JP2008239916A - Fuel oil for fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel oil for a fuel cell, capable of exceptionally elongating the life of the desulfurizing agent used in the fuel cell system and enabling the reduction of the frequency of exchanging the desulfurizing agent in the desulfurization of the fuel oil for the fuel cell by a fuel cell system. <P>SOLUTION: This fuel oil for the fuel cell is characterized by having a distillation profile of 135 to 170°C initial distillation point and ≤270°C of 95% distilled out temperature, and having ≤80 mass ppm total sulfur content and ≤1 mass ppm sulfur content derived from a sulfur compound heavier than dibenzothiophene and lighter than 4-methyl dibenzothiophene as measured by a GC-SCD (a gas chromatography having a sulfur chemiluminescence detector). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel oil for a fuel cell used in a fuel cell system. More specifically, it is possible to easily perform a desulfurization treatment with a desulfurizing agent, to greatly extend the life of the desulfurizing agent, and to reduce the replacement frequency of the desulfurizing agent used in the fuel cell system. The present invention relates to fuel oil for fuel cells using hydrogen oil.

In recent years, as an energy source, a new energy technology capable of reducing the burden on the environment more than conventional energy has attracted attention, and a fuel cell has attracted particular attention among the technologies. A fuel cell is a reverse reaction of the principle of electrolysis of water. Chemical energy generated by the reaction of hydrogen (fuel) and oxygen in the air (oxidant) is converted indirectly or directly into electrical energy. By doing so, high power generation efficiency can be obtained.
Known types of fuel cells include solid polymer fuel cells, phosphoric acid fuel cells, molten carbonate fuel cells, solid oxide fuel cells, and are used as stationary and mobile power sources. Yes. For stationary use, various power sources such as portable power sources for mobile phones and notebook computers, household or commercial power sources or cogeneration systems, auxiliary power sources, disaster power sources, industrial medium and large-scale power generation have been proposed. For transportation purposes, vehicles and railways have been proposed.
Examples of raw materials that generate hydrogen used in fuel cells include methane-based city gas, natural gas, LPG, naphtha, kerosene, light oil and other petroleum hydrocarbons, and oxygen-containing compounds such as methanol, ethanol and dimethyl ether. There are researches on how to use these raw materials.

  Petroleum hydrocarbons vary depending on the type of crude oil, fractions, etc., but sulfur such as mercaptans, thiophenes, benzothiophenes (BT), dibenzothiophenes (DBT), alkyldibenzothiophenes (R-DBT) A small amount of the compound is contained, and this sulfur content is disadvantageous in the hydrogen production process in the fuel cell system. That is, when a petroleum hydrocarbon containing such sulfur content is used as fuel oil for fuel cells, the reforming catalyst in the hydrogen production process is poisoned by the sulfur content in the fuel oil for fuel cell used. The service life is reduced. In order to avoid this problem, the fuel cell system generally uses a method in which the sulfur content in the fuel oil for the fuel cell is reduced by a desulfurization treatment using a desulfurizing agent, and then the fuel oil for the fuel cell is used in the hydrogen production process. It has been.

In addition, a method for regulating the sulfur content of the fuel oil for the fuel cell to be supplied to the fuel cell system has been proposed. As such a method, all sulfur compounds in the fuel oil for the fuel cell to be supplied to the fuel cell system are proposed. A method for regulating the content (for example, see Patent Document 1), a method for regulating the content of a specific sulfur compound such as alkyldibenzothiophene in the fuel oil for fuel cells (for example, Patent Document 2), and the like have been proposed. ing.
However, it is difficult to sufficiently extend the life of the desulfurization agent in the desulfurization treatment in the fuel cell system even when the fuel oil for fuel cell with the sulfur content regulated previously proposed is used. Has a problem that the replacement frequency of the desulfurizing agent is high or a large amount of desulfurizing agent needs to be used.
JP 2002-83626 A JP 2001-294874 A

  The present invention has been made in view of the above circumstances, and uses petroleum-based hydrocarbon oil as fuel oil for a fuel cell. When the fuel oil for fuel cell is desulfurized by the fuel cell system, the present invention is used in the fuel cell system. An object of the present invention is to provide a fuel oil for a fuel cell that can prolong the life of the desulfurizing agent and can reduce the replacement frequency of the desulfurizing agent.

