CN117065772A - Preparation method and application of supported noble metal catalyst based on Mxene - Google Patents

Preparation method and application of supported noble metal catalyst based on Mxene Download PDF

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CN117065772A
CN117065772A CN202311325503.1A CN202311325503A CN117065772A CN 117065772 A CN117065772 A CN 117065772A CN 202311325503 A CN202311325503 A CN 202311325503A CN 117065772 A CN117065772 A CN 117065772A
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carrier
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mxene
noble metal
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CN117065772B (en
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苏慧娟
孙立波
祁彩霞
孙逊
赵立军
景和顺
谢清泰
谭文宇
刘学晴
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Yantai University
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    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
    • B01J27/20—Carbon compounds
    • B01J27/22—Carbides
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
    • B01J23/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals of the platinum group metals
    • B01J23/44—Palladium
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    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/08—Heat treatment
    • B01J37/10—Heat treatment in the presence of water, e.g. steam
    • B—PERFORMING OPERATIONS; TRANSPORTING
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    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/16—Reducing
    • B—PERFORMING OPERATIONS; TRANSPORTING
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    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/16—Reducing
    • B01J37/18—Reducing with gases containing free hydrogen
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    • C07C209/32—Preparation of compounds containing amino groups bound to a carbon skeleton by reduction of nitrogen-to-oxygen or nitrogen-to-nitrogen bonds by reduction of nitro groups
    • C07C209/36—Preparation of compounds containing amino groups bound to a carbon skeleton by reduction of nitrogen-to-oxygen or nitrogen-to-nitrogen bonds by reduction of nitro groups by reduction of nitro groups bound to carbon atoms of six-membered aromatic rings in presence of hydrogen-containing gases and a catalyst
    • C07C209/365—Preparation of compounds containing amino groups bound to a carbon skeleton by reduction of nitrogen-to-oxygen or nitrogen-to-nitrogen bonds by reduction of nitro groups by reduction of nitro groups bound to carbon atoms of six-membered aromatic rings in presence of hydrogen-containing gases and a catalyst by reduction with preservation of halogen-atoms in compounds containing nitro groups and halogen atoms bound to the same carbon skeleton
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    • Y02P20/584—Recycling of catalysts

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Abstract

The application relates to a preparation method and application of a supported noble metal catalyst based on Mxene, belonging to the technical field of preparation and application of supported noble metal catalysts. The layered ternary metal titanium carbon aluminum material is intercalated after an aluminum layer is etched to obtain an MD carrier or the MD carrier is further processed to obtain a TTS composite carrier, and Pd nano particles are loaded and applied to a p-CNB hydrogenation reduction reaction. The catalyst prepared by the application has a special accordion structure, can provide more active sites for catalytic reaction, and the interaction between noble metal and carrier stabilizes Pd nano particles and modulates the electronic state of Pd surface, so that the catalyst has the advantages of high activity, high selectivity and high stability, and has wide application prospect.

Description

Preparation method and application of supported noble metal catalyst based on Mxene
Technical Field
The application relates to a preparation method of a supported noble metal catalyst based on a two-dimensional ordered Mxene material, and also relates to application of the prepared catalyst in p-chloronitrobenzene (p-CNB) preparation p-chloroaniline (p-CAN) reaction. Belongs to the technical field of preparation and application of supported noble metal catalysts.
Background
Halogenated nitroarenes are important chemical raw materials in the chemical industry. Aromatic amines are important intermediates in chemical synthesis processes in the industries of dyes, pesticides, medicines and the like. Thus, the selective hydrogenation of nitroaromatics to the corresponding aromatic amines is of great importance. The reduction of industrial nitro compounds mostly adopts an iron powder reduction method or a hydrazine hydrate reduction method, and the process can generate a great deal of environmental pollution and is gradually eliminated. Recent studies of the subject group of the present inventors have shown that catalytic hydrogenation has more environmental and energy-saving advantages (Applied Surface Science 623 (2023) 157107;Molecular Catalysis 525 (2022) 112362). The catalytic hydrogenation has the characteristics of easy separation of the catalyst, mild reaction conditions, low cost and the like, and has the main challenges of inhibiting dehalogenation side reaction to improve the product selectivity and inhibiting the deactivation of the catalyst to improve the service life of the catalyst. Therefore, it is important to construct a catalyst having high activity, high selectivity and high stability. The selection of a suitable support to stabilize the size of the nano noble metal particles is critical to improving catalyst stability, while the interaction of the support with the noble metal particles provides convenience for achieving modulation of product selectivity in the catalytic process.
