Tin-based eutectic solvent, preparation method thereof and application of tin-based eutectic solvent in fuel oil desulfurization

Abstract

The invention belongs to the technical field of fuel oil catalytic oxidation desulfurization, and discloses a tin-based eutectic solvent, a preparation method thereof and application of the tin-based eutectic solvent in fuel oil desulfurization. According to the invention, stannic chloride pentahydrate (SnCl4. 5H2O) and an acid hydrogen bond donor are used as raw materials and are mixed under a certain condition to obtain the stannic chloride-hydrogen bond composite material; the oxidation desulfurization comprises the following steps: adding the tin-based eutectic solvent into an oil product containing dibenzothiophene, and adding hydrogen peroxide as an oxidant to carry out an oxidation desulfurization reaction. According to the method, raw materials used for synthesizing the eutectic solvent are cheap and easy to obtain, the eutectic solvent can be prepared through one-step stirring, the prepared eutectic solvent is more environmentally friendly, the sulfur removal rate reaches 99.9%, the desulfurization effect is good, and the eutectic solvent can be recycled.

Description

Technical Field

[0001] The invention relates to the technical field of fuel oil desulfurization, and in particular to a method for desulfurizing fuel oil by catalytic oxidation with a tin-based low eutectic solvent. Background Art

[0002] A large amount of sulfur oxides (SOx) are released during fuel combustion. Sulfur oxides are one of the main air pollutants. They react with water vapor and oxygen in the atmosphere to form sulfuric acid and sulfates, which eventually lead to the formation of acid rain. This acidic deposition not only directly damages vegetation, waters and soil, but also poses a potential threat to buildings, cultural heritage and human health. Therefore, legislators and environmental organizations around the world have gradually strengthened the control of sulfur oxide emissions, promoting the research and application of fuel oil desulfurization technology.

[0003] Under the pressure of regulations and standards, industry and scientific research institutions are actively seeking efficient, economical and environmentally friendly desulfurization solutions. Traditional fuel oil has a high sulfur content. In order to meet strict emission standards, the sulfur content must be reduced to a level that meets regulatory requirements. Oxidative desulfurization technology is a mature and reliable desulfurization method. It introduces oxidants or catalysts to oxidize sulfides in the fuel into an easily removable form, thereby achieving desulfurization. Compared with traditional physical adsorption or alkaline washing, this method has higher efficiency and wider applicability, especially for heavy oil and fuel oil with high sulfur content.

[0004] With the advancement of technology and the development of catalyst material science, new oxidative desulfurization catalysts continue to emerge, which can efficiently catalyze sulfur oxidation reactions under low temperature and relatively mild conditions, greatly improving desulfurization efficiency and reducing energy consumption costs. For example, some new low eutectic solvents show excellent catalytic activity under appropriate reaction conditions. The research on these catalysts not only promotes the application of technology, but also lays the foundation for the development of future fuel desulfurization technology.

[0005] At present, regarding the research on the use of low eutectic solvents for catalytic oxidative desulfurization, researchers such as Jiang and Li have prepared different types of metal-based low eutectic solvents for catalytic oxidative desulfurization. Some low eutectic solvents have shown excellent desulfurization activity, which also proves the prospect of low eutectic solvents for catalytic oxidative desulfurization. In recent years, metal-based low eutectic solvents have been widely used in the field of desulfurization. The metals that constitute these low eutectic solvents are mostly transition metal chlorides. Compared with commonly used metal chlorides (AlCl3, ZnCl2), SnCl4.5H2O can exist stably in water and is considered to be a greener and safer transition metal chloride. So far, DESs containing SnCl4.5H2O have not been used in the field of ODS. Summary of the invention

[0006] In view of the deficiencies in the prior art, the present invention aims to solve one of the problems and provide a method for catalytic oxidation desulfurization using a tin-based low eutectic solvent; the raw materials of the present invention are readily available, the reaction conditions are mild, the operation is simple, and the sulfide in the oil can be effectively removed.

