Method for aldehyde synergistic nickel porphyrin catalytic oxidation desulfurization and application

Abstract

The application discloses a kind of aldehyde class synergistic nickel porphyrin catalytic oxidation desulfurization method and application, belong to the technical field of petrochemical industry.The method includes the following steps: (1) with octaethyl nickel porphyrin as main catalyst, aldehyde compound is as cocatalyst, and mixed with oil containing sulfur compound;(2) under normal temperature and pressure, oxygen or air is introduced, and stirring reaction is carried out for 6~12 hours, and after reaction, oxidation product is separated by extraction or adsorption.The application realizes coordination regulation and oxygen receiving double mechanism synergistic catalysis by the synergistic effect of electron-donating diethylamino in 4- (diethylamino) salicylaldehyde, ortho hydroxyl and aldehyde group, and 4, 6-dimethyl dibenzothiophene, pentyl sulfide and dibenzothiophene and other sulfur-containing compounds can be efficiently oxidized under normal temperature and pressure.The application has mild reaction condition, low energy consumption, and less catalyst consumption, and excellent oxidation removal effect is shown to difficult-to-remove thiophene sulfide, and has good industrial application prospect.

Description

Technical Field

[0001] This invention belongs to the field of petrochemicals, specifically relating to a method and application of aldehyde-synergistic nickel porphyrin-catalyzed oxidative desulfurization. Background Technology

[0002] With the continued growth of global energy demand and increasing concern about environmental pollution, the removal of sulfur-containing compounds from petroleum has become an urgent issue. Existing petroleum desulfurization technologies mainly include hydrodesulfurization (HDS), oxidative desulfurization (ODS), adsorption desulfurization, extraction desulfurization, and biological desulfurization. Hydrodesulfurization has always been the most widely used desulfurization technology in the industry. Although HDS reacts with hydrogen under high temperature and pressure to achieve deep desulfurization, it requires a large investment in equipment and a large amount of hydrogen, significantly increasing the cost of raw materials. Achieving ultra-low sulfur emissions usually requires a more complex operating process and harsh reaction conditions (high temperature and pressure, >300°C, >3 MPa). When encountering sulfur-containing compounds such as dibenzothiophene (DBT) and its alkylated derivatives such as 4,6-dimethyldibenzothiophene (4,6-DMDBT), the effectiveness of HDS decreases significantly because the stability of sulfur-containing compounds at sulfur centers and the accessibility of sterically hindered catalytic sites are reduced. Other desulfurization technologies also have their own problems: ultra-high temperature desulfurization, high temperature oxidation desulfurization, vacuum high temperature desulfurization, co-heat reduction desulfurization, hydrodesulfurization, hot alkali treatment desulfurization, and oxidative desulfurization are either too energy-intensive or too expensive, making it difficult to meet the economic requirements of industrial production. Oxidative desulfurization (ODS), on the other hand, has attracted much attention due to its mild reaction conditions, low equipment cost, and high desulfurization efficiency.

[0003] Compared to hydrodesulfurization, oxidative desulfurization (ODS) offers significant advantages. ODS can be effectively performed under ambient temperature and pressure conditions, with mild reaction conditions, low energy consumption, and no need for high-pressure hydrogen or related equipment, resulting in lower equipment investment and operating / maintenance costs. In terms of desulfurization efficiency, ODS can selectively oxidize thiophene sulfides in oil products that are difficult to remove via hydrodesulfurization into highly polar sulfones or sulfoxides. The products can then be separated from the oil phase through methods such as polar solvent extraction, solid-phase adsorption, or distillation, achieving deep desulfurization.

