High-activity catalyst for direct hydrogenation methanation of CO2 as well as forming preparation method and application of high-activity catalyst

Abstract

The invention discloses a CO2 direct hydrogenation methanation high-activity catalyst and a forming preparation method and application thereof.The preparation method of the catalyst comprises the steps that an additive is added into NiCeZr catalyst powder, the additive comprises binder urea and a release agent, and the mixture is transferred into a mortar to be ground and mixed to be uniform; the grinding mixture is prepared from the following three components in percentage by weight: 5-20wt% of binder urea, 1-2wt% of release agent and the balance of NiCeZr catalyst, and carrying out tabletting molding on the ground mixture by using a tabletting mold, demolding to obtain catalyst particles, adding the catalyst particles into a muffle furnace, and calcining to remove the additive and pore-forming the catalyst at the same time to complete the preparation. The urea is added into the catalyst powder, so that the mechanical strength of the formed NiCeZr catalyst can be remarkably improved, meanwhile, after roasting, the mechanical strength of the reacted catalyst particles is still kept high, and the catalytic performance of the catalyst is kept stable. The catalyst disclosed by the invention has very high catalytic activity and stability for preparing methane by direct hydrogenation of CO2.

Description

Technical Field

[0001] The present invention belongs to the technical field of methanation catalysts and particularly relates to a CO 2 A high-activity catalyst for direct hydrogenation and methanation, and a molding preparation method and application thereof. Background Art

[0002] CO 2 Hydrogenation methanation is the process of using green hydrogen produced by electrolyzing water with green energy to react with carbon dioxide in flue gas to produce methane. This can not only achieve the dual carbon goals by reducing carbon emissions, but also reduce CO 2 The utilization of this abundant C1 resource can even alleviate the energy shortage. At the same time, methane is easier to transport and store than hydrogen, and the use of water electrolysis to produce green hydrogen also provides a new path for the storage and utilization of impure electricity.

[0003] At present, important progress has been made in methanation catalysts, such as:

[0004] 1) Chinese patent CN116899568A discloses a method for preparing inverse Ni / CeO by gel method 2 Catalyst, the catalyst includes a carrier CeO 2 and the active component Ni loaded on the carrier, the loading amount of the active component Ni is 50-94.9%, and the catalyst is CO at 300℃ 2 The highest hydrogenation activity, CO 2 The conversion rate is as high as 93.7%. However, since the methanation reaction is a highly exothermic reaction, the high activation condition of 300°C makes it easy for the endothermic reverse water gas reaction to occur, resulting in reduced selectivity. The high reaction temperature allows the catalyst to have a lower temperature rise range in the industrial production process, and the large amount of heat released during the methanation process causes the temperature to rise further. According to thermodynamic limitations, high temperature will inhibit the methanation reaction and will result in greater operating costs during the production process.

[0005] 2) The research group of this application has also conducted a series of studies on methanation catalysts. For details, please refer to the literature “EngineeringMOx / Niinverse catalysts for low-temperature CO 2 The study found that the CeZr / Ni reverse catalyst prepared by co-precipitation method can activate high methane yields in CO 2It has excellent catalytic activity in the methanation reaction, and has a lower activation temperature and a high conversion rate (the carbon dioxide conversion rate at 200°C is more than 90%) compared to conventional Ni-based catalysts. However, in the industrial production of carbon dioxide hydrogenation and methanation, the powder catalyst cannot meet the production conditions. The loading and production of the powder catalyst will cause excessive pressure drop, block the reaction pipeline, and even be unfavorable for heat release. Therefore, it is of great significance to study the industrial molding of high-performance NiCeZr powder catalysts.

[0006] The common methods of methanation catalyst molding are extrusion molding and compression molding, such as:

[0007] 1) The NiMgAl catalyst with Ni as the active component disclosed in patent CN105013495B adopts extrusion molding. Nickel salt is dissolved in water, acid is added to make a nickel salt solution, the obtained nickel salt solution is dispersed in aluminum sol, and mixed with auxiliary agent lanthanum oxide to make a mixed sol to form a composite surface modified adhesive; the composite surface modified adhesive is kneaded with carrier powder aluminum oxide, magnesium oxide and starch in a kneader, and after the material mass is formed, the particles are extruded in an extruder, dried and roasted to obtain a methanation catalyst with magnesium aluminum composite oxide as the carrier.

