Modified graphene supported iron-based catalysts, methods of making and using the same

Abstract

The application belongs to the technical field of iron-based catalysts, in particular to a modified graphene supported iron-based catalyst and a preparation method and application thereof, which comprises the following components in the following mass contents: iron oxide 20-60%, modified graphene oxide 10-80%, and an additive 3-20%. The modified graphene oxide is modified by silicon, wherein the mass content of Si in the modified graphene oxide is 2-5%. The additive is selected from the following: an alkali metal additive, an alkaline earth metal additive, a non-metal additive, or a combination of these additives. By loading the active component and the additive on the graphene carrier with a large specific surface area, the dispersion performance of the active component is effectively improved. By modifying the carrier, the interaction between the active component and the carrier is reduced, the interaction between the active component and the additive is further enhanced, the CO2 conversion rate is improved, the selectivity to CO and CH4 is reduced, and the service life of the catalyst is prolonged.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of iron-based catalysts, and particularly relates to a modified graphene-loaded iron-based catalyst and a preparation method and application thereof. BACKGROUND

[0002] CO2 is the most inexpensive and abundant resource in the C1 family, and its storage on the earth is extremely rich. With the continuous development of human society, the use of fossil energy has increased dramatically, and its content in the atmosphere has increased day by day, which not only aggravates the greenhouse effect, but also causes huge waste of carbon resources. It is of great significance to carry out conversion and utilization research to turn waste into treasure, whether from economic benefits or social benefits.

[0003] Patent CN 104624194A provides a preparation method of a carbon dioxide hydrogenation catalyst for low-carbon olefin. The catalyst composition elements are iron, zirconium, potassium and oxygen, and the element content is zirconium / iron at 0-1:1 and iron / potassium at 10:1 in terms of atomic mole ratio. Iron and zirconium are precipitated using a microwave-induced precipitation method, dried and calcined. Then, potassium is impregnated, dried, tabletized, granulated and reduced to obtain a catalyst sample.

[0004] Patent CN 107497437B provides a catalyst for directly preparing low-carbon olefin from CO2 hydrogenation and its application. The catalyst is prepared by adding two or more metal solutions such as cobalt, zinc and copper to an iron ion solution, co-precipitating, inducing slow growth of the crystal of the precipitated product, and inhibiting the agglomeration of the crystal in a low-temperature environment. The finally split and grown crystal is calcined to form an iron-based composite metal oxide catalyst with high specific surface area and high CO2 hydrogenation activity.

[0005] The above-mentioned catalyst system has made good progress in the preparation of low-carbon olefin from CO2 hydrogenation, but there are problems such as low CO2 conversion rate, high CO and methane selectivity, and the stability of the catalyst needs to be further improved. How to efficiently activate chemically stable CO2 is still a problem to be solved in this field. SUMMARY

[0006] According to one aspect of the application, a modified graphene-loaded iron-based catalyst and its application in the synthesis of hydrocarbon compounds from carbon dioxide hydrogenation are provided. By loading the active component and the additive on the graphene carrier with a large specific surface area, the dispersion performance of the active component is effectively improved. By modifying the carrier, the interaction between the active component and the carrier is reduced, the interaction between the active component and the additive is further enhanced, the CO2 conversion rate is improved, the selectivity to CO and CH4 is reduced, and the service life of the catalyst is prolonged.

[0007] In order to achieve the above-mentioned purpose, the technical solutions adopted by the application are as follows:

[0008] A modified graphene supported iron-based catalyst, comprising the following mass content of each component:

[0009] Iron oxide 20-60%, modified graphene oxide 10-80%, and adjuvant 3-20%; preferably, iron oxide 25-55%, modified graphene oxide 15-65%, and adjuvant 5-15%.

[0010] In some technical solutions, the iron oxide mainly consists of Fe2O3; and / or,

[0011] The modified graphene oxide is modified by silicon, wherein the mass content of Si in the modified graphene oxide is 2-5%; and / or,

[0012] The adjuvant is selected from the following group: alkali metal adjuvant, alkaline earth metal adjuvant, non-metal adjuvant, or a combination of these adjuvants.

