A Pd-Ni-Co / NaOH-Hβ catalyst, its preparation method and application

Abstract

The present invention discloses a Pd-Ni-Co / NaOH-Hβ catalyst, its preparation method and application. The catalyst uses Hβ molecular sieve as a carrier, which is modified by NaOH and then loaded with Pd, Ni and Co. The preparation method of the catalyst is as follows: (1) After the Hβ molecular sieve is activated, it is mixed with a NaOH solution and heated for reaction, then cooled, washed with water, filtered by suction and dried. The obtained solid is placed in an NH4Cl solution for ion exchange and suction filtration, and then dried, ground and activated to obtain NaOH-Hβ; (2) The NaOH-Hβ is impregnated with an equal volume in a mixed solution containing nickel salt, cobalt salt and palladium salt, allowed to stand, dried and ground, and then activated and reduced to obtain the Pd-Ni-Co / NaOH-Hβ catalyst, which can be used in the isomerization reaction of mesitylene. In the present invention, Pd is used as a carbon deposition inhibition component, and Ni and Co are used as co-active components. The prepared Pd-Ni-Co / NaOH-Hβ catalyst not only retains the high stability performance of traditional microporous molecular sieves, but also has higher conversion rate and anti-coking ability, and can effectively extend the service life of the catalyst.

Description

Technical Field

[0001] The present invention relates to a catalyst, a preparation method and an application thereof, and particularly relates to a Pd-Ni-Co / NaOH-Hβ catalyst, a preparation method and an application thereof. Background Art

[0002] Pseudocumene is the main component of reformed aromatic hydrocarbons, with a content of about 35%-40%. It can be purified to more than 99% by conventional distillation methods. Therefore, most pseudocumene in industry is obtained by separation, and the research on pseudocumene mostly focuses on the synthesis of other important industrial raw materials. Mesitylene is the component with the highest added value in C9 aromatics, and its industrial uses are very extensive. It is widely used in departments such as electronics, aviation, printing and dyeing, and machinery manufacturing, and is a fine chemical raw material with good market prospects. The world is rich in C9 aromatics. If this part of precious resources can be fully utilized, it will not only promote the economic benefits of the refining industry, but also promote the development of fine chemical industry in China. The methods for producing pseudocumene and mesitylene reported in domestic and foreign literatures mainly include: HF-BF3 solvent separation, extractive distillation method, isomerization method, alkylation method, etc. In some current studies on trimethylbenzene isomerization, most use high-purity pseudocumene as raw material and mordenite as catalyst. However, for the isomerization reaction of 1,2,3-trimethylbenzene in mixed C9, Hβ molecular sieve shows relatively high catalytic performance; but a large amount of by-products will be generated, resulting in rapid coking deactivation of the catalyst, which limits its further industrial application. Therefore, it is of important industrial application value to develop micro-mesoporous molecular sieves with higher conversion rate, anti-coking ability and extended catalyst life.

[0003] In some studies on trimethylbenzene isomerization, aluminum trichloride, HM and WO3 / ZrO2 show relatively low mesitylene yields, which are about 14%, 21.55% and 18.7% respectively. Hβ molecular sieve shows relatively high yields of pseudocumene and mesitylene and is considered to be an effective catalyst for the isomerization reaction of 1,2,3-trimethylbenzene. However, the unique microporous structure of commercial Hβ zeolite indicates that due to diffusion limitations, the acidic sites inside the pores cannot be fully utilized, showing relatively low activity of 1,2,3-trimethylbenzene at low temperatures, and large molecular by-products cannot diffuse out of the pores in time, which will lead to rapid coking deactivation of the catalyst and limit its further industrial application.

[0004] In the article "Synthesis of Mesitylene and 1,2,4,5-Tetramethylbenzene from Mixed Trimethylbenzenes" by Sun Tao et al., using mixed trimethylbenzenes as raw material and Ni-Mo / HM as catalyst, the isomerization reaction of mixed trimethylbenzenes was carried out under the conditions of reaction temperature 280°C, reaction pressure 1.2 MPa, mass space velocity 1.0 h -1 , and hydrogen-oil ratio 6, and the conversion rate of 1,2,3-trimethylbenzene was 77.76%, and the total selectivity and total yield of pseudocumene and mesitylene were 72.93% and 56.71% respectively. Summary of the Invention

[0005] Object of the Invention: The present invention aims to provide a Pd-Ni-Co / NaOH-Hβ catalyst with good catalytic effect, and the present invention also provides a preparation method and application of the Pd-Ni-Co / NaOH-Hβ catalyst.

