A method for preparing a carbon dioxide hydrogenation catalyst

Abstract

The invention discloses a method for preparing a carbon dioxide hydrogenation catalyst. The invention significantly improves the dispersibility and surface activity of carbon nanotubes through silane modification, increases the binding ability between the carbon nanotube surface and the metal precursor, ensures the efficient loading of the metal precursor on the carbon nanotube, and realizes the uniform distribution of metal particles. This uniform distribution not only avoids the agglomeration of metal particles, but also prevents the sintering and deactivation of metal particles under high temperature reaction conditions, thereby greatly increasing the number of active sites of the catalyst and the stability of long-term use. In addition, the uniformly dispersed metal particles provide more active sites, which are beneficial to the adsorption and conversion of reactants, thereby improving the activity of the catalyst. The efficient metal loading and distribution uniformity make the catalyst have higher selectivity during the reaction process, and can more accurately catalyze the reaction of carbon dioxide and hydrogen to generate the target product.

Description

Technical Field

[0001] The invention belongs to the field of carbon dioxide hydrogenation catalysts, and in particular relates to a method for preparing a carbon dioxide hydrogenation catalyst. Background Art

[0002] As global warming and energy crises intensify, using carbon dioxide hydrogenation to produce useful chemicals and fuels has become an important way to solve environmental and energy problems. However, existing carbon dioxide hydrogenation catalysts have problems such as low activity, poor selectivity, and insufficient stability.

[0003] In view of this, the present invention is proposed. Summary of the invention

[0004] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a method for preparing a carbon dioxide hydrogenation catalyst, thereby solving the problems raised in the above-mentioned background technology.

[0005] In order to solve the above technical problems, the basic concept of the technical solution adopted by the present invention is:

[0006] A method for preparing a carbon dioxide hydrogenation catalyst comprises the following steps:

[0007] Step (1), selecting a metal precursor and dissolving the metal precursor in deionized water to form a metal salt solution with a concentration of 0.1-1M;

[0008] Step (2), selecting a nanostructured carrier, dispersing the nanostructured carrier in ethanol and placing it in a stirrer for stirring to form a carbon nanotube suspension, then adding a silane modifier dropwise to the suspension, filtering the suspension after the reaction to separate the modified carbon nanotubes, drying and filtering the washed carbon nanotubes to obtain product I; the silane modification significantly improves the dispersibility and surface activity of the carbon nanotubes, increases the binding ability between the carbon nanotube surface and the metal precursor, ensures the efficient loading of the metal precursor on the carbon nanotubes, and achieves uniform distribution of metal particles. This uniform distribution not only avoids the agglomeration of metal particles, but also prevents the sintering and deactivation of metal particles under high temperature reaction conditions, thereby greatly increasing the number of active sites of the catalyst and the stability of long-term use. In addition, the uniformly dispersed metal particles provide more active sites, which are conducive to the adsorption and conversion of reactants, thereby improving the activity of the catalyst. The efficient metal loading and uniform distribution make the catalyst more selective during the reaction process, and can more accurately catalyze the reaction of carbon dioxide and hydrogen to generate the target product.

[0009] Step (3), adding the obtained product I to a metal salt solution, so that the product I is completely immersed in the metal salt solution, to obtain a mixed solution;

[0010] Step (4), using ionized water to adjust the pH value of the mixed solution to 5-7, and gradually adding a reducing agent to the mixed solution to reduce the metal ions to form product II;

[0011] Step (5), drying the obtained product II to remove water and solvent to obtain a dried sample;

[0012] Step (6), calcining the dried sample in a nitrogen atmosphere to convert the metal precursor into metal oxide and evenly distribute it on the surface of the carrier;

[0013] Step (7), reducing the calcined sample in a hydrogen atmosphere to form a catalyst for carbon dioxide hydrogenation reaction.

[0014] Optionally, the metal precursor is selected from nitrates or chlorides of nickel, iron, cobalt or ruthenium, and the mass ratio is 10% of the carrier.

[0015] Optionally, the nanostructure carrier is selected from one or more of carbon nanotubes, graphene, nanofibers or nanosheets.

[0016] Optionally, the silane modifier includes, but is not limited to, one or more of 3-aminopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, and 3-chloropropyltrimethoxysilane.

[0017] Optionally, in step (2), the mass ratio of the silane modifier to the carbon nanotubes is (1-3):(8-15), the stirring reaction time is 4 hours, and the washed carbon nanotubes are placed in an oven at 60° C. and dried for 12 hours.

