WO2001077266A1 - Fuel for use in fuel cell system - Google Patents

Abstract

A fuel for use in a fuel cell system which has a total content of hydrocarbons having 7 to 8 carbon atoms of 20 vol % or more, and a total content of hydrocarbons having 10 or more carbon atoms of 20 vol % or less. The fuel exhibits an increased energy output generated per its weight and per amount of CO2 formed, an improved fuel consumption, a decreased evaporative emission, good handling properties such as good storage stability and a suitable flash point, and reduced calories required for preheating. Further, the fuel allows a fuel cell system using the fuel to keep its initial performance for a long period of time, since it reduces the deterioration of a fuel cell system, that is, a reforming catalyst, a water gas shift reaction catalyst, a carbon monoxide removal catalyst, a fuel cell stack and the like.

Description

 Fuel for fuel cell system Technical field Akira

 The present invention relates to a fuel used for a fuel cell system.

 Field background technology

In recent years, the growing sense of danger to the global environment in the future has demanded the development of an energy-friendly energy supply system. In particular, the reduction of co ₂ for prevention of global warming, THC (unreacted hydrocarbons in the exhaust gas), NO x, PM (particulate matter in exhaust gas: soot, high-boiling-fuel-lubricant The ability to achieve a high degree of reduction of harmful substances such as unburned polymer components) is required. Specific examples of the system include an automobile power system that replaces the conventional Otto's diesel system or a power generation system that replaces thermal power.

Thus we have the energy efficiency is close to ideal, essentially fuel cells do not appear discharge only H ₂ 0 and C 0 ₂ has been expected promising systems also have to meet the needs of society. To achieve such a system, it is indispensable to develop not only equipment technology but also the optimal fuel for it.

 Conventionally, hydrogen, methanol, and hydrocarbon fuels have been considered as fuels for fuel cell systems.

 As a fuel for fuel cell systems, hydrogen is advantageous in that it does not require a special reformer, but because it is a gas at room temperature, it has problems with storage and mounting on vehicles, etc. Special equipment is required. Also, there is a high risk of bow I fire, so care must be taken when handling.

On the other hand, methanol has the advantage of being relatively easy to reform into hydrogen, and its power generation per unit weight is small. In addition, since it is corrosive, special equipment is required for storage and supply. As described above, no fuel has yet been developed to achieve the full potential of the fuel cell system. In particular, as the fuel for a fuel cell system, it is often the power generation amount per weight, it generation amount of C 0 ₂ emissions per often, that overall fuel consumption of the fuel cell system is good, the evaporation gas (fuel vapor E Mission) Power s' low, reforming catalyst, water gas shift reaction catalyst, carbon monoxide removal catalyst, fuel cell stack, etc., fuel cell system with low deterioration and long-term initial performance, system startup time power s short, Good handling properties such as storage stability and bow I fire point are required.In a fuel cell system, it is necessary to maintain the temperature of the fuel and reformer at a given temperature s'. The amount of power generated by subtracting the required amount of heat (the amount of heat that balances the endothermic heat generated by preheating and the reaction) is the amount of power generated by the entire fuel cell system. Therefore, the temperature force required to reform the fuel is lower and the preheating amount s' is more advantageous, and the system startup time is shorter. It is also necessary that the calorific power is small. Insufficient preheating can lead to high unreacted hydrocarbons (THC) in the exhaust gas, not only reducing power generation per weight but also causing air pollution. Conversely, when the same system is operated at the same temperature, it is advantageous to have a low THC power in the exhaust gas and a high conversion rate to hydrogen.

 In view of such circumstances, an object of the present invention is to provide a fuel suitable for a fuel cell system satisfying the above-mentioned required properties in a well-balanced manner. Disclosure of the invention

 The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that a fuel containing a specific amount of a hydrocarbon compound having a specific carbon number is suitable for a fuel cell system.

