The hydrothermal synthesis of NZP family phosphate crystalline compound
|School||Kunming University of Science and Technology|
|Keywords||NZP family phosphate compounds Hydrothermal crystallization Mineralizing agent Templating agent Pore structure|
In this thesis (NH4) 2HP04 phosphorus source, ZrO (NO3) 2 the zirconium source with the hydrothermal crystallization method, co-precipitation synthesized compounds have a crystal structure of the NZP family NH4Zr2 (PO4) 3 hydrothermal temperature hydrothermal mineralizing agent F-dosage, seeded and hydrothermal reaction system, the pH of the NH4Zr2 (PO4) 3 material phase. Physical parameters through the single factor experiment to explore the most suitable hydrothermal synthesis conditions, and physical prepared under hydrothermal conditions most suitable NH4Zr2 (PO4) 3 phase, morphology, specific surface area, total pore volume and pore size distribution characterized. In addition, in order to H3P04 as phosphorus source water thermal synthesis of alkali metal occupy M Ⅰ M Ⅱ Zr2P3012 M Ⅰ bit of NaZr2 (PO4) 3 and KZr2 (PO4) 3 Two NZP family crystal compounds, and the preparation of NaZr2 (PO4) 3 carried the matter phase, surface area, total pore volume, average pore size and pore size distribution characterization. , Learn from the molecular sieves and mesoporous materials synthesis method based on this preliminary study introduced templating agent in the hydrothermal process NH4Zr2 (PO4) 3 and the NaZr2 (PO4) 3 The ratio of surface area, total pore volume and pore size distribution and other effects, in order to obtain a new type of catalytic material having a large surface area and uniform pore size distribution of the NZP family. The results show that: (1) does not add the seed crystal and the mineralizing agent under the premise, the use of hydrothermal crystallization to obtain good crystallinity NH4Zr2 (PO4) 3 compound required for the hydrothermal treatment temperature of about 250 ℃; Add the total product mass. 15% of the seed crystal formed NH4Zr2 (PO4) 3 crystals hydrothermal treatment temperature to 200 ° C decreased from 25 ℃; added in amount of F-mineralizing agent in the molar ratio n (F-) / n (ZrO2) = 0.5 ~~ 4 between 100 ℃ ~ 200 ℃ for 20h-24h hydrothermal crystallization reaction, able to obtain pure phase Nn4Zr2 (PO4) 3 crystals. (2) F-NZP family is formed crystal structure of an ideal structure-directing agent; an alkali metal cation Na, organic amines the EDA and quaternary ammonium CTAB using a hydrothermal reaction conditions in the present study (150 ℃ hydrothermal treatment at 24h) under no obvious structure directing role on the formation of the crystal structure of the NZP family. NH4Zr2 (PO4) 3 (3) by the molar ratio n (F-) / n (ZrO2) = 1 introduction of HF, the addition amount of the 15% of the total product mass seeded hydrothermal treatment at 50 ℃ 24h obtained pure phase crystal; studies have shown that the reaction system in the acidic environment is conducive to the formation NH4Zr2 hydrothermal crystallization (PO4) 3. XRD and TEM characterization of the product obtained results show that under this condition: the product phase pure, no impurity phase particles uniformly distributed without agglomeration. A specific surface area of the powder is 3.173m2 / g, a total pore volume as 0.00493mL / g, average pore diameter of 3.1lnm, but the pore size distribution is extremely uneven. (4) in H3PO4 as the phosphorus source can be a good crystalline form of hydrothermal synthesis NaZr2 (PO4) 3, and of KZr2 (PO4) 3, but the specific surface area and total pore volume of the crystalline compound of the NaZr2 (PO4) 3 is almost 0. (5) cetyl trimethyl ammonium bromide (CTAB), ethylenediamine (EDA), twelve amine (DDA), 1,6 - hexanediamine (HDA) and polyethylene glycol (PEG) etc. introduced separately synthesized NH4Zr2 (PO4) 3 and the NaZr2 (PO4) 3 Hydrothermal reaction system, the resulting product phase, than the characterization results of the surface area and pore structure of the display, in the presence of templating agent EDA, DDA, these two NZP crystal compounds specific surface area and total pore volume than non-template agent significantly improved, but still not able to form ordered pore structure.