Desulfurization method for liquid fuel containing sulfur compounds

Abstract

To provide a desulfurization method capable of easily removing elemental sulfur from a liquid fuel containing a sulfur-containing compound without removing useful hydrocarbons in the compound.SOLUTION: A desulfurization method of a liquid fuel comprises: irradiating the liquid fuel containing a sulfur-containing compound with ultraviolet light having a wavelength of 100 to 350 nm; precipitating elemental sulfur; and removing the precipitated elemental sulfur.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a method for desulfurizing liquid fuel containing sulfur-containing compounds.

Background Art

[0002] Liquid fuels for automobiles and the like usually contain sulfur-containing compounds such as benzothiophenes and dibenzothiophenes. When such liquid fuel containing sulfur-containing compounds is used as fuel, it is known that sulfur oxides are generated, which causes air pollution. For this reason, various studies have been conducted on methods for desulfurizing liquid fuels.

[0003] For example, Patent Document 1 discloses a method for desulfurizing hydrocarbons, which includes a light irradiation step of irradiating hydrocarbons containing benzothiophenes and / or dibenzothiophenes with light in the presence of a photocatalyst and oxygen.

[0004] Further, Patent Document 2 discloses a method for desulfurizing petroleum oils, which is characterized by irradiating ultraviolet rays while supplying an oxygen-containing gas in the presence of a polar organic solvent to the petroleum oils.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, the desulfurization methods disclosed in Patent Documents 1 and 2 are both methods of oxidizing sulfur-containing compounds to oxides in the form of sulfoxides or sulfones and then removing these oxides. Therefore, the conventional desulfurization methods have problems of simultaneously removing beneficial hydrocarbons and the like in the sulfur-containing compounds and the difficulty of removing sulfur-containing compounds.

[0007] Therefore, in view of the above circumstances, the present disclosure has been made, and an object thereof is to provide a desulfurization method for removing elemental sulfur by an easy method without removing beneficial hydrocarbons in a compound from a liquid fuel containing a sulfur-containing compound.

Means for Solving the Problems

[0008] As a result of intensive studies, the inventors of the present disclosure have found that the above problems can be solved by the following means.

[0009] 〈Aspect 1〉 Irradiating a liquid fuel containing a sulfur-containing compound with ultraviolet light having a wavelength of 100 to 350 nm to precipitate elemental sulfur, and Removing the precipitated elemental sulfur, A desulfurization method for liquid fuel, comprising: 〈Aspect 2〉 The method according to Aspect 1, comprising removing the elemental sulfur by filtration or centrifugation. 〈Aspect 3〉 The method according to Aspect 1 or 2, comprising irradiating the ultraviolet light for 1 hour or more.

Effects of the Invention

[0010] According to the desulfurization method of the present disclosure, elemental sulfur can be removed alone by an easy method without removing beneficial hydrocarbons in the compound from a liquid fuel containing a sulfur-containing compound.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Mode for Carrying Out the Invention

[0012] Hereinafter, embodiments of the present disclosure will be described in detail. Note that the present disclosure is not limited to the following embodiments and can be variously modified and implemented within the scope of the gist of the invention.

[0013] 《Desulfurization Method》 The desulfurization method of the present disclosure (hereinafter, also simply referred to as "the method of the present disclosure") is irradiating a liquid fuel containing a sulfur-containing compound with ultraviolet light having a wavelength of 100 to 350 nm to precipitate elemental sulfur, and removing the precipitated elemental sulfur, and includes.

[0014] In the present disclosure, the liquid fuel containing a sulfur-containing compound (hereinafter, also simply referred to as "liquid fuel") refers to petroleum-based fuels such as gasoline, gasoline base materials, kerosene, gas oil, and gas oil base materials.

[0015] It is generally known that such liquid fuels contain sulfur-containing compounds such as benzothiophenes or dibenzothiophenes.

