A carbon dioxide hydrogenation catalyst and its preparation method and application

Abstract

The present invention relates to the technical field of carbon dioxide hydrogenation catalysts, and specifically discloses a carbon dioxide hydrogenation catalyst, a preparation method thereof, and an application thereof. The carbon dioxide hydrogenation catalyst provided by the present invention uses alkali-modified power plant ash and aminosilane coupling agent-modified red mud as carriers, the carrier surface is fluffy, the specific surface area and pore volume are increased, and the dispersibility of the active component and the auxiliary agent is increased; a noble metal-based lanthanide metal bimetallic material is used as the active component, which is present on the carrier surface in a highly dispersed form, thereby improving the catalytic activity and selectivity; a transition metal oxide is used as an auxiliary agent, further improving the adsorption performance for CO2 and the selectivity for formic acid substances; by controlling the content of the carrier, the active component, and the auxiliary agent, a strong interaction is generated between the metal-carrier, thereby improving the catalytic activity, selectivity, and stability of the catalyst, and can realize the conversion of CO2 hydrogenation into formic acid and its derivatives under mild conditions.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon dioxide hydrogenation catalysts, and in particular to a carbon dioxide hydrogenation catalyst, a preparation method and an application thereof. Background Art

[0002] With population growth and the acceleration of global industrialization, CO2 emissions are increasing. These massive CO2 emissions have already caused serious environmental problems, including the greenhouse effect and global warming. However, CO2 is also the world's most abundant carbon resource, and its effective development and utilization are crucial for addressing both environmental and energy challenges. CO2 can react with hydrogen to produce low-carbon compounds such as methane, methanol, methyl ether, formic acid, and its derivatives. In recent years, the process of hydrogenating CO2 to formate (reaction equation: CO2 + H2 → HCOOH) has garnered increasing attention, as the conversion of CO2 to formate is the first elementary step in the synthesis of methanol, methane, and high-value-added hydrocarbons from CO2. Furthermore, formic acid can serve as a safe hydrogen carrier, offering advantages such as high volumetric hydrogen density (53g H2 per liter of HCOOH), good chemical stability, and low toxicity.

[0003] For the CO2 hydrogenation reaction to formic acid, the most efficient catalyst systems currently being widely studied, both domestically and internationally, are primarily homogeneous catalytic systems, immobilized quasi-homogeneous catalytic systems, and supported nano-precious metal catalyst systems. While homogeneous catalytic systems exhibit the highest catalytic activity, they suffer from issues such as poor reaction continuity, catalyst loss, and difficulty in product separation, hindering their potential for large-scale application. Immobilized quasi-homogeneous catalytic systems immobilize the aforementioned homogeneous complexes on a support surface through complexation with functional groups on the support surface, enabling easy catalyst recovery and separation. However, these systems still suffer from issues such as easy loss of active components, poor cyclic stability, and a significant decrease in activity. Heterogeneous catalytic systems offer advantages such as good reaction continuity and easy catalyst recovery, making them potentially practical catalyst systems for CO2 hydrogenation to formic acid. However, they struggle to manipulate the structure and electronic properties of precious metals at the atomic scale, resulting in lower catalytic performance than homogeneous catalytic systems, and the reaction conditions are harsh. Therefore, developing an efficient catalytic system to achieve the conversion of CO2 hydrogenation to formic acid and its derivatives under mild conditions will undoubtedly have a significant impact on the resource utilization of CO2 and the large-scale application of hydrogen energy. Summary of the Invention

[0004] In response to the above problems, the present invention provides a carbon dioxide hydrogenation catalyst, a preparation method and an application thereof. The carbon dioxide hydrogenation catalyst has high catalytic activity, selectivity and stability, and can realize the conversion of CO2 into formic acid and its derivatives under mild conditions.

[0005] In order to solve the above technical problems, the technical solution provided by the present invention is:

[0006] A carbon dioxide hydrogenation catalyst comprising a carrier, an active component, and an additive; the carrier is alkali-modified power plant ash and aminosilane coupling agent-modified red mud; the active component is a noble metal-based bimetallic material, the first metal of the noble metal-based bimetallic material is a Group VIII noble metal, the second metal is a lanthanide metal, and the additive is a transition metal oxide;

[0007] Among them, in terms of mass percentage, the first metal accounts for 0.01% to 1%, the second metal accounts for 0.01% to 1%, and the auxiliary agent accounts for 10% to 20%; the mass ratio of alkali-modified power plant ash and the aminosilane coupling agent-modified red mud in the carrier is 1:(0.5 to 1.5).

