CN111545198A

CN111545198A - Catalyst for preparing methane by carbon dioxide hydrogenation and preparation and application thereof

Info

Publication number: CN111545198A
Application number: CN202010410872.0A
Authority: CN
Inventors: 刘小浩; 姜枫; 胥月兵; 刘冰
Original assignee: Jiangnan University
Current assignee: Jiangnan University
Priority date: 2020-05-15
Filing date: 2020-05-15
Publication date: 2020-08-18
Anticipated expiration: 2040-05-15
Also published as: CN111545198B

Abstract

The invention discloses a catalyst for preparing methane by carbon dioxide hydrogenation, and preparation and application thereof, and belongs to the technical field of carbon dioxide conversion. Pd/CeO prepared by the invention₂The catalyst has active component Pd accounting for 5-20 wt% of the catalyst and metal Pd grain size greater than 10 nm. Pd/CeO prepared by the invention₂The catalyst has high methane selectivity close to 100%. In the vicinity of such Pd particles of larger particle diameter, oxygenThe higher concentration of vacancies favors CO₂CO is formed by dissociative adsorption, and the higher concentration of dissociated H species on the Pd particles facilitates further hydrogenation of CO to methane. Pd/CeO in the invention₂The catalyst has simple preparation method and wide industrial application prospect.

Description

Catalyst for preparing methane by carbon dioxide hydrogenation and preparation and application thereof

Technical Field

The invention relates to a catalyst for preparing methane by carbon dioxide hydrogenation, and preparation and application thereof, and belongs to the technical field of carbon dioxide conversion.

Background

CO₂Is an important greenhouse gas and can cause a series of severe environmental problems, such as climate abnormality, global warming, ocean acidification, glacier ablation, ecological damage and the like. The worldwide attention has been paid to the emission reduction and the catalytic conversion, wherein the hydrogen production by photocatalysis and photoelectrocatalysis by utilizing renewable energy sources such as solar energy is one of the hot spots of research. Sabatier and sendendens first proposed a carbon dioxide methanation reaction in 1902, i.e. the reaction of carbon dioxide with hydrogen to form methane. The reaction utilizes carbon dioxide and the generated methane as energy to be applied to production and life, and relieves the energy structure characteristic of less gas in China. Although carbon dioxide has other conversion routes, some higher value chemicals, such as methanol and dimethyl carbonate, can be produced. However, these reactions generally require more severe reaction conditions and the conversion of carbon dioxide is relatively low, generally not exceeding 20%. First, the reaction conditions of the methanation reaction of carbon dioxide are mild, and high temperature (C) is not required>500 ℃) is carried out; secondly, the conversion rate of the methanation reaction of the carbon dioxide is high, the byproducts are less, the selectivity of the methane is higher, and the cost of product separation is lower; thirdly, the produced methane can be recycled as energy and can be transported through the existing natural gas pipeline without additional cost for storage and transportation.

Although methanation of carbon dioxide is an exothermic reaction and can be achieved thermodynamically, the reaction often requires a highly active catalyst to assist in the process because the eight-electron structure of carbon dioxide is very stable and activation is difficult. Noble metal catalysts have high stability, good carbon deposition resistance and high reactivity, and are therefore frequently used for the reaction. Commonly used noble metal catalysts include Ru, Pt, Pd, and the like. The carrier has an important influence on the dispersibility, distribution, adsorption properties, etc. of the metal catalyst, which is usually carried on the carrier. In the research of the carbon dioxide methanation reaction catalyst, metals are generally selected to be loaded on a carrier with high specific surface area so as to increase the dispersity of the metals, thereby obtaining higher methane selectivity.

Disclosure of Invention

Compared with the prior art, the method adopts the cerium dioxide carrier to load the large-particle Pd to prepare the catalyst for preparing the methane by the hydrogenation of the carbon dioxide, the cerium dioxide carrier has small specific surface area, but rich oxygen vacancies are beneficial to the activation of the carbon dioxide, and the catalyst has the selectivity close to 100 percent for the methane and the preparation method is simple.

