CN107029804B

CN107029804B - Catalyst with erasable performance and preparation method and application thereof

Info

Publication number: CN107029804B
Application number: CN201710285478.7A
Authority: CN
Inventors: 夏立新; 张海冉; 张谦; 周鹏宇; 李超琪
Original assignee: Liaoning University
Current assignee: Liaoning University
Priority date: 2017-04-27
Filing date: 2017-04-27
Publication date: 2020-02-07
Anticipated expiration: 2037-04-27
Also published as: CN107029804A

Abstract

The invention relates to a catalyst carrier PIL-rGO with erasable performance and a preparation method and application thereof. Dissolving appropriate amount of 1-vinyl-3-ethylimidazole bromine salt in chloroform, adding azobisisobutyronitrile, carrying out reflux reaction under the protection of nitrogen, cooling, washing and drying to obtain Br as an anion^‑Modified polymeric ionic liquid PIL-Br; ultrasonically dispersing GO in water, adjusting the pH value to 12, dropwise adding PIL-Br and hydrazine hydrate under stirring, performing reflux reaction, filtering, washing with water, and freeze-drying to obtain Br as an anion^‑PIL-rGO. The invention designs and synthesizes a novel functional material PIL-rGO with erasable performance for the first time, realizes the replacement of different catalytic active centers and the self-renewal of the carrier on the same catalyst carrier by utilizing the reversible exchange between the PIL on the PIL-rGO carrier and acid anions, and the designed catalyst is beneficial to the uniform distribution of the catalytic active centers on the surface of the carrier and effectively improves the catalytic efficiency of fuel oil desulfurization.

Description

Catalyst with erasable performance and preparation method and application thereof

Technical Field

The invention belongs to the field of heterogeneous catalysts, and particularly relates to a method for implanting an erasable concept into a catalyst design, which can realize the loading and replacement of catalytic active centers of different types on the same catalyst carrier, thereby realizing more flexible dynamic design and controllable regulation of catalytic reaction while keeping the stability of the catalyst.

Background

With the rapid development of social economy, the number of vehicles in the world is increasing, so that the demand and consumption of fuel oil are greatly increased, and sulfur oxides SOx generated by sulfur-containing compounds in the fuel oil during high-temperature combustion are the main reasons for causing environmental pollution problems such as acid rain and the like. Therefore, how to reduce the sulfide in the fuel oil and fundamentally solve the problems related to environmental pollution become a common concern of all circles.

The sulfide in petroleum exists in various forms, and sulfide in gasoline and diesel oil mainly contains thiophene, belongs to thermally stable inactive sulfide, and is difficult to remove by using a conventional desulfurization method. Such substances are mainly Thiophene (T), Benzothiophene (BT), Dibenzothiophene (DBT) and their derivatives. According to the property and characteristics of sulfide contained in oil products, the currently adopted physical or chemical fuel oil desulfurization technologies at home and abroad are mainly divided into two categories: namely hydrodesulfurization techniques and non-hydrodesulfurization techniques. Wherein, the non-hydrodesulfurization technology comprises methods such as extraction desulfurization, oxidation desulfurization, biological desulfurization and the like. Among the various desulfurization methods, Oxidative Desulfurization (ODS) is a desulfurization method with good application prospects. The method can be carried out at low temperature and normal pressure, more importantly, the electron cloud density on the sulfur atom of the thiophene sulfur-containing compounds in the oil product is high, and the stable sulfides can be easily removed by ODS. In addition, the oxidative desulfurization equipment is less in investment, has higher desulfurization efficiency on thiophene compounds, can realize ultra-deep desulfurization, and is an efficient desulfurization technology.

In the catalytic oxidation desulfurization process, the acidic active center is an important factor for restricting the improvement of the catalytic efficiency. Therefore, it is important to increase the sites of acid centers. Due to the fact that graphene has a huge specific surface area, in recent years, more and more attention is paid to the research in the field of catalysis, and the graphene serving as a carrier not only can realize the loading of more catalysts and expose more active centers, but also can embody some synergistic effects of a graphene substrate. At present, most of the combination modes of the catalyst and the carrier are static irreversible processes, namely, once the catalyst is combined with the carrier, the existing catalytic performance of the catalyst which is difficult to change is kept. Therefore, if a proper method is found to realize the loading and replacement of different types of catalysts on the same carrier, namely the erasable process of the catalysts on the carrier is realized, the method has better flexibility for optimizing the functional composite catalyst, and the catalytic performance of different catalytic active centers can be seen more intuitively. Therefore, if graphene is used as a carrier of a catalyst to realize the design of different acidic catalysts on the same substrate, the graphene can be well promoted to develop in the field of catalysis.

Disclosure of Invention

In order to solve the problems, the invention provides a catalyst carrier PIL-rGO with erasable performance, which realizes the loading and replacement of different types of acid anions on the same carrier, namely, the erasable process of the acid anions on the catalyst carrier PIL-rGO is realized, and the design of different acid catalysts on the same substrate is realized.

The technical scheme adopted by the invention is as follows: the preparation method of the catalyst carrier PIL-rGO with the erasable performance comprises the following steps:

1) dissolving a proper amount of 1-vinyl-3-ethylimidazole bromine salt monomer in chloroform, adding Azobisisobutyronitrile (AIBN), stirring for dissolving, carrying out reflux reaction for 5-6h under the protection of nitrogen, cooling to room temperature, washing, and drying to obtain PIL-Br;

2) adding graphene oxide GO into deionized water, performing ultrasonic dispersion to obtain a GO dispersion system, adjusting the pH value of the GO dispersion system to 11-12, dropwise adding PIL-Br under stirring, and stirring after dropwise addingThen, continuously dropwise adding hydrazine hydrate, carrying out reflux reaction at 100 ℃ for 24-25h, filtering the filtrate by using a filter membrane, washing by using water, and freeze-drying to obtain Br-loaded^-The catalyst carrier PIL-rGO with erasable performance.

