JP2011241320A - Method for desulfurizing hydrocarbon - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for desulfurizing a hydrocarbon, by which sulfur components in the hydrocarbon can be removed at ordinary temperature and at the atmospheric pressure without an oxidizing agent having a problem on safety, such as hydrogen peroxide.SOLUTION: The method for desulfurizing the hydrocarbon includes a light irradiation process for irradiating the hydrocarbon containing benzothiophene compounds and/or dibenzothiophene compounds with light in the presence of a light catalyst and oxygen. The light is preferably ultraviolet rays. The method for desulfurizing the hydrocarbon may further have contact process for contacting the hydrocarbon treated in the light irradiation process with an adsorbent.

Description

  The present invention relates to a hydrocarbon desulfurization method.

  Hydrocarbons such as natural gas, LPG, naphtha, and kerosene are widely used as fuels and raw materials for fuel gas for fuel cells. Such hydrocarbons usually contain sulfur-containing aromatic compounds such as benzothiophene and dibenzothiophene. When hydrocarbons containing this sulfur-containing aromatic compound are used as fuel, sulfur oxides are generated, causing air pollution, and when used as a fuel gas raw material for fuel cells, fuel gas It becomes a problem to act as a catalyst poison in the hydrogen production process or the like.

  Therefore, the above-mentioned hydrocarbon is usually used after being desulfurized. As a desulfurization method, a method of treating at high temperature and high pressure in the presence of a catalyst such as nickel-zinc or copper-zinc is common. However, since this method requires high temperature and high pressure and has low energy efficiency, a desulfurization method at normal temperature and normal pressure with high energy efficiency is desired.

  As one of the desulfurization methods at normal temperature and normal pressure, benzothiophene or dibenzothiophene is oxidized to sulfoxide or sulfone, and the sulfoxide or sulfone (hereinafter also referred to as “oxidized body”) is adsorbed by an adsorbent. There is. For example, in Patent Document 1, after oxidizing benzothiophene or dibenzothiophene using an oxidant such as hydrogen peroxide and a predetermined oxidation catalyst, an oxidant is adsorbed by a general adsorbent and desulfurized. Proposed.

JP 2004-195445 A

  However, the method of oxidizing using an oxidizing agent such as hydrogen peroxide is not practical due to safety problems.

  Accordingly, the present invention provides a hydrocarbon desulfurization method capable of removing sulfur components in hydrocarbons at room temperature and pressure without using an oxidant such as hydrogen peroxide solution that has safety problems. Objective.

  In order to solve the above problems, the present invention provides a hydrocarbon desulfurization method comprising a light irradiation step of irradiating a hydrocarbon containing benzothiophenes and / or dibenzothiophenes in the presence of a photocatalyst and oxygen. .

  According to this hydrocarbon desulfurization method, it is possible to remove sulfur components in hydrocarbons at a normal temperature and normal pressure using relatively safe oxygen as an oxidizing agent. Furthermore, in the conventional desulfurization method such as Patent Document 1, two stages of oxidation and adsorption are necessary for desulfurization. However, according to the hydrocarbon desulfurization method, desulfurization is possible in one stage.

  According to the hydrocarbon desulfurization method of the present invention, after the benzothiophenes and dibenzothiophenes are oxidized to sulfoxide and sulfone, these oxides are adsorbed on the photocatalyst, so that the above effect can be obtained. The inventors are thinking.

  The light is preferably ultraviolet light from the viewpoint that the efficiency of oxidation can be improved.

  The hydrocarbon desulfurization method of the present invention may further include a contact step of bringing the hydrocarbon treated in the light irradiation step into contact with the adsorbent. Thereby, the oxide which was not adsorb | sucked by the photocatalyst is adsorb | sucked, and also the density | concentration of the sulfur component in hydrocarbon can be reduced.

  According to the hydrocarbon desulfurization method of the present invention, it is possible to remove sulfur components in hydrocarbons at room temperature and normal pressure without using an oxidant having a safety problem such as aqueous hydrogen peroxide.

It is a conceptual diagram which shows an example of a fuel cell system provided with the desulfurizer to which the hydrocarbon desulfurization method of this invention is applied.

  Hereinafter, preferred embodiments of the present invention will be described in detail, but the present invention is not limited thereto.

