CN111437862A - Catalyst for preparing methanol by carbon dioxide hydrogenation and preparation method thereof - Google Patents

Catalyst for preparing methanol by carbon dioxide hydrogenation and preparation method thereof Download PDF

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CN111437862A
CN111437862A CN202010258502.XA CN202010258502A CN111437862A CN 111437862 A CN111437862 A CN 111437862A CN 202010258502 A CN202010258502 A CN 202010258502A CN 111437862 A CN111437862 A CN 111437862A
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catalyst
graphite
carbon nitride
phase carbon
roasting
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马清祥
张一凡
赵天生
张建利
高新华
李鹏
范辉
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Ningxia University
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Ningxia University
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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
    • B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
    • B01J27/24—Nitrogen compounds
    • B01J35/61—
    • 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
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • B01J37/03—Precipitation; Co-precipitation
    • B01J37/031—Precipitation
    • 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
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/08—Heat treatment
    • 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
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/08—Heat treatment
    • B01J37/082—Decomposition and pyrolysis
    • B01J37/088—Decomposition of a metal salt
    • 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
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/16—Reducing
    • B01J37/18—Reducing with gases containing free hydrogen
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
    • C07C29/15—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively
    • C07C29/151—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively with hydrogen or hydrogen-containing gases
    • C07C29/153—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively with hydrogen or hydrogen-containing gases characterised by the catalyst used
    • C07C29/154—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively with hydrogen or hydrogen-containing gases characterised by the catalyst used containing copper, silver, gold, or compounds thereof
    • 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

Abstract

The invention relates to the technical field of catalysts, in particular to a catalyst for preparing methanol by carbon dioxide hydrogenation and a preparation method thereof. The catalyst provided by the invention comprises graphite-phase carbon nitride and Cu, ZnO and Al which are dispersed in a lamellar structure of the graphite-phase carbon nitride2O3(ii) a The Cu, ZnO and Al2O3The ratio of the total mass of the graphite phase to the mass of the graphite phase carbon nitride is (80-100): (0-20); and the amount of the graphite phase carbon nitride is not 0. The catalyst provided by the invention utilizes the special structure of graphite-phase carbon nitride (a two-dimensional material which is formed by mutually and alternately forming six-membered rings by carbon and nitrogen atoms and mutually connecting the six-membered rings through carbon-carbon bonds and is a graphite-like layered structure) and excellent adsorption performance, increases the specific surface area of the catalyst, enhances the adsorption capacity of the catalyst on raw material gas, and improves the conversion rate of carbon dioxide and the selectivity of methanol.

Description

Catalyst for preparing methanol by carbon dioxide hydrogenation and preparation method thereof
Technical Field
The invention relates to the technical field of catalysts, in particular to a catalyst for preparing methanol by carbon dioxide hydrogenation and a preparation method thereof.
Background
Combustion of fossil fuels and emission of industrial exhaust gases results in atmospheric CO2The concentration of (a) is increasing, which in turn leads to global warming, water resource acidification and frequent occurrence of disastrous climates. Thus, CO2Emission reduction becomes a common responsibility worldwide. The methanol has wide application prospect as basic organic chemical raw materials and power fuel, and CO2The hydrogenation for synthesizing the methanol is to reasonably utilize CO2One of the ways of (1).
At present, for CO2The copper-based catalyst for synthesizing methanol by hydrogenation is mostly obtained by improvement on the basis of a catalyst for preparing methanol by hydrogenation of synthesis gas. The improvement method generally comprises the steps of adding an auxiliary agent, selecting different carriers, different preparation methods, optimizing reaction conditions and the like. Due to CO2The conversion rate and the methanol selectivity are low, and the like, and the dispersion degree of the active components of the catalyst can be effectively improved by adding a proper auxiliary agent in the catalyst preparation process, so that the specific surface area of the catalyst is improved.
Chinese patent with publication number CN103272607A discloses a method for CO2A copper-based catalyst for synthesizing methanol by hydrogenation uses high-molecular polymer as stabilizer and adopts a parallel-flow coprecipitation method to prepare Cu/ZheZn/Al/Zr based catalyst, at 250 deg.C, 5.0MPa, H2/CO2＝3/1、GHSV＝4000h-1Under the reaction conditions of (3), the catalyst stability is good, but CO2The conversion and methanol selectivity are low.
