RU2525287C1 - Non-catalytic oxidative desulfurisation of hydrocarbon fuels (versions) - Google Patents

Abstract

FIELD: oil-and-gas industry.

SUBSTANCE: invention relates to non-catalytic oxidative desulfurisation of hydrocarbon fuels containing DBT by aldehyde/molecular oxygen system. It comprises oxidative desulfurisation by forcing oxygen-containing gas into reaction mix. Benzaldehyde is used as aldehyde while air is used as oxygen-containing gas. Oxidative desulfurisation is conducted at the room temperature at illumination of reaction mix by UV light and DBT:benzaldehyde molar ratio of 1:15-20.Besides, it relates to oxidative desulfurisation performed by forcing oxygen-bearing gas into reaction mix. Benzaldehyde is used as aldehyde while air is used as oxygen-containing gas. Oxidative desulfurisation is conducted at the temperature of at 40-70°C and DBT:benzaldehyde molar ratio of 1:15-20.

EFFECT: accelerated oxidation, hence simplified process, higher safety, lower costs.

3 cl, 2 dwg, 3 tbl

Description

The invention relates to methods for oxidative desulfurization of hydrocarbon fuels and can be used in the oil refining industry.

Tighter requirements for the sulfur content in motor fuels makes it relevant to search for new ways to clean hydrocarbon materials from sulfur compounds.

To date, the most common method for the desulfurization of hydrocarbon fuels is hydrodesulfurization, in which the fuel interacts with hydrogen gas at 350-450 ° C and high pressure (3 MPa) in the presence of an expensive catalyst (Babich JV, Moulijn JA Fuel, 2003, 82, p. 607-631; Song G. Catal. Today, 2003, 16, p. 3213). Hydrotreating can reduce the sulfur content in the fuel to 300-500 ppm, while in most countries no more than 10-50 ppm is required. In addition, the following limitations are inherent in the hydrodesulfurization process: if mercaptans, thioesters, and disulfides are relatively easily removed, then thiophene, benzothiophene, dibenzothiophene (DBT) and its alkyl substituted analogues require such harsh conditions that decomposition of the fuel itself and its quality are reduced. It should be noted that in the crude oil of some fields, the content of thiophene analogues is from 40 to 70% of the total sulfur content, which, in turn, can reach 3-10 wt.% (When the oil is distilled with an increase in the boiling temperature of the fractions, the amount of sulfur in them increasing). It is not surprising that thiophene and its analogues are in the center of attention of researchers when developing methods for the desulfurization of hydrocarbon fuels.

Known methods for the oxidative desulfurization of hydrocarbon fuels using hydrogen peroxide or alkyl hydroperoxides as an oxidizing agent in combination with various catalysts (RU 2235112, C10G 27/10, C10G 27/12, C10G 29/24, publ. 08.28.2004; Sharipov A.Kh. et al. Chemistry and Technology of Fuels and Oils, 2006, No. 6, pp. 45-51; Yunming Fang, Haoguan Hu. Catalysis Commun., 2007, v.8, No. 5, p. 817-820). Since this process proceeds in a two-phase system, in patent RU 2235754, C10G 27/12, C10G 32/00, B01J 19/10, publ. 09/10/2004, it is proposed to facilitate the interaction of the resulting mixture of reagents with ultrasound. The use of peroxides in the presence of catalysts allows the oxidation of various organosulfur compounds, but sulfides are most successful.

Known methods for the catalytic oxidative desulfurization of hydrocarbon fuels using oxygen as an oxidizing agent in the presence of a system consisting of metal ions and aldehydes. Acetates of cobalt (II), nickel (II), or manganese (II) in the presence of n-octanal or n-hexanal provide 99% conversion of DBT to sulfone (in the model mixture) in 15 min at 40 ° C in an oxygen atmosphere in static conditions or while purging air through the reaction mixture (Murata S., Murata K., Kidena K., Nomura M. "A Novel Oxidative Desulfurization System for Diesel Fuels with Molecular Oxigen in the Presence of Cobalt Catalysts and Aldehydes." Energy & Fuels, 2004, v. 18, No. 1, p. 116-121). The supported Co / Al ₂ O ₃ and Mn / Al ₂ O ₃ catalysts prepared from acetates in the presence of n-octanal at 50 ° C while purging the O ₂ / N ₂ mixture (oxygen pressure 0.2 bar) are also quite active in oxidation DBT (conversion up to 62%) (Dumont V., Oliviero L., Mauge F., Houalla M. "Oxidation of dibenzothiophene by metal-oxygen-aldehyde system." Catalysis Tuday, 2008, v. 130, No. 1, p. 195-198). The disadvantage of these known methods is the need to use catalysts.

