as dimethyl ether are used. Reforming reaction of raw fuel containing carbon and hydrogen with catalyst on steam, partial oxidation reaction with oxygen-containing gas, or self-heat recovery type reforming reaction in a system where steam and oxygen-containing gas coexist In general, a gas containing hydrogen and carbon monoxide is generated, and a process for reducing or removing carbon monoxide is generally used as a fuel for a fuel cell.

  However, sulfur compounds are often present in these raw fuels, particularly petroleum-derived raw fuels, as impurities, or in the case of natural gas or the like as odorants for detecting leaks. When is used, it is inevitable that sulfur-containing compounds are mixed in the fuel hydrogen for fuel cells. Each process of raw fuel reforming and carbon monoxide removal for producing fuel hydrogen for fuel cells, and as a cathode electrocatalyst, metals such as noble metals or copper are often used in a reduced state. In contrast to this metal catalyst, the sulfur compound acts as a catalyst poison, and there is a problem that the catalytic activity of the hydrogen production process or the battery itself is lowered, and the efficiency as the battery is lowered. Therefore, it is necessary to sufficiently remove the sulfur contained in the raw fuel so that the catalyst used in the hydrogen production process, and further, the electrode catalyst of the battery can be used stably for a long time with its original performance. It is essential.

  Since the concentration of sulfur in the raw fuel for fuel cells needs to be reduced to the extent that the catalyst used in the reforming process functions sufficiently, the desulfurization process for removing sulfur in the raw fuel is basically a hydrogen production process. It is provided before the process. Conventionally, the sulfur concentration in the raw fuel treated in the desulfurization process has been said to be 0.1 mass ppm or less or 0.05 mass ppm (50 mass ppb) or less as a sulfur atom. The required performance has become strict, and it has been required to be 0.02 mass ppm (20 mass ppb) or less.

  Until now, as a method for desulfurizing raw fuel for fuel cells, a hydrodesulfurization catalyst was used to hydrodesulfurize a difficult-to-desulfurize organic sulfur compound to convert it into hydrogen sulfide that can be easily adsorbed and removed. It seems that the method of processing is suitable. However, while a general hydrodesulfurization catalyst requires high hydrogen pressure, the pressure in the fuel cell system aims to develop a technology that makes the pressure at atmospheric pressure or at most about 1 MPa. The present situation is that a desulfurization process using a hydrodesulfurization catalyst cannot be adopted.

  For this reason, in the development of fuel cell power generation systems, research has been conducted on a desulfurization agent that can sufficiently exhibit a desulfurization function even under low pressure or in the absence of hydrogen, and a desulfurization agent in which nickel is supported on an inorganic carrier has been proposed. ing. Various studies have been made to improve the desulfurization activity and life. For example, Patent Document 1 below discloses a desulfurization agent containing 95% or more of metallic nickel with respect to the total nickel content. Patent Document 2 below discloses a desulfurization agent in which 80 mol% or more of the nickel component is in a metal state and the metal crystallite diameter is 4.0 nm or less. Patent Document 3 below discloses a desulfurization agent in which nickel and copper are supported on a carrier, 60% or more of nickel is a metal, and the hydrogen adsorption amount is 0.15 mmol / g or more. In these prior arts, when only nickel is used as the active metal, a high degree of nickel reduction (ratio of the amount of metallic nickel to the total nickel content) and good nickel metal particle dispersion required to enhance desulfurization performance It is difficult to achieve both, and copper is used as the active metal together with nickel. By the way, in a household fuel cell system, an operation called “Daily Start-up Shut-down (DSS) operation”, in which start and stop are repeated every day, is assumed. Along with this operation, the desulfurization agent used in the system receives a repeated heat history of temperature increase / decrease. The desulfurization agent using the supported nickel-copper as the active metal has a problem that the metal particles easily aggregate due to the thermal history, and the desulfurization performance is deteriorated in a short period of time. Therefore, development of a desulfurization agent not containing copper is desired.

  On the other hand, the present applicant has filed a patent application for a desulfurization agent for kerosene containing nickel oxide, zinc oxide, and silica, suppressing carbon deposition, and having high activity and long life (see Patent Document 4 below). However, further improvement in performance is desired in response to market needs for higher performance and longer life.

  Patent Document 5 listed below discloses a catalyst adsorbent containing a nickel compound or nickel hydroxy carbonate supported on a silica carrier, an alumina promoter and an alkaline earth metal compound promoter. There is a description that the catalyst adsorbent can be activated by a reduction treatment at a lower temperature than a conventional desulfurizing agent. However, the preferable reduction temperature is still as high as 400 ° C., and the performance of the desulfurizing agent obtained thereby is desired to be further improved.

  Furthermore, the conventional desulfurization agent for fuel cell systems has a high manufacturing temperature due to the high temperature when the precursor is reduced and activated, and the manufacturing cost is increased. It was.

JP 2001-279259 A JP 2005-146054 A JP 2004-75778 A JP 2008-115309 A Japanese translation of PCT publication No. 2006-501065

  As described above, in a fuel cell system using hydrocarbon as a raw material, in a conventional desulfurization process using a desulfurization agent, a subsequent process for producing fuel hydrogen and a power generation process are performed under low pressure, particularly in the absence of hydrogen. It has been difficult to maintain sufficient desulfurization for a long time so that it can be stably operated for a long time. Therefore, it has been desired to develop a desulfurizing agent that can sufficiently remove sulfur in hydrocarbons, maintain its desulfurization performance for a long time, and can simplify the manufacturing process. .

  The present invention has a desulfurization performance that removes the sulfur content in hydrocarbons, particularly kerosene, to a low concentration (about 20 mass ppb) even in the absence of hydrogen, has excellent durability, and simplifies the manufacturing process. An object is to provide a hydrocarbon desulfurization agent. It is another object of the present invention to provide a method for producing the desulfurizing agent, a method for desulfurizing hydrocarbons using the desulfurizing agent, and a fuel cell system using hydrocarbons using the desulfurizing agent as raw fuel.