[0008] It is worth noting that the mass ratio in the present invention is based on the total mass of the carbon dioxide hydrogenation catalyst.

[0009] Compared with the existing technology, the carbon dioxide hydrogenation catalyst provided by the present invention uses power plant ash and red mud as carriers. The power plant ash is naturally mixed with a variety of metal or non-metal oxides, the main component of which is SiO2, supplemented by Al2O3, CaO, Fe2O3, TiO2, MgO and K2O. The various metal oxides have an activation effect; the use of alkali to modify the power plant ash can enhance the adhesion and mechanical strength of the power plant ash. Red mud, primarily composed of lamellar micron sheets and granular nanospheres (20-100 nm in size), is characterized by good monodispersity and a gradient in particle size distribution. Surface modification of red mud with an aminosilane coupling agent yields highly dispersible red mud with an amino structure, known as amine-functionalized red mud, which improves selectivity for formic acid. Furthermore, red mud is alkaline, and during the CO2 hydrogenation process to produce formic acid and its derivatives, the alkali in the mud is dissolved, facilitating the reaction. The synergistic effect of alkali-modified power plant ash and aminosilane-modified red mud results in a fluffy support surface, increasing the specific surface area and pore volume. This further enhances the dispersion of active components and additives, laying the foundation for a robust metal-support bond. Furthermore, the highly dispersible support reduces the active component content, reducing raw material costs while improving catalytic activity and stability.

[0010] The carbon dioxide hydrogenation catalyst provided by the present invention utilizes a noble metal-based bimetallic material as the active component, present in a highly dispersed form on the support surface. Group VIII noble metals and lanthanide metals serve as active centers for H2 dissociation, and their combined action enhances the catalyst's catalytic activity and selectivity. The addition of a transition metal oxide as a promoter further enhances the catalyst's adsorption of CO2 and selectivity for formic acid (increasing the yield and purity of formic acid). The synergistic effect of the active component and the promoter further enables the conversion of CO2 hydrogenation to formic acid and its derivatives under mild conditions.

[0011] By controlling the contents of the support, active component, and additive, this invention creates a strong metal-support interaction, resulting in a carbon dioxide hydrogenation catalyst with high catalytic activity, selectivity, and stability. This allows for the conversion of CO2 hydrogenation to formic acid and its derivatives under mild conditions. Furthermore, this invention achieves the comprehensive utilization of power plant ash and red mud, which are agricultural, forestry, or industrial solid wastes, making them more environmentally friendly and significantly reducing costs, thus possessing high practical and promotional value.

[0012] Preferably, in terms of mass percentage, the first metal accounts for 0.01% to 0.3%, and the second metal accounts for 0.01% to 0.3%; more preferably, the first metal accounts for 0.01% to 0.1%, and the second metal accounts for 0.01% to 0.1%.

[0013] Preferably, the Group VIII noble metal includes ruthenium, rhodium or palladium.

[0014] Preferably, the lanthanide metal includes lanthanum, cerium or samarium.

[0015] Preferably, the transition metal oxide includes nickel oxide, manganese oxide, cobalt oxide, chromium oxide or iron oxide.

[0016] For example, the power plant ash is at least one of wood ash and rice husk ash.

[0017] Preferably, the method for preparing the alkali-modified power plant ash comprises the following steps:

[0018] The power plant ash is added into an alkaline solution, impregnated at 90-100°C, and then roasted at 450-500°C to obtain the alkali-modified power plant ash.

[0019] Further preferably, the alkaline solution is at least one of a sodium hydroxide aqueous solution, a potassium hydroxide aqueous solution or a calcium hydroxide aqueous solution with a mass concentration of 40% to 50%.

[0020] Further preferably, the mass volume ratio of the power plant ash to the alkaline solution is 1 g: (1 to 1.5) mL.

[0021] More preferably, the immersion time is 1 to 1.5 hours.

[0022] More preferably, the roasting is carried out by microwave heating, and the holding time is 15 to 30 minutes.

[0023] The present invention controls the conditions of alkali-modified power plant ash, thereby improving reaction efficiency, further activating the components of the power plant ash, increasing its specific surface area and pore volume, and enhancing the cohesiveness and mechanical strength of the power plant ash.

[0024] Preferably, the preparation method of aminosilane coupling agent modified red mud comprises the following steps:

[0025] The aminosilane coupling agent is added into an organic solvent, uniformly sprayed onto the red mud, stirred and mixed, and a coupling reaction is carried out at 100-120 DEG C to obtain the aminosilane coupling agent modified red mud.