 That is, the fuel for a fuel cell system according to the present invention is:

(1) The total content of hydrocarbon compounds having 7 and 8 carbon atoms is 20% by volume or more, and the total content of hydrocarbon compounds having 10 or more carbon atoms is 20% by volume or less. It is. It is more preferable that the fuel containing the specific amount of the hydrocarbon compound having the specific number of carbon atoms further satisfies the following requirements.

 (2) Fuel for a fuel cell system having a sulfur content of 50 mass ppm or less.

(3) A fuel for a fuel cell system having a saturated content of 30% by volume or more.

 (4) Fuel for a fuel cell system having an olefin content of 35% by volume or less.

 (5) A fuel for a fuel cell system having an aromatic content of 50% by volume or less.

 (6) Fuel for a fuel cell system in which the proportion of paraffin in the saturated content is 60% by volume or more.

 (7) Fuel for fuel cell systems in which the proportion of branched paraffin in the paraffin content is 30% by volume or more. BRIEF DESCRIPTION OF THE FIGURES

 FIG. 1 is a flowchart of a steam reforming fuel cell system used for evaluating fuel for a fuel cell system according to the present invention. FIG. 2 is a flowchart of a partial oxidation fuel cell system used for evaluating fuel for a fuel cell system of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION

 Hereinafter, the contents of the present invention will be described in more detail.

In the present invention, the amount of the hydrocarbon compound having a specific carbon number is as follows. In the present invention, the total content of hydrocarbon compounds having 7 and 8 carbon atoms (V (C ₇ + C ₈ )) is the total content of hydrocarbon compounds having 7 and 8 carbon atoms based on the total amount of fuel. are shown, it is often the power generation amount per weight, it forces C 0 ₂ generation amount per power generation multi Ikoto, etc. good fuel power s of the entire fuel cell system, it is on 2 0% by volume or less It is necessary, and the force S is preferably 25% by volume or more, more preferably 30% by volume or more, even more preferably 35% by volume or more, and 40% by volume or more. That power is most preferred.

Further, in the present invention, the content of the hydrocarbon compound having 10 or more carbon atoms means that the amount of power generation per CO 2 generation amount is large, that the fuel efficiency of the fuel cell system as a whole is good, and that the reforming catalyst is deteriorated. Small initial capacity s It is necessary that the total amount of hydrocarbon compounds having 10 or more carbon atoms (V (C ₁₀ +)) be not more than 20% by volume based on the amount, and preferably not more than ₁₀ % by volume. Most preferably, the volume is 5% by volume or less.

In the present invention, the content of the hydrocarbon compound having 4 carbon atoms is not particularly limited, but the content of the hydrocarbon compound having 4 carbon atoms (V (C ₄

)) Is preferably 15% by volume or less, and more preferably 10% by volume or less from the viewpoint that the amount of evaporative gas (evaporation) can be kept low and the handling properties such as the flash point are good. More preferably, the power is most preferably 5% by volume or less. The content of the hydrocarbon compound having 5 carbon atoms is not particularly limited, but the content of the hydrocarbon compound having 5 carbon atoms (V (C ₅ )) based on the whole fuel is usually less than 5% by volume. Are preferably used.

The content of the hydrocarbon compound having 6 carbon atoms is not particularly limited, but the content of the hydrocarbon compound having 6 carbon atoms (V (C ₆ )) based on the total fuel amount is usually less than 10% by volume. Are preferably used.

Note that V (C ₄ ), V (C _S ), V (C _E ), V (CT + CS), and V (C ₁₀ +) described above are values determined by the gas chromatography method described below. It is. In other words, a column of methyl silicon cantilever is used for the column, helium or nitrogen is used for the carrier gas, and a hydrogen ionization detector (FID) is used for the detector.The power ram length is 25 to 50 m, and the carrier gas flow is 0.5 to 1.5 ml Zmin, split ratio 1: 50 ~: 1: 250, inlet temperature 1 50 ~ 2 50 ° initial column temperature 1 10 ~ 10 ° C, final column temperature 150 ~ 250 ° C, It is a value measured at a detector temperature of 150 to 250 ° C.

