CN111617772B - Supported Ni-Ga-Pd catalyst and preparation method and application thereof - Google Patents

Abstract

The invention discloses a supported Ni-Ga-Pd catalyst and a preparation method and application thereof. The preparation method comprises the following steps: (1) Preparing mixed metal nitrate solution by using nitrates of Ni, ga, mg and Al, and preparing a Ni/Ga/Mg/Al quaternary layered hydroxide material M by using a coprecipitation method; (2) Dissolving the material M in a proper amount of water, adding a proper amount of palladium precursor species for ion exchange, filtering, washing and drying to obtain a Ni/Ga/Pd/Mg/Al quinary layered hydroxide material PM; (3) And carrying out thermal reduction on the PM material to obtain the supported Ni-Ga-Pd catalyst. In the mixed metal nitrate solution, the molar ratio of Ni ions, ga ions, mg ions and Al ions is 1 (0.25-1), 3-6, (1-1.75), and the concentration of the Ni ions is 0.05-0.15 mol/L. In the catalyst, the loading amount of palladium is 10-200 ppm. The catalyst has the characteristics of high catalytic activity, good selectivity and long service life, and can obviously reduce the reaction temperature and avoid the generation of green oil aggravated by high temperature.

Description

Supported Ni-Ga-Pd catalyst and its preparation method and application

technical field

The invention belongs to the technical field of catalyst preparation, and in particular relates to a supported Ni-Ga-Pd catalyst and its preparation method and application.

Background technique

As the cornerstone of the modern chemical industry, ethylene is mainly produced through steam cracking of naphtha. The ethylene product from the naphtha steam cracking furnace contains a small amount of acetylene (0.5% to 2%), and these small amounts of acetylene will poison the catalyst in the downstream polymerization process. Therefore, according to the specific requirements of the downstream process conditions, it is necessary to reduce the acetylene content in the ethylene product to less than 5ppm. Theoretically, there are many methods for the purification of ethylene, such as solvent absorption method, acetylene copper precipitation method, low-temperature rectification extraction method, and catalytic hydrogenation. However, based on the technical cost and efficiency considerations at the present stage, the selective hydrogenation of acetylene is commonly used in industry. craft. This process can not only remove trace acetylene in ethylene products, but also increase ethylene production. However, in the hydrogenation process, acetylene is prone to deep hydrogenation to generate ethane, and it is also easy to generate "green oil" through oligomerization, which leads to catalyst deactivation.

At present, highly optimized PdAg catalysts are usually used in industry to reduce the activity of deep hydrogenation of acetylene to improve catalyst selectivity. However, the microstructure of the PdAg catalyst is disordered, and there are still multi-dentate adsorption configurations on the surface of the catalyst, and the weakening effect on the activity of deep hydrogenation of acetylene is not obvious. In order to optimize and upgrade existing industrial catalysts and design new efficient and stable catalysts, researchers have begun to pay attention to structurally ordered and stable Pd-M intermetallic compounds in recent years, for example: journal literature ACS Catalysis.2016,6(2): 1054-1061, reported that the supported PdZn intermetallic compound catalyst could be obtained by using ZnO as a carrier to support Pd salt solution and then calcining and reducing at 400 °C. The spatial isolation of the Pd active site in the PdZn intermetallic compound structure makes acetylene adsorb on the catalyst surface in the form of a σ bond, that is, two C atoms are combined with two adjacent Pd atoms; while ethylene can only be adsorbed on a single Pd site. It is weakly adsorbed on the surface of the catalyst in the form of π bonds. When the conversion rate of acetylene reaches 100%, the selectivity of ethylene is not lower than 90%. Patent CN108940277 A reports that by finely controlling the "metal-support interaction" between the Pd-ZnO system, the electronic structure and crystal structure of Pd are regulated, and its performance of selective hydrogenation with acetylene is correlated. The Zn-doped Pd structure catalyst dominated by the electronic effect exhibits the most excellent performance: the ethylene selectivity reaches 85%, and the hydrogenation activity is 15 to 35 times that of the PdZn intermetallic compound catalyst. However, the Pd-M alloy catalyst has a high load of noble metal Pd (generally 1% to 5%), and the process requires a large amount of catalyst, so the cost of the catalyst is relatively high.

Non-noble metal Ni is another commonly used active component of hydrogenation catalysts. In recent years, Ni catalysts have gradually attracted the attention of researchers as a potential catalyst for the selective hydrogenation of acetylene. For example, the journal document AdvancedMaterials.2016,28(23):4747-4754 reported that NiGa and NiSn binary metal particles with uniform particle size and controllable composition were prepared by liquid phase co-reduction method, and the XRD and electron microscope characterization results showed that The synthesized binary metal nanoparticles are intermetallic compounds with ordered structure. This type of catalyst exhibits excellent performance in both liquid phase and gas phase selective hydrogenation of alkynes, especially the Ni ₃ Ga catalyst has an ethylene selectivity as high as about 80% at a conversion rate of acetylene of 90%. Since the hydrogenation activity of Ni-based catalysts is lower than that of Pd-based catalysts, the reaction temperature required for the complete conversion of acetylene is higher, usually reaching 180 °C or even higher. However, a higher reaction temperature is thermodynamically more favorable for the formation of "green oil". Therefore, from the perspective of practical application, it is necessary to further improve the catalytic activity of Ni-based catalysts so that acetylene can be completely converted in a relatively low temperature range while ensuring high ethylene selectivity.

In summary, in the prior art, Pd-M intermetallic compound catalysts have a high load of noble metal Pd, and the amount of catalyst used is large, resulting in high catalyst costs; Ni-M alloy catalysts have low hydrogenation activity and are required for complete conversion of acetylene. The disadvantage of higher reaction temperature. Therefore, it is necessary to develop new catalysts to solve the above problems.

Contents of the invention

The first object of the present invention is to provide a preparation method of supported Ni-Ga-Pd catalyst. The inventors of the present invention, in the process of in-depth research on Pd-M intermetallic compound catalysts and Ni-M alloy catalysts, unexpectedly found that by loading on Ni/Ga/Mg/Al quaternary layered double hydroxide materials A very low amount of Pd can significantly reduce the reaction temperature, and the Ni-based catalyst has the characteristics of high catalytic activity, good selectivity and long life.

In order to achieve the above purpose, the following technical solutions are adopted:

A preparation method of a supported Ni-Ga-Pd catalyst, specifically comprising the steps of:

(1) Using nitrates of Ni, Ga, Mg, and Al as metal precursors, and configuring them into mixed metal nitrate solutions, and then preparing Ni/Ga/Mg/Al quaternary layered hydroxides by co-precipitation method material M;

(2), the Ni/Ga/Mg/Al quaternary layered hydroxide material M of step (1) is dissolved in an appropriate amount of water, and an appropriate amount of palladium precursor species is added for ion exchange, and then filtered, washed, Dry to obtain the Ni/Ga/Pd/Mg/Al five-element layered hydroxide material PM;

(3), the Ni/Ga/Pd/Mg/Al five-element layered hydroxide material PM of step (2) is through thermal reduction, obtains supported Ni-Ga-Pd catalyst;

In the mixed metal nitrate solution of the step (1), the molar ratio of Ni, Ga, Mg, and Al ions is 1:(0.25～1):(3～6):(1～1.75); The concentration is 0.05～0.15mol/L.

In the supported Ni-Ga-Pd catalyst obtained in the step (3), the loading amount of the palladium is 10-200 ppm.

