Preparation method of carbon-based gold-containing bimetallic catalyst

Abstract

The invention relates to a preparation method of a carbon-based gold-containing bimetallic catalyst. The specific method comprises the following steps: carrying out secondary doping on eigenstate polyaniline, carrying out high-temperature pyrolysis in an inert atmosphere to obtain a heteroatom-doped carbon-based carrier, and changing the variety, the content and the distribution of heteroatoms on the carbon surface of the carrier by adjusting the variety and the content of acid. And preparing gold-containing bimetallic nanoparticles by using a colloid method, and depositing bimetallic particles by virtue of adsorption of the carbon carrier and bimetallic to obtain the carbon-based gold-containing bimetallic catalyst. Wherein the doping element can anchor and disperse the noble metal, and the introduced second metal can improve the hydrogenation activity of the catalyst. The catalyst is simple in preparation process, good in activity, excellent in selectivity and excellent in cycling stability, is particularly suitable for a reaction for preparing 4-chloroaniline through catalytic hydrogenation of 4-chloronitrobenzene, and has good application potential.

Description

Technical Field

[0001] The invention relates to a method for preparing a carbon-based gold-containing bimetallic catalyst, and belongs to the field of preparation technology and technical application of noble metal catalysts. Background Art

[0002] In recent years, nano-gold catalysts have achieved exciting results in the field of selective hydrogenation of halonitrobenzenes, especially in the precise catalytic production of halogenated anilines, showing extraordinary selectivity. B. Yang and his collaborators found that despite relatively low conversion (less than 25%), the Au / CeO2 catalyst exhibited extremely high selectivity (up to 100%) in the hydrogenation of 4-chloronitrobenzene to 4-chloroaniline (Catalysis Letters 2018, 148, 1490-1498). Y.-W. Chen and Y.-T. Tsu found that regardless of whether CeO2, TiO2, ZrO2, ZnO or Fe2O3 was used as a support, these gold-supported catalysts showed extremely high 4-chloroaniline selectivity (>98%). However, in terms of 4-chloronitrobenzene conversion, with the exception of the relatively well-performing Au / TiO2 catalyst, the conversion rates of other catalysts were unsatisfactory, ranging from 25.4% to 77.8% (Journal of Nanoscience and Nanotechnology 2018, 18, 301-308). CH Campos and his collaborators also demonstrated the high selectivity of gold catalysts in the hydrogenation of 4-chloronitrobenzene to 4-chloroaniline (Journal of Chemistry 2017, 2017, 7941853). Therefore, improving the conversion rate of gold catalysts in the hydrogenation of 4-chloronitrobenzene has become a core challenge and a key step in achieving its widespread application.

[0003] In recent years, carbon materials have become an important choice for catalyst supports due to their porous structure and tunable surface properties. Heteroatoms, such as N, P, S, and B, can stabilize and disperse metal particles while also adjusting their electronic properties (ChemSuSChem2022, 15, e202200411). Heteroatom doping and the regulation of metal active sites synergistically enhance the activity of catalytic reactions (Advanced Energy Materials2023, 13, 2202871). Conductive polymers, such as polyaniline and polypyrrole, have attracted considerable attention in recent years due to their facile synthesis, reversible doping / dedoping processes, and ability to effectively disperse precious metals (Chinese Journal of Catalysis2021, 42, 1205). These polymers, as precursors to carbon materials, can load precious metal nanoparticles onto doped carbon supports, utilizing the heteroatoms in the carbon to stabilize the precious metal particles. Furthermore, the reversible doping / dedoping process of the conductive polymers can be used to adjust the type and distribution of heteroatoms on the surface of the carbon support after pyrolysis. This adjustment relies on the interaction between heteroatoms and noble metals, thereby changing the electronic state of the metal surface and optimizing the adsorption and activation processes during catalysis. This strategy provides a new approach for the development of highly active and stable supported noble metal catalysts.

