An acid-modified magnesium-aluminum hydrotalcite supported ruthenium catalyst, a preparation method and application thereof

Abstract

This invention discloses an acid-modified magnesium aluminum layered double hydroxide (MLD) supported ruthenium catalyst, its preparation method, and its application, belonging to the field of chemical technology. The catalyst uses hydrochloric acid-modified water-dispersible magnesium aluminum layered double hydroxide as a support, and metallic ruthenium as the hydrogenation active component; the mass of metallic ruthenium is 3.4~13.6% of the total catalyst mass. The preparation method is as follows: a ruthenium salt solution is added to a water-dispersible acid-modified magnesium aluminum layered double hydroxide colloid at room temperature, stirred and mixed, and then sodium borohydride solution is added dropwise. After centrifugation, washing, and redispersing, the catalyst is obtained. The catalyst of this invention utilizes the two-dimensional structure and high water dispersibility of the acid-modified layered double hydroxide to achieve high dispersion of ruthenium nanoparticles. When applied to the hydrogenation of phenol to cyclohexanol, it exhibits excellent conversion rate and cyclohexanol selectivity under mild conditions. At 2 MPa H2 and room temperature for 0.5 h, the phenol conversion rate reaches 69.95%, and the cyclohexanol selectivity reaches 90.17%. The catalyst preparation method of this invention is simple and low-cost, making it very suitable for industrial production.

Description

Technical Field

[0001] This invention belongs to the field of chemical technology, specifically relating to a water-dispersible acid-modified magnesium aluminum layered double hydroxide supported ruthenium nanoparticle catalyst, its preparation method, and its application in the hydrogenation reaction of phenol. Background Technology

[0002] Magnesium aluminum hydrotalcite has a unique two-dimensional layered structure, making it an ideal carrier for water-dispersible two-dimensional nanosheet catalysts. However, existing studies have shown that carbonate-type magnesium aluminum hydrotalcite has poor water dispersibility, and the catalysts prepared from it have problems such as small specific surface area and low surface acidity.

[0003] Cyclohexanol is an important intermediate in the production of caprolactam, nylon 66, and other products. Biomass pyrolysis yields large quantities of phenol, and the aqueous-phase catalytic hydrogenation of phenol to cyclohexanol is a green route with high atom economy. Commonly used noble metal ruthenium-based catalysts exhibit high activity at low temperatures, but they typically suffer from problems such as easy aggregation and poor stability. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, the purpose of this invention is to provide a water-dispersible acid-modified magnesium aluminum layered double hydroxide supported ruthenium catalyst and its preparation method, with the aim of having a simple and low-cost preparation method, and the prepared magnesium aluminum layered double hydroxide supported highly dispersed ruthenium catalyst having high water dispersibility, large specific surface area and abundant surface acidity.

[0005] Another objective of this invention is to provide the application of the above-mentioned catalyst in the hydrogenation of phenol to cyclohexanol, in order to improve the hydrogenation performance of phenol and solve the technical problems that urgently need to be solved in this field.

[0006] The above-mentioned objective of this invention is achieved through the following technical solutions.

[0007] This invention provides a method for preparing an acid-modified magnesium aluminum layered double hydroxide supported ruthenium catalyst, specifically comprising the following steps:

[0008] (1) The carbonate-type magnesium aluminum hydrotalcite was calcined under a nitrogen atmosphere, and then the calcined product was placed in a sodium chloride solution and stirred thoroughly. Finally, it was centrifuged, washed and dried to obtain magnesium aluminum hydrotalcite. The magnesium aluminum hydrotalcite was mixed with water at a mass ratio of 1:1000 and stirred at room temperature for 2-4 hours. Then, it was ultrasonically dispersed to obtain highly dispersed magnesium aluminum hydrotalcite colloid.