The present invention is based on the characteristics of adjustable composition and elements of the main layer of LDHs materials, and uses the co-precipitation method to prepare Ni/Ga/Mg/Al quaternary LDHs, and then introduces a very small amount of Pd through ion exchange to prepare Ni/Ga/Pd/Mg/Al The five-element LDHs is used as the precursor of the Ni-Ga-Pd catalyst, and then the Ni-Ga-Pd catalyst is obtained through reduction. To explore the influence of the preparation process on the reaction performance of the catalyst, in order to develop a method for the controllable preparation of Ni-Ga-Pd catalyst with an ordered and stable structure.

The inventors of the present invention considered the unique properties of single-atom Pd catalysts, introduced a small amount of Pd into Ni-M intermetallic compound catalysts to prepare supported Ni-M-Pd catalysts, and developed a new synergistic strategy for Ni-M and single-atom Pd , to become a new technical solution to solve the problems in the prior art.

Preferably, in the mixed metal nitrate solution of the step (1), the molar ratio of Ni, Ga, Mg, and Al ions is 1:(0.25～1):5:(1～1.75), and the molar ratio of Ni ions The concentration is 0.1mol/L.

In the supported Ni-Ga-Pd catalyst obtained in the step (3), the loading amount of the palladium is 10-150 ppm.

Preferably, in the step (1), the nitrates of Ni, Ga, Mg and Al are respectively nickel nitrate hexahydrate, gallium nitrate hydrate, magnesium nitrate hexahydrate and aluminum nitrate nonahydrate.

According to a preferred technical solution of the present invention, in the step (1), add the mixed metal nitrate solution and the pH regulator to the precipitant under stirring conditions at the same time, maintain the temperature of the reaction system at 60-70 ° C, and control The pH value of the reaction system is 10±1; after the feeding is completed, continue to stir and react for 18 to 36 hours, and finally filter, wash and dry to obtain the Ni/Ga/Mg/Al quaternary layered hydroxide material M ;

Control the adding rate of the mixed metal nitrate solution to be 1.0±0.2mL/min.

More preferably, in the step (1), the mixed metal nitrate solution and the pH regulator are simultaneously added to the precipitant under stirring conditions, the temperature of the reaction system is maintained at 65° C., and the pH value of the reaction system is controlled to be 10 ; After the addition is completed, continue to stir and react for 24 hours, and finally filter, wash and dry to obtain the Ni/Ga/Mg/Al quaternary layered hydroxide material M;

Control the adding rate of the mixed metal nitrate solution to be 1.0 mL/min.

Preferably, in the step (1), the drying condition is 80±5°C for 6-18 hours.

Preferably, the precipitation agent is selected from one of sodium carbonate solution, ammonia water, sodium bicarbonate solution, potassium carbonate solution, and potassium bicarbonate solution. Sodium carbonate solution is more preferred.

The pH regulator is selected from one of sodium hydroxide solution and potassium hydroxide solution.

More preferably, the pH regulator is sodium hydroxide solution, and the molar concentration of the sodium hydroxide solution is 1.0±0.2 mol/L.

Preferably, in the step (2), the Ni/Ga/Mg/Al quaternary layered hydroxide material M of the step (1) is dispersed in water at a mass ratio of 1:(20-40), and the pH value is added It is the precursor species of palladium of 4-6, ion-exchanged at 30-60°C for 8-40 hours, then filtered, washed and dried to obtain Ni/Ga/Pd/Mg/Al five-element layered hydroxide material .

It should be noted that, in the technical solution of the present invention, by ion exchange, in the precursor species of palladium added, almost all Pd elements are ion-exchanged into the Ni/Ga/Mg/Al quaternary layered hydroxide material M.

It should be noted that the ion exchange mentioned in the present invention refers to anion exchange. In the present invention, after the Ni/Ga/Mg/Al cations enter the main laminate, the laminate is positively charged, and the interlayers of LDHs have exchangeable anions NO ₃ ^- , or contain both NO ₃ ^- and CO ₃ ^2- , thus The LDHs are electrically neutral as a whole.

Generally, the order of ion stability of anions between LDHs layers is CO ₃ ^2- >SO ₄ ^2- >PdCl ₄ ^2- >F ^- >Cl ^- >B(OH) ₄ ^- >NO ₃ ^- , where NO ₃ ^- Most easily exchanged by other anions. Therefore, different anions of Pd (such as PdCl ₄ ²⁻ ) can be inserted between LDHs layers to form Ni/Ga/Pd/Mg/Al pentad layered hydroxide material PM.

Preferably, the ion exchange is carried out at 30-60° C. for 18-36 hours.

Preferably, in the step (2), the Ni/Ga/Mg/Al quaternary layered hydroxide material M of the step (1) is dispersed in water at a mass ratio of 1:30, and palladium with a pH value of 6 is added The precursor species were ion-exchanged at 45°C for 18 hours.

Preferably, in the step (2), the precursor species of palladium is one or more of sodium chloropalladate, palladium chloride, and palladium nitrate. Sodium chloropalladate is more preferred.

Preferably, in the step (3), the thermal reduction temperature is 500-900° C., the reduction time is 3-6 hours, and the reducing gas is H ₂ /Ar (H ₂ :Ar=1:4).

More preferably, the thermal reduction temperature is 600-900°C.

It should be noted that the temperature of the reduction reaction is reasonably selected in the range of 500-900°C according to the position of the H ₂ -TPR peak, and the time of the reduction reaction is within 3-6 hours according to the selection of the reduction temperature Appropriate adjustments. On this basis, it is also possible to appropriately extend the reaction time.

Further preferably, the thermal reduction temperature is 800° C., and the reduction time is 4 hours.

It should be noted that when the thermal reduction temperature is lower than 500 °C, the reaction speed is slow, the growth of Ni-Ga-Pd particles is slow, and the particle size is the smallest. The dispersion measured by adsorption decreases, and the number of active sites on the surface of the catalyst decreases, making the catalytic effect poor. When the thermal reduction temperature is higher than 900 °C, the reaction speed is faster, the Ni-Ga-Pd particles grow faster, the particle size is larger, the dispersion measured by chemical adsorption decreases, the number of active sites on the catalyst surface decreases, and the catalytic effect is not good. When the reduction temperature is 800°C, the reaction speed is moderate, the obtained Ni-Ga-Pd particles are evenly loaded on the surface of the carrier, the dispersion measured by chemical adsorption is the highest, the number of active sites on the catalyst surface is the largest, and the catalytic effect is good.

The second object of the present invention is to provide a supported Ni-Ga-Pd catalyst, which is prepared by the above-mentioned preparation method of the supported Ni-Ga-Pd catalyst.

Preferably, the Ni/Ga/Pd/Mg/Al quinary layered double hydroxide material obtained by loading Pd on the Ni/Ga/Mg/Al quaternary layered double hydroxide material; the loading of the Pd The amount is 10 to 200 ppm, preferably 10 to 150 ppm, more preferably 50 ppm.

Under the conditions of the loading range of 10-150ppm, the supported Ni-Ga-Pd catalyst has very good catalytic activity under low temperature reaction conditions. Both selectivity and yield are good.

The third object of the present invention is to provide the application of the above-mentioned supported Ni-Ga-Pd catalyst for the reaction of selective hydrogenation of acetylene to ethylene.

Preferably, the reaction temperature of the selective hydrogenation of acetylene to ethylene is 80-130°C.