Chinese patent with publication number CN107008332A discloses a method for CO2The copper-based catalyst for synthesizing methanol by hydrogenation adopts a method of fractional precipitation or a method of firstly precipitating an accelerant and then precipitating and pulping with an active component, can effectively improve the conversion rate of carbon dioxide, but has low selectivity of methanol.
Thus, it is currently used for CO2The catalyst for synthesizing methanol by hydrogenation cannot simultaneously have good stability, higher carbon dioxide conversion rate and higher methanol selectivity.
Disclosure of Invention
The invention aims to provide a catalyst for preparing methanol by carbon dioxide hydrogenation and a preparation method thereof, wherein the catalyst has high stability and CO2High conversion rate and good methanol selectivity.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a catalyst for preparing methanol by carbon dioxide hydrogenation, which comprises graphite-phase carbon nitride and Cu, ZnO and Al dispersed in a lamellar structure of the graphite-phase carbon nitride2O3；
The Cu, ZnO and Al2O3The ratio of the total mass of the graphite phase to the mass of the graphite phase carbon nitride is (80-100): (0-20);
and the amount of the graphite phase carbon nitride is not 0.
Preferably, the Cu, ZnO and Al2O3The mass ratio of (4-6): (2.5-3.5): (2.5-3.5).
The invention also provides a preparation method of the catalyst in the technical scheme, which comprises the following steps:
mixing soluble copper salt, soluble zinc salt, soluble aluminum salt and water to obtain a mixed solution;
mixing the mixed solution, a sodium carbonate solution and water, and carrying out coprecipitation reaction to obtain a precipitate;
carrying out first roasting on the precipitate to obtain an intermediate product;
mixing the intermediate product with graphite-phase carbon nitride, and performing second roasting to obtain a catalyst precursor;
with H2And N2The mixed gas is used as a reducing gas to reduce the catalyst precursor to obtain the catalyst.
Preferably, the temperature of the coprecipitation reaction is 60 to 80 ℃, and the pH of a reaction solution in which the coprecipitation reaction occurs is 6 to 8.
Preferably, the coprecipitation reaction is carried out under stirring conditions;
the stirring speed is 650-900 r/min, and the stirring time is 1-5 h.
Preferably, the first roasting temperature is 200-400 ℃, and the first roasting time is 2-6 h.
Preferably, the second firing is performed in a nitrogen atmosphere;
the temperature of the second roasting is 400-700 ℃, and the time of the second roasting is 2-5 h.
Preferably, said H2And N2In a volume ratio of 5: 95;
said H2And N2The flow velocity of the mixed gas is 45-55 m L/min;
the reduction temperature is 250-350 ℃.
Preferably, after the coprecipitation reaction is finished, aging, solid-liquid separation and drying are sequentially carried out on a generated liquid obtained after the coprecipitation reaction;
the aging temperature is 20-50 ℃, and the aging time is 10-15 h;
the drying temperature is 60-100 ℃, and the drying time is 5-15 h.
Preferably, the graphite phase carbon nitride is prepared by thermal polymerization of cyanamide, dicyandiamide, melamine or urea;
the temperature of the thermal polymerization is 400-700 ℃.
The invention provides a catalyst for preparing methanol by carbon dioxide hydrogenation, which comprises graphite-phase carbon nitride and Cu, ZnO and Al dispersed in a lamellar structure of the graphite-phase carbon nitride2O3(ii) a The Cu, ZnO and Al2O3The ratio of the total mass of the graphite phase to the mass of the graphite phase carbon nitride is (80-100): (0-20); and the amount of the graphite phase carbon nitride is not 0. The catalyst of the invention utilizes the special structure of graphite phase carbon nitride (a two-dimensional material which is formed by mutually and alternately forming six-membered rings by carbon and nitrogen atoms and mutually connecting the six-membered rings through carbon-carbon bonds and is a graphite-like layered structure), increases the specific surface area of the catalyst and also enhances the CO-carbon ratio2And H2Adsorption capacity of (C) to make the reaction gas (CO)2And H2) The catalyst is easier to adhere to the surface of the catalyst, so that methanol is easier to synthesize under the action of the catalyst, carbon monoxide is not generated through side reaction, and the carbon dioxide and conversion rate and the selectivity of methanol are improved.