[0004] Invention patent CN202110574999.0 discloses a carbon-doped single-atom Pt catalyst that is carbonized by pyrolysis of polyaniline and is applied to the hydrogenation of aromatic nitro compounds. The preparation process of the catalyst does not involve the selection and optimization of the carrier doping element, and the optimal reaction time (5h) and hydrogen pressure (2MPa) are relatively high, which is not conducive to its industrial application.

[0005] Invention patent CN202311165380.X coordinates phytic acid with ruthenium to form a Ru-phytic acid complex, and then mixes this complex with polyaniline in an aqueous solution to achieve doping. Subsequently, it is filtered and dried. Finally, the solid product is pyrolyzed at high temperature to uniformly and stably distribute ruthenium on the surface of polyaniline and in situ phosphating. At the same time, the polyaniline is converted into a carbon material to prepare a ruthenium-doped carbon material catalyst, which is applied to the deuteration reaction of hexamethylenediamine. However, the active components, doping elements, and catalytic reactions used in this patent are different from those of the present invention, and the optimization of the doping elements is not involved.

[0006] Invention patent CN202411024840.1 discloses a method for preparing a black phosphorus-modified nitrogen-doped precious metal / carbon catalyst. This invention utilizes ball milling to compound black phosphorus, a nitrogen source, and a carbon support. After calcination under an inert atmosphere, the precious metal is loaded via thermal reflux. This technology also focuses solely on the interaction between the doping element P and the carbon support and precious metal.

[0007] In summary, the existing technology does not involve research on utilizing the doping / dedoping advantages of polyaniline to regulate the types and distribution of heteroatoms on the doped carbon surface generated after its pyrolysis, nor does it study the effects of gold and the second component metal in the gold-containing bimetallic system on the reaction. The above indicators are crucial for obtaining highly active, stable and long-lived catalysts.

[0008] The boron-nitrogen co-doped carbon (BNC) prepared by pyrolysis of boric acid-doped polyaniline prepared in the present invention is used as a carrier. The prepared 0.05% Pd-0.5% Au / BNC has a TOF of 5178h for the conversion of 4-chloronitrobenzene under the reaction conditions of 0.8MPa H2 and 333K. -1 The catalyst developed by the present invention has the advantages of high catalytic efficiency and good stability, and has good industrial application potential. Summary of the Invention

[0009] This invention provides a method for preparing a carbon-based gold-containing bimetallic catalyst. By doping polyaniline with a secondary acid followed by pyrolysis, gold-containing precious metal nanoparticles stabilized on a carbon support are prepared. By introducing a second metal into the gold-containing catalyst to enhance its hydrogenation ability, a highly active and stable catalyst is obtained, which can be used to reduce 4-chloronitrobenzene to produce 4-chloroaniline.

[0010] The present invention is achieved through the following technical solutions:

[0011] A method for preparing a carbon-based gold-containing bimetallic catalyst is prepared by the following method:

[0012] (1) Preparation of the carrier: Dissolve 1-2 mL of aniline in 50 mL of hydrochloric acid (0.1 mol / L), then dissolve 2-3 g of ammonium persulfate in the same 50 mL of hydrochloric acid. Mix the two solutions rapidly, disperse them ultrasonically, and allow to react in the dark for 4-8 hours. Wash the resulting hydrochloric acid-doped polyaniline, then dedope it by soaking it in 150 mL of ammonia (0.1 mol / L) for 15-45 minutes. Wash, dry, and bake to obtain the intrinsic polyaniline.

[0013] 0.2-0.6g of native polyaniline was dispersed in 20-60mL of a 0.5-1.5mol / L doping acid solution containing one of boric acid, phosphoric acid, citric acid, and hydrochloric acid. After stirring at room temperature for 4-8h, the solution was washed and dried to obtain the secondary acid-doped polyaniline. The prepared secondary acid-doped polyaniline was pyrolyzed at 500-800°C under a nitrogen atmosphere for 0.5-2h, cooled, and ground to obtain the heteroatom-doped carbon support XNC, where X was BNC, PNC, ONC, or ClNC, depending on the doping acid. For comparison, the nitrogen-doped carbon support obtained by pyrolysis of native polyaniline without secondary acid doping was named NC.

