JP3564533B2 - Method for oxidative desulfurization of fuel oil - Google Patents

Description

【００３７】
実施例８
燃料油として、深度脱硫軽油（硫黄分，５６６ｐｐｍ）１００ｍｌを用い、反応時間を３時間とした他は、実施例１と同じ条件下に酸化反応を行った。反応終了後、アセトニトリルを分液した処理油を、水洗および脱水し、アルミナ吸着処理後、硫黄分を分析した。結果を以下に記す表２に示した。
反応処理後の硫黄分が２０７ｐｐｍ（脱硫率，６３％）へと大きく低下したことから、深度脱硫軽油の場合にも、本発明による酸化脱硫法が有効に作用することが確認できた。
【００３８】
比較例２
アセトニトリルを添加しない他は、実施例８と同じ条件下に、酸化反応を行った。
結果を以下に記す表２に示した。反応処理後の硫黄分は４８９ｐｐｍ（脱硫率，１４％）であり、アセトニトリル添加の場合に比べて脱硫率がかなり低いことがわかった。この結果から、反応系へのアセトニトリルの添加が酸化脱硫に有効であることを確認できた。
【００３９】
比較例３
遷移金属触媒および過酸化水素を添加せずに、実施例８と同じ溶媒比で軽油とアセトニトリルを混合し、アセトニトリルを分液後、水洗および脱水し、アルミナ吸着処理後、硫黄分を分析した。結果を以下に記す表２に示した。
アセトニトリルによる抽出処理後の硫黄分は４８９ｐｐｍ（脱硫率，１４％）であり、酸化処理を組み合わせた場合に比べて脱硫率がかなり低いことがわかった。この結果から、反応系へのアセトニトリルの添加に酸化反応を組み合わせた酸化脱硫法が燃料油の脱硫に有効であることを確認できた。
【００４０】
実施例９
遷移金属触媒の効果を確認するために、遷移金属触媒として酸化バナジウムを用いた他は、実施例８と同じ条件下に、酸化反応を行った。結果を以下に記す表２に示した。
【００４１】
実施例１０〜１２
軽油とアセトニトリルとの溶媒比を変更した他は、実施例８と同じ条件下に、酸化反応を繰り返した。結果を以下に記す表２に示した。
【００４２】
実施例１３
反応系にアセトニトリルとベンゼンの混合溶媒を添加した他は、実施例８と同じ条件下に、酸化反応を繰り返した。結果を以下に記す表２に示した。
【００４３】
【表２】

【００４４】
【発明の効果】
本発明によれば、硫黄化合物特に有機硫黄化合物を含有する液体燃料油を、極性有機溶剤と遷移金属触媒の存在下に、過酸化水素により酸化することにより、有機硫黄化合物を含酸素有機硫黄化合物に選択的に変換し、燃料油中から除去、すなわち、脱硫することが出来る。この脱硫方法では、従来から知られている水素化反応を利用する脱硫法では脱硫することが困難であったアルキル置換ジベンジチオフェン類等の難脱硫性化合物を除去できるものであり、その含有量も少ない量にまで脱硫する超深度脱硫が可能となる。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for oxidative desulfurization of a fuel oil containing a sulfur compound.
[0002]
[Prior art]
2. Description of the Related Art Generally, various sulfur compounds such as organic sulfur compounds are contained in fuel oil obtained from fossil resources such as petroleum and coal. Since these sulfur compounds generate sulfur oxides during combustion and generate harmful gases to the human body and cause acid rain, etc., to prevent air pollution, before and after the use of fossil fuel resources, There is a need for removal of sulfur compounds.
For this reason, the desulfurization technology of sulfur compounds contained in fuel oil has been actively developed, and currently, at a refinery, a hydrodesulfurization method in which a hydrotreatment is performed in the presence of a catalyst is performed. ing.
[0003]
On the other hand, in recent years, air pollution due to photochemical oxidants, acid rain, etc. has become serious in large urban areas, mainly due to nitrogen oxides and particulate matter contained in exhaust gas from diesel vehicles using diesel fuel. Substances and hydrocarbons are mentioned.
