CN116943683A - Mn modified gamma-Fe 2 O 3 Nanometer hollow microsphere catalyst and preparation method and application thereof - Google Patents
Mn modified gamma-Fe 2 O 3 Nanometer hollow microsphere catalyst and preparation method and application thereof Download PDFInfo
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- ALIMWUQMDCBYFM-UHFFFAOYSA-N manganese(2+);dinitrate;tetrahydrate Chemical compound O.O.O.O.[Mn+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O ALIMWUQMDCBYFM-UHFFFAOYSA-N 0.000 claims abstract description 8
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- NDLPOXTZKUMGOV-UHFFFAOYSA-N oxo(oxoferriooxy)iron hydrate Chemical compound O.O=[Fe]O[Fe]=O NDLPOXTZKUMGOV-UHFFFAOYSA-N 0.000 description 1
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Classifications
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- 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
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Abstract
The invention provides Mn modified gamma-Fe 2 O 3 The preparation method of the nano hollow microsphere catalyst comprises the following steps: s1, dissolving ferric nitrate nonahydrate, manganese nitrate tetrahydrate and urea in ethylene glycol, and uniformly mixing to obtain a mixed solution 1; s2, dissolving microcrystalline cellulose and NaOH in ethylene glycol to obtain a cellulose solution, pouring the cellulose solution into the mixed solution 1, and stirring to obtain a mixed solution 2; s3, pouring the mixed solution 2 into a reaction kettle for solvothermal reaction, centrifuging, washing and drying the precipitate obtained after the reaction is finished to obtain a precursor; s4, calcining the precursor to obtain Mn modified gamma-Fe 2 O 3 A powder; s5, weighing sodium carbonate to prepare a solution, and mixing the solution with Mn modified gamma-Fe 2 O 3 Soaking the powder in equal volume, and vacuum drying to obtain the Mn modified gamma-Fe 2 O 3 A nano hollow microsphere catalyst. The hollow microsphere catalyst prepared by the invention can promote CO 2 The formation of the hydrogenated active phase iron carbide improves the selectivity of the olefin product and has better stability.
Description
Technical Field
The present invention relates to CO 2 The technical field of hydrogenation catalysts, in particular to Mn modified gamma-Fe 2 O 3 A nano hollow microsphere catalyst, a preparation method and application thereof.
Background
Fossil fuels play an important role in human social development, and their combustion utilization results in carbon dioxide (CO 2 ) High emissions cause a series of environmental problems such as climate change, global warming and ocean acidification, and are responsible for the human living environment and social processesThe economic effect is greatly affected. How to realize CO 2 Emission reduction and resource utilization have attracted extensive attention from researchers in various countries. CO 2 Although being a greenhouse gas, the catalyst is also a cheap carbon source, and can be catalytically activated and selectively converted into high-added-value chemicals, thereby not only relieving CO 2 Environmental problems caused by excessive emission and dependence of chemicals on petroleum resources, and can also realize CO 2 And (5) recycling. CO 2 The research on the conversion of hydrogenation selectivity into high value-added chemicals is mainly focused on the fields of electricity, light and thermocatalysis, wherein the electricity and the photocatalysis limit the large-scale application due to the very low conversion efficiency, and thermocatalysis has higher conversion efficiency and has been widely studied.
The green hydrogen prepared by using renewable energy sources can be directly used as energy sources, and the problem of high carbon emission caused by fossil resource hydrogen production in the traditional chemical process can be solved. Green hydrogen as a hub and bridge with CO 2 Coupling to make high value chemicals, can store energy from renewable sources in the high value chemicals, and reduce CO 2 Emissions, thus, CO 2 The coupling green hydrogen technology has important practical significance in preparing high-added-value chemicals through thermocatalytic hydrogenation.
Existing CO 2 The hydrogenation catalyst system has low selectivity of high-low carbon olefin and is accompanied by higher methane selectivity and lower CO 2 The present application was filed based on the present invention, which has a conversion rate and a product distribution that follows ASF distribution restrictions, and Fe-based catalysts have higher water gas shift activity in the reaction, but has little research on how to modulate the product distribution by byproduct water.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides Mn modified gamma-Fe 2 O 3 The Mn modified cellulose prepared by the invention synthesizes gamma-Fe 2 O 3 The nano hollow microsphere catalyst is modified by surface hydrophilic groups, so that the olefin selectivity is improvedThe distribution rule of the product is influenced, the raw materials are environment-friendly, and the preparation method is simple and convenient.
