Preparation method of supported dimer heteropoly acid quaternary ammonium salt catalyst
阅读说明：本技术 一种负载型二聚体杂多酸季铵盐催化剂的制备方法 (Preparation method of supported dimer heteropoly acid quaternary ammonium salt catalyst ) 是由 薛莹雪 李文亮 韩丽琴 于 2021-01-11 设计创作，主要内容包括：一种负载型二聚体杂多酸季铵盐催化剂的制备方法,是以Na-2WO-4·2H-2O、Na-2HPO-4和Fe(NO-3)-3·9H-2O作为原料制备杂多酸盐溶液,以纳米二氧化硅(SiO-2)作为载体溶解于去离子水中,升温至50～70℃,搅拌后静置60～80min形成胶体溶液,然后边搅拌边滴加溴化十六烷基吡啶形成混合液,再边搅拌边滴加杂多酸盐溶液,滴加完成后加入碳酸氢钠调节pH至4～4.8,持续搅拌1～2h形成[C-(21)H-(38)N]-(10)[(PW-(11)FeO-(39))-2O]/SiO-2,最后过滤后洗涤、干燥。本发明制备的负载型催化剂中[C-(21)H-(38)N]-(10)[(PW-(11)FeO-(39))-2O]在SiO-2表面和孔道高效、均匀负载,结合力强,催化过程不易脱落,具有优异的催化性能,催化H-2O-2氧化苯甲醇制备苯甲醛的转化率达到96.7%,苯甲醛的选择性达到92.9%,本发明制备催化剂[C-(21)H-(38)N]-(10)[(PW-(11)FeO-(39))-2O]/SiO-2参与催化反应后回收率高,重复使用5次后回收率依然达到95%以上。(A process for preparing the supported dimer heteropoly acid quaternary ammonium salt catalyst uses Na 2 WO 4 ·2H 2 O、Na 2 HPO 4 And Fe (NO) 3 ) 3 ·9H 2 O as raw material to prepare heteropoly acid salt solution, and nanometer silicon dioxide (SiO) 2 ) Dissolving the carrier in deionized water, heating to 50-70 ℃, stirring, standing for 60-80 min to form a colloidal solution, and then dropwise adding cetylpyridinium bromide while stirringForming mixed liquor by pyridine, dropwise adding heteropoly acid salt solution while stirring, adding sodium bicarbonate after dropwise adding to adjust the pH to 4-4.8, and continuously stirring for 1-2 h to form [ C ] 21 H 38 N] 10 [(PW 11 FeO 39 ) 2 O]/SiO 2 And finally, filtering, washing and drying. In the supported catalyst prepared by the invention, [ C ] 21 H 38 N] 10 [(PW 11 FeO 39 ) 2 O]In SiO 2 The surface and the pore channel are efficiently and uniformly loaded, the binding force is strong, the catalyst is not easy to fall off in the catalytic process, the catalyst has excellent catalytic performance and can catalyze H 2 O 2 The conversion rate of the benzaldehyde prepared by oxidizing the benzyl alcohol reaches 96.7 percent, the selectivity of the benzaldehyde reaches 92.9 percent, and the catalyst [ C ] prepared by the invention 21 H 38 N] 10 [(PW 11 FeO 39 ) 2 O]/SiO 2 The recovery rate is high after the catalyst participates in catalytic reaction, and the recovery rate still reaches more than 95 percent after the catalyst is repeatedly used for 5 times.)
1. A preparation method of a supported dimer heteropoly acid quaternary ammonium salt catalyst is characterized in that: is Na2WO4·2H2O、Na2HPO4And Fe (NO)3)3·9H2O as raw material for preparing heteropoly acid salt solution and nano silicon dioxide (SiO)2) Cetylpyridinium bromide (C) as a Carrier21H38NBr) and heteropolyacid salt on a carrier while synthesizing and loading to form [ C ]21H38N]10[(PW11FeO39)2O]/SiO2(ii) a The load during synthesis is that the nano silicon dioxide is dissolved in deionized water, the temperature is raised to 50-70 ℃, the mixture is stirred and then stands for 60-80 min to form a colloidal solution, then cetyl pyridine bromide is dropwise added while stirring to form a mixed solution, a heteropoly acid salt solution is dropwise added while stirring, after the dropwise addition is completed, sodium bicarbonate is added to adjust the pH value to 4-4.8, the stirring is continued for 1-2 h, and finally, the mixture is filtered, washed and dried.
2. The process for preparing a supported dimeric heteropolyacid quaternary ammonium salt catalyst as claimed in claim 1, wherein: the mass-volume ratio of the nano silicon dioxide to the deionized water is 1-5 g: 50-65 mL, stirring speed of 100-150 rpm, and stirring time of 10-30 min.