[0009] (2) Mix acid and water at a volume ratio of 1:300~1000 and stir thoroughly at room temperature to obtain an acid solution with a concentration of 0.012~0.04 mol / L; mix the acid solution with the magnesium aluminum hydrotalcite colloid obtained in step (1) at a volume ratio of 1:1 and stir for 10~30 minutes, then centrifuge, wash, dry and dehydrate to obtain acid-modified magnesium aluminum hydrotalcite solid powder; mix the acid-modified magnesium aluminum hydrotalcite solid powder with water at a mass ratio of 1:1000~2000, stir at room temperature for 2~4 hours, and then disperse with ultrasonic assistance to obtain water-dispersible acid-modified magnesium aluminum hydrotalcite;

[0010] (3) Mix ruthenium chloride trihydrate with water at a mass ratio of 1:200~400, stir at room temperature until fully dissolved to obtain a ruthenium chloride solution with a concentration of 0.0096~0.0192 mol / L;

[0011] (4) Sodium borohydride and water are mixed at a mass ratio of 0.03~0.06:1 and stirred at room temperature until fully dissolved to obtain a sodium borohydride solution with a concentration of 0.0158~0.0317 mol / L;

[0012] (5) The ruthenium chloride solution obtained in step (3) and the water-dispersible acid-modified hydrotalcite obtained in step (2) are mixed at a volume ratio of 0.044~0.088:1. Then, while stirring, the sodium borohydride solution obtained in step (4) is added dropwise. After the addition is completed, stirring is continued for 2~4 h. Finally, the mixture is centrifuged and washed, and then redispersed in water to obtain the acid-modified hydrotalcite supported ruthenium catalyst.

[0013] The mass of the metallic ruthenium is 3.4 to 13.6% of the total mass of the catalyst.

[0014] Furthermore, the roasting in nitrogen atmosphere in step (1) refers to roasting in nitrogen atmosphere at 450°C for 4 hours.

[0015] Furthermore, in step (1), the concentration of the sodium chloride solution is 2 mol / L, the stirring temperature is 40 ℃, and the stirring time is 2 hours.

[0016] Furthermore, the acid in step (3) is concentrated hydrochloric acid with a mass fraction of 37%.

[0017] The acid-modified magnesium aluminum layered double hydroxide supported ruthenium catalyst obtained by the above preparation method.

[0018] The acid-modified magnesium aluminum layered double hydroxide supported ruthenium catalyst described above can be used in the hydrogenation reaction of phenol.

[0019] Furthermore, the hydrogenation product of the phenol is cyclohexanol.

[0020] Furthermore, the conditions for the hydrogenation reaction of phenol are: reaction temperature at room temperature, hydrogen pressure at 2 MPa, and water as solvent.

[0021] The performance test of the phenol hydrogenation to cyclohexanol using the acid-modified magnesium aluminum layered double hydroxide supported ruthenium catalyst of this invention was conducted under the following specific steps and conditions: The phenol hydrogenation reaction was carried out in a 100 mL batch high-pressure reactor. 10 mL of the above-mentioned water-dispersible acid-modified magnesium aluminum layered double hydroxide supported ruthenium catalyst was added to the reactor, followed by 4 mmol of phenol and 10 mL of deionized water solvent. The reaction temperature was room temperature, the hydrogen pressure was 2 MPa, and the reaction time was 0.5 hours. The hydrogenation product was analyzed using an Agilent 8860 gas chromatograph.

[0022] Compared with the prior art, the present invention has the following technical effects:

[0023] (1) Magnesium aluminum hydrotalcite itself is almost non-acidic. This invention uses acid modification pretreatment to dissolve some metal ions in the magnesium aluminum hydrotalcite layers, thereby changing the surface acidity of magnesium aluminum hydrotalcite. The acidity can also be controlled by changing the hydrochloric acid treatment time and concentration, and the catalyst performance can be optimized.

[0024] (2) The water-dispersible acid-modified magnesium aluminum layered double hydroxide supported ruthenium catalyst of the present invention, the hydrochloric acid modification pretreatment can dissolve some metal ions in the magnesium aluminum layered double hydroxide plates, thereby increasing the specific surface area and pore volume of the catalyst, up to 47.5m. 2 / g and 0.41cm 3 / g.

