A method for preparing Pd(II) / SiO2@PEI composite aerogel using a microdroplet template method and its application

Abstract

The present invention discloses a method for preparing Pd(II) / SiO2@PEI composite aerogel using a micro-droplet template method and its application. The preparation method comprises: preparing a micro-droplet template solution, preparing a gel containing the micro-droplet template, aging and modifying the obtained composite alcohol gel, removing the micro-droplet template, adding n-hexane, stirring and replacing the micro-droplet template, and obtaining a Pd(II) / SiO2@PEI composite aerogel. The present invention uses micro-droplets formed by stirring n-heptane in a polar solvent to dissolve thiophene compounds as templates, hybridizes a silicon source with an amine source, and dopes Pb into the aerogel. 2+ The modified Pd(II) / SiO2@PEI composite aerogel has regular pores and guides the adsorption active sites to be enriched on the inner surface. Compared with similar composite aerogels prepared by conventional methods, the composite aerogel obtained by the present invention has better adsorption performance for thiophene sulfides in simulated gasoline and simulated aromatic products.

Description

Technical Field

[0001] The present invention belongs to the technical field of material preparation and processing, and specifically relates to a preparation method of Pd(II) / SiO2@PEI composite aerogel by using a micro-droplet template method and application thereof. Background Art

[0002] When sulfur compounds in fossil fuels are burned, SO x When released into the air, these compounds form acid rain and smog, further polluting the environment and impacting human health. Aromatic hydrocarbons are a major petrochemical raw material, with benzene and paraxylene serving as the primary raw materials for polyester and polyamide fibers, two of the most widely used synthetic fibers in the modern textile industry. Aromatic hydrocarbons are primarily derived from the catalytic reforming of petroleum hydrocarbons and the cracking of gasoline. Therefore, aromatic hydrocarbon products also contain certain sulfides, which can poison catalysts during subsequent processing. Consequently, governments around the world have established strict regulations on the sulfur content of fuel oil and aromatic hydrocarbons, making the removal of sulfides from these fuel oils and aromatic hydrocarbons a research hotspot in modern petrochemical production.

[0003] Currently, refineries commonly use hydrodesulfurization (HDS) to remove sulfides from oil products, but this technology is ineffective for removing aromatic sulfides (thiophene and thiophene derivatives). Therefore, there is an urgent need to find new deep desulfurization methods to remove thiophene sulfides from fuel oil and aromatics. Adsorption desulfurization (ADS) offers advantages such as mild operating conditions, no reduction in gasoline octane rating, and the selective removal of thiophene sulfides, making it one of the most promising deep desulfurization technologies.

[0004] The core of adsorption desulfurization technology lies in the selection of suitable adsorbents. Aerogel is a nanoporous material with a continuous network structure formed by the mutual aggregation of nano-scale colloidal particles. It has the characteristics of high specific surface area, high porosity, and easy molding. It is widely used as an adsorbent carrier. Zhejiang University of Technology (Publication No. CN 108893138 A), (Publication No. CN105709685 A), (Publication No. CN 106590728 A) have developed aerogel by doping Zr 4+ 、Ag + 、Co + 、Cu + 、Al 3+SiO2 composite aerogels prepared by metal ions such as iodine and thiophene can have a good adsorption effect on thiophene sulfides in fuel oil. Zhejiang University of Technology (publication number CN113713723A) prepared SiO2@PEI composite aerogels by sol-gel and atmospheric pressure drying methods, which showed good adsorption performance in fuel oil and aromatic hydrocarbons. However, the aerogels prepared by the above conventional methods all have a disadvantage, that is, the pore distribution of the aerogel adsorbent is wide and irregular in shape, which affects the diffusion of the adsorbate. In addition, during the preparation of the aerogel, some of the adsorption active sites are buried and cannot be fully exposed, making it difficult to contact with thiophene compounds, resulting in a loss of adsorption performance. Summary of the Invention

[0005] In view of the defects of the Pd(II) / SiO2@PEI composite aerogel prepared by the above conventional method, the purpose of the present invention is to provide a preparation method of Pd(II) / SiO2@PEI composite aerogel using a microdroplet template method and its application.