[0008] 2) Patent CN105709794B discloses a special-shaped methanation catalyst and its forming process, which is to mix nickel-based methanation catalyst powder with a particle size of less than 0.15 mm with graphite and place it in a wet mixer, and continuously mix HNO with a mass concentration of 3% while the material powder is rotating. 3 The aqueous solution is sprayed onto the surface of the mixed powder in a mist form, and after all the liquid is sprayed, wet mixing is continued for 60 minutes; the nickel-based synthesis gas methanation catalyst powder is pressed or extruded into a porous columnar particle catalyst with a regular and symmetrical geometric shape.

[0009] Literature shows that the extrusion molding process is complicated, there are many types of molding additives, and the mechanical strength of the catalyst finally formed by extrusion is also poor. Secondly, the cumbersome and complicated molding process also consumes a lot of manpower and material resources during industrial production. Some additives added in the molding process or other auxiliary drugs in the molding process may be toxic, polluting, or even corrosive to the equipment. Compared with extrusion molding, compression molding process is relatively simple, and the strength of the catalyst particles formed is also higher than that of extrusion molding.

[0010] However, in the existing compression molding technology for methanation catalysts, one type is to first mix the materials by wet method and then perform compression molding after a series of operations, such as the patent CN 105080616A discloses that the binder triethylhexyl phosphate, sodium lauryl sulfate, methyl amyl alcohol, cellulose derivatives, polyacrylamide, gum, ethylene glycol, polyethylene glycol, fatty acid polyethylene glycol ester, glycerol, one or two of which are added to the methanation catalyst material mixture and mixed evenly by wet method, then the mixed material is granulated and dried, and finally the release agent graphite is added to mix evenly to form, however, this type of wet mixing molding scheme can make the materials more evenly mixed, but because it has gone through two more steps of wetting and drying, it also makes the process more cumbersome. Another type of molding scheme is to directly dry mix the materials with the binder and the release agent and then perform molding, such as the patent CN105727920A discloses a tablet molding with one or more of cellulose, methyl cellulose, nitrocellulose, sesbania powder, and cellulose acetate as a binder. Patent CN 112427039 A discloses that lubricants, molding aids, and structural aids are added to the prepared catalyst powder, and then ball milled and sieved. Powders larger than 250 mesh are granulated, sieved, tableted, cured, and calcined to obtain a molded catalyst. Although this type of molding reduces the steps required for molding, it still requires multiple steps. At the same time, a certain proportion of binder, pore-forming agent, and release agent need to be added during the dry molding process, so that the molded catalyst particles retain higher catalytic activity while also having higher mechanical strength and smoothness of pressing. Therefore, the selection of binder and release agent is crucial.

[0011] The applicant found that the CeZr / Ni reverse catalyst prepared by co-precipitation and the 80wt% Ni / CeZr / Ni catalyst with high Ni loading prepared by mechanical grinding method can be used to synthesize the CeZr / Ni reverse catalyst. 1 Zr 1 Catalysts, when using traditional inorganic binders as molding aids, although the loss of mechanical strength before and after the reaction is not large, the inorganic components in the host may damage the catalytic performance of the catalyst, and since the inorganic additives cannot be removed by calcination, this leads to a reduction in the content of effective ingredients in the catalyst after molding; and if conventional cellulose, methyl cellulose, cellulose nitrate, field sesbania powder and other organic binders are used for molding, after high-temperature calcination to remove the organic components, the mechanical strength of the catalyst particles is greatly reduced, and it is difficult to ensure the mechanical strength of the catalyst particles. At the same time, the mechanical strength will be further reduced after the reaction.

