CN112642421A - MnCeOXMetal oxide and method for producing same - Google Patents

MnCeOXMetal oxide and method for producing same Download PDF

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CN112642421A
CN112642421A CN201910958640.6A CN201910958640A CN112642421A CN 112642421 A CN112642421 A CN 112642421A CN 201910958640 A CN201910958640 A CN 201910958640A CN 112642421 A CN112642421 A CN 112642421A
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frequency
metal oxide
mnceo
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salt
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CN112642421B (en
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张光明
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China National Petroleum Corp
CNPC Research Institute of Safety and Environmental Technology Co Ltd
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China National Petroleum Corp
CNPC Research Institute of Safety and Environmental Technology Co Ltd
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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
    • B01J23/002—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
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    • B01J23/32—Manganese, technetium or rhenium
    • B01J23/34—Manganese
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    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/40—Catalysts, in general, characterised by their form or physical properties characterised by dimensions, e.g. grain size
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/72—Treatment of water, waste water, or sewage by oxidation
    • C02F1/722—Oxidation by peroxides
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/72—Treatment of water, waste water, or sewage by oxidation
    • C02F1/725—Treatment of water, waste water, or sewage by oxidation by catalytic oxidation
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
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    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
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    • Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
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Abstract

The invention provides MnCeOxMetal oxides and methods for their preparation. The preparation method of the metal oxide comprises the following steps: dissolving precursors of metal oxide, namely Mn salt and Ce salt, in water to obtain a mixture A, then performing catalytic oxidation on the mixture A by using low-frequency ultrasonic radiation of 20kHz-40kHz for 15min, and adding a precipitant solution into the mixture A subjected to the low-frequency ultrasonic radiation to obtain a mixture B; and carrying out solid-liquid separation, drying and roasting on the mixture B to obtain the metal oxide. In the metal oxide, Ce4+And Ce3+In a ratio of 3-4:1, Mn4+With Mn3+In a ratio of 1.7-2.4: 1. The preparation method can effectively adjust MnCeOxCe in metal oxide4+/Ce3+、Mn4+/Mn3+The proportion relation of (A) optimizes the surface active oxygen component and improves MnCeOxCatalytic properties of metal oxides.

Description

MnCeOxMetal oxide and method for producing same
Technical Field
The invention belongs to the field of novel material preparation, and particularly relates to MnCeOxMetal oxides and methods for their preparation.
Background
The transition metal-rare earth metal oxide compound is a high-efficiency catalyst and can be used for catalyzing, oxidizing and decomposing pollutants in the environment. Wherein MnCeOxHas received a great deal of attention. The catalyst obtained by different preparation methods has huge difference in structure and performance.
In the prior art, the catalytic performance of the transition metal-rare earth metal oxide compound is improved from the viewpoint of optimizing the particle size of the catalyst. For example, ultrasonic assisted co-precipitation methods are currently of great interest; the ultrasonic-assisted coprecipitation method is a novel and efficient catalyst preparation method, and can shorten the preparation time of the catalyst and improve the particle size of the catalyst to make the catalyst more uniform and smaller. The ultrasonic-assisted preparation of the catalyst utilizes the mechanical effect of ultrasonic waves, and can promote better dispersion, so that more uniform catalyst particles are obtained.
No optimization of MnCeO has been foundxThe proportion of Mn ions and Ce ions in each valence state can improve MnCeOxThe catalytic activity is reported, and even less, the optimization of the ratio of Mn ions and Ce ions in each valence state in MnCeOx can be realized by introducing low-frequency ultrasound for a specific time.
Disclosure of Invention
The invention aims to provide a method for effectively adjusting MnCeOxThe proportion relation of Ce (IV)/Ce (III), Mn (IV)/Mn (III) in the metal oxide optimizes the MnCeO of the surface active oxygen componentxA method for preparing a metal oxide; the MnCeO prepared by the preparation methodxThe metal oxide is preferably used as a catalyst.
In order to achieve the above object, the present invention provides MnCeOxA method for preparing a metal oxide, wherein the method comprises:
1) dissolving precursors of metal oxide, namely Mn salt and Ce salt, in water to obtain a mixture A, adding a precipitator solution into the mixture A, and performing catalytic oxidation by using low-frequency ultrasonic radiation for 13-17min to obtain a mixture B; the frequency of the low-frequency ultrasound is 20kHz-48 kHz;
2) solid-liquid separation, drying and roasting of the mixture B to obtain the MnCeOxA metal oxide.