The invention provides the following technical scheme:
the invention provides Mn modified gamma-Fe 2 O 3 The preparation method of the nano hollow microsphere catalyst comprises the following steps:
s1, dissolving ferric nitrate nonahydrate, manganese nitrate tetrahydrate and urea in ethylene glycol, and uniformly mixing to obtain a mixed solution 1;
s2, dissolving microcrystalline cellulose and NaOH in ethylene glycol to obtain a cellulose solution, pouring the cellulose solution into the mixed solution 1, and stirring to obtain a mixed solution 2;
s3, pouring the mixed solution 2 into a reaction kettle for solvothermal reaction, centrifuging, washing and drying the precipitate obtained after the reaction is finished to obtain a precursor;
s4, calcining the precursor to obtain Mn modified gamma-Fe 2 O 3 A powder;
s5, weighing sodium carbonate to prepare a solution, and mixing the solution with Mn modified gamma-Fe 2 O 3 Soaking the powder in equal volume, and vacuum drying to obtain the Mn modified gamma-Fe 2 O 3 A nano hollow microsphere catalyst.
The invention adds Mn to gamma-Fe 2 O 3 The modification can effectively reduce the quantity of weakly adsorbed hydrogen atoms in the catalytic stage and reduce the hydrogenation capacity, thereby improving the yield of the low-carbon olefin;
the cellulose is a green and environment-friendly renewable resource, mainly contains three elements of carbon, hydrogen and oxygen, is a chain-shaped high polymer compound connected by glucose through glycosidic bonds, has hydroxyl hydrophilic groups connected to the surface of the basic unit, has good water absorption, and can be adhered to Fe 2 O 3 To make Fe on the surface of 2 O 3 The hydroxyl on the surface is increased, the hydrophilicity is enhanced, the secondary reaction of primary olefin is reduced by facilitating the product diffusion, the selectivity of olefin is improved, the catalyst can also be used as an electronic auxiliary agent to improve the activity of the reaction, the high cellulose content can influence the crystallinity of ferric oxide, and the biomass microcrystalline cellulose is used as a precursor to synthesize goldBelongs to a composite material, and cellulose is dispersed in Mn modified gamma-Fe 2 O 3 The surface of the catalyst is improved, the catalyst is effectively prevented from agglomerating in the reaction process, and then the active sites are reduced, so that the problem of low selectivity of the low-carbon olefin is solved;
the invention finally utilizes sodium carbonate impregnation to enhance the chain growth in the catalytic reaction, thereby improving the selectivity of the low-carbon olefin.
The invention synthesizes Mn modified gamma-Fe by adopting solvothermal cellulose 2 O 3 The shape of the nano hollow microsphere has higher specific surface area and pore volume, and macropores are beneficial to the diffusion of reactants and products and promote CO 2 The hydrogenation active phase iron carbide is formed, so that the selectivity of an olefin product is improved, the thermal stability of the sample is good, and the appearance of the nano-structure hollow microsphere is not changed after high-temperature roasting.
Further, in step S1, the molar ratio n (fe+mn): n (urea) =1: 2, molar ratio n (Fe): n (Mn) =1: 0.5 to 5.
Further, in the step S2, the dosage ratio of microcrystalline cellulose, naOH and glycol in the cellulose solution is (1-5) g; (0-1) g; (50-100) mL.
Further, in step S2, the ratio of the mixed solution 1 to the cellulose solution is (100-200) mL; (50-100) mL.
Further, in the step S3, the solvothermal reaction condition is that the reaction is carried out for 20-24 hours at the temperature of 150-190 ℃.
Further, step S4 is specifically to put the precursor into a muffle furnace, and heat up to 300-330 ℃ under the air atmosphere to calcine for 2-4 hours at constant temperature.
Further, in step S5, mn-modified gamma-Fe 2 O 3 The mass ratio of the powder to the sodium carbonate is 1:0.2-0.4.