[0006] Technical Solution: The Pd-Ni-Co / NaOH-Hβ catalyst described in the present invention uses Hβ molecular sieve as a carrier. After being modified by NaOH, it is loaded with Pd, Ni, and Co. The mass ratio of Pd, Ni, and Co is 0.4 - 0.6:0.8 - 1.2:0.5 - 0.7, and the silica-alumina ratio of the Hβ molecular sieve is 40.

[0007] The preparation method of the Pd-Ni-Co / NaOH-Hβ catalyst described in the present invention includes the following steps:

[0008] (1) After the Hβ molecular sieve is activated, it is mixed with an NaOH solution for heating reaction. After completion, it is cooled, washed with water, filtered by suction, and dried. The obtained solid is placed in an NH4Cl solution for ion exchange and suction filtration. After sufficient reaction, it is dried and ground, and then activated again to obtain the microporous and mesoporous Hβ molecular sieve NaOH-Hβ.

[0009] (2) The NaOH-Hβ is impregnated with an equal volume in a mixed solution containing nickel salt, cobalt salt, and palladium salt. After standing, it is dried and ground, and then activated. After completion, reduction treatment is carried out to obtain the Pd-Ni-Co / NaOH-Hβ catalyst.

[0010] Further, in step (1), the solid-liquid ratio of the Hβ molecular sieve to the NaOH solution is 1g:10 - 30ml, the temperature of the heating reaction is 60 - 70°C, and the time is 0.1 - 1h; the concentration of the NH4Cl solution is 0.1 - 1mol / L, and the temperature of the ion exchange is 50 - 60°C.

[0011] Further, in step (2), the nickel salt is nickel nitrate, the cobalt salt is cobalt nitrate, the palladium salt is potassium tetrachloropalladate, and the mass ratio of NaOH-Hβ, nickel nitrate, cobalt nitrate, and potassium tetrachloropalladate is 5:0.12 - 0.13:0.2 - 0.3:0.08 - 0.1; the time of equal-volume impregnation is 12 - 24h, the temperature of standing is 50 - 60°C, and the time of standing is 4 - 8h; the conditions of the reduction treatment are: reduction in a hydrogen atmosphere, the hydrogen rate is 10 - 15ml / min, the reduction time is 2 - 6h, and the reduction temperature is 350 - 550°C.

[0012] Further, in steps (1) and (2), the conditions for the activation treatment are as follows: the activation temperature is 500 - 600 °C, the activation time is 3 - 5 h, and the conditions for drying are: drying at 100 - 120 °C for 8 - 12 h.

[0013] The application of the Pd-Ni-Co / NaOH-Hβ catalyst described in the present invention in the pseudocumene isomerization reaction comprises the following steps: using the pseudocumene-enriched liquid in the mixed C9 as the reaction raw material, preheating it and mixing it with hydrogen and the Pd-Ni-Co / NaOH-Hβ catalyst for the isomerization reaction, and after completion, separating the gas and liquid to obtain the product.

[0014] Further, the composition of the pseudocumene-enriched liquid in the mixed C9 is as follows: 9.82 - 10.54% of 1,2,4-trimethylbenzene, 37.49 - 39.84% of pseudocumene, and 49.62 - 50.91% of heavy components. The conditions for the isomerization reaction are: the reaction temperature is 290 - 310 °C, the reaction pressure is 1.3 - 1.8 MPa, the mass space velocity of the reaction raw material is 0.6 - 1.4 h -1 , and the hydrogen-oil ratio is 8 - 12:1.