[0006] The present invention provides a method for preparing a Pd(II) / SiO2@PEI composite aerogel using a micro-droplet template method. The composite aerogel is prepared using a micro-droplet template method based on a sol-gel method combined with a normal pressure drying method, and specifically comprises the following steps:

[0007] 1) Preparing a microdroplet template solution: dissolving a certain amount of thiophene compound in n-heptane to form a template solution;

[0008] 2) preparing a gel containing microdroplet templates: adding a certain amount of the template solution of step 1) to a polar solution obtained by mixing an amine source, anhydrous ethanol, a silicon source, and water; stirring the solution at a certain speed under acidic conditions; since the template solution is a non-polar solution, microdroplets will be formed when stirred in the polar solution, thereby obtaining a SiO2@PEI sol containing microdroplet templates; and adjusting the pH to cause gelation to obtain a composite alcohol gel;

[0009] 3) Aging: adding an aging solution composed of anhydrous ethanol and ethyl orthosilicate to the composite alcohol gel prepared in step 2) to perform aging to strengthen its skeleton structure;

[0010] 4) Modification: Grind and wash the aged composite alcohol gel from step 3), dissolve the palladium source in water, and then add it to the washed composite alcohol gel, stir and let it stand. In the embodiment of the present invention, stir for 6 hours and then let it stand;

[0011] 5) Removing the microdroplet template: adding n-hexane to the gel obtained in step 4) and stirring to displace the microdroplet template in the pores. In the embodiment of the present invention, stirring is performed for 1.5 hours;

[0012] 6) Drying: The composite alcohol gel obtained in step 5) is placed in a drying oven at 120° C. and dried under normal pressure to remove the residual microdroplet template, thereby finally obtaining a Pd(II) / SiO2@PEI composite aerogel.

[0013] Furthermore, the present invention also defines the micro-droplet template solution in step 1) as an n-heptane solution in which a thiophene compound is dissolved, wherein the thiophene sulfide is at least one of thiophene, benzothiophene or dibenzothiophene, and the concentration of the thiophene compound in the micro-droplet template solution is 2 mg-S / g.

[0014] Furthermore, the present invention also defines the silicon source in step 2) as Further, the present invention also defines the preparation method of Pd(II) / SiO2@PEI composite aerogel by drop template method, which is characterized in that the palladium source in step 4) is palladium chloride.

[0015] Furthermore, the present invention also limits the feeding molar ratio of the amine source to the ethyl orthosilicate to 1:400, the feeding molar ratio of the palladium source to the silicon source to 1:316, and the feeding volume ratio of the total volume of anhydrous ethanol and water to the feeding volume of the template solution to 12:1-12, preferably 12:6-10, and optimally 12:8.

[0016] Furthermore, the present invention also defines that the rotation speed during step 2) gel formation is 400-1200 r / min, preferably 800 r / min.

[0017] Furthermore, the present invention also limits the volume ratio of ethyl orthosilicate to anhydrous ethanol in the aging solution in step 3) to 15:25.

[0018] Furthermore, the present invention also defines the stirring time of removing the micro-droplet template solution with n-hexane in step 5) as 1-2 hours, preferably 1.5 hours.

[0019] Furthermore, the present invention also defines the application of the Pd(II) / SiO2@PEI composite aerogel obtained by the preparation method as a desulfurization adsorbent. The specific operation steps are as follows: quantitatively loading the prepared Pd(II) / SiO2@PEI composite aerogel into a fixed bed adsorption device for 2 hours. -1 Simulated gasoline containing thiophene compounds and simulated aromatic products are introduced into a fixed bed adsorption device at an air velocity of 100 ℃ for adsorption; the simulated gasoline in the embodiment of the present invention is composed of n-heptane in which thiophene sulfides are dissolved; the simulated aromatic products are composed of benzene or p-xylene in which thiophene compounds are dissolved, and the thiophene sulfides are at least one of thiophene, benzothiophene or dibenzothiophene.