[0004] Metalloporphyrins, as an important class of biomimetic catalysts, have received widespread attention in the field of catalytic oxidation in recent years. Metalloporphyrins possess an active center structure similar to cytochrome P-450 monooxygenase, enabling them to mimic the catalytic mechanism of biological enzymes and activate molecular oxygen or peroxides under mild conditions, achieving selective oxidation of organic matter. In the field of oxidative desulfurization, studies have already applied metalloporphyrins to the catalytic oxidation of sulfur-containing compounds. For example, patent CN101301627B uses metalloporphyrin as a catalyst to oxidize sulfides under high temperature and high pressure conditions, but the oxidized sulfides still exist in the oil phase; patent CN104277870A uses metalloporphyrin or phthalocyanine as catalysts to achieve CS bond breaking through photocatalytic oxidation, thereby desulfurizing; patent CN105419853A uses metalloporphyrin as a catalyst, ionic liquid as an extractant, and hydrogen peroxide as an oxidant for extractive catalytic oxidative desulfurization. Patent CN106083867A discloses a method for preparing modified metalloporphyrins, which improves the catalytic activity of metalloporphyrins by replacing axial ligands. In addition, previous studies have reported methods for the highly selective transfer and activation of oxygen molecules and the catalytic oxidation of organic matter under mild conditions using metal phthalocyanines and metalloporphyrins as catalysts.

[0005] However, several problems remain to be solved in existing metalloporphyrin-catalyzed desulfurization systems. First, most systems require high temperature, high pressure, or external light exposure, increasing energy consumption and equipment costs. Second, without suitable co-catalysts, metalloporphyrins have weak binding affinity to oxygen molecules, resulting in limited oxidation capacity and very low desulfurization efficiency for thiophene-based sulfur compounds (especially 4,6-dimethyldibenzothiophene with significant steric hindrance). Third, although studies have used aldehydes as co-reducing agents in metalloporphyrin-catalyzed olefin epoxidation and other reactions, the systematic influence of aldehyde co-catalysts on the desulfurization efficiency of petroleum sulfur compounds, particularly the synergistic effects between aldehyde co-catalysts with different electronic effects, steric hindrance, and functional groups and porphyrins with different metal centers (such as nickel and vanadium), is still lacking in systematic and in-depth research. In particular, how to significantly improve the catalytic oxidation efficiency of nickel porphyrin for various sulfur-containing compounds (including the difficult-to-remove 4,6-dimethyldibenzothiophene) under mild conditions of ambient temperature and pressure through structural optimization of the co-catalyst remains a technical challenge that urgently needs to be overcome in this field.

[0006] Therefore, developing a nickel porphyrin-aldehyde synergistic catalytic system capable of efficiently catalyzing the oxidation of sulfur-containing compounds in petroleum under ambient temperature and pressure conditions, systematically screening suitable aldehyde co-catalysts, and elucidating their synergistic mechanism are of great theoretical and practical significance for promoting the industrial application of oxidative desulfurization technology. Summary of the Invention

[0007] The purpose of this invention is to provide a method and application of aldehyde-synergistic nickel porphyrin catalytic oxidation desulfurization. By selecting appropriate catalytic promoters, the catalytic oxidation efficiency of metal porphyrins on sulfides can be improved. At the same time, a highly efficient and stable oxidation desulfurization catalytic system can be developed, providing a certain theoretical basis and technical support for the preparation of ultra-low sulfur fuel oil.

[0008] To achieve the above-mentioned technical effects, the present invention adopts the following technical solution: A method for aldehyde-synergistic nickel porphyrin-catalyzed oxidative desulfurization includes the following steps: (1) Using octaethylnickel porphyrin as the main catalyst and aldehydes as co-catalysts, it is mixed with oil containing sulfur compounds; (2) Under normal temperature and pressure conditions, oxygen or air is introduced and the oxidation desulfurization reaction is carried out under stirring conditions. After the reaction is completed, the oxidation products are separated by extraction or adsorption.

[0009] Preferably, in step (1), the molar ratio of the co-catalyst, octaethylnickel porphyrin and the sulfur-containing compound is (100~120):1:(0.8~1.2).

[0010] Preferably, the co-catalyst is 4-(diethylamino)salicylaldehyde.

[0011] Preferably, in step (1), the molar ratio of 4-(diethylamino)salicylaldehyde, octaethylnickel porphyrin and sulfur-containing compound is 104:1:1.

[0012] Preferably, the sulfur-containing compound includes one or more of 4,6-dimethyldibenzothiophene, pentyl sulfide, and dibenzothiophene.

[0013] Preferably, the stirring speed is 200~300 rpm.

[0014] Preferably, the reaction time is 6 to 12 hours.

