An indium-manganese composite catalyst for carbon dioxide hydrogenation to methanol, a preparation method and application thereof

Abstract

The application discloses an indium-manganese composite catalyst for carbon dioxide hydrogenation to prepare methanol, a preparation method and application thereof. The composite catalyst is obtained by uniformly mixing In2O3 and MnCO3 according to a proportion and high-temperature calcination in a CO2 atmosphere furnace, and in the calcination process, active sites for efficient CO2 adsorption, activation and conversion are in-situ constructed on the surface of the composite catalyst. The MnCO3 is applied to the field of CO2 hydrogenation to prepare methanol for the first time, and from the results, the oxygen vacancies of In2O3 and MnCO3 are more matched, the high-temperature calcination under the high-pressure CO2 atmosphere makes the strong interaction between In2O3 and MnCO3 easier, the In-O-Mn active unit is easily in-situ formed at the interface of In2O3 and MnCO3, can be used as the active site for CO2 adsorption, activation and hydrogenation conversion, and can promote the continuous hydrogenation of CO2 on the active site to generate methanol, so that the continuous catalytic CO2 hydrogenation performance of the catalyst is greatly improved.

Description

TECHNICAL FIELD

[0001] The application relates to the field of carbon dioxide hydrogenation to prepare methanol, in particular to an indium-manganese composite catalyst, a preparation method and application. BACKGROUND

[0002] Methanol is a key component in modern chemical industry, and is also an excellent hydrogen storage material and clean energy. Preparing methanol from CO2 and H2 as raw materials can alleviate the pressure of CO2 emission. Therefore, the research on the catalyst for preparing methanol from CO2 and H2 with high efficiency and industrialization prospect has attracted extensive attention of researchers at home and abroad.

[0003] At present, the research on the methanol catalyst is relatively extensive at home and abroad, but mainly focuses on the research on Cu-based and In-based catalysts and related derivative catalysts, including the Cu and metal oxide supported catalyst, the noble metal modified In-based catalyst, the In2O3 supported metal oxide and the like. The metal supported catalyst mainly using the Cu-based catalyst is prone to form a metal solid solution between the metal active component and the metal carrier under a high-temperature and high-pressure environment, which is not conducive to the conduction of electrons and the formation and conversion of methanol intermediates in the CO2 hydrogenation reaction process, resulting in the disadvantages of low yield and low selectivity; although the In-based catalyst modified by the noble metal (such as Ru, Au, Pd, Pt and the like) has a certain degree of improvement in selectivity and yield, the noble metal atoms are prone to agglomeration under the reaction condition, and are also prone to form an alloy with the metal indium, which is not conducive to the full play of the active sites, and the price of the In-based catalyst and the noble metal is generally high, so the catalyst does not have a good development prospect in the industrialization of methanol.

[0004] Manganese carbonate (MnCO3) is a common carbonate, and compared with other carbonate compounds, is easier to decompose CO3 2- starting intermediates under a CO2 atmosphere, and the CO3 2- decomposed from the MnCO3 under the CO2 atmosphere can be replenished again, so that the overall structure of the MnCO3 is not changed, and the dynamic balance of CO2 in the MnCO3 structure is maintained. Compared with other works, the application firstly proposes to apply the MnCO3 to the field of CO2 hydrogenation to prepare methanol, and also firstly proposes the related reaction mechanism. Compared with other catalysts for preparing methanol from CO2 hydrogenation, the application in-situ constructs the reaction active sites, so that the CO2 is continuously adsorbed, activated, converted and desorbed on the surface of the catalyst, thereby providing a new reaction path, and finally the activity of the catalyst is increased by 3-5 times. Meanwhile, the price of the carbonate material is relatively low, which provides a possibility for the industrialization of the preparation of methanol from CO2 hydrogenation. SUMMARY

[0005] In view of the deficiencies of the existing CO2 hydrogenation to methanol catalyst, the purpose of the present application is to provide a catalyst with high catalytic activity and low cost.

[0006] The purpose of the present application is achieved by the following technical solutions: an indium-manganese composite catalyst and a preparation method thereof, wherein In2O3 and MnCO3 are uniformly mixed in proportion, and then the composite catalyst is obtained by high-temperature calcination in a CO2 atmosphere furnace, and in the calcination process, active sites for efficient adsorption, activation and conversion of CO2 are constructed in situ on the surface of the composite catalyst.

[0007] Preferably, the particle size of In2O3 and MnCO3 is more than 200 mesh.

[0008] Preferably, In2O3 and MnCO3 are mixed in proportion and then ground, wherein the mass ratio of In2O3 to MnCO3 is 0.5:9.5 to 2:8.