Due to the large specific surface area, rich functional groups and the space-limiting effect, various 2D materials such as graphene and graphite carbonitride have excellent performance as carriers for metal nanoparticle deposition. Titanium-based MXene has attracted extensive research interest due to its superior physical and chemical properties. By etching Ti compared with the complicated process of preparing graphene 3 AlC 2 The middle Al layer can conveniently obtain Ti 3 C 2 MXene. Although there has been much progress in hydrogen evolution and photoelectrocatalysis using MXene as a support-supported metal nanoparticle, the use of this material-supported noble metal Pd nanoparticle as a catalyst for selective hydrogenation remains challenging. Pd nanoparticles are prone to agglomeration and deactivation due to their extremely high surface area and excellent hydrogenation capacity, and the selectivity of the target product is poor, which severely limits their industrial application in catalytic hydrogenation reactions.
The Chinese patent application publication No. CN115178284A discloses a composite carrier material loaded with platinum nano particles, a preparation method and application thereof, which adopts HF to etch Ti 3 AlC 2 Obtaining Ti 3 C 2 And annealing to obtain TiO 2 /Ti 3 C 2 The composite carrier and the Pt-based catalyst obtained after loading the Pt nano particles can obviously improve the performance of the catalyst in low-temperature catalytic degradation of formaldehyde. In the method, the carrier preparation step does not carry out DMSO intercalation treatment, so that the interlayer spacing expansion cannot be obtained, and the anchoring load of noble metal particles is not facilitated.
Disclosure of Invention
Aiming at the problems of poor stability and poor selectivity of Pd-based catalysts, pd nano particles are stabilized through MD or TTS, the surface electronic state of the Pd particles is modulated by the interaction of Pd and a carrier, the selectivity of the Pd-based catalysts in p-CNB hydrogenation reaction is improved, and the noble metal catalysts with high activity, high stability and long service life are obtained.
The application is realized by the following technical scheme:
the preparation method of the supported noble metal catalyst based on Mxene comprises the following steps:
(1) And (3) preparing a carrier: layered ternary metal titanium carbon aluminum material Ti 3 AlC 2 Immersing in HF solution, stirring continuously to etch the aluminum layer, centrifugal washing and drying to obtain two-dimensional Ti 3 C 2 T x Material, then two-dimensional Ti 3 C 2 T x Dispersing the material in dimethyl sulfoxide solution for intercalation to obtain carrier MD;
(2) And (3) preparing a catalyst:
dispersing carrier MD in water, ultrasonic treating, adding H 2 PdCl 4 Stirring and mixing the solution, and adding NaBH 4 Continuously stirring until bubbles disappear, washing with water, and vacuum drying to obtain the MD supported Pd catalyst; or,
will H 2 PdCl 4 Adding the solution into KOH solution, adding carrier MD into vibration, ultrasonic treating, standing, soaking in ammonia water, washing with water, drying, and H at 300deg.C 2 Reducing to obtain a catalyst of MD supported Pd; or,
dispersing urea in water, adding H under stirring 2 PdCl 4 Adding carrier MD into the solution, ultrasonic treating, oil-bathing at 80deg.C, cooling, standing, washing with water to remove Cl - Drying, and roasting in air at 200 ℃ to obtain the MD supported Pd catalyst; or,
dispersing carrier MD in water, ultrasonic treating, adding H 2 PdCl 4 Stirring, washing with water, vacuum drying, and H at 300 deg.C 2 The MD supported Pd catalyst is obtained by reduction.
Preferably, the concentration of the HF solution is 40%; the etching time is 20h; the theoretical loading of Pd was 0.5%.
The catalyst is applied to the reduction of p-chloronitrobenzene to prepare p-chloroaniline.
Preferably, the catalyst is applied to the reaction of preparing the p-chloroaniline by reducing the p-chloronitrobenzeneAt 100℃and reaction H 2 The pressure is 1.2MPa, the concentration of the substrate p-chloronitrobenzene is 0.2 mol/L, and the reaction time is 2h.
Another preparation method of the supported noble metal catalyst based on Mxene comprises the following steps:
(1) And (3) preparing a carrier: layered ternary metal titanium carbon aluminum material Ti 3 AlC 2 Immersing in HF solution, stirring continuously to etch the aluminum layer, centrifugal washing and drying to obtain two-dimensional Ti 3 C 2 T x Material, then two-dimensional Ti 3 C 2 T x Dispersing the material in dimethyl sulfoxide solution for intercalation to obtain carrier MD;
adding the prepared MD into water, carrying out ultrasonic treatment, transferring into an autoclave, carrying out hydrothermal treatment, and carrying out suction filtration to obtain a TTS composite carrier;
(2) And (3) preparing a catalyst: dispersing urea in water, adding H 2 PdCl 4 Adding the solution into the prepared TTS carrier, performing ultrasonic treatment, oil-bath at 80 ℃, cooling, standing, and washing off Cl - Drying and roasting at 200 ℃ to obtain the catalyst of TTS supported Pd.