[0007] In order to achieve the above purpose, the operating steps of the present invention are as follows:

[0008] (1) preparing a low eutectic solvent: heating tin tetrachloride pentahydrate (SnCl4.5H2O) and an acidic hydrogen bond donor in an oil bath at 50° C. for 4 h, and then cooling to room temperature to obtain a uniform liquid, i.e., the tin-based low eutectic solvent; the molar ratio of the tin tetrachloride pentahydrate (SnCl4.5H2O) and the acidic hydrogen bond donor is 1:1 to 3;

[0009] (2) Dissolving the sulfide in dodecane to prepare fuel oil with different sulfur contents; then mixing the fuel oil and the low eutectic solvent prepared in step (1) at room temperature and pressure, adding hydrogen peroxide, and performing a catalytic oxidation reaction at a certain temperature. After the oxidation desulfurization reaction is completed, the low eutectic solvent phase and the simulated oil are first separated by a separatory funnel. Adding carbon tetrachloride to the low eutectic solvent phase, extracting the sulfide in the low eutectic solvent phase by back extraction, and then recovering the low eutectic solvent. The mass ratio of the fuel oil to the low eutectic solvent is 1-50:1-5; the concentration of the hydrogen peroxide is 30wt%, and the ratio of the amount of hydrogen peroxide to the sulfide substance in the fuel oil is 2:1-10:1.

[0010] Preferably, the acidic hydrogen bond donor in step (1) is selected from one of phosphoric acid, straight-chain saturated monocarboxylic acid (formic acid, acetic acid, propionic acid), and straight-chain saturated dicarboxylic acid (oxalic acid, malonic acid).

[0011] Preferably, the sulfide in step (2) is dibenzothiophene, 4-methyldibenzothiophene or 4,6-dimethyldibenzothiophene, and the sulfur content of the fuel oil is 5ppm to 1000ppm.

[0012] Preferably, the temperature of the catalytic oxidation reaction in step (2) is 0°C to 50°C, and the time is 10min to 120min.

[0013] Preferably, the volume ratio of the remaining liquid containing the low eutectic solvent to carbon tetrachloride in step (2) is 1:1-5.

[0014] The present invention has the following advantages:

[0015] The tin-based low eutectic solvent synthesized by the present invention uses SnCl4.5H2O, which has good stability, low toxicity, low price and is easily available, as a raw material, and SnCl4.5H2O can stably exist in water and is considered to be a greener and safer transition metal chloride. The low eutectic solvent is easy to synthesize and has high reactant utilization efficiency.

[0016] The low eutectic solvent prepared by the present invention has a sulfur removal rate of 99.9% and has high catalytic oxidation desulfurization performance; and after the reaction is completed, the low eutectic solvent can be recovered by a simple method, thereby realizing the recycling of the low eutectic solvent. DETAILED DESCRIPTION

[0017] The present invention is described with the following embodiments, but the present invention is not limited to the following embodiments, and variations are included in the technical scope of the present invention without departing from the scope of the above-mentioned purpose.

[0018] Embodiment 1:

[0019] (1) preparing a deep eutectic solvent No. 1 (DES1) from tin tetrachloride pentahydrate and phosphoric acid in a molar ratio of 1:1;

[0020] (2) Dissolving dibenzothiophene (DBT) in dodecane to prepare a fuel oil with a sulfur content of 200 ppm; adding 0.1 g of DES1 to 5 g of the fuel oil with a sulfur content of 200 ppm, and then adding 30 wt% H2O2, the molar ratio of H2O2 to the sulfide (DBT) in the fuel oil is 2:1, at this time, the low eutectic solvent phase is in the lower layer, the oil phase is in the upper layer, and H2O2 is dissolved in the low eutectic solvent; after magnetic stirring at 30°C for 30 min, the fuel oil is separated, and the DBT content in the oil is detected by GC-FID, and the sulfur removal rate is calculated to be 84.5%;

[0021] (3) Recovery of low eutectic solvent: After the fuel oil is separated, one volume of carbon tetrachloride is added to the remaining liquid containing the low eutectic solvent and mixed. Since the low eutectic solvent is insoluble in carbon tetrachloride, while the sulfide and its reaction products are soluble in carbon tetrachloride, the low eutectic solvent can be recovered by separating the carbon tetrachloride phase.