In the above preparation method, preferably, the time of the low-frequency ultrasonic radiation is 15 min. The optimization effect of the proportional relation of Ce (IV)/Ce (III), Mn (IV)/Mn (III) by low-frequency ultrasonic radiation for 15min is better, and the prepared MnCeOxThe catalytic performance of the metal oxide is better.
In the above production method, the frequency of the low-frequency ultrasound is preferably 20 to 40kHz, for example, 28 kHz. The low-frequency ultrasound with too high and too low frequency is not beneficial to realizing the catalytic oxidation reaction initiated by the low-frequency ultrasound, but the adjustment of the proportional relation of Ce (IV)/Ce (III), Mn (IV)/Mn (III) is not obviously influenced by the difference of the frequency of the low-frequency ultrasound in the available frequency range.
In the above production method, preferably, the concentration of the Mn salt in the mixture A is 0.1 to 0.4 mol/L.
In the above production method, preferably, the concentration of the Ce salt in the mixture A is 0.1 to 0.4 mol/L.
In the above production method, it is preferable that the molar ratio of Mn in the Mn salt to Ce in the Ce salt is 1: 1.
In the above preparation method, preferably, the Mn salt includes a divalent Mn salt and KMnO4At least one of; wherein the divalent Mn salt may be MnCl2But is not limited thereto.
In the above preparation method, preferably, the Ce salt comprises CeCl4。
In the above production method, preferably, the concentration of the precipitant in the precipitant solution is 0.5 to 2 mol/L; for example 1mol/L.
In the above preparation method, preferably, the precipitant solution is added to the mixture a in an amount such that the pH of the mixture of the precipitant solution and the mixture a after the low frequency ultrasonic irradiation is 11. In a preferred embodiment, 1mol/L sodium hydroxide solution is used as precipitant solution, and the volume ratio of precipitant solution to mixture A is 1: 50.
In the above production method, preferably, the precipitant includes at least one of NaOH and KOH; more preferably NaOH.
In the above preparation method, preferably, the precipitant solution is added dropwise.
In the above production method, preferably, the mixture B is subjected to an aging treatment before being subjected to solid-liquid separation; more preferably, the high frequency ultrasonic radiation is applied continuously during the aging treatment; wherein the frequency of the high-frequency ultrasound is 100-800 kHz; further preferably, the time for applying the high-frequency ultrasonic radiation is 45min-4 h; most preferably, the time of applying the high frequency ultrasonic radiation is 45 min. High-frequency ultrasonic waves are introduced in the aging treatment stage of catalyst preparation, so that the average particle size can be effectively controlled, and the nano-sized catalyst with uniformly dispersed average particle size is prepared.
In one embodiment, the above preparation method comprises:
1) dissolving precursors of metal oxide, namely Mn salt and Ce salt, in water to obtain a mixture A, dropwise adding a precipitator solution into the mixture A until the pH value of the mixture of the Mn salt and the Ce salt is 11, and then performing catalytic oxidation by using low-frequency ultrasonic radiation of 20kHz-40kHz for 15min to obtain a mixture B;
wherein the molar ratio of Mn in the Mn salt to Mn in the Ce salt is 1: 1; the concentration of Mn salt in the mixture A is 0.1-0.4 mol/L; the concentration of Ce salt in the mixture A is 0.1-0.4 mol/L; the concentration of the precipitant in the precipitant solution is 1 mol/L; wherein,
the Mn salt is MnCl2And KMnO4At least one of; the Ce salt is CeCl4(ii) a The precipitator is NaOH;
2) aging the mixture B for 45min, continuously applying 100-800kHz high-frequency ultrasonic radiation during the aging treatment, and performing solid-liquid separation, drying and roasting on the aged mixture B to obtain the MnCeOxA metal oxide; the MnCeOxThe average particle diameter of the metal oxide is nano-sized.