The invention also provides Mn modified gamma-Fe prepared by the preparation method 2 O 3 A nano hollow microsphere catalyst. Mn modified gamma-Fe 2 O 3 The thickness of the lamellar layer of the nano hollow microsphere catalyst is 80-120 nm.
The invention also provides the Mn modified gamma-Fe 2 O 3 Catalytic CO with nano hollow microsphere catalyst 2 Application in hydrogenation. The catalyst is directly applied to direct CO 2 Hydrogenation to prepare olefin, reaction of catalyst in fixed bed, CO 2 /H 2 The ratio of the catalyst to the catalyst is 1:1-5, the reaction temperature is 300-500 ℃, the reaction pressure is 1.0-5.0 MPa, and the airspeed is W/F=10-30 g.mol -1 ·h -1 The olefin is prepared under the condition.
The invention has the following beneficial effects:
1. the invention utilizes Mn to gamma-Fe 2 O 3 The modification ensures that the prepared catalyst effectively reduces the quantity of weakly adsorbed hydrogen atoms and reduces the hydrogenation capacity in the catalytic stage, thereby improving the yield of low-carbon olefin, promoting the reaction of CO and H and the formation of C-C bonds, reducing the secondary hydrogenation reaction rate of olefin, preventing the oxidation of Fe phase in the reaction process and obviously improving Fe 5 C 2 Stability of the gamma-Fe prepared by the traditional hydrothermal method is effectively solved 2 O 3 Poor reproducibility of the evaluation effect.
2. The Mn modified gamma-Fe prepared by synthesizing the metal composite material by taking biomass microcrystalline cellulose as a precursor 2 O 3 The nano hollow microsphere catalyst has small grain size, and has more active centers after reduction, thereby improving the selectivity of olefin.
Drawings
In order to more clearly illustrate the embodiments of the invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, it being obvious that the drawings in the following description are only some embodiments of the invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 shows Mn-modified gamma-Fe prepared in example 2 of the present invention 2 O 3 SEM image of the nano hollow microsphere catalyst.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The embodiment of the invention provides Mn modified gamma-Fe 2 O 3 The preparation method of the nano hollow microsphere catalyst comprises the following steps:
s1, dissolving ferric nitrate nonahydrate, manganese nitrate tetrahydrate and urea in ethylene glycol, and uniformly mixing to obtain a mixed solution 1;
s2, dissolving microcrystalline cellulose and NaOH in ethylene glycol to obtain a cellulose solution, pouring the cellulose solution into the mixed solution 1, and stirring to obtain a mixed solution 2;
s3, pouring the mixed solution 2 into a reaction kettle for solvothermal reaction, centrifuging, washing and drying the precipitate obtained after the reaction is finished to obtain a precursor;
s4, calcining the precursor to obtain Mn modified gamma-Fe 2 O 3 A powder;
s5, weighing sodium carbonate to prepare a solution, and mixing the solution with Mn modified gamma-Fe 2 O 3 Soaking the powder in equal volume, and vacuum drying to obtain the Mn modified gamma-Fe 2 O 3 A nano hollow microsphere catalyst.
Preferably, in step S1, the molar ratio n (fe+mn): n (urea) =1: 2, molar ratio n (Fe): n (Mn) =1: 0.5 to 5.
In the step S2, the dosage ratio of microcrystalline cellulose, naOH and glycol in the cellulose solution is (1-5) g; (0-1) g; (50-100) mL.
Preferably, in step S2, the ratio of the mixed solution 1 to the cellulose solution is (100-200) mL; (50-100) mL.
Preferably, in the step S3, the solvothermal reaction condition is that the reaction is carried out for 20-24 hours at the temperature of 150-190 ℃.
As a preferable scheme, the step S4 is specifically that the precursor is put into a muffle furnace, and the temperature is raised to 300-330 ℃ in an air atmosphere for constant-temperature calcination for 2-4 hours.
As a preferred embodiment, in step S5, mn-modified gamma-Fe 2 O 3 The mass ratio of the powder to the sodium carbonate is 1:0.2-0.4.