3. A process for the preparation of a supported dimeric heteropolyacid quaternary ammonium salt catalyst as claimed in claim 1 or 2, wherein: the mass ratio of the cetylpyridinium bromide to the nano silicon dioxide is 0.16-0.185: 1.
4. a process for the preparation of a supported dimeric heteropolyacid quaternary ammonium salt catalyst as claimed in any of claims 1-3, wherein: the mass ratio of the heteropoly acid salt to the cetyl pyridinium bromide is 1:5, the drop acceleration of the heteropoly acid salt solution is 0.08-0.15 mL/min, and the stirring speed is 20-30 rpm.
5. The method of claim 4A preparation method of a supported dimer heteropoly acid quaternary ammonium salt catalyst is characterized in that: the preparation of the heteropoly acid salt solution is to mix Na2WO4·2H2Adding O into deionized water, stirring to dissolve to form solution A, adding Na into solution A2HPO4Continuously stirring and mixing at 40-60 ℃ to form a solution B, heating the solution B to 85-90 ℃, preserving heat for 40-70 min, dropwise adding concentrated nitric acid to adjust the pH to 4.5-5, preserving heat for 20-40 min, and finally dropwise adding Fe (NO)3)3·9H2And (4) O solution.
6. The process for preparing a supported dimeric heteropolyacid quaternary ammonium salt catalyst as claimed in claim 5, wherein: the Na is2WO4·2H2The mass-volume ratio of O to deionized water is 5-8 g:100mL, Na2WO4·2H2O、Na2HPO4And Fe (NO)3)3·9H2The mass ratio of O is 11:1: 1-1.3.
7. A preparation method of a supported dimer heteropoly acid quaternary ammonium salt catalyst is characterized by comprising the following steps:
1. preparation of heteropolyacid salt solutions
Mixing Na2WO4·2H2Adding O into deionized water according to the mass-volume ratio of 5-8 g to 100mL, stirring and dissolving to form a solution A, and adding Na into the solution A2HPO4Continuously stirring and mixing at 40-60 ℃ to form a solution B, heating the solution B to 85-90 ℃, preserving heat for 40-70 min, dropwise adding concentrated nitric acid to adjust the pH to 4.5-5, preserving heat for 20-40 min, and finally dropwise adding Fe (NO)3)3·9H2Solution of O prepared, Na2WO4·2H2O、Na2HPO4And Fe (NO)3)3·9H2The mass ratio of O is 11:1: 1-1.3;
2. preparation of Supported catalysts
(1) And (3) mixing nano silicon dioxide and deionized water in a mass-volume ratio of 1-5 g: heating 50-65 mL of the mixture to 50-70 ℃, stirring at 100-150 rpm for 10-30 min, and standing for 60-80 min;
(2) dropwise adding cetylpyridinium bromide while stirring the solution formed in the step (1) at 20-30 rpm, continuously stirring for 60-80 min to form a mixed solution after adding, then dropwise adding a heteropoly acid salt solution at the speed of 0.08-0.15 mL/min while continuously stirring, adding sodium bicarbonate to adjust the pH to 4-4.8 after dropwise adding, continuously stirring for 1-2 h, wherein the mass ratio of the cetylpyridinium bromide to the nano-silica is 0.16-0.185: 1, and the heteropoly acid salt Na is4PW11Fe(H2O)O39And cetylpyridinium bromide in a 1:5 mass ratio;
(3) and (3) after the reaction in the step (2) is finished, filtering out solid matters, sequentially washing in distilled water and ethyl acetate solution for 2-4 times respectively, and then drying for 6-8 hours at the temperature of 70-80 ℃ and under-90 KPa.
Technical Field
The invention relates to the technical field of catalysts, in particular to a preparation method of a supported dimer heteropoly acid quaternary ammonium salt catalyst.
Background
The heteropoly acid quaternary ammonium salt is formed by compounding heteropoly acid and quaternary ammonium salt, consists of counter ions and heteropolyanions, is a novel excellent acid catalyst and redox catalyst for phase transfer, has strong acidity and redox performance, a determined structure, certain electron and proton transfer/storage capacity and good thermal stability, is easy to dissolve in water and organic solvents, can be loaded on substances such as silica gel or active carbon and the like, shows high catalytic capacity and selectivity, and can modify or modify heteropoly acid salts to change the structure and the composition of heteropoly acid quaternary ammonium salt so as to change the catalytic performance of heteropoly acid quaternary ammonium salt. In recent years, synthesis, characterization and catalytic performance of Fe-substituted heteropoly acid salts with different structures are reported, the catalytic performance of Fe-substituted Keggin type heteropoly acid quaternary ammonium salt with a dimer structure is higher than that of single-polymer heteropoly acid quaternary ammonium salt, after the heteropoly acid quaternary ammonium salt with the dimer structure is immobilized, a catalyst can be effectively separated from a reaction medium in reactions such as liquid-phase oxidation, acid catalysis and the like, the homogeneous catalysis reactions can be heterogenized to realize effective recovery of the catalyst, the specific surface area of the catalyst is increased, and the mechanical strength and the thermal stability of the catalyst are enhanced.