Although the sulfur content of the fuel of the present invention is not limited at all, the initial performance of the fuel cell system such as a reforming catalyst, a water gas shift reaction catalyst, a carbon monoxide removal catalyst, and a fuel cell stack is small and the initial performance is long. In view of the fact that the fuel can be maintained for a long time, it is preferable that the amount be 50 mass ppm or less, more preferably 30 mass ppm or less, even more preferably 10 mass ppm or less, and It is even more preferred that the content be less than or equal to ppm, most preferably less than or equal to 0.1 ppm by mass. Here, when the sulfur content is 1 mass ppm or more, the sulfur content measured by JIS 2541 "Crude oil and petroleum products-sulfur content test method" is used. When the sulfur content is less than 1 mass ppm, ASTM D4045-96 "Standard Test It means the sulfur content measured by the “Method for Sulfur in Petroleum Products by Hydrogenolysis and Rateometric Colorimetry”.

 In the present invention, the content of each of the saturated component, the olefin component and the aromatic component is not limited, but the saturated component (V (S)) is 30% by volume or more, and the olefin component (V (0)) is 35% by volume. % Or less, and the aromatic content (V (Ar)) is preferably 50% by volume or less. Hereinafter, these will be individually described.

V (S) is often power generation amount per weight, it generation per C0 ₂ generation amount is large, good fuel economy force S of the entire fuel cell system, it is not less THC force s in the exhaust gas, It is preferably at least 30% by volume, more preferably at least 40% by volume, still more preferably at least 50% by volume, and more preferably at least 60% by volume because of a short system startup time. Is even more preferably 70% by volume or more, still more preferably 80% by volume or more, even more preferably 90% by volume or more, and even more preferably 90% by volume or more. % Force is the most preferable.

V (0) is often power generation amount per weight, it generation per C0 ₂ generation amount is large, the deterioration of the reforming catalyst can last reduced initial resistance capability S long, that good storage stability For this reason, the force is preferably 35% by volume or less, more preferably 25% by volume or less, still more preferably 20% by volume or less, and even more preferably 15% by volume or less. Most preferably, it is 10% by volume or less.

V (Ar) is often power generation amount per weight, C0 ₂ generation amount per power generation multi Ikoto, good fuel economy power s of the entire fuel cell system, it THC in the exhaust gas is small, the system The starting time is short, the deterioration of the reforming catalyst is small, and the initial performance can be maintained for a long time. Therefore, the capacity is preferably 50% by volume or less, more preferably 45% by volume or less, and 40% by volume or less. More preferably, it is even more preferably 35% by volume or less, even more preferably 30% by volume or less. It is even more preferred that it is below, even more preferably 20% by volume or less, even more preferably 10% by volume or less, and most preferably 5% by volume or less.

 It is most preferable that the preferable range of the sulfur content and the preferable range of the aromatic content are satisfied, because the deterioration of the reforming catalyst is small and the initial performance can be maintained for a long time.

 The above V (S), V (0) and V (A r) are all values measured by the fluorescent indicator adsorption method of JIS K 2 536 “Petroleum product-hydrocarbon type test method”.

Further, in the present invention is not in any way limit for the percentage of the paraffin component in the saturated component of the fuel, and the like are often power generation amount per weight, it generation amount of C 0 ₂ emissions per often, saturated components Preferably, the paraffin content is at least 60% by volume, more preferably at least 65% by volume, even more preferably at least 70% by volume, and at least 75% by volume. Is still more preferably 80% by volume or more, still more preferably 85% by volume or more, even more preferably 85% by volume or more, and even more preferably 90% by volume or more. Most preferably, it is 95% by volume or more.

