Method for preparing carbon dioxide hydrogenation methanation catalyst by recycling aluminum-based waste catalyst recovery carrier

Abstract

The invention discloses a method for preparing a carbon dioxide hydrogenation methanation catalyst by recycling an aluminum-based waste catalyst recovery carrier. The method comprises the following steps: (1) mixing and roasting the aluminum-based waste catalyst and sodium hydroxide to obtain a sodium salt roasting product; (2) a weakly alkaline solution is added for leaching treatment, and a sodium metaaluminate leaching solution is obtained; (3) dropwise adding into an acidic solution, adjusting the pH value to be alkaline, aging, separating and drying to obtain an aluminum oxide precursor; (4) roasting the aluminum oxide precursor to obtain mesoporous aluminum oxide; (5) adding mesoporous alumina into a metal salt solution, sequentially carrying out ultrasonic treatment and dipping treatment, and drying and roasting the catalyst precursor; the metal salt solution contains first metal Ni; and (6) heating the catalyst precursor under a hydrogen gas flow for reduction to obtain the carbon dioxide hydrogenation methanation catalyst. The method realizes efficient recovery of the aluminum-based waste catalyst, the process is green and environment-friendly, the recovery efficiency is high, and the catalytic performance of the recovered product is good.

Description

Technical Field

[0001] The invention relates to the technical field of aluminum-based waste catalyst regeneration, and in particular to a method for preparing a carbon dioxide hydrogenation methanation catalyst by recycling a carrier of an aluminum-based waste catalyst. Background Art

[0002] Aluminum-based catalysts occupy a vital position in the petrochemical industry. They are indispensable catalytic materials in the petrochemical production process and are widely used in many key links such as catalytic cracking, hydrocracking, polymerization reaction and isomerization reaction. The high thermal stability, mechanical strength and unique catalytic properties of aluminum-based catalysts make them a key factor in improving petrochemical production efficiency and product quality. In addition, the application of aluminum-based catalysts in the field of environmental protection is also becoming more and more extensive. For example, in the process of waste gas treatment and sewage treatment, it can effectively reduce pollutant emissions and significantly improve environmental quality. Therefore, aluminum-based catalysts are not only an important driving force for promoting technological progress in the petrochemical industry, but also an indispensable key material for promoting green chemical industry and sustainable development. The recovery of aluminum-based waste catalysts has important environmental significance and resource utilization value. In addition to active metals, the most critical component of aluminum-based catalysts is Al2O3 as a carrier with the highest content. Recovering aluminum from aluminum-based waste catalysts is not only technically feasible, but also has high economic value. In addition, the catalyst will adsorb harmful substances such as arsenic, sulfur, chlorine, and carbonyl nickel during use. If these waste catalysts are not properly handled, they will cause serious pollution to the environment. Therefore, the recycling of aluminum-based waste catalysts can not only reduce environmental pollution, but also effectively alleviate the current situation of resource shortage, and has significant economic benefits and environmental protection significance.

[0003] Carbon dioxide hydrogenation methanation catalysts are of great significance in the field of carbon fixation. First of all, this technology provides a way to convert greenhouse gas carbon dioxide into valuable energy products, which plays a positive role in mitigating global climate change. Under the action of the catalyst, CO2 reacts with hydrogen to produce methane, which not only effectively reduces CO2 emissions, but also produces a clean energy source. The research progress of CO2 methanation catalysts shows that by optimizing the structure and composition of the catalyst, low-temperature and efficient conversion of CO2 can be achieved. This not only improves the utilization rate of CO2, but also significantly reduces energy consumption, which has important practical significance. In addition, this technology also helps to promote the development of carbon capture, utilization and storage (CCUS) technology, and provides technical support for achieving carbon neutrality goals. Therefore, carbon dioxide hydrogenation methanation catalysts play a vital role in carbon fixation and energy conversion, and have a far-reaching impact on promoting environmental protection and achieving sustainable energy development.