[0026] Further preferably, the aminosilane coupling agent includes at least one of 3-aminopropyltriethoxysilane, 3-ureapropyltrimethoxysilane or isopropoxytris(ethylenediamino N-ethoxy)titanate.

[0027] Further preferably, the organic solvent includes at least one of ethanol, isopropanol, tetrahydrofuran or N,N-dimethylformamide.

[0028] Further preferably, the mass ratio of the red mud, the aminosilane coupling agent and the organic solvent is (200-250):1:(5-10).

[0029] More preferably, the modification treatment time is 1.5 to 2.5 hours.

[0030] The present invention controls the conditions for modifying red mud with an aminosilane coupling agent, thereby further activating the components of the red mud, improving the monodispersity of the red mud, uniformly distributing the gradient of different particle sizes, increasing the specific surface area and pore volume of the red mud, and ultimately obtaining highly dispersible red mud with an amino structure.

[0031] The present invention provides a method for preparing a carbon dioxide hydrogenation catalyst, comprising the following steps:

[0032] S1, adding the support to a transition metal nitrate solution, adjusting the pH to 7-8, impregnating, solid-liquid separation, drying, and performing a first calcination to obtain a support containing a transition metal oxide;

[0033] S2, adding the transition metal oxide-containing support, the first metal nitrate, and the second metal nitrate to an ethanol solution, and mixing them uniformly to obtain a precursor solution;

[0034] S3, heating the precursor solution to perform a reflux reaction, adding a NaBH4 solution to perform a reduction reaction, performing solid-liquid separation, drying, and performing a second calcination to obtain a carbon dioxide hydrogenation catalyst.

[0035] The present invention provides a method for preparing a carbon dioxide hydrogenation catalyst. This method utilizes a coprecipitation method to first prepare a transition metal oxide-containing support, followed by an in-situ reduction method using NaBH4 to prepare a dual-active metal catalyst. This method is simple and easy to implement, producing a carbon dioxide hydrogenation catalyst with a highly dispersed active component, making it suitable for large-scale production.

[0036] Further preferably, in step S1, the concentration of transition metal ions in the transition metal nitrate solution is 8 to 12 mmol / L.

[0037] Further preferably, in step S1, the mass-to-volume ratio of the carrier to the transition metal nitrate solution is 1 g:(170-300) mL.

[0038] More preferably, in step S1, the immersion temperature is 70-90° C. and the immersion time is 1-1.5 h.

[0039] Further preferably, in step S1, the first calcination is carried out by heating the temperature to 350-400°C in a gradient heating manner, with a heating rate of 3-5°C / min and a holding time of 2.5-3.5h.

[0040] Further preferably, in step S2, the concentration of the first metal ion in the precursor solution is 3-5 mmol / L.

[0041] Further preferably, in step S2, the mass ratio of the transition metal oxide-containing support, the first metal nitrate and the second metal nitrate is (3000-5000):(1-15):(1-100).

[0042] Further preferably, in step S3, the reflux reaction time is 10 to 12 hours.

[0043] Further preferably, in step S3, the concentration of the NaBH4 solution is 0.08 to 0.12 mol / L.

[0044] The preferred method of adding NaBH4 solution in the present invention is dropwise addition. There is no requirement for the dropwise addition rate of the NaBH4 solution, and continuous dropwise addition is sufficient. The amount of NaBH4 solution added is excessive to ensure that the noble metal ions and lanthanide metal ions in the precursor solution are completely reduced.

[0045] Further preferably, in step S3, the reduction reaction is carried out for 1.5 to 2.5 hours under stirring.

[0046] Further preferably, in step S3, the second calcination is carried out by heating the temperature to 450-500°C in a gradient manner, with a heating rate of 3-5°C / min and a holding time of 2.5-3.5h.

[0047] For example, in steps S1 and S3, the drying is performed by vacuum drying at a temperature of 70 to 90° C. for 6 to 10 hours.

[0048] The present invention also provides an application of a carbon dioxide hydrogenation catalyst in the preparation of formic acid and its derivatives by hydrogenation of carbon dioxide.

[0049] Preferably, the reaction conditions for preparing formic acid and its derivatives by hydrogenating carbon dioxide include: the volume ratio of H2 and CO2 in the raw gas is (1-3):1; the total reaction pressure is 6.0-10.0 MPa; the reaction temperature is 50-80°C, and the reaction time is 1-3 hours.