Compared with the prior art, the present invention has the following beneficial technical effects:

(1), the preparation method of supported Ni-Ga-Pd catalyst of the present invention, utilizes the main layer plate composition of layered hydroxide (LDHs) material and the characteristic that element is adjustable, prepares Ni/Ga/Mg/Al four Elementary LDHs, using the exchangeability of anions between layers of LDHs materials, introduces a small amount of Pd anion groups through ion exchange between Ni/Ga/Mg/Al quaternary LDHs layers, and combined with the subsequent thermal reduction process to achieve different Ni- Controlled preparation of Ga-Pd intermetallic compounds. During the thermal reduction process, Ni-Ga-Pd alloy particles and Mg(Al)O metal oxides are simultaneously generated, so that there is a strong interaction between the generated alloy particles and metal oxides, avoiding the high-temperature roasting in the traditional impregnation method. And high temperature reduction leads to the phenomenon of agglomeration of metal particles, which can improve the utilization rate of active components Ni and Pd, thereby reducing the loading of Ni and Pd, and improving the catalytic activity.

In addition, through DFT calculations, it was found that acetylene was preferentially adsorbed on the Pd site in the π configuration, while hydrogen was more easily activated on the Ni site. These research results show that there may be a synergistic effect between Ni and Pd sites in the supported Ni-Ga-Pd catalyst prepared under the conditions of the technical scheme of the present invention, which promotes the selective hydrogenation activity of acetylene while improving the acetylene selective hydrogenation activity. Desorption of ethylene on the catalyst surface.

(2), compared with traditional Ni-based catalysts, the supported Ni-Ga-Pd catalyst of the present invention has the characteristics of high dispersion of catalyst metal particles, high catalytic activity, good selectivity and long life due to the introduction of Pd, making Acetylene can be completely converted in a relatively low temperature range, thereby avoiding the formation of green oil aggravated by high temperature. At the same time, the loading of Pd is extremely low, which greatly reduces the cost of the existing catalysts for the selective hydrogenation of acetylene to ethylene, and has a good prospect for industrial application.

Description of drawings

Fig. 1 is a scanning electron micrograph of Ni/Ga/Mg/Al quaternary LDH material M1 prepared in Example 1 of the present invention.

Fig. 2 is the XRD spectrum of the Ni/Ga/Mg/Al quaternary LDH material M1 prepared in Example 1 of the present invention.

3 is a TG-DTA curve of the Ni/Ga/Mg/Al quaternary LDH material M1 prepared in Example 1 of the present invention.

Fig. 4 is a transmission electron micrograph of the Ni-Ga intermetallic compound catalyst M1-800 prepared in Example 4 of the present invention.

Fig. 5 is a scanning electron micrograph of Ni/Ga/Pd/Mg/Al quinary LDH material P1M1 prepared in Example 7 of the present invention.

Fig. 6 is the XRD spectrum of the Ni/Ga/Pd/Mg/Al quinary LDH material P1M1 prepared in Example 7 of the present invention.

Fig. 7 is a TG-DTA curve of the Ni/Ga/Pd/Mg/Al quinary LDH material P1M1 prepared in Example 7 of the present invention.

Fig. 8 is the XPS spectrum of Ni2p of Ni-Ga-Pd intermetallic compound catalyst 50ppm-P1M1-800 prepared in Example 7 of the present invention.

Fig. 9 is the XPS spectrum of Ga2p of Ni-Ga-Pd intermetallic compound catalyst 50ppm-P1M1-800 prepared in Example 7 of the present invention.

Detailed ways

The present invention will be further described below in conjunction with specific embodiments. It should be understood that the following examples are only used to illustrate the present invention but not to limit the scope of the present invention.

The preparation of the precursor solution of preparation example 1, palladium

(1), preparation sodium chloropalladate solution

(a), weigh 0.10g of sodium chloropalladate, and ultrasonically dissolve in ultrapure water to obtain 100mL of sodium chloropalladate solution with a concentration of 1.0×10 ^-3 g/mL;

(b), get 13.80mL from the sodium chloropalladate solution gained in step (a) and carry out ultrasonic dissolution in ultrapure water, and carry out pH value adjustment with 0.10mol/L dilute hydrochloric acid, obtain 100mL pH value and be 6, concentration It is 1.38×10 ^-4 g/mL sodium chloropalladate solution.

(2), preparation palladium chloride solution

(a), take 0.10g of palladium chloride, ultrasonically dissolve in ultrapure water to obtain 100mL of palladium chloride solution with a concentration of 1.0×10 ^-3 g/mL;

(b), take 8.33mL from the 1.0×10 ^-3 g/mL palladium chloride solution obtained in step (a) and carry out ultrasonic dissolution in ultrapure water, and adjust the pH value with 0.10mol/L dilute hydrochloric acid to obtain 100 mL of palladium chloride solution with a pH value of 5 and a concentration of 8.33×10 ^-5 g/mL.

(3), preparation palladium nitrate solution

(a), weigh 0.10g of palladium nitrate, and ultrasonically dissolve in ultrapure water to obtain 100mL of palladium nitrate solution with a concentration of 1.0×10 ^-3 g/mL;

(b), take 10.82mL from the 1.0×10 ^-3 g/mL palladium nitrate solution obtained in step (a) in ultrapure water for ultrasonic dissolution, and adjust the pH value with 0.10mol/L dilute hydrochloric acid to obtain 100mL Palladium nitrate solution with a pH value of 4 and a concentration of 1.08×10 ^-4 g/mL.

Example 1. Preparation of Ni/Ga/Mg/Al quaternary LDH material M1 by co-precipitation method

The preparation of the Ni/Ga/Mg/Al quaternary LDH material of this embodiment includes the following steps:

(1), 2.91g nickel nitrate hexahydrate, 2.56g gallium nitrate hydrate, 12.82g magnesium nitrate hexahydrate and 3.75g aluminum nitrate nonahydrate are dissolved in 100mL ultrapure water for ultrasonic dispersion, and are recorded as mixed metal nitrate solution; 4. Dissolve 24g of sodium carbonate in 100mL of ultrapure water for ultrasonic dispersion to obtain a precipitant; dissolve 10.00g of sodium hydroxide in 250mL of ultrapure water for ultrasonic dispersion to obtain a pH regulator.

(2), transfer the precipitating agent in step (1) to a three-necked flask, and place it in a water bath at 65°C to keep the temperature constant, then add the mixed metal nitric acid in step (1) dropwise under the condition of 100r/min at a rotating speed For saline solution, use a constant flow pump to control its flow rate to 0.8mL/min. Simultaneously, the pH adjusting agent of step (1) was added dropwise, so that the pH of the reaction system in the three-necked flask was kept constant at 10. After the addition was completed, stirring was continued at 65° C. for 24 hours, then filtered and washed to obtain a light green solid.

(3) The light green solid obtained in step (2) was dried at 80° C. for 12 hours to obtain a Ni/Ga/Mg/Al quaternary LDH material, marked as M1.

The above-mentioned M1 was observed with a scanning electron microscope, and the microscopic appearance is shown in Fig. 1 . It can be seen from FIG. 1 that the M1 prepared in this example is a typical sheet-like morphology of a double-layer hydroxide material.

Figure 2 is the XRD spectrum of M1. There are diffraction peaks with different intensities at 11.2°, 22.7°, 34.2°, 38.5°, 45.2°, 60.5° and 61.8°. Compared with the XRD standard card of LDH (JCPDS 14-0191), The diffraction peaks can be assigned to the (003), (006), (021), (015), (018), (110) and (113) planes of LDH materials, respectively. There are no miscellaneous peaks of other phases in the XRD spectrum, indicating that the prepared LDH material is a pure-phase layered double hydroxide structure, that is, Ni and Ga cations have entered the layered structure.

