Catalyst for photo-thermal CO2 methanation reaction, preparation method of catalyst and methane preparation method

Abstract

The invention relates to a catalyst for photo-thermal CO2 methanation reaction, a preparation method of the catalyst and a methane preparation method, and the catalyst is a single-layer CoB hydroxide nanosheet. The catalyst is a single-layer CoB hydroxide nanosheet formed after a CoB catalyst is subjected to hydroxide oxidation. And the electron-deficient boron is proved to promote the generation of CH4 in the CO2 methanation reaction. Meanwhile, the energy source of the reaction completely comes from a xenon lamp light source, and the photo-thermal CO2 hydrogenation reaction is effectively realized through photochemical-thermochemical conversion. The surface of the catalyst is irradiated through a xenon lamp, the high temperature of about 330 DEG C can be achieved, and under the condition, the yield of CH4 can reach 181.5 mmol g <-1 > h <-1 > through CO2 methanation. And meanwhile, a considerable reaction yield can be achieved under an outdoor simulation condition. According to the method, energy completely comes from sunlight, and an effective solution is provided for CO2 resource utilization.

Description

Technical Field

[0001] The present invention belongs to the field of new energy utilization and CO 2 Resource utilization field; specifically, a method for photothermal CO 2 Method for synthesizing catalysts for methanation reaction. Background Art

[0002] The reduction of fossil energy and the increasing severity of environmental pollution have forced people to seek clean and renewable alternative energy in recent years. 2 ) is a well-known greenhouse gas that can also be used as a zero-cost or even negative-cost carbon feedstock in the production of valuable chemicals and fuels. The technology reduces carbon dioxide through the Sabatier reaction, also known as methanation. This process converts carbon dioxide into methane (CH 4 ) is the process of converting CO 2 One of the most attractive and promising technologies for converting hydrogen into renewable chemical energy. In this way, it is possible to circumvent the considerable difficulties associated with hydrogen storage, transportation and large-scale utilization. In addition, CH 4 It has several advantages over hydrogen, as it is easily liquefied, can be stored and transported more safely, and is widely used in energy-intensive applications as the main component of natural gas.

[0003] For the catalytic CO 2 For the methanation reaction, cobalt metal, which is abundant and relatively low in cost, is an ideal candidate and its application has been widely explored. Since the methanation reaction is highly exothermic, efforts have been made to anchor or fix Co nanoparticles on support materials to mitigate high-temperature sintering. However, the design and fabrication of Co nanoparticles for CH 4 Generating Co catalysts with high selectivity over the competing reverse water-gas shift reaction remains a major challenge. Furthermore, the reaction mechanism of Co catalysts remains largely undefined, both under laboratory conditions and for industrial applications.

[0004] Solar energy has the advantages of abundant resources, wide coverage, convenient conversion and utilization, no pollution and renewable. Therefore, if sunlight can be used as CO 2 The energy source of methanogenesis will be an effective way to realize the resource utilization of carbon dioxide.

[0005] Traditional catalysts for carbon dioxide methanation mainly include non-precious metal-based (such as Ni, Cr, Fe, Mo) and precious metal-based (such as Ru, Rh, Pt, Pb). Among non-precious metals, Ni-based catalysts have good catalytic activity, but have the disadvantages of low stability and easy loss of catalytic activity. The catalytic activity of iron, chromium, and molybdenum is lower than that of nickel, and they will be deactivated by sulfidation. Although precious metal-based catalysts have excellent low-temperature methanation activity, they are limited in resources, expensive, and difficult to apply on a large scale.

[0006] Based on this, it is expected to obtain a better catalyst that can achieve an environmentally friendly and economically feasible CO 2 Leveraging technology to better achieve CO 2 Resource utilization, high utilization efficiency and mild reaction conditions. Summary of the invention

[0007] In view of the defects in the prior art, the present invention aims to provide a method for 2 A catalyst for methanation reaction and a preparation method thereof, and a method for preparing methane.

[0008] In order to achieve the above-mentioned object, the present invention proposes a method for photothermal CO 2 A catalyst for methanation reaction, wherein the catalyst is a single-layer CoB hydroxide nanosheet.

[0009] The synthesized single-layer CoB hydroxide nanosheets have uniform size and excellent CO 2 Catalytic activity of hydrogenation to methane.

