WO2023159703A1 - 改性硅酸钙基镍系催化剂及其制备方法、应用 - Google Patents

改性硅酸钙基镍系催化剂及其制备方法、应用 Download PDF

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WO2023159703A1
WO2023159703A1 PCT/CN2022/081740 CN2022081740W WO2023159703A1 WO 2023159703 A1 WO2023159703 A1 WO 2023159703A1 CN 2022081740 W CN2022081740 W CN 2022081740W WO 2023159703 A1 WO2023159703 A1 WO 2023159703A1
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nickel
calcium silicate
modified calcium
silicate
carrier
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PCT/CN2022/081740
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English (en)
French (fr)
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颜枫
曲凡
张作泰
李春艳
陈黑锦
沈雪华
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深碳科技(深圳)有限公司
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Priority to US18/136,226 priority Critical patent/US11826727B2/en
Publication of WO2023159703A1 publication Critical patent/WO2023159703A1/zh

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
    • B01J23/76—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
    • B01J23/83—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36 with rare earths or actinides
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/002—Mixed oxides other than spinels, e.g. perovskite
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/10—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of rare earths
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B3/00—Hydrogen; Gaseous mixtures containing hydrogen; Separation of hydrogen from mixtures containing it; Purification of hydrogen
    • C01B3/02—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen
    • C01B3/32—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by reaction of gaseous or liquid organic compounds with gasifying agents, e.g. water, carbon dioxide, air
    • C01B3/34—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by reaction of gaseous or liquid organic compounds with gasifying agents, e.g. water, carbon dioxide, air by reaction of hydrocarbons with gasifying agents
    • C01B3/38—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by reaction of gaseous or liquid organic compounds with gasifying agents, e.g. water, carbon dioxide, air by reaction of hydrocarbons with gasifying agents using catalysts
    • C01B3/40—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by reaction of gaseous or liquid organic compounds with gasifying agents, e.g. water, carbon dioxide, air by reaction of hydrocarbons with gasifying agents using catalysts characterised by the catalyst
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2523/00—Constitutive chemical elements of heterogeneous catalysts
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2203/00—Integrated processes for the production of hydrogen or synthesis gas
    • C01B2203/02—Processes for making hydrogen or synthesis gas
    • C01B2203/0205—Processes for making hydrogen or synthesis gas containing a reforming step
    • C01B2203/0227—Processes for making hydrogen or synthesis gas containing a reforming step containing a catalytic reforming step
    • C01B2203/0238—Processes for making hydrogen or synthesis gas containing a reforming step containing a catalytic reforming step the reforming step being a carbon dioxide reforming step
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2203/00—Integrated processes for the production of hydrogen or synthesis gas
    • C01B2203/10—Catalysts for performing the hydrogen forming reactions
    • C01B2203/1041—Composition of the catalyst
    • C01B2203/1047—Group VIII metal catalysts
    • C01B2203/1052—Nickel or cobalt catalysts
    • C01B2203/1058—Nickel catalysts
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2203/00—Integrated processes for the production of hydrogen or synthesis gas
    • C01B2203/10—Catalysts for performing the hydrogen forming reactions
    • C01B2203/1041—Composition of the catalyst
    • C01B2203/1082—Composition of support materials
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2203/00—Integrated processes for the production of hydrogen or synthesis gas
    • C01B2203/12—Feeding the process for making hydrogen or synthesis gas
    • C01B2203/1205—Composition of the feed
    • C01B2203/1211—Organic compounds or organic mixtures used in the process for making hydrogen or synthesis gas
    • C01B2203/1235—Hydrocarbons
    • C01B2203/1241—Natural gas or methane
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/50—Improvements relating to the production of bulk chemicals
    • Y02P20/52—Improvements relating to the production of bulk chemicals using catalysts, e.g. selective catalysts

Definitions

  • the invention relates to the technical fields of biogas, industrial solid waste resource utilization and catalyst preparation, and in particular to a modified calcium silicate-based nickel catalyst and its preparation method and application.
  • Biogas reforming technology is a promising biogas resource utilization technology.
  • the biogas reforming reaction can simultaneously utilize methane and carbon dioxide in the biogas and convert them into synthesis gas with higher application value.
  • Catalysts play an important role in the biogas reforming reaction, but the catalysts currently used in the biogas reforming reaction have problems such as high cost and easy deactivation, which limit the industrial application of the biogas reforming reaction.
  • the present application provides a modified calcium silicate-based nickel-based catalyst and its preparation method and application to solve the problems of high cost and easy deactivation of existing catalysts used in biogas reforming reactions.
  • the present application provides a method for preparing a modified calcium silicate-based nickel-based catalyst, the preparation method comprising the following steps:
  • Leaching leaching silicon-based solid waste with alkaline agent to obtain silicate leaching solution
  • Loading Disperse the modified calcium silicate carrier in an anhydrous alcohol solvent to obtain a mixed suspension, drop the alcohol solution of nickel salt into the mixed suspension for the second precipitation reaction, heat Stir until the alcohol in the anhydrous alcohol solvent and the alcohol solution of the nickel salt volatilizes, dry and calcinate to obtain the modified calcium silicate-based nickel-based catalyst.
  • the silicon-based solid waste includes at least one of rice husk ash, fly ash, metallurgical slag or blast furnace iron slag;
  • the alkali agent includes sodium hydroxide, potassium hydroxide, sodium carbonate or potassium carbonate at least one of
  • the anhydrous alcohol solvent is absolute ethanol, anhydrous methanol or anhydrous propanol, and the alcohol used for the nickel salt alcohol solution is the same as the anhydrous alcohol solvent.
  • the nitrate solution corresponding to the lanthanide metal includes at least one of cerium nitrate, lanthanum nitrate, samarium nitrate or praseodymium nitrate;
  • the molar ratio of the silicate ions in the silicate leaching solution to the calcium hydroxide in the calcium hydroxide suspension is 0.9:1 to 1.1:1; the lanthanide metal element
  • the doping amount in the modified calcium silicate carrier is 1wt%-10wt%.
  • the dropping rate of the silicate leaching solution is 20mL/h-30mL/h
  • the dropping rate of the nitrate solution corresponding to the lanthanide metal is 10mL/h- 15mL/h
  • the first precipitation reaction is carried out at a temperature of 25°C-60°C and a stirring rate of 450rpm-550rpm for 2h-8h.
  • the precipitate formed by the reaction is washed at least once with water and at least once with an alcohol solvent after filtering and before drying, and the drying condition is to dry at 75°C to 85°C for 10 hours ⁇ 14h, the roasting condition is to roast at 500°C ⁇ 800°C for 1.8h ⁇ 2.5h.
  • the modified calcium silicate carrier is added to the absolute ethanol and ultrasonically dispersed for 10 minutes to 15 minutes to obtain the mixed suspension, wherein the modified calcium silicate
  • the solid-to-liquid ratio of the carrier to the absolute ethanol is 1g:30mL-1g:60mL
  • the nickel element loading in the modified calcium silicate-based nickel catalyst is 0.5wt%-10wt%.
  • the alcohol solution of the nickel salt is the ethanol solution of the nickel salt
  • the dropping rate of the ethanol solution of the nickel salt is 50mL/h ⁇ 100mL/h
  • the second time The precipitation reaction is carried out at a temperature of 65° C. to 68° C. and a stirring rate of 450 rpm to 550 rpm until all the alcohol in the anhydrous alcohol solvent and the ethanol solution of the nickel salt is volatilized.
  • the drying condition is 75°C-85°C for 1.5h-3h
  • the calcination condition is 400°C-500°C for 4h-5h.
  • the embodiment of the present application provides a modified calcium silicate-based nickel-based catalyst, which is prepared by the preparation method as described in the first aspect.
  • the embodiment of the present application provides an application of a modified calcium silicate-based nickel-based catalyst
  • the modified calcium-silicate-based nickel-based catalyst is prepared by the preparation method as described in the first aspect, and the The modified calcium silicate-based nickel catalyst is used for biogas reforming reaction.
  • biogas reforming reaction comprises the following steps:
  • the modified calcium silicate-based nickel-based catalyst Pass reducing gas into the modified calcium silicate-based nickel-based catalyst, and reduce the modified calcium-silicate-based nickel-based catalyst at 650°C to 900°C; wherein, the reducing gas contains 10vol% to 20vol% hydrogen;
  • the raw material gas is composed of 20vol%-40vol% CH4 , 20vol%-40vol% CO2 and 20vol%-60vol% inert gas, the inert gas is nitrogen, helium, neon or argon at least one.
  • the reaction temperature is greater than or equal to 750°C
  • the methane conversion rate is greater than or equal to 80%
  • the carbon dioxide conversion rate is greater than or equal to 87%
  • the H2 /CO selectivity coefficient is greater than or equal to 0.8 .
  • the modified calcium-nickel silicate catalyst obtained by the preparation method in the embodiment of the present application has the advantages of low cost, high stability and high activity, and has an industrial application prospect.
  • the catalysts in the examples of this application do not use commonly used materials such as carbon-based, nano-silica, or nano-alumina as carriers, but use modified calcium silicate as a carrier, using the alkalinity and The nickel salt undergoes a precipitation reaction to load the active metal nickel. Without the need to add a precipitant such as ammonia water, the nickel element is uniformly precipitated on the surface of the calcium silicate carrier through the above precipitation reaction to achieve the active metal nickel on the calcium silicate carrier. The purpose of high dispersion degree and relatively strong force between metal and carrier.
  • Such a degree of dispersion of active metal nickel makes it possible to achieve a good catalytic effect when the loading of nickel in the catalyst is low, which not only satisfies the catalytic performance, but also saves the amount of nickel and reduces the production cost of the nickel-based catalyst.
  • calcium silicate is further modified, and lanthanide metal elements are incorporated into silicon in a more uniform and highly dispersed manner through co-precipitation reaction.
  • the sintering and carbon deposition under high temperature conditions can be effectively suppressed, and the catalytic performance of the modified calcium silicate-based nickel catalyst can be further improved. activity and stability.
  • the modified calcium silicate-based nickel-based catalyst prepared in the examples of the present application has good industrial application prospects.
  • Using the silicate leaching solution extracted from silicon-based solid waste as raw material not only has the advantages of wide source of raw materials and low cost, but also makes resource utilization of solid waste more friendly to the environment.