[0022] Embodiment 2:

[0023] (1) preparing a deep eutectic solvent No. 2 (DES2) from tin tetrachloride pentahydrate and formic acid in a molar ratio of 1:1;

[0024] (2) Dissolving dibenzothiophene (DBT) in dodecane to prepare a fuel oil with a sulfur content of 500 ppm; adding 1 g of DES2 to 5 g of the fuel oil with a sulfur content of 500 ppm, and then adding 30 wt% H2O2, the molar ratio of H2O2 to the sulfide (DBT) in the fuel oil is 4:1, at this time, the low eutectic solvent phase is in the lower layer, the oil phase is in the upper layer, and H2O2 is dissolved in the low eutectic solvent; after magnetic stirring at 40°C for 60 min, the fuel oil is separated, and the DBT content in the oil is detected by GC-FID, and the sulfur removal rate is calculated to be 99.9%;

[0025] (3) Recovery of low eutectic solvent: After the fuel oil is separated, 2 times the volume of carbon tetrachloride is added to the remaining liquid containing the low eutectic solvent and mixed. Since the low eutectic solvent is insoluble in carbon tetrachloride, while the sulfide and its reaction products are soluble in carbon tetrachloride, the low eutectic solvent can be recovered by separating the carbon tetrachloride phase.

[0026] Embodiment 3:

[0027] (1) preparing a deep eutectic solvent No. 3 (DES3) from tin tetrachloride pentahydrate and acetic acid in a molar ratio of 1:1;

[0028] (2) 4-Methyldibenzothiophene (4-MDBT) was dissolved in dodecane to prepare a fuel oil with a sulfur content of 200 ppm; 5 g of DES3 was added to 5 g of the fuel oil with a sulfur content of 200 ppm, and then 30 wt% H2O2 was added, the molar ratio of H2O2 to the sulfide (4-MDBT) in the fuel oil was 6:1, at this time, the low eutectic solvent phase was in the lower layer, the oil phase was in the upper layer, and H2O2 was dissolved in the low eutectic solvent; after magnetic stirring at 50°C for 60 min, the fuel oil was separated, and the content of 4-MDBT in the oil was detected by GC-FID, and the sulfur removal rate was calculated to be 95.6%;

[0029] (3) Recovery of low eutectic solvent: After the fuel oil is separated, three times the volume of carbon tetrachloride is added to the remaining liquid containing the low eutectic solvent and mixed. Since the low eutectic solvent is insoluble in carbon tetrachloride, while the sulfide and its reaction products are soluble in carbon tetrachloride, the low eutectic solvent can be recovered by separating the carbon tetrachloride phase.

[0030] Embodiment 4:

[0031] (1) preparing a deep eutectic solvent No. 4 (DES4) from tin tetrachloride pentahydrate and propionic acid in a molar ratio of 1:1;

[0032] (2) 4,6-dimethyldibenzothiophene (4,6-DMDBT) was dissolved in dodecane to prepare a fuel oil with a sulfur content of 200 ppm; 5 g of DES4 was added to 5 g of the fuel oil with a sulfur content of 200 ppm, and then 30 wt% H2O2 was added, the molar ratio of H2O2 to the sulfide (4,6-DMDBT) in the fuel oil was 8:1, at this time, the low eutectic solvent phase was in the lower layer, the oil phase was in the upper layer, and H2O2 was dissolved in the low eutectic solvent; after magnetic stirring at 50°C for 120 min, the fuel oil was separated, and the content of 4,6-DMDBT in the oil was detected by GC-FID, and the sulfur removal rate was calculated to be 90.8%;

[0033] (3) Recovery of low eutectic solvent: After the fuel oil is separated, 4 times the volume of carbon tetrachloride is added to the remaining liquid containing the low eutectic solvent and mixed. Since the low eutectic solvent is insoluble in carbon tetrachloride, while the sulfide and its reaction products are soluble in carbon tetrachloride, the low eutectic solvent can be recovered by separating the carbon tetrachloride phase.

[0034] Embodiment 5:

[0035] (1) preparing a deep eutectic solvent No. 5 (DES5) from tin tetrachloride pentahydrate and oxalic acid in a molar ratio of 1:2;

[0036] (2) Dissolve dibenzothiophene (DBT) in dodecane to prepare a fuel oil with a sulfur content of 800 ppm; add 1 g of DES5 to 5 g of the fuel oil with a sulfur content of 800 ppm, and then add 30 wt% H2O2, the molar ratio of H2O2 to the sulfide (DBT) in the fuel oil is 10:1, at this time, the low eutectic solvent phase is in the lower layer, the oil phase is in the upper layer, and H2O2 is dissolved in the low eutectic solvent; after magnetic stirring at 50°C for 10 min, separate the fuel oil, use GC-FID to detect the DBT content in the oil, and calculate the sulfur removal rate to be 65.4%;

[0037] (3) Recovery of low eutectic solvent: After the fuel oil is separated, 5 times the volume of carbon tetrachloride is added to the remaining liquid containing the low eutectic solvent and mixed. Since the low eutectic solvent is insoluble in carbon tetrachloride, while the sulfide and its reaction products are soluble in carbon tetrachloride, the low eutectic solvent can be recovered by separating the carbon tetrachloride phase.