However, the problem faced in the prior art for preparing supported heteropolyacid quaternary ammonium salt is that in the loading process, because dimer heteropolyacid quaternary ammonium salt has poor solubility, the dimer heteropolyacid quaternary ammonium salt cannot be completely dissolved in water and organic solvent, so that the loading is difficult, the dimer is agglomerated and stacked on the carrier, so that the catalytic activity is reduced, the binding force between the supported dimer heteropolyacid quaternary ammonium salt and the carrier is poor, so that the dimer heteropolyacid quaternary ammonium salt falls off from the carrier in the catalytic process, the dimer structure has poor stability, and the dimer heteropolyacid quaternary ammonium salt is easy to decompose into a single polymer structure in the catalytic process, so that the recovery rate and the catalytic performance after recovery are not high.
Disclosure of Invention
The invention aims to provide a supported dimer heteropoly acid quaternary ammonium salt catalyst [ C ]21H38N]10[(PW11FeO39)2O]/SiO2The prepared dimer heteropoly acid quaternary ammonium salt has excellent stability, excellent binding force with a carrier, excellent catalytic performance and easy recovery.
The purpose of the invention is realized by the following technical scheme:
a preparation method of a supported dimer heteropoly acid quaternary ammonium salt catalyst is characterized in that: with Na2WO4·2H2O、Na2HPO4And Fe (NO)3)3·9H2O as raw material for preparing heteropoly acid salt solution and nano silicon dioxide (SiO)2) Cetylpyridinium bromide (C) as a Carrier21H38NBr) and heteropolyacid salt on a carrier while synthesizing and loading to form [ C ]21H38N]10[(PW11FeO39)2O]/SiO2(ii) a The load during synthesis is that the nano silicon dioxide is dissolved in deionized water, the temperature is raised to 50-70 ℃, the mixture is stirred and then stands for 60-80 min to form a colloidal solution, then cetyl pyridine bromide is dropwise added while stirring to form a mixed solution, a heteropoly acid salt solution is dropwise added while stirring, after the dropwise addition is completed, sodium bicarbonate is added to adjust the pH value to 4-4.8, the stirring is continued for 1-2 h, and finally, the mixture is filtered, washed and dried.
As is known in the art, the synthesis of the quaternary ammonium salt after the reaction with the heteropolyacid salt is a monomer structure, and the heteropolyacid salt Na prepared in the invention4PW11Fe(H2O)O39Contains M-Fe-OH structure, and provides the following dimer formationThe precondition is that two M-Fe-OH structures can be dehydrated to form Fe-O-Fe linkage connection under a weak acid environment to form a dimer structure. If directly mix C21H38The structure stability of the dimer structure generated by the reaction of NBr and the prepared heteropoly acid salt is poor, and the dimer structure is easily decomposed into monomer [ C ] in the catalytic process21H38N]4[PW11Fe(H2O)O39]Resulting in a decrease in activity. Therefore, the method adopts the prior preparation of the heteropoly acid salt Na4PW11Fe(H2O)O39Then reacting with C in the weak acid environment of the nano-silica carrier21H38The NBr reaction is carried out complexation, the pH value of a complexation system is subsequently adjusted, and the two heteropoly acid salt units are promoted to be connected through the Fe-O-Fe bond under the environment to form a stable dimer structure.
The invention firstly leads the nano-silica to form hydrosol colloid, adopts cetylpyridinium bromide as counter cation in the environment of the existence of the nano-silica carrier, firstly enters the nano-silica colloid, on one hand, a cetylpyridinium bromide long carbon chain is wound on the nano-silica hydrosol to form physical winding and fixing, on the other hand, a hydrogen bond is formed between a pyridine group contained in the cetylpyridinium bromide and the nano-silica to enhance chemical bonding force, the cetylpyridinium bromide forms anchoring on the nano-silica hydrosol through the physical and chemical actions, and simultaneously, the cetylpyridinium bromide and the prepared heteropoly acid salt generate complexation to form a dimer structure, the synthesis of the dimer in the system directly occurs on the nano-silica carrier, and the loading of the dimer is completed while synthesizing the dimer, the generated dimer is uniformly dispersed on the surface of the carrier and in the pore channel to form stable load.
According to the invention, cetyl pyridine bromide is used as a counter cation, except for the anchoring effect of a hydrophobic chain and a pyridine group on a nano-silica carrier, the cetyl pyridine bromide has a looser structure after forming a dimer structure with a heteropoly acid salt due to a longer hydrophobic carbon chain, and is more fully contacted with a substrate, and the addition of the pyridine group reduces the crystallization degree of the dimer and improves the amorphous degree of the dimer, so that the specific surface area of the catalyst is increased, the catalytic performance of the catalyst is improved, the stability of the prepared dimer after being loaded on the nano-silica is improved, the dimer is not easy to decompose into a monomer structure in a catalytic reaction, the catalytic performance of the catalyst and the selectivity of a target product are enhanced, meanwhile, the recovery rate of the catalyst is high, and the recovered catalyst can be directly reused.