Sulfur in gas oil affects the reliability and durability of post-exhaust treatment equipment such as oxidation catalysts, nitrogen oxide reduction catalysts, and exhaust particulate removal filters, which are expected to be a countermeasure against exhaust gas from diesel vehicles. Due to concerns about this, it is considered the first target for tightening regulations.
[0004]
Therefore, in Japan, as part of measures to purify exhaust gas from diesel vehicles, measures to increase the sulfur content in light oil from the current regulation value of 500 ppm to 50 ppm or less in the future will be taken. In this sense, there is a strong demand for reducing the sulfur content in light oil.
[0005]
By the way, in such fuel oils as gas oils, there are organic sulfur compounds that are extremely difficult to remove by hydrodesulfurization, especially alkyl-substituted dibenzo having a sterically hindered substituent such as an alkyl group around a sulfur atom. Since thiophenes are contained, it is necessary to effectively desulfurize organic sulfur compounds, particularly alkyl-substituted dibenzothiophenes, in order to achieve ultra-deep desulfurization of 50 ppm or less.
[0006]
Therefore, in order to achieve ultra-deep desulfurization, it is urgently necessary to develop a new desulfurization technique capable of effectively removing such hard-to-removable sulfur compounds.
[0007]
As a new desulfurization method, an oxidative desulfurization method in which the sulfur compound is oxidized to be removed from the fuel oil is considered to be effective. This is because, in the oxidation reaction, contrary to the hydrogenation reaction, the relative reactivity of the alkyl-substituted dibenzothiophenes is further increased.
That is, according to this oxidation method, by converting these dibenzothiophenes into polar compounds such as sulfoxides and sulfone derivatives, it is possible to efficiently separate them from fuel oil by utilizing extraction and adsorption operations. This is because it is considered possible.
[0008]
Various methods have been known for the oxidation reaction of dibenzothiophenes. Examples of such a method include, for example, a method using nitrogen dioxide, nitric acid, or an organic hydroperoxide (such as t-butyl hydroperoxide) as an oxidizing agent in performing an oxidation reaction, and using a metal catalyst such as molybdenum hexacarbonyl. Examples of the method include a method in which hydrogen peroxide is used as an oxidizing agent and a method using a combination of hydrogen peroxide and a phosphotungstic acid as a catalyst, and a method using an organic peracid generated from hydrogen peroxide and trifluoroacetic acid.
[0009]
However, none of these oxidation methods has substrate selectivity, and not only oxidizes dibenzothiophenes, but also oxidizes hydrocarbons, which are the main components of fuel oil, and is expensive in the reaction. There are problems such as the necessity of using chemicals, and it has not been put to practical use as an actual industrial method.
[0010]
As a method for oxidizing benzothiophenes which are organic sulfur compounds, a photo-oxidation reaction, for example, a method of irradiating light of a specific wavelength such as ultraviolet light, a method of performing light irradiation in the presence of hydrogen peroxide, and a method of light irradiation A method in which titanium oxide as a photocatalyst and 9,10-dicyanoanthracene as a photosensitizer are used is known.
However, these methods also involve many problems such as scale-up when industrialized because of utilizing photoreaction.
[0011]
For this reason, there is a demand for the development of an oxidative desulfurization method by selective oxidation of dibenzothiophenes, which can reduce the content of organic sulfur compounds, especially dibenzothiophenes, contained in fuel oil. .
[0012]
[Problems to be solved by the invention]
The present invention provides an industrially advantageous oxidative desulfurization method capable of selectively and efficiently oxidizing and removing hardly removable sulfur compounds, for example, organic sulfur compounds, particularly dibenzothiophenes, contained in fuel oil. The purpose is to:
[0013]
[Means to solve the problem]
According to the present invention, first, there is provided a method for oxidative desulfurization of a fuel oil, comprising treating a fuel oil containing a sulfur compound with hydrogen peroxide in the presence of a polar organic solvent and a transition metal catalyst. You.
