A copper-iron-magnesium-based catalyst and its preparation method and application

Abstract

The present invention discloses a copper-iron-magnesium-based catalyst and its preparation method and application. The preparation method of the copper-iron-magnesium-based catalyst of the present invention is as follows: magnesium salt, copper salt and iron salt are added to deionized water, and stirred to dissolve to obtain a clear and uniform mixed solution. An alkaline solution is added dropwise to the mixed solution under stirring, and after stirring for a period of time, a glucose solution is added dropwise, and after stirring evenly, the mixed solution is transferred to a reactor for reaction; after the reaction is completed, the precipitate is centrifuged, washed and dried to obtain a copper-iron-magnesium-based catalyst. The present invention dopes magnesium into the copper-iron catalyst and catalyzes CO2 hydrogenation to produce C5 + In terms of hydrocarbons, the CO2 conversion rate and C5 + The addition of glucose makes the catalyst have lower CO selectivity, higher CO2 conversion rate and C5 + The hydrocarbon selectivity and good stability significantly improve the catalytic CO2 hydrogenation performance.

Description

Technical Field

[0001] The present invention belongs to the field of catalyst preparation technology, and specifically relates to the preparation of copper-iron-magnesium based catalysts and their application in catalyzing CO2 hydrogenation to produce C5 + Applications of hydrocarbons. Background Art

[0002] Technologies that convert CO2 into value-added chemicals and fuels facilitate the recycling of CO2, significantly reducing CO2 emissions. Due to CO2's high thermodynamic stability, hydrogenating CO2 to hydrocarbons is very difficult. Furthermore, the relatively low heat of adsorption of CO2 on the catalyst surface facilitates the rapid hydrogenation of surface-adsorbed intermediates, easily generating methane. This results in high selectivity for short-chain products and low selectivity for long-chain products.

[0003] Iron-based catalysts are the preferred catalysts for the CO2-FTS process due to their excellent activity in the reverse water-gas reaction (RWGS) and Fischer-Tropsch synthesis (FTS). Generally, iron-based catalysts require synergistic action with alkali metals or transition metals to achieve the desired activity and selectivity.

[0004] Yo Han Choi et al. [Applied Catalysis B: Environmental. 2017, 202: 605-610.] reported a CuFeO2 catalyst prepared by hydrothermal synthesis using propionaldehyde as a reducing agent for CO2 hydrogenation to synthesize heavy hydrocarbons. However, the CO2 conversion rate of the catalyst is relatively low, and the CO selectivity is very high; in addition, the raw material propionaldehyde is volatile, flammable and toxic, making it not an ideal reducing agent. Chinese patent CN 116060009 A discloses a method for preparing a copper-iron alloy catalyst, which uses copper salt, magnesium salt and iron salt as raw materials, and prepares CuFeO2 with different copper-iron ratios on magnesium oxide as a carrier by a nucleation crystallization isolation method. x Fe y -MgO catalyst. This catalyst has high activity in reverse water gas reaction at 600℃, with CO selectivity reaching over 96%, but its selectivity for hydrocarbons is very low. If CO2 is to be converted into long-chain products and obtain higher C5 + The catalyst disclosed in the present invention significantly improves the CO2 conversion rate and C5 + The selectivity of hydrocarbons reduces the CO selectivity. The selected reducing agent glucose is non-toxic and chemically stable, which gives the copper-iron-magnesium based catalyst excellent reaction performance and good stability. Summary of the Invention

[0005] In view of the above technical problems existing in the prior art, the purpose of the present invention is to provide a copper-iron-magnesium-based catalyst and its preparation method and application. The prepared copper-iron-magnesium-based catalyst can be used for CO2 hydrogenation to C5 + The catalyst has the advantages of good CO2 hydrogenation activity, high product selectivity and good stability.

[0006] The technical solution adopted in the present invention is as follows:

[0007] A method for preparing a copper-iron-magnesium based catalyst comprises the following steps:

[0008] 1) adding Mg salt, Cu salt and Fe salt to deionized water and stirring at room temperature to obtain a uniform mixed solution;

[0009] 2) slowly adding alkaline solution dropwise to the mixed uniform solution of step 1), and stirring the mixture under alkaline conditions for 20 to 60 minutes;

[0010] 3) Slowly adding glucose solution dropwise to the suspension in step 2) and stirring for 5 to 20 minutes;

[0011] 4) The suspension from step 3) is transferred to a reactor, which is then placed in an oven at 170-200° C. for heating and reacting for 5-15 hours; the reactor is cooled, and the product is obtained by centrifugation, which is then washed with deionized water and dried to obtain a copper-iron-magnesium-based catalyst.