[0050] The carbon dioxide hydrogenation catalyst provided by the present invention is applied to the preparation of formic acid and its derivatives by carbon dioxide hydrogenation. The reaction conditions are very mild, the yield and purity of the prepared formic acid and its derivatives are high, the selectivity can reach 100%, and the conversion frequency TOF value of the catalyst can reach 15h -1 above. DETAILED DESCRIPTION

[0051] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0052] Example 1

[0053] This embodiment provides a carbon dioxide hydrogenation catalyst, wherein the carrier is NaOH-modified power plant ash and 3-aminopropyltriethoxysilane (SCA-A10E) surface-modified red mud, with a mass ratio of 1:1; the active components are the precious metals Ru and La, with a mass proportion of 0.05% and 0.05%, respectively; and the additive is NiO, with a mass proportion of 15%.

[0054] The preparation method of the carbon dioxide hydrogenation catalyst comprises the following steps:

[0055] S1, 20 g of power plant ash was immersed in 25 mL of a 45 wt% NaOH aqueous solution at 95° C., stirred for 1.5 h, and then calcined at 470° C. for 25 min using microwave heating to obtain alkali-modified power plant ash.

[0056] S2, 0.1 g of SCA-A10E and 0.8 g of ethanol were mixed, sprayed evenly onto 23 g of red mud, stirred and mixed, and subjected to coupling reaction at 110° C. for 2 h to obtain aminosilane coupling agent-modified red mud.

[0057] It is worth noting that there is no order for steps S1 and S2.

[0058] S3, take 20g of the above-mentioned alkali-modified power plant ash and 20g of the above-mentioned aminosilane coupling agent-modified red mud, respectively, and immerse them in 9.4L of 10mmol / L Ni(NO3)2·6H2O solution, adjust the pH to 7-8 with ammonia water, keep it at 80°C for 1.3h, separate the solid and liquid, vacuum dry it at 80°C for 8h, raise the temperature to 380°C at a rate of 4°C / min for the first calcination, and keep it warm for 3h to obtain a NiO-containing carrier.

[0059] S4, adding 0.06g of Ru(NO)(NO3)3 and 0.06g of La(NO3)3·6H2O to an ethanol solution with a ruthenium ion concentration of 4mmol / L, taking 40g of the above-mentioned NiO-containing carrier and mixing them evenly with the solution to obtain a precursor solution.

[0060] S5, after the above-mentioned precursor solution is refluxed for 11 hours, an excess of 0.1 mol / L NaBH4 solution is continuously added dropwise, and the reduction reaction is carried out with stirring for 2 hours. The solid-liquid separation is carried out, and the mixture is vacuum-dried at 80°C for 8 hours. The temperature is raised to 470°C at a rate of 4°C / min for a second calcination, and the temperature is kept for 3 hours to obtain a carbon dioxide hydrogenation catalyst.

[0061] Example 2

[0062] This embodiment provides a carbon dioxide hydrogenation catalyst, wherein the carrier is KOH-modified power plant ash and 3-ureapropyltrimethoxysilane (SCA-U60M) surface-modified red mud, with a mass ratio of 1:0.5; the active components are precious metals Rh and Ce, with a mass proportion of 0.01% and 0.1%, respectively; and the auxiliary agent is MnO, with a mass proportion of 10%.

[0063] The preparation method of the carbon dioxide hydrogenation catalyst comprises the following steps:

[0064] S1, 20 g of power plant ash was immersed in 20 mL of a 50 wt% KOH aqueous solution at 90° C., stirred for 1.5 h, and then calcined at 450° C. for 30 min using microwave heating to obtain alkali-modified power plant ash.

[0065] S2, 0.1g SCA-U60M and 0.5g isopropyl alcohol were mixed, sprayed evenly onto 20g red mud, stirred and mixed, and a coupling reaction was carried out at 100°C for 2.5h to obtain aminosilane coupling agent-modified red mud.

[0066] It is worth noting that there is no order for steps S1 and S2.

[0067] S3, take 20g of the above-mentioned alkali-modified power plant ash and 10g of the above-mentioned aminosilane coupling agent-modified red mud, respectively, and immerse them in 5.9L of 8mmol / L Mn(NO3)2·6H2O solution, adjust the pH to 7-8 with ammonia water, keep it at 70°C for 1.5h, separate the solid and liquid, vacuum dry it at 80°C for 8h, raise the temperature to 350°C at a rate of 3°C / min for the first calcination, and keep it warm for 3.5h to obtain a MnO-containing carrier.