[0014] (2) Preparation of bimetallic colloid: Take 20-60 mL of homemade gold colloid solution (the preparation of gold colloid refers to the patent technology CN202210197236.3 of Shandong Gold Engineering Technology Research Center / Yantai Key Laboratory of Gold Catalysis and Process of our laboratory), add 1-8 mL of ascorbic acid solution (0.1 mol / L), mix well, and then add 0.01-1 mL (1 mg / mL) of one of chloropalladic acid, chloroplatinic acid, silver nitrate or nickel nitrate solution, stir and disperse, and react for 4-20 h to obtain gold-containing bimetallic colloid M-Au, where M is Pd, Pt, Ag or Ni.

[0015] (3) Preparation of a carbon-based gold-containing bimetallic catalyst: 0.05–0.25 g of a doped carbon support was dispersed in 2–5 mL of water. 10–35 mL of bimetallic colloid M-Au was then added. The mixture was stirred and adsorbed for 0.5–24 h, followed by washing and drying to obtain the carbon-based gold-containing bimetallic catalyst M-Au / XNC. This catalyst can be efficiently used in the catalytic hydrogenation of 4-chloronitrobenzene to produce 4-chloroaniline.

[0016] The present invention integrates the theories of nanomaterials, heterogeneous catalysis and polymer chemistry to innovatively construct a carbon-based gold-containing bimetallic catalyst with a carrier heteroatom and a noble metal. The heteroatom-doped carbon-based carrier is constructed by the controlled pyrolysis technology of polyaniline with the help of its secondary acid doping process, achieving the stability and high dispersion of the gold-containing bimetallic particles. The interaction between the carbon-based carrier heteroatom and the noble metal particles is used to modulate the electronic state of the noble metal particle surface. By optimizing the type and ratio of the bimetallic, while ensuring the high selectivity of the formation of 4-chloroaniline, the conversion efficiency of the catalytic hydrogenation of 4-chloronitrobenzene is improved. The prepared catalyst exhibits excellent catalytic performance. The boron-nitrogen co-doped carbon (BNC) generated by the pyrolysis of boric acid-doped polyaniline prepared by the present invention is used as a carrier. The prepared 0.05% Pd-0.5% Au / BNC has a TOF of 5178h for the conversion of para-chloronitrobenzene under the reaction conditions of 0.8MPa H2 and 333K. -1 The activation energy is 16.94 kJ / mol. After five cycles, the conversion rate decreased by only 15%, while the selectivity remained as high as 97%. The initial activity and selectivity showed no significant decrease after 60 days of storage, demonstrating significant prospects for industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1Figure 1 shows the catalytic activity of x%My%Au / XNC catalysts with varying loadings, prepared by the colloidal adsorption method in Examples 1-4 of the present invention. (x and y represent the theoretical metal loadings; M represents Pt, Ag, Pd, and Ni; X represents the doping element, O, Cl, P, and B, respectively. Reaction conditions: reaction temperature, 100°C; H₂ pressure, 1.2 MPa; reaction time, 1 h; substrate, 5 mmol 4-chloronitrobenzene; solvent, 25 mL methanol.)

[0018] Figure 2 TEM images of the catalysts prepared in Examples 1-5 of the present invention and their particle size distribution

[0019] Figure 3 XRD and Raman images of the catalysts prepared in Examples 1-5 of the present invention

[0020] Figure 4 The Au 4f and Pd 3d XPS patterns of the catalyst 0.05% Pd-0.5% Au / BNC prepared in Example 5 of the present invention

[0021] Figure 5 The catalytic activity of the catalyst 0.05% Pd-0.5% Au / BNC prepared in Example 5 of the present invention varies with temperature and pressure. (Reaction conditions: reaction time, 1 h; substrate amount, 5 mmol 4-chloronitrobenzene; solvent amount, 25 mL methanol).