[0013] In some technical solutions, in the process of synthesizing hydrocarbon compounds by carbon dioxide hydrogenation using the modified graphene supported iron-based catalyst, the reduction conditions are as follows: the reduction gas includes H2 or CO, the pressure is 0.5-1.5 MPa, the space velocity is 5000-15000 h-1, the temperature is 350-450℃, and the reduction time is 10-24 h; the synthesis reaction conditions are as follows: the temperature is 200-400℃, the pressure is 0.5-5 MPa, the space velocity is 1000-15000 h-1, and the H2 / CO2 volume ratio in the raw material gas is (2-4):1. -1 -1 -1

[0014] According to another aspect of the present application, the present application further provides a preparation method of a modified graphene supported iron-based catalyst, which is pollution-free, simple in preparation process, short in operation period, easy to mass industrial production, and more conducive to industrial application.

[0015] In order to achieve the above-mentioned purposes, the technical solutions adopted by the present application are as follows:

[0016] The preparation method of the modified graphene supported iron-based catalyst comprises the following steps:

[0017] ​​​Preparation of modified graphene: graphene oxide is added to anhydrous ethanol and ultrasonic dispersion is performed to obtain a uniform graphene oxide dispersion liquid; a proper amount of tetraethyl orthosilicate or tetramethyl orthosilicate or tetrapropyl orthosilicate is dispersed in anhydrous ethanol, and then added dropwise into the above graphene oxide dispersion liquid, and reacted at 40-70 DEG C for 0.5-2h, and kept under a vacuum degree of-0.02 to-0.08 MPa for 0.5-2h; then kept at a temperature of 80-95 DEG C and a vacuum degree of-0.08 to-0.095 MPa for 0.5-2h to obtain a dried solid; the dried solid is purged under a nitrogen atmosphere at 150-300 DEG C for 3-6h to prepare a silicon-modified graphene carrier;

[0018] Preparation of the catalyst: the silicon-modified graphene carrier obtained above is added to deionized water, ultrasonic dispersion is performed to form a suspension, and stirring is performed for 1-5h; a mixed solution of a soluble iron salt, an alkaline earth metal salt or / and an acid solution of a non-metallic additive is added according to a metering ratio, stirring is performed for 1-2h, the mixed solution is heated to 80-100 DEG C, and a basic precipitator solution is added under the condition of vigorous stirring until the pH value of the mixed solution is 6-8, and the reaction is kept for 1-5h; the above precipitate solution is suction filtered and washed, the obtained solid is vacuum dried, and purged under a nitrogen atmosphere at 350-550 DEG C for 3-6h to prepare a modified graphene supported iron-based catalyst.

[0019] In some technical solutions, the soluble iron salt is selected from ferric nitrate; and / or,

[0020] The alkaline earth metal salt is selected from the following group consisting of magnesium nitrate, calcium nitrate, strontium nitrate or a mixture of these salts; and / or,

[0021] The acid solution of the non-metallic additive is selected from boric acid, phosphoric acid or a mixed solution of the two;

[0022] The basic precipitator is selected from at least one of sodium carbonate and potassium carbonate.

[0023] In some technical solutions, the amount of the tetraethyl orthosilicate or tetramethyl orthosilicate or tetrapropyl orthosilicate is 15-50g / 100g of graphene oxide, and the amount of the anhydrous ethanol is 100-500mL / 100g of graphene oxide.

[0024] The above technical solutions have at least the following beneficial effects:

[0025] 1. The provided catalyst can realize the resource conversion and utilization of CO2 which has an impact on the climate environment, and convert it into high value-added chemicals through hydrogenation treatment, which is of great significance under the current double carbon background;

[0026] 2. Using graphene, with its large specific surface area, as a support can, on the one hand, better disperse and stabilize the active components, thereby improving the catalyst's activity in the CO2 hydrogenation reaction; on the other hand, the abundant oxygen-containing functional groups on the graphene support surface, such as hydroxyl, epoxy, carboxyl, and carbonyl groups, react with tetraethyl or tetramethyl or tetrapropyl or tetraethyl ...

[0027] 3. The catalyst preparation process of this invention is pollution-free, the preparation process is simple and the operation cycle is short, it is easy to carry out large-scale industrial production, and it is more conducive to industrial promotion and application;

[0028] 4. Based on the acid-base synergistic catalytic mechanism, the various co-catalysts involved in this invention effectively regulate the ratio of acidic oxides (B2O3, P2O5) and basic oxides (K2O, Na2O, MgO, CaO, SrO) to control the acid-base ratio on the catalyst surface, achieving a suitable range of interaction with iron active species, effectively inhibiting the carbonization and growth of iron species, avoiding deactivation caused by carbon deposition, and maintaining the high activity and stability of the catalyst;

