Method for controllable synthesis of co3o4-in2o3 catalysts with different in2o3 crystal phases and applications thereof

Abstract

The application relates to a method for controllably synthesizing Co3O4-In2O3 catalysts with different In2O3 crystal phases and application, wherein the method takes a soluble indium salt as raw material, Co3O4 as a carrier, and citric acid as a crystal type regulator, and the Co3O4-In2O3 catalyst with different In2O3 crystal phases is controllably prepared through an impregnation calcination method. In the synthesis, scientific Co / In molar ratios are adopted, the charge properties of the Co3O4 carrier surface can be changed by simply regulating the amount of citric acid, the Co3O4-In2O3 catalyst obtained after calcination contains different In2O3 crystal phases (cubic phase In2O3, hexagonal phase In2O3, mixed phase In2O3 of the cubic phase and the hexagonal phase), has relatively excellent methanol synthesis performance, and provides a train of thought for developing a non-aqueous method for regulating and synthesizing h-In2O3 crystal phases.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of CO2 catalytic conversion, and particularly relates to a method for controllably synthesizing Co3O4-In2O3 catalysts with different In2O3 crystal phases and application thereof. BACKGROUND

[0002] With the comprehensive development of industry and economy, a large amount of non-renewable coal and fossil energy is used, and a large amount of CO2 is generated in the use and conversion process of these energy. Fossil resources are produced by natural carbon hydrogenation in the process of photosynthesis, and inspired by this, CO2 can be used as a carbon source by carbon capture and utilization technology, and hydrogenated to replace the consumption of fossil energy, so as to form a closed carbon cycle. Among the possible CO2 hydrogenation products, methanol is an important chemical raw material, which is widely used in organic synthesis, medicine, paint, automobile and national defense industries, and at the same time, methanol is also an important energy material, which can develop to replace traditional fossil fuels, so it is popular in the market. At present, although most of the researches are carried out on the classic Cu-based catalyst, it is still a great challenge to improve the selectivity and stability of methanol, therefore, the development of new methanol catalyst has important economic value and application prospect.

[0003] In2O3 is a new type of n-type semiconductor functional material, which has the advantage of high efficiency in generating methanol at high temperature compared with traditional copper-based catalysts. Even at a reaction temperature of 300 DEG C, it has a methanol selectivity as high as 50%. Oxygen vacancies on In2O3 act as active sites for CO2 activation and H2 dissociation, which can stabilize the key intermediates. However, since In2O3 is an oxide catalyst, the insufficient H2 dissociation capacity limits its practical application. Metal Co has strong H2 dissociation capacity, and hydrogen atoms are easy to diffuse from metal Co to In2O3 to promote the reduction of In2O3, so that it is easier to form oxygen vacancies on the surface, which is beneficial to improve the catalytic performance. Therefore, the combination of Co and In2O3 becomes an important idea to modify indium-based catalysts and improve the catalytic activity of CO2 catalytic hydrogenation to methanol.

[0004] In addition, In2O3 has three crystal phases, cubic phase (c-In2O3), corundum type hexagonal phase (h-In2O3) and Rh2O3 (II) type rhombic crystal phase (o-In2O3). Among the three crystal phases, c-In2O3 and h-In2O3 are stable in the temperature range of the CO2 hydrogenation to methanol reaction (200-300℃), and therefore both can be used as catalysts for the reaction. Different In2O3 crystal phases will inevitably affect the interaction between Co species and In2O3, thereby changing the electron transfer between Co species and In2O3, resulting in different CO2 hydrogenation to methanol performances. However, h-In2O3 can only be synthesized by solvothermal or hydrothermal methods at present, but the yield and output of the method are low, which will cause waste of high-value indium salt, and also involves waste liquid treatment. Moreover, the safety requirement of the equipment is high, the process is complex, and it is difficult to accurately control the suitable Co / In molar ratio or to stably synthesize the catalyst with a fixed Co / In molar ratio during synthesis. For Co-In catalysts, methanol synthesis follows a dual-site model, and oxygen vacancies on In2O3 are responsible for adsorbing and activating CO2, and metal Co is the active site for H2 adsorption and dissociation. The dissociated hydrogen atoms diffuse to In2O3 to react with activated CO2, promoting methanol synthesis. Therefore, it is also necessary to control the suitable Co / In molar ratio.