As a result of intensive studies to achieve the above object, the present inventors have conducted a desulfurization treatment of fuel oil using a desulfurization agent, and certain sulfur compound species remain in the fuel oil even after the desulfurization treatment. This sulfur compound species was thought to have an effect on the life of the desulfurization agent. Then, if this specific sulfur compound species is reduced in advance, the sustainability of the desulfurization agent in the desulfurization treatment of the fuel cell system can be greatly reduced, and the above object can be achieved, and the present invention is completed. It came to do.
That is, the fuel oil for a fuel cell according to the present invention has a distillation property with an initial boiling point of 135 to 170 ° C., a 95% distillation temperature of 270 ° C. or less, and a total sulfur content of 80 mass ppm or less. 1 mass ppm of sulfur derived from a sulfur compound that is heavier than dibenzothiophene and lighter than 4-methyldibenzothiophene as measured by GC-SCD (gas chromatography with chemiluminescence sulfur detector) It is characterized by the following.

  If the fuel oil for fuel cells of the present invention is used, in the fuel cell system, the desulfurization agent in the desulfurization treatment of the fuel oil for fuel cells can be used for a long period of time, and the replacement frequency and use amount of the desulfurization agent can be reduced.

The contents of the present invention will be described in more detail below.
The distillation properties of the fuel oil for a fuel cell of the present invention have an initial boiling point of 135 to 170 ° C, preferably 140 to 170 ° C, a 95% distillation temperature of 270 ° C or less, preferably 230 to 270 ° C, more preferably 240 to 270. ° C. If the initial boiling point is lower than 170 ° C., the load on the desulfurizing agent can be reduced, which is preferable. Moreover, if the initial boiling point is higher than 135 ° C., the amount of hydrogen generated per unit capacity is increased, the flash point is not too low, and safety is increased during handling. If the 95% distillation temperature is lower than 270 ° C., it is preferable because carbon deposition can be suppressed in the reforming step and the load on the desulfurizing agent can be reduced. Moreover, if the 95% distillation temperature is higher than 230 ° C., the amount of hydrogen generated per unit volume increases, which is preferable.

  The total sulfur content of the fuel oil for fuel cells of the present invention is preferably 80 mass ppm or less, more preferably 10 mass ppm or less. The total sulfur content in the present invention is a value measured according to JIS K2541 microcoulometric titration method. Further, the total sulfur content here means all sulfur content contained in fuel oil for fuel cells such as hydrogen sulfide, mercaptans, alkyl sulfides, cyclic sulfides, thiophenes and the like. In order to improve the sustainability of the desulfurizing agent, the total sulfur content is preferably 80 mass ppm or less.

The fuel oil for fuel cells of the present invention is measured by GC (gas chromatography). Examples of the detector include AED (atomic emission detector), SCD (chemiluminescence sulfur detector), and the like. Although not limited thereto, SCD is preferable. The fuel oil for fuel cells of the present invention has a sulfur content derived from a sulfur compound that is heavier than dibenzothiophene and lighter than 4-methyldibenzothiophene, as measured by GC-SCD (gas chromatography with chemiluminescence sulfur detector). The mass is ppm or less. If the content of sulfur compounds that are heavier than dibenzothiophene and lighter than 4-methyldibenzothiophene (hereinafter also referred to as “target sulfur compounds”) is 1 ppm by mass or less, the durability of the desulfurizing agent is improved. can do. The sulfur content derived from the target sulfur compound is preferably 0.5 mass ppm or less. The sulfur content is preferably as small as possible, and most preferably 0 ppm by mass.
The target sulfur compound is considered to be a compound having an aromatic ring such as alkylbenzothiophenes. By reducing alkyl benzothiophenes having a bulky structure, desulfurization treatment can be performed more effectively.