[0004] At present, the research on recycling and reuse of aluminum-based catalysts is mainly focused on the recovery of precious metals, and the chemicals used in the recycling process, such as aqua regia, are highly corrosive, and the treatment of leachate and secondary pollution are not considered. Although Al2O3 is a commonly used carrier for carbon dioxide hydrogenation and methanation catalysts, the specific surface area and pore size distribution of Al2O3 carriers prepared by different methods are different, and the dispersion and stability of active metals on the carrier surface are also different. The catalytic activity exhibited by them for carbon dioxide hydrogenation and methanation is also different. How to recycle and reuse aluminum-based catalysts to prepare carbon dioxide hydrogenation and methanation catalysts with high catalytic activity is still a technical problem that needs to be solved urgently. Summary of the invention

[0005] Based on the above content, in view of the problems existing in the existing process, such as incomplete metal resource recovery, strong corrosiveness of waste acid in the recovery process, large usage amount and failure to make high-value utilization of the recovered products, the present invention provides a method for preparing a carbon dioxide hydrogenation methanation catalyst by recycling a carrier of an aluminum-based waste catalyst, recovering the aluminum-based waste catalyst, preparing a high-purity carrier mesoporous alumina material through the intermediate product sodium metaaluminate, and preparing a regenerated carbon dioxide hydrogenation methanation catalyst with this, and greatly reducing the usage of strong acid in the whole process. On the one hand, the process of the present invention realizes the green and efficient leaching of metallic aluminum, and on the other hand, the carbon fixation catalyst prepared in the present invention has good catalytic performance, realizing the resource utilization of the recovered product. The present invention has the advantages of simple process, strong operability, cost saving and green environmental protection.

[0006] In a first aspect, the present invention provides a method for recovering a carrier of an aluminum-based waste catalyst and reusing it to prepare a carbon dioxide hydrogenation methanation catalyst, comprising the following steps: (1) mixing the aluminum-based waste catalyst with sodium hydroxide and calcining the mixture to obtain a sodium-calcined product; (2) adding a weak alkaline solution to the sodium-treated roasted product for leaching to obtain a sodium aluminate leaching solution; (3) adding the sodium aluminate leaching solution dropwise into an acidic solution, adjusting the pH value to alkaline, and obtaining an alumina precursor through aging, separation and drying; (4) calcining the alumina precursor to obtain mesoporous alumina; (5) adding the mesoporous alumina into a metal salt solution, sequentially performing ultrasonic treatment and impregnation treatment, and then drying and calcining to obtain a catalyst precursor; the metal in the metal salt solution comprises a first metal Ni; (6) The catalyst precursor is heated under a hydrogen gas flow for reduction to obtain the carbon dioxide hydrogenation and methanation catalyst.

[0007] In the above-mentioned method for recycling the carrier of aluminum-based waste catalyst and reusing it to prepare carbon dioxide hydrogenation methanation catalyst, further, the mass percentage of aluminum oxide in the aluminum-based waste catalyst is ≥98%; further, the aluminum-based waste catalyst is Fe-doped Pt-Sn / Al2O3 waste catalyst, which contains aluminum oxide, platinum dioxide, iron oxide and tin oxide; as an example, the aluminum-based waste catalyst is Fe-doped Pt-Sn / Al2O3 waste catalyst used in light oil catalytic reforming process, wherein the mass percentage of aluminum oxide is 98%, the mass percentage of active ingredient platinum dioxide is 0.35%, the mass percentage of iron oxide is 0.19%, and the mass percentage of tin oxide is 0.18%. In the present invention, after the aluminum-based waste catalyst is sodium-treated, roasted and leached, the aluminum element is converted into easily soluble sodium aluminate and all exists in the leachate, while other metal elements are basically left in the insoluble leaching residue.

[0008] In the above-mentioned method for recovering the carrier of aluminum-based waste catalyst and reusing it to prepare carbon dioxide hydrogenation methanation catalyst, the method further comprises before step (1): roasting the aluminum-based waste catalyst at 500°C for 2h to remove carbon and then ball milling to obtain waste catalyst powder. This pretreatment can remove residual oil and coke on the surface of the waste catalyst. The roasting is specifically carried out in a muffle furnace.

[0009] In the above-mentioned method for recovering the carrier of the aluminum-based waste catalyst and reusing it to prepare the carbon dioxide hydrogenation methanation catalyst, further, in step (1), the mass ratio of the aluminum-based waste catalyst to sodium hydroxide is 1: (0.8-1.5), such as 1:1.2, the roasting temperature is 300-500°C, and the roasting time is 1-2.5h, such as roasting at 450°C for 2h. Wherein, as an example, the roasting of the aluminum-based waste catalyst and sodium hydroxide is carried out under aerobic conditions.