[0005] Therefore, it is urgent to develop a preparation method of a Co-In catalyst with high catalytic performance in CO2 hydrogenation to methanol, and simple operation process and high yield. SUMMARY

[0006] The technical problem to be solved by the present application is that the present application provides a method for controllably synthesizing Co3O4-In2O3 catalysts with different In2O3 crystal phases and application thereof. The non-hydrothermal synthesis method can regulate the In2O3 crystal phase of the synthesized Co3O4-In2O3 catalyst, accurately control the suitable Co / In molar ratio, and has simple operation process and high yield, thereby avoiding unnecessary waste and loss of expensive indium salt, and having excellent methanol synthesis performance in the application of CO2 hydrogenation to methanol.

[0007] To solve the above technical problems, the technical scheme adopted by the present application is as follows:

[0008] The present application provides a method for controllably synthesizing Co3O4-In2O3 catalysts with different In2O3 crystal phases. The method uses soluble indium salt as raw material, Co3O4 as carrier, and citric acid as crystal type regulator, and can controllably prepare Co3O4-In2O3 catalysts with different In2O3 crystal phases by impregnation calcination method.

[0009] The application provides a method for controllably synthesizing Co3O4-In2O3 catalysts with different In2O3 crystal phases.

[0010] Optionally, the method for controllably synthesizing Co3O4-In2O3 catalysts with different In2O3 crystal phases specifically comprises the following steps.

[0011] S1, preparing Co3O4;

[0012] S2, pouring a soluble indium salt and citric acid into a beaker containing deionized water, and stirring uniformly at room temperature;

[0013] S3, immersing the solution obtained in step S2 into the Co3O4 obtained in step S1, and placing in a drying oven after standing;

[0014] S4, placing the dried substance obtained in step S3 into a muffle furnace, and calcining at a constant temperature in air to obtain the Co3O4-In2O3 catalyst with different In2O3 crystal phases.

[0015] Optionally, the preparation method of the Co3O4 in step S1 can be one of a sol-gel method, a coprecipitation method or a hydrothermal method.

[0016] Optionally, the soluble indium salt is one of indium nitrate, indium chloride or a hydrate of the above-mentioned salt.

[0017] Optionally, the molar amount of the soluble indium salt, the molar amount of citric acid and the volume ratio of deionized water in step S2 are 3 mmol:0-0.9 mmol:5 mL, and the stirring time is 0.5-2 h.

[0018] Optionally, the standing time in step S3 is 1-10 h, the drying temperature is 60-100 DEG C, and the drying time is 4-18 h.

[0019] Optionally, in step S4, the temperature is raised to 350-500 DEG C at a temperature rising rate of 1-5 DEG C / min, and the constant temperature calcination time is 1.5-4 h.

[0020] The Co3O4-In2O3 catalyst with different In2O3 crystal phases obtained by the above-mentioned method.

[0021] The application of the Co3O4-In2O3 catalyst with different In2O3 crystal phases in the catalytic hydrogenation of CO2 to methanol. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 XRD spectra of the Co3O4-In2O3 catalyst samples synthesized with different citric acid addition amounts on the Co3O4 support prepared in Example 1;

[0023] Figure 2 CO2 conversion and methanol selectivity curves of the Co3O4-In2O3 catalyst samples synthesized with different citric acid addition amounts on the Co3O4 support prepared in Example 1 at 300℃;

[0024] Figure 3 SEM spectra of the flaky Co3O4 support prepared in Example 2;

[0025] Figure 4 XRD spectra of the Co3O4-In2O3 catalyst samples synthesized with different citric acid addition amounts on the flaky Co3O4 support prepared in Example 2;

[0026] Figure 5 SEM spectra of the rod-like Co3O4 support prepared in Example 3;

[0027] Figure 6 XRD spectra of the Co3O4-In2O3 catalyst samples synthesized with different citric acid addition amounts on the rod-like Co3O4 support prepared in Example 3. DETAILED DESCRIPTION

[0028] In order to better understand the above technical solutions, the exemplary embodiments of the present application will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present application are shown in the drawings, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided so that the present application can be more clearly, thoroughly understood and the scope of the present application can be completely conveyed to those skilled in the art.