[0018] Optionally, the reducing agent is gradually added in step (4) by gradually adding hydrogen or sodium borohydride at a rate of 0.1-0.5 ml / min.

[0019] Optionally, the drying process in step (5) is carried out at 100-120° C. for 12-24 hours to ensure that the moisture and solvent in the sample are completely removed.

[0020] Optionally, the calcination process in step (6) is carried out in a nitrogen or argon atmosphere at 400° C. for 3 hours to completely convert the metal precursor into metal oxide.

[0021] Optionally, the reduction process in step (7) is carried out in a hydrogen atmosphere at 400° C. for 3 hours.

[0022] Optionally, the mass ratio of product I and metal salt solution is (1-4):(15-18).

[0023] After adopting the above technical solution, the present invention has the following beneficial effects compared with the prior art. Of course, any product implementing the present invention does not necessarily need to achieve all the advantages described below at the same time:

[0024] Silane modification significantly improves the dispersibility and surface activity of carbon nanotubes, increases the binding ability between the carbon nanotube surface and the metal precursor, ensures the efficient loading of the metal precursor on the carbon nanotubes, and achieves uniform distribution of metal particles. This uniform distribution not only avoids the agglomeration of metal particles, but also prevents the sintering and deactivation of metal particles under high-temperature reaction conditions, thereby greatly increasing the number of active sites of the catalyst and its long-term stability. In addition, the evenly dispersed metal particles provide more active sites, which are conducive to the adsorption and conversion of reactants, thereby improving the activity of the catalyst. The efficient metal loading and uniform distribution make the catalyst more selective during the reaction process, and can more accurately catalyze the reaction of carbon dioxide and hydrogen to produce the target product.

[0025] The specific implementation modes of the present invention are further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The drawings described below are only some embodiments. For those skilled in the art, other drawings can be obtained based on these drawings without creative work. In the drawings:

[0027] Figure 1 This is a schematic diagram of the composition of the reaction product of Example 1 in GC detection;

[0028] Figure 2 This is a schematic diagram of the composition of the reaction product of Example 2 in GC detection;

[0029] Figure 3 This is a schematic diagram of the composition of the reaction products of Example 3 in GC detection.

[0030] It should be noted that these drawings and textual descriptions are not intended to limit the conceptual scope of the present invention in any way, but are intended to illustrate the concept of the present invention for those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0031] The embodiment of the present invention discloses a high-durability rubber concrete and a method for preparing a carbon dioxide hydrogenation catalyst, comprising the following steps:

[0032] Step (1), selecting a metal precursor and dissolving the metal precursor in deionized water to form a metal salt solution with a concentration of 0.1-1M;

[0033] Step (2), selecting a nanostructured carrier, dispersing the nanostructured carrier in ethanol and stirring the nanostructured carrier in a stirrer to form a carbon nanotube suspension, then adding a silane modifier dropwise to the suspension, filtering the suspension after the reaction to separate the modified carbon nanotubes, and drying and filtering the washed carbon nanotubes to obtain product I;

[0034] Step (3), adding the obtained product I to a metal salt solution, so that the product I is completely immersed in the metal salt solution, to obtain a mixed solution;

[0035] Step (4), using ionized water to adjust the pH value of the mixed solution to 5-7, and gradually adding a reducing agent to the mixed solution to reduce the metal ions to form product II;

[0036] Step (5), drying the obtained product II to remove water and solvent to obtain a dried sample;

[0037] Step (6), calcining the dried sample in a nitrogen atmosphere to convert the metal precursor into metal oxide and evenly distribute it on the surface of the carrier;

[0038] Step (7), reducing the calcined sample in a hydrogen atmosphere to form a catalyst for carbon dioxide hydrogenation reaction.

[0039] In some preferred embodiments, the metal precursor is selected from nitrates or chlorides of nickel, iron, cobalt or ruthenium, and the mass ratio is 10% of the carrier.

[0040] In some preferred embodiments, the nanostructured carrier is selected from one or more of carbon nanotubes, graphene, nanofibers or nanosheets.

[0041] In some preferred embodiments, the silane modifier includes, but is not limited to, one or more of 3-aminopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, and 3-chloropropyltrimethoxysilane.

[0042] In some preferred embodiments, the mass ratio of the silane modifier to the carbon nanotubes in step (2) is (1-3): (8-15), the stirring reaction time is 4 hours, and the washed carbon nanotubes are placed in an oven at 60° C. and dried for 12 hours.