  The hydrocarbon desulfurization method of the present embodiment includes a light irradiation step of irradiating a hydrocarbon containing benzothiophenes and / or dibenzothiophenes in the presence of a photocatalyst and oxygen.

  The benzothiophenes are a general term for compounds having a benzothiophene skeleton represented by the following formula (1). Specific examples thereof include benzothiophene, alkylbenzothiophene, and dialkylbenzothiophene, and more specifically, benzothiophene, methylbenzothiophene, and dimethylbenzothiophene. The dibenzothiophenes are a general term for compounds having a dibenzothiophene skeleton represented by the following formula (2). Specific examples thereof include dibenzothiophene, alkyldibenzothiophene, and dialkyldibenzothiophene, and more specifically, dibenzothiophene, methyldibenzothiophene, and dimethyldibenzothiophene.

Examples of the photocatalyst include titanium dioxide, zinc oxide, iron (III) oxide, and tungsten oxide.
The light used for light irradiation may be any light, but from the viewpoint of energy efficiency, ultraviolet light is preferable, and it is particularly ultraviolet light irradiated from a light source specialized in the ultraviolet region (less than 400 nm). preferable.

  Although the quantity of a photocatalyst is not specifically limited, For example, it is 0.1-20 mass parts with respect to 100 mass parts of hydrocarbons which are the object to desulfurize.

  The oxygen may be pure oxygen or a gas containing oxygen such as air, but air is preferable from the viewpoint of cost. An example of a method for causing oxygen to act is bubbling.

The light irradiation step can be performed at normal temperature and normal pressure, but pressure may be applied or the temperature may be increased. The contact time can be appropriately adjusted depending on the reaction scale and the like, and can be, for example, 0.01 to 2 hours.
In the light irradiation step, benzothiophenes and / or dibenzothiophenes are oxidized by a photocatalyst, and at the same time, oxides of benzothiophenes and / or dibenzothiophenes are adsorbed and removed by the photocatalyst to desulfurize hydrocarbons. be able to.

  The hydrocarbon desulfurization method of the present embodiment may further include a contact step of bringing the hydrocarbon treated in the light irradiation step into contact with the adsorbent.

  Examples of the adsorbent include general adsorbents such as activated carbon, activated alumina, silica gel, silica-alumina, and zeolite, and adsorbents in which a rare earth element compound and / or a copper compound is supported on a porous inorganic compound. Can be used.

  Examples of the porous inorganic compound include zeolite, mesoporous silica, activated carbon, silica, alumina and silica-alumina, and faujasite type zeolite, mesoporous silica and activated carbon are preferable.

  Specific examples of the faujasite type zeolite include NaX type zeolite, HX type zeolite, NH4X type zeolite, NaY type zeolite, HY type zeolite, NH4Y type zeolite and the like. Specific examples of mesoporous silica include MCM-41, FSM-16, MCM-48, MCM-50, SBA-15 and the like.

  Examples of the rare earth element include lanthanum, yttrium, cerium, scandium, ytterbium, gadolinium, and samarium, and among these, cerium or lanthanum is preferable. Of course, two or more kinds of rare earth elements can be used in combination.

  As the rare earth element compound and the copper compound, for example, chlorides, nitrates, sulfates, organic acid salts, and oxides of the respective metals can be used. Preferable specific examples of rare earth element compounds and copper compounds include cerium nitrate (III), cerium chloride (III), lanthanum nitrate (III), lanthanum chloride (III), copper nitrate (II), copper chloride (II ).

  There are no particular limitations on the method for supporting the rare earth element compound or the copper compound, and a known method such as a normal impregnation method or an ion exchange method can be used. For example, in the impregnation method, a rare earth element compound or a copper compound is dissolved in a solvent such as water, ethanol or acetone, particularly preferably water, and then impregnated into a carrier, and then dried, fired, etc. A supported catalyst can be obtained. The rare earth element compound or the copper compound can be used without particular limitation as long as it is soluble in a solvent.

  Although the amount of the rare earth element compound and / or the copper compound supported in the adsorbent is not particularly limited, it can be, for example, 10 to 50% by mass in terms of oxide.