[0025] (3) The catalyst of the present invention utilizes the two-dimensional structure and high water dispersibility of acid-modified hydrotalcite to achieve high dispersion of ruthenium nanoparticles; when applied to the hydrogenation of phenol to cyclohexanol, it exhibits excellent conversion rate and cyclohexanol selectivity under mild conditions (room temperature, 2 MPa H2). At 2 MPa H2 and room temperature for 0.5 h, the phenol conversion rate reaches 69.95% and the cyclohexanol selectivity reaches 90.17%.

[0026] (4) The catalyst preparation method of the present invention is simple and low in cost, making it very suitable for industrial production. At the same time, the unique two-dimensional structure, large specific surface area and abundant surface acidity of the acid-modified magnesium aluminum layered double hydroxide supported ruthenium catalyst of the present invention also broaden the application field of the catalyst. Attached Figure Description

[0027] Figure 1 This is a photograph of the LDH-5 and Ru / LDH-5 catalysts of the present invention after being placed for 48 hours.

[0028] Figure 2 This is the XRD pattern of the Ru / LDH-5 catalyst of the present invention.

[0029] Figure 3This is a SEM image of the Ru / LDH-5 catalyst of the present invention.

[0030] Figure 4 This is the EDS energy spectrum of the Ru / LDH-5 catalyst of the present invention.

[0031] Figure 5 This is the nitrogen physisorption isotherm diagram of the Ru / LDH-5 catalyst of the present invention.

[0032] Figure 6 This is the NH3-TPD diagram of the Ru / LDH-5 catalyst of the present invention. Detailed Implementation

[0033] To further illustrate the present invention, the following embodiments are provided, but they do not limit the scope of the invention as defined by the claims.

[0034] I. Preparation of water-dispersible magnesium aluminum hydrotalcite

[0035] Example 1

[0036] 10g of carbonate-type magnesium aluminum hydrotalcite was calcined at 450℃ under a nitrogen atmosphere for 4 hours. The calcined product was then placed in a 2mol / L sodium chloride solution and stirred at 40℃ for 2 hours. After centrifugation, washing, and drying, solid magnesium aluminum hydrotalcite was obtained. 5g of the solid magnesium aluminum hydrotalcite was mixed with water at a mass ratio of 1:1000, stirred at room temperature for 2 hours, and then ultrasonically dispersed to obtain a highly dispersed magnesium aluminum hydrotalcite colloid.

[0037] II. Preparation of water-dispersible acid-modified magnesium aluminum layered double hydroxide supported ruthenium catalyst

[0038] Example 2

[0039] Take 100 ml of the magnesium-aluminum hydrotalcite colloid from Example 1, mix it with a 0.012 mol / L acid solution at a volume ratio of 1:1, stir for 30 minutes, centrifuge, wash, and dry to obtain acid-modified magnesium-aluminum hydrotalcite solid powder. Take 0.05 g of the acid-modified magnesium-aluminum hydrotalcite solid powder and mix it with water at a mass ratio of 1:1000, stir, and then perform ultrasonic dispersion to obtain acid-modified magnesium-aluminum hydrotalcite colloid. Add 2.2 ml of a 0.0152 mol / L ruthenium chloride solution to the above acid-modified magnesium-aluminum hydrotalcite colloid and stir at room temperature for 0.5 hours. Subsequently, 5 ml of a 0.21 mol / L sodium borohydride solution was added dropwise while stirring. After the addition was complete, stirring was continued for 2 hours. After multiple centrifugation and washing, the resulting solid was redispersed in water at a mass ratio of 1:1000 with the mass of the acid-modified magnesium aluminum layered double hydroxide solid powder to obtain a water-dispersible acid-modified magnesium aluminum layered double hydroxide supported ruthenium catalyst, denoted as Ru / LDH-1.