In the above production method, preferably, the average particle diameter of the produced MnCeOx metal oxide is controlled by controlling the frequency of the high-frequency ultrasound while applying the high-frequency ultrasound radiation, specifically:
when the frequency of the high-frequency ultrasound is controlled to be not less than 100kHz, the prepared MnCeOxThe average particle size of the metal oxide is not more than 420 nm;
when the frequency of the high-frequency ultrasound is controlled to be not less than 200kHz, the prepared MnCeOxThe average particle size of the metal oxide is not more than 300 nm;
when the frequency of the high-frequency ultrasound is controlled to be not lower than 300kHz, the prepared MnCeOxThe average particle size of the metal oxide is not more than 270 nm;
when the frequency of the high-frequency ultrasound is controlled to be not less than 500kHz, the prepared MnCeOxThe average particle size of the metal oxide is not more than 190 nm;
when the frequency of the high-frequency ultrasound is controlled to be not less than 800kHz, the prepared MnCeOxThe metal oxide has an average particle diameter of not more than 90 nm.
More preferably, the prepared MnCeO is subjected to ultrasonic treatment while controlling the frequency of the high-frequency ultrasonic wave at 100-200kHzxThe average particle size of the metal oxide is 420nm-300 nm; when the frequency of the high-frequency ultrasonic is controlled at 200-300kHz, the prepared MnCeOxThe average particle size of the metal oxide is 300nm-270 nm; when the frequency of the high-frequency ultrasonic is controlled at 300-500kHz, the prepared MnCeOxThe average grain diameter of the metal oxide is 270nm-190 nm; when the frequency of the high-frequency ultrasonic is controlled at 500-800kHz, the average grain diameter of the prepared MnCeOx metal oxide is 190nm-90 nm.
Further preferably, MnCeO is prepared while controlling the frequency of the high-frequency ultrasound at 100kHzxThe average particle size of the metal oxide is 420 nm; when the frequency of the high-frequency ultrasound is controlled at 200kHz, the prepared MnCeOxThe average particle size of the metal oxide is 300 nm; when the frequency of the high-frequency ultrasound is controlled at 300kHz, the prepared MnCeOxThe average particle size of the metal oxide is 270 nm; when the frequency of the high-frequency ultrasound is controlled at 500kHz, the prepared MnCeOxThe average particle size of the metal oxide is 190 nm; when the frequency of the high-frequency ultrasound is controlled at 800kHzPrepared MnCeOxThe average particle diameter of the metal oxide was 90 nm.
The preferred scheme provides a frequency selection basis of high-frequency ultrasound for the first time, and realizes that the proper high-frequency ultrasound frequency is selected according to the requirement on the average particle size of the prepared product.
In the above production method, preferably, the intensity of the low-frequency ultrasound is 3.0 to 12W/cm2(ii) a More preferably, the intensity of the low frequency ultrasound is 3.0-8.0W/cm2. Applying a low frequency of relatively high intensity is more favorable for the low frequency ultrasound to initiate the catalytic oxidation reaction.
In the above production method, preferably, the intensity of the high-frequency ultrasound is 0.5 to 1.5W/cm2。
In the above production method, preferably, the temperature of the calcination is 500 ℃.
In the above preparation method, preferably, the calcination time is 4 to 12 hours, for example, 4 hours.
In the above preparation method, the temperature of the drying may be 120 ℃, but is not limited thereto.
In the above preparation method, the drying time may be 12 hours, but is not limited thereto.
In the above preparation method, the water in step 1) may be deionized water, but is not limited thereto.
In the above preparation method, the solid-liquid separation may be achieved by centrifugation, but is not limited thereto.
In the above preparation method, after the solid-liquid separation is performed, the solid product after the solid-liquid separation may be washed before drying, and in a preferred embodiment, the solid product is washed with distilled water for not less than 3 times.
In the above preparation method, preferably, the method further comprises adding the MnCeOxThe metal oxide is ground.
The invention also provides MnCeO prepared by the preparation methodxA metal oxide, wherein the MnCeOxCe of metal oxide4+And Ce3+In a ratio of 3-4:1, Mn4+With Mn3+In a ratio of 1.7-2.4: 1.
In the above MnCeOxIn the metal oxide, preferably, the average particle diameter of the metal oxide is not more than 420 nm; more preferably, the average particle size is no greater than 300 nm; further preferably, the average particle size is not more than 270 nm; still more preferably, the average particle size is not greater than 190 nm; most preferably, the average particle size is no greater than 90 nm.