[0010] Furthermore, the present invention provides application of the above catalyst in photothermal catalytic reaction.

[0011] In addition, the present invention proposes a method for preparing the above-mentioned catalyst, the preparation method comprising the following steps:

[0012] Step S1: fully dissolving the Co source material in anhydrous ethanol, and fully stirring in an ice water bath to obtain solution A;

[0013] Step S2: NaBH 4 The solution is added to solution A, and after being stirred for 1 to 4 hours, the precipitate is washed and dissolved in anhydrous ethanol to obtain solution B;

[0014] Step S3: adding KOH or NaOH aqueous solution to solution B, leaving it to stand for 10-15 min, taking out the precipitate, washing it by centrifugation with water and ethanol in turn, and drying it in air at room temperature to obtain the catalyst.

[0015] Preferably, in step S1, the stirring is for 2 hours.

[0016] Preferably, in step S2, the dropping is performed at a rate of 4 to 8 mL / min.

[0017] Preferably, the Co source is selected from cobalt chloride, cobalt nitrate and cobalt acetate.

[0018] Preferably, the NaBH 4The amount ratio of KOH or NaOH to the Co element in the Co source is 25-100 g: 1 mol. More preferably, it is 25-50 g: 1 mol. Preferably, in the step S3, the concentration of KOH or NaOH is 0.125 M to 1 M, more preferably 0.25 to 0.5 M. In terms of Co element, the molar ratio of KOH or NaOH to the Co source is 15-125, preferably 30-64.

[0019] In addition, the present invention provides a methane production method, wherein the methane production method uses CO 2 As raw material, hydrogen is added to generate methane under light conditions, and the catalyst used in the reaction is the above-mentioned catalyst.

[0020] Preferably, the methane production method satisfies at least one of the following conditions:

[0021] The reaction temperature is between 230 and 330°C;

[0022] The reaction conditions are normal pressure;

[0023] The reaction light source is sunlight or xenon lamp.

[0024] More preferably, the reaction temperature is 270-330°C, more preferably 300-330°C.

[0025] In addition, the present invention proposes a methane preparation reaction system, which includes a reactor. The reactor is used to react and prepare methane, and its preparation method adopts the above-mentioned methane preparation method.

[0026] Preferably, the reactor comprises a quartz photothermal gas-solid phase reactor and a borosilicate quartz filter membrane placed in the quartz photothermal gas-solid phase reactor.

[0027] In some preferred embodiments, the catalyst preparation method of the present invention comprises the following steps:

[0028] 16mmol Co(OAc) 2 ·4H 2 O was fully dissolved in 200 mL of anhydrous ethanol and stirred for 2 hours in an ice-water bath to obtain solution A. 0.8 g of NaBH 4 The product was dissolved in 40 mL of cold water and slowly added dropwise to solution A at a rate of 4 mL / min. After being fully stirred for 2 hours, the precipitate was washed and dissolved in 100 mL of anhydrous ethanol to obtain solution B. 100 mL of 1 M KOH aqueous solution was added to solution B. After standing for 10 min, the product was centrifugally washed with water and ethanol in turn, and dried in air at room temperature to obtain a single-layer CoB hydroxide nanomaterial.

[0029] Furthermore, a solar thermal conversion unit is used to convert CO 2 After photothermal catalytic reaction, three products are obtained, namely methane and a small amount of ethane and carbon monoxide.

[0030] Based on the above CO 2 CO conversion system 2 The methanogenation method comprises the following steps:

[0031] (1) placing 10 to 50 mg of the obtained single-layer CoB hydroxide nanosheet in a quartz photothermal solid phase reactor;

[0032] (2) introducing feed gas containing carbon dioxide and hydrogen into the reactor and exhausting the gas for half an hour;

[0033] (3) Control the distance between the xenon lamp light source and the catalyst surface so that the reaction temperature on the catalyst surface is constant at 170-330°C;

[0034] (4) After a certain reaction time, the generated gas phase product is detected by gas chromatography to analyze the conversion rate and selectivity.