Further, the mass volume ratio of the nano silicon dioxide to the deionized water is 1-5 g: 50-65 mL, stirring speed of 100-150 rpm, and stirring time of 10-30 min.
Further, the mass ratio of the cetyl pyridinium bromide to the nano silicon dioxide is 0.16-0.185: 1, the dropping speed of the cetyl pyridine bromide is 0.01-0.05 g/min, the stirring speed is 20-30 rpm, and the stirring is continued for 60-80 min after the dropping is finished.
Further, the heteropoly acid salt Na4PW11Fe(H2O)O39The mass ratio of the heteropoly acid salt solution to the cetyl pyridine bromide is 1:5, the drop acceleration of the heteropoly acid salt solution is 0.08-0.15 mL/min, and the stirring speed is 20-30 rpm.
If the control is not good in the process of reaction and loading, the heteropolyacid salt and the cetylpyridinium bromide are not uniformly distributed, some local heteropolyacid salts are more, some local heteropolyacid salts are less, and the heteropolyacid salts are more, and the heteropolyacid salts can not completely react with the cetylpyridinium bromide, a large amount of heteropolyacid salts are directly loaded on the carrier, and the catalyst is accumulated and agglomerated on the surface of the nano silicon dioxide, so that the catalytic activity of the finally prepared supported catalyst can not be ensured. The method comprises the steps of dissolving nano silicon dioxide to form gel colloid, dropwise adding cetylpyridinium bromide at a certain speed under low-speed stirring to uniformly disperse the cetylpyridinium bromide on the surface and in pore channels of the nano silicon dioxide colloid to form fixation, simultaneously not destroying the colloid structure of the nano silicon dioxide, adding heteropoly acid salt in a dropwise adding mode in the slow stirring process, controlling the dropwise adding speed to uniformly disperse the cetylpyridinium bromide in a system, uniformly and fully reacting with the cetylpyridinium bromide, and ensuring that a subsequently formed dimer has excellent dispersibility and does not generate agglomeration accumulation.
Further, the washing and drying are specifically that the filtered solid is washed for 2-4 times by sequentially adopting distilled water and an ethyl acetate solution, and then dried for 6-8 hours at the temperature of 70-80 ℃ and below-90 KPa.
Further, the above-mentioned preparation of the heteropoly acid salt solution is concretely carried out by mixing Na2WO4·2H2Adding O into deionized water, stirring to dissolve to form solution A, adding Na into solution A2HPO4Continuously stirring and mixing at 40-60 ℃ to form a solution B, heating the solution B to 85-90 ℃, preserving heat for 40-70 min, dropwise adding concentrated nitric acid to adjust the pH to 4.5-5, preserving heat for 20-40 min, and finally dropwise adding Fe (NO)3)3·9H2And (4) O solution.
Further, Na as described above2WO4·2H2The mass-volume ratio of O to deionized water is 5-8 g:100mL, Na2WO4·2H2O、Na2HPO4And Fe (NO)3)3·9H2The mass ratio of O is 11:1: 1-1.3.
Further, Fe (NO)3)3·9H2The concentration of the O solution is 0.8mol/L, and the dropping speed is 0.05-0.1 mL/min.
Mixing Fe (NO)3)3·9H2O is prepared into a solution with the concentration of 0.8mol/L, and the solution is dispersed more uniformly in the system by adopting a dripping mode, thereby forming uniform Na4PW11Fe(H2O)O39If the compound is directly added with solid or the adding speed is not properly controlled, other forms of compounds can be formed, the M-Fe-OH structure is reduced, and the formation of the dimer at the later stage is difficult.