In the above MnCeOxAmong the metal oxides, preferably, the metal oxide has an average particle diameter of 420nm to 300 nm; more preferably, the average particle size is 300nm to 270 nm; further preferably, the average particle diameter is preferably 270nm to 190 nm; still more preferably, the average particle size is 190nm to 90 nm.
In the above MnCeOxIn the metal oxide, preferably, the average particle diameter of the metal oxide is 420 nm; more preferably, the average particle size is 300 nm; further preferably, the average particle size is 270 nm; still more preferably, the average particle size is 190 nm; most preferably, the average particle size is 90 nm.
The preparation method provided by the invention realizes MnCeO by means of low-frequency ultrasoundxAdjusting the proportion relation of Ce (IV)/Ce (III), Mn (IV)/Mn (III) in the metal oxide and optimizing the surface active oxygen component; the high intensity ultrasonic wave energy at low frequency causes the splitting of water molecules to form strong oxidants such as hydroxyl radicals and hydrogen peroxide, thereby initiating oxidation reactions, and when metal oxide particles exist in the solution, the metal oxides can be used as catalysts to enhance the reactions. During the preparation of the catalyst, ultrasonic wave is introduced to bring self-catalytic effect (in other words, during the preparation, catalytic oxidation reaction takes place simultaneously, and the added metal oxide takes place different reaction from that without ultrasonic wave under the action of ultrasonic wave, so that the valence state of the prepared product is changedxIn (1), i.e. initially added Mn ion, Ce ion (e.g. Mn)2+,Mn7+,Ce4+) Oxidation-reduction reaction is carried out to generate Mn ions and Ce ions with different proportions and different valence states. Through the change of the valence state and the proportion, catalysts with different activities are brought, and the low-frequency ultrasonic time is a core factor influencing the proportion of ions with different valence statesAnd (4) element.
The preparation method provided by the invention aims at adjusting MnCeOxThe proportion relation of Ce (IV)/Ce (III), Mn (IV)/Mn (III) in the metal oxide, the optimization of surface active oxygen component, and provides a brand new MnCeOxA method for preparing metal oxide. The technical scheme provided by the invention realizes the adjustment of the proportional relation of Ce (IV)/Ce (III), Mn (IV)/Mn (III) by regulating and controlling the time of low-frequency ultrasonic radiation, and optimizes the prepared MnCeOxA surface active oxygen component of a metal oxide; MnCeO prepared by the methodxThe metal oxide has improved catalytic activity and is more suitable for use as a catalyst. The technical scheme provided by the invention realizes MnCeO by using low-frequency ultrasound with specific durationxPartial catalytic oxidation of Mn and Ce elements in metal oxide, and partial change of obtained MnCeOxThe redox potentials of Mn and Ce elements in the metal oxide realize the improvement of the proportional relation of Ce (IV)/Ce (III) and Mn (IV)/Mn (III) and the optimization of surface active oxygen components, and are beneficial to the promotion of catalytic activity; meanwhile, the technical scheme provided by the invention promotes CeO2The (200 crystal face) is exposed, so that the migration of lattice oxygen from the lattice structure to the surface is facilitated, and the promotion of catalytic activity is facilitated. In addition, the MnCeO prepared by the inventionxThe metal oxide also presents a certain amount of oxygen vacancies, the presence of which also contributes to some extent to MnCeOxActivity of metal oxide.
Drawings
FIG. 1A shows MnCeO as provided in example 1xHRTEM of (g).
FIG. 1B shows MnCeO provided in example 1xThe energy distribution of the HRTEM image of (1).
FIG. 1C shows MnCeO as provided in example 1xDiffraction fringe pattern of the HRTEM image of (1).
FIG. 2A shows MnCeO provided in example 1xSEM image of (d).
FIG. 2B shows MnCeO provided in example 1xDistribution diagram of Ce element.
FIG. 2C is MnCeO provided in example 1xDistribution diagram of Mn element (2).
FIG. 2D shows an example1 MnCeOxDistribution diagram of the O element.
FIG. 3A is MnCeO provided in example 1xXPS chart of (a).
FIG. 3B is MnCeO provided in example 1xXPS pattern of Ce3d (g).
FIG. 3C is MnCeO provided in example 1xXPS map of Mn2p (g).
FIG. 3D is MnCeO provided in example 1xXPS map of O1s (g).
