Preparation and application of halloysite composite nanomaterial based on electrostatic adsorption of cationic surfactant

Abstract

This invention discloses the preparation and application of halloysite composite nanomaterials based on electrostatic adsorption of cationic surfactants, belonging to the field of nanomaterial surface modification technology. In this invention, a quaternary ammonium polyether cationic surfactant is stirred with alkali-activated halloysite nanotubes in an aqueous phase. The surfactant is loaded onto the outer surface of the halloysite nanotubes through electrostatic adsorption. After separation, washing, and drying, the halloysite composite nanomaterial modified with electrostatic adsorption cationic surfactant is obtained. The alkali activation treatment of the halloysite nanotubes enhances the negative charge on their outer walls, enabling the quaternary ammonium polyether cationic surfactant to be efficiently and stably loaded onto the outer walls of the halloysite nanotubes (HNTs) through electrostatic adsorption, forming a well-defined inorganic reverse micelle composite nanomaterial. The resulting composite nanomaterial exhibits good interfacial activity and emulsifying properties, and can efficiently stabilize Pickering emulsions, expanding its application prospects in the field of emulsion catalysis.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterial surface modification technology, specifically relating to the preparation and application of halloysite composite nanomaterials based on electrostatic adsorption of cationic surfactants. Background Technology

[0002] Halloysite nanotubes (HNTs) are naturally occurring layered aluminosilicate minerals, typically exhibiting a tubular structure with a length of 1–2 μm, an outer diameter of 50–100 nm, and an inner diameter of 10–50 nm. Their molecular formula is Al₂Si₂O₅(OH)₄·nH₂O, and their structural unit consists of an outer layer of Si-O tetrahedra and an inner layer of Al-OH octahedra. Due to lattice mismatch between the different constituent layers, the layered structure curls up to form a hollow tubular morphology. The chemical composition of HNTs differs significantly between their inner and outer surfaces: the outer wall is dominated by silicon-oxygen bonds (Si-O-Si) and silanol groups (Si-OH), while the inner wall is dominated by aluminum hydroxyl groups (Al-OH). This structural difference leads to differentiated surface charges in HNTs under different pH conditions—the outer wall silanol groups dissociate, making them negatively charged, while the inner wall aluminum hydroxyl groups protonate, making them positively charged. This characteristic naturally endows HNTs with the ability to selectively adsorb cations or anions, providing a structural basis for functional modification.

[0003] Cationic surfactants are widely used for the functional modification of the outer surface of hydrogen nitrates (HNTs) due to their excellent interfacial activity, positive charge, and designable molecular structure. Loading cationic surfactants onto the outer wall of HNTs via electrostatic adsorption can impart tunable amphiphilicity to the material while maintaining the integrity of the internal cavity structure, expanding its application potential in Pickering emulsion stabilization, interfacial catalysis, antibacterial materials, and oilfield chemicals. However, existing composite systems based on HNTs and cationic surfactants still have the following shortcomings:

[0004] First, the compatibility between surfactants and carriers needs optimization. Existing studies mostly use commercially available cationic surfactants (such as hexadecyltrimethylammonium bromide, dodecyltrimethylammonium bromide, etc.) for physical mixing or simple adsorption, without designing molecular structures to address the interfacial characteristics of HNTs, such as charge density, surface curvature, and silanol distribution. This results in low adsorption efficiency of surfactants on the outer wall of HNTs, a loose adsorption layer structure, and difficulty in forming stable functionalized interfaces.

[0005] Second, the adsorption stability and controllability are insufficient. Under physical adsorption, the surfactant and HNTs are bound only by electrostatic attraction and hydrophobic interaction, resulting in relatively weak binding forces. In complex operating environments (such as high salt, high shear, and extreme pH conditions), desorption easily occurs, leading to material performance degradation. At the same time, existing methods lack effective means to control the adsorption amount, arrangement, and hydrophobicity of surfactants on the HNT surface, making it difficult to achieve precise design of interfacial properties.

[0006] Third, the functional integration is low. Existing modification strategies are mostly limited to the single function of surface wettability regulation, failing to fully utilize the molecular designability of cationic surfactants to integrate functions such as hydrophobic modification, charge regulation, and catalytic active site anchoring. This limits the performance of composite materials in high-end applications such as heterogeneous catalysis and interfacial reactions.