The first purpose of the invention is to provide Pd/CeO for preparing methane by hydrogenation of carbon dioxide₂The catalyst comprises an active component of metal Pd, wherein the content of the metal Pd accounts for 5-20% of the mass of the catalyst, and the particle size of the active component Pd is 5-30 nm; the carrier is CeO₂The content of the catalyst accounts for 80 to 95 percent of the mass of the catalyst.

In one embodiment of the invention, the active component of the catalyst is metal Pd, the content of the metal Pd accounts for 5-10% of the mass of the catalyst, and the particle size of the active component Pd is 10-20 nm; the carrier is CeO₂The content of the catalyst accounts for 90 to 95 percent of the mass of the catalyst.

It is a second object of the present invention to provide a method for preparing the Pd/CeO₂The preparation method of the catalyst is any one of the following two preparation methods:

the first method comprises the following steps: the dipping method comprises the following steps: dissolving soluble Pd salt in solvent to form solution, and soaking the solution in CeO₂On a carrier, drying after dipping, and then roasting at 300-600 ℃ for 2-10 h to obtain Pd/CeO₂A catalyst sample;

and the second method comprises the following steps: physical mixing method: firstly preparing Pd or PdO particles, then dispersing the Pd or PdO particles in a solvent, and then adding CeO₂The carrier is dispersed in the same solvent,finally, the dispersion containing Pd or PdO particles and CeO₂Mixing and drying the dispersion of the carrier, and then roasting for 2-10 h at 300-600 ℃ to obtain Pd/CeO₂A catalyst.

In one embodiment of the present invention, the soluble salt containing Pd in the first preparation method is: any one or more of palladium nitrate, palladium acetylacetonate, palladium chloride, palladium acetate, tetraaminopalladium nitrate, ammonium chloropalladate and palladium hexafluoroacetylacetonate.

In one embodiment of the present invention, the solvent in the first preparation method is: any one or more of water, ethanol, methanol, acetone, cyclohexane and ethylene glycol.

In one embodiment of the present invention, the time for the impregnation in the first preparation method is 0.5 to 24 hours.

In one embodiment of the present invention, the conditions of the calcination in the first production method are: calcining at 500 deg.C for 3 h.

In one embodiment of the present invention, the method for preparing Pd or PdO particles in the second preparation method is any one of a hydrothermal method, a precipitation method, and a liquid-phase reduction method.

In one embodiment of the present invention, the solvent in the second preparation method is: any one of water, ethanol, cyclohexane, methanol and acetone.

In one embodiment of the present invention, the Pd or PdO particles and CeO in the second preparation method₂The carrier dispersion mode is as follows: and ultrasonically dispersing for 0.5-3 h.

In one embodiment of the present invention, the conditions of the calcination in the second production method are: calcining at 400 deg.C for 3 h.

It is a third object of the present invention to provide the above Pd/CeO₂The catalyst is applied to catalyzing carbon dioxide methanation reaction.

In one embodiment of the invention, the Pd/CeO₂The catalyst needs to be pre-reduced before catalyzing the methanation reaction of the carbon dioxide, and the reducing atmosphere is H₂Or H₂/CO₂MixingThe reduction temperature of the gas is 400-700 ℃, and the reduction space velocity is 2-20L/g_catThe reduction pressure is 0.1-1 MPa.

In one embodiment of the invention, the Pd/CeO₂The reaction conditions of the catalyst in catalyzing the methanation of the carbon dioxide are as follows: CO 2₂/H₂1: 1-10, and the airspeed of 1-20L/g_catThe reaction temperature is 300-500 ℃, and the reaction pressure is 0.1-5 MPa.