[0020] By adopting the above technology, compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] The present invention uses n-heptane in which thiophene compounds are dissolved as a micro-droplet template solution, which is added to a polar solution composed of tetraethyl orthosilicate, polyethyleneimine, ethanol and water and stirred at high speed. Since the micro-droplet template solution is a non-polar solution and is immiscible with the polar solution, the non-polar solution will form tiny droplets during high-speed stirring. The tiny droplets act as template directing agents in the sol-gel process, making the pores in the sol-gel skeleton regular. The thiophene compounds dissolved in the non-polar n-heptane can be regarded as amphoteric substances. The aromatic groups of the thiophene compounds are non-polar and thus face the interior of the n-heptane micro-droplets, while the S atoms in the thiophene compounds are weakly polar and tend to be distributed on the surface of the n-heptane micro-droplets. In the sol-gel process, the S atoms in the thiophene can form hydrogen bonds with -Si-OH and -NH2 in the polyethyleneimine, and with Pd 2+ Forming S-Pd bonds and other interactions, guiding these groups and Pd 2+ Aggregate to the surface of the microdroplets, and these groups and Pd 2+ These are active sites for adsorption of thiophene compounds. When rinsed with the non-polar solvent n-hexane to remove the microdroplet template, these active sites are concentrated on the inner surface of the pores and fully exposed. Therefore, aerogels prepared using the microdroplet template method can improve the regularity of the pores, thereby improving the diffusion properties of the adsorbate. Furthermore, the active sites can be concentrated on the inner surface of the pores, effectively improving the adsorption performance of the adsorbent. This preparation method is simple to operate, environmentally friendly, uses readily available raw materials, and has low template costs. DETAILED DESCRIPTION

[0022] The present invention will be further described below with reference to specific embodiments, but the protection scope of the present invention is not limited thereto.

[0023] Examples 1 to 5: Effect of the total volume ratio of ethanol and water to the volume of the added microdroplet template (n-heptane solution of thiophene compounds) on the adsorption performance of Pd(II) / SiO2@PEI composite aerogel for thiophene sulfides in simulated gasoline.

[0024] Example 1: When the total volume ratio of ethanol and water to the added thiophene microdroplet template (n-heptane solution of dissolved thiophene) is 12:4, the TP-Pd(II) / SiO2@PEI composite aerogel prepared by the microdroplet template method is as follows:

[0025] 1) Dissolve thiophene in n-heptane to prepare a mixed solution with a concentration of 2 mg-S / g, which serves as the microdroplet template solution;

[0026] 2) Dissolve 0.077 g of polyethyleneimine in 2 ml of deionized water, then add 10 ml of anhydrous ethanol and 8 ml of tetraethyl orthosilicate. Add 4 ml of the template solution prepared in step 1) to the mixed solution. Adjust the pH of the solution to approximately 1.5 with 10% dilute hydrochloric acid solution. Stir at 800 rpm for 1.5 hours at room temperature.

[0027] 3) adding 5% ammonia water dropwise to the sol obtained in step 2) to adjust the pH of the solution to about 6.5, and allowing the solution to stand at room temperature for 10 minutes to obtain a composite alcohol gel;

[0028] 4) adding 40 ml of a mixed solution of ethyl orthosilicate and ethanol in a volume ratio of 15:25 to the composite alcohol gel obtained in step 3), and then aging the composite alcohol gel in a 40° C. water bath for 16 hours to strengthen the skeleton structure of the gel. The aged composite alcohol gel is crushed and washed to obtain an aerogel for later use;

[0029] 5) Dissolve 0.02 g of palladium chloride in a mixed solution of 2 mL of ethanol and hydrochloric acid, then add the palladium chloride solution dropwise to the aerogel from step 4), stir in a water bath at 45° C. for 6 h, and then let it stand;

[0030] 6) adding n-hexane to the sample obtained in step 5) to wash and replace it, replacing the n-hexane every 6 hours, and replacing it twice to remove the microdroplet template solution, ethanol, water and other organic molecules in the pores of the gel;

[0031] 7) The gel obtained in step 6) was placed at 120° C. and dried at normal pressure for 12 h to finally obtain a TP-Pd(II) / SiO2@PEI composite aerogel containing a thiophene microdroplet template.

