Preparation method and application of a novel supported polyacid-based ionic liquid oxidation desulfurization catalyst

Abstract

The application relates to preparation of a novel supported polyacid-based ionic liquid and application of the novel supported polyacid-based ionic liquid in fuel desulfurization oxidation desulfurization. 12 O 40 ]·21H2O (K4VW 12 ) as an active center, a CNT@C4VW 12 novel composite material is synthesized by a one-step method. The carbon nanotube is a good electron transmission carrier, has strong stability and adsorption capacity, (C4MIM)Br is used as a linker, is combined with the carbon nanotube through pi-pi stacking on one hand, and is anchored to K4VW 12 on the other hand through electrostatic interaction. The catalyst prepared in the application is prepared through the synergistic effect of three components, greatly reduces the dosage of the active center K4VW 12 , is a heterogeneous catalyst, can realize removal of aromatic sulfides in fuel oil without an extractant, at a lower temperature and in a shorter time. Meanwhile, the system does not use any extractant, is convenient to recover, has good recycling performance, is easy to operate and can meet the demand of green chemical processes.

Description

Technical Field

[0001] This invention belongs to the field of multiphase oxidation, specifically relating to a novel method for preparing a supported polyacid-based ionic liquid and its application in fuel oil oxidative desulfurization. Background Technology

[0002] Fuel desulfurization has always been a significant issue in fuel refining because the combustion of sulfur-containing fuels results in large amounts of SO2. x Emissions from hydrogen pollutants cause serious environmental problems and even endanger human health. Compared to traditional processes, ODS (Optical Desulfurization System) requires no stringent reaction conditions and consumes large amounts of hydrogen energy, making it a hot topic in the desulfurization field. The key lies in developing high-performance catalysts.

[0003] Polyacids readily react with hydrogen peroxide to form electrophilic intermediates, which are considered effective drivers of organic saturation (ODS). However, their water solubility limits their industrial applications. Therefore, to increase the reusability of polyacids, research on loading them onto porous supports is increasing. Commonly used supports include molecular sieves, graphene, and carbon nanotubes. Carbon nanotubes are a novel type of finite carbon structure composed of needle-like tubes. Multi-walled carbon nanotubes are composed of several coaxial single-walled nanotubes and are often used as catalyst supports due to their large specific surface area and excellent conductivity. However, uniformly loading hydrophilic polyacids onto the surface of hydrophobic carbon nanotubes remains a challenge.

[0004] In summary, introducing a support with strong stability and adsorption capacity, increasing the specific surface area of ​​the polyacid-based ionic liquid catalyst, and improving its dispersibility in the reaction system are urgent needs for obtaining clean fuel with deep desulfurization. Summary of the Invention

[0005] Based on the current research status, this invention provides a method for preparing a novel supported polyacid-based ionic liquid oxidative desulfurization catalyst. This method can solve the problems of difficult recovery of oxidation products and poor selectivity in existing oxidative desulfurization technologies.

[0006] This invention uses a one-step method to prepare CNT@C4VW 12 Catalyst. This method has advantages such as simple operation, uniform distribution of polyacid active components, and minimal loss of active components. Fuel oil, catalyst, and oxidant are mixed and reacted for oxidative desulfurization, achieving deep desulfurization. This catalyst exhibits high conversion rate, high selectivity, and high stability in oxidative desulfurization applications.

[0007] A method for preparing a novel supported polyacid-based ionic liquid oxidative desulfurization catalyst includes the following steps:

[0008] (1) Preparation of polyoxometalate POM;

[0009] (2) Preparation of supported polyacid-based ionic liquid CNT@C4VW 12 ;

[0010] Furthermore, the polyoxometalate POM is composed of K4VW 12 The ionic liquid was prepared from (C4MIM)Br.

[0011] Furthermore, K4VW 12 With PW 12 Preparation of precursors.

[0012] Furthermore, the supported polyacid-based ionic liquid CNT@C4VW 12 The preparation method is as follows: multi-walled carbon nanotubes are added to distilled water, ultrasonically dispersed for 30 min, and then (C4MIM)Br and K4VW are added sequentially under magnetic stirring. 12 Stirred at room temperature for 24 hours, filtered and washed with water several times, then the black powder was collected and dried in a vacuum drying oven at 60°C for 12 hours. The powder was labeled CNT@C4VW. 12 .

[0013] Furthermore, the multi-walled carbon nanotubes, (C4MIM)Br, and K4VW 12 The mass ratio is 0.25g:0.22g:0.21g.