[0007] To address the aforementioned issues, if cationic surfactants with suitable charge density, molecular configuration, and hydrophobic chain length can be designed and synthesized based on the charge distribution characteristics, geometric structure, and interfacial chemical properties of the outer surface of HNTs, and a controllable electrostatic self-assembly process can be established, it is expected to significantly improve the interfacial compatibility between surfactants and HNTs and the overall performance of composite materials.

[0008] Based on this, the present invention proposes to synthesize a class of quaternary ammonium polyether cationic surfactants, enhance the negative charge on the outer surface of HNTs through alkali activation, and achieve efficient and stable loading of surfactants on the outer wall by utilizing electrostatic adsorption, thereby constructing an inorganic reverse micelle material with controllable structure and tunable interface properties, and further expanding its application potential in Pickering emulsion catalysis and other fields. Summary of the Invention

[0009] To address the shortcomings of existing technologies, this invention aims to provide a method for preparing and applying halloysite composite nanomaterials based on electrostatic adsorption of cationic surfactants. First, halloysite nanotubes are alkali-activated to enhance the negative charge on their outer walls. Then, using terminal amino polyether M2070 as a raw material, three terminal tertiary amino polyether intermediates are synthesized via reductive amination reactions with paraformaldehyde, n-butyraldehyde, and n-octaldehyde, respectively. These intermediates are then protonated with hydrochloric acid to obtain a quaternary ammonium polyether cationic surfactant. Utilizing electrostatic adsorption, this cationic surfactant is efficiently loaded onto the outer surface of the halloysite nanotubes, achieving hydrophobicity and functional modification of the outer wall, thus constructing an inorganic reverse micelle composite nanomaterial. The modified halloysite nanotubes exhibit good interfacial activity and Pickering emulsion stability. After loading with palladium, they can be used to catalyze the selective hydrogenation reaction of p-chloronitrobenzene, demonstrating high conversion rate, high selectivity, and excellent recyclability. This invention provides an efficient modification strategy for the outer surface of halloysite nanotubes, expanding its application prospects in the fields of heterogeneous catalysis and interfacial reactions.

[0010] To achieve the above objectives, the present invention adopts the following technical solution:

[0011] A method for preparing halloysite composite nanomaterials based on electrostatic adsorption of cationic surfactants includes the following steps:

[0012] (1) Alkali activation treatment was performed on halloysite nanotubes to enhance the negative charge on the outer wall; (2) Quaternary ammonium polyether cationic surfactant was electrostatically adsorbed with halloysite nanotubes activated in step (1) in an aqueous phase.

[0013] (3) Separate, wash and dry to obtain halloysite nanotube inorganic reverse micelle composite nanomaterials with electrostatic adsorption of cationic surfactants.

[0014] As a preferred embodiment of the present invention, the alkaline activation treatment in step (1) is to adjust the pH to 9-11 with an alkaline solution.

[0015] As a preferred embodiment of the present invention, the electrostatic adsorption reaction temperature in step (2) is room temperature, the aqueous phase stirring reaction time is 12-24 hours, and the pH is 7-9.

[0016] As a preferred embodiment of the present invention, the preparation method of the quaternary ammonium polyether cationic surfactant in step (2) includes the following steps:

[0017] S1: Add the amino-terminated polyether M2070 dissolved in the solvent to the autoclave, then add the catalyst Raney Ni and aldehyde compounds, seal the autoclave and replace the gas inside the autoclave with N2 and H2 in turn more than 3 times, and stir magnetically at a certain temperature for a certain time.

[0018] S2: After the reaction is complete, the temperature is controlled to a certain level, and the solvent is removed by rotary evaporation under reduced pressure to obtain a terminal tertiary amine polyether surfactant.

[0019] S3: Dissolve the synthesized tertiary amine polyether surfactant in deionized water, then add hydrochloric acid to the above solution at a molar ratio of tertiary amine group to hydrochloric acid of 1:1.1, and sonicate the sample to obtain an aqueous solution containing quaternary ammonium polyether surfactant.

[0020] In a preferred embodiment of the present invention, the aldehyde compound in step S1 includes any one of paraformaldehyde, n-butyraldehyde, and n-octanaldehyde.

[0021] In a preferred embodiment of the present invention, the solvent in step S1 is methanol.

[0022] In a preferred embodiment of the present invention, the reaction temperature in step S1 is 140°C, the reaction time is 5-10 h, and the H2 pressure is 1.6 MPa.

