A carbon nitride-based catalyst for carbon dioxide hydrogenation to methanol, and a preparation method and application thereof

Abstract

The application belongs to the technical field of carbon dioxide hydrogenation, and particularly relates to a supported catalyst for promoting the selectivity of carbon dioxide hydrogenation to methanol and application thereof. Specifically, a uniformly ground precursor mixture is directly placed in a 5vol% hydrogen-argon atmosphere and subjected to one-step heat treatment to obtain a supported catalyst PdCu@C3N4 loaded with PdCu alloy particles. The supported catalyst can effectively activate carbon dioxide and hydrogen at a relatively low temperature, and the selectivity of methanol generation is as high as 100%, which can effectively solve the problems of poor stability, low activity and low selectivity of traditional supported catalysts. The synthesis method of the supported catalyst is simple, the yield is considerable, and the supported catalyst can selectively generate methanol from carbon dioxide hydrogenation at a relatively low temperature, which is conducive to the popularization and application in the existing carbon dioxide hydrogenation to methanol process.

Description

Technical Field

[0001] This invention belongs to the field of carbon dioxide hydrogenation technology, specifically relating to a supported catalyst that promotes the selective production of methanol from carbon dioxide through hydrogenation. Background Technology

[0002] Carbon dioxide (CO2) is a major greenhouse gas that contributes to climate change and related adverse environmental impacts, making the mitigation of anthropogenic CO2 production a significant challenge. CO2 capture and conversion into energy is currently considered an effective way to mitigate the effects of global warming and find alternatives to fossil fuels. Currently, catalytic hydrogenation technology can be used to convert CO2 into various fuels such as formic acid, methanol, olefins, and aromatics. Among the many value-added products from CO2 conversion, methanol is an ideal outcome because it is both a liquid fuel that can serve as a fossil fuel alternative and an important platform molecule for the production of high-value-added olefins and aromatics.

[0003] Currently, methanol is produced industrially using a thermocatalytic carbon dioxide hydrogenation reduction process, primarily employing Cu / ZnO / Al2O3 as the catalyst. However, this catalyst suffers from low activity, low selectivity for methanol, and poor stability. Therefore, there is an urgent need to develop carbon dioxide hydrogenation catalysts with high activity, high selectivity, and high stability under mild conditions.

[0004] Nitrogen compounds (C3N4) have shown great promise for catalytic carbon dioxide hydrogenation due to their simplicity, thermal stability, chemical stability, and low toxicity. Adding a small amount of noble metal as a co-catalyst to C3N4 is an effective strategy to improve its performance in catalytic carbon dioxide hydrogenation to methanol. This is because noble metals can promote the activation of carbon dioxide and hydrogen, and provide catalytically active sites for the reaction, thereby improving reaction activity and selectivity. Currently, palladium nanoparticles are commonly used in hydrogenation reactions due to their excellent H2 activation ability. However, palladium's activation-promoting effect on CO2 is not significant, and its price is relatively high. Alloying Cu with Pd can fully utilize the strong activation abilities of Pd and Cu for H2 and CO2, respectively, while also reducing costs. Therefore, we directly obtained a PdCu@C3N4 catalyst based on C3N4 supported with a PdCu alloy through a one-step heat treatment. The interaction between Cu and Pd facilitates better dispersion of Cu and Pd atoms and improves reduction performance. At a relatively low temperature (160℃), this catalyst can effectively activate carbon dioxide and hydrogen, while achieving a methanol production selectivity of up to 100%. Summary of the Invention

[0005] The purpose of this invention is to provide a carbon nitride-based supported catalyst for the selective hydrogenation of carbon dioxide to methanol. Addressing the shortcomings of existing catalysts, this invention synthesizes a supported catalyst that combines high activity, high stability, and high selectivity. This supported catalyst can effectively activate carbon dioxide and hydrogen at a relatively low temperature (160 °C), while achieving 100% selectivity in methanol production. It is expected to solve the problems of poor stability, low activity, and low selectivity of traditional supported catalysts. The synthesis method of this supported catalyst is simple, and the yield is considerable. Furthermore, its ability to catalyze the selective hydrogenation of carbon dioxide to methanol at a relatively low temperature facilitates its widespread application in existing carbon dioxide hydrogenation to methanol processes.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A carbon nitride-based supported catalyst for the selective hydrogenation of carbon dioxide to methanol is prepared by introducing a PdCu alloy as a co-catalyst into C3N4, resulting in a supported catalyst PdCu@C3N4. The loading of the PdCu alloy is approximately 0.2 wt%, and the loading is controllable.

[0008] The preparation method of the supported catalyst includes the following steps:

[0009] (1) Grind all the precursors thoroughly in a mortar;

[0010] (2) The ground mixture was placed in a 5 vol% hydrogen-argon atmosphere and subjected to one-step heat treatment to obtain a supported catalyst PdCu@C3N4 loaded with PdCu alloy particles.

[0011] The specific steps are as follows:

[0012] (1) Grind 20 mg of palladium acetylacetone, 20 mg of copper acetylacetone, and 5 g of dicyandiamide thoroughly in a mortar;

[0013] (2) The uniformly ground precursor was placed in a 5 vol% hydrogen-argon atmosphere and calcined at 550 °C for 4 h at a heating rate of 5 °C / min to obtain the supported catalyst PdCu@C3N4 with PdCu alloy particles.