[0015] Principle of the invention: In the above preparation method, the process of alkali treatment is adopted first. Since the desilication by alkali treatment will damage the Si-O-Si and Si-O-Al bonds in the Hβ zeolite, mesoporous structures are generated in the Hβ zeolite, resulting in the transformation of framework aluminum in the original structure into non-framework aluminum, thereby generating more acid sites. When further treated with metal ions, the role of palladium is to crack by-products, prevent catalyst coking, and improve the catalyst life. Cobalt is used to reduce Lewis acid sites, and the addition of nickel increases the dispersion of cobalt and palladium. The pseudocumene reactant reacts on the acid sites on the outer surface and inside the pores of the molecular sieve, and the transfer of 1,2-alkyl groups in the benzene ring is realized through the protonation of alkylbenzene molecules, and the isomerization product diffuses out of the pores. Therefore, increasing acid sites and reducing Lewis acid sites are beneficial to increasing the selectivity of pseudocumene isomerization and reducing the occurrence of side reactions such as disproportionation. Beneficial effects: Compared with the prior art, the present invention has the following remarkable advantages:

[0016] (1) The micro-mesoporous metal Pd-Ni-Co / NaOH-Hβ catalyst prepared by the present invention not only retains the high stability performance of traditional microporous molecular sieves, but also has higher conversion rate and anti-coking ability, effectively prolongs the life of the catalyst, and has certain industrial application value;

[0017] (2) The preparation method of the catalyst of the present invention is simple and has strong operability;

[0018] (3) The catalyst of the present invention has high selectivity for pseudocumene isomerization, can effectively reduce the generation of side reactions such as disproportionation, and improves the yield of the target product.

[0019] (3) The present invention uses a Pd-Ni-Co / NaOH-Hβ catalyst for the isomerization reaction of mesitylene in mixed C9. It has high catalytic efficiency and a long service life. Description of the Drawings

[0020] Figure 1 It is the elemental distribution map of the Pd-Ni-Co / NaOH-Hβ catalyst prepared in Example 1 of the present invention;

[0021] Figure 2 It is the elemental distribution map of the Hβ molecular sieve in Comparative Example 1 of the present invention;

[0022] Figure 3 It is the elemental distribution map of the NaOH-Hβ catalyst prepared in Comparative Example 2 of the present invention;

[0023] Figure 4 It is the infrared spectrum diagram of the catalysts prepared in Example 1, Comparative Example 1 and Comparative Example 2 of the present invention;

[0024] Figure 5 It is the nitrogen adsorption-desorption diagram of the catalysts prepared in Example 1, Comparative Example 1 and Comparative Example 2 of the present invention;

[0025] Figure 6 It is the pore size distribution diagram of the catalysts prepared in Example 1, Comparative Example 1 and Comparative Example 2 of the present invention;

[0026] Figure 7 It is the XRD comparison diagram of the catalysts prepared in Example 1, Comparative Example 1 and Comparative Example 2 of the present invention;

[0027] Figure 8 It is the trend diagram of the experimental results of the Pd-Ni-Co / NaOH-Hβ catalyst life investigation in Example 8 of the present invention. Detailed Embodiments

[0028] The technical solutions of the present invention will be further described below in conjunction with the embodiments and the drawings.

[0029] Example 1: The preparation method of the Pd-Ni-Co / NaOH-Hβ catalyst described in the present invention includes the following steps:

[0030] (1) After the Hβ molecular sieve was activated at 550 °C for 4 h, it was mixed with 0.2 mol / L NaOH solution at a solid-liquid ratio of 1 g:20 ml and reacted at 65 °C for 0.5 h. After completion, it was placed in water and cooled to room temperature, washed with water and filtered by suction until the pH = 7, dried at 110 °C for 10 h. The obtained solid was ground into powder, placed in 0.5 mol / L NH4Cl solution at a solid-liquid ratio of 1 g:20 ml for ion exchange for 1 h and filtered by suction. The above operation was repeated 4 times, washed with normal temperature water until no chloride ions were contained, then dried at 110 °C for 10 h, ground into powder and placed in a muffle furnace, and activated at 550 °C for 4 h to obtain the micro-mesoporous Hβ molecular sieve NaOH-Hβ;