  • Fig. 1 is the flow chart of the preparation method of the embodiment modified calcium silicate-based nickel-based catalyst of the present application
  • Fig. 2 is the scanning electron micrograph of embodiment 1 modified calcium silicate-based nickel series catalyst
  • Fig. 3 is the catalytic conversion figure of embodiment 1 modified calcium silicate-based nickel-based catalyst at different temperatures;
  • Fig. 4 is the stability test result figure of embodiment 1 modified calcium silicate-based nickel-based catalyst
  • Fig. 5 is the catalytic conversion figure of embodiment 5 modified calcium silicate-based nickel-based catalysts at different temperatures;
  • Fig. 6 is the catalytic conversion figure of embodiment 6 modified calcium silicate-based nickel-based catalysts at different temperatures;
  • Fig. 7 is a graph showing the stability test results of the modified calcium silicate-based nickel-based catalyst in Example 6.
  • installed disposed
  • provided a connection or an integral structure
  • it may be a mechanical connection or an electrical connection
  • it may be a direct connection or an indirect connection through an intermediary
  • internal connectivity Those of ordinary skill in the art can understand the specific meanings of the above terms in this application according to specific situations.
  • first means two or more.
  • biogas resource utilization technology mainly has two directions. One is to use the calorific value of methane in biogas for power generation, gas bloom technology, etc., and the other is to use biogas as a chemical raw material to produce more valuable products through biogas reforming technology. Hydrogen or Syngas.
  • biogas reforming technology can simultaneously use methane and carbon dioxide in biogas to react, which saves the need for carbon dioxide removal. steps, and can simultaneously consume two greenhouse gases, methane and carbon dioxide, so biogas reforming technology is a more valuable biogas resource utilization technology.
  • the biogas reforming reaction requires the participation of a catalyst, but the application of the catalyst in the biogas reforming reaction is limited in the related art.
  • the biogas reforming reaction is a strong endothermic reaction, so to maintain a high conversion rate of methane and carbon dioxide in the biogas, a higher energy input is required, that is, a higher reaction temperature is required.
  • a higher reaction temperature will lead to sintering and carbon deposition of the active metal in the catalyst at high temperature, resulting in rapid deactivation of the catalyst.
  • the above-mentioned catalysts also have the problem of high cost, which limits their industrial application.
  • the embodiment of the present application provides a modified calcium silicate-based nickel-based catalyst and its preparation method and application, so as to solve the problems of high cost and easy deactivation of existing catalysts in biogas reforming reactions.
  • the embodiment of the present application provides a method for preparing a modified calcium silicate-based nickel-based catalyst, as shown in Figure 1, which is the process flow for the preparation method of the modified calcium-silicate-based nickel-based catalyst of the embodiment of the present application diagram, including the following steps:
  • Leaching leaching silicon-based solid waste with alkaline agent to obtain silicate leaching solution
  • Loading Disperse the modified calcium silicate carrier in an anhydrous alcohol solvent to obtain a mixed suspension, add the nickel salt alcohol solution to the mixed suspension for the second precipitation reaction, heat and stir until dry The alcohol in the alcohol solvent and the alcohol solution of the nickel salt is volatilized, dried and calcined to obtain a modified calcium silicate-based nickel catalyst.
  • the modified calcium-nickel silicate catalyst obtained by the preparation method in the embodiment of the present application has the advantages of low cost, high stability and high activity, and has an industrial application prospect.
  • the catalysts in the examples of this application do not use commonly used materials such as carbon-based, nano-silica, or nano-alumina as carriers, but use modified calcium silicate as a carrier, using the alkalinity and The nickel salt undergoes a precipitation reaction to load the active metal nickel. Without the need to add a precipitant such as ammonia water, the nickel element is uniformly precipitated on the surface of the calcium silicate carrier through the above precipitation reaction to achieve the active metal nickel on the calcium silicate carrier. The purpose of high dispersion degree and relatively strong force between metal and carrier.
  • Such a degree of dispersion of active metal nickel makes it possible to achieve a good catalytic effect when the loading of nickel in the catalyst is low, which not only satisfies the catalytic performance, but also saves the amount of nickel and reduces the production cost of the nickel-based catalyst.
  • calcium silicate is further modified, and lanthanide metal elements are incorporated into silicon in a more uniform and highly dispersed manner through co-precipitation reaction.
  • the sintering and carbon deposition under high temperature conditions can be effectively suppressed, and the catalytic performance of the modified calcium silicate-based nickel catalyst can be further improved. activity and stability.
  • modified calcium silicate-based nickel-based catalysts prepared in the examples of the present application have good industrial application prospects.
  • silicate leaching solution extracted from silicon-based solid waste as raw material not only has the advantages of wide source of raw materials and low cost, but also makes resource utilization of solid waste more friendly to the environment.
  • the commonly used supports for loading nickel in this field are usually carbon-based supports, silica and other supports, and the common means of using these supports to support nickel is generally the equal volume impregnation method.
  • the above-mentioned carrier is mostly a material with a larger pore size, and the nickel salt solution containing the metal active component can penetrate into the pores of the carrier through capillary pressure, so as to achieve the purpose of impregnating the nickel element on the carrier.
  • calcium silicate is not a commonly used carrier in this field. The use of calcium silicate as a carrier for loading nickel elements proposed by this application is one of the important invention points of this application.
  • the present application found that the calcium silicate carrier is dispersed in an anhydrous alcohol solvent, and the pH presents an alkalinity greater than or equal to 12.
  • nickel salt is added dropwise in the turbid liquid, a precipitation reaction will occur, that is, under the condition that no precipitant (such as ammonia water, etc.) is needed, nickel ions can be precipitated into nickel hydroxide, so that through this precipitation reaction, the nickel element Loaded on the surface of calcium silicate in a more uniform and highly dispersed manner.
  • the interaction between the two is closer, and the prepared nickel-based catalyst has higher stability;
  • the distribution on the calcium carrier is more uniform and dispersed, so the present application can obtain a good catalytic effect under the condition of using a smaller amount of nickel element.
  • the silicon-based solid waste includes at least one of rice husk ash, fly ash, metallurgical slag or blast furnace iron slag.
  • the above-mentioned silicon-based solid wastes come from a wide range of sources and are low in cost. Dissolving them with alkali and extracting the silicate leaching solution as a raw material for preparing calcium silicate carriers is not only low in cost, but also can realize the resource recovery of these silicon-based solid wastes. recycling.
  • the silicon-based solid waste in the embodiment of the present application is fly ash. It only needs to be leached by alkaline agent and then filtered to obtain the silicate leaching solution without high energy consumption such as high-temperature calcination of fly ash. Complicated operation steps.
  • the alkaline agent includes at least one of sodium hydroxide or potassium hydroxide.
  • an alkaline agent is used to leach silicon-based solid waste, specifically, a hydrothermal reaction occurs between the alkaline agent and the silicon-based solid waste to obtain a silicate leaching solution.
  • the alkali agent is an aqueous solution of sodium hydroxide
  • the fly ash is leached with an aqueous solution of sodium hydroxide. The two are mixed in a hydrothermal synthesis reaction kettle, heated at 110°C for 0.5h, and separated by filtration to obtain silicic acid Sodium Leachate.
  • the anhydrous alcohol solvent is absolute ethanol, anhydrous methanol or anhydrous propanol
  • the alcohol used for the nickel salt alcohol solution is the same as the anhydrous alcohol solvent.
  • the anhydrous alcohol solvent used to disperse the modified calcium silicate carrier is absolute ethanol
  • the alcohol selected for dissolving the nickel salt is ethanol.
  • the nitrate solution corresponding to the lanthanide metal includes at least one of cerium nitrate, lanthanum nitrate, samarium nitrate or praseodymium nitrate;
  • the molar ratio of calcium hydroxide in the turbid liquid is 0.9:1-1.1:1; the doping amount of lanthanide metal elements in the modified calcium silicate carrier is 1wt%-10wt%.
  • the molar ratio of the silicate ions in the silicate leaching solution to the calcium hydroxide in the calcium hydroxide suspension is 0.9:1 to 1.1:1 including any point value within the molar ratio range, for example, the silicate leaching solution
  • the molar ratio of the silicate ions in the suspension to the calcium hydroxide in the calcium hydroxide suspension is 0.9:1, 1:1 or 1.1:1.
  • the doping amount of the lanthanide metal element in the modified calcium silicate carrier is 1wt% to 10wt%, including any point value within the numerical range of the doping amount, for example, the modified calcium silicate carrier of the lanthanide metal element
  • the doping amount in the carrier is 1wt%, 2wt%, 5wt%, 8wt% or 10wt%.
  • the dropping rate of the silicate leaching solution is 20mL/h-30mL/h
  • the dropping rate of the nitrate solution corresponding to the lanthanide metal is 10mL/h-15mL/h
  • the first The secondary precipitation reaction is carried out at a temperature of 25° C. to 60° C. and a stirring rate of 450 rpm to 550 rpm for 2 hours to 8 hours.
  • the carrier When the carrier is prepared in the present application, it is prepared by the co-precipitation reaction of sodium silicate and calcium hydroxide, and lanthanide metals are added in the process so that the generated calcium silicate carrier is doped with lanthanide metal elements. Improve the anti-coking ability of the catalyst at high temperature.
  • the step of preparing the carrier when the dropping rate of the silicate leaching solution, the nitrate solution corresponding to the lanthanide metal, and the first precipitation reaction conditions are controlled within the above-mentioned condition range, the particles of calcium silicate that are conducive to generation The size is more appropriate and regular, making its porous structure more suitable as a catalyst carrier.
  • the dropping rate of the silicate leaching solution is 20mL/h ⁇ 30mL/h including any point value within this value range, for example, the dropping rate of the silicate leaching solution is 20mL/h, 22mL/h, 25mL/h, 28mL/h or 30mL/h.
  • the titration rate of the nitrate solution corresponding to the lanthanide metal is 10mL/h ⁇ 15mL/h including any point within this value range, for example, the titration rate of the nitrate solution corresponding to the lanthanide metal is 10mL/h, 12mL/h h, 13mL/h or 15mL/h.
  • the reaction temperature of the first precipitation reaction is 25°C to 60°C including any point within this temperature range, for example, the reaction temperature of the first precipitation reaction is 25°C, 35°C, 45°C or 60°C.
  • the stirring rate of the first precipitation reaction is 450rpm-550rpm including any value within the stirring rate range, for example, the stirring rate of the first precipitation reaction is 450rpm, 500rpm or 550rpm.
  • the reaction time of the first precipitation reaction is 2h to 8h including any value within the reaction time range, for example, the reaction time of the first precipitation reaction is 2h, 4h, 6h or 8h.
  • the precipitate formed by the reaction is washed at least once with water and at least once with an alcohol solvent in sequence after filtering and before drying, and the drying condition is to dry at 75°C to 85°C for 10h to 14h , the firing conditions are firing at 500°C to 800°C for 1.8h to 2.5h.