Secondly, there is provided the method for oxidative desulfurization of fuel oil according to the first aspect, wherein the sulfur compound is an organic sulfur compound.
Thirdly, there is provided the fuel oil oxidative desulfurization method according to the first or second aspect, wherein the organic sulfur compound is a dibenzothiophene.
Fourth, the oxidative desulfurization method for fuel oil according to the first to third aspects, wherein the polar organic solvent is acetonitrile.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
The fuel oil that is the object of the present invention means a fuel oil derived from fossil fuel, and is not limited to petroleum, and may be a fuel oil derived from organic fossil resources such as coal, oil sand, oil shale, and orimulsion. .
Specific examples include petroleum-based products such as gasoline, kerosene, gas oil, and heavy oils, and distillation products and crude oils, and coal-based products include coal tar and liquefied oil. In the above, extracts from oil sand, oil shale, orimulsion, etc., and liquids such as refined oils are used.
[0015]
The sulfur compound contained in the fuel oil includes an inorganic sulfur compound and an organic sulfur compound.
Examples of the organic sulfur compound include compounds containing a sulfur atom in a carbon chain constituting an aliphatic hydrocarbon, for example, a group containing a sulfur atom in a carbon chain as a substituent of an aromatic hydrocarbon, such as thiols and thioethers. Such as thiophenols and thioanisoles; and heterocyclic compounds containing a sulfur atom in the skeleton such as thiophenes, benzothiophenes and dibenzothiophenes.
[0016]
In general, the heterocyclic compound containing a sulfur atom in the skeleton, particularly dibenzothiophenes having a substituent such as an alkyl group around the sulfur atom, can be decomposed by the influence of steric hindrance in a normal hydrodesulfurization method. Although it is a difficult compound, the present invention is particularly effective as a method for removing such a sulfur compound because such a sulfur compound can be converted into another organic compound and easily separated and removed.
According to the present invention, the above-mentioned organic sulfur compounds can be effectively oxidized and removed from the fuel oil, but the application to dibenzothiophenes is particularly effective. Examples of the compounds included in the dibenzothiophenes include dibenzothiophenes, alkylated derivatives such as monoalkylated or dialkylated dibenzothiophenes, and compounds having a dibenzothiophene skeleton in the molecule.
[0017]
These organic sulfur compounds are those contained in fuel oils mainly containing hydrocarbons such as aliphatic hydrocarbons, aromatic hydrocarbons, alicyclic hydrocarbons, and condensed polycyclic compounds. .
The fuel oil to be used in the present invention may be a mixture containing these components as appropriate. Further, these fuel oils may be a mixture containing an organic sulfur compound after a specific desulfurization operation.
In the present invention, it is particularly effective to target a fuel oil containing an appropriate proportion of an organic sulfur compound that could not be decomposed by hydrodesulfurization contained in the fuel oil after hydrodesulfurization. is there.
[0018]
The proportion of the sulfur compound contained in the fuel oil can be appropriately selected, but usually, the content of the organic sulfur compound is preferably 1 × 10 ⁻⁴ (1 ppm) to 100% by weight as sulfur. .
[0019]
In the present invention, the above-mentioned sulfur compound, preferably a fuel oil containing an organic sulfur compound, is treated with hydrogen peroxide in the presence of a polar organic solvent and a transition metal catalyst to produce a sulfur compound, preferably an organic sulfur oxide. Is separated and removed from fuel oil.
[0020]
The polar organic solvent functions as an extraction solvent for sulfur compounds contained in the fuel, especially for the organic sulfur compounds and their oxidation products. Examples of such a polar organic solvent include, for example, acetonitrile, propionitrile, butyronitrile, valeronitrile, acetic acid, propionic acid, butyric acid, methanol, ethanol, propanol, butanol, acetone, 2-butanone, acetylacetone, nitromethane, nitroethane, Examples thereof include nitropropane, N, N'-dimethylformamide, N, N'-dimethylacetamide, trimethyl phosphate, triethyl phosphate, hexamethyl phosphate, and the like. In the present invention, acetonitrile is particularly preferred.