[0068] S4, adding 0.01 g of Rh(NO3)3·2H2O and 0.94 g of Ce(NO3)3·6H2O to an ethanol solution with a rhodium ion concentration of 3 mmol / L, taking 30 g of the above-mentioned MnO-containing carrier and mixing them evenly with the solution to obtain a precursor solution.

[0069] S5, after the above-mentioned precursor solution is refluxed for 10 hours, an excess of 0.08 mol / L NaBH4 solution is continuously added dropwise, and the reduction reaction is carried out with stirring for 1.5 hours. The solid-liquid separation is carried out, and the mixture is vacuum-dried at 80°C for 8 hours. The temperature is raised to 450°C at a rate of 3°C / min for a second calcination, and the temperature is kept at this temperature for 3.5 hours to obtain a carbon dioxide hydrogenation catalyst.

[0070] Example 3

[0071] This embodiment provides a carbon dioxide hydrogenation catalyst, the carrier of which is Ca(OH)2-modified power plant ash and isopropoxy tris(ethylenediamine N-ethoxy) titanate (TCA-K44) surface-modified red mud, with a mass ratio of 1:1.5; the active components are precious metals Pd and Sm, with a mass proportion of 0.1% and 0.01%, respectively; and the additive is CoO, with a mass proportion of 20%.

[0072] The preparation method of the carbon dioxide hydrogenation catalyst comprises the following steps:

[0073] S1, 20g of power plant ash was immersed in 30mL of 40wt% Ca(OH)2 aqueous solution at 100℃, stirred for 1h, and then calcined at 500℃ for 15min using microwave heating to obtain alkali-modified power plant ash.

[0074] S2, 0.12g TCA-K44 and 1.2g tetrahydrofuran were mixed, sprayed evenly onto 30g red mud, stirred and mixed, and a coupling reaction was carried out at 120°C for 1.5h to obtain aminosilane coupling agent modified red mud.

[0075] It is worth noting that there is no order for steps S1 and S2.

[0076] S3, take 20g of the above-mentioned alkali-modified power plant ash and 30g of the above-mentioned aminosilane coupling agent-modified red mud, respectively, and immerse them in 13.9L of 12mmol / L Co(NO3)2·6H2O solution, adjust the pH to 7-8 with ammonia water, keep it at 90°C for 1h, separate the solid and liquid, vacuum dry it at 80°C for 8h, raise the temperature to 400°C at a rate of 5°C / min for the first calcination, and keep it warm for 2.5h to obtain a CoO-containing carrier.

[0077] S4, adding 0.13 g of Pd(NO3)3·2H2O and 0.01 g of Sm(NO3)3·6H2O to an ethanol solution with a palladium ion concentration of 5 mmol / L, taking 50 g of the above-mentioned CoO-containing carrier and mixing them evenly with the solution to obtain a precursor solution.

[0078] S5, after the above-mentioned precursor solution is refluxed for 12 hours, an excess of 0.12 mol / L NaBH4 solution is continuously added dropwise, and the reduction reaction is carried out with stirring for 2.5 hours. The solid-liquid separation is carried out, and the mixture is vacuum-dried at 80°C for 8 hours. The temperature is raised to 500°C at a rate of 5°C / min for a second calcination, and the temperature is kept for 2.5 hours to obtain a carbon dioxide hydrogenation catalyst.

[0079] Example 4

[0080] This embodiment provides a carbon dioxide hydrogenation catalyst, the carrier of which is NaOH-modified power plant ash and 3-aminopropyltriethoxysilane (SCA-A10E) surface-modified red mud, with a mass ratio of 1:1; the active components are precious metals Ir and La, with a mass proportion of 0.05% and 0.05%, respectively; and the additive is Cr2O3, with a mass proportion of 15%.

[0081] The preparation method of the carbon dioxide hydrogenation catalyst comprises the following steps:

[0082] S1, same as Example 1.

[0083] S2, 0.1g SCA-A10E and 0.8g N,N-dimethylformamide were mixed, sprayed evenly onto 23g red mud, stirred and mixed, and a coupling reaction was carried out at 110°C for 2h to obtain aminosilane coupling agent-modified red mud.

[0084] It is worth noting that there is no order for steps S1 and S2.

[0085] S3, take 20g of the above-mentioned alkali-modified power plant ash and 20g of the above-mentioned aminosilane coupling agent-modified red mud, respectively, and immerse them in 9.3L of 10mmol / L Cr(NO3)3·9H2O solution, adjust the pH to 7-8 with ammonia water, keep it at 80°C for 1.3h, separate the solid and liquid, vacuum dry it at 80°C for 8h, raise the temperature to 380°C at a rate of 4°C / min for the first calcination, and keep it warm for 3h to obtain a carrier containing Cr2O3.

