CN111617772B

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

Info

Publication number: CN111617772B
Application number: CN202010493989.XA
Authority: CN
Inventors: 曹约强; 葛小虎; 段学志; 李雨柔; 周兴贵
Original assignee: East China University of Science and Technology
Current assignee: East China University of Science and Technology
Priority date: 2020-06-03
Filing date: 2020-06-03
Publication date: 2023-03-28
Anticipated expiration: 2040-06-03
Also published as: CN111617772A

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 preparation method and application thereof

Technical Field

The invention belongs to the technical field of catalyst preparation, and particularly relates to a supported Ni-Ga-Pd catalyst as well as a preparation method and application thereof.

Background

Ethylene is used as a base stone in modern chemical industry, and the main production process route is naphtha steam cracking route. Ethylene products from naphtha steam cracking furnaces contain trace amounts of acetylene (0.5% to 2%) which poison the catalyst in downstream polymerization processes. Thus, it is desirable to reduce the acetylene content of the ethylene product to less than 5ppm levels depending on the specific process conditions downstream. Theoretically, ethylene purification includes various methods such as a solvent absorption method, a copper acetylide precipitation method, a low-temperature rectification extraction method, catalytic hydrogenation and the like, but an acetylene selective hydrogenation process is generally used in industry on the basis of the current technical cost and efficiency. The process can not only remove trace amount of acetylene in ethylene products, but also increase the yield of ethylene. However, deep hydrogenation of acetylene to ethane is prone to occur in the hydrogenation process, and catalyst deactivation is also prone to occur by oligomerization to "green oil".

Currently, highly optimized PdAg catalysts are generally used in the industry to reduce the activity of deep hydrogenation of acetylene to improve the selectivity of the catalyst. However, the microstructure of the PdAg catalyst has disorder, a multidentate adsorption configuration still exists 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 the upgrading of existing industrial catalysts and to design new efficient, stable catalysts, researchers have recently begun to focus on structurally ordered stable Pd-M intermetallics, such as: journal literature ACS catalysis.2016,6 (2): 1054-1061 reports that a Pd salt solution is loaded on ZnO as a carrier and then the loaded PdZn intermetallic compound catalyst can be obtained by roasting and reducing at 400 ℃. The active site of Pd in the PdZn intermetallic compound structure is isolated in space, so that acetylene is adsorbed on the surface of the catalyst in a sigma bond form, namely two C atoms are combined with two adjacent Pd atoms; ethylene can only be weakly adsorbed on the surface of the catalyst in a pi bond form on a single Pd site, and when the acetylene conversion rate reaches 100%, the ethylene selectivity is not lower than 90%. Patent CN 108940277A reports that the electronic and crystalline structure of Pd is modulated by fine control of the "metal-support interaction" between the Pd — ZnO systems, and correlates its performance with the selective hydrogenation of acetylene. Zn-doped Pd-structured catalysts, when dominated by electronic effects, show the most excellent performance: the ethylene selectivity reaches 85 percent, and the hydrogenation activity is 15 to 35 times of that of the PdZn intermetallic compound catalyst. However, the Pd-M alloy catalyst has high load of noble metal Pd (generally 1-5%), and the catalyst used in the process is large, so the catalyst cost is high.

Non-noble metal Ni is another commonly used hydrogenation catalyst active component. In recent years, ni catalysts have been attracting attention as a potential catalyst for selective hydrogenation of acetylene. For example, advanced materials.2016,28 (23): 4747-4754, reported that the NiGa and NiSn binary metal particles with uniform particle size and controllable composition are prepared by a liquid-phase co-reduction method, and XRD and electron microscope characterization results show that the synthesized binary metal nanoparticles are in an ordered structure, namely, an intermetallic compound structure. The catalyst shows excellent performance in liquid-phase and gas-phase alkyne selective hydrogenation reactions, in particular to Ni ₃ The Ga catalyst has ethylene selectivity as high as about 80% under the condition of 90% acetylene conversion rate. Due to the low hydrogenation activity of Ni-based catalysts compared to Pd-based catalysts, the reaction temperature required for the complete conversion of acetylene is higher, typically up to 180 ℃ or even higher. However, higher reaction temperatures are more thermodynamically favored for the formation of "green oil". Therefore, from the practical point of view, there is a need to further improve the catalyst activity of Ni-based catalysts to achieve complete conversion of acetylene at relatively low temperature intervals while ensuring high ethylene selectivity.

In summary, in the prior art, the Pd-M intermetallic compound catalyst has high loading of noble metal Pd and large catalyst usage, which results in high catalyst cost; the Ni-M alloy catalyst has the defects of low hydrogenation activity and higher reaction temperature required by complete conversion of acetylene. For this reason, it is necessary to develop a novel catalyst to solve the above problems.

Disclosure of Invention

The first purpose of the invention is to provide a preparation method of a supported Ni-Ga-Pd catalyst. The inventor of the invention, in the process of deeply researching a Pd-M intermetallic compound catalyst and a Ni-M alloy catalyst, unexpectedly finds that the reaction temperature can be remarkably reduced by loading an extremely low amount of Pd on a Ni/Ga/Mg/Al quaternary layered double hydroxide material, and meanwhile, the Ni-based catalyst has the characteristics of high catalytic activity, good selectivity and long service life.

In order to realize the purpose, the following technical scheme is adopted:

a preparation method of a supported Ni-Ga-Pd catalyst specifically comprises the following steps:

(1) Taking nitrates of Ni, ga, mg and Al as metal precursors, preparing into mixed metal nitrate solution, and preparing into a Ni/Ga/Mg/Al quaternary layered hydroxide material M by adopting a coprecipitation method;

(2) Dissolving the Ni/Ga/Mg/Al quaternary layered hydroxide material M in the step (1) in a proper amount of water, adding a proper amount of palladium precursor species for ion exchange, and then filtering, washing and drying to obtain a Ni/Ga/Pd/Mg/Al quinary layered hydroxide material PM;

(3) Carrying out thermal reduction on the Ni/Ga/Pd/Mg/Al quinary layered hydroxide material PM in the step (2) to obtain a supported Ni-Ga-Pd catalyst;

in the mixed metal nitrate solution in the step (1), the molar ratio of Ni ions, ga ions, mg ions and Al ions is 1 (0.25-1) to 3-6 to 1-1.75; the concentration of Ni ions is 0.05-0.15 mol/L.

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

Based on the characteristics of LDHs material main body laminate composition and element adjustability, the Ni/Ga/Mg/Al quaternary LDHs is prepared by a coprecipitation method, then Ni/Ga/Pd/Mg/Al quinary LDHs is prepared by introducing trace Pd through ion exchange and is used as a precursor of a Ni-Ga-Pd catalyst, and the Ni-Ga-Pd catalyst is obtained through reduction. The influence rule of the preparation process on the catalyst reaction performance is explored to develop a controllable preparation method of the Ni-Ga-Pd catalyst with ordered and stable structure.

