Mechanically-ball-milled noble metal catalyst, preparation method thereof and application of mechanically-ball-milled noble metal catalyst in liquid-phase benzene hydrogenation

Abstract

The invention discloses a mechanically ball-milled noble metal catalyst and a preparation method and application thereof in liquid-phase benzene hydrogenation.The preparation process of the catalyst comprises the steps that metal oxide and noble metal precursor salt are subjected to mechanical ball milling under specific conditions, then roasted in a muffle furnace and subjected to reduction treatment in a reducing atmosphere, and the catalyst is obtained. And finally obtaining the oxide confinement noble metal catalyst which is used for liquid-phase benzene hydrogenation reaction. According to the oxide confinement noble metal catalyst prepared by adopting a mechanical ball milling method, the stability of the catalyst is improved, and the catalyst is simple to prepare and easy to produce in an enlarged manner, and has an excellent industrial application value.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of liquid phase hydrogenation reaction catalysts, and specifically relates to a mechanical ball milling noble metal catalyst and a preparation method thereof and application thereof in liquid phase benzene hydrogenation. Background Art

[0002] Cyclohexane is an important raw material for chemical production. It is mainly used to prepare nylon-6 and nylon-66. It can also be used for oxidation reactions to prepare cyclohexanone, cyclohexanol, adipic acid, polycaprolactam, and polyhexamethylene adipamide. High-purity cyclohexane is also an excellent solvent for cellulose, resin, asphalt, and rubber. At present, there are two main routes for the preparation of cyclohexane in industry, namely, benzene hydrogenation and fractionation and refining of petroleum hydrocarbon fractions. With the increasing demand for cyclohexane in industrial production, benzene hydrogenation has become the main route for preparing cyclohexane. According to different reaction conditions, benzene hydrogenation is divided into two categories: gas phase method and liquid phase method. The gas phase method for preparing cyclohexane mainly uses a fixed bed device. Benzene and hydrogen are evenly mixed, the reaction pressure is low, and the conversion rate and yield are relatively high. However, due to the excessively violent reaction, the "flying temperature" phenomenon is prone to occur, which is difficult to operate. At the same time, high temperature conditions will also cause catalyst sintering and deactivation. Compared with gas-phase benzene hydrogenation, liquid-phase benzene hydrogenation is relatively mild, has lower equipment requirements, and the reaction process is easy to control, but its hydrogen utilization rate is low, and subsequent reactions are usually required to improve the hydrogen utilization rate.

[0003] Bi et al. used the Cr-Al bimetallic organic framework material MIL-53 (Cr-Al) as a carrier, impregnated it with RuCl3 solution, and reduced it with KBH4 to obtain the Ru-B / MIL-53 (Cr-Al) catalyst. Various spectral characterizations and electron microscopy results show that the presence of the Cr-Al bimetallic intensifies the generation of unsaturated coordination in MIL-53 (Cr-Al), allowing the MIL-53 (Cr-Al) carrier to effectively anchor Ru particles, making the Ru species have a higher dispersion. In the benzene hydrogenation activity test, when the reaction temperature was 30°C and the H2 pressure was 1MPa, the TOF was 6.4S -1 . It exhibits excellent low-temperature and low-pressure benzene hydrogenation activity, and the catalyst also has good activity in other aromatic hydrocarbon hydrogenation reactions (Green Chemistry, 2016, 18 (7): 2216-2221.). Michalska et al. found that the Ni / Al2O3 catalyst with single metal Ni has low selectivity for cyclohexane in the benzene hydrogenation test, and produces a large amount of methylcyclohexane and methylcyclopentane. Although the introduction of the additive Cu can effectively improve the selectivity of cyclohexane, Cu and Ni are prone to form alloy sintering, which leads to a decrease in catalytic activity (Applied Catalysis a-General, 2016, 523: 54-60.).

