Method for preparing nickel-based catalyst through solid-phase reaction, nickel-based catalyst and preparation method of synthesis gas

Abstract

The invention relates to the field of catalysis, in particular to a method for preparing a nickel-based catalyst through a solid-phase reaction, the nickel-based catalyst and a preparation method of synthesis gas. The invention provides a method for preparing a nickel-based catalyst through solid-phase reaction, which comprises the following steps of: 1, respectively mixing cerium nitrate and a silicon dioxide carrier with water to obtain two mixed solutions, mixing the two mixed solutions, adding a dilute ammonia water solution to adjust the pH value, adding an ammonia water solution of nickel nitrate, uniformly mixing, transferring into a hydrothermal kettle, and carrying out hydrothermal treatment to obtain a nickel-based catalyst precursor; the catalyst is separated by rotary evaporation. And 2, sequentially carrying out high-temperature heat treatment on the catalyst in a vacuum atmosphere and a hydrogen atmosphere to obtain a catalyst product. The preparation method provided by the invention is a solid-phase reaction strategy and is generally a two-step preparation method. The catalyst prepared by the method is used in a methane dry reforming reaction, and can maintain extremely high catalytic activity and high stability.

Description

Technical Field

[0001] The present invention relates to the field of catalysis, and particularly to a method for preparing a nickel-based catalyst by solid-phase reaction, a nickel-based catalyst, and a method for preparing syngas. Background Art

[0002] With the continuous acceleration of the industrialization process, the human dependence on fossil fuels has been continuously increasing, which has directly led to the aggravation of environmental problems, especially the intensification of the greenhouse effect. Among numerous greenhouse gases, methane (CH4) and carbon dioxide (CO2) are one of the most important representatives. They are not only important factors of environmental problems but also valuable carbon resources. Therefore, how to achieve the efficient resource utilization of methane and carbon dioxide has become a hot issue of global concern.

[0003] Compared with the traditional methane steam reforming process, the methane dry reforming reaction of methane and carbon dioxide at high temperature (600 - 1000 °C) is a more efficient and economical conversion method. This process can convert methane and carbon dioxide into a mixture of hydrogen (H2) and carbon monoxide (CO) (syngas). More importantly, the molar ratio of H2 to CO in the syngas produced by dry reforming is close to 1:1, which is very suitable for subsequent Fischer-Tropsch synthesis process to prepare high-value-added chemicals such as long-chain olefins.

[0004] Currently, the catalysts for methane dry reforming reaction are mainly divided into two categories: noble metal-based catalysts (such as rhodium Rh, ruthenium Ru, etc.) and non-noble metal-based catalysts (such as nickel Ni, cobalt Co, etc.). Although noble metal-based catalysts have excellent activity and stability, their high cost severely limits their wide application on an industrial scale. Among non-noble metal-based catalysts, nickel-based catalysts have attracted much attention due to their low cost and activity close to noble metal catalysts. However, nickel-based catalysts are prone to carbon deposition and sintering during the reaction process, resulting in rapid deactivation of the catalyst. To improve the stability of nickel-based catalysts, it is usually necessary to reduce the reaction temperature and space velocity, but this inevitably reduces the activity of the catalyst. Therefore, how to develop a nickel-based methane dry reforming catalyst with both high activity and high stability remains a major challenge in the current research field. Summary of the Invention

[0005] In view of this, the present invention provides a method for preparing a nickel-based catalyst by solid-phase reaction, a nickel-based catalyst, and a method for preparing syngas. The catalyst prepared by the present invention can effectively improve the catalytic activity and catalytic stability of the methane dry reforming reaction.

[0006] The present invention provides a method for preparing a nickel-based catalyst by solid-phase reaction, comprising the following steps:

[0007] S1: Mix cerium nitrate with water to obtain a first mixed solution;

[0008] S2: Mix silicon dioxide with water to obtain a second mixed solution;

[0009] S3: Mix the first mixed solution with the second mixed solution to obtain a third mixed solution;

[0010] S4: Add ammonia water to the third mixed solution to obtain a fourth mixed solution;

[0011] S5: Mix the ammonia aqueous solution of nickel nitrate with the fourth mixed solution to obtain a fifth mixed solution;

[0012] S6: Perform hydrothermal treatment at high temperature on the fifth mixed solution, and perform rotary evaporation separation to obtain an initial catalyst;

[0013] S7: Heat-treat the initial catalyst successively under vacuum conditions and in a hydrogen atmosphere to obtain a catalyst;

[0014] Among them, there is no order restriction for step S1 and step S2.

[0015] Preferably, in step S6, the temperature of the hydrothermal treatment at high temperature is 150 - 300 °C;

[0016] The temperature of the rotary evaporation is 60 - 100 °C.