[0031] (2) 5 g of NaOH-Hβ was impregnated isovolumetrically in a mixed solution containing 0.12386 g of nickel nitrate, 0.2469 g of cobalt nitrate and 0.092 g of potassium tetrachloropalladate for 12 h, then left standing at 60 °C for 4 h, dried at 110 °C for 10 h. The obtained solid was ground into powder, and then placed in a muffle furnace, activated at 550 °C for 4 h. After completion, it was reduced in a hydrogen atmosphere, the hydrogen rate was 15 ml / min, the reduction time was 4 h, and the reduction temperature was 420 °C to obtain the Pd-Ni-Co / NaOH-Hβ catalyst, and its element distribution diagram is Figure 1 , and the mass percentages of local O, Si, Al, Co, Ni, Pd are 50.6:45.1:2.9:0.6:0.6:0.3.

[0032] Comparative Example 1: The untreated Hβ molecular sieve, its element distribution is as Figure 2 shown, and the mass percentages of O, Si, Al are 59.9:38.4:1.7.

[0033] Comparative Example 2: The difference from Example 1 is that: step (2) is not included, and the prepared material is the micro-mesoporous Hβ molecular sieve NaOH-Hβ, and its element distribution is as Figure 3 shown, and the mass percentages of O, Si, Al are 57.8:39.8:2.4.

[0034] Comparative Example 3: The difference from Example 1 is that: in step (2), NaOH-Hβ was impregnated isovolumetrically in a solution containing only nickel nitrate.

[0035] Comparative Example 4: The difference from Example 1 is that: in step (2), NaOH-Hβ was impregnated isovolumetrically in a solution containing only cobalt nitrate.

[0036] Comparative Example 5: The difference from Example 1 is that: in step (2), NaOH-Hβ was impregnated isovolumetrically in a solution containing only potassium tetrachloropalladate.

[0037] Comparative Example 6: The difference from Example 1 is that in step (2), NaOH-Hβ was impregnated in an equal volume in a solution containing only cobalt nitrate and potassium tetrachloropalladate.

[0038] Comparative Example 7: The difference from Example 1 is that in step (2), NaOH-Hβ was impregnated in an equal volume in a solution containing only nickel nitrate and cobalt nitrate.

[0039] Example 2: The Pd-Ni-Co / NaOH-Hβ catalyst prepared in Example 1 was used in the pseudocumene isomerization reaction. The steps were as follows: Using the pseudocumene-enriched liquid in mixed C9 as the reaction raw material, after preheating to 293 °C, it was mixed with hydrogen and 1.65 g of the Pd-Ni-Co / NaOH-Hβ catalyst for the isomerization reaction. The reaction temperature for isomerization was 290 °C, the pressure was 1.8 MPa, and the mass space velocity of the raw material was 1.0 h -1 , after completion, gas-liquid separation was carried out, the isomerization product was collected, and GC7700 gas-phase hydrogen flame chromatography was used for detection.

[0040] Comparative Example 8: The difference from Example 2 is that the catalyst used was the catalyst prepared in Comparative Examples 3-7.

[0041] Figure 4 are the infrared spectra of the three catalysts, Hβ, NaOH-Hβ, and Pd-Ni-Co / NaOH-Hβ, in the range of 1800-400 cm -1 The absorption peak between 1236-1093 cm -1 is the asymmetric stretching vibration peak of the internal tetrahedron. The absorption peak near 806 cm -1 is the symmetric stretching vibration peak of the Si-O-Si bond. The absorption peaks near 577 cm -1 and 525 cm -1 are the vibration peaks of the framework double four-membered ring and the framework double five-membered ring respectively. Compared with the Hβ molecular sieve, the positions of the characteristic peaks in the NaOH-Hβ and Pd-Ni-Co / NaOH-Hβ samples did not change, indicating that the dealumination modification did not affect the crystal phase structure of the Hβ molecular sieve, but the framework structure was damaged to a certain extent.

