JP2009046587A - Fuel oil for fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel oil for fuel cells, which can sufficiently maintain the life of a desulfurizer, when desulfurized in a fuel cell system, while using a petroleum-based hydrocarbon oil as the fuel oil for the fuel cells, and enables the stable continuation in the operation of the fuel cell system for a long period. <P>SOLUTION: This fuel oil for the fuel cells is characterized by having distillation properties comprising an initial boiling point of 135 to 170°C and a 95% distillation temperature of ≤270°C, a peroxide content of ≤160 mass ppm, a sulfur content originated from sulfur compounds having boiling points having mol.wts. of >330°C and <334°C in an amount of ≤1 mass ppm, and a total sulfur content of ≤80 mass ppm. <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, by sufficiently maintaining the life of the desulfurizing agent, the replacement frequency of the desulfurizing agent used in the fuel cell system can be lowered, and the operation of the fuel cell system can be continued stably for a long period of time. TECHNICAL FIELD The present invention relates to a fuel oil for a fuel cell using a system hydrocarbon oil.

  In recent years, attention has been paid to new energy capable of reducing the burden on the environment more than conventional energy, and fuel cells are particularly attracting attention among the technologies. 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. Research on how to use the raw materials is in progress.

  Petroleum hydrocarbons such as naphtha, kerosene, and light oil vary depending on the type of crude oil and fraction, but mercaptans, thiophenes, benzothiophene (BT), dibenzothiophene (DBT), alkyldibenzothiophene (R). -DBT) and other sulfur compounds are contained in a trace amount, 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, and the reforming catalyst 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 the desulfurization treatment in this fuel cell system, a relatively low cost adsorption desulfurization method is generally used. As the adsorptive desulfurization agent, an adsorbent in which nickel is supported on an inorganic oxide carrier has been proposed because the sulfur content can achieve a high desulfurization level of ppb order.

  In addition, a method for regulating the sulfur content of the fuel oil for the fuel cell itself to be supplied to the fuel cell system has been proposed, and as such a method, the total sulfur compounds of 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.

JP 2002-83626 A JP 2001-294874 A

  However, it is difficult to sufficiently maintain the life of the desulfurization agent for the desulfurization treatment in the fuel cell system even if the fuel oil for fuel cell in which the proposed sulfur content is regulated is used. There is a problem that the replacement frequency of the desulfurizing agent in the system is high or a large amount of desulfurizing agent needs to be used.

  The present invention has been made in view of the above circumstances, and uses petroleum-based hydrocarbon oil as a fuel oil for a fuel cell. When desulfurizing the fuel oil for a fuel cell with a fuel cell system, the life of the desulfurizing agent is increased. An object of the present invention is to provide a fuel oil for a fuel cell that can be sufficiently maintained and that can stably operate the fuel cell system for a long time.

As a result of intensive studies to achieve the above object, the present inventors have found that the impurities having an oxidizing ability in the petroleum hydrocarbon feedstock have an influence on the life of the desulfurization agent, and further, certain sulfur It has been found that the compound species affects the life of the desulfurizing agent, and by reducing these, it has been found that the above object can be achieved, and the present invention has been completed.
That is, the present invention provides the following fuel oil for fuel cells.
(1) It has a distillation property with an initial boiling point of 135 to 170 ° C. and a 95% distillation temperature of 270 ° C. or less, a peroxide content of 160 mass ppm or less, a boiling point exceeding 330 ° C. and a temperature of less than 334 ° C. A fuel oil for a fuel cell, characterized in that the sulfur content derived from sulfur compounds in the range is 1 mass ppm or less and the total sulfur content is 80 mass ppm or less.
(2) The fuel oil for a fuel cell as described in (1) above, wherein a sulfur content derived from a lighter sulfur compound than dibenzothiophene is 10 ppm by mass or less.

  By using the fuel oil for fuel cells of the present invention, 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. Thus, the operation of the fuel cell system can be continued.

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.

