Background and overview[1][2]
Heteropolyacid is one of the most active catalysts used in today’s acid catalytic reactions and redox reactions. It has good catalytic properties for hydration and esterification reactions of olefins, etherification reactions of epoxides, condensation reactions of olefins and aldehydes, alkylation, olefin epoxidation reactions, alkyl aromatic reactions, etc. In addition, as a catalyst, heteropolyacid has the advantages of high catalytic activity, high selectivity, low corrosion, and easy control of the reaction. In addition, its structure is stable and can be regenerated and recycled. Therefore, it has attracted widespread attention, especially in the petrochemical industry. has broad applications.
Phosphotungstic acid is the most widely used among heteropolyacids, and its purity directly affects the conversion rate of the system it catalyzes. Therefore, it is particularly important to prepare high-purity phosphotungstic acid. H.S. Booth and others first reported the synthesis method of phosphotungstic acid in 1939. One of the synthesis methods of phosphotungstic acid invented by him is still in use today, namely the ether acidification extraction method. Ether acidification extraction method can be used to purify phosphotungstic acid. That is, a solution of industrial phosphotungstic acid is mixed with diethyl ether for phase separation to obtain a complex of diethyl ether phosphotungstic acid, which separates the phosphotungstic acid from impurity anions and impurity cations, and then evaporates the diethyl ether in the adduct to obtain the purified product. of phosphotungstic acid crystals.
However, a big disadvantage of this method is that ether is easy to volatilize, which is potentially dangerous to the environment and worker safety. Chinese patent document 201210457552.6 provides a method of using sulfur-phosphorus mixed acid to decompose scheelite and extract tungsten. The method of preparing phosphotungstic acid using scheelite as raw material greatly reduces the preparation cost of phosphotungstic acid. However, scheelite often contains a large number of other impurity ions such as iron ions, manganese ions, calcium ions, sulfate ions, and phosphate ions. Ions, etc., are adsorbed on the surface of phosphotungstic acid during the primary cooling and crystallization process of phosphotungstic acid. In this patent, the obtained primary phosphotungstic acid crystals are dissolved in water, inorganic acid is added to the solution, and the phosphotungstic acid crystals are purified through secondary cooling crystallization. However, the cooling of phosphotungstic acid in a relatively concentrated inorganic acid solution During the precipitation process, it is inevitable that inorganic acid impurity ions will be adsorbed on the surface of phosphotungstic acid and are difficult to remove.
Phosphotungstic acid
Apply[3]
1. Preparation of three-dimensional graphene-coated cesium phosphotungstate microspheres
1) Preparation of cesium phosphotungstate microspheres:
Take 100mL of cesium chloride aqueous solution with a concentration of 3×10-2mol/L and slowly add it to a 250mL three-necked flask containing 100mL of phosphotungstic acid aqueous solution with a concentration of 10×10-4mol/L. Raise the temperature to 100°C and stir for 1 hour. , forming an emulsion of cesium phosphotungstate microspheres. After the reaction is completed, the emulsion is cooled to room temperature and separated by suction filtration to obtain cesium phosphotungstate microspheres.
2) Preparation of polyaniline-coated cesium phosphotungstate microspheres:
Put 0.86g of the cesium phosphotungstate microspheres prepared in step 1) into a polytetrafluoroethylene bottle, then add 10 mL of the 10 mg/mL graphene oxide aqueous solution prepared in advance, and stir the mixed solution at room temperature. Let it fully react for an hour, then put the polytetrafluoroethylene bottle into the hydrothermal reaction kettle, and finally put the hydrothermal reaction kettle into an electric constant-temperature blast drying box and react at 180°C for 12 hours. After the reaction is completed, cool After reaching room temperature, the solid agglomerates are taken out and freeze-dried to obtain the 3D graphene-coated cesium phosphotungstate microspheres to be prepared.