[0012] Therefore, in order to solve the problems of complicated operation steps and unsatisfactory molding effect of conventional binders in the existing methanation catalyst compression molding, we developed a CO 2The molding technology of direct hydrogenation methanation high-activity catalyst uses urea as a binder and grinds and mixes the materials before one-step molding. It has excellent molding effect and is more suitable for industrial molding production. Summary of the invention

[0013] In view of the technical problems that the powder catalyst in the prior art is not conducive to industrial application, the methanation catalyst molding has complicated operation steps, and the conventional binder molding effect is not ideal, the purpose of the present invention is to provide a CO 2 Direct hydrogenation methanation high-activity catalyst and its molding preparation method and application. The present invention adopts a new type of binder-urea. Compared with conventional organic molding aids, adding urea to the catalyst powder can significantly improve the mechanical strength of the NiCeZr catalyst after molding. At the same time, after roasting and reaction, the mechanical strength of the catalyst particles still maintains a large mechanical strength, and the catalytic performance of the catalyst remains stable. Secondly, this technology adopts a one-step compression molding method with the assistance of urea, which reduces the molding process without reducing the strength after molding, which makes it more conducive to industrial molding production.

[0014] The technical solution adopted by the present invention is as follows:

[0015] A CO 2 The molding preparation method of the direct hydrogenation methanation high-activity catalyst comprises the following steps:

[0016] S1 grinding and mixing: adding additives to the NiCeZr catalyst powder, the additives including a binder urea and a release agent, and transferring the mixture to a mortar for grinding and mixing, wherein the ground mixture consists of the following three components in terms of weight percentage: 5-20wt% of the binder urea, 1-2wt% of the release agent, and the balance is the NiCeZr catalyst;

[0017] S2 one-step compression molding: the mixture ground in step S1 is compressed into tablets using a tableting mold, and the mold is removed to obtain catalyst particles;

[0018] S3 Calcination and pore formation: The catalyst particles obtained in step S2 are added into a muffle furnace, and the catalyst is pore-formed while removing the additives by calcination, and the preparation is completed.

[0019] Furthermore, in step S1, the grinding mixture is composed of the following three components in terms of weight percentage: 5-10wt% of urea as a binder, 1-2wt% of a release agent, and the balance is a NiCeZr catalyst.

[0020] Furthermore, the release agent is magnesium stearate.

[0021] Furthermore, the calcination temperature in step S3 is carried out in two steps: the first step is calcination at 100-150°C for 1-3h, and the second step is calcination at 300-400°C for 1-3h.

[0022] The present invention also discloses that the catalyst is used to catalyze CO 2 Application in direct hydrogenation to prepare methane, the application method comprising the following steps:

[0023] 1) loading the catalyst into a fixed bed reactor and reducing it at 400-500° C. for 1-4 h under the condition of introducing reducing gas;

[0024] 2) Then the gas introduced into the fixed bed reactor is switched to the reaction gas, and the CO in the reaction gas 2 The volume fraction is 10-25%, H 2 The volume fraction is 60-80%, and the rest is N 2 , catalytic CO at 160-240℃ 2 Direct hydrogenation reaction to produce methane.

[0025] Furthermore, the reducing gas in step 1) is H 2 The volume fraction of H is 5-15% 2 -N 2 Mixed gas, preferably H 2 The volume fraction of H is 10%. 2 -N 2 Mixed gas.

[0026] Furthermore, in step 2), CO 2 The volume fraction is 15-20%, H 2 The volume fraction is 70-75%, and the rest is N 2 .

[0027] Furthermore, in step 2), the reaction temperature is 180-200° C., and the reaction space velocity is 1000-10000 mL / (g catalyst·h), preferably 4000-8000 mL / (g catalyst·h).

[0028] Compared with the prior art, the beneficial effects achieved by the present application are: the urea used in the molding process of the present invention is used as a binder, which makes the raw material cost low in the molding process, and the molding process only requires grinding and mixing before direct molding, which reduces the cost. The catalyst has an excellent catalytic activity of 90% conversion rate at 180°C, and has higher economic benefits than the 300°C methanation catalyst currently used in the market. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1This is a photo of the calcined catalyst of Example 3.

[0030] Figure 2 These are the mechanical strength test results of the molded catalysts prepared by using different binders in Example 3 and Comparative Examples 1-4 after "calcination" and "reaction".

[0031] Figure 3 These are the mechanical strength test results of the shaped catalysts prepared in Examples 1-5 using different doping amounts of binders in each state of "before calcination", "after calcination" and "after reaction".