The inventor of the invention considers the unique performance of the monatomic Pd catalyst, introduces a trace amount of Pd into the Ni-M intermetallic compound catalyst to prepare the supported Ni-M-Pd catalyst, develops a new synergetic strategy of Ni-M and monatomic Pd, and becomes a new technical scheme for solving the problems in the prior art.

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

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

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

According to a preferred technical scheme of the invention, in the step (1), the mixed metal nitrate solution and the pH regulator are added into the precipitator simultaneously under the stirring condition, the temperature of the reaction system is maintained at 60-70 ℃, and the pH value of the reaction system is controlled to be 10 +/-1; after the feeding is finished, continuously stirring and reacting for 18-36 hours, and finally filtering, washing and drying to obtain the Ni/Ga/Mg/Al quaternary layered hydroxide material M;

and controlling the adding speed of the mixed metal nitrate solution to be 1.0 +/-0.2 mL/min.

More preferably, in the step (1), the mixed metal nitrate solution and the pH regulator are added to the precipitant while stirring, the temperature of the reaction system is maintained at 65 ℃, and the pH of the reaction system is controlled to 10; after the charging is finished, continuously stirring and reacting for 24 hours, and finally filtering, washing and drying to obtain the Ni/Ga/Mg/Al quaternary layered hydroxide material M;

the adding speed of the mixed metal nitrate solution is controlled to be 1.0mL/min.

Preferably, in the step (1), the drying condition is 80 +/-5 ℃ and the drying time is 6-18 h.

Preferably, the precipitant is selected from one of sodium carbonate solution, ammonia water, sodium bicarbonate solution, potassium carbonate solution and potassium bicarbonate solution. Further preferred is a sodium carbonate solution.

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 in the step (1) is dispersed in water according to the mass ratio of 1 (20-40), a precursor species of palladium with the pH value of 4-6 is added, ion exchange is carried out for 8-40 hours at the temperature of 30-60 ℃, and then the Ni/Ga/Pd/Mg/Al quinary layered hydroxide material is obtained after filtration, washing and drying.

In the technical scheme of the invention, almost all Pd in the added palladium precursor species is ion-exchanged into the Ni/Ga/Mg/Al quaternary layered hydroxide material M through ion exchange.

In the present invention, the ion exchange means anion exchange. In the invention, after Ni/Ga/Mg/Al cations enter the main layer plate, the layer plate is positively charged, and exchangeable anions NO are arranged between the layers of LDHs ₃ ^- Or together with NO ₃ ^- And CO ₃ ^2- Thereby making the LDHs electrically neutral as a whole.

Generally, the order of ionic stability of the anion between the layers of the LDHs is CO ₃ ^2- >SO ₄ ^2- >PdCl ₄ ^2- >F ^- >Cl ^- >B(OH) ₄ ^- >NO ₃ ^- In which NO ₃ ^- Most easily exchanged by other anions. Thus different anions of Pd (e.g. PdCl) ₄ ^2- ) Inserted into the LDHs layers to form a Ni/Ga/Pd/Mg/Al quinary layered hydroxide material PM。

Preferably, ion exchange is carried out at 30 to 60 ℃ for 18 to 36 hours.

Preferably, in the step (2), the Ni/Ga/Mg/Al quaternary layered hydroxide material M in the step (1) is dispersed in water according to the mass ratio of 1.

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

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

More preferably, the thermal reduction temperature is 600 to 900 ℃.

The temperature of the reduction reaction is determined by H ₂ The difference of TPR peak position is reasonably selected in the range of 500-900 ℃, and the time of the reduction reaction is properly adjusted in 3-6 hours according to the selection of the reduction temperature. It is also possible to suitably prolong the reaction time on the basis of this.

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

It should be noted that, when the thermal reduction temperature is lower than 500 ℃, the reaction speed is slow, the Ni-Ga-Pd particles grow slowly and have the smallest particle size, and the smaller Ni-Ga-Pd particles easily penetrate into the carrier pore channels, so that the dispersity measured by chemisorption is reduced, the number of active sites on the surface of the catalyst is reduced, and the catalytic effect is poor. When the thermal reduction temperature is higher than 900 ℃, the reaction speed is high, the Ni-Ga-Pd particles grow fast, the particle size is large, the dispersity measured by chemical adsorption is reduced, the number of active sites on the surface of the catalyst is reduced, and the catalytic effect is poor. When the reduction temperature is 800 ℃, the reaction speed is moderate, the obtained Ni-Ga-Pd particles are uniformly loaded on the surface of the carrier, the dispersion degree measured by chemical adsorption is highest, the number of active sites on the surface of the catalyst is the largest, and the catalytic effect is good.

The second purpose of the invention is to provide a supported Ni-Ga-Pd catalyst, which is prepared by adopting the preparation method of the supported Ni-Ga-Pd catalyst.

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

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

The third purpose of the invention is to provide the application of the supported Ni-Ga-Pd catalyst, which is used for the reaction of preparing ethylene by selective hydrogenation of acetylene.

Preferably, the reaction temperature for preparing ethylene by selective hydrogenation of acetylene is 80-130 ℃.

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

(1) The preparation method of the supported Ni-Ga-Pd catalyst utilizes the main body laminate composition and element adjustable characteristic of a layered hydroxide (LDHs) material to prepare Ni/Ga/Mg/Al quaternary LDHs, utilizes the interchangeability of anions between layers of the LDHs material to introduce trace Pd anion groups between the laminates of the Ni/Ga/Mg/Al quaternary LDHs through ion exchange, and combines the subsequent thermal reduction process to realize the controllable preparation of different Ni-Ga-Pd intermetallic compounds. In the thermal reduction process, ni-Ga-Pd alloy particles and Mg (Al) O metal oxide are generated simultaneously, so that the generated alloy particles and the metal oxide have stronger action, and the phenomenon of metal particle agglomeration caused by high-temperature roasting and high-temperature reduction in the traditional impregnation method is avoided, so that the utilization rates of active components Ni and Pd can be improved, the loading amounts of Ni and Pd are reduced, and the catalytic activity is improved.

Further, by DFT calculation, it is found that: acetylene preferentially adsorbs in the pi configuration on the Pd sites, while hydrogen is more readily activated on the Ni sites. The research results show that the Ni and Pd sites in the supported Ni-Ga-Pd catalyst prepared under the technical scheme of the invention possibly have a synergistic effect, so that the desorption of ethylene on the surface of the catalyst is promoted while the selective hydrogenation activity of acetylene is improved.

(2) Compared with the traditional Ni-based catalyst, the supported Ni-Ga-Pd catalyst has the characteristics of high dispersion degree of catalyst metal particles, high catalytic activity, good selectivity and long service life due to the introduction of Pd, so that acetylene can be completely converted in a relatively low temperature range, and the generation of green oil aggravated by high temperature is avoided. Meanwhile, the load capacity of Pd is extremely low, the cost of the conventional catalyst for preparing ethylene by selective hydrogenation of acetylene is greatly reduced, and the catalyst has a good industrial application prospect.

