Methods for producing heavy hydrocarbons by hydrogenation of carbon dioxide

Abstract

The present application relates to a kind of heavy hydrocarbon of carbon dioxide hydrogenation method, it includes the following steps: carbon dioxide is completed in the presence of hydrogen, carbon dioxide and catalyst and makes heavy hydrocarbon hydrogenation reaction;Wherein, the catalyst includes carrier, active metal and adjuvant, the carrier is silicon nitride;The active metal is iron;The adjuvant is potassium.The carbon dioxide hydrogenation method provided by the present application has high carbon dioxide conversion rate, good carbon monoxide selectivity and product selectivity, and has better technical effect compared with other methods of prior art.

Description

Technical Field

[0001] This invention relates to the field of catalytic reaction technology, and more specifically, to a method for producing heavy hydrocarbons by hydrogenation of carbon dioxide. Background Technology

[0002] The continued global consumption of fossil fuels is exacerbating the greenhouse effect, causing negative and even irreversible impacts on the climate. Therefore, it is imperative to reduce atmospheric CO2 concentrations. Developing efficient carbon resource processing and utilization plays a significant role in reducing CO2 emissions, mitigating the greenhouse effect, and lowering overall carbon emissions. Hydrogenating CO2 into high-value fuels and chemicals through processes such as thermocatalysis, electrocatalysis, or photocatalysis reduces greenhouse gas emissions and fossil resource consumption. The efficient conversion and utilization of the greenhouse gas carbon dioxide to produce hydrocarbon products is of great importance in alleviating the pressure of the oil resource crisis.

[0003] Carbon dioxide hydrogenation readily produces C1 products such as CO and CH4, while the preparation of C2+ products via C-C coupling presents significant challenges, making the development of highly efficient catalysts a major hurdle. Currently, iron-based catalysts, possessing both Fe3O4 and Fe5C2 phases, are considered suitable for CO2 hydrogenation to hydrocarbon products. It is generally believed that CO2 hydrogenation to C2+ hydrocarbons on iron-based catalysts involves two main steps: the reverse water-gas shift reaction (CO2 + H2 → CO + H2O) and CO hydrogenation to hydrocarbons (CO + H2 → -(CH2)- + H2O). However, single Fe catalysts exhibit weak CO2 adsorption, resulting in a low CO2 / H2 ratio on the catalyst surface, leading to continuous hydrogenation to CH4 rather than C2+ products. This study explored the use of various promoters to improve the selectivity of C2+ olefins on iron-based catalysts. Alkali metals (such as Na, K) or non-metallic elements (such as N, S) were added to modify the reducing and carbonization properties of Fe catalysts. Furthermore, the support is also a key factor affecting catalyst performance, as it can effectively anchor metals and improve metal dispersion, thus significantly enhancing catalyst performance. Therefore, selecting a suitable support is of paramount importance.

[0004] Chinese invention patent application publication CN111185180A discloses a method for preparing a single-walled carbon nanotube supported iron-potassium catalyst and its application in the hydrogenation of carbon dioxide to produce high-carbon olefins. Under certain conditions, the catalyst achieves a CO2 conversion rate of over 62% and a carbon hydrocarbon selectivity of over 62%. However, there is a strong interaction between the support and the metal, which makes it difficult for the metal to be reduced and carbonized.

[0005] The literature (Ru catalysts supported by Si3N4 for Fischer-Tropsch synthesis, Applied Surface Science, 2020, 526, 146631) uses silicon nitride as a Ru-based catalyst for the Fischer-Tropsch reaction. Compared with SiO2 support, silicon nitride has less interaction with the metal active phase and higher metal dispersion, exhibiting excellent catalytic performance. However, silicon nitride has a low specific surface area, limiting its metal dispersion.

[0006] Patent ZL201810088867.5 provides a catalyst for carbon dioxide hydrogenation to oil production. This catalyst has high selectivity for C2-C4 olefins and C5+ hydrocarbons at low temperatures, but the carbon dioxide conversion rate is low, and the additive is Pd, which results in high cost. Summary of the Invention

[0007] In order to overcome the problems existing in the prior art, the inventors of this invention have conducted extensive and in-depth research and provided a method for producing heavy hydrocarbons by hydrogenating carbon dioxide. By using a Fe-based catalyst for producing heavy hydrocarbons by hydrogenating carbon dioxide with high surface area silicon nitride as support and K as an auxiliary agent, the carbon dioxide conversion rate is high and the selectivity of heavy hydrocarbons is good.

[0008] To achieve the above objectives, the present invention provides a method for producing heavy hydrocarbons by hydrogenation of carbon dioxide, comprising the steps of: hydrogenating carbon dioxide to heavy hydrocarbons in the presence of hydrogen, carbon dioxide, and a catalyst; wherein the catalyst comprises a support, an active metal, and an auxiliary agent. The support is silicon nitride; the active metal is iron; and the auxiliary agent is potassium.