In the present invention, the oxidation reaction of the sulfur compound selectively proceeds in such a polar organic solvent, and the oxidation reaction of hydrocarbons, which are the main components of the fuel oil, is suppressed. Is significantly improved.
In the present invention, it is preferable to add an auxiliary solvent in order to increase the extraction efficiency of the sulfur compound and its oxidation product. Examples of such an auxiliary solvent include benzene, toluene, xylene, benzonitrile, acetophenone, and benzophenone.
The amount of the polar organic solvent used is not particularly limited, but is usually added at a ratio of 1/20 to 20 v / v (volume ratio) to the fuel oil, preferably at a ratio of 1/10 to 10 v / v. You.
When an auxiliary solvent is used, the amount of the auxiliary solvent is usually 1/100 to 1/2 v / v (volume ratio), preferably 5/100 to 1/3 v / v, based on the polar organic solvent. It is added in proportions.
[0021]
The transition metal catalyst acts on the oxidizing agent to promote the oxidation of the organic sulfur compounds.
Examples of such transition metal catalysts include telopolyacid salts, oxides, halides, and complex salts thereof of metals belonging to Groups IIIa, IVa, Va, VIa, VIIa, and VIII of the Periodic Table. Specific examples thereof include heteropolyacid salts such as tungsten, vanadium, molybdenum, titanium, chromium, osmium, and rhenium, oxides, halides, and complex salts thereof.
Specific examples of the tungsten compound include phosphotungstic acid (H ₃ [PW ₁₂ O ₄₀ ], etc.), tungsten oxide (WO ₃ , etc.), and tungsten chloride (WCl ₆ , WOCl ₄ , WO ₂ Cl ₂ , etc.) ) And the like.
Specific examples of the vanadium compound include vanadium oxide (V ₂ O ₅ , etc.), vanadium oxide acetylacetone complex (VO (acac) ₂ , etc.), and vanadium chloride (VOCl ₃ , etc.).
Specific examples of molybdenum compounds include molybdenum oxide (MoO ₃ , etc.), molybdenum oxide acetylacetone complex (MoO ₂ (acac) ₂ , etc.), and phosphomolybdic acid (H _{3 [} PMo ₁₂ O ₄₀ ], etc.). Can be mentioned.
The amount of these transition metal catalysts is not particularly limited, but is usually 1 × 10 ⁻⁵ to 10 g / L, preferably 1 × 10 ⁻⁴ to 1 g / L with respect to the fuel oil. Is added.
[0022]
Hydrogen peroxide is used as the oxidizing agent. This hydrogen peroxide reacts with an organic sulfur compound such as dibenzothiophenes in a molar ratio of 1: 2 to give sulfones as main oxidation products. The use concentration of hydrogen peroxide can be appropriately set depending on the reaction conditions, but it is preferable to use it as a readily available 30% aqueous solution. The amount of hydrogen peroxide to be added can be appropriately set according to the reaction conditions, but it is generally preferable to add hydrogen peroxide in an amount at least twice the amount of sulfur contained in the fuel oil. Specifically, it is sufficient to set a 30% aqueous hydrogen peroxide solution to about 1.5 ml or more for 1 L of light oil having a sulfur content of 500 ppm.
[0023]
Although there is no particular limitation on the embodiment of the method of the present invention, the fuel oil containing the organic sulfur compound described above is reacted in a liquid state with the polar organic solvent containing the transition metal catalyst and the oxidizing agent. It is preferable to adopt a mode of supplying to a vessel.
[0024]
The reaction temperature can be appropriately set as long as the reaction raw material can maintain a liquid state. For this reason, the reaction can be generally performed at -100 to 120C, preferably at -50 to 80C.
In order to achieve reproducibility of the reaction, it is effective to control the temperature to keep the reactor in the above temperature range. Heating and heat removal for temperature control can be performed using a heating medium from the outer wall of the reactor. In some cases, it is also possible to install the temperature control device directly in the reactor.
At the time of the reaction, it is effective to stir the reaction raw material so that the raw material sufficiently contacts the polar organic solvent. The reactor can be operated in a flow system, a batch system, or a semi-batch system.
