本文選題：水熱反應 + 焦綠石型��； 參考：《中南大學》2011年碩士論文

【摘要】：焦綠石型三氧化鎢(WO3·0.5H_2O)以扭曲的WO6八面體為結構基元、通過W-O剛性骨架的角頂構筑形成具有圓環(huán)孔道的層狀結構,由于其具有分子篩的網狀結構和介穩(wěn)性,在材料科學領域擁有廣泛的應用前景,同時在鎢冶煉領域,能夠作為制備氧化鎢的中間體,有希望減少鎢工藝流程,實現堿液循環(huán)。目前,通過利用水熱法制備焦綠石型氧化鎢已經能夠保證一定的反應率,但是含鎢酸鈉的水熱體系結構比較復雜,限制了該法的推廣應用。因此,如何強化和優(yōu)化水熱反應過程,制備出比較符合工業(yè)要求的焦綠石型氧化鎢產品,對于實現工業(yè)化生產具有重要的意義。 鑒于WO3易溶于鎢酸鈉溶液,起到改變水熱體系pH值的作用,本文主要選擇三氧化鎢為添加劑制備焦綠石型氧化鎢,并輔以二氧化碳、草酸預處理鎢酸鈉溶液,詳細地研究了不同條件下所得產品的結構形態(tài)以及溶液反應率,對影響反應過程的各項因素進行了分析。根據實驗數據以及紅外譜圖分析手段,初步探討了水熱法制備焦綠石型三氧化鎢的反應機理。研究結果表明： (1)單獨利用三氧化鎢為添加劑能夠穩(wěn)定水熱體系的pH,并且制得焦綠石型氧化鎢產品,其反應率能達到80%以上。而以草酸、CO2預處理鎢酸鈉溶液后,則利于改變反應速率,將反應時間由原來的24h以上縮短至8h以內。 (2)進一步證明了堿性體系下也能夠制得焦綠石型三氧化鎢產品,所需要pH范圍拓展至3.5～8.9之間。 (3)經XRD、SEM等檢測手段分析,所制得的產品均具有良好的立方體結構,顆粒的粒徑平均尺寸都在1μm左右。 (4)以三氧化鎢為添加物的產品具有較好的分散性,但是,產品中容易夾帶Na元素,用少量稀鹽酸進行洗滌能基本去除Na元素。 (5)采用紅外檢測初步認為W_2O_7~(2-)是制備焦綠石型氧化鎢的生長基元,探討了鎢酸鈉溶液在水熱反應過程中以及酸化過程中多組分平衡情況,對水熱反應機理提出了合理的假設。
[Abstract]:Pyrochlore tungsten trioxide (WO _ 3) 0.5H _ 2O) takes the twisted WO6 octahedron as the structural unit, and forms a layered structure with a circular pore channel through the angle-top of the W-O rigid skeleton. Because of its network structure and dielectric stability of molecular sieve, It has a wide application prospect in the field of material science. At the same time, it can be used as the intermediate for the preparation of tungsten oxide in the field of tungsten smelting. It is hopeful to reduce the tungsten technological process and realize the lye circulation. At present, pyrochlore tungsten oxide can be prepared by hydrothermal method, but the structure of hydrothermal system containing sodium tungstate is complex, which limits the application of the method. Therefore, how to strengthen and optimize the hydrothermal reaction process and prepare pyrochlore tungsten oxide products which meet the industrial requirements is of great significance for the realization of industrial production. In view of the fact that WO3 is soluble in sodium tungstate solution and plays a role in changing pH value of hydrothermal system, pyrochlorite type tungsten oxide is prepared by tungsten trioxide as additive, and sodium tungstate solution is pretreated with carbon dioxide and oxalic acid. The structure morphology and solution reaction rate of the products obtained under different conditions were studied in detail. The factors affecting the reaction process were analyzed. Based on the experimental data and infrared spectrum analysis, the reaction mechanism of pyrochlore tungsten trioxide prepared by hydrothermal method was preliminarily discussed. The results show that: 1) the pH of hydrothermal system can be stabilized by using tungsten trioxide as additive alone, and pyrochlore type tungsten oxide can be prepared. The reaction rate of pyrochlorite type tungsten oxide can reach more than 80%. When sodium tungstate solution was pretreated with oxalic acid CO _ 2, the reaction rate was changed, and the reaction time was shortened from more than 24 h to less than 8 h. 2) it is further proved that pyrochlorite tungsten trioxide products can also be prepared in alkaline system, and the required pH range is extended to 3.58.9. The results show that all the products have good cube structure and the average particle size is about 1 渭 m. (4) the product with tungsten trioxide as additive has good dispersibility, however, Na element is easily entrained in the product, and the Na element can be basically removed by washing with a small amount of dilute hydrochloric acid. (5) it is preliminarily considered that W _ S _ 2O _ 2 _ 7 ~ (2) is the growth unit of pyrochlore type tungsten oxide by infrared detection. The multicomponent equilibrium of sodium tungstate solution during hydrothermal reaction and acidification is discussed, and the reasonable hypothesis of hydrothermal reaction mechanism is put forward.
【學位授予單位】：中南大學
【學位級別】：碩士
【學位授予年份】：2011
【分類號】：O614.613

【引證文獻】

相關碩士學位論文 前1條

1 吳旭;從鎢酸鈉溶液中制備焦綠石型氧化鎢的研究[D];中南大學;2012年

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本文編號：1822004