In order to measure the sulfur content derived from the target sulfur compound according to the present invention, the fuel oil is first analyzed by GC-SCD, and a chromatogram representing the peak intensity of each component in the fuel oil separated by the retention time is obtained. . Next, in the obtained chromatogram, peaks indicating dibenzothiophene and 4-methyldibenzothiophene are identified, and the total area of peaks detected during the retention time of dibenzothiophene and 4-methyldibenzothiophene (of the target sulfur compound) From the peak area, the sulfur concentration derived from the target sulfur compound can be determined by the following formula.
formula:
Sulfur concentration derived from target sulfur compound (mass ppm) = total sulfur concentration in fuel oil × (peak area of target sulfur compound detected by GC-SCD / peak area of all sulfur compounds detected by GC-SCD)

  The total sulfur concentration in the fuel oil in the above formula can be determined by, for example, JIS K2541 microcoulometric titration method. When calculating the peak area, the baseline is set by connecting the average peak intensity between the start of measurement and the first peak detection and the average peak intensity between the end of peak detection and the end of analysis with a straight line. . In addition, the peak positions of dibenzothiophene and 4-methyldibenzothiophene were prepared in advance by dissolving dibenzothiophene and 4-methyldibenzothiophene in isooctane for HPLC in which no sulfur content was detected, and this was analyzed by GC-SCD. The peak position can be identified using the data as standard data.

The fuel cell fuel oil production method of the present invention is not particularly limited as long as the fuel cell fuel oil to be produced has the properties defined in the present invention, using various petroleum-based raw materials, Moreover, the fuel oil for fuel cells of the present invention can be produced by various methods. For example, desulfurized kerosene obtained by desulfurizing a kerosene fraction obtained by atmospheric distillation of crude oil can be used. Furthermore, a desulfurized kerosene obtained by desulfurizing a directly desulfurized kerosene fraction obtained from a direct desulfurization apparatus, a kerosene fraction obtained by hydrocracking, thermal cracking or catalytic cracking of heavy oil or residual oil can be used. Moreover, you may mix the commercially available solvent and the kerosene fraction manufactured by the Fischer-Tropsch synthesis described in the patent publication gazette represented by Unexamined-Japanese-Patent No. 6-1558058.
In addition, as a general desulfurization method for the various petroleum fractions described above, a reaction temperature of 200 to 600 is used by using a catalyst containing a transition metal such as nickel, cobalt, molybdenum, and tungsten in an appropriate ratio in an inorganic oxide carrier. Using a method of hydrodesulfurization at 400 ° C. and a reaction pressure of 2 to 20 MPa-G, or using a desulfurization agent containing a metal such as nickel, copper or zinc, the reaction temperature is from room temperature to 300 ° C., and the reaction pressure is from normal pressure to A method of performing adsorptive desulfurization at 1 MPa-G or a method in which both are combined can be used.
In addition, the fuel oil for a fuel cell is prepared so as to have the properties defined in the present invention, generally by easily selecting the distillation properties and sulfur content of the petroleum fraction used as the raw material, particularly the sulfur content. be able to.

  Various additives can be appropriately blended in the fuel oil for a fuel cell of the present invention as necessary. These additives include phenolic and amine antioxidants, metal deactivators such as thioamide compounds, surface ignition inhibitors such as organophosphorus compounds, succinimides, polyalkylamines, polyetheramines, polyamines. Detergents such as isobutylene amine, anti-freezing agents such as polyhydric alcohols and ethers thereof, organic acid alkali metal or alkaline earth metal salts, auxiliary alcohols such as higher alcohol sulfates, anionic surfactants, cationic systems Known fuel additives such as antistatic agents such as surfactants and amphoteric surfactants, rust inhibitors such as alkenyl succinates, and colorants such as azo dyes can be used. These can be added singly or in combination. The addition amount of these fuel additives is arbitrary, but the total amount of the additives is usually 0.1% by mass or less, preferably 0.05% by mass or less of the fuel oil.