The invention has the beneficial effects that:

(1) Pd/CeO prepared by the invention₂The catalyst has high methane selectivity close to 100%. In the vicinity of such Pd particles of larger particle diameter, the higher concentration of oxygen vacancies favors CO₂CO is formed by dissociative adsorption, and the higher concentration of dissociated H species on the Pd particles facilitates further hydrogenation of CO to methane. On the Pd particles with small particle size, the generated intermediate product CO can not be adsorbed on the surface of the Pd particles to carry out further hydrogenation reaction, but is directly desorbed from the surface of the catalyst, so that higher CO selectivity is obtained.

(2) The preparation method of the catalyst is simple, specifically comprises an impregnation method and a physical mixing method, and the two methods have the advantages of simple and convenient operation steps, low equipment requirement and industrial application prospect.

Drawings

FIG. 1 is a transmission electron micrograph of the catalyst prepared in example 1.

Fig. 2 is a particle size statistical chart of Pd particles supported on the catalyst prepared in example 1.

FIG. 3 is a transmission electron micrograph of the catalyst prepared in example 7.

Fig. 4 is a particle size statistical chart of Pd particles supported on the catalyst prepared in example 7.

Fig. 5 is a transmission electron micrograph of the catalyst prepared in comparative example 1.

Detailed Description

The invention will now be further illustrated by reference to specific examples, which are intended to be illustrative only and not to limit the scope of the invention. Further, it should be understood that various changes or modifications of the present invention may be made by those skilled in the art after reading the teaching of the present invention, and such equivalents may fall within the scope of the present invention as defined in the appended claims.

1. Evaluation of catalyst Performance: in the following examples, the reaction for preparing methane by catalyzing carbon dioxide is carried out in a stainless steel fixed bed or slurry bed reactor, and the specific catalytic performance test, namely the evaluation method, is as follows:

1g of catalyst was mixed with 2.0g of quartz sand and placed in a reactor, followed by CO₂/H₂The reaction pressure is gradually increased to the set pressure, and the reaction temperature is gradually increased to the set temperature to start the reaction. The product is subjected to cold trap and then is subjected to normal pressure on-line analysis, and the product is analyzed by a gas chromatograph which is simultaneously provided with a thermal conductivity cell and a hydrogen ion flame detector under the chromatographic conditions of a 5A molecular sieve packed column and a

Filling a capillary column (50 meters), and raising the temperature by a program (the initial temperature is 50 ℃, keeping the temperature for 10 minutes, and then raising the temperature to 200 ℃ at the speed of 5 ℃/min, keeping the temperature for 10 minutes); the product in the cold trap was analyzed offline by another gas chromatograph equipped with a hydrogen ion flame detector, under the chromatographic conditions of HP-1 capillary packed column (50 m), and temperature programmed (initial temperature 50 ℃ for 5 minutes, followed by 5 ℃/min to 250 ℃ for 10 minutes).

CO₂Conversion rate (import CO)₂mole-Outlet CO₂Mole)/inlet CO₂The mole number is × 100 percent

Product selectivity-moles of export product × number of carbon atoms in product molecule/(import CO)₂mole-Outlet CO₂Mole number) × 100%

2. The Pd dispersion degree is calculated by adopting a CO pulse adsorption method. The specific method comprises the following steps: and (4) performing CO pulse adsorption by adopting BEL-CAT-BInsmeasuring. Placing 50mg of catalyst in a quartz tube, and carrying out in-situ reduction on the catalyst by adopting the condition during catalyst reduction; then, the temperature is reduced to room temperature under the atmosphere of He, and pulse adsorption is carried out by using 5% CO/He until the solution is saturated. The dispersion of Pd was calculated by the total number of molecules of CO adsorbed on the catalyst surface, where Pd/CO (molar ratio) was 1: 1. The average particle diameter (D, nm) of Pd can be calculated from the dispersion (D,%) of Pd, and D (nm) is 112/D.