[0023] In a preferred embodiment of the present invention, the temperature of rotary evaporation in step S2 is 50°C.

[0024] A quaternary ammonium polyether cationic surfactant prepared by the above method, wherein the molecular structure of the quaternary ammonium polyether cationic surfactant is as follows:

[0025] Among them, when the aldehyde compound is paraformaldehyde, n=1; when it is butyraldehyde, n=4; and when it is octanal, n=8.

[0026] Halloysite composite nanomaterial modified with electrostatic adsorption cationic surfactant prepared according to the above method; the halloysite composite nanomaterial includes a halloysite nanotube matrix and a quaternary ammonium polyether cationic surfactant loaded on the outer surface of the halloysite nanotubes through electrostatic adsorption; the loading amount of the quaternary ammonium polyether cationic surfactant is 0.5-1 mmol / g halloysite nanotubes.

[0027] The application of the above-mentioned electrostatically adsorbed cationic surfactant-modified halloysite composite nanomaterial in Pickering emulsion catalysis, including applications in Pickering emulsion catalyst carriers, antibacterial materials, emulsion stabilizers, oilfield chemicals, or wastewater treatment.

[0028] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0029] 1. This invention, for the first time, targets the chemical composition and charge distribution characteristics of the outer wall of halloysite nanotubes, modulating its surface negative charge through alkali activation treatment, and designs and synthesizes a matching quaternary ammonium polyether cationic surfactant. This surfactant possesses suitable charge density, molecular configuration, and hydrophobic chain length, enabling it to be efficiently and stably loaded onto the outer surface of halloysite through electrostatic adsorption. This overcomes the shortcomings of traditional physical adsorption methods, such as low adsorption efficiency, weak binding force, and loose structure, achieving controllable hydrophobicization and functional modification of the outer wall of halloysite nanotubes.

[0030] 2. This invention utilizes electrostatic self-assembly technology to directionally anchor quaternary ammonium polyether cationic surfactants onto the outer surface of halloysite nanotubes, forming a well-defined and stable inorganic reverse micelle composite nanomaterial. In this material, the hydrophilic quaternary ammonium head groups are adsorbed onto the inorganic tube wall, while the hydrophobic polyether long chains extend outward, forming a micelle-like reverse configuration, endowing the material with excellent amphiphilicity and interface control capabilities.

[0031] 3. The halloysite composite nanomaterials modified by this invention possess excellent interfacial activity and emulsifying properties, enabling efficient stabilization of Pickering emulsions. They are suitable for heterogeneous catalysis, interfacial reactions, and other systems, expanding their application prospects in emulsion catalysis. Compared to commercially available cationic surfactants (such as DTAB), the results combined with Zeta potential analysis indicate that the modified halloysite composite nanomaterials have superior catalytic hydrogenation potential. Attached Figure Description

[0032] Figure 1 shows the 1H NMR spectrum of the C1-M2070 terminal tertiary amine polyether surfactant from Example 1.

[0033] Figure 2 shows Example 1 C1 + -H NMR spectrum of M2070 quaternary ammonium polyether surfactant.

[0034] Figure 3 shows the flight mass spectrum of polyetheramine M2070.

[0035] Figure 4. Flight mass spectrum of C1-M2070 terminal tertiary amine polyether surfactant. Detailed Implementation

[0036] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0037] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0038] It should be clarified that the embodiments listed herein are merely illustrative examples of the technical solutions of the present invention, and not an exhaustive limitation on the scope of protection. Based on the general understanding of the prior art by those skilled in the art, any technical solutions derived from parameter adjustments, component substitutions, or process optimizations of the embodiments through conventional experimental methods without departing from the core concept of the present invention are all considered to fall within the scope of protection of the claims of the present invention. Unless otherwise expressly defined, the technical terms used herein shall be interpreted according to their common meaning in the art; if the same term has multiple interpretations, the meaning defined in the context of this specification shall prevail.