[0040] Example 3

[0041] Take 100 ml of the magnesium-aluminum hydrotalcite colloid from Example 1, mix it with a 0.024 mol / L acid solution at a volume ratio of 1:1, stir for 30 minutes, centrifuge, wash, and dry to obtain acid-modified magnesium-aluminum hydrotalcite solid powder. Take 0.05 g of the acid-modified magnesium-aluminum hydrotalcite solid powder and mix it with water at a mass ratio of 1:1000, stir, and then perform ultrasonic dispersion to obtain acid-modified magnesium-aluminum hydrotalcite colloid. Add 2.2 ml of a 0.0152 mol / L ruthenium chloride solution to the above acid-modified magnesium-aluminum hydrotalcite colloid and stir at room temperature for 0.5 hours. Subsequently, 5 ml of a 0.21 mol / L sodium borohydride solution was added dropwise while stirring. After the addition was complete, stirring was continued for 2 hours. After multiple centrifugation and washing, the resulting solid was redispersed in water at a mass ratio of 1:1000 with the mass of the acid-modified magnesium aluminum layered double hydroxide solid powder to obtain a water-dispersible acid-modified magnesium aluminum layered double hydroxide supported ruthenium catalyst, denoted as Ru / LDH-2.

[0042] Example 4

[0043] Take 100 ml of the magnesium-aluminum hydrotalcite colloid from Example 1, mix it with an acid solution of 0.036 mol / L at a volume ratio of 1:1, stir for 10 minutes, centrifuge, wash, and dry to obtain acid-modified magnesium-aluminum hydrotalcite solid powder. Take 0.05 g of the acid-modified magnesium-aluminum hydrotalcite solid powder and mix it with water at a mass ratio of 1:1000, stir, and then perform ultrasonic dispersion to obtain acid-modified magnesium-aluminum hydrotalcite colloid. Add 2.2 ml of ruthenium chloride solution of 0.0152 mol / L to the above acid-modified magnesium-aluminum hydrotalcite colloid and stir at room temperature for 0.5 hours. Subsequently, 5 ml of a 0.21 mol / L sodium borohydride solution was added dropwise while stirring. After the addition was complete, stirring was continued for 2 hours. Then, the mixture was centrifuged and washed multiple times. The resulting solid was redispersed in water at a mass ratio of 1:1000 with the mass of the acid-modified magnesium aluminum layered double hydroxide solid powder to obtain a water-dispersible acid-modified magnesium aluminum layered double hydroxide supported ruthenium catalyst, denoted as Ru / LDH-3.

[0044] Example 5

[0045] Take 100 ml of the magnesium-aluminum hydrotalcite colloid from Example 1, mix it with an acid solution of 0.036 mol / L at a volume ratio of 1:1, stir for 20 minutes, centrifuge, wash, and dry to obtain acid-modified magnesium-aluminum hydrotalcite solid powder. Take 0.05 g of this acid-modified magnesium-aluminum hydrotalcite solid powder and mix it with water at a mass ratio of 1:1000, stir, and then use ultrasonic dispersion to prepare acid-modified magnesium-aluminum hydrotalcite colloid. Add 2.2 ml of ruthenium chloride solution of 0.0152 mol / L to the above acid-modified magnesium-aluminum hydrotalcite colloid and stir at room temperature for 0.5 hours. Subsequently, 5 ml of a 0.21 mol / L sodium borohydride solution was added dropwise while stirring. After the addition was complete, stirring was continued for 2 hours. After multiple centrifugation and washing, the resulting solid was redispersed in water at a mass ratio of 1:1000 with the mass of the acid-modified magnesium aluminum layered double hydroxide solid powder to obtain a water-dispersible acid-modified magnesium aluminum layered double hydroxide supported ruthenium catalyst, denoted as Ru / LDH-4.

