A catalyst for promoting the hydrogenation of carbon dioxide to methanol and its application

Abstract

The present invention discloses a supported catalyst for promoting the hydrogenation of carbon dioxide to methanol, and a preparation method and application thereof, wherein the metal organic framework material In-MIL-68 is first synthesized by a solvothermal method, and then Pt is adsorbed as a co-catalyst by the porous confinement effect of In-MIL-68, and Pt@In-MIL-68 is prepared by a bottom-up method. 2 O 3 Supported catalyst. The supported catalyst can effectively promote the activation of carbon dioxide and hydrogen, and can also inhibit the high-temperature deactivation of the catalyst, effectively solving the problems of poor stability, low activity, and low selectivity of traditional supported catalysts. The synthesis method is simple, the yield is considerable, and the temperature required for catalytic hydrogenation of carbon dioxide to methanol is lower, which is conducive to the promotion and application of the supported catalyst in the existing process of hydrogenation of carbon dioxide to methanol.

Description

Technical Field

[0001] The invention belongs to the technical field of carbon dioxide hydrogenation, and specifically relates to a supported catalyst for promoting carbon dioxide hydrogenation to produce methanol, and a preparation method and application thereof. Background Art

[0002] Carbon dioxide is considered to be the main cause of global warming and ocean acidification. Therefore, the continued increase in atmospheric carbon dioxide concentrations caused by human activities has become a serious issue of concern to the world. In order to support the national strategy of "carbon peak and carbon neutrality", researchers are committed to converting carbon dioxide into value-added chemicals, which can not only reduce the concentration of carbon dioxide in the atmosphere, but also provide high-energy chemical fuels as a substitute for traditional fossil fuels. At present, catalytic hydrogenation technology can be used to convert carbon dioxide into a variety of fuels such as aromatics, olefins, formic acid, methanol, etc. Among the many carbon dioxide conversion products, methanol, as a liquid fuel and an important platform molecule for the production of high-value-added olefins and aromatics, is one of the ideal products.

[0003] At present, the catalyst used in the industrial production of methanol by thermal catalytic carbon dioxide hydrogenation reduction process is mainly Cu / ZnO / Al2O3. However, this catalyst has problems such as low activity, low methanol selectivity, and poor stability. Therefore, it is urgent to develop a carbon dioxide hydrogenation catalyst with high activity, high selectivity and high stability under mild conditions.

[0004] Indium oxide-based catalysts have been proven to be able to be used to catalyze the hydrogenation of carbon dioxide to produce methanol. However, most traditional indium oxide materials are bulk structures with small specific surface areas and low exposure rates of surface catalytic active sites, which are not conducive to the adsorption and activation of carbon dioxide; at the same time, traditional indium oxide-based catalysts also have problems such as low selectivity for methanol and poor stability. Adding a small amount of precious metals as co-catalysts to the surface of indium oxide is one of the effective strategies to improve its catalytic performance of hydrogenation of carbon dioxide to produce methanol. This is because precious metals can promote the activation of carbon dioxide and hydrogen and provide catalytic active sites for the reaction, thereby improving the reaction activity and selectivity. However, precious metal co-catalysts loaded by conventional impregnation methods are often prone to sintering / agglomeration during the reaction, resulting in easy deactivation of the catalyst. In response to the above problems, the present invention utilizes the porous confinement effect of MOF materials to effectively inhibit the migration and aggregation of the loaded metal co-catalysts, that is, by embedding the precious metal Pt, it enters the porous precursor with confinement effect, and then undergoes a step of heat treatment to obtain a loaded indium oxide catalyst with high activity, high selectivity and stability. Summary of the invention

[0005] The present invention aims at the deficiencies of existing catalysts and provides a supported catalyst for promoting the hydrogenation of carbon dioxide to methanol and its preparation method and application. The supported catalyst can effectively activate carbon dioxide and hydrogen, and also has high activity and high stability, and can inhibit the high-temperature deactivation of the catalyst, thereby solving the shortcomings of traditional catalysts such as poor stability, low activity, and low selectivity.

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

[0007] A supported catalyst for promoting the hydrogenation of carbon dioxide to methanol is prepared by adsorbing a Pt precursor on a metal organic framework (MOF) material In-MIL-68 and subjecting the catalyst to a one-step heat treatment in an air atmosphere to obtain a supported catalyst Pt@In2O3. The preparation steps are as follows:

[0008] (1) Indium nitrate and terephthalic acid were dissolved in N,N-dimethylformamide (DMF) and reacted at 120 °C for 30 min. The resulting precipitate was washed and dried to obtain the metal organic framework material In-MIL-68;

[0009] (2) Add 7.4 mg ml of -1 The supported catalyst Pt is obtained by stirring, adsorbing, washing and drying the solution of chloroplatinic acid, and then calcining at 500 °C in air atmosphere for 2 h. x @In2O3.

[0010] Furthermore, the mass ratio of indium nitrate to terephthalic acid in step (1) is 1:1.

[0011] Furthermore, the loading amount of Pt on In2O3 in the obtained supported catalyst is 0.5-6wt%.

[0012] The supported catalyst obtained by the invention can be used in the reaction of preparing methanol by hydrogenating carbon dioxide.