In addition, the thermal stability of the prepared Ni/Ga/Mg/Al quaternary LDH material M1 at room temperature to 800°C was tested by thermogravimetric analysis, and the results are shown in FIG. 3 . It can be seen from Figure 3 that the weight loss curve of the Ni/Ga/Mg/Al quaternary LDH material mainly has two weight loss peaks: the weight loss between normal temperature and 200 °C is the volatilization of water physically adsorbed on the surface of the LDH material and the desorption of interlayer water molecules. The removal process; the weight loss between 250 and 410 °C is the process of decarbonylation and dehydroxylation of LDH materials, which eventually leads to the collapse of the layered structure of LDH.

The above characterization results show that under the preparation conditions of Example 1, Ni and Ga have entered the structure of the LDH material, which means that the Ni/Ga/Mg/Al quaternary LDH material has been prepared as a catalyst precursor by co-precipitation.

Example 2. Preparation of Ni/Ga/Mg/Al quaternary LDH material M2 by co-precipitation method

The preparation method of the present embodiment is basically the same as that of Example 1, the difference is that:

In step (1), 1.46g nickel nitrate hexahydrate, 0.64g gallium nitrate hydrate, 3.85g magnesium nitrate hexahydrate and 2.82g aluminum nitrate nonahydrate were dissolved in 100mL ultrapure water for ultrasonic dispersion;

In step (2), the control temperature is 60°C, the control speed is 150r/min, the addition rate of the mixed metal nitrate solution is controlled to be 1.0mL/min, and the pH of the reaction system in the three-necked flask is constant at 9. After the addition is completed, , and continued to stir for 36 hours.

A Ni/Ga/Mg/Al quaternary LDH material was obtained, marked as M2.

The above-mentioned M2 was observed with a scanning electron microscope, and the microscopic appearance was similar to that in Fig. 1 .

In the XRD pattern of M2 prepared in this example, compared with JCPDS 14-0191, there are diffraction peaks with different intensities at 11.2°, 22.7°, 34.2°, 38.5°, 45.2°, 60.5° and 61.8°, and no miscellaneous peaks appear.

In addition, in the TG-DTA curve of M2, the physical adsorption of water volatilization on the surface of LDH material and the removal of interlayer water molecules appeared between normal temperature and 200 °C; the removal of LDH material appeared between 250 and 410 °C Carbonyl and dehydroxylation.

The above characterization results show that under the preparation conditions of Example 2, Ni and Ga have entered the structure of the LDH material, which means that the Ni/Ga/Mg/Al quaternary LDH material has been prepared as a catalyst precursor by coprecipitation.

Example 3, preparation of Ni/Ga/Mg/Al quaternary LDH material by co-precipitation method

The preparation method of the present embodiment is basically the same as that of Example 1, the difference is that:

In step (1), 4.37g nickel nitrate hexahydrate, 0.90g gallium nitrate hydrate, 23.08g magnesium nitrate hexahydrate and 9.84g aluminum nitrate nonahydrate were dissolved in 100mL ultrapure water for ultrasonic dispersion;

In step (2), the control temperature is 70°C, the control speed is 100r/min, the addition rate of the mixed metal nitrate solution is controlled to be 1.2mL/min, and the pH of the reaction system in the three-necked flask is constant at 11. After the addition is completed, , and continued to stir for 18 hours.

A Ni/Ga/Mg/Al quaternary LDH material was obtained, marked as M3.

The above-mentioned M3 was observed with a scanning electron microscope, and the microscopic appearance was similar to that in Fig. 1 .

In the XRD pattern of M3 prepared in this example, compared with JCPDS 14-0191, there are diffraction peaks with different intensities at 11.2°, 22.7°, 34.2°, 38.5°, 45.2°, 60.5° and 61.8°, and no miscellaneous peaks appear.

In addition, in the TG-DTA curve of M3, the physical adsorption of water volatilization on the surface of LDH material and the removal of interlayer water molecules appeared between normal temperature and 200 °C; the removal of LDH material appeared between 250 and 410 °C. Carbonyl and dehydroxylation.

The above characterization results show that under the preparation conditions of Example 3, Ni and Ga have entered the structure of the LDH material, which confirms that the Ni/Ga/Mg/Al quaternary LDH material has been prepared as a catalyst precursor by coprecipitation.

The morphology of Ni/Ga/Mg/Al quaternary LDH materials M1-M3 prepared under the process conditions of Examples 1-3 is a typical sheet-like morphology of layered double hydroxide materials, and Ni, Ga, Mg, and Al are uniform Distributed on LDH material.

The preparation of embodiment 4-6, Ni-Ga intermetallic compound catalyst

In this example, Ni/Ga/Mg/Al quaternary LDH materials M1-M3 are thermally reduced to obtain a Ni-Ga intermetallic compound catalyst. The specific steps are as follows:

M1-M3 prepared in Examples 1-3 were reduced for 4 hours at 800°C in an H ₂ /Ar atmosphere (volume ratio 1:4) to obtain Ni-Ga intermetallic compound catalysts, which were denoted as M1-800 and M2 respectively. -800 and M3-800.

The M1-800 catalyst was observed with a transmission electron microscope, and the microscopic appearance is shown in Figure 4. It can be seen from Fig. 4 that in the M1-800 catalyst prepared in this example, the metal particles in the catalyst obtained by reducing M1 are well dispersed, the particle size is uniform, the average size of the metal particles is 9.9±1.6nm, and the metal dispersion is 15.1%.

The transmission electron microscope image of the M2-800 catalyst is similar to that in Figure 4. The metal particles in the catalyst obtained by reducing M2 are well dispersed and uniform in particle size. The average size of the metal particles is 9.6±1.6nm, and the metal dispersion is 15.5%.

The transmission electron microscope image of the M3-800 catalyst is similar to that in Figure 4. The metal particles in the catalyst obtained by reducing M3 are well dispersed and uniform in particle size. The average size of the metal particles is 9.6±1.6nm, and the metal dispersion is 15.2%.

The average particle diameters of the metal particles on the three Ni-Ga intermetallic compound catalysts prepared under the process conditions of Examples 4-6 are similar, and their distribution ranges are also similar. This indicates that the catalyst metal particle size obtained by reduction of LDH precursors with different Ni/Ga/Mg/Al ratios is not affected by its composition.

Embodiment 7, preparation of supported Ni-Ga-Pd catalyst

The preparation of the supported Ni-Ga-Pd catalyst of the present embodiment comprises the following steps:

(1) Disperse 6.0 g of M1 in 180 g of ultrapure water, then add 1.00 mL of the sodium chloropalladate solution of Preparation Example 1, carry out ion exchange at 45° C. with stirring for 18 hours, then cool to room temperature, and filter. A filtrate and a solid were obtained, which were washed to give a pale green solid.

(2) The light green solid prepared in step (1) was dried at 80° C. for 12 hours to obtain a Ni/Ga/Pd/Mg/Al quinary LDH material, marked as P1M1.

(3) The P1M1 prepared in step (2) was reduced at 800° C. for 4 hours in an H ₂ /Ar atmosphere to obtain 1 g of Ni—Ga—Pd intermetallic compound catalyst.