The invention also provides a preparation method of the catalyst, which comprises the following steps: mixing soluble copper salt, soluble zinc salt, soluble aluminum salt and water to obtain a mixed solution; mixing the mixed solution with a sodium carbonate solution, and carrying out coprecipitation reaction to obtain a precipitate; carrying out first roasting on the precipitate to obtain an intermediate product; mixing the intermediate product with graphite-phase carbon nitride, and performing second roasting to obtain a catalyst precursor; with H2And N2The mixed gas is used as a reducing gas to reduce the catalyst precursor to obtain the catalyst. The preparation method provided by the invention is simple, short in period, free of toxic and harmful substances in the preparation process and safe; in addition, the method can prepare the catalyst with uniform particle size distribution.
Drawings
Fig. 1 is a graph showing the change of the conversion rate of carbon dioxide and the selectivity of methanol with time in the process of preparing methanol by hydrogenating carbon dioxide using the catalyst prepared in example 3.
Detailed Description
The invention provides a catalyst for preparing methanol by carbon dioxide hydrogenation, which comprises graphite-phase carbon nitride and Cu, ZnO and Al dispersed in a lamellar structure of the graphite-phase carbon nitride2O3；
The Cu, ZnO and Al2O3The ratio of the total mass of the graphite phase to the mass of the graphite phase carbon nitride is (80-100): (0-20);
and the amount of the graphite phase carbon nitride is not 0.
In the present invention, the Cu, ZnO and Al2O3The ratio of the total mass of the graphite phase to the mass of the graphite phase carbon nitride is (80-100): (0-20), preferably (85-95): (5-15), more preferably (88-92): (8-12).
In the present invention, the Cu, ZnO and Al2O3The mass ratio of (1) to (6): (2.5-3.5): (2.5-3.5), and more preferably 4:3: 3.
In the invention, the particle size of the catalyst is preferably 20-40 meshes.
In the present invention, the Cu, ZnO and Al are2O3Preferably uniformly dispersed in the graphite phase carbon nitride in a physically mixed manner.
The invention also provides a preparation method of the catalyst in the technical scheme, which comprises the following steps:
mixing soluble copper salt, soluble zinc salt, soluble aluminum salt and water to obtain a mixed solution;
mixing the mixed solution with a sodium carbonate solution, and carrying out coprecipitation reaction to obtain a precipitate;
carrying out first roasting on the precipitate to obtain an intermediate product;
mixing the intermediate product with graphite-phase carbon nitride, and performing second roasting to obtain a catalyst precursor;
with H2And N2The mixed gas is used as a reducing gas to reduce the catalyst precursor to obtain the catalyst.
In the present invention, all the raw material components are commercially available products well known to those skilled in the art unless otherwise specified.
According to the invention, soluble copper salt, soluble zinc salt, soluble aluminum salt and water are mixed to obtain a mixed solution. In the invention, the soluble copper salt is preferably copper nitrate or copper acetate, and the copper nitrate is preferably copper nitrate trihydrate; the soluble zinc salt is preferably zinc nitrate or zinc acetate, and the zinc nitrate is preferably zinc nitrate hexahydrate; the soluble aluminium salt is preferably aluminium nitrate or aluminium acetate, and the aluminium nitrate is preferably aluminium nitrate nonahydrate. In the present invention, the soluble copper salt, soluble zinc salt and soluble aluminum salt are preferably used in amounts of Cu, ZnO and Al2O3The mass ratio of (4-6): (2.5-3.5): (2.5-3.5) mixing. The present invention does not limit the mixing in any particular way, and the mixing may be carried out by a process known to those skilled in the art.
In the invention, the total concentration of the solute in the mixed solution is preferably (0.5-2) mol/L, and more preferably (0.8-1.2) mol/L.
After a mixed solution is obtained, the mixed solution, a sodium carbonate solution and water are mixed to perform a coprecipitation reaction to obtain a precipitate, wherein the sodium carbonate solution is preferably a sodium carbonate aqueous solution, the concentration of the sodium carbonate solution is preferably 1 mol/L, and the water is preferably deionized water.