  As a result of diligent research on the above problems, the present inventors have not been able to obtain by a conventional technique by subjecting a precursor of a hydrocarbon desulfurization agent having a specific property to a calcination treatment and / or a reduction treatment under specific conditions. The present inventors have found that a hydrocarbon desulfurization agent having an excellent structure and excellent desulfurization performance and durability can be obtained.

  That is, in one aspect of the present invention, 10 to 30% by mass of a porous inorganic oxide, 3 to 40% by mass of zinc oxide, and 45 to 75% by mass in terms of nickel oxide based on the total mass of the desulfurizing agent. Desulfurization for hydrocarbons, characterized in that the reduction degree of nickel atoms is 50 to 80% and the hydrogen adsorption amount per unit mass of desulfurization agent is 3.5 to 4.6 ml / g It is an agent.

  In the hydrocarbon desulfurization agent of the above-described aspect, the porous inorganic oxide is preferably silica or alumina.

  Moreover, in the hydrocarbon desulfurization agent of the aspect mentioned above, it is preferable that the silica is modified with aluminum.

  Moreover, the other aspect of this invention is 45-75 in conversion of 10-30 mass% porous inorganic oxide, 3-40 mass% zinc oxide, and nickel oxide on the basis of the desulfurization agent precursor total mass. A hydrocarbon desulfurizing agent precursor containing a mass% of nickel atoms and carbon atoms and having a carbon atom / nickel atom molar ratio of 0.065 to 0.094 is reduced at 200 to 300 ° C. It is a manufacturing method of the desulfurization agent for hydrocarbons characterized by including a process.

  Still another embodiment of the present invention is a porous inorganic oxide of 10 to 30% by mass, 3 to 40% by mass of zinc oxide, and 45 to 45% in terms of nickel oxide based on the total mass of the desulfurizing agent precursor. A hydrocarbon desulfurization agent precursor containing 75 mass% nickel atoms and carbon atoms and having a carbon atom / nickel molar ratio of 0.065 to 0.094 is calcined at 160 to 300 ° C. And a step of producing a calcined precursor and a step of reducing the calcined precursor at 200 to 300 ° C., which is a method for producing a hydrocarbon desulfurization agent.

  In the method for producing a hydrocarbon desulfurization agent of the above-described aspect, the porous inorganic oxide is preferably silica or alumina.

  Moreover, in the manufacturing method of the hydrocarbon desulfurization agent of the aspect mentioned above, it is preferable that the silica is modified with aluminum.

  According to still another aspect of the present invention, in the reduction treatment step, the hydrocarbon desulfurization agent precursor or the firing precursor is filled in a desulfurization reactor for a fuel cell system. It is a manufacturing method of the desulfurization agent for hydrocarbons for fuel cell systems by the manufacturing method of the desulfurization agent for hydrogen.

  Yet another embodiment of the present invention is a hydrocarbon desulfurization method comprising contacting the hydrocarbon desulfurization agent of the above-described embodiment with a hydrocarbon containing a sulfur compound.

  In the hydrocarbon desulfurization method of the aspect described above, the hydrocarbon is preferably kerosene.

  Still another aspect of the present invention is a fuel cell using a hydrocarbon as a raw fuel, comprising a hydrocarbon desulfurization device having a reactor filled with the hydrocarbon desulfurization agent of the above-described aspect. System.

  According to the present invention, sulfur contained in hydrocarbons, particularly kerosene, can be efficiently removed even in the absence of hydrogen, and the durability for maintaining a certain desulfurization performance is significantly improved. A long-lived hydrocarbon desulfurization agent is provided. In addition, a fuel cell system using a hydrocarbon having a desulfurization process filled with the desulfurizing agent as a raw fuel can stably generate power efficiently for a long time. Furthermore, it is possible to provide a desulfurization agent having high desulfurization performance by reduction treatment at a low temperature, eliminating the need for equipment and stabilization treatment for reduction treatment at a high temperature, and simplifying the production process and reducing costs of the desulfurization agent. It becomes.

1 is a schematic diagram illustrating an example of a fuel cell system according to an embodiment.

  Hereinafter, preferred embodiments of the present invention will be described in detail.

  A hydrocarbon desulfurization agent (hereinafter, also referred to as “desulfurization agent of this embodiment”) according to an embodiment will be described. In the present application, the hydrocarbon desulfurizing agent is a function of adsorbing a sulfur compound contained in the hydrocarbon, a catalytic function of converting the sulfur compound into a sulfur compound that is more easily adsorbed, and the converted sulfur compound. It has at least one kind of function of adsorbing.

  The content of the porous inorganic oxide contained in the desulfurizing agent of the present embodiment on the basis of the total mass of the desulfurizing agent is 10 to 30% by mass, preferably 15 to 30% by mass. When the content is less than 10% by mass, the specific surface area of the desulfurizing agent is decreased, so that the desulfurization performance and the durability time in which the desulfurization performance can be maintained, that is, the durability tends to decrease. On the other hand, when the content exceeds 30% by mass, the content of the nickel component is relatively reduced, and the desulfurization performance and durability of the desulfurization agent tend to be reduced.

  Although it does not specifically limit as said porous inorganic oxide, At least 1 sort (s), such as a silica, an alumina, a boria, a magnesia, a zirconia, a titania, a manganese oxide, these mixtures, and the complex oxide which consists of these components is used preferably. In particular, silica is preferable from the viewpoint of suppressing the deposition of the carbonaceous material on the desulfurizing agent and improving the durability.

  The porous inorganic oxide is preferably alumina from the viewpoint of improving the desulfurization performance and durability of the desulfurization agent of the present embodiment.

  In the porous inorganic oxide, the silica is preferably modified with aluminum from the viewpoint of further improving the desulfurization performance and durability of the desulfurization agent of the present embodiment. Here, the silica modified with aluminum is not particularly limited as long as it is a silica containing aluminum atoms, but the aluminum atoms are preferably introduced into the silica as alumina. Alumina may be mixed with silica, but is preferably silica-alumina, which is a composite oxide composed of silica and an alumina component. The content of aluminum in the silica modified with aluminum is 5 to 20, preferably 7 to 15, as a silica / alumina molar ratio.