Most particularly, the preparation method of the supported dimer heteropoly acid quaternary ammonium salt catalyst is characterized by comprising the following steps:
1. preparation of heteropolyacid salt solutions
Mixing Na2WO4·2H2Adding O into deionized water according to the mass-to-volume ratio of 5-8 g:100mL of the O to the deionized water, stirring and dissolving to form a solution A, and dissolving in the solution AAdding Na2HPO4Continuously stirring and mixing at 40-60 ℃ to form a solution B, heating the solution B to 85-90 ℃, preserving heat for 40-70 min, dropwise adding concentrated nitric acid to adjust the pH to 4.5-5, preserving heat for 20-40 min, and finally dropwise adding Fe (NO)3)3·9H2Solution of O prepared, Na2WO4·2H2O、Na2HPO4And Fe (NO)3)3·9H2The mass ratio of O is 11:1: 1-1.3, Fe (NO)3)3·9H2The concentration of the O solution is 0.8mol/L, and the dropping speed is 0.05-0.1 mL/min;
2. preparation of Supported catalysts
(1) And (3) mixing nano silicon dioxide and deionized water in a mass-volume ratio of 1-5 g: heating 50-65 mL of the mixture to 50-70 ℃, stirring at 100-150 rpm for 10-30 min, and standing for 60-80 min;
(2) adding cetylpyridinium bromide into the solution formed in the step (1) at a speed of 0.01-0.05 g/min while stirring at 20-30 rpm, continuously stirring for 60-80 min after the addition is finished to form a mixed solution, then dropwise adding a heteropoly acid salt solution at a speed of 0.08-0.15 mL/min while continuously stirring, adding sodium bicarbonate after the dropwise adding is finished to adjust the pH to 4-4.8, continuously stirring for 1-2 h, wherein the mass ratio of the cetylpyridinium bromide to the nano-silica is 0.16-0.185: 1, and the heteropoly acid salt Na is4PW11Fe(H2O)O39And cetylpyridinium bromide in a 1:5 mass ratio;
(3) and (3) after the reaction in the step (2) is finished, filtering out solid matters, washing in distilled water and ethyl acetate solution for 2-4 times respectively in sequence, and then drying for 6-8 hours at the temperature of 70-80 ℃ and under-90 KPa.
The invention has the following technical effects:
the supported dimer heteropoly acid quaternary ammonium salt catalyst [ C ] prepared by the invention21H38N]10[(PW11FeO39)2O]/SiO2Dimer heteropoly acid quaternary ammonium salt [ C21H38N]10[(PW11FeO39)2O]In the nano SiO2The surface and the pore canal are uniformly loaded with the loading capacity of34.8-40.2 wt%, no agglomeration and accumulation, dimer heteropoly acid quaternary ammonium salt and nano SiO2The catalyst has strong binding force, excellent stability, difficult shedding in the catalytic process, excellent catalytic performance and H catalysis, can be effectively applied to solid-liquid catalysis, and can catalyze2O2The conversion rate of the benzaldehyde prepared by oxidizing the benzyl alcohol reaches 96.7 percent, the selectivity of the benzaldehyde reaches 92.9 percent, and the catalyst [ C ] prepared by the invention21H38N]10[(PW11FeO39)2O]/SiO2The recovery rate is high after the catalyst participates in catalytic reaction, the recovery rate still reaches more than 95% after the catalyst is repeatedly used for 5 times, and the catalytic performance still effectively keeps more than 90% after the catalyst is recovered.
Drawings
FIG. 1: [ C ]21H38N]10[(PW11FeO39)2O]/SiO2An infrared spectrum of (1).
FIG. 2: [ C ]21H38N]10[(PW11FeO39)2O]/SiO2Ultraviolet spectrogram.
FIG. 3: [ C ]21H38N]10[(PW11FeO39)2O]/SiO2XRD pattern of (a).
FIG. 4: [ C ]21H38N]10[(PW11FeO39)2O]/SiO2Scanning electron microscope images.
FIG. 5: [ C ]21H38N]10[(PW11FeO39)2O]/SiO2The catalytic activity of p-benzyl alcohol is shown in a graph.
Detailed Description
The present invention is described in detail below by way of examples, it should be noted that the following examples are only for illustrating the present invention and should not be construed as limiting the scope of the present invention, and those skilled in the art can make some insubstantial modifications and adaptations of the present invention based on the above-mentioned disclosure.
Example 1
A preparation method of a supported dimer heteropoly acid quaternary ammonium salt catalyst comprises the following steps:
1. preparation of heteropolyacid salt solutions
Mixing Na2WO4·2H2Adding O into deionized water according to the mass-volume ratio of 5g to 100mL of the deionized water, stirring to dissolve the O to form a solution A, and adding Na into the solution A2HPO4Continuously stirring and mixing at 40 deg.C to obtain solution B, heating to 85 deg.C, maintaining the temperature for 70min, adding concentrated nitric acid dropwise to adjust pH to 4.5, maintaining the temperature for 20min, and adding Fe (NO) dropwise3)3·9H2O, forming heteropolyacid salt Na4PW11Fe(H2O)O39，Na2WO4·2H2O、Na2HPO4And Fe (NO)3)3·9H2The mass ratio of O is 11:1:1, Fe (NO)3)3·9H2The concentration of the O solution is 0.8mol/L, and the dropping speed is 0.05 mL/min;
2. preparation of Supported catalysts
(1) And (2) mixing nano silicon dioxide and deionized water in a mass-volume ratio of 1 g: heating to 50 ℃ after 50mL of the mixture is mixed, stirring for 30min at 100rpm, and then standing for 60 min;
(2) adding cetylpyridinium bromide at the speed of 0.01g/min while stirring the solution formed in the step (1) at 20rpm, continuously stirring for 60min after the addition is finished to form a mixed solution, then continuously dropwise adding a heteropoly acid salt solution at the speed of 0.08mL/min while stirring, adding sodium bicarbonate after the dropwise adding is finished to adjust the pH to 4, continuously stirring for 2h, wherein the mass ratio of the cetylpyridinium bromide to the nano silicon dioxide is 0.16:1, and the heteropoly acid salt Na4PW11Fe(H2O)O39And cetylpyridinium bromide in a 1:5 mass ratio;
(3) after the reaction in the step (2) is finished, filtering out solid substances, washing for 2 times in distilled water, washing for 2 times in ethyl acetate solution, and then drying for 8 hours at the temperature of 70 ℃ below-90 KPa to obtain the supported type [ C ]21H38N]10[(PW11FeO39)2O]/SiO2A catalyst.