2. Preparation of hollow spherical mesoporous silica carrier:
Add 1.0 g of three-segment copolymer polyethylene glycol-polyglycerol-polyethylene glycol (Aldrich Company, P123) and 1.69 g of ethanol to 28 ml of a buffer solution of acetic acid and sodium acetate (pH=4.4) in, stir at 15°C until polyethylene glycol-polyglycerol-polyethylene glycol is completely dissolved, then add 6g of trimethylpentane to the above solution, stir at 15°C for 8 hours, then add 2.13g Tetramethoxysilane was added to the above solution, and after stirring at 15°C for 20 hours, the solution was transferred to a polytetrafluoroethylene-lined reactor, crystallized in an oven at 120°C for 30 hours, filtered, washed with distilled water, and dried. Finally, hollow spherical mesoporous silica raw powder is obtained. The raw hollow spherical mesoporous silica powder was calcined in a muffle furnace at 550°C for 24 hours to obtain hollow spherical mesoporous silica (named MS-1).
3. Preparation of supported phosphotungstic acid catalyst:
The hollow spherical mesoporous silica MS‑1 was maintained in nitrogen.Calculate at 10°C for 10 hours to remove hydroxyl groups and residual moisture, thereby obtaining thermally activated hollow sphere mesoporous silica. At 40°C, 1 gram of heat-activated hollow sphere mesoporous silica and 1 gram of phosphotungstic acid were stirred in 20 ml of 7 mol/L n-butanol for 24 hours. After filtration and drying, 1.2 grams of the target product was obtained. The supported phosphotungstic acid catalyst is named MS‑HPA, which is calculated based on the content of the carrier = the weight of the added carrier/the weight of the supported metallocene catalyst × 100%, based on the total amount of the supported phosphotungstic acid catalyst. , the content of phosphotungstic acid is 16.7% by weight, and the content of the hollow spherical mesoporous silica carrier is 83.3% by weight. The supported phosphotungstic acid catalyst was characterized using XRD, nitrogen adsorption-desorption experiments, transmission electron microscopy, scanning electron microscopy, X-ray energy spectrometer and ICP elemental analysis.
Preparation[2]
Purification method:
Method 1:
Dissolve 568g of industrial phosphotungstic acid (without molybdenum impurities) in water, and then add hydrochloric acid so that the tungsten trioxide in the solution is 80g/L and the hydrochloric acid concentration is 3mol/L. Use 15% secondary octanol as the extraction agent and the diluent as sulfonated kerosene, and then perform four-stage countercurrent extraction; use distilled water as the stripping reagent for the loaded organic phase to perform five-stage countercurrent stripping. The stripping liquid was evaporated and crystallized to obtain 542g of high-purity white phosphotungstic acid, with a yield of 95.4%.
Method 2:
Dissolve 860g of industrial phosphotungstic acid (containing molybdenum impurities) in water, and then add nitric acid to make the tungsten trioxide in the solution 150g/L and the nitric acid concentration 1mol/L. Use 30% undecanol as the extraction agent and the diluent as sulfonated kerosene, and then perform three-stage countercurrent extraction of Cabot carbon black; use distilled water as the back-extraction reagent for the loaded organic phase to perform six-stage countercurrent back-extraction. Add 30% hydrogen peroxide with 2.5 times the molar amount of tungsten and molybdenum to the stripping liquid, and then use three-stage countercurrent extraction of molybdenum with tributyl phosphate. The obtained molybdenum extraction residual liquid is evaporated and crystallized to obtain 845g of high-purity white phosphotungstic acid, with a yield of 98.2%. .
Main reference materials
Imported polymer flocculant
[1] Lin Jin, & Zhang Yanfeng. (2000). Research on the synthesis of diethyl sebacate catalyzed by phosphotungstic acid. Fine Chemicals, 17(2), 86-87.
[2] Li Lei, Xu Li, & Wang Yuxin. (2004). Phosphotungstic acid/sulfonated polyetheretherketone proton conductive composite membrane. Journal of Chemistry in Colleges and Universities, 25(2), 000388-390.
[3] Zhang Yingqun, Wang Chun, Li Guishen, & Li Jingci. (2003). Phosphotungstic acid catalyzed oxidation of cyclohexene with hydrogen peroxide to synthesize adipic acid. Organic Chemistry, 23(1), 104-105.
