Method for selective oxidation desulfurization in petroleum and products thereof

Abstract

The invention belongs to the field of energy and chemical industry, and particularly discloses a method for selective oxidation desulfurization in petroleum and products thereof. According to the method, in a polar phase composed of water and acetonitrile, organic sulfide in a non-polar phase oil solution is selectively removed through active substances generated by direct oxidation of peroxy organic acid and activation of the peroxy organic acid by a catalyst. In the polar phase, the perpropionic acid is used as an oxidizing agent, and low-valence transition metal is used as a catalyst to activate the perpropionic acid to generate an active substance so as to realize oxidative removal of the organic sulfur in the non-polar phase. The process is suitable for direct removal of organic sulfur in petroleum and selective removal of organic sulfur in petroleum products, and can be widely applied to selective desulfurization of various liquid phase systems, such as desulfurization of waste tire pyrolysis liquid. The process is suitable for reaction at normal temperature and normal pressure, and the process flow is simple and can be flexibly adjusted according to actual requirements.

Description

Technical Field

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

[0002] Crude oil usually contains 0.1-6% sulfide, among which organic sulfides such as dibenzothiophene and its homologues are easy to coexist with crude oil due to their low polarity. Organic sulfur in liquid fuel forms toxic sulfur oxides and acidic gas sulfur dioxide during combustion, which not only corrodes automobile engines but also causes serious pollution to the atmospheric environment. Therefore, environmental regulations in many countries and regions require that the total sulfur content in fuel be less than 10ppm.

[0003] Petrochemical products such as anthracene and pyrene extracted from coal tar in crude oil by fractionation are usually used as chemical raw materials. However, the presence of organic sulfides in the production process will lead to catalyst poisoning or affect the quality of the final product. For example, dibenzothiophene, an organic sulfide, is difficult to separate because its boiling point is close to that of anthracene oil. In the process of using anthracene oil to produce superconducting carbon black, sulfides may form defects or uneven distribution on the carbon matrix, thereby reducing the conductivity of carbon black. Therefore, in this process, the organic sulfur content in anthracene oil is usually required to be less than 500ppm to ensure the quality of the final product.

[0004] Although there is a great demand for the removal of organic sulfur in petroleum and its products in the energy and chemical industry, there is currently a lack of technology that can achieve efficient desulfurization at a low investment cost. The commonly used hydrodesulfurization technology is to convert sulfides into H by hydrogenation under the condition of using a catalyst. 2 S gas is removed. However, this process often requires a high temperature and high pressure environment and has high requirements on the strength of the equipment. Since the π bond in olefins is relatively active, it will react with hydrogen first during the hydrogenation process, thereby competing with the desulfurization reaction. Dibenzothiophene and its derivatives, as the main organic sulfides in petroleum and its products, have poor effects in hydrodesulfurization due to the presence of carbon-carbon double bonds (C=C) in their molecular structure. In contrast, oxidative desulfurization technology uses a suitable oxidant to continuously oxidize organic sulfur to produce products with higher polarity, such as sulfoxides or sulfones, which can then be easily removed from the fuel by separation methods such as adsorption. However, this technology has high requirements on the oxidizing ability of the oxidant. On the one hand, since the sulfur atoms in dibenzothiophene are not active, oxidants with weak oxidizing ability cannot achieve the oxidation and desulfurization of 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 a major problem at present, but it has broad application prospects.

[0005] Based on the existing organic sulfur removal methods, the oxidative desulfurization technology can effectively act on most mercaptans and sulfide compounds, and oxidize organic sulfur into products with increased polarity, which is convenient for separation. For the reaction system of this process, since the polarity of petroleum and its products and organic sulfur are very low, they exist in the form of a mixture in a non-polar oil phase with petroleum as the solvent. However, the key oxidant is usually present in the polar water phase, and the reaction between the oxidant and organic sulfur is limited due to the large polarity difference between the two phases. To improve this problem, acetonitrile, which has a polarity between water and oil, is usually introduced to improve the exchange efficiency of organic sulfur between the polar phase and the non-polar phase, and to make the oxidation products of organic sulfur easier to separate from other components. Specifically, in a non-polar phase system with n-decane as the upper layer and a polar phase system composed of water and acetonitrile as the lower layer, part of the organic sulfur can migrate from the non-polar phase to the polar phase containing acetonitrile to react with the oxidant to form an organic sulfur oxidation product 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, uses a catalyst to activate the peroxy organic acid in an acetonitrile / water mixed solution to produce active substances, thereby achieving 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, so as to reduce 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 which the organic sulfide in the non-polar phase oil solution is selectively removed by direct oxidation of peroxy organic acid and active substances generated by activation of the peroxy organic acid by a catalyst in a polar phase composed of water and acetonitrile;