The catalyst carrier PIL-rGO with the erasable performance is applied to oxidative desulfurization of fuel oil. The method comprises the following steps:

1) writing process of acid anion: loading Br as above^-Dissolving the catalyst carrier PIL-rGO with erasable performance in a small amount of deionized water, performing ultrasonic dispersion to obtain a dispersion system, adding the dispersion system into an acid solution, reacting for 24-25h under magnetic stirring, filtering a product with a filter membrane, and washing with water to obtain an acid anion catalyst loaded with acid anions;

2) acid anion wiping process: dissolving an acidic anion catalyst in a small amount of deionized water, performing ultrasonic dispersion to obtain a dispersion system, adding the dispersion system into a potassium bromide aqueous solution, reacting for 24-25h under magnetic stirring, filtering the product with a filter membrane, washing with water, and reducing to load Br^-The catalyst carrier PIL-rGO with erasable performance;

3) acid anion rewriting process: loading reduced Br^-Dissolving the catalyst carrier PIL-rGO with erasable performance in a small amount of deionized water, performing ultrasonic dispersion to obtain a dispersion system, adding the dispersion system into the acid solution again, reacting for 24-25h under magnetic stirring, filtering the product with a filter membrane, and washing with water to obtain the acid anion catalyst loaded with acid anions again;

4) oxidation desulfurization: adding an extracting agent, an acidic anion catalyst and an oxidizing agent into gasoline or diesel oil containing sulfide, and reacting for 2-3h at 15-65 ℃.

Preferably, the acidic anion is [ HSO ]₄]^-、[PW₁₂O₄₀]^3-、[PMo₁₂O₄₀]^3-Or [ SiW ]₁₂O₄₀]^4-。

Preferably, the acidic solution is an aqueous sodium bisulfate solution, an aqueous phosphotungstic acid solution, an aqueous phosphomolybdic acid solution or an aqueous silicotungstic acid solution.

Preferably, the acidic anionic catalyst is [ HSO ]₄]^--PIL-rGO、[PW₁₂O₄₀]^3--PIL-rGO、[PMo₁₂O₄₀]^3--PIL-rGO or [ SiW₁₂O₄₀]^4--PIL-rGO。

Preferably, the sulfide is dibenzothiophene, 4, 6-dimethyldibenzothiophene, benzothiophene or thiophene.

Preferably, the extractant is [ BMIM]BF₄(ii) a The oxidant is hydrogen peroxide.

The invention has the beneficial effects that:

1. in the present invention, the anion is Br^-The polymeric ionic liquid (PIL-Br) of (a) is selected as a surface modifier for the catalyst support. For graphene, how to realize the loading and the stability of a proper acidic anion on a graphene substrate has practical significance. According to the invention, through pi-pi interaction between the PIL and the graphene carrier, the PIL-Br can be effectively adsorbed on the graphene carrier, so that the PIL can be used as a tie between the loaded acidic anion and the graphene substrate, and grafting of a functional group on the graphene carrier is realized. The PIL can be used as a surface modifier of a graphene substrate by reversible ion exchange, so that the loading of acid anions on graphene is promoted, reversible writing and erasing among different acid anions can be realized by the reversible ion exchange, and the dynamic reversible immobilization process is favorable for selection and optimization of a catalyst in the fuel oil desulfurization process.

2. In the present invention, the PIL has a unique ion-exchange property, and it is noted that the ion-exchange property has a certain reversibility, which means that after the anion having a catalytic action is loaded on the PIL, the writing and erasing processes, i.e. the erasable process of the anion on the carrier, can be realized by the ion-exchange. Therefore, the graphene and the PIL are combined, a catalytic reaction model which has a huge surface area and can realize flexible erasable performance can be realized through ion exchange.

3. The invention compounds the acidic anion with catalytic activity and the PIL-rGO carrier, and applies the acidic anion and the PIL-rGO carrier to an oxidation desulfurization system of fuel oil. The application of the composite form of the catalyst enables the original liquid-liquid desulfurization mode to be converted into solid-liquid catalytic reaction, on one hand, the huge specific surface area of the PIL-rGO carrier provides a place for loading the catalyst, so that more active sites are exposed, and the catalytic desulfurization efficiency is improved, on the other hand, the combination of the catalyst and the carrier increases the stability of the catalyst, and the catalyst is favorable for recycling.

4. According to the invention, a novel functional material PIL-rGO with erasable performance is designed and synthesized for the first time, and the two-dimensional open structure of the PIL-rGO carrier ensures that the PIL-rGO carrier has a huge specific surface area, so that the uniform distribution of catalytic active centers on the surface of the carrier is facilitated, more active sites are exposed, and the catalytic efficiency of fuel oil desulfurization is effectively improved.

5. According to the invention, the reversible exchange between the PIL and the acidic anion on the PIL-rGO carrier is utilized to realize the replacement of different catalytic active centers on the same catalyst carrier and the self-renewal of the carrier.

6. According to the invention, PIL-rGO realizes writing and exchange of different acidic anions on the same catalyst carrier through anion exchange. On one hand, the raw material investment is saved, and more importantly, the simple anion exchange can realize the replacement of different acid sites on the same carrier, thereby eliminating the influence on the performance of the catalyst due to different carriers or different carrier qualities, and being beneficial to researching the performance difference of different types of catalysts in the desulfurization process under the same condition.

7. The invention utilizes the ion exchange design of a PIL-rGO carrier to synthesize four different acid anion modified supported catalysts: [ PW₁₂O₄₀]^3--PIL-rGO、[PMo₁₂O₄₀]^3--PIL-rGO、[SiW₁₂O₄₀]^4--PIL-rGO and [ HSO₄]^-PIL-rGO, and the catalytic efficiency is improved in a fuel oil oxidation desulfurization system.

8. The invention inspects DBT desulfurization of different systems under the best desulfurization condition and finds that the PIL-rGO carrier is utilizedBlank desulfurization efficiency of body and simple utilization of ionic liquid BMIM]BF₄The extraction desulfurization efficiency of the catalyst is equivalent, which indicates that the PIL-rGO carrier does not have larger desulfurization capability. H simply using the same load₃PW₁₂O₄₀Efficiency of liquid-liquid desulfurization and utilization of catalyst [ PW₁₂O₄₀]^3-Compared with the solid-liquid desulfurization efficiency of the PIL-rGO, the solid-liquid desulfurization efficiency of the PIL-rGO shows higher desulfurization efficiency, so that the combination of the catalyst and the PIL-rGO carrier is illustrated, the removal efficiency of sulfur-containing compounds in fuel oil is greatly improved, and the coordination effect of the catalyst and the carrier is reflected.