[0046] Example 6

[0047] Take 100 ml of the magnesium-aluminum hydrotalcite colloid from Example 1, mix it with an acid solution of 0.036 mol / L at a volume ratio of 1:1, stir for 30 minutes, centrifuge, wash, and dry to obtain acid-modified magnesium-aluminum hydrotalcite solid powder. Take 0.05 g of this acid-modified magnesium-aluminum hydrotalcite solid powder and mix it with water at a mass ratio of 1:1000, stir, and then perform ultrasonic dispersion to obtain acid-modified magnesium-aluminum hydrotalcite colloid. Add 2.2 ml of ruthenium chloride solution of 0.0152 mol / L to the above acid-modified magnesium-aluminum hydrotalcite colloid and stir at room temperature for 0.5 hours. Subsequently, 5 ml of a 0.21 mol / L sodium borohydride solution was added dropwise while stirring. After the addition was complete, stirring was continued for 2 hours. After multiple centrifugation and washing, the resulting solid was redispersed in water at a mass ratio of 1:1000 with the mass of the acid-modified magnesium aluminum layered double hydroxide solid powder to obtain a water-dispersible acid-modified magnesium aluminum layered double hydroxide supported ruthenium catalyst, denoted as Ru / LDH-5.

[0048] Example 7

[0049] Take 100 ml of the magnesium-aluminum hydrotalcite colloid from Example 1, mix it with an acid solution of 0.036 mol / L at a volume ratio of 1:1, stir for 30 minutes, centrifuge, wash, and dry to obtain acid-modified magnesium-aluminum hydrotalcite solid powder. Take 0.1 g of this acid-modified magnesium-aluminum hydrotalcite solid powder and mix it with water at a mass ratio of 1:1000, stir, and then perform ultrasonic dispersion to obtain acid-modified magnesium-aluminum hydrotalcite colloid. Add 2.2 ml of ruthenium chloride solution of 0.0152 mol / L to the above acid-modified magnesium-aluminum hydrotalcite colloid and stir at room temperature for 0.5 hours. Subsequently, 5 ml of a 0.21 mol / L sodium borohydride solution was added dropwise while stirring. After the addition was complete, stirring was continued for 2 hours. After multiple centrifugation and washing, the resulting solid was redispersed in water at a mass ratio of 1:1000 with the mass of the acid-modified magnesium aluminum layered double hydroxide solid powder to obtain a water-dispersible acid-modified magnesium aluminum layered double hydroxide supported ruthenium catalyst, denoted as Ru / LDH-6.

[0050] Example 8

[0051] Take 100 ml of the magnesium-aluminum hydrotalcite colloid from Example 1, mix it with an acid solution of 0.036 mol / L at a volume ratio of 1:1, stir for 30 minutes, centrifuge, wash, and dry to obtain acid-modified magnesium-aluminum hydrotalcite solid powder. Take 0.025 g of this acid-modified magnesium-aluminum hydrotalcite solid powder and mix it with water at a mass ratio of 1:2000, stir, and then perform ultrasonic dispersion to obtain acid-modified magnesium-aluminum hydrotalcite colloid. Add 1.1 ml of 0.0152 mol / L ruthenium chloride solution to the above acid-modified magnesium-aluminum hydrotalcite colloid and stir at room temperature for 0.5 hours. Subsequently, 5 ml of a 0.21 mol / L sodium borohydride solution was added dropwise while stirring. After the addition was complete, stirring was continued for 2 hours. After multiple centrifugation and washing, the resulting solid was redispersed in water at a mass ratio of 1:2000 with the mass of the acid-modified magnesium aluminum layered double hydroxide solid powder to obtain a water-dispersible acid-modified magnesium aluminum layered double hydroxide supported ruthenium catalyst, denoted as Ru / LDH-7.

[0052] Figure 1 The static sedimentation experiments of LDH-5 and Ru / LDH-5 catalysts were demonstrated. It was found that no obvious precipitation occurred after standing for 48 hours, indicating that the catalyst was highly dispersed in the aqueous solution.