[0029] In one aspect, the present application provides a method for controllably synthesizing Co3O4-In2O3 catalysts with different In2O3 crystal phases. The method uses soluble indium salt as raw material, Co3O4 as support, and citric acid as crystal phase regulator, and controllably prepares Co3O4-In2O3 catalysts with different In2O3 crystal phases through impregnation and calcination.

[0030] The method for controllably synthesizing Co3O4-In2O3 catalysts with different In2O3 crystal phases specifically includes the following steps:

[0031] S1, preparing Co3O4;

[0032] Preferably, the preparation method of Co3O4 in step S1 can be one of sol-gel method, coprecipitation method or hydrothermal method;

[0033] In a preferred embodiment of the present application, the sol-gel method is used to prepare Co3O4.

[0034] In a preferred embodiment of the present application, the hydrothermal method is used to prepare Co3O4.

[0035] S2, pour the soluble indium salt and citric acid into a beaker containing deionized water, and stir uniformly at room temperature;

[0036] Preferably, the soluble indium salt in step S2 is one of indium nitrate, indium chloride or hydrate of the above-mentioned salt.

[0037] In a preferred embodiment of the present application, the soluble indium salt in step S2 is indium nitrate.

[0038] Preferably, the molar ratio of the soluble indium salt, the molar amount of citric acid and the volume of deionized water in step S2 is 3 mmol:0-0.9 mmol:5 mL, and the stirring time is 0.5-2 h.

[0039] In a preferred embodiment of the present application, the molar amount of citric acid is 0, 0.3, 0.6 and 0.9 mmol, and the stirring time is 0.5 h.

[0040] S3, immerse the solution obtained in step S2 into Co3O4 obtained in step S1, and then place it in an oven after standing;

[0041] Preferably, the standing time in step S3 is 1-10 h, the drying temperature is 60-100°C, and the drying time is 4-18 h.

[0042] In a preferred embodiment of the present application, the standing time in step S3 is 5 h, the drying temperature is 80°C, and the drying time is 6 h.

[0043] S4, place the dried material obtained in step S3 into a muffle furnace, and calcine it at a constant temperature in air to obtain a Co3O4-In2O3 catalyst with different In2O3 crystal phases;

[0044] Preferably, the temperature is raised to 350-500°C at a rate of 1-5°C / min in step S4, and the constant temperature calcination time is 1.5-4 h.

[0045] In a preferred embodiment of the present application, the temperature is raised to 400°C at a rate of 2°C / min in step S4, and the constant temperature calcination time is 2 h.

[0046] In another aspect of the present application, there is provided a Co3O4-In2O3 catalyst with different In2O3 crystal phases prepared according to any of the above embodiments.

[0047] In another aspect of the present application, there is provided a use of a Co3O4-In2O3 catalyst with different In2O3 crystal phases prepared according to any of the above embodiments in catalyzing the hydrogenation of CO2 to methanol.

[0048] Example 1

[0049] A method for controllably synthesizing a Co3O4-In2O3 catalyst with different In2O3 crystal phases, using a soluble indium salt as a raw material, Co3O4 as a carrier, and citric acid as a crystal phase regulator, and controllably preparing the Co3O4-In2O3 catalyst with different In2O3 crystal phases by an impregnation calcination method.

