A method for preparing a catalyst for dry reforming of methane

Abstract

The application discloses a preparation method of a methane dry reforming catalyst. First, a soluble nickel salt solution is added into an oxidized dysprosium water dispersion, and ultrasonic treatment is performed to make the nickel ions fully contact with the carrier oxidized dysprosium. Water is removed by rotary evaporation to obtain a solid powder, and a nickel-based catalyst used for a methane dry reforming reaction is obtained after high-temperature reduction treatment. The nickel-based catalyst obtained by the impregnation-reduction method can realize efficient conversion of carbon dioxide and methane and preparation of synthesis gas, the process flow is simple, the operability is strong, and the nickel-based catalyst has a wide application prospect.

Description

Technical Field

[0001] This invention relates to a method for preparing a methane dry reforming catalyst, belonging to the field of catalyst preparation and heterogeneous catalysis technology. Background Technology

[0002] With the rapid development of human society and the improvement of living standards, the consumption of traditional energy sources, mainly coal, oil, and natural gas, has increased dramatically. This has led to an energy crisis, and the increasing levels of greenhouse gases, primarily carbon dioxide and methane, in the atmosphere have caused a series of environmental problems. As a cheap and readily available carbon source, the resource utilization of carbon dioxide has become a current research hotspot. Among these, the dry reforming of methane (DRM, CH4 + CO2 → 2H2 + 2CO) consumes both CO2 and CH4, the two main greenhouse gases, while producing syngas with an H2 / CO ratio close to 1. This syngas can be used as the reaction gas in Fischer-Tropsch synthesis and can be further used to produce hydrocarbons with higher added value. Therefore, research on technologies for producing syngas through dry reforming of methane is of great significance in both catalysis and environmental protection fields.

[0003] As a strongly endothermic reaction, the reactants CO2 and CH4 possess high thermal stability, thus requiring high temperatures to proceed. However, excessively high temperatures can lead to catalyst sintering. Furthermore, the reaction inevitably involves methane cracking (CH4→C+2H2) and CO disproportionation (2CO→C+CO2), resulting in carbon deposits that clog the catalyst's active sites and deactivate the catalyst. This is the primary reason why DRM technology has not yet achieved large-scale industrial application. Therefore, developing economical, efficient, and stable methane dry reforming catalysts is crucial for industrial applications.

[0004] In the catalysts for methane dry reforming, nickel-based catalysts have attracted widespread attention due to their abundant resources, low cost, and high activity. However, compared to noble metal catalysts, Ni-based catalysts are more prone to sintering and carbon deposition, which can reduce reaction activity or even deactivate the catalyst. Therefore, it is necessary to use a suitable support to stabilize and disperse the active components. Improving the dispersion of metallic nickel and reducing the size of nickel particles can enhance the activity and stability of nickel-based catalysts. Summary of the Invention

[0005] To improve the efficiency and stability of methane dry reforming reaction, this invention provides a novel method for preparing a nickel-based catalyst and a method for methane dry reforming.

[0006] The objective of this invention is achieved through the following solution:

[0007] A method for preparing a methane dry reforming catalyst includes the following steps:

[0008] (1) Dysprosium oxide was added to deionized water and ultrasonically dispersed to prepare an aqueous dispersion of dysprosium oxide with a content of 2-5 wt%;

[0009] (2) Add a soluble nickel salt solution with a Ni content of 5~20 mg / mL to the dysprosium oxide aqueous dispersion;

[0010] (3) Remove water from the dispersion to obtain a solid product;

[0011] (4) The solid product was reduced at 400~600 °C in an H2 / Ar atmosphere to obtain a methane dry reforming catalyst Ni / Dy2O3 with a Ni content of 0.1~4 wt%.

[0012] In step (2) above, the soluble nickel salt is selected from one or more of nickel nitrate, nickel chloride, nickel acetylacetone, and nickel acetate.

[0013] In step (3) above, the water in the dispersion is removed by vacuum distillation at a temperature of 55~65 °C and a vacuum degree of 100 mbar.