[0015] The method described in this invention is applied in the oxidative desulfurization of petroleum distillate oil, diesel oil, or gasoline.

[0016] The diethylamino group (-N(Et)2) in the 4-(diethylamino)salicylaldehyde molecule is a strong electron-donating group. In the oxidative desulfurization mechanism, the electron cloud density of the sulfur atom in the sulfide molecule (such as dibenzothiophene) is key to determining its ease of oxidation; the higher the electron cloud density on the sulfur atom, the higher the reactivity. Here, the co-catalyst is an aldehyde compound, and the presence of the electron-donating group can indirectly affect the polarity of the reaction medium or create an environment where the sulfur atom is easily attacked by electrophilic oxygen through weak interactions with the catalyst. Introducing electron-withdrawing groups onto the benzene ring of metalloporphyrins can improve catalytic activity; electronic effects have a significant impact on the entire catalytic system. The electronic properties of the co-catalyst, its synergy with the main catalyst, and its regulation of the reaction pathway all contribute to its effectiveness. In salicylaldehyde, the ortho-hydroxyl group (-OH) forms an intramolecular hydrogen bond with the aldehyde group (-CHO), which increases the molecular stability and enables it to have specific orientation and reactivity in the reaction system. This aldehyde has moderate steric hindrance; compared to some polycyclic or highly substituted aldehydes (such as 2,5-dibromophenyl-1,4-dicarboxaldehyde), its structure is relatively planar and has moderate steric hindrance. This facilitates its diffusion to the vicinity of the catalytically active site to effectively interact with reactive oxygen species or reaction intermediates without being hindered by excessive steric hindrance. 4-(diethylamino)salicylaldehyde exhibits excellent desulfurization efficiency due to its unique synergistic effect of the electron-donating amino group and ortho-hydroxyl group, as well as its moderate steric structure. Its structural characteristics enable it to effectively promote the generation or transfer of key reactive oxygen species in the nickel porphyrin catalytic cycle, thereby significantly improving the oxidation conversion rate of sulfides.

[0017] Compared with the prior art, the beneficial effects of the present invention are: 1) The reaction conditions of this invention are extremely mild, and it can be carried out efficiently at room temperature and pressure without the need for high temperature, high pressure or external light. It has low energy consumption, low equipment investment, and is safe and easy to operate.

[0018] (2) This invention first discovered the synergistic mechanism of the co-catalyst 4-(diethylamino)salicylaldehyde and nickel porphyrin, namely a dual-mechanism synergistic catalytic system of coordination regulation and oxygen acceptance. The dual-mechanism synergistic effect gives the catalytic system excellent desulfurization efficiency. It shows high efficiency in oxidizing sulfur-containing compounds such as 4,6-dimethyldibenzothiophene, dibenzothiophene and pentyl sulfide, which are difficult to remove. Under optimal conditions, the desulfurization rate can reach more than 55%, which is significantly higher than the effect of any single catalyst. The synergistic effect between the co-catalyst and the main catalyst is significant, which greatly improves the catalytic activity of nickel porphyrin. Moreover, the catalyst dosage is small and the cost is controllable, which has good prospects for industrial application. Detailed Implementation

[0019] The technical solution of the present invention will be further described below with reference to specific embodiments, but is not limited thereto. The specific specifications and manufacturer information of the sulfur model compound standard, nickel porphyrin and aldehyde co-catalyst used in the present invention are shown in Table 1.

[0020] Table 1 Specifications and manufacturers of experimental reagents used Example 1 A method for aldehyde-synergistic nickel porphyrin-catalyzed oxidative desulfurization includes the following steps: A hexadecane solution containing 4,6-dimethyldibenzothiophene (4,6-DMDBT) was used as a simulated oil. Octaethylnickel porphyrin (NiOEP, 0.05 mmol), 4-(diethylamino)salicylaldehyde (5.2 mmol), and the simulated oil (containing 0.05 mmol of 4,6-DMDBT) were added to a reaction flask at room temperature (25 °C) and atmospheric pressure, making a molar ratio of 1:104:1. Stirring was started at 250 rpm, and air was simultaneously purged at a flow rate of 50 mL / min. The reaction was allowed to proceed for 10 hours. After the reaction was complete, 1 mL of each solution was analyzed by GC-MS, and the conversion rate was calculated using the internal standard method.

