A method for selective oxidation desulfurization in petroleum and its products

Abstract

The present invention belongs to the field of energy and chemical industry, and specifically discloses a method for selective oxidative desulfurization in petroleum and its products. In this method, in a polar phase composed of water and acetonitrile, organic sulfides in a non-polar phase oil solution are selectively removed by direct oxidation of peroxy organic acid and activation of the peroxy organic acid by a catalyst to produce active substances. In the polar phase, peroxypropionic acid is used as an oxidant, and low-valent transition metals are used as catalysts to activate the peroxypropionic acid to produce active substances to achieve oxidative removal of organic sulfur in the non-polar phase. This process is suitable for the direct removal of organic sulfur in petroleum and the selective removal of organic sulfur in petroleum products, and can be expanded to the selective desulfurization of various liquid phase systems, such as the desulfurization of waste tire pyrolysis liquid. This process is suitable for reactions under normal temperature and pressure, and the process flow is simple and can be flexibly adjusted according to actual needs.

Description

Technical Field

[0001] The present invention belongs to the field of energy and chemical engineering and relates to a method for selective oxidative desulfurization in petroleum and its products. It mainly describes the selective oxidation of dibenzothiophene by the formation of related active substances under the catalytic action of an oxidant, thereby reducing the organic sulfur content in petroleum and its products. Background Art

[0002] Crude oil typically contains 0.1-6% sulfide. Organic sulfides, such as dibenzothiophene and its homologues, readily coexist with crude oil due to their low polarity. Organic sulfur in liquid fuels forms toxic sulfur oxides and the acidic gas sulfur dioxide during combustion, which not only corrodes vehicle engines but also causes severe atmospheric pollution. Consequently, environmental regulations in many countries and regions require a total sulfur content in fuels to be less than 10 ppm.

[0003] Petrochemical products such as anthracene and pyrene, extracted through fractional distillation of coal tar from crude oil, are commonly used as chemical raw materials. However, the presence of organic sulfides during the production process can poison catalysts or affect the quality of the final product. For example, dibenzothiophene, an organic sulfide, is difficult to separate due to its similar boiling point to anthracene oil. In the production of superconductive carbon black using anthracene oil, the sulfides can form defects or uneven distribution on the carbon matrix, reducing the carbon black's conductivity. Therefore, the organic sulfur content in the anthracene oil is typically required to be below 500 ppm to ensure the quality of the final product.

[0004] Despite the significant demand for removing organic sulfur from petroleum and its products in the energy and chemical industries, there is currently a lack of technologies that can achieve efficient desulfurization at a low investment cost. Commonly used hydrodesulfurization technology involves converting sulfides into H2S gas through hydrogenation under catalytic conditions, which is then removed. However, this process often requires high temperatures and pressures, and places high demands on the equipment. Due to the high reactivity of the π bond in olefins, they preferentially react with hydrogen during hydrogenation, competing with the desulfurization reaction. Dibenzothiophene and its derivatives, the primary organic sulfur compounds in petroleum and its products, exhibit poor hydrodesulfurization performance due to the presence of carbon-carbon double bonds (C=C) in their molecular structure. In contrast, oxidative desulfurization utilizes a suitable oxidant to continuously oxidize organic sulfur to produce more polar products, such as sulfoxides or sulfones, which are then easily removed from the fuel through separation methods such as adsorption. However, this technology places high demands on the oxidizing agent's oxidizing power. On the one hand, because the sulfur atoms in dibenzothiophene are inactive, weak oxidants are unable to oxidize and desulfurize dibenzothiophene. On the other hand, strong oxidants may damage other components in the fuel. Therefore, developing an efficient, low-cost, and selective desulfurization technology is currently a major challenge, but it has broad application prospects.

[0005] Combining existing organic sulfur removal methods, oxidative desulfurization technology is effective against most mercaptans and sulfides, oxidizing organic sulfur into products with increased polarity, thus facilitating separation. In this process, because petroleum and its products, as well as organic sulfur, have very low polarity, they exist as a mixture in a nonpolar oil phase containing petroleum as the solvent. However, the critical oxidant is typically present in a polar aqueous phase, and the significant polarity difference between the two phases limits the reaction between the oxidant and organic sulfur. To address this issue, acetonitrile, with a polarity intermediate between water and oil, is often introduced to enhance the exchange efficiency of organic sulfur between the polar and nonpolar phases and facilitate the separation of organic sulfur oxidation products from other components. Specifically, in a system consisting of an upper nonpolar phase of n-decane and a lower polar phase of water and acetonitrile, some organic sulfur can migrate from the nonpolar phase to the polar phase containing acetonitrile, reacting with the oxidant and forming organic sulfur oxidation products with increased polarity. Summary of the Invention

[0006] In view of the demand for efficient and selective removal of organic sulfur in petroleum and its products, the present invention uses peroxy organic acid as an oxidant and uses a catalyst to activate the peroxy organic acid in an acetonitrile / water mixed solution to produce an active substance, thereby achieving the desulfurization of petroleum and its products.

[0007] The object of the present invention is to provide a method for selective oxidative desulfurization in petroleum and its products, thereby reducing the impact of organic sulfur in petroleum and its products on equipment, final products and the atmospheric environment during production and use.