Drawings

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

FIG. 2 is an XRD spectrum of the Ni/Ga/Mg/Al quaternary LDH material M1 prepared in example 1 of the invention.

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

FIG. 4 is a transmission electron micrograph of Ni-Ga intermetallic compound catalysts M1 to 800 obtained in example 4 of the present invention.

FIG. 5 is a scanning electron micrograph of a Ni/Ga/Pd/Mg/Al pentabasic LDH material P1M1 prepared in example 7 of the present invention.

FIG. 6 is an XRD pattern of the Ni/Ga/Pd/Mg/Al pentabasic LDH material P1M1 prepared in example 7 of the invention.

FIG. 7 is the TG-DTA curve of the Ni/Ga/Pd/Mg/Al quinary LDH material P1M1 prepared in example 7 of the invention.

FIG. 8 is an XPS spectrum of Ni 2P of Ni-Ga-Pd intermetallic compound catalyst 50ppm-P1M1-800 obtained in example 7 of the present invention.

FIG. 9 is an XPS spectrum of Ga 2P of Ni-Ga-Pd intermetallic compound catalyst 50ppm-P1M1-800 prepared in example 7 of the present invention.

Detailed Description

The present invention is further illustrated by the following examples. It should be understood that the following examples are illustrative only and are not intended to limit the scope of the present invention.

Preparation example 1 preparation of a Palladium precursor solution

(I) preparing sodium chloropalladate solution

(a) Weighing 0.10g of sodium chloropalladate, and carrying out ultrasonic dissolution in ultrapure water to obtain 100mL of solution with the concentration of 1.0 multiplied by 10 ^-3 g/mL of sodium chloropalladate solution;

(b) Taking 13.80mL of the sodium chloropalladate solution obtained in the step (a) to be dissolved in ultrapure water by ultrasonic, and adjusting the pH value by using 0.10mol/L dilute hydrochloric acid to obtain 100mL of the solution with the pH value of 6 and the concentration of 1.38 multiplied by 10 ^-4 g/mL of sodium chloropalladate solution.

(II) preparing a palladium chloride solution

(a) 0.10g of palladium chloride was weighed and dissolved in ultrapure water by ultrasonic wave to obtain 100mL of a solution having a concentration of 1.0X 10 ^-3 g/mL of palladium chloride solution;

(b) 1.0X 10 from step (a) ^-3 Taking 8.33mL of the palladium chloride solution in g/mL of ultrapure water for ultrasonic dissolution, and adjusting the pH value by using 0.10mol/L of dilute hydrochloric acid to obtain 100mL of solution with the pH value of 5 and the concentration of 8.33 multiplied by 10 ^-5 g/mL of palladium chloride solution.

(III) preparing a palladium nitrate solution

(a) 0.10g of palladium nitrate was weighed and dissolved in ultrapure water by ultrasonic wave to obtain 100mL of a solution having a concentration of 1.0X 10 ^-3 g/mL of palladium nitrate solution;

(b) 1.0X 10 from step (a) ^-3 10.82mL of the g/mL palladium nitrate solution was dissolved in ultrapure water by ultrasonic wave, and the pH was adjusted with 0.10mol/L dilute hydrochloric acid to give 100mL of a solution having a pH of 4 and a concentration of 1.08X 10 ^-4 g/mL of palladium nitrate solution.

Example 1 preparation of Ni/Ga/Mg/Al Quaternary LDH Material M1 by coprecipitation method

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

(1) Dissolving 2.91g of nickel nitrate hexahydrate, 2.56g of gallium nitrate hydrate, 12.82g of magnesium nitrate hexahydrate and 3.75g of aluminum nitrate nonahydrate in 100mL of ultrapure water, and ultrasonically dispersing to obtain a mixed metal nitrate solution; dissolving 4.24g of sodium carbonate in 100mL of ultrapure water, and performing ultrasonic dispersion to obtain a precipitator; 10.00g of sodium hydroxide was dissolved in 250mL of ultrapure water and dispersed by ultrasonic to obtain a pH adjusting agent.

(2) Transferring the precipitator in the step (1) into a three-neck flask, placing the three-neck flask in a water bath kettle at 65 ℃ for constant temperature, then dropwise adding the mixed metal nitrate solution in the step (1) under the condition that the rotating speed is 100r/min, and controlling the flow rate to be 0.8mL/min by using a constant flow pump. And (2) simultaneously, dropwise adding the pH regulator obtained in the step (1) to ensure that the pH of the reaction system in the three-neck flask is constant at 10, continuing stirring at 65 ℃ for 24 hours after the addition is finished, and then filtering and washing to obtain a light green solid.

(3) And (3) drying the light green solid obtained in the step (2) at the temperature of 80 ℃ for 12 hours to obtain the Ni/Ga/Mg/Al quaternary LDH material, which is marked as M1.

The microscopic appearance of the M1 is shown in FIG. 1 by observing with a scanning electron microscope. As can be seen from FIG. 1, M1 prepared in this example is a plate-like morphology of a typical double-layer hydroxide material.

Figure 2 is an XRD spectrum of M1 with diffraction peaks of different intensities at 11.2 °, 22.7 °, 34.2 °, 38.5 °, 45.2 °, 60.5 ° and 61.8 °, which are assigned to the (003), (006), (021), (015), (018), (110) and (113) planes of LDH material, respectively, compared to XRD standard card for LDH (JCPDS 14-0191). No other peaks of other phases appear in the XRD spectrogram, which indicates that the prepared LDH material is a pure-phase layered double hydroxide structure, namely Ni and Ga cations enter a layered plate structure.

In addition, the thermal stability of the prepared Ni/Ga/Mg/Al quaternary LDH material M1 at the temperature between normal temperature and 800 ℃ is tested by thermogravimetric analysis, and the result is shown in FIG. 3. As can be seen from fig. 3, the weight loss curve of the Ni/Ga/Mg/Al quaternary LDH material mainly has two weight loss peaks: the weight loss between the normal temperature and 200 ℃ is the process of water volatilization and interlayer water molecule removal of physical adsorption on the surface of the LDH material; weight loss between 250 and 410 ℃ is a decarbonylation and dehydroxylation process of the LDH material, eventually leading to the collapse of the layered structure of the LDH.

The above characterization results show that under the preparation conditions of example 1, ni and Ga enter the structure of the LDH material, i.e., it is confirmed that the Ni/Ga/Mg/Al quaternary LDH material as a catalyst precursor has been prepared by a coprecipitation method.