[0050] The method for controllably synthesizing the Co3O4-In2O3 catalyst with different In2O3 crystal phases specifically comprises the following steps:

[0051] S1, preparing Co3O4 by a sol-gel method:

[0052] 3 mmol of Co(NO3)2·6H2O and 3 mmol of citric acid were weighed into a beaker containing 40 mL of deionized water, and continuously stirred at room temperature for 1 h. The dried gel was placed in a muffle furnace and calcined at 450℃ for 3 h, with a heating rate of 2℃ / min, to obtain a Co3O4 carrier.

[0053] S2, 3 mmol of In(NO3)3 and a certain amount of citric acid (0, 0.3, 0.6 and 0.9 mmol) were poured into a beaker containing 5 mL of deionized water, and stirred at room temperature for 0.5 h.

[0054] S3, the solution obtained in step S2 was impregnated into 0.56 g of Co3O4 obtained in step S1, and after standing for 5 h, was placed in an oven at 80℃ for drying for 6 h.

[0055] S4, the dried product obtained in step S3 was placed in a muffle furnace, and heated to 400℃ at a heating rate of 2℃ / min in an air atmosphere, and calcined at a constant temperature for 2 h, to obtain a Co3O4-In2O3 catalyst with different In2O3 crystal phases.

[0056] According to the amount of citric acid added, the samples were named as Co3O4-In2O3-0 mmol citric acid, Co3O4-In2O3-0.3 mmol citric acid, Co3O4-In2O3-0.6 mmol citric acid, and Co3O4-In2O3-0.9 mmol citric acid.

[0057] Figure 1 The XRD patterns of the Co3O4 support and Co3O4-In2O3 catalyst prepared in Example 1 are shown. As can be seen from the figures, the main phase of the Co3O4 support is cubic Co3O4 (JCPDS NO. 76-1802). For the catalyst without citric acid in the impregnation solution (Co3O4-In2O3 with 0 mmol citric acid), a diffraction peak at 2θ (32.6°) related to h-In2O3 was observed. When citric acid was added to the impregnation solution, the intensity of the h-In2O3 diffraction peak in the obtained catalyst decreased, and a diffraction peak at 35.5° (2θ) belonging to c-In2O3 (JCPDS NO. 44-1087) was observed. Furthermore, the intensity of the c-In2O3 diffraction peak increased with increasing citric acid content. In particular, when the molar amount of citric acid reached 0.9 mmol, the h-In2O3 diffraction peak disappeared, yielding pure c-In2O3 supported on Co3O4. The above results indicate that by adjusting the amount of citric acid in the mixed solution and changing the charge properties on the surface of the Co3O4 support, different In2O3 crystal phases (cubic In2O3, hexagonal In2O3, and a mixed phase of cubic and hexagonal In2O3) can be obtained in the Co3O4-In2O3 catalyst prepared by calcination.

[0058] The CO2 hydrogenation performance of the Co3O4-In2O3 catalysts with different In2O3 crystal phases obtained in this embodiment was tested, and the results are as follows: Figure 2 As shown, after pretreatment with 5% vol H2 / Ar at 300℃ for 2 h, the CO2 conversion rate of all catalysts increased with increasing reaction time, stabilizing after 8 h, while the methanol selectivity of the catalysts did not change significantly with the reaction. Except for the Co3O4-In2O3 catalyst without citric acid, although the initial CO2 conversion rates of the other catalysts differed, their final CO2 conversion rates were similar. The Co3O4-In2O3 catalyst without citric acid exhibited the highest methanol selectivity and the lowest CO2 conversion rate, which is related to the different crystal phases of In2O3 in the catalyst. In conclusion, the methanol selectivity and CO2 conversion rate of the Co3O4-In2O3 catalyst can be modified by controlling the In2O3 crystal phase, thereby further optimizing the catalytic performance of the catalyst.

[0059] Example 2

[0060] A method for controllably synthesizing Co3O4-In2O3 catalysts with different In2O3 crystal phases is disclosed. The method uses soluble indium salt as raw material, Co3O4 as support, and citric acid as crystal form regulator. Co3O4-In2O3 catalysts with different In2O3 crystal phases can be controlledly prepared by impregnation and calcination.

