Nickel-silicon spinel catalyst doped with rare earth metal and based on attapulgite-based silicon source as well as preparation method and application of nickel-silicon spinel catalyst

Abstract

The invention discloses a nickel-silicon spinel catalyst doped with rare earth metal and based on an attapulgite-based silicon source as well as a preparation method and application of the nickel-silicon spinel catalyst, the catalyst comprises the attapulgite-based silicon source serving as a carrier, nickel which is loaded on the carrier and serves as an active component, and rare earth metal serving as an auxiliary agent, the catalyst forms a nickel silicon spinel structure. When the catalyst is used for catalyzing CH4-CO2 reforming to prepare synthesis gas, the methane / carbon dioxide conversion rate exceeds 80%, the high methane / carbon dioxide conversion rate can still be achieved within 650 h, the H2 / CO ratio in the synthesis gas is 0.8-1.2, and it is indicated that the catalyst has good stability and long service life.

Description

Technical Field

[0001] The present invention relates to the technical field of methane dry reforming, and in particular to a rare earth metal-doped nickel-silicon spinel catalyst based on an attapulgite-based silicon source, and a preparation method and application thereof. Background Art

[0002] The direct emission of greenhouse gases such as carbon dioxide and methane has led to a large amount of resource waste and a serious greenhouse effect. Therefore, it is urgent to take effective measures to transform and utilize the emitted methane and carbon dioxide into resources.

[0003] The study of dry reforming of methane (DRM) reaction can be traced back to the early 20th century. Researchers found that methane and carbon dioxide can react at high temperatures, but the reaction rate is slow. In the mid-20th century, researchers found that Ni has a low activation energy and can effectively reduce the starting temperature of the reaction, thereby showing high catalytic activity in the DRM reaction. At the same time, Ni-based catalysts can significantly improve the anti-carbon deposition performance of Ni-based catalysts by adding co-catalysts (such as MgO, CeO2, etc.) or adopting special preparation methods (such as impregnation, co-precipitation, etc.), especially under high temperature conditions. In addition, compared with precious metals (such as Pt, Pd, Rh, etc.), Ni is a relatively cheap metal with significantly lower cost, which makes Ni-based catalysts have significant economic advantages in large-scale industrial applications.

[0004] However, numerous studies have shown that nickel-based catalysts still suffer from poor stability in DRM reactions, attributed to sintering of active components on the surface of the Ni-based catalysts and the formation of carbon deposits during the reaction. Therefore, overcoming these issues is crucial for the further industrial application of DRM and the large-scale production of syngas. Summary of the Invention

[0005] The main purpose of the present invention is to provide a nickel-silicon spinel catalyst based on a attapulgite-based silicon source doped with rare earth metals with high catalytic activity and good stability in catalytic CH4-CO2 reforming to produce synthesis gas, as well as a preparation method and application thereof.

[0006] To achieve the above-mentioned purpose, the present invention provides a nickel-silicon spinel catalyst based on a attapulgite-based silicon source doped with rare earth metals, comprising a attapulgite-based silicon source as a carrier, nickel as an active component loaded on the carrier, and a rare earth metal acting as an auxiliary agent, wherein the catalyst forms a nickel-silicon spinel structure.

[0007] Furthermore, the rare earth metal is selected from any one or more of yttrium, lanthanum, cerium and samarium.

[0008] Furthermore, in the catalyst, the nickel content is 5-20 wt%, and the rare earth metal content is 0.5-2 wt%.

[0009] Furthermore, the attapulgite-based silicon source is prepared by the following method: placing attapulgite clay in a 3-10 mol / L hydrochloric acid solution, stirring at room temperature for 5-10 hours, then transferring it to a hydrothermal reactor, hydrothermally treating it at 150-220°C for 10-15 hours, and finally filtering it, and drying the obtained filter residue at 100-120°C for 8-12 hours to obtain the attapulgite-based silicon source.