[0022] Figure 6 This is a cyclic activity diagram for the catalyst 0.05% Pd-0.5% Au / BNC prepared in Example 5 of the present invention. (Reaction conditions: reaction temperature, 60°C; H2 pressure, 0.8 MPa; reaction time, 0.5 h; substrate amount, 5 mmol 4-chloronitrobenzene; solvent amount, 25 mL methanol) DETAILED DESCRIPTION

[0023] The present invention will be further explained below with reference to specific embodiments and accompanying drawings:

[0024] Example 1: Preparation of 0.17% Pt-0.6% Au / ONC Catalyst

[0025] Dissolve 2 mL of aniline in 50 mL of hydrochloric acid (0.1 mol / L), followed by dissolving 3 g of ammonium persulfate in the same 50 mL of hydrochloric acid. Rapidly mix the two solutions, disperse them ultrasonically, and allow them to react in the dark for 8 hours. The resulting hydrochloric acid-doped polyaniline was washed and then dedoped by soaking in 150 mL of aqueous ammonia (0.1 mol / L) for 45 minutes. The native polyaniline was then washed, dried, and oven-dried.

[0026] 0.4 g of native polyaniline was dispersed in 40 mL of a 1 mol / L citric acid solution for secondary acid doping. After stirring at room temperature for 8 hours, the solution was washed and dried to obtain citric acid-doped polyaniline. The prepared citric acid-doped polyaniline was pyrolyzed at 700°C for 1 hour under a nitrogen atmosphere, cooled, and ground to obtain an oxygen-doped carbon support (ONC).

[0027] Take 60 mL of homemade gold colloid solution, add 8.0 mL of ascorbic acid solution (0.1 mol / L), mix well, add 0.5 mL (1 mg / mL) of chloroplatinic acid, stir and disperse, react for 20 hours, and obtain gold-containing bimetallic colloid Pt-Au.

[0028] 0.15g of the ONC support was dispersed in 2.5mL of water, followed by the addition of 35mL of a bimetallic Pt-Au colloid. After stirring and adsorption for 24 hours, the catalyst was washed and dried to obtain a carbon-based gold-containing bimetallic catalyst, 0.17% Pt-0.6% Au / ONC. This catalyst was highly effective in the catalytic hydrogenation of 4-chloronitrobenzene to produce 4-chloroaniline.

[0029] Example 2: Preparation of 0.15% Ni-0.35% Au / ClNC Catalyst

[0030] Dissolve 1 mL of aniline in 40 mL of hydrochloric acid (0.1 mol / L), followed by dissolving 2 g of ammonium persulfate in the same 40 mL of hydrochloric acid. Rapidly mix the two solutions, disperse them ultrasonically, and react in the dark for 8 hours. The resulting hydrochloric acid-doped polyaniline is washed and then dedoped by soaking in 100 mL of aqueous ammonia (0.1 mol / L) for 10 minutes. Wash, dry, and oven-dry to obtain native polyaniline.

[0031] 0.6 g of native polyaniline was dispersed in 60 mL of 1 mol / L hydrochloric acid solution for secondary acid doping. After stirring at room temperature for 8 hours, the solution was washed and dried to obtain hydrochloric acid-doped polyaniline. The prepared hydrochloric acid-doped polyaniline was pyrolyzed at 600°C for 1 hour under a nitrogen atmosphere, cooled, and ground to obtain the chlorine-doped carbon support ClNC.