[0032] Examples 2 to 5: The preparation steps are the same as those in Example 1, except that in step 2), the amount of the microdroplet template added in Example 2 is 6 ml, the amount of the microdroplet template added in Example 3 is 8 ml, the amount of the microdroplet template added in Example 4 is 10 ml, and the amount of the microdroplet template added in Example 5 is 12 ml, so that the total volume of ethanol and water in Examples 2 to 5 and the feeding volume ratio of the added microdroplet template solution are 12:6, 12:8, 12:10, and 12:12, respectively.

[0033] Comparative Example 1: The preparation method is the same as that of Example 1, except that the micro-droplet template solution prepared in step 1) does not need to be added in step 2).

[0034] Comparative Example 2: The preparation method is the same as that of Example 1, except that the template solution prepared in step 1) is a pure n-heptane solution.

[0035] In Examples 1 to 5 and Comparative Examples 1 to 2, simulated gasoline and penetration adsorption experiments were used to evaluate the adsorption performance of the prepared Pd(II) / SiO2@PEI composite aerogel for thiophene sulfides. The specific penetration adsorption experimental steps are as follows:

[0036] In the fixed bed adsorption device, the bottom layer was filled with an appropriate amount of absorbent cotton, followed by the prepared 1g Pd(II) / SiO2@PEI composite aerogel, and the top was filled with an appropriate amount of quartz sand. Before the adsorption experiment began, the adsorbent was fully moistened with n-heptane and then -1 Simulated gasoline (MF, composed of n-heptane and thiophene sulfides, including thiophene TP, benzothiophene BT, or dibenzothiophene DBT, with a sulfur concentration of 2 mg-S / g) was introduced at a space velocity of 1.5 s.m.p.m. The adsorbed simulated gasoline was collected at the reactor's lower outlet and analyzed by chromatography. The breakthrough point was determined when the sulfur concentration in the effluent reached 0.005 mg-S / g. The adsorption results are shown in Table 1.

[0037] Table 1 Effect of the total volume ratio of ethanol and water to the volume of the added thiophene microdroplet template solution on the adsorption performance of Pd(II) / SiO2@PEI composite aerogels for thiophene sulfides in simulated gasoline

[0038]

[0039]

[0040] As can be seen from Table 1, compared with Comparative Example 1 and Comparative Example 2, the adsorption capacity of the adsorbents prepared in Examples 1 to 5 is improved, and as the total volume of ethanol and water and the feed volume ratio of n-heptane decrease (the amount of micro-droplet template solution increases), the penetration adsorption capacity of Pd(II) / SiO2@PEI composite aerogel adsorbent for thiophene, benzothiophene and dibenzothiophene in simulated fuel first increases and then decreases. When the total volume of ethanol and water and the feed volume ratio of the added thiophene micro-droplet template are 12:8, the penetration adsorption capacity of thiophene, benzothiophene and dibenzothiophene reaches the maximum. Compared with Comparative Example 1, it can be seen that the addition of micro-droplet templates can effectively improve the adsorption capacity of the adsorbent, which is attributed to the fact that the addition of micro-droplet templates makes the pores in the aerogel skeleton more regular, thereby improving the diffusion performance of the adsorbate. Secondly, the S atoms in the thiophene compounds in the micro-droplet templates can guide -Si-OH, -NH2, Pd 2+ The adsorption active sites are enriched on the inner surface of the aerogel skeleton and are fully exposed, thereby improving the adsorption capacity. Compared with the adsorbent prepared with pure n-heptane as the microdroplet template in Comparative Example 2, the microdroplet template containing thiophene sulfide has a higher adsorption capacity. This is attributed to the fact that the S atoms in the thiophene in the microdroplet can form hydrogen bonds with -Si-OH and -NH2 in polyethyleneimine, and with Pd2+ Forming S-Pd bonds and other interactions, guiding these groups and Pd 2+ Aggregate to the surface of the microdroplets, and these groups and Pd 2+ These are the active sites for adsorbing thiophene compounds. When rinsed with a non-polar solvent, n-hexane, and the microdroplet template is removed, these active sites are enriched on the inner surface of the pores and fully exposed, thereby effectively improving the adsorption performance of the adsorbent.