Example 2 preparation of Ni/Ga/Mg/Al Quaternary LDH Material M2 by coprecipitation method

The preparation method of the present example is substantially the same as that of example 1, except that:

in the step (1), 1.46g of nickel nitrate hexahydrate, 0.64g of gallium nitrate hydrate, 3.85g of magnesium nitrate hexahydrate and 2.82g of aluminum nitrate nonahydrate are dissolved in 100mL of ultrapure water and ultrasonically dispersed;

in the step (2), the temperature is controlled to be 60 ℃, the rotating speed is controlled to be 150r/min, the adding speed of the mixed metal nitrate solution is controlled to be 1.0mL/min, the pH value of a reaction system in the three-neck flask is constant to be 9, and after the adding is finished, the stirring is continuously carried out for 36 hours.

Obtaining the Ni/Ga/Mg/Al quaternary LDH material which is marked as M2.

The microstructure of the M2 observed by a scanning electron microscope is similar to that of the image 1.

In the XRD pattern of M2 prepared in this example, compared with JCPDS 14-0191, diffraction peaks with different intensities at 11.2 degrees, 22.7 degrees, 34.2 degrees, 38.5 degrees, 45.2 degrees, 60.5 degrees and 61.8 degrees are present, and no impurity peak appears.

In addition, in a TG-DTA curve of M2, water volatilization and interlayer water molecule removal of LDH material surface physical adsorption occur between normal temperature and 200 ℃; decarbonylation and dehydroxylation of LDH materials occurred between 250 and 410 ℃.

The above characterization results show that under the preparation conditions of example 2, ni and Ga enter the structure of the LDH material, i.e., it is confirmed that the Ni/Ga/Mg/Al quaternary LDH material as a catalyst precursor has been prepared by a coprecipitation method.

Example 3 preparation of Ni/Ga/Mg/Al Quaternary LDH Material by coprecipitation method

The preparation method of this example is substantially the same as that of example 1, except that:

in the step (1), 4.37g of nickel nitrate hexahydrate, 0.90g of gallium nitrate hydrate, 23.08g of magnesium nitrate hexahydrate and 9.84g of aluminum nitrate nonahydrate are dissolved in 100mL of ultrapure water and ultrasonically dispersed;

in the step (2), the temperature is controlled to be 70 ℃, the rotating speed is controlled to be 100r/min, the adding speed of the mixed metal nitrate solution is controlled to be 1.2mL/min, the pH value of a reaction system in the three-neck flask is constant to be 11, and the stirring is continued for 18 hours after the adding is finished.

Obtaining the Ni/Ga/Mg/Al quaternary LDH material which is marked as M3.

The microstructure of the M3 is similar to that of FIG. 1 when observed by a scanning electron microscope.

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 impurity peak appears.

In addition, in a TG-DTA curve of M3, water volatilization of physical adsorption on the surface of an LDH material and removal of interlayer water molecules occur between normal temperature and 200 ℃; decarbonylation and dehydroxylation of LDH materials occurred between 250 and 410 ℃.

The above characterization results show that under the preparation conditions of example 3, ni and Ga enter the structure of the LDH material, i.e., it is confirmed that the Ni/Ga/Mg/Al quaternary LDH material as a catalyst precursor has been prepared by a coprecipitation method.

The Ni/Ga/Mg/Al quaternary LDH materials M1 to M3 prepared under the process conditions of the embodiments 1 to 3 have typical sheet-shaped morphologies of layered double hydroxide materials, and Ni, ga, mg and Al are uniformly distributed on the LDH materials.

Examples 4 to 6 preparation of Ni-Ga intermetallic Compound catalyst

In this embodiment, a Ni/Ga/Mg/Al quaternary LDH material M1-M3 is subjected to thermal reduction treatment to obtain a Ni-Ga intermetallic compound catalyst, which includes the following specific steps:

m1 to M3 prepared in examples 1 to 3 were reacted at 800 ℃ in H ₂ And reducing the mixture in an Ar atmosphere (volume ratio of 1.

The microscopic morphology of the M1-800 catalyst is shown in FIG. 4 by transmission electron microscopy. As shown in fig. 4, in the catalysts M1-800 prepared in this example, the metal particles in the catalyst obtained by reducing M1 were well dispersed and uniform in particle size, the average size of the metal particles was 9.9 ± 1.6nm, and the metal dispersion degree was 15.1%.

The transmission electron micrograph of the M2-800 catalyst is similar to that of FIG. 4, and the catalyst obtained by reducing M2 has good dispersion of metal particles, uniform particle size, average size of the metal particles of 9.6 +/-1.6 nm and metal dispersion degree of 15.5%.

The transmission electron micrograph of the M3-800 catalyst is similar to that of FIG. 4, and the catalyst obtained by reducing M3 has good dispersion of metal particles, uniform particle size, average size of the metal particles of 9.6 +/-1.6 nm and metal dispersion degree of 15.2%.

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

Example 7 preparation of Supported Ni-Ga-Pd catalyst

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

(1) 6.0g of M1 was dispersed in 180g of ultrapure water, and then 1.00mL of the sodium chloropalladate solution of preparation example 1 was added, ion exchange was performed at 45 ℃ under stirring for 18 hours, and then cooled to room temperature, filtration was performed to obtain a filtrate and a solid, and the solid was washed to obtain a pale green solid.

(2) And (2) drying the light green solid prepared in the step (1) at 80 ℃ for 12 hours to obtain the Ni/Ga/Pd/Mg/Al quinary LDH material, which is marked as P1M1.

(3) The P1M1 prepared in the step (2) is at 800 ℃ and H ₂ Reducing for 4 hours in a/Ar atmosphere to obtain 1g of Ni-Ga-Pd intermetallic compound catalyst.

And (2) detecting the filtrate obtained in the step (1) by inductively coupled plasma atomic emission spectrometry (ICP-AES), wherein Pd cannot be detected. Therefore, in this example, almost all of Pd was ion-exchanged into the interior of the Ni-Ga-Pd intermetallic compound catalyst. The Pd content of the catalyst was calculated to be 50ppm, and the catalyst of this example was labeled 50ppm-P1M1-800.

The microstructure of P1M1 is shown in FIG. 5 by observing with a scanning electron microscope. As can be seen from the comparison of FIGS. 1 and 5, the morphology of P1M1 is not significantly changed from that of M1.

The XRD pattern of 50ppm-P1M1-800 prepared in this example is shown in FIG. 6, and compared with JCPDS 14-0191, diffraction peaks with different intensities at 11.2 degrees, 22.7 degrees, 34.2 degrees, 38.5 degrees, 45.2 degrees, 60.5 degrees and 61.8 degrees are present, and no impurity peak appears.

In addition, the TG-DTA curve of 50ppm-P1M1-800 is shown in figure 7, and water volatilization and interlayer water molecule removal of LDH material surface physical adsorption occur between normal temperature and 200 ℃; decarbonylation and dehydroxylation of LDH materials occurred between 250 and 410 ℃. As explained above, the introduction of the palladium precursor species does not destroy the microstructure of the original quaternary LDH material.