  In the fuel oil for fuel cells of the present invention, the peroxide content is 160 mass ppm or less, preferably 30 mass ppm or less. In general, a metal catalyst (such as nickel) contained in a desulfurizing agent is used in a reduced state. However, if impurities having an oxidizing ability are present in fuel oil for fuel cells, the metal is oxidized and the desulfurization performance is lowered. There is a concern that the life of the desulfurizing agent will be shortened. Therefore, when the peroxide content is 160 mass ppm or less as in the present invention, oxidation of the metal catalyst by peroxide can be suppressed, and the desulfurization performance can be prevented from being lowered.

  Here, as the peroxide in the present invention, various peroxides generated by the oxidative degradation reaction of petroleum hydrocarbon raw materials are targeted, and the catalytic metal can be oxidized by these. The organic peroxide includes any compound having a divalent —O—O— bond. More specifically, cumene hydroperoxide, tertiary butyl peroxide and the like can be mentioned. Hydroxy acids, in particular, can become an insoluble sludge and deposit of oil due to polymerization and condensation, which can be a major cause of filling the oil path.

  Moreover, the measurement of content of a peroxide can be performed based on JPI-5S-46-96.

  The fuel oil for fuel cells of the present invention has a sulfur content of 1 mass ppm or less derived from a sulfur compound having a boiling point exceeding 330 ° C. and less than 334 ° C. (hereinafter also referred to as “target sulfur compound”). Yes, preferably 0.5 ppm by mass or less. If the sulfur content derived from the sulfur compound having a boiling point exceeding 330 ° C and less than 334 ° C is 1 mass ppm or less, the sustainability of the desulfurizing agent can be improved. The sulfur content is preferably as small as possible, and most preferably 0 ppm by mass. As the target sulfur compound, compounds having an aromatic ring such as alkylbenzothiophenes can be considered.

The measurement of the sulfur content derived from the target sulfur compound can be obtained by the following method. First, the total sulfur concentration in the sample oil before and after the desulfurization treatment is analyzed according to JISK2541 microcoulometric titration method. Next, in the chromatogram obtained by GC-SCD (gas chromatograph with chemiluminescence sulfur detector) analysis equipped with a boiling point column corresponding to the order of the boiling points and retention times of the sulfur compounds, the boiling points are 330 ° C. and 334 ° C. The peak which a sulfur compound shows is specified, and the total area (peak area derived from an object sulfur compound) of the peak detected during these holding times, and the peak area of all sulfur compounds are calculated. Using these measurement results, “the amount of sulfur derived from a sulfur compound having a boiling point exceeding 330 ° C. and less than 334 ° C.” contained in the sample oil can be calculated according to the following formula (1). In addition, the peak which the sulfur compound whose boiling point is 330 degreeC, and the sulfur compound whose boiling point is 334 degreeC can identify with the GC-SCD peak of dibenzothiophene and 4 methyldibenzothiophene, respectively.
Formula (1):
Sulfur content derived from sulfur compounds having a boiling point exceeding 330 ° C. and less than 334 ° C. (mass ppm) = total sulfur concentration in the sample × (boiling point obtained by GC-SCD exceeds 330 ° C. and less than 334 ° C. Area value of sulfur compounds in range / area value of all sulfur compounds determined by GC-SCD)

  Furthermore, the fuel oil for fuel cells of the present invention has a total sulfur content of 80 ppm by mass or less, and preferably 10 ppm by mass 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 80 mass ppm or less.

  Moreover, it is preferable that the fuel oil for fuel cells of this invention is 10 mass ppm or less in sulfur content derived from a sulfur compound lighter than dibenzothiophene (DBT). If the sulfur content derived from such a sulfur compound is 10 mass ppm or less, the load of the sulfur content can be reduced, so that the sustainability of the desulfurizing agent can be improved. Here, the lighter sulfur compound than dibenzothiophene means a sulfur compound having a retention time shorter than that of dibenzothiophene in GC-SCD (gas chromatography with chemiluminescence sulfur detector) analysis. Specific examples include alkyl mercaptans and alkylthiophenes.