[0039] Example 1

[0040] The preparation method of the quaternary ammonium polyether cationic surfactant in this embodiment includes the following steps:

[0041] S1: 20 g of amino-terminated polyether M2070 (10 mmol), 5 wt.% catalyst Raney Ni, 2 g of paraformaldehyde (66 mmol), and 100 mL of anhydrous methanol were sequentially added to a 500 mL magnetically stirred reactor. The reactor was sealed, and the gas inside was replaced with N2 and H2 alternately at least three times, ultimately maintaining an H2 pressure of 1.6 MPa. The reactor temperature was raised to 130℃, and the reaction time was 5 h. Timing was started at 1000 rpm. After the reaction was complete, the reactor was allowed to cool to room temperature, and the pressure was safely released. The catalyst Raney Ni was recovered by N2 pressure filtration. The filtered reaction solution was then solvent-removed, yielding a transparent viscous liquid, which was the target product, N,N-dimethyl polyetheramine surfactant C1-M2070, with a yield of 99%.

[0042] S2: Dissolve C1-M2070 in deionized water, then add hydrochloric acid (36 wt.%) to the solution at a molar ratio of 1:1.1, and sonicate the sample for 3 min to obtain C1 containing quaternary ammonium polyether surfactant. + -An aqueous solution of M2070.

[0043] The preparation of halloysite composite nanomaterials for electrostatic adsorption of cationic surfactants in this embodiment includes the following steps:

[0044] S3: Disperse 5g halloysite nanotubes (HNTs) in 500mL of deionized water, sonicate for 15min, adjust pH to 10 with 0.1M NaOH, stir for 3h, centrifuge and wash until neutral, redisperse in water, and prepare a 2wt% dispersion for later use.

[0045] S4: Take 0.17g of C1 synthesized in Example 1 + -M2070 was dissolved in 10 mL of deionized water to prepare an 8.3 mM solution, which was then ultrasonically dispersed. Under stirring conditions at room temperature (25°C), 5 mL of the halloysite dispersion was added dropwise to an 8.3 mM Cl solution. + The solution was added dropwise to M2070. After the addition was complete, the pH was adjusted to 8 with 0.1M NaOH, and the reaction was continued with stirring for 12 hours. After the reaction was completed, the mixture was centrifuged at 8000 rpm for 10 minutes, washed four times with deionized water, vacuum dried at 60℃ for 12 hours, and ground to obtain halloysite composite nanomaterials with electrostatic adsorption of cationic surfactants, denoted as HNTs-C1. + .

[0046] Figure 1 Analysis of the 1H NMR spectrum of C1-M2070: Through detailed analysis, the singlet at 3.39 ppm was determined to belong to the terminal methoxy group, with an integrated area of ​​3H. Based on this, a singlet at 2.24 ppm belonging to the two methyl groups of the tertiary amine structure was further identified, with an integrated area of ​​6H, thus confirming the synthesis of the N,N-dimethyl structure.

[0047] Figure 2 C1 + - Deciphering the 1H NMR spectrum of M2070: When the tertiary amine structure transforms into a quaternary ammonium structure, the chemical environment of the H atoms on adjacent carbon atoms also changes. Therefore, in the analysis 1 When analyzing ¹H NMR spectra, it is crucial to pay close attention to the chemical shift changes of H atoms adjacent to the carbon atoms in tertiary amines. Careful analysis is essential. Figure 2 It was found that the H atoms on the carbons adjacent to the tertiary amine shifted to a lower field after quaternization modification. This result confirms that terminal tertiary amine polyether surfactants were successfully transformed into quaternary ammonium polyether surfactants C1. + -M2070.

[0048] The comparison of the 1H NMR spectrum analysis results of the two substances proves that Example 1 successfully prepared a quaternary ammonium polyether cationic surfactant.

[0049] Figure 3 and Figure 4 The results are obtained by flight mass spectrometry for polyetheramine M2070 and the terminal tertiary amine polyether surfactant prepared in Example 1, respectively. Figure 3The molecular weight of polyetheramine M2070 can be found to be approximately 2000. Figure 4 The molecular weight of the terminal tertiary amine polyether surfactant C1-M2070 can be found to be 2028, which is consistent with the molecular structure of the compound.

[0050] Example 2:

[0051] The difference from Example 1 is that n-butyraldehyde is replaced in S1, the temperature is changed to 150°C, and the reaction time is 10 hours. The other parameters and steps are the same as in Example 1.

[0052] The final C4 obtained + -M2070 is a pure quaternary ammonium polyether surfactant with a yield of 98%.

[0053] Example 3:

[0054] The difference from Example 1 is that S1 is replaced with n-octanal, the temperature is changed to 150°C, and the reaction time is 10 hours. The other parameters and steps are the same as in Example 1.