[0010] In the above-mentioned method for recovering the carrier of aluminum-based waste catalyst and reusing it to prepare carbon dioxide hydrogenation methanation catalyst, further, in step (2), the weak alkaline solution is a NaOH solution with a pH of 7.0 to 9.5 (such as pH=8.5), the liquid-to-solid ratio in the leaching treatment step is (20 to 30) mL:1g (such as 20 mL:1g), and the temperature is 25 to 65°C, such as 35°C; In step (3), the acidic solution is an inorganic acid, including nitric acid, such as a 0.1 mol / L nitric acid solution; the dripping rate is 2 mL / min, and the pH value is adjusted to alkaline by adjusting the pH to 10; In step (4), the calcination temperature is 400-600°C, preferably 450°C, and the calcination time is 1-2 hours.

[0011] In the above-mentioned method for recovering the carrier of aluminum-based waste catalyst and reusing it to prepare carbon dioxide hydrogenation and methanation catalyst, further, based on the mass of the carbon dioxide hydrogenation and methanation catalyst, the Ni loading amount is 10% to 25%, preferably 15% to 25%, more preferably 20% to 25%, and further preferably 20%.

[0012] Furthermore, the metal in the metal salt solution also includes a second metal, and the second metal is any one of Mn, Mo, Co, V, and Ce; preferably, based on the mass of the carbon dioxide hydrogenation methanation catalyst, the loading amount of the second metal is 0.5% to 3%, preferably 1% to 3%; more preferably, the second metal is V, and based on the mass of the carbon dioxide hydrogenation methanation catalyst, the loading amount of Ni is 20%, and the loading amount of V is 1%.

[0013] In the above-mentioned method for recovering the carrier of aluminum-based waste catalyst and reusing it to prepare carbon dioxide hydrogenation methanation catalyst, in step (5), in the ultrasonic treatment step, the temperature is 15 to 35°C (such as room temperature 20 to 25°C) and the time is 30 to 60 minutes (such as 60 minutes); In step (5), the temperature of the immersion treatment step is 15 to 35°C (such as room temperature 20 to 25°C) and the time is 10 to 18 hours (such as 12 hours); In step (5), the calcination temperature is 300-500°C, such as 500°C, and the calcination time is 2-6 hours, such as 4 hours. The calcination is specifically carried out in a muffle furnace; In step (6), the reduction temperature is 500-700°C and the time is 1-2h. If the reduction is carried out at 500°C for 1h, the metal Ni is stably present in the form of NiO. Therefore, the reduction step is usually carried out before the catalytic reaction. Specifically, the catalyst can be placed in a fixed bed and reduced under a hydrogen flow. After the reduction, the temperature is lowered and the reaction gas is passed through to carry out the catalytic reaction.

[0014] In a second aspect, the present invention provides a carbon dioxide hydrogenation methanation catalyst prepared by any of the methods described above.

[0015] In a third aspect, the present invention provides a method for producing methane by hydrogenating carbon dioxide, comprising the following steps: A mixed gas consisting of carbon dioxide, hydrogen and a balance gas is contacted with the carbon dioxide hydrogenation methanation catalyst as described above to react and obtain methane.

[0016] In the above-mentioned method for producing methane by hydrogenating carbon dioxide, as an example, the size of the carbon dioxide hydrogenation methanation catalyst is 30 to 50 μm; The volume ratio of the carbon dioxide to the hydrogen is 1:4; The volume fraction of the carbon dioxide in the mixed gas is 16%; The balance gas is nitrogen; The reaction temperature is 200-700°C, such as 300°C; The reaction pressure is normal pressure; The reaction time and space velocity of the carbon dioxide hydrogenation methanation catalyst is 4000-4500h -1 , such as the gas space velocity is 4248h -1 ; Wherein, the time-space velocity refers to the reaction gas passing through per m³ per unit time, in units of m 3 catalyst / h), i.e. h -1 .

[0017] The present invention has the following beneficial effects: (1) The method for recovering the aluminum-based waste catalyst carrier and reusing it to prepare a carbon-fixing catalyst provided by the present invention has a simple process, high recovery efficiency, and is green and environmentally friendly. It can achieve efficient recovery of the Al component in the waste catalyst. The prepared mesoporous alumina sample has high purity, large specific surface area, and strong stability, which fully meets the requirements as a catalyst carrier material.