9. The invention is applicable to catalyst [ PW₁₂O₄₀]^3-The recycling rate of the-PIL-rGO is examined, and the catalyst [ PW ] is found after eight times of repeated use₁₂O₄₀]^3-The catalytic desulfurization efficiency of PIL-rGO is not obviously changed, the DBT removal efficiency can still reach 96.5 percent, and the catalyst [ PW₁₂O₄₀]^3--PIL-rGO excellent catalytic performance and good stability of the catalyst.

Drawings

FIG. 1 is a schematic diagram of the preparation of a catalyst carrier PIL-rGO with erasable performance and the application thereof in fuel oil oxidative desulfurization.

FIG. 2 is a Transmission Electron Micrograph (TEM) of a catalyst support PIL-rGO with rewritable properties of example 2;

wherein a is PIL-rGO;

b:[HSO₄]^--PIL-rGO (writing process);

c PIL-rGO (KBr and [ HSO ]₄]^--after ion exchange of PIL-rGO, wipe-off process);

d:[PW₁₂O₄₀]^3--PIL-rGO([PW₁₂O₄₀]^3-ion exchange with reduced PIL-rGO, rewrite).

FIG. 3 is an infrared spectrum (FT-IR) of PIL-rGO, a catalyst support with rewritable properties of example 2;

wherein a is PIL-rGO;

b:[HSO₄]^--PIL-rGO (writing process);

FIG. 4a is X-ray photoelectron spectroscopy (XPS) of PIL-rGO.

FIG. 4b is [ HSO ]₄]^--X-ray photoelectron spectroscopy (XPS) of PIL-rGO (writing process).

FIG. 4c is PIL-rGO (KBr and [ HSO ]₄]^--rubbing off process after ion exchange of PIL-rGO) X-ray photoelectron spectroscopy (XPS).

FIG. 4d is [ PW₁₂O₄₀]^3--PIL-rGO([PW₁₂O₄₀]^3-Ion exchange with reduced PIL-rGO, rewritten) X-ray photoelectron spectroscopy (XPS).

FIG. 5 is a Transmission Electron Micrograph (TEM) of three heteropolyacid anion-modified PIL-rGO of example 3 having erasable properties;

wherein, a is [ PW ]₁₂O₄₀]^3--PIL-rGO；b:[PMo₁₂O₄₀]^3--PIL-rGO；c:[SiW₁₂O₄₀]^4--PIL-rGO。

FIG. 6 is an infrared spectrum (FT-IR) of three heteropolyacid anion-modified PIL-rGO of example 3 having erasable properties;

FIG. 7a is [ PW₁₂O₄₀]^3--X-ray photoelectron spectroscopy (XPS) of PIL-rGO.

FIG. 7b is [ PMo ]₁₂O₄₀]^3--X-ray photoelectron spectroscopy (XPS) of PIL-rGO.

FIG. 7c is [ SiW ]₁₂O₄₀]^4--PIL-X-ray photoelectron spectroscopy (XPS) of rGO.

FIG. 8 is a comparative desulfurization of four catalysts in example 4.

FIG. 9 is DBT desulfurization at various catalyst loadings for example 4.

FIG. 10 is a DBT desulfurization at various O/S conditions in example 4.

FIG. 11 is the DBT desulfurization at various temperatures in example 4.

FIG. 12 is a DBT desulfurization with different systems in example 4.

FIG. 13 is the desulfurization of various sulfur-containing substrates in example 4.

FIG. 14 is a graph showing the recycling of the catalyst in example 5.

Detailed Description

For better understanding of the technical solution of the present invention, specific examples are described in further detail, but the solution is not limited thereto.

EXAMPLE 1 catalyst support with erasable Properties PIL-rGO

The preparation method comprises the following steps:

1) preparation of polymerized ionic liquid 1-vinyl-3-ethylimidazole bromine salt Poly [ ViBIm ] Br (PIL-Br)

20g of 1-vinyl-3-ethylimidazole bromide monomer was weighed out accurately and charged into a 250mL round-bottomed flask, and after dissolving it with chloroform, 0.4g of AIBN was added and dissolved with stirring. And (3) introducing nitrogen into the system for 30min, and carrying out reflux reaction for 5h under the protection of nitrogen. After the reaction was complete, the reaction was cooled to room temperature and the product was washed three times with chloroform and dried under vacuum to give a yellow solid, Poly [ ViBIm ] Br (PIL-Br).

2) Loaded with Br^-Preparation of a catalyst support (PIL-rGO) with erasable properties

Adding 0.1g of Graphene Oxide (GO) into a round-bottom flask containing 100mL of deionized water, performing ultrasonic dispersion to obtain a black GO dispersion system, adjusting the pH value of the dispersion system to be 12 by using ammonia water, adding 0.15g of PIL-Br into 10mL of deionized water for dissolving, dropwise adding a PIL-Br aqueous solution into the GO dispersion system under stirring, continuously dropwise adding 5mL of hydrazine hydrate under stirring after dropwise adding is finished, and performing reflux reaction at 100 DEG CAnd (5) 24 h. After the reaction is finished, removing unreacted precipitate, filtering and washing the solution with a filter membrane for three times, and freeze-drying to obtain the supported Br^-The catalyst support PIL-rGO with rewritable properties of (1) was used in the following examples.

EXAMPLE 2 Erasable Performance study of PIL-rGO

Based on the ion-exchange property of PIL-Br, this example examined different anions and Br in PIL-rGO^-Reversible exchange between them, i.e., the erasable properties of PIL-rGO.