[0014] In step (4) above, the heating rate of the reduction treatment is 2~10 °C / min, and the volume ratio of hydrogen to argon is (2~10):(90~98).

[0015] The Ni / Dy2O3 catalyst prepared based on the above technical solutions has unique metal-support interactions, which can achieve high dispersion of active nickel.

[0016] The Ni / Dy2O3-catalyzed dry reforming reaction for producing syngas from methane in this invention is carried out in a fixed reaction bed. The specific steps and conditions are as follows:

[0017] The prepared catalyst was pressed into particles with a diameter of 40-60 mesh. 100 mg of sieved Ni / Dy2O3 catalyst was loaded into a fixed reaction bed and pre-reduced by heating to 500 °C. After cooling to room temperature, a reaction gas was introduced into the system and the temperature was raised to 300-900 °C. The resulting product was analyzed online by gas chromatography.

[0018] Preferably, the mixed gas used in the pre-reduction is 5 vol% H2 + 95 vol% Ar, the heating rate is 10 °C / min, and the gas flow rate is 20 sccm.

[0019] Preferably, the volume ratio of CO2, CH4, and N2 used in the reaction gas is 1:1:2, the heating rate during the reaction is 10°C / min, and the total gas flow rate is 20~50 sccm.

[0020] Dysprosium oxide is a basic oxide. The inventors discovered that dysprosium oxide can adsorb and activate carbon dioxide during the dry reforming of methane, which is beneficial to the reaction. The atomic / ionic radii of transition metals are much smaller than those of rare earth atoms, making them easier to interstitial doping on the dysprosium oxide support, achieving high dispersion. This weakens the CC coupling generated by methane cracking on nickel particles in traditional nickel nanoparticle catalysts, reducing carbon deposition on the catalyst surface to some extent. Furthermore, dysprosium oxide possesses excellent thermal stability and is not prone to phase transition under high-temperature reaction conditions. Therefore, the Ni / Dy2O3 catalyst prepared using nickel supported on dysprosium oxide has the potential for highly efficient and stable catalysis of the dry reforming of methane to produce syngas.

[0021] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0022] This invention presents a novel Ni / Dy₂O₃ catalyst prepared via an impregnation-reduction method. The process is simple and highly operable. It innovatively employs dysprosium oxide-supported nickel, utilizing the unique interaction between nickel and dysprosium oxide to achieve high dispersion of the active nickel component. Compared to traditional Ni-based catalysts, Ni / Dy₂O₃ catalysts with varying metal loadings exhibit excellent catalytic activity, enabling efficient and stable methane dry reforming to produce syngas. They are reusable and possess promising prospects for industrial application. Attached Figure Description

[0023] Figure 1 This is a transmission electron microscopy elemental mapping of the Ni / Dy2O3 catalyst of the present invention;

[0024] Figure 2 The XRD pattern of the Ni / Dy2O3 catalyst of this invention is shown below.

[0025] Figure 3 The methane conversion rate of the methane dry reforming reaction using the Ni / Dy2O3 catalyst and the Ni / SiO2 and Ni / Al2O3 catalysts of this invention;

[0026] Figure 4 The carbon dioxide conversion rate of methane dry reforming reaction using the Ni / Dy2O3 catalyst and the Ni / SiO2 and Ni / Al2O3 catalysts of this invention;

[0027] Figure 5 The methane conversion rate of the Ni / Dy2O3-catalyzed dry reforming reaction of methane in this invention;

[0028] Figure 6 The carbon dioxide conversion rate of the Ni / Dy2O3-catalyzed dry reforming reaction of methane in this invention is shown. Detailed Implementation

[0029] The present invention will now be described in further detail with reference to the accompanying drawings, but the embodiments of the present invention are not limited thereto. In the description of the present invention, it should be noted that any embodiment described herein as "exemplary" is not necessarily to be construed as superior to or better than other embodiments. Unless otherwise specified, the reagents used in the embodiments are commercially available. Example 1