This implementationExample prepared of [ C21H38N]10[(PW11FeO39)2O]/SiO2Has a higher loading amount, [ C ]21H38N]10[(PW11FeO39)2O]In the nano SiO2The loading on the catalyst reached 34.8 wt.% ([ C ]21H38N]10[(PW11FeO39)2O]In a supported catalyst [ C ]21H38N]10[(PW11FeO39)2O]/SiO2Mass ratio of (1).
Example 2
A preparation method of a supported dimer heteropoly acid quaternary ammonium salt catalyst comprises the following steps:
1. preparation of heteropolyacid salt solutions
Mixing Na2WO4·2H2Adding O into deionized water according to the mass-volume ratio of 8g to 100mL of the deionized water, stirring to dissolve the O to form a solution A, and adding Na into the solution A2HPO4Continuously stirring and mixing at 40-60 ℃ to form a solution B, heating the solution B to 90 ℃, preserving heat for 40min, dropwise adding concentrated nitric acid to adjust the pH to 4.5, preserving heat for 40min, and finally dropwise adding Fe (NO)3)3·9H2O, forming heteropolyacid salt Na4PW11Fe(H2O)O39，Na2WO4·2H2O、Na2HPO4And Fe (NO)3)3·9H2The mass ratio of O is 11:1:1.3, Fe (NO)3)3·9H2The concentration of the O solution is 0.8mol/L, and the dropping speed is 0.1 mL/min;
2. preparation of Supported catalysts
(1) And (2) mixing nano silicon dioxide and deionized water in a mass-volume ratio of 5g: mixing 65mL of the mixture, heating to 70 ℃, stirring at 150rpm for 10min, and then standing for 80 min;
(2) adding cetylpyridinium bromide at the speed of 0.05g/min while stirring the solution formed in the step (1) at the speed of 20-30 rpm, continuously stirring for 80min after the addition is finished to form a mixed solution, and then continuously dripping the mixed solution at the speed of 0.15mL/min while stirringAdding heteropoly acid salt solution, adding sodium bicarbonate after dropwise adding, adjusting the pH value to 4.8, continuously stirring for 2h, wherein the mass ratio of the cetyl pyridine bromide to the nano silicon dioxide is 0.185:1, and the heteropoly acid salt Na4PW11Fe(H2O)O39And cetylpyridinium bromide in a 1:5 mass ratio;
(3) after the reaction in the step (2) is finished, filtering out solid matters, washing in distilled water for 4 times, then washing in ethyl acetate solution for 4 times, and then drying at the temperature of 80 ℃ of less than-90 KPa for 6 hours to obtain the supported type [ C ]21H38N]10[(PW11FeO39)2O]/SiO2A catalyst.
[ C ] prepared in this example21H38N]10[(PW11FeO39)2O]/SiO2Has a higher loading amount, [ C ]21H38N]10[(PW11FeO39)2O]In the nano SiO2The loading on the catalyst reached 40.2 wt%.
Example 3
A preparation method of a supported dimer heteropoly acid quaternary ammonium salt catalyst comprises the following steps:
1. preparation of heteropolyacid salt solutions
Mixing Na2WO4·2H2Adding O into deionized water according to the mass-to-volume ratio of 6g to 100mL of the deionized water, stirring to dissolve the O to form a solution A, and adding Na into the solution A2HPO4Continuously stirring and mixing at 40-60 ℃ to form a solution B, heating the solution B to 88 ℃, preserving heat for 60min, dropwise adding concentrated nitric acid to adjust the pH to 4.8, preserving heat for 30min, and finally dropwise adding Fe (NO)3)3·9H2O, forming heteropolyacid salt Na4PW11Fe(H2O)O39，Na2WO4·2H2O、Na2HPO4And Fe (NO)3)3·9H2The mass ratio of O is 11:1: 1-1.2, Fe (NO)3)3·9H2The concentration of the O solution is 0.8mol/L, and the dropping speed is 0.05-0.1 mL/min;
2. preparation of Supported catalysts
(1) And (2) mixing nano silicon dioxide and deionized water in a mass-volume ratio of 1 g: 55mL of the mixture is heated to 60 ℃, stirred at 120rpm for 20min and then kept stand for 70 min;
(2) adding cetylpyridinium bromide at the speed of 0.02g/min while stirring the solution formed in the step (1) at 25rpm, continuously stirring for 70min after the addition is finished to form a mixed solution, then continuously dropwise adding a heteropoly acid salt solution at the speed of 0.1mL/min while stirring, adding sodium bicarbonate after the dropwise adding is finished to adjust the pH to 4.5, continuously stirring for 1.5h, wherein the mass ratio of the cetylpyridinium bromide to the nano-silica is 0.17:1, and the heteropoly acid salt Na is4PW11Fe(H2O)O39And cetylpyridinium bromide in a 1:5 mass ratio;
(3) after the reaction in the step (2) is finished, filtering out solid matters, washing in distilled water for 3 times, then washing in ethyl acetate solution for 3 times, and then drying at the temperature of 75 ℃ below-90 KPa for 7 hours to obtain the supported type [ C ]21H38N]10[(PW11FeO39)2O]/SiO2A catalyst.