[0018] (2) The carbon dioxide hydrogenation methanation catalyst prepared by the method for recovering the carrier of the aluminum-based waste catalyst provided by the present invention and reusing it to prepare a carbon fixation catalyst has good catalytic performance, thus realizing the resource utilization of Al in the aluminum-based waste catalyst. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The present invention is a process flow chart of the method for recovering the carrier of the aluminum-based waste catalyst and reusing it to prepare a carbon dioxide hydrogenation methanation catalyst.

[0020] Figure 2 This is the XRD characterization of the Ni-V / Al2O3 catalyst precursor synthesized in Example 9 of the present invention.

[0021] Figure 3 This is the SEM characterization of the Ni-V / Al2O3 catalyst precursor synthesized in Example 9 of the present invention.

[0022] Figure 4 This is a performance test of the Ni-V / Al2O3 catalyst synthesized in Example 9 of the present invention. DETAILED DESCRIPTION

[0023] The present invention is further described in detail below in conjunction with specific embodiments, and the examples provided are only for illustrating the present invention, rather than for limiting the scope of the present invention. The examples provided below can be used as a guide for further improvements by those of ordinary skill in the art, and do not constitute a limitation of the present invention in any way.

[0024] The calculation formula in the following embodiments is as follows: (1) Carbon dioxide conversion rate

[0025] (2) Methane yield

[0026] Among them, C CO2 , Y CH4 are the conversion rate of carbon dioxide and the yield of methane, respectively.

[0027] The methods used in the following examples, unless otherwise specified, are all conventional methods, carried out according to the techniques or conditions described in the literature in the art or according to the product instructions. The materials, reagents, etc. used in the following examples, unless otherwise specified, can all be obtained from commercial sources.

[0028] The aluminum-based waste catalyst in the following embodiment is a Fe-doped Pt-Sn / Al2O3 waste catalyst used in the light oil catalytic reforming process, wherein, by mass percentage, aluminum oxide accounts for 98%, active ingredient platinum dioxide accounts for 0.35%, and other small amounts of elements are also contained, such as iron oxide accounts for 0.19%, tin oxide accounts for 0.18%, etc.

[0029] Example 1 This embodiment provides a method for recovering the carrier of aluminum-based waste catalyst and reusing it to prepare a 5% Ni / Al2O3 carbon dioxide hydrogenation methanation catalyst, such as Figure 1 As shown, the specific steps are as follows: (1) Take 10g of aluminum-based waste catalyst and place it in a porcelain boat. Put it into a muffle furnace and bake it at 500℃ for 2h. After cooling to room temperature, take out the sample.

[0030] (2) Take 5 g of the sample obtained in step (1) and grind it thoroughly in a mortar for 0.5 h. After grinding, pass the sample through a 100-mesh sieve for later use.

[0031] (3) Take 2 g of the sample in step (2) and mix it with 2.4 g of sodium hydroxide, then grind it thoroughly in a mortar. Place the mixed sample in a porcelain boat, and bake it in a muffle furnace at 450° C. for 2 h to obtain a baked mixed sample.

[0032] (4) Dilute the NaOH solution to pH = 8.5 to obtain a weak alkaline solution, add 40 mL of the weak alkaline solution to 2 g of the mixed sample obtained after calcination in step (3), place it in a constant temperature water bath at 35°C, stir and leach, and filter to obtain a sodium aluminate solution. ICP detection of the leachate composition shows that the metal elements are only Al and Na, and almost no other metal impurities.

[0033] (5) The sodium aluminate solution obtained in step (4) is added dropwise into a 0.1 mol / L nitric acid solution at a flow rate of 2 mL / min through a peristaltic pump, and the pH is adjusted to 10. After aging, filtration, washing and drying, an alumina precursor is obtained.

[0034] (6) The alumina precursor was placed in a muffle furnace and calcined at 500 °C for 2 h to obtain a mesoporous alumina sample.

[0035] (7) Add 1.24 g of nickel nitrate hexahydrate into 10 mL of deionized water and place on a magnetic stirrer for thorough stirring.

[0036] (8) Weigh 5 g of the recovered mesoporous alumina sample and slowly add it to the stirring mixed solution. Stir the obtained mixed sample for 30 min to ensure uniform mixing. Transfer the stirred mixed sample to a CNC ultrasonic cleaner and perform ultrasonic treatment for 60 min. Then, immerse the sample at room temperature for 12 h.

[0037] (9) The impregnated sample was placed in an electric heated air drying oven and dried for 18 h. After sufficient drying, the obtained block sample was ground into powder using a mortar.