[0053] The Ru / LDH-5 catalyst was characterized by XRD. The XRD tests were performed on a Rigaku SmartLab X-ray diffractometer in Japan, and the results are shown below. Figure 2The figure shows that the measured catalyst exhibits clear characteristic diffraction peaks at 2θ = 11.4°, 22.8°, 39.2°, 46.4°, 52.2°, 60.6°, 61.9°, and 65.7°. Even after acid modification and Ru loading, the characteristic diffraction peaks of magnesium aluminum layered double hydroxide (MLD) in the catalyst sample remain clearly distinguishable, and their positions do not show significant shifts. This indicates that the acid treatment and subsequent Ru loading process did not damage the main layered framework of the MLD support, and did not cause structural collapse or significant loss of long-range order. Further observation of the XRD pattern of the Ru / LDH-5 catalyst reveals that no characteristic diffraction peaks attributable to metallic Ru (PDF #06-0663) were detected. This is because the Ru loading in the Ru / LDH-5 catalyst is 6.8 wt%, but no characteristic diffraction peaks attributable to metallic Ru (PDF #06-0663) were observed in the catalyst XRD characterization. This phenomenon indicates that Ru species are highly dispersed on the surface and between layers of the magnesium aluminum hydrotalcite carrier or exist in an amorphous form, hence the absence of characteristic Ru diffraction peaks in the XRD pattern.

[0054] The Ru / LDH-5 catalyst was characterized by scanning electron microscopy (SEM). SEM measurements were performed using a Zeiss Gemini SEM 360 scanning electron microscope manufactured by FEI (USA). The results are as follows: Figure 3 .from Figure 3 Numerous irregularly shaped and unevenly sized nanosheet structures can be clearly observed in a. Figure 3 Enlarge the area within the red box in a () Figure 3 (b) It can be observed that the catalyst's main morphology consists of irregular nanosheets. The nanosheet surfaces are not smooth and flat, but exhibit obvious undulations and a rough texture. These morphological characteristics clearly indicate that the Ru / LDH-5 catalyst mainly exists in the form of two-dimensional nanosheets, and the nanosheet surfaces possess abundant rough structures. This open and rough lamellar morphology is beneficial for the exposure of active sites and the diffusion and mass transfer of reactant molecules. To determine the composition of the catalyst...

[0055] EDS analysis was performed on the Ru / LDH-5 catalyst. The EDS spectra were obtained using an Oxford spectrometer from FEI Corporation, USA. The EDS results are as follows: Figure 4 .from Figure 4 The data shows that the magnesium-aluminum ratio of the Ru / LDH-5 catalyst is approximately 1.38:1. In contrast, the magnesium-aluminum ratio of the ruthenium supported on hydrotalcite prepared by conventional co-precipitation methods is typically around 2:1. The Ru / LDH-5 ratio is much lower than that of conventional Ru / LDH, indicating that hydrochloric acid pretreatment dissolves some of the metal ions in the magnesium-aluminum hydrotalcite layers.

[0056] In this invention, the Ru / LDH-5 catalyst was tested for nitrogen physical adsorption using a Micromeritics ASAP 2420 physical adsorption analyzer, and the results are as follows: Figure 5 As shown, after treatment with 0.036 mmol / L acid for 30 min, the specific surface area and pore volume of the Ru / LDH-5 catalyst reached as high as 47.5 m². 2 / g and 0.41cm 3 / g.

[0057] The acidity test (NH3-TPD) of the Ru / LDH-5 catalyst in this invention was performed on a CHEMBET-3000 chemisorption analyzer manufactured by Quanta Computer in the United States. The NH3-TPD results are as follows: Figure 6 As shown. The Ru / LDH-5 catalyst was pretreated at 450℃ before the test. (The text abruptly ends here.) Figure 6 It can be seen that the Ru / LDH-5 catalyst exhibits a significant NH3 desorption peak near 118℃, with high peak intensity and broad peak width, indicating that the Ru / LDH-5 catalyst has abundant weak acid sites.