Detailed Description
The technical solutions of the present invention will be described in detail below in order to clearly understand the technical features, objects, and advantages of the present invention, but the present invention is not limited to the practical scope of the present invention.
Example 1
The present example provides a MnCeOxMetal oxide of the MnCeOxThe preparation method of the metal oxide comprises the following steps:
1) 3.95g of KMnO4、7.41g MnCl2And 23.28g CeCl4Dissolving the mixture in 250mL of deionized water to obtain a mixture A, dropwise adding 2mol/L NaOH solution into the mixture A until the pH value of the mixture A and the mixture A is 11, and then performing catalytic oxidation by using 28kHz low-frequency ultrasonic radiation for 15min to obtain a mixture B; wherein the intensity of the low frequency ultrasound is 5W/cm2；
2) Aging the mixture B for 1h, continuously applying 300kHz high-frequency ultrasonic radiation for 45min during the aging, centrifuging the aged mixture B, washing (washing with distilled water for 3 times), drying at 120 ℃ for 12h, and roasting at 500 ℃ for 4h to obtain the MnCeOxA metal oxide; wherein the intensity of the high-frequency ultrasound is 0.6W/cm2。
The MnCeO provided in this example was examinedxThe average grain size of the metal oxide is detected to obtain MnCeOxThe average particle diameter of the metal oxide is 270nm, and CeO on the surface of the metal oxidexThe average particle diameter of the particles is 2.9nm, and the particles of the active substance are small.
For MnCeO provided in this examplexSubjecting the metal oxide to crystal phase structure analysis to obtain MnCeOxMetallic oxygenHRTEM images of the compounds are shown in FIGS. 1A-1C; as can be seen from FIG. 1C, there are lattice fringes at 2.04 ℃ A, 2.70 ℃ A and 3.11 ℃ A corresponding to CeO, respectively2The (220), (200) and (111) crystal planes. Since crystal plane (111) has the smallest surface energy, it is the most stable crystal plane, which is advantageous for maintaining the stability of the crystal. Since the crystal face (200) has a higher surface energy, it can further improve the catalytic activity. Therefore, the catalyst with the exposed crystal face of (200) is successfully prepared by adopting an ultrasonic impregnation method, and the structure is favorable for the migration of lattice oxygen from the lattice structure to the surface. And the catalyst prepared by the traditional method does not have a (200) crystal face. In addition, the formation of oxygen vacancies in the (200) plane is also relatively superior to the (220) and (111) planes.
Testing of MnCeO provided in the present examplexAs a result of SEM image of the metal oxide, as shown in fig. 2A to 2D, the MnCeOx metal oxide had a rough surface and the elements were uniformly distributed.
Testing of MnCeO provided in the present examplexXPS plots of metal oxides with results shown in figures 3A-3D; as can be seen from FIG. 3A, the peak corresponding to the 641.356eV position is Mn2p3/2Further, further can be classified into Mn3+(643.194eV)、Mn4+(641.554 eV). Wherein Mn is4+67.73% (based on the total content of Mn element: 100%) of Mn4+With Mn3+The ratio of (A) to (B) is about 2:1, which is a sufficient indication that ultrasound exerts a catalytic oxidation effect during the reaction. FIG. 3B shows Ce3d, wherein u`、v`Marked by Ce3+，u```,u``,u,v```,v``V denotes Ce4+Wherein, Ce4+80.3 percent (based on the total amount of Ce element as 100 percent) of Ce4 +And Ce3+Is about 4: 1.
FIG. 3C is an XPS peak for O1s, 529.231eV is assigned to vacancy oxygen e OlattThe peak of 530.966eV belongs to surface active oxygen OsurfaceAnd the peak of 532.654eV belongs to the adsorption of molecular oxygen OadsShows MnCeO provided in this examplexThe metal oxide has a certain amount of vacancy oxygen and surface active oxygen.
Example 2
The true bookThe embodiment provides MnCeOxMetal oxide of the MnCeOxPreparation method of metal oxide and MnCeO provided in example 1xThe preparation methods of the metal oxides are different only in the ultrasonic frequency of the high-frequency ultrasonic radiation, which is 150kHz in this embodiment.
MnCeO provided in this examplexIn the metal oxide, the average particle diameter was 372 nm.