[0055] The final C8 obtained + -M2070 is a pure quaternary ammonium polyether surfactant with a yield of 92%.

[0056] Example 4:

[0057] The difference from Example 1 is that the reaction time in S1 is 6 hours, while the other parameters and steps are the same as in Example 1.

[0058] The final C1 + -M2070 is a pure quaternary ammonium polyether surfactant with a yield of 99%.

[0059] Example 5:

[0060] The difference from Example 1 is that n-butyraldehyde is replaced in S1, the temperature is changed to 140°C, and the reaction time is 10 hours. The other parameters and steps are the same as in Example 1.

[0061] The final C4 obtained + -M2070 is a pure quaternary ammonium polyether surfactant with a yield of 97%.

[0062] Example 6:

[0063] The difference from Example 1 is that n-butyraldehyde is replaced in S1, the temperature is changed to 140°C, and the reaction time is 11 hours. The remaining parameters and steps are the same as in Example 1.

[0064] The final C4 obtained +-M2070 is a pure quaternary ammonium polyether surfactant with a yield of 97%.

[0065] Example 7:

[0066] The difference from Example 1 is that n-butyraldehyde is replaced in S1, the temperature is changed to 140°C, and the reaction time is 8 hours. The other parameters and steps are the same as in Example 1.

[0067] The final C4 obtained + -M2070 is a pure quaternary ammonium polyether surfactant with a yield of 89%.

[0068] Example 8:

[0069] The difference from Example 1 is that n-butyraldehyde is replaced in S1, the temperature is changed to 140°C, and the reaction time is 8 hours. The other parameters and steps are the same as in Example 1.

[0070] The final C4 obtained + -M2070 is a pure quaternary ammonium polyether surfactant with a yield of 89%.

[0071] Example 9:

[0072] The difference from Example 1 is that S1 is replaced with n-octanal, the temperature is changed to 160℃, and the reaction time is 10h. The other parameters and steps are the same as in Example 1.

[0073] The final C8 obtained + -M2070 is a pure quaternary ammonium polyether surfactant with a yield of 93%.

[0074] Example 10:

[0075] The difference from Example 1 is that S1 is replaced with n-octanal, the temperature is changed to 150°C, and the reaction time is 11h. The remaining parameters and steps are the same as in Example 1.

[0076] The final C8 obtained + -M2070 is a pure quaternary ammonium polyether surfactant with a yield of 93%.

[0077] Comparative example: Commercially available cationic surfactant (DTAB) was used as the control group.

[0078] The DTAB cationic surfactant from the comparative example and C1 from Example 1 were used. + The Zeta potential of the M2070 cationic surfactant was tested, and the specific procedure is as follows:

[0079] Zeta potential testing method: Halloysite nanotubes (HNTs) are dispersed in different concentrations of DTAB or Cl. + A series of surface-modified HNT dispersions were prepared using an aqueous solution of the cationic surfactant M2070. The Zeta potentials of different samples were measured at 25.0±0.1℃ using an electrophoretic light scattering analyzer (Malvern Zetasizer Nano ZS90) at electrophoretic light scattering. Before measurement, the instrument was calibrated using a Zeta potential standard. The uniformly dispersed sample solution was slowly injected into the U-shaped capillary sample cell, ensuring no air bubbles were generated, and the sample cell was inserted into the instrument's sample slot. Test parameters were set as follows: temperature 25.0±0.1℃, equilibration time 120 seconds, automatic test mode, and three consecutive measurements for each sample. The average value was taken as the result, and the error between two consecutive measurements should not exceed 5mV or the relative standard deviation should not exceed 5%. Fresh samples were used after each test to avoid cross-contamination. Experimental data are shown in Table 1.

[0080] Table 1. Zeta potential test results (pH=7, deionized water)

[0081]

[0082] As shown in Table 1, in the low concentration range (0-1.0 mmol / L) during the charge neutralization phase, compared to the commercially available cationic surfactant DTAB, the synthesized C1 + -M2070 quaternary ammonium polyether surfactant exhibits stronger adsorption capacity and a faster rate of zeta potential rise, indicating a stronger affinity for the outer surface of halloysite nanotubes. C1 + - The saturated adsorption zeta potential of M2070 reached +36.8 mV, which is 12.0 mV higher than that of DTAB (+24.8 mV); C1 + -M2070 reaches saturation at 5-6 mmol / L, while DTAB requires 8-10 mmol / L. Therefore, C1 + -M2070 cationic surfactant forms a denser and more stable positively charged layer.