Closest to the proposed invention is a method of oxidative desulfurization of hydrocarbon fuel with an aldehyde / molecular oxygen system in the absence of a metal catalyst (Rao TV, Sain B. et al. "Oxidative Desulfurization of HDS Diesel Using Aldehyde / Molecular Oxigen Oxidation System". Energy & Fuels, 2007 , v. 21, No. 6, p. 3420-3424 - prototype). The prototype method is as follows: the solvent is mixed with the required amount of aldehyde (molar ratio of sulfur: aldehyde = 1: 32-64) and kept under stirring in an oxygen atmosphere (oxygen from the balloon is passed) for 30 minutes at 40 ° C. The mixing and transmission of oxygen is stopped and diesel fuel (hydrodesulfurized) is added containing 448 ppm of sulfur compounds in the form of DBT and its alkyl derivatives (DBT is shown to be the least reactive in this oxidation reaction.) Resume mixing and transmission of oxygen. Samples are periodically taken for analysis on a gas chromatograph. The best result - a decrease in the total sulfur content from 448 to 77 ppm (83% conversion) was obtained with isobutyric aldehyde for 180 min at 40 ° C in acetonitrile as a solvent. Other aldehydes studied (benzaldehyde, octanal and n-butyric aldehyde) showed under these conditions a decrease in the total sulfur content from 448 to 205-222 ppm (45–50% conversion).

The prototype method for the first time showed the possibility of oxidative desulfurization in the absence of a metal catalyst, however, the prototype method is characterized by a low oxidation rate, which leads to the need for heating the reaction mixture, introducing a large excess of aldehyde and the use of oxygen cylinders, which complicates the process and makes it unsafe.

The objective of the invention is to develop such a method (options) of non-catalytic oxidative desulfurization of hydrocarbon fuels, which will have a higher oxidation reaction rate, which will simplify the process technology, make it safe by using air instead of oxygen, will significantly reduce the excess of aldehyde and, in one of the options will allow the process to be carried out at room temperature.

The solution to this problem is achieved by the proposed:

- by the method of non-catalytic oxidative desulfurization of hydrocarbon fuels containing dibenzothiophene with an aldehyde / molecular oxygen system, including the process of oxidative desulfurization by passing an oxygen-containing gas into a reaction mixture in which benzaldehyde is used as an aldehyde, air is used as an oxygen-containing gas, and the oxidative desulfurization process is carried out at room temperature when illuminating the reaction mixture with UV light and a molar ratio of dibenzothiophene: benzaldehyde equal to 1: 15-20.

The reaction mixture can be illuminated with UV light for 1 minute of the oxidative desulfurization process and then, to achieve 100% conversion of dibenzothiophene, for every 10 minutes of the process, lasting 150-160 minutes,

- by the method of non-catalytic oxidative desulfurization of hydrocarbon fuels containing dibenzothiophene with an aldehyde / molecular oxygen system, including the process of oxidative desulfurization by passing an oxygen-containing gas into a reaction mixture in which benzaldehyde is used as an aldehyde, air is used as an oxygen-containing gas, and the oxidative desulfurization process is carried out at a temperature of 40-70 ° C and a molar ratio of dibenzothiophene: benzaldehyde equal to 1: 15-20.

When developing the proposed method (options), experimental studies were carried out on the influence on the reaction rate of the DBT of the benzaldehyde / molecular oxygen system of air of process conditions such as illumination of the reaction mixture with UV light and lighting conditions, reaction temperature, its duration and ratio of reagents.

It was found that the greatest influence on the reaction rate of DBT oxidation is exerted by UV light and the reaction temperature. Thus, it turned out that without UV light, the oxidation rate at room temperature (23 ° C) is very low - the conversion of DBT to sulfone in 60 minutes was only 5%, and in 160 minutes it did not exceed 25%, while when the reaction mixture was illuminated with UV with light, the reaction rate increases sharply (see table 1 and figure 1). The experiments made it possible to choose the optimal UV illumination mode for reliable process control: the duration of illumination should not exceed 1 min with an interval of 9 min. With this lighting mode, 100% conversion of DBT (97-99%) is achieved at room temperature in 150-160 minutes. Figure 1 shows the kinetic curves of DBT conversion at room temperature (23 ° C, molar ratio of DBT: benzaldehyde = 1:20) when illuminated with UV light and without light (curve 1 - without UV light; curve 2 - at UV light).

Table 1 The effect of UV illumination of the reaction mixture on the conversion of DBT at 23 ° C (molar ratio of DBT: benzaldehyde = 1:20). The duration of the reaction, min Conversion% Without UV light When illuminated with UV light four 2 - fourteen - eighteen 21 3 22 thirty - 24 40 3 28 60 5 37 73 - 43 80 10 - 92 fourteen 53 BY 17 67 130 23 92 150 23 97 160 25 99

Table 2 shows the results of experiments on the influence of the process temperature on the rate of oxidation of DBT without irradiation with UV light. An increase in temperature significantly accelerates the DBT oxidation reaction: if at room temperature for 60 minutes the conversion of DBT was only 5%, then at 40 ° C for 60 minutes the conversion was 73% (100% conversion at 40 ° C is achieved in 140 minutes) , at 60 ° C in 60 minutes 100% conversion is achieved, at 68 ° C 100% conversion is achieved even faster - in 40 minutes.