In the present invention, the ratio of the mass of sodium carbonate in the sodium carbonate solution to the total mass of the soluble copper salt, the soluble zinc salt, and the soluble aluminum salt is preferably (0.3 to 1.2): 1, more preferably (0.5 to 0.6): 1.
in the present invention, the mixing process is preferably: the mixed solution and the sodium carbonate solution were co-flowed in water with stirring. In the invention, the volume ratio of the water to the sodium carbonate solution is preferably (1-3): 1, more preferably (1.5 to 2.5): 1. in the invention, the stirring speed is preferably 650-900 r/min, more preferably 700-850 r/min, and most preferably 750-800 r/min; the stirring time is preferably 1-5 h, and more preferably 2-4 h.
In the invention, the temperature of the coprecipitation reaction is preferably 60-80 ℃, more preferably 65-75 ℃, and most preferably 70 ℃; the pH of the reaction solution in which the coprecipitation reaction occurs is preferably 6 to 8, and more preferably 7.
After the coprecipitation reaction is finished, the invention also preferably comprises the steps of sequentially aging, solid-liquid separation and drying the generated liquid obtained after the coprecipitation reaction is finished. In the invention, the aging temperature is preferably 20-50 ℃, more preferably 25-45 ℃, and most preferably 30-40 ℃; the aging time is preferably 2-5 h, and more preferably 3-4 h. In the present invention, the solid-liquid separation is preferably filtration. The filtration is not particularly limited in the present invention and may be carried out by a process known to those skilled in the art. After the filtration is finished, the solid obtained by the filtration is preferably washed and dried; the washing is not particularly limited in the present invention, and may be carried out by a procedure well known to those skilled in the art. In the invention, the drying temperature is preferably 60-100 ℃, more preferably 70-90 ℃, and most preferably 75-85 ℃; the drying time is preferably 5-15 hours, and more preferably 8-12 hours.
After the precipitate is obtained, the invention carries out first roasting on the precipitate to obtain an intermediate product. In the invention, the temperature of the first roasting is preferably 200-400 ℃, more preferably 250-350 ℃, and most preferably 280-320 ℃; the first roasting time is preferably 2-6 hours, and more preferably 3-5 hours.
In the present invention, the metal carbonate prepared by the coprecipitation reaction is thermally decomposed at the first firing to prepare the metal oxide.
After the intermediate product is obtained, the intermediate product and the graphite-phase carbon nitride are mixed and then subjected to second roasting to obtain the catalyst precursor. In the present invention, the graphite-phase carbon nitride is preferably prepared from cyanamide, dicyandiamide, melamine or urea by thermal polymerization; the preparation process preferably comprises the following steps: and grinding cyanamide, dicyandiamide, melamine or urea, and roasting to obtain the graphite-phase carbon nitride. The grinding is not particularly limited in the present invention, and may be carried out by a process known to those skilled in the art. In the present invention, the calcination is preferably performed under a nitrogen atmosphere; the roasting temperature is preferably 400-700 ℃, more preferably 450-650 ℃, and most preferably 500-600 ℃; the roasting time is preferably 2-5 hours, and more preferably 3-4 hours. In the invention, the heating rate of heating to the roasting temperature is preferably 2-5 ℃/min, and more preferably 3-4 ℃/min. After the calcination is completed, the invention also preferably includes cooling and grinding; the cooling mode is preferably natural cooling, and the target temperature of cooling is preferably room temperature; the grinding is not particularly limited in the present invention, and may be carried out by a process known to those skilled in the art.
In the present invention, the mixing of the intermediate product and the graphite phase carbon nitride is preferably achieved by means of milling. In the present invention, the time for the grinding is preferably 1 h; the present invention does not have any particular limitation on the specific process of the grinding, and the grinding can be performed by a process well known to those skilled in the art.
In the present invention, the second firing is preferably performed under a nitrogen atmosphere; the second roasting temperature is preferably 400-700 ℃, more preferably 450-650 ℃, and most preferably 500-600 ℃; the second roasting time is preferably 2-5 hours, and more preferably 3-4 hours.