[0012] Furthermore, in step 1), the anions of the Mg salt, Cu salt and Fe salt are all nitrates, the molar ratio of the Mg salt, Cu salt and Fe salt is 0.01-0.2:1:1-3, and the total salt concentration of the mixed solution is 0.2-2 mol / L.

[0013] Furthermore, the molar ratio of Mg salt, Cu salt and Fe salt is 0.016-0.15:1:1.5-2, and more preferably 0.033:1:1.5-2, and the total salt concentration of the mixed solution is 0.3-1.0 mol / L.

[0014] Furthermore, in step 2), the alkaline solution is an aqueous solution of a strong base with a concentration of 1 to 10 mol / L, and the strong base is one or both of NaOH and KOH.

[0015] Furthermore, the molar ratio of the added amount of the strong base to the Cu salt is 5 to 25:1, preferably 10 to 20:1.

[0016] Furthermore, in step 3), the molar ratio of the added amount of glucose to the Cu salt is 0.4-3:1, preferably 0.7-1:1; the concentration of the glucose solution is 0.1-5.5 mol / L, preferably 2-3 mol / L.

[0017] Furthermore, in step 4), the heating reaction temperature is 180-190° C., and the reaction time is 8-9 h.

[0018] The present invention also provides a copper-iron-magnesium-based catalyst for catalyzing CO2 hydrogenation to produce C5 + The application method is as follows: the copper-iron-magnesium-based catalyst is filled in a fixed bed reactor, first reduced and activated for 2-6 hours under a H2 atmosphere at normal pressure and 350-400°C to obtain an activated catalyst, and then introduced a H2 / CO2 mixed gas with a volume ratio of 2-4:1 at 300-340°C to catalyze CO2 hydrogenation to produce C5 + wherein the catalyst filling amount is 1g and the volume of the H2 / CO2 mixture introduced is 20-100mL / min.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) The copper-iron-magnesium-based catalyst disclosed in the present invention has a very obvious effect on improving the activity when the added Mg element is at a very low content.

[0021] (2) The copper-iron-magnesium-based catalyst disclosed in the present invention, the added glucose acts as a reducing agent to reduce the Cu 2+ Reduction to Cu + , which promotes the formation of Cu-Fe5C2 interface; it is also beneficial to the formation of catalyst pores, increases the specific surface area of ​​the catalyst, and obtains more active sites; and glucose is non-toxic and chemically stable, and can be safely used in catalyst preparation.

[0022] (3) Compared with other copper-iron catalysts, such as CuFeO2-6 catalyst [Applied Catalysis B: Environmental. 2017, 202: 605-610.], Cu1Fe1-MgO catalyst [Chinese patent CN 116060009A], etc., the copper-iron-magnesium-based catalyst disclosed in the present invention has higher CO2 conversion rate and C5 + In the CO2 hydrogenation reaction using the catalyst of the present invention, the CO2 conversion rate was 41.83%, the CO selectivity was 7.96%, and the C5 + The selectivity to hydrocarbons was 66.15%. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The graph is a change curve of CO2 conversion rate within 24 hours for the catalysts obtained in Example 1 of the present invention and Comparative Examples 1, 2, and 3. DETAILED DESCRIPTION

[0024] The present invention will be further described below with reference to specific embodiments, but the protection scope of the present invention is not limited thereto.

[0025] The solvents used in the alkaline solutions and glucose solutions in the following examples and comparative examples are all deionized water.

[0026] Example 1

[0027] The catalyst preparation method specifically comprises the following steps:

[0028] (1) Weigh 0.0005 mol Mg(NO3)2·6H2O, 0.015 mol Cu(NO3)2·3H2O, and 0.02625 mol Fe(NO3)3·9H2O and add them to 80 mL of deionized water. Stir for 20 min to fully dissolve them and obtain a clear mixed solution.

[0029] (2) Slowly adding 40 mL of 5 mol / L KOH solution to the clarified mixed solution of step (1) under stirring; after the addition is complete, stirring for 30 minutes to obtain a suspension;

[0030] (3) Slowly add 5 mL of 2.22 mol / L glucose solution to the suspension in step (2) under stirring and stir for 5 min to obtain a uniform mixed suspension;

[0031] (4) placing the uniform mixed suspension obtained in step (3) in a polytetrafluoroethylene-lined stainless steel reactor and heating it in an oven at 180° C. for 8 h;

[0032] (5) After the reaction is completed, the reactor is cooled to room temperature, the product is obtained by centrifugation, and then washed with deionized water four times; the washed product is transferred to a beaker and placed in an oven at 60°C for 12 hours to obtain a copper-iron-magnesium-based catalyst.