table 2 The influence of the process temperature on the conversion of DBT without illumination with UV light (molar ratio of DBT: benzaldehyde = 1:20) The duration of the reaction, min Conversion% Temperature 23 ° C Temperature 40 ° C Temperature 60 ° C Temperature, 68 ° C four 2 10 - - 6 - - eighteen eighteen 10 - 16 22 25 twenty 3 24 39 fifty thirty - 36 51 76 40 3 52 67 99 fifty - 68 86 - 60 5 73 99 - 75 8 84 - - 90 13 87 - - 110 17 92 - - 120 - 96 140 23 99

When studying the effect of UV illumination on the process speed at a temperature of 40 ° C (the results are shown in Table 3 and in Fig. 2), it was found that the difference in the oxidation rates of DBT under illumination with UV light and without illumination when heated is not so great as at room temperature ( see figure 2), that is, to achieve high conversion values during oxidation of DBT with a benzaldehyde / molecular oxygen system, air should either be carried out at room temperature and under UV light

- 1st embodiment of the invention, either without UV light, but when heated to 40-70 ° C

- 2nd embodiment of the invention.

Table 3 The effect of UV illumination of the reaction mixture on the conversion of DBT at 40 ° C (molar ratio of DBT: benzaldehyde = 1:15) The duration of the reaction, min Conversion% Without UV light When illuminated with UV light four eleven 13 eleven 16 - twenty 24 thirty thirty - 44 32 38 - 44 58 - fifty - 72 55 71 - 70 - 88 75 84 - 90 87 94 110 90 95

When studying the influence of the molar ratio of reagents (DBT: benzaldehyde), it was found that when the molar excess of introduced benzaldehyde is reduced to a 10-fold oxidation reaction of DBT without illumination with UV light at 40-68 ° C does not occur, with UV light at the indicated excess of benzaldehyde the reaction both at room temperature and at 40 ° C is small - the conversion in 60 minutes did not exceed 10%. The optimal molar ratio of DBT: benzaldehyde equal to 1: 15-20 was experimentally established. A further increase in the excess of benzaldehyde does not lead to a noticeable increase in the rate of the oxidation reaction.

The proposed method (options) is as follows.

In the first embodiment of the invention, the oxidation process is carried out under UV light and at room temperature: octane is mixed with the required amounts of benzaldehyde and DBT (molar ratio of DBT: benzaldehyde = 1: 15-20, the sulfur content in the solution is 1000 ppm) and is continuously passed under stirring in air solution and illuminate the reaction mixture (located in a quartz glass flask) with UV light for 1 minute of the process and then for every 10 minutes of the process. Samples are periodically taken for analysis on a gas chromatograph. The results are shown in table 1. 100% conversion is achieved in 150-160 minutes (As the DBT oxidizes to the corresponding sulfone, the resulting sulfone precipitates).

In a second embodiment of the invention, the oxidation process is carried out at a temperature of from 40 ° C to 70 ° C (without UV light): octane is mixed with the required amounts of benzaldehyde and DBT (molar ratio of DBT: benzaldehyde = 1: 15-20, sulfur content in solution 1000 ppm) and with stirring, heat the reaction mixture to the desired temperature and continuously pass air into it. Samples are periodically taken for analysis on a gas chromatograph. The results are shown in tables 2 and 3. The duration of the process until 100% conversion, depending on the reaction temperature, is from 40 to 140 minutes (As the DBT oxidizes into the corresponding sulfone, the sulfone formed precipitates).

(As you can see, in the proposed method (options) does not require pre-saturation of the reaction mixture with oxygen, which eliminates the need for phased addition of reagents).

Thus, it can be seen from the above data that the proposed method (options) of non-catalytic oxidative desulfurization of hydrocarbon fuels has a higher oxidation reaction rate, which simplified the process technology, increased its safety (by using air instead of oxygen), significantly reduced the aldehyde excess and , in one embodiment of the invention, allowed the process to be carried out at room temperature.

Claims (3)

1. The method of non-catalytic oxidative desulfurization of hydrocarbon fuels containing dibenzothiophene with an aldehyde / molecular oxygen system, comprising the process of oxidative desulfurization by passing an oxygen-containing gas into the reaction mixture, characterized in that benzaldehyde is used as the aldehyde, air is used as the oxygen-containing gas, and the oxidative process desulfurization is carried out at room temperature while illuminating the reaction mixture with UV light and a diba molar ratio Nzothiophene: benzaldehyde equal to 1: 15-20. 2. The method according to claim 1, characterized in that the reaction mixture is illuminated with UV light for 1 minute of the oxidative desulfurization process and then, to achieve 100% conversion of dibenzothiophene, for every 10th minute of the process, lasting 150- 160 minutes 3. A method of non-catalytic oxidative desulfurization of hydrocarbon fuels containing dibenzothiophene with an aldehyde / molecular oxygen system, comprising the process of oxidative desulfurization by passing an oxygen-containing gas into the reaction mixture, characterized in that benzaldehyde is used as the aldehyde, air is used as the oxygen-containing gas, and the oxidizing process desulfurization is carried out at a temperature of 40-70 ° C and a molar ratio of dibenzothiophene: benzaldehyde equal to 1: 15-20.

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