In the present invention, the second firing causes a solid-phase reaction to occur, causing metal oxides (CuO, ZnO and Al)2O3) Uniformly attached in a lamellar structure of graphite phase carbon nitride.
After the catalyst precursor is obtained, the catalyst precursor is treated by H2And N2The mixed gas is used as a reducing gas to reduce the catalyst precursor to obtain the catalyst. In the present invention, said H2And N2Is preferably 5: 95; said H2And N2The flow rate of the mixed gas is preferably 45-55 m L/min, more preferably 50m L/min, in the invention, the reduction temperature is preferably 250-350 ℃, more preferably 280-320 ℃, and most preferably 300 ℃, and the reduction reaction time is preferably 5.5-6.5 h, more preferablyThe time is selected to be 5.8-6.2 hours, and the most preferable time is 6 hours.
The catalyst for preparing methanol by hydrogenation of carbon dioxide and the preparation method thereof provided by the present invention will be described in detail with reference to the following examples, but they should not be construed as limiting the scope of the present invention.
Example 1
According to Cu: ZnO: al (Al)2O36g of Cu (NO) at a mass ratio of 4:3:33)2·3H2O、4.4g Zn(NO3)2·6H2O、8.8gAl(NO3)3·9H2Mixing O with 63m L water to obtain a mixed solution;
adding 10.6g of Na2CO3Mixing with 100m L of water to obtain a sodium carbonate solution;
under the condition of stirring, enabling the mixed solution and a sodium carbonate solution to flow in water of 200m L in parallel, carrying out coprecipitation reaction (70 ℃, pH 7 and 2h), standing and aging at 30 ℃ for 12h, filtering to obtain a solid substance, washing, drying (80 ℃, 12h) and carrying out first roasting (350 ℃, 5h) on the solid substance in sequence to obtain an intermediate;
grinding cyanamide, heating to 550 ℃ at the heating rate of 5 ℃/min under the nitrogen atmosphere, reacting for 300min, naturally cooling to room temperature, and grinding to obtain graphite-phase carbon nitride;
mixing and grinding the intermediate and 0.10g of graphite-phase carbon nitride for 1h, and performing second roasting (under a nitrogen atmosphere, at 400 ℃ for 3h) to obtain a catalyst precursor;
with H2And N2Mixed gas (H) of (2)2And N2At a flow rate of 50m L/min) as a reducing gas, and reducing the catalyst precursor (300 ℃, 6h) to obtain the catalyst for preparing methanol by carbon dioxide hydrogenation, which is recorded as 2.5% CN-CZA.
Example 2
According to Cu: ZnO: al (Al)2O36g of Cu (NO) at a mass ratio of 4:3:33)2·3H2O、4.4g Zn(NO3)2·6H2O、8.8gAl(NO3)3·9H2Mixing O with 63m L water to obtain a mixed solution;
adding 10.6g of Na2CO3Mixing with 100m L of water to obtain a sodium carbonate solution;
under the condition of stirring, enabling the mixed solution and a sodium carbonate solution to flow in water of 200m L in parallel, carrying out coprecipitation reaction (70 ℃, pH 7 and 2h), standing and aging at 30 ℃ for 12h, filtering to obtain a solid substance, washing, drying (80 ℃, 12h) and carrying out first roasting (350 ℃, 5h) on the solid substance in sequence to obtain an intermediate;
grinding dicyandiamide, heating to 550 ℃ at a heating rate of 5 ℃/min in a nitrogen atmosphere, reacting for 300min, naturally cooling to room temperature, and grinding to obtain graphite-phase carbon nitride;
mixing and grinding the intermediate and 0.21g of graphite-phase carbon nitride for 1h, and performing second roasting (under a nitrogen atmosphere, at 400 ℃ for 3h) to obtain a catalyst precursor;
with H2And N2Mixed gas (H) of (2)2And N2At a flow rate of 50m L/min) as a reducing gas, and reducing the catalyst precursor (300 ℃, 6h) to obtain the catalyst for preparing methanol by carbon dioxide hydrogenation, which is recorded as 5% CN-CZA.