[0035] Compared with the prior art, the advantages and positive effects of the present invention are:

[0036] (1) In the technical solution described in the present invention, the present invention adopts solar energy, normal pressure, high temperature CO 2 A catalyst synthesis method for methanation provides an energy-saving, simple system, low-cost and efficient CO 2 Resource utilization method, the system uses solar energy as a single energy source, CO 2 High efficiency of methane production, achieving CO 2 resource utilization.

[0037] (2) The technical solution described in the present invention has the following outstanding features: first, the reaction process uses solar energy or xenon lamp as the light source, without the need to use other resources or external heat source, which is clean and environmentally friendly; second, the reaction time is greatly reduced; third, the reaction temperature is greatly reduced. Compared with thermal catalysis, the system can generate a temperature of 330°C, which is very effective for CO 2 Fourth, the reaction environment is relatively simple and the conditions are relatively mild. Using xenon light as the only energy source for the reaction can achieve relatively mild reaction conditions for CO 2 Methanation reaction.

[0038] (3) The technical solution described in the present invention proves that electron-deficient boron can be used in CO 2 The methanogenic reaction promotes CH 4At the same time, the energy source of the reaction comes entirely from the xenon lamp light source, and photothermal CO is achieved through photochemical-thermochemical conversion. 2 The effective realization of hydrogenation reaction. By irradiating the catalyst surface with a xenon lamp, a high temperature of about 330°C can be achieved. Under this condition, CO 2 Methanation can reach 181.5mmol g -1 h -1 CH 4 At the same time, a considerable reaction yield can be achieved under outdoor simulation conditions. The energy of this method comes entirely from sunlight, which is CO 2 Resource utilization provides an effective solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is an electron microscope image of the catalyst prepared in Example 1;

[0040] Figure 2 The diagram shows the detection of the catalyst surface temperature by controlling the distance between the xenon lamp light source and the catalyst using the catalyst of the present invention;

[0041] Figure 3 The yield of the reaction product of the catalyst of the present invention at different reaction temperatures is shown;

[0042] Figure 4 The yield of the reaction product of the catalyst of the present invention at different catalyst dosages is shown;

[0043] Figure 5 It shows that the catalyst of the present invention has 4 The yield of reaction products under different catalyst dosages;

[0044] Figure 6 The yields of different catalyst reaction products of the catalyst of the present invention at different KOH dosages are shown;

[0045] Figure 7 The product yield of the catalyst described in the present invention under long-term reaction is shown. DETAILED DESCRIPTION

[0046] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0047] The present invention will be further described below in conjunction with embodiments:

[0048] Embodiment 1:

[0049] 16mmol Co(OAc) 2 ·4H 2 O was fully dissolved in 200 mL of anhydrous ethanol and stirred for 2 hours in an ice-water bath to obtain solution A. 0.8 g of NaBH 4 The product was dissolved in 40 mL of cold water and slowly added dropwise to solution A at a rate of 4 mL / min. After being fully stirred for 2 hours, the precipitate was washed and dissolved in 100 mL of anhydrous ethanol to obtain solution B. 100 mL of 1M KOH aqueous solution was added to B. After standing for 10 minutes, the product was washed by centrifugation with water and ethanol in turn, and dried in air at room temperature to obtain a single-layer CoB hydroxide nanomaterial, i.e., the catalyst in this case.

[0050] The obtained catalyst electron micrograph is shown in Figure 1 shown. Figure 1 This is an electron microscope image of the catalyst prepared in Example 1.

[0051] Embodiment 2 and 3:

[0052] The only difference from Example 1 is the cobalt source, which is cobalt chloride and cobalt nitrate, respectively. The phase compositions of the obtained products are consistent, and the methane yields are similar.

[0053] Embodiments 4, 5, 6 and 7:

[0054] The only difference from Example 1 is that NaBH 4 The dosage of NaBH4 in Examples 4, 5, 6 and 7 is different. The dosage of NaBH4 is 0g, 0.4g, 1.2g and 1.6g respectively. The phase composition of the obtained products is consistent. 4 The catalyst has the best methane production under the dosage.

[0055] Examples 8, 9, 10, 11, 12 and 13:

[0056] The only difference from Example 1 is the different KOH concentrations used. The KOH concentrations of Examples 8, 9, 10, 11, 12 and 13 are 0 M, 0.1 M, 0.25 M, 0.5 M, 2 M and 3 M, respectively. The phase compositions of the obtained products are consistent, and the catalyst has the best methane production at a KOH dosage of 1 M.