[0086] S4, 0.04g Ir(NO3)3 and 0.06g La(NO3)3·6H2O are added to an ethanol solution with an iridium ion concentration of 4mmol / L, 40g of the above-mentioned carrier containing Cr2O3 is taken and mixed evenly with the solution to obtain a precursor solution.

[0087] S5, same as Example 1.

[0088] Example 5

[0089] This embodiment provides a carbon dioxide hydrogenation catalyst, wherein the carrier is NaOH-modified power plant ash and 3-aminopropyltriethoxysilane (SCA-A10E) surface-modified red mud, with a mass ratio of 1:1; the active components are precious metals Pt and La, with a mass proportion of 0.05% and 0.05%, respectively; and the additive is NiO, with a mass proportion of 15%.

[0090] The preparation method of the carbon dioxide hydrogenation catalyst comprises the following steps:

[0091] S1 to S3 are the same as those in Example 1.

[0092] S4, 0.03 g of Pt(NO3)2 and 0.06 g of La(NO3)3·6H2O were added to an ethanol solution with a platinum ion concentration of 4 mmol / L, and 40 g of the above-mentioned NiO-containing support was mixed evenly with the solution to obtain a precursor solution.

[0093] S5, same as Example 1.

[0094] Example 6

[0095] This embodiment provides a carbon dioxide hydrogenation catalyst (the content of active components is different from that in Example 1), wherein the carrier is NaOH-modified power plant ash and 3-aminopropyltriethoxysilane (SCA-A10E) surface-modified red mud, the mass ratio of the two being 1:1; the active components are the precious metals Ru and La, accounting for 1% and 1% by mass, respectively; and the additive is NiO, accounting for 15% by mass, respectively.

[0096] In the preparation method of the carbon dioxide hydrogenation catalyst, all reaction conditions are the same as those in Example 1, except that the material ratio is designed according to this example.

[0097] Comparative Example 1

[0098] This comparative example provides a carbon dioxide hydrogenation catalyst (which does not contain an additive compared to Example 1), the carrier of which is NaOH-modified power plant ash and 3-aminopropyltriethoxysilane (SCA-A10E) surface-modified red mud, the mass ratio of the two being 1:1; the active components are the precious metals Ru and La, with mass proportions of 0.05% and 0.05%, respectively.

[0099] The above-mentioned preparation method of the carbon dioxide hydrogenation catalyst has all the same reaction conditions as Example 1, except that step S3 is omitted and the material ratio is designed according to this comparative example. The specific steps are as follows:

[0100] S1~S2 are the same as those in Example 1.

[0101] S3, 0.06g N4O 10 Ru and 0.06 g La(NO3)3·6H2O were added to an ethanol solution with a ruthenium ion concentration of 4 mmol / L. 20 g of the above-mentioned alkali-modified power plant ash and 20 g of the above-mentioned aminosilane coupling agent-modified red mud were taken and mixed evenly with the solution to obtain a precursor solution.

[0102] S4 is the same as S5 in Example 1.

[0103] Comparative Example 2

[0104] This comparative example provides a carbon dioxide hydrogenation catalyst (the carrier is different from that in Example 1), the carrier being NaOH-modified power plant ash; the active components being the precious metals Ru and La, accounting for 0.05% and 0.05% by mass respectively; and the auxiliary agent being NiO, accounting for 15% by mass respectively.

[0105] The preparation method of the carbon dioxide hydrogenation catalyst is the same as that of Example 1, except that step S2 is omitted and the material ratio is designed according to this comparative example. The specific steps are as follows:

[0106] S1, 40 g of power plant ash was immersed in 50 mL of a 45 wt% NaOH aqueous solution at 95° C., stirred for 1.5 h, and then calcined at 470° C. for 25 min using microwave heating to obtain alkali-modified power plant ash.

[0107] S2. Take 40g of the above-mentioned alkali-modified power plant ash and immerse it in 9.4L of 10mmol / L Ni(NO3)2·6H2O solution. Adjust the pH to 7-8 with ammonia water. Keep it at 80℃ for 1.3h, separate the solid and liquid, and vacuum dry it at 80℃ for 8h. Heat it to 380℃ at a rate of 4℃ / min for the first calcination and keep it at this temperature for 3h to obtain a NiO-containing carrier.