[0029] 5. When this catalyst is applied to the process of hydrogenating carbon dioxide to synthesize hydrocarbons, the CO2 conversion rate is above 44%, the CH4 selectivity is below 15%, and the α-olefin content in the liquid is above 45%. Detailed Implementation

[0030] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0031] Comparative Example 1

[0032] A mixed solution of 101g Fe(NO3)3·9H2O, 55.6g Mg(NO3)2, and 2.2g boric acid was prepared and heated to 80℃. A 1M sodium carbonate solution was added under vigorous stirring until the pH of the mixed solution reached 6.8. Stirring was continued for 2 hours. The solution was then filtered, washed, and the Na content was controlled by adjusting the degree of washing of the filter cake. The resulting solid was dried at 100℃ for 12 hours under vacuum and then purged at 400℃ for 3 hours under nitrogen purging to obtain the catalyst, designated B-1. Catalyst B-1 contained 78% iron oxide, 15% magnesium oxide, 5% boron oxide, and 2% sodium oxide.

[0033] 3g catalyst B-1, H2 flow at 0.5 MPa, 350°C, space velocity 8000 h-1 -1 under the conditions of 320°C, 1.0 MPa, 10000 h-1 for 12 h, and then the synthesis reaction was carried out -1 The H2 / CO2 volume ratio in the raw material gas was 3. The reaction results are listed in Table 1.

[0034] Comparative Example 2

[0035] First, 25 g of graphene oxide was added to 100 mL of deionized water, ultrasonically dispersed into a suspension, and stirred for 1 h; then a mixed solution of 69.5 g of Fe(NO3)3·9H2O, 55.6 g of Mg(NO3)2, and 2.2 g of boric acid was added, and a 1M sodium carbonate solution was added under the condition of heating to 80°C and vigorous stirring until the pH value of the mixed solution was 6.8. Stirring was continued for 2 h, and the filter cake was washed to control the Na content. The obtained solid was dried under vacuum at 100°C for 12 h, and then purged at 400°C for 3 h under nitrogen blowing to obtain the catalyst, which was recorded as B-2. The iron oxide content in catalyst B-2 was 53%, the graphene oxide content was 25%, the magnesium oxide content was 15%, the boron oxide content was 5%, and the sodium oxide content was 2%.

[0036] 3g catalyst B-2, H2 flow at 0.5 MPa, 350°C, space velocity 8000 h-1 -1 under the conditions of 320°C, 1.0 MPa, 10000 h-1 for 12 h, and then the synthesis reaction was carried out -1 The H2 / CO2 volume ratio in the raw material gas was 3. The reaction results are listed in Table 1.

[0037] Example 1

[0038] 50 g of graphene oxide was added to 100 mL of anhydrous ethanol and ultrasonically dispersed to obtain a uniform graphene oxide dispersion; 10 g of tetraethyl orthosilicate was dispersed in 10 mL of anhydrous ethanol, and then added dropwise to the above graphene oxide dispersion at 60°C for 1 h. The vacuum degree was -0.05 MPa for 0.5 h, and then the vacuum degree was -0.090 MPa at 95°C for about 0.5 h to obtain a dried solid. The dried solid was purged at 180°C for 5 h under a nitrogen atmosphere to obtain a silicon-modified graphene carrier.

[0039] First, 25 g of silicon-modified graphene support was added to 100 mL of deionized water, ultrasonically dispersed into a suspension, and stirred for 1 h; then a mixed solution of 69.5 g of Fe(NO3)3·9H2O, 50.6 g of Mg(NO3)2, and 2.2 g of boric acid was added, heated to 80°C, and 1M sodium carbonate solution was added under vigorous stirring until the pH value of the mixed solution was 6.8, and stirring was continued for 2 h. The filter cake was washed to control the Na content, the obtained solid was dried at 100°C under vacuum for 12 h, and the catalyst was prepared by purging under nitrogen at 400°C for 3 h, which was recorded as FK-1. The iron oxide content in the catalyst FK-1 was 53%, the modified graphene oxide content was 25%, the magnesium oxide content was 10%, the boron oxide content was 5%, and the sodium oxide content was 2%.

[0040] 3 g of catalyst FK-1 was reduced by purging with H2 at 0.5 MPa, 350°C, and a space velocity of 8000 h-1 for 12 h. After reduction, the synthesis reaction was carried out under the conditions of 320°C, 1.0 MPa, and a space velocity of 10000 h-1, and the H2 / CO2 volume ratio in the raw material gas was 3. The reaction results are shown in Table 1. -1 -1 After reduction, the synthesis reaction was carried out under the conditions of 320°C, 1.0 MPa, and a space velocity of 10000 h-1, and the H2 / CO2 volume ratio in the raw material gas was 3. The reaction results are shown in Table 1.