[0041] Examples 6-7: Effects of different micro-droplet template compositions on the adsorption performance of thiophene sulfides by Pd(II) / SiO2@PEI composite aerogels.

[0042] Example 6: The preparation method is the same as that of Example 3, except that the template selected in step 1) is a benzothiophene solution dissolved in n-heptane.

[0043] Example 7: The preparation method is the same as that of Example 3, except that the template solution selected in step 1) is a dibenzothiophene solution dissolved in n-heptane.

[0044] The adsorbents prepared in Examples 6 to 7 were evaluated in the same manner as in Examples 1 to 5. The specific results are shown in Table 2.

[0045] Table 2 Effect of different microdroplet templates on the adsorption performance of thiophene sulfides on Pd(II) / SiO2@PEI composite aerogel.

[0046]

[0047] As shown in Table 2, the Pd(II) / SiO2@PEI composite aerogels synthesized after adding different micro-droplet templates have different adsorption effects on thiophene sulfides in fuel. Among them, the adsorbent prepared with thiophene micro-droplet template has the best adsorption effect on thiophene, benzothiophene or dibenzothiophene. This may be attributed to the fact that compared with benzothiophene and dibenzothiophene, thiophene molecules are smaller and the number of them in the micro-droplet template of the same size is relatively large, which makes -Si-OH, -NH2 and Pd 2+ The aggregation of isoactive sites is greater, thereby increasing the adsorption capacity.

[0048] Examples 8-9: Adsorption performance of Pd(II) / SiO2@PEI composite aerogel adsorbent prepared by micro-droplet template method for thiophene compounds in simulated aromatic hydrocarbon products. The adsorbent used is the same as that in Example 3.

[0049] Comparative Examples 3-4: Adsorption performance of Pd(II) / SiO2@PEI composite aerogel adsorbent prepared by conventional method for thiophene compounds in simulated aromatic hydrocarbon products. The adsorbent used is the same as that in Comparative Example 1. The adsorption results are shown in Table 3.

[0050] Table 3 Adsorption performance of Pd(II) / SiO2@PEI composite aerogels prepared by microdroplet template method and conventional method for thiophene compounds in simulated aromatic products

[0051]

[0052]

[0053] It can be seen from Table 3 that, similar to the results of removing thiophene compounds from simulated gasoline, the Pd(II) / SiO2@PEI composite aerogel prepared by the droplet template method has better adsorption effect in aromatic hydrocarbons than the Pd(II) / SiO2@PEI composite aerogel prepared by the conventional method, which further illustrates that the aerogel prepared by the micro-droplet template method can improve the regularity of the pores to improve the diffusion performance of the adsorbate. In addition, the adsorption active sites can be enriched on the inner surface of the pores, thereby effectively improving the adsorption performance of the adsorbent.

[0054] Examples 10-13: Effect of sol rotation speed in the micro-droplet template method on the adsorption performance of thiophene sulfides by Pd(II) / SiO2@PEI composite aerogel adsorbent prepared by the micro-droplet template method.

[0055] The preparation steps are the same as those in Example 3, except that after the microdroplet template is added in step 2), the rotation speed during stirring is 400 r / min in Example 10, 600 r / min in Example 11, 1000 r / min in Example 12, and 1200 r / min in Example 13.

[0056] The adsorbents prepared in Examples 10 to 13 were evaluated in the same manner as in Examples 1 to 5. The specific results are shown in Table 4.

[0057] Table 4 Adsorption performance of Pd(II) / SiO2@PEI composite aerogels prepared at different sol rotation speeds in the microdroplet template method for thiophene sulfides in simulated gasoline

[0058]

[0059]

[0060] It can be seen from Table 4 that with the increase of the rotation speed, the penetration adsorption capacity of thiophene, benzothiophene and dibenzothiophene will first increase and then decrease. When the rotation speed is 800 r / min, the penetration adsorption capacity of thiophene sulfides is the best. In this state, the micro-droplet balls formed by the non-polar micro-droplet template after stirring and the three-dimensional network structure of the aerogel maintain the most stable state, so the preferred rotation speed is 800 r / min.