[0057] Embodiment 14:

[0058] This embodiment uses a solar thermal conversion unit to convert CO 2 After the photothermal catalytic reaction, three products are obtained, mainly methane and a small amount of ethane and carbon monoxide.2 CO conversion system 2 Methanation method. 30 mg of the obtained single-layer CoB hydroxide nanosheets were placed in a photothermal gas solid phase reactor. The raw gas (15% CO 2 、60%H 2 and 25% Ar) were introduced into the reactor at a flow rate of 10 mL / min, and the exhaust was continued for half an hour. The distance between the xenon lamp light source and the catalyst surface was controlled to keep the reaction temperature on the catalyst surface constant at 330° C. The gas was continued to be introduced and reacted at normal pressure for 1 hour. The gas phase products were detected by gas chromatography to analyze the conversion rate and selectivity.

[0059] It should be noted that the inventors of this case have tried different raw material gas ratios to explore the reaction conditions under different raw material gases, including but not limited to the following ratios (the following ratios are volume percentages), which have similar effects:

[0060] 15% CO 2 、60%H 2 and 25% Ar;

[0061] 18.25% CO 2 56.25% H 2 and 25% Ar;

[0062] 25% CO 2 , 50% H 2 and 25% Ar;

[0063] 37.5% CO 2 、37.5%H 2 and 25% Ar;

[0064] 50% CO 2 , 25% H 2 and 25% Ar;

[0065] 56.25% CO 2 、18.25%H 2 and 25% Ar;

[0066] or 60% CO 2 、15%H 2 and 25% Ar.

[0067] Examples 15, 16, 17 and 18:

[0068] The only difference from Example 14 is the different amounts of catalyst used. The amounts of catalyst used in Examples 15, 16, 17 and 18 are 10 mg, 20 mg, 40 mg and 50 mg, respectively. The obtained product compositions are consistent, and the catalyst with a catalyst amount of 30 mg has the best methane yield:

[0069] Examples 19, 20, 21, 22 and 23:

[0070] The only difference from Example 14 is the reaction temperature. The reaction temperatures of Examples 19, 20, 21, 22 and 23 are 170°C, 200°C, 230°C, 270°C and 300°C, respectively. The resulting product compositions are consistent, and the catalyst has the best methane yield at a reaction temperature of 330°C.

[0071] The test results of the above embodiments 1 to 23 are shown in Figure 2 to Figure 7 ,in, Figure 2 This is a detection diagram of the catalyst surface temperature by controlling the distance from the xenon lamp light source to the catalyst by the system of the present invention.

[0072] like Figure 2 As shown in the figure, the horizontal axis is the reaction time, the vertical axis is the reaction temperature, and different curves represent the detection diagram of the catalyst surface temperature when the distance from the xenon lamp light source to the catalyst is different using the above-mentioned solar thermal conversion unit.

[0073] Figure 3 It is the yield of the reaction product at different reaction temperatures of the present invention.

[0074] like Figure 3 As shown, the horizontal axis in the figure is the reaction temperature, that is, the temperature of the catalyst in Example 1 and the catalyst in Examples 19 to 23, and the vertical axis is the yield. Figure 3 It can be seen that the methane production is highest at 330 °C.

[0075] Figure 4 is the yield of the reaction product under different catalyst dosages of the present invention

[0076] like Figure 4 As shown in the figure, the horizontal axis is the catalyst dosage, that is, the catalyst dosage of Examples 1 and 15 to 18, and the vertical axis is the output. Figure 3 It can be seen that the compositions of the products obtained in Examples 1 and 15 to 18 are consistent, wherein the catalyst with a catalyst dosage of 30 mg has the best methane yield.

[0077] Figure 5 The catalyst of the present invention is different from NaBH 4 The yield of reaction products under different catalyst dosages.

[0078] like Figure 5 As shown, the horizontal axis in the figure is different NaBH 4 The reaction products of different catalysts obtained by adding different amounts, namely, NaBH 4The dosage (0g, 0.4g, 0.8g, 1.2g and 1.6g), the vertical axis is the yield. Figure 4 It can be seen that the phase compositions of the products obtained in Examples 1 and 4 to 7 are consistent, wherein 0.8 g of NaBH 4 Dosage (i.e. Example 1, corresponding to CoB in the figure 1 -OH(1)) has the best methane production.