[0042] Figure 5 and Figure 6 are the nitrogen adsorption-desorption curves and pore size distribution curves of Hβ, NaOH-Hβ, and Pd-Ni-Co / NaOH-Hβ. From Figure 5It can be seen that the isotherm of Hβ shows a rapid increase in the low-pressure region, and the adsorption curve rises rapidly, indicating micropore adsorption within the micropores, showing a typical type I isotherm, which proves the microporous structure of the Hβ sample. At the same time, an H4-type hysteresis loop belonging to narrow slit-shaped pores can be observed at P / P0 > 0.5, indicating the existence of irregular pore voids between Hβ particles. For the NaOH-Hβ sample, the adsorption and desorption curves coincide in the low P / P0 region, and there is a sudden increase, and an H4-type hysteresis loop gradually appears, indicating that both micropores and mesopores exist in the sample. The generation of mesopores is attributed to the removal of framework silicon, forming framework cavities. The Pd-Ni-Co / NaOH-Hβ sample still maintains similar characteristics to the NaOH-Hβ sample. From Figure 6 the pore size distribution diagram, it can also be seen that the NaOH-Hβ and Pd-Ni-Co / NaOH-Hβ samples have more mesopores than the Hβ molecular sieve, and the mesopore size range is concentrated between 2 - 10 nm. However, due to the loading of Pd, Ni, and Co, which may have a certain impact on the pore size and pore volume of the sample, the pore size and pore volume are slightly smaller than those of the NaOH-Hβ sample.

[0043] Figure 7 XRD patterns of three catalysts, namely Hβ, NaOH-Hβ, and Pd-Ni-Co / NaOH-Hβ. Through Figure 7 It can be seen that characteristic diffraction peaks of Hβ appear at diffraction angles 2θ = 7.8° and 22.4° for all three samples, indicating that the treatment with NaOH solution does not change the crystal structure of the Hβ molecular sieve. The intensity of the diffraction peak reflects the integrity of the crystal structure of the molecular sieve. Compared with Hβ, the intensity of the diffraction peak of NaOH-Hβ decreases, indicating that the treatment with NaOH solution has a desilication effect and a certain destructive effect on the framework silicon, resulting in a decrease in the crystallinity of the sample. The positions of the characteristic diffraction peaks of PdO, NiO, and CoO are around 2θ = 33.8°, 43°, and 54° respectively, and no relevant diffraction peaks appear in Pd-Ni-Co / NaOH-Hβ. This may be due to the low metal loading or because the loaded metals are evenly dispersed on the surface of the catalyst without forming metal clusters.

[0044] The results measured in Example 2 and Comparative Example 8 are shown in Table 1. Hβ zeolite itself has good catalytic activity for the isomerization reaction of mesitylene. However, with the prolongation of the reaction time, the activity of the catalyst decreases rapidly. In order to improve the service life of the catalyst, Hβ zeolite is first treated with alkali, and then an anti-coking metal component is added. Ni and Pd have a hydrogenation effect and can better inhibit the deposition of coke on the catalyst in the presence of hydrogen. Co can reduce the Lewis sites on the catalyst surface and reduce the formation of by-products. Therefore, when the Ni content is 0.5%, the Co content is 1.0%, and the Pd content is 0.6%, the Pd-Ni-Co / NaOH-Hβ catalyst has good catalytic activity for the isomerization of mesitylene to pseudocumene and hemimellitene, and can achieve a mesitylene conversion rate of 89.18% and a total yield of pseudocumene and hemimellitene of 64.50%.

[0045] Table 1 Catalysts Prepared in Example 1 and Comparative Examples 3-7

[0046]

[0047] Example 3: The difference from Example 2 is that the temperature of the isomerization reaction is 310 °C.

[0048] Example 4: The difference from Example 2 is that the pressure of the isomerization reaction is 1.3 MPa.

[0049] Example 5: The difference from Example 2 is that the mass space velocity of the raw material is 0.6 h -1 .

[0050] Example 6: The difference from Example 2 is that the mass space velocity of the raw material is 1.4 h -1 .

[0051] Comparative Example 9: The difference from Example 2 is that the temperature of the isomerization reaction is 270 °C.

[0052] Comparative Example 10: The difference from Example 2 is that the temperature of the isomerization reaction is 330 °C.