[0017] Preferably, in step S7, the temperature of the heat treatment is 800 - 1000 °C.

[0018] Preferably, in step S7, the vacuum degree of the vacuum condition is 0.1 - 0.5 Torr;

[0019] The hydrogen atmosphere is an atmosphere containing hydrogen, wherein the volume ratio of H2 is 5% - 20%.

[0020] Preferably, in step S7, the heat preservation time for the heat treatment under vacuum conditions is 0.5 - 2 h;

[0021] The time for the heat treatment in the hydrogen atmosphere is 0.5 - 1.5 h.

[0022] Preferably, in step S3, when mixing the first mixed solution with the second mixed solution, control the mass ratio of Ce in SiO2∶H2O∶cerium nitrate to be 1∶(50 - 100)∶(0.02 - 0.15);

[0023] In step S5, when mixing the ammonia aqueous solution of nickel nitrate with the fourth mixed solution, control the mass ratio of Ni in the ammonia aqueous solution of nickel nitrate to SiO2 in the fourth mixed solution to be (0.01 - 0.03)∶1.

[0024] Preferably, in step S4, ammonia water is added to adjust the pH value to 8-10;

[0025] In step S5, the nickel nitrate ammonia aqueous solution is prepared by the following method: mixing nickel nitrate with concentrated ammonia water to obtain a nickel nitrate ammonia aqueous solution;

[0026] Wherein, the dosage ratio of nickel nitrate to concentrated ammonia water is 102.2 mg:(5-25) mL.

[0027] The present invention also provides a nickel-based catalyst prepared by the preparation method described in the above technical solution.

[0028] The present invention also provides a method for preparing syngas, including:

[0029] Under the action of a catalyst, a dry reforming reaction of methane and carbon dioxide is carried out to obtain syngas;

[0030] Wherein, the catalyst is the nickel-based catalyst described in the above technical solution.

[0031] Preferably, the temperature of the reaction is 750-850 °C;

[0032] The raw material gas used in the reaction is a mixed gas of methane, carbon dioxide and nitrogen; wherein, the volume ratio of methane:carbon dioxide:nitrogen is (2-4):(2-4):1; the flow rate of the raw material gas is 10-100 sccm.

[0033] For the preparation method of the catalyst provided by the present invention, in the first step, cerium nitrate and a silica support are respectively mixed with water to obtain two mixed solutions, and then these two mixed solutions are mixed, and a dilute ammonia aqueous solution is added to adjust the pH value. Then, a nickel nitrate ammonia aqueous solution is added, and after mixing evenly, it is transferred to a hydrothermal autoclave for hydrothermal treatment, and the catalyst is separated by rotary evaporation. In the second step, the above catalyst is subjected to high-temperature heat treatment in a vacuum atmosphere and a hydrogen atmosphere in sequence, thereby obtaining a catalyst product. The preparation method of the present invention is a solid-phase reaction strategy and is generally a two-step preparation. The catalyst prepared by the above method can maintain extremely high catalytic activity and high stability in the methane dry reforming reaction.

[0034] The test results show that for the catalyst obtained by the present invention, at 800 °C and a space velocity of 200 L / g cat / h, the reaction is carried out for 10 h, and the methane conversion rate reaches more than 73%. After the reaction for 30 h, the methane conversion rate still remains above 73%, proving that the catalyst of the present invention reaches high activity and high stability. The performance test of the catalyst in Example 1 at a longer time and a higher space velocity (100 h, 300 L / g cat / h) shows that the methane conversion rate reaches 1000 μmol CH4 ·g cat-1 ·s -1 Above, it shows ultra-high activity. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the provided drawings.

[0036] Figure 1 It is the TEM image of the initial catalyst obtained in step S6 of Example 1;

[0037] Figure 2 It is the XRD pattern of the catalyst obtained in step S7 of Example 1;

[0038] Figure 3 It is the effect diagram of the reaction performance of the catalysts in Example 1 and Comparative Example 1 in dry reforming of methane; among them, Figure 3 (a) is the effect diagram of methane conversion rate, Figure 3 (b) is the effect diagram of H2 / CO ratio;

[0039] Figure 4 It is the effect diagram of the dry reforming performance of methane of the final catalyst obtained in Example 1 at a space velocity of 300 L / g cat / h;

[0040] Figure 5 It is the effect diagram of the reaction performance of the catalysts obtained in Examples 2-3 in dry reforming of methane; among them, Figure 5 (a) is the effect diagram of methane conversion rate, Figure 5 (b) is the effect diagram of H2 / CO ratio. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which this application belongs. The terms used in the description of this application herein are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0042] In this article, among the technical features described in an open-ended manner, it includes a closed technical solution composed of the listed features, and also includes an open technical solution containing the listed features.