  Content of the nickel atom which the desulfurization agent of this embodiment contains is 45-75 mass% in conversion of nickel oxide (NiO) on the basis of the total desulfurization agent mass, Preferably it is 50-70 mass%. If the content is less than 45% by mass, the desulfurization performance and durability of the desulfurization agent tend to be reduced due to the insufficient amount of nickel atoms. In addition, the specific surface area of the desulfurizing agent is reduced because the content of the porous inorganic oxide is reduced, and the nickel component is liable to agglomerate and its dispersion is lowered, so that the desulfurization performance and durability tend to be lowered. .

The degree of reduction of nickel atoms contained in the desulfurizing agent of the present embodiment is 50 to 80%, preferably 60 to 80%. When the degree of reduction is less than 50%, the active species are insufficient and the desulfurization performance and durability tend to be insufficient. On the other hand, when the degree of reduction exceeds 80%, the dispersion of nickel metal particles tends to decrease, the amount of effective active sites is insufficient, and the desulfurization performance and durability tend to be insufficient. In addition, in this application, the reduction degree of a nickel atom means the ratio (%) of metallic nickel (Ni (0)) with respect to all the nickel atoms contained in a desulfurization agent. The reduction degree was measured using a TPR measuring device. That is, TPR measurement is performed after performing reduction treatment under a predetermined condition in the same apparatus, and calculation is performed from the MASS18 (H ₂ O) amount ratio generated between the TPR measurement and the unreduced treatment sample.

  The hydrogen adsorption amount per unit mass of the desulfurizing agent of the desulfurizing agent of this embodiment is 3.5 to 4.6 ml / g, preferably 4.0 to 4.6 ml / g. When the hydrogen adsorption amount is less than 3.5 ml / g, the desulfurization performance and durability tend to be insufficient. On the other hand, it is technically difficult for the hydrogen adsorption amount to exceed 4.6 ml / g. In the present application, the hydrogen adsorption amount was measured using a high-functional specific surface area / pore distribution measuring device (ASAP2020 (trade name) manufactured by SHIMAZU). After the catalyst is hydrogen reduced under predetermined conditions, hydrogen is adsorbed at 50 ° C. under vacuum to obtain an adsorption isotherm. Next, the amount of hydrogen that is chemically adsorbed is calculated by exhausting and excluding hydrogen for physical adsorption. In the desulfurization agent of the present embodiment, hydrogen is mainly adsorbed on the surface of the metal nickel particles, and the amount of adsorption is an index reflecting the dispersion of the nickel metal particles.

  The desulfurizing agent of this embodiment contains 3 to 40% by mass, preferably 5 to 30% by mass of zinc oxide (ZnO) based on the total mass of the desulfurizing agent, in addition to the porous inorganic oxide and nickel atom. desirable. When the zinc oxide is less than 3% by mass, the effect of adding zinc oxide that suppresses the formation of carbonaceous substances and improves the durability of the desulfurizing agent tends to be insufficient. On the other hand, when it exceeds 40% by mass, the contents of the nickel component and the porous inorganic oxide are relatively reduced, so that the desulfurization performance tends to be lowered. By containing zinc oxide in the above range, the desulfurization performance and durability of the desulfurization agent are improved.

  The desulfurizing agent of this embodiment may contain copper atoms in addition to nickel atoms as the active metal component, but the content thereof is less than 10% by mass based on the total desulfurizing agent in terms of CuO, preferably 5 The desulfurization agent of the present embodiment is substantially free of copper atoms, most preferably 1% by mass or less, more preferably 1% by mass or less. Here, “substantially contains no copper atom” means that the desulfurization agent of the present embodiment contains a copper atom other than the copper atom derived from impurities contained in each raw material used in producing the desulfurization agent. It means that it was produced without the intended addition of copper atoms. In the case where the copper atom is contained in an amount of 10% by mass or more, when the desulfurization agent is used in a fuel cell system that is subjected to DSS operation, nickel metal containing copper may be caused by repeated heating / falling thermal history. There is a tendency that the particles aggregate and the desulfurization activity decreases with time.

  Next, the manufacturing method of the desulfurization agent of this embodiment is demonstrated.

  The desulfurization agent of this embodiment is 10 to 30% by mass of porous inorganic oxide, 3 to 40% by mass of zinc oxide, and 45 to 75% by mass in terms of nickel oxide based on the total mass of the desulfurization agent precursor. Including a step of reducing a desulfurization agent precursor having a carbon atom / nickel atom molar ratio of 0.065 to 0.094 at 200 to 300 ° C. It is preferably manufactured by the manufacturing method of the desulfurizing agent characterized. In addition, the desulfurization agent precursor as used in this application means what gives the desulfurization agent for hydrocarbons by carrying out a baking process and / or a reduction process.

  Moreover, the desulfurization agent of this embodiment is a process which manufactures a baking precursor by baking the said desulfurizing agent precursor at 160-300 degreeC, and reduces the said baking precursor at 200-300 degreeC. It is preferable to manufacture by the manufacturing method of the desulfurization agent characterized by providing a process.

  Here, the desulfurizing agent precursor (hereinafter, also referred to as “precursor of the present embodiment”) used in the production of the desulfurizing agent of the present embodiment will be described.

  The method for producing the precursor of this embodiment is not particularly limited, but the following production method is preferred.

  In a preferred method for producing the precursor of the present embodiment, an aqueous solution containing a nickel compound and a basic salt containing a carbonate group or a hydrogen carbonate group are included in the presence of the porous inorganic oxide and / or its precursor. An aqueous solution is mixed to form a precipitate of a nickel compound hardly soluble in water on the porous inorganic oxide. The porous inorganic oxide and / or precursor thereof is preferably dissolved or suspended in an aqueous solution containing the nickel compound and / or an aqueous solution containing a basic salt.