[0061] The method for controllably synthesizing Co3O4-In2O3 catalysts with different In2O3 crystal phases specifically comprises the following steps:

[0062] S1, preparing flaky Co3O4 by a hydrothermal method:

[0063] 6 mmol of Co(NO3)2·6H2O and 24 mmol of urea were weighed in a beaker containing 150 ml of deionized water, and after stirring for 1 h, the mixed solution was transferred into a 200 mL polytetrafluoroethylene reactor liner, a high-pressure reactor was installed, and the reactor was placed in a 140°C oven for reaction for 16 h. After being taken out, centrifuged and washed, and dried, the precursor was calcined at 450°C in air at a rate of 2°C / min for 2 h to obtain flaky Co3O4.

[0064] S2, 3 mmol of In(NO3)3 and a certain amount of citric acid (0 and 0.9 mmol) were poured into a beaker containing 5 mL of deionized water, and stirred at room temperature for 0.5 h.

[0065] S3, the solution obtained in step S2 was impregnated into 0.56 g of Co3O4 obtained in step S1, and after standing for 5 h, it was placed in a 80°C oven for drying for 6 h.

[0066] S4, the dried product obtained in step S3 was placed in a muffle furnace, and heated to 400°C at a rate of 2°C / min in an air atmosphere, and calcined at constant temperature for 2 h to obtain Co3O4-In2O3 catalysts with different In2O3 crystal phases.

[0067] According to the amount of citric acid added, the samples were named as flaky Co3O4-In2O3-0 mmol citric acid and flaky Co3O4-In2O3-0.9 mmol citric acid.

[0068] Figure 3 SEM image of the flaky Co3O4 support prepared in Example 2. As can be seen from the figure, many uniform nanosheets can be seen in the Co3O4 sample. Figure 4 XRD spectrum of the flaky Co3O4 support and Co3O4-In2O3 catalyst prepared in Example 2. As can be seen from the figure, the main phase of the flaky Co3O4 support is cubic Co3O4 (JCPDS NO. 76-1802). For the catalyst without citric acid in the impregnation solution, a diffraction peak at 2θ of 32.6° related to h-In2O3 was observed. When 0.9 mmol of citric acid was added to the impregnation solution, the h-In2O3 diffraction peak disappeared in the obtained catalyst, and a diffraction peak at 35.5° (2θ) attributed to c-In2O3 (JCPDS NO. 44-1087) appeared.

[0069] Example 3

[0070] A method for controllably synthesizing Co3O4-In2O3 catalysts with different In2O3 crystal phases, using a soluble indium salt as a raw material, Co3O4 as a carrier, and citric acid as a crystal phase regulator, to controllably prepare Co3O4-In2O3 catalysts with different In2O3 crystal phases by an impregnation calcination method.

[0071] The method for controllably synthesizing Co3O4-In2O3 catalysts with different In2O3 crystal phases specifically comprises the following steps:

[0072] S1, preparing rod-shaped Co3O4 by a hydrothermal method:

[0073] 10 mmol of CoCl2·6H2O and 10 mmol of urea were weighed into a beaker containing 80 ml of deionized water, and after stirring for 1 h, the mixed solution was transferred into a 100 mL polytetrafluoroethylene reaction kettle liner, a high-pressure reaction kettle was installed, and the reaction kettle was placed in a 160°C oven for 8 h. After taking out, centrifugal washing and drying, the precursor was calcined at 450°C in air at a rate of 2°C / min for 2 h to obtain rod-shaped Co3O4.

[0074] S2, 3 mmol of In(NO3)3 and a certain amount of citric acid (0 and 0.9 mmol) were poured into a beaker containing 5 mL of deionized water, and stirred at room temperature for 0.5 h.

[0075] S3, the solution obtained in step S2 was impregnated into 0.56 g of Co3O4 obtained in step S1, and after standing for 5 h, it was placed in an 80°C oven for drying for 6 h.