[0033] Example 2

[0034] (1) Weigh 0.00025 mol Mg(NO3)2·6H2O, 0.015 mol Cu(NO3)2·3H2O, and 0.02625 mol Fe(NO3)3·9H2O and add them to 80 mL of deionized water. Stir for 20 min to fully dissolve them and obtain a clear mixed solution.

[0035] (2) Slowly adding 40 mL of 5 mol / L KOH solution to the clarified mixed solution of step (1) under stirring; after the addition is complete, stirring for 30 minutes to obtain a suspension;

[0036] (3) Slowly add 5 mL of 2.22 mol / L glucose solution to the suspension in step (2) under stirring and stir for 5 min to obtain a uniform mixed suspension;

[0037] (4) placing the uniform mixed suspension obtained in step (3) in a polytetrafluoroethylene-lined stainless steel reactor and heating it in an oven at 180° C. for 8 h;

[0038] (5) After the reaction is completed, the reactor is cooled to room temperature, the product is obtained by centrifugation, and then washed with deionized water four times; the washed product is transferred to a beaker and placed in an oven at 60°C for 12 hours to obtain a copper-iron-magnesium-based catalyst.

[0039] Example 3

[0040] (1) Weigh 0.001 mol Mg(NO3)2·6H2O, 0.015 mol Cu(NO3)2·3H2O, and 0.02625 mol Fe(NO3)3·9H2O and add them to 80 mL of deionized water. Stir for 20 min to fully dissolve them and obtain a clear mixed solution.

[0041] (2) Slowly adding 40 mL of 5 mol / L KOH solution to the clarified mixed solution of step (1) under stirring; after the addition is complete, stirring for 30 minutes to obtain a suspension;

[0042] (3) Slowly add 5 mL of 2.22 mol / L glucose solution to the suspension in step (2) under stirring and stir for 5 min to obtain a uniform mixed suspension;

[0043] (4) placing the uniform mixed suspension obtained in step (3) in a polytetrafluoroethylene-lined stainless steel reactor and heating it in an oven at 180° C. for 8 h;

[0044] (5) After the reaction is completed, the reactor is cooled to room temperature, the product is obtained by centrifugation, and then washed with deionized water four times; the washed product is transferred to a beaker and placed in an oven at 60°C for 12 hours to obtain a copper-iron-magnesium-based catalyst.

[0045] Example 4

[0046] (1) Weigh 0.002 mol Mg(NO3)2·6H2O, 0.015 mol Cu(NO3)2·3H2O, and 0.02625 mol Fe(NO3)3·9H2O and add them to 80 mL of deionized water. Stir for 20 min to fully dissolve them and obtain a clear mixed solution.

[0047] (2) Slowly adding 40 mL of 5 mol / L KOH solution to the clarified mixed solution of step (1) under stirring; after the addition is complete, stirring for 30 minutes to obtain a suspension;

[0048] (3) Slowly add 5 mL of 2.22 mol / L glucose solution to the suspension in step (2) under stirring and stir for 5 min to obtain a uniform mixed suspension;

[0049] (4) placing the uniform mixed suspension obtained in step (3) in a polytetrafluoroethylene-lined stainless steel reactor and heating it in an oven at 180° C. for 8 h;

[0050] (5) After the reaction is completed, the reactor is cooled to room temperature, the product is obtained by centrifugation, and then washed with deionized water four times; the washed product is transferred to a beaker and placed in a 70°C oven to dry for 16 hours to obtain a copper-iron-magnesium-based catalyst.

[0051] Example 5

[0052] (1) Weigh 0.0005 mol Mg(NO3)2·6H2O, 0.015 mol Cu(NO3)2·3H2O, and 0.02625 mol Fe(NO3)3·9H2O and add them to 80 mL of deionized water. Stir for 15 min to fully dissolve them and obtain a clear mixed solution.