The sulfur content derived from a sulfur compound lighter than dibenzothiophene (DBT) can be determined by the following method. First, similarly to the calculation formula (1), the total sulfur concentration in the sample oil is obtained. Then, a chromatogram representing the peak intensity of each component in the fuel oil separated by the retention time is obtained by the GC-SCD method. Next, a peak indicating dibenzothiophene is identified in the obtained chromatogram, and the peak is calculated from the area ratio of the peak having a shorter retention time than dibenzothiophene relative to the total peak area. That is, it can be calculated according to the following calculation formula (2).
Formula (2):
Sulfur content derived from sulfur compounds lighter than dibenzothiophene (DBT) (mass ppm) = total sulfur concentration in the sample × (area value of sulfur compounds lighter than DBT determined by GC-SCD / total determined by GC-SCD Area value of sulfur compounds)

  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 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 order to reduce the peroxide in the fuel oil for the fuel cell, it is possible to pass through a polar substance such as silica to remove them. Further, this method can be used in combination with an antioxidant added to the petroleum-based raw material in advance.

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 isobutyleneamine, anti-icing agents such as polyhydric alcohols and ethers thereof, organic acid alkali metals and 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 exhibited, 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 conditions at this time are preferably such that the temperature is from room temperature to 500 ° C., the pressure is from normal pressure to 2 MPa, and the liquid space velocity (LHSV) is from 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>
Example 1
Straight-run kerosene (distillation cut range 150-250 ° C., sulfur content 0.006% by mass) obtained from atmospheric crude oil by atmospheric distillation is used as a raw material oil, and this raw material oil is used as a hydrodesulfurization catalyst for Co-Mo type desulfurization. Using a catalyst (KF757, manufactured by Nippon Ketjen Co., Ltd.), hydrogenation was performed under the conditions of a reaction temperature (WABT) of 315 ° C., a hydrogen partial pressure of 4.5 MPa, and a liquid space velocity (LHSV) of 3 h ^−1. A hydrodesulfurized kerosene composition (fuel oil A) having a property of 1 was obtained.

Example 2
The hydrodesulfurized kerosene composition (fuel oil A) obtained in Example 1 was oxidized and deteriorated according to ASTM D 4625 to obtain a hydrodesulfurized kerosene composition (fuel oil B) having the properties shown in Table 1. .

Example 3
Straight-run kerosene (distillation cut range 150-250 ° C., sulfur content 0.25% 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 for Co-Mo type desulfurization. Using a catalyst (KF757, manufactured by Nippon Ketjen Co., Ltd.), hydrogenation treatment was performed under the conditions of a reaction temperature (WABT) of 305 ° C., a hydrogen partial pressure of 4.0 MPa, and a liquid space velocity (LHSV) of 4h ⁻¹ Was subjected to oxidative degradation in accordance with ASTM D 4625 to obtain a hydrodesulfurized kerosene composition (fuel oil C) having the properties shown in Table 1.

Example 4
Commercially available catalysts (60% by volume of hydrodesulfurized kerosene composition (fuel oil C) obtained in Example 3 and a wax having 30 or more carbon atoms (not including sulfur) obtained by Fischer-Tropsch synthesis as a hydrogenation catalyst ( After hydrocracking using 0.5% by mass Pt / USY zeolite catalyst manufactured by Catalytic Chemical Industry Co., Ltd., the kerosene fraction obtained by distillation (distillation cut range 150-250 ° C) was mixed with 40% by volume. A hydrodesulfurized kerosene composition (fuel oil D) having the properties shown in Table 1 was obtained.

Comparative Example 1
Straight-run kerosene (distillation cut range 150-250 ° C., sulfur content 0.25% 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 for Co-Mo type desulfurization. Using a catalyst (KF757, manufactured by Nippon Ketjen Co., Ltd.), hydrogenation was performed under the conditions of a reaction temperature (WABT) of 310 ° C., a hydrogen partial pressure of 4.0 MPa, and a liquid space velocity of 4 h ⁻¹ , and cumene as a peroxide. Hydroperoxide was added to obtain a hydrodesulfurized kerosene composition (fuel oil a) having the properties shown in Table 1.