[0058] Comparison Example 1

[0059] 10g of magnesium aluminum hydrotalcite carbonate was calcined at 450℃ under a nitrogen atmosphere for 4 hours to obtain layered bimetallic oxide (LDO). 0.05g of LDO was added to 50ml of water and stirred thoroughly on a magnetic stirrer, followed by ultrasonic dispersion to prepare an LDO aqueous solution. 2.2ml of a 0.0152 mol / L ruthenium chloride solution was added to the LDO aqueous solution, and the mixture was stirred at room temperature for 0.5 hours. Subsequently, 5ml of a 0.21 mol / L sodium borohydride solution was added dropwise while stirring. After the addition was complete, stirring was continued for 2 hours. The mixture was then centrifuged and washed multiple times, and the resulting solid was redispersed in 50ml of water to obtain a layered bimetallic oxide-supported ruthenium catalyst, denoted as Ru / LDO.

[0060] II. Activity Evaluation of the Water-Dispersible Acid-Modified Magnesium Aluminum Layered Double Hydroxide-Supported Ruthenium Catalyst of the Present Invention

[0061] Example 9

[0062] Evaluation of the phenol hydrogenation activity of the water-dispersible acid-modified Ru / LDH-1 catalyst: The phenol hydrogenation performance of the Ru / LDH-1 catalyst was evaluated in a 100 mL batch high-pressure reactor. The specific operating steps and reaction conditions are as follows: 10 mL of 0.00080256 mol / L Ru / LDH-1 catalyst was added to the reactor, followed by 4 mmol of phenol reactant and 10 mL of deionized water solvent. The reaction temperature was room temperature, the hydrogen pressure was 2 MPa, and the reaction time was 0.5 hours. The hydrogenation products were analyzed using an Agilent 8860 gas chromatograph.

[0063] The conditions for evaluating the activity of Ru / LDO, Ru / LDH-2, Ru / LDH-3, Ru / LDH-4, Ru / LDH-5, Ru / LDH-6 and Ru / LDH-7 catalysts in the hydrogenation of phenol to cyclohexanol were the same as those for the Ru / LDH-1 catalyst, and the reaction results are shown in Table 1.

[0064] Table 1. Phenol hydrogenation performance of acid-modified water-dispersed Ru / LDH catalyst

[0065] catalyst Phenol conversion rate (%) Cyclohexanol selectivity (%) <![CDATA[TOF (h ‒1 ) a ]]> Ru / LDO 14.94 83.46 148.92 Ru / LDH-1 41.46 95.28 413.28 Ru / LDH-2 30.73 92.61 306.32 Ru / LDH-3 33.85 95.52 337.42 Ru / LDH-4 36.53 92.77 364.14 Ru / LDH-5 69.95 90.17 697.27 Ru / LDH-6 53.54 92.55 533.69 Ru / LDH-7 40.12 90.79 399.92

[0066] Reaction conditions: room temperature, 2 MPa, 0.5 h, 4 mmol phenol, n Ru :n 苯酚 =1:500.

[0067] The TOF value is defined as the number of moles of phenol converted per hour per mole of Ru. Calculation formula:

[0068] TOF = The unit is h -1

[0069] Table 1 shows that the water-dispersible acid-modified magnesium aluminum layered double hydroxide supported ruthenium catalyst prepared in this invention exhibits excellent phenol hydrogenation performance. According to the reaction results, at room temperature and 2 MPa hydrogen pressure, the phenol conversion rate of the Ru / LDO catalyst was only 14.94%. In contrast, the phenol conversion rate of the Ru / LDH-1 catalyst increased by 177.5%, the Ru / LDH-2 catalyst by 105.7%, the Ru / LDH-3 catalyst by 126.6%, and the Ru / LDH-4 catalyst by 144.5%, with cyclohexanol selectivity exceeding 92% in all cases. The Ru / LDH-5 catalyst showed the highest hydrogenation activity; after 0.5 hours of reaction, its phenol conversion rate reached 69.95%, its cyclohexanol selectivity reached 90.17%, and its TOF value was as high as 697.27 h⁻¹. -1The TOF value of the Ru / LDH-5 catalyst was increased by 368.2% compared to the Ru / LDO catalyst. Furthermore, a comparison of the Ru / LDH-5 and Ru / LDH-7 catalysts showed that the former had a 74.4% higher TOF value than the latter, indicating that moderately reducing the Ru loading is beneficial for improving catalyst activity.