[0009] In this invention, heavy hydrocarbons refer to C5+ hydrocarbons.

[0010] According to the present invention, in the silicon nitride carrier, the proportion of macropores with a pore size greater than 50 nm is 1% to 5% relative to all pores in the silicon nitride carrier, the proportion of mesopores with a pore size of 2 to 50 nm is 95% to 99%, and the porosity of the silicon nitride carrier is 50% to 95%.

[0011] In some embodiments of the present invention, the specific surface area of ​​the carrier is not less than 300 m². 2 / g, more preferably 400-700m 2 / g, for example 400m 2 / g、500m 2 / g、550m 2 / g、580m 2 / g、600m 2 / g、650m 2 / g、700m 2 / g.

[0012] In some embodiments of the present invention, the method for preparing the silicon nitride support includes the following steps:

[0013] (1) Under normal pressure, inert atmosphere and low temperature of 0-10℃, the silicon precursor is dispersed in an organic solvent. While stirring, a reaction gas is introduced into the solvent and reacts with the silicon precursor to obtain a silicon nitride precursor solution. The reaction gas is ammonia or a mixture of ammonia and an inert gas.

[0014] (2) The silicon nitride precursor solution is centrifuged to obtain the silicon nitride precursor;

[0015] (3) The silicon nitride precursor is subjected to high-temperature pyrolysis in a flowing oxygen-free atmosphere at 400-1800°C to obtain the silicon nitride support.

[0016] In some embodiments of the present invention, in step (1) above, the low temperature condition is 2 to 10°C.

[0017] In some embodiments of the present invention, in step (1) above, the silicon precursor may be one or more of silicon chloride (also known as "silicon tetrachloride"), silicon fluoride (also known as "silicon tetrafluoride"), silicon bromide (also known as "silicon tetrabromide"), silicon iodide (also known as "silicon tetraiodide"), and silimide. In some preferred embodiments, in step (a) above, the silimide is prepared by ammonolysis of silicon halide.

[0018] In some embodiments of the present invention, in step (1) above, the organic solvent may be one or more of n-alkanes, cycloalkanes, and aromatic hydrocarbons. Examples of n-alkanes include n-pentane, n-hexane, n-heptane, or n-octane; examples of cycloalkanes include cyclopentane or cyclohexane; and examples of aromatic hydrocarbons include toluene or xylene, but are not limited thereto.

[0019] In some embodiments of the present invention, in step (1) above, the inert gas may be one or more of nitrogen, helium, neon, and argon, but is not limited to these.

[0020] In some embodiments of the present invention, in step (1) above, the mass ratio of the silicon precursor to the organic solvent is 1:(1-30), preferably 1:(2.5-25).

[0021] In some embodiments of the present invention, in step (1) above, the reaction gas is a mixture of ammonia and an inert gas, wherein the volume ratio of ammonia to inert gas is (0.1-10):1, preferably (0.5-8):1.

[0022] In some embodiments of the present invention, in step (1) above, the reaction is carried out at a temperature of 0 to 10°C, preferably 2 to 8°C (e.g., 2°C, 3°C, 4°C, 5°C, 6°C, 7°C, 8°C).

[0023] In some embodiments of the present invention, in step (3) above, the oxygen-free atmosphere can be one or more of ammonia, inert gases (e.g., nitrogen, helium, neon, argon), and hydrogen. In this document, the volume ratio of ammonia to inert gas can be any ratio, such as 10:90, 20:80, 50:50, or 80:20. In other, more preferred embodiments, the volume ratio of hydrogen to inert gas can be (1-100):100, preferably (5-50):100, more preferably (5-15):100, and the volume ratio of ammonia to inert gas can be (0.1-10):1, preferably (0.4-4):1, more preferably (0.6-1.5):1.

[0024] In some embodiments of the present invention, in step (3) above, the temperature of the high-temperature pyrolysis is 600 to 1400°C, preferably 800 to 1100°C, for example 800°C, 900°C, 1000°C, or 1100°C.

[0025] In some embodiments of the present invention, in step (3) above, the specific surface area of ​​the silicon nitride support is not less than 300 m². 2 / g, more preferably 400-700m 2 / g, for example 400m 2 / g、500m 2 / g、550m 2 / g、580m 2 / g、600m 2 / g、、650m 2 / g, 700m 2 / g.

[0026] In some embodiments of the present invention, in step (3) above, the high-temperature pyrolysis is roasting.

[0027] In some embodiments of the present invention, the mass ratio of the active metal to the support in the catalyst is (5-50):100, preferably (5-30):100.

[0028] In some embodiments of the present invention, the mass ratio of the adjuvant to the carrier is (0.1-5):100, preferably (0.5-3):100.

[0029] In some embodiments of the present invention, the specific surface area of ​​the catalyst is 400–700 m². 2 / g.