1) Acid anion [ HSO ]₄]^-In the write process

120mL of saturated aqueous solution of sodium bisulfate was added to the round-bottom flask, and 0.1g of supported Br was weighed^-The catalyst carrier PIL-rGO with the erasable performance is dissolved in a small amount of deionized water, and a black dispersion system is obtained after ultrasonic dispersion. The resulting black dispersion was transferred to a round bottom flask and reacted for 24h with magnetic stirring. After the reaction is finished, filtering a product filter membrane, washing with water for three times, and freeze-drying to obtain the loaded acid anion [ HSO ]₄]^-Acid anion catalyst of ([ HSO ]₄]^--PIL-rGO)。

2) Acid anion [ HSO ]₄]^-Wiping off process of

120mL of a saturated aqueous solution of potassium bromide was added to the round-bottom flask, and 0.1g of [ HSO ] was weighed₄]^-Dissolving PIL-rGO in a small amount of deionized water, and performing ultrasonic dispersion to obtain a black dispersion system. Will [ HSO ]₄]^-The dispersion of-PIL-rGO was transferred to a round bottom flask and reacted for 24h with magnetic stirring. Filtering and washing the product with filter membrane for three times after the reaction is finished, and obtaining the loaded Br again after freeze-drying^-The catalyst carrier PIL-rGO with erasable performance.

3) Heteropoly acid anion [ PW₁₂O₄₀]^3-Is rewritten into

Adding 120mL of phosphotungstic acid aqueous solution into a round-bottom flask, and weighing 0.1g of renewed supported Br^-The catalyst carrier PIL-rGO with the erasable performance is dissolved in a small amount of deionized water, and a black dispersion system is obtained after ultrasonic dispersion. Transfer the resulting black dispersion to a circleIn a bottom flask, the reaction was carried out for 24h under magnetic stirring. After the reaction is finished, the product is filtered and washed by a filter membrane for three times, and is freeze-dried to obtain the loaded acidic anion [ PW₁₂O₄₀]^3-Acid anion catalyst of ([ PW)₁₂O₄₀]^3--PIL-rGO)。

The erasable process and characterization of the related PIL-rGO are shown in FIG. 1, FIG. 2, FIG. 3, FIG. 4 a-FIG. 4 d.

FIG. 1 is a schematic diagram of the erasing process of PIL-rGO, as shown in FIG. 1: and realizing in-situ immobilization of the PIL on the surface of the GO by utilizing the pi-pi complexation between the GO and the PIL-Br to obtain the PIL-grafted polymer ionic liquid-based reduced graphene oxide PIL-rGO. Thanks to the reversible ion exchange performance of the PIL group, the writing and erasing of different catalytic anions on the same carrier PIL-rGO are realized by utilizing the ion exchange reaction between different types of acid anions and the PIL, namely the erasable process of different anions by the PIL-rGO carrier. The catalyst modified by different acidic anions is further applied to the oxidation desulfurization process of fuel Oil, taking model Oil-DBT as an example, a sulfur-containing compound DBT in an Oil phase is firstly extracted to a two-phase interface, and the acidic active center of the catalyst is in an oxidant H₂O₂Under the action of the ion source, DBT molecules are oxidized into peroxy acid radical ions, and the DBT molecules are converted into corresponding polar sulfones or sulfoxides under the oxidation action of the peroxy acid radical ions and then extracted into an ionic liquid main body phase, so that the transfer of sulfur-containing substances from an oil phase to an ionic liquid phase is realized, and the aim of fuel oil desulfurization is fulfilled. After the desulfurization process is finished, the catalyst can return to the original PIL-rGO state through simple ion exchange, and the catalyst is updated and recycled.

FIG. 2 is a Transmission Electron Micrograph (TEM) of different anionically modified PIL-rGO. Wherein FIG. 2-a shows the anion is Br^-TEM images of modified PIL-rGO, as can be seen by contrast with other positions: the synthesized PIL-rGO nano sheet has smooth surface, light and thin structure and single-layer sheet material with silk-like gauze texture, and the huge surface area of the nano sheet can be observed, thereby providing a structural basis for the load of a catalytic active center. As can be seen from FIG. 2-b, by [ HSO ]₄]^-With Br on PIL-rGO^-By ion exchange between [ HSO ]₄]^-The morphology of the PIL-rGO is not obviously changed, and the silk-like thin sheet structure of the PIL-rGO nano sheet is still maintained. FIG. 2-c is a graph using KBr and the [ HSO ]₄]^-Br obtained by reduction of anion exchange reaction between-PIL-rGO^-The modified PIL-rGO nano sheet has a single-layer silk-like structure, which indicates that the appearance of the PIL-rGO is kept. Continuing to use PIL-rGO and [ PW ] prepared in FIGS. 2-c₁₂O₄₀]^3-Ion exchange therebetween to obtain [ PW₁₂O₄₀]^3-PIL-rGO (FIG. 2-d), which found that the originally thin monolithic structure resulted from the dyeing of heteropoly acids [ PW₁₂O₄₀]^3-The contrast of the PIL-rGO nano-sheet is deepened compared with that of other positions, and the occurrence of wrinkles indicates that the flake structure of the PIL-rGO still keeps. Therefore, PIL-rGO realizes writing and conversion of different types of acid active centers on the same catalyst carrier through anion exchange reaction, and the structure of the PIL-rGO is kept stable and is not obviously changed in the writing and conversion processes of different anions.