[0021] Example 2 A method for aldehyde-synergistic nickel porphyrin-catalyzed oxidative desulfurization includes the following steps: A hexadecane solution containing 4,6-dimethyldibenzothiophene (4,6-DMDBT) was used as a simulated oil. Octaethylnickel porphyrin (NiOEP, 0.05 mmol), 4-(diethylamino)salicylaldehyde (5.0 mmol), and the simulated oil (containing 0.04 mmol of 4,6-DMDBT) were added to a reaction flask at room temperature (25 °C) and atmospheric pressure, making a molar ratio of 1:100:1. Stirring was started at 250 rpm, and air was simultaneously bubbled through at a flow rate of 50 mL / min. The reaction was allowed to proceed for 10 hours. After the reaction was complete, 1 mL of each solution was analyzed by GC-MS, and the conversion rate was calculated using the internal standard method.

[0022] Example 3 A method for aldehyde-synergistic nickel porphyrin-catalyzed oxidative desulfurization includes the following steps: A hexadecane solution containing 4,6-dimethyldibenzothiophene (4,6-DMDBT) was used as a simulated oil. Octaethylnickel porphyrin (NiOEP, 0.05 mmol), 4-(diethylamino)salicylaldehyde (6.0 mmol), and the simulated oil (containing 0.06 mmol of 4,6-DMDBT) were added to a reaction flask at room temperature (25 °C) and atmospheric pressure, making a molar ratio of 1:120:1. Stirring was started at 250 rpm, and air was simultaneously purged at a flow rate of 50 mL / min. The reaction was allowed to proceed for 10 hours. After the reaction was complete, 1 mL of each solution was analyzed by GC-MS, and the conversion rate was calculated using the internal standard method.

[0023] Example 4 A method for aldehyde-synergistic nickel porphyrin-catalyzed oxidative desulfurization includes the following steps: A hexadecane solution containing pentyl sulfide was used as a simulated oil. Octaethylnickel porphyrin (NiOEP, 0.05 mmol), 4-(diethylamino)salicylaldehyde (5.2 mmol), and the simulated oil (containing 0.05 mmol of pentyl sulfide) were added to the reaction flask at room temperature (25 °C) and atmospheric pressure. Stirring was started at 250 rpm, and air was simultaneously purged at a flow rate of 50 mL / min. The reaction was allowed to proceed for 10 hours. After the reaction was complete, 1 mL of each solution was analyzed by GC-MS, and the conversion rate was calculated using the internal standard method.

[0024] Example 5 A method for aldehyde-synergistic nickel porphyrin-catalyzed oxidative desulfurization includes the following steps: A hexadecane solution containing dibenzothiophene (DBT) was used to simulate the oil. Octaethylnickel porphyrin (NiOEP, 0.05 mmol), 4-(diethylamino)salicylaldehyde (5.2 mmol), and the simulated oil (containing 0.05 mmol DBT) were added to a reaction flask at room temperature (25 °C) and atmospheric pressure, making a molar ratio of 1:104:1. Stirring was started at 250 rpm, and air was simultaneously bubbled through at a flow rate of 50 mL / min. The reaction was allowed to proceed for 10 hours. After the reaction was complete, 1 mL of each solution was analyzed by GC-MS, and the conversion rate was calculated using the internal standard method.

[0025] Comparative Example 1 A method for nickel porphyrin catalytic oxidative desulfurization includes the following steps: A hexadecane solution containing 4,6-dimethyldibenzothiophene (4,6-DMDBT) was used as a simulated oil. Octaethylnickel porphyrin (NiOEP, 0.05 mmol) and the simulated oil (containing 0.05 mmol of 4,6-DMDBT) were added to the reaction flask at room temperature (25 °C) and atmospheric pressure. Stirring was started at 250 rpm, and air was simultaneously purged at a flow rate of 50 mL / min. The reaction was allowed to proceed for 10 hours. After the reaction was complete, 1 mL of each solution was analyzed by GC-MS, and the conversion rate was calculated using the internal standard method.