Example 1

(1) 0.482g of palladium nitrate is dissolved in a proper amount of water, the solution is soaked on 2g of cerium dioxide carrier in equal volume, the soaked solution is dried at 120 ℃ overnight after being soaked for 10 hours, and then the solution is roasted at 500 ℃ for 3 hours to obtain Pd/CeO with the Pd content of 10 percent₂A catalyst.

(2) According to the reduction conditions at the time of use of the catalyst, that is: normal pressure and H₂The catalyst is reduced under the atmosphere at the space velocity of 6L/g/h and the temperature of 500 ℃ for 2 h. After the reduction is finished, the catalyst is cooled down, and after the temperature is reduced to normal temperature, 1 percent of O is adopted₂/N₂The catalyst is passivated for 2 h. The catalyst was then characterized by Transmission Electron Microscopy (TEM) and the results are shown in figure 1. The Pd metal particles in the figure were subjected to particle size statistics and the average particle size was 12.4nm, as shown in fig. 2. Meanwhile, the dispersion degree of Pd after reduction was measured by CO pulse adsorption method and was 8.7%, from which the average particle diameter of Pd was calculated to be 12.9nm, similarly to TEM result.

(3) And (3) activity test: the prepared catalyst is evaluated in a fixed bed reactor, and the catalyst is reduced in situ before reaction under the following conditions: at normal pressure and H₂Reducing for 2h at 500 ℃ in the atmosphere, wherein the space velocity is 6L/g/h. After in-situ reduction, the catalytic activity test is carried out, and the reaction conditions are as follows: h₂/CO₂The temperature was 360 ℃, the pressure was 3.0MPa, the space velocity was 2L/g/h, and the results of the activity tests are shown in table 1.

Example 2

(1) 0.482g of palladium nitrate is dissolved in a proper amount of water, the solution is soaked on 2g of cerium dioxide carrier in equal volume, the soaked solution is dried at 120 ℃ overnight after being soaked for 10 hours, and then the dried solution is roasted at 300 ℃ for 3 hours to obtain Pd/CeO with the Pd content of 10 percent₂A catalyst.

(2) The activity test was the same as in example 1. The results of the activity test are shown in Table 1. Meanwhile, under the reduction condition, the dispersion degree of Pd is tested by using a CO pulse adsorption method, the average particle size of Pd is calculated, the dispersion degree of Pd is 10.7 percent, and the average particle size of Pd is 10.5 nm.

Example 3

(1) The catalyst preparation was the same as in example 1.

(2) And (3) activity test: the prepared catalyst is evaluated in a fixed bed reactor, and the catalyst is reduced in situ before reaction under the following conditions: at normal pressure and H₂Reducing for 2h at 400 ℃ in the atmosphere, wherein the space velocity is 6L/g/h. After in-situ reduction, catalytic activity test was performed under the same reaction conditions as in example 1, and the results of the activity test are shown in Table 1. Meanwhile, under the reduction condition, the dispersion degree of Pd is tested by using a CO pulse adsorption method, the average particle size of Pd is calculated, the dispersion degree of Pd is 9.8 percent, and the average particle size of Pd is 11.4 nm.

Example 4

(1) The catalyst preparation was the same as in example 1.

(2) And (3) activity test: the prepared catalyst was evaluated in a fixed bed reactor, and the catalyst was reduced in situ before the reaction, under the same conditions as in example 1. After reduction, the catalytic activity test is carried out, and the reaction conditions are as follows: h₂/CO₂The temperature was 360 ℃, the pressure was 3.0MPa, the space velocity was 2L/g/h, and the results of the activity tests are shown in table 1.

Example 5

(1) The catalyst preparation was the same as in example 1.

(2) And (3) activity test: the prepared catalyst was evaluated in a fixed bed reactor, and the catalyst was reduced in situ before the reaction, under the same conditions as in example 1. After reduction, the catalytic activity test is carried out, and the reaction conditions are as follows: h₂/CO₂The temperature was 300 ℃, the pressure was 3.0MPa, the space velocity was 2L/g/h, and the results of the activity tests are shown in table 1.