[0043] The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0044] In this text, when it comes to numerical ranges, unless otherwise specified, the above numerical ranges are considered continuous and include the minimum and maximum values of the range, as well as every value between such minimum and maximum values. Further, when the range refers to integers, it includes every integer between the minimum and maximum values of the range. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be combined. In other words, unless otherwise indicated, all ranges disclosed herein should be understood to include any and all sub-ranges subsumed therein.

[0045] In this text, regarding the units of data ranges, if the unit is only attached after the right endpoint, it means that the units of the left endpoint and the right endpoint are the same. For example, 150~300℃ means that the units of the left endpoint "150" and the right endpoint "300" are both ℃.

[0046] A method for preparing a nickel-based catalyst by solid-phase reaction, comprising the following steps:

[0047] S1: Mix cerium nitrate with water to obtain a first mixed solution;

[0048] S2: Mix silicon dioxide with water to obtain a second mixed solution;

[0049] S3: Mix the first mixed solution with the second mixed solution to obtain a third mixed solution;

[0050] S4: Add ammonia water to the third mixed solution to obtain a fourth mixed solution;

[0051] S5: Mix an ammonia aqueous solution of nickel nitrate with the fourth mixed solution to obtain a fifth mixed solution;

[0052] S6: Perform high-temperature hydrothermal treatment on the fifth mixed solution, and perform rotary evaporation separation to obtain an initial catalyst;

[0053] S7: Perform heat treatment on the initial catalyst successively under vacuum conditions and in a hydrogen atmosphere to obtain a catalyst;

[0054] Among them, there is no order restriction between step S1 and step S2.

[0055] [Regarding step S1]:

[0056] S1: Mix cerium nitrate with water to obtain a first mixed solution.

[0057] In the present invention, the source of the cerium nitrate is not particularly limited and can be a commercially available product. Cerium nitrate is a common chemical raw material, which has multiple Chinese names, including: cerium nitrate (hexahydrate), cerium(III) nitrate hexahydrate, cerium nitrate hexahydrate, etc., and its chemical formula is Ce(NO3)3·6H2O.

[0058] In the present invention, the water is preferably deionized water.

[0059] In the present invention, there is no special limitation on the dosage ratio of cerium nitrate to water, as long as cerium nitrate can be fully dissolved. Preferably, it is 155 mg∶(5 - 20) mL.

[0060] In the present invention, the method of mixing cerium nitrate and water is preferably ultrasonic treatment, that is, dissolving under ultrasonic assistance. There is no special limitation on the conditions of the ultrasonic treatment, as long as the materials can be fully dissolved. After the above mixing, an aqueous solution of cerium nitrate, that is, the first mixed solution, is obtained.

[0061] [Regarding step S2]:

[0062] S2: Mix silicon dioxide and water to obtain a second mixed solution.

[0063] In the present invention, there is no special limitation on the source of the silicon dioxide, and it can be a conventional commercially available silicon dioxide solid.

[0064] In the present invention, the water is preferably deionized water.

[0065] In the present invention, the dosage ratio of silicon dioxide to water is preferably 1 g∶(20 - 50) mL.

[0066] In the present invention, the method of mixing silicon dioxide and water is preferably ultrasonic dispersion. In the present invention, there is no special limitation on the conditions of the ultrasonic dispersion, as long as the silicon dioxide can be uniformly dispersed in water. After the above ultrasonic dispersion treatment, an aqueous dispersion of silicon dioxide, that is, the second mixed solution, is obtained.

[0067] The present invention has no order limitation on the above step S1 and step S2.

[0068] [Regarding step S3]:

[0069] S3: Mix the first mixed solution and the second mixed solution to obtain a third mixed solution.

[0070] In the present invention, when mixing the first mixed solution and the second mixed solution, it is preferably to control the mass ratio of SiO2∶H2O∶Ce in cerium nitrate to be 1∶(50 - 100)∶(0.02 - 0.15), more preferably 1∶(50 - 60)∶(0.1 - 0.15). Among them, H2O is the total amount of water from the first mixed solution and the second mixed solution.

[0071] In the present invention, it is preferably to mix the first mixed solution and the second mixed solution under stirring conditions. After the two raw material solutions are poured together, continue to stir and mix to make them fully mixed, thereby obtaining the third mixed solution.

[0072] [Regarding step S4]:

[0073] S4: Add ammonia water to the third mixed solution to obtain a fourth mixed solution.

[0074] In the present invention, the concentration of the ammonia water is preferably 1% - 3%, that is, dilute ammonia water. In the present invention, adding ammonia water increases the pH value. Preferably, the pH value is adjusted to 8 - 10, specifically it can be 8, 9, 10, and more preferably 9. In the present invention, the way of adding ammonia water is preferably dropwise addition. After adding ammonia water to adjust the pH, a fourth mixed solution is obtained.