  More specifically, a porous inorganic oxide and / or a precursor thereof is mixed in an aqueous solution containing a nickel compound, and an aqueous solution of a basic salt containing a carbonate group or a hydrogen carbonate group is dropped into the mixed solution. Alternatively, a porous inorganic oxide and / or precursor thereof is mixed in an aqueous solution of a basic salt, and an aqueous solution containing a nickel compound is dropped into the mixed solution to form a nickel compound precipitate on the porous inorganic oxide. . The latter method is more preferable.

  When silica is used as the porous inorganic oxide, at least one selected from silica powder, silica sol, and silica gel is preferably used as the silica source. These average particle diameters are preferably 1 to 100 nm, more preferably 1 to 25 nm.

  Examples of the alumina source when alumina is used as the porous inorganic oxide include alumina hydrates such as alumina powder, pseudoboehmite, boehmite alumina, bayerite, and gypsite.

  In the case of using silica modified with aluminum as the porous inorganic oxide, the above-mentioned compound is used as the silica source, and as the aluminum source, aluminum chloride, aluminum nitrate, Examples thereof include aluminum sulfate, aluminum acetate, and aluminum hydroxide.

  As a nickel compound used as a raw material in the method for producing a desulfurizing agent precursor of the present embodiment, nickel chloride, nickel nitrate, nickel sulfate, nickel acetate and the like are preferable.

  As the basic salt containing a carbonate group or a hydrogen carbonate group used as a precipitant, sodium carbonate, potassium carbonate, lithium carbonate, ammonium carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, lithium hydrogen carbonate, ammonium hydrogen carbonate, etc. are preferably used. it can. By using these salts as a precipitating agent, a precipitate to be formed, that is, a nickel compound containing a carbonate group in the precursor of the present embodiment is formed.

  The amount of the basic salt is 1.0 to 1.5 times, preferably 1.1 to 1.1, with respect to the equivalent of the nickel compound to be used, from the viewpoint of surely generating a precipitate of the nickel compound. Four times is desirable. Moreover, it is preferable that pH of the mixed solution of the aqueous solution containing a production | generation nickel compound and the aqueous solution containing a basic salt shall be about 7-9.

  The temperature of the solution when the aqueous solution containing the nickel compound and the aqueous solution containing the basic salt are mixed to form a precipitate is 50 to 100 ° C., preferably 70 to 90 ° C.

  The carbon atoms contained in the precursor of the present embodiment are mainly derived from the carbonate group constituting the nickel compound containing nickel atoms. Examples of the nickel compound containing a carbonate group (hereinafter sometimes referred to as “carbonate group-containing nickel compound”) include nickel carbonate and nickel hydroxycarbonate. The desulfurization agent precursor of this embodiment contains nickel compounds, such as nickel hydroxide and nickel oxide, in addition to the carbonate group-containing nickel compound.

  The molar ratio (C / Ni) of carbon atom / nickel atom in the precursor of this embodiment is 0.065 to 0.094, preferably 0.070 to 0.092. The larger the C / Ni value, the higher the proportion of the carbonate group-containing nickel compound in the total nickel compound. When this is less than 0.065, the desulfurization performance of the desulfurizing agent obtained from the precursor is sufficient. Tend not to. On the other hand, it is difficult to obtain the precursor of this embodiment in which C / Ni exceeds 0.094. When C / Ni is within the above range, the desulfurizing agent obtained therefrom has excellent desulfurization performance and durability.

  In the production of the precursor of the present embodiment, it is preferable that the aqueous solution containing the nickel compound further includes a zinc compound, and includes a precipitation step of obtaining a precipitate containing the nickel compound, the porous inorganic oxide, and the zinc compound. As the zinc compound used at that time, zinc chloride, zinc nitrate, zinc sulfate, zinc acetate, zinc hydroxide and the like are preferable.

  After the nickel compound precipitate is formed on the porous inorganic oxide, the produced solid is filtered and washed with ion exchange water or the like. Insufficient washing leaves chlorine, nitrate radical, sulfate radical, acetate radical, sodium ion, potassium ion, etc. on the catalyst, which adversely affects the performance of the desulfurization agent. When ion-exchanged water cannot be sufficiently washed, an aqueous solution of a base such as ammonia, sodium carbonate, sodium hydrogen carbonate, or potassium carbonate may be used as the washing liquid. In this case, it is preferable to first wash the solid with an aqueous base solution and then wash with ion-exchanged water. In particular, residual sodium ions adversely affect the performance of the desulfurization agent, and thus it is desirable to perform washing until the amount of residual sodium is 0.1% by mass or less, preferably 0.05% by mass or less.

  The solid after washing is pulverized and then dried. The drying method is not particularly limited, and examples thereof include heat drying in air, degassing drying under reduced pressure, and spray drying. When drying by heating in an air atmosphere, drying is preferably performed at 100 to 150 ° C. for 5 to 15 hours.

  The precursor of the above-described embodiment may be used for hydrocarbon desulfurization as it is, or may be subjected to a reduction treatment to be a desulfurization agent of the embodiment. However, from the viewpoint of improving the desulfurization performance and durability of the desulfurization agent, the desulfurization agent of the present embodiment is obtained by performing the calcining treatment under specific conditions before the reduction treatment and then performing the reduction treatment. Is preferred. In addition, in this application, a baking precursor means what baked the precursor of the said this embodiment.

  The calcining precursor used in the production of the desulfurizing agent of the present embodiment (hereinafter sometimes referred to as “the calcining precursor of the present embodiment”) is the precursor of the present embodiment, preferably 160 to 300 ° C. Is obtained by firing at 200 to 300 ° C., more preferably 220 to 300 ° C., preferably in an atmosphere containing molecular oxygen, more preferably in an air atmosphere. When the firing temperature is lower than 160 ° C., the above-mentioned effect due to firing tends to be insufficient. On the other hand, when it exceeds 300 ° C., the desulfurization agent obtained by reducing the firing precursor of the present embodiment. There is a tendency that the desulfurization performance and durability are not sufficiently improved. Although the firing time varies depending on the firing temperature, it is generally 0.1 to 10 hours, preferably 1 to 5 hours. In the production of the desulfurizing agent precursor of the present embodiment described above, if the washing after the precipitation is insufficient, the washing may be performed again after the baking treatment. In this case, ion-exchanged water or an aqueous solution of the above-mentioned base can be used.