[0053] Comparative Example 11: The difference from Example 2 is that the temperature of the isomerization reaction is 350 °C.

[0054] Comparative Example 12: The difference from Example 2 is that the pressure of the isomerization reaction is 0.3 MPa.

[0055] Comparative Example 13: The difference from Example 2 is that the pressure of the isomerization reaction is 0.8 MPa.

[0056] Comparative Example 14: The difference from Example 2 is that the pressure of the isomerization reaction is 2.3 MPa.

[0057] Comparative Example 15: The difference from Example 2 is that the mass hourly space velocity of the raw materials is 1.8 h -1 .

[0058] Comparative Example 16: The difference from Example 2 is that the mass hourly space velocity of the raw materials is 2.2 h -1 .

[0059] The results measured in Examples 2 - 6 and Comparative Examples 9 - 16 were summarized in Tables 2 to 4.

[0060] As can be seen from Table 2, different reaction temperatures have a great influence on the activity of the Pd-Ni-Co / NaOH-Hβ catalyst. As the reaction temperature increases, the conversion rate of mesitylene continuously rises, but it is not beneficial to the total selectivity and total yield of pseudocumene and durene; and a higher reaction temperature is likely to cause the catalyst coking to accelerate, resulting in a decrease in the activity of the Pd-Ni-Co / NaOH-Hβ catalyst. Therefore, considering comprehensively, the more suitable reaction temperature for this reaction is 290 - 310 °C.

[0061] Table 2 Summary table of the conversion rate of mesitylene and the selectivity and yield of pseudocumene and durene of the catalysts prepared in Examples 2 - 3 and Comparative Examples 9 - 11

[0062] Reaction temperature / °C Conversion rate / % Selectivity / % Yield / % Comparative Example 9 270 77.37 72.34 55.97 Example 2 290 89.26 72.27 64.51 Example 3 310 92.14 56.76 52.30 Comparative Example 10 330 92.40 54.45 50.31 Comparative Example 11 350 93.19 46.32 43.16

[0063] As can be seen from Table 3, different reaction pressures have a small influence on the activity of the Pd-Ni-Co / NaOH-Hβ catalyst. In the pressure range of 0.3 - 2.3 MPa, when the pressure is greater than 1.8 MPa, the conversion rate of mesitylene and the yield of durene are almost not affected by the pressure and remain stable. From the perspective of chemical equilibrium, the isomerization reaction of pseudocumene is an equimolecular reaction, and the number of molecules does not change before and after the reaction, so the reaction pressure has little influence on the isomerization reaction of mesitylene. However, during the reaction process, the reaction pressure has a great influence on side reactions such as disproportionation reaction, and a higher reaction pressure will cause energy waste during the operation process. Therefore, considering comprehensively, the more suitable reaction pressure for this reaction is 1.3 - 1.8 MPa.

[0064] Table 3 Summary table of the conversion rate of mesitylene and the selectivity and yield of pseudocumene and durene of the catalysts prepared in Example 2, Example 4 and Comparative Examples 12 - 14

[0065] Reaction pressure / MPa Conversion rate / % Selectivity / % Yield / % Comparative Example 12 0.3 81.72 70.93 57.96 Comparative Example 13 0.8 89.52 67.64 60.55 Example 4 1.3 90.36 70.87 64.04 Example 2 1.8 89.26 72.27 64.51 Comparative Example 14 2.3 88.71 71.68 63.59

[0066] As can be seen from Table 4, different mass space velocities of the raw materials have a great influence on the activity of the Pd-Ni-Co / NaOH-Hβ catalyst. With the increase of the mass space velocity of the raw materials, the reaction residence time decreases, resulting in a gradual decrease in the conversion rate of mesitylene and the total yield of pseudocumene and hemimellitene. Therefore, considering comprehensively, the more suitable mass space velocity for this reaction is 0.6-1.4 h -1 .