Preferably, the concentration of the HF solution is 40%; the etching time is 20h; the theoretical loading of Pd was 0.3%.
Preferably, the reaction temperature of the hydrothermal treatment is 200 ℃; the hydrothermal treatment reaction time is 18-30 h.
The catalyst is applied to the reduction of p-chloronitrobenzene to prepare p-chloroaniline.
Preferably, the reaction temperature of the catalyst for preparing the p-chloroaniline by reducing the p-chloronitrobenzene is 60 ℃, and the reaction is H 2 The pressure is 1.5MPa, the concentration of the substrate p-chloronitrobenzene is 0.2 mol/L, and the reaction time is 10min.
The application has the advantages that,
according to the application, the Pd nano particles are stabilized through MD or TTS, the surface electronic state of the Pd particles is modulated by means of the interaction of Pd and a carrier, the selectivity of the Pd-based catalyst in the p-CNB hydrogenation reaction is improved, and the noble metal catalyst with high activity, high stability and long service life is obtained. The catalyst has the advantages of simple preparation, strong recycling property and good adaptability in a wider temperature and pressure range, and has great significance on the improvement and upgrading of the old production line of enterprises or series catalysis with certain requirements on the catalyst use temperature and pressure in the catalyst application process, and the better temperature and pressure adaptability of the catalyst can save huge funds for the improvement and upgrading of the production line of small and medium enterprises, so that the catalyst is easy to industrially popularize.
The application firstly immerses MAX into HF solution to etch aluminum layer, and then two-dimensional Ti 3 C 2 T x The (MXene) material was dispersed in a dimethylsulfoxide solution (DMSO) to perform intercalation to obtain MD (MXene-DMSO). This technical measure is critical, because it will be more favorable to the anchoring and dispersion of noble metal nanoparticles, and more favorable to the contact of the reaction substrate and noble metal active sites after the development of DMSO intercalation. Experiments prove that compared with the phase diffraction peak of the original MAX material, the diffraction peak of the material treated by HF and DMSO is slightly reduced and increased in width, so that the layer stack of the carrier material becomes loose and defective, and more active sites are exposed, thereby being beneficial to enhancing the catalytic reaction. In the application, DMSO is used as an internal ligand to enable massive MXene to be intercalated and peeled off, and an electronically transparent MXene nano sheet thin layer MD can be obtained by ultrasonic treatment.
Drawings
FIG. 1 is a diagram of Ti in example 1 of the present application 3 AlC 2 (MAX), MXene after HF treatment, MD after DMSO intercalation and catalyst in example 4 0.5% Pd/MD (H 2 ) Is a XRD spectrum of (C).
FIG. 2 is an SEM image of the catalyst of example 1-3 of the application involving a support and the catalyst prepared in example 4. (a: MAX; b: MXene; c: MD; d: 0.5% Pd/MD).
FIG. 3 is a comparative bar graph of the effect of different preparation methods on catalyst activity.
Fig. 4 is a graph showing TEM and particle size distribution of catalysts prepared by different methods. [ a, b:0.5% Pd/MD (NaBH) 4 ）；c，d: 0.5%Pd/MD（IMP）；e，f : 0.5%Pd/MD（DP）； g，h : 0.5%Pd/MD（H 2 ）]。
FIG. 5 shows the present application0.5% Pd/MD (H) prepared by example 4 2 ) Cycling stability profile of the catalyst.
FIG. 6 is a graph showing the effect of Pd loading, reaction temperature, pressure and substrate concentration on catalyst activity. (a: different Pd loadings; b: different reaction temperatures; c: different reaction pressures; d: different reaction substrate concentrations).
Fig. 7 is a thermogravimetric plot of the composite support TTSx prepared in example 7 of the present application.
Fig. 8 is an XRD spectrum of the composite carrier TTSx prepared in example 7 of the present application and the corresponding catalyst.