[0041] Example 2

[0042] 50 g of graphene oxide was added to 150 mL of anhydrous ethanol and ultrasonically dispersed to obtain a uniform graphene oxide dispersion. 22 g of tetraethyl orthosilicate was dispersed in 10 mL of anhydrous ethanol, and then added dropwise to the above graphene oxide dispersion. The reaction was carried out at 50°C for 1.5 h, and then the vacuum degree was maintained at -0.04 MPa for 1 h. Subsequently, the vacuum degree was maintained at -0.092 MPa at 90°C for about 1 h to obtain a dried solid. The silicon-modified graphene support was obtained by purging under nitrogen at 250°C for 3 h.

[0043] First, 40 g of silicon-modified graphene support was added to 100 mL of deionized water, ultrasonically dispersed into a suspension, and stirred for 2 h; then a mixed solution of 50.5 g of Fe(NO3)3·9H2O, 38.1 g of Ca(NO3)2, and 1.3 g of boric acid was added, heated to 80°C, and 1M potassium carbonate solution was added under vigorous stirring until the pH value of the mixed solution was 7.5, and stirring was continued for 1.5 h. The filter cake was washed to control the K content, the obtained solid was dried at 100°C under vacuum for 12 h, and the catalyst was prepared by purging under nitrogen at 350°C for 5 h, which was recorded as FK-2. The iron oxide content in the catalyst FK-2 was 40%, the modified graphene oxide content was 40%, the calcium oxide content was 13%, the boron oxide content was 3%, and the potassium oxide content was 4%.

[0044] ​3g catalyst FK-2, CO was introduced at 0.5 MPa, 400℃, space velocity 10000 h -1 under the condition, reduction was carried out for 15 h, after reduction was completed, synthesis reaction was carried out, reaction condition was 330℃, 1.5 MPa, 12000 h -1 , H2 / CO2 volume ratio in raw material gas was 3. Reaction result is listed in Table 1.

[0045] Example 3

[0046] 50 g of graphene oxide was added into 120 mL of anhydrous ethanol, ultrasonic dispersion was carried out, and uniform graphene oxide dispersion liquid was obtained; 8 g of tetraethyl orthosilicate was dispersed into 10 mL of anhydrous ethanol, and then was added drop by drop into the above graphene oxide dispersion liquid, reaction was carried out at 55℃ for 2 h, under the condition of vacuum degree-0.072 MPa, 1 h was maintained, then under the condition of vacuum degree-0.088 MPa at 90℃, about 2 h was maintained, dry solid was obtained, and under nitrogen atmosphere, 6 h was blown at 220℃, and silicon modified graphene carrier was obtained;

[0047] 35 g of silicon modified graphene carrier was first added into 100 mL of deionized water, ultrasonic dispersion was carried out into suspension, and stirring was carried out for 2 h; then a mixed solution of 65.6 g of Fe(NO3)3·9H2O, 33.4 g of Sr(NO3)2, and 0.7 g of phosphoric acid was added, 1M potassium carbonate solution was added under the condition of heating to 80℃ and vigorous stirring, until the pH value of the mixed solution was 7.2, stirring was continuously maintained for 2 h, suction filtration and washing were carried out, K content was controlled by controlling the washing degree of filter cake, the obtained solid was dried under vacuum condition at 100℃ for 12 h, and under nitrogen blowing, 4 h was blown at 300℃, and catalyst was prepared, which was recorded as FK-3. The content of iron oxide in catalyst FK-3 was 52%, the content of modified graphene oxide was 35%, the content of magnesium oxide was 8%, the content of diaphosphorus pentoxide was 2%, and the content of potassium oxide was 2%.

[0048] 3g catalyst FK-3, CO was introduced at 0.5 MPa, 370℃, space velocity 6000 h -1 under the condition, reduction was carried out for 20 h, after reduction was completed, synthesis reaction was carried out, reaction condition was 320℃, 2.0 MPa, 8000 h -1 , H2 / CO2 volume ratio in raw material gas was 3.5. Reaction result is listed in Table 1.