[0004] In summary, the activity of benzene hydrogenation of non-precious metal catalysts is low, and the selectivity of the target product cyclohexane is also low. Although precious metal catalysts have high benzene hydrogenation activity and cyclohexane selectivity, they are expensive, so it is necessary to improve the dispersion of precious metals. At the same time, metal-supported catalysts all have the problem of deactivation due to the loss of active phases, so the development of a class of catalysts with high precious metal utilization and stability is the key direction of benzene hydrogenation catalyst research. Summary of the invention

[0005] The present invention aims at the deficiencies of the prior art and provides a mechanical ball-milled noble metal catalyst and a preparation method thereof and application thereof in liquid-phase benzene hydrogenation.

[0006] The specific technical solutions are as follows:

[0007] The invention provides a preparation method of a mechanically ball-milled noble metal catalyst, comprising the following steps: placing a metal oxide and a noble metal precursor salt in a ball mill, with the mass ratio of the grinding balls to the raw materials being 10:1, mechanically ball milling under specific conditions, then calcining in a muffle furnace, and then performing a reduction treatment in a reducing atmosphere, and finally obtaining an oxide-confined noble metal catalyst, which is used for a liquid-phase benzene hydrogenation reaction.

[0008] Furthermore, the metal oxide is one of Al2O3, CeO2, MgO, La2O3, TiO2 and Sm2O3, and preferably the metal oxide is one of Al2O3, CeO2, MgO and TiO2; the noble metal precursor salt is one of RuCl3, (NH4)2PdCl4 and (NH4)2PtCl6, and preferably the noble metal salt precursor is RuCl3; the mass ratio of the oxide to the noble metal element is 100:5 to 1000:1; the preferred mass ratio is 100:5 to 500:1.

[0009] Furthermore, the ball milling conditions are as follows: the ball milling speed is 200-500 r / min, preferably the ball milling speed is 300-400 r / min; the ball milling time is 1-8 h, preferably the ball milling time is 3-5 h.

[0010] Furthermore, the calcination temperature is 300-800°C, preferably 450-650°C; the calcination time is 2-8h, preferably 3-5h; the reducing atmosphere is a H2 / N2 mixed gas, the volume ratio of H2 / N2 is 1 / 10, the total flow rate is 100mL / min, the reduction temperature is 300°C, and the reduction treatment time is 2h.

[0011] The present invention also provides a mechanical ball-milled noble metal catalyst prepared by the method.

[0012] The invention also provides an application of a mechanically ball-milled noble metal catalyst in liquid-phase benzene hydrogenation.

[0013] By adopting the above technology, compared with the prior art, the present invention has the following beneficial effects:

[0014] 1) The present invention uses mechanical ball milling to confine the noble metal in the metal oxide, disperses the noble metal species through oxygen vacancies in the metal oxide, and anchors the noble metal species on the oxygen vacancies through oxygen bridge bonds, thereby improving the stability of the catalyst.

[0015] 2) The catalyst preparation process is simple, no three wastes are generated, it is easy to scale up industrial production, and has excellent industrial application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is the TEM image of the product prepared in Example 1. DETAILED DESCRIPTION

[0017] The present invention will be further described below in conjunction with specific embodiments, but the present invention is not limited to these specific embodiments. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solution and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered within the protection scope of the present invention.

[0018] Example 1

[0019] 50 g of Al2O3 and 0.21 g of RuCl3 were added to a stainless steel ball mill, and 500 g of grinding balls were added. The ball mill speed was 300 r / min and the ball milling time was 3 h. After the ball milling was completed, it was calcined at 450 ° C in a muffle furnace for 3 h. After the calcination was completed, it was reduced in a tubular furnace in a H2 / N2 mixed atmosphere with a volume ratio of H2 / N2 of 1 / 10, a total flow rate of 100 mL / min, a reduction temperature of 300 ° C, and a reduction treatment time of 2 h. Finally, Ru@Al2O3 catalyst was obtained, denoted as S-1. The TEM image of catalyst S-1 is shown in FIG. Figure 1 From the figure, we can find that the particle size of Ru particles is uniform and the dispersion is high.