[0025]
After the completion of the reaction, the oxidation reaction product is separated. The organic sulfur compound is converted into an organic sulfur oxide combined with oxygen by being oxidized. For example, dibenzothiophenes are oxidized and mainly changed to dibenzothiophenesulfones. That is, dibenzothiophene is dibenzothiophene sulfone, and 4,6-dimethyldibenzothiophene is 4,6-dimethyldibenzothiophene sulfone.
[0026]
The generated organic sulfur oxides can be removed using various separation operations such as extraction and adsorption. Examples of the adsorbent for the adsorption operation include zeolite, clay mineral, activated carbon and the like. Examples of the extractant for the extraction operation include acetonitrile, methanol, dimethylsulfoxide, dimethylformamide, sulfolane and the like.
In this reaction system, as an additional solvent, a polar organic solvent such as acetonitrile which is not mixed with the fuel oil to be subjected to the desulfurization treatment is used, and thus, the above-mentioned organic sulfur oxide is mainly distributed in the polar solvent. Most of the fuel oil can be removed, and the fuel oil after liquid separation can be further purified by further extraction and adsorption operations.
[0027]
The fuel oil from which the organic sulfur oxide as a reaction product has been removed can be used for the intended use as it is from which the organic sulfur compound has been removed. Further, a part can be recycled to the reaction raw material. Furthermore, by separating and recovering the hydrocarbons distributed in the added acetonitrile, the yield of the processed product can be improved.
[0028]
【Example】
Hereinafter, the contents of the present invention will be specifically described with reference to examples. However, the following examples are merely examples, and the present invention is not limited to these examples.
[0029]
Example 1
In a glass reactor having an inner volume of 250 cc, 10 mg of phosphotungstic acid (H ₃ [PW ₁₂ O ₄₀ ] hydrate, transition metal catalyst) was taken, and 1 ml of a 30% aqueous hydrogen peroxide solution (20 times the sulfur compound). (About a molar amount), the mixture is stirred, and 50 ml of acetonitrile is further added. Thereafter, 50 ml of an n-octane solution of dibenzothiophene (DBT, an organic sulfur compound) prepared as a model fuel oil (DBT concentration, 10 mM) is put into the reactor.
After installing a reflux condenser in the reactor, the reactor was immersed in a water bath maintained at 60 ° C., and an oxidation reaction was performed while stirring the liquid in the reactor with a magnetic stirrer. The oxidation reaction of dibenzothiophene proceeded rapidly in the acetonitrile phase. As a result of analyzing the reaction product by gas chromatography and liquid chromatography, it was confirmed that the main reaction product was dibenzothiophene sulfone.
The results are shown in Table 1 below. Two hours after the start of the reaction, the reaction rate of the reaction raw material was 100%. The yield of dibenzothiophene sulfone was 97 mol%.
[0030]
Comparative Example 1
The oxidation reaction was performed under the same conditions as in Example 1 except that no acetonitrile was added.
The results are shown in Table 1 below. After 2 hours from the start of the reaction, the reaction hardly proceeded, and the conversion was 1.3%.
[0031]
Examples 2 and 3
In order to confirm the effect of the transition metal catalyst, the type of the transition metal catalyst was changed, and the oxidation reaction was repeated under the same other conditions as in Example 1.
As the transition metal catalyst, vanadium oxide (Example 2) and a vanadium oxide acetylacetone complex (vanadyl acetylacetonate, Example 3) were used, respectively. The results are shown in Table 1 below.
[0032]
Example 4
Regarding the sulfur compound as a substrate, the oxidation reaction was repeated under the same conditions as in Example 1 except that the DBT used in Example 1 was changed to 4,6-dimethyldibenzothiophene (DMDBT). The results are shown in Table 1 below.
[0033]
Example 5
With respect to the amounts of the transition metal catalyst and the 30% aqueous hydrogen peroxide solution used, the amount used in Example 1 was changed, and the oxidation reaction was carried out under the same other conditions as in Example 1. The results are shown in Table 1 below.