Claims

1. A method for preparing Pd(II) / SiO2@PEI composite aerogel using a micro-droplet template method, wherein the composite aerogel is prepared by a micro-droplet template method based on a sol-gel method combined with a normal pressure drying method, characterized in that The specific steps include: 1) Preparation of microdroplet template solution: Dissolve a certain amount of thiophene compound in n-heptane to form a template solution; 2) Preparing a gel containing microdroplet templates: adding a certain amount of the template solution from step 1) to a polar solution obtained by mixing an amine source, anhydrous ethanol, a silicon source, and water, and stirring at a certain speed under acidic conditions. Since the template solution is a non-polar solution, microdroplets will form when stirred in the polar solution, thereby obtaining a SiO2@PEI sol containing microdroplet templates. The pH is adjusted to cause gelation to obtain a composite alcohol gel; 3) Aging: adding an aging solution composed of anhydrous ethanol and ethyl orthosilicate to the composite alcohol gel prepared in step 2) to perform aging to strengthen its skeleton structure; 4) Modification: Grind and wash the aged composite alcohol gel from step 3), dissolve the palladium source in water, and then add the palladium source to the washed composite alcohol gel, stir, and allow to stand. 5) Removing the microdroplet template: adding n-hexane to the gel obtained in step 4) and stirring to displace the microdroplet template in the pores; 6) Drying: The composite alcohol gel obtained in step 5) was placed in a drying oven at 120° C. and dried under normal pressure to remove the residual microdroplet template, thereby obtaining a Pd(II) / SiO2@PEI composite aerogel.

2. The method for preparing Pd(II) / SiO2@PEI composite aerogel by using a micro-droplet template method according to claim 1, characterized in that In step 1), the micro-droplet template solution is an n-heptane solution in which a thiophene compound is dissolved. The thiophene compound is at least one of thiophene, benzothiophene or dibenzothiophene. The concentration of the thiophene compound in the micro-droplet template solution is 2 mg-S / g.

3. The method for preparing Pd(II) / SiO2@PEI composite aerogel by using a micro-droplet template method according to claim 1, characterized in that In step 2), the silicon source is ethyl orthosilicate, and the amine source is polyethyleneimine solution.

4. The method for preparing Pd(II) / SiO2@PEI composite aerogel by using a micro-droplet template method according to claim 1, characterized in that The palladium source in step 4) is palladium chloride.

5. The method for preparing Pd(II) / SiO2@PEI composite aerogel by using a micro-droplet template method according to any one of claims 1 to 4, characterized in that The molar ratio of the amine source to the ethyl orthosilicate is 1:400, the molar ratio of the palladium source to the silicon source is 1:316, and the volume ratio of the total volume of anhydrous ethanol and water to the volume of the template solution is 12:1-12.

6. The method for preparing Pd(II) / SiO2@PEI composite aerogel by using a micro-droplet template method according to any one of claims 1 to 4, characterized in that Step 2) The rotation speed during gel formation is 400 to 1200 r / min.

7. The method for preparing Pd(II) / SiO2@PEI composite aerogel by using a micro-droplet template method according to any one of claims 1 to 4, characterized in that The volume ratio of ethyl orthosilicate to anhydrous ethanol in the aging solution in step 3) is 15:

25.

8. The method for preparing Pd(II) / SiO2@PEI composite aerogel by using a micro-droplet template method according to any one of claims 1 to 4, characterized in that In step 5), the stirring time for removing the micro-droplet template solution with n-hexane is 1-2 hours.

9. Application of the Pd(II) / SiO2@PEI composite aerogel obtained by the preparation method according to claim 1 as a desulfurization adsorbent, characterized in that The specific steps are as follows: The prepared Pd(II) / SiO2@PEI composite aerogel was quantitatively loaded into a fixed bed adsorption device and heated for 2 h. -1 Simulated gasoline and simulated aromatic products containing thiophene compounds were introduced into the fixed bed adsorption device at an air velocity of 100 ℃ for adsorption.

10. The use according to claim 9, characterized in that The simulated gasoline is composed of n-heptane dissolving thiophene sulfides; the simulated aromatics product is composed of benzene or p-xylene dissolving thiophene compounds, and the thiophene sulfides are at least one of thiophene, benzothiophene or dibenzothiophene.

Images