Although the details of the structure of the nickel compound contained in the precursor of this embodiment are not clear, a part of the carbonate group-containing nickel compound contained in the precursor of this embodiment is nickel oxide, and one of the nickel hydroxides. Part is converted to nickel oxide by a decomposition reaction.

  The precursor of the present embodiment or the calcined precursor of the present embodiment can be used for hydrocarbon desulfurization as it is, but it is reduced by the method for producing a desulfurization agent of the present embodiment from the viewpoint of improving desulfurization performance and durability. It is preferable to perform the treatment to obtain the desulfurization agent of the present embodiment. The reduction treatment is desirably performed at a temperature of 150 to 300 ° C., preferably 200 to 300 ° C., more preferably 250 to 300 ° C. under a hydrogen flow. Although the reduction treatment time varies depending on the reduction treatment temperature, it is generally 0.1 to 15 hours, preferably 2 to 10 hours.

  In the case of producing a hydrocarbon desulfurization agent for a fuel cell system using the desulfurization agent production method of this embodiment, the precursor of this embodiment or the firing precursor of this embodiment is used for the fuel cell system. It is preferable to charge the desulfurization reactor and reduce it. The conventional reduction treatment of the desulfurizing agent precursor or the firing precursor is typically performed at a temperature of about 350 to 450 ° C. in a hydrogen atmosphere. For this reason, it is often difficult to perform the reduction process at the manufacturing site of the fuel cell system due to problems in equipment. Further, the operating temperature of the desulfurization reactor constituting the fuel cell system is typically about 100 to 260 ° C., and by design, the desulfurization agent precursor or the calcining precursor is charged into the reactor of the same device. It is often difficult to perform the reduction treatment at a temperature of about 350 to 450 ° C. using an apparatus. Therefore, in a catalyst manufacturer having facilities capable of reduction treatment at high temperature, the desulfurization agent precursor or the calcining precursor is in a bulk state (in a state where the desulfurization reactor for each fuel cell system is not filled). In general, reduction treatment is performed. The activated bulk desulfurization agent is transferred to the manufacturing site of the fuel cell system. Since the activated desulfurization agent has a deactivation due to contact with air and safety problems, it is usually subjected to a so-called stabilization treatment in which only the surface layer is slightly oxidized following the reduction treatment. Shipped. At the place where the fuel cell system is manufactured, each desulfurization reactor for the fuel cell system is filled with this, and the reduction treatment is performed at a relatively low temperature in order to remove the stabilization treatment layer and reactivate it. Do.

  In the method for producing a desulfurizing agent of the present embodiment, a high desulfurization performance is obtained by reducing the precursor of the present embodiment or the calcined precursor of the present embodiment at a low temperature of 300 ° C. or lower compared to the conventional technique. And a durable desulfurizing agent. Therefore, these precursors are transferred to the production site of the fuel cell system without being subjected to reduction treatment and stabilization treatment at the production site, and are charged into individual desulfurization reactors for the fuel cell system at a low temperature. It can be activated by the reduction treatment. This eliminates the need for two processes of a high temperature reduction process and a stabilization process in a bulk state, and it is possible to reduce the manufacturing cost of the desulfurization agent accordingly.

  The shape of the precursor of the present embodiment is not particularly limited, and the precursor obtained as a powder may be used as it is or may be a molded body. From the viewpoint of reducing the pressure loss of hydrocarbons in the reactor during hydrocarbon desulfurization or preventing channeling, the desulfurizing agent is preferably a molded body, and the precursor is also preferably a molded body. The molding method may be tableting, and the molded product may be sized in an appropriate range after pulverization. Furthermore, extrusion molding may be used. In molding, an appropriate binder may be blended. The binder is not particularly limited, but alumina, silica, titania, zirconia, carbon black, or a mixture thereof is used. As a compounding quantity of a binder, it is 30 mass% or less normally with respect to the total amount with the mass of the precursor of this embodiment, Preferably it is 10 mass% or less. Also, a molding aid made of an organic substance can be used for molding. The precursor of this embodiment made into a molded body is subjected to a firing treatment and / or a reduction treatment, and becomes a desulfurization agent of this embodiment as a molded body. Moreover, it is good also as a desulfurization agent of this embodiment as a molded object by making the baking precursor of this embodiment into a molded object, and reducing this.

  Examples of the hydrocarbon to be desulfurized using the desulfurizing agent of the present embodiment include natural gas, LPG, naphtha, kerosene, and the like, among which kerosene is preferable. The case where kerosene is used will be described below.

  The kerosene used as a raw material in the hydrocarbon desulfurization method of the present embodiment is kerosene containing a sulfur content, and may be kerosene used as a general fuel. The sulfur concentration in the kerosene is 0.1 to 30 ppm by mass, preferably 1 to 25 ppm by mass, more preferably 5 to 20 ppm by mass. The sulfur content of the kerosene is preferably as low as possible from the viewpoint of performance, but desulfurization of sulfur to less than 0.1 ppm by mass in a normal petroleum refining process is not preferable because the equipment cost and operation cost increase. On the other hand, when the sulfur content exceeds 30 ppm by mass, the desulfurization agent of the present embodiment used in the desulfurization method of the present embodiment is not preferable because it cannot maintain the desulfurization performance in a short time. The sulfur content in the present embodiment is a general term for various sulfur, inorganic sulfur compounds, and organic sulfur compounds that are usually included in hydrocarbons. Moreover, as a sulfur content density | concentration, it uses the mass reference | standard of kerosene, the notation in conversion of a sulfur atom, and uses the value quantified by the gas chromatography (GC-SCD) method with a chemiluminescence sulfur detector.