Example 3
The present example provides a MnCeOxMetal oxide of the MnCeOxPreparation method of metal oxide and MnCeO provided in example 1xThe preparation methods of the metal oxides are different only in the ultrasonic frequency of the high-frequency ultrasonic radiation, and the ultrasonic frequency of the high-frequency ultrasonic radiation in the embodiment is 500 kHz.
MnCeO provided in this examplexIn the metal oxide, the average particle diameter was 190 nm.
Example 4
The present example provides a MnCeOxMetal oxide of the MnCeOxPreparation method of metal oxide and MnCeO provided in example 1xThe preparation methods of the metal oxides are different only in the ultrasonic frequency of the high-frequency ultrasonic radiation, which is 105kHz in this embodiment.
MnCeO provided in this examplexIn the metal oxide, the average particle diameter was 408 nm.
Example 5
The present example provides a MnCeOxMetal oxide of the MnCeOxPreparation method of metal oxide and MnCeO provided in example 1xThe preparation methods of the metal oxide are different only in the ultrasonic frequency of the high-frequency ultrasonic radiation, and the ultrasonic frequency of the high-frequency ultrasonic radiation in the embodiment is 800 kHz.
MnCeO provided in this examplexIn the metal oxide, the average particle diameter was 88 nm.
Example 6
The comparative example provides MnCeOxA metal oxide ofMnCeOxPreparation method of metal oxide and MnCeO provided in example 1xThe preparation methods of the metal oxides are different only in the low-frequency ultrasonic irradiation time, which is 13min in the embodiment.
Example 7
The comparative example provides MnCeOxMetal oxide of the MnCeOxPreparation method of metal oxide and MnCeO provided in example 1xThe preparation methods of the metal oxide are different only in the low-frequency ultrasonic irradiation time, which is 17min in the embodiment.
Comparative example 1
The comparative example provides MnCeOxMetal oxide of the MnCeOxThe preparation method of the metal oxide comprises the following steps:
1) 3.95g of KMnO4，7.41g MnCl2And 23.28g CeCl4Dissolving the mixture in 250mL of deionized water to obtain a mixture A, dropwise adding 2mol/L of NaOH solution into the mixture A until the pH value of the mixture is 11, and then stirring the mixture for 15min by using a magnetic heating stirrer to uniformly mix the mixture to obtain a mixture B;
2) and aging the mixture B for 2 hours, centrifuging and washing the aged mixture B (washing the mixture B for 3 times by distilled water), drying the mixture B for 12 hours at 120 ℃, and roasting the dried mixture B for 4 hours at 500 ℃ to obtain the MnCeOx metal oxide.
The MnCeO provided in this example was examinedxThe average particle size of the metal oxide was measured, and it was found that the MnCeOx metal oxide had an average particle size of 102 μm, the CeOx particles had an average particle size of 28nm, and the active material particles were significantly larger than those of example 1.
Comparative example 2
The comparative example provides MnCeOxMetal oxide of the MnCeOxPreparation method of metal oxide and MnCeO provided in example 1xThe preparation methods of the metal oxides are different only in the low-frequency ultrasonic irradiation time, and the low-frequency ultrasonic irradiation is carried out for 10min in the comparative example.
MnCeO provided by the comparative examplexIn the metal oxide, Ce4+/Ce3+Mn ratio of 4.7:14+/Mn3+In a ratio of 2.5: 1.
Comparative example 3
The comparative example provides MnCeOxMetal oxide of the MnCeOxPreparation method of metal oxide and MnCeO provided in example 1xThe preparation methods of the metal oxides are different only in the low-frequency ultrasonic irradiation time, and the comparative example is subjected to low-frequency ultrasonic irradiation for 30 min.
MnCeO provided by the comparative examplexIn the metal oxide, Ce4+/Ce3+Mn ratio of 2.8:14+/Mn3+In a ratio of 2.9: 1.
Experimental example 1
The experimental examples provide MnCeO provided in example 1, example 6, example 7, comparative example 1, comparative example 2, and comparative example 3xThe catalytic performance of the metal oxide is tested, and the specific test is as follows:
the capability of the catalyst to be tested in catalyzing hydrogen peroxide to oxidize dye wastewater is tested, the reaction is carried out at room temperature, the concentration of the acid orange 7 pollutant in the dye wastewater is 20mg/L, the pH value of the dye wastewater is 3.5, the adding amount of the hydrogen peroxide is 40mg/L and the adding amount of the catalyst is 1.0g/L based on the dye wastewater.