[0038] (10) The powdered sample was placed in a muffle furnace and calcined at 500 °C for 4 h to obtain a catalyst precursor; (11) 0.5 g of the catalyst precursor was reduced under H2 gas flow at 500 °C for 1 h. After the reduction was completed, the temperature was lowered to 200 °C to obtain a 5% Ni / Al2O3 catalyst sample.

[0039] Example 2 This embodiment provides a method for recovering an aluminum-based waste catalyst carrier and reusing it to prepare a carbon dioxide hydrogenation methanation catalyst 10% Ni / Al2O3. The specific steps are similar to those of the method used in Example 1, except that in step (7), 1.24 g of nickel nitrate hexahydrate is replaced with 2.48 g of nickel nitrate hexahydrate.

[0040] Example 3 This embodiment provides a method for recovering an aluminum-based waste catalyst carrier and reusing it to prepare a carbon dioxide hydrogenation methanation catalyst 15% Ni / Al2O3. The specific steps are similar to those of the method used in Example 1, except that in step (7), 1.24 g of nickel nitrate hexahydrate is replaced with 3.72 g of nickel nitrate hexahydrate.

[0041] Example 4 This embodiment provides a method for recovering a carrier of an aluminum-based waste catalyst and reusing it to prepare a 20% Ni / Al2O3 carbon dioxide hydrogenation methanation catalyst. The specific steps are similar to those of the method of Example 1, except that in step (7), 1.24 g of nickel nitrate hexahydrate is replaced with 4.96 g of nickel nitrate hexahydrate.

[0042] Example 5 This embodiment provides a method for recovering an aluminum-based waste catalyst carrier and reusing it to prepare a carbon dioxide hydrogenation methanation catalyst 25% Ni / Al2O3. The specific steps are similar to those of the method used in Example 1, except that in step (7), 1.24 g of nickel nitrate hexahydrate is replaced with 6.19 g of nickel nitrate hexahydrate.

[0043] Example 6 This embodiment provides a method for recovering and reusing an aluminum-based waste catalyst carrier to prepare a carbon dioxide hydrogenation methanation catalyst 20% Ni-1% Mn / Al2O3 catalyst. The specific steps are similar to those of the method used in Example 1, except that in step (7), 1.24 g of nickel nitrate hexahydrate is replaced with 4.96 g of nickel nitrate hexahydrate, and 0.23 g of manganese nitrate tetrahydrate is added.

[0044] Example 7 This embodiment provides a method for recovering and reusing an aluminum-based waste catalyst carrier to prepare a carbon dioxide hydrogenation methanation catalyst 20% Ni-1% Mo / Al2O3 catalyst. The specific steps are similar to those of the method used in Example 1, except that in step (7), 1.24 g of nickel nitrate hexahydrate is replaced with 4.96 g of nickel nitrate hexahydrate, and 0.10 g of ammonium heptamolybdate tetrahydrate is added.

[0045] Example 8 This embodiment provides a method for recovering and reusing an aluminum-based waste catalyst carrier to prepare a carbon dioxide hydrogenation methanation catalyst 20% Ni-1% Co / Al2O3 catalyst. The specific steps are similar to those of the method used in Example 1, except that in step (7), 1.24 g of nickel nitrate hexahydrate is replaced with 4.96 g of nickel nitrate hexahydrate, and 0.25 g of cobalt nitrate hexahydrate is added.

[0046] Example 9 This embodiment provides a method for recovering an aluminum-based waste catalyst carrier and reusing it to prepare a carbon dioxide hydrogenation methanation catalyst 20% Ni-1% V / Al2O3 catalyst. The specific steps are similar to the method used in Example 1, except that in step (7), 1.24 g of nickel nitrate hexahydrate is replaced with 4.96 g of nickel nitrate hexahydrate, and 0.12 g of ammonium metavanadate is added.

[0047] Example 10 This embodiment provides a method for recovering and reusing an aluminum-based waste catalyst carrier to prepare a carbon dioxide hydrogenation methanation catalyst 20% Ni-0.5% V / Al2O3 catalyst. The specific steps are similar to those of the method used in Example 1, except that in step (7), 1.24 g of nickel nitrate hexahydrate is replaced with 4.96 g of nickel nitrate hexahydrate, and 0.06 g of ammonium metavanadate is added.