 The above-mentioned saturated content and paraffin content are values determined by the above-described gas chromatography method.

Further, such is no limitation on the proportion of branched paraffins in the paraffins Iga, many power generation amount per weight, it generation amount of C 0 ₂ emissions per is large, overall fuel consumption of fuel cells system It is preferable that the percentage of branched paraffins in the paraffin content is 30% by volume or more, because of its good performance, low THC power in exhaust gas, and short system startup time s'. % Or more, and most preferably 70% or more by volume.

 The above-mentioned paraffin content and the amount of branched paraffin are values determined by the above-mentioned gas chromatography method.

There is no particular limitation on the method for producing the fuel of the present invention. Specifically, for example, light naphtha obtained by distilling crude oil at normal pressure, heavy naphtha obtained by distilling crude oil at normal pressure Desulfurized light naphtha desulfurized light naphtha, desulfurized heavy naphtha desulfurized heavy naphtha, isomerized gasoline obtained by converting light naphtha to isoparaffin with an isomerizer, Alkylate obtained by addition (alkylation), desulfurized alkylate obtained by desulfurizing alkylate, low sulfur alkylate obtained by using desulfurized hydrocarbon such as isobutane, and desulfurized lower olefin, catalytic reforming method Reformed gasoline obtained in the above, rough rice extracted from aromatic gas extracted from reformed gasoline, light fraction of reformed gasoline, medium and heavy fraction of reformed gasoline, and heavy of reformed gasoline Distillate, cracked gasoline obtained by catalytic cracking, hydrocracking, etc. Light fraction of cracked gasoline, heavy fraction of cracked gasoline, cracked gasoline Desulfurization desulfurization cracked gasoline, desulfurization light quality degradation gasoline a light fraction and desulfurization of cracked gasoline, heavy fraction of cracked gasoline was desulfurization desulfurization heavy cracked gasoline

Light fraction of GTL (Gas to Liquids) obtained by F-T (Fischer-Tropsch) synthesis after decomposing natural gas into carbon monoxide and hydrogen, desulfurized LPG obtained by desulfurizing LPG, etc. It is manufactured using one or two or more base materials. Further, it can also be produced by mixing one or more of the above-mentioned base materials and then desulfurizing them by hydrogenation or adsorption.

 Among them, preferred as the base material for producing the fuel of the present invention are heavy naphtha, desulfurized heavy naphtha, alkylate, desulfurized alkylate obtained by desulfurizing alkylate, desulfurized hydrocarbon such as isobutane, and desulfurized hydrocarbon. Low-sulfur alkylate using low-grade olefins, desulfurized light cracked gasoline obtained by desulfurizing the light fraction of cracked gasoline, roughened oil, light fraction of GTL, desulfurized LPG obtained by desulfurizing LPG, etc. .

 The fuel for the fuel cell system of the present invention includes a colorant for identification, an antioxidant for improving oxidative stability, a metal deactivator, a corrosion inhibitor for corrosion prevention, and cleanliness of the fuel line. Additives such as a detergent for maintaining the lubrication and a lubricity improver for improving the lubricity can be added.

However, since the deterioration of the reforming catalyst is small and the initial capacity s' can be maintained for a long time, the colorant is preferably 1 Oppm or less, more preferably 5 ppm or less. For the same reason, the antioxidant is preferably at most 300 ppm, more preferably at most 200 ppm. In addition, 1 OO ppm or less power s is even more preferable, and 1 O ppm or less power s is most preferable. For the same reason, the metal deactivator is preferably 50 ppm or less, more preferably 30 ppm or less, even more preferably 1 Oppm or less, and even more preferably 5 ppm or less. Similarly, since the deterioration of the reforming catalyst is small and the initial performance can be maintained for a long time, the corrosion inhibitor is preferably 5 Oppm or less, more preferably 30 ppm or less, still more preferably 1 Oppm or less, and most preferably 5 ppm or less. preferable. For the same reason, the detergent is preferably 300 ppm or less, more preferably 200 pm or less, most preferably 100 ppm or less. For the same reason, the lubricity improver preferably has a force of 300 ppm or less, more preferably 200 ppm or less, and even more preferably 100 ppm or less.