[0008] The technical solution of the present invention is a method for selective oxidative desulfurization in petroleum and its products. In this method, in a polar phase composed of water and acetonitrile, organic sulfides in a non-polar phase oil solution are selectively removed by direct oxidation of peroxy organic acid and activation of the peroxy organic acid by a catalyst to produce active substances.

[0009] First, acetonitrile and water are added to the non-polar phase of petroleum and its products to form an upper and lower layer of solution, of which the lower layer is a polar phase in which acetonitrile and water are miscible, and the mixed solution is thoroughly mixed by shaking or stirring;

[0010] Then, an oxidizing agent, peroxy organic acid, is prepared, and the oxidizing agent and catalyst are added to the above solution to start the desulfurization reaction;

[0011] The catalyst is selected from low-valent transition metal ions, and any one of Co(II), Fe(II), Cu(II) and Mn(II) is selected, and the metal salts used are all chlorides;

[0012] The peroxy organic acid is peracetic acid or peroxypropionic acid;

[0013] The water content in the polar phase is 30-40%;

[0014] Catalyst concentration was 0–9.1 mM;

[0015] Oxidant concentration was 14.4–172.8 mM;

[0016] Dibenzothiophene is used as a representative organic sulfide that is difficult to remove, and pyrene among polycyclic aromatic hydrocarbons is used as a representative petroleum product; propionic acid, hydrogen peroxide and sulfuric acid are reacted to form peroxypropionic acid.

[0017] Furthermore, the water content in the polar phase was 30%, the concentrations of the catalyst Co(II) and the oxidant peroxypropionic acid were 9.1 mM and 86.4 mM, respectively, and the reaction time was controlled at 90 min.

[0018] Furthermore, the peroxy organic acid is preferably peroxypropionic acid.

[0019] Furthermore, the concentration of the oxidant is 43.2-172.8 mM.

[0020] Furthermore, the concentration of the oxidant is 43.2-86.4 mM.

[0021] Furthermore, the concentration of the oxidant is 86.4-172.8 mM.

[0022] Furthermore, when selective desulfurization is the top priority, the desulfurization process is carried out under conditions of low catalyst concentration or no catalyst, at a slightly slower desulfurization rate to ensure that coexisting petroleum products are not affected.

[0023] Furthermore, the method is applicable to the removal of organic sulfides from crude oil, diesel, fuel oil, or other sulfur-containing petroleum products. Furthermore, when efficient desulfurization is the top priority, the catalytic oxidation desulfurization process using Cu(II) as a catalyst achieves an organic sulfur removal rate of nearly 90% within 30 minutes.

[0024] Furthermore, after the desulfurization process is completed, the non-polar phase and the polar phase are recovered by phase separation so that the oil phase, the petroleum and its products and the lower catalytic oxidation system can be reused.

[0025] From the structural analysis, dibenzothiophene (such as Figure 1As a representative organic sulfide, the sulfur atom in its molecule is directly connected to an electron-withdrawing group, which reduces the charge density of the sulfur atom, resulting in a slow reaction rate in conventional direct oxidation. Therefore, the development of new oxidants and oxidation systems will help achieve selective oxidation and remove organic sulfur while ensuring the quality of petroleum products. In the polar phase composed of water and acetonitrile, the addition of an oxidant can not only exert its oxidizing effect, but also activate the production of a large number of active substances with moderate oxidizing ability through the addition of an external catalyst to promote the desulfurization reaction. In addition, in order to minimize the impact on petroleum products during the desulfurization reaction and enhance the value of petroleum products, the selective desulfurization process must also be considered. There are significant reaction differences between organic sulfides represented by dibenzothiophene and petroleum products represented by pyrene among polycyclic aromatic hydrocarbons. The sulfur atoms in dibenzothiophene can serve as active sites in the catalytic oxidation process, making dibenzothiophene more susceptible to interacting with active substances than pyrene.

[0026] Among them, peroxypropionic acid is an oxidant formed by the reaction of hydrogen peroxide and propionic acid under the action of sulfuric acid. Peroxypropionic acid has a certain oxidizing ability. Peroxypropionic acid in the polar phase can be activated by transition metal catalysis and is conducive to the oxidative removal of dibenzothiophene in the non-polar phase. Specifically, while peroxypropionic acid can directly oxidize dibenzothiophene, it can also be activated by Co(II) to generate active substances to further accelerate the desulfurization reaction rate, ultimately allowing dibenzothiophene in the oil phase to be transferred to the aqueous phase in the form of its oxide. In addition, when dibenzothiophene coexists with polycyclic aromatic hydrocarbons in petroleum products in the oil phase, the direct oxidation of peroxypropionic acid in the aqueous phase and the catalytic oxidation of peroxypropionic acid by Co(II) can effectively selectively oxidize and remove dibenzothiophene. In summary, using Co(II) to activate peroxypropionic acid to achieve desulfurization of petroleum and its products is a technical means that is convenient to operate, simple in equipment, efficient in processing, and inexpensive.

[0027] Beneficial effects

[0028] Compared with the existing desulfurization technology, the present invention has the following beneficial effects:

[0029] 1) The Co(II)-activated peroxypropionic acid system can remove more than 90% of organic sulfur within 90 minutes.

[0030] 2) The process effectively removes a large amount of organic sulfides while only affecting a small amount of coexisting polycyclic aromatic hydrocarbons.

[0031] 3) The reactivity and selectivity requirements can be achieved by adjusting the amount of Co(II). For example, preferential selectivity can be achieved by adding less or no Co(II).