[0030] In some embodiments of the present invention, the dispersion of the active metal in the catalyst is 30%–90%; the metal particle size of the catalyst is 1.5–4.0 nm. In the present invention, the dispersion of the active metal in the catalyst can be 40%–50%.

[0031] The catalyst of this invention utilizes the excellent thermal conductivity, high specific surface area, and anchoring effect of silicon nitride to greatly improve metal dispersion and reduce metal particle size, thereby enabling the silicon nitride-supported catalyst of this invention to have high dispersion, high metal utilization, high catalytic activity, and selectivity for the target product.

[0032] The catalyst of this invention exhibits the characteristic of easy reduction and carbonization, which can improve reaction activity and target product selectivity. At the same time, the catalyst exhibits good wear resistance and high hydrothermal stability, which is beneficial to enhancing the stability of the catalytic reaction.

[0033] In this invention, active metals and additives can be anchored on the surface of a carrier by methods such as impregnation, co-precipitation, chemical vapor deposition, and precipitation deposition.

[0034] In some embodiments of the present invention, the method for preparing the catalyst includes the following steps:

[0035] S1. Provide catalyst precursor I containing an active metal source and the support; provide catalyst precursor II containing a potassium source;

[0036] S2. The catalyst precursor I is subjected to a first calcination treatment to obtain catalyst intermediate I;

[0037] S3. Mix the catalyst precursor II and the catalyst intermediate I, and dry them to obtain catalyst intermediate II;

[0038] S4. The catalyst intermediate II is subjected to a second calcination treatment to obtain the catalyst.

[0039] In some embodiments of the present invention, in step S1, the active metal source is selected from one or more of ferric nitrate (preferably ferric nitrate nonahydrate), ferric chloride (preferably ferric chloride hexahydrate), ferrous chloride, ferrous acetate, ferric ammonium oxalate trihydrate, and ferric ammonium citrate.

[0040] In some embodiments of the present invention, the potassium source is selected from soluble potassium salts; preferably, the soluble potassium salt is selected from one or more of potassium sulfate, potassium nitrate, potassium carbonate and potassium chloride.

[0041] In this invention, after anchoring an active metal source onto the surface of a silicon nitride support to obtain catalyst precursor I, it is dried at 40–180°C to obtain catalyst precursor I. Preferably, the drying can be carried out in air, an inert atmosphere, or a vacuum, and the drying time is 4–24 hours. Similarly, after obtaining catalyst precursor II containing an auxiliary source, it is dried at 40–180°C.

[0042] In some embodiments of the present invention, in step S2, the conditions for the first calcination treatment include: a temperature of 300°C to 900°C; a time of 1 to 12 hours; preferably, the first calcination treatment is carried out in an inert gas atmosphere; preferably, the inert gas is selected from one or more of nitrogen, argon, neon, and helium.

[0043] In some embodiments of the present invention, in step S3, the drying conditions include: a temperature of 40°C to 180°C; and a time of 4 to 24 hours. Preferably, the drying process can be carried out in air, an inert gas atmosphere, or a vacuum.

[0044] In some embodiments of the present invention, in step S4, the conditions for the second calcination treatment include: a temperature of 300°C to 900°C, preferably 300°C to 600°C; and a time of 1 to 12 hours.

[0045] In some embodiments of the present invention, the molar ratio of hydrogen to carbon dioxide is 1 to 4:1.

[0046] In some embodiments of the present invention, the conditions for the hydrogenation reaction include: a reaction temperature of 200°C to 500°C, preferably 260°C to 400°C; and a space velocity of 1000-20000 NL kg. -1 ·1 -1 Preferably 2000-10000 NLkg -1 ·1 -1 The pressure is 0.1–5 MPa, preferably 1–4 MPa.

[0047] In some embodiments of the present invention, the catalyst is activated before the hydrogenation reaction is carried out.

[0048] In some embodiments of the present invention, the activation treatment conditions include: the activation atmosphere being hydrogen, carbon monoxide, or synthesis gas; wherein the molar ratio of hydrogen to carbon monoxide in the synthesis gas is (1-500):1, preferably (1-200):1;

[0049] The activation pressure is 0.1–4 MPa, preferably 0.1–3 MPa;

[0050] The activation temperature is 200℃~800℃, preferably 250℃~600℃;

[0051] The activation time is 2 to 48 hours, preferably 6 to 48 hours.

[0052] In this invention, the catalyst is activated and reduced before the hydrogenation reaction to generate metal active sites.

[0053] According to the present invention, the reaction process of carbon dioxide hydrogenation to carbon monoxide can be analyzed online by gas chromatography to monitor the reaction.

[0054] In some embodiments of the present invention, the method for producing heavy hydrocarbons by carbon dioxide hydrogenation includes the following steps: granulating the catalyst obtained by the above preparation method to obtain catalyst particles of 20-40 mesh; then placing 0.1-1 g of catalyst in the isothermal zone of a fixed-bed reactor, with quartz sand filling both sides; activating the catalyst with hydrogen or syngas at 250-600°C and 0.1-3 MPa for 2-48 h; after activation, lowering the temperature to 100°C; switching the gas to an H2 / CO2 mixture with a molar ratio of 3; reacting at a pressure of 0.1-5 MPa and a temperature of 200-500°C; and analyzing the product composition online using gas chromatography.