[0009] First, acetonitrile and water are added to the non-polar phase of petroleum and its products to form an upper and lower solution, wherein the lower layer is a polar phase in which acetonitrile and water are miscible, and the mixed solution is fully 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 a low-valent transition metal ion, any one of Co(II), Fe(II), Cu(II) and Mn(II), and the metal salts used are all chlorides;

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

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

[0014] The 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 without a 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 in crude oil, diesel, fuel oil or other sulfur-containing petroleum products. Furthermore, when efficient desulfurization is the top priority, the catalytic oxidation desulfurization process uses Cu(II) as a catalyst and 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 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 the electron-withdrawing group, which leads to a decrease in the charge density of the sulfur atom, so that the reaction rate is slow in conventional direct oxidation. Therefore, the development of new oxidants and oxidation systems will help to 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 play its oxidizing effect, but also activate and produce a large number of active substances with moderate oxidizing ability by adding a catalyst to promote the desulfurization reaction. In addition, in order to minimize the impact on petroleum products in the desulfurization reaction and enhance the value of petroleum products, the process of selective desulfurization needs to be considered. There is a significant reaction difference between organic sulfides represented by dibenzothiophene and petroleum products represented by pyrene in polycyclic aromatic hydrocarbons. The sulfur atom in dibenzothiophene can become an active site in the catalytic oxidation process, so dibenzothiophene can react with active substances more 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. The 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 reaction rate of desulfurization, and finally transfer dibenzothiophene in the oil phase to the water phase in the form of its oxide. In addition, when dibenzothiophene coexists with polycyclic aromatic hydrocarbons of petroleum products in the oil phase, the direct oxidation of peroxypropionic acid in the water phase and the catalytic oxidation process 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 requirements for reactivity and selectivity can be achieved by adjusting the amount of Co(II). For example, selectivity can be prioritized 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 reused after adsorption recovery.

[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 This is 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 figure shows the effects of different concentrations of the oxidant peroxypropionic acid on dibenzothiophene and pyrene in different systems.

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

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

[0044] Fig.10 The effect 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. Peroxypropionic acid and Co(II) are added to the polar phase of water / acetonitrile to selectively oxidize the organic sulfur in the oil phase. The oxidation product of the organic sulfur is separated from the oil phase due to the increase in polarity, thereby achieving desulfurization of the oil phase, thereby eliminating the impact of the presence of organic sulfur in 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 shown. The following example simulates petroleum and its products containing organic sulfur. 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) are selected as the oxidant and catalyst, respectively, to study the desulfurization effect.

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

[0047] The test scheme proposed by the present invention to solve the technical problems proposed 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 shaking 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) Adding peroxypropionic acid and Co(II) to the two-phase mixed solution to start 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 of 15.625 mM dibenzothiophene (organic sulfur content 500 ppm) was prepared using n-decane as solvent, and 7.7 mL acetonitrile and 2.3 mL water were added thereto to form a miscible polar phase solution. The two-phase mixture was mixed at room temperature at a speed of 250 rpm for 30 min to achieve distribution equilibrium of dibenzothiophene in the two phases.

[0055] 2) Prepare and detect the concentration of peracetic acid and peroxypropionic acid stock solutions on HPLC using the MTS-TPP method. The peroxypropionic acid stock solution prepared on the spot is formed by reacting 59.52% propionic acid, 35.71% hydrogen peroxide and 4.76% sulfuric acid at 40° C. for 8 minutes, and then put into a refrigerator for standby use.

[0056] 3) Add an oxidant or an oxidant and a catalyst to the two-phase mixture to start the desulfurization reaction. Since the introduction of the solution causes a volume change, the final volume of the polar phase is set to 11 mL (water content 30%). The concentration of peracetic acid and peroxypropionic acid as oxidants is 86.4 mM, and the catalyst CoCl 2 The concentration is 9.1 mM.