[0038] Embodiment 6:

[0039] (1) preparing a deep eutectic solvent No. 6 (DES6) from tin tetrachloride pentahydrate and malonic acid in a molar ratio of 1:2;

[0040] (2) Dissolving dibenzothiophene (DBT) in dodecane to prepare a fuel oil with a sulfur content of 1000 ppm; adding 1 g of DES6 to 5 g of the fuel oil with a sulfur content of 1000 ppm, and then adding 30 wt% H2O2, the molar ratio of H2O2 to the sulfide (DBT) in the fuel oil is 10:1, at this time, the low eutectic solvent phase is in the lower layer, the oil phase is in the upper layer, and H2O2 is dissolved in the low eutectic solvent; after magnetic stirring at 50°C for 90 min, the fuel oil is separated, and the DBT content in the oil is detected by GC-FID, and the sulfur removal rate is calculated to be 56.4%;

[0041] (3) Recovery of low eutectic solvent: After the fuel oil is separated, 5 times the volume of carbon tetrachloride is added to the remaining liquid containing the low eutectic solvent and mixed. Since the low eutectic solvent is insoluble in carbon tetrachloride, while the sulfide and its reaction products are soluble in carbon tetrachloride, the low eutectic solvent can be recovered by separating the carbon tetrachloride phase.

[0042] Embodiment 7:

[0043] (1) preparing a deep eutectic solvent No. 7 (DES7) from tin tetrachloride pentahydrate and formic acid in a molar ratio of 1:2;

[0044] (2) Dissolve dibenzothiophene (DBT) in dodecane to prepare a fuel oil with a sulfur content of 5 ppm; add 0.5 g of DES7 to 5 g of the fuel oil with a sulfur content of 5 ppm, and then add 30 wt% H2O2, the molar ratio of H2O2 to the sulfide (DBT) in the fuel oil is 2:1, at this time, the low eutectic solvent phase is in the lower layer, the oil phase is in the upper layer, and H2O2 is dissolved in the low eutectic solvent; after magnetic stirring at 50°C for 10 min, separate the fuel oil, use GC-FID to detect the DBT content in the oil, and calculate the sulfur removal rate to be 99.9%;

[0045] (3) Recovery of low eutectic solvent: After the fuel oil is separated, 5 times the volume of carbon tetrachloride is added to the remaining liquid containing the low eutectic solvent and mixed. Since the low eutectic solvent is insoluble in carbon tetrachloride, while the sulfide and its reaction products are soluble in carbon tetrachloride, the low eutectic solvent can be recovered by separating the carbon tetrachloride phase.

[0046] Embodiment 8:

[0047] (1) preparing a deep eutectic solvent No. 8 (DES8) from tin tetrachloride pentahydrate and formic acid in a molar ratio of 1:3;

[0048] (2) Dissolving dibenzothiophene (DBT) in dodecane to prepare a fuel oil with a sulfur content of 1000 ppm; adding 5 g of DES8 to 1 g of fuel oil with a sulfur content of 800 ppm, and then adding 30 wt% H2O2, the molar ratio of H2O2 to the sulfide (DBT) in the fuel oil is 10:1, at this time, the low eutectic solvent phase is in the lower layer, the oil phase is in the upper layer, and H2O2 is dissolved in the low eutectic solvent; after magnetic stirring at 0°C for 120 min, the fuel oil is separated, and the DBT content in the oil is detected by GC-FID, and the sulfur removal rate is calculated to be 99.9%;

[0049] (3) Recovery of low eutectic solvent: After the fuel oil is separated, one volume of carbon tetrachloride is added to the remaining liquid containing the low eutectic solvent and mixed. Since the low eutectic solvent is insoluble in carbon tetrachloride, while the sulfide and its reaction products are soluble in carbon tetrachloride, the low eutectic solvent can be recovered by separating the carbon tetrachloride phase.