[0016] Here, benzothiophenes are a general term for compounds having a benzothiophene skeleton represented by the following formula (1). Specific examples thereof include benzothiophene, alkylbenzothiophene, dialkylbenzothiophene, etc. More specifically, for example, benzothiophene, methylbenzothiophene, dimethylbenzothiophene, etc. can be mentioned, but it is not limited thereto. Also, dibenzothiophenes are a general term for compounds having a dibenzothiophene skeleton represented by the following formula (2). Specific examples thereof include dibenzothiophene, alkyldibenzothiophene, dialkyldibenzothiophene, etc. More specifically, dibenzothiophene, methyldibenzothiophene, dimethyldibenzothiophene, etc. can be mentioned, but it is not limited thereto.

[0017]

Chemical formula

[0018] Regarding the reason why the method of the present disclosure can remove elemental sulfur alone, although it is not limited to theory, it is presumed to be based on the following reaction scheme.

[0019]

Chemical formula

[0020] The reaction scheme shown above exemplarily uses dibenzothiophene that may be contained in liquid fuel as a starting material. More specifically, first, dibenzothiophene is irradiated with ultraviolet light having a wavelength of 254 nm in air. As a result, dibenzothiophene is oxidized to obtain dibenzothiophene-5-sulfoxide. Then, while continuing to irradiate with ultraviolet light, intermediate compound 1 is formed from dibenzothiophene-5-sulfoxide by a homolytic cleavage (radical cleavage) reaction, and then intermediate compound 2 is formed by a cyclization reaction, and thereafter intermediate compound 3 is formed by an electrocyclic reaction, and through intermediate compound 4 having a thiirane structure, elemental sulfur is precipitated as a precipitate. By removing this precipitated elemental sulfur, elemental sulfur can be removed alone from the liquid fuel without removing useful hydrocarbons in the sulfur-containing compound (for example, dibenzofuran in the reaction scheme). In the reaction scheme, although the output of the light source of the ultraviolet light is indicated as 8 W, it is not limited thereto.

[0021] In addition, in the above reaction scheme, intermediate compounds 1 to 4 are speculative, but it is considered that even if there are some changes, the precipitation of elemental sulfur as the target substance and its removal cannot be prevented.

[0022] Also, the conventional desulfurization methods disclosed in Patent Documents 1 and 2 are methods in which dibenzothiophene is oxidized to dibenzothiophene-5-sulfoxide, and then desulfurization is performed by operations such as adsorption or extraction using the polarity of dibenzothiophene-5-sulfoxide. That is, in the conventional desulfurization method, the reaction only proceeds until dibenzothiophene-5-sulfoxide is produced in the above reaction scheme, and there is no suggestion of proceeding the reaction until elemental sulfur precipitates as in the present disclosure, nor even a suggestion that sulfur can precipitate.

[0023] In contrast, based on the novel idea of continuously irradiating with ultraviolet light until elemental sulfur is precipitated, the method of the present disclosure can remove elemental sulfur alone in an easy manner without removing beneficial hydrocarbons in sulfur-containing compounds from liquid fuels. Further, compared with conventional desulfurization methods, the method of the present disclosure can achieve desulfurization from liquid fuels containing sulfur-containing compounds by a simpler method under mild and safe conditions without actively using photocatalysts, adsorbents, or extraction solvents, etc.

[0024] The method of the present disclosure includes irradiating a liquid fuel containing a sulfur-containing compound with ultraviolet light having a wavelength of 100 to 350 nm to precipitate elemental sulfur.

[0025] The ultraviolet light has a wavelength of 100 to 350 nm, and more specifically, it may be 100 nm or more, 120 nm or more, 150 nm or more, 170 nm or more, or 200 nm or more, and may also be 350 nm or less, 335 nm or less, or 280 nm or less.

[0026] Also, as the ultraviolet light irradiation device, there is no particular limitation as long as it is a lamp that emits light rays having the above wavelength of 100 to 350 nm. For example, a UV lamp, a mercury lamp, an LED lamp, a deuterium lamp, etc. can be mentioned, but it is not limited thereto. Among these devices, those with higher output are preferably used.