[0083] Application Example 1

[0084] HNTs-C1 in this application example + The selective hydrogenation of p-chloronitrobenzene to p-chloroaniline via a Pd-supported metal-stabilized Pickering emulsion includes the following steps:

[0085] Step (1): Catalyst Pd / HNTs-C1 + Preparation of M2070:

[0086] First, prepare 8.3 mM Cl.+ -10 mL of aqueous solution of M2070 cationic surfactant was ultrasonically dispersed.

[0087] Next, 0.212 g of halloysite nanotubes (HNTs) particles that have undergone alkali activation treatment were added to the pressure-resistant tube, followed by 9 mL of the above-mentioned surfactant aqueous solution, and stirred overnight to ensure that the surfactant was fully adsorbed on the outer surface of the HNTs.

[0088] Then, 100 μL of Na₂PdCl₄ aqueous solution (0.1 mol / L) was added to the above solution, and the mixture was stirred for 2 h to allow Pd to react. 2+ The impregnation is applied to the outer surface of HNTs. After impregnation, Pd / HNTs-C1 is obtained. + -M2070 catalyst aqueous solution.

[0089] Step (2): Pickering emulsion catalysis for selective hydrogenation of chloronitrobenzene

[0090] 4 mmol of p-chloronitrobenzene, 1 mmol of m-xylene (internal standard), 10 mL of toluene, and 10 mL of catalyst aqueous solution were added separately to 100 mL magnetically stirred reactors and homogenized at 10,000 rpm for 3 min to obtain a Pickering emulsion. The reactor was then sealed and the gas inside was purged. The reaction was carried out at 25 °C and 2 MPa H₂ pressure with stirring at 1000 rpm for 3 h. After the reaction, the products were separated by centrifugation, and the upper oil phase was analyzed by gas chromatography to calculate the conversion and selectivity of p-chloronitrobenzene. The lower catalyst aqueous solution could be recycled.

[0091] The conversion rate of the hydrogenation reaction of p-chloronitrobenzene in this application example was determined to be 99.40% and the selectivity for chloroaniline to be 84.84% using a Shimadzu GC gas chromatograph (GC-FID, HP-5 capillary column). The catalyst (Pd / HNTs-C1) after the reaction was collected... + -M2070) was centrifuged, washed three times with deionized water, and vacuum dried at 60℃. It was then reused under the same reaction conditions, with catalytic performance measured every other cycle. Experiments showed that Pd / HNTs-C1 + The M2070 catalyst initially achieved a 99.40% conversion rate for chloronitrobenzene and a 84.84% selectivity for chloroaniline. After five cycles, the conversion rate remained at 95.32%, and the selectivity at 82.51%. After ten cycles, the conversion rate was 92.14%, and the selectivity at 80.81%. These results indicate that the Pd / HNTs-C1 catalyst prepared in this invention... + The M2070 catalyst exhibits good stability during recycling and the ability to maintain catalytic activity.

[0092] Application Example 2:

[0093] The difference from Application Example 1 is that in step (1), the cationic surfactant used is C4. + -M2070, the cationic surfactant aqueous solution was prepared with a concentration of 12.2 mM, and the remaining parameters and steps were the same as those in the halloysite modification method in Example 1, to obtain Pd / HNTs-C4. + -M2070 catalyst aqueous solution.

[0094] The conversion rate of the hydrogenation reaction of p-chloronitrobenzene in this application example was determined to be 99.93% using a Shimadzu GC gas chromatograph, and the selectivity for p-chloroaniline was 84.71%. The catalyst (Pd / HNTs-C4) after the reaction was collected... + -M2070 was centrifuged, washed three times with deionized water, and vacuum dried at 60°C. It was then reused under the same reaction conditions, with catalytic performance measured every other cycle. Experiments showed that Pd / HNTs-C4... + The M2070 catalyst initially achieved a 99.93% conversion rate for chloronitrobenzene and a 84.71% selectivity for chloroaniline. After five cycles, the conversion rate remained at 97.35%, and the selectivity at 82.94%. After ten cycles, the conversion rate reached 95.46%, and the selectivity at 81.28%. These results demonstrate that the Pd / HNTs-C4 catalyst prepared in this invention… + The M2070 catalyst exhibits good stability during recycling and the ability to maintain catalytic activity.