  • the drying temperature condition is 75°C to 85°C including any point within this temperature range, for example, the drying temperature condition is 75°C, 78°C, 80°C, 82°C or 85°C;
  • the drying time is 10h ⁇ 14h including any point value in this time range, for example, the drying time is 10h, 12h or 14h;
  • the temperature condition of calcination is 500 °C ⁇ 800 °C including any point value in this temperature range, such as calcination
  • the temperature conditions are 500°C, 600°C, 700°C or 800°C;
  • the roasting time is 1.8h to 2.5h including any point within this time range, for example, the roasting time is 1.8h, 2h, 2.2h or 2.5h .
  • the anhydrous alcohol solvent is absolute ethanol
  • the modified calcium silicate carrier is added to absolute ethanol for ultrasonic dispersion for 10-15 minutes to obtain a mixed suspension, wherein the modified silicon
  • the solid-to-liquid ratio of the calcium acid carrier and absolute ethanol is 0.8g:50mL-1.2g:50mL
  • the loading amount of the nickel element in the modified calcium silicate-based nickel catalyst is 0.5wt%-10wt%.
  • 10 min to 15 min of ultrasonic dispersion includes any value within the ultrasonic time range, for example, 10 min, 12 min or 15 min of ultrasonic dispersion.
  • the solid-to-liquid ratio of the modified calcium silicate carrier to absolute ethanol is 0.8g:50mL ⁇ 1.2g:50mL including any point within the range of the solid-to-liquid ratio, for example, the ratio of modified calcium silicate carrier to absolute ethanol
  • the solid-to-liquid ratio is 0.8g:50mL, 1g:50mL or 1.2g:50mL.
  • the loading of nickel element in the modified calcium silicate-based nickel-based catalyst is 0.5wt% to 10wt%, including any point value within the loading range, such as the loading of nickel element in the modified calcium silicate-based nickel-based catalyst
  • the amount is 0.5 wt%, 1 wt%, 2 wt%, 5 wt%, 8 wt% or 10 wt%.
  • the alcoholic solution of the nickel salt is the ethanol solution of the nickel salt
  • the rate of dropping the ethanol solution of the nickel salt is 50mL/h ⁇ 100mL/h
  • the second precipitation reaction is carried out at a temperature of 65° C. React under the conditions of 68° C. and a stirring rate of 450 rpm to 550 rpm until all the alcohol in the anhydrous alcohol solvent and the ethanol solution of the nickel salt is volatilized.
  • the titration rate of the ethanol solution of the nickel salt is 50mL/h ⁇ 100mL/h including any point value in this value range, for example, the titration rate of the ethanol solution of the nickel salt is 50mL/h, 60mL/h, 70mL/h h, 80mL/h, 90mL/h or 100mL/h.
  • the reaction temperature of the second precipitation reaction is 65°C-68°C including any point within this temperature range, for example, the reaction temperature of the second precipitation reaction is 65°C, 66°C, 67°C or 68°C.
  • the stirring rate of the second precipitation reaction is 450rpm-550rpm including any value within the stirring rate range, for example, the stirring rate of the second precipitation reaction is 450rpm, 500rpm or 550rpm.
  • this application loads nickel elements on the modified calcium silicate carrier, it is based on the fact that the modified calcium silicate carrier will exhibit alkaline properties when dispersed in anhydrous alcohol solvent, so that the nickel ions will pass through the second precipitation.
  • the reaction is loaded on the modified calcium silicate carrier, so the application is in the step of loading, when the drop rate of the alcoholic solution of nickel salt and the second precipitation reaction conditions are controlled in the above-mentioned condition range, it is beneficial to make The nickel element is more uniformly loaded on the surface of the modified calcium silicate carrier with a higher degree of dispersion.
  • the drying condition is 1.5h-3h at 75°C-85°C
  • the calcination condition is 4h-5h at 400°C-500°C.
  • the drying temperature condition is 75°C to 85°C including any point value in this temperature range, for example, the drying temperature condition is 75°C, 78°C, 80°C, 82°C or 85°C;
  • the time of drying is 1.5h ⁇ 3h including any point value in this time range, for example, the drying time is 1.5h, 2h or 3h;
  • the temperature condition of roasting is 400°C ⁇ 500°C including any point value in this temperature range, for example
  • the temperature condition for calcination is 400°C, 450°C or 500°C; the calcination time is 4h-5h including any value within this time range, for example, the calcination time is 4h, 4.5h or 5h.
  • the embodiment of the present application also provides a modified calcium silicate-based nickel-based catalyst, which is prepared by the preparation method as described in the first aspect.
  • the modified calcium silicate-based nickel-based catalyst prepared in the examples of the present application has the advantages of low cost but good catalytic activity and stability.
  • the examples of this application propose for the first time that calcium silicate is used as the carrier of nickel-based catalysts, and the alkaline nature of calcium silicate itself is used to make the nickel element more uniform and more dispersed in the form of precipitation without the need for additional precipitating agents.
  • the modified calcium silicate carrier is calcium silicate doped with lanthanide metal elements Support, so the calcium silicate support modified by lanthanide metal elements and the active metal nickel can be used together to further improve the anti-coking performance of nickel-based catalysts.
  • the embodiment of the present application provides an application of a modified calcium silicate-based nickel-based catalyst.
  • the modified calcium-silicate-based nickel-based catalyst is prepared by the preparation method as described in the first aspect.
  • the modified Calcium silicate-based nickel-based catalysts for biogas reforming reactions are prepared by the preparation method as described in the first aspect.
  • biogas reforming reaction includes the following steps:
  • the volume space velocity is 10000mL/g/h ⁇ 60000mL/g/h, and the reaction takes place at 650°C ⁇ 900°C; among them, the raw material gas It consists of 20vol%-40vol% CH 4 , 20vol%-40vol% CO 2 and 20vol%-60vol% inert gas, the inert gas being at least one of nitrogen, helium, neon or argon.
  • the reduction temperature used when reducing the modified calcium silicate-based nickel-based catalyst is 650°C to 900°C including any point in this temperature range, for example, the reduction temperature used is 650°C, 700°C, 750°C, 800°C °C, 850°C or 900°C.
  • the volume space velocity is 10000mL/g/h ⁇ 60000mL/g/h including any point value within this value range, for example, the volume space velocity
  • the speed is 10000mL/g/h, 20000mL/g/h, 30000mL/g/h, 40000mL/g/h, 50000mL/g/h or 60000mL/g/h
  • the reaction temperature is 650°C ⁇ 900°C including this temperature range Any point within the range, for example, the reaction temperature is 650°C, 700°C, 750°C, 800°C, 850°C or 900°C
  • the volume fraction of CH 4 in the feed gas is 20vol% to 40vol%, including any point within this value range ,
  • the volume fraction of CH4 is 20vol%, 25vol%, 30vol%, 35vol% or 40vol%
  • the volume fraction of CO2 in the feed gas is 20vol% to 40vol%, including any point in
  • the reaction temperature is greater than or equal to 750°C
  • the methane conversion rate is greater than or equal to 80%
  • the carbon dioxide conversion rate is greater than or equal to 87%
  • the H 2 /CO selectivity coefficient is greater than or equal to 0.8.
  • the biogas reforming reaction is biogas dry reforming reaction, biogas steam reforming reaction, methane partial oxidation reforming reaction or methane autothermal reforming reaction.
  • the catalyst used for biogas reforming reaction is usually composed of carbon-based materials (such as activated carbon or carbon nitride, etc.) loaded onto the carrier surface.
  • the catalytic activity of nickel is mainly used to promote the reaction of methane and carbon dioxide into synthesis gas.
  • the modified calcium silicate-based nickel-based catalysts in the examples of this application are different from conventional catalysts.
  • the modified calcium silicate carrier in the examples of this application not only plays the role of supporting active metal nickel, but also plays an auxiliary role in adsorption. The role of carbon dioxide.
  • the embodiment of the present application utilizes the basic nature of the modified calcium silicate carrier, which makes it easier to absorb acidic carbon dioxide during the biogas reforming reaction, making it easier for carbon dioxide to be firmly adsorbed on the modified calcium silicate
  • the nickel element evenly dispersed on the surface of the modified calcium silicate carrier can play a more effective catalytic effect on the reaction of carbon dioxide and methane, and improve the efficiency of the catalytic reaction.
  • This embodiment provides a modified calcium silicate-based nickel-based catalyst, and the preparation method of the modified calcium-silicate-based nickel-based catalyst includes the following steps:
  • Leaching fly ash with aqueous sodium hydroxide solution the two are mixed and heated at 110°C to undergo a hydrothermal reaction for 0.5h, filtered and separated to obtain a sodium silicate leaching solution; dilute the sodium silicate leaching solution to 0.3mol/L, and wait for use;
  • This embodiment provides a modified calcium silicate-based nickel-based catalyst, and the preparation method of the modified calcium-silicate-based nickel-based catalyst includes the following steps:
  • Leaching leaching rice husk ash with aqueous sodium hydroxide solution, the two are mixed and heated at 110°C for 0.5h to undergo a hydrothermal reaction, filtered and separated to obtain a sodium silicate leaching solution; dilute the sodium silicate leaching solution to 0.3mol/L, and wait for use;
  • This embodiment provides a modified calcium silicate-based nickel-based catalyst, and the preparation method of the modified calcium-silicate-based nickel-based catalyst includes the following steps:
  • Leaching leaching metallurgical slag with sodium hydroxide aqueous solution, the two are mixed and heated at 110°C for 0.5h to undergo hydrothermal reaction, filtered and separated to obtain sodium silicate leaching solution; dilute the sodium silicate leaching solution to 0.3mol/L, and set aside ;
  • This embodiment provides a modified calcium silicate-based nickel-based catalyst, and the preparation method of the modified calcium-silicate-based nickel-based catalyst includes the following steps:
  • Leaching fly ash with aqueous sodium hydroxide solution the two are mixed and heated at 110°C to undergo a hydrothermal reaction for 0.5h, filtered and separated to obtain a sodium silicate leaching solution; dilute the sodium silicate leaching solution to 0.3mol/L, and wait for use;
  • This embodiment provides a modified calcium silicate-based nickel-based catalyst, and the preparation method of the modified calcium-silicate-based nickel-based catalyst includes the following steps:
  • Leaching fly ash with aqueous sodium hydroxide solution the two are mixed and heated at 110°C to undergo a hydrothermal reaction for 0.5h, filtered and separated to obtain a sodium silicate leaching solution; dilute the sodium silicate leaching solution to 0.3mol/L, and wait for use;
  • This embodiment provides a modified calcium silicate-based nickel-based catalyst, and the preparation method of the modified calcium-silicate-based nickel-based catalyst includes the following steps:
  • Leaching fly ash with aqueous sodium hydroxide solution the two are mixed and heated at 110°C to undergo a hydrothermal reaction for 0.5h, filtered and separated to obtain a sodium silicate leaching solution; dilute the sodium silicate leaching solution to 0.3mol/L, and wait for use;
  • This application example provides an application of a modified calcium silicate-based nickel-based catalyst in a biogas reforming reaction.