Using MnCeO as provided in example 1xThe metal oxide catalyzes hydrogen peroxide to oxidize dye wastewater, and the removal rate of acid orange 7 is 86%; MnCeO provided in example 6xThe metal oxide catalyzes hydrogen peroxide to oxidize dye wastewater, and the removal rate of acid orange 7 is 78%; MnCeO provided in example 7xThe metal oxide catalyzes hydrogen peroxide to oxidize dye wastewater, and the removal rate of acid orange 7 is 76%; using MnCeO as provided in comparative example 1xThe metal oxide catalyzes hydrogen peroxide to oxidize dye wastewater, and the removal rate of acid orange 7 is 58%; using MnCeO as provided in comparative example 2xThe metal oxide catalyzes hydrogen peroxide to oxidize dye wastewater, and the removal rate of acid orange 7 is 63%; using MnCeO as provided in comparative example 3xThe metal oxide catalyzes hydrogen peroxide to oxidize dye wastewater, and the removal rate of acid orange 7 is 48%.
When the dye wastewater with the pH value of 3.5 contains methyl orange with the concentration of 20mg/L or active violet with the concentration of 20mg/L, the adding amount of hydrogen peroxide is 40mg/L in terms of the dye wastewater under the condition of room temperature,the amount of the catalyst added was 1.0g/L, and MnCeO was provided in examples 1, 6 and 7xThe metal oxide exhibits excellent methyl orange removing ability as well as active violet removing ability.

Claims (13)

1. MnCeOxA method for preparing a metal oxide, wherein the method comprises:
1) dissolving precursors of metal oxide, namely Mn salt and Ce salt, in water to obtain a mixture A, adding a precipitator solution into the mixture A, radiating the mixture A for 13-17min by using low-frequency ultrasonic waves, and then carrying out catalytic oxidation to obtain a mixture B; the frequency of the low-frequency ultrasound is 20kHz-48 kHz;
2) solid-liquid separation, drying and roasting of the mixture B to obtain the MnCeOxA metal oxide.
2. The preparation method according to claim 1, wherein the time of the low-frequency ultrasonic radiation is 15 min; the frequency of the low-frequency ultrasound is 20-40 kHz.
3. The production method according to claim 1, wherein the concentration of the Mn salt in the mixture a is 0.1 to 0.4mol/L based on the volume of the mixture a; the concentration of Ce salt in the mixture A is 0.1-0.4 mol/L; preferably, the molar ratio of Mn in the Mn salt to Ce in the Ce salt is 1: 1.
4. The method of claim 1, wherein the Mn salt comprises a divalent Mn salt and KMnO4At least one of; preferably, the divalent Mn salt is MnCl2；
The Ce salt comprises CeCl4；
The precipitant comprises at least one of NaOH and KOH; preferably, the precipitant is 0.5-2mol/L alkali solution, more preferably 1mol/L.
5. The production method according to claim 1 or 4, wherein the concentration of the precipitant in the precipitant solution is 0.5 to 2 mol/L; preferably 1 mol/L;
the amount of precipitant solution used is such that the precipitant solution is added to mixture A until the pH of the mixture is 11.
6. The production method according to claim 1, wherein before performing solid-liquid separation, the mixture B is subjected to an aging treatment during which high-frequency ultrasonic radiation is continuously applied; wherein the frequency of the high-frequency ultrasound is 100-800 kHz;
preferably, the time for applying the high-frequency ultrasonic radiation is 45min-4 h; more preferably 45 min.
7. The preparation method according to claim 1, wherein the preparation method comprises the following specific steps:
1) dissolving precursors of metal oxide, namely Mn salt and Ce salt, in water to obtain a mixture A, dropwise adding a precipitator solution into the mixture A until the pH value of the mixture of the Mn salt and the Ce salt is 11, and then performing catalytic oxidation by using low-frequency ultrasonic radiation of 20kHz-40kHz for 15min to obtain a mixture B;
wherein the molar ratio of Mn in the Mn salt to Mn in the Ce salt is 1: 1; the concentration of Mn salt in the mixture A is 0.1-0.4 mol/L; the concentration of Ce salt in the mixture A is 0.1-0.4 mol/L; the concentration of the precipitant in the precipitant solution is 1 mol/L;
the Mn salt is MnCl2And KMnO4At least one of; the Ce salt is CeCl2(ii) a The precipitator is NaOH;
2) aging the mixture B for 45min, continuously applying 100-800kHz high-frequency ultrasonic radiation during the aging treatment, and performing solid-liquid separation, drying and roasting on the aged mixture B to obtain the MnCeOxA metal oxide.