[0009] Preferably, In2O3 and MnCO3 are mixed in proportion and then ground, wherein the mass ratio of In2O3 to MnCO3 is 0.5:9.5 to 2:8.

[0010] Preferably, In2O3 is prepared by calcining indium nitrate trihydrate under air, wherein the calcination temperature is 400℃, the calcination time is 2h, and the heating rate is 5℃ / min.

[0011] Preferably, the high-temperature calcination is carried out in a CO2 atmosphere furnace, the CO2 flow rate is 32 mL / min, the pressure is 1.5 MPa, the calcination temperature is 400 o C, the heating rate is 10 o C / min, and the calcination time is 3h.

[0012] The present application also provides a use of the indium-manganese composite catalyst in the preparation of methanol from carbon dioxide hydrogenation.

[0013] Compared with the prior art, the present application has the following advantages:

[0014] 1. MnCO3 is applied to the preparation of methanol from CO2 hydrogenation for the first time, which greatly improves the catalytic activity of the catalyst.

[0015] 2. The In2O3 / MnCO3 composite catalyst is calcined in an atmosphere furnace to reconstruct active sites in situ, generating In-O-Mn active units, so that CO2 molecules are continuously adsorbed, activated and converted on the catalyst active units.

[0016] 3. Compared with pure In2O3, the In2O3 / MnCO3 composite catalyst has the advantages of low cost and simple preparation method. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 The scanning electron microscope image of the In2O3 / MnCO3 (1 / 9) composite catalyst in Example 1.

[0018] Figure 2 The activity comparison chart of In2O3 / MnCO3 (1 / 9) in Example 1 before and after the calcination treatment in the atmosphere furnace.

[0019] Figure 3 The activity comparison chart of In2O3 / MnCO3 (1 / 9) composite catalysts with different mass ratios of In2O3 to MnCO3 in Example 2.

[0020] Figure 4 The activity comparison chart of In2O3 catalyst, MnCO3 catalyst and In2O3 / MnCO3 (1 / 9) composite catalyst in Example 3.

[0021] Figure 5 The EPR chart of MnCO3 precursor and In2O3 precursor and the obtained In2O3 / MnCO3 (1 / 9).

[0022] Figure 6 The XRD chart of In2O3 / MnCO3 (1 / 9) in Example 1 before and after the calcination treatment in the atmosphere furnace. DETAILED DESCRIPTION

[0023] The application will be further described in detail below in combination with the examples and the drawings.

[0024] The application first applies MnCO3 to the field of CO2 hydrogenation to methanol. From the results, the oxygen vacancies of In2O3 and MnCO3 are more matched, and under high-pressure CO2 atmosphere and high-temperature calcination, strong interaction between them is more likely to occur. In2O3 and MnCO3 are prone to form In-O-Mn active units in situ at the interface, which can act as a site for CO2 adsorption and activation and hydrogenation conversion, and promote CO2 to continuously hydrogenate to methanol at the active site, thereby greatly improving the performance of the catalyst in continuous catalytic CO2 hydrogenation.

[0025] Example 1:

[0026] Grind 3 g of indium nitrate trihydrate and put it into a porcelain boat, then put the porcelain boat into a muffle furnace and calcine it in air at 400 o C for 2 h, and cool it to room temperature after calcination. The obtained yellow solid is In2O3. Grind the In2O3 and sieve it to obtain In2O3 solid with a particle size of more than 200 mesh.

[0027] The treatment of MnCO3 is the same as that of In2O3. Commercial MnCO3 is ground and sieved to obtain MnCO3 solid with a particle size of more than 200 mesh.

[0028] In2O3 and MnCO3 with a particle size of 200 mesh or larger are mixed at a mass ratio of 1:9 and then ground in a mortar to obtain an In2O3 / MnCO3 (1 / 9) precursor.

[0029] An In₂O₃ / MnCO₃ (1 / 9) precursor was calcined in a CO₂ atmosphere furnace to obtain an In₂O₃ / MnCO₃ (1 / 9) composite catalyst. The CO₂ flow rate was 32 mL / min, the pressure was 1.5 MPa, and the calcination temperature was 400 °C. o C, heating rate is 10 o The calcination time was 3 h, and the furnace tube was a Φ78 mm × 1 m stainless steel tube. The scanning electron microscope image of the obtained In2O3 / MnCO3 (1 / 9) composite catalyst is shown below. Figure 1 As shown.