[0010] The present invention also provides a method for preparing the above-mentioned rare earth metal-doped nickel-silicon spinel catalyst based on a attapulgite-based silicon source, comprising the following steps: taking a attapulgite-based silicon source, a nickel precursor salt and a rare earth metal precursor salt, using a urea hydrothermal synthesis method to load nickel and rare earth metals on the attapulgite-based silicon source, and then calcining at a high temperature to form a nickel-silicon spinel structure, thereby obtaining the rare earth metal-doped nickel-silicon spinel catalyst based on a attapulgite-based silicon source.

[0011] Furthermore, the operation process of the urea hydrothermal synthesis method is: add nickel nitrate or sulfate, rare earth metal nitrate or sulfate, and attapulgite-based silicon source to deionized water, stir at room temperature for 2 to 5 hours, then add urea, dissolve completely at 80 to 100°C, transfer to a hydrothermal reactor, hydrothermally treat at 160 to 200°C for 3 to 6 hours, and finally filter, and the obtained filter residue is dried at 100 to 120°C for 12 to 16 hours.

[0012] Furthermore, the high-temperature calcination process is as follows: heating the temperature to 800-1600° C. at a heating rate of 1-5° C. / min in an air atmosphere and calcining for 4-10 hours.

[0013] The present invention also provides the use of the above-mentioned rare earth metal-doped nickel-silicon spinel catalyst based on attapulgite-based silicon source in catalyzing the reforming of low-concentration coal mine gas to produce synthesis gas.

[0014] The present invention also provides a method for catalytically reforming low-concentration coal mine gas to produce synthesis gas, comprising grinding and uniformly mixing the above-mentioned rare earth metal-doped nickel silicon spinel catalyst based on attapulgite-based silicon source with inert silicon carbide, and then reducing them in a 10 vol% H2 / N2 atmosphere at 650-750°C for 2-4 hours, and finally carrying out a catalytic low-concentration coal mine gas reforming reaction to produce synthesis gas.

[0015] Furthermore, the catalyst is mixed with inert silicon carbide in a mass ratio of 1:1 to 5, and the reaction conditions are: catalyst dosage 0.05 to 0.4 g, CH4 to CO2 molar ratio in the reaction feed is 1 to 1.25, and the gas feed space velocity is 40,000 to 120,000 mL·h -1 ·gcat-1 , the reaction temperature is 350~850℃.

[0016] Attapulgite is an aluminosilicate with a high silicon content. Using attapulgite as a silicon source, Al / Mg and impurities in the attapulgite are removed under the action of inorganic acid, which not only retains the high structural stability of the attapulgite, but also optimizes the specific surface area and pore structure, which is conducive to the high dispersion of nickel metal.

[0017] Compared with nickel / attapulgite-based silicon sources, the doping of rare earth metal elements improves the anti-sintering ability of active metals by enhancing the interaction with active components and supports; at the same time, the large number of alkaline sites on the catalyst surface are conducive to promoting the activation of CO2 and the removal of carbon deposits, thereby enhancing the stability of the catalyst.

[0018] Lanthanum, as a rare earth metal element, has good redox properties and anti-sintering properties. The present invention prepares a nickel-silicon spinel catalyst with good stability through high-temperature calcination, which is beneficial to promote the removal of carbon on the catalyst surface, while improving the interaction between the bimetallic / support and realizing the anchoring of the active metal.

[0019] The beneficial effects of the present invention are embodied in:

[0020] 1. The catalyst of the present invention has the characteristics of green economy and high structural stability. When used in the catalytic CH4-CO2 reforming reaction to produce synthesis gas, the methane / carbon dioxide conversion rate exceeds 80%, and the methane / carbon dioxide conversion rate is still high after 650 hours. The H2 / CO ratio in the synthesis gas is 0.8-1.2.

[0021] 2. The catalyst of the present invention uses nickel as the active metal, which can ensure that the catalyst has high activity in cracking methane C-H bonds. The use of the attapulgite-based silicon source carrier saves catalyst preparation costs while promoting the dispersion of the active components.

[0022] 3. Compared to other nickel-based catalysts, the catalyst of this invention enhances the interaction between the active component and the support through the synergistic effect of lanthanum and nickel, improving the active metal's resistance to sintering. Furthermore, the high concentration of basic sites on the catalyst surface facilitates CO activation and thus the removal of carbon deposits. As a result, the catalyst exhibits high resistance to active component sintering and carbon deposition, as well as high catalytic stability, meeting the requirements for industrial catalyst use.