The filtrate in step (1) is detected by inductively coupled plasma atomic emission spectrometry (ICP-AES), and no Pd has been detected. Therefore, in this embodiment, almost all of the Pd is ion-exchanged into the interior of the Ni-Ga-Pd intermetallic compound catalyst. After calculation, the content of Pd in the catalyst is 50ppm, and the catalyst of this embodiment is marked as 50ppm-P1M1-800.

P1M1 was observed with a scanning electron microscope, and the microscopic appearance is shown in Figure 5. From the comparison of Figure 1 and Figure 5, it can be seen that the morphology of P1M1 has no obvious change compared with that of M1.

The XRD pattern of 50ppm-P1M1-800 prepared in this example is shown in Figure 6. Compared with JCPDS 14-0191, there are diffraction peaks with different intensities at 11.2°, 22.7°, 34.2°, 38.5°, 45.2°, 60.5° and 61.8° , no miscellaneous peaks appear.

In addition, the TG-DTA curve of 50ppm-P1M1-800 is shown in Figure 7. Water volatilization by physical adsorption on the surface of the LDH material and removal of interlayer water molecules appear between normal temperature and 200°C; decarbonylation and dehydroxylation of LDH materials. The above shows that the introduction of palladium precursor species did not destroy the microstructure of the original quaternary LDH material.

Figure 8 and Figure 9 are the XPS spectra of Ni 2p and Ga 2p in the 50ppm-P1M1-800 catalyst: when PdCl ₄ ^2- is introduced, the Ni ⁰ 2p _3/2 peak shifts to the lower position, while the Ga ⁰ 2p _{3/ 2} The peak shifts to a higher place, indicating that more electrons are transferred from Ga atoms to Ni atoms, and the presence of Pd at this time makes the electron density of Ni increase.

In the 50ppm-P1M1-800 catalyst prepared in this example, the average size of metal particles is 9.9±1.5nm, and the metal dispersion is 15.1%.

Embodiment 8, preparation of supported Ni-Ga-Pd catalyst

The preparation of the supported Ni-Ga-Pd catalyst of the present embodiment comprises the following steps:

(1), disperse 6.0g M2 in 120g ultrapure water, then add 1.00mL of the sodium chloropalladate solution of Preparation Example 1, carry out ion exchange at 60°C for 24 hours under stirring conditions, then cool to room temperature, filter, A filtrate and a solid were obtained, which were washed to give a pale green solid.

(2) The light green solid prepared in step (1) was dried at 80° C. for 12 hours to obtain a Ni/Ga/Pd/Mg/Al quinary LDH material, marked as P1M2.

(3) The P1M2 prepared in step (2) was reduced at 800° C. for 4 hours in an H ₂ /Ar atmosphere to obtain 1 g of Ni—Ga—Pd intermetallic compound catalyst.

The filtrate of step (1) is detected by ICP-AES, and no Pd has been detected. Therefore, in this embodiment, almost all of the Pd is ion-exchanged into the interior of the Ni-Ga-Pd intermetallic compound catalyst. After calculation, the content of Pd in the catalyst is 50ppm, and the catalyst of this embodiment is marked as 50ppm-P1M2-800.

The XRD pattern, TG-DTA curve and XPS pattern are similar to the 50ppm-P1M1-800 of Example 7.

In the 50ppm-P1M2-800 catalyst prepared in this example, the average size of metal particles is 9.7±1.4nm, and the metal dispersion is 14.8%.

Embodiment 9, preparation of supported Ni-Ga-Pd catalyst

The preparation of the supported Ni-Ga-Pd catalyst of the present embodiment comprises the following steps:

(1), disperse 6.0g M3 in 240g ultrapure water, then add 1.00mL of the sodium chloropalladate solution of Preparation Example 1, perform ion exchange at 30°C for 36 hours under stirring conditions, then cool to room temperature, and filter , the filtrate and solid were obtained, and the solid was washed to obtain a light green solid.

(2) The light green solid prepared in step (1) was dried at 80° C. for 12 hours to obtain a Ni/Ga/Pd/Mg/Al quinary LDH material, marked as P1M3.

(3) The P1M3 prepared in step (2) was reduced at 800° C. for 4 hours in an H ₂ /Ar atmosphere to obtain 1 g of Ni—Ga—Pd intermetallic compound catalyst.

The filtrate of step (1) is detected by ICP-AES, and no Pd has been detected. Therefore, in this embodiment, almost all of the Pd is ion-exchanged into the interior of the Ni-Ga-Pd intermetallic compound catalyst. After calculation, the content of Pd in the catalyst is 50ppm, and the catalyst of this embodiment is marked as 50ppm-P1M3-800.

The XRD pattern, TG-DTA curve and XPS pattern are similar to the 50ppm-P1M1-800 of Example 7.

In the 50ppm-P1M3-800 catalyst prepared in this example, the average size of metal particles is 9.5±1.3nm, and the metal dispersion is 15.3%.

Embodiment 10, preparation of supported Ni-Ga-Pd catalyst

The basic steps of this embodiment are the same as in Embodiment 7, the difference is:

In step (1), 0.20 mL of the sodium chloropalladate solution of Preparation Example 1 was added. Step (2) obtains Ni/Ga/Pd/Mg/Al quinary LDH material, marked as P2M1.

Step (3) obtained 10ppm-P2M1-800.

After testing, in the 10ppm-P2M1-800 catalyst prepared in this example, the average size of metal particles is 9.9±1.1nm, and the metal dispersion is 15.4%.

Embodiment 11, preparation of supported Ni-Ga-Pd catalyst

The basic steps of this embodiment are the same as in Embodiment 7, the difference is:

In step (1), 0.50 mL of the sodium chloropalladate solution of Preparation Example 1 was added. Step (2) obtains Ni/Ga/Pd/Mg/Al quinary LDH material, marked as P2M1.

Step (3) yields 25ppm-P3M1-800.

After testing, in the 25ppm-P3M1-800 catalyst prepared in this example, the average size of metal particles is 9.8±1.7nm, and the metal dispersion is 15.0%.

Embodiment 12, preparation of supported Ni-Ga-Pd catalyst

The basic steps of this embodiment are the same as in Embodiment 7, the difference is:

In step (1), 1.5 mL of the sodium chloropalladate solution of Preparation Example 1 was added. Step (2) obtains Ni/Ga/Pd/Mg/Al quinary LDH material, marked as P4M1.

Step (3) yields 75ppm-P4M1-800.

After testing, in the 75ppm-P4M1-800 catalyst prepared in this example, the average size of metal particles is 9.7±1.3nm, and the metal dispersion is 15.2%.

Embodiment 13, preparation of supported Ni-Ga-Pd catalyst

The basic steps of this embodiment are the same as in Embodiment 7, the difference is:

In step (1), 2.0 mL of the sodium chloropalladate solution of Preparation Example 1 was added. Step (2) obtains Ni/Ga/Pd/Mg/Al quinary LDH material, marked as P5M1.

Step (3) obtained 100ppm-P5M1-800.

After testing, in the 100ppm-P5M1-800 catalyst prepared in this example, the average size of metal particles is 9.9±1.4nm, and the metal dispersion is 14.7%.

Embodiment 14, preparation of supported Ni-Ga-Pd catalyst

The basic steps of this embodiment are the same as in Embodiment 7, the difference is:

In step (1), 2.5 mL of the sodium chloropalladate solution of Preparation Example 1 was added. Step (2) obtains Ni/Ga/Pd/Mg/Al quinary LDH material, marked as P6M1.

Step (3) yields 125ppm-P6M1-800.