[0030] In Example 1, the catalytic activity of the composite catalyst before and after calcination in a CO2 atmosphere, namely the In2O3 / MnCO3(1 / 9) precursor and the In2O3 / MnCO3(1 / 9) composite catalyst, was compared for CO2 hydrogenation. Figure 2 It can be seen that, compared with the In2O3 / MnCO3(1 / 9) precursor, the In2O3 / MnCO3(1 / 9) composite catalyst has significantly improved the activity of CO2 catalytic hydrogenation to methanol, increasing by nearly 100%, indicating that CO2 atmosphere calcination helps to generate active sites for CO2 adsorption activation and catalytic conversion.

[0031] Meanwhile, XRD analysis was performed on the In2O3 / MnCO3 precursor and the In2O3 / MnCO3 (1 / 9) composite catalyst, and the results are as follows: Figure 6 As shown. By Figure 6 Analysis showed that the crystal structure of the In2O3 / MnCO3 composite catalyst remained unchanged before and after calcination in a CO2 atmosphere. Therefore, the catalyst exhibits good stability in a CO2 atmosphere.

[0032] Example 2:

[0033] In2O3 and MnCO3 with a particle size of 200 mesh or larger were ground and mixed evenly in a mortar at four different mass ratios of 0.5:9.5, 1:9, 1.5:8.5 and 2:8, and then calcined in a CO2 atmosphere furnace (calcination process is the same as in Example 1) to obtain In2O3 / MnCO3 composite catalysts with different In2O3 and MnCO3 mass ratios.

[0034] In Example 2, the catalytic activity of In2O3 / MnCO3 composite catalysts with different In2O3 and MnCO3 mass ratios for CO2 hydrogenation was compared.Figure 3 It can be seen that with the increase of In2O3 content, the yield of methanol shows a volcano type of first increase and then decrease, when the mass ratio of In2O3 and MnCO3 is 1:9, the yield of methanol is the highest, reaching 2.1 mmol·g -1 ·h -1 , which shows that the increase of In2O3 content helps to increase the number of active sites for CO2 adsorption and activation and catalytic conversion, thereby increasing the activity, but when the content of In2O3 is too high, In2O3 is easy to agglomerate, which may inhibit the activity.

[0035] Example three:

[0036] Put In2O3 above 200 mesh into a CO2 atmosphere furnace for calcination (calcination process is the same as example one), to obtain In2O3 catalyst; put MnCO3 above 200 mesh into a CO2 atmosphere furnace for calcination (calcination process is the same as example one), to obtain MnCO3 catalyst.

[0037] Catalytic hydrogenation activity test was carried out on In2O3 catalyst, MnCO3 catalyst and In2O3 / MnCO3(1 / 9) composite catalyst, and the results are shown in Figure 4 It can be seen from Figure 4 that MnCO3 catalyst has no activity, and the activity of In2O3 / MnCO3 composite catalyst is more than 9 times higher than that of In2O3 catalyst.

[0038] EPR test was carried out on the three catalysts recorded in example three, i.e. MnCO3 catalyst, In2O3 catalyst and In2O3 / MnCO3(1 / 9) composite catalyst, to analyze the change of oxygen vacancy number.

[0039] From the analysis of EPR spectrum in Figure 5 , it can be seen that MnCO3 catalyst and In2O3 catalyst both contain a large number of oxygen vacancies. The number of oxygen vacancies in In2O3 / MnCO3 composite catalyst is relatively reduced. Therefore, the oxygen vacancies of the two provide important sites in the composite.

Claims

1. A method for preparing an indium-manganese composite catalyst, characterized by, After In2O3 and MnCO3 are mixed uniformly in proportion, the mass ratio of In2O3 to MnCO3 is 0.5:9.5 to 2:8, and then the mixture is calcined at 400 o C high-temperature calcination for 3 h to obtain the composite catalyst; The particle size of In2O3 and MnCO3 is above 200 mesh; The In2O3 is prepared by calcining indium nitrate trihydrate under air, wherein the calcining temperature is 400 DEG C, the calcining time is 2h, and the temperature rising rate is 5 DEG C / min.

2. The method of claim 1, wherein, The In2O3 and MnCO3 are mixed and grinded in proportion, wherein the mass ratio of In2O3 to MnCO3 is 5:95 to 20:80 according to mass percentage.

3. The method of claim 1, wherein, In a high-pressure CO2atmosphere furnace, high-temperature calcination was carried out at a CO2flow rate of 32 mL / min, a pressure of 1.5 MPa, and a temperature increase rate of 10 o C / min.

4. The indium-manganese composite catalyst prepared by the method according to any one of claims 1-3.

5. The use of the indium-manganese composite catalyst prepared by the method according to any one of claims 1-3 in the carbon dioxide hydrogenation to prepare methanol.

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