Fig. 9 is an SEM and TEM spectrum of the catalyst and its support and a particle size distribution of Pd. [ (a, b): SEM profile of TTS 18; (c, d): SEM spectrogram of 0.3% Pd/TTS 18; e TEM spectrum of 0.3% Pd/TTS 18; f: particle size distribution of Pd in 0.3% Pd/TTS18 catalyst ].
FIG. 10 is a graph showing the results of evaluation of hydrogenation performance of Pd/TTS18 catalysts having different Pd loadings.
FIG. 11 is a diagram showing N of the vectors prepared in example 1 and example 7 of the present application 2 An adsorption-desorption isothermal curve and a corresponding pore size distribution curve.
FIG. 12 is an XPS spectrum of a 0.3% Pd/TTS18 catalyst prepared in example 7 of the present application.
Detailed Description
The application is further illustrated by reference to specific examples, experimental data and figures.
Example 1:0.5% Pd/MD (NaBH) 4 ) Preparation of the catalyst
Preparation of carrier MD material: 1 g of Ti is weighed 3 AlC 2 (MAX) powder was immersed in HF at a concentration of 40% of 15 mL, stirred at room temperature for 20h, the suspension was centrifuged and washed with ultra-pure water until the pH was raised to 6, and the resulting powder was vacuum dried at 80℃for 8h to give Ti 3 C 2 T x (MXene) material. 0.3g of MXene material is weighed and dispersed in 6.25 mL dimethyl sulfoxide (DMSO), stirred at room temperature for 24 h, ultrasonically treated with 2h, washed with water and alcohol to remove DMSO, the product is collected, and dried in vacuum at 80 ℃ for 8h to obtain a DMSO intercalated MXene material MXene-DMSO, which is recorded asMD。
Preparation of the catalyst: 0.4 g of MD carrier is weighed and dispersed in 50 mL ultrapure water, ultrasonic is carried out for 5 min, and H with the concentration of 2 mL of 1mg/mL is added 2 PdCl 4 The solution was stirred for 30 min until mixing was complete, 5 mL NaBH was added 4 At this time, a large amount of bubbles were generated, pd was reduced, rapid stirring was continued for 2 min until the bubbles disappeared, immediately washing with ultra-pure water 3 times, and vacuum drying at room temperature for 12 h to obtain 0.5% Pd/MD (NaBH) 4 ) A catalyst.
Example 2: preparation of 0.5% Pd/MD (IMP) catalyst by impregnation
The catalyst was prepared using the carrier MD material in example 1. 0.75 mg/mL H was measured out at a concentration of 0.75 mL 2 PdCl 4 Dropwise adding 50 μl of KOH solution with concentration of 1mol/mL, slowly adding 0.15 g MD while shaking, ultrasound for 2 min, standing 5H, soaking in ammonia water overnight, washing 5 times, drying at 60deg.C for 12H, and standing 300 deg.C H 2 Reduction 2h, heating rate 5 ℃/min, gives 0.5% Pd/MD (IMP) catalyst.
Example 3: preparation of 0.5% Pd/MD (DP) catalyst by precipitation
The catalyst was prepared using the carrier MD material in example 1. Dispersing 0.045. 0.045 g urea in 3.75: 3.75 mL water, adding 0.75: 0.75 mL concentration of 1mg/mL H under stirring 2 PdCl 4 The solution was then added with 0.15 g MD material, sonicated for 5 min, oil bath 4 at 80℃ 4h, cooled to room temperature overnight, and water washed to remove Cl - Drying 12. 12 h at 110℃and calcining 5. 5 h at 200℃in air gives a 0.5% Pd/MD (DP) catalyst.
Example 4:0.5% Pd/MD (H) 2 ) Preparation of the catalyst
The catalyst was prepared using the carrier MD material in example 1. Dispersing 0.4 g MD material in 160 mL water, ultrasonic for 10min, and rapidly adding 2 mL to 1mg/mL H 2 PdCl 4 Stirring the solution at 800 r/min for 4-H, washing with water for 3 times, vacuum drying at room temperature for 12H at 300deg.C H 2 Reduction of 2H gave 0.5% Pd/MD (H 2 ) A catalyst.
First, the morphology of the carriers of examples 1 to 4 and the catalyst prepared in example 4 were determined, and XRD results thereof are shown in fig. 1, which shows that the treated carriers have high purity and good crystallinity. At the same time, compared with the phase diffraction peak of the original MAX material, the diffraction peak of the material treated by HF and DMSO is slightly reduced and increased in width, so that the layer stack of the carrier material becomes loose and defective, and more active sites are exposed, thereby being beneficial to enhancing the catalytic reaction.