FIG. 3 is an infrared characterization (FT-IR) of the rewritable properties of PIL-rGO. Wherein, FIG. 3-a is the infrared spectrum of PIL-rGO, from which 3000cm can be seen^-1Below, the saturated C-H stretching vibration is 3000cm^-1The above nearby is benzene ring and N-H stretching vibration peak; at 1460cm^-1And 1600cm^-1The position is a benzene ring C ═ C skeleton vibration peak; 1155cm^-1The absorption peak is the in-plane deformation effect of C-H in the imidazole ring. FIG. 3-b is a scheme for utilizing [ HSO ]₄]^-[ HSO ] obtained by ion exchange reaction with PIL-rGO₄]^-IR spectrum of PIL-rGO, FIG. 3-b at 618cm, compare with FIG. 3-a^-1Is shown by [ HSO ]₄]^-Characteristic absorption peak of [ HSO ]₄]^-Have been successfully introduced into PIL-rGO nano-sheets. Continued use of KBr with the above [ HSO ]₄]^-After ion exchange reaction of-PIL-rGO, the original 618cm is found^-1Of (C) [ HSO ]₄]^-The characteristic absorption peak disappears (FIG. 3-c), and then returns to the value shown in FIG. 3-aThe state of PIL-rGO, the comparison result shows that KBr and [ HSO ] are utilized₄]^-The anion [ HSO ] has been successfully converted by ion exchange reaction₄]^-And (3) removing, namely, realizing the wiping process of the acidic catalytic center on the PIL-rGO substrate, and restoring and updating the carrier. Using heteropoly acid anions [ PW₁₂O₄₀]^3-Further ion exchange with the updated PIL-rGO, found at 1075cm^-1，975cm^-1And 810cm^-1Respectively show [ PW ] at₁₂O₄₀]^3-Characteristic absorption peaks of P-O, W ═ O, W-Oe-W of (A) are shown. Therefore, the replacement among different types of acidic catalytic centers and the updating of a catalyst carrier can be realized through simple anion exchange, and the excellent erasable performance of the PIL-rGO serving as the carrier under the condition of keeping self stability is reflected.

In order to further verify the erasable performance of the PIL-rGO nano-sheet as a carrier, X-ray photoelectron spectroscopy (XPS) is carried out, and the results are shown in FIGS. 4a to 4 d. It can be seen that: by [ HSO ]₄]^-With Br in PIL-rGO^-The original PIL-rGO has Br with binding energy of about 75eV^-The peak disappeared (FIG. 4a), and correspondingly the characteristic peak of S2 p appeared around 168eV (FIG. 4b), indicating [ HSO ]₄]^-Has been successfully introduced into a PIL-rGO nano-chip to finally obtain [ HSO ]₄]^--PIL-rGO. FIG. 4c is a graph showing the use of KBr and [ HSO ]₄]^-Anions in-PIL-rGO [ HSO₄]^-The PIL-rGO obtained after ion exchange between the two was found to have disappeared the S2 p characteristic peak at 168eV and, correspondingly, to have reappeared Br at 75eV, compared with FIG. 4b^-The characteristic peak of (A) is heavy and returns to the original state of the PIL-rGO. Continued use of the recovered PIL-rGO Br^-And H₃PW₁₂O₄₀After anion exchange, Br around 75eV was clearly observed^-The disappearance of the characteristic peaks, and the appearance of characteristic peaks for P2P, W4 f and W4 d5 at around 135eV, 36eV and 252eV (FIG. 4d), respectively, thus demonstrating [ PW₁₂O₄₀]^3-Successfully introduced into a PIL-rGO carrierThe above. Experimental results strongly prove that the ion exchange realizes the exchange of different acidic anions on the same carrier, and simultaneously shows the superiority of the PIL-rGO nano-sheet as a catalyst carrier. On one hand, the huge specific surface area of the PIL-rGO provides a foundation for the loading of the active sites of the catalyst; on the other hand, due to the ion exchange property of the PIL group on the PIL-rGO carrier, the exchange of different acidic anions and the self-renewal of the carrier are realized. The erasability of different catalytic active centers on the same catalyst carrier makes the design of catalytic reaction more flexible, and avoids the difference of catalytic performance caused by different carriers.

EXAMPLE 3 Synthesis of different heteropolyacid anion modified PIL-rGO catalysts

[ PW ]₁₂O₄₀]^3-Preparation of-PIL-rGO

120mL of phosphotungstic acid aqueous solution was added to a round bottom flask, 0.1g of the PIL-rGO prepared in example 1 was weighed and dissolved in a small amount of deionized water, and a black dispersion was obtained after sonication. The PIL-rGO dispersion was transferred to a round bottom flask and reacted for 24h with magnetic stirring. After the reaction is finished, filtering the product by using a filter membrane, washing the product for three times, and freeze-drying the product to obtain the loaded acid anion [ PW₁₂O₄₀]^3-Acid anion catalyst of ([ PW)₁₂O₄₀]^3--PIL-rGO)。

(II) [ PMo₁₂O₄₀]^3-Preparation of-PIL-rGO

120mL of phosphomolybdic acid aqueous solution was added to a round bottom flask, 0.1g of the PIL-rGO prepared in example 1 was weighed and dissolved in a small amount of deionized water, and a black dispersion was obtained after ultrasonic dispersion. The PIL-rGO dispersion was transferred to a round bottom flask and reacted for 24h with magnetic stirring. After the reaction is finished, filtering the product by using a filter membrane, washing the product for three times by using water, and freeze-drying the product to obtain the loaded acidic anion [ PMo ]₁₂O₄₀]^3-Acid anion catalyst of ([ PMo)₁₂O₄₀]^3--PIL-rGO)。

(III) [ SiW₁₂O₄₀]^4-Preparation of-PIL-rGO

Adding 1 into a round-bottom flask20mL of silicotungstic acid aqueous solution, 0.1g of the PIL-rGO prepared in the example 1 is weighed and dissolved in a small amount of deionized water, and a black dispersion system is obtained after ultrasonic dispersion. The PIL-rGO dispersion was transferred to a round bottom flask and reacted for 24h with magnetic stirring. After the reaction is finished, filtering the product by using a filter membrane, washing the product for three times by using water, and freeze-drying the product to obtain the loaded acid anion [ SiW ]₁₂O₄₀]^4-Acid anion catalyst ([ SiW)₁₂O₄₀]^4--PIL-rGO)。

Relevant characterization of different heteropolyacid anion-modified PIL-rGO nanosheets is shown in fig. 5, 6, 7a, 7b and 7 c.