 The fuel of the present invention is used as a fuel for a fuel cell system. The fuel cell system according to the present invention includes a fuel reformer, a carbon monoxide purifier, a fuel cell, and the like. The fuel of the present invention is suitably used in any fuel cell system.

 The fuel reformer is for reforming the fuel to obtain hydrogen, which is the fuel of the fuel cell. As a reformer, specifically, for example,

 (1) A steam reforming reformer that mixes heated and vaporized fuel with steam and reacts by heating in a catalyst such as copper, nickel, platinum, ruthenium, etc., to obtain a product containing hydrogen as a main component.

 (2) A partially oxidized reformer that mixes heated and vaporized fuel with air and reacts with or without a catalyst such as copper, nickel, platinum, ruthenium, etc. to obtain a product containing hydrogen as a main component.

 (3) The heated and vaporized fuel is mixed with steam and air, and the partial oxidation reforming of (2) is performed in the former stage of the catalyst layer such as copper, nickel, platinum, and ruthenium, and the partial oxidation reaction is performed in the latter stage The steam reforming of (1) is performed by utilizing the heat generation of the steam to form a partial oxygen-steam reforming reformer that obtains a product containing hydrogen as a main component.

And the like.

 The carbon monoxide purifier removes carbon monoxide contained in the gas generated by the above reformer and becomes a catalyst poison of the fuel cell.

(1) Mix reformed gas and heated steam to form copper, nickel, platinum, ruthenium Water gas shift reactor, which produces carbon dioxide and hydrogen as products from carbon monoxide and water vapor by reacting in a catalyst such as

 (2) A selective oxidation reactor that converts carbon monoxide into carbon dioxide by mixing the reformed gas with compressed air and reacting it in a catalyst such as platinum or ruthenium is mentioned. used.

 Specific examples of fuel cells include solid polymer fuel cells (PEFC), phosphoric acid fuel cells (PAFC), molten carbonate fuel cells (MCFC), and solid oxide fuel cells (SOFC) And the like.

 The fuel cell system as described above is used for an electric vehicle, a conventional hybrid vehicle with an engine and electricity, a portable power source, a distributed power source, a home power source, a cogeneration system, and the like. Example

 Table 1 shows the properties and the like of the base materials used for each fuel in the examples and comparative examples.

 The heat capacity and latent heat of vaporization are described in the contents of each component determined by the gas chromatography method described above and in `` Vol.1, Chap.1 General Data, Table 1C1J '' of `` Technical Data Book-Petroleum RefiningJ ''. It was calculated based on the numerical value per unit weight for each component.

Table 2 shows the properties of each fuel used in Examples and Comparative Examples.

Table 1

Ten

Replacement form (Rule 26) Table 1 (continued)

11

Replacement form (Rule 26) Table 2

For each of these fuels, a fuel cell system evaluation test, evaporative gas test, and storage stability test were performed.

Fuel cell system evaluation test

 (1) Steam reforming type

 The fuel and water were vaporized by electric heating and led to a reformer, which was filled with a noble metal catalyst and maintained at a specified temperature with an electric heater, to generate reformed gas rich in hydrogen.

 The temperature of the reformer was set to the lowest temperature at which reforming was completely performed in the initial stage of the test (the lowest temperature at which THC was not contained in the reformed gas).

 The reformed gas is led to a carbon monoxide treatment device (water gas shift reaction) together with water vapor to convert carbon monoxide in the reformed gas into carbon dioxide, and the generated gas is guided to a polymer electrolyte fuel cell to generate electricity. Natsuta

 Fig. 1 shows a flowchart of the steam reforming type fuel cell system used for the evaluation.