  Examples of the method for bringing the hydrocarbon into contact with the adsorbent in the contacting step include a method in which the adsorbent is added to the hydrocarbon and stirring, and a flow-type fixed bed system. In the case of the circulation type fixed bed system, 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.

  The contact step can be performed at normal temperature and normal pressure, but pressure may be applied or the temperature may be increased. The contact time can be appropriately adjusted depending on the scale of the reaction, and can be 0.5 to 8 hours, for example.

  The hydrocarbon desulfurization method of the present embodiment can be suitably used for desulfurization of hydrocarbons such as fuel, natural gas, LPG, naphtha, kerosene and the like used as a raw material for fuel gas for fuel cells.

  Hereinafter, an example of a fuel cell system including a desulfurizer to which the hydrocarbon desulfurization method of the present embodiment is applied will be described. FIG. 1 is a conceptual diagram showing an example of a fuel cell system including an oxidative desulfurization reactor to which the hydrocarbon desulfurization method of the present embodiment is applied.

  In FIG. 1, the fuel in the fuel tank 3 passes through a fuel pump 4 and is oxidized in a hydrocarbon hydrocarbon of the fuel in an oxidative desulfurization reactor 5 filled with a photocatalyst, and the oxides. The desulfurizer 6 further removes the benzothiophene and / or dibenzothiophene oxides by adsorption in the desulfurizer 6 as necessary. At this time, if necessary, a hydrogen-containing gas from at least one of the downstream of the reformer 8, the downstream of the shift reactor 10, the downstream of the carbon monoxide selective oxidation reactor 11, and the anode off-gas can be added. The fuel desulfurized in the desulfurizer 6 is mixed with water from the water tank 1 through the water pump 2, introduced into the vaporizer 7, vaporized, and sent to the reformer 8.

  As the catalyst charged in the reformer 8, a nickel-based, ruthenium-based, or rhodium-based catalyst can be used. The reaction tube of the reformer 8 is heated by a burner 18 using fuel from the fuel tank 3 and anode off gas as fuel, and is preferably adjusted to a range of 350 to 700 ° C.

  The reformed gas containing hydrogen and carbon monoxide produced in this manner is passed through the shift reactor 10 and the carbon monoxide selective oxidation reactor 11 in order so as not to affect the characteristics of the fuel cell. The carbon monoxide concentration is reduced. Examples of the catalyst used in these reactors include an iron-chromium-based catalyst and / or a copper-zinc-based catalyst in the shift reactor 10 and a ruthenium-based catalyst in the carbon monoxide selective oxidation reactor 11. it can.

  The polymer electrolyte fuel cell 17 includes an anode 12, a cathode 13, and a solid polymer electrolyte 14, and a raw material gas having a reduced carbon monoxide concentration obtained by the above method is provided on the anode 12 side. The air sent from the air blower 9 is introduced after an appropriate humidification treatment if necessary. At this time, a reaction in which hydrogen gas becomes protons and emits electrons proceeds at the anode 12, and a reaction in which oxygen gas obtains electrons and protons to become water proceeds at the cathode 13. 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 12, and platinum black and Pt catalyst supported on activated carbon are used for the cathode 13, respectively. In general, both the anode 12 and cathode 13 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, the above-mentioned porous catalyst layer is laminated on both sides of a polymer electrolyte membrane known by a trade name such as Nafion (DuPont), Gore (Gore), Flemion (Asahi Glass), Aciplex (Asahi Kasei), etc. Then, a MEA (Membrane Electrode Assembly) is formed. 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 12 and the cathode 13. The anode off gas is consumed in the 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
In a beaker charged with a stirrer, benzothiophene corresponding to a sulfur concentration of 200 ppm by mass is placed in 50 cc of normal dodecane (n-C12) as a raw material, and further, TiO ₂ for photocatalyst (trade name: ST-01, 0.2 g of powder manufactured by Ishihara Sangyo Co., Ltd. was added.
The resulting mixed solution was irradiated with UV light with a Xe short arc lamp while bubbling air, and stirred at room temperature for 2 hours.