Example 6

(1) The catalyst preparation was the same as in example 1.

(2) And (3) activity test: the prepared catalyst was evaluated in a fixed bed reactor, and the catalyst was reduced in situ before the reaction, under the same conditions as in example 1. After reduction, the catalytic activity test is carried out, and the reaction conditions are as follows: h₂/CO₂6.0 deg.C, 360 deg.C, 3.0MPa, and airThe speed is 8L/g/h, and the activity test results are shown in Table 1.

Example 7

(1) 0.228g of palladium nitrate is dissolved in a proper amount of water, the solution is soaked on 2g of cerium dioxide carrier in equal volume, the soaked solution is dried at 120 ℃ overnight after being soaked for 10 hours, and then the solution is roasted at 500 ℃ for 3 hours to obtain Pd/CeO with the Pd content of 5 percent₂A catalyst.

(2) The activity test conditions were the same as in example 1, and the test results are shown in Table 1. The reduced catalyst was also TEM characterized as in example 1. Fig. 3 is a TEM image of the catalyst after reduction, and fig. 4 is a particle size distribution diagram of the Pd particles on the catalyst, showing that the average particle size of the Pd particles on the catalyst is 8.4 nm. Meanwhile, under the reduction condition, the dispersion degree of Pd is tested by using a CO pulse adsorption method, the average particle size of Pd is calculated, the dispersion degree of Pd is 13.0 percent, and the average particle size of Pd is 8.6 nm.

Example 8

(1) 0.766g of palladium nitrate is dissolved in a proper amount of water, the solution is soaked on 2g of cerium dioxide carrier in the same volume, the soaked solution is dried at 120 ℃ overnight after being soaked for 10 hours, and then the solution is roasted at 500 ℃ for 3 hours to obtain Pd/CeO with 15 percent of Pd content₂A catalyst.

(2) The activity test conditions were the same as in example 1, and the test results are shown in Table 1. Meanwhile, under the reduction condition, the dispersion degree of Pd is tested by using a CO pulse adsorption method, the average particle size of Pd is calculated, the dispersion degree of Pd is 6.3 percent, and the average particle size of Pd is 17.8 nm.

Example 9

(1) 0.482g of palladium nitrate is dissolved in a proper amount of water, the solution is soaked on 2g of cerium dioxide carrier in equal volume, the soaked solution is dried at 120 ℃ overnight after being soaked for 10 hours, and then the dried solution is roasted at 200 ℃ for 3 hours to obtain Pd/CeO with the Pd content of 10 percent₂A catalyst.

(2) And (3) activity test: the prepared catalyst is evaluated in a fixed bed reactor, and the catalyst is reduced in situ before reaction under the following conditions: at normal pressure and H₂Reducing for 2h at 200 ℃ in the atmosphere, wherein the space velocity is 6L/g/h. After in-situ reduction, catalytic activity test was performed under the same reaction conditions as in example 1, and the results of the activity test are shown in Table 1. At the same time, the CO pulse is utilized under the reducing conditionThe dispersion degree of Pd is tested by a flushing adsorption method, the average particle size of Pd is calculated, the dispersion degree of Pd is 19.0 percent, and the average particle size of Pd is 5.9 nm.

Example 10

(1) 0.65g of palladium acetylacetonate was added to a mixture of 45mL of 1-octadecene and 50mL of oleylamine and heated to 100 ℃ under nitrogen to form a transparent solution A. 1.3g of morpholine borane was dissolved in 12mL of oleylamine and injected into solution A, then heated to 150 ℃ for 10 min. And cooling the solution to room temperature, adding 50mL of ethanol, and performing ultrasonic separation to obtain the Pd metal nanoparticles. Dispersing the obtained Pd particles in 30mL of n-hexane solution, and carrying out ultrasonic treatment for 10 min; then 2g of the ceria support was dispersed in 30mL of n-hexane solution and sonicated for 30 min. Then mixing the two suspensions, performing ultrasonic treatment for 1h, centrifuging, drying at 80 ℃ overnight, and then roasting at 500 ℃ for 3h to obtain Pd/CeO with the load of 10%₂A catalyst.