[0050] Embodiment 9:

[0051] (1) preparing a deep eutectic solvent No. 9 (DES9) from tin tetrachloride pentahydrate and formic acid in a molar ratio of 1:1;

[0052] (2) Dissolving dibenzothiophene (DBT) in dodecane to prepare a fuel oil with a sulfur content of 200 ppm; adding 5 g of DES9 to 5 g of the fuel oil with a sulfur content of 200 ppm, and then adding 30 wt% H2O2, the molar ratio of H2O2 to the sulfide (DBT) in the fuel oil is 2:1, at this time, the low eutectic solvent phase is in the lower layer, the oil phase is in the upper layer, and H2O2 is dissolved in the low eutectic solvent; after magnetic stirring at 50°C for 120 min, the fuel oil is separated, and the DBT content in the oil is detected by GC-FID, and the sulfur removal rate is calculated to be 99.9%;

[0053] (3) Recovery of low eutectic solvent: After the fuel oil is separated, one volume of carbon tetrachloride is added to the remaining liquid containing the low eutectic solvent and mixed. Since the low eutectic solvent is insoluble in carbon tetrachloride, while the sulfide and its reaction products are soluble in carbon tetrachloride, the low eutectic solvent can be recovered by separating the carbon tetrachloride phase.

[0054] Note: The above embodiments are only used to illustrate the present invention and are not intended to limit the technical solutions described in the present invention; therefore, although this specification has described the present invention in detail with reference to the above embodiments, a person skilled in the art should understand that the present invention can still be modified or replaced by equivalents; and all technical solutions and improvements thereof that do not depart from the spirit and scope of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A method for desulfurizing fuel oil by catalytic oxidation using a tin-based deep eutectic solvent, characterized in that , follow the steps below: (1) preparing a low eutectic solvent: heating tin tetrachloride pentahydrate (SnCl4.5H2O) and an acidic hydrogen bond donor in an oil bath at 50° C. for 4 h, and then cooling to room temperature to obtain a uniform liquid, i.e., the tin-based low eutectic solvent; the molar ratio of the tin tetrachloride pentahydrate (SnCl4.5H2O) and the acidic hydrogen bond donor is 1:1 to 3; (2) Dissolving the sulfide in dodecane to prepare fuel oil with different sulfur contents; then mixing the fuel oil and the low eutectic solvent prepared in step (1) at room temperature and pressure, adding hydrogen peroxide, and performing a catalytic oxidation reaction at a certain temperature. After the oxidation desulfurization reaction is completed, the low eutectic solvent phase and the simulated oil are first separated by a separatory funnel. Adding carbon tetrachloride to the low eutectic solvent phase, extracting the sulfide in the low eutectic solvent phase by back extraction, and then recovering the low eutectic solvent. The mass ratio of the fuel oil to the low eutectic solvent is 1-50:1-5; the concentration of the hydrogen peroxide is 30wt%, and the ratio of the amount of hydrogen peroxide to the sulfide substance in the fuel oil is 2:1-10:

1.

2. The method for desulfurization of fuel oil by catalytic oxidation using a tin-based deep eutectic solvent according to claim 1, characterized in that: The hydrogen bond acceptor is tin tetrachloride pentahydrate (SnCl4.5H2O).

3. The method for desulfurization of fuel oil by catalytic oxidation using a tin-based deep eutectic solvent according to claim 1, characterized in that: The acidic hydrogen bond donor is selected from one of phosphoric acid, straight-chain saturated monocarboxylic acid (formic acid, acetic acid, propionic acid), and straight-chain saturated dicarboxylic acid (oxalic acid, malonic acid). The general formula of the straight-chain saturated monocarboxylic acid is R-COOH, wherein R is a saturated straight-chain hydrocarbon group, and the general formula of the straight-chain saturated dicarboxylic acid is R(COOH)2, wherein R is a saturated straight-chain hydrocarbon group.

4. The method for desulfurizing fuel oil by catalytic oxidation using a tin-based deep eutectic solvent according to claim 1, characterized in that: The sulfide in step (2) is dibenzothiophene, 4-methyldibenzothiophene or 4,6-dimethyldibenzothiophene, and the sulfur content of the fuel oil is 5ppm to 1000ppm.

5. The method for desulfurization of fuel oil by catalytic oxidation using a tin-based deep eutectic solvent according to claim 1, characterized in that: The temperature of the catalytic oxidation reaction in step (2) is 0°C to 50°C, and the time is 10min to 120min.

6. The method for desulfurizing fuel oil by catalytic oxidation using a tin-based deep eutectic solvent according to claim 1, characterized in that: The volume ratio of the remaining liquid containing the low eutectic solvent to carbon tetrachloride in step (2) is 1:1-5.