[0014] Furthermore, the aforementioned CNT@C4VW 12 The active centers are uniformly distributed on the outside of the carbon nanotubes.

[0015] A CNT@C4VW 12 The application method of the catalyst is relatively simple and the conditions are mild. It has great practical value in the field of oxidative desulfurization. The technical solution adopted is as follows:

[0016] Pour 5 mL of fuel oil into a gas chromatograph (500 ppm) and add 10 mg of CNT@C4VW. 12 Stir at 60℃ for 30 min, then add 34 μL of oxidant H2O2 (30%), take a sample every 5 min, heat and stir for 30 min, and test the remaining sulfur content using gas chromatography.

[0017] Compared with existing technologies, the beneficial effects of this invention are as follows:

[0018] The supported polyacid-based ionic liquid catalyst prepared in this invention has a large specific surface area and advantages such as simple preparation and environmental friendliness. Because POM alone has good water solubility as a catalyst, its stability in cycling is not good. Therefore, this invention uses CNT@C4VW... 12In catalytic materials, carbon nanotubes provide skeletal support and a conductive network, improving the dispersibility of the original POM-based ionic liquid.

[0019] This invention introduces ionic liquids into the active component polyoxometalates. The polyoxometalate nanoclusters provide superior catalytic activity, while the ionic liquid acts as an anchoring carrier for the polyoxometalates. This not only reduces the dissolution and desorption of polyoxometalates during the reaction but also increases the ability to capture DBT in the oil phase. Under conditions where no extractant is used, this synergistic catalysis achieves better catalytic oxidation desulfurization performance.

[0020] Compared with existing supported catalysts, this catalyst has high catalytic efficiency, can be recycled multiple times, produces no other toxic byproducts, and the products can be recovered purely. Furthermore, the reaction process of this invention is simple to operate and does not require high temperature and high pressure. Attached Figure Description

[0021] Figure 1 Flowchart of the preparation and application method of supported polyacid-based ionic liquid oxidative desulfurization catalyst

[0022] Figure 2 The infrared spectrum of the catalyst composite prepared in the embodiments of the present invention;

[0023] Figure 3 CNTs, C4VW prepared for embodiments of the present invention 12 CNT@C4VW 12 X-ray powder diffraction pattern;

[0024] Figure 4 Aberration-corrected electron micrograph and mapping of the catalyst prepared in the embodiments of the present invention;

[0025] Figure 5 This is a schematic diagram of the assembly of the catalyst prepared in an embodiment of the present invention;

[0026] Figure 6 Gas chromatography-mass spectrometry (GC-MS) of the lower acetonitrile phase in an embodiment of the present invention;

[0027] Figure 7 The image shows the cyclic stability of the catalyst prepared in an embodiment of the present invention. Detailed Implementation

[0028] To enable those skilled in the art to better understand this invention and to make its purpose and technical solutions clearer, the invention will be further described in detail below with reference to embodiments and accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the invention.

[0029] Example 1

[0030] like Figure 1 As shown, the novel supported polyacid-based ionic liquid oxidative desulfurization catalyst provided by this invention patent is prepared by first preparing K4VW 12 Then, a one-step method was used to self-assemble ionic liquids and polyacids on carbon nanotubes to prepare CNT@C4VW. 12 Finally, a certain amount of catalyst, model oil, and oxidant are mixed and heated under certain conditions to react. The desulfurization rate is then analyzed by gas chromatography.

[0031] Specifically, the preparation method of the supported polyacid-based ionic liquid oxidative desulfurization catalyst provided in this embodiment includes the following steps:

[0032] (1) A one-step method was used to self-assemble ionic liquids and polyacids on carbon nanotubes to prepare CNT@C4VW 12 The method is as follows: 0.25g of multi-walled carbon nanotubes are added to distilled water and ultrasonically dispersed for 30 minutes. Then, under magnetic stirring, 0.22g of (C4MIM)Br and 0.21g of K4VW are added sequentially. 12 Stir at room temperature for 24 hours. Filter with water while filtration, rinsing several times to collect the black powder, and dry it in a vacuum drying oven at 60°C for 12 hours. Label it as CNT@C4VW. 12 ;

[0033] (2) Take 5 mL of model oil and add it to an 8 mL gas chromatograph. Add 10 mg of catalyst and stir at 60 °C for 30 min for extraction and heating. Then add 34 μL of 30% H2O2 by mass. Take a sample every five minutes and monitor the remaining sulfur content by gas chromatography. After 30 min, the sulfur removal rate reaches 100%.