[0075] [Regarding step S5]:

[0076] S5: Mix the ammonia aqueous solution of nickel nitrate with the fourth mixed solution to obtain a fifth mixed solution.

[0077] In the present invention, the ammonia aqueous solution of nickel nitrate is prepared by the following method: Mix nickel nitrate with concentrated ammonia water to obtain an ammonia aqueous solution of nickel nitrate. Among them, the source of the nickel nitrate has no special limitation and can be a commercially available product. It has multiple Chinese names, including: nickel nitrate hexahydrate, nickel(II) nitrate hexahydrate, etc., and the chemical formula is Ni(NO3)2·6H2O. The concentrated ammonia water can be a conventional commercially available concentrated ammonia water. The marked concentration of commercially available concentrated ammonia water is generally 25% - 28%. The dosage ratio of nickel nitrate to concentrated ammonia water is preferably 102.2 mg∶(15 - 25) mL. Mix nickel nitrate with concentrated ammonia water to dissolve nickel nitrate in concentrated ammonia water to obtain an ammonia aqueous solution of nickel nitrate.

[0078] In the present invention, when mixing the ammonia aqueous solution of nickel nitrate with the fourth mixed solution, it is preferably controlled that the mass ratio of Ni in the ammonia aqueous solution of nickel nitrate to SiO2 in the fourth mixed solution is (0.01 - 0.03)∶1, and more preferably (0.015 - 0.025)∶1.

[0079] In the present invention, the way of mixing the ammonia aqueous solution of nickel nitrate with the fourth mixed solution has no special limitation, as long as the materials can be mixed evenly, such as stirring and mixing. After mixing evenly, a fifth mixed solution is obtained.

[0080] [Regarding step S6]:

[0081] S6: Perform high-temperature hydrothermal treatment on the fifth mixed solution, and perform rotary evaporation separation to obtain an initial catalyst.

[0082] In the present invention, the high-temperature hydrothermal treatment can be carried out in a hydrothermal autoclave. The temperature of the high-temperature hydrothermal treatment is 150 - 300 °C, specifically, it can be 150 °C, 160 °C, 170 °C, 180 °C, 190 °C, 200 °C, 210 °C, 220 °C, 230 °C, 240 °C, 250 °C, 260 °C, 270 °C, 280 °C, 290 °C, 300 °C. The time of the high-temperature hydrothermal treatment is 20 - 40 h, specifically, it can be 20 h, 24 h, 36 h, 40 h. After the above high-temperature hydrothermal treatment, a nickel silicate with a fibrous morphology is formed by the reaction between the nickel nitrate precursor salt and the silica support.

[0083] In the present invention, after the above high-temperature hydrothermal treatment, the initial catalyst is collected by rotary evaporation separation. Among them, the temperature of the rotary evaporation is preferably 60 - 100 °C, specifically, it can be 60 °C, 65 °C, 70 °C, 75 °C, 80 °C, 85 °C, 90 °C, 95 °C, 100 °C. The degree of the rotary evaporation treatment is until most of the liquid volatilizes and a solid product is obtained.

[0084] [Regarding step S7]:

[0085] S7: The initial catalyst is heat-treated successively under vacuum conditions and in a hydrogen atmosphere to obtain the catalyst.

[0086] In the present invention, the initial catalyst obtained in step S6 is first heat-treated under vacuum conditions. Among them, the vacuum degree of the vacuum conditions is preferably 0.1 - 0.3 Torr, specifically, it can be 0.2 Torr.

[0087] In the present invention, the hydrogen atmosphere is an atmosphere containing hydrogen, preferably a mixed gas of hydrogen and an inert gas; among them, the volume ratio of H2 in the mixed gas is preferably 5% - 20%, specifically, it can be 20%. The type of the inert gas is not particularly limited and can be a conventional inert gas in the art, such as nitrogen, argon, etc., preferably argon.

[0088] In the present invention, the heat treatment can be carried out in a tube furnace. The temperature of the heat treatment is preferably 800 - 1000 °C, more preferably 950 - 1000 °C, specifically, it can be 950 °C, 955 °C, 960 °C, 965 °C, 970 °C, 975 °C, 980 °C, 985 °C, 990 °C, 995 °C, 1000 °C. In the present invention, the heating rate of the heat treatment is preferably 5 - 15 °C / min, specifically, it can be 10 °C / min.

[0089] In the present invention, the above steps can specifically include: heating the initial catalyst to the target temperature of the heat treatment under vacuum conditions and maintaining the heat treatment, and then switching the atmosphere to a 20% hydrogen atmosphere at 100 mL / min. At this time, the vacuum degree becomes 0.5 - 1 Torr, and the heat treatment is continued to obtain the catalyst.