[0049] Example 4

[0050] The 50 g of graphene oxide was added to 125 mL of anhydrous ethanol and ultrasonically dispersed to obtain a uniform graphene oxide dispersion; 18 g of tetraethyl orthosilicate was dispersed in 10 mL of anhydrous ethanol and then added dropwise to the graphene oxide dispersion, and the mixture was reacted at 45°C for 2 h, maintained at a vacuum of -0.06 MPa for 0.5 h, and then maintained at a vacuum of -0.095 MPa at 85°C for about 2 h to obtain a dried solid, which was purged under a nitrogen atmosphere at 280°C for 3 h to obtain a silicon-modified graphene support;

[0051] The 50 g of graphene oxide was added to 125 mL of anhydrous ethanol and ultrasonically dispersed to obtain a uniform graphene oxide dispersion; 18 g of tetraethyl orthosilicate was dispersed in 10 mL of anhydrous ethanol and then added dropwise to the graphene oxide dispersion, and the mixture was reacted at 45°C for 2 h, maintained at a vacuum of -0.06 MPa for 0.5 h, and then maintained at a vacuum of -0.095 MPa at 85°C for about 2 h to obtain a dried solid, which was purged under a nitrogen atmosphere at 280°C for 3 h to obtain a silicon-modified graphene support;

[0052] 3 g of the catalyst FK-4 was reduced by introducing CO at 1.0 MPa, 350°C, and a space velocity of 6000 h -1 for 20 h, and after reduction was complete, a synthesis reaction was performed under the conditions of 340°C, 1.5 MPa, and a space velocity of 6000 h -1 , with a H2 / CO2 volume ratio of 3.0 in the raw material gas. The reaction results are shown in Table 1.

[0053] Table 1 Reaction activity and selectivity of the catalyst for the synthesis of light hydrocarbons from CO2 hydrogenation

[0054]

[0055] In addition, under the reaction conditions of 320°C, 2.0 MPa, and a space velocity of 8000 h -1 , with a H2 / CO2 volume ratio of 3.5 in the raw material gas, the long-term life of the catalyst FK-3 of Example 3 was further investigated, and the cumulative evaluation time exceeded 1000 h. At 500 h, the CO2 conversion rate of the catalyst was 43.1%, the CO selectivity was 9.2%, the CH4 selectivity was 13.3%, the C2-C4 selectivity was 30.0%, and the C 5+Hydrocarbon selectivity 56.7%, alpha-olefin content in liquid 49.7%; CO2 conversion of the catalyst 40.8%, CO selectivity 11.2%, CH4 selectivity 14.3%, C2-C4 selectivity 34.0%, C5-C12 selectivity 40.3% at 1000 h. 5+ Hydrocarbon selectivity 51.7%, alpha-olefin content in liquid 48.9%. The catalyst has good life stability.

[0056] The above described embodiments only express several embodiments of the present application, which are described in more detail and in more detail, but cannot be understood as limiting the scope of the patent of the present application. It should be noted that for ordinary skilled in the art, without departing from the concept of the present application, several modifications and improvements can be made, which belong to the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the appended claims.

Claims

1. A modified graphene supported iron-based catalyst, characterized in that, Each component comprises the following mass content: Iron oxide 20-60%, modified graphene oxide 10-80%, and auxiliary agent 3-20%, the sum of the content of each component being 100%; The preparation steps of the modified graphene are as follows: graphene oxide is added to anhydrous ethanol and ultrasonic dispersion is performed to obtain a uniform graphene oxide dispersion solution; a proper amount of tetraethyl orthosilicate or tetramethyl orthosilicate or tetrapropyl orthosilicate is dispersed in anhydrous ethanol, and then added dropwise into the above graphene oxide dispersion solution; after sufficient reaction, a silicon-modified graphene carrier is obtained by drying. The specific process of the silicon-modified graphene carrier after sufficient reaction and drying is as follows: The reaction is carried out at 40-70℃ for 0.5-2h, and maintained at a vacuum degree of-0.02~-0.08MPa for 0.5-2h; then maintained at a temperature of 80-95℃ and a vacuum degree of-0.08~-0.095MPa for 0.5-2h to obtain a dried solid; the obtained dried solid is purged at 150-300℃ under a nitrogen atmosphere for 3-6h to prepare the silicon-modified graphene carrier. The auxiliary agent comprises an alkali metal auxiliary agent, an alkaline earth metal auxiliary agent, and a non-metal auxiliary agent, wherein the non-metal auxiliary agent is derived from an acid solution of boric acid, phosphoric acid, or a mixture of the two.