[0032] Figure 4 The catalyst activity changes after the catalyst is calcined and then subjected to cyclic heating and cooling at 180°C, 25°C, and 400°C.

[0033] Figure 5 The catalyst of Example 3 was calcined at 500°C for 1 h. 2 Results of conversion rate changes over time.

[0034] Figure 6 These are the catalytic activity results of the catalyst in Example 3 at different catalytic temperatures in the "uncalcined" and "calcined" states after molding.

[0035] Figure 7 These are the catalytic activity results of the molded catalysts prepared at different urea doping amounts in Examples 1-5 at different catalytic temperatures after calcination.

[0036] Figure 8 These are the catalytic activity results of the formed catalyst in Example 3 at different reaction space velocities after calcination. DETAILED DESCRIPTION

[0037] Blank Example 1: Preparation of NiCeZr catalyst, including the following steps

[0038] 1) Use an electronic balance to weigh 62.291 g of nickel nitrate hexahydrate, 5.881 g of zirconium nitrate pentahydrate, 5.815 g of nitric acid hexahydrate, and 33.836 g of oxalic acid dihydrate into a 200 ml ball mill, add zirconium beads as ball milling media, and prepare another 200 ml ball mill to add the same mass of the same substances.

[0039] 2) Place two 200ml ball mills in step 1) symmetrically on the planetary ball mill and fix them tightly. Set the ball milling parameters to 400r / min, 180min, and 30min / time. That is, the planetary ball mill stops running for 5 minutes after each 30-minute ball milling to prevent the planetary ball mill from overheating due to continuous operation. After the ball milling is completed, a blue paste catalyst precursor is obtained.

[0040] 3) The blue paste catalyst precursor obtained in step 2) is placed in a blast oven and dried at 80°C for 5h to obtain a catalyst precursor, the dried catalyst precursor is transferred into a 100ml ceramic crucible, and the crucible is placed in a muffle furnace and calcined at 400°C for 3h to prepare the NiCeZr catalyst.

[0041] The catalyst powders used in preparing the molded catalysts in the examples of the present invention are all NiCeZr catalysts prepared in Blank Example 1.

[0042] Example 1: Preparation of a shaped catalyst doped with 0 wt% urea and 1 wt% magnesium stearate

[0043] Weigh 50.0g of catalyst powder and 0.0g of urea into a ceramic mortar and grind for 5min to mix evenly, add 0.5g of magnesium stearate to the mixture and grind for 1min to mix evenly and transfer to a sample bag. Put the prepared catalyst powder into the feed hopper of an automatic tablet press equipped with a 4.0mm particle size mold, adjust the powder input to 0.7g, obtain a catalyst tablet thickness of 3.0mm through the molding pressure, and start the tablet press for tableting.

[0044] Example 2: Preparation of a shaped catalyst doped with 5 wt% urea and 1 wt% magnesium stearate

[0045] Weigh 47.5g of catalyst powder and 2.5g of urea into a ceramic mortar and grind for 5min to mix evenly, add 0.5g of magnesium stearate to the mixture and grind for 1min to mix evenly and transfer to a sample bag. Put the prepared catalyst powder into the feed hopper of an automatic tablet press equipped with a 4.0mm particle size mold, adjust the powder input to 0.7g, obtain a catalyst tablet thickness of 3.0mm through the molding pressure, and start the tablet press for tableting.

[0046] Example 3: Preparation of a shaped catalyst doped with 10 wt% urea and 1 wt% magnesium stearate

[0047] Weigh 45.0g of catalyst powder and 5.0g of urea into a ceramic mortar and grind for 5min to mix evenly, add 0.5g of magnesium stearate to the mixture and grind for 1min to mix evenly and transfer to a sample bag. Put the prepared catalyst powder into the feed hopper of an automatic tablet press equipped with a 4.0mm particle size mold, adjust the powder input to 0.7g, obtain a catalyst tablet thickness of 3.0mm through the molding pressure, and start the tablet press for tableting.