[0053] (2) Slowly adding 40 mL of 5 mol / L KOH solution to the clarified mixed solution of step (1) under stirring; after the addition is complete, stirring for 35 minutes to obtain a suspension;

[0054] (3) Slowly add 5 mL of 1.61 mol / L glucose solution to the suspension in step (2) under stirring and stir for 10 min to obtain a uniform mixed suspension;

[0055] (4) placing the uniform mixed suspension obtained in step (3) in a polytetrafluoroethylene-lined stainless steel reactor and heating it in an oven at 180° C. for 8 h;

[0056] (5) After the reaction is completed, the reactor is cooled to room temperature, the product is obtained by centrifugation, and then washed with deionized water four times; the washed product is transferred to a beaker and placed in an oven at 60°C for 12 hours to obtain a copper-iron-magnesium-based catalyst.

[0057] Example 6

[0058] (1) Weigh 0.0005 mol Mg(NO3)2·6H2O, 0.015 mol Cu(NO3)2·3H2O, and 0.02625 mol Fe(NO3)3·9H2O and add them to 80 mL of deionized water. Stir for 20 min to fully dissolve them and obtain a clear mixed solution.

[0059] (2) Slowly adding 35 mL of 5 mol / L KOH solution to the clarified mixed solution of step (1) under stirring; after the addition is complete, stirring for 30 min to obtain a suspension;

[0060] (3) Slowly add 10 mL of 4.44 mol / L glucose solution to the suspension in step (2) under stirring and stir for 5 min to obtain a uniform mixed suspension;

[0061] (4) placing the uniform mixed suspension obtained in step (3) in a polytetrafluoroethylene-lined stainless steel reactor and heating it in an oven at 180° C. for 8 h;

[0062] (5) After the reaction is completed, the reactor is cooled to room temperature, the product is obtained by centrifugation, and then washed with deionized water four times; the washed product is transferred to a beaker and placed in an oven at 60°C for 12 hours to obtain a copper-iron-magnesium-based catalyst.

[0063] Comparative Example 1

[0064] Comparative Example 1 provides a method for preparing a CuFe catalyst, which specifically comprises the following steps:

[0065] (1) Weigh 0.015 mol Cu(NO3)2·3H2O and 0.02625 mol Fe(NO3)3·9H2O and add them to 80 mL of deionized water. Stir for 20 min to fully dissolve them and obtain a clear mixed solution.

[0066] (2) Slowly adding 40 mL of 5 mol / L KOH solution to the clarified mixed solution of step (1) under stirring; after the addition is complete, stirring for 30 minutes to obtain a suspension;

[0067] (3) Slowly add 5 mL of deionized water to the suspension of step (2) under stirring and stir for 5 min to obtain a uniform mixed suspension;

[0068] (4) placing the uniform mixed suspension obtained in step (3) in a polytetrafluoroethylene-lined stainless steel reactor and heating it in an oven at 180° C. for 8 h;

[0069] (5) After the reaction is completed, the reactor is cooled to room temperature, the product is obtained by centrifugation, and then washed four times with deionized water; the washed product is transferred to a beaker and placed in a 60°C oven to dry for 12 hours to obtain the CuFe catalyst.

[0070] Comparative Example 2

[0071] Comparative Example 2 provides a method for preparing a CuFeMg catalyst, which specifically comprises the following steps:

[0072] (1) Weigh 0.0005 mol Mg(NO3)2·6H2O, 0.015 mol Cu(NO3)2·3H2O, and 0.02625 mol Fe(NO3)3·9H2O and add them to 80 mL of deionized water. Stir for 20 min to fully dissolve them and obtain a clear mixed solution.

[0073] (2) Slowly adding 40 mL of 5 mol / L KOH solution to the clarified mixed solution of step (1) under stirring; after the addition is complete, stirring for 30 minutes to obtain a suspension;

[0074] (3) Slowly add 5 mL of deionized water to the suspension of step (2) under stirring and stir for 5 min to obtain a uniform mixed suspension;

[0075] (4) placing the uniform mixed suspension obtained in step (3) in a polytetrafluoroethylene-lined stainless steel reactor and heating it in an oven at 180° C. for 8 h;

[0076] (5) After the reaction is completed, the reactor is cooled to room temperature, the product is obtained by centrifugation, and then washed four times with deionized water; the washed product is transferred to a beaker and placed in an oven at 60°C for 12 hours to obtain the CuFeMg catalyst.

[0077] Comparative Example 3

[0078] Comparative Example 3 provides a method for preparing a CuFe glucose catalyst, which specifically comprises the following steps:

[0079] (1) Weigh 0.015 mol Cu(NO3)2·3H2O and 0.02625 mol Fe(NO3)3·9H2O and add them to 80 mL of deionized water. Stir for 20 min to fully dissolve them and obtain a clear mixed solution.