[0108] S3~S4 are the same as S4~S5 of Example 1.

[0109] Comparative Example 3

[0110] This comparative example provides a carbon dioxide hydrogenation catalyst (the carrier is different from that in Example 1), wherein the carrier is 3-aminopropyltriethoxysilane (SCA-A10E) surface-modified red mud; the active components are the precious metals Ru and La, with a mass proportion of 0.05% and 0.05%, respectively; and the auxiliary agent is NiO, with a mass proportion of 15%, respectively.

[0111] The preparation method of the carbon dioxide hydrogenation catalyst is the same as that of Example 1, except that step S1 is omitted and the material ratio is designed according to this comparative example. The specific steps are as follows:

[0112] S1: Mix 0.2 g of SCA-A10E and 1.6 g of ethanol, spray evenly onto 45 g of red mud, stir and mix, and perform coupling reaction at 110°C for 2 h to obtain aminosilane coupling agent-modified red mud.

[0113] S2, take 40g of the above-mentioned aminosilane coupling agent modified red mud, immerse it in 9.4L of 10mmol / L Ni(NO3)2·6H2O solution, adjust the pH to 7-8 with ammonia water, keep it at 80℃ for 1.3h, separate the solid and liquid, vacuum dry it at 80℃ for 8h, heat it to 380℃ at a rate of 4℃ / min for the first calcination, keep it warm for 3h, and obtain a NiO-containing carrier.

[0114] S3~S4 are the same as S4~S5 of Example 1.

[0115] Comparative Example 4

[0116] This comparative example provides a carbon dioxide hydrogenation catalyst (the carrier is different from that in Example 1), wherein the carrier is power plant ash and red mud, and the mass ratio of the two is 1:1; the active components are precious metals Ru and La, with a mass proportion of 0.05% and 0.05% respectively; and the auxiliary agent is NiO, with a mass proportion of 15% respectively.

[0117] The preparation method of the carbon dioxide hydrogenation catalyst is the same as that of Example 1, except that steps S1 to S2 are omitted and the material ratio is designed according to this comparative example. The specific steps are as follows:

[0118] S1, take 20g of power plant ash and 20g of red mud, soak them separately in 9.4L of 10mmol / L Ni(NO3)2·6H2O solution, adjust the pH to 7-8 with ammonia water, keep it at 80℃ for 1.3h, separate the solid and liquid, vacuum dry it at 80℃ for 8h, heat it to 380℃ at a rate of 4℃ / min for the first calcination, keep it at this temperature for 3h, and obtain a NiO-containing carrier.

[0119] S2~S3 are the same as S4~S5 of Example 1.

[0120] Effect Examples

[0121] In order to further demonstrate the technical effect of the carbon dioxide hydrogenation catalyst provided by the present invention, the present invention conducted catalytic effect tests on the carbon dioxide hydrogenation catalysts provided in the examples and comparative examples. The specific test methods are as follows:

[0122] 5 mL of 1 mol / L sodium bicarbonate solution and 20 mg of carbon dioxide hydrogenation catalyst were loaded into the autoclave, and the air in the autoclave was replaced with N2. The autoclave was then heated to a reaction temperature of 70°C. H2 was introduced into the autoclave under stirring. When the pressure of the autoclave reached 5 MPa, H2 was turned off. At the same time, liquefied CO2 was introduced into the autoclave to make the total pressure of the autoclave reach the reaction pressure of 8 MPa. After stabilization, the introduction of CO2 was stopped. After reacting for 2 h, the autoclave was cooled and the pressure was released.

[0123] The concentration of formic acid in the product was detected by HPLC, and the yield of formic acid and the catalytic TOF value were calculated (calculation formula: TOF = formic acid concentration / (catalyst concentration × reaction time). The results are shown in Table 1.

[0124] Table 1 Test results of carbon dioxide hydrogenation catalysts provided in various embodiments and comparative examples

[0125]

[0126] It can be seen from Table 1 that the carbon dioxide hydrogenation catalysts provided in Examples 1 to 6 of the present invention can catalyze the conversion of carbon dioxide into formic acid, and have high catalytic activity, with a TOF value of up to 12h -1 As described above, the content of formic acid obtained can reach above 1.68 mmol, and the selectivity is 100%, which further confirms that the carbon dioxide hydrogenation catalyst provided by the present invention has excellent catalytic performance.