(Example 2)
After stirring at room temperature for 2 hours in Example 1, 0.2 g of adsorbent A was added to the resulting mixture, and further, desulfurization reaction was performed by stirring for 2 hours at normal pressure and temperature of 20 ° C. .
Adsorbent A was prepared by the following method.
By immersing a 30% by mass cerium nitrate (III) aqueous solution in commercially available NaX powder (Si / Al = 1.4) and heating and stirring at 80 ° C., ion exchange between cerium ions and Al protons is performed. It was. Then, the adsorbent A was obtained by drying at 120 degreeC for 8 hours or more, and carrying out air baking at 400 degreeC for 2 hours.

(Comparative Example 1)
A blank experiment was performed in the same manner as in Example 1 except that UV light was not irradiated.

(Comparative Example 2)
Experiments were performed in the same manner as in Example 1 using SiO ₂ instead of TiO ₂ .

(Comparative Example 3)
An experiment was conducted in the same manner as in Example 1 using Al ₂ O ₃ instead of TiO ₂ .

[Measurement of residual S amount]
The amount of sulfur contained in the products obtained in Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 3 (residual S amount, unit: mass ppm) was measured. The results are shown in Table 1.

(Example 3)
A UV irradiation source (Xe short arc lamp) and an air line were installed in the oxidation desulfurization reactor 5 filled with photocatalyst TiO ₂ (ST-01, manufactured by Ishihara Sangyo Co., Ltd., powder, 50 g). While irradiating UV and bubbling air at 5 cc / min, JIS No. 1 kerosene (sulfur concentration: 10 mass ppm, aromatic content part: 19.0 vol%, bicyclic: 0.4 vol%, tricyclic: Photooxidation desulfurization was performed by passing oil through 0.1% by volume. It was 3.1 mass ppm when it measured in the kerosene obtained from the oxidation desulfurization reactor 5 exit.

Example 4
In Example 3, the flow-through fixed bed system (LHSV = 0.25 h ⁻¹ ) at normal pressure and temperature of 20 ° C. in the desulfurizer 6 filled with the adsorbent A installed downstream of the oxidative desulfurization reactor 5. The desulfurization reaction was performed. When the sulfur concentration in the kerosene obtained from the desulfurizer 6 outlet was measured, it was less than 20 mass ppb.

As is clear from Table 1, in Example 1 in which UV light was irradiated while bubbling air in the presence of a photocatalyst, the amount of residual S was reduced from 200 ppm to 147 ppm, whereas UV light irradiation was performed. In Comparative Example 1, which did not, the amount of residual S did not change. From this result, in Example 1, it is presumed that the generated sulfoxide or sulfone was adsorbed on the photocatalyst after the benzothiophene was oxidized to sulfoxide or sulfone. On the other hand, in SiO ₂ and Al ₂ O ₃ that do not have an oxidative desulfurization action by a photocatalyst, the amount of residual S did not change even when irradiated with UV light. Moreover, in Example 2 which contacted with adsorbent after performing UV light irradiation in presence of a photocatalyst, it turns out that residual sulfur content reduces to 56 ppm and can further accelerate | stimulate desulfurization.

  In the fuel cell system shown in FIG. 1, it can be seen from the results of Example 3 and Example 4 in which the oxidative desulfurization reaction was performed using a photocatalyst, the sulfur concentration of kerosene as a raw material can be reduced even in the actual machine.

  DESCRIPTION OF SYMBOLS 1 ... Water tank, 2 ... Water pump, 3 ... Fuel tank, 4 ... Fuel pump, 5 ... Oxidation desulfurization reactor, 6 ... Desulfurizer, 7 ... Vaporizer, 8 ... Reformer, 9 ... Air blower, 10 ... Shift reactor, 11 ... carbon monoxide selective oxidation reactor, 12 ... anode, 13 ... cathode, 14 ... solid polymer electrolyte, 15 ... electric load, 16 ... exhaust port, 17 ... solid polymer fuel cell, 18 ... burner.

Claims (3)

  A hydrocarbon desulfurization method comprising a light irradiation step of irradiating a hydrocarbon containing benzothiophenes and / or dibenzothiophenes with light in the presence of a photocatalyst and oxygen.   The hydrocarbon desulfurization method according to claim 1, wherein the light is ultraviolet light.   The hydrocarbon desulfurization method according to claim 1, further comprising a contact step of bringing the hydrocarbon treated in the light irradiation step into contact with an adsorbent.

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