[0032] Take 40 mL of homemade gold colloid solution, add 6.0 mL of ascorbic acid solution (0.1 mol / L), mix well, add 0.5 mL (1 mg / mL) of nickel nitrate, stir and disperse, react for 20 hours, and obtain gold-containing bimetallic colloid Ni-Au.

[0033] 0.25g of ClNC support was dispersed in 5mL of water, followed by the addition of 35mL of bimetallic Ni-Au colloid. After stirring and adsorption for 24 hours, the catalyst was washed and dried to obtain a carbon-based gold-containing bimetallic catalyst, 0.15% Ni-0.35% Au / ClNC. This catalyst was highly effective in the catalytic hydrogenation of 4-chloronitrobenzene to 4-chloroaniline.

[0034] Example 3: Preparation of 0.1% Ag-0.6% Au / PNC Catalyst

[0035] Dissolve 2 mL of aniline in 50 mL of hydrochloric acid (0.1 mol / L), followed by dissolving 3 g of ammonium persulfate in the same 50 mL of hydrochloric acid. Rapidly mix the two solutions, disperse them ultrasonically, and allow them to react in the dark for 8 hours. The resulting hydrochloric acid-doped polyaniline was washed and then dedoped by soaking in 150 mL of aqueous ammonia (0.1 mol / L) for 45 minutes. The native polyaniline was then washed, dried, and oven-dried.

[0036] 0.6 g of native polyaniline was dispersed in 60 mL of 1.5 mol / L phosphoric acid solution for secondary acid doping. After stirring at room temperature for 8 hours, the solution was washed and dried to obtain phosphoric acid-doped polyaniline. The prepared phosphoric acid-doped polyaniline was pyrolyzed at 800°C for 1 hour under a nitrogen atmosphere, cooled, and ground to obtain a phosphorus-doped carbon support (PNC).

[0037] Take 60 mL of homemade gold colloid solution, add 4.0 mL of ascorbic acid solution (0.1 mol / L), mix well, add 0.3 mL (1 mg / mL) of silver nitrate, stir and disperse, react for 20 hours, and obtain gold-containing bimetallic colloid Ag-Au.

[0038] 0.15g of the PNC support was dispersed in 5mL of water, followed by the addition of 35mL of bimetallic colloid Ag-Au. After stirring and adsorption for 24 hours, the mixture was washed and dried to obtain a carbon-based gold-containing bimetallic catalyst (0.1% Ag-0.6% Au / PNC). This catalyst was highly effective in the catalytic hydrogenation of 4-chloronitrobenzene to produce 4-chloroaniline.

[0039] Example 4: Preparation of 0.1% Pd-1% Au / NC catalyst

[0040] Dissolve 2 mL of aniline in 55 mL of hydrochloric acid (0.1 mol / L), followed by dissolving 3 g of ammonium persulfate in the same 55 mL of hydrochloric acid. Rapidly mix the two solutions, disperse them ultrasonically, and react in the dark for 8 hours. The resulting hydrochloric acid-doped polyaniline was washed and then dedoped by soaking in 200 mL of aqueous ammonia (0.1 mol / L) for 45 minutes. The native polyaniline was then washed, dried, and oven-dried.

[0041] The prepared intrinsic polyaniline was pyrolyzed at 800°C for 1 h under a nitrogen atmosphere, and then cooled and ground to obtain the nitrogen-doped carbon support NC.

[0042] Take 40 mL of homemade gold colloid solution, add 3.6 mL of ascorbic acid solution (0.1 mol / L), mix well, add 0.115 mL (1 mg / mL) of chloropalladic acid, stir and disperse, react for 24 hours, and obtain gold-containing bimetallic colloid Pd-Au.

[0043] 0.1g of the NC support was dispersed in 5mL of water, followed by the addition of 38mL of bimetallic Pd-Au colloid. After stirring and adsorption for 24 hours, the catalyst was washed and dried to obtain a carbon-based gold-containing bimetallic catalyst, 0.1% Pd-1% Au / NC. This catalyst was highly effective in the catalytic hydrogenation of 4-chloronitrobenzene to produce 4-chloroaniline.

