CN106732701B - solid acid catalyst of iron-doped niobium phosphate - Google Patents
solid acid catalyst of iron-doped niobium phosphate Download PDFInfo
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- CN106732701B CN106732701B CN201710020283.XA CN201710020283A CN106732701B CN 106732701 B CN106732701 B CN 106732701B CN 201710020283 A CN201710020283 A CN 201710020283A CN 106732701 B CN106732701 B CN 106732701B
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- B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
- B01J27/14—Phosphorus; Compounds thereof
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- B01J27/195—Phosphorus; Compounds thereof with arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium with vanadium, niobium or tantalum
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Abstract
The invention relates to iron-doped niobium phosphate solid acid catalysts and a preparation method thereof, wherein the catalysts mainly comprise niobium citrate, diammonium phosphate and ferric nitrate according to the volume ratio of 20:20:0.5-1.5, and the catalysts prepared from the main raw materials can solve the problems that most of the traditional levulinic acid preparation methods adopt a homogeneous phase catalysis method, the catalysts are liquid acids (such as concentrated sulfuric acid, hydrochloric acid and the like), and although higher levulinic acid yield can be obtained, the defects of complex process, high cost, large amount of waste water, difficult separation of the catalysts and products, difficult reuse of the catalysts and the like exist, and in addition, the single solid acid has poor activity performance in the catalytic preparation of levulinic acid and is not beneficial to the preparation of the levulinic acid.
Description
Technical Field
The invention relates to iron-doped niobium phosphate solid acid catalysts, in particular to preparation of fibrous mesoporous iron-doped niobium phosphate solid acid catalysts and application of the catalysts in preparation of levulinic acid by catalyzing glucose, and belongs to the field of catalysts.
Background
With the rapid development of the world economy, the consumption of global petrochemical resources is increasing, and the exhaust gas (such as sulfur oxide, carbon dioxide and the like) discharged after the combustion of petrochemical fuel can cause environmental pollution and deteriorate the ecological environment.
The energy department of the United states lists levulinic acid as which is an important platform micromolecule in biomass conversion, because levulinic acid can obtain levulinic acid ester compounds widely applied to the flavor industry through esterification, liquid fuel gamma-valerolactone capable of being continuously utilized is obtained through hydrogenation-cyclization, and series of derivatives with high added values, such as succinic acid, diphenolic acid, pyrrolidine and the like, can be obtained through catalytic oxidation, condensation and reductive amination.
The traditional levulinic acid preparation method mostly adopts a homogeneous phase catalysis method, a catalyst is liquid acid (such as concentrated sulfuric acid, hydrochloric acid and the like), a large amount of water is required to dilute in the production process due to the use of concentrated sulfuric acid, hydrochloric acid and the like, so that a large amount of wastewater is generated, and although higher levulinic acid yield can be obtained, the method has the defects of complex process, high cost, difficult separation of the catalyst and products, difficult reuse of the catalyst and the like.
The novel solid acid catalyst is adopted to replace a homogeneous catalyst, so that the method has the advantages of easy separation of products and the catalyst, no waste liquid generation, reusability of the catalyst and the like. The preparation of levulinic acid from sugars requires Lewis acid to catalyze the sugar isomerization reaction and
the acid is catalyzed to rehydrate to obtain the levulinic acid, so that the single solid acid NbP has poor activity performance in the catalytic preparation of the levulinic acid and is not beneficial to the preparation of the levulinic acid
Reports of acid bifunctional solid acid for catalyzing conversion of glucose into levulinic acid, such as reports of N.A.S.Ramli, N.A.S.Amin, applied.Catal.B 163(2015)487-498, but a technology of applying a fibrous mesoporous structure catalyst with B, L acid sites to catalyzing preparation of levulinic acid is blank.
Disclosure of Invention
The invention aims to provide iron-doped niobium phosphate solid acid catalysts, which are prepared by taking self-made niobium citrate as a niobium source through a simple hydrothermal preparation method, and show high catalytic activity in the reaction for catalyzing glucose to prepare levulinic acid.