  • the biogas reforming reaction includes the following steps:
  • Feed raw material gas into the reduced modified calcium silicate-based nickel-based catalyst the volume space velocity is 60000mL/g/h, and the reaction takes place at 650°C-900°C.
  • Reaction activity results comprising methane conversion rate, carbon dioxide conversion rate and H 2 /CO selectivity coefficient etc.
  • feed gas is by 20vol % CH 4 , 20 vol % CO 2 and 60 vol % nitrogen.
  • Catalytic conversion efficiency analysis In order to test the catalytic conversion efficiency of the modified calcium silicate-based nickel-based catalyst of the embodiment of the application in the biogas reforming reaction, the application uses gas chromatography to analyze the catalytic conversion efficiency of embodiment 1, embodiment 5 and embodiment 6
  • the modified calcium silicate-based nickel-based catalyst of the modified calcium silicate-based nickel catalyst has been tested for conversion under different reaction temperatures, and the results are shown in Figure 3, Figure 5 and Figure 6, and Figure 3 shows the modified calcium silicate-based nickel of Example 1
  • Figure 5 shows the catalytic conversion rate figure of embodiment 5 modified calcium silicate-based nickel-based catalyst at different temperatures
  • Figure 6 shows the catalytic conversion rate figure of embodiment 6 modified Catalytic conversion rate diagram of calcium silicate-based nickel-based catalyst at different temperatures.
  • Catalytic stability analysis In order to test the catalytic stability of the modified calcium silicate-based nickel-based catalyst of the embodiment of the application in the biogas reforming reaction, the application uses gas chromatography to test the modified silicon dioxide of the embodiment 1 and the embodiment 6. Calcium silicate-based nickel-based catalysts were tested for stability at 750°C, and the results are shown in Figure 4 and Figure 7.
  • Figure 4 shows the stability test results of the modified calcium-silicate-based nickel-based catalysts in Example 1
  • Figure 7 shows the stability test results of the modified calcium silicate-based nickel-based catalyst in Example 6.
  • the modified calcium silicate-based nickel-based catalyst of the embodiment of the present application uses the silicate leaching solution extracted from silicon-based solid waste as a raw material to prepare a modified calcium silicate carrier as a catalyst carrier. While effectively reducing production costs, it can still show excellent catalytic conversion efficiency and catalytic stability, which provides a new preparation idea for simultaneously realizing the resource utilization of silicon-based solid waste and the reuse of high-value resources of biogas And a modified calcium silicate-based nickel catalyst with excellent catalytic performance.
  • a modified calcium silicate-based nickel-based catalyst disclosed in the embodiments of the present application and its preparation method and application have been introduced in detail above.
  • specific examples have been used to illustrate the principles and implementation methods of the present application.
  • the above examples The description is only used to help understand the technical solution of the application and its core idea; at the same time, for those of ordinary skill in the art, according to the idea of the application, there will be changes in the specific implementation and application scope.
  • the contents of this specification should not be construed as limiting the application.

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Abstract

本发明涉及沼气、工业固废资源化利用及催化剂制备技术领域，尤其涉及改性硅酸钙基镍系催化剂及其制备方法、应用。制备方法包括：用碱剂浸出硅基固体废弃物，得到硅酸盐浸出液；将硅酸盐浸出液、镧系金属对应的硝酸盐溶液滴加至氢氧化钙悬浊液中进行第一次沉淀反应，反应生成的沉淀物经过滤、干燥、焙烧后得到改性的硅酸钙载体；将改性的硅酸钙载体分散于无水的醇溶剂中得到混合悬浊液，将镍盐的醇溶液滴加至混合悬浊液中进行第二次沉淀反应，加热搅拌至无水的醇溶剂和镍盐的醇溶液中的醇挥发，干燥、焙烧，得到改性硅酸钙基镍系催化剂。该制备方法所得到的改性硅酸钙镍系催化剂具有成本低、稳定性和活性较高的优点，具有工业化应用前景。

Description

改性硅酸钙基镍系催化剂及其制备方法、应用 技术领域
本发明涉及沼气、工业固废资源化利用及催化剂制备技术领域，尤其涉及一种改性硅酸钙基镍系催化剂及其制备方法、应用。
背景技术
沼气重整技术是一种前景广阔的沼气资源化利用技术。沼气重整反应可同时利用沼气中的甲烷和二氧化碳，将二者转化为具有更高应用价值的合成气。
催化剂在沼气重整反应中起到重要作用，但目前应用于沼气重整反应的催化剂存在成本高、易失活等问题，使得沼气重整反应的工业化应用受到限制。
发明内容
本申请提供一种改性硅酸钙基镍系催化剂及其制备方法、应用，以解决现有的应用于沼气重整反应的催化剂存在成本高、易失活等问题。
第一个方面，本申请提供一种改性硅酸钙基镍系催化剂的制备方法，所述制备方法包括以下步骤：
浸出：用碱剂浸出硅基固体废弃物，得到硅酸盐浸出液；