 (2) Partial oxidation type

 The fuel was vaporized by electric heating, filled with a precious metal catalyst together with preheated air, and led to a reformer maintained at 110 ° C. by an electric heater to generate a reformed gas rich in hydrogen.

 The reformed gas is led to a carbon monoxide treatment device (water gas shift reaction) together with water vapor to convert carbon monoxide in the reformed gas into carbon dioxide, and the generated gas is guided to a polymer electrolyte fuel cell to generate electricity. Natsuta

 Figure 2 shows a flowchart of the partial oxidation fuel cell system used for the evaluation.

(3) Evaluation method

Evaluation H _2, CO in the reformed gas generated from the reformer immediately after the start of the test, were measured for C 0 _2, THC amount. Similarly, the evaluation test immediately after the start of H ₂ in the reformed gas generated from the carbon monoxide processor, CO, C 0 _2, THC amount measured immediately after the evaluation test start was performed on and start 1 0 0 hour after the fuel cell power generation, fuel consumption, and were measured for C 0 ₂ amount discharged from the fuel cell in. The amount of heat (preheat amount) required to guide each fuel to a predetermined reformer temperature was calculated from the heat capacity and latent heat of vaporization.

 From these measured and calculated values and the calorific value of the fuel, the performance degradation rate of the reforming catalyst is calculated.

(The amount of power generated 100 hours after the start of the test z The amount of power generated immediately after the start of the test), the thermal efficiency (the amount of power generated immediately after the start of the test / the amount of heat generated by the fuel), and the preheat ratio (the amount of preheat Z generated power) were calculated. Evaporative gas test

 A sample filling hose was attached to the filler port of a 20-litre gasoline carrying can, and the attachment part was completely sealed. Each liter was filled with 5 liters of fuel while the vent valve of the can was open. After filling, the air vent valve was closed and left for 30 minutes. After standing, an activated carbon adsorption device was attached to the tip of the air release valve, and the valve was opened. Immediately, 10 liters of each fuel were supplied from the filler port. Five minutes after refueling, leaving the air release valve open, the activated carbon was allowed to absorb steam, and then the weight increase of the activated carbon was measured. The test was 25. The test was performed at a constant temperature of C.

Storage stability test

 Each fuel was filled in a pressure-resistant sealed container together with oxygen, heated to 100 ° C., allowed to stand for 24 hours while maintaining the temperature, and evaluated by the real gum test method specified in JIS K2261.

Table 3 shows the measured values and calculated values.

Table 3

 2) Electric energy Fuel calorific value

 3) The amount of heat required to bring the fuel to the specified reformer temperature

4) Preheating amount / electric energy

Industrial applicability

 As described above, the fuel for a fuel cell system according to the present invention is a fuel that can obtain high-output electric energy with a small performance deterioration ratio and that satisfies various performances for a fuel cell.

Claims

The scope of the claims  1. A fuel cell in which the total content of hydrocarbon compounds having 7 and 8 carbon atoms is 20% by volume or more, and the total content of hydrocarbon compounds having 10 or more carbon atoms is 20% by volume or less. System fuel.  2. The fuel for a fuel cell system according to claim 1, wherein the sulfur content is 50 mass ppm or less.  3. The fuel for a fuel cell system according to claim 1, wherein the saturated content is 30% by volume or more.  4. The fuel for a fuel cell system according to any one of claims 1 to 3, wherein the olefin content is 35% by volume or less.  5. The fuel for a fuel cell system according to any one of claims 1 to 4, wherein the aromatic component is 50% by volume or less.  6. The fuel for a fuel cell system according to any one of claims 1 to 5, wherein the proportion of the paraffin component in the saturated component is 60% by volume or more.  7. The fuel for a fuel cell system according to any one of claims 1 to 6, wherein the proportion of the branched paraffin in the paraffin content is 30% by volume or more.