[0090] In the present invention, the holding time for heat treatment under vacuum conditions is preferably 0.5 to 2 h, more preferably 0.5 to 1.5 h, and specifically can be 0.5 h, 1 h, or 1.5 h. In the present invention, the time for heat treatment under a hydrogen atmosphere is preferably 0.5 to 1.5 h, and specifically can be 0.5 h, 1 h, or 1.5 h. Through the above high-temperature vacuum and subsequent hydrogen treatment in the present invention, cerium silicate is formed by solid-phase reaction between cerium oxide and the silica support. After the above heat treatment, the temperature is lowered to room temperature, and the product is discharged to obtain the catalyst.

[0091] The present invention also provides a catalyst prepared by the method for preparing a nickel-based catalyst by solid-phase reaction described in the above technical solution.

[0092] In the present invention, the obtained catalyst includes: silica, nickel silicate, and cerium silicate. Among them, silica is the support. Through the first solid-phase reaction in step S6, nickel nitrate precursor salt reacts with the silica support to form nickel silicate with a fibrous morphology. Then, through the second solid-phase reaction in step S7, cerium oxide reacts with the silica support to form cerium silicate.

[0093] In the present invention, the mass percentage of Ce in the catalyst is preferably 5% to 20%, and specifically can be 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, or 20%.

[0094] In the present invention, the mass percentage of Ni in the catalyst is preferably 1% to 5%, and specifically can be 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, or 5.0%.

[0095] The present invention also provides a method for preparing syngas, including: under the action of a catalyst, carrying out dry reforming of methane and carbon dioxide to obtain syngas; wherein, the catalyst is the catalyst described in the above technical solution.

[0096] In the present invention, before starting the methane dry reforming reaction after loading the catalyst into the reaction device, it is preferably to carry out in-situ reduction treatment on the catalyst first. In the present invention, the reduction treatment is preferably carried out under a hydrogen-containing atmosphere. The hydrogen-containing atmosphere is preferably a mixed gas of hydrogen and an inert gas; wherein, the volume percentage of H2 in the mixed gas is preferably 5% to 20%, and specifically can be 10%. The type of the inert gas is not particularly limited and can be a conventional inert gas in the art, such as nitrogen, argon, etc. In the present invention, the temperature of the reduction treatment is preferably 750 to 850 °C, more preferably 800 °C; the time of the reduction treatment is preferably 0.5 to 1.5 h, more preferably 1 h.

[0097] In the present invention, after the above-mentioned reduction treatment, the dry reforming reaction of methane and carbon dioxide is carried out. In the present invention, the raw material gas for the dry reforming reaction of methane and carbon dioxide is preferably a mixed gas of methane, carbon dioxide and nitrogen. Among them, the volume ratio of methane: carbon dioxide: nitrogen is preferably (2-4):(2-4):1, more preferably (2-3):(2-3):1, and most preferably 2:2:1. The flow rate of the reaction gas is preferably 10-100 sccm, specifically, it can be 10 sccm, 15 sccm, 20 sccm, 25 sccm, 30 sccm, 35 sccm, 40 sccm, 45 sccm, 50 sccm, 60 sccm, 70 sccm, 80 sccm, 90 sccm, 100 sccm. In the present invention, the temperature of the dry reforming reaction of methane and carbon dioxide is preferably 750-800 °C, more preferably 800 °C. Through the above dry reforming reaction of methane and carbon dioxide, methane (CH4) and carbon dioxide (CO2) are converted into syngas mainly composed of carbon monoxide (CO) and hydrogen (H2).

[0098] The preparation method of the catalyst provided by the present invention is the hydrothermal method, and the post-treatment process is high-temperature vacuum hydrogen treatment. No organic solvents are involved in the synthesis process. The method is simple and easy to industrialize. The prepared catalyst shows extremely high catalytic activity and excellent stability in the dry reforming reaction of methane.

[0099] The test results show that the catalyst obtained in the present invention, at 800 °C and a space velocity of 200 L / g cat / h, reacts for 10 h, and the methane conversion rate reaches more than 73%. After reacting for 30 h, the methane conversion rate still remains above 73%, proving that the catalyst of the present invention has high activity and high stability. The catalyst of Example 1 was tested at a longer time and a higher space velocity (100 h, 300 L / g cat / h). The methane conversion rate reached 1000 μmol CH4 ·g cat -1 ·s -1 or more, showing ultra-high activity.