制备载体：将所述硅酸盐浸出液、镧系金属对应的硝酸盐溶液滴加至氢氧化钙悬浊液中进行第一次沉淀反应，反应生成的沉淀物经过滤、干燥、焙烧后得到改性的硅酸钙载体；
负载：将所述改性的硅酸钙载体分散于无水的醇溶剂中得到混合悬浊液，将镍盐的醇溶液滴加至所述混合悬浊液中进行第二次沉淀反应，加热搅拌至所述无水的醇溶剂和所述镍盐的醇溶液中的醇挥发，干燥、焙烧，得到所述改性硅酸钙基镍系催化剂。
进一步地，所述硅基固体废弃物包括稻壳灰、粉煤灰、冶金渣或高炉铁渣中的至少一种；所述碱剂包括氢氧化钠、氢氧化钾、碳酸钠或碳酸钾中的至少一种；
在所述负载的步骤中，所述无水的醇溶剂为无水乙醇、无水甲醇或无水丙醇，所述镍盐的醇溶液使用的醇与所述无水的醇溶剂相同。
进一步地，所述镧系金属对应的硝酸盐溶液包括硝酸铈、硝酸镧、硝酸钐或硝酸镨中的至少一种；
在所述制备载体的步骤中，所述硅酸盐浸出液中的硅酸根离子与所述氢氧化钙悬浊液中的氢氧化钙的摩尔比为0.9:1～1.1:1；镧系金属元素在所述改性后的 硅酸钙载体中的掺杂量为1wt％～10wt％。
进一步地，在所述制备载体的步骤中，所述硅酸盐浸出液的滴加速率为20mL/h～30mL/h，所述镧系金属对应的硝酸盐溶液的滴加速率为10mL/h～15mL/h，所述第一次沉淀反应在温度为25℃～60℃、搅拌速率为450rpm～550rpm的条件下反应2h～8h。
进一步地，在所述制备载体的步骤中，反应生成的沉淀物在过滤之后、干燥之前还依次用水洗涤至少一次、用醇溶剂洗涤至少一次，干燥的条件为在75℃～85℃下干燥10h～14h，焙烧的条件为在500℃～800℃下焙烧1.8h～2.5h。
进一步地，在所述负载的步骤中，将改性的硅酸钙载体加入到所述无水乙醇中超声分散10min～15min得到所述混合悬浊液，其中，所述改性的硅酸钙载体与所述无水乙醇的固液比为1g:30mL～1g:60mL，所述改性硅酸钙基镍系催化剂中的镍元素的负载量为0.5wt％～10wt％。
进一步地，在所述负载的步骤中，所述镍盐的醇溶液为镍盐的乙醇溶液，所述镍盐的乙醇溶液的滴加速率为50mL/h～100mL/h，所述第二次沉淀反应在温度为65℃～68℃、搅拌速率为450rpm～550rpm的条件下反应，直至所述无水的醇溶剂和所述镍盐的乙醇溶液中的醇全部挥发。
进一步地，在所述负载的步骤中，干燥的条件为在75℃～85℃下干燥1.5h～3h，焙烧的条件为在400℃～500℃下焙烧4h～5h。
第二个方面，本申请实施例提供一种改性硅酸钙基镍系催化剂，所述改性硅酸钙基镍系催化剂通过如第一个方面所述的制备方法制得。
第三个方面，本申请实施例提供一种改性硅酸钙基镍系催化剂的应用，所述改性硅酸钙基镍系催化剂通过如第一个方面所述的制备方法制得，所述改性硅酸钙基镍系催化剂用于沼气重整反应。
进一步地，所述沼气重整反应包括以下步骤：
向所述改性硅酸钙基镍系催化剂中通入还原气，在650℃～900℃条件下还原所述改性硅酸钙基镍系催化剂；其中，所述还原气中含有10vol％～20vol％的氢气；
向还原后的所述改性硅酸钙基镍系催化剂中通入原料气，体积空速为10000mL/g/h～60000mL/g/h，在650℃～900℃条件下发生反应；其中，所述原料气由20vol％～40vol％的CH 4、20vol％～40vol％的CO 2以及20vol％～60vol％的惰性气体组成，所述惰性气体为氮气、氦气、氖气或氩气中的至少一种。
进一步地，在所述沼气重整反应中，反应温度大于或者等于750℃时，甲烷转化率大于或者等于80％，二氧化碳转化率大于或者等于87％，H 2/CO选择性系数 大于或者等于0.8。
与现有技术相比，本申请具有如下有益效果：
本申请实施例制备方法所得到的改性硅酸钙镍系催化剂具有成本低、稳定性和活性较高的优点，具有工业化应用前景。
首先，本申请实施例的催化剂并未采用常用的碳基、纳米二氧化硅或纳米氧化铝等材料作为载体，而是以改性的硅酸钙作为载体，利用硅酸钙自身的碱性与镍盐发生沉淀反应来负载活性金属镍，在不需要添加氨水等沉淀剂的情况下，通过上述沉淀反应使镍元素均匀地沉淀至硅酸钙载体的表面，达到活性金属镍在硅酸钙载体上分散程度高，金属-载体之间作用力相对较强的目的。这样的活性金属镍分散程度，使得催化剂中镍的负载量较低时，即可达到很好的催化效果，既满足了催化性能，又节省了镍的用量、降低镍系催化剂的生产成本。
其次，本申请实施例在使用硅酸钙作为载体的基础上，还对硅酸钙做进一步改性，通过共沉淀反应将镧系金属元素以更均匀、更高分散程度的方式掺入到硅酸钙中，从而通过镧系金属改性过的硅酸钙载体与活性金属镍的相互作用，有效抑制高温条件下的烧结和积碳现象，进一步提高改性硅酸钙基镍系催化剂的催化活性和稳定性。
最后，本申请实施例制备的改性硅酸钙基镍系催化剂具有良好的工业化应用前景。以硅基固体废弃物中提取的硅酸盐浸出液为原料，不仅具有原料来源广泛、成本低的优势，而且将固体废弃物进行资源化利用、对环境更友好。
附图说明
为了更清楚地说明本申请实施例中的技术方案，下面将对实施例中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本申请的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其他的附图。
图1是本申请实施例改性硅酸钙基镍系催化剂的制备方法的流程图；
图2是实施例1改性硅酸钙基镍系催化剂的扫描电镜图；
图3是实施例1改性硅酸钙基镍系催化剂在不同温度下的催化转化率图；
图4是实施例1改性硅酸钙基镍系催化剂的稳定性测试结果图；
图5是实施例5改性硅酸钙基镍系催化剂在不同温度下的催化转化率图；
图6是实施例6改性硅酸钙基镍系催化剂在不同温度下的催化转化率图；
图7是实施例6改性硅酸钙基镍系催化剂的稳定性测试结果图。
具体实施方式
下面将结合本申请实施例中的附图，对本申请实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例仅是本申请一部分实施例，而不是全部的实施例。基于本申请中的实施例，本领域普通技术人员在没有做出创造性劳动前提下所获得的所有其他实施例，都属于本申请保护的范围。
在本申请中，术语“上”、“下”、“左”、“右”、“前”、“后”、“顶”、“底”、“内”、“外”、“中”、“竖直”、“水平”、“横向”、“纵向”等指示的方位或位置关系为基于附图所示的方位或位置关系。这些术语主要是为了更好地描述本申请及其实施例，并非用于限定所指示的装置、元件或组成部分必须具有特定方位，或以特定方位进行构造和操作。
并且，上述部分术语除了可以用于表示方位或位置关系以外，还可能用于表示其他含义，例如术语“上”在某些情况下也可能用于表示某种依附关系或连接关系。对于本领域普通技术人员而言，可以根据具体情况理解这些术语在本申请中的具体含义。
此外，术语“安装”、“设置”、“设有”、“连接”、“相连”应做广义理解。例如，可以是固定连接，可拆卸连接，或整体式构造；可以是机械连接，或电连接；可以是直接相连，或者是通过中间媒介间接相连，又或者是两个装置、元件或组成部分之间内部的连通。对于本领域普通技术人员而言，可以根据具体情况理解上述术语在本申请中的具体含义。
此外，术语“第一”、“第二”等主要是用于区分不同的装置、元件或组成部分(具体的种类和构造可能相同也可能不同)，并非用于表明或暗示所指示装置、元件或组成部分的相对重要性和数量。除非另有说明，“多个”的含义为两个或两个以上。
下面将结合具体实施例和附图对本申请的技术方案作进一步的说明。
沼气中90％以上的组分是甲烷和二氧化碳，由于这两种温室气体直接排放会加剧温室效应，且甲烷为易燃气体，直接排放存在安全隐患，加上甲烷热值很高，因此沼气的资源化利用具有重要意义。相关技术中，沼气资源化利用技术主要有两个方向，一是利用沼气中甲烷的热值进行发电、燃气华技术等，二是通过沼气重整技术将沼气作为化工原料生产具备更高价值的氢气或合成气。其中，利用沼气中甲烷的热值进行发电等技术，仍需面对沼气中二氧化碳的捕集问题，而沼气重整技术则能够同时利用沼气中的甲烷和二氧化碳进行反应，既省去了二氧化碳去除的步骤，又能同时消耗甲烷和二氧化碳两种温室气体，故沼气重整技术是更具高价值的沼气资源化利用技术。
沼气重整反应需要催化剂的参与，但相关技术中催化剂在沼气重整反应中的应用却受到一定限制。沼气重整反应为强吸热反应，故要维持沼气中甲烷和二氧化碳等的高转化率，就必须有较高的能量输入，也即需要较高的反应温度。但是较高的反应温度会导致催化剂中的活性金属在高温下烧结和积碳，从而导致催化剂快速失活。此外，上述催化剂还存在成本较高的问题，使其产业化应用受到限制。
基于上述分析，本申请实施例提供一种改性硅酸钙基镍系催化剂及其制备方法、应用，以解决现有催化剂应用在沼气重整反应中存在成本高、易失活等问题。
第一个方面，本申请实施例提供一种改性硅酸钙基镍系催化剂的制备方法，如图1所示，为本申请实施例改性硅酸钙基镍系催化剂的制备方法的流程图，包括以下步骤：
浸出：用碱剂浸出硅基固体废弃物，得到硅酸盐浸出液；
制备载体：将硅酸盐浸出液、镧系金属对应的硝酸盐溶液滴加至氢氧化钙悬浊液中进行第一次沉淀反应，反应生成的沉淀物经过滤、干燥、焙烧后得到改性的硅酸钙载体；
负载：将改性的硅酸钙载体分散于无水的醇溶剂中得到混合悬浊液，将镍盐的醇溶液滴加至混合悬浊液中进行第二次沉淀反应，加热搅拌至无水的醇溶剂和镍盐的醇溶液中的醇挥发，干燥、焙烧，得到改性硅酸钙基镍系催化剂。
本申请实施例制备方法所得到的改性硅酸钙镍系催化剂具有成本低、稳定性和活性较高的优点，具有工业化应用前景。
首先，本申请实施例的催化剂并未采用常用的碳基、纳米二氧化硅或纳米氧化铝等材料作为载体，而是以改性的硅酸钙作为载体，利用硅酸钙自身的碱性与镍盐发生沉淀反应来负载活性金属镍，在不需要添加氨水等沉淀剂的情况下，通过上述沉淀反应使镍元素均匀地沉淀至硅酸钙载体的表面，达到活性金属镍在硅酸钙载体上分散程度高，金属-载体之间作用力相对较强的目的。这样的活性金属镍分散程度，使得催化剂中镍的负载量较低时，即可达到很好的催化效果，既满足了催化性能，又节省了镍的用量、降低镍系催化剂的生产成本。