[0032] 4) The organic sulfur oxidation products are clear and easy to separate from the oil phase, and can be recycled after adsorption.

[0033] 5) The process can be carried out at room temperature and pressure without the use of hydrogen, and has low requirements for equipment design and construction.

[0034] 6) The process can be flexibly adjusted according to the needs of production scale. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 Schematic diagram of the reaction system for selective oxidative desulfurization in petroleum and its products.

[0036] Figure 2 The content of dibenzothiophene and its oxidation products in different systems changes with time.

[0037] Figure 3 The content of dibenzothiophene and dibenzofuran in different systems changes with time.

[0038] Figure 4 The content of dibenzothiophene and pyrene in different systems changes with time.

[0039] Figure 5 The effect of different transition metal ions on dibenzothiophene and pyrene in the system.

[0040] Figure 6 The effect of different pH on dibenzothiophene and pyrene in different systems.

[0041] Figure 7 The effects of different concentrations of the oxidant peroxypropionic acid on dibenzothiophene and pyrene in different systems.

[0042] Figure 8 The effects of different concentrations of catalyst Co(II) on dibenzothiophene and pyrene.

[0043] Figure 9 This is the effect of changes in the water content of the polar phase on dibenzothiophene and pyrene in different systems.

[0044] Figure 10 The effects of different cycle periods on dibenzothiophene and pyrene in the peroxypropionic acid-Co(II) system. DETAILED DESCRIPTION

[0045] The present invention provides a method for selectively removing organic sulfur. By adding peroxypropionic acid and Co(II) to a polar phase of water / acetonitrile, the organic sulfur in the oil phase is selectively oxidized. The oxidation products of the organic sulfur are separated from the oil phase due to increased polarity, thereby achieving desulfurization of the oil phase, thereby eliminating the impact of the presence of organic sulfur on the production and application of petroleum and its products. The present invention is further described below through specific examples and drawings. Figure 1The schematic diagram of the reaction system is shown. The following example simulates petroleum containing organic sulfur and its products. Decane is selected as the model oil, dibenzothiophene as the difficult-to-remove organic sulfur, pyrene as the petroleum product, and peroxypropionic acid and Co(II) as the oxidant and catalyst, respectively, to study the desulfurization effect.

[0046] The embodiments of the present invention are intended to help those skilled in the art better understand the present invention, and are not intended to limit the present invention in any way.

[0047] The experimental scheme proposed by the present invention to solve the technical problems raised in the prior art mainly includes the following steps:

[0048] 1) Using dibenzothiophene as a representative organic sulfide that is difficult to remove, and using pyrene among polycyclic aromatic hydrocarbons as a representative petroleum product;

[0049] 2) mixing the model oil containing dibenzothiophene and pyrene with an acetonitrile / water solution by oscillation to form a two-phase solution, so that the distribution of dibenzothiophene and pyrene in the two phases reaches equilibrium;

[0050] 3) using propionic acid, hydrogen peroxide and sulfuric acid to react to form peroxypropionic acid;

[0051] 4) Peroxypropionic acid and Co(II) are added to the two-phase mixed solution to initiate the selective desulfurization reaction.

[0052] Example 1

[0053] In order to study the desulfurization process of petroleum, peracetic acid and peroxypropionic acid were used as oxidants and the desulfurization effect was studied with and without the addition of Co(II). The details are as follows:

[0054] 1) A 5 mL non-polar phase solution containing 15.625 mM dibenzothiophene (organic sulfur content 500 ppm) was prepared in n-decane. 7.7 mL of acetonitrile and 2.3 mL of water were added to form a miscible polar phase solution. The two phases were mixed at room temperature at 250 rpm for 30 minutes to achieve equilibrium distribution of dibenzothiophene in the two phases.

[0055] 2) Prepare and measure the concentrations of peracetic acid and peroxypropionic acid stock solutions using the MTS-TPP method on HPLC. The peroxypropionic acid stock solution prepared fresh was prepared by reacting 59.52% propionic acid, 35.71% hydrogen peroxide, and 4.76% sulfuric acid at 40°C for 8 minutes and then refrigerated for later use.

[0056] 3) Adding an oxidant or an oxidant and catalyst to the two-phase mixture to initiate the desulfurization reaction. Due to the volume change caused by the introduction of the solution, the final volume of the polar phase was fixed to 11 mL (30% water content). The concentrations of peracetic acid and peroxypropionic acid as oxidants were 86.4 mM, while the concentration of the catalyst, CoCl2, was 9.1 mM.

[0057] 4) During the kinetic reaction, 10 μL of the upper non-polar oil phase solution was diluted into 1 mL of ethanol and analyzed by HPLC for the remaining amount of dibenzothiophene. 10 μL of the lower polar phase solution was diluted into 1 mL of ethanol and analyzed by HPLC for the amount of dibenzothiophene oxidation products. 10 μL of the lower polar phase solution was added to the MTS and TPP solutions, respectively, and the remaining amount of peroxypropionic acid was analyzed by HPLC.