[0034] like Figure 2 As shown, CNT@C4VW 12 The infrared spectrum showed absorption peaks for (C4MIM)Br and polyacids. The results indicate that both (C4MIM)Br and polyacids were successfully loaded into CNTs.

[0035] like Figure 3 As shown, characteristic peaks of CNTs, C4VW, can be detected in the composite sample. 12 Both sharp and broad peaks can be observed in the catalyst. This indicates that C4VW 12 The successful integration with CNTs did not disrupt the structure of CNTs.

[0036] like Figure 4 As shown in the figure, the catalyst as a whole is composed of carbon nanotubes and polyacids (bright spots) on them, with the polyacids distributed very evenly around the carbon nanotubes. From Figure 5 In the -hj dataset, W metal atoms (green) are observed to be distributed outside of C elements (red), indicating that C4VW 12They are mainly distributed around the periphery of carbon nanotubes.

[0037] like Figure 5 As shown, the ionic liquid is combined with carbon nanotubes through π-π stacking, coating the outside of the tubes, and then anchoring the polyacid anions through electrostatic interaction, so that the polyacids are uniformly distributed on the carbon nanotubes.

[0038] like Figure 6 As shown, in the oil phase, DBT has been completely oxidized, and only the peak of DBTO2 exists, indicating that DBT has been completely converted and only converted to DBTO2, which shows that this catalytic reaction has high selectivity.

[0039] like Figure 7 As shown, the catalyst can be cycled five times without a significant decrease in activity. This indicates that the catalyst has certain cycling stability and is promising for application in this field.

[0040] To determine the active components in the catalyst, the properties of different components were tested under the optimal reaction conditions explored above.

[0041] Table 1 Comparison of desulfurization effects of different samples

[0042] serial number name Desulfurization rate (%) 1 CNT 8.7 2 <![CDATA[C4VW 12 ]]> 23.2 3 <![CDATA[CNT-(C4MIM)Br]]> 14.2 4 <![CDATA[CNT-VW 12 ]]> 27 5 <![CDATA[CNT@C4VW 12 ]]> 100

[0043] The above results show that the catalyst in this embodiment can achieve high desulfurization efficiency in a relatively short reaction time. CNT@C4VW 12 Its high efficiency is due to its structure; the ionic liquid can adsorb the reaction substrate outside the tube, pulling the DBT to the active center VW. 12 The carbon nanotubes, without functionalization, maintain their structural and electronic integrity, thus playing a role in electron transport and accelerating the reaction process. Furthermore, loading significantly increases the C4VW. 12 The high specific surface area further promotes the contact between reactants and catalytic active centers, thereby improving reaction efficiency.

[0044] In summary, the catalyst prepared by this invention has advantages such as high desulfurization efficiency, good cycle stability, high selectivity, mild and safe conditions, and easy product recovery.

[0045] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Therefore, all equivalent changes or modifications made to the structure, features and principles described in the claims of the present invention should be included within the scope of the present invention.

Claims

1. A method for preparing a supported polyacid-based ionic liquid catalyst for the catalytic oxidation removal of aromatic sulfides from diesel fuel, characterized in that, The catalyst consists of multi-walled carbon nanotubes as a support, along with a polyoxometalate (POM) and an ionic liquid on the support; the catalyst composition is represented as CNT@C4VW. 12 CNT stands for multi-walled carbon nanotubes, C4 represents the imidazole ionic liquid cation, and VW 12 The catalyst is a vanadate anion; in this catalyst, the active centers are uniformly distributed on the outside of the carbon nanotubes; the preparation method of the catalyst includes the following steps: Multi-walled carbon nanotubes were added to distilled water and ultrasonically dispersed for 30 min. Then, (C4MIM)Br and K4VW were added sequentially under magnetic stirring. 12 Stirred at room temperature for 24 hours, filtered and washed with water several times, then the black powder was collected and dried in a vacuum drying oven at 60°C for 12 hours. The powder was labeled CNT@C4VW. 12 .

2. The preparation method according to claim 1, characterized in that, The K4VW 12 From precursor H3[α-PW 12 O 40 ](PW 12 It was prepared by ).

3. The preparation method according to claim 1, characterized in that, Multi-walled carbon nanotubes, (C4MIM)Br and K4VW 12 The mass ratio is 0.25g:0.22g:0.21g.

4. The catalyst CNT@C4VW obtained by the preparation method according to any one of claims 1 to 3 12 Applications in the catalytic oxidation removal of aromatic sulfides from diesel fuel.

Images