The preparation method of perovskite type metal oxide catalyst
Technical field
The present invention relates to catalyst technical field, is the preparation method about a kind of perovskite type metal oxide catalyst.
Background technology
The perovskite type metal oxide catalyst material has that cost is low, catalytic activity is high, raw material obtain easily and advantage such as reserves are abundant, has a wide range of applications in industries such as electrochmical power source, electrolysis, tail gas (waste gas) processing, chemical industry.
The preparation method of perovskite type metal oxide catalyst mainly contains the acetate decomposition method, and as document G.Karlsson.J.Power Sources, 1983 (10): 319 is described; Coprecipitation, as document J.O ' M.Bockris, the T.Ottagawa. U.S. Pat: 4497698,1985 is described; Precursor process etc.Wherein, precursor process has tangible advantage and has caused numerous researchers' attention.This method is the earliest by Richard, J.Brook.MaterialsSciences and Technology, and 1967 (17A): 82 propose.Be characterized in adopting complexing agent to add the amorphous presoma that forms complexing in the metal salt solution to, further heat treated generates thin oxide powder at last.The advantage of this method is the stoichiometric proportion that can be good at controlling metal ion.In research process, Chinese scholars has proposed many acid to be helped improving one's methods of method, as document R.E.Carbonio, C.Fierro, D.Tryk, E.Yeager. power technology (J.Power SourceS), 1988 (22): 387 and Zhou Zhentao, Yu Dongsheng. Chinese patent application CN:1529374A, 2003 is described, mainly comprises the adjustment of complexing agent addition and the kind of change complexing agent agent etc.But these methods generally need roasting at high temperature when the preparation perovskite type metal oxide catalyst, then prepared catalyst granules is easy to assemble, and forms bigger particle, and this has directly influenced the catalytic activity of catalyst, and its performance remains further to be improved.
Therefore in the prior art, need provide a kind of and stop or weaken in heat treatment formation catalyst process, catalyst granules is assembled the preparation method who grows up.
Summary of the invention
The objective of the invention is to:, provide a kind of preparation method of perovskite type metal oxide catalyst for overcoming the deficiencies in the prior art.The present invention be a kind of stop or weaken in roasting form in the process of perovskite type metal oxide catalyst, catalyst granules is assembled the preparation method who grows up, obtain having the perovskite type metal oxide catalyst of high specific surface area, thereby improve the catalytic activity of catalyst.This is that its specific area is big more because as catalyst, and then the catalytic reaction activity position in unit volume (unit mass) catalyst is many more, and its catalytic activity will be high more.
Technical scheme of the present invention is:
The perovskite type metal oxide catalyst general formula that the present invention is used to prepare is A
1-xB
xC
1-yD
yO
3, in the formula, A is a thulium, and B is an alkali earth metal, and C represents different or identical transition metal with D, is generally iron, cobalt, nickel, manganese, copper; 0≤x≤1,0≤y≤1.
The preparation method of the perovskite type metal oxide catalyst that the present invention proposes may further comprise the steps:
1. according to the composition of the perovskite type metal oxide catalyst material of need preparations, the salt of required metallic element by the stoichiometry mixed in molar ratio of determining, is added deionized water dissolving and obtains dissolving mixt.The salt of wherein said metallic element is one or more mixture of nitrate, malate, propionate, oxalates, tartrate, alicyclic ring hydrochlorate, acetate, high polymer salt, soap, fragrant hydrochlorate.
2. add the dissolving mixt that a certain amount of complexing agent obtains complexing in the dissolving mixt that obtains in step 1, the mol ratio of complexing agent and metal ion summation is 0.5-10.Wherein said complexing agent is one or more the mixture in ethylenediamine tetra-acetic acid, sulfosalicylic acid, lactic acid, hydroxybenzoic acid, tartaric acid, the acid of horse Lay, citric acid, malic acid, salicylic acid, nitrilotriacetic acid, glycolic acid, diethyl three ammonia pentaacetic acids, glycine, tyrosine, lysine, glutamic acid, aspartic acid, ethylene glycol, propane diols, glycerine, butanediol, the pentanediol.Carry out the 3rd following step then, also can skip for the 3rd step and directly carry out for the 4th step.
3. add one or more mixture in carbonic hydroammonium, ammonium acetate, ammonium carbonate, the ammonium nitrate in the dissolving mixt of the complexing that in step 2, obtains as auxiliary additive, obtain containing the dissolving mixt of the complexing of auxiliary additive.Carry out the 4th following step then, also can skip for the 4th step and directly carry out for the 5th step.