[0100] To further understand the present invention, the preferred implementation schemes of the present invention will be described below in conjunction with examples. However, it should be understood that these descriptions are only for further explaining the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0101] Unless otherwise specified, the raw materials and reagents used in the following examples are all commercially available products or can be prepared by known methods. The instruments are all conventional selections in the art.

[0102] Example 1

[0103] 1. Preparation of the catalyst

[0104] S1: Weigh 155 mg of Ce(NO3)3·6H2O, add it to 10 mL of deionized water, and dissolve it under ultrasonic assistance to obtain the first mixed solution.

[0105] S2: Weigh 1 g of SiO2, add it to 50 mL of deionized water, and perform ultrasonic dispersion to obtain the second mixed solution.

[0106] S3: Under continuous stirring, pour the above first mixed solution into the second mixed solution, and then continue stirring for 30 min to obtain the third mixed solution.

[0107] S4: Dropwise add ammonia water to the above third mixed solution to raise the pH value to 9 to obtain the fourth mixed solution.

[0108] S5: Weigh 102.2 mg of Ni(NO3)2·6H2O and dissolve it in 50 mL of concentrated ammonia water to obtain an ammonia aqueous solution of nickel nitrate. Pour the obtained ammonia aqueous solution of nickel nitrate into the fourth mixed solution obtained in step S4, stir and mix evenly to obtain the fifth mixed solution.

[0109] S6: Transfer the fifth mixed solution to a hydrothermal autoclave, perform hydrothermal treatment at 250 °C for 24 h, and collect the initial catalyst by rotary evaporation.

[0110] S7: Transfer the obtained initial catalyst to a tubular furnace. First, raise the temperature to 950 °C at a heating rate of 10 °C / min in vacuum (0.2 Torr) and maintain it for 0.5 h. Then, switch the atmosphere to 20% H2 / Ar and continue heat treatment for 0.5 h. After cooling to room temperature, take out the sample to obtain the catalyst.

[0111] Figure 1 It is the TEM image of the initial catalyst obtained in step S6 of Example 1. Among them, nickel silicate with a fibrous morphology is formed by the reaction between the nickel nitrate precursor salt and the silica support.

[0112] Figure 2 It is the XRD pattern of the catalyst obtained in step S7 of Example 1. The results show that after high-temperature vacuum and subsequent hydrogen treatment, cerium silicate is formed by the solid-phase reaction between cerium oxide and the silica support.

[0113] 2. Performance evaluation of the catalyst

[0114] The evaluation process of the catalytic reaction is as follows: Weigh 15 mg of the catalyst and place it in a fixed-bed reactor. Introduce 40 sccm of 10% H2 / Ar, and heat it at a heating rate of 10 °C / min to 800 °C for in-situ reduction treatment at atmospheric pressure for 1 h. Then, initiate the dry reforming of methane with carbon dioxide: Maintain the reaction temperature at 800 °C, introduce a certain flow rate of CH4 / CO2 / N2 (volume fraction 2 / 2 / 1) for continuous reaction at atmospheric pressure, with a reaction gas flow rate of 50 sccm and a corresponding space velocity of 200 L / g cat / h. Among them, N2 is used as an internal standard gas to calculate the conversion rates of CH4 and CO2. The products are analyzed online at atmospheric pressure after passing through a cold trap, and the products are analyzed by a gas chromatograph equipped with a TCD. The chromatographic conditions are a 5A molecular sieve packed column and a capillary packed column (50 m).

[0115] Use the initial catalyst obtained in step S6 and the final catalyst obtained in step S7 as catalysts for the above tests, and the results are shown in Figure 3 ; among them, Figure 3 (a) is the effect diagram of methane conversion rate, Figure 3 (b) is the effect diagram of H2 / CO ratio. Figure 3 The effects of (a) are summarized in Table 1.

[0116] Comparative Example 1

[0117] 1. Preparation of the catalyst

[0118] K1: Weigh 102.2 mg of Ni(NO3)2·6H2O and 155 mg of Ce(NO3)3·6H2O and add them to 1 mL of deionized water, and dissolve them with ultrasonic assistance to obtain a mixed solution.

[0119] K2: Weigh 500 mg of hydrophilic fumed silica, add the mixed solution obtained in step K1 to the silica in 4 portions, and stir while adding until a gel is formed; after drying the above gel overnight, transfer it to an oven at 80 °C and dry it overnight to obtain the Ni / Ce-SiO2 catalyst.

[0120] 2. Performance evaluation of the catalyst

[0121] Perform tests according to the test method in Example 1, and the results are shown in Figure 3 and Table 1.