[0014] The resulting supported catalyst can promote the hydrogenation of carbon dioxide to methanol reaction.

[0015] The significant advantages of this invention are:

[0016] (1) The present invention loads PdCu alloy on C3N4, which promotes the activation and dissociation of carbon dioxide and hydrogen, and can significantly improve the efficiency of catalytic reaction.

[0017] (2) The present invention can effectively activate carbon dioxide and hydrogen at a relatively low temperature (160 °C), while the selectivity of methanol generation is up to 100%.

[0018] (3) This invention is simple and easy to implement, and has high methanol selectivity, which is beneficial for its application in existing processes. Attached Figure Description

[0019] Figure 1 XRD patterns of C3N4 and PdCu@C3N4.

[0020] Figure 2 SEM images of C3N4 and PdCu@C3N4.

[0021] Figure 3 A comparison of the activity of C3N4 and PdCu@C3N4 catalysts for the hydrogenation of carbon dioxide to methanol.

[0022] Figure 4 The XRD patterns are shown before and after the reaction of PdCu@C3N4. Detailed Implementation

[0023] To make the content of this invention easier to understand, the technical solution of this invention will be further described below with reference to specific embodiments, but this invention is not limited thereto.

[0024] Example 1: Preparation of PdCu@C3N4

[0025] After thoroughly grinding 20 mg of palladium acetylacetone, 20 mg of copper acetylacetone, and 5 g of dicyandiamide in a mortar, the mixture was placed in a 5 vol% hydrogen-argon atmosphere and heated at 5 °C for 1 min. -1 The catalyst PdCu@C3N4, which is supported on PdCu alloy particles, was prepared by calcining at 550℃ for 4 hours.

[0026] Application Example 1: Activity Evaluation of PdCu@C3N4 Carbon Dioxide Hydrogenation to Methanol

[0027] The efficiency evaluation experiment of the PdCu@C3N4 supported catalyst for the hydrogenation of carbon dioxide to methanol obtained in Example 1 was carried out in a stainless steel high-pressure reactor. The yields of methanol and CO were detected by an Agilent 7890B gas chromatograph. The experimental procedure was as follows: 25 mg of catalyst was placed in a stainless steel high-pressure reactor, and a feed gas with H2 / CO2 = 3:1 (v / v) was introduced to a pressure of 4 MPa. The reaction was carried out at 160 °C for 5 h.

[0028] Figure 1 The XRD patterns of C3N4 and PdCu@C3N4 are shown. Figure 1As shown, the XRD pattern of the PdCu@C3N4 supported catalyst contains all the characteristic peaks of C3N4. The characteristic peaks of the PdCu alloy are not shown in the pattern, mainly due to the low content and small particle size of the PdCu alloy.

[0029] Figure 2 SEM images of C3N4 and PdCu@C3N4. From Figure 2 It can be seen that both C3N4 and PdCu@C3N4 catalysts exhibit ultrathin nanosheet morphology.

[0030] Figure 3 A comparison of the activity of C3N4 and PdCu@C3N4 in the hydrogenation of carbon dioxide to methanol. From... Figure 3 As can be seen, pure C3N4 did not produce methanol and CO, while the PdCu@C3N4 supported catalyst significantly improved the efficiency and selectivity of carbon dioxide hydrogenation to methanol, achieving 100% selectivity for methanol. This is mainly because the PdCu alloy can promote the activation of CO2 and the dissociation of H2, thereby improving the efficiency of selective hydrogenation of carbon dioxide to methanol.

[0031] Figure 4 The XRD patterns of PdCu@C3N4 before and after the catalytic reaction are shown. Comparison of the XRD patterns before and after the reaction reveals that the supported catalyst did not undergo significant changes compared to before the reaction; no impurity peaks or characteristic peaks of the PdCu alloy appeared. This indicates that the PdCu@C3N4 catalyst is stable and has not decomposed, and that the PdCu alloy particles have not shown significant agglomeration.

[0032] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. Application of carbon nitride-based catalyst PdCu@C3N4 in selective methanol production reaction of carbon dioxide hydrogenation, characterized in that: The carbon nitride-based catalyst PdCu@C3N4 is prepared by directly placing a uniformly ground precursor mixture of palladium acetylacetone, copper acetylacetone, and dicyandiamine in a 5 vol% hydrogen-argon atmosphere and subjecting it to a one-step heat treatment to obtain a supported catalyst PdCu@C3N4 with PdCu alloy particles; the loading amount of PdCu alloy on C3N4 is 0.2 wt%; the application involves placing 25 mg of the catalyst in a stainless steel high-pressure reactor, charging it with a raw material gas of H2 / CO2 = 3:1 to 4 MPa, and reacting at 160 ℃ for 5 h, where 3:1 is a volume ratio.

2. Use according to claim 1, characterized in that: The specific steps for preparing the carbon nitride-based catalyst PdCu@C3N4 are as follows: After grinding a mixture of 20 mg palladium acetylacetone, 20 mg copper acetylacetone, and 5 g dicyandiamine evenly, the mixture is calcined at 550 °C in a 5 vol% hydrogen-argon atmosphere to obtain the catalyst PdCu@C3N4.

3. The application according to claim 2, characterized in that: The calcination time was 4 hours, and the heating rate was 5 ℃ / min.

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