4. the pH value with the dissolving mixt of the complexing that obtains in ammoniacal liquor regulating step 2 or the step 3 is 1-7.
5. add a certain amount of powdered carbon and/or CNT in the dissolving mixt of the complexing that in step 2, step 3 or step 4, obtains and mix, obtain powdered carbon and/or carbon nano tube-doped colloidal sol.The mass ratio of powdered carbon and/or CNT and slaine summation is 0.1-20.Wherein said powdered carbon be can be under 400-1000 ℃, oxygen or air atmosphere the powdered carbon of combustion decomposition.Wherein said CNT be can be under 400-1000 ℃, oxygen or air atmosphere the carbon nanotube powder of combustion decomposition.
6. the powdered carbon that obtains in the step 5 and/or carbon nano tube-doped colloidal sol are obtained preparing perovskite type metal oxide catalyst at 50-270 ℃ of following drying and dehydrating presoma.
With the presoma that obtains in the step 6 in air or oxygen atmosphere in 400-1000 ℃ of following roasting 20-720 minute, cool off the roasting afterproduct just obtains having the Ca-Ti ore type crystalline structure to room temperature metal oxide catalyst then.
The invention has the beneficial effects as follows:
1. employing the technology of the present invention, the heated oxide reaction that can make component metals salt be converted into perovskite type metal oxide catalyst is evenly carried out, and can effectively stop or weaken the gathering that forms catalyst granules in the process of catalyst in roasting and grow up, thereby obtain the less and evengranular form of particle diameter catalyst preferably.
2. employing the technology of the present invention can be prepared the perovskite type metal oxide catalyst with high specific surface area.Higher specific surface area makes prepared catalyst have advantages of high catalytic activity, thereby has using value preferably.
3. therefore the perovskite type metal oxide catalyst that adopts the technology of the present invention preparation can reduce the consumption of eelctro-catalyst in actual applications because of having the reactivity of raising, reduces cost.
4. raw materials usedly in the technology of the present invention obtain easily, cheap, this makes the cost of whole process of preparation lower.
5. adopt the technology of the present invention to prepare perovskite type metal oxide catalyst, the product purity height, method is easy, control easily, good reproducibility is easy to amplify, and helps reducing preparation cost, and this industrialization for preparation process is significant.
Description of drawings
Fig. 1 is X-ray diffraction (XRD) spectrogram of the prepared perovskite type metal oxide catalyst of embodiment 1.
Fig. 2 is the SEAD photo of the prepared perovskite type metal oxide catalyst of embodiment 2.
Fig. 3 carries out the extensive scan cycle volt-ampere spectrum of 60 circulations for embodiment 4 prepared perovskite type metal oxide catalysts.
The specific embodiment
The invention provides a kind of preparation method of perovskite type metal oxide catalyst.Detailed preparation process is described the face summary of the invention part of seing before.Below further set forth the present invention with embodiment.But these embodiment only are used for explanation, and do not mean that in any form the scope of the invention is limited.
Embodiment 1
By stoichiometry mol ratio La: Ca: Co takes by weighing lanthanum nitrate, calcium acetate, cobalt oxalate at 3: 2: 5, adds in the beaker and fully dissolves with deionized water.Citric acid in molar ratio then: metal ion summation=0.5 adds the dissolving mixt that citric acid complexing agent obtains complexing.In the dissolving mixt of complexing, add a certain amount of acetylene black and mix, obtain the colloidal sol that acetylene black is mixed.The addition of acetylene black is pressed acetylene black: calculate the mass ratio of slaine summation=0.1.The colloidal sol that acetylene black is mixed obtains presoma at 265 ℃ of following drying and dehydratings.With this presoma in air atmosphere in 450 ℃ of following roastings 720 minutes, cool off roasting afterproduct to room temperature then and just obtain metal oxide catalyst.
Fig. 1 is X-ray diffraction (XRD) spectrum of prepared metal oxide catalyst.Through checking relatively proof with standard x RD spectrogram, the crystalline structure of resulting catalyst is the Ca-Ti ore type crystalline structure.And except that characteristic diffraction peak, not name assorted peak appearance in the drawings, interpret sample purity height does not have impurity.This explanation adopts the inventive method can prepare pure perovskite type metal oxide catalyst.