Example 1
Mn-modified gamma-Fe in this example 2 O 3 The preparation method of the hollow microsphere catalyst specifically comprises the following steps:
s1, preparing a soluble nitrate mixed solution 1: in a molar ratio n (Fe+Mn): n (urea) =1: 2, n (Fe): n (Mn) =1: 1, dissolving ferric nitrate nonahydrate, manganese nitrate tetrahydrate and urea into 100mL of glycol solution, and mechanically stirring for 30min at the rotating speed of 600rad/min to obtain a soluble nitrate mixed solution 1;
s2, preparing a cellulose solution: 1.5g of microcrystalline cellulose and 0.48g of NaOH are weighed and dissolved in 50mL of ethylene glycol, and the mixture is mechanically stirred for 5min at a rotation speed of 500rad/min to obtain a cellulose solution.
S3, pouring the cellulose solution obtained in the step S2 into the soluble nitrate solution obtained in the step S1, and ultrasonically stirring the mixed solution for 30min until the cellulose solution and the mixed solution are completely dissolved to obtain a uniform mixed solution 2; transferring the mixed solution 2 into a stainless steel reaction kettle with a polytetrafluoroethylene lining with the volume of 300mL, sealing, heating the reaction kettle to 160 ℃ for solvothermal reaction for 24 hours, cooling to room temperature after the reaction is finished, alternately centrifuging and washing the obtained precipitate with deionized water for 3 times, drying the obtained solid product in an oven at the drying temperature of 80 ℃ overnight to obtain a precursor;
s4, placing the precursor obtained in the step S3 in a muffle furnace, heating to 300 ℃ under an air atmosphere, and calcining for 2 hours at constant temperature to obtain Mn modified gamma-Fe after calcining 2 O 3 And (3) powder.
S5, weighing the powder, and modifying gamma-Fe according to Mn 2 O 3 Powder and Na + The mass ratio of (2) is 1:0.2, and a certain amount of Na is weighed 2 CO 3 Na is mixed with 2 CO 3 Dissolving in 50mL deionized water, mechanically stirring at 500rad/minAfter 10min, preparing a solution with a certain concentration, dripping the powder, and then drying under vacuum at 60 ℃ overnight to obtain Mn modified gamma-Fe 2 O 3 Hollow microsphere catalyst, named 1-Mn/gamma-Fe 2 O 3 。
Example 2
Mn-modified gamma-Fe of the present example 2 O 3 A method for preparing a hollow microsphere catalyst, said method being substantially identical to example 1, except that: the mixed solvent of example 1 was changed in proportion, and the other steps were similar to those of example 1. The specific operation steps are as follows:
s1, preparing a soluble nitrate mixed solution 1: in a molar ratio n (Fe+Mn): n (urea) =1: 2, n (Fe): n (Mn) =1: 2, dissolving ferric nitrate nonahydrate, manganese nitrate tetrahydrate and urea into 100mL of glycol solution, and mechanically stirring for 30min at the rotating speed of 600rad/min to obtain a soluble nitrate mixed solution 1;
s2, preparing a cellulose solution: 1.5g of microcrystalline cellulose and 0.48g of NaOH are weighed and dissolved in 50mL of ethylene glycol, and the mixture is mechanically stirred for 5min at a rotation speed of 500rad/min to obtain a cellulose solution.
S3, pouring the cellulose solution obtained in the step S2 into the soluble nitrate solution obtained in the step S1, and ultrasonically stirring the mixed solution for 30min until the cellulose solution and the mixed solution are completely dissolved to obtain a uniform mixed solution 2; transferring the mixed solution 2 into a stainless steel reaction kettle with a polytetrafluoroethylene lining with the volume of 300mL, sealing, heating the reaction kettle to 160 ℃ for solvothermal reaction for 24 hours, cooling to room temperature after the reaction is finished, alternately centrifuging and washing the obtained precipitate with deionized water for 3 times, drying the obtained solid product in an oven at the drying temperature of 80 ℃ overnight to obtain a precursor;
s4, placing the precursor obtained in the step S3 in a muffle furnace, heating to 300 ℃ under an air atmosphere, and calcining for 2 hours at constant temperature to obtain Mn modified gamma-Fe after calcining 2 O 3 And (3) powder.