FIG. 2 shows the SEM test results of the support material and the catalyst involved in the preparation of the catalysts in examples 1-4, ti 3 AlC 2 The precursor showed a close-packed morphology, similar to that of the unpeeled graphite, and after HF etching, the closely packed layers were observed to separate significantly from each other, transforming into a loose accordion-like structure with significant layer space due to Al atom loss, indicating that individual grains exfoliated along basal planes, compared to untreated Ti 3 AlC 2 Is significantly different. The electron transparent MXene nanoplatelet sheet MD can be obtained by ultrasonic treatment by intercalating and exfoliating large blocks of MXene using DMSO as an internal ligand.
The catalysts prepared by the different preparation methods of examples 1-4 are respectively applied to experiments of the reduction of p-chloronitrobenzene to prepare p-chloroaniline. The reaction condition is that the hydrogen pressure is 1.2MPa, the temperature is 100 ℃, the reaction time is 2 hours, and the substrate concentration is 0.2 mol/L. The experimental results (see fig. 3) show that the reactivity of p-chloroaniline (p-CAN) prepared by reduction of p-chloronitrobenzene (p-CNB) in different preparation methods is different. This is because the nano-size of palladium as an active component is different, so that nano-palladium with small size has better activity, and the palladium loading can be controlled by adjusting the introduction amount of palladium precursor. Obviously, nano palladium catalysts with different loading amounts and different particle sizes can be obtained through the selection and optimization of the preparation method.
FIG. 4 shows the microstructure and morphology of 0.5% Pd/MD prepared by the different methods of the previous examples, and it can be seen that Pd nanoparticles are clearly distributed on the surface of the carrier, and the MD can make the nanoparticles highly dispersed without obvious agglomeration, indicating that Pd particles are successfully loaded on the surface of the MD. However, there are significant differences in the size and dispersion of Pd NPs in the differently supported Pd NPs catalysts. 0.5% Pd/MD (H) 2 ) The average size of the medium Pd NPs was 12.92 nm, and 0.5% Pd/MD (NaBH 4 ) (13.47 nm), 0.5% Pd/MD (IMP) (16.51 nm) and 0.5% Pd/MD (DP) (15.78 nm) are smaller, and the smaller Pd NPs in the prepared catalyst are, the higher the selective hydrogenation activity of p-CNB is, which indicates that the smaller particle size is favorable for the reaction. The catalyst prepared in example 4 was 0.5% Pd/MD (H 2 ) The catalytic effect of the reaction for preparing p-chloroaniline by reducing p-chloronitrobenzene is optimal.
The stability of the catalyst is also an important factor in measuring its performance. Selecting 0.5% Pd/MD (H) 2 ) The catalyst was tested for stability and the results are shown in figure 5. As CAN be seen from FIG. 5, good catalytic performance was exhibited in the continuous 6-cycle reaction, and the yield of p-CAN was still nearly 70% after 6 cycles, indicating 0.5% Pd/MD (H 2 ) Has good cycle stability.
Example 5: carrier etching time and influence of different carriers on catalytic performance of catalyst
By operating in accordance with example 1, with only varying the etching times, i.e. stirring at room temperature for 4h, 20, h and 48h, respectively, the catalysts prepared were expressed as 0.5% Pd/MD, respectively 4 （H 2 ）、0.5%Pd/MD 20 （H 2 ) And 0.5% Pd/MD 48 （H 2 ). The three groups of catalysts were combined with pure carrier MD, 0.5% Pd/MAX (H) 2 ) 0.5% Pd/MXene (H) 2 ) The catalytic properties of (2) were compared to obtain Table 1.
The catalytic performance of the catalysts supported by the different etching times of the carriers and the catalytic performance results of the catalysts of the different carriers are shown in table 1. It can be seen that the conversion rate of the carrier by HF etching for 4h p-CNB is 76.36%, the conversion rate of etching 48h is 89.12%, and both the conversion rates are lower than that of etching 20h (99.99%). The shorter or longer etching treatment is not beneficial to the p-CNB hydrogenation, the shorter etching time leads to incomplete etching of the Al layer, the MAX phase is not completely stripped, the longer time leads to serious fragmentation of the nano-sheet, and the proper etching time CAN lead to higher yield of the p-CAN, so that the etching time of the carrier is optimal for 20 hours. Meanwhile, as can be seen from the results in Table 1, the catalytic effect of both the pure carrier MD and the MAX-supported Pd NPs was poor. The pure carrier MD has no catalytic capability, and 0.5% Pd/MAX is loaded with Pd with strong catalytic hydrogenation capability, but the catalytic efficiency is still poor, but when MAX is subjected to HF etching treatment and intercalation in DMSO, the catalytic performance of the loaded Pd is greatly improved, because the accordion structure obtained by removing the Al layer provides more reaction sites, which is consistent with the structural characteristics of the carrier of FIG. 1.