[0048] Example 3 The shaped catalyst was calcined in a muffle furnace at 350°C for 2 hours and then cooled to room temperature. The product photo is shown in Figure 1 It can be seen that the catalyst particles have a very high regularity, and the catalyst tablets are 3.0 mm thick and 4 mm in diameter.

[0049] Example 4: Preparation of a shaped catalyst doped with 15 wt% urea and 1 wt% magnesium stearate

[0050] Weigh 42.5g of catalyst powder and 7.5g of urea into a ceramic mortar and grind for 5min to mix evenly, add 0.5g of magnesium stearate to the mixture and grind for 1min to mix evenly and transfer to a sample bag. Put the prepared catalyst powder into the feed hopper of an automatic tablet press equipped with a 4.0mm particle size mold, adjust the powder input to 0.7g, obtain a catalyst tablet thickness of 3.0mm through the molding pressure, and start the tablet press for tableting.

[0051] Example 5: Preparation of a shaped catalyst doped with 20 wt% urea and 1 wt% magnesium stearate

[0052] Weigh 40.0g of catalyst powder and 10.0g of urea into a ceramic mortar and grind for 5min to mix evenly, add 0.5g of magnesium stearate to the mixture and grind for 1min to mix evenly and transfer to a sample bag. Put the prepared catalyst powder into the feed hopper of an automatic tablet press equipped with a 4.0mm particle size mold, adjust the powder input to 0.7g, obtain a catalyst tablet thickness of 3.0mm through the molding pressure, and start the tablet press for tableting.

[0053] Comparative Example 1: Preparation of a 10 wt% sucrose-doped catalyst

[0054] Weigh 45.0g of catalyst powder and 5.0g of sucrose into a ceramic mortar and grind for 5 minutes to mix evenly, add 0.5g of magnesium stearate to the mixture and grind for 1 minute to mix evenly and transfer to a sample bag. Put the prepared catalyst powder into the feed hopper of an automatic tablet press equipped with a 4.0mm particle size mold, adjust the powder input to 0.7g, obtain a catalyst tablet thickness of 3.0mm through the molding pressure, and start the tablet press for tableting.

[0055] Comparative Example 2: Preparation of a 10 wt% soluble starch-doped catalyst

[0056] Weigh 45.0g of catalyst powder and 5.0g of soluble starch in a ceramic mortar and grind for 5min to mix evenly, add 0.5g of magnesium stearate to the mixture and grind for 1min to mix evenly and transfer to a sample bag. Put the prepared catalyst powder into the feed hopper of an automatic tablet press equipped with a 4.0mm particle size mold, adjust the powder input to 0.7g, obtain a catalyst tablet thickness of 3.0mm through the molding pressure, and start the tablet press for tableting.

[0057] Comparative Example 3: Preparation of a shaped catalyst doped with 10 wt% carboxymethyl cellulose

[0058] Weigh 45.0g of catalyst powder and 5.0g of carboxymethyl cellulose in a ceramic mortar and grind for 5 minutes to mix evenly, add 0.5g of magnesium stearate to the mixture and grind for 1 minute to mix evenly and transfer to a sample bag. Put the prepared catalyst powder into the feed hopper of an automatic tablet press equipped with a 4.0mm particle size mold, adjust the powder input to 0.7g, and obtain a catalyst tablet thickness of 3.0mm through the molding pressure, and start the tablet press for tableting.

[0059] Comparative Example 4: Preparation of a 10 wt% cellulose powder-doped catalyst

[0060] Weigh 45.0g of catalyst powder and 5.0g of cellulose powder into a ceramic mortar and grind for 5 minutes to mix evenly. Add 0.5g of magnesium stearate to the mixture and grind for 1 minute to mix evenly and transfer to a sample bag. Put the prepared catalyst powder into the feed hopper of an automatic tablet press equipped with a 4.0mm particle size mold, adjust the powder input to 0.7g, and obtain a catalyst tablet thickness of 3.0mm through the molding pressure, and start the tablet press for tableting.

[0061] Catalyst mechanical strength test process: Take the freshly pressed catalyst particles, the calcined catalyst particles, and the reacted catalyst particles and place them on the loading platform of the HB-KQD particle strength tester respectively, and slowly turn the handle to test the pressure required for the catalyst to break radially.