(2) The activity test was the same as in example 1. The results of the activity test are shown in Table 1. Then, under the reducing condition, the dispersion degree of Pd is tested by using a CO pulse adsorption method, the average particle size of Pd is calculated, the dispersion degree of Pd is 9.1 percent, and the average particle size of Pd is 12.3 nm.

Table 1 reactivity of different catalysts in the examples

It is understood from examples 1 to 3 and 9 that the calcination temperature of the catalyst greatly affects the activity of the catalyst and the selectivity of methane, and that a lower calcination or reduction temperature can improve the activity of the catalyst within a small range, but is not favorable for reducing the selectivity of methane and separating subsequent products. As can be seen from examples 1, 4, 5 and 6, the reaction conditions such as H were varied₂/CO₂The ratio, reaction temperature, and space velocity of the reaction can all be varied to alter the activity and selectivity of the catalyst and increase H overall₂/CO₂The ratio and the reaction temperature are favorable for improving the reaction activity, and the methane selectivity is not influenced and is basically close to 100 percent. Under appropriate conditions (example 4), CO₂The conversion rate is close toEquilibrium conversion and methane selectivity close to 100%. It is clear from examples 1, 7 and 8 that the particle size of Pd can be varied by varying the amount of Pd supported in the catalyst, thereby affecting the activity and selectivity. When the Pd loading capacity is small, the number of the reaction active centers is small, and the reaction activity is low; meanwhile, the particle size of Pd is small, and the selectivity of methane is low. When the Pd loading capacity is larger, the data of the reaction activity center is increased, and the reaction activity is increased; meanwhile, the particle size of Pd is large, and the selectivity of methane is high. However, when the loading is too large, the atomic utilization of Pd is low and the increase of the catalytic activity is insignificant, although the methane selectivity is always kept at a high level, which is close to 100%, so that the loading of Pd is at an appropriate level. It can be seen from examples 1 and 10 that the catalysts obtained by the two preparation methods have similar performance when the palladium loading and particle size are at the same level.

Comparative example 1

(1) 0.022g of palladium nitrate is dissolved in a proper amount of water, the solution is soaked on 10g of cerium dioxide carrier in equal volume, the soaked solution is dried at 120 ℃ overnight after being soaked for 10 hours, and then the solution is roasted at 500 ℃ for 3 hours to obtain Pd/CeO with 0.1 percent of Pd content₂A catalyst.

(2) The activity test was the same as in example 1, and the results of the activity test are shown in Table 2. Meanwhile, the reduced catalyst was characterized by a transmission electron microscope, and the results are shown in fig. 5. The Pd species are highly dispersed on the support and no Pd particles are visible in the electron micrograph. Meanwhile, under the reduction condition, the dispersion degree of Pd is tested by using a CO pulse adsorption method, the average particle size of Pd is calculated, the dispersion degree of the reduced catalyst is measured to be 90.1%, and the average particle size of Pd is about 1.2 nm.

Comparative example 2

(1) 0.108g of palladium nitrate is dissolved in a proper amount of water, the solution is soaked on 5g of cerium dioxide carrier in equal volume, the soaked solution is dried at 120 ℃ overnight after being soaked for 10 hours, and then the solution is roasted at 500 ℃ for 3 hours to obtain Pd/CeO with the Pd content of 1 percent₂A catalyst.

(2) The activity test was the same as in example 1, and the results of the activity test are shown in Table 2. Meanwhile, under the reduction condition, the dispersion degree of Pd is tested by using a CO pulse adsorption method, the average particle size of Pd is calculated, the dispersion degree of Pd is 33.2 percent, and the average particle size of Pd is 3.4 nm.