[0048] Embodiment 11 This embodiment provides a method for recovering an aluminum-based waste catalyst carrier and reusing it to prepare a carbon dioxide hydrogenation methanation catalyst 20% Ni-2% V / Al2O3 catalyst. The specific steps are similar to the method used in Example 1, except that in step (7), 1.24 g of nickel nitrate hexahydrate is replaced with 4.96 g of nickel nitrate hexahydrate, and 0.24 g of ammonium metavanadate is added.

[0049] Example 12 This embodiment provides a method for recovering an aluminum-based waste catalyst carrier and reusing it to prepare a carbon dioxide hydrogenation methanation catalyst 20% Ni-3% V / Al2O3 catalyst. The specific steps are similar to the method used in Example 1, except that in step (7), 1.24 g of nickel nitrate hexahydrate is replaced with 4.96 g of nickel nitrate hexahydrate, and 0.36 g of ammonium metavanadate is added.

[0050] Embodiment 13 This embodiment provides a method for recovering and reusing an aluminum-based waste catalyst carrier to prepare a carbon dioxide hydrogenation methanation catalyst 20% Ni-1% Ce / Al2O3 catalyst. The specific steps are similar to those of the method used in Example 1, except that in step (7), 1.24 g of nickel nitrate hexahydrate is replaced with 4.96 g of nickel nitrate hexahydrate, and 0.16 g of cerium nitrate hexahydrate is added.

[0051] Embodiment 14 This embodiment provides a method for recovering and reusing an aluminum-based waste catalyst carrier to prepare a carbon dioxide hydrogenation methanation catalyst 20% Ni-1% Ce / Al2O3 catalyst. The specific steps are similar to the method used in Example 1, except that in step (7), 1.24 g of nickel nitrate hexahydrate is replaced with 4.96 g of nickel nitrate hexahydrate, and 0.32 g of cerium nitrate hexahydrate is added.

[0052] Embodiment 15 This embodiment provides a method for recovering a carrier of an aluminum-based waste catalyst and reusing it to prepare a 20% Ni-1% Ce / Al2O3 catalyst for the hydrogenation and methanation of carbon dioxide. The specific steps are similar to those of the method used in Example 1, except that in step (7), 1.24 g of nickel nitrate hexahydrate is replaced with 4.96 g of nickel nitrate hexahydrate, and 0.48 g of cerium nitrate hexahydrate is added.

[0053] Example 16 This embodiment provides a method for recovering a carrier of an aluminum-based waste catalyst and reusing it to prepare a 20% Ni-1% Ce / Al2O3 catalyst for the hydrogenation and methanation of carbon dioxide. The specific steps are similar to those of the method of Example 1, except that in step (7), 1.24 g of nickel nitrate hexahydrate is replaced with 4.96 g of nickel nitrate hexahydrate, and 0.16 g of ruthenium nitrate is added.

[0054] Embodiment 17 This embodiment provides a method for recovering and reusing an aluminum-based waste catalyst carrier to prepare a carbon dioxide hydrogenation methanation catalyst 20% Ni-1% Ce / Al2O3 catalyst. The specific steps are similar to the method used in Example 1, except that in step (7), 1.24 g of nickel nitrate hexahydrate is replaced with 4.96 g of nickel nitrate hexahydrate, and 0.16 g of lanthanum nitrate hexahydrate is added.

[0055] Comparative Example 1 The method is similar to that used in Example 4, except that steps (1) to (4) are omitted, and the obtained sodium aluminate solution is replaced by a directly prepared sodium aluminate solution, the sodium aluminate concentration is consistent with that in Example 4, and steps (5) to (10) are consistent with those in Example 4.

[0056] Comparative Example 2 The method is similar to that used in Example 9, except that steps (1) to (4) are omitted, and the obtained sodium aluminate solution is replaced by a directly prepared sodium aluminate solution. The sodium aluminate concentration is consistent with that in Example 1, and steps (5) to (10) are consistent with those in Example 9.

[0057] Performance Testing 1. Alumina performance test The performance parameters of the mesoporous alumina sample prepared in step (6) of Example 4 and the alumina sample prepared in Comparative Example 1 were tested. The results are shown in Table 1.

[0058] Table 1. Comparison of alumina performance

[0059] It can be seen from Table 1 that although the purity of the aluminum oxide samples prepared from different raw materials is the same, the specific surface area, pore size and porosity of the aluminum oxide prepared by recycling sodium aluminate in the present invention are much higher than those prepared from pure sodium aluminate. It can be seen that the mesoporous aluminum oxide sample prepared by the present invention has high purity, large specific surface area and strong stability, and is more suitable as a catalyst carrier material.