Comparative Example 2
Straight-run kerosene (distillation cut range 150-250 ° C., sulfur content 0.22 mass%) obtained from Middle Eastern crude oil by atmospheric distillation is used as a feedstock oil, and Co-Mo series desulfurization using the feedstock oil as a hydrodesulfurization catalyst. Using a catalyst (KF757, manufactured by Nippon Ketjen Co., Ltd.), hydrogenation treatment was performed under the conditions of a reaction temperature (WABT) of 335 ° C., a hydrogen partial pressure of 4.5 MPa, and a liquid space velocity of 3.5 h ^−1. The hydrodesulfurized kerosene composition (fuel oil b) having the properties shown in Table 1 was obtained by oxidative degradation in accordance with ASTM D 4625.

Comparative Example 3
Straight-run kerosene (distillation cut range 150-250 ° C., sulfur content 0.30% by mass) obtained from Middle Eastern crude oil by atmospheric distillation is used as a raw oil, and Co-Mo-based desulfurization using the raw oil as a hydrodesulfurization catalyst. Using a catalyst (KF757, manufactured by Nippon Ketjen Co., Ltd.), hydrogenation treatment was performed under the conditions of a reaction temperature (WABT) of 335 ° C., a hydrogen partial pressure of 3.0 MPa, and a liquid space velocity of 5 h ^−1. After oxidative degradation in accordance with D 4625, 110 mass ppm of butyl hydroperoxide was added as a peroxide to obtain a hydrodesulfurized kerosene composition (fuel oil c) having the properties shown in Table 1.

<Analysis of peroxide>
The peroxide content in the fuel oils obtained in Examples and Comparative Examples was determined based on JPI-5S-46-96.

<Analysis of sulfur content in fuel oil>
The sulfur content of each fuel oil was analyzed as follows. A sulfur content (mass ppm) derived from a sulfur compound having a boiling point exceeding 330 ° C. and less than 334 ° C. was calculated by the above-described calculation formula (1). The sulfur content (mass ppm) derived from the lighter sulfur compound than dibenzothiophene (DBT) was calculated by the above-described calculation formula (2). The analysis conditions of GC-SCD at the time of this analysis are shown below.

<GC-SCD>
Equipment: GC: GC-2010 (SHIMAZU)
SCD: 7090S (ANTEK)
Column: HP-1MS
Column temperature: 40 ° C.-280 ° C. (temperature increase)
Measurement time: 30 min
Inlet temperature: 260 ° C., detector temperature: 280 ° C.
Carrier gas: He; 90 kPa
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 said Example and the comparative example was produced as follows.
Boehmite AP-3 (manufactured by Catalysts & Chemicals Industries) 1.24 g and 1N HNO ₃ solution 40ml and the post-heating in addition to 80 ° C. in deionized water 1 liter by adding 149g 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, (NH 4)} a _{6 Mo 7 O 24 · 5H 2} O was added 3 g 80 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 15 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. As an operation method, the fuel oils obtained in Examples and Comparative Examples were respectively supplied for a certain period of time. The desulfurized oil that flowed out of the reaction tube was collected, and the total sulfur content in the oil was measured.
The oil passage time from the start of the desulfurization treatment until the total sulfur content reached 100 mass ppb was defined as the breakthrough time.

  As is clear from Table 1, the fuel oils of Examples 1 to 4 according to the present invention have a life of the desulfurizing agent (total sulfur content of the desulfurized fuel oil is less than that of Comparative Examples 1 to 3. It can be seen that (evaluated by the time to reach 100 mass ppb) is much longer.

Claims (2)

  It has distillation characteristics with an initial boiling point of 135 to 170 ° C. and a 95% distillation temperature of 270 ° C. or less, a peroxide content of 160 mass ppm or less, a boiling point of more than 330 ° C. and a range of less than 334 ° C. A fuel oil for a fuel cell, characterized in that a sulfur content derived from a sulfur compound is 1 mass ppm or less and a total sulfur content is 80 mass ppm or less.   The fuel oil for fuel cells according to claim 1, wherein the sulfur content derived from a sulfur compound lighter than dibenzothiophene is 10 mass ppm or less.