2. The iron-based catalyst according to claim 1, characterized in that, The mass composition of the iron-based catalyst is: iron oxide 25-55%, modified graphene oxide 15-65%, and auxiliary agent 5-15%, the sum of the content of each component being 100%.

3. The iron-based catalyst according to claim 1, characterized in that, The iron oxide mainly consists of Fe2O3.

4. The method of producing a modified graphene supported iron-based catalyst according to any one of claims 1 to 3, wherein The preparation method comprises the following steps: Preparation of modified graphene: graphene oxide is added to anhydrous ethanol and ultrasonic dispersion is performed to obtain a uniform graphene oxide dispersion solution; a proper amount of tetraethyl orthosilicate or tetramethyl orthosilicate or tetrapropyl orthosilicate is dispersed in anhydrous ethanol, and then added dropwise into the above graphene oxide dispersion solution; after sufficient reaction, a silicon-modified graphene carrier is obtained by drying. Preparation of the catalyst: the obtained silicon-modified graphene carrier is added to deionized water, ultrasonic dispersion is performed to form a suspension, and stirring is performed; a mixed solution of a soluble iron salt, an alkaline earth metal salt, and an acid solution of a non-metal auxiliary agent is added according to a metering ratio, heated, and added with a proper amount of an alkaline precipitator solution under stirring conditions, and fully reacted under a suitable pH value; the obtained precipitate solution is suction filtered, washed, and the obtained solid is vacuum dried to prepare a modified graphene-loaded iron-based catalyst.

5. The preparation method according to claim 4, characterized in that, In the preparation step of the modified graphene, the specific process of the silicon-modified graphene carrier after sufficient reaction and drying is as follows: reacting at 40-70℃ for 0.5-2h and keeping vacuum degree at -0.02~-0.08MPa for 0.5-2h; then keeping temperature at 80-95℃ and vacuum degree at -0.08~-0.095MPa for 0.5-2h to obtain dried solid; and purging the dried solid at 150-300℃ under nitrogen atmosphere for 3-6h to obtain silicon-modified graphene carrier; The preparation steps of the catalyst are specifically as follows: The silicon-modified graphene carrier obtained above is added into deionized water, ultrasonically dispersed into a suspension, and stirred for 1-5h; a mixed solution prepared by adding soluble iron salt, alkaline earth metal salt and acid solution of non-metallic additive is added according to a metering ratio, stirred for 1-2h, heated to 80-100℃, and a basic precipitator solution is added under the condition of intense stirring until the pH value of the mixed solution is 6-8, and the reaction is kept for 1-5h; the above precipitated solution is suction filtered and washed, the obtained solid is vacuum dried, and purged at 350-550℃ under nitrogen atmosphere for 3-6h to obtain modified graphene supported iron-based catalyst.

6. The preparation method according to claim 4, characterized in that, the soluble iron salt is selected from ferric nitrate; and / or, the alkaline earth metal salt is selected from the group consisting of magnesium nitrate, calcium nitrate, strontium nitrate or a mixture of these salts; and / or, the basic precipitator is selected from at least one of sodium carbonate and potassium carbonate.

7. The preparation method according to claim 4, characterized in that, the amount of tetraethyl orthosilicate or tetramethyl orthosilicate or tetrapropyl orthosilicate is 15-50g / 100g graphene oxide, and the amount of anhydrous ethanol is 100-500mL / 100g graphene oxide.

8. Use of a modified graphene supported iron-based catalyst according to any one of claims 1 to 3, characterized in that, used as a catalyst in the process of synthesizing hydrocarbon compounds by carbon dioxide hydrogenation.

9. The use according to claim 8, characterized in that, In the process of synthesizing hydrocarbon compounds by carbon dioxide hydrogenation using modified graphene supported iron-based catalyst, the reduction conditions are: the reduction gas includes H2 or CO, the pressure is 0.5-1.5 MPa, the space velocity is 5000-15000 h -1 -15000 h -1 , the temperature is 350-450℃, the reduction time is 10-24h; the synthesis reaction conditions are: the temperature is 200-400℃, the pressure is 0.5-5 MPa, the space velocity is 1000-15000 h -1 , and the volume ratio of H2 / CO2 in the raw material gas is (2-4):

1.

10. The use according to claim 9, characterized in that, the CO2 conversion rate of the process of synthesizing hydrocarbon compounds by carbon dioxide hydrogenation is above 44%, the CH4 selectivity is below 15%, and the content of α-olefins in the liquid is above 45%.

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