[0127] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A carbon dioxide hydrogenation catalyst, characterized in that The invention comprises a carrier, an active component and an auxiliary agent; the carrier is alkali-modified power plant ash and aminosilane coupling agent-modified red mud; the active component is a noble metal-based bimetallic material; the first metal of the noble metal-based bimetallic material is a Group VIII noble metal, the second metal is a lanthanide metal, and the auxiliary agent is a transition metal oxide; Wherein, in terms of mass percentage, the first metal accounts for 0.01% to 1%, the second metal accounts for 0.01% to 1%, and the additive accounts for 10% to 20%; the mass ratio of the alkali-modified power plant ash and the aminosilane coupling agent-modified red mud in the carrier is 1:(0.5-1.5); The preparation method of the alkali-modified power plant ash comprises the following steps: Add power plant ash into an alkaline solution, soak at 90-100°C, and then roast at 450-500°C to obtain alkali-modified power plant ash; The preparation method of the aminosilane coupling agent modified red mud comprises the following steps: The aminosilane coupling agent is dissolved in an organic solvent, sprayed evenly onto the red mud, stirred and mixed, and a coupling reaction is carried out at 100-120° C. to obtain aminosilane coupling agent-modified red mud.

2. The carbon dioxide hydrogenation catalyst according to claim 1, wherein The Group VIII noble metal comprises ruthenium, rhodium or palladium; and / or The lanthanide metal comprises lanthanum, cerium or samarium; and / or The transition metal oxide includes nickel oxide, manganese oxide, cobalt oxide, chromium oxide or iron oxide.

3. The carbon dioxide hydrogenation catalyst according to claim 1, wherein The alkaline solution is at least one of a sodium hydroxide aqueous solution, a potassium hydroxide aqueous solution or a calcium hydroxide aqueous solution with a mass concentration of 40% to 50%; and / or The mass volume ratio of the power plant ash to the alkaline solution is 1g:(1-1.5)mL.

4. The carbon dioxide hydrogenation catalyst according to claim 1, wherein The aminosilane coupling agent includes at least one of 3-aminopropyltriethoxysilane, 3-ureapropyltrimethoxysilane or isopropoxytris(ethylenediamino N-ethoxy)titanate; and / or The organic solvent comprises at least one of ethanol, isopropanol, tetrahydrofuran or N,N-dimethylformamide; and / or The mass ratio of the red mud, the aminosilane coupling agent and the organic solvent is (200-250):1:(5-10).

5. The method for preparing the carbon dioxide hydrogenation catalyst according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1, adding the support to a transition metal nitrate solution, adjusting the pH to 7-8, impregnating, solid-liquid separation, drying, and performing a first calcination to obtain a support containing a transition metal oxide; S2, adding the transition metal oxide-containing support, the first metal nitrate, and the second metal nitrate to an ethanol solution, and mixing them uniformly to obtain a precursor solution; S3, heating the precursor solution to perform a reflux reaction, adding a NaBH4 solution to perform a reduction reaction, performing solid-liquid separation, drying, and performing a second calcination to obtain a carbon dioxide hydrogenation catalyst.

6. The method for preparing a carbon dioxide hydrogenation catalyst according to claim 5, wherein: In step S1, the immersion temperature is 70-90°C and the time is 1-1.5 hours; and / or In step S1, the first calcination is carried out by heating the temperature to 350-400°C in a gradient manner, with a heating rate of 3-5°C / min and a holding time of 2.5-3.5h; and / or In step S3, the second calcination is carried out by heating the temperature to 450-500°C in a gradient manner, with a heating rate of 3-5°C / min and a holding time of 2.5-3.5h.

7. The method for preparing a carbon dioxide hydrogenation catalyst according to claim 5, wherein: In step S1, the concentration of transition metal ions in the transition metal nitrate solution is 8-12 mmol / L; and / or In step S1, the mass volume ratio of the support and the transition metal nitrate solution is 1 g: (170-300) mL; and / or In step S2, the concentration of the first metal ion in the precursor solution is 3-5 mmol / L; and / or In step S2, the mass ratio of the transition metal oxide-containing support, the first metal nitrate and the second metal nitrate is (3000-5000):(1-15):(1-100); and / or In step S3, the concentration of the NaBH4 solution is 0.08~0.12mol / L.

8. Use of the carbon dioxide hydrogenation catalyst according to any one of claims 1 to 4 or the carbon dioxide hydrogenation catalyst prepared by the preparation method of the carbon dioxide hydrogenation catalyst according to any one of claims 5 to 7 in the preparation of formic acid and its derivatives by carbon dioxide hydrogenation.

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