FIGS. 8 and 9 are XPS spectra of Ni 2P and Ga 2P in a 50ppm-P1M1-800 catalyst: when PdCl is used ₄ ^2- When introduced, ni ⁰ 2p _3/2 The peak shifts to a low position, and Ga ⁰ 2p _3/2 The peak shifts to a higher position, indicating that more electrons are transferred from the Ga atom to the Ni atom, at which time the presence of Pd increases the electron density of Ni.

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

Example 8 preparation of Supported Ni-Ga-Pd catalyst

(1) Dispersing 6.0g of M2 in 120g of ultrapure water, adding 1.00mL of the sodium chloropalladate solution prepared in the preparation example 1, carrying out ion exchange at 60 ℃ for 24 hours under stirring, cooling to room temperature, filtering to obtain a filtrate and a solid, and washing the solid to obtain a light green solid.

(2) And (2) drying the light green solid prepared in the step (1) at 80 ℃ for 12 hours to obtain the Ni/Ga/Pd/Mg/Al quinary LDH material, wherein the mark is P1M2.

(3) The P1M2 prepared in the step (2) is at 800 ℃ and H ₂ Reducing for 4 hours in a/Ar atmosphere to obtain 1g of the Ni-Ga-Pd intermetallic compound catalyst.

And (3) detecting the filtrate obtained in the step (1) by ICP-AES, wherein Pd cannot be detected. Therefore, in this example, almost all of Pd was ion-exchanged into the interior of the Ni-Ga-Pd intermetallic compound catalyst. The Pd content of the catalyst was calculated to be 50ppm, and the catalyst of this example was labeled 50ppm-P1M2-800.

The XRD pattern, TG-DTA curve and XPS spectrum were similar to 50ppm-P1M1-800 of example 7.

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

Example 9 preparation of Supported Ni-Ga-Pd catalyst

(1) After 6.0g of M3 was dispersed in 240g of ultrapure water, 1.00mL of the sodium chloropalladate solution of preparation example 1 was added, ion exchange was performed at 30 ℃ for 36 hours under stirring, and then cooling to room temperature and filtration were performed to obtain a filtrate and a solid, and the solid was washed to obtain a pale green solid.

(2) And (2) drying the light green solid prepared in the step (1) at 80 ℃ for 12 hours to obtain the Ni/Ga/Pd/Mg/Al quinary LDH material, which is marked as P1M3.

(3) The P1M3 prepared in the step (2) is put in H at 800 DEG C ₂ Reducing for 4 hours in a/Ar atmosphere to obtain 1g of the Ni-Ga-Pd intermetallic compound catalyst.

And (3) detecting the filtrate obtained in the step (1) by ICP-AES, wherein Pd cannot be detected. Therefore, in this example, almost all of Pd was ion-exchanged into the interior of the Ni-Ga-Pd intermetallic compound catalyst. The Pd content of the catalyst was calculated to be 50ppm, and the catalyst of this example was labeled 50ppm-P1M3-800.

The XRD pattern, TG-DTA profile and XPS spectrum were similar to 50ppm-P1M1-800 of example 7.

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

Example 10 preparation of Supported Ni-Ga-Pd catalyst

The basic steps of this example are the same as example 7, except that:

in step (1), 0.20mL of the sodium chloropalladate solution of preparation example 1 was added. And (3) obtaining the Ni/Ga/Pd/Mg/Al quinary LDH material marked as P2M1 in the step (2).

The 10ppm-P2M1-800 is obtained in the step (3).

According to detection, in the 10ppm-P2M1-800 catalyst prepared in the embodiment, the average size of metal particles is 9.9 +/-1.1 nm, and the metal dispersion degree is 15.4%.

Example 11 preparation of Supported Ni-Ga-Pd catalyst

The basic steps of this example are the same as example 7, except that:

in step (1), 0.50mL of the sodium chloropalladate solution of preparation example 1 was added. And (3) obtaining the Ni/Ga/Pd/Mg/Al quinary LDH material marked as P2M1 in the step (2).

The 25ppm-P3M1-800 is obtained in the step (3).

Through detection, in the 25ppm-P3M1-800 catalyst prepared in the embodiment, the average size of metal particles is 9.8 +/-1.7 nm, and the metal dispersion degree is 15.0%.

Example 12 preparation of Supported Ni-Ga-Pd catalyst

The basic steps of this example are the same as example 7, except that:

in step (1), 1.5mL of the sodium chloropalladate solution of preparation example 1 was added. And (3) obtaining the Ni/Ga/Pd/Mg/Al quinary LDH material marked as P4M1 in the step (2).

75ppm-P4M1-800 is obtained in the step (3).

According to detection, in the 75ppm-P4M1-800 catalyst prepared in the embodiment, the average size of metal particles is 9.7 +/-1.3 nm, and the metal dispersion degree is 15.2%.

Example 13 preparation of Supported Ni-Ga-Pd catalyst

The basic steps of this example are the same as example 7, except that:

in step (1), 2.0mL of the sodium chloropalladate solution of preparation example 1 was added. And (3) obtaining the Ni/Ga/Pd/Mg/Al quinary LDH material marked as P5M1 in the step (2).

The step (3) obtains 100ppm-P5M1-800.

According to detection, in the 100ppm-P5M1-800 catalyst prepared in the embodiment, the average size of metal particles is 9.9 +/-1.4 nm, and the metal dispersion degree is 14.7%.

Example 14 preparation of Supported Ni-Ga-Pd catalyst

The basic steps of this example are the same as example 7, except that:

in step (1), 2.5mL of the sodium chloropalladate solution of preparation example 1 was added. And (3) obtaining the Ni/Ga/Pd/Mg/Al quinary LDH material marked as P6M1 in the step (2).

125ppm-P6M1-800 is obtained in the step (3).

According to detection, in the 125ppm-P6M1-800 catalyst prepared in the embodiment, the average size of metal particles is 9.9 +/-1.7 nm, and the metal dispersion degree is 15.4%.

Example 15 preparation of Supported Ni-Ga-Pd catalyst

The basic steps of this example are the same as example 7, except that:

in step (1), 3.0mL of the sodium chloropalladate solution of preparation example 1 was added. And (3) obtaining the Ni/Ga/Pd/Mg/Al quinary LDH material marked as P7M1 in the step (2).

150ppm-P7M1-800 is obtained in the step (3).

According to detection, in the 150ppm-P7M1-800 catalyst prepared in the embodiment, the average size of metal particles is 9.9 +/-1.0 nm, and the metal dispersion degree is 14.5%.

Example 16 preparation of Supported Ni-Ga-Pd catalyst

The basic steps of this example are the same as example 7, except that:

in step (1), 3.5mL of the sodium chloropalladate solution of preparation example 1 was added. And (3) obtaining the Ni/Ga/Pd/Mg/Al quinary LDH material marked as P8M1 in the step (2).

175ppm-P8M1-800 is obtained in step (3).