After testing, in the 125ppm-P6M1-800 catalyst prepared in this example, the average size of metal particles is 9.9±1.7nm, and the metal dispersion is 15.4%.

Embodiment 15, preparation of supported Ni-Ga-Pd catalyst

The basic steps of this embodiment are the same as in Embodiment 7, the difference is:

In step (1), 3.0 mL of the sodium chloropalladate solution of Preparation Example 1 was added. Step (2) obtains Ni/Ga/Pd/Mg/Al quinary LDH material, marked as P7M1.

Step (3) yields 150ppm-P7M1-800.

After testing, in the 150ppm-P7M1-800 catalyst prepared in this example, the average size of metal particles is 9.9±1.0nm, and the metal dispersion is 14.5%.

Embodiment 16, preparation of supported Ni-Ga-Pd catalyst

The basic steps of this embodiment are the same as in Embodiment 7, the difference is:

In step (1), 3.5 mL of the sodium chloropalladate solution of Preparation Example 1 was added. Step (2) obtains Ni/Ga/Pd/Mg/Al quinary LDH material, marked as P8M1.

Step (3) yielded 175ppm-P8M1-800.

After testing, in the 175ppm-P8M1-800 catalyst prepared in this example, the average size of metal particles is 10.1±1.1nm, and the metal dispersion is 14.9%.

Embodiment 17, preparation of supported Ni-Ga-Pd catalyst

The basic steps of this embodiment are the same as in Embodiment 7, the difference is:

In step (1), 4.0 mL of the sodium chloropalladate solution of Preparation Example 1 was added. Step (2) obtains Ni/Ga/Pd/Mg/Al quinary LDH material, marked as P9M1.

Step (3) yields 200ppm-P9M1-800.

After testing, in the 200ppm-P9M1-800 catalyst prepared in this example, the average size of metal particles is 10.1±0.9nm, and the metal dispersion is 15.5%.

Embodiment 18, preparation of supported Ni-Ga-Pd catalyst

The basic steps of this example are the same as those of Example 7, except that the reduction temperature of P1M1 is 600°C, the reduction time is about 6 hours, and the final catalyst is marked as 50ppm-P1M1-600.

After testing, in the 50ppm-P1M1-600 catalyst prepared in this example, the average size of metal particles is 9.7±2.3nm, and the metal dispersion is 15.5%.

Embodiment 19, preparation of supported Ni-Ga-Pd catalyst

In this example, the basic steps for preparing the Ni-Ga-Pd intermetallic compound catalyst are the same as in Example 7, the difference is that the reduction temperature of P1M1 is 700°C, the reduction time is about 5 hours, and the final catalyst is marked as 50ppm- P1M1-700.

After testing, in the 50ppm-P1M1-700 catalyst prepared in this example, the average size of metal particles is 9.9±1.1nm, and the metal dispersion is 15.4%.

Embodiment 20, preparation of supported Ni-Ga-Pd catalyst

In this example, the basic steps for preparing the supported Ni-Ga-Pd catalyst are the same as in Example 7, the difference is that the reduction temperature of P1M1 is 900°C, the reduction time is about 3 hours, and the final catalyst is marked as 50ppm-P1M1 -900.

After testing, in the 50ppm-P1M1-900 catalyst prepared in this example, the average size of metal particles is 9.8±2.6nm, and the metal dispersion is 15.2%.

Example 21, preparation of supported Ni-Ga-Pd catalyst

In this embodiment, the basic steps of preparing the supported Ni-Ga-Pd catalyst are the same as in Example 7, the difference is that: M2 is used, and the precursor species of palladium used is palladium chloride, and the specific steps are as follows:

(1), disperse 6.0g M2 in 180g ultrapure water, then add 1.00mL palladium chloride solution of Preparation Example 1, carry out ion exchange at 45°C for 18 hours under stirring conditions, then cool to room temperature, filter and wash , to obtain a light green solid.

(2) The light green solid prepared in step (1) was dried at 80° C. for 12 hours to obtain a Ni/Ga/Pd/Mg/Al quinary LDH material, marked as P10M2.

(3) The P10M2 prepared in step (2) was reduced at 800° C. for 4 hours in an H ₂ /Ar atmosphere to obtain a Ni-Ga-Pd intermetallic compound catalyst, marked as 50 ppm-P10M2-800.

After testing, in the 50ppm-P10M2-800 catalyst prepared in this example, the average size of metal particles is 9.8±1.8nm, and the metal dispersion is 15.1%.

Example 22, preparation of supported Ni-Ga-Pd catalyst

In this embodiment, the basic steps of preparing the supported Ni-Ga-Pd catalyst are the same as in Example 7, the difference is that: M3 is used, and the precursor species of palladium used is palladium nitrate, and the specific steps are as follows:

(1), disperse 6.0g M3 in 180g ultrapure water, then add 1.00mL palladium nitrate solution of Preparation Example 1, carry out ion exchange at 45°C for 18 hours under stirring conditions, then cool to room temperature, filter, wash, A pale green solid was obtained.

(2) The light green solid prepared in step (1) was dried at 80° C. for 12 hours to obtain a Ni/Ga/Pd/Mg/Al quinary LDH material, marked as P11M3.

(3) The P11M3 prepared in step (2) was reduced at 800° C. for 4 hours in an H ₂ /Ar atmosphere to obtain a Ni-Ga-Pd intermetallic compound catalyst, marked as 50 ppm-P11M3-800.

After testing, in the 50ppm-P11M3-800 catalyst prepared in this example, the average size of metal particles is 9.9±2.2nm, and the metal dispersion is 15.7%.

Embodiment 23, catalyst catalytic performance evaluation

The supported Ni-Ga-Pd catalysts prepared in Examples 4-22 were used to evaluate the catalytic hydrogenation activity of acetylene; the evaluation of the hydrogenation reaction performance of acetylene was carried out on the ZKJC-RJ-X system of Beijing Wanlonghe Technology Co., Ltd., wherein:

The components in the reactants and products were analyzed online using a four-channel microchromatography micro GC 3000 (INFICON, USA).

Molecular sieve columns are used for hydrogen and nitrogen, Plot-U columns are used for acetylene, alumina columns are used for ethylene and ethane, and the extremely low amount of impurity C4 components in the feed gas are analyzed using OV-1 capillary chromatographic column, and the detector is a thermal conductivity cell Detector (Thermal Conductivity Detector, TCD), the carrier gas is argon and helium.

Evaluation conditions: the total flow rate of intake air is 120mL/min, the raw material gas is 1.0% C ₂ H ₂ , 20.0% C ₂ H ₄ , 5.0% H ₂ , and the rest is N ₂ ; the reaction temperature is 80-130°C ; The reaction pressure is an absolute pressure of 0.1MPa. The loading amount of the catalyst is 0.05g.

Weigh 0.05g of the catalyst sample, mix it with 10 times the mass of quartz sand, and then fill it in the constant temperature zone of the stainless steel reaction tube. After the catalyst is loaded, first check the reaction system for leaks, and pass a certain pressure of nitrogen (10bar) into the reaction system. If the pressure can remain unchanged, it shows that the reaction system is well sealed and can be used for evaluation experiments.