[0043] In some preferred embodiments, the reducing agent is gradually added in step (4) by gradually adding hydrogen or sodium borohydride at a rate of 0.1-0.5 ml / min.

[0044] In some preferred embodiments, the drying process in step (5) is carried out at 100-120° C. for 12-24 hours to ensure that the moisture and solvent in the sample are completely removed.

[0045] In some preferred embodiments, the calcination process in step (6) is carried out in a nitrogen or argon atmosphere at 400° C. for 3 hours to completely convert the metal precursor into metal oxide.

[0046] In some preferred embodiments, the reduction process in step (7) is carried out in a hydrogen atmosphere at 400° C. for 3 hours.

[0047] In some preferred embodiments, the mass ratio of product I to metal salt solution is (1-4):(15-18).

[0048] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0049] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0050] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to the skilled artisan. The present invention description and examples are exemplary only.

[0051] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0052] It should be noted that all raw materials in the examples of the present invention were obtained through commercial sources.

[0053] Example 1: In this example, a method for preparing a carbon dioxide hydrogenation catalyst is provided, comprising the following steps:

[0054] Step (1), selecting nickel nitrate as a metal precursor and dissolving it in deionized water to form a metal salt solution with a concentration of 0.5 M;

[0055] Step (2), select carbon nanotubes as nanostructure carriers, disperse the carbon nanotubes in ethanol and stir them in a stirrer to form a uniform carbon nanotube suspension. Add 3-aminopropyltriethoxysilane (APTES) dropwise to the suspension as a silane modifier, the mass ratio of the silane modifier to the carbon nanotubes is 1:10, and continue stirring to react for 4 hours. Filter the suspension after the reaction to separate the modified carbon nanotubes. Wash the filtered carbon nanotubes with deionized water and ethanol several times, and dry the washed carbon nanotubes in an oven at 60°C for 12 hours to obtain product I

[0056] Step (3), adding the obtained product I into the metal salt solution at a mass ratio of 1:10, so that the product I is completely immersed in the metal salt solution to obtain a mixed solution.

[0057] Step (4), using ionized water to adjust the pH value of the mixed solution to 6, and gradually adding hydrogen reducing agent to the mixed solution at a rate of 0.1 ml / min to perform a reduction reaction to form product II.

[0058] Step (5), drying the obtained product II at 110° C. for 24 hours to remove moisture and solvent to obtain a dried sample.

[0059] Step (6), calcining the dried sample at 400° C. for 3 hours in a nitrogen atmosphere to convert the metal precursor into metal oxide and evenly distribute it on the surface of the carrier.

[0060] Step (7), reducing the calcined sample in a hydrogen atmosphere at 400° C. for 3 hours to form a final catalyst for carbon dioxide hydrogenation reaction.

[0061] Example 2: In this example, a method for preparing a carbon dioxide hydrogenation catalyst is provided, comprising the following steps:

[0062] Step (1): iron chloride is selected as a metal precursor and dissolved in deionized water to form a metal salt solution with a concentration of 0.7 M.

[0063] Step (2): Graphene is selected as a nanostructure carrier, and the graphene is dispersed in ethanol and stirred in a stirrer to form a uniform graphene suspension. 3-Mercaptopropyltrimethoxysilane (MPTS) is added dropwise to the suspension as a silane modifier, and the mass ratio of the silane modifier to graphene is 2:12. The reaction is continued by stirring for 4 hours. The suspension after the reaction is filtered to separate the modified graphene. The filtered graphene is washed with deionized water and ethanol several times, and the washed graphene is placed in an oven at 60°C and dried for 12 hours to obtain product I.

[0064] Step (3): Add the obtained product I into a metal salt solution at a mass ratio of 1:12, so that the product I is completely immersed in the metal salt solution to obtain a mixed solution.

[0065] Step (4): The pH value of the mixed solution is adjusted to 5.5 using ionized water, and sodium borohydride reducing agent is gradually added to the mixed solution at a rate of 0.2 ml / min to carry out a reduction reaction to form product II.

[0066] Step (5): Dry the obtained product II at 120° C. for 20 hours to remove moisture and solvent to obtain a dried sample.

[0067] Step (6): The dried sample was calcined at 400° C. for 3 hours in an argon atmosphere to convert the metal precursor into metal oxide and evenly distribute it on the surface of the carrier.

[0068] Step (7): The calcined sample is reduced in a hydrogen atmosphere at 400° C. for 3 hours to form the final catalyst for carbon dioxide hydrogenation reaction.