[0095] Application Example 3:

[0096] The difference from Application Example 1 is that in step (1), the cationic surfactant used is C8. + -M2070, the cationic surfactant aqueous solution was prepared with a concentration of 16.6 mM, and the remaining parameters and steps were the same as those in the halloysite modification method in Example 1, to obtain Pd / HNTs-C8. + -M2070 catalyst aqueous solution.

[0097] The conversion rate of the hydrogenation reaction of p-chloronitrobenzene in this application example was determined to be 99.07% using a Shimadzu GC gas chromatograph, and the selectivity for p-chloroaniline was 85.62%. The catalyst (Pd / HNTs-C8) after the reaction was collected... + -M2070) was centrifuged, washed three times with deionized water, and vacuum dried at 60℃. It was then reused under the same reaction conditions, with catalytic performance measured every other cycle. Experiments showed that Pd / HNTs-C8 +The M2070 catalyst initially achieved a 99.07% conversion rate for chloronitrobenzene and a 85.62% selectivity for chloroaniline. After five cycles, the conversion rate remained at 96.29%, and the selectivity at 83.14%. After ten cycles, the conversion rate reached 95.78%, and the selectivity at 80.28%. These results demonstrate that the Pd / HNTs-C8 catalyst prepared in this invention… + The M2070 catalyst exhibits good stability during recycling and the ability to maintain catalytic activity.

[0098] Application Example 4:

[0099] The difference from Application Example 1 is that the amount of halloysite nanotubes used in step (1) is changed to 0.106g, while the remaining parameters and steps are the same as the halloysite modification method in Example 1.

[0100] The conversion rate of the hydrogenation reaction of p-chloronitrobenzene in this application example was determined to be 93.21% and the selectivity for p-chloroaniline was 80.14% using a Shimadzu GC gas chromatograph. The catalyst (Pd / HNTs-C1) after the reaction was taken... + -M2070) was centrifuged, washed three times with deionized water, and vacuum dried at 60°C. It was then reused under the same reaction conditions, with catalytic performance measured every few cycles. Experiments showed that the catalyst initially achieved a 93.21% conversion rate for chloronitrobenzene and a 80.14% selectivity for chloroaniline. After five cycles, the conversion rate remained at 90.23% and the selectivity at 77.16%. After ten cycles, the conversion rate reached 85.58% and the selectivity remained at 75.23%. These results indicate that the Pd / HNTs-C1 catalyst prepared in this invention... + The M2070 catalyst exhibits good stability during recycling and the ability to maintain catalytic activity.

[0101] Application Example 5:

[0102] The difference from Application Example 1 is that the reaction pressure in step (1) is 1 MPa and the reaction time is 5 h. The other parameters and steps are the same as those in the halloysite modification method in Example 1.

[0103] The conversion rate of the hydrogenation reaction of p-chloronitrobenzene in this application example was determined to be 94.23% and the selectivity for p-chloroaniline to be 82.12% using a Shimadzu GC gas chromatograph. The catalyst (Pd / HNTs-C1) after the reaction was taken... +-M2070) was centrifuged, washed three times with deionized water, and vacuum dried at 60°C. It was then reused under the same reaction conditions, with catalytic performance measured every few cycles. Experiments showed that the catalyst in this application example achieved a 94.23% conversion rate for chloronitrobenzene and a 82.12% selectivity for chloroaniline upon initial use. After five cycles, the conversion rate remained at 91.33%, and the selectivity at 78.66%. After ten cycles, the conversion rate was 88.56%, and the selectivity at 73.24%. These results indicate that the Pd / HNTs-C1 catalyst prepared in this invention... + The M2070 catalyst exhibits good stability during recycling and the ability to maintain catalytic activity.

[0104] Application Example 6:

[0105] The difference from Application Example 1 is that the reaction pressure in step (1) is 1 MPa and the reaction time is 12 h. The other parameters and steps are the same as those in the halloysite modification method in Example 1.