Embodiment 2
By stoichiometry mol ratio Pr: Ca: Mn: Fe is 2: 8: 1: 9 take by weighing praseodymium nitrate, calcium malate, manganese oxalate, propionic acid iron, add in the beaker fully to dissolve with deionized water.(tartaric acid+horse Lay acid+propane diols) then in molar ratio: metal ion summation=10 add (tartaric acid+horse Lay acid+propane diols) mixed twine mixture, obtain the dissolving mixt of complexing, and tartaric acid, the acid of horse Lay, propane diols volume ratio are 1: 5: 7.Add the carbonic hydroammonium auxiliary additive in the dissolving mixt of complexing, the stoichiometry mol ratio of auxiliary additive and slaine is 0.15, obtains containing the dissolving mixt of the complexing of auxiliary additive.The pH value of regulating the dissolving mixt of the complexing that contains auxiliary additive with ammoniacal liquor is about 1.In the dissolving mixt of complexing, add a certain amount of Peal blackberry then and mix and obtain the colloidal sol that Peal blackberry mixes.The addition of Peal blackberry is pressed Peal blackberry: calculate the mass ratio of slaine summation=10.The colloidal sol that Peal blackberry is mixed obtains presoma at 200 ℃ of following drying and dehydratings.With this presoma in oxygen atmosphere in 900 ℃ of following roastings 120 minutes, cool off roasting afterproduct to room temperature then and just obtain perovskite type metal oxide catalyst.
With the prepared perovskite type metal oxide catalyst of transmission electron microscope observation as can be known, the size of catalyst granules is between the 40-100 nanometer, and is in the majority with the crystal grain of 60-70 nanometer, and the ratio of accounting for is 80%.Fig. 2 is the SEAD figure of prepared perovskite type metal oxide catalyst.As can be seen from the figure, diffraction spot is clear, regular, and this has just reflected the electronic diffraction character of nano material, and shows that prepared electrocatalyst materials is a mono-crystalline structures.
This explanation employing the inventive method can be prepared has nano-scale particle, perovskite type metal oxide catalyst that particle diameter is evenly distributed, pure.
Embodiment 3
By stoichiometry mol ratio Ce: Ba: Cu: Mn is 8: 2: 3: 7 take by weighing cerous nitrate, barium nitrate, copper nitrate, manganese tartrate, add in the beaker fully to dissolve with deionized water.(ethylenediamine tetra-acetic acid+malic acid+ethylene glycol) then in molar ratio: metal ion summation=5 add (ethylenediamine tetra-acetic acid+malic acid+ethylene glycol) mixed twine mixture, obtain the dissolving mixt of complexing, ethylenediamine tetra-acetic acid, malic acid, ethylene glycol volume ratio are 2: 1: 1.Add (ammonium acetate+ammonium carbonate) auxiliary additive in the dissolving mixt of complexing, obtain containing the dissolving mixt of the complexing of auxiliary additive, the stoichiometry mol ratio of auxiliary additive and slaine is 29, and ammonium acetate, ammonium carbonate mass ratio are 4: 1.In the dissolving mixt of complexing, add a certain amount of carbon black then and mix and obtain the colloidal sol that carbon black mixes.The addition of carbon black is pressed carbon black: calculate the mass ratio of slaine summation=20.The colloidal sol that carbon black is mixed obtains presoma at 55 ℃ of following drying and dehydratings.With this presoma in oxygen atmosphere in 1000 ℃ of following roastings 20 minutes, cool off roasting afterproduct to room temperature then and just obtain perovskite type metal oxide catalyst.
Adopt the specific area of the prepared perovskite type metal oxide catalyst of BET method test, it has bigger specific area as a result, reaches 20.6m
2/ g.