[ C ] prepared in this example21H38N]10[(PW11FeO39)2O]/SiO2Has a higher loading amount, [ C ]21H38N]10[(PW11FeO39)2O]In the nano SiO2The loading on the catalyst reached 36.9 wt%.
1. Characterization by fourier transform infrared spectroscopy (FT-IR):
infrared spectroscopy of the samples was carried out using a NICOLET-IMPACT 400FTIR model infrared spectrometer, and the samples were mixed with KBr (1:100), ground and tabletted. Resolution was 4cm-1The wave number is 400-4000 cm-1The characterization results are shown in the attached figure 1: 1092cm-1、1057cm-1Characteristic vibration peak ascribed to P-O bond, 953cm-1Is classified as W ═ OdCharacteristic peak of key vibration, 883cm-1Is classified as W-ObCharacteristic vibration peak of W bond, 812cm-1Is classified as W-OcCharacteristic vibration peak of W bond, description [ C21H38N]10[(PW11FeO39)2O]Has a Keggin type structure. And at 750, 720cm-1The absorption peak at (A) is attributed to the characteristic vibration peak of Fe-O-Fe bond, which indicates that [ C21H38N]10[(PW11FeO39)2O]Has a dimer structure. Carrier nano SiO2At 1095cm-1,959cm-1,810cm-1And 468cm-1Has characteristic absorption peaks respectively assigned as vas(Si-O-Si),v(Si-OH),vsCharacteristic absorption peaks of (Si-O-Si) and delta (Si-O-Si). At 1620--1The absorption peak in the range is assigned to the bending vibration peak of H-O-H. For [ C ]21H38N]10[(PW11FeO39)2O]/SiO2，[C21H38N]10[(PW11FeO39)2O]After loading, the absorption peak of the P-O bond is not observed because of the supported nano SiO2At 1095cm-1Covered by the absorption peak at 700-1100cm-1The region still has a stretching vibration peak (883 cm) of the W-O-W bond of the dimer phosphotungstate-1) And stretching vibration peak of Fe-O-Fe bond (749, 724 cm)-1). Indicating dimer [ C21H38N]10[(PW11FeO39)2O]Successfully loaded on a carrier nano SiO2The above.
2. Characterized by ultraviolet-visible diffuse reflectance spectroscopy (DRS UV-vis):
[C21H38N]10[(PW11FeO39)2O]/SiO2the DRS UV-vis characterization of (1) is carried out on a SHIMADZU UV-1601PC spectrometer, BaSO4As a back bottom, [ C ]21H38N]10[(PW11FeO39)2O]/SiO2Is pressed on the glass substrate, the thickness is 2mm, the scanning range is 200 and 900nm, and the characterization result is shown in the attached figure 2: 288. 363nm is assigned to the charge-transfer transitions of O → W and O → Fe, respectively. 363nm is the characteristic absorption peak of the Fe-O-Fe bond. 462. 609nm are all assigned to the O → Fe charge-transfer transition, again indicating [ C-21H38N]10[(PW11FeO39)2O]Contains Fe-O-Fe bonds and has a dimer structure. For supported catalysts [ C ]21H38N]10[(PW11FeO39)2O]/SiO2，[C21H38N]10[(PW11FeO39)2O]After loading, there are also absorption peaks at 292, 362, 462, 605nm, DRS UV-vis results also indicate dimer [ C21H38N]10[(PW11FeO39)2O]Successfully loaded on a carrier nano SiO2The above.