S5, weighing the powder, and modifying gamma-Fe according to Mn 2 O 3 Powder and Na + The mass ratio of (2) is 1:0.2, and a certain amount of Na is weighed 2 CO 3 Na is mixed with 2 CO 3 Dissolving in 50mL deionized water, mechanically stirring at 500rad/min for 10min to obtain solution with certain concentration, dripping into the above powder, and vacuum drying at 60deg.C overnight to obtain Mn-modified gamma-Fe 2 O 3 Hollow microsphere catalyst, named 2-Mn/gamma-Fe 2 O 3 。
Example 3
Mn-modified gamma-Fe of the present example 2 O 3 A method for preparing a hollow microsphere catalyst, said method being substantially identical to example 1, except that: the mixed solvent of example 1 was changed in proportion, and the other steps were similar to those of example 1. The specific operation steps are as follows:
s1, preparing a soluble nitrate mixed solution 1: in a molar ratio n (Fe+Mn): n (urea) =1: 2, n (Fe): n (Mn) =1: 3, dissolving ferric nitrate nonahydrate, manganese nitrate tetrahydrate and urea into 100mL of glycol solution, and mechanically stirring for 30min at the rotating speed of 600rad/min to obtain a soluble nitrate mixed solution 1;
s2, preparing a cellulose solution: 1.5g of microcrystalline cellulose and 0.48g of NaOH are weighed and dissolved in 50mL of ethylene glycol, and the mixture is mechanically stirred for 5min at a rotation speed of 500rad/min to obtain a cellulose solution.
S3, pouring the cellulose solution obtained in the step S2 into the soluble nitrate solution obtained in the step S1, and ultrasonically stirring the mixed solution for 30min until the cellulose solution and the mixed solution are completely dissolved to obtain a uniform mixed solution 2; transferring the mixed solution 2 into a stainless steel reaction kettle with a polytetrafluoroethylene lining with the volume of 300mL, sealing, heating the reaction kettle to 160 ℃ for solvothermal reaction for 24 hours, cooling to room temperature after the reaction is finished, alternately centrifuging and washing the obtained precipitate with deionized water for 3 times, drying the obtained solid product in an oven at the drying temperature of 80 ℃ overnight to obtain a precursor;
s4, placing the precursor obtained in the step S3 in a muffle furnace, heating to 300 ℃ under an air atmosphere, and calcining for 2 hours at constant temperature to obtain Mn modified gamma-Fe after calcining 2 O 3 And (3) powder.
S5, weighing the powder, and modifying gamma-Fe according to Mn 2 O 3 Powder and Na + The mass ratio of (2) is 1:0.2, and a certain amount of Na is weighed 2 CO 3 Na is mixed with 2 CO 3 Dissolving in 50mL deionized water, mechanically stirring at 500rad/min for 10min to obtain solution with certain concentration, dripping into the above powder, and vacuum drying at 60deg.C overnight to obtain Mn-modified gamma-Fe 2 O 3 Hollow microsphere catalyst, designated 3-Mn/gamma-Fe 2 O 3 。
Example 4
Mn-modified gamma-Fe of the present example 2 O 3 A method for preparing a hollow microsphere catalyst, said method being substantially identical to example 1, except that: the mixed solvent of example 1 was changed in proportion, and the other steps were similar to those of example 1. The specific operation steps are as follows:
s1, preparing a soluble nitrate mixed solution 1: in a molar ratio n (Fe+Mn): n (urea) =1: 2, n (Fe): n (Mn) =1: 3, dissolving ferric nitrate nonahydrate, manganese nitrate tetrahydrate and urea into 100mL of glycol solution, and mechanically stirring for 30min at the rotating speed of 600rad/min to obtain a soluble nitrate mixed solution 1;
s2, preparing a cellulose solution: 1.5g of microcrystalline cellulose and 0.48g of NaOH are weighed and dissolved in 50mL of ethylene glycol, and the mixture is mechanically stirred for 5min at a rotation speed of 500rad/min to obtain a cellulose solution.
S3, pouring the cellulose solution obtained in the step S2 into the soluble nitrate solution obtained in the step S1, and ultrasonically stirring the mixed solution for 30min until the cellulose solution and the mixed solution are completely dissolved to obtain a uniform mixed solution 2; transferring the mixed solution 2 into a stainless steel reaction kettle with a polytetrafluoroethylene lining with the volume of 300mL, sealing, heating the reaction kettle to 160 ℃ for solvothermal reaction for 24 hours, cooling to room temperature after the reaction is finished, alternately centrifuging and washing the obtained precipitate with deionized water for 3 times, drying the obtained solid product in an oven at the drying temperature of 80 ℃ overnight to obtain a precursor;
s4, placing the precursor obtained in the step S3 in a muffle furnace, and heating to 300 ℃ in an air atmosphereCalcining at constant temperature for 2h at the temperature, and obtaining Mn modified gamma-Fe after the calcining is finished 2 O 3 And (3) powder.