[0055] Compared with existing technologies, the method for producing heavy hydrocarbons by carbon dioxide hydrogenation provided by this invention has a high carbon dioxide conversion rate, good selectivity for carbon monoxide and products, and has better technical effects than other existing methods. Attached Figure Description

[0056] Figure 1 The XRD pattern of the catalyst Exam-2 prepared in Example 2 of this invention is shown;

[0057] Figure 2 The TEM image of the catalyst Exam-2 prepared in Example 2 of this invention is shown.

[0058] Figure 3 The reaction activity curve of the catalyst Exam-1 prepared in Example 1 of the present invention as a function of time is shown. Detailed Implementation

[0059] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0060] In this invention, unless otherwise stated, the terms "active component", "active phase metal" and "metal active phase" are used interchangeably and all refer to the metal component of the active phase used as a hydrogenation catalyst.

[0061] In this invention, unless otherwise stated, the term "grain size" refers to the size of the crystalline particles of the catalyst, which can be determined by scanning electron microscopy or transmission electron microscopy, but is not limited thereto.

[0062] In this invention, unless otherwise stated, the term "atmospheric pressure" refers to one standard atmosphere.

[0063] In the following examples, the composition of the catalyst obtained is such as 10Fe0.5K / SiN, where 10 indicates that the iron content is 10wt% of the silicon nitride support mass, and 0.5 indicates that the potassium content is 0.5wt% of the silicon nitride support mass.

[0064] The present invention will be described in detail below through embodiments, but the scope of protection of the present invention is not limited to the following description.

[0065] In this invention, the specific surface area is determined using the BET method (Brubauer-Emmet-Teller), as described in, for example, the standard NFX11-62.

[0066] In this invention, the method for determining the dispersity can include CO chemisorption, H2 chemisorption, hydrogen-oxygen titration, TEM, etc., but is not limited to these. In the following examples, the dispersity was determined by TEM.

[0067] In this invention, the method for calculating the selectivity of CO is as follows:

[0068]

[0069] In the formula, n(CO) out () indicates the amount of CO in the exhaust gas; This indicates the amount of CO2 in the raw gas. This indicates the amount of CO2 in the exhaust gas.

[0070] In this invention, the CO2 conversion rate is calculated as follows:

[0071]

[0072] In the formula, This indicates the amount of CO2 in the raw gas. This indicates the amount of CO2 in the exhaust gas.

[0073] Unless otherwise specified in the examples, the conditions shall be performed under conventional conditions or conditions recommended by the manufacturer. Raw materials, reagents, or instruments whose manufacturers are not specified are all commercially available products or prepared according to publicly disclosed methods.

[0074] In the following embodiments, the specific surface area is 500 m². 2 The preparation method of / g silicon nitride is as follows:

[0075] (1) Replace the air in the 2000mL three-necked flask with argon, and then weigh 900g of n-heptane and 280g of silicon tetrachloride and place them in the three-necked flask under normal pressure and 4℃ to obtain a mixture.

[0076] (2) While mechanically stirring, ammonia (50 mL / min) and Ar (10 mL / min) were introduced into the mixture from step (1). The mechanical stirring rate was 400 r / min. The mixture was reacted with silicon tetrachloride at 4 °C for 36 h to obtain a silicon nitride precursor solution.

[0077] (3) After the reaction is complete, the silicon nitride precursor solution generated in step (2) is centrifuged at a speed of 8000 r / min to obtain the silicon nitride precursor.

[0078] (4) The silicon nitride precursor was loaded into a high-temperature tube furnace, and 5% H2 / 95% N2 (volume ratio, flow rate 300 mL / min) was introduced. The furnace was then calcined at 1200 °C for 2 hours to obtain a silicon nitride precursor with a specific surface area of ​​500 m². 2 / g of silicon nitride support; wherein, macropores with a pore size greater than 50nm account for 4.0%, and mesopores with a pore size of 2-50nm account for 96.0%; the porosity of the silicon nitride support is 91.0%.

[0079] In the following embodiments, the specific surface area is 700 m². 2 The preparation method of / g silicon nitride is as follows:

[0080] (1) Replace the air in the 2000mL three-necked flask with argon, and then weigh 900g of n-pentane and 100g of silicon tetrachloride and place them in the three-necked flask under normal pressure and 5℃ to obtain a mixture.

[0081] (2) While mechanically stirring, ammonia (50 mL / min) and Ar (10 mL / min) are introduced into the mixture from step (1). The mechanical stirring rate is 500 r / min. The mixture is reacted with silicon tetrachloride at 5 °C for 24 h to obtain a silicon nitride precursor solution.