[0030] In this embodiment, dysprosium oxide is used as the catalyst support, and nickel nitrate aqueous solution is used as the catalyst metal precursor, wherein Ni accounts for 0.3 wt% of the total catalyst mass. The specific steps for preparing the catalyst for dry reforming methane to syngas are as follows:

[0031] (1) 997 mg of dysprosium oxide was added to 40 mL of deionized water to obtain an aqueous dispersion of dysprosium oxide. 300 μL of nickel nitrate aqueous solution (nickel content 10 mg / mL) was injected into the aqueous dispersion of dysprosium oxide. The mixture was briefly sonicated for 10 min to ensure that the nickel ions were fully mixed with the aqueous dispersion of dysprosium oxide to obtain Ni. 2+ / Dy2O3 mixture;

[0032] (2) The mixture obtained in step (1) was distilled under reduced pressure at 60 °C and 100 mbar for 40 min using a rotary evaporator to remove water, and a solid product was obtained. The solid product was then dried in an oven at 75 °C for 12 hours to obtain the catalyst precursor.

[0033] (3) After grinding the solid catalyst precursor obtained in step (2) thoroughly, heat it to 400 °C at a rate of 5 °C / min in a tube furnace in a mixture of 5 vol% H2 + 95 vol% Ar gas, and keep it at 400 °C for 2 h to carry out high-temperature reduction to obtain a 0.3% Ni / Dy2O3 catalyst that can be used for the dry reforming reaction of methane to produce syngas;

[0034] (4) 100 mg of sieved 40-60 mesh 0.3% Ni / Dy2O3 catalyst was loaded into a fixed reaction bed, heated to 500°C, and then a mixture of 5 vol% H2 + 95 vol% Ar gas was introduced to pretreat the catalyst for 1 h. After cooling to room temperature, the reaction gas (CO2: CH4: N2 = 10 sccm: 10 sccm: 20 sccm) was introduced into the system, and the temperature was increased at a rate of 10 °C / min from 300 to 900 °C. The obtained product was analyzed by gas chromatography.

[0035] Figure 1 The image shows a transmission electron microscopy (TEM) elemental mapping of the Ni / Dy2O3 catalyst of this invention, which shows that Ni is uniformly dispersed on the Dy2O3 support. Figure 2The XRD pattern of the Ni / Dy2O3 catalyst of this invention shows that no diffraction peaks of Ni-related species appeared on the Ni-supported catalyst, indicating that Ni is highly dispersed on the Dy2O3 support, which is consistent with the TEM results.

[0036] Figure 3 and Figure 4 The figures represent the methane conversion and carbon dioxide conversion rates of the dry reforming reaction of methane catalyzed by the catalyst. Specifically, the CH4 conversion rate of the dry reforming reaction of methane catalyzed by 0.3% Ni / Dy2O3 at 800 °C was 83.8%, and the CO2 conversion rate was 87.1%.

[0037] Table 1 lists the CH4 conversion rates of methane dry reforming using common nickel-based catalysts. It can be seen that, at the same temperature, the Ni / Dy2O3 catalyst prepared in this invention has a much higher activity than existing technologies.

[0038]

[0039] References:

[0040] [1] Luisetto I, Tuti S, Romano C, et al. Dry reforming of methaneover Ni supported on doped CeO2: New insight on the role of dopants for CO2activation[J]. Journal of CO2 Utilization, 2019, 30: 63-78.

[0041] [2] Rosha P, Mohapatra SK, Mahla SK, et al. Catalytic reforming ofsynthetic biogas for hydrogen enrichment over Ni supported on ZnO-CeO2 mixedcatalyst[J]. Biomass and Bioenergy, 2019, 125: 70-78.

[0042] [3] Ahmad Salam Farooqi, Basem M. Al-Swai, Farida Hamimi BintiRuslan, et al. Syngas production via dry reforming of methane over Ni basedcatalysts[J]. IOP Conference Series: Materials Science and Engineering, 2020,736: 042007-042014.