[0026] The difference between the above comparative example and Example 1 is that no aldehyde co-catalyst was added to the reaction system, which contained only octaethylnickel porphyrin.

[0027] Comparative Example 2 A hexadecane solution containing 4,6-dimethyldibenzothiophene (4,6-DMDBT) was used to simulate oil. The reaction was carried out at room temperature (25°C) and atmospheric pressure, with stirring at 250 rpm and air purging at a flow rate of 50 mL / min for 10 hours. After the reaction, 1 mL of each solution was analyzed by GC-MS, and the conversion rate was calculated using the internal standard method.

[0028] The difference between the above comparative example and Example 1 is that neither the main catalyst octaethylnickelporphyrin nor aldehyde co-catalysts are added to the reaction system.

[0029] Comparative Example 3 A hexadecane solution containing 4,6-dimethyldibenzothiophene (4,6-DMDBT) was used as a simulated oil. At room temperature (25°C) and atmospheric pressure, 5.2 mmol of 4-(diethylamino)salicylaldehyde and 0.05 mmol of the simulated oil (containing 4,6-DMDBT) were added to the reaction flask. Stirring was started at 250 rpm, and air was simultaneously bubbled through at a flow rate of 50 mL / min. The reaction was allowed to proceed for 10 hours. After the reaction was complete, 1 mL of each solution was analyzed by GC-MS, and the conversion rate was calculated using the internal standard method.

[0030] The difference between the above comparative example and Example 1 is that the main catalyst octaethylnickel porphyrin is not added to the reaction system, and only 4-(diethylamino)salicylaldehyde is contained.

[0031] Comparative Example 4 A method for desulfurization by aldehyde synergistic nickel porphyrin catalysis is basically the same as in Example 1, except that the co-catalyst 4-(diethylamino)salicylaldehyde is replaced with an equimolar amount of 4,6-dichlorosalicylaldehyde, and the other conditions are the same as in Example 1.

[0032] Comparative Example 5 A method for desulfurization by aldehyde synergistic nickel porphyrin catalysis is basically the same as in Example 1, except that the cocatalyst 4-(diethylamino)salicylaldehyde is replaced with an equimolar amount of 2-chloropropanedialdehyde, and the other conditions are the same as in Example 1.

[0033] Comparative Example 6 A method for desulfurization by aldehyde synergistic nickel porphyrin catalysis is basically the same as in Example 1, except that the co-catalyst 4-(diethylamino)salicylaldehyde is replaced with an equimolar amount of 2,5-dibromobenzene-1,4-dicarboxaldehyde, and the other conditions are the same as in Example 1.

[0034] Comparative Example 7 A method for desulfurization by aldehyde synergistic nickel porphyrin catalysis is basically the same as in Example 1, except that the co-catalyst 4-(diethylamino)salicylaldehyde is replaced with an equimolar amount of isobutyraldehyde, and the other conditions are the same as in Example 1.

[0035] Comparative Example 8 A method for desulfurization by aldehyde synergistic nickel porphyrin catalysis is basically the same as in Example 1, except that the co-catalyst 4-(diethylamino)salicylaldehyde is replaced with an equimolar amount of furfural, and the other conditions are the same as in Example 1.

[0036] Performance testing In this invention, gas chromatography-mass spectrometry (GC-MS) (Thermo Fisher TSQ 8000 EVO gas chromatograph-mass spectrometer) was used for testing.

[0037] Preparation of standard solutions Accurately weigh 1.5 mmol each of three sulfur-containing model compounds: 4,6-dimethyldibenzothiophene (4,6-DMDBT), dibenzothiophene (DBT), and pentyl sulfide. Also accurately weigh 1.5 mmol of the internal standard n-hexadecane and 1.5 mmol of the main catalyst octaethylnickel porphyrin (NiOEP). Place all compounds in a 300 mL volumetric flask and dilute to the mark with n-hexadecane as the solvent. Sonicate for 10 min to obtain the standard stock solution. The concentrations of each sulfur-containing substrate, internal standard, and main catalyst in this standard stock solution are all 5.0 mmol / L.