According to detection, in the 175ppm-P8M1-800 catalyst prepared in the example, the average size of metal particles is 10.1 +/-1.1 nm, and the metal dispersion degree is 14.9%.

Example 17 preparation of Supported Ni-Ga-Pd catalyst

The basic steps of this example are the same as example 7, except that:

in step (1), 4.0mL of the sodium chloropalladate solution of preparation example 1 was added. And (3) obtaining the Ni/Ga/Pd/Mg/Al quinary LDH material marked as P9M1 in the step (2).

200ppm-P9M1-800 is obtained in the step (3).

According to detection, in the catalyst of 200ppm-P9M1-800 prepared in the embodiment, the average size of metal particles is 10.1 +/-0.9 nm, and the metal dispersion degree is 15.5%.

Example 18 preparation of Supported Ni-Ga-Pd catalyst

The basic steps of this example are the same as example 7, except that: the reduction temperature of P1M1 was 600 ℃ and the reduction time was about 6 hours, and the final catalyst was labeled 50ppm-P1M1-600.

Through detection, in the 50ppm-P1M1-600 catalyst prepared in the embodiment, the average size of metal particles is 9.7 +/-2.3 nm, and the metal dispersion degree is 15.5%.

Example 19 preparation of Supported Ni-Ga-Pd catalyst

In this example, the basic procedure for preparing a Ni-Ga-Pd intermetallic compound catalyst was the same as in example 7 except that: the reduction temperature of P1M1 was 700 ℃ and the reduction time was about 5 hours, and the final catalyst was designated 50ppm-P1M1-700.

According to detection, in the 50ppm-P1M1-700 catalyst prepared in the embodiment, the average size of metal particles is 9.9 +/-1.1 nm, and the metal dispersion degree is 15.4%.

Example 20 preparation of Supported Ni-Ga-Pd catalyst

In this example, the basic procedure for preparing a supported Ni-Ga-Pd catalyst is the same as in example 7, except that: the reduction temperature of P1M1 was 900 ℃ and the reduction time was about 3 hours, and the final catalyst was designated 50ppm-P1M1-900.

According to detection, in the 50ppm-P1M1-900 catalyst prepared in the embodiment, the average size of metal particles is 9.8 +/-2.6 nm, and the metal dispersion degree is 15.2%.

Example 21 preparation of Supported Ni-Ga-Pd catalyst

In this example, the basic procedure for preparing a supported Ni-Ga-Pd catalyst was the same as in example 7, except that: adopting M2, the precursor species of the used palladium is palladium chloride, and the specific steps are as follows:

(1) After 6.0g of M2 was dispersed in 180g of ultrapure water, 1.00mL of the palladium chloride solution of preparation example 1 was added, ion exchange was carried out at 45 ℃ for 18 hours under stirring, and then cooling to room temperature, filtration and washing were carried out to obtain a pale green solid.

(2) And (2) drying the light green solid prepared in the step (1) at 80 ℃ for 12 hours to obtain the Ni/Ga/Pd/Mg/Al five-membered LDH material, which is marked as P10M2.

(3) The P10M2 prepared in the step (2) is put in H at 800 DEG C ₂ And reducing for 4 hours in an/Ar atmosphere to obtain the Ni-Ga-Pd intermetallic compound catalyst which is marked as 50ppm-P10M2-800.

According to detection, in the 50ppm-P10M2-800 catalyst prepared in the embodiment, the average size of metal particles is 9.8 +/-1.8 nm, and the metal dispersion degree is 15.1%.

Example 22 preparation of Supported Ni-Ga-Pd catalyst

In this example, the basic procedure for preparing a supported Ni-Ga-Pd catalyst was the same as in example 7, except that: adopting M3, wherein the used precursor species of palladium is palladium nitrate, and the specific steps are as follows:

(1) After 6.0g of M3 was dispersed in 180g of ultrapure water, 1.00mL of the palladium nitrate solution of preparation example 1 was added, ion-exchanged at 45 ℃ for 18 hours under stirring, and then cooled to room temperature, filtered, and washed to obtain a pale green solid.

(2) And (2) drying the light green solid prepared in the step (1) at 80 ℃ for 12 hours to obtain the Ni/Ga/Pd/Mg/Al quinary LDH material, which is marked as P11M3.

(3) P11M3 prepared in step (2) at 800 ℃ in H ₂ And reducing the mixture for 4 hours in a/Ar atmosphere to obtain the Ni-Ga-Pd intermetallic compound catalyst marked as 50ppm-P11M3-800.

According to detection, in the 50ppm-P11M3-800 catalyst prepared in the embodiment, the average size of metal particles is 9.9 +/-2.2 nm, and the metal dispersion degree is 15.7%.

Example 23 evaluation of catalytic Performance of catalyst

Acetylene catalytic hydrogenation activity was evaluated using the supported Ni-Ga-Pd catalysts prepared in examples 4 to 22; the evaluation of acetylene hydrogenation reaction performance is carried out on a ZKJC-RJ-X system of Beijing Wanlong and science and technology Co., ltd, wherein:

the components in the reactants and products were analyzed on-line using a four-channel micro-chromatography GC 3000 (incicon corporation, usa).

Hydrogen and nitrogen were analyzed using molecular sieve columns, acetylene using Plot-U columns, ethylene and ethane using alumina columns, very low levels of C4 components as impurities in the feed gas were analyzed using OV-1 capillary chromatography columns, thermal Conductivity cell detectors (TCD), and argon and helium as carrier gases.

Evaluation conditions were as follows: the total flow of inlet gas is 120mL/min, the raw material gas is 1.0 percent of C ₂ H ₂ 20.0% of C ₂ H ₄ 5.0% of H ₂ The rest gas is N ₂ (ii) a The reaction temperature is 80-130 ℃; the reaction pressure was 0.1MPa abs. Catalyst loading was 0.05g.

0.05g of a catalyst sample is weighed, mixed uniformly with 10 times of quartz sand by mass and then filled in a constant temperature area in a stainless steel reaction tube. After the catalyst is filled, leak detection is carried out on the reaction system, nitrogen (10 bar) with certain pressure is introduced into the reaction system, the pressure can be kept unchanged, the reaction system is proved to have good tightness, and evaluation experiments can be carried out.

Setting the nitrogen flow rate to be 20sccm (standard cubic centrifuge per minute), and heating to the reduction temperature; then, closing the nitrogen, setting the hydrogen flow to be 20sccm, and closing the hydrogen after reducing for a certain time; the nitrogen flow is set to 20sccm, the temperature is reduced to the reaction temperature, and the pressure required by the reaction is set. After the reaction conditions are stable, setting the flow of each reaction component, and cutting the Furnace six-way valve into a bypass, so that the mixed gas directly enters a chromatograph to detect the concentration of each component before the reaction. After the stabilization, the Furnace six-way valve is switched back to the reaction tube to start the reaction, and the gas at the outlet of the reaction tube enters the online chromatographic detection.