其次，本申请实施例在使用硅酸钙作为载体的基础上，还对硅酸钙做进一步改性，通过共沉淀反应将镧系金属元素以更均匀、更高分散程度的方式掺入到硅酸钙中，从而通过镧系金属改性过的硅酸钙载体与活性金属镍的相互作用，有效抑制高温条件下的烧结和积碳现象，进一步提高改性硅酸钙基镍系催化剂的催化活性和稳定性。
最后，本申请实施例制备的改性硅酸钙基镍系催化剂具有良好的工业化应用 前景。以硅基固体废弃物中提取的硅酸盐浸出液为原料，不仅具有原料来源广泛、成本低的优势，而且将固体废弃物进行资源化利用、对环境更友好。
需要说明的是，在本领域中用于负载镍的常用载体通常是碳基载体、二氧化硅等载体，使用这些载体负载镍的常用手段一般是等体积浸渍法。这主要是要利用上述载体多为孔径更大出的材料，可通过毛细管压力使含有金属活性组分的镍盐溶液渗透到载体的孔道内，从而达到镍元素浸渍到载体上的目的。但是硅酸钙并非本领域常用载体，本申请提出的使用硅酸钙作为负载镍元素的载体，是本申请重要发明点之一。本申请经过大量实验发现，硅酸钙载体分散于无水的醇溶剂中，pH呈现出大于或者等于12的碱性，这样的性质使得向硅酸钙载体与无水的醇溶剂形成的混合悬浊液中滴加镍盐时会发生沉淀反应，即在不需要使用沉淀剂(例如氨水等)的条件下，可使镍离子变成氢氧化镍沉淀，从而通过这种沉淀反应，使镍元素以更加均匀、分散度更高的方式负载在硅酸钙表面。进一步地，也正由于活性金属镍与硅酸钙载体的这种结合方式，使得二者之间的相互作用更紧密，所制得的镍系催化剂稳定性更高；同时由于镍元素在硅酸钙载体上的分布更加均匀且更加分散，故本申请可在使用更少量镍元素的条件下，即可得到良好的催化效果。
可选地，硅基固体废弃物包括稻壳灰、粉煤灰、冶金渣或高炉铁渣中的至少一种。上述这些硅基固体废弃物的来源广泛且成本低廉，用碱将其溶解后提取硅酸盐浸出液作为制备硅酸钙载体的原料，不仅成本低廉，而且可实现对这些硅基固体废弃物的资源化回收再利用。优选地，本申请实施例中的硅基固体废弃物为粉煤灰，只需要通过碱剂浸出后再过滤，即可得到硅酸盐浸出液，无需对粉煤灰进行高温煅烧等能耗高且复杂的操作步骤。
可选地，碱剂包括氢氧化钠或氢氧化钾中的至少一种。本申请实施例利用碱剂对硅基固体废弃物进行浸出，具体是使碱剂与硅基固体废弃物发生水热反应，得到硅酸盐浸出液。优选地，碱剂为氢氧化钠水溶液，用氢氧化钠水溶液浸出粉煤灰，二者在水热合成反应釜中经混合、加热在110℃发生水热反应0.5h，过滤分离，得到硅酸钠浸出液。
进一步地，在负载的步骤中，无水的醇溶剂为无水乙醇、无水甲醇或无水丙醇，镍盐的醇溶液使用的醇与无水的醇溶剂相同。优选地，用于分散改性的硅酸钙载体的无水的醇溶剂为无水乙醇，用于溶解镍盐的醇溶液所选用的醇为乙醇。这样，改性的硅酸钙载体与镍盐在同一种醇的体系中进行第二次沉淀反应，方便在相同的温度条件下使醇完全挥发，操作更便捷，也更利于镍元素在改性的硅酸钙载体上的均匀分散。
进一步地，镧系金属对应的硝酸盐溶液包括硝酸铈、硝酸镧、硝酸钐或硝酸镨中的至少一种；在制备载体的步骤中，硅酸盐浸出液中的硅酸根离子与氢氧化钙悬浊液中的氢氧化钙的摩尔比为0.9:1～1.1:1；镧系金属元素在改性后的硅酸钙载体中的掺杂量为1wt％～10wt％。通过第一次沉淀反应，将这些镧系金属离子掺杂到硅酸钙中以对硅酸钙进行改性，可起到更好的防积碳效果。
其中，硅酸盐浸出液中的硅酸根离子与氢氧化钙悬浊液中的氢氧化钙的摩尔比为0.9:1～1.1:1包括该摩尔比范围内的任一点值，例如硅酸盐浸出液中的硅酸根离子与氢氧化钙悬浊液中的氢氧化钙的摩尔比为0.9:1、1:1或1.1:1。镧系金属元素在改性后的硅酸钙载体中的掺杂量为1wt％～10wt％包括该掺杂量数值范围内的任一点值，例如镧系金属元素在改性后的硅酸钙载体中的掺杂量为1wt％、2wt％、5wt％、8wt％或10wt％。
进一步地，在制备载体的步骤中，硅酸盐浸出液的滴加速率为20mL/h～30mL/h，镧系金属对应的硝酸盐溶液的滴加速率为10mL/h～15mL/h，第一次沉淀反应在温度为25℃～60℃、搅拌速率为450rpm～550rpm的条件下反应2h～8h。
本申请制备载体时是通过硅酸钠与氢氧化钙的共沉淀反应来进行制备的，并在此过程中掺入镧系金属以使生成的硅酸钙载体中掺杂有镧系金属元素来提高催化剂在高温下的抗积碳能力。通过在制备载体的步骤中，将硅酸盐浸出液、镧系金属对应的硝酸盐溶液的滴加速率以及第一次沉淀反应条件控制在上述条件范围内时，有利于生成的硅酸钙的颗粒大小更合适且规则，使其多孔结构更适合于作为催化剂的载体。
其中，硅酸盐浸出液的滴加速率为20mL/h～30mL/h包括该数值范围内的任一点值，例如硅酸盐浸出液的滴加速率为20mL/h、22mL/h、25mL/h、28mL/h或30mL/h。镧系金属对应的硝酸盐溶液的滴加速率为10mL/h～15mL/h包括该数值范围内的任一点值，例如镧系金属对应的硝酸盐溶液的滴加速率为10mL/h、12mL/h、13mL/h或15mL/h。第一次沉淀反应的反应温度为25℃～60℃包括该温度范围内的任一点值，例如第一次沉淀反应的反应温度为25℃、35℃、45℃或60℃。第一次沉淀反应的搅拌速率为450rpm～550rpm包括该搅拌速率范围内的任一点值，例如第一次沉淀反应的搅拌速率为450rpm、500rpm或550rpm。第一次沉淀反应的反应时间为2h～8h包括该反应时间范围内的任一点值，例如第一次沉淀反应的反应时间为2h、4h、6h或8h。
进一步地，在制备载体的步骤中，反应生成的沉淀物在过滤之后、干燥之前还依次用水洗涤至少一次、用醇溶剂洗涤至少一次，干燥的条件为在75℃～85℃下干燥10h～14h，焙烧的条件为在500℃～800℃下焙烧1.8h～2.5h。
其中，在制备载体的步骤中，干燥的温度条件为75℃～85℃包括该温度范围内的任一点值，例如干燥的温度条件为75℃、78℃、80℃、82℃或85℃；干燥的时间为10h～14h包括该时间范围内的任一点值，例如干燥的时间为10h、12h或14h；焙烧的温度条件为500℃～800℃包括该温度范围内的任一点值，例如焙烧的温度条件为500℃、600℃、700℃或800℃；焙烧的时间为1.8h～2.5h包括该时间范围内的任一点值，例如焙烧的时间为1.8h、2h、2.2h或2.5h。
进一步地，在负载的步骤中，无水的醇溶剂为无水乙醇，将改性的硅酸钙载体加入到无水乙醇中超声分散10min～15min得到混合悬浊液，其中，改性的硅酸钙载体与无水乙醇的固液比为0.8g:50mL～1.2g:50mL，改性硅酸钙基镍系催化剂中的镍元素的负载量为0.5wt％～10wt％。
其中，超声分散10min～15min包括该超声时间范围内的任一点值，例如超声分散10min、12min或15min。改性的硅酸钙载体与无水乙醇的固液比为0.8g:50mL～1.2g:50mL包括该固液比范围内的任一点值，例如改性的硅酸钙载体与无水乙醇的固液比为0.8g:50mL、1g:50mL或1.2g:50mL。改性硅酸钙基镍系催化剂中的镍元素的负载量为0.5wt％～10wt％包括该负载量范围内的任一点值，例如改性硅酸钙基镍系催化剂中的镍元素的负载量为0.5wt％、1wt％、2wt％、5wt％、8wt％或10wt％。
进一步地，在负载的步骤中，镍盐的醇溶液为镍盐的乙醇溶液，镍盐的乙醇溶液的滴加速率为50mL/h～100mL/h，第二次沉淀反应在温度为65℃～68℃、搅拌速率为450rpm～550rpm的条件下反应，直至无水的醇溶剂和镍盐的乙醇溶液中的醇全部挥发。
其中，镍盐的乙醇溶液的滴加速率为50mL/h～100mL/h包括该数值范围内的任一点值，例如镍盐的乙醇溶液的滴加速率为50mL/h、60mL/h、70mL/h、80mL/h、90mL/h或100mL/h。第二次沉淀反应的反应温度为65℃～68℃包括该温度范围内的任一点值，例如第二次沉淀反应的反应温度为65℃、66℃、67℃或68℃。第二次沉淀反应的搅拌速率为450rpm～550rpm包括该搅拌速率范围内的任一点值，例如第二次沉淀反应的搅拌速率为450rpm、500rpm或550rpm。
本申请在改性的硅酸钙载体上负载镍元素时，是利用改性的硅酸钙载体分散于无水的醇溶剂中时会呈现出碱性的性质，使镍离子通过第二次沉淀反应负载到改性的硅酸钙载体上的，因此本申请在负载的步骤中，将镍盐的醇溶液的滴加速率以及第二次沉淀反应条件控制在上述条件范围内时，有利于使镍元素更加均匀、以更高分散程度负载于改性的硅酸钙载体表面。
进一步地，在负载的步骤中，干燥的条件为在75℃～85℃下干燥1.5h～3h， 焙烧的条件为在400℃～500℃下焙烧4h～5h。
其中，在负载的步骤中，干燥的温度条件为75℃～85℃包括该温度范围内的任一点值，例如干燥的温度条件为75℃、78℃、80℃、82℃或85℃；干燥的时间为1.5h～3h包括该时间范围内的任一点值，例如干燥的时间为1.5h、2h或3h；焙烧的温度条件为400℃～500℃包括该温度范围内的任一点值，例如焙烧的温度条件为400℃、450℃或500℃；焙烧的时间为4h～5h包括该时间范围内的任一点值，例如焙烧的时间为4h、4.5h或5h。
第二个方面，本申请实施例还提供一种改性硅酸钙基镍系催化剂，该改性硅酸钙基镍系催化剂通过如第一个方面所述的制备方法制得。
本申请实施例制备的改性硅酸钙基镍系催化剂，具有成本低但催化活性和稳定性较好的优点。本申请实施例首次提出以硅酸钙作为镍系催化剂的载体，利用硅酸钙自身的碱性性质，在无需额外添加沉淀剂的情况下，使镍元素以沉淀的方式更加均匀、更高分散性的负载在硅酸钙载体表面；与此同时，由于该硅酸钙载体还利用镧系金属进行了改性，即改性的硅酸钙载体是掺杂有镧系金属元素的硅酸钙载体，故可利用镧系金属元素改性的硅酸钙载体与活性金属镍的共同作用，来进一步提高镍系催化剂的抗积碳性能。
第三个方面，本申请实施例提供一种改性硅酸钙基镍系催化剂的应用，该改性硅酸钙基镍系催化剂通过如第一个方面所述的制备方法制得，该改性硅酸钙基镍系催化剂用于沼气重整反应。
进一步地，沼气重整反应包括以下步骤：