8. The production method according to claim 1 or 7, wherein the MnCeO produced is controlled by controlling the frequency of the high-frequency ultrasound while applying the high-frequency ultrasound radiationxAverage particle diameter of metal oxide:
when the frequency of the high-frequency ultrasound is controlled to be not less than 100kHz, the prepared MnCeOxThe average particle diameter of the metal oxide is not largeAt 420 nm;
when the frequency of the high-frequency ultrasound is controlled to be not less than 200kHz, the prepared MnCeOxThe average particle size of the metal oxide is not more than 300 nm;
when the frequency of the high-frequency ultrasound is controlled to be not lower than 300kHz, the prepared MnCeOxThe average particle size of the metal oxide is not more than 270 nm;
when the frequency of the high-frequency ultrasound is controlled to be not less than 500kHz, the prepared MnCeOxThe average particle size of the metal oxide is not more than 190 nm;
when the frequency of the high-frequency ultrasound is controlled to be not less than 800kHz, the prepared MnCeOxThe average particle size of the metal oxide is not more than 90 nm;
preferably, the prepared MnCeO is subjected to ultrasonic treatment when the frequency of the high-frequency ultrasonic is controlled to be 100-200kHzxThe average particle size of the metal oxide is 420nm-300 nm; when the frequency of the high-frequency ultrasonic is controlled at 200-300kHz, the prepared MnCeOxThe average particle size of the metal oxide is 300nm-270 nm; when the frequency of the high-frequency ultrasonic is controlled at 300-500kHz, the prepared MnCeOxThe average grain diameter of the metal oxide is 270nm-190 nm; when the frequency of the high-frequency ultrasonic is controlled at 500-800kHz, the prepared MnCeOxThe average particle size of the metal oxide is 190nm-90 nm;
more preferably, MnCeO is prepared while controlling the frequency of the high frequency ultrasound at 100kHzxThe average particle size of the metal oxide is 420 nm; when the frequency of the high-frequency ultrasound is controlled at 200kHz, the prepared MnCeOxThe average particle size of the metal oxide is 300 nm; when the frequency of the high-frequency ultrasound is controlled at 300kHz, the prepared MnCeOxThe average particle size of the metal oxide is 270 nm; when the frequency of the high-frequency ultrasound is controlled at 500kHz, the prepared MnCeOxThe average particle size of the metal oxide is 190 nm; when the frequency of the high-frequency ultrasound is controlled at 800kHz, the prepared MnCeOxThe average particle diameter of the metal oxide was 90 nm.
9. The production method according to claim 1 or 7, wherein the intensity of the low-frequency ultrasound is 3.0-12W/cm2(ii) a Preferably 3.0-8.0W/cm2。
10. The production method according to claim 6 or 7, wherein the intensity of the high-frequency ultrasound is 0.5 to 1.5W/cm2。
11. The production method according to claim 1 or 7, wherein the temperature of the firing is 500 ℃; the roasting time is 4-12 h.
12. The MnCeOx metal oxide prepared by the preparation method according to any one of claims 1 to 11, wherein the MnCeOxCe of metal oxide4+And Ce3+In a ratio of 3-4:1, Mn4+With Mn3+In a ratio of 1.7-2.4: 1.
13. The MnCeO of claim 12xA metal oxide, wherein the MnCeOxThe average particle size of the metal oxide is not more than 420 nm;
preferably, the average particle size is not greater than 300 nm;
more preferably, the average particle size is not greater than 270 nm;
further preferably, the average particle size is not more than 190 nm;
still more preferably, the average particle size is not greater than 90 nm.
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CN114797841A (en) * 2022-03-24 2022-07-29 绍兴文理学院 Mn (manganese) 4+ And Ce 3+ Preparation method of enhanced Mn-M-Ti-O ultralow-temperature denitration catalyst

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