Acetylene conversion rate C (C) of the supported Ni-Ga-Pd intermetallic compound catalysts prepared in examples 4 to 22 was measured ₂ H ₂ ) Ethylene selectivity S (C) ₂ H ₄ ) And yield Y (C) ₂ H ₄ ) To evaluate the catalytic performance of the catalyst on the reaction of preparing ethylene by selective hydrogenation of acetylene, wherein:

Y(C ₂ H ₄ )＝C(C ₂ H ₂ )×S(C ₂ H ₄ )

this example uses the following two references of catalysts and their catalytic performance compared to the catalysts and their catalytic performance of the invention prepared in examples 4-22. Different metal components are respectively introduced into the two documents, and the supported Ni-based catalyst is prepared by a coprecipitation method and a co-impregnation method. Wherein:

the first document: journal of Catalysis 359 (2018) 251-260, the catalyst preparation part of the Journal of Catalysis 359 uses Ni/CuMg/Al quaternary layered bimetallic material as a precursor, and the Ni-Cu alloy catalyst (pre-NiCu/MMO) is prepared by direct reduction of hydrogen, according to the description of the Journal, the evaluation conditions of the catalyst are as follows: the loading of the catalyst is 0.10g, the reaction temperature range is 60-240 ℃, and the space velocity is 8040h ^-1 C with the relative reaction pressure of 0.2MPa and the feed gas content of 0.33 percent ₂ H ₂ 34.5% of C ₂ H ₄ 0.66% of H ₂ And 1% of C ₃ H ₈ Composition, the balance being N ₂ . And (3) reaction results: at a reaction temperature of 130 deg.C, the acetylene conversion was 67.50% and the ethylene selectivity was 85.50% for the catalyst pre-NiCu/MMO. At 80 deg.C, the acetylene conversion is 16.5% and the ethylene selectivity is 89.30% for the catalyst pre-NiCu/MMO. At 100 deg.C, the conversion rate of acetylene is 29.20% and the selectivity of ethylene is 88.30% for the catalyst pre-NiCu/MMO.

The second document: journal of Energy Chemistry 29 (2019) 40-49, catalyst preparation was partially done by co-impregnation on SiO ₂ Ni and Ga are loaded on the catalyst to obtain Ni catalyst _x -Ga/SiO ₂ . According to the journal literature, the catalyst was evaluated under the following conditions: catalytic converterThe loading of the catalyst is 0.20g, the reaction temperature is 180 ℃, and the space velocity is 36000 mL.h ^-1 1.0% of C in the raw material gas ₂ H ₂ 5.0% of H ₂ The rest gas is N ₂ The reaction pressure was 0.40MPa. And (3) reaction results: ni for catalyst when reaction temperature is 180 DEG C ₅ Ga/SiO ₂ The acetylene conversion was 100% and the ethylene selectivity was 77.00%.

It is noted that in the second document, in order to eliminate the interference of excess ethylene (for example, competitive adsorption with acetylene and subsequent over-hydrogenation and polymerization reactions), a feed free of ethylene is used. In the case of feed gas without ethylene, the results of the catalyst selectivity test for ethylene were higher compared to when the feed gas contained ethylene. That is, in the second document, if the feed gas contains ethylene, the ethylene selectivity data is definitely lower than the current 77.00%.

It should be noted that: c is neglected in the ethylene selectivity evaluation formula of the related catalysts of the two documents ₂ H ₆ And C ₄ The results thus obtained are high compared to reality, i.e. the actual results are lower than those listed in the present invention.

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

TABLE 1 evaluation results of catalytic Performance of catalysts

The average particle diameters of the metal particles of examples 4 to 22 in Table 1 were determined by statistical analysis of the particle diameters from STEM photographs, and the metal dispersion degrees were determined by dynamic chemical adsorption hydrogen-oxygen titration.

From the results in table 1, it can be seen that, in the case of feeding ethylene into the feed gas, when the reaction temperature is 130 ℃, the acetylene conversion rate and the ethylene yield of the catalyst pre-NiCu/MMO are both significantly lower than those of the supported Ni-Ga-Pd catalyst of the present invention, which indicates that the activity of the catalyst pre-NiCu/MMO in the low-temperature reaction region is much lower than that of the supported Ni-Ga-Pd intermetallic compound catalyst of the present invention.

In the case of no ethylene feed, although the catalyst Ni ₅ Ga/SiO ₂ The conversion rate of acetylene reaches 100%, but the selectivity and yield of ethylene are still significantly lower than those of the supported Ni-Ga-Pd intermetallic compound catalyst.

In the invention, the evaluation of the catalytic hydrogenation activity of acetylene is carried out under more severe reaction conditions, namely, the loading amount of the catalyst is less, the reaction temperature is lower, the reaction pressure is normal pressure, and the reaction raw material gas is rich in ethylene.

The alloy particles of the supported Ni-Ga-Pd catalyst have uniform particle size and similar distribution range, and the utilization rate of the noble metal component Pd in the catalytic reaction is high. The Pd loading capacity of the supported Ni-Ga-Pd intermetallic compound catalyst is in ppm level, but the acetylene conversion rate, the selectivity and the yield are obviously improved within the reaction temperature range of 80-130 ℃, and the acetylene conversion rate almost reaches 100%; the selectivity of ethylene is more than or equal to 85.0 percent and can reach 91.10 percent at most; the yield is more than or equal to 85.50 percent and can reach 91.10 percent at most. The supported Ni-Ga-Pd catalyst prepared by the technical scheme of the invention can obviously improve the acetylene conversion rate, the ethylene selectivity and the yield.

As is easily understood by the technical personnel in the field, under the condition of the same other catalytic conditions, compared with the traditional Ni-based catalyst, the supported Ni-Ga-Pd intermetallic compound catalyst prepared by the invention has the advantages that because a trace amount of Pd is introduced into the Ni-Ga intermetallic compound, the activity of the catalyst is further improved, so that acetylene is completely converted at a relatively low temperature range, the green oil generation intensified by high temperature is avoided, and the selectivity and the yield of the obtained ethylene are higher than those of the catalyst pre-NiCu/MMO and the catalyst Ni ₅ Ga/SiO ₂ 。

In conclusion, the supported Ni-Ga-Pd catalyst disclosed by the invention has the advantages that the required catalytic reaction temperature is lower, the catalytic activity is very excellent, the loading capacity of the noble metal Pd is in the ppm level, the cost for preparing the Ni-Ga-Pd alloy catalyst disclosed by the invention is obviously reduced, the industrial application of the Ni-based catalyst is more facilitated, and a good way is provided for the industrial application of the Ni-based catalyst.