TABLE 2 reactivity of the catalysts of the comparative examples

Comparing the results in tables 1 and 2, it can be seen that in the examples, the catalyst has a high Pd loading, a large Pd particle size, and a high methane selectivity close to 100%; on the catalyst described in the comparative example, the Pd loading was lower, the dispersion was better and the methane proportion in the product was very low.

Although the present invention has been described with reference to the preferred embodiments, it should be understood that various changes and modifications can be made therein by those skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. Pd/CeO for preparing methane by carbon dioxide hydrogenation₂The catalyst is characterized in that the active component of the catalyst is metal Pd, the content of the metal Pd accounts for 5-20% of the mass of the catalyst, and the particle size of the active component Pd is 5-30 nm; the carrier is CeO₂The content of the catalyst accounts for 80 to 95 percent of the mass of the catalyst.

2. Pd/CeO for preparing methane by hydrogenating carbon dioxide as set forth in claim 1₂The catalyst is characterized in that the active component of the catalyst is metal Pd, the content of the metal Pd accounts for 5-10% of the mass of the catalyst, and the particle size of the active component Pd is 10-20 nm; the carrier is CeO₂The content of the catalyst accounts for 90 to 95 percent of the mass of the catalyst.

3. Preparation of Pd/CeO for preparing methane by hydrogenation of carbon dioxide as described in claim 1₂A method for preparing a catalyst, characterized in that the method is any one of the following two preparation methods:

the first method comprises the following steps: the dipping method comprises the following steps: dissolving soluble Pd salt in solvent to form solution, and soaking the solution in CeO₂On a carrier, drying after dipping, and then roasting at 300-600 ℃ for 2-10 h to obtain Pd/CeO₂A catalyst;

and the second method comprises the following steps: physical mixing method: firstly preparing Pd or PdO particles, then dispersing the Pd or PdO particles in a solvent, and then adding CeO₂Dispersing the carrier in the same solvent, and finally dispersing the dispersion containing Pd or PdO particles and the CeO₂Mixing and drying the dispersion of the carrier, and then roasting for 2-10 h at 300-600 ℃ to obtain Pd/CeO₂A catalyst.

4. The method of claim 3, wherein the soluble Pd-containing salt in the first preparation method is: any one or more of palladium nitrate, palladium acetylacetonate, palladium chloride, palladium acetate, tetraaminopalladium nitrate, ammonium chloropalladate and palladium hexafluoroacetylacetonate.

5. The method according to claim 3, wherein the conditions for the calcination in the first production method are: calcining at 500 deg.C for 3 h.

6. The method according to claim 3, wherein the method for preparing Pd or PdO particles in the second preparation method is any one of a hydrothermal method, a precipitation method and a liquid-phase reduction method.

7. The method as claimed in claim 3, wherein the conditions of the calcination in the second preparation method are: calcining at 400 deg.C for 3 h.

8. Pd/CeO as defined in claim 1 or 2₂The catalyst is applied to catalyzing carbon dioxide methanation reaction.

9. Use according to claim 8, wherein the Pd/CeO is used in catalytic methanation of carbon dioxide₂The catalyst needs to be pre-reduced before catalyzing the methanation reaction of the carbon dioxide, and the reducing atmosphere is H₂Or H₂/CO₂The reduction temperature of the mixed gas is 400-700 ℃, and the reduction space velocity is 2-20L/g_catThe reduction pressure is 0.1-1 MPa.

10. Use according to claim 8, wherein the Pd/CeO is used in catalytic methanation of carbon dioxide₂The reaction conditions of the catalyst in catalyzing the methanation of the carbon dioxide are as follows: CO 2₂/H₂1: 1-10, and the airspeed of 1-20L/g_catThe reaction temperature is 300-500 ℃, and the reaction pressure is 0.1-5 MPa.