[0080] (2) Slowly adding 40 mL of 5 mol / L KOH solution to the clarified mixed solution of step (1) under stirring; after the addition is complete, stirring for 30 minutes to obtain a suspension;

[0081] (3) Slowly add 5 mL of 2.22 mol / L glucose solution to the suspension in step (2) under stirring and stir for 5 min to obtain a uniform mixed suspension;

[0082] (4) placing the uniform mixed suspension obtained in step (3) in a polytetrafluoroethylene-lined stainless steel reactor and heating it in an oven at 180° C. for 8 h;

[0083] (5) After the reaction is completed, the reactor is cooled to room temperature, the product is obtained by centrifugation, and then washed four times with deionized water; the washed product is transferred to a beaker and placed in a 60°C oven to dry for 12 hours to obtain the CuFe glucose catalyst.

[0084] Comparative Example 4

[0085] Comparative Example 4 provides a method for preparing a CuFeMg acetaldehyde catalyst, which specifically comprises the following steps:

[0086] (1) Weigh 0.0005 mol Mg(NO3)2·6H2O, 0.015 mol Cu(NO3)2·3H2O, and 0.02625 mol Fe(NO3)3·9H2O and add them to 80 mL of deionized water. Stir for 20 min to fully dissolve them and obtain a clear mixed solution.

[0087] (2) Slowly adding 40 mL of 5 mol / L KOH solution to the clarified mixed solution of step (1) under stirring; after the addition is complete, stirring for 30 minutes to obtain a suspension;

[0088] (3) Slowly add 5 mL of 2.22 mol / L acetaldehyde aqueous solution to the suspension in step (2) under stirring and stir for 5 min to obtain a uniform mixed suspension;

[0089] (4) placing the uniform mixed suspension obtained in step (3) in a polytetrafluoroethylene-lined stainless steel reactor and heating it in an oven at 180° C. for 8 h;

[0090] (5) After the reaction is completed, the reactor is cooled to room temperature, the product is obtained by centrifugation, and then washed with deionized water four times; the washed product is transferred to a beaker and placed in an oven at 60°C for 12 hours to obtain the CuFeMg acetaldehyde catalyst.

[0091] Evaluation method for CO2 hydrogenation performance of catalyst:

[0092] The catalysts of the above embodiments and comparative examples were all tested for CO2 hydrogenation reaction performance under the same reaction conditions. The specific reaction conditions were as follows: 0.5 g of the catalyst was mixed with 0.5 g of quartz sand and loaded into a fixed bed reactor for evaluation. The mixture was first reduced at normal pressure, 400°C, and in a pure H2 atmosphere for 5 h. The mixture was then reacted at 320°C, 3.0 MPa, H2 / CO2=3, and a mixed gas flow rate of 20 mL / min for 24 h. The products were analyzed using a gas chromatograph equipped with a thermal conductivity detector (TCD) and a hydrogen flame ionization detector (FID).

[0093] The experimental results of the catalytic evaluation reaction for 24 hours are shown in Table 1. From the activity data of the catalyst in Example 1 and the catalyst in Comparative Example 1, it can be seen that the CO2 conversion rate and C5 + The selectivity of hydrocarbons is the lowest; when Mg and glucose are added to the catalyst of Example 1, the CO2 conversion rate increases by about 10% compared with the CuFe catalyst, and the C5 + The selectivity of hydrocarbons increased by about 17%; compared with the catalyst of Example 1 and the catalyst of Comparative Example 2 with only Mg added, or with the catalyst of Comparative Example 3 with only glucose added, the CO2 conversion rate and C5 + The hydrocarbon selectivity is lower than that of the catalyst in Example 1, indicating that the simultaneous addition of Mg element and glucose can further enhance the CO2 hydrogenation activity of the copper-iron catalyst.

[0094] As shown in Table 1, it can be seen from the catalysts of Examples 1, 2, 3, and 4 that with the increase of Mg content, the CO2 conversion rate and C5 + The selectivity of hydrocarbons showed a trend of increasing first and then decreasing; the selectivity of CO showed a trend of decreasing first and then increasing; this shows that when the content of Mg is relatively low, it has a very significant effect on improving the activity of CO2 hydrogenation. When the Mg:Cu molar ratio is 0.033, the catalyst hydrogenation performance is the highest, at which time the CO2 conversion rate is 41.83%, the CO selectivity is 7.96%, and the C5 + The selectivity to hydrocarbons was 66.15%.