[0082] (3) After the reaction is complete, the silicon nitride precursor solution generated in step (2) is centrifuged at a speed of 10000 r / min to obtain the silicon nitride precursor.

[0083] (4) The silicon nitride precursor was loaded into a high-temperature tube furnace, ammonia gas was introduced (flow rate of 300 mL / min), and calcined at 800 °C for 2 h to obtain a specific surface area of ​​700 m². 2 / g of silicon nitride support; wherein, macropores with a pore size greater than 50nm account for 1.3%, and mesopores with a pore size of 2-50nm account for 98.7%; the porosity of the silicon nitride support is 94.6%.

[0084] In the following examples, fumed silica was purchased from Aladdin, CAS: 112945-52-5.

[0085] Example 1

[0086] In this embodiment, the preparation method of the catalyst includes the following steps:

[0087] (1) Weigh 4.02g of ferric nitrate nonahydrate and place it in a container. Add 60mL of anhydrous ethanol and dissolve it completely to prepare an iron salt solution.

[0088] (2) Then weigh 5g of silicon nitride (500m 2 Place the carrier in a beaker, add the iron salt solution dropwise onto the carrier, stir well, and let stand for 24 hours;

[0089] (3) The beaker from step (2) above was placed in an oven at 120°C and dried for 12 hours to obtain catalyst precursor I;

[0090] (4) Place catalyst precursor I in a tube furnace, introduce argon gas, program the temperature to 400℃, hold for 5 hours for calcination, and then cool naturally to room temperature to obtain catalyst intermediate I.

[0091] (5) Weigh 0.065g of potassium nitrate into a beaker, add 45ml of anhydrous ethanol, dissolve it completely, and prepare a potassium salt solution.

[0092] (6) Place catalyst intermediate I in a beaker, add potassium salt solution dropwise into it, stir evenly, and let stand for 24 hours;

[0093] (7) The beaker from step (6) above was placed in an oven at 120°C and dried for 12 hours to obtain catalyst intermediate II;

[0094] (8) Catalyst intermediate II was placed in a tube furnace, argon gas was introduced, the temperature was programmed to 400℃, and it was calcined for 5 hours. After cooling naturally to room temperature, the sample was taken out to obtain the iron-potassium metal catalyst with the composition 10Fe0.5K / SiN, denoted as Exam-1.

[0095] The relevant parameters of catalyst Exam-1 are shown in Table 1 below.

[0096] The method for producing heavy hydrocarbons by carbon dioxide hydrogenation in this embodiment includes the following steps:

[0097] The catalyst Exam-1 obtained by the above preparation method was granulated to obtain catalyst particles of 20-40 mesh. Then, 1g of catalyst was placed in the isothermal zone of a fixed-bed reactor, with quartz sand filling both sides. The catalyst was activated for 24h at 280℃ and 0.1MPa using H2 / CO with a molar ratio of 10. After activation, the temperature was lowered to 100℃, and the gas was switched to a H2 / CO2 mixture with a molar ratio of 3. The reaction pressure was 3MPa, the reaction temperature was 340℃, and the reaction was carried out at 2000NL·kg⁻¹. -1 ·h -1 The CO2 hydrogenation reaction is carried out below.

[0098] The product composition was analyzed online using gas chromatography. The activity and selectivity results of the hydrogenation reaction are shown in Table 2 below. The hydrogenation reaction of this embodiment was continuously carried out, and the reaction activity versus time curves are shown below. Figure 3 As shown, the reactivity of catalyst Exam-1 did not change significantly, indicating that the catalyst exhibits good anti-wear ability and high hydrothermal stability.

[0099] Example 2

[0100] In this embodiment, the preparation method of the catalyst includes the following steps:

[0101] (1) Weigh 15.50g of ferric nitrate nonahydrate and dissolve it in 60mL of ethanol to form a metal precursor solution;

[0102] (2) Weigh 5g of silicon nitride (500m) 2 / g) The metal precursor solution was dropped onto the carrier and stirred until homogeneous, then allowed to stand for 24 hours.

[0103] (3) Place the sample obtained in step (2) above in an oven at 80°C and dry the sample for 1 hour;

[0104] (4) Place the sample obtained in step (3) in a tube furnace and introduce 10% ammonia / nitrogen (volume ratio) at a flow rate of 100 mL / min for 8 hours.

[0105] (5) Take out the sample from step (4), wash it with ethanol, and dry it in an oven at 100°C for 24 hours to obtain catalyst precursor I;

[0106] (6) Place catalyst precursor I in a tube furnace, heat it to 500°C under a nitrogen atmosphere, and calcine it at that temperature for 5 hours to obtain catalyst intermediate I;

[0107] (7) Weigh 0.130g of potassium nitrate into a beaker, add 45ml of anhydrous ethanol, dissolve it completely, and prepare a potassium salt solution.