  When kerosene is used as a raw material in the hydrocarbon desulfurization method of the present embodiment, kerosene may be brought into contact with the desulfurization agent of the present embodiment in any of a liquid phase, a gas phase, and a gas-liquid mixed phase. From the viewpoint of suppressing the deterioration of the desulfurization performance over time due to the deposition of the carbonaceous material on the surface, and maintaining the desulfurization performance for a long time, it is preferable to employ a liquid phase.

In the hydrocarbon desulfurization method of the present embodiment, when kerosene is used as the hydrocarbon, the operating pressure is preferably a low pressure in the range of normal pressure to 0.9 MPa in consideration of economics, safety, etc. of the fuel cell system, In particular, normal pressure to 0.7 MPa is preferable. The reaction temperature is not particularly limited as long as it lowers the concentration of sulfur, but it is preferable to work effectively from a low temperature in consideration of the start of the equipment, and also in consideration of the steady state. 0 ° C to 400 ° C is preferable. More preferably, 0 ° C to 300 ° C, particularly preferably 100 ° C to 260 ° C is employed. By selecting such conditions, kerosene can be kept in a liquid phase. If the LHSV is too high, the desulfurization efficiency is lowered. On the other hand, if the LHSV is too low, the apparatus becomes large. Preferably in the range of 0.01～15H ^-1 as LHSV, more preferably in the range of 0.05~5h ^-1, range 0.1～3H ^-1 it is particularly preferred. The desulfurization method of this embodiment is characterized in that the sulfur content in kerosene can be sufficiently desulfurized even in the absence of hydrogen, but a small amount of hydrogen may be introduced. The flow rate of hydrogen at that time is, for example, 0.05 to 1.0 NL per 1 g of kerosene.

  Although the form of the desulfurization apparatus used for the hydrocarbon desulfurization method of this embodiment is not particularly limited, for example, a flow-through fixed bed system can be used. The shape of the desulfurization device can be any known shape depending on the purpose of each process, such as a cylindrical shape or a flat plate shape.

  When kerosene is used as a raw fuel in the hydrocarbon desulfurization method of the present embodiment, the sulfur concentration of kerosene containing the above-described sulfur content can be reduced to 20 mass ppb or less under hydrogen non-coexistence conditions.

  Hereinafter, the case where kerosene is used as the raw fuel will be described for the fuel cell system using the hydrocarbon of the present embodiment as the raw fuel.

The kerosene having a sulfur concentration preferably desulfurized to about 20 mass ppb or less is then subjected to a reforming reaction step to generate a gas rich in hydrogen. The reforming reaction step is not particularly limited, but a steam reforming reaction in which raw fuel is reformed with steam at a high temperature on a catalyst, a partial oxidation reaction using an oxygen-containing gas, or steam For example, autothermal reforming that performs a self-heat recovery type reforming reaction in a system in which an oxygen-containing gas coexists can be used. The catalyst used generally contains ruthenium. The reaction conditions for the reforming reaction step are not limited, but the reaction temperature is preferably 200 to 1000 ° C, particularly 500 to 850 ° C. The reaction pressure is preferably from normal pressure to 1 MPa, and particularly preferably from normal pressure to 0.2 MPa. LHSV is preferably 0.01 to 40 h ⁻¹ , particularly preferably 0.1 to 10 h ⁻¹ .

  The mixed gas containing carbon monoxide and hydrogen obtained by the reforming reaction step can be used as a fuel for a fuel cell as it is in the case of a solid oxide fuel cell. For fuel cells that require removal of impurities, particularly carbon monoxide, in the fuel gas, such as phosphoric acid fuel cells and polymer electrolyte fuel cells, the mixed gas has a carbon monoxide content. In order to reduce this, it is subjected to a shift reaction step.

The shift reaction step is a step of reacting carbon monoxide with water to convert it into hydrogen and carbon dioxide. For example, a mixed oxide of iron-chromium, a mixed oxide of copper-zinc, platinum, ruthenium, iridium, etc. The carbon monoxide content in the mixed gas is reduced to 2 vol% or less, preferably 1 vol% or less, more preferably 0.5 vol% or less. The conditions for the shift reaction are not necessarily limited by the reformed gas composition or the like as a raw material, but the reaction temperature is preferably 120 to 500 ° C, and particularly preferably 150 to 450 ° C. The pressure is preferably normal pressure to 1 MPa, particularly preferably normal pressure to 0.2 MPa. GHSV is preferably 100~50000h ^-1, especially 300～10000H ^-1 are preferred. In the shift reaction step, two reactors of a high temperature shift reactor and a low temperature shift reactor may be provided in series. An iron-chromium catalyst is preferably used for the high temperature shift reactor, and a copper-zinc catalyst is preferably used for the low temperature shift reactor. Usually, in the phosphoric acid fuel cell, the mixed gas in this state can be used as fuel.

In a polymer electrolyte fuel cell, since it is necessary to further reduce the carbon monoxide concentration, it is desirable to provide a step of further removing carbon monoxide. This step is not particularly limited, and various methods such as an adsorption separation method, a hydrogen separation membrane method, and a carbon monoxide selective oxidation step can be used. It is particularly preferable to employ a process using a carbon monoxide selective oxidation reaction. In this step, a catalyst containing iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium, platinum, zinc, silver, gold, etc. is used, and 0.5 to 10 times the remaining number of moles of carbon monoxide. Mole, preferably 0.7 to 5 times mol, more preferably 1 to 3 times mol of oxygen is added to reduce the carbon monoxide concentration by selectively converting carbon monoxide to carbon dioxide. Although the reaction conditions of this method are not limited, the reaction temperature is preferably 80 to 350 ° C, particularly preferably 100 to 300 ° C. The pressure is preferably normal pressure to 1 MPa, particularly preferably normal pressure to 0.2 MPa. GHSV is preferably 1000~50000h ^-1, especially 3000～30000H ^-1 are preferred. 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.

  Hereinafter, the fuel cell system will be described with reference to FIG. 1 by taking a solid polymer fuel cell as an example.