[0027] Also, in the method of the present disclosure, an ultraviolet light irradiation device with low discharge tube power is preferably used. For example, those with a discharge tube power of 300 W or less, 200 W or less, 100 W or less, 50 W or less, 20 W or less, 10 W or less, or 8 W or less may be used, and those with a discharge tube power of 2 W or more, 4 W or more, or 8 W or more may also be used.

[0028] In the method of the present disclosure, the ultraviolet light irradiation may be performed at normal temperature and normal pressure, or pressure may be applied or the temperature may be increased. Also, the irradiation time of the ultraviolet light is the time until elemental sulfur is precipitated, and may be appropriately adjusted according to the amount of the liquid fuel. For example, the ultraviolet light may be irradiated to the liquid fuel for 1 hour or more, 5 hours or more, 12 hours or more, 20 hours or more, 24 hours or more, or 36 hours or more, and may also be irradiated for 240 hours or less, 120 hours or less, or 72 hours or less.

[0029] In the method of the present disclosure, when irradiating the liquid fuel with ultraviolet light, the closer the distance between the light source of the ultraviolet light and the liquid fuel, the more preferable. For example, the shortest distance from the light source of the ultraviolet light to the surface of the liquid fuel may be 100 cm or less, 80 cm or less, 50 cm or less, or 20 cm or less, and may also be 1.0 cm or more. Also, the light source can be disposed in the liquid fuel.

[0030] Also, in the method of the present disclosure, the container for accommodating the liquid fuel during desulfurization is not particularly limited. For example, when the light source of the ultraviolet light is present outside the container, a container that does not absorb ultraviolet light is preferable. More specifically, for example, a quartz container or the like is preferably used. Also, when the light source is disposed inside the container, the material of the container is not particularly limited, and it may be, for example, a resin container or a metal container. Therefore, the method of the present disclosure can be carried out in a fuel tank of a vehicle or the like.

[0031] Note that in the oxidation reaction at the initial stage of the reaction (for example, the oxidation reaction from dibenzothiophene to dibenzothiophene-5-sulfoxide in the above reaction scheme) of the method of the present disclosure, air or oxygen is required. Generally, since air or oxygen is contained in the liquid fuel, the liquid fuel may be directly irradiated with ultraviolet light having a wavelength of 100 to 350 nm, or air or oxygen may be bubbled into the liquid fuel.

[0032] In addition, when irradiating with ultraviolet light, the method of the present disclosure may include a stirring operation from the viewpoint of promoting the reaction. In particular, when using a light source of ultraviolet light with a relatively weak output or when including a liquid fuel that can absorb ultraviolet light, it is preferable to include a stirring operation.

[0033] The method of the present disclosure includes removing the elemental sulfur precipitated by irradiating with the above-described ultraviolet light.

[0034] Here, when elemental sulfur begins to precipitate from the liquid fuel, the elemental sulfur may be removed, or after all the sulfur contained in the liquid fuel has precipitated as an element, the elemental sulfur may be removed. In the former case, more specifically, for example, while irradiating the liquid fuel with ultraviolet light having a wavelength of 100 to 350 nm, the elemental sulfur may be removed every 10 minutes, every 30 minutes, every hour, every 2 hours, every 5 hours, every 12 hours, or every 24 hours. Note that the removal of elemental sulfur can be performed immediately before using the liquid fuel.

[0035] In the method of the present disclosure, the elemental sulfur may be removed by filtration or centrifugation.

[0036] Filtration may be performed, for example, by a filter press, gravity filtration, pressure filtration, vacuum filtration, or centrifugal filtration. Further, as the filter medium, for example, paper, cloth, net, packed bed, or porous substance may be used.

[0037] In addition, centrifugation may be performed, for example, by a separator such as a disc type, cylindrical type, or decanter type.

[0038] In addition, after performing filtration or centrifugation, the elemental sulfur can be removed by a method such as decantation.