[0108] (8) Then, place catalyst intermediate I in a beaker, add potassium salt solution dropwise into it, stir evenly, and let stand for 24 hours;

[0109] (9) The beaker from step (8) above was placed in an oven at 100°C and dried for 12 hours to obtain catalyst intermediate II;

[0110] (10) Catalyst intermediate II was placed in a tube furnace, nitrogen was introduced, the temperature was programmed to 450°C, and it was calcined for 6 hours. After cooling naturally to room temperature, the sample was taken out to obtain the iron-potassium metal catalyst with the composition 30Fe1K / SiN, denoted as Exam-2.

[0111] The relevant parameters of catalyst Exam-2 are shown in Table 1 below. The XRD and TEM images of catalyst Exam-2 are shown below. Figure 1 and Figure 2 As shown. By Figure 1 and Figure 2 It can be seen that the prepared metal particles have a small size.

[0112] The carbon dioxide hydrogenation to heavy hydrocarbon production in this embodiment includes the following steps:

[0113] The catalyst Exam-2 obtained by the above preparation method was granulated to obtain catalyst particles of 20-40 mesh. Then, 1g of catalyst was placed in the isothermal zone of a fixed-bed reactor, with quartz sand filling both sides. The catalyst was activated for 24h at 300℃ and 0.1MPa using H2 / CO with a molar ratio of 20. After activation, the temperature was lowered to 100℃, and the gas was switched to a H2 / CO2 mixture with a molar ratio of 3. The reaction pressure was 2MPa, the reaction temperature was 320℃, and the reaction was carried out at 5000NL·kg⁻¹. -1 ·h -1 The CO2 hydrogenation reaction is carried out below.

[0114] The product composition was analyzed online using gas chromatography. The activity and selectivity results of the hydrogenation reaction are shown in Table 2 below.

[0115] Example 3

[0116] This embodiment is basically the same as Example 2, except that 0.195g of potassium nitrate was used instead of 0.130g of potassium nitrate to obtain catalyst Exam-3, with a composition of 30Fe1.5K / SiN. The relevant parameters of catalyst Exam-3 are shown in Table 1 below.

[0117] Carbon dioxide hydrogenation to heavy hydrocarbons was carried out using catalyst Exam-3 under the same conditions as in Example 2. The product composition was analyzed online by gas chromatography. The activity and selectivity results of the hydrogenation reaction are shown in Table 2 below.

[0118] Example 4

[0119] This embodiment is basically the same as Example 2, except that 0.650g of potassium nitrate was used instead of 0.130g of potassium nitrate to obtain catalyst Exam-4, with a composition of 30Fe5K / SiN. The relevant parameters of catalyst Exam-4 are shown in Table 1 below.

[0120] The hydrogenation of carbon dioxide to heavy hydrocarbons was carried out using catalyst Exam-4 under the same conditions as in Example 2. The product composition was analyzed online by gas chromatography. The activity and selectivity of the hydrogenation reaction are shown in Table 2 below.

[0121] Example 5

[0122] This embodiment is basically the same as Embodiment 2, except that: 5g of silicon nitride (700m) is used. 2 / g) replace 5g silicon nitride (500m) 2 The catalyst Exam-5, with a composition of 30Fe1K / SiN, was obtained by reacting 30Fe1K / SiN with 30Fe1K / SiN. The relevant parameters of catalyst Exam-5 are shown in Table 1 below.

[0123] The hydrogenation of carbon dioxide to heavy hydrocarbons was carried out using catalyst Exam-5 under essentially the same conditions as in Example 2, except that 10,000 NL·kg⁻¹ was used. -1 ·h -1 Replace 5000 NL·kg -1 ·h -1 The product composition was analyzed online using gas chromatography. The activity and selectivity results of the hydrogenation reaction are shown in Table 2 below.

[0124] Example 6

[0125] This embodiment is basically the same as Example 2, except that 9.02g of ferric nitrate nonahydrate was used instead of 15.50g of ferric nitrate nonahydrate to obtain catalyst Exam-6 with a composition of 20Fe1K / SiN. The relevant parameters of catalyst Exam-6 are shown in Table 1 below.

[0126] The hydrogenation of carbon dioxide to heavy hydrocarbons was carried out using catalyst Exam-6 under the same conditions as in Example 1, except that 5000 NL·kg⁻¹ was used. -1 ·h -1 Replace 2000 NL·kg -1 ·h -1 The product composition was analyzed online using gas chromatography. The hydrogenation reactivity and selectivity results are shown in Table 2 below.

[0127] Example 7

[0128] This embodiment is basically the same as Embodiment 2, except that 1.81g of ferric nitrate nonahydrate is used instead of 15.50g of ferric nitrate nonahydrate, and 0.065g of potassium nitrate is used instead of 0.130g of potassium nitrate, to obtain catalyst Exam-7 with a composition of 5Fe0.5K / SiN. The relevant parameters of catalyst Exam-7 are shown in Table 1 below.