[0058] Figure 2 The figure shows the removal of dibenzothiophene as a representative organic sulfide in different reaction systems. Figure 2 Results show that dibenzothiophene can be degraded in direct oxidation with peracetic acid and peroxypropionic acid, but after 180 minutes of treatment, it is still impossible to achieve complete removal of organic sulfides. In the activation system of Co(II), peracetic acid as an oxidant is completely consumed after 30 minutes of reaction, and then dibenzothiophene as an organic sulfide is no longer degraded. The peroxypropionic acid-Co(II) system can achieve efficient and continuous degradation of dibenzothiophene, while also being accompanied by the continuous generation of oxidation products of organic sulfides in the polar phase. This embodiment illustrates that organic sulfur can be effectively removed in the peroxypropionic acid-Co(II) system, while also achieving the accumulation of oxidation products of organic sulfur in the polar phase.

[0059] Example 2

[0060] Based on the removal of dibenzothiophene in the model oil in Example 1, in order to clarify the direct action site of the oxidation and catalytic system on organic sulfides, while studying the removal of organic sulfides represented by dibenzothiophene, dibenzofuran, which has a very similar chemical structure to dibenzothiophene, was added for verification. Figure 3 As shown, Figure 3 The chemical structures of dibenzothiophene and dibenzofuran are shown on the upper left and upper right of the figure, respectively. The difference between them is that the sulfur atom in dibenzothiophene is replaced by an oxygen atom to form dibenzofuran. Other experimental conditions remain unchanged, as follows:

[0061] 1) A 5 mL non-polar phase solution containing 15.625 mM dibenzothiophene (organic sulfur content: 500 ppm) and 15.625 mM dibenzofuran was prepared in n-decane. 7.7 mL of acetonitrile and 2.3 mL of water were added to the solution to form a miscible polar phase solution. The two phases were mixed at room temperature at 250 rpm for 30 minutes to achieve equilibrium distribution of dibenzothiophene and dibenzofuran in the two phases.

[0062] 2) Prepare and measure the concentrations of peracetic acid and peroxypropionic acid stock solutions using the MTS-TPP method on HPLC. The peroxypropionic acid stock solution prepared fresh was prepared by reacting 59.52% propionic acid, 35.71% hydrogen peroxide, and 4.76% sulfuric acid at 40°C for 8 minutes and then refrigerated for later use.

[0063] 3) Adding an oxidant or an oxidant and catalyst to the two-phase mixture to initiate the desulfurization reaction. Due to the volume change caused by the introduction of the solution, the final volume of the polar phase was fixed to 11 mL (30% water content). The concentrations of peracetic acid and peroxypropionic acid as oxidants were 86.4 mM, while the concentration of the catalyst, CoCl2, was 9.1 mM.

[0064] 4) During the kinetic reaction, 10 μL of the non-polar oil phase solution was taken and diluted into 1 mL of ethanol solution, and the remaining amounts of dibenzothiophene and dibenzofuran were analyzed using HPLC.

[0065] The content of dibenzothiophene and dibenzofuran in different systems changes with time. Figure 3 As shown. The experimental results of this section show that both direct oxidation and activated oxidation systems only work on dibenzothiophene, while the coexisting dibenzofuran is not affected at all, indicating that the sulfur in the dibenzothiophene molecule is affected by peroxypropionic acid or active substances related to peroxypropionic acid, and desulfurization is achieved based on the oxidation of the sulfur in the molecule. After sulfide is oxidized, functional groups such as sulfoxide or sulfone are usually formed. In combination with Example 1, it was detected that the amount of dibenzothiophene oxidation products in the lower polar phase solution gradually increased, indicating that the polarity of dibenzothiophene oxidation products has greatly increased compared to dibenzothiophene. Therefore, this process can not only remove organic sulfur in oil, but also achieve the accumulation of dibenzothiophene oxidation products in the polar phase.

[0066] Example 3

[0067] Because the presence of organic sulfur in some petroleum products can directly affect the quality of the final chemical product, desulfurization of petroleum products is also a critical requirement. Because petroleum products often contain polycyclic aromatic hydrocarbons (PAHs), this laboratory-based detection technique uses pyrene as a representative petroleum product. To study desulfurization in petroleum and its products, pyrene and dibenzothiophene were added to n-decane while other experimental conditions remained unchanged. The details are as follows:

[0068] 1) A 5 mL non-polar phase solution containing 15.625 mM dibenzothiophene (organic sulfur content: 500 ppm) and 15.625 mM pyrene was prepared in n-decane. 7.7 mL of acetonitrile and 2.3 mL of water were added to form a miscible polar phase solution. The two phases were mixed at room temperature at 250 rpm for 30 minutes to achieve equilibrium distribution of dibenzothiophene and pyrene in the two phases.

[0069] 2) Prepare and measure the concentrations of peracetic acid and peroxypropionic acid stock solutions using the MTS-TPP method on HPLC. The peroxypropionic acid stock solution prepared fresh was prepared by reacting 59.52% propionic acid, 35.71% hydrogen peroxide, and 4.76% sulfuric acid at 40°C for 8 minutes and then refrigerated for later use.

[0070] 3) Adding an oxidant or an oxidant and catalyst to the two-phase mixture to initiate the desulfurization reaction. Due to the volume change caused by the introduction of the solution, the final volume of the polar phase was fixed to 11 mL (30% water content). The concentrations of peracetic acid and peroxypropionic acid as oxidants were 86.4 mM, while the concentration of the catalyst, CoCl2, was 9.1 mM.