[0057] 4) During the kinetic reaction, 10 μL of the upper non-polar oil phase solution was taken and diluted into 1 mL of ethanol solution, and the remaining amount of dibenzothiophene was analyzed by HPLC. 10 μL of the lower polar solution was taken and diluted into 1 mL of ethanol solution, and the amount of dibenzothiophene oxidation product was analyzed by HPLC. 10 μL of the lower polar solution was taken and added to 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 From the results, dibenzothiophene can be degraded in the direct oxidation of peracetic acid and peroxypropionic acid, but after 180 minutes of treatment, it is still impossible to achieve the complete removal of organic sulfide. 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, and is also accompanied by the continuous generation of oxidation products of organic sulfide in the polar phase. This embodiment illustrates that organic sulfur can be effectively removed in the peroxypropionic acid-Co (II) system, and the accumulation of oxidation products of organic sulfur in the polar phase can also be achieved.

[0059] Example 2

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

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

[0062] 2) Prepare and detect the concentration of peracetic acid and peroxypropionic acid stock solutions on HPLC using the MTS-TPP method. The peroxypropionic acid stock solution prepared on the spot is formed by reacting 59.52% propionic acid, 35.71% hydrogen peroxide and 4.76% sulfuric acid at 40° C. for 8 minutes, and then put into a refrigerator for standby use.

[0063] 3) Add an oxidant or an oxidant and a catalyst to the two-phase mixture to start the desulfurization reaction. Since the introduction of the solution causes a volume change, the final volume of the polar phase is set to 11 mL (water content 30%). The concentration of peracetic acid and peroxypropionic acid as oxidants is 86.4 mM, and the catalyst CoCl 2 The concentration is 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 amount of dibenzothiophene and dibenzofuran was analyzed by HPLC.

[0065] The content of dibenzothiophene and dibenzofuran in different systems changes with time. Figure 3 As shown. The experimental results of this part 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 with dibenzothiophene. Therefore, this process can not only achieve the removal of organic sulfur in oil, but also achieve the accumulation of dibenzothiophene oxidation products in the polar phase.

[0066] Example 3

[0067] Since the presence of organic sulfur in some petroleum products will also directly affect the quality of the final chemical products, the desulfurization of petroleum products is also an important demand. Since petroleum products usually contain polycyclic aromatic hydrocarbons, pyrene is used as a representative petroleum product in this laboratory-based detection technology. In order to study the desulfurization of petroleum and its products, pyrene and dibenzothiophene were added to n-decane together, while other experimental conditions remained unchanged. The details are as follows:

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

[0069] 2) Prepare and detect the concentration of peracetic acid and peroxypropionic acid stock solutions on HPLC using the MTS-TPP method. The peroxypropionic acid stock solution prepared on the spot is formed by reacting 59.52% propionic acid, 35.71% hydrogen peroxide and 4.76% sulfuric acid at 40° C. for 8 minutes, and then put into a refrigerator for standby use.

[0070] 3) Add an oxidant or an oxidant and a catalyst to the two-phase mixture to start the desulfurization reaction. Since the introduction of the solution causes a volume change, the final volume of the polar phase is set to 11 mL (water content 30%). The concentration of peracetic acid and peroxypropionic acid as oxidants is 86.4 mM, and the catalyst CoCl 2 The concentration is 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, and the remaining amount of dibenzothiophene and pyrene and the amount of pyrene oxidation product generated 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 compound. 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 effect on pyrene. Under the catalytic action of Co(II), the reaction stopped 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 was also affected, accompanied by the generation of pyrene oxidation products. Therefore, the system can be adjusted to meet different needs. For the desulfurization of petroleum products with high selectivity requirements, peroxypropionic acid oxidation can be used directly to fully guarantee the selectivity. When the focus is on high-efficiency desulfurization, the use of peroxypropionic acid-Co (II) oxidation can maximize the high-efficiency desulfurization and guarantee most of the selectivity.

[0073] Example 4

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

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

[0076] 2) Prepare and detect the concentration of peroxypropionic acid stock solution on HPLC using MTS-TPP method. The peroxypropionic acid stock solution prepared on the spot is formed by reacting 59.52% propionic acid, 35.71% hydrogen peroxide and 4.76% sulfuric acid at 40° C. for 8 minutes, and then put into refrigerator for standby use.