[0023] 4. The catalyst of the present invention is used in the catalytic CH4-CO2 reforming reaction to produce synthesis gas, which can significantly enhance the catalytic adsorption and activation ability of CH4 and CO2 molecules, has high CH4 and CO2 conversion rates, and shows good prospects for industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1The XRD patterns of the D1 catalyst prepared in Comparative Example 1 and the D2 catalyst prepared in Comparative Example 2 are shown;

[0025] Figure 2 is the N2 adsorption-desorption isotherm of the D1 catalyst prepared in Comparative Example 1;

[0026] Figure 3 This is the pore size distribution diagram of the D1 catalyst prepared in Comparative Example 1;

[0027] Figure 4 FTIR spectrum of the D1 catalyst prepared in Comparative Example 1;

[0028] Figure 5 TEM image of catalyst #1 prepared in Example 2;

[0029] Figure 6 1# is a lattice fringe spacing analysis diagram of catalyst 1 prepared in Example 2;

[0030] Figure 7 The CO2-TPD diagrams are those of the D1 catalyst prepared in Comparative Example 1 and the 1# catalyst prepared in Example 2. DETAILED DESCRIPTION

[0031] In order to make the technical solution of the present invention more clearly understood by those skilled in the art, the following examples are given for illustration. It should be noted that the following examples do not limit the scope of protection claimed by the present invention.

[0032] Unless otherwise specified, the raw materials, reagents, or devices used in the following examples can be obtained from conventional commercial channels or by existing known methods; unless otherwise specified, the methods used in the examples of the present invention are methods known to those skilled in the art.

[0033] Example 1

[0034] Preparation of carrier attapulgite-based silicon source

[0035] The preparation method is as follows:

[0036] 20 g of attapulgite clay was weighed and placed in 120 mL of 6 mol / L hydrochloric acid solution, stirred at 300 r / min at room temperature for 5 h, then transferred to a hydrothermal reactor and hydrothermally treated at 180 ° C for 12 h. After that, it was filtered and washed until neutral. The filter residue was dried at 105 ° C for 10 h to obtain the attapulgite-based silicon source.

[0037] Example 2

[0038] Preparation of rare earth metal-doped nickel-silicon spinel catalyst based on attapulgite-based silicon source

[0039] The theoretical content of the catalyst components prepared in this embodiment is: nickel content 15wt%, lanthanum content 1wt%, and the remaining component is attapulgite-based silicon source support. The preparation method is as follows:

[0040] 2 g of the attapulgite-based silicon source obtained in Example 1, 1.774 g of nickel nitrate hexahydrate, and 0.067652 g of lanthanum nitrate hexahydrate were weighed and added to 100 mL of deionized water. The mixture was stirred at 300 r / min at room temperature for 2 h, 1.1367245 g of urea was added, and stirred at 300 r / min at 90 ° C for 2 h to completely dissolve the urea. The mixture was then transferred to a polytetrafluoroethylene-lined hydrothermal synthesis reactor and stirred at 300 r / min at 180 ° C for 3 h. Finally, it was filtered and washed until neutral. The filter residue was first placed in an oven at 105 ° C for 8 h, and then heated to 1200 ° C at a heating rate of 4 ° C / min in an air atmosphere and calcined at a constant temperature for 4 h to obtain a nickel-silicon spinel catalyst based on a attapulgite-based silicon source doped with rare earth metals, numbered as catalyst 1#.

[0041] Example 3

[0042] Preparation of rare earth metal-doped nickel-silicon spinel catalyst based on attapulgite-based silicon source

[0043] The theoretical content of the catalyst components prepared in this embodiment is: nickel content is 5wt%, cerium content is 2wt%, and the remaining component is attapulgite-based silicon source support. The preparation method is as follows:

[0044] 2 g of the attapulgite-based silicon source obtained in Example 1, 0.5326 g of nickel nitrate hexahydrate, and 0.13327 g of cerium nitrate hexahydrate were weighed and added to 100 mL of deionized water, stirred at room temperature for 2 h, 0.3853 g of urea was added, and stirred at 90 ° C for 2 h to completely dissolve the urea. Then, the mixture was transferred to a polytetrafluoroethylene-lined hydrothermal synthesis reactor and stirred at 180 ° C for 3 h. Finally, it was filtered and washed until neutral. The filter residue was first placed in an oven at 105 ° C for 8 h, and then heated to 1400 ° C at a heating rate of 4 ° C / min in an air atmosphere and calcined at a constant temperature for 4 h to obtain a nickel silicon spinel catalyst based on a attapulgite-based silicon source doped with rare earth metals, No. 2# catalyst.