[0106] The conversion rate of the hydrogenation reaction of p-chloronitrobenzene in this application example was determined to be 95.13% and the selectivity for p-chloroaniline to be 81.34% using a Shimadzu GC gas chromatograph. The catalyst (Pd / HNTs-C1) after the reaction was taken... + -M2070) was centrifuged, washed three times with deionized water, and vacuum dried at 60°C. It was then reused under the same reaction conditions, with catalytic performance measured every few cycles. Experiments showed that the catalyst in this application example achieved a 95.13% conversion rate for chloronitrobenzene and a 81.34% selectivity for chloroaniline upon initial use. After five cycles, the conversion rate remained at 92.63%, and the selectivity at 77.46%. After ten cycles, the conversion rate reached 89.36%, and the selectivity at 71.28%. These results indicate that the Pd / HNTs-C1 catalyst prepared in this invention... + The M2070 catalyst exhibits good stability during recycling and the ability to maintain catalytic activity.

[0107] The quaternary ammonium salt cationic surfactant synthesized in this invention exhibits significantly better electrostatic adsorption efficiency on the outer wall of halloysite than commercially available products, and the resulting composite material demonstrates excellent dispersion stability and Pickering emulsion catalytic selective hydrogenation reaction performance.

[0108] This invention is not limited to the specific embodiments described above. Any reasonable modifications and improvements made based on the core technical solution of this invention, including but not limited to the following aspects, should be considered to fall within the protection scope of this invention. All technical solutions implemented under the guidance of the technical concept of this invention through equivalent substitution or adaptive modification are within the protection scope of this invention.

Claims

1. A method for preparing halloysite composite nanomaterials based on electrostatic adsorption of cationic surfactants, characterized in that: Includes the following steps: (1) Alkali activation treatment of halloysite nanotubes enhances the negative charge of the outer wall; (2) The quaternary ammonium polyether cationic surfactant and the halloysite nanotubes activated in step (1) are electrostatically adsorbed in an aqueous phase by stirring. (3) Separate, wash and dry to obtain halloysite nanotube inorganic reverse micelle composite nanomaterials with electrostatic adsorption of cationic surfactants.

2. The method according to claim 1, characterized in that: The alkaline activation treatment in step (1) involves adjusting the pH to 9-11 using an alkaline solution.

3. The method according to claim 1, characterized in that: The electrostatic adsorption reaction in step (2) is carried out at room temperature, with a stirring reaction time of 12-24 hours in the aqueous phase and a pH of 7-9.

4. The method according to claim 1, characterized in that: The preparation method of the quaternary ammonium polyether cationic surfactant in step (2) includes the following steps: S1: Add the amino-terminated polyether M2070 dissolved in the solvent to the autoclave, then add the catalyst Raney Ni and aldehyde compounds, seal the autoclave and replace the gas inside the autoclave with N2 and H2 in turn more than 3 times, and stir magnetically at a certain temperature for a certain time. S2: After the reaction is complete, the temperature is controlled to a certain level, and the solvent is removed by rotary evaporation under reduced pressure to obtain a terminal tertiary amine polyether surfactant. S3: Dissolve the synthesized tertiary amine polyether surfactant in deionized water, then add hydrochloric acid to the above solution at a molar ratio of tertiary amine group to hydrochloric acid of 1:1.1, and sonicate the sample to obtain an aqueous solution containing quaternary ammonium polyether surfactant.

5. The method according to claim 4, characterized in that, The aldehyde compound mentioned in S1 includes any one of paraformaldehyde, n-butyraldehyde, and n-octanaldehyde; the solvent mentioned in S1 is methanol; the reaction temperature is 140℃, the reaction time is 5~10h, and the H2 pressure is 1.6 MPa.

6. The method according to claim 4, characterized in that, The rotary evaporation temperature described in S2 is 50°C.

7. The quaternary ammonium polyether cationic surfactant prepared by the method according to claim 4, characterized in that: Its molecular structure is as follows: Among them, when the aldehyde compound is paraformaldehyde, n=1; when it is butyraldehyde, n=4; and when it is octanal, n=8.

8. A halloysite composite nanomaterial modified with an external surface electrostatic adsorption cationic surfactant, prepared by the method described in claim 1.

9. The halloysite composite nanomaterial with electrostatic adsorption of cationic surfactants on its outer surface according to claim 8, characterized in that: The halloysite composite nanomaterial comprises a halloysite nanotube matrix and a quaternary ammonium polyether cationic surfactant loaded on the outer surface of the halloysite nanotubes through electrostatic adsorption; the loading amount of the quaternary ammonium polyether cationic surfactant is 0.5-1 mmol / g halloysite nanotubes.

10. The application of halloysite composite nanomaterials modified with electrostatic adsorption cationic surfactants as described in claim 8 in Pickering emulsion catalysis.

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