[0044] Example 5: Preparation of 0.05% Pd-0.5% Au / BNC Catalyst

[0045] Dissolve 1.5 mL of aniline in 50 mL of hydrochloric acid (0.1 mol / L), followed by dissolving 1.8 g of ammonium persulfate in the same 50 mL of hydrochloric acid. Rapidly mix the two solutions, disperse them ultrasonically, and react in the dark for 6 hours. The resulting hydrochloric acid-doped polyaniline was washed and then dedoped by soaking in 150 mL of aqueous ammonia (0.1 mol / L) for 45 minutes. The native polyaniline was then washed, dried, and oven-dried.

[0046] 0.3 g of native polyaniline was dispersed in 40 mL of a 1.0 mol / L boric acid solution for secondary acid doping. After stirring at room temperature for 6 hours, the solution was washed and dried to obtain boric acid-doped polyaniline. The prepared boric acid-doped polyaniline was pyrolyzed at 600°C for 1 hour under a nitrogen atmosphere, cooled, and ground to obtain a boron-doped carbon support (BNC).

[0047] Take 40 mL of homemade gold colloid solution, add 3.6 mL of ascorbic acid solution (0.1 mol / L), mix well, add 0.115 mL (1 mg / mL) of chloropalladic acid, stir and disperse, react for 12 hours, and obtain gold-containing bimetallic colloid Pd-Au.

[0048] 0.1g of the BNC support was dispersed in 2.5mL of water, followed by the addition of 18.75mL of bimetallic colloid Pd-Au. After stirring and adsorption for 12 hours, the mixture was washed and dried to obtain a carbon-based gold-containing bimetallic catalyst, 0.05% Pd-0.5% Au / BNC. The prepared catalyst was highly effective in the catalytic hydrogenation of 4-chloronitrobenzene to 4-chloroaniline. At 60°C and 0.8MPa of H₂ pressure, the 0.05% Pd-0.5% Au / BNC catalyst exhibited 100% conversion and 90.7% selectivity. Even after 60 days of storage, the catalyst exhibited no significant decrease in activity (conversion of 98.6% and selectivity of 91.0%).

[0049] Figure 1 The catalytic activities of the x%My%Au / XNC catalysts with different metal loadings prepared in Examples 1-4 were analyzed by Figure 1It can be seen that the synergistic effect between Au and the different metals M (Pt, Pd, Ag, and Ni) significantly influences the catalytic activity. Among the selected precious metals, except for Ag, which exhibits a relatively low reactivity with a conversion rate of only 11.3%, the remaining precious metals, Pd and Pt, all achieve complete conversion of 4-chloronitrobenzene. However, in terms of selectivity, Ag (98.7%) and Pd (83.4%) both outperform Pt (42.1%). Ni exhibits poor reactivity, with a conversion rate of only 73.5% and a selectivity of 86.2%. This is because Pt has a higher hydrogenation capacity than Pd, allowing the product 4-chloroaniline to continue hydrogenating to form aniline. However, the relatively low hydrogenation capacities of Ag and Ni prevent the complete conversion of the reactants in a short period of time.

[0050] Figure 2 TEM images of the catalysts prepared in Examples 1-5 are shown. Metal nanoparticles with a particle size of approximately 3.29 to 3.90 nm are uniformly dispersed on the doped carbon support, demonstrating that the support obtained by doping with an acid containing a heteroelement can effectively stabilize the metal nanoparticles. The nanoparticles in the 0.05% Pd-0.5% Au / BNC catalyst have the smallest particle size (3.29 nm), demonstrating the superior dispersibility of the B element. In contrast, the 0.1% Pd-1% Au / NC catalyst prepared using a support made from intrinsic polyaniline has the largest particle size (3.90 nm). Some metal nanoparticles can be seen agglomerated in the field of view, demonstrating that heteroelement doping effectively promotes the dispersion of metal nanoparticles on the support surface.