[0077] 3) Add an oxidant or an oxidant and a catalyst to the two-phase mixture to start the desulfurization reaction. Since the introduction of the solution causes a volume change, the final volume of the polar phase is set to 11 mL (water content 30%). The concentration of peroxypropionic acid as an oxidant is 86.4 mM, and the catalyst CoCl 2 , FeCl 2 , CuCl 2 and MnCl 2 The concentration is 9.1 mM.

[0078] 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 amount of dibenzothiophene and pyrene and the amount of pyrene oxidation product generated were analyzed by HPLC. 10 μL of the lower polar solution was taken and MTS and TPP were added in sequence, and the remaining amount of peroxypropionic acid was analyzed by HPLC.

[0079] The degradation of dibenzothiophene in the nonpolar phase was achieved by activating peroxypropionic acid with different transition metal ions. Figure 5 In the table, the contents of dibenzothiophene, pyrene, pyrene oxidation products and peroxypropionic acid change with time. Under the action of Co(II), Fe(II) and Mn(II), the reduction of dibenzothiophene, pyrene and peroxypropionic acid during the reaction process showed similar trends. However, the effect of Cu(II) is different from that of other transition metals. In the experiment with Cu(II) as a catalyst, it can remove more than 85% of dibenzothiophene within 30 minutes, but the process also consumes a large amount of oxidant peroxypropionic acid and affects pyrene. Although Cu(II) shows strong catalytic oxidation activity for the removal of dibenzothiophene, in order to have both 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 the process has a great influence on the generation of active substances and the desulfurization process, this study is 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 of 15.625 mM dibenzothiophene (organic sulfur content 500 ppm) and 15.625 mM pyrene was prepared with n-decane as solvent, and 7.7 mL acetonitrile and 2.3 mL water were added thereto to form a miscible polar phase solution. The two-phase mixture was mixed at room temperature at a speed of 250 rpm for 30 min to achieve distribution equilibrium of dibenzothiophene and pyrene in the two phases.

[0083] 2) Prepare and detect the concentration of peroxypropionic acid stock solution on HPLC using MTS-TPP method. The peroxypropionic acid stock solution prepared on the spot is formed by reacting 59.52% propionic acid, 35.71% hydrogen peroxide and 4.76% sulfuric acid at 40° C. for 8 minutes, and then put into refrigerator for standby use.

[0084] 3) While adding the oxidant or the oxidant and the catalyst to the two-phase mixture, sodium hydroxide is added to the acetonitrile / water mixture to adjust the pH to the target. Since the introduction of the solution causes a volume change, the final volume of the polar phase is set to 11 mL (water content 30%). The concentration of peroxypropionic acid as the oxidant is 86.4 mM, while the catalyst CoCl 2 The concentration is 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 amount of dibenzothiophene and pyrene was analyzed by HPLC.

[0086] like Figure 6 As shown, when the pH is not adjusted, the initial pH of the reaction system is about 0.8. In the direct oxidation of peroxypropionic acid, the increase of pH to 3 can slightly promote desulfurization, and the influence of the system on desulfurization when the pH is increased to 5 is consistent with that 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 Co (II) to peroxypropionic acid, the increase of pH leads to the appearance of 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 of pH will also cause a large amount of pyrene to be consumed. Therefore, there is no need to adjust the pH additionally 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 application scope of the reaction system, it is necessary to pay attention to the effect of the dosage of the oxidant on the reaction process. The concentration of the oxidant was changed during the experiment 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 of 15.625 mM dibenzothiophene (organic sulfur content 500 ppm) and 15.625 mM pyrene was prepared with n-decane as solvent, and 7.7 mL acetonitrile and 2.3 mL water were added thereto to form a miscible polar phase solution. The two-phase mixture was mixed at room temperature at a speed of 250 rpm for 30 min to achieve distribution equilibrium of dibenzothiophene and pyrene in the two phases.

[0090] 2) Prepare and detect the concentration of peroxypropionic acid stock solution on HPLC using MTS-TPP method. The peroxypropionic acid stock solution prepared on the spot is formed by reacting 59.52% propionic acid, 35.71% hydrogen peroxide and 4.76% sulfuric acid at 40° C. for 8 minutes, and then put into refrigerator for standby use.