  The raw fuel (kerosene) in the fuel tank 3 flows into the desulfurizer 5 through the fuel pump 4. At this time, if necessary, the hydrogen-containing gas from the carbon monoxide selective oxidation reactor 11 or the low temperature shift reactor 10 can be added. The desulfurizer 5 is filled with the desulfurization catalyst of this embodiment. The fuel desulfurized in the desulfurizer 5 is mixed with water from the water tank 1 through the water pump 2, introduced into the vaporizer 6, and sent into the reformer 7.

  The reformer 7 is heated by a heating burner 18. As the fuel for the heating burner 18, the anode off gas of the fuel cell 17 is mainly used, but the fuel discharged from the fuel pump 4 can be supplemented as necessary. As the catalyst filled in the reformer 7, a nickel-based, ruthenium-based, or rhodium-based catalyst can be used.

  The gas containing hydrogen and carbon monoxide produced in this way is passed through the high temperature shift reactor 9, the low temperature shift reactor 10, and the carbon monoxide selective oxidation reactor 11 in order, so that the carbon monoxide concentration is adjusted to the fuel cell. It is reduced to the extent that it does not affect the characteristics of

  The fuel cell 17 includes an anode 12, a cathode 13, and a solid polymer electrolyte 14. Fuel gas containing high-purity hydrogen obtained by the above method is sent to the anode side, and air blower 8 is sent to the cathode side. If necessary, air is introduced after appropriate humidification treatment (a humidifier is not shown). 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 Pt catalyst or Pt-Ru alloy catalyst supported on activated carbon are used for the anode, and platinum black and Pt catalyst supported on activated carbon are used for the cathode. Usually, 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.

  Next, both sides of a polymer electrolyte membrane known by Nafion (manufactured by DuPont, registered trademark), Gore (manufactured by Gore, registered trademark), Flemion (manufactured by Asahi Glass, registered trademark), Aciplex (registered trademark by Asahi Kasei Co., Ltd.), etc. The porous catalyst layer is laminated to form MEA (Membrane Electrode Assembly). Further, the fuel cell is assembled by sandwiching the MEA with a separator having a gas supply function, a current collecting function, particularly an important drainage function in the cathode, and the like made of a metal material, graphite, carbon composite and the like. The electric load 15 is electrically connected to the anode and the cathode. The anode off gas is consumed in the heating burner 18. The cathode off gas is discharged from the exhaust port 16.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

Example 1
<Production of desulfurization agent precursor>
Nickel nitrate hexahydrate (commercial reagent special grade) 43.7 g and zinc nitrate hexahydrate (commercial reagent special grade) 5.30 g were dissolved in ion-exchanged water to prepare 150 ml of an aqueous solution. 24.0 g of sodium carbonate (commercial reagent special grade) was dissolved in ion-exchanged water, mixed with 20.6 g of commercially available silica sol (particle size: about 7 nm) (silica content: 3.30 g), and a solution made up to 300 ml was designated as solution B. . The solution B was stirred while maintaining the temperature at 80 ° C., and the solution A was added dropwise to form a precipitate. After completion of the dropwise addition, heating and stirring were continued for 2 hours to complete the precipitation. Thereafter, the precipitate was collected by filtration, washed with ion-exchanged water, the obtained cake was pulverized, and dried in air at 120 ° C. for 10 hours to obtain a powdery desulfurization agent precursor. A part of this was sampled, and carbon atoms contained were quantified by a high-frequency exothermic carbon / sulfur analyzer to calculate C / Ni.

<Manufacture of firing precursor>
The desulfurizing agent precursor obtained as described above was calcined at 230 ° C. for 3 hours in air to obtain 15 g of a powdery calcining precursor. The composition was Ni (NiO conversion) / ZnO / SiO ₂ = 65 mass% / 10 mass% / 25 mass%, and the residual Na was 0.05 mass% or less. Further, the carbon atoms contained were quantified in the same manner as the desulfurizing agent precursor, and C / Ni was calculated.

<Manufacture of desulfurization agent>
The calcined precursor obtained above was tableted and crushed more coarsely, and then the particle size was adjusted to 1.18-2.0 mm. 1 g of this was charged into a flow-type reaction tube having a diameter of 1.27 cm, and reduced in a hydrogen stream at 280 ° C. for 7 hours to obtain a desulfurization agent. The reduction degree of nickel atoms in the desulfurizing agent and the hydrogen adsorption amount of the desulfurizing agent were each sampled by a small amount of the calcined precursor, and pretreated under the same reducing treatment conditions as those described above by the method described above. Measurements were made after this.

<Desulfurization test>
The desulfurization agent obtained above was transferred to a stainless steel autoclave reactor under a nitrogen atmosphere. Subsequently, as a model raw material for kerosene, a solution obtained by adding benzothiophene as a sulfur compound to a reagent normal dodecane so as to be 200 mass ppm as a sulfur atom based on the mass standard of normal dodecane, a reaction temperature of 200 ° C., normal pressure The desulfurization test was conducted in a nitrogen atmosphere. After performing the reaction for 2 hours, the reactor is cooled, the residual sulfur concentration in the model raw material is quantified by the GC-SCD method, the sulfur adsorption amount per unit mass of the desulfurizing agent is calculated, and the performance index of the desulfurizing agent did. Based on experience, it has been understood that a desulfurization agent that exhibits a high sulfur adsorption amount in the test exhibits high desulfurization activity and excellent durability even in a long-term desulfurization test of real kerosene by the continuous flow method. Yes. Table 1 shows the composition of the desulfurizing agent precursor (desulfurizing agent), C / Ni, calcining temperature, C / Ni of the calcining precursor, conditions for reduction treatment with hydrogen, the degree of reduction of nickel atoms in the desulfurizing agent, and desulfurization reaction 2 The sulfur adsorption amount after time is shown.

(Examples 2-9)
In each production of the desulfurizing agent precursor, a desulfurizing agent precursor having the composition shown in Table 1 was produced in the same manner as in Example 1 except that the amount of the raw material used in Example 1 was adjusted. . In Example 8, alumina was used as the porous inorganic oxide in place of the silica of Example 1, and in Example 9, silica / alumina was used.