The technical scheme of the invention is that iron-doped niobium phosphate solid acid catalysts are mainly prepared from a niobium citrate solution, a diammonium phosphate solution and an iron nitrate solution according to the volume ratio of 20:20:0.5-1.5 respectively, and the preparation method comprises the following steps:
, respectively preparing a niobium citrate solution, a diammonium phosphate solution, an iron nitrate solution and a hexadecyl trimethyl ammonium bromide solution, and then forming a mixed solution of the niobium citrate solution, the diammonium phosphate solution and the iron nitrate solution according to the volume ratio;
secondly, dripping the mixed solution obtained in the step into a hexadecyl trimethyl ammonium bromide solution with the temperature of 35 ℃, stirring for 1 hour, transferring the mixed solution into a stainless steel autoclave with a polytetrafluoroethylene lining after stirring, keeping the temperature in the stainless steel autoclave at 160 ℃, aging for 24 hours, filtering and separating to obtain a precipitate, washing the precipitate with deionized water, drying and grinding to obtain a precursor, and finally calcining to obtain mesoporous niobium phosphate solid acid catalysts with various volume ratios of niobium citrate solution, diammonium hydrogen phosphate solution and ferric nitrate solution;
the preparation method of the niobium citrate solution comprises the following steps: weighing 5g of niobium oxide, adding the niobium oxide into 40mL of hydrofluoric acid solution with the mass percentage concentration of 40%, heating the solution in an oil bath to 100 ℃ and keeping the solution for 5 hours, naturally cooling the solution to 25 ℃, slowly adding 14 wt% ammonia water with the volume being 10 times that of the solution, then carrying out centrifugal separation, washing the obtained precipitate with deionized water, immediately adding the washing solution into 75mL of citric acid solution with the concentration of 1.1mol/L after the washing solution is neutral, and heating the solution in the oil bath to 50 ℃ and keeping the solution for 0.5 hour to obtain 0.5mol/L of clear niobium citrate solution;
the diammonium phosphate solution is phosphoric acid with the mass percentage concentration of 85%, and the regulating concentration of the diammonium phosphate solution is 0.5mol/L until the pH value is 2;
the ferric nitrate solution is 1mol/L ferric nitrate aqueous solution;
the cetyl trimethyl ammonium bromide solution is a CTAB aqueous solution with the concentration of 0.2 mol/L;
the calcination is to dry the dried and ground precursor for 12 hours at the drying temperature of 80 ℃, and then calcine the precursor for 5 hours in a muffle furnace at the temperature of 550 ℃.
The preparation method of iron-doped niobium phosphate solid acid catalysts comprises the steps of preparing a diammonium hydrogen phosphate solution, an iron nitrate solution and a CTAB solution by self-making a niobium citrate solution, regulating the pH value of the diammonium hydrogen phosphate solution to be 2 by 85% phosphoric acid, forming a mixed solution with the niobium citrate solution and the iron nitrate solution, then dropwise adding a hexadecyl trimethyl ammonium bromide solution, mixing, preparing by a hydrothermal method, stirring, transferring into a polytetrafluoroethylene-lined stainless steel autoclave, keeping the temperature in the stainless steel autoclave at 160 ℃, aging for 24 hours, filtering, separating, washing an obtained precipitate with deionized water, drying, grinding to obtain a precursor, and finally calcining to obtain the mesoporous niobium phosphate solid acid catalysts.
The preparation method of the niobium citrate solution comprises the following steps: weighing 5g of niobium oxide, adding the niobium oxide into 40mL of hydrofluoric acid (40%) solution, heating the solution in an oil bath to 100 ℃ and keeping the temperature for 5 hours, naturally cooling the solution to 25 ℃, slowly adding 14 wt% ammonia water with 10 times of volume, then carrying out centrifugal separation, washing the obtained precipitate with deionized water, immediately adding the washed precipitate into 75mL of 1.1mol/L citric acid solution, heating the solution in the oil bath to 50 ℃ and keeping the temperature for 0.5 hour to obtain 0.5mol/L clear niobium citrate solution, and ensuring the quality of the niobium citrate solution by the above method, thereby ensuring the elements required by the whole chemical reaction to be finally ensured.
The diammonium hydrogen phosphate solution is a solution prepared by regulating 0.5mol/L diammonium hydrogen phosphate aqueous solution to pH 2 by 85% phosphoric acid, and a large number of experiments prove that the diammonium hydrogen phosphate solution is a solution prepared by regulating 0.5mol/L diammonium hydrogen phosphate aqueous solution to pH 2 by 85% phosphoric acid, and is a required optimal parameter for the whole chemical reaction.
The ferric nitrate solution is 1mol/L ferric nitrate aqueous solution, and a large number of experiments prove that the ferric nitrate solution is 1mol/L ferric nitrate aqueous solution, which is a required preferable parameter of the whole chemical reaction.
The cetyl trimethyl ammonium bromide solution is 0.2mol/L cetyl trimethyl ammonium bromide aqueous solution, and a large number of experiments prove that the cetyl trimethyl ammonium bromide solution is 0.2mol/L cetyl trimethyl ammonium bromide aqueous solution which is a required better parameter of the whole chemical reaction.
The calcination of the invention is to dry the dried and ground precursor for 12 hours at the drying temperature of 80 ℃ so as to fully dry the water of the precursor, and then calcine the precursor in a muffle furnace at 550 ℃ for 5 hours, so that the mesoporous niobium phosphate solid acid catalyst can be obtained by calcining the precursor finally.