[0129] The hydrogenation of carbon dioxide to heavy hydrocarbons was carried out using catalyst Exam-7 under essentially the same conditions as in Example 1. The product composition was analyzed online by gas chromatography. The hydrogenation reactivity and selectivity results are shown in Table 2 below.

[0130] Example 8

[0131] This embodiment is basically the same as Embodiment 2, except that 9.02g of ferric nitrate nonahydrate was used instead of 15.50g of ferric nitrate nonahydrate, and 0.390g of potassium nitrate was used instead of 0.130g of potassium nitrate, to obtain catalyst Exam-8 with a composition of 20Fe3K / SiN. The relevant parameters of catalyst Exam-8 are shown in Table 1 below.

[0132] Using catalyst Exam-8, carbon dioxide hydrogenation to heavy hydrocarbons was carried out under the same conditions as in Example 1, the only difference being the use of 5000 NL·kg⁻¹. -1 ·h -1 Replace 2000 NL·kg -1 ·h -1 The product composition was analyzed online using gas chromatography. The hydrogenation reactivity and selectivity results are shown in Table 2 below.

[0133] Comparative Example 1

[0134] Comparative Example 1 is basically the same as Example 6, except that: fumed silica (470m) was used. 2 By replacing the silicon nitride support in Example 1 with / g), catalyst CE-1 with the composition 20Fe1K / SiO2 was obtained. The relevant parameters of catalyst CE-1 are shown in Table 1 below.

[0135] Using catalyst CE-1, carbon dioxide hydrogenation to heavy hydrocarbons was carried out under the same conditions as in Example 6. The product composition was analyzed online by gas chromatography. The activity and selectivity results of the hydrogenation reaction are shown in Table 2 below.

[0136] Comparative Example 2

[0137] In this comparative example, the catalyst preparation method includes the following steps:

[0138] (1) Weigh 4.02g of ferric nitrate nonahydrate and place it in a container. Add 60mL of anhydrous ethanol and dissolve it completely to prepare an iron salt solution.

[0139] (2) Then weigh 5g of silicon nitride (500m 2 Place the carrier in a beaker, add the iron salt solution dropwise onto the carrier, stir well, and let stand for 24 hours;

[0140] (3) The beaker from step (2) above was placed in an oven at 120°C and dried for 12 hours to obtain catalyst precursor I;

[0141] (4) Place catalyst precursor I in a tube furnace, introduce argon gas, program the temperature to 400℃, hold for 5 hours for calcination, and then cool naturally to room temperature to obtain an iron metal catalyst with a composition of 10Fe / SiN, denoted as CE-2.

[0142] The relevant parameters of catalyst CE-2 are shown in Table 1 below.

[0143] Using catalyst CE-2, carbon dioxide hydrogenation to heavy hydrocarbons was carried out under the same conditions as in Example 1. The product composition was analyzed online by gas chromatography. The activity and selectivity of the hydrogenation reaction are shown in Table 2 below.

[0144] Comparative Example 3

[0145] The catalyst used in this comparative example is Exam-2 obtained in Example 2.

[0146] The comparative method for producing heavy hydrocarbons by hydrogenation of carbon dioxide includes the following steps:

[0147] The catalyst Exam-2 obtained by the above preparation method was granulated to obtain catalyst particles of 20-40 mesh. Then, 1g of catalyst was placed in the isothermal zone of a fixed-bed reactor, with quartz sand filling both sides. The catalyst was activated for 24h at 300℃ and 0.1MPa using H2 / CO with a molar ratio of 20. After activation, the temperature was lowered to 100℃, and the gas was switched to a H2 / CO2 mixture with a molar ratio of 4. The reaction pressure was 2MPa, the reaction temperature was 280℃, and the reaction was carried out at 5000NL·kg⁻¹. -1 ·h -1 The CO2 hydrogenation reaction is carried out below.

[0148] The product composition was analyzed online using gas chromatography. The activity and selectivity results of the hydrogenation reaction are shown in Table 2 below.

[0149]

[0150]

[0151]

[0152] As can be seen from the table above, compared with Comparative Examples 1-3, Examples 1-8, using silicon nitride with high specific surface area as a support and adding an appropriate amount of K as an auxiliary, effectively improved the carbon dioxide conversion rate and the selectivity of heavy hydrocarbons.

[0153] Any numerical value mentioned in this invention, if there is only a two-unit interval between any minimum and any maximum value, includes all values ​​that increase by one unit each time from the minimum to the maximum value. For example, if the amount of a component, or the value of a process variable such as temperature, pressure, or time, is stated as 50-90, in this specification it means specifically listing values ​​such as 51-89, 52-88… and 69-71 and 70-71, etc. For non-integer values, it may be appropriately considered that a unit is 0.1, 0.01, 0.001, or 0.0001. These are merely some specifically specified examples. In this application, in a similar manner, all possible combinations of numerical values ​​between the listed minimum and maximum values ​​are considered to have been disclosed.