[0013] The remarkable effects of the present invention are:

[0014] (1) The present invention loads Pt on In2O3, which can effectively inhibit the aggregation and deactivation of Pt on In2O3, improve the stability of the catalyst, and promote the activation and dissociation of carbon dioxide and hydrogen, which can significantly improve the efficiency of the catalytic reaction.

[0015] (2) The method of the present invention is simple and easy to implement, has a considerable yield, requires a lower temperature for catalytic hydrogenation of carbon dioxide to produce methanol, and has a higher methanol selectivity, which is conducive to promotion and application based on existing processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1In2O3 and the supported catalyst Pt prepared in Example 2 x @XRD comparison chart of In2O3.

[0017] Figure 2 In2O3 (a) and the supported catalyst Pt prepared in Example 2 0.5 SEM images of Pt2@In2O3 (b), Pt2@In2O3 (c) and Pt6@In2O3 (d).

[0018] Figure 3 In2O3 and the supported catalyst Pt prepared in Example 2 x @In2O3 catalytic activity comparison of carbon dioxide hydrogenation to methanol.

[0019] Figure 4 This is the XRD comparison diagram of the supported catalyst Pt2@In2O3 before and after the catalytic reaction. DETAILED DESCRIPTION

[0020] In order to make the contents of the present invention easier to understand, the technical solution of the present invention is further described below in conjunction with specific implementation methods, but the present invention is not limited thereto.

[0021] Example 1 Preparation of In-MIL-68

[0022] After 60 mg In(NO3)3·4.5H2O and 60 mg terephthalic acid were fully dissolved in 50 mL DMF, the mixture was reacted at 120°C for 30 min. The resulting white precipitate was washed and dried to obtain In-MIL-68.

[0023] Example 2 Pt x @Preparation of In2O3 supported catalyst

[0024] 200 mg of In-MIL-68 prepared in Example 1 was dispersed in 50 mL of ethanol, and then 0.135, 0.54, and 1.62 mL of 7.4 mg ml -1 The chloroplatinic acid solution was fully mixed and stirred for 12 h. The precipitate was washed and dried, and then calcined at 500 °C in air for 2 h to obtain catalysts with loadings of 0.5wt%, 2wt%, and 6wt%, respectively. x @In2O3 (x represents the loading amount of Pt on In2O3).

[0025] Figure 1 In2O3 and the catalyst Pt prepared in Example 2 x @XRD comparison chart of In2O3. Figure 1As shown, the XRD spectrum of the supported catalyst contains all the characteristic peaks of In2O3, but does not show the characteristic peaks of Pt, mainly due to the low content of Pt and the small particle size.

[0026] Figure 2 In2O3 (a) and the supported catalyst Pt prepared in Example 2 0.5 SEM images of Pt2@In2O3 (b), Pt2@In2O3 (c) and Pt6@In2O3 (d). Figure 2 It can be seen that pure In2O3 is in the shape of a hollow hexagonal prism. After loading Pt, the obtained supported catalyst still maintains a hollow hexagonal prism structure.

[0027] Example 3 Pt x Evaluation of the activity of @In2O3 catalytic hydrogenation of carbon dioxide to methanol

[0028] The efficiency evaluation experiment of the obtained catalyst for the hydrogenation of carbon dioxide to methanol was carried out in a stainless steel high-pressure reactor, and the production of methanol and CO was detected by Agilent 7890B gas chromatograph. The experimental process is as follows: the catalyst is placed in a stainless steel high-pressure reactor, and the raw gas of H2 / CO2 = 3:1 (v / v) is charged into it to 3 MPa, and the reaction is carried out at 260 °C for 2 h.

[0029] Figure 3 In2O3 and the supported catalyst Pt prepared in Example 2 x @In2O3 catalytic activity comparison chart of carbon dioxide hydrogenation to methanol. As can be seen from the figure, compared with pure In2O3, the supported catalyst can significantly improve the efficiency and selectivity of carbon dioxide hydrogenation to methanol. This is mainly because Pt can promote the activation of CO2 and the dissociation of H2, thereby improving the efficiency of carbon dioxide selective hydrogenation to methanol. Among them, when the Pt loading is 2wt%, the catalyst improves the efficiency and selectivity of carbon dioxide hydrogenation to methanol most significantly.

[0030] Figure 4 The XRD comparison of the supported catalyst Pt2@In2O3 before and after the catalytic reaction. By comparing the XRD patterns before and after the reaction, it can be seen that the supported catalyst did not undergo significant changes after the reaction, and no impurity peaks appeared, indicating that the structural confinement of porous In2O3 can effectively inhibit the migration and agglomeration of Pt, thereby improving the stability of the Pt2@In2O3 catalyst.

[0031] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. A method for preparing a supported catalyst for promoting the hydrogenation of carbon dioxide to methanol, characterized in that: Here are the steps: (1) After 60 mg In(NO3)3·4.5H2O and 60 mg terephthalic acid were fully dissolved in 50 mL DMF, the mixture was reacted at 120°C for 30 min. The resulting white precipitate was washed and dried to obtain In-MIL-68. (2) Disperse 200 mg of the prepared In-MIL-68 in 50 mL of ethanol, and then add 0.54 mL of 7.4 mg ml -1 The chloroplatinic acid solution was fully mixed and stirred for 12 h. The obtained precipitate was washed and dried, and then calcined at 500 °C in air atmosphere for 2 h to obtain a catalyst Pt2@In2O3 with a loading of 2 wt%.

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