[0043] [4] Xinyu Li DL, Hao Tian, ​​Liang Zeng, et al. Dry reforming ofmethane over Ni / La2O3 nanorod catalysts with stabilized Ni nanoparticles[J].Applied Catalysis B: Environmental, 2017, 202: 683-694.

[0044] [5] Taherian Z, Shahed Gharahshiran V, Khataee A, et al. Comparativestudy of modified Ni catalysts over mesoporous CaO-Al2O3 support for CO2methane reforming[J]. Catalysis Communications, 2020, 145: 106100-106104. Example 2

[0045] To investigate the performance differences of different supports, in this embodiment, silica was used as the catalyst support, and nickel nitrate aqueous solution was used as the catalyst metal precursor, wherein Ni accounted for 0.3 wt% of the total catalyst mass. The specific steps for preparing the catalyst for methane dry reforming to syngas are as follows:

[0046] (1) 997 mg of silica was added to 40 mL of deionized water to obtain a silica aqueous dispersion. 300 μL of nickel nitrate aqueous solution (nickel content 10 mg / mL) was injected into the silica aqueous dispersion. The mixture was briefly sonicated for 10 min to ensure that the nickel ions were fully mixed with the silica aqueous dispersion to obtain Ni. 2+ / SiO2 mixture;

[0047] (2) The mixture obtained in step (1) was distilled under reduced pressure at 60 °C and 100 mbar for 40 min using a rotary evaporator to remove water, and a solid product was obtained. The solid product was then dried in an oven at 75 °C for 12 hours to obtain the catalyst precursor.

[0048] (3) After grinding the solid catalyst precursor obtained in step (2) thoroughly, heat it to 400 °C at a rate of 5 °C / min in a tube furnace in a mixture of 5 vol% H2 + 95 vol% Ar gas, and keep it at 400 °C for 2 h to carry out high-temperature reduction to obtain a 0.3% Ni / SiO2 catalyst that can be used for the dry reforming reaction of methane to produce syngas.

[0049] (4) 100 mg of 0.3% Ni / SiO2 catalyst with a sieve of 40~60 mesh was loaded into a fixed reaction bed, heated to 500 °C, and then a mixture of 5 vol% H2 + 95 vol% Ar gas was introduced to pretreat the catalyst for 1 h. After cooling to room temperature, the reaction gas (CO2: CH4: N2 = 10 sccm: 10 sccm: 20 sccm) was introduced into the system, and the temperature was increased at a rate of 10 °C / min. The obtained product was analyzed by gas chromatography. Figure 3 , 4 The values ​​represent the conversion rates of methane and carbon dioxide during the programmed temperature rise process. Specifically, the CH4 conversion rate of 0.3% Ni / SiO2 catalyzing the dry reforming reaction of methane at 800 °C is 2.5%, and the CO2 conversion rate is 7.1%.

[0050] Example 3

[0051] To investigate the performance differences of different supports, alumina was used as the catalyst support in this embodiment, and nickel nitrate aqueous solution was used as the catalyst metal precursor, wherein Ni accounted for 0.3 wt% of the total catalyst mass. Similarly, a 0.3% Ni / Al2O3 catalyst was prepared using the same method. The 0.3% Ni / Al2O3 catalyst achieved a CH4 conversion of 10.6% and a CO2 conversion of 17.8% in the dry reforming of methane at 800 °C.

[0052] Example 4

[0053] In this embodiment, dysprosium oxide is used as the catalyst support, and nickel nitrate aqueous solution is used as the catalyst metal precursor, wherein Ni accounts for 1.2 wt% of the total catalyst mass. The specific steps for preparing the catalyst for dry reforming methane to syngas are as follows:

[0054] (1) Add 988 mg of dysprosium oxide to 40 mL of deionized water to obtain an aqueous dispersion of dysprosium oxide. Inject 1200 μL of nickel nitrate aqueous solution (nickel content 10 mg / mL) into the aqueous dispersion of dysprosium oxide and sonicate briefly for 10 min to ensure that nickel ions are fully mixed with the aqueous dispersion of dysprosium oxide to obtain Ni. 2+ / Dy2O3 mixture;

[0055] (2) The mixture obtained in step (1) was distilled under reduced pressure at 60 °C and 100 mbar for 40 min using a rotary evaporator to remove water, and a solid product was obtained. The solid product was then dried in an oven at 75 °C for 12 hours to obtain the catalyst precursor.