[0122] Table 1: Catalytic effects of the catalysts in Example 1 and Comparative Example 1

[0123]

[0124] From Figure 3As can be seen from Table 1, for the Ni / Ce-SiO2 catalyst obtained by the impregnation method in Comparative Example 1, within 10 h, the methane conversion gradually decreased from 83.5% to 75.9%, and then further decreased to 73.5% within the subsequent 20 h. In contrast, for the initial catalyst obtained in Step S6 of Example 1, the methane conversion rate gradually decreased from 81.7% to 75.2%, and during the subsequent 20 h of reaction, its methane conversion rate remained at about 75% without further decrease. Therefore, through the solid-phase reaction between Ni and silica, the stability of its dry reforming of methane has been improved.

[0125] Furthermore, the catalyst obtained in Step S7 of Example 1 exhibited the best stability. During the 30 h reaction, its methane conversion rate gradually increased from 66.8% to 82.5%. To further demonstrate its excellent performance, performance tests were carried out at a higher space velocity (100 h, 300 L / g cat / h) for a longer time, as Figure 4 shown, within 20 h, the methane conversion rate increased from 29.1% to 69.1%. During the subsequent 80 h test, the methane conversion rate remained at about 69%, and its methane conversion rate was calculated to be 1024 μmol CH4 ·g cat -1 ·s -1 , exceeding the highest activity reported so far. Therefore, based on the previous solid-phase reaction, the solid-phase reaction between cerium oxide and silica further improved the stability of the catalyst.

[0126] Example 2

[0127] 1. Preparation of catalyst

[0128] S1: Weigh 155 mg of Ce(NO3)3·6H2O, add it to 10 mL of deionized water, and dissolve it under ultrasonic assistance to obtain a first mixed solution.

[0129] S2: Weigh 1 g of SiO2, add it to 50 mL of deionized water, and perform ultrasonic dispersion to obtain a second mixed solution.

[0130] S3: Under continuous stirring, pour the above first mixed solution into the second mixed solution, and then continue stirring for 30 min to obtain a third mixed solution.

[0131] S4: Add ammonia water to the above third mixed solution to increase the pH value to 9 to obtain a fourth mixed solution.

[0132] S5: Weigh 76.5 mg of Ni(NO3)2·6H2O and dissolve it in 50 mL of concentrated ammonia water to obtain an ammonia aqueous solution of nickel nitrate. Pour the obtained ammonia aqueous solution of nickel nitrate into the fourth mixed solution obtained in Step S4, stir and mix well to obtain a fifth mixed solution.

[0133] S6: Transfer the fifth mixture into a hydrothermal autoclave, carry out hydrothermal treatment at 250 °C for 24 h, and collect the initial catalyst by rotary evaporation.

[0134] S7: Transfer the obtained initial catalyst into a tubular furnace. First, raise the temperature to 950 °C at a heating rate of 10 °C / min in vacuum (0.2 Torr) and maintain it for 0.5 h. Then, switch the atmosphere to 20% H2 / Ar and continue the heat treatment for 0.5 h. After cooling to room temperature, take out the sample to obtain the catalyst.

[0135] 2. Performance evaluation of the catalyst

[0136] The evaluation process of the catalytic reaction is as follows: According to the method in Example 1, first carry out reduction treatment. Then, start the dry reforming of methane with carbon dioxide: the same as in Example 1. The test results are shown in Figure 5 and Table 2.

[0137] Example 3

[0138] 1. Preparation of the catalyst

[0139] S1: Weigh 155 mg of Ce(NO3)3·6H2O, add it to 10 mL of deionized water, and dissolve it under ultrasonic assistance to obtain the first mixture.

[0140] S2: Weigh 1 g of SiO2, add it to 50 mL of deionized water, and carry out ultrasonic dispersion to obtain the second mixture.

[0141] S3: Under continuous stirring, pour the above first mixture into the second mixture, and then continue stirring for 30 min to obtain the third mixture.

[0142] S4: Add ammonia water to the above third mixture to raise the pH value to 9 to obtain the fourth mixture.

[0143] S5: Weigh 128.5 mg of Ni(NO3)2·6H2O and dissolve it in 50 mL of concentrated ammonia water to obtain an ammonia aqueous solution of nickel nitrate. Pour the obtained ammonia aqueous solution of nickel nitrate into the fourth mixture obtained in step S4, stir and mix evenly to obtain the fifth mixture.

[0144] S6: Transfer the fifth mixture into a hydrothermal autoclave, carry out hydrothermal treatment at 250 °C for 24 h, and collect the initial catalyst by rotary evaporation.

[0145] S7: Transfer the obtained initial catalyst into a tubular furnace. First, raise the temperature to 950 °C at a heating rate of 10 °C / min in vacuum (0.2 Torr) and maintain it for 0.5 h. Then, switch the atmosphere to 20% H2 / Ar and continue the heat treatment for 0.5 h. After cooling to room temperature, take out the sample to obtain the catalyst.