[0060] 2. Relevant Characterization The XRD and SEM characterization results of the precursor of the carbon dioxide hydrogenation methanation catalyst 20% Ni-1% V / Al2O3 catalyst prepared in step (10) of Example 9 are shown in Figure 2-3 .Depend on Figure 2 The characteristic peaks and Figure 3 It can be seen that metallic Ni is uniformly loaded on the support surface in the form of NiO, and is therefore subsequently converted into Ni in the reduction step (11).

[0061] 3. Catalytic performance The catalytic activity of the catalysts prepared in the above examples and comparative examples was evaluated, and the specific steps were as follows: a catalyst particle layer with a specific size (30-50 μm) was placed in the center of the reactor, and a thermocouple was inserted into the bottom of the catalyst bed to adjust the heating temperature. A feed stream (50 mL / min) containing hydrogen and carbon dioxide was introduced into the reactor at a molar ratio of 4:1, the balance gas was nitrogen (the volume fraction of carbon dioxide in the mixed gas was 16%), and the gas hourly space velocity (GHSV) = 4200h −1 The reaction was carried out in the temperature range of 200-700°C and the product stream was analyzed by an online gas chromatograph.

[0062] The CO2 conversion rate and CH4 yield of the Ni-V / Al2O3 catalyst synthesized in Example 9 at 200-700°C are as follows: Figure 4 As shown. Under normal pressure conditions, the reaction temperature is 300°C and the gas space velocity is 4248h -1 The experimental results are shown in Table 2.

[0063] Table 2. Catalyst activity evaluation results

[0064] As can be seen from Table 2, in Example 1, the loading amount of Ni in the catalyst sample reaches 5wt%, the carbon dioxide conversion rate is 37.0%, and the methane yield is 37.0%, showing poor catalytic performance. In Example 2, the loading amount of Ni in the catalyst sample reaches 10wt%, the carbon dioxide conversion rate is 84.5%, and the methane yield is 84.5%, showing good catalytic performance. In Example 3, the loading amount of Ni in the catalyst sample reaches 15%, the carbon dioxide conversion rate is 88.3%, and the methane yield is 88.3%, showing good catalytic performance. In Example 4, the loading amount of Ni in the catalyst sample reaches 20%, the carbon dioxide conversion rate is 90.6%, and the methane yield is 90.5%, and the catalytic activity is the best. In Example 5, the loading amount of Ni is further increased, and the catalytic activity does not change significantly. Further adding doping metal, when the Ni loading amount is 20wt% and 1% V metal is doped for modification, at a reaction temperature of 300°C, the carbon dioxide conversion rate is 93.0%, the methane yield is 93.0%, and all the carbon dioxide is converted into methane, with almost no other by-products generated. The catalytic activity reaches the highest, showing good low-temperature catalytic performance.

[0065] It can be seen from the comparison results of Example 4 and Comparative Example 1 that the carbon dioxide conversion rate and methane yield of Example 4 are both higher than those of Comparative Example 1. This is because the mesoporous alumina prepared by recycling aluminum-based waste catalysts using the method of the present invention has a higher specific surface area and stronger stability, and the catalytic activity of the prepared catalyst is higher, which is consistent with the results in Table 2. Similarly, in the comparison results of Example 9 and Comparative Example 2, the carbon dioxide conversion rate and methane yield of Example 9 are both higher than those of Comparative Example 2. The method of the present invention not only realizes the resource utilization of Al in aluminum-based waste catalysts, but also the prepared catalyst exhibits excellent catalytic performance for carbon dioxide hydrogenation and methanation.

[0066] The present invention has been described in detail above. For those skilled in the art, without departing from the purpose and scope of the present invention, can implement the present invention in a wider range under equivalent parameters, concentrations and conditions. Although the present invention provides specific embodiments, it should be understood that the present invention can be further improved. In a word, according to the principle of the present invention, the application is intended to include any changes, uses or improvements to the present invention, including departing from the disclosed scope in the application and the changes made with conventional techniques known in the art.