[0056] (3) After grinding the solid catalyst precursor obtained in step (2) thoroughly, heat it to 400 °C at a rate of 5 °C / min in a tube furnace in a mixture of 5 vol% H2 + 95 vol% Ar gas, and keep it at 400 °C for 2 h to carry out high-temperature reduction to obtain a 1.2% Ni / Dy2O3 catalyst that can be used for the dry reforming reaction of methane to produce syngas;

[0057] (4) 100 mg of sieved 40-60 mesh 1.2% Ni / Dy2O3 catalyst was loaded into a fixed reaction bed, heated to 500 °C, and then pretreated with a mixture of 5 vol% H2 and 95 vol% Ar for 1 h. After cooling to room temperature, the reaction gas (CO2: CH4: N2 = 10 sccm: 10 sccm: 20 sccm) was introduced into the system, and the temperature was increased at a rate of 10 °C / min. The obtained products were analyzed by gas chromatography. Among them, the CH4 conversion rate of 1.2% Ni / Dy2O3 in the dry reforming reaction of methane at 800 °C was 94.4%, and the CO2 conversion rate was 94.4%.

[0058] Example 5

[0059] In this embodiment, dysprosium oxide is used as the catalyst support, and nickel nitrate aqueous solution is used as the catalyst metal precursor, wherein Ni accounts for 0.6 wt% of the total catalyst mass. The specific steps for preparing the catalyst for dry reforming methane to syngas are as follows:

[0060] (1) Add 994 mg of dysprosium oxide to 40 mL of deionized water to obtain an aqueous dispersion of dysprosium oxide. Inject 600 μL of nickel nitrate aqueous solution (nickel content 10 mg / mL) into the aqueous dispersion of dysprosium oxide and sonicate briefly for 10 min to ensure that nickel ions are fully mixed with the aqueous dispersion of dysprosium oxide to obtain Ni. 2+ / Dy2O3 mixture;

[0061] (2) The mixture obtained in step (1) was distilled under reduced pressure at 60 °C and 100 mbar for 40 min using a rotary evaporator to remove water, and a solid product was obtained. The solid product was then dried in an oven at 75 °C for 12 hours to obtain the catalyst precursor.

[0062] (3) After grinding the solid catalyst precursor obtained in step (2) thoroughly, heat it to 400 °C at a rate of 5 °C / min in a tube furnace in a mixture of 5 vol% H2 + 95 vol% Ar gas, and keep it at 400 °C for 2 h to carry out high-temperature reduction to obtain a 0.6% Ni / Dy2O3 catalyst that can be used for the dry reforming reaction of methane to produce syngas;

[0063] (4) 100 mg of sieved 40-60 mesh 0.6% Ni / Dy2O3 catalyst was loaded into a fixed reaction bed, heated to 500 °C, and then pretreated with a mixture of 5 vol% H2 and 95 vol% Ar for 1 h. After cooling to room temperature, the reaction gas (CO2: CH4: N2 = 10 sccm: 10 sccm: 20 sccm) was introduced into the system, and the temperature was increased at a rate of 10 °C / min. The obtained products were analyzed by gas chromatography. Among them, the CH4 conversion rate of 0.6% Ni / Dy2O3 in the dry reforming reaction of methane at 800 °C was 90.5%, and the CO2 conversion rate was 93.5%.