[0071] 4) During the kinetic reaction, 10 μL of the non-polar oil phase solution was taken and diluted into 1 mL of ethanol solution. The remaining amounts of dibenzothiophene and pyrene and the amount of pyrene oxidation products produced were analyzed by HPLC.

[0072] The selective removal of organic sulfur was studied by using dibenzothiophene, a representative organic sulfur compound, and pyrene, a representative polycyclic aromatic hydrocarbon. Figure 4According to the experimental results, in the presence of pyrene, the degradation rate of dibenzothiophene is consistent with that in Example 1, indicating that the desulfurization of the system is not affected by other coexisting substances. In the non-activated system with only peroxypropionic acid as the oxidant, 80% desulfurization can be achieved after 180 minutes of reaction without any impact on pyrene. Under the catalytic action of Co(II), the reaction stops within 30 minutes due to the rapid activation of peracetic acid by Co(II). However, for the oxidant peroxypropionic acid, the addition of Co(II) can accelerate the degradation of dibenzothiophene and achieve a desulfurization efficiency of more than 90% within 90 minutes. However, after 90 minutes of reaction, about 10% of pyrene is also affected, accompanied by the formation of pyrene oxidation products. Therefore, the system can be adjusted to meet different needs. When desulfurizing petroleum products with high selectivity requirements, peroxypropionic acid oxidation can be used directly to fully guarantee selectivity. When the focus is on high-efficiency desulfurization, peroxypropionic acid-Co(II) oxidation can be used to maximize high-efficiency desulfurization and guarantee most selectivity.

[0073] Example 4

[0074] Different metal ions have varying effects on the activation efficiency of peroxypropionic acid and, consequently, the oxidation of dibenzothiophene. This study used different transition metal ions, such as Fe(II), Cu(II), and Mn(II), while other experimental conditions remained unchanged. The details are as follows:

[0075] 1) A 5 mL non-polar phase solution containing 15.625 mM dibenzothiophene (organic sulfur content: 500 ppm) and 15.625 mM pyrene was prepared in n-decane. 7.7 mL of acetonitrile and 2.3 mL of water were added to form a miscible polar phase solution. The two phases were mixed at room temperature at 250 rpm for 30 minutes to achieve equilibrium distribution of dibenzothiophene and pyrene in the two phases.

[0076] 2) Prepare and measure the concentration of a peroxypropionic acid stock solution using the MTS-TPP method on HPLC. The peroxypropionic acid stock solution prepared fresh was prepared by reacting 59.52% propionic acid, 35.71% hydrogen peroxide, and 4.76% sulfuric acid at 40°C for 8 minutes and then refrigerated for later use.

[0077] 3) Adding an oxidant or an oxidant and a catalyst to the two-phase mixture to initiate the desulfurization reaction. Due to the volume change caused by the introduction of the solution, the final volume of the polar phase was fixed to 11 mL (30% water content). The concentration of the peroxypropionic acid as the oxidant was 86.4 mM, while the concentration of the catalysts CoCl2, FeCl2, CuCl2, and MnCl2 was 9.1 mM.

[0078] 4) During the kinetic reaction, 10 μL of the nonpolar oil phase solution was diluted into 1 mL of ethanol and analyzed by HPLC for the remaining amounts of dibenzothiophene and pyrene, as well as the amount of pyrene oxidation products produced. 10 μL of the lower polar phase solution was added sequentially with MTS and TPP, and the remaining amount of peroxypropionic acid was analyzed by HPLC.

[0079] The degradation of dibenzothiophene in the non-polar phase was achieved by activating peroxypropionic acid with different transition metal ions. Figure 5 The time-dependent changes in the contents of dibenzothiophene, pyrene, pyrene oxidation products, and peroxypropionic acid are shown in the graphs (Figure 2). Under the action of Co(II), Fe(II), and Mn(II), the reduction of dibenzothiophene, pyrene, and peroxypropionic acid during the reaction showed similar trends. However, the effect of Cu(II) differed from that of other transition metals. In experiments using Cu(II) as a catalyst, it was able to remove over 85% of dibenzothiophene within 30 minutes, but this process also consumed a large amount of the oxidant peroxypropionic acid and affected pyrene. Although Cu(II) exhibited strong catalytic oxidation activity for the removal of dibenzothiophene, in order to achieve the desired selectivity in practical applications, it would be more appropriate to consider using Co(II) as a catalyst.

[0080] Example 5

[0081] Since the polar phase involves the activation of the oxidant by metal ions, and the pH in this process has a significant impact on the generation of active substances and the desulfurization process, this study was conducted here. During the experiment, the initial pH of the system was changed, while other experimental conditions remained unchanged. The details are as follows:

[0082] 1) A 5 mL non-polar phase solution containing 15.625 mM dibenzothiophene (organic sulfur content: 500 ppm) and 15.625 mM pyrene was prepared in n-decane. 7.7 mL of acetonitrile and 2.3 mL of water were added to form a miscible polar phase solution. The two phases were mixed at room temperature at 250 rpm for 30 minutes to achieve equilibrium distribution of dibenzothiophene and pyrene in the two phases.

[0083] 2) Prepare and measure the concentration of a peroxypropionic acid stock solution using the MTS-TPP method on HPLC. The peroxypropionic acid stock solution prepared fresh was prepared by reacting 59.52% propionic acid, 35.71% hydrogen peroxide, and 4.76% sulfuric acid at 40°C for 8 minutes and then refrigerated for later use.