Example 3
According to Cu: ZnO: al (Al)2O36g of Cu (NO) at a mass ratio of 4:3:33)2·3H2O、4.4g Zn(NO3)2·6H2O、8.8gAl(NO3)3·9H2Mixing O with 63m L water to obtain a mixed solution;
adding 10.6g of Na2CO3Mixing with 100m L of water to obtain a sodium carbonate solution;
under the condition of stirring, enabling the mixed solution and a sodium carbonate solution to flow in water of 200m L in parallel, carrying out coprecipitation reaction (70 ℃, pH 7 and 2h), standing and aging at 30 ℃ for 12h, filtering to obtain a solid substance, washing, drying (80 ℃, 12h) and carrying out first roasting (350 ℃, 5h) on the solid substance in sequence to obtain an intermediate;
grinding dicyandiamide, heating to 550 ℃ at a heating rate of 5 ℃/min in a nitrogen atmosphere, reacting for 300min, naturally cooling to room temperature, and grinding to obtain graphite-phase carbon nitride;
mixing and grinding the intermediate and 0.44g of graphite-phase carbon nitride for 1h, and performing second roasting (nitrogen atmosphere, 400 ℃, 3h) to obtain a catalyst precursor;
with H2And N2Mixed gas (H) of (2)2And N2At a flow rate of 50m L/min) as a reducing gas, and reducing the catalyst precursor (300 ℃, 6h) to obtain the catalyst for preparing methanol by carbon dioxide hydrogenation, which is recorded as 10% CN-CZA.
Example 4
According to Cu: ZnO: al (Al)2O36g of Cu (NO) at a mass ratio of 4:3:33)2·3H2O、4.4g Zn(NO3)2·6H2O、8.8gAl(NO3)3·9H2Mixing O with 63m L water to obtain a mixed solution;
adding 10.6g of Na2CO3Mixing with 100m L of water to obtain a sodium carbonate solution;
under the condition of stirring, enabling the mixed solution and a sodium carbonate solution to flow in water of 200m L in parallel, carrying out coprecipitation reaction (70 ℃, pH 7 and 2h), standing and aging at 30 ℃ for 12h, filtering to obtain a solid substance, washing, drying (80 ℃, 12h) and carrying out first roasting (350 ℃, 5h) on the solid substance in sequence to obtain an intermediate;
mixing urea, grinding, heating to 550 ℃ at a heating rate of 5 ℃/min in a nitrogen atmosphere, reacting for 300min, naturally cooling to room temperature, and grinding to obtain graphite-phase carbon nitride;
mixing and grinding the intermediate and 0.7g of graphite-phase carbon nitride for 1h, and performing second roasting (under a nitrogen atmosphere, at 400 ℃ for 3h) to obtain a catalyst precursor;
with H2And N2Mixed gas (H) of (2)2And N2At a flow rate of 50m L/min) as a reducing gas, and introducing the catalyst precursor into the reaction vesselReduction was carried out (300 ℃, 6h) to give the catalyst for the hydrogenation of carbon dioxide to methanol, noted 10% CN-CZA.
Comparative example 1
According to Cu: ZnO: al (Al)2O36g of Cu (NO) at a mass ratio of 4:3:33)2·3H2O、4.4g Zn(NO3)2·6H2O、8.8gAl(NO3)3·9H2Mixing O with 63m L water to obtain a mixed solution;
adding 10.6g of Na2CO3Mixing with 100m L of water to obtain a sodium carbonate solution;
under the condition of stirring, enabling the mixed solution and a sodium carbonate solution to flow in water of 200m L in parallel, carrying out coprecipitation reaction (70 ℃, pH 7 and 2h), standing and aging at 30 ℃ for 12h, filtering to obtain a solid substance, washing, drying (80 ℃, 12h) and carrying out first roasting (350 ℃, 5h) on the solid substance in sequence to obtain an intermediate;
carrying out second roasting (nitrogen atmosphere, 400 ℃, 3h) on the intermediate to obtain a catalyst precursor;
with H2And N2Mixed gas (H) of (2)2And N2At a flow rate of 50m L/min) as a reducing gas, and reducing the catalyst precursor (300 ℃, 6h) to obtain the catalyst for preparing methanol by carbon dioxide hydrogenation, which is noted as CZA.