FIG. 5 is a Transmission Electron Micrograph (TEM) of PIL-rGO modified with three heteropoly acid anions, from which it can be seen intuitively that the silk-like flakes of the original PIL-rGO nanosheets are darkened due to the dyeing effect of the heteropoly acid, but the morphology of the lamellar structure of PIL-rGO is still maintained, after the three heteropoly acid anions are used in combination with the PIL-rGO support. The corresponding infrared characterization is shown in fig. 6, and it can be seen that: in FIG. 6-a, 1080.6cm^-1，976.1cm^-1And 815.8cm^-1Are respectively assigned to [ PW₁₂O₄₀]^3-Characteristic absorption peaks for P-O, W ═ O and W-Oe-W in PIL-rGO. FIG. 6-b, 1082.0cm^-1，947.7cm^-1And 794.7cm^-1Are respectively assigned to [ PMo₁₂O₄₀]^3-Characteristic absorption peaks of P-O, Mo ═ O, Mo-Oe-Mo in PIL-rGO. FIG. 6-c, 1081.4cm^-1，972.8cm^-1，921.3cm^-1And 802.8cm^-1Are respectively [ SiW₁₂O₄₀]^4-Characteristic absorption peaks of Si-O, W ═ O, W-Oc-W and W-Oe-W in PIL-rGO. Characterization of three heteropolyacid anion modified PIL-rGO by XPS was continued and the results are shown in figures 7 a-7 c: FIG. 7a shows that characteristic peaks of P2P, W4 f and W4 d5 appear around 135eV, 36eV and 252eV, respectively, indicating that [ PW₁₂O₄₀]^3-Successful synthesis of PIL-rGO. Similarly, in FIG. 7b, characteristic peaks for P2P and Mo3d appear at 135eV and 234 eV. In FIG. 7c, the characteristic peaks for Si 2p, W4 f and W4 d5 appear at 102eV, 36eV and 252 eV. Thus proving [ PMo₁₂O₄₀]^3--PIL-rGO and [ SiW₁₂O₄₀]^4-Successful synthesis of PIL-rGO.

Example 4 application of different acidic anion modified PIL-rGO catalysts in oxidative desulfurization of fuel oil

Preparation of model oil

1) Model Oil-T: 0.2628g of thiophene is accurately weighed and dissolved in n-octane, and the volume is determined in a 100mL volumetric flask to prepare thiophene model Oil (Oil-T) with the sulfur content of 1000 mg/L.

2) Model Oil-BT: 0.4192g of benzothiophene is accurately weighed and dissolved in n-octane, and the volume is determined in a 100mL volumetric flask to prepare benzothiophene model Oil (Oil-BT) with the sulfur content of 1000 mg/L.

3) Model Oil-DBT: 0.576g of dibenzothiophene was accurately weighed and dissolved in n-octane, and the volume was determined in a 100mL volumetric flask to obtain dibenzothiophene model Oil (Oil-DBT) having a sulfur content of 1000 mg/L.

4) Model Oil-4, 6-DMDBT: 0.0663g of 4, 6-dimethyldibenzothiophene was accurately weighed and dissolved in n-octane, and the volume was determined in a 10mL volumetric flask to obtain dibenzothiophene model Oil (Oil-4,6-DMDBT) having a sulfur content of 1000 mg/L.

(II) extractant-Ionic liquid [ BMIM]BF₄Preparation of

Adding N-methylimidazole and 1-chlorobutane into a round-bottom flask, carrying out reflux reaction for 48 hours, distilling a product, adding acetonitrile into a system subjected to impurity removal until the product is completely dissolved, and then adding ethyl acetate until the solution is layered. Recrystallizing the product, and drying in vacuum to obtain Cl as anion^-1-butyl-3-methylimidazole ionic liquid ([ BMIM)]Cl). A certain amount of BMIM]Cl and NaBF₄Adding the mixture into a round-bottom flask, adding acetonitrile to dissolve the mixture, magnetically stirring the mixture for 26 hours, and rotatably evaporating the filtrate to remove the acetonitrile after the reaction is finished. Washing with dichloromethane for three times, filtering, removing dichloromethane from filtrate by rotary evaporation, and vacuum drying to obtain ionic liquid 1-butyl-3-methylimidazole [ BMIM ] tetrafluoroborate]BF₄。

(III) oxidative desulfurization of fuel oil

The method comprises the following steps: accurately weighing a certain amount of acidic anion catalyst, and ultrasonically dispersing the acidic anion catalyst in 3mL of ionic liquid [ BMIM ]]BF₄(IL) adding 5ml of prepared model oil, finally adding a certain amount of 30% aqueous hydrogen peroxide solution, magnetically stirring at a certain temperature, periodically sampling from the upper oil phase, and analyzing the sulfur content in different periods by using a high performance liquid chromatography.

This example explores the optimal reaction conditions for the oxidative desulfurization of model oils for catalyst type, catalyst amount, oxygen-to-sulfur molar ratio (O/S), reaction temperature, desulfurization for different systems, and different substrates, respectively. The relevant characteristics are shown in fig. 8, 9, 10, 11, 12 and 13.

1. Desulfurization efficiency comparison of four different catalysts

The experimental conditions are as follows: v_oil-DBT:V_IL＝5:3；O/S＝5；m_(catalyst)＝20mg；T＝60℃；t＝3h。

As shown in fig. 8, it can be seen that: the desulfurization efficiency of four different acidic anionic catalysts increased dramatically as the reaction proceeded, wherein the catalyst [ PW when the reaction proceeded for 90min₁₂O₄₀]^3-The first PIL-rGO to achieve 100% desulfurization, [ PMo ]₁₂O₄₀]^3-The catalytic desulfurization efficiency of the-PIL-rGO also reaches 99 percent. In contrast, the catalyst [ SiW ] at this time₁₂O₄₀]^4--PIL-rGO and catalyst [ HSO₄]^-The catalytic efficiency of-PIL-rGO was low, 76% and 70% after three hours of reaction, respectively. Therefore, the catalyst [ PW₁₂O₄₀]^3-PIL-rGO is the best catalyst for the desulfurization system.