[0084] 3) Simultaneously with the addition of the oxidant or oxidant and catalyst to the two-phase mixture, sodium hydroxide was added to the acetonitrile / water mixture to adjust the target pH. Due to the volume change caused by the introduction of the solution, the final volume of the polar phase was fixed to 11 mL (30% water content). The concentration of the peroxypropionic acid as the oxidant was 86.4 mM, while the concentration of the CoCl2 catalyst was 9.1 mM.

[0085] 4) During the kinetic reaction, 10 μL of the non-polar oil phase solution was taken and diluted into 1 mL of ethanol solution, and the remaining amounts of dibenzothiophene and pyrene were analyzed by HPLC.

[0086] like Figure 6 As shown, when the pH is not adjusted, the initial pH of the reaction system is around 0.8. In the direct oxidation of peroxypropionic acid, increasing the pH to 3 can slightly promote desulfurization. When the pH is increased to 5, the effect of the system on desulfurization is the same as when the pH is not adjusted, indicating that the direct oxidation process under acidic conditions has good pH adaptability. However, in the activation oxidation system of peroxypropionic acid by Co(II), the increase in pH leads to similar results as in the Co(II) activated peracetic acid system in Example 3: the reaction ends within 30 minutes and only a small amount of dibenzothiophene is removed, while the increase in pH will also cause a large amount of pyrene to be consumed. Therefore, there is no need to additionally adjust the pH in the activation oxidation desulfurization of peroxypropionic acid-Co(II). For the upper oil phase after desulfurization, since the oil phase mainly composed of alkanes does not ionize hydrogen ions and hydroxide ions like water, the upper non-polar oil phase is less affected by the pH of the lower polar phase.

[0087] Example 6

[0088] In order to study the applicability of the reaction system, it is necessary to focus on the effect of the oxidant dosage on the reaction process. During the experiment, the concentration of the oxidant was changed to study the selective desulfurization, while other experimental conditions remained unchanged. The details are as follows:

[0089] 1) A 5 mL non-polar phase solution containing 15.625 mM dibenzothiophene (organic sulfur content: 500 ppm) and 15.625 mM pyrene was prepared in n-decane. 7.7 mL of acetonitrile and 2.3 mL of water were added to form a miscible polar phase solution. The two phases were mixed at room temperature at 250 rpm for 30 minutes to achieve equilibrium distribution of dibenzothiophene and pyrene in the two phases.

[0090] 2) Prepare and measure the concentration of a peroxypropionic acid stock solution using the MTS-TPP method on HPLC. The peroxypropionic acid stock solution prepared fresh was prepared by reacting 59.52% propionic acid, 35.71% hydrogen peroxide, and 4.76% sulfuric acid at 40°C for 8 minutes and then refrigerated for later use.

[0091] 3) Adding varying concentrations of oxidant or a fixed amount of catalyst and varying concentrations of oxidant to the two-phase mixture to initiate the desulfurization reaction. Due to the volume change caused by the introduction of the solution, the final volume of the polar phase was fixed to 11 mL (30% water content). The concentration of the catalyst, CoCl2, was 9.1 mM.

[0092] 4) During the kinetic reaction, 10 μL of the non-polar oil phase solution was taken and diluted into 1 mL of ethanol solution, and the remaining amounts of dibenzothiophene and pyrene were analyzed by HPLC.

[0093] Figure 7 It shows the effect of different oxidant concentrations on the selective oxidation of organic sulfur. When the concentration of peroxypropionic acid is between 14.4mM and 172.8mM, direct oxidation can degrade dibenzothiophene, and the addition of Co(II) can further improve the removal of dibenzothiophene, but it will also cause more pyrene to be affected. When the reaction is carried out with a lower concentration of oxidant (43.2mM), about 90% of the organic sulfur can be removed after 180 minutes of reaction in the catalytic oxidation system. When the concentration of peroxypropionic acid is increased to 172.8mM, the organic sulfur can be completely removed within 30 minutes, and only dibenzothiophene is slightly affected. Therefore, during the implementation process, the dosage of the oxidant can be selected according to the desulfurization efficiency requirements and cost considerations.

[0094] Example 7

[0095] Transition metals act as catalysts in the desulfurization process, and their dosage significantly impacts both the reaction process and the cost. The experimental process varied the concentration of the transition metal Co(II) to investigate selective desulfurization, while other experimental conditions remained unchanged. The details are as follows:

[0096] 1) A 5 mL non-polar phase solution containing 15.625 mM dibenzothiophene (organic sulfur content: 500 ppm) and 15.625 mM pyrene was prepared in n-decane. 7.7 mL of acetonitrile and 2.3 mL of water were added to form a miscible polar phase solution. The two phases were mixed at room temperature at 250 rpm for 30 minutes to achieve equilibrium distribution of dibenzothiophene and pyrene in the two phases.

[0097] 2) Prepare and measure the concentration of a peroxypropionic acid stock solution using the MTS-TPP method on HPLC. The peroxypropionic acid stock solution prepared fresh was prepared by reacting 59.52% propionic acid, 35.71% hydrogen peroxide, and 4.76% sulfuric acid at 40°C for 8 minutes and then refrigerated for later use.