[0079] Figure 6 It is the yield of different catalyst reaction products under different KOH dosage of the catalyst of the present invention.

[0080] like Figure 6 As shown in the figure, the horizontal axis is the different catalyst reaction products obtained by different KOH dosages, that is, the KOH dosages of Examples 1 and 8 to 13, and the vertical axis is the yield. Figure 5 It can be seen that the phase compositions of the products obtained in Examples 1 and 8 to 13 are consistent, wherein ... 1 The catalyst with -OH1(1) had the best methane production.

[0081] Figure 7 It is the product yield of the catalyst of the present invention under long-term reaction.

[0082] like Figure 7 As shown in the figure, the horizontal axis is the reaction time and the vertical axis is the yield. Figure 7 It can be seen that the reaction time can be 1 to 12 hours, and the catalytic effect remains unchanged with long-term use.

[0083] Embodiment 24

[0084] The methane preparation reaction system includes a reactor and a xenon lamp light source. The reactor is used to react and prepare methane. The solar thermal conversion unit used in Examples 1 to 23 can use this reactor for reaction. In some embodiments, the methane preparation reaction system also includes a detection device to detect the intensity of the light source.

[0085] In this embodiment, the reactor includes a quartz photothermal gas-solid phase reactor and a borosilicate quartz filter membrane placed in the quartz photothermal gas-solid phase reactor.

[0086] It should be noted that the prior art in the protection scope of the present invention is not limited to the embodiments given in the present application documents, and all prior art that does not contradict the scheme of the present invention, including but not limited to prior patent documents, prior public publications, prior public uses, etc., can be included in the protection scope of the present invention.

[0087] In addition, the combination of the various technical features in this case is not limited to the combination described in the claims of this case or the combination described in the specific embodiments. All technical features recorded in this case can be freely combined or combined in any way unless there is a contradiction between them.

[0088] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. In the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

1. A catalyst for photothermal CO2 methanation reaction, characterized in that: The catalyst is a single-layer CoB hydroxide nanosheet.

2. Use of the catalyst as claimed in claim 1 in photothermal catalytic reactions.

3. A method for preparing the catalyst according to claim 1, characterized in that: The preparation method comprises the following steps: Step S1: fully dissolving the Co source material in anhydrous ethanol, and fully stirring in an ice water bath to obtain solution A; Step S2: slowly drop the NaBH4 solution into solution A, fully stir for 1 to 4 hours, wash the precipitate and dissolve it in anhydrous ethanol to obtain solution B; Step S3: adding KOH or NaOH aqueous solution to solution B, leaving it to stand for 10-15 min, taking out the precipitate, washing it by centrifugation with water and ethanol in turn, and drying it in air at room temperature to obtain the catalyst.

4. The preparation method according to claim 3, characterized in that: The Co source is selected from one of cobalt chloride, cobalt nitrate and cobalt acetate.

5. The preparation method according to claim 3, characterized in that: The usage ratio of the NaBH4 to the Co element in the Co source is 25-100 g: 1 mol.

6. The preparation method according to claim 3, characterized in that: In the step S3, the concentration of KOH or NaOH is 0.125M-1M, and the molar ratio of KOH or NaOH to Co source is 15-64 based on Co element.

7. A method for preparing methane, characterized in that: The methane preparation method uses CO2 as a raw material, adds hydrogen to generate methane under light conditions, and the catalyst used in the reaction is the catalyst as claimed in claim 1.

8. The method for producing methane according to claim 7, characterized in that: The methane production method satisfies at least one of the following conditions: The reaction temperature is between 230 and 330°C; The reaction conditions are normal pressure; The reaction light source is sunlight or xenon lamp.

9. A methane production reaction system, characterized in that: The methane preparation reaction system comprises a reactor, and the reactor is used for preparing methane by reaction, and the preparation method thereof adopts the methane preparation method as claimed in claim 7 or 8.

10. The methane production reaction system according to claim 9, wherein the reactor comprises a quartz photothermal gas-solid phase reactor and a borosilicate quartz filter membrane placed in the quartz photothermal gas-solid phase reactor.

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