  In addition, each of the obtained desulfurizing agent precursors was fired under the firing conditions shown in Table 1 to obtain a firing precursor. In Example 4, no baking treatment was performed.

  Further, each calcined precursor or (in Example 4) a desulfurizing agent precursor was subjected to reduction treatment under the conditions shown in Table 1 to produce a desulfurizing agent.

  A desulfurization test using a model raw material of kerosene was carried out in the same manner as in Example 1 except that the obtained desulfurizing agent was used. Table 1 shows the composition of each desulfurization agent precursor (desulfurization agent), C / Ni, firing temperature, C / Ni of the desulfurization agent firing precursor, conditions for reduction treatment with hydrogen, and the degree of reduction of nickel atoms in the desulfurization agent. And the sulfur adsorption amount after 2 hours of desulfurization reaction.

(Comparative Examples 1-7)
Each raw material composition was adjusted so as to have the composition of the desulfurizing agent precursor shown in Table 2, and each desulfurizing agent precursor was produced by the same operation as in Example 1.

  Each desulfurizing agent precursor obtained as described above was calcined under the conditions shown in Table 1, and further reduced under the respective conditions to produce each desulfurizing agent.

  A kerosene model raw material was used in the same manner as in Example 1 except that the obtained desulfurizing agent was used. Table 1 shows the composition of each desulfurization agent precursor (desulfurization agent), C / Ni, firing temperature, C / Ni of the desulfurization agent firing precursor, conditions for reduction treatment with hydrogen, and the degree of reduction of nickel atoms in the desulfurization agent. And the sulfur adsorption amount after 2 hours of desulfurization reaction.

  From the results of Table 1 and Table 2, the desulfurization agent obtained by calcining a desulfurization agent precursor having a specific range of C / Ni in a specific temperature range and reducing the specific temperature range is excellent. It became clear that it has desulfurization performance.

In the fuel cell system of FIG. 1, the desulfurizer 5 was filled with the desulfurizing agent obtained in Example 1, and a power generation test was performed using No. 1 kerosene (sulfur concentration: 27 mass ppm) as fuel. During the operation for 200 hours, the desulfurizer operated normally and no decrease in the activity of the desulfurizing agent was observed. The desulfurization conditions were a temperature of 220 ° C., 0.25 MPa (gauge pressure), no hydrogen flow, and LHSV = 0.5 h ⁻¹ . At this time, a catalyst containing ruthenium is used for steam reforming, and a catalyst containing copper-zinc is used in the shift step (low temperature shift reactor 10) under the conditions of S / C = 3, temperature 700 ° C., LHSV = 1h ^−1. In the carbon monoxide selective oxidation step (carbon monoxide selective oxidation reactor 11) under the conditions of 200 ° C. and GHSV = 2000h ⁻¹ , a catalyst containing ruthenium is used, O ₂ / CO = 3, temperature 150 ° C., GHSV = It operated on condition of 5000h- ¹ . The fuel cell also operated normally and the electric load 15 was operated smoothly.

DESCRIPTION OF SYMBOLS 1 Water tank 2 Water pump 3 Fuel tank 4 Fuel pump 5 Desulfurizer 6 Vaporizer 7 Reformer 8 Air blower 9 High temperature shift reactor 10 Low temperature shift reactor 11 Carbon monoxide selective oxidation reactor 12 Anode 13 Cathode 14 Solid height Molecular electrolyte 15 Electric load 16 Exhaust port 17 Fuel cell 18 Heating burner

Claims (11)

10-30% by mass of a porous inorganic oxide based on the total mass of the desulfurization agent,
3 to 40% by weight of zinc oxide;
45 to 75 mass% nickel atoms in terms of nickel oxide,
Including
A desulfurization agent for hydrocarbons, wherein the reduction degree of nickel atoms is 50 to 80%, and the hydrogen adsorption amount per unit mass of the desulfurization agent is 3.5 to 4.6 ml / g.   2. The hydrocarbon desulfurization agent according to claim 1, wherein the porous inorganic oxide is silica or alumina.   3. The hydrocarbon desulfurization agent according to claim 2, wherein the silica is modified with aluminum. 10-30% by weight of a porous inorganic oxide based on the total mass of the desulfurizing agent precursor,
3 to 40% by weight of zinc oxide;
45 to 75 mass% nickel atoms in terms of nickel oxide,
Carbon atoms,
Including
A hydrocarbon desulfurization agent comprising a step of reducing a hydrocarbon desulfurization agent precursor having a carbon atom / nickel molar ratio of 0.065 to 0.094 at 200 to 300 ° C. Production method. 10-30% by weight of a porous inorganic oxide based on the total mass of the desulfurizing agent precursor,
3 to 40% by weight of zinc oxide;
45 to 75 mass% nickel atoms in terms of nickel oxide,
Carbon atoms,
Including
A process for producing a calcined precursor by calcining a hydrocarbon desulfurization agent precursor having a carbon atom / nickel atom molar ratio of 0.065 to 0.094 at 160 to 300 ° C .;
Reducing the firing precursor at 200 to 300 ° C .;
A process for producing a hydrocarbon desulfurization agent, comprising:   The method for producing a hydrocarbon desulfurization agent according to claim 4 or 5, wherein the porous inorganic oxide is silica or alumina.   The method for producing a hydrocarbon desulfurization agent according to claim 6, wherein the silica is modified with aluminum.   8. The desulfurization agent precursor for hydrocarbon or the calcining precursor is filled in a desulfurization reactor for a fuel cell system in the reduction treatment step. 8. A method for producing a hydrocarbon desulfurization agent for a fuel cell system by the method.   A hydrocarbon desulfurization method according to any one of claims 1 to 3, and a hydrocarbon containing a sulfur compound are brought into contact with each other.   The hydrocarbon desulfurization method according to claim 9, wherein the hydrocarbon is kerosene.   A fuel cell system using a hydrocarbon as a raw fuel, comprising a hydrocarbon desulfurization device having a reactor filled with the hydrocarbon desulfurization agent according to any one of claims 1 to 3.

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