[0020] Example 2

[0021] Add 50g of La2O3 and 0.13g of (NH4)2PdCl4 into a stainless steel ball mill, and add 500g of grinding balls. The ball mill speed is 200r / min and the ball milling time is 1h. After the ball milling is completed, it is calcined at 300℃ in a muffle furnace for 2h. After the calcination is completed, it is reduced in a tubular furnace in a H2 / N2 mixed atmosphere with a volume ratio of H2 / N2 of 1 / 10, a total flow rate of 100mL / min, a reduction temperature of 300℃, and a reduction treatment time of 2h. Finally, Pd@La2O3 catalyst is obtained, which is recorded as S-2.

[0022] Example 3

[0023] 10 g of Sm2O3 and 1.14 g of (NH4)2PtCl6 were added to a stainless steel ball mill, and 100 g of grinding balls were added. The ball mill speed was 500 r / min and the ball milling time was 8 h. After the ball milling was completed, it was calcined at 800 °C in a muffle furnace for 8 h. After the calcination was completed, it was reduced in a tubular furnace in a H2 / N2 mixed atmosphere with a volume ratio of H2 / N2 of 1 / 10, a total flow rate of 100 mL / min, a reduction temperature of 300 °C, and a reduction treatment time of 2 h. Finally, Pt@Sm2O3 catalyst was obtained, which was recorded as S-3.

[0024] Example 4

[0025] Add 50g of CeO2 and 1.03g of RuCl3 into a stainless steel ball mill, and add 500g of grinding balls. The ball mill speed is 400r / min and the ball milling time is 5h. After the ball milling is completed, it is placed in a muffle furnace and calcined at 600℃ for 5h. After the calcination is completed, it is placed in a tubular furnace and reduced in a H2 / N2 mixed atmosphere with a volume ratio of H2 / N2 of 1 / 10. The total flow rate is 100mL / min, the reduction temperature is 300℃, and the reduction treatment time is 2h. Finally, Ru@CeO2 catalyst is obtained, which is recorded as S-4.

[0026] Example 5

[0027] Add 50g of MgO and 0.26g of RuCl3 into a stainless steel ball mill, and add 500g of grinding balls. The ball mill speed is 350r / min and the ball milling time is 4h. After the ball milling is completed, it is calcined at 500℃ in a muffle furnace for 4h. After the calcination is completed, it is reduced in a tubular furnace in a H2 / N2 mixed atmosphere with a volume ratio of H2 / N2 of 1 / 10, a total flow rate of 100mL / min, a reduction temperature of 300℃, and a reduction treatment time of 2h. Finally, Ru@MgO catalyst is obtained, which is recorded as S-5.

[0028] Example 6

[0029] Add 50g of TiO2 and 0.34g of RuCl3 into a stainless steel ball mill, and add 500g of grinding balls. The ball mill speed is 400r / min, and the ball milling time is 3h. After the ball milling is completed, it is calcined at 550℃ in a muffle furnace for 3h. After the calcination is completed, it is reduced in a tubular furnace in a H2 / N2 mixed atmosphere with a volume ratio of H2 / N2 of 1 / 10, a total flow rate of 100mL / min, a reduction temperature of 300℃, and a reduction treatment time of 2h. Finally, Ru@TiO2 catalyst is obtained, which is recorded as S-6.

[0030] Example 7

[0031] Add 50g of Al2O3 and 0.51g of RuCl3 into a stainless steel ball mill, and add 500g of grinding balls. The ball mill speed is 350r / min, and the ball milling time is 3h. After the ball milling is completed, it is calcined at 600℃ in a muffle furnace for 4h. After the calcination is completed, it is reduced in a tubular furnace in a H2 / N2 mixed atmosphere with a volume ratio of H2 / N2 of 1 / 10, a total flow rate of 100mL / min, a reduction temperature of 300℃, and a reduction treatment time of 2h. Finally, Ru@Al2O3 catalyst is obtained, which is recorded as S-7.

[0032] Example 8

[0033] Add 50g of CeO2 and 0.51g of RuCl3 into a stainless steel ball mill, and add 500g of grinding balls. The ball mill speed is 400r / min, and the ball milling time is 4h. After the ball milling is completed, it is calcined at 650℃ in a muffle furnace for 5h. After the calcination is completed, it is reduced in a tubular furnace in a H2 / N2 mixed atmosphere with a volume ratio of H2 / N2 of 1 / 10, a total flow rate of 100mL / min, a reduction temperature of 300℃, and a reduction treatment time of 2h. Finally, Ru@CeO2 catalyst is obtained, which is recorded as S-8.