In the fuel cell system, the desulfurization agent used for the desulfurization treatment of the fuel oil for fuel cells of the present invention can be a desulfurization agent used in a normal desulfurization treatment. This desulfurizing agent is preferably an inorganic oxide used as a carrier and an adsorbing active metal component supported or mixed on the carrier. Examples of the inorganic oxide of the carrier include silica, alumina, magnesia, silica-alumina, tungsten, zirconia, and the like. An oxide or mixture of these one or more elements, or a composite oxide of two or more elements In addition, crystalline compounds such as zeolite and MCM-41 may be mentioned. As a particularly preferable inorganic oxide, silica, alumina, and silica-alumina can be used. There is no restriction | limiting in particular about content of the inorganic oxide component in a desulfurization agent, What is necessary is just to select suitably as needed, such as use conditions, Usually, it is the range of 0.5-50 mass% on a desulfurization agent basis. If the content is 0.5% by mass or more, the effect as an inorganic oxide component is sufficiently exerted, and if it is 50% by mass or less, the desulfurization performance is reduced due to a decrease in the amount of adsorbing active metal component. This is preferable because it can be avoided.
As said adsorption active metal component, metal components, such as nickel, copper, manganese, lithium, chromium, iron, are mentioned. These metallic components are not supported and may be mixed with a carrier at the time of preparation. A preferable content of a metal component such as nickel is in the range of 50 to 99.5% by mass in terms of element based on desulfurization agent.

An example of a method for desulfurizing the fuel oil for a fuel cell of the present invention with a desulfurizing agent is shown below. Hydrogen is supplied to the packed tower filled with the desulfurizing agent, and the desulfurizing agent is first activated at a temperature of 100 to 500 ° C. Thereafter, fuel oil is supplied to the packed tower to perform desulfurization treatment. The supply of fuel oil to the packed tower may be an upward flow or a downward flow. The desulfurization treatment conditions at this time are preferably a temperature from room temperature to 500 ° C., a pressure from normal pressure to 2 MPa, and a liquid space velocity (LHSV) of 0.05 to 10 h ⁻¹ . Further, hydrogen can be supplied together with the fuel oil during the desulfurization treatment.

  EXAMPLES Next, although an Example and a comparative example are given and this invention is demonstrated in detail, this invention is not limited by these examples.

<Preparation of fuel oil for fuel cells>
Comparative Example 1
A straight-run kerosene (distillation cut range 150-270 ° C., sulfur content 0.24% by mass) obtained from Middle Eastern crude oil by atmospheric distillation is used as a raw material oil, and this raw material oil is used as a hydrodesulfurization catalyst as a commercial catalyst (Co- Mo type) (trade name: KF-757, manufactured by Nippon Ketjen Co., Ltd.) was used for hydrogenation under conditions of WABT 301 ° C., hydrogen partial pressure 4.5 MPa, liquid space velocity 6 h ^−1. Hydrosulfurized kerosene composition (fuel oil a, boiling range 149.0-290.0 ° C., sulfur compound heavier than dibenzothiophene measured by GC-SCD and lighter than 4-methyldibenzothiophene) Derived sulfur content 1.34 mass ppm). The results of the desulfurization test are also shown in Table 1.

Comparative Example 2
Using straight-run kerosene (distillation cut range 145 to 270 ° C., sulfur content 0.24 mass%) obtained from Middle Eastern crude oil by atmospheric distillation, the same catalyst as in Comparative Example 1 is used. The hydrodesulfurized kerosene composition having the properties shown in Table 1 (fuel oil b, boiling point range 146. boiling point 146.) was subjected to hydrotreatment under conditions of WABT 315 ° C., hydrogen partial pressure 4.5 MPa, and liquid space velocity 6 h ⁻¹ . 0 to 277.0 ° C., and a sulfur content derived from a sulfur compound heavier than dibenzothiophene and lighter than 4-methyldibenzothiophene as measured by GC-SCD was obtained. The results of the desulfurization test are also shown in Table 1.