向改性硅酸钙基镍系催化剂中通入还原气，在650℃～900℃条件下还原改性硅酸钙基镍系催化剂；其中，还原气中含有10vol％～20vol％的氢气；
向还原后的改性硅酸钙基镍系催化剂中通入原料气，体积空速为10000mL/g/h～60000mL/g/h，在650℃～900℃条件下发生反应；其中，原料气由20vol％～40vol％的CH 4、20vol％～40vol％的CO 2以及20vol％～60vol％的惰性气体组成，惰性气体为氮气、氦气、氖气或氩气中的至少一种。
其中，对改性硅酸钙基镍系催化剂进行还原时采用的还原温度为650℃～900℃包括该温度范围内任一点值，例如采用的还原温度为650℃、700℃、750℃、800℃、850℃或900℃。向还原后的改性硅酸钙基镍系催化剂中通入原料气的步骤中，体积空速为10000mL/g/h～60000mL/g/h包括该数值范围内的任一点值，例如体积空速为10000mL/g/h、20000mL/g/h、30000mL/g/h、40000mL/g/h、50000mL/g/h或60000mL/g/h；反应温度为650℃～900℃包括该温度范围内任一点值，例如反应温度为650℃、700℃、750℃、800℃、850℃或900℃；原料气 中CH 4的体积分数为20vol％～40vol％包括该数值范围内的任一点值，例如CH 4的体积分数为20vol％、25vol％、30vol％、35vol％或40vol％；原料气中CO 2的体积分数为20vol％～40vol％包括该数值范围内的任一点值，例如CO 2的体积分数为20vol％、25vol％、30vol％、35vol％或40vol％；原料气中惰性气体的体积分数为20vol％～60vol％包括该数值范围内的任一点值，例如惰性气体的体积分数为20vol％、30vol％、40vol％、50vol％或60vol％。
在沼气重整反应中，反应温度大于或者等于750℃时，甲烷转化率大于或者等于80％，二氧化碳转化率大于或者等于87％，H 2/CO选择性系数大于或者等于0.8。
可选地，所述沼气重整反应为沼气干重整反应、沼气蒸汽重整反应、甲烷部分氧化重整反应或甲烷自热重重整反应。
在本领域中，用于沼气重整反应的催化剂，其组成通常是以孔径较大的碳基材料(如活性炭或氮化碳等)或二氧化硅等作为载体，将镍元素通过浸渍法等负载到载体表面。在沼气重整反应中，主要利用镍元素的催化活性促使甲烷和二氧化碳发生反应转化为合成气等。但本申请实施例的改性硅酸钙基镍系催化剂则不同于常规的催化剂，本申请实施例中改性的硅酸钙载体不仅起到负载活性金属镍的作用，而且还起到辅助吸附二氧化碳的作用。本申请实施例利用改性的硅酸钙载体具有碱性这一性质，使其在沼气重整反应过程中更容易吸收具有酸性的二氧化碳，使得二氧化碳更容易被牢固吸附到改性的硅酸钙载体上，进而使均匀分散在改性的硅酸钙载体表面的镍元素对二氧化碳和甲烷的反应起到更有效的催化作用，提高催化反应的效率。
下面结合更具体的实施例和实验测试结果来进一步解释说明本申请的技术方案。
实施例1
本实施例提供一种改性硅酸钙基镍系催化剂，该改性硅酸钙基镍系催化剂的制备方法包括以下步骤：
浸出：用氢氧化钠水溶液浸出粉煤灰，二者经混合、加热在110℃发生水热反应0.5h，过滤分离，得到硅酸钠浸出液；将硅酸钠浸出液稀释至0.3mol/L，待用；
制备载体：将65mL浓度为0.3mol/L的硅酸钠浸出液、硝酸铈溶液滴加至100mL浓度为0.2mol/L的氢氧化钙悬浊液中，在反应温度为25℃、搅拌速率为500rpm的条件下进行第一次沉淀反应2h，反应生成的沉淀物经过滤、用去离子水洗涤三次、乙醇洗涤三次后，在80℃下干燥12h，再在700℃下焙烧2h，得到由铈元素改性的硅酸钙载体；其中，铈元素在改性的硅酸钙载体中的掺杂量 为5wt％，硅酸钠浸出液的滴加速率为25mL/h，硝酸铈溶液的滴加速率为13mL/h；
负载：将1g改性的硅酸钙载体加入到50mL无水乙醇中超声分散10min得到混合悬浊液，将硝酸镍乙醇溶液以100mL/h的滴加速率逐滴滴加至混合悬浊液中进行第二次沉淀反应，在温度为65℃、搅拌速率为500rpm的条件下加热搅拌至乙醇完全挥发，所得产物在80℃下干燥2h，再在500℃下焙烧4h，得到改性硅酸钙基镍系催化剂，其中，镍元素在改性硅酸钙基镍系催化剂中的负载量为10wt％。
实施例2
本实施例提供一种改性硅酸钙基镍系催化剂，该改性硅酸钙基镍系催化剂的制备方法包括以下步骤：
浸出：用氢氧化钠水溶液浸出稻壳灰，二者经混合、加热在110℃发生水热反应0.5h，过滤分离，得到硅酸钠浸出液；将硅酸钠浸出液稀释至0.3mol/L，待用；
制备载体：将65mL浓度为0.3mol/L的硅酸钠浸出液、硝酸镧溶液滴加至100mL浓度为0.2mol/L的氢氧化钙悬浊液中，在反应温度为40℃、搅拌速率为500rpm的条件下进行第一次沉淀反应4h，反应生成的沉淀物经过滤、用去离子水洗涤三次、乙醇洗涤三次后，在80℃下干燥12h，再在500℃下焙烧2h，得到由镧元素改性的硅酸钙载体；其中，镧元素在改性的硅酸钙载体中的掺杂量为10wt％，硅酸钠浸出液的滴加速率为20mL/h，硝酸镧溶液的滴加速率为10mL/h；
负载：将1g改性的硅酸钙载体加入到50mL无水乙醇中超声分散10min得到混合悬浊液，将硝酸镍乙醇溶液以50mL/h的滴加速率逐滴滴加至混合悬浊液中进行第二次沉淀反应，在温度为65℃、搅拌速率为500rpm的条件下加热搅拌至乙醇完全挥发，所得产物在80℃下干燥2h，再在400℃下焙烧4h，得到改性硅酸钙基镍系催化剂，其中，镍元素在改性硅酸钙基镍系催化剂中的负载量为0.5wt％。
实施例3
本实施例提供一种改性硅酸钙基镍系催化剂，该改性硅酸钙基镍系催化剂的制备方法包括以下步骤：
浸出：用氢氧化钠水溶液浸出冶金渣，二者经混合、加热在110℃发生水热反应0.5h，过滤分离，得到硅酸钠浸出液；将硅酸钠浸出液稀释至0.3mol/L，待用；
制备载体：将65mL浓度为0.3mol/L的硅酸钠浸出液、硝酸钐溶液滴加至 100mL浓度为0.2mol/L的氢氧化钙悬浊液中，在反应温度为50℃、搅拌速率为500rpm的条件下进行第一次沉淀反应6h，反应生成的沉淀物经过滤、用去离子水洗涤三次、乙醇洗涤三次后，在80℃下干燥12h，再在600℃下焙烧2h，得到由钐元素改性的硅酸钙载体；其中，镧元素在改性的硅酸钙载体中的掺杂量为2wt％，硅酸钠浸出液的滴加速率为30mL/h，硝酸钐溶液的滴加速率为15mL/h；
负载：将1g改性的硅酸钙载体加入到50mL无水乙醇中超声分散10min得到混合悬浊液，将硝酸镍乙醇溶液以60mL/h的滴加速率逐滴滴加至混合悬浊液中进行第二次沉淀反应，在温度为65℃、搅拌速率为500rpm的条件下加热搅拌至乙醇完全挥发，所得产物在80℃下干燥2h，再在450℃下焙烧4h，得到改性硅酸钙基镍系催化剂，其中，镍元素在改性硅酸钙基镍系催化剂中的负载量为10wt％。
实施例4
本实施例提供一种改性硅酸钙基镍系催化剂，该改性硅酸钙基镍系催化剂的制备方法包括以下步骤：
浸出：用氢氧化钠水溶液浸出粉煤灰，二者经混合、加热在110℃发生水热反应0.5h，过滤分离，得到硅酸钠浸出液；将硅酸钠浸出液稀释至0.3mol/L，待用；
制备载体：将65mL浓度为0.3mol/L的硅酸钠浸出液、硝酸镨溶液滴加至100mL浓度为0.2mol/L的氢氧化钙悬浊液中，在反应温度为60℃、搅拌速率为500rpm的条件下进行第一次沉淀反应8h，反应生成的沉淀物经过滤、用去离子水洗涤三次、乙醇洗涤三次后，在80℃下干燥12h，再在800℃下焙烧2h，得到由镨元素改性的硅酸钙载体；其中，镨元素在改性的硅酸钙载体中的掺杂量为1wt％，硅酸钠浸出液的滴加速率为30mL/h，硝酸镨溶液的滴加速率为15mL/h；
负载：将1g改性的硅酸钙载体加入到50mL无水乙醇中超声分散10min得到混合悬浊液，将硝酸镍乙醇溶液以70mL/h的滴加速率逐滴滴加至混合悬浊液中进行第二次沉淀反应，在温度为65℃、搅拌速率为500rpm的条件下加热搅拌至乙醇完全挥发，所得产物在80℃下干燥2h，再在500℃下焙烧4h，得到改性硅酸钙基镍系催化剂，其中，镍元素在改性硅酸钙基镍系催化剂中的负载量为5wt％。
实施例5
本实施例提供一种改性硅酸钙基镍系催化剂，该改性硅酸钙基镍系催化剂的制备方法包括以下步骤：
浸出：用氢氧化钠水溶液浸出粉煤灰，二者经混合、加热在110℃发生水热 反应0.5h，过滤分离，得到硅酸钠浸出液；将硅酸钠浸出液稀释至0.3mol/L，待用；
制备载体：将65mL浓度为0.3mol/L的硅酸钠浸出液、硝酸铈溶液滴加至100mL浓度为0.2mol/L的氢氧化钙悬浊液中，在反应温度为60℃、搅拌速率为500rpm的条件下进行第一次沉淀反应8h，反应生成的沉淀物经过滤、用去离子水洗涤三次、乙醇洗涤三次后，在80℃下干燥12h，再在800℃下焙烧2h，得到由铈元素改性的硅酸钙载体；其中，铈元素在改性的硅酸钙载体中的掺杂量为2wt％，硅酸钠浸出液的滴加速率为30mL/h，硝酸铈溶液的滴加速率为15mL/h；
负载：将1g改性的硅酸钙载体加入到50mL无水乙醇中超声分散10min得到混合悬浊液，将硝酸镍乙醇溶液以90mL/h的滴加速率逐滴滴加至混合悬浊液中进行第二次沉淀反应，在温度为65℃、搅拌速率为500rpm的条件下加热搅拌至乙醇完全挥发，所得产物在80℃下干燥2h，再在500℃下焙烧4h，得到改性硅酸钙基镍系催化剂，其中，镍元素在改性硅酸钙基镍系催化剂中的负载量为2wt％。
实施例6
本实施例提供一种改性硅酸钙基镍系催化剂，该改性硅酸钙基镍系催化剂的制备方法包括以下步骤：
浸出：用氢氧化钠水溶液浸出粉煤灰，二者经混合、加热在110℃发生水热反应0.5h，过滤分离，得到硅酸钠浸出液；将硅酸钠浸出液稀释至0.3mol/L，待用；
制备载体：将65mL浓度为0.3mol/L的硅酸钠浸出液、硝酸镧溶液滴加至100mL浓度为0.2mol/L的氢氧化钙悬浊液中，在反应温度为60℃、搅拌速率为500rpm的条件下进行第一次沉淀反应8h，反应生成的沉淀物经过滤、用去离子水洗涤三次、乙醇洗涤三次后，在80℃下干燥12h，再在800℃下焙烧2h，得到由镧元素改性的硅酸钙载体；其中，镧元素在改性的硅酸钙载体中的掺杂量为5wt％，硅酸钠浸出液的滴加速率为25mL/h，硝酸镧溶液的滴加速率为13mL/h；