[0095] As shown in Table 1, it can be seen from the catalysts of Examples 1, 5, 6 and Comparative Example 2 that as the glucose content increases, the CO2 conversion rate and C5 + The selectivity for hydrocarbons first increases and then decreases, while the selectivity for CO first decreases and then increases. The catalyst has the highest hydrogenation performance when the glucose concentration is 2.22 mol / L.

[0096] As shown in Table 1, it can be seen from the catalysts of Example 1 and Comparative Example 4 that, compared with the use of acetaldehyde as a reducing agent, the present application obtained better experimental results when glucose was selected as a reducing agent. The glucose added when preparing the copper-iron-magnesium-based catalyst in the present application not only acts as a reducing agent to reduce Cu2+ Reduction to Cu + , promoting the formation of the Cu-Fe5C2 interface; and facilitating the formation of catalyst pores, increasing the catalyst's specific surface area, obtaining more active sites, and achieving higher catalyst activity. The present application experimentally verified that the specific choice of reducing agent in the preparation of copper-iron-magnesium-based catalysts also has a significant impact on their catalytic activity.

[0097] Table 1 Catalytic CO2 hydrogenation reaction performance

[0098]

[0099] like Figure 1 The graph shows the CO2 conversion rate changes over 24 hours for the catalysts in Comparative Examples 1, 2, and 3, as well as the catalyst in Example 1. As can be seen, the activity of the catalysts in Comparative Examples 1, 2, and 3 first increases and then decreases with reaction time, indicating that these catalysts are not very stable and are prone to deactivation. In contrast, the catalyst in Example 1 is essentially stable after 12 hours, indicating that the addition of glucose and Mg enhances the stability of the copper-iron catalyst.

[0100] The contents described in this specification are merely an enumeration of implementation forms of the inventive concept, and the protection scope of the present invention should not be considered as being limited to the specific forms described in the embodiments.

Claims

1. A copper-iron-magnesium-based catalyst for catalytic CO2 hydrogenation to C5 + Application in hydrocarbons, characterized in that The preparation method of the copper-iron-magnesium based catalyst comprises the following steps: 1) Add Mg salt, Cu salt and Fe salt to deionized water and stir at room temperature to obtain a uniform mixed solution; 2) slowly adding alkaline solution dropwise to the mixed solution in step 1), stirring and reacting under alkaline conditions for 20 to 60 minutes; 3) Slowly add glucose solution dropwise to the suspension in step 2) and stir for 5-20 minutes; 4) transferring the suspension from step 3) to a reactor, and then heating the reactor in an oven at 170-200° C. for 5-15 hours; cooling the reactor, and centrifuging to obtain a product, which is then washed with deionized water and dried to obtain a copper-iron-magnesium-based catalyst; In step 1), the anions of the Mg salt, Cu salt, and Fe salt are all nitrates, the molar ratio of the Mg salt, Cu salt, and Fe salt is 0.016-0.15:1:1.5-2, and the total salt concentration of the mixed solution is 0.2-2 mol / L; In step 3), the molar ratio of the added amount of glucose to the Cu salt is 0.7-1:1, and the concentration of the glucose solution is 2-3 mol / L.

2. The use according to claim 1, characterized in that The total salt concentration of the mixed uniform solution of Mg salt, Cu salt and Fe salt is 0.3~1.0 mol / L.

3. The use according to claim 1, wherein the alkaline solution is an aqueous solution of a strong base with a concentration of 1 to 10 mol / L, and the strong base is one or both of NaOH and KOH.

4. The use according to claim 3, characterized in that The molar ratio of the added amount of the strong base to the Cu salt is 5-25:

1.

5. The use according to claim 4, characterized in that The molar ratio of the added amount of the strong base to the Cu salt is 10-20:

1.

6. The use according to claim 1, characterized in that In step 4), the heating reaction temperature is 180-190°C and the reaction time is 8-9 h.

7. The use according to claim 1, characterized in that The copper-iron-magnesium-based catalyst is filled in a fixed-bed reactor and first reduced and activated for 2-6 hours in a H2 atmosphere at normal pressure and 350-400°C to obtain an activated catalyst. Then, a H2 / CO2 mixed gas with a volume ratio of 2-4:1 is introduced at 300-340°C to catalyze CO2 hydrogenation to produce C5 + Reaction of hydrocarbons; wherein the filling amount of the catalyst is 1g, and the volume of the H2 / CO2 mixed gas introduced is 20-100 mL / min.

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