TABLE 1 Carrier etch time and catalytic Performance results for different Carrier catalysts
Example 6: pd loading, reaction temperature, pressure, and effect of substrate concentration on catalyst activity
The implementation steps of p-CNB hydrogenation to prepare p-CAN are as follows:
(a) Catalysts with different Pd loadings are added when the hydrogen pressure is 1.2MPa, the temperature is 100 ℃ and the reaction time is 2 hours and the substrate concentration is 0.2 mol/L, and the influence of the Pd amount of the active component of the catalyst on the reaction is examined.
(b) The effect of the temperature of 25-100℃on the reaction was examined with 0.5% Pd/MD catalyst at a hydrogen pressure of 1.2MPa for 2h with a substrate concentration of 0.2 mol/L.
(c) Substrate concentration 0.2 mol/L at 100℃for 2H with 0.5% Pd/MD catalyst H 2 The pressure is from 0.6 to 1.5Mpa, and the influence of the pressure.
(d) The effect of the substrate concentration was examined by changing the substrate p-CNB concentration from 0.1 to 0.5 mol/L with a 0.5% Pd/MD catalyst at a hydrogen pressure of 1.2MPa, a temperature of 100℃and a reaction time of 2 hours.
The effect of different Pd loadings (a), reaction temperature (b), pressure (c), substrate concentrations (d) on the catalytic performance of p-CNB hydrogenation to produce p-CAN is shown in FIG. 6, respectively, from which it CAN be seen that Pd loadings increase from 0.1% to 0.5%, the conversion of p-CNB increases continuously, the selectivity of p-CAN is relatively stable, p-CNB is almost fully converted as Pd loadings continue to increase, p-CAN selectivity decreases, possibly excessive Pd loadings resulting in excessive hydrogenation, and 0.5% Pd/MD is the optimal catalyst in the p-CNB hydrogenation reaction, considering atomic economy.
It can be seen from FIG. 6 (b) that as the reaction temperature increases from 25℃to 100℃the conversion of p-CNB increases from 18.65% to 99.99%, indicating that the reaction temperature has a significant effect on the reaction kinetics. The result that the conversion of p-CNB was about 99% and the selectivity of p-CAN remained unchanged and still 98% was reached when the temperature was continuously increased to 120℃shows that almost all the conversion of p-CNB was achieved with increasing temperature, but the increasing temperature did not affect the high selectivity of p-CAN, and in the hydrogenation of p-CNB, 100℃was the optimal reaction temperature.
H 2 The effect of pressure on the selective hydrogenation performance of p-CNB is shown in FIG. 6 (c), where the conversion of p-CNB is a function of H 2 The pressure increases with increasing pressure, preferably 1.2 MPa. In addition, the hydrogenation performance under different p-CNB concentrations was also studied, and as shown in (d) of FIG. 6, the selectivity of the target product was low when the substrate concentration was low, because the catalyst was highly catalytic and the selectivity was reduced when the substrate concentration was increased due to excessive hydrogenation, and the solubility was poor and the partial product was excessively hydrogenated. Thus, for a 0.5% Pd/MD catalyst, the best conditions for higher yields for p-CAN are at 100℃and 1.2MPa H 2 Pressure, 0.2 mol/L.
Example 7: preparation of Pd/TTSx catalyst
Preparation of the carrier: MD was obtained by the preparation method of example 1, 0.3g of the prepared MD material was added to 40 mL deionized water, sonicated for 1 h, the resulting dispersion was poured into an autoclave and kept at a temperature of 200℃for 24 h (the pressure in the autoclave was self-generated after heating, no pressurization nor control of pressure was required), suction filtration was performed to obtain Ti 3 C 2 /TiO 2 The nanocomposite was dried 24 h at 60 ℃. The TTS is prepared by hydrothermal treatment at different hydrothermal time and is marked as TTSx.
Preparation of the catalyst: 0.15 of g urea is weighed and dispersed in 12.5 of mL water, and then a proper amount of H with the concentration of 1mg/mL is added 2 PdCl 4 Adding 0.5 g TTSx, ultrasonic treating for 5 min, stirring at 80deg.C in oil bath for 4h, cooling to room temperature overnight, and washing to remove Cl - ，110. Drying at the temperature of 12 h, and roasting at the temperature of 200 ℃ for 5 h to obtain Pd/TTSx.