Claims

1. A method for recovering and reusing the carrier of aluminum-based waste catalyst to prepare a carbon dioxide hydrogenation methanation catalyst, characterized in that: The steps include: (1) mixing the aluminum-based waste catalyst with sodium hydroxide and calcining the mixture to obtain a sodium-calcined product; (2) adding a weak alkaline solution to the sodium-treated roasted product for leaching to obtain a sodium aluminate leaching solution; (3) adding the sodium aluminate leaching solution dropwise into an acidic solution, adjusting the pH value to alkaline, and obtaining an alumina precursor through aging, separation and drying; (4) calcining the alumina precursor to obtain mesoporous alumina; (5) adding the mesoporous alumina into a metal salt solution, sequentially performing ultrasonic treatment and impregnation treatment, and then drying and calcining to obtain a catalyst precursor; the metal in the metal salt solution comprises a first metal Ni; (6) The catalyst precursor is heated under a hydrogen gas flow for reduction to obtain the carbon dioxide hydrogenation and methanation catalyst.

2. The method for preparing a carbon dioxide hydrogenation methanation catalyst by recycling an aluminum-based waste catalyst carrier according to claim 1, characterized in that: The method further comprises, before step (1): calcining the aluminum-based waste catalyst at 500° C. for 2 h to remove carbon and then ball milling to obtain waste catalyst powder; and / or, In step (1), the mass ratio of the aluminum-based waste catalyst to sodium hydroxide is 1:(0.8-1.5), the roasting temperature is 300-500° C., and the roasting time is 1-2.5 h.

3. The method for recovering and reusing the aluminum-based waste catalyst carrier to prepare a carbon dioxide hydrogenation methanation catalyst according to any one of claims 1 to 2, characterized in that: In step (2), the weak alkaline solution is a NaOH solution with a pH of 7.0 to 9.5, the liquid-to-solid ratio in the leaching treatment step is (20 to 30) mL:1 g, and the temperature is 25 to 65° C.; and / or, In step (3), adjusting the pH value to alkaline is adjusting the pH to 10; and / or, In step (4), the calcination temperature is 400-600° C. and the calcination time is 1-2 h.

4. The method for recovering and reusing the aluminum-based waste catalyst carrier to prepare a carbon dioxide hydrogenation methanation catalyst according to any one of claims 1 to 3, characterized in that: Based on the mass of the carbon dioxide hydrogenation methanation catalyst, the Ni loading amount is 10% to 25%, preferably 15% to 25%, more preferably 20% to 25%, and further preferably 20%.

5. The method for preparing a carbon dioxide hydrogenation methanation catalyst by recycling a carrier of an aluminum-based waste catalyst according to claim 4, characterized in that: The metal in the metal salt solution also includes a second metal, which is any one of Mn, Mo, Co, V, and Ce; preferably, based on the mass of the carbon dioxide hydrogenation methanation catalyst, the loading amount of the second metal is 0.5% to 3%, preferably 1% to 3%.

6. The method for preparing a carbon dioxide hydrogenation methanation catalyst by recycling a carrier of an aluminum-based waste catalyst according to claim 5, characterized in that: The second metal is V. Based on the mass of the carbon dioxide hydrogenation and methanation catalyst, the loading amount of Ni is 20%, and the loading amount of V is 1%.

7. The method for recovering and reusing the aluminum-based waste catalyst carrier to prepare a carbon dioxide hydrogenation methanation catalyst according to any one of claims 1 to 6, characterized in that: In step (5), in the ultrasonic treatment step, the temperature is 15 to 35° C. and the time is 30 to 60 min; and / or, In step (5), in the immersion treatment step, the temperature is 15 to 35° C. and the time is 10 to 18 hours; and / or, In step (5), the calcination temperature is 300-500°C and the calcination time is 2-6 hours; and / or, In step (6), the reduction temperature is 500-700° C. and the time is 1-2 h.

8. A carbon dioxide hydrogenation methanation catalyst prepared by the method according to any one of claims 1 to 7.

9. A method for preparing methane by hydrogenating carbon dioxide, characterized in that: The steps include: A mixed gas consisting of carbon dioxide, hydrogen and a balance gas is contacted with the carbon dioxide hydrogenation methanation catalyst according to claim 8 to react and obtain methane.

10. The method for preparing methane by hydrogenating carbon dioxide according to claim 9, characterized in that: The volume ratio of the carbon dioxide to the hydrogen is 1:4; The volume fraction of the carbon dioxide in the mixed gas is 16%; The balance gas is nitrogen; The reaction temperature is 200-700°C; The reaction pressure is normal pressure; The reaction time and space velocity of the carbon dioxide hydrogenation methanation catalyst is 4000-4500h -1 .

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