Compared with the prior art, the traditional levulinic acid preparation method mostly adopts a homogeneous catalysis method, the catalyst is liquid acid (such as concentrated sulfuric acid, hydrochloric acid and the like), and a large amount of water is required to dilute in the production process due to the use of concentrated sulfuric acid, hydrochloric acid and the like, so that a large amount of wastewater is generated, and although higher levulinic acid yield can be obtained, the method has the defects of complex process, difficult separation of the catalyst and products, difficult reuse of the catalyst and the like; the preparation of levulinic acid from sugars requires Lewis acid to catalyze the sugar isomerization reaction and
the acid catalyzes the rehydration reaction to obtain the levulinic acid, so the activity of the solid acid of the mono in the catalytic preparation of the levulinic acid is poor, and the preparation of the levulinic acid is not favorable.
According to the technical scheme, the iron element is added on the basis of the traditional solid acid NbP, the used main raw materials are niobium citrate, diammonium hydrogen phosphate and ferric nitrate, the mixture is mixed with a cetyl trimethyl ammonium bromide solution, the mixture is subjected to moisture separation and then calcined, the material is common, the preparation method is simple, the cost is low, the defects that a large amount of waste water is not generated, the catalyst is difficult to separate from a product, the catalyst is difficult to reuse and the like are overcome, particularly, the ferric nitrate solution is added on the basis of the niobium citrate solution and the diammonium hydrogen phosphate solution, the moisture separation and the calcination are performed, the produced iron-doped niobium phosphate solid acid catalyst simultaneously has B, L acid sites and is in a fibrous mesopore structure, compared with the traditional catalyst adopting the single solid acid NbP, the catalyst has the fibrous mesopore structure, and therefore, the catalyst acid content is high, and the catalytic activity is obviously improved compared with the mesopore structure.
Drawings
FIG. 1 is a transmission electron microscope photograph of an iron-doped niobium phosphate catalyst;
FIG. 2 is a physisorption drawing of an iron-doped niobium phosphate catalyst;
FIG. 3 shows NH of iron-doped niobium phosphate catalyst3-a TPD map;
FIG. 4 is a pyridine-infrared diagram of an iron-doped niobium phosphate catalyst.
Detailed Description
To further clarify the objects, technical solutions and advantages of the present invention, a further detailed description of the invention will be made with reference to the accompanying drawings of fig. 1-4 of the present specification.
Example (b):
1. preparation of niobium citrate precursor solution
Weighing 5.0g Nb2O5Adding the niobium hydroxide into 40mL of HF (40 wt%), heating the solution in an oil bath at 100 ℃ for 5.0h to obtain a clarified niobium fluoride solution, slowly adding 10 times of ammonia water (14 wt%) to precipitate a white precipitate, washing the precipitate to be neutral to obtain niobium hydroxide, adding the niobium hydroxide into 75mL of citric acid (1.1mol/L) solution at 50 ℃ for 0.5h to obtain a clarified niobium citrate solution.
2. Preparation of diammonium hydrogen phosphate solution
Weighing 1.32g of diammonium hydrogen phosphate, adding 20mL of water, stirring and dissolving, and then, dropwise adding 85% phosphoric acid to prepare a diammonium hydrogen phosphate solution with the pH value of 2 to obtain a diammonium hydrogen phosphate solution.
3. Preparation of ferric nitrate solution
2.02g of ferric nitrate nonahydrate is weighed, added into 5mL of water, and stirred to dissolve to obtain a 1mol/L ferric nitrate solution.
4. Preparation of cetyl trimethyl ammonium bromide solution
1.0g of cetyltrimethylammonium bromide was weighed and dissolved in 13mL of water at 35 ℃ and stirred to dissolve it, thereby obtaining 0.2mol/L of cetyltrimethylammonium bromide solution.
5. Preparation of niobium citrate precursor solution
After the preparation of the niobium citrate, diammonium phosphate, ferric nitrate and cetyltrimethylammonium bromide solutions was completed, mixed solutions of the niobium citrate, diammonium phosphate and ferric nitrate solutions were composed in volume ratios of 20:20:0.5, 20:20:0.75, 20:20:1, 20:20:1.25 and 20:20:1.5, respectively.