[0038] Chromatographic conditions: Carrier gas: helium (purity ≥99.999%), argon (purity ≥99.999%); Injector temperature: 300℃; Transfer circuit temperature: 300℃; Injection volume: 1 μL; Temperature program: 40℃ for 2 min, ramp to 220℃ at 12℃ / min and hold for 5 min, then ramp to 300℃ at 8℃ / min and hold for 8 min; Carrier gas flow rate: 1.00 mL / min. Hexadecane was used as an internal standard.

[0039] b-mass spectrometry conditions: triple quadrupole detector, EI ionization source.

[0040] Conversion rate is calculated using the following internal standard method formula: X = (1- ) × 100% In the formula: X is the conversion rate (%) of the sulfur-containing substrate; S 前 The ratio of the peak area of ​​the sulfur-containing substrate to the internal standard hexadecane in the standard stock solution before the reaction (A) 底物 / A 内标 ); S 后 The ratio of the peak area of ​​the remaining sulfur-containing substrate in the sample after the reaction to that of the internal standard n-hexadecane (A)底物 / A 内标 The peak areas of each chromatographic element were extracted and quantified using GC-MS total ion chromatogram (TIC).

[0041] The final conversion rates of the reaction systems in Examples 1-5 and Comparative Examples 1-8 can all be measured using the above method. The specific test results are shown in Table 2 below.

[0042] Table 2 Summary of performance test results for each embodiment and comparative example The data in Table 2 show that when NiOEP and 4-(diethylamino)salicylaldehyde are used as the catalytic system, they exhibit good catalytic oxidation activity for three sulfur-containing substrates: 4,6-DMDBT, pentyl sulfide, and DBT, with conversion rates of 55.6%, 66.2%, and 41.9%, respectively. In contrast, in Comparative Examples 1-3, the conversion rates of using octaethylnickel porphyrin alone, using 4-(diethylamino)salicylaldehyde alone, and the blank experiment were 9.7%, 8.4%, and 1.8%, respectively. However, in Example 1, the conversion rate increased to 55.6% after using both in combination, approximately six times that of using either alone. This indicates a significant synergistic catalytic effect between the nickel porphyrin and the aldehyde co-catalyst described in this invention, and both are indispensable. This is mainly because the key step in achieving efficient catalytic oxidation in this invention is that the stronger the basicity (electron-donating ability) of the aldehyde co-catalyst ligand, the greater the binding energy with the metal porphyrin, promoting the activation of O2 and the formation of high-valence metal oxygen active species (such as Ni=O). (-N(Et)2)diethylamino is a strong electron-donating group. It can coordinate axially to the nickel (Ni) center, significantly increasing the electron density of Ni. The ortho-phenolic hydroxyl group (-OH), as a weak electron-donating group, forms an intramolecular hydrogen bond with the aldehyde group, which can stabilize the conformation of the cocatalyst itself and also affect its binding mode with the nickel center and the electron transfer path after coordination. The presence of the hydroxyl group enhances molecular polarity and improves its solubility and dispersion in the reaction system. The aldehyde group (-CHO) plays a dual role. It can act as an oxygen acceptor. In the metalloporphyrin / aldehyde / O2 system, the aldehyde can be oxidized by activated oxygen to generate acyl peroxy radicals (RCO3·), initiating a free radical chain reaction of sulfide oxidation. The carbon atom of the aldehyde group has a certain degree of electrophilicity. The strong electron-donating aromatic ring and amino group attached to it weaken its electrophilicity, making it more inclined to participate in free radical generation rather than undergoing side reactions with sulfides. 4-(diethylamino)salicylaldehyde binds tightly to nickel porphyrin via O,N-bident or strongly monodentate coordination, optimizing the electronic properties of the catalytic center. The aldehyde group effectively initiates free radical chain reactions, and the dual mechanisms of coordination regulation and oxygen acceptance achieve highly efficient synergy. In Comparative Examples 4-8, when 4-(diethylamino)salicylaldehyde was replaced with five other aldehyde compounds, the conversion rate decreased significantly, even to 0%, all far lower than the 55.6% of Example 1. These results further demonstrate that the four structural elements of 4-(diethylamino)salicylaldehyde selected in this invention—the electron-donating diethylamino group, the ortho-hydroxyl group, the aromatic ring conjugated structure, and the appropriate steric hindrance—work synergistically and are indispensable.