S5, weighing the powder, and modifying gamma-Fe according to Mn 2 O 3 Powder and Na + The mass ratio of (2) is 1:0.2, and a certain amount of Na is weighed 2 CO 3 Na is mixed with 2 CO 3 Dissolving in 50mL deionized water, mechanically stirring at 500rad/min for 10min to obtain solution with certain concentration, dripping into the above powder, and vacuum drying at 60deg.C overnight to obtain Mn-modified gamma-Fe 2 O 3 Hollow microsphere catalyst, designated 4-Mn/gamma-Fe 2 O 3 。
SEM test analysis is carried out on the hollow microsphere catalyst prepared in the embodiment, and the result is shown in figure 1, and according to SEM spectrograms under different multiplying power, the embodiment can be used for successfully synthesizing the nano-sheet self-assembled hollow microsphere precursor, the particle size is uniform, the thickness of a sheet layer is about 80-120 nm, the grain size is small, the active center generated after reduction is more, macropores are favorable for the diffusion of reactants and products, and the CO is promoted 2 Formation of hydrogenated active phase iron carbide.
Catalyst performance testing and characterization:
the catalyst is required to be strictly controlled to have uniform and proper particle size when participating in performance evaluation. The catalysts prepared in the above examples 1 to 4 of the present invention were all prepared into 20 to 50 mesh catalyst particles.
The catalysts prepared in examples 1 to 4 above were applied to CO 2 In the catalytic hydrogenation reaction, the invention adopts a micro fixed bed reactor to evaluate the catalyst, the process conditions are 0.2-4 g of 20-50 mesh catalyst, the reaction temperature is 300-500 ℃, the reaction pressure is 1.0-5.0 MPa, and the raw material gas CO 2 /H 2 =1:1 to 5, airspeed W/f=10 to 30 g.mol -1 ·h -1 。
For example, mn-modified gamma-Fe prepared in example 1 in a fixed bed reactor 2 O 3 The hollow microsphere catalyst is subjected to performance evaluation, and the specific operation steps are as follows: 0.4g of Mn-modified gamma-Fe prepared in example 1 was weighed out 2 O 3 Hollow microsphere catalyst is filled into a constant temperature area in the middle part of a reaction tube, and raw material gas H 2 /CO 2 =3, temperature 320 ℃, pressure 1.5MPa, space velocity W/f=30 g·mol -1 ·h -1 After reaching the steady state, sampling analysis is carried out, and sampling is carried out once at intervals of 2 h. The feed gas and the product were subjected to quantitative and qualitative analyses by gas chromatography. The specific results are shown in Table 1.
TABLE 1 Mn-modified gamma Fe prepared in examples 1-4 2 O 3 Hydrogenation catalytic reaction process parameters and performance test result comparison table of hollow microsphere catalyst
As can be seen from Table 1, in Mn-modified gamma-Fe 2 O 3 In the distribution of hydrogenation products of hollow microsphere catalysts, CO 2 The conversion rate is raised and then lowered, the CO selectivity change is not obvious, the CO selectivity is maintained at about 9%, and the distribution change of hydrocarbon products is obvious. Mn-modified gamma-Fe prepared in the examples of the present invention 2 O 3 In the hollow microsphere catalyst, 2-Mn/gamma-Fe prepared in example 2 2 O 3 Catalyst catalyzed CO 2 The hydrogenation performance is best, the selectivity of the low-carbon olefin is as high as 58.65%, and the olefin-alkane ratio (O/P) is 9.38.