[0039] As described above, the method of the present disclosure is simple and can be performed under mild and safe conditions. Therefore, for example, in a fuel purification plant, a fuel stand, inside a fuel transport tank, or inside an automobile fuel tank, desulfurization of a liquid fuel can be performed.

Example

[0040] The present disclosure will be described in more detail with reference to the following examples. However, the scope of the present disclosure is not limited by the examples.

[0041] 《Example 1》 In a two-sided quartz cell, a solution of dibenzothiophene dissolved in cyclohexane (about 3 ml) was irradiated with ultraviolet light of wavelength 254 nm for 24 hours using a handy UV lamp (discharge tube power 8 W, power consumption 11 W). -Experimental conditions- · Light source: Handy UV lamp (discharge tube power 8 W, power consumption 11 W) (λ = 254 nm) · Solvent: Cyclohexane (3 mL) · Sulfur-containing compound: Dibenzothiophene 100 mg / L, 128 wtppm (sulfur only 22.3 wtppm) · Irradiation time: 24 h

[0042] After 24 hours, the precipitate was precipitated with a centrifuge and then separated by decantation. Then, the recovered precipitate was redissolved in acetone for identification, and liquid chromatography analysis was performed using the following analytical instruments with commercially available elemental sulfur (S 8 ) as a standard. The results are shown in Figure 1.

[0043] -Analysis conditions- · HPLC column: XBridgeTM prep C 18 5 μm (10 × 150 mm) · Flow rate: 5.0 ml / min

[0044] As shown in Figure 1, the detection peak positions of the precipitate and the standard are in good agreement, indicating that the obtained precipitate is elemental sulfur.

[0045] 《Example 2》 In a two-sided quartz cell, a solution (about 3 ml) of the benzothiophenes and dibenzothiophenes shown below dissolved in cyclohexane was irradiated with ultraviolet light of wavelength 254 nm for 60 hours using a handy UV lamp (discharge tube power 8 W, power consumption 11 W).

[0046] · Breakdown of benzothiophenes and dibenzothiophenes (total sulfur content: 100 wtppm): · Benzothiophene (BT): sulfur content 20 wtppm · 2-Methylbenzothiophene (2-MBT): sulfur content 20 wtppm · Dibenzothiophene (DBT): sulfur content 20 wtppm · 4-Methyldibenzothiophene (4-MDBT): sulfur content 20 wtppm · 4,6-Dimethyldibenzothiophene (4,6-DMDBT): sulfur content 20 wtppm

[0047] From the start to the end of irradiation, the elemental sulfur precipitated every 24 hours (i.e., at 24 hours, 48 hours, and 60 hours from the start of irradiation) was separated and removed using an angle rotor type centrifuge, and the change in the sulfur concentration (wtppm) of each component of benzothiophenes and dibenzothiophenes was analyzed over time by gas chromatography. The results are shown in Figure 2.

[0048] As is clear from Figure 2, it was found that the sulfur concentration (wtppm) of each component of the benzothiophenes and dibenzothiophenes used in Example 2 decreased over time. In particular, at the 60-hour time point, it was found that the sulfur reduction rate (i.e., the desulfurization rate) reached about 93% on average for each component.

[0049] 《Example 3》 Gasoline desulfurization was carried out under the following experimental conditions. Note that gasoline containing dibenzothiophene (DBT) was used.

[0050] - Experimental conditions - · Light source: Handheld UV lamp (discharge tube power 4W, power consumption 9W) (λ = 254 nm) · Solvent: Gasoline (3 mL) · Sulfur-containing compound: DBT 100 mg / L, 128 wtppm (sulfur only 22.3 wtppm) · Irradiation time: 24 h

[0051] After 24 hours, the precipitate was precipitated with a centrifuge and then separated by decantation. As a result of analyzing the recovered precipitate by liquid chromatography, it was found to be elemental sulfur.

[0052] Also, in the desulfurization experiment of Example 3, the sulfur reduction rate of gasoline was 6.4%.