[0043] Further analysis of the conversion differences among different sulfur-containing substrates revealed that pentyl sulfide (open-chain structure with fully exposed sulfur atoms) had the highest conversion rate (66.2%); 4,6-DMDBT (containing two methyl groups, with the greatest steric hindrance) had a conversion rate of 55.6%, higher than DBT (41.9%). This result indicates that in the catalytic system of this invention, the electron cloud density of the sulfur atom is the primary factor determining oxidation efficiency. The electron-donating effect of the two methyl groups in 4,6-DMDBT increases the electron cloud density of the sulfur atom, making it more susceptible to electrophilic oxygen attack. Furthermore, the coordination regulation of the catalytic system effectively overcomes the steric hindrance caused by the methyl groups, and the combined effect results in a higher conversion rate than DBT. In summary, this invention, under mild conditions of ambient temperature and pressure, achieves highly efficient oxidative conversion of sulfur-containing compounds of various structural types through the synergistic catalysis of octaethylnickel porphyrin and 4-(diethylamino)salicylaldehyde, solving the technical problems of harsh reaction conditions or low efficiency in removing difficult-to-remove sulfides in existing technologies. Furthermore, the results from Comparative Examples 4-8 show that aldehyde co-catalysts with different structures significantly affect catalytic activity. While 4,6-dichlorosalicylaldehyde (Comparative Example 4) exhibits some activity (20.3%), it is far lower than that of 4-(diethylamino)salicylaldehyde. In contrast, co-catalysts such as 2-chloropropanedialdehyde, 2,5-dibromobenzene-1,4-dicarboxaldehyde, isobutyraldehyde, and furfural show almost no catalytic effect, further highlighting the crucial role of the diethylamino substituent in 4-(diethylamino)salicylaldehyde in enhancing catalytic performance.

[0044] Based on the above experimental results, this invention further investigated the effect of different reaction temperatures on the catalytic oxidation desulfurization efficiency. Taking the specific method of Example 1 as an example, except for the reaction temperature, all other conditions were kept consistent. The catalytic oxidation desulfurization performance of the system of this invention on sulfide-containing 4,6-dimethyldibenzothiophene oil was studied at three temperature gradients of 50℃, 70℃, and 100℃. The specific experimental results are shown in Table 3 below. The experimental results show that increasing the temperature does not lead to a significant increase in conversion rate. In fact, at 70℃ and 100℃, the sulfide conversion rate is extremely low or zero. This result is different from the expected acceleration of the reaction by increasing the temperature. Aldehyde co-catalysts will volatilize and decompose. In open systems or inadequately sealed conditions at 70℃ and 100℃, a large amount of co-catalyst will volatilize and be lost, resulting in a decrease in the actual concentration in the system and a reduction in catalytic efficiency. The peroxy acid generated in the experiment is thermally unstable, and its decomposition rate is accelerated at high temperatures, much greater than the peroxy acid formation rate, and the active oxygen carrier cannot be effectively accumulated. High temperatures can also accelerate the self-aggregation, decomposition, or irreversible side reactions of nickel porphyrin with solvents and products, leading to catalyst deactivation. Experimental results indicate that room temperature is the most suitable temperature, ensuring the stable existence of the co-catalyst and effective self-oxidation, resulting in a more complete nickel porphyrin catalytic center and fully embodying the principles of green chemistry.

[0045] Table 3 Effect of temperature on desulfurization efficiency of the catalytic system This invention also investigated the effect of different 4-(diethylamino)salicylaldehyde concentrations on the desulfurization rate of 4,6-dimethyldibenzothiophene. Based on Example 1, only the amount of 4-(diethylamino)salicylaldehyde added was changed, and the effect of different co-catalyst 4-(diethylamino)salicylaldehyde concentrations on the desulfurization efficiency was examined. The results are shown in Table 4.