[0067] Table 4 Summary table of the conversion rate of mesitylene, the selectivity and yield of pseudocumene and hemimellitene of the catalysts prepared in Example 2, Examples 5-6 and Comparative Examples 15-16

[0068] <![CDATA[Mass space velocity / h -1 > Conversion rate / % Selectivity / % Yield / % Example 5 0.6 89.05 70.29 62.60 Example 2 1.0 89.26 72.27 64.51 Example 6 1.4 81.21 74.54 60.53 Comparative Example 15 1.8 75.04 76.68 57.54 Comparative Example 16 2.2 71.82 77.93 55.97

[0069] Example 7: Life investigation experiment of Pd-Ni-Co / NaOH-Hβ catalyst

[0070] The enriched liquid of mesitylene in the mixed C9 aromatic hydrocarbon solvent oil was continuously catalytically reacted using the Pd-Ni-Co / NaOH-Hβ catalyst prepared in Example 1, and the reaction time was 25-200 h. From Figure 8 it can be seen that during the whole experiment, with the continuous increase of the reaction time, the activity and selectivity of the Pd-Ni-Co / NaOH-Hβ catalyst are relatively stable, indicating that the catalyst has a relatively high catalytic activity and a considerable catalyst life at the same time.

Claims

1. Application of Pd-Ni-Co / NaOH-Hβ catalyst in pseudocumene isomerization reaction, characterized in that, The catalyst uses Hβ zeolite as the carrier. After being modified by NaOH, it is loaded with Pd, Ni, and Co. The mass ratio of Pd, Ni, and Co is 0.4 - 0.6:0.8 - 1.2:0.5 - 0.

7. The preparation method of the Pd-Ni-Co / NaOH-Hβ catalyst includes the following steps: (1) After the Hβ zeolite is activated, it is mixed with a NaOH solution and heated for reaction. After completion, it is cooled, washed with water, filtered by suction, and dried. The obtained solid is placed in an NH4Cl solution for ion exchange and suction filtration. After sufficient reaction, it is dried and ground, and then activated again to obtain the micro-mesoporous Hβ zeolite NaOH-Hβ. (2) The NaOH-Hβ is impregnated with an equal volume in a mixed solution containing nickel salt, cobalt salt, and palladium salt. After standing, it is dried and ground, and then activated. After completion, reduction treatment is carried out to obtain the Pd-Ni-Co / NaOH-Hβ catalyst.

2. The application according to claim 1, characterized in that, In step (1), the solid-liquid ratio of the Hβ zeolite to the NaOH solution is 1 g:10 - 30 ml, the heating reaction temperature is 60 - 70 °C, and the time is 0.1 - 1 h.

3. The application according to claim 1, characterized in that, In step (2), the nickel salt is nickel nitrate, the cobalt salt is cobalt nitrate, the palladium salt is potassium tetrachloropalladate, and the mass ratio of NaOH-Hβ, nickel nitrate, cobalt nitrate, and potassium tetrachloropalladate is 5:0.12 - 0.13:0.2 - 0.3:0.08 - 0.

1.

4. The application according to claim 1, characterized in that, In step (2), the time for equal-volume impregnation is 12 - 24 h; the standing temperature is 50 - 60 °C, and the time is 4 - 8 h; the reduction treatment conditions are: reduction in a hydrogen atmosphere, the hydrogen rate is 10 - 15 ml / min, the reduction time is 2 - 6 h, and the reduction temperature is 350 - 550 °C.

5. The application according to claim 1, characterized in that, The steps of the application are as follows: Using the pseudocumene-enriched liquid in mixed C9 as the reaction raw material, after preheating, it is mixed with hydrogen and the Pd-Ni-Co / NaOH-Hβ catalyst for isomerization reaction. After completion, gas-liquid separation is carried out to obtain the product.

6. The application according to claim 5, characterized in that, The composition of the pseudocumene-enriched liquid in the mixed C9 is: 9.82 - 10.54% of 1,2,4-trimethylbenzene, 37.49 - 39.84% of pseudocumene, and 49.62 - 50.91% of heavy components.

7. The application according to claim 5, characterized in that, The conditions for the isomerization reaction are as follows: the reaction temperature is 290 - 310 °C, the reaction pressure is 1.3 - 1.8 MPa, the mass hourly space velocity of the reaction raw material is 0.6 - 1.4 h -1 , and the hydrogen-oil ratio is 8 - 12:1.

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