Embodiment 4
By stoichiometry mol ratio La: Sr: Co: Ni is 8: 2: 6: 4 take by weighing lanthanum nitrate, strontium nitrate, cobalt oxalate, nickel acetate, add in the beaker fully to dissolve with deionized water.(ethylenediamine tetra-acetic acid+glycerine+butanediol) then in molar ratio: metal ion summation=1 adds (ethylenediamine tetra-acetic acid+glycerine+butanediol) mixed twine mixture, obtain the dissolving mixt of complexing, ethylenediamine tetra-acetic acid, glycerine, butanediol volume ratio are 0.5: 1: 5.Add the carbonic hydroammonium auxiliary additive in the dissolving mixt of complexing, obtain containing the dissolving mixt of the complexing of auxiliary additive, the stoichiometry mol ratio of auxiliary additive and slaine is 10.The pH value of regulating the dissolving mixt of complexing with ammoniacal liquor is about 7.In the dissolving mixt of complexing, add the certain quantity of carbon nanometer pipe powder then and mix and obtain carbon nano tube-doped colloidal sol.The addition of CNT is pressed CNT: calculate the mass ratio of slaine summation=5.Carbon nano tube-doped colloidal sol is obtained presoma at 100 ℃ of following drying and dehydratings.With this presoma in air atmosphere in 800 ℃ of following roastings 500 minutes, cool off roasting afterproduct to room temperature then and just obtain perovskite type metal oxide catalyst.
Adopt microelectrode cyclic voltammetric method to characterize the electrocatalysis characteristic of prepared perovskite type metal oxide catalyst.The load amount of the perovskite type metal oxide catalyst in the experiment on the microelectrode is 0.072mg.The wide scope of cyclic voltammetry scan in the experiment, generally between-0.7V-0.8V, the scanning upper limit surpasses oxygen evolution potential, and electrolyte is 1MKOH solution.Probe temperature is 25 ℃, and sweep speed is 100mV/s, scans the stability of 60 weeks with the test eelctro-catalyst.
Fig. 3 has provided the extensive scan cycle volt-ampere spectrum of 60 circulations of perovskite type metal oxide catalyst.As can be seen, the multi-turn scanning curve is except that the initial initialization of several circles corresponding to catalyst, and all the other all reach stable state and overlap.From the state of superimposed curves, the distribution of curve is narrow, shows that the reaction of carrying out on catalyst remains unchanged substantially, this means that the performance of catalyst in cyclic process is constant substantially.Among the figure corresponding to the peak point current of analysing the oxygen peak through still almost completely consistent after the multi-turn circulation and do not reduce, and the take-off potential at this peak also remains unchanged, and also almost constant in cyclic process corresponding to the peak of oxygen reduction reaction, this shows that prepared perovskite type metal oxide catalyst has very advantages of higher stability.As seen from the figure, analyse the oxygen take-off potential and have very low value, be 0.576V, the low oxygen take-off potential of analysing shows that prepared perovskite type metal catalyst has good catalytic activity.
Above presentation of results adopts the technology of the present invention can prepare the perovskite type metal oxide catalyst with higher catalytic activity.
The comparison of the present invention and correlation technique
Comparative example 1
By stoichiometry mol ratio La: Ca: Co: Fe is 7: 3: 9: 1 takes by weighing lanthanum nitrate, calcium oxalate, cobalt nitrate, ferric acetate, adds in the beaker fully to dissolve with deionized water.(citric acid+butanediol) then in molar ratio: metal ion summation=1 adds (citric acid+butanediol) mixed twine mixture, obtains the dissolving mixt of complexing, and citric acid, butanediol volume ratio are 1: 2.The pH value of regulating the dissolving mixt of complexing with ammoniacal liquor is about 5.In the dissolving mixt of complexing, add the certain quantity of carbon nanometer pipe powder then and mix and obtain carbon nano tube-doped colloidal sol.The addition of CNT is pressed CNT: calculate the mass ratio of slaine summation=0.6.Carbon nano tube-doped colloidal sol is obtained presoma at 110 ℃ of following drying and dehydratings.With this presoma in air atmosphere in 700 ℃ of following roastings 240 minutes, cool off roasting afterproduct to room temperature then and just obtain perovskite type metal oxide catalyst.This catalyst is defined as the 1# catalyst.
Except in the dissolving mixt of complexing, not adding the certain quantity of carbon nanometer pipe powder, adopt and prepare perovskite type metal oxide catalyst with the identical step of above-mentioned process.This catalyst is defined as the 2# catalyst.
Adopt the specific area of two kinds of prepared catalyst of BET method test, test result is as shown in table 1.More as can be known, the prepared 1# catalyst of the inventive method has bigger specific area, has improved 66.5% than the specific area of the 2# catalyst of conventional method preparation.
High specific area means more surface-active position, thereby means higher catalytic activity.This explanation adopts the prepared perovskite type metal oxide catalyst technical indicator of the inventive method significantly to improve.
Table 1
| 1# | 2# |
Perovskite type metal oxide catalyst specific area (m
2/m)
| 28.3 | 17.0 |