2. Comparative desulfurization of catalyst dosage

The experimental conditions are as follows: v_oil-DBT:V_IL5: 3; O/S is 5; t is 60 ℃; t is 3 h; the catalyst is [ PW₁₂O₄₀]^3--PIL-rGO。

As shown in fig. 9, it can be seen that: as the reaction proceeds, when the catalyst [ PW₁₂O₄₀]^3-Gradually increasing the amount of PIL-rGO from 5mg to 20mg, gradually increasing the DBT removal efficiency in the model oil, and when the reaction time reaches 90min, [ PW₁₂O₄₀]^3--PIL-rGO is added in an amount ofWhen the amount of the catalyst is 20mg, 100 percent of desulfurization is achieved first, and complete DBT removal is realized. It is also noted that the desulfurization efficiency can still reach 100% in a short time even if the amount of the catalyst is only 10 mg. The catalyst mainly benefits from the larger two-dimensional specific surface area of the PIL-rGO carrier, the acid catalytic center is dispersed to a greater extent by the huge open surface, and the superiority of the rGO serving as the catalyst carrier structure is shown, so that the desulfurization efficiency is greatly improved compared with that of the traditional two-phase desulfurization system. By comparison, 20mg was used as the optimum catalyst [ PW₁₂O₄₀]^3--PIL-rGO amount.

3. Oxidizing agent H₂O₂Influence of the amount of (2) on the desulfurization efficiency

The experimental conditions are as follows: v_oil-DBT:V_IL＝5:3；m_(catalyst)20mg ═ 20 mg; t is 60 ℃; t is 3 h; the catalyst is [ PW₁₂O₄₀]^3--PIL-rGO。

As shown in FIG. 10, theoretical calculation indicates that 2mol H is consumed for complete oxidation of 1mol DBT to generate the corresponding sulfone in the reaction₂O₂. In the optimization experiment of the oxygen-sulfur ratio condition, the invention selects the oxygen-sulfur molar ratios of 4, 5, 6 and 8 respectively to carry out the comparative experiment, and the experimental result shows that: the DBT removal efficiency increases dramatically when O/S is increased from 4 to 5, with the model Oil-DBT achieving 100% desulfurization when the reaction is run for 90min and the O/S is 5, and the DBT removal efficiency is only 66% when the O/S is 4. The experimental results show that as the oxygen-sulfur ratio is increased, more acidic active centers are oxidized into peroxy acid radicals to participate in the later oxidative desulfurization process, thereby showing a great increase in desulfurization efficiency. It was found that the removal efficiency of DBT decreased to different degrees when the oxygen to sulfur ratio was increased from 5 to 6 and 8. This is due to: when the oxygen-sulfur ratio reaches saturation, the continuous increase of the oxygen-sulfur ratio does not cause the improvement of the efficiency of the oxidative desulfurization process any more, and H is used as the oxidant of the desulfurization reaction₂O₂The competition between the oxidation of the acid center and the self thermal decomposition exists in the reaction system, and when the oxygen and sulfur are less, H is₂O₂Mainly used for oxidizing acidic active sites when H₂O₂The addition amount reaches saturationThen, the increase is continued, and the excessive H₂O₂On the one hand, the excessive H does not cause the increase of the desulfurization efficiency₂O₂The heat is decomposed, resulting in the decrease of the desulfurization efficiency. After comparison, the O/S-5 is selected as the optimal oxygen-sulfur ratio dosage of the desulfurization system.

4. Comparison of DBT removal efficiencies at different temperatures

The experimental conditions are as follows: v_oil-DBT:V_IL＝5:3；O/S＝5；m_(catalyst)20mg ═ 20 mg; t is 3 h; the catalyst is [ PW₁₂O₄₀]^3--PIL-rGO。

As shown in fig. 11, it can be visually seen from the figure that the desulfurization efficiency sharply increases as the reaction temperature increases from 15 ℃ to 60 ℃, and finally reaches equilibrium. Wherein, when the temperature is 60 ℃, the reaction is carried out for 90min, the DBT removal efficiency reaches 100 percent firstly, and the complete desulfurization is realized. Therefore, 60 ℃ was selected as the optimum reaction temperature for the reaction.

5. DBT desulfurization under different systems

Simple ionic liquids [ BMIM]BF₄Also has certain extraction desulfurization efficiency, and through comparative experiments, as can be seen from figure 12: simple ionic liquids ([ BMIM)]BF₄) The desulfurization efficiency of the extraction desulfurization is increased along with the increase of the reaction time, and when the reaction is carried out for 3 hours, the desulfurization efficiency is about 45 percent. A blank desulfurization experiment is carried out by using the catalyst carrier PIL-rGO prepared in example 1, and the desulfurization efficiency is found to increase along with the increase of reaction time, and when the reaction is carried out for 3 hours, the desulfurization efficiency reaches 48 percent and is slightly higher than the extraction desulfurization by using the ionic liquid. This is due to: thanks to the pi-pi interaction between the exposed substrate part of the rGO and the DBT, the DBT is removed from the oil phase due to the pi-pi adsorption of the substrate, so that the desulfurization efficiency is slightly increased. Meanwhile, the comparison of the two results shows that the pure PIL-RGO substrate does not have good catalytic effect. By XPS vs [ PW₁₂O₄₀]^3-on-PIL-rGOQuantitative calculation of the catalyst loading yields: h₃PW₁₂O₄₀The loading of the anion accounts for about 54 percent of the mass fraction of the catalyst. Further utilizing the same amount of H₃PW₁₂O₄₀The two-phase system is subjected to extraction, catalytic oxidation and desulfurization, and the results show that: with the progress of the reaction, the DBT removal efficiency is increased and finally tends to be stable, and the desulfurization efficiency reaches 90% after the reaction is carried out for 3 hours. Finally, using [ PW₁₂O₄₀]^3-And (3) desulfurizing the DBT model oil by PIL-rGO, wherein experimental results show that the desulfurization efficiency of the DBT is sharply higher along with the increase of reaction time, and 100% desulfurization is achieved when the reaction is carried out for 1 hour. The desulfurization rates of the different reaction systems in which the reaction was carried out for 1 hour were compared to find that: pure PIL-RGO substrate pair DBT removal efficiency and ionic liquid BMIM]BF₄The extraction desulfurization efficiency of (A) was similar, about 40%, indicating that the PIL-RGO substrate did not have good catalytic performance. And, simply use H₃PW₁₂O₄₀The desulfurization efficiency of the catalyst is only 60%. However, H is₃PW₁₂O₄₀The DBT desulfurization efficiency after the anion is loaded on the PIL-RGO substrate through the ion exchange reaction reaches 100 percent in 1 hour, which is about the sum of the desulfurization efficiency of a single PIL-RGO substrate and the desulfurization efficiency of a catalyst which is only HPW, so that the promotion effect of the PIL-RGO as a catalyst carrier on the DBT desulfurization efficiency can be proved, and the superiority of the PIL-RGO as the substrate is embodied.