[0146] 2. Performance Evaluation of the Catalyst

[0147] The evaluation process of the catalytic reaction is as follows: According to the method in Example 1, perform reduction treatment first. Then, initiate the dry reforming reaction of methane and carbon dioxide: the same as in Example 1. The test results are shown in Figure 5 and Table 2.

[0148] Table 2: Catalytic Effects of the Catalysts Obtained in Each Example

[0149]

[0150] It can be seen from the test results in Table 2 that for the catalyst obtained by the two-step solid-phase reaction method of the present invention, in the 10-hour catalytic reaction, the methane conversion rate reaches over 73%; and the performance of the catalyst can be basically maintained stable within 30 hours; the above proves that the catalyst of the present invention has high activity and high stability.

[0151] In summary, for the preparation method of the catalyst provided by the present invention, through the solid-phase reaction strategy between two catalyst components and silica, the stability of the Ni-based methane dry reforming catalyst can be effectively improved, and finally a catalyst with both high activity and high stability is obtained.

[0152] In this article, specific examples are used to elaborate on the principle and implementation manner of the present invention. The description of the above examples is only used to help understand the method and its core idea of the present invention, including the best mode, and also enables any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that for those of ordinary skill in the art in this technical field, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention. The protection scope of the present invention patent is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements similar to the literal description of the claims, or if they include equivalent structural elements that have no substantial difference from the literal description of the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. A method for preparing a nickel-based catalyst by solid-phase reaction, characterized in that, It includes the following steps: S1: Mix cerium nitrate with water to obtain a first mixed solution; S2: Mix silicon dioxide with water to obtain a second mixed solution; S3: Mix the first mixed solution with the second mixed solution to obtain a third mixed solution; S4: Add ammonia water to the third mixed solution to obtain a fourth mixed solution; S5: Mix the ammonia aqueous solution of nickel nitrate with the fourth mixed solution to obtain a fifth mixed solution; S6: Perform hydrothermal treatment at high temperature on the fifth mixed solution, and perform rotary evaporation separation to obtain an initial catalyst; S7: Heat-treat the initial catalyst successively under vacuum conditions and in a hydrogen atmosphere to obtain a catalyst; Among them, there is no order limit for step S1 and step S2.

2. The preparation method according to claim 1, wherein In step S6, the temperature of the hydrothermal treatment at high temperature is 150 - 300 °C; The temperature of the rotary evaporation is 60 - 100 °C.

3. The preparation method according to claim 1, characterized in that, In step S7, the temperature of the heat treatment is 800 - 1000 °C.

4. The preparation method according to claim 1 or 3, characterized in that, In step S7, the vacuum degree of the vacuum condition is 0.1 - 0.5 Torr; The hydrogen atmosphere is an atmosphere containing hydrogen, where the volume ratio of H2 is 5% - 20%; 5. The preparation method according to claim 1 or 3, characterized in that, In step S7, the heat preservation time for heat treatment under vacuum conditions is 0.5 - 2 h; The time for heat treatment in a hydrogen atmosphere is 0.5 - 1.5 h.

6. The preparation method according to claim 1, wherein In step S3, when mixing the first mixed solution with the second mixed solution, control the mass ratio of SiO2∶H2O∶Ce in cerium nitrate to be 1∶(50 - 100)∶(0.02 - 0.15); In step S5, when mixing the ammonia aqueous solution of nickel nitrate with the fourth mixed solution, control the mass ratio of Ni in the ammonia aqueous solution of nickel nitrate to SiO2 in the fourth mixed solution to be (0.01 - 0.03)∶1.

7. The preparation method according to claim 1, characterized in that, In step S4, add ammonia water to make the pH value reach 8 - 10; In step S5, the ammonia aqueous solution of nickel nitrate is prepared by the following method: Mix nickel nitrate with concentrated ammonia water to obtain an ammonia aqueous solution of nickel nitrate; Among them, the dosage ratio of nickel nitrate to concentrated ammonia water is 102.2 mg∶(5 - 25) mL.

8. A nickel-based catalyst prepared by the preparation method according to any one of claims 1 - 7.

9. A method for preparing syngas, characterized in that, It includes: Under the action of the catalyst, carry out the dry reforming reaction of methane and carbon dioxide to obtain syngas; Among them, the catalyst is the nickel-based catalyst according to claim 8.

10. The preparation method according to claim 9, characterized in that, The temperature of the reaction is 750 - 850 °C; The raw material gas used in the reaction is a mixed gas of methane, carbon dioxide and nitrogen; among them, the volume ratio of methane∶carbon dioxide∶nitrogen is (2 - 4)∶(2 - 4)∶1; the flow rate of the raw material gas is 10 - 100 sccm.

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