[0091] 3) Add different concentrations of oxidant or a certain amount of catalyst and different concentrations of oxidant to the two-phase mixture to start the desulfurization reaction. Since the introduction of the solution causes a volume change, the final volume of the polar phase is set to 11 mL (water content 30%). Catalyst CoCl 2 The concentration is 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 amount of dibenzothiophene and pyrene was 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] As a catalyst in the desulfurization reaction, the dosage of transition metal has a great influence on both the reaction process and the cost. The concentration of transition metal Co(II) was changed in the experiment to study the selective desulfurization, while other experimental conditions remained unchanged. The details are as follows:

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

[0097] 2) Prepare and detect the concentration of peroxypropionic acid stock solution on HPLC using MTS-TPP method. The peroxypropionic acid stock solution prepared on the spot is formed by reacting 59.52% propionic acid, 35.71% hydrogen peroxide and 4.76% sulfuric acid at 40° C. for 8 minutes, and then put into refrigerator for standby use.

[0098] 3) Add oxidant and different concentrations of CoCl to the two-phase mixture2 As a catalyst to start the desulfurization reaction. Since the introduction of the solution causes a volume change, the final volume of the polar phase is fixed to 11 mL (water content 30%). The concentration of peroxypropionic acid as an oxidant is 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, and the remaining amount of dibenzothiophene and pyrene and the amount of pyrene oxidation product generated were analyzed by HPLC.

[0100] Figure 8 The figure shows the effect of different concentrations of Co(II) on the catalytic oxidation desulfurization process. The removal efficiency of the system for organic sulfur increases as the Co(II) concentration ranges from 0mM to 9.1mM, but when the Co(II) concentration is 13.6mM, it does not show better desulfurization efficiency, and more pyrene will be affected after 180 minutes of catalysis of 13.6mM Co(II). Therefore, 9.1mM Co(II) can ensure efficient removal of organic sulfur and has selectivity. However, for reaction systems that prioritize selectivity, desulfurization can be achieved by adding less or no Co(II) to ensure that pyrene is not affected.

[0101] Example 8

[0102] Although the active substances formed during the catalytic oxidation process are highly active, they mainly exist in the polar phase, so the transfer process 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 in the water phase and the oil phase. Its content in the polar phase will have a significant effect on the phase transfer of organic sulfur and petroleum products and the entire reaction process. The selective desulfurization process was studied by changing the ratio of acetonitrile and 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 of 15.625 mM dibenzothiophene (organic sulfur content 500 ppm) and 15.625 mM pyrene was prepared using n-decane as solvent, and acetonitrile and water in different proportions were added thereto to form a miscible polar phase solution. The two-phase mixture was stirred at room temperature for 30 min to achieve distribution equilibrium of dibenzothiophene and pyrene in the two phases.

[0104] 2) Prepare and detect the concentration of peroxypropionic acid stock solution on HPLC using MTS-TPP method. The peroxypropionic acid stock solution prepared on the spot is formed by reacting 59.52% propionic acid, 35.71% hydrogen peroxide and 4.76% sulfuric acid at 40° C. for 8 minutes, and then put into refrigerator for standby use.

[0105] 3) Add an oxidant or an oxidant and a catalyst to the two-phase mixture to start the desulfurization reaction. Since the introduction of the solution causes a volume change, the final volume of the polar phase is set to 11 mL. The concentration of peroxypropionic acid as an oxidant is 86.4 mM, while the catalyst CoCl 2 The concentration 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, and the remaining amount of dibenzothiophene and pyrene and the amount of pyrene oxidation product generated were analyzed by HPLC.

[0107] Fig. 9 The results show that changing the ratio of acetonitrile and water in the polar phase will first affect dibenzothiophene and pyrene entering the polar phase. The lower the proportion of water in the polar phase, the more it will be beneficial for dibenzothiophene and pyrene to enter the polar phase from the non-polar phase. The higher the proportion of water, the more it will help reduce the desulfurization cost. The results show that 30%-40% water in the polar phase will be beneficial to the removal of dibenzothiophene while ensuring selectivity as much as possible.

[0108] Example 9

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

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

[0111] 2) Prepare and detect the concentration of peroxypropionic acid stock solution on HPLC using MTS-TPP method. The peroxypropionic acid stock solution prepared on the spot is formed by reacting 59.52% propionic acid, 35.71% hydrogen peroxide and 4.76% sulfuric acid at 40° C. for 8 minutes, and then put into refrigerator for standby use.