Mn modified gamma-Fe prepared by the invention 2 O 3 Nano hollow microsphere catalyst changes CO 2 The characteristics and coverage rate of the surface active substances in the hydrogenation process promote the reaction of CO and H and the formation of C-C bonds, reduce the secondary hydrogenation reaction rate of olefin, prevent the oxidation of Fe phase in the reaction process, and obviously improve Fe 5 C 2 Stability of the gamma-Fe prepared by the traditional hydrothermal method is effectively solved 2 O 3 The Mn addition can effectively reduce the quantity of weakly adsorbed hydrogen atoms in the catalytic stage so as to reduce the hydrogenation capacity, and the Mn modified gamma-Fe prepared by synthesizing the metal composite material by taking biomass microcrystalline cellulose as a precursor 2 O 3 The nano hollow microsphere catalyst has small grain size and is produced after reductionThe active center is increased, thereby improving the yield of the low-carbon olefin.
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, alternatives, and improvements that fall within the spirit and scope of the invention.
Claims (9)
1. Mn modified gamma-Fe 2 O 3 The preparation method of the nano hollow microsphere catalyst is characterized by comprising the following steps:
s1, dissolving ferric nitrate nonahydrate, manganese nitrate tetrahydrate and urea in ethylene glycol, and uniformly mixing to obtain a mixed solution 1;
s2, dissolving microcrystalline cellulose and NaOH in ethylene glycol to obtain a cellulose solution, pouring the cellulose solution into the mixed solution 1, and stirring to obtain a mixed solution 2;
s3, pouring the mixed solution 2 into a reaction kettle for solvothermal reaction, centrifuging, washing and drying the precipitate obtained after the reaction is finished to obtain a precursor;
s4, calcining the precursor to obtain Mn modified gamma-Fe 2 O 3 A powder;
s5, weighing sodium carbonate to prepare a solution, and mixing the solution with Mn modified gamma-Fe 2 O 3 Soaking the powder in equal volume, and vacuum drying to obtain the Mn modified gamma-Fe 2 O 3 A nano hollow microsphere catalyst.
2. Mn-modified gamma-Fe according to claim 1 2 O 3 The preparation method of the nano hollow microsphere catalyst is characterized by comprising the following steps of: in step S1, the molar ratio n (fe+mn): n (urea) =1: 2, molar ratio n (Fe): n (Mn) =1: 0.5 to 5.
3. Mn-modified gamma-Fe according to claim 1 2 O 3 The preparation method of the nano hollow microsphere catalyst is characterized by comprising the following steps of: in the step S2, the dosage ratio of microcrystalline cellulose, naOH and glycol in the cellulose solution is (1-5) g; (0-1) g; (50-100) mL.
4. Mn-modified gamma-Fe according to claim 1 2 O 3 The preparation method of the nano hollow microsphere catalyst is characterized by comprising the following steps of: in the step S2, the ratio of the mixed solution 1 to the cellulose solution is (100-200) mL; (50-100) mL.
5. Mn-modified gamma-Fe according to claim 1 2 O 3 The preparation method of the nano hollow microsphere catalyst is characterized by comprising the following steps of: in the step S3, the solvothermal reaction condition is that the reaction is carried out for 20-24 hours at the temperature of 150-190 ℃.
6. Mn-modified gamma-Fe according to claim 1 2 O 3 The preparation method of the nano hollow microsphere catalyst is characterized by comprising the following steps of: and step S4, specifically, putting the precursor into a muffle furnace, heating to 300-330 ℃ in an air atmosphere, and calcining for 2-4 hours at constant temperature.
7. Mn-modified gamma-Fe according to claim 1 2 O 3 The preparation method of the nano hollow microsphere catalyst is characterized by comprising the following steps of: in step S5, mn-modified gamma-Fe 2 O 3 The mass ratio of the powder to the sodium carbonate is 1:0.2-0.4.
8. Mn-modified gamma-Fe prepared by the preparation method of any one of claims 1 to 7 2 O 3 A nano hollow microsphere catalyst.
9. Mn-modified gamma-Fe according to claim 8 2 O 3 Hollow microsphere catalyst for catalyzing CO 2 The use of the catalyst in hydrogenation, characterized in that the catalyst is directly applied to direct CO 2 Hydrogenation to prepare olefin, the catalyst reacts in a fixed bed, CO 2 /H 2 The ratio of the catalyst to the catalyst is 1:1-5, the reaction temperature is 300-500 ℃, the reaction pressure is 1.0-5.0 MPa, and the airspeed is W/F=10-30 g.mol -1 ·h -1 The olefin is prepared under the condition.
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