6. Comparative desulfurization experiment is carried out on model oil containing four sulfur substrates

The experimental conditions are as follows: v_Oil:V_IL＝5:3；O/S＝5；m_(catalyst)20mg ═ 20 mg; t is 60 ℃; t is 3 h; the catalyst is [ PW₁₂O₄₀]^3--PIL-rGO。

Under the optimal reaction conditions, as shown in FIG. 13, it can be seen visually that: with the advancement of reaction time, the desulfurization efficiency of model oils of four sulfur-containing substrates is increased sharply, and slowly, the model oils tend to be stable. Among them, DBT reaches 100% desulfurization in 1 hour first, and the removal efficiency of 4,6-DMDBT also reaches 100% in 2 hours, in contrast, BT and T are less efficient, and reach 72% and 68% when the reaction proceeds to 3 hours. The removal sequence for the four sulfur-containing substrates was therefore: DBT > 4,6-DMDBT > BT > T. The reason for this sequence can be summarized as: the difficulty of removing sulfur-containing substrates in model oils is related to the electron cloud density of the central sulfur atom and steric effects. Wherein the greater the electron cloud density of the central sulfur atom, the higher the oxidation activity. The electron cloud density of the four sulfur-containing organic substances is 5.696, 5.739, 5.758 and 5.760 in sequence. However, considering that the central sulfur atom of 4,6-DMDBT is more sterically hindered than DBT, the desulfurization efficiency is DBT > 4, 6-DMDBT. Therefore, combining the two effects, the desulfurization sequence is: DBT > 4,6-DMDBT > BT > T.

EXAMPLE 5 catalyst [ PW₁₂O₄₀]^3-Recycling of-PIL-rGO

After the desulfurization experiment was completed, the upper layer model oil was decanted off, and the lower layer ionic liquid phase was washed with diethyl ether to remove a small amount of unreacted H₂O₂And H₂And O, adding 5mL of prepared model oil again, carrying out the next cycle under the same reaction conditions, sampling from the upper oil phase at regular intervals, and analyzing the sulfur content by using a high performance liquid chromatography. The results are shown in FIG. 14.

As can be seen from fig. 14: using catalyst [ PW₁₂O₄₀]^3-The desulfurization rate of the model Oil-DBT by the-PIL-rGO nano sheet in the eighth desulfurization experiment is still kept at 96.5%, and is not obviously changed, and the result shows that the catalyst [ PW₁₂O₄₀]^3-Excellent recycling performance of the-PIL-rGO nano sheet.

Claims

1. The catalyst with erasable performance is characterized in that the preparation method comprises the following steps:

1) dissolving a proper amount of 1-vinyl-3-ethylimidazole bromine salt monomer in chloroform, adding azobisisobutyronitrile, stirring for dissolving, carrying out reflux reaction for 5-6h under the protection of nitrogen, cooling to room temperature, washing, and drying to obtain PIL-Br;

2) adding graphene oxide GO into deionized water, performing ultrasonic dispersion to obtain a GO dispersion system, adjusting the pH value of the GO dispersion system to 11-12, dropwise adding PIL-Br under stirring, continuously dropwise adding hydrazine hydrate under stirring, performing reflux reaction at 100 ℃ for 24-25h, filtering filtrate by using a filter membrane filter, washing with water, and freeze-drying to obtain Br-loaded^-The catalyst carrier PIL-rGO with erasable performance;

3) writing process of acid anion: will load Br^-Dissolving a catalyst carrier PIL-rGO with erasable performance in a small amount of deionized water, performing ultrasonic dispersion to obtain a dispersion system, adding the dispersion system into an acid solution, reacting for 24-25h under magnetic stirring, filtering a product by using a filter membrane filter, and washing with water to obtain an acid anion catalyst loaded with acid anions; the acidic anion is [ HSO ]₄]^-、[PW₁₂O₄₀]^3-、[PMo₁₂O₄₀]^3-Or [ SiW ]₁₂O₄₀]^4-；

4) Acid anion wiping process: dissolving an acidic anion catalyst in a small amount of deionized water, performing ultrasonic dispersion to obtain a dispersion system, adding the dispersion system into a potassium bromide aqueous solution, reacting for 24-25h under magnetic stirring, filtering the product with a filter membrane, washing with water, and reducing to load Br^-The catalyst carrier PIL-rGO with erasable performance;

5) acid anion rewriting process: loading reduced Br^-Dissolving the catalyst carrier PIL-rGO with the erasable performance in a small amount of deionized water, performing ultrasonic dispersion to obtain a dispersion system, adding the dispersion system into the acid solution again, reacting for 24-25h under magnetic stirring, filtering the product with a filter membrane filter, and washing with water to obtain the acid anion catalyst loaded with acid anions again.

2. A catalyst with erasable characteristics as claimed in claim 1, wherein said acidic solution is an aqueous solution of sodium bisulfate, phosphotungstic acid, phosphomolybdic acid or silicotungstic acid.

3. A catalyst as claimed in claim 1, wherein said acidic anionic catalyst is [ HSO ]₄]^--PIL-rGO、[PW₁₂O₄₀]^3--PIL-rGO、[PMo₁₂O₄₀]^3--PIL-rGO or [ SiW₁₂O₄₀]^4--PIL-rGO。

4. Use of a catalyst with erasability as recited in claim 1 for oxidative desulfurization of fuel oil.

5. Use according to claim 4, characterized in that the method comprises the following steps: oxidation desulfurization: adding an extracting agent, an acidic anion catalyst and an oxidizing agent into gasoline or diesel oil containing sulfide, and reacting for 2-3h at 15-65 ℃.

6. The use according to claim 5, wherein the sulfide is dibenzothiophene, 4, 6-dimethyldibenzothiophene, benzothiophene, or thiophene.

7. The use of claim 5, wherein the extractant is [ BMIM ]]BF₄(ii) a The oxidant is hydrogen peroxide.