[0112] 3) Add an oxidant or an oxidant and a catalyst to the two-phase mixture to start the desulfurization reaction. Since the introduction of the solution causes a volume change, the final volume of the polar phase is set to 11 mL (water content 30%). The concentration of peracetic acid and peroxypropionic acid as oxidants is 86.4 mM, and the catalyst CoCl 2 The concentration is 9.1 mM.

[0113] 4) With a cycle of 90 min, the upper oil phase was removed after each cycle, 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 taken and diluted into 1 mL of ethanol solution, and the remaining amount of dibenzothiophene, the remaining amount of pyrene, and the amount of pyrene oxidation products were analyzed by HPLC. 10 μL of the lower polar solution was taken and diluted into 1 mL of ethanol solution, and the amount of dibenzothiophene oxidation products was analyzed by HPLC. 10 μL of the lower polar solution was taken and added to MTS and TPP solutions respectively, and the remaining amount of peroxypropionic acid was analyzed by HPLC.

[0115] The reaction results are as follows Fig.10 As shown in the figure, with the increase of the number of reaction cycles, the removal effect of dibenzothiophene within 90 minutes shows a downward trend, but the amount of dibenzothiophene oxidation products entering the lower polar phase during the period is cumulatively increasing, which may affect the distribution of dibenzothiophene in the two phases and the removal efficiency in the new reaction cycle. The oxidant peroxypropionic acid still has 30% remaining after 6 cycles of reaction. However, regardless of the increase in the number of reaction cycles, pyrene, as a petroleum product, always maintains a high content, indicating that the reaction system has a high selectivity. In order to ensure the removal efficiency of dibenzothiophene throughout the process, the dibenzothiophene oxidation products in the polar phase can be separated in time by adsorption to ensure the distribution of dibenzothiophene in the two phases in the new cycle, and peroxypropionic acid can also be added to the reaction system in time.

[0116] Embodiment 10-34

[0117] Follow the test steps below:

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

[0119] 2) Prepare and detect the concentration of peracetic acid and peroxypropionic acid stock solutions on HPLC using the MTS-TPP method. The peroxypropionic acid stock solution prepared on the spot is formed by reacting 59.52% propionic acid, 35.71% hydrogen peroxide and 4.76% sulfuric acid at 40° C. for 8 minutes, and then put into a refrigerator for standby 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 taken and diluted into 1 mL of ethanol solution, and the remaining amount of dibenzothiophene was analyzed by HPLC. 10 μL of the lower polar solution was taken and diluted into 1 mL of ethanol solution, and the amount of dibenzothiophene oxidation product was analyzed by HPLC. 10 μL of the lower polar solution was taken and added to 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, the 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 selectively removes organic sulfides in a non-polar phase oil solution by direct oxidation of peroxy organic acid and activation of the peroxy organic acid by a catalyst in a polar phase composed of water and acetonitrile to produce active substances. Dibenzothiophene was used as a representative organic sulfide that is difficult to remove, and pyrene among polycyclic aromatic hydrocarbons was used as a representative petroleum product; First, acetonitrile and water are added to the non-polar phase of petroleum and its products to form an upper and lower solution, wherein the lower layer is a polar phase in which acetonitrile and water are miscible, and the mixed solution is fully mixed by shaking or stirring; Then, preparing an oxidizing agent, peroxy organic acid; Adding an oxidant and a catalyst to the above solution to start a desulfurization reaction; The catalyst is a low-valent transition metal ion, any one of Co(II), Fe(II), Cu(II) and Mn(II), and the metal salts used are all chlorides; The peroxy organic acid is peracetic acid or peroxy propionic acid; The water content of the polar phase is 30-40%; The catalyst concentration was 0-9.1 mM; The oxidant concentration was 14.4-172.8 mM.

2. The method according to claim 1, characterized in that The peroxy organic acid is peroxy propionic acid, which is formed by reacting propionic acid, hydrogen peroxide and sulfuric acid.

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

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

5. The method according to claim 1, characterized in that The oxidant concentration is 86.4-172.8 mM.

6. The method according to claim 1, characterized in that 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.

7. The method according to claim 1, characterized in that 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 co-existing petroleum products are not affected.

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

9. The method according to claim 1, characterized in that: When efficient desulfurization is the top priority, the catalytic oxidation desulfurization process uses Cu(II) as a catalyst and achieves an organic sulfur removal rate of nearly 90% within 30 minutes.

10. 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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