Test example
The catalysts described in examples 1-4 and comparative example 1 are used for preparing methanol by carbon dioxide hydrogenation in a micro fixed bed reactor to carry out activity evaluation test and stability test; reaction conditions are as follows: 1.0g of 20-40 mesh catalyst, feed gas H2、CO2And Ar in a volume ratio of 70: 23: contact time W/F (contact time of the catalyst and the raw material gas or gas flow rate of the raw material gas into the reaction tube) was 10g · h/mol, reaction pressure was 3.0MPa, reaction temperature was 200 ℃, and reaction time was 50 h. The activity evaluation test results are shown in table 1:
TABLE 1 evaluation results of Activity of catalysts described in examples 1 to 4 and comparative example 1
Figure BDA0002438372140000091
Figure BDA0002438372140000101
The stability test result is shown in fig. 1, and as can be seen from fig. 1, when the catalyst prepared in the embodiment of the present invention is used as a catalyst for preparing methanol by hydrogenating carbon dioxide, the carbon dioxide conversion rate and the methanol selectivity both gradually increase and tend to be stable with the increase of time, and the catalytic activity does not significantly decrease after the catalytic reaction is performed for 50 hours, which indicates that the catalyst provided by the present invention has excellent stability.
Therefore, the catalyst has high carbon dioxide conversion rate and methanol selectivity when being used for preparing methanol by carbon dioxide hydrogenation, and has good stability.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims (10)

1. A catalyst for preparing methanol by hydrogenating carbon dioxide comprises graphite-phase carbon nitride and Cu, ZnO and Al dispersed in a lamellar structure of the graphite-phase carbon nitride2O3；
The Cu, ZnO and Al2O3The mass ratio of the total mass of the graphite phase carbon nitride to the total mass of the graphite phase carbon nitride is (80-100): (0-20);
and the amount of the graphite phase carbon nitride is not 0.
2. The catalyst of claim 1, wherein the Cu, ZnO, and Al are2O3The mass ratio of (4-6): (2.5-3.5): (2.5-3.5).
3. A method for preparing the catalyst of claim 1 or 2, comprising the steps of:
mixing soluble copper salt, soluble zinc salt, soluble aluminum salt and water to obtain a mixed solution;
mixing the mixed solution, a sodium carbonate solution and water, and carrying out coprecipitation reaction to obtain a precipitate;
carrying out first roasting on the precipitate to obtain an intermediate product;
mixing the intermediate product with graphite-phase carbon nitride, and performing second roasting to obtain a catalyst precursor;
with H2And N2The mixed gas is used as a reducing gas to reduce the catalyst precursor to obtain the catalyst.
4. The method according to claim 3, wherein the temperature of the coprecipitation reaction is 60 to 80 ℃, and the pH of a reaction solution in which the coprecipitation reaction occurs is 6 to 8.
5. The production method according to claim 3 or 4, wherein the coprecipitation reaction is carried out under stirring;
the stirring speed is 650-900 r/min, and the stirring time is 1-5 h.
6. The preparation method according to claim 3, wherein the temperature of the first roasting is 200 to 400 ℃, and the time of the first roasting is 2 to 6 hours.
7. The production method according to claim 3, wherein the second baking is performed under a nitrogen atmosphere;
the temperature of the second roasting is 400-700 ℃, and the time of the second roasting is 2-5 h.
8. The method of claim 3, wherein H is2And N2In a volume ratio of 5: 95;
said H2And N2The flow velocity of the mixed gas is 45-55 m L/min;
the reduction temperature is 250-350 ℃.
9. The preparation method according to claim 5, wherein after the coprecipitation reaction is completed, the method further comprises aging, solid-liquid separation and drying the resultant solution obtained after the coprecipitation reaction in sequence;
the aging temperature is 20-50 ℃, and the aging time is 10-15 h;
the drying temperature is 60-100 ℃, and the drying time is 5-15 h.
10. The method according to claim 3, wherein the graphite-phase carbon nitride is prepared by thermal polymerization of cyanamide, dicyandiamide, melamine or urea;
the temperature of the thermal polymerization is 400-700 ℃.
CN202010258502.XA 2020-04-03 2020-04-03 Catalyst for preparing methanol by carbon dioxide hydrogenation and preparation method thereof Pending CN111437862A (en)

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