负载：将1g改性的硅酸钙载体加入到50mL无水乙醇中超声分散10min得到混合悬浊液，将硝酸镍乙醇溶液以80mL/h的滴加速率逐滴滴加至混合悬浊液中进行第二次沉淀反应，在温度为65℃、搅拌速率为500rpm的条件下加热搅拌至乙醇完全挥发，所得产物在80℃下干燥2h，再在500℃下焙烧4h，得到改性硅酸钙基镍系催化剂，其中，镍元素在改性硅酸钙基镍系催化剂中的负载量为5wt％。
应用例
本应用例提供一种改性硅酸钙基镍系催化剂在沼气重整反应中的应用，该沼气重整反应包括以下步骤：
向实施例1改性硅酸钙基镍系催化剂中通入还原气，在750℃条件下还原实施例1改性硅酸钙基镍系催化剂；其中，还原气中含有10vol％的氢气，剩余气体可以是氮气等惰性气体；
向还原后的改性硅酸钙基镍系催化剂中通入原料气，体积空速为60000mL/g/h，在650℃～900℃条件下发生反应，通过测试不同反应温度和反应时间后的反应活性结果(包括甲烷转化率、二氧化碳转化率和H 2/CO选择性系数等)，可以得知本申请实施例的改性硅酸钙基镍系催化剂的催化性能；其中，原料气由20vol％的CH 4、20vol％的CO 2以及60vol％的氮气组成。
性能测试
形貌分析：采用场发射扫描电镜对实施例1的改性硅酸钙基镍系催化剂的表面形貌进行表征，结果如图2所示，图2是实施例1改性硅酸钙基镍系催化剂的扫描电镜图。从图2可以看出，本申请实施例的改性硅酸钙基镍系催化剂的表面形成有大量褶皱，具有较大的比表面积。
催化转化效率分析：为测试本申请实施例的改性硅酸钙基镍系催化剂应用在沼气重整反应中的催化转化效率，本申请采用气相色谱对实施例1、实施例5、实施例6的改性硅酸钙基镍系催化剂进行了不同反应温度下的转化率测试，结果如图3、图5和图6所示，图3示出的是实施例1改性硅酸钙基镍系催化剂在不同温度下的催化转化率图，图5示出的是实施例5改性硅酸钙基镍系催化剂在不同温度下的催化转化率图，图6示出的是实施例6改性硅酸钙基镍系催化剂在不同温度下的催化转化率图。从图3可知，使用实施例1改性硅酸钙基镍系催化剂进行沼气重整反应时，在750℃时，二氧化碳转化率已达到87％，甲烷转化率已达到80％，H 2/CO选择性系数达到0.8，随着反应温度的升高二氧化碳转化率、甲烷转化率、H 2/CO选择性系数等指标也越来越高。从图5可知，使用实施例5改性硅酸钙基镍系催化剂进行沼气重整反应时，在750℃时，二氧化碳转化率已达到88％，甲烷转化率已达到80％，H 2/CO选择性系数达到0.86，随着反应温度的升高二氧化碳转化率、甲烷转化率、H 2/CO选择性系数等指标也越来越高。从图6可知，使用实施例6改性硅酸钙基镍系催化剂进行沼气重整反应时，在750℃时，二氧化碳转化率已达到91％，甲烷转化率已达到86％，H 2/CO选择性系数达到0.97，随着反应温度的升高二氧化碳转化率、甲烷转化率、H 2/CO选择性系数等指标也越来越高。上述实验结果表明，本申请实施的改性硅酸钙基镍系催化剂在较低的制备成本下，即具有较高的催化转化效率，适用于沼气重整反应，具有工业化应 用前景。
催化稳定性分析：为测试本申请实施例的改性硅酸钙基镍系催化剂应用在沼气重整反应中的催化稳定性，本申请采用气相色谱对实施例1、实施例6的改性硅酸钙基镍系催化剂在750℃条件下进行了稳定性测试，结果如图4和图7所示，图4示出的是实施例1改性硅酸钙基镍系催化剂的稳定性测试结果图，图7示出的是实施例6改性硅酸钙基镍系催化剂的稳定性测试结果图。从图4可知，当反应至200h时，实施例1的改性硅酸钙基镍系催化剂的转化率、H 2/CO选择性系数等指标并未发生明显衰减，与初始指标的数值大致持平。类似地，从图7可知，当反应至200h时，实施例6的改性硅酸钙基镍系催化剂的转化率、H 2/CO选择性系数等指标也未发生明显衰减，与初始指标的数值大致持平，维持在二氧化碳转化率89％～91％、甲烷转化率84％～86％、H 2/CO选择性系数0.96～0.98的水平。由此可见本申请实施例的改性硅酸钙基镍系催化剂在高温条件下具有较高的催化稳定性。
通过上述测试结果可知，本申请实施例的改性硅酸钙基镍系催化剂，以硅基固体废弃物中提取的硅酸盐浸出液为原料，制备出改性的硅酸钙载体作为催化剂载体，其在有效降低生产成本的同时，仍能体现出优异的催化转化效率和催化稳定性，为同时实现硅基固体废弃物的资源化利用、沼气的高价值资源再利用，提供了新的制备思路和催化性能优异的改性硅酸钙基镍系催化剂。
以上对本申请实施例公开的一种改性硅酸钙基镍系催化剂及其制备方法、应用进行了详细介绍，本文中应用了具体个例对本申请的原理及实施方式进行了阐述，以上实施例的说明只是用于帮助理解本申请的技术方案及其核心思想；同时，对于本领域的一般技术人员，依据本申请的思想，在具体实施方式及应用范围上均会有改变之处，综上，本说明书内容不应理解为对本申请的限制。

Claims (13)

  1. 一种改性硅酸钙基镍系催化剂的制备方法，其特征在于，所述制备方法包括以下步骤：
    浸出：用碱剂浸出硅基固体废弃物，得到硅酸盐浸出液；
    制备载体：将所述硅酸盐浸出液、镧系金属对应的硝酸盐溶液滴加至氢氧化钙悬浊液中进行第一次沉淀反应，反应生成的沉淀物经过滤、干燥、焙烧后得到改性的硅酸钙载体；
    负载：将所述改性的硅酸钙载体分散于无水的醇溶剂中得到混合悬浊液，将镍盐的醇溶液滴加至所述混合悬浊液中进行第二次沉淀反应，加热搅拌至所述无水的醇溶剂和所述镍盐的醇溶液中的醇挥发，干燥、焙烧，得到所述改性硅酸钙基镍系催化剂。
  2. 根据权利要求1所述的制备方法，其特征在于，所述硅基固体废弃物包括稻壳灰、粉煤灰、冶金渣或高炉铁渣中的至少一种；所述碱剂包括氢氧化钠、氢氧化钾、碳酸钠或碳酸钾中的至少一种；
    在所述负载的步骤中，所述无水的醇溶剂为无水乙醇、无水甲醇或无水丙醇，所述镍盐的醇溶液使用的醇与所述无水的醇溶剂相同。
  3. 根据权利要求1所述的制备方法，其特征在于，所述镧系金属对应的硝酸盐溶液包括硝酸铈、硝酸镧、硝酸钐或硝酸镨中的至少一种；
    在所述制备载体的步骤中，所述硅酸盐浸出液中的硅酸根离子与所述氢氧化钙悬浊液中的钙离子的摩尔比为0.9:1～1.1:1；镧系金属元素在所述改性后的硅酸钙载体中的掺杂量为1wt％～10wt％。
  4. 根据权利要求1所述的制备方法，其特征在于，所述镧系金属对应的硝酸盐溶液包括硝酸铈、硝酸镧、硝酸钐或硝酸镨中的至少一种；
    在所述制备载体的步骤中，所述硅酸盐浸出液中的硅酸根离子与所述氢氧化钙悬浊液中的氢氧化钙的摩尔比为0.9:1～1.1:1；镧系金属元素在所述改性后的硅酸钙载体中的掺杂量为1wt％～10wt％。
  5. 根据权利要求1所述的制备方法，其特征在于，在所述制备载体的步骤中，所述硅酸盐浸出液的滴加速率为20mL/h～30mL/h，所述镧系金属对应的硝酸盐溶液的滴加速率为10mL/h～15mL/h，所述第一次沉淀反应在温度为25℃～60℃、搅拌速率为450rpm～550rpm的条件下反应2h～8h。
  6. 根据权利要求1所述的制备方法，其特征在于，在所述制备载体的步骤中，反应生成的所述沉淀物在过滤之后、干燥之前还依次用水洗涤至少一次、用醇溶剂洗涤至少一次，干燥的条件为在75℃～85℃下干燥10h～14h，焙烧的条件为在500℃～800℃下焙烧1.8h～2.5h。
  7. 根据权利要求1至6任一项所述的制备方法，其特征在于，在所述负载的步骤中，将所述改性的硅酸钙载体加入到所述无水乙醇中超声分散10min～15min得到所述混合悬浊液，其中，所述改性的硅酸钙载体与所述无水乙醇的固液比为1g:30mL～1g:60mL，所述改性硅酸钙基镍系催化剂中的镍元素的负载量为0.5wt％～10wt％。
  8. 根据权利要求1至6任一项所述的制备方法，其特征在于，在所述负载的步骤中，所述镍盐的醇溶液为镍盐的乙醇溶液，所述镍盐的乙醇溶液的滴加速率为50mL/h～100mL/h，所述第二次沉淀反应在温度为65℃～68℃、搅拌速率为450rpm～550rpm的条件下反应，直至所述无水的醇溶剂和所述镍盐的乙醇溶液中的醇全部挥发。
  9. 根据权利要求1至6任一项所述的制备方法，其特征在于，在所述负载的步骤中，干燥的条件为在75℃～85℃下干燥1.5h～3h，焙烧的条件为在400℃～500℃下焙烧4h～5h。
  10. 一种改性硅酸钙基镍系催化剂，其特征在于，所述改性硅酸钙基镍系催化剂通过如权利要求1至9任一项所述的制备方法制得。
  11. 一种改性硅酸钙基镍系催化剂的应用，其特征在于，所述改性硅酸钙基镍系催化剂通过如权利要求1至9任一项所述的制备方法制得，所述改性硅酸钙基镍系催化剂用于沼气重整反应。
  12. 根据权利要求11所述的应用，其特征在于，所述沼气重整反应包括以下步骤：
    向所述改性硅酸钙基镍系催化剂中通入还原气，在650℃～900℃条件下还原所述改性硅酸钙基镍系催化剂；其中，所述还原气中含有10vol％～20vol％的氢气；
    向还原后的所述改性硅酸钙基镍系催化剂中通入原料气，体积空速为10000mL/g/h～60000mL/g/h，在650℃～900℃条件下发生反应；其中，所述原料气由20vol％～40vol％的CH 4、20vol％～40vol％的CO 2以及20vol％～60vol％的惰性气 体组成，所述惰性气体为氮气、氦气、氖气或氩气中的至少一种。
  13. 根据权利要求11所述的应用，其特征在于，在所述沼气重整反应中，反应温度大于或者等于750℃时，甲烷转化率大于或者等于80％，二氧化碳转化率大于或者等于87％，H 2/CO选择性系数大于或者等于0.8。
PCT/CN2022/081740 2022-02-25 2022-03-18 改性硅酸钙基镍系催化剂及其制备方法、应用 WO2023159703A1 (zh)

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