[0062] Catalyst before calcination: refers to the catalyst that has not undergone calcination, reduction, or reaction after being molded.

[0063] Calcined catalyst: refers to the catalyst that is formed by compression molding and then calcined in a muffle furnace at 350°C for 2 hours.

[0064] Post-reaction data: refers to the catalyst after the "calcined catalyst" is loaded into a fixed bed and has undergone a reduction process and a catalytic reaction process.

[0065] After the catalyst formed by compression molding is calcined at 350°C in a muffle furnace for 2 hours, its mechanical strength will change once, and it will undergo catalyst reduction activation and catalyst reaction, which will further affect the mechanical strength of the catalyst.

[0066] Application Example 1:

[0067] The process of evaluating the activity of the catalyst includes the following steps:

[0068] 1) Heating reduction: 1.0 g of the calcined catalyst particles were weighed and loaded into the lined quartz tube of the fixed bed reactor, and then the lined quartz tube was fixed in the fixed bed, and reduced at 450 ° C for 3 h under the condition of passing 50 ml / min of reducing gas, the reducing gas was H 2 The volume fraction of H is 10%. 2 -N 2 Mixed gas.

[0069] 2) Catalytic reaction: The catalyst is then heated to the reaction temperature, and the gas introduced into the fixed bed reactor is switched to the reaction gas, which has a volume ratio of CO 2 / H 2 / N 2 = 18 / 72 / 10 mixed gas, the mixed gas flow rate is 100ml / min, the catalytic reaction space velocity is 6000mL / (g catalyst·h), and the catalytic CO 2 Direct hydrogenation reaction to produce methane.

[0070] The "post-reaction" catalyst used for mechanical strength evaluation involves the following reduction process and catalytic reaction process: activity evaluation is performed according to the method steps of steps 1)-2) of Application Example 1, wherein the temperature of the catalytic reaction is heated according to the following program, starting from 160°C and uniformly heated to 240°C within 24 hours, then the reaction is stopped, and the catalyst is cooled to room temperature, which is recorded as the "post-reaction" catalyst.

[0071] The mechanical strength test results of the molded catalysts prepared by different binders in Example 3 and Comparative Examples 1-4 after "calcination" and "reaction" are summarized in Figure 2 The mechanical strength test results of the shaped catalysts prepared by using different doping amounts of binders in Examples 1-5, i.e. the catalysts before calcination, were respectively subjected to mechanical strength tests in various states of "after calcination" and "after reaction" and are summarized in Figure 3 middle.

[0072] In addition, in order to demonstrate the catalytic activity and stability of the catalyst of Example 3, its catalytic performance was further evaluated:

[0073] Experiment ①: The catalyst formed in Example 3 was first calcined in a muffle furnace at 350°C for 2h, then heated and reduced according to step 1) of Application Example 1, and then the catalytic performance was evaluated according to step 2) of Application Example 1. The catalytic reaction temperature was 180°C, 25°C, 400°C under cyclic heating and cooling. 2 The results of the change of conversion rate over time are shown in Figure 4 In. From Figure 4 It can be seen that the catalyst has high catalytic activity and stability.

[0074] Experiment ②: The catalyst formed in Example 3 was first calcined in a muffle furnace at 350°C for 2h, then heated and reduced according to step 1) of Application Example 1, and then the catalytic performance was evaluated according to step 2) of Application Example 1. The catalytic reaction temperature was 500°C for 1 hour. 2 The results of the change of conversion rate over time are shown in Figure 5 In. From Figure 5 It can be seen that the catalyst also exhibits high stability at high temperatures.

[0075] Experiment ③: The catalyst of Example 3 after molding is recorded as the "uncalcined" catalyst, the catalyst of Example 3 after molding is calcined in a muffle furnace at 350°C for 2h and recorded as the "calcined" catalyst, the catalyst of Example 3 after molding in the "uncalcined" and "calcined" states are respectively evaluated for activity according to the method steps of steps 1)-2) of Example 1, and the catalytic reaction temperatures are 160°C, 180°C, 200°C, 220°C and 240°C, respectively. The catalytic reaction results are shown in Figure 6 .