Example 1
The hydrodesulfurized composition obtained in Comparative Example 2 was precisely distilled at a reflux ratio of 15: 1 to obtain a kerosene composition from which heavy components were removed. The kerosene composition was withdrawn by adjusting the temperature at the top of the distillation tower to a temperature of 270 ° C. at the top of the tower so that the distillation distillate would be 95%. To the kerosene composition obtained by removing this heavy component, 1 mass ppm of dibenzothiophene, 2 mass ppm of 4-methyldibenzothiophene, and 1 mass ppm of 4,6-dimethyldibenzothiophene are added to obtain a total sulfur content. Hydrodesulfurized kerosene composition adjusted to 6 ppm by mass (fuel oil A, boiling range 145.0-265.0 ° C., heavier than dibenzothiophene as measured by GC-SCD and lighter than 4-methyldibenzothiophene Sulfur compound-derived sulfur content 0.00 mass ppm) was obtained. Table 1 shows the properties and desulfurization test results of this hydrodesulfurized kerosene composition.

Example 2
Using straight-run kerosene (distillation cut range 150 to 270 ° C., sulfur content 0.21 mass%) obtained from Middle Eastern crude oil by atmospheric distillation, the same catalyst as in Comparative Example 1 is used. The hydrodesulfurization kerosene composition having the properties shown in Table 1 (fuel oil B, boiling point range 149. boiling point 149.) was performed under conditions of WABT 315 ° C., hydrogen partial pressure 4.5 MPa, and liquid space velocity 3 h ⁻¹ . 0 to 247.5 ° C., 0.03 mass ppm of sulfur content derived from a sulfur compound heavier than dibenzothiophene and lighter than 4-methyldibenzothiophene as measured by GC-SCD. The results of the desulfurization test are also shown in Table 1.

Example 3
50% by volume of the hydrodesulfurized kerosene composition obtained in Comparative Example 1 and a wax content (not including sulfur content) of 30 or more carbon atoms obtained by Fischer-Tropsch synthesis were used as commercially available catalysts (catalyst conversion). After hydrocracking using 0.5% by mass Pt / USY zeolite catalyst manufactured by Kogyo Co., Ltd., a kerosene fraction (distillation cut range 150 to 250 ° C.) obtained by distillation was mixed 50% by volume. Hydrodesulfurized kerosene composition (fuel oil C, boiling point range 149.0-289.0 ° C., heavier than dibenzothiophene as measured by GC-SCD and lighter than 4-methyldibenzothiophene) Compound-derived sulfur content 0.67 mass ppm) was obtained.

<Analysis of sulfur content in fuel oil>
The total sulfur content in the fuel oils obtained in Examples and Comparative Examples was determined according to JIS K2541 microcoulometric titration method. For the sulfur content derived from the target sulfur compound (the sulfur content derived from a sulfur compound heavier than dibenzothiophene and lighter than 4-methyldibenzothiophene), the fuel oil was analyzed by GC-SCD and determined using the above formula. . The analysis conditions of GC-SCD are as follows.
Equipment: GC; GC-2010 (Shimadzu Corporation)
SCD; 7080S (ANTEK)
Column: HP-1MS
Column temperature: 40 ° C.-280 ° C.
Measurement time: 30 minutes Inlet temperature: 260 ° C., detector temperature: 280 ° C.
Carrier gas: He 90kPa
Control mode: Linear velocity Total flow: 21.7 mL / min, Charge flow: 3.0 mL / min Injection mode: Splitless, Split ratio 5: 1
Sample size: 2.0 μL