[0064] Example 6

[0065] In this embodiment, dysprosium oxide is used as the catalyst support, and nickel nitrate aqueous solution is used as the catalyst metal precursor, wherein Ni accounts for 2.4 wt% of the total catalyst mass. The specific steps for preparing the catalyst for dry reforming methane to syngas are as follows:

[0066] (1) 976 mg of dysprosium oxide was added to 40 mL of deionized water to obtain an aqueous dispersion of dysprosium oxide. 2400 μL of nickel nitrate aqueous solution (nickel content 10 mg / mL) was injected into the aqueous dispersion of dysprosium oxide. The mixture was briefly sonicated for 10 min to ensure that the nickel ions were fully mixed with the aqueous dispersion of dysprosium oxide to obtain Ni. 2+ / Dy2O3 mixture;

[0067] (2) The mixture obtained in step (1) was distilled under reduced pressure at 60 °C and 100 mbar for 40 min using a rotary evaporator to remove water, and a solid product was obtained. The solid product was then dried in an oven at 75 °C for 12 hours to obtain the catalyst precursor.

[0068] (3) After grinding the solid catalyst precursor obtained in step (2) thoroughly, heat it to 400 °C at a rate of 5 °C / min in a tube furnace in a mixture of 5 vol% H2 + 95 vol% Ar gas, and keep it at 400 °C for 2 h to carry out high-temperature reduction to obtain a 2.4% Ni / Dy2O3 catalyst that can be used for the dry reforming reaction of methane to produce syngas;

[0069] (4) 100 mg of sieved 40-60 mesh 2.4% Ni / Dy2O3 catalyst was loaded into a fixed reaction bed, heated to 500 °C, and then pretreated with a mixture of 5 vol% H2 and 95 vol% Ar for 1 h. After cooling to room temperature, the reaction gas (CO2: CH4: N2 = 10 sccm: 10 sccm: 20 sccm) was introduced into the system, and the temperature was increased at a rate of 10 °C / min. The obtained products were analyzed by gas chromatography. Among them, the CH4 conversion rate of 2.4% Ni / Dy2O3 in the dry reforming reaction of methane at 800 °C was 91.5%, and the CO2 conversion rate was 90.8%.

Claims

1. A method for preparing a Ni / Dy2O3 catalyst for dry reforming of methane, characterized in that... Includes the following steps: (1) Dysprosium oxide was added to deionized water and ultrasonically dispersed to prepare an aqueous dispersion of dysprosium oxide with a content of 2-5 wt%; (2) Add a soluble nickel salt solution with a Ni content of 5~20 mg / mL to the dysprosium oxide aqueous dispersion; (3) Remove water from the dispersion to obtain a solid product; (4) The solid product is reduced at 400~600 °C in H2 / Ar atmosphere to obtain a methane dry reforming catalyst Ni / Dy2O3 with Ni content of 0.1~4 wt%. The heating rate of the reduction treatment is 2~10 °C / min, the volume ratio of hydrogen to argon is (5~10):(90~95), and the reduction time is 1~3 h.

2. The method for preparing the Ni / Dy2O3 catalyst for dry reforming of methane according to claim 1, characterized in that: In step (1), dysprosium oxide is rapidly dispersed in deionized water under ultrasonic assistance to obtain a dispersion. The ultrasonic power is 50~120 W and the ultrasonic frequency is 40 Hz.

3. The method for preparing the Ni / Dy2O3 catalyst for dry reforming of methane according to claim 1, characterized in that: In step (2), the soluble nickel salt is selected from one or more of nickel nitrate, nickel chloride, nickel acetylacetone, and nickel acetate.

4. The method for preparing the Ni / Dy2O3 catalyst for dry reforming of methane according to claim 1, characterized in that: In step (3), the removal of water from the dispersion is carried out by vacuum distillation at a temperature of 55-65 °C and a vacuum degree of 100 mbar.

5. The Ni / Dy2O3 catalyst for dry reforming of methane prepared by the method according to claim 1.

6. The application of the Ni / Dy2O3 catalyst according to claim 5 in the dry reforming of methane, characterized in that: The dry reforming reaction temperature of methane is 800~900 °C.

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