[0053] 《Examples 4 and 5》 Examples 4 and 5 were carried out under the following experimental conditions. Using cyclohexane added with toluene that absorbs ultraviolet light as a solvent, desulfurization was performed on dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) respectively. The results are shown in Table 1 below.

[0054] - Experimental conditions - · Light source: Handheld UV lamp (discharge tube power 8W, power consumption 11W) (λ = 254 nm) · Solvent: Cyclohexane added with toluene (3 mL) · Irradiation time: 24 h

[0055]

Table 1

[0056] In both Examples 4 and 5, elemental sulfur could be desulfurized alone from the sulfur-containing compound, and the sulfur reduction rates after 24 hours were 86% (Example 4) and 94% (Example 5) respectively.

[0057] 《Example 6》 In Example 6, desulfurization was carried out using thiophene as the sulfur-containing compound under the following experimental conditions. - Experimental conditions - · Light source: Handy UV lamp (discharge tube power 8W, power consumption 11W) (λ = 254 nm) · Solvent: Cyclohexane (3 mL) · Sulfur-containing compound: Thiophene 100 mg / L, 128 wtppm (sulfur only 47 wtppm (0.11 mg)) · Irradiation time: 24 h

[0058] Cyclohexane, the solvent used in Example 6, and thiophene, the sulfur-containing compound, have very similar molecular weights (cyclohexane: 84.16; thiophene: 84.14) and boiling points (cyclohexane: 80.7 °C; thiophene: 84 °C). Therefore, desulfurization was evaluated by the XRF method (X-ray fluorescence analysis).

[0059] More specifically, after irradiating with ultraviolet light, the sample was treated with an evaporator to remove volatile components. Then, the obtained solid (elemental sulfur) was dissolved in 0.5 mL of acetone, and the whole amount was impregnated into filter paper and dried to obtain an XRF measurement sample. A calibration curve was prepared in advance based on the signal intensity of SKα in the XRF spectrum observed from samples with known sulfur amounts. When the sulfur content was calculated from the signal intensity of SKα obtained from the prepared XRF measurement sample, it was 0.11 mg. That is, it was found that the sulfur reduction rate after 24 hours was almost 100%.

[0060] <<Reference Example 1>> In Reference Example 1, the light absorption characteristics of dibenzothiophene (DBT) in cyclohexane were measured under the following conditions. The measurement results are shown in Figure 3.

[0061] - Experimental conditions - · Equipment: GeneQuant1300 manufactured by GE Healthcare Japan · Solvent: Cyclohexane · Measured substance: Dibenzothiophene (DBT) · Measurement wavelength: 200 - 700 nm · Maximum wavelength: 233 nm

[0062] "Examples 7 and Comparative Example 1" In accordance with the absorption characteristics of dibenzothiophene shown in Reference Example 1 above, for the sample of Reference Example 1, using a handy UV lamp (discharge tube power 8 W, power consumption 11 W), in Example 7, ultraviolet light of 254 nm and in Comparative Example 1, ultraviolet light of 365 nm were each irradiated for 24 hours to attempt desulfurization.

[0063] As a result, in Example 7, it was found that dibenzothiophene decomposed and elemental sulfur was precipitated.

[0064] On the other hand, in Comparative Example 1, dibenzothiophene did not decompose and remained as it was. From the results of Comparative Example 1, it was found that desulfurization of dibenzothiophene was not possible in the case of ultraviolet light of 365 nm.

Claims

Claim 1 Irradiating a liquid fuel containing a sulfur compound with ultraviolet light having a wavelength of 200 to 335 nm using a lamp with a discharge tube power of 2 W or more and 300 W or less to precipitate elemental sulfur, and removing the precipitated elemental sulfur, A desulfurization method for liquid fuels, comprising: Claim 2 The method according to claim 1, comprising removing the precipitated elemental sulfur by filtration or centrifugation. Claim 3 The method according to claim 1 or 2, comprising irradiating the ultraviolet light for 1 hour or more.

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