According to the reaction equation Ti 3 C 2 +5O 2 =3TiO 2 +2CO 2 Can calculate Ti 3 C 2 /TiO 2 Medium TiO 2 Is contained in the composition. FIG. 7 shows a thermogravimetric analysis of the carrier in an air atmosphere to obtain TiO in TTS18 2 Is 88.11% in TTS30 and 88.25% in TTS30, indicating that the hydrothermal time is relative to the TiO in the resulting TTS 2 The content has less influence. And it can be seen from fig. 8 that the peak at 2θ=25.6° corresponds to anatase TiO 2 (101) plane of (a). Peaks near 2θ=9° correspond to Ti 3 C 2 Characteristic peaks of (002) face of (C) indicating that part of Ti after hydrothermal treatment 3 C 2 Conversion to TiO 2 Successfully prepare Ti 3 C 2 /TiO 2 And (3) a composite carrier.
Fig. 9 shows SEM and TEM images of the support and catalyst and particle size distribution of Pd. From the figure, it can be seen that Ti 3 AlC 2 Etched into a layered nano-sheet with accordion structure, after hydrothermal treatment at 200 ℃ of 18 to h, ti 3 C 2 Is converted to TiO in situ due to MD 2 But the layered structure remained, and after loading the Pd NPs, the structure of the support did not change significantly, and it can be seen from (e) of TEM of 0.3% Pd/TTS18 that the Pd NPs was uniformly dispersed on the surface of TTS18, and (f) of fig. 9 gave a Pd average particle diameter of 7.96 nm. The results of both SEM and TEM indicate successful synthesis of Pd/TTS.
FIG. 10 shows the Ti produced by hydrothermal reaction at 18. 18 h under experimental conditions of 40℃and 1.2MPa for 10min 3 C 2 /TiO 2 As a result of the activity of the catalyst supporting different Pd loadings, the conversion rate of p-CNB was less than 20% when the Pd loading was 0.1% wt, the conversion rate and selectivity of the reaction were maintained at a higher level when the Pd loading was increased to 0.3% wt, the Pd loading was continuously increased to 0.5% wt, the yield of p-CAN was not significantly improved, and the Pd loading was controlled to 0.3% wt in view of the atomic utilization. The Pd loading was reduced while maintaining a higher yield of p-CAN compared to pure MD loaded Pd, see FIGS. 11 andthe 12 analysis, possibly an MXene 2D heterostructure, increases the surface area, provides more reaction sites, and accelerates electron transfer. The Mxene family material can be used for constructing high-performance in-situ heterostructure materials for the hydrogenation reduction of nitro compounds.
Example 8: effect of different reaction temperatures, pressures on the 0.3% Pd/TTS18 catalyst Performance
Tables 2 and 3 show the effect of the reaction temperature and pressure of p-CNB hydrogenation to produce p-CAN on the catalytic performance of 0.3% Pd/TTS 18. The temperature has an important effect on the reaction, the higher the temperature, the faster the reaction rate, while the pressure has little effect on the reaction. At a hydrogen pressure of 1.2MPa, the conversion of p-CNB was nearly 100% as the reaction temperature increased from 25℃to 100℃but the selectivity of p-CAN tended to decrease linearly as the temperature increased, indicating that the temperature had a significant effect on the reaction. Higher temperatures may cause further hydrodechlorination of the resulting p-CAN resulting in AN increase in by-product AN, and relatively mild conditions may cause the reaction to terminate at the stage of p-CAN formation. The application is comprehensively balanced, and the selected reaction temperature is 60 ℃. While the pressure was increased from 0.6 MPa to 1.5MPa, the conversion and selectivity of the reaction did not change significantly.
TABLE 2 influence of reaction temperature on the performance of 0.3% Pd/TTS18 catalyst
TABLE 3 influence of reaction pressure on the performance of 0.3% Pd/TTS18 catalyst
The embodiment of the application can show that the catalyst disclosed by the application is simple to prepare, strong in recycling property and good in adaptability in a wider temperature and pressure range, and has important significance for the improvement and upgrading of old production lines of enterprises or series catalysis with certain requirements on the catalyst use temperature and pressure in the catalyst application process, and the better temperature and pressure adaptability of the catalyst can save huge funds for the improvement and upgrading of production lines of small and medium enterprises, so that the catalyst is easy to industrially popularize.