[0076] The shaped catalysts prepared under different urea doping amounts in Examples 1-5 were first calcined in a muffle furnace at 350°C for 2h, and then the activity was evaluated according to the method steps of steps 1)-2) of Example 1. The catalytic reaction temperatures were 160°C, 180°C, 200°C, 220°C and 240°C, respectively. The catalytic reaction results are shown in Table 1. Figure 7 .

[0077] according to Figure 3 as well as Figure 7 The experimental results show that the catalyst activity will be slightly affected as the urea content increases. Since the binder will be burned during the calcination process, excessive binder will reduce the strength of the formed catalyst particles. Therefore, the mechanical strength of the formed catalyst should be taken into account while considering the activity. Overall, the catalyst has the best performance when the urea doping content is 10%.

[0078] Application Example 2:

[0079] After the formed catalyst was calcined in a muffle furnace at 350°C for 2h, the activity was evaluated according to the method steps of steps 1)-2) of Example 1, except that the flow rate of the mixed gas was changed to 25-666.6mlmin, so that the catalytic reaction space velocity was 1500-40000mL / (g catalyst·h)", the catalytic reaction temperature was set at 180°C, and the other conditions remained unchanged. 2 The relationship between conversion rate and catalytic reaction space velocity is shown in Figure 8 .

Claims

1. A method for preparing a high-activity catalyst for direct hydrogenation and methanation of CO2, characterized in that The following steps are involved: S1 grinding and mixing: adding additives to the NiCeZr catalyst powder, the additives including a binder urea and a release agent, and transferring the mixture to a mortar for grinding and mixing, wherein the ground mixture consists of the following three components in terms of weight percentage: 5-20wt% of the binder urea, 1-2wt% of the release agent, and the balance is the NiCeZr catalyst; S2 one-step compression molding: the mixture ground in step S1 is compressed into tablets using a tableting mold, and the mold is removed to obtain catalyst particles; S3 Calcination and pore formation: The catalyst particles obtained in step S2 are added into a muffle furnace, and the catalyst is pore-formed while removing the additives by calcination, and the preparation is completed.

2. The method for preparing a high-activity catalyst for direct CO2 hydrogenation and methanation as claimed in claim 1, characterized in that In step S1, the grinding mixture is composed of the following three components in terms of weight percentage: 5-10wt% of urea as a binder, 1-2wt% of a release agent, and the balance is a NiCeZr catalyst.

3. The method for preparing a high-activity catalyst for direct CO2 hydrogenation and methanation as claimed in claim 1, characterized in that The release agent is magnesium stearate.

4. The method for preparing a high-activity catalyst for direct CO2 hydrogenation and methanation as claimed in claim 1, characterized in that The calcination temperature in step S3 is carried out in two steps: the first step is calcination at 100-150° C. for 1-3 h, and the second step is calcination at 300-400° C. for 1-3 h.

5. A high-activity catalyst for direct hydrogenation and methanation of CO2 prepared by the method according to any one of claims 1 to 4.

6. Use of the catalyst as claimed in claim 5 in the catalytic direct hydrogenation of CO2 to produce methane.

7. The use according to claim 6, characterized in that The application method comprises the following steps: 1) The catalyst is loaded into a fixed bed reactor and reduced at 400-500° C. for 1-4 hours under the condition of introducing reducing gas; 2) Then the gas introduced into the fixed bed reactor is switched to a reaction gas, in which the volume fraction of CO2 is 10-25%, the volume fraction of H2 is 60-80%, and the rest is N2, and the reaction of catalytic direct hydrogenation of CO2 to produce methane is carried out at 160-240°C.

8. The use according to claim 7, characterized in that The reducing gas in step 1) is a H2-N2 mixed gas with a H2 volume fraction of 5-15%, preferably a H2-N2 mixed gas with a H2 volume fraction of 10%.

9. The use according to claim 7, characterized in that In step 2), the volume fraction of CO2 in the reaction gas is 15-20%, the volume fraction of H2 is 70-75%, and the rest is N2.

10. The use according to claim 7, characterized in that The reaction temperature in step 2) is 180-200°C.

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