[0034] Example 9

[0035] The reaction of preparing cyclohexane by liquid phase hydrogenation of benzene is carried out in a stainless steel high-pressure reactor with a polytetrafluoroethylene liner and a pressure gauge. 1g of catalyst, 50g of benzene and 150mL of n-hexane are added to the reactor. After the reactor is sealed, the reactor is replaced and purged 3 times with N2 at a pressure of 2MPa, and then replaced and purged 2 times with H2 at 3MPa. Then the reactor is heated to 80°C, and after heating to 80°C, H2 is introduced to 3MPa, and stirring is turned on at a speed of 600rpm. In order to maintain the hydrogen pressure at 3MPa during the reaction process, hydrogen is continuously introduced. The reaction is terminated after 2h of reaction, and then the reactor is opened for sampling and analysis. The catalyst performance test results are shown in Table 1.

[0036] Table 1 Benzene conversion and cyclohexane selectivity over different catalysts

[0037] catalyst Benzene conversion rate (%) Selectivity of cyclohexane (%) S-1 93 98 S-2 83 99 S-3 85 98 S-4 94 99 S-5 92 98 S-6 93 98 S-7 91 99 S-8 94 98

[0038] Example 10

[0039] The catalyst in Example 1 was used and the benzene hydrogenation conditions in Example 9 were repeated for 5 times. The catalytic results are shown in Table 2. The results are recorded as C-1 to C-5. It can be seen from Table 3 that the activity of the catalyst hardly decreases after being recycled.

[0040] Table 2 Experimental results of the catalyst of Example S-1

[0041] catalyst Benzene conversion rate (%) Selectivity of cyclohexane (%) C-1 93 98 C-2 92 98 C-3 94 99 C-4 93 99 C-5 92 98

[0042] The contents described in this specification are merely an enumeration of implementation forms of the inventive concept, and the protection scope of the present invention should not be regarded as being limited to the specific forms described in the embodiments.

Claims

1. A method for preparing a mechanically ball-milled noble metal catalyst, characterized in that: The method comprises the following steps: placing a metal oxide and a noble metal precursor salt in a ball mill for mechanical ball milling, then calcining them in a muffle furnace, and then reducing them in a reducing atmosphere to finally obtain an oxide-confined noble metal catalyst, wherein the metal oxide is Al2O3, CeO2, MgO, La2O3, TiO2 or Sm2O3, and the noble metal precursor salt is RuCl3, (NH4)2PdCl4 or (NH4)2PtCl6.

2. The method for preparing a mechanically ball-milled noble metal catalyst according to claim 1, characterized in that: The metal oxide is Al2O3, CeO2, MgO or TiO2; the noble metal precursor salt is RuCl3; the mass ratio of the metal oxide to the noble metal element is 100:5 to 1000:1; the preferred mass ratio is 100:5 to 500:

1.

3. The method for preparing a mechanically ball-milled noble metal catalyst according to claim 1, characterized in that: The ball milling speed is 200-500 r / min, preferably 300-400 r / min; the ball milling time is 1-8 h, preferably 3-5 h.

4. The method for preparing a mechanically ball-milled noble metal catalyst according to claim 1, characterized in that: The mass ratio of grinding balls to raw materials is 10:

1.

5. The method for preparing a mechanically ball-milled noble metal catalyst according to claim 1, characterized in that: The calcination temperature is 300-800°C, preferably 450-650°C; the calcination time is 2-8h, preferably 3-5h; the reducing atmosphere is a H2 / N2 mixed gas, the volume ratio of H2 / N2 is 1 / 10, the total flow rate is 100mL / min, the reduction temperature is 300°C, and the reduction treatment time is 2h.

6. A mechanically ball-milled noble metal catalyst prepared by the preparation method according to any one of claims 1 to 5.

7. Use of the mechanically ball-milled noble metal catalyst as claimed in claim 6 in liquid phase benzene hydrogenation.

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