Claims (9)

1. The preparation method of the supported noble metal catalyst based on Mxene is characterized by comprising the following steps of:
(1) And (3) preparing a carrier: layered ternary metal titanium carbon aluminum material Ti 3 AlC 2 Immersing in HF solution, stirring continuously to etch the aluminum layer, centrifugal washing and drying to obtain two-dimensional Ti 3 C 2 T x Material, then two-dimensional Ti 3 C 2 T x Dispersing the material in dimethyl sulfoxide solution for intercalation to obtain carrier MXene-DMSO (MD);
(2) And (3) preparing a catalyst:
dispersing carrier MD in water, ultrasonic treating, adding H 2 PdCl 4 Stirring and mixing the solution, and adding NaBH 4 Continuously stirring until bubbles disappear, washing with water, and vacuum drying to obtain the MD supported Pd catalyst; or,
will H 2 PdCl 4 Adding the solution into KOH solution, adding carrier MD into vibration, ultrasonic treating, standing, soaking in ammonia water, washing with water, drying, and H at 300deg.C 2 Reducing to obtain a catalyst of MD supported Pd; or,
dispersing urea in water, adding H under stirring 2 PdCl 4 Adding carrier MD into the solution, ultrasonic treating, oil-bathing at 80deg.C, cooling, standing, washing with water to remove Cl - Drying, and roasting in air at 200 ℃ to obtain the MD supported Pd catalyst; or,
dispersing carrier MD in water, ultrasonic treating, adding H 2 PdCl 4 Stirring, washing with water, vacuum drying, and H at 300 deg.C 2 The MD supported Pd catalyst is obtained by reduction.
2. The Mxene-based supported noble metal catalyst preparation method according to claim 1, characterized in that: the concentration of the HF solution is 40%; the etching time is 20h; the theoretical loading of Pd was 0.5%.
3. The method for applying the catalyst prepared by the Mxene-based supported noble metal catalyst preparation method according to claim 1 or 2, characterized in that: the catalyst is applied to the reduction of p-chloronitrobenzene to prepare p-chloroaniline.
4. A method of application according to claim 3, characterized in that: the reaction temperature of the catalyst applied to the preparation of p-chloroaniline by reduction of p-chloronitrobenzene is 100 ℃, and the reaction is H 2 The pressure is 1.2MPa, the concentration of the substrate p-chloronitrobenzene is 0.2 mol/L, and the reaction time is 2h.
5. The preparation method of the supported noble metal catalyst based on Mxene is characterized by comprising the following steps of:
(1) And (3) preparing a carrier: layered ternary metal titanium carbon aluminum material Ti 3 AlC 2 Immersing in HF solution, stirring continuously to etch the aluminum layer, centrifugal washing and drying to obtain two-dimensional Ti 3 C 2 T x Material, then two-dimensional Ti 3 C 2 T x Dispersing the material in dimethyl sulfoxide solution for intercalation to obtain carrier MD;
adding the prepared MD into water, performing ultrasonic treatment, transferring into an autoclave, performing hydrothermal treatment, and performing suction filtration to obtain Ti 3 C 2 / TiO 2 (TTS) composite carrier;
(2) And (3) preparing a catalyst: dispersing urea in water, adding H 2 PdCl 4 Adding the solution into the prepared TTS carrier, performing ultrasonic treatment, oil-bath at 80 ℃, cooling, standing, and washing off Cl - Drying and roasting at 200 ℃ to obtain Ti 3 C 2 / TiO 2 Pd-supported catalyst.
6. The Mxene-based supported noble metal catalyst preparation method according to claim 5, characterized in that: the concentration of the HF solution is 40%; the etching time is 20h; the theoretical loading of Pd was 0.3%.
7. The Mxene-based supported noble metal catalyst preparation method according to claim 5, characterized in that: the reaction temperature of the hydrothermal treatment is 200 ℃; the hydrothermal treatment reaction time is 18-30 h.
8. The method for applying the catalyst prepared by the Mxene-based supported noble metal catalyst preparation method according to claim 5 or 6 or 7, characterized in that: the catalyst is applied to the reduction of p-chloronitrobenzene to prepare p-chloroaniline.
9. The application method according to claim 8, wherein: the reaction temperature of the catalyst applied to the preparation of the p-chloroaniline by the reduction of the p-chloronitrobenzene is 60 ℃, and the reaction is H 2 The pressure is 1.5MPa, the concentration of the substrate p-chloronitrobenzene is 0.2 mol/L, and the reaction time is 10min.
CN202311325503.1A 2023-10-13 2023-10-13 Preparation method and application of supported noble metal catalyst based on Mxene Active CN117065772B (en)

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