[0051] Figure 3 The XRD and Raman spectra of the catalysts prepared in Examples 1-5 are shown. All samples exhibit a broad diffraction peak at 24° attributed to the carbon (002) crystal plane, indicating that they have an amorphous carbon structure. At the same time, the characteristic peak at 44° corresponds to the carbon (100) crystal plane, confirming the successful carbonization of the material. It is worth noting that a characteristic peak at 2θ = 38.3° attributed to the Au (111) crystal plane was found in 0.1% Pd-1% Au / NC, while no characteristic peaks of Au were found in the other four catalysts. This phenomenon means that the metal nanoparticles are small in size, below the XRD detection limit, or they exist in a highly dispersed form, thus failing to form a detectable crystalline phase, once again confirming that the doped carbon support has good stability for the metal nanoparticles.

[0052] The Raman spectrum also observed that the wavelength was about 1350-1850 cm -1 The characteristic peaks belonging to the D band and the G band confirm that the material is successfully carbonized. At the same time, there are many defect sites in the material, which can stabilize the metal nanoparticles.

[0053] Figure 4The XPS spectrum of the 0.05% Pd-0.5% Au / BNC catalyst in Example 5 is shown. 7 / 2 The binding energy of 84.05 eV is similar to that of the typical metallic Au 4f 7 / 2 Compared with the positive shift, it means that the surface of the Au particles is in an electron-deficient state. This shows that the introduction of B element into the NC carrier enhances the interaction between Au and the carrier, and electrons are transferred from Au to BNC. δ+ Species. In the Pd 3d spectrum, a species belonging to Pd appears at a binding energy of 338.32 eV. 4+ The signal of Pd appeared at the binding energy of 337.24eV. 2+ signal, high-valence Pd n+ The appearance of may be due to the interaction between B and Pd, but due to the low concentration of B, the Pd n+ It does not dominate. -NO2, which has a stronger electronegativity, is more easily adsorbed on Pd than -Cl. n+ sites, resulting in higher selectivity for 4-chloroaniline. Since the binding energies in both Au 4f and Pd 3d are positively shifted, it can be determined that strong interactions occur between the B-doped support and Au and Pd, promoting electron transfer.

[0054] Figure 5 The catalytic activity of the catalyst prepared in Example 5 of the present invention as a function of temperature and pressure is plotted. When the H2 pressure was 1.2 MPa and the reaction temperature varied between 60 and 100°C, the conversion of 4-chloronitrobenzene did not change significantly with decreasing reaction temperature, while the selectivity gradually increased. Ultimately, when the temperature was lowered to 60°C, the selectivity for 4-chloroaniline increased to 90.89%, a significant improvement over the 83.41% at 100°C. Testing the catalyst activity at 60°C by varying the H2 pressure showed no significant effect of the pressure reduction on the reaction activity. Therefore, the optimal hydrogenation conditions for this catalyst are 60°C and 0.8 MPa, under which it achieves 100% conversion and 90.7% selectivity.

[0055] Figure 6The cyclic activity diagram of the 0.05% Pd-0.5% Au / BNC catalyst prepared in Example 5 is shown. The reaction time is controlled at 0.5h. As shown in the figure, after five cycles, the conversion rate of the catalyst only decreased from 66.49% to 51.2%, and the selectivity was maintained at 97%, which has excellent cyclic stability, proving that the catalyst of the present invention has the characteristics of high efficiency and stability. At the same time, Table 1 shows the apparent activation energy and TOF of this catalyst and the catalyst reported in the literature. 0.05% Pd-0.5% Au / BNC has a lower apparent activation energy (16.94kJ / mol) and a higher TOF value (5178h -1 After 60 days of storage, the catalyst activity did not decrease significantly (the conversion rate and selectivity were 98.6% and 91.0%, respectively). Therefore, the catalyst prepared by the present invention has good cycle stability and storage stability.