[0045] Comparative Example 1

[0046] Preparation of nickel-silicon spinel catalyst based on attapulgite-based silicon source

[0047] The theoretical content of the catalyst components prepared in this comparative example is: nickel content is 15 wt%, and the remaining components are attapulgite-based silicon source carriers. The preparation method is the same as Example 2, except that the addition of lanthanum nitrate hexahydrate is omitted, the amount of nickel nitrate hexahydrate added is adjusted to 1.74871 g, and the amount of urea added is adjusted to 1.08354 g. Finally, a nickel-silicon spinel catalyst based on attapulgite-based silicon source is obtained, numbered catalyst D1.

[0048] Comparative Example 2

[0049] Preparation of rare earth metal-doped nickel-silicon catalyst based on attapulgite-based silicon source

[0050] The theoretical content of the catalyst components prepared in this comparative example is: 15 wt% nickel content, 1 wt% lanthanum content, and the remaining components are attapulgite-based silicon source carriers. The preparation method is the same as that in Example 2, except that the final calcination treatment is adjusted to increase the temperature to 1000°C at a heating rate of 4°C / min in an air atmosphere and calcined at a constant temperature for 4 hours, finally obtaining a nickel-silicon catalyst based on attapulgite-based silicon source doped with rare earth metals, numbered as catalyst D2.

[0051] Experimental Example 1

[0052] Catalyst structure determination

[0053] The structures of the catalyst D1 prepared in Comparative Example 1, the catalyst D2 prepared in Comparative Example 2 and the catalyst 1# prepared in Example 2 were analyzed. Figures 1 to 7 shown.

[0054] See also Figure 1 , XRD spectrum of nickel-silicon spinel catalyst based on attapulgite-based silicon source Figure 2 Characteristic diffraction peaks corresponding to the nickel-silicon spinel structure were detected at θ = 25.7°, 31.32°, 32.61°, 35.19°, 36.13°, and 52.9°, demonstrating that nickel-silicon spinel materials can be successfully prepared using attapulgite as a silicon source. Furthermore, no characteristic diffraction peaks corresponding to the nickel-silicon spinel structure were detected at the corresponding positions in the XRD pattern of the D2 catalyst, indicating that the D2 catalyst failed to form a nickel-silicon spinel structure.

[0055] See also Figure 2 According to the IUPAC classification, the nickel-silicon spinel catalyst based on attapulgite-based silicon exhibits a type III composite isotherm, accompanied by an H3-type hysteresis loop. This indicates that the synthesized nickel-silicon spinel based on attapulgite-based silicon has a composite pore structure consisting of ordered micropores and mesopores.

[0056] See also Figure 3The nickel-silicon spinel catalyst based on attapulgite-based silicon source exhibits a pore size distribution concentrated at 2.5nm and 3.9nm, further proving the existence of this microporous-mesoporous composite pore structure, which is beneficial to promote the dispersion of active metals on the surface of the support and promote reaction mass transfer.

[0057] See also Figure 4 FTIR spectrum of nickel-silicon spinel catalyst based on attapulgite-based silicon source. -1 The adsorption bands detected at 1095, 796, and 460 cm-1 correspond to the stretching vibrations of surface hydroxyl species and adsorbed water, respectively, while the adsorption bands detected at 1095, 796, and 460 cm-1 correspond to the stretching vibrations of surface hydroxyl species and adsorbed water, respectively. -1 The characteristic bands appearing at 620 cm correspond to the vibration of Si-O and Si-O-Si bonds in the support skeleton. -1 The vibration peak at NiO / Ni 2+ The Ni-O bond stretching of the species is related to the 1360 / 1394 cm -1 and 847cm -1 The peaks at and represent the vibration of the residual Si-O-Mg bonds in the formed nickel-silicon spinel structure and the stretching of silicate tetrahedrons, respectively. The presence of these vibration bands in attapulgite-based nickel-silicon spinel further demonstrates the feasibility of preparing nickel-silicon spinel materials using attapulgite as a silicon source.