[0034]
Example 6
With respect to the solvent ratio between n-octane and acetonitrile, the amount used in Example 5 was changed, and the oxidation reaction was performed under the same other conditions as in Example 5. The results are shown in Table 1 below.
[0035]
Example 7
Regarding the reaction temperature, the temperature employed in Example 1 was set at 40 ° C., and the oxidation reaction was repeated under the same other conditions as in Example 1. The results are shown in Table 1 below.
[0036]
[Table 1]

[0037]
Example 8
The oxidation reaction was carried out under the same conditions as in Example 1 except that 100 ml of deep desulfurized light oil (sulfur content, 566 ppm) was used as the fuel oil, and the reaction time was 3 hours. After the reaction was completed, the treated oil from which acetonitrile was separated was washed with water and dehydrated, and after the alumina adsorption treatment, the sulfur content was analyzed. The results are shown in Table 2 below.
Since the sulfur content after the reaction treatment was greatly reduced to 207 ppm (desulfurization rate, 63%), it was confirmed that the oxidative desulfurization method according to the present invention effectively works even in the case of deep desulfurized light oil.
[0038]
Comparative Example 2
The oxidation reaction was performed under the same conditions as in Example 8 except that no acetonitrile was added.
The results are shown in Table 2 below. The sulfur content after the reaction treatment was 489 ppm (desulfurization rate, 14%), indicating that the desulfurization rate was considerably lower than in the case of adding acetonitrile. From these results, it was confirmed that the addition of acetonitrile to the reaction system was effective for oxidative desulfurization.
[0039]
Comparative Example 3
Without adding the transition metal catalyst and hydrogen peroxide, light oil and acetonitrile were mixed at the same solvent ratio as in Example 8, the acetonitrile was separated, washed and dehydrated, and after the alumina adsorption treatment, the sulfur content was analyzed. The results are shown in Table 2 below.
The sulfur content after the extraction treatment with acetonitrile was 489 ppm (desulfurization rate, 14%), indicating that the desulfurization rate was considerably lower than that in the case where the oxidation treatment was combined. From these results, it was confirmed that the oxidative desulfurization method combining the addition of acetonitrile to the reaction system and the oxidation reaction was effective for the desulfurization of fuel oil.
[0040]
Example 9
In order to confirm the effect of the transition metal catalyst, an oxidation reaction was performed under the same conditions as in Example 8, except that vanadium oxide was used as the transition metal catalyst. The results are shown in Table 2 below.
[0041]
Examples 10 to 12
The oxidation reaction was repeated under the same conditions as in Example 8 except that the solvent ratio between light oil and acetonitrile was changed. The results are shown in Table 2 below.
[0042]
Example 13
The oxidation reaction was repeated under the same conditions as in Example 8, except that a mixed solvent of acetonitrile and benzene was added to the reaction system. The results are shown in Table 2 below.
[0043]
[Table 2]

[0044]
【The invention's effect】
According to the present invention, a liquid fuel oil containing a sulfur compound, particularly an organic sulfur compound, in the presence of a polar organic solvent and a transition metal catalyst, is oxidized with hydrogen peroxide to convert the organic sulfur compound into an oxygen-containing organic sulfur compound. And can be removed from the fuel oil, that is, desulfurized. This desulfurization method can remove difficult-to-desulfurize compounds such as alkyl-substituted dibendithiophenes, which have been difficult to desulfurize by a conventionally known desulfurization method using a hydrogenation reaction. Ultra-deep desulfurization, in which desulfurization is reduced to a small amount, becomes possible.

Claims (4)

A method for oxidative desulfurization of a fuel oil, comprising treating a fuel oil containing a sulfur compound with hydrogen peroxide in the presence of a polar organic solvent and a transition metal catalyst. The method according to claim 1, wherein the sulfur compound is an organic sulfur compound. Oxidative desulfurization method of a fuel oil according to claim 1 or 2 organic sulfur compound characterized in that it is a dibenzothiophenes. 4. The method for oxidative desulfurization of fuel oil according to claim 1, wherein the polar organic solvent is acetonitrile.