6. Preparation of iron-doped niobium phosphate solid acid catalyst
Mixing 20mL of niobium citrate solution and 20mL of diammonium hydrogen phosphate solution with 0.5, 0.75,1, 1.25 and 1.5mL of ferric nitrate solution with the concentration of 1mol/L respectively, slowly dropwise adding the mixed solution in various proportions into 3.25mL of hexadecyl trimethyl ammonium bromide template agent (0.2mol/L) respectively, stirring for 1h at 35 ℃, then transferring into a stainless steel autoclave with a polytetrafluoroethylene lining at 160 ℃, aging for 24h, naturally cooling to room temperature after reaction, washing with water and precipitating to neutrality, then drying for 12h at 80 ℃, calcining for 5h at 550 ℃ after grinding, and cooling to obtain the iron-doped niobium phosphate solid acid catalyst. The glucose conversion and levulinic acid yield for various amounts of doped iron added are shown in table 1.
TABLE 1
And finally, weighing 0.1g of glucose (0.56mmol) as a raw material, taking 0.05g of the iron-doped niobium phosphate solid acid catalyst, reacting for 3 hours at 180 ℃, and detecting by using a high performance liquid chromatograph after the reaction.
The characterization of the catalyst iron-doped niobium phosphate by a transmission scanning microscope can be seen from fig. 1, the iron-doped niobium phosphate has a fibrous structure; as can be seen from fig. 2, the iron-doped niobium phosphate has a mesoporous structure; as can be seen from FIG. 3, the acid content of the iron-doped niobium phosphate is as high as 3.59 mmol/g; as can be seen from FIG. 4, the iron-doped niobium phosphate catalyst has Lewis acid and
acid diacid catalytic sites.
Claims (1)
1, iron-doped niobium phosphate solid acid catalyst, which is characterized in that the catalyst is mainly prepared from a niobium citrate solution, a diammonium phosphate solution and an iron nitrate solution according to the volume ratio of 20:20:0.5-1.5, and the preparation method comprises the following steps:
, respectively preparing a niobium citrate solution, a diammonium phosphate solution, an iron nitrate solution and a hexadecyl trimethyl ammonium bromide solution, and then forming a mixed solution of the niobium citrate solution, the diammonium phosphate solution and the iron nitrate solution according to the volume ratio;
secondly, dripping the mixed solution obtained in the step into a hexadecyl trimethyl ammonium bromide solution with the temperature of 35 ℃, stirring for 1 hour, transferring the mixed solution into a stainless steel autoclave with a polytetrafluoroethylene lining after stirring, keeping the temperature in the stainless steel autoclave at 160 ℃, aging for 24 hours, filtering and separating to obtain a precipitate, washing the precipitate with deionized water, drying and grinding to obtain a precursor, and finally calcining to obtain mesoporous niobium phosphate solid acid catalysts with various volume ratios of niobium citrate solution, diammonium hydrogen phosphate solution and ferric nitrate solution;
the preparation method of the niobium citrate solution comprises the following steps: weighing 5g of niobium oxide, adding the niobium oxide into 40mL of hydrofluoric acid solution with the mass percentage concentration of 40%, heating the solution in an oil bath to 100 ℃ and keeping the solution for 5 hours, naturally cooling the solution to 25 ℃, slowly adding 14 wt% ammonia water with the volume being 10 times that of the solution, then carrying out centrifugal separation, washing the obtained precipitate with deionized water, immediately adding the washing solution into 75mL of citric acid solution with the concentration of 1.1mol/L after the washing solution is neutral, and heating the solution in the oil bath to 50 ℃ and keeping the solution for 0.5 hour to obtain 0.5mol/L of clear niobium citrate solution;
the diammonium phosphate solution is phosphoric acid with the mass percentage concentration of 85%, and the regulating concentration of the diammonium phosphate solution is 0.5mol/L until the pH value is 2;
the ferric nitrate solution is 1mol/L ferric nitrate aqueous solution;
the cetyl trimethyl ammonium bromide solution is a CTAB aqueous solution with the concentration of 0.2 mol/L;
the calcination is to dry the dried and ground precursor for 12 hours at the drying temperature of 80 ℃, and then calcine the precursor for 5 hours in a muffle furnace at the temperature of 550 ℃.
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| CN102962085A (en) * | 2011-09-01 | 2013-03-13 | 华东理工大学 | Preparation method of niobium phosphate solid acid catalyst and application in sugar dehydration |
| CN105536832A (en) * | 2015-12-10 | 2016-05-04 | 大连交通大学 | Method for preparing mesoporous niobium phosphate catalyst and application of mesoporous niobium phosphate catalyst in preparation of isosorbitol from sorbitol |
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| CN102962085A (en) * | 2011-09-01 | 2013-03-13 | 华东理工大学 | Preparation method of niobium phosphate solid acid catalyst and application in sugar dehydration |
| CN105536832A (en) * | 2015-12-10 | 2016-05-04 | 大连交通大学 | Method for preparing mesoporous niobium phosphate catalyst and application of mesoporous niobium phosphate catalyst in preparation of isosorbitol from sorbitol |
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