[0058] See also Figure 5 The TEM image of the nickel-silicon spinel catalyst based on attapulgite-based silicon source doped with rare earth metals shows that the active metals are highly dispersed on the surface of the layered attapulgite-based silicon source support, which is conducive to exposing more active centers and promoting the adsorption and activation of methane molecules in the catalytic CH4-CO2 reforming reaction to produce synthesis gas. In addition, through Figure 6 The lattice fringe spacing analysis of the rare earth metal-doped nickel-silicon spinel catalyst based on a attapulgite-based silicon source further confirms the highly uniform dispersion of the active metals. This regenerative synergistic effect of the two metals can inhibit the aggregation and growth of active metal particles, exposing more active sites and improving catalyst activity and stability.

[0059] See also Figure 7The CO2-TPD diagrams of catalyst D1 and catalyst 2# are shown. Both catalyst D1 and catalyst 1# show two desorption peaks, and the desorption peak signal intensity of catalyst 1# is significantly greater than that of catalyst D1, which confirms that lanthanum doping is conducive to the formation of more carbon dioxide adsorption centers. Among them, the desorption peak of catalyst D1 belongs to weak alkaline sites, and the desorption peak of catalyst 1# belongs to medium alkaline sites. This shows that the addition of lanthanum can promote the generation of medium alkaline sites, which is conducive to promoting the adsorption and activation of CO2 during the reaction process, forming active O* intermediate species, thereby promoting the removal of carbon deposits and improving the stability of the catalyst.

[0060] Experimental Example 2

[0061] Performance test of catalyst for CH4-CO2 reforming to synthesis gas

[0062] Test method: 0.05-0.4g of catalyst sample was taken and ground with inert silicon carbide at a mass ratio of 1:4 for 10 minutes. The sample was then placed in a vertical micro-fixed bed reactor and subjected to reduction treatment at 650-750°C for 2 hours under a 100mL / min 10vol% H2 / N2 flow. The catalytic reaction performance was then tested. Specifically, the molar ratio of methane to carbon dioxide in the raw gas feed was 1, and the raw gas feed space velocity was 40,000-120,000mL·h -1 ·g cat -1 , the reaction temperature is 650-850° C. The specific reaction conditions and results of each catalyst sample are shown in Table 1.

[0063] Table 1

[0064]

[0065] Note: Service life refers to the time it takes for the activity of the catalyst to decrease to 50% of its initial activity. The specific activity is measured in terms of methane conversion rate.

[0066] Experimental Example 3

[0067] Performance test of different catalysts for coal mine gas reforming to synthesis gas

[0068] Test method: 0.05-0.4 g of catalyst sample was taken, ground and mixed for 10 minutes, then loaded into a vertical micro fixed-bed reactor and reduced at 650-750° C. for 2 hours in a 100 mL / min 10 vol% H2 / N2 flow, and then the catalytic reaction performance was tested. Specifically, the raw gas was coalbed methane from Shaanxi Province (methane concentration 8%), coalbed methane from Ningxia Hui Autonomous Region (methane concentration 17%), and coalbed methane from Henan Province (methane concentration 20%), and the raw gas feed space velocity was 40,000-120,000 mL·h -1 ·g cat-1 , the reaction temperature is 650-850° C. Specific reaction conditions and results are shown in Table 2.

[0069] Table 2

[0070]

[0071]

[0072] Note: Service life refers to the time it takes for the activity of the catalyst to decrease to 50% of its initial activity. The specific activity is measured in terms of methane conversion rate.

[0073] It can be concluded from Experimental Examples 2 and 3 that the catalyst of the present invention has a methane / carbon dioxide conversion rate of more than 80% in the catalytic CH4-CO2 reforming reaction to produce synthesis gas, and can still show a high methane / carbon dioxide conversion rate after 650 hours. The H2 / CO ratio in the synthesis gas is 0.8 to 1.2, indicating that the catalyst has good stability and a long service life.