Claims

1. A process for the preparation of an acid-modified Mg-Al hydrotalcite supported ruthenium catalyst, characterized in that Includes the following steps: (1) The carbonate-type magnesium aluminum hydrotalcite was calcined under a nitrogen atmosphere, and then the calcined product was placed in a sodium chloride solution and stirred thoroughly. Finally, it was centrifuged, washed and dried to obtain magnesium aluminum hydrotalcite. The magnesium aluminum hydrotalcite was mixed with water at a mass ratio of 1:1000 and stirred at room temperature for 2-4 hours. Then, it was ultrasonically dispersed to obtain highly dispersed magnesium aluminum hydrotalcite colloid. (2) Mix acid and water at a volume ratio of 1:300~1000 and stir thoroughly at room temperature to obtain an acid solution with a concentration of 0.012~0.04mol / L; mix the acid solution with the magnesium aluminum hydrotalcite colloid obtained in step (1) at a volume ratio of 1:1 and stir for 10~30 minutes, then centrifuge, wash, dry and dehydrate to obtain acid-modified magnesium aluminum hydrotalcite solid powder; mix the acid-modified magnesium aluminum hydrotalcite solid powder with water at a mass ratio of 1:1000~2000, stir at room temperature for 2~4 hours, and then disperse with ultrasonic assistance to obtain water-dispersible acid-modified magnesium aluminum hydrotalcite; (3) Mix ruthenium chloride trihydrate with water at a mass ratio of 1:200~400, stir at room temperature until fully dissolved to obtain a ruthenium chloride solution with a concentration of 0.0096~0.0192 mol / L; (4) Sodium borohydride and water are mixed at a mass ratio of 0.03~0.06:1 and stirred at room temperature until fully dissolved to obtain a sodium borohydride solution with a concentration of 0.0158~0.0317 mol / L; (5) The ruthenium chloride solution obtained in step (3) and the water-dispersible acid-modified hydrotalcite obtained in step (2) are mixed at a volume ratio of 0.044~0.088:

1. Then, while stirring, the sodium borohydride solution obtained in step (4) is added dropwise. After the addition is completed, stirring is continued for 2~4 h. Finally, the mixture is centrifuged and washed, and then redispersed in water to obtain the acid-modified hydrotalcite supported ruthenium catalyst. The mass of the metallic ruthenium is 3.4 to 13.6% of the total mass of the catalyst.

2. The method for preparing an acid-modified Mg-Al hydrotalcite-supported ruthenium catalyst according to claim 1, characterized by, The roasting in nitrogen atmosphere in step (1) refers to roasting in nitrogen atmosphere at 450°C for 4 hours.

3. The preparation method of the acid-modified magnesium aluminum layered double hydroxide supported ruthenium catalyst as described in claim 1, characterized in that, The concentration of sodium chloride solution in step (1) is 2 mol / L.

4. The preparation method of the acid-modified magnesium aluminum layered double hydroxide supported ruthenium catalyst as described in claim 1, characterized in that, The acid in step (2) is concentrated hydrochloric acid with a mass fraction of 37%.

5. The acid-modified magnesium aluminum layered double hydroxide supported ruthenium catalyst obtained by the preparation method described in claim 1.

6. The application of the acid-modified magnesium aluminum layered double hydroxide supported ruthenium catalyst as described in claim 5 in the hydrogenation reaction of phenol.

7. The application of the acid-modified magnesium aluminum layered double hydroxide supported ruthenium catalyst as described in claim 6 in the hydrogenation reaction of phenol, characterized in that, The hydrogenation product of phenol is cyclohexanol.

8. The application of the acid-modified magnesium aluminum layered double hydroxide supported ruthenium catalyst as described in claim 6 in the hydrogenation reaction of phenol, characterized in that, The conditions for the hydrogenation reaction of phenol are: reaction temperature at room temperature, hydrogen pressure at 2 MPa, and water as solvent.

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