[0046] Table 4. Effect of different 4-(diethylamino)salicylaldehyde concentrations on desulfurization efficiency The experimental results show that when the molar ratio of the co-catalyst to NiOEP and substrate is 0:1:1 (i.e., without the addition of 4-(diethylamino)salicylaldehyde), the conversion rate of 4,6-dimethyldibenzothiophene is only 9.7%, indicating that the co-catalyst is crucial for desulfurization efficiency. However, the conversion rate does not increase linearly with the increase in the proportion of the co-catalyst. When the amount of 4-(diethylamino)salicylaldehyde added is extremely small, it not only fails to act as a co-catalyst but also acts as an inhibitor. This may be because the N and O in 4-(diethylamino)salicylaldehyde have strong lone pairs of electrons, resulting in a very strong coordination ability with the Ni (nickel) center. When added in small amounts, it quickly occupies the axial coordination sites of Ni, but the concentration is too low to form an effective Ni-aldehyde-O2 ternary activation ring. Because the sites are occupied, oxygen cannot effectively approach the Ni center for activation. This is equivalent to blocking the inlet of the catalytic cycle, leading to a significant suppression of the already weak oxidation activity of nickel porphyrin without the addition of aldehyde. When the mass of the co-catalyst precisely reaches the range described in the embodiments of this invention, a qualitative change occurs in the system: at this point, the aldehyde concentration is sufficient to form a stable axial coordination field around Ni, significantly increasing the electron cloud density at the Ni center, allowing O2 to be efficiently activated into a high-valence metal oxygen species (Ni=O); the high concentration of aldehyde ensures that the generation rate of acyl peroxide free radicals is greater than the quenching rate, thereby initiating an effective free radical chain reaction, overcoming the steric hindrance of 4,6-DMDBT, and achieving a leap in conversion rate. When this ratio is exceeded, excess aldehyde molecules will compete for coordination or form inactive dimers, hindering the effective binding of Ni centers and O2, leading to a further decrease in conversion rate. Therefore, the concentration of 4-(diethylamino)salicylaldehyde needs to be precisely controlled within a specific ratio range to achieve the best co-catalytic effect.

[0047] It should be noted that the above embodiments are merely some preferred embodiments of the present invention, and not all embodiments. Obviously, based on the above embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

Claims

1. A method for aldehyde-synergistic nickel porphyrin-catalyzed oxidative desulfurization, characterized in that, Includes the following steps: (1) Using octaethylnickel porphyrin as the main catalyst and aldehydes as co-catalysts, it is mixed with oil containing sulfur compounds; (2) Under normal temperature and pressure conditions, oxygen or air is introduced and the oxidation desulfurization reaction is carried out under stirring conditions. After the reaction is completed, the oxidation products are separated by extraction or adsorption.

2. The method for aldehyde-synergistic nickel porphyrin-catalyzed oxidative desulfurization according to claim 1, characterized in that, In step (1), the molar ratio of the co-catalyst, octaethylnickel porphyrin and the sulfur-containing compound is (100~120):1:(0.8~1.2).

3. The method for aldehyde-synergistic nickel porphyrin-catalyzed desulfurization according to claim 1 or 2, characterized in that, The co-catalyst is 4-(diethylamino)salicylaldehyde.

4. The method for aldehyde-synergistic nickel porphyrin-catalyzed oxidative desulfurization according to claim 3, characterized in that, In step (1), the molar ratio of 4-(diethylamino)salicylaldehyde, octaethylnickelporphyrin and sulfur-containing compound is 104:1:

1.

5. The method for aldehyde-synergistic nickel porphyrin-catalyzed oxidative desulfurization according to claim 1, characterized in that, The sulfur-containing compounds include one or more of 4,6-dimethyldibenzothiophene, pentyl sulfide, and dibenzothiophene.

6. The method for aldehyde-synergistic nickel porphyrin-catalyzed oxidative desulfurization according to claim 1, characterized in that, The stirring speed is 200~300 rpm.

7. The method for aldehyde-synergistic nickel porphyrin-catalyzed desulfurization according to claim 1, characterized in that, The reaction time is 6 to 12 hours.

8. The application of the method of claim 1 in the oxidative desulfurization of petroleum distillate oil, diesel oil, or gasoline.

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