Set the nitrogen flow rate to 20sccm (standard cubic centimeter per minute), and heat up to the reduction temperature; then turn off the nitrogen gas, set the hydrogen flow rate to 20sccm, and turn off the hydrogen gas after reducing for a certain period of time; set the nitrogen flow rate to 20sccm to cool down to the reaction temperature, and set the reaction temperature required pressure. After the reaction conditions are stable, set the flow rate of each reaction component, and cut the Furnace six-way valve as a bypass, so that the mixed gas can directly enter the chromatogram to detect the concentration of each component before the reaction. After stabilization, switch the Furnace six-way valve back into the reaction tube to start the reaction, and the gas at the outlet of the reaction tube enters the online chromatographic detection.

By testing the acetylene conversion C (C ₂ H ₂ ), the ethylene selectivity S (C ₂ H ₄ ) and the yield Y (C ₂ H ₄ ), to evaluate the catalytic performance of the catalyst for the selective hydrogenation of acetylene to produce ethylene, wherein:

Y(C ₂ H ₄ )＝C(C ₂ H ₂ )×S(C ₂ H ₄ )

In this example, the catalysts and their catalytic performances in the following two documents were used for comparison with the catalysts prepared in Examples 4-22 of the present invention and their catalytic performances. In the two literatures, different metal components were introduced, and the supported Ni-based catalysts were prepared by co-precipitation and co-impregnation methods. in:

The first document: Journal of Catalysis 359(2018) 251–260, the catalyst preparation part uses Ni/CuMg/Al quaternary layered bimetallic material as the precursor, and the Ni-Cu alloy catalyst is prepared by hydrogen direct reduction ( pre-NiCu/MMO), according to the records of the journal literature, the evaluation conditions of the catalyst are: catalyst loading 0.10g, reaction temperature range 60-240℃, space velocity 8040h ^-1 , reaction relative pressure 0.2MPa, raw material gas 0.33 % C ₂ H ₂ , 34.5% C ₂ H ₄ , 0.66% H ₂ and 1% C ₃ H ₈ , and the rest of the gas is N ₂ . Reaction result: when the reaction temperature is 130°C, for the catalyst pre-NiCu/MMO, the acetylene conversion rate is 67.50%, and the ethylene selectivity is 85.50%. At 80°C, for the catalyst pre-NiCu/MMO, the acetylene conversion rate is 16.5%, and the ethylene selectivity is 89.30%. At 100°C, for the catalyst pre-NiCu/MMO, the acetylene conversion rate is 29.20%, and the ethylene selectivity is 88.30%.

The second document: Journal of Energy Chemistry 29(2019) 40–49, the catalyst preparation part supports Ni and Ga on SiO ₂ by co-impregnation method to obtain catalyst Ni _x -Ga/SiO ₂ . According to the records in this journal, the catalyst evaluation conditions are: catalyst loading 0.20g, reaction temperature 180°C, space velocity 36000mL·h ^-1 , feed gas 1.0% C ₂ H ₂ , 5.0% H ₂ , the rest The gas is N ₂ , and the reaction pressure is 0.40MPa. Reaction result: when the reaction temperature is 180°C, for the catalyst Ni ₅ Ga/SiO ₂ , the acetylene conversion rate is 100%, and the ethylene selectivity is 77.00%.

It should be noted that in the second document, in order to eliminate the interference of excess ethylene (such as competitive adsorption with acetylene and subsequent excessive hydrogenation and polymerization reaction), ethylene-free feedstock was used. In the case that the feed gas does not contain ethylene, the test result of the selectivity of the catalyst to ethylene is higher than that when the feed gas contains ethylene. That is to say, in the second document, if the feed gas contains ethylene, its ethylene selectivity data must be lower than the current 77.00%.

It should be noted that: in the ethylene selectivity evaluation formulas of the relevant catalysts of the above two documents, the generation of C ₂ H ₆ and C ₄ is ignored, so the obtained results are higher than the actual ones, that is, the actual results are higher than those of the present invention. Listed results are low.

The data of the evaluation results of the catalytic performance of the relevant catalysts in the above two documents are also recorded in Table 1.

Table 1. Catalyst performance evaluation results

The average particle size of the metal particles in Examples 4 to 22 in Table 1 is obtained by statistical analysis of the particle size of the STEM photos, and the metal dispersion is measured by the dynamic chemical adsorption method of hydrogen-oxygen titration.

It can be seen from the results in Table 1 that when the feed gas is fed into ethylene, when the reaction temperature is 130°C, the acetylene conversion and ethylene yield of the catalyst pre-NiCu/MMO are significantly lower than those of the supported Ni The acetylene conversion rate and ethylene yield of the -Ga-Pd catalyst indicate that the activity of the catalyst pre-NiCu/MMO in the low temperature reaction zone is much lower than that of the supported Ni-Ga-Pd intermetallic compound catalyst of the present invention.

In the case that the raw material gas is not fed into ethylene, although the acetylene conversion rate of the catalyst _Ni5Ga / _SiO2 reaches 100%, its ethylene selectivity and yield are still significantly lower than the supported Ni-Ga-Pd metal of the present invention compound catalysts.

In the present invention, the evaluation of the catalytic hydrogenation activity of acetylene is carried out under harsher reaction conditions, that is, the loading amount of the catalyst is smaller, the reaction temperature is lower, the reaction pressure is normal pressure, and the reaction raw material gas is rich in ethylene.

The alloy particle size of the supported Ni-Ga-Pd catalyst of the invention is uniform, the distribution range is similar, and the utilization rate of the precious metal component Pd in the catalytic reaction is high. The Pd loading capacity of the supported Ni-Ga-Pd intermetallic compound catalyst of the present invention is at the ppm level, but in the range of 80-130°C for the reaction temperature, the conversion rate, selectivity and yield of acetylene are all significantly improved, and the conversion of acetylene The yield is almost 100%; the ethylene selectivity ≥ 85.0%, the highest can reach 91.10%; the yield ≥ 85.50%, the highest can reach 91.10%. It shows that the supported Ni-Ga-Pd catalyst prepared by adopting the technical scheme of the present invention can significantly improve the acetylene conversion rate, ethylene selectivity and yield.

Those skilled in the art can easily understand that under the same conditions of other catalysis, the supported Ni-Ga-Pd intermetallic compound catalyst prepared by the present invention, compared with the traditional Ni-based catalyst, due to the introduction of Ni-Ga intermetallic compound A very small amount of Pd further improves the activity of the catalyst so that acetylene can be completely converted in a relatively low temperature range, thereby avoiding the formation of green oil aggravated by high temperature, and the selectivity and yield of ethylene obtained are higher than those of pre-NiCu/MMO and catalyst Ni ₅ Ga/SiO ₂ .

In summary, the required catalytic reaction temperature of the supported Ni-Ga-Pd catalyst of the present invention is low, and has very excellent catalytic activity, and because the loading of the noble metal Pd is ppm level, the Ni-Ga-Pd catalyst of the present invention is prepared. The cost of Pd alloy catalyst is significantly reduced, which is more conducive to the industrial application of Ni-based catalysts, so it provides a good way for the industrial application of Ni-based catalysts.

Embodiment 24, catalyst stability evaluation

Randomly select the 50ppm-P1M1-800 catalyst prepared by embodiment 7, the 10ppm-P2M1-800 catalyst prepared by embodiment 10, the 25ppm-P3M1-800 catalyst prepared by embodiment 11, according to the catalytic performance test method of embodiment 18, respectively The stability of the catalyst was evaluated, and the data results of C(C ₂ H ₂ ), S(C ₂ H ₄ ) and Y(C ₂ H ₄ ) are shown in Table 2 to Table 4:

Table 2, 50ppm-P1M1-800 catalyst stability evaluation

As can be seen from the data in Table 2, the supported Ni-Ga-Pd intermetallic compound catalyst 50ppm-P1M1-800 prepared in Example 7, after experiencing 240h reaction evaluation, the conversion rate of acetylene is still maintained above 98.5%, ethylene The selectivity is maintained above 90.0%, while the ethylene yield is maintained above 89%. After 240 hours of reaction, the catalyst 50ppm-P1M1-800 was analyzed and measured: the dispersion degree of catalyst metal particles was 14.9%.