[0076] S4, the dried material obtained in step S3 was placed in a muffle furnace, and heated to 400°C at a rate of 2°C / min in an air atmosphere, and calcined at a constant temperature for 2 h to prepare Co3O4-In2O3 catalysts with different In2O3 crystal phases.

[0077] According to the amount of citric acid added, the samples were named as rod-shaped Co3O4-In2O3-0 mmol citric acid and rod-shaped Co3O4-In2O3-0.9 mmol citric acid.

[0078] Figure 5 SEM image of the rod-shaped Co3O4 carrier prepared in Example 3. As can be seen from the figure, many nanorods composed of nanoparticles can be seen in the Co3O4 sample. Figure 6XRD patterns of the rod-like Co304 support and Co304-In203catalysts prepared in Example 3. As can be seen from the figure, the main phase of the rod-like Co304 support is cubic Co304(JCPDS NO. 76-1802). For the catalyst prepared without citric acid in the impregnation solution, a diffraction peak at 2Θ = 32.6° associated with h-In203was observed. When 0.9 mmol of citric acid was added to the impregnation solution, the h-In203diffraction peak disappeared in the catalyst obtained, and a diffraction peak at 2Θ = 35.5° attributed to c-In203(JCPDS NO. 44-1087) appeared.

[0079] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application, and are not intended to limit the same; although the present application has been described in detail with reference to the foregoing examples, those of ordinary skill in the art will understand that they can still modify the technical solutions described in the foregoing examples, or make equivalent replacements for some or all of the technical features; and such modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method of controllably synthesizing a Co3O4-In2O3 catalyst having different In2O3 crystal phases, characterized by, The Co3O4-In2O3 catalyst with different In2O3 crystal phases is prepared by using a soluble indium salt as a raw material, Co3O4 as a carrier, and citric acid as a crystal phase regulator, and by controlling the amount of citric acid; Specifically, the method comprises the following steps: S1, preparing Co3O4; S2, pouring the soluble indium salt and the citric acid into a beaker containing deionized water, and stirring uniformly at room temperature; S3, immersing the solution obtained in step S2 into the Co3O4 obtained in step S1, and then placing the mixture in a drying oven after standing; S4, placing the dried mixture obtained in step S3 into a muffle furnace, and calcining the mixture in air at a constant temperature to obtain the Co3O4-In2O3 catalyst with different In2O3 crystal phases; In step S2, the molar amount of the soluble indium salt, the molar amount of the citric acid, and the volume ratio of the deionized water are 3 mmol, 0-0.9 mmol, and 5 mL, respectively.

2. The method of claim 1, wherein the Co3O4-In2O3 catalyst having different In2O3 crystal phases is controllably synthesized, and In step S1, the Co3O4 can be prepared by one of a sol-gel method, a coprecipitation method, and a hydrothermal method.

3. The method of claim 1, wherein the Co3O4-In2O3 catalyst having different In2O3 crystal phases is controllably synthesized, and The soluble indium salt is one of indium nitrate, indium chloride, or a hydrate of the above-mentioned salt.

4. The method of claim 1, wherein the Co3O4-In2O3 catalyst having different In2O3 crystal phases is controllably synthesized, and In step S2, the stirring time is 0.5-2 h.

5. The method of claim 1, wherein the Co3O4-In2O3 catalyst is controllably synthesized to have different In2O3 crystal phases, and In step S3, the standing time is 1-10 h, the drying temperature is 60-100 ℃, and the drying time is 4-18 h.

6. The method of claim 1, wherein the Co3O4-In2O3 catalyst is controllably synthesized to have different In2O3 crystal phases, and In step S4, the temperature is raised to 350-500 ℃ at a temperature raising rate of 1-5 ℃ / min, and the constant temperature calcination time is 1.5-4 h.

7. A Co3O4-In2O3 catalyst with different In2O3 crystal phases, which is prepared by the method according to any one of claims 1-6.

8. Use of the Co3O4-In2O3 catalyst with different In2O3 crystal phases according to claim 7 in catalyzing the CO2 hydrogenation to prepare methanol.

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