[0098] 3) An oxidant and various concentrations of CoCl2 as a catalyst were added to the two-phase mixture to initiate the desulfurization reaction. Due to the volume change caused by the introduction of the solution, the final volume of the polar phase was fixed to 11 mL (30% water content). The concentration of peroxypropionic acid as the oxidant was 86.4 mM.

[0099] 4) During the kinetic reaction, 10 μL of the non-polar oil phase solution was taken and diluted into 1 mL of ethanol solution. The remaining amounts of dibenzothiophene and pyrene and the amount of pyrene oxidation products produced were analyzed by HPLC.

[0100] Figure 8 Figure 2 shows the effect of different Co(II) concentrations on the catalytic oxidative desulfurization process. The system's organic sulfur removal efficiency increases as the Co(II) concentration ranges from 0 mM to 9.1 mM. However, a Co(II) concentration of 13.6 mM does not exhibit improved desulfurization efficiency, and after 180 minutes of catalytic activity at 13.6 mM Co(II), more pyrene is affected. Therefore, 9.1 mM Co(II) ensures both efficient organic sulfur removal and selectivity. However, for reaction systems prioritizing selectivity, desulfurization can be achieved by adding little or no Co(II) to ensure that pyrene is unaffected.

[0101] Example 8

[0102] Although the active substances formed during the catalytic oxidation process are highly active, they are mainly present in the polar phase. Therefore, the transfer of organic sulfur from the non-polar phase to the polar phase is also very important for the desulfurization reaction. Acetonitrile is an important solvent that promotes the transfer of organic sulfur between the aqueous phase and the oil phase. Its content in the polar phase has a significant impact on the phase transfer of organic sulfur and petroleum products and the entire reaction process. The selective desulfurization process was studied by varying the ratio of acetonitrile to water in the polar phase, while other experimental conditions remained unchanged. The details are as follows:

[0103] 1) A 5 mL non-polar phase solution containing 15.625 mM dibenzothiophene (organic sulfur content: 500 ppm) and 15.625 mM pyrene was prepared in n-decane. Acetonitrile and water in varying proportions were added to the solution to form a miscible polar phase solution. The two-phase mixture was stirred at room temperature for 30 minutes to allow dibenzothiophene and pyrene to reach equilibrium in the two phases.

[0104] 2) Prepare and measure the concentration of a peroxypropionic acid stock solution using the MTS-TPP method on HPLC. The peroxypropionic acid stock solution prepared fresh was prepared by reacting 59.52% propionic acid, 35.71% hydrogen peroxide, and 4.76% sulfuric acid at 40°C for 8 minutes and then refrigerated for later use.

[0105] 3) Add an oxidant, or an oxidant and catalyst, to the two-phase mixture to initiate the desulfurization reaction. Because the introduction of the solution causes a volume change, the final volume of the polar phase is fixed to 11 mL. The concentration of the peroxypropionic acid oxidant is 86.4 mM, while the concentration of the CoCl2 catalyst is 9.1 mM.

[0106] 4) During the kinetic reaction, 10 μL of the non-polar oil phase solution was taken and diluted into 1 mL of ethanol solution. The remaining amounts of dibenzothiophene and pyrene and the amount of pyrene oxidation products produced were analyzed by HPLC.

[0107] Figure 9 Results indicate that varying the acetonitrile-to-water ratio in the polar phase primarily affects the dibenzothiophene and pyrene that enter the polar phase. Lowering the water ratio in the polar phase facilitates the transfer of dibenzothiophene and pyrene from the non-polar phase into the polar phase. Higher water ratios, on the other hand, reduce desulfurization costs. Results indicate that a 30%-40% water ratio in the polar phase facilitates dibenzothiophene removal while maintaining selectivity.

[0108] Example 9

[0109] In a cyclic study of selective desulfurization, a peroxypropionic acid-Co(II) catalytic oxidation system was analyzed. Given that this system can achieve oxidation of most dibenzothiophene within 90 minutes while maintaining pyrene quality, the reaction time for each cycle was set to 90 minutes. After each cycle, the upper non-polar phase solution was removed and a new n-decane solution containing dibenzothiophene and pyrene was added, while other experimental conditions remained unchanged. The details are as follows:

[0110] 1) A 5 mL non-polar phase solution containing 15.625 mM dibenzothiophene (organic sulfur content: 500 ppm) and 15.625 mM pyrene was prepared in n-decane. 7.7 mL of acetonitrile and 2.3 mL of water were added to form a miscible polar phase solution. The two phases were mixed at room temperature at 250 rpm for 30 minutes to achieve equilibrium distribution of dibenzothiophene and pyrene in the two phases.

[0111] 2) Prepare and measure the concentration of a peroxypropionic acid stock solution using the MTS-TPP method on HPLC. The peroxypropionic acid stock solution prepared fresh was prepared by reacting 59.52% propionic acid, 35.71% hydrogen peroxide, and 4.76% sulfuric acid at 40°C for 8 minutes and then refrigerated for later use.

[0112] 3) Adding an oxidant or an oxidant and catalyst to the two-phase mixture to initiate the desulfurization reaction. Due to the volume change caused by the introduction of the solution, the final volume of the polar phase was fixed to 11 mL (30% water content). The concentrations of peracetic acid and peroxypropionic acid as oxidants were 86.4 mM, while the concentration of the catalyst, CoCl2, was 9.1 mM.

[0113] 4) Each cycle was 90 min. After each cycle, the upper oil phase was removed and 5 mL of a n-decane solution containing 15.625 mM dibenzothiophene and 15.625 mM pyrene was added to start a new reaction cycle.