[0074] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A rare earth metal-doped nickel-silicon spinel catalyst based on an attapulgite-based silicon source, characterized in that: The catalyst comprises an attapulgite-based silicon source as a carrier, nickel as an active component and a rare earth metal as an auxiliary agent supported on the carrier, and forms a nickel-silicon spinel structure.

2. The rare earth metal-doped nickel-silicon spinel catalyst based on attapulgite-based silicon source according to claim 1, characterized in that The rare earth metal is selected from any one or more of yttrium, lanthanum, cerium and samarium.

3. The rare earth metal-doped nickel-silicon spinel catalyst based on attapulgite-based silicon source according to claim 1, characterized in that: In the catalyst, the nickel content is 5-20wt%, and the rare earth metal content is 0.5-2wt%.

4. The rare earth metal-doped nickel-silicon spinel catalyst based on attapulgite-based silicon source according to claim 1, 2 or 3, characterized in that: The attapulgite-based silicon source is prepared by the following method: placing attapulgite clay in a 3-10 mol / L hydrochloric acid solution, stirring at room temperature for 5-10 hours, then transferring it to a hydrothermal reactor, hydrothermally treating it at 150-220° C. for 10-15 hours, and finally filtering it. The filter residue is dried at 100-120° C. for 8-12 hours to obtain the attapulgite-based silicon source.

5. The method for preparing a rare earth metal-doped nickel-silicon spinel catalyst based on an attapulgite-based silicon source according to any one of claims 1 to 4, characterized in that: The following steps are involved: Take a attapulgite-based silicon source, a nickel precursor salt and a rare earth metal precursor salt, use a urea hydrothermal synthesis method to load nickel and rare earth metals on the attapulgite-based silicon source, and then calcine at high temperature to form a nickel-silicon spinel structure to obtain the rare earth metal-doped nickel-silicon spinel catalyst based on the attapulgite-based silicon source.

6. The method for preparing a rare earth metal-doped nickel-silicon spinel catalyst based on an attapulgite-based silicon source according to claim 4, wherein: The operating process of the urea hydrothermal synthesis method is as follows: nickel nitrate or sulfate, rare earth metal nitrate or sulfate, and attapulgite-based silicon source are added to deionized water, stirred at room temperature for 2 to 5 hours, then urea is added and completely dissolved at 80 to 100°C, then transferred to a hydrothermal reactor, hydrothermally treated at 160 to 200°C for 3 to 6 hours, and finally filtered. The filter residue is then dried at 100 to 120°C for 12 to 16 hours.

7. The method for preparing a rare earth metal-doped nickel-silicon spinel catalyst based on an attapulgite-based silicon source according to claim 4, wherein: The operation process of high-temperature calcination is: heating to 800-1600° C. at a heating rate of 1-5° C. / min in an air atmosphere and calcining for 4-10 hours.

8. Use of the rare earth metal-doped nickel-silicon spinel catalyst based on attapulgite-based silicon source according to any one of claims 1 to 4 in catalytic reforming of low-concentration coal mine gas to produce synthesis gas.

9. A method for catalytically reforming low-concentration coal mine gas to produce synthesis gas, characterized in that: The following steps are involved: The rare earth metal-doped nickel silicon spinel catalyst based on attapulgite-based silicon source as described in any one of claims 1 to 4 is ground and mixed evenly with inert silicon carbide, and then reduced in a 10 vol% H2 / N2 atmosphere at 650-750°C for 2-4 hours, and finally catalyzed low-concentration coal mine gas reforming to produce synthesis gas reaction.

10. The method for producing synthesis gas by catalytic reforming of low-concentration coal mine gas according to claim 9, characterized in that: The catalyst is mixed with inert silicon carbide in a mass ratio of 1:1-5. The reaction conditions are: catalyst dosage 0.05-0.4 g, CH4 to CO2 molar ratio in the reaction feed of 1-1.25, gas feed space velocity of 40,000-120,000 mL·h -1 ·gcat -1 , the reaction temperature is 350~850℃.

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