[0069] Example 3: In this example, a method for preparing a carbon dioxide hydrogenation catalyst is provided, comprising the following steps:

[0070] Step (1): cobalt nitrate is selected as a metal precursor and dissolved in deionized water to form a metal salt solution with a concentration of 0.3 M.

[0071] Step (2): Select nanofibers as nanostructure carriers, disperse the nanofibers in ethanol and stir them in a stirrer to form a uniform nanofiber suspension.

[0072] 3-Chloropropyltrimethoxysilane (CPTMS) was added dropwise into the suspension as a silane modifier, with a mass ratio of the silane modifier to the nanofibers being 3:9, and the reaction was stirred continuously for 4 hours.

[0073] The suspension after the reaction is filtered to separate the modified nanofibers.

[0074] The nanofibers obtained by filtration were washed with deionized water and ethanol for multiple times, and the washed nanofibers were placed in an oven at 60° C. and dried for 12 hours to obtain product I.

[0075] Step (3): Add the obtained product I into a metal salt solution at a mass ratio of 1:15, so that the product I is completely immersed in the metal salt solution to obtain a mixed solution.

[0076] Step (4): Use ionized water to adjust the pH value of the mixed solution to 6.5, and gradually add hydrogen reducing agent to the mixed solution at a rate of 0.3 ml / min to carry out a reduction reaction to form product II.

[0077] Step (5): Dry the obtained product II at 100° C. for 18 hours to remove moisture and solvent to obtain a dried sample.

[0078] Step (6): calcine the dried sample at 400° C. for 3 hours in a nitrogen atmosphere to convert the metal precursor into metal oxide and evenly distribute it on the surface of the carrier.

[0079] Step (7): The calcined sample is reduced in a hydrogen atmosphere at 400° C. for 3 hours to form the final catalyst for carbon dioxide hydrogenation reaction.

[0080] For the sake of comparison, the evaluation conditions and results of the carbon dioxide to methanol application of the catalysts in Examples 1-3 are summarized in the application examples, and the evaluation results are listed in Table 1.

[0081] Application example: Evaluation of catalysts for the production of methanol from carbon dioxide

[0082] 2 g of catalyst was loaded into a fixed bed reactor, and the reaction was carried out at 300 °C and 2 MPa pressure. The feed flow rate was 200 mL / min, and the molar ratio of hydrogen to carbon dioxide was 3:1. During the application, an online gas chromatography (GC) was turned on to monitor the composition of the reaction products. The reaction experiment was carried out for 50 hours, and the reaction products were regularly collected and analyzed by online gas chromatography (GC). The CO 2 Conversion rate, methanol selectivity and catalyst stability data. Detailed data are shown in Table 1 Evaluation results of the catalyst's application in carbon dioxide to methanol.

[0083] Table 1: Evaluation results of catalysts for the production of methanol from carbon dioxide

[0084] sample <![CDATA[CO 2 Conversion rate (%)]]> <![CDATA[CH 3 OH selectivity (%)]]> Example 1 78.35 25.12 Example 2 75.68 22.47 Example 3 73.54 24.33

[0085] It can be seen from the experimental data of the above application examples that the catalysts of Examples 1-3 exhibit high CO 2 conversion rate and methanol selectivity, and has good stability. In particular, the catalyst of Example 1 2 The performance in terms of conversion rate and methanol selectivity is the best due to the following reasons:

[0086] In Example 1, the carbon nanotube carrier is modified with silane (3-aminopropyltriethoxysilane, APTES), which introduces active groups such as amino groups on the surface of the carrier, significantly improving the dispersibility of the metal precursor. These active groups can form a strong interaction with the metal precursor, thereby firmly anchoring the metal precursor so that it is evenly distributed on the surface of the carbon nanotube. In this way, the agglomeration of metal particles during high temperature treatment is effectively prevented, ensuring that the metal particles maintain nanoscale size and high dispersibility. The high dispersibility and nanometer size of the metal particles increase the number of active sites of the catalyst and significantly improve the overall activity of the catalyst. In addition, the introduction of active groups also enhances the interaction between the metal and the carrier, improves the mechanical stability and thermal stability of the catalyst during the reaction, thereby extending the service life of the catalyst. These improvements enable the catalyst in Example 1 to exhibit excellent catalytic performance and long-term stability in the carbon dioxide hydrogenation reaction.

[0087] The catalysts of Examples 2 and 3 were 2 The conversion rate and methanol selectivity are slightly lower than those in Example 1, but still show high catalytic performance and stability. This shows that iron and cobalt, as metal precursors, also have good catalytic activity, and the performance of the catalyst can be significantly improved through reasonable carrier selection and modification.