[0114] 5) During the reaction, 10 μL of the upper non-polar oil phase solution was diluted into 1 mL of ethanol and analyzed by HPLC for the remaining amount of dibenzothiophene, the remaining amount of pyrene, and the amount of pyrene oxidation products produced. 10 μL of the lower polar phase solution was diluted into 1 mL of ethanol and analyzed by HPLC for the amount of dibenzothiophene oxidation products. 10 μL of the lower polar phase solution was added to the MTS and TPP solutions, respectively, and the remaining amount of peroxypropionic acid was analyzed by HPLC.

[0115] The reaction results are as follows Figure 10 As shown, with increasing reaction cycles, the dibenzothiophene removal efficiency within 90 minutes shows a decreasing trend. However, the amount of dibenzothiophene oxidation products entering the lower polar phase accumulates during this period, potentially affecting the distribution of dibenzothiophene between the two phases and the removal efficiency in the next reaction cycle. The oxidant, peroxypropionic acid, still remains at 30% after six reaction cycles. However, regardless of the number of reaction cycles, the content of pyrene, a petroleum product, remains high, demonstrating the high selectivity of the reaction system. To ensure dibenzothiophene removal efficiency throughout the entire process, adsorption can be used to promptly separate the dibenzothiophene oxidation products from the polar phase to ensure dibenzothiophene distribution between the two phases in the next reaction cycle. Peroxypropionic acid can also be replenished to the reaction system.

[0116] Examples 10-34

[0117] Follow the test steps below:

[0118] 1) A 5 mL non-polar phase solution containing 15.625 mM dibenzothiophene (organic sulfur content 500 ppm) was prepared in n-decane. Acetonitrile and water were added to the solution to form a miscible polar phase solution. The two phases were mixed at room temperature at 250 rpm for 30 minutes to achieve equilibrium distribution of dibenzothiophene in the two phases.

[0119] 2) Prepare and measure the concentrations of peracetic acid and peroxypropionic acid stock solutions using the MTS-TPP method on HPLC. The peroxypropionic acid stock solution prepared fresh was prepared by reacting 59.52% propionic acid, 35.71% hydrogen peroxide, and 4.76% sulfuric acid at 40°C for 8 minutes and then refrigerated for later use.

[0120] 3) Adding an oxidant or an oxidant and a catalyst to the two-phase mixture to start the desulfurization reaction.

[0121] 4) During the kinetic reaction, 10 μL of the upper non-polar oil phase solution was diluted into 1 mL of ethanol and analyzed by HPLC for the remaining amount of dibenzothiophene. 10 μL of the lower polar phase solution was diluted into 1 mL of ethanol and analyzed by HPLC for the amount of dibenzothiophene oxidation products. 10 μL of the lower polar phase solution was added to the MTS and TPP solutions, respectively, and the remaining amount of peroxypropionic acid was analyzed by HPLC.

[0122]

[0123] The above table shows the main process parameters of Examples 10-34.

[0124] In general, efficient and selective removal of organic sulfur can be achieved by adopting a suitable catalytic oxidation process. The peroxypropionic acid catalytic oxidation system can remove more than 90% of organic sulfur within 90 minutes.

Claims

1. A method for selective oxidative desulfurization in petroleum and its products, characterized in that: The method is carried out at room temperature and pressure. In a polar phase composed of water and acetonitrile, organic sulfides in a non-polar phase oil solution are selectively removed by direct oxidation of peroxy organic acid and activation of the peroxy organic acid by a catalyst to produce active substances. First, acetonitrile and water are added to the non-polar phase of petroleum and its products to form an upper and lower layer of solution, of which the lower layer is a polar phase in which acetonitrile and water are miscible, and the mixed solution is thoroughly mixed by shaking or stirring; Then, preparing the oxidizing agent peroxy organic acid; Adding an oxidant and a catalyst to the above solution to start the desulfurization reaction; The catalyst is a low-valent transition metal ion, Co(II) is selected, and the metal salt used is chloride; The peroxy organic acid is peroxypropionic acid; The water content in the polar phase is 30-40%; The catalyst concentration was 4.5-9.1 mM; Oxidant concentration was 14.4–172.8 mM; The peroxy organic acid is prepared by reacting propionic acid, hydrogen peroxide, and sulfuric acid to form peroxypropionic acid.

2. The method according to claim 1, characterized in that The oxidant concentration is 43.2-172.8 mM.

3. The method according to claim 1, characterized in that The oxidant concentration is 43.2-86.4 mM.

4. The method according to claim 1, wherein The oxidant concentration is 86.4-172.8 mM.

5. The method according to claim 1, wherein The water content in the polar phase was 30%, the concentrations of the catalyst Co(II) and the oxidant peroxypropionic acid were 9.1 mM and 86.4 mM, respectively, and the reaction time was controlled at 90 min.

6. The method according to claim 1, characterized in that The method is suitable for removing organic sulfides from crude oil, fuel oil or other sulfur-containing petroleum products.

7. The method according to claim 1, characterized in that The method is applicable to diesel fuel.

8. The method according to claim 1, characterized in that After the desulfurization process is completed, the non-polar phase and the polar phase are recovered by phase separation so that the oil phase, its products and the lower catalytic oxidation system can be reused.

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