The above results show that the supported Ni-Ga-Pd catalyst 50ppm-P1M1-800 prepared in Example 7 has good stability.

Table 3, 10ppm-P2M1-800 catalyst stability evaluation

It can be seen from the data in Table 3 that the supported Ni-based catalyst 10ppm-P2M1-800 prepared in Example 10, after 240h of reaction evaluation, the acetylene conversion rate is still maintained above 98.0%, and the ethylene selectivity is maintained above 91.0%. , while the ethylene yield was maintained above 87.5%. The catalyst 10ppm-P2M1-800 after 240h of reaction was analyzed and measured: the dispersion degree of catalyst metal particles was 14.7%. The above results show that the supported Ni-Ga-Pd catalyst 10ppm-P2M1-800 prepared in Example 10 has good stability.

Table 4, 25ppm-P3M1-800 catalyst stability evaluation

As can be seen from the data in Table 4, the supported Ni-Ga-Pd intermetallic compound catalyst 25ppm-P3M1-800 prepared in Example 11, after undergoing 240h reaction evaluation, the conversion rate of acetylene is still maintained above 98.80%, ethylene The selectivity of ethylene is maintained above 89.90%, while the yield of ethylene is maintained above 89.00%. The catalyst 25ppm-P3M1-800 after 240 hours of reaction was analyzed and measured: the dispersion degree of catalyst metal particles was 14.7%.

The above results show that the supported Ni-Ga-Pd catalyst 25ppm-P3M1-800 prepared in Example 11 has good stability.

From the above stability test, it can be seen that the supported Ni-Ga-Pd catalyst prepared by the present invention has good catalytic stability, long catalyst life, reduces the use cost of the catalyst, and is beneficial to the industrial application of the supported Ni-based catalyst.

The specific embodiments of the present invention have been described in detail above, but they are only examples, and the present invention is not limited to the specific embodiments described above. For those skilled in the art, any equivalent modifications and substitutions to this practice are also within the scope of the present invention. Therefore, equivalent changes and modifications made without departing from the spirit and scope of the present invention shall fall within the scope of the present invention.

Claims (10)

1. the application of a supported Ni-Ga-Pd catalyst in the reaction of acetylene selective hydrogenation to ethylene, it is characterized in that, the preparation method of described supported Ni-Ga-Pd catalyst specifically comprises the steps: (1) Using nitrates of Ni, Ga, Mg, and Al as metal precursors, and preparing mixed metal nitrate solutions, and then preparing Ni/Ga/Mg/Al quaternary layered hydroxides by co-precipitation method material M; (2), the Ni/Ga/Mg/Al quaternary layered hydroxide material M in step (1) is dissolved in an appropriate amount of water, and an appropriate amount of palladium precursor species is added for ion exchange, and then filtered, washed, Dry to obtain the Ni/Ga/Pd/Mg/Al five-element layered hydroxide material PM; (3) The Ni/Ga/Pd/Mg/Al five-element layered hydroxide material PM in step (2) is thermally reduced to obtain a supported Ni-Ga-Pd catalyst; In the mixed metal nitrate solution in the step (1), the molar ratio of Ni, Ga, Mg, and Al ions is 1:(0.25-1):(3-6):(1-1.75), and Ni ions The concentration is 0.05～0.15 mol/L; In the supported Ni-Ga-Pd catalyst obtained in the step (3), the loading amount of the palladium is 50 ppm. 2. The application of the supported Ni-Ga-Pd catalyst according to claim 1 in the reaction of acetylene selective hydrogenation to ethylene, characterized in that, in the step (1), Ni, Ga, Mg, Al The nitrates are nickel nitrate hexahydrate, gallium nitrate hydrate, magnesium nitrate hexahydrate and aluminum nitrate nonahydrate. 3. The application of the supported Ni-Ga-Pd catalyst in the reaction of selective hydrogenation of acetylene to ethylene according to claim 1, characterized in that, in the step (1), the precipitating agent Add mixed metal nitrate solution and pH regulator to the mixture at the same time, maintain the temperature of the reaction system at 60-70°C, and control the pH value of the reaction system to 10±1; after the addition, continue to stir and react for 18-36 hours, and finally filtering, washing, and drying to obtain the Ni/Ga/Mg/Al quaternary layered double metal hydroxide material M; Control the addition rate of the mixed metal nitrate solution to be 1.0±0.2 mL/min. 4. The application of the supported Ni-Ga-Pd catalyst in the reaction of acetylene selective hydrogenation to ethylene according to claim 3, characterized in that, in the step (1), the precipitating agent Add mixed metal nitrate solution and pH regulator to the mixture at the same time, maintain the temperature of the reaction system at 65 ° C, and control the pH value of the reaction system to 10; after the addition is completed, continue to stir and react for 24 hours, and finally filter, wash, and dry. Obtain the Ni/Ga/Mg/Al quaternary layered hydroxide material M; Control the addition rate of the mixed metal nitrate solution to be 0.8 mL/min. 5. the application of supported Ni-Ga-Pd catalyst according to claim 3 in the reaction of the selective hydrogenation of acetylene to ethylene, is characterized in that, described precipitation agent is selected from sodium carbonate solution, ammoniacal liquor, sodium bicarbonate Solution, potassium carbonate solution, potassium bicarbonate solution; The pH regulator is selected from one of sodium hydroxide solution and potassium hydroxide solution. 6. The application of the supported Ni-Ga-Pd catalyst in the reaction of selective hydrogenation of acetylene to ethylene according to claim 1, characterized in that, in the step (2), the Ni /Ga/Mg/Al quaternary layered hydroxide material M is dispersed in water at a mass ratio of 1: (20~40), and the precursor species of palladium with a pH value of 4~6 is added. Exchange for 8-40 hours, and then filter, wash, and dry to obtain the Ni/Ga/Pd/Mg/Al five-element layered hydroxide material PM. 7. The application of the supported Ni-Ga-Pd catalyst in the reaction of selective hydrogenation of acetylene to ethylene according to claim 6, characterized in that, in the step (2), the Ni /Ga/Mg/Al quaternary layered hydroxide material M was dispersed in water at a mass ratio of 1:30, and a palladium precursor species with a pH value of 6 was added, and ion exchange was performed at 45 °C for 18 hours. 8. The application of the supported Ni-Ga-Pd catalyst in the reaction of selective hydrogenation of acetylene to ethylene according to claim 1, characterized in that, in the step (2), the precursor species of palladium It is one or more of sodium chloropalladate, palladium chloride and palladium nitrate. 9. The application of the supported Ni-Ga-Pd catalyst in the reaction of acetylene selective hydrogenation to ethylene according to claim 8, characterized in that the precursor species of palladium is sodium chloropalladate. 10. The application of the supported Ni-Ga-Pd catalyst in the reaction of selective hydrogenation of acetylene to ethylene according to claim 1, characterized in that, in the step (3), the thermal reduction temperature is 500 ~900 ℃, the reduction time is 3~6 hours, and the reducing gas is H ₂ /Ar.

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