<Preparation of desulfurizing agent>
The desulfurization agent used for the desulfurization test of the fuel oil obtained by the Example and the comparative example was produced as follows.
Add 1.24 g of boehmite AP-3 (manufactured by Catalyst Kasei Kogyo Co., Ltd.) and 40 ml of 1N HNO ₃ aqueous solution to 1 liter of ion-exchanged water, warm to 80 ° C., and then add 149 g of Ni (NO ₃ ) ₂ .6H ₂ O. Preparation liquid A was obtained. 33.9g separately prepared ion-exchanged water one liter of colloidal silica Snowtex XS (produced by Nissan Chemical), 99.4 g of sodium carbonate, 80 to 3g added _{(NH 4) 6 Mo 7 O} 24 .5H 2 O Heated to ° C. to obtain Preparation B. While maintaining the preparation liquids A and B at 80 ° C., the liquid B was instantaneously added to the liquid A to form a precipitate, followed by stirring for 1 hour. Thereafter, the precipitate was washed and filtered using 5 liters of ion-exchanged water, dried in air at 120 ° C. for 12 hours, and calcined at 400 ° C. for 1 hour. The desulfurization agent was obtained by crushing into a mesh.

<Desulfurization test>
Using the fuel oils obtained in the above Examples and Comparative Examples and the above prepared desulfurizing agent, a desulfurization test was conducted as follows.
A steel reaction tube having an inner diameter of 16 mm was filled with 12 ml of a desulfurizing agent, and the temperature was increased to 150 to 200 ° C. while supplying hydrogen downward at normal pressure, and the desulfurizing agent was activated by maintaining for 3 hours. Next, the fuel oils obtained in Examples and Comparative Examples were passed through the reaction tubes upward at 220 ° C., 0.3 MPa-G, and LHSV = 10 h ⁻¹ , respectively. The sample was collected and the total sulfur content was measured. The oil passage time from the start of the desulfurization treatment until the total sulfur content of the desulfurization treated oil flowing out of the reaction tube reached 100 mass ppb was defined as the breakthrough time. This breakthrough time is shown in Table 1.

  As is clear from Table 1, the fuel oils of Examples 1 to 3 according to the present invention have a longer life of the desulfurization agent (total sulfur content of the desulfurized fuel oil than the fuel oils of Comparative Examples 1 and 2). It can be seen that the time to reach 100 mass ppb (evaluated by breakthrough time) is much longer.

  1 and 2 show GC-SCD data of fuel oils for fuel cells obtained in Example 2 and Comparative Example 1, respectively. In each figure, the upper row shows dibenzothiophene (A), 4-methyldibenzothiophene (B), benzothiophene (C1), 4,6-dimethyldibenzothiophene (C2), and 2,8-dimethyldibenzothiophene (C3). Is the GC-SCD data (standard data) of the sample dissolved in isooctane for HPLC, and the lower row is the GC-SCD data for fuel oil for fuel cells. As can be seen from FIGS. 1 and 2, the fuel oil for fuel cell obtained in Example 2 hardly shows any target sulfur compound (a sulfur compound detected between A and B). It can be seen that a certain amount of the target sulfur compound is detected in the obtained fuel oil for fuel cells.

The GC-SCD data of the fuel oil for fuel cells obtained in Example 2 are shown. The GC-SCD data of the fuel oil for fuel cells obtained in Comparative Example 1 are shown.

Claims (1)

  A fuel oil for fuel cells having an initial distillation point of 135 to 170 ° C., a distillation property of 95% distillation temperature of 270 ° C. or less, and a total sulfur content of 80 ppm by mass or less, comprising GC-SCD (chemiluminescence) Fuel oil for fuel cells, characterized in that the sulfur content derived from a sulfur compound that is heavier than dibenzothiophene and lighter than 4-methyldibenzothiophene, measured by gas chromatography with a sulfur detector, is 1 mass ppm or less .

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