[0088] Furthermore, through the GC detection data, the generation of each reaction product and the difference in time points can be intuitively seen: each example has a methane peak at a different time point, Example 1 is the fastest, and Example 2 and Example 3 become slower in turn.

[0089] Depend on Figure 1 It can be seen that the methane (CH 4 ) peaks at around 2 minutes. 2 ) has a peak at around 3 minutes. Methanol (CH 3 OH) peaks at around 5 minutes.

[0090] Depend on Figure 2 It can be seen that the methane (CH 4 ) peaks at around 4 minutes. Carbon dioxide (CO 2 ) has a peak at around 6 minutes. Methanol (CH 3 OH) peaks at around 9 minutes.

[0091] Depend on Figure 3 It can be seen that the methane (CH 4 ) peaks at around 6 minutes. 2 ) has a peak at around 9 minutes. Methanol (CH 3OH) peaks at around 13 minutes.

[0092] Combined with the data in Table 1, the catalyst of Example 1 2 Conversion rate and CH 3 The OH selectivity was the best. This shows that the performance of the catalyst can be significantly improved through silane modification and optimized preparation methods, making it suitable for efficient carbon dioxide hydrogenation to methanol reaction.

[0093] The present invention is not limited to the above-mentioned embodiments. Anyone should be aware that any structural changes made under the enlightenment of the present invention, and any technical solutions that are the same or similar to the present invention, fall within the protection scope of the present invention. The technology, shape, and structural parts not described in detail in the present invention are all well-known technologies.

Claims

1. A method for preparing a catalyst for producing methanol by hydrogenating carbon dioxide, characterized in that: The following steps are involved: Step (1), selecting a metal precursor and dissolving the metal precursor in deionized water to form a metal salt solution with a concentration of 0.1-1M; Step (2), selecting carbon nanotubes, dispersing the carbon nanotubes in ethanol and placing them in a stirrer to stir to form a carbon nanotube suspension, then adding a silane modifier dropwise to the suspension, filtering the suspension after the reaction to separate the modified carbon nanotubes, drying and filtering the washed carbon nanotubes to obtain product I, wherein the mass ratio of the silane modifier to the carbon nanotubes is (1-3):(8-15), the stirring reaction time is 4 hours, and the washed carbon nanotubes are placed in an oven at 60° C. and dried for 12 hours, wherein the silane modifier includes but is not limited to one or more of 3-aminopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, and 3-chloropropyltrimethoxysilane; Step (3), adding the obtained product I to a metal salt solution, so that the product I is completely immersed in the metal salt solution, to obtain a mixed solution; Step (4), using ionized water to adjust the pH value of the mixed solution to 5-7, and gradually adding a reducing agent to the mixed solution to reduce the metal ions to form product II; Step (5), drying the obtained product II to remove water and solvent to obtain a dried sample; Step (6), calcining the dried sample in a nitrogen atmosphere to convert the metal into metal oxide and evenly distribute it on the surface of the carrier; Step (7), reducing the calcined sample in a hydrogen atmosphere to form a catalyst for carbon dioxide hydrogenation reaction; The metal precursor is selected from nitrates or chlorides of nickel, iron, cobalt or ruthenium, and the mass ratio is 10% of the carrier.

2. The method for preparing a catalyst for producing methanol by hydrogenation of carbon dioxide according to claim 1, characterized in that: The reducing agent is gradually added in step (4) by gradually adding hydrogen or sodium borohydride at a rate of 0.1-0.5 ml / min.

3. The method for preparing a catalyst for producing methanol by hydrogenation of carbon dioxide according to claim 1, characterized in that: The drying process in step (5) is carried out at 100-120°C for 12-24 hours to ensure that the moisture and solvent in the sample are completely removed.

4. The method for preparing a catalyst for producing methanol by hydrogenation of carbon dioxide according to claim 1, characterized in that: The calcination process in step (6) is carried out in a nitrogen atmosphere at 400° C. for 3 hours to completely convert the metal into metal oxide.

5. The method for preparing a catalyst for producing methanol by hydrogenation of carbon dioxide according to claim 1, characterized in that: The reduction process in step (7) is carried out in a hydrogen atmosphere at 400° C. for 3 hours.

6. The method for preparing a catalyst for producing methanol by hydrogenation of carbon dioxide according to claim 1, characterized in that: The mass ratio of product I and metal salt solution is (1-4):(15-18).

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