[0154] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A method for producing heavy hydrocarbons by hydrogenation of carbon dioxide, comprising the step of: allowing carbon dioxide to undergo a reaction for producing heavy hydrocarbons by hydrogenation in the presence of hydrogen, carbon dioxide, and a catalyst; wherein, The catalyst comprises a carrier, an active metal and an auxiliary agent, The carrier is silicon nitride; the active metal is iron; and the auxiliary agent is potassium.

2. The method of claim 1, wherein, In the catalyst, the mass ratio of the active metal to the carrier is (5-50):

100. And / or, the mass ratio of the auxiliary agent to the carrier is (0.1-5):

100.

3. The method of claim 2, wherein, In the catalyst, the mass ratio of the active metal to the carrier is (5-30):

100.

4. The method according to claim 2 or 3, characterized in that, The mass ratio of the auxiliary agent to the carrier is (0.5-3):

100.

5. The method according to any one of claims 1-3, characterized in that, The specific surface area of the catalyst is 400-700 m 2 / g.

6. The method according to any one of claims 1-3, characterized in that, The dispersion degree of the active metal in the catalyst is 30-90%; and the metal particle size of the catalyst is 1.5-4.0 nm.

7. The method of any one of claims 1-3, wherein, In the silicon nitride carrier, the proportion of macropores with a pore size greater than 50 nm is 1%-5%, and the proportion of mesopores with a pore size of 2-50 nm is 95%-99%; and the porosity of the silicon nitride carrier is 50%-95%. and / or the specific surface area of the support is not less than 300 m 2 / g.

8. The method of claim 7, wherein, The specific surface area of the carrier is 400-700 m 2 / g.

9. The method according to any one of claims 1-3 and 8, characterized in that, The preparation method of the catalyst comprises the following steps: S1. providing a catalyst precursor I containing an active metal source and the carrier; and providing a catalyst precursor II containing a potassium source; S2. performing first calcination treatment on the catalyst precursor I to obtain a catalyst intermediate I; S3. mixing the catalyst precursor II and the catalyst intermediate I, and performing drying treatment to obtain a catalyst intermediate II; S4. performing second calcination treatment on the catalyst intermediate II to obtain the catalyst.

10. The method of claim 9, wherein, In step S1, the active metal source is selected from one or more of iron nitrate, iron chloride, ferrous chloride, ferrous acetate, ammonium iron oxalate·trihydrate and ferric ammonium citrate. And / or, the potassium source is selected from a soluble potassium salt.

11. The method of claim 10, wherein, The soluble potassium salt is selected from one or more of potassium sulfate, potassium nitrate, potassium carbonate and potassium chloride.

12. The method of claim 9, wherein, In step S2, the first calcination treatment is performed at a temperature of 300°C-900°C for 1-12 h. And / or, in step S3, the drying treatment is performed at a temperature of 40°C-180°C for 4-24 h. And / or, in step S4, the second calcination treatment is performed at a temperature of 300°C-900°C for 1-12 h.

13. The method of claim 12, wherein, The first calcination treatment is performed in an inert gas atmosphere.

14. The method of claim 13, wherein, The inert gas is selected from one or more of nitrogen, argon, neon and helium.

15. The method according to any one of claims 10-14, characterized in that, In step S4, the second calcination treatment is performed at a temperature of 300°C-600°C for 1-12 h.

16. The method of any one of claims 1-3, 8, and 10-14, wherein, The molar ratio of hydrogen to carbon dioxide is 1-4:

1. And / or, the conditions of the hydrogenation reaction include: the reaction temperature is 200℃~500℃; the space velocity is 1000~20000 NL·kg -1 ·h -1 ; the pressure is 0.1~5 MPa.

17. The method of claim 16, wherein, The hydrogenation reaction is performed at a reaction temperature of 260°C-400°C.

18. The method of claim 16, wherein, The conditions of the hydrogenation reaction include: space velocity of 2000-10000 NL·kg -1 ·h -1 .

19. The method of claim 16, wherein, The hydrogenation reaction is performed at a pressure of 1-4 MPa.

20. The method of any one of claims 1-3, 8, 10-14, and 17-19, wherein, Before the hydrogenation reaction is performed, the catalyst is subjected to activation treatment; and the activation treatment is performed at a pressure of 0.1-4 MPa and a temperature of 200°C-800°C. The activation atmosphere is hydrogen, carbon monoxide or synthesis gas; wherein the molar ratio of hydrogen to carbon monoxide in the synthesis gas is (1-500):

1. The activation pressure is 0.1-4 MPa. The activation temperature is 200°C-800°C.

21. The method of claim 20, wherein, The molar ratio of hydrogen to carbon monoxide in the synthesis gas is (1-200):

1.

22. The method of claim 20, wherein, The activation treatment conditions include an activation pressure of 0.1 to 3 MPa.

23. The method of claim 20, wherein, The activation treatment conditions include an activation temperature of 250°C to 600°C.

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