[0056] Table 1 Comparison of Ea and TOF of 0.05% Pd-0.5% Au / BNC with reported values

[0057]

[0058] [1]ZHANG

[0059] [2]CAMPOS CH,URBANO BF,TORRES CC,et al.A novel synthesis of goldnanoparticles supported on hybrid polymer / metal oxide as catalysts for p-chloronitrobenzene hydrogenation[J].Journal of Chemistry,2017,2017:7941853.

[0060] [3]BUSTAMANTE T M,CAMPOS C H,FRAGA M A,et al.Promotional effect ofpalladiumin Co-SiO2 core@shell nanocatalysts for selective liquid phasehydrogenation of chloronitroarenes[J].Journal of Catalysis,2020,385:224-237.

[0061] [4]HAN X,ZHOU R,LAI G,et al.Effect of transition metal(Cr,Mn,Fe,Co,Niand Cu)on the hydrogenation properties of chloronitrobenzene over Pt / TiO2catalysts[J].Journal of Molecular Catalysis A:Chemical,2004,209:83-87.

[0062] [5]LU C,JI H,ZHU Q,et al.Superior suppression hydrodehalogenationperformanceof Pd nanoparticle decorated with metalloid-promoter GQDs for theselectivehydrogenation of halonitrobenzenes[J].Journal of Materials Science,2019,54:10153-10167.

Claims

1. A method for preparing a carbon-based gold-containing bimetallic catalyst, characterized in that: The gold-containing bimetallic catalyst is prepared by mixing and dispersing 0.05-0.25 g of the doped carbon support in 2-5 mL of water, then adding 10-35 mL of bimetallic colloid, stirring and adsorbing for 0.5-24 hours, and then washing and drying to obtain the carbon-based gold-containing bimetallic catalyst. The prepared catalyst can be efficiently used in the catalytic hydrogenation of 4-chloronitrobenzene to prepare 4-chloroaniline.

2. The method for preparing a carbon-based gold-containing bimetallic catalyst according to claim 1, characterized in that: The heteroatom-doped carbon support was prepared according to the following steps: 1-2 mL of aniline was dissolved in 50 mL of hydrochloric acid (0.1 mol / L), followed by dissolving 2-3 g of ammonium persulfate in the same 50 mL of hydrochloric acid. The two solutions were rapidly mixed and ultrasonically dispersed, and the mixture was allowed to react in the dark for 4-8 hours. The resulting hydrochloric acid-doped polyaniline was washed and then dedoped by soaking in 150 mL of ammonia (0.1 mol / L) for 15-45 minutes. The native polyaniline was then washed, dried, and oven-dried. Secondary acid doping was performed by dispersing 0.2-0.6 g of native polyaniline in 20-60 mL of a 0.5-1.5 mol / L doping acid solution (boric acid, phosphoric acid, citric acid, or hydrochloric acid). After stirring at room temperature for 4-8 hours, the solution was washed and dried to obtain the secondary acid-doped polyaniline. The prepared secondary acid-doped polyaniline was pyrolyzed at 500-800°C for 0.5-2 hours under a nitrogen atmosphere, cooled, and ground to obtain the heteroatom-doped carbon support.

3. The method for preparing a carbon-based gold-containing bimetallic catalyst according to claim 1, characterized in that: The gold-containing bimetallic colloid was prepared according to the following steps: 20-60 mL of a homemade gold colloid solution was added to 1-8 mL of an ascorbic acid solution (0.1 mol / L). After mixing evenly, 0.01-1 mL (1 mg / mL) of one of chloropalladic acid, chloroplatinic acid, silver nitrate, or nickel nitrate solutions was added. The mixture was stirred and dispersed, and the reaction was carried out for 4-20 hours to obtain a gold-containing bimetallic colloid.

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