Characterization by X-ray powder diffraction (XRD)
The XRD test uses SHIMADZU XRD-6000 type X-ray diffractometer, Cu ka target (λ is 0.1548nm), Ni filter, tube voltage 40KV, tube current 30mA, scanning range 2 θ is 5 ° -70 °, scanning rate 6 °/min, the characterization result is as shown in fig. 3: from the figure, the nano SiO carrier can be observed2A typical amorphous dispersion peak, [ C ], occurs at an angle of about 23 DEG 2 theta21H38N]10[(PW11FeO39)2O]Has wider diffraction peak in the range of 2 theta angle of 7.4-10 degrees and 20-35 degrees. For supported catalysts [ C ]21H38N]10[(PW11FeO39)2O]/SiO2When a broad diffraction peak appears in the range of 7.4 to 10 DEG and 20 to 35 DEG at an angle of 2 theta, XRD results also show that the dimer [ C ] is present21H38N]10[(PW11FeO39)2O]Successfully loaded on a carrier nano SiO2The above. And the diffraction peak of the supported heteropolyacid catalyst is still a wider diffraction peak after being supported and is in an amorphous crystal state, which shows that the heteropolyacid is in a highly dispersed state on the surface of the carrier and has no obvious agglomeration and accumulation phenomena.
4. Scanning Electron Microscope (SEM) characterization
The morphology of the catalyst samples was analyzed by means of a HITACHI model H-8110 scanning electron microscope. As can be seen from the SEM image, in accordance with the characterization result of XRD chart, the product had an amorphous morphology, and [ C ] was observed21H38N]10[(PW11FeO39)2O]Uniformly dispersed in nano SiO2A surface.
5.N2Physical adsorption
Table 1 shows the carrier of nano SiO2And a supported catalyst [ C21H38N]10[(PW11FeO39)2O]/SiO2Specific surface area, pore volume and average pore diameter.
Table 1: specific surface area, average pore diameter and specific pore volume of the catalyst.
It can be seen that the specific surface area of the supported catalyst is the same as that of the nano SiO2Compared with the obvious reduction, the thickness is reduced from 319.6 to 153.4m2The pore volume also decreased from 0.881 to 0.365cm3(ii) in terms of/g. This is because of the nano SiO2The specific surface area of the heteropoly acid compound is mainly provided by the inner surface of the nanometer pore canal, so the reduction of the pore volume and the specific surface area proves that the heteropoly acid compound is greatly loaded on the nanometer SiO2All samples have uniformly distributed mesoporous channels, and the successful uniform dispersion and loading of the dimer catalyst on the carrier nano SiO are also shown2In this way, the specific surface area of the carrier is drastically reduced without agglomeration and accumulation. Thus, the sum N is characterized from the electron microscope scan2Physical adsorption experiments show that the [ C ] prepared by the invention21H38N]10[(PW11FeO39)2O]/SiO2Middle, dimer [ C21H38N]10[(PW11FeO39)2O]Uniformly dispersed and loaded in nano SiO2The surface and the pore channels.
Example 4
Load type [ C ]21H38N]10[(PW11FeO39)2O]/SiO2Catalyst catalysis H2O2Oxidizing benzyl alcohol to prepare benzaldehyde:
examples of the invention3 preparation of [ C21H38N]10[(PW11FeO39)2O]/SiO2Dispersing 1mmol of catalyst in 10mL of organic solvent acetonitrile, adding 80mmol of benzyl alcohol, stirring, heating to 70 ℃, adding 160mmol of H with the mass concentration of 30%2O2Reacting for 6 hours at constant temperature, cooling, filtering, recovering the catalyst, and washing with ethanol;
in the reaction process, sampling and analyzing every 1h, and obtaining a result as shown in fig. 5, wherein the conversion rate of benzaldehyde is in an ascending trend along with the reaction time, when the reaction is carried out for 3h, the conversion rate reaches 96%, the conversion rate is basically stable, the change is not obvious, the conversion rate of benzaldehyde is finally 96.7%, the selectivity of the prepared product benzaldehyde slightly decreases along with the reaction, but the overall stability is basically maintained at more than 92.9%, and after recovery, the reaction solvent is detected to be basically free of any catalyst active ingredient residue.
The recovered catalyst is treated to form a new supported type of [ C ]21H38N]10[(PW11FeO39)2O]/SiO2The catalyst is put into use again, thereby achieving the purpose of recycling. The recovery rate was as shown in Table 2 as the number of reactions was increased.
Table 2: recovery of the catalyst after the reaction.
With the increase of the repeated use times, the recovery rate of the catalyzed catalyst with a dimer structure is reduced to a certain extent, but the recovery rates are all higher, more than 5 times of repetition and more than 95 percent, and the method can be seen in that the [ C ] prepared by the invention21H38N]10[(PW11FeO39)2O]/SiO2The catalyst has the advantages of good structural stability, excellent binding force between the active components of the catalyst and the carrier, no phenomena of falling, failure and the like in the catalytic reaction process, high recovery rate and high recycled catalytic activity.
- 上一篇：一种医用注射器针头装配设备
- 下一篇：臭氧分解催化剂及其制备方法与应用