Example 24 evaluation of catalyst stability

The catalysts prepared in example 7, 50ppm-P1M1-800, example 10, 10ppm-P2M1-800, example 11, and 25ppm-P3M1-800 were randomly selected and evaluated for stability according to the catalytic performance test method of example 18, C (C) ₂ H ₂ )、S(C ₂ H ₄ ) And Y (C) ₂ H ₄ ) Data results are shown in tables 2 to 4:

TABLE 2 evaluation of stability of 50ppm P1M1-800 catalyst

As can be seen from the data in Table 2, the supported Ni-Ga-Pd intermetallic compound catalyst prepared in example 7, 50ppm-P1M1-800, still maintained the conversion of acetylene above 98.5%, the selectivity of ethylene above 90.0% and the yield of ethylene above 89% after undergoing 240h reaction evaluation. Analysis of the catalyst after 240h of reaction at 50ppm-P1M1-800 determined: the catalyst metal particle dispersion 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 evaluation of catalyst stability at 10ppm-P2M1-800

As can be seen from the data in Table 3, the supported Ni-based catalyst 10ppm-P2M1-800 prepared in example 10 still maintained the acetylene conversion above 98.0%, the ethylene selectivity above 91.0% and the ethylene yield above 87.5% after undergoing the 240h reaction evaluation. 10ppm-P2M1-800 analysis of the catalyst after 240h of reaction found: the dispersion of the 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 evaluation of catalyst stability at 25ppm-P3M1-800

As can be seen from the data in Table 4, 25ppm-P3M1-800 of the supported Ni-Ga-Pd intermetallic compound catalyst prepared in example 11 still maintained the conversion of acetylene above 98.80%, the selectivity of ethylene above 89.90% and the yield of ethylene above 89.00% after 240h reaction evaluation. 25ppm-P3M1-800 analysis of the catalyst after 240h of reaction found: the dispersion of the 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.

The stability test shows that the supported Ni-Ga-Pd catalyst prepared by the invention has good catalytic stability and long service life, reduces the use cost of the catalyst and is beneficial to the industrial application of the supported Ni-based catalyst.

The embodiments of the present invention have been described in detail, but the embodiments are merely examples, and the present invention is not limited to the embodiments described above. Any equivalent modifications or alterations to this practice will occur to those skilled in the art and are intended to be within the scope of this invention. Accordingly, equivalent changes and modifications made without departing from the spirit and scope of the present invention should be covered by the present invention.

Claims

1. The application of the supported Ni-Ga-Pd catalyst in the reaction of preparing ethylene by selective hydrogenation of acetylene is characterized in that the preparation method of the supported Ni-Ga-Pd catalyst specifically comprises the following steps:

(1) Taking nitrates of Ni, ga, mg and Al as metal precursors, preparing mixed metal nitrate solution, and then preparing a Ni/Ga/Mg/Al quaternary layered hydroxide material M by adopting a coprecipitation method;

(2) Dissolving the Ni/Ga/Mg/Al quaternary layered hydroxide material M in a proper amount of water, adding a proper amount of palladium precursor species for ion exchange, and then filtering, washing and drying to obtain a Ni/Ga/Pd/Mg/Al quinary layered hydroxide material PM;

in the mixed metal nitrate solution in the step (1), the molar ratio of Ni ions, ga ions, mg ions and Al ions is 1 (0.25-1) to 3-6 to 1-1.75, and the concentration of the Ni ions is 0.05-0.15 mol/L;

in the supported Ni-Ga-Pd catalyst obtained in the step (3), the supported amount of the palladium is 50ppm.

2. The use of the supported Ni-Ga-Pd catalyst in the reaction for preparing ethylene by selective hydrogenation of acetylene according to claim 1, wherein in the step (1), the nitrates of Ni, ga, mg and Al are nickel nitrate hexahydrate, gallium nitrate hydrate, magnesium nitrate hexahydrate and aluminum nitrate nonahydrate respectively.

3. The use of the supported Ni-Ga-Pd catalyst according to claim 1 in the reaction for producing ethylene by selective hydrogenation of acetylene, wherein in step (1), a mixed metal nitrate solution and a pH regulator are added to a precipitant under stirring, the temperature of the reaction system is maintained at 60 to 70 ℃, and the pH of the reaction system is controlled to 10 ± 1; after the addition is finished, continuously stirring and reacting for 18-36 hours, and finally filtering, washing and drying to obtain the Ni/Ga/Mg/Al quaternary layered double-metal hydroxide material M;

the adding speed of the mixed metal nitrate solution is controlled to be 1.0 plus or minus 0.2mL/min.

4. The use of the supported Ni-Ga-Pd catalyst according to claim 3 in the reaction for producing ethylene by selective hydrogenation of acetylene, wherein in step (1), a mixed metal nitrate solution and a pH regulator are added simultaneously to a precipitant under stirring, the temperature of the reaction system is maintained at 65 ℃, and the pH of the reaction system is controlled to 10; after the charging is finished, continuously stirring and reacting for 24 hours, and finally filtering, washing and drying to obtain the Ni/Ga/Mg/Al quaternary layered hydroxide material M;

the adding speed of the mixed metal nitrate solution is controlled to be 0.8mL/min.

5. The use of the supported Ni-Ga-Pd catalyst in the reaction for preparing ethylene by selective hydrogenation of acetylene according to claim 3, wherein the precipitant is selected from one of sodium carbonate solution, ammonia water, sodium bicarbonate solution, potassium carbonate solution and potassium bicarbonate solution;

6. The application of the supported Ni-Ga-Pd catalyst in the reaction for preparing ethylene by selective hydrogenation of acetylene according to claim 1 is characterized in that in the step (2), the Ni/Ga/Mg/Al quaternary layered hydroxide material M in the step (1) is dispersed in water according to the mass ratio of 1 (20 to 40), a palladium precursor species with the pH value of 4-6 is added, ion exchange is carried out at the temperature of 30 to 60 ℃ for 8 to 40 hours, and then filtering, washing and drying are carried out, so that the Ni/Ga/Pd/Mg/Al quinary layered hydroxide material PM is obtained.

7. The use of the supported Ni-Ga-Pd catalyst according to claim 6 in the reaction of preparing ethylene by selective hydrogenation of acetylene, wherein in the step (2), the Ni/Ga/Mg/Al quaternary layered hydroxide material M in the step (1) is dispersed in water according to the mass ratio of 1.

8. The use of the supported Ni-Ga-Pd catalyst according to claim 1 in the reaction of selective hydrogenation of acetylene to ethylene, wherein in step (2), the precursor species of palladium is one or more of sodium chloropalladate, palladium chloride and palladium nitrate.

9. The use of the supported Ni-Ga-Pd catalyst according to claim 8 in reactions for the selective hydrogenation of acetylene to ethylene, wherein the precursor species of palladium is sodium chloropalladate.

10. The use of the supported Ni-Ga-Pd catalyst of claim 1 in the reaction of selective hydrogenation of acetylene to ethylene, wherein in the step (3), the thermal reduction temperature is 500-900 ℃, the reduction time is 3-6 hours, and the reduction gas is H ₂ /Ar。